Silicon Negative Electrode Material with High-Angle Grain Boundaries
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Solution Overview
Problem
Conventional silicon-based negative electrode active materials for lithium secondary batteries face limitations in reducing grain size, leading to restricted performance improvements due to large grain sizes and significant volume expansion during charging/discharging, which damages the conductive path and deteriorates battery characteristics.
Innovation Solution
A method involving rapid cooling of metallurgical grade silicon to form a plate-shaped silicon precursor, followed by grinding to achieve nano-sized grains with a high angle grain boundary ratio, optimizing the grain size and boundary ratio to enhance the performance of the negative electrode active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional silicon-based negative electrode active materials are used, then high discharge capacity can be achieved, but large grain size and significant volume expansion during charging/discharging damage the conductive path and deteriorate battery characteristics
Solution Approach 1:
The invention divides the silicon-based active material into fine grains with a grain size of 10 μm or less, creating a segmented structure that reduces volume expansion stress and prevents conductive path damage while maintaining high discharge capacity
Solution Approach 2:
The invention changes the grain size parameter to 10 μm or less and controls the high-angle grain boundary ratio to 30% or more, optimizing the microstructure to reduce volume expansion effects and maintain conductive path integrity during charging/discharging cycles
2Manufacturing precision
If rapid cooling process is applied to reduce grain size, then high angle grain boundary ratio can be increased, but additional processing steps are required
Solution Approach 1:
The invention performs preliminary action by controlling the cooling rate during the ingot formation stage to establish the desired grain structure before pulverization, simplifying subsequent processing while achieving precise grain size control
Solution Approach 2:
The invention utilizes phase transition during cooling by controlling the cooling rate to manipulate solidification behavior and grain formation, achieving fine grain structure with high-angle grain boundaries through the phase change process
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
This approach results in increased cycle capacity maintenance rate and initial capacity efficiency by preventing conductive path damage and improving battery performance, while controlling volume expansion during charging/discharging.
Implementation Method 1
rapidly cooling metal silicon to form a silicon precursor
Implementation Method 2
rapidly cooling metal silicon to form a silicon precursor
Implementation Method 3
grinding the silicon precursor to form a silicon-based active material
Data Source
AI summary
A negative electrode active material includes a silicon-based active material that includes silicon-based grains. A high angle grain boundary ratio in the silicon-based grains is 30% or more, and the silicon-based active material includes a composition that satisfies following Formulas 1 and 2:about 1 µm≤particle size (D50) of silicon-based active material≤10 µm[Formula 1]about 2 nm≤grain size of silicon-based active material≤1 µm.[Formula 2]