Low‐Cost Hollow Mesoporous Polymer Spheres and All‐Solid‐State Lithium, Sodium Batteries

A practical, low‐cost synthesis of hollow mesoporous organic polymer (HMOP) spheres is reported. The electrochemical properties of Li + /Na + ‐electrolyte membranes with these spheres substituting for oxide filler particles in poly(ethylene oxide) (PEO)‐filler composite are explored. The electrolyte membranes are mechanically robust, thermally stable to over 250 °C, and block dendrites from a metallic‐lithium/sodium anode. The Li + /Na + transfer impedance across the lithium/sodium–electrolyte interface is initially acceptable at 65 °C and scavenging of impurities by the porous‐spheres filler lowers this impedance relative to that with Al 2 O 3 . All‐solid‐state Li/LiFePO 4 and Na/NaTi 2 (PO4) 3 cells give stable discharge capacity of ≈130 and 80 mAh g −1 , respectively, at 0.5 C and 65 °C for 100 cycles.