JP2018056430A - Nonaqueous lithium-type storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous lithium-type storage element capable of high output and high capacity in a low voltage region of cell voltage 2V-3V.SOLUTION: Provided is a non-aqueous lithium-type storage element containing a lithium compound in a positive electrode, in which high output and high capacity can be taken out even in a low voltage region of cell voltage 2V-3V by adjusting the content of the lithium compound in the positive electrode to 1 mass% or more and 50 mass% or less based on the total mass of a positive electrode active material layer.SELECTED DRAWING: Figure 1

Description

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

In recent years, from the viewpoint of the conservation of the global environment and the effective use of energy aimed at saving 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 lithium ion capacitor has attracted attention and has been actively developed.
The energy of the capacitor is expressed by 1/2 · C · V ² (where C is a capacitance and V is a voltage).

A lithium ion capacitor is a kind of energy storage device (non-aqueous lithium energy storage device) that uses a non-aqueous electrolyte containing a lithium salt, and the negative electrode adsorbs the same as an electric double layer capacitor at about 3 V or more at the positive electrode. It is a power storage element that charges and discharges by a non-Faraday reaction by desorption, and a Faraday reaction by insertion and extraction of lithium ions in the negative electrode, similar to a lithium ion battery.
Summarizing the above electrode materials and their characteristics, when using materials such as activated carbon for the electrode and charging / discharging by adsorption / 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.
A lithium ion capacitor uses activated carbon (energy density 1 time) for the positive electrode and a carbon material (10 times energy density) for the negative electrode, and is charged and discharged by a non-Faraday reaction at the positive electrode and a Faraday reaction at the negative electrode. It is a novel asymmetric capacitor that combines the features of a multilayer capacitor and a lithium ion secondary battery. In addition, while having high output and high durability, it has a high energy density (positive electrode 1 ×× negative electrode 10 = 10), and there is no need to limit the depth of discharge unlike a lithium ion secondary battery. is there.

Patent Document 1 proposes a lithium ion capacitor having a higher capacity by controlling the BET specific surface area and electrode density of the positive electrode within a specific range. Patent Document 2 proposes a technique for increasing the capacity of a lithium ion capacitor by increasing the thickness of the positive electrode by using a three-dimensional porous metal body as a positive electrode current collector. Patent Document 3 proposes a method for recovering the capacity of a deteriorated power storage element by oxidizing various lithium compounds as oxides at the positive electrode.
However, these techniques have a problem that the ion diffusion capacity of the positive electrode active material layer is reduced and the output is reduced due to inhibition of electronic conduction between the active material particles due to the addition of the lithium compound. Moreover, in view of energy regeneration applications such as in-vehicle use, it is desirable that the battery is in a low charge state, that is, in a low voltage region of a cell voltage of 2V to 3V. There is no mention of resistance and battery capacity that can be removed.

JP 2012-235041 A JP2013-115179A Japanese Patent No. 5278467

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

The present invention has been made in view of the above situation.
Therefore, the problem to be solved by the present invention is to provide a lithium ion capacitor capable of high output and high capacity in a low voltage region of a cell voltage of 2V to 3V.

  The present invention has been made in view of the above situation. Accordingly, one of the problems to be solved by the present invention is a non-aqueous lithium storage element containing a lithium compound in the positive electrode, wherein the content of the lithium compound in the positive electrode is determined by the total mass of the positive electrode active material layer. As a reference, it is to provide a non-aqueous lithium storage element capable of taking out a high output and a large capacity even in a low voltage region by setting it to 1 mass% or more and 50 mass% or less.

The present invention has been made based on this finding. That is, the present invention is as follows.
[1] A non-aqueous lithium storage element comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions,
The negative electrode has a negative electrode current collector and a negative electrode active material layer including a negative electrode active material provided on one or both surfaces of the negative electrode current collector, and the negative electrode active material occludes lithium ions. Contains carbon material that can be released, and
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, and the positive electrode active material includes activated carbon. ,in addition,
The positive electrode contains 1% by mass to 50% by mass of a lithium compound other than the positive electrode active material, based on the total mass of the positive electrode active material layer; and
In the discharge curve when the electric storage element is subjected to constant current discharge from a voltage of 3.8 V to a voltage of 2.2 V at a current value of 4 C or less, with respect to a straight line AB connecting the discharge start point A and the discharge end point B, The discharge curve is a downward convex curve, and
_{L 1} the length of the straight line AB, the length of the discharge curve AB is taken as _{l 2,} 1.000 _<nonaqueous lithium-type power storage, which is a l 2 / _{l 1} ≦ 1.030 element.

  [2] The lithium compound is one or more selected from lithium carbonate, lithium oxide, lithium hydroxide, lithium fluoride, lithium chloride, lithium oxalate, lithium iodide, lithium nitride, lithium oxalate, and lithium acetate. The non-aqueous lithium storage element according to [1].

[3] When the average particle diameter of the lithium compound and _{X 1,} a 0.1μm ≦ _{X 1} ≦ 10μm, further, when the average particle diameter of the positive electrode active material _{Y 1, 2μm ≦ Y 1 ≦} 20μm And the non-aqueous lithium storage element according to any one of [1] or [2], wherein X ₁ <Y ₁ .

[4] The positive electrode active material contained in the positive electrode active material layer has an amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method as V1 (cc / g) and a diameter of 20 mm calculated by the MP method. When the amount of micropores derived from smaller pores is V2 (cc / g), it satisfies 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0, and is measured by the BET method The non-aqueous lithium storage element according to any one of [1] to [3], 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.
[5] The positive electrode active material contained in the positive electrode active material layer has a mesopore amount V1 (cc / g) derived from pores having a diameter of 20 to 500 mm calculated by BJH method of 0.8 <V1 ≦ 2. The specific surface area measured by the BET method when the amount of micropores V2 (cc / g) derived from pores having a diameter of less than 20 mm calculated by the MP method satisfies 0.8 <V2 ≦ 3.0. The non-aqueous lithium storage element according to any one of [1] to [3], wherein the activated carbon is 2300 m ² / g or more and 4,000 m ² / g or less.

[6] The non-aqueous lithium type according to any one of [1] to [5], 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. Power storage element.
[7] The non-aqueous lithium storage element according to any one of [1] to [6], 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.
[8] The non-aqueous lithium storage element according to any one of [1] to [5], 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. .
[9] The non-aqueous lithium-type electricity storage according to any one of [1] to [5] and [8], 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. element.
[10] The non-aqueous lithium storage element according to [8] or [9], wherein an average particle diameter of the negative electrode active material is 1 μm or more and 10 μm or less.
[11] The non-aqueous lithium storage element according to any one of [1] to [10], wherein the positive electrode current collector and the negative electrode current collector are metal foils having no through holes.

[12] In the nonaqueous lithium storage element according to any one of [1] to [11], an initial charging internal resistance at a cell voltage of 2.2 V is Ra (Ω), and a capacitance is F ( F), when the amount of electric power is E (Wh), and the volume of the exterior body containing the electrode stack is V (L), the following requirements (a) and (b):
(A) The product Ra · F of Ra and F is 0.3 or more and 3.0 or less,
(B) E / V is 15 or more and 50 or less,
A non-aqueous lithium storage element that satisfies

  According to the present invention, there is provided a non-aqueous lithium storage element containing 1% by mass or more and 50% by mass or less of a lithium compound other than the positive electrode active material based on the total mass of the positive electrode active material layer on the positive electrode. Can provide a non-aqueous lithium storage element capable of taking out a high output and a large capacity.

It is a figure explaining the discharge curve of the non-aqueous lithium electrical storage element in this embodiment. 6 is a diagram showing a discharge curve of the electricity storage device obtained in Example 1. FIG. 6 is a diagram showing a discharge curve of the electricity storage device obtained in Example 2. FIG. 6 is a diagram showing a discharge curve of a power storage element obtained in Comparative Example 1. FIG.

Hereinafter, a form for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist thereof.
In general, a non-aqueous lithium-type energy storage device mainly includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an outer package. As the electrolytic solution, an organic solvent in which a lithium salt is dissolved (hereinafter referred to as a non-aqueous electrolytic solution) is used.

[Positive electrode]
The positive electrode has a positive electrode current collector and a positive electrode active material layer present on one side or both sides thereof.
Moreover, it is preferable that a positive electrode contains a lithium compound as a positive electrode precursor before an electrical storage element assembly. As will be described later, in this embodiment, it is preferable that the negative electrode is pre-doped with lithium ions in the power storage element assembly step. In addition, it is preferable to apply a voltage between the positive electrode precursor and the negative electrode after assembling the electricity storage device using the non-aqueous electrolyte. The lithium compound is preferably contained in a positive electrode active material layer formed on the positive electrode current collector of the positive electrode precursor.
In this specification, the positive electrode state before the lithium doping step is defined as the positive electrode precursor, and the positive electrode state after the lithium doping step is defined as the positive electrode.

[Positive electrode active material layer]
The positive electrode active material layer included in the positive electrode contains a positive electrode active material containing activated carbon. In addition to this, the positive electrode active material layer may contain optional components such as a conductive filler, a binder, and a dispersion stabilizer as necessary.
The positive electrode active material layer of the positive electrode precursor preferably contains a lithium compound other than the positive electrode active material.

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

There is no restriction | limiting in particular in the kind of activated carbon used as a positive electrode active material, and its raw material. However, 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 V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is calculated. When V2 (cc / g)
(1) For high input / output characteristics, 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied, and the specific surface area measured by the BET method is 1,500 m ^2. / G or more and 3,000 m ² / g or less of activated carbon (hereinafter also referred to as activated carbon 1) is preferable,
(2) In order to obtain a high energy density, 0.8 <V1 ≦ 2.5 and 0.8 <V2 ≦ 3.0 are satisfied, and the specific surface area measured by the BET method is 2,300 m ^2. / G or more and 4,000 m < ² > / g or less activated carbon (henceforth also called activated carbon 2) 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 V1 of the activated carbon 1 is preferably a value larger than 0.3 cc / g from the viewpoint of increasing the input / output characteristics when incorporated in the energy storage device. On the other hand, it is preferably 0.8 cc / g or less from the viewpoint of suppressing a decrease in the bulk density of the positive electrode. V1 is more preferably 0.35 cc / g or more and 0.7 cc / g or less, and further preferably 0.4 cc / g or more and 0.6 cc / g or less.
The micropore amount V2 of the activated carbon 1 is preferably 0.5 cc / g or more in order to increase the specific surface area of the activated carbon and increase the capacity. On the other hand, it is preferably 1.0 cc / g or less from the viewpoint of suppressing the bulk of the activated carbon, increasing the density as an electrode, and increasing the capacity per unit volume. V2 is more preferably 0.6 cc / g or more and 1.0 cc / g or less, and further preferably 0.8 cc / g or more and 1.0 cc / g or less. The combination of the lower limit and the upper limit can be arbitrary.

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

  The average pore diameter of the activated carbon 1 is preferably 17 mm or more, more preferably 18 mm or more, and most preferably 20 mm or more from the viewpoint of maximizing the output of the obtained electricity storage device. Moreover, from the point of maximizing the capacity, the average pore diameter of the activated carbon 1 is preferably 25 mm or less.

BET specific surface area of the activated carbon 1 is preferably from 1,500 m ² / g or more 3,000 m ² / g, more preferably not more than 1,500 m ² / g or more 2,500 m ² / g. When the BET specific surface area is 1,500 m ² / g or more, good energy density is easily obtained. On the other hand, when the BET specific surface area is 3,000 m ² / g or less, the strength of the electrode is maintained. Since there is no need to add a large amount of binder, the performance per electrode volume is increased. The combination of the lower limit and the upper limit can be arbitrary.

The activated carbon 1 having the above-described features can be obtained using, for example, the raw materials and processing methods described below.
In this embodiment, the carbon source used as a raw material of the activated carbon 1 is not particularly limited. For example, plant materials such as wood, wood flour, coconut husk, pulp by-product, bagasse, molasses, etc .; peat, lignite, lignite, bituminous coal, anthracite, petroleum distillation residue components, petroleum pitch, coke, coal tar, etc. Fossil-based raw materials; various synthetic resins such as phenol resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin, celluloid, epoxy resin, polyurethane resin, polyester resin, polyamide resin; polybutylene, polybutadiene, polychloroprene, etc. Synthetic rubber, other synthetic wood, synthetic pulp and the like, and carbides thereof. Among these raw materials, from the viewpoint of mass production and cost, plant raw materials such as coconut shells and wood flour, and their carbides are preferable, and coconut shell carbides are particularly preferable.

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

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

The average particle diameter of the activated carbon 1 is preferably 2 to 20 μm.
When the average particle size is 2 μm or more, the capacity per electrode volume tends to be high because the density of the active material layer is high. Here, if the average particle size is small, there may be a drawback that the durability is low. However, if the average particle size is 2 μm or more, such a defect hardly occurs. On the other hand, when the average particle size is 20 μm or less, it tends to be easily adapted to high-speed charge / discharge. The average particle diameter is more preferably 2 to 15 μm, still more preferably 3 to 10 μm. The upper limit and the lower limit of the range of the average particle diameter can be arbitrarily combined.

[Activated carbon 2]
The mesopore amount V1 of the activated carbon 2 is preferably a value larger than 0.8 cc / g from the viewpoint of increasing the output characteristics when incorporated in the energy storage device. On the other hand, V1 is preferably 2.5 cc / g or less from the viewpoint of suppressing a decrease in the capacity of the power storage element. V1 is more preferably from 1.00 cc / g to 2.0 cc / g, and still more preferably from 1.2 cc / g to 1.8 cc / g.

  On the other hand, the micropore volume V2 of the activated carbon 2 is preferably larger than 0.8 cc / g in order to increase the specific surface area of the activated carbon and increase the capacity. On the other hand, V2 is 3.0 cc / g or less, more preferably more than 1.0 cc / g and 2.5 cc / g or less, from the viewpoint of increasing the density as an electrode of activated carbon and increasing the capacity per unit volume. More preferably, it is 1.5 cc / g or more and 2.5 cc / g or less.

The activated carbon 2 having the above-described mesopore size and micropore size has a higher BET specific surface area than activated carbon used for conventional electric double layer capacitors or lithium ion capacitors. The specific value of the BET specific surface area of the activated carbon 2 is preferably 2,300 m ² / g or more and 4,000 m ² / g or less. The lower limit of the BET specific surface area is more preferably 3,000 m ² / g or more, and further preferably 3,200 m ² / g or more. On the other hand, the upper limit of the BET specific surface area is more preferably 3,800 m ² / g or less. When the BET specific surface area is 2,300 m ² / g or more, a good energy density is easily obtained. On the other hand, when the BET specific surface area is 4,000 m ² / g or less, the strength of the electrode is maintained. Since there is no need to add a large amount of binder, the performance per electrode volume is increased.
In addition, about V1, V2, and BET specific surface area of activated carbon 2, the upper limit and lower limit of the suitable range demonstrated above can be combined arbitrarily, respectively.

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

  Examples of the method 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 preferably about 400 to 700 ° C. (for the lower limit, preferably 450 ° C. or more, more preferably 500 ° C. or more, preferably about 650 ° C. or less for the upper limit) for about 0.5 to 10 hours.

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

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

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

  The content ratio of the positive electrode active material in the positive electrode active material layer is preferably 35% by mass or more and 95% by mass or less based on the total mass of the positive electrode active material layer in the positive electrode precursor. As 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. On the other hand, 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, suitable charge / discharge characteristics are exhibited.

[Lithium compounds]
The positive electrode active material layer of the positive electrode precursor of this embodiment preferably contains a lithium compound other than the positive electrode active material. Moreover, the positive electrode active material layer of the positive electrode of this embodiment contains lithium compounds other than the positive electrode active material.
Examples of the lithium compound include lithium carbonate, lithium oxide, lithium hydroxide, lithium fluoride, lithium chloride, lithium oxalate, iodine, which can be decomposed at the positive electrode in the lithium doping step described later and release lithium ions. One or more selected from lithium fluoride, lithium nitride, lithium oxalate, and lithium acetate are preferably used. Among these, lithium carbonate, lithium oxide, and lithium hydroxide are more preferable, and lithium carbonate is more preferably used from the viewpoint that it can be handled in the air and has low hygroscopicity. Such a lithium compound is decomposed by the application of a voltage, functions as a lithium-doped dopant source for the negative electrode, and forms 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 most preferably 10 μm or less. On the other hand, the lower limit of the average particle size of the lithium compound contained in the positive electrode precursor is more preferably 0.3 μm or more, and further preferably 0.5 μm or more. If the average particle size of the lithium compound is 0.1 μm or more, the vacancies remaining after the oxidation reaction of the lithium compound in the positive electrode have a sufficient volume to hold the electrolytic solution. improves. 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.

[Lithium compound of positive electrode]
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, is preferably a 0.1μm ≦ X ₁ ≦ 10μm. 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.

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

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

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

[SEM-EDX]
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, gold, platinum, osmium, or the like can be surface-treated by a method such as vacuum deposition or sputtering. With respect to the SEM-EDX image measurement method, 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.

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

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

[Ion chromatography]
By analyzing the positive electrode distilled water washing solution by ion chromatography, the anion species eluted in water can be identified. 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 non-suppressor method using a solution with low conductivity as the eluent can be used. In addition, mass spectrometers and charged particle detection can be combined with detectors, so appropriate columns and detectors are combined based on lithium compounds identified from SEM-EDX, Raman, and XPS analysis results. It is 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.

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

により算出できる。 In the positive electrode cleaning method, the positive electrode is sufficiently immersed in a methanol solution 50 to 100 times the mass of the positive electrode for 3 days or more. At this time, it is preferable to take measures such as covering the container so that methanol does not volatilize. Thereafter, the positive electrode is taken out of the methanol and dried in a vacuum (temperature: 100 to 200 ° C., pressure: 0 to 10 kPa, time: 5 to 20 hours in which the remaining amount of methanol in the positive electrode is 1% by mass or less). Can be determined by measuring GC / MS of water after washing with distilled water, which will be described later, based on a calibration curve prepared in advance, and the mass of the positive electrode at that time is M ₀ [g]. And Subsequently, the positive electrode is sufficiently immersed for 3 days or more in distilled water 100 times the mass of the positive electrode (100 M ₀ [g]). At this time, it is preferable to take measures such as covering the container so that distilled water does not volatilize. After soaking for 3 days or more, the positive electrode is taken out from the distilled water (in the case of measuring the above-mentioned ion chromatography, the amount of the liquid is adjusted so that the amount of distilled water is 100 M ₀ [g]), and the above. Vacuum dry as in the methanol wash. The positive electrode active material layer on the current collector was measured using a spatula, a brush, a brush, etc. in order to measure the mass of the current collector of the obtained positive electrode with M ₁ [g]. Remove. When the mass of the obtained positive electrode current collector is M ₂ [g], the mass% Z of the lithium compound contained in the positive electrode is expressed by the following mathematical formula (1):

Can be calculated.

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

  The binder is not particularly limited. For example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, and the like. Can be used. The amount of the binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 3 parts by mass or more and 27 parts by mass or less, and still more preferably 5 parts by mass or more and 25 parts by mass with respect to 100 parts by mass of the positive electrode active material. Or less. If the usage-amount of a binder is 1 mass part or more, sufficient electrode intensity | strength will be expressed. On the other hand, if the usage-amount of a binder is 30 mass parts or less, a high input-output characteristic will be expressed, without inhibiting the entrance-and-extraction and spreading | diffusion of the ion to a positive electrode active material.

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

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

[Production of positive electrode precursor]
In the present embodiment, the positive electrode precursor serving as the positive electrode of the non-aqueous lithium storage element can be manufactured by an electrode manufacturing technique in a known lithium ion battery, electric double layer capacitor, or the like. For example, a positive electrode active material, a lithium compound, and other optional components used as 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. Further, the obtained positive electrode precursor may be pressed to adjust the film thickness or bulk density of the positive electrode active material layer. Alternatively, without using a solvent, the positive electrode active material and the lithium compound, and other optional components used as necessary, are mixed in a dry process, and the resulting mixture is press-molded and then conductively bonded. A method of attaching to the positive electrode current collector using an agent is also possible.

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

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

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

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

  The drying of the positive electrode precursor coating film is not particularly limited, but preferably a drying method such as hot air drying or infrared (IR) drying can be used. The coating film may be dried at a single temperature or may be dried by changing the temperature in multiple stages. Moreover, you may dry a coating film combining several drying methods. The drying temperature is preferably 25 ° C. or higher and 200 ° C. or lower, more preferably 40 ° C. or higher and 180 ° C. or lower, and further preferably 50 ° C. or higher and 160 ° C. or lower. When the drying temperature is 25 ° C. or higher, the solvent in the coating film can be sufficiently volatilized. On the other hand, if the drying temperature is 200 ° C. or lower, it is possible to suppress cracking of the coating film due to rapid volatilization of the solvent, uneven distribution of the binder due to migration, and oxidation of the positive electrode current collector and the positive electrode active material layer.

The press of the positive electrode precursor is not particularly limited, but preferably a press such as a hydraulic press or a vacuum press can be used. The film thickness, bulk density, and electrode strength of the positive electrode active material layer can be adjusted by the press pressure, the gap, and the surface temperature of the press part described later.
The pressing pressure is preferably 0.5 kN / cm or more and 20 kN / cm or less, more preferably 1 kN / cm or more and 10 kN / cm or less, and further preferably 2 kN / cm or more and 7 kN / cm or less. If the pressing pressure is 0.5 kN / cm or more, the electrode strength can be sufficiently increased. On the other hand, when the pressing pressure is 20 kN / cm or less, the positive electrode precursor can be adjusted to a desired positive electrode active material layer thickness and bulk density without causing bending or wrinkles.
In addition, the gap between the press rolls can be set to an arbitrary value according to the thickness of the positive electrode precursor after drying so as to have a desired thickness and bulk density of the positive electrode active material layer. Furthermore, the press speed can be set to an arbitrary speed at which the positive electrode precursor does not bend or wrinkle.
Moreover, the surface temperature of a press part may be room temperature, and you may heat a press part as needed. The lower limit of the surface temperature of the press part in the case of heating is preferably the melting point minus 60 ° C. or more of the binder used, more preferably the melting point minus 45 ° C. or more, and further preferably the melting point minus 30 ° C. or more. On the other hand, the upper limit of the surface temperature of the press part when heating is preferably the melting point plus 50 ° C. or less of the binder used, more preferably the melting point plus 30 ° C. or less, and further preferably the melting point plus 20 ° C. or less. For example, when PVdF (polyvinylidene fluoride: melting point 150 ° C.) is used as the binder, it is preferable to heat the surface of the press part to 90 ° C. or more and 200 ° C. or less, more preferably 105 ° C. or more and 180 ° C. or less, Preferably, the surface of the press part is heated to 120 ° C. or higher and 170 ° C. or lower. When a styrene-butadiene copolymer (melting point: 100 ° C.) is used as the binder, it is preferable to heat the surface of the press part to 40 ° C. or more and 150 ° C. or less, more preferably 55 ° C. or more and 130 ° C. or less. More preferably, the surface of the press part is heated to 70 ° C. or higher and 120 ° C. or lower.

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

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

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

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

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

[Negative electrode active material]
As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Specific examples include carbon materials, titanium oxide, silicon, silicon oxide, silicon alloys, silicon compounds, tin and tin compounds. Preferably, the content of the carbon material with respect to the total amount of the negative electrode active material is 50% by mass or more, and more preferably 70% by mass or more. Although the content of the carbon material may be 100% by mass, it is preferably 90% by mass or less, and preferably 80% by mass or less, for example, from the viewpoint of obtaining the effect of using other materials in combination.

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

  Examples of the carbon material include non-graphitizable carbon materials; graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon spherules; Amorphous carbonaceous material such as petroleum pitch, coal pitch, mesocarbon micro beads, coke, carbonaceous material obtained by heat treatment of carbonaceous material precursors such as synthetic resin (eg phenol resin); Examples include pyrolysates of furyl alcohol resin or novolak resin; fullerenes; carbon nanophones; and composite carbon materials thereof.

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

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

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

The BET specific surface area of the composite carbon material 1 is preferably 100 m ² / g or more and 1,500 m ² / g or less, more preferably 150 m ² / g or more and 1,100 m ² / g or less, further preferably 180 m ² / g or more and 550 m. ² / g or less. If this BET specific surface area is 100 m ² / g or more, the pores can be appropriately held and the lithium ion diffusion becomes good, so that high input / output characteristics can be exhibited. On the other hand, since it is 1,500 m ² / g or less, the charge / discharge efficiency of lithium ions is improved, so that the cycle durability is not impaired.

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

The doping amount of lithium ions per unit mass of the composite carbon material 1 is preferably 530 mAh / g or more and 2,500 mAh / g or less. More preferably, 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 lithium ions in composite carbon material 1 are inserted, and composite carbon material 1 for a desired lithium amount is further obtained. The amount of 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.
On the other hand, when the doping amount is 2,500 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal occur.

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

  If the mesopore amount Vm1 is 0.300 cc / g or less, the BET specific surface area can be increased, the lithium ion doping amount can be increased, and the bulk density of the negative electrode can be increased. As a result, the negative electrode can be thinned. Moreover, if the micropore amount Vm2 is 0.650 cc / g or less, high charge / discharge efficiency for lithium ions can be maintained. On the other hand, if the mesopore volume Vm1 and the micropore volume Vm2 are equal to or higher than the lower limit (0.010 ≦ Vm1, 0.001 ≦ Vm2), high input / output characteristics can be obtained.

The BET specific surface area of the composite carbon material 1a is preferably 100 m ² / g or more and 1,500 m ² / g or less. More preferably 150 meters ² / g or more 1,100m ² / g, more preferably not more than 180 m ² / g or more 550m ² / g. If the BET specific surface area is 100 m ² / g or more, the pores can be appropriately maintained, and the lithium ion diffusion becomes good, so that high input / output characteristics can be exhibited. Moreover, since the doping amount of lithium ions can be increased, the negative electrode can be made thin. On the other hand, since it is 1,500 m ² / g or less, the charge / discharge efficiency of lithium ions is improved, so that the cycle durability is not impaired.

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

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

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

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

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

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

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

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

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

The softening point of the pitch used is preferably 30 ° C. or higher and 250 ° C. or lower, and more preferably 60 ° C. or higher and 130 ° C. or lower. A pitch having a softening point of 30 ° C. or higher can be handled with high accuracy without any problem in handling properties. The pitch having a softening point of 250 ° C. or less contains a large amount of relatively low molecular weight compounds. Therefore, when the pitch is used, fine pores in the activated carbon can be deposited.
As a specific method for producing the composite carbon material 1a, for example, activated carbon is heat-treated in an inert atmosphere containing hydrocarbon gas volatilized from a carbonaceous material precursor, and the carbonaceous material is coated in a gas phase. The method of making it wear is mentioned. In addition, a method in which activated carbon and a carbonaceous material precursor are mixed in advance and heat-treated, or a method in which a carbonaceous material precursor dissolved in a solvent is applied to activated carbon and dried is then heat-treated.

  What the mass ratio with respect to this activated carbon of this carbonaceous material in the composite carbon material 1a is 10 mass% or more and 100 mass% or less is preferable. This mass ratio is preferably 15% by mass or more and 80% by mass or less. If the mass ratio of the carbonaceous material is 10% by mass or more, the micropores possessed by the activated carbon can be appropriately filled with the carbonaceous material, and the charge / discharge efficiency of lithium ions is improved. There is no loss of sex. Moreover, if the mass ratio of the carbonaceous material is 100% by mass or less, the pores of the composite carbon material 1a are appropriately maintained and the specific surface area is maintained large. Therefore, from the result that the doping amount of lithium ions can be increased, high output density and high durability can be maintained even if the negative electrode is thinned.

[Composite carbon material 2]
The composite carbon material 2 is the composite carbon material using one or more carbon materials having a BET specific surface area of 0.5 m ² / g to 80 m ² / g as the base material. The base material is not particularly limited, and natural graphite, artificial graphite, low crystal graphite, hard carbon, soft carbon, carbon black and the like can be suitably used.

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

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

  The mass ratio of the carbonaceous material to the base material in the composite carbon material 2 is preferably 1% by mass or more and 30% by mass or less. This mass ratio is more preferably 1.2% by mass or more and 25% by mass or less, and further preferably 1.5% by mass or more and 20% by mass or less. When the mass ratio of the carbonaceous material is 1% or more by mass, the carbonaceous material can sufficiently increase the reaction sites with lithium ions and facilitate the desolvation of lithium ions, so that high input / output characteristics can be obtained. Can show. On the other hand, if the mass ratio of the carbonaceous material is 20% by mass or less, lithium ion diffusion between the carbonaceous material and the substrate can be favorably maintained, and thus high input / output characteristics can be exhibited. I can do it. Moreover, since the charge / discharge efficiency of lithium ions can be improved, high cycle durability can be exhibited.

The doping amount of lithium ions per unit mass of the composite carbon material 2 is preferably 50 mAh / g or more and 700 mAh / g or less. More preferably, it is 70 mAh / g or more and 650 mAh / g or less, More preferably, it is 90 mAh / g or more and 600 mAh / g or less, Most 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.
When the doping amount is 50 mAh / g or more, lithium ions are favorably doped into irreversible sites that cannot be desorbed once lithium ions in the composite carbon material 2 are inserted, so that a high energy density is obtained. The larger the doping amount, the lower the negative electrode potential, and the input / output characteristics, energy density, and durability are improved.
On the other hand, when the doping amount is 700 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal occur.

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

  The average particle size of the composite carbon material 2a is preferably 1 μm or more and 10 μm or less. The average particle diameter is more preferably 2 μm or more and 8 μm or less, and further preferably 3 μm or more and 6 μm or less. When the average particle diameter is 1 μm or more, the charge / discharge efficiency of lithium ions can be improved, and thus high cycle durability can be exhibited. On the other hand, if it is 10 μm or less, the reaction area between the composite carbon material 2a and the non-aqueous electrolyte increases, so that high input / output characteristics can be exhibited.

The composite carbon material 2a preferably has a BET specific surface area of 1 m ² / g or more and 20 m ² / g or less. More preferably not more than ^{1 m} 2 / g or more ^{15 m} 2 / g. If this BET specific surface area is 1 m ² / g or more, a sufficient reaction field with lithium ions can be secured, and thus high input / output characteristics can be exhibited. On the other hand, if it is 20 m ² / g or less, the charge / discharge efficiency of lithium ions is improved and the decomposition reaction of the non-aqueous electrolyte during charge / discharge is suppressed, so that high cycle durability can be exhibited.

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

  The carbonaceous material precursor used as a raw material of the composite carbon material 2a is an organic material that can be dissolved in a solid, liquid, or solvent that can be composited with a graphite material by heat treatment. . Examples of the carbonaceous material precursor include pitch, mesocarbon microbeads, coke, and synthetic resin (for example, phenol resin). Among these carbonaceous material precursors, it is preferable in terms of production cost to use an inexpensive pitch. Pitch is roughly divided into petroleum pitch and coal pitch. Examples of petroleum pitches include crude oil distillation residue, fluid catalytic cracking residue (decant oil, etc.), bottom oil derived from thermal crackers, ethylene tar obtained during naphtha cracking, and the like.

  The mass ratio of the carbonaceous material to the graphite material in the composite carbon material 2a is preferably 1% by mass or more and 10% by mass or less. This mass ratio is more preferably 1.2% by mass to 8% by mass, further preferably 1.5% by mass to 6% by mass, and particularly preferably 2% by mass to 5% by mass. If the mass ratio of the carbonaceous material is 1% by mass or more, the carbonaceous material can sufficiently increase the number of reaction sites with lithium ions, and the desolvation of lithium ions is facilitated. Can show. On the other hand, if the mass ratio of the carbonaceous material is 20% by mass or less, lithium ion diffusion between the carbonaceous material and the graphite material can be satisfactorily maintained, and thus high input / output characteristics can be exhibited. I can do it. Moreover, since the charge / discharge efficiency of lithium ions can be improved, high cycle durability can be exhibited.

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

  The binder is not particularly limited. For example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, and the like. Can be used. The amount of the binder used is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the negative electrode active material. More preferably, they are 2 mass parts or more and 27 mass parts or less, More preferably, they are 3 mass parts or more and 25 mass parts or less. When the amount of the binder is 1 part by mass or more, sufficient electrode strength is exhibited. On the other hand, when the amount of the binder is 30 parts by mass or less, high input / output characteristics are exhibited without inhibiting lithium ions from entering and exiting the negative electrode active material.

  Although it does not restrict | limit especially as a dispersion stabilizer, For example, PVP (polyvinyl pyrrolidone), PVA (polyvinyl alcohol), a cellulose derivative etc. can be used. The amount of the dispersion stabilizer used is preferably 0 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material. When the amount of the dispersion stabilizer is 10 parts by mass or less, high input / output characteristics are exhibited without inhibiting lithium ions from entering and leaving the negative electrode active material.

[Negative electrode current collector]
The material constituting the negative electrode current collector in this embodiment is preferably a metal foil that has high electron conductivity and does not deteriorate due to elution into a non-aqueous electrolyte and reaction with an electrolyte or ions. There is no restriction | limiting in particular as such metal foil, For example, aluminum foil, copper foil, nickel foil, stainless steel foil, etc. are mentioned. The negative electrode current collector in the non-aqueous lithium storage element of this embodiment is preferably a copper foil.
The metal foil may be a normal metal foil having no irregularities or through holes, or a metal foil having irregularities subjected to embossing, chemical etching, electrolytic deposition, blasting, etc., expanded metal, punching metal Alternatively, a metal foil having a through hole such as an etching foil may be used. From the viewpoint of ease of electrode production, a metal foil having no through holes is more preferable.
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. When the negative electrode current collector has holes or irregularities, the thickness of the negative electrode current collector is measured based on a portion where no holes or irregularities exist.

[Manufacture of negative electrode]
The negative electrode has a negative electrode active material layer on one side or both sides of a negative electrode current collector. In a typical embodiment, the negative electrode active material layer is fixed to the negative electrode current collector.
The negative electrode can be manufactured by an electrode manufacturing technique in a known lithium ion battery, electric double layer capacitor or the like. For example, various materials including a negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry-like coating liquid, and this coating liquid is applied to one or both surfaces on a negative electrode current collector. A negative electrode can be obtained by forming a coating film and drying it. Further, the obtained negative electrode may be pressed to adjust the film thickness and bulk density of the negative electrode active material layer. Alternatively, it is possible to mix various materials including the negative electrode active material dry without using a solvent, press the resulting mixture, and then apply it to the negative electrode current collector using a conductive adhesive. is there.

  The coating liquid is prepared by dry blending a part or all of various material powders including the negative electrode active material, and then water or an organic solvent, and / or a liquid in which a binder or a dispersion stabilizer is dissolved or dispersed therein. You may adjust by adding a slurry-like substance. Further, various material powders including the negative electrode active material may be added to the liquid or slurry substance in which the binder or the dispersion stabilizer is dissolved or dispersed in water or an organic solvent. Although it does not restrict | limit especially in the adjustment of the said coating liquid, Dispersers, such as a homodisper, a multiaxial disperser, a planetary mixer, a thin film swirl | vortex type high speed mixer, etc. can be used suitably. In order to obtain a coating liquid in a good dispersion state, it is preferable to disperse at a peripheral speed of 1 m / s to 50 m / s. A peripheral speed of 1 m / s or more is preferable because various materials can be dissolved or dispersed well. Moreover, if it is 50 m / s or less, since various materials are not destroyed by the heat | fever and shear force by dispersion | distribution, and reaggregation does not arise, it is preferable.

The viscosity (ηb) of the coating solution is preferably 1,000 mPa · s or more and 20,000 mPa · s or less. More preferably, it is 1,500 mPa * s or more and 10,000 mPa * s or less, More preferably, it is 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. Moreover, if it is 20,000 mPa * s or less, it can apply stably with little pressure loss in the flow path of the coating liquid at the time of using a coating machine, and can control to below desired film thickness.
Further, the TI value (thixotropic index value) of the coating solution is preferably 1.1 or more. More preferably, it is 1.2 or more, More preferably, it is 1.5 or more. When the TI value is 1.1 or more, the coating film width and film thickness can be controlled well.

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

  Although the drying of the coating film is not particularly limited, a drying method such as hot air drying or infrared (IR) drying can be preferably used. The coating film may be dried at a single temperature, or may be dried at different temperatures. Moreover, you may dry combining several drying methods. The drying temperature is preferably 25 ° C. or higher and 200 ° C. or lower. More preferably, it is 40 degreeC or more and 180 degrees C or less, More preferably, it is 50 degreeC or more and 160 degrees C or less. When the drying temperature is 25 ° C. or higher, the solvent in the coating film can be sufficiently volatilized. On the other hand, if it is 200 degrees C or less, the crack of the coating film by rapid volatilization of a solvent, the uneven distribution of the binder by migration, and the oxidation of a negative electrode collector or a negative electrode active material layer can be suppressed.

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

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

[Measurement item]
The BET specific surface area, average pore diameter, mesopore volume, and micropore volume in the present embodiment 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. (Non-patent Document 1).
The MP method means a method for obtaining the micropore volume, micropore area, and micropore distribution using the “t-plot method” (Non-Patent Document 2). S. This is a method devised by Mikhal, Brunauer, and Bodor (Non-patent Document 3).

  The average particle size in the present embodiment is the particle size at which the cumulative curve is 50% when the particle size distribution is measured using a particle size distribution measuring device and the cumulative curve is determined with the total volume being 100% (that is, the cumulative curve is 50%). , 50% diameter (Median diameter)). This average particle diameter can be measured using a commercially available laser diffraction particle size distribution analyzer.

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

  The primary particle diameter in this embodiment is about 2,000 to 3,000 using a fully automatic image processing device or the like by taking several fields of powder with an electron microscope and using a fully automatic image processing apparatus or the like. It can be obtained by a method of measuring and arithmetically averaging these values as the primary particle diameter.

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

The viscosity (ηb) and the TI value in the present embodiment are values obtained by the following methods, respectively. First, a stable viscosity (ηa) after measurement for 2 minutes or more under the conditions of a temperature of 25 ° C. and a shear rate of 2 s ⁻¹ is obtained using an E-type viscometer. Next, the viscosity (ηb) measured under the same conditions as described above is obtained except that the shear rate is changed to 20 s ⁻¹ . Using the viscosity value obtained above, the TI value is calculated by the formula TI value = ηa / ηb. When the shear rate is increased from 2 s ⁻¹ to 20 s ⁻¹ , the shear rate 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.

  The thickness of the negative electrode active material layer is preferably 5 μm or more and 100 μm or less per side. The lower limit of the thickness of the negative electrode active material layer is more preferably 7 μm or more, and more preferably 10 μm or more. The upper limit of the film thickness of the negative electrode active material layer is more preferably 80 μm or less, and more preferably 60 μm or less. When the film thickness is 5 μm or more, no streaks or the like are generated when the negative electrode active material layer is applied, and the coating property is excellent. On the other hand, if this film thickness is 100 μm or less, a high energy density can be expressed by reducing the cell volume. Note that the film thickness of the negative electrode active material layer when the current collector has through-holes or unevenness means an average value of the film thickness per one side of the current collector that does not have through-holes or unevenness.

The bulk density of the negative electrode active material layer is preferably 0.30 g / cm ³ or more and 1.8 g / cm ³ or less, more preferably 0.40 g / cm ³ or more and 1.5 g / cm ³ or less, and still more preferably 0. .45g / cm ³ or more 1.3g / cm ³ or less. When the bulk density is 0.30 g / cm ³ or more, sufficient strength can be maintained and sufficient conductivity between the negative electrode active materials can be exhibited. Moreover, if it is 1.8 g / cm < ³ > or less, the void | hole which ion can fully spread | diffuse in a negative electrode active material layer is securable.

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

[Lithium salt]
The non-aqueous electrolyte solution of the present embodiment is, for example, (LiN (SO ₂ F) ₂ ), LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ ) as a lithium salt. _{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 and the} like can be used alone, or two or more kinds may be mixed and used. LiPF ₆ and / or LiN (SO ₂ F) ₂ are preferably included because high conductivity can be exhibited.
The lithium salt concentration in the non-aqueous electrolyte is preferably 0.5 mol / L or more, more preferably in the range of 0.5 mol / L to 2.0 mol / L, based on the total amount of the non-aqueous electrolyte. . If the lithium salt concentration is 0.5 mol / L or more, anions are sufficiently present, so that the capacity of the energy storage device can be sufficiently increased. Further, when the lithium salt concentration is 2.0 mol / L or less, it is possible to prevent undissolved lithium salt from precipitating in the non-aqueous electrolyte and preventing the viscosity of the electrolyte from becoming too high, resulting in a decrease in conductivity. And output characteristics are not deteriorated.

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

[Nonaqueous solvent]
The nonaqueous electrolytic solution of the present embodiment preferably contains a cyclic carbonate as a nonaqueous solvent. The nonaqueous electrolytic solution containing a cyclic carbonate is advantageous in that a lithium salt having a desired concentration is dissolved and an appropriate amount of a lithium compound is deposited on the positive electrode active material layer. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, and fluoroethylene carbonate.
The total content of the cyclic carbonate is preferably 15% by mass or more, more preferably 20% by mass or more, based on the total amount of the nonaqueous electrolytic solution. When the total content is 15% by mass or more, a lithium salt having a desired concentration can be dissolved, and high lithium ion conductivity can be expressed. Furthermore, an appropriate amount of lithium compound can be deposited on the positive electrode active material layer, and oxidative decomposition of the electrolytic solution can be suppressed.

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

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

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

｛式（２）中、Ｒ^１１〜Ｒ^１４は、水素原子、ハロゲン原子、炭素数１〜１２のアルキル基、又は炭素数１〜１２のハロゲン化アルキル基を表し、互いに同一であっても異なっていてもよく；そしてｎは０〜３の整数である。｝

｛式（３）中、Ｒ^１１〜Ｒ^１６は、水素原子、ハロゲン原子、炭素数１〜１２のアルキル基、又は炭素数１〜１２のハロゲン化アルキル基を表し、互いに同一であっても異なっていてもよい。｝ [Sultone compound]
Examples of the sultone compound include sultone compounds represented by the following general formulas (1) to (3). These sultone compounds may be used alone or in admixture of two or more.

{In Formula (1), 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. And n is an integer from 0 to 3. }

{In Formula (2), 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. }

{In Formula (3), 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. }

  In the present embodiment, as a sultone compound represented by the general formula (1), from the viewpoint of having a small adverse effect on resistance and suppressing gas generation by suppressing decomposition of the non-aqueous electrolyte at a high temperature, 1,3-propane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-butane sultone or 2,4-pentane sultone is preferable. 3-propene sultone or 1,4-butene sultone is preferable, and the sultone compound represented by the general formula (3) is 1,5,2,4-dioxadithiepan 2,2,4,4-tetraoxide. As other sultone compounds, methylene bis (benzenesulfonic acid), methylene bis (phenylmethanesulfonic acid), methylene bis (ethanes) Phonic acid), methylenebis (2,4,6, trimethylbenzenesulfonic acid), and methylenebis (2-trifluoromethylbenzenesulfonic acid) can be mentioned, and at least one selected from these is selected. It is preferable.

  The total content of sultone compounds in the non-aqueous electrolyte solution of the non-aqueous lithium storage element in this embodiment is preferably 0.5% by mass or more and 15% by mass or less based on the total amount of the non-aqueous electrolyte solution. . 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. On the other hand, if 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 from the viewpoint of achieving both high input / output characteristics and durability. Preferably they are 3 mass% or more and 8 mass% or less.

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

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

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

  The content of the 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 amount 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. On the other hand, 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 is possible to develop input / output 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]
The fluorine-containing cyclic carbonate is preferably selected from fluoroethylene carbonate (FEC) and difluoroethylene carbonate (dFEC) from the viewpoint of compatibility with other nonaqueous solvents.
The content of the cyclic carbonate containing a fluorine atom is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the 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. On the other hand, if the content of the cyclic carbonate containing fluorine atoms 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 is possible to develop advanced input / output characteristics. In addition, the cyclic carbonate containing a fluorine atom may be used alone or in combination of two or more.

[Cyclic carbonate]
For the cyclic carbonate, vinylene carbonate is preferred.
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 amount of the non-aqueous electrolyte 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. On the other hand, 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 characteristics.

[Cyclic carboxylic acid ester]
Examples of the cyclic carboxylic acid ester include gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone and the like, and it is preferable to use one or more selected from these. 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 amount 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. On the other hand, 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. It becomes possible to express output characteristics. In addition, said cyclic carboxylic acid ester may be used individually, or 2 or more types may be mixed and used for it.

[Cyclic anhydride]
The cyclic acid anhydride is preferably at least one selected from succinic anhydride, maleic anhydride, citraconic anhydride, and itaconic anhydride. Among them, it is preferable to select from succinic anhydride and maleic anhydride from the viewpoint that the production cost of the electrolytic solution can be suppressed due to industrial availability and that the electrolytic solution can be easily dissolved in the non-aqueous electrolytic solution.
The content of the cyclic acid anhydride is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total amount of the 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. On the other hand, 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, so that a high degree of input / output is possible. It becomes possible to express characteristics. In addition, said cyclic acid anhydride may be used individually, or 2 or more types may be mixed and used for it.

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

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

[assembly]
The electrode laminate obtained in the cell assembling process is obtained by connecting a positive electrode terminal and a negative electrode terminal to a laminate obtained by laminating a positive electrode precursor and a negative electrode cut into a sheet shape via a separator. The electrode winding body is obtained by connecting a positive electrode terminal and a negative electrode terminal to a winding body obtained by winding a positive electrode precursor and a negative electrode through a separator. The shape of the 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, but is 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.
The laminate packaging material is preferably a film in which a metal foil and a resin film are laminated, and an example of a three-layer structure comprising an outer layer resin film / metal foil / interior resin film is exemplified. The outer layer resin film is for preventing the metal foil from being damaged by contact or the like, and a resin such as nylon or polyester can be suitably used. The metal foil is for preventing the permeation of moisture and gas, and foils of copper, aluminum, stainless steel and the like can be suitably used. The interior resin film protects the metal foil from the non-aqueous electrolyte contained therein and melts and seals the exterior body during heat sealing. Polyolefin, acid-modified polyolefin, and the like can be suitably used.

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

[Dry]
It is preferable to remove the residual solvent by drying the electrode laminate or the electrode winding body housed in the outer package. Although there is no limitation in the drying method, it dries by vacuum drying etc. The residual solvent is preferably 1.5% by mass or less per mass of the positive electrode active material layer or the negative electrode active material layer. If the residual solvent is more than 1.5% by mass, the solvent remains in the system and the self-discharge characteristics and cycle characteristics are deteriorated, which is not preferable.

[Liquid injection, impregnation, sealing process]
After the assembly process is completed, a non-aqueous electrolyte solution is injected into the electrode laminate or the electrode winding body housed in the exterior body. After completion of the liquid injection step, it is desirable to further impregnate and sufficiently immerse the positive electrode, the negative electrode, and the separator with a non-aqueous electrolyte. In a state where the non-aqueous electrolyte solution is not immersed in at least a part of the positive electrode, the negative electrode, and the separator, dope proceeds non-uniformly in the lithium doping step described later, and thus the resistance of the obtained non-aqueous lithium storage element is It rises or the durability decreases. The impregnation method is not particularly limited. For example, the electrode laminate or the electrode winding body after injection is placed in a vacuum chamber with the exterior body opened, and the inside of the chamber is filled with a vacuum pump. A method of returning to atmospheric pressure again after reducing the pressure can be used. After completion of the impregnation step, the electrode laminate or electrode winding body with the exterior body opened is sealed by being reduced in pressure.

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

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

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

[Characteristic evaluation of non-aqueous lithium storage element]
[Capacitance]
In the present 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 a cell corresponding to a non-aqueous lithium storage element is set to 25 ° C. until reaching 3.8 V at a current value of 1 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 1 C up to 2.2V. A value calculated by F = Q / (3.8−2.2) is used by using Q obtained here.
[Discharge curve]
The transition of the integrated discharge capacity with respect to the cell voltage at the time of the capacitance measurement is defined as a discharge curve in this specification. In this discharge curve, when the discharge start point (cell voltage 3.8V) is A and the discharge end point (cell voltage 2.2V) is B, in this embodiment, a straight line AB connecting point A and point B is On the other hand, the discharge curve is convex downward. In the present specification, the downwardly convex discharge curve is a correlation coefficient when approximated by a quadratic polynomial by the least square method with respect to the plot of the integrated discharge capacity against the cell voltage during the capacitance measurement. When the square value of R is 0.9995 or more, and the starting point of the approximate curve is A and the end point is B, the approximate curve is a straight line with respect to the straight line AB connecting the points A and B. It means that the curve passes through the lower voltage side than AB.
Since the discharge curve is convex downward, as shown in FIG. 1, it is possible to take out a larger battery capacity in a low voltage region as compared with a conventional capacitor having a straight discharge curve.
The reason why the discharge curve is convex downward in this embodiment is not clear, but is presumed as follows. By including the lithium compound in the positive electrode, in addition to the adsorption / desorption reaction of lithium ions at the interface of the positive electrode active material layer, the lithium occlusion / release reaction of the lithium compound occurs simultaneously. Therefore, the transition of the positive electrode potential during charging / discharging is not the transition of linearity due to the electric double layer reaction as in the conventional lithium ion capacitor, but the transition of the quadratic curve, so that the cell voltage with respect to the capacity change in the low voltage region. Transition becomes smaller, and the discharge curve becomes a downwardly convex curve.
[Curvature]
When the length of the straight line AB connecting the start point A and the end point B of the approximate curve is l ₁ and the length of the approximate curve AB is l ₂ , the curvature l ₂ / l of the approximate curve AB with respect to the straight line AB. ₁ is preferably 1.000 <l ₂ / l ₁ ≦ 1.030. More preferably, 1.001 ≦ l ₂ / l ₁ ≦ 1.020, and even more preferably 1.002 ≦ l ₂ / l ₁ ≦ 1.015. When l ₂ / l ₁ is higher than 1.000, a large battery capacity can be taken out in a low voltage region. When l ₂ / l ₁ is 1.030 or less, the amount of lithium ions contributing to the occlusion / desorption reaction by the lithium compound in the positive electrode is reduced at the positive electrode active material layer interface. The output can be kept.

[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]
Although the volume of the non-aqueous lithium storage element is not particularly specified, a region where the positive electrode active material layer and the negative electrode active material layer are stacked in the electrode laminate or the electrode winding body is accommodated by the outer package. Refers to the volume of the part.
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 .
Also, in the case of the electrode winding body housed in a cylindrical metal can, the volume of the non-aqueous lithium storage element is the outer size of the metal can. 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).

[Normal charging internal resistance]
In the present specification, the room temperature charge internal resistance Ra (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 rising voltage ΔE = Eo−2. 2 and Ra = ΔE / (20C (current value A)).

The non-aqueous lithium storage element of this embodiment has an initial room temperature charging internal resistance of Ra (Ω), a capacitance of F (F), an electric energy of E (Wh), and a volume of the storage element of V (L). And the following:
It is preferable that (a) the product Ra · F of Ra and F is 0.3 to 3.0; and (b) E / V is 15 to 50;

  Regarding (a), Ra · F is preferably 3.0 or less, more preferably 2.6 or less, from the viewpoint of developing sufficient charge capacity and discharge capacity for a large current. Preferably it is 2.4 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 possible to sufficiently withstand a high load applied to the non-aqueous lithium storage element by combining a storage system using a non-aqueous lithium storage element and a high-efficiency engine, for example.

  With regard to (b), E / V is preferably 15 or more, more preferably 18 or more, and still more preferably 20 or more, from the viewpoint of developing sufficient charge capacity and discharge capacity. When E / V is equal to or higher than the above lower limit, a power storage element having an excellent volume energy density can be obtained. Therefore, when a power storage system using a power storage element is used in combination with, for example, an automobile engine, it is possible to install the power storage system in a limited narrow space in the automobile, which is preferable.

  Hereinafter, the present embodiment will be specifically described by way of examples and comparative examples, but the present invention is not limited thereto.

<Example 1>
[Crushing lithium carbonate]
<Lithium carbonate grinding>
200 g of lithium carbonate having an average particle size of 50 μm and 0.010 g of sodium oxalate were dry blended at 25 ° C. to obtain a mixture. After the resulting mixture was cooled to −196 ° C. with liquid nitrogen using a crusher (liquid nitrogen bead mill LNM) manufactured by Imex, 20 mm at a peripheral speed of 15.0 m / s using zirconia beads of φ1.0 mm. Lithium carbonate 1 was obtained by grinding for a minute. By cooling to −196 ° C., brittle fracture can be achieved while preventing thermal denaturation of lithium carbonate. When the average particle diameter of the obtained lithium carbonate 1 was measured, it was 1.5 μm.

[Preparation of positive electrode active material]
[Preparation of activated carbon 1]
The crushed palm shell carbide was carbonized in nitrogen in a small carbonization furnace at 550 ° C. for 3 hours to obtain a carbide. The obtained carbide was put into an activation furnace, and 1 kg / h of steam was introduced into the activation furnace while being heated in a preheating furnace, and the temperature was raised to 800 ° C. over 8 hours for activation. The activated carbide was taken out and cooled in a nitrogen atmosphere to obtain activated activated carbon. The obtained activated carbon was washed with water for 10 hours and then drained. Then, after drying for 10 hours in an electric dryer maintained at 115 ° C., the activated carbon 1 was obtained by pulverizing for 1 hour using a ball mill.
As a result of measuring the average particle diameter of this activated carbon 1 using a laser diffraction particle size distribution analyzer (SALD-2000J) manufactured by Shimadzu Corporation, it was 3.5 μm. Moreover, the pore distribution was measured using the pore distribution measuring apparatus (AUTOSORB-1 AS-1-MP) made from Yuasa Ionics. As a result, the BET specific surface area was 2060 m ² / g, the mesopore volume (V1) was 0.54 cc / g, the micropore volume (V2) was 0.75 cc / g, and V1 / V2 = 0.72.

[Preparation of activated carbon 2]
The phenol resin was subjected to carbonization treatment in a firing furnace at 650 ° 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 6.5 μm. The carbide and KOH were mixed at a mass ratio of 1: 5 and activated by heating in a firing furnace at 750 ° 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 size of 6.5 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 3327 m ² / g, the mesopore volume (V1) was 1.60 cc / g, the micropore volume (V2) was 2.01 cc / g, and V1 / V2 = 0.80.

[Preparation of cathode coating solution]
Using the activated carbon 1 or 2 obtained above as the positive electrode active material and the lithium carbonate 1 obtained above as the charged lithium compound, a positive electrode coating solution was produced by the following method.
57.5 parts by mass of activated carbon 1 or 2; 30.0 parts by mass of lithium carbonate; 3.0 parts by mass of ketjen black; 1.5 parts by mass of PVP (polyvinylpyrrolidone); and PVDF (polyvinylidene fluoride). 8.0 parts by mass and NMP (N-methylpyrrolidone) are mixed and dispersed using a thin film swirl type high-speed mixer film mix manufactured by PRIMIX under the condition of a peripheral speed of 17.0 m / s. A liquid was obtained.
The viscosity (ηb) and TI value of the obtained coating solution were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,700 mPa · s, and the TI value was 3.5. Moreover, the dispersion degree of the obtained coating liquid was measured using the grain gauge made from Yoshimitsu Seiki. As a result, the particle size was 35 μm.

[Preparation of positive electrode precursor]
The above coating solution is applied on one or both sides of an aluminum foil having a thickness of 15 μm using a die coater manufactured by Toray Engineering Co., Ltd. at a coating speed of 1 m / s, and dried at a drying temperature of 100 ° C. to obtain a positive electrode precursor. Obtained. The obtained positive electrode precursor was pressed using a roll press machine under the conditions of a pressure of 4 kN / cm and a surface temperature of the press part of 25 ° C. The average thickness of the positive electrode active material layer of the positive electrode precursor obtained above was measured at any 10 locations of the positive electrode precursor using a thickness gauge Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. The value was obtained by subtracting the thickness of the aluminum foil from the value. As a result, the thickness of the positive electrode active material layer was 60 μm per side.

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

<Manufacture of negative electrode A>
Next, a negative electrode was manufactured using the composite carbon material A as a negative electrode active material.
85 parts by mass of composite carbon material A, 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, the mixture was dispersed under the condition 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 above coating solution is applied to both sides of an electrolytic copper foil having a thickness of 10 μm without a through-hole 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. Thus, negative electrode A was obtained. The obtained negative electrode A was pressed using a roll press machine under conditions of a pressure of 4 kN / cm and a surface temperature of the pressed part of 25 ° C. The thickness of the negative electrode active material layer of the negative electrode A obtained above was determined from the average value of the thicknesses measured at any 10 locations on the negative electrode A 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 thickness of the negative electrode active material layer of the negative electrode A was 40 μm per side.

[Preparation of active material B]
Instead of the composite carbon material A, artificial graphite having an average particle diameter of 4.9 μm was used as a base material, the amount of coal-based pitch used was 50 g, and the heat treatment temperature was 1000 ° C. The composite carbon material B was manufactured and evaluated. As a result, the BET specific surface area of the composite carbon material B was 6.1 m ² / g. The mass ratio of carbonaceous material derived from coal-based pitch to artificial graphite was 2%.

<Manufacture of negative electrode B>
A negative electrode was produced using the composite carbon material B obtained above as a negative electrode active material.
80 parts by mass of composite carbon material B, 8 parts by mass of acetylene black, 12 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, the mixture was dispersed under the condition 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 2,798 mPa · s, and the TI value was 2.7. The above coating solution is applied to both sides of an electrolytic copper foil having a thickness of 10 μm without a through-hole 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. Thus, a negative electrode was obtained. The obtained negative electrode was pressed using a roll press machine under conditions of a pressure of 4 kN / cm and a surface temperature of the pressed part of 25 ° C. The thickness of the negative electrode active material layer of the negative electrode obtained above was measured from the average value of the thickness measured at any 10 locations on the negative electrode using a thickness gauge Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. Obtained by subtracting the thickness of the foil. As a result, the thickness of the negative electrode active material layer was 25 μm per side.

<Preparation of electrolyte>
As an organic solvent, a mixed solvent of ethylene carbonate (EC): methyl ethyl carbonate (EMC) = 33: 67 (volume ratio) is used, and the concentration ratio of LiN (SO ₂ F) ₂ and LiPF ₆ is relative to the total electrolyte. A solution obtained by dissolving each electrolyte salt so that the sum of the concentrations of LiN (SO ₂ F) ₂ and LiPF ₆ is 50:50 (molar ratio) is 1.2 mol / L. Used as a liquid.
The concentrations of LiN (SO ₂ F) ₂ and LiPF ₆ in the electrolytic solution prepared here were 0.6 mol / L and 0.6 mol / L, respectively.

<Assembly of storage element>
The obtained double-sided negative electrode A and double-sided positive electrode precursor A were cut into 10 cm × 10 cm (100 cm ² ). The uppermost and lowermost surfaces use a single-sided positive electrode precursor, and further use 21 double-sided negative electrodes and 20 double-sided positive electrode precursors, with a microporous membrane separator having a thickness of 15 μm sandwiched between the negative electrode and the positive electrode precursor. did. Thereafter, the negative electrode terminal and the positive electrode terminal were connected to the negative electrode and the positive electrode precursor, respectively, by ultrasonic welding to obtain an electrode laminate. This electrode laminate was vacuum-dried at 80 ° C. and 50 Pa for 60 hours. This electrode laminate is inserted into an outer package made of a laminate packaging material in a dry environment with a dew point of −45 ° C., and the electrode terminal part and the bottom part of the outer package 3 are heated at 180 ° C., 20 sec, 1.0 MPa. Sealed. A non-aqueous lithium storage element was assembled by injecting a non-aqueous electrolyte and sealing the outer package.

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

<Lithium doping process>
The obtained non-aqueous lithium-type electricity storage element was fixed using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo System Co., Ltd. until a voltage of 4.7 V was reached at a current value of 0.6 A in a 35 ° C. environment. After performing current charging, initial charging was performed by a technique in which 4.5 V constant voltage charging was continued for 8 hours, and the negative electrode was doped with lithium.

<Aging process>
Charge and discharge by constant current charging and constant current discharging between a lower limit voltage of 2.0 V and an upper limit voltage of 4.0 V, with a charging current of 1 A and a discharging current of 1 A in a non-aqueous lithium storage element after lithium doping at 25 ° C. The cycle was repeated 10 times.

<Degassing process>
A part of the aluminum laminate packaging material was unsealed in a dry air environment with a temperature of 25 ° C. and a dew point of −40 ° C. of the non-aqueous lithium storage element after aging. Subsequently, the non-aqueous lithium storage element was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to −80 kPa over 3 minutes using a diaphragm pump (N816.3KT.45.18) manufactured by KNF. The process of returning to atmospheric pressure over 3 minutes was repeated a total of 3 times. Then, after putting a non-aqueous lithium-type electrical storage element in a pressure reduction sealing machine and reducing the pressure to −90 kPa, the aluminum laminate packaging material was sealed by sealing at 200 ° C. for 10 seconds with a pressure of 0.1 MPa.

  <Evaluation of non-aqueous lithium storage element>

[Calculation of energy density]
Using the charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. in the thermostatic chamber set at 25 ° C., the electricity storage device obtained in the above process reaches 3.8V at a current value of 1C. Then, constant 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. Thereafter, the capacity when constant current discharge is performed at a current value of 2 C up to 2.2 V is defined as Q, and the capacitance F (F) calculated by F = Q / (3.8−2.2) is used. And
^{E / V = F × (3.8} 2 -2.2 2) / 2/3600 / was 27.0Wh / L was calculated in energy density by V.

[Calculation of l ₂ / l ₁ ]
The transition of the voltage and discharge capacity obtained during the capacitance measurement is plotted on a graph with the voltage (V) on the vertical axis and the integrated discharge capacity (mAh) on the horizontal axis, and a second-order polynomial by the least square method A discharge curve was obtained from the approximation. The shape of the discharge curve was convex downward. Discharge start point (voltage 3.8 V) A, when the discharge end point (voltage 2.2V) and by B, voltage, accumulated discharge of the line AB with the absolute value of the capacitance of the length _{l 1} and the discharge curve AB The length l ₂ was determined. l ₂ / l ₁ was 1.008.

[Calculation of Ra · F]
Using the charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. in a thermostat set at 25 ° C., the electricity storage device obtained in the above process reaches 2.2V at a current value of 20C. Constant current discharge until a constant voltage discharge of 2.2 V is applied for a total of 30 minutes, followed by a constant current charge of 3.8 V with a current value of 20 C, a charging curve ( Time-voltage). In this charging curve, the voltage at the 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 is Eo, the rising voltage ΔE = Eo−2.2, and The room temperature charge internal resistance Ra was calculated by R = ΔE / (20C (current value A)).
The product Ra · F of the capacitance F and the charging internal resistance Ra at 25 ° C. was 1.71ΩF.

<Quantification of lithium compound in positive electrode>
[Sample preparation]
The nonaqueous lithium storage element was disassembled in an argon box with a dew point temperature of −72 ° C., and the electrolytic solution, the negative electrode, and the positive electrode were taken out. A positive electrode having a positive electrode active material layer coated on both sides was cut into a size of 10 cm × 10 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 washed positive electrode was taken out of the argon box and dried for 20 hours under the conditions of a temperature of 25 ° C. and a pressure of 1 kPa using a vacuum dryer (manufactured by Yamato Kagaku, DP33) to obtain a positive electrode sample.

The obtained positive electrode sample was cut into a size of 5 cm × 5 cm, dipped in 20 g of methanol, covered with a container, and allowed to stand in a 25 ° C. environment for 3 days. Thereafter, the positive electrode sample was taken out and vacuum-dried at 120 ° C. and 5 kPa for 10 hours. About the methanol solution after washing | cleaning, GC / MS was measured on the conditions which created the analytical curve previously, and it confirmed that the abundance of diethyl carbonate was less than 1%. Subsequently, the positive electrode sample was impregnated with 25.20 g of distilled water, and the container was covered and allowed to stand in a 45 ° C. environment for 3 days. Thereafter, the positive electrode sample was taken out and vacuum-dried at 150 ° C. and 3 kPa for 12 hours. The weight M ₁ after vacuum drying is 0.239 g, and GC / MS is measured under the conditions in which a calibration curve has been prepared in advance for distilled water after washing, and it is confirmed that the amount of methanol present is less than 1%. did. According to the above-mentioned formulas (1) and (2), the positive electrode weight per unit area D [g / m ² ] and the basis weight E [g / m ² ] of the lithium compound contained in the positive electrode active material layer per one side of the positive electrode are obtained. It was 15 mass% when the quantity of the lithium compound contained in was computed.

<Examples 2 to 19 and Comparative Examples 1 to 12>
In Example 1, the negative electrode, the positive electrode precursor active material, the average particle size of the positive electrode precursor active material, the lithium compound, the average particle size of the lithium compound, and the composition ratio of the positive electrode precursor are as shown in Table 1, respectively. Other than the above, a non-aqueous lithium electricity storage device was produced in the same manner as in Example 1, and various evaluations were performed.
The evaluation results are shown in Table 2.

<Example 20>
<Assembly of storage element>
The obtained double-sided negative electrode B and double-sided positive electrode precursor B were cut into 10 cm × 10 cm (100 cm ² ). The uppermost and lowermost surfaces use a single-sided positive electrode precursor, and further use 21 double-sided negative electrodes and 20 double-sided positive electrode precursors, with a microporous membrane separator having a thickness of 15 μm sandwiched between the negative electrode and the positive electrode precursor. did. Thereafter, the negative electrode terminal and the positive electrode terminal were connected to the negative electrode and the positive electrode precursor, respectively, by ultrasonic welding to obtain an electrode laminate. This electrode laminate was vacuum-dried at 80 ° C. and 50 Pa for 60 hours. This electrode laminate is inserted into an outer package made of a laminate packaging material in a dry environment with a dew point of −45 ° C., and the electrode terminal part and the bottom part of the outer package 3 are heated at 180 ° C., 20 sec, 1.0 MPa. Sealed. A non-aqueous lithium storage element was assembled by injecting a non-aqueous electrolyte and sealing the outer package.

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

<Lithium doping process>
The obtained non-aqueous lithium-type electricity storage element was fixed using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo System Co., Ltd. until a voltage of 4.7 V was reached at a current value of 0.6 A in a 35 ° C. environment. After performing current charging, initial charging was performed by a technique in which 4.5 V constant voltage charging was continued for 8 hours, and the negative electrode was doped with lithium.

<Aging process>
Charge and discharge by constant current charge and constant current discharge between a lower limit voltage of 2.0V and an upper limit voltage of 4.3V with a non-aqueous lithium storage element after lithium doping in a 25 ° C environment with a charge current of 1A and a discharge current of 1A. The cycle was repeated 30 times.

A non-aqueous lithium storage element was produced in the same manner as in Example 1 except that the assembly, injection, impregnation, sealing process, lithium doping process, and aging process of the storage element were performed as described above, and various evaluations were made. Went.
The evaluation results are shown in Table 4.

<Example 21>

<Lithium doping process>
The obtained non-aqueous lithium-type electricity storage element was fixed using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo System Co., Ltd. until a voltage of 4.7 V was reached at a current value of 0.6 A in a 35 ° C. environment. After performing current charging, initial charging was performed by a technique in which 4.5 V constant voltage charging was continued for 8 hours, and the negative electrode was doped with lithium.

<Aging process>
Charge and discharge by constant current charge and constant current discharge between a lower limit voltage of 2.0V and an upper limit voltage of 3.8V with a non-aqueous lithium type storage element after lithium doping in a 25 ° C environment with a charge current of 1A and a discharge current of 1A. The cycle was repeated 5 times.

Except that the lithium doping step and the aging step were performed as described above, a non-aqueous lithium storage element was produced in the same manner as in Example 20, and various evaluations were performed.
The evaluation results are shown in Table 4.
<Example 22>

<Lithium doping process>
The obtained non-aqueous lithium-type electricity storage element was fixed using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo System Co., Ltd. until a voltage of 4.7 V was reached at a current value of 0.6 A in a 35 ° C. environment. After performing current charging, initial charging was performed by a technique in which 4.5 V constant voltage charging was continued for 8 hours, and the negative electrode was doped with lithium.

<Aging process>
Charge and discharge by constant current charge and constant current discharge between a lower limit voltage of 2.0V and an upper limit voltage of 3.6V with a non-aqueous lithium storage element after lithium doping in a 25 ° C environment with a charge current of 1A and a discharge current of 1A. The cycle was repeated twice.

Except that the lithium doping step and the aging step were performed as described above, a non-aqueous lithium storage element was produced in the same manner as in Example 20, and various evaluations were performed.
The evaluation results are shown in Table 4.

[Comparative Example 13]
<Manufacture of negative electrode C>
In the production of the negative electrode A, a negative electrode C was produced in the same manner except that the negative electrode current collector was a copper foil having a through hole having a thickness of 15 μm. As a result, the thickness of the negative electrode active material layer of the negative electrode C was 40 μm per side.
<Manufacture of negative electrode D>
In the production of the negative electrode B, a negative electrode D was produced in the same manner except that the negative electrode current collector was a copper foil having a through hole having a thickness of 15 μm. As a result, the thickness of the negative electrode active material layer of the negative electrode D was 25 μm per side.
<Assembly of storage element>
The double-sided negative electrode C and the double-sided positive electrode precursor were cut into 10 cm × 10 cm (100 cm ² ). A lithium metal foil corresponding to 760 mAh / g per unit mass of the composite porous material A was attached to one side of the double-sided negative electrode C. The uppermost surface and the lowermost surface use a single-sided positive electrode precursor, and further use 21 double-sided negative electrodes and 20 double-sided positive electrode precursors that have been subjected to the lithium bonding step. Lamination was performed with a porous membrane separator in between. Thereafter, the negative electrode terminal and the positive electrode terminal were connected to the negative electrode and the positive electrode precursor, respectively, by ultrasonic welding to obtain an electrode laminate. This electrode laminate was vacuum-dried at 80 ° C. and 50 Pa for 60 hours. This electrode laminate is inserted into a package body made of a laminate film in a dry environment with a dew point of −45 ° C., and the electrode terminal part and the bottom part of the package body 3 are heat sealed at 180 ° C., 20 sec, 1.0 MPa. did. A non-aqueous lithium storage element was assembled by injecting a non-aqueous electrolyte and sealing the outer package.

<Lithium doping process>
The obtained non-aqueous lithium storage element was left in a thermostatic chamber set at 45 ° C. for 21 hours to dope lithium into the negative electrode.

<Aging process>
The non-aqueous lithium storage element after lithium doping was adjusted to a cell voltage of 3.0 V, and then stored in a thermostat set at 45 ° C. for 24 hours. Subsequently, using a charging / discharging device manufactured by Asuka Electronics, the charging current is 10A and the discharging current is 10A, and the charging / discharging cycle by constant current charging and constant current discharging is performed between the lower limit voltage 2.0V and the upper limit voltage 4.0V. Repeated times.

A non-aqueous lithium storage element was produced in the same manner as in Example 1 except that the storage element assembly, lithium doping process, and aging process were performed as described above, and various evaluations were performed.
The evaluation results are shown in Table 4.

<Comparative Examples 14-16>
In the comparative example 13, except that the negative electrode, the active material of the positive electrode precursor, the active material particle size, the lithium compound, the average particle size of the lithium compound, and the composition ratio of the positive electrode precursor were as described in Table 3, respectively. In the same manner as in Example 1, a non-aqueous lithium storage element was produced and various evaluations were performed.
The evaluation results are shown in Table 4.

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

1 Straight line AB
2 Discharge line of lithium ion capacitor in this embodiment 3 Discharge curve of conventional lithium ion capacitor 21 Discharge curve of Example 1 31 Discharge curve of Example 2 41 Discharge curve of Comparative Example 1

Claims (12)

A non-aqueous lithium storage element comprising a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte containing lithium ions,
The negative electrode has a negative electrode current collector and a negative electrode active material layer including a negative electrode active material provided on one or both surfaces of the negative electrode current collector, and the negative electrode active material occludes lithium ions. Contains carbon material that can be released, and
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, and the positive electrode active material includes activated carbon, in addition,
The positive electrode contains 1% by mass to 50% by mass of a lithium compound other than the positive electrode active material, based on the total mass of the positive electrode active material layer; and
In the discharge curve when the electric storage element is subjected to constant current discharge from a voltage of 3.8 V to a voltage of 2.2 V at a current value of 4 C or less, with respect to a straight line AB connecting the discharge start point A and the discharge end point B, The discharge curve is a downward convex curve, and
_{L 1} the length of the straight line AB, the length of the discharge curve AB is taken as _{l 2,} 1.000 _<nonaqueous lithium-type power storage, which is a l 2 / _{l 1} ≦ 1.030 element.   The lithium compound is at least one selected from lithium carbonate, lithium oxide, lithium hydroxide, lithium fluoride, lithium chloride, lithium oxalate, lithium iodide, lithium nitride, lithium oxalate, and lithium acetate; The non-aqueous lithium storage element according to claim 1. When the average particle diameter of the lithium compound and _{X 1,} a 0.1μm ≦ _{X 1} ≦ 10μm, further, when the average particle diameter of the positive electrode active material _{Y 1,} a 2μm ≦ _{Y 1} ≦ 20μm, and _a X 1 _{<Y 1,} nonaqueous lithium-type storage element according to claim 1 or 2. 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 to 500 mm calculated by the BJH method as V1 (cc / g), and a fine particle having a diameter of less than 20 mm calculated by the MP method. When the amount of micropores derived from the holes is V2 (cc / g), a ratio that satisfies 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 and is measured by the BET method The non-aqueous lithium storage element according to any one of claims 1 to 3, which is activated carbon having a 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 V1 (cc / g) derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method satisfying 0.8 <V1 ≦ 2.5. The amount of micropores V2 (cc / g) derived from pores having a diameter of less than 20 mm calculated by the MP method satisfies 0.8 <V2 ≦ 3.0, and the specific surface area measured by the BET method is 2, activated carbon having the following 300 meters ² / g or more 4,000 m ² / g, the non-aqueous lithium-type storage element according to any one of claims 1-3.   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 nonaqueous 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 5, 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 claim 1, wherein the negative electrode active material has a BET specific surface area of 1 m ² / g or more and 50 m ² / g or less.   The nonaqueous lithium storage element according to claim 8 or 9, wherein an average particle diameter of the negative electrode active material is 1 µm or more and 10 µm or less.   The non-aqueous lithium storage element according to any one of claims 1 to 10, wherein the positive electrode current collector and the negative electrode current collector are metal foils having no through holes. 12. The non-aqueous lithium storage element according to claim 1, wherein an initial charging internal resistance at a cell voltage of 2.2 V is Ra (Ω), a capacitance is F (F), and an electric energy. Where E (Wh) and the volume of the outer package housing the electrode laminate are V (L), the following requirements (a) and (b):
(A) The product Ra · F of Ra and F is 0.3 or more and 3.0 or less,
(B) E / V is 15 or more and 50 or less,
A non-aqueous lithium storage element that satisfies

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