Preparation and performances of the modified gel composite electrolyte for application of quasi-solid-state lithium sulfur battery

Lithium-sulfur (Li-S) batteries have become candidate for the next-generation energy storage systems because of their high energy density and specific capacity. However, due to the shuttle effect of polysulfides and the safety problems caused by liquid organic electrolytes, practical commercial applications of Li-S battery have been severely limited. With the recent development of solid electrolyte, the strategy of replacing liquid electrolyte with the solid electrolyte has aroused extensive attention, which can both improve the safety of the battery and increase its energy density. However, in the absence of liquid components, poor interfacial contact and low ionic conductivity for solid electrolyte can seriously impair the electrochemical performance of solid-state Li-S batteries. By adding a certain amount of liquid plasticizer, the ionic conductivity is effectively ameliorated and the interface contact between the electrodes and the electrolyte is largely improved. Herein, a thermally polymerized composite gel polymer electrolyte (CPE) for quasi-solid-state Li-S battery is designed and fabricated. The CPE has a satisfactory ionic conductivity and wide electrochemical window of above 4.5 V. Especially, the addition of the garnet Li6.5La3Zr1.5Ta0.5O12 (LLZTO) powder improves the flame retardancy and thermal stability. In addition, the application of CPE in the Li-S battery can block the shuttle of polysulfide to some extent, and the quasi-solid-state Li-S battery assembled by CPE shows the good electrochemical performance and only a 0.22% decay per cycle in 200 cycles with 0.1C. Hence, this work provides a new strategy for design and development of the quasi-solid-state electrolyte for the application of Li-S battery. Moreover, due to its wide electrochemical window, CPE can also be applied in high-voltage cathode systems of lithium ion battery in the future.