Polyester Film Substrate for Battery Packaging Deep Drawing
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Solution Overview
Problem
The existing methods for producing packaging materials for power storage devices often result in breakage during deep recess formation due to heat-generated deterioration of the substrate layer during lamination, leading to insufficient deep drawing formability and adhesion issues between layers.
Innovation Solution
A packaging material structure comprising a polyester film substrate layer with specific thermal shrinkage and elongation stress properties, combined with an adhesion enhancement layer and anticorrosion treatment layers, to enhance deep drawing formability and adhesion between layers, including a metal foil layer and sealant layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment is applied during lamination to improve adhesion between layers, then adhesion strength is improved, but the substrate layer deteriorates and breaks during deep recess formation
Solution Approach 1:
The patent changes the temperature parameter from high heat treatment (causing deterioration) to mild heat treatment at 60-90°C, which provides sufficient adhesion without damaging the substrate layer. This parameter optimization resolves the contradiction between achieving strong adhesion and maintaining substrate integrity.
Solution Approach 2:
The patent introduces a polyolefin-based adhesive layer as an intermediary between the substrate layer and other layers. This adhesive layer acts as a buffer that provides strong bonding without requiring high temperatures that would damage the substrate, thus resolving the contradiction between adhesion strength and substrate integrity.
2Quantity of substance
If deep recess formation is performed to increase battery content storage, then energy density is improved, but the packaging material breaks due to insufficient formability
Solution Approach 1:
The patent optimizes the substrate layer's physical parameters including using biaxially stretched polyester film with specific thickness (6-40 μm) and controlling its crystallinity and orientation. These parameter changes enhance the material's deep drawing formability, enabling deep recess formation without breakage while maximizing battery content storage.
Solution Approach 2:
The patent creates a composite structure with multiple layers (substrate layer, adhesive layer, aluminum foil layer, sealant layer) where each layer contributes specific properties. The substrate layer provides formability, the adhesive layer provides bonding, and the aluminum foil layer provides barrier properties, collectively enabling deep recess formation without breakage.
3Weight of moving object
If multilayer film structure is used to reduce weight and cost, then weight and manufacturing cost are reduced, but adhesion between layers becomes insufficient
Solution Approach 1:
The patent uses a polyolefin-based adhesive layer as an intermediary between the substrate layer and aluminum foil layer. This adhesive layer is specifically designed to bond these dissimilar materials effectively at low temperatures, resolving the adhesion issue while maintaining the lightweight multilayer structure.
Solution Approach 2:
The patent optimizes the adhesive layer's parameters including using polyolefin-based adhesives with specific glass transition temperatures and bonding strengths. The mild heat treatment temperature (60-90°C) is optimized to activate the adhesive without causing substrate deterioration, achieving strong interlayer adhesion in the lightweight multilayer structure.
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 provides a packaging material with improved deep drawing formability and processability, reducing the likelihood of breakage and ensuring strong adhesion between layers, thereby enhancing the performance and reliability of power storage devices.
Implementation Method 1
a thermal shrinkage in a range of 1% to 15%, after heat treatment in a range of 160°C to 200°C
Implementation Method 2
an adhesion enhancement layer provided between the substrate layer and the adhesive layer
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(d)
AI summary
A packaging material for a power storage device having a structure including at least a substrate layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer laminated in this order. In the packaging material, the substrate layer is formed of a polyester film having a 50% elongation stress in the range of 100 to 180 MPa and a thermal shrinkage in the range of 1 to 15%, after heat treatment from 160°C to 200°C, or a polyester film having a difference ΔA in break elongation of 12% or more after heat treatment at 200°C and 160°C and having a 50% elongation stress of 75 MPa or more after heat treatment at 200°C.