Spiral-Wound Battery Anode Layers With Matched Graphite Porosity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In nonaqueous electrolyte secondary batteries with spirally wound electrode bodies, the negative electrode mixture layers at the inner and outer surfaces of the curved electrode plate experience different rates of degradation due to variations in packing density, leading to unbalanced component contents.
Innovation Solution
The battery design incorporates a negative electrode plate with a first mixture layer on the inner surface and a second mixture layer on the outer surface, using graphite particles with different internal void rates as the primary component in each layer, thereby controlling the packing density and maintaining balanced component distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the negative electrode plate is wound in a spiral configuration, then the battery structure is compact and manufacturable, but the packing density of the negative electrode mixture layer becomes non-uniform between the inner and outer surfaces
Solution Approach 1:
The patent applies local quality by using graphite particles with different internal void rates at different radial positions within the negative electrode mixture layer. Specifically, particles with lower internal void rates (5% or less) are used at the inner radius where compression is greater, while particles with higher internal void rates (10% or more) are used at the outer radius where stretching occurs. This spatial variation in material properties compensates for the non-uniform mechanical stress distribution in the spiral-wound structure, maintaining consistent packing density and preventing degradation.
2Reliability
If the packing density of the negative electrode mixture layer at the winding inner surface is decreased to match the outer surface, then degradation rates become more uniform, but the content balance of non-carbon components becomes unbalanced
Solution Approach 1:
The patent changes the physical parameter of the graphite particles (internal void rate) to resolve the contradiction. By selecting particles with lower internal void rates for the inner surface and higher internal void rates for the outer surface, the patent achieves uniform effective packing density without altering the overall composition or concentration of carbon and non-carbon components in the mixture layer. This parameter change at the particle level allows degradation uniformity while maintaining compositional stability.
3Ease of manufacture
If a single type of graphite particle is used throughout the negative electrode mixture layer, then the manufacturing process is simple, but the packing density cannot be optimized for both inner and outer surfaces simultaneously
Solution Approach 1:
The patent divides the negative electrode mixture layer into different radial zones and assigns different graphite particle types to each zone. The inner radius region uses graphite particles with internal void rates of 5% or less, while the outer radius region uses particles with internal void rates of 10% or more. This local differentiation optimizes the packing density and mechanical stability at each position, significantly improving cycle characteristics compared to using a single particle type throughout.
Data Source
AI summary
A nonaqueous electrolyte secondary battery according to an aspect of the present disclosure includes: an electrode body in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween; and an exterior package which receives the electrode body, the negative electrode plate includes a negative electrode collector, a first negative electrode mixture layer formed on a winding inside first surface of the negative electrode collector, and a second negative electrode mixture layer formed on a winding outside second surface of the negative electrode collector, the first negative electrode mixture layer contains first graphite particles as a primary component, the second negative electrode mixture layer contains second graphite particles as a primary component, and the first graphite particles has an internal void rate lower than an internal void rate of the second graphite particles.