Challenges and prospects of high-safety composite separators for lithium-ion batteries
The separator is a crucial structural component of lithium-ion batteries,responsible for preventing direct contact between the positive and negative electrodes,absorbing and immobilizing electrolyte,and facilitating ion transfer.Commercial separators are currently challenged by issues such as thermal shrinkage at high temperatures,which compromises the long-term safety of the battery.This paper begins with an overview of the requirements for lithium-ion battery separators,including pore structure,electrolyte wettability,and stability-structural,thermal,chemical,and electrochemical-as well as separator-electrolyte interactions.It then reviews recent literature on high-temperature-resistant polymer separators,highlighting research advancements.The focus is on the analysis of strategies for high-heat-resistant polymer-based separators,flame-retardant additive-coated separators,and polymer-substrate composites.The paper discusses the mechanism behind the enhancements provided by flame-retardant multifunctional composite separators and explores strategies for inhibiting lithium dendrite formation through physical barriers,lithium deposition homogenization,and modulation of lithium-ion migration fluxes.Comprehensive analysis indicates that reducing the thickness of polyolefin separators,while integrating high-performance thin coatings,doping with solid electrolytes,and developing high-heat-resistant polymer-based separators,can achieve high ionic conductivity and ensure enhanced safety.
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