Flexible Quasi‐Solid‐State Composite Electrolyte Membrane Derived from a Metal‐Organic Framework for Lithium‐Metal Batteries

In this work, we developed a new kind of flexible Li‐ion conductor membrane consisting of poly(vinylidene fluoride‐co‐hexafluoropropylene) matrix and ionic liquid absorbed in metal‐organic framework (MOF) particles. This composite membrane facilitates a homogeneous Li‐ion flux and exhibits an excellent ionic conductivity of about 4.3×10 −4  S cm −1 at room temperature, a wide electrochemical window of 4.8 V ( vs . Li + /Li), as well as good thermal stability and flexibility. The quasi‐solid‐state lithium metal battery assembled with the composite electrolyte membrane, a Li metal anode, and a composite cathode shows low interface impedance and a reversible discharge capacity of 149 mAh g −1 within 300 cycles at 0.1 C. This new kind of quasi‐solid‐state electrolyte membrane is a promising candidate for solid‐state lithium‐metal batteries with a high energy density.