Porous Silicon-Carbon Anode Composite for Volume Expansion Control
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Solution Overview
Problem
The large volume expansion of silicon particles during charging and discharging in secondary batteries leads to cracking and reduced electron conductivity, resulting in capacity loss and shortened cycle life, limiting the performance of non-graphite-based negative-electrode materials like silicon.
Innovation Solution
A silicon-carbon composite is developed with amorphous or amorphous-crystalline silicon particles and a porous carbon structure containing micropores, mesopores, and macropores, along with a carbon-based coating, to manage volume expansion and maintain electron conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as negative-electrode material to achieve high theoretical capacity, then capacity increases significantly, but volume expansion of about 400% occurs during charging and discharging causing particle breaking and reduced conductivity
Solution Approach 1:
Silicon particles are embedded within a porous carbon structure, where the carbon matrix acts as a container that accommodates silicon's volume expansion. The hierarchical pore structure (micropores, mesopores, macropores) provides nested spaces at different scales to absorb expansion stress while maintaining electrical conductivity pathways.
Solution Approach 2:
A porous carbon structure with specifically designed micropores (10-30 vol%), mesopores (20-40 vol%), and macropores (40-60 vol%) is used to encapsulate silicon particles. The porous structure provides void space for volume expansion during lithiation/delithiation cycles, preventing particle cracking while maintaining electrical conductivity through the carbon matrix.
2Quantity of substance
If silicon particles are used to achieve high capacity, then lithium storage per unit weight increases, but electron conductivity decreases due to particle breaking and carbon additive reduction
Solution Approach 1:
A composite structure is created where silicon particles are integrated within a conductive carbon matrix. The carbon phase provides continuous electron transport pathways, compensating for any conductivity loss from silicon particle fragmentation. The composite maintains both high capacity (from silicon) and good conductivity (from carbon).
Solution Approach 2:
The porous carbon structure acts as an intermediary between silicon particles and the electrolyte, providing stable electron conduction pathways. The carbon matrix mediates the electrical connection while the porous structure accommodates volume changes, preventing direct contact and potential breaking of silicon particles.
3Reliability
If graphite-based material is used as negative-electrode material, then excellent electrochemical performance and low cost are achieved, but theoretical capacity is limited to 370 mAh/g
Solution Approach 1:
The invention changes the material parameter from graphite (370 mAh/g theoretical capacity) to silicon-based materials (4000-4200 mAh/g theoretical capacity). By using amorphous or nanocrystalline silicon with controlled grain size (≤10 nm) and embedding in porous carbon, the system achieves both high capacity and acceptable electrochemical performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The silicon-carbon composite enhances initial discharge capacity, efficiency, and lifespan of secondary batteries by preventing silicon particle cracking and providing a void space for expansion, leading to improved battery performance.
Implementation Method 1
a large volume expansion of about 400% of silicon occurs during the charging and discharging process
Implementation Method 2
silicon has a theoretical capacity of 4000 to 4200 mAh/g, can store therein a very large amount of lithium per unit weight
Implementation Method 3
reduction of electron conductivity with a carbon additive and the current collector
Data Source
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AI summary
The present invention relates to a silicon-carbon composite for an anode material of a secondary battery and a method for manufacturing same and, more specifically, to a silicon-carbon composite for an anode material of a secondary battery and a method for manufacturing same, wherein when applied as an anode material, the silicon-carbon composite is capable of improving characteristics of a secondary battery by minimizing a volume change of silicon particles during charging and discharging processes of the secondary battery.