Polypropylene Insulation Member for Cylindrical Battery Shock Absorption
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Solution Overview
Problem
Cylindrical secondary batteries face short circuits and stability issues due to the mechanical limitations and combustibility of non-woven fabric insulation members, which fail to absorb external shocks and volume changes effectively.
Innovation Solution
A polypropylene insulation member with specific mechanical properties, including tensile strength and flexural modulus, is used between the top cap assembly and electrode assembly, featuring a fine pattern for enhanced adhesion and insulation, manufactured using a silicon master mold to improve shock resistance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a non-woven fabric insulation member is used, then ease of manufacture is improved, but mechanical strength and heat resistance deteriorate
Solution Approach 1:
The patent uses a composite structure consisting of a porous base layer (non-woven fabric) and a surface layer (thermoplastic resin). This composite structure combines the manufacturing ease and porosity of non-woven fabric with the mechanical strength and heat resistance of thermoplastic resin, resolving the contradiction between ease of manufacture and mechanical strength.
2Ease of manufacture
If a non-woven fabric insulation member is used, then ease of manufacture is improved, but heat resistance deteriorates
Solution Approach 1:
The surface layer made of thermoplastic resin provides heat resistance to the insulation member. This thermoplastic layer covers the porous base layer and maintains structural integrity at high temperatures, preventing combustion and maintaining mechanical properties under thermal stress while allowing the underlying non-woven fabric to provide manufacturing ease.
3Reliability
If the insulation member mechanical properties are increased, then short circuit prevention is improved, but shock-absorbing effect deteriorates
Solution Approach 1:
The insulation member has different properties in different layers: the porous base layer provides shock-absorbing effect through its porous structure and compressibility, while the surface layer provides mechanical strength and short circuit prevention. This local differentiation of properties allows the same component to fulfill both functions simultaneously.
4Ease of manufacture
If the insulation member is made combustible, then ease of manufacture is improved, but safety deteriorates
Solution Approach 1:
The thermoplastic resin surface layer acts as a protective barrier that is non-combustible and provides fire resistance. This layer prevents the porous base layer (which may be combustible) from direct exposure to fire, thereby improving safety while maintaining the manufacturing advantages of the non-woven fabric structure.
Data Source
AI summary
The present disclosure provides an insulation member having excellent mechanical properties having enough shock-absorbing effect in external shock and volume change in a battery and provides a cylindrical secondary battery including the insulation member. The insulation member according to the present disclosure has excellent mechanical properties in high temperature, is composed of polypropylene having narrow molecular weight, and has a fine pattern on the surface.