Functional material “Ionic liquid-supported MIL-101(Fe)” to enhance composite solid electrolyte for lithium metal batteries

Because of poor ionic conductivity, insufficient interfacial compatibility and other issues, all-solid-state lithium metal batteries (ASSLMBs) are difficult to commercialize. Here, a sort of composite solid-state polymer electrolytes (CSPEs) is prepared by compounding multifunctional fillers with polyethylene oxide (PEO), and the multifunctional filler is obtained by absorbing the ionic liquids (ILs) into the iron-containing metal-organic frameworks (MOFs). The porosity of MOFs can improve the path for Li+ transport and accelerate the Li+ transport after adsorbing ILs. This strategy endows the prepared CSPEs with high ionic conductivity of 8.46 × 10−4 S cm−1 at 60 °C and wide electrochemical window (5.2 V). In addition, the transference number of the CSPEs is increased to 0.54. After 250 cycles, the assembled LiFePO4/CSPE/Li battery has a discharge-specific capacity of 139.1 mAh g−1 and a capacity retention of 93.3% at 0.5 C under 60 °C. This work reveals a feasible strategy in constructing high-performance solid-state LMBs, as well as an important complement for material and structure development in the field of energy storage.