Battery Outer Casing Material Heat Sealing Insulation
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Solution Overview
Problem
Conventional outer casing materials for lithium secondary batteries have insufficient insulation performance, and existing techniques often compromise on cost and efficiency, particularly when using cross-linked polypropylene-based sealant layers near heat sources.
Innovation Solution
A laminated outer casing material comprising a heat-resistant resin film outer layer, a metal foil layer, and an inner thermoplastic resin film with a propylene-ethylene random copolymer sealant layer, where the sealant layer has a specific melt flow rate and composition, and the inner layer includes a base material layer with a controlled propylene and copolymer component ratio, enhancing insulation and heat-sealing properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low fluidity polypropylene layer is used near the heat source for heat sealing, then heat sealing stability is improved, but insulation performance deteriorates due to insufficient distance from the heat source
Solution Approach 1:
The patent divides the heat-resistant resin film into multiple layers: a first heat-resistant resin layer facing the heat source with high fluidity for heat dissipation, and a second heat-resistant resin layer away from the heat source with low fluidity for heat sealing stability. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between heat sealing stability and insulation performance.
Solution Approach 2:
Different regions of the heat-resistant resin film are assigned different material properties: the region closer to the heat source uses high fluidity polypropylene for thermal management, while the region farther from the heat source uses low fluidity polypropylene for reliable heat sealing. This local differentiation of material properties optimizes both heat sealing and insulation functions.
2Temperature
If a high melting point polypropylene layer is used near the metal foil layer for heat resistance, then thermal stability is improved, but insulation performance deteriorates due to proximity to heat source
Solution Approach 1:
The patent segments the heat-resistant resin film into functional layers: the first layer with high melting point and high fluidity faces the heat source for thermal stability, while the second layer with low fluidity is positioned away from the heat source to provide insulation. This layered segmentation resolves the contradiction between thermal stability and insulation performance.
3Temperature
If cross-linked polypropylene-based sealant layer is used near heat source, then heat resistance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces expensive cross-linked polypropylene with ordinary thermoplastic polypropylene having controlled fluidity characteristics. This substitution simplifies manufacturing processes and reduces costs while maintaining adequate heat resistance through proper material selection and layer configuration, abandoning the complex cross-linking technology in favor of simpler thermoplastic materials.
Solution Approach 2:
The patent changes the key parameter from cross-linking degree to fluidity control. By selecting polypropylene with specific fluidity characteristics (high fluidity for the first layer, low fluidity for the second layer), the patent achieves heat resistance and heat sealing performance without the complexity of cross-linking processes, thereby simplifying manufacturing.
4Ease of manufacture
If thermoplastic resin film is used for inner layer, then heat sealing properties are improved, but insulation performance deteriorates
Solution Approach 1:
The patent creates a composite structure by laminating the thermoplastic resin film (inner layer) with the multi-layer heat-resistant resin film (outer layer). This composite material structure combines the heat sealing advantages of thermoplastic resin with the insulation advantages of the heat-resistant resin film, resolving the contradiction between heat sealing properties and insulation performance.
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 excellent insulation performance and hermetic sealing for lithium secondary batteries, suitable for high-power applications like in-vehicle batteries, while maintaining cost-effectiveness and preventing internal short-circuits.
Implementation Method 1
heat-sealing properties are given to the resin layer of the inner layer
Implementation Method 2
By inserting a cell into such a packaging container and heat-sealing the inner layers
Implementation Method 3
excellent insulation performance is required for an outer casing material of the in-vehicle lithium secondary battery
Implementation Method 4
excellent insulation performance is required for an outer casing material of the in-vehicle lithium secondary battery
Data Source
AI summary
An outer casing material for a battery 4 is provided, wherein an outer layer 11, a metal foil layer 10 and an inner layer 8 are laminated via an adhesive layer 5; the inner layer 8 comprises a sealant layer 8b and a base material layer 8a; the sealant layer 8b is made from a propylene-ethylene random copolymer wherein a melt flow rate at 230° C. thereof is in a range of 3 to 30 g/10 minutes; the base material layer 8a is made of a resin composition wherein a melt flow rate at 230° C. thereof is in a range of 0.1 to 15 g/10 minutes, xylene-soluble component Xs thereof satisfies the predetermined conditions, and the resin composition comprises 50 to 80% by mass of a propylene component (A) and 50 to 20% by mass of a copolymer component (B) which is an elastomer of a copolymer of propylene and ethylene and/or α-olefin having 4 to 12 carbons and includes 50 to 85% by mass of a polymerization unit originated from propylene.