Negative electrode for nonaqueous electrolyte electricity storage element, and nonaqueous electrolyte electricity storage element

Abstract

A negative electrode for a non-aqueous electrolyte electricity storage element according to one aspect of the present invention is provided with a negative electrode active material layer containing negative electrode active material particles, the negative electrode active material particles containing natural graphite particles, and the internal porosity of the negative electrode active material particles being 2% or less. The volume of pores having a pore diameter of 7.8 nm or less in the negative electrode active material particles is 0.0030 cm3 / g or less, and the porosity of the negative electrode active material layer is 35-60%.

Description

TECHNICAL FIELD

[0001] The present application relates to a negative electrode for a nonaqueous electrolyte power storage element and a nonaqueous electrolyte power storage element. BACKGROUND

[0002] Nonaqueous electrolyte secondary batteries typified by lithium ion secondary batteries are used in electronic devices such as personal computers and communication terminals, and in automobiles and the like because of their high energy density. A nonaqueous electrolyte secondary battery is generally configured to have a pair of electrodes electrically separated by a separator and a nonaqueous electrolyte interposed between the electrodes, and performs charge and discharge by performing exchange of charge transport ions between the two electrodes. In addition, as nonaqueous electrolyte power storage elements other than nonaqueous electrolyte secondary batteries, capacitors such as lithium ion capacitors and electric double layer capacitors are also widely popular.

[0003] As a nonaqueous electrolyte power storage element, an electrode body in which a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material are overlapped with a separator interposed therebetween is generally provided. Such an electrode body is housed together with a nonaqueous electrolyte in a container to constitute a nonaqueous electrolyte power storage element. As a negative electrode active material, carbon materials such as natural graphite are widely used (see Patent Documents 1 and 2). PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0004] Patent Document 1: Japanese Patent Application Publication No. 2005-222933 Patent Document 2: Japanese Patent Application Publication No. 2017-069039 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] For a nonaqueous electrolyte power storage element, high input, high energy density and the like are required. Here, as one of methods for improving the energy density of a nonaqueous electrolyte power storage element, it is considered to increase the density of the active material layer of the electrode, specifically, to reduce the porosity of the porous active material layer. However, generally, in the case where the porosity of the negative electrode active material layer is excessively reduced, the amount of nonaqueous electrolyte held in the voids between the negative electrode active material particles decreases because the volume of the voids decreases, and thus there is a tendency that the input decreases. In particular, in the case where natural graphite is used as a negative electrode active material, generally, the volume of the voids inside the particles of natural graphite is large compared to that of artificial graphite, and accordingly, the volume of the voids between the negative electrode active material particles is small, and thus the input tends to decrease significantly. Note that the input refers to the energy (W) that can be charged per unit time at the time of charging. That is, a large input means that the electric power (W) that can be charged at the time of charging is large. A large input can also be referred to as excellent input performance.

[0006] An object of the present application is to provide a negative electrode for a nonaqueous electrolyte power storage element capable of increasing input of a nonaqueous electrolyte power storage element in a wide range of porosity of a negative electrode active material layer and a nonaqueous electrolyte power storage element provided with the negative electrode. Method for solving the problem

[0007] The negative electrode for a nonaqueous electrolyte power storage element of one aspect of the present application is provided with a negative electrode active material layer containing negative electrode active material particles, the negative electrode active material particles contain natural graphite particles, the internal porosity of the negative electrode active material particles is 2% or less, the pore volume of pores having a pore diameter of 7.8 nm or less in the negative electrode active material particles is 0.0030 cm 3 / g or less, and the porosity of the negative electrode active material layer is 35% or more and 60% or less.

[0008] Another aspect of the present application relates to a nonaqueous electrolyte power storage element provided with the negative electrode for a nonaqueous electrolyte power storage element of one aspect of the present application. Effects of the Invention

[0009] According to any one aspect of the present application, it is possible to provide a negative electrode for a nonaqueous electrolyte power storage element capable of increasing input of a nonaqueous electrolyte power storage element in a wide range of porosity of a negative electrode active material layer and a nonaqueous electrolyte power storage element provided with the negative electrode. BRIEF DESCRIPTION OF DRAWINGS

[0010] [ Figure 1 ] Figure 1 is a perspective view showing one embodiment of a nonaqueous electrolyte power storage element. [ Figure 2 ] Figure 2 is a schematic view showing one embodiment of a power storage device configured by collecting a plurality of nonaqueous electrolyte power storage elements. DETAILED DESCRIPTION

[0011] First, a summary of the negative electrode for a nonaqueous electrolyte power storage element and the nonaqueous electrolyte power storage element disclosed by the present specification will be described.

[0012] [1] The negative electrode for a nonaqueous electrolyte power storage element of one aspect of the present application is provided with a negative electrode active material layer containing negative electrode active material particles, the negative electrode active material particles contain natural graphite particles, the internal porosity of the negative electrode active material particles is 2% or less, the pore volume of pores having a pore diameter of 7.8 nm or less in the negative electrode active material particles is 0.0030 cm 002 / g or less, and the porosity of the negative electrode active material layer is 35% or more and 60% or less.

[0013] The negative electrode for a nonaqueous electrolyte power storage element according to the above [1] can increase the input of the nonaqueous electrolyte power storage element in a wide range of porosity of the negative electrode active material layer. That is, the negative electrode for a nonaqueous electrolyte power storage element according to the above [1] can increase the input of the nonaqueous electrolyte power storage element even if the porosity of the negative electrode active material layer is low. The reason is not certain, but is presumed as follows. The porosity of the negative electrode active material layer using negative electrode active material particles includes two elements, the voids between the negative electrode active material particles and the voids inside the negative electrode active material particles. The voids that contribute to the input performance are mainly the voids between the negative electrode active material particles. In the case where a negative electrode active material layer having the same porosity is formed, the negative electrode active material layer using negative electrode active material particles having a low internal void ratio has a larger volume of the voids between the negative electrode active material particles than the negative electrode active material layer using negative electrode active material particles having a high internal void ratio, and can hold a larger amount of nonaqueous electrolyte. Therefore, by using negative electrode active material particles having a low internal void ratio, depletion of the nonaqueous electrolyte impregnated in the negative electrode active material layer is less likely to occur. In addition, the volume of the pores having a pore diameter of 7.8 nm or less in the negative electrode active material particles is 0.0030 cm 3 / g or less means that the pores that open on the surface of the negative electrode active material particles are made smaller by clogging due to coating treatment or the like. In the case where such negative electrode active material particles are used, the volume of the voids between the negative electrode active material particles becomes larger, and thus depletion of the nonaqueous electrolyte is less likely to occur. Furthermore, natural graphite has a higher crystallinity than artificial graphite, and there is a tendency that the input increases. Based on such a reason, it is presumed that the negative electrode for a nonaqueous electrolyte power storage element according to the above [1] can increase the input of the nonaqueous electrolyte power storage element in a wide range of porosity of the negative electrode active material layer.

[0014] "Graphite" means a carbon material in which the average interlattice spacing (d 002 ) of the (002) plane determined by X-ray diffraction method before charge and discharge or in a discharged state is 0.33 nm or more and less than 0.34 nm. Here, the "discharged state" of the carbon material means a state in which the carbon material as a negative electrode active material is discharged in a manner that the charge transport ions capable of occluding and releasing with charge and discharge are sufficiently released. For example, in a half-cell using a negative electrode containing the carbon material as a negative electrode active material as a working electrode and using metallic Li as a counter electrode, it is a state in which the open circuit voltage is 0.6 V or more. In the case where the carbon material is prepared from the assembled nonaqueous electrolyte storage element, specifically, the carbon material can be brought to the above-described discharged state by the following method. First, the nonaqueous electrolyte storage element is discharged at a constant current of 0.1 C to the discharge termination voltage at the time of ordinary use. Then, the nonaqueous electrolyte storage element is disassembled, and the negative electrode is taken out. Using the taken-out negative electrode as a working electrode and using metallic Li as a counter electrode, a half-cell is assembled. In the case where the open-circuit voltage in the half-cell is less than 0.6 V, the half-cell is discharged at a current of 0.1 C so that the open-circuit voltage becomes 0.6 V or more. Note that the discharge in the above-described half-cell refers to an oxidation reaction in which charge-carrying ions are released from the carbon material (graphite) as the negative electrode active material. The half-cell is disassembled, and the negative electrode is taken out, washed sufficiently with dimethyl carbonate, and then subjected to reduced-pressure drying at room temperature. The operation from the disassembly of the nonaqueous electrolyte storage element to the preparation of the carbon material as the measurement target is performed in a dry air atmosphere at a dew point of -40°C or lower. Here, the time of ordinary use refers to a case where the nonaqueous electrolyte storage element is used under the charge-discharge conditions recommended or specified for the nonaqueous electrolyte storage element.

[0015] The "natural graphite" refers to graphite collected from natural resources. Note that a particle in which the surface of a natural graphite particle is coated with a material other than natural graphite is also a natural graphite particle. The natural graphite has four peaks in the range of diffraction angle 2Θ of 40° to 50° in an X-ray diffraction pattern using CuKα rays measured before charge-discharge or in a discharged state. The four peaks are two peaks from a hexagonal crystal structure and two peaks from a rhombohedral crystal structure. In the case of artificial graphite, generally, only two peaks from a hexagonal crystal structure are present. In the X-ray diffraction pattern, the ratio of the peak intensity from the (012) plane to the peak intensity from the (100) plane ((012) / (100)) is preferably 0.3 or more, and further preferably 0.4 or more. The above-described peak intensity ratio ((012) / (100)) is preferably 0.6 or less. Here, the (100) plane is derived from a hexagonal crystal structure, and the (012) plane is derived from a rhombohedral crystal structure.

[0016] The "internal porosity" of the negative electrode active material particle refers to the area ratio of the area of the voids within the particle to the entire area of the particle in the cross section of the particle observed in an SEM image obtained using a scanning electron microscope (SEM). The "internal porosity (area ratio of the area of the voids within the particle to the entire area of the particle)" in the negative electrode active material particle can be determined by the following steps. (1) Preparation of a measurement sample The negative electrode for which the measurement is to be performed is fixed with a thermosetting resin. For the negative electrode fixed with the resin, a cross section is exposed by an ion milling method, and a sample for measurement is prepared. Note that the negative electrode for which the measurement is to be performed is directly used in the case of a negative electrode before a nonaqueous electrolyte secondary battery can be prepared. In the case of a negative electrode for which the measurement is to be performed prepared from a nonaqueous electrolyte secondary battery after assembly, a negative electrode subjected to disassembly from the nonaqueous electrolyte secondary battery to reduced-pressure drying is used in accordance with the above-described procedure for preparing a carbon material for X-ray diffraction from a nonaqueous electrolyte secondary battery after assembly. (2) Acquisition of SEM image In the acquisition of the SEM image, JSM-7001F (manufactured by JEOL Ltd.) was used as a scanning electron microscope. The SEM image observes a secondary electron image. The acceleration voltage was set to 15 kV. The observation magnification was set to a magnification at which 3 or more and 15 or less of the negative electrode active material particles appear in one field of view. The obtained SEM image was saved as an image file. Furthermore, each condition of the spot diameter, the working distance, the irradiation current, the brightness, the focus, and the like was appropriately set in a manner that the outline of the negative electrode active material particle becomes clear. (3) Trimming of outline of negative electrode active material particle The outline of the negative electrode active material particle was trimmed from the acquired SEM image using the image trimming function of the image editing software Adobe Photoshop Elements 11. The trimming of the outline was performed using the quick selection tool to select the outside from the outline of the negative electrode active material particle, and editing the outside of the negative electrode active material particle as a black background. At this time, in the case where the negative electrode active material particles of which the outline can be trimmed are less than 3, the SEM image was acquired again until the negative electrode active material particles of which the outline can be trimmed become 3 or more. (4) Binaryzation processing For the image of the first negative electrode active material particle in the trimmed negative electrode active material particles, the binaryzation processing was performed using the image analysis software PopImaging 6.00, with a concentration 20% less than the concentration of the maximum intensity set as a threshold value. By the binaryzation processing, the area of the high concentration side was calculated, and thereby as "area S1 of voids in the particle". Next, for the image of the same first negative electrode active material particle as before, the binaryzation processing was performed with a concentration of 10% as a threshold value. By the binaryzation processing, the outer edge of the negative electrode active material particle was determined, and the area of the inside of the outer edge was calculated, and thereby as "area S0 of the entire particle". Using the above-calculated S1 and S0, the ratio of S1 to S0 (S1 / S0) was calculated, and thereby the "area ratio R1 of the area of the voids in the particle to the area of the entire particle" in the first negative electrode active material particle was calculated. For the images of the second and subsequent negative active material particles in the sheared negative active material particles, the above-described binarization processing is also performed, and the areas S1, S0 are calculated. Based on the calculated areas S1, S0, the area ratios R2, R3,... of the voids of the respective negative active material particles are calculated. (5) Determination of internal void ratio The average of the area ratios R1, R2, R3,... of all the voids calculated by the binarization processing is calculated, thereby determining the "internal void ratio (area ratio of the voids in the particles with respect to the area of the entire particles)". Note that, instead of the scanning electron microscope used in the above-described "acquisition of SEM images", the image editing software used in the "shearing of the profile of the negative active material particles", and the image analysis software used in the "binarization processing", a device and software, etc. that can perform equivalent measurement, image editing, and image analysis can be used.

[0017] Regarding the "pore volume of 7.8 nm or less" in the negative active material particles, for the negative active material particles before charge and discharge or in the discharged state, a pore distribution measuring device (TRISTAR II 2030 manufactured by Micromeritics Corporation) is used, and the pore volume of 7.8 nm or less is measured by a gas adsorption method based on the following conditions. The measurement gas is nitrogen. The range of the pore diameter to be measured is 0.1 nm to 300 nm. The number of measurement points in the range of the pore diameter to be measured is 30. The pore diameter (pore size) is plotted on the horizontal axis, and the pore volume is plotted on the vertical axis, and thus a cumulative pore volume curve is obtained. The "pore volume of 7.8 nm or less" is obtained from the cumulative pore volume curve. Note that it is confirmed that the "pore volume of 7.8 nm or less" in the negative active material particles based on the above-described measurement is substantially the same as the "pore volume of 7.8 nm or less" in the negative active material layer. The "pore volume of 7.8 nm or less" in the negative active material layer is measured under the same conditions as the "pore volume of 7.8 nm or less" in the negative active material particles. In addition, in the case where the negative active material layer contains any components such as a binder, a thickening agent, and a conductive agent, after at least the binder and the thickening agent among the components are removed by heating and decomposing the components to a temperature above the decomposition temperature of the binder and the thickening agent in an air atmosphere, the above-described measurement is performed.

[0018] In a case where the apparent volume (volume including voids) of the negative electrode active material layer is set to V1 and the sum of the actual volumes of the respective materials constituting the negative electrode active material layer is set to V2, the "porosity (%) of the negative electrode active material layer" is calculated by the formula (1 - V2 / V1) x 100. The sum V2 of the actual volumes of the respective materials constituting the negative electrode active material layer can be calculated from the content of each material in the negative electrode active material layer and the true density of each material.

[0019] [2] In the negative electrode for nonaqueous electrolyte accumulator element described in the above [1], the average particle diameter of the negative electrode active material particles can be 6 μm or more and 10 μm or less.

[0020] The negative electrode for nonaqueous electrolyte accumulator element according to the above [2] can further increase the input and the like of the nonaqueous electrolyte accumulator element.

[0021] The "average particle diameter" of the negative electrode active material particles and the other particles means the value at which the volume-based cumulative distribution calculated based on the particle size distribution obtained by measuring a diluted solution in which the particles are diluted with a solution by a laser diffraction scattering method according to JIS-Z-8825 (2013) becomes 50% according to JIS-Z-8819-2 (2001).

[0022] The negative electrode for nonaqueous electrolyte accumulator element, the nonaqueous electrolyte accumulator element, the accumulator device, the manufacturing method of the nonaqueous electrolyte accumulator element, and other embodiments of one embodiment of the present application are described in detail. Note that the names of the respective constituent members (the respective elements) used in each of the embodiments are sometimes different from the names of the respective constituent members (the respective elements) used in the background art.

[0023] <NEGATIVE ELECTRODE FOR NONAQUEOUS ELECTROLYTE ACCUMULATOR ELEMENT> The negative electrode for nonaqueous electrolyte accumulator element (hereinafter also referred to simply as "negative electrode") of one embodiment of the present application has a negative electrode substrate and a negative electrode active material layer provided directly or with an intermediate layer interposed therebetween on the negative electrode substrate. The negative electrode is used as a negative electrode of a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery and other nonaqueous electrolyte accumulator elements. The negative electrode is suitable as a negative electrode of a nonaqueous electrolyte accumulator element.

[0024] The negative electrode substrate has conductivity. As to whether or not it has "conductivity", the volume resistivity measured according to JIS-H-0505 (1975) is 10 -2Ωcm is the threshold value for the determination. As the material of the negative electrode substrate, a metal such as copper, nickel, stainless steel, nickel-plated steel, or an alloy thereof, a carbonaceous material, or the like can be used. Among them, copper or a copper alloy is preferable. As the negative electrode substrate, a foil, an evaporation film, a mesh, a porous material, or the like can be exemplified, and from the viewpoint of cost, a foil is preferable. Therefore, as the negative electrode substrate, a copper foil or a copper alloy foil is preferable. As examples of the copper foil, a rolled copper foil, an electrolytic copper foil, or the like can be exemplified.

[0025] The average thickness of the negative electrode substrate is preferably 2 μm or more and 35 μm or less, more preferably 3 μm or more and 30 μm or less, further preferably 4 μm or more and 25 μm or less, and particularly preferably 5 μm or more and 20 μm or less. By making the average thickness of the negative electrode substrate within the above range, the strength of the negative electrode substrate can be increased, and the energy density per unit volume of the nonaqueous electrolyte storage element can be increased.

[0026] The intermediate layer is a layer disposed between the negative electrode substrate and the negative electrode active material layer. The intermediate layer reduces the contact resistance between the negative electrode substrate and the negative electrode active material layer by containing a conductive agent such as carbon particles. The constitution of the intermediate layer is not particularly limited, and for example, contains a binder and a conductive agent.

[0027] The negative electrode active material layer contains negative electrode active material particles. The negative electrode active material layer contains, as necessary, any of a conductive agent, a binder, a thickening agent, a filler, or the like.

[0028] The negative electrode active material particles contain natural graphite particles. As the natural graphite constituting the natural graphite particles, flaky graphite (scale graphite), massive graphite, earthy graphite, or the like can be exemplified. The natural graphite particles can be graphite particles in which flaky graphite is spheroidized and subjected to a densification treatment. The natural graphite particles can be particles in which the surface is covered with a carbon material other than natural graphite particles (for example, non-graphitic carbon) or the like. The covering with the carbon material can be performed by, for example, allowing pitch to be coated on the surface of the natural graphite particles and performing a firing.

[0029] The negative electrode active material particles can further contain other negative electrode active material particles other than the natural graphite particles. As the negative electrode active material constituting the other negative electrode active material particles, artificial graphite and other various negative electrode active materials conventionally known can be used. As the other various negative electrode active materials conventionally known, for example, non-graphitic carbon, metallic lithium; a metal or semimetal such as Si and Sn; a metal oxide or semimetal oxide such as Si oxide, Ti oxide, and Sn oxide; a titanium-containing oxide such as Li4Ti5O12, LiTiO2, and TiNb2O7; a polyphosphoric acid compound; silicon carbide, or the like can be exemplified. The "non-graphitic carbon" among the other various negative electrode active materials conventionally known means a carbon material in which the average interlattice spacing (d002) of the (002) plane determined by X-ray diffraction method is 0.340 nm or more and 0.370 nm or less in the charged state or in the discharged state. 12 002 ​) is a carbon material having a crystallite size of 0.34 nm or more and 0.42 nm or less.

[0030] The natural graphite particles are preferably the main negative electrode active material particles. For example, in a cross-sectional SEM image of the negative electrode, the area ratio of the natural graphite particles (area of the natural graphite particles / area of the negative electrode active material particles) with respect to the area of the negative electrode active material particles is preferably 90% or more, more preferably 99% or more, and can be substantially 100%. Note that the cross-sectional SEM image of the negative electrode is obtained by the same procedure as that for determining the "internal void ratio (area ratio of the voids in the particles with respect to the entire area of the particles)" in the negative electrode active material particles. The area of the negative electrode active material particles is the entire area of the negative electrode active material particles (including the area of the voids), and the area of the natural graphite particles is the entire area of the natural graphite particles (including the area of the voids). Note that the area ratio of the natural graphite particles (area of the natural graphite particles / area of the negative electrode active material particles) with respect to the area of the negative electrode active material particles is calculated using a cross-sectional SEM image containing 10 or more negative electrode active material particles in one field of view. In addition, the content of the natural graphite particles in the entire negative electrode active material particles in the negative electrode active material layer is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 99% by mass or more, and can be substantially 100% by mass. That is, it is particularly preferable to use only the natural graphite particles as the negative electrode active material particles. In this way, the input is increased by mainly using the natural graphite particles as the negative electrode active material particles.

[0031] The upper limit of the internal void ratio of the negative electrode active material particles is 2%, preferably 1%, and more preferably 0.6%. By setting the internal void ratio of the negative electrode active material particles to be the above upper limit or less, the input of the nonaqueous electrolyte secondary battery element can be increased. The lower limit of the internal void ratio can be 0% or 0.1%. The internal void ratio can be the above lower limit or more and the above upper limit or less. The internal void ratio of the negative electrode active material particles containing the natural graphite particles can be set to a low value of 2% or less, for example, by performing a densification treatment on the spheroidized natural graphite particles. In addition, it is preferable that the internal void ratio of the graphite particles (natural graphite particles and artificial graphite particles) contained in the negative electrode active material particles be in the above range, and it is also preferable that the internal void ratio of the natural graphite particles be in the above range.

[0032] The upper limit of the fine pore volume of the fine pores having a diameter of 7.8 nm or less in the negative electrode active material particles is 0.0030 cm 3 / g, preferably 0.0028 cm 3 / g. By ensuring that the pore volume of the negative electrode active material particles, with a pore diameter of 7.8 nm or less, is below the aforementioned upper limit, the input of the non-aqueous electrolyte energy storage device can be increased. The lower limit of the aforementioned pore volume can be 0.0001 cm³. 3 / g, or 0.0010cm 3 / g. The aforementioned pore volume can be above any of the lower limits and below any of the upper limits. The pore volume of the negative electrode active material particles containing natural graphite particles with a pore diameter of 7.8 nm or less can be set to 0.0030 cm³ by applying a coating treatment to the particle surface based on carbon materials (e.g., non-graphitic carbon). 3 Values ​​as small as / g or less. By increasing the coating amount in the coating process, there is a tendency for the pore volume with a pore diameter of 7.8 nm or less to become smaller. In addition, it is preferable that the pore volume of the graphite particles contained in the negative electrode active material particles has a pore diameter of 7.8 nm or less within the above range, and it is also preferable that the pore volume of the natural graphite particles has a pore diameter of 7.8 nm or less within the above range.

[0033] The average particle size of the negative electrode active material particles can be, for example, 1 μm or more and 20 μm or less, or 3 μm or more and 15 μm or less, preferably 6 μm or more and 10 μm or less. Generally, the larger the particle size of the negative electrode active material, the greater the tendency for internal porosity to increase. Therefore, when an embodiment of the present invention is applied to a non-aqueous electrolyte energy storage element using negative electrode active material particles with an average particle size of 2% or more, a significant improvement in input performance is achieved by setting the internal porosity to 2% or less. On the other hand, when the average particle size of the negative electrode active material particles is 2% or less, the number of contact points between particles increases, the resistance of the negative electrode active material layer decreases, and the input of the non-aqueous electrolyte energy storage element becomes larger. Furthermore, it is preferable that the average particle size of the graphite particles contained in the negative electrode active material particles is within the above range, and it is also preferable that the average particle size of the natural graphite particles is within the above range.

[0034] To obtain powders such as negative electrode active material particles with a predetermined particle size, pulverizers and classifiers can be used. Examples of pulverizing methods include using mortars, ball mills, sand mills, vibratory ball mills, planetary ball mills, jet mills, reverse jet mills, cyclone jet mills, or sieves. Wet pulverization, which involves the coexistence of water or organic solvents such as hexane, can also be used. As for classification methods, sieves and air classifiers can be used in both dry and wet processes as needed.

[0035] The content of the negative electrode active material particles in the negative electrode active material layer is preferably 60% by mass or more and 99.5% by mass or less, and more preferably 90% by mass or more and 99% by mass or less. By setting the content of the negative electrode active material particles to the above range, both the high energy density of the negative electrode active material layer and the workability can be achieved, and the initial input can be further increased. In addition, the content of the graphite particles in the negative electrode active material layer is preferably in the above range, and the content of the natural graphite particles is also preferably in the above range.

[0036] The conductive agent is not particularly limited as long as it is a material having conductivity. As such a conductive agent, for example, carbonaceous materials, metals, conductive ceramics, and the like can be listed. As the carbonaceous materials, non-graphitic carbon, graphene-based carbon, and the like can be listed. As the non-graphitic carbon in the conductive agent, carbon nanofibers, pitch-based carbon fibers, carbon black, and the like can be listed. As the carbon black, furnace black, acetylene black, Ketjen black, and the like can be listed. As the graphene-based carbon, graphene, carbon nanotubes (CNTs), fullerene, and the like can be listed. However, the natural graphite particles, graphite such as artificial graphite, and other non-graphitic carbon in the above-described negative electrode active material layer are not included in the conductive agent. As the shape of the conductive agent, powdery, fibrous, and the like can be listed. As the conductive agent, one of these materials can be used alone, or two or more of these materials can be used in combination. In addition, these materials can be used in a composite. For example, a material in which carbon black and CNTs are combined can be used. Among them, from the viewpoints of electron conductivity and coatability, carbon black is preferred, and among them, acetylene black is preferred.

[0037] The content of the conductive agent in the negative electrode active material layer can be 3% by mass or less or 1% by mass or less, or the negative electrode active material layer can not contain the conductive agent.

[0038] As the binder, for example, thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and the like), polyethylene, polypropylene, polyacrylic acid, polyimide, and the like; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, and the like; polysaccharide polymers, and the like can be listed.

[0039] The content of the binder in the negative electrode active material layer is preferably 0.5% by mass or more and 5% by mass or less, and more preferably 0.8% by mass or more and 3% by mass or less. By setting the content of the binder to the above range, the negative electrode active material particles and the like can be stably held.

[0040] As the thickening agent, for example, polysaccharide polymers such as carboxymethyl cellulose (CMC), methyl cellulose, and the like can be listed. When the thickening agent has a functional group that reacts with lithium and the like, the functional group can be inactivated in advance by methylation or the like.

[0041] The content of the thickening agent in the negative electrode active material layer is, for example, preferably 0.1% by mass or more and 6% by mass or less, and more preferably 0.5% by mass or more and 3% by mass or less.

[0042] The filler is not particularly limited. As the filler, polypropylene, polyethylene, and the like polyolefins, silicon dioxide, aluminum oxide, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, inorganic oxides such as aluminosilicate, hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, carbonates such as calcium carbonate, insoluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate, nitrides such as aluminum nitride and silicon nitride, talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, mica, and the like substances derived from mineral resources or artificial substances thereof, and the like can be given.

[0043] The content of the filler in the negative electrode active material layer is, for example, 0.1% by mass or more and 8% by mass or less, or 0.5% by mass or more and 5% by mass or less. The content of the filler in the negative electrode active material layer can be 3% by mass or less, or 1% by mass or less, and the negative electrode active material layer can also be free of the filler.

[0044] The negative electrode active material layer can also contain, as components other than the negative electrode active material, the conductive agent, the binder, the thickening agent, and the filler, typical non-metallic elements such as B, N, P, F, Cl, Br, and I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W.

[0045] The porosity of the negative electrode active material layer is 35% or more and 60% or less. The lower limit of the porosity can be 40%, 45%, or 50%. By making the porosity of the negative electrode active material layer the above lower limit or more, there is a tendency for the input of the non-aqueous electrolyte storage element to become greater. On the other hand, the upper limit of the porosity can be 55%, 50%, 45%, or 40%. By making the porosity of the negative electrode active material layer the above upper limit or less, it is possible to improve the energy density and the like. The porosity of the negative electrode active material layer can be the above lower limit or more and the above upper limit or less (where the lower limit is less than the upper limit). The porosity of the negative electrode active material layer can be adjusted by the particle diameter of the negative electrode active material particles, the presence or absence of pressing at the time of manufacture, the pressure of the pressing, and the like. <Non-aqueous electrolyte storage element> The nonaqueous electrolyte power storage element (hereinafter, also simply referred to as "power storage element") of one embodiment of the present application includes an electrode body, a nonaqueous electrolyte, and a container. The electrode body includes a positive electrode, a negative electrode, and a separator. The container houses the electrode body and the nonaqueous electrolyte. The electrode body is typically a stacked type in which a plurality of positive electrodes and a plurality of negative electrodes are stacked with the separator therebetween, or a wound type in which a positive electrode and a negative electrode are wound with the separator therebetween. The nonaqueous electrolyte is present in a state of being impregnated in the positive electrode, the negative electrode, and the separator. As an example of the nonaqueous electrolyte power storage element, a nonaqueous electrolyte secondary battery (hereinafter, also simply referred to as "secondary battery") is described.

[0046] (Positive electrode) The positive electrode includes a positive electrode substrate and a positive electrode active material layer provided directly on or with an intermediate layer interposed therebetween on the positive electrode substrate. The intermediate layer is not particularly limited and can be selected from the above-described configurations of the negative electrode.

[0047] The positive electrode substrate has conductivity. As a material of the positive electrode substrate, a metal such as aluminum, titanium, tantalum, or stainless steel, or an alloy thereof can be used. Among them, from the viewpoints of high resistance to electric potential, high conductivity, and cost, aluminum or an aluminum alloy is preferable. As the positive electrode substrate, a foil, an evaporation film, a mesh, a porous material, or the like can be given, and from the viewpoint of cost, a foil is preferable. Thus, as the positive electrode substrate, an aluminum foil or an aluminum alloy foil is preferable. As the aluminum or the aluminum alloy, A1085, A3003, A1N30, or the like defined in JIS-H-4000 (2014) or JIS-H-4160 (2006) can be given.

[0048] The average thickness of the positive electrode substrate is preferably greater than or equal to 3 μm and less than or equal to 50 μm, more preferably greater than or equal to 5 μm and less than or equal to 40 μm, further preferably greater than or equal to 8 μm and less than or equal to 30 μm, and particularly preferably greater than or equal to 10 μm and less than or equal to 25 μm. By setting the average thickness of the positive electrode substrate to the above range, the strength of the positive electrode substrate can be increased, and the energy density per unit volume of the nonaqueous electrolyte power storage element can be increased.

[0049] The positive electrode active material layer includes a positive electrode active material. The positive electrode active material layer can include any of a conductive agent, a binder, a thickener, a filler, or the like as necessary. Any of the conductive agent, the binder, the thickener, the filler, or the like can be selected from the above-described materials exemplified for the negative electrode.

[0050] As the positive electrode active material, it can be appropriately selected from known positive electrode active materials. For positive electrode active materials used in lithium-ion secondary batteries, materials capable of absorbing and releasing lithium ions are typically used. Examples of positive electrode active materials include lithium transition metal composite oxides with an α-NaFeO2-type crystal structure, lithium transition metal composite oxides with a spinel-type crystal structure, polyanionic compounds, chalcogenides, and sulfur. For example, Li[Li] can be used as a lithium transition metal composite oxide with an α-NaFeO2-type crystal structure. x Ni (1-x) O2 (0≤x<0.5), Li[Li x Ni γ Co (1-x-γ) ]O2(0≤x<0.5, 0<γ<1, 0<1-x-γ), Li[Li x Co (1-x) O2 (0≤x<0.5), Li[Li x Ni γ Mn (1-x-γ) ]O2(0≤x<0.5, 0<γ<1, 0<1-x-γ), Li[Li x Ni γ Mn β Co (1-x-γ-β) ]O2(0≤x<0.5, 0<γ, 0<β, 0.5<γ+β<1, 0<1-x-γ-β), Li[Li x Ni γ Co β Al (1-x-γ-β) O2 (0≤x<0.5, 0<γ, 0<β, 0.5<γ+β<1, 0<1-x-γ-β), etc. As a lithium transition metal composite oxide with a spinel-type crystal structure, Li can be cited as an example. x Mn2O4, Li x Ni γ Mn (2-γ) Examples of polyanionic compounds include O4, LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, and Li2CoPO4F. Examples of chalcogenides include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. Atoms or polyanions in these materials can be partially replaced by atoms or anions composed of other elements. The surface of these materials can also be coated with other materials. One of these materials can be used alone, or two or more can be used in combination in the positive electrode active material layer.

[0051] The positive electrode active material is generally a particle (powder). The average particle diameter of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By making the average particle diameter of the positive electrode active material the above lower limit or more, the production or handling of the positive electrode active material becomes easy. By making the average particle diameter of the positive electrode active material the above upper limit or less, the electron conductivity of the positive electrode active material layer is improved. Note that, in the case of using a composite of the positive electrode active material and another material, the average particle diameter of the composite is taken as the average particle diameter of the positive electrode active material. In order to obtain a powder with a predetermined particle diameter, a pulverizer, a classifier, or the like is used. The pulverizing method and the classifying method can be selected, for example, from the methods exemplified above for the negative electrode.

[0052] The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass or more and 99% by mass or less, more preferably 70% by mass or more and 98% by mass or less, and further preferably 80% by mass or more and 95% by mass or less. By setting the content of the positive electrode active material to the above range, the high energy density of the positive electrode active material layer and the productivity can be both taken into account.

[0053] The content of the conductive agent in the positive electrode active material layer is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. By setting the content of the conductive agent to the above range, the energy density of the nonaqueous electrolyte power storage element can be improved.

[0054] The content of the binder in the positive electrode active material layer is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 9% by mass or less. By setting the content of the binder to the above range, the positive electrode active material can be stably maintained.

[0055] The content of the thickening agent in the positive electrode active material layer can be, for example, 0.1% by mass or more and 6% by mass or less, or 0.5% by mass or more and 3% by mass or less. The content of the thickening agent in the positive electrode active material layer can be 1% by mass or less, or the positive electrode active material layer can not contain the thickening agent.

[0056] The content of the filler in the positive electrode active material layer can be, for example, 0.1% by mass or more and 8% by mass or less, or 0.5% by mass or more and 5% by mass or less. The content of the filler in the positive electrode active material layer can be 3% by mass or less, or 1% by mass or less, or the positive electrode active material layer can not contain the filler.

[0057] The positive electrode active material layer may also contain typical non-metallic elements such as B, N, P, F, Cl, Br, I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb as components other than the positive electrode active material, conductive agent, binder, thickener, and filler.

[0058] (negative electrode) The negative electrode of the non-aqueous electrolyte storage element in one embodiment of the present invention is the negative electrode used in the non-aqueous electrolyte storage element of one embodiment of the present invention described above.

[0059] (Diaphragm) The diaphragm can be appropriately selected from known diaphragms. For example, a diaphragm consisting solely of a substrate layer, or a diaphragm with a heat-resistant layer containing heat-resistant particles and an adhesive formed on one or both sides of the substrate layer, can be used. The shape of the substrate layer of the diaphragm can be, for example, woven fabric, nonwoven fabric, or porous resin membrane. Among these shapes, porous resin membranes are preferred from the viewpoint of strength, while nonwoven fabrics are preferred from the viewpoint of retaining non-aqueous electrolytes. The material of the substrate layer of the diaphragm is preferred from the viewpoint of its shut-off function, such as polyolefins like polyethylene and polypropylene; and from the viewpoint of resistance to oxidative decomposition, such as polyimide and aromatic polyamide are preferred. A material composed of these resins can be used as the substrate layer of the diaphragm.

[0060] The heat-resistant particles contained in the heat-resistant layer preferably decrease in mass by less than 5% when heated from room temperature to 500°C in an air atmosphere at 1 atmosphere, and more preferably by less than 5% when heated from room temperature to 800°C. Inorganic compounds can be cited as materials for which the mass decreases to the predetermined level. Examples of inorganic compounds include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; insoluble ionic crystals such as calcium fluoride, barium fluoride, and barium titanate; covalently bonded crystals such as silicon and diamond; and substances derived from mineral resources or their synthetic forms, such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica. These substances can be used alone as monomers or in combination, or in mixtures of two or more. From the perspective of the safety of non-aqueous electrolyte storage devices, silicon oxide, aluminum oxide, or aluminosilicates are preferred among these inorganic compounds.

[0061] From the viewpoint of strength, the porosity of the separator is preferably 80% by volume or less, and from the viewpoint of discharge performance, it is preferably 20% by volume or more. Here, the "porosity" is a value on a volume basis, and is a value based on a measurement by a mercury porosimeter.

[0062] As the separator, a polymer gel composed of a polymer and a nonaqueous electrolyte can be used. As the polymer, for example, polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyvinylidene fluoride, or the like can be given. When a polymer gel is used, there is an effect of suppressing liquid leakage. As the separator, a porous resin film or a nonwoven fabric or the like as described above can be used in combination with a polymer gel.

[0063] (Nonaqueous electrolyte) As the nonaqueous electrolyte, an appropriate one can be selected from publicly known nonaqueous electrolytes. The nonaqueous electrolyte can use a nonaqueous electrolytic solution. The nonaqueous electrolytic solution contains a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent.

[0064] As the nonaqueous solvent, an appropriate one can be selected from publicly known nonaqueous solvents. As the nonaqueous solvent, cyclic carbonates, chain carbonates, carboxylic acid esters, phosphoric acid esters, sulfonic acid esters, ethers, amides, nitriles, or the like can be given. As the nonaqueous solvent, a solvent in which a part of hydrogen atoms contained in these compounds is substituted with a halogen can be used.

[0065] As the cyclic carbonate, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate, or the like can be given. Among them, EC is preferred.

[0066] As the chain carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diphenyl carbonate, trifluoromethylethyl carbonate, bis(trifluoroethyl) carbonate, or the like can be given. Among them, EMC is preferred.

[0067] As the nonaqueous solvent, it is preferred to use a cyclic carbonate or a chain carbonate, and it is more preferred to use a cyclic carbonate and a chain carbonate in combination. By using a cyclic carbonate, the dissociation of the electrolyte salt can be promoted, and the ionic conductivity of the nonaqueous electrolytic solution can be increased. By using a chain carbonate, the viscosity of the nonaqueous electrolytic solution can be suppressed to be low. In the case where a cyclic carbonate and a chain carbonate are used in combination, as the volume ratio of the cyclic carbonate to the chain carbonate (cyclic carbonate: chain carbonate), for example, it is preferred to be in the range of 5:95 to 50:50.

[0068] As the electrolyte salt, one can be appropriately selected from publicly known electrolyte salts. As the electrolyte salt, lithium salts, sodium salts, potassium salts, magnesium salts, onium salts, and the like can be given. Among them, lithium salts are preferred.

[0069] As the lithium salt, inorganic lithium salts such as LiPF6, LiPO2F2, LiBF4, LiClO4, LiN(SO2F)2, lithium oxalate salts such as lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiFOB), lithium bis(fluorodioxalato)phosphate (LiFOP), lithium salts having halogenated hydrocarbon groups such as LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, LiC(SO2C2F5)3, and the like can be given. Among them, inorganic lithium salts are preferred, and LiPF6is more preferred.

[0070] The content of the electrolyte salt in the nonaqueous electrolyte solution is preferably 0.1 mol / dm3or more, more preferably 0.3 mol / dm3or more, and even more preferably 0.5 mol / dm3or more at 20°C under 1 atm. 3 The content of the electrolyte salt in the nonaqueous electrolyte solution is preferably 0.1 mol / dm3or more, more preferably 0.3 mol / dm3or more, and even more preferably 0.5 mol / dm3or more at 20°C under 1 atm. 3 Further, the content of the electrolyte salt is more preferably 0.3 mol / dm3or more, and even more preferably 0.5 mol / dm3or more. 3 The content of the electrolyte salt in the nonaqueous electrolyte solution is preferably 0.1 mol / dm3or more, more preferably 0.3 mol / dm3or more, and even more preferably 0.5 mol / dm3or more at 20°C under 1 atm. 3 Further, the content of the electrolyte salt is more preferably 0.3 mol / dm3or more, and even more preferably 0.5 mol / dm3or more. 3 The content of the electrolyte salt in the nonaqueous electrolyte solution is preferably 0.1 mol / dm3or more, more preferably 0.3 mol / dm3or more, and even more preferably 0.5 mol / dm3or more at 20°C under 1 atm. 3 Further, the content of the electrolyte salt is more preferably 0.3 mol / dm3or more, and even more preferably 0.5 mol / dm3or more. 3 The content of the electrolyte salt in the nonaqueous electrolyte solution is preferably 0.1 mol / dm3or more, more preferably 0.3 mol / dm3or more, and even more preferably 0.5 mol / dm3or more at 20°C under 1 atm. 3 Further, the content of the electrolyte salt is more preferably 0.3 mol / dm3or more, and even more preferably 0.5 mol / dm3or more.

[0071] The nonaqueous electrolyte solution can contain an additive in addition to the nonaqueous solvent and the electrolyte salt. As the additive, for example, there can be mentioned aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, and the like; partially halogenated aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, and the like; halogenated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole, and the like; vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, gluconic anhydride, itaconic anhydride, cyclohexane dicarboxylic anhydride; vinyl sulfite, propylene sulfite, dimethyl sulfite, methyl methanesulfonate, busulfan, methyl tosylate, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 4,4'-bis(2,2-dioxo-l,3,2-dioxathiazolidine), 4-methylsulfonyloxymethyl-2,2-dioxo-l,3,2-dioxathiazolidine, thioanisole, diphenyl disulfide, dipyridinium disulfide, 1,3-propene sultone, 1,3-propane sultone, 1,4-butane sultone, 1,4-butene sultone, perfluorooctane, tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphate, tetra(trimethylsilyl) titanate, and the like. These additives can be used singly or in combination of two or more.

[0072] The content of the additive contained in the nonaqueous electrolyte solution is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 7% by mass or less, further preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less, relative to the total mass of the nonaqueous electrolyte solution. By setting the content of the additive within the above range, the capacity retention after high-temperature storage or the cycle performance can be improved, and the safety can be further improved.

[0073] The nonaqueous electrolyte can use a solid electrolyte, or a combination of a nonaqueous electrolyte solution and a solid electrolyte.

[0074] As the solid electrolyte, any material having ionic conductivity and being solid at ordinary temperature (e.g., 15°C to 25°C) such as lithium, sodium, calcium, and the like can be selected. As the solid electrolyte, for example, there can be mentioned sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, polymer solid electrolytes, and the like.

[0075] As the sulfide solid electrolyte, in the case of a lithium-ion secondary battery, for example, there can be mentioned Li2S-P2S5, LiI-Li2S-P2S5, Li 10 Ge-P2S12 and the like.

[0076] The shape of the nonaqueous electrolyte storage element of the present embodiment is not particularly limited, and examples thereof include a cylindrical battery, a prismatic battery, a flat battery, a coin-type battery, a button-type battery, and the like.

[0077] Figure 1 A nonaqueous electrolyte storage element 1 as an example of a prismatic battery is shown. Note that this figure is a perspective view of the inside of the container. An electrode body 2 having a positive electrode and a negative electrode wound with a separator interposed therebetween is housed in a prismatic container 3. The positive electrode is electrically connected to a positive electrode terminal 4 via a positive electrode lead 41. The negative electrode is electrically connected to a negative electrode terminal 5 via a negative electrode lead 51.

[0078] <Storage device> The nonaqueous electrolyte storage element of the present embodiment can be mounted on a power source for an automobile such as an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a power source for an electronic device such as a personal computer or a communication terminal, or a power storage power source, as a storage unit (battery module) configured by collecting a plurality of nonaqueous electrolyte storage elements. In this case, the technology of the present application can be applied to at least one nonaqueous electrolyte storage element included in the storage unit.

[0079] Figure 2 An example of a storage device 30 configured by further collecting a storage unit 20 configured by collecting two or more nonaqueous electrolyte storage elements 1 electrically connected to each other is shown. The storage device 30 can also be provided with a bus bar (not shown) for electrically connecting two or more nonaqueous electrolyte storage elements 1, a bus bar (not shown) for electrically connecting two or more storage units 20, and the like. The storage unit 20 or the storage device 30 can also be provided with a state monitoring device (not shown) for monitoring the state of one or more nonaqueous electrolyte storage elements.

[0080] <Method for manufacturing nonaqueous electrolyte storage element> The method for manufacturing the nonaqueous electrolyte storage element of the present embodiment can be appropriately selected from publicly known methods. The manufacturing method includes, for example, preparing an electrode body, preparing a nonaqueous electrolyte, and housing the electrode body and the nonaqueous electrolyte in a container. The preparation of the electrode body includes preparing a positive electrode and a negative electrode, and forming an electrode body by stacking or winding the positive electrode and the negative electrode with a separator interposed therebetween.

[0081] The preparation of the positive electrode can be performed, for example, by coating a positive electrode paste on a positive electrode substrate directly or with an intermediate layer interposed therebetween and drying it. The positive electrode paste described above contains components for forming a positive electrode active material layer such as a positive electrode active material and a dispersion medium. Pressing or the like can be performed after the coated positive electrode paste is dried.

[0082] The negative electrode can be prepared, for example, by coating a negative electrode mixture paste on a negative electrode base material directly or through an intermediate layer and drying it. The negative electrode mixture paste described above contains each component constituting the negative electrode active material layer such as natural graphite particles and a dispersion medium. After the coated negative electrode mixture paste is dried, pressing or the like can be performed. Depending on the presence or absence of the pressing and the pressure of the pressing or the like, the porosity of the negative electrode active material layer formed can be adjusted.

[0083] The non-aqueous electrolyte can be accommodated in the container appropriately selected from publicly known methods. For example, in the case where the non-aqueous electrolyte uses a non-aqueous electrolytic solution, after the non-aqueous electrolytic solution is injected from an injection port formed in the container, the injection port can be sealed.

[0084] [Other Embodiments] Note that the non-aqueous electrolyte storage element of the present application is not limited to the above-described embodiments and can be variously changed within a scope not departing from the gist of the present application. For example, the constitution of one embodiment can be supplemented with the constitution of another embodiment, and in addition, a part of the constitution of one embodiment can be replaced with the constitution of another embodiment or a publicly known technique. Further, a part of the constitution of one embodiment can be deleted. In addition, a publicly known technique can be added to the constitution of one embodiment.

[0085] In the above-described embodiments, the case where the non-aqueous electrolyte storage element is used as a non-aqueous electrolyte secondary battery (lithium ion secondary battery) capable of charge and discharge has been described, but the kind, shape, size, capacity, or the like of the non-aqueous electrolyte storage element is arbitrary. The present application can also be applied to various secondary batteries, electric double layer capacitors, or lithium ion capacitors and the like.

[0086] In the above-described embodiments, the electrode body in which the positive electrode and the negative electrode are laminated with the separator has been described, but the electrode body can not have the separator. For example, in a state where a layer not having conductivity is formed on the active material layer of the positive electrode or the negative electrode, the positive electrode and the negative electrode can directly contact. Example

[0087] Hereinafter, the present application will be described more specifically by examples, but the present application is not limited to the following examples.

[0088] [Example 1] (Production of Positive Electrode) LiNi 1 / 3 Mn 1 / 3 Co 1 / 3Anode active material paste was prepared using O2, acetylene black (AB) as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone (NMP) as a dispersion medium. Note that the mass ratio of the anode active material, AB, and PVDF was set to 93:5:2 (solid content conversion). Anode active material paste was applied to both sides of an aluminum foil as an anode base material in such a manner that the mass of the solid content became 6 mg / cm 2 , and dried. Then, rolling was performed to obtain an anode in which an anode active material layer was laminated on both sides of the anode base material.

[0089] (Negative electrode production) As negative electrode active material particles, natural graphite particles (internal void ratio 0.45%, pore volume of pores having a pore diameter of 7.8 nm or less 0.0028 cm 3 / g, average particle diameter 8 μm) on which densification treatment and coating treatment using a carbon material were performed were prepared. Anode active material paste was prepared using the above-described negative electrode active material particles, styrene-butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickening agent, and water as a dispersion medium. Note that the mass ratio of the negative electrode active material particles, SBR, and CMC was set to 98.5:1:0.5 (solid content conversion). Anode active material paste was applied to both sides of a copper foil as a negative electrode base material in such a manner that the mass of the solid content became 4 mg / cm 2 , and dried. Then, rolling was performed to obtain a negative electrode in which a negative electrode active material layer was laminated on both sides of the negative electrode base material. The porosity of the negative electrode active material layer was 35%.

[0090] (Nonaqueous electrolyte) LiPF6was dissolved in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) mixed at a volume ratio of 30:35:35 at a concentration of 1.0 mol / dm 3 to obtain a nonaqueous electrolyte.

[0091] (Separator) A polyolefin microporous film was used as a separator.

[0092] (Assembly of nonaqueous electrolyte storage element) A jelly-roll type electrode body was obtained using the above-described anode, cathode, and separator. The electrode body was housed in a container, a nonaqueous electrolyte was injected, and the container was sealed to obtain a nonaqueous electrolyte storage element of Example 1.

[0093] [Examples 2 and 3, Comparative Examples 1 to 11] Each nonaqueous electrolyte power storage element of Examples 2 and 3 and Comparative Examples 1 to 11 was obtained in the same manner as in Example 1 except that the kind of negative electrode active material particles and the porosity of the negative electrode active material layer were set as described in Table 1. The negative electrode active material particles were each natural graphite particles. The porosity of the negative electrode active material layer was adjusted by changing the pressure at the time of roll-pressing.

[0094] (initial charge and discharge) Each nonaqueous electrolyte power storage element obtained was subjected to initial charge and discharge under the following conditions. After constant current charging at a charge current of 1.0 C and a charge termination voltage of 4.10 V in a thermostat at 25°C, constant voltage charging was performed at 4.10 V. The end condition of the charging was set so that the total charge time reached 3 hours. Then, a pause period of 10 minutes was provided. Constant current discharge was performed at a discharge current of 1.0 C and a discharge termination voltage of 3.0 V. The discharge capacity at this time was taken as the rated capacity.

[0095] (determination of input) Each nonaqueous electrolyte power storage element of Examples 1 to 3 and Comparative Examples 1 to 11 was subjected to constant current charging at a current of 1.0 C at 25°C so that the SOC was 50%. Subsequently, after storage in a thermostat at -10°C for 4 hours, constant current charging was performed at 5 C, 10 C, 15 C, 20 C, or 25 C for 30 seconds each. The "SOC" (State of Charge) refers to the state of charge of the nonaqueous electrolyte power storage element determined in the voltage range normally used for the nonaqueous electrolyte power storage element, based on the rated capacity. After each charging, constant current discharge was performed at a current of 1.0 C so that the SOC was 50%. The relationship between the current in each charging and the voltage at the tenth second after the start of the charging was plotted, and the slope of the straight line obtained from the plot of 5 points was taken as the direct current resistance. The input at the tenth second after the start of the charging was calculated from the direct current resistance. The input of each nonaqueous electrolyte power storage element relative to the input of the nonaqueous electrolyte power storage element of Comparative Example 1 (100%) is shown in Table 1.

[0096] [table 1]

[0097] As shown in Table 1, the nonaqueous electrolyte power storage elements of Examples 2 and 3 and Comparative Examples 1 to 11 each had a fine pore volume of 0.0030 cm 3In each of the nonaqueous electrolyte power storage elements of Examples 1 to 3 in which the negative electrode active material particles (natural graphite particles) having a particle size of 10 μm or less and the negative electrode active material layer having a porosity in the range of 35% or more and 60% or less, the input (relative value) was 107% or more, and the input was large. Note that, from the results of Comparative Examples 2 to 7 and the results of Comparative Examples 8 to 11, it was found that, in the case where the negative electrode active material particles having an internal porosity exceeding 2%, a fine pore volume of 0.0030 cm3 / g or more, and a fine pore diameter of 7.8 nm or less were used, if the porosity of the negative electrode active material layer was reduced, there was a tendency for the input to be greatly reduced. On the other hand, from the results of Examples 1 to 3, it was found that, in the case where the negative electrode active material particles having an internal porosity of 2% or less, a fine pore volume of 0.0030 cm3 / g or less, and a fine pore diameter of 7.8 nm or less were used, even in the case where the porosity of the negative electrode active material layer was low, there was almost no reduction in the input. 3 / g of the negative electrode active material particles, if the porosity of the negative electrode active material layer was reduced, there was a tendency for the input to be greatly reduced. On the other hand, from the results of Examples 1 to 3, it was found that, in the case where the negative electrode active material particles having an internal porosity of 2% or less, a fine pore volume of 0.0030 cm3 / g or less, and a fine pore diameter of 7.8 nm or less were used, even in the case where the porosity of the negative electrode active material layer was low, there was almost no reduction in the input. 3 / g of the negative electrode active material particles, even in the case where the porosity of the negative electrode active material layer was low, there was almost no reduction in the input. Industrial applicability

[0098] The present application can be applied to a nonaqueous electrolyte power storage element or the like used as a power source for electronic devices such as personal computers, communication terminals, and the like, and automobiles and the like. Explanation of reference numerals

[0099] 1: nonaqueous electrolyte power storage element, 2: electrode body, 3: container, 4: positive electrode terminal, 41: positive electrode lead wire, 5: negative electrode terminal, 51: negative electrode lead wire, 20: power storage cell, 30: power storage device.

Claims

1. A negative electrode for a nonaqueous electrolyte power storage element, comprising a negative electrode active material layer containing negative electrode active material particles, the negative electrode active material particles contain natural graphite particles, an internal porosity of the negative electrode active material particles is 2% or less, The fine pore volume of fine pores having a diameter of 7.8 nm or less in the negative electrode active material particles is 0.0030 cm 3 / cm3 or less, a porosity of the negative electrode active material layer is 35% or more and 60% or less.

2. The negative electrode for a nonaqueous electrolyte power storage element according to claim 1, wherein an average particle diameter of the negative electrode active material particles is 6 μm or more and 10 μm or less.

3. A nonaqueous electrolyte power storage element comprising the negative electrode for a nonaqueous electrolyte power storage element according to claim 1 or 2.

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