JP2018056435A - Nonaqueous lithium power storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous lithium power storage element which achieves both of a high input/output density and high safety.SOLUTION: A nonaqueous lithium power storage element comprises: a positive electrode including a lithium compound other than a positive electrode active material; a negative electrode; a separator; and a nonaqueous electrolyte containing lithium ions. The positive electrode has: a positive electrode current collector; and a positive electrode active material layer provided on one or each of opposing faces of the positive electrode current collector, and including the positive electrode active material. The positive electrode active material includes active carbon. The lithium compound has an average particle diameter Xwhich satisfies 0.1 μm≤X≤10 μm, and the positive electrode active material has an average particle diameter Ywhich satisfies 2 μm≤Y≤20 μm, and they are in the relation given by X<Y. The content of the lithium compound in the positive electrode is 1-50 mass% to a total mass of the positive electrode active material layer. The separator includes a porous film, and an insulative porous layer formed on at least one face of the porous film. The percentage of a thickness of the insulative porous layer to a thickness of the porous film is 20-125%.SELECTED DRAWING: Figure 1

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. Further, its 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 depth of discharge is used in a range narrower than the range of 0 to 100%. 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 non-aqueous lithium storage element has attracted attention and has been actively developed.

  The non-aqueous lithium storage element is a kind of storage element (non-aqueous lithium storage element) that uses a non-aqueous electrolyte containing a lithium salt, and the negative electrode has a negative voltage similar to that of an electric double layer capacitor at about 3 V or more. It is a power storage element that charges and discharges by a non-Faraday reaction by adsorption and desorption of ions, and a Faraday reaction by occlusion and release of lithium ions in the negative electrode similar to a lithium ion battery.

  Summarizing the above electrode materials and their characteristics, when using materials such as activated carbon for the electrodes and charging and discharging by adsorption and desorption (non-Faraday reaction) of ions on the activated carbon surface, high output and high durability are achieved. However, the energy density is lowered (for example, 1 time). On the other hand, when an oxide or 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 characteristics are increased. There is a problem.

  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. Energy density (positive electrode 10 times × negative electrode 10 times = 100), however, there are 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.

  The non-aqueous lithium storage element is characterized by using activated carbon (energy density 1 time) for the positive electrode and carbon material (10 times energy density) for the negative electrode, and charging and discharging by non-Faraday reaction at the positive electrode and Faraday reaction at the negative electrode. And a novel asymmetric capacitor having the characteristics of an electric double layer 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.

  For example, Patent Document 1 has a membrane resistance equal to or lower than that of a conventional polyolefin microporous membrane and a high porosity (“high porosity”. In other words, a microporous membrane made of polyolefin (eg, polyethylene) having high output characteristics and a non-aqueous electrolyte secondary battery including the microporous membrane made of polyolefin have been proposed. Yes.

  As another example, Patent Document 2 discloses a multilayer porous membrane having a porous layer containing an inorganic filler and a resin binder on at least one surface of the porous membrane in order to provide insulation as a separator, and the multilayer porous membrane as a separator. A non-aqueous electrolyte secondary battery used as a battery has been proposed.

JP 2012-72263 A JP 2009-26733 A

  In a lithium ion battery, a polyolefin microporous membrane may be used as a separator. Such a polyolefin microporous membrane is a further electrochemical reaction by closing the pores (shutdown) when the temperature reaches the melting point of the microporous membrane due to runaway electrochemical reaction in the battery. It is intended for the function of suppressing However, the microporous membrane melts (melts down) in an environment where it is not possible to prevent the temperature from rising even though the electrochemical reaction is shut down, such as when the battery falls into high temperature oil. It was difficult to prevent a short circuit between the negative electrode body and the positive electrode body of the battery.

  On the other hand, the nonaqueous lithium storage element may have a lower energy density than the lithium ion battery, and even if the electrochemical reaction runs away, there is no need to prevent it by the shutdown function of the polyolefin microporous membrane. For this reason, paper separators that do not melt down at higher temperatures have been used.

  However, the present inventors have found that, even in a non-aqueous lithium storage element, there is a possibility of rupture or opening, a large amount of gasification, or smoke / ignition depending on conditions. It is considered that such necessity is increased as the capacity and output of the non-aqueous lithium storage element increase.

  For example, when the polyolefin microporous membrane described in Patent Document 1 is used as a separator for a non-aqueous lithium storage element, the non-aqueous lithium storage element has an internal structure even if the polyolefin microporous film has low resistance. When the short circuit occurs, the temperature rises rapidly, and there is a large amount of gasification, smoke, and ignition, which may open the package.

  When the multilayer porous membrane described in Patent Document 2 is used as a separator for a non-aqueous lithium storage element, gasification, smoke generation, and ignition can be suppressed during an internal short circuit, but the resistance of the non-aqueous lithium storage element is high. Thus, the output density of the non-aqueous lithium storage element is reduced.

  An object of the present invention is to provide a non-aqueous lithium storage element that achieves both high output density and high safety. More specifically, the present invention suppresses gasification, smoke generation, and ignition of a non-aqueous lithium storage element at the time of an internal short circuit, and has low resistance (that is, high input / output density), and can be stored at high temperature. One object is to provide a non-aqueous lithium storage element capable of suppressing an increase in resistance.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, in a non-aqueous lithium-type energy storage device, by using a multilayer separator that contains a lithium compound other than the positive electrode active material in the positive electrode and further includes a porous film and an insulating porous layer in a specific thickness ratio, high input / output is achieved. The present inventors have found that a non-aqueous lithium storage element having both high density and high safety can be obtained, and the present invention has been completed.

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

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

｛式（３）中、Ｒ^１は、炭素数１〜４のアルキレン基、又は炭素数１〜４のハロゲン化アルキレン基であり、Ｒ^２、Ｒ^３はそれぞれ独立に水素、炭素数１〜１０のアルキル基、炭素数１〜１０のモノ若しくはポリヒドロキシアルキル基、炭素数２〜１０のアルケニル基、炭素数２〜１０のモノ又はポリヒドロキシアルケニル基、炭素数３〜６のシクロアルキル基、又はアリール基であり、Ｘ^１、Ｘ^２はそれぞれ独立に−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝
〔９〕
上記正極活物質層における、上記式（１）〜（３）からなる群から選択される少なくとも１種の化合物の、上記正極活物質層の単位質量当たりの含有量をＡとし、上記負極活物質層における、上記式（１）〜（３）からなる群から選択される少なくとも１種の化合物の、上記負極活物質層の単位質量当たりの含有量をＢとしたとき、０．２≦Ａ／Ｂ≦２０である、項目１〜８のいずれか一項に記載の非水系リチウム型蓄電素子。
〔１０〕
上記リチウム化合物は、炭酸リチウム、酸化リチウム、及び水酸化リチウムからなる群から選択される少なくとも一種である、項目１〜９のいずれか一項に記載の非水系リチウム型蓄電素子。
〔１１〕
上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Ｖ_１（ｃｃ／ｇ）、ＭＰ法により算出した直径２０Å未満の細孔に由来するマイクロ孔量をＶ_２（ｃｃ／ｇ）とするとき、０．３＜Ｖ_１≦０．８、及び０．５≦Ｖ_２≦１．０を満たし、かつ、ＢＥＴ法により測定される比表面積が１，５００ｍ^２／ｇ以上３，０００ｍ^２／ｇ以下を示す活性炭である、項目１〜１０のいずれか一項に記載の非水系リチウム型蓄電素子。
〔１２〕
上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Ｖ_１（ｃｃ／ｇ）が０．８＜Ｖ_１≦２．５を満たし、ＭＰ法により算出した直径２０Å未満の細孔に由来するマイクロ孔量Ｖ_２（ｃｃ／ｇ）が０．８＜Ｖ_２≦３．０を満たし、かつ、ＢＥＴ法により測定される比表面積が２，３００ｍ^２／ｇ以上４，０００ｍ^２／ｇ以下を示す活性炭である、項目１〜１１のいずれか一項に記載の非水系リチウム型蓄電素子。
〔１３〕
上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、項目１〜１２のいずれか一項に記載の非水系リチウム型蓄電素子。
〔１４〕
上記負極活物質のＢＥＴ比表面積が１００ｍ^２／ｇ以上１，５００ｍ^２／ｇ以下である、項目１〜１３のいずれか一項のいずれか１項に記載の非水系リチウム型蓄電素子。
〔１５〕
上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、項目１〜１２のいずれか一項に記載の非水系リチウム型蓄電素子。
〔１６〕
上記負極活物質のＢＥＴ比表面積が１ｍ^２／ｇ以上５０ｍ^２／ｇ以下である、項目１〜１２及び１５のいずれか一項のいずれか１項に記載の非水系リチウム型蓄電素子。
〔１７〕
正極活物質以外のリチウム化合物を含む正極と、負極と、セパレータと、リチウムイオンを含む非水系電解液とを有する、非水系リチウム蓄電素子であって、
前記正極は、正極集電体と、前記正極集電体の片面又は両面上に設けられた、正極活物質を含む正極活物質層とを有し、前記正極活物質は、活性炭を含み、
上記セパレータは、多孔膜及び上記多孔膜の少なくとも片面に形成された絶縁多孔層を含み、かつ上記多孔膜の厚みに対する上記絶縁多孔層の厚みの割合が２０％〜１２５％であり、
上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）、初期の常温充電内部抵抗をＲｆ（Ω）、静電容量をＦ（Ｆ）としたとき、
以下の（ａ）、（ｂ）：
（ａ）ＲａとＦとの積Ｒａ・Ｆが０．３以上３．０以下である；
（ｂ）Ｒｆ／Ｒａが０．５以上１．５以下である；
を満たす、非水系リチウム型蓄電素子。
〔１８〕
正極活物質以外のリチウム化合物を含む正極と、負極と、セパレータと、リチウムイオンを含む非水系電解液とを有する、非水系リチウム蓄電素子であって、
上記セパレータは、多孔膜及び上記多孔膜の少なくとも片面に形成された絶縁多孔層を含み、かつ上記多孔膜の厚みに対する上記絶縁多孔層の厚みの割合が２０％〜１２５％であり、
上記非水系リチウム型蓄電素子の初期の常温放電内部抵抗をＲａ（Ω）、セル電圧４Ｖ及び環境温度６０℃において２か月間保存した後の２５℃における内部抵抗をＲｂ（Ω）としたとき、Ｒｂ／Ｒａが３．０以下である、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 having a positive electrode containing a lithium compound other than the positive electrode active material, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions,
The positive electrode has a positive electrode current collector, and a positive electrode active material layer including a positive electrode active material provided on one or both surfaces of the positive electrode current collector, the positive electrode active material includes activated carbon,
When the average particle size of the lithium compound and _{X 1,} a 0.1μm ≦ _{X 1} ≦ 10μm, when the average particle diameter of the positive electrode active material _{Y 1,} a _{2μm ≦ Y 1 ≦ 20μm, X} 1 <a Y _1, the amount of lithium compound contained in the positive electrode is not more than 50 wt% or more 1 wt% based on the total weight of the positive electrode active material layer as a reference,
The separator includes a porous membrane and an insulating porous layer formed on at least one surface of the porous membrane, and the ratio of the thickness of the insulating porous layer to the thickness of the porous membrane is 20% to 125%. Type storage element.
[2]
Item 2. The nonaqueous lithium storage element according to Item 1, wherein the porous film includes a polyolefin microporous film.
[3]
3. The non-aqueous lithium storage element according to item 1 or 2, wherein the insulating porous layer includes an inorganic filler and a resin binder.
[4]
The non-aqueous lithium storage element according to any one of Items 1 to 3, wherein the insulating porous layer has a thickness of 3 μm or more and 30 μm or less.
[5]
The non-aqueous lithium storage element according to any one of Items 1 to 4, wherein the porous film has a thickness of 5 μm or more and 35 μm or less.
[6]
The nonaqueous lithium according to any one of Items 1 to 5, wherein the pore diameter of the porous membrane is 0.03 μm to 0.1 μm, and the number of pores is 100 / μm ² to 250 / μm ^2. Type storage element.
[7]
The non-aqueous lithium storage element according to any one of items 1 to 6, wherein the porosity of the porous film is 45% to 75%.
[8]
The positive electrode active material layer contains at least one compound selected from the group consisting of the following formulas (1) to (3) from 1.60 × 10 ⁻⁴ mol / g per unit mass of the positive electrode active material layer. The non-aqueous lithium storage element according to any one of Items 1 to 7, containing 300 × 10 ⁻⁴ mol / g.

{In Formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are each independently — (COO) _n (here And n is 0 or 1.). }

{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} represents 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 each independently-(COO) _n (where n is 0 or 1). }

{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 hydrogen and 1 to 10 carbon atoms. An alkyl group, 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, X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1); }
[9]
In the positive electrode active material layer, the content per unit mass of the positive electrode active material layer of at least one compound selected from the group consisting of the formulas (1) to (3) is A, and the negative electrode active material When the content per unit mass of the negative electrode active material layer of at least one compound selected from the group consisting of the above formulas (1) to (3) in the layer is B ≦ 0.2 ≦ A / The non-aqueous lithium storage element according to any one of Items 1 to 8, wherein B ≦ 20.
[10]
The non-aqueous lithium storage element according to any one of Items 1 to 9, wherein the lithium compound is at least one selected from the group consisting of lithium carbonate, lithium oxide, and lithium hydroxide.
[11]
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 V ₁ (cc / g), and a diameter of less than 20 mm calculated by the MP method. When the amount of micropores derived from the pores is V ₂ (cc / g), 0.3 <V ₁ ≦ 0.8 and 0.5 ≦ V ₂ ≦ 1.0 are satisfied, and by the BET method The non-aqueous lithium storage element according to any one of Items 1 to 10, which is activated carbon having a specific surface area of 1,500 m ² / g or more and 3,000 m ² / g or less.
[12]
The positive electrode active material contained in the positive electrode active material layer has a mesopore volume V ₁ (cc / g) derived from pores having a diameter of 20 to 500 mm calculated by the BJH method of 0.8 <V ₁ ≦ 2.5. The ratio of micropores V ₂ (cc / g) derived from pores having a diameter of less than 20 mm calculated by the MP method satisfying 0.8 <V ₂ ≦ 3.0 and measured by the BET method The non-aqueous lithium storage element according to any one of Items 1 to 11, which is activated carbon having a surface area of 2,300 m ² / g or more and 4,000 m ² / g or less.
[13]
The non-aqueous lithium storage element according to any one of Items 1 to 12, 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.
[14]
The non-aqueous lithium storage element according to any one of Items 1 to 13, 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.
[15]
The non-aqueous lithium storage element according to any one of Items 1 to 12, 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.
[16]
The non-aqueous lithium storage element according to any one of Items 1 to 12 and 15, 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.
[17]
A non-aqueous lithium storage element having a positive electrode containing a lithium compound other than the positive electrode active material, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions,
The positive electrode includes a positive electrode current collector, and a positive electrode active material layer including a positive electrode active material provided on one or both surfaces of the positive electrode current collector, the positive electrode active material includes activated carbon,
The separator includes a porous membrane and an insulating porous layer formed on at least one side of the porous membrane, and the ratio of the thickness of the insulating porous layer to the thickness of the porous membrane is 20% to 125%,
In the nonaqueous lithium storage element, when the initial room temperature discharge internal resistance is Ra (Ω), the initial room temperature charge internal resistance is Rf (Ω), and the capacitance is F (F),
The following (a), (b):
(A) The product Ra · F of Ra and F is 0.3 or more and 3.0 or less;
(B) Rf / Ra is 0.5 or more and 1.5 or less;
A non-aqueous lithium storage element that satisfies the above requirements.
[18]
A non-aqueous lithium storage element having a positive electrode containing a lithium compound other than the positive electrode active material, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions,
The separator includes a porous membrane and an insulating porous layer formed on at least one side of the porous membrane, and the ratio of the thickness of the insulating porous layer to the thickness of the porous membrane is 20% to 125%,
When the initial room temperature discharge internal resistance of the non-aqueous lithium storage element is Ra (Ω), and the internal resistance at 25 ° C. after storage for 2 months at a cell voltage of 4 V and an environmental temperature of 60 ° C. is Rb (Ω), A non-aqueous lithium storage element having Rb / Ra of 3.0 or less.

  According to the present invention, a lithium separator other than the positive electrode active material is contained in the positive electrode, and a multilayer separator including a porous film and an insulating porous layer with a specific thickness is employed in the non-aqueous lithium storage element. Provided is a non-aqueous lithium storage element having excellent input / output characteristics and excellent safety.

It is a schematic diagram which shows the separator of the non-aqueous lithium electrical storage element of this embodiment.

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

《Non-aqueous lithium storage element》
A non-aqueous lithium storage element generally includes a positive electrode, a negative electrode, a separator, and an electrolytic solution as main components. As the electrolytic solution, an organic solvent in which a lithium salt is dissolved (hereinafter referred to as a non-aqueous electrolytic solution) is used.

The non-aqueous lithium storage element of the present embodiment is a non-aqueous lithium storage element having a positive electrode containing a lithium compound other than the positive electrode active material, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions. The positive electrode has a positive electrode current collector and a positive electrode active material layer including a positive electrode active material provided on one or both surfaces of the positive electrode current collector, the positive electrode active material includes activated carbon, when the average particle size of the lithium compound and _{X 1,} a 0.1μm ≦ _{X 1} ≦ 10μm, when the average particle diameter of the positive electrode active material _{Y 1,} a _{2μm ≦ Y 1 ≦ 20μm, X} 1 <a Y _1, the amount of a lithium compound contained in the positive electrode is not more than 50 wt% or more 1 wt% based on the total mass of the active material layer as a reference, the separator, the porous membrane and the porous membrane Formed on at least one side And wherein an insulating porous layer, and the ratio of the thickness of the insulating porous layer to the thickness of the porous film is 20% to 125%.

<Positive electrode>
The positive electrode has a positive electrode current collector and a positive electrode active material layer present on one or both surfaces of the positive electrode current collector.

  It is preferable that a positive electrode contains a lithium compound as a positive electrode precursor before assembling a non-aqueous lithium electrical storage element. In this embodiment, when assembling the non-aqueous lithium storage element, it is preferable to pre-dope lithium ions into the negative electrode. As a pre-doping method, after assembling a non-aqueous lithium storage element using a positive electrode precursor containing a lithium compound, a negative electrode, a separator, and a non-aqueous electrolyte, a voltage is applied between the positive electrode precursor and the negative electrode. It is preferable to apply. The positive electrode active material layer formed on the positive electrode current collector of the positive electrode precursor preferably contains a lithium compound.

  In this specification, the positive electrode state before lithium doping is defined as “positive electrode precursor”, and the positive electrode state after lithium doping is defined as “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 the positive electrode active material, 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 the 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.

  The content of the carbon material with respect to the total mass of the positive electrode active material is preferably 50% by mass or more, more preferably 70% by mass or more, or 100% by mass. From the viewpoint of obtaining favorable effects due to the combined use of other materials, the content of the carbon material with respect to the total mass of the positive electrode active material is, for example, preferably 90% by mass or less, and may be 80% by mass or less.

The kind of activated carbon used as a positive electrode active material and its raw material are not specifically limited. However, it is preferable to optimally control the pores of the activated carbon in order to achieve both high input / output characteristics and high energy density. Specifically, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is V ₁ (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method. Is V ₂ (cc / g),
(1) For high input / output characteristics, 0.3 <V ₁ ≦ 0.8 and 0.5 ≦ V ₂ ≦ 1.0 are satisfied, and the specific surface area measured by the BET method is 1, Activated carbon (hereinafter also referred to as activated carbon 1) having a mass of 500 m ² / g to 3,000 m ² / g is preferred.
(2) In order to obtain a high energy density, 0.8 <V ₁ ≦ 2.5 and 0.8 <V ₂ ≦ 3.0 are satisfied, and the specific surface area measured by the BET method is 2, Activated carbon (hereinafter also referred to as activated carbon 2) of 300 m ² / g to 4,000 m ² / g is preferable.

Hereinafter, the (1) activated carbon 1 and the (2) activated carbon 2 will be described individually and sequentially.
(Activated carbon 1)
The mesopore amount V ₁ of the activated carbon 1 is preferably a value greater than 0.3 cc / g in terms of increasing input / output characteristics when incorporated in the energy storage device. From the viewpoint of suppressing a decrease in the bulk density of the positive electrode, it is preferably 0.8 cc / g or less. V ₁ is more preferably 0.35 cc / g or more and 0.7 cc / g or less, and further preferably 0.4 cc / g or more and 0.6 cc / g or less.

The micropore amount V ₂ of the activated carbon 1 is preferably 0.5 cc / g or more in order to increase the specific surface area of the activated carbon and increase the capacity. From the viewpoint of suppressing the bulk of the activated carbon, increasing the density as an electrode, and increasing the capacity per unit volume, it is preferably 1.0 cc / g or less. V ₂ is more preferably 0.6 cc / g or more and 1.0 cc / g or less, and further preferably 0.8 cc / g or more and 1.0 cc / g or less. The combination of the lower limit and the upper limit is arbitrary.

The ratio of meso Anaryou _{V 1} relative to the micropore volume _{V 2 (V 1 / V 2} ) is preferably in the range of _{0.3 ≦ V 1 / V 2 ≦} 0.9. That is, V ₁ / V ₂ 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 the decrease in output characteristics can be suppressed while maintaining a high capacity. preferable. 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, V ₁ / V ₂ is preferably 0.9 or less. More preferred _V 1 / _{V 2} range _{0.4 ≦ V 1 / V 2 ≦} 0.7, further preferred _V 1 / _{V 2} range is _{0.55 ≦ V 1 / V 2 ≦} 0.7. The combination of the lower limit and the upper limit is 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 is 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 the carbonization and activation methods for obtaining the activated carbon 1 from these raw materials, 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 is mentioned at 400-700 degreeC using the mixed gas, Preferably it is about 450-600 degreeC.

  As a method for activating the carbide obtained by carbonization, a gas activation method in which firing is performed using an activation gas such as water vapor, carbon dioxide, and oxygen is preferably used. Among these, a method using water vapor or carbon dioxide as the activation gas is preferable.

  In the activation method, while supplying the activation gas at a rate of 0.5 to 3.0 kg / h, preferably 0.7 to 2.0 kg / h, the carbide is 3 to 12 hours, preferably 5 to 11 hours, It is preferable to activate by heating to 800 to 1,000 ° C. over 6 to 10 hours.

  Prior to the activation treatment of 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, or oxygen is usually preferable.

  By appropriately combining the calcination temperature and calcination time in the carbonization method with the activation gas supply amount, the temperature increase rate and the maximum activation temperature in the activation method, the activated carbon 1 having the above characteristics can be produced.

  The average particle diameter of the activated carbon 1 is preferably 2 to 20 μm. When the average particle diameter is 2 μm or more, the density per volume of the electrode tends to increase because the density of the active material layer is high. When the average particle diameter is 2 μm or more, it is easy to ensure the durability of the positive electrode active material layer. If the average particle size is 20 μm or less, it tends to be suitable for high-speed charge / discharge of a non-aqueous lithium electricity storage device. The average particle diameter is more preferably 2 to 15 μm, still more preferably 3 to 10 μm. The upper and lower limits of the average particle diameter range can be arbitrarily combined.

(Activated carbon 2)
The mesopore amount V ₁ of the activated carbon 2 is preferably a value larger than 0.8 cc / g from the viewpoint of increasing the output characteristics when incorporated in the energy storage device. V ₁ is preferably 2.5 cc / g or less from the viewpoint of suppressing a reduction in the capacity of the power storage element. V ₁ is more preferably 1.00 cc / g or more and 2.0 cc / g or less, and further preferably 1.2 cc / g or more and 1.8 cc / g or less.

The micropore amount V ₂ of the activated carbon ₂ is preferably a value larger than 0.8 cc / g in order to increase the specific surface area of the activated carbon and increase the capacity. V ₂ is preferably 3.0 cc / g or less from the viewpoint of increasing the density of the activated carbon as an electrode and increasing the capacity per unit volume. V ₂ 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 mesopore amount and the micropore amount described above has a BET specific surface area higher than that of the activated carbon used for the conventional electric double layer capacitor or non-aqueous lithium storage element. 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. 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. When the BET specific surface area is 4,000 m ² / g or less, a binder is used to maintain the strength of the electrode. Since it is not necessary to add a large amount, the performance per electrode volume is increased.

Regarding the V ₁ , V ₂ and BET specific surface area of the activated carbon 2, the upper limit and the lower limit of the preferred ranges described above can be arbitrarily combined.

  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. For example, plant raw materials such as wood, wood flour, and coconut shells; petroleum pitch, coke And various synthetic resins such as phenol resin, furan resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin, and the like. 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 the method for carbonizing these raw materials or the heating method during the 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 400 to 700 ° C, the lower limit is preferably 450 ° C or higher, more preferably 500 ° C or higher, and the upper limit is preferably 650 ° C or lower. The firing time is preferably 0.5 to 10 hours.

  As a method for activating the carbide after the carbonization treatment, there are a gas activation method for firing using an activation gas such as water vapor, carbon dioxide, oxygen, and an alkali metal activation method for performing a heat treatment after mixing with an alkali metal compound. An alkali metal activation method is preferable for producing activated carbon having a high specific surface area.

  In this activation method, for example, the mass ratio of carbide to an alkali metal compound such as potassium hydroxide (KOH) or sodium hydroxide (NaOH) is 1: 1 or more (that is, the amount of the alkali metal compound is equal to the amount of the carbide). The same or more) and then heated in an inert gas atmosphere at 600 to 900 ° C., preferably 650 ° C. to 850 ° C. for 0.5 to 5 hours, and then alkalinized. The metal compound can be washed and removed with an acid and water and further dried.

  The mass ratio of the carbide to the alkali metal compound (= carbide: alkali metal compound) is preferably 1: 1 or more, and the amount of mesopores increases as the amount of the alkali metal compound increases. However, since there is a tendency for the amount of pores to increase sharply at a mass ratio of about 1: 3.5, the mass ratio is preferably higher in alkali metal compound than 1: 3. As the mass ratio increases, the amount of pores increases as the number of alkali metal compounds increases, but it is preferably 1: 5.5 or less in consideration of the subsequent processing efficiency such as washing.

  In order to increase the amount of micropores and not increase the amount of mesopores, a larger amount of carbides 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 the alkali activation treatment.

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

(Use mode of activated carbon)
Each of the activated carbons 1 and 2 may be one type of activated carbon, or a mixture of two or more types of activated carbon, and each characteristic value described above may be shown as the entire mixture.

  The activated carbons 1 and 2 may be used by selecting any one of them, or may be used by mixing both.

The positive electrode active material, activated carbon 1 and 2 other than the materials, for example, active carbon not having the specific V ₁ and / or V _2, or material other than the activated carbon, for example, a composite oxide or the like of lithium and 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, 90 mass% or more is still more preferable, and it is still more preferable that it is 100 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 an upper limit 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. As a minimum 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, more suitable charge / discharge characteristics are exhibited.

[Lithium compounds]
The positive electrode active material layer of the positive electrode precursor of the present embodiment preferably contains a lithium compound other than the positive electrode active material. The positive electrode active material layer of the positive electrode of this embodiment contains a lithium compound other than the positive electrode active material.

  The lithium compound is preferably a compound capable of decomposing at the positive electrode in lithium dope and releasing lithium ions, such as lithium carbonate, lithium oxide, lithium hydroxide, lithium fluoride, lithium chloride, lithium oxalate, At least one selected from the group consisting of lithium iodide, lithium nitride, lithium oxalate, and lithium acetate is preferably used. Among these, at least one selected from the group consisting of lithium carbonate, lithium oxide, and lithium hydroxide is more preferable, lithium carbonate is more preferable from the viewpoint that it can be handled in the air and has low hygroscopicity. Used for. 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 vacancies in the positive electrode active material layer, so that it has excellent electrolyte retention and ion conductivity. 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 still more preferably 10 μm or less. 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. When the average particle size of the lithium compound is 100 μm or less, the surface area of the lithium compound does not become excessively small, so that the 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.

(Positive lithium compound)
The lithium compound other than the positive electrode active material contained in the positive electrode is preferably 1% by mass or more and 50% by mass or less, more preferably 2.5% by mass or more and 25% by mass based on the total mass of the positive electrode active material layer in the positive electrode. It is as follows. When the amount of the lithium compound is 1% by mass or more, the lithium compound suppresses the decomposition reaction of the electrolytic solution solvent on the positive electrode in a high temperature environment, so that the high temperature durability is improved. Becomes prominent. When the amount of the lithium compound is 50% by mass or less, the electron conductivity between the positive electrode active materials is relatively small to be inhibited by the lithium compound, so that high input / output characteristics are exhibited. This is particularly preferable from the viewpoint of input / output characteristics. The combination of the lower limit and the upper limit is arbitrary.

(Identification method of 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 X-ray photoelectron spectroscopy (XPS), disassemble the non-aqueous lithium storage element in an argon box, take out the positive electrode, and wash the electrolyte attached to the positive electrode surface. Preferably it is done. As for the solvent for washing the positive electrode, carbonate solvent such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate and the like can be preferably used because the electrolyte attached to the positive electrode surface may be washed away. 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 quantified 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.), Then SEM-EDX, Raman And XPS analysis.

  In ion chromatography, anions can be identified by analyzing the water after washing the positive electrode with distilled water.

  The anion species eluted in water can be identified by analyzing the positive electrode distilled water washing solution by ion chromatography (IC). As a column to be used, an ion exchange type, an ion exclusion type, or a reverse phase ion pair type can be used. As the detector, an electrical conductivity detector, an ultraviolet-visible absorption detector, an electrochemical detector, or the like can be used. A suppressor system in which a suppressor is installed in front of the detector, or an electric device without a suppressor being arranged. A non-suppressor method using a solution with low conductivity as the eluent can be used. Since mass spectrometers and charged particle detection can also be measured in combination with detectors, it is possible to combine appropriate columns and detectors based on lithium compounds identified from SEM-EDX, Raman, and XPS analysis results. preferable.

  The sample retention time is constant for each ionic species component if conditions such as the column to be used and the eluent are determined, and the magnitude of the peak response differs for each ionic species but is proportional to the concentration. It is possible to qualitatively and quantitatively determine the ionic species component by measuring in advance a standard solution having a known concentration in which traceability is ensured.

When a lithium compound cannot be identified by the above method, other analysis methods include solid state ⁷ Li-NMR, XRD (X-ray diffraction), TOF-SIMS (time-of-flight secondary ion mass spectrometry), AES (Auger electron spectroscopy). ), TPD / MS (heat generation gas mass spectrometry), DSC (differential scanning calorimetry), etc., the lithium compound can also be identified.

(Average particle size of lithium compound)
The positive electrode contains a lithium compound other than the positive electrode active material. The positive electrode contains, when the average particle diameter of the lithium compound other than the positive electrode active material and X _1, a 0.1μm ≦ X ₁ ≦ 10μm, when the average particle diameter of the positive electrode active material Y _1, 2 [mu] m ≦ It is preferable that Y ₁ ≦ 20 μm and X ₁ <Y ₁ . More preferably, 0.5 μm ≦ X ₁ ≦ 5 μm. When X ₁ is more than 0.1 [mu] m, high-load charge-discharge cycle characteristics are improved by adsorbing the fluorine ions generated by the high-load charging and discharging cycles. 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. If Y ₁ is not less than 2 [mu] m, it can be secured electronic conductivity between the positive electrode active material. If Y ₁ is 20μm or less, it can exhibit high output characteristics for reaction area with the electrolyte ions increases. When X ₁ <Y ₁ , the lithium compound is filled in the gap between the positive electrode active materials, so that the energy density can be increased while ensuring the electron conductivity between the positive electrode active materials.

X ₁ and measurement method of _{Y 1} is not particularly limited, can be calculated from the positive electrode sectional SEM image, and SEM-EDX image. As a method for forming the positive electrode cross section, BIB processing can be used in which an Ar beam is irradiated from the upper part of the positive electrode and a smooth cross section is produced along the end of the shielding plate placed immediately above the sample. When lithium carbonate is contained in the positive electrode, the distribution of carbonate ions can be obtained by measuring Raman imaging of the cross section of the positive electrode.

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

[Method of calculating the _{X 1} and _{Y 1]}
X ₁ and Y ₁ can be obtained by image analysis of an image obtained from the positive electrode cross section SEM-EDX measured in the same field of view as the positive electrode cross section SEM. The lithium compound particle X and other particles determined in the SEM image of the positive electrode cross section are the positive electrode active material particles Y, and the cross-sectional area of all the X and Y particles observed in the cross-sectional SEM image is as follows. S is obtained, and the particle diameter d calculated by the following mathematical formula (1) is obtained. (The circumference ratio is π.)

Obtained with a particle size d, determine the volume average particle diameter X ₀ and Y ₀ in the following equation (2).

5 or more positions are measured by changing the field of view of the positive electrode cross section, and the average value of each X ₀ and Y ₀ is defined as the average particle diameter X ₁ and Y ₁ .

  The lithium compound contained in the positive electrode is gradually decomposed and gasified when exposed to a high potential of about 4.0 V or more, and the generated gas inhibits diffusion of ions in the electrolyte. It will cause a rise. Therefore, it is preferable to form a film composed of a fluorine-containing compound on the surface of the lithium compound to suppress the reaction of the lithium compound.

[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 for cleaning the positive electrode is not particularly limited as long as it can remove the non-aqueous electrolyte decomposition product deposited on the surface of the positive electrode, but the lithium compound can be obtained by using an organic solvent having a lithium compound solubility of 2% or less. This is preferable because elution of is suppressed. As an organic solvent for washing the positive electrode, for example, a polar solvent such as methanol or acetone is preferably used.

As a method for cleaning the positive electrode, for example, 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 from methanol, vacuum-dried, and the mass of the positive electrode after vacuum drying is defined as M ₀ [g]. The conditions for vacuum drying are, for example, conditions in which the residual methanol in the positive electrode is 1% by mass or less in the range of temperature: 100 to 200 ° C., pressure: 0 to 10 kPa, and time: 5 to 20 hours. About the residual amount of methanol, GC / MS of the water after the distilled water washing | cleaning mentioned later can be measured, and it can quantify based on the analytical curve created beforehand. After vacuum drying, the positive electrode is sufficiently immersed in distilled water 100 times the mass of the positive electrode (100 M ₀ [g]) for 3 days or more. At this time, it is preferable to take measures such as covering the container so that distilled water does not volatilize. In the case of measuring ion chromatography, the amount of liquid is adjusted so that the amount of distilled water is 100 M ₀ [g]. After being immersed in distilled water for 3 days or more, the positive electrode is taken out from the distilled water and vacuum-dried in the same manner as the above methanol washing. 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 mathematical formula (3):
_{Z = 100 × [1- (M} 1 -M 2) / (M 0 -M 2)]. . . Formula (3)
Can be calculated.

[Optional components of positive electrode active material layer]
In addition to the positive electrode active material and the lithium compound, the positive electrode active material layer in the present embodiment may include optional components such as a conductive filler, a binder, and a dispersion stabilizer 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 more than 0 parts by mass and 30 parts by mass or less 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. If the usage-amount of an electroconductive filler is 30 mass parts or less, since the content rate of the positive electrode active material in a positive electrode active material layer can be increased and the energy density per positive electrode active material layer volume improves, it is preferable.

  The binder is not particularly limited. For example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, or the like may be used. it can. 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.

  The dispersion stabilizer is not particularly limited, and for example, PVP (polyvinyl pyrrolidone), PVA (polyvinyl alcohol), cellulose derivatives and the like 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 is unlikely to deteriorate due to elution into an electrolytic solution and reaction with an electrolyte or ions. 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 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, etching A metal foil having a through hole such as a 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 necessary are dispersed or dissolved in water or an organic solvent to prepare a slurry coating solution. A positive electrode precursor can be obtained by coating on one side or both sides of an electric conductor to form a coating film and drying it. 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 coating solution for the positive electrode precursor is obtained by dry blending part or all of various material powders including the positive electrode active material, and then water or an organic solvent and / or a binder or a dispersion stabilizer is dissolved or dispersed therein. You may prepare by adding a liquid or slurry-like substance. A coating liquid may be prepared by adding various material powders containing a positive electrode active material to a liquid or slurry substance in which a binder or dispersion stabilizer is dissolved or dispersed in water or an organic solvent. As a method of dry blending, for example, a positive mixing is performed in which a positive electrode active material and a lithium compound, and a conductive filler are mixed in advance using a ball mill or the like, and a conductive filler is coated on a lithium compound having low conductivity. May be. Thereby, the lithium compound is easily decomposed by the positive electrode precursor in lithium doping described later. When water is used as the solvent of 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 method for preparing the coating solution for the positive electrode precursor is not particularly limited, but preferably a disperser such as a homodisper, a multi-axis disperser, a planetary mixer, a thin film swirl type high-speed mixer or the like is used. Can do. 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 easily broken by heat or shearing force due to dispersion and re-aggregation hardly occurs.

  Regarding the degree of dispersion 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. When the particle size is 0.1 μm or more, various material powders including the positive electrode active material are preferably left without being excessively crushed during the preparation of the coating liquid. If the particle size is 100 μm or less, clogging during coating liquid discharge, generation of streaks in the coating film, and the like are reduced, 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 or more and 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. When the viscosity (ηb) 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 to a desired coating thickness or less is possible. .

  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 method for forming the coating film of the positive electrode precursor is not particularly limited, and a coating machine such as a die coater, a comma coater, a knife coater, or a gravure coating machine can be preferably used. The coating film may be formed by single layer coating or 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. If the coating speed is 100 m / min or less, sufficient coating accuracy can be secured.

  The method for drying the coating film of the positive electrode precursor is not particularly limited, and 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. The coating film may be dried by combining a plurality of drying methods. The drying temperature is preferably 25 ° C. or higher and 200 ° C. or lower, more preferably 40 ° C. or higher and 180 ° C. or lower, and further preferably 50 ° C. or higher and 160 ° C. or lower. When the drying temperature is 25 ° C. or higher, the solvent in the coating film can be sufficiently volatilized. When 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 method for pressing the positive electrode precursor is not particularly limited, and a press machine such as a hydraulic press machine or a vacuum press machine can be preferably used. The film thickness, bulk density, and electrode strength of the positive electrode active material layer can be adjusted by the press pressure, the gap, and the surface temperature of the press 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. When the pressing pressure is 20 kN / cm or less, the positive electrode precursor is less likely to bend or wrinkle, and can be adjusted to a desired positive electrode active material layer thickness or bulk density.

  If it is an expert, the clearance gap between press rolls can set arbitrary values according to the positive electrode precursor film thickness after drying so that it may become the film thickness and bulk density of a desired positive electrode active material layer. A person skilled in the art can set the press speed to an arbitrary speed at which the positive electrode precursor is not easily bent or wrinkled.

  The surface temperature of the press part may be room temperature, or the press part 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 the melting point minus 45 ° C. or more, and further preferably the melting point minus 30 ° C. or more. 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 still more 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 temperature of the press part is preferably 90 ° C. or higher and 200 ° C. or lower, more preferably 105 ° C. or higher and 180 ° C. or lower, and further preferably 120 ° C. It is not lower than 170 ° C. When a styrene-butadiene copolymer (melting point: 100 ° C.) is used as the binder, the surface temperature of the press part is preferably 40 ° C. or higher and 150 ° C. or lower, more preferably 55 ° C. or higher and 130 ° C. or lower, and still more preferably 70. It is at least 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.

  You may press several times, changing the conditions of a 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. If this film thickness is 200 μm or less, the ion diffusion resistance in the electrode can be kept low. As a result, sufficient output characteristics can be obtained, the cell volume can be reduced, and therefore 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. The film thickness of the positive electrode active material layer in the case where the current collector has through-holes or irregularities refers to the average value of the film thickness per one side of the current collector that does not have through-holes or irregularities.

[Positive electrode]
The bulk density of the positive electrode active material layer in the positive electrode after lithium doping is preferably 0.25 g / cm ³ or more, more preferably 0.30 g / cm ³ or more and 1.3 g / cm ³ or less. 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. 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 surfaces of the negative electrode current collector.

[Negative electrode active material layer]
The negative electrode active material layer includes a negative electrode active material capable of occluding and releasing lithium ions, and may include optional components such as a conductive filler, a binder, and a dispersion stabilizer in addition to the negative electrode active material. Good.

[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. The content of the carbon material with respect to the total mass of the negative electrode active material is preferably 50% by mass or more, more preferably 70% by mass or more, or 100% by mass. From the viewpoint of obtaining favorable effects due to the combined use of other materials, the content of the carbon material relative to the total mass of the negative electrode active material is, for example, preferably 90% by mass or less, and may be 80% by mass or less.

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 carbon materials include non-graphitizable carbon materials; graphitizable carbon materials; carbon blacks; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon microspheres; graphite whiskers; Amorphous carbonaceous materials; carbonaceous materials obtained by heat treating a carbonaceous material precursor; thermal decomposition products of furfuryl alcohol resin or novolac resin; fullerenes; carbon nanophones; and composite carbon materials thereof. . Examples of the carbonaceous material precursor include petroleum pitch, coal pitch, mesocarbon microbeads, coke, and synthetic resin (for example, phenol resin).

  Among these, from the viewpoint of lowering the resistance of the negative electrode, the base material and the carbonaceous material precursor are subjected to heat treatment in a state where at least one carbon material (hereinafter also referred to as a base material) and the carbonaceous material precursor coexist. A composite carbon material in which a carbonaceous material derived from the composite is combined is preferable. The carbonaceous material precursor is not particularly limited as long as it becomes a carbonaceous material by heat treatment, and 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 a carbonaceous material, preferably 400 ° C to 2500 ° C, more preferably 500 ° C to 2000 ° C. Hereinafter, it is more preferably 550 ° C. or higher and 1500 ° C. or lower. The atmosphere in which the heat treatment is performed is not particularly limited, and a non-oxidizing atmosphere is preferable.

  Preferred examples of the composite carbon material include 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 a composite carbon material using, as a base material, 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. 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. By being 1,500 m < ² > / g or less, since the charging / discharging efficiency of lithium ion improves, 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 to 200% by mass, more preferably 12% by mass to 180% by mass, and still more preferably 15% by mass to 160% by mass. Especially preferably, it is 18 mass% or more and 150 mass% or less. If the mass ratio of the carbonaceous material is 10% by mass or more, the micropores that the base material has can be appropriately filled with the carbonaceous material, and the charge / discharge efficiency of lithium ions is improved. It can show durability. 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, it is 620 mAh / g or more and 2,100 mAh / g or less, More preferably, it is 760 mAh / g or more and 1,700 mAh / g or less, Most preferably, it is 840 mAh / g or more and 1,500 mAh / g or less.

  Doping lithium ions lowers the negative electrode potential. Therefore, when the negative electrode containing the composite carbon material 1 doped with lithium ions is combined with the positive electrode, the voltage of the nonaqueous lithium storage element increases and the utilization capacity of the positive electrode increases. Therefore, the capacity and energy density of the obtained non-aqueous lithium storage element are increased.

  If 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 has a desired amount of lithium. The amount can be reduced. Therefore, the negative electrode film thickness 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. If the doping amount is 2,500 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal occur.

  As a preferred example of the composite carbon material 1, a composite carbon material 1a using activated carbon as a base material will be described.

The composite carbon material 1a has a mesopore amount derived from pores having a diameter of 20 to 500 mm calculated by the BJH method as V _m1 (cc / g), and a micropore derived from pores having a diameter of less than 20 mm calculated by the MP method. When the amount is V _m2 (cc / g), it is preferable that 0.010 ≦ V _m1 ≦ 0.300 and 0.001 ≦ V _m2 ≦ 0.650.

The mesopore amount V _m1 is more preferably 0.010 ≦ V _m1 ≦ 0.225, and further preferably 0.010 ≦ V _m1 ≦ 0.200. The micropore amount V _m2 is more preferably 0.001 ≦ V _m2 ≦ 0.200, further preferably 0.001 ≦ V _m2 ≦ 0.150, and particularly preferably 0.001 ≦ V _m2 ≦ 0.100. .

If the mesopore amount V _m1 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. As a result, the negative electrode can be thinned. When the micropore amount V _m2 is 0.650 cc / g or less, high charge / discharge efficiency for lithium ions can be maintained. If the mesopore volume V _m1 and the micropore volume V _m2 are equal to or higher than the lower limit (0.010 ≦ V _m1 , 0.001 ≦ V _m2 ), high input / output characteristics can be obtained.

The BET specific surface area of the composite carbon material 1a is preferably 100 m ² / g or more and 1,500 m ² / g or less, more preferably 150 m ² / g or more and 1,100 m ² / g or less, and further preferably 180 m ² / g or more and 550 m. 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. Since the doping amount of lithium ions can be increased, the negative electrode can be thinned. Since it is 1,500 m < ² > / g or less, since the charging / discharging efficiency of lithium ion improves, 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. From the viewpoint of high energy density, the average pore diameter is preferably 65 mm or less, and 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. 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 to 4.00 and the crystallite size in the c-axis direction obtained from the half width of this peak. Lc is preferably 8.0 to 20.0 Å, 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 11.0 Å. More preferably, it is 16.0 mm or less.

  There is no restriction | limiting in particular as activated carbon used as a base material of the 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. The average particle diameter of the activated carbon powder is preferably 1 μm or more and 15 μm or less, more preferably 2 μm or more and 10 μm or less.

  In order to obtain the composite carbon material 1a having the pore distribution range defined in the present embodiment, the pore distribution of the activated carbon used for the base material is important.

In activated carbon, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is V ₁ (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is used. When V ₂ (cc / g), 0.050 ≦ V ₁ ≦ 0.500, 0.005 ≦ V ₂ ≦ 1.000 and 0.2 ≦ V ₁ / V ₂ ≦ 20.0. It is preferable.

The meso Anaryou _{V 1,} more preferably _{0.050 ≦ V 1 ≦ 0.350, 0.100} ≦ V 1 ≦ 0.300 is more preferable. The micropore amount V ₂ is more preferably 0.005 ≦ V ₂ ≦ 0.850, and further preferably 0.100 ≦ V ₂ ≦ 0.800. The ratio of mesopore amount / micropore amount is more preferably 0.22 ≦ V ₁ / V ₂ ≦ 15.0, and further preferably 0.25 ≦ V ₁ / V ₂ ≦ 10.0. When the mesopore volume V _{1 of the} activated carbon is 0.500 or less and the micropore volume V ₂ is 1.000 or less, in order to obtain the pore structure of the composite carbon material 1a, an appropriate amount of carbonaceous material is coated. Since it is sufficient to wear it, it becomes easy to control the pore structure. When the mesopore volume V _{1 of the} activated carbon is 0.050 or more, when the micropore volume V ₂ is 0.005 or more, when V ₁ / V ₂ is 0.2 or more, and V ₁ / V ₂ The pore structure of the composite carbon material 1a can be easily obtained even when is 20.0 or less.

  The carbonaceous material precursor used as a raw material for the composite carbon material 1a is preferably an organic material that can be deposited on the activated carbon by being heat-treated, and that can be dissolved in a solid, liquid, or solvent. . 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 pitch is used, for example, the pitch is heat-treated in the presence of activated carbon, and the carbonaceous material is deposited on the activated carbon by thermally reacting the volatile component or pyrolyzed component of the pitch on the surface of the activated carbon. 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. . 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. The time for maintaining the peak temperature during the heat treatment is preferably 30 minutes to 10 hours, more preferably 1 hour to 7 hours, still more preferably 2 hours to 5 hours. For example, when the heat treatment is performed at a peak temperature of about 500 to 800 ° C. for 2 to 5 hours, the carbonaceous material deposited on the activated carbon surface is considered to be a polycyclic aromatic hydrocarbon.

  The softening point of the pitch 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 a hydrocarbon gas volatilized from a carbonaceous material precursor, and the carbonaceous material is deposited in a gas phase. A method is mentioned. 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 and then heat-treated is also possible.

  The mass ratio of the carbonaceous material to the activated carbon in the composite carbon material 1a is preferably 10% by mass 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 that the activated carbon has can be appropriately filled with the carbonaceous material, and the charge / discharge efficiency of lithium ions is improved. Less likely to be damaged. 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 maintained with a large specific surface area. 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 a composite carbon material using, as a base material, one or more carbon materials having a BET specific surface area of 0.5 m ² / g or more and 80 m ² / g or less. 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. If it is 50 m < ² > / g or less, since the charging / discharging efficiency of lithium ion will improve and the decomposition reaction of the nonaqueous electrolyte solution during charging / discharging will be 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. The average particle diameter is more preferably 2 μm or more and 8 μm or less, and further preferably 3 μm or more and 6 μm or less. 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. If it is 10 micrometers or less, since the reaction area of the composite carbon material 2 and a non-aqueous electrolyte solution will increase, a high input / output characteristic can be shown.

  The mass ratio of the carbonaceous material to the base material in the composite carbon material 2 is preferably 1% by mass or more and 30% by mass or less, more preferably 1.2% by mass or more and 25% by mass or less, and further preferably 1.5% by mass or more. It is 20 mass% or less. If the mass ratio of the carbonaceous material is 1% or more by mass, the carbonaceous material can sufficiently increase the reaction site with lithium ions and facilitates the desolvation of lithium ions. be able to. If the mass ratio of the carbonaceous material is 20% by mass or less, the diffusion of lithium ions between the carbonaceous material and the base material in the solid can be satisfactorily maintained, and thus high input / output characteristics can be exhibited. Since the charge / discharge efficiency of lithium ions can be improved, high cycle durability can be exhibited.

  The doping amount of lithium ions per unit mass of the composite carbon material 2 is preferably 50 mAh / g or more and 700 mAh / g or less, more preferably 70 mAh / g or more and 650 mAh / g or less, and further preferably 90 mAh / g or more and 600 mAh / g or less. Especially preferably, it is 100 mAh / g or more and 550 mAh / g or less.

  Doping lithium ions lowers the negative electrode potential. Therefore, when the negative electrode including the composite carbon material 2 doped with lithium ions is combined with the positive electrode, the voltage of the nonaqueous lithium storage element increases and the utilization capacity of the positive electrode increases. Therefore, the capacity and energy density of the obtained non-aqueous lithium storage element are increased.

  If the doping amount is 50 mAh / g or more, a high energy density can be obtained because lithium ions are well doped into irreversible sites that cannot be desorbed once the lithium ions in the composite carbon material 2 are inserted. The larger the doping amount, the lower the negative electrode potential, and the input / output characteristics, energy density, and durability are improved.

  If the doping amount is 700 mAh / g or less, there is little risk of side effects such as precipitation of lithium metal.

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

  The average particle diameter 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. If it is 10 micrometers or less, since the reaction area of the composite carbon material 2a and a non-aqueous electrolyte solution will increase, a high input / output characteristic can be shown.

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. If it is 20 m < ² > / g or less, since the charging / discharging efficiency of lithium ion will improve and the decomposition reaction of the non-aqueous electrolyte solution during charging / discharging will be suppressed, high cycle durability can be shown.

  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 preferably an organic material that can be combined with the graphite material by heat treatment and can be dissolved in a solid, liquid, or solvent. . 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, more preferably 1.2% by mass or more and 8% by mass or less, and further preferably 1.5% by mass or more. It is 6 mass% or less, Most preferably, it is 2 mass% or more and 5 mass% or less. If the mass ratio of the carbonaceous material is 1% by mass or more, the carbonaceous material can sufficiently increase the reaction sites with lithium ions, and the desolvation of lithium ions is facilitated, so that high input / output characteristics are exhibited. be able to. If the mass ratio of the carbonaceous material is 20% by mass or less, the diffusion of lithium ions in the solid between the carbonaceous material and the graphite material can be satisfactorily maintained, so that high input / output characteristics can be exhibited. Since the charge / discharge efficiency of lithium ions can be improved, high cycle durability can be exhibited.

[Optional component of negative electrode active material layer]
In addition to the negative electrode active material, the negative electrode active material layer in the present embodiment may include optional components such as a conductive filler, a binder, and a dispersion stabilizer 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 more than 0 parts by mass and less than 30 parts by mass, more preferably more than 0 parts by mass and less than 20 parts by mass, and even more preferably more than 0 parts by mass and more than 15 parts by mass with respect to 100 parts by mass of the negative electrode active material. Or less.

  The binder is not particularly limited. For example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, or the like may be used. it can. 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 still more preferably 3 parts by mass or more and 25 parts by mass with respect to 100 parts by mass of the negative electrode active material. Or less. When the amount of the binder is 1 part by mass or more, sufficient electrode strength is exhibited. 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.

  The dispersion stabilizer is not particularly limited, and for example, PVP (polyvinyl pyrrolidone), PVA (polyvinyl alcohol), cellulose derivatives and the like 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 in the present embodiment is preferably a metal foil that has high electron conductivity and is unlikely to 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 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, etching foil A metal foil having through-holes such as the like 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 negative electrode coating liquid, and this negative electrode coating liquid is applied to one or both surfaces on the 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 negative electrode coating solution is prepared by dry blending 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. Or you may adjust by adding a slurry-like substance. Alternatively, various material powders containing a negative electrode active material may be added to a liquid or slurry substance in which a binder or dispersion stabilizer is dissolved or dispersed in water or an organic solvent. The method for adjusting the negative electrode coating liquid is not particularly limited, and a disperser such as a homodisper, a multiaxial disperser, a planetary mixer, a thin film swirl type high-speed mixer, or the like can be preferably used. In order to obtain a negatively dispersed negative electrode coating liquid, 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. If it is 50 m / s or less, various materials are not easily destroyed by heat and shearing force due to dispersion, and reaggregation is unlikely to occur.

  The viscosity (ηb) of the negative electrode 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. 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 to a desired coating thickness or less can be achieved.

  The TI value (thixotropic index value) of the negative electrode 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 method for forming the negative electrode coating film is not particularly limited, and a coating machine such as a die coater, a comma coater, a knife coater, or a gravure coating machine can be preferably used. The coating film may be formed by single layer coating or may be formed by multilayer coating. The coating speed is preferably 0.1 m / min to 100 m / min, more preferably 0.5 m / min to 70 m / min, and further preferably 1 m / min to 50 m / min. If the coating speed is 0.1 m / min or more, stable coating can be achieved. If it is 100 m / min or less, sufficient coating accuracy can be secured.

  The method for drying the coating film is not particularly limited, and 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. A plurality of drying methods may be combined and dried. The drying temperature is preferably 25 ° C. or higher and 200 ° C. or lower, more preferably 40 ° C. or higher and 180 ° C. or lower, and further preferably 50 ° C. or higher and 160 ° C. or lower. When the drying temperature is 25 ° C. or higher, the solvent in the coating film can be sufficiently volatilized. 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.

  The method for pressing the negative electrode is not particularly limited, and 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. If it is 20 kN / cm or less, the negative electrode is less likely to bend and wrinkle, and can be adjusted to the desired negative electrode active material layer thickness and bulk density.

  A person skilled in the art can set an arbitrary value according to the thickness of the negative electrode after drying so that the gap between the press rolls has the desired thickness and bulk density of the negative electrode active material layer. A person skilled in the art can set the press speed to an arbitrary speed at which the negative electrode is not easily bent or wrinkled.

  The surface temperature of the press part may be room temperature or may be heated if necessary. The lower limit of the surface temperature of the 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. 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 still more preferably 20 ° C. or less. For example, when PVdF (polyvinylidene fluoride: melting point 150 ° C.) is used as the binder, the surface temperature of the press part is preferably 90 ° C. or higher and 200 ° C. or lower, more preferably 105 ° C. or higher and 180 ° C. or lower, and further preferably 120 ° C. It is not lower than 170 ° C. When a styrene-butadiene copolymer (melting point: 100 ° C.) is used as the binder, the surface temperature of the press part is preferably 40 ° C. or higher and 150 ° C. or lower, more preferably 55 ° C. or higher and 130 ° C. or lower, and still more preferably 70. It is at least 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.

  You may press several times, changing conditions of press pressure, a crevice, speed, and surface temperature of a press part.

  The film thickness of the negative electrode active material layer is preferably 5 μm or more and 100 μm or less per side, the lower limit is further preferably 7 μm or more, more preferably 10 μm or more, and the upper limit is further preferably 80 μm or less, more preferably. 60 μm or less. When the film thickness of the negative electrode active material layer is 5 μm or more per side, streaks or the like hardly occur when the negative electrode active material layer is applied, and the coating property is excellent. When the thickness of the negative electrode active material layer is 100 μm or less per side, a high energy density can be expressed by reducing the cell volume. The film thickness of the negative electrode active material layer in the case where the current collector has through holes or irregularities refers to the average value of the film thickness per one side of the portion of the current collector that does not have through holes or irregularities.

The bulk density of the negative electrode active material layer is preferably 0.30 g / cm ³ or more and 1.8 g / cm ³ or less, more preferably 0.40 g / cm ³ or more and 1.5 g / cm ³ or less, and 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. If it is 1.8 g / cm ³ or less, vacancies capable of sufficiently diffusing ions in the negative electrode active material layer can be secured.

<Compound in positive electrode active material layer and negative electrode active material layer>
[Compound in positive electrode active material layer]
In this embodiment, the positive electrode active material layer contains at least one compound selected from the group consisting of the following formulas (1) to (3) at 1.60 × 10 ⁻⁴ mol per unit mass of the positive electrode active material layer. / G to 300 × 10 ⁻⁴ mol / g is preferable.

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

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

｛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、Ｘ^１、Ｘ^２はそれぞれ独立に−（ＣＯＯ）_ｎ（ここで、ｎは０又は１である。）である。｝

{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} represents 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 each independently-(COO) _n (where n is 0 or 1). }

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

{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 hydrogen and 1 to 10 carbon atoms. An alkyl group, 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, X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1); }

Particularly preferred compounds as the compound of formula (1) are LiOC ₂ H ₄ OLi, LiOC ₃ H ₆ OLi, LiOC ₂ H ₄ OCOOLi, LiOCOOC ₃ H ₆ OLi, LiOCOOC ₂ H ₄ OCOOLi, and LiOCOOC ₃ H ₆ OCOOLi. The compound which is made is mentioned.

Particularly preferred compounds as the compound of formula (2) are LiOC ₂ H ₄ OH, LiOC ₃ H ₆ OH, LiOC ₂ H ₄ OCOOH, LiOC ₃ H ₆ OCOOH, LiOCOOC ₂ H ₄ OCOOH, LiOCOOC ₃ H ₆ OCOOH, LiOC _{2. H 4 OCH 3, LiOC 3 H} 6 OCH 3, LiOC 2 H 4 OCOOCH 3, LiOC 3 H 6 OCOOCH 3, LiOCOOC 2 H 4 OCOOCH 3, LiOCOOC 3 H 6 OCOOCH 3, LiOC 2 H 4 OC 2 H 5, LiOC ₃ H ₆ OC ₂ H ₅ , LiOC ₂ H ₄ OCOOC ₂ H ₅ , LiOC ₃ H ₆ OCOOC ₂ H ₅ , LiOCOOC ₂ H ₄ OCOOC ₂ H ₅ and a compound represented by LiOCOOC ₃ H ₆ OCOOC ₂ H ₅ All It is.

Particularly preferred compounds as the compound of formula (3) are HOC ₂ H ₄ OH, HOC ₃ H ₆ OH, HOC ₂ H ₄ OCOOH, HOC ₃ H ₆ OCOOH, HOCOOC ₂ H ₄ OCOOH, HOCOOC ₃ H ₆ OCOOH, HOC _{2 H 4 OCH 3, HOC 3 H} 6 OCH 3, HOC 2 H 4 OCOOCH 3, HOC 3 H 6 OCOOCH 3, HOCOOC 2 H 4 OCOOCH 3, HOCOOC 3 H 6 OCOOCH 3, HOC 2 H 4 OC 2 H 5, HOC ₃ H ₆ OC ₂ H ₅ , HOC ₂ H ₄ OCOOC ₂ H ₅ , HOC ₃ H ₆ OCOOC ₂ H ₅ , HOCOOC ₂ H ₄ OCOOC ₂ H ₅ , HOCOOC ₃ H ₆ OCOOC ₂ H ₅ , CH ₃ OC ₂ H _{4 OCH 3, CH 3 OC 3 H} 6 OCH _{, CH 3 OC 2 H 4 OCOOCH} 3, CH 3 OC 3 H 6 OCOOCH 3, CH 3 OCOOC 2 H 4 OCOOCH 3, CH 3 OCOOC 3 H 6 OCOOCH 3, CH 3 OC 2 H 4 OC 2 H 5, CH 3 OC ₃ H ₆ OC ₂ H ₅ , CH ₃ OC ₂ H ₄ OCOOC ₂ H ₅ , CH ₃ OC ₃ H ₆ OCOOC ₂ H ₅ , CH ₃ OCOOC ₂ H ₄ OCOOC ₂ H ₅ , CH ₃ OCOOC ₃ H ₆ OCOOC _{2 H 5, C 2 H 5 OC} 2 H 4 OC 2 H 5, C 2 H 5 OC 3 H 6 OC 2 H 5, C 2 H 5 OC 2 H 4 OCOOC 2 H 5, C 2 H 5 OC 3 H 6 OCOOC ₂ H ₅ , C ₂ H ₅ OCOOC ₂ H ₄ OCOOC ₂ H ₅ , and C ₂ H ₅ OCOOC ₃ H ₆ OCOOC _And a compound represented by ₂ H ₅ .

The total amount of the above compounds in the positive electrode active material layer is preferably 1.60 × 10 ⁻⁴ mol / g or more, and 5.0 × 10 ⁻⁴ mol / g or more per unit mass of the positive electrode active material. Is more preferable. When the total amount of the above compounds in the positive electrode active material layer is 1.60 × 10 ⁻⁴ mol / g or more per unit mass of the positive electrode active material layer, the non-aqueous electrolyte solution is less likely to come into contact with the positive electrode active material, and non-aqueous electrolysis It is possible to suppress generation of gas due to oxidative decomposition of the liquid.

The total amount of the compound in the positive electrode active material layer is 300 × 10 ⁻⁴ mol / g or less, more preferably 150 × 10 ⁻⁴ mol / g or less, and 100 × 10 ⁴ per unit mass of the positive electrode active material. More preferably, it is ^-4 mol / g or less. When the total amount of the compound is 300 × 10 ⁻⁴ mol / g or less per unit mass of the positive electrode active material, the diffusion of Li ions is hardly inhibited and high input / output characteristics can be exhibited.

[Compound in negative electrode active material layer]
In the present embodiment, the negative electrode active material layer contains at least one compound selected from the group consisting of the above formulas (1) to (3) at 0.50 × 10 ⁻⁴ mol per unit mass of the negative electrode active material layer. / G to 120 × 10 ⁻⁴ mol / g is preferable. Since the compounds of formulas (1) to (3) have been described above, the description thereof is omitted here.

The total amount of the compounds in the negative electrode active material layer is preferably 0.50 × 10 ⁻⁴ mol / g or more per unit mass of the negative electrode active material layer, and is 1.0 × 10 ⁻⁴ mol / g or more. Is more preferable. When the total amount of the above compounds in the negative electrode active material layer is 0.50 × 10 ⁻⁴ mol / g or more per unit mass of the negative electrode active material layer, the non-aqueous electrolyte solution is less likely to come into contact with the negative electrode active material, and non-aqueous electrolysis It is possible to suppress generation of gas due to reductive decomposition of the liquid.

The total amount of the compound in the negative electrode active material layer is preferably 120 × 10 ⁻⁴ mol / g or less per unit mass of the negative electrode active material layer, more preferably 100 × 10 ⁻⁴ mol / g or less, More preferably, it is 80 × 10 ⁻⁴ mol / g or less. When the total amount of the above compounds in the negative electrode active material layer is 120 × 10 ⁻⁴ mol / g or less per unit mass of the negative electrode active material layer, the diffusion of Li ions at the negative electrode interface is hardly inhibited, and high input / output characteristics Can be expressed.

[Quantity ratio of compound in positive electrode active material layer to compound in negative electrode active material layer (A / B)]
When the content per unit mass of the positive electrode active material layer of the compound in the positive electrode active material layer is A, and the content per unit mass of the negative electrode active material layer of the compound in the positive electrode active material layer is B, The ratio A / B is preferably 0.2 or more and 20 or less, more preferably 0.8 or more and 15 or less, and still more preferably 1.2 or more and 12 or less. When A / B is 0.2 or more, it is possible to suppress the nonaqueous electrolyte from oxidizing and decomposing at the positive electrode interface, and to inhibit the diffusion of Li ions at the negative electrode interface. When A / B is 20 or less, it is possible to suppress the non-aqueous electrolyte from reducing and decomposing at the negative electrode interface to generate gas, and the diffusion of Li ions at the positive electrode interface is hardly inhibited. Therefore, when A / B is 0.2 or more and 20 or less, it is possible to achieve both high temperature durability and high input / output characteristics over a wide range of temperatures.

[Method for introducing compound in positive electrode active material layer and negative electrode active material layer]
In the present embodiment, as a method for containing at least one compound selected from the group consisting of the above formulas (1) to (3) in the positive electrode active material layer, for example,
A method of mixing the above compound in the positive electrode active material layer,
A method of adsorbing the compound to the positive electrode active material layer;
Examples thereof include a method of electrochemically depositing the above compound on the positive electrode active material layer.

  Among them, a precursor that can be decomposed to produce the above-mentioned compounds is contained in the non-aqueous electrolyte solution, and the precursor is decomposed when producing the non-aqueous lithium ion storage element, so that the positive electrode active material layer A method of depositing the above compound therein is preferred.

In this embodiment, as a method for containing in the negative electrode active material layer at least one compound selected from the group consisting of the above formulas (1) to (3), for example,
A method of mixing the above compound in the negative electrode active material layer,
A method of adsorbing the compound to the negative electrode active material layer;
Examples thereof include a method of electrochemically depositing the above compound on the negative electrode active material layer.

  Among them, a precursor that can be decomposed to produce the above-mentioned compounds is contained in the non-aqueous electrolyte solution, and the precursor is decomposed when the non-aqueous lithium ion storage element is produced. A method of depositing the above compound therein is preferred.

  As the precursor for forming the compounds of the formulas (1) to (3), it is preferable to use at least one organic solvent selected from ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and fluoroethylene carbonate, More preferably, ethylene carbonate and propylene carbonate are used.

<Electrolyte>
In the present embodiment, the electrolytic solution is a non-aqueous electrolytic 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. When the lithium salt concentration is 2.0 mol / L or less, it is possible to prevent undissolved lithium salt from precipitating in the non-aqueous electrolyte solution and the viscosity of the electrolyte solution from becoming too high, and the conductivity does not decrease. This is preferable because the output characteristics do not deteriorate.

The non-aqueous electrolyte preferably contains LiN (SO ₂ F) ₂ at 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. If this value is 1.5 mol / L or less, precipitation of the electrolyte salt can be reduced during charging and discharging, and an increase in the viscosity of the electrolytic solution can be suppressed even after a long period.

[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. As the cyclic carbonate, for example, at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, and fluoroethylene carbonate is preferable.

  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 mass of the nonaqueous electrolytic solution. If the total content of the cyclic carbonate is 15% by mass or more, a lithium salt having a desired concentration can be dissolved, and high lithium ion conductivity can be expressed. In addition, an appropriate amount of a lithium compound can be deposited on the positive electrode active material layer, and oxidative decomposition of the electrolytic solution can be suppressed.

  The nonaqueous electrolytic solution of the present embodiment preferably contains a chain carbonate as a nonaqueous 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, based on the total mass of the nonaqueous electrolytic solution. It is as follows. When the content of the chain carbonate is 30% by mass or more, the viscosity of the electrolytic solution can be reduced, and high lithium ion conductivity can be expressed. When the content of the chain carbonate is 95% by mass or less, the electrolytic solution can further contain an additive described later.

[Additive]
The nonaqueous electrolytic solution may further contain an additive. Although it does not restrict | limit especially as an additive, For example, it selects from the group which consists of a sultone compound, cyclic phosphazene, acyclic fluorine-containing ether, fluorine-containing cyclic carbonate, cyclic carbonate, cyclic carboxylic acid ester, and cyclic acid anhydride. There is at least one kind. These additives can be used individually by 1 type, and may mix and use 2 or more types.

(Sultone compound)
Examples of the sultone compounds include sultone compounds represented by the following general formulas (5) to (7). These sultone compounds may be used alone or in combination of two or more.

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

{In Formula (5), R ^{11 to} R ¹⁶ represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or a halogenated alkyl group having 1 to 12 carbon atoms. And n is an integer from 0 to 3. }

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

{In Formula (6), R ^{11 to} R ¹⁴ represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or a halogenated alkyl group having 1 to 12 carbon atoms, and they may be the same or different from each other. And n is an integer from 0 to 3. }

｛式（７）中、Ｒ^１１〜Ｒ^１６は、水素原子、ハロゲン原子、炭素数１〜１２のアルキル基、又は炭素数１〜１２のハロゲン化アルキル基を表し、互いに同一であっても異なっていてもよい。｝

{In Formula (7), R ^{11 to} R ¹⁶ represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or a halogenated alkyl group having 1 to 12 carbon atoms, and they may be the same or different from each other. It may be. }

  As a sultone compound represented by the general formula (5), 1,3-propane is used from the viewpoint of less adverse effects on resistance and the suppression of gas generation by suppressing decomposition of the non-aqueous electrolyte at high temperature. Sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-butane sultone, or 2,4-pentane sultone is preferred. As the sultone compound represented by the general formula (6), 1,3-propene sultone or 1,4-butene sultone is preferable. As the sultone compound represented by the general formula (7), 1,5,2,4-dioxadithiepan 2,2,4,4-tetraoxide is preferable. Other sultone compounds include methylene bis (benzene sulfonic acid), methylene bis (phenylmethane sulfonic acid), methylene bis (ethane sulfonic acid), methylene bis (2,4,6, trimethylbenzene sulfonic acid), and methylene bis (2-trifluoro). Methylbenzenesulfonic acid). It is preferable to use at least one selected from these sultone compounds.

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

(Cyclic phosphazene)
As the cyclic phosphazene, for example, at least one selected from the group consisting of ethoxypentafluorocyclotriphosphazene, diethoxytetrafluorocyclotriphosphazene, and phenoxypentafluorocyclotriphosphazene is preferable.

  The content of cyclic phosphazene in the non-aqueous electrolyte is preferably 0.5% by mass or more and 20% by mass or less based on the total mass of the non-aqueous electrolyte. When this value is 0.5% by weight or more, it is possible to suppress gas generation by suppressing decomposition of the electrolytic solution at a high temperature. When this value is 20% by mass or less, it is possible to suppress a decrease in the ionic conductivity of the electrolytic solution, and it is possible to maintain high input / output characteristics. The content of cyclic phosphazene is more preferably 2% by mass or more and 15% by mass or less, and further preferably 4% by mass or more and 12% by mass or less. In addition, these cyclic phosphazenes may be used individually by 1 type, or may mix and use 2 or more types.

(Non-cyclic fluorine-containing ether)
Examples of the acyclic fluorine-containing ether include HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H, CF ₃ CFHCF ₂ OCH ₂ CF ₂ CF ₂ H, HCF ₂ CF ₂ CH ₂ OCH ₂ CF ₂ CF ₂ H, and CF ₃ CFHCF ₂ OCH ₂ CF ₂ CFHCF _{3 and the} like. Among them, HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H is preferable from the viewpoint of electrochemical stability.

  The content of the non-cyclic fluorine-containing ether is preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass or less, based on the total mass of the non-aqueous electrolyte solution. When the content of the non-cyclic fluorine-containing ether is 0.5% by mass or more, the stability of the non-aqueous electrolyte solution against oxidative decomposition is improved, and an electricity storage device having high durability at high temperatures can be obtained. If the content of the non-cyclic fluorine-containing ether is 15% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte can be kept high. It becomes possible to express characteristics. In addition, acyclic fluorine-containing ether may be used individually or may be used in mixture of 2 or more types.

(Fluorine-containing cyclic carbonate)
As the fluorine-containing cyclic carbonate, at least one selected from the group consisting of fluoroethylene carbonate (FEC) and difluoroethylene carbonate (dFEC) is preferably used from the viewpoint of compatibility with other non-aqueous solvents.

  The content of the cyclic carbonate containing a fluorine atom is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 5% by mass or less, based on the total mass of the nonaqueous electrolytic solution. . If the content of the cyclic carbonate containing a fluorine atom is 0.5% by mass or more, a good-quality film can be formed on the negative electrode, and by suppressing the reductive decomposition of the electrolytic solution on the negative electrode, A highly durable power storage element can be obtained. If the content of the cyclic carbonate containing a fluorine atom is 10% by mass or less, the solubility of the electrolyte salt can be maintained well, and the ionic conductivity of the non-aqueous electrolyte can be maintained high. It is possible to develop input / output characteristics. In addition, the cyclic carbonate containing said fluorine atom may be used individually by 1 type, or may mix and use 2 or more types.

(Cyclic carbonate)
As the cyclic carbonate, vinylene carbonate is preferable.

  The content of the cyclic carbonate is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 5% by mass or less, based on the total mass of the nonaqueous electrolytic solution. If the content of the cyclic carbonate is 0.5% by mass or more, a good-quality film on the negative electrode can be formed, and by suppressing the reductive decomposition of the electrolyte solution on the negative electrode, durability at high temperatures can be achieved. A high power storage element can be obtained. If the content of the cyclic carbonate is 10% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte can be kept high. It becomes possible to express.

(Cyclic carboxylic acid ester)
As the cyclic carboxylic acid ester, for example, it is preferable to use at least one selected from the group consisting of gamma butyrolactone, gamma valerolactone, gamma caprolactone, and epsilon caprolactone. Among these, gamma butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

  The content of the cyclic carboxylic acid ester is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total mass of the nonaqueous electrolytic solution. If the content of the cyclic acid anhydride is 0.5% by mass or more, a high-quality film on the negative electrode can be formed, and by suppressing reductive decomposition of the electrolytic solution on the negative electrode, durability at high temperatures Can be obtained. If the content of the cyclic carboxylic acid ester is 5% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte can be kept high. Can be expressed. In addition, said cyclic carboxylic acid ester may be used individually, or 2 or more types may be mixed and used for it.

(Cyclic acid anhydride)
The cyclic acid anhydride is preferably at least one selected from succinic anhydride, maleic anhydride, citraconic anhydride, and itaconic anhydride. Above all, at least one selected from the group consisting of succinic anhydride and maleic anhydride from the viewpoint that the production cost of the electrolytic solution is suppressed due to industrial availability, the solubility in the non-aqueous electrolytic solution, etc. Is preferred.

  The content of the cyclic acid anhydride is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total mass of the nonaqueous electrolytic solution. If the content of the cyclic acid anhydride is 0.5% by mass or more, a high-quality film can be formed on the negative electrode, and by suppressing the reductive decomposition of the electrolyte solution on the negative electrode, durability at high temperatures can be achieved. A high power storage element can be obtained. If the content of the cyclic acid anhydride is 10% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte can be kept high. It becomes possible to express. In addition, said cyclic acid anhydride may be used individually, or 2 or more types may be mixed and used for it.

<Separator>
In general, a separator plays a role of insulating a positive electrode body and a negative electrode body so that they are not in direct electrical contact, and holding an electrolytic solution in an internal space to form a lithium ion conduction path between the electrodes. Bear.

  In the present embodiment, the separator includes a porous film and an insulating porous layer formed on at least one side of the porous film. In the present embodiment, by providing an insulating porous layer on the separator, it is possible to suppress a temperature rise of the non-aqueous lithium electricity storage element at the time of an internal short circuit, suppress gasification, smoke generation, and ignition, and reduce resistance ( That is, a high output density) can be achieved.

  For example, as shown to Fig.1 (a), a separator can contain the insulating porous layer (2) formed in the single side | surface of the porous membrane (1) and the porous membrane (1) in one Embodiment.

  Alternatively, as shown in FIG. 1B, in another embodiment, the separator includes a porous membrane (1) and a plurality of insulating porous layers (2) formed on both surfaces of the porous membrane (1). Can do.

  In the separator, the ratio of the thickness of the insulating porous layer to the thickness of the porous film is 20% to 125%. When the ratio of the thickness of the insulating porous layer to the thickness of the porous film is 20% or more, a temperature increase of the nonaqueous lithium storage element can be sufficiently suppressed at the time of an internal short circuit, and is preferably 125% or less. It is preferable because a large increase in ion diffusion resistance can be suppressed and sufficient output characteristics can be exhibited.

  The total thickness of the separator may be 8 μm or more and 65 μm or less.

  The separator is a multilayer type including a porous film and an insulating porous layer, and is more preferably a two-layer separator composed of one porous film and one insulating porous layer.

  Hereinafter, the porous film and the insulating porous layer, which are constituent elements of the separator, will be described.

[Porous membrane]
The material of the porous film is not particularly limited, and examples thereof include a porous film formed of a polyolefin represented by polyethylene (PE) and polypropylene (PP), a porous film formed of cellulose, and the like. From the viewpoint of exhibiting good shutdown characteristics when a non-aqueous lithium-type energy storage device undergoes thermal runaway, in particular, a porous film formed of polyolefin (hereinafter also referred to as “polyolefin microporous film” in the present specification). ) Is preferred.

  In the present embodiment, the thickness of the porous film is preferably 5 μm or more and 35 μm or less. When the thickness of the porous film is 5 μm or more, it is preferable because it can suppress a fine short circuit of the non-aqueous lithium storage element and can be sufficiently impregnated with the electrolytic solution. This is preferable because the high output density of the non-aqueous lithium storage element can be expressed. The thickness of the porous film is more preferably 20 μm or less.

  In the present embodiment, the porosity of the porous film is preferably 45% to 75%. A porosity of 45% or more is preferable from the viewpoint of being able to follow the rapid movement of lithium ions at a high rate when the porous film is used as a part of the separator. If the porosity is 75% or less, it is preferable from the viewpoint of improving the film strength, and it is preferable from the viewpoint of suppressing self-discharge when the porous film is used as a part of the separator. The porosity is measured according to the method described in the examples described later.

The pore diameter of the porous membrane is preferably 0.03 μm to 0.1 μm, and the number of pores is preferably 100 to 250 / μm ² . If the pore diameter is 0.03 μm or more, ions can be sufficiently diffused, and if it is 0.1 μm or less, the roughness of the film surface can be reduced, so that a short circuit due to the electrode biting into the separator can be prevented. it can. When the number of pores is 100 / μm ² or more, there can be sufficient voids for ions to diffuse, and when the number is 250 / μm ² or less, the strength of the film can be maintained. The hole diameter and the number of holes are measured according to the method described in the examples described later.

  In the present embodiment, when a polyolefin microporous membrane is used as the porous membrane, the polyolefin preferably contains polyethylene. The polyolefin may be composed of one kind of polyethylene, or may be a polyolefin composition containing two or more kinds of polyolefin.

  Examples of the polyolefin include polyethylene, polypropylene, and poly-4-methyl-1-pentene. These may be used alone or in a mixture of two or more. Hereinafter, polyethylene may be abbreviated as “PE” and polypropylene may be abbreviated as “PP”.

  The viscosity average molecular weight (Mv) of polyolefin is preferably 50,000 to 3,000,000, more preferably 150,000 to 2,000,000. When the viscosity average molecular weight is 50,000 or more, a high-strength microporous film tends to be obtained, and when the viscosity average molecular weight is 3 million or less, an effect of facilitating extrusion can be obtained.

  The melting point of the polyolefin is preferably 100 ° C to 165 ° C, more preferably 110 ° C to 140 ° C. When the melting point is 100 ° C. or higher, the function in a high temperature environment tends to be stable, and when the melting point is 165 ° C. or lower, a meltdown occurs at a high temperature or a fuse effect tends to be obtained. The melting point means the temperature of the melting peak in differential scanning calorimetry (DSC) measurement. When the polyolefin is a mixture of two or more, the melting point of the polyolefin means the temperature of the peak having the largest melting peak area in the DSC measurement of the mixture.

  As the polyolefin, it is preferable to use high-density polyethylene from the viewpoint that heat fixation can be performed at a higher temperature while suppressing clogging of the pores.

  The ratio of the high density polyethylene contained in the polyolefin is preferably 5% by mass or more, more preferably 10% by mass or more, based on the total mass of the polyolefin. When the ratio is 5% by mass or more, heat fixation can be performed at a higher temperature while further suppressing the blockage of the holes. The proportion of the high density polyethylene contained in the polyolefin is preferably 99% by mass or less, more preferably 95% by mass or less, based on the total mass of the polyolefin. When the ratio of the high density polyethylene is 50% by mass or less, the polyethylene microporous membrane can have not only the effect of the high density polyethylene but also the effect of other polyolefins in a well-balanced manner.

  As the polyolefin, the viscosity average molecular weight (Mv) is 100,000 or more from the viewpoint of improving the shutdown characteristics when the microporous membrane is used as a separator of a non-aqueous lithium storage element or improving the safety of the nail penetration test. It is preferable to use 300,000 polyethylene.

  The ratio of polyethylene having a viscosity average molecular weight of 100,000 to 300,000 contained in the polyolefin is preferably 30% by mass or more, more preferably 45% by mass or more, based on the total mass of the polyolefin. When the ratio of polyethylene having a viscosity average molecular weight of 100,000 to 300,000 is 30% by mass or more, shutdown characteristics are improved, or safety of a nail penetration test tends to be improved, which is preferable. The ratio of the polyethylene having a viscosity average molecular weight of 100,000 to 300,000 contained in the polyolefin is preferably 100% by mass or less, more preferably 95% by mass or less, based on the total mass of the polyolefin.

  Polypropylene may be added and used as the polyolefin from the viewpoint of controlling the meltdown temperature.

  The proportion of polypropylene contained in the polyolefin is preferably 5% by mass or more, more preferably 8% by mass or more, based on the total mass of the polyolefin. If the proportion of polypropylene is 5% by mass or more, it is preferable from the viewpoint of improving the film resistance at high temperatures. The proportion of polypropylene contained in the polyolefin is preferably 20% by mass or less, more preferably 18% by mass or less. If the proportion of polypropylene is 20% by mass or less, the microporous membrane is preferable from the viewpoint of realizing a microporous membrane having not only the effect of polypropylene but also the effect of other polyolefins in a well-balanced manner.

[Insulating porous layer]
In the present specification, the insulating porous layer refers to a porous layer having electrical insulation.
The insulating porous layer only needs to be formed on at least one surface of the porous film.

  In the present embodiment, the insulating porous layer preferably includes insulating particles, and more preferably includes an inorganic filler and a resin binder.

  In the present embodiment, the thickness of the insulating porous layer is preferably 3 μm or more and 30 μm or less. When the thickness of the insulating porous layer is 3 μm or more, it is preferable that the temperature rise of the nonaqueous lithium storage element can be suppressed during internal short circuit, and gasification, smoke generation, and ignition can be more effectively suppressed. The following is preferable because an increase in ion diffusion resistance can be suppressed and a high output density can be expressed.

  The method for measuring the thickness of the porous film and the thickness of the insulating porous layer is not particularly limited, and examples thereof include measurement by a commercially available microthickness meter and a method of observing the cross section of the separator with a scanning electron microscope (cross section SEM). It is done.

In the case of measurement using a microthickness meter, the ambient temperature is measured at 23 ± 2 ° C. In the present embodiment, since a separator in which a porous film and an insulating porous layer are laminated is used, as a method for measuring each thickness, for example, first, the total thickness of the separator including each layer is measured, and then insulation is performed. The thickness of only the porous film can be measured by removing the porous layer, and the thickness of the insulating porous layer can be determined from the difference. For example, in the case of a separator having a two-layer structure in which an insulating porous layer is laminated on one side with a single porous film, the total thickness of the separator is t _all , the thickness of the porous film is t _s , and the thickness of the insulating porous layer is t _{i. When,} as represented by _{t i =} t all -t _s. Even when the separator is a multilayer film of three or more layers, the thickness of each layer can be measured from the difference by removing each layer and measuring the thickness each time.

  As a method of peeling the porous film and the insulating porous layer, there is a method of attaching a commercially available cellophane tape to the surface of the insulating porous layer, transferring the insulating porous layer to the adhesive layer of the cellophane tape, and peeling it.

Examples of the inorganic filler include oxide ceramics such as alumina (Al ₂ O ₃ ), silica (SiO ₂ , silicon oxide), titania, zirconia, magnesia, ceria, yttria, zinc oxide and iron oxide; silicon nitride, Nitride ceramics such as titanium nitride and boron nitride; silicon carbide, boehmite (AlOOH), calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay (Al ₂ O ₃ .nSiO ₂ etc.), Kaori Ceramics such as knight, halloysite, pyrophyllite, montmorillonite, sericite, mica, amicite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and quartz sand; glass fiber.

  The average particle size of the inorganic filler is preferably more than 0.1 μm and not more than 4.0 μm, more preferably more than 0.2 μm and not more than 3.5 μm, more than 0.4 μm and 3.0 μm. More preferably, it is as follows. When the average particle size of the inorganic filler is larger than 0.1 μm, it is preferable because an increase in ion diffusion resistance can be suppressed and a high output density is easily expressed. If the average particle diameter of the inorganic filler is 4.0 μm or less, it is preferable because the temperature rise of the nonaqueous lithium storage element can be suppressed and gasification, smoke generation, and ignition can be more easily suppressed during an internal short circuit. Examples of the method for adjusting the ratio of the particle diameter include a method of pulverizing the inorganic filler using a ball mill, a bead mill, a jet mill or the like to reduce the particle diameter.

  The identification method of the inorganic filler is not particularly limited. For example, powder X-ray diffraction measurement, elemental mapping by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS), etc. In order to improve the accuracy of analysis, it is preferable to identify a plurality of these in combination.

  The ratio of the insulating particles contained in the insulating porous layer can be appropriately determined from the viewpoints of the binding properties of the inorganic filler, the ion diffusion resistance of the multilayer porous film, the heat resistance, and the like, and preferably 50% by mass or more and 100% by mass. %, More preferably 70 mass% or more and 99.99 mass% or less, further preferably 80 mass% or more and 99.9 mass% or less, particularly preferably 90 mass% or more and 99 mass% or less.

  As the resin binder, it is preferable that an inorganic filler can be bound, it is insoluble in the electrolyte solution of the lithium ion secondary battery, and it is electrochemically stable within the use range of the lithium ion secondary battery.

  Examples of such resin binders include polyolefins such as polyethylene and polypropylene, fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, and ethylene-tetrafluoro. Fluorine-containing rubber such as ethylene copolymer, styrene-butadiene copolymer and its hydride, acrylonitrile-butadiene copolymer and its hydride, acrylonitrile-butadiene-styrene copolymer and its hydride, methacrylate ester-acrylic Acid ester copolymer, styrene-acrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer, ethylene propylene rubber, polyvinyl alcohol, polyvinyl acetate, etc. Rubbers, polyphenylene ether, polysulfone, polyether sulfone, polyphenylene sulfide, polyetherimide, polyamideimide, polyamide, melting point and / or glass transition temperature of such polyesters are 180 ° C. or more resins. These can be used alone or in combination of two or more.

  As the resin binder, a resin latex binder is preferable. When a resin latex binder is used, when a porous layer containing an inorganic filler and a binder is laminated on at least one surface of the porous film, the ion permeability is unlikely to decrease and high output characteristics are easily obtained. In addition, even when the temperature rise during abnormal heat generation is fast, a smooth shutdown is shown and high safety is easily obtained. When a resin latex binder is used, after part or all of the resin binder is dissolved in a solvent, it is laminated on at least one side of the porous membrane, and the resin binder is bound by immersing in a poor solvent or removing the solvent by drying. Compared with the case of making it, it is easy to obtain a high output characteristic, and it is easy to show a smooth shutdown characteristic, and there exists a tendency which is more excellent in safety.

  The average particle size of the resin binder in the present embodiment is preferably 50 to 500 nm, more preferably 60 to 460 nm, and still more preferably 80 to 250 nm. When the average particle diameter of the resin binder is 50 nm or more, when a porous layer containing an inorganic filler and a binder is laminated on at least one surface of the porous film, the ion permeability is hardly lowered and high output characteristics are easily obtained. In addition, even when the temperature rise during abnormal heat generation is fast, a smooth shutdown is shown and high safety is easily obtained. When the average particle size of the resin binder is 500 nm or less, good binding properties are expressed, and when a multilayer porous film is formed, heat shrinkage tends to be good and the safety tends to be excellent.

  The average particle size of the resin binder can be controlled by adjusting the polymerization time, polymerization temperature, raw material composition ratio, raw material charging order, pH and the like.

[Manufacturing method of separator]
The manufacturing method of the separator in this embodiment is illustrated exemplarily. However, it is possible to obtain a separator that includes a porous film and an insulating porous layer formed on at least one surface of the porous film, and the ratio of the thickness of the insulating porous layer to the thickness of the porous film is 20% to 125%. As long as the method for producing the separator is not limited to the type of polymer, the type of insulating particles, the type of solvent, the extrusion method, the stretching method, the extraction method, the opening method, the heat setting and the heat treatment method.

  From the viewpoint of appropriately controlling the balance between physical properties of permeability and membrane strength, the separator is produced by melting and kneading a polymer and a plasticizer or by melting and kneading a polymer, a plasticizer and a filler; Preferably; extracting a plasticizer (and filler if necessary); and heat setting.

More specifically, the separator manufacturing method can include, for example, the following operations (1) to (4).
(1) A polyolefin, a plasticizer, and a filler as necessary are kneaded to obtain a kneaded product.
(2) The obtained kneaded product is extruded, formed into a single-layered or multi-layered sheet shape, and cooled and solidified to obtain a sheet (hereinafter also referred to as “sheet-shaped formed body”).
(3) From the obtained sheet (sheet-like molded article), a plasticizer and / or filler is extracted as necessary, and the sheet (sheet-like molded article) is further stretched in a uniaxial direction or more to obtain a stretched sheet. To get.
(4) From the obtained stretched sheet, a plasticizer and / or filler is extracted as necessary, and further subjected to heat treatment to obtain a polyolefin microporous film.
(5) Applying a mixture containing insulating particles and a resin binder to at least one surface of the obtained polyolefin microporous membrane to obtain a separator.

  As polyolefin used by operation of (1), polyolefin explained above can be used. The polyolefin may be composed of one kind of polyethylene, or may be a polyolefin composition containing a plurality of kinds of polyolefins.

  The plasticizer used in the operation (1) may be those conventionally used for polyolefin microporous membranes, and may be abbreviated as, for example, dioctyl phthalate (hereinafter “DOP”). ), Phthalic acid esters such as diheptyl phthalate and dibutyl phthalate; organic acid esters other than phthalic acid esters such as adipic acid ester and glyceric acid ester; phosphoric acid esters such as trioctyl phosphate; liquid paraffin; solid wax; Mineral oil is mentioned. These may be used individually by 1 type, or may be used in combination of 2 or more type. Among these, liquid paraffin and phthalate are particularly preferable in consideration of compatibility with polyethylene.

  In the operation (1), a polyolefin and a plasticizer may be kneaded to form a kneaded product, or a polyolefin, a plasticizer, and a filler may be kneaded to form a kneaded product. As the filler used in the latter case, at least one of organic fine particles and inorganic fine particles can be used.

  Examples of the organic fine particles include modified polystyrene fine particles and modified acrylic resin particles.

Examples of the inorganic filler include oxide ceramics such as alumina (Al ₂ O ₃ ), silica (SiO ₂ , silicon oxide), titania, zirconia, magnesia, ceria, yttria, zinc oxide and iron oxide; silicon nitride, Nitride ceramics such as titanium nitride and boron nitride; silicon carbide, boehmite (AlOOH), calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay (Al ₂ O ₃ .nSiO ₂ etc.), Kaori And ceramics such as knight, halloysite, pyrophyllite, montmorillonite, sericite, mica, amicite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and quartz sand; and glass fiber.

  The blend ratio of the polyolefin, the plasticizer and the filler used as necessary in the operation of (1) is not particularly limited. The proportion of the filler contained in the polyolefin kneaded material is preferably 25 to 50% by mass based on the total mass of the microporous membrane from the viewpoint of the strength and film forming property of the microporous membrane to be obtained. The proportion of the filler contained in the plasticizer kneaded material is preferably 30 to 60% by mass based on the total mass of the microporous membrane from the viewpoint of obtaining a viscosity suitable for extrusion. The proportion of the filler contained in the kneaded product is preferably 10% by mass or more based on the total mass of the microporous membrane from the viewpoint of improving the uniformity of the pore diameter of the obtained microporous membrane. The mass% or less is preferable.

  If necessary, the kneaded product may be phenol-based, phosphorus-based, sulfur-based or the like such as pentaerythrityl-tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]. Antioxidants; metal soaps such as calcium stearate and zinc stearate; ultraviolet absorbers; light stabilizers; antistatic agents; antifogging agents; and various additives such as color pigments may be mixed.

  The kneading method in the operation (1) is not particularly limited, and may be a conventionally used kneading method. For example, the kneading order is a general mixture such as a Henschel mixer, a V-blender, a pro-shear mixer, and a ribbon blender in which a polyolefin, a plasticizer, and a part of a filler used as necessary are mixed in advance. After mixing in advance using a mixer, the remaining raw materials may be further kneaded, or all of the raw materials may be kneaded simultaneously.

  The apparatus used for kneading is not particularly limited, and for example, kneading can be performed using a melt kneading apparatus such as an extruder or a kneader.

  The operation of (2) includes, for example, extruding the kneaded product obtained in (1) into a sheet shape via a T die or the like, and bringing the extrudate into contact with a heat conductor to cool and solidify. As the heat conductor, metal, water, air, and the plasticizer itself can be used. Cooling and solidifying by sandwiching the extrudate between a pair of rolls is preferable from the viewpoint of increasing the film strength of the obtained sheet-like molded body and improving the surface smoothness of the sheet-like molded body.

  The operation (3) includes stretching a sheet (sheet-like formed body) obtained through the operation (2) to obtain a stretched sheet. As the sheet stretching method in stretching, MD uniaxial stretching by a roll stretching machine, TD uniaxial stretching by a tenter, a combination of a roll stretching machine and a tenter, or a sequential biaxial stretching by a combination of a tenter and a tenter, a simultaneous biaxial tenter or An example is simultaneous biaxial stretching by inflation molding. From the viewpoint of obtaining a more uniform film, the sheet stretching method is preferably simultaneous biaxial stretching. The total surface magnification at the time of stretching is preferably 8 times or more, more preferably 15 times or more, and more preferably 30 times or more from the viewpoint of film thickness uniformity and balance of tensile elongation, porosity and average pore diameter. Further preferred. When the total surface magnification is 30 times or more, a high-strength microporous film is easily obtained. The stretching temperature is preferably 121 ° C. or higher from the viewpoint of imparting high permeability and high temperature and low shrinkage, and is preferably 135 ° C. or lower from the viewpoint of film strength.

  The extraction in the operation of (3) or the extraction prior to the heat treatment in the operation of (4) can be performed by immersing the sheet or the stretched sheet in the extraction solvent, or by showering the extraction solvent on the sheet or the stretched sheet. it can. The extraction solvent is preferably a poor solvent for polyolefin and a good solvent for plasticizer and filler, and preferably has a boiling point lower than the melting point of polyolefin. Examples of such extraction solvents include hydrocarbons such as n-hexane and cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,1,1-trichloroethane and fluorocarbon; alcohols such as ethanol and isopropanol; acetone and 2 -Ketones such as butanone; and alkaline water. An extraction solvent is used individually by 1 type or in combination of 2 or more types.

  The filler may be extracted in whole or in part by any of the operations (1) to (4), or may be left in the finally obtained microporous membrane. The order, method and number of extraction are not particularly limited.

  As a heat treatment method in the operation of (4), a heat setting method in which a stretched sheet obtained through stretching is stretched and / or relaxed at a predetermined temperature using a tenter and / or a roll stretching machine. Is mentioned. The relaxation operation is a reduction operation performed at a predetermined relaxation rate on the MD and / or TD of the film. The relaxation rate is a value obtained by dividing the MD dimension of the film after the relaxation operation by the MD dimension of the film before the operation, or a value obtained by dividing the TD dimension after the relaxation operation by the TD dimension of the film before the operation, or MD In the case of relaxation by both TD and TD, it is a value obtained by multiplying the relaxation rate of MD and the relaxation rate of TD. The predetermined temperature is preferably 130 ° C. or lower and more preferably 123 ° C. or lower from the viewpoint of controlling porosity or controlling ion diffusion resistance. From the viewpoint of stretchability, the predetermined temperature is preferably 115 ° C. or higher. From the viewpoints of heat shrinkage and permeability, it is preferable to stretch the stretched sheet to TD 1.5 times or more and more preferably 1.8 times or more to TD in post-processing. From the viewpoint of safety, it is preferable to stretch the stretched sheet to TD to 6.0 times or less, and from the viewpoint of maintaining the balance between film strength and permeability, 4.0 times or less is more preferable. The predetermined relaxation rate is preferably 0.9 times or less from the viewpoint of suppression of heat shrinkage, and is preferably 0.6 times or more from the viewpoint of preventing wrinkle generation, porosity, and permeability. The relaxation operation may be performed in both directions of MD and TD, but may be a relaxation operation of only one of MD and TD. Even if the relaxation operation is performed on only one of MD and TD, it is possible to reduce the thermal contraction rate not only in the operation direction but also in the other direction.

  The operation of (5) can include forming a porous layer by applying and drying a coating liquid containing insulating particles and a resin binder on at least one side of the obtained polyolefin microporous film.

  As the solvent for the coating solution, those capable of uniformly and stably dispersing or dissolving the insulating particles and the resin binder are preferable. For example, N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, water, ethanol, Examples include toluene, hot xylene, methylene chloride, and hexane.

  The concentration of the coating solution ((mass of insulating particles + mass of resin binder) × 100 / mass of coating solution) is preferably 10 to 90%, more preferably 15 to 80%, and still more preferably 20 to 70%. Since the viscosity can be lowered if the concentration of the coating solution is 90% or less, thin film coating is facilitated. If the concentration of the coating solution is 10% or more, the drying time is short and the film thickness can be easily adjusted.

  Various additives such as surfactants, thickeners, wetting agents, antifoaming agents, PH preparations containing acids and alkalis are added to the coating solution to stabilize dispersion and improve coating properties. May be. These additives are preferably those that can be removed when the solvent is removed. However, these additives are electrochemically stable in the range of use of the lithium ion secondary battery or the non-aqueous lithium storage element, do not inhibit the battery reaction, and 200 It may remain in the porous layer if it is stable up to about ° C.

  The method for dispersing or dissolving the insulating particles and the resin binder in the solvent of the coating solution is not particularly limited as long as the dispersion property of the coating solution necessary for coating can be realized. Examples include ball mills, bead mills, planetary ball mills, vibrating ball mills, sand mills, colloid mills, attritors, roll mills, high-speed impeller dispersions, dispersers, homogenizers, high-speed impact mills, ultrasonic dispersion, and mechanical stirring with stirring blades. .

  The method for applying the coating solution to the porous film is not particularly limited as long as the required layer thickness or coating area can be realized. For example, a gravure coater method, a small diameter gravure coater method, a reverse roll coater method, a transfer roll Examples include coater method, kiss coater method, dip coater method, knife coater method, air doctor coater method, blade coater method, rod coater method, squeeze coater method, cast coater method, die coater method, screen printing method, and spray coating method. It is done.

  The method for removing the solvent from the coating film after coating is not particularly limited as long as it does not adversely affect the porous film. For example, a method of drying at a temperature below its melting point while fixing the porous membrane, a method of drying under reduced pressure at a low temperature and the like can be mentioned.

  In addition to the operations (1) to (5) above, the method for producing a separator can include obtaining a laminate by superimposing a plurality of single layer bodies. The method for producing the separator may include subjecting the porous film and the insulating porous layer to surface treatment such as electron beam irradiation, plasma irradiation, surfactant coating, and chemical modification.

<< Method for Manufacturing Nonaqueous Lithium Type Storage Element >>
The non-aqueous lithium storage element of this embodiment can be manufactured, for example, by housing an electrode laminate or an electrode winding body together with a non-aqueous electrolyte in an exterior body. Hereinafter, an exemplary manufacturing method of the non-aqueous lithium storage element will be described.

<Assembly and drying>
In cell assembly, typically, a positive electrode precursor and a negative electrode cut into a single-wafer shape are stacked via a separator to obtain an electrode stack, and the positive electrode terminal and the negative electrode terminal are connected to the electrode stack. . Alternatively, the positive electrode precursor and the negative electrode are stacked and wound via a separator to obtain an electrode winding body, and the positive electrode terminal and the negative electrode terminal are connected to the electrode winding body. The shape of the electrode winding body may be a cylindrical shape or a flat shape.

  The method for connecting the positive electrode terminal and the negative electrode terminal is not particularly limited, and can be performed by a method such as resistance welding or ultrasonic welding.

[Exterior body]
As the exterior body, a metal can, a laminate packaging material, or the like can be used. The metal can is preferably made of aluminum. As the laminate packaging material, a film in which a metal foil and a resin film are laminated is preferable, and a three-layer structure composed of an outer layer resin film / metal foil / interior resin film is exemplified. The outer layer resin film is for preventing the metal foil from being damaged by contact or the like, and a resin such as nylon or polyester can be 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. The sealing method of the exterior body is not particularly limited, and when a laminate packaging material is used, a method such as heat sealing or impulse sealing can be 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. The drying method is not limited, and drying can be performed by vacuum drying or the like. The residual solvent is preferably 1.5% by mass or less per mass of the positive electrode active material layer or the negative electrode active material layer. If the residual solvent is 1.5% by mass or less, the self-discharge characteristics and the cycle characteristics are hardly deteriorated, which is preferable.

<Liquid injection, impregnation, sealing>
A non-aqueous electrolyte solution is injected into the electrode laminate or electrode winding body that is dried and accommodated in the exterior body. It is desirable that the positive electrode, the negative electrode, and the separator be sufficiently impregnated with a nonaqueous electrolytic solution after the injection. In a state in which the non-aqueous electrolyte is not immersed in at least a part of the positive electrode, the negative electrode, and the separator, since the doping proceeds non-uniformly in lithium doping described later, the resistance of the obtained non-aqueous lithium storage element increases. Or the durability is reduced. The impregnation method is not particularly limited. For example, the electrode laminate or electrode winding body after injection is placed in a decompression chamber with the exterior body opened, and the inside of the chamber is decompressed using a vacuum pump. And a method of returning to atmospheric pressure again can be used. After the impregnation, the electrode laminated body or the electrode winding body in the state in which the exterior body is opened is sealed by sealing while reducing the pressure.

<Lithium dope>
As a preferred operation of lithium doping, 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 to release lithium ions, The anode active material layer is pre-doped with riotium ions by reducing the ions.

In lithium doping, 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 in which a voltage is applied in a state where a part of the exterior body is opened; in 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 A method of applying a voltage;

<aging>
It is preferable to age the electrode laminate or the electrode winding body after lithium doping. In aging, the solvent in the non-aqueous electrolyte is decomposed at the negative electrode, and a lithium ion permeable solid polymer film is formed on the negative electrode surface.

  The aging method is not particularly limited, and for example, a method of reacting a solvent in a nonaqueous electrolytic solution under a high temperature environment can be used.

<gas releasing>
It is preferable to further degas after aging to 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, a method in which an electrode laminate or an electrode winding body is installed in a decompression chamber with an exterior body opened, and the inside of the chamber is decompressed using a vacuum pump. Can be used.

《Characteristic evaluation of non-aqueous lithium storage element》
<Collecting separator>
The separator can be confirmed by disassembling the completed non-aqueous lithium storage element under anaerobic condition, washing the collected separator, and analyzing the dried sample. Hereinafter, an example of a separator collecting method will be described.

  It is preferable to perform measurement after disassembling the non-aqueous lithium storage element in an argon box, taking out the separator, and washing the electrolyte adhering to the separator surface. As the cleaning solvent for the separator, it is only necessary to wash away the electrolyte adhering to the separator surface. Therefore, carbonate solvents such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate can be suitably used. As a cleaning method, for example, the separator is immersed in a diethyl carbonate solvent 50 to 100 times the mass of the separator for 10 minutes or more, and then the solvent is changed and the separator is immersed again. Thereafter, the separator is preferably taken out from diethyl carbonate and vacuum-dried. The conditions for vacuum drying can be, for example, temperature: 0 to 200 ° C., pressure: 0 to 20 kPa, and time: 1 to 40 hours. It is preferable to set the temperature at such a level that the shape of the separator does not change during vacuum drying.

  By analyzing the separator obtained above, the thickness of the porous membrane, the thickness of the insulating porous layer, the material of the insulating porous layer, the pore diameter, the number of pores, and the porosity of the porous membrane can be obtained. These methods will be described in examples described later.

<Capacitance>
In this specification, the capacitance F (F) is 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.

<Electric energy>
In this specification, the electric energy E (Wh) is a value obtained by the following method.
A value calculated by F × (3.8 ² −2.2 ² ) / 2/3600 using the capacitance F (F) calculated by the method described above.

<volume>
The volume of the non-aqueous lithium storage element is, for example, the volume of the portion of the electrode laminate or electrode winding body in which the region where the positive electrode active material layer and the negative electrode active material layer are stacked is accommodated by the outer package. Point to.

For example, in the case of an electrode laminate or an electrode winding body accommodated by a laminate film, a region where the positive electrode active material layer and the negative electrode active material layer exist in the electrode laminate or the electrode winding body is cup-shaped. Although stored in the laminate film, the volume (V ₁ ) of this non-aqueous lithium-type electricity storage element is the outer dimension length (l ₁ ), outer dimension width (w ₁ ), and laminate film of this cup-molded part. V ₁ = l ₁ × w ₁ × t ₁ is calculated according to the thickness (t ₁ ) of the non-aqueous lithium storage element including

In the case of an electrode laminate or an electrode winding body housed in a rectangular metal can, the volume of the outer dimension of the metal can is simply used as the volume of the non-aqueous lithium storage element. That is, the volume (V ₂ ) of the non-aqueous lithium storage element is determined by the outer dimension length (l ₂ ), outer dimension width (w ₂ ), and outer dimension thickness (t ₂ ) of the square metal can. Calculated with ₂ = l ₂ × w ₂ × t ₂ .

In the case of an electrode winding body housed in a cylindrical metal can, the volume of the outer dimension of the metal can is used as the volume of the non-aqueous lithium storage element. That is, the volume (V ₃ ) of the non-aqueous lithium storage element is V ₃ = 3.14 depending on the outer dimension radius (r) and outer dimension length (l ₃ ) of the bottom or top surface of the cylindrical metal can. * R * r * l ₃ is calculated.

<Energy density>
In the present specification, the energy density is a value obtained by an equation of E / V _i (Wh / L) using an electric quantity E and a volume V _i (i = 1, 2, 3).

<Room temperature discharge internal resistance>
In the present specification, the room temperature discharge internal resistance Ra (Ω) is a value obtained by the following method.
First, 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. Subsequently, constant current discharge is performed up to 2.2 V with a current value of 20 C, and a discharge curve (time-voltage) is obtained. 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)).

<Normal charging internal resistance>
In this specification, the room temperature charge internal resistance Rf (Ω) is a value obtained by the following method.
First, a constant current discharge is performed in a thermostat set to 25 ° C. with a cell corresponding to a non-aqueous lithium storage element until the voltage reaches 20 V at a current value of 20 C, and then a constant voltage of 2.2 V is applied. The constant voltage discharge is performed for a total of 30 minutes. Subsequently, constant current charging is performed up to 3.8 V with a current value of 20 C to obtain a charging curve (time-voltage). In this charging curve, when the voltage at charging time = 0 seconds obtained by extrapolating from the voltage values at the charging time of 2 seconds and 4 seconds by linear approximation is Eo, the drop voltage ΔE = Eo−2. 2 and Rf = ΔE / (20C (current value A)).

When the initial room temperature discharge internal resistance is Ra (Ω), the initial room temperature charge internal resistance is Rf (Ω), and the capacitance is F (F), the non-aqueous lithium storage element of this embodiment is as follows. :
(A) The product Ra · F of Ra and F is 0.3 to 3.0; and (b) Rf / Ra is 0.5 to 1.5;
It is preferable that

  Regarding (a), Ra · F is preferably 3.0 or less, more preferably 2.4 or less, from the viewpoint of developing sufficient charge capacity and discharge capacity for a large current. Preferably it is 2.2 or less. When Ra · F is not more than the above upper limit value, a non-aqueous lithium storage element having excellent input / output characteristics can be obtained. Therefore, it is preferable because it can sufficiently withstand a high load applied to the non-aqueous lithium storage element by combining a storage system using the non-aqueous lithium storage element and, for example, a high-efficiency engine.

  Regarding (b), the ratio Rf / Ra of the room temperature charge internal resistance to the room temperature discharge internal resistance is preferably 0.5 or more and 1.5 or less, more preferably 0.7 or more and 1.3 or less, Preferably they are 0.8 or more and 1.2 or less, More preferably, they are 0.8 or more and 1.1 or less. If Rf / Ra is equal to or less than the above upper limit value, when the power storage system using the power storage element is combined with a high-efficiency engine such as an automobile, the power storage element increases the regeneration efficiency and leads to an improvement in fuel consumption. .

<High temperature storage test>
In this specification, the room temperature discharge internal resistance increase rate after the high temperature storage test is measured by the following method.

  First, constant-current charging is performed until a voltage of 100 C reaches 4.0 V in a thermostat set to 25 ° C. with a cell corresponding to the non-aqueous lithium storage element, and then a constant voltage of 4.0 V is applied. Perform constant voltage charging for 10 minutes. Thereafter, the cell is stored in a 60 ° C. environment, taken out from the 60 ° C. environment every two weeks, charged to the cell voltage of 4.0 V by the above-described charging operation, and then stored again in the 60 ° C. environment. . Repeat this operation and store for a total of 2 months.

  For a cell after a high temperature storage test, the resistance value obtained using the same measurement method as that for the room temperature discharge internal resistance is the room temperature discharge internal resistance Rb after the high temperature storage test. The rate of increase in room temperature discharge internal resistance after the high temperature storage test for the resistance Ra is calculated by Rb / Ra.

  The non-aqueous lithium storage element of this embodiment has an initial room temperature discharge internal resistance of Ra (Ω) and a room temperature discharge internal resistance of Rb (Ω) after storage for 2 months at a cell voltage of 4 V and an environmental temperature of 60 ° C. It is preferable that Rb / Ra satisfies 0.9 or more and 3.0 or less.

  Rb / Ra is preferably 3.0 or less, more preferably 2 from the viewpoint of developing sufficient charge capacity and discharge capacity for a large current when exposed to a high temperature environment for a long time. 0.0 or less, more preferably 1.5 or less. If Rb / Ra is less than or equal to the above upper limit value, excellent output characteristics can be obtained stably over a long period of time, leading to a longer life of the device.

<BET specific surface area and average pore diameter, mesopore volume, micropore volume>
In the present specification, the BET specific surface area, average pore diameter, mesopore amount, and 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)).

  The MP method uses a “t-plot method” (BC Lippens, JH de Boer, J. Catalysis, 4319 (1965)), and uses a micropore volume, a micropore area, and a micropore. Is a method for obtaining the distribution of M.M. It is a method devised by Mikhail, Brunauer, Bodor (RS Mikhal, S. Brunauer, EE Bodor, J. Colloid Interface Sci., 26, 45 (1968)).

<Particle size>
In the specification of the present application, the average particle size is the particle size at which the cumulative curve becomes 50% when the cumulative curve is determined with the total volume being 100% when the particle size distribution is measured using a particle size distribution measuring device. That is, it refers to a 50% diameter (Median diameter)). This average particle diameter can be measured using a commercially available laser diffraction particle size distribution analyzer.

  In the present specification, the primary particle size is 2,000 to 3,000 by using a fully automatic image processing apparatus and the like by photographing several fields of the powder with an electron microscope and using a fully automatic image processing device or the like. It can be obtained by a method of measuring the degree and making the arithmetic average of these values the primary particle diameter.

<Dispersity>
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. Place the scraper's long side parallel to the gauge width direction and place the blade tip in contact with the deep tip of the groove of the grain gauge. The surface of the gauge is pulled at a uniform speed to the groove depth of 0 to 1 second for 1 to 2 seconds, and the light is applied at an angle of 20 ° to 30 ° within 3 seconds after the drawing is finished. Read the depth at which the grain appears in the groove of the grain gauge.

<Viscosity and TI value>
In the present specification, 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. 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.

  Hereinafter, although an embodiment of the present invention is described concretely with an example and a comparative example, the present invention is not limited to these examples and a comparative example.

<Crushing of lithium carbonate>
200 g of lithium carbonate having an average particle size of 53 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 carrying out brittle fracture was 2.31 μm.

<Preparation of positive electrode active material>
[Preparation of activated carbon 1]
The crushed palm shell carbide was carbonized in a small carbonization furnace in a nitrogen atmosphere 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, introduced into the activation furnace, and heated 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. After drying for 10 hours in an electric dryer maintained at 115 ° C., pulverization was performed for 1 hour with a ball mill to obtain activated carbon 1.

It was 4.2 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). The pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 2360 m ² / g, the mesopore volume (V ₁ ) was 0.52 cc / g, the micropore volume (V ₂ ) was 0.88 cc / g, and V ₁ / V ₂ = 0.59. there were.

[Preparation 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 (V ₁ ) was 1.50 cc / g, the micropore volume (V ₂ ) was 2.28 cc / g, and V ₁ / V ₂ = 0.66. there were.

<Preparation of positive electrode 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.

<Preparation of positive electrode precursor>
The obtained coating solution was applied to one or both sides of a 15 μm thick aluminum foil using a die coater manufactured by Toray Engineering Co., Ltd. under a coating speed of 1 m / s, and dried at a drying temperature of 100 ° C. A precursor was obtained. The obtained positive electrode precursor was pressed using a roll press machine under conditions of a pressure of 4 kN / cm and a surface temperature of the pressing 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. The film thickness of the positive electrode active material layer was about 60 μm per side.

  Hereinafter, the single-sided positive electrode precursor and the double-sided positive electrode precursor using activated carbon 1 are referred to as single-sided positive electrode precursor 1 and double-sided positive electrode precursor 1 (collectively, “positive electrode precursor 1”), respectively. The single-sided positive electrode precursor and the double-sided positive electrode precursor using activated carbon 2 are referred to as single-sided positive electrode precursor 2 and double-sided positive electrode precursor 2 (collectively, “positive electrode precursor 2”), respectively.

<Preparation of negative electrode 1>
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.) is used. They were placed on a bat and both were placed in an electric furnace (effective size in furnace 300 mm × 300 mm × 300 mm). Under a nitrogen atmosphere, the temperature was raised to 600 ° C. over 8 hours, and kept at the same temperature for 4 hours, whereby both were subjected to a thermal reaction to obtain composite carbon material 1a. Then, after cooling to 60 degreeC by natural cooling, the composite carbon material 1a was taken out from the furnace.

About the obtained composite carbon material 1a, 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, the composite carbon material 1a was used as a negative electrode active material to produce a negative electrode.
85 parts by mass of composite carbon material 1a, 10 parts by mass of acetylene black, 5 parts by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) are mixed, and this is a thin film swirl type high speed made by PRIMIX Using a mixer fill mix, dispersion was performed under conditions of a peripheral speed of 15 m / s to obtain a coating solution. 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 obtained coating solution was coated on 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. A negative electrode 1 was obtained. The obtained negative electrode 1 was pressed using a roll press machine under conditions of a pressure of 4 kN / cm and a surface temperature of the pressing part of 25 ° C. The thickness of the negative electrode active material layer of the negative electrode 1 obtained above was determined from the average value of the thicknesses measured at any 10 locations of the negative electrode 1 using a thickness gauge Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. It was determined by subtracting the thickness of the copper foil. As a result, the film thickness of the negative electrode active material layer of the negative electrode 1 was 40 μm per side.

<Preparation example of negative electrodes 2-3>
The negative electrode active material was produced and evaluated in the same manner as the negative electrode 1 except that the base material and the amount thereof, the amount of coal-based pitch, and the heat treatment temperature were adjusted as shown in Table 1. The negative electrode was produced and evaluated in the same manner as in the preparation of the negative electrode 1 except that the negative electrode active material obtained above was used to adjust the coating liquid as shown in Table 1. The results are shown in Table 1.

表１における原料はそれぞれ、以下のとおりである。
ヤシ殻活性炭：平均粒子径３．０μｍ、ＢＥＴ比表面積１，７８０ｍ^２／ｇ
カーボンナノ粒子：平均粒子径５．２μｍ、ＢＥＴ比表面積８５９ｍ^２／ｇ、一次粒子径２０ｎｍ
人造黒鉛：平均粒子径４．８μｍ、ＢＥＴ比表面積３．１ｍ^２／ｇ
ピッチ：軟化点５０℃の石炭系ピッチ

The raw materials in Table 1 are as follows.
Coconut shell activated carbon: average particle size 3.0 μm, BET specific surface area 1,780 m ² / g
Carbon nanoparticles: average particle size 5.2 μm, BET specific surface area 859 m ² / g, primary particle size 20 nm
Artificial graphite: Average particle size 4.8 μm, BET specific surface area 3.1 m ² / g
Pitch: Coal pitch with a softening point of 50 ° C

Example 1
<Preparation of electrolyte>
As an organic solvent, a mixed solvent of ethylene carbonate (EC): methyl ethyl carbonate (MEC) = 33: 67 (volume ratio) was used, and LiN (SO ₂ F) ₂ and LiPF ₆ were used for the obtained non-aqueous electrolyte solution. Each electrolyte salt is dissolved in a mixed solvent so that the concentration ratio is 75:25 (molar ratio) and the sum of the concentrations of LiN (SO ₂ F) ₂ and LiPF ₆ is 1.2 mol / L. A non-aqueous electrolyte solution was obtained.

The concentrations of LiN (SO ₂ F) ₂ and LiPF _{6 in} the obtained nonaqueous electrolytic solution were 0.9 mol / L and 0.3 mol / L, respectively.

<Preparation of separator>
As a pure polymer, homopolymers of polyethylene having Mv of 250,000 and 700,000 were prepared in a weight ratio of 50:50, respectively. To 99% by mass of the pure polymer, 1.0% by mass of pentaerythrityl-tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] is added as an antioxidant, and a tumbler blender is used. By using and dry blending, a polymer mixture was obtained. The obtained mixture of polymers and the like was fed by a feeder under a nitrogen atmosphere to a twin-screw extruder in which the system was purged with nitrogen. Liquid paraffin as a plasticizer was injected into the cylinder of the extruder by a plunger pump. Feeder and pump are adjusted so that the ratio of liquid paraffin in the total mixture to be extruded is 68% by mass (that is, the ratio of mixture of polymers (PC) is 32% by mass). did. The melt kneading conditions were a set temperature of 200 ° C., a screw rotation speed of 100 rpm, and a discharge rate of 12 kg / hour.

  The obtained melt-kneaded product was extruded through a T-die onto a cooling roll controlled at a surface temperature of 40 ° C. and cast to obtain a gel sheet having a thickness of 1600 μm.

  The obtained gel sheet was guided to a simultaneous biaxial tenter stretching machine and biaxially stretched to obtain a stretched sheet. The set stretching conditions were an MD draw ratio of 7.0 times, a TD draw ratio of 6.1 times, and a set temperature of 121 ° C.

  The obtained stretched sheet was introduced into a methyl ethyl ketone bath and sufficiently immersed in methyl ethyl ketone to extract and remove liquid paraffin from the stretched sheet, and then methyl ethyl ketone was removed by drying.

  The stretched sheet from which methyl ethyl ketone had been removed by drying was guided to a TD tenter and heat-set to obtain a porous film. The heat setting temperature was 121 ° C., the TD maximum magnification was 2.0 times, and the relaxation rate was 0.90 times.

  96.0 parts by mass of alumina whose particle size was adjusted with a bead mill so that the average particle size (Dp50) was 1.0 μm, 4.0 parts by mass of acrylic latex (solid content concentration 40%, average particle size 145 nm) as a resin binder, Further, 1.0 part by mass of an aqueous solution of ammonium polycarboxylate (SN Dispersant 5468 manufactured by San Nopco) was uniformly dispersed in 100 parts by mass of water to obtain a coating liquid in which insulating alumina particles were dispersed. The obtained coating liquid in which the insulating alumina particles are dispersed is applied to one side of the obtained porous film using a micro gravure coater, and dried at 60 ° C. to form an insulating porous layer having a thickness of 5 μm on the porous film. Formed.

<Preparation of non-aqueous lithium storage element>
[assembly]
The obtained double-sided negative electrode 1, double-sided positive electrode precursor 1, and single-sided positive electrode precursor 1 were cut into 10 cm × 10 cm (100 cm ² ). The uppermost surface and the lowermost surface use a single-sided positive electrode precursor 1, and further use 21 double-sided negative electrodes 1 and 20 double-sided positive electrode precursors 1, with a microporous membrane separator 1 between the negative electrode and the positive electrode precursor. Laminated and sandwiched. A negative electrode terminal and a 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., and the electrode terminal part and the outer part of the bottom part are sealed at a temperature of 180 ° C. and a sealing time. Heat sealing was performed under the conditions of 20 sec and a sealing pressure of 1.0 MPa.

[Liquid injection, impregnation, sealing]
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. After depressurizing from normal pressure to -87 kPa and then returning to atmospheric pressure four times, the mixture was allowed to stand for 15 minutes. After reducing the pressure from normal pressure to -91 kPa, the pressure was returned to atmospheric pressure. Similarly, the operation of reducing the pressure and returning to the atmospheric pressure was repeated seven times in total (reduced pressure from normal pressure to -95, -96, -97, -81, -97, -97, and -97 kPa, respectively). The electrode laminate was impregnated with the non-aqueous electrolyte by the above procedure.

  The electrode laminate impregnated with the non-aqueous electrolyte solution is put into a vacuum sealing machine and sealed at 180 ° C. for 10 seconds at a pressure of 0.1 MPa, and the aluminum laminate packaging material is sealed. Thus, a non-aqueous lithium storage element was obtained.

[Lithium dope]
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]
The non-aqueous lithium-type storage element after lithium doping was subjected to a constant current discharge at 1.0 A under a 25 ° C. environment until reaching a voltage of 3.0 V, and then a 3.0 V constant voltage discharge was performed for 1 hour. Adjusted to 3.0V. The non-aqueous lithium storage element was stored in a constant temperature bath at 60 ° C. for 60 hours.

[gas releasing]
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. The non-aqueous lithium storage element is placed in a decompression chamber, and the pressure is reduced from atmospheric pressure to −80 kPa over 3 minutes using a diaphragm pump (N816.3KT.45.18) manufactured by KNF. The operation of returning to atmospheric pressure was repeated 3 times in total. The non-aqueous lithium storage element was placed in a vacuum sealer and the pressure was reduced to −90 kPa, and then sealed at 200 ° C. for 10 seconds at a pressure of 0.1 MPa to seal the aluminum laminate packaging material.

  The non-aqueous lithium storage element was completed by the above procedure.

<Measurement evaluation of non-aqueous lithium storage element>
[Collecting separator]
After adjusting the completed non-aqueous lithium storage element to 2.9 V, it is disassembled in an Ar box controlled at a dew point of −90 ° C. or less and an oxygen concentration of 1 ppm or less installed in a room at 23 ° C., and the separator is taken out. It was. The collected separator was immersed for 10 minutes or more in methyl ethyl carbonate (MEC) 100 times the weight of the separator, and then the MEC was replaced and the separator was immersed again. Thereafter, the separator was taken out from the MEC and vacuum-dried in a side box under the conditions of room temperature, pressure of 10 kPa, and 2 hours.

(1) Film thickness t (μm)
The film thickness t was measured at an ambient temperature of 23 ± 2 ° C. using KBM (trademark), which is a micro thickness gauge manufactured by Toyo Seiki. First, the total thickness of the collected separator was measured at nine locations, and the average value was taken as t _all . Bonding the adhesive layer of the cellophane tape on the surface of the insulating porous layer, peeling off the insulating porous layer by peeling, the thickness of the porous film was a single film was measured 9 points, and the average value t _s . The thickness _{t i} of insulating porous layer _was calculated by _t all -t _s. As a result, _{t s} is 16.1μm, _{t i} is 5.1μm, _t i / _{t s} to the thickness of the porous membrane is the ratio of the thickness of the insulating porous layer was 31.7%.

(2) Porosity D (%)
As in (1), the insulating porous layer is peeled off with a cellophane tape, and a sample of 10 cm × 10 cm square is cut out from the sample made into a single layer porous film, and its volume (cm ³ ) and mass (g) are obtained. From these and the film density (g / cm ³ ), the porosity was calculated using the following formula.
Porosity = (volume−mass / membrane density) / volume × 100
The film density was calculated from the fraction of the composition, with 0.95 for polyethylene and 0.91 for polypropylene. The density obtained by the density gradient tube method of JIS K-7112 can also be used as various film densities. When the porosity D was determined, the porosity of the separator was 65%.

(3) Pore diameter d (μm) and pore number B (pieces / μm ² ) of the microporous membrane
In the same manner as in (1), the insulating porous layer was peeled off with a cellophane tape to obtain a single-layer porous film, and the other samples were measured.

  It is known that the fluid inside the capillary follows the Knudsen flow when the mean free path of the fluid is larger than the pore size of the capillary, and the Poiseuille flow when it is small. Therefore, it is assumed that the air flow in the measurement of the permeability of the microporous membrane follows the Knudsen flow, and the water flow in the measurement of the permeability of the porous membrane follows the Poiseuille flow.

In this case, the pore diameter d (μm) and the curvature τ _a (dimensionless) of the porous membrane are the air permeation rate constant R _gas (m ³ / (m ² · sec · Pa)), the water permeation rate constant R _liq (m ³ / (m ² · sec · Pa)), air molecular velocity ν (m / sec), water viscosity η (Pa · sec), standard pressure P _s (= 101325 Pa), porosity ε (% ) And the film thickness L (μm) can be obtained using the following equation.
d = 2ν × (R _liq / R _gas ) × (16η / 3P _s ) × 10 ⁶
τ _a = (d × (ε / 100) × ν / (3L × P _s × R _gas )) ^1/2

Here, R _gas is obtained from the air permeability (sec) using the following equation.
R _gas = 0.0001 / (air permeability × (6.424 × 10 ⁻⁴ ) × (0.01276 × 101325))

R _liq is obtained from the water permeability (cm ³ / (cm ² · sec · Pa)) using the following equation.
R _liq = water permeability / 100

In addition, water permeability is calculated | required as follows. A microporous membrane previously immersed in alcohol was set in a stainless steel permeation cell having a diameter of 41 mm, and after the alcohol in the membrane was washed with water, water was permeated at a differential pressure of about 50000 Pa, and 120 seconds had elapsed. The water permeability per unit time, unit pressure, and unit area was calculated from the water permeability (cm ³ ) at the time, and this was used as the water permeability.

Ν is a gas constant R (= 8.314), an absolute temperature T (K), a circumference ratio π, and an average molecular weight M of air (= 2.896 × 10 ⁻² kg / mol), using the following formula. Desired.
ν = ((8R × T) / (π × M)) ^1/2

Further, the number of holes B (pieces / μm ² ) is obtained from the following equation.
B = 4 × (ε / 100) / (π × d ² × τ _a )
The separator had a hole diameter d of 0.055 μm and a hole number D of 187 / μm ² .

[Analysis of positive electrode active material layer]
After adjusting the completed non-aqueous lithium storage element to 2.9 V, it is disassembled in an Ar box controlled at a dew point of −90 ° C. or less and an oxygen concentration of 1 ppm or less installed in a room at 23 ° C., and the positive electrode is taken out. It was. The taken-out positive electrode was immersed and washed with dimethyl carbonate (DMC), and then vacuum-dried in a side box in a state where the air was not exposed.

The positive electrode after drying was transferred from the side box to the Ar box in a state where exposure to air was not performed, and immersion extraction was performed with heavy water to obtain a positive electrode extract. The analysis of the extract was performed by (1) ion chromatography (IC) and (2) ¹ H-NMR, the concentration A (mol / ml) of each compound in the obtained positive electrode extract, and heavy water used for extraction From the volume B (ml) and the mass C (g) of the positive electrode active material layer used for extraction, the following formula 1:
Abundance per unit mass (mol / g) = A × B ÷ C. . . (Formula 1)
Thus, the abundance (mol / g) per unit mass of the positive electrode active material layer of each compound deposited on the positive electrode active material layer was determined.

The mass of the positive electrode active material layer used for extraction was determined by the following method.
The positive electrode active material layer was peeled off from the positive electrode current collector remaining after the heavy water extraction, and the peeled off positive electrode active material layer was washed with water and then vacuum dried. The positive electrode active material layer obtained by vacuum drying was washed with NMP or DMF. Subsequently, the obtained positive electrode active material layer was vacuum-dried again and weighed to examine the mass of the positive electrode active material layer used for extraction.

Hereinafter, an analysis method of the extract is shown.
(1) The CO ₃ ^2- derived from LiCO ₃ Li was detected by IC measurement (negative mode) of the positive electrode extract, and the concentration A of CO ₃ ^2- was determined by the absolute calibration curve method.

(2) The same positive electrode extract as in (1) is placed in a 3 mmφ NMR tube (PN-002 manufactured by Shigemi Co., Ltd.), and a 5 mmφ NMR tube containing deuterated chloroform containing 1,2,4,5-tetrafluorobenzene (Japan) It was inserted into Precision Science Co., Ltd. N-5), and ¹ H NMR measurement was performed by a double tube method. Normalization was performed with a signal of 1,2,4,5-tetrafluorobenzene of 7.1 ppm (m, 2H), and an integral value of each observed compound was determined.

In addition, deuterated chloroform containing dimethyl sulfoxide of known concentration is put into a 3 mmφ NMR tube (PN-002 manufactured by Shigemi Co., Ltd.), and the same deuterated chloroform containing 1,2,4,5-tetrafluorobenzene as above. Was inserted into a 5 mmφ NMR tube (N-5 manufactured by Japan Precision Science Co., Ltd.), and ¹ H NMR measurement was performed by a double tube method. In the same manner as described above, the signal was normalized with 7.1 ppm (m, 2H) of 1,2,4,5-tetrafluorobenzene, and the integral value of 2.6 ppm (s, 6H) of dimethyl sulfoxide was obtained. From the relationship between the concentration of dimethyl sulfoxide used and the integral value, the concentration A of each compound in the positive electrode extract was determined.

Assignment of ¹ H NMR spectrum is as follows.
[About XOCH ₂ CH ₂ OX]
XOCH ₂ CH ₂ OX CH ₂ : 3.7 ppm (s, 4H)
CH ₃ OX: 3.3 ppm (s, 3H)
CH ₃ CH ₂ OX CH ₃ : 1.2 ppm (t, 3H)
CH ₃ CH ₂ OX of _{CH 2 O: 3.7ppm (q,} 2H)

As described _above, the signal (3.7 ppm) is XOCH 2 _CH 2 OX of CH _2, since the overlaps with CH ₃ CH ₂ OX of CH ₂ O signals (3.7 _ppm), the CH 3 _CH 2 OX The amount of XOCH ₂ CH ₂ OX is calculated by excluding the CH ₂ O equivalent of CH ₃ CH ₂ OX calculated from the CH ₃ signal (1.2 ppm).

In the above, each X is — (COO) _n Li or — (COO) _n R ¹ (where n is 0 or 1, R ¹ is an alkyl group having 1 to 4 carbon atoms, or 1 to 4 carbon atoms). Of the halogenated alkyl group.

From the concentration of each compound obtained by the analysis of (1) and (2) above, the volume of heavy water used for extraction, and the mass of the positive electrode active material layer used for extraction, XOCH of the positive electrode active material layer described above The amount A of ₂ CH ₂ OX was 75.5 × 10 ⁻⁴ mol / g.

[Analysis of negative electrode active material layer]
The negative electrode active material layer was analyzed by the same method as the analysis of the positive electrode active material layer. The amount B of XOCH ₂ CH ₂ OX in the negative electrode active material layer was 17.6 × 10 ⁻⁴ mol / g, and A / B was 4.3.

[Preparation of positive electrode sample]
For the remaining positive electrode obtained in [Analysis of Positive Electrode Active Material Layer], the average particle diameter [μm] of the lithium compound and the amount [% by mass] of the lithium compound contained in the positive electrode were measured. A positive electrode having a positive electrode active material layer coated on both sides was cut into a size of 10 cm × 5 cm, immersed in 30 g of diethyl carbonate solvent, and the positive electrode was occasionally moved with tweezers and washed for 10 minutes. Subsequently, the positive electrode was taken out, air-dried in an argon box for 5 minutes, immersed in 30 g of diethyl carbonate solvent newly prepared, and washed for 10 minutes in the same manner as described above. The positive electrode was taken out from the argon box and dried for 20 hours under the conditions of a temperature of 25 ° C. and a pressure of 1 kPa using a vacuum dryer (manufactured by Yamato Kagaku, DP33) to obtain a positive electrode sample 1.

[Positive electrode surface SEM and EDX measurement]
A small piece of 1 cm × 1 cm was cut out from the positive electrode sample 1, and the surface was coated with gold in a vacuum of 10 Pa by sputtering. Subsequently, SEM and EDX on the surface of the positive electrode were measured under atmospheric exposure under the following conditions.

(SEM-EDX measurement conditions)
・ Measurement device: manufactured by Hitachi High-Technology, field emission scanning electron microscope FE-SEM S-4700
・ Acceleration voltage: 10 kV
・ Emission current: 1μA
-Measurement magnification: 2000 times-Electron beam incident angle: 90 °
-X-ray extraction angle: 30 °
・ Dead time: 15%
Mapping element: C, O, F
Measurement pixel number: 256 × 256 pixels Measurement time: 60 sec.
-Number of integrations: 50 times-The brightness and contrast were adjusted so that there was no pixel that reached the maximum brightness, and the average brightness was in the range of 40% to 60%.

[Positive electrode cross section SEM and EDX measurement]
A 1 cm × 1 cm piece is cut out from the positive electrode sample 1, and a cross section perpendicular to the surface direction of the positive electrode sample 1 is used under the conditions of an acceleration voltage of 4 kV and a beam diameter of 500 μm, using SM-90020CP manufactured by JEOL. Produced. The positive electrode cross section SEM and EDX were measured by the method described above.

The image obtained from the positive cross-sectional SEM and EDX that the measurement was calculated average particle diameter Y ₁ having an average particle diameter of X ₁ and the positive electrode active material of a lithium compound by image analysis using an image analysis software (ImageJ) . With respect to the obtained oxygen mapping, particles containing 50% or more of bright areas binarized on the basis of the average value of brightness are lithium compound particles X, and the other particles are cathode active material particles Y, For all the X and Y particles observed in the cross-sectional SEM image, the cross-sectional area S was determined, and the particle diameter d calculated by the following formula (1) was determined. (The circumference ratio is π.)

得られた粒子径ｄを用いて、下記式（２）において体積平均粒子径Ｘ_０及びＹ_０を求めた。

Obtained with a particle size d, it was determined volume average particle diameter X ₀ and Y ₀ in formula (2).

正極断面の視野を変えて合計５ヶ所測定し、それぞれのＸ_０及びＹ_０の平均値である平均粒子径Ｘ_１は１．６６μｍ、Ｙ_１は４．４１μｍであった。

A total of five points were measured by changing the field of view of the positive electrode cross section, and the average particle diameter X _1, which is the average value of X ₀ and Y ₀ , was 1.66 μm and Y ₁ was 4.41 μm.

[Quantitative determination of lithium compounds]
The obtained positive electrode sample 1 was cut into a size of 5 cm × 5 cm (weight: 0.256 g), immersed in 20 g of methanol, covered with a container, and left in a 25 ° C. environment for 3 days. Thereafter, the positive electrode was taken out and vacuum-dried at 120 ° C. and 5 kPa for 10 hours. The positive electrode weight M ₀ at this time is 0.255 g, and GC / MS is measured under the conditions in which a calibration curve has been prepared in advance for the washed methanol solution, and the presence of diethyl carbonate is less than 1%. confirmed. Subsequently, 25.00 g of distilled water was impregnated with the positive electrode, and the container was covered and allowed to stand in a 45 ° C. environment for 3 days. Thereafter, the positive electrode was taken out and vacuum-dried at 150 ° C. and 3 kPa for 12 hours. The positive electrode weight M ₁ at this time is 0.236 g, and GC / MS is measured under the conditions in which a calibration curve has been prepared in advance for the distilled water after washing, and it is confirmed that the amount of methanol present is less than 1%. did. The active material layer on the positive electrode current collector was removed using a spatula, a brush, and a brush, and the weight M ₂ of the positive electrode current collector was measured to be 0.099 g. When the amount of lithium carbonate Z in the positive electrode was determined according to the formula (3), it was 12.4% by mass.

[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 1150 F, where Q is the capacity when constant current discharge was performed at a current value of 2 C up to 2.2 V.

[Calculation of Ra · F]
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 was calculated by R = ΔE / (20C (current value A)).
The product Ra · F of the capacitance F and the room temperature discharge internal resistance Ra was 2.04ΩF.

[Calculation of Rf / Ra]
About the obtained electrical storage element, in a thermostat set to 25 degreeC, it uses a charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. until a current value of 20C reaches 2.2V. A current discharge followed by a constant voltage discharge for applying a constant voltage of 2.2 V for a total of 30 minutes, followed by a constant current charge up to 3.8 V with a current value of 20 C, a charging curve (time-voltage ) In this charging curve, Eo is the voltage at charging time = 0 seconds obtained by extrapolating from the voltage values at the time of charging time 2 seconds and 4 seconds by linear approximation, and the drop voltage ΔE = Eo−2.2, and The room temperature charge internal resistance Rf was calculated from R = ΔE / (20C (current value A)).
Rf / Ra was 1.16.

[E / V calculation]
E / V includes the value of the capacitance F obtained by the above method, the outer dimension length (l ₁ ) and outer dimension width (w ₁ ) of the cup-molded portion of the laminate film of the electricity storage element, and the laminate film. by using the thickness of the storage element _{(t 1)} by _V 1 obtained _{(= l 1 × w 1 ×} t 1), E / V = F × (3.8 2 -2.2 2) / 7200 / V ₁ to 21.1 Wh / L.

[Calculation of Rb / Ra after high-temperature storage test]
About the obtained electrical storage element, in a thermostat set to 25 degreeC, it uses a charge / discharge device (5V, 360A) made by Fujitsu Telecom Networks Co., Ltd. until it reaches 4.0V at a current value of 100C. Current charging was performed, followed by constant voltage charging in which a constant voltage of 4.0 V was applied for a total of 10 minutes. The cell was stored in a 60 ° C. environment, taken out from the 60 ° C. environment every two weeks, charged with a similar charging operation to a cell voltage of 4.0 V, and then stored again in a 60 ° C. environment. This operation was repeated for 2 months. For the electricity storage device after the high temperature storage test, the room temperature discharge internal resistance Rb after the high temperature storage test was calculated in the same manner as in [Calculation of Ra · F]. The ratio Rb / Ra calculated by dividing this Rb (Ω) by the room temperature discharge internal resistance Ra (Ω) before the high-temperature storage test determined in [Calculation of Ra · F] was 1.67.

[Nail penetration test]
Testing machine: Shimadzu Autograph AG-X
Nail: φ2.5mm-SUS304
About evaluation: About the obtained electrical storage element, in a thermostat set to 25 ° C., the charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. was used to reach 2.2V at a current value of 20C. Then, a constant current discharge was performed until a constant voltage discharge was applied, and then a constant voltage discharge for applying a constant voltage of 3.8 V was performed for a total of 30 minutes, whereby the voltage of the storage element was adjusted to 3.8 V. This electricity storage element is fixed horizontally and inserted into the nail piercing position at the center of the electricity storage element until it penetrates the nail at a speed of 10 mm / sec, and whether or not the non-aqueous lithium electricity storage element is ignited, and non-aqueous lithium type The presence or absence of smoke from the storage element was observed.
In the nonaqueous lithium storage element of Example 1, neither ignition nor smoke occurred.

<< Examples 2 to 5 >>
Except for the activated carbon, the negative electrode, and the separator as shown in Table 2 below, the non-aqueous lithium storage elements of Examples 2 to 5 were produced in the same manner as in Example 1, and various evaluations were made. Went. The evaluation results of the obtained non-aqueous lithium storage element are shown in Tables 3 and 4 below.

<< Examples 6 to 28 >>
Activated carbon, a negative electrode, and a separator (made of insulating porous layer, the thickness t _i of thickness t _s and insulating porous layer of the porous _film), an average particle diameter of the lithium compound amount of the positive electrode precursor, respectively, the following Table 2 The nonaqueous lithium-type electricity storage devices of Examples 6 to 28 were produced in the same manner as in Example 1 except that they were as shown in FIG. The evaluation results of the obtained non-aqueous lithium storage element are shown in Tables 3 and 4 below.

<< Examples 29-53 >>
Activated carbon, negative electrode, separator (insulating porous layer material, pore diameter d, pore number D, porosity B), and lithium dope time were as shown in Table 2 below, respectively. Similarly, the non-aqueous lithium electricity storage elements of Examples 29 to 53 were produced, and various evaluations were performed. The evaluation results of the obtained non-aqueous lithium storage element are shown in Tables 3 and 4 below.

<< Examples 54-58 >>
Activated carbon, the negative electrode, the type of lithium compound, and a separator (made of insulating porous layer, the thickness t _i of the porous film thickness t _s and insulating porous _layer, the material of the porous membrane and insulating porous layer, pore diameter d, the number of holes D and porosity B) were each as shown in Table 2 below, except that non-aqueous lithium storage elements of Examples 54 to 58 were prepared in the same manner as Example 1, Evaluation was performed. The evaluation results of the obtained non-aqueous lithium storage element are shown in Tables 3 and 4 below.

<< Comparative Examples 1-12 >>
Activated carbon, the negative electrode, the type of lithium compound, and a separator (made of insulating porous layer, the thickness t _i of the porous film thickness t _s and insulating porous _layer, the material of the porous membrane and insulating porous layer, pore diameter d, the number of holes D, porosity B), the amount of the lithium compound of the positive electrode precursor and the average particle diameter were the same as in Example 1 except that they were as shown in Table 14 and Table 15 below, respectively. Twelve non-aqueous lithium-type electricity storage elements were produced, and various evaluations were performed. The evaluation results of the obtained non-aqueous lithium storage element are shown in Tables 3 and 4 below.

  By the above examples, the non-aqueous lithium storage element of the present embodiment is a non-aqueous lithium storage element that has excellent initial input / output characteristics, a small increase in resistance due to high-temperature storage, and a low risk of smoke and ignition due to nail penetration. It was verified that there was.

  The non-aqueous lithium storage element according to the present invention is excellent in initial input / output characteristics, has a small characteristic deterioration due to high-temperature storage, and has a low risk of smoke and ignition due to nail penetration. It can be suitably used in the field of hybrid drive systems that combine motors, power storage elements, and for assisting instantaneous power peaks.

1 Porous membrane 2 Insulating porous layer

Claims (18)

A non-aqueous lithium storage element having a positive electrode containing a lithium compound other than the positive electrode active material, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions,
The positive electrode has a positive electrode current collector, and a positive electrode active material layer including a positive electrode active material provided on one or both surfaces of the positive electrode current collector, the positive electrode active material includes activated carbon,
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 <a Y _1, the amount of lithium compound contained in the positive electrode is not more than 50 wt% or more 1 wt% based on the total weight of the positive electrode active material layer as a reference,
The separator includes a porous membrane and an insulating porous layer formed on at least one surface of the porous membrane, and the ratio of the thickness of the insulating porous layer to the thickness of the porous membrane is 20% to 125%. Type storage element.   The non-aqueous lithium storage element according to claim 1, wherein the porous film includes a polyolefin microporous film.   The non-aqueous lithium storage element according to claim 1, wherein the insulating porous layer includes an inorganic filler and a resin binder.   The non-aqueous lithium storage element according to claim 1, wherein the insulating porous layer has a thickness of 3 μm or more and 30 μm or less.   The thickness of the said porous film is a non-aqueous lithium storage element as described in any one of Claims 1-4 which are 5 micrometers or more and 35 micrometers or less. The non-aqueous system according to any one of claims 1 to 5, wherein the pore diameter of the porous membrane is 0.03 µm to 0.1 µm, and the number of pores is 100 / µm ² to 250 / µm ^2. Lithium type storage element.   The non-aqueous lithium storage element according to any one of claims 1 to 6, wherein the porosity of the porous film is 45% to 75%. The positive electrode active material layer contains at least one compound selected from the group consisting of the following formulas (1) to (3) from 1.60 × 10 ⁻⁴ mol / g per unit mass of the positive electrode active material layer. The non-aqueous lithium storage element according to claim 1, which contains 300 × 10 ⁻⁴ mol / g.

{In Formula (1), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are each independently — (COO) _n (here And n is 0 or 1.). }

{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} represents 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 each independently-(COO) _n (where n is 0 or 1). }

{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 hydrogen and 1 to 10 carbon atoms. An alkyl group, 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, X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1); }   In the positive electrode active material layer, the content per unit mass of the positive electrode active material layer of at least one compound selected from the group consisting of the formulas (1) to (3) is A, and the negative electrode active material When the content per unit mass of the negative electrode active material layer of at least one compound selected from the group consisting of the formulas (1) to (3) in the layer is B, 0.2 ≦ A / The nonaqueous lithium storage element according to claim 1, wherein B ≦ 20.   The non-aqueous lithium storage element according to claim 1, wherein the lithium compound is at least one selected from the group consisting of lithium carbonate, lithium oxide, and lithium hydroxide. 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 V ₁ (cc / g), and a diameter of less than 20 mm calculated by the MP method. When the amount of micropores derived from the pores is V ₂ (cc / g), 0.3 <V ₁ ≦ 0.8 and 0.5 ≦ V ₂ ≦ 1.0 are satisfied, and by the BET method The non-aqueous lithium storage element according to any one of claims 1 to 10, which is activated carbon having a specific surface area of 1,500 m ² / g or more and 3,000 m ² / g or less. The positive electrode active material contained in the positive electrode active material layer has a mesopore amount V ₁ (cc / g) derived from pores having a diameter of 20 to 500 mm calculated by BJH method of 0.8 <V ₁ ≦ 2.5. The ratio of micropores V ₂ (cc / g) derived from pores having a diameter of less than 20 mm calculated by the MP method satisfying 0.8 <V ₂ ≦ 3.0 and measured by the BET method The non-aqueous lithium storage element according to any one of claims 1 to 11, which is activated carbon having a surface area of 2,300 m ² / g or more and 4,000 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 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 any one of claims 1 to 12, 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. The non-aqueous lithium storage element according to any one of claims 1 to 12 and 15, 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. A non-aqueous lithium storage element having a positive electrode containing a lithium compound other than the positive electrode active material, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions,
The positive electrode includes a positive electrode current collector, and a positive electrode active material layer including a positive electrode active material provided on one or both surfaces of the positive electrode current collector, the positive electrode active material includes activated carbon,
The separator includes a porous membrane and an insulating porous layer formed on at least one surface of the porous membrane, and the ratio of the thickness of the insulating porous layer to the thickness of the porous membrane is 20% to 125%,
In the non-aqueous lithium storage element, when the initial room temperature discharge internal resistance is Ra (Ω), the initial room temperature charge internal resistance is Rf (Ω), and the capacitance is F (F),
The following (a), (b):
(A) The product Ra · F of Ra and F is 0.3 or more and 3.0 or less;
(B) Rf / Ra is 0.5 or more and 1.5 or less;
A non-aqueous lithium storage element that satisfies the above requirements. A non-aqueous lithium storage element having a positive electrode containing a lithium compound other than the positive electrode active material, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions,
The separator includes a porous membrane and an insulating porous layer formed on at least one surface of the porous membrane, and the ratio of the thickness of the insulating porous layer to the thickness of the porous membrane is 20% to 125%,
When the initial room temperature discharge internal resistance of the non-aqueous lithium storage element is Ra (Ω), and the internal resistance at 25 ° C. after storage for 2 months at a cell voltage of 4 V and an environmental temperature of 60 ° C. is Rb (Ω), A non-aqueous lithium storage element having Rb / Ra of 3.0 or less.

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