Propylene Elastomer Packaging for Li-Ion Battery Sealing
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Solution Overview
Problem
Conventional packaging materials for lithium ion batteries and similar electrochemical cells face issues with flexibility, heat resistance, sealing properties, and moldability, leading to potential cracks and electrolyte leakage, especially during folding or embossing processes, which compromise the battery's functionality.
Innovation Solution
A packaging material comprising a base material layer, a metal foil layer with a chemical conversion treatment, an acid-modified polyolefin layer, and a thermally adhesive resin layer, where the resin layer is composed of propylene-based elastomers, providing enhanced flexibility, heat resistance, and impact resistance, and is laminated using methods like dry lamination or thermal lamination to ensure stable sealing and insulation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic can is used as packaging material, then sealing properties and structural strength are improved, but flexibility and moldability deteriorate due to rigid container external wall
Solution Approach 1:
The patent employs a composite packaging structure consisting of a flexible pouch made from multiple layers (including aluminum foil for barrier properties and plastic layers for flexibility) combined with a rigid embossing tray for structural support. This composite approach allows the packaging to maintain both flexibility for molding and structural strength for protection, resolving the contradiction between these two properties.
2Ease of manufacture
If conventional packaging material is used, then manufacturing simplicity is maintained, but sealing properties and insulation properties deteriorate leading to cracks and electrolyte leakage
Solution Approach 1:
The packaging uses a multi-layer composite structure where each layer provides specific functions: aluminum foil layer for barrier and insulation properties, plastic layers for flexibility and sealing, and adhesive layers for bonding. This composite structure enhances sealing reliability and prevents electrolyte leakage while maintaining ease of manufacture through standardized lamination processes.
Solution Approach 2:
The packaging material is divided into multiple functional layers, each with specific properties. The embossing tray is also segmented into a tray portion and a separate sealing sheet, allowing independent optimization of each component's function while simplifying the manufacturing process through modular assembly.
3Reliability
If the packaging material is heat sealed, then sealing properties are improved, but flexibility deteriorates due to crystallization of thermally adhesive resin layer
Solution Approach 1:
The patent carefully controls the composition and molecular weight of the thermally adhesive resin to adjust its crystallization behavior. By selecting resins with appropriate melting points and crystallization temperatures, the packaging maintains flexibility after heat sealing while achieving reliable sealing. The embossing process parameters are also optimized to prevent excessive crystallization that would reduce flexibility.
4Adaptability or versatility
If embossing process is applied to packaging material, then moldability is improved, but insulation properties deteriorate due to separation between metal foil and thermally adhesive resin layer
Solution Approach 1:
The packaging structure is designed with adequate thickness and structural support in the embossing tray portion before the embossing process is applied. This preliminary structural preparation prevents excessive deformation and separation of the metal foil layer during embossing, thereby maintaining insulation properties while achieving the desired moldability for battery placement.
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 proposed packaging material significantly enhances flexibility and durability, preventing cracks and electrolyte exposure, thereby maintaining insulation and sealing integrity even after heat sealing and embossing, and improves the overall performance and longevity of lithium ion batteries and similar cells.
Implementation Method 1
a metal foil layer (7) having a chemical conversion treated layer (7a) on at least one surface thereof
Implementation Method 2
the metal terminals 4 are sandwiched by the exterior body 10, followed by heat sealing to secure sealing properties
Implementation Method 3
a propylene based elastomer resin; and/or the propylene based elastomer resin is a copolymer composed of a constitutional unit derived from propylene
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In a packaging material for electrochemical cell, a thermally adhesive resin layer 8 is configured of a resin having a propylene based elastomer resin in a propylene based resin. This propylene based elastomer resin is a copolymer composed of a constitutional unit derived from propylene and a constitutional unit derived from an α-olefin having from 2 to 20 carbon atoms; when the total sum of the constitutional unit derived from propylene and the constitutional unit derived from an α-olefin is defined as 100 % by mole, contains 50 % by mole or more of the constitutional unit derived from propylene; and is satisfied with (a) a Shore A hardness (ASTM D2240) of from 65 to 90, (b) a melting point of from 130 to 170°C, (c) a density (ASTM D1505) of from 860 to 875 kg/m3 and (d) a glass transition temperature as measured by DSC of from -25°C to -35°C.