Positive Electrode Particle Gradient for High-Capacity Battery Cycling
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Solution Overview
Problem
Existing non-aqueous electrolyte secondary batteries face a trade-off between high capacity and excellent cycle characteristics, as using non-aggregated particles improves cycle characteristics but lowers capacity, while secondary particles deteriorate cycle characteristics, and mixing both does not achieve both simultaneously.
Innovation Solution
A positive electrode mixture layer with non-aggregated and secondary lithium-metal composite oxide particles, where the content of non-aggregated particles on the surface side is higher than on the core side, optimizing the distribution to enhance electrolyte pathway and filling density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-aggregated particles are used as positive electrode active material, then cycle characteristics are improved, but battery capacity is lowered due to decrease in filling property
Solution Approach 1:
The patent applies local quality by creating a positive electrode mixture layer with non-uniform particle distribution. Specifically, non-aggregated particles (first particles) are concentrated in the surface region (first region) where electrolyte contact is critical for cycle stability, while aggregated particles (second particles) are concentrated in the core region (second region) where packing density determines capacity. This spatial differentiation of particle types resolves the contradiction between cycle characteristics and battery capacity.
2Quantity of substance
If secondary particles are used as positive electrode active material, then filling property is improved, but cycle characteristics deteriorate
Solution Approach 1:
The patent resolves this contradiction by applying aggregated particles (second particles) specifically in the core region (second region) of the positive electrode mixture layer, where high filling density is most beneficial for capacity. Meanwhile, non-aggregated particles (first particles) are placed in the surface region (first region) to maintain good cycle characteristics. This localized assignment of particle types allows each region to optimize for its specific function.
3Quantity of substance
If mixture of non-aggregated particles and secondary particles is used, then filling property is improved, but cycle characteristics cannot be maintained
Solution Approach 1:
The patent overcomes the limitation of simple mixing by implementing a stratified structure where non-aggregated particles (first particles) predominantly occupy the surface region (first region) and aggregated particles (second particles) predominantly occupy the core region (second region). This spatial separation ensures that the surface region maintains good electrolyte permeability and cycle stability, while the core region achieves high filling density and capacity.
Solution Approach 2:
The patent transitions from a one-dimensional mixture (random distribution) to a two-dimensional stratified structure by defining distinct first and second regions in the positive electrode mixture layer. This dimensional organization allows different particle types to be systematically positioned in different zones, enabling simultaneous optimization of both cycle characteristics and battery capacity.
Data Source
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AI summary
The purpose of the present disclosure is to provide a nonaqueous electrolyte secondary battery that has high capacity and excellent cycle characteristics. A nonaqueous electrolyte secondary battery according to one embodiment of the present invention is provided with a positive electrode, a negative electrode and a nonaqueous electrolyte. An electrode mixture layer of the positive electrode contains: first lithium metal composite oxide particles that are non-aggregated particles which have a volume-based median diameter of from 2 µm to 10 µm; and second lithium metal composite oxide particles that are secondary particles, in each of which primary particles having an average particle diameter of from 50 nm to 2 µm aggregate, and which have a volume-based median diameter of from 10 µm to 30 µm. If the positive electrode mixture layer is divided into equal halves in the thickness direction and the halves are defined as the first region and the second region sequentially from the surface side of the positive electrode mixture layer, the content of the first lithium metal composite oxide particles in the first region is higher than the content of the first lithium metal composite oxide particles in the second region.