Battery Separator Structure for Electrode Expansion Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional separators for nonaqueous electrolyte secondary batteries deform due to stress from volume expansion of negative electrodes during charge and discharge, leading to decreased battery characteristics and safety.
Innovation Solution
A nonaqueous electrolyte secondary battery separator with a polyolefin porous film and a porous layer containing a heat-resistant resin, where the maximum second derivative value of the stress-strain curve is not less than 0.15, obtained from a tension test, to prevent deformation under stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the weight per unit area of the porous layer is increased to prevent separator deformation, then the separator's resistance to stress improves, but the battery characteristics and safety may still deteriorate due to excessive rigidity
Solution Approach 1:
The patent changes the mechanical parameters of the porous layer by controlling its weight per unit area within a specific range (3.0-10.0 g/m²) and adjusting the maximum second derivative value of the stress-strain curve (≥0.15). This optimization balances stress resistance with flexibility, preventing both deformation and excessive rigidity that would harm battery performance and safety.
Solution Approach 2:
The separator employs a composite structure combining a polyolefin porous film base layer with a porous layer containing heat-resistant resin. This composite design provides both mechanical strength from the heat-resistant resin and flexibility from the polyolefin base, resolving the contradiction between stress resistance and battery reliability.
2Stability of the object's composition
If the porous layer is made thicker to resist deformation, then the separator's dimensional stability improves, but the battery characteristics and safety decrease due to stress from volume expansion
Solution Approach 1:
The patent optimizes the thickness and mechanical properties of the porous layer by controlling its weight per unit area (3.0-10.0 g/m²) and the maximum second derivative value of the stress-strain curve (≥0.15). This ensures the layer maintains dimensional stability while remaining flexible enough to accommodate electrode volume expansion during charge-discharge cycles.
3Ease of manufacture
If the separator structure is simplified to reduce manufacturing complexity, then the production process improves, but the ability to prevent deformation under stress deteriorates
Solution Approach 1:
The patent establishes specific parameter ranges for the porous layer (weight per unit area: 3.0-10.0 g/m², maximum second derivative value: ≥0.15) that can be achieved through conventional coating and drying processes. This allows manufacturers to produce high-performance separators using existing equipment and techniques without requiring complex manufacturing processes.
Data Source
AI summary
Provided is a nonaqueous electrolyte secondary battery separator that can prevent a decrease in battery characteristics and/or safety caused by a deformation of a separator due to stress resulting from volume expansion of a negative electrode during charge and discharge. The nonaqueous electrolyte secondary battery separator has a maximum value of a second derivative value of not less than 0.15 which has been calculated based on first derivative values obtained at intervals of 0.5 mm of an elongation amount in a range of a value of X of 0 mm to 7.0 mm on a stress-strain curve obtained from a result of a tension test.