Positive electrode active material, electrode and battery

Abstract

Improved rate characteristics. [Solution] The positive electrode active material includes primary particles. The primary particles include an olivine-type phosphate compound. A streaky structure is formed in at least a portion of the cross section of the primary particles. The streaky 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 streaky manner. The first region is divided into two or more regions by the second region.

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 particles of manganese-rich lithium manganese iron phosphate and granules of particles of iron-rich lithium manganese iron 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] Olivine-type phosphate compounds can be aggregates of primary particles (secondary particles). Olivine-type phosphate compounds tend to have poor rate characteristics. Previously, attempts have been made to improve the rate characteristics by applying a carbon coating to the surfaces of the primary particles. However, even if the surfaces of the primary particles are carbon-coated, it is believed that the ionic conductivity inside the primary particles remains unchanged. In other words, there is still room for improvement in the rate characteristics.

[0005] An object of the present disclosure is to improve rate characteristics. [Means for solving the problem]

[0006] 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.

[0007] 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. A streaky structure is formed in at least a portion of the cross section of the primary particles. The streaky 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 streaky manner. The first region is divided into two or more regions by the second region.

[0008] The second region contains a higher concentration of P than the first region. It is believed that ion conduction is promoted in the second region compared to the first region. Therefore, it is believed that the second region can function as an ion diffusion path. In the cross section of the primary particle, the second region extends in a stripe-like manner. Therefore, it is believed that the second region spreads in a layer-like manner within the primary particle. As the second region (ion diffusion layer) spreads so as to divide the first region (bulk), improvement in rate characteristics is expected.

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

[0010] The second region (ion diffusion layer) extends to connect to the outside of the primary particle, which is expected to improve rate characteristics.

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

[0012] Hereinafter, the “average width of the divided sections” will also be referred to as the “average division width.” By setting the average division width to 10 nm to 100 nm, improvement in rate characteristics is expected.

[0013] 4. The positive electrode active material described in the above item "3" may include, for example, the following configuration: The average division width is smaller than 1 / 2 of the maximum Feret's diameter of the primary particles.

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

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

[0016] The improvement of the rate characteristics is expected because the average division width is from 65 nm to 94 nm.

[0017] 6. The positive electrode active material described in any one of the above “1” to “5” may include, for example, 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 the above “1” to “6” 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).

[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 the above “1” to “7”.

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

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

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

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

[0025] 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]

[0026] [Figure 1] FIG. 2 is a conceptual diagram of a cross section 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

[0027] 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.

[0028] 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."

[0029] 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.

[0030] 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."

[0031] 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.

[0032] 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.

[0033] 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.

[0034] "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.

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

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

[0037] A mapping image of phosphorus (P) is obtained by mapping observation of the interior of the primary particle. The mapping image is normalized based on the maximum and minimum brightness of the mapping image. In the normalized mapping image, areas where the brightness is 75% or more of the maximum value are considered to be P-enriched areas (i.e., "second areas"). Areas where the brightness is less than 75% of the maximum value are considered to be "first areas."

[0038] FIG. 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 stripes (parallel lines). The first region 1a is divided into n sections by the second regions 1b in a direction intersecting the direction in which the second regions 1b extend. The width of each divided section is considered to be equal to the distance "d1, d2, . . . , dn" between adjacent second regions 1b. The average division width "Da" is calculated using the formula "Da = (d1 + d2 + . . . + dn) / n." If the second regions 1b are not parallel, a single straight line is drawn so as to intersect as many second regions 1b as possible at right angles. The length of each line segment in the line divided by the second regions 1b is considered to be the distance "d1, d2, . . . , dn."

[0039] Various dimensional measurements and shape analyses of SEM images, mapping images, etc. can be performed using, for example, image analysis software such as "ImageJ."

[0040] The "maximum Feret diameter" refers to the length of the long side of the minimum bounding rectangle (MBR) relative to the particle's outline in a two-dimensional image of the particle (for example, an SEM image).

[0041] 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.

[0042] 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.

[0043] 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.

[0044] "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.

[0045] 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.

[0046] primary particle The positive electrode active material includes primary particles 1. The primary particles 1 may exist alone. The primary particles 1 may form secondary particles 2, which will be described later. The primary particles 1 may have any shape. The primary particles 1 may be, for example, spherical, rod-like, angular, or scaly. The primary particles 1 include an olivine-type phosphate compound. Hereinafter, "olivine-type phosphate compound" may be abbreviated as "olivine."

[0047] 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.

[0048] A streak structure is formed in at least a part of the cross section of the primary particle 1. The streak structure may be formed over the entire cross section. The streak structure is expected to improve rate characteristics. The streak structure includes a first region 1a and a second region 1b. The second region 1b extends in a streak shape. The second region 1b may extend, for example, in a straight line. The second region 1b may extend, for example, in a curved line. The second region 1b may extend, for example, in a wavy line. The second region 1b may be, for example, in the shape of a series of parallel lines.

[0049] The second region 1b may extend continuously. The second region 1b may include discontinuous portions. For example, the discontinuity of the second region 1b may result in portions that look like dotted lines, broken lines, or the like.

[0050] The beginning and end of the second region 1b may be located, for example, inside the cross section. For example, at least one of the beginning and end 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, if the second region 1b (ion conductive layer) extends so as to cross the primary particle 1, improvement in rate characteristics is expected.

[0051] The second region 1b contains P at a higher concentration than the first region 1a. As described 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).

[0052] The first region 1a is divided into two or more regions by the second region 1b. For example, in FIG. 1, the first region 1a is divided into four regions. 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, 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, 65 nm to 94 nm.

[0054] The ratio "Da / D" of the average division width "Da" to the maximum Feret diameter "D" of the primary particles 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 second region 1b may be, for example, less than 10 nm. The width "w" of 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 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 2 is a conceptual diagram of secondary particles in this embodiment. The positive electrode active material may include secondary particles 2. The secondary particles 2 include a plurality of primary particles 1. 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.

[0057] The secondary particles 2 may have any shape. The secondary particles 2 may be, for example, spherical, rod-like, angular, or lumpy. The sphericity of the 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 the 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" refers to the circularity in a two-dimensional image (e.g., an SEM image). The sphericity (circularity) is calculated using the following formula. The sphericity refers to the arithmetic average of 30 secondary particles 2. ψ=4πS / L 2 ψ: Sphericity (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)

[0058] The carbon layer 5 may cover the surface of the primary particle 1. The carbon layer 5 may cover a portion of the surface of the primary particle 1, or may cover the entire surface of the primary particle 1. The carbon layer 5 may be derived from, for example, a sugar or the like. The amount of the carbon layer 5 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 olivine. The amount of carbon 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 olivine.

[0059] composition The primary particles 1 include 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 an XRD (X-Ray Diffraction) pattern.

[0060] Olivine may further include, for example, a crystallized glass phase (olivine structure), a glass phase, etc., in addition to a crystalline phase (olivine structure). For example, during synthesis, raw materials are heated to vitrify them, and then cooled, thereby forming a crystallized glass phase, etc. Depending on specific crystallization conditions (cooling conditions), polycrystals (lithium phosphate, etc.) may be formed in the gaps in the glass structure. The first region 1a is considered to be derived from the glass structure. The second region 1b is considered to be derived from the polycrystal. For example, the first region 1a may include at least one of an olivine crystalline phase and a crystallized glass phase. For example, the second region 1b may include lithium phosphate polycrystals.

[0061] 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.

[0062] 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.

[0063] 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.

[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 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

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

[0073] 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).

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] The carbon-based active material may include 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 include at least one selected from the group consisting of, for example, P, W, Al, and O. The different material may include 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 include 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 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.

[0085] 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.

[0086] 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.

[0087] 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.

[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 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.

[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 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.

[0092] Separator 20 may include, for example, a mixed layer, which includes both inorganic and organic particles.

[0093] 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.

[0094] 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.

[0095] 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."

[0096] 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."

[0097] 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.

[0098] 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."

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[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 a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a hydride solid electrolyte, and a nitride solid electrolyte.

[0108] 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.

[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, and Li 10 GeP2S 12 , Li4P2S6, Li7P3S 11 , Li3PS4, and Li7PS6.

[0110] 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)."

[0111] 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.

[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" may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0113] The sulfide solid electrolyte is, for example, represented by 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).

[0114] The sulfide solid electrolyte is, for example, represented by 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, 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.

[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 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] 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.

[0119] 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]

[0120] Sample preparation The experimental results are shown in a table in Figure 5. Positive electrode active materials No. 1 to No. 4 were produced 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 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, grinding and mixing is carried out in a mortar until the reaction stops, thereby forming a powder of the first precursor. At this time, the generation of gas 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 using the following procedure. First, the temperature inside the furnace is raised at a rate of 5°C / min until the temperature 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 one hour. After this hour, the furnace is cooled at a rate of 5°C / min until the temperature reaches 600°C. Then, the furnace is cooled at a rate of 15°C / min until the temperature reaches room temperature. This results in a glassy active material mass. The active material mass is pulverized using a mechanical pulverizer to form a second precursor.

[0123] 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 0.3 mm are used. The peripheral speed is 10 m / s. The pulverization 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 positive electrode active material (LMFP). The cross section (fracture surface) of the primary particles is evaluated.

[0125] No.2 A positive electrode active material was produced in the same manner as in No. 1, except that the temperature drop rate from 1100°C to 600°C during vitrification was changed to 10°C / min.

[0126] No.3 A positive electrode active material is produced in the same manner as in No. 1, except that cooling control is not performed during vitrification, and the material is simply allowed to cool (naturally cool) from 1100° C. to room temperature in the firing furnace.

[0127] No.4 In the vitrification, after maintaining the temperature 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, thereby producing a positive electrode active material in the same manner as in No. 1.

[0128] 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.

[0129] 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)

[0130] 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

[0131] 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.

[0132] Experimental results As shown in FIG. 5, when a streaky structure is observed in the cross section of the primary particle, the rate characteristics tend 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 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 include an olivine-type phosphate compound; a streaky structure is formed in at least a part of the cross section of the primary particle, the streaky structure includes a first region and a second region; the second region contains an ion conductor containing phosphorus at a higher concentration than the first region, The second region extends in a stripe shape, and The first region is divided into two or more regions 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 regions by the second region, and In a 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 smaller than 1 / 2 of the maximum Feret diameter of the primary particles; The positive electrode active material according to claim 3 .

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

6. Contains secondary particles, and The secondary particles include a plurality of the primary particles. The positive electrode active material according to claim 1 .

7. 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 .

8. a positive electrode layer, and The positive electrode layer contains the positive electrode active material according to any one of claims 1 to 5. electrode.

9. 9. The electrode of claim 8, battery.

10. having a bipolar structure, 10. The battery of claim 9.

Images