Dual-Density Negative Electrode for High-Capacity Ion Diffusion
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face a challenge in increasing capacity while maintaining input-output properties, as higher electrode coating weights can lead to longer ion-diffusion pathways and degradation of performance.
Innovation Solution
A negative electrode with a dual-density active material layer, comprising a high-density first region and a lower-density second region, where the second region has a density at least 7% less than the first region and occupies a volume ratio of 7-50%, and is structured in a grid or columnar form with a shortest distance of 50 μm or less between regions, enhancing ion diffusion and maintaining capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the coating weight of the negative electrode active material layer is increased to enhance capacity, then the battery capacity increases, but the ion-diffusion pathways become longer and input-output properties are degraded
Solution Approach 1:
The negative electrode active material layer is designed with spatially varying density: a first region with higher density (providing capacity) and a second region with lower density (providing short ion-diffusion pathways). This local quality differentiation allows simultaneous achievement of high capacity and good input-output properties by optimizing different regions for different functions.
Solution Approach 2:
The negative electrode active material layer is segmented into multiple regions with different densities. The first region (higher density) and second region (lower density) are distinct zones within the layer, each contributing differently to overall performance. This segmentation enables the layer to achieve both high capacity storage and efficient ion transport.
2Quantity of substance
If the negative electrode active material layer is formed solely of high density region to increase capacity, then capacity is enhanced, but ion-diffusion pathways become long causing degradation of input-output properties
Solution Approach 1:
Different regions of the negative electrode active material layer have different density characteristics. The first region has higher density for capacity, while the second region has lower density to provide short ion-diffusion pathways. This local quality variation resolves the contradiction between capacity enhancement and ion-diffusion path length.
3Productivity
If the negative electrode active material layer is formed solely of low density region to enhance input-output properties, then ion-diffusion is improved, but it becomes difficult to enhance capacity
Solution Approach 1:
The negative electrode active material layer incorporates regions with different density qualities optimized for different functions. The second region with lower density provides short ion-diffusion pathways for good input-output properties, while the first region with higher density provides capacity. This spatial differentiation of quality allows simultaneous optimization of both properties.
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
This configuration inhibits degradation of input-output properties by maintaining short ion-diffusion pathways and achieving higher capacity, with a coating weight of 20 mg/cm2 or more, thereby improving battery performance.
Implementation Method 1
ion-diffusion pathways for lithium ions and the like included in the electrolyte solution may become longer
Data Source
AI summary
A negative electrode comprising a negative electrode current collector and a negative electrode active material layer including a negative electrode active material, wherein the negative electrode active material layer includes a first region and a second region, a density of the second region is at least 7% less than a density of the first region, and a volume ratio of the second region to the negative electrode active material layer is more than 7% and not more than 50%.