Advances in Composite Polymer Electrolytes for Lithium Batteries and Beyond

Conventional lithium-ion batteries have approached their capacity and energy density limits. Use of lithium metal anode can enable high-energy batteries. However, the safety hazards and lithium dendrite formation associated with lithium metal require safe electrolytes to replace flammable liquid ones. In recent years, solid-state electrolytes have attracted tremendous attention. Among them, composite polymer electrolytes (CPEs) with different constitutions have the unique advantages of low interfacial resistance, high ionic conductivity, and flexible characteristics. Here, the basic properties and analysis methods related to CPEs are discussed. Following that, the components added into the polymer matrix, such as organic solvents, nanostructured ceramics, and fast-ion-conductive inorganics are classified. CPEs used in low-cost Na and K batteries are briefly discussed. It is hoped that the review can supply both advances and fundamentals to the researchers in this field and provide guidance for the development of CPEs for lithium battery systems, and beyond.