Single-Particle Cathode Material to Limit Gas and Cracking
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Solution Overview
Problem
Existing nickel-based layered structure positive electrode active materials for lithium-ion secondary batteries face issues such as gas generation, particle breakage due to volume changes, and reduced structural stability, leading to cell degradation, especially in small-diameter multi-particle active materials, and high-temperature sintering deteriorates electrochemical properties.
Innovation Solution
A small-diameter single-particle positive electrode active material is developed, with a controlled average particle diameter of 2 to 4 µm and inhibited (001) plane growth, manufactured through a top-down process using medium or large particle size precursors, followed by a pulverizing and coating process to enhance structural stability and electrochemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If small-diameter multi-particle active materials are used to achieve high electrode density, then electrode density is improved, but specific surface area increases leading to gas generation and cell degradation
Solution Approach 1:
The invention segments the multi-particle aggregate structure into single particles while controlling the particle diameter to minimize specific surface area. By using single particles with optimized size (2-4 μm), the patent reduces the total surface area exposed to electrolyte compared to multi-particle aggregates of equivalent electrode density, thereby reducing gas generation from side reactions.
Solution Approach 2:
The invention changes the particle size parameter to an optimal range (2-4 μm) and controls the particle morphology to achieve single particle form. This parameter optimization balances electrode density requirements with minimizing specific surface area, reducing harmful side reactions while maintaining high packing density.
2Volume of stationary object
If small-diameter multi-particle active materials are used to achieve high electrode density, then electrode density is improved, but structural stability deteriorates due to particle breakage and cracks
Solution Approach 1:
The invention eliminates the multi-particle aggregate structure and uses single particles only. This segmentation approach removes the interfaces between primary particles where cracks typically propagate during volume changes, thereby improving structural stability while maintaining high electrode density through optimized single particle size and morphology.
Solution Approach 2:
The invention optimizes particle size parameters (2-4 μm) and controls particle morphology to enhance mechanical strength. By adjusting these parameters, the patent achieves particles that can withstand volume changes during cycling without breaking or forming cracks, thereby improving structural stability.
3Shape
If sintering is performed at higher temperatures to synthesize single-particle active materials, then particle form is improved, but electrochemical properties deteriorate
Solution Approach 1:
The invention optimizes sintering temperature parameters to a specific range that achieves single particle formation without excessive heat treatment. By precisely controlling temperature and time parameters, the patent forms single particles while preserving electrochemical properties, avoiding the deterioration that occurs with higher temperature sintering.
Solution Approach 2:
The invention performs preliminary particle formation before final sintering, using a top-down approach where larger particles are broken down and reformed. This preliminary structuring allows for lower temperature final sintering that achieves single particle form without the electrochemical deterioration associated with high-temperature processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides improved structural stability, reduced side reactions, and enhanced electrochemical characteristics, including high capacity and safety, while maintaining high electrode density and productivity.
Implementation Method 1
sintering must be done at higher temperatures than for multi-particle positive electrode active materials
Implementation Method 2
a maximum pole density value of 20 or less at the (001) plane in a pole figure diagram obtained through Electron Back Scatter Diffraction (EBSD) analysis
Implementation Method 3
pulverizing the lithium transition metal oxide to form a lithium transition metal oxide in the form of a single particle
Data Source
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AI summary
The present invention relates to a positive electrode active material for a lithium secondary battery, comprising a lithium transition metal oxide containing nickel (Ni), wherein the lithium transition metal oxide is in form of a single particle, has an average particle diameter (D50) ranging from 2 µm to 4 µm, and exhibits a maximum pole density value of 20 or less at the (001) plane as determined by Electron Back Scatter Diffraction (EBSD) analysis of a pole figure diagram.