Positive electrode active material, electrode, battery, and method for manufacturing positive electrode active material

Abstract

The positive electrode active material contains secondary particles, the secondary particles contain a first particle group and a second particle group, the first particle group and the second particle group are each composed of primary particles, and the primary particles contain an olivine-type phosphate compound. The average particle diameter of the second particle group is larger than the average particle diameter of the first particle group. Within the secondary particles, the primary particles belonging to the first particle group and the primary particles belonging to the second particle group are dispersed from each other.

Description

Technical Field

[0001] This disclosure relates to positive electrode active materials, electrodes, batteries, and methods for manufacturing positive electrode active materials. Background Technology

[0002] Japanese Patent Application Publication No. 2021-009838 discloses granulated forms of manganese-rich lithium iron phosphate particles (average particle size 10 nm to 80 nm) and iron-rich lithium iron phosphate particles (average particle size 80 nm to 150 nm). Summary of the Invention

[0003] From the perspective of energy density and cycle resistance, a method has been proposed to form secondary particles (also known as "granules" or "aggregated particles") using two types of primary particles with different average particle sizes. However, from the perspective of balancing filling capacity and tortuosity, there is still room for improvement. "Tortuosity" is one of the indicators of ion conductivity within the electrode. It is believed that the smaller the tortuosity, the better the ion conductivity.

[0004] This disclosure provides a positive electrode active material, an electrode, a battery, and a method for manufacturing the positive electrode active material that balances flexibility and fillability.

[0005] The technical structure and effects of this disclosure are described below. However, the mechanism of action contains presumptions. The mechanism of action is not intended to limit the technical scope of this disclosure.

[0006] The positive electrode active material according to the first aspect of this disclosure is characterized in that it comprises secondary particles, said secondary particles containing a first particle group and a second particle group, said first particle group and said second particle group both being composed of primary particles.

[0007] The primary particles contain olivine-type phosphate compounds, the average particle size of the second particle group is larger than the average particle size of the first particle group, and within the secondary particles, the primary particles belonging to the first particle group and the primary particles belonging to the second particle group are dispersed from each other.

[0008] Hereinafter, "primary particles belonging to the first particle group" will also be referred to as "small particles". "Primary particles belonging to the second particle group" will also be referred to as "large particles".

[0009] Olivine-type phosphate compounds (hereinafter referred to as "olivine") tend to have high electrical resistivity. To achieve practical resistance, it is necessary to reduce the primary particles from the submicron to the nanometer scale. These fine primary particles tend to aggregate very easily. Previously, a scheme was proposed to prepare small and large particles separately, and then form secondary particles from these particles. However, as mentioned above, since primary particles aggregate very easily, it is conceivable to form separate primary aggregates of small and large particles, and then form secondary aggregates through the aggregation of these primary aggregates. It is foreseeable that during electrode compression, small particles will find it difficult to enter the gaps between large particles within the primary aggregates composed of large particles. Therefore, it is difficult to simultaneously achieve both filling capacity and flexibility.

[0010] In the secondary particles disclosed herein, small and large particles are dispersed from each other. Therefore, it can be assumed that during electrode compression, small particles enter the gaps between large particles, thereby easily filling the primary particles tightly. Thus, a balance between filling capacity and curvature can be expected.

[0011] In the positive electrode active material according to the first aspect of this disclosure, the relationship 1.5 ≤ d2 / d1 ≤ 10 can be satisfied. Here, d1 represents the average particle size of the first particle group. And d2 represents the average particle size of the second particle group.

[0012] By setting the average particle size ratio "d2 / d1" to 1.5 to 10, an improvement in tortuosity can be expected.

[0013] According to the first aspect of this disclosure, the positive electrode active material can satisfy the relationship 3.0 ≤ d2 / d1.

[0014] With an average particle size ratio "d2 / d1" of 3.0 or higher, an improvement in tortuosity can be expected.

[0015] According to the first aspect of this disclosure, the positive electrode active material can satisfy the relationship 5.0 ≤ d2 / d1.

[0016] An improvement in tortuosity can be expected by making the average particle size ratio "d2 / d1" greater than 5.0.

[0017] In the positive electrode active material according to the first aspect of this disclosure, the relationship 200nm≤d2≤500nm can be satisfied.

[0018] By increasing the average particle size of large particles to over 200 nm, improvements in tortuosity can be expected. By increasing the average particle size of large particles to below 500 nm, improvements in ionic conductivity within the large particles can be expected.

[0019] According to the first aspect of the present disclosure, the positive electrode active material may satisfy the relationship of 0.7000 < n1 / (n1 + n2) < 1.000. The n1 represents the number ratio of the primary particles belonging to the first particle group. The n2 represents the number ratio of the primary particles belonging to the second particle group.

[0020] The ratio "n1 / (n1 + n2)" represents the ratio of the number of small particles to the total of small particles and large particles. Since the number ratio of small particles exceeds 0.7000 and is less than 1.000, an improvement in the degree of curvature can be expected.

[0021] According to the first aspect of the present disclosure, the positive electrode active material may satisfy the relationship of 0.4 ≤ m1 / (m1 + m2) ≤ 0.6. The m1 represents the total mass of the primary particles belonging to the first particle group. The m2 represents the total mass of the primary particles belonging to the second particle group.

[0022] The ratio "m1 / (m1 + m2)" represents the mass ratio of small particles to the total of small particles and large particles. By setting the mass ratio of small particles to be 0.4 to 0.6, an improvement in the degree of curvature can be expected.

[0023] In the positive electrode active material according to the first aspect of the present invention, the olivine-type phosphate compound may contain at least one selected from lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate.

[0024] In addition, lithium iron phosphate is hereinafter also referred to as "LFP", lithium manganese phosphate is hereinafter also referred to as "LMP", and lithium manganese iron phosphate is hereinafter also referred to as "LMFP".

[0025] In the positive electrode active material of the first aspect of the present disclosure, an aggregate composed of the primary particles belonging to the first particle group and the primary particles belonging to the second particle group may contain 2 to 4 primary particles belonging to the second particle group.

[0026] In the positive electrode active material according to the first aspect of the present disclosure, the relationship of 5 nm ≤ d1 < 50 nm may be satisfied.

[0027] In the positive electrode active material according to the first aspect of the present disclosure, the relationship of 50 nm ≤ d2 ≤ 500 nm may be satisfied.

[0028] The electrode according to the second aspect of the present disclosure may include a positive electrode layer. The positive electrode layer may contain the positive electrode active material according to the first aspect.

[0029] The positive electrode layer may be referred to as a "positive electrode active material layer", a "positive electrode composite material layer", etc. The "electrode" only needs to contain a positive electrode layer, and may be a "single-pole electrode (positive electrode)" or a "bipolar electrode".

[0030] The battery according to the third aspect of this disclosure may contain the electrodes of the second aspect described above.

[0031] In the battery according to the third aspect of this disclosure, the battery may contain a bipolar structure.

[0032] Bipolar structures can be formed by stacking bipolar electrodes. For example, it is desirable to improve output characteristics through bipolar structures. However, in bipolar structures, a thick positive electrode layer is sometimes required. The thicker the positive electrode layer, the greater the influence of the filling properties of the positive electrode active material and the tortuosity of the positive electrode layer on the rate characteristics. The positive electrode active material described in the first embodiment is considered particularly suitable for bipolar structures.

[0033] The method for manufacturing the positive electrode active material according to the fourth aspect of this disclosure includes the following steps:

[0034] Prepare a variety of secondary particles containing olivine-type phosphate compounds, where the average particle size of the primary particles differs from that of the secondary particles.

[0035] By wet milling, the various secondary particles are broken down to the size of the primary particles, thereby forming a slurry in which the primary particles are dispersed.

[0036] New secondary particles are formed by spray drying a slurry containing multiple primary particles with different average particle sizes.

[0037] In this invention, secondary particles composed of small particles and secondary particles composed of large particles are prepared. Each secondary particle is temporarily broken down to the size of a primary particle. The slurry in which the small and large particles are dispersed at the size of primary particles is spray-dried to form secondary particles in which the large and small particles are dispersed among each other.

[0038] In the following description, one embodiment (hereinafter referred to as "this embodiment") and one example (hereinafter referred to as "this example") of the present disclosure will be described. However, this embodiment and this example are not intended to limit the technical scope of the present disclosure. This embodiment and this example are merely illustrative in all respects. This embodiment and this example are non-limiting. The technical scope of the present disclosure includes all modifications made with reference to the same meaning and scope as the claims. For example, any structure extracted from this embodiment and combined in any way will result in a solution that is intended to fall within the scope of the present invention from the outset. Attached Figure Description

[0039] Figure 1 A conceptual diagram of a secondary particle in the reference mode is shown.

[0040] Figure 2Shows a conceptual diagram of secondary particles in the present embodiment.

[0041] Figure 3 Shows an example of the number distribution of the particle sizes of primary particles.

[0042] Figure 4 Shows a schematic flowchart of the method for manufacturing the positive electrode active material in the present embodiment.

[0043] [[ID=ll]] Figure 5 Shows a schematic perspective view of the battery in the present embodiment.

[0044] Figure 6 Is a schematic cross-sectional view taken along line VI-VI in Figure 5 ...

[0045] Figure 7 Is a table showing the experimental results. Detailed Embodiments

[0046] The features, advantages, and industrial and technical significance of the embodiments of the present invention will be described below with reference to the accompanying drawings. Like reference symbols denote like elements.

[0047] Words and sentences

[0048] "Comprise", "include", "contain", "have" and their variant expressions are open-ended sentences. In addition to the necessary elements, the compositions expressed by open-ended sentences may or may not include additional elements. The description "consisting of..." is a closed-ended sentence. However, even for a composition expressed by a closed-ended sentence, it may include commonly incidental impurities or additional elements unrelated to the object technology. The description "substantially consisting of..." is a semi-closed-ended sentence. In a composition expressed by a semi-closed-ended sentence, elements that do not substantially affect the novelty and basic characteristics of the object technology are allowed.

[0049] Expressions such as "may" and "can" do not mean an obligation, that is, "not necessarily have to do", but mean permission to do, that is, "have the possibility of doing".

[0050] Geometric terms should not be understood strictly. As geometric terms, examples include "parallel", "perpendicular", "orthogonal", etc. For example, directions, angles, distances, etc. may have relative displacements within a range where substantially the same or similar functions can be obtained. Geometric terms may include tolerances, errors, etc. in design, operation, manufacturing, etc. The dimensional relationships in the respective drawings are sometimes inconsistent with the actual dimensional relationships. For the purpose of helping the reader understand, the dimensional relationships in the respective drawings are sometimes changed. For example, there are cases where lengths, widths, thicknesses, etc. are changed. There are also cases where a part of the structure is omitted. It should be noted that in the translation of item , the original text “中的VI-VI线的概略剖视图” seems to be incomplete. I translated it as “... in... along line VI-VI” for the sake of integrity, but it may need to be adjusted according to the complete context. Also, in item , the original text “与对象技术无关的附加要素” is a bit unclear. I translated it as “additional elements unrelated to the object technology” for a rough translation, and it may need to be refined based on the specific meaning of the patent content.

[0051] Unless otherwise specified, elements described in the "singular form" may also include plural forms. For example, "particle" sometimes refers to multiple particles (particle swarm), a collection of particles, and powder.

[0052] Unless otherwise specified, the numerical ranges such as "m~n%" include both upper and lower limits. That is, "m~n%" represents a numerical range "above m% and below n%". Furthermore, "above m% and below n%" includes "greater than m% and less than n%". "Above" and "below" are represented by inequality signs "≤" and "≥" with an equal sign. "Greater than" and "less than" are represented by inequality signs "<" and ">" without an equal sign. Any value selected from the numerical range can also be used as a new upper or lower limit. For example, a new numerical range can be set by arbitrarily combining values ​​within the numerical range with values ​​described in other parts of this specification, tables, figures, etc.

[0053] All numerical values ​​are modified by the word "approximately." "Approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​can be approximations that vary depending on the application of the technology. All numerical values ​​can be displayed with significant figures. Unless otherwise specified, the measured value can be the average of multiple measurements. The number of measurements can be 3 or more, 5 or more, or 10 or more. Generally, the more measurements, the higher the reliability of the average value can be expected. The measured value can be rounded to the nearest hundredth based on the number of significant figures. The measured value may include errors arising from factors such as the detection limits of the measuring device.

[0054] The apparatus and software used for measuring various values ​​are merely one example. Equivalent items, identical to those illustrated, may also be used. When using equivalent items, the measurement conditions may be adjusted accordingly based on the apparatus.

[0055] For example, size determination and shape analysis in various images can also be performed using image analysis software. For instance, image analysis software such as "Image J" can also be used.

[0056] "Primary particles" are particles that do not appear to have grain boundaries in SEM images taken by a field emission scanning electron microscope (FE-SEM) at magnifications of 20,000 to 100,000 times.

[0057] "Particle size" is determined by image analysis (microscopy). In SEM images, particle size is represented by the arithmetic mean of the long side (major axis diameter) and the short side (uniaxial diameter) in the minimum bounding rectangle (MBR) relative to the particle profile.

[0058] "Average particle size" refers to the average particle size. The average particle size is determined as follows: Obtain SEM images of the secondary particles (powder) using FE-SEM. The image magnification is from 20,000 to 100,000 times. From the SEM images, randomly select a total of 100 primary particles from multiple secondary particles. Measure the particle size of each primary particle. The arithmetic mean of the particle sizes of the 100 primary particles is taken as the average particle size of the primary particles. Similarly, the arithmetic mean of the particle sizes of the 100 secondary particles is taken as the average particle size of the secondary particles.

[0059] In secondary particles, the state of “small particles and large particles being dispersed from each other” is represented by a state that satisfies any one or more of the following conditions (1) to (6) in the SEM image (20000x) of secondary particles taken by FE-SEM.

[0060] (1) No condensate containing more than 5 large particles was formed. That is, a condensate composed of small and large particles may contain 2 to 4 large particles.

[0061] (2) In each of the 10 or more large particles randomly selected, more than 10% of the particles adjacent to that large particle are small particles.

[0062] (3) Among the three or more large particles in any 10 large particles, more than 30% of the particles adjacent to the large particle are small particles.

[0063] (4) In each of the five or more large particles in any arbitrarily selected 10 large particles, more than 30% of the particles adjacent to that large particle are small particles.

[0064] (5) In each of the five or more large particles in any arbitrarily selected 10 large particles, more than 50% of the particles adjacent to that large particle are small particles.

[0065] (6) Among 10 randomly selected large particles, the total length of the particle diameter of the large particles and the small particles is longer than the total length of the particle boundary of the large particles.

[0066] "Based on the number distribution (frequency distribution of the number baseline)," the existence of two or more particle groups with different average particle sizes can be confirmed. The number distribution is constructed according to the following steps: Prepare SEM images taken at magnifications of 20,000 to 100,000 using FE-SEM. Randomly select 10 secondary particles from the SEM images. Randomly select 100 primary particles from each secondary particle. That is, randomly select a total of 1,000 primary particles. Measure the particle size of each primary particle. Construct a number distribution based on the particle sizes of the 1,000 primary particles. In the number distribution, identify the peak with the largest height (highest peak). A convex region with a height greater than 0.1 times that of the highest peak is considered a peak. The number of peaks can correspond to the number of particle groups. The particle size of the peak of each peak is the "mode diameter." The mode diameter can correspond to the average particle size.

[0067] "D50" indicates the particle size at which the cumulative value reaches 50% in the volumetric cumulative distribution. The volumetric particle size distribution is determined by a laser diffraction particle size distribution measuring device.

[0068] "Circularity" is measured in the SEM image of the particles. Circularity is calculated using the following formula. The arithmetic mean of the circularity of 10 particles is used.

[0069] ψ=4πS / L 2

[0070] ψ: Circularity

[0071] π: Pi

[0072] S: Cross-sectional area of ​​the particle (the area enclosed by the particle's outline)

[0073] L: Particle perimeter (length of particle outline)

[0074] The chemical composition of a compound can be determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). A sample solution is prepared by dissolving 0.1 g of the sample (e.g., a positive electrode active material) in a mixed acid solution (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is then diluted to an appropriate concentration using a volumetric flask. After dilution, the composition is analyzed using an ICP-AES apparatus. Alternatively, an apparatus sold under the product name "PS3520UVDDII (manufactured by Hitachi High-Tech Science)" can also be used.

[0075] Stoichiometric composition indicates a representative example of a compound. Compounds can also have non-stoichiometric compositions. For example, "Al₂O₃" is not limited to compounds having a molar ratio of "Al / O = 2 / 3". Unless otherwise specified, "Al₂O₃" refers to a compound containing Al and O in any molar ratio. For example, trace elements may be doped into the compound. A portion of Al and O may be replaced by another element.

[0076] A "derivative" is a compound that is altered from a parent compound through at least one of the following methods: introduction of a functional group, substitution of atoms, oxidation, reduction, or other chemical reactions. The altered position can be one or more positions. The "substituent" may contain at least one selected from, for example, alkyl, alkenyl, alkynyl, cycloalkyl, unsaturated cycloalkyl, aromatic, heterocyclic, halogen atom (F, Cl, Br, I, etc.), OH, SH, CN, SCN, OCN, nitro, alkoxy, unsaturated alkoxy, amino, alkylamino, dialkylamino, aryloxy, acyl, alkoxycarbonyl, acyloxy, aryloxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, aminosulfonyl, carbamoyl, alkylthio, arylthio, sulfonyl, sulfinyl, urea, phosphoramidyl, sulfonyl, carboxyl, hydroxamic acid, sulfinyl group, hydrazine, imino, and silyl. These substituents may also be substituted. When there are two or more substituents, the substituents may be the same or different. Multiple substituents may combine to form a ring.

[0077] Positive electrode active material

[0078] The positive electrode active material contains secondary particles. The positive electrode active material can also be an aggregate (powder) of secondary particles. The D50 of the positive electrode active material can be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. Alternatively, the D50 of the positive electrode active material can be, for example, less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, or less than 10 μm.

[0079] Secondary particles

[0080] Secondary particles are condensations of primary particles. These condensations contain a first particle group and a second particle group. Both groups are composed of primary particles. The second particle group has a larger average particle size compared to the first. In other words, the average particle size of the second particle group is greater than that of the first. Furthermore, primary particles belonging to the first particle group are small particles, while those belonging to the second particle group are large particles.

[0081] Figure 1 This is a conceptual diagram of a secondary particle in the reference configuration. Secondary particle 2 contains primary particles. Each primary particle contains a small particle 1a and a large particle 1b. In the reference configuration, small particle 1a and large particle 1b are not dispersed within secondary particle 2. Small particle 1a and large particle 1b each form a primary aggregate. Gaps are formed between these primary aggregates.

[0082] Figure 2 This is a conceptual diagram of the secondary particles in this embodiment. In this embodiment, within the secondary particle 2, small particles 1a and large particles 1b are dispersed from each other. Therefore, it can be considered that small particles 1a and large particles 1b are easily and densely packed. That is, in this embodiment ( Figure 2 ) and reference method ( Figure 1 Compared to [previous method], improvements in filling properties can be expected. Furthermore, improvements in curvature are also expected by dispersing large particles 1b.

[0083] In this embodiment, the secondary particles 2 can have any shape. For example, the secondary particles 2 can be spherical, rod-shaped, angular, block-shaped, etc. The roundness of the secondary particles 2 can be, for example, 0.50 or higher, 0.60 or higher, 0.70 or higher, 0.80 or higher, 0.90 or higher, or 0.95 or higher. The roundness of the secondary particles 2 can be, for example, 1.00 or lower, 0.95 or lower, 0.90 or lower, 0.80 or lower, 0.70 or lower, or 0.60 or lower. The higher the roundness of the secondary particles 2, the better the filling performance can be expected.

[0084] The average particle size of secondary particles 2 can 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 average particle size of secondary particles 2 can be, for example, less than 20 μm, less than 15 μm, less than 10 μm, less than 5 μm, or less than 3 μm.

[0085] Secondary particle 2 only needs to contain a first particle group (small particle 1a) and a second particle group (large particle 1b), and may further contain additional particle groups. The number of additional particle groups can be, for example, more than one, more than two, more than three, or more than four. The number of additional particle groups can be, for example, less than five, less than four, less than three, or less than two. The additional particle groups can, for example, have an average particle size smaller than that of the first particle group (small particle 1a). The additional particle groups can also, for example, have an average particle size between that of the first particle group (small particle 1a) and the second particle group (large particle 1b). The additional particle groups can also, for example, have an average particle size larger than that of the second particle group (large particle 1b).

[0086] Primary particle

[0087] Primary particles can have any shape. That is, small particles 1a and large particles 1b can each independently have any shape. Small particles 1a and large particles 1b can each independently be, for example, spherical, rod-shaped, angular, block-shaped, etc. The roundness of small particles 1a and large particles 1b can each independently be, for example, 0.50 or higher, 0.60 or higher, 0.70 or higher, 0.80 or higher, 0.90 or higher, or 0.95 or higher. The roundness of small particles 1a and large particles 1b can each independently be, for example, 1.00 or lower, 0.95 or lower, 0.90 or lower, 0.80 or lower, 0.70 or lower, or 0.60 or lower. The higher the roundness of the primary particles, the better the filling performance can be expected.

[0088] The average particle size ratio "d2 / d1" between the first particle group (small particles 1a) and the second particle group (large particles 1b) can be, for example, 2.0 or higher, 3.0 or higher, 4.0 or higher, 5.0 or higher, 6.0 or higher, 7.0 or higher, 7.5 or higher, 8.0 or higher, 9.0 or higher, or 10 or higher. The average particle size ratio "d2 / d1" can be, for example, less than 15, less than 12, less than 10, less than 9.0, less than 8.0, less than 7.5, less than 7.0, less than 6.0, less than 5.0, less than 4.0, less than 3.0, or less than 2.0. For example, it can satisfy relationships such as "1.5 ≤ d2 / d1 ≤ 10", "3.0 ≤ d2 / d1 ≤ 10", and "5.0 ≤ d2 / d1 ≤ 10".

[0089] The average particle size "d2" of the second particle group (large particle 1b) can be, for example, 50 nm or more, 60 nm or more, 61 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, 100 nm or more, 120 nm or more, 140 nm or more, 160 nm or more, 180 nm or more, 200 nm or more, 220 nm or more, 240 nm or more, 260 nm or more, 280 nm or more, 298 nm or more, 300 nm or more, 320 nm or more, 360 nm or more, 380 nm or more, 400 nm or more, or 401 nm or more. The average particle size "d2" can be, for example, below 1000nm, below 750nm, below 500nm, below 450nm, below 401nm, below 400nm, below 380nm, below 360nm, below 340nm, below 320nm, below 300nm, below 298nm, below 280nm, below 260nm, below 240nm, below 220nm, below 200nm, below 180nm, below 160nm, below 140nm, below 120nm, below 100nm, below 90nm, below 80nm, below 70nm, below 61nm, or below 60nm. For example, it can satisfy relationships such as "50nm≤d2≤500nm", "200nm≤d2≤500nm", "298nm≤d2≤500nm", "200nm≤d2≤401nm", and "200nm≤d2≤298nm".

[0090] The average particle size "d1" of the first particle swarm (small particles 1a) can be, for example, less than 50 nm, less than 45 nm, less than 40 nm, less than 35 nm, less than 30 nm, less than 25 nm, less than 20 nm, less than 15 nm, or less than 10 nm. The average particle size "d1" can be, for example, greater than 5 nm, greater than 10 nm, greater than 15 nm, greater than 20 nm, greater than 25 nm, greater than 30 nm, greater than 35 nm, greater than 40 nm, or greater than 45 nm. For example, it can satisfy relationships such as "5 nm ≤ d1 < 50 nm", "10 nm ≤ d1 ≤ 40 nm", and "20 nm ≤ d1 ≤ 40 nm".

[0091] The number ratio "n1" of the small particles 1a belonging to the first particle group and the number ratio "n2" of the large particles 1b belonging to the second particle group may also satisfy, for example, the relationship of "0.5000 < n1 / (n1 + n2) < 1.000". The number ratio of the small particles 1a, "n1 / (n1 + n2)", may be, for example, 0.75 or more, 0.7801 or more, 0.8000 or more, 0.8500 or more, 0.8889 or more, 0.9000 or more, 0.9500 or more, 0.9643 or more, 0.9921 or more, or 0.9976 or more. The number ratio of the small particles 1a, "n1 / (n1 + n2)", may be, for example, 0.9990 or less, 0.9976 or less, 0.9921 or less, 0.9643 or less, 0.9500 or less, 0.9000 or less, 0.8889 or less, 0.8500 or less, 0.8000 or less, 0.7801 or less, or 0.7500 or less. For example, relationships such as "0.7000 < n1 / (n1 + n2) < 1.000" and "0.7801 ≤ n1 / (n1 + n2) ≤ 0.9990" may be satisfied.

[0092] The total mass "m1" of the small particles 1a belonging to the first particle group and the total mass "m2" of the large particles 1b belonging to the second particle group may satisfy, for example, the relationship of "0.1 ≤ m1 / (m1 + m2) ≤ 0.9". The mass ratio of the small particles 1a, "m1 / (m1 + m2)", may be, for example, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, or 0.8 or more. The mass ratio of the small particles 1a, "m1 / (m1 + m2)", may be, for example, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less. For example, relationships such as "0.2 ≤ m1 / (m1 + m2) ≤ 0.8", "0.3 ≤ m1 / (m1 + m2) ≤ 0.7", and "0.4 ≤ m1 / (m1 + m2) ≤ 0.6" may be satisfied.

[0093] Figure 3 It is an example of the number distribution of the particle diameters of the primary particles. The horizontal axis of the histogram is the particle diameter, and the vertical axis is the number frequency. The number of peaks in the number distribution corresponds to the number of particle groups contained in the secondary particles 2. The number distribution may be a bimodal distribution. That is, the number distribution may contain at least the first peak P1 and the second peak P2.

[0094] The first peak P1 has a mode diameter "d1". The second peak P2 has a mode diameter "d2". The mode diameter "d2" is larger than the mode diameter "d1". That is, the first peak P1 is composed of the first particle group (small particles 1a). The second peak P2 is composed of the second particle group (large particles 1b). The mode diameter of each peak can also be regarded as the average particle size of each particle group. The integral value (area) of each peak can correspond to the ratio of the number of first-order particles belonging to each peak. For example, the integral value of the first peak P1 can also be regarded as the ratio "n1" of the number of small particles 1a.

[0095] The number distribution can also be a multi-model distribution. That is, in addition to the first peak P1 and the second peak P2, there can be additional peaks. For example, the additional peaks can have a mode diameter smaller than the first peak P1. For example, the additional peaks can have a mode diameter between the first peak P1 and the second peak P2. For example, the additional peaks can have a mode diameter larger than the second peak P2. For example, the additional peaks can be shoulders of the first peak. For example, the additional peaks can be shoulders of the second peak.

[0096] composition

[0097] The primary particles contain olivine. Olivine has a crystal structure belonging to the space group Pnma. The space group to which the crystal structure belongs can be determined by X-ray diffraction (XRD) patterns. Small particles 1a and large particles 1b only need to contain olivine; they can have substantially the same composition or different compositions.

[0098] Peridotite may contain at least one selected from, for example, LFP, LMP, and LMFP. LMP and LMFP tend to have lower rate characteristics than LFP. Therefore, in the case of containing LMP and / or LMFP, smaller primary particles are required compared to the case of containing LFP. This embodiment is considered particularly suitable for LMP and LMFP.

[0099] Peridot has, for example, properties derived from the general formula "Li a Mn 1-x Fe xThe composition indicated by PO4. In the general formula, the Li composition ratio "a" can 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" can 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, "0.5 ≤" can also be satisfied. The relationship is "a ≤ 1.5". In the general formula, the Fe composition ratio "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, 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" can be, for example, less than 1.0, less than 0.9, less than 0.8, less than 0.7, less than 0.6, less than 0.5, less than 0.4, less than 0.3, less than 0.2, or less than 0.1. In the general formula, the relationship "0.2 ≤ x ≤ 0.5" can also be satisfied, for example.

[0100] Dopants can also be added to olivine. Dopants refer to elements other than lithium (Li), manganese (Mn), iron (Fe), phosphorus (P), and oxygen (O). The doping amount (mass fraction relative to the amount of Li) can be, for example, 0.01 to 0.1. The dopant may include at least one selected from boron (B), nitrogen (N), halogens, silicon (Si), sodium (Na), magnesium (Mg), aluminum (Al), chromium (Cr), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), selenium (Se), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), 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 actinides.

[0101] Primary particles can be covered with carbon material (not shown). Only a portion of the surface of the primary particle may be covered, or the entire surface of the primary particle may be covered. The coverage amount may also differ between small particles 1a and large particles 1b. The carbon material may be derived from, for example, sugars. The amount of carbon material attached, relative to secondary particles 2, may be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, or 10% or more by mass fraction. The amount of carbon material attached, for example, relative to secondary particles 2, may be less than 20% by mass fraction, less than 15% by mass, less than 10% by mass, less than 5% by mass, less than 4% by mass, or less than 3%.

[0102] The positive electrode active material may contain other components in addition to 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 powders of other components. Other components may contain at least one selected from the group consisting of, for example, Li[NiCoMn]O2 (layered structure), Li[NiCoAl]O2 (layered structure), LiMnO2 (rock salt structure), and Li[NiMn]2O4 (spinel structure). Furthermore, the description of [NiCoMn] etc. indicates that the total composition ratio within [ ] is 1. As long as the total is 1, the composition ratio of each component within [ ] can be any.

[0103] Method for manufacturing positive electrode active material

[0104] Figure 4 This is a simplified flowchart of the method for manufacturing the positive electrode active material in this embodiment. Hereinafter, the "method for manufacturing the positive electrode active material in this embodiment" can be simply referred to as "this method". This method includes steps a, b, and c. This method may also include step d. Step a involves preparing various secondary particles; step b involves wet pulverization; step c involves the recombination of the secondary particles; and step d is a calcination step.

[0105] Step a

[0106] This method includes steps for preparing various secondary particles. Each of these secondary particles contains olivine. The average particle size of the primary particles in these secondary particles differs from each other. Each secondary particle can be prepared independently. As an example, a method for synthesizing secondary particles of LMFP is described. Step a may include steps a1, a2, a3, and a4. Step a1 refers to blending, step a2 is wet pulverization, step a3 is granulation, and step a4 is calcination.

[0107] Step a1

[0108] For example, a slurry can be formed by mixing lithium compounds, manganese compounds, iron compounds, phosphoric acid compounds, and a dispersion medium. For example, the raw materials can be weighed to form a slurry with the general formula "LiaMn". 1-x Fe x The composition ratio (mass ratio) shown for PO4 (0.5 ≤ a ≤ 1.5, 0 < x < 1). As a lithium compound, it may contain, for example, lithium hydroxide. As a manganese compound, it may contain, for example, manganese carbonate. As an iron compound, it may contain, for example, iron phosphate. As a phosphoric acid compound, it may contain, for example, lithium dihydrogen phosphate.

[0109] Carbon materials can also be mixed into the slurry. The carbon materials can coat the surface of the primary particles. Examples of carbon materials that can be carbon materials include sugars and organic acids. Examples of carbon materials that can be carbon materials include glucose, sucrose, fructose, and citric acid. The amount of carbon materials added relative to the total solid components, by mass fraction, can be, for example, 1% to 20%.

[0110] The dispersion medium may contain, for example, water. The concentration of the solids in the slurry, expressed as a mass fraction, may be, for example, 30% ± 20%.

[0111] Step a2

[0112] For example, the average particle size of the primary particles can be adjusted by wet milling the slurry using a bead mill. That is, wet milling can be performed so that the primary particles have a desired average particle size. For example, wet milling can be performed to achieve a D50 of approximately 0.30 μm.

[0113] Step a3

[0114] For example, secondary particles can also be formed by spray drying the slurry. The primary particles contained in the secondary particles contain LMFP precursors.

[0115] Step a4

[0116] The precursor can be converted into LMFP by heat treatment of the secondary particles. In this method, any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The heat treatment atmosphere can also be, for example, a nitrogen atmosphere. The heat treatment temperature can be, for example, 400°C to 700°C. The heat treatment time can be, for example, 4 hours to 6 hours.

[0117] For example, by repeatedly performing steps a1 to a4 while changing the conditions of step a2, two or more types of secondary particles can be prepared. Two or more types of secondary particles are prepared such that the average particle size of the primary particles is different from each other.

[0118] Step b

[0119] First, step b may include the processes of pulverizing secondary particles and dispersing primary particles. This method involves wet-milling each of a variety of secondary particles to the size of primary particles, thereby forming a slurry in which primary particles are dispersed. For example, multiple slurries can be formed by separately wet-milling the various secondary particles. These multiple slurries are then mixed. Alternatively, a single slurry can be formed by simultaneously wet-milling the various secondary particles. In either case, the multiple primary particles with different average particle sizes are dispersed in the slurry. The solids concentration of the slurry, expressed as a mass fraction, can be, for example, 5% to 50%.

[0120] Wet milling is carried out in a manner that breaks down secondary particles to the size of primary particles and disperses the primary particles. Wet milling can be performed, for example, by a bead mill. The bead diameter is selected according to the size of the primary particles. The milling time is adjusted to break down secondary particles to the size of primary particles and disperse the primary particles. However, in order to prevent the primary particles from being crushed, the milling time is adjusted to be as short as possible. For example, if the primary particles are crushed, over-dispersion occurs, and it may be impossible to adjust the difference in average particle size between multiple primary particles to the desired range. In addition, jet mills crush materials by colliding with each other. Therefore, compared with bead mills that use beads as the crushing medium, jet mills tend to have weaker crushing force. It is believed that it is difficult to achieve a dispersed state of primary particle size in jet mills.

[0121] Step c

[0122] This method involves forming secondary particles by spray drying the slurry. The spray drying process can be, for example, the same as step a3.

[0123] Step d

[0124] This method may involve heat treatment of the secondary particles. The heat treatment process may be the same as step a4, for example.

[0125] liquid batteries

[0126] In some embodiments, the battery may be a liquid battery. "Liquid battery" refers to a battery containing an electrolyte. For example, polymer batteries, which contain an electrolyte, are liquid batteries. In some embodiments, the battery has a unipolar structure. In a unipolar structure, the conductive elements may be wound or laminated. In some embodiments, the battery has a bipolar structure. As an example, a battery with a bipolar structure (bipolar battery) is described.

[0127] Figure 5 This is a schematic perspective view of the battery according to this embodiment. Figure 6 It is along Figure 5A schematic cross-sectional view of line VI-VI. Hereinafter, "plane direction" refers to the normal direction relative to the surface of the sheet-like component (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction orthogonal to the plane direction. In the figures of this embodiment, the Z-axis direction corresponds to the plane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0128] The battery 100 includes a casing 90 and power generation elements. The power generation elements are housed within the casing 90. The casing 90 may, for example, include a first current collector 91, a first laminate 92, a second laminate 93, and a second current collector 94. The ends of the first laminate 92 and the second laminate 93 are joined together in the in-plane direction. A sealing material (not shown) may also be sandwiched between the first laminate 92 and the second laminate 93 at the joint.

[0129] The first current collector plate 91 and the second current collector plate 94 are joined to the power generation element at their ends in the lamination direction (Z-axis direction). A first laminate 92 is joined to the first current collector plate 91. A second laminate 93 is joined to the second current collector plate 94. A sealing material (not shown) may also be sandwiched between the current collector plate and the laminate at the joint.

[0130] The power generation element comprises multiple bipolar electrodes. These multiple bipolar electrodes are stacked in the plane (Z-axis direction). Each of the multiple bipolar electrodes sequentially comprises a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in the plane. In the in-plane direction (e.g., the X-axis direction), the current collector foil 13 extends outward compared to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collector foil 13 may extend outward compared to the positive electrode layer 11 and the negative electrode layer 12 throughout the entire in-plane direction.

[0131] The current collector foil 13 is a conductor. The current collector foil 13 may also contain, for example, a metal foil, a conductive resin layer, etc. For example, the current collector foil 13 may be formed by bonding an Al foil and a Cu foil. A carbon material may also be coated on the surface of the current collector foil 13. The carbon material may include, for example, carbon black.

[0132] The power generation element includes a sealing material 30. At its in-plane end, the sealing material 30 is bonded to the current collector foil 13. The sealing material 30 may also be thermally fused to the current collector foil 13. Alternatively, the sealing material 30 may be disposed along the entire periphery in the in-plane direction. The sealing material may also contain, for example, a resin material. The sealing material 30 seals adjacent current collector foils 13 in the vertical direction. By sealing the current collector foils 13 with the sealing material 30, battery cells are defined. A battery cell is the smallest unit of the power generation element. Since the battery 100 contains multiple battery cells, it can also be called a "bipolar module." The multiple battery cells are individually sealed. The multiple battery cells are isolated from each other. Each of the multiple battery cells includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0133] Positive electrode layer

[0134] The positive electrode layer 11 is attached to one side of the current collector foil 13. For example, a groove may be formed on the positive electrode layer 11. The positive electrode layer 11 may also be formed in a stripe pattern. The thickness of the positive electrode layer 11 may be, for example, 50 μm or more, 100 μm or more, 150 μm or more, 200 μm or more, 300 μm or more, 400 μm or more, 500 μm or more, 600 μm or more, 700 μm or more, 800 μm or more, or 900 μm or more. The thickness of the positive electrode layer 11 may also be, for example, less than 1000 μm, less than 900 μm, less than 800 μm, less than 700 μm, less than 600 μm, less than 500 μm, less than 400 μm, less than 300 μm, or less than 200 μm.

[0135] The positive electrode layer 11 contains a positive electrode active material. That is, the battery 100 contains a positive electrode active material. Details of the positive electrode active material are as described above. In addition to the positive electrode active material, the positive electrode layer 11 may further contain, for example, conductive materials and binders. The amount of conductive material relative to 100 parts by weight of the positive electrode active material can be, for example, 0.1 to 10 parts by weight. The conductive material may contain any components. The conductive material may contain at least one selected from, for example, graphite, acetylene black (AB), Ketjen black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene sheets (GF).

[0136] The amount of binder relative to 100 parts by weight of the positive electrode active material can be, for example, 0.1 to 10 parts by weight. The binder can contain any component. The binder may contain at least one selected from, for example, polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ethers, and derivatives thereof.

[0137] The positive electrode layer 11 may further include, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode layer may also include, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0138] negative electrode layer

[0139] The negative electrode layer 12 is attached to one side 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 thickness of the negative electrode layer 12 may be, for example, 50 μm or more, 100 μm or more, 150 μm or more, 200 μm or more, 300 μm or more, 400 μm or more, 500 μm or more, 600 μm or more, 700 μm or more, 800 μm or more, or 900 μm or more. The thickness of the negative electrode layer 12 may be, for example, less than 1000 μm, less than 900 μm, less than 800 μm, less than 700 μm, less than 600 μm, less than 500 μm, less than 400 μm, less than 300 μm, or less than 200 μm.

[0140] The negative electrode layer 12 contains a negative electrode active material. The negative electrode active material can be, for example, in particulate or sheet form. 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, less than 30 μm, less than 20 μm, less than 15 μm, or less than 10 μm.

[0141] The negative electrode active material can contain any components. For example, it can contain at least one selected from carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In some embodiments, the battery can be a Li metal negative electrode battery.

[0142] Carbon-based active materials may contain at least one of, for example, graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite can 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".

[0143] The surface of graphite can be covered, for example, with amorphous carbon. The surface of graphite can also be covered, for example, with a dissimilar material. The dissimilar material can include, for example, at least one selected from P, W, Al, and O. The dissimilar material can also include, for example, at least one selected from Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0144] The alloy-based active material may contain, for example, at least one selected from Si, lithium silicate, SiO, Si-based alloy, tin (Sn), SnO, and Sn-based alloy.

[0145] SiO may have, for example, a composition represented by the following general formula.

[0146] SiOx

[0147] In the formula, a relationship such as "0 < x < 2", "0.5 ≤ x ≤ 1.5", or "0.8 ≤ x ≤ 1.2" is satisfied.

[0148] "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 also be dispersed in carbon particles. For example, Si fine particles may also be dispersed in graphite particles. For example, lithium silicate particles may be covered with a carbon material (such as amorphous carbon).

[0149] Separator

[0150] The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulation. The separator 20 may contain, for example, at least one selected from a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may also contain, for example, a resin film and an inorganic particle layer.

[0151] The resin film is porous. The resin film may also contain, for example, a microporous membrane, non-woven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may also be continuously reticulated, for example. Fine pores are formed in the gaps of the resin skeleton. The resin film can allow the electrolyte to permeate. The resin film has an average pore diameter of, for example, 1 μm or less. The average pore diameter of the resin film may be, for example, 0.01 - 1 μm or 0.1 - 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gray Value of the resin film may be, for example, 50 - 250 s / 100 cm 3 . The "Gray Value" can be measured by the Gray test method.

[0152] The resin film may contain, for example, at least one selected from olefin-based resins, polyurethane-based resins, polyamide-based resins, cellulose-based resins, polyether-based resins, acrylic-based resins, and polyester-based resins, etc. The resin film may include at least one selected from, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamideimide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and their derivatives. The resin film can be formed, for example, by a stretching method, a phase separation method, etc. The thickness of the resin film may be, for example, 5 - 50 μm or 10 - 25 μm.

[0153] The resin membrane can also have a single-layer structure, for example. The resin membrane can also be composed of a PE layer. The framework of the PE layer is formed of PE. The PE layer can have a sealing function. The resin membrane can also have a multi-layer structure, for example. The resin membrane can include a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin membrane can also have a three-layer structure, for example. The resin membrane can also be formed by sequentially stacking a PP layer, a PE layer, and another PP layer. The thickness of the PE layer can also be, for example, 5~20 μm. The thickness of the PP layer can be, for example, 3~10 μm.

[0154] Inorganic particle layers can also be formed on the surface of the resin membrane. The inorganic particle layer can be formed on only one side of the resin membrane or on both sides. 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. Furthermore, 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.

[0155] The inorganic particle layer is porous. It contains inorganic particles, which can also be called "inorganic fillers." Fine pores are formed between the inorganic particles. The thickness of the inorganic particle layer can be, for example, 0.5–10 μm or 1–5 μm. The inorganic particles may contain heat-resistant materials. An inorganic particle layer containing heat-resistant materials is also called a "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from boehmite, alumina, zirconium oxide, titanium dioxide, magnesium oxide, and silicon dioxide. The inorganic particles can have any shape. For example, they can be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles can be, for example, 0.1–10 μm or 0.5–3 μm. The inorganic particle layer may also contain a binder. The binder may contain at least one selected from, for example, acrylic resins, polyamide resins, fluorinated resins, aromatic polyether resins, and liquid crystal polyester resins.

[0156] The diaphragm 20 may, for example, contain an organic particle layer. The diaphragm 20 may, for example, contain an organic particle layer instead of a resin membrane. The diaphragm 20 may, for example, contain an organic particle layer instead of an inorganic particle layer. The diaphragm 20 may simultaneously contain a resin membrane and an organic particle layer. The diaphragm 20 may simultaneously contain an inorganic particle layer and an organic particle layer. The diaphragm 20 may also contain a resin membrane, an inorganic particle layer, and an organic particle layer.

[0157] The thickness of the organic particle layer can be, for example, 0.1~50 μm, 0.5~20 μm, 0.5~10 μm, or 1~5 μm. The organic particle layer contains organic particles. These organic particles can also be referred to as "organic fillers." The organic particles may contain heat-resistant materials. The organic particles may contain at least one material selected from, for example, PE, PP, PTFE, PI, PAI, PA, and aromatic polyamides. The organic particles can be, for example, spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles can be, for example, 0.1~10 μm or 0.5~3 μm.

[0158] The membrane 20 may also include a hybrid layer, for example. The hybrid layer contains both inorganic and organic particles.

[0159] electrolyte

[0160] The electrolyte is a liquid electrolyte. It contains a solute and a solvent. The concentration of the solute is, for example, 0.5–1 mol / L, 1–1.5 mol / L, 1.5–2 mol / L, 2–2.5 mol / L, or 2.5–3 mol / L. Sometimes "mol / L" is also designated as "M". The solute contains a supporting salt (supporting electrolyte, Li salt). Solutes can include, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may also contain at least one of, for example, selected from 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 their derivatives.

[0161] The electrolyte may contain, for example, carbonate solvents. The solvent may contain, for example, cyclic carbonates, chain carbonates, fluorinated carbonates, etc. The solvent may contain at least one selected from, for example, ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene monofluorocarbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, monofluoropropylene carbonate, difluoropropylene carbonate, and their derivatives.

[0162] The solvent can contain cyclic carbonates (EC, PC, FEC, etc.) and chain carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to chain carbonates 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".

[0163] The solvent may contain cyclic carbonates (EC, PC, etc.) and fluorinated cyclic carbonates (FEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to fluorinated cyclic carbonates 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".

[0164] Solvents may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratios of the components may satisfy, for example, the following relationship.

[0165] V EC +V FEC +V EMC +V DMC +V DEC =10

[0166] In the relation, V EC V FEC V EMC V DMC V DEC Let V represent the volume ratios of EC, FEC, EMC, DMC, and DEC, respectively. These must satisfy the condition 1 ≤ V. EC ≤4”, 0≤V FEC ≤3”, V EC +V FEC ≤4”、

[0167] 0≤V EMC ≤9”, 0≤V DMC ≤9”, 0≤V DEC ≤9” and “6≤V” EMC +V DMC +V DEC The relationship is ≤9".

[0168] For example, satisfying "1≤V" EC ≤2” or “2≤V” EC The relationship is ≤3".

[0169] For example, satisfying "1≤V" FEC ≤2” or “2≤V” FECThe relationship is ≤4".

[0170] For example, satisfying "3≤V" EMC ≤4” or “6≤V” EMC The relationship is ≤8".

[0171] For example, satisfying "3≤V" DMC ≤4” or “6≤V” DMC The relationship is ≤8".

[0172] For example, satisfying "3≤V" DEC ≤4” or “6≤V” DEC The relationship is ≤8".

[0173] The solvent, for example, has a composition in volume ratios such as "EC / EMC=3 / 7", "EC / DMC=3 / 7", "EC / FEC / DEC=1 / 2 / 7", "EC / DMC / EMC=3 / 4 / 3", "EC / DMC / EMC=3 / 3 / 4", "EC / FEC / DMC / EMC=2 / 1 / 4 / 3", "EC / FEC / DMC / EMC=1 / 2 / 4 / 3", "EC / FEC / DMC / EMC=2 / 1 / 3 / 4", and "EC / FEC / DMC / EMC=1 / 2 / 3 / 4".

[0174] The electrolyte may also contain ether-based solvents. The electrolyte may contain at least one selected from, for example, tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylene glycol diethyl ether, triethylene glycol dimethyl ether (triglyme), tetraethylene glycol dimethyl ether (trtraglyme), and their derivatives.

[0175] The electrolyte may contain any additives. The amount added (as a percentage of the total mass of the electrolyte) may be, for example, 0.01–5%, 0.05–3%, or 0.1–1%. Additives may include, for example, SEI (solid electrolyte interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge inhibitors, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0176] As an additive, it may contain, for example, those selected from vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propanesulfonate lactone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), vinyl sulfate (ES), vinyl sulfite (DTD), γ-butyrolactone, phosphazene compounds, and 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-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.], fluorotoluenes (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluoromethyl... Benzene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzene-chloroform (e.g., benzene-chloroform, 2-fluorobenzene-chloroform, 3-fluorobenzene-chloroform, 4-fluorobenzene-chloroform, 2-methylbenzene-chloroform, 3-methylbenzene-chloroform, 4-methylbenzene-chloroform, etc.), fluoroxylenes (e.g., 3-fluoroo-xylene, 4-fluoroo-xylene, 2-fluorom-xylene, 5-fluorom-xylene, etc.) The following are included in the following categories: sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methylbenzothiazole, tetrathiofulvalene, etc.), nitrile compounds (e.g., adiponitrile, succinate, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic 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 at least one of their derivatives.

[0177] The aforementioned components described as solutes and solvents can be used as trace components (additives). As additives, they may include at least one selected from, for example, LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and their derivatives.

[0178] The electrolyte may contain ionic liquids. Ionic liquids may contain at least one selected from, for example, sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidineium salts, morpholinium salts, phosphonium salts, imidazoline salts, and their derivatives.

[0179] In some embodiments of this invention, the battery may comprise a gel electrolyte. That is, the battery may also be a polymer battery. The gel electrolyte may comprise an electrolyte and a polymeric material. The polymeric material may form a polymeric matrix. The polymeric material may comprise at least one selected from, for example, PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0180] Solid-state batteries

[0181] In some embodiments, the battery may be an all-solid-state battery. An all-solid-state battery may have a bipolar structure. The all-solid-state battery contains a solid electrolyte in place of the electrolyte and separator 20. The solid electrolyte may be contained within the positive electrode layer 11 and the negative electrode layer 12. The solid electrolyte layer, in place of the separator 20, separates the negative electrode layer 12 from the positive electrode layer 11. The solid electrolyte layer may contain, for example, a solid electrolyte and a binder.

[0182] Solid electrolytes can be, for example, powders. The D50 of a 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 a solid electrolyte can also be, for example, less than 5 μm, less than 4 μm, less than 3 μm, less than 2 μm, or less than 1 μm.

[0183] Solid electrolytes may include at least one selected from, for example, sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes and nitride solid electrolytes.

[0184] Sulfide solid electrolytes may contain at least one phase selected from amorphous phases, crystalline phases, and glass-ceramic (crystallized glass) phases. Crystalline phases may also be, for example, Argyrodite type, LGPS type, etc. Sulfide solid electrolytes contain Li and sulfur (S). Besides Li and S, sulfide solid electrolytes may contain any other components.

[0185] As a sulfide solid electrolyte, it contains, for example, compounds selected from 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 At least one of Li3PS4 and Li7PS6.

[0186] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. Sulfide solid electrolytes can also be produced via mechanochemical methods. The mixing ratio can also be determined by adding numbers before each raw material. For example, "10LiI-15LiBr-75Li3PS4" indicates a mixing ratio of "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (molar ratio)".

[0187] Sulfide solid electrolytes may also have a composition represented by the following general formula:

[0188] xLi2S-(1-x)P2S5

[0189] In the general formula, "x" can be, for example, greater than 0, greater than 0.1, greater than 0.2, greater than 0.25, greater than 0.3, greater than 0.4, greater than 0.5, greater than 0.6, greater than 0.7, greater than 0.75, greater than 0.8, or greater than 0.9. "x" can also be, for example, less than 1, less than 0.9, less than 0.8, less than 0.75, less than 0.7, less than 0.6, less than 0.5, less than 0.4, less than 0.3, less than 0.2, or less than 0.1. For example, when "x = 0.75", "xLi2S-(1-x)P2S5" can have the composition of Li3PS4.

[0190] Sulfide solid electrolytes may also have a composition represented by the following general formula:

[0191] yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5]

[0192] In the general formula, "x" can be, for example, 0.5 or higher, 0.6 or higher, 0.7 or higher, 0.75 or higher, 0.8 or higher, or 0.9 or higher. "x" can also be, for example, less than 1, less than 0.9, less than 0.8, less than 0.75, less than 0.7, or less than 0.6. "y" can be, for example, 0 or higher, 5 or higher, 10 or higher, 15 or higher, 20 or higher, or 25 or higher. "y" can also be, for example, less than 30, less than 25, less than 20, less than 15, less than 10, or less than 5. "z" can be, for example, 0 or higher, 5 or higher, 10 or higher, 15 or higher, 20 or higher, or 25 or higher. "z" can also be, for example, less than 30, less than 25, less than 20, less than 15, less than 10, or less than 5.

[0193] Sulfide solid electrolytes can have compositions, for example, represented by the following general formula:

[0194] Li 7-x-2y PS6-x-y X y

[0195] In the general formula, the relationships “0 < 7-x-2y”, “0 < 6-xy”, “0 ≤ x”, and “0 ≤ y” are satisfied. “X” may contain at least one selected from, for example, fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0196] Sulfide solid electrolytes can have compositions, for example, represented by the following general formula:

[0197] Li 4-x M 1-x P x S4

[0198] In the general formula, "x" can be, for example, greater than 0, greater than 0.1, greater than 0.2, greater than 0.3, greater than 0.4, greater than 0.5, greater than 0.6, greater than 0.7, greater than 0.8, or greater than 0.9. "x" can be, for example, less than 1, less than 0.9, less than 0.8, less than 0.7, less than 0.6, less than 0.5, less than 0.4, less than 0.3, less than 0.2, or less than 0.1. "M" can include, for example, at least one selected from Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0199] Sulfide solid electrolytes can have compositions, for example, represented by the following general formula:

[0200] Li 10+x Ge 1＋x P 2-x S 12

[0201] In the general 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 also 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, for example, contain an LGPS-type crystalline phase.

[0202] Halide solid electrolytes can have compositions, for example, represented by the following general formula:

[0203] Li 6-na M a X6

[0204] In the general formula, "n" represents the oxidation number of "M". "M" can contain, for example, atoms with an oxidation number of +3. "M" can, for example, contain atoms with an oxidation number of +4. As "M", it can contain, for example, at least one selected from Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship "0 < a < 2" can also be satisfied. For example, as "X", it can contain at least one selected from F, Cl, Br, and I.

[0205] The halide solid electrolyte can have, for example, a composition represented by the following general formula:

[0206] Li 3-a Ti a Al 1-a F6

[0207] In the general 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.

[0208] The halide solid electrolyte can have, for example, a composition represented by the following general formula:

[0209] Li3YCl a Br b I 6-a-b

[0210] In the general formula, for example, the relationship "0 ≤ a + b ≤ 6" can 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.

[0211] As the oxide solid electrolyte, it can contain, for example, at least one selected from LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3- x Li 3x TiO3 and Li7La3Zr2O 12 and the like. As the hydride solid electrolyte, it can contain, for example, LiBH4, etc. The nitride solid electrolyte can contain, for example, Li3N, Li3BN2, etc.

[0212] Specimen preparation

[0213] No.1

[0214] The positive electrode active material No. 1 was manufactured according to the following steps. Furthermore, regarding the manufacturing method, steps a, b, c, and d are the same as the steps described above. Additionally, regarding the manufacturing method, steps a1, a2, a3, and a4 are also the same as the steps described above.

[0215] Step a

[0216] Step a1

[0217] According to the composition "Li 1.04 Mn 0.6 Fe 0.4 Weigh lithium hydroxide monohydrate, manganese carbonate, iron phosphate, and lithium dihydrogen phosphate according to the composition ratio shown in "PO4". Weigh glucose at 8% 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% ± 20% by mass.

[0218] Step a2

[0219] The slurry is wet-milled using a bead mill to adjust the average particle size of the dispersion (primary particles).

[0220] Step a3

[0221] The slurry is spray-dried using a spray dryer to form secondary particles. These secondary particles contain LMFP precursors. The target D50 value for the secondary particles (powder) is 9 μm ± 5 μm. The spray dryer settings are as follows.

[0222] Inlet temperature: 250℃

[0223] Exhaust port temperature: 115℃±15℃

[0224] Intake pressure: 2.0 MPa

[0225] Nozzle pressure of the spray nozzle: 0.2±0.1MPa

[0226] Step a4

[0227] Secondary particles were placed in a calcination furnace under a nitrogen atmosphere. The furnace temperature was increased to 200°C at a rate of 3°C / min and maintained at 200°C for 1 hour. Next, the temperature was increased to 650°C at a rate of 5°C / min and maintained at 650°C for 5 hours. Then, the temperature was decreased to 400°C at a rate of 2°C / min. Finally, the temperature was decreased to room temperature at a rate of 15°C / min. Thus, the precursor was converted into LMFP.

[0228] Two types of secondary particles were prepared using the above procedure. The average particle size of the primary particles was measured for each type of secondary particle. In one type of secondary particle (particle group 1), the average particle size of the primary particles was 40 nm. In the other type of secondary particle (particle group 2), the average particle size of the primary particles was 61 nm.

[0229] Step b

[0230] A slurry is formed by mixing two types of secondary particles with water. The solids concentration of the slurry is 5% to 50% by mass fraction. The slurry is then wet-milled using a bead mill. Milling conditions are as follows.

[0231] Slurry processing capacity: 1.5kg

[0232] Bead diameter: 0.1mm

[0233] Grinding time: 10 min

[0234] The mill's circumferential speed: 13 m / s

[0235] Step c

[0236] The slurry is spray-dried using a spray dryer to form secondary particles. The settings of the spray dryer are the same as in step a3.

[0237] Step d

[0238] The secondary particles are subjected to heat treatment. The heat treatment conditions are the same as those in step a4.

[0239] No.2 to No.6

[0240] Figure 7 This is a table representing the experimental results. For example... Figure 7 As shown, except for changing the average particle size of the primary particles in the secondary particles of one side, the positive electrode active material is manufactured in the same way as No.1. The pulverization conditions are adjusted within the following range.

[0241] Bead diameter: 3mm~0.1mm

[0242] Grinding time: more than 10 minutes, and the shortest possible time to ensure that the particle size does not change during a single grinding process.

[0243] The mill's circumferential speed: 8 m / s to 14 m / s

[0244] In addition, for particles No.3 to No.6 with a large average particle size ratio, wet grinding was performed separately, and then two kinds of slurry were mixed.

[0245] No.7 to No.13

[0246] like Figure 7 As shown, the two particles prepared in step a are directly used as the positive electrode active material.

[0247] Evaluate

[0248] Each sample was evaluated using the following steps.

[0249] Electrode fabrication

[0250] 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 dispersion medium (N-methyl-2-pyrrolidone). The solids concentration of the paste is 50% by mass fraction. The positive electrode layer is formed by coating the paste onto the surface of an Al foil and drying it. The positive electrode layer is then compressed using a roller press to form the primary substrate. The primary substrate is subjected to vacuum drying at 120°C for 12 hours. After drying, the electrode (diameter: 14 mm) is removed from the primary substrate by punching.

[0251] Filling

[0252] The conditions of the roller press were the same for all samples. The density of the positive electrode layer in No. 7 was 1.8 g / cm³. 3 . Figure 7 The "filling" refers to the density of each sample. Figure 7 The density is a relative value when the density in No.7 is set to 1.

[0253] curvature

[0254] Prepare two uncharged electrodes. Form a laminate by stacking the electrodes with the positive electrode layers facing each other. Contain the laminate and electrolyte in a button-shaped casing to fabricate a button cell. Perform impedance measurements on the button cell under the following conditions.

[0255] SOC: 50%

[0256] Frequency range: 100000-0.01Hz

[0257] Temperature: 25℃

[0258] Voltage amplitude “ΔV”: ±5mV

[0259] The liquid bulk "Rion" is calculated by analyzing the impedance measurement results using the analytical software "ZView (registered trademark)". Then, the effective conductivity "κ" of the electrolyte is calculated using the following formula. eff pos ".

[0260] κ eff pos =L / (S・Rion)

[0261] L: Film thickness

[0262] S: Product of electrode area and electrode porosity

[0263] Calculate the porosity "ε" based on the electrode design values. Calculate the tortuosity "τ" using the following formula.

[0264] τ=(Kε) / κ eff pos

[0265] K: Conductivity of the bulk electrolyte

[0266] Figure 7 The curvature shown is a relative value when the curvature value of No.7 is set to 100.

[0267] result

[0268] exist Figure 7 Among the results from No. 7 to No. 13, when the primary particles constituting the secondary particles are distributed in a single model, larger primary particles tend to improve curvature. However, on the other hand, larger primary particles have lower density.

[0269] exist Figure 7 Among the results from No. 1 to No. 6, when the primary particles constituting the secondary particles are distributed in a dual-model configuration, the larger the average particle size ratio "d2 / d1", the more likely the curvature is to improve. Even when the large particles (primary particles) become larger, the density can be maintained.

[0270] exist Figure 7 Among the results from No.1 to No.6, when the relationship “1.5≤d2 / d1≤10” is satisfied, it can be seen that the curvature tends to improve.

[0271] exist Figure 7 Among the results from No.1 to No.6, when the relationship “3.0≤d2 / d1” is satisfied, it can be seen that the curvature tends to improve.

[0272] In Figure 7 among the results from No.1 to No.6, when the relationship of "5.0 ≤ d2 / d1" is satisfied, a tendency of improved curvature can be seen.

[0273] In Figure 7 among the results from No.1 to No.6, when the relationship of "200 nm ≤ d2" is satisfied, a tendency of improved curvature can be seen.

[0274] In Figure 7 among the results from No.1 to No.6, when the relationship of "0.7000 < n1 / (n1 + n2) < 1.000" is satisfied, a tendency of improved curvature is observed.

[0275] In Figure 7 among the results from No.1 to No.6, when the relationship of "0.4 ≤ m1 / (m1 + m2) ≤ 0.6" is satisfied, a tendency of improved curvature can be seen.

[0276] In Figure 7 from the results of No.7 to No.13, it can be considered that even if the primary particles constituting the secondary particles are bimodal distributed, when the large particles form primary aggregates within the secondary particles, the density decreases and it is difficult to balance the curvature and the filling property.

[0277] Note

[0278] The present disclosure also provides the following positive electrode active material.

[0279] Note 1. A positive electrode active material, characterized in that it contains secondary particles, and the secondary particles contain a first particle group and a second particle group,

[0280] both the first particle group and the second particle group are composed of primary particles,

[0281] the primary particles contain an olivine-type phosphate compound,

[0282] the average particle size of the second particle group is larger than the average particle size of the first particle group, and

[0283] within the secondary particles, the primary particles belonging to the first particle group and the primary particles belonging to the second particle group are dispersed from each other.

[0284] Note 2. The positive electrode active material according to Note 1, characterized in that the relationship of 1.5 ≤ d2 / d1 ≤ 10 is satisfied,

[0285] where d1 represents the average particle size of the first particle group and d2 represents the average particle size of the second particle group.

[0286] Note 3. The positive electrode active material as described in Note 2 is characterized in that it satisfies the relationship 3.0 ≤ d2 / d1.

[0287] Note 4. The positive electrode active material as described in Note 3 is characterized in that it satisfies the relationship 5.0 ≤ d2 / d1.

[0288] Note 5. The positive electrode active material as described in Note 2 is characterized in that it satisfies the relationship 200nm≤d2≤500nm.

[0289] Note 6. The positive electrode active material as described in any one of Notes 1 to 5 is characterized in that it satisfies the relationship 0.7000 < n1 / (n1 + n2) < 1.000.

[0290] The n1 represents the ratio of the number of primary particles belonging to the first particle group, and

[0291] The n2 represents the ratio of the number of primary particles belonging to the second particle group.

Claims

1. A positive electrode active material, characterized in that, It includes secondary particles, which contain a first particle group and a second particle group. Both the first particle group and the second particle group are composed of primary particles. The primary particles contain olivine-type phosphate compounds. The average particle size of the second particle group is greater than the average particle size of the first particle group, and Within the secondary particles, the primary particles belonging to the first particle group and the primary particles belonging to the second particle group are dispersed from each other.

2. The positive electrode active material according to claim 1, wherein The relationship 1.5 ≤ d2 / d1 ≤ 10 is satisfied. d1 represents the average particle size of the first particle group, and d2 represents the average particle size of the second particle group.

3. The positive electrode active material as described in claim 2, characterized in that, The relationship 3.0 ≤ d2 / d1 is satisfied.

4. The positive electrode active material as described in claim 3, characterized in that, The relationship 5.0 ≤ d2 / d1 is satisfied.

5. The positive electrode active material as described in claim 2, characterized in that, It satisfies the relationship 200nm≤d2≤500nm.

6. The positive electrode active material according to any one of claims 1 to 5, wherein The relationship 0.7000 < n1 / (n1 + n2) < 1.000 is satisfied. The n1 represents the ratio of the number of primary particles belonging to the first particle group, and The n2 represents the ratio of the number of primary particles belonging to the second particle group.

7. The positive electrode active material according to any one of claims 1 to 5, characterized in that, The relationship 0.4 ≤ m1 / (m1 + m2) ≤ 0.6 is satisfied. The m1 represents the total mass of the primary particles belonging to the first particle swarm, and The m2 represents the total mass of the primary particles belonging to the second particle group.

8. The positive electrode active material according to any one of claims 1 to 5, characterized in that, The olivine-type phosphate compound contains at least one selected from lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate.

9. The positive electrode active material as described in claim 1, characterized in that, The condensate, which consists of the primary particles belonging to the first particle group and the primary particles belonging to the second particle group, contains 2 to 4 primary particles belonging to the second particle group.

10. The positive electrode active material as described in claim 2, characterized in that, It satisfies the relationship 5nm≤d1<50nm.

11. The positive electrode active material as described in claim 10, characterized in that, It satisfies the relationship 50nm≤d2≤500nm.

12. An electrode characterized by, Includes a positive electrode layer. The positive electrode layer contains the positive electrode active material as described in any one of claims 1 to 5.

13. A battery, characterized by It contains the electrode as described in claim 12.

14. The battery of claim 13, wherein the cathode comprises a lithium metal oxide. It has a bipolar structure.

15. A method for producing a positive electrode active material, characterized by comprising the steps of, Includes the following steps: Prepare a variety of secondary particles containing olivine-type phosphate compounds, where the average particle size of the primary particles differs from that of the secondary particles. By wet milling, the various secondary particles are broken down to the size of the primary particles, thereby forming a slurry in which the primary particles are dispersed. New secondary particles are formed by spray drying a slurry containing multiple primary particles with different average particle sizes.

Images