Multi-Layer Silicon Anode Binder Gradient for Crack-Resistant Cycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face challenges with high volume expansion of silicon-based anode materials during charging and discharging, leading to cracks and deterioration in cycle life and fast-charging performance.
Innovation Solution
An anode with a multi-layer structure comprising a first and second anode active material layer, each containing a silicon-based active material, is designed with specific binder ratios and types, including a silicon-carbon composite, to control volume changes and improve adhesion, thereby enhancing cycle life and fast-charging capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase energy density, then capacity is improved, but volume expansion causes cracks and deteriorates cycle life
Solution Approach 1:
The anode active material layer is divided into multiple layers with different binder compositions. The first layer (near current collector) uses binder with lower cellulose-based content, while subsequent layers use binder with higher cellulose-based content. This segmentation allows each layer to handle volume expansion differently, preventing crack propagation through the entire structure while maintaining high silicon content for high capacity.
Solution Approach 2:
Different regions of the anode active material layer have different binder compositions tailored to their specific functions. The first layer near the current collector focuses on adhesion, while inner layers focus on accommodating volume expansion. This local quality optimization allows the structure to simultaneously achieve high capacity and long cycle life.
2Quantity of substance
If silicon-based active material is used to increase energy density, then capacity is improved, but fast-charging performance deteriorates
Solution Approach 1:
The multi-layer structure with gradient binder composition creates optimized pathways for lithium ion transport. The first layer's lower cellulose content provides better conductivity for fast charging, while inner layers accommodate expansion. This segmentation enables both high energy density and improved fast-charging performance.
3Reliability
If volume expansion of silicon is controlled to prevent cracks, then cycle life is improved, but adhesion and structural integrity worsen
Solution Approach 1:
The first layer near the current collector uses binder with lower cellulose-based content and higher rubber-based content, optimizing for adhesion strength. Inner layers use binder with higher cellulose-based content to accommodate volume expansion. This local quality differentiation ensures both strong adhesion and crack resistance.
Solution Approach 2:
The binder itself is a composite of rubber-based and cellulose-based materials, and the overall anode structure is a composite of multiple layers with different compositions. This composite approach allows simultaneous optimization of adhesion (rubber-based) and volume expansion accommodation (cellulose-based).
Data Source
AI summary
An anode according to embodiments of the present disclosure includes an anode current collector, a first anode active material layer which is disposed on at least one surface of the anode current collector, and includes a first silicon-based active material and a first binder including a first rubber-based binder and a first cellulose-based binder. The anode includes a second anode active material layer which is disposed on the first anode active material layer, and includes a second silicon-based active material and a second binder including a second rubber-based binder and a second cellulose-based binder. A weight ratio of the first cellulose-based binder to the first rubber-based binder in the first binder is lower than a weight ratio of the second cellulose-based binder to the second rubber-based binder in the second binder.