Systematic safety evaluation of quasi-solid-state lithium batteries: a case study

Abstract

It is widely believed that replacing flammable liquid electrolytes (LEs) with solid electrolytes can solve the safety problems of lithium batteries. However, the safety of solid-state batteries (SSBs) has rarely been discussed, so their reliability is still being questioned. This work shows the preparation of promising quasi-solid electrolytes (QSEs) for all-round safety evaluation. On this basis, it is proved that QSEs are more conducive to the uniform deposition of lithium and the formation of a more stable solid electrolyte interface (SEI), thereby promoting more uniform lithium deposition and reducing the formation of lithium dendrites. Therefore, the initial temperature of self-heating increases. The superior liquid retention of QSEs slows down solvent volatilization and decomposition, thus mitigating the exothermic reaction inside the battery. Besides, the polymer of QSEs inhibits the shrinkage of the separator in the battery at high temperatures, which makes it harder for large-scale internal short circuits of the battery to happen. Based on these, the trigger temperature of battery thermal runaway has skyrocketed, but QSEs will still experience thermal runaway after the polymer matrix melts. Even on the occasion of misapplication, the nonflammability of QSEs makes the battery more stable and reduces the severe destruction of the battery due to thermal runaway. Thus, this study paves the way to further understand the thermal runaway mechanism of quasi-solid-state batteries and the design concept of safer QSEs.