JP2020013875A - Non-aqueous lithium storage element - Google Patents

Abstract

To provide a non-aqueous lithium storage element that increases the capacity of a carbon material, suppresses a decrease in capacity and a rise in resistance during low-voltage and high-temperature storage, suppresses a lack of a positive electrode active material during pre-doping, and reduces a short circuit rate.SOLUTION: When the relative element concentration of aluminum atoms obtained by an x-ray photoelectron spectroscopy (XPS) measurement of the positive electrode surface is C1 (atomic%), the relative element concentration of oxygen atoms is C2 (atomic%), and the relative element concentration of carbon atoms is C3, 0.4≤C1≤18.0, 5.0≤C2≤50.0, and 28.0≤C3≤90.0 are satisfied, and the amount of water contained in a nonaqueous electrolyte is 1 ppm or more and 500 ppm or less, and the peel strength between a positive electrode active material layer and a positive electrode current collector is 0.01 N/cm or more and 2.00 N/cm or less.SELECTED DRAWING: None

Description

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

In recent years, from the viewpoint of effective use of energy aimed at preserving the global environment and conserving resources, a power smoothing system for wind power generation or a late-night power storage system, a home-use decentralized power storage system based on photovoltaic power generation technology, and power storage for electric vehicles The system is attracting attention.
The primary requirement for batteries used in these power storage systems is that they have high energy density. As a promising candidate for a high energy density battery capable of meeting such demands, the development of lithium ion batteries is being vigorously pursued.
The second requirement is that the output characteristics be high. For example, in a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell electric vehicle), a power storage system that exhibits high output discharge characteristics during acceleration is required. Have been. Currently, electric double layer capacitors, nickel-metal hydride batteries, and the like have been developed as high-output power storage devices.

Among the electric double layer capacitors, those using activated carbon for the electrodes have output characteristics of about 0.5 to 1 kW / L. This electric double layer capacitor not only has high output characteristics, but also has high durability (cycle characteristics and high-temperature storage characteristics), and has been considered to be an optimal device in the field where the above high output is required. However, since the energy density is only about 1 to 5 Wh / L, it is necessary to further improve the energy density.
On the other hand, a nickel-metal hydride battery currently generally used in a hybrid electric vehicle has a high output equivalent to an electric double layer capacitor and an energy density of about 160 Wh / L. However, researches for further increasing the energy density and output characteristics and enhancing the durability (especially, stability at high temperatures) are being vigorously pursued.
Research is also being conducted on high-output lithium-ion batteries. For example, a lithium ion battery capable of obtaining a high output exceeding 3 kW / L at a discharge depth (that is, a ratio (%) of a discharge amount to a discharge capacity of a power storage element) of 50% has been developed. However, the energy density is 100 Wh / L or less, and the design is intended to suppress the high energy density, which is the greatest feature of the lithium ion battery. Further, since its durability (cycle characteristics and high-temperature storage characteristics) is inferior to electric double layer capacitors, such lithium ion batteries have a discharge depth of 0 to 100% in order to have practical durability. Is used in a range narrower than the range. Since the capacity of a lithium ion battery that can be actually used is further reduced, research for further improving the durability is being vigorously pursued.

As described above, there is a strong demand for practical use of a power storage element having high energy density, high output characteristics, and high durability. However, since the above-described existing power storage elements have advantages and disadvantages, new power storage elements that satisfy these technical requirements are demanded. As a promising candidate, a power storage element called a lithium ion capacitor has attracted attention and has been actively developed.
A lithium ion capacitor is a type of a power storage element using a non-aqueous electrolyte containing a lithium salt (hereinafter, also referred to as a “non-aqueous lithium power storage element”). This is a power storage element that performs charging and discharging by a non-Faraday reaction by adsorption and desorption of similar anions, and a Faraday reaction by occlusion and release of lithium ions in a negative electrode similar to that of a lithium ion battery.

To summarize the electrode materials and their characteristics commonly used for the above-mentioned energy storage devices, in general, materials such as activated carbon are used for the electrodes, and charge and discharge are performed by adsorption and desorption of ions on the activated carbon surface (non-Faraday reaction). When this is performed, high output and high durability can be obtained, but the energy density is low (for example, it is assumed to be one time). On the other hand, in the case where charge or discharge is performed by a Faraday reaction using an oxide or a carbon material for an electrode, the energy density is increased (for example, 10 times that of a non-Faraday reaction using activated carbon), but durability and output are increased. There is a problem in characteristics.
As a combination of these electrode materials, the electric double layer capacitor uses activated carbon (energy density: 1) for the positive and negative electrodes, and performs charging and discharging by non-Faraday reaction for both the positive and negative electrodes. It has the characteristic of low energy density (1 time for the positive electrode × 1 time for the negative electrode = 1).
Lithium ion secondary batteries are characterized by using a lithium transition metal oxide (energy density 10 times) for the positive electrode, a carbon material (energy density 10 times) for the negative electrode, and charging and discharging both the positive and negative electrodes by a Faraday reaction. Although it has a high energy density (10 times the positive electrode × 10 times the negative electrode = 100), it has problems in output characteristics and durability. Further, in order to satisfy the high durability required for a hybrid electric vehicle or the like, the depth of discharge must be limited, and only 10 to 50% of the energy of a lithium ion secondary battery can be used.
Lithium ion capacitors are characterized by using activated carbon (energy density of 1) for the positive electrode, carbon material (energy density of 10) for the negative electrode, and performing non-Faraday reaction on the positive electrode and Faraday reaction on the negative electrode. This is an asymmetric capacitor having the characteristics of an electric double layer capacitor and a lithium ion secondary battery. Lithium ion capacitors have high energy density (1 time for positive electrode x 10 times for negative electrode = 10) while having high output and high durability, and there is no need to limit the depth of discharge unlike lithium ion secondary batteries. It is a feature.

Various studies have been made on further increasing the energy density of the lithium ion capacitor (Patent Documents 1 to 3).
Patent Literature 1 discloses a composite material including a carbon material and aluminum as a material having a core-shell structure in order to increase the voltage of a lithium ion capacitor.
Patent Literature 2 discloses a lithium-nickel composite oxide having a layer containing lithium carbonate, aluminum oxide, and aluminum hydroxide supported on the surface of an active material in order to improve high-temperature storage characteristics.
Patent Literature 3 proposes a lithium ion secondary battery in which the peel strength between a positive electrode active material layer and a positive electrode current collector is increased.
Patent Document 4 discloses a method of pre-doping a negative electrode using a lithium compound.
However, in each of the documents, the capacity of the carbon material is increased, the capacity is reduced during low-voltage and high-temperature storage, and the increase in resistance is suppressed. Is not considered at all.
In this specification, the meso porosity is calculated by the BJH method, and the micro porosity is calculated by the MP method, respectively. It refers to a method of obtaining the micropore volume, the micropore area, and the distribution of the micropores using the “plotting method” (Non-Patent Document 2), which is shown in Non-Patent Document 3.

JP 2012-74467 A JP 2005-322616 A Japanese Patent Application Laid-Open No. 2006-38962 International Publication No. WO 2017/126687

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

  In view of the above situation, the problem to be solved by the present invention is to increase the capacity of a carbon material, to suppress a decrease in capacity during low-voltage and high-temperature storage, and to suppress a rise in resistance, and to suppress the lack of a positive electrode active material during pre-doping. It is another object of the present invention to provide a non-aqueous lithium energy storage element having a low short circuit rate. The present invention has been made based on such findings.

The above problem is solved by the following technical means. That is, the present invention is as follows:
[1]
A positive electrode, a negative electrode, a separator, a non-aqueous lithium storage element having a non-aqueous electrolyte containing lithium ions,
The positive electrode has a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer includes a carbon material as a positive electrode active material,
The relative element concentration of aluminum atoms obtained by XPS (X-ray photoelectron spectroscopy) measurement on the surface of the positive electrode is C1 (atomic%), the relative element concentration of oxygen atoms is C2 (atomic%), and the relative element concentration of carbon atoms is When C3 (atomic%),
0.4 ≦ C1 ≦ 18.0,
5.0 ≦ C2 ≦ 50.0,
28.0 ≦ C3 ≦ 90.0,
The amount of water contained in the nonaqueous electrolyte is 1 ppm or more and 500 ppm or less, and the peel strength between the positive electrode active material layer and the positive electrode current collector is 0.01 N / cm or more and 2.00 N / cm or less. Water-based lithium storage element.
[2]
The relative element concentration of chlorine atoms obtained by XPS (X-ray photoelectron spectroscopy) measurement on the surface of the positive electrode is defined as C4 (atomic%), where 0.1 ≦ C4 ≦ 5.0, [1]. Non-aqueous lithium energy storage device.
[3]
The non-aqueous lithium storage element according to [1] or [2], wherein the non-aqueous electrolyte contains LiClO ₄ .
[4]
When the relative element concentration of fluorine atoms obtained by XPS (X-ray photoelectron spectroscopy) measurement on the surface of the positive electrode is C5 (atomic%), 3.0 ≦ C5 ≦ 20.0, [1] to [1]. 3] The non-aqueous lithium energy storage element according to any one of the above.
[5]
The method according to any one of [1] to [4], wherein the positive electrode contains at least one carbonate selected from the group consisting of lithium carbonate, sodium carbonate, and potassium carbonate in an amount of 1% by mass to 10% by mass. Non-aqueous lithium energy storage device.
[6]
The nonaqueous lithium energy storage device according to any one of [1] to [5], wherein the positive electrode contains lithium chloride and / or lithium fluoride in an amount of 0.1% by mass or more and 5% by mass or less.
[7]
A power storage module including the nonaqueous lithium storage element according to any one of [1] to [6], a power regeneration assist system, a power load leveling system, an uninterruptible power supply system, a non-contact power supply system, an energy harvesting system, Renewable energy storage system, electric power steering system, emergency power system, in-wheel motor system, idling stop system, electric vehicle, plug-in hybrid vehicle, electric motorcycle or fast charging system.

  According to the present invention, a non-aqueous lithium having a high capacity of a carbon material, suppressing a decrease in capacity during low-voltage high-temperature storage, and suppressing a rise in resistance, and suppressing a lack of a positive electrode active material during pre-doping, and having a low micro-short circuit rate An energy storage element can be provided.

Hereinafter, embodiments of the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail, but the present invention is not limited to the present embodiment. The upper limit value and the lower limit value in each numerical range of the present embodiment can be arbitrarily combined to form an arbitrary numerical range.
In general, a non-aqueous lithium energy storage element mainly includes a positive electrode, a negative electrode, a separator, and an electrolyte. As the electrolytic solution, an organic solvent containing an alkali metal ion (hereinafter, also referred to as “non-aqueous electrolytic solution”) is used.

<Positive electrode>
The positive electrode precursor in the present embodiment has a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material disposed thereon, more specifically, provided on one or both surfaces thereof. The positive electrode active material layer according to the present embodiment is characterized by containing a carbon material, and can contain an alkali metal compound if desired. As described later, in the present embodiment, it is preferable that the negative electrode be pre-doped with an alkali metal ion in the power storage device assembling step. It is preferable to apply a voltage between the positive electrode precursor and the negative electrode after assembling the power storage element using the non-aqueous electrolyte. The alkali metal compound may be contained in the positive electrode precursor in any form. For example, the alkali metal compound may be present between the positive electrode current collector and the positive electrode active material layer, or may be present on the surface of the positive electrode active material layer. The alkali metal compound is preferably contained in the positive electrode active material layer formed on the positive electrode current collector of the positive electrode precursor.
In this specification, the positive electrode before the alkali metal doping step is defined as a “positive electrode precursor”, and the positive electrode after the alkali metal doping step is defined as a “positive electrode”.

[Positive electrode active material layer]
The positive electrode active material layer preferably contains a positive electrode active material containing a carbon material, and, in addition to this, contains optional components such as a conductive filler, a binder, a dispersion stabilizer, and a pH adjuster, if necessary. You may go out.
The positive electrode active material layer preferably contains an alkali metal compound in the positive electrode active material layer of the positive electrode precursor or on the surface of the positive electrode active material layer.

[Positive electrode active material]
The positive electrode active material preferably contains a carbon material. As the carbon material, a carbon nanotube, a conductive polymer, or a porous carbon material is preferably used, and more preferably, activated carbon. One or more kinds of carbon materials may be mixed and used for the positive electrode active material.
In addition to the carbon material, a lithium transition metal oxide may be mixed and used as a positive electrode active material. As the lithium transition metal oxide, a known material used in a lithium ion battery can be used. One or more lithium transition metal oxides may be mixed and used in the positive electrode active material.

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

The BET specific surface area, the mesopore amount, the micropore amount, and the average pore diameter of the active material in the present embodiment are values obtained by the following methods, respectively. The sample is dried in a vacuum at 200 ° C. all day and night, and the adsorption and desorption isotherms are measured using nitrogen as an adsorbate. Using the adsorption-side isotherm obtained here, the BET specific surface area is calculated by the BET multipoint method or the BET one-point method, the mesopore amount is calculated by the BJH method, and the micropore amount is calculated by the MP method.
The BJH method is a calculation method generally used for analysis of mesopores, and has been proposed by Barrett, Joyner, Hallenda et al. (Non-Patent Document 1).
The MP method refers to a method of obtaining a micropore volume, a micropore area, and a distribution of micropores using a “t-plot method” (Non-Patent Document 2). S. This is a method devised by Mikhal, Brunauer, and Bodor (Non-Patent Document 3).
The average pore diameter is obtained by dividing the total pore volume per sample mass obtained by measuring each equilibrium adsorption amount of nitrogen gas at each relative pressure under liquid nitrogen temperature by the above BET specific surface area. Refers to what you asked for.
Incidentally, in addition to the case V ₁ of the above it is the lower limit value V ₂ at the upper limit value, combining is any of the respective upper and lower limits.
Hereinafter, the (1) activated carbon 1 and the (2) activated carbon 2 will be described individually and sequentially.

(Activated carbon 1)
Meso Anaryou V ₁ of the activated carbon 1, in terms of increasing the output characteristics when incorporating the positive electrode material in the capacitor is preferably 0.3 cc / g greater than. V ₁ is preferably 0.8 cc / g or less from the viewpoint of suppressing a decrease in the bulk density of the positive electrode. V ₁ was more preferably 0.35 cc / g or more 0.7 cc / g, more preferably not more than 0.4 cc / g or more 0.6 cc / g.
Micropore volume V ₂ of the activated carbon 1, to increase the specific surface area of the activated carbon, in order to increase the capacity, it is preferable that 0.5 cc / g or more. V ₂ is preferably 1.0 cc / g or less from the viewpoint of suppressing the bulk of activated carbon, increasing the density as an electrode, and increasing the capacity per unit volume. V ₂ is more preferably 0.6 cc / g or more 1.0 cc / g, more preferably not more than 0.8 cc / g or more 1.0 cc / g.
The ratio of meso Anaryou _{V 1} relative to the micropore volume _{V 2 (V 1 / V 2} ) is preferably in the range of _{0.3 ≦ V 1 / V 2 ≦} 0.9. That is, V ₁ / V ₂ should be 0.3 or more from the viewpoint that the ratio of the mesopore amount to the micropore amount is increased to such an extent that the deterioration of the output characteristics can be suppressed while maintaining a high capacity. preferable. On the other hand, V ₁ / V ₂ is 0.9 or less from the viewpoint of increasing the ratio of the amount of micropores to the amount of mesopores to such an extent that a reduction in capacity can be suppressed while maintaining high output characteristics. Is preferred. More preferred _V 1 / _{V 2} range _{0.4 ≦ V 1 / V 2 ≦} 0.7, further preferred _V 1 / _{V 2} range is _{0.55 ≦ V 1 / V 2 ≦} 0.7.

The average pore diameter of the activated carbon 1 is preferably 17 ° or more, more preferably 18 ° or more, and most preferably 20 ° or more from the viewpoint of maximizing the output of the obtained electricity storage device. From the viewpoint of maximizing the capacity, the average pore diameter of the activated carbon 1 is preferably 25 ° or less.
The BET specific surface area of the activated carbon 1 is preferably from 1,500 m ² / g to 3,000 m ² / g, more preferably from 1,500 m ² / g to 2,500 m ² / g. When the BET specific surface area is 1,500 m ² / g or more, a good energy density is easily obtained. On the other hand, when the BET specific surface area is 3,000 m ² / g or less, in order to maintain the strength of the electrode, Since it is not necessary to add a large amount of the binder, the performance per electrode volume is improved.

The activated carbon 1 having the above-mentioned characteristics can be obtained, for example, by using the raw materials and processing methods described below.
In the present embodiment, the carbon source used as a raw material of the activated carbon 1 is not particularly limited. For example, wood, wood flour, coconut shells, by-products during pulp production, bagasse, plant molasses such as molasses; 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 phenolic 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-based raw materials such as coconut shells and wood flour, and their carbides are preferable, and coconut carbides are particularly preferable.
Known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method can be adopted as a method of carbonizing and activating the raw material to form the activated carbon 1.
As a method of carbonizing these raw materials, nitrogen, carbon dioxide, helium, argon, xenon, neon, carbon monoxide, an inert gas such as combustion exhaust gas, or other gas containing these inert gases as a main component. A method of baking at about 400 to 700 ° C. (preferably 450 to 600 ° C.) for about 30 minutes to about 10 hours using a mixed gas may be used.
As a method for activating the carbide obtained by the above-described carbonization method, a gas activation method of firing using an activation gas such as water vapor, carbon dioxide, or oxygen is preferably used. Among these, a method using steam or carbon dioxide as the activation gas is preferable.
In this activation method, the obtained carbide is supplied for 3 to 12 hours (preferably 5 to 12 kg / h) 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 preferred that the activation be carried out by raising the temperature to 800 to 1,000 ° C. over a period of about 11 to 11 hours, more preferably 6 to 10 hours.
Further, prior to the carbide activation treatment described above, the carbide may be primarily activated in advance. In this primary activation, usually, a method of firing a carbon material by using an activation gas such as water vapor, carbon dioxide, oxygen or the like at a temperature of less than 900 ° C. to preferably activate the gas can be preferably employed.

By appropriately combining the calcination temperature and calcination time in the carbonization method described above with the supply amount of the activation gas, the heating rate, and the maximum activation temperature in the activation method, it is possible to produce the activated carbon 1 that can be used in the present embodiment. it can.
The average particle size of the activated carbon 1 is preferably 2 to 20 μm. When the average particle diameter is 2 μm or more, the capacity per electrode volume tends to increase because the density of the active material layer is high. When the average particle size is small, there may be a drawback that the durability is low. However, when the average particle size is 2 μm or more, such a defect hardly occurs. On the other hand, when the average particle diameter is 20 μm or less, there is a tendency that it is easy to adapt to high-speed charge and discharge. The average particle size of the activated carbon 1 is more preferably 2 to 15 μm, and still more preferably 3 to 10 μm.

(Activated carbon 2)
Meso Anaryou V ₁ of the activated carbon 2, from the viewpoint of increasing the output characteristics when incorporating the positive electrode material in the capacitor is preferably 0.8 cc / g greater than. V ₁ is preferably 2.5 cc / g or less from the viewpoint of suppressing a decrease in the capacity of the power storage element. V ₁ was more preferably 1.00 cc / g or more 2.0 cc / g or less, still more preferably not more than 1.2 cc / g or more 1.8 cc / g.
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. V ₂ is preferably 3.0 cc / g or less from the viewpoint of increasing the density of the activated carbon as an electrode and increasing the capacity per unit volume. V2 is more preferably more than 1.0 cc / g and not more than _2.5 cc / g, more preferably not less than 1.5 cc / g and not more than 2.5 cc / g.
The activated carbon 2 having the above-mentioned mesopores and micropores has a higher BET specific surface area than activated carbon used for a conventional electric double layer capacitor or lithium ion capacitor. The specific value of the BET specific surface area of the activated carbon 2 is preferably from 2,300 m ² / g to 4,000 m ² / g, and preferably from 3,000 m ² / g to 4,000 m ² / g. Is more preferably, and more preferably 3,200 m ² / g or more and 3,800 m ² / g or less. When the BET specific surface area is 2,300 m ² / g or more, good energy density is easily obtained, and when the BET specific surface area is 4,000 m ² / g or less, binding is performed to maintain electrode strength. Since it is not necessary to add a large amount of the agent, performance per electrode volume is improved.

The activated carbon 2 having the above-mentioned characteristics can be obtained, for example, by using a raw material and a processing method described below.
The carbonaceous material used as a raw material of the activated carbon 2 is not particularly limited as long as it is a carbon source usually used as a raw material of the activated carbon. Fossil-based raw materials such as coke; and various synthetic resins such as phenolic resin, furan resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, and resorcinol resin. Among these raw materials, a phenol resin and a furan resin are suitable for producing activated carbon having a high specific surface area, and are particularly preferable.
Examples of a method of carbonizing these raw materials or a 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 mixed gas of these inert gases as a main component and other gases. A method of firing at a carbonization temperature of about 400 to 700 ° C. for about 0.5 to 10 hours is generally used.
Examples of the method for activating the carbide include a gas activation method of firing using an activation gas such as water vapor, carbon dioxide, and oxygen, and an alkali metal activation method of performing heat treatment after mixing with an alkali metal compound. For producing activated carbon, 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 equal to or larger than the amount of the carbide). Thereafter, heating is performed in an inert gas atmosphere at a temperature of 600 to 900 ° C. for 0.5 to 5 hours. Thereafter, the alkali metal compound is washed and removed with an acid and water, and further dried.
In order to increase the amount of micropores and not increase the amount of mesopores, it is advisable to increase the amount of carbide during activation and mix with KOH. In order to increase both the micropore volume and the mesopore volume, it is advisable to use a larger amount of KOH. In order to mainly increase the mesopore amount, it is preferable to perform steam activation after performing alkali activation treatment.
The average particle diameter of the activated carbon 2 is preferably 2 μm or more and 20 μm or less. More preferably, it is 3 μm or more and 10 μm or less.

(Use 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 carbons, each of which may indicate the above-described characteristic values as a whole mixture.
As the activated carbons 1 and 2, either one of these may be selected and used, or both may be used in combination.
The positive electrode active material, activated carbon 1 and 2 other than the material (e.g., the activated carbon without a specific V ₁ and / or V ₂ is described, or activated carbon material other than (e.g., conductive polymer, etc.)) May be included. In the illustrated embodiment, the content of the activated carbon 1 in the positive electrode active material layer, the content of the activated carbon 2, or the total content of the active carbon 1 and 2, that is, the mass ratio of the carbon material of the positive electrode active material layer and A ₁ when, also, in the case where in the positive electrode precursor conductive filler, binder, include dispersion stabilizer or the like, when the total amount of the carbon material and these materials and a _1, a ₁ is 15 wt% It is preferably at least 65 mass% and more preferably at least 20 mass% and not more than 50 mass%. If A ₁ is more than 15 mass%, the contact area of the high carbon material electric conductivity and the alkali metal compound is increased, that promotes oxidation reaction of the alkali metal compound in the pre-doping process, the pre-doping in a short time it can. If A ₁ is 65 wt% or less, higher capacity increased bulk density of the positive electrode active material layer.

(Lithium transition metal oxide)
The lithium transition metal oxide includes a transition metal oxide capable of inserting and extracting lithium. There is no particular limitation on the transition metal oxide used as the positive electrode active material. Examples of the transition metal oxide include an oxide containing at least one element selected from the group consisting of cobalt, nickel, manganese, iron, vanadium, and chromium. Specifically, the transition metal oxide has the following formula:
Li _x CoO ₂ ０where x satisfies 0 ≦ x ≦ 1. ｝,
Li _x NiO ₂ } where x satisfies 0 ≦ x ≦ 1. ｝,
Li _x Ni _y M _(1-y) O ₂ } wherein M is at least one element selected from the group consisting of Co, Mn, Al, Fe, Mg, and Ti, and x is 0 ≦ x ≤ 1 and y satisfies 0.05 <y <0.97. ｝,
Li _x Ni _1/3 Co _1/3 Mn _1/3 O ₂中 where x satisfies 0 ≦ x ≦ 1. ｝,
Li _x MnO ₂ } where x satisfies 0 ≦ x ≦ 1. ｝,
α-Li _x FeO ₂ } where x satisfies 0 ≦ x ≦ 1. ｝,
During Li _x VO ₂ {wherein, x is satisfies the 0 ≦ x ≦ 1. ｝,
Li _x CrO ₂中 where x satisfies 0 ≦ x ≦ 1. ｝,
Li _x FePO ₄中 where x satisfies 0 ≦ x ≦ 1. ｝,
Li _x MnPO ₄中 where x satisfies 0 ≦ x ≦ 1. ｝,
Li _z V ₂ (PO ₄ ) ₃ {where, z satisfies 0 ≦ z ≦ 3. ｝,
Li _x Mn ₂ O ₄ {where x satisfies 0 ≦ x ≦ 1. ｝,
During _{Li x M y Mn (2-} y) O 4 { wherein, M is at least one element Co, Mn, Al, Fe, selected from the group consisting of Mg, and Ti, x is 0 ≦ x ≤ 1 and y satisfies 0.05 <y <0.97. ｝,
Li _x Ni _a Co _b Al _(1-ab) O ₂中 where x satisfies 0 ≦ x ≦ 1, and a and b are 0.05 <a <0.97 and 0.05 <b <0.97 is satisfied. ｝,
_{Li x Ni c Co d Mn (} 1-c-d) O 2 { wherein, x is satisfies the 0 ≦ x ≦ 1, and c and d are 0.05 <c <0.97 and 0.05 <d <0.97 is satisfied. ｝
And the like. Among these, from the viewpoints of high capacity, low resistance, cycle characteristics, decomposition of an alkali metal compound, and suppression of the loss of the positive electrode active material during pre-doping, the above formula Li _x Ni _a Co _b Al _{(1-ab) O 2, Li x Ni c Co} d Mn (1-c-d) O 2, Li x CoO 2, Li x Mn 2 O 4, Li x FePO 4, Li x MnPO 4, or _Li z _V 2 (PO ₄ ) ₃ is preferred.
In the present embodiment, if an alkali metal compound different from the positive electrode active material is contained in the positive electrode precursor, the alkali metal compound becomes a dopant source of the alkali metal in pre-doping, and the negative electrode can be pre-doped. Even if lithium ions are not contained in advance (that is, even if x = 0 or z = 0 in the above formula), electrochemical charging and discharging can be performed as the non-aqueous lithium energy storage element.

(Alkali metal compound)
Examples of the alkali metal compound according to the present embodiment include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, lithium oxide and lithium hydroxide, decompose in the positive electrode precursor to release cations, Lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, or at least one alkali metal carbonate selected from cesium carbonate, which can be pre-doped by reduction at the negative electrode, is preferably used, and lithium carbonate, Sodium carbonate or potassium carbonate is more preferably used, and lithium carbonate is more preferably used from the viewpoint of high capacity per unit weight.
The positive electrode precursor may contain one kind of alkali metal compound or two or more kinds of alkali metal compounds. Further, the positive electrode precursor according to the present embodiment only needs to contain at least one kind of alkali metal compound, and M is one or more kinds selected from Li, Na, K, Rb and Cs, and M ₂ O or the like. , A hydroxide such as MOH, a halide such as MF or MCl, or a carboxylate such as RCOOM (where R is H, an alkyl group or an aryl group). Good. Further, the alkali metal compound according to the present _{embodiment, BeCO 3, MgCO 3, CaCO} 3, SrCO 3, and alkaline earth metal carbonate selected from the group consisting of BaCO _3, alkaline earth metal oxides, alkaline earth One or more metal hydroxides, alkaline earth metal halides, or alkaline earth metal carboxylates may be contained.

It is preferable to prepare the positive electrode precursor such that the mass ratio of the alkali metal compound contained in the positive electrode active material layer of the positive electrode precursor is 10% by mass or more and 50% by mass or less. When the mass ratio is 10% by mass or more, a sufficient amount of alkali metal ions can be pre-doped in the negative electrode, and the capacity of the nonaqueous lithium energy storage element increases. On the other hand, when the mass ratio is 50% by mass or less, the electron conduction in the positive electrode precursor can be increased, so that the alkali metal compound can be efficiently decomposed.
When the positive electrode precursor contains the above two or more kinds of alkali metal compounds or an alkaline earth metal compound in addition to the alkali metal compound, the total amount of the alkali metal compound and the alkaline earth metal compound is per one surface of the positive electrode precursor. It is preferable to prepare the positive electrode precursor so that the ratio is 10% by mass or more and 50% by mass or less in the positive electrode active material layer.
Further, as one index indicating the achievement of the pre-doping, at least one carbonate selected from the group consisting of lithium carbonate, sodium carbonate and potassium carbonate is preferably contained in the positive electrode in an amount of 1% by mass or more and 10% by mass or less. Preferably, the content is 1.5% by mass or more and 9.5% by mass or less.

Various methods can be used for atomizing the alkali metal compound and the alkaline earth metal compound. For example, a pulverizer such as a ball mill, a bead mill, a ring mill, a jet mill, and a rod mill can be used.
The quantification of the alkali metal element and the alkaline earth metal element can be calculated by ICP-AES, atomic absorption spectrometry, X-ray fluorescence analysis, neutron activation analysis, ICP-MS, or the like.
In the present embodiment, the average particle size of the alkali metal compound is preferably 0.1 μm or more and 10 μm or less. When the average particle diameter is 0.1 μm or more, the dispersibility in the positive electrode precursor is excellent. When the average particle size is 10 μm or less, the decomposition reaction proceeds efficiently because the surface area of the alkali metal compound increases.
Further, it is preferable that the average particle diameter of the alkali metal compound is smaller than the average particle diameter of the carbon material described above. When the average particle diameter of the alkali metal compound is smaller than the average particle diameter of the carbon material, electron conductivity of the positive electrode active material layer is increased, which can contribute to lowering the resistance of the electrode body or the electric storage element.
The method for measuring the average particle diameter of the alkali metal compound in the positive electrode precursor is not particularly limited, but can be calculated from the SEM image and the SEM-EDX image of the cross section of the positive electrode. As a method for forming the cross section of the positive electrode, BIB processing for irradiating an Ar beam from above the positive electrode and producing a smooth cross section along the end of the shielding plate provided immediately above the sample can be used.

(Other components of the positive electrode active material layer)
In the positive electrode active material layer of the positive electrode precursor in the present invention, if necessary, in addition to the positive electrode active material and the alkali metal compound, a conductive filler, a binder, a dispersion stabilizer, an optional component such as a pH adjuster. May be included.
Examples of the conductive filler include a conductive carbonaceous material having higher conductivity than the positive electrode active material. As such a conductive filler, for example, Ketjen black, acetylene black, vapor-grown carbon fiber, graphite, flaky graphite, carbon nanotube, graphene, a mixture thereof and the like are preferable.
The mixing amount of the conductive filler in the positive electrode active material layer of the positive electrode precursor is preferably from 0 to 20 parts by mass, more preferably from 1 to 15 parts by mass, per 100 parts by mass of the positive electrode active material. It is preferable to mix the conductive filler from the viewpoint of high input. However, when the mixing amount is more than 20 parts by mass, the content ratio of the positive electrode active material in the positive electrode active material layer is reduced, so that the energy density per volume of the positive electrode active material layer decreases, which is not preferable.

  The binder is not particularly limited, but for example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, etc. Can be used. The amount of the binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 3 parts by mass or more and 27 parts by mass or less, and still more preferably 5 parts by mass or more with respect to 100 parts by mass of the positive electrode active material. 25 parts by mass or less. When the amount of the binder used is 1 part by mass or more based on 100 parts by mass of the positive electrode active material, sufficient electrode strength is exhibited. On the other hand, if the amount of the binder used is 30 parts by mass or less based on 100 parts by mass of the positive electrode active material, high input / output characteristics are exhibited without inhibiting the ingress and egress and diffusion of ions to and from the positive electrode active material. .

  The dispersion stabilizer is not particularly limited, but for example, PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), a cellulose derivative and the like can be used. The amount of the dispersion stabilizer to be used is preferably 0 parts by mass or more and 10 parts by mass or less based on 100 parts by mass of the positive electrode active material. When the use amount of the dispersion stabilizer is 10 parts by mass or less with respect to 100 parts by mass of the positive electrode active material, high input / output characteristics are exhibited without impeding the inflow and outflow and diffusion of ions to and from the positive electrode active material.

  When water is used as a solvent for the coating liquid, the coating liquid may be made alkaline by adding an alkali metal compound, and therefore, a pH adjuster may be added to the coating liquid as necessary. . Examples of the pH adjuster include, but are not particularly limited to, hydrogen halides such as hydrogen fluoride, hydrogen chloride, and hydrogen bromide; halogen oxoacids such as hypochlorous acid, chlorous acid, and chloric acid; and formic acid. Carboxylic acids such as acetic acid, citric acid, oxalic acid, lactic acid, maleic acid and fumaric acid, sulfonic acids such as methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, phosphoric acid, boric acid, and dioxide Acids such as carbon can be used.

[Positive electrode current collector]
The material constituting the positive electrode current collector according to the present embodiment is not particularly limited as long as the material has high electron conductivity and does not cause degradation due to elution into the electrolyte and reaction with the electrolyte or ions. Metal foils are preferred. As the positive electrode current collector in the nonaqueous lithium energy storage device according to the present embodiment, an aluminum foil is more preferable.
The metal foil may be a normal metal foil having no irregularities or through holes, or may be a metal foil having irregularities subjected to embossing, chemical etching, electrolytic deposition, blasting, or the like, expanded metal, punching metal, A metal foil having a through hole such as an etching foil may be used.
From the viewpoint of pro-doping treatment described later, non-porous aluminum foil is more preferable, and it is particularly preferable that the surface of the aluminum foil is roughened.
The thickness of the positive electrode current collector is not particularly limited as long as the shape and strength of the positive electrode can be sufficiently maintained, but is preferably, for example, 1 to 100 μm.
Further, it is preferable to provide an anchor layer containing a conductive material such as graphite, flaky graphite, carbon nanotube, graphene, Ketjen black, acetylene black, and vapor grown carbon fiber on the surface of the metal foil. By providing the anchor layer, electric conduction between the positive electrode current collector and the positive electrode active material layer is improved, and the resistance can be reduced. The thickness of the anchor layer is preferably 0.1 μm or more and 5 μm or less per one surface of the positive electrode current collector.

[Production of positive electrode precursor]
In the present embodiment, the positive electrode precursor serving as the positive electrode of the non-aqueous lithium energy storage device can be manufactured by a known electrode manufacturing technology in a lithium ion battery, an electric double layer capacitor, or the like. For example, a positive electrode active material and an alkali metal compound, and other optional components used as necessary are dispersed or dissolved in water or an organic solvent to prepare a slurry-like coating liquid, and this coating liquid is used as a positive electrode. A positive electrode precursor can be obtained by coating one or both surfaces of the current collector to form a coating film and drying the coating film. Further, the obtained positive electrode precursor may be pressed to adjust the thickness or bulk density of the positive electrode active material layer. Alternatively, without using a solvent, the positive electrode active material and the alkali metal compound, and other optional components used as necessary, are dry-mixed, and the resulting mixture is press-molded, and then subjected to electroconductivity. A method of attaching the mixture to the positive electrode current collector using an adhesive or a method of heating and pressing the obtained mixture on the positive electrode current collector to form a positive electrode active material layer is also possible.

The preparation of the coating solution for the positive electrode precursor is performed by dry blending a part or all of the various material powders including the positive electrode active material, and then water or an organic solvent, and / or a binder, a dispersion stabilizer or a pH adjuster. A liquid or slurry substance in which the agent is dissolved or dispersed may be additionally prepared. Further, in a liquid or slurry-like substance in which a binder, a dispersion stabilizer or a pH adjuster is dissolved or dispersed in water or an organic solvent, various material powders including a positive electrode active material may be additionally prepared. . As a dry blending method, for example, a positive electrode active material and an alkali metal compound are premixed using a ball mill or the like, and a conductive filler is preliminarily mixed as necessary, and premixing is performed to coat the conductive material on the low conductive alkali metal compound. May be. This makes it easier for the alkali metal compound to be decomposed in the positive electrode precursor in the pre-doping step described later.
The preparation of the coating solution for the positive electrode precursor is not particularly limited, but a homodisper, a multiaxial disperser, a planetary mixer, a disperser such as a thin-film swirling high-speed mixer, or the like can be preferably used. In order to obtain a coating liquid in a good dispersion state, the coating liquid is preferably dispersed at a peripheral speed of 1 m / s or more and 50 m / s or less. When the peripheral speed is 1 m / s or more, various materials are favorably dissolved or dispersed, which is preferable. A peripheral speed of 50 m / s or less is preferable because various materials are not destroyed by heat or shear force due to dispersion and reaggregation does not occur.

As for the degree of dispersion of the coating liquid, the particle size measured by 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 still more preferably 50 μm or less. If the particle size is less than 0.1 μm, the size becomes smaller than or equal to the particle size of various material powders including the positive electrode active material, and the material is crushed at the time of preparing the coating liquid, which is not preferable. In addition, when the particle size is 100 μm or less, there is no clogging at the time of discharging the coating liquid and no streaking of the coating film, and the coating can be performed stably.
The viscosity (ηb) of the coating solution of the positive electrode precursor is preferably from 1,000 mPa · s to 20,000 mPa · s, more preferably from 1,500 mPa · s to 10,000 mPa · s, and still more preferably 1,500 mPa · s or less. It is 700 mPa · s or more and 5,000 mPa · s or less. When the viscosity (ηb) is 1,000 mPa · s or more, liquid dripping during coating film formation is suppressed, and the coating film width and thickness can be controlled well. Further, when the viscosity is 20,000 mPa · s or less, the coating can be stably applied with a small pressure loss in the flow path of the coating liquid when the coating machine is used, and can be controlled to a desired thickness or less.
Further, the TI value (thixotropic index value) of the coating liquid is preferably 1.1 or more, more preferably 1.2 or more, and still more preferably 1.5 or more. When the TI value is 1.1 or more, the coating film width and thickness can be controlled well.

The coating of the positive electrode precursor is not particularly limited, but a coating machine such as a die coater, a comma coater, a knife coater, or a gravure coating machine can be preferably used. The coating film may be formed by single-layer coating or multi-layer coating. In the case of multilayer coating, the composition of the coating liquid may be adjusted so that the content of the alkali metal compound in each layer of the coating film is different. When applying a coating film on the positive electrode current collector, multi-coating, intermittent coating, or multi-intermittent coating may be performed. Alternatively, one side of the positive electrode current collector may be coated and dried, and then the other side may be sequentially coated and dried, or a coating liquid may be simultaneously applied to both sides of the positive electrode current collector. Alternatively, both sides may be simultaneously dried and dried. When the coating liquid is applied to both surfaces of the positive electrode current collector, the respective ratios of the carbon material, the lithium transition metal oxide, and the alkali metal compound on the front surface and the back surface are preferably 10% or less. For example, the mass ratio _{A 1} of the carbon material of the surface of the positive electrode current collector (Table) the ratio _{A 1} of the rear surface of the _{A 1} (back) (front) / _{A 1} (back) of 0.9 to 1.1 is there. Further, the ratio of the thickness of the positive electrode active material layer on the front surface to the thickness of the positive electrode active material layer on the back surface is preferably 10% or less. As the mass ratio between the front surface and the back surface and the film thickness ratio are closer to 1.0, the charge / discharge load does not concentrate on one surface, so that the high load charge / discharge cycle characteristics are improved.

The drying of the coating film of the positive electrode precursor is preferably performed by a drying method such as hot-air drying or infrared (IR) drying, and more preferably with far-infrared rays, near-infrared rays, or hot air of 80 ° C. or higher. The coating film may be dried at a single temperature or may be dried at multiple temperatures. Further, drying may be performed by combining a plurality of drying methods. The drying temperature is preferably from 25 ° C to 200 ° C. The temperature is more preferably 40 ° C or more and 180 ° C or less, and further preferably 50 ° C or more and 160 ° 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, when the temperature is 200 ° C. or less, uneven distribution of the binder due to cracking or migration of the coating film due to rapid volatilization of the solvent and oxidation of the positive electrode current collector or the positive electrode active material layer can be suppressed.
The moisture contained in the dried positive electrode precursor is preferably 0.1% or more and 10% or less, with the mass of the positive electrode active material layer being 100%. When the water content is 0.1% or more, deterioration of the binder due to excessive drying can be suppressed, and the resistance can be reduced. When the water content is 10% or less, deactivation of alkali metal ions in the nonaqueous lithium energy storage element can be suppressed, and the capacity can be increased.
When N-methyl-2-pyrrolidone (NMP) is used for preparing the coating solution, the content of NMP in the dried positive electrode precursor is 0.1% or more with respect to the mass of the positive electrode active material layer being 100%. % Is preferable. When NMP is 0.1% or more, deterioration of the binder due to excessive drying can be suppressed, and the resistance can be reduced. When the NMP is 10% or less, the self-discharge characteristics of the non-aqueous lithium energy storage device can be improved.
The moisture contained in the positive electrode precursor can be measured, for example, by Karl Fischer titration (JIS 0068 (2001) “Method for measuring moisture of chemical products”).
In addition, NMP contained in the positive electrode precursor is obtained by impregnating the positive electrode precursor with ethanol having a mass of 50 to 100 times the mass of the positive electrode active material layer for 24 hours under a 25 ° C. environment, and extracting GC / MS by GC / MS. It can be measured and quantified based on a calibration curve created in advance.

For pressing the positive electrode precursor, a press such as a hydraulic press or a vacuum press can be preferably used. The thickness, bulk density, and electrode strength of the positive electrode active material layer can be adjusted by the press pressure, the gap between the press rolls, and the surface temperature of the press section, which will be 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. When 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 does not bend or wrinkle, and can be adjusted to a desired positive electrode active material layer thickness or bulk density. Further, an arbitrary value can be set according to the thickness of the dried positive electrode precursor so that the gap between the press rolls has a desired thickness or bulk density of the positive electrode active material layer. Further, the pressing speed can be set to any speed that does not cause bending or wrinkling of the positive electrode precursor. Further, the surface temperature of the press section may be room temperature or may be heated if necessary. When heating, the lower limit of the surface temperature of the press part is preferably the melting point of the binder used minus 60 ° C or more, more preferably the melting point of the binder minus 45 ° C or more, and still more preferably the melting point of the binder minus 30 ° C. ° C or higher. On the other hand, when heating, the upper limit of the surface temperature of the press part is preferably the melting point of the binder used plus 50 ° C. or less, more preferably the melting point of the binder plus 30 ° C. or less, and still more preferably the melting point of the binder 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 to 90 ° C. or more and 200 ° C. or less, more preferably 105 ° C. or more and 180 ° C. or less, and further preferably 120 ° C. or more Heating to 170 ° C. or less. 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 55 ° C. or more and 130 ° C. or less, and further preferably 70 ° C. or less. The heating is to be performed at a temperature of not less than 120 ° C and not less than 120 ° C.
The melting point of the binder can be determined from the endothermic peak position in DSC (Differential Scanning Calorimetry). For example, using a differential scanning calorimeter “DSC7” manufactured by Perkin Elmer, 10 mg of a sample resin is set in a measurement cell, and the temperature is increased from 30 ° C. to 250 ° C. at a rate of 10 ° C./min in a nitrogen gas atmosphere. When the temperature is raised, the endothermic peak temperature in the temperature raising process becomes the melting point.

Pressing may be performed a plurality of times while changing the conditions of the pressing pressure, the gap, the speed, and the surface temperature of the pressing section.
When the positive electrode precursor is multi-coated, slitting is preferably performed before pressing. When the multi-coated positive electrode precursor is pressed without slitting, stress is applied to the current collector portion where the positive electrode active material layer is not applied, and wrinkles are formed. Further, after the pressing, the positive electrode precursor can be slit again.

  The thickness of the positive electrode active material layer according to this embodiment is preferably 10 μm or more and 200 μm or less per one side of the positive electrode current collector. The thickness of the positive electrode active material layer is more preferably 20 μm or more and 100 μm or less per side, and even more preferably 30 μm or more and 80 μm or less. When the thickness is 10 μm or more, a sufficient charge / discharge capacity can be exhibited. On the other hand, if the 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, and thus the energy density can be increased. Note that the thickness of the positive electrode active material layer in the case where the current collector has a through-hole or unevenness refers to an average value of the thickness of one side of the current collector which does not have the through-hole or unevenness.

<Negative electrode>
The negative electrode has a negative electrode current collector and a negative electrode active material layer present on one or both surfaces thereof.
[Negative electrode active material layer]
The negative electrode active material layer contains a negative electrode active material capable of occluding and releasing alkali metal ions, and may further contain optional components such as a conductive filler, a binder, and a dispersion stabilizer, as necessary.

[Negative electrode active material]
As the negative electrode active material, a substance that can occlude and release alkali metal ions can be used. Specific examples include a carbon material, titanium oxide, silicon, silicon oxide, silicon alloy, silicon compound, tin, and tin compound. 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 can be 100% by mass, it is preferably, for example, 90% by mass or less, and may be 80% by mass or less from the viewpoint of favorably obtaining the effect of the combined use of other materials. The upper and lower limits of the range of the content of the carbon material can be arbitrarily combined.
Examples of the carbon material include a non-graphitizable carbon material; a graphitizable carbon material; carbon black; carbon nanoparticles; activated carbon; artificial graphite; a natural graphite; a graphitized mesophase carbon microsphere; a graphite whisker; Amorphous carbonaceous material; petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, carbonaceous material obtained by heat-treating a carbon precursor such as synthetic resin (eg, phenolic resin); furfuryl alcohol resin Or a thermally decomposed product of a novolak resin; fullerene; carbon nanophone; and a composite carbon material thereof.

The BET specific surface area of the composite carbon material is preferably from 100 m ² / g to 350 m ² / g, more preferably from 150 m ² / g to 300 m ² / g. When the BET specific surface area is 100 m ² / g or more, the pre-doping amount of alkali metal ions can be sufficiently increased, so that the thickness of the negative electrode active material layer can be reduced. When the BET specific surface area is 350 m ² / g or less, the coatability of the negative electrode active material layer is excellent.
The composite carbon material was charged at a constant current of 0.5 mA / cm ² at a measurement temperature of 25 ° C. with a current value of 0.5 mA / cm ² until the voltage value reached 0.01 V using a lithium metal as a counter electrode. The initial charge capacity when performing constant voltage charging until the current reaches 01 mA / cm ² is preferably 300 mAh / g or more and 1,600 mAh / g or less, more preferably 400 mAh / g, per unit mass of the composite carbon material. g and 1,500 mAh / g or less, and more preferably 500 mAh / g or more and 1,450 mAh / g or less. If the initial charge capacity is 300 mAh / g or more, the pre-doping amount of the alkali metal ion can be sufficiently increased, so that high output characteristics can be obtained even when the negative electrode active material layer is thinned. Further, if the initial charge capacity is 1,600 mAh / g or less, the swelling and shrinkage of the composite carbon material when doping and undoping the composite carbon material with alkali metal ions is reduced, and the strength of the negative electrode is maintained. Dripping.

The above-described negative electrode active material is particularly preferably a composite porous material satisfying the following conditions (1) and (2) from the viewpoint of obtaining a good internal resistance value.
(1) When the amount of mesopores (the amount of pores having a diameter of 2 nm or more and 50 nm or less) Vm ₁ (cc / g) calculated by the above-described BJH method is 0.01 ≦ Vm ₁ <0.10. Fulfill.
(2) The micropore amount (the amount of pores having a diameter of less than 2 nm) Vm ₂ (cc / g) calculated by the MP method described above satisfies the condition of 0.01 ≦ Vm ₂ <0.30.

The negative electrode active material is preferably in the form of particles.
The particle diameters of silicon, silicon oxide, silicon alloy and silicon compound, and tin and tin compound are preferably 0.1 μm or more and 30 μm or less. When the particle diameter is 0.1 μm or more, the contact area with the electrolytic solution increases, so that the resistance of the nonaqueous lithium storage element can be reduced. When the particle diameter is 30 μm or less, swelling / shrinking of the negative electrode due to doping / de-doping of the negative electrode with the alkali metal ion during charging / discharging is reduced, and the strength of the negative electrode is maintained.
The silicon, silicon oxide, silicon alloy and silicon compound, and tin and tin compound can be finely divided by pulverization using a jet mill, a stirring ball mill, or the like built in a classifier. The crusher is provided with a centrifugal classifier, and fine particles crushed under an inert gas environment such as nitrogen or argon can be collected by a cyclone or a dust collector.
The content ratio of the negative electrode active material in the negative electrode active material layer of the negative electrode precursor is preferably 70% by mass or more, more preferably 80% by mass or more, based on the total mass of the negative electrode active material layer.

(Other components of the negative electrode active material layer)
The negative electrode active material layer according to the present embodiment may include optional components such as a binder, a conductive filler, and a dispersion stabilizer, as necessary, in addition to the negative electrode active material.
As the binder, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), fluororubber, latex, acrylic polymer and the like can be used. The amount of the binder used in the negative electrode active material layer is preferably 3 to 25 parts by mass, more preferably 5 to 20 parts by mass, per 100 parts by mass of the negative electrode active material. When the amount of the binder used is less than 3 parts by mass with respect to 100 parts by mass of the negative electrode active material, it is possible to secure sufficient adhesion between the current collector and the negative electrode active material layer in the negative electrode (precursor). No, the interface resistance between the current collector and the active material layer increases. On the other hand, if the amount of the binder used is greater than 25 parts by mass with respect to 100 parts by mass of the negative electrode active material, the surface of the active material of the negative electrode (precursor) is excessively covered with the binder, and the fine particles of the active material are used. The diffusion resistance of ions in the pores increases.
The conductive filler is preferably made of a conductive carbonaceous material having higher conductivity than the negative electrode active material. As such a conductive filler, for example, Ketjen black, acetylene black, vapor-grown carbon fiber, graphite, carbon nanotube, a mixture thereof and the like are preferable.
The mixing amount of the conductive filler in the negative electrode active material layer is preferably 20 parts by mass or less, and more preferably 1 to 15 parts by mass, per 100 parts by mass of the negative electrode active material. The conductive filler is preferably mixed with the negative electrode active material layer from the viewpoint of high input.However, when the mixing amount is more than 20 parts by mass, the content of the negative electrode active material in the negative electrode active material layer is reduced. However, it is not preferable because the energy density per volume decreases.

[Negative electrode current collector]
The material constituting the negative electrode current collector according to the present embodiment is preferably a metal foil that has high electron conductivity and does not degrade due to elution into the electrolytic solution and reaction with the electrolyte or ions. Such a metal foil is not particularly limited, and examples thereof include an aluminum foil, a copper foil, a nickel foil, and a stainless steel foil. As the negative electrode current collector in the non-aqueous lithium storage element according to the present embodiment, a copper foil is preferable. The metal foil may be a normal metal foil having no irregularities or through holes, or may be a metal foil having irregularities subjected to embossing, chemical etching, electrolytic deposition, blasting, or the like, expanded metal, punching metal, A metal foil having a through hole such as an etching foil may be used.
The thickness of the negative electrode current collector is not particularly limited as long as the shape and strength of the negative electrode can be sufficiently maintained, and is, for example, 1 to 100 μm.

[Production 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 a known electrode manufacturing technology in a lithium ion battery, an 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 solution, and this coating solution is applied to one or both surfaces of the negative electrode current collector. A negative electrode can be obtained by forming a coating film and drying it. Further, the obtained negative electrode may be pressed to adjust the thickness or bulk density of the negative electrode active material layer.
The thickness of the negative electrode active material layer is preferably 10 μm or more and 70 μm or less per side, more preferably 20 μm or more and 60 μm or less. When the thickness is 10 μm or more, good charge / discharge capacity can be exhibited. On the other hand, if the thickness is 70 μm or less, the cell volume can be reduced, so that the energy density can be increased. In the case where the current collector has holes, the thickness of the active material layer of the negative electrode refers to an average value of the thickness of one side of the current collector without holes.

<Separator>
The positive electrode precursor and the negative electrode are laminated or wound with a separator interposed therebetween to form an electrode laminate including the positive electrode precursor, the negative electrode, and the separator.
As the separator, a polyethylene microporous membrane or polypropylene microporous membrane used for a lithium ion secondary battery, a cellulose nonwoven paper used for 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 or both surfaces 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. When the thickness is 5 μm or more, self-discharge due to internal micro-short tends to be reduced, which is preferable. On the other hand, when the thickness is 35 μm or less, the output characteristics of the power storage element tend to increase, which is preferable.
The thickness of the film made of organic or inorganic fine particles is preferably 1 μm or more and 10 μm or less. When the thickness is 1 μm or more, self-discharge due to internal micro-short tends to be reduced, which is preferable. On the other hand, when the thickness is 10 μm or less, the output characteristics of the power storage element tend to be high, which is preferable.

<Outer body>
As the exterior body, a metal can, a laminated film, or the like can be used. The metal can is preferably made of aluminum. The metal can may be in the form of, for example, a square, a round, or a cylinder. As the laminate film, a film obtained by laminating a metal foil and a resin film is preferable, and a three-layer structure composed of an outer resin film / metal foil / interior resin film is exemplified. The outer 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 permeation of moisture and gas, and foils of copper, aluminum, stainless steel and the like can be suitably used. The interior resin film serves to protect the metal foil from the electrolytic solution contained therein and to melt-close the exterior body during heat sealing, and polyolefin, acid-modified polyolefin and the like can be suitably used.

<Electrolyte>
The electrolyte in this embodiment is a non-aqueous electrolyte. That is, the electrolyte contains a non-aqueous solvent. The non-aqueous electrolyte contains 0.5 mol / L or more alkali metal salt based on the total amount of the non-aqueous electrolyte. That is, the non-aqueous electrolyte contains an alkali metal salt as an electrolyte. Examples of the non-aqueous solvent contained in the non-aqueous electrolyte include a cyclic carbonate typified by ethylene carbonate, propylene carbonate, and the like, and a chain carbonate typified by dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like.
As the electrolyte salt containing an alkali metal ion dissolved in a non-aqueous solvent as described above, for example, MFSI, MBF ₄ , MPF ₆ , and MClO ₄ may be used, where M is Li, Na, K, Rb, or Cs. it can. From the viewpoint of reacting with the aluminum foil of the current collector during the pre-doping step and forming a dielectric layer composed of aluminum atoms and oxygen atoms on the surface of the carbon material, MClO ₄ is preferably used, and LiClO ₄ is more preferably used. Can be The non-aqueous electrolyte in the present embodiment may contain at least one or more alkali metal ions, and may contain two or more alkali metal salts, or may contain an alkali metal salt, a beryllium salt, and magnesium. It may contain an alkaline earth metal salt selected from salts, calcium salts, strontium salts and barium salts. When the non-aqueous electrolyte contains two or more alkali metal salts, the presence of cations having different Stokes radii in the non-aqueous electrolyte can suppress a rise in viscosity at low temperatures. The low-temperature characteristics of the aqueous lithium storage element are improved. When the non-aqueous electrolyte contains an alkaline earth metal ion other than the alkali metal ion, the non-aqueous lithium storage battery is used because beryllium ion, magnesium ion, calcium ion, strontium ion, and barium ion are divalent cations. The capacity of the element can be increased.

The method of including the two or more alkali metal salts in the non-aqueous electrolyte, or the method of including the alkali metal salt and the alkaline earth metal salt in the non-aqueous electrolyte is not particularly limited, In addition, an alkali metal salt composed of two or more alkali metal ions can be dissolved in advance, or an alkali metal salt and an alkaline earth metal salt can be dissolved. Further, in the positive electrode precursor, M in the following formula is one or more selected from Na, K, Rb, and Cs,
Carbonates such as M ₂ CO ₃ ,
Oxides such as M ₂ O,
Hydroxides such as MOH,
Halides such as MF and MCl,
A carboxylate such as RCOOM (where R is H, an alkyl group, or an aryl group) and / or an alkaline earth metal carbonate selected from BeCO ₃ , MgCO ₃ , CaCO ₃ , SrCO ₃ , or BaCO ₃ A method in which at least one kind of salt, an alkaline earth metal oxide, an alkaline earth metal hydroxide, an alkaline earth metal halide, and an alkaline earth metal carboxylate is contained and decomposed in a pre-doping step described below. Is mentioned.
The electrolyte salt concentration in the electrolyte is preferably in the range of 0.5 to 2.0 mol / L. At an electrolyte salt concentration of 0.5 mol / L or more, sufficient anions are present, and the capacity of the non-aqueous lithium storage element is maintained. On the other hand, when the electrolyte salt concentration is 2.0 mol / L or less, the salt is sufficiently dissolved in the electrolyte solution, and the appropriate viscosity and conductivity of the electrolyte solution are maintained.
When the non-aqueous electrolyte contains two or more kinds of alkali metal salts, or when it contains an alkali metal salt and an alkaline earth metal salt, the total value of these salt concentrations is 0.5 mol / L or more. Is more preferable, and more preferably in the range of 0.5 to 2.0 mol / L.

  In the present embodiment, the amount of water contained in the non-aqueous electrolyte is 1 ppm or more and 500 ppm or less. When the water content is 1 ppm or more, the alkali metal compound in the positive electrode precursor can be slightly dissolved, and pre-doping can be performed under mild conditions, so that the capacity can be increased and the resistance can be reduced. When the water content is 500 ppm or less, the decomposition reaction between water and the dielectric layer made of aluminum atoms and oxygen atoms formed on the surface of the carbon material is suppressed, so that low-voltage high-temperature storage characteristics are excellent. The amount of water in the electrolyte can be measured by the Karl Fischer method described above.

<Production method of non-aqueous lithium storage element>
[Assembly process Production of electrode body]
In an assembly process of an embodiment, for example, a positive electrode terminal and a negative electrode terminal are connected to a laminate obtained by laminating a positive electrode precursor and a negative electrode cut into a sheet shape via a separator, and the electrode laminate is formed. Make it. In another embodiment, a positive electrode terminal and a negative electrode terminal may be connected to a wound body obtained by laminating and winding a positive electrode precursor and a negative electrode via a separator, to produce an electrode wound body. The shape of the electrode winding body may be cylindrical or flat.
The method for connecting the positive electrode terminal and the negative electrode terminal is not particularly limited, but a method such as resistance welding or ultrasonic welding can be used.
It is preferable to remove the residual solvent by drying the electrode body (electrode laminate or electrode wound body) to which the terminal is connected. The drying method is not limited, but drying can be performed by vacuum drying or the like. The amount of the residual solvent is preferably 1.5% by mass or less based on the total mass of the positive electrode active material layer or the negative electrode active material layer. If the amount of the residual solvent is more than 1.5% by mass, the solvent remains in the system and the self-discharge characteristics are deteriorated, which is not preferable.
The dried electrode body is preferably housed in an exterior body represented by a metal can or a laminated film under a dry environment having a dew point of −40 ° C. or lower, and has an opening for injecting a non-aqueous electrolyte. It is preferable to seal only one side. If the dew point is higher than −40 ° C., moisture adheres to the electrode body, and water remains in the system, which deteriorates self-discharge characteristics, which is not preferable. The method for sealing the outer package is not particularly limited, but a method such as heat sealing or impulse sealing can be used.

[Injection, impregnation, sealing process]
After the assembling process, a non-aqueous electrolyte is injected into the electrode body housed in the exterior body. After the injection, further impregnation is preferably performed, and the positive electrode, the negative electrode, and the separator are preferably sufficiently immersed in the non-aqueous electrolyte. In a state in which the electrolyte is not immersed in at least a part of the positive electrode, the negative electrode, and the separator, in the alkali metal doping step described later, the alkali metal doping proceeds unevenly, so that the resistance of the obtained nonaqueous lithium energy storage element increases. It rises and durability decreases. The method of impregnation is not particularly limited.For example, the electrode body after liquid injection is placed in a reduced pressure chamber with the outer body opened, and the inside of the chamber is reduced in pressure using a vacuum pump, and the atmospheric pressure is again applied. And the like. After the impregnation, the electrode body in a state where the exterior body is open can be hermetically sealed by sealing while reducing the pressure.

[Alkali metal doping step]
In the alkali metal doping step, a voltage is applied between the positive electrode precursor and the negative electrode to decompose the alkali metal compound in the positive electrode precursor, release alkali metal ions, and reduce the alkali metal ions at the negative electrode. It is preferable to pre-dope the negative electrode active material layer with an alkali metal ion.
In the alkali metal doping step, a gas such as CO ₂ is generated with the oxidative decomposition of the alkali metal compound in the positive electrode precursor. Therefore, when applying a voltage, it is preferable to take measures to release the generated gas to the outside of the exterior body. As this means, for example, a method in which a voltage is applied in a state where a part of the exterior body is opened; in a state in which an appropriate gas releasing means such as a gas release valve and a gas permeable film is installed in a part of the exterior body in advance. A method of applying a voltage;

[Aging process]
It is preferable to perform aging on the electrode body after the alkali metal doping step. In the aging step, the solvent in the electrolytic solution is decomposed at the negative electrode, and a solid polymer film having alkali metal ion permeability is formed on the negative electrode surface.
The method of aging is not particularly limited, and for example, a method of reacting a solvent in an electrolytic solution under a high temperature environment can be used.

[Degassing process]
After the aging step, it is preferable to further remove the gas to surely remove the gas remaining in the electrolytic solution, the positive electrode, and the negative electrode. In a state where gas remains in at least a part of the electrolytic solution, the positive electrode, and the negative electrode, ion conduction is hindered, and the resistance of the obtained nonaqueous lithium energy storage element increases.
The method of degassing is not particularly limited. For example, a method in which the electrode laminate is placed in a decompression chamber with the outer body opened, and the inside of the chamber is depressurized using a vacuum pump, or the like can be used. . After degassing, the exterior body is sealed by sealing the exterior body, so that a non-aqueous lithium energy storage element can be manufactured.

<Higher capacity carbon materials>
In this embodiment, the capacity of the carbon material can be increased by forming a dielectric layer composed of aluminum atoms and oxygen atoms on the surface of the carbon material as the positive electrode active material. When the carbon material has a dielectric layer on the surface, the amount of anions and cations that can be adsorbed per unit area increases, so that a higher capacity can be achieved. That is, the relative element concentration of aluminum atoms obtained by XPS (X-ray photoelectron spectroscopy) measurement on the surface of the positive electrode is C1 (atomic%), the relative element concentration of oxygen atoms is C2 (atomic%), and the relative element concentration of carbon atoms is Is C3 (atomic%), 0.4 ≦ C1 ≦ 18.0, 5.0 ≦ C2 ≦ 50.0, and 28.0 ≦ C3 ≦ 90.0. When C1 is 0.4 or more, C2 is 5.0 or more, and C3 is 90.0 or less, high capacitance can be achieved because the surface of the carbon material is covered with the dielectric layer. When C1 is 18.0 or less, C2 is 50.0 or less, and C3 is 28.0 or more, the resistance can be reduced because the dielectric layer on the surface of the carbon material is not enlarged.
From the viewpoint of achieving both high capacity and low resistance, preferably 0.5 ≦ C1 ≦ 17.7, 5.2 ≦ C2 ≦ 44.5, and 28.2 ≦ C3 ≦ 89.5, and more preferably Preferably, 0.6 ≦ C1 ≦ 17.0, 5.5 ≦ C2 ≦ 44.0, and 28.5 ≦ C3 ≦ 89.0.

There is no particular limitation on the method of forming the dielectric layer composed of aluminum atoms and oxygen atoms on the surface of the carbon material.For example, a method of simultaneously firing a carbon material and a compound having aluminum atoms and oxygen atoms, A method of immersing in a solution in which a compound having an aluminum atom and an oxygen atom is dissolved can be given. As a particularly preferred method, M is converted into an alkali metal ion selected from Li, Na, and K _, and an oxidizing solid such as MCLO _4, MCLO _3, MCLO _2, and MNO ₃ is dissolved in the electrolytic solution. There is a method in which a compound having an aluminum atom and an oxygen atom generated by an oxidation reaction with an aluminum foil as a current collector is applied to a surface of a carbon material by applying a voltage.

Since the dielectric layer formed on the surface of the carbon material is decomposed by reacting with water in the electrolytic solution under a low voltage and high temperature environment, it is preferable that the dielectric layer further has a coating made of chlorine atoms or fluorine atoms. When the relative element concentration of chlorine atom is C4 (atomic%), 0.1 ≦ C4 ≦ 5.0, and when the relative element concentration of fluorine atom is C5 (atomic%), 3.0 ≦ C5 ≦ It is preferably 20.0. When C4 is 0.1 or more or C5 is 3.0 or more, the reaction between the dielectric layer and moisture is suppressed, and the low-voltage high-temperature storage characteristics are improved. When C4 is 5.0 or less or C5 is 20.0 or less, the resistance can be reduced because the coating on the surface of the carbon material is not enlarged. From the viewpoint of achieving both low-voltage high-temperature storage characteristics and low resistance, preferably 0.2 ≦ C4 ≦ 4.7 or 3.3 ≦ C5 ≦ 19.3, more preferably 0.4 ≦ C4 ≦. 4.1 or 3.8 ≦ C5 ≦ 18.8. Examples of the compound containing a chlorine atom include lithium chloride, and examples of the compound containing a fluorine atom include lithium fluoride. The type of the compound can be identified by XPS measurement described later. In the present embodiment, a sample used for XPS measurement is prepared by the following procedure. After adjusting the voltage of the non-aqueous lithium storage element to 3.5 V, the battery was disassembled in an argon box, the positive electrode was cut out into a size of 1 cm ² (1 cm × 1 cm), and the obtained positive electrode sample was subjected to ethyl methyl carbonate (EMC). ) And air-dried, and then taken out of the argon box. Subsequently, the positive electrode sample is immersed in distilled water for 24 hours in an environment of 25 ° C., and then dried in vacuum at a pressure of −95 to −100 kPa for 12 hours in an environment of 80 ° C.
In addition, from the viewpoint of achieving both low-voltage high-temperature storage characteristics and low resistance, the positive electrode according to the present embodiment preferably contains lithium chloride or / and lithium fluoride in an amount of preferably from 0.1% by mass to 5% by mass, More preferably, the content is 0.2% by mass to 4.8% by mass.

<Characteristic evaluation of non-aqueous lithium storage element>
[Capacitance]
In this specification, the capacity Qa (Ah) is a value obtained by the following method.
First, the cell corresponding to the non-aqueous lithium storage element is charged in a constant temperature bath set at 25 ° C. at a constant current of 2 C until the current reaches 4.0 V, and then a constant voltage of 4.0 V is applied. Is 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 Qa (Ah).
Here, the discharge rate of the current (also referred to as “C rate”) is a relative ratio of the current at the time of discharge to the discharge capacity. Generally, when performing constant current discharge from the upper limit voltage to the lower limit voltage, it takes one hour. The current value at which the discharge is completed is referred to as 1C. In this specification, the current value at which the discharge is completed in one hour when the constant current discharge is performed from the upper limit voltage of 4.0 V to the lower limit voltage of 2.2 V is defined as 1C.

[Internal resistance]
In this specification, the internal resistance Ra (Ω) is a value obtained by the following method:
First, a non-aqueous lithium storage element was charged in a constant temperature bath set at 25 ° C. at a constant current of 20 C until the voltage reached 4.0 V, and then a constant voltage charge of applying a constant voltage of 4.0 V was performed. Perform for a total of 30 minutes. Subsequently, a constant current discharge is performed to 2.2 V at a current value of 20 C with a sampling interval of 0.05 second to obtain a discharge curve (time-voltage). In this discharge curve, when the voltage at the discharge time = 0 second obtained by extrapolating by linear approximation from the voltage values at the discharge time of 1 second and 2 seconds is Eo, the drop voltage ΔE = 4.0− It is a value calculated from Eo as Ra = ΔE / (20C current value).

[Low voltage high temperature storage test]
In the present specification, the rate of change in capacity and resistance after storage at low voltage and high temperature is measured by the following method.
(Change rate of capacity and resistance after storage at low voltage and high temperature)
First, the cell corresponding to the nonaqueous lithium storage element is discharged in a constant temperature bath set at 25 ° C. at a constant current of 2 C until the voltage reaches 2.0 V, and then a constant voltage of 2.0 V is applied. A constant voltage discharge is performed for a total of 30 minutes. Subsequently, after storing for 2 weeks in an environment of 60 ° C., the capacitance Qb and the internal resistance Rb after low-voltage high-temperature storage are measured according to the above-described methods for measuring the capacitance and the internal resistance. Qb / Qa is the rate of change in capacitance after storage at low voltage and high temperature, and Rb / Ra is the rate of change in resistance after storage at low voltage and high temperature.

The peel strength of the positive electrode active material layer can be measured by a known method. For example, a peel test in accordance with JIS Z0237 (2009) “Testing method for pressure-sensitive adhesive tape / pressure-sensitive adhesive sheet” is used, or in the examples described later. The test method used may be used.
For the positive electrode for measuring the peel strength, the nonaqueous lithium storage element was disassembled in an argon box, the obtained positive electrode was washed twice with a solvent such as ethyl methyl carbonate (EMC), and the pressure was reduced at 25 ° C. for 24 hours. Use the sample obtained after drying.
The peel strength of the positive electrode active material layer according to the present embodiment from the positive electrode current collector is 0.01 N / cm or more and 2.00 N / cm or less. When the peel strength is 0.01 N / cm or more, it is possible to prevent the positive electrode active material layer from being lost due to gas generation in the pre-doping step, and to suppress a micro short circuit. When the peel strength is 2.00 N / cm or less, it means that there is no excessive binder or the like in the positive electrode active material layer, and therefore, the diffusion property of the electrolytic solution can be improved and the resistance can be reduced. From the viewpoint of achieving a balance between the suppression of micro short circuits and the reduction in resistance, the peel strength is preferably from 0.02 N / cm to 1.96 N / cm, more preferably from 0.03 N / cm to 1.90 N / cm. .

[Micro short-circuit inspection test]
In the present specification, the slight short circuit of the nonaqueous lithium storage element is determined by the following method.
First, a constant current discharge is performed to 2.5 V at a current value of 1 C, and then a constant current charge is performed to a voltage of 3.5 V at a current value of 1 C, and then a 3.5 V constant voltage charge is continued for 2 hours. Adjust to 3.5V. Subsequently, the electrode body is allowed to stand still for one week in a thermostat set at 25 ° C. while being pressurized at a pressure of 10 kPa, and a battery whose voltage has dropped to 3.0 V or less is determined to be a slight short circuit.

<Quantification of carbon material, lithium transition metal oxide, and alkali metal compound in positive electrode active material layer>
Mass ratio A ₁ of the carbon material contained in the positive electrode active material _layer, the mass ratio A ₂ of the lithium transition metal _oxides, and quantitative methods of mass ratio A ₃ of the alkali metal compound is not particularly limited, for example, the following method Can be determined.
Area of measurement for the positive electrode precursor is not particularly limited, but preferably from the viewpoint of reducing the variation in measurement is 5 cm ² or more 200 cm ² or less, more preferably 25 cm ² or more 150 cm ² or less. If the area is 5 cm ² or more, reproducibility of measurement is ensured. If the area is 200 cm ² or less, the sample is excellent in handleability.
First, the positive electrode precursor is cut into the above area, and dried in a vacuum. As the conditions for vacuum drying, for example, conditions in which the amount of residual moisture in the positive electrode precursor is 1% by mass or less in a range of temperature: 100 to 200 ° C., pressure: 0 to 10 kPa, and time: 5 to 20 hours are preferable. The remaining amount of water can be determined by the Karl Fischer method.
The weight (M ₀ ) of the positive electrode precursor obtained after vacuum drying is measured. Subsequently, the resultant is immersed in distilled water having a weight of 100 to 150 times the weight of the positive electrode precursor for 3 days or more to elute the alkali metal compound into the water. It is preferable to cover the container during immersion so that distilled water does not evaporate. After immersion for 3 days or more, the positive electrode precursor is taken out of distilled water and vacuum dried as above. The weight (M ₁ ) of the obtained positive electrode precursor is measured. Subsequently, the positive electrode active material layer applied to one or both surfaces of the positive electrode current collector is removed using a spatula, a brush, a brush, or the like. The weight (M ₂ ) of the remaining positive electrode current collector is measured, and the mass ratio A ₃ of the alkali metal compound is calculated by the following equation (1).
A ₃ = (M ₀ −M ₁ ) / (M ₀ −M ₂ ) × 100 Equation (1) Subsequently, in order to calculate A ₁ and A ₂ , the positive electrode active material obtained by removing the above alkali metal compound The TG curve of the layer is measured under the following conditions.
-Sample pan: Platinum-Gas: Air atmosphere or compressed air-Temperature rising rate: 0.5 ° C / min or less-Temperature range: 25 ° C to 500 ° C or higher and melting point of lithium transition metal oxide minus 50 ° C or lower

The mass at 25 ° C. of the obtained TG curve is defined as M _3, and the mass at the first temperature at which the mass reduction rate becomes M ₃ × 0.01 / min or less at a temperature of 500 ° C. or more is defined as M ₄ .
All carbon materials are oxidized and burned by heating at a temperature of 500 ° C. or lower under an oxygen-containing atmosphere (for example, an air atmosphere). On the other hand, the mass of the lithium transition metal oxide does not decrease up to the melting point of the lithium transition metal oxide minus 50 ° C. even in an oxygen-containing atmosphere.
Therefore, the content A ₂ of the lithium transition metal oxide in the positive electrode active material layer can be calculated by the following equation (2).
A ₂ = (M ₄ / M ₃ ) × {1- (M ₀ −M ₁ ) / (M ₀ −M ₂ )} × 100 (2) Further, the content A ₁ of the carbon material in the positive electrode active material layer Can be calculated by the following equation (3).
A ₁ = {(M ₃ −M ₄ ) / M ₃ } × {1− (M ₀ −M ₁ ) / (M ₀ −M ₂ )} × 100 Formula (3) where a plurality of alkali metal compounds are positive electrodes When contained in the active material layer; in addition to the alkali metal compound, M in the following formula is one or more selected from Na, K, Rb, and Cs, and an oxide such as M ₂ O and a hydroxide such as MOH And a carboxylate such as an oxalate such as M ₂ (CO ₂ ) ₂ , RCOOM (where R is H, an alkyl group or an aryl group); and a positive electrode. active material _{layer, BeCO 3, MgCO 3, CaCO} 3, SrCO 3, and alkaline earth metal carbonates selected from BaCO _3, or alkaline earth metal oxides, alkaline earth metal hydroxides, alkaline earth metal Halide, alkaline earth gold If oxalate, or containing an alkaline earth metal carboxylates calculates their total amount as the alkali metal compound amount.
Conductive material in the positive electrode active material layer, the binder, if it contains a thickener, and calculates the total amount of the carbon material and these materials as A _1.

<Method of identifying alkali metal in electrode>
The method for identifying the alkali metal compound contained in the positive electrode is not particularly limited, but can be identified, for example, by the following method. For the identification of the alkali metal compound, it is preferable to identify by combining a plurality of analysis methods described below.
Failure to identify an alkali metal compound in analytical techniques, other analytical ^techniques, 7 Li- solid NMR, XRD (X-ray diffraction), TOF-SIMS (time-of-flight secondary ion mass spectrometry), AES (Auger An alkali metal compound can also be identified by using electron spectroscopy, TPD / MS (heating mass spectrometry), DSC (differential scanning calorimetry), or the like.

[Raman microscopy]
The alkali metal carbonate and the positive electrode active material can be determined by Raman imaging of carbonate ions on the surface of the positive electrode precursor measured at an observation magnification of 1000 to 4000 times. As an example of the 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 measurement can be performed under the condition that the exposure time per point is 3 seconds, the number of integration is 1 and the noise filter is provided. For the measured Raman spectrum, a linear baseline is set in the range of 1071 to 1104 cm ⁻¹ , the area is calculated with a positive value from the baseline as the peak of the carbonate ion, and the frequency is integrated. The frequency for the carbonate ion peak area approximated by the Gaussian function is subtracted from the carbonate ion frequency distribution.

[X-ray photoelectric spectroscopy (XPS)]
The bonding state of the alkali metal compound can be determined by analyzing the electronic state by XPS. As an example of the measurement conditions, the X-ray source is monochromatic AlKα, the X-ray beam diameter is 100 μmφ (25 W, 15 kV), the pass energy is narrow scan: 58.70 eV, the charge is neutralized, and the sweep number is narrow scan: 10 times The energy step can be measured under the conditions of (carbon, oxygen) 20 times (fluorine) 30 times (phosphorus) 40 times (lithium element) 50 times (silicon), and the energy step is narrow scan: 0.25 eV. It is preferable to clean the surface of the positive electrode by sputtering before measuring XPS. As the sputtering conditions, for example, the surface of the positive electrode can be cleaned under the conditions 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 having a binding energy of 50 to 54 eV as LiO ₂ or Li—C bond;
The peak of _{55~60eV LiF, Li 2 CO 3,} Li x PO y F z ( wherein, x, y, and z are an integer from 1 to 6 respectively);
A peak at a binding energy of 285 eV is a C—C bond, a peak at 286 eV is a C—O bond, a peak at 288 eV is a COO, a peak at 290 to 292 eV is a CO ₃ ²⁻ , and a C—F bond;
The peak of binding energy 527~530eV of _{^{O1s O 2- (Li 2 O)}} , the peak of _{531~532eV CO, CO 3, OH,} PO x ( wherein, x is an integer of 1 to 4), SiO _x (where x is an integer of 1 to 4); peak at 533 eV is CO, SiO _x (where x is an integer of 1 to 4);
The peak of binding energy 685eV of F1s LiF, C-F bonds and a peak of 687 _eV, (wherein, x, y, and z are an integer from 1 to 6 _{respectively) Li x PO y F z,} PF 6 - ;
For the binding energy of P2p, the peak at 133 eV is PO _x (where x is an integer from 1 to 4) and the peak at 134 to 136 eV is PF _x (where x is an integer from 1 to 6);
The peak of binding energy 99eV of Si2p Si, silicides, 101～107EV the peak _Si x _{O y} (wherein, x, and y are arbitrary integers)
Can be attributed as
When peaks overlap in the obtained spectrum, it is preferable to assign a spectrum by assuming a Gaussian function or a Lorentz function to separate the peaks. From the obtained measurement result of the electronic state and the result of the existing element ratio, the existing alkali metal compound can be identified.

[Ion chromatography]
By washing the positive electrode precursor with distilled water and analyzing the washed water by ion chromatography, carbonate ions eluted in the water can be identified. As the column to be used, an ion exchange type, an ion exclusion type, and a reversed-phase ion pair type can be used. As the detector, an electric conductivity detector, an ultraviolet-visible absorption light detector, an electrochemical detector, and the like can be used, and a suppressor method in which a suppressor is installed in front of the detector, or an electric detector without a suppressor is used. A non-suppressor system using a solution having low conductivity as an eluent can be used. The measurement can also be performed by combining a mass spectrometer or a charged particle detector as a detector.
The sample retention time is constant for each ionic species component if the conditions of the column and eluent to be used are determined, and the magnitude of the peak response varies for each ionic species, but is proportional to the concentration of the ionic species. . The qualitative and quantitative determination of ionic species components is possible by measuring in advance a standard solution of known concentration with traceability.

<Alkali metal element determination method ICP-MS>
The measurement sample is acid-decomposed using a strong acid such as concentrated nitric acid, concentrated hydrochloric acid, or aqua regia, and the obtained solution is diluted with pure water to an acid concentration of 2% to 3%. For acid decomposition, the sample can be appropriately heated and pressurized. The obtained diluted solution is analyzed by ICP-MS. At this time, it is preferable to add a known amount of an element as an internal standard. When the alkali metal element to be measured is higher than the upper limit of the measurement, it is preferable to further dilute the solution while maintaining the acid concentration of the diluent. With respect to the obtained measurement results, each element can be quantified based on a calibration curve prepared in advance using a standard solution for chemical analysis.

<Applications of non-aqueous lithium energy storage device>
A power storage module can be manufactured by connecting a plurality of nonaqueous lithium power storage elements according to the present embodiment in series or in parallel. Further, since the non-aqueous lithium storage element and the storage module of the present embodiment can achieve both high input / output characteristics and high-temperature safety, the power regeneration assist system, the power load leveling system, the uninterruptible power supply system Used for non-contact power supply systems, energy harvesting systems, power storage systems (for example, renewable energy storage systems), electric power steering systems, emergency power supply systems, in-wheel motor systems, idling stop systems, quick charging systems, smart grid systems, etc. Can be done.
The power storage system is suitably used for natural power generation such as photovoltaic power generation or wind power generation, the power load leveling system is suitably used for microgrids and the like, and the uninterruptible power supply system is suitably used for factory production facilities and the like. In the non-contact power supply system, the non-aqueous lithium storage element is used for energy transmission and leveling of voltage fluctuations such as microwave transmission or electric field resonance. In order to use the generated electric power, each is suitably used.

In a power storage system, as a cell stack, a plurality of non-aqueous lithium storage elements are connected in series or in parallel, or a non-aqueous lithium storage element and a lead battery, a nickel hydrogen battery, a lithium ion secondary battery, or a fuel cell. Are connected in series or in parallel.
Further, the non-aqueous lithium energy storage device according to the present embodiment can achieve both high input / output characteristics and high-temperature safety, such as electric vehicles, plug-in hybrid vehicles, hybrid vehicles, and electric motorcycles. Can be mounted on vehicles. The power regeneration assist system, the electric power steering system, the emergency power supply system, the in-wheel motor system, the idling stop system, or a combination thereof described above is suitably mounted on a vehicle.

  Hereinafter, embodiments of the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the following examples and comparative examples.

<Example 1>
<Preparation of positive electrode active material>
The crushed coconut shell carbide was put into a small carbonization furnace and carbonized at 500 ° C. for 3 hours under a nitrogen atmosphere to obtain a carbide. The obtained carbide was put into the activation furnace, steam heated in the preheating furnace was introduced into the activation furnace at 1 kg / h, and the temperature was raised to 900 ° C. over 8 hours to activate. The activated carbide was taken out and cooled under a nitrogen atmosphere to obtain activated activated carbon. The activated carbon thus obtained was washed with water for 10 hours, drained, dried in an electric dryer maintained at 115 ° C. for 10 hours, and then pulverized with a ball mill for 1 hour to obtain activated carbon 1.
The average particle size of the activated carbon 1 was measured using a laser diffraction particle size distribution analyzer (SALD-2000J) manufactured by Shimadzu Corporation. Moreover, the pore distribution of the activated carbon 1 was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 2360 m ² / g, the mesopore volume (V ₁ ) was 0.52 cc / g, the micropore volume (V ₂ ) was 0.88 cc / g, and V ₁ / V ₂ = 0.59. there were.

<Production of positive electrode precursor>
A positive electrode precursor was manufactured using activated carbon 1 as a positive electrode active material.
55.0% by mass of activated carbon 1, 30.0% by mass of lithium carbonate, 4.0% by mass of Ketjen black, 1.5% by mass of PVP (polyvinylpyrrolidone), and 9.9% of PVDF (polyvinylidene fluoride). NMP (N-methyl-2-pyrrolidone) was mixed so that the mass ratio of the solid content was 5% by mass and the solid content was 18.5%, and the mixture was mixed with a PRIMIX thin-film swirling high-speed mixer “Filmix (registered). (Trademark)) and dispersed at a peripheral speed of 17 m / s for 3 minutes to obtain a positive electrode coating solution.
The viscosity (ηb) and TI value of the obtained positive electrode coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,810 mPa · s, and the TI value was 4.2. Further, the degree of dispersion of the obtained positive electrode coating liquid was measured using a particle gauge manufactured by Yoshimitsu Seiki Co., Ltd. As a result, the particle size was 21 μm.
Using a double-sided die coater manufactured by Toray Engineering Co., a positive electrode coating solution was applied to both sides of a 15 μm-thick aluminum foil at a coating speed of 1 m / s, and the temperature of the drying furnace was set to 70 ° C., 90 ° C. The temperature was adjusted in the order of 110 ° C. and 130 ° C. and dried to obtain a positive electrode precursor 1. The obtained positive electrode precursor 1 was pressed using a roll press under the conditions of a pressure of 6 kN / cm and a surface temperature of a pressing portion of 25 ° C. The total thickness of the positive electrode precursor 1 was measured at arbitrary 10 points of the positive electrode precursor 1 using a film thickness meter Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. From the obtained measurement results, the film thickness per side of the positive electrode active material layer of the positive electrode precursor 1 was 60 μm.

<Production of negative electrode>
NMP (84 parts by mass of artificial graphite having an average particle diameter of 4.5 μm, 10 parts by mass of acetylene black, 6 parts by mass of PVdF (polyvinylidene fluoride), and NMP (solid content: 24.5%). N-methyl-2-pyrrolidone), and disperse the mixture using a PRIMIX thin-film revolving high-speed mixer “Filmix (registered trademark)” at a peripheral speed of 17 m / s to coat the negative electrode. A liquid was obtained.
The viscosity (ηb) and TI value of the obtained negative electrode coating solution were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,440 mPa · s, and the TI value was 4.1.
Using a die coater manufactured by Toray Engineering Co., Ltd., a negative electrode coating solution was applied on both sides of an 8 μm thick electrolytic copper foil at a coating speed of 1 m / s and dried at a drying temperature of 120 ° C. to obtain a negative electrode 1 Was. Pressing was carried out using a roll press under the conditions of a pressure of 5 kN / cm and a surface temperature of the press section of 25 ° C. The total thickness of the pressed negative electrode 1 was measured at any 10 points on the negative electrode 1 using a Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. From the obtained measurement results, the thickness of the negative electrode active material layer of the negative electrode 1 was 30 μm per side.

<Preparation of electrolyte solution>
As the organic solvent, a mixed solvent of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 33: 67 (volume ratio) was used, and the concentration ratio between LiPF ₆ and LiClO ₄ was 1: 1 and a total of 1.2 mol. / L was dissolved in the electrolyte salt. Subsequently, distilled water was added to the mixed solvent to a concentration of 10 ppm to obtain a non-aqueous electrolyte 1.

<Preparation of non-aqueous lithium storage element>
Twenty sheets of the obtained positive electrode precursor 1 were cut out so that the size of the positive electrode active material layer was 10.0 cm × 10.0 cm (100 cm ² ). Subsequently, 21 negative electrodes 1 were cut out so that the negative electrode active material layer had a size of 10.1 cm × 10.1 cm (102 cm ² ). In addition, 40 sheets of 10.3 cm × 10.3 cm (106 cm ² ) polyethylene separators (manufactured by Asahi Kasei Corporation, thickness: 15 μm) were prepared. With respect to these, the negative electrode 1 is disposed in the outermost layer, and the positive electrode precursor 1, the separator, the negative electrode 1, and the separator are stacked in this order such that the positive electrode active material layer and the negative electrode active material layer face each other with the separator interposed therebetween. I got a body. The positive electrode terminal and the negative electrode terminal were ultrasonically welded to the obtained electrode laminate, placed in a container formed of an aluminum laminate packaging material, and three sides including the electrode terminal portions were sealed by heat sealing.
About 70 g of the non-aqueous electrolyte 1 was injected into the electrode laminate housed in the aluminum laminate packaging material under a dry air environment at atmospheric pressure, a temperature of 25 ° C., and a dew point of −40 ° C. or less. Subsequently, the aluminum laminate packaging material containing the electrode laminate and the non-aqueous electrolyte 1 was placed in a decompression chamber, the pressure was reduced from atmospheric pressure to -87 kPa, and then the pressure was returned to atmospheric pressure and left for 5 minutes. Thereafter, the process of reducing the pressure of the packaging material in the chamber from the atmospheric pressure to -87 kPa, and then returning the pressure to the atmospheric pressure was repeated four times, and then left at rest for 15 minutes. Through the above steps, the non-aqueous electrolyte 1 was impregnated into the electrode laminate.
Thereafter, the electrode laminate impregnated with the non-aqueous electrolyte 1 was placed in a pressure reducing sealing machine, and the pressure was reduced to −95 kPa, and the aluminum laminate was sealed at 180 ° C. for 10 seconds at a pressure of 0.1 MPa to obtain an aluminum laminate packaging material. After sealing, an electrode body was obtained.

[Alkali metal doping step]
The electrode body obtained after sealing was placed in a dry box at a temperature of 40 ° C. and a dew point of −40 ° C. or less. The excess portion of the aluminum laminate packaging material is cut off and opened, and a constant current charge is performed at a current value of 500 mA until the voltage reaches 4.5 V, and then a 4.5 V constant voltage charge is continuously performed for 5 hours. The battery was charged and the negative electrode was doped with an alkali metal. After the completion of the alkali metal doping, the aluminum laminate was sealed using a heat sealer (FA-300) manufactured by Fuji Impulse.
[Aging process]
The electrode body after the alkali metal doping is taken out of the dry box, and under a 25 ° C. environment, constant current discharge is performed at 100 mA until the voltage reaches 4.0 V, and then constant current discharge at 4.0 V is performed for 1 hour. , And the voltage was adjusted to 4.0V. Subsequently, the electrode body was stored in a thermostat at 60 ° C. for 24 hours.
[Degassing process]
With respect to the electrode body after aging, a part of the aluminum laminate packaging material was opened in a dry air environment at a temperature of 25 ° C. and a dew point of −40 ° C. Subsequently, a step of putting the electrode laminate in a decompression chamber, reducing the pressure from atmospheric pressure to −80 kPa over 3 minutes using a diaphragm pump, and then returning to atmospheric pressure over 3 minutes was repeated a total of three times. After that, the electrode body was put into a vacuum sealing machine, and after reducing the pressure to -90 kPa, the aluminum laminate packaging material was sealed by sealing at 200 ° C. for 10 seconds at a pressure of 0.1 MPa to produce a non-aqueous lithium storage element. did.
[Micro short-circuit inspection process]
Through the above steps, ten non-aqueous lithium energy storage devices were manufactured, and the above-mentioned micro short circuit inspection test was performed.

<Evaluation of non-aqueous lithium storage element>
[Measurement of capacitance Qa]
One of the obtained non-aqueous lithium energy storage devices was statically charged in a thermostat set at 25 ° C. using a charge / discharge device (5 V, 360 A) manufactured by Fujitsu Telecom Networks Fukushima Co., Ltd. according to the method described above. The capacitance Qa was measured.
[Measurement of internal resistance Ra]
The internal resistance Ra of the non-aqueous lithium storage element was calculated by the above-described method using a charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Fukushima Co., Ltd. in a thermostat set at 25 ° C.
[Low voltage high temperature storage test]
One of the obtained nonaqueous lithium energy storage devices was subjected to a low voltage and high temperature storage test by the above-described method. After the test, the capacitance Qb and the internal resistance Rb were measured.

[XPS (X-ray Photoelectron Spectroscopy) Measurement of Positive Surface]
(Sample preparation)
The voltage of one of the obtained nonaqueous lithium energy storage devices was adjusted to 3.5 V, then disassembled in an argon box, and the positive electrode was cut into a size of 1 cm ² (1 cm × 1 cm). The obtained positive electrode sample was washed twice with ethyl methyl carbonate (EMC), air-dried, and then taken out of the argon box. Subsequently, the positive electrode sample was immersed in distilled water for 24 hours in a 25 ° C. environment, and then dried in vacuum at 80 ° C. and at −97 kPa for 12 hours.
(XPS measurement)
With respect to the obtained positive electrode sample, XPS on the positive electrode surface was measured under the following conditions.
-Equipment used: ULVAC-Phi Versa probe II
・ Excitation source: monoAlKα 20kV × 5mA (100W)
・ Analysis size: 100 μm × 1.4 mm
・ Photoelectron extraction angle: 45 °
-Capture area Survey scan: 0 to 1100 eV
Narrow scan: O1s, Al2p, Cl2p (B1s), P2p, F1s, C1s, N1s
・ Pass Energy
Survey scan: 117.4 eV
Narrow scan: 46.95 eV

[Measurement of peel strength of positive electrode]
The positive electrode obtained after the EMC cleaning in the argon box was cut into a size of 25 mm × 100 mm. A 24 mm wide cellotape (registered trademark, CT405AP-24 manufactured by Nichiban) was cut into a length of 100 mm and attached to the positive electrode active material layer. Using Tensilon (STB-1225S, manufactured by A & D Corporation), the uncoated portion of the positive electrode current collector is placed on the lower clip jaw side, and the end of Cellotape (registered trademark) is placed on the upper clip jaw side. Was measured. The measurement of the peel strength was started within 3 minutes after attaching Cellotape (registered trademark) to the positive electrode active material layer.
・ Ambient temperature: 25 ° C
・ Sample width: 25mm
・ Stroke: 100mm
・ Speed: 50mm / min
Data acquisition: integral average load measurement of 25 to 65 mm was performed on a total of three samples, and the average value was defined as the peel strength of the positive electrode.

[Measurement of water content in electrolyte]
For the non-aqueous lithium energy storage device disassembled in the argon box, the amount of water in the obtained electrolytic solution was measured by Karl Fischer titration (JIS 0068 (2001) "Method for measuring water content of chemical products").
[Quantification of alkali metal compound in positive electrode]
For the positive electrode obtained after the EMC washing in the argon box, the alkali metal compound in the positive electrode was quantified according to the method described above.

<Examples 2 to 17, Comparative Examples 1 to 10>
In accordance with the configuration of the nonaqueous lithium energy storage device shown in Table 1 and the manufacturing conditions, an energy storage device was manufactured and various evaluations were performed.

  Table 2 shows the evaluation results of the nonaqueous lithium energy storage devices manufactured in Examples 1 to 17 and Comparative Examples 1 to 10.

  As shown in Table 1 or 2, the capacitance was increased by forming a dielectric layer coating composed of aluminum and oxygen on the positive electrode surface. Further, when the peel strength of the positive electrode was 0.01 N / cm or more, the fine short circuit rate could be reduced, and when it was 2.00 N / cm or less, the resistance could be reduced.

The non-aqueous lithium storage element of the present invention can be used to form a storage module by connecting a plurality of non-aqueous lithium storage elements in series or in parallel, for example. The non-aqueous lithium storage element and the storage module of the present invention can be used in various power storage systems, for example: a power regeneration system of a hybrid drive system of an automobile requiring high load charge / discharge cycle characteristics; Power load leveling system in a micro grid, etc .; Uninterruptible power supply system in factory production equipment, etc .; Non-contact power supply system for leveling voltage fluctuations such as microwave power transmission and electrolytic resonance and storing energy; Energy harvesting system for the purpose of using the electric power generated by electric vehicles, electric vehicles, plug-in hybrid vehicles, electric motorcycles, in-wheel motor systems, electric power steering systems as power sources for vehicles; Fast charging system that charges with current It can be used to apply.
The nonaqueous lithium energy storage device of the present invention is preferable, for example, when applied as a lithium ion capacitor or a lithium ion secondary battery, since the effects of the present invention are maximized.

Claims (7)

A positive electrode, a negative electrode, a separator, a non-aqueous lithium storage element having a non-aqueous electrolyte containing lithium ions,
The positive electrode has a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer includes a carbon material as a positive electrode active material,
The relative element concentration of aluminum atoms obtained by XPS (X-ray photoelectron spectroscopy) measurement on the surface of the positive electrode is C1 (atomic%), the relative element concentration of oxygen atoms is C2 (atomic%), and the relative element concentration of carbon atoms is When C3 (atomic%),
0.4 ≦ C1 ≦ 18.0,
5.0 ≦ C2 ≦ 50.0,
28.0 ≦ C3 ≦ 90.0,
The amount of water contained in the nonaqueous electrolyte is 1 ppm or more and 500 ppm or less, and the peel strength between the positive electrode active material layer and the positive electrode current collector is 0.01 N / cm or more and 2.00 N / cm or less. Water-based lithium storage element.   2. When the relative element concentration of chlorine atoms obtained by XPS (X-ray photoelectron spectroscopy) measurement of the surface of the positive electrode is C4 (atomic%), 0.1 ≦ C4 ≦ 5.0. Non-aqueous lithium energy storage device. The non-aqueous lithium energy storage device according to claim 1, wherein the non-aqueous electrolyte contains LiClO ₄ .   4. When the relative element concentration of fluorine atoms obtained by XPS (X-ray photoelectron spectroscopy) measurement on the surface of the positive electrode is C5 (atomic%), 3.0 ≦ C5 ≦ 20.0. The non-aqueous lithium energy storage element according to any one of the above.   The non-electrolyte according to any one of claims 1 to 4, wherein the positive electrode contains at least one carbonate selected from the group consisting of lithium carbonate, sodium carbonate, and potassium carbonate in an amount of 1 mass% to 10 mass%. Water-based lithium storage element.   The non-aqueous lithium energy storage device according to any one of claims 1 to 5, wherein the positive electrode contains lithium chloride and / or lithium fluoride in an amount of 0.1 mass% to 5 mass%.   A power storage module including the non-aqueous lithium storage element according to any one of claims 1 to 6, a power regeneration assist system, a power load leveling system, an uninterruptible power supply system, a contactless power supply system, an energy harvesting system, and natural energy. Power storage system, electric power steering system, emergency power supply system, in-wheel motor system, idling stop system, electric vehicle, plug-in hybrid vehicle, electric motorcycle or quick charging system.