Layered Silicon-Carbon Anode Composition for Crack-Resistant Capacity
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Solution Overview
Problem
Lithium secondary batteries face issues with capacity and lifespan due to cracks in the anode caused by volume expansion differences between silicon and carbon-based active materials during charging and discharging.
Innovation Solution
An anode for lithium secondary batteries is designed with a layered structure comprising a carbon-based active material, a first silicon-based active material in the form of a carbon-silicon composite, and a second silicon-based active material as silicon oxide, with controlled content ratios to minimize volume expansion and enhance lithium ion mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based active material is used to increase capacity, then energy density is improved, but cracks occur in the anode due to volume expansion differences between silicon and carbon
Solution Approach 1:
The anode active material layer is divided into multiple layers with different silicon-based active materials (first silicon-based and second silicon-based) and carbon-based active materials. Each layer has different thickness ratios, creating a segmented structure that distributes volume expansion stress across multiple interfaces, preventing crack formation while maintaining high capacity.
Solution Approach 2:
Different regions of the anode active material layer have different compositions and thickness ratios. The first and second anode active material layers contain different proportions of silicon-based to carbon-based active materials, creating local quality variations that accommodate different expansion behaviors in different zones, thereby preventing uniform crack propagation.
2Use of energy by moving object
If multiple silicon-based active materials with different expansion ratios are used, then capacity is improved, but manufacturing complexity increases
Solution Approach 1:
The anode is segmented into multiple active material layers, each containing different silicon-based active materials (such as silicon, silicon oxide, silicon oxynitride) with different volume expansion ratios. This segmentation allows each layer to contribute differently to capacity while managing expansion stress, achieving high capacity without excessive complexity.
Solution Approach 2:
The anode uses composite active material layers combining silicon-based active materials (first and second types) with carbon-based active materials. These composite structures integrate materials with different properties to achieve both high capacity and controlled expansion behavior, resolving the complexity issue through material composition rather than structural complexity.
Data Source
AI summary
An anode for a lithium secondary battery includes an anode current collector, and an anode active material layer formed on at least one surface of the anode current collector. The anode active material layer includes a carbon-based active material, a first silicon-based active material including a carbon-silicon composite active material, and a second silicon-based active material including a silicon oxide (SiOx, 0<x<2). A content of the first silicon-based active material is in a range from 2 wt % to 40 wt % based on a total weight of the anode active material layer.