UHMWPE Nanoporous Separator for Rapid Thermal Shutdown
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Solution Overview
Problem
Lithium-ion batteries face hazards such as fires and explosions due to thermal runaway, and existing safety devices are cumbersome, costly, and inefficient for portable-scale batteries.
Innovation Solution
A biaxial oriented UHMWPE nanoporous membrane with rapid thermal shutdown functionality is developed, which can be used as a separator in lithium-ion batteries, providing high porosity, mechanical strength, and corrosion resistance while shutting down pores in seconds and enhancing mechanical strength post-shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HDPE material is used for thermal shutdown separator, then thermal shutdown functionality is achieved, but mechanical strength is lost due to material softening at elevated temperatures
Solution Approach 1:
The patent uses UHMWPE as a composite material that combines thermal shutdown functionality with superior mechanical strength retention. UHMWPE maintains its structural integrity at elevated temperatures better than HDPE while still providing the necessary pore closure mechanism for thermal shutdown, thus resolving the contradiction between thermal shutdown reliability and mechanical strength
Solution Approach 2:
The patent changes the material parameter from HDPE to UHMWPE, which has different thermal and mechanical properties. UHMWPE has a higher molecular weight and different crystalline structure that allows it to maintain mechanical strength while providing thermal shutdown functionality, effectively changing the material parameters to resolve the contradiction
2Strength
If multi-layer stacking of PE and PP is used to maintain mechanical strength, then mechanical strength is improved, but separator thickness and resistance increase sacrificing battery performance
Solution Approach 1:
The patent extracts the need for multi-layer stacking by using a single-layer UHMWPE membrane that inherently provides both thermal shutdown functionality and mechanical strength. This eliminates the need for additional layers, thus reducing separator thickness and resistance while maintaining necessary mechanical properties
Solution Approach 2:
The UHMWPE single-layer membrane serves multiple functions simultaneously: it provides thermal shutdown functionality, maintains mechanical strength, and ensures low resistance. This multi-functionality in a single layer eliminates the need for multi-layer stacking, resolving the contradiction between mechanical strength and battery performance
3Reliability
If conventional safety devices are installed in battery systems, then safety protection is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the safety protection function directly into the separator membrane itself. The UHMWPE separator provides inherent thermal shutdown functionality and mechanical strength, eliminating the need for separate safety devices such as rupture valves, safety vents, or PTC devices. This integration resolves the contradiction between safety protection and device complexity
Solution Approach 2:
The separator membrane serves itself by providing both separation and safety protection functions. The UHMWPE material inherently provides thermal shutdown capability and mechanical strength without requiring external safety devices, making the system self-sufficient and reducing overall device complexity
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 membrane effectively mitigates thermal runaway risks by rapidly shutting down pores and enhancing mechanical strength, thereby improving the safety and performance of lithium-ion batteries.
Implementation Method 1
The shutdown mechanism can include recrystallization and annealing, which increases mechanical strength of the porous membrane after shutting down
Implementation Method 2
the shutdown mechanism can include recrystallization and annealing, which increases mechanical strength of the porous membrane after shutting down
Implementation Method 3
the shutdown mechanism can include recrystallization and annealing, which increases mechanical strength of the porous membrane after shutting down
Data Source
AI summary
Methods are provided for producing a biaxially oriented nanoporous UHMWPE membrane. The method can include combining a petroleum jelly, an ultra-high-molecular-weight polyethylene (UHMWPE), and an antioxidant, forming a suspension, feeding the suspension into an extruder to produce a gel filament, pressing the gel filament to form a gel film, subjecting the gel film to an annealing temperature, and extracting the petroleum jelly from the gel film.