JP6754657B2 - Non-aqueous lithium storage element - Google Patents

Description

The present invention relates to a non-aqueous lithium storage element.

In recent years, from the viewpoint of effective use of energy aiming at conservation of the global environment and resource saving, power smoothing system or midnight power storage system for wind power generation, distributed power storage system for home use based on solar power generation technology, power storage for electric vehicles Systems and the like are attracting attention.
The first requirement for batteries used in these power storage systems is high energy density. Lithium-ion batteries are being energetically developed as promising candidates for high-energy density batteries that can meet such demands.
The second requirement is that the output characteristics are high. 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 in the power storage system are required during acceleration. There is.

Currently, electric double layer capacitors, nickel-metal hydride batteries, and the like are being developed as high-power power storage devices.
Among the electric double layer capacitors, those using activated carbon for the electrodes have an output characteristic of about 0.5 to 1 kW / L. This electric double layer capacitor has high durability (cycle characteristics and high temperature storage characteristics), and has been considered to be the most suitable device in the field where high output is required. However, its energy density is only about 1 to 5 Wh / L. Therefore, it is necessary to further improve the energy density.

On the other hand, the nickel-metal hydride battery currently used in hybrid electric vehicles has a high output equivalent to that of an electric double layer capacitor and an energy density of about 160 Wh / L. However, research is being vigorously pursued to further increase its energy density and output and to improve its durability (particularly, stability at high temperatures).

In addition, research is underway to increase the output of lithium-ion batteries. For example, a lithium ion battery has been developed in which a high output exceeding 3 kW / L can be obtained at a discharge depth (a value indicating what percentage of the discharge capacity of the power storage element is discharged) of 50%. However, its energy density is 100 Wh / L or less, and the design is such that the high energy density, which is the greatest feature of the lithium ion battery, is intentionally suppressed. In addition, its durability (cycle characteristics and high temperature storage characteristics) is inferior to that of electric double layer capacitors. Therefore, in order to have practical durability, the discharge depth is in a range narrower than the range of 0 to 100%. It will be used in. Since the capacity that can be actually used becomes smaller, research for further improving durability is being vigorously pursued.

As described above, there is a strong demand for practical application of a power storage element having high energy density, high output characteristics, and durability. However, each of the existing power storage elements described above has advantages and disadvantages. Therefore, a new power storage element that satisfies these technical requirements is required. As a promising candidate, a power storage element called a lithium ion capacitor has attracted attention and is being actively developed.
A lithium ion capacitor is a type of power storage element (non-aqueous lithium type power storage element) that uses a non-aqueous electrolyte solution containing a lithium salt, and adsorbs anions similar to those of an electric double layer capacitor at about 3 V or higher at a positive electrode. -A power storage element that charges and discharges by a non-Faraday reaction by desorption and a Faraday reaction by the storage and release of lithium ions at the negative electrode, similar to a lithium ion battery.
To summarize the above-mentioned electrode materials and their characteristics, high output and high durability are achieved when a material such as activated carbon is used for the electrodes and charging / discharging is performed by adsorption / desorption (non-Faraday reaction) of ions on the surface of activated carbon. However, the energy density becomes low (for example, it is multiplied by 1). On the other hand, when an oxide or carbon material is used for the electrode and charging / discharging is performed by the Faraday reaction, the energy density becomes high (for example, 10 times that of the non-Faraday reaction using activated carbon), but the durability and output are increased. There is a problem with the characteristics.

As a combination of these electrode materials, the electric double layer capacitor is characterized by using activated carbon (energy density 1 times) for the positive electrode and the negative electrode and charging / discharging both the positive electrode and the negative electrode by a non-Faraday reaction, and has high output and high durability. However, it is characterized by low energy density (1x positive electrode x 1x negative electrode = 1).

The lithium ion secondary battery is characterized by using a lithium transition metal oxide (energy density 10 times) for the positive electrode and a carbon material (energy density 10 times) for the negative electrode, and charging and discharging both the positive electrode and the negative electrode by a Faraday reaction. Although the energy density is 10 times the positive electrode x 10 times the 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 discharge depth must be limited, and the lithium ion secondary battery can use only 10 to 50% of its energy.

Lithium-ion capacitors use activated carbon (1x energy density) for the positive electrode and carbon material (10x energy density) for the negative electrode, and are characterized by performing charging and discharging by a non-Faraday reaction at the positive electrode and a Faraday reaction at the negative electrode. It is a new asymmetric capacitor that combines the characteristics of a multi-layer capacitor and a lithium-ion secondary battery. The feature is that it has high energy density (1x positive electrode x 10x negative electrode = 10) while having high output and high durability, and it is not necessary to limit the discharge depth unlike a lithium ion secondary battery. is there.

Examples of applications using lithium ion capacitors include electric storage for railways, construction machinery, and automobiles. In these applications, the operating environment is harsh, so the capacitors used are required to have excellent input / output characteristics, high load charge / discharge cycle characteristics, and a high degree of safety at the same time.
As a countermeasure technology for such a requirement, a means for joining an energizing tab to the electrode layer and applying an AC current between the energizing tab and the electrode tab to make the potential distribution of the electrode uniform and improve durability (hereinafter referred to as “durability”). (Refer to Patent Document 1), a means for improving the uniformity of potential between electrodes by attaching terminals capable of measuring potential to electrodes and charging / discharging each terminal independently by referring to the potential obtained from the terminals. (See Patent Document 2 below) have been proposed respectively.

However, by attaching a terminal for measuring the potential to the electrode, the number of parts is increased, and a mechanism for managing the potential is required.
The technique of Patent Document 1 is capable of exhibiting excellent durability by making the lithium ion concentration in the electrode surface uniform. However, as the number of parts increases, the long-term cycle characteristics are not sufficient and there is room for improvement.
The technique of Patent Document 2 is capable of exhibiting excellent charge / discharge cycle characteristics by charging / discharging each electrode to improve the uniformity of potential between the electrodes. However, as the number of parts increases and there are electrode terminals in the laminate, there is a possibility of a short circuit when the laminate repeatedly expands and contracts due to charging and discharging, and there is room for improvement in safety.

Japanese Unexamined Patent Publication No. 2012-69314 JP-A-2002-50407

In view of the above-mentioned current situation, the problem to be solved by the present invention has not been obtained in the past while having high input / output characteristics by making the potential between electrodes uniform without increasing the number of parts. It is an object of the present invention to provide a non-aqueous lithium-type power storage element having both high long-term cycle characteristics and high safety at the same time.

As a result of diligent studies and experiments to solve the above problems, the present inventors have excellent input / output characteristics and high high input / output characteristics without increasing the number of parts because the positive electrode contains a lithium compound other than the active material. It has been found that a non-aqueous lithium-type power storage element having long-term cycle characteristics and high safety can be provided.
The present invention has been made based on such findings.

｛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、そしてＸ^１とＸ^２は、互いに独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝、又は下記式（２）：

｛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、又はアリール基であり、そしてＸ^１とＸ^２は、互いに独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝、又は下記式（３）：

｛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とＲ^３は、互いに独立に、水素原子、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、そしてＸ^１とＸ^２は、互いに独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝で表される１種以上の化合物を、前記正極物質層の単位質量当たり１．６０×１０^−４ｍｏｌ／ｇ〜３００×１０^−４ｍｏｌ／ｇ含有する、前記［１］〜［５］のいずれかに記載の前記非水系リチウム型蓄電素子。
［７］前記正極活物質層に含まれる正極活物質が、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Ｖ１（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Ｖ２（ｃｃ／ｇ）とするとき、０．３＜Ｖ１≦０．８、及び０．５≦Ｖ２≦１．０を満たし、かつ、ＢＥＴ法により測定される比表面積が１，５００ｍ２／ｇ以上３，０００ｍ^２／ｇ以下を示す活性炭である、前記［１］〜［６］のいずれかに記載の非水系リチウム型蓄電素子。
［８］前記正極活物質層に含まれる正極活物質が、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Ｖ１（ｃｃ／ｇ）が０．８＜Ｖ１≦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Ｖ２（ｃｃ／ｇ）が０．８＜Ｖ２≦３．０を満たし、かつ、ＢＥＴ法により測定される比表面積が２，３００ｍ２／ｇ以上４，０００ｍ^２／ｇ以下を示す活性炭である、前記［１］〜［６］のいずれかに記載の非水系リチウム型蓄電素子。
［９］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、前記［１］〜［８］のいずれかに記載の非水系リチウム型蓄電素子。
［１０］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、前記［１］〜［９］のいずれかに記載の非水系リチウム型蓄電素子。
［１１］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、前記［１］〜［８］のいずれかに記載の非水系リチウム型蓄電素子。
［１２］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、前記［１］〜［８］、及び［１１］のいずれかに記載の非水系リチウム型蓄電素子。
［１３］前記非水系リチウム型蓄電素子において、初期の常温放電内部抵抗をＲａ（Ω）、静電容量をＦ（Ｆ）、環境温度２５℃にて、セル電圧を２．２Ｖから３．８Ｖまで、３００Ｃのレートでの充放電サイクルを６０，０００回行った後の常温放電内部抵抗をＲｅ（Ω）、サイクル試験後の蓄電素子を４．５Ｖの定電圧充電を１時間行った後の静電容量をＦｅ（Ｆ）とするとき、以下の：
（ａ）Ｒｅ／Ｒａが０．９以上２．０以下である；及び
（ｂ）Ｆｅ／Ｆが１．０１以上である；
を満たすことを特徴とする、前記［１］〜［１２］のいずれかに記載の非水系リチウム型蓄電素子。 That is, the present invention is as follows:
[1] A laminate in which a positive electrode and a negative electrode are laminated via a separator, and a non-aqueous lithium-type power storage element containing a non-aqueous electrolytic solution containing lithium ions.
The positive electrode contains a lithium compound and contains
The positive electrode has a positive electrode current collector and a positive electrode active material layer on one side or both sides of the positive electrode current collector, and the former positive electrode active material layer contains a positive electrode active material made of activated carbon.
The negative electrode has a negative electrode current collector and a negative electrode active material layer on one side or both sides of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material capable of storing and releasing lithium ions.
When the negative electrode active material layer of the negative electrode in the outermost layer in the thickness direction of the laminate is viewed from above, the lithium ion concentration at the center is _C1o , and when the negative electrode active material layer of the negative electrode in the innermost layer in the thickness direction of the laminate is viewed from above. When the lithium ion concentration at the center of is C _1i , C _1o / C _1i is 0.85 or more and 1.15 or less.
The concentration of lithium ions is higher in the area region of 80% of the central portion of the negative electrode active material layer than in the area region of 20% of the peripheral portion of the negative electrode active material layer.
When the average particle size of the lithium compound is X ₁ , 0.1 μm ≤ X ₁ ≤ 10 μm, and when the average particle size of the positive electrode active material is Y ₁ , 2 μm ≤ Y ₁ ≤ 20 μm. _The non-aqueous lithium-type power storage element, wherein ₁ <Y ₁ and the amount of the lithium compound contained in the positive electrode is 1% by mass or more and 50% by mass or less.
[2] The thickness of the central negative electrode active material layer when the negative electrode active material layer of the negative electrode in the outermost layer in the thickness direction of the laminated body is viewed from above is T _1o , and the negative electrode active material of the negative electrode in the innermost layer in the thickness direction of the laminated body is T _1o . when the thickness of the negative electrode active material layer in the center when viewed from the top layer and _{T 1i, T 1o} / _{T 1i} is 0.85 to 1.15, the non-aqueous lithium power storage according to [1] element.
[3] A non-aqueous lithium-type power storage element composed of a wound body in which a positive electrode and a negative electrode are wound via a separator, and a non-aqueous electrolytic solution containing lithium ions.
The positive electrode contains a lithium compound and contains
The positive electrode has a positive electrode current collector and a positive electrode active material layer on one side or both sides of the positive electrode current collector, and the positive electrode active material layer contains a positive electrode active material made of activated carbon.
The negative electrode has a negative electrode current collector and a negative electrode active material layer on one side or both sides of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material capable of storing and releasing lithium ions.
The lithium ion concentration at the center when the negative electrode active material layer of the negative electrode on the outermost periphery in the radial direction excluding the peripheral edge is viewed from above is C _2o , which _faces the positive electrode of the wound _body , and _faces the positive electrode of the wound _body . _However , when the lithium ion concentration at the center of the innermost layer in the radial direction excluding the peripheral portion is C _2i when the negative electrode active material layer of the negative electrode is viewed from above, C _2o / C _2i is 0.85 or more and 1.15 or less. Yes,
The concentration of lithium ions is higher in the area region of 80% of the central portion of the negative electrode active material layer than in the area region of 20% of the peripheral portion of the negative electrode active material layer.
When the average particle size of the lithium compound is X ₁ , it is 0.1 μm ≤ X ₁ ≤ 10 μm, and when the average particle size of the positive electrode active material is Y ₁ , it is 2 μm ≤ Y ₁ ≤ 20 μm, and X ₁ <Y ₁ , and the amount of the lithium compound contained in the positive electrode is 1% by mass or more and 50% by mass or less, the non-aqueous lithium-type power storage element.
[4] The thickness of the center when the negative electrode active material layer of the negative electrode facing the positive electrode of the wound body and the outermost peripheral portion in the radial direction excluding the peripheral portion is viewed from above is T _2o , and the positive electrode of the wound _body is used. When the thickness of the center when the negative electrode active material layer of the negative electrode is viewed from above in the innermost layer in the radial direction facing each other and excluding the peripheral portion is T _2i , T _2o / T _2i is 0.85 or more and 1.15 or less. , The non-aqueous lithium power storage element according to the above [3].
[5] The non-aqueous lithium according to any one of [1] to [4] above, wherein the lithium compound is at least one lithium compound selected from the group consisting of lithium carbonate, lithium oxide, and lithium hydroxide. Type power storage element.
[6] The positive electrode active material layer has the following formula (1):

{In 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 independent of each other, − (COO) _n. (Here, n is 0 or 1.). } Or the following formula (2):

{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, and a carbon number of carbon atoms. It is a mono or polyhydroxyalkyl group having 1 to 10, 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, or an aryl group, and X ¹ and X ² are independently of each other- (COO) _n (where n is 0 or 1). } Or the following formula (3):

{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 independent of each other and have a hydrogen atom and 1 carbon atom. 10 to 10 alkyl groups, 1 to 10 carbon mono or polyhydroxyalkyl groups, 2 to 10 carbon alkenyl groups, 2 to 10 carbon mono or polyhydroxyalkenyl groups, 3 to 6 carbon cycloalkyl groups , Or an aryl group, and X ¹ and X ² are independently of each other- (COO) _n (where n is 0 or 1). One or more compounds represented by}, to unit mass per ^{1.60 × 10 -4 mol / g~300 ×} 10 -4 mol / g containing the positive electrode material layer, the [1] to [5] The non-aqueous lithium-type power storage element according to any one of.
[7] The amount of mesopores derived from the pores of the positive electrode active material contained in the positive electrode active material layer having a diameter of 20Å or more and 500Å or less calculated by the BJH method is V1 (cc / g), and the diameter is 20Å calculated by the MP method. When the amount of micropores derived from pores less than is V2 (cc / g), 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied, and the measurement is performed by the BET method. The non-aqueous lithium-type power storage element according to any one of [1] to [6] above, which is an activated carbon having a specific surface area of 1,500 m2 / g or more and 3,000 m ² / g or less.
[8] The mesopore amount V1 (cc / g) of the positive electrode active material contained in the positive electrode active material layer derived from pores having a diameter of 20Å or more and 500Å or less calculated by the BJH method is 0.8 <V1 ≦ 2. The specific surface area measured by the BET method while satisfying 5 and the micropore amount V2 (cc / g) derived from pores having a diameter of less than 20Å calculated by the MP method satisfies 0.8 <V2 ≦ 3.0. The non-aqueous lithium-type power storage element according to any one of [1] to [6] above, which is an activated carbon exhibiting a value of 2,300 m ² / g or more and 4,000 m ² / g or less.
[9] The non-aqueous lithium-type electricity storage according to any one of [1] to [8] above, wherein the amount of lithium ions doped in the negative electrode active material is 530 mAh / g or more and 2,500 mAh / g or less per unit mass. element.
[10] The non-aqueous lithium-type power storage element according to any one of [1] to [9], 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.
[11] The non-aqueous lithium-type power storage element according to any one of [1] to [8], wherein the amount of lithium ions doped in the negative electrode active material is 50 mAh / g or more and 700 mAh / g or less per unit mass.
[12] The non-aqueous lithium-type power storage device according to any one of [1] to [8] and [11] above, wherein the BET specific surface area of the negative electrode active material is 1 m ² / g or more and 50 m ² / g or less. ..
[13] In the non-aqueous lithium type power storage element, the initial room temperature discharge internal resistance is Ra (Ω), the capacitance is F (F), the environmental temperature is 25 ° C., and the cell voltage is 2.2 V to 3.8 V. After performing 60,000 charge / discharge cycles at a rate of 300 C, the internal resistance of normal temperature discharge is Re (Ω), and the power storage element after the cycle test is charged at a constant voltage of 4.5 V for 1 hour. When the capacitance is Fe (F), the following:
(A) Re / Ra is 0.9 or more and 2.0 or less; and (b) Fe / F is 1.01 or more;
The non-aqueous lithium-type power storage element according to any one of the above [1] to [12], which is characterized by satisfying the above conditions.

The non-aqueous lithium-type power storage element according to the present invention has high input / output characteristics by making the potential between electrodes uniform without increasing the number of parts, and has high long-term cycle characteristics and high characteristics which have not been obtained in the past. It has safety at the same time.

Description for specifying the area region (4) of the peripheral portion 20% and the area region (3) of the central portion 80% of the negative electrode active material layer (2) when the electrode laminate is a laminate of single-wafer electrodes. It is a figure. In the explanatory view for specifying the area region (4) of the peripheral portion 20% and the area region (3) of the central portion 80% of the negative electrode active material layer (2) when the electrode laminate is a wound laminate. is there. The length x ₂ of the cut-out wound laminated body in the long direction roughly corresponds to the electrode length in the long direction of the non-aqueous lithium storage element including the cut-out wound laminated body. It is explanatory drawing for specifying the negative electrode (5) in the outermost layer in the thickness direction of the laminated body, and the negative electrode (6) in the innermost layer in a thickness direction of the laminated body in the case where the electrode laminated body is a laminated body of single-wafer electrodes. .. When the electrode laminate is a wound laminate, the outer peripheral portion (9) of the wound body is the center of the negative electrode forming the wound body, which faces the positive electrode (8) and excludes the peripheral portion of the negative electrode. In the region of the part, it means the negative electrode active material layer for one round of the outermost circumference to be wound, and the inner peripheral part (7) of the wound body is opposed to the positive electrode (8) in the negative electrode forming the wound body. Moreover, it is a drawing for demonstrating that it means the negative electrode active material layer for one innermost circumference to be wound in the region of the central part excluding the peripheral part of the negative electrode.

Hereinafter, embodiments of the present invention will be described in detail.
The non-aqueous lithium-type power storage element generally includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an exterior body as main components. As the electrolytic solution, an organic solvent in which a lithium salt is dissolved (hereinafter, referred to as a non-aqueous electrolytic solution) is used.
[Positive electrode]
The positive electrode has a positive electrode current collector and a positive electrode active material layer existing on one side or both sides thereof.
Further, the positive electrode preferably contains a lithium compound as a positive electrode precursor before assembling the power storage element. As will be described later, in the present embodiment, it is preferable to pre-dope the negative electrode with lithium ions in the energy storage element assembly process, but as the pre-doping method, a positive electrode precursor containing the lithium compound, a negative electrode, a separator, an exterior body, and the like. It is preferable to apply a voltage between the positive electrode precursor and the negative electrode after assembling the power storage element using the non-aqueous electrolyte solution. The lithium compound is preferably contained in the positive electrode active material layer formed on the positive electrode current collector of the positive electrode precursor.
In the present specification, the positive electrode state before the lithium doping process is defined as a positive electrode precursor, and the positive electrode state after the lithium doping process is defined as a positive electrode.

[Positive electrode active material layer]
The positive electrode active material layer contained in the positive electrode contains a positive electrode active material containing activated carbon. In addition to this, the positive electrode active material layer may contain an optional component such as a conductive filler, a binder, and a dispersion stabilizer, if necessary.
Further, it is preferable that the positive electrode active material layer of the positive electrode precursor contains a lithium compound other than the positive electrode active material.

[Positive electrode active material]
The positive electrode active material contains activated carbon. As the positive electrode active material, only activated carbon may be used, or in addition to activated carbon, other carbon materials as described later may be used in combination. As the carbon material, it is more preferable to use carbon nanotubes, a conductive polymer, or a porous carbon material. The positive electrode active material may be used by mixing one or more kinds of carbon materials including activated carbon, or may contain a material other than the carbon material (for example, a composite oxide of lithium and a transition metal).
The content of the carbon material with respect to the total amount of the positive electrode active material is preferably 50% by mass or more, and more preferably 70% by mass or more. The content of the carbon material can be 100% by mass, but from the viewpoint of obtaining a good effect by the combined use of other materials, for example, it is preferably 90% by mass or less, and 80% by mass or less. May be good.

There are no particular restrictions on the type of activated carbon used as the positive electrode active material and its raw material. However, it is preferable to optimally control the pores of the activated carbon in order to achieve both high input / output characteristics and high energy density. Specifically, the amount of mesopores derived from pores having a diameter of 20Å or more and 500Å 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 20Å calculated by the MP method. When setting to V2 (cc / g)
(1) For high input / output characteristics, 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied, and the specific surface area measured by the BET method is 1,500 m ^2. Activated carbon with / g or more and 3,000 m ² / g or less (hereinafter, also referred to as activated carbon 1), or (2) 0.8 <V1 ≦ 2.5 and 0.8 in order to obtain a high energy density. Activated carbon (hereinafter, also referred to as activated carbon 2) that satisfies <V2 ≦ 3.0 and has a specific surface area measured by the BET method of 2,300 m ² / g or more and 4,000 m ² / g or less is preferable.

Hereinafter, activated carbon 1 and activated carbon 2 will be described.
[Activated carbon 1]
The mesopore amount V1 of the activated carbon 1 is preferably a value larger than 0.3 cc / g in terms of increasing the input / output characteristics when incorporated into the power storage element. On the other hand, it is preferably 0.8 cc / g or less from the viewpoint of suppressing a decrease in the bulk density of the positive electrode. The above V1 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 V2 of the activated carbon 1 is preferably 0.5 cc / g or more in order to increase the specific surface area and the capacity of the activated carbon. 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 as an electrode, and increasing the capacity per unit volume. The above V2 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 combination of the lower limit and the upper limit can be arbitrary.

The ratio of the mesopore amount V1 to the micropore amount V2 (V1 / V2) is preferably in the range of 0.3 ≦ V1 / V2 ≦ 0.9. That is, V1 / V2 is preferably 0.3 or more from the viewpoint of increasing the ratio of the mesopore amount to the micropore amount to the extent that the decrease in output characteristics can be suppressed while maintaining a high capacity. On the other hand, V1 / V2 is preferably 0.9 or less from the viewpoint of increasing the ratio of the micropore amount to the mesopore amount to the extent that the decrease in capacitance can be suppressed while maintaining the high output characteristics. A more preferable range of V1 / V2 is 0.4 ≦ V1 / V2 ≦ 0.7, and a more preferable range of V1 / V2 is 0.55 ≦ V1 / V2 ≦ 0.7. The combination of the lower limit and the upper limit can be arbitrary.

The average pore diameter of the activated carbon 1 is preferably 17 Å or more, more preferably 18 Å or more, and even more preferably 20 Å or more, from the viewpoint of maximizing the output of the obtained power storage element. Further, from the viewpoint of maximizing the capacity, the average pore diameter of the activated carbon 1 is preferably 25Å 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 can be easily obtained, while when the BET specific surface area is 3,000 m ² / g or less, in order to maintain the strength of the electrode. Since it is not necessary to add a large amount of binder, the performance per electrode volume is improved. The combination of the lower limit and the upper limit can be arbitrary.

Activated carbon 1 having the above characteristics can be obtained, for example, by using the raw materials and treatment methods described below.
In the present embodiment, the carbon source used as the raw material of the activated carbon 1 is not particularly limited. For example, plant-based raw materials such as wood, wood flour, coconut shells, by-products during pulp production, bagas, waste sugar honey; peat, sub-charcoal, brown charcoal, bituminous charcoal, smokeless charcoal, 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 carbonized products thereof. Among these raw materials, plant-based raw materials such as coconut shells and wood flour and their carbides are preferable, and coconut shell carbides are particularly preferable, from the viewpoint of mass production and cost.

As the carbonization and activation methods for converting these raw materials into the activated carbon 1, for example, 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.
Examples of the carbonization method for these raw materials include inert gases such as nitrogen, carbon dioxide, helium, argon, xenone, neon, carbon monoxide, and combustion exhaust gas, or other gases containing these inert gases as main components. Examples thereof include a method of firing at about 400 to 700 ° C. (preferably 450 to 600 ° C.) for about 30 minutes to 10 hours using a mixed gas.

As a method for activating the carbide obtained by the above carbonization method, a gas activation method of firing using an activation gas such as steam, carbon dioxide, or oxygen is preferably used. Of these, a method using steam or carbon dioxide as the activating gas is preferable.
In this activation method, the above-mentioned carbide is supplied for 3 to 12 hours (preferably 5 to 11) while supplying the activation gas at a ratio of 0.5 to 3.0 kg / h (preferably 0.7 to 2.0 kg / h). It is preferable to activate by raising the temperature to 800 to 1,000 ° C. over time, more preferably 6 to 10 hours).
Further, the carbide may be first activated in advance prior to the activation treatment of the carbide. In this primary activation, a method in which a carbon material is usually fired at a temperature of less than 900 ° C. using an activation gas such as steam, carbon dioxide, or oxygen to activate the gas can be preferably adopted.
By appropriately combining the calcination temperature and calcination time in the carbonization method with the activation gas supply amount, temperature rise rate, and maximum activation temperature in the activation method, activated carbon 1 having the above characteristics that can be used in the present embodiment is produced. can do.

The average particle size of the activated carbon 1 is preferably 2 to 20 μm.
When the average particle size is 2 μm or more, the capacity per electrode volume tends to be high because the density of the active material layer is high. Here, if the average particle size is small, the durability may be low, but if the average particle size is 2 μm or more, such a defect is unlikely to occur. On the other hand, when the average particle size is 20 μm or less, it tends to be easily adapted to high-speed charging / discharging. The average particle size is more preferably 2 to 15 μm, still more preferably 3 to 10 μm. The upper and lower limits of the average particle size range can be arbitrarily combined.

[Activated carbon 2]
The mesopore amount V1 of the activated carbon 2 is preferably a value larger than 0.8 cc / g from the viewpoint of increasing the output characteristics when incorporated in the power storage element. On the other hand, V1 is preferably 2.5 cc / g or less from the viewpoint of suppressing a decrease in the capacity of the power storage element. The above V1 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.

The micropore amount V2 of the activated carbon 2 is preferably a value larger than 0.8 cc / g in order to increase the specific surface area and the capacity of the activated carbon. On the other hand, V2 is preferably 3.0 cc / g or less from the viewpoint of increasing the density of activated carbon as an electrode and increasing the capacity per unit volume. The above V2 is more preferably larger 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 above-mentioned meso-pore amount and micro-pore amount 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 2,300 m ² / g or more and 4,000 m ² / g or less. The lower limit of the BET specific surface area is more preferably 3,000 m ² / g or more, and further preferably 3,200 m ² / g or more. On the other hand, the upper limit of the BET specific surface area is more preferably 3,800 m ² / g or less. When the BET specific surface area is 2,300 m ² / g or more, good energy density can be easily obtained, while when the BET specific surface area is 4,000 m ² / g or less, in order to maintain the strength of the electrode. Since it is not necessary to add a large amount of binder, the performance per electrode volume is improved.
Regarding the V1, V2 and BET specific surface areas of the activated carbon 2, the upper and lower limits of the preferable ranges described above can be arbitrarily combined.

Activated carbon 2 having the above characteristics can be obtained, for example, by using a raw material and a treatment method as described below.
The carbon source used as a raw material for the activated charcoal 2 is not particularly limited as long as it is a carbon source normally used as a raw material for activated charcoal. For example, plant-based raw materials such as wood, wood flour, and coconut shells; petroleum pitch, coke. Fossil-based raw materials such as, and various synthetic resins such as phenol resin, furan resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin and the like can be mentioned. Among these raw materials, phenol resin and furan resin are particularly preferable because they are suitable for producing activated carbon having a high specific surface area.

Examples of the method of carbonizing these raw materials or the heating method at the time of 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 the atmosphere at the time of heating, an inert gas such as nitrogen, carbon dioxide, helium, or argon, or a gas containing these inert gases as a main component and mixed with other gases is used. It is preferable to bake at a carbonization temperature of about 400 to 700 ° C. (the lower limit is preferably 450 ° C. or higher, more preferably 500 ° C. or higher, and the upper limit is preferably 650 ° C. or lower) for about 0.5 to 10 hours.

Examples of the method for activating the carbide after the carbonization treatment include a gas activation method in which the carbide is fired using an activated gas such as water vapor, carbon dioxide, and oxygen, and an alkali metal activation method in which heat treatment is performed after mixing with an alkali metal compound. The alkali metal activation method is preferable for producing activated carbon having a high specific surface area.
In this activation method, the carbides were mixed so that the mass ratio of the carbides to the alkali metal compounds such as KOH and NaOH was 1: 1 or more (the amount of the alkali metal compounds was the same as or larger than the amount of the carbides). Later, heating is carried out in the range of 600 to 900 ° C. (preferably 650 ° C. to 850 ° C.) in an inert gas atmosphere for 0.5 to 5 hours, after which the alkali metal compound is washed and removed with acid and water, and further dried. I do.

I mentioned earlier that the mass ratio of carbide to alkali metal compound (= carbide: alkali metal compound) is preferably 1: 1 or more, but as the amount of alkali metal compound increases, the amount of mesopores increases, but the mass ratio is 1: 1. Since the amount of pores tends to increase sharply around 3.5, the mass ratio is preferably more than 1: 3 and the amount of the alkali metal compound is preferably 1: 5.5 or less. The mass ratio increases as the amount of the alkali metal compound increases, but is preferably in the above range in consideration of treatment efficiency such as subsequent cleaning.
In order to increase the amount of micropores and not to increase the amount of mesopores, it is advisable to increase the amount of carbides when activating and mix with KOH. In order to increase both the amount of micropores and the amount of mesopores, it is advisable to use a large amount of KOH. Further, in order to mainly increase the amount of mesopores, it is preferable to perform steam activation after performing alkali activation treatment.
The average particle size 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.

[Usage of activated carbon]
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 each of the above-mentioned characteristic values may be shown as a whole mixture.
As the activated carbons 1 and 2 described above, 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 activated carbon 1 and 2 (for example, activated carbon that does not have the specific V1 and / or V2, or a material other than activated carbon (for example, a composite oxide of lithium and a transition metal)). It may be included. In an exemplary embodiment, the content of activated carbon 1, the content of activated carbon 2, or the total content of activated carbons 1 and 2 is preferably more than 50% by mass, respectively, and 70% by mass or more of the total positive electrode active material. More preferably, 90% by mass or more is further preferable, and 100% by mass is most preferable.

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 lower 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 upper limit of the content ratio of the positive electrode active material is more preferably 90% by mass or less, and further preferably 80% by mass or less. By setting the content ratio in this range, suitable charge / discharge characteristics are exhibited.

[Lithium compound]
The positive electrode active material layer of the positive electrode precursor of the present embodiment preferably contains a lithium compound other than the positive electrode active material. Further, the positive electrode active material layer of the positive electrode of the present embodiment contains a lithium compound other than the positive electrode active material.
The lithium compound can be decomposed at the positive electrode in the lithium doping step described later to release lithium ions, such as lithium carbonate, lithium oxide, lithium hydroxide, lithium fluoride, lithium chloride, lithium oxalate, and iodine. One or more selected from lithium carbonate, lithium nitride, lithium oxalate, and lithium acetate are preferably used. Among them, lithium carbonate, lithium oxide, and lithium hydroxide are more preferable, and lithium carbonate is more preferably used from the viewpoint that it can be handled in the air and has low hygroscopicity. Such a lithium compound decomposes when a voltage is applied, functions as a dopant source for lithium doping to the negative electrode, and forms pores in the positive electrode active material layer, so that the electrolytic solution has excellent retention and ion conduction. It is possible to form a positive electrode having excellent properties.

[Lithium compound of positive electrode precursor]
The lithium compound is preferably in the form of particles. The average particle size of the lithium compound contained in the positive electrode precursor is preferably 0.1 μm or more and 100 μm or less. The upper limit of the average particle size of the lithium compound contained in the positive electrode precursor is more preferably 50 μm or less, further preferably 20 μm or less, and most preferably 10 μm or less. On the other hand, the lower limit of the average particle size of the lithium compound contained in the positive electrode precursor is more preferably 0.3 μm or more, and further preferably 0.5 μm or more. When the average particle size of the lithium compound is 0.1 μm or more, the pores remaining after the oxidation reaction of the lithium compound in the positive electrode have a sufficient volume to hold the electrolytic solution, so that the high load charge / discharge characteristics are exhibited. improves. When the average particle size of the lithium compound is 10 μm or less, the surface area of the lithium compound does not become excessively small, so that the rate of oxidation reaction of the lithium compound can be ensured. The upper and lower limits of the range of the average particle size of the lithium compound can be arbitrarily combined.
Various methods can be used for atomizing the lithium 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 content ratio of the lithium compound in the positive electrode active material layer of the positive electrode precursor is preferably 5% 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, and is preferably 10% by mass or more and 50% by mass or more. It is more preferably mass% or less. By setting the content ratio in this range, it is possible to exert a suitable function as a dopant source for the negative electrode and to impart an appropriate degree of porosity to the positive electrode, and both of them achieve high load charge / discharge efficiency. It is preferable because it can provide an excellent power storage element. The upper and lower limits of this content ratio range can be arbitrarily combined.

[Lithium compound of positive electrode]
The positive electrode contains a lithium compound other than the positive electrode active material. When the average particle size of the lithium compound other than the positive electrode active material contained in the positive electrode is X ₁ , it is preferably 0.1 μm ≤ X ₁ ≤ 10 μm, and more preferably 0.5 μm ≤ X ₁ ≤ 5 μm. is there. When X ₁ is 0.1 μm or more, the high load charge / discharge cycle characteristics are improved by adsorbing the fluorine ions generated in the high load charge / discharge cycle. On the other hand, when X ₁ is 10 μm or less, the reaction area with the fluorine ions generated in the high load charge / discharge cycle increases, so that the adsorption of fluorine ions can be performed efficiently.

The lithium compound contained in the positive electrode other than the positive electrode active material is characterized by being 1% by mass or more and 50% by mass or less based on the total mass of the positive electrode active material layer in the positive electrode, and is 2.5% by mass or more and 25% by mass. More preferably, it is less than%. When the amount of the lithium compound is 1% by mass or more, lithium carbonate suppresses the decomposition reaction of the electrolytic solution solvent on the positive electrode in a high temperature environment, so that the high temperature durability is improved, and the effect is improved when the amount is 2.5% by mass or more. Becomes noticeable. Further, when the amount of the lithium compound is 50% by mass or less, the electron conductivity between the positive electrode active materials is relatively small to be inhibited by the lithium compound, so that high input / output characteristics are exhibited, and the amount is 25% by mass or less. , Especially preferable from the viewpoint of input / output characteristics. The combination of the lower limit and the upper limit can be arbitrary.

[Method for identifying lithium compounds in positive electrode]
The method for identifying the lithium compound contained in the positive electrode is not particularly limited, but for example, it can be identified by the following method. For the identification of the lithium compound, it is preferable to identify by combining a plurality of analysis methods described below.
When measuring SEM-EDX, Raman, and XPS described below, disassemble the non-aqueous lithium-type power storage element in an argon box, take out the positive electrode, clean the electrolyte adhering to the positive electrode surface, and then perform the measurement. Is preferable. As for the method for cleaning the positive electrode, since the electrolyte adhering to the surface of the positive electrode may be washed away, a carbonate solvent such as dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate can be preferably used. As a cleaning method, for example, the positive electrode is immersed in a diethyl carbonate solvent having a mass of 50 to 100 times 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 diethyl carbonate, and vacuum dried (temperature: 0 to 200 ° C., pressure: 0 to 20 kPa, time: 1 to 40 hours, and the condition is that the residual diethyl carbonate in the positive electrode is 1% by mass or less. The residual amount of diethyl carbonate can be quantified based on the calibration line prepared in advance by measuring the GC / MS of the water after washing with distilled water and adjusting the liquid amount, which will be described later.) -Perform EDX, Raman, and XPS analysis.

Regarding ion chromatography described later, anions can be identified by analyzing the water after washing the positive electrode with distilled water.
If the lithium compound cannot be identified by the above analysis method, other analysis methods include solid ⁷ Li-NMR, XRD (X-ray diffraction), TOF-SIMS (time-of-flight secondary ion mass spectrometry), and AES (Auger). Lithium compounds can also be identified by using electron spectroscopy), TPD / MS (mass spectrometry of heated generated gas), DSC (differential scanning calorimeter analysis) and the like.

[Raman]
The lithium 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 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 measured for 3 seconds, the number of integrations can be measured once, and the measurement can be performed under the condition of having a noise filter. For the measured Raman spectrum, a straight baseline is set in the range of 1071-1104 cm ^-1 , the area is calculated with a positive value from the baseline as the peak of carbonate ions, and the frequency is integrated. At this time, the noise component is added. The frequency for the carbonate ion peak area approximated by the Gaussian function is subtracted from the carbonate ion frequency distribution.

[Method for quantifying lithium compounds]
The method for quantifying the lithium compound contained in the positive electrode is described below.
The positive electrode is washed with an organic solvent, then washed with distilled water, and the lithium compound can be quantified from the change in positive electrode mass before and after washing with distilled water. Although area measurement is positive is not particularly limited, it is preferably, more preferably 25 cm ² or more 150 cm ² or less from the viewpoint of reducing the variation in measurement is 5 cm ² or more 200 cm ² or less. If the area is 5 cm ² or more, the reproducibility of measurement is ensured. If the area is 200 cm ² or less, the handling of the sample is excellent. For cleaning with an organic solvent, the organic solvent is not particularly limited as long as the non-aqueous electrolyte decomposition product deposited on the positive electrode surface can be removed. However, by using an organic solvent having a solubility of the lithium compound of 2% or less, the lithium compound can be used. It is preferable because the elution of the solvent is suppressed. For example, a polar solvent such as methanol or acetone is preferably used.

The method for cleaning the positive electrode is to sufficiently immerse the positive electrode in a methanol solution 50 to 100 times the mass 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 methanol does not volatilize. After that, the positive electrode is taken out from methanol and vacuum dried (temperature: 100 to 200 ° C., pressure: 0 to 10 kPa, time: 5 to 20 hours, and the condition is that the residual amount of methanol in the positive electrode is 1% by mass or less. The residual amount of the above can be measured by measuring the GC / MS of the water after washing with distilled water, which will be described later, and quantifying based on the calibration line prepared in advance.) The mass of the positive electrode at that time is M ₀ [g]. And. Subsequently, the positive electrode is sufficiently immersed in distilled water having 100 times the mass of the positive electrode (100M ₀ [g]) for 3 days or more. At this time, it is preferable to take measures such as covering the container so that the distilled water does not volatilize. After immersion least 3 days, a distilled water outlet of the positive electrode (when measuring the above-described ion chromatography, the amount of distilled water to adjust the volume so that the 100M 0 _[g].), Of the Vacuum dry in the same way as methanol washing. The mass of the positive electrode at this time is set to M ₁ [g], and subsequently, in order to measure the mass of the obtained current collector of the positive electrode, a positive electrode active material layer on the current collector is used using a spatula, a brush, a brush, or the like. Get rid of. Assuming that the mass of the obtained positive electrode current collector is M ₂ [g], the mass% Z of the lithium compound contained in the positive electrode is the following formula (1):
Z = 100 × [1- (M _1- M ₂ ) / (M _0- M ₂ )]. .. .. Equation (1)
Can be calculated by

[Arbitrary component of positive electrode active material layer]
If necessary, the positive electrode active material layer in the present embodiment may contain optional components such as a conductive filler, a binder, and a dispersion stabilizer in addition to the positive electrode active material and the lithium compound.
The conductive filler is not particularly limited, and for example, acetylene black, ketjen black, vapor-grown carbon fiber, graphite, carbon nanotubes, a mixture thereof and the like can be used. The amount of the conductive filler used is preferably 0 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. It is more preferably 0.01 parts by mass or more and 20 parts by mass or less, and further preferably 1 part by mass or more and 15 parts by mass or less. If the amount of the conductive filler used is more than 30 parts by mass, the content ratio of the positive electrode active material in the positive electrode active material layer is small, and the energy density per volume of the positive electrode active material layer is lowered, 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 and 25 parts by mass with respect to 100 parts by mass of the positive electrode active material. It is less than a part. When the amount of the binder used is 1 part by mass or more, sufficient electrode strength is exhibited. On the other hand, when the amount of the binder used is 30 parts by mass or less, high input / output characteristics are exhibited without inhibiting the entry / exit and diffusion of ions into the positive electrode active material.

The dispersion stabilizer is not particularly limited, but for example, PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), a cellulose derivative and the like can be used. The amount of the dispersion stabilizer used is preferably 0 parts by mass or 0.1 parts 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 used is 10 parts by mass or less, high input / output characteristics are exhibited without inhibiting the entry / exit and diffusion of ions into the positive electrode active material.

[Positive current collector]
The material constituting the positive electrode current collector in the present embodiment is not particularly limited as long as it has high electron conductivity and does not deteriorate due to elution into the electrolytic solution and reaction with the electrolyte or ions. Foil is preferred. Aluminum foil is particularly preferable as the positive electrode current collector in the non-aqueous lithium power storage device of the present embodiment.
The metal foil may be an ordinary metal foil having no irregularities or through holes, a metal foil having irregularities subjected to embossing, chemical etching, electrolytic precipitation, blasting, etc., expanded metal, punching metal, etc. , A metal foil having through holes 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.

[Manufacturing of positive electrode precursor]
In the present embodiment, the positive electrode precursor serving as the positive electrode of the non-aqueous lithium-type power storage element can be manufactured by a technique for manufacturing electrodes in known lithium ion batteries, electric double layer capacitors, and the like. For example, a positive electrode active material, a lithium compound, and other optional components used as necessary are dispersed or dissolved in water or an organic solvent to prepare a slurry coating solution, and the coating solution is used as a positive electrode current collector. A positive electrode precursor can be obtained by applying a coating film on one or both sides of the body to form a coating film and drying the coating film. Further, the obtained positive electrode precursor may be pressed to adjust the film thickness or bulk density of the positive electrode active material layer. Alternatively, without the use of solvents, the positive electrode active material and lithium compound, and any other optional ingredients used as needed, are dry mixed, the resulting mixture is press molded and then conductively bonded. It is also possible to attach it to the positive electrode current collector using an agent.

The coating liquid of the positive electrode precursor is a dry blend of a part or all of various material powders including a positive electrode active material, and then water or an organic solvent and / or a binder or a dispersion stabilizer is dissolved or dispersed therein. The liquid or slurry-like substance may be added and prepared. Further, a coating liquid may be prepared by adding various material powders containing a positive electrode active material to a liquid or slurry substance in which a binder or a dispersion stabilizer is dissolved or dispersed in water or an organic solvent. Good. As the method of dry blending, for example, a positive electrode active material and a lithium compound are premixed using a ball mill or the like, and if necessary, a conductive filler is premixed to coat a low conductive lithium compound with the conductive filler. You may do. As a result, the lithium compound is easily decomposed in the positive electrode precursor in the lithium doping step described later. When water is used as the solvent of the coating liquid, the coating liquid may become alkaline by adding the lithium compound, so that a pH adjuster may be added if necessary.

The preparation of the coating liquid for the positive electrode precursor is not particularly limited, but preferably a disperser such as a homodisper, a multi-axis disperser, a planetary mixer, or a thin film swirling high-speed mixer is used. Can be done. In order to obtain a coating liquid in a well-dispersed 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. Further, when the peripheral speed is 50 m / s or less, various materials are not destroyed by heat or shearing force due to dispersion, and reaggregation does not occur, which is preferable.
The dispersity of the coating liquid is preferably such that the particle size measured by the grain gauge is 0.1 μm or more and 100 μm or less. The upper limit of the degree of dispersion is more preferably 80 μm or less in particle size, and further preferably 50 μm or less in particle size. If the particle size is less than 0.1 μm, the size is smaller 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 liquid, which is not preferable. Further, when the particle size is 100 μm or less, stable coating can be performed without clogging at the time of discharging the coating liquid or generation of streaks on the coating film.

The viscosity (ηb) of the coating liquid 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, still more 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 coating film formation is suppressed, and the coating film width and film thickness can be satisfactorily controlled. Further, when the viscosity (ηb) is 20,000 mPa · s or less, the pressure loss in the flow path of the coating liquid when using the coating machine is small and stable coating can be performed, and the coating film thickness is less than the desired one. Can be controlled.
The TI value (thixotropy index value) of the coating liquid is preferably 1.1 or more, more preferably 1.2 or more, and further preferably 1.5 or more. When the TI value is 1.1 or more, the coating film width and the film thickness can be satisfactorily controlled.

The 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 multi-layer coating. In the case of multi-layer coating, the coating liquid composition may be adjusted so that the content of the lithium 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 the coating speed is 100 m / min or less, sufficient coating accuracy can be ensured.

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. The coating film may be dried at a single temperature, or may be dried at different temperatures in multiple stages. Further, the coating film may be dried by combining a plurality of drying methods. 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 drying temperature is 200 ° C. or lower, cracks in 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 press of the positive electrode precursor 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 positive electrode active material layer can be adjusted by the press pressure, the gap, and the surface temperature of the press portion, which will be described later.
The press 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. When the press pressure is 0.5 kN / cm or more, the electrode strength can be sufficiently increased. On the other hand, when the press pressure is 20 kN / cm or less, the positive electrode precursor does not bend or wrinkle, 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 an arbitrary value according to the film thickness of the positive electrode precursor after drying so as to have a desired film thickness and bulk density of the positive electrode active material layer. Further, the pressing speed can be set to an arbitrary speed at which the positive electrode precursor does not bend or wrinkle.
Further, the surface temperature of the press portion may be room temperature, or the press portion may be heated if necessary. The lower limit of the surface temperature of the pressed portion at the time of heating is preferably a melting point of minus 60 ° C. or higher, more preferably minus 45 ° C. or higher, and further preferably minus 30 ° C. or higher of the melting point of the binder to be used. On the other hand, the upper limit of the surface temperature of the pressed portion when heating is preferably the melting point of the binder used plus 50 ° C. or lower, more preferably the melting point plus 30 ° C. or lower, and further preferably the melting point plus 20 ° C. or lower. For example, when PVdF (polyvinylidene fluoride: melting point 150 ° C.) is used as the binder, it is preferable to heat the surface of the pressed portion to 90 ° C. or higher and 200 ° C. or lower, more preferably 105 ° C. or higher and 180 ° C. or lower, further preferably. Is heating to 120 ° C. or higher and 170 ° C. or lower. When a styrene-butadiene copolymer (melting point 100 ° C.) is used as the binder, the surface of the pressed portion is preferably heated to 40 ° C. or higher and 150 ° C. or lower, more preferably 55 ° C. or higher and 130 ° C. or lower. More preferably, it is heated to 70 ° C. or higher and 120 ° C. or lower.

The melting point of the binder can be determined from the endothermic peak position of DSC (Differential Scanning Calorimetry, differential scanning calorimetry). For example, using a differential scanning calorimeter "DSC7" manufactured by PerkinElmer, 10 mg of sample resin is set in a measurement cell, and the temperature rises from 30 ° C. to 250 ° C. at a heating rate of 10 ° C./min in a nitrogen gas atmosphere. The temperature is raised, and the endothermic peak temperature in the temperature raising process becomes the melting point.
Further, the press may be performed a plurality of times while changing the conditions of the press pressure, the gap, the speed, and the surface temperature of the press portion.

The film thickness of the positive electrode active material layer is preferably 20 μm or more and 200 μm or less per one side of the positive electrode current collector. The film thickness of the positive electrode active material layer is more preferably 25 μm or more and 100 μm or less, and further preferably 30 μm or more and 80 μm or less per side surface. When this film thickness is 20 μm or more, a sufficient charge / discharge capacity can be developed. On the other hand, when this film 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 upper and lower limits of the film thickness range of the positive electrode active material layer can be arbitrarily combined. The film thickness of the positive electrode active material layer when the current collector has through holes or irregularities refers to the average value of the film thickness per side of the portion of the current collector that does not have through holes or irregularities.

[Positive electrode]
The bulk density of the positive electrode active material layer in the positive electrode after the lithium doping step described later is preferably 0.25 g / cm ³ or more, more preferably 0.30 g / cm ³ or more and 1.3 g / cm ³ or less. Is. When the bulk density of the positive electrode active material layer is 0.25 g / cm ³ or more, a high energy density can be exhibited and the miniaturization of the power storage element can be achieved. Further, when the bulk density is 1.3 g / cm ³ or less, the electrolytic solution is sufficiently diffused in the pores in the positive electrode active material layer, and high output characteristics can be obtained.

[Negative electrode]
The negative electrode has a negative electrode current collector and a negative electrode active material layer existing on one side or both sides thereof.

[Negative electrode active material layer]
The negative electrode active material layer contains a negative electrode active material that can occlude and release lithium ions. In addition to this, if necessary, an optional component such as a conductive filler, a binder, and a dispersion stabilizer may be contained.

[Negative electrode active material]
As the negative electrode active material, a substance capable of storing and releasing lithium ions can be used. Specific examples thereof include carbon materials, titanium oxides, silicon, silicon oxides, silicon alloys, silicon compounds, tin and tin compounds. The content 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 of the carbon material can be 100% by mass, but from the viewpoint of obtaining a good effect by the combined use of other materials, for example, it is preferably 90% by mass or less, and 80% by mass or less. May be good.

The negative electrode active material is preferably doped with lithium ions. In the present specification, the lithium ions doped in the negative electrode active material mainly include three forms.
The first form is lithium ions that are occluded in advance as a design value in the negative electrode active material before the non-aqueous lithium-type power storage element is manufactured.
The second form is lithium ions occluded in the negative electrode active material when a non-aqueous lithium-type power storage element is manufactured and shipped.
The third form is lithium ions occluded in the negative electrode active material after using the non-aqueous lithium-type power storage element as a device.
By doping the negative electrode active material with lithium ions, it is possible to satisfactorily control the capacity and operating voltage of the obtained non-aqueous lithium-type power storage element.

Examples of the carbon material include non-graphitizable carbon materials; easily graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon globules; graphite whiskers; polyacene-based substances. Amorphous carbonaceous materials such as; petroleum-based pitches, coal-based pitches, carbonaceous materials such as mesocarbon microbeads, coke, synthetic resins (for example, phenolic resins, etc.), etc. Thermal decomposition products of furfuryl alcohol resin or novolak resin; fullerene; carbon nanophones; and composite carbon materials thereof can be mentioned.

Among these, from the viewpoint of lowering the resistance of the negative electrode, heat treatment is performed in a state where one or more of the carbon materials (hereinafter, also referred to as a base material) and the carbonaceous material precursor coexist, and the base material and the carbon are coexisted. A composite carbon material in which a carbon material derived from a quality material precursor is compounded is preferable. The carbonaceous material precursor is not particularly limited as long as it becomes the carbonaceous material by heat treatment, but a petroleum-based pitch or a coal-based pitch is particularly preferable. The base material and the carbonaceous material precursor may be mixed at a temperature higher than the melting point of the carbonaceous material precursor before the heat treatment. The heat treatment temperature may be any temperature as long as the component generated by volatilization or thermal decomposition of the carbonaceous material precursor used becomes the carbonaceous material, but is preferably 400 ° C. or higher and 2500 ° C. or lower, more preferably 500 ° C. It is 2000 ° C. or lower, more preferably 550 ° C. or higher and 1500 ° C. or lower. The atmosphere in which the heat treatment is performed is not particularly limited, but a non-oxidizing atmosphere is preferable.

Preferred examples of the composite carbon material are composite carbon materials 1 and 2 described later. Either of these may be selected and used, or both of them may be used in combination.

[Composite carbon material 1]
The composite carbon material 1 is the composite carbon material using 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 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 BET specific surface area of the composite carbon material 1 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. When the BET specific surface area is 100 m ² / g or more, the pores can be appropriately retained and the diffusion of lithium ions becomes good, so that high input / output characteristics can be exhibited. On the other hand, when it is 1,500 m ² / g or less, the charge / discharge efficiency of lithium ions is improved, so that the cycle durability is not impaired.

The mass ratio of the carbonaceous material to the base material in the composite carbon material 1 is preferably 10% by mass or more and 200% by mass or less. This mass ratio is preferably 12% by mass or more and 180% by mass or less, more preferably 15% by mass or more and 160% by mass or less, and particularly preferably 18% by mass or more and 150% by mass or less. When the mass ratio of the carbonaceous material is 10% by mass or more, the micropores of the base material can be appropriately filled with the carbonaceous material, and the charge / discharge efficiency of lithium ions is improved, which is good. Cycle durability can be shown. Further, when the mass ratio of the carbonaceous material is 200% by mass or less, the pores can be appropriately retained and the diffusion of lithium ions becomes good, so that high input / output characteristics can be exhibited.

The doping amount of lithium ions per unit mass of the composite carbon material 1 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, still more preferably 760 mAh. It is / g or more and 1,700 mAh / g or less, particularly preferably 840 mAh / g or more and 1,500 mAh / g or less.
Since the negative electrode potential is lowered by doping with lithium ions, when the negative electrode containing the lithium ion-doped composite carbon material 1 is combined with the positive electrode, the voltage of the non-aqueous lithium-type power storage element is increased and the voltage is increased. As a result of increasing the utilization capacity of the positive electrode, the capacity and energy density of the obtained non-aqueous lithium-type power storage element are increased.
When the doping amount is 530 mAh / g or more, the lithium ions are well doped in the irreversible sites that cannot be desorbed once the lithium ions in the composite carbon material 1 are inserted, and the composite carbon material 1 with respect to the desired lithium amount is further doped. Since the amount of the negative electrode can be reduced, the thickness of the negative electrode can be reduced, and a high energy density can be obtained. As the amount of doping increases, the negative electrode potential decreases, and the input / output characteristics, energy density, and durability improve.
On the other hand, when the doping amount is 2,500 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal will occur.

Hereinafter, as a preferable example of the composite carbon material 1, the composite carbon material 1a using activated carbon as the base material will be described.
The composite carbon material 1a has a mesopore amount of Vm1 (cc / g) derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method, and a micropore amount derived from pores having a diameter of less than 20 Å calculated by the MP method. When Vm2 (cc / g), 0.010 ≦ Vm1 ≦ 0.300 and 0.001 ≦ Vm2 ≦ 0.650 are preferable.
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, the amount of lithium ion doped can be increased, and the bulk density of the negative electrode can be increased, so that the negative electrode can be increased. Can be thinned. Further, when the micropore amount Vm2 is 0.650 cc / g or less, high charge / discharge efficiency for lithium ions can be maintained. On the other hand, when the mesopore amount Vm1 and the micropore amount Vm2 are equal to or higher 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. When the BET specific surface area is 100 m ² / g or more, the pores can be appropriately retained, and the diffusion of lithium ions becomes good, so that high input / output characteristics can be exhibited. Moreover, since the doping amount of lithium 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 / discharge efficiency of lithium ions is improved, so that the 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 even more preferably 30 Å or more, from the viewpoint of obtaining high input / output characteristics. On the other hand, from the viewpoint of increasing the energy density, the average pore diameter is preferably 65 Å or less, and more preferably 60 Å or less.

The average particle size 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, still more preferably 2.5 μm or more. The upper limit is more preferably 6 μm or less, still more preferably 4 μm or less. Good durability is maintained when the average particle size is 1 μm or more and 10 μm or less.

The atomic number ratio (H / C) of hydrogen atoms / carbon atoms 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 the H / C is 0.35 or less, the structure of the carbonaceous material adhered to the surface of the activated carbon (typically, the polycyclic aromatic conjugated structure) is well developed and the capacity (energy). Density) and charge / discharge efficiency increase. On the other hand, when the H / C is 0.05 or more, carbonization does not proceed excessively, so that a 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, and at the same time, has a crystal structure mainly derived from the adhered carbonaceous material. According to the X-ray wide-angle diffraction method, the composite carbon material 1a has a (002) plane spacing d002 of 3.60 Å or more and 4.00 Å or less, and crystallites in the c-axis direction obtained from the half-value width of this peak. The size Lc is preferably 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 range of this peak is 11. More preferably, it is 0Å or more and 16.0Å 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 properties. For example, commercially available products obtained from various raw materials such as petroleum-based, coal-based, plant-based, and polymer-based 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, and 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 specified in the present embodiment, 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 20Å or more and 500Å 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 20Å calculated by the MP method. 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 even more preferable. Regarding the micropore amount V2, 0.005 ≦ V2 ≦ 0.850 is more preferable, and 0.100 ≦ V2 ≦ 0.800 is even more preferable. 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 even more preferable. When the mesopore amount V1 of the activated carbon is 0.500 or less and the micropore amount V2 is 1.000 or less, an appropriate amount of carbonaceous material is used to obtain the pore structure of the composite carbon material 1a in the present embodiment. Since it is sufficient to adhere the material, it becomes easy to control the pore structure. On the other hand, when the mesopore amount V1 of the 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 can be easily obtained even in the following cases.

The carbonaceous material precursor used as the raw material of the composite carbon material 1a is a solid, liquid, or solvent-soluble organic material capable of adhering the carbonaceous material to the 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 an inexpensive pitch in terms of manufacturing cost. The pitch is roughly divided into petroleum-based pitch and coal-based pitch. Examples of petroleum-based pitches include distillation residue of crude oil, fluid contact decomposition residue (decant oil, etc.), bottom oil derived from thermal crackers, ethylene tar obtained during naphtha cracking, and the like.

When the above pitch is used, the pitch is heat-treated in the coexistence with the activated carbon, and the volatile component or the pyrolysis component of the pitch is thermally reacted on the surface of the activated carbon to coat the activated carbon with a carbonaceous material. Material 1a is obtained. In this case, the adhesion of the volatile component or the pyrolysis component of the pitch into the activated carbon pores proceeds at a temperature of about 200 to 500 ° C., and the reaction in which the adhered component becomes a carbonaceous material proceeds at 400 ° C. or higher. To do. The peak temperature (maximum temperature reached) during the heat treatment is appropriately determined depending on 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 400 ° C. or higher. 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-treating at a peak temperature of about 500 to 800 ° C. for 2 hours to 5 hours, it is considered that the carbonaceous material adhered to 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 hinder handleability and can be charged with high accuracy. A pitch having a softening point of 250 ° C. or lower contains a large amount of a relatively low molecular weight compound. Therefore, when the pitch is used, even fine pores in the activated carbon can be adhered.
As a specific method for producing the above-mentioned composite carbon material 1a, for example, the activated carbon is heat-treated in an inert atmosphere containing a hydrocarbon gas volatilized from the carbonaceous material precursor, and the carbonaceous material is covered with a vapor phase. There is a method of dressing. Further, a method in which the activated carbon and the carbonaceous material precursor are mixed in advance and heat-treated, or a method in which the carbonic material precursor dissolved in a solvent is applied to the activated carbon, dried, and then heat-treated is also possible.

The mass ratio of the carbonaceous material to the activated carbon in the composite carbon material 1a is preferably 10% by mass or more and 100% by mass or less, and more preferably 15% by mass or more and 80% by mass or less. When the mass ratio of the carbonaceous material is 10% by mass or more, the micropores of the activated carbon can be appropriately filled with the carbonic material, and the charge / discharge efficiency of lithium ions is improved, so that the cycle durability is improved. The sex is not impaired. Further, when the mass ratio of the carbonaceous material is 100% by mass or less, the pores of the composite carbon material 1a are appropriately retained and the specific surface area is maintained large. Therefore, from the result that the doping amount of lithium ions can be increased, high output density and high durability can be maintained even if the negative electrode is thinned.

[Composite carbon material 2]
The composite carbon material 2 is the composite carbon material using one or more carbon materials 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 2, ^{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 / It is less than or equal to g. When the BET specific surface area is 1 m ² / g or more, a sufficient reaction field with lithium ions can be secured, so that 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 lithium 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 size of the composite carbon material 2 is preferably 1 μm or more and 10 μm or less, 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 size is 1 μm or more, the charge / discharge efficiency of lithium ions can be improved, so that high cycle durability can be exhibited. On the other hand, if it is 10 μm or less, the reaction area between the composite carbon material 2 and the non-aqueous electrolytic 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 2 is preferably 1% by mass or more and 30% by mass or less, more preferably 1.2% by mass or more and 25% by mass or less, and further preferably 1.5% by mass. It is 20% by mass or less. When the mass ratio of the carbonaceous material is 1% or more by mass, the carbonaceous material can sufficiently increase the reaction sites with lithium ions, and the desolvation of lithium ions becomes easy, so that high input / output characteristics can be obtained. Can be shown. On the other hand, when the mass ratio of the carbonaceous material is 20% by mass or less, the diffusion of lithium ions between the carbonaceous material and the base material in the solid can be well maintained, so that high input / output characteristics can be exhibited. it can. Moreover, since the charge / discharge efficiency of lithium ions is improved, high cycle durability can be exhibited.

The doping amount of lithium ions per unit mass of the composite carbon material 2 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.
Since the negative electrode potential is lowered by doping with lithium ions, when the negative electrode containing the lithium ion-doped composite carbon material 2 is combined with the positive electrode, the voltage of the non-aqueous lithium-type power storage element is increased and the voltage is increased. The capacity of the positive electrode is increased. As a result, the capacity and energy density of the obtained non-aqueous lithium-type power storage element are increased.
When the doping amount is 50 mAh / g or more, lithium ions are satisfactorily doped even at irreversible sites that cannot be desorbed once the lithium ions in the composite carbon material 2 are inserted, so that a high energy density can be obtained. As the amount of doping increases, the negative electrode potential decreases, and the input / output characteristics, energy density, and durability improve.
On the other hand, when the doping amount is 700 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal will occur.

Hereinafter, as a preferable example of the composite carbon material 2, the composite carbon material 2a using a graphite material as the base material will be described.

The average particle size of the composite carbon material 2a is preferably 1 μm or more and 10 μm or less, 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 size is 1 μm or more, the charge / discharge efficiency of lithium ions can be improved, so that high cycle durability can be exhibited. On the other hand, if it is 10 μm or less, the reaction area between the composite carbon material 2a and the non-aqueous electrolytic solution increases, so that high input / output characteristics can be exhibited.

The BET specific surface area of the composite carbon material 2a 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. When the BET specific surface area is 1 m ² / g or more, a sufficient reaction field with lithium ions can be secured, so that 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 lithium 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 2a exhibits desired properties. For example, artificial graphite, natural graphite, graphitized mesophase carbon spherules, graphite whiskers and the like can be used. The average particle size of the graphite material is preferably 1 μm or more and 10 μm or less, and more preferably 2 μm or more and 8 μm or less.

The carbonaceous material precursor used as the raw material of the composite carbon material 2a is a solid, liquid, or solvent-soluble organic material capable of combining 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 an inexpensive pitch in terms of manufacturing cost. The pitch is roughly divided into petroleum-based pitch and coal-based pitch. Examples of petroleum-based pitches include distillation residue of crude oil, fluid contact decomposition residue (decant oil, etc.), bottom oil derived from thermal crackers, 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 2a is preferably 1% by mass or more and 10% by mass or less. This mass ratio is more preferably 1.2% by mass or more and 8% by mass or less, further preferably 1.5% by mass or more and 6% by mass or less, and particularly preferably 2% by mass or more and 5% by mass or less. When the mass ratio of the carbonaceous material is 1% by mass or more, the carbonaceous material can sufficiently increase the reaction sites with lithium ions and desolvate the lithium ions easily, so that high input / output characteristics can be obtained. Can be shown. On the other hand, when the mass ratio of the carbonaceous material is 20% by mass or less, the diffusion of lithium ions between the carbonaceous material and the graphite material in the solid can be well maintained, so that high input / output characteristics can be exhibited. it can. Moreover, since the charge / discharge efficiency of lithium ions can be improved, high cycle durability can be exhibited.

[Arbitrary ingredient]
If necessary, the negative electrode active material layer may contain an optional component such as a conductive filler, a binder, and a dispersion stabilizer in addition to the negative electrode active material.
The type of the conductive filler is not particularly limited, and 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 0 parts by mass or more 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 part 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 inhibiting the entry and exit of lithium ions into the negative electrode active material.

The dispersion stabilizer is not particularly limited, but for example, PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), a cellulose derivative and the like can be used. The amount of the dispersion stabilizer used is preferably 0 parts 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, high input / output characteristics are exhibited without inhibiting the entry and exit of lithium ions into the negative electrode active material.

[Negative electrode current collector]
The material constituting the negative electrode current collector is preferably a metal foil having high electron conductivity and not deteriorating due to elution into a non-aqueous electrolyte solution and reaction with an electrolyte or ions. Such metal foil is not particularly limited, and examples thereof include aluminum foil, copper foil, nickel foil, and stainless steel foil. Copper foil is preferable as the negative electrode current collector in the non-aqueous lithium-type power storage element of the present embodiment.
The metal foil may be an ordinary metal foil having no irregularities or through holes, a metal foil having irregularities subjected to embossing, chemical etching, electrolytic precipitation, blasting, etc., expanded metal, punching metal, etc. , A metal foil having through holes 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 maintained, but is preferably 1 to 100 μm, for example.

[Manufacturing of negative electrode]
The negative electrode has a negative electrode active material layer on one side or both sides 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 technique for manufacturing electrodes in known lithium ion batteries, electric double layer capacitors and the like. For example, various materials including a negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to one or both sides 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, it is also possible to dry-mix various materials including the negative electrode active material without using a solvent, press-mold the obtained mixture, and then attach it to the negative electrode current collector using a conductive adhesive. is there.

The coating liquid is prepared by dry-blending a part or all of various material powders including the negative electrode active material, and then water or an organic solvent and / or a liquid or a dispersion in which a binder or a dispersion stabilizer is dissolved or dispersed. A slurry-like substance may be added to prepare the mixture. Further, various material powders containing a negative electrode active material may be added to a liquid or slurry substance in which a binder or a dispersion stabilizer is dissolved or dispersed in water or an organic solvent. Although the adjustment of the coating liquid is not particularly limited, a disperser such as a homodisper, a multi-axis disperser, a planetary mixer, or a thin film swirl type high-speed mixer can be preferably used. In order to obtain a coating liquid in a well-dispersed 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. On the other hand, when it is 50 m / s or less, it is preferable because various materials are not destroyed by heat or shearing force due to dispersion and reaggregation does not occur.

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, still more preferably 1,700 mPa · s. It is 5,000 mPa · s or less. When the viscosity (ηb) is 1,000 mPa · s or more, liquid dripping during coating film formation is suppressed, and the coating film width and film thickness can be satisfactorily controlled. On the other hand, when it is 20,000 mPa · s or less, the pressure loss in the flow path of the coating liquid when using the coating machine is small and stable coating can be performed, and the coating film thickness can be controlled to be less than the desired coating film thickness.
The TI value (thixotropy index value) of the coating liquid is preferably 1.1 or more, more preferably 1.2 or more, and further preferably 1.5 or more. When the TI value is 1.1 or more, the coating film width and the film thickness can be satisfactorily controlled.

The 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 single-layer coating or multi-layer 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 ensured.

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. The coating film may be dried at a single temperature, or may be dried at different temperatures in multiple stages. Moreover, you may dry by combining a plurality of drying methods. 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 lower, cracks in the coating film due to rapid volatilization of the solvent, 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 press pressure, the gap, and the surface temperature of the press portion, which will be described later. The press 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. When the press 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 does not bend or wrinkle, and the film thickness and bulk density of the negative electrode active material can be adjusted to a desired value. Further, the gap between the press rolls can be set to an arbitrary value according to the film thickness of the negative electrode after drying so as to have a desired film thickness and bulk density of the negative electrode active material layer. Further, the pressing speed can be set to an arbitrary speed at which the negative electrode does not bend or wrinkle. Further, the surface temperature of the pressed portion may be room temperature or may be heated if necessary. The lower limit of the surface temperature of the pressed portion at the time of heating is preferably the melting point of the binder to be used of minus 60 ° C. or higher, more preferably 45 ° C. or higher, still more preferably 30 ° C. or higher. On the other hand, the upper limit of the surface temperature of the pressed portion when heating 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, and further preferably 120 ° C. Warm 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 even more preferably. Warm to 70 ° C or higher and 120 ° C or lower.

The melting point of the binder can be determined from the endothermic peak position of DSC (Differential Scanning Calorimetry, differential scanning calorimetry). For example, using a differential scanning calorimeter "DSC7" manufactured by PerkinElmer, 10 mg of sample resin is set in a measurement cell, and the temperature rises from 30 ° C. to 250 ° C. at a heating rate of 10 ° C./min in a nitrogen gas atmosphere. The temperature is raised, and the endothermic peak temperature in the temperature raising process becomes the melting point. Further, the press may be performed a plurality of times while changing the conditions of the press pressure, the gap, the speed, and the surface temperature of the press portion.

The film thickness of the negative electrode active material layer is preferably 5 μm or more and 100 μm or less per side. The lower limit of the film thickness of the negative electrode active material layer is more preferably 7 μm or more, still more preferably 10 μm or more. The upper limit of the film thickness of the negative electrode active material layer is more preferably 80 μm or less, and further preferably 60 μm or less. When this film thickness is 5 μm or more, no streaks or the like are generated when the negative electrode active material layer is applied, and the coatability is excellent. On the other hand, when this film thickness is 100 μm or less, a high energy density can be developed by reducing the cell volume. The film thickness of the negative electrode active material layer when the current collector has through holes or irregularities means the average value of the film thickness per side of the portion 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 the negative electrode active materials can be exhibited. On the other hand, if 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.

[Measuring method]
In the present specification, the BET specific surface area, the average pore diameter, the mesopore amount, and the micropore amount are values obtained by the following methods, respectively. The sample is vacuum dried at 200 ° C. for 24 hours, and the isotherm of adsorption / desorption is measured using nitrogen as an adsorbent. Using the adsorption isotherm obtained here, the BET specific surface area is the BET multi-point method or the BET one-point method, and the average pore diameter is the mesopores by dividing the total pore volume per mass by the BET specific surface area. The amount is calculated by the BJH method, and the amount of micropores is calculated by the MP method.
The BJH method is a calculation method generally used for the analysis of mesopores, and was proposed by Barrett, Joiner, Hallenda et al. (E.P. Barrett, L.G. Joiner and P. Hallenda, J. Am. Chem. Soc., 73, 373 (1951)).
Further, the MP method is a micropore volume, a micropore area, and a micropore area using the "t-plot method" (BC Lippens, JH de Boer, J. Catalysis, 4319 (1965)). It means a method for obtaining the distribution of micropores, and M.I. It is a method devised by Mikhair, Brunauer, and Bodor (RS Mikhair, S. Brunauer, EE Bodor, J. Colloid Interface Sci., 26, 45 (1968)).

The average particle size is the particle size (that is, 50% diameter) at the point where the cumulative curve is 50% when the cumulative curve is obtained with the total product as 100% when the particle size distribution is measured using a particle size distribution measuring device. (Median diameter)). This average particle size can be measured using a commercially available laser diffraction type particle size distribution measuring device.

The amount of lithium ions doped in the negative electrode active material in the non-aqueous lithium-type power storage element at the time of shipment and after use can be known, for example, as follows.
First, the negative electrode active material layer in the present embodiment is washed with ethyl methyl carbonate or dimethyl carbonate and air-dried, and then an extract extracted with a mixed solvent consisting of methanol and isopropanol and an extracted negative electrode active material layer are obtained. This extraction is typically carried out in an Ar box at an ambient temperature of 23 ° C.
The amount of lithium contained in the extract obtained as described above and the negative electrode active material layer after extraction is quantified using, for example, ICP-MS (inductively coupled plasma mass spectrometer) or the like. By obtaining the total, the amount of lithium ion doped in the negative electrode active material can be known. Then, the obtained value may be allocated by the amount of the negative electrode active material used for extraction to calculate the numerical value of the above unit.

For the primary particle size, the powder is photographed in several fields with an electron microscope, and the particle size of the particles in those fields is measured by about 2,000 to 3,000 using a fully automatic image processing device or the like. Can be obtained by a method in which the arithmetic mean value of is used as the primary particle size.

In the present specification, the dispersity is a value obtained by a dispersity evaluation test using a grain gauge specified in JIS K5600. That is, a sufficient amount of sample is poured into the tip of the deeper groove of the grain gauge having a groove of a desired depth according to the size of the grain, and the sample is slightly overflowed from the groove. Next, the long side of the scraper becomes parallel to the width direction of the gauge, and the cutting edge is placed so as to contact the deep tip of the groove of the grain gauge, and the scraper is held so as to be the surface of the gauge while the long side direction of the groove. Pull the surface of the gauge at a right angle to the groove depth of 0 at a uniform speed for 1 to 2 seconds, and shine light at an angle of 20 ° to 30 ° within 3 seconds after the pulling is completed. Observe and read the depth at which the grains appear in the grooves of the grain gauge.

The viscosity (ηb) and the TI value are values obtained by the following methods, respectively. First, a stable viscosity (ηa) is obtained after measuring for 2 minutes or more under the conditions of a temperature of 25 ° C. and a shear rate of 2s- ¹ using an E-type viscometer. Next, the viscosity (ηb) measured under the same conditions as above is obtained except that the shear rate is changed to 20s ^-1 . Using the viscosity value obtained above, the TI value is calculated by the formula TI value = ηa / ηb. When increasing the shear rate from 2s ^-1 to 20s ^-1 , the shear rate may be increased in one step, or the shear rate may be increased in multiple steps within the above range, and the viscosity at the shear rate may be appropriately obtained. You may let me.

[Electrolytic solution]
The electrolytic solution of this embodiment is a non-aqueous electrolytic solution. That is, this electrolytic solution contains a non-aqueous solvent described later. The non-aqueous electrolyte solution preferably contains 0.5 mol / L or more of a lithium salt based on the total amount of the non-aqueous electrolyte solution. That is, the non-aqueous electrolyte solution contains lithium ions as an electrolyte.

[Lithium salt]
The non-aqueous electrolyte solution is, for example, (LiN (SO ₂ F) ₂ ), LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) ( SO ₂ C ₂ F ₅ ), LiN (SO ₂ CF ₃ ) (SO ₂ C ₂ F ₄ H), LiC (SO ₂ F) ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiC (SO ₂ C ₂ F ₅₎ ) ₃ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiPF ₆ , LiBF _4, etc. can be used alone, or two or more of them may be mixed and used. It is preferable to contain LiPF ₆ and / or LiN (SO ₂ F) ₂ because it can exhibit high conductivity.
The lithium salt concentration in the non-aqueous electrolyte solution is preferably 0.5 mol / L or more, more preferably 0.5 mol / L or more and 2.0 mol / L or less, based on the total amount of the non-aqueous electrolyte solution. .. When the lithium salt concentration is 0.5 mol / L or more, anions are sufficiently present, so that the capacity of the power storage element can be sufficiently increased. Further, when the lithium salt concentration is 2.0 mol / L or less, it is possible to prevent undissolved lithium salt from precipitating in the non-aqueous electrolytic solution and the viscosity of the electrolytic solution from becoming too high, resulting in a decrease in conductivity. It is preferable because it does not reduce the output characteristics.

The non-aqueous electrolyte solution preferably contains LiN (SO ₂ F) ₂ having a concentration of 0.1 mol / L or more and 1.5 mol / L or less based on the total amount of the non-aqueous electrolyte solution, and more preferably 0.3 mol. / L or more and 1.2 mol / L or less. When LiN (SO ₂ F) ₂ is 0.1 mol / L or more, the ionic conductivity of the electrolytic solution is increased, and an appropriate amount of an electrolyte film is deposited on the negative electrode interface, thereby reducing the gas caused by the decomposition of the electrolytic solution. can do. On the other hand, when this value is 1.5 mol / L or less, precipitation of the electrolyte salt does not occur during charging and discharging, and the viscosity of the electrolytic solution does not increase even after a long period of time.

[Non-aqueous solvent]
The non-aqueous electrolyte solution preferably contains a cyclic carbonate as a non-aqueous solvent. The inclusion of the cyclic carbonate in the non-aqueous electrolyte solution is advantageous in that it dissolves a lithium salt having a desired concentration and that an appropriate amount of the lithium compound is deposited on the positive electrode active material layer. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate and the like.
The total content of the cyclic carbonate is preferably 15% by mass or more, more preferably 20% by mass or more, based on the total amount of the non-aqueous electrolyte solution. When the total content is 15% by mass or more, a lithium salt having a desired concentration can be dissolved, and high lithium ion conductivity can be exhibited. Further, an appropriate amount of the lithium compound can be deposited on the positive electrode active material layer, and oxidative decomposition of the electrolytic solution can be suppressed.

The non-aqueous electrolyte solution of the present embodiment preferably contains a chain carbonate as a non-aqueous solvent. It is advantageous that the non-aqueous electrolyte solution contains a chain carbonate in that it exhibits high lithium ion conductivity. Examples of the chain carbonate include dialkyl carbonate compounds typified by dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, dibutyl carbonate and the like. Dialkyl carbonate compounds are typically unsubstituted.
The total content of the chain carbonate is preferably 30% by mass or more, more preferably 35% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, based on the total amount of the non-aqueous electrolyte solution. is there. When the content of the chain carbonate is 30% by mass or more, the viscosity of the electrolytic solution can be reduced and high lithium ion conductivity can be exhibited. When the total concentration is 95% by mass or less, the electrolytic solution can further contain the additives described later.

[Additive]
The non-aqueous electrolyte solution may further contain additives. The additive is not particularly limited, and for example, a sultone compound, cyclic phosphazene, acyclic fluorinated ether, fluorinated cyclic carbonate, cyclic carbonate, cyclic carboxylic acid ester, cyclic acid anhydride and the like may be used alone. It is possible, and two or more kinds may be mixed and used.

[Separator]
The positive electrode precursor and the negative electrode are laminated or wound via a separator to form an electrode laminate or an electrode wound body having the positive electrode precursor, the negative electrode and the separator.
As the separator, a polyethylene microporous membrane or polypropylene microporous membrane used in a lithium ion secondary battery, a cellulose non-woven paper used in an electric double layer capacitor, or the like can be used. A film made of organic or inorganic fine particles may be laminated on one side or both sides 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. A thickness of 5 μm or more is preferable because self-discharge due to internal microshorts tends to be small. On the other hand, a thickness of 35 μm or less is preferable because the input / output characteristics of the non-aqueous lithium-type power storage element tend to be improved.
The film made of organic or inorganic fine particles is preferably 1 μm or more and 10 μm or less. A thickness of 1 μm or more is preferable because self-discharge due to internal microshorts tends to be small. On the other hand, a thickness of 10 μm or less is preferable because the input / output characteristics of the non-aqueous lithium-type power storage element tend to be improved.

[Non-aqueous lithium-type power storage element]
The non-aqueous lithium-type power storage element of the present embodiment is configured such that an electrode laminate or an electrode winding body, which will be described later, is housed in the exterior body together with the non-aqueous electrolytic solution.

[assembly]
The electrode laminate obtained in the cell assembly step is a laminate in which a positive electrode precursor and a negative electrode cut into a single-wafer shape are laminated via a separator, and a positive electrode terminal and a negative electrode terminal are connected to the laminate. Further, the electrode winding body is formed 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 wound body may be a flat shape or a cylindrical shape, and the flat shape may be an electrode body in which a positive electrode precursor and a negative electrode are wound into a flat shape via a separator. An electrode body in which a positive electrode precursor and a negative electrode are wound through a separator and then deformed into a flat shape may be used.
The positive electrode terminal and the negative electrode terminal are preferably joined by welding. The method of joining the electrode terminal and the uncoated portion is not particularly limited, but a method such as ultrasonic welding, spot welding, or resistance welding is used.

[Area area of 20% of the peripheral portion and 80% of the central portion of the negative electrode active material layer]
In the non-aqueous lithium storage element according to the present embodiment, the concentration of lithium ions is higher in the area region of 80% of the central portion than in the area region of 20% of the peripheral portion of the negative electrode active material layer.
In the present specification, the area region of the central portion x% of the negative electrode active material layer is, in principle, the region when the electrode on which the negative electrode active material layer is arranged is viewed from above in the area region facing the positive electrode active material. Refers to a region in which the estimation line separating the regions is closed without intersecting any end of the electrode, but when the estimation line separating the regions overlaps the pair of opposing electrode ends, the center of the negative electrode active material layer. The area region of the portion x% also includes a region overlapping with a maximum of three sides of the continuous electrode end portions.
For example, when the electrode laminate is a laminate of single-wafer electrodes, according to the above definition, as illustrated in FIG. 1, a position where the length from each of the four sides of the negative electrode end is 5% is determined. It can be defined as an area region (4) of 20% of the peripheral portion of the negative electrode active material layer (2), whereby the outer peripheral portion of the area region (3) of 80% of the central portion of the negative electrode active material layer (2) is also defined. It is decided.
Further, when the electrode stack is wound laminate, as illustrated in FIG. 2, the longitudinal direction of the length of the electrode when projected view from the direction perpendicular to the winding center axes x ₂ The wound laminate is cut at the position of, and an area region (3) of 80% of the central portion and an area region (4) of 20% of the peripheral portion are defined by using an open electrode. As illustrated in FIG. 2, the length x ₂ of the cut-out wound laminate in the long direction roughly corresponds to the electrode length in the long direction of the non-aqueous lithium storage element including the cut-out wound laminate. To do.
In the non-aqueous lithium storage device according to the present embodiment, there is a correlation between the lithium ion concentration and the thickness of the active material layer. In the region where the lithium ion concentration is high, the active material layer contains a large amount of lithium ions, so that the active material expands and the active material layer becomes thick.
In the non-aqueous lithium storage element according to the present embodiment, it is preferable that the concentration of lithium ions is higher in the area region of 80% of the central portion than in the area region of 20% of the peripheral portion of the negative electrode active material layer. If the concentration of lithium ions is higher in the area region of 80% of the central portion than in the area region of 20% of the peripheral portion of the negative electrode active material layer, the precipitation of metallic lithium in the high load charge / discharge cycle can be suppressed.

[Outermost layer and innermost layer in the thickness direction of the laminate]
In the non-aqueous lithium storage element according to the present embodiment, as illustrated in FIG. 3, the lithium ion concentration C _{1o at} the center when the negative electrode active material layer of the negative electrode (5) in the outermost layer in the thickness direction of the laminate is viewed from above. When the lithium ion concentration C _{1i at} the center of the negative electrode active material layer of the negative electrode (6) in the innermost layer in the thickness direction of the laminate is taken as C _1i , C _1o / C _1i is 0.85 or more and 1.15 or less. is there. The outermost layer in the thickness direction of the laminate means the negative electrode laminated on the outermost layer in the thickness direction among the negative electrodes forming the laminate, and the innermost layer in the thickness direction of the laminate is the negative electrode centered in the thickness direction of the laminate. Means. When there are two negative electrodes in the outermost layer and the innermost layer, the lithium ion concentration is the average value of the two negative electrodes.

[Outer circumference and inner circumference of winding body]
In the non-aqueous lithium storage element according to the present embodiment, the lithium ion concentration C _{2o at} the center when the negative electrode active material layer of the negative electrode on the outer peripheral portion of the wound _{body is viewed} from above, and the negative electrode on the inner peripheral portion of the wound _body . When the lithium ion concentration C _{2i at} the center when the negative electrode active material layer is viewed from above, C _2o / C _2i is 0.85 or more and 1.15 or less. As shown in FIG. 4, the outer peripheral portion (9) of the wound body is opposed to the positive electrode (8) in the negative electrode forming the wound body, and is wound in the central region excluding the peripheral portion of the negative electrode. It means the negative electrode active material layer for one circumference of the outermost circumference, and the inner peripheral portion (7) of the wound body is the negative electrode forming the wound body, which faces the positive electrode (8) and is the peripheral portion of the negative electrode. It means the negative electrode active material layer for one innermost circumference to be wound in the central region excluding.

In the non-aqueous lithium power storage element according to the present embodiment, the negative electrode negative electrode of the negative electrode in the outermost layer in the thickness direction of the laminate has the central lithium ion concentration _C1o when the active material layer is viewed from above, and the negative electrode in the innermost layer in the thickness direction of the laminate. The central lithium ion concentration C _1i when the negative electrode active material layer is viewed from above, and the central lithium ion concentration C _2o when the negative electrode active material layer of the negative electrode is viewed from above on the outer periphery of the wound body. When the central lithium ion concentration C _2i when the negative electrode active material layer of the negative electrode in the inner peripheral portion of the wound body is viewed from above, both C _1o / C _1i and C _2o / C _2i are 0.85. It is preferably 1.15 or less. When C _1o / C _1i and C _2o / C _2i are 0.85 or more and 1.15 or less, the variation of the potential in the plane of the negative electrode is small, gas generation due to the reaction with the electrolytic solution is suppressed, and the non-aqueous system is used. When the lithium storage element is subjected to a long-term charge / discharge test, an increase in resistance can be suppressed. C _1o / C _1i and C _2o / C _2i are more preferably 0.90 or more and 1.10 or less.

The thickness of the central negative electrode active material layer when the negative electrode active material layer of the negative electrode in the outermost layer in the thickness direction of the laminate is viewed from above is T _1o , and the negative electrode active material layer of the negative electrode in the innermost layer in the thickness direction of the laminate is the upper surface. When the thickness of the negative electrode active material layer at the center when viewed is T _1i , it is preferable that T _1o / T _1i is 0.85 or more and 1.15 or less.
Further, the thickness of the center facing the positive electrode of the wound _body and facing the negative electrode active material layer of the negative electrode on the outermost radius in the radial direction excluding the peripheral portion is T _2o , facing the positive electrode of the wound _body . when the anode active material layer thickness of the center when viewed from the top of the negative electrode in the radial direction innermost layer except for the life-and-death periphery and T _2i, it T _2o / T _2i is 0.85 to 1.15 Is preferable.
When T _1o / T _1i and T _2o / T _2i are 0.85 or more and 1.15 or less, respectively, the variation in potential in the plane of the negative electrode is reduced, and gas generation due to the reaction with the electrolytic solution is suppressed. When a non-aqueous lithium storage element is subjected to a long-term charge / discharge test, an increase in resistance can be suppressed. T _1o / T _1i and T _2o / T _2i are more preferably 0.90 or more and 1.10 or less.

[Exterior body]
As the exterior body, a metal can, a laminated packaging material, or the like can be used.
The metal can is not particularly limited, and for example, a metal material such as aluminum or iron can be used, but aluminum is preferable from the viewpoint of reducing the weight of the obtained winding type.
As the laminated packaging material, a film obtained by laminating a metal foil and a resin film is preferable, and a three-layer structure composed of an outer layer resin film / metal foil / interior resin film is exemplified. 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 such as copper, aluminum, and stainless steel can be preferably used. Further, the interior resin film is for protecting the metal foil from the non-aqueous electrolyte solution stored inside and for melting and sealing the exterior body at the time of heat sealing, and polyolefins, acid-modified polyolefins and the like can be preferably used.

[Storage in the exterior]
It is preferable that the dried electrode laminate or electrode wound body is housed in an exterior body typified by a metal can or a laminate packaging material, and sealed with only one opening left. The sealing method of the outer body is not particularly limited, but when a laminated packaging material is used, a method such as heat sealing or impulse sealing is used.

[Dry]
It is preferable that the electrode laminate or the electrode wound body housed in the outer body is dried to remove the residual solvent. The drying method is not limited, but it is dried by vacuum drying or the like. The residual solvent is preferably 1.5% by mass or less per mass of the positive electrode active material layer or the negative electrode active material layer. If the residual solvent is more than 1.5% by mass, the solvent remains in the system and the self-discharge characteristics and cycle characteristics are deteriorated, which is not preferable.

[Liquid injection, impregnation, sealing process]
After the assembly process is completed, the non-aqueous electrolyte solution is injected into the electrode laminate or electrode winding body housed in the exterior body. After the completion of the liquid injection step, it is desirable to further impregnate and sufficiently immerse the positive electrode, the negative electrode, and the separator with a non-aqueous electrolytic solution. When the non-aqueous electrolyte solution is not immersed in at least a part of the positive electrode, the negative electrode, and the separator, the doping proceeds non-uniformly in the lithium doping step described later, so that the resistance of the obtained non-aqueous lithium storage element becomes high. It rises or becomes less durable. The impregnation method is not particularly limited, but for example, the electrode laminate or electrode winding body after injection is installed in a decompression chamber with the outer body open, and the inside of the chamber is used with a vacuum pump. A method of reducing the pressure and returning the pressure to atmospheric pressure can be used. After the impregnation step is completed, the electrode laminate or the electrode wound body with the outer body open is sealed while reducing the pressure.

[Lithium dope process]
In the lithium doping step, a preferable step is to apply a voltage between the positive electrode precursor and the negative electrode to decompose the lithium compound, thereby decomposing the lithium compound in the positive electrode precursor and releasing lithium ions. By reducing lithium ions at the negative electrode, liotium ions are pre-doped into the negative electrode active material layer.
In this lithium doping step, gas such as CO ₂ is generated due to oxidative decomposition of the lithium compound in the positive electrode precursor. Therefore, when applying a voltage, it is preferable to take measures to release the generated gas to the outside of the exterior body. As this means, for example, a method of applying a voltage with a part of the exterior body opened; a state in which an appropriate gas release means such as a gas vent valve or a gas permeable film is previously installed in the part of the exterior body. A method of applying a voltage with the above;

[Aging process]
After the lithium doping step is completed, it is preferable to age the electrode laminate or the electrode wound body. In the aging step, the solvent in the non-aqueous electrolyte solution is decomposed at the negative electrode, and a lithium ion permeable solid polymer film is formed on the surface of the negative electrode.
The aging method is not particularly limited, and for example, a method of reacting a solvent in a non-aqueous electrolyte solution in a high temperature environment can be used.

[Degassing process]
After the aging step is completed, it is preferable to further degas to surely remove the gas remaining in the non-aqueous electrolyte solution, the positive electrode, and the negative electrode. In a state where gas remains in at least a part of the non-aqueous electrolyte solution, the positive electrode, and the negative electrode, ion conduction is inhibited, so that the resistance of the obtained non-aqueous lithium power storage element increases.
The degassing method is not particularly limited, but for example, the electrode laminate or the electrode winding body is installed in the decompression chamber with the exterior body open, and the inside of the chamber is depressurized by using a vacuum pump. A method or the like can be used.

[Characteristic evaluation of non-aqueous lithium-type power storage element]
[Capacitance]
The capacitance F (F) was a value obtained by the following method.
First, in a constant temperature bath in which the cell corresponding to the non-aqueous lithium-type power storage element is set to 25 ° C, constant current charging is performed until the current value of 20C reaches 3.8V, and then a constant voltage of 3.8V is applied. The constant voltage charging to be applied is performed for a total of 30 minutes. After that, let Q be the capacitance when constant current discharge is performed with a current value of 2C up to 2.2V. It means a value calculated by F = Q / (3.8-2.2) using the Q obtained here.

[Room temperature discharge internal resistance]
The room temperature discharge internal resistance Ra (Ω) was a value obtained by the following method.
First, the cell corresponding to the non-aqueous lithium-type power storage element is charged with a constant current at a current value of 20C until it reaches 3.8V in a constant temperature bath set at 25 ° C., and then a constant voltage of 3.8V is applied. Constant voltage charging is performed for a total of 30 minutes. Next, a constant current discharge is performed up to 2.2 V with a current value of 20 C to obtain a discharge curve (time-voltage). In this discharge curve, when the voltage at the discharge time = 0 seconds obtained by extrapolating from the voltage values at the discharge times of 2 seconds and 4 seconds is set to Eo, the drop voltage ΔE = 3.8- It is a value calculated by Eo and Ra = ΔE / (20C (current value A)).

[Rate of increase in internal resistance of normal temperature discharge after high load charge / discharge cycle test]
The rate of increase in internal resistance of normal temperature discharge after the high load charge / discharge cycle test was measured by the following method.
First, the cell corresponding to the non-aqueous lithium-type power storage element is charged at a constant current in a constant temperature bath set at 25 ° C. until it reaches 3.8 V at a current value of 300 C, and then 2.2 V at a current value of 300 C. Constant current discharge is performed until reaches. The charge / discharge process is repeated 60,000 times, and the internal resistance of normal temperature discharge is measured before the start of the test and after the end of the test. When Ω) is set, the resistance increase rate after the high load charge / discharge cycle test before the start of the test is calculated by Re / Ra.

[Capacity recovery rate after high load charge / discharge cycle test]
The capacity retention rate after the high load charge / discharge cycle test was measured by the following method.
First, the cell corresponding to the non-aqueous lithium-type power storage element is charged at a constant current in a constant temperature bath set at 25 ° C. until it reaches 3.8 V at a current value of 300 C, and then 2.2 V at a current value of 300 C. Constant current discharge is performed until reaches. The charge / discharge step is repeated 60,000 times, and after the voltage reaches 4.5 V at a current value of 20 C, the battery is charged at a constant voltage for 1 hour. After that, when the capacitance value obtained by using the same measurement method as the capacitance is the capacitance Fe after the high load charge / discharge cycle test, the capacitance value is the capacitance before the start of the high load charge / discharge cycle test. The capacitance recovery rate after the high load charge / discharge cycle test for F is calculated by Fe / F.

The non-aqueous lithium type power storage element of the present embodiment has an initial room temperature discharge internal resistance of Ra (Ω), a capacitance of F (F), an ambient temperature of 25 ° C., and a cell voltage of 2.2 V to 3.8 V. After performing 60,000 charge / discharge cycles at a rate of 300 C, the internal resistance of normal temperature discharge is Re (Ω), and the power storage element after the cycle test is charged at a constant voltage of 4.5 V for 1 hour. When the capacitance is Fe (F), the following:
(A) Re / Ra is 0.9 or more and 2.0 or less; and (b) Fe / F is 1.01 or more;
Is preferably satisfied at the same time.
Regarding (a) above, the room temperature discharge internal resistance increase rate Re / Ra after the high load charge / discharge cycle test is preferably 2.0 or less, more preferably 1.5 or less, and further preferably 1. It is 2 or less. If the resistance increase rate after the high load charge / discharge cycle test is not more than the above upper limit value, the characteristics of the device are maintained even if charging / discharging is repeated. Therefore, it is possible to stably obtain excellent output characteristics for a long period of time, which leads to a long life of the device.

Regarding (b), if Fe / F is 1.01 or more, even a power storage element that has been charged and discharged for a long period of time can take out a sufficient amount of energy, so that the replacement cycle of the power storage element can be extended. preferable.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
[Crushing lithium carbonate]
200 g of lithium carbonate having an average particle size of 51 μm is cooled to -196 ° C. with liquid nitrogen using a crusher (liquid nitrogen bead mill LNM) manufactured by Imex, and then using dry ice beads at a peripheral speed of 10.0 m / s. Was crushed for 9 minutes. The charged lithium carbonate particle size was determined by measuring the average particle size of lithium carbonate obtained by preventing thermal denaturation at -196 ° C. and brittle fracture, and found to be 2.5 μm.

[Preparation of positive electrode active material]
[Preparation of activated carbon 1]
The crushed coconut shell carbide was carbonized in nitrogen at 500 ° C. for 3 hours in a small carbonization furnace to obtain carbonized material. The obtained carbide was put into an activation furnace, and 1 kg / h of steam was introduced into the activation furnace in a state of being heated in the preheating furnace, and the temperature was raised to 900 ° C. over 8 hours for activation. The activated carbon was taken out and cooled in a nitrogen atmosphere to obtain activated activated carbon. The obtained activated carbon was washed with water for 10 hours and then drained. Then, after drying in an electric dryer maintained at 115 ° C. for 10 hours, activated carbon 1 was obtained by pulverizing with a ball mill for 1 hour.
The average particle size of this activated carbon 1 was measured using a laser diffraction type particle size distribution measuring device (SALD-2000J) manufactured by Shimadzu Corporation and found to be 4.1 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 2360 m ² / g, the mesopore amount (V1) was 0.52 cc / g, the micropore amount (V2) was 0.88 cc / g, and V1 / V2 = 0.59.

[Preparation of activated carbon 2]
The phenol resin was carbonized in a firing furnace at 600 ° C. for 2 hours in a nitrogen atmosphere, then pulverized by a ball mill and classified to obtain a carbide having an average particle diameter of 7.0 μm. This carbide and KOH were mixed at a mass ratio of 1: 5, and activated by heating in a firing furnace at 800 ° C. for 1 hour in a nitrogen atmosphere. Then, activated carbon 2 was obtained by stirring and washing in dilute hydrochloric acid adjusted to a concentration of 2 mol / L for 1 hour, boiling and washing with distilled water until the pH became stable between 5 and 6, and then drying.
The average particle size of this activated carbon 2 was measured using a laser diffraction type particle size distribution measuring device (SALD-2000J) manufactured by Shimadzu Corporation and found to be 7.1 μm. 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 amount (V1) was 1.50 cc / g, the micropore amount (V2) was 2.28 cc / g, and V1 / V2 = 0.66.

[Preparation of positive electrode coating liquid]
Using the activated carbon 1 or 2 obtained above as the positive electrode active material and the lithium carbonate obtained above as the charged lithium compound, a positive electrode coating liquid was produced by the following method.
Activated carbon 1 or 2 59.5 parts by mass, lithium carbonate 28.0 parts by mass, Ketjen Black 3.0 parts by mass, PVP (polyvinylpyrrolidone) 1.5 parts by mass, and PVdF (polyvinylidene fluoride) 8.0 parts by mass and NMP (N-methylpyrrolidone) are mixed, and the mixture is dispersed and coated under the condition of peripheral speed of 17.0 m / s using a thin film swirling high-speed mixer fill mix manufactured by PRIMIX. I got the 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 2,700 mPa · s, and the TI value was 3.5. Moreover, the degree of dispersion of the obtained coating liquid was measured using a grain gauge manufactured by Yoshimitsu Seiki Co., Ltd. As a result, the particle size was 35 μm.

[Preparation of positive electrode precursor]
The above coating liquid is applied to one or both sides of an aluminum foil having a thickness of 15 μm using a die coater manufactured by Toray Engineering Co., Ltd. at a coating speed of 1 m / s, and dried at a drying temperature of 100 ° C. to obtain a positive electrode precursor. Obtained. The obtained positive electrode precursor was pressed using a roll press machine under the conditions of a pressure of 4 kN / cm and a surface temperature of the press portion of 25 ° C. The average thickness of the positive electrode active material layer of the positive electrode precursor obtained above was measured at any 10 locations of the positive electrode precursor using a film thickness meter Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. It was calculated by subtracting the thickness of the aluminum foil from the value. As a result, the film thickness of the positive electrode active material layer was 61 μm per one side.

[Preparation of negative electrode]
Made of stainless steel containing 150 g of commercially available coconut shell activated carbon with an average particle size of 3.0 μm and a BET specific surface area of 1,780 m ² / g in a stainless steel mesh cage and 270 g of coal-based pitch (softening point: 50 ° C.). A composite carbon material was obtained by placing them on a bat, placing both in an electric furnace (effective dimensions in the furnace 300 mm × 300 mm × 300 mm), and conducting a thermal reaction. This heat treatment was carried out in a nitrogen atmosphere, the temperature was raised to 600 ° C. in 8 hours, and the temperature was maintained at the same temperature for 4 hours. Subsequently, after cooling to 60 ° C. by natural cooling, the composite carbon material 1 was taken out from the furnace.
The average particle size and BET specific surface area of the obtained composite carbon material were measured by the same method as described above. As a result, the average particle size was 3.2 μm and the BET specific surface area was 262 m ² / g. The mass ratio of the carbonaceous material derived from the carbonaceous pitch to the activated carbon was 78%.

Next, a negative electrode was manufactured using the composite carbon material as the negative electrode active material.
85 parts by mass of composite carbon material, 10 parts by mass of acetylene black, 5 parts by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) are mixed and mixed with a thin film swirling high-speed mixer manufactured by PRIMIX Corporation. A coating liquid was obtained by dispersing using a fill mix under the condition of a peripheral speed of 15 m / s. 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 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 1 m / s, and dried at a drying temperature of 85 ° C. to obtain a negative electrode. .. The obtained negative electrode was pressed using a roll press machine under the conditions of a pressure of 4 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 obtained above was measured from the average value of the thickness measured at any 10 points of the negative electrode using a film thickness meter Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. It was calculated by subtracting the thickness of the foil. As a result, the film thickness of the negative electrode active material layer of the negative electrode was 40 μm per one side.

[Preparation of electrolyte]
As the organic solvent, a mixed solvent of ethylene carbonate (EC): methyl ethyl carbonate (MEC) = 33: 67 (volume ratio) was used, and the concentration ratio of LiN (SO ₂ F) ₂ and LiPF _{6 to} the total electrolytic solution was The solution obtained by dissolving each electrolyte salt so that the sum of the concentrations of LiN (SO ₂ F) ₂ and LiPF ₆ is 1.2 mol / L at 75:25 (molar ratio) is non-aqueous electrolysis. Used as a liquid.
The concentrations of LiN (SO ₂ F) ₂ and LiPF ₆ in the electrolytic solution prepared here were 0.3 mol / L and 0.9 mol / L, respectively.

[Example 1]
[Preparation of non-aqueous lithium-type power storage element]
[Assembly process]
The obtained double-sided negative electrode and double-sided positive electrode precursor were cut into 10 cm × 10 cm (100 cm ² ). A single-sided positive electrode precursor is used for the uppermost surface and the lowermost surface, 21 double-sided negative electrodes and 20 double-sided positive electrode precursors are used, and a microporous membrane separator having a thickness of 15 μm is sandwiched between the negative electrode and the positive electrode precursor. Laminated with. Then, the negative electrode terminal and the positive electrode terminal were connected to the negative electrode and the positive electrode precursor by ultrasonic welding, respectively, to form an electrode laminate. This electrode laminate was vacuum dried at a temperature of 80 ° C. and a pressure of 50 Pa under the conditions of a drying time of 60 hr. The dried electrode laminate is housed in an exterior body made of an aluminum laminate packaging material under a dry environment with a dew point of −45 ° C., and the three outer bodies of the electrode terminal portion and the bottom portion are placed at a temperature of 180 ° C. and a sealing time of 20 sec. Heat sealing was performed under the condition of a sealing pressure of 1.0 MPa.

[Liquid injection, impregnation, sealing process]
Approximately 80 g of the non-aqueous electrolyte solution was injected under atmospheric pressure into the electrode laminate housed in the aluminum laminate packaging material in a dry air environment at a temperature of 25 ° C. and a dew point of −40 ° C. or lower. Subsequently, the non-aqueous lithium-type power storage element was placed in the decompression chamber, the pressure was reduced from normal pressure to −87 kPa, the pressure was returned to atmospheric pressure, and the mixture was allowed to stand for 5 minutes. Then, the pressure was reduced from normal pressure to −87 kPa, the process of returning to atmospheric pressure was repeated 4 times, and then the mixture was allowed to stand for 15 minutes. Further, the pressure was reduced from normal pressure to -91 kPa, and then returned to atmospheric pressure. Similarly, the steps of depressurizing and returning to atmospheric pressure were repeated 7 times in total (reduced pressure to -95, 96, 97, 81, 97, 97, 97 kPa, respectively). Through the above steps, the electrode laminate was impregnated with the non-aqueous electrolytic solution.
Then, the non-aqueous lithium-type power storage element was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at 180 ° C. for 10 seconds at a pressure of 0.1 MPa with the pressure reduced to −95 kPa.

[Lithium dope process]
The obtained non-aqueous lithium-type power storage element is charged with a constant current using a charging / discharging device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd. in a 25 ° C environment at a current value of 50 mA until a voltage of 4.5 V is reached. After that, the initial charge was continuously performed by a method of continuing 4.5 V constant voltage charging for 72 hours, and lithium doping was performed on the negative electrode.

[Aging process]
The non-aqueous lithium power storage device after lithium doping is subjected to constant current discharge at 1.0 A at 1.0 A until the voltage reaches 3.0 V, and then 3.0 V constant current discharge is performed for 1 hour to increase the voltage. Adjusted to 3.0V. Then, the non-aqueous lithium-type power storage element was stored in a constant temperature bath at 60 ° C. for 60 hours.

[Degassing process]
A part of the aluminum laminate packaging material was opened in a dry air environment at a temperature of 25 ° C. and a dew point of −40 ° C. for the aged non-aqueous lithium-type power storage element. Next, the non-aqueous lithium-type power storage element is placed in the decompression chamber, and the pressure is reduced from atmospheric pressure to -80 kPa using a diaphragm pump (N816.3KT.45.18) manufactured by KNF for 3 minutes, and then 3 The process of returning to atmospheric pressure over a minute was repeated a total of 3 times. Then, a non-aqueous lithium-type power storage element was placed in a vacuum sealing machine, 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.
Through the above steps, the non-aqueous lithium-type power storage element was completed.

[Evaluation of power storage element]
[Measurement of capacitance]
The obtained power storage element is fixed in a constant temperature bath set at 25 ° C. using a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Limited until it reaches 3.8V at a current value of 20C. Current charging was performed, and then constant voltage charging to which a constant voltage of 3.8 V was applied was performed for a total of 30 minutes. The capacitance F when constant current discharge was performed with a current value of 2C up to 2.2V was defined as Q, and the capacitance F calculated by F = Q / (3.8-2.2) was 1000F.

[Calculation of Ra]
The obtained power storage element is fixed in a constant temperature bath set at 25 ° C. using a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. until it reaches 3.8V at a current value of 20C. Current charging, then constant voltage charging to apply a constant voltage of 3.8V for a total of 30 minutes, then constant current discharge to 2.2V with a current value of 20C, discharge curve (time-voltage) Got In this discharge curve, the voltage at the discharge time = 0 second obtained by extrapolating from the voltage values at the time points of the discharge time of 2 seconds and 4 seconds is defined as Eo, the drop voltage ΔE = 3.8-Eo, and The normal temperature discharge internal resistance Ra calculated from R = ΔE / (20C (current value A)) was 2.01 mΩ.

[Rate of increase in internal resistance of normal temperature discharge after high load charge / discharge cycle test]
The obtained power storage element is fixed in a constant temperature bath set at 25 ° C. using a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Limited until it reaches 3.8V at a current value of 300C. The charging / discharging step of charging with a current and then performing a constant current discharge with a current value of 300 C until reaching 2.2 V was repeated 60,000 times. After the high load charge / discharge cycle test, the normal temperature discharge internal resistance Re after the high load charge / discharge cycle test was calculated in the same manner as in the above [Calculation of Ra / F]. The ratio Re / Ra calculated by dividing this Re (Ω) by the internal resistance Ra (Ω) before the high load charge / discharge cycle test obtained in the above [Calculation of Ra / F] was 1.24.

[Capacity recovery rate after high load charge / discharge cycle test]
The obtained power storage element is fixed in a constant temperature bath set at 25 ° C. using a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Limited until it reaches 3.8V at a current value of 300C. The charging / discharging step of charging with a current and then performing a constant current discharge with a current value of 300 C until reaching 2.2 V was repeated 60,000 times. After the end of the cycle, the battery was charged to 4.5 V with a current value of 20 C, and then constant voltage charging was continued for 1 hour. After that, the capacitance Fe was measured and found to be 1030F, and Fe / F = 1.03.

[Examples 2 to 15, Comparative Examples 1 to 8]
Same as in Example 1 except that the crushing time of the positive electrode activated carbons 1 and 2 by the ball mill and the mixing ratio of the positive electrode coating liquid were changed to prepare a positive electrode, and the aging conditions were set as shown in Table 1 below. Then, the non-aqueous lithium-type power storage elements of Examples 2 to 15 and Comparative Examples 1 to 8 were respectively produced and evaluated in various ways. The evaluation results of the obtained non-aqueous lithium-type power storage element are shown in Table 1 below.

[Example 16]
A positive electrode was prepared by changing the crushing time of the positive electrode activated carbons 1 and 2 by a ball mill and the blending ratio of the positive electrode coating liquid. The obtained double-sided negative electrode and double-sided positive electrode precursor were cut into 12 cm × 230 cm (2760 cm ² ). The negative electrode and the positive electrode precursor each have an uncoated portion. This uncoated portion was formed with a width of 2 cm from the end side. A microporous membrane separator having a thickness of 15 μm is sandwiched so that the uncoated portions are in opposite directions, and the uncoated portion is wound in an elliptical shape so as to protrude from the separator, and the wound body is pressed. Molded into a flat shape. Then, the electrode terminals were bonded to the negative electrode and the positive electrode precursor by ultrasonic welding to form an electrode wound body. This electrode winding body was housed in an exterior body made of an aluminum laminated packaging material, and the three outer bodies of the electrode terminal portion and the bottom portion were heat-sealed under the conditions of a temperature of 180 ° C., a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. .. This was vacuum-dried at a temperature of 80 ° C. and a pressure of 50 Pa under a drying time of 60 hr. A non-aqueous lithium-type power storage device was produced in the same manner as in Example 1 and various evaluations were performed. The evaluation results of the obtained non-aqueous lithium-type power storage element are shown in Table 2 below.

[Examples 17 to 30, Comparative Examples 9 to 16]
A positive electrode was prepared by changing the crushing time of the positive electrode activated carbons 1 and 2 by a ball mill and the blending ratio of the positive electrode coating liquid. Non-aqueous lithium-type power storage devices of Examples 17 to 30 and Comparative Examples 9 to 16 were produced in the same manner as in Example 16 except that the positive electrode and the aging conditions were set as shown in Table 2 below. Various evaluations were performed. The evaluation results of the obtained non-aqueous lithium-type power storage element are shown in Table 2 below.

According to the above embodiment, the power storage element of the present embodiment has excellent initial input characteristics by making the potential between the electrodes uniform without increasing the number of parts, and has high long-term cycle characteristics and high safety which have not been obtained in the past. It was verified to have sex.

The non-aqueous lithium-type power storage element of the present invention has excellent initial input / output characteristics and high long-term cycle characteristics by making the potential between electrodes uniform without increasing the number of parts. Therefore, for example, an internal combustion engine in an automobile. The field of a hybrid drive system in which a fuel cell or a motor and a power storage element are combined; it can be suitably used as an assist power source application at a peak of instantaneous power.

Claims (5)

A laminate in which a positive electrode and a negative electrode are laminated via a separator, and a non-aqueous lithium-type power storage element containing a non-aqueous electrolyte solution containing lithium ions.
The positive electrode contains at least one lithium compound selected from the group consisting of lithium carbonate and lithium oxide as a lithium compound other than the positive electrode active material .
The positive electrode has a positive electrode current collector and a positive electrode active material layer on one side or both sides of the positive electrode current collector, and the former positive electrode active material layer contains a positive electrode active material made of activated carbon.
The negative electrode has a negative electrode current collector and a negative electrode active material layer on one side or both sides of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material capable of storing and releasing lithium ions.
When the negative electrode active material layer of the negative electrode in the outermost layer in the thickness direction of the laminate is viewed from above, the lithium ion concentration at the center is _C1o , and when the negative electrode active material layer of the negative electrode in the innermost layer in the thickness direction of the laminate is viewed from above. When the lithium ion concentration at the center of is C _1i , C _1o / C _1i is 0.85 or more and 1.15 or less.
The concentration of lithium ions is higher in the area region of 80% of the central portion of the negative electrode active material layer than in the area region of 20% of the peripheral portion of the negative electrode active material layer.
When the average particle size of the lithium compound is X ₁ , 0.1 μm ≤ X ₁ ≤ 10 μm, and when the average particle size of the positive electrode active material is Y ₁ , 2 μm ≤ Y ₁ ≤ 20 μm. _The non-aqueous lithium-type power storage element, wherein ₁ <Y ₁ and the amount of the lithium compound contained in the positive electrode is 1% by mass or more and 50% by mass or less. The thickness of the central negative electrode active material layer when the negative electrode active material layer of the negative electrode in the outermost layer in the thickness direction of the laminate is viewed from above is T _1o , and the negative electrode active material layer of the negative electrode in the innermost layer in the thickness direction of the laminate is the upper surface. when the thickness of the negative electrode active material layer in the center when the viewing and _{T 1i, T 1o} / _{T 1i} is 0.85 to 1.15, the non-aqueous lithium electric storage device according to claim 1. A non-aqueous lithium-type power storage element composed of a wound body in which a positive electrode and a negative electrode are wound via a separator, and a non-aqueous electrolytic solution containing lithium ions.
The positive electrode contains at least one lithium compound selected from the group consisting of lithium carbonate and lithium oxide as a lithium compound other than the positive electrode active material .
The positive electrode has a positive electrode current collector and a positive electrode active material layer on one side or both sides of the positive electrode current collector, and the positive electrode active material layer contains a positive electrode active material made of activated carbon.
The negative electrode has a negative electrode current collector and a negative electrode active material layer on one side or both sides of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material capable of storing and releasing lithium ions.
The lithium ion concentration at the center when the negative electrode active material layer of the negative electrode on the outermost periphery in the radial direction excluding the peripheral edge is viewed from above is C _2o , which _faces the positive electrode of the wound _body , and _faces the positive electrode of the wound _body . _However , when the lithium ion concentration at the center of the innermost layer in the radial direction excluding the peripheral portion is C _2i when the negative electrode active material layer of the negative electrode is viewed from above, C _2o / C _2i is 0.85 or more and 1.15 or less. Yes,
The concentration of lithium ions is higher in the area region of 80% of the central portion of the negative electrode active material layer than in the area region of 20% of the peripheral portion of the negative electrode active material layer.
When the average particle size of the lithium compound is X ₁ , it is 0.1 μm ≤ X ₁ ≤ 10 μm, and when the average particle size of the positive electrode active material is Y ₁ , it is 2 μm ≤ Y ₁ ≤ 20 μm, and X ₁ <Y ₁ , and the amount of the lithium compound contained in the positive electrode is 1% by mass or more and 50% by mass or less, the non-aqueous lithium-type power storage element. The thickness of the center of the negative electrode, which _faces the positive electrode of the wound _body and is the outermost peripheral electrode in the radial direction excluding the peripheral portion, is T _2o , and _faces the positive electrode of the wound _body . when the thickness of the center when the anode active material layer of the negative electrode was viewed in the radial direction innermost layer except the peripheral part and T _2i, T _2o / T _2i is 0.85 to 1.15, claims 3. The non-aqueous lithium power storage element according to 3. The separator is made of a resin film made of polyolefin having a porous structure as a base material, and an inorganic layer made of inorganic fine particles is laminated on at least one surface thereof.
In the non-aqueous lithium type power storage element, the initial room temperature discharge internal resistance is Ra (Ω), the capacitance is F (F), the environmental temperature is 25 ° C., and the cell voltage is 300C from 2.2V to 3.8V. The internal resistance of normal temperature discharge after 60,000 charge / discharge cycles at the rate of Re (Ω), and the capacitance after constant voltage charging of 4.5 V for the power storage element after the cycle test for 1 hour. When is Fe (F), the following:
(A) Re / Ra is 0.9 or more and 2.0 or less; and (b) Fe / F is 1.01 or more;
The non-aqueous lithium-type power storage element according to any one of claims 1 to 4 , wherein the non-aqueous lithium-type power storage element satisfies.

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