Positive electrode active material, electrode, and lithium ion secondary battery

Abstract

The invention relates to a positive electrode active material, an electrode, and a lithium ion secondary battery. The present disclosure can achieve an improvement in cycle characteristics. This positive electrode active material contains a powder containing single crystal particles. The single crystal particles contain a lithium transition metal composite oxide. The lithium transition metal composite oxide has a crystal structure belonging to space group R-3m, and contains at least nickel. In a scanning electron microscope image of the powder, the single crystal particle is a single particle that is independent and does not agglomerate. The single crystal particles are polyhedral. The single crystal particle includes a longest side and a short side. The longest side extends along the 003 plane. And the short side is connected with the tail end of the longest side. The interior angle formed by the longest side and the short side is 60-120 degrees (inclusive). The ratio of the longest side to the short side is 1.10 or more.

Description

Technical Field

[0001] This disclosure relates to positive electrode active materials, electrodes, and lithium-ion secondary batteries. Background Technology

[0002] Japanese Patent Application Publication No. 2022-064294 discloses the synthesis of single particles via a flux method. Summary of the Invention

[0003] A single-crystal cathode active material was proposed. This active material can contain lithium transition metal composite oxides. The lithium transition metal composite oxides can have a crystal structure belonging to R-3m (layered structure). The layered structure is formed by alternating layers of 3a sites (Li layers) and 3b sites (transition metal layers). Including nickel (Ni) ions at the 3b sites, for example, can be expected to increase the discharge capacity.

[0004] During charging, Li ions are extracted from and extracted from the Li layer. This extraction causes the Li layer to contract along the stacking direction (c-axis). During this contraction, an exchange of Li ions between the Li layer and Ni ions between the transition metal layer occurs. This phenomenon is also known as "cation mixing." Due to this mixing, a portion of the layered structure transforms into a rock salt structure. Because of this irreversible structural change, the discharge capacity decreases. It is believed that the impact of structural change is significant in single-crystal cathode active materials. It is also believed that capacity degradation, accompanying structural changes, is progressively accelerated by repeated charge-discharge cycles.

[0005] This disclosure provides improvements in cyclic characteristics.

[0006] The following describes the technical solution and effects of this disclosure. However, the mechanism of action includes presumptions. The mechanism of action does not limit the technical scope of this disclosure.

[0007] The first aspect of this disclosure is a positive electrode active material comprising powder. The powder comprises single crystal particles. The single crystal particles comprise lithium transition metal composite oxide. The lithium transition metal composite oxide has a crystal structure belonging to space group R-3m. The lithium transition metal composite oxide contains at least nickel. In a scanning electron microscope image of the powder, the single crystal particle is an independent, non-aggregated single particle. The single crystal particle is polyhedral. The single crystal particle comprises a longest side and a short side. The longest side extends along the 003 plane. The short side is connected to the end of the longest side. The interior angle formed by the longest side and the short side is 60° or more and 120° or less. The ratio of the longest side to the short side is 1.10 or more.

[0008] In the following, the ratio of the longest side "a" to the shortest side "b", "a / b", is also referred to as the "length-to-width ratio". Figure 1This is a first conceptual diagram illustrating the relationship between particle shape and crystal structure. The single-crystal particles have a small aspect ratio, specifically less than 1.10. The 3a site (Li layer) extends along the 003 plane. During charging, Li ions are extracted from and extracted from the Li layer. In shapes with small aspect ratios, the extension of the Li layer along the 003 plane is small. Therefore, it is assumed that the extraction of Li ions from the Li layer can proceed rapidly. It is also assumed that the Li layer rapidly contracts due to falling into a Li-ion-deficient state. This rapid contraction of the Li layer is considered a triggering factor for cation mixing.

[0009] Figure 2 This is a second conceptual diagram illustrating the relationship between particle shape and crystal structure. The single-crystal particles in this disclosure have a polyhedral shape with a large aspect ratio. Furthermore, the longest side extends along the 003 plane. Therefore, it is considered that... Figure 1 Compared to the Li layer, the Li layer is significantly wider. It is believed that because the Li layer is wider along the 003 plane, the detachment of Li ions from the Li layer occurs relatively slowly. The residual Li ions in the Li layer are thought to act as so-called pillars, thereby mitigating the shrinkage of the Li layer. Therefore, by reducing cation mixing, improvements in cycling characteristics can be expected.

[0010] In the first method described above, the ratio of the longest side to the shortest side can also be greater than 2.00 and less than 6.10.

[0011] Improved cycling performance can be expected when the aspect ratio is 2.00 or higher and 6.10 or lower.

[0012] In the first method described above, the interior angle can also be greater than 82° and less than 94°.

[0013] Improved cycling characteristics can be expected when the interior angle is above 82° and below 94°.

[0014] In the first method described above, the edge angle of the single crystal particles can also be 451~584.

[0015] When the edge angle is 451~584, an improvement in cycle characteristics can be expected.

[0016] In the first method described above, the proportion of single crystal particles with an interior angle of 60° to 120° in the powder can also be more than 21%.

[0017] The powder may contain single crystal particles of other shapes as long as it contains single crystal particles with the shape described in the first aspect above. When the proportion of single crystal particles with the shape described in the first aspect above in the powder is 21% or more, an improvement in cycling characteristics can be expected.

[0018] In the first method described above, the longest side can be 1.59~3.48μm. The shortest side can be 0.377~1.45μm.

[0019] When the longest side is 1.59~3.48μm and the short side is 0.377~1.45μm, an improvement in cycling characteristics can be expected.

[0020] In the first method described above, single-crystal particles can also possess the properties of the general formula "Li". x Ni a Co b Mn c O y The general formula represents the composition of x, a, b, c, y. In the general formula, x, a, b, c, y can also satisfy the relationships of 0.1≤x≤1.5, 0.5≤a≤1.0, 0≤b≤0.3, 0≤c≤0.3, a+b+c=1.0 and 1.5≤y≤2.1.

[0021] In the first method described above, the 3b site (transition metal layer) may contain other elements besides Ni. For example, the 3b site may also contain Co and Mn. By having a Ni composition ratio "a" of 0.5 or higher, an increase in initial discharge capacity can be expected, for example.

[0022] The second aspect of this disclosure is an electrode. The electrode includes a positive electrode layer. The positive electrode layer includes the positive electrode active material of the first aspect described above.

[0023] The positive electrode layer can also be called the "positive electrode active material layer" or the "positive electrode compound layer". As long as an "electrode" contains a positive electrode layer, it can be either a "monopolar electrode (positive electrode)" or a "bipolar electrode".

[0024] The third aspect of this disclosure is a lithium-ion secondary battery. The lithium-ion secondary battery includes the electrodes of the second aspect described above. Hereinafter, the lithium-ion secondary battery may also be simply referred to as a "battery".

[0025] In the third method described above, the lithium-ion secondary battery can also have a bipolar structure.

[0026] Bipolar structures can be formed by stacking bipolar electrodes. Through bipolar structures, improvements in output characteristics can be expected, for example.

[0027] The following describes one embodiment (hereinafter referred to as "this embodiment") and one example of this disclosure (hereinafter referred to as "this example"). However, this embodiment and this example do not limit the technical scope of this disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are non-limiting. The technical scope of this disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it includes from the outset the possibility of extracting arbitrary structures from this embodiment and combining them arbitrarily. Attached Figure Description

[0028] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention are described below with reference to the accompanying drawings, in which the same reference numerals denote the same elements.

[0029] Figure 1 This is the first concept diagram representing the relationship between particle shape and crystal structure.

[0030] Figure 2 This is the second concept diagram representing the relationship between particle shape and crystal structure.

[0031] Figure 3 This is a conceptual diagram of the single-crystal particles in this embodiment.

[0032] Figure 4 This is an explanatory diagram of HAADF-STEM analysis.

[0033] Figure 5 This is an explanatory diagram of the method for measuring edge angles.

[0034] Figure 6 This is a schematic perspective view of the lithium-ion secondary battery in this embodiment.

[0035] Figure 7 It is along Figure 6 A schematic cross-sectional view of line VII-VII in the diagram.

[0036] Figure 8 This is a table representing the experimental results.

[0037] Figure 9 This is the first firing curve.

[0038] Figure 10 This is the second firing curve. Detailed Implementation

[0039] Terms and phrases

[0040] "Possessing," "Including," "Having," and their variations are open-ended expressions. Structures expressed in an open-ended manner may include additional elements besides the necessary ones, or they may not include additional elements. The statement "Composed of..." is a closed-ended expression. However, even structures expressed in a closed-ended manner may include usually accompanying impurities and additional elements unrelated to the target technology. The statement "Substantially composed of..." is a semi-closed-ended expression. In structures expressed in a semi-closed manner, it is permissible to add elements that do not substantially affect the basic and new characteristics of the target technology.

[0041] The expressions "maybe" and "can" are not used in an obligatory sense (meaning "must do this"), but rather in a permissive sense (meaning "this possibility exists").

[0042] Geometric terms should not be interpreted strictly. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For instance, directions, angles, and distances can also be relative displacements within a range where substantially the same or similar functions can be achieved. Geometric terms can also include tolerances and errors in design, operation, and manufacturing. Dimensional relationships in drawings sometimes differ from actual dimensional relationships. To aid understanding, dimensional relationships in drawings are sometimes altered. For example, length, width, and thickness may be changed. Sometimes, parts of the structure may be omitted.

[0043] Unless otherwise specified, elements described in the "singular form" may also include plural forms. For example, "particle" can sometimes refer to multiple particles (particle swarm), a collection of particles, or powder.

[0044] Unless otherwise specified, the numerical range of "m~n%" includes both an upper and lower limit. That is, "m~n%" represents a numerical range of "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. Alternatively, a new upper or lower limit can be set by arbitrarily selecting a value from the numerical range. For example, a new numerical range can be set by arbitrarily combining values ​​from the numerical range with values ​​recorded in other parts of this specification, tables, and figures.

[0045] All numerical values ​​are modified by the term "approximately". The term "approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​can be approximate values ​​that may vary depending on the application of the technology. All numerical values ​​can be expressed 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 based on the number of significant figures. The measured value may include, for example, errors such as the detection limits of the accompanying measuring device.

[0046] The apparatus and software used in the determination of various values ​​are just one example. Products equivalent to the illustrated apparatus can also be used. When using equivalent products, the measurement conditions can be adjusted in conjunction with the apparatus.

[0047] The space group to which a crystal structure belongs is determined by the XRD (X-ray Diffraction) pattern. XRD patterns can be obtained through powder XRD analysis. The analysis conditions are described below.

[0048] Analysis method: Wide-angle method

[0049] Measurement apparatus: Smart Lab II (manufactured by Rigaku Corporation)

[0050] Measurement angle: 10° to 120°

[0051] Tube: CuKα

[0052] Tube voltage: 45kV

[0053] Tube current: 200mA

[0054] Determination method: Continuous method

[0055] Step length: 0.02

[0056] Speed: 2° / minute

[0057] IS: 1 / 2

[0058] RS: 20mm

[0059] Detection mode: One-dimensional

[0060] Various size measurements and shape analyses in scanning electron microscope (SEM) images, transmission electron microscope (TEM) images, etc., can be performed using image analysis software such as "Image J".

[0061] "Single crystal particle" refers to a single particle (primary particle) that appears independent and non-aggregated in a SEM image. Single crystal particles do not appear to have grain boundaries in SEM images. The magnification of SEM images can be, for example, 10,000x to 30,000x. SEM images can be SEM images of powder cross-sections.

[0062] Figure 3 This is a conceptual diagram of the single-crystal particle according to this embodiment. "Longest side 1a" represents the seemingly longest side in the SEM image of the single-crystal particle 1. "Short side 1b" connects to the end of the longest side 1a. The short side 1b represents the seemingly longest side in the SEM image among the sides connected to the longest side 1a. The short side 1b extends from the end of the longest side 1a in a direction intersecting the direction in which the longest side 1a extends. For example, the longest side 1a and the short side 1b can also extend in a straight line. The longest side 1a and the short side 1b can also be curved, for example. In the case of a curved edge, the length of the edge represents the distance between the two ends of the edge.

[0063] In the SEM image, single crystal particles 1 are extracted where the interior angle "θ" formed by the longest side 1a and the shortest side 1b satisfies the relationship "60°≤θ≤120°". Ten single crystal particles 1 are randomly selected from the extracted single crystal particles 1. Among the ten single crystal particles 1, the longest side "a", the shortest side "b", and the interior angle "θ" are measured. The average values ​​of the longest side "a", the shortest side "b", and the interior angle "θ" are taken from the ten single crystal particles 1.

[0064] In the SEM image, for 100 randomly selected single crystal particles 1, the interior angle "θ" formed by the longest side "a" and the shortest side "b" is measured. By counting the number of single crystal particles 1 that satisfy the relationship "60°≤θ≤120°", the proportion of single crystal particles 1 that satisfy the relationship "60°≤θ≤120°" is calculated.

[0065] The "003 plane" can be identified in high-angle scattering annular dark-field scanning transmission electron microscopy (HAADF-SEM) images. For example, the powder is embedded in epoxy resin. For example, the sample is prepared by thinning the powder together with the resin using methods such as argon ion milling. Figure 4 This is an explanatory diagram of HAADF-STEM analysis. First, single crystal particles 1 are sampled at low magnification. The longest side 1a of single crystal particle 1 is determined. Next, single crystal particle 1 is observed at high magnification, thereby determining the 003 plane. When the angle between the 003 plane and the longest side 1a is 0° to 30°, the longest side 1a is considered to extend along the 003 plane. In the STEM image, if the longest side 1a extends along the 003 plane in more than one of the randomly sampled single crystal particles 1, then the longest side 1a is considered to extend along the 003 plane in the entire powder.

[0066] "Edge Angle" refers to the edge angle of Lees. total "Lees's angularity" A total The determination was performed using the method described in "Lees, G.: A New Method for Determining the Angularity of Particles, Sedimentology, 3, 2-21, 1964". Figure 5 This is an explanatory diagram of the method for measuring edge angles. At one corner in the two-dimensional projection of the particle, the angle "α", the distance "x" between the corner tip and the center of the largest inscribed circle (MIC), and the radius "r" of the MIC are measured. Based on the calculation formula "A..." i = (180° - α)x / r"Calculate the angularity of the corner"A i ". All corners of A i The total is the edge angle "A" total"Edge Angle"A total "Use the average value of 10 single crystal particles1."

[0067] "D50" indicates the particle size at which the cumulative frequency reaches 50% in a volumetric particle size distribution (cumulative distribution). D50 can be determined, for example, by laser diffraction. Similarly, the particle size at which the cumulative frequency reaches 10% is also denoted as "D10", and the particle size at which the cumulative frequency reaches 90% is also denoted as "D90".

[0068] The chemical composition of a compound can be determined using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). 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 the appropriate concentration using a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES apparatus. For example, product names such as "PS3520UVDD II (manufactured by Hitachi High Technology Co., Ltd.)" can also be used.

[0069] A stoichiometric formula represents 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 can be doped into the compound. A portion of Al and O can also be replaced by other elements.

[0070] "Derivative" refers to a compound that has been altered in part by at least one of the following chemical reactions: introduction of a functional group, substitution of an atom, oxidation, reduction, and others. The alteration may occur at one or more sites. "Substituents" may include, for example, at least one of the following: alkyl, alkenyl, alkynyl, cycloalkyl, unsaturated cycloalkyl, aryl, heterocyclic, halogen (F, Cl, Br, I, etc.), OH, SH, CN, SCN, OCN, nitro, alkoxy, unsaturated alkoxy, amino, alkylamino, dialkylamino, aryloxy, acyl, alkoxycarbonyl, acyloxy, aryloxycarbonyl, acylamino, alkoxycarbonyl, aminoaryloxycarbonylamino, sulfonylamino, aminosulfonyl, carbamoyl, alkylthio, arylthio, sulfonyl, sulfinyl group, urea, phosphoramide, sulfonyl, carboxyl, oxime, sulfino group, hydrazine, imino, and silyl. These substituents can be further substituted. When there are two or more substituents, the substituents can be the same or different. Multiple substituents can combine to form a ring.

[0071] Positive active material

[0072] The positive electrode active material is used in the battery. Details of the battery will be described later. The positive electrode active material comprises powder (an aggregate of particles). The D50 of the powder 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. Alternatively, the D50 of the powder can be, for example, less than 30 μm, less than 20 μm, or less than 10 μm.

[0073] Powders contain single-crystal particles. Single-crystal particles are primary particles that exist independently and do not aggregate. Powders containing single-crystal particles can also contain polycrystalline particles. Polycrystalline particles are aggregates of primary particles. The number of primary particles constituting a polycrystalline particle can be, for example, 2 or more, 5 or more, or 10 or more. The number of primary particles constituting a polycrystalline particle can be, for example, less than 100, less than 50, less than 20, or less than 10. Polycrystalline particles can have substantially the same composition and crystal structure as single-crystal particles. In powders, the proportion of single-crystal particles to the total number of single-crystal particles and polycrystalline particles can be, for example, more than 1%, more than 5%, more than 10%, more than 20%, more than 30%, more than 40%, more than 50%, more than 60%, more than 70%, more than 80%, or more than 90%. In powder, the proportion of single crystal particles to the total number of single crystal particles and polycrystalline particles can be, for example, less than 100%, less than 90%, less than 80%, less than 70%, less than 60%, less than 50%, less than 40%, less than 30%, less than 20%, less than 10%, or less than 5%.

[0074] The positive electrode active material can be monodisperse. By containing single-crystal particles and being monodisperse, improved cycling characteristics can be expected, for example. For instance, the powder can have a span of 1 or less. "Span" refers to the value calculated using the formula "(D90-D10) / D50". A smaller span is considered to indicate a narrower particle size distribution. The span of the powder can be, for example, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less. The span of the powder can be, for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, or 0.5 or more.

[0075] The single crystal particle 1 has a polyhedral shape. For example, the shape of the single crystal particle 1 can be hexahedral, octahedral, etc. The shape of the single crystal particle 1 can also be cuboid.

[0076] Single crystal particle 1 comprises a longest side 1a and a short side 1b. The longest side 1a extends along the 003 plane. The angle between the longest side 1a and the 003 plane can be, for example, less than 25°, less than 15°, less than 10°, less than 5°, less than 3°, or less than 1°. Among 10 single crystal particles 1 randomly selected from the STEM image of the powder, the proportion of single crystal particles 1 with the longest side 1a along the 003 plane can be, for example, more than 20%, more than 30%, more than 40%, more than 50%, more than 60%, more than 70%, more than 80%, or more than 90%.

[0077] The aspect ratio "a / b" is 1.10 or higher. For example, aspect ratios "a / b" can be 1.20 or higher, 1.40 or higher, 1.60 or higher, 1.80 or higher, 2.00 or higher, 2.20 or higher, 2.40 or higher, 2.60 or higher, 2.80 or higher, 3.00 or higher, 3.20 or higher, 3.40 or higher, 3.60 or higher, 3.80 or higher, 4.00 or higher, 4.20 or higher, 4.40 or higher, 4.60 or higher, 4.80 or higher, 5.00 or higher, 5.20 or higher, 5.40 or higher, 5.60 or higher, 5.80 or higher, 6.00 or higher, 6.10 or higher, 6.20 or higher, 6.40 or higher, 6.60 or higher, 6.80 or higher, or 7.00 or higher. The aspect ratio "a / b" can be, for example, below 10.0, 9.00, 8.00, 7.00, 6.80, 6.60, 6.40, 6.20, 6.10, 6.00, 5.80, 5.60, 5.40, 5.20, 5.00, 4.80, 4.60, 4.40, 4.20, 4.00, 3.80, 3.60, 3.40, 3.20, 3.00, 2.80, 2.60, 2.40, 2.20, 2.00, 1.80, 1.60, 1.40, or 1.20. The aspect ratio "a / b" can also be between 2.00 and 6.10.

[0078] The longest side 1a can be, for example, 1.40μm or more, 1.59μm or more, 1.80μm or more, 2.00μm or more, 2.20μm or more, 2.30μm or more, 2.40μm or more, 2.60μm or more, 2.73μm or more, 2.80μm or more, 3.00μm or more, 3.20μm or more, 3.40μm or more, 3.48μm or more, 3.60μm or more, 3.80μm or more, or 4.00μm or more. The longest side 1a can be, for example, less than 6.00 μm, less than 5.00 μm, less than 4.00 μm, less than 3.80 μm, less than 3.60 μm, less than 3.48 μm, less than 3.40 μm, less than 3.20 μm, less than 3.00 μm, less than 2.80 μm, less than 2.73 μm, less than 2.60 μm, less than 2.40 μm, less than 2.30 μm, less than 2.20 μm, less than 2.00 μm, less than 1.80 μm, or less than 1.59 μm. The longest side 1a can also be, for example, between 1.59 and 3.48 μm.

[0079] The short side 1b can be 0.200μm or larger, 0.300μm or larger, 0.380μm or larger, 0.400μm or larger, 0.500μm or larger, 0.600μm or larger, 0.700μm or larger, 0.800μm or larger, 0.830μm or larger, 0.900μm or larger, 0.980μm or larger, 1.00μm or larger, 1.10μm or larger, 1.20μm or larger, 1.30μm or larger, 1.40μm or larger, 1.45μm or larger, 1.50μm or larger, 1.60μm or larger, 1.70μm or larger, 1.80μm or larger, 1.90μm or larger, or 2.00μm or larger. The short side 1b can be, for example, less than 5.00 μm, less than 4.00 μm, less than 3.00 μm, less than 2.00 μm, less than 1.90 μm, less than 1.80 μm, less than 1.70 μm, less than 1.60 μm, less than 1.50 μm, less than 1.45 μm, less than 1.40 μm, less than 1.30 μm, less than 1.20 μm, less than 1.10 μm, less than 1.00 μm, less than 0.980 μm, less than 0.900 μm, less than 0.830 μm, less than 0.800 μm, less than 0.700 μm, less than 0.600 μm, less than 0.500 μm, less than 0.400 μm, or less than 0.380 μm. The short side 1b can also be, for example, 0.380~1.45 μm.

[0080] The interior angle "θ" formed by the longest side 1a and the shortest side 1b is between 60° and 120°. For example, the interior angle "θ" can be greater than 62°, greater than 64°, greater than 66°, greater than 68°, greater than 70°, greater than 72°, greater than 74°, greater than 76°, greater than 78°, greater than 80°, greater than 82°, greater than 83°, greater than 84°, greater than 86°, greater than 87°, greater than 88°, greater than 90°, greater than 92°, greater than 94°, greater than 96°, greater than 98°, greater than 100°, greater than 102°, greater than 104°, greater than 106°, greater than 108°, greater than 110°, greater than 112°, greater than 114°, greater than 116°, or greater than 118°. An interior angle "θ" can be, for example, below 118°, below 116°, below 114°, below 112°, below 110°, below 108°, below 106°, below 104°, below 102°, below 100°, below 98°, below 96°, below 94°, below 92°, below 90°, below 88°, below 87°, below 86°, below 84°, below 83°, below 82°, below 80°, below 78°, below 76°, below 74°, below 72°, below 70°, below 68°, below 66°, below 64°, or below 62°. An interior angle "θ" can also be between 82° and 94°.

[0081] In the powder, the proportion of single crystal particles 1 that satisfy the relationship "60°≤θ≤120°" can be, for example, 21% or more. This proportion can be, for example, 25% or more, 30% or more, 34% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, 58% or more, 60% or more, 65% or more, or 70% or more. This proportion can be, for example, less than 100%, less than 90%, less than 80%, less than 70%, less than 65%, less than 58%, less than 55%, less than 50%, less than 45%, less than 40%, less than 35%, less than 30%, or less than 25%.

[0082] The edge angle of single crystal particle 1 can be, for example, 451~584. The edge angle of single crystal particle 1 can be, for example, 475 or higher, 500 or higher, 502 or higher, 525 or higher, 550 or higher, 553 or higher, or 575 or higher. The edge angle of single crystal particle 1 can be, for example, less than 575, less than 553, less than 550, less than 525, less than 502, less than 500, or less than 475. When the edge angle is 400~599, there is a tendency for the two-dimensional image of the particle to form a shape close to a rectangle. It is considered that the three-dimensional shape of the particle becomes close to a cuboid shape.

[0083] Single crystal particle 1 contains a lithium transition metal complex oxide. The lithium transition metal complex oxide has a crystal structure belonging to space group R-3m. This structure is also known as a "layered structure". The layered structure can be determined by XRD patterning.

[0084] In the XRD pattern of the positive electrode active material, the intensity of the diffraction peak corresponding to the 003 plane is "I 003 "Relative to the intensity of the diffraction peak corresponding to plane 104" 104 "ratio" I 003 / I 104 "For example, it can be greater than 2.7. This is achieved through the strength ratio"I 003 / I 104 "A value greater than 2.7, for example, suggests an improvement in cycling characteristics. Strength ratio "I 003 / I 104 "For example, it can be 2.8 or higher, 2.9 or higher, 3.0 or higher, 3.2 or higher, 3.4 or higher, 3.6 or higher, 3.8 or higher, or 4.0 or higher. Strength ratio"I 003 / I 104 "For example, it can be below 5.0, below 4.0, below 3.8, below 3.6, below 3.4, below 3.2, or below 3.0."

[0085] Lithium transition metal composite oxides comprise Li, a transition metal (TM), and oxygen. The TM contains at least Ni. That is, lithium transition metal composite oxides contain at least Ni. For example, lithium transition metal composite oxides may contain LiNiO2. Besides Ni, the TM may also contain, for example, Co, Mn, Al, etc.

[0086] Single crystal particles 1, for example, can have the properties of the general formula "Li x Ni a Co b Mn c O y The composition is indicated by "". In the general formula, the Li composition ratio "x" can, for example, satisfy the relationship "0.1≤x≤1.5". The Li composition ratio "x" can, for example, be 0.4 or higher, 0.6 or higher, 0.8 or higher, 1.0 or higher, 1.2 or higher, or 1.4 or higher. The Li composition ratio "x" can, for example, be less than 1.4 or less than 1.2.

[0087] In the above general formula, the ratio "y" of component O can, for example, satisfy the relationship "1.5≤y≤2.1". The ratio "y" of component O can, for example, be 1.6 or higher, 1.7 or higher, 1.8 or higher, 1.9 or higher, or 2.0 or higher. The ratio "y" of component O can, for example, be less than 2.0, less than 1.9, less than 1.8, less than 1.7, or less than 1.6.

[0088] In the above general formula, the Ni composition ratio "a", the Co composition ratio "b", and the Mn composition ratio "c" can satisfy the relationship "a + b + c = 1.0". The Ni composition ratio "a" can, for example, satisfy the relationship "0.5 ≤ a ≤ 1.0". The Ni composition ratio "a" can, for example, be 0.6 or higher, 0.7 or higher, 0.8 or higher, or 0.9 or higher. The Ni composition ratio "a" can, for example, be 0.9 or lower, 0.8 or lower, 0.7 or lower, or 0.6 or lower.

[0089] In the above general formula, the Co composition ratio "b" can, for example, satisfy the relationship "0 ≤ b ≤ 0.3". The Co composition ratio "b" can, for example, be 0.01 or higher, 0.02 or higher, 0.03 or higher, 0.04 or higher, 0.05 or higher, 0.06 or higher, 0.07 or higher, 0.08 or higher, 0.09 or higher, 0.10 or higher, 0.15 or higher, 0.20 or higher, or 0.25 or higher. The Co composition ratio "b" can, for example, be less than 0.25, less than 0.20, less than 0.15, less than 0.10, less than 0.09, less than 0.08, less than 0.07, less than 0.06, less than 0.05, less than 0.04, less than 0.03, less than 0.02, or less than 0.01.

[0090] In the above general formula, the composition ratio "c" of Mn can, for example, satisfy the relationship "0 ≤ c ≤ 0.3". The composition ratio "c" of Mn can, for example, be 0.01 or higher, 0.02 or higher, 0.03 or higher, 0.04 or higher, 0.05 or higher, 0.06 or higher, 0.07 or higher, 0.08 or higher, 0.09 or higher, 0.10 or higher, 0.15 or higher, 0.20 or higher, or 0.25 or higher. The composition ratio "c" of Mn can, for example, be less than 0.25, less than 0.20, less than 0.15, less than 0.10, less than 0.09, less than 0.08, less than 0.07, less than 0.06, less than 0.05, less than 0.04, less than 0.03, less than 0.02, or less than 0.01.

[0091] Furthermore, in the above general formula, all or part of Mn can also be replaced by Al, etc. That is, lithium transition metal composite oxides can, for example, have the general formula "Li x Ni a Co b Al c O y The composition indicated by "c". The range of the Al composition ratio "c" is the same as that of the Mn composition ratio "c" mentioned above.

[0092] Any dopant can be added to the lithium transition metal composite oxide. The dopant refers to an element other than Li, Ni, Co, Mn, and O. For example, the dopant may contain at least one element selected from Zr, Mo, W, Mg, Ca, Na, Fe, Cr, Zn, Si, Sn, Al, and Ag. The dopant composition ratio can, for example, be 0.005 or more, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more. Alternatively, the dopant composition ratio can, for example, be less than 0.05, less than 0.04, less than 0.03, less than 0.02, or less than 0.01.

[0093] The positive electrode active material, in addition to containing lithium transition metal composite oxide, may also contain other components. The mixing ratio (mass ratio) of the lithium transition metal composite oxide and other components can be, for example, "lithium transition metal composite oxide / other components = 9 / 1 to 1 / 9", "lithium transition metal composite oxide / other components = 8 / 2 to 2 / 8", "lithium transition metal composite oxide / other components = 7 / 3 to 3 / 7", or "lithium transition metal composite oxide / other components = 6 / 4 to 4 / 6". The positive electrode active material can be, for example, a mixture of lithium transition metal composite oxide powder and powders of other components. Other components may include, for example, at least one selected from lithium iron phosphate (olivine structure), lithium manganese phosphate (olivine structure), lithium manganese iron phosphate (olivine structure), LiMnO2 (rock salt structure), Li(NiMn)2O4 (spinel structure), and LiCoO2 (layered structure). Other components can be single-crystal particles or polycrystalline particles.

[0094] Lithium-ion secondary batteries

[0095] Liquid batteries

[0096] In some embodiments, the battery may be a liquid-based battery. "Liquid-based battery" refers to a battery containing an electrolyte. For example, polymer batteries contain an electrolyte and are therefore liquid-based batteries. In some embodiments, the battery has a unipolar structure. In a unipolar structure, the power generation element may be wound or stacked. In some embodiments, the battery has a bipolar structure. As an example, a battery with a bipolar structure (bipolar battery) will be described.

[0097] Figure 6 This is a schematic perspective view of the lithium-ion secondary battery according to this embodiment. Figure 7 It is along Figure 6 A schematic cross-sectional view of line VII-VII. Hereinafter, "plane-perpendicular direction" refers to the normal direction relative to the surface of the sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction orthogonal to the plane-perpendicular direction. In the figures of this embodiment, the Z-axis direction corresponds to the plane-perpendicular direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0098] The battery 100 includes an outer casing 90 and a power generation element 50. The outer casing 90 houses the power generation element 50. The outer casing 90 may also include, for example, 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. At the joint between the first laminate 92 and the second laminate 93, a sealing material (not shown) may also be placed between the first laminate 92 and the second laminate 93.

[0099] The first collector plate 91 and the second collector plate 94 are joined to the power generation element 50 at their ends in the lamination direction (Z-axis direction). A first laminate 92 is joined to the first collector plate 91. A second laminate 93 is joined to the second collector plate 94. At the junction of the collector plate and the laminate, a sealing material (not shown) may also be placed between the collector plate and the laminate.

[0100] The power generation element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in a plane-perpendicular direction (Z-axis direction). Each of the plurality of bipolar electrodes 10 sequentially includes a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in the plane-perpendicular direction. 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 throughout the entire in-plane direction compared to the positive electrode layer 11 and the negative electrode layer 12.

[0101] The current collector foil 13 is a conductor. The current collector foil 13 may include, for example, a metal foil, a conductive resin layer, etc. For example, the current collector foil 13 can also be formed by bonding Al foil and 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.

[0102] The power generation element 50 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 heat-fused to the current collector foil 13, for example. Alternatively, the sealing material 30 may be disposed along the entire periphery in the in-plane direction. The sealing material 30 may also contain, for example, a resin material. The sealing material 30 seals adjacent current collector foils 13 in the perpendicular direction between the planes. By sealing the current collector foils 13 with the sealing material 30, units 40 are defined. Unit 40 is the smallest unit of the power generation element 50. The battery 100 includes multiple units 40 and is therefore also referred to as a "bipolar module." The multiple units 40 are individually sealed. The multiple units 40 are isolated from each other. Each of the multiple units 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0103] Positive electrode layer

[0104] A positive electrode layer 11 is attached to one side of the current 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 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.

[0105] In addition to the positive electrode active material, the positive electrode layer 11 may also include, for example, conductive materials and binders. The amount of conductive material relative to 100 parts by mass of the positive electrode active material may be, for example, 0.1 to 10 parts by mass. The conductive material may contain optional components. For example, the conductive material may contain at least one selected from graphite, acetylene black (AB), Ketjen black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene sheets (GF).

[0106] 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 may contain optional components. For example, the binder may contain at least one selected from 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.

[0107] The positive electrode layer 11 may also contain, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode active material layer may contain, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, silane coupling agent, MoS2, WO3, etc.

[0108] Negative electrode layer

[0109] 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 area of the negative electrode layer 12 may be larger than that of the positive electrode layer 11. The negative electrode layer 12 contains a negative electrode active material.

[0110] The negative electrode active material may be, for example, particulate or flaky. The D50 of the negative electrode active material may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material may be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0111] The negative electrode active material may contain optional components. The negative electrode active material may contain, for example, at least one selected from carbon-based active materials, alloy-based active materials, Si-C composites, Li metal, Li-based alloys, and lithium titanate. In some embodiments of the present invention, the battery may also be a Li metal negative electrode battery.

[0112] The carbon-based active material may contain, for example, at least one selected from graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may also 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".

[0113] The surface of the graphite may be covered with amorphous carbon, for example. The surface of the graphite may also be covered with a foreign material. The foreign material may contain, for example, at least one selected from P, W, Al, and O. The foreign material may contain, for example, at least one selected from Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0114] The alloy-based active material may contain, for example, at least one selected from Si, lithium silicate, SiO, Si-based alloys, tin (Sn), SnO, and Sn-based alloys.

[0115] SiO may have, for example, a composition represented by the general formula "SiO x ". In the general formula, the relationship "0 < x < 2", "0.5 ≤ x ≤ 1.5", or "0.8 ≤ x ≤ 1.2" may be satisfied, for example.

[0116] "Si-C composite material" refers to a composite material of carbon-based active materials (such as graphite) and alloy-based active materials (such as Si). For example, Si particles may be dispersed within carbon particles. For example, Si particles may be dispersed within graphite particles. For example, Li silicate particles may be covered by carbon materials (such as amorphous carbon).

[0117] diaphragm

[0118] The separator 20 is capable of separating the positive electrode layer 11 from the negative electrode layer 12. The separator 20 is electrically insulating. The separator 20 may contain at least one selected from, for example, a resin membrane (polymer membrane), an inorganic particle layer, and an organic particle layer. The separator 20 may contain, for example, a resin membrane and an inorganic particle layer.

[0119] The resin membrane is porous. It can include, for example, microporous membranes or nonwoven fabrics. The resin membrane comprises a resin backbone, which can be, for example, a continuous network. Fine pores are formed in the gaps between the resin backbone. The resin membrane allows electrolyte to permeate. The average pore size of the resin membrane can be, for example, less than 1 μm. The average pore size of the resin membrane can be, for example, 0.01~1 μm or 0.1~0.5 μm. The "average pore size" can be determined by mercury porosimetry. The Gurley value of the resin membrane can be, for example, 50~250 s / 100 cm⁻¹. 3 The "Gerley value" can be determined using the Gerley test method.

[0120] The resin membrane may contain at least one selected from, for example, olefin-based resins, polyurethane-based resins, polyamide-based resins, cellulose-based resins, polyether-based resins, acrylic resins, and polyester-based resins. The resin membrane may also contain at least one selected from, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamides, polyphenylene ether (PPE), and their derivatives. The resin membrane can be formed by, for example, stretching or phase separation. The thickness of the resin membrane may be, for example, 5-50 μm or 10-25 μm.

[0121] The resin membrane can have, for example, a single-layer structure. The resin membrane can be composed of, for example, 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, for example, a multi-layer structure. The resin membrane can include, for example, a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin membrane can also have, for example, a three-layer structure. The resin membrane can be formed by, for example, sequentially stacking a PP layer, a PE layer, and another PP layer. The thickness of the PE layer can, for example, be 5~20 μm. The thickness of the PP layer can, for example, be 3~10 μm.

[0122] The inorganic particle layer can 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.

[0123] The inorganic particle layer is porous. It contains inorganic particles, which can also be referred to as "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, for example, 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 oxide, magnesium oxide, and silicon oxide. The inorganic particles can have any shape. They can be, for example, 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 an adhesive. The adhesive may contain, for example, at least one selected from acrylic resins, polyamide resins, fluorinated resins, aromatic polyether resins, and liquid crystal polyester resins.

[0124] The membrane 20 may include, for example, an organic particle layer. The membrane 20 may also include, for example, an organic particle layer instead of a resin membrane. The membrane 20 may include, for example, an organic particle layer instead of an inorganic particle layer. The membrane 20 may also simultaneously include a resin membrane and an organic particle layer. The membrane 20 may also simultaneously include an inorganic particle layer and an organic particle layer. The membrane 20 may also include a resin membrane, an inorganic particle layer, and an organic particle layer.

[0125] 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.

[0126] The membrane 20 may also include, for example, a hybrid layer. The hybrid layer contains both inorganic and organic particles.

[0127] electrolyte

[0128] The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute can be, 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. "mol / L" is sometimes expressed as "M". The solute contains a supporting electrolyte (Li salt). The solute can contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute can contain, for example, at least one 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.

[0129] The electrolyte may contain, for example, a carbonate-based solvent or a carbonate-ester-based solvent. The solvent may contain, for example, cyclic carbonates, chain carbonates, fluorinated carbonates, etc. The solvent may contain, for example, at least one selected from 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, fluoropropylene carbonate, difluoropropylene carbonate, and their derivatives.

[0130] 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 and 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".

[0131] The solvent may contain cyclic carbonates (EC, PC, etc.) and fluorinated cyclic carbonates (FEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates and fluorinated cyclic carbonates may be, for example, "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1~90 / 10", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1~1 / 9", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1~7 / 3" or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7~1 / 9".

[0132] Solvents may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component can satisfy, for example, the relationship "V EC +V FEC +V EMC +V DMC +V DEC =10" represents a relation. In the relation expression, "V" represents a relationship. EC V FEC V EMC V DMC V DEC "Represent the volume ratios of EC, FEC, EMC, DMC, and DEC, respectively. Satisfying "1 ≤ V EC ≤4", "0≤V" FEC ≤3", "V EC +V FEC ≤4", "0≤V" EMC ≤9", "0≤V" DMC ≤9", "0≤V" DEC ≤9", "6≤V" EMC +V DMC +V DEC The relationship ≤ 9. For example, it can also satisfy "1 ≤ V". EC ≤2" or "2≤V" EC The relationship is "≤3". For example, it can also satisfy "1≤V". FEC ≤2" or "2≤V" FEC The relationship is ≤4. For example, it can also satisfy "3≤V". EMC ≤4" or "6≤V" EMC The relationship is ≤8. For example, it can also satisfy "3≤V". DMC ≤4" or "6≤V" DMC The relationship is ≤8. For example, it can also satisfy "3≤V". DEC ≤4" or "6≤V" DEC The relationship is ≤8".

[0133] The solvent may have, for example, 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", "EC / FEC / DMC / EMC=1 / 2 / 3 / 4", etc.

[0134] The electrolyte may contain ether-based solvents. The electrolyte may contain, for example, solvents selected from tetrahydrofuran (THF), 1,4-dihydrofuran, etc. At least one of the following: alkylene (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and their derivatives.

[0135] The electrolyte may contain optional additives. The amount added (relative to the total mass fraction 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 interface) formation promoters, SEI formation inhibitors, gas generators, overcharge preventers, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0136] Additives may include, for example, those selected from vinylene carbonate (VC), ethylene ethylene carbonate (VEC), 1,3-propanesulfonate lactone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfide (ES), ethylene sulfide (DTD), γ-butyrolactone, phosphazene compounds, and carboxylic acid esters (e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DE)). 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.), and fluorotoluenes (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, etc.). -Difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), trifluorotoluene (e.g., trifluorotoluene, 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.), The following are included in the list of 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 their derivatives.

[0137] The components described above as solutes and solvents can be used as trace components (additives). Additives may contain at least one selected from, for example, LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and their derivatives.

[0138] Electrolytes may also contain ionic liquids. Ionic liquids may also contain, for example, salts selected from sulfonium salts, ammonium salts, pyridinium salts, piperidine salts, pyrrolidine salts, morpholine salts, etc. Salt, imidazole At least one of salts and their derivatives.

[0139] In some embodiments of this invention, the battery may comprise a gel electrolyte. That is, the battery may 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, for example, at least one selected from PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0140] All-solid-state batteries

[0141] In some embodiments, the battery may be an all-solid-state battery. An all-solid-state battery may have a bipolar structure. An all-solid-state battery includes a solid electrolyte in place of the electrolyte and separator 20. The solid electrolyte may also be included in the positive electrode layer 11 and the negative electrode layer 12. The 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.

[0142] Solid electrolytes can also 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.

[0143] 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.

[0144] The sulfide solid electrolyte may contain at least one selected from amorphous phases, crystalline phases, and glass-ceramic (crystalline glass) phases. The crystalline phase may be, for example, argillite-germanium sulfide or LGPS type. The sulfide solid electrolyte contains Li and sulfur (S). In addition to Li and S, the sulfide solid electrolyte may also contain optional components.

[0145] Sulfide solid electrolytes may contain, 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.

[0146] 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 be produced, for example, by a mechanochemical method. 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)".

[0147] Sulfide solid electrolytes can have compositions, for example, represented by the general formula "xLi₂S-(1-x)P₂S₅". In this formula, "x" can be greater than 0, or greater than 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, or 0.9. "x" can also be less than 1, less than 0.9, less than 0.8, less than 0.7, less than 0.75, 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 a composition of Li₃PS₄.

[0148] The sulfide solid electrolyte can have a composition, for example, represented by the general formula "yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5]". In the general formula, "x" can be, for example, 0.5 or more, 0.6 or more, 0.7 or more, 0.75 or more, 0.8 or more, or 0.9 or more. "x" can be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.75 or less, 0.7 or less, or 0.6 or less. "y" can be, for example, 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. "y" can be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. "z" can be, for example, 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. "z" can be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0149] Sulfide solid electrolytes can have, for example, properties derived from the general formula "Li". 7-x-2y PS 6-x-y X y The composition is represented by the formula. In the general formula, the relationships "0 < 7-x-2y", "0 < 6-xy", "0 ≤ x", and "0 ≤ y" are satisfied. "X" may contain at least one of, for example, fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0150] Sulfide solid electrolytes can have, for example, properties derived from the general formula "Li". 4-x M 1-x P x The composition represented by "S4". In the general formula, "x" can be 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 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 contain at least one of, for example, selected from Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0151] Sulfide solid electrolytes can have, for example, properties derived from the general formula "Li". 10+x Ge 1+x P 2-x S 12 The composition is indicated by the formula. 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 be, for example, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. The sulfide solid electrolyte represented by the above general formula may contain, for example, a crystalline phase of the LGPS type.

[0152] Halogenated solid electrolytes can have, for example, properties derived from the general formula "Li". 6-na M a The composition represented by "X6" is as follows. In the general formula, "n" represents the oxidation number of "M". For example, "M" may contain atoms with an oxidation number of +3. For example, "M" may contain atoms with an oxidation number of +4. For example, "M" may contain at least one selected from Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship "0 < a < 2" may also be satisfied. "X" may contain at least one selected from, for example, F, Cl, Br, and I.

[0153] Halogenated solid electrolytes can have, for example, properties derived from the general formula "Li". 3-a Ti a Al 1-a F6 represents the composition. 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, 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.

[0154] Halogen solid electrolytes can have, for example, properties derived from the general formula "Li3YCl". a Br b I 6-a-b The formula represents the composition of a given expression. In this expression, a relationship such as "0 ≤ a + b ≤ 6" can be satisfied. "a" can be 0 or higher, 1 or higher, 2 or higher, 3 or higher, 4 or higher, or 5 or higher. "a" can also be 6 or lower, 5 or lower, 4 or lower, 3 or lower, 2 or lower, or 1 or lower. "b" can be 0 or higher, 1 or higher, 2 or higher, 3 or higher, 4 or higher, or 5 or higher. "b" can also be 6 or lower, 5 or lower, 4 or lower, 3 or lower, 2 or lower, or 1 or lower.

[0155] Oxide solid electrolytes may contain, for example, those selected from LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 At least one of the following. Hydride solid electrolytes may contain, for example, LiBH4. Nitride solid electrolytes may contain, for example, Li3N, Li3BN2, etc.

[0156] Example

[0157] Sample preparation

[0158] Figure 8 This is a table showing the experimental results. The positive electrode active materials (LiNi) No. 1 to No. 6 were manufactured in the following order. 0.90 Co 0.05 Mn 0.05 O2).

[0159] Preparation of raw material liquid

[0160] The feed solution was prepared by dissolving NiSO4, CoSO4, and MnSO4 in ion-exchange water. The ratio of NiSO4, CoSO4, and MnSO4 was adjusted to "Ni / Co / Mn = 90 / 5 / 5 (molar ratio)". The molar concentration of the feed solution was 0.2%.

[0161] Hydrothermal synthesis

[0162] A predetermined amount of NH3 aqueous solution is added to the reaction vessel. Nitrogen purging is performed while stirring the reaction vessel. The pH of the aqueous solution is adjusted to alkaline by adding NaOH to the reaction vessel. While maintaining the temperature and pH of the aqueous solution within a certain range (essentially a constant value), the raw material solution is added dropwise, thereby forming a precipitate of TM hydroxide. The precipitate is then dehydrated and pre-calcined. The pre-calcination temperature is 120℃~220℃. The pre-calcination time is 4 hours~10 hours. The pre-calcination pressure is 0.2MPa~1.0MPa.

[0163] Precursor recycling

[0164] After pre-calcination, the precipitate is washed with water. The residue (TM hydroxide) is recovered by filtration. Moisture is removed by drying the TM hydroxide at 110°C for 12 hours. Through these steps, the precursor (TM hydroxide) is prepared.

[0165] Li raw material mixing

[0166] The mixture is prepared by mixing a precursor (TM hydroxide) and lithium compounds (LiOH, Li₂CO₃, etc.). In this experiment, the ratio of the amount of Li to the total amount of the transition metal (TM), "Li / TM", is adjusted to be greater than 1. As a result, during calcination, the excess lithium compound forms a molten salt (flux), thereby promoting the monocrystallization of the positive electrode active material.

[0167] Firing

[0168] The mixture is subjected to heat treatment (firing). Firing can be carried out, for example, in a muffle furnace. The firing atmosphere can also be, for example, an oxygen atmosphere.

[0169] Stage 1 firing

[0170] Figure 9This is the first firing curve. The firing processes in No. 1 and No. 2 are shown in the first firing curve. The mixture is prepared by mixing the precursor and lithium compound in a "Li / TM=2.0" ratio. The mixture is placed in a firing furnace. The furnace temperature is raised to Y℃, which is in the range of 800℃ to 1100℃. Y℃ is maintained for a predetermined time. The holding time at Y℃ is 5 to 15 hours. After the predetermined time, the furnace temperature is cooled to room temperature. Through the above steps, the positive electrode active material is synthesized.

[0171] 4-stage firing

[0172] Figure 10 This is the second firing curve. The firing processes for No. 3 to No. 6 are shown in the second firing curve. First, a mixture is prepared by mixing the precursor and lithium compound in a ratio of "Li / TM = 1.0". The mixture is placed in a firing furnace. The furnace temperature is raised to X-300°C. X-300°C is maintained for a predetermined time. After the predetermined time, lithium compound is added to the mixture in a ratio of "Li / TM = 1.3". After adding the lithium compound, the furnace temperature is raised to X-200°C. X-200°C is maintained for a predetermined time. After the predetermined time, lithium compound is added to the mixture in a ratio of "Li / TM = 1.6". After adding the lithium compound, the furnace temperature is raised to X-100°C. X-100°C is maintained for a predetermined time. After the predetermined time, lithium compound is added to the mixture in a ratio of "Li / TM = 1.9". After adding the lithium compound, the furnace temperature is raised to X°C, which is within the range of 800°C to 1100°C. This temperature is maintained at X°C for a predetermined time. After the predetermined time, the furnace temperature is cooled to room temperature. The total maintenance time at each temperature is 5 to 15 hours. The maintenance time at each temperature is the same. Through the above steps, the positive electrode active material is synthesized.

[0173] After firing, the positive electrode active material is crushed in an agate mortar until the particle size is below 0.2 mm. A slurry is formed by dispersing the positive electrode active material in 500 mL of pure water. The slurry is vigorously stirred for 1 minute. The slurry is filtered using filter paper and a Buchner funnel. The residue is washed with 500 mL of pure water, thus forming a filter cake. The filter cake is vacuum dried at 90°C. After drying, the filter cake is crushed in an agate mortar, thereby adjusting it to the predetermined particle size. For example, a laboratory grinder or other mill can be used instead of an agate mortar.

[0174] Furthermore, the flux can be completely removed by water washing after firing, or a portion may remain. The mass ratio of the residual flux to the positive electrode active material can be, for example, 0.100 or less, 0.050 or less, 0.040 or less, 0.030 or less, 0.020 or less, 0.010 or less, 0.005 or less, 0.003 or less, or 0.001 or less. The mass ratio of the residual flux to the positive electrode active material can be, for example, 0 or more, 0.001 or more, 0.003 or more, 0.005 or more, 0.010 or more, 0.020 or more, 0.030 or more, 0.040 or more, or 0.050 or more. The residual flux may, for example, contain at least one selected from Li₂CO₃ and LiHCO₃.

[0175] evaluate

[0176] Prepare the laminated unit. A laminated unit refers to a unit containing a power-generating element housed in a flexible package made of Al laminated film. The power-generating element is constructed as described below.

[0177] Positive electrode: Positive electrode active material, conductive material (acetylene black)

[0178] Negative electrode: Active material for negative electrode (natural graphite)

[0179] Electrolytes: LiPF6 (1 mol / L), EC / DMC / EMC = 3 / 4 / 3 (volume ratio)

[0180] The positive and negative electrodes are manufactured by coating a slurry onto the surface of a substrate (metal foil). For example, a film coater (with film thickness adjustment function) manufactured by All Good can be used as the coating device. After coating, the film is dried at 80°C for 5 minutes.

[0181] In the laminated unit, a cyclic test was performed under the following conditions.

[0182] Ambient temperature: 60℃

[0183] Number of cycles: 50

[0184] Current ratio: 0.3C

[0185] Voltage range: 4.25V to 2.5V

[0186] At a current rate of 1C, the rated capacity of the cell is measured over 1 hour. 0.3C is 0.3 times that of 1C. The capacity retention rate is calculated by dividing the discharge capacity of the 50th cycle by the discharge capacity of the 1st cycle. A higher capacity retention rate is considered to indicate better cycle characteristics.

[0187] Experimental results

[0188] exist Figure 8When the relationships "1.10≤a / b" and "60°≤θ≤120°" are satisfied, an improvement in the cycle characteristics can be observed.

[0189] When the relationship "2.00≤a / b≤6.10" is satisfied, an improvement in the cyclic properties can be observed.

[0190] When the relationship "82°≤θ≤94°" is satisfied, an improvement in cycle characteristics can be observed.

[0191] Satisfying "451≤A total When the relationship is ≤584", a tendency to improve the cycle characteristics can be observed.

[0192] When the proportion of single-crystal particles satisfying the relationship "60°≤θ≤120°" is above 21%, an improvement in cycle characteristics can be observed.

[0193] When the relationships "1.59μm≤a≤3.48μm" and "0.377μm≤b≤1.45μm" are satisfied, an improvement in cycle performance can be observed.

Claims

1. A positive electrode active material, characterized in that, It contains powder, wherein the powder comprises single-crystal particles. The single-crystal particles contain lithium transition metal composite oxides; The lithium transition metal composite oxide has a crystal structure belonging to space group R-3m; The lithium transition metal composite oxide contains at least nickel; In the scanning electron microscope image of the powder, the single crystal particle is an independent and non-aggregated single particle; The single crystal particles are polyhedral in shape; The single crystal particle contains a longest side and a short side; The longest side extends along face 003; The shorter side is connected to the end of the longest side; The interior angle formed by the longest side and the shortest side is 60°~120°; and The ratio of the longest side to the shortest side is 1.10 or higher.

2. The positive electrode active material according to claim 1, characterized in that, The ratio of the longest side to the shortest side is greater than 2.00 and less than 6.

10.

3. The positive electrode active material according to claim 1 or 2, characterized in that, The interior angle is 82°~94°.

4. The positive electrode active material according to claim 1 or 2, characterized in that, The edge angle of the single crystal particles is 451~584.

5. The positive electrode active material according to claim 1 or 2, characterized in that, In the powder, the proportion of single crystal particles with an inner angle of 60° to 120° is more than 21%.

6. The positive electrode active material according to claim 1 or 2, characterized in that, The longest side is 1.59~3.48μm, and, The short side has a diameter of 0.377~1.45μm.

7. The positive electrode active material according to claim 1 or 2, characterized in that, The single-crystal particles have the characteristics represented by the following general formula. composition: Li x Ni a Co b Mr c O y , In the general formula, x, a, b, c, and y satisfy the relationships 0.1≤x≤1.5, 0.5≤a≤1.0, 0≤b≤0.3, 0≤c≤0.3, a+b+c=1.0 and 1.5≤y≤2.

1.

8. An electrode, characterized in that, Includes a positive electrode layer. The positive electrode layer comprises the positive electrode active material as described in claim 1 or 2.

9. A lithium-ion secondary battery, characterized in that, It includes the electrode as described in claim 8.

10. The lithium-ion secondary battery according to claim 9, characterized in that, The lithium-ion secondary battery has a bipolar structure.

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