Positive electrode active material, electrode, and battery

Abstract

Improved rate characteristics. [Solution] The positive electrode active material includes primary particles. The primary particles contain an olivine-type phosphate compound. A striated structure is formed on at least a portion of the cross-section of the primary particles. The striated structure includes a first region and a second region. The second region contains phosphorus at a higher concentration than the first region. The second region extends in a striated manner. The first region is divided into two or more parts by the second region.

Description

Technical Field

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

Background Art

[0002] JP-A-2021-009838 discloses an agglomerate of particles of manganese-rich lithium manganese iron phosphate and particles of iron-rich lithium manganese iron phosphate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Olivine-type phosphate compounds can be aggregates of primary particles (secondary particles). Olivine-type phosphate compounds tend to have low rate characteristics. Conventionally, attempts have been made to improve the rate characteristics by applying a carbon coating to the surface of the primary particles. However, even when a carbon coating is applied to the surface of the primary particles, it is considered that the ionic conductivity inside the primary particles does not change. That is, there is still room for improvement in the rate characteristics.

[0005] An object of the present disclosure is to improve the rate characteristics.

Means for Solving the Problems

[0006] Hereinafter, the technical configuration and operation and effect of the present disclosure will be described. However, the operation mechanism includes assumptions. The operation mechanism does not limit the technical scope of the present disclosure.

[0007] 1. One aspect of the present disclosure is a positive electrode active material. The positive electrode active material comprises primary particles. The primary particles contain an olivine-type phosphate compound. A striated structure is formed on at least a portion of the cross-section of the primary particles. The striated structure comprises a first region and a second region. The second region contains phosphorus at a higher concentration than the first region. The second region extends in a striated manner. The first region is divided into two or more parts by the second region.

[0008] The second region contains phosphorus (P) at a higher concentration than the first region. Ion conduction is thought to be promoted in the second region compared to the first region. Therefore, the second region is thought to function as an ion diffusion path. In the cross-section of the primary particle, the second region extends in a streaky manner. Therefore, the second region is thought to spread in layers within the primary particle. The spread of the second region (ion diffusion layer) in a manner that divides the first region (bulk) is expected to improve the rate characteristics.

[0009] 2. The positive electrode active material described in "1" above may include, for example, the following configuration: Both ends of the second region are located on the surface of the primary particles.

[0010] The extension of the second region (ion diffusion layer) to connect with the outside of the primary particles is expected to improve the rate characteristics.

[0011] 3. The positive electrode active material described in "1" or "2" above may include, for example, the following configuration: The first region is divided into three or more sections by the second region. In the direction intersecting the direction in which the second region extends, the average width of the divided sections is 10 nm to 100 nm.

[0012] Hereafter, "average width of divided sections" will also be referred to as "average division width." An average division width of 10nm to 100nm is expected to improve rate characteristics.

[0013] 4. The positive electrode active material described in "3" above may include, for example, the following configuration: The average division width is less than half of the maximum Ferret diameter of the primary particles.

[0014] When the average dividing width “Da” is smaller than 1 / 2 of the maximum Feret diameter “D” of the primary particles, an improvement in rate characteristics is expected. That is, when the relationship “Da < D / 2” is satisfied, an improvement in rate characteristics is expected.

[0015] 5. The positive electrode active material described in “3” or “4” above may, for example, include the following configuration. The average dividing width is from 65 nm to 94 nm.

[0016] When the average dividing width is from 65 nm to 94 nm, an improvement in rate characteristics is expected.

[0017] 6. The positive electrode active material described in any one of “1” to “5” above may, for example, include the following configuration. The positive electrode active material includes secondary particles. The secondary particles include a plurality of primary particles.

[0018] The primary particles may exist alone or may form secondary particles.

[0019] 7. The positive electrode active material described in any one of “1” to “6” above may, for example, include 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).

[0020] 8. 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 “1” to “7” above.

[0021] The positive electrode layer can be equivalently referred to as a “positive electrode active material layer”, a “positive electrode composite material layer”, etc. The “electrode” may be a “monopolar electrode (positive electrode)” or a “bipolar electrode” as long as it includes the positive electrode layer.

[0022] 9. One aspect of the present disclosure is a battery. The battery includes the electrode described in “8” above.

[0023] 10. The battery described in "9" above may include, for example, the following configuration: The battery has a bipolar structure.

[0024] A bipolar structure can be formed by stacking bipolar electrodes. This bipolar structure is expected to improve, for example, output characteristics.

[0025] Hereinafter, one embodiment of the present disclosure (which may be abbreviated as "this embodiment") and one example of the present disclosure (which may be abbreviated as "this example") will be described. However, this embodiment and this example will 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 not restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from this embodiment and combined in any way. [Brief explanation of the drawing]

[0026] [Figure 1] This is a conceptual diagram of the cross-section of a primary particle in this embodiment. [Figure 2] This is a conceptual diagram of secondary particles in this embodiment. [Figure 3] This is a schematic perspective view of the battery in this embodiment. [Figure 4] This is a schematic cross-sectional view along the line IV-IV in Figure 3. [Figure 5] This is a table showing the experimental results. [Modes for carrying out the invention]

[0027] Terms, phrases "Equipped with," "includes," "possesses," and variations thereof are open-ended expressions. Configurations expressed in an open-ended manner may or may not include additional elements in addition to the essential elements. The statement "consists of" is a closed expression. However, even configurations expressed in a closed manner may include additional elements that are usually incidental impurities or irrelevant to the subject technology. The statement "substantially consists of..." is a semi-closed expression. In configurations expressed in a semi-closed manner, the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology is permitted.

[0028] Expressions such as "may do" and "may be" are used in a permissive sense, meaning "there is a possibility," rather than in an obligatory sense, meaning "it must be done."

[0029] Geometric terms should not be interpreted strictly. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For example, direction, angle, distance, etc., may be relatively distorted within a range where substantially the same or similar function is obtained. Geometric terms may include tolerances, errors, etc., in design, operation, and manufacturing. Dimensional relationships in each figure may not match actual dimensional relationships. Dimensional relationships in each figure may be modified to aid the reader's understanding. For example, length, width, thickness, etc., may be changed. Some components may be omitted.

[0030] Elements described in the singular form may also include plural forms unless otherwise specified. For example, "particle" may refer to multiple particles, a collection of particles, or a granular material. Note that "multiple particles" can be rephrased as "group of particles."

[0031] Numerical ranges such as "m to n%" include upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less". Also, "m% or more and n% or less" includes "greater than m% and less than n%". "Greater than or equal to" and "less than or equal to" are represented by the equals sign inequality signs "≦" and "≧". "Greater than" and "less than" are represented by the inequality signs without an equals sign "<" and ">". A number 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 number within the numerical range with a number listed in another part of this specification, in a table, in a figure, etc.

[0032] All numerical values ​​are modified by the term "approximately." The term "approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximations that can vary depending on the application of the technology in question. All numerical values ​​may be expressed with significant figures. Unless otherwise specified, measured values ​​may be the average of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. Generally, the more measurements taken, 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.

[0033] The devices, software, etc., used for measuring various values ​​are merely examples. Equivalent devices may be used. If equivalent devices are used, the measurement conditions may be adjusted to suit the device.

[0034] "Primary particles" refer to particles that appear to lack grain boundaries in a Scanning Electron Microscope (SEM) image of a powder. The magnification of the SEM image may be, for example, 10,000x to 30,000x.

[0035] The cross-section of the primary particles is evaluated by the following procedure: The positive electrode active material (powder) is subjected to crushing, polishing, etc., to form a cross-section in which the interior of the primary particles is exposed. The cross-section may be, for example, a fracture surface, a cut surface, a polished surface, a machined surface, etc. The cross-section is observed using SEM-EDS (SEM-Energy Dispersive x-ray Spectroscopy), TEM-EDS (Transmission Electron Microscope-EDS), or EPMA (Electron Probe Micro Analyzer), etc.

[0036] When a carbon layer is formed on the surface of a primary particle, the elemental concentration ratio of phosphorus "P" to carbon "C" ("P / C") can be obtained by qualitative analysis during mapping observation of the entire cross-section. Regions where the elemental concentration ratio "P / C" exceeds 0.2 are considered to be the interior of the primary particle (i.e., the part other than the carbon layer).

[0037] A mapping image of phosphorus "P" is obtained by mapping observations of the interior of primary particles. The mapping image is normalized based on the maximum and minimum brightness of the mapping image. In the normalized mapping image, regions where the brightness is 75% or more of the maximum value are considered to be regions of P concentration (i.e., "second region"). Regions where the brightness is less than 75% of the maximum value are considered to be "first region".

[0038] Figure 1 is a conceptual diagram of a cross-section of a primary particle in this embodiment. The primary particle 1 includes a first region 1a and a second region 1b. The second region 1b extends in a striated (parallel) manner. In the direction intersecting the direction in which the second region 1b extends, the first region 1a is divided into n sections by the second region 1b. The width of the divided sections is considered to be equal to the intervals between adjacent second regions 1b "d1, d2, ..., dn". The average division width "Da" can be calculated using the formula "Da = (d1 + d2 + ... + dn) / n". If each second region 1b is not parallel, a straight line is drawn so as to be perpendicular to as many second regions 1b as possible. The length of each line segment within the straight line divided by the second region 1b is considered to be the interval "d1, d2, ..., dn".

[0039] Furthermore, various dimensional measurements and shape analyses in SEM images, mapping images, etc., can be performed using image analysis software such as "ImageJ".

[0040] "Maximum Ferret diameter" refers to the length of the longer side of the minimum bounding rectangle (MBR) relative to the particle's contour line in a two-dimensional image of the particle (e.g., a SEM image).

[0041] The chemical composition of the compound can be measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). A sample solution is prepared by dissolving 0.1 g of the sample (e.g., positive electrode active material) in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is diluted to an appropriate concentration in a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES instrument. For example, a product name such as "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0042] The stoichiometric composition formula shows a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to compounds with a molar ratio of "Al / O = 2 / 3". Unless otherwise specified, "Al2O3" refers to a compound containing Al and O in any molar ratio. For example, the compound may be doped with trace elements. Some of the Al and O may be substituted with other elements.

[0043] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of a functional group, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" 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 (F, Cl, Br, I, etc.), 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, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring.

[0044] "D50" indicates the particle size at which the cumulative value in the volume-based particle size distribution (cumulative distribution) reaches 50%. The volume-based particle size distribution is measured using a laser diffraction particle size analyzer.

[0045] positive electrode active material The positive electrode active material may, for example, be in the form of 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.

[0046] primary particle The positive electrode active material includes primary particles 1. Primary particles 1 may exist alone. Primary particles 1 may form secondary particles 2, which will be described later. Primary particles 1 may have any shape. Primary particles 1 may be spherical, rod-shaped, horn-shaped, flaky, etc. Primary particles 1 include an olivine-type phosphate compound. Hereinafter, "olivine-type phosphate compound" may be abbreviated as "olivine".

[0047] The maximum Ferret diameter of the primary particles may be, for example, 20 nm to 300 nm. The maximum Ferret 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 Ferret 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.

[0048] A striated structure is formed on at least a portion of the cross-section of the primary particle 1. The striated structure may be formed throughout the entire cross-section. The striated structure is expected to improve rate characteristics. The striated structure includes a first region 1a and a second region 1b. The second region 1b extends in a striated manner. The second region 1b may extend in a straight line, for example. The second region 1b may extend in a curved shape, for example. The second region 1b may extend in a wavy line shape, for example. The second region 1b may be linear (a collection of parallel lines), for example.

[0049] The second region 1b may, for example, extend continuously. The second region 1b may, for example, include discontinuous portions. For example, due to the discontinuity of the second region 1b, there may be portions that appear as dotted lines, broken lines, etc.

[0050] The start and end points of the second region 1b may, for example, be located inside the cross-section. For example, at least one of the start and end points of the second region 1b may be located on the surface of the primary particle. For example, both ends of the second region 1b may be located on the surface of the primary particle 1. For example, an improvement in rate characteristics can be expected if the second region 1b (ion conducting layer) extends across the primary particle 1.

[0051] The second region 1b contains P at a higher concentration than the first region 1a. As mentioned above, the level of concentration is determined by the brightness in the mapping image. The first region 1a may contain, for example, olivine (LiMPO4, M=Fe, Mn). The second region 1b may contain, for example, lithium phosphate (Li3PO4), etc.

[0052] The first region 1a is divided into two or more parts by the second region 1b. For example, in Figure 1, the first region 1a is divided into four parts. The first region 1a and the second region 1b may be arranged alternately. The number of divisions of the first region 1a may be, for example, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 25 or more, or 50 or more. The number of divisions of the first region 1a may be, for example, 100 or less, 75 or less, 50 or less, 25 or less, 10 or less, or 5 or less.

[0053] The average division width "Da" may be, for example, from 10 nm to 100 nm. The average division width "Da" may be, for example, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 65 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, or 94 nm or more. The average division width "Da" may be, for example, 94 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 65 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, or 20 nm or less. The average division width "Da" may be, for example, from 65 nm to 94 nm.

[0054] The ratio "Da / D" of the average division width "Da" to the maximum Ferret diameter "D" of the primary particle 1 may be, for example, less than 0.5. The ratio "Da / D" may be, for example, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. The ratio "Da / D" may be, for example, 0.01 or more, 0.05 or more, 0.1 or more, 0.2 or more, 0.3 or more, or 0.4 or more.

[0055] The width "w" of the second region 1b may be, for example, less than 10 nm. The width "w" of the second region 1b may be, for example, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, 3 nm or less, or 2 nm or less. The width of the second region 1b may be, for example, 2 nm or more, 3 nm or more, 4 nm or more, 5 nm or more, 6 nm or more, 7 nm or more, 8 nm or more, or 9 nm or more.

[0056] secondary particles Figure 2 is a conceptual diagram of secondary particles in this embodiment. The positive electrode active material may contain secondary particles 2. The secondary particles 2 contain a plurality of primary particles 1. The maximum Ferret 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 Ferret 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.

[0057] Secondary particles 2 can have any shape. For example, secondary particles 2 may be spherical, rod-shaped, angular, lumpy, etc. The sphericity of secondary particles 2 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 sphericity of secondary particles 2 may be, for example, 1.00 or less, 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, or 0.50 or less. "Sphericity" indicates the circularity in a two-dimensional image (e.g., an SEM image). Sphericity (circularity) is calculated by the following formula. Sphericity represents the arithmetic mean of 30 secondary particles 2. ψ = 4πS / L 2 ψ: Sphericity (Circularity) π: Pi S: Particle cross-section (area of ​​the region enclosed by the particle's outline) L: Particle circumference (length of the particle's outline)

[0058] The carbon layer 5 may cover the surface of the primary particle 1. The carbon layer 5 may cover a part of the surface of the primary particle 1, or it may cover the entire surface of the primary particle 1. The carbon layer 5 may be derived from, for example, sugars. The amount of carbon layer 5 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 by mass fraction relative to olivine. 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 by mass fraction relative to olivine.

[0059] composition Primary particle 1 contains olivine. The olivine has a crystal structure (olivine structure) that belongs to the space group Pnma. The space group to which the crystal structure belongs can be identified by the XRD (X-Ray Diffraction) pattern.

[0060] Olivine may further contain, for example, a crystalline glass phase (olivine structure), a glass phase, etc., in addition to the crystalline phase (olivine structure). For example, during synthesis, the raw materials may be vitrified by heating and then cooled to form the crystalline glass phase, etc. Under specific crystallization conditions (cooling conditions), polycrystalline material (such as lithium phosphate) may be formed in the gaps of the glass structure. The first region 1a is thought to originate from the glass structure. The second region 1b is thought to originate from polycrystalline material. For example, the first region 1a may contain at least one of the crystalline phase and the crystalline glass phase of olivine. For example, the second region 1b may contain polycrystalline lithium phosphate.

[0061] The olivine may include, for example, at least one selected from the group consisting of LFP, LMP, and LMFP. LMP and LMFP tend to have lower rate characteristics compared to LFP. This embodiment is considered particularly suitable for LMP and LMFP.

[0062] Olivine, for example, has the general formula "Li a Mn 1-x Fe x It may have a composition represented by "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.

[0063] Olivine may contain dopants. The dopants represent elements other than lithium (Li), manganese (Mn), iron (Fe), phosphorus (P), and oxygen (O). The doping amount (molecular fraction relative to the amount of Li) may be, for example, 0.01 to 0.1. Examples of dopants include boron (B), nitrogen (N), halogens, 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), and lead (Pb). It may also contain at least one selected from the group consisting of 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 actinides.

[0064] 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 other component powder. The other components may include, for example, 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 the notation [NiCoMn] etc. indicates that the sum of the composition ratios in [] is 1. As long as the sum is 1, each component in [] can take on any composition ratio.

[0065] liquid battery In some embodiments, the battery may be an electrolyte battery. An "electrolyte battery" refers to a battery that contains an electrolyte. For example, polymer batteries, which contain an electrolyte, belong to the category of electrolyte batteries. In some embodiments, the battery has a monopolar structure. In a monopolar structure, the power generation element may be wound or stacked. In some embodiments, the battery has a bipolar structure. As an example, a battery having a bipolar structure (bipolar battery) is described.

[0066] Figure 3 is a schematic perspective view of the battery in this embodiment. Figure 4 is a schematic cross-sectional view along the line IV-IV in Figure 3. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In the figures of this embodiment, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0067] The battery 100 includes an outer casing 90 and a power generation element 50. The outer casing 90 houses the power generation element 50. The outer casing 90 may include, for example, a first current collector plate 91, a first laminate film 92, a second laminate film 93, and a second current collector plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane edges. At the joint between the first laminate film 92 and the second laminate film 93, a sealing material (not shown) may be interposed between the first laminate film 92 and the second laminate film 93.

[0068] The first current collector plate 91 and the second current collector plate 94 are joined to the power generation element 50 at their ends in the stacking direction (Z-axis direction). The first laminate film 92 is joined to the first current collector plate 91. The second laminate film 93 is joined to the second current collector plate 94. A sealing material (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.

[0069] The power generation 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, in the direction perpendicular to the plane, a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in this order. In the in-plane direction (for example, in the X-axis direction), the current collector foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collector foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire circumference in the in-plane direction.

[0070] The current collector foil 13 is a conductor. The current collector foil 13 may include, for example, a metal foil, a conductive resin layer, etc. For example, the current collector foil 13 may be formed by bonding an Al foil and a Cu foil together. A carbon material may be coated on the surface of the current collector foil 13. The carbon material may include, for example, carbon black.

[0071] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is joined to the current collector foil 13. The sealing material 30 may, for example, be heat-welded to the current collector foil 13. For example, the sealing material 30 may be arranged around the entire circumference of the in-plane periphery. The sealing material may include, for example, a resin material. The sealing material 30 seals between adjacent current collector foils 13 in the direction perpendicular to the plane. The sealing material 30 between the current collector foils 13 partitions the cells 40. A cell 40 is the smallest unit of the power generation element 50. The battery 100 includes multiple cells 40 and may also be called a "bipolar module". Each of the multiple cells 40 is sealed. The multiple cells 40 are isolated from each other. Each of the multiple cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0072] Positive electrode layer The positive electrode layer 11 is attached to one side of the current collector foil 13. For example, grooves may be formed in the positive electrode layer 11. The positive electrode layer 11 may be formed in a striped pattern, for example. The positive electrode layer 11 contains a positive electrode active material. That is, the battery 100 contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0073] The positive electrode layer 11 may further contain, for example, a conductive material and a binder, in addition to the positive electrode active material. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The conductive material may contain any components. For example, the conductive material may contain at least one selected from the group consisting of graphite, acetylene black (AB), Ketjenblack (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0074] The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The binder may contain any components. 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), carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ethers, and derivatives thereof.

[0075] The positive electrode layer 11 may further contain, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode layer may also contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0076] Negative electrode layer The negative electrode layer 12 is attached to one side of the current collector foil 13. The negative electrode layer 12 is located 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 contains a negative electrode active material.

[0077] The negative electrode active material may be in the form of parts or sheets, for example. 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.

[0078] The negative electrode active material may contain any components. For example, the negative electrode active material may include at least one selected from the group consisting of carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In some embodiments of this invention, the battery may be a Li metal negative electrode battery.

[0079] 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".

[0080] 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 Li3PO4.

[0081] 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.

[0082] 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.

[0083] "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).

[0084] Separator The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulating 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.

[0085] The resin film is porous. The resin film may include, for example, a microporous membrane, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a mesh-like manner. Pores are formed in the gaps of the resin skeleton. The resin film can permeate the electrolyte. 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 the mercury intrusion method. The Gaurle value of the resin film is, for example, 50 to 250 s / 100 cm. 3 It may also be the case that the "Gehré value" can be measured by the Gehré test method.

[0086] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may also contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film can be formed, for example, by 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.

[0087] The resin film may have, for example, a single-layer structure. The resin film may consist of, for example, a PE layer. The framework of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multilayer structure. The resin film may include, for example, a PP layer and a PE layer. The framework 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 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.

[0088] 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.

[0089] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles may also be called "inorganic fillers." 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 called an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. For example, the inorganic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. 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 include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluororesins, aromatic polyether resins, and liquid crystal polyester resins.

[0090] 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.

[0091] 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 called "organic fillers". The organic particles may contain heat-resistant materials. The organic particles may contain at least one selected from the group consisting of, for example, PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm.

[0092] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0093] electrolyte The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute may be, for example, 0.5 to 1 mole / L, 1 to 1.5 mole / L, 1.5 to 2 mole / L, 2 to 2.5 mole / L, or 2.5 to 3 mole / L. "mol / L" may also be written as "M". The solute contains a supporting salt (Li salt). The solute may also contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, 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.

[0094] The electrolyte may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, cyclic carbonates, linear carbonates, fluorinated carbonates, etc. 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.

[0095] The solvent may contain a cyclic carbonate (such as EC, PC, FEC, etc.) and a chain carbonate (such as EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate and 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".

[0096] The solvent may contain a cyclic carbonate (such as EC, PC, etc.) and a fluorinated cyclic carbonate (such as FEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate and 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".

[0097] The solvent may contain, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy, for example, the relationship expressed by the formula "V EC +V FEC +V EMC +V DMC +V DEC =10". In the formula, "V EC 、V FEC 、V EMC 、V DMC 、V DEC " respectively represent the volume ratios of EC, FEC, EMC, DMC, and DEC. The relationships "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" are satisfied. For example, "1≦V EC ≦2" or "2≦VEC The relationship "≤3" may also be satisfied. For example, "1 ≤ V" FEC ≤2" or "2 ≤ V" FEC The relationship "≤4" may also be satisfied. For example, "3 ≤ V" EMC ≤4" or "6 ≤ V" EMC The relationship "≤8" may also be satisfied. For example, "3 ≤ V" DMC ≤4" or "6 ≤ V" DMC The relationship "≤8" may also be satisfied. For example, "3 ≤ V" DEC ≤4" or "6 ≤ V" DEC The relationship "≤8" may also be satisfied.

[0098] The solvent may have compositions such as "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", and "EC / FEC / DMC / EMC=1 / 2 / 3 / 4" in volume ratio.

[0099] The electrolyte may contain an ether-based solvent. The electrolyte may contain, for example, 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), ethylglycyle, triglycyle, tetraglycyle, and derivatives thereof.

[0100] The electrolyte may contain any additives. The amount of additive (mass fraction of the total electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additives may include, for example, SEI (Solid Electrolyte Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge inhibitors, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0101] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesaltone (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.], and fluorobenzenes [e.g., monofluorobenzene (FB), 1,2-di-butylbenzene]. 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.), fluorotoluene (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-methyl benzothiazole) It may contain at least one selected from the group consisting of (e.g., nzothiazole, tetrathiafulvalene), nitrile compounds (e.g., adiponitrile, succinonitrile), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether), and derivatives thereof.

[0102] The components mentioned above may be used as solutes and solvents, or as trace components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0103] The electrolyte may contain an ionic liquid. The ionic liquid may contain, 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.

[0104] In some embodiments of this 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.

[0105] All solid state battery In some embodiments of this 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 an electrolyte and a separator 20. The solid electrolyte may also be included in the positive electrode layer 11 and the negative electrode layer 12. Instead of a separator 20, the solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11. The solid electrolyte layer includes, for example, a solid electrolyte and a binder.

[0106] 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.

[0107] The solid electrolyte may include, for example, at least one selected from the group consisting of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, and nitride solid electrolytes.

[0108] The sulfide solid electrolyte may contain at least one 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). In addition to Li and S, the sulfide solid electrolyte may further contain any other components.

[0109] 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, Li 10 GeP2S 12 Li4P2S6, Li7P3S 11 It may include at least one selected from the group consisting of Li3PS4 and Li7PS6.

[0110] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. The mixing ratio may be specified by prefixing each raw material with a number. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (molar ratio)".

[0111] A sulfide solid electrolyte may have a composition represented by the general formula "xLi2S-(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 also 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", "xLi2S-(1-x)P2S5" may have the composition of Li3PS4.

[0112] 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" could be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0113] Sulfide solid electrolytes are, for example, those with the general formula "Li 7-x-2y PS 6-x-y X y It may have a composition represented by the formula: 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 selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0114] Sulfide solid electrolytes are, for example, those with 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.

[0115] 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, or 0.5 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.

[0116] 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.

[0117] The halide solid electrolyte may have, for example, a composition represented by the general formula "Li 3-a Tia Al 1-a It may have a composition represented by "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.

[0118] Halide solid electrolytes include, for example, those with the general formula "Li3YCl a Br b I 6-a-b It may have a composition represented by ". 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.

[0119] Oxide solid electrolytes include, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 It may contain at least one selected from the group consisting of the following. The hydride solid electrolyte may include, for example, LiBH4. The nitride solid electrolyte may include, for example, Li3N, Li3BN2, etc. [Examples]

[0120] Sample preparation Figure 5 is a table showing the experimental results. The positive electrode active materials No. 1 to No. 4 were manufactured according to the following procedure.

[0121] No.1 raw material mixture Compositional formula “Li1Mn 0.8 Fe 0.2 The raw materials, lithium carbonate, manganese carbonate, iron oxalate, and phosphoric acid, are weighed out to match the composition ratio shown in "PO4". A powder mixture is formed by mixing the powder materials other than phosphoric acid. The mixture is then ground and mixed in a mortar while phosphoric acid is added until the reaction stops, forming the first precursor powder. At this time, gas generation can be suppressed by gradually adding phosphoric acid.

[0122] Vitrification The powder of the first precursor 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 it reaches 1100°C. This is thought to cause the first precursor to melt and become glassy. The furnace temperature of 1100°C is maintained for 1 hour. After 1 hour, the furnace temperature is cooled at a rate of 5°C / min until it reaches 600°C. Then, the furnace temperature is cooled at a rate of 15°C / min until it reaches room temperature. This yields a glassy active material mass. The active material mass is then crushed using a mechanical crushing device to form the second precursor.

[0123] Wet grinding A third precursor is formed by adding 10% fructose by mass fraction to the second precursor. A fourth precursor is formed by grinding the third precursor in an aqueous solvent using a bead mill. Beads (grinding media) with a diameter (φ) of 0.3 mm are used during grinding. The peripheral speed is 10 m / s. The grinding time is 30 min.

[0124] 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 fourth precursor is fired at 650°C to produce the cathode active material (LMFP). The cross-section (fracture surface) of the primary particles is evaluated.

[0125] No.2 In the vitrification process, the cathode active material is manufactured in the same manner as in No. 1, except that the cooling rate from 1100°C to 600°C is changed to 10°C / min.

[0126] No.3 In the vitrification process, the cathode active material is produced in the same manner as in No. 1, except that cooling control is not implemented and the material is simply allowed to cool from 1100°C to room temperature (natural cooling) inside the firing furnace.

[0127] No. 4 In the vitrification process, the cathode active material is produced in the same manner as in No. 1, except that after being maintained at 1100°C for 1 hour, the first precursor in a glassy state is removed from the firing furnace and rapidly cooled in the open air.

[0128] evaluation Coin cell production 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 content concentration of the paste is 50% by mass fraction. The positive electrode layer is formed by applying the paste to the surface of an aluminum foil and drying it. The density of the positive electrode layer is 1.8 g / cm³ by roll pressing. 3 The cathode raw material is formed by adjusting the temperature. The cathode raw material is subjected to a vacuum drying treatment at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) is removed from the cathode raw material by punching.

[0129] The coin cell is assembled inside the glove compartment. The cell configuration is as follows: Working electrode: Disc sample (positive electrode) Opposite pole: Li foil Separator: Polymer porous membrane Electrolyte: "EC / DMC=3 / 7 (volume ratio)", LiPF6 (1mol / L)

[0130] Evaluation of Rate Characteristics The rate equivalent to 1C is determined based on the discharge capacity (theoretical capacity) obtained from the coating mass of the positive electrode layer. "C" is a symbol indicating the current rate (time rate). At a rate of 1C, the theoretical capacity is supplied 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 Maximum charging voltage: 4.3V Current cutoff rate during CV charging: 0.01C

[0131] After charging, CC discharge is performed at 25°C at a rate of 0.1C up to 3.0V, and the discharge capacity "A" at 0.1C discharge is measured. The coin cell is then charged again by the same CCCV charging method described above. After charging, CC discharge is performed at 25°C at a rate of 1C up to 3.0V, and the discharge capacity "B" at 1C discharge is measured. The ratio "1C capacity / 0.1C capacity" can be calculated using the formula "B / A". A larger ratio "1C capacity / 0.1C capacity" indicates better rate characteristics.

[0132] Experimental results As shown in Figure 5, when a striated structure is observed in the cross-section of the primary particle, there is a tendency for the rate characteristics to improve. [Explanation of symbols]

[0133] 1 Primary particle, 1a First region, 1b Second region, 2 Secondary particle, 5 Carbon layer, 10 Bipolar electrode, 11 Positive electrode layer, 12 Negative electrode layer, 13 Current collector foil, 20 Separator, 30 Sealing material, 40 Cell, 50 Power generation element, 90 Outer casing, 91 First current collector plate, 92 First laminate film, 93 Second laminate film, 94 Second current collector plate, 100 Battery.

Claims

1. Contains primary particles, The primary particles contain an olivine-type phosphate compound. A striated structure is formed on at least a portion of the cross-section of the primary particle. The aforementioned striated structure includes a first region and a second region, The second region contains phosphorus at a higher concentration than the first region. The second region extends in a striated manner, and The first region is divided into two or more parts by the second region. Cathode active material.

2. Both ends of the second region are located on the surface of the primary particle, The positive electrode active material according to claim 1.

3. The first region is divided into three or more parts by the second region, and In the direction intersecting the direction in which the second region extends, the average width of the divided sections is 10 nm to 100 nm. The positive electrode active material according to claim 1.

4. The average width is less than half of the maximum Ferret diameter of the primary particles. The positive electrode active material according to claim 3.

5. The average width is 65 nm to 94 nm. The positive electrode active material according to claim 3.

6. It contains secondary particles, and The secondary particle comprises a plurality of the primary particles, The positive electrode active material according to any one of claims 1 to 5.

7. The olivine-type phosphate compound comprises 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 any one of claims 1 to 5.

8. It includes a positive electrode layer, and The positive electrode layer comprises the positive electrode active material described in any one of claims 1 to 5. electrode.

9. The electrode included in claim 8, battery.

10. Having a bipolar structure, The battery according to claim 9.

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