Asymmetric Positive Electrode Layers for Short-Circuit Heat Suppression
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face a reduction in battery capacity and temperature rise issues due to the presence of insulating particles in intermediate layers, which are intended to suppress internal shorts.
Innovation Solution
A positive electrode design with a first intermediate layer of smaller thickness and lower insulating particle mass per unit area compared to a second intermediate layer, applied on both sides of the current collector, effectively manages compressive and tensile stresses during winding, thereby preventing capacity reduction and temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an intermediate layer including insulating particles is disposed between the positive electrode current collector and the positive electrode mixture layer, then temperature rise of the battery upon internal short is suppressed, but battery capacity per unit volume is reduced
Solution Approach 1:
The patent applies different intermediate layer configurations to different sides of the current collector. The first intermediate layer (inner peripheral side) has smaller thickness and lower insulating particle mass per unit area, while the second intermediate layer (outer peripheral side) has larger thickness and higher insulating particle mass per unit area. This local differentiation optimizes the balance between suppressing temperature rise and maintaining battery capacity.
Solution Approach 2:
The patent creates an asymmetric structure where the intermediate layers on the two sides of the current collector have different properties. Specifically, the thickness and insulating particle mass per unit area vary between the first and second intermediate layers, breaking the symmetry to achieve optimal performance in both temperature suppression and capacity maintenance.
2Reliability
If the intermediate layer has larger thickness and more insulating particles, then temperature rise upon internal short is better suppressed, but the proportion of positive electrode mixture layer is reduced
Solution Approach 1:
The patent implements local quality by assigning different thickness and insulating particle densities to different regions. The first intermediate layer has reduced thickness and insulating particle mass compared to the second intermediate layer, allowing the positive electrode mixture layer to occupy more volume on the inner peripheral side while maintaining adequate temperature suppression where it is most needed.
Data Source
AI summary
A positive electrode (11) according to one embodiment is provided with: a positive electrode collector (30); a first middle layer (32) disposed on one of two surfaces of the positive electrode collector (30), the surface being on the inner circumferential side when the positive electrode collector (30) is wound; a second middle layer (34) that is disposed on the other surface that is on the outer circumferential side; and a positive electrode mixed material layer (36) disposed on the first middle layer (32) and on the second middle layer (34). The first middle layer (32) and the second middle layer (34) contain insulating particles and an electrical conductor, and the thickness of the first middle layer (32) is less than the thickness of the second middle layer (34).