Silicon Negative Electrode Three-Layer Structure
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Solution Overview
Problem
Silicon-based negative electrode active materials for lithium batteries face challenges such as volume change and conductivity issues during charging/discharging, leading to reduced cycle life and capacity, due to the formation of dendrites and cracks.
Innovation Solution
A three-layer structured negative electrode active material is developed, comprising a crystalline silicon layer, an amorphous matrix layer, and a nano grain matrix layer, which forms a coherent interface to suppress volume expansion and enhance bonding, thereby reducing crack formation and maintaining capacity over cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to achieve high capacity, then the battery capacity increases, but volume expansion and crack formation occur during charging/discharging
Solution Approach 1:
The silicon-based negative electrode active material is divided into fine particles with a diameter of 10 μm or less, and these particles are dispersed in a porous carbon material matrix. This segmentation prevents the formation of large cracks during volume expansion while maintaining high capacity, as the fine particles can expand individually without causing structural failure.
Solution Approach 2:
A porous carbon material coating is formed on the surface of the silicon-based active material particles. This carbon shell acts as a flexible buffer that accommodates volume expansion during lithiation while maintaining structural integrity. The porous structure allows lithium ion diffusion while preventing crack propagation.
2Duration of action of stationary object
If thin film coating is applied to suppress volume expansion, then cycle stability improves, but lithium ion diffusion resistance increases
Solution Approach 1:
The carbon material used for coating has a porous structure with controlled pore size and distribution. This porous structure provides multiple diffusion pathways for lithium ions, reducing diffusion resistance while the carbon matrix suppresses volume expansion. The porosity allows fast ion transport while the overall structure maintains mechanical stability during cycling.
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 three-layer structure effectively suppresses dispersal and crack phenomena, maintaining initial efficiency and capacity, with a small volume change during charging/discharging, leading to improved cycle stability and battery performance.
Implementation Method 1
an amorphous matrix layer outside the Si layer; and a nano grain matrix layer formed on an interface between the Si layer and the amorphous matrix layer
Implementation Method 2
suppresses dispersal and crack phenomena, maintaining initial efficiency and capacity, with a small volume change during charging/discharging
Data Source
AI summary
Provided are a negative electrode active material for a secondary battery, in which a silicon-based negative electrode active material is formed in a three-layer structure including an amorphous matrix, thereby suppressing a dispersal phenomenon of the negative electrode active material during charging/discharging. The negative electrode active material having a three-layer structure includes: a silicon (Si) layer; an amorphous matrix layer outside the Si layer; and a nano grain matrix layer formed on an interface between the Si layer and the amorphous matrix layer.