Protective Layer for Battery Positive Electrode
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Solution Overview
Problem
Rechargeable electric storage devices, such as lithium ion batteries, experience performance degradation due to binder elution from the separator, which intensively decomposes the positive active material, leading to reduced efficiency and capacity.
Innovation Solution
An electric storage device configuration with a positive electrode, negative electrode, and a separator featuring an inorganic layer with a binder on the separator substrate, where the inorganic layer is larger in width than the positive active material layer and a protective layer covers the positive active material layer's side surfaces to prevent binder elution and decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator with an inorganic layer containing binder is used to prevent short circuits, then reliability is improved, but binder elution occurs causing performance degradation
Solution Approach 1:
A protective layer is introduced as an intermediary between the inorganic layer containing binder and the positive active material layer. This protective layer prevents direct contact between the binder and positive active material, blocking the harmful elution and decomposition reactions while maintaining the separator's short circuit prevention function.
Solution Approach 2:
The separator structure is segmented into multiple functional layers: the inorganic layer for electrical insulation and short circuit prevention, and the protective layer for preventing binder elution. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between reliability improvement and harmful factor generation.
2Reliability
If the inorganic layer is made larger in width than the positive active material layer to ensure coverage, then reliability is improved, but the protective layer must also be extended increasing device complexity
Solution Approach 1:
The protective layer is designed to serve multiple functions: preventing binder elution, protecting the positive active material layer, and maintaining structural integrity. By making the protective layer larger in width than the positive active material layer, it simultaneously provides edge protection and ensures complete coverage, reducing the need for additional protective measures.
Data Source
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AI summary
An electric storage device includes a positive electrode 11, a negative electrode 13, and a separator 12 placed between the positive electrode 11 and the negative electrode 13, the positive electrode 11 has a positive electrode substrate 11A, a positive active material layer 11B formed on the positive electrode substrate 11A, and a protective layer 11C for covering at least one of side surfaces in a width direction of the positive active material layer 11B, the negative electrode 13 has a negative electrode substrate 13A and a negative active material layer 13B formed on the negative electrode substrate 13A, the separator 12 has a separator substrate 12A opposed to the negative active material layer 13B, and an inorganic layer 12B containing a binder, which is formed on the separator substrate 12A and opposed to the positive active material 11B, the inorganic layer 12B is larger in width than the positive active material layer 11B, and the protective layer 11C is adapted to protect the positive active material layer 11B from a component eluted from the binder.