Layered Silicon Negative Electrode for Uniform Lithium Intercalation
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Solution Overview
Problem
Lithium secondary batteries using silicon-based active materials face challenges such as volume expansion, cracking, and degradation due to non-uniform components, especially at high voltages, limiting their energy density and life performance.
Innovation Solution
A negative electrode with a sequentially stacked structure of a first and second active material layer on a current collector, where the first silicon-containing compound is doped with a higher metal ratio than the second, and the binder ratio is adjusted within a specific range to ensure uniform lithium intercalation and adhesion, reducing thickness expansion and improving life performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase capacity, then energy density is improved, but volume expansion and cracking occur leading to degraded life characteristics
Solution Approach 1:
The negative electrode active material layer is divided into multiple layers with different silicon content. The first layer (near current collector) has higher silicon content for high capacity, while the second layer (near separator) has lower silicon content for structural stability. This segmentation allows the electrode to achieve high energy density while maintaining reliability during charge-discharge cycles.
Solution Approach 2:
Different regions of the negative electrode are assigned different compositions tailored to their specific functions. The first layer with higher silicon content (3-15 wt%) is positioned where high capacity is needed, while the second layer with lower silicon content (1-5 wt%) is positioned to provide structural support and prevent cracking. This local quality optimization resolves the contradiction between capacity and life characteristics.
2Quantity of substance
If silicon-based active material is used at high voltage, then energy density is improved, but excessive SEI layer formation and electrolyte depletion occur
Solution Approach 1:
The invention changes the compositional parameter of silicon content across different layers of the negative electrode. By creating a gradient structure where silicon content decreases from the first layer to the second layer, the electrode achieves high energy density in the high-voltage region while the lower silicon content in the second layer reduces excessive SEI formation and electrolyte consumption.
3Ease of manufacture
If uniform binder distribution is used, then manufacturing simplicity is maintained, but adhesion uniformity and thickness expansion control are insufficient
Solution Approach 1:
The binder distribution is optimized locally in each layer rather than being uniformly distributed. The first layer contains binder at 1-5 wt% to provide adhesion for high silicon content material, while the second layer contains binder at 2-7 wt% to ensure proper adhesion and control thickness expansion. This localized optimization achieves manufacturing precision without significantly complicating the manufacturing process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly enhances the life performance and energy density of the negative electrode and secondary battery, particularly at high voltages, by achieving uniform lithium intercalation and improved adhesion, thereby extending the battery's lifespan and capacity.
Implementation Method 1
uniform lithium intercalation and deintercalation may be achieved in the entire negative electrode
Implementation Method 2
a metal doping ratio of a first silicon-based active material included in the first negative electrode active material layer is greater than a metal doping ratio of a second silicon-based active material included in the second negative electrode active material layer
Data Source
AI summary
A negative electrode including a negative electrode current collector; a first negative electrode active material layer on the negative electrode current collector and a second negative electrode active material layer on the first negative electrode active material layer. The first negative electrode active material layer includes a first carbon-containing active material, a first silicon-containing active material, and a first binder. The second carbon-containing active material, a second silicon-containing active material, and a second binder. The first silicon-containing active material includes a first silicon-containing compound and a first metal doped in the first silicon-containing compound. The second silicon-containing active material includes a second silicon-containing compound and a second metal doped in the second silicon-containing compound.