Graphite-Coated Silicon-Carbon Particles for Stable Li-Ion Anodes
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Solution Overview
Problem
Silicon-based negative electrode materials for lithium-ion batteries face challenges due to low conductivity, significant volume expansion, and unstable solid electrolyte interface, leading to poor cycling performance and electrical contact failures, especially when combined with graphite, where the high viscosity of carbon nanotube dispersions limits their effective use.
Innovation Solution
A silicon-carbon composite particle is developed with graphite particles of specific sizes and amounts coated on silicon-based particles, compounded through granulation to enhance bonding and electrical contact, reducing swelling and improving cycling performance by matching particle sizes and increasing contact points, and incorporating an oxide or polymer layer for further stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CMC dispersion of carbon nanotubes is added during slurry preparation to improve electrical conductivity, then electrical contact is improved, but slurry viscosity becomes extremely high (>10000 mpa·s) resulting in low solid content
Solution Approach 1:
The patent extracts the conductive carbon material from the CMC dispersion form and uses it as dry powder or granulated form instead, eliminating the viscosity problem while maintaining electrical conductivity function
Solution Approach 2:
The patent changes the physical state and form of the conductive agent from high-viscosity dispersion to dry powder or granulated form, fundamentally altering the rheological properties while preserving electrical conductivity
2Quantity of substance
If graphite particles and silicon-based particles are mixed to form composite negative electrode material, then capacity is improved, but volume expansion and contraction occurs during lithium intercalation and deintercalation causing electrical contact failure
Solution Approach 1:
The patent performs granulation treatment in advance to pre-bond graphite and silicon-based particles together before battery assembly, creating a mechanically robust composite structure that can withstand subsequent volume changes during cycling
Solution Approach 2:
The patent creates a composite granulated material where graphite particles and silicon-based particles are mechanically bonded together, forming a unified structure that combines the high capacity of silicon with the structural stability of graphite
3Quantity of substance
If silicon-based particles are used to achieve high gram capacity (1500-4200 mAh/g), then capacity is improved, but low conductivity (>108 Ω·cm) and volume expansion around 300% occur hindering application
Solution Approach 1:
The patent creates a composite material system combining silicon-based particles with graphite particles and conductive carbon materials, leveraging the high capacity of silicon while using graphite and conductive agents to provide structural stability and electrical conductivity
Solution Approach 2:
The patent introduces conductive carbon materials and graphite particles as intermediary components that mediate between the low-conductivity silicon-based particles and the external circuit, ensuring efficient electron transport while accommodating silicon's volume changes
Data Source
AI summary
A silicon-carbon composite particle includes a silicon-based particle and a plurality of graphite particles on surface of the silicon-based particle, where the graphite particles have a particle size of M μm, the silicon-based particle has a particle size of N μm, M<N, and 2<N≤10. Also, a preparation method of silicon-carbon composite particle. A lithium-ion battery prepared using the active material containing the silicon-carbon composite particles as the negative electrode has good cycling performance and low swelling rate.