Silicon Oxide Mixture for Lithium Battery Negative Electrode
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium rechargeable batteries face volume expansion issues during charge and discharge, leading to reduced cycle-life due to crystalline structure changes, low conductivity, and small specific surface area, resulting in shorter battery life.
Innovation Solution
A negative electrode active material composed of a mixture of first and second silicon oxides with different particle diameters and specific surface areas, combined with a binder and a coating layer, to prevent volume change and maintain conductivity during charge and discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material, then high capacity is achieved, but volume expansion occurs during charge and discharge leading to reduced cycle-life
Solution Approach 1:
The negative electrode active material is divided into two distinct components: silicon particles (providing high capacity) and silicon oxide particles (providing structural stability). This segmentation allows each component to fulfill its specific function - silicon for capacity and silicon oxide for volume stability during charge-discharge cycles.
Solution Approach 2:
The invention creates a composite material system combining silicon and silicon oxide in specific weight ratios (70:30 to 90:10). This composite structure leverages the high capacity of silicon while the silicon oxide component compensates for volume expansion, achieving both high capacity and long cycle-life simultaneously.
2Duration of action of stationary object
If silicon oxide is used to reduce volume expansion, then cycle-life is improved, but electrical conductivity remains low
Solution Approach 1:
The invention optimizes the particle size parameters of both silicon and silicon oxide components. By controlling the D50 particle diameter within specific ranges (silicon: 3-10 μm, silicon oxide: 1-5 μm) and maintaining appropriate specific surface area ratios, the material achieves both low volume expansion and sufficient electrical conductivity for battery operation.
3Volume of stationary object
If silicon oxide with small specific surface area is used, then volume expansion is reduced, but conductivity and reaction efficiency decrease
Solution Approach 1:
The invention precisely controls the specific surface area of silicon oxide particles (1-5 m²/g) and maintains an optimal specific surface area ratio between silicon and silicon oxide (5-50). This parameter optimization ensures that the silicon oxide provides sufficient volume stability while maintaining adequate conductivity and electrochemical reaction efficiency.
Data Source
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AI summary
Provided are a negative electrode active material for a rechargeable lithium battery, which includes a first silicon oxide and a second silicon oxide with a particle diameter differing from the one of the first silicon oxide, a negative electrode including the negative electrode active material, and a method of manufacturing the negative electrode, and a rechargeable lithium battery including the negative electrode.