Layered Silicon Anode Composition for Adhesion and Swelling Control
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Solution Overview
Problem
Silicon-based active materials in anodes for lithium-ion secondary batteries experience significant volume expansion, leading to electrode deintercalation, increased internal resistance, and reduced lifespan due to their high discharge capacity compared to graphite.
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, both having different binder and conductive material compositions 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 discharge capacity and high energy density, then the capacity increases, but volume expansion occurs during charging/discharging cycles
Solution Approach 1:
The anode is divided into multiple layers with different compositions. The first anode mixture layer contains a first silicon-based active material with specific properties, while the second anode mixture layer contains a second silicon-based active material with different properties. This segmentation allows each layer to handle different aspects of volume expansion, with the total silicon content controlled at 1-30 wt% of the active material layer. The layered structure enables gradual accommodation of expansion stresses rather than concentrated stress in a single layer.
Solution Approach 2:
Different regions of the anode are given different local properties through the multilayer structure. The first and second anode mixture layers have different silicon-based active materials, binders, and conductive materials in different ratios. This local quality differentiation allows the anode to have optimized performance in different zones, with each layer tailored to specific functional requirements while collectively managing volume expansion.
2Quantity of substance
If silicon-based active materials are used to increase capacity, then energy density improves, but adhesive force between current collector and active material decreases due to deintercalation
Solution Approach 1:
The anode mixture layer is segmented into first and second layers with different binder contents and types. The first anode mixture layer contains a first binder and the second anode mixture layer contains a second binder, with different ratios of binder to active material. This segmentation ensures that adhesive force is distributed across multiple interfaces rather than concentrated at a single collector-layer interface, preventing delamination during cycling.
Solution Approach 2:
The anode employs a composite multilayer structure where each layer combines silicon-based active materials with carbon-based materials, binders, and conductive materials in specific ratios. The first anode mixture layer has a first composition ratio and the second has a second composition ratio. This composite approach creates a mechanically robust structure that maintains adhesive force while accommodating the high capacity requirements of silicon-based materials.
3Quantity of substance
If high content of silicon-based active material is used to achieve high capacity, then discharge capacity increases, but internal resistance increases due to side reactions with electrolyte
Solution Approach 1:
The total silicon-based active material content of 1-30 wt% is segmented across two different layers rather than concentrated in one layer. The first anode mixture layer contains a first silicon-based active material and the second contains a second silicon-based active material, each at different local concentrations. This segmentation reduces the local concentration of silicon that would otherwise react with electrolyte, thereby reducing side reactions and internal resistance while maintaining overall high capacity.
Solution Approach 2:
Different local regions have different silicon-based active material compositions and concentrations. The first and second anode mixture layers have different silicon content ratios, allowing zones with lower silicon concentration (and thus lower reactivity with electrolyte) to be interspersed with zones of higher silicon content. This local quality variation optimizes the balance between capacity and resistance by reducing harmful side reactions in high-silicon zones.
4Productivity
If repeated charging/discharging cycles are performed to utilize high capacity, then energy output increases, but lifespan decreases due to contraction/expansion
Solution Approach 1:
The anode structure is segmented into multiple layers that can independently accommodate expansion and contraction. During charging/discharging cycles, each layer experiences stress but the multilayer configuration distributes mechanical stresses and prevents crack propagation that would occur in a single-layer structure. This segmentation enables the anode to withstand repeated cycles while maintaining structural integrity and lifespan.
Solution Approach 2:
The composite multilayer anode combines different silicon-based active materials, carbon-based materials, binders, and conductive materials in specific ratios. This composite structure creates a mechanically resilient material system where the different components have complementary mechanical properties. The composite nature allows the anode to accommodate volume changes during cycling without structural failure, thereby extending lifespan while maintaining high energy output.
Data Source
Figure 1
AI summary
An anode for a lithium-ion secondary battery is disclosed. 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.