In situ formation of poly(butyl acrylate)-based non-flammable elastic quasi-solid electrolyte for dendrite-free flexible lithium metal batteries with long cycle life for wearable devices

With the rapid development of wearable devices, there is an increasing demand for ultra-safe flexible lithium-ion batteries (LIBs) capable of delivering high energy density. Because it can provide the highest possible capacity of 3860 mAh g^-1, lithium metal has drawn tremendous research attention. However, Li is a highly reactive metal that grows dendrites during the cycling of lithium-metal batteries (LMBs). To resolve the problem, we developed a new non-flammable elastic quasi-solid electrolyte (QSE), which can be polymerized in situ and whose composition is tailored to achieve high elasticity. Moreover, the incorporation of trimethyl phosphate (TMP) renders the electrolyte non-flammable. Thanks to the solid electrolyte interphase (SEI) formed, the LMB with QSE displays excellent cycling stability as it can be operated for 500 cycles, with a capacity retention of 94%. The corresponding symmetric cell cycled stably for more than 500 h. Scanning electron microscopy (SEM) and density functional theory (DFT) calculations reveal that fluoroethylene carbonate (FEC) is critical in forming the LiF-rich SEI that enables long-term cycling stability. In brief, a non-flammable, elastic, and stable QSE is reported for the first time, which is very promising in the application of the next-generation wearable devices.