Silicon-Graphite Battery Electrode for Low Expansion Cycling
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Solution Overview
Problem
Silicon-based negative electrodes in batteries suffer from high expansion rates and stability issues, limiting their use in secondary batteries due to the large volume changes during charging and affecting the performance and lifespan of the battery.
Innovation Solution
A battery design incorporating a negative electrode active material layer composed of a combination of first and second graphite particles and silicon-carbon particles, with specific particle size distributions, and a positive electrode active material with a chemical formula LiaNixCoyMnzMkO2, where 0.8≤a≤1.2, 0.8≤x≤0.95, 0<y<0.2, 0<z<0.2, and M comprising certain elements, to enhance energy density and reduce expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon is used as the negative electrode active material to improve energy density, then the theoretical capacity per gram reaches 4200 mAh/g, but the expansion rate reaches 300% when the battery is fully charged
Solution Approach 1:
The patent uses a composite material system consisting of silicon-carbon alloy particles embedded in a graphite matrix. The graphite provides structural stability with low expansion rate, while the silicon-carbon alloy provides high capacity. This composite structure resolves the contradiction by combining materials with complementary properties to achieve both high energy density and low expansion.
Solution Approach 2:
The patent creates local quality differences by distributing silicon-carbon alloy particles of specific sizes within the graphite matrix. The silicon-carbon particles are confined to specific size ranges (Dv10≥8μm and Dv90≤15μm) to optimize local stress distribution and prevent excessive expansion while maintaining high capacity regions.
2Speed
If the particle size Dv50 of graphite particles is increased to improve kinetic performance, then the diffusion path for lithium ions is reduced, but the specific capacity per gram decreases
Solution Approach 1:
The patent optimizes the particle size parameters of graphite particles by specifying Dv50 ranges (3μm-8μm) and establishing relationships between different percentile sizes (Dv10, Dv50, Dv90). This parameter optimization balances the kinetic performance (faster ion diffusion with larger particles) and specific capacity (higher with smaller particles) by finding the optimal size distribution.
Data Source
AI summary
A battery comprises a positive electrode plate and a negative electrode plate. The negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer located on a surface on at least one side of the negative electrode current collector. The negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises graphite particles and silicon-carbon particles. The graphite particles comprise first graphite particles and second graphite particles. The particle size Dv50 of the first graphite particles is greater than that of the second graphite particles. The positive electrode plate comprises a positive electrode active material, and the positive electrode active material comprises a material with a chemical formula of LiaNixCoyMnzMkO2. The battery of the present disclosure can have high energy density, low expansion rate and excellent cycling performance.