ZIF-8@MXene-reinforced flame-retardant and highly conductive polymer composite electrolyte for dendrite-free lithium metal batteries.

Though polymer electrolytes have been regarded as promising separators for solid-state lithium metal batteries, their low ionic conductivity, poor thermostability and inflammability limit their practical applications. Herein, a polymer composite electrolyte consisting of metal-organic frameworks modified TiC-MXene nanosheets (ZIF-8@MXene) and polymer mixture (PE-ZIF-8@MXene) was fabricated. The fabricated nonflammable ZIF-8@MXene nanosheets have abundant functional groups and Lewis acid sites as well as high specific surface area. In the composite electrolyte, ZIF-8@MXene nanosheets increased the dissociation of lithium salts and provided channels for transporting ions, accelerating the Li ion transportation. They also enhanced the tensile strength, thermostability and flame resistance of PE-ZIF-8@MXene. Consequently, the fabricated flame-retardant PE-ZIF-8@MXene presented high ionic conductivity (4.4 mS cm), impressive Li transference number (0.76) and enhanced tensile strength (3.77 MPa). In addition, the assembled Li|PE-ZIF-8@MXene|Li had a long cycle life of 2000 h, and Li|PE-ZIF-8@MXene|LiFePO batteries displayed a capacity retention of 89.6% after 500 cycles.