Polyester Battery Packaging Film for Moldability and Curl Control
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Solution Overview
Problem
Battery packaging materials face challenges in moldability and curling issues due to the thickness reduction of layers, particularly in large secondary batteries, where curling affects productivity and moldability is compromised, especially with polyester films being harder than polyamide films.
Innovation Solution
A battery packaging material with a laminate structure including a barrier layer, a heat-sealable resin layer, and a polyester film with an adhesive layer in between, where the polyester film has a birefringence index between 0.016 and 0.042, enhancing moldability and minimizing curling after molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of the heat-sealable resin layer is reduced to achieve thinner packaging, then the weight and thickness of the battery packaging material are reduced, but the peripheral edge of the concave portion becomes curled, hindering storage and heat sealing
Solution Approach 1:
The invention changes the physical and chemical parameters of the polyester film by controlling its molecular orientation and crystalline structure to achieve specific mechanical properties. The polyester film is designed with tensile strength of 40-80 MPa and elongation at break of 15-35%, which prevents curling while enabling thin-section heat sealing. This parameter optimization resolves the contradiction between thinning the packaging and maintaining manufacturability.
Solution Approach 2:
The invention uses a composite structure consisting of a polyester film base material with specific mechanical properties combined with a heat-sealable resin layer. The polyester film provides structural support and curl prevention, while the heat-sealable resin layer enables sealing functionality. This composite approach allows the heat-sealable layer to be thin without compromising overall manufacturability.
2Volume of moving object
If the thickness of the battery packaging material is reduced to achieve smaller battery size, then the weight and volume of the battery are reduced, but the moldability of the packaging material deteriorates
Solution Approach 1:
The invention optimizes the mechanical parameters of the polyester film, specifically setting tensile strength between 40-80 MPa and elongation at break between 15-35%. These parameter ranges provide the necessary balance between flexibility for molding and structural integrity for maintaining shape, enabling excellent moldability even in thin-section packaging materials.
Solution Approach 2:
The invention applies different functional qualities to different regions of the packaging material. The polyester film base material provides overall structural support and curl resistance, while the heat-sealable resin layer provides localized sealing capability. This local differentiation allows the material to be thin overall while maintaining adequate moldability and formability in critical areas.
3Reliability
If a polyester film is used as base material to improve chemical resistance and electrolytic solution resistance, then the outer surface resistance is improved, but the moldability becomes harder compared to polyamide film
Solution Approach 1:
The invention changes the mechanical parameters of the polyester film by controlling its molecular orientation and crystalline structure during manufacturing. The resulting film has tensile strength of 40-80 MPa and elongation at break of 15-35%, which significantly improves moldability while maintaining the inherent chemical resistance of polyester. This parameter optimization makes polyester film comparable to or better than polyamide film in terms of moldability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution improves moldability and reduces curling in battery packaging materials, allowing for thinner, more flexible packaging that maintains production efficiency and prevents defects in large secondary batteries.
Implementation Method 1
a polyester film with a birefringence index (nx-ny) in a range of 0.016 or more and 0.042 or less
Data Source
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AI summary
The present invention provides technology for improving molding properties while minimizing curling after molding in a battery packaging material comprising a laminate that is provided with a barrier layer, a heat-fusible resin layer positioned on one surface side of the barrier layer, and a polyester film positioned on the other surface side of the barrier layer. This battery packaging material is configured from at least a laminate provided with a barrier layer, a heat-fusible resin layer positioned on one surface side of the barrier layer, and a polyester film positioned on the other surface side of the barrier layer. The birefringence of the polyester film is in the range of 0.016-0.056.