JP6829573B2 - Winding non-aqueous lithium storage element - Google Patents

Description

The present invention relates to a non-aqueous lithium storage element assembled by a winding method.

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 it is designed to intentionally suppress the high energy density, which is the greatest feature of lithium-ion batteries. Moreover, 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, it is used in a range where the discharge depth is narrower than the range of 0 to 100%. 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 kind 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 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 characteristics There is a problem in.

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 (positive electrode 10 times x negative electrode 10 times = 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 has 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 capacitors used are required to have excellent energy density, high input / output characteristics, and durability against high load charge / discharge cycles.

As a countermeasure technique for such a demand, there is known a technique of treating a non-opposing portion of a negative electrode in a wound body in which an opposing positive electrode does not exist.
For example, there is known a technique for preventing permeation so that the electrolytic solution does not permeate into the non-opposing portion. (Patent Document 1) This prevents lithium ions from being diffused to the non-opposing portion of the negative electrode due to diffusion from other parts of the negative electrode active material layer or wraparound from the positive electrode active material layer, and the capacity of the power storage element. It is possible to prevent the decrease.

There is also a technique for providing an insulating insulating member interposed at least a part between the non-opposing portion of the negative electrode active material layer and the negative electrode current collector. (Patent Document 2) This can suppress the exchange of electrons between this portion and the negative electrode current collector plate at a portion of the negative electrode active material layer in which an insulating member is interposed. Therefore, the region of the non-opposing portion into which the lithium ions are inserted can be reduced by the amount of the insulating member interposed therebetween, and the decrease in the battery capacity can be suppressed.

However, in the technique of Patent Document 1, there is a concern that the film formed by the permeation prevention treatment deteriorates and separates during a long-term test such as a high load cycle test, floats as an impurity in the electrolytic solution, and becomes a resistance component. .. Further, the increase in the thickness and the volume of the non-opposing portion due to the film formation also become a factor of lowering the energy density when viewed as a power storage element.

Further, in the technique of Patent Document 2, since the insulating member is interposed between the negative electrode active material and the negative electrode current collector in the non-opposing portion, the film thickness of the non-opposing portion of the negative electrode is increased and the volume of the power storage element is increased. Therefore, it causes a decrease in energy density.
As described above, no technology has been found that can sufficiently secure high input / output characteristics and durability against a high load charge / discharge cycle, as well as an excellent energy density that is important for practical use.

Japanese Unexamined Patent Publication No. 2011-12408 Japanese Patent No. 5381588

The present invention has been made in view of the above situation.
Therefore, the problem to be solved by the present invention is to suppress the movement of lithium ions to the non-opposing portion of the negative electrode, which is difficult to contribute to the charge / discharge reaction in the wound power storage element, and to have excellent energy density and high input / output characteristics. It is an object of the present invention to provide a non-aqueous lithium-type power storage element having a high load charge / discharge cycle durability.

The present inventors diligently studied and repeated experiments in order to solve the above-mentioned problems. As a result, the positive electrode contains a lithium compound, and by controlling the coating of the negative electrode interface in the facing portion and the negative electrode interface in the non-opposing portion, it has excellent energy density and high input / output characteristics, and is suitable for a high load charge / discharge cycle. We have found that it is possible to provide a non-aqueous lithium-type power storage element with durability.

｛式（１）中、Ｒ^１は、炭素数１〜４のアルキレン基、炭素数１〜４のハロゲン化アルキレン基であり、Ｘ^１、Ｘ^２はそれぞれ独立に−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝

｛式（２）中、Ｒ^１は、炭素数１〜４のアルキレン基、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、Ｘ^１、Ｘ^２はそれぞれ独立に−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝

｛式（３）中、Ｒ^１は、炭素数１〜４のアルキレン基、炭素数１〜４のハロゲン化アルキレン基であり、Ｒ^２、Ｒ^３はそれぞれ独立に水素、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、又はアリール基であり、Ｘ^１、Ｘ^２はそれぞれ独立に−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝
[２]前記対向部の負極の膜厚に対する前記非対向部の負極の膜厚の比が、０．８０以上０．９５以下である、[１]に記載の非水系リチウム型蓄電素子。
[３]前記リチウム化合物は、炭酸リチウム、酸化リチウム、及び水酸化リチウムからなる群から選択される少なくとも一種のリチウム化合物である、[１]又は[２]に記載の非水系リチウム型蓄電素子。
[４]前記負極活物質層の固体^７Ｌｉ−ＮＭＲスペクトルにおいて、４ｐｐｍ〜３０ｐｐｍの間にピークの最大値を有し、４ｐｐｍ〜３０ｐｐｍに観測されるピークの面積より計算されるリチウム量が、前記リチウムイオンを吸蔵した負極活物質層の単位質量当たり０．１ｍｍｏｌ／ｇ以上１０ｍｍｏｌ／ｇ以下である、[１]〜[３]のいずれか一項に記載の非水系リチウム型蓄電素子。
[５]前記負極活物質層の単位体積当たりのＢＥＴ比表面積が、１ｍ^２／ｃｃ以上５０ｍ^２／ｃｃ以下である、[１]〜[４]のいずれか一項に記載の非水系リチウム型蓄電素子。
[６]前記正極活物質層が、上記式（１）〜（３）から選択される１種以上の化合物を前記正極物質層の単位質量当たり１．６０×１０^−４ｍｏｌ／ｇ 以上３００×１０^−４ｍｏｌ／ｇ 以下含有する、[１]〜[５]のいずれか一項に記載の非水系リチウム型蓄電素子。
[７]前記正極が、前記正極活物質層の全質量を基準として、正極活物質以外のリチウム化合物を１質量％以上５０質量％以下含有し、かつ、前記非水系電解液のＡｌ濃度が、１ｐｐｍ以上３００ｐｐｍ以下である、[１]〜[６]のいずれか一項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をＶ１（ｃｃ／ｇ）とし、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１，５００ｍ^２／ｇ以上３，０００ｍ^２／ｇ以下を示す活性炭である、[１]〜[７]のいずれか一項に記載の非水系リチウム型蓄電素子。
[９]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、かつ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、さらに、ＢＥＴ法により測定される比表面積が２，３００ｍ^２／ｇ以上４，０００ｍ^２／ｇ以下を示す活性炭である、[１]〜[７]のいずれか一項に記載の非水系リチウム型蓄電素子。 The present invention has been made based on this finding.
That is, the present invention is as follows:
[1] A non-aqueous lithium-type power storage element composed of a positive electrode containing a lithium compound other than an active material, a negative electrode, a separator, and a non-aqueous electrolytic solution containing lithium ions.
The positive electrode has a positive electrode current collector, a positive electrode active material layer composed of an active material and a lithium compound is provided on the current collector, and the negative electrode can occlude and release lithium ions on the negative electrode current collector. Contains active material, and also
The positive electrode and the negative electrode consist of an electrode wound body wound via a separator, and in addition,
The negative electrode has a portion facing the positive electrode and the negative electrode facing each other with the separator interposed therebetween.
With the separator interposed therebetween, it has a non-opposing portion in which the opposite positive electrode does not exist, and
Of the compound selected from the following formulas (1) to (3),
The content per unit mass of the active material in the non-opposing portion is X, and the content per unit mass of the active material in the facing portion is Y.
A non-aqueous lithium-type power storage element, characterized in that X / Y <0.80.

{In formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms and a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are independently − (COO) _n (here). , N is 0 or 1.). }

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

{In formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms and a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and having 1 to 10 carbon atoms, respectively. Alkyl group, mono or polyhydroxyalkyl group with 1 to 10 carbon atoms, alkenyl group with 2 to 10 carbon atoms, mono or polyhydroxyalkenyl group with 2 to 10 carbon atoms, cycloalkyl group with 3 to 6 carbon atoms, or aryl It is a group, and X ¹ and X ² are independently − (COO) _n (where n is 0 or 1). }
[2] The non-aqueous lithium storage element according to [1], wherein the ratio of the film thickness of the negative electrode of the non-opposing portion to the film thickness of the negative electrode of the facing portion is 0.80 or more and 0.95 or less.
[3] The non-aqueous lithium-type power storage element according to [1] or [2], wherein the lithium compound is at least one lithium compound selected from the group consisting of lithium carbonate, lithium oxide, and lithium hydroxide.
[4] In the solid ⁷ Li-NMR spectrum of the negative electrode active material layer, the amount of lithium having a maximum peak value between 4 ppm and 30 ppm and calculated from the area of the peak observed at 4 ppm to 30 ppm is the above. The non-aqueous lithium-type power storage element according to any one of [1] to [3], which is 0.1 mmol / g or more and 10 mmol / g or less per unit mass of the negative electrode active material layer in which lithium ions are occluded.
[5] The non-aqueous lithium type according to any one of [1] to [4], wherein the BET specific surface area per unit volume of the negative electrode active material layer is 1 m ² / cc or more and 50 m ² / cc or less. Power storage element.
[6] The positive electrode active material layer contains one or more compounds selected from the above formulas (1) to (3) at 1.60 × 10 ^-4 mol / g or more per unit mass of the positive electrode material layer 300 × The non-aqueous lithium-type power storage element according to any one of [1] to [5], which contains 10 ^-4 mol / g or less.
[7] The positive electrode contains 1% by mass or more and 50% by mass or less of a lithium compound other than the positive electrode active material based on the total mass of the positive electrode active material layer, and the Al concentration of the non-aqueous electrolyte solution is high. The non-aqueous lithium-type power storage element according to any one of [1] to [6], which is 1 ppm or more and 300 ppm or less.
[8] The amount of mesopores derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method for the positive electrode active material contained in the positive electrode active material layer is V1 (cc / g), and the diameter calculated by the MP method When the amount of micropores derived from pores of less than 20 Å is V2 (cc / g), 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied, and the BET method is used. The non-aqueous lithium-type power storage element according to any one of [1] to [7], which is an activated carbon having a measured specific surface area of 1,500 m ² / g or more and 3,000 m ² / g or less.
[9] The amount of mesopores V1 (cc / g) of the positive electrode active material contained in the positive electrode active material layer derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method is 0.8 <V1 ≦ 2. The ratio of micropores V2 (cc / g) derived from pores having a diameter of less than 20 Å calculated by the MP method and satisfying 5 satisfies 0.8 <V2 ≦ 3.0, and further measured by the BET method. The non-aqueous lithium-type power storage element according to any one of [1] to [7], which is an activated carbon having a surface area of 2,300 m ² / g or more and 4,000 m ² / g or less.

According to the present invention, it is possible to provide a non-aqueous lithium-type power storage element having excellent energy density, high input / output characteristics, and durability against a high load charge / discharge cycle.

An example of a wound body is shown. The disassembled side view of the wound body is shown.

Hereinafter, embodiments of the present invention will be described in detail.
Non-aqueous lithium-type power storage elements generally include a positive electrode, a negative electrode, a separator, an electrolytic solution, and an exterior body as main components.

[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 step is defined as a positive electrode precursor, and the positive electrode state after the lithium doping step 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 using other materials in combination, 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 20 Å or more and 500 Å or less calculated by the BJH method is V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 Å calculated by the MP method. 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 having a / g or more and 3,000 m ² / g or less (hereinafter, also referred to as activated carbon 1) is preferable.
(2) In order to obtain a high energy density, 0.8 <V1 ≦ 2.5 and 0.8 <V2 ≦ 3.0 are satisfied, and the specific surface area measured by the BET method is 2,300 m ^2. Activated carbon having an / g or more and 4,000 m ² / g or less (hereinafter, also referred to as activated carbon 2) is preferable.
Hereinafter, the (1) activated carbon 1 and the (2) activated carbon 2 will be described individually in sequence.

[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 in 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 most 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 25 Å or less.

BET specific surface area of the activated carbon 1 is preferably from 1,500 m ² / g or more 3,000 m ² / g, more preferably not more than 1,500 m ² / g or more 2,500 m ² / g. When the BET specific surface area is 1,500 m ² / g or more, a good energy density 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 a carbonization and activation method 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 in which the carbide is fired 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 calcined 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.

On the other hand, 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 3.0 cc / g or less, more preferably more than 1.0 cc / g and 2.5 cc / g or less, from the viewpoint of increasing the density of activated carbon as an electrode and increasing the capacity per unit volume. More preferably, it is 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, a 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 by using, for example, the raw materials and treatment methods described below.
The carbon source used as a raw material for activated carbon 2 is not particularly limited as long as it is a carbon source normally used as a raw material for activated carbon. For example, plant-based raw materials such as wood, wood flour, and coconut shell; petroleum pitch, coke. Fossil-based raw materials such as, phenol resin, furan resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, various synthetic resins such as 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 steam, 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. However, 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 it 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 at the time of activation 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 upper limit of the content ratio of the positive electrode active material is more preferably 45% by mass or more, and further preferably 55% by mass or more. On the other hand, the lower limit of the content ratio of the positive electrode active material is more preferably 90% by mass or less, and further preferably 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. Therefore, the electrolytic solution has excellent retention and ionic conductivity. It is possible to form an excellent positive electrode.
Further, since the lithium compound decomposed by the voltage is preferentially doped into the non-opposing portion of the negative electrode over the non-opposing portion of the negative electrode, lithium doping into the non-opposing portion of the negative electrode is suppressed, and the negative electrode potential can be increased. .. The negative electrode potential in the present specification indicates a potential based on metallic lithium.

[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 100 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. More preferably, it is 0.5 μm ≦ X ₁ ≦ 5 μm. 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. 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 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 (heat-of-flight mass spectrometry), DSC (differential scanning calorie analysis), and the like.

[SEM-EDX]
The oxygen-containing lithium compound and the positive electrode active material can be identified by oxygen mapping using an SEM-EDX image of the positive electrode surface measured at an observation magnification of 1000 to 4000 times. As a measurement example of the SEM-EDX image, the acceleration voltage can be measured as 10 kV, the emission current as 1 μA, the number of measurement pixels as 256 × 256 pixels, and the number of integrations as 50 times. In order to prevent the sample from being charged, gold, platinum, osmium or the like can be surface-treated by a method such as vacuum deposition or sputtering. Regarding the method for measuring the SEM-EDX image, it is preferable to adjust the brightness and contrast so that the brightness does not reach the maximum brightness and the average value of the brightness is in the range of 40% to 60%. Particles containing 50% or more of bright areas binarized with respect to the obtained oxygen mapping based on the average value of brightness are designated as lithium compounds.

[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 ion, 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.

[XPS]
The bonding state of lithium can be determined by analyzing the electronic state of lithium by XPS. As an example of measurement conditions, the X-ray source is monochromatic AlKα, the X-ray beam diameter is 100 μmφ (25 W, 15 kV), the path energy is narrow scan: 58.70 eV, there is charge neutralization, and the number of sweeps is narrow scan: 10 times. (Carbon, oxygen) 20 times (fluorine) 30 times (phosphorus) 40 times (lithium) 50 times (silicon), energy steps can be measured under the conditions of narrow scan: 0.25 eV. It is preferable to clean the surface of the positive electrode by sputtering before measuring XPS. As the sputtering conditions, for example, the surface of the positive electrode can be cleaned under the condition of an acceleration voltage of 1.0 kV, 2 mm × 2 mm for 1 minute (1.25 nm / min in terms of SiO ₂ ). Regarding the obtained XPS spectrum, the peak of Li1s binding energy of 50 to 54 eV is LiO ₂ or Li-C bond, and the peak of 55 to 60 eV is LiF, Li ₂ CO ₃ , Li _x PO _y F _z (x in the formula, x, y, z is an integer from 1 to 6), the peak of C1s of the bond energy 285 eV C-C bonds, the peak of 286 eV CO bond, COO peaks 288 eV, the peak of 290~292eV _CO ^{3 2 −} , CF binding, binding energy of O1s 527 to 530 eV peak is O ^2- (Li ₂ O), 531 to 532 eV peak is CO, CO ₃ , OH, PO _x (in the formula, x is 1 to 4) (In the formula, x is an integer of 1 to 4), SiO _x (in the formula, x is an integer of 1 to 4), the peak of 533 eV is CO, SiO _x (in the formula, x is an integer of 1 to 4), F1s. the peak of binding energy 685eV LiF, a peak of 687 eV C-F _bond, Li x _PO y _{F z} (wherein, x, y, z are an integer of 1 to _6), ^PF 6 _-, the binding energy of P2p For, the peak of 133 eV is PO _x (in the formula, x is an integer of 1 to 4), the peak of 134 to 136 eV is PF _x (in the formula, x is an integer of 1 to 6), and the binding energy of Si2p. the peak of 99 eV Si, silicides, (wherein, x, y are arbitrary integers) peaks 101~107eV _Si x _{O y} can be assigned as. When the peaks of the obtained spectrum overlap, it is preferable to separate the peaks assuming a Gaussian function or a Lorentz function and assign the spectra. The existing lithium compound can be identified from the measurement result of the electronic state and the result of the presence element ratio obtained above.

[Ion chromatography]
By analyzing the distilled water washing solution of the positive electrode by ion chromatography (IC), the anion species eluted in water can be identified. As the column to be used, an ion exchange type, an ion exclusion type, and a reverse phase ion pair type can be used. As the detector, an electric conductivity detector, an ultraviolet visible absorptiometric detector, an electrochemical detector, etc. can be used, and a suppressor method in which a suppressor is installed in front of the detector, or electricity without a suppressor. A non-suppressor method using a solution having low conductivity as an eluent can be used. In addition, since mass spectrometer and charged particle detection can be measured in combination with a detector, an appropriate column and detector are combined based on the lithium compound identified from the analysis results of SEM-EDX, Raman, and XPS. Is preferable.
The retention time of the sample is constant for each ion species component if conditions such as the column to be used and the eluent are determined, and the magnitude of the peak response differs for each ion species but is proportional to the concentration. By measuring in advance a standard solution having a known concentration that ensures traceability, it is possible to qualitatively and quantify the ionic species component.

[Method for quantifying lithium compounds]
The method for quantifying the lithium compound contained in the positive electrode is described below.
The positive electrode can be washed with an organic solvent, then washed with distilled water, and the lithium compound can be quantified from the change in positive 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 surface of the positive electrode 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, polar solvents such as methanol and acetone are preferably used.

により算出できる。 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 quantified by measuring the GC / MS of the water after washing with distilled water, which will be described later, 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 collected positive electrode of the obtained 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 calculated by the following mathematical formula (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 decreases, and the energy density per volume of the positive electrode active material layer decreases, which is not preferable.
The binder is not particularly limited, but for example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer and the like. 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 this coating solution is collected as a positive electrode. A positive electrode precursor can be obtained by applying a coating film on one or both sides of an electric 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 a solvent, the positive electrode active material and the lithium compound, and any other optional components used as needed, are dry mixed, the resulting mixture is press molded and then conductively bonded. It is also possible to attach the agent to the positive electrode current collector.

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, even if various material powders containing a positive electrode active material are added to a liquid or slurry-like substance in which a binder or a dispersion stabilizer is dissolved or dispersed in water or an organic solvent to prepare a coating liquid. 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, and a lithium compound having low conductivity is coated 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 good 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 dispersity is more preferably a particle size of 80 μm or less, and further preferably a particle size of 50 μm or less. 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 film 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 the binder to be used of minus 60 ° C. or higher, more preferably a melting point of minus 45 ° C. or higher, and further preferably a melting point of minus 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 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, and further. It is preferable to heat the surface of the press portion 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, the surface of the pressed portion 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, more preferably 25 μm or more and 100 μm or less per one side, and further preferably 30 μm or more and 80 μm or less. 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, so that sufficient output characteristics can be obtained, the cell volume can be reduced, and therefore the energy density can be increased. be able to. 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.

｛式（１）中、Ｒ^１は、炭素数１〜４のアルキレン基、又は炭素数１〜４のハロゲン化アルキレン基であり、Ｘ^１、Ｘ^２はそれぞれ独立に−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝

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

｛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、Ｒ^３はそれぞれ独立に水素、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、及びアリール基からなる群から選択される基であり、Ｘ^１、Ｘ^２はそれぞれ独立に−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝ [Compound in positive electrode active material layer]
The positive electrode active material layer according to the present invention contains one or more compounds selected from the following formulas (1) to (3) at 1.60 × 10 ^-4 mol / g to 100 × per unit mass of the positive electrode material layer. It preferably contains 10 ^-4 mol / g.

{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 independently − (COO) _n (here). And n is 0 or 1). }

{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. From the group consisting of 1 to 10 mono or polyhydroxyalkyl groups, alkenyl groups with 2 to 10 carbon atoms, mono or polyhydroxyalkenyl groups with 2 to 10 carbon atoms, cycloalkyl groups with 3 to 6 carbon atoms, and aryl groups. It is a group to be selected, and X ¹ and X ² are independently − (COO) _n (where n is 0 or 1). }

{In the formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and 1 to 10 carbon atoms, respectively. Alkyl group, mono or polyhydroxyalkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms, mono or polyhydroxyalkenyl group having 2 to 10 carbon atoms, cycloalkyl group having 3 to 6 carbon atoms, and It is a group selected from the group consisting of aryl groups, and X ¹ and X ² are independently − (COO) _n (where n is 0 or 1). }

In the formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are independently − (COO) _n (here). , N is 0 or 1.).
Particularly preferred compounds are
It is a compound represented by LiOC ₂ H ₄ OLi, LiOC ₃ H ₆ OLi, LiOC ₂ H ₄ OCOOLi, LiOCOOC ₃ H ₆ OLi, LiOCOOC ₂ H ₄ OCOOLi and LiOCOOC ₃ H ₆ OCOOLi.

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 1 carbon atom. Select from the group consisting of a mono or polyhydroxyalkyl group having 10 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a mono or polyhydroxyalkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group. X ¹ and X ² are independently − (COO) _n (where n is 0 or 1).
Particularly preferred compounds are
LiOC ₂ H ₄ OH, LiOC ₃ H ₆ OH, LiOC ₂ H ₄ OCOOH, LiOC ₃ H ₆ OCOOH, LiOCOC ₂ H ₄ OCOOH, LiOCOC ₃ H ₆ OCOOH, LiOC ₂ H ₄ OCH ₃ , LiOC ₃ H ₆ OCH _{3 LiOC 2 H 4 OCOOCH 3, LiOC} 3 H 6 OCOOCH 3, LiOCOOC 2 H 4 OCOOCH 3, LiOCOOC 3 H 6 OCOOCH 3, LiOC 2 H 4 OC 2 H 5, LiOC 3 H 6 OC 2 H 5, LiOC 2 H 4 It is a compound represented by OCOC ₂ H ₅ , LiOC ₃ H ₆ OCOC ₂ H ₅ , LiOCOC ₂ H ₄ OCOC ₂ H ₅ , LiOCOC ₃ H ₆ OCOC ₂ H ₅ .

In the formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and 1 to 10 carbon atoms, respectively. Alkyl groups, mono or polyhydroxyalkyl groups with 1 to 10 carbon atoms, alkenyl groups with 2 to 10 carbon atoms, mono or polyhydroxyalkenyl groups with 2 to 10 carbon atoms, cycloalkyl groups with 3 to 6 carbon atoms, and aryl It is a group selected from the group consisting of groups, and X ¹ and X ² are independently − (COO) _n (where n is 0 or 1).
Particularly preferred compounds are
HOC ₂ H ₄ OH, HOC ₃ H ₆ OH, HOC ₂ H ₄ OCOOH, HOC ₃ H ₆ OCOOH, HOCOC ₂ H ₄ OCOOH, HOCOC ₃ H ₆ OCOOH, HOC ₂ H ₄ OCH ₃ , HOC ₃ H ₆ OCH _{3 HOC 2 H 4 OCOOCH 3, HOC} 3 H 6 OCOOCH 3, HOCOOC 2 H 4 OCOOCH 3, HOCOOC 3 H 6 OCOOCH 3, HOC 2 H 4 OC 2 H 5, HOC 3 H 6 OC 2 H 5, HOC 2 H 4 OCOOC ₂ H ₅ , HOC ₃ H ₆ OCOOC ₂ H ₅ , HOCOOC ₂ H ₄ OCOOC ₂ H ₅ , HOCOOC ₃ H ₆ OCOOC ₂ H ₅ , CH ₃ OC ₂ H ₄ OCH ₃ , CH ₃ OC ₃ H ₆ OCH _{3 CH 3 OC 2 H 4 OCOOCH 3} , CH 3 OC 3 H 6 OCOOCH 3, CH 3 OCOOC 2 H 4 OCOOCH 3, CH 3 OCOOC 3 H 6 OCOOCH 3, CH 3 OC 2 H 4 OC 2 H 5, CH 3 OC ₃ H ₆ OC ₂ H ₅ , CH ₃ OC ₂ H ₄ OCOC ₂ H ₅ , CH ₃ OC ₃ H ₆ OCOC ₂ H ₅ , CH ₃ OCOC ₂ H ₄ OCOC ₂ H ₅ , CH ₃ OCOC ₃ H ₆ OCOC ₂ H ₅ , C ₂ H ₅ OC ₂ H ₄ OC ₂ H ₅ , C ₂ H ₅ OC ₃ H ₆ OC ₂ H ₅ , C ₂ H ₅ OC ₂ H ₄ OCOC ₂ H ₅ , C ₂ H ₅ OC ₃ H ₆ OCOC ₂ H ₅ , C ₂ H ₅ OCOC ₂ H ₄ OCOC ₂ H ₅ , C ₂ H ₅ OCOC ₃ H ₆ OCOC ₂ H ₅
It is a compound represented by.

As a method for incorporating the above-mentioned compound in the positive electrode active material layer in the present invention, for example,
A method of mixing the compound with the positive electrode active material layer,
A method of adsorbing the compound on the positive electrode active material layer,
Examples thereof include a method of electrochemically precipitating the compound on the positive electrode active material layer.
Above all, a positive electrode active material layer is contained in a non-aqueous electrolytic solution that can be decomposed to produce these compounds, and the decomposition reaction of the precursor in the step of producing a power storage element is utilized. A method of depositing the compound inside is preferable.

As the precursor for forming the compound, it is preferable to use at least one organic solvent selected from ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and fluoroethylene carbonate, and ethylene carbonate and propylene. It is more preferred to use carbonate.

Here, the total amount of the compound is preferably 1.60 × 10 ^-4 mol / g or more, and preferably 5.0 × 10 ^-4 mol / g or more, per unit mass of the positive electrode active material layer. Is more preferable. When the total amount of the compound is 1.60 × 10 ^-4 mol / g or more per unit mass of the positive electrode active material layer, the non-aqueous electrolyte solution does not come into contact with the positive electrode active material, and the non-aqueous electrolyte solution is oxidatively decomposed. It is possible to suppress the generation of gas and suppress the increase in resistance.
The total amount of the compound is preferably 100 × 10 ^-4 mol / g or less, more preferably 80 × 10 ^-4 mol / g or less, and more preferably 70 × 10 ^-4 mol / g or less, per unit mass of the positive electrode active material layer. Most preferably, it is × 10 ^-4 mol / g or less. When the total amount of the compound is 100 × 10 ^-4 mol / g or less per unit mass of the positive electrode active material layer, high input / output characteristics can be exhibited without inhibiting the diffusion of Li ions at the positive electrode interface. ..
In the present specification, the amount of lithium contained in the positive electrode active material layer can be calculated by the following method from the solid ⁷ Li-NMR spectrum.

In the embodiment of the present invention, the amount of lithium in the positive electrode active material layer is calculated from the area of the peak observed at -40 ppm to 40 ppm in the solid ⁷ Li-NMR spectrum, and the amount of lithium is 10.0 × 10 ^-4. It is preferably mol / g or more and 300 × 10 ^-4 mol / g or less. The amount of lithium is preferably 12.0 × 10 ^-4 mol / g or more and 280 × 10 ^-4 mol / g or less, more preferably 15.0 × 10 ^-4 mol / g or more and 260 × 10 ^-4 mol / g. Below, more preferably 17.0 × 10 ^-4 mol / g or more and 240 × 10 ^-4 mol / g or less, particularly preferably 20.0 × 10 ^-4 mol / g or more and 220 × 10 ^-4 mol / g or less. is there.

As a solid ⁷ Li-NMR measuring device, a commercially available device can be used. In a room temperature environment, the rotation speed of the magic angle spinning is 14.5 kHz, the irradiation pulse width is 45 ° pulse, and the measurement is performed by the single pulse method. When measuring, set so that there is a sufficient waiting time for repetition between measurements.
A 1 mol / L lithium chloride aqueous solution is used as a shift reference, and the shift position measured separately as an external standard is 0 ppm. When measuring the lithium chloride aqueous solution, the sample is not rotated, and the irradiation pulse width is set to 45 ° pulse, and the measurement is performed by the single pulse method.
From the solid ⁷ Li-NMR spectrum of the positive electrode active material layer obtained under the above conditions, the peak area of the component observed in the range of -40 ppm to 40 ppm is obtained. Then, these peak areas are divided by the peak area of the 1 mol / L lithium chloride aqueous solution measured by setting the sample height in the measuring rotor to be the same as that at the time of measuring the positive electrode active material layer, and further, the positive electrode active material layer used for the measurement. The amount of lithium can be calculated by dividing by the mass of.
The amount of lithium is the total amount of lithium including the lithium compound, the lithium-containing compound represented by the formula (1) and the formula (2), and other lithium-containing compounds.

[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 may be 100% by mass, but from the viewpoint of obtaining a good effect by using other materials in combination, for example, it is preferably 90% by mass or less, and preferably 80% by mass or less.

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 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 the non-aqueous lithium-type power storage element is used 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 (eg, phenolic resins, etc.) Carbonated materials obtained by heat treatment of precursors; full Thermal decomposition products of frill 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 obtained by combining a carbon material derived from a quality material precursor 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 substrate 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 to be 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 carbonic 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. It is more preferably 620 mAh / g or more and 2,100 mAh / g or less, further preferably 760 mAh / g or more and 1,700 mAh / g or less, and particularly preferably 840 mAh / g or more and 1,500 mAh / g or less.
By doping with lithium ions, the negative electrode potential is lowered. Therefore, 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 becomes high and the utilization capacity of the positive electrode becomes large. Therefore, 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. The amount of can be reduced. Therefore, the film thickness of the negative electrode can be reduced, and a high energy density can be obtained. As the doping amount increases, the negative electrode potential decreases, and the input / output characteristics, energy density, and durability improve.
On the other hand, if 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 doping amount of lithium ions can be increased, and the bulk density of the negative electrode can be increased. As a result, the negative electrode can be thinned. Further, when the micropore amount Vm2 is 0.650 cc / g or less, high charge / discharge efficiency for 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. It is 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 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 providing 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 atom / carbon atom 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 width of this peak is 11. More preferably, it is 0 Å or more and 16.0 Å or less.

The activated carbon used as the base material of the composite carbon material 1a is not particularly limited as long as the obtained composite carbon material 1a exhibits desired 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. The average particle size is more preferably 2 μm or more and 10 μm or less.

In order to obtain the composite carbon material 1a having the pore distribution range 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 20 Å or more and 500 Å or less calculated by the BJH method is V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 Å calculated by the MP method. 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 obtained in order 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 carbonic 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. Pitches are roughly divided into petroleum-based pitches and coal-based pitches. 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 thermal decomposition 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. The pitch at which the softening point is 250 ° C. or lower contains a large amount of relatively low molecular weight compounds, and 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 carbon material precursor, and the carbon 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.

It is preferable that the mass ratio of the carbonaceous material to the activated carbon in the composite carbon material 1a is 10% by mass or more and 100% by mass or less. This mass ratio is 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. The average particle size is more preferably 2 μm or more and 8 μm or less, and further preferably 3 μm or more and 6 μm or less. When the average particle 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. This mass ratio is more preferably 1.2% by mass or more and 25% by mass or less, and further preferably 1.5% by mass or more and 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 carbonic material and the base material in the solid can be well maintained, so that high input / output characteristics can be exhibited. You can. Moreover, since the charge / discharge efficiency of lithium ions can be 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. It is more preferably 70 mAh / g or more and 650 mAh / g or less, further preferably 90 mAh / g or more and 600 mAh / g or less, and particularly preferably 100 mAh / g or more and 550 mAh / g or less.
By doping with lithium ions, the negative electrode potential is lowered. Therefore, 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 becomes high and the utilization capacity of the positive electrode becomes large. Therefore, 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 doping amount increases, the negative electrode potential decreases, and the input / output characteristics, energy density, and durability improve.
On the other hand, if 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. The average particle size is more preferably 2 μm or more and 8 μm or less, and further preferably 3 μm or more and 6 μm or less. When the average particle 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. More preferably, it is 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 globules, 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 carbonic 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. Pitches are roughly divided into petroleum-based pitches and coal-based pitches. 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 carbonic material and the graphite material in the solid can be well maintained, so that high input / output characteristics can be exhibited. You can. Moreover, since the charge / discharge efficiency of lithium ions can be improved, high cycle durability can be exhibited.

In the negative electrode using the composite carbon material 2a, the solid ⁷ Li-NMR spectrum of the negative electrode active material layer has a maximum peak value between 4 ppm and 30 ppm in the spectrum range of -10 ppm to 35 ppm, and has a peak area of 4 ppm to 30 ppm. The amount of lithium per unit mass of the negative electrode active material layer occluded by lithium ions (hereinafter, also referred to as “the amount of lithium in the negative electrode active material layer”) is 0.1 mmol / g or more and 10 mmol / g or less. is there. The amount of lithium in the negative electrode active material layer is preferably 0.3 mmol / g or more and 9 mmol / g or less, more preferably 0.5 mmol / g or more and 8 mmol / g or less, and further preferably 0.8 mmol / g or more and 7.5 mmol / g. It is g or less, particularly preferably 1 mmol / g or more and 7 mmol / g or less.

The negative electrode using the composite carbon material 2a contains a graphite-based carbon material as the negative electrode active material, and the solid ⁷ Li-NMR spectrum of the negative electrode active material layer has a peak between 4 ppm and 30 ppm in the spectrum range of -10 ppm to 35 ppm. Non-aqueous lithium type using this by adjusting the amount of lithium per unit mass of the negative electrode active material layer that has the maximum value and occludes lithium ions calculated from the peak area of 4 ppm to 30 ppm to a specific range. The power storage element exhibits high input / output characteristics and durability against high load charge / discharge cycles. The principle is not clear and is not limited to theory, but it is inferred as follows. The spectrum observed at 30 ppm to 60 ppm in the solid ⁷ Li-NMR of the negative electrode active material layer is derived from the lithium ions occluded in the carbon hexagonal network layers of the graphitic portion of the graphite-based carbon material. Since the lithium ions in such an occluded state strongly interact with the carbon hexagonal network surface, a large amount of energy is required to release the lithium ions, and the resistance becomes high. On the other hand, the spectra observed at 4 ppm to 30 ppm in the solid ⁷ Li-NMR of the negative electrode active material layer are the amorphous part of the graphite-based carbon material, the interface between the graphitic part and the amorphous part, and the vicinity of this interface. It is considered that the lithium ions occluded in the carbon hexagonal network layers of the graphitic part are exchanged and act on each other. Lithium ions in such an occluded state do not require a large amount of energy to release lithium ions because they have a weak interaction with carbon atoms. Further, it is considered that the lithium ions in the occluded state are occluded and released from the non-aqueous electrolyte solution through the amorphous portion having more reaction sites than the graphitized portion. Therefore, the solid ⁷ Li-NMR spectrum of the negative electrode active material layer has a maximum peak value between 4 ppm and 30 ppm in the spectrum range of -10 ppm to 35 ppm, and the amount of lithium calculated from the peak area of 4 ppm to 30 ppm. It is considered that the input / output resistance can be reduced and high input / output characteristics can be exhibited by adjusting the value to an appropriate range. Further, the lithium ion in such an occlusion state can sufficiently respond to a high load charge / discharge cycle in which a large current charge / discharge is repeated for the reason described above, and can exhibit good high load charge / discharge cycle characteristics.

If the amount of lithium in the negative electrode active material layer is 0.1 mmol / g or more, the non-aqueous lithium-type power storage element using this negative electrode exhibits high input / output characteristics and durability against a high load charge / discharge cycle for the reasons described above. .. On the other hand, when the amount of lithium in the negative electrode active material layer is 10 mmol / g or less, it is possible to suppress the release of lithium ions occluded in the negative electrode active material by self-discharge. As a result, the released lithium ions can be suppressed from reacting with the non-aqueous electrolyte solution in the negative electrode active material layer to increase the amount of coatings and deposits, so that the non-aqueous lithium storage element using this negative electrode is expensive. Has durability against load charge / discharge cycles.

The BET specific surface area per unit volume of the negative electrode active material layer is preferably 1 m ² / cc or more and 50 m ² / cc or less, more preferably 2 m ² / cc or more and 40 m ² / cc or less, and further preferably 3 m ² / cc or more and 35 m ² or less. It is / cc or less, particularly preferably 4 m ² / cc or more and 30 m ² / cc or less, and most preferably 5 m ² / cc or more and 20 m ² / cc or less.

[Arbitrary component]
If necessary, the negative electrode active material layer in the present invention 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 with respect to 100 parts by mass of the negative electrode active material. It is more preferably 0 parts by mass or more and 20 parts by mass or less, and further preferably 0 parts by mass or more and 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 and the like. Can be used. The amount of the binder used is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the negative electrode active material. It is more preferably 2 parts by mass or more and 27 parts by mass or less, and further preferably 3 parts by mass or more and 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 in the present invention 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 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 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 in which a binder or a dispersion stabilizer is dissolved or dispersed therein. 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 the liquid or slurry-like 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 homodisper, a multi-axis disperser, a planetary mixer, a disperser such as a thin film swirl type high-speed mixer, or the like can be preferably used. In order to obtain a coating liquid in a good dispersed state, it is preferable to disperse at a peripheral speed of 1 m / s or more and 50 m / s or less. A peripheral speed of 1 m / s or more is preferable because various materials are satisfactorily dissolved or dispersed. Further, when it 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 viscosity (ηb) of the coating liquid is preferably 1,000 mPa · s or more and 20,000 mPa · s or less. It is more preferably 1,500 mPa · s or more and 10,000 mPa · s or less, and further preferably 1,700 mPa · s or more and 5,000 mPa · s or less. When the viscosity (ηb) is 1,000 mPa · s or more, liquid dripping during coating film formation is suppressed, and the coating film width and film thickness can be satisfactorily controlled. Further, 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. It is more preferably 1.2 or more, still more preferably 1.5 or more. When the TI value is 1.1 or more, the coating film width and 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 a single-layer coating or a multi-layer coating. The coating speed is preferably 0.1 m / min or more and 100 m / min or less. It is 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. It is 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. It is 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 preferable to heat it to 90 ° C. or higher and 200 ° C. or lower. It is more preferably 105 ° C. or higher and 180 ° C. or lower, and further preferably 120 ° C. or higher and 170 ° C. or lower. When a styrene-butadiene copolymer (melting point 100 ° C.) is used as the binder, it is preferable to heat the mixture to 40 ° C. or higher and 150 ° C. or lower. It is more preferably 55 ° C. or higher and 130 ° C. or lower, and further preferably 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, and 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 more 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. Further, if the amount is 1.8 g / cm ³ or less, pores capable of sufficiently diffusing ions can be secured in the negative electrode active material layer.

[Measurement item]
The BET specific surface area, average pore diameter, mesopore amount, and micropore amount in the present invention are values obtained by the following methods, respectively. The sample is vacuum-dried at 200 ° C. for 24 hours, and the isotherms of adsorption and desorption are measured using nitrogen as an adsorbent. Using the adsorption-side 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 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 R. S. 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 in the present invention is the particle size 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 the particle size distribution measuring device (that is,). Refers to 50% diameter (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 ion doped in the negative electrode active material in the non-aqueous lithium-type power storage device at the time of shipment and after use in the present invention 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 performed in an Ar box at an environmental 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 by 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 in the present invention, 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. However, it can be obtained by a method in which the value obtained by arithmetically averaging these 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 depth of the groove 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 TI value in the present invention 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 of 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.

When the BET specific surface area per unit volume of the negative electrode active material layer is 1 m ² / cc or more, the reaction sites of lithium ions in the non-aqueous electrolyte solution and the negative electrode active material layer per unit volume can be sufficiently increased. The non-aqueous lithium-type power storage element using the above can exhibit high input / output characteristics and high load charge / discharge cycle characteristics. On the other hand, if the BET specific surface area per unit volume of the negative electrode active material layer is 50 m ² / cc or less, excessive reductive decomposition of the non-aqueous electrolyte solution in the negative electrode active material layer can be suppressed, so that the non-aqueous lithium type using this can be suppressed. The power storage element can exhibit high load charge / discharge cycle characteristics.
In the present specification, the BET specific surface area per unit volume of the negative electrode active material layer and the average pore diameter of the negative electrode active material layer can be calculated by the following methods.

As the sample used for the measurement, a negative electrode not incorporated in the non-aqueous lithium storage element (hereinafter, also referred to as “pre-use negative electrode”) may be used, or a negative electrode incorporated in the non-aqueous lithium storage element (hereinafter, also referred to as “negative electrode”). , Also referred to as "negative electrode after use").
When the negative electrode incorporated in the non-aqueous lithium storage element is used for the measurement sample, it is preferable to use, for example, the following method as the pretreatment of the measurement sample.
First, the non-aqueous lithium-type power storage element is disassembled in an inert atmosphere such as argon, and the negative electrode is taken out. The removed negative electrode is immersed in a chain carbonate (for example, methyl ethyl carbonate, dimethyl carbonate, etc.) to remove a non-aqueous electrolyte solution, lithium salt, etc., and air-dried. Then, for example, it is preferable to use the following methods 1), 2), or 3).
1) The obtained negative electrode is immersed in a mixed solvent composed of methanol and isopropanol to inactivate the lithium ions occluded in the negative electrode active material, and air-dried. Then, a measurement sample can be obtained by removing the chain carbonate, the organic solvent, etc. contained in the negative electrode obtained by vacuum drying or the like.
2) In an inert atmosphere such as argon, the obtained negative electrode is used as the working electrode and metallic lithium is used as the counter electrode and the reference electrode, and these are immersed in a non-aqueous electrolytic solution to prepare an electrochemical cell. The negative electrode potential (vs. Li / Li ⁺ ) of the obtained electrochemical cell is adjusted to be in the range of 1.5 V to 3.5 V by using a charger / discharger or the like. Next, the negative electrode is taken out from the electrochemical cell under an inert atmosphere such as argon, immersed in a chain carbonate, the non-aqueous electrolyte solution, lithium salt and the like are removed, and the electrode is air-dried. Then, a measurement sample can be obtained by removing the chain carbonate and the like contained in the negative electrode obtained by vacuum drying or the like.
3) The negative electrode obtained above can be used as it is as a measurement sample.
The volume _Vano (cc) of the negative electrode active material layer is measured for the measurement sample obtained above. When the horizontal plane with respect to the stacking direction of the negative electrode current collector and the negative electrode active material layer is a cross section and the plane perpendicular to the horizontal plane is a flat surface, the geometric area of the plane of the measurement sample is _Sano , and the above-mentioned negative electrode active material layer when was the _{t ano} total film thickness, the volume of the negative electrode active material layer can be calculated by _{V ano = S ano × t ano} .

Using the measurement sample obtained above, the isotherms of adsorption and desorption are measured using nitrogen or argon as an adsorbent. Using suction side of the isotherm obtained here, BET by multipoint method or BET1 point method to calculate the BET specific surface area, a BET specific surface area per anode active material layer per unit volume by dividing this in V _ano calculate. The average pore diameter of the negative electrode active material layer is calculated by dividing the total pore volume calculated by the above measurement by the BET specific surface area.

[Compounds in the negative electrode active material layer]
The negative electrode active material layer according to the present invention contains one or more compounds selected from the formulas (1) to (3) at 0.50 × 10 ^-4 mol / g to 120 × per unit mass of the negative electrode material layer. It preferably contains 10 ^-4 mol / g.

As a method for incorporating the above-mentioned compound in the negative electrode active material layer in the present invention, for example,
A method of mixing the compound with the negative electrode active material layer,
A method of adsorbing the compound on the negative electrode active material layer,
Examples thereof include a method of electrochemically precipitating the compound on the negative electrode active material layer.
Above all, a negative electrode active material layer is contained in a non-aqueous electrolytic solution that can be decomposed to produce these compounds, and the decomposition reaction of the precursor in the step of producing a power storage element is utilized. A method of depositing the compound inside is preferable.

As the precursor for forming the compound, it is preferable to use at least one organic solvent selected from ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and fluoroethylene carbonate, and ethylene carbonate and propylene carbonate are used. It is more preferable to do so.

Here, the total amount of the compound is preferably 0.50 × 10 ^-4 mol / g or more, and more than 1.0 × 10 ^-4 mol / g, per unit mass of the negative electrode active material layer. Is more preferable. When the total amount of the compound is 0.50 × 10 ^-4 mol / g or more per unit mass of the negative electrode active material layer, the non-aqueous electrolyte solution does not come into contact with the negative electrode active material, and the non-aqueous electrolyte solution is reduced and decomposed. It is possible to suppress the generation of gas.
The total amount of the compound is preferably 120 × 10 ^-4 mol / g or less, more preferably 100 × 10 ^-4 mol / g or less, and more preferably 80 per unit mass of the negative electrode active material layer. Most preferably, it is × 10 ^-4 mol / g or less. When the total amount of the compound is 120 × 10 ^-4 mol / g or less per unit mass of the negative electrode active material layer, high input / output characteristics can be exhibited without inhibiting the diffusion of Li ions at the negative electrode interface. it can.

In the present invention, the content X of the deposits present in the non-opposing portion of the negative electrode having no facing positive electrode and the content Y of the deposits existing in the facing portion of the negative electrode having the facing positive electrodes of the compound are defined. When, it is preferable that X / Y <0.80. More preferably, X / Y <0.65. When X / Y <0.80, a lithium-containing film having good ionic conductivity is intensively formed on the facing portion of the negative electrode, so that lithium ions can be occluded and discharged more smoothly than in the non-opposing portion. The situation can be created at the opposite part that contributes to the charge / discharge reaction. In this situation, the lithium ions are preferentially occluded and released in the facing portion having a relatively low resistance, so that the lithium ions escaping to the non-opposing portion can be suppressed and the capacity of the power storage element is reduced. Can be suppressed. This effect shows a high capacity recovery rate even during a high load charge / discharge cycle, and can also have durability.

[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 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 of the present embodiment has, as lithium salts, 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 electrolyte solution and the viscosity of the electrolyte 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 of the present embodiment 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, more preferably. Is 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 gas due to 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 / 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 of the present embodiment 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 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, and 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.

[aluminum]
The non-aqueous electrolyte solution in the present embodiment is characterized by containing aluminum of 1 ppm or more and 300 ppm or less based on the mass of the non-aqueous electrolyte solution, and is preferably 5 ppm or more and 200 ppm or less, preferably 10 ppm or more and 150 ppm or less. Is more preferable. When the aluminum concentration is 1 ppm or more, excellent high temperature durability is exhibited. Although the detailed mechanism is not clear, the aluminum present in the electrolytic solution and the lithium compound in the positive electrode are oxidatively decomposed at the positive electrode, and the reaction product of the lithium compound eluted in the electrolytic solution is reduced on the negative electrode. It is presumed that the reduction decomposition reaction of the non-aqueous solvent on the negative electrode in a high temperature environment is suppressed in order to form a preferable film, and the high temperature durability is improved. Further, since the aluminum ion is a multivalent ion, the effect of increasing the capacity can be obtained. When the aluminum concentration is 300 ppm or less, reduction precipitation of aluminum on the negative electrode can be suppressed, and high load charge / discharge cycle durability can be kept good, which is preferable. The combination of the lower limit and the upper limit can be arbitrary.

[Aluminum content method]
The method of adding aluminum to the non-aqueous electrolyte solution of the present embodiment is not particularly limited, but for example, a method of adding a compound containing aluminum to the non-aqueous electrolyte solution before injection and dissolving it; a non-aqueous lithium storage element. A method of eluting aluminum in a positive electrode current collector into a non-aqueous electrolyte solution by oxidatively decomposing it by applying a high voltage to the positive electrode current collector can be mentioned.

[Aluminum quantification method]
For the quantification of aluminum in the non-aqueous electrolyte solution of the present embodiment, after the cell is completed, the non-aqueous electrolyte solution is taken out from the cell, and ICP-AES, atomic absorption spectrometry, fluorescent X-ray analysis, neutron activation analysis, ICP -Can be calculated by MS or the like.

[Additive]
The non-aqueous electrolyte solution of the present embodiment may further contain an additive. 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.

｛式（５）中、Ｒ^１１〜Ｒ^１６は、水素原子、ハロゲン原子、炭素数１〜１２のアルキル基、又は炭素数１〜１２のハロゲン化アルキル基を表し、互いに同一であっても異なっていてもよく；そしてｎは０〜３の整数である。｝

｛式（６）中、Ｒ^１１〜Ｒ^１４は、水素原子、ハロゲン原子、炭素数１〜１２のアルキル基、又は炭素数１〜１２のハロゲン化アルキル基を表し、互いに同一であっても異なっていてもよく；そしてｎは０〜３の整数である。｝

｛式（７）中、Ｒ^１１〜Ｒ^１６は、水素原子、ハロゲン原子、炭素数１〜１２のアルキル基、又は炭素数１〜１２のハロゲン化アルキル基を表し、互いに同一であっても異なっていてもよい。｝ [Sultone compound]
Examples of the sultone compound include sultone compounds represented by the following general formulas (5) to (7). These sultone compounds may be used alone or in combination of two or more.

{In formula (5), R ^{11 to} R ¹⁶ represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkyl halide group having 1 to 12 carbon atoms, and they are different even if they are the same. May be; and n is an integer from 0 to 3. }

{In formula (6), R ^{11 to} R ¹⁴ represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkyl halide group having 1 to 12 carbon atoms, and they are different even if they are the same. May be; and n is an integer from 0 to 3. }

{In formula (7), R ^{11 to} R ¹⁶ represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkyl halide group having 1 to 12 carbon atoms, and they are different even if they are the same. May be. }

In the present embodiment, the sultone compound represented by the general formula (5) is selected from the viewpoint of having little adverse effect on resistance and suppressing decomposition of the non-aqueous electrolyte solution at high temperature to suppress gas generation. 1,3-Propane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-butane sultone or 2,4-pentane sultone are preferable, and the sultone compound represented by the general formula (6) is 1, 3-Propens sultone or 1,4-butene sultone is preferable, and the sultone compound represented by the general formula (7) is 1,5,2,4-dioxadithioepan 2,2,4,4-tetraoxide. As the other sultone compounds, methylenebis (benzenesulfonic acid), methylenebis (phenylmethanesulfonic acid), methylenebis (ethanesulfonic acid), methylenebis (2,4,6,trimethylbenzenesulfonic acid), and methylenebis (2). -Trifluoromethylbenzene sulfonic acid), and it is preferable to select at least one selected from these.

The total content of the sultone compound in the non-aqueous electrolyte solution of the non-aqueous lithium-type power storage element in the present embodiment is preferably 0.5% by mass or more and 15% by mass or less based on the total amount of the non-aqueous electrolyte solution. .. When the total content of the sultone compound in the non-aqueous electrolytic solution is 0.5% by mass or more, it is possible to suppress the decomposition of the electrolytic solution at a high temperature and suppress the gas generation. On the other hand, when the total content is 15% by mass or less, the decrease in ionic conductivity of the electrolytic solution can be suppressed, and high input / output characteristics can be maintained. Further, the content of the sultone compound present in the non-aqueous electrolyte solution of the non-aqueous lithium-type power storage element is preferably 1% by mass or more and 10% by mass or less from the viewpoint of achieving both high input / output characteristics and durability. It is preferably 3% by mass or more and 8% by mass or less.

[Circular phosphazene]
Examples of the cyclic phosphazene include ethoxypentafluorocyclotriphosphazene, diethoxytetrafluorocyclotriphosphazene, and phenoxypentafluorocyclotriphosphazene, and one or more selected from these is preferable.

The content of cyclic phosphazene in the non-aqueous electrolyte solution is preferably 0.5% by mass or more and 20% by mass or less based on the total amount of the non-aqueous electrolyte solution. When this value is 0.5% by weight or more, it is possible to suppress the decomposition of the electrolytic solution at a high temperature and suppress the gas generation. On the other hand, when this value is 20% by mass or less, it is possible to suppress a decrease in the ionic conductivity of the electrolytic solution and maintain high input / output characteristics. The content of cyclic phosphazene is more preferably 2% by mass or more and 15% by mass or less, and further preferably 4% by mass or more and 12% by mass or less. These cyclic phosphazenes may be used alone or in combination of two or more.

[Acyclic fluorine-containing ether]
Examples of the acyclic fluorine-containing ether include HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H, CF ₃ CFHCF ₂ OCH ₂ CF ₂ CF ₂ H, HCF ₂ CF ₂ CH ₂ OCH ₂ CF ₂ CF ₂ H, CF ₃ CFHCF ₂ OCH ₂ CF ₂ CFHCF _{3 and the} like can be mentioned, and among them, HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H is preferable from the viewpoint of electrochemical stability.

The content of the acyclic fluorinated ether is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the acyclic fluorinated ether is 0.5% by mass or more, the stability of the non-aqueous electrolyte solution against oxidative decomposition is enhanced, and a power storage element having high durability at high temperatures can be obtained. On the other hand, when the content of the acyclic fluorinated ether is 15% by mass or less, the solubility of the electrolyte salt can be kept good and the ionic conductivity of the non-aqueous electrolyte solution can be kept high, so that the concentration is high. It is possible to express input / output characteristics. The acyclic fluorine-containing ether may be used alone or in combination of two or more.

[Fluorine-containing cyclic carbonate]
The fluorine-containing cyclic carbonate is preferably used by selecting from fluoroethylene carbonate (FEC) and difluoroethylene carbonate (dFEC) from the viewpoint of compatibility with other non-aqueous solvents.
The content of the cyclic carbonate containing a fluorine atom is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the cyclic carbonate containing a fluorine atom is 0.5% by mass or more, a high-quality film can be formed on the negative electrode, and by suppressing the reductive decomposition of the electrolytic solution on the negative electrode, the temperature is high. A power storage element with high durability can be obtained. On the other hand, when the content of the cyclic carbonate containing a fluorine atom is 10% by mass or less, the solubility of the electrolyte salt can be kept good and the ionic conductivity of the non-aqueous electrolyte solution can be kept high. It is possible to express a high degree of input / output characteristics. The above-mentioned cyclic carbonate containing a fluorine atom may be used alone or in combination of two or more.

[Cyclic carbonate]
As for the cyclic carbonate, vinylene carbonate is preferable.
The content of the cyclic carbonate is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the cyclic carbonate is 0.5% by mass or more, a high-quality film can be formed on the negative electrode, and by suppressing the reductive decomposition of the electrolytic solution on the negative electrode, the durability at high temperature can be improved. A high power storage element can be obtained. On the other hand, when the content of the cyclic carbonate is 10% by mass or less, the solubility of the electrolyte salt can be kept good and the ionic conductivity of the non-aqueous electrolyte solution can be maintained high, so that the input / output is highly high. It becomes possible to express the property.

[Cyclic carboxylic acid ester]
Examples of the cyclic carboxylic acid ester include gamma-butyrolactone, gamma valerolactone, gamma caprolactone, and epsilon caprolactone, and it is preferable to use one or more selected from these. Of these, gamma-butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.
The content of the cyclic carboxylic acid ester is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of cyclic acid anhydride is 0.5% by mass or more, a high-quality film can be formed on the negative electrode, and by suppressing the reductive decomposition of the electrolytic solution on the negative electrode, durability at high temperature is achieved. A high power storage element can be obtained. On the other hand, when the content of the cyclic carboxylic acid ester is 5% by mass or less, the solubility of the electrolyte salt can be kept good and the ionic conductivity of the non-aqueous electrolyte solution can be maintained high, so that the content is high. It is possible to express output characteristics. The above cyclic carboxylic acid ester may be used alone or in combination of two or more.

[Cyclic acid anhydride]
As the cyclic acid anhydride, one or more selected from succinic anhydride, maleic anhydride, citraconic anhydride, and itaconic anhydride are preferable. Among them, it is preferable to select from succinic anhydride and maleic anhydride from the viewpoint that the production cost of the electrolytic solution can be suppressed due to the industrial availability and the dissolution in the non-aqueous electrolytic solution is easy.
The content of the cyclic acid anhydride is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of cyclic acid anhydride is 0.5% by mass or more, a high-quality film can be formed on the negative electrode, and by suppressing the reductive decomposition of the electrolytic solution on the negative electrode, the durability at high temperature can be improved. A high power storage element can be obtained. On the other hand, when the content of the cyclic acid anhydride is 10% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte solution can be maintained high, and therefore a high degree of input / output can be maintained. It becomes possible to express the property. The above cyclic acid anhydride may be used alone or in combination of two or more.

[Separator]
The positive electrode precursor and the negative electrode are wound via a separator to form an electrode wound body having the positive electrode precursor, the negative electrode and the separator.
As the separator, a polyethylene microporous film or polypropylene microporous film 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 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 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 winding body, which will be described later, is housed in the exterior body together with the non-aqueous electrolytic solution.

[assembly]
The electrode winding body obtained in the cell assembly step is a winding body formed by winding a positive electrode precursor and a negative electrode via a separator, and connecting a positive electrode terminal and a negative electrode terminal to the winding body. The shape of the wound body may be cylindrical or flat.
The method of connecting the positive electrode terminal and the negative electrode terminal is not particularly limited, but a method such as resistance welding or ultrasonic welding is used.

[Opposite and non-opposing parts]
The power storage element having a structure in which the positive electrode active material layer of the positive electrode precursor and the negative electrode active material layer of the negative electrode face each other via a separator is designed so that the area of the negative electrode is slightly larger than the area of the positive electrode. This is to reduce the variation in the facing areas of the positive and negative electrodes and to prevent lithium from precipitating in a portion other than the negative electrode active material layer. Therefore, in the negative electrode active material layer, an opposing portion facing the positive electrode active material layer and a non-opposing portion not facing the positive electrode active material layer coexist via the separator. In particular, in the winding type power storage element, there are remarkable non-opposing portions at the winding start portion and the winding end portion in the circumferential direction rather than the non-opposing portion in the winding axis direction.
When lithium ions move to a non-opposing portion of the negative electrode and are occluded, the occluded lithium ions are unlikely to contribute to the charge / discharge reaction, and there is a concern that the capacity of the power storage element may decrease. Therefore, it is preferable to mask the non-opposing portion to reduce the amount of lithium ions doped into the non-opposing portion in the lithium doping step described later. By reducing the doping amount of the non-opposing portion, the negative electrode potential of the non-opposing portion becomes relatively higher than the negative electrode potential of the facing portion. Therefore, it is difficult for lithium ions to move to the non-opposing portion, and it is possible to suppress a decrease in capacity.
The masking is preferably made of an ion-impermeable member made of a material that does not allow lithium ions to permeate, such as a polyolefin-based resin such as polyethylene or polypropylene. It is advisable to attach a handle to the masking so that it can be removed in the degassing step described later. Since it does not remain in the completed power storage element, there is no concern that the volume and weight will increase.
Further, in order to generate a difference in the negative electrode potential between the facing portion and the non-opposing portion, it is possible to control the current value in the lithium doping step in addition to the above masking.

[Exterior body]
As the exterior body, a metal can, a laminated packaging material, or the like can be used.
The metal can is preferably made of aluminum.
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 a foil such as copper, aluminum, or 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 wound body is housed in an outer body typified by a metal can or a laminated 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 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 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 winding body after injection is installed in a decompression chamber with the outer body open, and the inside of the chamber is decompressed using a vacuum pump. A method of returning to atmospheric pressure or the like can be used. After the impregnation step is completed, the electrode wound body with the outer body open is sealed while reducing the pressure.

[Lithium doping 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 active material layer facing the negative electrode. On the other hand, in the non-opposing portion of the negative electrode, since there is no facing positive electrode, reduction of lithium ions is unlikely to occur, and the lithium ion concentration is relatively low. Therefore, the amount of negative electrode deposits in the non-opposing portion is relatively reduced as compared with the facing portion. In order to make this relative difference in the amount of negative electrode deposits more remarkable, a method of masking the non-opposing portion of the negative electrode and a method of controlling the doping current value can be mentioned. When the non-opposing portion of the negative electrode is masked, lithium ions do not permeate and predoping to the non-opposing portion is suppressed. At this time, the non-opposing portion is slightly reduced by the lithium ions diffused from the active material layer on the facing portion of the negative electrode and the electrolytic solution containing lithium ions permeating through the gap between the masking and the active material layer on the non-opposing portion. Doped.
As described above, in order to make a difference in the amount of negative electrode deposits between the facing portion and the non-opposing portion, a method of masking the non-opposing portion of the negative electrode to physically suppress doping and controlling the doping current value to deposit deposits. There is a way to make spots. Both of these methods may be used in combination, or only the control of the doping current value may be used to create a good difference in the amount of deposits.
In the masking method, a gap through which the electrolytic solution permeates may or may not be provided between the masking and the negative electrode. Regarding the method of controlling the doping current value, the difference in the amount of deposits between the facing portion and the non-opposing portion tends to increase by increasing the current value. On the other hand, when the doping current value is reduced, the diffusion direction of lithium ions is less likely to be limited, and the number of lithium ions diffused in the non-opposing portion increases. As a result, lithium ions react with the electrolytic solution, and deposits are likely to be formed in the non-opposing portion, and the difference in the amount of deposits between the facing portion and the non-opposing portion tends to decrease.
Further, 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]
It is preferable to age the electrode wound body after the lithium doping step is completed. 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 method for degassing is not particularly limited, but for example, a method is used in which the electrode winding body is installed in a decompression chamber with the exterior body opened and the inside of the chamber is decompressed using a vacuum pump. be able to. Further, when the non-opposing portion of the negative electrode is masked, it is preferable to remove the masking when the exterior body is opened in the degassing step.

[Completed non-aqueous lithium-type power storage element]
[Negative electrode deposits in facing and non-opposing parts]
The negative electrode deposit preferably contains a compound selected from the above formulas (1) to (3). The formulas (1) to (3) are lithium-containing coatings, and if any of them is contained, high input / output characteristics and durability against a high load charge / discharge cycle can be obtained. The detailed principle for improving this characteristic is not clear, but it is inferred as follows. Since the lithium-containing film is internally polarized, it has high ionic conductivity, can smoothly occlude and release lithium ions, and can provide a low-resistance power storage element. Furthermore, compared to the organic and inorganic coating components that do not contain lithium ions, the lithium-containing coating exists more stably in the charge / discharge process, so the coating is less likely to be destroyed even if an extremely large number of charge / discharge cycles are repeated. No oxidative decomposition of the non-aqueous electrolyte solution occurs. Therefore, it can have durability against a high load charge / discharge cycle.
Further, the content of the compound selected from the formulas (1) to (3) per unit mass of the active material in the non-opposing portion is X, and the content per unit mass of the active material in the facing portion is Y. When this is done, it is preferable that X / Y <0.80. More preferably, X / Y <0.65. When X / Y <0.80, a lithium-containing film having good ionic conductivity is intensively formed on the facing portion of the negative electrode, so that lithium ions can be occluded and discharged more smoothly than in the non-opposing portion. The situation can be created at the opposite part that contributes to the charge / discharge reaction. In this situation, the lithium ions are preferentially occluded and released in the facing portion having a relatively low resistance, so that the lithium ions escaping to the non-opposing portion can be suppressed and the capacity of the power storage element is reduced. Can be suppressed. This effect shows a high capacity recovery rate even during a high load charge / discharge cycle, and can be provided with durability.

[Film thickness of negative electrode in facing and non-facing]
The ratio of the film thickness of the negative electrode of the non-opposing portion to the film thickness of the negative electrode of the facing portion is preferably 0.80 or more and 0.95 or less. If the ratio of the film thickness of the negative electrode of the non-opposing portion to the facing portion is 0.80 or more, the stress generated at the boundary between the facing portion and the non-opposing portion during expansion and contraction of the negative electrode can be relaxed, and the charge / discharge cycle or the like Durability is improved. Further, if the ratio of the film thickness of the negative electrode of the non-opposing portion to the facing portion is 0.95 or less, it is possible to contribute to the miniaturization of the power storage element, which leads to the improvement of the energy density per volume. In addition, there are two hypotheses as factors that cause a difference in film thickness. The first is that the negative electrode active material in the facing portion has a sufficient amount of deposits formed by the compounds of the formulas (1) to (3), whereas the negative electrode active material in the non-opposing portion has the above formula. This is the difference in film thickness caused by the relatively small amount of deposits due to the compounds (1) to (3). The other is that there is a difference in the ease of occlusion of lithium ions due to the difference in the amount of deposits between the facing portion and the non-opposing portion. In the facing portion, a sufficient amount of deposits are formed, and lithium ions are also preferentially occluded. On the other hand, in the non-opposing portion, a sufficient amount of film is not formed, and the amount of lithium ions occluded is relatively small as compared with the facing portion. That is, the second factor is considered to be the difference in the degree of expansion of the negative electrode active material due to the occlusion of lithium ions.

[Characteristic evaluation of non-aqueous lithium-type power storage element]
[Capacitance]
In the present specification, the capacitance F (F) is 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.

[Electric energy]
In the present specification, the electric energy E (Wh) is a value obtained by the following method:
It refers to a value calculated by F × (3.8 ² -2.2 ² ) / 2/3600 using the capacitance F (F) calculated by the method described above.

[volume]
The volume of the non-aqueous lithium power storage element is not particularly specified, but the volume of the portion of the electrode winding body in which the positive electrode active material layer and the negative electrode active material layer are stacked is the volume of the portion housed by the exterior body. Point to.
For example, in the case of an electrode wound body housed by a laminate film, a region of the electrode wound body in which the positive electrode active material layer and the negative electrode active material layer exist is stored in the cup-formed laminate film. However, the volume (V ₁ ) of this non-aqueous lithium-type storage element is the outer dimension length (l ₁ ), outer dimension width (w ₁ ), and non-aqueous lithium storage element of the cup-molded portion. It is calculated by V ₁ = l ₁ × w ₁ × t _{1 according} to the thickness of the element (t ₁ ).
In the case of an electrode winding body housed in a square metal can, the volume of the non-aqueous lithium power storage element is simply the volume of the outer dimension of the metal can. That is, the volume (V ₂ ) of this non-aqueous lithium-type power storage element is V depending on the outer dimension length (l ₂ ), outer dimension width (w ₂ ), and outer dimension thickness (t ₂ ) of the square metal can. It is calculated by ₂ = l ₂ × w ₂ × t ₂ .
Further, even in the case of the electrode wound body housed in the cylindrical metal can, the volume of the non-aqueous lithium power storage element is the volume of the outer dimension of the metal can. That is, the volume (V ₃ ) of this non-aqueous lithium type power storage element is V ₃ = 3.14 depending on the outer dimension radius (r) and the outer dimension length (l ₃ ) of the bottom surface or the upper surface of the cylindrical metal can. It is calculated by × r × r × l ₃ .
[Energy density]
In the present specification, the energy density is a value obtained by the equation of _{E / V i (Wh / L} ) using the amount of electricity E and the volume _V i (i = 1,2,3).

[Room temperature discharge internal resistance]
In the present specification, the room temperature discharge internal resistance Ra (Ω) is 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 20 C until it reaches 3.8 V in a constant temperature bath set at 25 ° C., and then a constant voltage of 3.8 V is applied. The constant voltage charging is performed for a total of 30 minutes. Subsequently, 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 second obtained by extrapolating from the voltage values at the discharge times of 2 seconds and 4 seconds is set to Eo, the voltage drop 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]
In the present specification, the rate of increase in internal resistance of normal temperature discharge after a high load charge / discharge cycle test is 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]
In the present specification, the capacity recovery rate after the high load charge / discharge cycle test is 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 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.

[Measurement of sediments in opposite and non-opposed areas]
When the completed retractable non-aqueous lithium power storage element is disassembled so that the positive electrode and the negative electrode do not come into contact with each other, the schematic diagram shown in FIG. 2 is obtained. As shown in FIG. 2, the negative electrode active material obtained after dismantling has an opposing portion facing the positive electrode active material and a non-opposing portion not facing the positive electrode active material, and both sides of the negative electrode are facing portions. There are a portion, a portion where one side is a facing portion, and a portion where both sides are non-opposing portions. The non-opposing portion deposit in the present specification is measured at a portion where both sides of the negative electrode are non-opposing portions. On the other hand, the deposit on the facing portion is measured at a portion where both sides of the negative electrode are facing portions. The method of measuring the deposits in the facing portion and the non-opposing portion of the negative electrode is as follows. The measurement is carried out in an argon atmosphere because the electrodes that occlude lithium are handled.
1. 1. Cut out portion where both sides of the facing portion anode becomes the opposing part, the analysis of the extract, (1) is performed by ion chromatography (IC) and (2) 1 ^H-NMR, the compound of the negative electrode extract obtained It is calculated by A × B / C from the concentration A (mol / ml) of the above, the volume B (ml) of the heavy water used for the extraction, and the mass C (g) of the negative electrode active material layer used for the extraction.
2. 2. Non-opposing part Cut out the part where both sides of the negative electrode are non-opposing parts. Measure in the same way as the facing part.

[Measurement of negative electrode thickness ratio of non-opposing part to facing part]
The measurement is carried out in an argon atmosphere. In the negative electrode taken out by disassembling the power storage element, the film thickness T1 of the facing portion is measured by measuring the film thickness of the portion facing each other on both sides and the portion not facing each other with a micrometer and taking an average. And the film thickness T2 of the non-opposing portion is obtained. The thickness ratio is calculated by obtaining the ratio of the film thickness T2 of the non-opposing portion to the film thickness T1 of the facing portion, T2 / T1.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
[Example 1]
[Crushing lithium carbonate]
200 g of lithium carbonate having an average particle diameter of 53 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 the lithium carbonate obtained by preventing thermal denaturation at -196 ° C. and brittle fracture, and found to be 2.0 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 by 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.
As a result of measuring the average particle size of this activated carbon 1 using a laser diffraction type particle size distribution measuring device (SALD-2000J) manufactured by Shimadzu Corporation, it was 4.2 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 with 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.
59.5 parts by mass of activated carbon 1 or 2, 28.0 parts by mass of lithium carbonate, 3.0 parts by mass of Ketjen Black, 1.5 parts by mass of PVP (polyvinylidene), 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. Obtained liquid.

[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.

[Preparation of negative electrode active material]
[Preparation of active material A]
150 g of artificial graphite with an average particle size of 4.9 μm was placed in a stainless steel mesh cage and placed on a stainless steel bat containing 15 g of carbon-based pitch (softening point: 50 ° C.), and both were placed in an electric furnace (effective in the furnace). The composite carbon material A was obtained by installing it in a size of 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 1200 ° 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 A was taken out from the furnace.
With respect to the obtained composite carbon material A, the average particle size and the BET specific surface area were measured by the same method as described above. As a result, the average particle size was 4.9 μm and the BET specific surface area was 8.0 m ² / g. The mass ratio of the carboniferous material derived from the carboniferous pitch to the activated carbon was 2%.

<Manufacturing of negative electrode A>
Next, a negative electrode was manufactured using the composite carbon material A as the negative electrode active material.
80 parts by mass of composite carbon material A, 8 parts by mass of acetylene black, 12 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 2,798 mPa · s, and the TI value was 2.7. The above coating liquid was applied to both sides of an electrolytic copper foil having a thickness of 10 μm and having no through holes 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. Obtained a negative electrode A. The obtained negative electrode A was pressed using a roll press machine under the conditions of a pressure of 4 kN / cm and a surface temperature of the pressed portion of 25 ° C. The film thickness of the negative electrode active material layer of the negative electrode A obtained above was measured from the average value of the thickness measured at any 10 locations of the negative electrode A using a film thickness meter Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. , Calculated by subtracting the thickness of the copper foil. As a result, the film thickness of the negative electrode active material layer of the negative electrode A was 25 μm per one side.

[Adjustment of electrolyte]
As an organic solvent, a mixed solvent of ethylene carbonate (EC): methyl ethyl carbonate (EMC) = 40: 60 (volume ratio) was used, and the concentration ratio of LiN (SO ₂ F) ₂ and LiPF _{6 to} the total electrolytic solution was A 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 50:50 (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 0.6 mol / L and 0.6 mol / L, respectively.

[Aluminum immersion]
1 g of aluminum hydroxide (Wako Pure Chemical Industries, Ltd., 014-01925) powder is added to 100 g of the obtained non-aqueous electrolyte solution, and the mixture is allowed to stand in an environment of 45 ° C. and a dew point of -40 ° C. or less for 5 hours. , Aluminum was contained in the non-aqueous electrolyte solution. Then, the insoluble component of aluminum hydroxide was removed by filtration.

[Preparation of non-aqueous lithium-type power storage element]
[Assembly process]
The obtained double-sided negative electrode was cut into 12.2 cm × 450 cm, and the double-sided positive electrode precursor was cut into 12.0 cm × 300 cm. The negative electrode and the positive electrode precursor each have an uncoated portion. This uncoated portion was formed so as to have 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 the conditions of a drying time of 60 hr.

[Liquid injection, impregnation, sealing process]
Approximately 80 g of the non-aqueous electrolyte solution was injected under atmospheric pressure into the electrode winding body 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 electrolyte 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 doping 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 1000 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. Further, the non-opposing portion of the negative electrode was masked in advance with a polyethylene film at the time of assembly to prevent the non-opposing portion from being doped with lithium ions.

[Aging process]
The non-aqueous lithium power storage element after lithium doping is subjected to constant current discharge at 1.0 A in a 25 ° C environment 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, after removing the masking attached to the non-opposing portion of the negative electrode, the non-aqueous lithium-type power storage element was placed in the decompression chamber, and a diaphragm pump (N816.3KT.45.18) manufactured by KNF was used. After depressurizing from atmospheric pressure to −80 kPa over 3 minutes, the process of returning to atmospheric pressure over 3 minutes 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 then 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]

[Calculation of energy density]
In a constant temperature bath set at 25 ° C., a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Limited is used to perform constant current charging until the current value of 2C reaches 3.8V, followed by constant current charging. A constant voltage charge of applying a constant voltage of 3.8 V was 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, and use the capacitance F (F) calculated by F = Q / (3.8-2.2). The energy density was calculated by E / V ₁ = F × (3.8 ² -2.2 ² ) / 2/3600 / V and found to be 32.6 Wh / L.
The volume V ₁ (= l ₁ × w ₁ × t ₁ ) of the power storage element is the outer dimension length (l ₁ ) and outer dimension width (w ₁ ) of the cup-molded portion of the laminate film of the power storage element, and the laminate film. The value obtained by the thickness (t ₁ ) of the power storage element including the value was used.

[Calculation of discharge internal resistance R]
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 discharge times of 2 seconds and 4 seconds is defined as Eo, the voltage drop ΔE = 3.8-Eo, and The room temperature discharge internal resistance R was calculated by R = ΔE / (20C (current value A)). The obtained room temperature internal resistance R was 2.10 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 charge / discharge 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 discharge internal resistance R]. The ratio Re / R calculated by dividing this Re (Ω) by the internal resistance R (Ω) before the high load charge / discharge cycle test obtained in the above [Calculation of discharge internal resistance R] was 1.21. ..

[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 charge / discharge 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. The value obtained by measuring the subsequent capacitance Fe and dividing by the capacitance F before the high load charge / discharge cycle was Fe / F = 0.84.

により、負極活物質層に堆積する各化合物の、負極活物質層の単位質量当たりの存在量（ｍｏｌ／ｇ）を求めた。
なお、抽出に用いた負極活物質層の質量は、以下の方法によって求めた。
重水抽出後に残った負極の集電体から負極活物質層を剥がし取り、剥がし取った負極活物質層を、水洗した後、真空乾燥した。真空乾燥して得た負極活物質層を、ＮＭＰ又はＤＭＦにより洗浄した。続いて、得られた負極活物質層を再度真空乾燥した後、秤量することにより、抽出に用いた負極活物質層の質量を調べた。 [Quantitative amount of aluminum]
The power storage element obtained in the above step was disassembled in an Ar box installed in a room at 23 ° C. and controlled at a dew point of −90 ° C. or lower and an oxygen concentration of 1 ppm or less, and 0.2 g of a non-aqueous electrolyte solution was added. I took it out. 0.2 g of the non-aqueous electrolyte solution was placed in a Teflon (registered trademark) container, and 4 cc of 60% nitric acid was added. It was decomposed using a microwave decomposition apparatus (Milestone General, ETHOS PLUS). This was made up to 50 ml with pure water. The measurement of this non-aqueous electrolyte solution was performed by ICP / MS (Thermo Fisher Scientific Co., Ltd., X series 2), and the aluminum concentration (ppm) per unit mass of the non-aqueous electrolyte solution was determined to be 310 ppm.
[Analysis of negative electrode active material layer of negative electrode]
[Analysis of active material layer between facing and non-facing parts]
After adjusting the completed non-aqueous lithium-type power storage element to 2.9V, disassemble it in an Ar box installed in a room at 23 ° C and controlled at a dew point of -90 ° C or less and an oxygen concentration of 1 ppm or less, and take out the negative electrode. It was. The removed negative electrode was cut out by dividing it into a facing portion and a non-opposing portion. After dipping and washing with dimethyl carbonate (DMC), it was vacuum dried in a side box while maintaining no air exposure.
The dried negative electrode was transferred from the side box to the Ar box while maintaining non-exposure to the atmosphere, and immersed in heavy water for extraction to obtain a negative electrode extract. The extract was analyzed by (1) IC and (2) ¹ H-NMR, and the concentration A (mol / ml) of each compound in the negative electrode extract and the volume B (ml) of the heavy water used for the extraction were obtained. ), And the mass C (g) of the negative electrode active material layer used for extraction, the following formula 2:

The abundance (mol / g) of each compound deposited on the negative electrode active material layer per unit mass of the negative electrode active material layer was determined.
The mass of the negative electrode active material layer used for extraction was determined by the following method.
The negative electrode active material layer was peeled off from the negative electrode current collector remaining after extraction with heavy water, and the peeled negative electrode active material layer was washed with water and then vacuum dried. The negative electrode active material layer obtained by vacuum drying was washed with NMP or DMF. Subsequently, the obtained negative electrode active material layer was vacuum-dried again and then weighed to examine the mass of the negative electrode active material layer used for extraction.

The negative electrode extract was placed in a 3 mmφ NMR tube (PN-002 manufactured by Shigemi Co., Ltd.), and a 5 mmφ NMR tube containing deuterated chloroform containing 1,2,4,5-tetrafluorobenzene (N-5 manufactured by Nippon Seimitsu Kagaku Co., Ltd.). ), And ¹ H NMR measurement was performed by the double tube method. The signal of 1,2,4,5-tetrafluorobenzene was standardized at 7.1 ppm (m, 2H), and the integrated value of each observed compound was obtained.
In addition, deuterated chloroform containing dimethyl sulfoxide of known concentration was placed in a 3 mmφ NMR tube (PN-002 manufactured by Shigemi Co., Ltd.), and the same 1,2,4,5-tetrafluorobenzene-containing deuterated chloroform as described above was placed. It was inserted into a 5 mmφ NMR tube (N-5 manufactured by Nippon Seimitsu Kagaku Co., Ltd.) containing chloroform, and ¹ H NMR measurement was performed by the double tube method. In the same manner as above, the signal of 1,2,4,5-tetrafluorobenzene was standardized at 7.1 ppm (m, 2H), and the integrated value of the signal of dimethyl sulfoxide at 2.6 ppm (s, 6H) was obtained. From the relationship between the concentration of dimethyl sulfoxide used and the integrated value, the concentration A of each compound in the negative electrode extract was determined.

¹ The attribution of the ¹ H NMR spectrum is as follows.
[About XOCH ₂ CH ₂ OX]
XOCH ₂ CH ₂ OX CH ₂ : 3.7ppm (s, 4H)
CH ₃ OX: 3.3 ppm (s, 3H)
CH ₃ CH ₂ OX CH ₃ : 1.2 ppm (t, 3H)
CH ₃ CH ₂ OX CH ₂ O: 3.7 ppm (q, 2 H) As described above, the signal of CH ₂ of XOCH ₂ CH ₂ OX (3.7 ppm) is _that of CH ₂ O of CH ₃ CH ₂ OX. since overlaps the signal (3.7 _ppm), with the exception of the CH ₂ O equivalent of _CH 3 _CH 2 OX calculated from the signal of CH 3 _CH 2 OX of _{CH 3 (1.2ppm), XOCH 2} CH 2 Calculate the amount of OX.
((In the above, X is − (COO) _n Li or − (COO) _n R ¹ (where n is 0 or 1, R ¹ is an alkyl group having 1 to 4 carbon atoms and 1 carbon atom, respectively). It is an alkyl halide group of ~ 4).

Based on the concentration of each compound in the extract obtained by the above analysis, the volume of heavy water used for extraction, and the mass of the negative electrode active material layer used for extraction, the negative electrode active material layer in the non-opposite portion of the negative electrode has XOCH ₂ CH. ₂ OX was present at 9.6 × 10 ^-4 mol / g. Further, 96.0 × 10 ^-4 mol / g of XOCH ₂ CH ₂ OX was present in the negative electrode active material layer in the facing portion. That is, the ratio of the deposit amount X of the non-opposing portion to the deposit amount Y of the facing portion was X / Y = 0.10.

[Measurement of negative electrode film thickness between facing and non-facing parts]
The power storage element was disassembled in an argon atmosphere, and for the negative electrode taken out, the part where both sides of the negative electrode were opposed and the part where both sides of the negative electrode were non-opposed were the film thickness meters Liner Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. Was calculated by calculating the average value of the thickness measured at any 10 locations using. From the calculated value, the ratio of the film thickness of the non-opposing portion to the film thickness of the facing portion was 0.82.
With respect to the negative electrode of the non-aqueous lithium type power storage element obtained above, the BET specific surface area per unit volume of the negative electrode active material layer of the negative electrode after use and the average pore diameter of the negative electrode active material layer were measured.

[Analysis of physical properties of the negative electrode active material of the negative electrode]
First, for the non-aqueous lithium-type power storage element manufactured above, a charging / discharging device (ACD-01) manufactured by Asuka Electronics Co., Ltd. is used to set a current of 50 mA up to 2.9 V at an ambient temperature of 25 ° C. After current charging, constant current constant voltage charging was performed by applying a constant voltage of 2.9 V for 15 hours.

Next, the negative electrode was sampled in an argon atmosphere. The non-aqueous lithium storage element was disassembled in an argon atmosphere, and the negative electrode was taken out. Subsequently, the obtained negative electrode was immersed in diethyl carbonate for 2 minutes or more to remove non-aqueous electrolyte solution, lithium salt and the like, and air-dried. Then, the obtained negative electrode 1 was immersed in a mixed solvent composed of methanol and isopropanol for 15 hours to inactivate the lithium ions occluded in the negative electrode active material and air-dried. Next, the obtained negative electrode 1 was vacuum-dried for 12 hours at a temperature of 170 ° C. using a vacuum dryer to obtain a measurement sample. With respect to the obtained measurement sample, using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics Co., Ltd., using nitrogen as an adsorbent, the negative electrode active material layer unit volume of the negative electrode was carried out by the above method. When the BET specific surface area per hit was determined, it was 8.5 cc / g.
[Solid negative electrode ⁷ Li-NMR measurement]
For the negative electrode 1 of the non-aqueous lithium-type power storage element obtained above, solid ⁷ Li-NMR measurement of the negative electrode active material layer was performed.
First, for the non-aqueous lithium-type power storage element manufactured above, a charging / discharging device (ACD-01) manufactured by Asuka Electronics Co., Ltd. is used to set a current of 50 mA up to 2.9 V at an ambient temperature of 25 ° C. After current charging, constant current constant voltage charging was performed by applying a constant voltage of 2.9 V for 15 hours.
Next, the negative electrode active material layer was sampled in an argon atmosphere. The non-aqueous lithium-type power storage element was disassembled in an argon atmosphere, and the negative electrode 1 was taken out. Subsequently, the obtained negative electrode 1 was immersed in diethyl carbonate for 2 minutes or more to remove lithium salts and the like. After another immersion in diethyl carbonate under the same conditions, it was air-dried. Then, the negative electrode active material layer was collected from the negative electrode 1 and weighed.
Using the obtained negative electrode active material layer as a sample, solid ⁷ Li-NMR measurement was performed. Using JEOL RESONANCE ECA700 (7Li-NMR resonance frequency is 272.1 MHz) as a measuring device, the rotation speed of magic angle spinning is 14.5 kHz and the irradiation pulse width is 45 ° pulse in a room temperature environment. It was measured by the single pulse method. A 1 mol / L lithium chloride aqueous solution was used as a shift reference, and the shift position measured separately as an external standard was set to 0 ppm. When measuring the 1 mol / L lithium chloride aqueous solution, the sample was not rotated, and the irradiation pulse width was set to 45 ° pulse, and the measurement was performed by the single pulse method.
In the solid ⁷ Li-NMR spectrum of the negative electrode active material layer obtained by the above method, the position of the maximum value of the peak in the spectrum range of -10 ppm to 35 ppm was 15 ppm. Further, the amount of lithium per unit mass of the negative electrode active material layer in which lithium ions were occluded was calculated for the solid ⁷ Li-NMR spectrum of the obtained negative electrode active material layer by the above-mentioned method and found to be 4.2 mmol / g. ..
[Quantification of lithium compounds]
The positive electrode sample was cut into a size of 5 cm × 5 cm (weight 0.256 g), immersed in 20 g of methanol, the container was covered, and the sample was allowed to stand in an environment of 25 ° C. for 3 days. Then, the positive electrode was taken out and vacuum dried at 120 ° C. and 5 kPa for 10 hours. At this time, the positive weight M ₀ is 0.250 g, and the GC / MS of the methanol solution after washing is measured under the condition that a calibration curve is prepared in advance, and the abundance of diethyl carbonate is less than 1%. confirmed. Subsequently, 25.00 g of distilled water was impregnated with a positive electrode, the container was covered, and the mixture was allowed to stand in an environment of 45 ° C. for 3 days. Since the weight of distilled water after standing for 3 days was 24.65 g, 0.35 g of distilled water was added. Then, the positive electrode was taken out and vacuum dried at 150 ° C. and 3 kPa for 12 hours. At this time, the positive weight M ₁ was 0.223 g, and GC / MS was measured on the distilled water after washing under the condition that a calibration curve was prepared in advance, and it was confirmed that the abundance of methanol was less than 1%. did. Then, a spatula, a brush, remove the active material layer on the positive electrode current collector by using a brush, it was 0.099g was weighed M ₂ of the positive electrode current collector. When the lithium carbonate in the positive electrode was quantified by the above formula (1), it was 30.0% by mass.

[Examples 2-28 and Comparative Examples 1-6]
The non-aqueous lithium-type storage devices of Examples 2 to 28 and Comparative Examples 1 to 6 were similarly manufactured in the same manner as in Example 1 except that the manufacturing conditions of the non-aqueous lithium storage elements were as shown in Table 1 below. Each element was manufactured and various evaluations were performed. The evaluation results of the obtained non-aqueous lithium-type power storage element are shown in Table 2 below. In addition, supplementary preparation conditions for Comparative Examples 1 to 6 are described below.

[Evaluation criteria]
[Discharge internal resistance]
The result of the discharge internal resistance (mΩ) was evaluated as follows.
AA: 2.00 or less A: 2.00 or more and 2.50 or less B: 2.50 or more and 3.00 or less C: 3.00 or more

[Energy density]
The results of energy density (Wh / L) were evaluated as follows.
AA: 33.0 or more A: 28.0 or more and less than 33.0 B: 21.0 or more and less than 28.0 C: less than 21.0

[Internal resistance increase rate during charge / discharge cycle]
The results of the internal resistance increase rate during the charge / discharge cycle were evaluated as follows.
AA: 1.25 or less A: 1.25 or more and 1.50 or less B: 1.50 or more and 2.00 or less C: 2.00 or more

[Capacity recovery rate during charge / discharge cycle]
The results of the capacity recovery rate during the charge / discharge cycle were evaluated as follows.
AA: 0.85 or more A: 0.80 or more and less than 0.85 B: 0.75 or more and less than 0.80 C: less than 0.75

The evaluation results of Examples 1 to 4 were all A, and the evaluation results of Examples 5 to 28 were all AA. From the results of the above examples, it can be seen that the non-aqueous lithium storage device of the present invention can provide excellent energy density, high input / output characteristics, and durability against a high load charge / discharge cycle.

The non-aqueous lithium type power storage element of the present invention is suitable, for example, in the field of a hybrid drive system in which an internal combustion engine, a fuel cell, or a motor in an automobile and a power storage element are combined; as an assist power source application at a peak of instantaneous power. Can be used for.

1 Winding body 2 Double-sided positive electrode 3 Double-sided negative electrode 4 Separator 5 Disassembling side view of the wound body 6 Facing part 7 Non-opposing part

Claims (5)

A non-aqueous lithium-type power storage element composed of a positive electrode containing a lithium compound other than an active material, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions.
The positive electrode has a positive electrode current collector, a positive electrode active material layer composed of an active material and a lithium compound is provided on the current collector, and the negative electrode can occlude and release lithium ions on the negative electrode current collector. Contains active material, and also
The positive electrode and the negative electrode consist of an electrode wound body wound via a separator, and in addition,
The negative electrode has a portion facing the positive electrode and the negative electrode facing each other with the separator interposed therebetween.
With the separator interposed therebetween, it has a non-opposing portion in which the opposite positive electrode does not exist, and
Of the compound selected from the following formulas (1) to (3),
The content per unit mass of the active material in the non-opposing portion is X, and the content per unit mass of the active material in the facing portion is Y.
When, X / Y <0.80, and
The lithium compound is a non-aqueous lithium-type power storage element which is at least one lithium compound selected from the group consisting of lithium carbonate, lithium oxide, and lithium hydroxide .

{In formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms and a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are independently − (COO) _n (here). , N is 0 or 1.). }

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

{In formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms and a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and having 1 to 10 carbon atoms, respectively. Alkyl group, mono or polyhydroxyalkyl group with 1 to 10 carbon atoms, alkenyl group with 2 to 10 carbon atoms, mono or polyhydroxyalkenyl group with 2 to 10 carbon atoms, cycloalkyl group with 3 to 6 carbon atoms, or aryl It is a group, and X ¹ and X ² are independently − (COO) _n (where n is 0 or 1). } The non-aqueous lithium-type power storage element according to claim 1, wherein the ratio of the film thickness of the negative electrode of the non-opposing portion to the film thickness of the negative electrode of the facing portion is 0.80 or more and 0.95 or less. In the solid ⁷ Li-NMR spectrum of the negative electrode active material layer, the lithium ion has the maximum value of the peak between 4 ppm and 30 ppm and is calculated from the area of the peak observed at 4 ppm to 30 ppm. The non-aqueous lithium-type power storage element according to claim 1 or 2 , wherein the stored negative electrode active material layer is 0.1 mmol / g or more and 10 mmol / g or less per unit mass. The non-aqueous lithium-type power storage element according to any one of claims 1 to 3 , wherein the BET specific surface area per unit volume of the negative electrode active material layer is 1 m ² / cc or more and 50 m ² / cc or less. Based on the total mass of the positive electrode active material layer, the positive electrode contains 1% by mass or more and 50% by mass or less of a lithium compound other than the positive electrode active material, and the Al concentration of the non-aqueous electrolyte solution is 1 ppm or more and 300 ppm. The non-aqueous lithium-type power storage element according to any one of claims 1 to 4 , which is as follows.

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