Battery Packaging Laminate Using Polyester Orientation for Moldability
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Solution Overview
Problem
Conventional battery packaging materials, particularly those using metallic and stretched polyester films, face challenges in moldability and curling issues, which hinder the reduction in thickness and weight of batteries, especially in large secondary batteries, leading to productivity losses.
Innovation Solution
A battery packaging material comprising a laminate structure with a barrier layer, a heat-sealable resin layer, and a polyester film, where the polyester film has a specific surface orientation ratio between 1.4 and 2.7, as measured by infrared absorption spectra, to enhance moldability and minimize curling after molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the thickness of the battery packaging material is reduced to achieve thinner and lighter batteries, then the weight and thickness of the battery are reduced, but the peripheral edges of concave portions become curled, hindering storage of battery elements and heat sealing operations
Solution Approach 1:
The invention changes the physical-chemical parameters of the polyester film by controlling its degree of crystallinity (30-70%) and orientation ratio (1.05-1.30). These parameter changes enable the film to maintain dimensional stability and resist curling even when the overall packaging material thickness is reduced, thus allowing thinner batteries without compromising manufacturing processability
Solution Approach 2:
The invention uses a composite structure consisting of multiple layers: polyester film, polyamide film, aluminum foil, and heat-sealable resin layers. This composite material structure combines the advantages of each material - the polyester film provides dimensional stability, the polyamide film provides strength, the aluminum foil provides barrier properties, and the heat-sealable resin enables sealing - allowing the packaging material to be thin yet maintain good formability and resist curling
2Reliability
If a stretched polyester film is used as the base material to improve chemical resistance and electrolytic solution resistance, then the outer surface resistance is improved, but the moldability deteriorates due to the film being harder and less moldable
Solution Approach 1:
The invention optimizes the degree of crystallinity of the polyester film within 30-70% and controls the orientation ratio between 1.05-1.30. These parameter changes reduce the hardness and improve the moldability of the polyester film while maintaining its chemical resistance properties, resolving the contradiction between reliability and ease of manufacture
3Length of stationary object
If the battery packaging material is made thinner to reduce battery size, then the thickness is reduced, but the material becomes more prone to curling after molding, affecting productivity
Solution Approach 1:
The invention controls the degree of crystallinity of the polyester film within 30-70% and the orientation ratio between 1.05-1.30. These parameter changes enhance the dimensional stability of the thin packaging material, preventing curling after molding even when the thickness is reduced, thus maintaining productivity
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 significantly improves moldability and reduces curling in battery packaging materials, allowing for thinner, lighter batteries with improved production efficiency, particularly beneficial for large secondary batteries.
Implementation Method 1
a polyester film having a ratio in a range of 1.4 or more and 2.7 or less between a maximum value Ymax and a minimum value Ymin (degree of surface orientation: Ymax/Ymin), with the maximum value Ymax and the minimum value Ymin respectively representing a maximum value and a minimum value of a ratio between an absorption peak intensity Y1340 at 1340 cm-1
Data Source
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AI summary
The present invention related to 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, and a polyester film situated on the other surface side of the barrier layer, the thickness of the barrier layer being 100 µm or less, the polyester film having a ratio in a range of 1.4 or more and 2.7 or less between a maximum value Ymax and a minimum value Ymin (degree of surface orientation: Ymax/Ymin), with the maximum value Ymax and the minimum value Ymin respectively representing a maximum value and a minimum value of a ratio between an absorption peak intensity Y1340 at 1340 cm-1 and an absorption peak intensity Y1410 at 1410 cm-1 (Y1340/Y1410) in infrared absorption spectra acquired for 18 directions at intervals of 10° from 0° to 180° on a surface of the polyester film according to attenuated total reflection of Fourier transform infrared spectroscopy, determined as disclosed in the description.