Silicon Negative Electrode Layering for Capacity Retention
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Solution Overview
Problem
The low energy density and capacity retention rate of lithium secondary batteries are limitations due to the use of graphite as a negative electrode material, necessitating the development of new materials and manufacturing methods to enhance performance.
Innovation Solution
A negative electrode structure with a dual-layered mixture layer comprising a first layer with a binder and a second layer without a binder, optimized with a weight ratio of binders in the upper half of the first layer to the second layer of 5:1 or more, using a silicon-based material and specific conductive materials to improve conductivity and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If graphite is used as negative electrode material, then the battery structure is simple and manufacturing is easy, but the energy density and capacity retention rate are low
Solution Approach 1:
The patent uses a composite negative electrode structure combining graphite particles (first particle group) with silicon-based material particles (second particle group). This composite approach achieves high energy density (silicon has higher theoretical capacity than graphite) while maintaining structural stability through the graphite matrix, resolving the contradiction between ease of manufacture and energy density.
Solution Approach 2:
The patent creates different local regions within the negative electrode: an inner region containing primarily graphite particles for structural stability and adhesion, and an outer region containing silicon-based particles for high capacity. This local differentiation allows the electrode to simultaneously achieve high energy density from silicon while maintaining manufacturability and structural integrity from graphite.
2Quantity of substance
If silicon-based material is used to increase energy density, then the capacity retention rate improves, but the electrode structure becomes more complex
Solution Approach 1:
The patent segments the negative electrode into distinct particle groups: first particles (graphite) and second particles (silicon-based materials) with different size ranges. The silicon-based particles are positioned in the outer region while graphite particles form the inner region. This segmentation allows the complex high-capacity silicon material to be integrated systematically, managing structural complexity while achieving high energy density.
Solution Approach 2:
The patent creates a nested structure where silicon-based material particles are positioned within the overall negative electrode matrix formed by graphite particles. The outer peripheral region contains silicon particles while the inner region contains graphite particles, creating a nested arrangement that integrates the high-capacity silicon material into the existing graphite-based electrode structure without excessive complexity.
Data Source
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AI summary
A negative electrode according to an embodiment of the present invention, comprises: a negative electrode current collector; and a negative electrode mixture layer formed on at least one side of the negative electrode current collector and including a silicon-based material and a binder, wherein the negative electrode mixture layer includes a first layer in contact with the negative electrode current collector on the negative electrode current collector and a second layer in contact with the first layer on the first layer, and the weight ratio of the binders respectively included in the upper half of the first layer in the thickness direction and the second layer may be 5:1 or more.