Silicon-Graphite Anode Structure for Expansion-Stable Cycling
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Solution Overview
Problem
Silicon-based negative electrode materials for batteries exhibit high theoretical specific capacity but suffer from severe expansion during charging and low first discharge efficiency, leading to poor cycle stability in silicon-carbon composite negative electrode active materials.
Innovation Solution
A negative electrode active material comprising expanded graphite with a porous carbon layer and silicon particles, where the porous carbon layer is distributed on the interlayer surfaces of the graphite layers, and silicon particles are distributed in the pore channels of the porous carbon layer, enhancing mechanical strength and conductivity while providing space for silicon expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material, then theoretical specific capacity is improved, but expansion during charging increases and cycle stability deteriorates
Solution Approach 1:
Silicon particles are nested within the pore channels of the porous carbon layer, which itself is distributed on the interlayer surfaces of expanded graphite layers. This multi-level nested structure allows silicon to be contained within a protective carbon framework that accommodates expansion while maintaining overall structural integrity during cycling.
Solution Approach 2:
A porous carbon layer with controlled pore channels is constructed to envelop silicon particles. The porous structure provides sufficient space for silicon volume expansion during lithiation while maintaining structural integrity, preventing particle aggregation and electrode disintegration that would otherwise occur with pure silicon materials.
2Quantity of substance
If silicon-based material is used as negative electrode active material, then theoretical specific capacity is improved, but first discharge efficiency decreases
Solution Approach 1:
A composite structure is constructed comprising expanded graphite as the base material, porous carbon layer as the intermediate framework, and silicon particles as the active material distributed within the carbon pores. This composite architecture combines the high capacity of silicon with the structural stability and conductivity of carbon materials, enabling both high capacity and improved first discharge efficiency.
3Quantity of substance
If silicon particles are added to carbon-based material to form composite, then specific capacity is improved, but cycle stability remains at low level
Solution Approach 1:
The porous carbon layer is specifically designed with controlled pore channels that locally accommodate silicon particles. This localized structure provides tailored mechanical properties and chemical environment for silicon at the particle level, while the overall expanded graphite framework provides macrostructural stability, creating a hierarchical quality distribution that simultaneously enables high capacity and good cycle stability.
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 proposed material achieves high specific capacity and improved cycle stability, along with enhanced rate performance of the secondary battery.
Implementation Method 1
silicon particles are at least distributed in pore channels of porous carbon of the porous carbon layer
Implementation Method 2
enhancing mechanical strength and conductivity while providing space for silicon expansion
Data Source
AI summary
The present application relates to a negative electrode active material and a preparation method therefor, a negative electrode sheet, a secondary battery, and an electric device. The negative electrode active material comprises expanded graphite, a porous carbon layer, and silicon particles; the expanded graphite comprises a plurality of graphite layers; the porous carbon layer is at least distributed on an interlayer surface of one graphite layer, and the silicon particles are at least distributed in pore channels of porous carbon of the porous carbon layer.