Silicon Composite Anode Material for Volume Change and Conductivity Stability
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Solution Overview
Problem
Silicon-based materials in lithium-ion batteries experience significant volume changes during charging and discharging, leading to material breakage and loss of conductivity, which affects cycle performance and fast charging capabilities.
Innovation Solution
A silicon composite material is developed with a core and coating layers, comprising a flexible conductive material and a conductive carbon material, which enhances expansion inhibition and conductivity, improving cycle and fast charging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used to increase capacity, then energy density is improved, but volume changes cause material breakage and loss of conductivity
Solution Approach 1:
The patent embeds silicon-based materials inside graphite particles, creating a core-shell structure where the silicon core is nested within the graphite shell. This nesting approach allows the high-capacity silicon to be protected by the flexible graphite matrix that can accommodate volume changes, thereby maintaining structural integrity and conductivity throughout charge-discharge cycles.
Solution Approach 2:
The patent creates a composite material system combining silicon-based materials with graphite and conductive carbon materials. This composite structure leverages the high capacity of silicon while utilizing the mechanical flexibility and conductivity of graphite to mitigate volume expansion issues, thus improving both energy density and cycle performance.
2Quantity of substance
If silicon-based materials are used to increase capacity, then energy density is improved, but conductive networks collapse affecting fast charging performance
Solution Approach 1:
The patent develops a composite material where silicon-based particles are embedded in a graphite matrix with added conductive carbon materials. This composite structure maintains a continuous conductive network even during volume changes, ensuring efficient electron transport and thus improving fast charging performance while retaining high capacity.
Solution Approach 2:
The patent applies different materials with specific local functions: silicon cores provide high capacity, graphite provides mechanical flexibility and baseline conductivity, and conductive carbon materials are strategically added to ensure continuous conductive pathways. This local optimization of material properties throughout the composite structure maintains conductivity during volume changes.
Data Source
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AI summary
A silicon composite material and a preparation method therefor, a negative electrode sheet, a secondary battery, and an electric device. The silicon composite material comprises a core and a first coating layer covering the surface of the core; the core comprises a first core and a second core; the first core comprises a first conductive material; the first conductive material comprises a flexible conductive material; the second core comprises a silicon-based material of which the surface is coated with a second coating layer; and the second coating layer contains a second conductive material. The silicon composite material has the characteristics of good cycle performance and fast charging performance.