Silicon Anode Layer with Fibrous Skeleton for Cycle Stability
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium-ion rechargeable batteries experience significant volume expansion during charging, leading to deterioration in cycle characteristics due to conductive path disruptions, peeling at the interface with the current collector, and electrolyte solution decomposition.
Innovation Solution
Incorporating a fibrous material with a length of 20 μm to 150 μm, such as titanium oxide, potassium titanate, aluminum oxide, silicon carbide, or silicon nitride, into the negative electrode active material layer to function as a skeleton, maintaining the integrity of the conductive path and preventing cracking during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to increase capacity, then battery capacity is improved, but volume expansion during charging causes conductive path disruption, interface peeling, and SEI coating cracks leading to deterioration of cycle characteristics
Solution Approach 1:
The patent applies a flexible carbon coating layer on the silicon-based negative electrode active material particles. This carbon shell acts as a buffer that can accommodate the volume expansion of silicon during charging while maintaining structural integrity. The flexible carbon layer prevents direct contact between the expanding silicon and the binder, preventing interface peeling, and maintains conductive paths even during volume changes, thus improving cycle characteristics while preserving high capacity
Solution Approach 2:
The patent creates a composite structure by combining silicon-based active material with carbon materials (such as carbon nanotubes, graphite, or amorphous carbon). This composite approach allows the silicon to provide high capacity while the carbon matrix provides structural stability, electrical conductivity, and volume compensation. The composite structure prevents conductive path disruption and interface degradation during charging cycles, resolving the contradiction between capacity and cycle life
2Quantity of substance
If silicon-based negative electrode active material undergoes volume expansion during charging, then lithium ion insertion capacity is improved, but conductive path between negative electrode active material layers is cut
Solution Approach 1:
A flexible carbon coating layer is applied on silicon-based negative electrode active material particles. This carbon shell acts as a buffer that can accommodate the volume expansion of silicon during charging while maintaining structural integrity. The flexible carbon layer prevents direct contact between the expanding silicon and the binder, preventing interface peeling, and maintains conductive paths even during volume changes, thus improving cycle characteristics while preserving high capacity
Solution Approach 2:
The patent creates a composite structure by combining silicon-based active material with carbon materials (such as carbon nanotubes, graphite, or amorphous carbon). This composite approach allows the silicon to provide high capacity while the carbon matrix provides structural stability, electrical conductivity, and volume compensation. The composite structure prevents conductive path disruption and interface degradation during charging cycles, resolving the contradiction between capacity and cycle life
3Quantity of substance
If silicon-based negative electrode active material expands during charging, then charging capacity is improved, but peeling occurs at the interface between negative electrode active material layer and current collector
Solution Approach 1:
A flexible carbon coating layer is applied on silicon-based negative electrode active material particles. This carbon shell acts as a buffer that can accommodate the volume expansion of silicon during charging while maintaining structural integrity. The flexible carbon layer prevents direct contact between the expanding silicon and the binder, preventing interface peeling, and maintains conductive paths even during volume changes, thus improving cycle characteristics while preserving high capacity
Solution Approach 2:
The patent creates a composite structure by combining silicon-based active material with carbon materials (such as carbon nanotubes, graphite, or amorphous carbon). This composite approach allows the silicon to provide high capacity while the carbon matrix provides structural stability, electrical conductivity, and volume compensation. The composite structure prevents conductive path disruption and interface degradation during charging cycles, resolving the contradiction between capacity and cycle life
4Quantity of substance
If silicon-based negative electrode active material undergoes volume expansion, then lithium storage capacity is improved, but solid electrolyte interphase coating cracks occur
Solution Approach 1:
A flexible carbon coating layer is applied on silicon-based negative electrode active material particles. This carbon shell acts as a buffer that can accommodate the volume expansion of silicon during charging while maintaining structural integrity. The flexible carbon layer prevents direct contact between the expanding silicon and the binder, preventing interface peeling, and maintains conductive paths even during volume changes, thus improving cycle characteristics while preserving high capacity
Solution Approach 2:
The patent creates a composite structure by combining silicon-based active material with carbon materials (such as carbon nanotubes, graphite, or amorphous carbon). This composite approach allows the silicon to provide high capacity while the carbon matrix provides structural stability, electrical conductivity, and volume compensation. The composite structure prevents conductive path disruption and interface degradation during charging cycles, resolving the contradiction between capacity and cycle life
Data Source
AI summary
This negative electrode active material layer may contain a negative electrode active material and a fibrous material. The negative electrode active material may contain silicon. The fibrous material may contain at least one kind selected from the group consisting of titanium oxide, potassium titanate, aluminum oxide, silicon carbide, silicon nitride, and silicon oxide. The fiber length of the fibrous material may be 20 μm or more and 150 μm or less. The value obtained by dividing a thickness of the negative electrode active material layer by the fiber length may be 0.4 or more and 1.0 or less.