Interface engineering by gelling sulfolane for durable and safe Li/LiCoO2 batteries in wide temperature range

Lithium-metal batteries (LMBs) with high energy densities have aroused intensive interest in electrical energy storage devices but suffer from the risk of thermal runaway, especially under harsh conditions of high temperature or thermal abuse. Pursuing intrinsically thermally stable electrolytes with higher performance and higher safety beyond commercial liquid electrolytes is a major challenge in this field. Here we report on a unique, highly durable sulfolane-based gel electrolyte constructed by a facile gelling strategy. This method takes advantages of thermotolerant sulfolane as a plasticizer and strong dipole-dipole interactions to achieve the gelation of polymer polyvinylidene fluoride/polyethylene oxide. We systematically investigated the influence of gelled sulfolane on gel formation, lithium plating/stripping, and solid electrolyte interphase. Benefiting from favorable interface engineering, the sulfolane-based gel electrolyte remarkably enhances the cyclic and safety performances of LMBs. When used in the Li/LiCoO2 battery, the resulting gel electrolyte enables long-term cycling stability at high temperatures up to 90°C. Moreover, the thermal safety of practical Li/LiCoO2 pouch cells (up to 190°C) has also been demonstrated by accelerating rate calorimetry. These results contribute to the development of high-safety LMBs that require abuse tolerance, high energy, and long calendar life.