Pouch Battery Laminate Sealing with Crosslinked Inner Resin
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Solution Overview
Problem
Existing pouch-type secondary batteries face issues with deteriorating insulation properties and sealing force due to thermal fusion of the sealing part, leading to potential exposure of the metal barrier layer and venting problems.
Innovation Solution
A method involving the use of a laminate sheet with an inner resin layer comprising polypropylene or polyethylene and a crosslinking agent, followed by electron beam or radiation-induced graft polymerization to enhance the inner resin layer's strength and insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pressure and temperature are excessively set when the laminate sheet is thermally fused, then the sealing force is improved, but the metal barrier layer may be exposed while the thickness of the inner resin layer becomes thin, thereby causing a problem of deteriorating the insulation property
Solution Approach 1:
The patent introduces a crosslinking agent into the inner resin layer that undergoes crosslinking reactions under electron beam or radiation irradiation. This chemical transformation changes the physical and chemical properties of the resin, increasing its melting point and structural stability. As a result, the resin maintains its protective function at higher temperatures and pressures during thermal fusion, preventing metal barrier layer exposure while preserving insulation properties even when the resin layer thickness is reduced.
Solution Approach 2:
The patent creates a composite structure by incorporating a crosslinking agent (such as polyvinylidene fluoride) into the polypropylene or polyethylene inner resin layer. This composite material combines the thermal fusion capabilities of the base resin with the high-temperature stability and enhanced mechanical properties of the crosslinked network, allowing the laminate to withstand excessive pressure and temperature during sealing without compromising the metal barrier layer.
2Loss of substance
If the thickness of the inner resin layer is reduced to minimize material usage, then the manufacturing cost is reduced, but the insulation property deteriorates
Solution Approach 1:
By introducing the crosslinking agent and applying electron beam or radiation irradiation, the resin undergoes crosslinking that fundamentally changes its properties. The crosslinked structure increases the resin's melting point, structural integrity, and insulation performance. This allows the use of thinner resin layers while maintaining or even improving insulation properties, as the crosslinked network provides enhanced protective capabilities per unit thickness.
3Temperature
If the battery is stored at a high temperature, then the storage capacity is maintained, but the bonding of the thermally fused inner resin layer is weakened, thereby causing a problem of venting
Solution Approach 1:
The crosslinking agent undergoes crosslinking reactions under electron beam or radiation irradiation, creating a three-dimensional network structure that fundamentally changes the resin's thermal behavior. This crosslinked structure maintains bonding strength at high storage temperatures, preventing the weakening that would otherwise lead to venting. The crosslinked network provides thermal stability and structural reinforcement that preserves sealing integrity under elevated temperature conditions.
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 method improves the sealing force and insulation properties by preventing cracks and increasing the melting point of the inner resin layer, ensuring high temperature storage stability and reducing material usage.
Implementation Method 1
irradiating an electron beam or radiation to the battery cell
Implementation Method 2
electron beam or radiation-induced graft polymerization to enhance the inner resin layer's strength and insulation
Implementation Method 3
thermally fusing the case
Data Source
Figure 1
Figure 2(a)~2(d)
Figure 3
AI summary
Disclosed herein is a method of manufacturing a pouch-type secondary battery comprising the steps of: (a) preparing an electrode assembly having a separator interposed between a positive electrode and a negative electrode; (b) forming a receiving part of the electrode assembly in a case made of a laminate sheet; and (c) manufacturing a battery cell by receiving the electrode assembly in the receiving part and thermally fusing the case, wherein the laminate sheet comprises an outer resin layer, a metal barrier layer and an inner resin layer, the inner resin layer comprising polypropylene or polyethylene, and a crosslinking agent.