Carbon-Silicon Composite Shell for High-Capacity Low-Swelling Anodes
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Solution Overview
Problem
Lithium secondary batteries face challenges with carbon-based anode materials due to limitations in theoretical maximum capacity, safety issues, and decreased productivity from silicon swelling, which limits the use of silicon to 10% content, leading to electrode destruction and reduced cycle life.
Innovation Solution
A carbon-silicon composite is developed with a core containing carbon material and uniformly distributed silicon particles, surrounded by an amorphous or crystalline carbon shell, allowing for high silicon content while suppressing volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon content is increased to improve battery capacity, then energy density increases, but volume expansion causes electrode destruction and reduced cycle life
Solution Approach 1:
The patent embeds silicon particles inside carbon-based hollow spheres, creating a nested structure where silicon is contained within the carbon matrix. This nesting approach allows high silicon content (30-70 wt%) while the carbon shell constrains volume expansion, preventing electrode destruction and maintaining cycle life.
Solution Approach 2:
The patent employs a carbon-based hollow sphere shell that flexibly accommodates silicon volume expansion during lithiation. The hollow spherical structure acts as a buffer, allowing the shell to expand and contract with silicon while maintaining structural integrity, thus preventing electrode destruction and preserving cycle life at high silicon contents.
2Quantity of substance
If silicon content is increased to improve battery capacity, then energy density increases, but mechanical strength decreases due to swelling
Solution Approach 1:
Silicon particles are nested within carbon-based hollow spheres, where the carbon matrix provides mechanical strength while containing silicon. This nested configuration allows high silicon content (30-70 wt%) without compromising overall composite strength, as the carbon shell bears the mechanical load during swelling.
Solution Approach 2:
The patent creates a composite material combining silicon particles with carbon-based hollow spheres. This composite structure leverages the high capacity of silicon while the carbon component provides mechanical strength and structural stability, maintaining integrity even at 30-70 wt% silicon content.
3Quantity of substance
If uniform silicon distribution is achieved to improve capacity utilization, then battery performance increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent pre-forms carbon-based hollow spheres with controlled pore structures before introducing silicon particles. This preliminary preparation of the carbon matrix creates predetermined pathways and spaces that guide uniform silicon distribution during subsequent infiltration, achieving homogeneous dispersion without requiring extremely precise manufacturing control.
Solution Approach 2:
The patent utilizes porous carbon-based hollow spheres as the matrix for silicon particles. The porous structure provides channels and spaces that facilitate uniform silicon infiltration and distribution throughout the carbon matrix, achieving homogeneous silicon dispersion (as confirmed by EDS analysis) while using commercially feasible manufacturing processes.
Data Source
AI summary
The present invention relates to a carbon-silicon composite and a preparation method therefor. An aspect of the present invention provides a carbon-silicon composite comprising: a core including a carbon material and silicon particles; and a shell which is formed on the surface of the core and includes amorphous carbon, wherein the silicon particles are uniformly distributed from the center to the surface of the core.