Pouch Film Laminate Structure for Deep-Draw Battery Cases
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Solution Overview
Problem
Conventional pouch film laminates for secondary batteries have limitations in forming deeper cup portions and reducing the radius of filleting, leading to increased dead space and decreased energy efficiency due to low formability.
Innovation Solution
A pouch film laminate with specific thicknesses and compositions of layers, including a gas barrier layer of 50-70 μm, sealant layer of 70-100 μm, and aluminum alloy thin film with 10-13 μm grain size, enhances tensile strength and elongation, allowing for improved formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional pouch film laminate with thin aluminum alloy (about 40 μm) is used, then the weight and cost are reduced, but the formability is poor and the cup portion cannot be formed deeply
Solution Approach 1:
The patent changes the thickness parameter of the aluminum alloy thin film from the conventional 40 μm to 50-70 μm. This parameter change directly improves the formability and enables deep cup portion formation without pinholes or cracks, while still maintaining reasonable weight and cost characteristics.
Solution Approach 2:
The patent uses a composite laminate structure consisting of multiple layers: sealant layer, gas barrier layer (aluminum alloy), surface protection layer, and drawing assistance layer. This composite structure combines the advantages of each material to achieve both deep formability and structural integrity.
2Volume of moving object
If the pouch film laminate is made thinner to reduce dead space, then the energy efficiency is improved, but the tensile strength and elongation are insufficient leading to poor formability
Solution Approach 1:
The patent employs a multi-layer composite structure where each layer contributes specific properties: the sealant layer provides sealing strength, the gas barrier layer provides structural support and gas barrier function, the surface protection layer provides mechanical protection, and the drawing assistance layer facilitates forming. This composite approach achieves both reduced dead space and sufficient tensile strength.
Solution Approach 2:
The patent optimizes the thickness of each layer locally according to its specific function. The gas barrier layer is thickened to 50-70 μm for formability, while the surface protection layer is kept at 5-25 μm to minimize dead space. This local optimization balances strength requirements with space efficiency.
3Volume of moving object
If the cup portion is formed deeper to increase accommodation space, then the energy efficiency is improved, but pinholes and cracks occur in the film
Solution Approach 1:
The patent changes the thickness parameter of the gas barrier layer to 50-70 μm, which provides sufficient structural support to prevent pinholes and cracks during deep forming while still allowing the cup portion to be formed deeply for increased accommodation space.
Solution Approach 2:
The multi-layer composite structure distributes the mechanical stresses during deep forming across different layers, preventing concentration of stress that would cause pinholes or cracks. The drawing assistance layer specifically helps manage stress during the forming process.
4Volume of moving object
If the radius of curvature of cup edges is reduced to accommodate larger electrode assembly, then the space utilization is improved, but the formability is compromised
Solution Approach 1:
The increased thickness of the gas barrier layer to 50-70 μm provides the necessary structural support and ductility to reduce the radius of curvature of cup edges while maintaining formability and preventing defects during the forming process.
Solution Approach 2:
The composite laminate structure, particularly the combination of the gas barrier layer with the drawing assistance layer, enables complex forming operations including sharp edge radii reduction while maintaining manufacturing feasibility and product quality.
Data Source
AI summary
A pouch film laminate for preparing a pouch type battery case accommodating an electrode assembly is provided. The pouch film laminate includes a sealant layer formed of a first polymer as an innermost layer, a surface protection layer formed of a second polymer as an outermost layer, an aluminum alloy thin film having a grain size of 10 μm to 13 μm, and a gas barrier layer laminated between the surface protection layer and the sealant layer, wherein the gas barrier layer has a thickness of 50 μm to 70 μm, and the sealant layer has a thickness of 70 μm to 100 μm.