Composite powder material containing carbon material and lithium carbonate

Abstract

To provide a composite powder material including a carbon material and a lithium carbonate capable of realizing a non-aqueous lithium power storage element having excellent initial resistance and high-temperature storage durability.SOLUTION: There is provided a composite powder material including a carbon material and a lithium carbonate. In the Li1s spectrum obtained by X-ray photoelectron spectroscopy (XPS) of the composite powder material, when the peak area of the 56 eV component is A and the peak area of the 58 eV component is B, 0.2≤A / (A+B)≤0.9 is satisfied. In the composite powder material, the amount of pores V [cc / g] of 2 nm to 35 nm per unit weight of the carbon material is 0.01≤V≤0.25.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a composite powder material comprising a carbon material and lithium carbonate. [Background technology]

[0002] In recent years, from the perspective of protecting the global environment and effectively utilizing energy to conserve resources, attention has been drawn to wind power generation power smoothing systems or late-night power storage systems, distributed home energy storage systems based on solar power generation technology, and energy storage systems for electric vehicles.

[0003] The primary requirement for batteries used in these energy storage systems is a high energy density, and the development of lithium-ion batteries is being actively pursued as a promising candidate for a high-energy-density battery that can meet this requirement.

[0004] The second requirement is high output characteristics. For example, in a combination of a high-efficiency engine and a power storage system (e.g., a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (e.g., a fuel cell electric vehicle), high output discharge characteristics are required in the power storage system during acceleration. Currently, electric double layer capacitors, nickel-metal hydride batteries, etc. are being developed as high-output power storage devices.

[0005] Among electric double layer capacitors, those that use activated carbon for the electrodes have output characteristics of approximately 0.5kW / L to 1kW / L. These electric double layer capacitors also have high durability (cycle characteristics and high-temperature storage durability), and have been considered the optimal device for fields requiring high output. However, their energy density is only approximately 1Wh / L to 5Wh / L. Therefore, further improvements in energy density are necessary.

[0006] On the other hand, nickel-metal hydride batteries currently used in hybrid electric vehicles have high output equivalent to that of electric double-layer capacitors and an energy density of about 160 Wh / L. However, vigorous research is being conducted to further increase their energy density and output, as well as to improve their durability (especially their high-temperature storage durability).

[0007] Research is also underway to increase the output of lithium-ion batteries. For example, lithium-ion batteries have been developed that can achieve high output of over 3 kW / L at a discharge depth of 50% (a value indicating the percentage of the discharge capacity of the storage element that has been discharged). However, their energy density is below 100 Wh / L, a design that deliberately suppresses the high energy density that is the greatest feature of lithium-ion batteries. Furthermore, their durability (cycle characteristics and high-temperature storage durability) is inferior to that of electric double-layer capacitors. Therefore, to ensure practical durability, they must be used within a narrower range of discharge depth than 0 to 100%. Because the actual usable capacity is even smaller, vigorous research is being conducted to further improve durability.

[0008] As described above, there is a strong demand for practical application of energy storage devices that combine high energy density, high output characteristics, and durability. However, the existing energy storage devices described above each have their own advantages and disadvantages. Therefore, new energy storage devices that satisfy these technical requirements are needed. As a promising candidate, an energy storage device called a lithium-ion capacitor has attracted attention and is being actively developed.

[0009] A lithium ion capacitor is a type of energy storage element (non-aqueous lithium energy storage element) that uses a non-aqueous electrolyte containing lithium salt. At the positive electrode, at approximately 3 V or higher, a non-Faradic reaction occurs due to the adsorption and desorption of anions, similar to an electric double layer capacitor, and at the negative electrode, a Faradic reaction occurs due to the absorption and release of lithium ions, similar to a lithium ion battery.

[0010] To summarize the above-mentioned electrode materials and their characteristics, when materials such as activated carbon are used for the electrodes and charging and discharging is performed by the adsorption and desorption of ions on the surface of the activated carbon (non-Faradaic reaction), high output and durability are achieved, but the energy density is low (for example, 1x).On the other hand, when oxides or carbon materials are used for the electrodes and charging and discharging is performed by the Faradaic reaction, the energy density is high (for example, 10x that of non-Faradaic reactions using activated carbon), but there are issues with durability and output characteristics.

[0011] As a combination of these electrode materials, electric double layer capacitors use activated carbon (energy density 1x) for the positive and negative electrodes, and are characterized by charging and discharging through non-Faradic reactions at both the positive and negative electrodes.They have high output and high durability, but low energy density (positive electrode 1x x negative electrode 1x = 1).

[0012] Lithium-ion secondary batteries use lithium transition metal oxides (10 times the energy density) for the positive electrode and carbon materials (10 times the energy density) for the negative electrode, and are characterized by charging and discharging via the Faraday reaction at both the positive and negative electrodes. While they have a high energy density (10 times the positive electrode x 10 times the negative electrode = 100), they have issues with output characteristics and durability. Furthermore, to meet the high durability required for hybrid electric vehicles and the like, the depth of discharge must be limited, and lithium-ion secondary batteries can only use 10% to 50% of their energy.

[0013] Lithium-ion capacitors are a new asymmetric capacitor that combines the features of electric double-layer capacitors and lithium-ion secondary batteries. They use activated carbon (energy density 1x) for the positive electrode and carbon material (energy density 10x) for the negative electrode, and charge and discharge is carried out by a non-Faradic reaction at the positive electrode and a Faradic reaction at the negative electrode. They are characterized by high output and durability, as well as a high energy density (positive electrode 1x x negative electrode 10x = 10), and do not require limitations on the depth of discharge as with lithium-ion secondary batteries.

[0014] Lithium ion capacitors are used in applications such as power storage elements for railways, construction machinery, and automobiles. Because the operating environments in these applications are harsh, the capacitors used are required to have both excellent low resistance and high-temperature storage durability.

[0015] As a countermeasure to such demands, Patent Document 1 proposes a technology that can suppress an increase in electrode resistance after the initial charge / discharge of a lithium-ion secondary battery by combining a carbon material with a lithium compound. Even after the lithium compound in the positive electrode active material layer decomposes during the initial charge / discharge, a skeleton made of a carbon material with vacancies remains, thereby suppressing an increase in electrode resistance. However, sufficient consideration has not been given to the remaining lithium compound after the initial charge / discharge and the by-products generated during the decomposition reaction, leaving room for improvement in terms of initial resistance and high-temperature storage durability.

[0016] As described above, no technology has been found that can achieve both the initial resistance and high-temperature storage durability that are important for practical use of non-aqueous lithium storage elements using composite powder materials of carbon materials and lithium compounds. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Publication No. 2021-96928 Summary of the Invention [Problem to be solved by the invention]

[0018] The present disclosure aims to provide a composite powder material containing a carbon material and lithium carbonate, which can realize a nonaqueous lithium energy storage element having excellent initial resistance and high-temperature storage durability. [Means for solving the problem]

[0019] The present inventors have discovered that by appropriately controlling the pore size distribution and XPS spectrum properties of a composite powder material containing a carbon material and lithium carbonate, a nonaqueous lithium energy storage element with excellent initial resistance and high-temperature storage durability can be realized, and have completed the present disclosure. Examples of embodiments of the present disclosure are listed in the following items [1] to [8]. [1] A composite powder material containing a carbon material and lithium carbonate, In the Li1s spectrum obtained by X-ray photoelectron spectroscopy (XPS) of the composite powder material, when the peak area of ​​the 56 eV component is A and the peak area of ​​the 58 eV component is B, 0.2≦A / (A+B)≦0.9; The composite powder material is a composite powder material in which the amount of pores of 2 nm to 35 nm per unit weight of the carbon material, V [cc / g], satisfies the range of 0.01≦V≦0.25. [2] 2. The composite powder material of claim 1, wherein the carbon material is activated carbon. [3] 3. The composite powder material according to claim 1, wherein the weight of the carbon material is M1 and the weight of the lithium carbonate is M2, and the composite powder material satisfies 0.1≦M2 / M1≦2. [4] 4. The composite powder material according to claim 1, wherein 0.3≦A / (A+B)≦0.7. [5] 5. The composite powder material according to claim 1, wherein 0.05≦V≦0.15. [6] A positive electrode precursor having a positive electrode current collector and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector, 6. A positive electrode precursor, wherein the positive electrode active material layer comprises the composite powder material according to claim 1. [7] A method for producing a non-aqueous lithium storage element including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions, the method comprising: a coating solution containing the composite powder material according to any one of claims 1 to 5 and water or an organic solvent is applied to one or both surfaces of a positive electrode current collector to form a coating film, and the coating film is dried to obtain a positive electrode precursor; assembling an electricity storage element including the positive electrode precursor, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions, and applying a voltage between the positive electrode precursor and the negative electrode; A method for producing a non-aqueous lithium storage element, comprising: [8] 7. The positive electrode precursor according to claim 6, for use in at least one selected from the group consisting of a power storage module, a power regeneration assist system, a power load leveling system, an uninterruptible power supply system, a contactless power supply system, an energy harvesting system, a natural energy storage system, an electric power steering system, an emergency power supply system, an in-wheel motor system, an idling stop system, an electric vehicle, a plug-in hybrid vehicle, an electric motorcycle, a smart grid system, and a rapid charging system. [Effects of the Invention]

[0020] According to the present disclosure, a nonaqueous lithium storage element having excellent initial resistance and high-temperature storage durability can be provided. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is an XPS spectrum of the composite powder material of Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to these embodiments. The upper and lower limits of each numerical range in the present disclosure can be arbitrarily combined to form any numerical range. In the present disclosure, various numerical ranges of the content are intended to be within the numerical range as long as any one of the charged amount and the value obtained according to the measurement method in the present disclosure is included in the numerical range.

[0023] 《Composite powder material》 The composite powder material of the present disclosure contains a carbon material and lithium carbonate. In the Li1s spectrum obtained by X-ray photoelectron spectroscopy (XPS), the composite powder material satisfies 0.2≦A / (A+B)≦0.9, where A is the peak area of ​​the 56 eV component and B is the peak area of ​​the 58 eV component. The composite powder material has a pore volume V [cc / g] of 2 nm to 35 nm per unit weight of the carbon material in the composite powder material, which satisfies 0.01≦V≦0.25. By controlling the peak area ratio A / (A+B) in the XPS spectrum of the composite powder material containing the carbon material and lithium carbonate and the pore volume V of the composite powder material within the above ranges, a nonaqueous lithium storage element having excellent initial resistance and high-temperature storage durability can be provided.

[0024] Without being limited by theory, conventionally, in lithium storage elements having a positive electrode precursor containing lithium carbonate, there have been problems such as: (1) insufficient electrical contact between the lithium carbonate and the positive electrode active material, the decomposition reaction of lithium carbonate does not proceed sufficiently during the doping process, and the remaining lithium carbonate becomes a resistance component; and (2) if the decomposition reaction of lithium carbonate does not proceed sufficiently during the doping process, the application of high voltage causes side reactions other than the decomposition reaction of lithium carbonate (such as the decomposition reaction of lithium salts), and when the completed storage element is placed in a high-temperature environment, the side reaction products of the doping process react on the surface of the activated carbon of the positive electrode active material, resulting in a deterioration in high-temperature storage durability (such as increased gas generation). However, in the present disclosure, the inventors have discovered that, in the Li1s spectrum obtained by X-ray photoelectron spectroscopy (XPS), when A / (A+B) is 0.2≦A / (A+B)≦0.9 and V [cc / g] per weight of carbon material is 0.01≦V≦0.25, the above problems (1) and (2) are unlikely to occur, and the initial resistance and high-temperature storage durability of the lithium storage element can be improved.

[0025] The lower limit of A / (A+B) is preferably 0.2 or greater, more preferably 0.3 or greater. The lower limit of V [cc / g] is preferably 0.01 or greater, more preferably 0.05 or greater. While the reason is not entirely clear and not limited by theory, when A / (A+B) is 0.2 or greater and V [cc / g] is 0.01 or greater, sufficient electrical contact between lithium carbonate and the carbon material is achieved, facilitating the electrochemical oxidative decomposition reaction via the carbon material. Furthermore, since the composite powder material retains a sufficient amount of electrolyte, it is believed that the oxidative decomposition reaction of lithium carbonate, for example, via an oxidation-reduction reaction of the electrolyte solvent, also proceeds easily. As a result, the decomposition reaction of lithium carbonate proceeds easily during the doping process, reducing the amount of lithium carbonate remaining, which is desirable because it reduces the resistance of the completed lithium energy storage device. Furthermore, side reactions other than the decomposition reaction of lithium carbonate (e.g., decomposition reaction of lithium salts) are suppressed during the doping process, which is desirable because it suppresses gas generation at high temperatures in the completed lithium energy storage device.

[0026] The upper limit of A / (A+B) is preferably 0.9 or less, and more preferably 0.7 or less. The upper limit of V [cc / g] is preferably 0.25 or less, and more preferably 0.15 or less. While the reason is unclear and not limited by theory, it is believed that when A / (A+B) exceeds 0.9 and V exceeds 0.2, a large amount of lithium carbonate with low electrical conductivity adheres to the surface of the carbon material, hindering electronic conduction between the carbon materials and limiting the electronic conduction path. As a result, the decomposition reaction of lithium carbonate becomes difficult to proceed, increasing the resistance of the completed lithium energy storage device. Furthermore, during the doping process, side reactions other than the decomposition reaction of lithium carbonate (e.g., decomposition reaction of lithium salts) become more likely to proceed, resulting in increased gas generation from the completed lithium energy storage device at high temperatures. For these reasons, it is desirable that A / (A+B) is 0.9 or less and V is 0.25 or less.

[0027] <XPS spectrum> In the present disclosure, the XPS spectrum of the composite powder material is obtained by XPS measurement in a charge neutralization-off state. By measuring in a charge neutralization-off state, it is possible to separately quantify lithium carbonate that is in electrical contact with the carbon material and lithium carbonate that is not in electrical contact with the carbon material. This is because lithium carbonate that is not in electrical contact with the carbon material is thought to be observed on the higher energy side compared to lithium carbonate that is in contact with the carbon material. Specifically, the XPS spectrum of the composite powder material can be measured and analyzed by the following method. Equipment used: Thermofuser ESCALAB250 Excitation source: Monochromated AlKα 15kV x 10mA Analysis size: Approximately 1 mm (oval shape) Photoelectron acceptance angle: 0° (the axis of the spectrometer is perpendicular to the sample surface)

[0028] Capture Area Survey scan: 0 to 1,100 eV Narrow scan: Li1s, O1s, C1s For the Li 1s spectrum, data was acquired 100 times to ensure an S / N of 5 or higher, allowing curve fitting.

[0029] Pass Energy Survey scan: 100 eV Narrow scan: 20 eV Energy step Survey scan: 1 eV Narrow scan: 0.1 eV

[0030] Data import time Survey scan: 50ms / step Narrow scan: 100ms / step

[0031] Neutralization Conditions Unit: E401 Auxiliary Neutralization: None Filament current: 3.2A Emission Current: Flow

[0032] Peak position correction The observed peak positions were corrected based on the C1s (284.6 eV) of the carbon material.

[0033] Curve fitting of the Li1s spectrum Using the data processing function of the instrument's software (Avantage 5.927), a curve fit was performed on the Li1s spectrum obtained in the charge neutralization-off measurement after charge correction. The peak area A (unit: cps·eV) of the 56 eV component, the peak area B (unit: cps·eV) of the 58 eV component, and A / (A+B) were derived. The curve fit was performed under the following constraints (1) to (5): (1) the number of components was two (56 eV and 58 eV), (2) the energy difference between the 56 eV and 58 eV components was 2.8 eV, (3) the difference in full width at half maximum (FWHM) between the 56 eV and 58 eV components was 0.86 eV, (4) both the 56 eV and 58 eV components were symmetric, and (5) the Gaussian / Lorentzian ratio for both the 56 eV and 58 eV components was 30% Lorentzian.

[0034] <Amount of pores> In the present disclosure, the amount of pores V (cc / g) of pores having a diameter of 2 nm to 35 nm in the composite powder material is defined as the volume (cc) of pores having a diameter of 2 nm to 35 nm per unit weight of the carbon material.

[0035] When the weight of the composite powder material is W (g), the amount of pores of 2 nm to 35 nm in the composite powder material of W (g) is Z (cc), the weight ratio of the carbon material in the composite powder material is m1 (wt%), and the weight ratio of lithium carbonate is m2 (wt%), the amount of pores can be calculated as V = Z / (W × m1 / 100).

[0036] The weight ratio m1 (wt%) of the carbon material and the weight ratio m2 (wt%) of the lithium carbonate in the composite powder material are determined as follows: The weight W (g) of the composite powder material is measured. To remove the lithium carbonate, the composite powder material is immersed in a large excess of water to dissolve the lithium carbonate in the water, and the supernatant lithium carbonate aqueous solution is removed by centrifugation, filtration, or other methods. Because the lithium carbonate aqueous solution is alkaline, this lithium carbonate removal procedure is repeated multiple times until the supernatant water becomes neutral, thereby removing the lithium carbonate from the composite powder material. Water is removed from the carbon material from which the lithium carbonate has been removed by high-temperature vacuum drying. The drying temperature can be 100°C to 200°C, the pressure can be 0 kPa to 10 kPa, and the drying time can be 5 to 20 hours. The weight W2 of the carbon material in the composite powder material is measured. The weight ratios are obtained as m1 = W2 / W × 100 and m2 = 100 - m1, respectively.

[0037] When the composite powder material contains materials other than a carbon material and lithium carbonate, it is desirable to (1) selectively remove the mixture using a method suitable for the mixture, then remove the lithium carbonate using the above method, and quantify the weight of the carbon material, (2) remove the lithium carbonate using the above method, then remove the mixture using a method suitable for the mixture, and quantify the weight of the carbon material, or (3) remove the lithium carbonate using the above method, and then quantify the weight of the carbon material using a method that can separate and quantify the weight of the carbon material from the mixture. For example, when the composite powder material contains a lithium transition metal oxide in addition to the carbon material and lithium carbonate, the weight of the carbon material can be separated and quantified using a thermogravimetry (TG) curve.

[0038] The pore volume Z (cc) of a composite powder material with a diameter of 2 to 35 nm is determined by the following method. The sample is vacuum dried at 250°C for at least 3 hours, and the adsorption / desorption isotherm is measured using nitrogen as the adsorbate. The cumulative pore volume distribution is obtained for the resulting adsorption isotherm using the QSDFT method. The cumulative pore volume Z (cc) of the pore diameter range of 2 to 35 nm is obtained by subtracting the cumulative pore volume up to 2 nm from the cumulative pore volume up to 35 nm.

[0039] <Method for synthesizing composite powder material> The method for synthesizing the composite powder material is not particularly limited, as long as the resulting composite powder material containing lithium carbonate and a carbon material satisfies 0.2≦A / (A+B)≦0.9 and 0.01≦V≦0.25. For example, a preferred method involves mixing lithium carbonate and a carbon material and firing the mixture at a temperature above the melting point of lithium carbonate (723°C). Specifically, the composite powder material of the present disclosure can be obtained by mixing lithium carbonate and a carbon material, placing the mixture in an electric furnace, and then heat-treating the mixture in a carbon dioxide gas flow to a temperature above the melting point of lithium carbonate (e.g., above 723°C and not higher than 740°C). Alternatively, the heat-treatment temperature can be appropriately adjusted to activate the carbon material simultaneously with the compounding.

[0040] On the other hand, composite powder materials obtained by the following methods (1) to (3) have peak area ratios of less than 0.2, and thus do not yield the composite powder material according to the present disclosure. These methods are undesirable as composite powder material synthesis methods. These methods include (1) a dry mixing process in which lithium carbonate and a carbonaceous material are mixed in powder form, (2) a wet mixing process in which lithium carbonate and a carbonaceous material are dispersed and mixed in a solvent, and (3) a mechanochemical process in which lithium carbonate and a carbonaceous material are mixed by applying mechanical energy. While the reason for this is unclear and without being limited by theory, it is believed that these methods result in peak area ratios of less than 0.2 because sufficient electrical contact between the lithium carbonate and the carbonaceous material cannot be obtained.

[0041] <Carbon materials> The carbon material is not particularly limited, but examples thereof include carbon nanotubes, graphene, graphene oxide, conductive polymers, and porous carbon materials such as mesoporous carbon and activated carbon. As the carbon material, porous carbon materials such as mesoporous carbon and activated carbon are more preferred, and activated carbon is even more preferred from the viewpoint of high-temperature storage durability (gas generation and capacity maintenance). Furthermore, a mixture of multiple carbon materials may be used as the carbon material.

[0042] The carbon material contained in the composite powder material preferably functions as a positive electrode active material. Examples of the carbon material as a positive electrode active material include ketjen black, acetylene black, vapor-grown carbon fiber, graphite, flake graphite, carbon nanotubes, graphene, graphene oxide, conductive polymers, mesoporous carbon, and activated carbon. The carbon material as a positive electrode active material is preferably a porous carbon material such as mesoporous carbon or activated carbon, and more preferably activated carbon. To obtain a high energy density, the carbon material should have a specific surface area of ​​1,500 m2 measured by the BET method. 2 / g or more 4,000m 2 Activated carbon having a Cr content of 0.1 to 1.0 wt % or less is even more preferred. The positive electrode active material may be a mixture of one or more carbon materials.

[0043] When activated carbon is used as the positive electrode active material, the type and raw material of the activated carbon are not particularly limited. For example, activated carbon that can be obtained by the methods described below (gas activation method, alkali activation method) can be used.

[0044] (gas-activated activated carbon) The carbon source used as the raw material for gas-activated activated carbon is not particularly limited. Examples of carbon sources include plant-based raw materials such as wood, wood flour, coconut shells, pulp production by-products, bagasse, and blackstrap molasses; fossil-based raw materials such as peat, lignite, brown coal, bituminous coal, anthracite, petroleum distillation residue components, petroleum pitch, coke, and coal tar; various synthetic resins such as phenolic resins, vinyl chloride resins, vinyl acetate resins, melamine resins, urea resins, resorcinol resins, celluloid, epoxy resins, polyurethane resins, polyester resins, and polyamide resins; synthetic rubbers such as polybutylene, polybutadiene, and polychloroprene; other synthetic woods, synthetic pulps, and carbonized versions thereof. Among these raw materials, plant-based raw materials such as coconut shells and wood flour, and carbonized versions thereof, are preferred from the standpoints of mass production and cost, with coconut shell carbonized versions being particularly preferred.

[0045] As a method for carbonizing and activating these raw materials to produce activated carbon, known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, a rotary kiln method, etc. can be used.

[0046] Examples of carbonization methods for these raw materials include a method of firing them using an inert gas such as nitrogen, carbon dioxide, helium, argon, xenon, neon, carbon monoxide, or combustion exhaust gas, or a mixed gas containing these inert gases as the main component with other gases, at 400°C to 700°C, preferably about 450°C to 600°C, for about 30 minutes to 10 hours.

[0047] The carbonized material obtained by the carbonization method is preferably activated by a gas activation method in which the carbonized material is fired using an activation gas such as water vapor, carbon dioxide, or oxygen. Of these, the method using water vapor or carbon dioxide as the activation gas is preferred. In this activation method, the carbonized material is preferably activated by heating the material to 800°C to 1,000°C over 3 to 12 hours, preferably 5 to 11 hours, and more preferably 6 to 10 hours while supplying the activation gas at a rate of 0.5 kg / h to 3.0 kg / h, preferably 0.7 kg / h to 2.0 kg / h.

[0048] Furthermore, prior to the activation treatment of the carbonized material, the carbonized material may be subjected to primary activation in advance. In this primary activation, a method of gas activation in which the carbon material is fired at a temperature of less than 900°C using an activation gas such as water vapor, carbon dioxide, or oxygen is preferably employed.

[0049] By appropriately combining the calcination temperature and calcination time in the carbonization method with the activation gas supply amount, temperature rise rate, and maximum activation temperature in the activation method, it is possible to produce gas-activated activated carbon having the characteristics that can be used in the present disclosure.

[0050] The average particle diameter of the gas-activated activated carbon is preferably 2 μm to 20 μm. When the average particle diameter of the gas-activated activated carbon is 2 μm or more, the density of the active material layer is high, and therefore the capacity per electrode volume tends to be high. Furthermore, when the average particle diameter is 2 μm or more, durability tends to be high. On the other hand, when the average particle diameter is 20 μm or less, it tends to be easily adapted to high-speed charging and discharging. The average particle diameter is more preferably 2 μm to 15 μm, and even more preferably 3 μm to 10 μm.

[0051] (Alkali activated carbon) The carbonaceous material used as a raw material for alkali-activated activated carbon is not particularly limited as long as it is a carbon source commonly used as a raw material for activated carbon, and examples thereof include plant-based raw materials such as wood, wood flour, coconut shells, etc.; fossil-based raw materials such as petroleum pitch, coke, etc.; and various synthetic resins such as phenolic resins, furan resins, vinyl chloride resins, vinyl acetate resins, melamine resins, urea resins, resorcinol resins, etc. Among these raw materials, phenolic resins and furan resins are particularly preferred because they are suitable for producing activated carbon with a high specific surface area.

[0052] Methods for carbonizing these raw materials or heating methods during activation treatment include known methods such as fixed bed, moving bed, fluidized bed, slurry, and rotary kiln. The atmosphere used during heating is an inert gas such as nitrogen, carbon dioxide, helium, or argon, or a gas mixture containing these inert gases as the main component with other gases. Carbonization is generally performed at a temperature of about 400°C to 700°C for about 0.5 to 10 hours.

[0053] To produce activated carbon with a high specific surface area, a preferred activation method for carbide is to mix it with an alkali metal compound and then heat-treat it. In this activation method, the carbide is mixed with an alkali metal compound such as KOH or NaOH in a mass ratio of 1:1 or more (the amount of alkali metal compound is equal to or greater than the amount of carbide), and then heated in an inert gas atmosphere at 600°C to 900°C for 0.5 to 5 hours. The alkali metal compound is then removed by washing with acid and water, and the mixture is then dried.

[0054] To increase the micropore volume without increasing the mesopore volume, it is recommended to mix a larger amount of carbide with KOH during activation. To increase both the micropore volume and the mesopore volume, it is recommended to use a larger amount of KOH. Furthermore, to mainly increase the mesopore volume, it is preferable to perform steam activation after alkali activation treatment.

[0055] The average particle size of the alkali-activated activated carbon is preferably 2 μm or more and 20 μm or less, and more preferably 3 μm or more and 10 μm or less. The reason why this range is preferable is as described above for the gas-activated activated carbon.

[0056] (Activated carbon usage) The activated carbon used in the present disclosure may be one type of activated carbon or a mixture of two or more types of activated carbon. The positive electrode active material may contain a material other than activated carbon, such as a composite oxide of lithium and a transition metal. The activated carbon content is preferably more than 50 mass% of the total mass of the composite powder material, more preferably 70 mass% or more, even more preferably 90 mass% or more, and most preferably 100 mass%.

[0057] <Lithium carbonate, etc.> In the present disclosure, the composite powder material contains lithium carbonate. In the pre-doping process described below, lithium carbonate is decomposed in the positive electrode precursor to release lithium ions, which are then reduced at the negative electrode, allowing metallic lithium to be pre-doped into the negative electrode. In addition to lithium carbonate, the composite powder material may also contain other alkali metal compounds, such as sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate. It may also contain one or more oxides such as MO, hydroxides such as MOH, halides such as MF and MCl, and carboxylates such as RCOOM. In these formulas, M is independently one or more selected from the group consisting of Li, Na, K, Rb, and Cs, and R is selected from the group consisting of H, an alkyl group, and an aryl group. In the present disclosure, the composite powder material may also contain at least one selected from the group consisting of alkaline earth metal oxides, alkaline earth metal hydroxides, alkaline earth metal halides, and alkaline earth metal carboxylates.

[0058] When the composite powder material contains, in addition to lithium carbonate, an alkali metal compound other than lithium carbonate or an alkaline earth metal compound, the total amount of these compounds is preferably 10 mass % or more and 50 mass % or less relative to the total mass of the composite powder material.

[0059] <Weight ratio of carbon material to lithium carbonate> When the weight of the carbon material in the composite powder material is M1 and the weight of the lithium carbonate is M2, it is preferable that the ratio M2 / M1 be 0.1≦M2≦2. A weight ratio of 0.1 or greater ensures that the decomposition reaction of lithium carbonate proceeds sufficiently during the doping process, and the resulting carbon dioxide gas reacts with the negative electrode to form a stable lithium carbonate coating, thereby suppressing lithium deactivation at the negative electrode and improving the capacity retention rate at high temperatures. On the other hand, a weight ratio of 2 or less ensures that the amount of lithium carbonate relative to the carbon material is not too high, ensuring sufficient contact between the carbon materials within the positive electrode. As a result, even if the completed lithium storage device is subjected to high temperatures, a decrease in the capacity retention rate at high temperatures can be suppressed, even if strain within the positive electrode due to high-temperature binder degradation or other factors causes a loss of electrical contact between the carbon materials, resulting in the generation of carbon materials that do not contribute to capacity.

[0060] <Positive electrode precursor> The positive electrode precursor of the present disclosure has a positive electrode current collector and a positive electrode active material layer present on one or both sides thereof. The positive electrode active material layer preferably contains the composite powder material of the present disclosure, which contains a carbon material and lithium carbonate, in the positive electrode precursor before assembly of the energy storage device. As described below, in the present disclosure, it is preferable to pre-dope the negative electrode with lithium ions during the energy storage device assembly process. As a pre-doping method, it is preferable to assemble the energy storage device using a positive electrode precursor, a negative electrode, a separator, an outer casing, and a non-aqueous electrolyte solution, and then apply a voltage between the positive electrode precursor and the negative electrode. In the present disclosure, the positive electrode before pre-doping is referred to as a "positive electrode precursor."

[0061] <Cathode active material layer> The positive electrode active material layer of the positive electrode precursor according to the present disclosure includes the composite powder material according to the present disclosure, which includes a carbon material and lithium carbonate. The positive electrode active material layer may further include a material other than the materials described in the above section "Composite Powder Material." Furthermore, lithium carbonate may be present on the surface of the positive electrode active material layer of the positive electrode precursor.

[0062] In the positive electrode active material layer of the positive electrode precursor in the present invention, optional components such as positive electrode active materials other than the composite powder material, lithium carbonate other than the composite powder material, lithium transition metal oxides, conductive fillers, binders, dispersion stabilizers, pH adjusters, etc. may be included as necessary.

[0063] (Lithium transition metal oxide) The composite powder material may contain a lithium transition metal oxide as a positive electrode active material in addition to the carbon material. As the lithium transition metal oxide, known materials used in lithium ion batteries can be used.

[0064] The lithium transition metal oxide includes a transition metal oxide capable of occluding and releasing lithium. There is no particular limitation on the lithium transition metal oxide used as the positive electrode active material. Examples of the transition metal oxide include oxides 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 CoO2 {where x satisfies 0 ≦ x ≦ 1.} Li x NiO2 {where x satisfies 0 ≦ x ≦ 1.} Li x Ni y M (1-y) O2 {where M is at least one element selected from the group consisting of Co, Mn, Al, Fe, Mg, and Ti, x satisfies 0 ≦ x ≦ 1, and y satisfies 0.02 < y < 0.97.} Li x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2 {where x satisfies 0 ≦ x ≦ 1.} Li x MnO2 {where x satisfies 0 ≦ x ≦ 1.} α-Li x FeO2 {where x satisfies 0 ≦ x ≦ 1.} Li x VO2 {where x satisfies 0 ≦ x ≦ 1.} Li xCrO2 {where x satisfies 0 ≦ x ≦ 1.} Li x FePO4 {where x satisfies 0 ≦ x ≦ 1.} Li x MnPO4 {where x satisfies 0 ≦ x ≦ 1.} Li z V2(PO4)3 {where z satisfies 0 ≦ z ≦ 3.} Li x Mn2O4 {where x satisfies 0 ≦ x ≦ 1.} Li x M y Mn (2-y) O4 {where M is at least one element selected from the group consisting of Co, Mn, Al, Fe, Mg, and Ti, x satisfies 0 ≦ x ≦ 1, and y satisfies 0.02 < y < 0.97.} Li x Ni a Co b Al (1-a-b) O2 {where x satisfies 0 ≦ x ≦ 1, and a and b satisfy 0.02 < a < 0.97 and 0.02 < b < 0.97.} Li x Ni c Co d Mn (1-c-d) O2 {where x satisfies 0 ≦ x ≦ 1, and c and d satisfy 0.02 < c < 0.97 and 0.02 < d < 0.97.} Compounds represented by the above formula etc. may be mentioned.

[0065] Among these, from the viewpoints of high capacity, low resistance, cycle characteristics, decomposition of lithium carbonate, and suppression of loss of the positive electrode active material during pre-doping, the above formula Li x Ni a Co b Al (1-a-b) O2, Li x Ni c Co d Mn (1-c-d) O2, Li x CoO2, Li x Mn2O4, Li x FePO4, Li x MnPO4, or Li zCompounds represented by V2(PO4)3 are preferred.

[0066] In the present disclosure, lithium carbonate serves as a lithium dopant source during pre-doping, allowing the negative electrode to be pre-doped. Therefore, even if the transition metal compound does not contain lithium ions in advance (i.e., even if x=0 or z=0), the non-aqueous lithium storage element can be electrochemically charged and discharged.

[0067] The average particle size of the lithium transition metal oxide is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, and even more preferably 1 μm to 10 μm.

[0068] When the average particle size of the lithium transition metal oxide is 0.1 μm or more, the density of the active material layer is high, and therefore the capacity per electrode volume tends to be high. When the average particle size is 0.1 μm or more, durability tends to be high. On the other hand, when the average particle size of the lithium transition metal oxide is 20 μm or less, it tends to be more suitable for high-speed charging and discharging. The average particle size of the lithium transition metal oxide is preferably smaller than the average particle size of the carbon material. When the average particle size of the lithium transition metal oxide is small, the lithium transition metal oxide is arranged in the voids formed by the carbon material with a large average particle size, thereby reducing resistance.

[0069] The lithium transition metal oxide may be used singly or may be a mixture of two or more materials, each of which exhibits the above-mentioned characteristic values ​​as a whole mixture.

[0070] The positive electrode active material may contain a material other than the lithium transition metal oxide, for example, a conductive polymer, etc. When the content of the lithium transition metal oxide in the total solid content of the positive electrode coating liquid is A2, A2 is preferably 5% by mass or more and 35% by mass or less, and more preferably 10% by mass or more and 30% by mass or less.

[0071] The ratio A2 / A1 of the lithium transition metal oxide content A2 to the carbon material content A1 is preferably 0.1 or more and 10.0 or less, more preferably 0.2 or more and 5.0 or less. If A2 / A1 is 0.1 or more, the bulk density of the positive electrode active material layer can be increased, resulting in a high capacity. If A2 / A1 is 10.0 or less, the electronic conduction between the activated carbons is increased, resulting in a low resistance, and the contact area between the activated carbon and lithium carbonate is increased, resulting in a promotion of decomposition of lithium carbonate.

[0072] (Conductive filler) The conductive filler may be a conductive carbonaceous material having higher conductivity than the positive electrode active material, such as ketjen black, acetylene black, vapor-grown carbon fiber, graphite, flake graphite, carbon nanotubes, graphene, graphene oxide, or a mixture thereof.

[0073] The amount of conductive filler mixed in the positive electrode active material layer of the positive electrode precursor is preferably 0 to 20 parts by mass, more preferably 1 to 15 parts by mass, per 100 parts by mass of the positive electrode active material. Mixing a conductive filler is preferable from the viewpoint of high input power. However, if the amount mixed exceeds 20 parts by mass, the content of the positive electrode active material in the positive electrode active material layer decreases, which is undesirable because it reduces the energy density per volume of the positive electrode active material layer.

[0074] (binder) The binder is not particularly limited, and examples thereof include PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, polyacrylic acid, and polyglutamic acid. The amount of binder used is preferably 1 to 30 parts by mass per 100 parts by mass of the positive electrode active material. More preferably, it is 3 to 27 parts by mass, and even more preferably, it is 5 to 25 parts by mass. When the amount of binder is 1% by mass or more, sufficient electrode strength is achieved. On the other hand, when the amount of binder is 30 parts by mass or less, the ingress and egress of ions into and diffusion from the positive electrode active material are not hindered, and high input / output characteristics are achieved.

[0075] (Dispersion stabilizer) The dispersion stabilizer is not particularly limited, and examples thereof include PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), and cellulose derivatives. The amount of the dispersion stabilizer used is preferably 0 to 10 parts by mass relative to 100 parts by mass of the positive electrode active material. When the amount of the dispersion stabilizer is 10 parts by mass or less, the ingress and egress of ions into and diffusion from the positive electrode active material are not inhibited, and high input / output characteristics are achieved.

[0076] (pH adjuster) When water is used as the solvent for the coating liquid, the addition of lithium carbonate may cause the coating liquid to become alkaline, so a pH adjuster may be added to the coating liquid as needed. The pH adjuster is not particularly limited, and examples thereof include hydrogen halides such as hydrogen fluoride, hydrogen chloride, and hydrogen bromide, halogen oxoacids such as hypochlorous acid, chlorous acid, and chloric acid, carboxylic acids such as formic acid, acetic acid, citric acid, oxalic acid, lactic acid, maleic acid, and fumaric acid, sulfonic acids such as methanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid, and acids such as nitric acid, sulfuric acid, phosphoric acid, boric acid, and carbon dioxide.

[0077] <Positive electrode current collector> The material for the positive electrode current collector according to the present disclosure is not particularly limited as long as it has high electronic conductivity and is not susceptible to degradation due to elution in the electrolyte or reaction with the electrolyte or ions, but metal foil is preferred. Aluminum foil is more preferred as the positive electrode current collector in the nonaqueous lithium energy storage element according to the present disclosure.

[0078] The metal foil may be a normal metal foil without irregularities or through holes, or may be a metal foil with irregularities obtained by embossing, chemical etching, electrolytic deposition, blasting, etc., or may be a metal foil with through holes such as expanded metal, punched metal, etched foil, etc. From the viewpoint of the pro-dope treatment described later, non-porous aluminum foil is more preferred, and it is particularly preferred that the surface of the aluminum foil is roughened.

[0079] There are no particular restrictions on the thickness of the positive electrode current collector as long as it can sufficiently maintain the shape and strength of the positive electrode, but it is preferably 1 μm to 100 μm, for example.

[0080] It is preferable to provide an anchor layer containing a conductive material such as graphite, flake graphite, carbon nanotubes, graphene, ketjen black, acetylene black, or vapor-grown carbon fiber on the surface of the metal foil. The provision of the anchor layer improves electrical conductivity between the positive electrode current collector and the positive electrode active material layer, thereby reducing resistance. The thickness of the anchor layer is preferably 0.1 μm or more and 5 μm or less per side of the positive electrode current collector.

[0081] <Method for producing positive electrode precursor> The positive electrode precursor for the positive electrode of the nonaqueous lithium storage battery element of the present disclosure includes the composite powder material of the present disclosure, which contains a carbon material and lithium carbonate. The positive electrode precursor of the present disclosure can be produced by known electrode manufacturing techniques for lithium ion batteries, electric double layer capacitors, etc., except for the synthesis of the composite powder material of the present disclosure. For example, the composite powder material of the present disclosure, and optionally other materials, are dispersed or dissolved in water or an organic solvent to prepare a slurry-like coating liquid. This coating liquid is then applied to one or both sides of a positive electrode current collector to form a coating film, which is then dried to obtain a positive electrode precursor. The resulting positive electrode precursor may then be pressed to adjust the film thickness or bulk density of the positive electrode active material layer. Alternatively, a method is also possible in which the positive electrode active material, lithium carbonate, and other optional components are dry-mixed without using a solvent, the resulting mixture is press-molded, and then attached to the positive electrode current collector using a conductive adhesive. Alternatively, the resulting mixture is hot-pressed onto the positive electrode current collector to form the positive electrode active material layer.

[0082] The coating solution for the positive electrode precursor may be prepared by dry-blending some or all of the various material powders, including the composite powder material, followed by the addition of water or an organic solvent, and / or a liquid or slurry-like substance in which a binder, a dispersion stabilizer, or a pH adjuster is dissolved or dispersed therein. Alternatively, the coating solution may be prepared by adding various material powders, including the positive electrode active material, to 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. As a dry-blending method, the composite powder material and, if necessary, other materials may be premixed using, for example, a ball mill, to coat the low-conductivity lithium carbonate with the conductive material. This facilitates decomposition of the lithium carbonate in the positive electrode precursor during the pre-doping step described below.

[0083] The preparation of the coating solution for the positive electrode precursor is not particularly limited, but preferably a disperser such as a homodisper, a multi-axis disperser, a planetary mixer, or a thin film rotary high-speed mixer can be used. To obtain a coating solution in a well-dispersed state, the coating solution is preferably dispersed at a peripheral speed of 1 m / s or more and 50 m / s or less. A peripheral speed of 1 m / s or more is preferred because various materials are well dissolved or dispersed. Furthermore, a peripheral speed of 50 m / s or less is preferred because various materials are not destroyed by heat or shear force due to dispersion, and re-aggregation does not occur.

[0084] The degree of dispersion of the coating liquid is preferably 0.1 μm or more and 100 μm or less, as measured with a particle gauge. The upper limit of the degree of dispersion is more preferably 80 μm or less, and even more preferably 50 μm or less. A particle size of 0.1 μm or less is less than the particle size of the powders of various materials, including the positive electrode active material, and is therefore undesirable because the materials are crushed during preparation of the coating liquid. Furthermore, a particle size of 100 μm or less allows stable coating without clogging during discharge of the coating liquid or streaks in the coating film.

[0085] The viscosity (ηb) of the coating solution for the positive electrode precursor is preferably 100 mPa·s or more and 10,000 mPa·s or less, more preferably 500 mPa·s or more and 7,000 mPa·s or less, and even more preferably 1,000 mPa·s or more and 4,000 mPa·s or less. A viscosity (ηb) of 100 mPa·s or more suppresses dripping during coating film formation, allowing for good control of the coating film width and thickness. Furthermore, a viscosity of 10,000 mPa·s or less allows for stable coating with minimal pressure loss in the coating solution flow path when using a coating machine, and also allows for control of the coating film thickness to the desired level.

[0086] The TI value (thixotropy index value) of the coating liquid is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.5 or more. If the TI value is 1.1 or more, the width and thickness of the coating film can be well controlled.

[0087] The coating film of the positive electrode precursor is not particularly limited, but a coating machine such as a die coater, comma coater, knife coater, or gravure coater can be suitably used. The coating film may be formed by single-layer coating or multi-layer coating. In the case of multi-layer coating, the coating liquid composition may be adjusted so that the lithium carbonate content in each layer of the coating film is different. When applying the coating film to the positive electrode current collector, multi-line coating, intermittent coating, or multi-line intermittent coating may be used. In addition, sequential coating may be performed by coating one side of the positive electrode current collector and drying, and then coating the other side and drying, or simultaneous double-sided coating may be performed by simultaneously coating both sides of the positive electrode current collector with the coating liquid and drying.

[0088] The coating speed is preferably 0.1 m / min or more and 100 m / min or less, more preferably 0.5 m / min or more and 70 m / min or less, and even more preferably 1 m / min or more and 50 m / min or less. If the coating speed is 0.1 m / min or more, stable coating can be achieved. On the other hand, if the coating speed is 100 m / min or less, sufficient coating accuracy can be ensured.

[0089] The coating film of the positive electrode precursor is preferably dried using a drying method such as hot air drying or infrared (IR) drying, more preferably using far infrared rays, near infrared rays, or hot air at 80°C or higher. The coating film may be dried at a single temperature or by varying the temperature in multiple stages. Alternatively, a combination of multiple drying methods may be used. The drying temperature is preferably 25°C or higher and 200°C or lower, more preferably 40°C or higher and 180°C or lower, and even more preferably 50°C or higher and 160°C or lower. A drying temperature of 25°C or higher can sufficiently volatilize the solvent in the coating film. On the other hand, a drying temperature of 200°C or lower can suppress cracking of the coating film due to rapid solvent evaporation, uneven distribution of the binder due to migration, and oxidation of the positive electrode current collector or positive electrode active material layer.

[0090] A press such as a hydraulic press or a vacuum press can be suitably used to press the positive electrode precursor. 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 unit, as described below. The press pressure is preferably 0.5 kN / cm or more and 20 kN / cm or less, more preferably 1 kN / cm or more and 10 kN / cm or less, and even more preferably 2 kN / cm or more and 7 kN / cm or less. If the press pressure is 0.5 kN / cm or more, the electrode strength can be sufficiently high. On the other hand, if the press pressure is 20 kN / cm or less, the positive electrode precursor does not bend or wrinkle, and the positive electrode active material layer can be adjusted to the desired thickness or bulk density.

[0091] The gap between the press rolls can be set to any value depending on the film thickness of the positive electrode precursor after drying so as to achieve the desired film thickness or bulk density of the positive electrode active material layer, and the pressing speed can be set to any speed that does not cause sagging or wrinkling of the positive electrode precursor.

[0092] The surface temperature of the press part may be room temperature, or may be heated as necessary. When heated, the lower limit of the surface temperature of the press part is preferably at least 60°C below the melting point of the binder used, more preferably at least 45°C below the melting point of the binder, and even more preferably at least 30°C below the melting point of the binder. On the other hand, when heated, the upper limit of the surface temperature of the press part is preferably at most 50°C above the melting point of the binder used, more preferably at most 30°C above the melting point of the binder, and even more preferably at most 20°C above the melting point of the binder. For example, when PVdF (polyvinylidene fluoride: melting point 150°C) is used as the binder, the temperature is preferably 90°C to 200°C, more preferably at most 105°C to 180°C, and even more preferably at most 120°C to 170°C. Furthermore, when a styrene-butadiene copolymer (melting point 100°C) is used as the binder, it is preferable to heat the mixture to a temperature of 40°C or higher and 150°C or lower, more preferably 55°C or higher and 130°C or lower, and even more preferably 70°C or higher and 120°C or lower.

[0093] The melting point of the binder can be determined from the endothermic peak position in DSC (Differential Scanning Calorimetry). For example, using a PerkinElmer DSC7 differential scanning calorimeter, 10 mg of sample resin is placed in the measurement cell, and the temperature is raised from 30°C to 250°C at a rate of 10°C / min in a nitrogen gas atmosphere. The endothermic peak temperature during the temperature rise is the melting point.

[0094] Pressing may be performed multiple times while changing the conditions of the press pressure, gap, speed, and surface temperature of the press part.

[0095] When the positive electrode precursor is multi-line coated, it is preferable to slit it before pressing. If the multi-line coated positive electrode precursor is pressed without slitting, stress is applied to the current collector portion not coated with the positive electrode active material layer, causing wrinkles. Alternatively, the positive electrode precursor can be slit again after pressing.

[0096] The thickness of the positive electrode active material layer according to the present disclosure is preferably 10 μm or more and 200 μm or less per side of the positive electrode current collector. The thickness of the positive electrode active material layer is more preferably 20 μm or more and 100 μm or less per side, and even more preferably 30 μm or more and 80 μm or less. A thickness of 10 μm or more can achieve sufficient charge / discharge capacity. On the other hand, a thickness of 200 μm or less can maintain low ion diffusion resistance within the electrode. Therefore, sufficient output characteristics can be obtained, and the cell volume can be reduced, thereby increasing the energy density. Note that when the current collector has through-holes or irregularities, the thickness of the positive electrode active material layer refers to the average thickness per side of the portion of the current collector that does not have through-holes or irregularities.

[0097] The weight ratio A3 of lithium carbonate in the positive electrode active material layer of the positive electrode precursor is preferably 10% by mass or more and 50% by mass or less. When A3 is 10% by mass or more, a sufficient amount of lithium ions can be pre-doped into the negative electrode, increasing the capacity of the nonaqueous lithium metal energy storage element. When A3 is 50% or less, electronic conductivity in the positive electrode precursor can be increased, thereby efficiently decomposing lithium carbonate.

[0098] When the positive electrode precursor contains lithium carbonate or an alkaline earth metal compound in addition to lithium carbonate, the positive electrode precursor is preferably produced so that the total amount of lithium carbonate and the alkaline earth metal compound is 10% by mass or more and 50% by mass or less with respect to the positive electrode active material layer of the positive electrode precursor.

[0099] <Quantitative determination of carbon material, lithium transition metal oxide, and lithium carbonate in the positive electrode precursor and the positive electrode active material layer of the positive electrode> (1) Quantitative determination of carbon materials contained in the positive electrode precursor and the positive electrode active material layer The mass proportion A1 of the carbon material, the mass proportion A2 of the lithium transition metal oxide, and the mass proportion A3 of the lithium carbonate contained in the positive electrode active material layer of the positive electrode precursor can be determined by the following method. This method of determining the carbon material can also be applied to the positive electrode.

[0100] The area of ​​the positive electrode precursor to be measured is not particularly limited, but in order to reduce the variation in the measurement, a 5 cm 2 More than 200cm 2 Preferably it is less than 25cm 2 More than 150cm 2 The area is 5cm or less. 2 If the area is 200cm or more, the reproducibility of the measurement is ensured. 2 If the value is less than this, the sample is easy to handle.

[0101] First, the positive electrode precursor is cut to the above-mentioned area and vacuum-dried. The vacuum drying conditions are preferably, for example, a temperature of 100°C to 200°C, a pressure of 0 kPa to 10 kPa, and a time of 5 to 20 hours, such that the residual moisture content in the positive electrode precursor is 1% by mass or less. The residual moisture content can be quantified by the Karl Fischer method.

[0102] The weight (M0) of the positive electrode precursor obtained after vacuum drying is measured. Then, the positive electrode precursor is immersed in distilled water in an amount 100 to 150 times the weight of the positive electrode precursor for at least three days to dissolve the lithium carbonate into the water. It is preferable to cover the container during immersion to prevent the distilled water from volatilizing. After immersion for at least three days, the positive electrode precursor is removed from the distilled water and vacuum dried in the same manner as above. The weight (M1) of the resulting positive electrode precursor is measured. Next, the positive electrode active material layer applied to one or both sides of the positive electrode current collector is removed using a spatula, brush, paintbrush, or the like. The weight (M2) of the remaining positive electrode current collector is measured, and the mass proportion A3 of lithium carbonate is calculated using the following formula (1): A3=(M0-M1) / (M0-M2)×100 (1)

[0103] Next, in order to calculate A1 and A2, the TG curve of the positive electrode active material layer obtained by removing the lithium carbonate is measured under the following conditions. Sample pan: platinum Gas: atmospheric air or compressed air Heating rate: 0.5℃ / min or less Temperature range: 25°C to 500°C (or higher) (50°C below the melting point of lithium transition metal oxide)

[0104] The mass at 25°C on the obtained TG curve is designated as M3, and the mass at the first temperature above 500°C at which the mass loss rate becomes M3 x 0.01 / min or less is designated as M4.

[0105] Carbon materials are oxidized and burned when heated at temperatures below 500°C in an oxygen-containing atmosphere (e.g., air). On the other hand, lithium transition metal oxides do not lose mass even in an oxygen-containing atmosphere up to a temperature 50°C below their melting point.

[0106] Therefore, the content A2 of the lithium transition metal oxide in the positive electrode active material layer can be calculated by the following formula (2). A2=(M4 / M3)×{1-(M0-M1) / (M0-M2)}×100 ···(2)

[0107] The content A1 of the carbon material in the positive electrode active material layer can be calculated by the following formula (3). A1={(M3-M4) / M3}×{1-(M0-M1) / (M0-M2)}×100 ···(3)

[0108] When the positive electrode active material layer contains a conductive material, a binder, a thickener, etc., the total amount of the carbon material and these materials is calculated as A1.

[0109] (2) Identification method for lithium carbonate in the positive electrode precursor and the positive electrode The method for identifying lithium carbonate contained in the positive electrode is not particularly limited, but it can be identified, for example, by the following method. For identifying lithium carbonate, it is preferable to combine the following analytical techniques. Note that this method for identifying lithium carbonate can also be applied to the positive electrode precursor.

[0110] If lithium carbonate cannot be identified using the analytical method, other analytical methods include: 7 Lithium carbonate can also be identified using Li-solid-state NMR, XRD (X-ray diffraction), TOF-SIMS (time-of-flight secondary ion mass spectrometry), AES (Auger electron spectroscopy), TPD / MS (thermal evolved gas mass spectrometry), DSC (differential scanning calorimetry), etc.

[0111] Scanning Electron Microscopy-Energy Dispersive X-ray Analysis (SEM-EDX): When the positive electrode active material does not contain a lithium transition metal oxide, lithium carbonate and the positive electrode active material can be distinguished by oxygen mapping using SEM-EDX images of the positive electrode surface measured at magnifications of 1000x to 4000x. For example, SEM-EDX images can be measured at an acceleration voltage of 10 kV, an emission current of 10 μA, 256 × 256 pixel measurement, and 50 integration times. To prevent sample charging, surface treatment with gold, platinum, osmium, or the like can be performed using methods such as vacuum deposition or sputtering. Regarding the SEM-EDX image measurement method, it is preferable to adjust the brightness and contrast so that no pixels reach the maximum brightness value in the mapping image and the average brightness value is within the range of 40% to 60% of the maximum brightness value. Particles containing bright areas binarized based on the average brightness value in the obtained oxygen mapping, which account for 50% or more of their area, are considered to be lithium carbonate.

[0112] Raman microscopy: Lithium carbonate and the positive electrode active material can be distinguished by Raman imaging of carbonate ions on the positive electrode surface, measured at a magnification of 1000x to 4000x. Measurement conditions include an excitation light of 532 nm, an excitation light intensity of 1%, a long working distance of the objective lens of 50x, a diffraction grating of 1800 gr / mm, a point scanning mapping method (slit 65 mm, binning 5 pix), 1 mm steps, an exposure time of 3 seconds per point, one integration, and a noise filter. The measured Raman spectrum shows peaks from 1071 to 1104 cm. -1 A linear baseline is set in the range, and the area is calculated assuming that positive values ​​from the baseline are carbonate ion peaks, and the frequency is integrated. At this time, the frequency for the carbonate ion peak area, which is approximated by a Gaussian function for noise components, is subtracted from the carbonate ion frequency distribution.

[0113] Ion Chromatography: The anion species eluted into the water can be identified by analyzing the distilled water wash solution from the positive electrode using ion chromatography. Columns that can be used include ion exchange, ion exclusion, and reversed-phase ion pair types. Detectors that can be used include electrical conductivity detectors, ultraviolet-visible absorbance detectors, and electrochemical detectors. Suppressor-based detectors, which use a suppressor before the detector, and non-suppressor-based detectors, which use a low-conductivity solution as the eluent without a suppressor, can also be used. Measurements can also be performed in combination with a mass spectrometer or a charged aerosol detector.

[0114] Once the conditions, such as the column and eluent, are determined, the sample retention time is constant for each ionic species, and the magnitude of the peak response differs for each ionic species but is proportional to the concentration. Qualitative and quantitative determination of ionic species is possible by measuring standard solutions of known concentrations with traceability in advance.

[0115] 《Negative electrode》 The negative electrode has a negative electrode current collector and a negative electrode active material layer present on one or both sides of the negative electrode current collector.

[0116] <Negative electrode active material layer> The negative electrode active material layer contains a negative electrode active material capable of absorbing and releasing lithium ions, and may further contain optional components such as a conductive filler, a binder, a dispersant, etc., as necessary.

[0117] <Negative electrode active material> The negative electrode active material may be a material capable of absorbing and releasing lithium ions. Specific examples include carbon materials, titanium oxides, silicon, silicon oxides, silicon alloys, silicon compounds, tin, and tin compounds. The carbon material content relative to the total amount of the negative electrode active material is preferably 50% by mass or more, and more preferably 70% by mass or more. While the carbon material content can be 100% by mass, from the viewpoint of obtaining the desired effect of the combined use of other materials, it is preferably 90% by mass or less, and may be 80% by mass or less. The upper and lower limits of the range of the carbon material content can be arbitrarily combined.

[0118] Examples of carbon materials include non-graphitizable carbon materials; graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon microspheres; graphite whiskers; amorphous carbonaceous materials such as polyacene-based substances; carbonaceous materials obtained by heat-treating carbon precursors such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and synthetic resins (e.g., phenolic resins); pyrolysates of furfuryl alcohol resins or novolac resins; fullerenes; carbon nanophones; and composite carbon materials thereof.

[0119] <Other Optional Components of Negative Electrode Active Material Layer> The negative electrode active material layer according to the present disclosure may contain optional components such as a binder, a conductive filler, a dispersant, and the like, in addition to the negative electrode active material, as needed.

[0120] Examples of binders that can be used include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide, fluororubber, latex, styrene-butadiene copolymer, fluororubber, and acrylic copolymer. The amount of binder used in the negative electrode active material layer is preferably 1 to 30 parts by mass, more preferably 2 to 25 parts by mass, per 100 parts by mass of the negative electrode active material. If the amount of binder used is less than 1 part by mass per 100 parts by mass of the negative electrode active material, sufficient adhesion cannot be ensured between the current collector and the negative electrode active material layer in the negative electrode (precursor), resulting in increased interfacial resistance between the current collector and the active material layer. On the other hand, if the amount of binder used is more than 30 parts by mass per 100 parts by mass of the negative electrode active material, the binder will excessively cover the surface of the active material in the negative electrode (precursor), increasing the ion diffusion resistance within the active material pores.

[0121] The conductive filler is preferably made of a conductive carbonaceous material having higher conductivity than the negative electrode active material. Examples of such conductive fillers include ketjen black, acetylene black, vapor-grown carbon fiber, graphite, flake graphite, carbon nanotubes, graphene, graphene oxide, and mixtures thereof. The amount of conductive filler mixed in the negative electrode active material layer is preferably 20 parts by mass or less, more preferably 1 to 15 parts by mass, per 100 parts by mass of the negative electrode active material. While mixing the conductive filler in the negative electrode active material layer is preferable from the viewpoint of high input power, mixing the conductive filler in an amount greater than 20 parts by mass is undesirable because the content of the negative electrode active material in the negative electrode active material layer decreases, resulting in a decrease in energy density per volume.

[0122] The dispersion stabilizer is not particularly limited, and examples thereof include PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), and cellulose derivatives. The amount of the dispersion stabilizer used is preferably 0 to 10 parts by mass relative to 100 parts by mass of the negative electrode active material. When the amount of the dispersion stabilizer is 10 parts by mass or less, the ingress and egress of ions into and diffusion from the negative electrode active material are not inhibited, and high input / output characteristics are achieved.

[0123] <Negative electrode current collector> The material constituting the negative electrode current collector according to the present disclosure is preferably a metal foil that has high electronic conductivity and is not susceptible to degradation due to leaching into the electrolyte or reaction with the electrolyte or ions. Such metal foils are not particularly limited, and examples thereof include aluminum foil, copper foil, nickel foil, and stainless steel foil. Copper foil is preferred as the negative electrode current collector in the nonaqueous lithium storage element according to the present disclosure. The metal foil may be a normal metal foil without irregularities or through holes, or a metal foil with irregularities obtained by embossing, chemical etching, electrolytic deposition, blasting, or the like, or a metal foil with through holes such as expanded metal, punched metal, or etched foil.

[0124] The thickness of the negative electrode current collector is not particularly limited as long as it can sufficiently maintain the shape and strength of the negative electrode, and is, for example, 1 to 100 μm.

[0125] <Production of negative electrodes> The negative electrode comprises a negative electrode active material layer on one or both sides of a negative electrode current collector. In a typical embodiment, the negative electrode active material layer is adhered to the negative electrode current collector.

[0126] The negative electrode can be manufactured by known electrode manufacturing techniques for lithium ion batteries, electric double layer capacitors, etc. For example, various materials including the negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to one or both sides of a negative electrode current collector to form a coating film, which is then dried to obtain a negative electrode. The obtained negative electrode may then be pressed to adjust the film thickness or bulk density of the negative electrode active material layer.

[0127] The coating solution may be prepared by dry-blending some or all of the various material powders, including the negative electrode active material, and then adding water or an organic solvent and / or a liquid or slurry-like substance in which a binder and a dispersion stabilizer are dissolved or dispersed therein. Alternatively, the coating solution may be prepared by adding the various material powders, including the negative electrode active material, to a liquid or slurry-like substance in which a binder and a dispersion stabilizer are dissolved or dispersed in water or an organic solvent. While the method for preparing the coating solution is not particularly limited, dispersers such as a homodisper, a multi-axis disperser, a planetary mixer, and a thin-film rotary high-speed mixer can be used. To obtain a coating solution in a well-dispersed state, dispersion is preferably performed at a peripheral speed of 1 m / s to 50 m / s. A peripheral speed of 1 m / s or higher is preferred because the various materials are well dissolved or dispersed. A speed of 50 m / s or lower is preferred because the various materials are not destroyed by the heat or shear force generated by dispersion, and re-agglomeration does not occur.

[0128] The viscosity (ηb) of the coating fluid is preferably 500 mPa·s or more and 20,000 mPa·s or less, more preferably 1,000 mPa·s or more and 10,000 mPa·s or less, and even more preferably 1,500 mPa·s or more and 5,000 mPa·s or less. A viscosity (ηb) of 500 mPa·s or more suppresses dripping during coating film formation, allowing for good control of the coating film width and thickness. Furthermore, a viscosity of 20,000 mPa·s or less allows for stable coating with minimal pressure loss in the coating fluid flow path when using a coating machine, and allows for control of the coating film thickness to a desired level or less.

[0129] The TI value (thixotropy index value) of the coating liquid is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.5 or more. If the TI value is 1.1 or more, the coating film width and film thickness can be well controlled.

[0130] The method for forming the coating film is not particularly limited, but coating machines such as a die coater, comma coater, knife coater, or gravure coater can be suitably used. The coating film may be formed by single-layer coating or multi-layer coating. The coating speed is preferably 0.1 m / min or more and 100 m / min or less, more preferably 0.5 m / min or more and 70 m / min or less, and even more preferably 1 m / min or more and 50 m / min or less. If the coating speed is 0.1 m / min or more, stable coating can be achieved. On the other hand, if the coating speed is 100 m / min or less, sufficient coating precision can be ensured.

[0131] The method for drying the coating film is not particularly limited, but suitable drying methods include hot air drying and infrared (IR) drying. The coating film may be dried at a single temperature or at multiple stages with varying temperatures. Alternatively, a combination of multiple drying methods may be used. The drying temperature is preferably 25°C or higher and 200°C or lower, more preferably 40°C or higher and 180°C or lower, and even more preferably 50°C or higher and 160°C or lower. A drying temperature of 25°C or higher can sufficiently volatilize the solvent in the coating film. On the other hand, a drying temperature of 200°C or lower can suppress cracking of the coating film due to rapid solvent evaporation, uneven distribution of the binder due to migration, and oxidation of the negative electrode current collector and negative electrode active material layer.

[0132] The method for pressing the negative electrode is not particularly limited, but a press such as a hydraulic press or a vacuum press can be preferably used. The film thickness, bulk density, and electrode strength of the negative electrode active material layer can be adjusted by the press pressure, gap, and surface temperature of the press unit, as described below. The press pressure is preferably 0.5 kN / cm or more and 20 kN / cm or less. It is more preferably 1 kN / cm or more and 10 kN / cm or less, and even more preferably 2 kN / cm or more and 7 kN / cm or less. A press pressure of 0.5 kN / cm or more can sufficiently increase the electrode strength. On the other hand, a press pressure of 20 kN / cm or less can be adjusted to the desired film thickness and bulk density of the negative electrode active material layer without causing bending or wrinkling in the negative electrode. The gap between the press rolls can be set to any value depending on the film thickness of the negative electrode after drying so as to achieve the desired film thickness and bulk density of the negative electrode active material layer. Furthermore, the press speed can be set to any speed that does not cause bending or wrinkling in the negative electrode. The surface temperature of the press unit can be room temperature, or it can be heated as necessary. The lower limit of the surface temperature of the press part when heated is preferably 60°C minus the melting point of the binder used, more preferably 45°C or higher, and even more preferably 30°C or higher. On the other hand, the upper limit of the surface temperature of the press part when heated is preferably 50°C or lower than the melting point of the binder used, more preferably 30°C or lower, and even more preferably 20°C or lower. For example, when PVdF (polyvinylidene fluoride: melting point 150°C) is used as the binder, heating is preferably from 90°C to 200°C. Heating is more preferably from 105°C to 180°C, and even more preferably from 120°C to 170°C. Furthermore, when styrene-butadiene copolymer (melting point 100°C) is used as the binder, heating is preferably from 40°C to 150°C. Heating is more preferably from 55°C to 130°C, and even more preferably from 70°C to 120°C.

[0133] <Negative electrode properties> The thickness of the negative electrode active material layer is preferably 5 μm to 100 μm per side, more preferably 10 μm to 60 μm per side. A thickness of 10 μm or more allows for good charge / discharge capacity. On the other hand, a thickness of 100 μm or less allows for a reduction in cell volume, thereby increasing energy density. When the current collector has pores, the thickness of the negative electrode active material layer refers to the average thickness of the non-pore portion of the current collector per side. Furthermore, the porosity (%) = (1 - true density / actual volume) × 100, calculated from the true density (cc / g) expressed as solid content (mass%) / material true density (g / cc) and the actual volume (cc / g) expressed as 1 / electrode bulk density (g / cc), is preferably 50% or more.

[0134] 《Non-aqueous electrolyte》 The electrolyte solution of the present disclosure is a non-aqueous electrolyte solution. That is, this electrolyte solution contains a non-aqueous solvent described below. The non-aqueous electrolyte solution preferably contains 0.5 mol / L or more of a lithium salt based on the total amount of the non-aqueous electrolyte solution. That is, the non-aqueous electrolyte solution preferably contains lithium ions as an electrolyte.

[0135] <Lithium salt> The nonaqueous electrolyte solution of the present disclosure may use, as the lithium salt, for example, (LiN(SO2F)2), LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C2F5), LiN(SO2CF3)(SO2C2F4H), LiC(SO2F)3, LiC(SO2CF3)3, LiC(SO2C2F5)3, LiCF3SO3, LiC4F9SO3, LiPF6, LiBF4, etc., either alone or in combination. Because high conductivity can be achieved, the nonaqueous electrolyte solution preferably contains at least one selected from the group consisting of LiPF6, LiN(SO2F)2, and LiBF4, and more preferably contains LiPF6 and / or LiBF4 and LiN(SO2F)2.

[0136] The lithium salt concentration in the nonaqueous electrolyte solution is preferably 0.5 mol / L or more, more preferably 0.5 mol / L or more and 2.0 mol / L or less, based on the total amount of the nonaqueous electrolyte solution. If the lithium salt concentration is 0.5 mol / L or more, sufficient anions are present, allowing the capacity of the energy storage device to be sufficiently high. Furthermore, if the lithium salt concentration is 2.0 mol / L or less, this is preferable because it can prevent undissolved lithium salt from precipitating in the nonaqueous electrolyte solution and the viscosity of the nonaqueous electrolyte solution from becoming too high, preventing a decrease in conductivity and a decrease in output characteristics.

[0137] The nonaqueous electrolyte solution of the present disclosure preferably contains LiN(SO2F)2 at a concentration of 0.1 mol / L to 1.5 mol / L, based on the total volume of the nonaqueous electrolyte solution. The LiN(SO2F)2 concentration is more preferably 0.4 mol / L to 1.2 mol / L. A LiN(SO2F)2 concentration of 0.1 mol / L or higher increases the ionic conductivity of the nonaqueous electrolyte solution, and an appropriate amount of electrolyte film is deposited at the negative electrode interface, thereby reducing gas generation due to decomposition of the nonaqueous electrolyte solution. On the other hand, a concentration of 1.5 mol / L or lower prevents precipitation of electrolyte salt during charge and discharge, and prevents an increase in the viscosity of the nonaqueous electrolyte solution even after a long period of time.

[0138] <Non-aqueous solvent> The nonaqueous electrolyte solution of the present disclosure preferably contains a cyclic carbonate as a nonaqueous solvent. The inclusion of a cyclic carbonate in the nonaqueous electrolyte solution is advantageous in that it dissolves a lithium salt at a desired concentration and deposits an appropriate amount of a lithium compound on the positive electrode active material layer. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate, butylene carbonate, vinylene carbonate, and fluoroethylene carbonate.

[0139] The total content of the cyclic carbonate is preferably 15% by mass or more, more preferably 20% by mass or more, based on the total amount of the non-aqueous electrolyte. When the total content is 15% by mass or more, it is possible to dissolve a lithium salt at a desired concentration, and high lithium ion conductivity can be achieved. Furthermore, it is possible to deposit an appropriate amount of lithium compound on the positive electrode active material layer, and it is possible to suppress oxidative decomposition of the non-aqueous electrolyte.

[0140] The nonaqueous electrolyte solution of the present disclosure preferably contains, as a nonaqueous solvent, chain carbonate compounds dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC). The volume ratio of ethyl methyl carbonate to dimethyl carbonate (DMC / EMC) is preferably 0.5 or more and 8.0 or less, more preferably 0.8 or more and 6.0 or less, and even more preferably 1.0 or more and 4.0 or less. When the DMC / EMC is 0.5 or more, the viscosity of the nonaqueous electrolyte solution can be reduced, and high lithium ion conductivity can be achieved. When the DMC / EMC is 8.0 or less, the melting point of the mixed solvent can be kept low, and high input / output characteristics can be achieved even in low-temperature environments.

[0141] The nonaqueous electrolyte solution of the present disclosure may also contain other chain carbonates as the nonaqueous solvent. Examples of other chain carbonates include dialkyl carbonate compounds such as diethyl carbonate, dipropyl carbonate, and dibutyl carbonate. The dialkyl carbonate compounds are typically unsubstituted.

[0142] The total content of the chain carbonate is preferably 30% by mass or more, more preferably 35% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, based on the total amount of the non-aqueous electrolyte solution. If the content of the chain carbonate is 30% by mass or more, the viscosity of the non-aqueous electrolyte solution can be reduced, and high lithium ion conductivity can be achieved. If the total concentration is 95% by mass or less, the non-aqueous electrolyte solution can further contain the additives described below.

[0143] <Additives> The nonaqueous electrolyte solution of the present disclosure may further contain an additive. The additive is not particularly limited, and examples thereof include sulfur-containing compounds, phosphate ester compounds, acyclic fluorine-containing ethers, cyclic phosphazenes, fluorine-containing cyclic carbonates, cyclic carbonate esters, cyclic carboxylic acid esters, and cyclic acid anhydrides, which may be used alone or in combination of two or more.

[0144] Among these, it is preferable to contain an additive selected from a sulfur-containing compound selected from compounds represented by the following chemical formulas (1-2) to (1-6), a phosphate ester compound selected from compounds represented by the following chemical formula (2), and an acyclic fluorine-containing ether represented by the following general formula (3).

[0145] It is preferable that the non-aqueous electrolyte solution contains a sulfur-containing compound selected from compounds represented by the following general formulas (1-2) to (1-6), in which the compound represented by (1-2) is thiophene, 2-methylthiophene, 3-methylthiophene, 2-cyanothiophene, 3-cyanothiophene, 2,5-dimethylthiophene, 2-methoxythiophene, 3-methoxythiophene, 2-chlorothiophene, 3-chlorothiophene, 2-acetylthiophene, or 3-acetylthiophene, and the sultone compound represented by (1-3) is 1, It is more preferable that the nonaqueous electrolyte solution contains one or more compounds selected from the group consisting of 3-propane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-butane sultone, and 2,4-pentane sultone; the sultone compound represented by (1-4) is 1,3-propene sultone or 1,4-butene sultone; the compound represented by (1-5) is 3-sulfolene; and the cyclic sulfite compound represented by (1-6) is ethylene sulfite, 1,2-propylene sulfite, and 1,3-propylene sulfite.

[0146] [ka]

[0147] {R in general formula (1-2) 1 ~R 4 each independently represents a hydrogen atom, a halogen atom, a formyl group, an acetyl group, a nitrile group, an acetyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkyl ester having 1 to 6 carbon atoms.}

[0148] {R in general formula (1-3) 9 ~R 14 each independently represents one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, and a halogenated alkyl group having 1 to 12 carbon atoms, and may be the same or different; and n is an integer of 0 to 3.

[0149] {R in general formula (1-4) 15 ~R 20 each independently represents one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, and a halogenated alkyl group having 1 to 12 carbon atoms, and may be the same or different; and n is an integer of 0 to 3.

[0150] {R in general formula (1-5) 21 ~R 26 each independently represents one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, and a halogenated alkyl group having 1 to 12 carbon atoms, and may be the same or different.}

[0151] {R in general formula (1-6) 27 ~R 30 each independently represents one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, and a halogenated alkyl group having 1 to 12 carbon atoms, and may be the same or different; and n is an integer of 0 to 3.

[0152] The total content of sulfur-containing compounds in the nonaqueous electrolyte solution of the nonaqueous lithium storage element of the present disclosure is preferably 0.1% by mass or more and 5% by mass or less, based on the total amount of the nonaqueous electrolyte solution. When the total content of sultone compounds in the nonaqueous electrolyte solution is 0.1% by mass or more, decomposition of the nonaqueous electrolyte solution at high temperatures can be suppressed, thereby suppressing gas generation. On the other hand, when this total content is 5% by mass or less, a decrease in the ionic conductivity of the nonaqueous electrolyte solution can be suppressed, thereby maintaining high input / output characteristics. Furthermore, from the viewpoint of achieving both high input / output characteristics and durability, the content of sultone compounds present in the nonaqueous electrolyte solution of the nonaqueous lithium storage element is preferably 0.3% by mass or more and 4% by mass or less, more preferably 0.5% by mass or more and 3% by mass or less.

[0153] <Phosphate ester compounds> It is preferable that the non-aqueous electrolyte solution contains a phosphate ester compound selected from compounds represented by the following general formula (2). [ka]

[0154] Examples of the compound represented by the general formula (2) include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tris(trimethylsilyl) phosphate, tritolyl phosphate, triphenyl phosphate, dioctyl phosphate, trioctyl phosphate, and tris(4-nitrophenyl) phosphate, and one or more selected from these are preferred.

[0155] The content of the phosphate ester compound is preferably 0.1% by mass or more and 3% by mass or less, and more preferably 0.3% by mass or more and 2.5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. If the content of the phosphate ester compound is 0.1% by mass or more, the stability of the non-aqueous electrolyte solution against oxidative decomposition is improved, and capacity degradation at high temperatures can be suppressed. On the other hand, if the content of the phosphate ester compound is 3% by mass or less, the reaction resistance at the interface between the positive electrode and the non-aqueous electrolyte solution can be kept low, making it possible to exhibit high input / output characteristics. The phosphate ester compounds may be used alone or in combination of two or more.

[0156] <Acyclic fluorine-containing ether> It is preferable that the non-aqueous electrolyte solution contains an acyclic fluorine-containing ether selected from compounds represented by the following general formula (3). R 1 -OR 2 (3) {where, R 1 is a halogen atom or a halogenated alkyl group having 1 to 12 carbon atoms, and R 2 is a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or a halogenated alkyl group having 1 to 12 carbon atoms.}

[0157] The compounds represented by the general formula (3) include C2F5OC2F5, C3F7OC3F7, C4F9OC4F9, and C6F 13 OC6F 13 , C2F5OCH3, C3F7OCH3, C4F9OCH3, C6F 13 OCH3, C2F5OCH5, C3F7OCH5, C4F9OC2H5, C2F5CF(OCH3)C3F7, CF3CH2OCF2CF2H, CHF2CF2OCH2CF3, CHF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CHF2, CF3CH2OCF2CHFCF3, and C3HF6CH(CH3)OC3HF6, among which at least one compound is preferably selected.

[0158] The content of the acyclic fluorine-containing ether is preferably 0.1% by mass or more and 3% by mass or less, and more preferably 0.3% by mass or more and 2.5% by mass or less, based on the total amount of the nonaqueous electrolyte solution. When the content of the acyclic fluorine-containing ether is 0.1% by mass or more, the stability of the nonaqueous electrolyte solution against oxidative decomposition is improved, and capacity deterioration at high temperatures can be suppressed. Furthermore, when aluminum foil is used as the positive electrode current collector of a nonaqueous alkaline storage element, a highly corrosion-resistant fluorine-containing protective coating is formed on the surface of the positive electrode current collector, preventing aluminum from eluting into the nonaqueous electrolyte solution and suppressing deterioration of the nonaqueous electrolyte solution. On the other hand, when the content of the acyclic fluorine-containing ether is 3% by mass or less, the solubility of the electrolyte salt is maintained well, and the ionic conductivity of the nonaqueous electrolyte solution can be maintained high, thereby enabling the development of advanced input / output characteristics. The acyclic fluorine-containing ethers may be used alone or in combination of two or more.

[0159] <Cyclic phosphazene> Examples of cyclic phosphazenes include ethoxypentafluorocyclotriphosphazene, diethoxytetrafluorocyclotriphosphazene, and phenoxypentafluorocyclotriphosphazene, and it is preferable to use at least one selected from these.

[0160] The content of cyclic phosphazene in the non-aqueous electrolyte is preferably 0.5% by mass or more and 20% by mass or less, based on the total amount of the non-aqueous electrolyte. If this value is 0.5% by mass or more, it is possible to suppress decomposition of the non-aqueous electrolyte at high temperatures and suppress gas generation. On the other hand, if this value is 20% by mass or less, it is possible to suppress a decrease in the ionic conductivity of the non-aqueous electrolyte and maintain high input / output characteristics. The content of cyclic phosphazene is more preferably 2% by mass or more and 15% by mass or less, and even more preferably 4% by mass or more and 12% by mass or less.

[0161] These cyclic phosphazenes may be used alone or in combination of two or more.

[0162] <Fluorine-containing cyclic carbonate> The fluorine-containing cyclic carbonate is preferably selected from fluoroethylene carbonate (FEC) and difluoroethylene carbonate (dFEC) from the viewpoint of compatibility with other non-aqueous solvents.

[0163] The content of the fluorine atom-containing cyclic carbonate is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the fluorine atom-containing cyclic carbonate is 0.5% by mass or more, a high-quality coating can be formed on the negative electrode, and by suppressing the reductive decomposition of the non-aqueous electrolyte solution on the negative electrode, an energy storage device with high high-temperature storage durability can be obtained. Furthermore, when aluminum foil is used as the positive electrode current collector of a non-aqueous alkaline energy storage device, a highly corrosion-resistant fluorine-containing protective coating is formed on the surface of the positive electrode current collector, preventing the aluminum from leaching into the non-aqueous electrolyte solution and suppressing deterioration of the non-aqueous electrolyte solution. On the other hand, when the content of the fluorine atom-containing cyclic carbonate is 10% by mass or less, the solubility of the electrolyte salt can be maintained well, and the ionic conductivity of the non-aqueous electrolyte solution can be maintained high, thereby enabling the development of high-level input / output characteristics. The above-mentioned fluorine atom-containing cyclic carbonates may be used alone or in combination of two or more.

[0164] <Cyclic carbonate> Of the cyclic carbonates, vinylene carbonate is preferred.

[0165] The content of the cyclic carbonate is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. If the content of the cyclic carbonate is 0.5% by mass or more, a high-quality coating can be formed on the negative electrode, and reductive decomposition of the non-aqueous electrolyte solution on the negative electrode can be suppressed, thereby obtaining an energy storage device with high high-temperature storage durability. On the other hand, if the content of the cyclic carbonate is 10% by mass or less, the solubility of the electrolyte salt can be maintained well and the ionic conductivity of the non-aqueous electrolyte solution can be maintained high, making it possible to exhibit high input / output characteristics.

[0166] <Cyclic carboxylic acid ester> Examples of cyclic carboxylic acid esters include gamma-butyrolactone, gamma-valerolactone, gamma-caprolactone, and epsilon-caprolactone, and it is preferable to use one or more selected from these. Among these, gamma-butyrolactone is particularly preferable from the viewpoint of improving the battery characteristics due to the improvement in the degree of lithium ion dissociation.

[0167] The content of the cyclic carboxylic acid ester is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. If the content of the cyclic acid anhydride is 0.5% by mass or more, a high-quality coating can be formed on the negative electrode, and by suppressing reductive decomposition of the non-aqueous electrolyte solution on the negative electrode, a storage element with high high-temperature storage durability can be obtained. On the other hand, if the content of the cyclic carboxylic acid ester is 15% by mass or less, the solubility of the electrolyte salt can be maintained well and the ionic conductivity of the non-aqueous electrolyte solution can be maintained high, making it possible to exhibit high input / output characteristics. The above-mentioned cyclic carboxylic acid esters may be used alone or in combination of two or more.

[0168] <Cyclic acid anhydride> The cyclic acid anhydride is preferably one or more selected from succinic anhydride, maleic anhydride, citraconic anhydride, and itaconic anhydride. Of these, succinic anhydride and maleic anhydride are preferred because they are readily available industrially, thereby reducing the production cost of the non-aqueous electrolyte solution, and they are easily soluble in the non-aqueous electrolyte solution.

[0169] The content of the cyclic acid anhydride is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total amount of the non-aqueous electrolyte solution. If the content of the cyclic acid anhydride is 0.5% by mass or more, a high-quality coating can be formed on the negative electrode, and the reductive decomposition of the non-aqueous electrolyte solution on the negative electrode can be suppressed, thereby obtaining a storage element with high high-temperature storage durability. On the other hand, if the content of the cyclic acid anhydride is 15% by mass or less, the solubility of the electrolyte salt can be maintained well, and the ionic conductivity of the non-aqueous electrolyte solution can be maintained high, thereby enabling the development of high-level input / output characteristics. The above-mentioned cyclic acid anhydrides may be used alone or in combination of two or more.

[0170] <Separator> The positive electrode precursor and the negative electrode are stacked with a separator interposed therebetween, or are stacked and wound together, to form an electrode stack or an electrode wound body having the positive electrode precursor, the separator, and the negative electrode.

[0171] As the separator, separators used in lithium ion secondary batteries, electric double layer capacitors, lithium ion capacitors, etc. can be suitably used.

[0172] The separator in the present disclosure is preferably a separator containing at least one selected from the group consisting of polyolefin, cellulose, and aramid resin. Examples of the separator in the present disclosure include a separator containing a polyolefin microporous membrane, a separator that is a laminate having a film made of inorganic fine particles on at least one surface of a polyolefin microporous membrane, a separator that is a laminate having a coating layer containing an aramid resin on at least one surface of a polyolefin microporous membrane, and a separator that contains cellulose nonwoven paper.

[0173] Examples of polyolefins include polyethylene, polypropylene, etc. The separator may contain organic or inorganic fine particles inside.

[0174] <<Non-aqueous lithium storage element and manufacturing method thereof>> A nonaqueous lithium storage element generally comprises a positive electrode, a negative electrode, a separator, an electrolyte, and an exterior body as its main components. The electrolyte is an organic solvent in which a lithium salt is dissolved (hereinafter referred to as a nonaqueous electrolyte). The method for producing a nonaqueous lithium storage element of the present disclosure relates to a nonaqueous lithium storage element configured by housing an electrode stack or an electrode wound body, which will be described later, in an exterior body together with the nonaqueous electrolyte.

[0175] <Secondary drying of electrodes> The residual solvent in the positive electrode precursor and the negative electrode can be further reduced by secondary drying. Secondary drying is preferably performed using methods such as hot air drying, infrared (IR) drying, and vacuum drying. Far-infrared drying, hot air drying, and vacuum drying are more preferred, and a combination of multiple drying methods may also be used. Secondary drying may be performed at a single temperature or at multiple stages with varying temperatures. Hot air drying and infrared (IR) drying can be performed using a roll-to-roll method, eliminating the need to individually transport long electrodes and improving mass productivity. Infrared (IR) drying allows for efficient drying in a short time because energy radiated from a heat source is directly directed toward the material to be dried, rather than heat transfer through the atmosphere as in convection. The drying oven does not need to be filled with air; it can easily be filled with an inert gas to prevent oxidation of the material to be dried. To prevent oxidation and eliminate potential flammable or explosive elements, it is preferable to maintain the oxygen concentration in the drying oven below 20% by supplying and exhausting an inert gas. In addition, in the case of vacuum drying, the boiling point of the solvent decreases under reduced pressure, accelerating the evaporation rate. -5 The pressure is preferably from 0.1 Pa to 10 Pa, and more preferably from 0.1 Pa to 10 Pa. -5 If the pressure is 1000 Pa or higher, the cost of the equipment can be reduced. On the other hand, if the pressure is 1000 Pa or lower, the boiling point of the solvent is lowered and the evaporation rate is sufficiently accelerated, allowing for efficient drying.

[0176] The secondary drying temperature of the positive electrode precursor is preferably 60°C or higher and 250°C or lower, more preferably 65°C or higher and 240°C or lower, and even more preferably 70°C or higher and 235°C or lower. If the drying temperature is 60°C or higher, the solvent remaining in the positive electrode active material layer can be efficiently reduced. On the other hand, if the drying temperature is 250°C or lower, sliding off of the positive electrode active material layer due to embrittlement of the binder can be suppressed.

[0177] The secondary drying temperature for the negative electrode is preferably 60°C or higher and 200°C or lower, more preferably 65°C or higher and 190°C or lower, and even more preferably 70°C or higher and 180°C or lower. A drying temperature of 60°C or higher can efficiently reduce the amount of solvent remaining in the negative electrode active material layer. On the other hand, a drying temperature of 200°C or lower can suppress the sliding of the negative electrode active material layer due to embrittlement of the binder and the oxidation of the negative electrode current collector foil.

[0178] After secondary drying, the positive electrode precursor and the negative electrode are preferably stored in a dry environment with a dew point of −30° C. or less to avoid adsorption of moisture from the atmosphere.

[0179] <Measurement of remaining solvent amount> In the present disclosure, the residual solvent amount is a value determined by the following method. The positive electrode precursor and current collector are cut into 80 mm x 80 mm pieces and weighed using an electronic balance. The resulting measurements are designated as weights W1 [g] and W2 [g], respectively. Next, the front surface is heated and dried at 170°C for 5 minutes using a heat-dry moisture meter. If a positive electrode active material layer is applied to both sides, the back surface is also heated and dried at 170°C for 5 minutes. The heated and dried positive electrode precursor is transferred to an electronic balance, and its weight W3 [g] is recorded 10 seconds after the end of the heat-drying process. The residual solvent amount is calculated using the following formula: Residual solvent amount = {(W1-W3) / (W1-W2)} x 100 (%)

[0180] <Residual solvent amount> In the present disclosure, when the solvent is water, the residual solvent amount is preferably 0.0010% by mass or more and 7.0% by mass or less, and more preferably 0.005% by mass or more and 3.0% by mass or less. If it is 0.0010% by mass or more, the positive electrode active material layer will not peel off and will maintain a moderate strength. On the other hand, if it is 7.0% by mass or less, a good energy density can be obtained. Furthermore, when the solvent contains an organic solvent, the residual solvent amount is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 6% by mass or less. If it is 0.1% by mass or more, the positive electrode active material layer will not peel off and will maintain a moderate strength. On the other hand, if it is 10% by mass or less, a good energy density can be obtained.

[0181] <assembly> In the assembly process, typically, the positive electrode precursor and the negative electrode cut into sheets are stacked with a separator interposed therebetween to obtain an electrode laminate, and a positive electrode terminal and a negative electrode terminal are connected to the electrode laminate. Alternatively, the positive electrode precursor and the negative electrode are stacked with a separator interposed therebetween and wound to obtain an electrode wound body, and a positive electrode terminal and a negative electrode terminal are connected to the electrode wound body. The electrode wound body may be cylindrical or flat.

[0182] The method for connecting the positive electrode terminal and the negative electrode terminal is not particularly limited, but may be resistance welding, ultrasonic welding, or the like.

[0183] (Stored in an exterior body) The electrode laminate or electrode wound body is preferably housed in an exterior body such as a metal can or a laminate packaging material, and sealed with only one opening remaining. The method for sealing the exterior body is not particularly limited, and when a laminate packaging material is used, methods such as heat sealing and impulse sealing can be used.

[0184] (Dry) The electrode laminate or electrode wound body housed in the outer casing is preferably dried to remove the remaining solvent. The drying method is not limited, and drying by vacuum drying or the like is possible. The remaining solvent is preferably 1.5 mass % or less per mass of the positive electrode active material layer or the negative electrode active material layer. If the remaining solvent is 1.5 mass % or less, the self-discharge characteristics and cycle characteristics are less likely to deteriorate, which is preferable.

[0185] (pressurized) It is preferable to apply pressure from both sides of the exterior of the package containing the dried electrode laminate or electrode wound body in a direction perpendicular to the electrode surface. The pressure is 0.01 kgf / cm. 2 More than 1000kgf / cm 2 Preferably less than 0.01kgf / cm 2 More than 100kgf / cm 2 Less than 0.01 kgf / cm is more preferable. 2 More than 30kgf / cm 2The following is even more preferred:

[0186] Pressure is 0.01kgf / cm 2 If the above conditions are met, distortions in the positive electrode precursor and the negative electrode are corrected by pressure, and the distance between the opposing positive electrode precursor and the negative electrode becomes uniform within the plane. This allows uniform doping within the plane in the lithium doping step, and improves durability, which is preferable.

[0187] Any tool capable of applying pressure may be used as a means for applying pressure from the outside of the exterior housing containing the dried electrode stack or electrode wound body. As an example, a pair of flat metal plates may be prepared, aligned with the surface of the electrode stack, and the four corners of the metal plates may be screwed together to apply pressure.

[0188] The pressure is measured using the surface pressure distribution measurement system I-SCAN (manufactured by Nitta Corporation). The sensor sheet used to measure the surface pressure preferably has an area that covers the entire pressure surface of the exterior body. For example, if the pressure surface is 60 mm long x 100 mm wide, an I-SCAN100 sensor (measurement surface dimensions: 112 mm x 112 mm) can be used. The sensor sheet is placed between the main surface of the exterior body and a pair of jigs that have a pressure surface. The maximum measurement pressure of the sensor sheet is preferably equal to or greater than the maximum pressure applied to the exterior body, but not greater than three times the maximum pressure. For example, if the maximum pressure applied to the exterior body is 5 kgf / cm 2 In this case, the maximum measurement pressure of the sensor sheet is 5kgf / cm 2 Above, 15kgf / cm 2 The following is preferable, so for example, the sensor sheet should be I-SCAN100(R) (maximum measurement pressure: 13 kgf / cm 2 It is preferable to use a sensor sheet having a maximum measurement pressure that is equal to or greater than the maximum pressure applied to the exterior body and is equal to or less than three times the maximum pressure, since this allows for accurate measurement of the in-plane pressure applied to the exterior body.

[0189] The number of sensors on the sensor sheet is preferably 400 points (20 points vertically × 20 points horizontally) or more, and more preferably 900 points or more (30 points vertically × 30 points horizontally). For example, when the pressure area S1 is 60 mm vertically × 100 mm horizontally (60 cm 2 ), I-SCAN100 sensor (measurement area S s :112mm×112mm=125.44cm 2 By applying the 1936 sensor points, the number of sensors used on the entire pressure surface is S1 / S s × 1936 points = 926 points, which is preferable.

[0190] In this specification, the unit of pressure is kgf / cm 2 is used as an example, but any unit that indicates pressure may be used, such as Pa, mmHg, Bar, or atm.

[0191] The data obtained by I-SCAN as described above is not used as data for evaluating pressure unevenness within the surface, as it is easy to detect excessive pressure unrelated to the actual pressure applied at the edges and corners of the jig due to the influence of burrs on the jig. Specifically, of the total pressure data measured within the pressure surface, three points of data on the four sides are not used as data. For example, if the data within the pressure surface is 44 vertical points x 30 horizontal points, the first three-point row and the last three-point row are deleted from the 44 vertical points, and the first three-point column and the last three-point column are deleted from the 30 horizontal points, and the pressure distribution within the surface is obtained using this data. The average value P of the obtained pressure distribution is avg Equation (4) is the pressure applied to the exterior body.

[0192]

number

[0193] <Injection, impregnation, and sealing processes> After the assembly process is completed, the nonaqueous electrolyte solution is poured into the electrode stack or electrode winding housed in the outer casing. The pouring method can be a method of pouring the electrode stack or electrode winding under atmospheric pressure or reduced pressure, with pouring under reduced pressure being preferred. By pouring under reduced pressure, the time required for the pouring process can be shortened, improving production efficiency. Furthermore, the positive electrode, negative electrode, and separator can be uniformly impregnated with the nonaqueous electrolyte solution.

[0194] When at least a portion of the positive electrode, negative electrode, and separator is not immersed in a nonaqueous electrolyte solution, the lithium compounds present in the portion of the positive electrode precursor not immersed in the nonaqueous electrolyte solution, or in the portion of the negative electrode not immersed in the nonaqueous electrolyte solution and the portion of the positive electrode precursor facing the separator remain undecomposed during the lithium doping process described below. As a result, when a storage device in which the nonaqueous electrolyte solution has sufficiently penetrated into the pores of the positive electrode, negative electrode, and separator is exposed to high temperature and high voltage, a decomposition reaction of the lithium compounds occurs, generating gas. Furthermore, since the doping proceeds unevenly, in-plane doping spots and localized Li precipitation occur, resulting in increased resistance, reduced durability, and reduced yield of the resulting nonaqueous lithium storage device. Examples of storage devices in which the nonaqueous electrolyte solution has sufficiently penetrated into the pores of the positive electrode, negative electrode, and separator include completed storage devices and storage devices that have been used for a long time.

[0195] The injection is preferably carried out under reduced pressure of -10 kPa to -1000 kPa, more preferably -50 kPa to -300 kPa, based on normal atmospheric pressure. Injecting the solution in an environment of -10 kPa or less based on normal atmospheric pressure allows the positive electrode, negative electrode, and separator to be uniformly impregnated with the nonaqueous electrolyte solution. On the other hand, an environment of -1000 kPa or more suppresses evaporation of the nonaqueous solvent in the electrolyte solution during injection, preventing changes in the composition of the nonaqueous electrolyte solution and stabilizing the characteristics of the resulting nonaqueous lithium storage element.

[0196] The temperature of the nonaqueous electrolyte solution during injection is preferably 5°C to 60°C, more preferably 15°C to 45°C. If the temperature of the nonaqueous electrolyte solution during injection is 5°C or higher, the viscosity of the nonaqueous electrolyte solution can be prevented from increasing, and the positive electrode, negative electrode, and separator can be uniformly impregnated with the nonaqueous electrolyte solution. On the other hand, if the temperature of the nonaqueous electrolyte solution during injection is 60°C or lower, evaporation of the nonaqueous solvent in the nonaqueous electrolyte solution during injection can be prevented, and changes in the composition of the nonaqueous electrolyte solution can be prevented, thereby stabilizing the characteristics of the resulting nonaqueous lithium storage element.

[0197] After the injection step, it is desirable to further perform impregnation so that the positive electrode, negative electrode, and separator are sufficiently immersed in the nonaqueous electrolyte. The impregnation method is not particularly limited, but for example, a method can be used in which the electrode laminate or electrode wound body after injection is placed in a reduced pressure chamber with the outer casing open, the chamber is reduced in pressure using a vacuum pump, and the pressure is returned to atmospheric pressure. After the injection step and the impregnation step, if a laminate packaging material is used, the electrode laminate or electrode wound body with the outer casing open is sealed while being reduced in pressure to be sealed. If a metal can is used, a sealing method such as welding or crimping is used.

[0198] <Re-pressurization> After the injection, it is preferable to increase the pressure applied from the outside of the exterior body. The pressure is 0.1 kgf / cm 2 More than 1000kgf / cm 2 Less than 0.5kgf / cm is preferable. 2 More than 100kgf / cm 2 Less than 1kgf / cm is more preferable. 2 More than 10kgf / cm 2 The following is even more preferred:

[0199] Pressure is 0.1kgf / cm 2 When the pressure is 1000 kgf / cm or more, distortions in the positive electrode precursor and the negative electrode are corrected by the pressure, and the distance between the opposing positive electrode precursor and the negative electrode becomes uniform within the plane, so that lithium doping is uniform within the plane during the lithium doping step, and durability is improved, which is preferable. 2If the pressure is less than this, excessive pressure is not applied to the electrode laminate or the electrode wound body, and the constituent materials, that is, the positive electrode precursor, the negative electrode, and the separator, are not damaged, which is preferable.

[0200] <Doping process> A preferred operation of lithium doping is to apply a voltage between the positive electrode precursor and the negative electrode, decompose the lithium compound in the positive electrode precursor to release lithium ions, and reduce the lithium ions at the negative electrode, thereby pre-doping the negative electrode active material layer with liolium ions. Specifically, a method can be used in which a constant current is applied at the beginning of lithium doping to increase the voltage, and after reaching a desired voltage, a constant voltage is applied.

[0201] The voltage applied during lithium doping at a constant voltage is preferably 4.4 V or more and 4.8 V or less, and more preferably 4.4 V or more and 4.6 V or less. A voltage of 4.4 V or more applied during lithium doping is preferable because the lithium compound contained in the positive electrode precursor decomposes efficiently and lithium is released into the non-aqueous electrolyte. A voltage of 4.8 V or less is preferable because the withstand voltage of the separator exceeds the potential difference between the positive and negative electrodes, and micro-short circuits can be suppressed by lithium doping.

[0202] The current value at a constant current applied to the positive and negative electrodes during lithium doping is preferably 1 C or more and 10 C or less, and more preferably 1 C or more and 30 C or less, calculated at a C rate. A current value of 1 C or more is preferred because lithium doping can be carried out quickly, improving workability. A current value of 30 C or less is preferred because overvoltage is not applied to the positive electrode precursor, suppressing corrosion of the positive electrode current collector.

[0203] The temperature of the exterior body during lithium doping is preferably 30°C or higher and 70°C or lower, and more preferably 30°C or higher and 55°C or lower. A temperature of 30°C or higher is preferable because the lithium compound contained in the positive electrode precursor decomposes efficiently and lithium can be released into the nonaqueous electrolyte solution. A temperature of 70°C or lower is preferable because decomposition of the nonaqueous electrolyte solution can be suppressed and the resistance of the nonaqueous lithium-type storage element can be reduced.

[0204] The time for lithium doping is preferably 0.25 hours or more and 24 hours or less, and more preferably 0.5 hours or more and 4 hours or less. If the time for lithium doping is 0.25 hours or more, lithium doping can be carried out quickly, which is preferable, and workability can be improved. If the time for lithium doping is 24 hours or less, decomposition of the nonaqueous electrolyte can be suppressed, which can reduce the resistance of the nonaqueous lithium-type storage element, which is preferable.

[0205] During lithium doping, gases such as CO2 are generated due to the oxidative decomposition of the lithium compound in the positive electrode precursor. Therefore, when applying a voltage, it is preferable to take measures to release the generated gas to the outside of the exterior body. Examples of such measures include a method of applying a voltage with a part of the exterior body open; a method of applying a voltage with an appropriate gas release means, such as a gas vent valve or a gas permeable film, previously installed in a part of the exterior body; etc.

[0206] <Charge / discharge cycle process> The electrode laminate or electrode wound body is preferably subjected to a charge-discharge cycle process in which it is repeatedly charged and discharged. The effects of the cycle process include: (1) repeated charge-discharge cycles allow cations, anions, and solvents coordinated to the anions in the nonaqueous electrolyte to enter and exit the pores of the positive electrode activated carbon, stabilizing unstable functional groups on the surface of the activated carbon (the positive electrode active material), thereby improving cycle durability; (2) exposing the positive electrode to a high potential completely decomposes lithium carbonate that was not completely decomposed during the doping process, thereby improving high-temperature storage durability; and (3) consuming by-products of the oxidative decomposition reaction of lithium carbonate generated during the doping process, thereby improving high-temperature storage durability. Because performing the cycle process under excessive load increases the resistance of nonaqueous lithium storage elements, the charge-discharge cycle process must be performed under appropriate conditions (e.g., temperature, voltage, and number of charge-discharge cycles).

[0207] The method of the charge-discharge cycle step is not particularly limited, but examples include a method in which the voltage of the nonaqueous lithium storage element is repeatedly charged and discharged within a target voltage range using a charging method typified by constant current charging, constant current / constant voltage charging, pulse charging, etc., or a discharging method typified by constant current discharging, constant current / constant voltage discharging, or pulse discharging.

[0208] There are no particular limitations on the current rate during constant current charging / discharging and pulse charging / discharging, but it is preferably 0.2 C or more and 50 C or less, based on the capacity at 4-2 V described below. If it is 0.2 C or more, the time required for charging / discharging can be shortened, thereby reducing the equipment load and improving production efficiency. If it is 50 C or less, the current distribution becomes uniform, so the above-mentioned effects of the cycle process can be significantly obtained.

[0209] The time for maintaining the constant voltage when using constant-current, constant-voltage charging is not particularly limited, but is preferably 0.5 minutes or more and 120 minutes or less. If it is 0.5 minutes or more, the above-mentioned effects of the cycle process can be significantly obtained. If it is 120 minutes or less, the time required for charging and discharging can be shortened, thereby reducing the equipment load and improving production efficiency.

[0210] In the charge-discharge cycle, charge and discharge are preferably performed within the range of the upper and lower voltage limits described below. The upper voltage limit is preferably 3.8V or higher and 4.8V or lower, more preferably 4.0V or higher and 4.7V or lower, and particularly preferably 4.1V or higher and 4.6V or lower. If the upper voltage limit is 3.8V or higher, the rate of increase in resistance after a high-temperature, high-load cycle test can be suppressed. If the upper voltage limit is 4.8V or lower, the nonaqueous lithium storage element can be maintained at low resistance. The lower voltage limit is preferably 1.5V or higher and 3.5V or lower, more preferably 1.6V or higher and 3.4V or lower, particularly preferably 1.7V or higher and 3.3V or lower, and most preferably 1.75V or higher and 3.0V or lower. If the lower voltage limit is 1.5V or higher, the elution of copper, which is the negative electrode current collector, can be suppressed, and the nonaqueous lithium storage element can be maintained at low resistance. If the lower voltage limit is 3.5V or lower, the rate of increase in resistance after a high-temperature, high-load cycle test can be suppressed.

[0211] The temperature in the charge-discharge cycle step is preferably 30°C or higher and 100°C or lower, more preferably 35°C or higher and 85°C or lower, and particularly preferably 35°C or higher and 75°C or lower. If the temperature is 30°C or higher, the rate of increase in resistance after a high-temperature, high-load cycle test can be suppressed. If the temperature is 100°C or lower, the resistance of the nonaqueous lithium storage element can be maintained at a low level, and the equipment load required for temperature increase can be suppressed, thereby improving production efficiency.

[0212] The number of cycles in the charge-discharge cycling step is preferably 1 to 10, more preferably 2 to 8. Conducting the cycle at least once has the effect of suppressing the rate of resistance increase after a high-temperature, high-load cycle test. Conducting the cycle at 10 or less allows the nonaqueous lithium storage element to maintain low resistance. Conducting the cycle at 10 or less also reduces the load on the necessary charge-discharge equipment, which is preferable from the standpoint of production efficiency.

[0213] In the charge-discharge cycle process, it is preferable to increase the pressure applied from the outside of the exterior body. 2 More than 1000kgf / cm 2 Less than 0.5kgf / cm is preferable. 2 More than 100kgf / cm 2 Less than 1kgf / cm is more preferable. 2 More than 10kgf / cm 2 The following is even more preferred:

[0214] Pressure is 0.1kgf / cm 2 When the pressure is 1000 kgf / cm or more, distortions in the positive electrode precursor and the negative electrode are corrected by the pressure, and the distance between the opposing positive electrode precursor and the negative electrode becomes uniform in the plane, so that the reaction in the charge-discharge cycle process proceeds uniformly, and durability under high temperature and high load cycles is improved, which is preferable. 2 If the thickness is less than this, a space for the non-aqueous electrolyte solution to penetrate into the electrode laminate or electrode wound body is ensured, and durability at high temperatures and high load cycles is improved, which is preferable.

[0215] <High-temperature aging process> The electrode stack or electrode wound body is preferably subjected to a high-temperature aging process in which it is heated. The effects of the aging process include (1) improving durability by decomposing the solvents and additives in the nonaqueous electrolyte and forming organic or inorganic coatings on the surfaces of the positive and negative electrodes, and (2) improving cycle durability by chemically stabilizing unstable functional groups on the surface of the activated carbon (the positive electrode active material) and impurities contained in the positive and negative electrodes, separator, and electrolyte. While organic and inorganic coatings improve high-temperature storage durability, the formation of excessive coatings increases the resistance of nonaqueous lithium-ion storage devices. Therefore, the high-temperature aging process must be performed under appropriate conditions (e.g., temperature, voltage, and time).

[0216] The method for the high-temperature aging step is not particularly limited, but examples include a method in which the voltage of the nonaqueous lithium storage element is adjusted to a target voltage by a charging method typified by constant current charging, constant current / constant voltage charging, pulse charging, etc., or a discharging method typified by constant current discharging, constant current / constant voltage discharging, or pulse discharging, and then charging and discharging are stopped and the element is stored in a high-temperature environment for a certain period of time.

[0217] The high-temperature aging process is (1) High-voltage storage step: This step includes adjusting the voltage of the nonaqueous lithium storage element precursor to a high voltage, and then adjusting the temperature of the aqueous lithium storage element precursor to 45°C or higher and 100°C or lower and storing the precursor. The voltage is preferably 4.03V or higher and 5.0V or lower, more preferably 4.05V or higher and 4.8V or lower, and particularly preferably 4.1V or higher and 4.5V or lower. If the voltage is 4.03V or higher, the rate of increase in resistance after a high-temperature, high-load cycle test can be suppressed. If the voltage is 5.0V or lower, excessive film formation can be prevented, thereby maintaining low resistance of the nonaqueous lithium storage element.

[0218] The high-temperature aging step may further include (2) a low-voltage step in addition to (1) a high-voltage step.

[0219] (2) Low-voltage storage step: This step involves adjusting the voltage of the nonaqueous lithium storage element precursor to a low voltage, and then adjusting the temperature of the aqueous lithium storage element precursor to 45°C or higher and 100°C or lower, and storing the precursor. The voltage is preferably 1.5V or higher and 2.8V or lower, more preferably 1.6V or higher and 2.7V or lower, and particularly preferably 1.7V or higher and 2.5V or lower. If the voltage is 2.8V or lower, the capacity retention rate after a high-temperature, high-load cycle test can be improved. If the voltage is 1.5V or higher, the elution of copper, which is the negative electrode current collector, can be suppressed, and low resistance can be maintained. The order of the high-voltage storage step and the low-voltage storage step is not particularly limited.

[0220] The temperature in the high-voltage storage step and the low-voltage storage step is preferably 45°C or higher and 100°C or lower, more preferably 50°C or higher and 85°C or lower, and particularly preferably 55°C or higher and 75°C or lower. A temperature of 45°C or higher has the effect of suppressing the rate of increase in resistance after a high-temperature, high-load cycle test and improving the capacity retention rate after a high-temperature, high-load cycle test. A temperature of 100°C or lower can maintain low resistance of the nonaqueous lithium storage element and can reduce the equipment load required for temperature increase, thereby improving production efficiency. The temperature may be constant during the aging step, or may be varied in multiple stages to produce a coating in stages or to form a uniform coating.

[0221] The aging time is preferably 0.25 to 340 hours, more preferably 0.5 to 100 hours, and most preferably 1 to 50 hours. Aging for 0.25 hours or longer has the effect of suppressing the rate of resistance increase after high-temperature, high-load cycle testing and improving the capacity retention rate after high-temperature, high-load cycle testing. Aging for 340 hours or shorter can maintain low resistance of the nonaqueous lithium storage element, and also reduces the time and number of facilities required for aging, thereby improving production efficiency.

[0222] In the aging process, it is preferable to increase the pressure applied from the outside of the exterior body. The pressure is 0.1 kgf / cm 2 More than 1000kgf / cm 2 Less than 0.5kgf / cm is preferable. 2 More than 100kgf / cm 2Less than 1kgf / cm is more preferable. 2 More than 10kgf / cm 2 The following is even more preferred:

[0223] Pressure is 0.1kgf / cm 2 When the pressure is 1000 kgf / cm or more, distortions in the positive electrode precursor and the negative electrode are corrected by the pressure, and the distance between the opposing positive electrode precursor and the negative electrode becomes uniform in the plane, so that the reaction in the high-temperature aging step proceeds uniformly, improving the durability under high-temperature and high-load cycles. 2 If the thickness is less than this, a space for the non-aqueous electrolyte solution to penetrate into the electrode laminate or electrode wound body is ensured, and durability at high temperatures and high load cycles is improved, which is preferable.

[0224] <Order of doping process, cycle process, and aging process> Regarding the order of performing the doping step, the cycling step, and the aging step, it is preferable to perform the doping step first. There are no particular restrictions on the order or number of times that the cycling step and the aging step are performed thereafter. The doping step may also be performed multiple times.

[0225] <Gas removal process> After the aging step, degassing may be further performed to completely remove gas remaining in the nonaqueous electrolyte, the positive electrode, and the negative electrode. Degassing improves durability. The degassing method is not particularly limited, but for example, a method can be used in which the electrode stack or the electrode wound body is placed in a reduced-pressure chamber with the outer casing open, and the chamber is reduced in pressure using a vacuum pump.

[0226] <Characteristics evaluation of non-aqueous lithium energy storage elements> (capacitance) In this specification, the capacitance Fa (F) is a value obtained by the following method. First, a cell corresponding to the nonaqueous lithium-type storage element is subjected to constant current charging at a current value of 20 C in a thermostatic chamber set at 25°C until the voltage reaches 4.0 V, and then constant voltage charging at a constant voltage of 4.0 V is performed for a total of 30 minutes. After that, the capacity when constant current discharging is performed at a current value of 2 C until the voltage reaches 2.0 V is defined as Q. Using the Q obtained here, Fa refers to a value calculated by the formula Fa = Q / (4.0 - 2.0).

[0227] (Electric energy) In this specification, the amount of electric energy E (Wh) is calculated by using the capacitance Fa (F) calculated by the method described above, and then multiplying it by Fa × (4.0 2 -2.0 2 ) / 2 / 3600.

[0228] (volume) The volume of the nonaqueous lithium-type storage element is not particularly specified, but refers to the volume of the part of the electrode laminate or electrode wound body where the region where the positive electrode active material layer and the negative electrode active material layer are stacked is enclosed by the exterior body.

[0229] For example, in the case of an electrode laminate or electrode wound body housed in a laminate film, the region of the electrode laminate or electrode wound body where the positive electrode active material layer and the negative electrode active material layer are present is housed in a cup-shaped laminate film, and the volume (V1) of this nonaqueous lithium-type storage element is calculated as V1 = l1 × w1 × t1, where V1 is the outer length (l1) and outer width (w1) of this cup-shaped portion, and the thickness (t1) of the nonaqueous lithium-type storage element including the laminate film.

[0230] In the case of an electrode laminate or electrode wound body housed in a prismatic metal can, the volume of the nonaqueous lithium-ion storage element is simply the volume of the metal can based on its external dimensions. That is, the volume (V2) of the nonaqueous lithium-ion storage element is calculated using the external length (l2), width (w2), and thickness (t2) of the prismatic metal can as V2 = l2 × w2 × t2.

[0231] Furthermore, even in the case of an electrode wound body housed in a cylindrical metal can, the volume of the nonaqueous lithium-ion storage element is the volume of the metal can based on its outer dimensions. That is, the volume (V3) of this nonaqueous lithium-ion storage element is calculated as V3 = 3.14 × r × r × l3, where r is the outer radius of the bottom or top surface of the cylindrical metal can, and l3 is the outer length.

[0232] (energy density) In this specification, energy density refers to the ratio of the quantity of electricity E to the volume V i (i=1, 2, 3) E / V i The energy density is a value obtained by the formula (Wh / L). From the viewpoint of achieving sufficient charge capacity and discharge capacity, the energy density is preferably 15 or more, more preferably 18 or more, and even more preferably 20 or more. When the energy density is equal to or more than the above lower limit, an energy storage element having excellent volumetric energy density can be obtained. Therefore, when an energy storage system using the energy storage element is used in combination with, for example, an automobile engine, it becomes possible to install the energy storage system in the limited, narrow space inside the automobile, which is preferable. (Normal temperature discharge internal resistance) In this specification, the room-temperature discharge internal resistance Ra (Ω) is a value obtained by the following method. First, a cell corresponding to the nonaqueous lithium-ion storage element is charged at a constant current of 20 C in a thermostatic chamber set at 25°C until the voltage reaches 4.0 V. Subsequently, a constant voltage of 4.0 V is applied and constant-voltage charging is performed for a total of 30 minutes. Next, a constant-current discharge is performed at a current of 20 C until the voltage reaches 2.0 V, and a discharge curve (time-voltage) is obtained. In this discharge curve, the voltage at the time of discharge time = 0 second, which is obtained by linearly extrapolating the voltage values ​​at the time points of 2 seconds and 4 seconds of discharge, is defined as Eo. The value Ra is calculated by the voltage drop ΔE = 4.0 - Eo and Ra = ΔE / (20 C (current value A)).

[0233] From the viewpoint of achieving sufficient charge and discharge capacities at large currents, the product Ra·Fa is preferably 2.0 or less, more preferably 1.0 or less. When Ra·Fa is equal to or less than the above upper limit, a nonaqueous lithium-ion battery element having excellent input / output characteristics can be obtained. Therefore, when a battery system using the nonaqueous lithium-ion battery element is combined with, for example, a high-efficiency engine, the nonaqueous lithium-ion battery element can adequately withstand the high loads applied thereto, which is preferable.

[0234] (High temperature and high voltage storage test) In this specification, the amount of gas generated during the high-temperature storage test and the room-temperature discharge internal resistance increase rate after the high-temperature storage test are measured using the following method. First, a cell corresponding to the nonaqueous lithium-ion storage element is charged at a constant current of 20 C in a thermostatic chamber set at 25°C until the voltage reaches 4.0 V, followed by 10 minutes of constant-voltage charging at 4.0 V. The cell is then stored in a 70°C environment, removed from the 70°C environment every week, charged to 4.0 V using the aforementioned charging process, and then stored again in a 70°C environment. This process is repeated, and the cell volume Va before the high-temperature, high-voltage storage test and the cell volume Vb two months after the storage test are measured using the Archimedes method. The capacitance value obtained for the cell before the high-temperature, high-voltage storage test using the measurement method described above in the "Capacitance" section is defined as the capacitance Fa before the high-temperature, high-voltage storage test. The amount of gas generated during the high-temperature, high-voltage storage test is defined as (Vb - Va) / Fa.

[0235] The amount of gas generated during a high-temperature, high-voltage storage test is preferably 0.05 cc / F or less, and more preferably 0.02 cc / F or less. If the amount of gas generated under the above conditions is equal to or less than the upper limit, there is no risk of the cell expanding due to gas generation, even if the device is exposed to high temperatures for a long period of time. Therefore, it is possible to obtain an energy storage element with sufficient safety and durability.

[0236] The capacitance value obtained for the cell before the high-temperature, high-voltage storage test using the measurement method described above in the "Capacitance" section is defined as the capacitance before the high-temperature, high-voltage storage test, Fa, and the capacitance value obtained for the cell after the high-temperature, high-voltage storage test using the measurement method described above in the "Capacitance" section is defined as the capacitance after the high-temperature, high-voltage storage test, Fb, where Fb / Fa is the capacity retention rate after the high-temperature, high-voltage storage test.

[0237] From the viewpoint of achieving sufficient capacity when exposed to a high-temperature environment for a long period of time, Fb / Fa is preferably 0.7 or more, and more preferably 0.9 or more. If Fb / Fa is equal to or more than the above lower limit, the device will have a longer life. [Example]

[0238] Examples and comparative examples of the present disclosure will be specifically described below, but the present disclosure is not limited to these.

[0239] <<Measurement and Evaluation Methods>> <Average particle size> The average particle size in the present disclosure refers to the particle size at the point where the cumulative curve is 50% when the total volume is set to 100% when the particle size distribution is measured using a particle size distribution analyzer (i.e., the 50% diameter (Median diameter)). This average particle size can be measured using a commercially available laser diffraction particle size distribution analyzer.

[0240] <Amount of lithium ions doped into negative electrode active material> The amount of lithium ions doped in the negative electrode active material of a nonaqueous lithium storage element according to the present disclosure at the time of shipment and after use can be determined, for example, as follows. First, the negative electrode active material layer is washed with ethyl methyl carbonate or dimethyl carbonate and air-dried. Then, an extract is obtained by extracting the negative electrode active material layer with a mixed solvent of methanol and isopropanol. This extraction is typically performed in an Ar box at an ambient temperature of 23°C. The amount of lithium contained in the extract and the negative electrode active material layer after extraction are quantified using, for example, an inductively coupled plasma mass spectrometry (ICP-MS), and the sum of these values ​​is calculated to determine the amount of lithium ions doped in the negative electrode active material. The obtained value is then assigned to the amount of negative electrode active material used in the extraction to calculate the numerical value in the above unit.

[0241] <Primary particle size> The primary particle diameter in the present disclosure can be obtained by photographing several fields of view of a powder using an electron microscope, measuring the particle diameters of approximately 2,000 to 3,000 particles in those fields of view using a fully automatic image processing device or the like, and taking the arithmetic average of these values ​​as the primary particle diameter.

[0242] <Degree of dispersion> In this disclosure, the degree of dispersion is a value determined by a dispersion evaluation test using a particle gauge as specified in JIS K5600. Specifically, a sufficient amount of sample is poured into the deep end of a particle gauge groove with a desired depth corresponding to the particle size, allowing it to slightly overflow the groove. Next, the long side of the scraper is placed parallel to the width of the gauge, with the cutting edge in contact with the deep end of the groove of the particle gauge. While holding the scraper so that it is on the surface of the gauge, the scraper is pulled across the surface of the gauge at a uniform speed perpendicular to the long side of the groove to a depth of 0 over 1 to 2 seconds. Within 3 seconds of completing the pull, the scraper is observed by shining light at an angle of 20° to 30°, and the depth at which the particles appear in the groove of the particle gauge is read.

[0243] Viscosity (ηb) and TI value The viscosity (ηb) and TI value in this disclosure are values ​​determined by the following methods: First, an E-type viscometer was used to measure the viscosity at a temperature of 25°C and a shear rate of 2 s -1 After measuring for more than 2 minutes under the above conditions, a stable viscosity (ηa) was obtained. Then, the shear rate was increased to 20 s -1 The viscosity (ηb) was measured under the same conditions as above, except that the shear rate was changed to . The TI value was calculated using the viscosity value obtained above using the formula TI value = ηa / ηb. -1 From the 20s -1 When increasing the shear rate, the increase may be made in one step, or the shear rate may be increased in multiple steps within the above range, while appropriately obtaining the viscosity at each shear rate.

[0244] <XPS measurement of composite powder materials> The composite powder material was placed on a dish-shaped sample holder of 2 mmφ×0.3 mmD and subjected to XPS measurement under the following conditions. Equipment used: Thermofuser ESCALAB250 Excitation source: Monochromated AlKα 15kV x 10mA Analysis size: Approximately 1 mm (oval shape) Photoelectron acceptance angle: 0° (the axis of the spectrometer is perpendicular to the sample surface)

[0245] Capture Area Survey scan: 0 to 1,100 eV Narrow scan: Li1s, O1s, C1s For the Li 1s spectrum, data was acquired 100 times to ensure an S / N of 5 or higher, allowing curve fitting.

[0246] Pass Energy Survey scan: 100 eV Narrow scan: 20 eV Energy step Survey scan: 1 eV Narrow scan: 0.1 eV

[0247] Data import time Survey scan: 50ms / step Narrow scan: 100ms / step

[0248] Neutralization Conditions Unit: E401 Auxiliary Neutralization: None Filament current: 3.2A Emission Current: Flow

[0249] Peak position correction The observed peak positions were corrected based on the C1s (284.6 eV) of the carbon material.

[0250] Curve fitting of the Li1s spectrum Using the data processing function of the instrument's software (Avantage 5.927), a curve fit was performed on the Li1s spectrum obtained in the charge neutralization-off measurement after charge correction. The peak area A (unit: cps·eV) of the 56 eV component, the peak area B (unit: cps·eV) of the 58 eV component, and A / (A+B) were derived. The curve fit was performed under the following constraints (1) to (5): (1) the number of components was two (56 eV and 58 eV), (2) the energy difference between the 56 eV and 58 eV components was 2.8 eV, (3) the difference in full width at half maximum (FWHM) between the 56 eV and 58 eV components was 0.86 eV, (4) both the 56 eV and 58 eV components were symmetric, and (5) the Gaussian / Lorentzian ratio for both the 56 eV and 58 eV components was 30% Lorentzian.

[0251] More specifically, Figure 1 shows an example of a curve fit performed on the Li1s spectrum (solid line) obtained in the charge neutralization-off measurement in Example 4 after charge correction. The dashed line indicates the composite function obtained by fitting. The peak area A (unit: cps·eV) of the 56 eV component is the area enclosed by the baseline (two-dot chain line) and the right-hand peak (20) indicated by the dashed-dotted line. The peak area B (unit: cps·eV) of the 58 eV component is the area enclosed by the baseline (two-dot chain line) and the left-hand peak (10) indicated by the dashed-dotted line.

[0252] <Measurement of pore volume in composite powder materials> Measurement equipment: Autosorb-iQ2 (Anton Paar Japan Co., Ltd.) was used to dry a composite powder material sample in a glass cell, a 9 mm glass cell / large sphere (hereinafter referred to as the cell) at 100°C for 10 hours, and then its weight was measured. Next, the composite powder material was placed in the cell. Using a vacuum drying device, the cell with the sample placed in it was vacuum dried at 250°C for 3 hours. After drying, the weight of the cell was measured, and it was then set in the measurement device to measure the amount of gas adsorption. During the measurement, N2 gas was used as the adsorbate, and a relative pressure of 1 x 10 ―7 Measurements were performed at 101 points (adsorption: 61 points, desorption: 40 points) in the range of 1 to 1. The cumulative pore volume distribution was obtained using the QSDFT method for the adsorption isotherm. The cumulative pore volume Z (cc) for pores with a diameter of 2 nm was obtained by subtracting the cumulative pore volume for pores with a diameter of 2 nm from the cumulative pore volume for pores with a diameter of 35 nm. The pore volume V (cc / g) per unit weight of the carbon material was calculated using the equation V = Z ÷ (W × m / 100), where Z (cc) is the pore volume for pores with a diameter of 2 nm to 35 nm in the composite powder material (W (g)) and m1 (wt%) is the weight ratio of the carbon material in the composite powder material.

[0253] <Characteristics evaluation of non-aqueous lithium energy storage elements> (Normal temperature discharge internal resistance (Ra·Fa)) The obtained energy storage element was charged at a constant current of 20 C using a charge / discharge device (5 V, 360 A) manufactured by Fujitsu Telecom Networks Limited in a thermostatic chamber set at 25° C. until the voltage reached 4.0 V, and then constant voltage charging was performed for a total of 30 minutes by applying a constant voltage of 4.0 V. The capacitance when constant current discharge was performed at a current of 2 C to 2.0 V was defined as Q, and the electrostatic capacitance Fa was calculated by Fa = Q / (4.0 - 2.0).

[0254] Next, the resulting energy storage device was charged at a constant current of 20 C using a charge / discharge device (5 V, 360 A) manufactured by Fujitsu Telecom Networks Limited in a thermostatic chamber set at 25°C until the voltage reached 4.0 V. This was followed by a constant-voltage charge of 4.0 V for a total of 30 minutes, followed by a constant-current discharge at 20 C until the voltage reached 2.0 V. A discharge curve (time-voltage) was obtained. The voltage at 0 seconds of discharge, obtained by linearly extrapolating the voltage values ​​at 2 and 4 seconds of discharge, was defined as Eo. The room-temperature discharge internal resistance Ra was calculated using the voltage drop ΔE = 4.0 - Eo and R = ΔE / (20 C (current value A)). The room-temperature discharge internal resistance was calculated as Ra·Fa, the product of capacitance Fa and room-temperature discharge internal resistance Ra.

[0255] (High temperature storage durability test) In this specification, the amount of gas generated during the high-temperature storage test and the rate of increase in room-temperature discharge internal resistance after the high-temperature storage test were measured by the following method.

[0256] First, the resulting energy storage device was charged at a constant current of 20 C in a thermostatic chamber set at 25°C until the voltage reached 4.0 V, followed by 10 minutes of constant-voltage charging at 4.0 V. The cell was then stored in a 70°C environment, removed from the 70°C environment every week, and charged to 4.0 V using the charging process described above. The cell was then stored again in a 70°C environment. This process was repeated, and the cell volume Va before the high-temperature, high-voltage storage test and the cell volume Vb after two months of storage were measured using the Archimedes method. The capacitance value of the cell before the high-temperature, high-voltage storage test, measured using the measurement method described above in the "Room-Temperature Discharge Internal Resistance" section, was used as the capacitance Fa before the high-temperature, high-voltage storage test. The amount of gas generated during the high-temperature, high-voltage storage test was calculated using the formula (Vb - Va) / Fa.

[0257] The capacitance value obtained for the cell before the high-temperature, high-voltage storage test using the measurement method described above in the section "Room-temperature discharge internal resistance" was defined as the capacitance before the high-temperature, high-voltage storage test, Fa. The capacitance value obtained for the cell after the high-temperature, high-voltage storage test using the measurement method described above in the section "Room-temperature discharge internal resistance" was defined as the capacitance after the high-temperature, high-voltage storage test, Fb. The capacity retention rate after the high-temperature, high-voltage storage test was calculated from Fb / Fa.

[0258] <Preparation of carbon material> [Preparation of activated carbon 1] The crushed coconut shell carbonized material was placed in a small carbonization furnace and carbonized at 500°C for 6 hours under a nitrogen atmosphere to obtain a carbonized material. The obtained carbonized material was placed in an activation furnace, and steam heated in a preheating furnace was introduced into the furnace at 1 kg / h. The temperature was raised to 1000°C over 6 hours to activate the material. After activation, the carbonized material was removed and cooled under a nitrogen atmosphere to obtain activated activated carbon. The obtained activated activated carbon was washed with water for 10 hours, drained, dried for 10 hours in an electric dryer maintained at 115°C, and then pulverized in a ball mill for 1 hour to obtain activated carbon 1.

[0259] The pore size distribution of activated carbon 1 was measured using a pore size distribution analyzer Autosorb-iQ2 (Anton Paar Japan Co., Ltd.). As a result, the pore volume V of 2 to 35 nm was found to be 0.30 cc / g.

[0260] [Preparation of activated carbon 2] The phenolic resin was placed in a calcination furnace and carbonized at 600°C for 2 hours under a nitrogen atmosphere. The resulting carbonized material was then crushed in a ball mill and classified to obtain a carbonized material with an average particle size of 7 μm. The resulting carbonized material was mixed with KOH in a mass ratio of 1:5, placed in a calcination furnace, and activated by heating at 780°C for 0.5 hours under a nitrogen atmosphere. The activated carbonized material was removed and washed with stirring in dilute hydrochloric acid adjusted to a concentration of 2 mol / L for 1 hour. It was then boiled and washed with distilled water until the pH stabilized between 5 and 6, and then dried to obtain activated carbon 2.

[0261] The pore size distribution of activated carbon 1 was measured using a pore size distribution analyzer Autosorb-iQ2 (Anton Paar Japan Co., Ltd.). As a result, the pore volume V of 2 to 35 nm was found to be 0.27 cc / g.

[0262] [Preparation of mesoporous carbon] Mesoporous carbon was prepared using SBA-15 (synthesized by the sol-gel method; K. Miyazawa and S. Inagaki, "Control of the microporosity within the pore walls of ordered mesoporous silica SBA-15", Chem. Commun., p. 2121, (2000)) as the mesoporous silica and sucrose as the carbon source, according to a method known from S. Jun J Am Chem Soc 2000 122 10712. Hydrofluoric acid was used to remove the silica.

[0263] [Carbon black] As carbon black, EC600JD manufactured by Lion Specialty Chemicals Co., Ltd. was prepared.

[0264] <<Preparation of negative electrode>> 83 parts by mass of artificial graphite with an average particle size of 4.5 μm, 4 parts by mass of composite carbon material, and 9 parts by mass of acetylene black were dry-blended in powder form in a planetary mixer, to which 2 parts by mass of styrene-butadiene copolymer and an aqueous CMC (carboxymethyl cellulose) solution were added, and the solid content was gradually reduced while dispersing. Finally, 2 parts by mass of CMC was added, and water was added to the mixed solution so that the solid content was 39% by mass, to obtain a negative electrode coating solution.

[0265] The viscosity (ηb) and TI value of the resulting negative electrode coating solution were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. The viscosity (ηb) was 3,221 mPa·s and the TI value was 2.1.

[0266] Using a die coater manufactured by Toray Engineering Co., Ltd., the negative electrode coating solution was applied to both sides of a 10 μm thick electrolytic copper foil at a coating speed of 1 m / s until the negative electrode active material layer had a weight of 40 g / m on both sides. 2 The negative electrode was obtained by drying at a drying temperature of 60°C, and then pressed using a roll press under conditions of a pressure of 5 kN / cm and a surface temperature of the press part of 25°C.

[0267] <Preparation of Electrolyte> As the organic solvent, a mixed solvent of ethylene carbonate (EC): dimethyl carbonate (DMC): methyl ethyl carbonate (EMC) = 34:44:22 (volume ratio) was used, and the concentration ratio of LiN(SO2F)2 and LiPF6 to the total non-aqueous electrolyte solution was 10:90 (molar ratio), and the sum of the concentrations of LiN(SO2F)2 and LiPF6 was 1.2 mol / L. The concentrations of LiN(SO2F)2 and LiPF6 in the non-aqueous electrolyte solution prepared here were 0.12 mol / L and 1.08 mol / L, respectively.

[0268] Example 1 <Materials and weight ratios used in composite powder materials> Activated carbon 1 was used as the carbon material, and lithium carbonate with an average particle size of 2 μm was used. When the weight of the carbon material was M1 and the weight of the lithium carbonate was M2, the powders were mixed in advance at a weight ratio of M2 / M1 = 0.5.

[0269] <Combination treatment method> The materials to be used for the composite powder material were packed into a ceramic container and placed in an electric furnace. After evacuating the furnace, the temperature was raised to 150°C at 5°C / min, then 2°C / min from 150°C, and then held at 740°C for 1 hour while carbon dioxide gas was flowing at 2 L / min. This heat treatment yielded a composite powder material of carbon material and lithium carbonate. When the peak area of ​​the 56 eV component is A and the peak area of ​​the 58 eV component is B, A / (A+B) = 0.2. The volume of pores of 2 nm to 35 nm per unit weight of the carbon material, V, was 0.12 (cc / g).

[0270] <Production of Positive Electrode Precursor> 90.0 parts by mass of the composite powder material, 4.0 parts by mass of acetylene black, 3.5 parts by mass of acrylic latex, 1.5 parts by mass of CMC (carboxymethyl cellulose), 1.0 part by mass of PVP (polyvinylpyrrolidone), and distilled water were mixed so that the mass ratio of solids was 43.0%, and the mixture was dispersed for 2 minutes using a thin film swirling high-speed mixer "FILMIX (registered trademark)" manufactured by PRIMIX Corporation at a peripheral speed of 10 m / s to obtain a positive electrode coating solution.

[0271] Using a double-sided die coater manufactured by Toray Engineering Co., Ltd., the positive electrode coating solution was applied to both sides of a 15 μm thick aluminum foil at a coating speed of 1 m / s until the weight of the positive electrode active material layer on both sides was 90 g / m. 2 The positive electrode precursor was then pressed using a roll press under conditions of a pressure of 6 kN / cm and a surface temperature of the press part of 25°C.

[0272] <Production of non-aqueous lithium storage element> (Secondary drying of electrodes) The positive electrode precursor and negative electrode were dried roll-to-roll using far-infrared light at a temperature of 80°C, a drying time of 5 minutes, and an oxygen concentration of 1000 ppm in the drying oven. The positive electrode precursor emerging from the drying oven was wound up in a dry environment with a dew point of -45°C.

[0273] (Assembly process) The obtained positive electrode precursor was placed in a container with a positive electrode active material layer of 10.0 cm × 10.0 cm (100 cm 2 Then, the negative electrode 1 was cut into 20 pieces with a negative electrode active material layer of 10.1 cm × 10.1 cm (102 cm 2 ) size, cut out 21 pieces, 10.3cm x 10.3cm (106cm 2Forty polyethylene separators (manufactured by Asahi Kasei, thickness 10 μm) were prepared. These were stacked in the order of positive electrode precursor, separator, and negative electrode, with the outermost layer being negative electrode 1, so that the positive electrode active material layer and the negative electrode active material layer faced each other with the separator sandwiched between them, to obtain an electrode laminate. A positive electrode terminal and a negative electrode terminal were ultrasonically welded to the obtained electrode laminate, which was then placed in a container made of aluminum laminate packaging material, and the three sides including the electrode terminals were heat-sealed.

[0274] (Pressure process) The aluminum laminate packaging was sandwiched between a pair of metal plates (height 150 mm x width 150 mm x thickness 5 mm) from the outside, and pressure was applied by screwing the four corners of the metal plates. When the pressure was measured using the I-SCAN surface pressure distribution measurement system (manufactured by Nitta Corporation) and the I-SCAN100 sensor (measurement surface dimensions: 112 mm x 112 mm), the confining pressure was found to be 0.08 kgf / cm. 2 It was.

[0275] (Injection, impregnation, sealing process) The electrode stack housed in the aluminum laminate packaging material was placed in a vacuum chamber in a dry air environment with a temperature of 25°C and a dew point of -40°C or less, and the pressure was reduced from normal pressure to -100 kPa. After that, approximately 80 g of the nonaqueous electrolyte solution at a liquid temperature of 25°C was poured into the chamber. The pressure was then returned to normal pressure and the chamber was left standing for 60 minutes. Next, the nonaqueous lithium storage element was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at a pressure of 0.1 MPa at 180°C for 10 seconds under a reduced pressure of -95 kPa.

[0276] (Re-pressurization process) After the injection, the pressure was increased to 1.2 kgf / cm by further tightening the screws on the metal plate that held the non-aqueous lithium storage element. 2 I did.

[0277] (Lithium doping process) The resulting nonaqueous lithium-type energy storage element was subjected to initial charging using a charge / discharge tester (ACD-10APS(01)) manufactured by Asuka Electronics Co., Ltd., at a constant current of 6 mA in a 60°C environment until a voltage of 4.5 V was reached, followed by a constant voltage charge of 4.5 V for 1 hour, thereby doping the negative electrode with lithium. The total time required for lithium doping was 2 hours.

[0278] (Charge / discharge cycle process) Pressure: 1.2kgf / cm 2 The doped nonaqueous lithium storage element was placed in an environment of 30°C. (1) The battery was charged at a constant current of 10.0 A until the voltage reached 4.3 V, and then charged at a constant voltage of 4.3 V for 5 minutes. (2) A constant current discharge of 10.0 A was performed until the voltage reached 2.0 V, and then a constant voltage discharge of 2.0 V was performed for 5 minutes. (1) and (2) constitute one cycle, and a total of five cycles were performed.

[0279] (High temperature aging process) (1) High voltage storage process: 1.2 kgf / cm 2 The nonaqueous lithium storage element after the charge-discharge cycle process was subjected to constant current discharge at 10.0 A in a 25°C environment until the voltage reached 4.2 V, and then subjected to constant current charging at 4.2 V for 30 minutes to adjust the voltage to 4.2 V. Thereafter, the nonaqueous lithium storage element was stored in a thermostatic chamber at 60°C for 10 hours. (2) Low voltage storage process: 1.2 kgf / cm 2 The nonaqueous lithium storage element after the high-voltage storage step was subjected to constant current discharge at 10.0 A in a 25°C environment until the voltage reached 2.0 V, and then subjected to constant current charging at 2.0 V for 30 minutes to adjust the voltage to 2.0 V. Thereafter, the nonaqueous lithium storage element was stored in a thermostatic chamber at 60°C for 10 hours.

[0280] (gassing and sealing process) The aged nonaqueous lithium-ion storage element was placed in a dry air environment at a temperature of 25°C and a dew point of -40°C, and the aluminum laminate packaging was partially opened. The nonaqueous lithium-ion storage element was then placed in a vacuum chamber, and a KNF diaphragm pump (N816.3KT.45.18) was used to reduce the pressure from atmospheric pressure to -80 kPa over three minutes, and then the pressure was returned to atmospheric pressure over three minutes. This process was repeated three times. The nonaqueous lithium-ion storage element was then placed in a vacuum sealing machine, and the pressure was reduced to -90 kPa. The aluminum laminate packaging was then sealed at 200°C for 10 seconds at a pressure of 0.1 MPa. Through these processes, a nonaqueous lithium-ion storage element was completed.

[0281] <Evaluation of Energy Storage Element> The room-temperature discharge internal resistance of the obtained energy storage element, expressed as the product Ra·Fa of the capacitance Fa and the room-temperature discharge internal resistance Ra, was 0.63 ΩF. The amount of gas generated during the high-temperature, high-voltage storage test was calculated as (Vb-Va) / Fa and was 0.005 (cc / F). Furthermore, the capacity retention rate after the high-temperature, high-voltage storage test was calculated as Fb / Fa and was 0.79.

[0282] Examples 2 to 19 A nonaqueous lithium storage element was produced and evaluated in the same manner as in Example 1, except for the conditions shown in Table 1. The results are shown in Table 2. The XPS spectrum of Example 4 is shown in FIG.

[0283] Comparative Examples 1 to 4, 7 to 10, 13 to 16, and 19 A nonaqueous lithium storage element was produced and evaluated in the same manner as in Example 1, except for the conditions shown in Table 1. The results are shown in Table 2.

[0284] Comparative Examples 5, 11, and 17 A nonaqueous lithium storage element was produced and evaluated in the same manner as in Example 1, except for the conditions shown in Table 1 and the following [composite treatment method]. The results are shown in Table 2.

[0285] <Combination treatment method> The materials to be used for the composite powder material were placed in a sample container and then dry mixed at 1000 rpm for 10 minutes using a Thinky Mixer to obtain the composite powder material.

[0286] Comparative Examples 6, 12, and 18 A nonaqueous lithium storage element was produced and evaluated in the same manner as in Example 1, except for the conditions shown in Table 1 and the following [composite treatment method]. The results are shown in Table 2.

[0287] <Combination treatment method> The materials to be used for the composite powder material were placed in a sample container and then subjected to mechanochemical treatment using a bead mill for 1 hour to produce the composite powder material.

[0288] Example 20 A nonaqueous lithium storage battery element was produced and evaluated in the same manner as in Example 1, except for the conditions shown in Table 1 and the following <Materials and weight ratios used in the composite powder material>, <Compositing method>, and <Production of positive electrode precursor>. The results are shown in Table 2.

[0289] <Materials and weight ratios used in composite powder materials> The carbon materials used were activated carbon 1, carbon black, and lithium carbonate with an average particle size of 2 μm. The weight of the carbon materials (activated carbon 1 90 wt% and carbon black 10 wt%) was defined as M1, and the weight of the lithium carbonate as M2. The powders were mixed in advance at a weight ratio of M2 / M1 = 0.5.

[0290] <Combination treatment method> The materials to be used for the composite powder material were packed into a ceramic container and placed in an electric furnace. After evacuating the furnace, the temperature was raised to 150°C at 5°C / min, then 2°C / min from 150°C, and then held at 740°C for 1 hour while carbon dioxide gas was flowing at 2 L / min. This heat treatment produced a composite powder material of carbon material and lithium carbonate.

[0291] <Production of Positive Electrode Precursor> 90.0 parts by mass of the composite powder material, 4.0 parts by mass of acetylene black, 3.5 parts by mass of acrylic latex, 1.5 parts by mass of CMC (carboxymethyl cellulose), 1.0 part by mass of PVP (polyvinylpyrrolidone), and distilled water were mixed so that the mass ratio of solids was 43.0%, and the mixture was dispersed for 2 minutes using a thin film swirling high-speed mixer "FILMIX (registered trademark)" manufactured by PRIMIX Corporation at a peripheral speed of 10 m / s to obtain a positive electrode coating solution.

[0292] Using a double-sided die coater manufactured by Toray Engineering Co., Ltd., the positive electrode coating solution was applied to both sides of a 15 μm thick aluminum foil at a coating speed of 1 m / s until the weight of the positive electrode active material layer on both sides was 90 g / m. 2 The positive electrode precursor was then pressed using a roll press under conditions of a pressure of 6 kN / cm and a surface temperature of the press part of 25°C.

[0293] Comparative Example 20 A nonaqueous lithium storage battery element was produced and evaluated in the same manner as in Example 1, except for the conditions shown in Table 1 and the following <Materials and weight ratios used in the composite powder material>, <Compositing method>, and <Production of positive electrode precursor>. The results are shown in Table 2.

[0294] <Materials and weight ratios used in composite powder materials> Activated carbon 1, carbon black, and lithium carbonate with an average particle size of 2 μm were used as carbon materials.

[0295] When the weight of the carbon material (90 wt% activated carbon 1 and 10 wt% carbon black) is M1 and the weight of lithium carbonate is M2, the powders were mixed in advance at a weight ratio of M2 / M1 = 0.5.

[0296] <Combination treatment method> 90.0 parts by mass of the materials used for the composite powder material, 3.5 parts by mass of acrylic latex, 1.5 parts by mass of CMC (carboxymethyl cellulose), 1.0 part by mass of PVP (polyvinylpyrrolidone), and distilled water were mixed so that the mass ratio of solids was 43.0%, and the mixture was wet-dispersed for 2 minutes using a thin-film swirling high-speed mixer "Filmix (registered trademark)" manufactured by PRIMIX Corporation at a peripheral speed of 10 m / s to obtain a slurry, which was solidified by vacuum drying and pulverized to obtain a composite powder material.

[0297] <Production of Positive Electrode Precursor> 96.0 parts by mass of the composite powder material, 4.0 parts by mass of acetylene black, and distilled water were mixed so that the mass ratio of the solid content was 43.0%, and the mixture was dispersed for 2 minutes using a thin film rotary high-speed mixer "FILMIX (registered trademark)" manufactured by PRIMIX Corporation at a peripheral speed of 10 m / s to obtain a positive electrode coating solution.

[0298] Using a double-sided die coater manufactured by Toray Engineering Co., Ltd., the positive electrode coating solution was applied to both sides of a 15 μm thick aluminum foil at a coating speed of 1 m / s until the weight of the positive electrode active material layer on both sides was 90 g / m. 2 The positive electrode precursor was then pressed using a roll press under conditions of a pressure of 6 kN / cm and a surface temperature of the press part of 25°C.

[0299] [Table 1]

[0300] [Table 2]

[0301] The above examples verify that the composite powder material of a carbon material and lithium carbonate according to the present disclosure can realize a non-aqueous lithium energy storage element having excellent initial resistance and high-temperature storage durability.

[0302] The composite powder material of a carbon material and lithium carbonate according to the present disclosure has excellent initial resistance and high-temperature storage durability, and therefore can be used in at least one selected from the group consisting of an electricity storage module, a power regeneration assist system, a power load leveling system, an uninterruptible power supply system, a contactless power supply system, an energy harvesting system, a natural energy storage system, an electric power steering system, an emergency power supply system, an in-wheel motor system, an idling stop system, an electric vehicle, a plug-in hybrid vehicle, an electric motorcycle, a smart grid system, and a quick charging system. For example, the composite powder material can be suitably used in the field of hybrid drive systems in automobiles that combine an internal combustion engine or a fuel cell, a motor, and an electricity storage element, as well as for assisting instantaneous power peaks. [Explanation of symbols]

[0303] 10 58eV component 20 56eV component

Claims

1. A composite powder material containing a carbon material and lithium carbonate, In a Li1s spectrum obtained by X-ray photoelectron spectroscopy (XPS) of the composite powder material, when the peak area of ​​the 56 eV component is A and the peak area of ​​the 58 eV component is B, 0.2≦A / (A+B)≦0.9; The composite powder material has a pore volume V [cc / g] of 2 nm to 35 nm per unit weight of the carbon material, which is 0.01≦V≦0.

25.

2. The composite powder material of claim 1 , wherein the carbon material is activated carbon.

3. 3. The composite powder material according to claim 1, wherein, when a weight of the carbon material is M1 and a weight of the lithium carbonate is M2, 0.1≦M2 / M1≦2 is satisfied.

4. The composite powder material according to any one of claims 1 to 3, wherein 0.3≦A / (A+B)≦0.

7.

5. The composite powder material according to any one of claims 1 to 4, wherein 0.05≦V≦0.

15.

6. A positive electrode precursor having a positive electrode current collector and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector, A positive electrode precursor, wherein the positive electrode active material layer comprises the composite powder material according to any one of claims 1 to 5.

7. A method for producing a non-aqueous lithium storage element including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions, the method comprising: a coating solution containing the composite powder material according to any one of claims 1 to 5 and water or an organic solvent is applied to one or both surfaces of a positive electrode current collector to form a coating film, and the coating film is dried to obtain a positive electrode precursor; assembling an electric storage element including the positive electrode precursor, a negative electrode, a separator, and a non-aqueous electrolyte solution containing lithium ions, and applying a voltage between the positive electrode precursor and the negative electrode; A method for producing a non-aqueous lithium storage element, comprising:

8. 7. The positive electrode precursor according to claim 6, which is used in at least one selected from the group consisting of a power storage module, a power regeneration assist system, a power load leveling system, an uninterruptible power supply system, a contactless power supply system, an energy harvesting system, a natural energy storage system, an electric power steering system, an emergency power supply system, an in-wheel motor system, an idling stop system, an electric vehicle, a plug-in hybrid vehicle, an electric motorcycle, a smart grid system, and a rapid charging system.

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