JP2018056411A - Nonaqueous lithium type power storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous lithium type power storage element which is superior in high output property and durability.SOLUTION: A nonaqueous lithium type power storage element comprises: a laminate or wound body arranged by laminating or winding a positive electrode and a negative electrode with a separator interposed therebetween; and a nonaqueous electrolyte including lithium ions. The positive electrode includes a lithium compound at a concentration of 1-50 mass%. The positive electrode has a positive electrode current collector and a positive electrode active material layer including active carbon. The negative electrode has a negative electrode current collector, and a negative electrode active material layer including a negative electrode active material capable of occluding and releasing a lithium ion. The ratio of a lithium ion concentration at a center in top view of the negative electrode active material layer of the negative electrode in an outermost layer of the laminate, and a lithium ion concentration at a center in top view of the negative electrode active material layer of the negative electrode in an innermost layer of the laminate is a particular ratio. In the nonaqueous lithium type power storage element, a lithium ion concentration is higher in a center portion rather than a peripheral edge of the negative electrode active material layer. The average particle diameter of the lithium compound, and the average particle diameter of the positive electrode active material are in predetermined value ranges.SELECTED DRAWING: None

Description

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

In recent years, from the viewpoint of the effective use of energy aiming to preserve the global environment and conserve resources, wind power generation smoothing system or midnight power storage system, home-use distributed storage system based on solar power generation technology, storage for electric vehicles The system is drawing attention.
The first requirement for batteries used in these power storage systems is high energy density. As a promising candidate for a high energy density battery capable of meeting such demands, development of a lithium ion battery has been vigorously advanced.
The second requirement is high output characteristics. For example, in a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell electric vehicle), high output discharge characteristics in the power storage system are required during acceleration. Yes.

Currently, electric double layer capacitors, nickel metal hydride batteries, and the like have been developed as high-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 as an optimum device in the field where the high output is required. However, the energy density is only about 1 to 5 Wh / L. Therefore, further improvement in energy density is necessary.

  On the other hand, nickel-metal hydride batteries currently used in hybrid electric vehicles have a high output equivalent to that of electric double layer capacitors and an energy density of about 160 Wh / L. However, research for increasing the energy density and output and further improving durability (particularly stability at high temperatures) has been energetically advanced.

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

As described above, there is a strong demand for the practical use of a power storage device 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 demanded. As a promising candidate, a storage element called a lithium ion capacitor has attracted attention and has been actively developed.
A lithium ion capacitor is a kind of energy storage device (non-aqueous lithium energy storage device) that uses a non-aqueous electrolyte containing a lithium salt, and the negative electrode adsorbs the same as an electric double layer capacitor at about 3 V or more at the positive electrode. It is a power storage element that charges and discharges by a non-Faraday reaction by desorption, and a Faraday reaction by insertion and extraction of lithium ions in the negative electrode, similar to a lithium ion battery.
The above-mentioned electrode materials and their characteristics can be summarized as follows: High output and high durability are achieved when materials such as activated carbon are used for the electrodes and charging / discharging is performed by ion adsorption / desorption (non-Faraday reaction) on the activated carbon surface. However, the energy density is lowered (for example, 1 time). On the other hand, when an oxide or a carbon material is used for the electrode and charging / discharging is performed by a Faraday reaction, the energy density is increased (for example, 10 times that of a non-Faraday reaction using activated carbon), but durability and output are increased. There is a problem with the characteristics.

  As a combination of these electrode materials, the electric double layer capacitor is characterized in that the positive and negative electrodes use activated carbon (energy density 1 time), and the positive and negative electrodes are charged and discharged by a non-Faraday reaction, resulting in high output and high durability. However, the energy density is low (positive electrode 1 ×× negative electrode 1 = 1).

  A lithium ion secondary battery uses a lithium transition metal oxide (energy density 10 times) for a positive electrode, a carbon material (energy density 10 times) for a negative electrode, and charges and discharges by a Faraday reaction for both positive and negative electrodes. The energy density (positive electrode 10 times × negative electrode 10 times = 100) has problems in output characteristics and durability. Furthermore, in order to satisfy the high durability required for a hybrid electric vehicle or the like, the depth of discharge must be limited, and in the lithium ion secondary battery, only 10 to 50% of the energy can be used.

  A lithium ion capacitor uses activated carbon (energy density 1 time) for the positive electrode and a carbon material (10 times energy density) for the negative electrode, and is charged and discharged by a non-Faraday reaction at the positive electrode and a Faraday reaction at the negative electrode. It is a novel asymmetric capacitor that combines the features of a multilayer capacitor and a lithium ion secondary battery. In addition, while having high output and high durability, it has a high energy density (positive electrode 1 ×× negative electrode 10 = 10), and there is no need to limit the depth of discharge unlike a lithium ion secondary battery. is there.

Examples of the use of the lithium ion capacitor include railways, construction machinery, automobile power storage, and the like. In these applications, since the operating environment is harsh, the capacitor to be used is required to have high input / output characteristics, high load charge / discharge cycle characteristics, and high safety at the same time.
As a countermeasure technique for such a demand, a means for joining a current-carrying tab to an electrode layer and applying an alternating current between the current-carrying tab and the electrode tab to make the potential distribution of the electrode uniform and improve durability (hereinafter referred to as the following) Patent Document 1), and means for improving the uniformity of the potential between the electrodes by attaching a terminal capable of measuring the potential to the electrode and charging and discharging each terminal independently by referring to the potential obtained from the terminal. (See the following Patent Document 2).

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

JP 2012-69314 A Japanese Patent Laid-Open No. 2002-50407

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

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

｛式（１）中、Ｒ^１は、炭素数１〜４のアルキレン基又は炭素数１〜４のハロゲン化アルキレン基であり、そしてＸ^１とＸ^２は、互いに独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝、又は下記式（２）：

｛式（２）中、Ｒ^１は、炭素数１〜４のアルキレン基又は炭素数１〜４のハロゲン化アルキレン基であり、Ｒ^２は、水素、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、又はアリール基であり、そしてＸ^１とＸ^２は、互いに独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝、又は下記式（３）：

｛式（３）中、Ｒ^１は、炭素数１〜４のアルキレン基又は炭素数１〜４のハロゲン化アルキレン基であり、Ｒ^２とＲ^３は、互いに独立に、水素原子、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、又はアリール基であり、そしてＸ^１とＸ^２は、互いに独立に、−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝で表される１種以上の化合物を、前記正極物質層の単位質量当たり１．６０×１０^−４ｍｏｌ／ｇ〜３００×１０^−４ｍｏｌ／ｇ含有する、前記［１］〜［５］のいずれかに記載の前記非水系リチウム型蓄電素子。
［７］前記正極活物質層に含まれる正極活物質が、ＢＪＨ法により算出した直径２０Å以上５００Å以下の細孔に由来するメソ孔量をＶ１（ｃｃ／ｇ）、ＭＰ法により算出した直径２０Å未満の細孔に由来するマイクロ孔量をＶ２（ｃｃ／ｇ）とするとき、０．３＜Ｖ１≦０．８、及び０．５≦Ｖ２≦１．０を満たし、かつ、ＢＥＴ法により測定される比表面積が１，５００ｍ２／ｇ以上３，０００ｍ^２／ｇ以下を示す活性炭である、前記［１］〜［６］のいずれかに記載の非水系リチウム型蓄電素子。
［８］前記正極活物質層に含まれる正極活物質が、ＢＪＨ法により算出した直径２０Å以上５００Å以下の細孔に由来するメソ孔量Ｖ１（ｃｃ／ｇ）が０．８＜Ｖ１≦２．５を満たし、ＭＰ法により算出した直径２０Å未満の細孔に由来するマイクロ孔量Ｖ２（ｃｃ／ｇ）が０．８＜Ｖ２≦３．０を満たし、かつ、ＢＥＴ法により測定される比表面積が２，３００ｍ２／ｇ以上４，０００ｍ^２／ｇ以下を示す活性炭である、前記［１］〜［６］のいずれかに記載の非水系リチウム型蓄電素子。
［９］前記負極活物質のリチウムイオンのドープ量が、単位質量当たり５３０ｍＡｈ／ｇ以上２，５００ｍＡｈ／ｇ以下である、前記［１］〜［８］のいずれかに記載の非水系リチウム型蓄電素子。
［１０］前記負極活物質のＢＥＴ比表面積が１００ｍ^２／ｇ以上１，５００ｍ^２／ｇ以下である、前記［１］〜［９］のいずれかに記載の非水系リチウム型蓄電素子。
［１１］前記負極活物質のリチウムイオンのドープ量が、単位質量当たり５０ｍＡｈ／ｇ以上７００ｍＡｈ／ｇ以下である、前記［１］〜［８］のいずれかに記載の非水系リチウム型蓄電素子。
［１２］前記負極活物質のＢＥＴ比表面積が１ｍ^２／ｇ以上５０ｍ^２／ｇ以下である、前記［１］〜［８］、及び［１１］のいずれかに記載の非水系リチウム型蓄電素子。
［１３］前記非水系リチウム型蓄電素子において、初期の常温放電内部抵抗をＲａ（Ω）、静電容量をＦ（Ｆ）、環境温度２５℃にて、セル電圧を２．２Ｖから３．８Ｖまで、３００Ｃのレートでの充放電サイクルを６０，０００回行った後の常温放電内部抵抗をＲｅ（Ω）、サイクル試験後の蓄電素子を４．５Ｖの定電圧充電を１時間行った後の静電容量をＦｅ（Ｆ）とするとき、以下の：
（ａ）Ｒｅ／Ｒａが０．９以上２．０以下である；及び
（ｂ）Ｆｅ／Ｆが１．０１以上である；
を満たすことを特徴とする、前記［１］〜［１２］のいずれかに記載の非水系リチウム型蓄電素子。 That is, the present invention is as follows:
[1] A non-aqueous lithium storage element including a laminate in which a positive electrode and a negative electrode are laminated via a separator, and a non-aqueous electrolyte containing lithium ions,
The positive electrode includes a lithium compound,
The positive electrode has a positive electrode current collector and a positive electrode active material layer on one or both sides of the positive electrode current collector, and the positive electrode active material layer contains a positive electrode active material made of activated carbon,
The negative electrode has a negative electrode current collector and a negative electrode active material layer on one or both sides of the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material capable of inserting and extracting lithium ions,
When the negative electrode active material layer of the negative electrode in the thickness direction outermost layer of the laminate is viewed from above, the central lithium ion concentration is C _1o , and when the negative electrode active material layer of the negative electrode in the thickness direction innermost layer of the laminate is viewed from above _{C 1o} / _{C 1i} when the lithium ion concentration of the centers of the _{C 1i} is 0.85 to 1.15,
The concentration of lithium ions is higher in the area of 80% of the central part of the negative electrode active material layer than in the area of 20% of the peripheral part of the negative electrode active material layer,
When the average particle diameter of the lithium compound and _{X 1,} a 0.1μm ≦ _{X 1} ≦ 10μm, when the average particle diameter of the positive electrode active material and _{Y 1,} a 2μm ≦ _{Y 1} ≦ 20μm, X ₁ <Y ₁ and the amount of the lithium compound contained in the positive electrode is 1% by mass or more and 50% by mass or less.
[2] The thickness of the negative electrode active material layer at the center when the negative electrode active material layer of the negative electrode in the outermost layer in the thickness direction of the laminate is viewed from above is T _1o , and the negative electrode active material of the negative electrode in the innermost layer in the thickness direction of the laminate when the thickness of the negative electrode active material layer in the center when viewed from the top layer and _{T 1i, T 1o} / _{T 1i} is 0.85 to 1.15, the non-aqueous lithium power storage according to [1] element.
[3] A non-aqueous lithium storage element comprising a wound body in which a positive electrode and a negative electrode are wound through a separator, and a non-aqueous electrolyte containing lithium ions,
The positive electrode includes a lithium compound,
The positive electrode has a positive electrode current collector and a positive electrode active material layer on one or both sides of the positive electrode current collector, the positive electrode active material layer contains a positive electrode active material made of activated carbon,
The negative electrode has a negative electrode current collector and a negative electrode active material layer on one or both sides of the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material capable of inserting and extracting lithium ions,
Opposite to the positive electrode of the wound body, and the center lithium ion concentration of the negative electrode active material layer of the negative electrode in the outermost radial direction excluding the peripheral portion is C _2o , facing the positive electrode of the wound _body when the lithium ion concentration in the center when the anode active material layer of the negative electrode was viewed in the radial direction innermost layer except for the life-and-death periphery and C _2i, C _2o / C _2i is 0.85 to 1.15 Yes,
The concentration of lithium ions is higher in the area of 80% of the central part of the negative electrode active material layer than in the area of 20% of the peripheral part of the negative electrode active material layer,
When the average particle diameter of the lithium compound is X ₁ , 0.1 μm ≦ X ₁ ≦ 10 μm, and when the average particle diameter of the positive electrode active material is Y ₁ , 2 μm ≦ Y ₁ ≦ 20 μm and X ₁ The non-aqueous lithium storage element, wherein <Y ₁ and the amount of the lithium compound contained in the positive electrode is 1% by mass or more and 50% by mass or less.
[4] The center thickness of the negative electrode active material layer of the negative electrode at the outermost radial direction excluding the peripheral portion, which is opposed to the positive electrode of the wound _body , when viewed from above, is T _2o , T _2o / T _2i is 0.85 or more and 1.15 or less when the thickness of the negative electrode active material layer of the negative electrode in the radially innermost layer that is opposite and excluding the peripheral portion is T _2i when viewed from above. The non-aqueous lithium storage element according to [3].
[5] The non-aqueous lithium according to any one of [1] to [4], wherein the lithium compound is at least one lithium compound selected from the group consisting of lithium carbonate, lithium oxide, and lithium hydroxide. Type storage element.
[6] The positive electrode active material layer has the following formula (1):

{In Formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are independently of each other — (COO) _n. (Where n is 0 or 1). } Or the following formula (2):

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

{In 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 each independently a hydrogen atom, 1 carbon atom. -10 alkyl group, C1-C10 mono- or polyhydroxyalkyl group, C2-C10 alkenyl group, C2-C10 mono- or polyhydroxyalkenyl group, C3-C6 cycloalkyl group Or an aryl group and X ¹ and X ² are independently of each other — (COO) _n (where n is 0 or 1). One or more compounds represented by}, to unit mass per ^{1.60 × 10 -4 mol / g~300 ×} 10 -4 mol / g containing the positive electrode material layer, the [1] to [5] The non-aqueous lithium storage element according to any one of the above.
[7] The positive electrode active material contained in the positive electrode active material layer has a mesopore amount derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method as V1 (cc / g), and a diameter of 20 mm calculated by the MP method. When the amount of micropores derived from smaller pores is V2 (cc / g), it satisfies 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0, and is measured by the BET method The nonaqueous lithium storage element according to any one of the above [1] to [6], wherein the specific surface area is activated carbon having a specific surface area of 1,500 m ² / g or more and 3,000 m ² / g or less.
[8] The positive electrode active material contained in the positive electrode active material layer has a mesopore volume V1 (cc / g) derived from pores having a diameter of 20 to 500 mm calculated by the BJH method of 0.8 <V1 ≦ 2. The specific surface area measured by the BET method when the amount of micropores V2 (cc / g) derived from pores having a diameter of less than 20 mm calculated by the MP method satisfies 0.8 <V2 ≦ 3.0. There 2,300m2 / g is activated carbon having the following more 4,000 m ² / g, wherein [1] nonaqueous lithium-type storage element according to any one of to [6].
[9] The non-aqueous lithium-type electricity storage according to any one of [1] to [8], wherein a doping amount of lithium ions of the negative electrode active material is 530 mAh / g or more and 2,500 mAh / g or less per unit mass. element.
[10] The non-aqueous lithium storage element according to any one of [1] to [9], wherein the negative electrode active material has a BET specific surface area of 100 m ² / g or more and 1,500 m ² / g or less.
[11] The non-aqueous lithium storage element according to any one of [1] to [8], wherein a doping amount of lithium ions of the negative electrode active material is 50 mAh / g or more and 700 mAh / g or less per unit mass.
[12] The non-aqueous lithium storage element according to any one of [1] to [8] and [11], wherein the negative electrode active material has a BET specific surface area of 1 m ² / g or more and 50 m ² / g or less. .
[13] In the non-aqueous lithium storage element, the initial normal temperature discharge internal resistance is Ra (Ω), the capacitance is F (F), the ambient temperature is 25 ° C., and the cell voltage is 2.2 V to 3.8 V. Until the room temperature discharge internal resistance after performing 60,000 charge / discharge cycles at a rate of 300 C is Re (Ω), and the storage element after the cycle test is charged with a constant voltage of 4.5 V for 1 hour. When the capacitance is Fe (F), the following:
(A) Re / Ra is 0.9 or more and 2.0 or less; and (b) Fe / F is 1.01 or more;
The nonaqueous lithium storage element according to any one of [1] to [12], wherein:

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

Explanation for specifying the area region (4) of the peripheral portion 20% and the area region (3) of the central portion 80% of the negative electrode active material layer (2) when the electrode laminate is a laminate of single-wafer electrodes. FIG. It is explanatory drawing for specifying the area region (4) of the peripheral part 20% of the negative electrode active material layer (2) and the area region (3) of the central part 80% when the electrode laminated body is a wound laminated body. is there. Length x ₂ in the longitudinal direction of the wound laminate cut generally corresponds to the longitudinal direction of the electrode length of the non-aqueous lithium storage element including a cutout wound laminate. It is explanatory drawing for specifying the negative electrode (5) in the thickness direction outermost layer of a laminated body, and the negative electrode (6) in the thickness direction innermost layer of the said laminated body in the case where an electrode laminated body is a laminated body of a sheet-like electrode. . In the case where the electrode laminate is a wound laminate, the outer periphery (9) of the wound body is the negative electrode that forms the wound body, and is opposed to the positive electrode (8) and is the center excluding the peripheral edge of the negative electrode Means the negative electrode active material layer of the outermost circumference that is wound in the region of the part, and the inner peripheral part (7) of the wound body is the negative electrode that forms the wound body and faces the positive electrode (8) And it is drawing for demonstrating the negative electrode active material layer for the innermost circumference | surroundings 1 round wound in the area | region of the center part except the peripheral part of a negative electrode.

Hereinafter, embodiments of the present invention will be described in detail.
In general, a non-aqueous lithium-type energy storage device mainly includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an outer package. As the electrolytic solution, an organic solvent in which a lithium salt is dissolved (hereinafter referred to as a non-aqueous electrolytic solution) is used.
[Positive electrode]
The positive electrode has a positive electrode current collector and a positive electrode active material layer present on one side or both sides thereof.
Moreover, it is preferable that a positive electrode contains a lithium compound as a positive electrode precursor before an electrical storage element assembly. As will be described later, in this embodiment, it is preferable that the negative electrode is pre-doped with lithium ions in the power storage element assembly step. In addition, it is preferable to apply a voltage between the positive electrode precursor and the negative electrode after assembling the electricity storage device using the non-aqueous electrolyte. The lithium compound is preferably contained in a positive electrode active material layer formed on the positive electrode current collector of the positive electrode precursor.
In this specification, the positive electrode state before the lithium doping step is defined as the positive electrode precursor, and the positive electrode state after the lithium doping step is defined as the positive electrode.

[Positive electrode active material layer]
The positive electrode active material layer included 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 optional components such as a conductive filler, a binder, and a dispersion stabilizer as necessary.
The positive electrode active material layer of the positive electrode precursor preferably contains a lithium compound other than the positive electrode active material.

[Positive electrode active material]
The positive electrode active material includes activated carbon. As the positive electrode active material, only activated carbon may be used, or other carbon materials as described later may be used in combination with activated carbon. As this carbon material, it is more preferable to use a carbon nanotube, a conductive polymer, or a porous carbon material. As the positive electrode active material, one or more kinds of carbon materials including activated carbon may be mixed and used, or a material other than the carbon material (for example, a composite oxide of lithium and a transition metal) may be included.
Preferably, the content of the carbon material with respect to the total amount of the positive electrode active material is 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 the effect of using other materials in combination, for example, the content is preferably 90% by mass or less, and 80% by mass or less. Also good.

There is no restriction | limiting in particular in the kind of activated carbon used as a positive electrode active material, and its raw material. However, in order to achieve both high input / output characteristics and high energy density, it is preferable to optimally control the pores of the activated carbon. Specifically, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is calculated. When 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. / g or more 3,000 m ² / g or less is activated carbon (hereinafter, also referred to as activated carbon 1.), or (2) in order to obtain a high energy density, 0.8 <V1 ≦ 2.5, and 0.8 Activated carbon (hereinafter also referred to as activated carbon 2) satisfying <V2 ≦ 3.0 and having a specific surface area measured by the BET method of 2,300 m ² / g or more and 4,000 m ² / g or less is preferable.

Hereinafter, the activated carbon 1 and the activated carbon 2 will be described.
[Activated carbon 1]
The mesopore amount V1 of the activated carbon 1 is preferably a value larger than 0.3 cc / g from the viewpoint of increasing the input / output characteristics when incorporated in the energy storage device. 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. 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 of the activated carbon and increase the capacity. On the other hand, it is preferably 1.0 cc / g or less from the viewpoint of suppressing the bulk of the activated carbon, increasing the density as an electrode, and increasing the capacity per unit volume. 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 volume V1 to the micropore volume V2 (V1 / V2) is preferably in the range of 0.3 ≦ V1 / V2 ≦ 0.9. That is, it is preferable that V1 / V2 is 0.3 or more from the viewpoint of increasing the ratio of the mesopore amount to the micropore amount to such an extent that a 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 such an extent that the decrease in capacity can be suppressed while maintaining 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 mm or more, more preferably 18 mm or more, and still more preferably 20 mm or more, from the viewpoint of maximizing the output of the obtained electricity storage device. Moreover, from the point of maximizing the capacity, the average pore diameter of the activated carbon 1 is preferably 25 mm 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, good energy density is easily obtained. On the other hand, when the BET specific surface area is 3,000 m ² / g or less, the strength of the electrode is maintained. Since there is no need to add a large amount of binder, the performance per electrode volume is increased. The combination of the lower limit and the upper limit can be arbitrary.

The activated carbon 1 having the above-described features can be obtained using, for example, the raw materials and processing methods described below.
In this embodiment, the carbon source used as a raw material of the activated carbon 1 is not particularly limited. For example, plant materials such as wood, wood flour, coconut husk, pulp by-product, bagasse, molasses, etc .; peat, lignite, lignite, bituminous coal, anthracite, petroleum distillation residue components, petroleum pitch, coke, coal tar, etc. Fossil-based 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 and the like, and carbides thereof. Among these raw materials, from the viewpoint of mass production and cost, plant raw materials such as coconut shells and wood flour, and their carbides are preferable, and coconut shell carbides are particularly preferable.

As a carbonization and activation method for making these raw materials into the activated carbon 1, 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 employed.
As a carbonization method of these raw materials, nitrogen, carbon dioxide, helium, argon, xenon, neon, carbon monoxide, an exhaust gas such as combustion exhaust gas, or other gases mainly composed of these inert gases. The method of baking for about 30 minutes-about 10 hours at about 400-700 degreeC (preferably 450-600 degreeC) using mixed gas is mentioned.

As a method for activating the carbide obtained by the carbonization method, a gas activation method in which firing is performed using an activation gas such as water vapor, carbon dioxide, or oxygen is preferably used. Among these, a method using water vapor or carbon dioxide as the activation gas is preferable.
In this activation method, the carbide is supplied for 3 to 12 hours (preferably 5 to 11) while supplying the activation gas at a rate of 0.5 to 3.0 kg / h (preferably 0.7 to 2.0 kg / h). It is preferable to activate by heating to 800 to 1,000 ° C. over a period of time, more preferably 6 to 10 hours.
Furthermore, prior to the activation treatment of the carbide, the carbide may be activated in advance. In this primary activation, a method of gas activation by firing a carbon material at a temperature of less than 900 ° C. using an activation gas such as water vapor, carbon dioxide, oxygen or the like can be preferably employed.
By appropriately combining the firing temperature and firing time in the carbonization method with the activation gas supply amount, the heating rate and the maximum activation temperature in the activation method, the activated carbon 1 having the above characteristics that can be used in the present embodiment is manufactured. can do.

The average particle diameter 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, there may be a drawback that the durability is low. However, if the average particle size is 2 μm or more, such a defect hardly occurs. On the other hand, when the average particle size is 20 μm or less, it tends to be easily adapted to high-speed charge / discharge. The average particle diameter is more preferably 2 to 15 μm, still more preferably 3 to 10 μm. The upper limit and the lower limit of the range of the average particle diameter 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 energy storage device. 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. V1 is more preferably from 1.00 cc / g to 2.0 cc / g, and still more preferably from 1.2 cc / g to 1.8 cc / g.

  The micropore amount V2 of the activated carbon 2 is preferably larger than 0.8 cc / g in order to increase the specific surface area of the activated carbon and increase the capacity. On the other hand, V2 is preferably 3.0 cc / g or less from the viewpoint of increasing the density of the activated carbon as an electrode and increasing the capacity per unit volume. V2 is more preferably greater than 1.0 cc / g and not greater than 2.5 cc / g, and still more preferably not less than 1.5 cc / g and not greater than 2.5 cc / g.

The activated carbon 2 having the above-described mesopore size and micropore size has a higher BET specific surface area than 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 is easily obtained. On the other hand, when the BET specific surface area is 4,000 m ² / g or less, the strength of the electrode is maintained. Since there is no need to add a large amount of binder, the performance per electrode volume is increased.
In addition, about V1, V2, and BET specific surface area of activated carbon 2, the upper limit and lower limit of the suitable range demonstrated above can be combined arbitrarily, respectively.

The activated carbon 2 having the characteristics as described above can be obtained by using, for example, raw materials and processing methods as described below.
The carbon source used as a raw material for the activated carbon 2 is not particularly limited as long as it is a carbon source that is usually used as a raw material for activated carbon. Fossil-based raw materials such as phenol resins, furan resins, vinyl chloride resins, vinyl acetate resins, melamine resins, urea resins, resorcinol resins and the like. Among these raw materials, a phenol resin and a furan resin are particularly preferable because they are suitable for producing activated carbon having a high specific surface area.

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

As the activation method of the carbide after the carbonization treatment, there are a gas activation method in which firing is performed using an activation gas such as water vapor, carbon dioxide, oxygen, and an alkali metal activation method in which heat treatment is performed after mixing with an alkali metal compound. In order to produce activated carbon having a high specific surface area, an alkali metal activation method is preferred.
In this activation method, mixing was performed so that the mass ratio of the carbide to the alkali metal compound such as KOH or NaOH was 1: 1 or more (the amount of the alkali metal compound was the same as or greater than the amount of the carbide). Thereafter, heating is performed in the range of 600 to 900 ° C. (preferably 650 to 850 ° C.) in an inert gas atmosphere for 0.5 to 5 hours, and then the alkali metal compound is washed and removed with an acid and water, followed by drying. I do.

As described above, the mass ratio of the carbide to the alkali metal compound (= carbide: alkali metal compound) is preferably 1: 1 or more. However, as the amount of the alkali metal compound increases, the amount of mesopores increases. Since the amount of pores tends to increase sharply around 3.5, the mass ratio is preferably more alkali metal compounds than 1: 3, more preferably 1: 5.5 or less. As the mass ratio increases, the amount of pores increases as the number of alkali metal compounds increases.
In order to increase the amount of micropores and not increase the amount of mesopores, a larger amount of carbide may be mixed with KOH when activated. In order to increase both the amount of micropores and the amount of mesopores, a larger amount of KOH may be used. In order to mainly increase the amount of mesopores, it is preferable to perform water vapor activation after alkali activation treatment.
The average particle diameter of the activated carbon 2 is preferably 2 μm or more and 20 μm or less, and more preferably 3 μm or more and 10 μm or less.

[Usage of activated carbon]
Each of the activated carbons 1 and 2 may be one type of activated carbon, or a mixture of two or more types of activated carbon, and each characteristic value described above may be shown as the entire mixture.
Said activated carbon 1 and 2 may select and use any one of these, and may mix and use both.
The positive electrode active material is a material other than activated carbon 1 and 2 (for example, activated carbon not having the specific V1 and / or V2, or a material other than activated carbon (for example, a composite oxide of lithium and a transition metal)). May be included. In the illustrated embodiment, the content of the activated carbon 1, or the content of the activated carbon 2, or the total content of the activated carbons 1 and 2, is preferably more than 50% by mass of the total positive electrode active material, and 70% by mass or more. More preferably, it is more preferably 90% by mass or more, and most preferably 100% by mass.

  The content ratio of the positive electrode active material in the positive electrode active material layer is preferably 35% by mass or more and 95% by mass or less based on the total mass of the positive electrode active material layer in the positive electrode precursor. As a minimum of the content rate of a positive electrode active material, it is more preferable that it is 45 mass% or more, and it is further more preferable that it is 55 mass% or more. On the other hand, as an upper limit of the content rate of a positive electrode active material, it is more preferable that it is 90 mass% or less, and it is still more preferable that it is 80 mass% or less. By setting the content ratio in this range, suitable charge / discharge characteristics are exhibited.

[Lithium compounds]
The positive electrode active material layer of the positive electrode precursor of this embodiment preferably contains a lithium compound other than the positive electrode active material. Moreover, the positive electrode active material layer of the positive electrode of this embodiment contains lithium compounds other than the positive electrode active material.
Examples of the lithium compound include lithium carbonate, lithium oxide, lithium hydroxide, lithium fluoride, lithium chloride, lithium oxalate, iodine, which can be decomposed at the positive electrode in the lithium doping step described later and release lithium ions. One or more selected from lithium fluoride, lithium nitride, lithium oxalate, and lithium acetate are preferably used. Among these, 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 is decomposed by the application of a voltage, functions as a lithium-doped dopant source for the negative electrode, and forms a vacancy in the positive electrode active material layer. A positive electrode having excellent properties can be formed.

[Lithium compound of positive electrode precursor]
The lithium compound is preferably particulate. 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. If the average particle size of the lithium compound is 0.1 μm or more, the vacancies remaining after the oxidation reaction of the lithium compound in the positive electrode have a sufficient volume to hold the electrolytic solution. improves. If the average particle diameter of the lithium compound is 10 μm or less, the surface area of the lithium compound does not become excessively small, so that the speed of the oxidation reaction of the lithium compound can be ensured. The upper limit and the lower limit of the range of the average particle diameter of the lithium compound can be arbitrarily combined.
Various methods can be used for micronization of the lithium compound. For example, a pulverizer 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, preferably 10% 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 precursor. It is more preferable that the amount is not more than mass%. By setting the content ratio in this range, while exhibiting a suitable function as a dopant source for the negative electrode, it is possible to impart an appropriate degree of porosity to the positive electrode, and in combination with both, high load charge / discharge efficiency is achieved. An excellent power storage element can be provided, which is preferable. The upper limit and the lower limit of the 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. The positive electrode contains, the average particle diameter of the lithium compound other than the positive electrode active material when the _{X 1,} preferably from 0.1μm ≦ _{X 1} ≦ 10μm, more preferably, at 0.5μm ≦ _{X 1} ≦ 5μm is there. When X ₁ is a 0.1μm or more, high load charge-discharge cycle characteristics are improved by adsorbing the fluorine ions generated by the high-load charging and discharging cycles. On the other hand, when X ₁ is a 10μm or less, since the reaction area with the fluorine ions generated by the high-load charging and discharging cycles increases, it is possible to efficiently adsorb the fluorine ions.

  The lithium compound other than the positive electrode active material contained in the positive electrode is 1% by mass to 50% by mass based on the total mass of the positive electrode active material layer in the positive electrode, and is 2.5% by mass to 25% by mass. % Or less is more preferable. When the amount of the lithium compound is 1% by mass or more, the lithium carbonate suppresses the decomposition reaction of the electrolyte solvent on the positive electrode in a high temperature environment, so that the high temperature durability is improved. Becomes prominent. 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. Particularly preferred from the viewpoint of input / output characteristics. The combination of the lower limit and the upper limit can be arbitrary.

[Method for identifying lithium compound in positive electrode]
Although the identification method of the lithium compound contained in a positive electrode is not specifically limited, For example, it can identify by the following method. It is preferable to identify a lithium compound by combining a plurality of analysis methods described below.
When measuring SEM-EDX, Raman, and XPS described below, measurement should be performed after disassembling the non-aqueous lithium storage element in an argon box, taking out the positive electrode, and washing the electrolyte adhering to the positive electrode surface. Is preferred. Regarding the method for cleaning the positive electrode, it is only necessary to wash away the electrolyte adhering to the surface of the positive electrode. Therefore, carbonate solvents such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate can be suitably used. As a cleaning method, for example, the positive electrode is immersed in a diethyl carbonate solvent 50 to 100 times the mass of the positive electrode for 10 minutes or more, and then the solvent is changed and the positive electrode is immersed again. Thereafter, the positive electrode is taken out from diethyl carbonate and dried in a vacuum (temperature: 0 to 200 ° C., pressure: 0 to 20 kPa, time: 1 to 40 hours in which diethyl carbonate remains in the positive electrode within a range of 1% by mass or less. The residual amount of diethyl carbonate can be determined based on a calibration curve prepared in advance by measuring the GC / MS of water after washing with distilled water and adjusting the liquid volume, which will be described later. -Perform EDX, Raman and XPS analyses.

As for ion chromatography described later, anions can be identified by analyzing the water after washing the positive electrode with distilled water.
When a 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), AES (Auger) Lithium compounds can also be identified by using electron spectroscopy, TPD / MS (heat generation gas mass spectrometry), DSC (differential scanning calorimetry), or the like.

[Raman]
The lithium compound and positive electrode active material comprising carbonate ions can be distinguished 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 is 1, and measurement can be performed with a noise filter. For the measured Raman spectrum, a straight baseline is set in the range of 1071 to 1104 cm ^{−1, and} the area is calculated with a positive value from the baseline as the peak of carbonate ions, and the frequency is integrated. The frequency for the carbonate ion peak area approximated by a Gaussian function is subtracted from the carbonate ion frequency distribution.

[Quantitative determination method of lithium compounds]
A method for quantifying the lithium compound contained in the positive electrode is described below.
The positive electrode is washed with an organic solvent, then washed with distilled water, and the lithium compound can be quantified from the change in the mass of the positive electrode 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 the measurement is ensured. If the area is 200 cm ² or less, the sample is easy to handle. The organic solvent is not particularly limited as long as it can remove the non-aqueous electrolyte solution deposited on the surface of the positive electrode for cleaning with an organic solvent, but the lithium compound has a solubility of 2% or less by using an organic solvent. This is preferable because elution of is suppressed. For example, polar solvents such as methanol and acetone are preferably used.

In the positive electrode cleaning method, the positive electrode is sufficiently immersed 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. Thereafter, the positive electrode is taken out of the methanol and dried in a vacuum (temperature: 100 to 200 ° C., pressure: 0 to 10 kPa, time: 5 to 20 hours in which the remaining amount of methanol in the positive electrode is 1% by mass or less). Can be determined by measuring GC / MS of water after washing with distilled water, which will be described later, based on a calibration curve prepared in advance, and the mass of the positive electrode at that time is M ₀ [g]. And Subsequently, the positive electrode is sufficiently immersed for 3 days or more in distilled water 100 times the mass of the positive electrode (100 M ₀ [g]). At this time, it is preferable to take measures such as covering the container so that distilled water does not volatilize. After soaking for 3 days or more, the positive electrode is taken out from the distilled water (in the case of measuring the above-mentioned ion chromatography, the amount of the liquid is adjusted so that the amount of distilled water is 100 M ₀ [g]), and the above. Vacuum dry as in the methanol wash. The positive electrode active material layer on the current collector was measured using a spatula, a brush, a brush, etc. in order to measure the mass of the current collector of the obtained positive electrode with M ₁ [g]. Remove. When 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 expressed by the following formula (1):
_{Z = 100 × [1- (M} 1 -M 2) / (M 0 -M 2)]. . . Formula (1)
Can be calculated.

[Optional components of positive electrode active material layer]
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 as necessary.
The conductive filler is not particularly limited, and for example, acetylene black, ketjen black, vapor grown carbon fiber, graphite, carbon nanotube, a mixture thereof, and the like can be used. The amount of the conductive filler used is preferably 0 to 30 parts by mass with respect to 100 parts by mass of the positive electrode active material. More preferably, they are 0.01 mass part or more and 20 mass parts or less, More preferably, they are 1 mass part or more and 15 mass parts or less. When the amount of the conductive filler used is more than 30 parts by mass, the content ratio of the positive electrode active material in the positive electrode active material layer is decreased, so that the energy density per volume of the positive electrode active material layer is lowered, which is not preferable.

  The binder is not particularly limited. For example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer. Etc. can be used. The amount of the binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 3 parts by mass or more and 27 parts by mass or less, and still more 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. Or less. If the usage-amount of a binder is 1 mass part or more, sufficient electrode intensity | strength will be expressed. On the other hand, if the usage-amount of a binder is 30 mass parts or less, a high input / output characteristic will be expressed, without inhibiting the entrance-and-extraction and spreading | diffusion of the ion to a positive electrode active material.

  Although it does not restrict | limit especially as a dispersion stabilizer, For example, PVP (polyvinyl pyrrolidone), PVA (polyvinyl alcohol), a cellulose derivative etc. can be used. The amount of the dispersion stabilizer used is preferably 0 part by mass or 0.1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. When the amount of the dispersion stabilizer used is 10 parts by mass or less, high input / output characteristics are exhibited without impeding ion entry and exit and diffusion into the positive electrode active material.

[Positive electrode current collector]
The material constituting the positive electrode current collector in the present embodiment is not particularly limited as long as it is a material that has high electron conductivity and does not deteriorate due to elution into the electrolytic solution and reaction with the electrolyte or ions. A foil is preferred. As the positive electrode current collector in the non-aqueous lithium storage element of the present embodiment, an aluminum foil is particularly preferable.
The metal foil may be a normal metal foil having no irregularities or through holes, or a metal foil having irregularities subjected to embossing, chemical etching, electrolytic deposition, blasting, etc., expanded metal, punching metal Alternatively, a metal foil having a through hole such as an etching foil may be used.
Although 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, for example, 1 to 100 μm is preferable.

[Production of positive electrode precursor]
In the present embodiment, the positive electrode precursor serving as the positive electrode of the non-aqueous lithium storage element can be manufactured by an electrode manufacturing technique in a known lithium ion battery, electric double layer capacitor, or the like. For example, a positive electrode active material, a lithium compound, and other optional components used as needed are dispersed or dissolved in water or an organic solvent to prepare a slurry-like coating liquid, and this coating liquid is used as a positive electrode current collector. A positive electrode precursor can be obtained by coating on one or both sides of the body to form a coating film and drying it. 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 using a solvent, the positive electrode active material and the lithium compound, and other optional components used as necessary, are mixed in a dry process, and the resulting mixture is press-molded and then conductively bonded. A method of attaching to the positive electrode current collector using an agent is also possible.

  The positive electrode precursor coating solution is obtained by dry blending 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. It may be prepared by adding a liquid or slurry substance. Alternatively, a coating liquid may be prepared by adding various material powders including a positive electrode active material to a liquid or slurry substance in which a binder or dispersion stabilizer is dissolved or dispersed in water or an organic solvent. Good. As the dry blending method, for example, premixing the positive electrode active material and the lithium compound using a ball mill or the like and preliminarily mixing the conductive filler as necessary, and coating the conductive filler on the low conductive lithium compound is performed. You may do. Thereby, a lithium compound becomes easy to decompose | disassemble with a positive electrode precursor in the lithium dope process mentioned later. When water is used as the solvent for the coating solution, the addition of a lithium compound may make the coating solution alkaline, so a pH adjuster may be added as necessary.

The preparation of the positive electrode precursor coating solution is not particularly limited, but preferably a homodisper, a multi-axis disperser, a planetary mixer, a thin film swirl type high-speed mixer, or the like is used. I can do it. In order to obtain a coating liquid in a good dispersion state, it is preferable to disperse at a peripheral speed of 1 m / s to 50 m / s. A peripheral speed of 1 m / s or more is preferable because various materials can be dissolved or dispersed satisfactorily. A peripheral speed of 50 m / s or less is preferable because various materials are not destroyed by heat or shearing force due to dispersion and reaggregation does not occur.
As for the dispersion degree of the coating liquid, the particle size measured with a particle gauge is preferably 0.1 μm or more and 100 μm or less. As the upper limit of the degree of dispersion, the particle size is more preferably 80 μm or less, and further preferably the particle size is 50 μm or less. If the particle size is less than 0.1 μm, it is not preferable because the particle size is not more than the particle size of various material powders including the positive electrode active material, and the material is crushed during the preparation of the coating liquid. In addition, when the particle size is 100 μm or less, there is no clogging at the time of discharging the coating liquid, no streaking of the coating film, etc., and coating can be performed stably.

The viscosity (ηb) of the coating solution for the positive electrode precursor is preferably 1,000 mPa · s to 20,000 mPa · s, more preferably 1,500 mPa · s to 10,000 mPa · s, and still more preferably 1 700 mPa · s to 5,000 mPa · s. When the viscosity (ηb) is 1,000 mPa · s or more, dripping at the time of forming the coating film is suppressed, and the coating film width and film thickness can be controlled well. 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 a coating machine can be reduced and the coating can be stably performed, and the coating thickness can be less than the desired coating thickness. Can be controlled.
Further, the TI value (thixotropic index value) of the coating solution 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 film thickness can be controlled well.

  The formation of the coating film of the positive electrode precursor is not particularly limited, but preferably a coating machine such as a die coater, a comma coater, a knife coater, or a gravure coating machine can be used. The coating film may be formed by single layer coating or multilayer coating. In the case of multilayer coating, the coating solution composition may be adjusted so that the lithium compound content in each layer of the coating film is different. The coating speed is preferably from 0.1 m / min to 100 m / min, more preferably from 0.5 m / min to 70 m / min, still more preferably from 1 m / min to 50 m / min. If the coating speed is 0.1 m / min or more, stable coating can be achieved. On the other hand, if the coating speed is 100 m / min or less, sufficient coating accuracy can be secured.

  The drying of the coating film of the positive electrode precursor is not particularly limited, but a drying method such as hot air drying or infrared (IR) drying can be preferably used. The coating film may be dried at a single temperature or may be dried by changing the temperature in multiple stages. Moreover, you may dry a coating film combining several 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, if the drying temperature is 200 ° C. or lower, it is possible to suppress cracking of the coating film due to rapid volatilization of the solvent, uneven distribution of the binder due to migration, and oxidation of the positive electrode current collector and the positive electrode active material layer.

The press of the positive electrode precursor is not particularly limited, but preferably a press such as a hydraulic press or a vacuum press can be 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 part described later.
The pressing pressure is preferably 0.5 kN / cm or more and 20 kN / cm or less, more preferably 1 kN / cm or more and 10 kN / cm or less, and further preferably 2 kN / cm or more and 7 kN / cm or less. If the pressing pressure is 0.5 kN / cm or more, the electrode strength can be sufficiently increased. On the other hand, when the pressing pressure is 20 kN / cm or less, the positive electrode precursor can be adjusted to a desired positive electrode active material layer thickness and bulk density without causing bending or wrinkles.
In addition, the gap between the press rolls can be set to an arbitrary value according to the thickness of the positive electrode precursor after drying so as to have a desired thickness and bulk density of the positive electrode active material layer. Furthermore, the press speed can be set to an arbitrary speed at which the positive electrode precursor does not bend or wrinkle.
Moreover, the surface temperature of a press part may be room temperature, and you may heat a press part as needed. The lower limit of the surface temperature of the press part in the case of heating is preferably the melting point minus 60 ° C. or more of the binder used, more preferably the melting point minus 45 ° C. or more, and further preferably the melting point minus 30 ° C. or more. On the other hand, the upper limit of the surface temperature of the press part when heating is preferably the melting point plus 50 ° C. or less of the binder used, more preferably the melting point plus 30 ° C. or less, and further preferably the melting point plus 20 ° C. or less. For example, when PVdF (polyvinylidene fluoride: melting point 150 ° C.) is used as the binder, the surface of the press part is preferably heated to 90 ° C. or more and 200 ° C. or less, more preferably 105 ° C. or more and 180 ° C. or less, and further preferably Is heating to 120 ° C or higher and 170 ° C or lower. Further, when a styrene-butadiene copolymer (melting point: 100 ° C.) is used as the binder, the surface of the press part 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 heating is performed at 70 ° C. or higher and 120 ° C. or lower.

The melting point of the binder can be determined at the endothermic peak position of DSC (Differential Scanning Calorimetry). For example, using a differential scanning calorimeter “DSC7” manufactured by PerkinElmer Co., Ltd., 10 mg of sample resin is set in a measurement cell, and the temperature is increased from 30 ° C. to 250 ° C. at a temperature increase 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.
Moreover, you may press several times, changing the conditions of press pressure, a clearance gap, speed | rate, and the surface temperature of a press part.

  The thickness of the positive electrode active material layer is preferably 20 μm or more and 200 μm or less per side of the positive electrode current collector. The thickness of the positive electrode active material layer is more preferably 25 μm or more and 100 μm or less, more preferably 30 μm or more and 80 μm or less per side. If this film thickness is 20 μm or more, sufficient charge / discharge capacity can be exhibited. On the other hand, if this film thickness is 200 μm or less, the ion diffusion resistance in the electrode can be kept low. Therefore, sufficient output characteristics can be obtained and the cell volume can be reduced, so that the energy density can be increased. The upper limit and the lower limit of the thickness range of the positive electrode active material layer can be arbitrarily combined. In addition, the film thickness of the positive electrode active material layer in the case where the current collector has through holes or unevenness means the average value of the film thickness per one side of the current collector that does not have through holes or unevenness.

[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 in the range of 0.30 g / cm ³ or more and 1.3 g / cm ³ or less. It 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 expressed, and miniaturization of the power storage element can be achieved. Further, when the bulk density is 1.3 g / cm ³ or less, the electrolyte solution is sufficiently diffused in the pores in the positive electrode active material layer, and high output characteristics are obtained.

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

[Negative electrode active material layer]
The negative electrode active material layer includes a negative electrode active material capable of inserting and extracting lithium ions. In addition to this, optional components such as a conductive filler, a binder, and a dispersion stabilizer may be included as necessary.

[Negative electrode active material]
As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Specific examples include carbon materials, titanium oxide, silicon, silicon oxide, silicon alloys, silicon compounds, tin and tin compounds. Preferably, the content of the carbon material with respect to the total amount of the negative electrode active material is 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 the effect of using other materials in combination, for example, the content is preferably 90% by mass or less, and 80% by mass or less. Also good.

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

  Examples of the carbon material include non-graphitizable carbon materials; graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon spherules; Amorphous carbonaceous materials such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and carbonaceous materials obtained by heat treatment of carbonaceous material precursors such as synthetic resins (for example, phenol resins); The thermal decomposition product of a furfuryl alcohol resin or a novolak resin; fullerene; carbon nanophone; and these composite carbon materials can be mentioned.

  Among these, from the viewpoint of reducing the resistance of the negative electrode, heat treatment is performed in a state where at least one of the carbon materials (hereinafter also referred to as a base material) and the carbonaceous material precursor coexist. A composite carbon material obtained by combining a carbonaceous material derived from a carbonaceous material precursor is preferred. The carbonaceous material precursor is not particularly limited as long as it becomes the carbonaceous material by heat treatment, but petroleum-based pitch or coal-based pitch is particularly preferable. Prior to the heat treatment, the substrate and the carbonaceous material precursor may be mixed at a temperature higher than the melting point of the carbonaceous material precursor. The heat treatment temperature may be a temperature at which a component generated by volatilization or thermal decomposition of the carbonaceous material precursor to be used becomes the carbonaceous material, preferably 400 ° C to 2500 ° C, more preferably 500 ° C. The temperature is 2000 ° C. or lower, more preferably 550 ° C. or higher and 1500 ° C. or lower. The atmosphere for performing the heat treatment 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 substrate is not particularly limited, and activated carbon, carbon black, template porous carbon, high specific surface area graphite, carbon nanoparticles, and the like can be suitably 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, further preferably 180 m ² / g or more and 550 m. ² / g or less. If this BET specific surface area is 100 m ² / g or more, the pores can be appropriately held and the diffusion of lithium ions becomes good, so that high input / output characteristics can be exhibited. On the other hand, since 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. If the mass ratio of the carbonaceous material is 10% by mass or more, the micropores of the base material can be appropriately filled with the carbonaceous material, and the charge / discharge efficiency of lithium ions is improved. Cycle durability can be shown. Moreover, if the mass ratio of the carbonaceous material is 200% by mass or less, the pores can be appropriately maintained and lithium ion diffusion is improved, and thus 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 2500 mAh / g or less, more preferably 620 mAh / g or more and 2,100 mAh / g or less, and further preferably 760 mAh. / G to 1,700 mAh / g, particularly preferably 840 mAh / g to 1,500 mAh / g.
Since the negative electrode potential is reduced by doping lithium ions, when the negative electrode including the composite carbon material 1 doped with lithium ions is combined with the positive electrode, the voltage of the non-aqueous lithium storage element increases. As a result, the capacity and energy density of the obtained non-aqueous lithium storage element are increased.
When the doping amount is 530 mAh / g or more, lithium ions are well doped into 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 amount of lithium. Therefore, the thickness of the negative electrode can be reduced and a high energy density can be obtained. The larger the doping amount, the lower the negative electrode potential, and the input / output characteristics, energy density, and durability are improved.
On the other hand, when the doping amount is 2,500 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal occur.

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

  If the mesopore amount Vm1 is 0.300 cc / g or less, the BET specific surface area can be increased, the lithium ion doping amount can be increased, and the bulk density of the negative electrode can be increased. Can be thinned. Moreover, if 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, if the mesopore volume Vm1 and the micropore volume 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 from 100 m ² / g to 1,500 m ² / g, more preferably from 150 m ² / g to 1,100 m ² / g, and even more preferably from 180 m ² / g to 550 m. ² / g or less. When the BET specific surface area is 100 m ² / g or more, the pores can be appropriately maintained, and the lithium ion diffusion 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 made thin. On the other hand, since 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 mm or more, more preferably 25 mm or more, and further preferably 30 mm or more from the viewpoint of achieving high input / output characteristics. On the other hand, from the viewpoint of high energy density, the average pore diameter is preferably 65 mm or less, more preferably 60 mm or less.

  The average particle diameter of the composite carbon material 1a is preferably 1 μm or more and 10 μm or less. About a lower limit, More preferably, it is 2 micrometers or more, More preferably, it is 2.5 micrometers or more. About an upper limit, More preferably, it is 6 micrometers or less, More preferably, it is 4 micrometers or less. If the average particle diameter is 1 μm or more and 10 μm or less, good durability is maintained.

  The hydrogen atom / carbon atom number ratio (H / C) of the composite carbon material 1a is preferably 0.05 or more and 0.35 or less, and more preferably 0.05 or more and 0.15 or less. When H / C is 0.35 or less, the structure (typically polycyclic aromatic conjugated structure) of the carbonaceous material deposited on the activated carbon surface is well developed and the capacity (energy Density) and charge / discharge efficiency are increased. On the other hand, when H / C is 0.05 or more, since carbonization does not proceed excessively, 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, but at the same time has a crystal structure mainly derived from the deposited 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 mm to 4.00 mm, and a crystallite in the c-axis direction obtained from the half width of this peak. The size Lc is preferably 8.0 to 20.0 and d002 is 3.60 to 3.75 and the crystallite size Lc in the c-axis direction obtained from the half width of this peak is 11. The range of 0 to 16.0 is more preferable.

  There is no restriction | limiting in particular as said activated carbon used as this base material of said composite carbon material 1a, as long as the obtained composite carbon material 1a exhibits a desired characteristic. For example, commercially available products obtained from various raw materials such as petroleum-based, coal-based, plant-based, and polymer-based materials can be used. In particular, it is preferable to use activated carbon powder having an average particle diameter of 1 μm to 15 μm, and more preferably 2 μm to 10 μm.

In order to obtain the composite carbon material 1a having the pore distribution range defined in the present embodiment, the pore distribution of the activated carbon used for the substrate is important.
In the activated carbon, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is used. When V2 (cc / g), 0.050 ≦ V1 ≦ 0.500, 0.005 ≦ V2 ≦ 1.000, and 0.2 ≦ V1 / V2 ≦ 20.0 are preferable.

  About mesopore amount V1, 0.050 <= V1 <= 0.350 is more preferable, and 0.100 <= V1 <= 0.300 is still more preferable. The micropore amount V2 is more preferably 0.005 ≦ V2 ≦ 0.850, and further preferably 0.100 ≦ V2 ≦ 0.800. The ratio of mesopore amount / micropore amount is more preferably 0.22 ≦ V1 / V2 ≦ 15.0, and further preferably 0.25 ≦ V1 / V2 ≦ 10.0. When the mesopore volume V1 of the activated carbon is 0.500 or less and when the micropore volume V2 is 1.000 or less, an appropriate amount of carbonaceous matter is required to obtain the pore structure of the composite carbon material 1a in the present embodiment. Since it is sufficient to deposit a material, the pore structure can be easily controlled. On the other hand, when the mesopore volume V1 of the activated carbon is 0.050 or more, when the micropore volume V2 is 0.005 or more, when V1 / V2 is 0.2 or more, and when V1 / V2 is 20.0. The structure can be easily obtained even in the following cases.

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

  When the pitch is used, the pitch is heat-treated in the presence of activated carbon, and a carbonaceous material is deposited on the activated carbon by thermally reacting the volatile component or pyrolysis component of the pitch on the surface of the activated carbon. Material 1a is obtained. In this case, at a temperature of about 200 to 500 ° C., the deposition of pitch volatile components or pyrolysis components into the activated carbon pores proceeds, and at 400 ° C. or higher, the reaction in which the deposited components become carbonaceous materials proceeds. To do. The peak temperature (maximum temperature reached) during the heat treatment is appropriately determined depending on the characteristics of the composite carbon material 1a to be obtained, the thermal reaction pattern, the thermal reaction atmosphere, etc., but is preferably 400 ° C. or higher. Is 450 ° C. to 1,000 ° C., more preferably about 500 to 800 ° C. Moreover, it is preferable that the time which maintains the peak temperature at the time of heat processing is 30 minutes-10 hours, More preferably, they are 1 hour-7 hours, More preferably, they are 2 hours-5 hours. For example, when heat treatment is performed for 2 hours to 5 hours at a peak temperature of about 500 to 800 ° C., the carbonaceous material deposited on the activated carbon surface is considered to be 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 can be handled with high accuracy without any problem in handling properties. The pitch having a softening point of 250 ° C. or less contains a large amount of relatively low molecular weight compounds. Therefore, when the pitch is used, fine pores in the activated carbon can be deposited.
As a specific method for producing the composite carbon material 1a, for example, activated carbon is heat-treated in an inert atmosphere containing hydrocarbon gas volatilized from a carbonaceous material precursor, and the carbonaceous material is coated in a gas phase. The method of making it wear is mentioned. In addition, a method in which activated carbon and a carbonaceous material precursor are mixed in advance and heat-treated, or a method in which a carbonaceous material precursor dissolved in a solvent is applied to activated carbon and dried is then heat-treated.

  In the composite carbon material 1a, the mass ratio of the carbonaceous material to the activated carbon is preferably 10% by mass to 100% by mass, and more preferably 15% by mass to 80% by mass. If the mass ratio of the carbonaceous material is 10% by mass or more, the micropores possessed by the activated carbon can be appropriately filled with the carbonaceous material, and the charge / discharge efficiency of lithium ions is improved. There is no loss of sex. Moreover, if the mass ratio of the carbonaceous material is 100% by mass or less, the pores of the composite carbon material 1a are appropriately maintained 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 to 80 m ² / g as the base material. The base material is not particularly limited, and natural graphite, artificial graphite, low crystal graphite, hard carbon, soft carbon, carbon black and the like can be suitably 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 / g or less. If this BET specific surface area is 1 m ² / g or more, a sufficient reaction field with lithium ions can be secured, and thus high input / output characteristics can be exhibited. On the other hand, if it is 50 m < ² > / g or less, since the charging / discharging efficiency of lithium ion improves and the decomposition reaction of the nonaqueous electrolyte solution during charging / discharging is suppressed, high cycle durability can be shown.

  The average particle size of the composite carbon material 2 is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less, and further preferably 3 μm or more and 6 μm or less. If the average particle diameter is 1 μm or more, the charge / discharge efficiency of lithium ions can be improved, and thus 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 electrolyte 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 to 30% by mass, more preferably 1.2% by mass to 25% by mass, and still more preferably 1.5% by mass. It is 20 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 facilitate the desolvation of lithium ions, so that high input / output characteristics can be obtained. Can show. On the other hand, if the mass ratio of the carbonaceous material is 20% by mass or less, lithium ion diffusion between the carbonaceous material and the substrate can be favorably maintained, and thus high input / output characteristics can be exhibited. it can. Moreover, since the charge / discharge efficiency of lithium ions is improved, high cycle durability can be exhibited.

The doping amount of lithium ions per unit mass of the composite carbon material 2 is preferably 50 mAh / g or more and 700 mAh / g or less, more preferably 70 mAh / g or more and 650 mAh / g or less, and further preferably 90 mAh / g or more and 600 mAh or less. / G or less, particularly preferably 100 mAh / g or more and 550 mAh / g or less.
Since the negative electrode potential is lowered by doping lithium ions, when the negative electrode including the composite carbon material 2 doped with lithium ions is combined with the positive electrode, the voltage of the non-aqueous lithium storage element increases, The utilization capacity of the positive electrode is increased. As a result, the capacity and energy density of the obtained non-aqueous lithium storage element are increased.
When the doping amount is 50 mAh / g or more, lithium ions are favorably doped into irreversible sites that cannot be desorbed once lithium ions in the composite carbon material 2 are inserted, so that a high energy density is obtained. The larger the doping amount, the lower the negative electrode potential, and the input / output characteristics, energy density, and durability are improved.
On the other hand, when the doping amount is 700 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal occur.

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

  The average particle size of the composite carbon material 2a is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less, and further preferably 3 μm or more and 6 μm or less. If the average particle diameter is 1 μm or more, the charge / discharge efficiency of lithium ions can be improved, and thus 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 electrolyte 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 1 m ² / g or more and 15 m ² / g or less. If this BET specific surface area is 1 m ² / g or more, a sufficient reaction field with lithium ions can be secured, and thus high input / output characteristics can be exhibited. On the other hand, if 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 during charge / discharge is suppressed, so that high cycle durability can be exhibited.

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

  The carbonaceous material precursor used as a raw material of the composite carbon material 2a is an organic material that can be dissolved in a solid, liquid, or solvent that can be composited with a graphite material by heat treatment. . Examples of the carbonaceous material precursor include pitch, mesocarbon microbeads, coke, and synthetic resin (for example, phenol resin). Among these carbonaceous material precursors, it is preferable in terms of production cost to use an inexpensive pitch. Pitch is roughly divided into petroleum pitch and coal pitch. Examples of petroleum pitches include crude oil distillation residue, fluid catalytic cracking 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 to 8% by mass, further preferably 1.5% by mass to 6% by mass, and particularly preferably 2% by mass to 5% by mass. If the mass ratio of the carbonaceous material is 1% by mass or more, the carbonaceous material can sufficiently increase the number of reaction sites with lithium ions, and the desolvation of lithium ions is facilitated. Can show. On the other hand, if the mass ratio of the carbonaceous material is 20% by mass or less, lithium ion diffusion between the carbonaceous material and the graphite material can be satisfactorily maintained, and thus high input / output characteristics can be exhibited. it can. Moreover, since the charge / discharge efficiency of lithium ions can be improved, high cycle durability can be exhibited.

[Optional ingredients]
The negative electrode active material layer may contain optional components such as a conductive filler, a binder, and a dispersion stabilizer in addition to the negative electrode active material as necessary.
The type of the conductive filler is not particularly limited, and examples thereof include acetylene black, ketjen black, and vapor grown carbon fiber. The amount of the conductive filler used is preferably 0 parts by mass or more and 30 parts by mass or less, more preferably 0 parts by mass or more and 20 parts by mass or less, and further preferably 0 parts by mass or more with respect to 100 parts by mass of the negative electrode active material. 15 parts by mass or less.

  The binder is not particularly limited. For example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer. Etc. can be used. The amount of the binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 2 parts by mass or more and 27 parts by mass or less, and further preferably 3 parts by mass or more with respect to 100 parts by mass of the negative electrode active material. 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 lithium ions from entering and leaving the negative electrode active material.

  Although it does not restrict | limit especially as a dispersion stabilizer, For example, PVP (polyvinyl pyrrolidone), PVA (polyvinyl alcohol), a cellulose derivative etc. can be used. The amount of the dispersion stabilizer used is preferably 0 to 10 parts by mass 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 lithium ions from entering and leaving the negative electrode active material.

[Negative electrode current collector]
The material constituting the negative electrode current collector is preferably a metal foil that has high electron conductivity and does not deteriorate due to elution into a non-aqueous electrolyte and reaction with an electrolyte or ions. There is no restriction | limiting in particular as such metal foil, For example, aluminum foil, copper foil, nickel foil, stainless steel foil, etc. are mentioned. The negative electrode current collector in the non-aqueous lithium storage element of this embodiment is preferably a copper foil.
The metal foil may be a normal metal foil having no irregularities or through holes, or a metal foil having irregularities subjected to embossing, chemical etching, electrolytic deposition, blasting, etc., expanded metal, punching metal Alternatively, a metal foil having a through hole such as an etching foil may be used.
The thickness of the negative electrode current collector is not particularly limited as long as the shape and strength of the negative electrode can be sufficiently maintained, but for example, 1 to 100 μm is preferable.

[Manufacture of negative electrode]
The negative electrode has a negative electrode active material layer on one 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 an electrode manufacturing technique in a known lithium ion battery, electric double layer capacitor or 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-like coating liquid, and this coating liquid is applied to one or both surfaces on 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 possible to mix various materials including the negative electrode active material dry without using a solvent, press the resulting mixture, and then apply 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. You may adjust by adding a slurry-like substance. Further, various material powders including the negative electrode active material may be added to the liquid or slurry substance in which the binder or the dispersion stabilizer is dissolved or dispersed in water or an organic solvent. Although it does not restrict | limit especially in the adjustment of the said coating liquid, Dispersers, such as a homodisper, a multiaxial disperser, a planetary mixer, a thin film swirl | vortex type high speed mixer, etc. can be used suitably. In order to obtain a coating liquid in a good dispersion state, it is preferable to disperse at a peripheral speed of 1 m / s to 50 m / s. A peripheral speed of 1 m / s or more is preferable because various materials can be dissolved or dispersed well. On the other hand, if it is 50 m / s or less, since various materials are not destroyed by the heat | fever and shear force by dispersion | distribution, and reaggregation does not arise, it is preferable.

The viscosity (ηb) of the coating solution is preferably 1,000 mPa · s to 20,000 mPa · s, more preferably 1,500 mPa · s to 10,000 mPa · s, and still more preferably 1,700 mPa · s. It is 5,000 mPa · s or less. When the viscosity (ηb) is 1,000 mPa · s or more, dripping at the time of forming the coating film is suppressed, and the coating film width and film thickness can be controlled well. On the other hand, if it is 20,000 mPa · s or less, there is little pressure loss in the flow path of the coating liquid when a coating machine is used, and coating can be performed stably, and control can be carried out to a desired coating thickness or less.
The TI value (thixotropic index value) of the coating solution 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 film thickness can be controlled well.

  The formation of the coating film is not particularly limited, but preferably a coating machine such as a die coater, a comma coater, a knife coater, or a gravure coating machine can be used. The coating film may be formed by single layer coating or may be formed by multilayer coating. The coating speed is preferably from 0.1 m / min to 100 m / min, more preferably from 0.5 m / min to 70 m / min, still more preferably from 1 m / min to 50 m / min. If the coating speed is 0.1 m / min or more, stable coating can be achieved. On the other hand, if it is 100 m / min or less, sufficient coating accuracy can be secured.

  Although the drying of the coating film is not particularly limited, 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 by changing the temperature in multiple stages. Moreover, you may dry combining several 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, if it is 200 degrees C or less, the crack of the coating film by rapid volatilization of a solvent, the uneven distribution of the binder by migration, and the oxidation of a negative electrode collector or a negative electrode active material layer can be suppressed.

  Although the press of the negative electrode is not particularly limited, a press such as a hydraulic press or a vacuum press 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, gap, and surface temperature of the press part described later. The pressing pressure is preferably 0.5 kN / cm or more and 20 kN / cm or less, more preferably 1 kN / cm or more and 10 kN / cm or less, and further preferably 2 kN / cm or more and 7 kN / cm or less. If the pressing pressure is 0.5 kN / cm or more, the electrode strength can be sufficiently increased. On the other hand, if it is 20 kN / cm or less, the negative electrode is not bent or wrinkled, and can be adjusted to the desired negative electrode active material layer thickness and bulk density. In addition, the gap between the press rolls can be set to an arbitrary value according to the negative electrode film thickness after drying so as to be a desired film thickness or bulk density of the negative electrode active material layer. Furthermore, the press speed can be set to an arbitrary speed at which the negative electrode is not bent or wrinkled. Moreover, the surface temperature of a press part may be room temperature, and may be heated if necessary. The lower limit of the surface temperature of the press part in the case of heating is preferably the melting point minus 60 ° C. or more of the binder used, more preferably 45 ° C. or more, and further preferably 30 ° C. or more. On the other hand, the upper limit of the surface temperature of the press part in the case of heating is preferably the melting point of the binder used plus 50 ° C. or less, more preferably 30 ° C. or less, and further preferably 20 ° C. or less. For example, when PVdF (polyvinylidene fluoride: melting point 150 ° C.) is used as the binder, it is preferably heated to 90 ° C. or higher and 200 ° C. or lower, more preferably 105 ° C. or higher and 180 ° C. or lower, and still more preferably 120 ° C. Heat to 170 ° C. or lower. When a styrene-butadiene copolymer (melting point: 100 ° C.) is used as the binder, it is preferably heated to 40 ° C. or higher and 150 ° C. or lower, more preferably 55 ° C. or higher and 130 ° C. or lower, and still more preferably. Heat to 70 ° C to 120 ° C.

  The melting point of the binder can be determined at the endothermic peak position of DSC (Differential Scanning Calorimetry). For example, using a differential scanning calorimeter “DSC7” manufactured by PerkinElmer Co., Ltd., 10 mg of sample resin is set in a measurement cell, and the temperature is increased from 30 ° C. to 250 ° C. at a temperature increase 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. Moreover, you may press several times, changing the conditions of press pressure, a clearance gap, speed | rate, and the surface temperature of a press part.

  The 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 further 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 even more preferably 60 μm or less. When the 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 coating property is excellent. On the other hand, if this film thickness is 100 μm or less, a high energy density can be expressed by reducing the cell volume. In addition, the film thickness of the negative electrode active material layer in the case where the current collector has through holes or unevenness means the average value of the film thickness per one side of the portion of the current collector that does not have through holes or unevenness.

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 still more preferably 0. .45g / cm ³ or more 1.3g / cm ³ or less. When the bulk density is 0.30 g / cm ³ or more, sufficient strength can be maintained and sufficient conductivity between the negative electrode active materials can be exhibited. On the other hand, if it is 1.8 g / cm ³ or less, a hole capable of sufficiently diffusing ions in the negative electrode active material layer can be secured.

[Measuring method]
In the present specification, the BET specific surface area, the average pore diameter, the mesopore amount, and the micropore amount are values determined by the following methods, respectively. The sample is vacuum-dried at 200 ° C. all day and night, and adsorption and desorption isotherms are measured using nitrogen as an adsorbate. Using the isotherm on the adsorption side obtained here, the BET specific surface area is determined by the BET multipoint method or the BET single point method, and the average pore diameter is obtained 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, Joyner, Halenda et al. (EP Barrett, LG Joyner and P. Halenda, J. Am. Chem. Soc., 73, 373 (1951)).
In addition, the MP method is a “t-plot method” (BC Lippens, JH de Boer, J. Catalysis, 4319 (1965)). Means a method for determining the distribution of micropores; It is a method devised by Mikhail, Brunauer, Bodor (RS Mikhal, S. Brunauer, EE Bodor, J. Colloid Interface Sci., 26, 45 (1968)).

  When the particle size distribution is measured using a particle size distribution measuring device, the average particle size is the particle size at which the cumulative curve becomes 50% when the total volume is 100% (that is, the 50% diameter). (Median diameter)). This average particle diameter can be measured using a commercially available laser diffraction particle size distribution analyzer.

The amount of lithium ion doping of the negative electrode active material in the non-aqueous lithium storage element at the time of shipment and after use can be known, for example, as follows.
First, after the negative electrode active material layer in this embodiment is washed with ethyl methyl carbonate or dimethyl carbonate and air-dried, an extract extracted with a mixed solvent composed of methanol and isopropanol and a negative electrode active material layer after extraction are obtained. This extraction is typically performed in an Ar box at an ambient temperature of 23 ° C.
The amount of lithium contained in the extract obtained as described above and the negative electrode active material layer after extraction is quantified using, for example, ICP-MS (inductively coupled plasma mass spectrometer). By obtaining the total, the doping amount of lithium ions in the negative electrode active material can be known. And the numerical value of the said unit should just be calculated by allocating the obtained value by the amount of negative electrode active materials used for extraction.

  The primary particle size is obtained by taking several fields of powder with an electron microscope and measuring about 2,000 to 3,000 particles in the field using a fully automatic image processor. Can be obtained by a method in which a value obtained by arithmetically averaging is used as a primary particle diameter.

  In the present specification, the dispersity is a value determined by a dispersity evaluation test using a grain gauge specified in JIS K5600. That is, a sufficient amount of sample is poured into the deeper end of the groove and slightly overflows from the groove gauge having a groove with a desired depth according to the size of the grain. Next, place the scraper so that the long side of the scraper is parallel to the width direction of the gauge and the cutting edge is in contact with the deep tip of the grain gauge groove, and hold the scraper so that it is on the surface of the gauge. The surface of the gauge is drawn at a uniform speed to the groove depth of 0 to 1 second for 1 to 2 seconds, and light is applied at an angle of 20 ° to 30 ° within 3 seconds after the drawing is finished. Observe and read the depth at which the grain appears in the groove of the grain gauge.

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

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

[Lithium salt]
The non-aqueous electrolyte includes lithium salts such as (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 or the like may be used alone, or two or more kinds may be mixed and used. LiPF ₆ and / or LiN (SO ₂ F) ₂ are preferably included because high conductivity can be exhibited.
The lithium salt concentration in the non-aqueous electrolyte is preferably 0.5 mol / L or more, more preferably in the range of 0.5 mol / L to 2.0 mol / L, based on the total amount of the non-aqueous electrolyte. . If the lithium salt concentration is 0.5 mol / L or more, anions are sufficiently present, so that the capacity of the energy storage device 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 and preventing the viscosity of the electrolyte from becoming too high, resulting in a decrease in conductivity. And output characteristics are not deteriorated.

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

[Nonaqueous solvent]
The nonaqueous electrolytic solution preferably contains a cyclic carbonate as a nonaqueous solvent. The nonaqueous electrolytic solution containing a cyclic carbonate is advantageous in that a lithium salt having a desired concentration is dissolved and an appropriate amount of a 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, and fluoroethylene carbonate.
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 nonaqueous electrolytic 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 expressed. Furthermore, 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. The nonaqueous electrolytic solution containing chain carbonate is advantageous in that it exhibits high lithium ion conductivity. Examples of the chain carbonate include dialkyl carbonate compounds represented by dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, dibutyl carbonate and the like. The dialkyl carbonate compound is typically unsubstituted.
The total content of the chain carbonate is preferably 30% by mass or more, more preferably 35% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, based on the total amount of the non-aqueous electrolyte solution. is there. If content of the said chain carbonate is 30 mass% or more, the viscosity of electrolyte solution can be lowered | hung and high lithium ion conductivity can be expressed. If the said total concentration is 95 mass% or less, electrolyte solution can further contain the additive mentioned later.

[Additive]
The nonaqueous electrolytic solution may further contain an additive. Although it does not restrict | limit especially as an additive, For example, using a sultone compound, cyclic phosphazene, acyclic fluorine-containing ether, a fluorine-containing cyclic carbonate, cyclic carbonate ester, cyclic carboxylate ester, cyclic acid anhydride, etc. independently. In addition, two or more kinds may be mixed and used.

[Separator]
The positive electrode precursor and the negative electrode are laminated or wound through a separator, and an electrode laminate or an electrode winding body having the positive electrode precursor, the negative electrode, and the separator is formed.
As the separator, a polyethylene microporous film or a polypropylene microporous film used in a lithium ion secondary battery, a cellulose nonwoven 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 micro-shorts tends to be small. On the other hand, a thickness of 35 μm or less is preferable because the input / output characteristics of the nonaqueous lithium storage element tend to be high.
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 micro-shorts 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 storage element tend to be high.

[Non-aqueous lithium storage element]
The non-aqueous lithium storage element of this embodiment is configured such that an electrode laminate or an electrode winding body, which will be described later, is housed in the outer package together with the non-aqueous electrolyte.

[assembly]
The electrode laminate obtained in the cell assembling step is obtained by connecting a positive electrode terminal and a negative electrode terminal to a laminate obtained by laminating a positive electrode precursor and a negative electrode cut into a sheet shape via a separator. The electrode winding body is obtained by connecting a positive electrode terminal and a negative electrode terminal to a winding body obtained by winding a positive electrode precursor and a negative electrode through a separator. The shape of the wound body may be a flat shape or a cylindrical shape, and the flat shape may be an electrode body obtained by winding a positive electrode precursor and a negative electrode into a flat shape via a separator, An electrode body in which the positive electrode precursor and the negative electrode are wound through a separator and then deformed into a flat shape may be used.
The positive terminal and the negative terminal are preferably joined by welding. Although it does not specifically limit as a joining method of an electrode terminal and an uncoated part, It carries out by methods, such as ultrasonic welding, spot welding, and resistance welding.

[Area area of peripheral edge 20% and center area 80% of negative electrode active material layer]
In the non-aqueous lithium energy storage device according to this embodiment, the concentration of lithium ions is higher in the area region of 80% of the central part than in the area region of 20% of the peripheral part of the negative electrode active material layer.
In this specification, the area area of the central part x% of the negative electrode active material layer is, as a general rule, the area when the electrode on which the negative electrode active material layer is disposed is viewed from the top within the area area facing the positive electrode active material. The estimated line that separates the regions is closed without intersecting any end of the electrode, but when the estimated line that separates the regions overlaps a pair of opposing electrode ends, the center of the negative electrode active material layer The area region of the part x% includes a region overlapping with the maximum three sides of the continuous electrode end.
For example, when the electrode laminate is a laminate of single-wafer electrodes, according to the above definition, as illustrated in FIG. 1, a position where the length from each of the four sides of the negative electrode end is 5%, The negative electrode active material layer (2) can be defined as an area region (4) of the peripheral portion 20%, and thereby the outer peripheral portion of the area region (3) of the central portion 80% of the negative electrode active material layer (2) Determined.
When the electrode laminate is a wound laminate, as illustrated in FIG. 2, the length in the longitudinal direction of the electrode when projected from the direction perpendicular to the winding center axis is x _2. The wound laminated body is cut at the position of, and an area region (3) of the central part 80% and an area region (4) of the peripheral part 20% are defined using the opened electrodes. As illustrated in FIG. 2, the length x _{2 in the} longitudinal direction of the cut wound laminated body generally corresponds to the electrode length in the longitudinal direction of the nonaqueous lithium storage element including the cut wound laminated body. To do.
In the non-aqueous lithium energy storage device according to this embodiment, there is a correlation between the lithium ion concentration and the thickness of the active material layer. In a region where the lithium ion concentration is high, the active material layer contains a large amount of lithium ions, so that the active material expands and the active material layer becomes thick.
In the non-aqueous lithium storage element according to this embodiment, it is preferable that the concentration of lithium ions is higher in the area region of 80% of the central part than in the area region of 20% of the peripheral part of the negative electrode active material layer. If the concentration of lithium ions is higher in the area region of 80% of the central part than the area region of 20% of the peripheral part of the negative electrode active material layer, the deposition of metallic lithium in the high load charge / discharge cycle can be suppressed.

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

[Outer perimeter and inner perimeter of wound body]
In the non-aqueous lithium energy storage device according to the present embodiment, the central lithium ion concentration C _2o when the negative electrode active material layer of the negative electrode in the outer peripheral part of the wound _{body is viewed} from above, the negative electrode in the inner peripheral part of the wound _{body C 2o} / _{C 2i} when the lithium ion concentration _{C 2i} center when the negative electrode active material layer was viewed is 0.85 to 1.15. As shown in FIG. 4, in the negative electrode forming the wound body, the outer peripheral portion (9) of the wound body is opposed to the positive electrode (8) and is wound in the central region excluding the peripheral edge of the negative electrode. Means the negative electrode active material layer for one round of the outermost circumference, and the inner peripheral part (7) of the wound body is the negative electrode forming the wound body, facing the positive electrode (8), and the peripheral part of the negative electrode In the region of the central part excluding, it means a negative electrode active material layer for one innermost circumference that is wound.

In the non-aqueous lithium storage element according to this embodiment, the lithium ion concentration C _{1o at} the center when the negative electrode active material layer of the negative electrode in the thickness direction outermost layer of the laminate is viewed from above, the negative electrode in the thickness direction innermost layer of the laminate negative active when the material layer and the lithium ion concentration C _1i center when viewed from the top, and wound lithium ion concentration in the center when the anode active material layer of the negative electrode in an outer peripheral portion viewed from above the body C _2o of C _1o / C _1i and C _2o / C _2i are both 0.85 when the central lithium ion concentration C _2i when the negative electrode active material layer of the negative electrode in the inner peripheral portion of the wound body is viewed from the top. It is preferable that it is 1.15 or more. If C _1o / C _1i and C _2o / C _2i are not less than 0.85 and not more than 1.15, the variation in potential in the negative electrode surface is reduced, and gas generation due to reaction with the electrolyte is suppressed. When a lithium storage element is subjected to a long-term charge / discharge test, an increase in resistance can be suppressed. C _1o / C _1i and C _2o / C _2i are more preferably 0.90 or more and 1.10 or less.

T _{1o is} the thickness of the negative electrode active material layer at the center when the negative electrode active material layer of the negative electrode in the outermost layer in the thickness direction of the laminate is viewed from above, and the negative electrode active material layer of the negative electrode in the innermost layer in the thickness direction of the laminate is the upper surface When the thickness of the negative electrode active material layer at the center when viewed is T _1i , T _1o / T _1i is preferably 0.85 or more and 1.15 or less.
Further, the thickness of the negative electrode active material layer of the negative electrode at the outermost radial direction excluding the peripheral portion is opposed to the positive electrode of the wound body, and the center thickness when viewed from above is T _2o , and opposed to the positive electrode of the wound _body And T _2o / T _2i is 0.85 or more and 1.15 or less, when T _2i is the thickness of the center of the negative electrode active material layer of the negative electrode in the radially innermost layer excluding the peripheral portion when viewed from above. Is preferred.
When T _1o / T _1i and T _2o / T _2i are each 0.85 or more and 1.15 or less, variation in potential in the surface of the negative electrode is reduced, and gas generation due to reaction with the electrolyte is suppressed, When a non-aqueous lithium storage element is subjected to a long-term charge / discharge test, an increase in resistance can be suppressed. T _1o / T _1i and T _2o / T _2i are more preferably 0.90 or more and 1.10 or less.

[Exterior body]
As the exterior body, a metal can, a laminate packaging material, or the like can be used.
The metal can is not particularly limited. For example, a metal material such as aluminum or iron can be used, but aluminum is preferable from the viewpoint of reducing the weight of the obtained wound mold.
The laminate packaging material is preferably a film in which a metal foil and a resin film are laminated, and an example of a three-layer structure comprising 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 suitably used. The metal foil is for preventing the permeation of moisture and gas, and foils of copper, aluminum, stainless steel and the like can be suitably used. The interior resin film protects the metal foil from the non-aqueous electrolyte contained therein and melts and seals the exterior body during heat sealing. Polyolefin, acid-modified polyolefin, and the like can be suitably used.

[Storage in exterior body]
The dried electrode laminate or electrode winding body is preferably housed in an exterior body typified by a metal can or laminate packaging material, and sealed with only one opening left. Although the sealing method of an exterior body is not specifically limited, When using a laminate packaging material, methods, such as a heat seal and an impulse seal, are used.

[Dry]
It is preferable to remove the residual solvent by drying the electrode laminate or the electrode winding body housed in the outer package. Although there is no limitation in the drying method, it dries by vacuum drying etc. 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, a non-aqueous electrolyte solution is injected into the electrode laminate or the electrode winding body housed in the exterior body. After 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 electrolyte. In a state where the non-aqueous electrolyte solution is not immersed in at least a part of the positive electrode, the negative electrode, and the separator, dope proceeds non-uniformly in the lithium doping step described later, and thus the resistance of the obtained non-aqueous lithium storage element is It rises or the durability decreases. The impregnation method is not particularly limited. For example, the electrode laminate or the electrode winding body after injection is placed in a vacuum chamber with the exterior body opened, and the inside of the chamber is filled with a vacuum pump. A method of returning to atmospheric pressure again after reducing the pressure can be used. After completion of the impregnation step, the electrode laminate or electrode winding body with the exterior body opened is sealed by being reduced in pressure.

[Lithium doping process]
In the lithium doping step, as a preferable step, a voltage is applied 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. The anode active material layer is pre-doped with riotium ions by reducing lithium ions at the anode.
In this lithium doping step, a gas such as CO ₂ is generated with the oxidative decomposition of the lithium compound in the positive electrode precursor. Therefore, when applying a voltage, it is preferable to provide a means for releasing the generated gas to the outside of the exterior body. As this means, for example, a method of applying a voltage in a state in which a part of the exterior body is opened; a state in which an appropriate gas releasing means such as a gas vent valve or a gas permeable film is previously installed in a part of the exterior body And a method of applying a voltage;

[Aging process]
After completion of the lithium doping step, it is preferable to perform aging on the electrode laminate or the electrode winding body. In the aging process, the solvent in the nonaqueous electrolytic solution is decomposed at the negative electrode, and a lithium ion permeable solid polymer film is formed on the negative electrode surface.
Although it does not restrict | limit especially as a method of the said aging, For example, the method of making the solvent in a non-aqueous electrolyte solution react in a high temperature environment etc. can be used.

[Degassing process]
After the aging step is completed, it is preferable to further degas and reliably remove the gas remaining in the non-aqueous electrolyte, the positive electrode, and the negative electrode. When gas remains in at least a part of the non-aqueous electrolyte, the positive electrode, and the negative electrode, ion conduction is inhibited, and thus the resistance of the obtained non-aqueous lithium storage element increases.
The degassing method is not particularly limited. For example, the electrode laminate or the electrode winding body is placed in a decompression chamber with the exterior body opened, and the inside of the chamber is decompressed using a vacuum pump. A method or the like can be used.

[Characteristic evaluation of non-aqueous lithium storage element]
[Capacitance]
The capacitance F (F) was a value obtained by the following method.
First, constant-current charging is performed in a thermostatic chamber in which the cell corresponding to the nonaqueous lithium storage element is set to 25 ° C. until reaching 3.8 V at a current value of 20 C, and then a constant voltage of 3.8 V is applied. The applied constant voltage charge is performed for a total of 30 minutes. Thereafter, Q is the capacity when constant current discharge is performed at a current value of 2 C up to 2.2 V. A value calculated by F = Q / (3.8−2.2) is used by using Q obtained here.

[Normal discharge internal resistance]
The room temperature discharge internal resistance Ra (Ω) was a value obtained by the following method.
First, in a thermostatic chamber set at 25 ° C. with a cell corresponding to a non-aqueous lithium storage element, constant current charging is performed until a current value of 20 C reaches 3.8 V, and then a constant voltage of 3.8 V is applied. The constant voltage charging is performed for a total of 30 minutes. Next, a constant current discharge is performed up to 2.2 V at 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 time of the discharge time of 2 seconds and 4 seconds by linear approximation is Eo, the drop voltage ΔE = 3.8− Eo and Ra = ΔE / (20C (current value A)).

[Rate of increase in internal resistance at room temperature after high load charge / discharge cycle test]
The room temperature discharge internal resistance increase rate after the high load charge / discharge cycle test was measured by the following method.
First, constant-current charging is performed in a thermostatic chamber set to 25 ° C. with a non-aqueous lithium storage element and a cell corresponding to a current value of 300 C until reaching 3.8 V, and then a current value of 300 C is 2.2 V. The constant current discharge is performed until it reaches. The charge / discharge process is repeated 60000 times, and room temperature discharge internal resistance is measured before and after the start of the test. The room temperature discharge internal resistance before the start of the test is Ra (Ω), and the room temperature discharge internal resistance after the end of the test is Re ( Ω), the rate of increase in resistance after the high load charge / discharge cycle test before the start of the test is calculated by Re / Ra.

[Capacity recovery rate after high-load charge / discharge cycle test]
The capacity retention rate after the high load charge / discharge cycle test was measured by the following method.
First, constant-current charging is performed in a thermostatic chamber set to 25 ° C. with a non-aqueous lithium storage element and a cell corresponding to a current value of 300 C until reaching 3.8 V, and then a current value of 300 C is 2.2 V. The constant current discharge is performed until it reaches. The charging / discharging process is repeated 60000 times, and after reaching a voltage of 4.5 V at a current value of 20 C, charging is performed at a constant voltage for 1 hour. Then, when the capacitance value obtained using the same measurement method as the capacitance is defined as 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 capacity recovery rate after the high load charge / discharge cycle test for F is calculated by Fe / F.

The non-aqueous lithium storage element of this embodiment has an initial room temperature discharge internal resistance of Ra (Ω), a capacitance of F (F), an ambient temperature of 25 ° C., and a cell voltage of 2.2 V to 3.8 V. Until the room temperature discharge internal resistance after performing 60,000 charge / discharge cycles at a rate of 300 C is Re (Ω), and the storage element after the cycle test is charged with a constant voltage of 4.5 V for 1 hour. When the capacitance is Fe (F), the following:
(A) Re / Ra is 0.9 or more and 2.0 or less; and (b) Fe / F is 1.01 or more;
Are preferably satisfied simultaneously.
With regard to (a), the room temperature discharge internal resistance increase rate Re / Ra after the high load charge / discharge cycle test is preferably 2.0 or less, more preferably 1.5 or less, still more preferably 1. 2 or less. If the rate of increase in resistance after the high-load charge / discharge cycle test is not more than the above upper limit value, the characteristics of the device are maintained even after repeated charge / discharge. Therefore, excellent output characteristics can be obtained stably for a long period of time, leading to a longer life of the device.

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

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these.
[Crushing lithium carbonate]
200 g of lithium carbonate having an average particle diameter of 51 μm was cooled to −196 ° C. with liquid nitrogen using a crusher (liquid nitrogen bead mill LNM) manufactured by Imex Co., Ltd., and peripheral speed was 10.0 m / s using dry ice beads. For 9 minutes. The lithium carbonate particle diameter obtained by measuring the average particle diameter of lithium carbonate obtained by preventing thermal denaturation at −196 ° C. and brittle fracture was 2.5 μm.

[Preparation of positive electrode active material]
[Preparation of activated carbon 1]
The crushed coconut shell carbide was carbonized in a small carbonization furnace in nitrogen at 500 ° C. for 3 hours to obtain a carbide. The obtained carbide was put into an activation furnace, 1 kg / h of steam was heated in the preheating furnace and introduced into the activation furnace, and the temperature was raised to 900 ° C. over 8 hours for activation. The activated carbide 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 for 10 hours in an electric dryer maintained at 115 ° C., the activated carbon 1 was obtained by pulverizing for 1 hour using a ball mill.
It was 4.1 micrometers as a result of measuring the average particle diameter about this activated carbon 1 using the Shimadzu Corporation laser diffraction type particle size distribution analyzer (SALD-2000J). Moreover, the pore distribution was measured using the pore distribution measuring apparatus (AUTOSORB-1 AS-1-MP) made from Yuasa Ionics. As a result, the BET specific surface area was 2360 m ² / g, the mesopore volume (V1) was 0.52 cc / g, the micropore volume (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 size 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. Thereafter, the mixture was washed with stirring in dilute hydrochloric acid adjusted to a concentration of 2 mol / L for 1 hour, then boiled and washed with distilled water until it was stabilized at pH 5 to 6, and then dried to obtain activated carbon 2.
The activated carbon 2 was measured to have an average particle diameter of 7.1 μm using a laser diffraction particle size distribution analyzer (SALD-2000J) manufactured by Shimadzu Corporation. The pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 3627 m ² / g, the mesopore volume (V1) was 1.50 cc / g, the micropore volume (V2) was 2.28 cc / g, and V1 / V2 = 0.66.

[Preparation of cathode coating solution]
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 solution 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 (polyvinylpyrrolidone); and PVdF (polyvinylidene fluoride). 8.0 parts by mass and NMP (N-methylpyrrolidone) are mixed and dispersed using a thin film swirl type high-speed mixer film mix manufactured by PRIMIX under the condition of a peripheral speed of 17.0 m / s. A liquid was obtained.
The viscosity (ηb) and TI value of the obtained coating solution were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,700 mPa · s, and the TI value was 3.5. Moreover, the dispersion degree of the obtained coating liquid was measured using the grain gauge made from Yoshimitsu Seiki. As a result, the particle size was 35 μm.

[Preparation of positive electrode precursor]
The above coating solution is applied on 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 part of 25 ° C. The average thickness of the positive electrode active material layer of the positive electrode precursor obtained above was measured at any 10 locations of the positive electrode precursor using a thickness gauge Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. The value was obtained by subtracting the thickness of the aluminum foil from the value. As a result, the film thickness of the positive electrode active material layer was 61 μm per side.

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

Next, a negative electrode was manufactured using the composite carbon material as a negative electrode active material.
85 parts by mass of composite carbon material, 10 parts by mass of acetylene black, 5 parts by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) are mixed, and this is mixed with a thin film swirl type high speed mixer manufactured by PRIMIX Using a fill mix, the coating liquid was obtained by dispersing under conditions of a peripheral speed of 15 m / s. The viscosity (ηb) and TI value of the obtained coating solution were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,789 mPa · s, and the TI value was 4.3. The above coating solution was applied to both sides of an electrolytic copper foil having a thickness of 10 μm using a die coater manufactured by Toray Engineering Co., Ltd. at a coating speed of 1 m / s, and dried at a drying temperature of 85 ° C. to obtain a negative electrode. . The obtained negative electrode was pressed using a roll press machine under conditions of a pressure of 4 kN / cm and a surface temperature of the pressed part of 25 ° C. The thickness of the negative electrode active material layer of the negative electrode obtained above was measured from the average value of the thickness measured at any 10 locations on the negative electrode using a thickness gauge Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. Obtained by subtracting the thickness of the foil. As a result, the film thickness of the negative electrode active material layer of the negative electrode was 40 μm per side.

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

[Example 1]
[Preparation of non-aqueous lithium storage element]
[Assembly process]
The obtained double-sided negative electrode and double-sided positive electrode precursor were cut into 10 cm × 10 cm (100 cm ² ). The uppermost and lowermost surfaces use a single-sided positive electrode precursor, 21 double-sided negative electrodes and 20 double-sided positive electrode precursors, and a microporous membrane separator having a thickness of 15 μm is sandwiched between the negative electrode and the positive electrode precursor. Laminated. Thereafter, the negative electrode terminal and the positive electrode terminal were connected to the negative electrode and the positive electrode precursor, respectively, by ultrasonic welding to obtain an electrode laminate. This electrode laminate was vacuum-dried under the conditions of a temperature of 80 ° C., a pressure of 50 Pa, and a drying time of 60 hours. The dried electrode laminate is housed in an outer package made of an aluminum laminate packaging material in a dry environment with a dew point of -45 ° C. Heat sealing was performed under conditions of a sealing pressure of 1.0 MPa.

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

[Lithium doping process]
Using the charge / discharge device (TOSCAT-3100U) manufactured by Toyo System Co., Ltd., the obtained non-aqueous lithium storage element was charged at a constant current until reaching a voltage of 4.5 V at a current value of 50 mA in a 25 ° C. environment. Then, initial charging was performed by a technique of continuing 4.5 V constant voltage charging for 72 hours, and lithium doping was performed on the negative electrode.

[Aging process]
The non-aqueous lithium storage element after lithium doping was subjected to constant current discharge at 1.0 A until reaching a voltage of 3.0 V in a 25 ° C. environment, and then subjected to 3.0 V constant current discharge for 1 hour. Adjusted to 3.0V. Thereafter, the non-aqueous lithium 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 unsealed in a dry air environment with a temperature of 25 ° C. and a dew point of −40 ° C. of the non-aqueous lithium storage element after aging. Next, the non-aqueous lithium storage element was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to −80 kPa over 3 minutes using a diaphragm pump (N816.3KT.45.18) manufactured by KNF. The process of returning to atmospheric pressure over a period of time was repeated a total of 3 times. Then, after putting a non-aqueous lithium-type electrical storage element in a pressure reduction sealing machine and reducing the pressure to −90 kPa, the aluminum laminate packaging material was sealed by sealing at 200 ° C. for 10 seconds with a pressure of 0.1 MPa.
The non-aqueous lithium storage element was completed through the above steps.

[Evaluation of storage element]
[Capacitance measurement]
Using the charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. in a thermostatic chamber set at 25 ° C., the obtained electricity storage device was fixed until it reached 3.8V at a current value of 20C. Current charging was performed, and then constant voltage charging in which a constant voltage of 3.8 V was applied was performed for a total of 30 minutes. Capacitance F calculated by F = Q / (3.8−2.2) was 1000 F, where Q was the capacity when constant current discharge was performed at a current value of 2 C up to 2.2 V.

[Calculation of Ra]
Using the charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. in a thermostatic chamber set at 25 ° C., the obtained electricity storage element was fixed until it reached 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 discharging 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 seconds obtained by extrapolating from the voltage values at the time points of the discharge time of 2 seconds and 4 seconds by linear approximation is Eo, and the drop voltage ΔE = 3.8−Eo, and The room temperature discharge internal resistance Ra calculated by R = ΔE / (20C (current value A)) was 2.01 mΩ.

[Rate of increase in internal resistance at room temperature after high load charge / discharge cycle test]
Using the charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. in a thermostatic chamber set at 25 ° C., the obtained electricity storage element was fixed until it reached 3.8V at a current value of 300C. The charging / discharging process which carries out an electric current charge and performs constant current discharge until it reaches to 2.2V with the electric current value of 300C was repeated 60000 times. After the high load charge / discharge cycle test, the room temperature discharge internal resistance Re after the high load charge / discharge cycle test was calculated in the same manner as in [Calculation of Ra · F]. The ratio Re / Ra calculated by dividing this Re (Ω) by the internal resistance Ra (Ω) before the high-load charge / discharge cycle test determined in [Calculation of Ra · F] was 1.24.

[Capacity recovery rate after high-load charge / discharge cycle test]
Using the charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. in a thermostatic chamber set at 25 ° C., the obtained electricity storage element was fixed until it reached 3.8V at a current value of 300C. The charging / discharging process which carries out an electric current charge and performs constant current discharge until it reaches to 2.2V with the electric current value of 300C was repeated 60000 times. After the end of the cycle, the battery was charged to 4.5 V at a current value of 20 C, and then constant voltage charging was continued for 1 hour. The subsequent capacitance Fe was measured and found to be 1030F and Fe / F = 1.03.

[Examples 2 to 15, Comparative Examples 1 to 8]
The positive electrode activated carbons 1 and 2 were pulverized by a ball mill and the mixing ratio of the positive electrode coating solution was changed to produce a positive electrode. The aging conditions were the same as in Example 1 except that the aging conditions were as shown in Table 1 below. Then, the non-aqueous lithium storage elements of Examples 2 to 15 and Comparative Examples 1 to 8 were produced, and various evaluations were performed. The evaluation results of the obtained nonaqueous lithium storage element are shown in Table 1 below.

[Example 16]
The positive electrode activated carbons 1 and 2 were pulverized by a ball mill and the positive electrode coating liquid was mixed at different ratios to produce positive electrodes. The obtained double-sided negative electrode and double-sided positive electrode precursor were cut into 12 cm × 230 cm (2760 cm ² ). Each of the negative electrode and the positive electrode precursor has an uncoated portion. This uncoated portion was formed with a width of 2 cm from the end side. Sandwich the microporous membrane separator with a thickness of 15 μm so that the uncoated parts are opposite to each other, and wind the wound body into an oval shape so that the uncoated parts protrude from the separator. Molded into a flat shape. Then, the electrode terminal was joined to the negative electrode and the positive electrode precursor by ultrasonic welding to obtain an electrode winding body. This electrode winding body was housed in an outer package made of an aluminum laminate packaging material, and the electrode terminal part and the bottom part of the outer package 3 were heat-sealed under conditions of a temperature of 180 ° C., a sealing time of 20 sec, and a sealing pressure of 1.0 MPa. . A non-aqueous lithium storage element was produced in the same manner as in Example 1 except that this was vacuum-dried under conditions of a temperature of 80 ° C. and a pressure of 50 Pa and a drying time of 60 hours, and various evaluations were performed. The evaluation results of the obtained non-aqueous lithium storage element are shown in Table 2 below.

[Examples 17 to 30, Comparative Examples 9 to 16]
The positive electrode activated carbons 1 and 2 were pulverized by a ball mill and the positive electrode coating liquid was mixed at different ratios to produce positive electrodes. Except that the positive electrode and aging conditions were as shown in Table 2 below, respectively, non-aqueous lithium storage elements of Examples 17 to 30 and Comparative Examples 9 to 16 were produced in the same manner as Example 16, Various evaluations were performed. The evaluation results of the obtained non-aqueous lithium storage element are shown in Table 2 below.

  As a result of the above examples, the electricity storage device of this embodiment has excellent initial input characteristics by making the potential between the electrodes uniform without increasing the number of parts, and has high long-term cycle characteristics and high safety that have not been obtained conventionally. It was verified to have sex.

  The non-aqueous lithium storage element of the present invention has excellent initial input / output characteristics and high long-term cycle characteristics by making the potential between the electrodes uniform without increasing the number of parts. It can be suitably used in the field of hybrid drive systems in which a fuel cell or a motor and a power storage element are combined;

Claims (13)

A laminate in which a positive electrode and a negative electrode are laminated via a separator, and a non-aqueous lithium storage element including a non-aqueous electrolyte containing lithium ions,
The positive electrode includes a lithium compound,
The positive electrode has a positive electrode current collector and a positive electrode active material layer on one or both sides of the positive electrode current collector, and the positive electrode active material layer contains a positive electrode active material made of activated carbon,
The negative electrode has a negative electrode current collector and a negative electrode active material layer on one or both sides of the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material capable of inserting and extracting lithium ions,
When the negative electrode active material layer of the negative electrode in the thickness direction outermost layer of the laminate is viewed from above, the central lithium ion concentration is C _1o , and when the negative electrode active material layer of the negative electrode in the thickness direction innermost layer of the laminate is viewed from above _{C 1o} / _{C 1i} when the lithium ion concentration of the centers of the _{C 1i} is 0.85 to 1.15,
The concentration of lithium ions is higher in the area of 80% of the central part of the negative electrode active material layer than in the area of 20% of the peripheral part of the negative electrode active material layer,
When the average particle diameter of the lithium compound and _{X 1,} a 0.1μm ≦ _{X 1} ≦ 10μm, when the average particle diameter of the positive electrode active material and _{Y 1,} a 2μm ≦ _{Y 1} ≦ 20μm, X ₁ <Y ₁ and the amount of the lithium compound contained in the positive electrode is 1% by mass or more and 50% by mass or less. T _{1o is} the thickness of the negative electrode active material layer at the center when the negative electrode active material layer of the negative electrode in the outermost layer in the thickness direction of the laminate is viewed from above, and the negative electrode active material layer of the negative electrode in the innermost layer in the thickness direction of the laminate is the upper surface when the thickness of the negative electrode active material layer in the center when the viewing and _{T 1i, T 1o} / _{T 1i} is 0.85 to 1.15, the non-aqueous lithium electric storage device according to claim 1. A non-aqueous lithium storage element comprising a wound body in which a positive electrode and a negative electrode are wound through a separator, and a non-aqueous electrolyte containing lithium ions,
The positive electrode includes a lithium compound,
The positive electrode has a positive electrode current collector and a positive electrode active material layer on one or both sides of the positive electrode current collector, the positive electrode active material layer contains a positive electrode active material made of activated carbon,
The negative electrode has a negative electrode current collector and a negative electrode active material layer on one or both sides of the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material capable of inserting and extracting lithium ions,
Opposite to the positive electrode of the wound body, and the center lithium ion concentration of the negative electrode active material layer of the negative electrode in the outermost radial direction excluding the peripheral portion is C _2o , facing the positive electrode of the wound _body when the lithium ion concentration in the center when the anode active material layer of the negative electrode was viewed in the radial direction innermost layer except for the life-and-death periphery and C _2i, C _2o / C _2i is 0.85 to 1.15 Yes,
The concentration of lithium ions is higher in the area of 80% of the central part of the negative electrode active material layer than in the area of 20% of the peripheral part of the negative electrode active material layer,
When the average particle diameter of the lithium compound is X ₁ , 0.1 μm ≦ X ₁ ≦ 10 μm, and when the average particle diameter of the positive electrode active material is Y ₁ , 2 μm ≦ Y ₁ ≦ 20 μm and X ₁ The non-aqueous lithium storage element, wherein <Y ₁ and the amount of the lithium compound contained in the positive electrode is 1% by mass or more and 50% by mass or less. The center thickness of the negative electrode active material layer of the negative electrode at the outermost radial direction excluding the peripheral portion is T _2o , facing the positive electrode of the wound _body , and facing the positive electrode of the wound _body ; when the thickness of the center when the anode active material layer of the negative electrode was viewed in the radial direction innermost layer except the peripheral part and T _2i, T _2o / T _2i is 0.85 to 1.15, claims 4. A non-aqueous lithium storage element according to 3.   The non-aqueous lithium storage element according to any one of claims 1 to 4, wherein the lithium compound is at least one lithium compound selected from the group consisting of lithium carbonate, lithium oxide, and lithium hydroxide. The positive electrode active material layer has the following formula (1):

{In Formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are independently of each other — (COO) _n. (Where n is 0 or 1). } Or the following formula (2):

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

{In 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 each independently a hydrogen atom, 1 carbon atom. -10 alkyl group, C1-C10 mono- or polyhydroxyalkyl group, C2-C10 alkenyl group, C2-C10 mono- or polyhydroxyalkenyl group, C3-C6 cycloalkyl group Or an aryl group and X ¹ and X ² are independently of each other — (COO) _n (where n is 0 or 1). One or more compounds represented by}, wherein to unit mass per ^{1.60 × 10 -4 mol / g~300 ×} 10 -4 mol / g containing the positive electrode material layer, any one of claims 1 to 5 The non-aqueous lithium storage element according to claim 1. The positive electrode active material contained in the positive electrode active material layer has a mesopore amount derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method as V1 (cc / g), and a fine particle having a diameter of less than 20 mm calculated by the MP method. When the amount of micropores derived from the holes is V2 (cc / g), a ratio that satisfies 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 and is measured by the BET method surface area of activated carbon having the following 1,500m2 / g or more 3,000 m ² / g, the non-aqueous lithium-type storage element according to any one of claims 1-6. The positive electrode active material contained in the positive electrode active material layer has a mesopore amount V1 (cc / g) derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method satisfying 0.8 <V1 ≦ 2.5. The amount of micropores V2 (cc / g) derived from pores having a diameter of less than 20 mm calculated by the MP method satisfies 0.8 <V2 ≦ 3.0, and the specific surface area measured by the BET method is 2, activated carbon showing a 300 m @ 2 / g or more 4,000 m ² / g or less, a non-aqueous lithium-type storage element according to any one of claims 1-6.   The non-aqueous lithium storage element according to any one of claims 1 to 8, wherein a doping amount of lithium ions of the negative electrode active material is 530 mAh / g or more and 2,500 mAh / g or less per unit mass. The non-aqueous lithium storage element according to claim 1, wherein the negative electrode active material has a BET specific surface area of 100 m ² / g or more and 1,500 m ² / g or less.   The non-aqueous lithium storage element according to claim 1, wherein a doping amount of lithium ions of the negative electrode active material is 50 mAh / g or more and 700 mAh / g or less per unit mass. 12. The non-aqueous lithium storage element according to claim 1, wherein the negative electrode active material has a BET specific surface area of 1 m ² / g or more and 50 m ² / g or less. The separator is based on a resin film made of polyolefin having a porous structure, and an inorganic layer made of inorganic fine particles is laminated on at least one surface,
In the non-aqueous lithium storage element, the initial room temperature discharge internal resistance is Ra (Ω), the capacitance is F (F), the ambient temperature is 25 ° C., the cell voltage is from 2.2 V to 3.8 V, 300 C The room temperature discharge internal resistance after 60,000 charge / discharge cycles at a rate of 5 (Re) was obtained, and the capacitance after the cycle test was performed at a constant voltage of 4.5 V for 1 hour. Is Fe (F), the following:
(A) Re / Ra is 0.9 or more and 2.0 or less; and (b) Fe / F is 1.01 or more;
The non-aqueous lithium storage element according to claim 1, wherein

Images