Carbon-Coated Silicon Oxide Anode for High First Coulomb Efficiency
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Solution Overview
Problem
Existing silicon oxide materials for lithium ion secondary batteries suffer from low first coulomb efficiency and limited cycle performance due to excessive lithium consumption in forming the SEI film during the first charge.
Innovation Solution
A negative electrode material comprising a carbon coating layer and a core layer with lithium polysilicate and silicon oxide, where the lithium polysilicate includes specific lithium silicate compositions and the carbon coating layer is optimized in mass percentage, enhancing the equilibrium level between lithium polysilicate and other lithium silicates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide materials are used to increase theoretical capacity, then capacity increases, but first coulomb efficiency decreases due to high lithium consumption in SEI film formation
Solution Approach 1:
The patent changes the chemical composition parameters of the negative electrode material by introducing specific lithium silicate compounds (Li4SiO4, Li2SiO3, LiSiO3) with controlled ratios. This compositional parameter change modifies the electrochemical behavior to reduce irreversible lithium consumption while maintaining high capacity, thereby improving first coulomb efficiency without sacrificing theoretical capacity.
Solution Approach 2:
The patent creates a composite negative electrode material comprising silicon oxide combined with specific lithium silicate compounds. This composite structure leverages the high capacity of silicon oxide while the lithium silicate components provide a protective effect that reduces SEI film formation losses, achieving both high capacity and high first coulomb efficiency simultaneously.
2Duration of action of stationary object
If conventional graphite is used, then cycle performance is maintained, but volumetric energy density is limited
Solution Approach 1:
The patent develops a composite negative electrode material that combines silicon oxide (providing high volumetric capacity) with lithium silicate compounds (providing structural stability and protection). This composite approach enables the material to achieve both long cycle life comparable to conventional graphite and significantly higher volumetric energy density.
Solution Approach 2:
The lithium silicate compounds act as an intermediary protective phase between the silicon oxide and the electrolyte. This intermediary layer reduces direct harmful interactions, stabilizes the electrode structure during cycling, and enables silicon oxide to maintain both high capacity and long cycle performance.
Data Source
AI summary
A negative electrode material of a lithium ion secondary battery includes a carbon coating layer and a core layer. The core layer comprises lithium polysilicate and silicon oxide. A preparation method for the negative electrode material and a use therefor are described. The negative electrode material has high first coulomb efficiency, long cycle performance, excellent rate performance, and high safety.