Secondary Battery Separator Bent Portion and Thickness
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Solution Overview
Problem
Secondary batteries face challenges in maintaining high reliability due to insufficient discussion on the shape and bonding of separators to electrode plates, leading to potential issues with the slide down of active material mix layers and contact with insulating sheets.
Innovation Solution
A secondary battery configuration with a first and second electrode plate, where the first separator is bonded to the first active material mix layer and the second separator to the second active material mix layer, featuring a bent portion towards the second separator, and the second active material mix layer having a reduced thickness at the central portion, which suppresses the slide down of active material mix layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If separators are bonded to both surfaces of electrode plates to facilitate production, then productivity is improved, but the active material mix layers may slide down and contact insulating sheets, reducing reliability
Solution Approach 1:
The separator is designed with a bent portion (curved structure) at its end, extending toward the electrode plate. This curvature allows the separator to conform to the electrode plate surface while maintaining bonding stability, preventing the active material mix layer from sliding down and contacting the insulating sheet, thus resolving the contradiction between productivity and reliability
Solution Approach 2:
The separator has different structural characteristics at different locations: the central portion is flat for optimal bonding, while the end portion is bent to provide mechanical support and prevent slide-down. This local differentiation allows the separator to simultaneously achieve easy bonding (productivity) and prevent active material displacement (reliability)
2Ease of manufacture
If the active material mix layer has uniform thickness, then manufacturing is simpler, but the separator cannot effectively prevent slide down at the electrode plate edges
Solution Approach 1:
The active material mix layer is designed with non-uniform thickness: the central portion has standard thickness for normal electrochemical function, while the end portion has reduced thickness to create a stepped structure. This local thickness variation works synergistically with the bent separator to prevent slide-down at edges while maintaining ease of manufacturing through a simple thickness modification rather than complex multi-layer construction
Data Source
AI summary
A secondary battery has an electrode assembly including a negative electrode plate and a positive electrode plate and a battery case accommodating the electrode assembly. The negative electrode plate includes a negative electrode core body and first and second negative electrode active material mix layers disposed on the respective surfaces of the negative electrode core body. A first separator is bonded to the first negative electrode active material mix layer, and a second separator is bonded to the second negative electrode active material mix layer. In at least one side edge portion of the negative electrode plate, the first separator has a first bent portion bent toward the second separator, the negative electrode core body has a second bent portion bent toward the second separator, and the second negative electrode active material mix layer includes a region having a thickness less than the thickness of the central portion.