Power Storage Exterior Laminate for Deep Draw and Curl Control
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Solution Overview
Problem
Film-shaped exterior materials for electrical storage devices face challenges such as cracking and pinhole generation during concave portion formation, and shrinkage issues during manufacturing, leading to reduced production efficiency and moldability.
Innovation Solution
A laminate structure comprising a base material layer, a barrier layer, and a heat-sealable resin layer, where the resin film has a specific shrinkage ratio and stress value, ensuring excellent moldability and minimizing curling, with a stress value of 100 MPa or more in both machine and transverse directions after a 10% tensile test.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a deep concave portion is formed by cold molding to increase energy density, then the housing capacity is improved, but cracks and pinholes are likely to be generated
Solution Approach 1:
The patent applies parameter changes by controlling the shrinkage ratio of the resin film within a specific range (1.0% or more and less than 5.0%) and adjusting the stress value to 100 MPa or more. These parameter optimizations enable the film to withstand deep concave portion formation without generating cracks or pinholes, thus resolving the contradiction between energy density improvement and reliability maintenance.
2Ease of manufacture
If the base material layer is shrunk by heating during manufacturing, then the film can be processed, but when wound into an extended roll and later unwound, the base material layer unwinds in a curled shape, hindering housing and heat-sealing operations
Solution Approach 1:
The patent controls the shrinkage ratio parameter within a specific range (1.0% or more and less than 5.0%) to balance the film's shrinkage behavior during manufacturing with its unwinding behavior during storage and transport. This parameter optimization prevents excessive curling while maintaining processability, thereby resolving the contradiction between ease of manufacture and ease of operation.
3Weight of stationary object
If the film is made thinner to achieve weight reduction and thickness reduction, then the performance is improved, but the film becomes more susceptible to cracking and pinhole generation
Solution Approach 1:
The patent employs a laminated composite structure consisting of a resin film base material layer and a heat-sealable resin layer. This composite material design allows the use of thinner films for weight reduction while the layered structure provides enhanced mechanical strength and defect resistance, resolving the contradiction between weight reduction and crack/pinhole resistance.
Solution Approach 2:
The patent optimizes the stress value parameter to 100 MPa or more, which enhances the mechanical strength of the thin film structure. This parameter control enables the thin film to maintain sufficient resistance against cracking and pinhole generation during molding and handling operations.
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 an exterior material with improved moldability and reduced curling, enhancing the production efficiency and reliability of electrical storage devices by preventing cracking and pinhole formation.
Implementation Method 1
a shrinkage ratio of the resin film immersed in hot water at 95° C. for 30 minutes is within a predetermined range
Implementation Method 2
heat-sealable resin layers are heat-sealed to each other to obtain an electrical storage device in which electrical storage device elements are housed in an exterior material
Data Source
AI summary
An exterior material for power storage devices which is formed from at least a layered body comprising a base material layer, a barrier layer, and a heat-fusible resin layer in this order, wherein the base material layer contains a resin film, the resin film has a shrinkage ratio of 1.0% to less than 5.0% when immersed in hot water at 95° C. for 30 minutes, and the resin film has a stress value, at 10% stretching in the tensile test described hereafter, of 100 MPa or higher in both the machine direction and the transverse direction. After storing a sample in a 23° C., 40% RH environment for 24 hours, the tensile test is performed under conditions of a sample width of 6 mm, a gauge length of 35 mm, and a tension rate of 300 mm/min in a 23° C., 40% RH environment, and the stress value at 10% stretching (displacement of 3.5 mm) is measured.