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

Abstract

Improved cycle characteristics. [Solution] The positive electrode active material includes powder. The powder includes single crystal particles. The single crystal particles include lithium transition metal composite oxide. The lithium transition metal composite oxide has a crystal structure assigned to space group R-3m. The lithium transition metal composite oxide contains at least nickel. In scanning electron microscope images of the powder, the single crystal particles are not aggregated and are independent particles. The single crystal particles are polyhedral. The single crystal particles include 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 between 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.

Description

Technical Field

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

Background Art

[0002] Japanese Patent Application Laid-Open No. 2022-064294 discloses synthesizing single particles by the flux method.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Single crystal type positive electrode active materials have been proposed. The positive electrode active material may include a lithium transition metal composite oxide. The lithium transition metal composite oxide may have a crystal structure (layered structure) belonging to R-3m. The layered structure is formed by alternately stacking 3a sites (Li layers) and 3b sites (transition metal layers). By including nickel (Ni) ions in the 3b sites, for example, an increase in discharge capacity is expected.

[0005] During charging, Li ions are extracted from the Li layer. Due to the extraction of Li ions, the Li layer may contract in the stacking direction (c-axis direction). When the Li layer contracts, an exchange phenomenon between the Li ions in the Li layer and the Ni ions in the transition metal layer may occur. This phenomenon is also referred to as "cation mixing". Due to the occurrence of cation mixing, a part of the layered structure may change to a rock salt structure. Due to the irreversible structural change, the discharge capacity may decrease. In the single crystal type positive electrode active material, it is considered that the influence of the structural change is large. It is considered that the capacity degradation accompanying the structural change progresses due to repeated charge and discharge.

[0006] The purpose of this disclosure is to improve cycle characteristics. [Means for solving the problem]

[0007] The technical configuration and effects of this disclosure are described below. However, the mechanism of action includes assumptions. The mechanism of action does not limit the technical scope of this disclosure.

[0008] 1. One aspect of this disclosure is a positive electrode active material. The positive electrode active material comprises a powder. The powder comprises single crystal particles. The single crystal particles comprise a lithium transition metal composite oxide. The lithium transition metal composite oxide has a crystalline structure assigned to space group R-3m. The lithium transition metal composite oxide comprises at least nickel. In scanning electron microscope images of the powder, the single crystal particles are not aggregated and are independent particles. The single crystal particles are polyhedral. The single crystal particles have 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 between 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.

[0009] Hereafter, the ratio of the longest side "a" to the shortest side "b", "a / b", is also referred to as the "aspect ratio". Figure 1 is the first conceptual diagram showing the relationship between particle shape and crystal structure. Conventionally, single crystal particles have a shape with a small aspect ratio. That is, the aspect ratio is less than 1.10. The 3a site (Li layer) extends along the 003 plane. During charging, Li ions are extracted from the Li layer. In a shape with a small aspect ratio, the extension of the Li layer in the direction along the 003 plane is small. Therefore, it is thought that the desorption of Li ions from the Li layer can proceed rapidly. It is thought that the Li layer rapidly contracts when it falls into a Li ion depletion state. The rapid contraction of the Li layer is thought to be the trigger for cation mixing.

[0010] Figure 2 is a second conceptual diagram showing 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, the Li layer is considered to be much more extensive than in the conventional design (Figure 1). Because the Li layer is wider in the direction along the 003 plane, the desorption of Li ions from the Li layer is thought to proceed relatively slowly. The Li ions remaining in the Li layer are thought to function as pillars, thereby mitigating the contraction of the Li layer. Therefore, improved cycle characteristics are expected due to reduced cation mixing.

[0011] 2. The positive electrode active material described in "1" above may include, for example, the following configuration: The ratio of the longest side to the shortest side is 2.00 or more and 6.10 or less.

[0012] When the aspect ratio is between 2.00 and 6.10, an improvement in cycle characteristics can be expected.

[0013] 3. The positive electrode active material described in "1" or "2" above may include, for example, the following configuration: an interior angle of 82° or more and 94° or less.

[0014] When the interior angle is between 82° and 94°, an improvement in cycle characteristics can be expected.

[0015] 4. The positive electrode active material described in any one of items "1" to "3" above may include, for example, the following configuration: The angularity of the single crystal grains is 451 to 584.

[0016] When the angularity is between 451 and 584, an improvement in cycle characteristics can be expected.

[0017] 5. The positive electrode active material described in any one of items "1" to "4" above may include, for example, the following composition: In the powder, the number proportion of single crystal particles with an internal angle of 60° to 120° is 21% or more.

[0018] The powder may contain single crystal particles of other shapes, as long as it contains single crystal particles having the shape described in "1" above. When the number proportion of single crystal particles having the shape described in "1" above in the powder is 21% or more, an improvement in cycle characteristics can be expected.

[0019] 6. The positive electrode active material described in any one of items "1" to "5" above may include, for example, the following configuration: The longest side is 1.59 μm to 3.48 μm, and the shortest side is 0.377 μm to 1.45 μm.

[0020] When the longest side is between 1.59 μm and 3.48 μm, and the shortest side is between 0.377 μm and 1.45 μm, an improvement in cycle characteristics can be expected.

[0021] 7. The positive electrode active material described in any one of items "1" to "6" above may include, for example, the following configuration: Single crystal particles of the general formula "Li x Ni a Co b Mn c O y It has the composition represented by the formula. In the general formula, "x, a, b, c, y" satisfy the following 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".

[0022] The 3b site may contain other elements in addition to Ni. For example, the 3b site may further 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.

[0023] 8. One aspect of the present disclosure is an electrode. The electrode includes a positive electrode layer. The positive electrode layer includes a positive electrode active material as described in any one of the above items "1" to "7".

[0024] The positive electrode layer can be referred to as the "positive electrode active material layer," "positive electrode composite material layer," etc. The "electrode" may be a "monopolar electrode (positive electrode)" or a "bipolar electrode," as long as it includes the positive electrode layer.

[0025] 9. One aspect of this disclosure is a lithium-ion secondary battery. The lithium-ion secondary battery includes the electrodes described in "8" above. Hereinafter, the lithium-ion secondary battery may be abbreviated as "battery".

[0026] 10. The lithium-ion secondary battery described in "9" above may include, for example, the following configuration: The lithium-ion secondary battery has a bipolar structure.

[0027] A bipolar structure can be formed by stacking bipolar electrodes. This bipolar structure is expected to improve, for example, output characteristics.

[0028] Hereinafter, one embodiment of the present disclosure (which may be abbreviated as "this embodiment") and one example of the present disclosure (which may be abbreviated as "this example") will be described. However, this embodiment and this example will not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are not restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from this embodiment and combined in any way. [Brief explanation of the drawing]

[0029] [Figure 1] This is the first conceptual diagram showing the relationship between particle shape and crystal structure. [Figure 2] This is the second conceptual diagram showing the relationship between particle shape and crystal structure. [Figure 3] This is a conceptual diagram of single crystal particles in this embodiment. [Figure 4] This is an explanatory diagram of HAADF-STEM analysis. [Figure 5] This is an explanatory diagram of the method for measuring angularity. [Figure 6] This is a schematic perspective view of the lithium-ion secondary battery in this embodiment. [Figure 7]This is a schematic cross-sectional view along the line VII-VII in Figure 6. [Figure 8] This is a table showing the experimental results. [Figure 9] This is the first firing profile. [Figure 10] This is the second firing profile. [Modes for carrying out the invention]

[0030] Terms, phrases "Equipped with," "includes," "possesses," and variations thereof are open-ended expressions. Configurations expressed in an open-ended manner may or may not include additional elements in addition to the essential elements. The statement "consists of" is a closed expression. However, even configurations expressed in a closed manner may include additional elements that are usually incidental impurities or irrelevant to the subject technology. The statement "substantially consists of..." is a semi-closed expression. In configurations expressed in a semi-closed manner, the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology is permitted.

[0031] Expressions such as "may do" and "may be" are used in a permissive sense, meaning "there is a possibility," rather than in an obligatory sense, meaning "it must be done."

[0032] Geometric terms should not be interpreted strictly. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For example, direction, angle, distance, etc., may be relatively distorted within a range where substantially the same or similar function is obtained. Geometric terms may include tolerances, errors, etc., in design, operation, and manufacturing. Dimensional relationships in each figure may not match actual dimensional relationships. Dimensional relationships in each figure may be modified to aid the reader's understanding. For example, length, width, thickness, etc., may be changed. Some components may be omitted.

[0033] Elements described in the singular form may also include plural forms unless otherwise specified. For example, "particle" may refer to multiple particles (groups of particles), a collection of particles, or a powder.

[0034] Numerical ranges such as "m to n%" include upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less". Also, "m% or more and n% or less" includes "greater than m% and less than n%". "Greater than or equal to" and "less than or equal to" are represented by the equals sign inequality signs "≦" and "≧". "Greater than" and "less than" are represented by the inequality signs without an equals sign "<" and ">". A number arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a number within the numerical range with a number listed in another part of this specification, in a table, in a figure, etc.

[0035] All numerical values ​​are modified by the term "approximately." The term "approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximations that can vary depending on the application of the technology in question. All numerical values ​​may be expressed with significant figures. Unless otherwise specified, measured values ​​may be the average of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. Generally, the more measurements taken, the more reliable the average value is expected to be. Measured values ​​may be rounded to the nearest significant figure. Measured values ​​may include errors such as those associated with the detection limits of the measuring device.

[0036] The devices, software, etc., used for measuring various values ​​are merely examples. Equivalent devices may be used. If equivalent devices are used, the measurement conditions may be adjusted to suit the device.

[0037] The space group to which the crystal structure belongs is determined by the XRD (X-Ray Diffraction) pattern. The XRD pattern can be obtained by powder XRD measurement. The measurement conditions are, for example, as follows: Analysis method: Wide-angle method Measurement device: Smart Lab II (manufactured by Rigaku Corporation) Measurement angle: 10° to 120° Tube:CuKα Tube voltage: 45kV Tube current: 200mA Measurement method: Continuous method Step: 0.02 Speed: 2° / min IS:1 / 2 RS: 20mm Detection mode: 1D

[0038] Various dimensional measurements and shape analyses in scanning electron microscope (SEM) images, transmission electron microscope (TEM) images, etc., can be performed using, for example, image analysis software such as "ImageJ".

[0039] A "single-crystal particle" appears in the SEM image as a single, independent particle (primary particle) that does not appear to aggregate. Single-crystal particles appear to have no grain boundaries in the SEM image. The magnification of the SEM image may be, for example, 10,000x to 30,000x. The SEM image may also be a cross-sectional image of the powder.

[0040] Figure 3 is a conceptual diagram of a single crystal grain in this embodiment. "Longest side 1a" indicates the longest apparent side in the SEM image of the single crystal grain 1. "Short side 1b" is connected to the end of the longest side 1a. Short side 1b indicates the longest apparent side in the SEM image among the sides connected to the longest side 1a. 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. The longest side 1a and short side 1b may extend in a straight line, for example. The longest side 1a and short side 1b may be curved, for example. If the side is curved, the length of the side indicates the distance between the two ends of the side.

[0041] In the SEM image, single crystal grains 1 that satisfy the relationship "60°≦θ≦120°" for the interior angle "θ" between the longest side 1a and the shortest side 1b are extracted. Ten single crystal grains 1 are randomly selected from the extracted single crystal grains 1. For the ten single crystal grains, the longest side "a", shortest side "b", and interior angle "θ" are measured. The average values ​​of the longest side "a", shortest side "b", and interior angle "θ" from the ten single crystal grains 1 are adopted.

[0042] In the SEM image, the interior angle "θ" between the longest side "a" and the shortest side "b" is measured for 100 randomly selected single crystal grains 1. By counting the number of single crystal grains 1 that satisfy the relationship "60°≦θ≦120°", the proportion of single crystal grains 1 that satisfy the relationship "60°≦θ≦120°" is calculated.

[0043] The "003 plane" can be identified in high-angle scattering annular dark-field scanning transmission microscope (HAADF-STEM) images. For example, powder is embedded in epoxy resin. For example, a sample is prepared by thinning the powder together with the resin using a method such as argon ion milling. Figure 4 is an explanatory diagram of HAADF-STEM analysis. First, single crystal particles 1 are extracted at low magnification. The longest side 1a of the single crystal particle 1 is identified. Next, the 003 plane is identified by observing the single crystal particle 1 at high magnification. If the angle between the 003 plane and the longest side 1a is between 0° and 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 one or more of the 10 randomly extracted single crystal particles 1, the longest side 1a is considered to extend along the 003 plane in the entire powder.

[0044] "Angularity" is Lees' angularity "A total This indicates Lees' angularity "A total" is measured by the method described in "Lees, G.: A New Method for Determining the Angularity of Particles, Sedimentology, 3, 2 - 21, 1964". Figure 5 is an explanatory diagram of the method for measuring angularity. In one corner of the two-dimensional projection image of the particle, the angle "α" of the corner, the distance "x" between the tip of the corner and the center of the maximum inscribed circle (MIC), and the radius "r" of the MIC are measured. By the calculation formula "A i =(180° - α)x / r", the Angularity "A i " of the said corner is calculated. The sum of the A i of all corners is the angularity "A total ". The angularity "A total " is the average value of 10 single crystal particles 1.

[0045] "D50" indicates the particle diameter at which the cumulative frequency is 50% in the volume-based particle size distribution (cumulative distribution). D50 can be measured, for example, by the laser diffraction method. Similar to D50, the particle diameter at which the cumulative frequency is 10% is also denoted as "D10", and the particle diameter at which the cumulative frequency is 90% is also denoted as "D90".

[0046] The chemical composition of the compound can be measured by ICP - AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). A sample solution is prepared by dissolving 0.1 g of a sample (for example, the positive electrode active material) in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is diluted to an appropriate concentration with a volumetric flask. After dilution, a composition analysis is performed using an ICP - AES apparatus. For example, a product name such as "PS3520 UVDD II (manufactured by Hitachi High - Technologies Corporation)" may be used.

[0047] The stoichiometric composition formula shows a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to compounds with a molar ratio of "Al / O = 2 / 3". Unless otherwise specified, "Al2O3" refers to a compound containing Al and O in any molar ratio. For example, the compound may be doped with trace elements. Some of the Al and O may be substituted with other elements.

[0048] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of a functional group, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring.

[0049] positive electrode active material The positive electrode active material is for batteries. Details of the battery will be described later. The positive electrode active material includes powder (an aggregate of particles). The D50 of the powder may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, or 15 μm or more. The D50 of the powder may also be, for example, 30 μm or less, 20 μm or less, or 10 μm or less.

[0050] The powder contains single-crystal particles. Single-crystal particles are primary particles that exist individually and do not aggregate. The powder may also contain polycrystalline particles, as long as it contains single-crystal particles. Polycrystalline particles are aggregates of primary particles. The number of primary particles constituting a polycrystalline particle may be, for example, 2 or more, 5 or more, or 10 or more. The number of primary particles constituting a polycrystalline particle may be, for example, 100 or less, 50 or less, 20 or less, or 10 or less. Polycrystalline particles may have substantially the same composition and crystal structure as single-crystal particles. In the powder, the ratio of single-crystal particles to the total number of single-crystal particles and polycrystalline particles may be, for example, 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more. In a powder, the ratio of single-crystal particles to the total number of single-crystal particles and polycrystalline particles may be, for example, 100% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

[0051] The positive electrode active material may be a monodisperse system. If the powder contains single-crystal particles and is a monodisperse system, improvements in cycle characteristics can be expected, for example. The powder may have a span of, for example, 1 or less. "Span" refers to the value obtained by the calculation formula "(D90-D10) / D50". A smaller span indicates a sharper particle size distribution. The span of the powder may 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 may also be, for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, or 0.5 or more.

[0052] The shape of the single crystal grain 1 is polyhedral. The shape of the single crystal grain 1 may be, for example, hexahedral, octahedral, or the like. The shape of the single crystal grain 1 may also be, for example, rectangular parallelepiped.

[0053] A single crystal particle 1 includes 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 may be, for example, 25° or less, 15° or less, 10° or less, 5° or less, 3° or less, or 1° or less. Among 10 single crystal particles 1 randomly extracted from a STEM image of the powder, the proportion of single crystal particles 1 whose longest side 1a is aligned with the 003 plane may be, for example, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more.

[0054] The aspect ratio "a / b" is 1.10 or greater. The aspect ratio "a / b" may also be, for example, 1.20 or greater, 1.40 or greater, 1.60 or greater, 1.80 or greater, 2.00 or greater, 2.20 or greater, 2.40 or greater, 2.60 or greater, 2.80 or greater, 3.00 or greater, 3.20 or greater, 3.40 or greater, 3.60 or greater, 3.80 or greater, 4.00 or greater, 4.20 or greater, 4.40 or greater, 4.60 or greater, 4.80 or greater, 5.00 or greater, 5.20 or greater, 5.40 or greater, 5.60 or greater, 5.80 or greater, 6.00 or greater, 6.10 or greater, 6.20 or greater, 6.40 or greater, 6.60 or greater, 6.80 or greater, or 7.00 or greater. The aspect ratio "a / b" may be, for example, 10.0 or less, 9.00 or less, 8.00 or less, 7.00 or less, 6.80 or less, 6.60 or less, 6.40 or less, 6.20 or less, 6.10 or less, 6.00 or less, 5.80 or less, 5.60 or less, 5.40 or less, 5.20 or less, 5.00 or less, 4.80 or less, 4.60 or less, 4.40 or less, 4.20 or less, 4.00 or less, 3.80 or less, 3.60 or less, 3.40 or less, 3.20 or less, 3.00 or less, 2.80 or less, 2.60 or less, 2.40 or less, 2.20 or less, 2.00 or less, 1.80 or less, 1.60 or less, 1.40 or less, or 1.20 or less. The aspect ratio "a / b" may also be, for example, from 2.00 to 6.10.

[0055] The longest side 1a may be, for example, 1.40 μm or more, 1.59 μm or more, 1.80 μm or more, 2.00 μm or more, 2.20 μm or more, 2.30 μm or more, 2.40 μm or more, 2.60 μm or more, 2.73 μm or more, 2.80 μm or more, 3.00 μm or more, 3.20 μm or more, 3.40 μm or more, 3.48 μm or more, 3.60 μm or more, 3.80 μm or more, or 4.00 μm or more. The longest side 1a may be, for example, 6.00 μm or less, 5.00 μm or less, 4.00 μm or less, 3.80 μm or less, 3.60 μm or less, 3.48 μm or less, 3.40 μm or less, 3.20 μm or less, 3.00 μm or less, 2.80 μm or less, 2.73 μm or less, 2.60 μm or less, 2.40 μm or less, 2.30 μm or less, 2.20 μm or less, 2.00 μm or less, 1.80 μm or less, or 1.59 μm or less. The longest side 1a may also be, for example, between 1.59 μm and 3.48 μm.

[0056] The shorter side 1b may be, for example, 0.200 μm or more, 0.300 μm or more, 0.380 μm or more, 0.400 μm or more, 0.500 μm or more, 0.600 μm or more, 0.700 μm or more, 0.800 μm or more, 0.830 μm or more, 0.900 μm or more, 0.980 μm or more, 1.00 μm or more, 1.10 μm or more, 1.20 μm or more, 1.30 μm or more, 1.40 μm or more, 1.45 μm or more, 1.50 μm or more, 1.60 μm or more, 1.70 μm or more, 1.80 μm or more, 1.90 μm or more, or 2.00 μm or more. The short side 1b may be, for example, 5.00 μm or less, 4.00 μm or less, 3.00 μm or less, 2.00 μm or less, 1.90 μm or less, 1.80 μm or less, 1.70 μm or less, 1.60 μm or less, 1.50 μm or less, 1.45 μm or less, 1.40 μm or less, 1.30 μm or less, 1.20 μm or less, 1.10 μm or less, 1.00 μm or less, 0.980 μm or less, 0.900 μm or less, 0.830 μm or less, 0.800 μm or less, 0.700 μm or less, 0.600 μm or less, 0.500 μm or less, 0.400 μm or less, or 0.380 μm or less. The short side 1b may also be, for example, between 0.380 μm and 1.45 μm.

[0057] The interior angle "θ" between the longest side 1a and the shortest side 1b is between 60° and 120°. The interior angle "θ" may also be, for example, 62° or more, 64° or more, 66° or more, 68° or more, 70° or more, 72° or more, 74° or more, 76° or more, 78° or more, 80° or more, 82° or more, 83° or more, 84° or more, 86° or more, 87° or more, 88° or more, 90° or more, 92° or more, 94° or more, 96° or more, 98° or more, 100° or more, 102° or more, 104° or more, 106° or more, 108° or more, 110° or more, 112° or more, 114° or more, 116° or more, or 118° or more. The interior angle "θ" may be, for example, 118° or less, 116° or less, 114° or less, 112° or less, 110° or less, 108° or less, 106° or less, 104° or less, 102° or less, 100° or less, 98° or less, 96° or less, 94° or less, 92° or less, 90° or less, 88° or less, 87° or less, 86° or less, 84° or less, 83° or less, 82° or less, 80° or less, 78° or less, 76° or less, 74° or less, 72° or less, 70° or less, 68° or less, 66° or less, 64° or less, or 62° or less. The interior angle "θ" may be, for example, between 82° and 94°.

[0058] In a powder, the proportion of single crystal particles satisfying the relationship "60°≦θ≦120°" may be, for example, 21% or more. This proportion may also 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 may also be, for example, 100% or less, 90% or less, 80% or less, 70% or less, 65% or less, 58% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, or 25% or less.

[0059] The angularity of single crystal grain 1 may be, for example, 451 to 584. The angularity of single crystal grain 1 may be, for example, 475 or more, 500 or more, 502 or more, 525 or more, 550 or more, 553 or more, or 575 or more. The angularity of single crystal grain 1 may be, for example, 575 or less, 553 or less, 550 or less, 525 or less, 502 or less, 500 or less, or 475 or less. When the angularity is between 400 and 599, the two-dimensional image of the grain tends to take on a shape close to a rectangle. The three-dimensional shape of the grain is considered to be close to a rectangular parallelepiped.

[0060] The single-crystal grains contain lithium transition metal composite oxides. These lithium transition metal composite oxides have a crystal structure assigned to the space group R-3m. This structure is also referred to as a "layered structure." The layered structure can be identified by XRD patterns.

[0061] In the XRD pattern of the positive electrode active material, the intensity of the diffraction peak corresponding to the 10⁴ plane is "I 104 The intensity of the diffraction peak corresponding to the 003 plane for "" 003 The ratio of "I 003 / I 104 For example, the intensity ratio "I 003 / I 104 When the intensity ratio "I" is greater than 2.7, for example, improvements in cycle characteristics can be expected. 003 / I 104 " may be, for example, 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. Intensity ratio "I 003 / I 104 For example, "5.0 or less, 4.0 or less, 3.8 or less, 3.6 or less, 3.4 or less, 3.2 or less, or 3.0 or less."

[0062] Lithium transition metal composite oxides contain Li, a transition metal (TM), and oxygen. TM contains at least Ni. That is, lithium transition metal composite oxides contain at least Ni. Lithium transition metal composite oxides may also contain, for example, LiNiO2. In addition to Ni, TM may further contain, for example, Co, Mn, Al, etc.

[0063] Single crystal particles are, for example, those with the general formula "Li x Ni a Co b Mn c O y It may have a composition represented by the formula ". In the general formula, the Li composition ratio "x" may satisfy, for example, the relationship "0.1 ≤ x ≤ 1.5". The Li composition ratio "x" may be, for example, 0.4 or more, 0.6 or more, 0.8 or more, 1.0 or more, 1.2 or more, or 1.4 or more. The Li composition ratio "x" may be, for example, 1.4 or less, or 1.2 or less.

[0064] In the general formula above, the O composition ratio "y" may satisfy, for example, the relationship "1.5 ≤ y ≤ 2.1". The O composition ratio "y" may be, for example, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, or 2.0 or more. The O composition ratio "y" may be, for example, 2.0 or less, 1.9 or less, 1.8 or less, 1.7 or less, or 1.6 or less.

[0065] In the above general formula, the Ni composition ratio "a", Co composition ratio "b", and Mn composition ratio "c" may satisfy the relationship "a + b + c = 1.0". The Ni composition ratio "a" may, for example, satisfy the relationship "0.5 ≤ a ≤ 1.0". The Ni composition ratio "a" may, for example, be 0.6 or greater, 0.7 or greater, 0.8 or greater, or 0.9 or greater. The Ni composition ratio "a" may, for example, be 0.9 or less, 0.8 or less, 0.7 or less, or 0.6 or less.

[0066] In the general formula above, the Co composition ratio "b" may satisfy, for example, the relationship "0 ≤ b ≤ 0.3". The Co composition ratio "b" may be, for example, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or more. The Co composition ratio "b" may be, for example, 0.25 or less, 0.20 or less, 0.15 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less.

[0067] In the above general formula, the Mn composition ratio "c" may satisfy, for example, the relationship "0 ≤ c ≤ 0.3". The Mn composition ratio "c" may be, for example, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.15 or more, 0.20 or more, or 0.25 or more. The Mn composition ratio "c" may be, for example, 0.25 or less, 0.20 or less, 0.15 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less.

[0068] In addition, in the above general formula, all or part of Mn may be substituted with Al, etc. That is, lithium transition metal composite oxides are, for example, those with the general formula "Li x Ni a Co b Al c O y It may have a composition represented by ". The range of the Al composition ratio "c" is the same as that of the Mn composition ratio "c" above.

[0069] Lithium transition metal composite oxides may contain any dopant. The dopant represents an element other than Li, Ni, Co, Mn, and O. For example, the dopant may contain at least one selected from the group consisting of Zr, Mo, W, Mg, Ca, Na, Fe, Cr, Zn, Si, Sn, Al, and Ag. The composition ratio of the dopant may be, for example, 0.005 or more, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more. The composition ratio of the dopant may be, for example, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less.

[0070] The positive electrode active material may further contain other components, as long as it contains a lithium transition metal composite oxide. The mixing ratio (mass ratio) of the lithium transition metal composite oxide to the other components may 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 may be, for example, a mixture of a lithium transition metal composite oxide powder and a powder of the other components. The other components may include, for example, at least one selected from the group consisting of lithium iron phosphate (olivine structure), lithium manganese phosphate (olivine structure), lithium iron manganese phosphate (olivine structure), LiMnO2 (rock salt structure), Li(NiMn)2O4 (spinel structure), and LiCoO2 (layered structure). The other components may be single crystal particles or polycrystalline particles.

[0071] Lithium-ion rechargeable battery liquid battery In some embodiments, the battery may be an electrolyte battery. An "electrolyte battery" refers to a battery that contains an electrolyte. For example, polymer batteries, which contain an electrolyte, belong to the category of electrolyte batteries. In some embodiments, the battery has a monopolar structure. In a monopolar structure, the power generation element may be wound or stacked. In some embodiments, the battery has a bipolar structure. As an example, a battery having a bipolar structure (bipolar battery) is described.

[0072] Figure 6 is a schematic perspective view of the lithium-ion secondary battery in this embodiment. Figure 7 is a schematic cross-sectional view along the line VII-VII in Figure 6. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In the figures of this embodiment, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0073] The battery 100 includes an outer casing 90 and a power generation element 50. The outer casing 90 houses the power generation element 50. The outer casing 90 may include, for example, a first current collector plate 91, a first laminate film 92, a second laminate film 93, and a second current collector plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane edges. At the joint between the first laminate film 92 and the second laminate film 93, a sealing material (not shown) may be interposed between the first laminate film 92 and the second laminate film 93.

[0074] The first current collector plate 91 and the second current collector plate 94 are joined to the power generation element 50 at their ends in the stacking direction (Z-axis direction). The first laminate film 92 is joined to the first current collector plate 91. The second laminate film 93 is joined to the second current collector plate 94. A sealing material (not shown) may be interposed between the current collector plate and the laminate film at the joint between the current collector plate and the laminate film.

[0075] The power generation element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the direction perpendicular to the plane (Z-axis direction). Each of the plurality of bipolar electrodes 10 includes, in the direction perpendicular to the plane, a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in this order. In the in-plane direction (for example, in the X-axis direction), the current collector foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collector foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire circumference in the in-plane direction.

[0076] The current collector foil 13 is a conductor. The current collector foil 13 may include, for example, a metal foil, a conductive resin layer, etc. For example, the current collector foil 13 may be formed by bonding an Al foil and a Cu foil together. A carbon material may be coated on the surface of the current collector foil 13. The carbon material may include, for example, carbon black.

[0077] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is joined to the current collector foil 13. The sealing material 30 may, for example, be heat-welded to the current collector foil 13. For example, the sealing material 30 may be arranged around the entire circumference of the in-plane periphery. The sealing material may include, for example, a resin material. The sealing material 30 seals between adjacent current collector foils 13 in the direction perpendicular to the plane. The sealing material 30 between the current collector foils 13 partitions the cells 40. A cell 40 is the smallest unit of the power generation element 50. The battery 100 includes multiple cells 40 and may also be called a "bipolar module". Each of the multiple cells 40 is sealed. The multiple cells 40 are isolated from each other. Each of the multiple cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0078] Positive electrode layer The positive electrode layer 11 is attached to one side of the current collector foil 13. For example, grooves may be formed in the positive electrode layer 11. The positive electrode layer 11 may be formed in a striped pattern, for example. The positive electrode layer 11 contains a positive electrode active material. That is, the battery 100 contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0079] The positive electrode layer 11 may further contain, for example, a conductive material and a binder, in addition to the positive electrode active material. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The conductive material may contain any components. For example, the conductive material may contain at least one selected from the group consisting of graphite, acetylene black (AB), Ketjenblack (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0080] The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The binder may contain any components. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ethers, and derivatives thereof.

[0081] The positive electrode layer 11 may further contain, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode active material layer may contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0082] Negative electrode layer The negative electrode layer 12 is attached to one side of the current collector foil 13. The negative electrode layer 12 is located on the back side of the positive electrode layer 11. The negative electrode layer 12 may have a larger area than the positive electrode layer 11. The negative electrode layer 12 contains a negative electrode active material.

[0083] The negative electrode active material may be in the form of parts or sheets, for example. The D50 of the negative electrode active material may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material may be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0084] The negative electrode active material may contain any components. For example, the negative electrode active material may include at least one selected from the group consisting of carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In some embodiments of this invention, the battery may be a Li metal negative electrode battery.

[0085] The carbon-based active material may include, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. 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".

[0086] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a dissimilar material. The dissimilar material may include, for example, at least one selected from the group consisting of P, W, Al, and O. The dissimilar material may include, for example, at least one selected from the group consisting of Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0087] The alloying active material may include, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloys, tin (Sn), SnO, and Sn-based alloys.

[0088] SiO is, for example, the general formula "SiO xIt may have a composition represented by "」. In the general formula, for example, the relationship of "0 < x < 2", "0.5 ≤ x ≤ 1.5" or "0.8 ≤ x ≤ 1.2" may be satisfied.

[0089] The "Si-C composite material" refers to a composite material of a carbon-based active material (such as graphite) and an alloy-based active material (such as Si). For example, Si fine particles may be dispersed in carbon particles. For example, Si fine particles may be dispersed in graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0090] Separator 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 include at least one selected from the group consisting of, for example, a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may include, for example, a resin film and an inorganic particle layer.

[0091] The resin film is porous. The resin film may include, for example, a microporous film, a non-woven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuously reticulated, for example. Pores are formed in the gaps of the resin skeleton. The resin film can permeate an electrolyte. The resin film may have an average pore diameter of 1 μm or less, for example. The average pore diameter of the resin film may be, for example, from 0.01 to 1 μm, or from 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gurley value of the resin film may be, for example, from 50 to 250 s / 100 cm 3 and may be. The "Gurley value" can be measured by the Gurley test method.

[0092] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may also contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film can be formed, for example, by stretching, phase separation, or the like. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0093] The resin film may have, for example, a single-layer structure. The resin film may consist of, for example, a PE layer. The framework of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multilayer structure. The resin film may include, for example, a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin film may have, for example, a three-layer structure. The resin film may be formed by laminating a PP layer, a PE layer and a PP layer in this order. The thickness of the PE layer may be, for example, 5 to 20 μm. The thickness of the PP layer may be, for example, 3 to 10 μm.

[0094] The inorganic particle layer may be formed on the surface of the resin film. The inorganic particle layer may be formed on only one side of the resin film or on both sides. The inorganic particle layer may be formed on the surface facing the positive electrode layer 11 or on the surface facing the negative electrode layer 12. The inorganic particle layer may be formed on the surface of the positive electrode layer 11 or on the surface of the negative electrode layer 12.

[0095] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles may also be called "inorganic fillers." Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also called an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. For example, the inorganic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluororesins, aromatic polyether resins, and liquid crystal polyester resins.

[0096] The separator 20 may include, for example, an organic particle layer. The separator 20 may include, for example, an organic particle layer instead of a resin film. The separator 20 may include, for example, an organic particle layer instead of an inorganic particle layer. The separator 20 may include both a resin film and an organic particle layer. The separator 20 may include both an inorganic particle layer and an organic particle layer. The separator 20 may include a resin film, an inorganic particle layer, and an organic particle layer.

[0097] The thickness of the organic particle layer may be, for example, 0.1 to 50 μm, 0.5 to 20 μm, 0.5 to 10 μm, or 1 to 5 μm. The organic particle layer contains organic particles. The organic particles may also be called "organic fillers". The organic particles may contain heat-resistant materials. The organic particles may contain at least one selected from the group consisting of, for example, PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm.

[0098] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0099] electrolyte The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute may be, for example, 0.5 to 1 mole / L, 1 to 1.5 mole / L, 1.5 to 2 mole / L, 2 to 2.5 mole / L, or 2.5 to 3 mole / L. "mol / L" may also be written as "M". The solute contains a supporting salt (Li salt). The solute may also contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0100] The electrolyte may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, cyclic carbonates, linear carbonates, fluorinated carbonates, etc. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0101] The solvent may contain cyclic carbonates (EC, PC, FEC, etc.) and linear carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to linear carbonates may be, for example, "cyclic carbonate / linear carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / linear carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / linear carbonate = 3 / 7 to 4 / 6".

[0102] 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".

[0103] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component can be expressed, for example, by the relationship "V EC +V FEC +V EMC +VDMC +V DEC The relationship expressed by "=10" may also be satisfied. In the relationship, "V EC , V FEC , V EMC , V DMC , V DEC " indicates the volume ratio of EC, FEC, EMC, DMC, and DEC, respectively. "1≦V EC ≤4, 0 ≤V FEC ≤3", V EC +V FEC ≤4, 0 ≤V EMC ≤9, 0 ≤V DMC ≤9, 0 ≤V DEC ≤9, 6 ≤V EMC +V DMC +V DEC The relationship "≤9" is satisfied. For example, "1 ≤ V" EC ≤2" or "2 ≤ V" EC The relationship "≤3" may also be satisfied. For example, "1 ≤ V" FEC ≤2" or "2 ≤ V" FEC The relationship "≤4" may also be satisfied. For example, "3 ≤ V" EMC ≤4" or "6 ≤ V" EMC The relationship "≤8" may also be satisfied. For example, "3 ≤ V" DMC ≤4" or "6 ≤ V" DMC The relationship "≤8" may also be satisfied. For example, "3 ≤ V" DEC ≤4" or "6 ≤ V" DEC The relationship "≤8" may also be satisfied.

[0104] The solvent may have compositions such as "EC / EMC=3 / 7", "EC / DMC=3 / 7", "EC / FEC / DEC=1 / 2 / 7", "EC / DMC / EMC=3 / 4 / 3", "EC / DMC / EMC=3 / 3 / 4", "EC / FEC / DMC / EMC=2 / 1 / 4 / 3", "EC / FEC / DMC / EMC=1 / 2 / 4 / 3", "EC / FEC / DMC / EMC=2 / 1 / 3 / 4", and "EC / FEC / DMC / EMC=1 / 2 / 3 / 4" in volume ratio.

[0105] The electrolyte may contain an ether-based solvent. The electrolyte may contain, for example, at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylglycyle, triglycyle, tetraglycyle, and derivatives thereof.

[0106] The electrolyte may contain any additives. The amount of additive (mass fraction of the total electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additives may include, for example, SEI (Solid Electrolyte Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge inhibitors, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0107] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesaltone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), ethylene sulfate (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters [e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.], and fluorobenzenes [e.g., monofluorobenzene (FB), 1,2-di-butylbenzene]. Fluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.), fluorotoluene (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluorides (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylenes (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methyl benzothiazole) It may contain at least one selected from the group consisting of (e.g., nzothiazole, tetrathiafulvalene), nitrile compounds (e.g., adiponitrile, succinonitrile), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether), and derivatives thereof.

[0108] The components mentioned above may be used as solutes and solvents, or as trace components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0109] The electrolyte may contain an ionic liquid. The ionic liquid may contain, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0110] In some embodiments of this invention, the battery may include a gel electrolyte; that is, the battery may be a polymer battery. The gel electrolyte may include an electrolyte solution and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0111] all solid state battery In some embodiments of this invention, the battery may be an all-solid-state battery. The all-solid-state battery may have a bipolar structure. The all-solid-state battery includes a solid electrolyte instead of an electrolyte and a separator 20. The solid electrolyte may also be included in the positive electrode layer 11 and the negative electrode layer 12. Instead of a separator 20, the solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11. The solid electrolyte layer includes, for example, a solid electrolyte and a binder.

[0112] The solid electrolyte may be, for example, a powder. The D50 of the solid electrolyte may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1 μm or more. The D50 of the solid electrolyte may be, for example, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0113] The solid electrolyte may include, for example, at least one selected from the group consisting of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, and nitride solid electrolytes.

[0114] The sulfide solid electrolyte may contain at least one selected from the group consisting of an amorphous phase, a crystalline phase, and a glass ceramic (crystallized glass) phase. The crystalline phase may be, for example, an argyrodite type or an LGPS type. The sulfide solid electrolyte contains Li and sulfur (S). In addition to Li and S, the sulfide solid electrolyte may further contain any other components.

[0115] Examples of sulfide solid electrolytes include LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2-P2S5, Li2S-P2S5, Li 10 GeP2S 12 Li4P2S6, Li7P3S 11 It may include at least one selected from the group consisting of Li3PS4 and Li7PS6.

[0116] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. The mixing ratio may be specified by prefixing each raw material with a number. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (molar ratio)".

[0117] A sulfide solid electrolyte may have a composition represented by the general formula "xLi2S-(1-x)P2S5". In the general formula, "x" may be, for example, greater than 0, 0.1 or greater, 0.2 or greater, 0.25 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. "x" may also be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.75 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. For example, when "x = 0.75", "xLi2S-(1-x)P2S5" may have the composition of Li3PS4.

[0118] The sulfide solid electrolyte may have a composition represented by the general formula "yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5]". In the general formula, "x" may be, for example, 0.5 or more, 0.6 or more, 0.7 or more, 0.75 or more, 0.8 or more, or 0.9 or more. "x" may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.75 or less, 0.7 or less, or 0.6 or less. "y" may be, for example, 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. "y" may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. "z" may be, for example, 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. "z" could be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0119] Sulfide solid electrolytes are, for example, those with the general formula "Li 7-x-2y PS 6-x-y X y It may have a composition represented by the formula: In the general formula, the relationships "0 < 7-x-2y", "0 < 6-xy", "0 ≤ x", and "0 ≤ y" are satisfied. "X" may include, for example, at least one selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0120] Sulfide solid electrolytes are, for example, those with the general formula "Li4-x M 1-x P x It may have a composition represented by "S4". In the general formula, "x" may be, for example, greater than 0, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. "x" may be, for example, less than 1, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. "M" may contain, for example, at least one selected from the group consisting of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0121] The sulfide solid electrolyte may, for example, have a composition represented by the general formula "Li 10+x Ge 1+x P 2-x S 12 ". In the general formula, "x" may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.6 or more. "x" may be, for example, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. The sulfide solid electrolyte represented by the above general formula may contain, for example, a LGPS-type crystal phase.

[0122] The halide solid electrolyte may, for example, have a composition represented by the general formula "Li 6-na M a X6". In the general formula, "n" indicates the oxidation number of "M". "M" may contain, for example, an atom having an oxidation number of +3. "M" may contain, for example, an atom having an oxidation number of +4. "M" may contain, for example, at least one selected from the group consisting of Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship of "0 < a < 2" may be satisfied. "X" may contain, for example, at least one selected from the group consisting of F, Cl, Br, and I.

[0123] The halide solid electrolyte may, for example, have a composition represented by the general formula "Li 3-a Tia Al 1-a It may have a composition represented by "F6". In the general formula, "a" may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. "a" may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0124] The halide solid electrolyte may have, for example, a composition represented by the general formula "Li3YCl a Br b I 6-a-b ". In the general formula, for example, the relationship of "0≦a + b≦6" may be satisfied. "a" may be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. "a" may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. "b" may be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. "b" may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0125] The oxide solid electrolyte may contain, for example, at least one selected from the group consisting of LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3, and Li7La3Zr2O 12 . The hydride solid electrolyte may contain, for example, LiBH4 or the like. The nitride solid electrolyte may contain, for example, Li3N, Li3BN2 or the like.

Examples

[0126] Preparation of Samples Figure 8 is a table showing experimental results. By the following procedure, the cathode active materials (LiNi 0.90 Co 0.05 Mn 0.05 O2) from No.1 to No.6 were produced.

[0127] Preparation of raw material liquid The raw material solution is prepared by dissolving NiSO4, CoSO4, and MnSO4 in deionized water. The mixing ratio of NiSO4, CoSO4, and MnSO4 is adjusted to "Ni / Co / Mn = 90 / 5 / 5 (mole ratio)". The mole concentration of the raw material solution is 0.2%.

[0128] hydrothermal synthesis A predetermined amount of NH3 aqueous solution is placed in the reaction vessel. The reaction vessel is stirred with a stirrer while being purged with nitrogen. NaOH is added to the reaction vessel to adjust the pH of the aqueous solution to alkaline. The raw material solution is added dropwise while the temperature and pH of the aqueous solution are adjusted to maintain a constant range (effectively constant value), forming a precipitate of TM hydroxide. The precipitate is dehydrated and calcined. The calcination temperature is 120°C to 220°C. The calcination time is 4 to 10 hours. The calcination pressure is 0.2 MPa to 1.0 MPa.

[0129] Precursor recovery After calcination, the precipitate is washed with water. The residue (TM hydroxide) is recovered by filtration. The TM hydroxide is dried at 110°C for 12 hours to remove the water. Thus, the precursor (TM hydroxide) is prepared.

[0130] Mixing of Li raw materials A mixture is prepared by mixing a precursor (TM hydroxide) and a lithium compound (LiOH, Li2CO3, etc.). In this experiment, the ratio of the amount of Li to the total amount of transition metal (TM), "Li / TM," is adjusted to be greater than 1. This promotes the single crystallization of the positive electrode active material by causing the excess lithium compound to form a molten salt (flux) during calcination.

[0131] firing The mixture is subjected to heat treatment (calcination). Calcination can be carried out, for example, in a muffle furnace. The calcination atmosphere may be, for example, an oxygen atmosphere.

[0132] One-stage baking Figure 9 shows the first calcination profile. Calcination in No. 1 and No. 2 is shown in the first calcination profile. The mixture is prepared by mixing the precursor and lithium compound so that "Li / TM = 2.0". The mixture is placed in the calcination furnace. The furnace temperature is raised to Y°C, which is in the range of 800°C to 1100°C. Y°C is maintained for a predetermined time. The maintenance time at Y°C is 5 to 15 hours. After the predetermined time has elapsed, the furnace temperature is lowered to room temperature. Thus, the cathode active material is synthesized.

[0133] 4-stage baking Figure 10 shows the second firing profile. The firings in No. 3 to No. 6 are shown in the second firing profile. First, the mixture is prepared by mixing the precursor and lithium compound so that "Li / TM = 1.0". The mixture is placed in the firing furnace. The furnace temperature is raised to X-300°C. X-300°C is maintained for a predetermined time. After the predetermined time has elapsed, lithium compound is added to the mixture so that the total "Li / TM = 1.3". After the addition of lithium compound, the furnace temperature is raised to X-200°C. X-200°C is maintained for a predetermined time. After the predetermined time has elapsed, lithium compound is added to the mixture so that the total "Li / TM = 1.6". After the addition of lithium compound, the furnace temperature is raised to X-100°C. X-100°C is maintained for a predetermined time. After a predetermined time has elapsed, a lithium compound is added to the mixture so that the total ratio of Li / TM becomes 1.9. After the addition of the lithium compound, the furnace temperature is raised to X°C, which is within the range of 800°C to 1100°C. X°C is maintained for a predetermined time. After the predetermined time has elapsed, the furnace temperature is lowered to room temperature. The total maintenance time at each temperature is between 5 and 15 hours. The maintenance time at each temperature is the same. Thus, the positive electrode active material is synthesized.

[0134] After firing, the positive electrode active material is crushed in an agate mortar until the particle size is 0.2 mm or less. The positive electrode active material is dispersed in 500 mL of pure water to form a slurry. The slurry is vigorously stirred for 1 minute. The slurry is filtered using filter paper and a Buchner funnel. The residue is rinsed with 500 mL of pure water to form a cake. The cake is vacuum-dried at 90°C. After drying, the cake is crushed in an agate mortar to adjust it to the desired particle size. For example, a lab mill or other mill may be used instead of an agate mortar.

[0135] The flux may be completely removed by washing after firing, or some may remain. The mass ratio of the remaining flux to the positive electrode active material may 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 remaining flux to the positive electrode active material may 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 remaining flux may contain, for example, at least one selected from the group consisting of Li2CO3 and LiHCO3.

[0136] evaluation A laminated cell is prepared. A laminated cell is a cell in which the power generation elements are housed in a pouch made of aluminum laminate film. The configuration of the power generation elements is as follows: Positive electrode: Positive electrode active material, conductive material (acetylene black) Negative electrode: Negative electrode active material (natural graphite) Electrolytes: LiPF6 (1 ml / L), EC / DMC / EMC = 3 / 4 / 3 (volume ratio)

[0137] The positive and negative electrodes are manufactured by coating the surface of a substrate (metal foil) with a slurry. For example, a film applicator (with film thickness adjustment function) manufactured by Allgood is used as the coating equipment. After coating with the slurry, the coating is dried at 80°C for 5 minutes.

[0138] A cycle test will be performed on the laminated cell under the following conditions. Ambient temperature: 60℃ Number of cycles: 50 Current rate: 0.3C Voltage range: 4.25V to 2.5V

[0139] At a current rate of 1C, the rated capacity of the cell is supplied in one hour. 0.3C is 0.3 times 1C. The capacity retention rate can be calculated by dividing the discharge capacity at the 50th cycle by the discharge capacity at the 1st cycle. A higher capacity retention rate indicates better cycle characteristics.

[0140] Experimental results In Figure 8, when the relationships "1.10 ≤ a / b" and "60° ≤ θ ≤ 120°" are satisfied, there is a tendency for the cycle characteristics to improve.

[0141] When the relationship "2.00 ≤ a / b ≤ 6.10" is satisfied, there is a tendency for the cycle characteristics to improve.

[0142] When the relationship "82°≦θ≦94°" is satisfied, there is a tendency for the cycle characteristics to improve.

[0143] "451≦A total When the relationship "≤584" is satisfied, there is a tendency for the cycle characteristics to improve.

[0144] When the proportion of single crystal grains satisfying the relationship "60°≦θ≦120°" is 21% or more, there is a tendency for the cycle characteristics to improve.

[0145] When the relationships "1.59μm ≤ a ≤ 3.48μm" and "0.377μm ≤ b ≤ 1.45μm" are satisfied, there is a tendency for the cycle characteristics to improve. [Explanation of Symbols]

[0146] 1 Single crystal particle, 1a Longest side, 1b Shortest side, 10 Bipolar electrode, 11 Positive electrode layer, 12 Negative electrode layer, 13 Current collector foil, 20 Separator, 30 Sealing material, 40 Cell, 50 Power generation element, 90 Outer casing, 91 First current collector plate, 92 First laminate film, 93 Second laminate film, 94 Second current collector plate, 100 Battery.

Claims

1. Contains powder, The aforementioned powder contains single crystal particles, The single crystal particles contain a lithium transition metal composite oxide. The aforementioned lithium transition metal composite oxide has a crystal structure that belongs 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 particles are independent and do not aggregate. The aforementioned single crystal grains are polyhedral in shape, The single crystal grain includes the longest side and the shortest side, The longest side extends along the plane 003, The shorter side is connected to the end of the longest side, The interior angle between the longest side and the shortest side is between 60° and 120°, and The ratio of the longest side to the shortest side is 1.10 or greater. Cathode active material.

2. The ratio of the longest side to the shortest side is 2.00 or more and 6.10 or less. The positive electrode active material according to claim 1.

3. The aforementioned interior angle is between 82° and 94°. The positive electrode active material according to claim 1 or claim 2.

4. The angularity of the single crystal grain is 451 to 584. The positive electrode active material according to claim 1 or claim 2.

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

6. The longest side is between 1.59 μm and 3.48 μm, and The aforementioned shorter side is 0.377 μm to 1.45 μm. The positive electrode active material according to claim 1 or claim 2.

7. The aforementioned single crystal grain is given by the general formula: Li x Ni a Co b Mn c O y It has a composition represented by, In the above general formula, x, a, b, c, and y satisfy the following 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. The positive electrode active material according to claim 1 or claim 2.

8. It includes a positive electrode layer, and The positive electrode layer comprises the positive electrode active material described in claim 1 or claim 2. electrode.

9. The electrode included in claim 8, Lithium-ion rechargeable battery.

10. Having a bipolar structure, The lithium-ion secondary battery according to claim 9.

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