Synergistic effect of TiCT MXene/PAN nanofiber and LLZTO particles on high-performance PEO-based solid electrolyte for lithium metal battery.

Solid polymer electrolytes (SPEs) have been considered the most promising separators for all-solid-state lithium metal batteries (ASSLMBs) due to their ease of processing and low cost. However, the practical applications of SPEs in ASSLMBs are limited by their low ionic conductivities and mechanical strength. Herein, we developed a three-dimensional (3D) interconnected MXene (TiCT) network and LiLaZrTaO (LLZTO) particles synergistically reinforced polyethylene oxide (PEO)-based SPE, where the association of Li with ether-oxygen in PEO could be significantly weakened through the Lewis acid-base interactions between the electron-absorbing group (Ti-F, -O-) of TiCT and Li. Besides, the TFSI in lithium salts could be immobilized by hydrogen bonds from the Ti-OH of TiCT. The 3D interconnected TiCT network not only alleviated the agglomeration of inorganic fillers (LLZTO), but also improved the mechanical strength of composite solid electrolyte (CSE). Consequently, the assembled Li||CSE||Li symmetric battery showed excellent cycling stability at 35 ℃ (stable cycling over 3000 h at 0.1 mA cm, 0.1 mAh cm) and -2 ℃ (stable cycling over 2500 h at 0.05 mA cm, 0.05 mAh cm). Impressively, the LiFePO||CSE||Li battery showed a high discharge capacity of 145.3 mAh/g at 0.3 C after 300 cycles at 35 ℃. This rational structural design provided a new strategy for the preparation of high-performance solid-state electrolytes for lithium metal batteries.