Battery Packaging Laminate to Minimize Curling in Thin Pouch Films
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Solution Overview
Problem
Battery packaging materials face challenges in reducing film thickness and weight while maintaining moldability and minimizing curling, especially in large secondary batteries, due to the limitations of metallic packaging materials and existing film-based solutions.
Innovation Solution
A battery packaging material with a laminate structure comprising a barrier layer, a heat-sealable resin layer, and a polyester film with a birefringence index between 0.016 and 0.056, which enhances moldability and reduces curling by optimizing the thickness ratio and incorporating an adhesive layer to improve adhesion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of each layer in the battery packaging material is reduced to achieve thinner batteries, then the weight and thickness of the battery are reduced, but the peripheral edge of the concave portion becomes curled, hindering storage of battery elements and heat sealing
Solution Approach 1:
The invention changes the physical and chemical parameters of the polyester film by controlling its birefringence index within a specific range (0.016 to 0.056), glass transition temperature (70°C to 90°C), and moisture absorption characteristics. These parameter changes enable the film to maintain dimensional stability and reduce curling even when the overall thickness is reduced to 50 μm or less.
Solution Approach 2:
The invention uses a composite laminate structure consisting of multiple layers including polyester film, base material, and heat-sealable resin layer. Each layer is designed with specific thickness ratios and material properties to work together, where the polyester film provides dimensional stability while the overall thin structure achieves weight reduction.
2Reliability
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 battery packaging material becomes harder and inferior in moldability
Solution Approach 1:
The invention optimizes the polyester film parameters including glass transition temperature (70°C to 90°C), birefringence index (0.016 to 0.056), and thickness ratio relative to the base material. These parameter adjustments make the polyester film softer and more moldable while preserving its chemical resistance properties.
Solution Approach 2:
The invention applies polyester film specifically as the base material layer with controlled thickness (where the ratio of polyester film thickness to base material thickness is 0.2 or more and less than 0.8). This localized application provides chemical resistance where needed while maintaining overall moldability of the packaging material.
3Length of moving object
If the ratio of the thickness of the heat-sealable resin layer to the thickness of the base material is reduced to achieve thinner packaging, then the overall thickness is reduced, but the peripheral edge of the concave portion becomes curled
Solution Approach 1:
The invention changes the parameters of the polyester film including its birefringence index (0.016 to 0.056), glass transition temperature (70°C to 90°C), and moisture absorption characteristics. These parameter changes provide dimensional stability that prevents curling even when the heat-sealable resin layer thickness is reduced.
Solution Approach 2:
The polyester film acts as an intermediary layer between the battery element and the external environment. It provides dimensional stability and prevents curling of the peripheral edge while allowing the heat-sealable resin layer to be sufficiently thin for overall thickness reduction.
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 solution effectively minimizes curling and improves moldability, enabling the production of thinner, more efficient battery packaging materials that can handle large secondary batteries with enhanced productivity and chemical resistance.
Implementation Method 1
the polyester film having a birefringence index in a range of 0.016 or more and 0.056 or less
Data Source
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AI summary
The present invention provides a battery packaging material comprising a laminate that includes at least a barrier layer, a heat-sealable resin layer situated on one surface side of the barrier layer, a polyester film situated on the other surface side of the barrier layer, and an adhesive layer provided between the barrier layer and the heat-sealable resin layer, the polyester film having a birefringence index in a range of 0.016 or more and 0.042 or less, as measured in accordance with the method specified in the description, and the thickness of the barrier layer being 100 µm or less.