Positive electrode active material, electrode and battery

Abstract

Improved rate characteristics. The positive electrode active material includes primary particles, the primary particles including an olivine-type phosphate compound, and the primary particles have a circularity of 0.60 or less.

Description

[Technical Field]

[0001] The present disclosure relates to a positive electrode active material, an electrode, and a battery. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2021-009838 discloses a granule of particles of manganese-rich manganese iron lithium phosphate and particles of iron-rich manganese iron lithium phosphate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-009838 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to improve the rate capability of batteries. [Means for solving the problem]

[0005] The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action includes speculation. The mechanism of action does not limit the technical scope of the present disclosure.

[0006] 1. One aspect of the present disclosure is a positive electrode active material. The positive electrode active material includes primary particles. The primary particles include an olivine-type phosphate compound. The primary particles have a circularity of 0.60 or less.

[0007] Conventionally, primary particles of olivine-type phosphate compounds are synthesized to approximate a spherical shape. This is thought to be because spherical primary particles are expected to improve packing, i.e., energy density. Spherical particles have a high degree of circularity. Hereinafter, primary particles with a circularity of 0.80 or more will also be referred to as "spherical particles."

[0008] The primary particles of the present disclosure have a circularity of 0.60 or less. Hereinafter, primary particles having a circularity of 0.60 or less are also referred to as "non-spherical particles." Non-spherical particles have a distorted shape. Non-spherical particles may have, for example, angular portions. In an electrode (positive electrode layer), non-spherical particles tend to be oriented such that the angular portions are aligned along the thickness direction of the electrode. The inclusion of non-spherical particles in an electrode is expected to linearize the permeation path of the electrolyte in the thickness direction of the electrode. Improved diffusion of the electrolyte in the thickness direction of the electrode is expected to improve rate characteristics.

[0009] 2. The positive electrode active material described in "1" above may have, for example, the following configuration. The positive electrode active material includes secondary particles. The secondary particles include first primary particles and second primary particles. The first primary particles and the second primary particles each include an olivine-type phosphate compound. The first primary particles have a circularity of 0.80 or more. The second primary particles have a circularity of 0.60 or less.

[0010] The spherical particles and the non-spherical particles may form secondary particles. The combination of the spherical particles and the non-spherical particles is expected to improve the balance between the rate characteristics and the packing property, for example.

[0011] 3. The positive electrode active material described in the above item "2" may include, for example, the following configuration: The secondary particles are "0.05 B / (S A +S B )<0.30" relationship is satisfied. A " indicates the total area of the first primary particles in the cross section of the secondary particle. "S B " indicates the total area of the second primary particles in the cross section of the secondary particle.

[0012] The inclusion of a specific ratio of non-spherical particles in the secondary particles is expected to improve rate characteristics.

[0013] ​4. The positive electrode active material described in "3" above may have, for example, the following configuration: The first primary particles have a circularity of 0.87 to 0.91. The second primary particles have a circularity of 0.40 to 0.60. The secondary particles have a circularity of "0.14≦S B / (S A +S B )≦0.20.

[0014] When these conditions are met, improved rate performance is expected.

[0015] 5. The positive electrode active material according to any one of the above items "1" to "4" may include, for example, the following configuration: The olivine-type phosphate compound includes at least one selected from the group consisting of lithium iron phosphate (LFP), lithium manganese phosphate (LMP), and lithium manganese iron phosphate (LMFP).

[0016] 6. One aspect of the present disclosure is an electrode. The electrode includes a positive electrode layer. The positive electrode layer includes the positive electrode active material described in any one of the above items "1" to "5".

[0017] The positive electrode layer can be alternatively referred to as a "positive electrode active material layer," a "positive electrode composite layer," etc. The "electrode" may be a "monopolar electrode (positive electrode)" or a "bipolar electrode" as long as it includes a positive electrode layer.

[0018] 7. One aspect of the present disclosure is a battery. The battery includes the electrode described in "6" above.

[0019] 8. The battery described in "7" above may include, for example, the following configuration: The battery has a bipolar structure.

[0020] A bipolar structure can be formed by stacking bipolar electrodes. A bipolar structure is expected to improve output characteristics, for example. However, a bipolar structure may require a thick positive electrode layer. In a thick positive electrode layer, the diffusibility of the electrolyte in the thickness direction of the positive electrode layer can affect the rate characteristics. The positive electrode active material described in "1" above is considered to be particularly suitable for a bipolar structure.

[0021] Hereinafter, one embodiment of the present disclosure (hereinafter may be abbreviated as "this embodiment") and one example of the present disclosure (hereinafter may be abbreviated as "this example") will be described. However, this embodiment and this example do not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are non-restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is originally intended that any configurations may be extracted from this embodiment and arbitrarily combined. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 2 is a conceptual diagram of a primary particle in the present embodiment. [Figure 2] FIG. 2 is a conceptual diagram of a secondary particle in the present embodiment. [Figure 3] 1 is a schematic perspective view of a battery according to an embodiment of the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. [Figure 5] 10 is a table showing experimental results. DETAILED DESCRIPTION OF THE INVENTION

[0023] Terms and phrases "Comprises," "includes," "has," and variations thereof are open-ended expressions. An open-ended structure may or may not further include additional elements in addition to the required elements. "Consists of" is a closed expression. However, even a closed structure may include additional elements that are normally associated impurities or unrelated to the subject technology. "Consists essentially of..." is a semi-closed expression. A semi-closed structure allows the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology.

[0024] Expressions such as "may" and "may" are used in the permissive sense, meaning "to have the possibility," rather than in the obligatory sense, meaning "to have to."

[0025] Geometric terms should not be interpreted in a strict sense. Examples of geometric terms include "parallel," "perpendicular," and the like. For example, directions, angles, distances, and the like may be displaced relative to one another as long as substantially the same or similar functions are obtained. Geometric terms may include, for example, tolerances, errors, and the like in design, work, manufacturing, and the like. The dimensional relationships in each figure may not match the actual dimensional relationships. The dimensional relationships in each figure may be changed to aid the reader's understanding. For example, length, width, thickness, and the like may be changed. Some components may be omitted.

[0026] Elements described in the "singular" can also include the plural unless otherwise specified. For example, a particle can refer to a plurality of particles, a collection of particles, and a powder or granular material. Note that "a plurality of particles" can be alternatively expressed as "a group of particles."

[0027] Numerical ranges such as "m to n%" include the upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "more than m% and less than n%." "Equal to or more" and "equal to or less" are represented by inequality signs with an equal sign "≦, ≧." "More than" and "less than" are represented by inequality signs without an equal sign "<, >." A numerical value arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, a figure, or the like.

[0028] All numerical values are modified by the term "about." The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values may be approximate values that may vary depending on the application of the subject technology. All numerical values may be expressed with significant figures. Unless otherwise specified, measured values may be average values of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. In general, the more measurements are made, the more reliable the average value is expected to be. Measured values may be rounded to the nearest significant figure. Measured values may include errors, such as those associated with the detection limits of the measuring device.

[0029] The devices, software, etc. used to measure various values are merely examples. Products equivalent to the devices, etc. exemplified may also be used. When equivalent products are used, the measurement conditions may be adjusted to suit the device.

[0030] "Primary particles" refer to particles that appear to have no grain boundaries in a scanning electron microscope (SEM) image of the powder. The magnification of the SEM image may be, for example, 10,000 to 30,000 times.

[0031] The shapes of primary particles and secondary particles are evaluated using the following procedure. For example, 1 g of positive electrode active material (powder) is dispersed in 10 g of epoxy resin (product name "EPOTEX JP", manufactured by Nissin EM Co., Ltd.) to form a dispersion. The dispersion is stirred and mixed for 1 minute using a mixer (product name "Awatori Rentaro", manufactured by Thinky Corporation). The stirring speed may be, for example, about 2000 rpm. The dispersion is vacuum degassed. After vacuum degassing, the epoxy resin is cured inside a silicon mold to obtain a plate-shaped cured product. A cross-section sample with a smooth cross section is prepared by cross-sectionally processing the plate-shaped cured product using a Cross-Section Polisher (registered trademark). The smooth cross section is observed using an SEM to obtain a cross-sectional SEM image.

[0032] Fifty primary particles whose entire periphery is observable are extracted from a cross-sectional SEM image. The circularity of each of the 50 primary particles is measured. The "circularity" is calculated using the following formula: ψ=4πS / L 2 ψ: circularity π: Pi S: Cross-sectional area of the particle (area of the region enclosed by the particle outline) L: Particle perimeter (length of particle outline)

[0033] Particles with a circularity of 0.8 or more are classified as spherical particles (first primary particles). The average value of the circularity in a collection of spherical particles is the "average circularity of spherical particles." Particles with a circularity of 0.6 or less are classified as non-spherical particles (second primary particles). The average value of the circularity in a collection of non-spherical particles is the "average circularity of non-spherical particles."

[0034] In the cross-sectional SEM image of the secondary particles, the total area of the spherical particles, "S A ”, and the total area of the non-spherical particles “S B " is measured. "S A " and "S B " and "S B " is divided, the area ratio "S B / (S A+S B )" is obtained.

[0035] Various dimensional measurements and shape analyses of cross-sectional SEM images can be performed using, for example, image analysis software such as "ImageJ."

[0036] The "maximum Feret diameter" indicates the length of the long side of the minimum bounding rectangle (MBR) relative to the particle outline in a cross-sectional SEM image.

[0037] The chemical composition of the compound can be measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). 0.1 g of a sample (e.g., a positive electrode active material) is dissolved in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid to prepare a sample solution. The sample solution is diluted to an appropriate concentration using a measuring flask. After dilution, composition analysis is performed using an ICP-AES device. For example, a product named "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0038] The stoichiometric composition formula indicates a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to a compound having a molar ratio of "Al / O=2 / 3". Unless otherwise specified, "Al2O3" indicates a compound containing Al and O in any molar ratio. For example, the compound may be doped with a trace element. A portion of the Al and O may be substituted with another element.

[0039] The term "derivative" refers to a compound in which a part of a parent compound has been modified by at least one method selected from the group consisting of the introduction of a functional group, atomic substitution, oxidation, reduction, and other chemical reactions. The modification may be at one or more locations. The "substituent" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (e.g., F, Cl, Br, I), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphoric acid amide groups, sulfo groups, carboxy groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. When there are two or more substituents, the substituents may be the same or different. A plurality of substituents may be bonded to each other to form a ring.

[0040] "D50" indicates the particle size at which the cumulative value reaches 50% in the volume-based particle size distribution (cumulative distribution). The volume-based particle size distribution is measured using a laser diffraction particle size distribution analyzer.

[0041] positive electrode active material The positive electrode active material may be in the form of, for example, a powder. The D50 of the positive electrode active material may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 of the positive electrode active material may be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0042] primary particle FIG. 1 is a conceptual diagram of primary particles in this embodiment. The positive electrode active material contains primary particles (non-spherical particles 1b). The non-spherical particles 1b have a circularity of 0.60 or less. The inclusion of distorted primary particles in the electrode is expected to improve rate characteristics.

[0043] The average circularity of the non-spherical particles 1b may be, for example, 0.55 or less, 0.50 or less, 0.45 or less, 0.40 or less, or 0.35 or less. The average circularity of the non-spherical particles 1b may be 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, or 0.55 or more. The average circularity of the non-spherical particles 1b may be, for example, 0.40 to 0.60.

[0044] The non-spherical particles 1b may be, for example, angular particles. "Angular particles" refer to particles having an acute angle "θ" of 60° or less. The "acute angle" refers to the smallest acute angle among the interior angles formed by the outline of a particle in a cross-sectional SEM image. The acute angle may be, for example, 55° or less, 50° or less, 45° or less, 40° or less, 35° or less, 30° or less, 25° or less, 20° or less, or 15° or less. The acute angle may be, for example, 10° or more, 15° or more, 20° or more, 25° or more, 30° or more, 35° or more, 40° or more, 45° or more, 50° or more, or 55° or more.

[0045] The non-spherical particles 1b may be, for example, scale-like particles. "Scale-like particles" are plate-like particles and angular particles. "Plate-like particles" have a planar direction (plate surface direction) and a thickness direction. "First aspect ratio" refers to the ratio of the maximum Feret diameter "d1" in the plate surface direction to the thickness "t" of the plate-like particle. The first aspect ratio "d1 / t" may be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, or 9 or more. The first aspect ratio "d1 / t" may be, for example, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, or 3 or less.

[0046] In plate-like particles, the plate surface can have any shape. The "plate surface" refers to the surface having the largest apparent area. The plate surface may be, for example, a polygon, hexagon, pentagon, square, parallelogram, or rectangle. The "second aspect ratio" refers to the ratio of the long side "d1" to the short side "d2" in the MBR for the plate surface. The second aspect ratio "d1 / d2" may be, for example, 1.2 or more, 1.5 or more, 1.8 or more, 2.1 or more, 2.4 or more, 2.7 or more, 3.0 or more, 4.0 or more, or 5.0 or more. The second aspect ratio "d1 / d2" may be, for example, 10.0 or less, 5.0 or less, 4.0 or less, 3.0 or less, or 2.0 or less.

[0047] secondary particles FIG. 2 is a conceptual diagram of secondary particles in this embodiment. Non-spherical particles 1b may exist independently without agglomeration. Non-spherical particles 1b may form aggregates. That is, the positive electrode active material may contain secondary particles 2. Secondary particles 2 may be composed of non-spherical particles 1b. Secondary particles 2 may have any shape as long as they contain non-spherical particles 1b. Secondary particles may be, for example, spherical, rod-like, angular, or lumpy. The circularity of the secondary particles may be, for example, 0.50 or more, 0.60 or more, 0.70 or more, 0.80 or more, or 0.90 or more. The circularity of the secondary particles may be, for example, 0.90 or less, 0.80 or less, 0.70 or less, or 0.60 or less.

[0048] The secondary particles 2 may further include spherical particles 1a in addition to the non-spherical particles 1b. That is, the secondary particles 2 may include first primary particles (spherical particles 1a) and second primary particles (non-spherical particles 1b). The spherical particles 1a have a circularity of 0.80 or more. The average circularity of the spherical particles 1a may be, for example, 0.85 or more, 0.87 or more, 0.89 or more, 0.90 or more, 0.91 or more, or 0.93 or more. The average circularity of the spherical particles 1a may be, for example, 0.95 or less, 0.93 or less, 0.91 or less, 0.89 or less, 0.87 or less, or 0.85 or less. The average circularity of the spherical particles 1a may be, for example, 0.87 to 0.91.

[0049] The secondary particles 2 may contain non-spherical particles 1b at a specific ratio. B / (S A +S B By satisfying the relationship "S )<0.30", improvement in rate characteristics is expected. B / (S A +S B )" may be, for example, 0.07 or more, 0.09 or more, 0.11 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.17 or more, 0.19 or more, 0.20 or more, 0.21 or more, 0.23 or more, 0.25 or more, 0.27 or more, or 0.29 or more. B / (S A +S B )" may be, for example, 0.29 or less, 0.27 or less, 0.25 or less, 0.23 or less, 0.21 or less, 0.20 or less, 0.19 or less, 0.17 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.11 or less, 0.09 or less, or 0.07 or less. B / (S A +S B )≦0.20”.

[0050] The maximum Feret diameter of the primary particles may be, for example, 20 nm to 300 nm. The maximum Feret diameter of the primary particles may be, for example, 25 nm or more, 50 nm or more, 75 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, or 250 nm or more. The maximum Feret diameter of the primary particles may be, for example, 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, 75 nm or less, or 50 nm or less. The maximum Feret diameter of the primary particles represents the arithmetic average of 30 primary particles. The maximum Feret diameters of the spherical particles 1a and the non-spherical particles 1b may be the same or different from each other.

[0051] ​The surface of the primary particles may be coated with carbon. That is, a carbon layer may be formed on the surface of the primary particles. The carbon may coat a portion of the surface of the primary particles, or may coat the entire surface of the primary particles. The carbon may be derived from, for example, sugars. The amount of carbon attached may be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, or 10% or more in mass fraction relative to the secondary particles 2. The amount of carbon attached may be, for example, 20% or less, 15% or less, 10% or less, 5% or less, 4% or less, or 3% or less in mass fraction relative to the secondary particles 2.

[0052] The maximum Feret diameter of the secondary particles 2 may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, or 15 μm or more. The maximum Feret diameter of the secondary particles 2 may be, for example, 20 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, or 3 μm or less.

[0053] composition The primary particles include an olivine-type phosphate compound. That is, the positive electrode active material includes an olivine-type phosphate compound. Hereinafter, the olivine-type phosphate compound may be abbreviated as "olivine." Olivine has a crystal structure that belongs to the space group Pnma. The space group to which the crystal structure belongs can be identified by an X-ray diffraction (XRD) pattern.

[0054] Olivine may further contain, for example, a glass phase, a crystallized glass phase, or the like in addition to a crystalline phase. For example, non-spherical particles 1b may be formed by appropriately grinding a material containing glass. For example, a crystallized glass phase or the like may be formed by first vitrifying the raw material during synthesis and then crystallizing it.

[0055] The olivine may contain, for example, at least one selected from the group consisting of LFP, LMP, and LMFP. The olivine may contain, for example, at least one selected from the group consisting of LMP and LMFP. LMP and LMFP tend to have lower rate characteristics than LFP. This embodiment is considered to be particularly suitable for LMP and LMFP.

[0056] Olivine can be, for example, of the general formula "Li a Mn 1-x Fe x PO4". In the general formula, the Li composition ratio "a" may be, for example, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.1 or more, 1.2 or more, 1.3 or more, or 1.4 or more. In the general formula, the Li composition ratio "a" may be, for example, 2.0 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, or 0.6 or less. In the general formula, for example, the relationship "0.5≦a≦1.5" may be satisfied. In the general formula, the Fe composition ratio "x" may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. In the general formula, the Fe composition ratio "x" may be, for example, 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. In the general formula, for example, the relationship "0.2≦x≦0.5" may be satisfied.

[0057] A dopant may be added to the olivine. The dopant refers to an element other than lithium (Li), manganese (Mn), iron (Fe), phosphorus (P), and oxygen (O). The doping amount (amount of substance fraction relative to the amount of substance of Li) may be, for example, 0.01 to 0.1. The dopant may be, for example, boron (B), nitrogen (N), halogen, silicon (Si), sodium (Na), magnesium (Mg), aluminum (Al), chromium (Cr), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), selenium (Se), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), or lead (Pb). , bismuth (Bi), antimony (Sb), tin (Sn), tungsten (W), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and at least one selected from the group consisting of actinides.

[0058] The positive electrode active material may further contain other components as long as it contains olivine. The mixing ratio (mass ratio) of olivine to other components may be, for example, "olivine / other components = 9 / 1 to 1 / 9," "olivine / other components = 8 / 2 to 2 / 8," "olivine / other components = 7 / 3 to 3 / 7," or "olivine / other components = 6 / 4 to 4 / 6." The positive electrode active material may be, for example, a mixture of olivine powder and powder of other components. The other components may include at least one selected from the group consisting of Li[NiCoMn]O2 (layered structure), Li[NiCoAl]O2 (layered structure), LiMnO2 (rock salt structure), and Li[NiMn]2O4 (spinel structure). Note that descriptions such as [NiCoMn] indicate that the sum of the compositional ratios in [ ] is 1. As long as the sum is 1, the components in [ ] may have any compositional ratio.

[0059] liquid battery In some of the present embodiments, the battery may be a liquid battery. "Liquid battery" refers to a battery containing an electrolyte. For example, a polymer battery is a liquid battery because it contains an electrolyte. In some of the present embodiments, the battery has a monopolar structure. In a monopolar structure, the power generating element may be wound or stacked. In some of the present embodiments, the battery has a bipolar structure. As an example, a battery having a bipolar structure (bipolar battery) will be described.

[0060] Fig. 3 is a schematic perspective view of a battery in this embodiment. Fig. 4 is a schematic cross-sectional view taken along line IV-IV in Fig. 3. Hereinafter, "plane-perpendicular direction" refers to the normal direction to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the plane-perpendicular direction. In the drawings of this embodiment, the Z-axis direction corresponds to the plane-perpendicular direction. The X-axis direction and the Y-axis direction are examples of in-plane directions.

[0061] The battery 100 includes an exterior body 90 and a power generating element 50. The exterior body 90 houses the power generating element 50. The exterior body 90 may include, for example, a first current collecting plate 91, a first laminate film 92, a second laminate film 93, and a second current collecting plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane end portions. At the joint between the first laminate film 92 and the second laminate film 93, a sealant (not shown) may be interposed between the first laminate film 92 and the second laminate film 93.

[0062] The first current collector plate 91 and the second current collector plate 94 are joined to the power generating element 50 at their ends in the stacking direction (Z-axis direction). A first laminate film 92 is joined to the first current collector plate 91. A second laminate film 93 is joined to the second current collector plate 94. A sealant (not shown) may be interposed between the current collector plate and the laminate film at the joint between the current collector plate and the laminate film.

[0063] The power generating element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the direction perpendicular to the plane (Z-axis direction). Each of the plurality of bipolar electrodes 10 includes a positive electrode layer 11, a current collecting foil 13, and a negative electrode layer 12, in this order, in the direction perpendicular to the plane. In the in-plane direction (e.g., the X-axis direction), the current collecting foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collecting foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire periphery in the in-plane direction.

[0064] The current collecting foil 13 is a conductor. The current collecting foil 13 may include, for example, a metal foil, a conductive resin layer, or the like. For example, the current collecting foil 13 may be formed by laminating an Al foil and a Cu foil together. A carbon material may be applied to the surface of the current collecting foil 13. The carbon material may include, for example, carbon black, or the like.

[0065] The power generating element 50 includes a sealing material 30. The sealing material 30 is bonded to the current collecting foil 13 at an end in the in-plane direction. The sealing material 30 may be, for example, heat-welded to the current collecting foil 13. For example, the sealing material 30 may be disposed around the entire periphery in the in-plane direction. The sealing material may include, for example, a resin material. The sealing material 30 seals between adjacent current collecting foils 13 in the direction perpendicular to the surface. The sealing material 30 seals between the current collecting foils 13, thereby dividing them into cells 40. A cell 40 is the smallest unit of the power generating element 50. The battery 100 includes multiple cells 40, and may therefore also be referred to as a "bipolar module." Each of the multiple cells 40 is sealed. The multiple cells 40 are isolated from one another. Each of the multiple cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0066] Positive electrode layer The positive electrode layer 11 is attached to one surface of the current collector foil 13. The thickness of the positive electrode layer 11 may be, for example, 50 μm to 1000 μm. The thickness of the positive electrode layer 11 may be, for example, 100 μm or more, 200 μm or more, 300 μm or more, 400 μm or more, or 500 μm or more. The thickness of the positive electrode layer 11 may be, for example, 750 μm or less, 500 μm or less, or 400 μm or less. For example, grooves may be formed in the positive electrode layer 11. The positive electrode layer 11 may be formed, for example, in a striped pattern. The positive electrode layer 11 contains a positive electrode active material. That is, the electrode contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0067] The positive electrode layer 11 may further contain, in addition to the positive electrode active material, for example, a conductive material and a binder. The amount of the conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the positive electrode active material. The conductive material may contain any component. For example, the conductive material may contain at least one material selected from the group consisting of graphite, acetylene black (AB), Ketjen Black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0068] The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the positive electrode active material. The binder may contain any component. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0069] The positive electrode layer 11 may further contain, for example, an inorganic filler, an organic filler, a solid electrolyte, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The positive electrode layer may also contain, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, a silane coupling agent, MoS2, WO3, etc.

[0070] negative electrode layer The negative electrode layer 12 is attached to one surface of the current collector foil 13. The negative electrode layer 12 is disposed on the back side of the positive electrode layer 11. The negative electrode layer 12 may have a larger area than the positive electrode layer 11. The negative electrode layer 12 includes a negative electrode active material.

[0071] The negative electrode active material may be, for example, in the form of particles or a sheet. The D50 of the negative electrode active material may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material may be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0072] The negative electrode active material may include any component. For example, the negative electrode active material may include at least one selected from the group consisting of a carbon-based active material, an alloy-based active material, a Si-C composite material, Li metal, a Li-based alloy, and lithium titanate. In some embodiments of the present invention, the battery may be a Li metal negative electrode battery.

[0073] The carbon-based active material may contain at least one selected from the group consisting of, for example, graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) may be, for example, "natural graphite / artificial graphite = 1 / 9 to 9 / 1", "natural graphite / artificial graphite = 2 / 8 to 8 / 2", or "natural graphite / artificial graphite = 3 / 7 to 7 / 3".

[0074] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a different material. The different material may contain at least one selected from the group consisting of, for example, P, W, Al, and O. The different material may contain at least one selected from the group consisting of, for example, Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO 3、 and at least one selected from the group consisting of Li3PO4.

[0075] The alloy-based active material may contain at least one selected from the group consisting of, for example, Si, Li silicate, SiO, Si-based alloy, tin (Sn), SnO, and Sn-based alloy.

[0076] SiO may have a composition represented by, for example, the general formula "SiO x ". In the general formula, for example, the relationship of "0 < x < 2", "0.5 ≤ x ≤ 1.5", or "0.8 ≤ x ≤ 1.2" may be satisfied.

[0077] "Si-C composite material" refers to a composite material of a carbon-based active material (such as graphite) and an alloy-based active material (such as Si). For example, Si fine particles may be dispersed in carbon particles. For example, Si fine particles may be dispersed in graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0078] Separator The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulation properties. The separator 20 may include, for example, at least one selected from the group consisting of a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may include, for example, a resin film and an inorganic particle layer.

[0079] The resin film is porous. The resin film may include, for example, a microporous film, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a network form. Pores are formed in the gaps in the resin skeleton. The resin film is permeable to an electrolyte solution. The resin film may have, for example, an average pore diameter of 1 μm or less. The average pore diameter of the resin film may be, for example, 0.01 to 1 μm, or 0.1 to 0.5 μm. The "average pore diameter" can be measured by mercury intrusion porosimetry. The Gurley value of the resin film is, for example, 50 to 250 s / 100 cm. 3 The "Gurley value" can be measured by the Gurley test method.

[0080] The resin film may contain at least one selected from the group consisting of, for example, olefin-based resins, polyurethane-based resins, polyamide-based resins, cellulose-based resins, polyether-based resins, acrylic-based resins, and polyester-based resins. The resin film may contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamideimide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film may be formed by, for example, a stretching method, a phase separation method, or the like. The thickness of the resin film may be, for example, 5 to 50 μm, or 10 to 25 μm.

[0081] The resin film may have, for example, a single-layer structure. The resin film may be composed of, for example, a PE layer. The skeleton of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multi-layer structure. The resin film may include, for example, a PP layer and a PE layer. The skeleton of the PP layer is formed of PP. The resin film may have, for example, a three-layer structure. The resin film may be formed by laminating, for example, a PP layer, a PE layer, and a PP layer in this order. The thickness of the PE layer may be, for example, 5 to 20 μm. The thickness of the PP layer may be, for example, 3 to 10 μm.

[0082] The inorganic particle layer may be formed on the surface of the resin film. The inorganic particle layer may be formed on only one side of the resin film, or on both sides. The inorganic particle layer may be formed on the surface facing the positive electrode layer 11, or on the surface facing the negative electrode layer 12. The inorganic particle layer may be formed on the surface of the positive electrode layer 11, or on the surface of the negative electrode layer 12.

[0083] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles may also be referred to as "inorganic filler." Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm, or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also referred to as an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, silica, and the like. The inorganic particles may have any shape. The inorganic particles may be, for example, spherical, rod-like, plate-like, fibrous, or the like. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may contain, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluorine resins, aromatic polyether resins, and liquid crystal polyester resins.

[0084] The separator 20 may include, for example, an organic particle layer. The separator 20 may include, for example, an organic particle layer instead of a resin film. The separator 20 may include, for example, an organic particle layer instead of an inorganic particle layer. The separator 20 may include both a resin film and an organic particle layer. The separator 20 may include both an inorganic particle layer and an organic particle layer. The separator 20 may include a resin film, an inorganic particle layer, and an organic particle layer.

[0085] The thickness of the organic particle layer may be, for example, 0.1 to 50 μm, 0.5 to 20 μm, 0.5 to 10 μm, or 1 to 5 μm. The organic particle layer contains organic particles. The organic particles may also be referred to as "organic filler." The organic particles may contain a heat-resistant material. The organic particles may include, for example, at least one selected from the group consisting of PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be, for example, spherical, rod-like, plate-like, fibrous, or the like. The D50 of the organic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm.

[0086] Separator 20 may include, for example, a mixed layer, which includes both inorganic and organic particles.

[0087] electrolyte The electrolyte is a liquid electrolyte. The electrolyte includes a solute and a solvent. The concentration of the solute may be, for example, 0.5 to 1 mol / L, 1 to 1.5 mol / L, 1.5 to 2 mol / L, 2 to 2.5 mol / L, or 2.5 to 3 mol / L. "mol / L" may also be written as "M." The solute includes a supporting salt (Li salt). The solute may include, for example, an inorganic acid salt, an imide salt, an oxalate complex, a halide, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0088] The electrolytic solution may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, a cyclic carbonate, a chain carbonate, a fluorinated carbonate, or the like. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0089] The solvent may contain a cyclic carbonate (EC, PC, FEC, etc.) and a chain carbonate (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate to the chain carbonate may be, for example, "cyclic carbonate / chain carbonate = 1 / 9 to 4 / 6," "cyclic carbonate / chain carbonate = 2 / 8 to 3 / 7," or "cyclic carbonate / chain carbonate = 3 / 7 to 4 / 6."

[0090] The solvent may contain a cyclic carbonate (EC, PC, etc.) and a fluorinated cyclic carbonate (FEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate to the fluorinated cyclic carbonate may be, for example, "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1 to 90 / 10," "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 1 / 9," "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 7 / 3," or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7 to 1 / 9."

[0091] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may be determined, for example, by the relationship "V EC +V FEC +V EMC +V DMC +V DEC =10". In the relational expression, "V EC , V FEC , V EMC , V DMC , V DEC " indicates the volume ratio of EC, FEC, EMC, DMC, and DEC, respectively. "1≦V EC ≦4", 0≦V FEC ≦3", "V EC +V FEC ≦4", 0≦V EMC ≦9", 0≦V DMC ≦9", 0≦V DEC ≦9” and “6≦V EMC +V DMC +V DEC ≦9". For example, "1≦V EC ≦2” or “2≦VEC ≦3". For example, the relationship "1 ≦ V FEC ≦2” or “2≦V FEC ≦4". For example, the relationship "3≦V EMC ≦4” or “6≦V EMC ≦8". For example, the relationship "3≦V DMC ≦4” or “6≦V DMC ≦8". For example, the relationship "3≦V DEC ≦4” or “6≦V DEC ≦8" may be satisfied.

[0092] The solvent may have a composition, for example, in volume ratios of "EC / EMC=3 / 7," "EC / DMC=3 / 7," "EC / FEC / DEC=1 / 2 / 7," "EC / DMC / EMC=3 / 4 / 3," "EC / DMC / EMC=3 / 3 / 4," "EC / FEC / DMC / EMC=2 / 1 / 4 / 3," "EC / FEC / DMC / EMC=1 / 2 / 4 / 3," "EC / FEC / DMC / EMC=2 / 1 / 3 / 4," or "EC / FEC / DMC / EMC=1 / 2 / 3 / 4."

[0093] The electrolyte may contain an ether-based solvent, such as at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylglyme, triglyme, tetraglyme, and derivatives thereof.

[0094] The electrolyte may contain any additive. The amount of additive (mass fraction relative to the total amount of the electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additive may include, for example, an SEI (Solid Electrolyte Interphase) formation promoter, an SEI formation inhibitor, a gas generating agent, an overcharge inhibitor, a flame retardant, an antioxidant, an electrode protectant, a surfactant, etc.

[0095] Examples of the additives include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), ethylene sulfate (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters (e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.), fluorobenzenes (e.g., monofluorobenzene (FB), 1,2-difluoropropane (DEM), etc.), and the like. fluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.), fluorotoluenes (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluorides (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylenes (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methylbenzotrifluoride, The solvent may contain at least one selected from the group consisting of benzotriazole, benzotriazole, tetrathiafulvalene, etc.), nitrile compounds (e.g., adiponitrile, succinonitrile, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and derivatives thereof.

[0096] The components described above as solutes and solvents may be used as minor components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPOF, FSOLi, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0097] The electrolyte solution may contain an ionic liquid, which may include, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0098] In some embodiments of the present invention, the battery may include a gel electrolyte. That is, the battery may be a polymer battery. The gel electrolyte may include an electrolyte solution and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0099] All solid state battery In some embodiments of the present invention, the battery may be an all-solid-state battery. The all-solid-state battery may have a bipolar structure. The all-solid-state battery includes a solid electrolyte instead of the electrolyte solution and the separator 20. The solid electrolyte may also be included in the positive electrode layer 11 and the negative electrode layer 12. Instead of the separator 20, a solid electrolyte layer separates the positive electrode layer 11 from the negative electrode layer 12. The solid electrolyte layer includes, for example, a solid electrolyte and a binder. In the electrode (positive electrode layer) of the all-solid-state battery, the non-spherical particles 1b are also expected to promote ion conduction in the thickness direction.

[0100] The solid electrolyte may be, for example, a powder. The D50 of the solid electrolyte may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1 μm or more. The D50 of the solid electrolyte may be, for example, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0101] The solid electrolyte may include, for example, at least one selected from the group consisting of a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a hydride solid electrolyte, and a nitride solid electrolyte.

[0102] The sulfide solid electrolyte may contain at least one phase selected from the group consisting of an amorphous phase, a crystalline phase, and a glass ceramic (crystallized glass) phase. The crystalline phase may be, for example, an argyrodite type or an LGPS type. The sulfide solid electrolyte contains Li and sulfur (S). The sulfide solid electrolyte may further contain any optional component in addition to Li and S.

[0103] Examples of sulfide solid electrolytes include LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2-P2S5, Li2S-P2S5, and Li 10 GeP2S 12 , Li4P2S6, Li7P3S 11 , Li3PS4, and Li7PS6.

[0104] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in an arbitrary ratio by mass. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. The mixing ratio may be specified by adding a number before each raw material. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4=10 / 15 / 75 (mass ratio)."

[0105] The sulfide solid electrolyte may have a composition represented by the general formula "xLiS-(1-x)P2S5." In the general formula, "x" may be, for example, greater than 0, 0.1 or greater, 0.2 or greater, 0.25 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. "x" may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.75 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. For example, when "x=0.75," "xLiS-(1-x)P2S5" may have a composition of Li3PS4.

[0106] The sulfide solid electrolyte may have a composition represented by the general formula "yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5]". In the general formula, "x" may be, for example, 0.5 or more, 0.6 or more, 0.7 or more, 0.75 or more, 0.8 or more, or 0.9 or more. "x" may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.75 or less, 0.7 or less, or 0.6 or less. "y" may be, for example, 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. "y" may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. "z" may be, for example, 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. "z" may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0107] The sulfide solid electrolyte is, for example, a sulfide solid electrolyte having the general formula "Li 7-x-2y PS 6-x-y X y In the general formula, the relationships "0<7-x-2y", "0<6-xy", "0≦x", and "0≦y" are satisfied. "X" may include, for example, at least one element selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0108] The sulfide solid electrolyte is, for example, a sulfide solid electrolyte having the general formula "Li4-x M 1-x P x It may have a composition represented by "S4". In the general formula, "x" may be, for example, greater than 0, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. "x" may be, for example, less than 1, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. "M" may contain, for example, at least one selected from the group consisting of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0109] The sulfide solid electrolyte may have, for example, a composition represented by the general formula "Li 10+x Ge 1+x P 2-x S 12 ". In the general formula, "x" may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.6 or more. "x" may be, for example, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. The sulfide solid electrolyte represented by the above general formula may contain, for example, a LGPS-type crystal phase.

[0110] The halide solid electrolyte may have, for example, a composition represented by the general formula "Li 6-na M a X6". In the general formula, "n" indicates the oxidation number of "M". "M" may contain, for example, an atom having an oxidation number of +3. "M" may contain, for example, an atom having an oxidation number of +4. "M" may contain, for example, at least one selected from the group consisting of Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship of "0 < a < 2" may be satisfied. "X" may contain, for example, at least one selected from the group consisting of F, Cl, Br, and I.

[0111] The halide solid electrolyte may have, for example, a composition represented by the general formula "Li 3-a Tia Al 1-a F6". In the general formula, "a" may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. "a" may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0112] The halide solid electrolyte is, for example, a compound represented by the general formula "Li3YCl a Br b I 6-a-b " In the general formula, for example, the relationship "0≦a+b≦6" may be satisfied. "a" may be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. "a" may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. "b" may be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. "b" may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0113] The oxide solid electrolyte is, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 The hydride solid electrolyte may contain, for example, LiBH4, etc. The nitride solid electrolyte may contain, for example, Li3N, Li3BN2, etc. [Example]

[0114] Sample preparation The experimental results are shown in a table in Figure 5. Positive electrode active materials No. 1 to No. 3 were produced according to the following procedure.

[0115] No.1 Glass precursor preparation Compositional formula “Li1Mn 0.8 Fe 0.2 The raw materials, lithium carbonate, manganese carbonate, iron oxalate, and phosphoric acid, are weighed out so as to achieve the composition ratio shown in "PO4". Powder materials other than phosphoric acid are mixed to form a powder mixture. While phosphoric acid is added to the powder mixture, the mixture is ground and mixed in a mortar until the reaction stops, thereby forming a first precursor powder. At this time, the phosphoric acid is gradually added to suppress gas generation. The first precursor powder is placed in a graphite crucible. The graphite crucible is placed in a firing furnace. Firing is carried out in an inert atmosphere according to the following procedure. First, the furnace temperature is increased at a rate of 5°C / min until the furnace temperature reaches 1100°C. This furnace temperature is maintained at 1100°C for one hour. After maintaining this temperature for one hour, the furnace temperature is cooled at a rate of 5°C / min until the furnace temperature reaches 600°C. Then, the furnace temperature is cooled at a rate of 15°C / min until the furnace temperature reaches room temperature. This results in a glassy active material block. The active material mass is pulverized by a mechanical pulverizer to form a second precursor.

[0116] Wet grinding A third precursor is formed by adding 10% fructose by mass fraction to the second precursor. The third precursor is pulverized in an aqueous solvent using a bead mill to form a fourth precursor. During pulverization, beads (pulverization media) with a diameter (φ) of 0.5 mm are used. The peripheral speed is 10 m / s. The pulverization time is 30 min.

[0117] Firing The fourth precursor is dried. After drying, the fourth precursor is placed in a graphite crucible. The graphite crucible is placed in a firing furnace. The temperature is increased at a rate of 5°C / min until the temperature inside the furnace reaches 650°C. The temperature inside the furnace is maintained at 650°C for 1 hour. After that, the furnace is cooled until the temperature inside the furnace reaches room temperature. This produces a positive electrode active material (LMFP). A cross-sectional SEM image of the positive electrode active material is obtained. The circularity of the primary particles is evaluated in the cross-sectional SEM image.

[0118] No.2 A positive electrode active material was prepared in the same manner as in No. 1, except that the wet grinding time was changed to 60 minutes.

[0119] No.3 A positive electrode active material was produced in the same manner as in No. 2, except that beads having a diameter (φ) of 0.1 mm were used in the wet grinding.

[0120] evaluation Coin cell fabrication A mixture is formed by mixing the positive electrode active material, conductive material (acetylene black), and binder (PVdF). The mixing ratio (mass ratio) is "positive electrode active material / conductive material / binder = 92 / 5 / 3". A paste is formed by dispersing the mixture in a solvent (N-methyl-2-pyrrolidone). The solid concentration of the paste is 50% by mass. The paste is applied to the surface of Al foil and dried to form a positive electrode layer. The density of the positive electrode layer is reduced to 1.8 g / cm by roll pressing. 3 The cathode blank is then subjected to a vacuum drying process at 120°C for 12 hours. After drying, a disk sample (diameter: 14 mm) is cut out from the cathode blank by punching.

[0121] In the glove box, a coin cell is assembled. The cell configuration is as follows: Working electrode: disk sample (positive electrode) Counter electrode: Li foil Separator: Porous polymer membrane Electrolyte: "EC / DMC=3 / 7 (volume ratio)", LiPF6 (1mol / L)

[0122] Evaluation of rate characteristics A rate equivalent to 1C is determined based on the discharge capacity (theoretical capacity) calculated from the applied mass of the positive electrode layer. "C" is the symbol for the current rate (time rate). At a rate of 1C, the theoretical capacity flows over one hour. At 25°C, the coin cell is charged by constant current-constant voltage (CCCV) charging under the following conditions: CC charging rate: 0.1C Charging voltage limit: 4.3V CV charging cutoff current rate: 0.01C

[0123] After charging, CC discharge is performed at 25°C at a rate of 0.1C to 3.0V, and the discharge capacity at 0.1C discharge, "A," is measured. The coin cell is again charged using the above CCCV charging. After charging, CC discharge is performed at 25°C at a rate of 1C to 3.0V, and the discharge capacity at 1C discharge, "B," is measured. The ratio "1C capacity / 0.1C capacity" is calculated using the formula "B / A." The higher the ratio "1C capacity / 0.1C capacity," the better the rate characteristics are considered to be.

[0124] Experimental results As shown in FIG. 5, when the positive electrode active material contains non-spherical particles (primary particles) having a circularity of 0.60 or less, the rate characteristics tend to improve.

[0125] Even when secondary particles containing spherical particles and non-spherical particles are formed, the rate characteristics tend to improve.

[0126] In samples with good rate characteristics, the secondary particles are B / (S A +S B )<0.30" relationship. [Explanation of symbols]

[0127] ​1a spherical particles, 1b non-spherical particles, 2 secondary particles, 10 bipolar electrode, 11 positive electrode layer, 12 negative electrode layer, 13 current collecting foil, 20 separator, 30 sealing material, 40 cell, 50 power generating element, 90 exterior body, 91 first current collecting plate, 92 first laminate film, 93 second laminate film, 94 second current collecting plate, 100 battery.

Claims

1. Contains primary particles, the primary particles are scale-like particles, The primary particles include an olivine-type phosphate compound, and The primary particles have a circularity of 0.60 or less. Cathode active material.

2. Contains secondary particles, the secondary particles include first primary particles and second primary particles, each of the first primary particles and the second primary particles contains the olivine-type phosphate compound; The first primary particles have a circularity of 0.80 or more, and The second primary particles have a circularity of 0.60 or less. The positive electrode active material according to claim 1 .

3. The secondary particles are 0.05<S B / (S A +S B )<0.30 Fulfilling the relationship, The S A represents the total area of the first primary particles in the cross section of the secondary particle, and The S B represents the total area of the second primary particles in the cross section of the secondary particle, The positive electrode active material according to claim 2 .

4. the first primary particles have an average circularity of 0.87 to 0.91; The second primary particles have an average circularity of 0.40 to 0.60, and The secondary particles are 0.14≦S B / (S A +S B )≦0.20 Satisfy the relationship of The positive electrode active material according to claim 3 .

5. The olivine-type phosphate compound includes at least one selected from the group consisting of lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate. The positive electrode active material according to claim 1 .

6. a positive electrode layer, and The positive electrode layer contains the positive electrode active material according to any one of claims 1 to 4. electrode.

7. 7. The electrode of claim 6, battery.

8. having a bipolar structure, The battery of claim 7.

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