Porous Separator Membrane Composition for Adhesion and Shutdown
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Solution Overview
Problem
High density polyethylene membranes used in electrochemical cells, such as lithium ion batteries, face challenges with adhesive properties and shutdown temperatures, which affect their efficiency and safety.
Innovation Solution
A polymer composition combining high density polyethylene with an ethylene vinyl acetate copolymer, optimized for gel extrusion, enhances adhesive bond strength and reduces shutdown temperature while maintaining mechanical stability, improving wettability and ion mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high density polyethylene is used to make membranes for electrochemical cells, then mechanical stability and chemical resistance are improved, but adhesive properties and wettability are insufficient
Solution Approach 1:
The patent combines high density polyethylene with ethylene vinyl acetate copolymer to create a composite membrane material. The HDPE provides mechanical stability and chemical resistance, while the EVA copolymer enhances adhesive properties and wettability, resolving the contradiction between mechanical strength and adhesion reliability
Solution Approach 2:
The invention introduces vinyl acetate units at specific locations within the polymer structure (as copolymer segments) to provide localized adhesive enhancement and wettability improvement, while the majority of the membrane maintains the mechanical properties of HDPE
2Strength
If high density polyethylene is used to make membranes, then mechanical stability is maintained, but shutdown temperature is too high for optimal safety
Solution Approach 1:
The patent modifies the thermal properties of the membrane by incorporating ethylene vinyl acetate copolymer, which has a lower melting point than HDPE. This changes the shutdown temperature parameter from typically above 160°C to a lower range (100-150°C), optimizing safety while the composite structure maintains adequate mechanical stability
Solution Approach 2:
By creating a composite of HDPE and EVA copolymer, the patent achieves a balance where the membrane maintains sufficient mechanical stability from the HDPE component while the EVA component lowers the overall shutdown temperature for enhanced safety
3Reliability
If polyethylene membranes have low shutdown temperature for safety, then thermal runaway prevention is improved, but mechanical stability may be compromised
Solution Approach 1:
The composite structure allows the HDPE component to provide mechanical stability while the EVA copolymer component provides low shutdown temperature for safety, achieving both requirements simultaneously through material composition rather than sacrificing one for the other
Solution Approach 2:
The vinyl acetate units are distributed as copolymer segments within the HDPE matrix, providing localized thermal response for shutdown function while the continuous HDPE phase maintains overall mechanical stability
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 polymer composition improves the adhesive properties and reduces shutdown temperature, leading to increased battery efficiency and safety by enhancing ion mobility and wettability with electrolyte solutions.
Implementation Method 1
producing a porous membrane that may be used in electrochemical cells
Implementation Method 2
the microporous membrane permits ions to pass through due to the porous nature of the material
Implementation Method 3
The shutdown effect refers to the self-closing of micro-pores within the polyethylene separator when it surpasses a certain temperature
Data Source
AI summary
A polymer composition for producing gel extruded articles is described. The polymer composition contains one or more high density polyethylene polymers combined with one or more olefinic copolymers. In order to form gel extruded articles, the polymer composition is combined with a plasticizer. In one embodiment, the polymer composition is used to form a porous membrane for use as a separator in electronic devices. The presence of the olefinic copolymer can increase the adhesive characteristics of membranes made from the composition when placed in contact with an anode and/or a cathode. When producing porous membranes, the olefin copolymer can also decrease the shutdown temperature and increase wettability properties.