Positive electrode for non-aqueous electrolyte energy storage element, non-aqueous electrolyte energy storage element, method for manufacturing positive electrode paste for non-aqueous electrolyte energy storage element, method for manufacturing positive electrode for non-aqueous electrolyte energy storage element, and method for manufacturing non-aqueous electrolyte energy storage element

Abstract

The present invention provides a positive electrode for a non-aqueous electrolyte energy storage element that can improve the capacity retention rate after charge-discharge cycles and reduce the resistance increase rate. [Solution] A positive electrode for a non-aqueous electrolyte energy storage element according to one aspect of the present invention comprises a positive electrode active material layer 6 containing positive electrode active material particles, an inorganic solid electrolyte, a conductive agent, and a binder, wherein the value of the active material aggregate density parameter, based on a two-dimensional image obtained by observing a cross-section of the positive electrode active material layer 6, is 0.05 or less, and the value of the solid electrolyte aggregate density parameter is 0.05 or less.

Description

Technical Field

[0001] The present invention relates to a positive electrode for a non-aqueous electrolyte storage element, a non-aqueous electrolyte storage element, a method for manufacturing a positive electrode paste for a non-aqueous electrolyte storage element, a method for manufacturing a positive electrode for a non-aqueous electrolyte storage element, and a method for manufacturing a non-aqueous electrolyte storage element.

Background Art

[0002] Non-aqueous electrolyte secondary batteries typified by lithium-ion secondary batteries are widely used in electronic devices such as personal computers and communication terminals, and automobiles because of their high energy density. A non-aqueous electrolyte secondary battery generally has a pair of electrodes electrically isolated from each other and a non-aqueous electrolyte interposed between the electrodes, and is configured to charge and discharge by transferring charge-transporting ions between both electrodes. As non-aqueous electrolyte storage elements other than non-aqueous electrolyte secondary batteries, capacitors such as lithium-ion capacitors and electric double layer capacitors are also widely popular.

[0003] In recent years, for the purpose of improving the safety of non-aqueous electrolyte storage elements, etc., storage elements using inorganic solid electrolytes such as sulfide-based solid electrolytes instead of non-aqueous electrolytic solutions as non-aqueous electrolytes have been proposed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Various charge-discharge performances are required for non-aqueous electrolyte storage elements, and it is desirable that the performance does not easily deteriorate even when charge-discharge is repeated. Even in non-aqueous electrolyte storage elements using inorganic solid electrolytes, it is desirable that a decrease in discharge capacity and an increase in resistance due to charge-discharge cycles do not easily occur.

[0006] The present invention aims to provide a positive electrode for a non-aqueous electrolyte storage element that can increase the capacity retention rate and lower the resistance increase rate after charge-discharge cycles, as well as a method for manufacturing a positive electrode paste for a non-aqueous electrolyte storage element and a method for manufacturing a positive electrode for a non-aqueous electrolyte storage element capable of manufacturing such a positive electrode. Another object of the present invention is to provide a non-aqueous electrolyte storage element having a high capacity retention rate and a low resistance increase rate after charge-discharge cycles, and a method for manufacturing such a non-aqueous electrolyte storage element.

Means for Solving the Problems

[0007] The positive electrode for a non-aqueous electrolyte storage element according to one aspect of the present invention includes a positive electrode active material layer containing positive electrode active material particles, an inorganic solid electrolyte, a conductive agent, and a binder, and the value of the active material aggregate presence density parameter based on a two-dimensional image obtained by observing the cross-section of the positive electrode active material layer is 0.05 or less, and the value of the solid electrolyte aggregate presence density parameter is 0.05 or less.

[0008] The non-aqueous electrolyte storage element according to another aspect of the present invention is an all-solid-state storage element including the positive electrode for a non-aqueous electrolyte storage element according to one aspect of the present invention.

[0009] The method for manufacturing a positive electrode paste for a non-aqueous electrolyte storage element according to another aspect of the present invention includes obtaining a composite of the positive electrode active material particles and the first inorganic solid electrolyte by dry composite treatment of the positive electrode active material particles and the first inorganic solid electrolyte, and mixing the composite, the second inorganic solid electrolyte, the conductive agent, the binder, and the dispersion medium, and the mixing includes a dispersion treatment.

[0010] The method for manufacturing a positive electrode for a non-aqueous electrolyte storage element according to another aspect of the present invention includes coating a positive electrode paste for a non-aqueous electrolyte storage element obtained by the method for manufacturing a positive electrode paste for a non-aqueous electrolyte storage element according to one aspect of the present invention.

[0011] The method for manufacturing a non-aqueous electrolyte storage element according to another aspect of the present invention includes the method for manufacturing a positive electrode for a non-aqueous electrolyte storage element according to one aspect of the present invention. [Effects of the Invention]

[0012] According to any aspect of the present invention, it is possible to provide a positive electrode for a non-aqueous electrolyte energy storage element that can increase the capacity retention rate and decrease the resistance increase rate after charge-discharge cycles in the non-aqueous electrolyte energy storage element, as well as a method for manufacturing a positive electrode paste for a non-aqueous electrolyte energy storage element and a method for manufacturing a positive electrode for a non-aqueous electrolyte energy storage element that can produce such a positive electrode. Furthermore, it is also possible to provide a non-aqueous electrolyte energy storage element that has a high capacity retention rate and a low resistance increase rate after charge-discharge cycles, and a method for manufacturing such a non-aqueous electrolyte energy storage element. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic diagram showing a portion of a two-dimensional cross-sectional image of the positive electrode to illustrate the procedure for calculating the density parameters of active material aggregates and solid electrolyte aggregates. [Figure 2] Figure 2 is a schematic cross-sectional view showing an all-solid-state secondary battery, which is one embodiment of the non-aqueous electrolyte energy storage element of the present invention. [Figure 3] Figure 3 is a schematic diagram showing an energy storage device comprising a non-aqueous electrolyte energy storage element according to multiple embodiments of the present invention. [Modes for carrying out the invention]

[0014] First, an overview of the positive electrode for a non-aqueous electrolyte energy storage element, the non-aqueous electrolyte energy storage element, the method for manufacturing the positive electrode paste for the non-aqueous electrolyte energy storage element, the method for manufacturing the positive electrode for the non-aqueous electrolyte energy storage element, and the method for manufacturing the non-aqueous electrolyte energy storage element disclosed herein will be described.

[0015] [1] A positive electrode for a non-aqueous electrolyte energy storage element according to one aspect of the present invention comprises a positive electrode active material layer containing positive electrode active material particles, an inorganic solid electrolyte, a conductive agent, and a binder, wherein the value of the active material aggregate density parameter, based on a two-dimensional image obtained by observing a cross-section of the positive electrode active material layer, is 0.05 or less, and the value of the solid electrolyte aggregate density parameter is 0.05 or less.

[0016] The positive electrode for non-aqueous electrolyte energy storage elements described in [1] above (hereinafter also simply referred to as "positive electrode") can increase the capacity retention rate after charge-discharge cycles in non-aqueous electrolyte energy storage elements and reduce the resistance increase rate. The reason for this is not clear, but the following reason is speculated. In the positive electrode described in [1] above, the value of the active material aggregate density parameter (hereinafter also referred to as "parameter P1") is 0.05 or less, and the value of the solid electrolyte aggregate density parameter (hereinafter also referred to as "parameter P2") is 0.05 or less. This is thought to indicate that the positive electrode active material particles and the inorganic solid electrolyte are well dispersed in the positive electrode active material layer, and in particular, that each positive electrode active material particle is sufficiently and firmly coated with the inorganic solid electrolyte. In such a case, a good interface is formed between the positive electrode active material particles and the inorganic solid electrolyte, the charge transfer resistance is reduced, and resistance increases due to reaction unevenness are less likely to occur. Furthermore, if the positive electrode active material particles are sufficiently and firmly coated with an inorganic solid electrolyte, interfacial bonding defects caused by the expansion and contraction of the positive electrode active material particles are less likely to progress. While a large contact area between the positive electrode active material particles and the inorganic solid electrolyte can accelerate side reactions and degrade the performance of a non-aqueous electrolyte energy storage element, if the positive electrode active material particles are sufficiently and firmly coated with an inorganic solid electrolyte, the effect of suppressing the progression of interfacial bonding defects and maintaining performance is considered to outweigh the effect of performance degradation due to accelerated side reactions. For these reasons, it is presumed that non-aqueous electrolyte energy storage elements using the positive electrode described in [1] above exhibit a low resistance increase rate and a high capacity retention rate after charge-discharge cycles.

[0017] Parameter P1 and parameter P2 are calculated using the following procedure. (1) Prepare the positive electrode to be measured. If the positive electrode to be measured is incorporated into a non-aqueous electrolyte energy storage element, the measurement shall be performed on the electrode processed according to the following procedure. First, the non-aqueous electrolyte energy storage element shall be charged with a constant current of 0.05C until it reaches the charging termination voltage for normal use, and be brought to a fully charged state. After a 30-minute rest, it shall be discharged with a constant current of 0.05C until it reaches the discharge termination voltage for normal use. Next, the non-aqueous electrolyte energy storage element shall be disassembled and the laminate shall be removed. The removed laminate shall be made to a size suitable for the following measurements, including the positive electrode, as necessary, and shall be used as the measurement sample. "Normal use" refers to the case in which the non-aqueous electrolyte energy storage element is used by adopting the charge and discharge conditions recommended or specified for the non-aqueous electrolyte energy storage element, and if equipment for using the non-aqueous electrolyte energy storage element is available, it refers to the case in which the non-aqueous electrolyte energy storage element is used by applying that equipment. (2) The cross section of the positive electrode or the sample for measurement is subjected to ion milling and observed with a scanning electron microscope (SEM) to obtain a two-dimensional cross-sectional image of the positive electrode active material layer. In the two-dimensional cross-sectional image, 20 of the largest positive electrode active material particles (if they are secondary particles, the entire set of secondary particles is considered as one particle) are selected, and the major and minor diameters are measured for each particle. Here, the "major diameter" of a particle is defined as the length of the longest line segment connecting any two points on the outer edge of the particle in the two-dimensional cross-sectional image, and the "minor diameter" is defined as the length of the shortest line segment passing through the midpoint of the major diameter and connecting any two points on the outer edge of the particle. The 20 positive electrode active material particles selected are those that are not aggregated with other positive electrode active material particles and are essentially independent as single particles. The average of the measured major and minor diameters is calculated as the particle diameter of that particle. The average of the particle diameters of these 20 particles is determined as the average particle diameter r (μm). (3) Observe and analyze the cross-section of the positive electrode or the sample for measurement using scanning electron microscope energy-dispersive X-ray spectroscopy (SEM-EDX) at the highest magnification in which the entire thickness of one positive electrode active material layer is included in the observation field, and measure the size (maximum length d1) of each aggregate of the positive electrode active material and the size (maximum length d2) of each aggregate of the inorganic solid electrolyte according to the following procedure. When performing elemental mapping as described later, elemental mapping may be performed based on a two-dimensional cross-sectional image of the positive electrode active material layer magnified to a higher magnification (magnification in which the entire thickness of one positive electrode active material layer is not included), and the regions in which positive electrode active material particles and regions in which inorganic solid electrolyte are present may be identified. The apparatus to be used for SEM-EDX is as follows. If it is not possible to measure using the following models of measuring equipment, other models that are expected to produce equivalent measurement results may be used. The same applies to other measuring equipment and analysis software in this specification. Equipment: Scanning electron microscope "JSM-IT500HR" (manufactured by JEOL) EDX detector "EX-74600U4L2Q Dry SD30 detector unit" (manufactured by JEOL) The measurement conditions in SEM-EDX can be appropriately set according to the type of elements to be mapped, including those contained in the positive electrode active material particles and the inorganic solid electrolyte. For example, if the positive electrode active material particles are a lithium transition metal composite oxide containing at least one of nickel, cobalt, and manganese, and the inorganic solid electrolyte is a sulfide-based solid electrolyte, and the elements to be mapped are at least one of nickel, cobalt, and manganese and oxygen, and the elements to be mapped are phosphorus and sulfur, as well as those contained in the inorganic solid electrolyte (sulfide-based solid electrolyte), the measurement will be performed under the following conditions. Acceleration voltage: 5kV Working distance (WD): 10.0 mm Resolution: 512 x 384 pixels Duel time (measurement time per pixel): 0.2ms Process time: T3 Number of sweeps: 10 The irradiation current should be adjusted so that the count rate is around 10,000 cps. Furthermore, the irradiation current, resolution, duel time, and number of sweeps should be adjusted as appropriate to improve the resolution of the mapping image. For observation and analysis using SEM-EDX, two cross-sectional two-dimensional images of the positive electrode active material layer shall be used, each covering a different region and taken at the highest magnification that simultaneously satisfies the following conditions (a) and (b). However, if satisfying condition (b) would mean not satisfying condition (a), the highest magnification that satisfies condition (b) shall be selected. (a) The thickness direction of the positive electrode active material layer includes the entire thickness of one positive electrode active material layer. (b) At least 20 through-lines, as described below, can be drawn in a direction perpendicular to the thickness direction of the positive electrode active material layer. Furthermore, the two cross-sectional two-dimensional images used are selected from at least ten cross-sectional two-dimensional images of entirely different regions. These images are then removed from any images that show an extremely large or small aggregated region compared to the other cross-sectional two-dimensional images, and the two images used are confirmed to represent the average state of the positive electrode of the subject being observed. (3-1) The following explanation will be given with reference to Figure 1, a schematic diagram of a two-dimensional cross-sectional image of the positive electrode. In the schematic diagram of Figure 1, "5" is the positive electrode substrate and "6" is the positive electrode active material layer. Elemental mapping is performed on the two-dimensional cross-sectional image of the positive electrode active material layer, and the region where peaks mainly attributable to the main elements constituting the positive electrode active material particles are detected is defined as the region 12 where the positive electrode active material particles exist. Similarly, the region where peaks mainly attributable to the main elements constituting the inorganic solid electrolyte are detected is defined as the region 13 where the inorganic solid electrolyte exists. For example, if the positive electrode active material particles are lithium transition metal composite oxide and the inorganic solid electrolyte is a sulfide-based solid electrolyte, the region where peaks mainly attributable to the transition metal elements and oxygen, which are the main elements constituting the lithium transition metal composite oxide, are detected is defined as the region 12 where the positive electrode active material particles exist. The region where peaks mainly attributable to the phosphorus and sulfur elements, which are the main elements constituting the sulfide-based solid electrolyte, are detected is defined as the region 13 where the inorganic solid electrolyte exists. The data analysis software "SMILE VIEW Lab" (manufactured by JEOL) is used to analyze the elemental mapping images. (3-2) In a two-dimensional cross-sectional image of the positive electrode active material layer in which the region 12 containing positive electrode active material particles and the region 13 containing the inorganic solid electrolyte are identified, 20 or more through lines 14 with a pitch of 2r (μm) at equal intervals are drawn in a direction perpendicular to the thickness direction of the positive electrode active material layer 6. That is, each through line 14 is drawn parallel to the normal to the surface of the positive electrode active material layer 6. Note that in Figure 1, only 8 through lines 14 are shown, but this is because, for explanatory purposes, only a portion of the central part of the two-dimensional cross-sectional image of the positive electrode active material layer in which 20 or more through lines have been drawn is shown. (3-3) For a two-dimensional cross-sectional image of the positive electrode active material layer in which the region 12 containing positive electrode active material particles and the region 13 containing the inorganic solid electrolyte have been identified, all regions in the region 12 containing positive electrode active material particles whose maximum length d1 (μm) is 3r (μm) or more are extracted. The "maximum length d1" of the region 12 containing positive electrode active material particles is defined as the distance between the two furthest points in a single "region 12 containing positive electrode active material particles". The direction of the "maximum length d1" is not considered. The ratio d1 / t of the maximum length d1 (μm) of the above region to the average thickness t (μm) of the positive electrode active material layer is calculated, and regions where the ratio d1 / t is greater than 0.15 are defined as active material aggregate regions. In this specification, "average thickness" means the average value of the thickness measured at any five locations. The value obtained by dividing the maximum length d1 of the active material aggregate region by 2r is defined as the number of through lines crossing the active material aggregate region. For each active material aggregate region, the number of through-lines crossing the active material aggregate region is determined. The ratio n1 / m of the sum of the number of through-lines crossing each active material aggregate region to the total number of through-lines m in the two-dimensional cross-sectional images of the two positive electrode active material layers is calculated as parameter P1. (3-4) For a two-dimensional cross-sectional image of the positive electrode active material layer in which the region 12 containing positive electrode active material particles and the region 13 containing inorganic solid electrolyte have been identified, all regions in the region 13 containing inorganic solid electrolyte in which the maximum length d2 (μm) is 3r (μm) or more are extracted. The "maximum length d2" of the region 13 containing inorganic solid electrolyte is defined as the distance between the two furthest points in a single "region 13 containing inorganic solid electrolyte". The direction of the "maximum length d2" is not considered. The ratio d2 / t of the maximum length d2 (μm) of the above region to the average thickness t (μm) of the positive electrode active material layer is calculated, and regions where the ratio d2 / t is greater than 0.15 are defined as solid electrolyte aggregate regions. However, regions where the "region 12 containing positive electrode active material particles" is located between the two furthest points in a single "region 13 containing inorganic solid electrolyte" are not included in the solid electrolyte aggregate regions. The number of through lines crossing the solid electrolyte aggregate region is defined as the maximum length d2 of the solid electrolyte aggregate region divided by 2r. The number of through lines crossing the solid electrolyte aggregate region is determined for each solid electrolyte aggregate region. The ratio n2 / m of the sum of the number of through lines crossing each solid electrolyte aggregate region to the total number of through lines m in the two-dimensional cross-sectional images of the two positive electrode active material layers is calculated as parameter P2.

[0018] The following explanation will use specific values ​​based on Figure 1. As mentioned above, each parameter is calculated using two cross-sectional two-dimensional images of two positive electrode active material layers, each with 20 or more through-lines. However, in the following explanation, only a single schematic diagram (Figure 1) with 8 through-lines is used for the calculations. In Figure 1, assume that r (average particle diameter of positive electrode active material particles) is 10 μm and t (average thickness of positive electrode active material layer) is 250 μm. (Calculation of parameter P1) In Figure 1, of the regions 12 where positive electrode active material particles exist, only regions 12A (d1=60μm) and 12B (d1=30μm) correspond to regions where the maximum length d1 is 3r (=30μm) or greater. Region 12A is an active material aggregate region because d1 / t=60 / 250=0.24 (>0.15), and the number of through-lines crossing this active material aggregate region (region 12A) is 3.0 (=d1 / 2r=60 / 20). Region 12B is not an active material aggregate region because d1 / t=30 / 250=0.12 (≦0.15). The total number of through-lines m in Figure 1 is 8, and the sum of the number of through-lines n1 crossing each active material aggregate region is 3.0. Therefore, the parameter P1 at the positive electrode in Figure 1 is approximately 0.38 (n1 / m=3.0 / 8). (Calculation of parameter P2) In Figure 1, of the regions 13 where the inorganic solid electrolyte exists, only region 13A (d2=50μm) corresponds to a region where the maximum length d2 is 3r (=30μm) or greater. Since region 13A has d2 / t=50 / 250=0.20 (>0.15), it is a solid electrolyte aggregate region, and the number of through-lines crossing this solid electrolyte aggregate region (region 13A) is 2.5 (=d2 / 2r=50 / 20). The total number of through-lines m in Figure 1 is 8, and the sum of the number of through-lines n2 crossing each solid electrolyte aggregate region is 2.5. Therefore, the parameter P2 at the positive electrode in Figure 1 is approximately 0.31 (n2 / m=2.5 / 8).

[0019] [2] In the positive electrode for the non-aqueous electrolyte energy storage element described in [1] above, the sum of the value of the active material aggregate density parameter and the value of the solid electrolyte aggregate density parameter may be 0.05 or less.

[0020] The positive electrode for the non-aqueous electrolyte energy storage element described in [2] above can increase the capacity retention rate and decrease the resistance increase rate after charge-discharge cycles in the non-aqueous electrolyte energy storage element.

[0021] [3] In the positive electrode for a non-aqueous electrolyte energy storage element described in [1] or [2] above, the positive electrode active material particles and at least a portion of the inorganic solid electrolyte form a composite, and in the composite, at least a portion of the surface of the positive electrode active material particles may be covered with at least a portion of the inorganic solid electrolyte.

[0022] The positive electrode for the non-aqueous electrolyte energy storage element described in [3] above can increase the capacity retention rate and decrease the resistance increase rate after charge-discharge cycles in the non-aqueous electrolyte energy storage element.

[0023] A "composite" refers to a particle that contains multiple components (positive electrode active material and inorganic solid electrolyte) within a single particle.

[0024] [4] Another aspect of the present invention is a non-aqueous electrolyte energy storage element comprising a positive electrode for a non-aqueous electrolyte energy storage element as described in any one of [1] to [3] above, all solid-state energy storage element.

[0025] The non-aqueous electrolyte energy storage element described in [4] above has a high capacity retention rate and a low resistance increase rate after charge-discharge cycles. Furthermore, since the non-aqueous electrolyte energy storage element described in [4] above is an all-solid-state energy storage element, the advantages arising from the formation of a good interface between the positive electrode active material particles and the inorganic solid electrolyte are particularly effectively utilized.

[0026] [5] A method for producing a positive electrode paste for a non-aqueous electrolyte energy storage element according to another aspect of the present invention comprises obtaining a composite of positive electrode active material particles and a first inorganic solid electrolyte by dry composite treatment of positive electrode active material particles and a first inorganic solid electrolyte, and mixing the composite, a second inorganic solid electrolyte, a conductive agent, a binder and a dispersion medium, wherein the mixing includes a dispersion treatment.

[0027] By using the method for manufacturing the positive electrode paste for non-aqueous electrolyte energy storage elements (hereinafter also simply referred to as "positive electrode paste") described in [5] above, it is possible to manufacture a positive electrode that can increase the capacity retention rate and decrease the resistance increase rate after charge-discharge cycles in a non-aqueous electrolyte energy storage element. The reason for this is not clear, but it is presumed that by forming a composite of positive electrode active material particles and the first inorganic solid electrolyte through a dry composite treatment of the positive electrode active material particles and the first inorganic solid electrolyte, the positive electrode active material particles become sufficiently and firmly coated with the first inorganic solid electrolyte, and that the positive electrode active material particles and the inorganic solid electrolyte are well dispersed by performing a dispersion treatment when the composite, the second inorganic solid electrolyte, the conductive agent, the binder and the dispersion medium are mixed.

[0028] "Dry compounding treatment" refers to a process that obtains a composite material in an environment that does not contain liquid.

[0029] [6] In the method for producing a positive electrode paste for a non-aqueous electrolyte energy storage element described in [5] above, the dispersion treatment may be carried out by a thin-film swirling high-speed mixer.

[0030] According to the method for manufacturing a positive electrode paste for a non-aqueous electrolyte energy storage element described in [6] above, a positive electrode can be manufactured that can further increase the capacity retention rate and further decrease the resistance increase rate after a charge-discharge cycle in a non-aqueous electrolyte energy storage element, as each of the positive electrode active material particles and the inorganic solid electrolyte is particularly well dispersed.

[0031] [7] Another aspect of the present invention relates to a method for manufacturing a positive electrode for a non-aqueous electrolyte energy storage element, which comprises coating a positive electrode paste obtained by the method for manufacturing a positive electrode paste described in [5] or [6] above.

[0032] According to the method for manufacturing a positive electrode described in [7] above, it is possible to manufacture a positive electrode that can increase the capacity retention rate after charge-discharge cycles in a non-aqueous electrolyte energy storage element and reduce the resistance increase rate.

[0033] [8] A method for manufacturing a non-aqueous electrolyte energy storage element according to another aspect of the present invention includes the method for manufacturing a positive electrode for a non-aqueous electrolyte energy storage element described in [7] above.

[0034] According to the method for manufacturing a non-aqueous electrolyte energy storage element described in [8] above, it is possible to manufacture a non-aqueous electrolyte energy storage element that has a high capacity retention rate and a low resistance increase rate after charge-discharge cycles.

[0035] The following describes in detail a positive electrode for a non-aqueous electrolyte energy storage element, a method for manufacturing a positive electrode paste for a non-aqueous electrolyte energy storage element, a method for manufacturing a positive electrode for a non-aqueous electrolyte energy storage element, a non-aqueous electrolyte energy storage element, a method for manufacturing a non-aqueous electrolyte energy storage element, and other embodiments according to one embodiment of the present invention.

[0036] Furthermore, the lower and upper limits of each numerical range described in the embodiments of the present invention can be combined in any way.

[0037] <Positive electrode for non-aqueous electrolyte energy storage elements> A positive electrode (positive electrode for a non-aqueous electrolyte energy storage element) according to one embodiment of the present invention comprises a positive electrode substrate and a positive electrode active material layer laminated directly to the positive electrode substrate or via an intermediate layer. Typically, the positive electrode has a portion where the positive electrode substrate is exposed. This exposed portion of the positive electrode substrate is typically connected to a positive electrode lead, which will be described later. The positive electrode may have a shape such as a sheet, plate, or strip. The positive electrode may be for a non-aqueous electrolyte secondary battery, an all-solid-state energy storage element, or an all-solid-state secondary battery.

[0038] The thickness of the positive electrode is set appropriately according to the application of the non-aqueous electrolyte energy storage element. The average thickness of the positive electrode may be, for example, 30 μm or more and 1,000 μm or less. The lower limit of the average thickness of the positive electrode may be 50 μm, 100 μm, or 200 μm. The upper limit of the average thickness of the positive electrode may be 500 μm, 400 μm, 300 μm, 200 μm, or 100 μm. The average thickness of the positive electrode is the average thickness of the portion in which the positive electrode active material layer is laminated directly onto the positive electrode substrate or via an intermediate layer. If both portions exist in which the positive electrode active material layer is laminated on both sides of the positive electrode substrate and portions in which the positive electrode active material layer is laminated on only one side of the positive electrode substrate, then the average thickness of the portion in which the positive electrode active material layer is laminated on both sides of the positive electrode substrate shall be used.

[0039] The positive electrode substrate is conductive. In this specification, "conductive" means that the volume resistivity is 10 -2 This means that it is Ω·cm or less. The volume resistivity shall be the value measured in accordance with JIS-H-0505 (1975). On the other hand, in this specification, "not conductive" or "having (electrical) insulating properties" means that the above volume resistivity is 10 7 This means it is greater than or equal to Ω·cm.

[0040] Examples of materials for the positive electrode substrate include metals such as aluminum, titanium, iron, and their alloys (stainless steel, etc.). Among these, aluminum or aluminum alloys are preferred from the viewpoint of high potential resistance, high electronic conductivity, and cost.

[0041] The positive electrode substrate has a shape such as a sheet, plate, or strip. Examples of positive electrode substrate forms include foil, vapor-deposited film, mesh, and porous material, with foil being preferred. The positive electrode substrate may also be, for example, aluminum foil or aluminum alloy foil.

[0042] The average thickness of the positive electrode substrate may be, for example, 3 μm or more and 50 μm or less. The lower limit of the average thickness of the positive electrode substrate may be 5 μm, 8 μm, 10 μm, or 15 μm. The upper limit of the average thickness of the positive electrode substrate may be 40 μm, 30 μm, 20 μm, or 15 μm.

[0043] The intermediate layer is a layer placed between the positive electrode substrate and the positive electrode active material layer. The intermediate layer includes, for example, a conductive agent and a binder. When the intermediate layer contains a conductive agent, the contact resistance between the positive electrode substrate and the positive electrode active material layer can be reduced. Examples of conductive agents and binders used in the intermediate layer are the same as those used in the positive electrode active material layer, which will be described later.

[0044] The positive electrode active material layer contains positive electrode active material particles, an inorganic solid electrolyte, a conductive agent, and a binder. The positive electrode active material layer may optionally contain components such as a thickener and a filler. The positive electrode active material layer may also be formed from a positive electrode mixture containing positive electrode active material particles, an inorganic solid electrolyte, a conductive agent, a binder, and other optional components. As shown in the non-aqueous electrolyte energy storage element 1 in Figure 2, which will be described later, the positive electrode active material layer may be provided on only one side of a positive electrode substrate having a shape such as a sheet. In another embodiment, the positive electrode active material layer may be provided on both sides of the positive electrode substrate.

[0045] The positive electrode active material particles are particulate positive electrode active material. Known positive electrode active materials can be used to form the positive electrode active material particles. For lithium-ion secondary batteries, the positive electrode active material is typically a material capable of intercalating and releasing lithium ions. Examples of positive electrode active materials include lithium transition metal composite oxides, polyanion compounds, chalcogen compounds, sulfur-based materials, and lithium oxide. One or more positive electrode active materials can be used.

[0046] Examples of transition metal elements included in lithium transition metal composite oxides include nickel, cobalt, and manganese. Lithium transition metal composite oxides may also contain typical metal elements such as aluminum. Examples of lithium transition metal composite oxides include those having an α-NaFeO2 crystal structure and those having a spinel crystal structure.

[0047] Li1+α Ma 1-α O2 (Ma is a metal element other than lithium element, containing one or more transition metal elements. 0 ≦ α < 1). Examples thereof include those represented by this formula. Ma preferably contains one or more of Ni, Co, and Mn. As the total content of Ni, Co, and Mn with respect to Ma ((Ni + Co + Mn) / Ma), 90 mol% or more is preferable, and 98 mol% or more is more preferable.

[0048] As the lithium transition metal composite oxide having a spinel crystal structure, Li β Mb2O4 (Mb is a metal element other than lithium element, containing one or more transition metal elements. 0 < β ≦ 1.2). Examples thereof include those represented by this formula. Mb preferably contains Mn. As the content of Mn with respect to Mb (Mn / Mb), 50 mol% or more is preferable, and 80 mol% or more is more preferable.

[0049] The polyanion compound is a compound composed of a polyanion (that is, a polyvalent oxoacid anion) and a cation. The polyanion compound preferably contains a lithium cation and a transition metal cation as the cation. Examples of the polyanion compound include LiFePO4, LiMnPO4, LiMn x Fe 1-x PO4 (0 < x < 1), LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, Li2CoPO4F, etc. The surface of the particles of the polyanion compound may be coated with other materials (such as the carbon material described later).

[0050] Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, molybdenum dioxide, etc.

[0051] Examples of the sulfur-based material include elemental sulfur, metal sulfides such as lithium sulfide, organic disulfide compounds, organic sulfur compounds such as carbon sulfide compounds, etc.

[0052] As the positive electrode active material, among these, a lithium transition metal composite oxide or a polyanion compound is preferable, a lithium transition metal composite oxide is more preferable, and a lithium transition metal composite oxide having an α-NaFeO2-type crystal structure is even more preferable. Further, the lithium transition metal composite oxide preferably contains a nickel element, and more preferably contains a nickel element, a cobalt element, and an aluminum element.

[0053] Atoms or polyanions in these materials that are positive electrode active materials may be partially substituted with atoms or anion species composed of other elements.

[0054] The positive electrode active material particles preferably have a coating layer that coats the positive electrode active material as the base material. By having a coating layer, the positive electrode active material particles can suppress side reactions with the inorganic solid electrolyte. Examples of the material constituting the coating layer include oxides containing a Group 4 element or a Group 5 element and a lithium element, such as LiNbO3, LiTaO3, Li2ZrO3, Li 4 / 3 Ti 5 / 3 O4, Li2TiO3, etc., and LiNbO3 is preferable.

[0055] The average particle diameter (r) of the positive electrode active material particles is preferably, for example, 0.1 μm or more and 20 μm or less. As the lower limit of the average particle diameter, 0.5 μm is more preferable, 1.0 μm is even more preferable, and 1.5 μm, 2.0 μm, 2.5 μm, or 3.0 μm is even more preferable. By setting the average particle diameter of the positive electrode active material particles to be at least the above lower limit, the production or handling of the positive electrode active material particles becomes easy. As the upper limit of the average particle diameter, 10 μm is more preferable, 8.0 μm is even more preferable, and 6.0 μm, 5.0 μm, 4.0 μm, or 3.5 μm is even more preferable. By setting the average particle diameter of the positive electrode active material particles to be at most the above upper limit, the electron conductivity of the positive electrode active material layer is improved. For the method of obtaining particles such as the positive electrode active material and the negative electrode active material described later with a predetermined particle diameter, for example, a known method using a pulverizer, a classifier, etc. can be adopted.

[0056] The lower limit of the content of positive electrode active material particles in the positive electrode active material layer is preferably 50% by mass, more preferably 60% by mass, even more preferably 70% by mass, and even more preferably 75% by mass. On the other hand, the upper limit of the content of positive electrode active material particles is preferably 95% by mass, more preferably 90% by mass, even more preferably 85% by mass, and even more preferably 80% by mass. By setting the content of positive electrode active material particles within the above range, it is possible to achieve both high energy density and manufacturability in the positive electrode active material layer.

[0057] An inorganic solid electrolyte is an electrolyte that maintains a solid state at 25°C under a nitrogen atmosphere. Preferably, the inorganic solid electrolyte has lithium ion conductivity. The inorganic solid electrolyte may be crystalline or amorphous. In one embodiment of the present invention, the inorganic solid electrolyte may be crystalline. A crystalline solid electrolyte is a solid electrolyte in which peaks originating from the solid electrolyte are observed in the X-ray diffraction pattern. An amorphous solid electrolyte is a solid electrolyte in which the X-ray diffraction pattern is a halo pattern, in which substantially no peaks other than those originating from the raw materials are observed. One or more types of inorganic solid electrolytes can be used.

[0058] Examples of inorganic solid electrolytes include sulfide-based solid electrolytes, oxide-based solid electrolytes, and halide-based solid electrolytes, with sulfide-based solid electrolytes being preferred. The upper limit of the oxygen content in sulfide-based solid electrolytes may be 10 mol%, 1 mol%, or 0.1 mol%.

[0059] The sulfide-based solid electrolyte preferably contains at least the element sulfur, and more preferably the element lithium. The sulfide-based solid electrolyte may also preferably contain the element phosphorus, and more preferably the element halogen. The sulfide-based solid electrolyte may contain the element chlorine as the halogen.

[0060] When a sulfide-based solid electrolyte is a crystalline solid electrolyte, its crystal structure can be an argyrodite type crystal structure, a Li3PS4 crystal structure, a Li4P2S6 crystal structure, or a Li7P3S crystal structure.11 Crystal structure, Li 10 GeP2S 12 Examples of sulfide-based solid electrolytes include crystal structures such as a crystalline structure, a thio-lisicon-type crystal structure, an inverse fluorite-type crystal structure, a crystal structure having diffraction peaks in the ranges of 19.9°±0.5° and 29.3°±0.5° in the X-ray diffraction pattern using CuKα rays, a crystal structure having diffraction peaks in the ranges of 21.0±0.5° and 28.0±0.5° in the X-ray diffraction pattern using CuKα rays, and a crystal structure having different diffraction peaks in the ranges of 17.9°±0.5° or 19.1°±0.5°, 29.1°±0.5°, and 29.8°±0.5°, with one of these diffraction peaks being the largest diffraction peak. The sulfide-based solid electrolyte may also have an argyrodite-type crystal structure.

[0061] Examples of sulfide-based solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-Li3N, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z. m S 2n (However, m and n are positive numbers, and Z is one of Ge, Zn, or Ga.) Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (However, x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, or In.) Li 10 GeP2S 12 These are some examples.

[0062] As an oxide-based solid electrolyte, Li7La3Zr2O 12 Li0.5 La 0.5 Examples include TiO3, LiTi2(PO4)3, Li3BO3-Li2CO3, and Li3BO3-Li2SO4.

[0063] Examples of halogen-based solid electrolytes include Li3YCl6, Li3YBr6, Li3YI6, Li3InCl6, Li3InBr6, Li3InF6, Li2ZrCl6, Li3ErCl6, Li3ErBr6, Li3DyCl6, Li3DyBr6, Li3GdCl6, Li3GdBr6, Li3HoCl6, Li3HoBr6, Li3LaCl6, Li3LaBr6, Li3NdCl6, Li3NdBr6, Li3ScCl6, Li3ScBr6, Li3ScF6, Li3SmCl6, Li3SmBr6, Li3TbCl6, Li3TbBr6, Li3TmCl6, Li3TmBr6, Li3AlF6, Li3TiF6, Li3GaF6, and Li3GeF6.

[0064] The lower limit of the inorganic solid electrolyte content in the positive electrode active material layer is preferably 5% by mass, more preferably 10% by mass, even more preferably 15% by mass, and still more preferably 18% by mass. The upper limit of the inorganic solid electrolyte content is preferably 40% by mass, more preferably 35% by mass, even more preferably 30% by mass, and still more preferably 25% by mass. When the inorganic solid electrolyte content is within the above range, the positive electrode active material particles and the inorganic solid electrolyte can form a sufficient interface, which can lead to a higher capacity retention rate and a lower resistance increase rate in the non-aqueous electrolyte energy storage element after charge-discharge cycles.

[0065] In the positive electrode active material layer, a portion of the inorganic solid electrolyte may form a composite with the positive electrode active material particles. The composite may be a state in which each component (positive electrode active material and inorganic solid electrolyte) is mechanically combined. The composite may be formed by, for example, a dry compounding treatment described later. The composite has a form in which at least a portion of the surface of the positive electrode active material particles is coated with the inorganic solid electrolyte. When the composite exists in such a state in which at least a portion of the surface of the positive electrode active material particles is coated with the inorganic solid electrolyte, it is possible to further increase the capacity retention rate after charge-discharge cycles in the non-aqueous electrolyte energy storage element and further decrease the resistance increase rate.

[0066] The content of the positive electrode active material in the composite of positive electrode active material particles and inorganic solid electrolyte is preferably 80% to 99% by mass, more preferably 90% to 98% by mass, and even more preferably 93% to 97% by mass. The content of the inorganic solid electrolyte in the above composite is preferably 1% to 20% by mass, more preferably 2% to 10% by mass, and even more preferably 3% to 7% by mass. The lower limit of the total content of positive electrode active material and inorganic solid electrolyte in the above composite may be 90% by mass, 95% by mass, or 99% by mass. The upper limit of the total content may be 100% by mass.

[0067] When a portion of an inorganic solid electrolyte forms a composite with positive electrode active material particles, the inorganic solid electrolyte forming the composite and the other inorganic solid electrolytes may be of the same type or of different types. In one embodiment of the present invention, the inorganic solid electrolyte forming the composite and the other inorganic solid electrolytes may be of the same type.

[0068] The positive electrode active material layer may further contain other solid electrolytes besides the inorganic solid electrolyte (such as dry polymer electrolytes or gel polymer electrolytes). However, the lower limit of the inorganic solid electrolyte content relative to all solid electrolytes in the positive electrode active material layer is preferably 90% by mass, and more preferably 99% by mass. The upper limit of the inorganic solid electrolyte content may be 100% by mass.

[0069] Conductive agents are typically components made of conductive materials. Even if the volume resistivity of a conductive agent cannot be directly measured, if the volume resistivity is 10 -2 Materials whose conductivity is known to be Ω·cm or less are classified as conductive agents. Examples of conductive agents include carbon materials, metals, and conductive ceramics. A carbon material is a material whose main constituent element is carbon. The main constituent element is the element that is present in the largest quantity by mass. For example, the carbon content in a carbon material may be 80% by mass or more, 90% by mass or more, 95% by mass, 99% by mass, or 99.9% by mass or more. It is preferable that the carbon material is a carbon material other than a non-carbonized polymer compound. Examples of carbon materials include graphite, non-graphitic carbon, and graphene-based carbon. Examples of non-graphitic carbon include carbon nanofibers, pitch-based carbon fibers, and carbon black. Examples of carbon black include furnace black, acetylene black, and Ketjen black. Examples of graphene-based carbon include graphene, carbon nanotubes (CNTs), and fullerenes. Conductive agents can take the form of powder or fibers. One or more types of conductive agents can be used. These materials may also be used as a composite of conductive agents. For example, a composite material of carbon black and CNTs may be used.

[0070] The conductive agent used in the positive electrode active material layer is preferably a carbon material. Furthermore, the conductive agent used in the positive electrode active material layer is also preferably a fibrous conductive agent. Preferred fibrous carbon conductive agents include single-layer or multi-layer carbon nanotubes (CNTs), other carbon fibers, and so on.

[0071] The conductive agent content in the positive electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 9% by mass or less. The upper limit of the conductive agent content may be 8% by mass, 5% by mass, 4% by mass, 3% by mass, or 2.5% by mass. The lower limit of the conductive agent content may be 1.5% by mass. By setting the conductive agent content within the above range, it is possible to increase the energy density of the non-aqueous electrolyte energy storage element.

[0072] Examples of binders include water-based binders and organic solvent-based binders.

[0073] A water-based binder is a binder that dissolves or disperses in water. A water-based binder may be one that dissolves or disperses in 100 parts by mass or more per 100 parts by mass of water at 20°C. When forming a positive electrode active material layer using a positive electrode mixture paste in which the dispersion medium is water or a mixed solvent mainly composed of water, a water-based binder (water-soluble or water-dispersible polymer material) can be used. Examples of water-based binders include polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polytetrafluoroethylene, styrene-butadiene rubber, polyethylene, polypropylene, nitrile-butadiene rubber, and cellulose.

[0074] An organic solvent-based binder is a binder that dissolves or disperses in an organic solvent (e.g., N-methylpyrrolidone). An organic solvent-based binder may be a binder that dissolves or disperses at 1 part by mass or more per 100 parts by mass of an organic solvent (e.g., N-methylpyrrolidone) at 20°C. When forming a positive electrode active material layer using a positive electrode mixture paste in which the dispersion medium is an organic solvent or a mixed solvent mainly composed of an organic solvent, an organic solvent-based binder (a polymer material having solubility or dispersibility in an organic solvent) can be used. Examples of organic solvent-based binders include polyvinylidene fluoride, copolymers of vinylidene fluoride and hexafluoropropylene, copolymers of ethylene and vinyl alcohol, polyacrylonitrile, polyphosphazene, polysiloxane, polyvinyl acetate, polymethyl methacrylate, polystyrene, polycarbonate, polyamide, polyimide, polyamideimide, crosslinked polymers of cellulose and chitosan pyrrolidone carboxylate, and derivatives of chitosan.

[0075] The binder may be a fluororesin (polytetrafluoroethylene, polyvinylidene fluoride, etc.), a polyolefin (polyethylene, polypropylene, etc.), an elastomer (ethylene propylene diene rubber, styrene butadiene rubber, fluororubber, etc.), a polysaccharide polymer (cellulose, chitosan derivatives, etc.), etc. Fluororesins are preferred as the binder, and polyvinylidene fluoride is more preferred. One or more types of binders can be used.

[0076] The binder content in the positive electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, preferably 0.5% by mass or more and 8% by mass or less, and more preferably 1.0% by mass or more and 5% by mass or less. The upper limit of the binder content may be 4% by mass, 3% by mass, 2% by mass, or 1.5% by mass. By setting the binder content within the above range, it is possible to stably hold positive electrode active material particles, etc.

[0077] Examples of thickening agents include polysaccharide polymers such as carboxymethylcellulose, methylcellulose, and ethylcellulose. If the thickening agent has a functional group that reacts with lithium, etc., this functional group may be deactivated beforehand by methylation or the like. The thickening agent may also function as a binder. One or more types of thickening agents can be used. When the positive electrode active material layer contains a thickening agent, the content of the thickening agent in the positive electrode active material layer is preferably 0.1% by mass or more and 8% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less. The technology disclosed herein can also be carried out in a form in which the positive electrode active material layer does not contain a thickening agent.

[0078] The filler is not particularly limited. The filler may be a component other than the positive electrode active material particles, solid electrolyte, conductive agent, binder, and thickener, and may be a component that is intentionally included. The filler may be included as a component that fills gaps in the positive electrode active material layer, or it may be included for other purposes. The filler may be an organic substance such as a polyolefin, or an inorganic substance such as an inorganic oxide, hydroxide, or carbonate. One or more types of fillers may be used. When the positive electrode active material layer contains a filler, the filler content in the positive electrode active material layer can be 0.1% by mass or more and 8% by mass or less, usually preferably 5% by mass or less, and more preferably 2% by mass or less. The technology disclosed herein can also be carried out in a form in which the positive electrode active material layer does not contain a filler.

[0079] The positive electrode active material layer may further contain other components besides positive electrode active material particles, solid electrolyte, conductive agent, binder, thickener, and filler. These other components may include those unintentionally present in the positive electrode active material layer. The positive electrode active material layer may also contain impurities unintentionally present as these other components, insofar as they achieve the effects of the present invention. The upper limit of the content of these other components in the positive electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of unintentionally present components in the positive electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of unintentionally present impurities in the positive electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass.

[0080] The lower limit of the total content of positive electrode active material particles, inorganic solid electrolyte, conductive agent, and binder in the positive electrode active material layer is preferably 90% by mass, more preferably 95% by mass, and even more preferably 99% by mass. The upper limit of the above total content may be 100% by mass.

[0081] The upper limit of the value of the active material aggregate density parameter (parameter P1), based on a two-dimensional image obtained by observing a cross-section of the positive electrode active material layer, is 0.05, preferably 0.03, and more preferably 0.01. When the value of parameter P1 is less than or equal to the above upper limit, the positive electrode active material particles are dispersed in a good state within the positive electrode active material layer, which can increase the capacity retention rate after charge-discharge cycles in the non-aqueous electrolyte energy storage element and reduce the resistance increase rate. The lower limit of the value of parameter P1 may be 0. Furthermore, the value of parameter P1 may be 0. As will be described later, a positive electrode with a small value of parameter P1 can be obtained by manufacturing a positive electrode using a positive electrode paste containing a composite formed by a dry compounding treatment of positive electrode active material particles and an inorganic solid electrolyte.

[0082] The upper limit of the solid electrolyte aggregate density parameter (parameter P2), based on a two-dimensional image obtained by observing a cross-section of the positive electrode active material layer, is 0.05, preferably 0.03, and more preferably 0.01. When the value of parameter P2 is below the above upper limit, the inorganic solid electrolyte is well dispersed in the positive electrode active material layer, which can increase the capacity retention rate after charge-discharge cycles in the non-aqueous electrolyte energy storage element and reduce the resistance increase rate. The lower limit of the value of parameter P2 may be 0. Furthermore, the value of parameter P2 may be 0. As will be described later, a positive electrode with a small value of parameter P2 can be obtained by manufacturing a positive electrode using a positive electrode paste that has undergone a predetermined dispersion treatment.

[0083] The upper limit of the sum of the value of the active material aggregate density parameter and the value of the solid electrolyte aggregate density parameter (the sum of the value of parameter P1 and the value of parameter P2) is preferably 0.05, more preferably 0.03, and even more preferably 0.01. When the sum of the value of parameter P1 and the value of parameter P2 is less than or equal to the above upper limit, the positive electrode active material particles and inorganic solid electrolyte are dispersed in a particularly good state in the positive electrode active material layer, which can increase the capacity retention rate and decrease the resistance increase rate after charge-discharge cycles in the non-aqueous electrolyte energy storage element. The lower limit of the sum of the value of parameter P1 and the value of parameter P2 may be 0. Furthermore, the sum of the value of parameter P1 and the value of parameter P2 itself may be 0.

[0084] The thickness of the positive electrode active material layer is set appropriately according to the type of positive electrode active material, the application of the non-aqueous electrolyte energy storage element, etc. The average thickness of one positive electrode active material layer may be, for example, 5 μm or more and 1,000 μm or less. The lower limit of the average thickness of one positive electrode active material layer may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, or 60 μm. The upper limit of the average thickness of one positive electrode active material layer may be 800 μm, 500 μm, 200 μm, 100 μm, or 80 μm. The mass per unit area of ​​one positive electrode active material layer may be, for example, 4 mg / cm². 2 More than 100mg / cm 2 The following is also acceptable: The lower limit of the mass per unit area of ​​one positive electrode active material layer is 10 mg / cm².2 , 15 mg / cm³ 2 or 18 mg / cm³ 2 It may also be the case that the upper limit of the mass per unit area of ​​one positive electrode active material layer is 50 mg / cm². 2 , 40 mg / cm³ 2 , 30 mg / cm³ 2 or 25 mg / cm³ 2 That's fine.

[0085] <Method for manufacturing positive electrode paste for non-aqueous electrolyte energy storage elements> The following describes a method for manufacturing a positive electrode paste for a non-aqueous electrolyte energy storage element, as part of a method for manufacturing a positive electrode according to one embodiment of the present invention. The method for manufacturing a positive electrode paste (positive electrode paste for a non-aqueous electrolyte energy storage element) according to one embodiment of the present invention comprises obtaining a composite of positive electrode active material particles and a first inorganic solid electrolyte (step 1), and mixing the composite, a second inorganic solid electrolyte, a conductive agent, a binder, and a dispersion medium (step 2).

[0086] The first inorganic solid electrolyte and the second inorganic solid electrolyte may be of the same type or of different types. Preferably, both the first and second inorganic solid electrolytes are sulfide-based solid electrolytes. The inorganic solid electrolyte used in this manufacturing method may have an average particle size of 1 μm or less. The average particle size of the inorganic solid electrolyte used in this manufacturing method may be, for example, 0.1 μm or more and 1 μm or less, 0.3 μm or more and 0.9 μm or less, or 0.5 μm or more and 0.8 μm or less. When an inorganic solid electrolyte with a small average particle size is used in this way, although an interface with the positive electrode active material particles is sufficiently formed, aggregation of the inorganic solid electrolyte tends to occur. On the other hand, in this manufacturing method, even when an inorganic solid electrolyte with an average particle size of 1 μm or less is used, the inorganic solid electrolyte is sufficiently dispersed, and as a result, a good interface is sufficiently formed between the positive electrode active material particles and the inorganic solid electrolyte, and both the positive electrode active material particles and the inorganic solid electrolyte are well dispersed. The "average particle size" of inorganic solid electrolytes refers to the value (D50) at which the volume-based integrated distribution, calculated in accordance with JIS-Z-8819-2 (2001), becomes 50%, based on the particle size distribution measured by laser diffraction / scattering on a dilution obtained by diluting particles with a solvent, in accordance with JIS-Z-8825 (2013).

[0087] In step 1, a composite of positive electrode active material particles and a first inorganic solid electrolyte is obtained by a dry composite treatment of positive electrode active material particles and a first inorganic solid electrolyte. The resulting composite may have at least a portion of the surface of the positive electrode active material particles coated with the inorganic solid electrolyte.

[0088] Dry compounding treatment includes, for example, a method of mixing positive electrode active material particles and an inorganic solid electrolyte while applying mechanical energy such as impact, compression, and shear force. The apparatus that can be used in dry compounding treatment is not particularly limited, but preferably includes particle compounding apparatus such as a ball mill, Hosokawa Micron's "Mechanofusion® System", Hosokawa Micron's "Nobilta®", and Nara Machine Works' "Hybridization System®". Among these, the "Mechanofusion System", "Nobilta", and "Hybridization System", which can effectively apply mechanical energy, are more preferred, the "Mechanofusion System" and "Nobilta" are even more preferred, and "Nobilta" is even more preferred.

[0089] The "hybridization system" is a particle compounding device that uses a compounding technology called the high-speed airflow impact method, which imparts mechanical energy to particles in a high-speed airflow. In the "hybridization system," raw material particles are introduced into a device that includes a high-speed rotating rotor, stator, and circulation circuit, and mechanical energy such as impact, compression, and shear force can be applied to the raw material particles while they are dispersed within the device. The raw material particles introduced into the device are impacted by the high-speed rotating rotor and carried to the outer periphery with the airflow. A circulation path is provided at the outer periphery, and the raw material particles are transported again to the center of the rotor with the airflow and subjected to the same impact action. Mechanical energy is imparted to the raw material particles through this repeated action. Conditions such as the rotor rotation speed, processing time, input amount, and circulating gas can be adjusted as appropriate.

[0090] The "Mechanofusion System" is a particle composite device that uses a composite technology to impart strong mechanical energy to multiple different material particles. In the "Mechanofusion System," powdered raw materials fed into a rotating container are fixed to the inner wall of the container by centrifugal force, and mechanical energy is imparted to the raw material particles by repeatedly applying strong compression and shearing forces by a press head. The reason why the "Mechanofusion System" is preferable is that large compression and shearing forces are applied to the raw material particles between the inner wall of the rotating container and the press head, imparting mechanical energy that results in a composite with sufficient coverage and adhesion strength. In this way, particle composite formation progresses as the compression and shearing process is repeated at high speed. Specifically, a composite with a strong bonding interface can be created by going through a stage in which different types of fine particles adhere to the surface of core particles that have been activated by mechanical action, and a stage in which, after a certain amount of different types of fine particles have adhered to the surface of the core particles, further fine particles are stacked and the fine particle layer itself is compacted to form a composite fine particle layer. Conditions such as the rotor rotation speed, processing time, and amount of material can be adjusted as appropriate.

[0091] "Nobilta" is a particle compounding device that uses compounding technology to impart mechanical energy of impact, compression, and shear to multiple raw material particles. In "Nobilta," an impeller (also called a rotor, rotating blade, or vane wheel) is positioned in a mixing container with a predetermined gap between it and the inner wall of the mixing container. This impeller rotates at high speed, forcing the raw material particles to pass through the gap multiple times. This process uniformly applies impact, compression, and shear forces to multiple raw material particles, enabling compounding of the multiple raw material particles. The reason why Nobilta is preferred is that the process of forcing the raw material particles to pass through the gap between the inner wall of the mixing container and the impeller applies significant impact, compression, and shear forces to the raw material particles, imparting mechanical energy that results in a composite with sufficient coverage and adhesion strength. In particular, it is easier to compound nano-order raw material particles. Conditions such as the rotation speed of the impeller, processing time, and amount of material can be adjusted as appropriate. A common feature of the "Mechanofusion System" and "Nobilta" is the application of large compressive and shearing forces to the raw material particles between the inner wall of the mixing container and a pressing jig called a press head or impeller. In addition to compressive and shearing forces, "Nobilta" can uniformly apply impact force to the raw material particles.

[0092] The rotational speed of the impeller in "Nobilta" is adjusted as appropriate according to the size of the impeller, etc., but is preferably 1,000 rpm to 10,000 rpm, more preferably 2,000 rpm or more, more preferably 4,000 rpm or more, and more preferably 6,000 rpm or more. The processing time in the above process is preferably 0.5 minutes to 30 minutes, more preferably 1 minute to 20 minutes, and even more preferably 2 minutes to 10 minutes. The process may be carried out in multiple stages, in which case it is preferable that the total processing time is within the above range.

[0093] A ball mill is a particle compounding device that uses compounding technology to impart mechanical energy to multiple raw material particles by mixing them with pebbles of a predetermined weight and diameter, such as zirconia balls. In a ball mill, multiple raw material particles are placed in a pot of a predetermined diameter in a dry state along with pebbles, and the pot is rotated at a predetermined speed to mix the raw material particles for a predetermined time. At this time, it is desirable to rotate the pot while water cooling it to prevent the temperature of the raw material particles from rising and the particle size from increasing. As a result, other raw material particles are embedded in the surface of the raw material particles, and a composite can be obtained. In the case of a ball mill, although a certain amount of mechanical energy can be imparted, the amount of mechanical energy that can be imparted to the raw material particles is lower compared to the "mechanofusion system," "Nobilta," and "hybridization system," and therefore it requires a longer processing time compared to the "mechanofusion system," "Nobilta," and "hybridization system."

[0094] In step 2, the obtained composite, the second inorganic solid electrolyte, the conductive agent, the binder, and the dispersion medium are mixed. In step 2, a dispersion treatment is performed when mixing each component. A dispersion medium used in the preparation of conventionally known positive electrode pastes can be used as the dispersion medium. Examples of dispersion media include hydrocarbons, carboxylic acid esters, ethers, amides, sulfoxides, etc. In one embodiment of the present invention, the dispersion medium may be a carboxylic acid ester such as ethyl acetate, butyl acetate, butyl propionate, butyl butyrate, or propyl butyrate, or butyl butyrate.

[0095] Mixing of the components can be done, for example, by stirring and mixing each component using a kneader. Examples of kneaders include rotary and orbital mixers.

[0096] In this process, the mixture of each component is further dispersed. This dispersion process effectively disperses the inorganic solid electrolyte in the mixture.

[0097] Dispersion processing is preferably carried out using a thin-film swirling high-speed mixer. A thin-film swirling high-speed mixer is a device that disperses materials by applying centrifugal force and shear stress to them. Therefore, dispersing using a thin-film swirling high-speed mixer is particularly effective in dispersing inorganic solid electrolytes and other components in the mixture.

[0098] When performing dispersion processing using a thin-film swirling high-speed mixer, the rotation speed of the thin-film swirling high-speed mixer is adjusted appropriately according to the size of the apparatus, etc., but is preferably 5,000 rpm to 30,000 rpm, more preferably 10,000 rpm or more, and more preferably 15,000 rpm or more. The processing time in the above process may be, for example, 0.5 minutes to 3 minutes. The process may be performed in multiple stages, in which case it is preferable that the total processing time is within the above range. Furthermore, the solid content concentration of the mixed liquid subjected to dispersion processing may be, for example, 50% by mass to 90% by mass or 60% by mass to 80% by mass.

[0099] After steps 1 and 2, a positive electrode paste is obtained. The positive electrode paste is subjected to a shear rate of 0.1 s using a rheometer. -1 from 1,000s -1 The hysteresis area value obtained by performing a hysteresis loop measurement within the range is 10s -1 It is preferable that the value be less than or equal to 7s mPa·s. -1 It is more preferable that it be less than or equal to 5s mPa·s. -1 It is even more preferable that the value of the hysteresis area is less than or equal to the above upper limit. When the value of the hysteresis area is less than or equal to the above upper limit, the positive electrode active material particles and inorganic solid electrolyte are sufficiently dispersed in the positive electrode paste, and by manufacturing a positive electrode using such a positive electrode paste, the capacity retention rate after charge-discharge cycles in a non-aqueous electrolyte energy storage element can be increased and the resistance increase rate can be decreased. The lower limit of the value of the hysteresis area is, for example, 0.1s. -1 It may also be mPa·s, 1s -1 mPa·s may also be used.

[0100] The hysteresis loop measurement described above is performed using an Anton Paar rheometer (MCR702e) and Anton Paar rheometer operating software (Rheocompass version 1.33) following the procedure below, and the value of the hysteresis area is calculated by automatic analysis using the software. The measurement is performed by placing a positive electrode paste as a sample between the rheometer stage and the plate, and rotating the plate. Anton Paar cone plate CP25-3 (diameter 24.960 mm, cone angle 2.991°) is used as the plate, and the sample volume is 0.21 mL. The distance between the tip of the plate and the stage is 169 μm. The measurement temperature is 25°C, and the measurement is performed in a glove box filled with argon gas. First, the shear rate is set to 0.1 s. -1 from 1,000s -1 The viscosity is measured by increasing the viscosity to a certain level, and a curve (flow curve 1) is obtained. Subsequently, the shear rate is increased to 1,000 s. -1 from 0.1s -1 The viscosity is reduced to a certain level, and a curve (flow curve 2) is obtained by measuring the viscosity. The area between the obtained flow curve 1 and flow curve 2 (hysteresis area) is taken as the hysteresis area value and calculated by automatic analysis using software. Here, the number of data points is set to "21", the data acquisition time is set to "steady state", and the timeout is set to 300s. In addition, the steady state conditions are set to a test value duration of 1s and an allowable error of 3%. With these settings, the shear rate is 0.1s -1 from 1,000s -1 When the viscosity measured as the shear rate is increased is plotted on a logarithmic scale, the number of equally spaced plots is 21. Furthermore, for each shear rate, intermittent measurements are taken every second using the corresponding shear rate, and the measurement taken when the difference from the measurement taken one second earlier is within 3% is adopted.

[0101] <Method for manufacturing a positive electrode for a non-aqueous electrolyte energy storage element> A method for manufacturing a positive electrode (positive electrode for a non-aqueous electrolyte energy storage element) according to one embodiment of the present invention comprises coating the positive electrode paste obtained by a method for manufacturing a positive electrode paste according to one embodiment of the present invention.

[0102] The cathode paste is applied, for example, by applying it directly to the cathode substrate or via an intermediate layer. The application can be carried out using a known application machine such as a doctor blade. After application, the cathode active material layer is formed by drying the applied cathode paste. After drying, the cathode active material layer may be pressed or otherwise treated.

[0103] <Non-aqueous electrolyte energy storage element> A non-aqueous electrolyte energy storage element according to one embodiment of the present invention comprises a positive electrode, a negative electrode, an isolation layer, and a container housing these. The isolation layer is interposed between the positive electrode and the negative electrode and electrically insulates the positive electrode and the negative electrode, and contains a solid electrolyte which is a non-aqueous electrolyte. The solid electrolyte may also be contained in the positive electrode and the negative electrode. A non-aqueous electrolyte energy storage element according to one embodiment of the present invention is an all-solid-state energy storage element and may also be an all-solid-state secondary battery.

[0104] The non-aqueous electrolyte energy storage element 1 shown in Figure 2, which is one embodiment of the present invention, is an all-solid-state secondary battery, which is an example of an all-solid-state energy storage element, and is a secondary battery in which a positive electrode 2 and a negative electrode 3 are arranged with an isolation layer 4 in between. The positive electrode 2 has a positive electrode substrate 5 and a positive electrode active material layer 6, with the positive electrode substrate 5 being the outermost layer of the positive electrode 2. The negative electrode 3 has a negative electrode substrate 7 and a negative electrode active material layer 8, with the negative electrode substrate 7 being the outermost layer of the negative electrode 2. In the non-aqueous electrolyte energy storage element 1 shown in Figure 2, the negative electrode active material layer 8, isolation layer 4, positive electrode active material layer 6, and positive electrode substrate 5 are stacked in this order on the negative electrode substrate 7. An intermediate layer may be provided between the positive electrode substrate 5 and the positive electrode active material layer 6. Similarly, an intermediate layer may be provided between the negative electrode substrate 7 and the negative electrode active material layer 8. The non-aqueous electrolyte energy storage element according to one embodiment of the present invention may further include other members such as a container. In the non-aqueous electrolyte energy storage element 1 shown in Figure 2, other members such as a container are omitted.

[0105] A non-aqueous electrolyte energy storage element according to one embodiment of the present invention may further include, for example, a positive electrode lead, a positive electrode external terminal, a negative electrode lead, and a negative electrode external terminal. The positive electrode lead and the negative electrode lead are housed inside a container. The positive electrode external terminal and the negative electrode external terminal are provided outside the container. The positive electrode is electrically connected to the positive electrode external terminal via the positive electrode lead. The negative electrode is electrically connected to the negative electrode external terminal via the negative electrode lead.

[0106] The following will provide a detailed explanation of the main components constituting the non-aqueous electrolyte energy storage element according to one embodiment of the present invention, focusing primarily on the case where the non-aqueous electrolyte energy storage element is an all-solid-state secondary battery, but this is not intended to limit the scope of application of the present invention.

[0107] (positive electrode) The positive electrode is the positive electrode according to the embodiment of the present invention described above.

[0108] (Negative electrode) As described above, the negative electrode comprises a negative electrode substrate and a negative electrode active material layer laminated directly to the negative electrode substrate or via an intermediate layer. Typically, the negative electrode has a portion where the negative electrode substrate is exposed. This exposed portion of the negative electrode substrate is usually connected to the negative electrode lead described above. The negative electrode may have a shape such as a sheet, plate, or strip.

[0109] The thickness of the negative electrode is set appropriately according to the application of the non-aqueous electrolyte energy storage element. The average thickness of the negative electrode may be, for example, 30 μm or more and 1,000 μm or less. The lower limit of the average thickness of the negative electrode may be 50 μm, 100 μm, or 200 μm. The upper limit of the average thickness of the negative electrode may be 500 μm, 400 μm, 300 μm, 200 μm, or 100 μm. The average thickness of the negative electrode is the average thickness of the portion in which the negative electrode active material layer is laminated directly to the negative electrode substrate or via an intermediate layer. If there are portions in which the negative electrode active material layer is laminated on both sides of the negative electrode substrate and portions in which the negative electrode active material layer is laminated on only one side of the negative electrode substrate, then the average thickness of the portion in which the negative electrode active material layer is laminated on both sides of the negative electrode substrate shall be used.

[0110] The negative electrode substrate is electrically conductive. Examples of materials for the negative electrode substrate include metals such as copper, nickel, iron, and their alloys (such as stainless steel), as well as carbon materials. Among these, copper or copper alloys are preferred.

[0111] The negative electrode substrate has a shape such as a sheet, plate, or strip. Examples of negative electrode substrate forms include foil, vapor-deposited film, mesh, and porous material, with foil being preferred. The negative electrode substrate may also be, for example, copper foil or copper alloy foil.

[0112] The average thickness of the negative electrode substrate may be, for example, 2 μm or more and 35 μm or less. The lower limit of the average thickness of the negative electrode substrate may be 3 μm, 4 μm, 5 μm, or 10 μm. The upper limit of the average thickness of the negative electrode substrate may be 30 μm, 20 μm, 15 μm, or 10 μm.

[0113] The configuration of the negative electrode intermediate layer is not particularly limited; for example, it can be selected from the configurations exemplified for the positive electrode intermediate layer.

[0114] The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer optionally contains components such as a solid electrolyte, a conductive agent, a binder, a thickener, and a filler. The solid electrolyte used in the negative electrode active material layer may be an inorganic solid electrolyte or another solid electrolyte, but it is preferably an inorganic solid electrolyte, and more preferably a sulfide-based solid electrolyte. The solid electrolyte, conductive agent, binder, thickener, filler, and other optional components can be selected from the materials exemplified in the positive electrode above. The negative electrode active material layer may be formed from a negative electrode mixture containing the negative electrode active material and other optional components. As shown in the non-aqueous electrolyte energy storage element 1 in Figure 2, the negative electrode active material layer may be provided on only one side of a negative electrode substrate having a shape such as a sheet. In another embodiment, the negative electrode active material layer may be provided on both sides of the negative electrode substrate.

[0115] For the negative electrode active material, known negative electrode active materials can be used. For lithium-ion secondary batteries, materials capable of intercalating and releasing lithium ions are typically used as negative electrode active materials. Examples of negative electrode active materials include: metallic lithium; metals or metalloids such as silicon and tin; metal oxides or metalloids such as silicon oxide, titanium oxide, and tin oxide; and Li4Ti5O 12 LiTiO 2、 Examples include titanium-containing oxides such as TiNb2O7; polyphosphate compounds; silicon carbide; and carbon materials such as graphite and non-graphitic carbon. The graphite may have its surface coated with other materials such as non-graphitic carbon. One or more types of negative electrode active materials can be used.

[0116] "Graphite" refers to the average lattice plane spacing (d) of the (002) plane, determined by X-ray diffraction before charging or discharging, or during the discharge state. 002 This refers to carbon materials with a n-scale between 0.33 nm and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite.

[0117] "Non-graphite carbon" refers to the average lattice plane spacing (d) of the (002) plane, which is determined by X-ray diffraction before charging / discharging or during the discharge state. 002 ) refers to carbon materials with a nautical index of 0.34 nm to 0.42 nm. Non-graphitic carbons include poorly graphitizable carbons and easily graphitizable carbons. "Potentially graphitizable carbon" refers to the above d 002 This refers to carbon materials with a wavelength of 0.36 nm or more and 0.42 nm or less. "Easily graphitizable carbon" refers to the above d 002 This refers to carbon materials with a wavelength of 0.34 nm or more and less than 0.36 nm.

[0118] Here, the "discharge state" of the carbon material refers to a state in which sufficient lithium ions that can be absorbed and released during charging and discharging are released from the carbon material, which is the negative electrode active material. For example, in a half-cell using a negative electrode containing a carbon material as the negative electrode active material as the working electrode and metallic lithium as the counter electrode, this is a state in which the open-circuit voltage is 0.7V or higher.

[0119] The negative electrode active material may be in particulate form. The average particle size of the negative electrode active material can be, for example, 1 nm to 100 μm. If the negative electrode active material is a carbon material, titanium-containing oxide, or polyphosphate compound, its average particle size may be 1 μm to 100 μm. If the negative electrode active material is Si, Sn, Si oxide, or Sn oxide, its average particle size may be 1 nm to 1 μm. Setting the average particle size of the negative electrode active material above the lower limit makes it easier to manufacture or handle. Setting the average particle size of the negative electrode active material below the upper limit improves the electronic conductivity of the negative electrode active material layer.

[0120] The content of the negative electrode active material in the negative electrode active material layer is preferably, for example, 60% to 99% by mass, and more preferably 90% to 98% by mass. By setting the content of the negative electrode active material within the above range, it is possible to achieve both high energy density and manufacturability in the negative electrode active material layer.

[0121] When the negative electrode active material is a metal such as metallic lithium, the negative electrode active material layer may be in the form of foil. The metallic lithium may exist as pure metallic lithium consisting substantially of the element lithium alone, or as a lithium alloy containing other metallic elements. When the negative electrode active material is a metal such as metallic lithium, the lithium element content in the negative electrode active material layer may be 90% by mass or more, 99% by mass or more, or 100% by mass.

[0122] When the negative electrode active material layer contains a conductive agent, the content of the conductive agent in the negative 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. The content of the conductive agent in the negative electrode active material layer may be 5% by mass or less, or 2% by mass or less. The technology disclosed herein can also be carried out in a form in which the negative electrode active material layer does not contain a conductive agent.

[0123] If the negative electrode active material layer contains a solid electrolyte, the solid electrolyte content is preferably 5% by mass or more and 90% by mass or less, but may also be 10% by mass or more and 70% by mass or less, or 20% by mass or more and 50% by mass or less.

[0124] When the negative electrode active material layer contains a binder, the binder content in the negative electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less. The binder content in the negative electrode active material layer may be 5% by mass or less, or 2% by mass or less. The technology disclosed herein can also be carried out in a form in which the negative electrode active material layer does not contain a binder.

[0125] When the negative electrode active material layer contains a thickening agent, the content of the thickening agent in the negative electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less. The content of the thickening agent in the negative electrode active material layer may be 5% by mass or less, or 2% by mass or less. The technology disclosed herein can also be carried out in a form in which the negative electrode active material layer does not contain a thickening agent.

[0126] The filler in the negative electrode active material layer is a component other than the negative electrode active material, solid electrolyte, conductive agent, binder, and thickener, and may be a component that is intentionally included. The filler may be included as a component that fills gaps in the negative electrode active material layer, or it may be included for other purposes. When the negative electrode active material layer contains a filler, the filler content in the negative electrode active material layer can be 0.1% by mass or more and 8% by mass or less, usually preferably 5% by mass or less, and more preferably 2% by mass or less. The technology disclosed herein can also be carried out in a form in which the negative electrode active material layer does not contain a filler.

[0127] The negative electrode active material layer may further contain other components besides the negative electrode active material, solid electrolyte, conductive agent, binder, thickener, and filler. These other components may include those unintentionally present in the negative electrode active material layer. Furthermore, the negative electrode active material layer may contain impurities unintentionally present as these other components, insofar as they achieve the effects of the present invention. The upper limit of the content of these other components in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of unintentionally present components in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of unintentionally present impurities in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass.

[0128] The thickness of the negative electrode active material layer is set appropriately according to the type of negative electrode active material, the application of the non-aqueous electrolyte energy storage element, etc. The average thickness of one negative electrode active material layer may be, for example, 5 μm or more and 1,000 μm or less. The lower limit of the average thickness of one negative electrode active material layer may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, or 100 μm. The upper limit of the average thickness of one negative electrode active material layer may be 800 μm, 500 μm, 200 μm, 100 μm, 80 μm, 60 μm, or 40 μm. The mass per unit area of ​​one negative electrode active material layer may be, for example, 2 mg / cm². 2 More than 50mg / cm 2 The following is also acceptable: The lower limit of the mass per unit area of ​​one negative electrode active material layer is 3 mg / cm². 2 , 4 mg / cm³ 2 , 5 mg / cm³ 2 or 6 mg / cm³ 2 It may also be the case that the upper limit of the mass per unit area of ​​one negative electrode active material layer is 30 mg / cm³. 2 , 20 mg / cm³ 2 , 15 mg / cm³ 2 , 12 mg / cm³ 2 or 10 mg / cm³ 2 That's fine.

[0129] (isolation layer) The isolation layer typically contains a solid electrolyte. The solid electrolyte used in the isolation layer may be an inorganic solid electrolyte or another type of solid electrolyte, but it is preferably an inorganic solid electrolyte, and more preferably a sulfide-based solid electrolyte. The solid electrolyte can be selected from the materials exemplified above for the positive electrode. The solid electrolyte content in the isolation layer is preferably 70% by mass or more and 100% by mass or less. The solid electrolyte content in the isolation layer may be 90% by mass or more, 99% by mass or more, or 100% by mass.

[0130] The isolation layer may contain optional components such as additives (e.g., phosphoric acid compounds such as Li3PO4, oxides, halogen compounds), binders, thickeners, and fillers. These optional components can be selected from the materials exemplified in the positive electrode described above.

[0131] The average thickness of the isolation layer is preferably 1 μm to 100 μm, more preferably 2 μm to 50 μm, and even more preferably 3 μm to 20 μm. By setting the average thickness of the isolation layer to above the lower limit, it becomes possible to reliably insulate the positive electrode and the negative electrode. By setting the average thickness of the isolation layer to below the upper limit, it becomes possible to increase the energy density of the non-aqueous electrolyte energy storage element.

[0132] (container) The container houses the positive electrode, negative electrode, etc., within its internal space. The container material can be a metal material such as aluminum or stainless steel, or a resin material; metal materials are preferred from the viewpoint of strength, etc. Composite materials of metal and resin materials can also be used.

[0133] The shape of the container is not particularly limited, but it can be cylindrical, rectangular (square), disc-shaped, etc. The container may also be in the form of a sheet or other shape formed from a metal-resin composite film.

[0134] (Shape, application, etc. of non-aqueous electrolyte energy storage elements) The shape of the non-aqueous electrolyte energy storage element according to one embodiment of the present invention is not particularly limited. The non-aqueous electrolyte energy storage element may be, for example, a cylindrical battery, a prismatic battery, a flat battery, a coin cell battery, a button cell battery, etc.

[0135] The applications of the non-aqueous electrolyte energy storage element according to one embodiment of the present invention are not particularly limited. The non-aqueous electrolyte energy storage element can be used, for example, as a power source for automobiles such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles, as a power source for electronic devices such as personal computers and communication terminals, and as a power storage power source.

[0136] The non-aqueous electrolyte energy storage element of the present invention can be used individually or in combination. The non-aqueous electrolyte energy storage element may be used individually when the required output and voltage are small. On the other hand, when at least one of the required output and voltage is large, the non-aqueous electrolyte energy storage element may be used as part of an energy storage device combined with other non-aqueous electrolyte energy storage elements. In an energy storage device composed of multiple non-aqueous electrolyte energy storage elements, at least one of the non-aqueous electrolyte energy storage elements included in the energy storage device may be a non-aqueous electrolyte energy storage element according to one embodiment of the present invention. The energy storage device will be described in detail later.

[0137] In the non-aqueous electrolyte energy storage element according to one embodiment of the present invention, the container may be restrained to maintain a certain thickness, or it may not be restrained in such a way. Alternatively, the container may be restrained to have a certain load applied to it. When the container is restrained, expansion of the container due to charge-discharge cycles, etc., may be suppressed, and a decrease in charge-discharge performance may be suppressed. When the container is restrained, the positive and negative electrodes inside the container may or may not have a load applied to them. For example, the non-aqueous electrolyte energy storage element or energy storage device may be provided with a restraining member that performs such restraint.

[0138] <Method for manufacturing a non-aqueous electrolyte energy storage element> A non-aqueous electrolyte energy storage element according to one embodiment of the present invention can be manufactured by known methods. The method for manufacturing the non-aqueous electrolyte energy storage element includes, for example, a method for manufacturing a positive electrode according to one embodiment of the present invention. In other words, the method for manufacturing the non-aqueous electrolyte energy storage element manufactures the non-aqueous electrolyte energy storage element using a positive electrode obtained by the method for manufacturing a positive electrode according to one embodiment of the present invention. The method for manufacturing the non-aqueous electrolyte energy storage element may also include preparing a material for the isolation layer, preparing a negative electrode, and laminating the positive electrode, isolation layer, and negative electrode.

[0139] Preparing materials for isolation layers may also mean fabricating materials for isolation layers. Solid electrolytes used as isolation layer materials can be fabricated by conventionally known methods. For example, they can be obtained by processing a predetermined material by mechanical milling. Alternatively, isolation layer materials may be fabricated by heating a predetermined material above its melting temperature using a melt-and-cool method, melting and mixing the two in a predetermined ratio, and then rapidly cooling. Other methods for fabricating isolation layer materials include, for example, solid-phase methods such as encapsulation under reduced pressure and calcination, liquid-phase methods such as dissolution extraction, gas-phase methods (PLD), and calcination under an argon atmosphere after processing by mechanical milling.

[0140] Preparing the negative electrode may also involve preparing a negative electrode mixture. When using a metal such as metallic lithium as the negative electrode active material, instead of preparing a negative electrode mixture, a metal foil that will form the negative electrode active material layer may be prepared.

[0141] In laminating a positive electrode, an isolation layer, and a negative electrode, for example, a positive electrode having a positive electrode substrate and a positive electrode active material layer, an isolation layer, and a negative electrode having a negative electrode substrate and a negative electrode active material layer are laminated. In this process, the positive electrode, isolation layer, and negative electrode may be formed sequentially in this order, or in reverse order, and the order of formation of each layer is not particularly limited. The positive electrode can be manufactured by the method described above. The negative electrode can be manufactured, for example, by coating a negative electrode mixture paste onto a negative electrode substrate and drying to provide a negative electrode active material layer, and the isolation layer can be formed, for example, by coating a paste of isolation layer material and drying. The negative electrode active material layer and the isolation layer can also be formed by pressure molding of the negative electrode mixture and isolation layer material.

[0142] <Energy storage device> The energy storage device 30 in Figure 3 comprises a plurality of energy storage units 20. Each energy storage unit 20 comprises a plurality of electrically connected non-aqueous electrolyte energy storage elements 1. The energy storage device 30 may also include busbars (not shown) for electrically connecting the plurality of non-aqueous electrolyte energy storage elements 1, busbars (not shown) for electrically connecting the plurality of energy storage units 20, etc. The energy storage unit 20 or the energy storage device 30 may also include a condition monitoring device (not shown) for monitoring the state of one or more non-aqueous electrolyte energy storage elements 1.

[0143] <Other Embodiments> The positive electrode for a non-aqueous electrolyte energy storage element, the non-aqueous electrolyte energy storage element, the method for manufacturing a positive electrode paste for a non-aqueous electrolyte energy storage element, the method for manufacturing a positive electrode for a non-aqueous electrolyte energy storage element, and the method for manufacturing a non-aqueous electrolyte energy storage element of the present invention are not limited to the embodiments described above, and various modifications may be made without departing from the spirit of the present invention. For example, the configuration of one embodiment may be added to the configuration of another embodiment, and a part of the configuration of one embodiment may be replaced with the configuration of another embodiment or with well-known technology. Furthermore, a part of the configuration of one embodiment may be deleted. Also, well-known technology may be added to the configuration of one embodiment.

[0144] In the above embodiment, a case in which the non-aqueous electrolyte energy storage element is used as a fully solid-state secondary battery capable of charging and discharging has been described, but the type, shape, dimensions, capacity, etc. of the non-aqueous electrolyte energy storage element are arbitrary. The present invention can also be applied to various secondary batteries, electric double-layer capacitors, lithium-ion capacitors, and other capacitors. For example, the non-aqueous electrolyte energy storage element according to the present invention may include layers other than the positive electrode, isolation layer, and negative electrode. [Examples]

[0145] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0146] [Example 1] [Manufacturing of positive electrode paste] As the positive electrode active material particles, LiNi is coated with LiNbO3 as a coating layer on its surface. 0.8 Co 0.15 Al 0.05 O2 particles were prepared. Based on the two-dimensional cross-sectional image of the obtained positive electrode active material layer, the average particle size (r) of the positive electrode active material particles was 3.2 μm. In addition, Li6PS5Cl (average particle size 0.6 μm), which has an argyrodite-type crystal structure, was prepared as an inorganic solid electrolyte.

[0147] (Dry compounding treatment) The following dry composite treatment was performed using the above-mentioned positive electrode active material particles and inorganic solid electrolyte. The positive electrode active material particles and inorganic solid electrolyte were placed in a Hosokawa Micron "NOB-MINI" in a mass ratio of 95:5 and stirred. The stirring speed was 7,000 rpm, and the stirring time was 2 minutes, repeated twice. Through this treatment, a composite of positive electrode active material particles and inorganic solid electrolyte was obtained.

[0148] (Mixing of each component of the positive electrode paste) The components of the positive electrode paste were mixed according to the following procedure. First, a dispersion was prepared by pre-dispersing polyvinylidene fluoride (PVDF) as a binder in butyl butyrate as a dispersion medium. Fibrous carbon (gas-phase carbon fiber) as a conductive agent was added to the dispersion, and the mixture was heated in a rotating / revolving mixer for 2 minutes to obtain the first paste. Next, an inorganic solid electrolyte (Li6PS5Cl having an argyrodite-type crystal structure: average particle size 0.6 μm) and butyl butyrate to adjust the solid content concentration were added to the first paste, and the mixture was heated in a rotating / revolving mixer for 2 minutes to obtain the second paste. The composite and butyl butyrate to adjust the solid content concentration were added to the second paste, and the components of the positive electrode paste were mixed by heating in a rotating / revolving mixer for 2 minutes. The positive electrode active material particles (positive electrode active material particles contained in the composite), inorganic solid electrolyte (total of inorganic solid electrolyte contained in the composite and other inorganic solid electrolytes), conductive agent, and binder were mixed in a mass ratio (on a solid content basis) of 76.0:20.8:2.0:1.2. A Thinky "AR-100" was used as the rotation / revolution mixer, and the rotation speed was set to 2,000 rpm.

[0149] (Distributed processing) After mixing the components of the cathode paste, the mixture was dispersed using a Primix "Filmix (30-L type)" thin-film swirling high-speed mixer. The solid content concentration of the mixture subjected to dispersion treatment was 73% by mass. The stirring speed was 20,000 rpm and the stirring time was 1 minute. Through the above treatment, the cathode paste of Example 1 was obtained.

[0150] [Manufacturing of non-aqueous electrolyte energy storage devices] The resulting positive electrode paste was applied to the aluminum foil, which served as the positive electrode substrate, with a dry coating density of 20 mg / cm². 2 The substrate was coated in this manner. Next, it was dried in a 100°C argon atmosphere under normal pressure for 20 minutes, and then dried under reduced pressure for 15 minutes to form a positive electrode active material layer on the positive electrode substrate. After that, it was punched out into a circle with a diameter of 10 mm to be used as the positive electrode for evaluation. Next, Li6PS5Cl, an inorganic solid electrolyte, was placed in a powder molding machine with an inner diameter of 10 mm as the material for the isolation layer. The isolation layer was then pressurized at 50 MPa using a uniaxial press to produce it. After the pressure was released, the positive electrode was placed on one side of the isolation layer so that the positive electrode active material layer faced it, and it was pressurized at 400 MPa and 160°C. On the side opposite the bonding surface of the positive electrode, indium foil and lithium foil were placed as the negative electrode, and copper foil as the negative electrode base material. These were then joined by a uniaxial press at a pressure of 50 MPa for several seconds. This resulted in a 10 mm diameter laminate in which the positive electrode base material, positive electrode active material layer, isolation layer, negative electrode active material layer, and negative electrode base material were stacked in this order. A rectangular polytetrafluoroethylene (PTFE) plate, approximately 30 mm square, with a through hole of approximately 10 mm in diameter in the center, was prepared. The obtained laminate was placed in this through hole, and the center of the PTFE plate was sandwiched between two stainless steel foils. This was placed inside a container made of aluminum-metal-resin composite film and sealed under reduced pressure by heat welding. At this time, each end of the lead terminals made of nickel foil, which were pre-attached to each stainless steel foil, was led out from the sealed part of the container to serve as external terminals. In this way, the non-aqueous electrolyte energy storage element (all-solid-state secondary battery) of Example 1 was obtained. The positive electrode and the non-aqueous electrolyte energy storage element were fabricated in a glove box with an argon atmosphere and a dew point of -70°C or lower.

[0151] [Comparative Example 1] A positive electrode paste and a non-aqueous electrolyte energy storage element of Comparative Example 1 were obtained in the same manner as in Example 1, except that a dispersion treatment was not performed during the manufacturing of the positive electrode paste.

[0152] [Comparative Example 2] A positive electrode paste and a non-aqueous electrolyte energy storage element of Comparative Example 2 were obtained in the same manner as in Example 1, except that a dry compounding treatment was not performed during the manufacturing of the positive electrode paste.

[0153] [Comparative Example 3] A positive electrode paste and a non-aqueous electrolyte energy storage element of Comparative Example 3 were obtained in the same manner as in Example 1, except that dry compounding and dispersion treatments were not performed during the manufacturing of the positive electrode paste.

[0154] (Hysteresis loop measurement) For each of the obtained positive electrode pastes, hysteresis loop measurements were performed using the method described above, and the value of the hysteresis area was determined. The results are shown in Table 1.

[0155] (Measurement of parameters P1 and P2) For each of the obtained non-aqueous electrolyte energy storage elements, a two-dimensional cross-sectional image of the positive electrode active material layer was obtained using the method described above, and parameter P1 (active material aggregate density parameter) and parameter P2 (solid electrolyte aggregate density parameter) were determined using the above-described apparatus and measurement conditions. Table 1 shows the values ​​of each parameter (P1, P2) obtained, and the sum of parameter P1 and parameter P2 (P1+P2). Table 1 also shows the total number of through-wires (m), the sum of the number of through-wires crossing each active material aggregate region (n1), and the sum of the number of through-wires crossing each solid electrolyte aggregate (n2), which were used to calculate each parameter. Furthermore, two non-aqueous electrolyte energy storage elements were fabricated: one for the parameter measurements described above, and another for the charge-discharge cycle tests described below.

[0156] [evaluation] (1) Discharge capacity confirmation test Each obtained non-aqueous electrolyte energy storage element underwent an initial discharge capacity verification test under the following conditions: In a constant temperature bath at 25°C, the elements were charged with a constant current of 0.1C up to 3.75V, followed by constant voltage charging at 3.75V. Charging was terminated when the charging current during constant voltage charging reached 0.025C. After a 10-minute rest period following charging, the elements were discharged with a constant current of 0.1C down to 2.25V. (Note: 1C is equivalent to 3.0mA / cm²) 2 The discharge was performed with a 10-minute pause after each discharge. The discharge capacity at this time is shown in Table 1 as the initial discharge capacity.

[0157] (2) Charge-discharge cycle test Next, a charge-discharge cycle test was conducted under the following conditions. At 25°C, charging was performed using constant current and constant voltage charging with a current of 0.2C and a voltage of 3.75V, and the charging termination condition was when the charging current during constant voltage charging became 0.05C. Discharging was performed using constant current discharge with a current of 0.2C and a termination voltage of 2.25V. This charge-discharge cycle was performed 50 times. A 10-minute rest period was provided after both charging and discharging. The capacity retention rate after 50 cycles was calculated by dividing the discharge capacity at the 50th cycle by the discharge capacity at the 1st cycle. The results are shown in Table 1.

[0158] (3) Resistance measurement Furthermore, AC impedance measurements were performed for each non-aqueous electrolyte energy storage element before and after the charge-discharge cycle test described above, using a frequency range of 1 MHz to 10 mHz, an amplitude voltage of 5 mV, and a measurement temperature of 25°C. Each non-aqueous electrolyte energy storage element was charged under the same conditions as the discharge capacity confirmation test described above to reach a charged state. The diameter of the arc in the obtained Nyquist plot was determined as the charge transfer resistance. Table 1 shows the charge transfer resistance before the cycle test, the charge transfer resistance after the cycle test, and the rate of increase in the charge transfer resistance after the cycle test relative to the charge transfer resistance before the cycle test (resistance increase rate).

[0159] [Table 1]

[0160] As shown in Table 1, the non-aqueous electrolyte energy storage element of Example 1, manufactured using a positive electrode paste subjected to both dry compounding and dispersion treatments, had an active material aggregate density parameter (P1) of 0.05 or less and a solid electrolyte aggregate density parameter (P2) of 0.05 or less, resulting in a high capacity retention rate and a low resistance increase rate after charge-discharge cycles.

[0161] On the other hand, the non-aqueous electrolyte energy storage elements in Comparative Examples 1 to 3, manufactured using cathode pastes that did not undergo at least one of the dry compounding treatment and dispersion treatment, and in which at least one of the active material aggregate density parameter (P1) and the solid electrolyte aggregate density parameter (P2) was greater than 0.05, showed low capacity retention rates and high resistance increase rates after charge-discharge cycles. In particular, regarding the resistance increase rate, the non-aqueous electrolyte energy storage elements in Comparative Examples 1 and 2, manufactured using cathode pastes that underwent either the dry compounding treatment or dispersion treatment, showed a higher resistance increase rate compared to the non-aqueous electrolyte energy storage element in Comparative Example 3, which was manufactured using cathode pastes that underwent neither the dry compounding treatment nor the dispersion treatment. In contrast to these, the non-aqueous electrolyte energy storage element in Example 1, manufactured using cathode pastes that underwent both the dry compounding treatment and the dispersion treatment, showed a significantly lower resistance increase rate compared to the non-aqueous electrolyte energy storage element in Comparative Example 3.

[0162] Furthermore, it was found that by performing both dry compounding and dispersion treatments during the manufacturing of the cathode paste, a cathode paste with a small hysteresis area could be obtained. Using such a cathode paste, it was possible to form a cathode active material layer in which both the cathode active material particles and the inorganic solid electrolyte were sufficiently dispersed, and both the active material aggregate density parameter (P1) and the solid electrolyte aggregate density parameter (P2) were 0.05 or less. [Industrial applicability]

[0163] This invention can be applied to non-aqueous electrolyte energy storage elements used as power sources for electronic devices such as personal computers and communication terminals, as well as for automobiles and industrial applications. [Explanation of Symbols]

[0164] 1. Non-aqueous electrolyte energy storage element 2 Positive electrode 3 negative electrode 4 isolation layer 5. Positive electrode substrate 6 Cathode active material layer 7. Negative electrode substrate 8 Negative electrode active material layer 12, 12A, 12B Regions where positive electrode active material particles exist 13, 13A Regions where inorganic solid electrolytes exist 14 Through Line 20 Energy storage units 30 Energy storage devices

Claims

1. The positive electrode comprises a positive electrode active material layer containing positive electrode active material particles, an inorganic solid electrolyte, a conductive agent, and a binder. A positive electrode for a non-aqueous electrolyte energy storage element, wherein the value of the active material aggregate density parameter, based on a two-dimensional image obtained by observing the cross-section of the positive electrode active material layer, is 0.05 or less, and the value of the solid electrolyte aggregate density parameter is 0.05 or less.

2. The positive electrode for a non-aqueous electrolyte energy storage element according to claim 1, wherein the sum of the value of the active material aggregate density parameter and the value of the solid electrolyte aggregate density parameter is 0.05 or less.

3. The positive electrode for a non-aqueous electrolyte energy storage element according to claim 1 or claim 2, wherein the positive electrode active material particles and at least a portion of the inorganic solid electrolyte form a composite, and in the composite, at least a portion of the surface of the positive electrode active material particles is coated with at least a portion of the inorganic solid electrolyte.

4. A non-aqueous electrolyte energy storage element, which is an all-solid-state energy storage element comprising a positive electrode for a non-aqueous electrolyte energy storage element as described in claim 1 or claim 2.

5. A composite of positive electrode active material particles and a first inorganic solid electrolyte is obtained by a dry composite treatment of positive electrode active material particles and a first inorganic solid electrolyte, and Mixing the above composite, a second inorganic solid electrolyte, a conductive agent, a binder, and a dispersion medium. Equipped with, A method for producing a positive electrode paste for a non-aqueous electrolyte energy storage element, wherein the above mixing process includes a dispersion treatment.

6. A method for producing a positive electrode paste for a non-aqueous electrolyte energy storage element according to claim 5, wherein the above dispersion treatment is performed by a thin-film swirling high-speed mixer.

7. A method for manufacturing a positive electrode for a non-aqueous electrolyte energy storage element, comprising coating the positive electrode paste for a non-aqueous electrolyte energy storage element obtained by the method for manufacturing a positive electrode paste for a non-aqueous electrolyte energy storage element described in claim 5 or claim 6.

8. A method for manufacturing a non-aqueous electrolyte energy storage element, comprising the method for manufacturing a positive electrode for a non-aqueous electrolyte energy storage element as described in claim 7.

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