Lithium Battery Packaging Adhesive for Interlaminar Strength
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Solution Overview
Problem
Conventional laminate packaging materials for lithium ion polymer secondary batteries suffer from insufficient interlaminar strength, which can lead to deterioration due to electrolyte reactions, heat generation, and expansion/contraction during charging/discharging, resulting in poor sealing performance.
Innovation Solution
A molding packaging material comprising a heat-resistant resin layer, a polypropylene layer, and a metal foil layer, where the inner side surface of the metal foil is subjected to chemical conversion treatment, and the polypropylene layer is laminated onto the treated surface via an adhesive containing a polyolefin resin with a carboxyl group and a multifunctional isocyanate compound, enhancing interlaminar strength and sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional laminate packaging material is used, then the structure is simple and easy to manufacture, but the interlaminar strength is insufficient leading to deterioration under electrolyte exposure and thermal conditions
Solution Approach 1:
The patent applies composite materials by creating a multi-layer laminate structure consisting of a polypropylene resin layer, a metal foil layer (aluminum or stainless steel), and a heat-resistant resin layer. Each layer serves specific functions: the polypropylene provides sealing and adhesion, the metal foil provides barrier properties against moisture and oxygen, and the heat-resistant resin provides thermal stability. This composite structure resolves the contradiction by achieving high interlaminar strength through proper material selection and interface treatment while maintaining manufacturing feasibility through established lamination processes
Solution Approach 2:
The patent applies parameter changes by optimizing the chemical conversion treatment parameters of the metal foil surface, including controlling the treatment time, temperature, and composition of the treatment solution. The adhesion promoter application parameters are also optimized, including solvent type, concentration, and drying conditions. These parameter optimizations enable strong interlaminar bonding without requiring excessively complex processing equipment or procedures, thus resolving the contradiction between strength improvement and manufacturing complexity
2Reliability
If the laminate structure is simplified for easy manufacture, then the production process is straightforward, but the sealing performance deteriorates under heat generation and expansion/contraction conditions
Solution Approach 1:
The patent applies local quality by providing different functional characteristics to different regions and layers of the packaging material. The polypropylene resin layer provides sealing functionality at the bottom where it contacts the battery, the metal foil layer provides barrier properties in the middle section, and the heat-resistant resin layer provides thermal stability at the top. The chemical conversion treatment is applied specifically to the metal foil surface that contacts the polypropylene, creating localized adhesion enhancement. This functional differentiation achieves reliable sealing performance under thermal and mechanical stress while maintaining a relatively simple overall structure that can be manufactured using standard processes
3Strength
If a chemical conversion treatment is applied to the metal foil surface, then the adhesion strength improves, but the production time and process complexity increase
Solution Approach 1:
The patent applies preliminary action by performing the chemical conversion treatment on the metal foil surface before lamination, preparing the surface in advance to receive the adhesion promoter and subsequent layers. This pre-treatment creates a receptive surface that enhances adhesion without requiring additional treatment steps after lamination. The adhesion promoter is also applied in advance to the chemically treated surface, creating a ready-to-bond interface. These preliminary actions consolidate multiple functions into sequential steps that can be integrated into the production line, reducing overall production cycle time while achieving strong adhesion
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 significantly improves interlaminar strength and electrolyte resistance, ensuring secure sealing performance even under conditions of heat generation and expansion/contraction, effectively preventing corrosion and maintaining integrity for battery cases and other applications.
Implementation Method 1
at least an inner side surface of the metal foil layer is subjected to a chemical conversion treatment
Implementation Method 2
the polypropylene layer is laminated on the chemical conversion treatment surface of an inner side of the metal foil layer via an adhesive layer
Implementation Method 3
the adhesive containing at least an organic solvent, a polyolefin resin having a carboxyl group dissolved in the organic solvent and having an MFR of 5 g/10 min to 42 g/10 min measured at 130° C., and a multifunctional isocyanate compound
Data Source
AI summary
A molding packaging material excellent in interlaminar lamination strength is provided, in which it is possible to prevent deterioration of the interlaminar strength due to influences of electrolytes and also possible to prevent deterioration of the interlaminar strength due to influences of heat generation and/or expansion/contraction of the packaging material caused by repetition of charging/discharging. The molding packaging material of the present invention includes a heat resistant resin layer 2 as an outer layer, a polypropylene layer 3 as an inner layer, a metal foil layer 5 arranged between the heat resistant resin layer and the polypropylene layer, wherein at least an inner side surface of the metal foil layer 4 is subjected to a chemical conversion treatment, and the polypropylene layer 3 is laminated on the chemical conversion treatment surface of the metal foil layer via an adhesive layer 5, wherein the adhesive layer 5 is formed by applying an adhesive to the chemical conversion treatment surface of the inner side surface of the metal foil layer 4, the adhesive containing at least an organic solvent, a polyolefin resin having a carboxyl group in which the organic solvent is dissolved and an MFR measured at 130° C. is 5 g/10 min to 42 g/10 min, and a multifunctional isocyanate compound.