JP6705899B2 - Non-aqueous alkali metal ion capacitor - Google Patents

Description

The present invention relates to non-aqueous alkali metal ion capacitors and the like.

In recent years, from the viewpoint of effective use of energy for conservation of the global environment and resource saving, a power smoothing system for wind power generation or a midnight power storage system, a household distributed power storage system based on solar power generation technology, an electric vehicle Power storage systems are attracting attention.
The first requirement of the power storage device used in these power storage systems is high energy density. As a promising candidate for a high energy density battery that can meet such requirements, development of a lithium ion battery is being vigorously pursued.
The second requirement is high output characteristics. For example, in a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell electric vehicle), high output discharge characteristics of the power storage system are required during acceleration. There is.
Currently, electric double layer capacitors, nickel hydrogen batteries, and the like are being developed as high-power storage elements.

Among electric double layer capacitors, those using activated carbon for electrodes have output characteristics of about 0.5 kW/L to about 1 kW/L. This electric double layer capacitor has high durability (cycle characteristics and high temperature storage characteristics), and has been considered to be an optimum device in the field where high output is required. However, its energy density is only about 1 Wh/L to about 5 Wh/L. Therefore, it is necessary to further improve the energy density.

On the other hand, the nickel hydrogen battery currently used in the hybrid electric vehicle has a high output equivalent to that of an electric double layer capacitor and an energy density of about 160 Wh/L. However, research has been vigorously pursued to further increase the energy density and output and to improve durability (in particular, stability at high temperature).
In addition, research is also progressing toward higher output in lithium-ion batteries. For example, a lithium-ion battery has been developed that can obtain a high output exceeding 3 kW/L at a discharge depth of 50% (a value indicating what percentage of the discharge capacity of a storage element is discharged). However, the energy density is 100 Wh/L or less, and the design is such that the high energy density, which is the most important feature of lithium ion batteries, is intentionally suppressed. Further, its durability (cycle characteristics and high temperature storage characteristics) is inferior to that of the electric double layer capacitor. Therefore, in order to provide the lithium ion battery with practical durability, it is used in a range where the depth of discharge is narrower than the range of 0 to 100%. Since the capacity of a lithium-ion battery that can be actually used is further reduced, research for further improving durability is being vigorously pursued.
As described above, there is a strong demand for the practical application of an electricity storage device having both high energy density, high output characteristics, and durability. However, each of the above-described existing power storage elements has advantages and disadvantages. Therefore, there is a demand for a new storage element that satisfies these technical requirements. As a promising candidate, a storage element called a lithium ion capacitor has been attracting attention and is being actively developed.

The above is a summary of the electrode materials for the storage elements and their characteristics. When using a material such as activated carbon for the electrodes and performing charge/discharge by adsorption/desorption of ions on the activated carbon surface (non-Faraday reaction), high output and high durability are achieved. However, the energy density becomes low (for example, 1 time). On the other hand, when an oxide or a carbon material is used for the electrode and charging/discharging is performed by the Faraday reaction, the energy density is high (for example, 10 times that of the non-Faraday reaction using activated carbon), but the durability and output characteristics. There are challenges.
As a combination of these electrode materials, the electric double layer capacitor is characterized by using activated carbon (1 time energy density) for the positive and negative electrodes, and charging and discharging by positive and negative electrodes by non-Faraday reaction, high output and high durability. However, there is a feature that the energy density is low (1 times positive electrode×1 times negative electrode=1).
A lithium-ion secondary battery is characterized by using a lithium transition metal oxide (energy density 10 times) for a positive electrode and a carbon material (energy density 10 times) for a negative electrode, and charging and discharging by positive and negative Faraday reaction. Although it has an energy density (10 times positive electrode×10 times negative electrode=100), there are problems in output characteristics and durability. Further, in order to satisfy the high durability required for a hybrid electric vehicle or the like, the depth of discharge must be limited, and a lithium ion secondary battery can use only 10 to 50% of its energy.

The lithium-ion capacitor is characterized in that activated carbon (energy density is 1 time) is used for the positive electrode, carbon material (energy density is 10 times) is used for the negative electrode, and charging and discharging are performed by a non-Faraday reaction in the positive electrode and a Faraday reaction in the negative electrode. This is a novel asymmetric capacitor that combines the characteristics of a multilayer capacitor and a lithium-ion secondary battery. The lithium ion capacitor has high energy density (1 times positive electrode×10 times negative electrode=10) while having high output and high durability, and does not need to limit the depth of discharge like a lithium ion secondary battery. Is also a feature.
However, the important lithium concentration is only about 20 ppm in the crust on average, and there is a problem that the production sites are unevenly distributed. In the future, it is necessary to substitute lithium with more universally existing elements, and research using alkali metals such as sodium or potassium for a power storage element is energetically advanced.

Patent Document 1 proposes increasing the output of a sodium ion capacitor by filling a porous portion of a positive electrode current collector made of a metal porous body with a material capable of adsorbing or absorbing and desorbing sodium. Patent Document 2 proposes a lithium ion secondary battery that uses a positive electrode containing lithium carbonate in the positive electrode and has a current cutoff mechanism that operates according to an increase in the internal pressure of the battery. Patent Document 3 proposes a method of recovering the capacity of a deteriorated power storage element by oxidizing various lithium compounds as oxides at the positive electrode. Patent Document 4 proposes a technique for suppressing gas generation by incorporating an antacid such as carbonate, hydroxide or silicate into a positive electrode made of activated carbon.
However, in the methods described in Patent Documents 1 to 4, further increase in capacity and increase in output are not taken into consideration, and gas generation by electrolytic solution decomposition on the surface of the positive electrode and alkali metal compound remaining in the positive electrode There was room for further improvement in gas generation due to its own decomposition, and the reduction in electrostatic capacity in the high load charge/discharge cycle caused by these.

Non-Patent Documents 1 to 3 describe the analysis of mesopores or micropores in an electrode active material used for a power storage element or a raw material thereof.

JP, 2013-38170, A JP-A-4-328278 JP2012-174437A JP, 2006-261516, A

E. P. Barrett, L.; G. Joyner and P.P. Halenda, J.; Am. Chem. Soc. , 73, 373 (1951) B. C. Lippens, J. et al. H. de Boer, J.M. Catalysis, 4319 (1965). R. S. Mikhail, S.; Brunauer, E.; E. Bodor, J.M. Colloid Interface Sci. , 26, 45 (1968)

The present invention has been made in view of the above circumstances.
Therefore, the problem to be solved by the present invention is to provide a high-capacity and high-output non-aqueous alkali metal ion capacitor, and suppress gas generation due to electrolyte decomposition on the positive electrode and gas generation due to decomposition of alkali metal compounds. In addition, it is to suppress the capacity decrease in the high load charge/discharge cycle.

｛式（１）中、Ｒ^１は、炭素数１〜４のアルキレン基、又は炭素数１〜４のハロゲン化アルキレン基であり、Ｘ^１及びＸ^２は、それぞれ独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）であり、かつＭ^１及びＭ^２は、それぞれ独立に、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、及びＣｓから成る群から選ばれるアルカリ金属である。｝

｛式（２）中、Ｒ^１は、炭素数１〜４のアルキレン基、又は炭素数１〜４のハロゲン化アルキレン基であり、Ｒ^２は、水素、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、及びアリール基から成る群から選択される基であり、Ｘ^１及びＸ^２は、それぞれ独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）であり、かつＭ^１は、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、及びＣｓから成る群から選ばれるアルカリ金属である。｝

｛式（３）中、Ｒ^１は、炭素数１〜４のアルキレン基、又は炭素数１〜４のハロゲン化アルキレン基であり、Ｒ^２及びＲ^３は、それぞれ独立に、水素、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、及びアリール基から成る群から選択される基であり、かつＸ^１及びＸ^２は、それぞれ独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝
から選択される１種以上の化合物を該正極物質層の単位質量当たり１．６０×１０^−４ｍｏｌ／ｇ〜３００×１０^−４ｍｏｌ／ｇ含有する、［１］〜［４］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［６］
前記正極活物質層が、下記式（４）及び（５）：

｛式（４）中、Ｍ^１及びＭ^２は、それぞれ独立に、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、及びＣｓから成る群から選ばれるアルカリ金属である。｝

｛式（５）中、Ｒ^１は、水素、炭素数１〜１０のアルキル基、又は炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、及びアリール基からなる群から選択される基であり、かつＭは、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、及びＣｓから成る群から選ばれるアルカリ金属である。｝
から選択される１種以上の化合物を前記正極物質層の単位質量当たり２．７０×１０^−４ｍｏｌ／ｇ〜１５０×１０^−４ｍｏｌ／ｇ含有する、［１］〜［５］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［７］
前記非水系電解液は２種以上４種以下のアルカリ金属イオンを含み、かつ前記非水系電解液中の第１のアルカリ金属イオンの物質量比は１％以上９９％以下であり、第２のアルカリ金属イオンの物質量比は１％以上９９％以下であり、第３及び第４のアルカリ金属イオンの物質量比は０％以上９８％以下である、［１］〜［６］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［８］
前記負極は、アルカリ金属イオンを吸蔵及び放出でき、
前記非水系電解液は、１種以上のアルカリ金属イオン及び１種以上のアルカリ土類金属イオンを含み、
前記アルカリ金属イオンを陽イオンとして有するアルカリ金属化合物、及び／又は前記アルカリ土類金属イオンを陽イオンとして有するアルカリ土類金属化合物が、前記正極の正極活物質層中に１．０質量％以上２０．０質量％以下含まれ、かつ
前記非水系電解液中の前記アルカリ金属イオンのモル濃度をＸ（ｍｏｌ／Ｌ）とし、前記アルカリ土類金属イオンのモル濃度をＹ（ｍｏｌ／Ｌ）とするとき、Ｘ／（Ｘ＋Ｙ）が０．０７以上０．９２以下である、［１］に記載の非水系アルカリ金属イオンキャパシタ。
［９］
前記Ｘ／（Ｘ＋Ｙ）が、０．１０以上０．９０以下である、［８］に記載の非水系アルカリ金属イオンキャパシタ。
［１０］
前記正極の表面の走査型電子顕微鏡−エネルギー分散型Ｘ線分析（ＳＥＭ−ＥＤＸ）により得られる元素マッピングにおいて、輝度値の平均値を基準に二値化した酸素マッピングに対するフッ素マッピングの面積重複率Ａ_１が、４０％以上９９％以下である、［８］又は［９］に記載の非水系アルカリ金属イオンキャパシタ。
［１１］
ブロードイオンビーム（ＢＩＢ）加工した前記正極の断面のＳＥＭ−ＥＤＸにより得られる元素マッピングにおいて、輝度値の平均値を基準に二値化した酸素マッピングに対するフッ素マッピングの面積重複率Ａ_２が、１０％以上６０％以下である、［８］〜［１０］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［１２］
前記アルカリ金属化合物及び／又は前記アルカリ土類金属化合物が、炭酸塩である、［８］〜［１１］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［１３］
前記アルカリ土類金属イオンが、カルシウムイオンである、［８］〜［１２］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［１４］
前記アルカリ金属イオンが、リチウムイオン、ナトリウムイオン、及びカリウムイオンから成る群から選ばれる１種以上である、［８］〜［１３］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［１５］
前記正極が、正極集電体と、前記正極集電体の片面上又は両面上に設けられた、正極活物質を含む正極活物質層とを有し、前記正極活物質層に含まれる前記正極活物質が、ＢＪＨ法により算出した直径２０Å以上５００Å以下の細孔に由来するメソ孔量をＶ_１（ｃｃ／ｇ）、ＭＰ法により算出した直径２０Å未満の細孔に由来するマイクロ孔量をＶ_２（ｃｃ／ｇ）とするとき、０．３＜Ｖ_１≦０．８、及び０．５≦Ｖ_２≦１．０を満たし、かつ、ＢＥＴ法により測定される比表面積が１，５００ｍ^２／ｇ以上３，０００ｍ^２／ｇ以下を示す活性炭である、［１］〜［１４］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［１６］
前記正極活物質層に含まれる前記正極活物質が、ＢＪＨ法により算出した直径２０Å以上５００Å以下の細孔に由来するメソ孔量Ｖ_１（ｃｃ／ｇ）が０．８＜Ｖ_１≦２．５を満たし、ＭＰ法により算出した直径２０Å未満の細孔に由来するマイクロ孔量Ｖ_２（ｃｃ／ｇ）が０．８＜Ｖ_２≦３．０を満たし、かつ、ＢＥＴ法により測定される比表面積が２，３００ｍ^２／ｇ以上４，０００ｍ^２／ｇ以下を示す活性炭である、［１］〜［１４］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［１７］
前記負極が負極活物質を含み、前記負極活物質のリチウムイオンのドープ量が、単位質量当たり５３０ｍＡｈ／ｇ以上２，５００ｍＡｈ／ｇ以下である、［１］〜［１６］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［１８］
前記負極活物質のＢＥＴ比表面積が１００ｍ^２／ｇ以上１，５００ｍ^２／ｇ以下である、［１７］に記載の非水系アルカリ金属イオンキャパシタ。
［１９］
前記負極が負極活物質を含み、前記負極活物質のリチウムイオンのドープ量が、単位質量当たり５０ｍＡｈ／ｇ以上７００ｍＡｈ／ｇ以下である、［１］〜［１６］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［２０］
前記負極活物質のＢＥＴ比表面積が１ｍ^２／ｇ以上５０ｍ^２／ｇ以下である、［１９］に記載の非水系アルカリ金属イオンキャパシタ。
［２１］
前記負極活物質の平均粒子径が１μｍ以上１０μｍ以下である、［１７］〜［２０］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［２２］
前記非水系アルカリ金属イオンキャパシタにおいて、セル電圧４Ｖ及び環境温度６０℃において２か月間保存した後の、セル電圧４Ｖでの内部抵抗をＲｂ（Ω）、保存前の内部抵抗をＲａ（Ω）、保存前の静電容量をＦａ（Ｆ）とした時、以下の（ａ）および（ｂ）の要件：
（ａ）Ｒｂ／Ｒａが３．０以下である、並びに
（ｂ）セル電圧４Ｖ及び環境温度６０℃において２か月間保存した時に発生するガス量を静電容量Ｆａで規格化した値Ｂが３０×１０^−３ｃｃ／Ｆ以下である、
のすべてを同時に満たす、［１］〜［２１］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタ。
［２３］
前記非水系アルカリ金属イオンキャパシタにおいて、環境温度２５℃にて、セル電圧を２．２Ｖから３．８Ｖまで、電流値２００Ｃのレートでの充放電サイクルを６０，０００回行い、セルを４．５Ｖの定電圧充電を１時間行った後の静電容量をＦｂ（Ｆ）とした時、Ｆｂ／Ｆａが１．０１以上である、［２２］に記載の非水系アルカリ金属イオンキャパシタ。
［２４］
活性炭と、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、及びＣｓから成る群から選ばれる２種以上のアルカリ金属イオンを陽イオンとして有するアルカリ金属化合物とを含む正極前駆体であって、第１のアルカリ金属化合物の物質量比は２％以上９８％以下であり、第２のアルカリ金属化合物の物質量比は２％以上９８％以下であり、第３及び第４のアルカリ金属イオンの物質量比は０％以上９６％以下である正極前駆体。
［２５］
前記アルカリ金属化合物が、炭酸塩、水酸化物、又は酸化物である、［２４］に記載の正極前駆体。
［２６］
［１］〜［２３］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタを用いた蓄電モジュール。
［２７］
［１］〜［２３］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタを用いた電力回生システム。
［２８］
［１］〜［２３］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタを用いた電力負荷平準化システム。
［２９］
［１］〜［２３］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタを用いた無停電電源システム。
［３０］
［１］〜［２３］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタを用いた非接触給電システム。
［３１］
［１］〜［２３］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタを用いたエナジーハーベストシステム。
［３２］
［１］〜［２３］のいずれか一項に記載の非水系アルカリ金属イオンキャパシタを用いた蓄電システム。The problems described above can be solved by the following technical means.
[1]
A non-aqueous alkali metal ion capacitor comprising a positive electrode containing activated carbon, a negative electrode, a separator, and a non-aqueous electrolytic solution containing two or more cations, wherein at least one of the two or more cations is A non-aqueous alkali metal ion capacitor in which the compound containing an alkali metal ion and the same kind of element as the two or more cations is contained in the positive electrode in an amount of 1.0% by mass or more and 25.0% by mass or less.
[2]
The negative electrode can store and release alkali metal ions, and the compound contained in the positive electrode is a compound of two or more kinds of alkali metals selected from the group consisting of Li, Na, K, Rb, and Cs, The non-aqueous alkali metal ion capacitor according to [1], wherein the positive electrode contains the alkali metal compound in an amount of 1% by mass or more and 25% by mass or less.
[3]
The positive electrode includes a positive electrode current collector, the negative electrode includes a negative electrode current collector, and the positive electrode current collector and the negative electrode current collector are metal foils having no through holes. [1] or [2] ] The non-aqueous alkali metal ion capacitor as described in.
[4]
The non-aqueous alkali metal ion capacitor according to any one of [1] to [3], wherein the compound of the alkali metal is one or more selected from the group consisting of carbonates, hydroxides, and oxides. ..
[5]
The positive electrode has the positive electrode current collector and a positive electrode active material layer containing a positive electrode active material, which is provided on one surface or both surfaces of the positive electrode current collector, and the positive electrode active material layer has the following formula: (1)-(3):

{In the formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are each independently -(COO) _n. (Where n is 0 or 1) and M ¹ and M ² are each independently an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs. }

{In the formula (2), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² is hydrogen, an alkyl group having 1 to 10 carbon atoms, carbon Group consisting of mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms, mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, cycloalkyl group having 3 to 6 carbon atoms, and aryl group X ¹ and X ² are each independently —(COO) _n (where n is 0 or 1), and M ¹ is Li, Na, K. Is an alkali metal selected from the group consisting of Rb, Rb, and Cs. }

{In the formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and 1 carbon atoms. -10 alkyl group, mono- or polyhydroxyalkyl group having 1-10 carbon atoms, alkenyl group having 2-10 carbon atoms, mono- or polyhydroxyalkenyl group having 2-10 carbon atoms, cycloalkyl group having 3-6 carbon atoms , And an aryl group, and X ¹ and X ² are each independently —(COO) _n (where n is 0 or 1). }
To per unit mass ^{1.60 × 10 -4 mol / g~300 ×} 10 -4 mol / g containing positive electrode material layer one or more compounds selected from any one of [1] to [4] The non-aqueous alkali metal ion capacitor according to item 1.
[6]
The positive electrode active material layer has the following formulas (4) and (5):

{In the formula (4), M ¹ and M ² are each independently an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs. }

{In the formula (5), R ¹ is hydrogen, an alkyl group having 1 to 10 carbon atoms, or a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and 2 to 10 carbon atoms. A mono- or polyhydroxyalkenyl group, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group, and M is a group consisting of Li, Na, K, Rb, and Cs. It is the alkali metal of choice. }
One or more compounds of which per unit mass ^{2.70 × 10 -4 mol / g~150 ×} 10 -4 mol / g containing the cathode material layer is selected from any one of [1] to [5] The non-aqueous alkali metal ion capacitor according to item 1.
[7]
The non-aqueous electrolyte solution contains two or more and four or less alkali metal ions, and the substance ratio of the first alkali metal ions in the non-aqueous electrolyte solution is 1% or more and 99% or less, and the second Any of [1] to [6], wherein the substance ratio of the alkali metal ions is 1% or more and 99% or less, and the substance ratio of the third and fourth alkali metal ions is 0% or more and 98% or less. The non-aqueous alkali metal ion capacitor according to item 1.
[8]
The negative electrode can store and release alkali metal ions,
The non-aqueous electrolyte solution contains at least one alkali metal ion and at least one alkaline earth metal ion,
The alkali metal compound having the alkali metal ion as a cation and/or the alkaline earth metal compound having the alkali earth metal ion as a cation is 1.0% by mass or more in the positive electrode active material layer of the positive electrode 20 0.0 mass% or less, and the molar concentration of the alkali metal ions in the non-aqueous electrolyte is X (mol/L), and the molar concentration of the alkaline earth metal ions is Y (mol/L). At this time, the non-aqueous alkali metal ion capacitor according to [1], wherein X/(X+Y) is 0.07 or more and 0.92 or less.
[9]
The non-aqueous alkali metal ion capacitor according to [8], wherein X/(X+Y) is 0.10 or more and 0.90 or less.
[10]
In the elemental mapping obtained by scanning electron microscope-energy dispersive X-ray analysis (SEM-EDX) on the surface of the positive electrode, the area overlap ratio A of fluorine mapping with respect to oxygen mapping binarized based on the average value of luminance values is shown. ₁ is 40% or more and 99% or less, The non-aqueous alkali metal ion capacitor as described in [8] or [9].
[11]
In the elemental mapping obtained by SEM-EDX of the cross section of the positive electrode processed by broad ion beam (BIB), the area overlapping rate A ₂ of the fluorine mapping with respect to the oxygen mapping binarized based on the average value of the brightness value is 10%. The nonaqueous alkali metal ion capacitor according to any one of [8] to [10], which is 60% or less.
[12]
The non-aqueous alkali metal ion capacitor according to any one of [8] to [11], wherein the alkali metal compound and/or the alkaline earth metal compound is a carbonate.
[13]
The non-aqueous alkali metal ion capacitor according to any one of [8] to [12], wherein the alkaline earth metal ion is calcium ion.
[14]
The non-aqueous alkali metal ion capacitor according to any one of [8] to [13], wherein the alkali metal ion is one or more selected from the group consisting of lithium ion, sodium ion, and potassium ion.
[15]
The positive electrode has a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material provided on one surface or both surfaces of the positive electrode current collector, and the positive electrode included in the positive electrode active material layer. The active material has V ₁ (cc/g) as the mesopore amount derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method, and the micropore amount derived from pores having a diameter of less than 20 Å calculated by the MP method. When V ₂ (cc/g), 0.3<V ₁ ≦0.8 and 0.5≦V ₂ ≦1.0 are satisfied, and the specific surface area measured by the BET method is 1,500 m. activated carbon having the following ² / g or more 3,000 m ² / g, [1] a non-aqueous alkali metal ion capacitor according to any one of - [14].
[16]
The positive electrode active material contained in the positive electrode active material layer has a mesopore amount V ₁ (cc/g) derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method of 0.8<V ₁ ≦2. 5, the micropore amount V ₂ (cc/g) derived from the pores having a diameter of less than 20Å calculated by the MP method satisfies 0.8<V ₂ ≦3.0, and is measured by the BET method. The non-aqueous alkali metal ion capacitor according to any one of [1] to [14], which is activated carbon having a specific surface area of 2,300 m ² /g or more and 4,000 m ² /g or less.
[17]
The negative electrode contains a negative electrode active material, and the doping amount of lithium ions in the negative electrode active material is 530 mAh/g or more and 2,500 mAh/g or less per unit mass, [1] to [16] The non-aqueous alkali metal ion capacitor described.
[18]
The non-aqueous alkali metal ion capacitor according to [17], wherein the negative electrode active material has a BET specific surface area of 100 m ² /g or more and 1,500 m ² /g or less.
[19]
The negative electrode contains a negative electrode active material, and a doping amount of lithium ions in the negative electrode active material is 50 mAh/g or more and 700 mAh/g or less per unit mass, [1] to [16]. Non-aqueous alkali metal ion capacitor.
[20]
The non-aqueous alkali metal ion capacitor according to [19], wherein the negative electrode active material has a BET specific surface area of 1 m ² /g or more and 50 m ² /g or less.
[21]
The non-aqueous alkali metal ion capacitor according to any one of [17] to [20], wherein the negative electrode active material has an average particle size of 1 μm or more and 10 μm or less.
[22]
In the non-aqueous alkali metal ion capacitor, after being stored at a cell voltage of 4 V and an environmental temperature of 60° C. for 2 months, the internal resistance at a cell voltage of 4 V is Rb (Ω), the internal resistance before storage is Ra (Ω), When the capacitance before storage is Fa(F), the following requirements (a) and (b):
(A) Rb/Ra is 3.0 or less, and (b) the value B obtained by normalizing the amount of gas generated when stored for 2 months at a cell voltage of 4 V and an environmental temperature of 60° C. by the capacitance Fa is 30. ×10 ⁻³ cc/F or less,
The non-aqueous alkali metal ion capacitor according to any one of [1] to [21], which simultaneously satisfies all of the above.
[23]
In the non-aqueous alkali metal ion capacitor, the cell voltage was changed from 2.2 V to 3.8 V and the charge/discharge cycle was performed 60,000 times at a current value of 200 C at an ambient temperature of 25° C. The non-aqueous alkali metal ion capacitor according to [22], wherein Fb/Fa is 1.01 or more when the electrostatic capacity after performing constant voltage charging for 1 hour is Fb(F).
[24]
A positive electrode precursor containing activated carbon and an alkali metal compound having two or more kinds of alkali metal ions selected from the group consisting of Li, Na, K, Rb, and Cs as cations, the first alkali metal compound Is 2% or more and 98% or less, the second alkali metal compound is 2% or more and 98% or less, and the third and fourth alkali metal ion is 0%. A positive electrode precursor having a content of not less than 96%.
[25]
The positive electrode precursor according to [24], wherein the alkali metal compound is a carbonate, a hydroxide, or an oxide.
[26]
An electricity storage module using the non-aqueous alkali metal ion capacitor according to any one of [1] to [23].
[27]
A power regeneration system using the non-aqueous alkali metal ion capacitor according to any one of [1] to [23].
[28]
An electric power load leveling system using the non-aqueous alkali metal ion capacitor according to any one of [1] to [23].
[29]
An uninterruptible power supply system using the non-aqueous alkali metal ion capacitor according to any one of [1] to [23].
[30]
A non-contact power feeding system using the non-aqueous alkali metal ion capacitor according to any one of [1] to [23].
[31]
An energy harvesting system using the non-aqueous alkali metal ion capacitor according to any one of [1] to [23].
[32]
An electricity storage system using the non-aqueous alkali metal ion capacitor according to any one of [1] to [23].

The above problem can also be solved by the following technical means.
[33]
A positive electrode containing activated carbon,
A negative electrode capable of inserting and extracting alkali metal ions,
A separator,
A non-aqueous electrolyte containing at least one alkali metal ion and at least one alkaline earth metal ion;
A non-aqueous alkali metal ion capacitor containing:
The alkali metal compound having the alkali metal ion as a cation and/or the alkaline earth metal compound having the alkali earth metal ion as a cation is 1.0% by mass or more in the positive electrode active material layer of the positive electrode 20 0.0 mass% or less, and the molar concentration of the alkali metal ions in the non-aqueous electrolyte is X (mol/L), and the molar concentration of the alkaline earth metal ions is Y (mol/L). At this time, a non-aqueous alkali metal ion capacitor having X/(X+Y) of 0.07 or more and 0.92 or less.

According to the present invention, it has a high capacity and high output, suppresses gas generation due to electrolyte decomposition on the positive electrode and gas generation due to decomposition of an alkali metal compound, and suppresses capacity decrease in a high load charge/discharge cycle. An aqueous alkali metal ion capacitor is provided.

Hereinafter, embodiments of the present invention (hereinafter, referred to as “embodiments”) will be described in detail, but the present invention is not limited to the embodiments. The upper limit value and the lower limit value in each numerical range of this embodiment can be arbitrarily combined to form an arbitrary numerical range.

Generally, a non-aqueous alkali metal ion capacitor mainly comprises a positive electrode, a negative electrode, a separator, an electrolytic solution, and an outer package. As the electrolytic solution, an organic solvent in which an alkali metal salt is dissolved (hereinafter referred to as a non-aqueous electrolytic solution) is used.

In the non-aqueous alkali metal ion capacitor according to the first embodiment, the non-aqueous electrolytic solution contains two or more cations, and at least one of the two or more cations is an alkali metal ion, and 2 A compound containing one or more kinds of cations and the same kind of element is contained in the positive electrode in an amount of 1.0% by mass or more and 25.0% by mass or less.

In the non-aqueous alkali metal ion capacitor according to the second embodiment, the non-aqueous electrolytic solution contains one or more kinds of alkali metal ions and one or more kinds of alkaline earth metal ions, and has an alkali metal ion as a cation. The positive electrode active material layer of the positive electrode contains a metal compound and/or an alkaline earth metal compound having an alkaline earth metal ion as a cation in an amount of 1.0% by mass or more and 20.0% by mass or less, and a non-aqueous electrolyte solution. X/(X+Y) is 0.07 or more and 0.92 or less, where X (mol/L) is the molar concentration of alkali metal ions and Y (mol/L) is the molar concentration of alkaline earth metal ions. Is.

The components of the non-aqueous alkali metal ion capacitor and their manufacturing methods will be described below.

<Positive electrode>
The positive electrode has a positive electrode current collector and a positive electrode active material layer present on one surface or both surfaces thereof.
Further, the positive electrode preferably contains an alkali metal compound and/or an alkaline earth metal compound as a positive electrode precursor before assembling the power storage element. As will be described later, in the present embodiment, in the storage element assembling step, it is preferable to pre-dope the negative electrode with an alkali metal ion and/or an alkaline earth metal ion, and as the pre-doping method, the alkali metal compound and/or It is preferable to apply a voltage between the positive electrode precursor and the negative electrode after assembling the electricity storage device using the positive electrode precursor containing the alkaline earth metal compound, the negative electrode, the separator, the outer casing, and the non-aqueous electrolyte solution.
Here, in this specification, a positive electrode state before the alkali metal doping step is defined as a positive electrode precursor, and a positive electrode state after the alkali metal doping step is defined as a positive electrode.

The positive electrode precursor according to the third embodiment contains activated carbon and an alkali metal compound having two or more kinds of alkali metal ions as cations, and the substance amount ratio of the first alkali metal compound is 2% or more and 98% or more. The amount ratio of the second alkali metal compound is 2% or more and 98% or less. When the positive electrode precursor contains an alkali metal compound having 2 or more and 4 or less alkali metal ions as cations, the substance ratio of the first alkali metal compound is 2% or more and 98% or less. The substance amount ratio of the alkali metal compound is 2% or more and 98% or less, and the substance amount ratio of the third and fourth alkali metal ions is 0% or more and 96% or less.

[Cathode active material layer]
The positive electrode active material layer preferably contains a positive electrode active material containing a carbon material, and, in addition to this, may contain an optional component such as a conductive filler, a binder, and a dispersion stabilizer, if necessary. Good.
The positive electrode active material layer of the positive electrode precursor preferably contains an alkali metal compound and/or an alkaline earth metal compound. Here, the alkali metal compound and the alkaline earth metal compound are alkali metal compounds other than the alkali metal-containing compound deposited in the positive electrode active material layer by utilizing the decomposition reaction of the active material and the precursor described later. Say.

[Cathode active material]
The positive electrode active material preferably contains a carbon material. As the carbon material, it is more preferable to use a carbon nanotube, a conductive polymer, or a porous carbon material, and it is more preferable to use activated carbon. One or more kinds of materials may be mixed and used as the positive electrode active material, and materials other than the carbon material (for example, a composite oxide of an alkali metal and a transition metal) may be included.
The content ratio of the carbon material with respect to the total amount of the positive electrode active material is preferably 50% by mass or more, more preferably 70% by mass or more. The content rate of the carbon material may be 100% by mass, but from the viewpoint of obtaining a good effect by the combined use of other materials, it is preferably 90% by mass or less, and 80% by mass or less, for example. Good.
When activated carbon is used as the positive electrode active material, the type of activated carbon and its raw material are not particularly limited. However, in order to achieve both high input/output characteristics and high energy density, it is preferable to optimally control the pores of activated carbon. Specifically, the amount of mesopores derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method is V ₁ (cc/g), and the amount of micropores derived from pores having a diameter of less than 20 Å calculated by the MP method. Is V ₂ (cc/g),
(1) For high input/output characteristics, 0.3<V ₁ ≦0.8 and 0.5≦V ₂ ≦1.0 are satisfied, and the specific surface area measured by the BET method is 1, Activated carbon of 500 m ² /g or more and 3,000 m ² /g or less (hereinafter, also referred to as activated carbon 1) is preferable, and
(2) In order to obtain a high energy density, 0.8<V ₁ ≦2.5 and 0.8<V ₂ ≦3.0 are satisfied, and the specific surface area measured by the BET method is 2, Activated carbon of 300 m ² /g or more and 4,000 m ² /g or less (hereinafter, also referred to as activated carbon 2) is preferable.

Hereinafter, the (1) activated carbon 1 and the (2) activated carbon 2 will be sequentially described individually.
(Activated carbon 1)
The mesopore amount V ₁ of the activated carbon 1 is preferably a value larger than 0.3 cc/g from the viewpoint of increasing the input/output characteristics when the positive electrode material is incorporated in the electricity storage device. On the other hand, from the viewpoint of suppressing the decrease in bulk density of the positive electrode, it is preferably 0.8 cc/g or less. The V ₁ is more preferably 0.35 cc/g or more and 0.7 cc/g or less, and further preferably 0.4 cc/g or more and 0.6 cc/g or less.
The micropore amount V ₂ of the activated carbon 1 is preferably 0.5 cc/g or more in order to increase the specific surface area of the activated carbon and increase the capacity. On the other hand, it is preferably 1.0 cc/g or less from the viewpoint of suppressing the bulk of the activated carbon, increasing the density of the electrode, and increasing the capacity per unit volume. The V ₂ is more preferably 0.6 cc/g or more and 1.0 cc/g or less, and further preferably 0.8 cc/g or more and 1.0 cc/g or less.

The ratio of the mesopore amount V ₁ to the micropore amount V ₂ (V ₁ /V ₂ ) is preferably in the range of 0.3≦V ₁ /V ₂ ≦0.9. That is, V ₁ /V ₂ may be 0.3 or more from the viewpoint of increasing the ratio of the amount of mesopores to the amount of micropores to the extent that deterioration of output characteristics can be suppressed while maintaining high capacity. preferable. On the other hand, V ₁ /V ₂ is 0.9 or less from the viewpoint of increasing the ratio of the amount of micropores to the amount of mesopores so that the decrease in capacity can be suppressed while maintaining high output characteristics. Is more preferable, the more preferable range of V ₁ /V ₂ is 0.4≦V ₁ /V ₂ ≦0.7, and the still more preferable range of V ₁ /V ₂ is 0.55≦V ₁ /V ₂ ≦0.7. Is.
The upper limit value and the lower limit value of V _{1 and} the upper limit value and the lower limit value of V ₂ can be arbitrarily combined. The same applies to combinations of upper limit values and lower limit values of the other constituents in the present specification.
The average pore diameter of the activated carbon 1 is preferably 17 Å or more, more preferably 18 Å or more, and most preferably 20 Å or more from the viewpoint of maximizing the output of the obtained electric storage device. From the viewpoint of maximizing the capacity, the activated carbon 1 preferably has an average pore diameter of 25 Å or less.

BET specific surface area of the activated carbon 1 is preferably from 1,500 m ² / g or more 3,000 m ² / g, more preferably not more than 1,500 m ² / g or more 2,500 m ² / g. When the BET specific surface area is 1,500 m ² /g or more, a good energy density is easily obtained, while when the BET specific surface area is 3,000 m ² /g or less, the strength of the electrode is maintained. Since it is not necessary to add a large amount of binder, the performance per electrode volume is improved.
The activated carbon 1 having the characteristics as described above can be obtained, for example, by using the raw materials and processing methods described below.
The carbon source used as a raw material for the activated carbon 1 is not particularly limited. For example, wood, wood powder, coconut shells, by-products of pulp production, bagasse, molasses, and other plant-based raw materials; peat, lignite, brown coal, bituminous coal, anthracite, petroleum distillation residue components, petroleum pitch, coke, coal tar, etc. Fossil raw materials; various synthetic resins such as phenol resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin, celluloid, epoxy resin, polyurethane resin, polyester resin, polyamide resin; polybutylene, polybutadiene, polychloroprene, etc. Synthetic rubber; other synthetic wood, synthetic pulp, etc., and their carbides. Among these raw materials, plant-based raw materials such as coconut shells and wood flour and their carbonized materials are preferable, and coconut shell carbonized materials are particularly preferable, from the viewpoint of mass production and cost.
Known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method can be adopted as a method of carbonizing and activating the raw materials to form the activated carbon 1.

As a method for carbonizing these raw materials, nitrogen, carbon dioxide, helium, argon, xenon, neon, carbon monoxide, an inert gas such as a combustion exhaust gas, or another gas containing these inert gas as a main component is used. A method of using a mixed gas and firing at about 400 to 700° C. (preferably 450 to 600° C.) for about 30 minutes to 10 hours can be mentioned.
As a method of activating the carbonized material obtained by the carbonization method, a gas activation method of firing using an activation gas such as steam, carbon dioxide, or oxygen is used. Among these, the method of using steam or carbon dioxide as the activating gas is preferable.
In this activation method, while the activation gas is supplied at a rate of 0.5 to 3.0 kg/h (preferably 0.7 to 2.0 kg/h), the carbide is kept for 3 to 12 hours (preferably 5 to 11). It is preferable to raise the temperature to 800 to 1,000° C. over a period of time, more preferably 6 to 10 hours, for activation.

Furthermore, prior to the activation treatment of the carbide, the carbide may be primarily activated in advance. In this primary activation, usually, a method of activating the carbon material by activating it with a activating gas such as steam, carbon dioxide, oxygen or the like at a temperature of less than 900° C. can be preferably adopted.
By appropriately combining the firing temperature and firing time in the carbonization method, the activation gas supply amount in the activation method, the heating rate and the maximum activation temperature, it can be used in the first, second and third embodiments, Activated carbon 1 having the characteristics of can be produced.
The activated carbon 1 preferably has an average particle size of 2 to 20 μm.
When the average particle diameter is 2 μm or more, the capacity per electrode volume tends to increase due to the high density of the active material layer. Here, if the average particle size is small, it may cause a defect that durability is low, but if the average particle size is 2 μm or more, such a defect is hard to occur. On the other hand, if the average particle size is 20 μm or less, it tends to be suitable for high-speed charging/discharging. The average particle diameter is more preferably 2 to 15 μm, further preferably 3 to 10 μm.

(Activated carbon 2)
The mesopore amount V ₁ of the activated carbon 2 is preferably a value larger than 0.8 cc/g from the viewpoint of increasing the output characteristics when the positive electrode material is incorporated in the electricity storage device. On the other hand, the mesopore amount V ₁ is preferably 2.5 cc/g or less from the viewpoint of suppressing the decrease in the capacity of the electricity storage device. The V ₁ is more preferably 1.00 cc/g or more and 2.0 cc/g or less, and further preferably 1.2 cc/g or more and 1.8 cc/g or less.
On the other hand, the micropore amount V ₂ of the activated carbon ₂ is preferably a value larger than 0.8 cc/g in order to increase the specific surface area of the activated carbon and increase the capacity. On the other hand, the micropore amount V ₂ is preferably 3.0 cc/g or less from the viewpoint of increasing the density of the activated carbon as an electrode and increasing the capacity per unit volume. The V ₂ is more preferably more than 1.0 cc/g and 2.5 cc/g or less, and further preferably 1.5 cc/g or more and 2.5 cc/g or less.
The activated carbon 2 having the amount of mesopores and the amount of micropores described above has a higher BET specific surface area than the activated carbon used for conventional electric double layer capacitors or lithium ion capacitors. The specific value of the BET specific surface area of the activated carbon 2 is preferably 3,000 m ² /g or more and 4,000 m ² /g or less, and is 3,200 m ² /g or more and 3,800 m ² /g or less. Is more preferable. When the BET specific surface area is 3,000 m ² /g or more, good energy density is easily obtained, while when the BET specific surface area is 4,000 m ² /g or less, the strength of the electrode is maintained. Since it is not necessary to add a large amount of binder, the performance per electrode volume is improved.
The activated carbon 2 having the above-mentioned characteristics can be obtained, for example, by using the raw materials and processing methods described below.

The carbonaceous material used as the raw material of the activated carbon 2 is not particularly limited as long as it is a carbon source usually used as the activated carbon raw material, and examples thereof include plant-based raw materials such as wood, wood flour, and coconut shells; petroleum pitch, Fossil raw materials such as coke; various synthetic resins such as phenol resin, furan resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin and resorcinol resin. Among these raw materials, the phenol resin and the furan resin are particularly preferable because they are suitable for producing activated carbon having a high specific surface area.
Examples of a method of carbonizing these raw materials or a heating method during activation treatment include known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method. As an atmosphere for heating, an inert gas such as nitrogen, carbon dioxide, helium, or argon, or a gas containing these inert gas as a main component and another gas is used. Generally, the carbonization temperature is about 400 to 700° C. and the firing is performed for about 0.5 to 10 hours.
Examples of the method for activating the carbide include steam activation, carbon dioxide activation, a gas activation method in which an activation gas such as oxygen is used for firing, and an alkali metal activation method in which a heat treatment is performed after mixing with an alkali metal compound. The alkali metal activation method is preferable for producing activated carbon.
In this activation method, the carbide and the alkali metal compound such as KOH or NaOH were mixed so that the mass ratio was 1:1 or more (the amount of the alkali metal compound was equal to or larger than the amount of the carbide). After that, heating is performed in the range of 600 to 900° C. for 0.5 to 5 hours in an inert gas atmosphere, then the alkali metal compound is washed and removed with an acid and water, and further dried.
In order to increase the amount of micropores and not the amount of mesopores, it is advisable to increase the amount of carbides and mix with KOH when activating. In order to increase both the amount of micropores and the amount of mesopores, it is preferable to use a large amount of KOH. In order to increase the amount of mesopores, it is preferable to perform steam activation after performing alkali activation treatment.

The average particle diameter of the activated carbon 2 is preferably 2 μm or more and 20 μm or less, and more preferably 3 μm or more and 10 μm or less.

(Use mode of activated carbon)
Each of the activated carbons 1 and 2 may be one type of activated carbon, or may be a mixture of two or more types of activated carbon and show the above-mentioned characteristic values as a whole mixture.
As the above-mentioned activated carbons 1 and 2, either one of them may be selected and used, or both may be mixed and used.
The positive electrode active material is a material other than the activated carbons 1 and 2 (for example, activated carbon not having the specific V ₁ and/or V ₂ or a material other than the activated carbon (for example, a composite oxide of an alkali metal and a transition metal, etc.). )) may be included. In the illustrated embodiment, the content of the activated carbon 1, the content of the activated carbon 2, or the total content of the activated carbons 1 and 2 is preferably more than 50% by mass of all the positive electrode active materials, and 70% by mass or more. It is more preferably 90% by mass or more, still more preferably 100% by mass.

The content ratio of the positive electrode active material in the positive electrode active material layer is preferably 35% by mass or more and 95% by mass or less based on the total mass of the positive electrode active material layer in the positive electrode precursor. The upper limit of the content ratio of the positive electrode active material is more preferably 45% by mass or more, and further preferably 55% by mass or more. On the other hand, the lower limit of the content ratio of the positive electrode active material is more preferably 90% by mass or less, and further preferably 85% by mass or less. When the content ratio is within this range, suitable charge/discharge characteristics are exhibited.

<Compound containing two or more kinds of elements corresponding to two or more kinds of cations contained in the electrolytic solution>
In the first embodiment, a compound containing two or more cations contained in the electrolytic solution and two or more elements of the same type is contained in the positive electrode. At least one of the two or more cations is an alkali metal ion. The remaining cations are not particularly limited as long as they participate in charge/discharge of the non-aqueous capacitor, and examples thereof include alkaline earth metal ions, transition metal ions, aluminum ions, ammonium ions, pyridinium ions, imidazolium ions, phosphonium ions. Etc. Therefore, the compound may be, for example, an alkali metal compound, an alkaline earth metal compound, a transition metal compound, an aluminum compound, an ammonium salt, a pyridinium salt, an imidazolium salt, a phosphonium salt, or the like.

In the first embodiment, the capacity and the output of the non-aqueous alkali metal ion capacitor are improved, the gas generation due to the electrolytic solution decomposition on the positive electrode and the gas generation due to the decomposition of the alkali metal compound are suppressed, and the high load charge/discharge cycle is performed. From the viewpoint of suppressing the capacity decrease in the above, it is preferable that the compound contained in the positive electrode contains an alkali metal compound and an alkaline earth metal compound.

(Alkali metal compounds, alkaline earth metal compounds)
The alkali metal compound or an alkaline earth metal compound, in formula, the ^{M A Li, Na, K,} Rb, and one or more selected from the group consisting of Cs, Be the ^{M B,} Mg, Ca, Sr, and as one or more selected from _{^{Ba, M a 2 CO 3,}} M B CO 3 and the like ^carbonates, _M a 2 O, an oxide such as ^{M B O, M a OH,} M B (OH) _2, etc. Hydroxides, halides of M ^A F, M ^A Cl, M ^A Br, M ^A I, M ^B F ₂ , M ^B Cl ₂ , M ^B Br ₂ , M ^B I _2, etc., M ^A ₂ (CO ₂ ) ₂ , oxalates such as M ^B (CO ₂ ) ₂ , RCOOM ^A , and carboxylates such as (RCOO) ₂ M ^B (wherein R represents H, an alkyl group, or an aryl group) 1 More than one species are preferably used. Among these, carbonates, oxides, and hydroxides are more preferable, and carbonates are more preferably used from the viewpoints of handling in air and low basicity. Among these carbonates, Li ₂ CO ₃ , Na ₂ CO ₃ and K ₂ CO ₃ are alkaline earth carbonates from the viewpoint that the acid reduction potential of the cation forming the compound is low. CaCO ₃ is particularly preferably used as the metal carbonate.
Various methods can be used for atomizing the alkali metal compound or the alkaline earth metal compound. For example, a crusher such as a ball mill, a bead mill, a ring mill, a jet mill or a rod mill can be used.
The amount of the alkali metal compound and/or the alkaline earth metal compound contained in the positive electrode is preferably 1.0% by mass or more and 25.0% by mass or less, more preferably 1.5% by mass or more and 20.0% by mass or more. It is not more than mass %. When the amount of the alkali metal compound and/or the alkaline earth metal compound is 1.0% by mass or more, there is a sufficient amount of carbonate to adsorb the fluorine ions generated in the high load charge/discharge cycle, and thus the high load charge is high. The discharge cycle characteristics are improved. When the amount of the alkali metal compound and/or the alkaline earth metal compound is 25.0 mass% or less, the energy density of the non-aqueous alkali metal ion capacitor can be increased.

From the viewpoint of achieving high capacity and high output of the electric storage element and suppressing gas generation during charge/discharge, in the positive electrode according to the second embodiment of the present invention, an alkali metal ion as a cation The alkaline earth metal compound having a metal compound and/or an alkaline earth metal ion as a cation is preferably contained in an amount of 1.0% by mass or more and 20.0% by mass or less based on the mass of the positive electrode active material layer, It is more preferable that the content is 2.0% by mass or more and 19.0% by mass or less.
When the positive electrode contains plural kinds of alkali metal compounds and/or plural kinds of alkaline earth metal compounds, the total content of all kinds in the positive electrode is preferably 1 based on the mass of the positive electrode active material layer. 0.0 mass% or more and 20.0 mass% or less, more preferably 2.0 mass% or more and 19.0 mass% or less.
The method for calculating the content rate of the alkali metal compound and/or the alkaline earth metal compound in the positive electrode is as described in detail in the following items <Method for quantifying alkali metal compound and alkaline earth metal compound> and Examples. is there.

The content ratio of the alkali metal compound and/or the alkaline earth metal compound in the positive electrode precursor is preferably 10% by mass or more and 60% by mass or less based on the total mass of the positive electrode active material layer in the positive electrode precursor, 20 It is more preferable that the content is at least 50% by mass. By setting the content ratio in this range, while exhibiting a suitable function as a dopant source for the negative electrode, it is possible to impart an appropriate degree of porosity to the positive electrode, and in combination with both, high load charging/discharging efficiency. It is preferable because an excellent power storage element can be provided. At this time, by containing a compound consisting of a plurality of alkali metal and/or alkaline earth metal compounds, a plurality of alkali metal ions and/or alkaline earth metal ions are present in the electrolytic solution at the time of alkali metal doping described later. It is preferable because it is possible.

｛式（１）中、Ｒ^１は、炭素数１〜４のアルキレン基、又は炭素数１〜４のハロゲン化アルキレン基であり、Ｘ^１及びＸ^２は、それぞれ独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）であり、かつＭ^１及びＭ^２は、それぞれ独立に、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、及びＣｓから成る群から選ばれるアルカリ金属である。｝

｛式（２）中、Ｒ^１は、炭素数１〜４のアルキレン基、又は炭素数１〜４のハロゲン化アルキレン基であり、Ｒ^２は、水素、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、及びアリール基からなる群から選択される基であり、Ｘ^１及びＸ^２は、それぞれ、独立に−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）であり、かつＭ^１は、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、及びＣｓから成る群から選ばれるアルカリ金属である。｝

｛式（３）中、Ｒ^１は、炭素数１〜４のアルキレン基、又は炭素数１〜４のハロゲン化アルキレン基であり、Ｒ^２及びＲ^３は、それぞれ独立に、水素、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、及びアリール基からなる群から選択される基であり、かつＸ^１及びＸ^２は、それぞれ独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝(Compounds of Formulas (1) to (3))
The non-aqueous electrolyte solution and the alkali metal compound and/or alkaline earth metal compound contained in the positive electrode were gradually decomposed and gasified when exposed to a high potential of about 4.0 V or more, and were generated. The gas hinders the diffusion of ions in the electrolytic solution, which causes an increase in resistance. Therefore, the positive electrode active material layer according to the present invention contains one or more compounds selected from the following formulas (1) to (3) per unit mass of the positive electrode material: 1.60×10 ⁻⁴ mol/g to 300. It is preferable to contain ^{x10 -4} mol/g.

{In the formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are each independently -(COO) _n. (Where n is 0 or 1) and M ¹ and M ² are each independently an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs. }

{In the formula (2), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² is hydrogen, an alkyl group having 1 to 10 carbon atoms, carbon A group consisting of a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group. X ¹ and X ² are each independently —(COO) _n (where n is 0 or 1), and M ¹ is Li, Na, K. Is an alkali metal selected from the group consisting of Rb, Rb, and Cs. }

{In the formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and 1 carbon atoms. -10 alkyl group, mono- or polyhydroxyalkyl group having 1-10 carbon atoms, alkenyl group having 2-10 carbon atoms, mono- or polyhydroxyalkenyl group having 2-10 carbon atoms, cycloalkyl group having 3-6 carbon atoms , And an aryl group, and X ¹ and X ² are each independently —(COO) _n (where n is 0 or 1). }

In formula (1), R ¹ is an alkyl group having 1 to 4 carbon atoms or a halogenated alkyl group having 1 to 4 carbon atoms, and X ¹ and X ² are each independently —(COO) _n. (Where n is 0 or 1).

Preferred compounds represented by Formula (1) include MOC ₂ H ₄ OM, MOC ₃ H ₆ OM, MOC ₂ H ₄ OCOOM, MOCOOC ₃ H ₆ OM, MOCOOC ₂ H ₄ OCOOM and MOCOOC ₃ H ₆ OCOOM (in the formula). , M are each independently an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs).

In formula (2), R ¹ is an alkyl group having 1 to 4 carbon atoms or a halogenated alkyl group having 1 to 4 carbon atoms, and R ² is hydrogen, an alkyl group having 1 to 10 carbon atoms, or a carbon number. 1-10 mono- or polyhydroxyalkyl group or lithium alkoxide thereof, alkenyl group having 2-10 carbon atoms, mono- or polyhydroxyalkenyl group having 2-10 carbon atoms, cycloalkyl group having 3-6 carbon atoms, and aryl group Is a group selected from the group consisting of, and X ¹ and X ² are each independently —(COO) _n (where n is 0 or 1).

Preferred compounds represented by formula (2) include MOC ₂ H ₄ OH, MOC ₃ H ₆ OH, MOC ₂ H ₄ OCOOH, MOC ₃ H ₆ OCOOH, MOCOOC ₂ H ₄ OCOOH, MOCOOC ₃ H ₆ OCOOH, MOC _{2 H 4 OCH 3, MOC 3 H} 6 OCH 3, MOC 2 H 4 OCOOCH 3, MOC 3 H 6 OCOOCH 3, MOCOOC 2 H 4 OCOOCH 3, MOCOOC 3 H 6 OCOOCH 3, MOC 2 H 4 OC 2 H 5, MOC ₃ H ₆ OC ₂ H ₅ , MOC ₂ H ₄ OCOOC ₂ H ₅ , MOC ₃ H ₆ OCOOC ₂ H ₅ , MOCOOC ₂ H ₄ OCOOC ₂ H ₅ , or MOCOOC ₃ H ₆ OCOOC ₂ H ₅ (where M is Each independently being an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs.).

In formula (3), R ¹ is an alkyl group having 1 to 4 carbon atoms or a halogenated alkyl group having 1 to 4 carbon atoms, and R ² and R ³ are each independently hydrogen, 1 to 1 carbon atoms. Alkyl group having 10 to 10 carbon atoms, mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms or lithium alkoxide thereof, alkenyl group having 2 to 10 carbon atoms, mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, and 3 to 6 carbon atoms It is a group selected from the group consisting of a cycloalkyl group and an aryl group, and X ¹ and X ² are each independently —(COO) _n (where n is 0 or 1). ..

Preferred compounds represented by the formula (3) include HOC ₂ H ₄ OH, HOC ₃ H ₆ OH, HOC ₂ H ₄ OCOOH, HOC ₃ H ₆ OCOOH, HOCOOC ₂ H ₄ OCOOH, HOCOOC ₃ H ₆ OCOOH and HOC _{2. H 4 OCH 3, HOC 3 H} 6 OCH 3, HOC 2 H 4 OCOOCH 3, HOC 3 H 6 OCOOCH 3, HOCOOC 2 H 4 OCOOCH 3, HOCOOC 3 H 6 OCOOCH 3, HOC 2 H 4 OC 2 H 5, HOC ₃ H ₆ OC ₂ H ₅ , HOC ₂ H ₄ OCOOC ₂ H ₅ , HOC ₃ H ₆ OCOOC ₂ H ₅ , HOCOOC ₂ H ₄ OCOOC ₂ H ₅ , HOCOOC ₃ H ₆ OCOOC ₂ H ₅ , CH ₃ OC ₂ H _{4 OCH 3, CH 3 OC 3 H} 6 OCH 3, CH 3 OC 2 H 4 OCOOCH 3, CH 3 OC 3 H 6 OCOOCH 3, CH 3 OCOOC 2 H 4 OCOOCH 3, CH 3 OCOOC 3 H 6 OCOOCH 3, CH 3 _{OC 2 H 4 OC 2 H 5} , CH 3 OC 3 H 6 OC 2 H 5, CH 3 OC 2 H 4 OCOOC 2 H 5, CH 3 OC 3 H 6 OCOOC 2 H 5, CH 3 OCOOC 2 H 4 OCOOC 2 _{H 5, CH 3 OCOOC 3 H} 6 OCOOC 2 H 5, C 2 H 5 OC 2 H 4 OC 2 H 5, C 2 H 5 OC 3 H 6 OC 2 H 5, C 2 H 5 OC 2 H 4 OCOOC 2 It is a compound represented by H ₅ , C ₂ H ₅ OC ₃ H ₆ OCOOC ₂ H ₅ , C ₂ H ₅ OCOOC ₂ H ₄ OCOOC ₂ H ₅ , or C ₂ H ₅ OCOOC ₃ H ₆ OCOOC ₂ H ₅ .

｛式（４）中、Ｍ^１及びＭ^２は、それぞれ独立に、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、及びＣｓから成る群から選ばれるアルカリ金属である。｝

｛式（５）中、Ｒ^１は、水素、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、又はアリール基であり、かつＭはＬｉ、Ｎａ、Ｋ、Ｒｂ、及びＣｓから成る群から選ばれるアルカリ金属である。｝Further, the positive electrode active material layer contains the compound represented by the following formula (4) or formula (5) in an amount of 2.70×10 ⁻⁴ mol/g to 150×10 ⁻⁴ mol per unit mass of the positive electrode active material layer. / g preferably contains, and more preferably contains ^{2.70 × 10 -4 mol / g~130 ×} 10 -4 mol / g.

{In the formula (4), M ¹ and M ² are each independently an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs. }

{In the formula (5), R ¹ is hydrogen, an alkyl group having 1 to 10 carbon atoms, a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and an alkyl group having 2 to 10 carbon atoms. It is a mono- or polyhydroxyalkenyl group, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group, and M is an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs. }

Examples of the method for incorporating the above compound in the present invention into the positive electrode active material layer include:
A method of mixing the compound into the positive electrode active material layer,
A method of adsorbing the compound to the positive electrode active material layer,
Examples thereof include a method of electrochemically depositing the above compound on the positive electrode active material layer.
Among them, in the non-aqueous electrolyte solution, a precursor capable of decomposing to produce these compounds is contained, and the decomposition reaction of the precursor in the step of producing a power storage device is used to make a positive electrode active material layer. A method of depositing the compound therein is preferred.

As the precursor for forming the compound, it is preferable to use at least one organic solvent selected from ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and fluoroethylene carbonate, and ethylene carbonate and propylene carbonate are used. More preferably.
Here, the total amount of the compound is preferably 1.60×10 ⁻⁴ mol/g or more, and 5.0×10 ⁻⁴ mol/g or more per unit mass of the positive electrode active material. Most preferred. When the total amount of the compounds is 1.60×10 ⁻⁴ mol/g or more per unit mass of the positive electrode active material layer, the non-aqueous electrolyte solution does not come into contact with the positive electrode active material and the non-aqueous electrolyte solution is oxidatively decomposed. Can be suppressed.

In addition, the total amount of the compounds is 300×10 ⁻⁴ mol/g or less, preferably 150×10 ⁻⁴ mol/g or less, and 100×10 ⁻⁴ mol per unit mass of the positive electrode active material. /G or less is more preferable. When the total amount of the compounds is 300×10 ⁻⁴ mol/g or less per unit mass of the positive electrode active material, high input/output characteristics can be exhibited without inhibiting diffusion of alkali metal ions.
Further, it is preferable to form a film made of a fluorine-containing compound on the surface of the alkali metal compound and/or the alkaline earth metal compound to suppress the reaction of the alkali metal compound and/or the alkaline earth metal compound.
The upper limit value and the lower limit value of the above compounds can be combined in any desired manner.
The method for forming the film of the fluorine-containing compound is not particularly limited, but a fluorine-containing compound that decomposes at high potential is contained in the electrolytic solution, and a high voltage that is higher than the decomposition potential of the fluorine-containing compound is applied to the non-aqueous alkali metal ion capacitor. And a method of applying a temperature equal to or higher than the decomposition temperature.
The coverage of the fluorine compound coating the surface of the alkali metal compound and/or the alkaline earth metal compound (area overlap ratio A ₁ of fluorine mapping to oxygen mapping in the positive electrode surface SEM-EDX image) is 40% or more and 99% or less. Is preferred. When A ₁ is 40% or more, decomposition of the alkali metal compound can be suppressed. When A ₁ is 99% or less, the vicinity of the positive electrode can be kept basic, so that the high load cycle characteristics are excellent.

As a method of measuring the coverage, in elemental mapping obtained by SEM-EDX on the surface of the positive electrode, it was determined by calculating the area overlap ratio of fluorine mapping with respect to oxygen mapping binarized based on the average value of luminance values. Be done.
The measurement conditions for elemental mapping of SEM-EDX are not particularly limited, but the number of pixels is preferably in the range of 128×128 pixels to 512×512 pixels, and there is no pixel that reaches the maximum luminance value in the mapping image, It is preferable to adjust the brightness and contrast so that the average value falls within the range of 40% to 60% of the maximum brightness value.
In the elemental mapping obtained by SEM-EDX on the cross section of the positive electrode, it is preferable that the area overlapping rate A ₂ of the fluorine mapping with respect to the oxygen mapping binarized based on the average value of the brightness values is 10% or more and 60% or less. When A ₂ is 10% or more, decomposition of the alkali metal compound can be suppressed. When A ₂ is 60% or less, the interior of the alkali metal compound is not fluorinated, so that the vicinity of the positive electrode can be kept basic and excellent in high load cycle characteristics.

(Other components of positive electrode active material layer)
The positive electrode active material layer in the present invention may optionally contain an optional component such as a conductive filler, a binder and a dispersion stabilizer in addition to the positive electrode active material and the alkali metal compound.
Examples of the conductive filler include a conductive carbonaceous material having higher conductivity than the positive electrode active material. As such a conductive filler, for example, Ketjen black, acetylene black, vapor grown carbon fiber, graphite, carbon nanotube, a mixture thereof, or the like is preferable.
The mixing amount of the conductive filler in the positive electrode active material layer is preferably 0 to 20 parts by mass, and more preferably 1 to 15 parts by mass with respect to 100 parts by mass of the positive electrode active material. It is preferable to mix the conductive filler from the viewpoint of high input. However, if the mixing amount is more than 20 parts by mass, the content ratio of the positive electrode active material in the positive electrode active material layer decreases, and the energy density per volume of the positive electrode active material layer decreases, which is not preferable.

The binder is not particularly limited, but for example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, etc. Can be used. The amount of the binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 3 parts by mass or more and 27 parts by mass or less, and further preferably 5 parts by mass or more with respect to 100 parts by mass of the positive electrode active material. It is 25 parts by mass or less. When the amount of the binder is 1% by mass or more, sufficient electrode strength is exhibited. On the other hand, when the amount of the binder is 30 parts by mass or less, high input/output characteristics are exhibited without hindering the entry/exit and diffusion of ions to/from the positive electrode active material.
The dispersion stabilizer is not particularly limited, but, for example, PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), cellulose derivative or the like can be used. The amount of the dispersion stabilizer used is preferably 0 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. When the amount of the dispersion stabilizer is 10 parts by mass or less, high input/output characteristics are exhibited without hindering the entry/exit and diffusion of ions to/from the positive electrode active material.

[Positive electrode collector]
The material constituting the positive electrode current collector in the present invention is not particularly limited as long as it has high electron conductivity and does not cause deterioration due to elution into an electrolytic solution and reaction with an electrolyte or ions, but a metal foil. Is preferred. Aluminum foil is particularly preferable as the positive electrode current collector in the non-aqueous alkali metal ion capacitors of the first, second and third embodiments.
The metal foil may be a normal metal foil having no irregularities or through holes, or a metal foil having irregularities subjected to embossing, chemical etching, electrolytic deposition, blasting, etc., expanded metal, punching metal. Alternatively, a metal foil having a through hole such as an etching foil may be used.
The thickness of the positive electrode current collector is not particularly limited as long as the shape and strength of the positive electrode can be sufficiently maintained, but is preferably 1 to 100 μm, for example.

[Production of positive electrode precursor]
In the present invention, the positive electrode precursor that becomes the positive electrode of the non-aqueous alkali metal ion capacitor can be manufactured by a known electrode manufacturing technique for lithium ion batteries, electric double layer capacitors and the like. For example, a positive electrode active material, an alkali metal compound, and other optional components used as necessary are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and the coating liquid is used as a positive electrode. A positive electrode precursor can be obtained by applying a coating film on one or both surfaces of a current collector to form a coating film and drying the coating film. Further, the obtained positive electrode precursor may be pressed to adjust the film thickness and bulk density of the positive electrode active material layer. Alternatively, without using a solvent, the positive electrode active material and the alkali metal compound, and other optional components used as necessary are dry mixed, and the resulting mixture is press-molded, and then a conductive adhesive is formed. A method of using and attaching to the positive electrode current collector is also possible.
The preparation of the coating liquid for the positive electrode precursor is performed by dry blending a part or all of various material powders containing a positive electrode active material, and then dissolving a binder or a dispersion stabilizer in water or an organic solvent, and/or them. Alternatively, it may be prepared by additionally adding a dispersed liquid or slurry substance. Alternatively, various material powders containing the positive electrode active material may be added to and prepared in a liquid or slurry substance in which a binder or a dispersion stabilizer is dissolved or dispersed in water or an organic solvent. As the method of dry blending, for example, a ball mill or the like is used to premix the positive electrode active material and the alkali metal compound, and the conductive filler if necessary, and the alkali metal compound having low conductivity is coated with the conductive material. You may mix. This facilitates decomposition of the alkali metal compound in the positive electrode precursor in the alkali metal doping step described below. When water is used as the solvent for the coating liquid, the coating liquid may become alkaline by adding an alkali metal compound, and therefore a pH adjuster may be added as necessary.

The preparation of the coating liquid for the positive electrode precursor is not particularly limited, but a homodisper, a multi-axis disperser, a planetary mixer, a disperser such as a thin film rotation type high speed mixer, or the like can be preferably used. .. In order to obtain a coating liquid in a good dispersion state, it is preferable to disperse at a peripheral speed of 1 m/s or more and 50 m/s or less. When the peripheral speed is 1 m/s or more, various materials are preferably dissolved or dispersed, which is preferable. Further, if it is 50 m/s or less, various materials are not destroyed by heat and shearing force due to dispersion and re-aggregation does not occur, which is preferable.
The dispersion degree of the coating liquid is preferably such that the particle size measured by a particle gauge is 0.1 μm or more and 100 μm or less. The upper limit of the dispersity is more preferably 80 μm or less, and further preferably 50 μm or less. If the particle size is 0.1 μm or less, the particle size is not more than the particle size of various material powders containing the positive electrode active material, and the material is crushed during the preparation of the coating solution, which is not preferable. Further, when the particle size is 100 μm or less, stable coating can be performed without causing clogging or streaking of the coating film when the coating liquid is discharged.

The viscosity (ηb) of the coating solution of the positive electrode precursor is preferably 1,000 mPa·s or more and 20,000 mPa·s or less, more preferably 1,500 mPa·s or more and 10,000 mPa·s or less, and further preferably 1 , 700 mPa·s or more and 5,000 mPa·s or less. When the viscosity (ηb) is 1,000 mPa·s or more, liquid dripping during the coating film formation is suppressed, and the coating film width and thickness can be well controlled. Further, when it is 20,000 mPa·s or less, pressure loss in the flow path of the coating liquid when using a coating machine is small, stable coating can be performed, and it can be controlled to a desired coating film thickness or less.
The TI value (thixotropy index value) of the coating liquid is preferably 1.1 or more, more preferably 1.2 or more, still more preferably 1.5 or more. When the TI value is 1.1 or more, the coating film width and thickness can be well controlled.

Formation of the coating film of the positive electrode precursor is not particularly limited, but a coating machine such as a die coater, a comma coater, a knife coater, or a gravure coating machine can be preferably used. The coating film may be formed by a single layer coating or a multilayer coating. In the case of multilayer coating, the coating liquid composition may be adjusted so that the content of the alkali metal compound in each layer of the coating film is different. The coating speed is preferably 0.1 m/min or more and 100 m/min or less, more preferably 0.5 m/min or more and 70 m/min or less, and further preferably 1 m/min or more and 50 m/min or less. If the coating speed is 0.1 m/min or more, stable coating can be performed. On the other hand, if it is 100 m/min or less, sufficient coating accuracy can be secured.
The drying of the coating film of the positive electrode precursor is not particularly limited, but a drying method such as hot air drying or infrared (IR) drying can be preferably used. Drying of the coating film may be performed at a single temperature or may be performed by changing the temperature in multiple stages. Also, a plurality of drying methods may be combined and dried. The drying temperature is preferably 25°C or higher and 200°C or lower, more preferably 40°C or higher and 180°C or lower, and further preferably 50°C or higher and 160°C or lower. When the drying temperature is 25°C or higher, the solvent in the coating film can be sufficiently volatilized. On the other hand, when the temperature is 200° C. or less, cracking of the coating film due to rapid volatilization of the solvent, uneven distribution of the binder due to migration, and oxidation of the positive electrode current collector and the positive electrode active material layer can be suppressed.

The pressing of the positive electrode precursor is not particularly limited, but a pressing machine such as a hydraulic pressing machine or a vacuum pressing machine can be preferably used. The film thickness, bulk density, and electrode strength of the positive electrode active material layer can be adjusted by the pressing pressure, the gap, and the surface temperature of the pressing portion described later. The pressing pressure is preferably 0.5 kN/cm or more and 20 kN/cm or less, more preferably 1 kN/cm or more and 10 kN/cm or less, and further preferably 2 kN/cm or more and 7 kN/cm or less. If the pressing pressure is 0.5 kN/cm or more, the electrode strength can be sufficiently increased. On the other hand, if it is 20 kN/cm or less, the positive electrode precursor is not bent or wrinkled, and the desired positive electrode active material layer thickness and bulk density can be adjusted. Further, the gap between the press rolls can be set to any value depending on the thickness of the positive electrode precursor after drying so that the desired thickness and bulk density of the positive electrode active material layer can be obtained. Further, the pressing speed can be set to an arbitrary speed at which the positive electrode precursor does not bend or wrinkle. The surface temperature of the press part may be room temperature or may be heated if necessary. The lower limit of the surface temperature of the pressed portion when heating is preferably the melting point of the binder used minus 60°C or higher, more preferably 45°C or higher, and further preferably 30°C or higher. On the other hand, the upper limit of the surface temperature of the pressed part when heated is preferably the melting point of the binder used plus 50°C or lower, more preferably 30°C or lower, and further preferably 20°C or lower. For example, when PVdF (polyvinylidene fluoride: melting point 150° C.) is used as the binder, it is preferably heated to 90° C. or higher and 200° C. or lower, more preferably 105° C. or higher and 180° C. or lower, still more preferably 120° C. or higher. It is to heat to 170° C. or lower. When a styrene-butadiene copolymer (melting point 100°C) is used as the binder, it is preferably heated to 40°C or higher and 150°C or lower, more preferably 55°C or higher and 130°C or lower, and further preferably 70°C. That is, heating is performed at a temperature of not less than 0°C and not more than 120°C.

The melting point of the binder can be determined by the endothermic peak position of DSC (Differential Scanning Calorimetry). For example, using a differential scanning calorimeter “DSC7” manufactured by Perkin Elmer Co., Ltd., 10 mg of the sample resin is set in the measuring cell, and the temperature is increased from 30° C. to 250° C. at a heating rate of 10° C./min in a nitrogen gas atmosphere. The temperature rises, and the endothermic peak temperature in the temperature rising process becomes the melting point.
Further, the pressing may be carried out plural times while changing the conditions of the pressing pressure, the gap, the speed, and the surface temperature of the pressing portion.
The thickness of the positive electrode active material layer is preferably 20 μm or more and 200 μm or less per one surface of the positive electrode current collector, more preferably 25 μm or more and 100 μm or less per one surface, and further preferably 30 μm or more and 80 μm or less. When this thickness is 20 μm or more, a sufficient charge/discharge capacity can be exhibited. On the other hand, if the thickness is 200 μm or less, the ion diffusion resistance in the electrode can be kept low. Therefore, sufficient output characteristics can be obtained, and the cell volume can be reduced, so that the energy density can be increased. The thickness of the positive electrode active material layer in the case where the current collector has through holes or irregularities refers to the average value of the thickness per surface of the portion of the current collector that does not have through holes or irregularities.
The bulk density of the positive electrode active material layer in the positive electrode after the alkali metal doping step described below is preferably 0.30 g/cm ³ or more, more preferably 0.4 g/cm ³ or more and 1.3 g/cm ³ or less. It is a range. When the positive electrode active material layer has a bulk density of 0.30 g/cm ³ or more, a high energy density can be exhibited and a power storage element can be downsized. Further, when the bulk density is 1.3 g/cm ³ or less, diffusion of the electrolytic solution in the pores in the positive electrode active material layer becomes sufficient, and high output characteristics can be obtained.

<Negative electrode>
The negative electrode of the present invention has a negative electrode current collector and a negative electrode active material layer present on one surface or both surfaces thereof.

[Negative electrode active material layer]
The negative electrode active material layer contains a negative electrode active material capable of occluding and releasing alkali metal ions and/or alkaline earth metal ions. In addition to this, an optional component such as a conductive filler, a binder, and a dispersion stabilizer may be included if necessary.

[Negative electrode active material]
As the negative electrode active material, a material capable of storing and releasing alkali metal ions and/or alkaline earth metal ions can be used. Specific examples include carbon materials, titanium oxides, silicon, silicon oxides, silicon alloys, silicon compounds, tin and tin compounds. The content ratio of the carbon material with respect to the total amount of the negative electrode active material is preferably 50% by mass or more, and more preferably 70% by mass or more. The content rate of the carbon material may be 100% by mass, but from the viewpoint of obtaining a good effect by the combined use of other materials, it is preferably 90% by mass or less, and 80% by mass or less, for example. Good.

The negative electrode active material is preferably doped with two or more kinds of alkali metal ions and/or alkaline earth metal ions. In the present specification, the two or more kinds of alkali metal ions and/or alkaline earth metal ions doped in the negative electrode active material mainly include three forms.
The first mode is two or more kinds of alkali metal ions and/or alkaline earth metal ions that are stored in the negative electrode active material as design values before the non-aqueous alkali metal ion capacitor is manufactured.
The second mode is two or more kinds of alkali metal ions and/or alkaline earth metal ions stored in the negative electrode active material at the time of manufacturing and shipping a non-aqueous alkali metal ion capacitor.
The third form is two or more kinds of alkali metal ions and/or alkaline earth metal ions stored in the negative electrode active material after using the non-aqueous alkali metal ion capacitor as a device.
By doping the negative electrode active material with two or more kinds of alkali metal ions and/or alkaline earth metal ions, it is possible to satisfactorily control the capacity and operating voltage of the obtained non-aqueous alkali metal ion capacitor. .

Examples of the carbon material include non-graphitizable carbon material; graphitizable carbon material; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon microspheres; graphite whiskers; polyacene-based material. Amorphous carbonaceous materials such as; carbonaceous materials obtained by heat-treating carbon precursors such as petroleum-based pitches, coal-based pitches, mesocarbon microbeads, cokes, synthetic resins (eg phenolic resins); furfuryl alcohol Examples thereof include thermal decomposition products of resins or novolac resins; fullerenes; carbon nanophones; and composite carbon materials thereof.
Among these, from the viewpoint of lowering the resistance of the negative electrode, a pitch composite carbon material, which can be obtained by heat treatment in the state where one or more kinds of the carbon materials and coexistence of petroleum-based pitch or coal-based pitch are present, is preferable. . Before the heat treatment, the carbon material and the pitch may be mixed at a temperature higher than the melting point of the pitch. The heat treatment temperature may be a temperature at which a component generated by volatilization or thermal decomposition of the pitch used becomes a carbonaceous material. As an atmosphere for heat treatment, a non-oxidizing atmosphere is preferable.

Preferable examples of the pitch composite carbon material are pitch composite carbon materials 1a and 2a described later. Either of these may be selected and used, or both of them may be used in combination.
The pitch composite carbon material 1a is obtained by heat treatment in the state where one or more carbon materials having a BET specific surface area of 100 m ² /g or more and 3000 m ² /g or less and petroleum-based pitch or coal-based pitch coexist. You can
The carbon material is not particularly limited, but activated carbon, carbon black, template porous carbon, high specific surface area graphite, carbon nanoparticles and the like can be preferably used.

-Composite carbon material 1a-
The composite carbon material 1a is the composite carbon material using at least one carbon material having a BET specific surface area of 100 m ² /g or more and 3000 m ² /g or less as the base material. The base material is not particularly limited, but activated carbon, carbon black, template porous carbon, high specific surface area graphite, carbon nanoparticles and the like can be preferably used.

The mass ratio of the carbonaceous material to the base material in the composite carbon material 1a is preferably 10% or more and 200% or less. This mass ratio is preferably 12% or more and 180% or less, more preferably 15% or more and 160% or less, and particularly preferably 18% or more and 150% or less. If the mass ratio of the carbonaceous material is 10% or more, the micropores possessed by the base material can be appropriately filled with the carbonaceous material, and two or more kinds of alkali metal ions and/or alkaline earth Since the charge/discharge efficiency of metal ions is improved, good cycle durability can be exhibited. Further, when the mass ratio of the carbonaceous material is 200% or less, the pores can be appropriately held, and the diffusion of two or more kinds of alkali metal ions and/or alkaline earth metal ions is good, which is high. Input/output characteristics can be shown.

Regarding the doping amount of the alkali metal ion and/or the alkaline earth metal ion to the negative electrode, the lithium ion having the smallest ionic radius shows the largest doping amount. Therefore, it is preferable to adjust the doping amount of alkali metal ions based on the doping amount of lithium ions. From the above viewpoint, the doping amount of lithium ions per unit mass of the composite carbon material 1a is preferably 530 mAh/g or more and 2,500 mAh/g or less, more preferably 620 mAh/g or more and 2,100 mAh/g or less, It is more preferably 760 mAh/g or more and 1,700 mAh/g or less, and particularly preferably 840 mAh/g or more and 1,500 mAh/g or less.
Doping with two or more kinds of alkali metal ions and/or alkaline earth metal ions lowers the negative electrode potential. Therefore, when the negative electrode including the composite carbon material 1a doped with the ions is combined with the positive electrode, the voltage of the non-aqueous alkali metal ion capacitor increases and the usable capacity of the positive electrode increases. Therefore, the capacity and energy density of the obtained non-aqueous alkali metal ion capacitor are increased.
If the doping amount of the lithium ions is 530 mAh/g or more, the ions are also present at irreversible sites that cannot be desorbed once the two or more kinds of alkali metal ions and/or alkaline earth metal ions in the composite carbon material 1a are inserted. Can be well doped, and the amount of the composite carbon material 1a with respect to the desired amount of two or more kinds of alkali metals and/or alkaline earth metals can be reduced. Therefore, the negative electrode film thickness can be reduced, and high energy density can be obtained. The larger the doping amount of the alkali metal ion and/or the alkaline earth metal ion, the lower the negative electrode potential, and the better the input/output characteristics, the energy density, and the durability.
On the other hand, if the doping amount of lithium ions is 2,500 mAh/g or less, side effects such as precipitation of alkali metal and/or alkaline earth metal do not occur.

Hereinafter, as a preferable example of the composite carbon material 1a, the composite carbon material 1a using activated carbon as the base material will be described.
In the composite carbon material 1a, the mesopore amount derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method is Vm1 (cc/g), and the micropore amount derived from pores having a diameter of less than 20 Å calculated by the MP method. Is Vm2 (cc/g), it is preferable that 0.010≦Vm1≦0.300 and 0.001≦Vm2≦0.650.
The mesopore amount Vm1 is more preferably 0.010≦Vm1≦0.225, and further preferably 0.010≦Vm1≦0.200. The micropore amount Vm2 is more preferably 0.001≦Vm2≦0.200, further preferably 0.001≦Vm2≦0.150, and particularly preferably 0.001≦Vm2≦0.100.

When the mesopore amount Vm1 is 0.300 cc/g or less, the BET specific surface area can be increased and the doping amount of two or more kinds of alkali metal ions and/or alkaline earth metal ions can be increased. The bulk density of the negative electrode can be increased. As a result, the negative electrode can be thinned. Further, when the micropore amount Vm2 is 0.650 cc/g or less, high charge/discharge efficiency for the ions can be maintained. On the other hand, when the mesopore amount Vm1 and the micropore amount Vm2 are not less than the lower limit (0.010≦Vm1, 0.001≦Vm2), high input/output characteristics can be obtained.

The BET specific surface area of the composite carbon material 1a is preferably 100 m ² /g or more and 1,500 m ² /g or less, more preferably 150 m ² /g or more and 1,100 m ² /g or less, and further preferably 180 m ² /g or more and 550 m. ^{It is 2} /g or less. If the BET specific surface area is 100 m ² /g or more, the pores can be appropriately held, and thus the diffusion of two or more kinds of alkali metal ions and/or alkaline earth metal ions becomes good, which is high. Input/output characteristics can be shown. Further, since the doping amount of the ions can be increased, the negative electrode can be thinned. On the other hand, when it is 1,500 m ² /g or less, the charge and discharge efficiency of the ions is improved, and thus cycle durability is not impaired.

The average pore diameter of the composite carbon material 1a is preferably 20 Å or more, more preferably 25 Å or more, and further preferably 30 Å or more, from the viewpoint of achieving high input/output characteristics. On the other hand, from the viewpoint of achieving high energy density, the average pore diameter is preferably 65 Å or less, and more preferably 60 Å or less.

The average particle diameter of the composite carbon material 1a is preferably 1 μm or more and 10 μm or less. The lower limit is more preferably 2 μm or more, further preferably 2.5 μm or more. The upper limit is more preferably 6 μm or less, further preferably 4 μm or less. When the average particle diameter is 1 μm or more and 10 μm or less, good durability is maintained.

The hydrogen atom/carbon atom atomic ratio (H/C) of the composite carbon material 1a is preferably 0.05 or more and 0.35 or less, and more preferably 0.05 or more and 0.15 or less. .. When H/C is 0.35 or less, the structure (typically, a polycyclic aromatic conjugated structure) of the carbonaceous material deposited on the surface of the activated carbon is well developed and the capacity (energy) is increased. Density) and charge/discharge efficiency are increased. On the other hand, when H/C is 0.05 or more, carbonization does not proceed excessively, so that good energy density can be obtained. H/C is measured by an elemental analyzer.

The composite carbon material 1a has an amorphous structure derived from the activated carbon of the base material, but at the same time has a crystal structure derived mainly from the deposited carbonaceous material. According to the X-ray wide-angle diffraction method, the composite carbon material A has an interplanar spacing d002 of (002) planes of 3.60 Å or more and 4.00 Å or less, and the crystallite in the c-axis direction obtained from the half width of this peak. It is preferable that the size Lc is 8.0 Å or more and 20.0 Å or less, d002 is 3.60 Å or more and 3.75 Å or less, and the crystallite size Lc in the c-axis direction obtained from the half-value width of this peak is 11. It is more preferably 0 Å or more and 16.0 Å or less.

The activated carbon used as the base material of the composite carbon material 1a is not particularly limited as long as the obtained composite carbon material 1a exhibits desired characteristics. For example, commercially available products obtained from various raw materials such as petroleum-based, coal-based, plant-based and polymer-based materials can be used. In particular, it is preferable to use activated carbon powder having an average particle size of 1 μm or more and 15 μm or less. The average particle diameter is more preferably 2 μm or more and 10 μm or less.

In order to obtain the composite carbon material 1a having the pore distribution range defined in the first and second embodiments, the pore distribution of the activated carbon used for the base material is important.
In the activated carbon, the amount of mesopores derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method is V1 (cc/g), and the amount of micropores derived from pores having a diameter of less than 20 Å calculated by the MP method is When V2 (cc/g) is set, it is preferable that 0.050≦V1≦0.500, 0.005≦V2≦1.000, and 0.2≦V1/V2≦20.0.

Regarding the mesopore amount V1, 0.050≦V1≦0.350 is more preferable, and 0.100≦V1≦0.300 is further preferable. The micropore amount V2 is more preferably 0.005≦V2≦0.850 and even more preferably 0.100≦V2≦0.800. Regarding the ratio of mesopore amount/micropore amount, 0.22≦V1/V2≦15.0 is more preferable, and 0.25≦V1/V2≦10.0 is further preferable. When the mesopore volume V1 of the activated carbon is 0.500 or less and the micropore volume V2 is 1.000 or less, an appropriate amount of carbonaceous material is required to obtain the pore structure of the composite carbon material 1a in the above embodiment. It suffices to deposit the above, so that it becomes easy to control the pore structure. On the other hand, when the mesopore amount V1 of activated carbon is 0.050 or more, the micropore amount V2 is 0.005 or more, V1/V2 is 0.2 or more, and V1/V2 is 20.0. The structure is easily obtained even in the following cases.

The carbonaceous material precursor used as a raw material of the above-mentioned composite carbon material 1a is a solid, liquid, or organic material that can be dissolved in a solvent, by which carbonaceous material can be deposited on activated carbon by heat treatment. .. Examples of the carbonaceous material precursor include pitch, mesocarbon microbeads, coke, synthetic resin (for example, phenol resin, etc.), and the like. Among these carbonaceous material precursors, it is preferable to use inexpensive pitch in terms of manufacturing cost. The pitch is roughly classified into a petroleum pitch and a coal pitch. Examples of the petroleum-based pitch include distillation residue of crude oil, fluid catalytic cracking residue (decant oil, etc.), bottom oil derived from thermal cracker, ethylene tar obtained during naphtha cracking, and the like.

When the pitch is used, the pitch is heat-treated in the coexistence with activated carbon, and a volatile component or a thermal decomposition component of the pitch is thermally reacted on the surface of the activated carbon to deposit a carbonaceous material on the activated carbon to obtain a composite carbon. Material 1a is obtained. In this case, at a temperature of about 200 to 500°C, deposition of pitch volatile components or thermal decomposition components into activated carbon pores proceeds, and at 400°C or higher, a reaction in which the deposited components become a carbonaceous material proceeds. To do. The peak temperature (maximum temperature reached) during the heat treatment is appropriately determined according to the characteristics of the obtained composite carbon material 1a, the thermal reaction pattern, the thermal reaction atmosphere, etc., but is preferably 400° C. or higher, more preferably Is 450° C. to 1,000° C., more preferably about 500 to 800° C. The time for maintaining the peak temperature during the heat treatment is preferably 30 minutes to 10 hours, more preferably 1 hour to 7 hours, and further preferably 2 hours to 5 hours. For example, when heat treatment is performed at a peak temperature of about 500 to 800° C. for 2 to 5 hours, it is considered that the carbonaceous material deposited on the surface of the activated carbon is a polycyclic aromatic hydrocarbon. ..

The softening point of the pitch used is preferably 30°C or higher and 250°C or lower, and more preferably 60°C or higher and 130°C or lower. A pitch having a softening point of 30° C. or higher does not affect the handling property and can be charged with high accuracy. The pitch having a softening point of 250° C. or less contains a large amount of relatively low molecular weight compounds, and therefore, when the pitch is used, it is possible to deposit even fine pores in the activated carbon.
As a specific method for producing the above-mentioned composite carbon material 1a, for example, activated carbon is heat-treated in an inert atmosphere containing a hydrocarbon gas volatilized from a carbonaceous material precursor, and the carbonaceous material is coated in a vapor phase. There is a method of wearing. Further, a method of preliminarily mixing activated carbon and a carbonaceous material precursor and heat treatment, or a method of applying a carbonaceous material precursor dissolved in a solvent to activated carbon and drying it and then heat treating it is also possible.

The mass ratio of the carbonaceous material to the activated carbon in the composite carbon material 1a is preferably 10% or more and 100% or less. This mass ratio is preferably 15% or more and 80% or less. If the mass ratio of the carbonaceous material is 10% or more, the micropores of the activated carbon can be appropriately filled with the carbonaceous material, and two or more kinds of alkali metal ions and/or alkaline earth metals can be used. Since the charge/discharge efficiency of ions is improved, the cycle durability is not impaired. Further, if the mass ratio of the carbonaceous material is 100% or less, the pores of the composite carbon material 1a are appropriately held and the specific surface area is maintained large. Therefore, as a result of being able to increase the doping amount of two or more kinds of alkali metal ions and/or alkaline earth metal ions, high output density and high durability can be maintained even if the negative electrode is thinned.

-Composite carbon material 1b-
The composite carbon material 1b is the composite carbon material using at least one carbon material having a BET specific surface area of 0.5 m ² /g or more and 80 m ² /g or less as the base material. The base material is not particularly limited, but natural graphite, artificial graphite, low crystal graphite, hard carbon, soft carbon, carbon black and the like can be preferably used.

BET specific surface area of the composite carbon material. 1b, ^{1 m} 2 / g or more ^{50 m} 2 / g or less, more preferably 1.5 m ² / g or more ^{40 m} 2 / g or less, more preferably ^2m 2 / g or more ^{25 m} 2 / g or less. If the BET specific surface area is 1 m ² /g or more, a reaction field with two or more kinds of alkali metal ions and/or alkaline earth metal ions can be sufficiently secured, and thus high input/output characteristics can be exhibited. On the other hand, when it is 50 m ² /g or less, the charge/discharge efficiency of the ions is improved, and the decomposition reaction of the non-aqueous electrolyte solution during charge/discharge is suppressed, so that high cycle durability can be exhibited.

The average particle diameter of the composite carbon material 1b is preferably 1 μm or more and 10 μm or less. The average particle diameter is more preferably 2 μm or more and 8 μm or less, and further preferably 3 μm or more and 6 μm or less. When the average particle diameter is 1 μm or more, the charge/discharge efficiency of two or more kinds of alkali metal ions and/or alkaline earth metal ions can be improved, and thus high cycle durability can be exhibited. On the other hand, when the thickness is 10 μm or less, the reaction area between the composite carbon material 1b and the non-aqueous electrolyte solution increases, so that high input/output characteristics can be exhibited.

The mass ratio of the carbonaceous material to the base material in the composite carbon material 1b is preferably 1% or more and 30% or less. This mass ratio is more preferably 1.2% or more and 25% or less, and further preferably 1.5% or more and 20% or less. When the mass ratio of the carbonaceous material is 1% or more, the carbonaceous material can sufficiently increase the reaction sites with two or more kinds of alkali metal ions and/or alkaline earth metal ions, and desolvate the ions. Since the sum is easy, high input/output characteristics can be exhibited. On the other hand, when the mass ratio of the carbonaceous material is 20% or less, diffusion of two or more kinds of alkali metal ions and/or alkaline earth metal ions between the carbonaceous material and the base material in the solid state can be favorably performed. Since it can be held, high input/output characteristics can be exhibited. Further, since the charge/discharge efficiency of the ions can be improved, high cycle durability can be exhibited.

The doping amount of lithium ions per unit mass of the composite carbon material 1b is preferably 50 mAh/g or more and 700 mAh/g or less, more preferably 70 mAh/g or more and 650 mAh/g or less, and further preferably 90 mAh/g or more and 600 mAh or less. /G or less, particularly preferably 100 mAh/g or more and 550 mAh/g or less.
Doping with two or more kinds of alkali metal ions and/or alkaline earth metal ions lowers the negative electrode potential. Therefore, when the negative electrode including the composite carbon material 1b doped with the ions is combined with the positive electrode, the voltage of the non-aqueous alkali metal ion capacitor increases and the usable capacity of the positive electrode increases. Therefore, the capacity and energy density of the obtained non-aqueous alkali metal ion capacitor are increased.
If the doping amount is 50 mAh/g or more, the ion is good even in an irreversible site where two or more kinds of alkali metal ions and/or alkaline earth metal ions in the composite carbon material 1b cannot be desorbed once inserted. A high energy density can be obtained because it is doped with. The larger the doping amount, the lower the negative electrode potential and the better the input/output characteristics, energy density, and durability.
On the other hand, if the doping amount of lithium ions is 700 mAh/g or less, side effects such as precipitation of alkali metal are unlikely to occur.

Hereinafter, as a preferred example of the composite carbon material 1b, the composite carbon material 1b using a graphite material as the base material will be described.

The average particle diameter of the composite carbon material 1b is preferably 1 μm or more and 10 μm or less. The average particle diameter is more preferably 2 μm or more and 8 μm or less, and further preferably 3 μm or more and 6 μm or less. When the average particle diameter is 1 μm or more, the charge/discharge efficiency of two or more kinds of alkali metal ions and/or alkaline earth metal ions can be improved, and thus high cycle durability can be exhibited. On the other hand, when the thickness is 10 μm or less, the reaction area between the composite carbon material 1b and the non-aqueous electrolyte solution increases, so that high input/output characteristics can be exhibited.

The BET specific surface area of the composite carbon material 1b is preferably 1 m ² /g or more and 20 m ² /g or less, and more preferably 1 m ² /g or more and 15 m ² /g or less. If the BET specific surface area is 1 m ² /g or more, a reaction field with two or more kinds of alkali metal ions and/or alkaline earth metal ions can be sufficiently secured, and thus high input/output characteristics can be exhibited. On the other hand, when it is 20 m ² /g or less, the charge/discharge efficiency of the ions is improved and the decomposition reaction of the non-aqueous electrolyte solution during charge/discharge is suppressed, so that high cycle durability can be exhibited.

The graphite material used as the base material is not particularly limited as long as the obtained composite carbon material 1b exhibits desired characteristics. For example, artificial graphite, natural graphite, graphitized mesophase carbon microspheres, graphite whiskers and the like can be used. The average particle diameter of the graphite material is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less.

The carbonaceous material precursor used as a raw material of the above-mentioned composite carbon material 1b is a solid, liquid, or an organic material that can be dissolved in a solvent, which is capable of compounding the carbonaceous material with the graphite material by heat treatment. .. Examples of the carbonaceous material precursor include pitch, mesocarbon microbeads, coke, synthetic resin (for example, phenol resin, etc.), and the like. Among these carbonaceous material precursors, it is preferable to use inexpensive pitch in terms of manufacturing cost. The pitch is roughly classified into a petroleum pitch and a coal pitch. Examples of the petroleum-based pitch include distillation residue of crude oil, fluid catalytic cracking residue (decant oil, etc.), bottom oil derived from thermal cracker, ethylene tar obtained during naphtha cracking, and the like.

The mass ratio of the carbonaceous material to the graphite material in the composite carbon material 1b is preferably 1% or more and 10% or less. This mass ratio is more preferably 1.2% or more and 8% or less, further preferably 1.5% or more and 6% or less, and particularly preferably 2% or more and 5% or less. When the mass ratio of the carbonaceous material is 1% or more, the carbonaceous material can sufficiently increase the reaction sites with two or more kinds of alkali metal ions and/or alkaline earth metal ions, and desolvate the ions. Since the sum is easy, high input/output characteristics can be exhibited. On the other hand, when the mass ratio of the carbonaceous material is 20% or less, the diffusion of the ions in the solid between the carbonaceous material and the graphite material can be favorably maintained, so that high input/output characteristics can be exhibited. .. Further, since the charge/discharge efficiency of the ions can be improved, high cycle durability can be exhibited.

(Other components of the negative electrode active material layer)
The negative electrode active material layer in the present invention may optionally contain an optional component such as a conductive filler, a binder, a dispersion stabilizer, etc., in addition to the negative electrode active material.

The type of conductive filler is not particularly limited, but examples thereof include acetylene black, Ketjen black, and vapor grown carbon fiber. The amount of the conductive filler used is preferably 0 parts by mass or more and 30 parts by mass or less, more preferably 0 parts by mass or more and 20 parts by mass or less, and further preferably more than 0 parts by mass with respect to 100 parts by mass of the negative electrode active material. It is 15 parts by mass or less.
The binder is not particularly limited, but for example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, etc. Can be used. The amount of the binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 2 parts by mass or more and 27 parts by mass or less, and further preferably 3 parts by mass or more with respect to 100 parts by mass of the negative electrode active material. It is 25 parts by mass or less. When the amount of the binder is 1% by mass or more, sufficient electrode strength is exhibited. On the other hand, when the amount of the binder is 30 parts by mass or less, the input/output of alkali metal ions and/or alkaline earth metal ions to/from the negative electrode active material is not hindered, and high input/output characteristics are exhibited.
The dispersion stabilizer is not particularly limited, but, for example, PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), cellulose derivative or the like can be used. The amount of the dispersion stabilizer used is preferably 0 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the negative electrode active material. When the amount of the dispersion stabilizer is 10 parts by mass or less, the input/output of alkali metal ions and/or alkaline earth metal ions to/from the negative electrode active material is not hindered, and high input/output characteristics are exhibited.

[Negative electrode current collector]
The material forming the negative electrode current collector in the present invention is preferably a metal foil which has high electron conductivity and does not deteriorate due to elution into an electrolytic solution or reaction with an electrolyte or ions. The metal foil is not particularly limited, and examples thereof include aluminum foil, copper foil, nickel foil, and stainless steel foil. A copper foil is preferred as the negative electrode current collector in the non-aqueous alkali metal ion capacitors of the first and second embodiments.
The metal foil may be a normal metal foil having no irregularities or through holes, or a metal foil having irregularities subjected to embossing, chemical etching, electrolytic deposition, blasting, etc., expanded metal, punching metal. Alternatively, a metal foil having a through hole such as an etching foil may be used.
The thickness of the negative electrode current collector is not particularly limited as long as the shape and strength of the negative electrode can be sufficiently retained, but for example, 1 to 100 μm is preferable.

[Manufacture of negative electrode]
The negative electrode has a negative electrode active material layer on one surface or both surfaces of the negative electrode current collector. In a typical embodiment, the negative electrode active material layer is fixed to the negative electrode current collector.
The negative electrode can be manufactured by a known electrode manufacturing technique for a lithium ion battery, an electric double layer capacitor, or the like. For example, various materials containing a negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and the coating liquid is applied to one surface or both surfaces of a negative electrode current collector. A negative electrode can be obtained by forming a coating film and drying it. Further, the obtained negative electrode may be pressed to adjust the film thickness and bulk density of the negative electrode active material layer. Alternatively, a method of dry-mixing various materials including a negative electrode active material without using a solvent, press-molding the obtained mixture, and then sticking the mixture to a negative electrode current collector using a conductive adhesive is also possible. is there.
The coating liquid is prepared by dry blending a part or all of various material powders containing the negative electrode active material, and then dissolving or dispersing water or an organic solvent, and/or a binder or a dispersion stabilizer into a liquid or A slurry-like substance may be additionally prepared. Further, various material powders containing the negative electrode active material may be added to and prepared in a liquid or slurry substance in which a binder or a dispersion stabilizer is dissolved or dispersed in water or an organic solvent. The preparation of the coating solution is not particularly limited, but a homodisper, a multi-axis disperser, a planetary mixer, a thin film swirl type high speed mixer, or the like can be preferably used. In order to obtain a coating liquid in a good dispersion state, it is preferable to disperse at a peripheral speed of 1 m/s or more and 50 m/s or less. When the peripheral speed is 1 m/s or more, various materials are preferably dissolved or dispersed, which is preferable. Further, if it is 50 m/s or less, various materials are not destroyed by heat and shearing force due to dispersion and re-aggregation does not occur, which is preferable.

The viscosity (ηb) of the coating liquid is preferably 1,000 mPa·s or more and 20,000 mPa·s or less, more preferably 1,500 mPa·s or more and 10,000 mPa·s or less, and further preferably 1,700 mPa·s. The above is 5,000 mPa·s or less. When the viscosity (ηb) is 1,000 mPa·s or more, liquid dripping during the coating film formation is suppressed, and the coating film width and thickness can be well controlled. Further, when it is 20,000 mPa·s or less, pressure loss in the flow path of the coating liquid when using a coating machine is small, stable coating can be performed, and it can be controlled to a desired coating film thickness or less.
The TI value (thixotropy index value) of the coating liquid is preferably 1.1 or more, more preferably 1.2 or more, still more preferably 1.5 or more. When the TI value is 1.1 or more, the coating film width and thickness can be well controlled.
Formation of the coating film is not particularly limited, but a coating machine such as a die coater, a comma coater, a knife coater, or a gravure coating machine can be preferably used. The coating film may be formed by a single layer coating or a multilayer coating. The coating speed is preferably 0.1 m/min or more and 100 m/min or less, more preferably 0.5 m/min or more and 70 m/min or less, and further preferably 1 m/min or more and 50 m/min or less. If the coating speed is 0.1 m/min or more, stable coating can be performed. On the other hand, if it is 100 m/min or less, sufficient coating accuracy can be secured.

The drying of the coating film is not particularly limited, but a drying method such as hot air drying or infrared (IR) drying can be preferably used. Drying of the coating film may be performed at a single temperature or may be performed by changing the temperature in multiple stages. Also, a plurality of drying methods may be combined and dried. The drying temperature is preferably 25°C or higher and 200°C or lower, more preferably 40°C or higher and 180°C or lower, and further preferably 50°C or higher and 160°C or lower. When the drying temperature is 25°C or higher, the solvent in the coating film can be sufficiently volatilized. On the other hand, when the temperature is 200° C. or less, cracking of the coating film due to rapid volatilization of the solvent and uneven distribution of the binder due to migration, and oxidation of the negative electrode current collector and the negative electrode active material layer can be suppressed.
The press of the negative electrode is not particularly limited, but a press machine such as a hydraulic press machine or a vacuum press machine can be preferably used. The film thickness, bulk density, and electrode strength of the negative electrode active material layer can be adjusted by the pressing pressure, the gap, and the surface temperature of the pressing part described later. The pressing pressure is preferably 0.5 kN/cm or more and 20 kN/cm or less, more preferably 1 kN/cm or more and 10 kN/cm or less, and further preferably 2 kN/cm or more and 7 kN/cm or less. If the pressing pressure is 0.5 kN/cm or more, the electrode strength can be sufficiently increased. On the other hand, when it is 20 kN/cm or less, the negative electrode is not bent or wrinkled, and the desired negative electrode active material layer thickness and bulk density can be adjusted. Further, the gap between the press rolls can be set to an arbitrary value according to the thickness of the negative electrode after drying so that the desired thickness and bulk density of the negative electrode active material layer can be obtained. Further, the pressing speed can be set to any speed at which the negative electrode does not bend or wrinkle. The surface temperature of the press part may be room temperature or may be heated if necessary. The lower limit of the surface temperature of the pressed part when heating is preferably the melting point of the binder used minus 60°C or higher, more preferably 45°C or higher, and further preferably 30°C or higher. On the other hand, the upper limit of the surface temperature of the pressed part when heated is preferably the melting point of the binder used plus 50° C. or lower, more preferably 30° C. or lower, and further preferably 20° C. or lower. For example, when PVdF (polyvinylidene fluoride: melting point 150° C.) is used as the binder, it is preferably heated to 90° C. or higher and 200° C. or lower, more preferably 105° C. or higher and 180° C. or lower, still more preferably 120° C. or higher. It is to heat to 170° C. or lower. When a styrene-butadiene copolymer (melting point 100°C) is used as the binder, it is preferably heated to 40°C or higher and 150°C or lower, more preferably 55°C or higher and 130°C or lower, and further preferably 70°C. It is to heat above ℃ and below 120 ℃.

The melting point of the binder can be determined by the endothermic peak position of DSC (Differential Scanning Calorimetry). For example, using a differential scanning calorimeter “DSC7” manufactured by Perkin Elmer Co., Ltd., 10 mg of the sample resin is set in the measuring cell, and the temperature is increased from 30° C. to 250° C. at a heating rate of 10° C./min in a nitrogen gas atmosphere. The temperature rises, and the endothermic peak temperature in the temperature rising process becomes the melting point.
Further, the pressing may be carried out plural times while changing the conditions of the pressing pressure, the gap, the speed, and the surface temperature of the pressing portion.
The thickness of the negative electrode active material layer is preferably 5 μm or more and 100 μm or less per one surface. The lower limit of the thickness of the negative electrode active material layer is more preferably 7 μm or more, further preferably 10 μm or more. The upper limit of the thickness of the negative electrode active material layer is more preferably 80 μm or less, further preferably 60 μm or less. When the thickness is 5 μm or more, streaks and the like do not occur when the negative electrode active material layer is applied, and the coatability is excellent. On the other hand, if this thickness is 100 μm or less, a high energy density can be exhibited by reducing the cell volume. The thickness of the negative electrode active material layer in the case where the current collector has through holes or irregularities refers to the average value of the thickness of one side of the current collector that does not have through holes or irregularities.
The bulk density of the negative electrode active material layer is preferably 0.30 g/cm ³ or more and 1.8 g/cm ³ or less, more preferably 0.40 g/cm ³ or more and 1.5 g/cm ³ or less, and further preferably 0. .45g / cm ³ or more 1.3g / cm ³ or less. When the bulk density is 0.30 g/cm ³ or more, sufficient strength can be maintained and sufficient conductivity between negative electrode active materials can be exhibited. Further, when it is 1.8 g/cm ³ or less, pores capable of sufficiently diffusing ions can be secured in the negative electrode active material layer.

The BET specific surface area, the amount of mesopores, and the amount of micropores in the present invention are values obtained by the following methods. The sample is vacuum dried at 200° C. for a whole day and night, and adsorption and desorption isotherms are measured using nitrogen as an adsorbate. Using the adsorption-side isotherm obtained here, the BET specific surface area is calculated by the BET multipoint method or the BET one-point method, the mesopore amount is calculated by the BJH method, and the micropore amount is calculated by the MP method.
The BJH method is a calculation method generally used for mesopore analysis, and is proposed by Barrett, Joyner, Halenda et al. (Non-patent Document 1).
Further, the MP method means a method of obtaining a micropore volume, a micropore area, and a distribution of micropores by utilizing the “t-plot method” (Non-Patent Document 2). This is a method devised by Mikhail, Brunauer, Bodor (Non-Patent Document 3).

<Separator>
The positive electrode precursor and the negative electrode are laminated or wound via a separator to form an electrode laminate having the positive electrode precursor, the negative electrode and the separator.
As the separator, a microporous film made of polyethylene or a microporous film made of polypropylene used in a lithium ion secondary battery, or a cellulose non-woven paper used in an electric double layer capacitor can be used. A film made of organic or inorganic fine particles may be laminated on one surface or both surfaces of these separators. Further, organic or inorganic fine particles may be contained inside the separator.
The thickness of the separator is preferably 5 μm or more and 35 μm or less. The thickness of 5 μm or more is preferable because self-discharge due to an internal micro short circuit tends to be small. On the other hand, a thickness of 35 μm or less is preferable because the output characteristics of the electricity storage device tend to be improved.
The film made of organic or inorganic fine particles preferably has a thickness of 1 μm or more and 10 μm or less. The thickness of 1 μm or more is preferable because self-discharge due to an internal micro short circuit tends to be small. On the other hand, a thickness of 10 μm or less is preferable because the output characteristics of the electricity storage device tend to be improved.

<Exterior body>
As the outer package, a metal can, a laminated film, or the like can be used.
The metal can is preferably made of aluminum.
The laminate film is preferably a film obtained by laminating a metal foil and a resin film, and is exemplified by a three-layered film composed of outer layer resin film/metal foil/interior resin film. The outer layer resin film is for preventing the metal foil from being damaged by contact or the like, and a resin such as nylon or polyester can be preferably used. The metal foil is for preventing the permeation of moisture and gas, and foils of copper, aluminum, stainless steel and the like can be preferably used. The interior resin film is for protecting the metal foil from the electrolytic solution contained therein and for melting and sealing at the time of heat-sealing the exterior body, and polyolefin, acid-modified polyolefin or the like can be preferably used.

[Electrolyte]
The electrolytic solution in the first and second embodiments is a non-aqueous electrolytic solution. That is, this electrolytic solution contains a non-aqueous solvent described later. In the first embodiment, the non-aqueous electrolyte solution preferably contains 0.5 mol/L or more of an alkali metal salt and/or an alkaline earth metal salt based on the total amount of the non-aqueous electrolyte solution. In the second embodiment, the non-aqueous electrolyte solution contains at least one alkali metal ion and at least one alkaline earth metal ion as electrolytes.
In the first embodiment of the present invention, it is preferable that two or more different alkali metal ions are contained in the electrolytic solution of the non-aqueous alkali metal ion capacitor, and two or more and four or less alkali metal ions are contained. More preferably, it is included. During charging/discharging of the non-aqueous alkali metal ion capacitor, an alkali metal ion insertion/desorption reaction proceeds on the surface of the positive electrode activated carbon. At this time, when two or more kinds of alkali metal ions having different ionic radii exist in the electrolytic solution, the alkali metal ions having a large ionic radius expand the pores of the activated carbon, so that the alkali metal ions having a small ionic radius can be efficiently used. The insertion/elimination reaction can be carried out effectively, and the high output characteristics are improved.

From the above viewpoint, the material ratio of the first alkali metal ions in the non-aqueous electrolyte is 1% or more and 99% or less, and the material ratio of the second alkali metal ions is 1% or more and 99% or less, The substance amount ratio of the third and fourth alkali metal ions is preferably 0% or more and 98% or less. More preferably, the substance ratio of the first alkali metal ion in the non-aqueous electrolyte is 3% or more and 97% or less, and the substance ratio of the second alkali metal ion is 3% or more and 97% or less, The substance ratio of the third and fourth alkali metal ions is 0% or more and 94% or less. More preferably, the substance ratio of the first alkali metal ion in the non-aqueous electrolyte is 5% or more and 95% or less, and the substance ratio of the second alkali metal ion is 5% or more and 95% or less, The substance ratio of the third and fourth alkali metal ions is 0% or more and 90% or less. Even more preferably, the substance amount ratio of the third and fourth alkali metal ions is 1% or more and 90% or less, or 5% or more and 90% or less.
The alkali metal ions present in the electrolytic solution may be two or more kinds, and may contain three or more kinds of alkali metal ions. It is preferable that each alkali metal ion is contained in an amount of 1% or more as a substance amount, because ions involved in expanding the pores of the activated carbon and in charge and discharge can work respectively.

The method of incorporating different alkali metal ions in the electrolytic solution is not particularly limited, and two or more kinds of alkaline metal salts can be dissolved in the electrolytic solution, or two or more kinds of alkaline metal compounds can be added to the positive electrode or the negative electrode. A substance having different cations can be used as the alkali metal salt contained in the electrolytic solution and the alkali metal compound dissolved in the positive electrode or the negative electrode to be redox decomposed. In particular, the method of adding a plurality of alkali metal compounds (Compound 1 to Compound 4) to the positive electrode precursor and performing redox decomposition is particularly preferable because a plurality of alkali metal ions can be contained in the electrolytic solution.
The non-aqueous electrolyte solution in the first and second embodiments is, for example, (MN(SO ₂ F) ₂ ), MN(SO ₂ CF ₃ ) ₂ , MN(SO ₂ C ₂ F ₅ ) as an alkali metal salt. ₂ , MN(SO ₂ CF ₃ )(SO ₂ C ₂ F ₅ ), MN(SO ₂ CF ₃ )(SO ₂ C ₂ F ₄ H), MC(SO ₂ F) ₃ , MC(SO ₂ CF ₃ ). ₃ , MC(SO ₂ C ₂ F ₅ ) ₃ , MCF ₃ SO ₃ , MC ₄ F ₉ SO ₃ , MPF ₆ , MBF _4, etc. (M is an alkali selected from Li, Na, K, Rb and Cs, respectively. A metal) may be used alone or in combination of two or more. It is preferable to contain MPF ₆ and/or MN(SO ₂ F) ₂ since high conductivity can be expressed.

Regarding charge/discharge of the non-aqueous alkali metal ion capacitor according to the second embodiment of the present invention, in the positive electrode, the capacity is expressed by the electric double layer formed at the interface of the positive electrode active material. Therefore, the capacity per unit weight of the positive electrode active material is increased by using an element having a large valence of ions. On the other hand, when the valence of ions is large, more solvation radius is attracted to attract more solvent molecules in the non-aqueous electrolyte, and the resistance increases. In view of the above reason, coexistence of an alkali metal ion, which is a monovalent cation, and an alkaline earth metal ion, which is a divalent cation, in a non-aqueous electrolytic solution reduces the resistance of the alkali metal ion, The metal-metal ions contribute to the increase in capacity, and the non-aqueous alkali metal ion capacitor can have high capacity and high output.

The electrolytic solution in the second embodiment of the present invention is a non-aqueous electrolytic solution containing alkali metal ions and alkaline earth metal ions. The non-aqueous electrolyte solution contains a non-aqueous solvent described later. The non-aqueous electrolytic solution preferably contains 0.5 mol/L or more of an alkali metal salt and/or an alkaline earth metal salt based on the total volume of the non-aqueous electrolytic solution.

The non-aqueous electrolyte solution according to the second embodiment of the present invention includes, for example, MN(SO ₂ F) ₂ , MN(SO ₂ CF ₃ ) ₂ , MN(SO ₂ C ₂ F ₅ ) ₂ , as an alkali metal salt. _{MN (SO 2 CF 3) (} SO 2 C 2 F 5), MN (SO 2 CF 3) (SO 2 C 2 F 4 H), MC (SO 2 F) 3, MC (SO 2 CF 3) 3, MC(SO ₂ C ₂ F ₅ ) ₃ , MCF ₃ SO ₃ , MC ₄ F ₉ SO ₃ , MPF ₆ , MBF _4, etc. (in all the formulas, M is independently Li, Na, K, Rb and Cs Alkali metal selected from the group consisting of) can be used alone or in combination of two or more kinds. The non-aqueous electrolyte solution preferably contains MPF ₆ and/or MN(SO ₂ F) ₂ because high conductivity can be exhibited.

The non-aqueous electrolyte solution according to the second embodiment of the present invention is, for example, M[N(SO ₂ F) ₂ ] ₂ , M[N(SO ₂ CF ₃ ) ₂ ] ₂ , M as an alkaline earth metal salt. [N(SO ₂ C ₂ F ₅ ) ₂ ] ₂ , M[N(SO ₂ CF ₃ )(SO ₂ C ₂ F ₅ )] ₂ , M[N(SO ₂ CF ₃ )(SO ₂ C ₂ F ₄ H)] ₂ , M[C(SO ₂ F) ₃ ] ₂ , M[C(SO ₂ CF ₃ ) ₃ ] ₂ , M[C(SO ₂ C ₂ F ₅ ) ₃ ] ₂ , M(CF ₃ SO _{3) 2, M (C 4} F 9 SO 3) 2, M (PF 6) 2, M (BF 4) in _two equal (all the formula, M, Be independently, Mg, Ca, Sr and Ba Alkaline earth metal selected from the group consisting of) can be used alone or in combination of two or more. The non-aqueous electrolyte solution preferably contains M(PF ₆ ) ₂ and/or M[N(SO ₂ F) ₂ ] ₂ because high conductivity can be exhibited.

When the positive electrode precursor contains an alkali metal compound, it is also possible to use the alkaline earth metal salt alone in the preparation of the non-aqueous electrolyte solution, when the positive electrode precursor contains an alkaline earth metal compound Alternatively, the alkali metal salt may be used alone when preparing the non-aqueous electrolyte solution. By doing so, one or more kinds of alkali metal ions and alkaline earth metal ions can be present in the non-aqueous electrolyte solution after pre-doping.
Even if one or both of the alkali metal compound and the alkaline earth metal compound may be used during preparation of the non-aqueous electrolyte solution or preparation of the positive electrode precursor, it is said that both low resistance and high capacity of the electricity storage element are achieved. From the viewpoint, in the non-aqueous electrolyte solution after pre-doping, as an alkali metal ion, at least one selected from the group consisting of lithium ion, sodium ion and potassium ion is contained, and/or as an alkaline earth metal ion, It is preferable that calcium ions are included.

When the molar concentration of alkali metal ions in the non-aqueous electrolyte is X (mol/L) and the molar concentration of alkaline earth metal ions is Y (mol/L), X/(X+Y) is 0.07. It is preferably not less than 0.92 and not more than 0.92. When X/(X+Y) is 0.07 or more, the electric storage device can have a low resistance because a sufficient amount of alkali metal ions are present in the non-aqueous electrolyte solution. When X/(X+Y) is 0.92 or less, the storage element can have a high capacity because a sufficient amount of alkaline earth metal ions are present in the non-aqueous electrolyte solution. X/(X+Y) is more preferably 0.09 or more and less than 0.93, and further preferably 0.10 or more and 0.90 or less.

The concentration of the alkali metal salt and/or the alkaline earth metal salt in the non-aqueous electrolyte solution is preferably 0.5 mol/L or more, and more preferably 0.5 to 2.0 mol/L. preferable. When a mixed salt of an alkali metal salt and an alkaline earth metal salt is used, the total value is preferably within the range of 0.5 to 2.0 mol/L. When the concentration of the alkali metal salt and/or the alkaline earth metal salt is 0.5 mol/L or more, the anions are sufficiently present, so that the capacity of the electricity storage device can be sufficiently increased. When the concentration of the alkali metal salt and/or the alkaline earth metal salt is 2.0 mol/L or less, the undissolved alkali metal salt and/or the alkaline earth metal salt should be deposited in the non-aqueous electrolyte solution. , And the viscosity of the electrolytic solution can be prevented from becoming too high, the conductivity is not lowered, and the output characteristics are not lowered, which is preferable.

The non-aqueous electrolytic solution preferably contains a cyclic carbonate and a chain carbonate as the non-aqueous solvent. The inclusion of the cyclic carbonate and the chain carbonate in the non-aqueous electrolytic solution is advantageous in that it dissolves an alkali metal salt at a desired concentration and that it exhibits high alkali metal ion conductivity. Examples of the cyclic carbonate include alkylene carbonate compounds represented by ethylene carbonate, propylene carbonate, butylene carbonate and the like. The alkylene carbonate compound is typically unsubstituted. Examples of chain carbonates include dialkyl carbonate compounds represented by dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, dipropyl carbonate, dibutyl carbonate and the like. The dialkyl carbonate compound is typically unsubstituted.
The lower limit of the total content of the cyclic carbonate and the chain carbonate is preferably 50 mass% or more, more preferably 65 mass% or more, based on the total amount of the non-aqueous electrolyte solution. The upper limit of this total content is preferably 95 mass% or less, more preferably 90 mass% or less, based on the total amount of the non-aqueous electrolyte solution. When the total content is 50% by mass or more, it is possible to dissolve a desired concentration of the alkali metal salt and/or the alkaline earth metal salt, and it is possible to exhibit high ionic conductivity. When the total concentration is 95% by mass or less, the electrolytic solution can further contain the additive described below.

The non-aqueous electrolyte solution may further contain an additive. The additive is not particularly limited, but for example, a sultone compound, a cyclic phosphazene, an acyclic fluorine-containing ether, a fluorine-containing cyclic carbonate, a cyclic carbonic acid ester, a cyclic carboxylic acid ester, and a cyclic acid anhydride may be used alone. It is possible, and two or more kinds may be mixed and used.
From the viewpoint of less adverse effect on resistance, and from the viewpoint of suppressing decomposition of the non-aqueous electrolyte solution at high temperature to suppress gas generation, the saturated cyclic sultone compound is 1,3-propane sultone or 2,4-butane sultone. , 1,4-butane sultone, 1,3-butane sultone or 2,4-pentane sultone is preferable, the unsaturated cyclic sultone compound is preferably 1,3-propene sultone or 1,4-butene sultone, and other sultone compound is Is methylenebis(benzenesulfonic acid), methylenebis(phenylmethanesulfonic acid), methylenebis(ethanesulfonic acid), methylenebis(2,4,6,trimethylbenzenesulfonic acid), and methylenebis(2-trifluoromethylbenzenesulfonic acid). And at least one selected from these is preferably selected.

The total content of the sultone compound in the non-aqueous electrolytic solution of the non-aqueous alkaline metal ion capacitor is preferably 0.1% by mass to 15% by mass based on the total amount of the non-aqueous electrolytic solution. When the total content of the sultone compound in the non-aqueous electrolyte solution is 0.1% by mass or more, it is possible to suppress decomposition of the electrolyte solution at high temperature and suppress gas generation. On the other hand, when the total content is 15% by mass or less, it is possible to suppress a decrease in the ionic conductivity of the electrolytic solution and maintain high input/output characteristics. Further, the content of the sultone compound present in the non-aqueous electrolyte of the non-aqueous alkali metal ion capacitor is preferably 0.5% by mass or more and 10% by mass or less from the viewpoint of achieving both high input/output characteristics and durability. , And more preferably 1 mass% or more and 5 mass% or less.
Examples of the cyclic phosphazene include ethoxypentafluorocyclotriphosphazene, diethoxytetrafluorocyclotriphosphazene, and phenoxypentafluorocyclotriphosphazene. One or more selected from these are preferable.

The content of cyclic phosphazene in the non-aqueous electrolytic solution is preferably 0.5% by mass to 20% by mass based on the total amount of the non-aqueous electrolytic solution. When this value is 0.5% by mass or more, it is possible to suppress decomposition of the electrolytic solution at high temperature and suppress gas generation. On the other hand, when this value is 20% by mass or less, it is possible to suppress a decrease in the ionic conductivity of the electrolytic solution and maintain high input/output characteristics. For the above reasons, the content of cyclic phosphazene is preferably 2% by mass or more and 15% by mass or less, and more preferably 4% by mass or more and 12% by mass or less.
Incidentally, these cyclic phosphazenes may be used alone or in combination of two or more kinds.
Examples of the acyclic fluorine-containing ether include HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H, CF ₃ CFHCF ₂ OCH ₂ CF ₂ CF ₂ H, HCF ₂ CF ₂ CH ₂ OCH ₂ CF ₂ CF ₂ H, CF ₃ CFHCF. ₂ OCH ₂ CF ₂ CFHCF _{3 and the} like are mentioned, and among them, HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H is preferable from the viewpoint of electrochemical stability.

The content of the non-cyclic fluorinated ether is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the non-cyclic fluorinated ether is 0.5% by mass or more, the stability of the non-aqueous electrolyte solution against oxidative decomposition is enhanced, and the electricity storage device having high durability at high temperature can be obtained. On the other hand, when the content of the non-cyclic fluorinated ether is 15% by mass or less, the solubility of the electrolyte salt can be favorably maintained, and the ionic conductivity of the non-aqueous electrolyte solution can be kept high, and therefore, the high degree of It becomes possible to express the input/output characteristics.
The acyclic fluorine-containing ethers may be used alone or in combination of two or more.

The fluorinated cyclic carbonate is preferably selected from fluoroethylene carbonate (FEC) and difluoroethylene carbonate (dFEC) from the viewpoint of compatibility with other non-aqueous solvents.
The content of the cyclic carbonate containing a fluorine atom is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. . When the content of the cyclic carbonate containing a fluorine atom is 0.5% by mass or more, a high-quality coating can be formed on the negative electrode, and the reductive decomposition of the electrolytic solution on the negative electrode can be suppressed, so that high temperature An electricity storage device having high durability can be obtained. On the other hand, when the content of the cyclic carbonate containing a fluorine atom is 10% by mass or less, the solubility of the electrolyte salt can be favorably maintained, and the ionic conductivity of the non-aqueous electrolytic solution can be maintained high, and It becomes possible to express a high degree of input/output characteristics.
The above-mentioned cyclic carbonate containing a fluorine atom may be used alone or in combination of two or more kinds.

For cyclic carbonates, vinylene carbonate is preferred.
The content of the cyclic carbonic acid ester is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the cyclic carbonic acid ester is 0.5% by mass or more, a high-quality coating film can be formed on the negative electrode, and the reductive decomposition of the electrolytic solution on the negative electrode can be suppressed to improve the durability at high temperature. A high power storage device can be obtained. On the other hand, when the content of the cyclic carbonic acid ester is 10% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolytic solution can be kept high, so that high input/output characteristics can be obtained. Can be expressed.
Examples of the cyclic carboxylic acid ester include gamma butyrolactone, gamma valerolactone, gamma caprolactone, and epsilon caprolactone, and it is preferable to use one or more selected from these. Among them, gamma-butyrolactone is particularly preferable from the viewpoint of improving the battery characteristics resulting from the improvement in the degree of alkali metal ion dissociation.
The content of the cyclic carboxylic acid ester is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the cyclic acid anhydride is 0.5% by mass or more, it is possible to form a good quality coating film on the negative electrode, and suppress the reductive decomposition of the electrolytic solution on the negative electrode to improve the durability at high temperature. An electric storage device having high efficiency can be obtained. On the other hand, when the content of the cyclic carboxylic acid ester is 5% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte solution can be kept high, so that high input/output can be achieved. It becomes possible to express the characteristics.
The cyclic carboxylic acid esters may be used alone or in combination of two or more.

The cyclic acid anhydride is preferably one or more selected from succinic anhydride, maleic anhydride, citraconic anhydride, and itaconic anhydride. Among them, it is preferable to select from succinic anhydride and maleic anhydride, because the production cost of the electrolytic solution can be suppressed by industrial availability, and the electrolytic solution can be easily dissolved in the non-aqueous electrolytic solution.
The content of the cyclic acid anhydride is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the cyclic acid anhydride is 0.5% by mass or more, a good quality coating can be formed on the negative electrode, and the reductive decomposition of the electrolytic solution on the negative electrode can be suppressed to improve the durability at high temperature. A high power storage device can be obtained. On the other hand, when the content of the cyclic acid anhydride is 10% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte solution can be kept high, so that high input/output can be achieved. It becomes possible to express the characteristics.
The cyclic acid anhydrides may be used alone or in combination of two or more.

[Assembly process]
The electrode laminated body obtained in the assembling step is one in which the positive electrode terminal and the negative electrode terminal are connected to the laminated body formed by laminating the positive electrode precursor and the negative electrode, which are cut into a sheet shape, via the separator. Further, the electrode winding body is obtained by connecting a positive electrode terminal and a negative electrode terminal to a winding body formed by winding a positive electrode precursor and a negative electrode via a separator. The shape of the electrode winding body may be cylindrical or flat.
The method of connecting the positive electrode terminal and the negative electrode terminal is not particularly limited, but a method such as resistance welding or ultrasonic welding can be used.
It is preferable to remove the residual solvent by drying the electrode laminate or the electrode wound body to which the terminals are connected. Although the drying method is not limited, it is dried by vacuum drying or the like. The residual solvent is preferably 1.5% or less based on the weight of the positive electrode active material layer or the negative electrode active material layer. If the residual solvent content is more than 1.5%, the solvent remains in the system and deteriorates the self-discharge characteristics, which is not preferable.
The dried electrode laminated body or the electrode wound body is preferably housed in an outer body typified by a metal can or a laminated film in a dry environment having a dew point of −40° C. or lower, leaving only one opening. It is preferable to seal in the closed state. When the dew point is higher than −40° C., water adheres to the electrode laminated body or the electrode wound body, water remains in the system, and self-discharge characteristics are deteriorated, which is not preferable. The method of sealing the outer package is not particularly limited, but a method such as heat sealing or impulse sealing can be used.

[Filling, impregnation, sealing process]
After the assembly process is completed, the non-aqueous electrolyte solution is poured into the electrode laminate housed in the exterior body. It is desirable to further perform impregnation after the completion of the liquid injection step and sufficiently immerse the positive electrode, the negative electrode, and the separator in the non-aqueous electrolyte solution. In a state where the electrolytic solution is not immersed in at least a part of the positive electrode, the negative electrode, and the separator, in the alkali metal dope step described below, the doping proceeds nonuniformly, so that the resistance of the resulting non-aqueous alkali metal ion capacitor increases. Or the durability is reduced. The method of impregnation is not particularly limited, but for example, a non-aqueous alkali metal ion capacitor after liquid injection is placed in a decompression chamber with the exterior body opened, and the chamber is decompressed using a vacuum pump. Then, the method of returning to atmospheric pressure again can be used. After the impregnation step is completed, the non-aqueous alkali metal ion capacitor with the exterior body opened is sealed while being depressurized.

[Alkali metal doping process]
In the alkali metal doping step, as a preferable step, by applying a voltage between the positive electrode precursor and the negative electrode to decompose the alkali metal compound and/or the alkaline earth metal compound, the alkali in the positive electrode precursor A negative electrode active material by decomposing a metal compound and/or an alkaline earth metal compound to release an alkali metal ion and/or an alkaline earth metal ion, and reducing the alkali metal ion and/or the alkaline earth metal ion at the negative electrode The layer is pre-doped with alkali metal ions and/or alkaline earth metal ions. This method is preferable because the negative electrode can be pre-doped with the alkali metal and/or alkaline earth metal without using, for example, metal sodium or metal potassium that ignites in the air.
In this alkali metal doping step, a gas such as CO ₂ is generated along with the oxidative decomposition of the alkali metal compound and/or the alkaline earth metal compound in the positive electrode precursor. Therefore, when applying the voltage, it is preferable to provide a means for discharging the generated gas to the outside of the exterior body. As this means, for example, a method of applying a voltage in a state where a part of the exterior body is opened; a state in which an appropriate gas releasing means such as a gas vent valve and a gas permeable film is previously installed in a part of the exterior body Method of applying voltage with;
Etc. can be mentioned.

[Aging process]
It is preferable to age the non-aqueous alkali metal ion capacitor after the completion of the alkali metal doping step. In the aging step, the solvent in the electrolytic solution decomposes at the positive electrode and the negative electrode, and a solid polymer film permeable to alkali metal ions and/or alkaline earth metal ions is formed on the surfaces of the positive electrode and the negative electrode.
The aging method is not particularly limited, but, for example, a method of reacting the solvent in the electrolytic solution in a high temperature environment can be used.

[Degassing process]
After completion of the aging step, it is preferable to further perform degassing to surely remove the gas remaining in the electrolytic solution, the positive electrode, and the negative electrode. When gas remains in at least a part of the electrolytic solution, the positive electrode, and the negative electrode, ionic conduction is hindered, so that the resistance of the obtained non-aqueous alkali metal ion capacitor increases.
The method of degassing is not particularly limited, but for example, a method of installing a non-aqueous alkali metal ion capacitor in a decompression chamber in a state where the exterior body is opened, and decompressing the chamber using a vacuum pump, etc. Can be used.

[Characteristic evaluation of power storage element]
(Capacitance)
As used herein, the capacitance F(F) is a value obtained by the following method:
First, the cell corresponding to the non-aqueous alkali metal ion capacitor is charged with constant current in a constant temperature bath set at 25°C until the current value of 2C reaches 3.8V, and then a constant voltage of 3.8V is applied. The applied constant voltage charging is performed for a total of 30 minutes. Then, the capacity when constant current discharge is performed at a current value of 2 C up to 2.2 V is defined as Q(C). A value calculated by the capacitance F=Q/ΔV _x =Q/(3.8-2.2) using the Q and the voltage change ΔV _x (V) obtained here.
Here, the C rate of the current is referred to as 1C when the constant current discharge from the upper limit voltage to the lower limit voltage is performed, and the current value at which the discharge is completed in 1 hour. In this specification, the current value at which discharge is completed in 1 hour when performing constant current discharge from the upper limit voltage of 3.8 V to the lower limit voltage of 2.2 V is defined as 1C.

(Internal resistance)
In this specification, the internal resistance Ra (Ω) is a value obtained by the following method, respectively:
First, a non-aqueous alkali metal ion capacitor is charged at a constant current in a constant temperature bath set at 25° C. until a current value of 20 C reaches 3.8 V, and then a constant voltage charge at which a constant voltage of 3.8 V is applied. For a total of 30 minutes. Subsequently, the sampling interval is set to 0.1 second, and constant current discharge is performed at a current value of 20 C up to 2.2 V to obtain a discharge curve (time-voltage). In this discharge curve, when the voltage at the discharge time=0 seconds obtained by extrapolating by linear approximation from the voltage values at the discharge time of 2 seconds and 4 seconds is Vo, the drop voltage ΔV=3.8− It is a value calculated from Vo as Ra=ΔV/(current value of 20 C).

(Amount of gas generated after high temperature storage test)
As used herein, the amount of gas generated during a high temperature storage test is measured by the following method:
First, the cell corresponding to the non-aqueous alkali metal ion capacitor is charged with a constant current in a constant temperature bath set at 25° C. until it reaches 4.0 V at a current value of 100 C, and then a constant voltage of 4.0 V is applied. The constant voltage charging is performed for 10 minutes. After that, the cell is stored in a 60° C. environment, taken out of the 60° C. environment every two weeks, charged to a cell voltage of 4.0 V in the above-mentioned charging step, and then stored again in the 60° C. environment. . This process is repeated and the cell volume Va before the start of storage and the cell volume Vb after 2 months of the storage test are measured by the Archimedes method. The solvent used for volume measurement by the Archimedes method is not particularly limited, but it is preferable to use a solvent having an electric conductivity of 10 μS/cm or less and which does not cause electrolysis when the non-aqueous alkali metal ion capacitor is immersed. For example, pure water and fluorine-based inert liquid are preferably used. In particular, from the viewpoint of having a high specific gravity and an excellent electric insulating property, a fluorine-based inert liquid such as Fluorinert (registered trademark, 3M Japan Co., Ltd.) FC-40, FC-43 is preferably used. The amount of gas generated when Vb-Va is stored for 2 months at a cell voltage of 4.0 V and an environmental temperature of 60°C.

The resistance value obtained by using the same measurement method as the room temperature internal resistance for the cell after the high temperature storage test is defined as the internal resistance after the high temperature storage test.
Regarding the condition (a), Rb/Ra is 3.0 or less from the viewpoint of exhibiting sufficient charge capacity and discharge capacity for a large current when exposed to a high temperature environment for a long time. It is preferably 1.5 or less, more preferably 1.2 or less. When Rc/Ra is not more than the above upper limit value, excellent output characteristics can be stably obtained for a long period of time, which leads to a longer device life.
Regarding the condition (b), the value B obtained by normalizing the amount of gas generated when stored for 2 months at a cell voltage of 4.0 V and an environmental temperature of 60° C. with the capacitance Fa is such that the characteristics of the element deteriorate due to the generated gas. From the viewpoint of not allowing it, the value measured at 25° C. is preferably 30×10 ⁻³ cc/F or less, more preferably 15×10 ⁻³ cc/F or less, and further preferably 5×10 3. ^-3 cc/F or less. If the amount of gas generated under the above conditions is less than or equal to the above upper limit value, there is no risk of the cells expanding due to gas generation even when the device is exposed to high temperature for a long period of time. Therefore, a power storage element having sufficient safety and durability can be obtained.

(High load charge/discharge cycle test)
As used herein, the capacity retention rate after a high load charge/discharge cycle test is measured by the following method:
First, a cell corresponding to a non-aqueous alkali metal ion capacitor is charged with a constant current in a constant temperature bath set at 25° C. until a current value of 200 C reaches 3.8 V, and then a current value of 200 C is 2.2 V. Constant current discharge is performed until the temperature reaches. The charging/discharging process is repeated 60,000 times, and after reaching a voltage of 4.5 V at a current value of 20 C, the battery is charged at a constant voltage for 1 hour. After that, Fb is obtained by measuring the capacitance by the method described above, and compared with the capacitance Fa before the start of the test to obtain the capacity retention ratio after the high load charge/discharge cycle test before the start of the test. Be done. At this time, if Fb/Fa is 1.01 or more, for example, even a power storage element that has been charged and discharged for a long period of time can extract sufficient energy, and thus the replacement cycle of the power storage element can be extended, which is preferable. ..

<Method of identifying alkali metal compound in electrode>
The method for identifying the alkali metal compound contained in the positive electrode is not particularly limited, but it can be identified by, for example, the following method. In order to identify the alkali metal compound and/or the alkaline earth metal compound, it is preferable to identify them by combining a plurality of analysis methods described below.
When measuring SEM-EDX, Raman, and XPS described below, disassemble the non-aqueous alkali metal ion capacitor in an argon box to take out the positive electrode, and wash the electrolyte adhering to the positive electrode surface before performing the measurement. Is preferred. As for the method of cleaning the positive electrode, it suffices to wash away the electrolyte attached to the surface of the positive electrode. Therefore, a carbonate solvent such as dimethyl carbonate, ethylmethyl carbonate, or diethyl carbonate can be preferably used. As a cleaning method, for example, the positive electrode is immersed in a diethyl carbonate solvent of 50 to 100 times the weight of the positive electrode for 10 minutes or more, and then the solvent is replaced and the positive electrode is immersed again. After that, the positive electrode is taken out from the diethyl carbonate and vacuum-dried (temperature: 0 to 200° C., pressure: 0 to 20 kPa, time: 1 to 40 hours, so that the remaining amount of diethyl carbonate in the positive electrode is 1% by mass or less). The residual amount of diethyl carbonate can be quantified on the basis of a calibration curve prepared in advance by measuring the GC/MS of water after washing with distilled water and adjusting the liquid amount described below.), and then performing the SEM. -Perform EDX, Raman, XPS analysis.

Regarding ion chromatography described below, anions can be identified by analyzing water after washing the positive electrode with distilled water.
Moreover, the element of an alkali metal and/or an alkaline earth metal can be identified by using ICP issue spectroscopy, ICP-OES, ICP-MS, or the like.
When the alkali metal compound and/or the alkaline earth metal compound cannot be identified by the analysis method, other analysis methods include ⁷ Li-solid state NMR, XRD (X-ray diffraction), TOF-SIMS (time-of-flight type Secondary ion mass spectrometry), AES (Auger electron spectroscopy), TPD/MS (heat generated gas mass spectrometry), DSC (differential scanning calorimetry) and the like are used to identify an alkali metal compound and/or an alkaline earth metal. You can also

[Scanning electron microscope-energy dispersive X-ray analysis (SEM-EDX)]
The oxygen-containing alkali metal compound and/or alkaline earth metal compound, and the positive electrode active material can be identified by oxygen mapping by a SEM-EDX image of the positive electrode surface measured at an observation magnification of 1000 to 4000 times. As an example of the SEM-EDX image measurement, the acceleration voltage is 10 kV, the emission current is 1 μA, the number of measurement pixels is 256×256 pixels, and the number of times of integration is 50. In order to prevent the sample from being charged, gold, platinum, osmium or the like can be surface-treated by a method such as vacuum deposition or sputtering. Regarding the measuring method of the SEM-EDX image, it is possible to adjust the brightness and contrast so that there is no pixel that reaches the maximum brightness value in the mapping image and the average value of the brightness values falls within the range of the maximum brightness value of 40% to 60%. preferable. In the obtained oxygen mapping, particles containing 50% or more in area of a bright portion binarized on the basis of the average value of luminance values are used as an alkali metal compound and/or an alkaline earth metal compound.

[Micro Raman spectroscopy]
The alkali metal compound and/or alkaline earth metal compound composed of carbonate ions and the positive electrode active material can be identified by Raman imaging of the positive electrode surface measured at an observation magnification of 1000 to 4000 times. As an example of the measurement conditions, the excitation light is 532 nm, the excitation light intensity is 1%, the long operation of the objective lens is 50 times, the diffraction grating is 1800 gr/mm, the mapping method is point scanning (slit 65 mm, binning 5 pix), 1 mm step, The exposure time per point can be 3 seconds, the number of times of integration can be 1, and the measurement can be performed with a noise filter. Regarding the measured Raman spectrum, a linear baseline is set in the range of 1071 to 1104 cm ⁻¹ , the area is calculated by using a positive value from the baseline as the peak of carbonate ion, and the frequency is integrated. The frequency for the carbonate ion peak area approximated by the Gaussian function is subtracted from the frequency distribution of the carbonate ion.

[X-ray Photoelectric Spectroscopy (XPS)]
By analyzing the electronic state of the alkali metal and/or the alkaline earth metal by XPS, the binding state of the alkali metal and/or the alkaline earth metal can be determined. As an example of the measurement conditions, the X-ray source is monochromatic AlKα, the X-ray beam diameter is 100 μmφ (25 W, 15 kV), the pass energy is narrow scan: 58.70 eV, charge neutralization is performed, and the number of sweeps is narrow scan: 10 times. (Carbon, oxygen) 20 times (fluorine) 30 times (phosphorus) 40 times (alkali metal) 50 times (silicon), energy step can be measured under the condition of narrow scan: 0.25 eV. It is preferable to clean the surface of the positive electrode by sputtering before measuring XPS. As the sputtering conditions, for example, the surface of the positive electrode can be cleaned under the conditions of an acceleration voltage of 1.0 kV and a range of 2 mm×2 mm for 1 minute (1.25 nm/min in terms of SiO ₂ ). In the obtained XPS spectrum, the peak of C1s binding energy of 285 eV is C—C bond, the peak of 286 eV is C—O bond, the peak of 288 eV is COO, the peak of 290 to 292 eV is CO ₃ ²⁻ , and the C—F bond. , O1s having a binding energy of 527 to 530 eV is O ²⁻ , 531 to 532 eV is CO, CO ₃ , OH, PO _x (x is an integer of 1 to 4), SiO _x (x is an integer of 1 to 4). ), the peak at 533 eV is C—O, SiO _x (x is an integer of 1 to 4), the peak at binding energy of F1s is 685 eV is F ⁻ , the peak at 687 eV is C—F bond, M _x PO _y F _z (M Is an alkali metal selected from Li, Na, K, Rb, and Cs, x, y, and z are integers of 1 to 6), and PF ₆ ⁻ and P2p have binding energies of 133 eV at PO _x (x is 1 to ₆ ). 4), a peak of 134 to 136 eV is PF _x (x is an integer of 1 to 6), a peak of Si2p with a binding energy of 99 eV is Si, and a peak of silicide is 101 to 107 eV is Si _x O _y (x and y are: Arbitrary integer). When peaks overlap in the obtained spectrum, it is preferable to assign a spectrum by assuming a Gaussian function or a Lorentz function and separating the peaks. The existing alkali metal compound and/or alkaline earth metal compound can be identified from the measurement result of the electronic state and the result of the existing element ratio obtained above.

[Ion chromatography]
The anion species eluted in water can be identified by analyzing the distilled water washing liquid of the positive electrode by ion chromatography (IC). As a column to be used, an ion exchange type, an ion exclusion type, or a reverse phase ion pair type can be used. As the detector, an electrical conductivity detector, an ultraviolet-visible absorptiometry detector, an electrochemical detector, etc. can be used.A suppressor system in which a suppressor is installed in front of the detector, or an electric detector without a suppressor is used. A non-suppressor system that uses a solution having low conductivity as an eluent can be used. Further, since the measurement can be performed by combining with a mass spectrometer or a charged particle device, it is suitable based on the alkali metal compound and/or the alkaline earth metal compound identified from the analysis results of SEM-EDX, Raman, and XPS. It is preferable to combine a column and a detector.
The retention time of the sample is constant for each ion species component if conditions such as the column to be used and the eluent are determined, and the magnitude of the peak response is different for each ion species but is proportional to the concentration. It is possible to qualitatively and quantitatively determine the ionic species component by measuring in advance a standard solution of known concentration for which traceability is secured.

<Quantification method of alkali metal element ICP-MS>
The positive electrode and the non-aqueous electrolyte solution are acid-decomposed using a strong acid such as concentrated nitric acid, concentrated hydrochloric acid, and aqua regia, and the resulting solution is diluted with pure water to an acid concentration of 2% to 3%. Regarding acid decomposition, it can be decomposed by appropriately heating and pressurizing. The obtained diluted solution is analyzed by ICP-MS, and it is preferable to add a known amount of element as an internal standard at this time. When the alkali metal element and the alkaline earth metal element to be measured reach the upper limit concentrations of the measurement or higher, it is preferable to further dilute while maintaining the acid concentration of the diluent. Each element can be quantified with respect to the obtained measurement result based on a calibration curve prepared in advance using a standard solution for chemical analysis. For the non-aqueous electrolyte solution, X/(X+Y) can be calculated from the obtained measurement results, where X is the molar concentration of the alkali metal ion and Y is the molar concentration of the alkaline earth metal ion.

<Method for quantifying alkali metal compound and/or alkaline earth metal compound>
The method for quantifying the alkali metal compound and/or the alkaline earth metal compound contained in the positive electrode will be described below. The positive electrode can be washed with an organic solvent and then with distilled water, and the alkali metal compound and/or the alkaline earth metal compound can be quantified from the change in the weight of the positive electrode before and after the washing with distilled water. Area of measurement for the positive electrode is not particularly limited but is preferably from the viewpoint of reducing the variation in measurement is 5 cm ² or more 200 cm ² or less, more preferably 25 cm ² or more 150 cm ² or less. If the area is 5 cm ² or more, reproducibility of measurement is secured. When the area is 200 cm ² or less, the sample is easy to handle. Regarding the cleaning with the organic solvent, the organic solvent is not particularly limited as long as the decomposition product of the electrolytic solution deposited on the surface of the positive electrode can be removed. It is preferable to use since the elution of the alkali metal compound is suppressed. For example, polar solvents such as methanol, ethanol, acetone and methyl acetate are preferably used.

As a method of cleaning the positive electrode, for example, the positive electrode is sufficiently immersed in an ethanol solution of 50 to 100 times the weight of the positive electrode for 3 days or more. At this time, it is preferable to take measures such as covering the container so that ethanol does not volatilize. After that, the positive electrode is taken out from ethanol and dried under vacuum (temperature: 100 to 200° C., pressure: 0 to 10 kPa, time: 5 to 20 hours, so that the amount of ethanol remaining in the positive electrode is 1% by mass or less. The residual amount can be determined by measuring GC/MS of water after washing with distilled water described below and quantifying it based on a calibration curve prepared in advance.), and the weight of the positive electrode at that time is M ₀ (g). And Subsequently, the positive electrode is sufficiently immersed in distilled water 100 times the weight of the positive electrode (100 M ₀ (g)) for 3 days or more. At this time, it is preferable to take measures such as covering the container with a lid so that the distilled water will not volatilize. After soaking for 3 days or more, the positive electrode was taken out from the distilled water (when measuring the above-mentioned ion chromatography, the liquid amount is adjusted so that the amount of distilled water becomes 100 M ₀ (g)), and the above-mentioned ethanol. Vacuum-dry as well as wash. Let the weight of the positive electrode at this time be M ₁ (g), and subsequently, in order to measure the weight of the obtained current collector of the positive electrode, a positive electrode active material layer on the current collector using a spatula, a brush, a brush or the like. Get rid of. When the weight of the obtained positive electrode current collector is M ₂ (g), the mass% Z of the alkali metal compound contained in the positive electrode can be calculated by the formula (6).
Z=100×(M ₀ −M ₁ )/(M ₀ −M ₂ )... (6)
When a plurality of alkali metal compounds and/or alkaline earth metal compounds are contained in the positive electrode active material layer, the total amount thereof is calculated as the amount of alkali metal compounds and/or alkaline earth metal compounds.
Further, the total amount C ₁ (% by mass) of the active material, the conductive filler, the binder, the dispersion stabilizer and the like contained in the positive electrode active material layer can be calculated by the formula (7).
C ₁ =100−Z (7)

Hereinafter, examples and comparative examples will be shown to further clarify the features of the present invention. However, the present invention is not limited to the following examples.

Hereinafter, the first embodiment will be specifically described.
<Example 1>
<Preparation of positive electrode active material>
[Preparation Example 1a]
The crushed coconut shell carbide was carbonized in a small carbonization furnace in nitrogen at 500° C. for 3 hours to obtain a carbide. The obtained carbide was placed in an activation furnace, and 1 kg/h of steam was heated in a preheating furnace and then introduced into the activation furnace. The temperature was raised to 900° C. over 8 hours for activation. The activated carbide was taken out and cooled under a nitrogen atmosphere to obtain activated activated carbon. The activated carbon obtained was washed with water for 12 hours and then drained. Then, after drying for 10 hours in an electric dryer maintained at 125° C., crushing was performed for 1 hour with a ball mill to obtain activated carbon 1a.
The average particle size of this activated carbon 1a was 12.7 μm as a result of measurement with a laser diffraction particle size distribution analyzer (SALD-2000J) manufactured by Shimadzu Corporation. In addition, the pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 2330 m ² /g, the mesopore amount (V ₁ ) was 0.52 cc/g, the micropore amount (V ₂ ) was 0.88 cc/g, and V ₁ /V ₂ =0.59. there were.

[Preparation Example 2a]
The phenol resin was carbonized in a firing furnace at 600° C. for 2 hours in a nitrogen atmosphere, pulverized with a ball mill and classified to obtain a carbide having an average particle diameter of 7 μm. The carbide and KOH were mixed at a mass ratio of 1:5, and heated at 800° C. for 1 hour in a firing furnace in a nitrogen atmosphere to activate. The activated carbon is stirred and washed for 1 hour in dilute hydrochloric acid adjusted to a concentration of 2 mol/L, and is further washed by boiling with distilled water until it becomes stable between pH 5 and 6, followed by drying, thereby activating the activated carbon 2a. Got
The average particle diameter of the activated carbon 2a was measured using a laser diffraction particle size distribution analyzer (SALD-2000J) manufactured by Shimadzu Corporation, and the result was 7.0 μm. In addition, the pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 3627 m ² /g, the mesopore volume (V ₁ ) was 1.50 cc/g, the micropore volume (V ₂ ) was 2.28 cc/g, and V ₁ /V ₂ =0.66. there were.

<Crushing of lithium carbonate>
After 200 g of lithium carbonate having an average particle diameter of 46 μm was cooled to −196° C. with liquid nitrogen, it was ground for 20 minutes at a peripheral speed of 10.0 m/s using dry ice beads. The average particle diameter of lithium carbonate 1 obtained by preventing thermal denaturation at −196° C. and obtained by brittle fracture was 2.5 μm.

<Pulverization of potassium carbonate>
200 g of potassium carbonate having an average particle diameter of 53 μm was cooled to −196° C. with liquid nitrogen, and then pulverized with dry ice beads at a peripheral speed of 10.0 m/s for 20 minutes. The average particle diameter of potassium carbonate 1 obtained by preventing thermal denaturation at −196° C. and obtained by brittle fracture was 3.2 μm.

<Production of positive electrode precursor>
A positive electrode precursor was prepared using the activated carbon 2a as the positive electrode active material and the lithium carbonate 1 and the potassium carbonate 1 as the alkali metal compound.
54.5 parts by mass of activated carbon 2a, 23.0 parts by mass of lithium carbonate 1, 13.0 parts by mass of potassium carbonate 1, 3.0 parts by mass of Ketjen Black, 1.5 parts by mass of PVP (polyvinylpyrrolidone). , And PVDF (polyvinylidene fluoride) 5.0 parts by mass, and NMP (N-methylpyrrolidone) were mixed, and the peripheral speed was 17 m/s using a thin film swirl type high speed mixer fill mix manufactured by PRIMIX. The coating liquid was obtained by dispersing under the conditions. The viscosity (ηb) and TI value of the obtained coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,360 mPa·s and the TI value was 3.7. Further, the dispersity of the obtained coating liquid was measured using a grain gauge manufactured by Yoshimitsu Seiki. As a result, the particle size was 31 μm. Using a die coater manufactured by Toray Engineering Co., Ltd., the coating liquid is applied to one or both sides of an aluminum foil having a thickness of 15 μm at a coating speed of 1 m/s and dried at a drying temperature of 120° C. Positive electrode precursor 1 (one side) and positive electrode precursor 1 (both sides) were obtained. The positive electrode precursor 1 (one side) and the positive electrode precursor 1 (both sides) thus obtained were pressed using a roll press machine under the conditions of a pressure of 6 kN/cm and a surface temperature of the press section of 25°C. The thicknesses of the positive electrode precursor 1 (one side) and the positive electrode active material layers of the positive electrode precursor 1 (both sides) obtained above were measured using a positive gauge precursor 1 using a thickness gauge Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. It was determined by subtracting the thickness of the aluminum foil from the average value of the thicknesses measured at 10 arbitrary points. As a result, the thickness of the positive electrode active material layer was 63 μm on each side.

<Preparation of Negative Electrode Active Material Preparation Example 1>
The BET specific surface area and the pore distribution of commercially available artificial graphite were measured by the method described above using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 3.1 m ² /g and the average particle size was 4.8 μm.
300 g of this artificial graphite is put into a basket made of stainless steel mesh, and placed on a stainless steel bat containing 30 g of coal-based pitch (softening point: 50° C.), and both are placed in an electric furnace (effective size in furnace 300 mm × 300 mm × 300 mm). ), and by carrying out a thermal reaction, a composite porous carbon material 1b was obtained. This heat treatment was performed by a method of raising the temperature to 1000° C. in 12 hours in a nitrogen atmosphere and holding the same temperature for 5 hours. Then, after cooling to 60° C. by natural cooling, the composite carbon material 1b was taken out of the furnace.
The BET specific surface area and pore distribution of the obtained composite carbon material 1b were measured by the same method as described above. As a result, the BET specific surface area was 6.1 m ² /g and the average particle size was 4.9 μm. In the composite carbon material 1b, the mass ratio of the carbonaceous material derived from coal-based pitch to the activated carbon was 2.0%.

<Manufacture of negative electrode>
A negative electrode was manufactured using the composite carbon material 1b as a negative electrode active material.
84 parts by mass of the composite carbon material 1b, 10 parts by mass of acetylene black, 6 parts by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed, and the mixture was a thin film swirl type high speed manufactured by PRIMIX. A mixer fill mix was used to disperse under a condition of a peripheral speed of 17 m/s to obtain a coating liquid. The viscosity (ηb) and TI value of the obtained coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,326 mPa·s and the TI value was 2.7. The above coating liquid was applied to both sides of an electrolytic copper foil having a thickness of 10 μm using a die coater manufactured by Toray Engineering Co., Ltd. at a coating speed of 2 m/s and dried at a drying temperature of 120° C. to form the negative electrode 1. Obtained. The obtained negative electrode 1 was pressed using a roll press machine under the conditions of a pressure of 5 kN/cm and a surface temperature of the press portion of 25°C. The film thickness of the negative electrode active material layer of the negative electrode 1 obtained above was measured using an Ono Keiki Co., Ltd. film thickness meter Linear Gauge Sensor GS-551, at an average value of 10 thicknesses of the negative electrode 1. It was calculated by subtracting the thickness of the copper foil. As a result, the film thickness of the negative electrode active material layer was 30 μm on each side.

[Measurement of capacity per unit weight of negative electrode]
One piece of the negative electrode 1 obtained above was cut into a size of 1.4 cm×2.0 cm (2.8 cm ² ) and one layer of the negative electrode active material layer coated on both sides of the copper foil was replaced with a spatula, Using a brush or a brush to make a working electrode, using a lithium metal as the counter electrode and a reference electrode, respectively, and using an electrolyte solution of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:1 as a mixed solvent. An electrochemical cell was prepared in an argon box using a non-aqueous solution in which LiPF ₆ was dissolved at a concentration of 1.0 mol/L.
The initial charge capacity of the obtained electrochemical cell was measured by the following procedure using a charging/discharging device (TOSCAT-3100U) manufactured by Toyo System Co., Ltd.
Against the electrochemical cell, at a temperature 25 ° C., after the voltage value at a current value 0.5 mA / cm ² was subjected to constant current charging until 0.01 V, further the current value reached 0.01 mA / cm ² Constant voltage charging was performed. When the charge capacity during constant current charging and constant voltage charging was evaluated as the initial charge capacity, it was 0.72 mAh, and the capacity per unit mass of the negative electrode 1 (lithium ion doping amount) was 550 mAh/g. .

<Preparation of electrolyte>
As the organic solvent, a mixed solvent of ethylene carbonate (EC):ethyl methyl carbonate (EMC)=33:67 (volume ratio) was used, and the concentration ratio of LiN(SO ₂ F) ₂ and LiPF ₆ was relative to the total electrolytic solution. 75:25 (molar ratio), and each electrolyte salt was dissolved so that the sum of the concentrations of LiN(SO ₂ F) ₂ and LiPF ₆ was 1.2 mol/L to obtain the non-aqueous electrolyte solution 1. It was The concentrations of LiN(SO ₂ F) ₂ and LiPF ₆ in the electrolytic solution 1 were 0.9 mol/L and 0.3 mol/L, respectively.

<Preparation of non-aqueous alkali metal ion capacitor>
The obtained positive electrode precursor was prepared so that the positive electrode active material layer had a size of 10.0 cm×10.0 cm (100 cm ² ), ^two positive electrode precursors 1 (one side), and one positive electrode precursor 1 (both sides). 19 sheets were cut out. Then, 20 sheets of the negative electrode 1 were cut out so that the negative electrode active material layer had a size of 10.1 cm×10.1 cm (102 cm ² ). In addition, 40 sheets of 10.3 cm×10.3 cm (106 cm ² ) polyethylene separators (Asahi Kasei, thickness 10 μm) were prepared. These are laminated such that the positive electrode active material layer and the negative electrode active material layer face each other with the positive electrode precursor, the separator, and the negative electrode sandwiched in this order so that the outermost layer is the positive electrode precursor 1 (one surface), and the electrode is laminated. Got the body A positive electrode terminal and a negative electrode terminal were ultrasonically welded to the obtained electrode laminate, placed in a container formed of an aluminum laminate packaging material, and three sides including the electrode terminal portion were sealed by heat sealing. About 70 g of the non-aqueous electrolyte solution 1 was injected into the electrode laminate housed in the aluminum laminate packaging material at a temperature of 25° C. and a dew point of −40° C. or less under atmospheric pressure to A water-based alkali metal ion capacitor was produced. Then, the non-aqueous alkali metal ion capacitor was placed in a decompression chamber, decompressed from atmospheric pressure to -87 kPa, returned to atmospheric pressure, and left standing for 5 minutes. Then, after depressurizing from atmospheric pressure to -87 kPa, the process of returning to atmospheric pressure was repeated 4 times, and then allowed to stand for 15 minutes. Furthermore, the pressure was reduced from atmospheric pressure to -91 kPa, and then returned to atmospheric pressure. Similarly, the step of decompressing and returning to atmospheric pressure was repeated 7 times in total (reduced to -95, -96, -97, -81, -97, -97, -97 kPa, respectively). Through the above steps, the non-aqueous electrolyte solution 1 was impregnated into the electrode laminate.
Then, the non-aqueous alkali metal ion capacitor was put in a decompression sealing machine, and under reduced pressure of -95 kPa, the aluminum laminate packaging material was sealed by sealing at 180°C for 10 seconds at a pressure of 0.1 MPa.

[Alkali metal doping process]
The obtained non-aqueous alkali metal ion capacitor was placed in an argon box having a temperature of 25° C., a dew point of −60° C., and an oxygen concentration of 1 ppm. The excess part of the aluminum laminate packaging material of the non-aqueous alkali metal ion capacitor was cut and opened, and a voltage of 4.5V was reached at a current value of 50 mA using a power source (P4LT18-0.2) manufactured by Matsusada Precision Co., Ltd. After constant-current charging until, the initial charging was carried out by a method of continuously continuing 4.5V constant-voltage charging for 72 hours, and the negative electrode was doped with an alkali metal (lithium and potassium). After the alkali metal dope (lithium and potassium dope) was completed, the aluminum laminate was sealed using a heat sealing machine (FA-300) manufactured by Fuji Impulse.

[Aging process]
The non-aqueous alkali metal ion capacitor after alkali metal dope (lithium and potassium dope) was taken out from the argon box and subjected to constant current discharge at 50 mA at 25° C. until the voltage reached 3.0 V, and then at 3.0 V constant. The voltage was adjusted to 3.0 V by performing current discharge for 1 hour. Then, the non-aqueous alkali metal ion capacitor was stored in a constant temperature bath at 60° C. for 48 hours.

[Degassing process]
The non-aqueous alkali metal ion capacitor after aging was opened at a temperature of 25° C. and a dew point of −40° C. in a dry air environment to partially open the aluminum laminate packaging material. Subsequently, the non-aqueous alkali metal ion capacitor was placed in a decompression chamber, and a diaphragm pump (N816.3KT.45.18, manufactured by KNF) was used to decompress it from atmospheric pressure to -80 kPa for 3 minutes, and then, The process of taking 3 minutes and returning to normal pressure was repeated 3 times in total. Then, the non-aqueous alkali metal ion capacitor was put in a vacuum sealer, the pressure was reduced to -90 kPa, and the aluminum laminate packaging material was sealed by sealing at 200° C. for 10 seconds at a pressure of 0.1 MPa.

<Evaluation of non-aqueous alkali metal ion capacitors>
[Measurement of capacitance Fa]
About one of the non-aqueous alkali metal ion capacitors obtained in the above step, using a charging/discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Fukushima Co., Ltd. in a constant temperature bath set at 25° C. Constant current charging was performed at a current value of 2 C (1.2 A) until reaching 3.8 V, and then constant voltage charging for applying a constant voltage of 3.8 V was performed for a total of 30 minutes. Then, the electrostatic capacity calculated by F=Q/(3.8-2.2), where Q(C) is the capacity when constant-current discharge is performed at a current value of 2C (1.2A) up to 2.2V. The capacity Fa was 1385F.

[Calculation of internal resistance Ra]
Regarding the non-aqueous alkali metal ion capacitor, a charging/discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Fukushima Co., Ltd. was used in a thermostatic chamber set at 25° C. and a current value (12A) of 20 C was applied to 3. Constant current charging was performed until the voltage reached 8 V, and then constant voltage charging in which a constant voltage of 3.8 V was applied was performed for a total of 30 minutes. After that, the sampling time was set to 0.1 second, and constant current discharge was performed up to 2.2 V at a current value (12 A) of 20 C to obtain a discharge curve (time-voltage). In this discharge curve, the voltage at discharge time=0 second obtained by extrapolating by linear approximation from the voltage values at the discharge time of 2 seconds and 4 seconds is Eo, and the drop voltage ΔE=3.8−Eo, and When the internal resistance Ra was calculated from R=ΔE/(current value 20 C), it was 0.48 mΩ.

[High temperature storage test]
Regarding the non-aqueous alkali metal ion capacitor, a charging/discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. was used in a constant temperature bath set at 25° C., and a current value (60A) of 100C was 4.0V. Constant current charging was performed until a constant voltage of 4.0 V was applied, and then constant voltage charging in which a constant voltage of 4.0 V was applied was performed for a total of 10 minutes. After that, the cell was stored in a 60° C. environment, taken out of the 60° C. environment every two weeks, charged to a cell voltage of 4.0 V in the same charging step, and then stored again in the 60° C. environment. . This step was repeated for 2 months, and the cell volume Va before the storage test was started and the cell volume Vb after 2 months of the storage test were measured using Fluorinert (trademark registered, 3M Japan Co., Ltd.) FC-40 as a measurement solvent at 25°C. Under the environment, it was measured by the Archimedes method. The value B obtained by normalizing the gas generation amount obtained by Vb-Va by the capacitance Fa was 2.34×10 ⁻³ cc/F.
The internal resistance Rb of the non-aqueous alkali metal ion capacitor after the high temperature storage test was calculated to be 0.50 mΩ, and the value of Rb/Ra was 1.04.

[High load charge/discharge cycle test]
Regarding the non-aqueous alkali metal ion capacitor, a charging/discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Fukushima Co., Ltd. was used at a current value of 200C (120A) in a thermostatic chamber set at 25°C. The charging/discharging step of performing constant current charging until reaching 8 V and then performing constant current discharging at a current value of 200 C until reaching 2.2 V was repeated 60,000 times under non-paused conditions. After the cycle was completed, the battery was charged to 4.5 V at a current value (12 A) of 20 C, and then constant voltage charging was continued for 1 hour. After that, the capacitance Fb was measured and found to be 1439F and Fb/Fa=1.04.

<Analysis of positive electrode active material layer>
After adjusting the voltage to 2.9V, the remaining non-aqueous alkali metal ion capacitors were disassembled in an Ar box, which was installed in a room at 23°C and was controlled at a dew point of -90°C or less and an oxygen concentration of 1ppm or less. Then, the positive electrode body was taken out. Two positive electrodes each having a positive electrode active material layer coated on both sides were cut into a size of 10 cm×5 cm to prepare two positive electrode samples 1. One of the obtained positive electrode samples 1 was immersed in 30 g of a diethyl carbonate solvent, and the positive electrode was occasionally moved with tweezers to wash for 10 minutes. Subsequently, the positive electrode was taken out, air-dried in an argon box for 5 minutes, immersed in 30 g of a newly prepared diethyl carbonate solvent, and washed for 10 minutes by the same method as described above. Subsequently, the positive electrode sample was vacuum-dried in the side box while keeping the atmosphere unexposed.
The dried positive electrode body was transferred from the side box to the Ar box in a state where it was not exposed to the atmosphere, and immersion extraction was performed with heavy water to obtain a positive electrode body extract solution. The analysis of the extract was carried out by ion chromatography (IC) and ¹ H-NMR, and the concentration C (mol/ml) of each compound in the extract of the positive electrode body obtained and the volume D of heavy water used for extraction ( ml) and the mass E (g) of the positive electrode active material used for extraction, the following formula (8):
Abundance per unit mass W (mol/g)=C×D÷E (8)
Thus, the amount of each compound deposited on the positive electrode body (mol/g) per unit mass of the positive electrode active material was determined.
The mass of the positive electrode active material layer used for extraction was determined by the following method.
The positive electrode active material layer was peeled off from the current collector of the positive electrode body remaining after extraction with heavy water using a spatula, a brush, or a brush, and the peeled positive electrode active material layer was washed with water and then vacuum dried. The positive electrode active material layer obtained by vacuum drying was washed with NMP. Subsequently, the obtained positive electrode active material layer was vacuum dried again, and then weighed to check the mass of the positive electrode active material layer used for extraction.

[Measurement of ¹ H-NMR]
The positive electrode body extract was put in a 3 mmφ NMR tube (PN-002 manufactured by Shigemi Co., Ltd.), and a 5 mmφ NMR tube containing deuterated chloroform containing 1,2,4,5-tetrafluorobenzene (Nippon Seimitsu Scientific Co., Ltd. N -5) and ¹ H NMR measurement was performed by the double tube method. The signal of 1,2,4,5-tetrafluorobenzene was normalized by 7.1 ppm (m, 2H), and the integrated value of each observed compound was obtained.
Further, deuterated chloroform containing dimethylsulfoxide of known concentration was placed in a 3 mmφ NMR tube (PN-002 manufactured by Shigemi Co., Ltd.), and the same deuterated chloroform containing 1,2,4,5-tetrafluorobenzene as described above was added. The sample was inserted into a 5 mmφ NMR tube (N-5 manufactured by Japan Precision Science Co., Ltd.), and ¹ H NMR measurement was performed by the double tube method. In the same manner as above, the signal of 1,2,4,5-tetrafluorobenzene was normalized to 7.1 ppm (m, 2H), and the integrated value of the signal of dimethyl sulfoxide, 2.6 ppm (s, 6H) was obtained. The concentration C of each compound in the positive electrode body extract was determined from the relationship between the concentration of dimethyl sulfoxide used and the integrated value.
Assignment of ¹ H NMR spectrum is as follows.
[About XOCH ₂ CH ₂ OX]
XOCH ₂ CH ₂ OX of _{CH 2: 3.7ppm (s, 4H} )
CH ₃ OX: 3.3 ppm (s, 3H)
CH ₃ CH ₂ OX of _{CH 3: 1.2ppm (t, 3H} )
CH ₂ O of CH ₃ CH ₂ OX: 3.7 ppm (q, 2H)
As described _above, the signal (3.7 ppm) is XOCH 2 _CH 2 OX of CH _2, since the overlaps with CH ₃ CH ₂ OX of CH ₂ O signals (3.7 _ppm), the CH 3 _CH 2 OX The amount of XOCH ₂ CH ₂ OX is calculated by removing the CH ₂ O equivalent of CH ₃ CH ₂ OX calculated from the signal of CH ₃ (1.2 ppm).
In the above formulas, X is each, - _{(COO) n} M or - _(COO) n ^{R 1} (wherein, M is an alkali metal selected Li, Na, K, Rb, and from the group consisting of Cs. ).
From the concentration of each compound in the extract obtained by the above analysis, the volume of heavy water used for extraction, and the mass of the positive electrode active material used for extraction, the concentration W of XOCH ₂ CH ₂ OX contained in the positive electrode sample 1 was determined. It could be calculated to be 100.9×10 ⁻⁴ mol/g.

<A ₁ ,A ₂ Nosanshutsu_>
The remaining positive electrode sample 1 prepared above was immersed in 30 g of a diethyl carbonate solvent, and the positive electrode was occasionally moved with tweezers to wash for 10 minutes. Subsequently, the positive electrode was taken out, air-dried in an argon box for 5 minutes, immersed in 30 g of a newly prepared diethyl carbonate solvent, and washed for 10 minutes by the same method as described above. The positive electrode was taken out from the argon box and dried for 20 hours under the conditions of a temperature of 25° C. and a pressure of 1 kPa using a vacuum dryer (DP33, manufactured by Yamato Scientific Co., Ltd.).

[SEM and EDX measurement of positive electrode surface]
A small piece of 1 cm×1 cm was cut out from the positive electrode sample 1 obtained above, and the surface was coated with gold in a vacuum of 10 Pa by sputtering. Then, under the conditions shown below, SEM and EDX of the positive electrode surface were measured under atmospheric exposure.
(SEM-EDX measurement conditions)
・Measuring device: Hitachi High-Technology, field emission scanning electron microscope FE-SEM S-4700, manufactured by Horiba, energy dispersive X-ray analyzer EMAX
・Acceleration voltage: 10 kV
・Emission current: 10 μA
・Measurement magnification: 2000 times ・Electron beam incident angle: 90°
・X-ray extraction angle: 30°
・Dead time: 15%
・Mapping elements: C, O, F
-Number of measurement pixels: 256 x 256 pixels-Measurement time: 60 sec.
-Number of integration: 50 times-The brightness and contrast were adjusted so that there were no pixels reaching the maximum brightness value in the mapping image and the average value of the brightness values was within the range of 40% to 60% of the maximum brightness value.
(Analysis of SEM-EDX)
For the obtained oxygen mapping and fluorine mapping, image analysis software (ImageJ) was used to perform binarization based on the average value of the brightness values. At this time, the area of oxygen mapping was 16.2% with respect to the entire image, and the area of fluorine mapping was 31.3%. The overlapping area of the oxygen mapping and the fluorine mapping obtained by the binarization is 14.9% for all images, and the area overlapping ratio of the fluorine mapping to the oxygen mapping is A ₁ (%),
It was possible to calculate 92.0% from A ₁ =100×14.9/16.2.

[Cathode cross section SEM and EDX measurement]
A small piece of 1 cm x 1 cm was cut out from the positive electrode sample 1, and SM-09020CP manufactured by JEOL Ltd. was used, and argon gas was used. A cross section was prepared. Then, the positive electrode cross section SEM and EDX were measured by the above-mentioned method.
With respect to the obtained SEM-EDX of the cross section of the positive electrode, oxygen mapping and fluorine mapping were binarized in the same manner as above, and the area overlap ratio A ₂ of fluorine mapping with respect to oxygen mapping was calculated to be 39.4%.

<Quantification of alkali metal compounds>
The positive electrode sample 1 was cut into a size of 5 cm×5 cm (weight: 0.275 g), dipped in 20 g of ethanol in the container, covered with the container, and allowed to stand in a 25° C. environment for 3 days. Then, the positive electrode was taken out of the container and vacuum dried at 120° C. and 5 kPa for 10 hours. The positive electrode weight M ₀ at this time was 0.252 g, and GC/MS of the ethanol solution after washing was measured under the conditions in which a calibration curve was prepared in advance, and it was confirmed that the amount of diethyl carbonate present was less than 1%. confirmed.
Subsequently, 25.20 g of distilled water in another container was impregnated with the positive electrode, the container was covered, and the container was allowed to stand in a 45° C. environment for 3 days. The weight of distilled water after standing for 3 days was 25.02 g, so 0.18 g of distilled water was added. Then, the positive electrode was taken out from the container and vacuum dried at 150° C. and 3 kPa for 12 hours. The positive electrode weight M ₁ at this time was 0.238 g, and GC/MS of the distilled water after washing was measured under the condition that a calibration curve was prepared in advance, and it was confirmed that the amount of ethanol present was less than 1%. did.
Then, the active material layer on the positive electrode current collector was removed using a spatula, a brush, or a brush, and the weight M ₂ of the positive electrode current collector was measured and found to be 0.099 g. When the total amount Z of lithium carbonate and potassium carbonate in the positive electrode was quantified according to the above formula (6), it was 9.2 mass %.

<Example 2>
Initially charge the non-aqueous alkali metal ion capacitor by constant current charging at a current value of 100 mA until it reaches a voltage of 4.6 V, and then perform continuous 4.6 V constant voltage charging for 40 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 1 except that doping with lithium and potassium was performed.
<Example 3>
Initially charge the non-aqueous alkali metal ion capacitor by constant current charging at a current value of 200 mA until the voltage reaches 4.3 V, and then perform 4.3 V constant voltage charging for 10 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 1 except that doping with lithium and potassium was performed.
<Example 4>
Lithium carbonate and potassium carbonate were cooled to −196° C. with liquid nitrogen, and then zirconia beads having a diameter of 1.0 mm were used, followed by grinding for 10 minutes at a peripheral speed of 10.0 m/s. A non-aqueous alkali metal ion capacitor was produced by the method.
<Example 5>
Lithium carbonate and potassium carbonate were cooled to -196° C. with liquid nitrogen, and then zirconia beads having a diameter of 1.0 mm were used, and then pulverized at a peripheral speed of 10.0 m/s for 5 minutes. A non-aqueous alkali metal ion capacitor was produced by the method.
<Example 6>
Lithium carbonate and potassium carbonate were cooled to −196° C. with liquid nitrogen, and then zirconia beads of φ1.0 mm were used and pulverized at a peripheral speed of 10.0 m/s for 3 minutes. A non-aqueous alkali metal ion capacitor was produced by the method.

<Example 7>
Lithium carbonate and potassium carbonate were cooled to −196° C. with liquid nitrogen, pulverized with φ1.0 mm zirconia beads at a peripheral speed of 10.0 m/s for 20 minutes, and a non-aqueous alkali metal ion capacitor was used. Initial charging is performed in a 45° C. environment at a current value of 200 mA until a voltage of 4.5 V is reached, and then 4.5 V constant voltage charging is continued for 20 hours. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 1 except that potassium doping was performed.

<Example 8>
The initial charge of the non-aqueous alkali metal ion capacitor is performed by constant current charge at a current value of 200 mA until the voltage reaches 4.3 V, and then the constant voltage charge of 4.3 V is continuously performed for 10 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 7 except that lithium and potassium were doped.

<Example 9>
Initially charge the non-aqueous alkali metal ion capacitor at constant current until the voltage reaches 4.3V at a current value of 200mA, and then perform continuous 4.5V constant voltage charging for 5 hours. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 7 except that lithium and potassium were doped.

<Example 10>
Lithium carbonate and potassium carbonate were cooled to −196° C. with liquid nitrogen, and then zirconia beads of φ1.0 mm were used and pulverized at a peripheral speed of 10.0 m/s for 5 minutes. A non-aqueous alkali metal ion capacitor was produced by the method.

<Example 11>
Initially charge the non-aqueous alkali metal ion capacitor by constant current charging at a current value of 200 mA until the voltage reaches 4.3 V, and then perform 4.3 V constant voltage charging for 2 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 10 except that lithium and potassium were doped.

<Example 12>
Initially charge the non-aqueous alkali metal ion capacitor by constant current charging at a current value of 200 mA until it reaches a voltage of 4.5 V, and then carry out 4.5 V constant voltage charging for 6 hours. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 10 except that lithium and potassium were doped.

<Example 13>
Initially charge the non-aqueous alkaline metal ion capacitor by constant current charging at a current value of 200 mA until the voltage reaches 4.5 V, and then perform continuous 4.5 V constant voltage charging for 1 hour to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 10 except that lithium and potassium were doped.

<Example 14>
Initially charge the non-aqueous alkali metal ion capacitor by constant current charging at a current value of 100 mA until the voltage reaches 4.2 V, and then carry out 4.2 V constant voltage charging for 1 hour to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 10 except that lithium and potassium were doped.

<Comparative Example 1>
A non-aqueous alkali metal ion was prepared in the same manner as in Example 1 except that lithium carbonate and potassium carbonate were pulverized in a 25° C. environment using φ1.0 mm zirconia beads at a peripheral speed of 10.0 m/s for 5 minutes. A capacitor was produced.

<Comparative example 2>
The initial charge of the non-aqueous alkali metal ion capacitor is carried out by constant current charging at a current value of 100 mA until the voltage reaches 4.6 V, and then continuously charged by 4.6 V constant voltage for 40 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 1 except that lithium and potassium were doped.

<Comparative example 3>
The initial charge of the non-aqueous alkali metal ion capacitor is performed by constant current charge at a current value of 200 mA until the voltage reaches 4.3 V, and then the constant voltage charge of 4.3 V is continuously performed for 10 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 1 except that lithium and potassium were doped.

<Comparative example 4>
Non-aqueous alkali metal ion in the same manner as in Example 1 except that lithium carbonate and potassium carbonate were crushed for 2 minutes at a peripheral speed of 10.0 m/s in a 25° C. environment using φ1.0 mm zirconia beads. A capacitor was produced.

<Comparative Example 5>
The initial charge of the non-aqueous alkali metal ion capacitor is carried out by constant current charging at a current value of 100 mA until the voltage reaches 4.6 V, and then continuously charged by 4.6 V constant voltage for 40 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 4 except that lithium and potassium were doped.

<Comparative example 6>
The initial charge of the non-aqueous alkali metal ion capacitor is performed by constant current charge at a current value of 200 mA until the voltage reaches 4.3 V, and then the constant voltage charge of 4.3 V is continuously performed for 10 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 4 except that lithium and potassium were doped.

<Comparative Example 7>
A method of initially charging a non-aqueous alkali metal ion capacitor in a 45° C. environment at a current value of 200 mA until a voltage of 4.5 V is reached, and then continuously performing 4.5 V constant voltage charging for 20 hours. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 1 except that the negative electrode was doped with lithium and potassium.

<Comparative Example 8>
The initial charge of the non-aqueous alkali metal ion capacitor is carried out by constant current charging at a current value of 100 mA until the voltage reaches 4.6 V, and then continuously charged by 4.6 V constant voltage for 40 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 7 except that lithium and potassium were doped.

<Comparative Example 9>
The initial charge of the non-aqueous alkali metal ion capacitor is performed by constant current charge at a current value of 200 mA until the voltage reaches 4.3 V, and then the constant voltage charge of 4.3 V is continuously performed for 10 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 7 except that lithium and potassium were doped.

<Comparative Example 10>
A method of initially charging the non-aqueous alkali metal ion capacitor at 0° C. at a current value of 200 mA until constant voltage of 4.5 V is reached, and then continuously charging at 4.5 V of constant voltage for 20 hours. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 1 except that the negative electrode was doped with lithium and potassium.

<Comparative Example 11>
The initial charge of the non-aqueous alkali metal ion capacitor is carried out by constant current charging at a current value of 100 mA until the voltage reaches 4.6 V, and then continuously charged by 4.6 V constant voltage for 40 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 10 except that lithium and potassium were doped.

<Comparative Example 12>
The initial charge of the non-aqueous alkali metal ion capacitor is performed by constant current charge at a current value of 200 mA until the voltage reaches 4.3 V, and then the constant voltage charge of 4.3 V is continuously performed for 10 hours to obtain a negative electrode. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 10 except that lithium and potassium were doped.

<Comparative Example 13>
A method of initially charging a non-aqueous alkali metal ion capacitor under constant temperature charging at a current value of 200 mA at 60° C. until a voltage of 4.8 V is reached, and then continuing 4.8 V constant voltage charging for 72 hours. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 1 except that the negative electrode was doped with lithium and potassium.

<Comparative Example 14>
A method of initially charging a non-aqueous alkali metal ion capacitor at 45° C. under constant current charging at a current value of 200 mA until a voltage of 5.0 V is reached, and then continuing 5.0 V constant voltage charging for 72 hours. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 1 except that the negative electrode was doped with lithium and potassium.

<Comparative Example 15>
A method of initially charging the non-aqueous alkali metal ion capacitor under constant temperature of 45° C. at a current value of 200 mA until the voltage reaches 5.0 V, and then continuing 5.0 V constant voltage charging for 96 hours. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 1 except that the negative electrode was doped with lithium and potassium.

Table 1 shows the evaluation results of the non-aqueous alkali metal ion capacitors of Examples 1 to 14 and Comparative Examples 1 to 15.

It is considered that by crushing the alkali metal compound under the extremely low temperature condition of -196° C., the generation of defects on the surface of the alkali metal compound particles could be suppressed without being affected by the temperature increase during the crushing. As a result, it is considered that the re-aggregation of the alkali metal compound particles could be suppressed and the electrolyte solution and the electrolyte could be efficiently decomposed on the surface of the alkali metal compound particles, and the compound (1 It is considered that the fluorine compounds are evenly deposited on the surface of the alkali metal compound along with the deposition of (5) to (5), and the high temperature storage characteristics and the high load charge/discharge characteristics are improved.

<Example 15>
<Crushing of sodium carbonate>
After 200 g of sodium carbonate having an average particle diameter of 55 μm was cooled to −196° C. with liquid nitrogen, it was ground with dry ice beads at a peripheral speed of 10.0 m/s for 20 minutes. When the average particle diameter of sodium carbonate 1 obtained by brittle fracture was measured at −196° C. to prevent thermal denaturation, the average particle diameter was 3.4 μm.

<Production of positive electrode precursor>
A positive electrode precursor was manufactured using the activated carbon 1a as a positive electrode active material and the lithium carbonate 1 (compound 1) and sodium carbonate 1 (compound 2) as an alkali metal compound.
50.5 parts by mass of activated carbon 1a, a total of 40.0 parts by mass of lithium carbonate 1 and sodium carbonate 1 (mixing ratio 96:4), 3.0 parts by mass of Ketjen black, and 1.5 parts of PVP (polyvinylpyrrolidone). By mass, and 5.0 parts by mass of PVDF (polyvinylidene fluoride) and NMP (N-methylpyrrolidone) are mixed, and the mixture is subjected to a peripheral speed of 17 m/by using a thin film swirl type high speed mixer FILMIX manufactured by PRIMIX. It was dispersed under the condition of s to obtain a coating liquid. The viscosity (ηb) and TI value of the obtained coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,370 mPa·s and the TI value was 3.8. Further, the dispersity of the obtained coating liquid was measured using a particle gauge manufactured by Yoshimitsu Seiki. As a result, the particle size was 37 μm. The coating solution was applied to one or both sides of an aluminum foil having a thickness of 15 μm at a coating speed of 1 m/s using a die coater manufactured by Toray Engineering Co., Ltd., and dried at a drying temperature of 120° C. to obtain a positive electrode. A precursor 2 (one side) and a positive electrode precursor 2 (both sides) were obtained. The positive electrode precursor 2 (one side) and the positive electrode precursor 2 (both sides) thus obtained were pressed using a roll press machine under the conditions of a pressure of 6 kN/cm and a surface temperature of the press section of 25°C. The film thickness of the positive electrode active material layer of the positive electrode precursor 2 (one side) and the positive electrode precursor 2 (both sides) obtained above was measured using a film thickness meter, Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. It was determined by subtracting the thickness of the aluminum foil from the average value of the thicknesses measured at arbitrary 10 points in 2. As a result, the thickness of the positive electrode active material layer was 63 μm on each side.

<Preparation of Negative Electrode Active Material Preparation Example 2>
The BET specific surface area and the pore distribution of the commercially available coconut shell activated carbon were measured by the method described above using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 1,790 m ² /g, the mesopore volume (V ₁ ) was 0.199 cc/g, the micropore volume (V ₂ ) was 0.698 cc/g, and V ₁ /V ₂ =0. 29, and the average pore diameter was 20.1Å.
300 g of this coconut shell activated carbon was placed in a basket made of stainless steel mesh and placed on a stainless steel bat containing 540 g of coal-based pitch (softening point: 50° C.), and both were placed in an electric furnace (effective size in the furnace 300 mm × 300 mm × The composite porous carbon material 1a was obtained by placing it within 300 mm and performing a thermal reaction. This heat treatment was performed by a method in which the temperature was raised to 600° C. in 8 hours in a nitrogen atmosphere and the temperature was kept for 4 hours. Then, after cooling to 60° C. by natural cooling, the composite carbon material 1a was taken out of the furnace.
For the obtained composite carbon material 1a, the BET specific surface area and pore distribution were measured by the same method as described above. As a result, the BET specific surface area was 262 m ² /g, the mesopore amount (V _m1 ) was 0.186 cc/g, the micropore amount (V _m2 ) was 0.082 cc/g, and V _m1 /V _m2 =2.27. there were. In the composite carbon material 1a, the mass ratio of the carbonaceous material derived from coal-based pitch to the activated carbon was 78%.

<Manufacture of negative electrode>
A negative electrode was manufactured using the composite carbon material 1a as a negative electrode active material.
84 parts by mass of the composite carbon material 1a, 10 parts by mass of acetylene black, 6 parts by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) are mixed, and the mixture is a thin film swirl type high speed manufactured by PRIMIX. A mixer fill mix was used to disperse under a condition of a peripheral speed of 17 m/s to obtain a coating liquid. The viscosity (ηb) and TI value of the obtained coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,789 mPa·s and the TI value was 4.3. The coating liquid was applied to both sides of an electrolytic copper foil having a thickness of 10 μm at a coating speed of 2 m/s using a die coater manufactured by Toray Engineering Co., Ltd., and dried at a drying temperature of 120° C. to obtain a negative electrode 2. Got The obtained negative electrode 2 was pressed using a roll press machine under the conditions of a pressure of 5 kN/cm and a surface temperature of the press portion of 25°C. The film thickness of the negative electrode active material layer of the negative electrode 2 obtained above was measured using an Ono Keiki Co. film thickness meter, Linear Gauge Sensor GS-551, at an average of the thicknesses of the negative electrode 2 measured at any 10 positions. It was calculated by subtracting the thickness of the copper foil. As a result, the thickness of the negative electrode active material layer was 40 μm on each side.

[Measurement of capacity per unit weight of negative electrode]
One piece of the negative electrode 2 obtained above was cut into a size of 1.4 cm×2.0 cm (2.8 cm ² ), and one of the negative electrode active material layers coated on both sides of the copper foil was used as a spatula or a brush. , Or using a brush to make a working electrode, using lithium metal as a counter electrode and a reference electrode, respectively, and a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 1:1 as an electrolytic solution. An electrochemical cell was produced in an argon box using a non-aqueous solution in which LiPF ₆ was dissolved at a concentration of 1.0 mol/L.
The initial charge capacity of the obtained electrochemical cell was measured by the following procedure using a charging/discharging device (TOSCAT-3100U) manufactured by Toyo System Co., Ltd.
Against the electrochemical cell, at a temperature 25 ° C., after the voltage value at a current value 0.5 mA / cm ² was subjected to constant current charging until 0.01 V, further the current value reached 0.01 mA / cm ² Constant voltage charging was performed. When the charge capacity during constant current charging and constant voltage charging was evaluated as the initial charge capacity, it was 1.5 mAh, and the capacity per unit mass of the negative electrode 2 (lithium ion doping amount) was 1470 mAh/g. ..

<Preparation of non-aqueous alkali metal ion capacitor>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 1 except that the positive electrode precursor 2 (one side), the positive electrode precursor 2 (both sides), and the negative electrode 2 were used and the electrolytic solution 1 was used.
When the electrostatic capacity Fa of the non-aqueous alkali metal ion capacitor was measured in the same manner as in Example 1, it was 1101 F, and the internal resistance Ra was measured, and it was 0.53 mΩ.
Subsequently, the non-aqueous lithium type electricity storage device was disassembled in an argon box having a dew point temperature of -72°C to collect an electrolyte solution, and the concentrations of Li and Na were measured by ICP-OES. The substance amount ratio was 97.7. %: 2.3%.

<Example 16>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that the compounding ratio of lithium carbonate 1 and sodium carbonate 1 in the positive electrode precursor was changed to 90:10.

<Example 17>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that the compounding ratio of lithium carbonate 1 and sodium carbonate 1 in the positive electrode precursor was changed to 70:30.

<Example 18>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that the compounding ratio of lithium carbonate 1 and sodium carbonate 1 in the positive electrode precursor was changed to 50:50.

<Example 19>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that the compounding ratio of lithium carbonate 1 and sodium carbonate 1 in the positive electrode precursor was changed to 10:90.

<Example 20>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that the compounding ratio of lithium carbonate 1 and sodium carbonate 1 in the positive electrode precursor was changed to 2:98.

<Example 21>
Example 1 except that lithium carbonate 1 (compound 1) was used as the alkali metal compound, and sodium hydroxide (compound 2) crushed in the same manner as in Example 1 was used, and the respective compounding ratios were changed to 90:10. A non-aqueous alkali metal ion capacitor was produced by the same method as 15.

<Example 22>
Example 15 except that lithium carbonate 1 (compound 1) was used as the alkali metal compound, and sodium oxide (compound 2) crushed in the same manner as in Example 1 was used, and the mixing ratio of each was changed to 90:10. A non-aqueous alkali metal ion capacitor was produced by the same method as described above.

<Example 23>
A non-aqueous alkali metal was prepared in the same manner as in Example 15 except that lithium carbonate 1 (compound 1) and potassium carbonate 1 (compound 2) were used as the alkali metal compound and the respective compounding ratios were changed to 96:4. An ion capacitor was produced.

<Example 24>
A non-aqueous alkali metal was prepared in the same manner as in Example 15 except that lithium carbonate 1 (compound 1) and potassium carbonate 1 (compound 2) were used as the alkali metal compound, and the respective mixing ratios were changed to 70:30. An ion capacitor was produced.

<Example 25>
A non-aqueous alkali metal was prepared in the same manner as in Example 15 except that lithium carbonate 1 (compound 1) and potassium carbonate 1 (compound 2) were used as the alkali metal compound and the mixing ratio of each was changed to 2:98. An ion capacitor was produced.

<Example 26>
Example 15 except that lithium carbonate 1 (compound 1) was used as the alkali metal compound and rubidium carbonate (compound 2) crushed in the same manner as in Example 1 was used, and the mixing ratio of each was changed to 70:30. A non-aqueous alkali metal ion capacitor was produced by the same method as described above.

<Example 27>
Example 15 except that lithium carbonate 1 (compound 1) was used as the alkali metal compound and cesium carbonate (compound 2) crushed in the same manner as in Example 1 was used, and the mixing ratio of each was changed to 70:30. A non-aqueous alkali metal ion capacitor was produced by the same method as described above.

<Comparative Example 16>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that lithium carbonate 1 (compound 1 only) was used as the alkali metal compound.

<Comparative Example 17>
A non-aqueous alkali metal was prepared in the same manner as in Example 15 except that the compounding ratio of lithium carbonate 1 (compound 1) and sodium carbonate 1 (compound 2) in the positive electrode precursor was changed to 99.5:0.5. An ion capacitor was produced.

<Comparative Example 18>
Nonaqueous alkali metal was prepared in the same manner as in Example 15 except that the compounding ratio of lithium carbonate 1 (compound 1) and potassium carbonate 1 (compound 2) in the positive electrode precursor was changed to 99.5:0.5. An ion capacitor was produced.

<Comparative Example 19>
Lithium carbonate 1 (compound 1) was used as the alkali metal compound, and sodium hydroxide (compound 2) crushed in the same manner as in Example 1 was used, and the respective compounding ratios were changed to 99.5:0.5. A nonaqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except for the above.

<Comparative Example 20>
Lithium carbonate 1 (compound 1) was used as the alkali metal compound, and sodium oxide (compound 2) ground in the same manner as in Example 1 was used, except that the compounding ratio of each was changed to 99.5:0.5. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15.

<Example 28>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that the compounding ratio of sodium carbonate 1 (compound 1) and potassium carbonate 1 (compound 2) in the positive electrode precursor was changed to 70:30. did.

<Example 29>
Example 15 except that sodium carbonate 1 (compound 1) was used as the alkali metal compound, and rubidium carbonate (compound 2) crushed in the same manner as in Example 1 was used, and the mixing ratio of each was changed to 70:30. A non-aqueous alkali metal ion capacitor was produced by the same method as described above.

<Example 30>
Example 15 except that sodium carbonate 1 (compound 1) was used as the alkali metal compound, and cesium carbonate (compound 2) crushed in the same manner as in Example 1 was used, and the respective compounding ratios were changed to 70:30. A non-aqueous alkali metal ion capacitor was produced by the same method as described above.

<Comparative Example 21>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that sodium carbonate 1 (compound 1 only) was used as the alkali metal compound.

<Comparative Example 22>
Non-aqueous alkali metal in the same manner as in Example 15 except that the compounding ratio of sodium carbonate 1 (compound 1) and potassium carbonate 1 (compound 2) in the positive electrode precursor was changed to 99.5:0.5. An ion capacitor was produced.

<Example 31>
Lithium hydroxide (compound 1) pulverized in the same manner as in Example 1 and sodium hydroxide (compound 2) pulverized in the same manner as in Example 1 were used, and the mixing ratio of each was 70:30. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that the above was changed.

<Example 32>
Lithium oxide (Compound 1) pulverized in the same manner as in Example 1 and sodium oxide (Compound 2) pulverized in the same manner as in Example 1 were used, and the respective compounding ratios were changed to 70:30. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except for the above.

<Comparative Example 23>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that lithium hydroxide (compound 1 only) pulverized in the same manner as in Example 1 was used.

<Comparative Example 24>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that lithium oxide (compound 1 only) pulverized in the same manner as in Example 1 was used.

<Example 33>
Same as Example 15 except that the compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), and potassium carbonate 1 (compound 3) in the positive electrode precursor was changed to 96:3:1. A non-aqueous alkali metal ion capacitor was produced by the method.

<Example 34>
Same as Example 15 except that the compounding ratio of lithium carbonate 1 (Compound 1), sodium carbonate 1 (Compound 2), and potassium carbonate 1 (Compound 3) in the positive electrode precursor was changed to 80:15:5. A non-aqueous alkali metal ion capacitor was produced by the method.

<Example 35>
Same as Example 15 except that the compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), and potassium carbonate 1 (compound 3) in the positive electrode precursor was changed to 70:20:10. A non-aqueous alkali metal ion capacitor was produced by the method.

<Example 36>
Same as Example 15 except that the compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), and potassium carbonate 1 (compound 3) in the positive electrode precursor was changed to 3:96:1. A non-aqueous alkali metal ion capacitor was produced by the method.

<Example 37>
Same as Example 15 except that the compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), and potassium carbonate 1 (compound 3) in the positive electrode precursor was changed to 3:1:96. A non-aqueous alkali metal ion capacitor was produced by the method.

<Example 38>
Compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), potassium carbonate 1 (compound 3), and rubidium carbonate (compound 4) ground in the same manner as in Example 1 in the positive electrode precursor. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that the ratio was changed to 85:5:5:5.

<Example 39>
Compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), potassium carbonate 1 (compound 3), and cesium carbonate (compound 4) ground in the same manner as in Example 1 in the positive electrode precursor. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15 except that the ratio was changed to 85:5:5:5.

<Comparative Example 25>
Except that the compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), and potassium carbonate 1 (compound 3) in the positive electrode precursor was changed to 99.6:0.2:0.2. A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 15.

<Comparative Example 26>
Example except that the compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), and potassium carbonate 1 (compound 3) in the positive electrode precursor was changed to 99:0.5:0.5. A non-aqueous alkali metal ion capacitor was produced by the same method as 15.

<Comparative Example 27>
Compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), potassium carbonate 1 (compound 3), and rubidium carbonate (compound 4) ground in the same manner as in Example 1 in the positive electrode precursor. Was changed to 99.4:0.2:0.2:0.2 to prepare a non-aqueous alkali metal ion capacitor in the same manner as in Example 15.

<Comparative Example 28>
Compounding ratio of lithium carbonate 1 (compound 1), sodium carbonate 1 (compound 2), potassium carbonate 1 (compound 3), and cesium carbonate (compound 4) ground in the same manner as in Example 1 in the positive electrode precursor. Was changed to 99.4:0.2:0.2:0.2 to prepare a non-aqueous alkali metal ion capacitor in the same manner as in Example 15.

Table 2 shows the evaluation results of the non-aqueous alkali metal ion capacitors of Examples 15 to 39 and Comparative Examples 16 to 28 and the substance amount ratio of the alkali metal ions in the electrolytic solution.

The presence of 1% or more of a plurality of alkali metal ions having different ionic radii in the non-aqueous electrolyte solution of the non-aqueous alkali metal ion capacitor allows the alkali metal ions having a large ionic radius according to the first embodiment to function as the negative electrode active material. It is considered that the high output characteristics are improved because the pores are expanded and the alkali metal ions having a small ionic radius can efficiently perform the insertion-desorption reaction.

Hereinafter, the second embodiment will be specifically described.
<Example 40>
<Preparation of positive electrode active material>
[Preparation Example 1b]
The crushed coconut shell carbide was put into a small carbonization furnace and carbonized at 500° C. for 3 hours in a nitrogen atmosphere to obtain a carbide. The obtained carbide was placed in an activation furnace, steam heated in a preheating furnace was introduced into the activation furnace at 1 kg/h, and the temperature was raised to 900° C. over 8 hours for activation. The activated carbide was taken out and cooled under a nitrogen atmosphere to obtain activated activated carbon. The activated carbon thus obtained was washed with water for 10 hours, then drained, dried in an electric dryer kept at 115° C. for 10 hours, and then pulverized with a ball mill for 1 hour to obtain activated carbon 1b.
The average particle diameter of the activated carbon 1b was measured with a laser diffraction particle size distribution analyzer (SALD-2000J) manufactured by Shimadzu Corporation, and it was 4.2 μm. Moreover, the pore distribution of the activated carbon 1b was measured using the pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 2360 m ² /g, the mesopore volume (V ₁ ) was 0.52 cc/g, the micropore volume (V ₂ ) was 0.88 cc/g, and V ₁ /V ₂ =0.59. there were.

[Preparation Example 2b]
The phenol resin was placed in a firing furnace, carbonized at 600° C. for 2 hours in a nitrogen atmosphere, crushed by a ball mill and classified to obtain a carbide having an average particle diameter of 7 μm. The obtained carbide and KOH were mixed at a mass ratio of 1:5, put into a firing furnace, and heated at 800° C. for 1 hour in a nitrogen atmosphere to be activated. The activated carbon was taken out, washed with stirring in dilute hydrochloric acid adjusted to a concentration of 2 mol/L for 1 hour, washed with boiling water until it became stable between pH 5 and 6, and then dried to obtain activated carbon 2b.
The average particle diameter of the activated carbon 2b was measured using a laser diffraction particle size distribution analyzer (SALD-2000J) manufactured by Shimadzu Corporation, and the result was 7.0 μm. Moreover, the pore distribution of the activated carbon 2b was measured using the pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 3627 m ² /g, the mesopore volume (V ₁ ) was 1.50 cc/g, the micropore volume (V ₂ ) was 2.28 cc/g, and V ₁ /V ₂ =0.66. there were.

<Crushing of alkali metal compound and alkaline earth metal compound>
After dry blending 100 g of lithium carbonate having an average particle diameter of 53 μm and 100 g of calcium carbonate having an average particle diameter of 60 μm, the mixture was cooled to −196° C. with liquid nitrogen using a grinder (liquid nitrogen bead mill LNM) manufactured by Imex Co., and then φ1. Using 0 mm zirconia beads, the mixture was ground for 20 minutes at a peripheral speed of 10.0 m/s to obtain a carbonate mixture 1. By cooling to -196°C, brittle fracture can be performed while preventing thermal denaturation of lithium carbonate and calcium carbonate. The average particle size of the obtained carbonate mixture 1 was measured and found to be 2.9 μm.

<Production of positive electrode precursor>
A positive electrode precursor was manufactured using activated carbon 2b as a positive electrode active material.
54.5 parts by mass of activated carbon 2b, 33.0 parts by mass of carbonate mixture 1, 3.0 parts by mass of Ketjen Black, 1.5 parts by mass of PVP (polyvinylpyrrolidone), and PVDF (polyvinylidene fluoride). 8.0 parts by mass, and a mixed solvent of NMP (N-methylpyrrolidone) and pure water of 99:1 were mixed, and the mixture was rotated at a peripheral speed of 17 m/m by using a thin film swirl type high speed mixer fill mix manufactured by PRIMIX. It was dispersed under the condition of s to obtain a coating liquid. The viscosity (ηb) and TI value of the obtained coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,820 mPa·s and the TI value was 4.1. Further, the dispersity of the obtained coating liquid was measured using a grain gauge manufactured by Yoshimitsu Seiki. As a result, the particle size was 33 μm. Using a die coater manufactured by Toray Engineering Co., Ltd., the coating liquid was applied to one side or both sides of a 15 μm thick aluminum foil at a coating speed of 1 m/s and dried at a drying temperature of 120° C. to prepare a positive electrode precursor. Body 3 (one side) and positive electrode precursor 3 (both sides) were obtained. The obtained positive electrode precursor 3 (one side) and positive electrode precursor 3 (both sides) were pressed under the conditions of a pressure of 6 kN/cm and a surface temperature of the press section of 25° C. using a roll press machine. The total thickness of the pressed positive electrode precursor 3 (one side) and the positive electrode precursor 3 (both sides) was measured by using a film thickness meter Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. The measurement was performed at arbitrary 10 points on the body 3 (both sides). The thickness of the aluminum foil was subtracted from the average value of the measured total thicknesses to obtain the film thicknesses of the positive electrode precursor 3 (one side) and the positive electrode active material layers of the positive electrode precursor 3 (both sides). As a result, the thickness of the positive electrode active material layer was 58 μm on each side.

<Preparation of Negative Electrode Active Material Preparation Example 3>
The BET specific surface area and the pore distribution of commercially available artificial graphite were measured by the method described above using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 3.1 m ² /g and the average particle size was 4.8 μm.

300 g of this artificial graphite was placed in a basket made of stainless steel mesh and placed on a stainless steel bat containing 30 g of coal-based pitch (softening point: 50° C.), and both were placed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). ) Installed inside. The artificial graphite and the coal-based pitch were heated to 1000° C. in a nitrogen atmosphere for 12 hours and kept at the same temperature for 5 hours for thermal reaction to obtain a composite porous carbon material 1b. The obtained composite porous carbon material 1b was cooled to 60° C. by natural cooling and taken out from the electric furnace.

The BET specific surface area and pore distribution of the obtained composite porous carbon material 1b were measured by the same method as described above. As a result, the BET specific surface area was 6.1 m ² /g and the average particle size was 4.9 μm. In the composite porous carbon material 1b, the mass ratio of the carbonaceous material derived from the coal-based pitch to the activated carbon was 2.0%.

<Manufacture of negative electrode>
A negative electrode was manufactured using the composite porous carbon material 1b as a negative electrode active material.
84 parts by mass of the composite porous carbon material 1b, 10 parts by mass of acetylene black, 6 parts by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed, and the mixture was a thin film manufactured by PRIMIX. A swirling high-speed mixer FILMIX was used to disperse under a condition of a peripheral speed of 17 m/s to obtain a coating liquid. The viscosity (ηb) and TI value of the obtained coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,310 mPa·s and the TI value was 2.9. Using a die coater manufactured by Toray Engineering Co., Ltd., the coating liquid was applied to both sides of an electrolytic copper foil having a thickness of 10 μm at a coating speed of 2 m/s and dried at a drying temperature of 120° C. to form the negative electrode 3. Obtained. The obtained negative electrode 3 was pressed using a roll press machine under the conditions of a pressure of 5 kN/cm and a surface temperature of the press section of 25°C. The total thickness of the pressed negative electrode 3 was measured at 10 arbitrary positions on the negative electrode 3 using a film thickness meter Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. The thickness of the negative electrode active material layer of the negative electrode 3 was obtained by subtracting the thickness of the copper foil from the average value of the measured total thickness. As a result, the film thickness of the negative electrode active material layer was 31 μm on each side.

[Measurement of capacity per unit weight of negative electrode]
One piece of the obtained negative electrode 3 was cut into a size of 1.4 cm×2.0 cm (2.8 cm ² ), and one layer of the negative electrode active material layer coated on both sides of the copper foil was replaced with a spatula, a brush, or It was removed using a brush to make a working electrode. LiPF ₆ was dissolved at a concentration of 1.0 mol/L in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:1 using metallic lithium as a counter electrode and a reference electrode, respectively. An electrochemical cell was prepared in an argon box using a non-aqueous solution.
The initial charge capacity of the obtained electrochemical cell was measured by the following procedure using a charging/discharging device (TOSCAT-3100U) manufactured by Toyo System Co., Ltd.
Against the electrochemical cell, at a temperature 25 ° C., after the voltage value at a current value 0.5 mA / cm ² was subjected to constant current charging until 0.01 V, further the current value reached 0.01 mA / cm ² Constant voltage charging was performed. When the charge capacity at the time of constant current charge and constant voltage charge was evaluated as the initial charge capacity, it was 0.74 mAh, and the capacity per unit mass of the negative electrode 3 (lithium ion doping amount) was 545 mAh/g. ..

<Preparation of electrolyte>
As the organic solvent, a mixed solvent of ethylene carbonate (EC):ethyl methyl carbonate (EMC)=33:67 (volume ratio) was used, and the concentration of LiPF ₆ was 1.2 mol/L with respect to the total electrolytic solution. The electrolyte salt was dissolved to obtain a non-aqueous electrolyte solution 2.

<Preparation of non-aqueous alkali metal ion capacitor>
The obtained positive electrode precursor 3 was prepared so that the positive electrode active material layer had a size of 10.0 cm×10.0 cm (100 cm ² ), ^two positive electrode precursors 3 (one side), and three positive electrode precursors 3 (both sides). 19 sheets were cut out. Then, 20 sheets of the negative electrode 3 were cut out so that the negative electrode active material layer had a size of 10.1 cm×10.1 cm (102 cm ² ). In addition, 40 sheets of 10.3 cm×10.3 cm (106 cm ² ) polyethylene separator (Asahi Kasei Corporation, thickness 10 μm) were prepared. These are laminated so that the positive electrode active material layer and the negative electrode active material layer face each other with the positive electrode precursor 3, the separator, and the negative electrode 3 sandwiched in this order so that the outermost layer is the positive electrode precursor 3 (one surface). An electrode laminate was obtained. A positive electrode terminal and a negative electrode terminal were ultrasonically welded to the obtained electrode laminate, placed in a container formed of an aluminum laminate packaging material, and three sides including the electrode terminal portion were sealed by heat sealing.

About 70 g of the non-aqueous electrolyte solution 2 was injected into the electrode laminate housed in the aluminum laminate packaging material under atmospheric pressure at a temperature of 25° C. and a dew point of −40° C. or less in a dry air environment. Subsequently, the aluminum laminate packaging material containing the electrode laminate and the non-aqueous electrolyte solution was placed in a decompression chamber, the pressure was reduced from atmospheric pressure to -87 kPa, the pressure was returned to atmospheric pressure, and the mixture was left standing for 5 minutes. Then, after depressurizing the packaging material in the chamber from atmospheric pressure to −87 kPa, the process of returning to atmospheric pressure was repeated 4 times, and then allowed to stand for 15 minutes. Furthermore, the packaging material in the chamber was depressurized from atmospheric pressure to -91 kPa and then returned to atmospheric pressure. Similarly, the step of decompressing and returning to atmospheric pressure was repeated 7 times in total (from atmospheric pressure to -95, -96, -97, -81, -97, -97, -97 kPa, respectively). Through the above steps, the non-aqueous electrolyte solution 2 was impregnated into the electrode laminate.

Then, the electrode laminate impregnated with the non-aqueous electrolyte solution 1 was placed in a vacuum sealer, and the aluminum laminate packaging material was sealed at 180° C. for 10 seconds under a pressure of 0.1 MPa under a reduced pressure of −95 kPa. Sealed.

[Pre-doping process]
The electrode laminate obtained after the sealing was placed in an argon box having a temperature of 25° C., a dew point of −60° C. and an oxygen concentration of 1 ppm. The excess portion of the aluminum laminate packaging material was cut and opened, and constant-current charging was performed using a power source (P4LT18-0.2) manufactured by Matsusada Precision Co., Ltd. at a current value of 100 mA until a voltage of 4.5 V was reached. After that, initial charging was performed by a method of continuously performing 4.5 V constant voltage charging for 72 hours, and the negative electrode was pre-doped. After the pre-doping was completed, the aluminum laminate was sealed using a heat sealing machine (FA-300) manufactured by Fuji Impulse.

[Aging process]
The electrode layered body after pre-doping was taken out from the argon box and subjected to constant current discharge at 100 mA under a 25° C. environment until the voltage reached 3.8 V, and then 3.8 V constant current discharge was performed for 1 hour to change the voltage. Adjusted to 3.8V. Then, the electrode laminate was stored in a constant temperature bath at 60° C. for 48 hours.

[Degassing process]
A part of the aluminum laminate packaging material of the electrode laminate after aging was opened in a dry air environment having a temperature of 25° C. and a dew point of −40° C. Subsequently, the electrode laminate was put into a decompression chamber, and a diaphragm pump (N816, KT.45.18, manufactured by KNF) was used to reduce the pressure from atmospheric pressure to -80 kPa for 3 minutes, and then for 3 minutes. The process of returning to atmospheric pressure was repeated three times in total. After that, the electrode laminate was put in a vacuum sealing machine, the pressure was reduced to -90 kPa, and then the aluminum laminate packaging material was sealed by sealing at 200° C. for 10 seconds at a pressure of 0.1 MPa to obtain a non-aqueous alkali metal ion capacitor. Was produced. Two non-aqueous alkali metal ion capacitors were produced by the above process.

<Evaluation of non-aqueous alkali metal ion capacitors>
[Measurement of capacitance Fa]
About one of the obtained non-aqueous alkali metal ion capacitors, using a charging/discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Fukushima Co., Ltd. in a constant temperature bath set at 25° C., a current of 2C Constant current charging was performed until the value (1.6 A) reached 3.8 V, and then constant voltage charging for applying a constant voltage of 3.8 V was performed for a total of 30 minutes. Then, the electrostatic capacity calculated by F=Q/(3.8-2.2), where Q(C) is the capacity when constant current discharge is performed at a current value of 2C (1.6A) up to 2.2V. The capacity Fa was 2046F.

[Measurement of internal resistance Ra]
Regarding the non-aqueous alkali metal ion capacitor obtained in the above step, using a charging/discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Fukushima Co., Ltd. in a constant temperature bath set at 25°C, a current value of 20C ( 16 A), constant current charging was performed until reaching 3.8 V, and then constant voltage charging for applying a constant voltage of 3.8 V was performed for a total of 30 minutes. After that, the sampling time was set to 0.1 seconds, and constant current discharge was performed at a current value of 20 C (16 A) to 2.2 V to obtain a discharge curve (time-voltage). In this discharge curve, the voltage at discharge time=0 second obtained by extrapolating by linear approximation from the voltage values at the discharge time of 2 seconds and 4 seconds is Eo, and the drop voltage ΔE=3.8−Eo, and When the internal resistance Ra was calculated from R=ΔE/(current value 20 C), it was 0.68 mΩ.

[High temperature storage test]
With respect to the non-aqueous alkali metal ion capacitor, a charging/discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. was used in a constant temperature bath set at 25° C. and a current value (60A) of 100C was 4.0V. Constant-current charging was carried out until the temperature reached 10° C., and then constant-voltage charging applying a constant voltage of 4.0 V was performed for a total of 10 minutes. Then, the cell was stored in a 60° C. environment, taken out of the 60° C. environment every two weeks, charged to a cell voltage of 4.0 V in the same charging step, and then stored again in the 60° C. environment. .. This step was repeated for 2 months, and the cell volume Va before the storage test was started and the cell volume Vb after 2 months of the storage test were measured using Fluorinert (trademark registered, 3M Japan Co., Ltd.) FC-40 as a measurement solvent at 25°C. Under the environment, it was measured by the Archimedes method. The value B obtained by normalizing the gas generation amount (cc) obtained by Vb-Va by the capacitance Fa was 2.41×10 ⁻³ cc/F.
The calculated internal resistance Rb of the non-aqueous alkali metal ion capacitor after the high temperature storage test was 0.77 mΩ. As a result, Rb/Ra was calculated as 1.13.

<Determination of alkali metal ions and alkaline earth metal ions in non-aqueous electrolyte>
The obtained remaining non-aqueous alkali metal ion capacitor was cut in one side of the outer package in an argon box having a dew point temperature of −72° C., and 1.323 g of a non-aqueous electrolytic solution was collected using a pipette. By analyzing the obtained non-aqueous electrolytic solution by ICP-MS, the molar concentration X (mol/L) of alkali metal ions and the molar concentration Y (mol/L) of alkaline earth metal ions in the electrolytic solution were determined as follows. It was possible to calculate X/(X+Y)=0.71.

<Quantification of alkali metal compound and alkaline earth metal compound in positive electrode>
[Preparation of positive electrode sample]
The non-aqueous alkali metal ion capacitor was disassembled in an argon box with a dew point temperature of -72°C, and two positive electrodes each having a positive electrode active material layer coated on both sides were cut into a size of 5 cm x 5 cm (weight 0.278 g). Each of the obtained positive electrodes was immersed in 30 g of a diethyl carbonate solvent, the positive electrodes were occasionally moved with tweezers, and the positive electrodes were washed for 10 minutes. Subsequently, the positive electrode was taken out of the solvent, air-dried in an argon box for 5 minutes, immersed in a newly prepared 30 g of a diethyl carbonate solvent, and washed for 10 minutes by the same method as above. The washed positive electrode was taken out from the argon box and dried for 20 hours under the conditions of a temperature of 25° C. and a pressure of 1 kPa using a vacuum dryer (DP33 manufactured by Yamato Scientific Co., Ltd.) to obtain two positive electrode samples 2.

[Calculation of Amount C of Alkali Metal Compound and/or Alkaline Earth Metal Compound in Positive Electrode Active Material]
One piece of the positive electrode sample 2 was immersed in 30 g of an ethanol solvent, the container was covered, and the container was left standing in a 25° C. environment for 3 days. After that, the positive electrode sample 2 was taken out and dried under vacuum at 120° C. and 5 kPa for 10 hours, and the weight M ₀ was 0.263 g. With respect to the washed ethanol solution, GC/MS was measured under the condition that a calibration curve was prepared in advance, and it was confirmed that the amount of diethyl carbonate present was less than 1%. After that, the positive electrode sample 2 was impregnated with 26.3 g of distilled water, the container was capped, and the container was allowed to stand in a 45° C. environment for 3 days. Thereafter, the positive electrode sample 2 was taken out and vacuum dried under the conditions of 150° C. and 3 kPa for 12 hours. The weight M ₁ of the positive electrode sample 2 after vacuum drying was 0.255 g. With respect to distilled water after washing, GC/MS was measured under the condition that a calibration curve was prepared in advance, and it was confirmed that the amount of ethanol present was less than 1%. Then, the active material layer on the positive electrode current collector was removed using a spatula, a brush, or a brush, and the weight of the positive electrode current collector was measured, and it was M ₂ =0.099 g. Z=4.9 was calculated from the weights M ₀ , M ₁ and M ₂ according to the equation (6).

<A ₁ OyobiA ₂ Nosanshutsu_>
[SEM and EDX measurement of positive electrode surface]
The remaining positive electrode sample 2 prepared above was immersed in 30 g of a diethyl carbonate solvent, the positive electrode was occasionally moved with tweezers, and washed for 10 minutes. Then, the positive electrode was taken out from the solvent, air-dried in an argon box for 5 minutes, immersed in a newly prepared 30 g of diethyl carbonate solvent, and washed for 10 minutes by the same method as described above. The positive electrode was taken out of the argon box, and dried for 20 hours under the conditions of a temperature of 25° C. and a pressure of 1 kPa using a vacuum dryer (DP33 manufactured by Yamato Scientific Co., Ltd.). A small piece of 1 cm×1 cm was cut out from the obtained positive electrode sample 2, and the surface was coated with gold by sputtering in a vacuum of 10 Pa. Then, under the conditions shown below, SEM and EDX of the positive electrode surface were measured under atmospheric exposure.
(SEM-EDX measurement conditions)
・Measuring device: Hitachi High-Technology, field emission scanning electron microscope FE-SEM S-4700, manufactured by Horiba, energy dispersive X-ray analyzer EMAX
・Acceleration voltage: 10 kV
・Emission current: 10 μA
・Measurement magnification: 2000 times ・Electron beam incident angle: 90°
・X-ray extraction angle: 30°
・Dead time: 15%
・Mapping elements: C, O, F
-Number of measurement pixels: 256 x 256 pixels-Measurement time: 60 sec.
-Number of integration: 50 times-The brightness and contrast were adjusted so that there were no pixels reaching the maximum brightness value in the mapping image and the average value of the brightness values was within the range of 40% to 60% of the maximum brightness value.

(Analysis of SEM-EDX)
For the obtained oxygen mapping and fluorine mapping, image analysis software (ImageJ) was used to perform binarization based on the average value of the brightness values. The area of oxygen mapping at this time was 15.4% and the area of fluorine mapping was 31.4% with respect to all images. The overlapping area of the oxygen mapping and the fluorine mapping obtained by binarization is 13.1% for all images, and when the area overlapping ratio of the fluorine mapping to the oxygen mapping is A ₁ (%), A ₁ =100 From X13.1/15.4, it was 85.1%.

[Cathode cross section SEM and EDX measurement]
A small piece of 1 cm x 1 cm was cut out from the positive electrode sample 2, and SM-0902CP manufactured by JEOL Ltd. was used, and argon gas was used. A cross section was prepared. Then, the positive electrode cross section SEM and EDX were measured by the above-mentioned method.
Regarding the obtained SEM-EDX of the cross section of the positive electrode, oxygen mapping and fluorine mapping were binarized in the same manner as above, and the area overlap ratio A ₂ of fluorine mapping with respect to oxygen mapping was calculated to be 38.4%.

<Example 41>
In the initial charge of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, then 4.5 V constant voltage charging was continued for 36 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the negative electrode was pre-doped.

<Example 42>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, and then 4.5 V constant voltage charging was continued for 12 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the negative electrode was pre-doped.

<Example 43>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.6 V, by continuously continuing 4.6 V constant voltage charging for 72 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the negative electrode was pre-doped.

<Example 44>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.6 V, by continuously continuing 4.6 V constant voltage charging for 36 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 43 except that the negative electrode was pre-doped.

<Example 45>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was carried out at a current value of 100 mA until the voltage reached 4.6 V, by continuing 4.6 V constant voltage charging for 12 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 43 except that the negative electrode was pre-doped.

<Example 46>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.3 V, by continuing 4.3 V constant voltage charging for 72 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the negative electrode was pre-doped.

<Example 47>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.3 V, by continuing 4.3 V constant voltage charging for 36 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 46 except that the negative electrode was pre-doped.

<Example 48>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was carried out at a current value of 100 mA until the voltage reached 4.3 V, by continuing 4.3 V constant voltage charging for 12 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 46 except that the negative electrode was pre-doped.

<Example 49>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the carbonate mixture was prepared using 150 g of lithium carbonate and 50 g of calcium carbonate.

<Example 50>
In the initial charge of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, then 4.5 V constant voltage charging was continued for 36 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 49 except that the negative electrode was pre-doped.

<Example 51>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, and then 4.5 V constant voltage charging was continued for 12 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 49 except that the negative electrode was pre-doped.

<Example 52>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that a carbonate mixture was prepared using 75 g of lithium carbonate and 125 g of calcium carbonate.

<Example 53>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the carbonate mixture was prepared using 30 g of lithium carbonate and 170 g of calcium carbonate.

<Example 54>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the carbonate mixture was prepared using 10 g of lithium carbonate and 190 g of calcium carbonate.

<Example 55>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the carbonate mixture was prepared using 200 g of calcium carbonate.

<Example 56>
In the initial charge of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, then 4.5 V constant voltage charging was continued for 36 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 55 except that the negative electrode was pre-doped.

<Example 57>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, and then 4.5 V constant voltage charging was continued for 12 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 55 except that the negative electrode was pre-doped.

<Comparative Example 29>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the carbonate mixture was prepared by using only 200 g of lithium carbonate instead of 100 g of lithium carbonate and 100 g of calcium carbonate.

<Comparative Example 30>
In the initial charge of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, then 4.5 V constant voltage charging was continued for 36 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 29 except that the negative electrode was pre-doped.

<Comparative Example 31>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, and then 4.5 V constant voltage charging was continued for 12 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 29 except that the negative electrode was pre-doped.

<Comparative Example 32>
A carbonate mixture was prepared by using only 200 g of calcium carbonate instead of 100 g of lithium carbonate and 100 g of calcium carbonate, and ethylene carbonate (EC):ethyl methyl carbonate (EMC)=33:67 (volume ratio) was used as an electrolytic solution. Nonaqueous alkaline earth metal was prepared in the same manner as in Example 40 except that a nonaqueous electrolytic solution in which an electrolyte salt was dissolved was used in the mixed solvent so that the concentration of Ca(PF ₆ ) ₂ was 0.6 mol/L. A power storage element was produced.

<Comparative Example 33>
In the initial charge of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, then 4.5 V constant voltage charging was continued for 36 hours, A non-aqueous alkaline earth metal storage element was produced in the same manner as in Comparative Example 32 except that the negative electrode was pre-doped.

<Comparative Example 34>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, and then 4.5 V constant voltage charging was continued for 12 hours, A non-aqueous alkaline earth metal storage element was produced in the same manner as in Comparative Example 32 except that the negative electrode was pre-doped.

<Comparative Example 35>
A carbonate mixture was prepared using 10 g of lithium carbonate and 190 g of calcium carbonate, and Ca(PF ₆ ) was added to a mixed solvent of ethylene carbonate (EC):ethyl methyl carbonate (EMC)=33:67 (volume ratio) as an electrolytic solution. ) A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that the non-aqueous electrolytic solution in which the electrolyte salt was dissolved was used so that the concentration of ₂ became 0.6 mol/L.

<Comparative Example 36>
In the initial charge of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, then 4.5 V constant voltage charging was continued for 36 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 35 except that the negative electrode was pre-doped.

<Comparative Example 37>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, and then 4.5 V constant voltage charging was continued for 12 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 35 except that the negative electrode was pre-doped.

<Comparative Example 38>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 40 except that a carbonate mixture was prepared using 190 g of lithium carbonate and 10 g of calcium carbonate.

<Comparative Example 39>
In the initial charge of the non-aqueous alkali metal ion capacitor in the pre-doping step, after constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, then 4.5 V constant voltage charging was continued for 36 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 38 except that the negative electrode was pre-doped.

<Comparative Example 40>
In the initial charging of the non-aqueous alkali metal ion capacitor in the pre-doping step, constant current charging was performed at a current value of 100 mA until the voltage reached 4.5 V, and then 4.5 V constant voltage charging was continued for 12 hours, A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 38 except that the negative electrode was pre-doped.

<Comparative Example 41>
Lithium carbonate was crushed for 5 minutes at a peripheral speed of 10.0 m/s for 5 minutes in a 25° C. environment using φ1.0 mm zirconia beads, and a coating solution was prepared by using a 100% solvent of NMP (N-methylpyrrolidone). A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 29 except that the above was used.

<Comparative Example 42>
Lithium carbonate was crushed for 5 minutes at a peripheral speed of 10.0 m/s for 5 minutes in a 25° C. environment using φ1.0 mm zirconia beads, and a coating solution was prepared by using a 100% solvent of NMP (N-methylpyrrolidone). A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 30 except that the above was used.

<Comparative Example 43>
Lithium carbonate was crushed for 5 minutes at a peripheral speed of 10.0 m/s for 5 minutes in a 25° C. environment using φ1.0 mm zirconia beads, and a coating solution was prepared by using a 100% solvent of NMP (N-methylpyrrolidone). A non-aqueous alkali metal ion capacitor was produced in the same manner as in Comparative Example 31 except that the above procedure was performed.

<Comparative Example 44>
Calcium carbonate was crushed for 5 minutes at a peripheral speed of 10.0 m/s in a 25° C. environment using φ1.0 mm zirconia beads, and the coating solution was prepared as a 100% solvent of NMP (N-methylpyrrolidone). A non-aqueous alkaline earth metal storage element was produced in the same manner as in Comparative Example 32 except that the above was used.

<Comparative Example 45>
Calcium carbonate was crushed for 5 minutes at a peripheral speed of 10.0 m/s in a 25° C. environment using φ1.0 mm zirconia beads, and the coating solution was prepared as a 100% solvent of NMP (N-methylpyrrolidone). A non-aqueous alkaline earth metal storage element was produced in the same manner as in Comparative Example 33 except that the above was used.

<Comparative Example 46>
Calcium carbonate was crushed for 5 minutes at a peripheral speed of 10.0 m/s in a 25° C. environment using φ1.0 mm zirconia beads, and the coating solution was prepared as a 100% solvent of NMP (N-methylpyrrolidone). A non-aqueous alkaline earth metal storage element was produced in the same manner as in Comparative Example 34 except that the above procedure was performed.

Table 3 shows the evaluation results of Examples 40 to 57 and Comparative Examples 29 to 46.

<Example 58>
<Crushing of alkali metal compound and alkaline earth metal compound>
100 g of sodium carbonate having an average particle diameter of 55 μm and 100 g of calcium carbonate having an average particle diameter of 60 μm were dry-blended and cooled to −196° C. with liquid nitrogen using a grinder (liquid nitrogen bead mill LNM) manufactured by IMEX Co., and then φ1. Using 0 mm zirconia beads, the mixture was ground for 20 minutes at a peripheral speed of 10.0 m/s to obtain a carbonate mixture 2. By cooling to -196°C, brittle fracture can be performed while preventing thermal denaturation of sodium carbonate and calcium carbonate. The average particle size of the obtained carbonate mixture 2 was measured and found to be 3.0 μm.

<Production of positive electrode precursor>
50.5 parts by mass of activated carbon 1b, 40.0 parts by mass of carbonate mixture 2, 3.0 parts by mass of Ketjen Black, 1.5 parts by mass of PVP (polyvinylpyrrolidone), and PVDF (polyvinylidene fluoride). Positive electrode precursor 4 (single-sided) and positive electrode precursor 4 were prepared in the same manner as in Example 40 except that 5.0 parts by mass and a mixed solvent of NMP (N-methylpyrrolidone) and pure water of 99:1 were mixed. (Both sides) was prepared.

<Preparation of Negative Electrode Active Material Preparation Example 2>
The BET specific surface area and the pore distribution of the commercially available coconut shell activated carbon were measured by the method described above using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 1,790 m ² /g, the mesopore volume (V ₁ ) was 0.199 cc/g, the micropore volume (V ₂ ) was 0.698 cc/g, and V ₁ /V ₂ =0. 29, and the average pore diameter was 20.1Å.
300 g of this coconut shell activated carbon was placed in a basket made of stainless steel mesh and placed on a stainless steel bat containing 540 g of coal-based pitch (softening point: 50° C.), and both were placed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). The coconut shell activated carbon and the coal-based pitch were heated to 600° C. in a nitrogen atmosphere for 8 hours and kept at the same temperature for 4 hours for thermal reaction to obtain a composite porous carbon material 1a. The obtained composite porous carbon material 1a was cooled to 60° C. by natural cooling and then taken out from the electric furnace.
The BET specific surface area and the pore distribution of the obtained composite porous carbon material 1a were measured by the same method as described above. As a result, the BET specific surface area was 262 m ² /g, the mesopore amount (V _m1 ) was 0.186 cc/g, the micropore amount (V _m2 ) was 0.082 cc/g, and V _m1 /V _m2 =2.27. there were. In the composite porous carbon material 1a, the mass ratio of the carbonaceous material derived from coal-based pitch to the activated carbon was 78%.

<Manufacture of negative electrode>
A negative electrode was manufactured using the composite porous carbon material 1a as a negative electrode active material.
84 parts by mass of the composite porous carbon material 1a, 10 parts by mass of acetylene black, 6 parts by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed, and the mixture was a thin film manufactured by PRIMIX. A swirling high-speed mixer FILMIX was used to disperse under a condition of a peripheral speed of 17 m/s to obtain a coating liquid. The viscosity (ηb) and TI value of the obtained coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,789 mPa·s and the TI value was 4.3. Using a die coater manufactured by Toray Engineering Co., Ltd., the coating liquid was applied on both sides of an electrolytic copper foil having a thickness of 10 μm at a coating speed of 2 m/s and dried at a drying temperature of 120° C. to obtain a negative electrode 4. It was The obtained negative electrode 4 was pressed using a roll press machine under the conditions of a pressure of 5 kN/cm and a surface temperature of the press section of 25°C. The total thickness of the pressed negative electrode 4 was measured at 10 arbitrary positions on the negative electrode 4 using a film thickness meter Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. The thickness of the negative electrode active material layer of the negative electrode 4 was obtained by subtracting the thickness of the copper foil from the average value of the measured total thickness. As a result, the thickness of the negative electrode active material layer was 40 μm on each side.

[Measurement of capacity per unit weight of negative electrode]
One piece of the obtained negative electrode 4 was cut into a size of 1.4 cm×2.0 cm (2.8 cm ² ) and one layer of the negative electrode active material layer coated on both sides of the copper foil was replaced with a spatula, a brush, or It was removed using a brush to make a working electrode. LiPF ₆ was dissolved at a concentration of 1.0 mol/L in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:1 using metallic lithium as a counter electrode and a reference electrode, respectively. An electrochemical cell was prepared in an argon box using a non-aqueous solution.
The initial charge capacity of the obtained electrochemical cell was measured by the following procedure using a charging/discharging device (TOSCAT-3100U) manufactured by Toyo System Co., Ltd.
Against the electrochemical cell, at a temperature 25 ° C., after the voltage value at a current value 0.5 mA / cm ² was subjected to constant current charging until 0.01 V, further the current value reached 0.01 mA / cm ² Constant voltage charging was performed. When the charging capacity during constant current charging and constant voltage charging was evaluated as the initial charging capacity, it was 1.6 mAh, and the capacity per unit mass of the negative electrode 4 (lithium ion doping amount) was 1460 mAh/g. ..

<Preparation and evaluation of non-aqueous lithium storage element>
A nonaqueous lithium electricity storage element was prepared and evaluated in the same manner as in Example 40 except that two positive electrode precursors 4 (one side), nineteen positive electrode precursors 4 (both sides) and twenty negative electrodes 4 were used. did.

<Example 59>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of potassium carbonate and 100 g of calcium carbonate.

<Example 60>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of rubidium carbonate and 100 g of calcium carbonate.

<Example 61>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of cesium carbonate and 100 g of calcium carbonate.

<Example 62>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium carbonate and 100 g of magnesium carbonate.

<Example 63>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium carbonate and 100 g of beryllium carbonate.

<Example 64>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that a carbonate mixture was prepared using 100 g of lithium carbonate and 100 g of strontium carbonate.

<Example 65>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium carbonate and 100 g of barium carbonate.

<Example 66>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium oxide and 100 g of calcium carbonate.

<Example 67>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium hydroxide and 100 g of calcium carbonate.

<Example 68>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that a carbonate mixture was prepared using 50 g of lithium hydroxide, 50 g of lithium oxide, and 100 g of calcium carbonate.

<Example 69>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium carbonate and 100 g of calcium oxide.

<Example 70>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium carbonate and 100 g of calcium hydroxide.

<Example 71>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium carbonate and 100 g of magnesium oxide.

<Example 72>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium carbonate and 100 g of magnesium hydroxide.

<Example 73>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium oxide and 100 g of calcium oxide.

<Example 74>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of lithium oxide and 100 g of calcium hydroxide.

<Example 75>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of sodium oxide and 100 g of calcium oxide.

<Example 76>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared using 100 g of sodium oxide and 100 g of calcium hydroxide.

<Comparative Example 47>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that a carbonate mixture was prepared by using only 200 g of sodium carbonate instead of 100 g of sodium carbonate and 100 g of calcium carbonate.

<Comparative Example 48>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that a carbonate mixture was prepared by using only 200 g of potassium carbonate instead of 100 g of sodium carbonate and 100 g of calcium carbonate.

<Comparative Example 49>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared by using only 200 g of rubidium carbonate instead of 100 g of sodium carbonate and 100 g of calcium carbonate.

<Comparative Example 50>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture was prepared by using only 200 g of cesium carbonate instead of 100 g of sodium carbonate and 100 g of calcium carbonate.

<Comparative Example 51>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture 2 was replaced with a pulverized product containing only 200 g of sodium oxide.

<Comparative Example 52>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture 2 was replaced with a pulverized product containing only 200 g of potassium oxide.

<Comparative Example 53>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture 2 was replaced with a pulverized product containing only 200 g of sodium hydroxide.

<Comparative Example 54>
A non-aqueous alkali metal ion capacitor was produced in the same manner as in Example 58 except that the carbonate mixture 2 was replaced with a pulverized product containing only 200 g of potassium hydroxide.

<Comparative Example 55>
The carbonate mixture 2 was replaced with a pulverized product of only 200 g of calcium oxide, and as an electrolytic solution, Ca(PF ₆ ) was added to a mixed solvent of ethylene carbonate (EC):ethyl methyl carbonate (EMC)=33:67 (volume ratio). ) A non-aqueous alkaline earth metal storage element was produced in the same manner as in Example 58 except that the non-aqueous electrolytic solution in which the electrolyte salt was dissolved was used so that the concentration of ₂ was 0.6 mol/L.

<Comparative Example 56>
The carbonate mixture 2 was replaced with a pulverized product of only 200 g of calcium hydroxide, and as an electrolytic solution, Ca(PF) was added to a mixed solvent of ethylene carbonate (EC):ethyl methyl carbonate (EMC)=33:67 (volume ratio). ₆ ) A non-aqueous alkaline earth metal storage element was produced in the same manner as in Example 58 except that the non-aqueous electrolytic solution in which the electrolyte salt was dissolved was used so that the concentration of ₂ was 0.6 mol/L.

<Comparative Example 57>
The carbonate mixture 2 was replaced with a pulverized product of only 200 g of magnesium oxide, and as an electrolytic solution, Ca(PF ₆ ) was added to a mixed solvent of ethylene carbonate (EC):ethyl methyl carbonate (EMC)=33:67 (volume ratio). ) A non-aqueous alkaline earth metal storage element was produced in the same manner as in Example 58 except that the non-aqueous electrolytic solution in which the electrolyte salt was dissolved was used so that the concentration of ₂ was 0.6 mol/L.

<Comparative Example 58>
The carbonate mixture 2 was replaced with a pulverized product of only 200 g of magnesium hydroxide, and as an electrolytic solution, Ca(PF) was added to a mixed solvent of ethylene carbonate (EC):ethyl methyl carbonate (EMC)=33:67 (volume ratio). ₆ ) A non-aqueous alkaline earth metal storage element was produced in the same manner as in Example 58 except that the non-aqueous electrolytic solution in which the electrolyte salt was dissolved was used so that the concentration of ₂ was 0.6 mol/L.

Table 4 shows the evaluation results of Examples 58 to 76 and Comparative Examples 47 to 58.

From Table 3 and Table 4, when the non-aqueous electrolyte solution contains an alkali metal ion, the resistance of the electricity storage element can be lowered, and when the non-aqueous electrolyte solution contains an alkaline earth ion metal, the electricity storage element is reduced. It can be seen that the capacity can be increased. Coexistence of these alkali metal ions and alkaline earth ions in the non-aqueous electrolyte makes it possible to achieve both low resistance and high capacity of the electricity storage device.

Further, from Table 3, it was found that the crushing of the alkali metal compound and/or the alkaline earth metal compound was carried out under the extremely low temperature condition of -196° C., so that the generation of defects on the particle surface was not affected by the temperature rise during the crushing. It is thought that it could be suppressed. As a result, it is considered that the reaggregation of the alkali metal compound and/or the alkaline earth metal compound could be suppressed. Furthermore, the surface of the alkali metal compound and/or the alkaline earth metal compound is activated by adding a small amount of water when preparing the coating liquid, and LiPF _6, which is a fluorine-containing electrolyte, is efficiently formed on the surface of the particles. It is considered that the compound can be decomposed, and the resulting fluorine compound is evenly deposited, and the high temperature storage property is improved.

In the non-aqueous alkali metal ion capacitor of the present invention, for example, a plurality of non-aqueous alkali metal ion capacitors can be connected in series or in parallel to make an electricity storage module. The non-aqueous alkali metal ion capacitor and the electricity storage module of the present invention are a power regeneration system for a hybrid drive system of an automobile that requires high-load charge/discharge cycle characteristics, natural power generation such as solar power generation and wind power generation, and power generation in a microgrid. Load leveling system, uninterruptible power supply system in factory production equipment, contactless power supply system for leveling voltage fluctuations such as microwave power transmission and electric field resonance, and energy storage, and power generated by vibration power generation. It can be suitably used for energy harvesting systems intended for use.
The non-aqueous alkali metal ion capacitor of the present invention is preferable because the effect of the present invention can be maximized when it is applied as an alkali metal ion capacitor or an alkali metal ion secondary battery.

Claims (32)

A non-aqueous alkali metal ion capacitor comprising a positive electrode containing activated carbon, a negative electrode, a separator, and a non-aqueous electrolytic solution containing two or more cations, wherein at least one of the two or more cations is A non-aqueous alkali metal ion capacitor in which the compound containing an alkali metal ion and the same kind of element as the two or more cations is contained in the positive electrode in an amount of 1.0% by mass or more and 25.0% by mass or less. The negative electrode can store and release alkali metal ions, and the compound contained in the positive electrode is a compound of two or more kinds of alkali metals selected from the group consisting of Li, Na, K, Rb, and Cs, The non-aqueous alkali metal ion capacitor according to claim 1, wherein the positive electrode contains the alkali metal compound in an amount of 1% by mass or more and 25% by mass or less. The positive electrode includes a positive electrode current collector, the negative electrode includes a negative electrode current collector, and the positive electrode current collector and the negative electrode current collector are metal foils having no through holes. The non-aqueous alkali metal ion capacitor described. The non-aqueous alkali metal ion capacitor according to any one of claims 1 to 3, wherein the compound of the alkali metal is one or more selected from the group consisting of carbonates, hydroxides, and oxides. The positive electrode comprises a positive electrode current collector, wherein provided on the positive electrode current collector one side or on both sides on, and a positive electrode active material layer containing a positive electrode active material, the positive active material layer is a compound represented by the following formula (1)-(3):

{In the formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are each independently -(COO) _n. (Where n is 0 or 1) and M ¹ and M ² are each independently an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs. }

{In the formula (2), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² is hydrogen, an alkyl group having 1 to 10 carbon atoms, carbon Group consisting of mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms, mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, cycloalkyl group having 3 to 6 carbon atoms, and aryl group X ¹ and X ² are each independently —(COO) _n (where n is 0 or 1), and M ¹ is Li, Na, K. Is an alkali metal selected from the group consisting of Rb, Rb, and Cs. }

{In the formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and 1 carbon atoms. -10 alkyl group, mono- or polyhydroxyalkyl group having 1-10 carbon atoms, alkenyl group having 2-10 carbon atoms, mono- or polyhydroxyalkenyl group having 2-10 carbon atoms, cycloalkyl group having 3-6 carbon atoms , And an aryl group, and X ¹ and X ² are each independently —(COO) _n (where n is 0 or 1). }
Is to one or more compounds positive electrode active material layer per unit mass ^{1.60 × 10 -4 mol / g~300 ×} 10 -4 mol / g containing a is selected from any of claims 1 to 4 one A non-aqueous alkali metal ion capacitor according to item. The positive electrode active material layer has the following formulas (4) and (5):

{In the formula (4), M ¹ and M ² are each independently an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs. }

{In the formula (5), R ¹ is hydrogen, an alkyl group having 1 to 10 carbon atoms, or a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and 2 to 10 carbon atoms. A mono- or polyhydroxyalkenyl group, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group, and M is a group consisting of Li, Na, K, Rb, and Cs. It is the alkali metal of choice. }
One or more compounds to the positive electrode active material layer per unit mass ^{2.70 × 10 -4 mol / g~150 ×} 10 -4 mol / g containing selected from non-aqueous alkali of claim 5 Metal ion capacitor. The non-aqueous electrolyte solution contains two or more and four or less alkali metal ions, and the substance ratio of the first alkali metal ions in the non-aqueous electrolyte solution is 1% or more and 99% or less, and the second 7. The substance amount ratio of the alkali metal ions is 1% or more and 99% or less, and the substance amount ratio of the third and fourth alkali metal ions is 0% or more and 98% or less. The non-aqueous alkali metal ion capacitor described in. The negative electrode can store and release alkali metal ions,
The non-aqueous electrolyte solution contains at least one alkali metal ion and at least one alkaline earth metal ion,
The alkali metal compound having the alkali metal ion as a cation and/or the alkaline earth metal compound having the alkali earth metal ion as a cation is 1.0% by mass or more in the positive electrode active material layer of the positive electrode 20 0.0 mass% or less, and the molar concentration of the alkali metal ions in the non-aqueous electrolyte is X (mol/L), and the molar concentration of the alkaline earth metal ions is Y (mol/L). At this time, X/(X+Y) is 0.07 or more and 0.92 or less,
The non-aqueous alkali metal ion capacitor according to claim 1. The non-aqueous alkali metal ion capacitor according to claim 8, wherein the X/(X+Y) is 0.10 or more and 0.90 or less. In the elemental mapping obtained by scanning electron microscope-energy dispersive X-ray analysis (SEM-EDX) on the surface of the positive electrode, the area overlap ratio A of fluorine mapping with respect to oxygen mapping binarized based on the average value of luminance values is shown. The non-aqueous alkali metal ion capacitor according to claim 8 or 9, wherein ₁ is 40% or more and 99% or less. In the elemental mapping obtained by SEM-EDX of the cross section of the positive electrode processed by broad ion beam (BIB), the area overlapping rate A ₂ of the fluorine mapping with respect to the oxygen mapping binarized based on the average value of the brightness value is 10%. The non-aqueous alkali metal ion capacitor according to any one of claims 8 to 10, which is not less than 60%. The non-aqueous alkali metal ion capacitor according to any one of claims 8 to 11, wherein the alkali metal compound and/or the alkaline earth metal compound is a carbonate. The non-aqueous alkali metal ion capacitor according to any one of claims 8 to 12, wherein the alkaline earth metal ion is calcium ion. The non-aqueous alkali metal ion capacitor according to any one of claims 8 to 13, wherein the alkali metal ion is one or more selected from the group consisting of lithium ion, sodium ion, and potassium ion. The positive electrode has a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material provided on one surface or both surfaces of the positive electrode current collector, and the positive electrode included in the positive electrode active material layer. The active material has V ₁ (cc/g) as the mesopore amount derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method, and the micropore amount derived from pores having a diameter of less than 20 Å calculated by the MP method. When V ₂ (cc/g), 0.3<V ₁ ≦0.8 and 0.5≦V ₂ ≦1.0 are satisfied, and the specific surface area measured by the BET method is 1,500 m. activated carbon showing a ² / g or more 3,000 m ² / g or less, non-aqueous alkali metal ion capacitor according to any one of claims 1 to 14. The positive electrode has a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material provided on one surface or both surfaces of the positive electrode current collector, and the positive electrode included in the positive electrode active material layer. The active material has a mesopore amount V ₁ (cc/g) derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method that satisfies 0.8<V ₁ ≦2.5, and a diameter calculated by the MP method. The micropore amount V ₂ (cc/g) derived from pores of less than 20Å satisfies 0.8<V ₂ ≦3.0, and the specific surface area measured by the BET method is 2,300 m ² /g or more. The non-aqueous alkali metal ion capacitor according to any one of claims 1 to 14, which is an activated carbon showing 4,000 m ² /g or less. The negative electrode contains a negative electrode active material, and a doping amount of lithium ions of the negative electrode active material is 530 mAh/g or more and 2,500 mAh/g or less per unit mass, according to any one of claims 1 to 16. Non-aqueous alkali metal ion capacitor. The non-aqueous alkali metal ion capacitor according to claim 17, wherein the negative electrode active material has a BET specific surface area of 100 m ² /g or more and 1,500 m ² /g or less. The non-aqueous system according to any one of claims 1 to 16, wherein the negative electrode contains a negative electrode active material, and a doping amount of lithium ions in the negative electrode active material is 50 mAh/g or more and 700 mAh/g or less per unit mass. Alkali metal ion capacitor. The non-aqueous alkali metal ion capacitor according to claim 19, wherein the negative electrode active material has a BET specific surface area of 1 m ² /g or more and 50 m ² /g or less. The non-aqueous alkali metal ion capacitor according to any one of claims 17 to 20, wherein the negative electrode active material has an average particle size of 1 µm or more and 10 µm or less. In the non-aqueous alkali metal ion capacitor, after being stored at a cell voltage of 4 V and an environmental temperature of 60° C. for 2 months, the internal resistance at a cell voltage of 4 V is Rb (Ω), the internal resistance before storage is Ra (Ω), When the capacitance before storage is Fa(F), the following requirements (a) and (b):
(A) Rb/Ra is 3.0 or less, and (b) the value B obtained by normalizing the amount of gas generated when stored for 2 months at a cell voltage of 4 V and an environmental temperature of 60° C. by the capacitance Fa is 30. ×10 ⁻³ cc/F or less,
22. The non-aqueous alkali metal ion capacitor according to any one of claims 1 to 21, which simultaneously satisfies all of the above. In the non-aqueous alkali metal ion capacitor, the cell voltage was changed from 2.2 V to 3.8 V and the charge/discharge cycle was performed 60,000 times at a current value of 200 C at an ambient temperature of 25° C. 23. The non-aqueous alkali metal ion capacitor according to claim 22, wherein Fb/Fa is 1.01 or more, where Fb(F) is a capacitance after the constant voltage charging of 1 hour is performed. A positive electrode precursor containing activated carbon and an alkali metal compound having two or more kinds of alkali metal ions selected from the group consisting of Li, Na, K, Rb, and Cs as cations, the first alkali metal compound Is 2% or more and 98% or less, the second alkali metal compound is 2% or more and 98% or less, and the third and fourth alkali metal ion is 0%. A positive electrode precursor having a content of not less than 96%. The positive electrode precursor according to claim 24, wherein the alkali metal compound is a carbonate, a hydroxide, or an oxide. An electricity storage module using the non-aqueous alkali metal ion capacitor according to any one of claims 1 to 23. A power regeneration system using the non-aqueous alkali metal ion capacitor according to any one of claims 1 to 23. A power load leveling system using the non-aqueous alkali metal ion capacitor according to any one of claims 1 to 23. An uninterruptible power supply system using the non-aqueous alkali metal ion capacitor according to any one of claims 1 to 23. A non-contact power feeding system using the non-aqueous alkali metal ion capacitor according to claim 1. An energy harvesting system using the non-aqueous alkali metal ion capacitor according to any one of claims 1 to 23. An electricity storage system using the non-aqueous alkali metal ion capacitor according to any one of claims 1 to 23.