JP-2026075388-A - Positive electrode active material for lithium-ion secondary batteries

Abstract

[Challenge] Improve cycle characteristics. [Solution] The positive electrode active material for lithium-ion secondary batteries contains single crystal particles. The single crystal particles include a first pyramidal portion and a second pyramidal portion. The first pyramidal portion protrudes in a first direction. The first pyramidal portion has a first outer diameter. The first outer diameter indicates the diameter of the smallest circumscribed circle for the first pyramidal portion. The second pyramidal portion protrudes in a second direction. The second pyramidal portion has a second outer diameter. The second outer diameter indicates the diameter of the smallest circumscribed circle for the second pyramidal portion. The first outer diameter is larger than the second outer diameter. The angle between the first direction and the second direction is greater than 0° and 45° or less. [Selection Diagram] Figure 2

Inventors

• 大澤 良輔

Assignees

• トヨタ自動車株式会社

Dates

Publication Date

20260508

Application Date

20241022

Claims (5)

1. Contains single crystal particles, The single crystal grain includes a first pyramidal portion and a second pyramidal portion, The first pyramidal portion protrudes in the first direction, The first pyramidal portion has a first outer diameter, The first outer diameter indicates the diameter of the smallest circumscribed circle for the first pyramidal portion. The second pyramidal portion protrudes in the second direction, The second pyramidal portion has a second outer diameter, The second outer diameter indicates the diameter of the smallest circumscribed circle for the second pyramidal portion. The first outer diameter is larger than the second outer diameter, The angle between the first direction and the second direction is greater than 0° and 45° or less. Positive electrode active material for lithium-ion secondary batteries.
2. 0.010<D b /D a ≦0.750 Satisfying the relationship, The D a represents the first outer diameter, and, The aforementioned Db represents the second outer diameter. The positive electrode active material for a lithium-ion secondary battery according to claim 1.
3. The base of the second pyramidal section is fused with the side surface of the first pyramidal section. The positive electrode active material for a lithium-ion secondary battery according to claim 1 or claim 2.
4. The single crystal grain further comprises a third pyramidal portion, The aforementioned triangular pyramidal portion protrudes in a third direction, The first direction, the second direction, and the third direction are different from each other, The base of the third pyramidal portion is fused with the base of the first pyramidal portion. The positive electrode active material for a lithium-ion secondary battery according to claim 1 or claim 2.
5. It has a crystal structure that belongs to the space group R-3m. The positive electrode active material for a lithium-ion secondary battery according to claim 1 or claim 2.

Description

This disclosure relates to a positive electrode active material for lithium-ion secondary batteries. Japanese Patent Publication No. 2023-036570 discloses a ternary cathode material. Japanese Patent Publication No. 2023-036570 This is the first conceptual diagram showing the single crystal particles in this embodiment.This is a second conceptual diagram showing the single crystal particles in this embodiment.This is a table showing the experimental results. Terminology and Phrases: 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. "Single-crystal particles" refer to particles that cannot be divided into smaller units by dispersers or grinders. Single-crystal particles can be rephrased as primary particles, aggregates, etc. Aggregates of single-crystal particles can be rephrased as secondary particles, agglomerates, etc. The space group to which the crystal structure belongs can be identified by powder XRD (X-ray diffraction) measurements. The shape of the single crystal grain and the shape of each pyramidal region can be determined by at least one of three-dimensional SEM (Scanning Electron Microscope) observation and cross-sectional SEM observation. The direction of the pyramidal region's projection indicates the direction from the center of the pyramidal base toward the apex. In the case of a cross-sectional image, it indicates the direction from the midpoint of the base of the triangle toward the apex. The angle between two directions (two lines) indicates a sub-angle. The determination (fitting) of the minimum circumscribed circle for each pyramidal section can be performed using image analysis software. For example, "ImageJ" may be used. The diameter of the minimum circumscribed circle is considered to be the outer diameter of the pyramidal section. Positive electrode active material The positive electrode active material is for lithium-ion secondary batteries. The lithium-ion secondary battery (hereinafter abbreviated as "battery") may be an liquid-based battery or an all-solid-state battery. The battery may have any structure. The battery may have, for example, a wound-type or stacked-type power generation element. The battery may have, for example, a unipolar structure or a bipolar structure. Figure 1 is a first conceptual diagram showing the single-crystal grain in this embodiment. Figure 2 is a second conceptual diagram showing the single-crystal grain in this embodiment. The second conceptual diagram shows a cross-section of the single-crystal grain 10 shown in Figure 1. The single crystal grain 10 includes a first pyramidal portion 11 and a second pyramidal portion 12. The outer diameter of the first pyramidal portion 11 (first outer diameter "D a ") is larger than the outer diameter of the second pyramidal portion 12 (second outer diameter "D b "), that is, the relationship "D b / D a <1" is satisfied. The outer diameter ratio "D b / D a " may be, for example, 0.900 or less, 0.800 or less, 0.750 or less, 0.500 or less, 0.250 or less, 0.100 or less, 0.075 or less, 0.050 or less, or 0.025 or less. The outer diameter ratio " Db / Da " may be, for example, 0.010 or more, greater than 0.010, 0.013 or more, 0.015 or more, 0.020 or more, 0.025 or more, 0.050 or more, 0.075 or more, 0.100 or more, 0.150 or more, 0.300 or more, 0.450 or more, or 0.600 or more. For example, the relationship "0.010 < Db /Da ≤ 0.750" may be satisfied. Satisfying this relationship is expected to improve cycle characteristics. The first pyramidal portion 11 protrudes in the first direction A1. The second pyramidal portion 12 protrudes in the second direction A2. The angle θ 12 between the first direction A1 and the second direction A2 is greater than 0° and 45° or less. By satisfying the relationship "0° < θ 12 ≤ 45°", improvement in cycle characteristics can be expected. The angle θ 12 may be, for example, 40° or less, 39° or less, 38° or less, 36° or less, 35° or less, 34° or less, 33° or less, 32° or less, 31° or less, or 30° or less. The angle θ 12 may also be, for example, 5° or more, 10° or more, 15° or more, 20° or more, or 25° or more. The second pyramidal section 12 may be directly connected to the first pyramidal section 11. For example, the base of the second pyramidal section 12 may be fused to the side surface of the first pyramidal section 11. At the fused section, the boundary between the two pyramidal sections may b