Silicon Anode Composition for Stable Conductive Paths
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Solution Overview
Problem
The use of silicon-based active materials in negative electrodes for lithium secondary batteries is limited by rapid volume expansion during charging, leading to disconnected conductive paths, reduced electrode adhesion, and decreased life performance due to particle agglomeration and difficulty in uniform dispersion.
Innovation Solution
A negative electrode composition comprising a silicon-based active material with a particle size of several microns and a point-like conductive material with a central particle diameter between 30% and 60% of the silicon-based active material, enhancing dispersibility and securing a pore structure to improve electrode quality and life performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material with high capacity is used, then battery capacity increases, but volume expansion during charging causes conductive path disconnection and adhesion deterioration
Solution Approach 1:
A coating layer comprising a polymer and a inorganic filler is formed on the silicon-based active material particles. The polymer provides flexibility to accommodate volume expansion, while the inorganic filler maintains structural integrity and conductivity. This flexible coating shell prevents conductive path disconnection during charging cycles.
Solution Approach 2:
The negative electrode uses a composite structure combining silicon-based active material with graphite particles, where graphite provides structural stability and maintains conductive paths. The coating layer itself is a composite of polymer and inorganic filler, combining the benefits of both materials to prevent adhesion deterioration while allowing capacity expansion.
2Duration of action of stationary object
If silicon-based active material particle size is reduced to improve life performance, then cycle life increases, but particle agglomeration occurs and uniform dispersion becomes difficult
Solution Approach 1:
The coating layer acts as a protective shell around each micron-sized silicon-based particle, preventing direct particle-to-particle contact that causes agglomeration. This shell maintains uniform dispersion by providing steric hindrance while allowing the small particle size needed for long cycle life.
Solution Approach 2:
The polymer-coated silicon-based particles are introduced as an intermediary form between raw silicon particles and the electrode matrix. This intermediary coating prevents direct interaction between silicon particles that would cause agglomeration, while still allowing lithium ion transport and maintaining electrical conductivity through the inorganic filler.
3Strength
If conventional coating methods are used on silicon-based active material, then adhesion improves, but coating uniformity deteriorates due to particle agglomeration
Solution Approach 1:
The coating layer is formed on the silicon-based active material particles before electrode fabrication. This preliminary coating prevents particle agglomeration during subsequent mixing and coating processes, ensuring uniform distribution of coated particles throughout the electrode slurry and achieving both good adhesion and coating uniformity.
Solution Approach 2:
The flexible polymer coating provides good adhesion to the silicon-based particles while maintaining a thin, uniform structure. The coating forms a consistent shell that adheres well to the particle surface without causing aggregation, achieving both strong electrode adhesion and uniform coating distribution.
Data Source
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AI summary
The present application relates to a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including a negative electrode.