Simultaneously Boosting the Ionic Conductivity and Mechanical Strength of Polymer Gel Electrolyte Membranes by Confining Ionic Liquids into Hollow Silica Nanocavities

Abstract A central problem of solid polymer electrolytes is their inability to achieve robust mechanical strength with fast ionic conductivities required for commercialization of lithium metal batteries (LMBs). At present, state‐of‐the‐art offers superiority of one at the expense of the other. Here, this dilemma has been solved by fabricating mechanically robust solid composite polymer electrolytes (SCPEs) with superior ionic conductivity (0.5 mS cm −1 at 20 °C) by confining ionic liquids (ILs) in the hollow scaffold offered by hollow silica (HS) nanospheres with unique architecture. Mechanical robustness was verified by the performance of a Li||Li symmetric cell cycling for extended hours without short‐circuiting. In addition, SCPEs with HS have higher thermal and electrochemical stabilities than those without HS, due to strong interaction and coordination of HS nanoparticles with polymer and ionic liquids. Electrode compatibility and flexibility of the membrane could advance the LMBs technology.