Porous PBI Battery Separator for High-Temperature Dimensional Stability
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Solution Overview
Problem
Current lithium ion battery separators, such as polyolefin-based membranes, face issues with dimensional stability at elevated temperatures, leading to potential internal shorting and safety risks due to melting, and have poor wettability with electrolytes, which affects lithium ion migration and battery safety.
Innovation Solution
A porous, amorphous polybenzimidazole (PBI) film with added fillers like silica or calcium carbonate is developed, providing improved thermal stability, mechanical strength, and enhanced lithium ion conductivity, while maintaining dimensional integrity up to 375°C and better wettability with polar electrolytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyolefin-based separators are used, then manufacturing cost is reduced and ease of manufacture is improved, but dimensional stability at elevated temperatures deteriorates and safety is compromised
Solution Approach 1:
The patent uses polybenzimidazole, a high-performance polymer with exceptional thermal stability (maintains integrity up to 375°C), replacing polyolefin-based separators. This composite material approach provides both dimensional stability at elevated temperatures and acceptable manufacturing properties, resolving the contradiction between ease of manufacture and reliability.
2Ease of manufacture
If polyolefin membranes are used, then manufacturing cost is reduced, but wettability with electrolyte deteriorates and lithium ion migration is affected
Solution Approach 1:
The patent changes the chemical parameter of the separator material from polyolefin to polybenzimidazole, which has inherent polar groups that provide excellent wettability with electrolyte. This parameter change improves both wettability and lithium ion migration while maintaining manufacturing feasibility, resolving the contradiction between manufacturing cost and wettability.
3Reliability
If polyethylene or polypropylene separators are used, then shutdown temperature is achieved, but meltdown temperature is too low causing safety risks at high temperatures
Solution Approach 1:
The patent changes the thermal parameter of the separator material by using polybenzimidazole with a glass transition temperature of 420-450°C, providing both shutdown functionality and high-temperature stability. This parameter change eliminates the safety risk of meltdown at high temperatures while maintaining shutdown protection, resolving the contradiction between shutdown temperature and safety risk.
4Reliability
If porosity is increased to improve lithium ion migration, then ion conductivity is improved, but susceptibility to dendrite crossover increases
Solution Approach 1:
The patent employs porous polybenzimidazole material with optimized pore structure that allows efficient lithium ion migration while the high thermal stability of the polymer matrix prevents dendrite penetration. The porous structure provides ion conductivity pathways, while the thermally stable framework maintains mechanical integrity to block dendrites, resolving the contradiction between ion migration and dendrite crossover.
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 PBI film exhibits higher lithium ion conductivity and improved safety by maintaining structural integrity at high temperatures, reducing the risk of thermal shrinkage and flammability, and enhancing electrolyte interaction, thus addressing the limitations of existing separators.
Implementation Method 1
improved lithium ion conductivity
Implementation Method 2
enhancing electrolyte interaction
Data Source
AI summary
The present invention discloses a film comprising porous, amorphous polybenzimidazole (PBI) and at least one filler for use as a separator in a lithium ion battery and a process for preparation thereof.