Layered Silicon Anode Composition for Capacity and Cycle Life
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with silicon-based active materials due to large volume expansion, leading to electrode deintercalation, increased internal resistance, and reduced lifespan characteristics, which complicates achieving high-capacity and high-energy density requirements.
Innovation Solution
A multilayer anode structure is implemented, with a first anode mixture layer containing a silicon oxide-based active material and a second anode mixture layer with a Si-C composite, using different binders and conductive materials to manage volume expansion and enhance adhesive force and resistance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active materials are applied to anodes to achieve high capacity and high energy density, then discharge capacity is improved, but volume expansion occurs during charging/discharging causing electrode deintercalation, increased internal resistance, and reduced lifespan
Solution Approach 1:
The anode is divided into multiple layers with different compositions. The first anode mixture layer contains silicon-based active material with first binder and first conductive material, while the second anode mixture layer contains different silicon-based active material with second binder and second conductive material. This segmentation allows each layer to handle different aspects of volume expansion, resolving the contradiction between high capacity and lifespan
Solution Approach 2:
Each anode mixture layer uses composite materials combining silicon-based active material with binders and conductive materials. The first and second anode mixture layers use different composite formulations, allowing the structure to accommodate volume expansion while maintaining electrical conductivity and mechanical integrity, thus improving both capacity and lifespan
2Quantity of substance
If silicon-based active materials are used to increase energy density, then battery capacity is improved, but adhesive force between current collector and active material deteriorates due to volume expansion
Solution Approach 1:
The anode is segmented into first and second mixture layers, each with different binder and conductive material compositions. This allows the first layer to provide strong initial adhesion to the current collector while the second layer maintains adhesion during volume expansion, preserving both energy density and adhesive force
Solution Approach 2:
The binder and conductive material parameters are changed between layers. The first anode mixture layer uses first binder and first conductive material with specific properties, while the second layer uses different binders and conductive materials. This parameter variation optimizes adhesion at different stages of battery operation, maintaining strong bonding despite volume changes
3Quantity of substance
If silicon-based active materials are applied to achieve high capacity, then discharge capacity is improved, but internal resistance increases due to deintercalation and side reactions
Solution Approach 1:
Composite materials are used in both anode mixture layers, combining silicon-based active material with binders and conductive materials in different ratios. The first conductive material and second conductive material have different contents, creating a gradient structure that maintains electrical pathways during volume expansion, reducing internal resistance while preserving high capacity
Solution Approach 2:
Different local compositions are created in the first and second anode mixture layers. The first layer has specific ratios of silicon-based material, binder, and conductive material, while the second layer has different ratios. This local quality variation optimizes both capacity and resistance characteristics at different locations within the anode structure
Data Source
AI summary
In some implementations, the anode includes a current collector, a first anode mixture layer formed on at least one surface of the current collector, and a second anode mixture layer formed on the first anode mixture layer. The first anode mixture layer and the second anode mixture layer include a carbon-based active material, respectively. The first anode mixture layer includes a first binder, a first silicon-based active material, and a first conductive material. The second anode mixture layer includes a second binder, a second silicon-based active material, and a second conductive material. Contents of the first conductive material and the second conductive material are different from each other with respect to the total combined weight of the first anode mixture layer and the second anode mixture layer. Types of the first silicon-based active material and the second silicon-based active material are different from each other.