Positive electrode active material, electrode, and battery

Abstract

The invention relates to a positive active material, an electrode and a battery. An object of the present disclosure is to improve magnification characteristics. A positive electrode active material includes a powder. The powder includes a plurality of secondary particles. Each of the plurality of secondary particles includes a plurality of primary particles. Each of the plurality of primary particles contains an olivine-type phosphate compound. Carbon adheres to at least part of the surface of the primary particles. In at least some of the plurality of secondary particles, linearly extending grooves are formed in the surfaces of the secondary particles.

Description

TECHNICAL FIELD

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

[0002] International Publication No. 2020 / 261879 discloses a lithium iron manganese phosphate having an average secondary particle diameter of 3 μm or more and 20 μm or less. SUMMARY

[0003] As a positive electrode active material, an olivine-type phosphate compound has been developed. The olivine-type phosphate compound has a tendency to have low electronic conductivity. Therefore, in the past, in a secondary particle (granulated body), an attempt has been made to improve the electronic conductivity by forming a carbon layer on the surface of a primary particle. However, there is still room for improvement in the rate characteristics of the battery.

[0004] An object of the present disclosure is to improve the rate characteristics.

[0005] The technical solutions and effects of the present disclosure are described below. However, the mechanism of action of the present disclosure contains a presumption. The mechanism of action does not limit the technical scope of the present disclosure.

[0006] 1. One embodiment of the present disclosure is a positive electrode active material. The positive electrode active material includes a powder. The powder includes a plurality of secondary particles. Each of the plurality of secondary particles includes a plurality of primary particles. Each of the plurality of primary particles includes an olivine-type phosphate compound. Carbon is attached to at least part of the surface of the primary particle. In at least a part of the plurality of secondary particles, a groove extending in a linear shape is formed on the surface of the secondary particle.

[0007] In the past, the secondary particles have been granulated in such a manner as to have a smooth surface. It has been found that, by adjusting the granulation conditions, a groove extending in a linear shape is formed on the surface of the secondary particle. For example, during granulation, by collision and adhesion of two or more secondary particles (precursors), two or more secondary particles can fuse to form one secondary particle. It is considered that the groove originates from the adhesion portion (joint interface) between the secondary particles. It is considered that, at the groove (joint interface), a complex of carbon and lithium phosphate is concentrated. It is expected that the complex functions as both an electronic conduction phase and an ionic conduction phase. It is considered that the joint interface extends to the inside of the secondary particle. That is, it is considered that the electronic conduction phase and the ionic conduction phase extend to the inside of the secondary particle. Therefore, improvement in the rate characteristics is expected.

[0008] 2. The positive electrode active material described in "1" above may, for example, include the following. The division particle rate of the plurality of secondary particles exceeds 30%. The "division particle rate" indicates the ratio of the secondary particles whose surface is divided into two or more regions by the groove in the scanning electron microscope (SEM) image of the powder.

[0009] By the split particle rate exceeding 30%, improvement in the rate characteristic is expected.

[0010] 3. The positive electrode active material described in "1" or "2" above may, for example, include the following aspect. The average number of divisions of the plurality of secondary particles exceeds 2. The "average number of divisions" indicates the average number of regions divided by a groove among the plurality of secondary particles included in the powder.

[0011] By the average number of divisions exceeding 2, improvement in the rate characteristic is expected.

[0012] 4. The positive electrode active material described in "2" or "3" above may, for example, include the following aspect. The split particle rate is measured in the secondary particles having a maximum Feret diameter of 5 μm or more.

[0013] It is considered that the split particle rate measured in the group of secondary particles grown to a certain extent (particle group) well reflects the properties of the entire powder. The same applies to the average number of divisions.

[0014] 5. The positive electrode active material described in any one of "1" to "4" above may, for example, include the following aspect. The primary particles have a maximum Feret diameter of 10 to 90 nm.

[0015] 6. The positive electrode active material described in any one of "1" to "5" above may, for example, include the following aspect. The olivine-type phosphate compound includes lithium manganese phosphate.

[0016] Lithium manganese phosphate is expected to have a high discharge voltage. By the positive electrode active material including lithium manganese phosphate, for example, improvement in the output characteristic is expected.

[0017] 7. 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 "6" above.

[0018] 8. One aspect of the present disclosure is a battery. The battery includes the electrode described in "7" above.

[0019] 9. The battery described in "8" above may, for example, include the following aspect. The battery has a bipolar structure.

[0020] The bipolar structure can be formed by stacking of bipolar electrodes. By the bipolar structure, for example, improvement in the output characteristic is expected.

[0021] Hereinafter, an embodiment of the present disclosure (hereinafter, which can be referred to simply as "the present embodiment") and an example of the present disclosure (hereinafter, which can be referred to simply as "the present example") will be described. However, the present embodiment and the present example do not limit the technical scope of the present disclosure. The present embodiment and the present example are illustrative in all respects. The present embodiment and the present example are non-limiting. The technical scope of the present disclosure includes all modifications within the meaning and range equivalent to the recitations of the claims. For example, it is intended to include any arbitrary combination of the technical concepts extracted from the present embodiment and their arbitrary combinations.

[0022] The above and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a conceptual diagram showing an example of image processing.

[0024] Figure 2 is a conceptual diagram showing a positive electrode active material of the present embodiment.

[0025] Figure 3 is a conceptual diagram showing a secondary particle of the present embodiment.

[0026] Figure 4 is a schematic flowchart showing a manufacturing method of a positive electrode active material of the present embodiment.

[0027] Figure 5 is a schematic perspective view of a battery of the present embodiment.

[0028] Figure 6 is a schematic cross-sectional view along the line VI-VI in Figure 5

[0029] Figure 7 is a table showing experimental results.

[0030] Figure 8 is a temperature profile at the time of firing. DETAILED DESCRIPTION

[0031] TERMS AND PHRASES

[0032] "Have", "contain", "include" and their conjugations are open expressions. A structure expressed in an open expression can include additional elements in addition to the essential elements, or can not include additional elements. The recitation of "consist of" is a closed expression. However, even in a structure expressed in a closed expression, impurities and additional elements that are normally attached and are irrelevant to the object technology can be included. The recitation of "consist essentially of" is a semi-closed expression. In a structure expressed in a semi-closed expression, additional elements that do not substantially affect the basic and novel characteristics of the object technology are allowed.​

[0033] "Also" and "may" are used in a permissive sense (i.e., meaning having the potential to), and not a mandatory sense (i.e., meaning must).

[0034] The order of execution or performance of the steps, actions, or blocks in various embodiments need not be limited to the order presented in the figure unless otherwise specified. For example, multiple steps can be performed at once or in an order different than that presented.

[0035] The use of "first", "second", etc. does not limit the number of elements. These designations can be made only to distinguish between two or more elements or instances of an element. Such designations are not to be construed as limiting those elements. For example, such designations relate to the order, importance, etc. of the elements they are attached to.

[0036] Geometric terms should not be interpreted in a strict sense. As geometric terms, for example, "parallel", "perpendicular", "orthogonal", etc. are used. For example, directions, angles, distances, etc. can also be displaced within a range where substantially the same or similar functions are obtained. For example, geometric terms can include tolerances, errors, etc. in design, operation, manufacture, etc. The dimensional relationships in the figures are sometimes different from the actual dimensional relationships. In order to help the reader understand, the dimensional relationships in the figures are sometimes changed. For example, lengths, widths, thicknesses, etc. are sometimes changed. Sometimes, part of the structure is omitted.

[0037] An element described in the singular can also include the plural unless specifically stated otherwise. For example, a particle can also mean a plurality of particles, a collection of particles, and a powder. Also, "a plurality of particles" can be referred to as "a particle group".

[0038] A numerical range such as "m to n%" includes the upper limit value and the lower limit value unless otherwise specified. That is, "m to n%" means a numerical range of "m% or more and n% or less". In addition, "m% or more and n% or less" includes "more than m% and less than n%". "Or more" and "or less" are indicated by the inequality sign with an equal sign "<, >". "More than" and "less than" are indicated by the inequality sign without an equal sign "<, >". A value arbitrarily selected from a numerical range can also be used as a new upper limit value or a new lower limit value. For example, a new numerical range can be set by arbitrarily combining a value within a numerical range and a value described in other parts of the specification, in a table, in a figure.

[0039] All numerical values are modified by the term "about". The term "about" can mean, for example, ±5%, ±3%, ±1%, and the like. All numerical values can be approximate values that can vary depending on the usage form of the subject technique. All numerical values can be expressed in significant figures. Unless otherwise specified, measured values can be average values of multiple measurements. The number of measurements can be 3 or more, can be 5 or more, or can be 10 or more. In general, it can be expected that the more the number of measurements, the higher the reliability of the average value. Measured values can be rounded off by rounding based on the number of significant figures. Measured values can include, for example, errors and the like accompanying the detection limit of a measuring device and the like.

[0040] The device, software, and the like used in the measurement of various values and the like are nothing more than an example. Products equivalent to the exemplified device and the like can also be used. In the case of using equivalent products, the measurement conditions can also be adjusted in coordination with the device.

[0041] "Groove" means a portion that is sunken lower than the surroundings on the surface of a secondary particle. The groove is determined by the following steps. The powder (positive electrode active material) is scattered on the surface of a carbon tape. The powder on the carbon tape is observed by SEM, whereby an SEM image of the powder is obtained. The observation magnification is adjusted so that 30 or more secondary particles are included in the field of view. The observation magnification can be adjusted, for example, in the range of 5000 to 15000 times (for example, around 10000 times). In a plurality of fields of view (for example, around 5 fields of view), 30 secondary particles in total are picked up. For example, 30 secondary particles having a predetermined size can also be picked up. For example, 30 secondary particles having a maximum Feret diameter of 5 μm or more can also be picked up. The SEM image is evaluated with 8-bit gradation. For example, an image processing software "Image J" or the like can be used. The maximum brightness is determined in one secondary particle. A portion having a brightness of 80% or less with respect to the maximum brightness is regarded as a "groove".

[0042] The "divided particle rate" is calculated in the following order. In the above-described SEM image, secondary particles whose surfaces are divided into two or more regions by grooves extending in a linear shape are counted. The divided particle rate is calculated by the following formula.

[0043] (Divided particle rate) = N / (N + M)

[0044] N: Number of secondary particles divided into two or more regions

[0045] M: Number of secondary particles not divided into two or more regions

[0046] The "average division number" is calculated in the following order. In the above-described SEM image, for each of the 30 secondary particles picked up, the number of regions divided by grooves is counted. The arithmetic average of the number of divided regions in the 30 secondary particles is regarded as the "average division number".

[0047] For example, the number of regions to be segmented can also be determined by the following image processing. Figure 1 is a conceptual diagram showing an example of image processing. As an example, the maximum brightness within the secondary particle 2 is 220. 80% of the maximum brightness is 176. The brightness of the groove 3 is 154. By the groove 3, the surface of the secondary particle 2 is segmented into three regions 2a, 2b, 2c. Image processing is performed on the SEM image so that the region having a brightness above the threshold value remains. For example, the threshold value is set in the range of 176 to 220. By the image processing, the three regions 2a, 2b, 2c can be clearly confirmed in a separated state. After the image processing, the number of regions can be counted.

[0048] The "maximum Feret diameter" of a particle represents the length of the long side of the circumscribed rectangle (oblong or square) of the particle. In the case where the circumscribed rectangle is a square, the length of the long side represents the length of the side. The maximum Feret diameter of a primary particle can be measured, for example, in a transmission electron microscopy (TEM) image.

[0049] "D50" represents the particle diameter at which the cumulative value becomes 50% in the volume-based particle size distribution (cumulative distribution). The volume-based particle size distribution is measured by a laser diffraction type particle size distribution measuring device.

[0050] The chemical composition of a compound can be measured by ICP-AES (Inductively coupled plasma atomic emission spectroscopy). A sample solution is prepared by dissolving a sample (for example, a positive electrode active material) of 0.1 g in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is diluted to an appropriate concentration with a volumetric flask. After dilution, composition analysis is performed with an ICP-AES device. For example, a product with the product name "PS3520UVDDII" (manufactured by Hitachi High-Tech Corporation) or the like can be used.

[0051] "Derivative" means a compound which has been changed by at least one of introduction of a functional group, substitution of an atom, oxidation, reduction, and other chemical reactions in a part of the compound as a parent. The change site can be one or multiple. "Substituent" can include, for example, at least one selected from the group consisting of alkyl group, alkenyl group, alkynyl group, cycloalkyl group, unsaturated cycloalkyl group, aryl group, heterocyclic group, halogen atom (F, Cl, Br, I, etc.), OH group, SH group, CN group, SCN group, OCN group, nitro group, alkoxy group, unsaturated alkoxy group, amino group, alkylamino group, dialkylamino group, aryloxy group, acyl group, alkoxycarbonyl group, acyloxy group, aryloxycarbonyl group, acylamino group, alkoxycarbonyl group, aminoaryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, sulfo group, carboxyl group, hydroxamic acid group, sulfino group, hydrazino group, imino group, and silyl group. These substituents can be further substituted. In the case where there are two or more substituents, the substituents can be the same or different. Multiple substituents can be combined with each other to form a ring.

[0052] Positive electrode active material

[0053] Figure 2 is a conceptual diagram showing the positive electrode active material of the present embodiment. For example, Figure 2 The trajectory of the SEM image of the powder can be made. The positive electrode active material contains a powder. The D50 of the powder can be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 can be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0054] The powder contains a plurality of secondary particles 2. The plurality of secondary particles 2 contains secondary particles 2p. The secondary particle 2p has a groove 3 extending in a linear shape on the surface thereof. The plurality of secondary particles 2 can further contain secondary particles 2q as long as the plurality of secondary particles 2 contains the secondary particles 2p. The secondary particle 2q does not have the groove 3. Further, in the secondary particle 2q, it is also possible to have the groove 3 at a position that is not visible from the SEM image, but the presence or absence of the groove 3 is determined from the appearance in the SEM image.

[0055] The groove 3 may, for example, extend linearly or curvilinearly. The groove 3 can be a single one or a plurality of grooves. The groove 3 can also branch into a plurality of grooves. The number of branches of the groove 3 may, for example, be 2 or more, 3 or more, 4 or more, or 5 or more. The number of branches of the groove 3 may, for example, be 10 or less, 8 or less, 6 or less, 5 or less, or 4 or less. The groove 3 may, for example, extend in a ring shape. The groove 3 may, for example, form a closed ring. The groove 3 can extend in a manner that divides the surface of the secondary particle 2 into a plurality of regions. The groove 3 can also not divide the surface of the secondary particle 2. The groove 3 can cross the surface of the secondary particle 2 or can not cross the surface.

[0056] The total path length of the groove 3 may, for example, be 0.1 times or more, 0.2 times or more, 0.3 times or more, 0.4 times or more, 0.5 times or more, 1 time or more, 1.5 times or more, 2 times or more, 2.5 times or more, or 3 times or more of the maximum Feret diameter of the secondary particle 2. The total path length of the groove 3 may, for example, be 10 times or less, 5 times or less, 3 times or less, or 2 times or less of the maximum Feret diameter of the secondary particle 2. The total path length of the groove 3 may, for example, be measured by an image processing software "Image J" or the like.

[0057] The depth of the groove 3 may, for example, be 100 nm or more. The depth of the groove 3 may, for example, be 1 μm or less, 500 nm or less, or 250 nm or less. The width of the groove 3 may, for example, be 100 nm or more. The width of the groove 3 may, for example, be 1 μm or less, 500 nm or less, or 250 nm or less.

[0058] The divided particle rate can exceed 0%. By the divided particle rate exceeding 0%, improvement in the rate characteristic can be expected. The divided particle rate may, for example, be 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, or 80% or more. The divided particle rate may, for example, be 100% or less, 90% or less, or 80% or less. For example, by the divided particle rate exceeding 30%, improvement in the rate characteristic can be expected. Further, for example, by the divided particle rate being 70% or more, improvement in the rate characteristic can be expected.

[0059] The average number of divisions can also be 1 or more. By the average number of divisions being 1 or more, improvement in the rate characteristic is expected. The average number of divisions can be, for example, 1.2 or more, 1.4 or more, 1.6 or more, 1.8 or more, 2 or more, 2.5 or more, 3 or more, 3.5 or more, 4 or more, 4.5 or more, 5 or more, 5.5 or more, or 6 or more. The average number of divisions can be, for example, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4.5 or less, 4 or less, or 3.5 or less. For example, by the average number of divisions being more than 2, improvement in the rate characteristic is expected. For example, by the average number of divisions being 3 or more, improvement in the rate characteristic is expected. For example, by the average number of divisions being 3.5 or more, improvement in the rate characteristic is expected.

[0060] The average value of the maximum Feret diameter in the 30 secondary particles 2 can be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The average value of the maximum Feret diameter can be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0061] The division particle rate can also be, for example, a value for the secondary particles 2 having a maximum Feret diameter of 5 μm or more. The division particle rate can also be, for example, a value for the secondary particles 2 having a maximum Feret diameter of 10 μm or more. The division particle rate can also be, for example, a value for the secondary particles 2 having a maximum Feret diameter of 10 μm or less. The same applies to the average number of divisions.

[0062] For example, in the EDS (Energy Dispersive X-ray Spectroscopy) element mapping of the secondary particle 2p, the carbon (C) concentration and the phosphorus (P) concentration in the portion corresponding to the groove 3 can also be higher than in the portion other than the groove 3.

[0063] Figure 3 is a conceptual diagram showing the secondary particle of the present embodiment. The secondary particle 2p is a collection of primary particles 1. That is, the secondary particle 2p contains a plurality of primary particles 1. Although not shown, the same applies to the secondary particle 2q.

[0064] The average value of the maximum Feret diameter in the 30 primary particles 1 can be, for example, 10 to 90 nm. That is, the maximum Feret diameter of the primary particle 1 can be, for example, 10 to 90 nm. The maximum Feret diameter of the primary particle 1 can be, for example, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, or 80 nm or more. The maximum Feret diameter of the primary particle 1 can be, for example, 80 nm or less or 60 nm or less.

[0065] Carbon is attached to at least part of the surface of the primary particles 1. The carbon can be attached to part of the surface of the primary particles 1, or can be attached to the entire surface of the primary particles 1. The carbon can also form a carbon layer 4. The amount of carbon attached can be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more, in terms of mass fraction, with respect to the secondary particles 2. The amount of carbon attached can be, for example, 5% or less, 4% or less, or 3% or less, in terms of mass fraction, with respect to the secondary particles 2.

[0066] Each of the plurality of primary particles 1 contains an olivine-type phosphate compound. "Olivine-type" indicates a crystal structure belonging to space group Pnma. The space group is identified by powder X-ray diffraction (XRD) measurement. The primary particles 1 can also be, for example, a single-phase compound. The primary particles 1 can also contain a phase belonging to other space groups as long as they contain an olivine-type crystalline phase. The primary particles 1 can also further contain an amorphous phase or the like, for example.

[0067] The olivine-type phosphate compound can contain, for example, lithium iron phosphate (LFP), lithium manganese phosphate (LMP), or the like. In the LMP, part of the manganese (Mn) can be substituted with iron (Fe). The Fe-substituted LMP is also referred to as lithium manganese iron phosphate (LMFP). The LMP can have, for example, a composition represented by the following general formula.

[0068] Li 1-a Mn 1-x Fe x PO4

[0069] For example, the relationship -0.5 ≤ a ≤ 0.5 can also be satisfied. The Fe substitution amount (x) can be, for example, 0 or more, 0.05 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. The Fe substitution amount (x) can be, for example, 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.

[0070] In the LMP, elements other than lithium (Li), Mn, Fe, phosphorus (P), and oxygen (O) (dopants) can also be doped. The amount of doping (mass fraction relative to the mass of Li) can be, for example, 0.01 to 0.1. The dopants can include, for example, at least one selected from 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), 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 actinide elements.

[0071] The positive electrode active material can also include other components as long as it includes the olivine-type phosphate compound. The other components can include, for example, lithium-nickel composite oxide (LNO), lithium-cobalt composite oxide (LCO), lithium-manganese composite oxide (LMO), or the like. The mixing ratio of the olivine-type phosphate compound and the other components, "mass ratio", can be, for example, "olivine-type phosphate compound / other components = 9 / 1 to 1 / 9", "olivine-type phosphate compound / other components = 8 / 2 to 2 / 8", "olivine-type phosphate compound / other components = 7 / 3 to 3 / 7", or "olivine-type phosphate compound / other components = 6 / 4 to 4 / 6". The positive electrode active material can be, for example, a mixture of a powder of the olivine-type phosphate compound and a powder of the other components.

[0072] The LNO can also have, for example, a crystal structure belonging to space group R-3m. The LNO can have, for example, a composition represented by the following general formula.

[0073] Li 1-a Ni x M 1-x O2

[0074] wherein -0.5 ≤ a ≤ 0.5, 0 ≤ x ≤ 1. M may, for example, include at least one selected from Co, Mn, and Al. For example, the relationship 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x ≤ 1 may be satisfied. For example, the relationship -0.4 ≤ a ≤ 0.4, -0.3 ≤ a ≤ 0.3, -0.2 ≤ a ≤ 0.2, or -0.1 ≤ a ≤ 0.1 may be satisfied.

[0075] LNO may, for example, include at least one selected from LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and LiNiO2.

[0076] LNO may, for example, be represented by the following general formula. A compound represented by the following general formula can also be referred to as "NCM".

[0077] Li 1-a Ni x Co y Mn z O2

[0078] wherein -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1. For example, the relationship 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1 may be satisfied. For example, the relationship 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1 may be satisfied. For example, the relationship 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1 may be satisfied.

[0079] NCM may, for example, include at least one selected from LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2 and LiNi 0.9 Co 0.05 Mn 0.05 At least one of O2.

[0080] LNO can be represented by the following general formula. Compounds represented by the following general formula can also be called "NCA".

[0081] Li 1-a Ni x Co y Al z O2

[0082] wherein the following relations are satisfied: -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1. For example, the following relations can be satisfied: 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1. For example, the following relations can be satisfied: 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1. For example, the following relations can be satisfied: 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1.

[0083] The NCA may, for example, contain at least one selected from LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1 Al 0.1 O2, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, and LiNi 0.9 Co 0.05 Al 0.05 O2.

[0084] Method for manufacturing positive electrode active material

[0085] Figure 4 is a schematic flowchart showing the method for manufacturing a positive electrode active material of the present embodiment. Hereinafter, the "method for manufacturing a positive electrode active material of the present embodiment" can be simply referred to as "the present method". The present method can include, for example, "(a) formation of a slurry", "(b) granulation", and "(c) firing", and the like.

[0086] (a) formation of a slurry

[0087] The present method can include a step of forming a slurry by mixing a lithium compound, a manganese compound, a phosphoric acid compound, a carbon source, and a solvent. In the case where LMFP is a target substance, an iron compound is added to the raw material mixture. For example, the lithium compound, the manganese compound, the phosphoric acid compound, and the iron compound can be weighed so as to become a composition ratio (mass ratio of substances) represented by the composition formula "Li 1-a Mn 1-x Fe x PO4(-0.5≤a≤0.5, 0≤x<1)". The lithium compound can include lithium hydroxide or the like, for example. The manganese compound can include manganese carbonate or the like, for example. The phosphoric acid compound can include lithium dihydrogen phosphate or the like, for example. The iron compound can include iron phosphate or the like, for example.

[0088] The carbon source is a raw material of carbon adhering to the surface of the primary particles. The carbon source can include a saccharide, an organic acid, or the like, for example. The carbon source can include glucose, sucrose, fructose, citric acid, or the like, for example. The addition amount of the carbon source can be 1 to 20% in terms of mass fraction with respect to the raw material mixture, for example.

[0089] The solvent can include water or the like, for example. The solid content concentration of the slurry can be 20 to 40% in terms of mass fraction, for example.

[0090] By performing wet pulverization, the particle size in the slurry can be adjusted. For example, wet pulverization can be performed so that D50 becomes 0.10 to 1 μm.

[0091] (b) granulation

[0092] The present method can include a step of granulating the secondary particles (precursors) by drying the slurry. For example, the secondary particles can also be granulated by a spray drying (spray granulation) method. The secondary particles formed by the granulation operation are also referred to as "granules". That is, the secondary particles can also be referred to as granules.

[0093] The details of the mechanism of the formation of the grooves on the surface of the secondary particles are not quite clear. For example, it can be considered that the grooves are formed by the following mechanism. When the fine droplets are sprayed, a film is formed on the surface of the droplets. It is considered that the film contains relatively much of the carbon source and the phosphoric acid compound. Due to the pressure of the spraying gas, the drying gas, or the like, collisions between the secondary particles can occur. When the secondary particles that are not completely dried collide with each other, the secondary particles can fuse with each other by liquid adhesion. After the liquid adhesion, drying is performed by hot air. As the drying proceeds, a fused body is formed. It is considered that by firing the fused body, the portion corresponding to the liquid adhesion (film) becomes a groove.

[0094] Therefore, it is considered that the shape of the groove, the split particle rate, and the average number of splits change depending on the balance of the droplet size, the gas flow, the droplet density, and the drying speed at the time of spray drying, and the like. For example, if drying is too fast and the droplets are excessively fine, collision between secondary particles does not occur, and drying is performed as single secondary particles, thereby forming secondary particles having no groove. The split particle rate and the average number of splits can be adjusted, for example, by a combination of the suction port temperature, the spray speed, and the spray pressure in the spray dryer, and the like. The suction port temperature can be adjusted, for example, in the range of 200 to 240°C. The spray speed can be adjusted, for example, in the range of 14 to 18 mL / minute. The spray pressure can be adjusted, for example, in the range of 0.2 to 0.3 MPa.

[0095] (c) firing

[0096] The present method can include a step of producing the olivine-type phosphate compound by subjecting the secondary particles (precursors) to heat treatment. Any heat treatment furnace (for example, an electric furnace, a muffle furnace, or the like) can be used. The heat treatment atmosphere can be, for example, a nitrogen atmosphere. The heat treatment temperature can be, for example, 400 to 700°C. The heat treatment time can be, for example, 4 to 6 hours.

[0097] - liquid battery -

[0098] In some embodiments, the battery is a liquid battery. A liquid battery contains an electrolyte solution. In some embodiments, the battery has a single-pole structure. In some embodiments, the battery has a double-pole structure. As an example, a battery having a double-pole structure (a double-pole battery) is described.

[0099] Figure 5 is a schematic perspective view of a battery of the present embodiment. Figure 6 is a schematic cross-sectional view along the VI-VI line in Figure 5 Hereinafter, the "surface normal direction" indicates the normal direction with respect to the surface of a sheet-shaped member (for example, a foil, an electrode, or the like). The "in-plane direction" indicates an arbitrary direction orthogonal to the surface normal direction. In Figure 6 In, the Z-axis direction corresponds to the surface normal direction. The X-axis direction and the Y-axis direction are examples of the in-plane direction.

[0100] The battery 100 includes an exterior body 90 and a power generating element 50. The power generating element 50 is housed in the exterior body 90. The exterior body 90 can also include, for example, a first current collecting plate 91, a first laminated film 92, a second laminated film 93, and a second current collecting plate 94. The first laminated film 92 and the second laminated film 93 are joined to each other at the end portions in the in-plane direction. At the joint portion of the first laminated film 92 and the second laminated film 93, a sealing material (not shown) can be interposed between the first laminated film 92 and the second laminated film 93.

[0101] The first collector plate 91 and the second collector plate 94 are joined to the power generating element 50 at the end portion in the stacking direction (Z-axis direction). The first lamination film 92 is joined to the first collector plate 91. The second lamination film 93 is joined to the second collector plate 94. A sealing material (not shown) can be interposed between the collector plate and the lamination film at the joint portion.

[0102] The power generating element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the face normal direction (Z-axis direction). Each of the plurality of bipolar electrodes 10 includes, in the face normal direction, in order, a positive electrode layer 11, a collector foil 13, and a negative electrode layer 12. In the in-plane direction (for example, the X-axis direction), the collector foil 13 extends outwardly compared to the positive electrode layer 11 and the negative electrode layer 12. For example, the collector foil 13 can extend outwardly compared to the positive electrode layer 11 and the negative electrode layer 12 in the entire circumference in the in-plane direction.

[0103] The collector foil 13 is a conductor. The collector foil 13 can include, for example, a metal foil, a conductive resin layer, or the like. For example, the collector foil 13 can be formed by bonding an Al foil and a Cu foil. A carbon material can be applied to the surface of the collector foil 13. The carbon material can include, for example, carbon black or the like.

[0104] The power generating element 50 includes a sealing material 30. The sealing material 30 is joined to the collector foil 13 at the end portion in the in-plane direction. The sealing material 30 can also be heat-sealed to the collector foil 13, for example. For example, the sealing material 30 can be disposed at the entire circumference in the in-plane direction. The sealing material 30 can include, for example, a resin material or the like. The sealing material 30 seals the collector foils 13 adjacent to each other in the face normal direction. The collector foils 13 are sealed to each other by the sealing material 30, thereby dividing cells 40. The cell 40 is the smallest unit of the power generating element 50. The battery 100 includes a plurality of cells 40, and can also be referred to as a "bipolar module". The plurality of cells 40 are each sealed. The plurality of cells 40 are isolated from each other. Each of the plurality of cells 40 includes the positive electrode layer 11, the separator 20, the negative electrode layer 12, and the electrolyte solution.

[0105] Positive electrode layer

[0106] The positive electrode layer 11 is attached to a single face of the collector foil 13. For example, a groove can be formed in the positive electrode layer 11. The positive electrode layer 11 can be formed in a strip shape, for example. The positive electrode layer 11 includes a positive electrode active material. That is, the electrode includes the positive electrode active material. Details of the positive electrode active material are as described above.

[0107] The positive electrode layer 11 can contain, in addition to the positive electrode active material, for example, a conductive material and a binder, and the like. The blending amount of the conductive material can be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The conductive material can contain an optional component. The conductive material can contain, for example, at least one selected from the group consisting of graphite, acetylene black (AB), Ketjen black (registered trademark), vapor grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flake (GF).

[0108] The blending amount of the binder can be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The binder can contain an optional component. The binder can contain, for example, 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.

[0109] The positive electrode layer 11 can 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 fluxing agent, a coupling agent, an adsorbent, and the like. The positive electrode active material layer can contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agent, MoS2, WO3, and the like.

[0110] Negative electrode layer

[0111] The negative electrode layer 12 is attached to one face of the current collecting foil 13. The negative electrode layer 12 is disposed on the back face side of the positive electrode layer 11. The negative electrode layer 12 can have a larger area than the positive electrode layer 11. The negative electrode layer 12 contains a negative electrode active material.

[0112] The negative electrode active material can be, for example, in a particle shape or in a sheet shape. The D50 of the negative electrode active material can be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material can be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0113] The negative electrode active material can contain an optional component. The negative electrode active material can contain, for example, at least one selected from the group consisting of carbon-based active material, alloy-based active material, Si-C composite material, Li metal, Li-based alloy, and lithium titanate. In some embodiments, the battery can be a Li metal negative electrode battery.

[0114] The carbon-based active material can contain, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. The graphite can also be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) can 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".

[0115] The surface of the graphite can be covered, for example, with amorphous carbon. The surface of the graphite can also be covered, for example, with a foreign material. The foreign material can contain, for example, at least one selected from the group consisting of P, W, Al, and O. The foreign material can contain, for example, at least one selected from the group consisting of Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0116] The alloy-based active material can contain, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloy, tin (Sn), SnO, and Sn-based alloy.

[0117] The SiO can be represented, for example, by the following general formula.

[0118] SiO x

[0119] In the formula, the relationship 0 < x < 2 is satisfied. For example, the relationship 0.5 ≤ x ≤ 1.5 or 0.8 ≤ x ≤ 1.2 can also be satisfied.

[0120] The "Si-C composite" indicates a composite of the carbon-based active material (graphite, etc.) and the alloy-based active material (Si, etc.). For example, Si fine particles can be dispersed within carbon particles. For example, Si fine particles can be dispersed within graphite particles. For example, Li silicate particles can be covered with a carbon material (amorphous carbon, etc.).

[0121] Separator

[0122] 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 can contain, 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 can contain, for example, a resin film and an inorganic particle layer.

[0123] The resin film is porous. The resin film can include, for example, a microporous film, a nonwoven fabric, or the like. The resin film includes a resin skeleton. The resin skeleton can be, for example, continuous in a network. Fine pores are formed in the gaps of the resin skeleton. The resin film is capable of allowing electrolyte to permeate. The average fine pore diameter of the resin film can be, for example, 1 μm or less. The average fine pore diameter of the resin film can be, for example, 0.01 to 1 μm or 0.1 to 0.5 μm. The "average fine pore diameter" can be measured by a mercury porosimetry. The Gurley value of the resin film can be, for example, 50 to 250 s / 100 cm 3 The "Gurley value" can be measured by a Gurley test method.

[0124] The resin film can include, for example, at least one selected from the group consisting of an olefin-based resin, a polyurethane-based resin, a polyamide-based resin, a cellulose-based resin, a polyether-based resin, an acrylic-based resin, and a polyester-based resin, and the like. The resin film can include, for example, at least one selected from the group consisting of 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 by, for example, a stretching method, a phase separation method, or the like. The thickness of the resin film can be, for example, 5 to 50 μm or 10 to 25 μm.

[0125] The resin film can have, for example, a single-layer structure. The resin film can be composed of, for example, a PE layer. The skeleton of the PE layer is formed of PE. The PE layer can have a closing function. The resin film can have, for example, a multi-layer structure. The resin film can include, for example, a PP layer and a PE layer. The skeleton of the PP layer is formed of PP. The resin film can have, for example, a three-layer structure. The resin film can be formed by, for example, sequentially laminating a PP layer, a PE layer, and a PP layer. The thickness of the PE layer can be, for example, 5 to 20 μm. The thickness of the PP layer can be, for example, 3 to 10 μm.

[0126] An inorganic particle layer can be formed on the surface of the resin film. The inorganic particle layer can be formed on only one surface of the resin film, or on both surfaces. The inorganic particle layer can be formed on the surface opposite to the positive electrode layer 11, or on the surface opposite to the negative electrode layer 12. Further, the inorganic particle layer can be formed on the surface of the positive electrode layer 11, or on the surface of the negative electrode layer 12.

[0127] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles can also be referred to as "inorganic fillers". Fine pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer can be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles can contain, for example, heat-resistant materials. The inorganic particle layer containing heat-resistant materials is also referred to as "HRL (Heat Resistance Layer)". The inorganic particles can contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles can have any shape. The inorganic particles can be, for example, spherical, rod-shaped, plate-shaped, fibrous, or the like. The D50 of the inorganic particles can be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer can also contain a binder. The binder can 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.

[0128] The separator 20 can contain, for example, an organic particle layer. The separator 20 can also contain, for example, an organic particle layer instead of a resin film. The separator 20 can contain, for example, an organic particle layer instead of an inorganic particle layer. The separator 20 can also contain both a resin film and an organic particle layer. The separator 20 can contain both an inorganic particle layer and an organic particle layer. The separator 20 can also contain a resin film, an inorganic particle layer, and an organic particle layer.

[0129] The thickness of the organic particle layer can 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 can also be referred to as "organic fillers". The organic particles can contain heat-resistant materials. The organic particles can contain, for example, at least one selected from the group consisting of PE, PP, PTFE, PI, PAI, PA, and aromatic polyamide. The organic particles can be, for example, spherical, rod-shaped, plate-shaped, fibrous, or the like. The D50 of the organic particles can be, for example, 0.1 to 10 μm or 0.5 to 3 μm.

[0130] The separator 20 can also contain, for example, a mixed layer. The mixed layer contains both inorganic particles and organic particles.

[0131] Electrolyte solution

[0132] The electrolyte is a liquid electrolyte. The electrolyte includes a solute and a solvent. The concentration of the solute can 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" is sometimes indicated as "M". The solute includes a supporting electrolyte (Li salt). The solute can include, for example, an inorganic acid salt, an imide salt, an oxalate complex, a halide, or the like. The solute can 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.

[0133] The electrolyte can include, for example, a carbonate-based solvent. The solvent can include, for example, a cyclic carbonate, a chain carbonate, a fluorinated carbonate, or the like. The solvent can include, 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), ethylmethyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluorinated propylene carbonate, difluorinated propylene carbonate, and derivatives thereof.

[0134] The solvent can include a cyclic carbonate (EC, PC, FEC, or the like) and a chain carbonate (EMC, DMC, DEC, or the like). The mixing ratio (volume ratio) of the cyclic carbonate and the chain carbonate can 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".

[0135] The solvent can include a cyclic carbonate (EC, PC, or the like) and a fluorinated cyclic carbonate (FEC or the like). The mixing ratio (volume ratio) of the cyclic carbonate and the fluorinated cyclic carbonate can 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".

[0136] The solvent can contain, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component can also satisfy, for example, a relationship represented by the following formula.

[0137] V EC +V FEC +V EMC +V DMC +V DEC = 10

[0138] In the above formula, V EC , V FEC , V EMC , V DMC , and V DEC represent the volume ratio of EC, FEC, EMC, DMC, and DEC, respectively.

[0139] The following relationships are satisfied:

[0140] 1≤V EC ≤4, 0≤V FEC ≤3, V EC +V FEC ≤4,

[0141] 0≤V EMC ≤9, 0≤V DMC ≤9, 0≤V DEC ≤9, 6≤V EMC +V DMC +V DEC ≤9.

[0142] For example, the relationship 1≤V EC ≤2 or 2≤V EC ≤3 can be satisfied.

[0143] For example, the relationship 1≤V FEC ≤2 or 2≤V FEC ≤4 can be satisfied.

[0144] For example, the relationship 3≤V EMC ≤4 or 6≤V EMC ≤8 can be satisfied.

[0145] For example, the relationship 3≤V DMC ≤4 or 6≤V DMC ≤8 can be satisfied.

[0146] For example, the relationship 3≤V DEC ≤4 or 6≤V DEC ≤8 can be satisfied.

[0147] The solvent can have a composition of, for example, "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", "EC / FEC / DMC / EMC = 1 / 2 / 3 / 4", or the like, in terms of volume ratio.

[0148] The electrolyte solution can include an ether-based solvent. The electrolyte solution can include, 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), glyme, triglyme, tetraglyme, and derivatives thereof. The electrolyte solution can include an ether-based solvent. The electrolyte solution can include, 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), glyme, triglyme, tetraglyme, and derivatives thereof.

[0149] The electrolyte solution can include an optional additive. The additive amount (mass fraction relative to the entire electrolyte solution) can be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additive can include, for example, an SEI (solid electrolyte interface) formation promoter, an SEI formation inhibitor, a gas generation agent, an overcharge prevention agent, a flame retardant, an antioxidant, an electrode protection agent, a surfactant, or the like.

[0150] The additive can include, for example, at least one selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfide (ES), propanesultone (PS), ethylene sulfide (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters (e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.), fluorobenzene (e.g., monofluorobenzene (FB), 1,2-difluorobenzene, 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.), trifluorotoluene (e.g., trifluoromethylbenzene, 2-fluorotrifluorotoluene, 3-fluorotrifluorotoluene, 4-fluorotrifluorotoluene, 2-methyltrifluorotoluene, 3-methyltrifluorotoluene, 4-methyltrifluorotoluene, etc.), fluoroxylene (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-methylbenzothiazole, 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-propanol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and derivatives thereof.

[0151] The components described as solutes and solvents can be used as trace components (additives). The additive can 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.

[0152] The electrolyte can include an ionic liquid. The ionic liquid can include, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, imidazolium salts, and derivatives thereof.

[0153] ​In some embodiments, the battery can include a gel electrolyte. That is, the battery can be a polymer battery. The gel electrolyte can include an electrolytic solution and a high molecular material. The high molecular material can form a high molecular matrix. The high molecular material can 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.

[0154] - all-solid battery -

[0155] In some embodiments, the battery is an all-solid battery. The all-solid battery can have a bipolar structure. The all-solid battery includes a solid electrolyte in place of the electrolytic solution and the separator 20. That is, a solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11 in place of the separator 20. The solid electrolyte layer includes, for example, a solid electrolyte and a binder. The positive electrode layer 11 and the negative electrode layer 12 can also include a solid electrolyte.

[0156] The solid electrolyte can also be, for example, a powder. The D50 of the solid electrolyte can 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 can be 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0157] The solid electrolyte can 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.

[0158] The sulfide solid electrolyte can include 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 can be, for example, argyrodite type, LGPS type, or the like. The sulfide solid electrolyte includes Li and sulfur (S). The sulfide solid electrolyte can include an optional component in addition to Li and S.

[0159] The sulfide solid electrolyte can include, for example, at least one selected from the group consisting of 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 , Li3PS4, and Li7PS6.

[0160] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte generated by mixing LiI, LiBr, and Li3PS4in any mass ratio. For example, the sulfide solid electrolyte can be generated by a mechanochemical method. The mixing ratio can also be determined by adding a number in front of each raw material. For example, "10LiI-15LiBr-75Li3PS4" indicates a mixing ratio of "LiI / LiBr / Li3PS4= 10 / 15 / 75 (mass ratio)".

[0161] The sulfide solid electrolyte may, for example, have a composition represented by the following general formula.

[0162] xLi2S-(1-x)P2S5

[0163] In the formula, x may, for example, be greater than 0, 0.1 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.4 or more, 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, for example, be 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" can have the composition of Li3PS4.

[0164] The sulfide solid electrolyte may, for example, have a composition represented by the following general formula.

[0165] yLiI-zLiBr-(100-y-z)[xLi2S-(1-x)P2S5]

[0166] In the formula, x may, for example, be 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, for example, be 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, for example, be 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. Y may, for example, be 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. Z may, for example, be 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. Z may, for example, be 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0167] The sulfide solid electrolyte may, for example, have a composition represented by the following general formula.

[0168] Li 7-x-2y PS 6-x-y X y

[0169] In the formula, the relations of "0 < 7 - x - 2y", "0 < 6 - x - y", "0 ≤ x", and "0 ≤ y" are satisfied. X can include, for example, at least one selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0170] The sulfide solid electrolyte can have, for example, a composition represented by the following general formula.

[0171] Li 4-x M 1-x P x S4

[0172] In the formula, x can 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 can 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 can include, for example, at least one selected from Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0173] The sulfide solid electrolyte can have, for example, a composition represented by the following general formula.

[0174] Li 10+x Ge 1+x P 2-x S 12

[0175] In the formula, x can 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 can 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 can include, for example, a crystal phase of the LGPS type.

[0176] The halide solid electrolyte can have, for example, a composition represented by the following general formula.

[0177] Li 6-na M a X6

[0178] In the formula, n represents the oxidation number of M. M can include, for example, an atom having an oxidation number of +3. M can include, for example, an atom having an oxidation number of +4. M can include, for example, at least one selected from Y, Al, Ti, Zr, Ca, and Mg. The relation of "0 < a < 2" can be satisfied, for example. X can include, for example, at least one selected from F, Cl, Br, and I.

[0179] The halide solid electrolyte can have, for example, a composition represented by the following general formula.

[0180] Li 3-a Ti a Al 1-a F6

[0181] In the formula, a can 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 can 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.

[0182] The halide solid electrolyte can have, for example, a composition represented by the following general formula.

[0183] Li3YCl a Br b I 6-a-b

[0184] In the formula, a relationship of, for example, "0≤a+b≤6" can also be satisfied. a can be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. a can be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. b can be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. b can be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0185] The oxide solid electrolyte can contain, for example, at least one selected from the group consisting of LiNb03, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x Ti03, and Li7La3Zr20 12 The hydride solid electrolyte can contain, for example, LiBH4or the like. The nitride solid electrolyte can contain, for example, Li3N, Li3BN2, or the like.

[0186] Embodiment

[0187] Manufacture of Positive Electrode Active Material

[0188] No. 1

[0189] Formation of Slurry

[0190] to become a composition formula "Li 1.04 Mn 0.6 Fe 0.4As shown in the composition ratio of "PO4", weigh lithium hydroxide monohydrate, manganese carbonate, iron phosphate, and lithium dihydrogen phosphate. Weigh 8% glucose by mass relative to the total mass of the raw materials. Mix the weighed materials with water to form a slurry. The solids concentration of the slurry is 30% by mass. Perform wet milling to achieve a D50 of 0.30 μm.

[0191] (b) Granulation

[0192] Secondary particles are formed by spray drying the slurry. The target D50 value for the secondary particles is 9 ± 1 μm. Figure 7 This is a table showing the experimental results. The settings for the spray dryer are as follows: Figure 7 As shown.

[0193] (c) Firing

[0194] LMFP was synthesized by sintering secondary particles under a nitrogen atmosphere. Figure 8 This is the temperature profile during firing. First, the furnace temperature is increased to 200°C at a rate of 3°C / min. This temperature is maintained at 200°C for 1 hour. Next, the furnace temperature is increased to 650°C at a rate of 5°C / min. This temperature is maintained at 650°C for 5 hours. Afterward, the furnace temperature is cooled to 400°C at a rate of 2°C / min. Finally, the furnace temperature is cooled to room temperature at a rate of 15°C / min.

[0195] No.2 to No.4

[0196] like Figure 7 As shown, except for changing the granulation conditions (spray dryer settings), the positive electrode active material is manufactured in the same way as No.1.

[0197] -evaluate-

[0198] Making button units

[0199] A mixture was formed by combining a positive electrode active material, a conductive material (acetylene black), and a binder (PVdF). The mixing ratio (mass ratio) was "positive electrode active material / conductive material / binder = 92 / 5 / 3". A paste was formed by dispersing the mixture in a solvent (N-methyl-2-pyrrolidone). The solids concentration of the paste was 50% by mass fraction. The positive electrode layer was formed by coating the paste onto the surface of an Al foil and drying it. The density of the positive electrode layer was adjusted to 1.8 g / cm³ by rolling. 3 This process forms the positive electrode plate. The positive electrode plate is then subjected to vacuum drying at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) is removed from the positive electrode plate by stamping.

[0200] A coin cell was assembled in a glove box. The cell structure is described below.

[0201] Working electrode: disk sample (positive electrode)

[0202] Counter electrode: Li foil

[0203] Separator: polymer porous membrane

[0204] Electrolyte: "EC / DMC = 3 / 7 (volume ratio)", LiPF6 (1 mol / L)

[0205] Rate characteristics

[0206] The discharge capacity ratio (1C / 0.1C) was measured by the following procedure. The greater the discharge capacity ratio (1C / 0.1C) was considered to be, the better the rate characteristics were.

[0207] The rate corresponding to 1C was determined based on the discharge capacity (theoretical capacity) calculated from the coating quality of the positive electrode layer. "C" is a notation indicating the rate (time rate) of current. At the rate of 1C, the theoretical capacity was made to flow for 1 hour. The coin cell was charged by constant current-constant voltage (CCCV) charging under the following conditions at 25°C.

[0208] Rate at the time of CC charging: 0.1C

[0209] Upper limit voltage of charging: 4.3 V

[0210] Rate of cutoff current at the time of CV charging: 0.01C

[0211] After the charging, CC discharge was performed at 25°C at a rate of 0.1C until 3.0 V, whereby the discharge capacity (0.1C) was measured. The coin cell was charged again by the above-described CCCV charging. After the charging, CC discharge was performed at 25°C at a rate of 1C until 3.0 V, whereby the discharge capacity (1C) was measured. The discharge capacity ratio (1C / 0.1C) was calculated by dividing the discharge capacity (1C) by the discharge capacity (0.1C).

[0212] -Results-

[0213] In Table 1, Figure 7 In Table 1, the higher the split particle ratio was, the more the rate characteristics were improved. Also, the greater the average number of splits was, the more the rate characteristics were improved. Therefore, it was considered that the improvement in the rate characteristics could be expected by forming grooves extending in a linear shape on the surface of the secondary particles.

Claims

1. A positive electrode active material, comprising powder, The powder contains multiple secondary particles. Each of the plurality of secondary particles comprises a plurality of primary particles. Each of the plurality of said primary particles contains an olivine-type phosphate compound. At least a portion of the surface of the primary particle is coated with carbon, and, At least a portion of the plurality of secondary particles have grooves extending in a linear shape formed on the surface of the secondary particles.

2. The positive electrode active material according to claim 1, The particle splitting rate of the multiple secondary particles exceeds 30%, and, The fractionated particle ratio is expressed in the scanning electron microscope image of the powder. The ratio of secondary particles in which the surface is divided into two or more regions by the groove.

3. The positive electrode active material according to claim 2, The average number of segments of the plurality of said secondary particles exceeds 2, and, The average number of divisions represents the average number of regions divided by the groove among the plurality of secondary particles contained in the powder.

4. The positive electrode active material according to claim 2 or 3, The fractionation rate was measured in the secondary particles with a maximum Feretta diameter of 5 μm or more.

5. The positive electrode active material according to any one of claims 1 to 3, The maximum Feret diameter of the primary particle is 10–90 nm.

6. The positive electrode active material according to any one of claims 1 to 3, The olivine-type phosphate compound includes lithium manganese phosphate.

7. An electrode, It contains a positive electrode layer, and, The positive electrode layer comprises the positive electrode active material according to any one of claims 1 to 3.

8. A type of battery, It includes the electrode as described in claim 7.

9. The battery according to claim 8, It has a bipolar structure.

Images