Layered Positive Electrode Structure for Faster Electrolyte Permeation
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face a decrease in electrolyte solution permeation due to increased positive electrode density, leading to impaired productivity, especially in batteries with large areas.
Innovation Solution
A multilayer positive electrode active material layer structure is implemented, comprising a first layer with a unimodal particle size distribution and a second layer with a multimodal particle size distribution, optimized by specific D10/D90, D50, and thickness ratios, to enhance packing properties and liquid permeation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the density of the positive electrode active material layer is increased to improve packing properties, then the capacity is improved, but the porosity decreases leading to reduced electrolyte solution permeation
Solution Approach 1:
The positive electrode active material layer is divided into multiple layers with different particle size distributions. The lower layer (near substrate) uses multimodal distribution for high packing density, while the upper layer (near surface) uses unimodal distribution with controlled D10/D90 ratio to maintain porosity. This segmentation allows each layer to optimize its function without compromising the other.
Solution Approach 2:
Different regions of the positive electrode active material layer are given different particle size distribution characteristics. The lower layer has multimodal distribution optimized for density, while the upper layer has unimodal distribution optimized for permeation. This local differentiation resolves the contradiction between density and porosity requirements in different spatial zones.
2Quantity of substance
If the area of the positive electrode is increased to improve capacity, then the energy storage is improved, but the electrolyte solution permeation time increases
Solution Approach 1:
The upper layer of the positive electrode active material layer is specifically designed with unimodal particle size distribution and controlled D10/D90 ratio to maintain high porosity. This ensures that even in large-area electrodes, the electrolyte solution can rapidly permeate through the upper region where it is most needed, reducing overall permeation time.
Solution Approach 2:
The invention addresses the permeation time issue by creating a vertical gradient in particle size distribution within the layer structure. The unimodal upper layer with optimized D10/D90 ratio creates a high-permeability zone that accelerates electrolyte solution transport in the thickness direction, effectively reducing permeation time across the entire electrode area.
Data Source
AI summary
A non-aqueous electrolyte secondary battery comprises a positive electrode, a negative electrode, and an electrolyte solution. The positive electrode includes a positive electrode substrate and a positive electrode active material layer. The positive electrode active material layer includes a first layer and a second layer. The second layer is interposed between the positive electrode substrate and the first layer. The first layer includes a first positive electrode active material. The second layer includes a second positive electrode active material. The first positive electrode active material has a first particle size distribution based on volume. The first particle size distribution is unimodal. In the first particle size distribution, a ratio of D10 to D90 is from 0.18 to 0.52. The second positive electrode active material has a second particle size distribution based on volume. The second particle size distribution is multimodal.