Hollow mesoporous SiO2 submicro-spheres enabling PEO-based electrolytes with superior electrochemical performance for Li metal batteries

Solid electrolytes have shown great application potential in high safety and energy-density Li metal batteries. Poly (ethylene oxide) (PEO), as one of the most well-known polymer electrolytes, is limited by its low ionic conductivity, poor lithium-ion transference number (tLi+) and undesired mechanical properties. In this work, M-hSiO2@IL active fillers composed of hollow mesoporous SiO2 submicro-spheres loaded with ionic liquid-LiTFSI are designed for PEO-based solid electrolytes. Owing to the introduction of M-hSiO2@IL active fillers, the obtained solid-state PMI electrolyte shows significantly improved physical and electrochemical performance compared to PEO-LiTFSI electrolyte, including improved tensile strength, high Li+ transference number (0.49), enhanced ionic conductivity (1.07 × 10−4 S cm−1 at 30 °C), widened electrochemical stability window (4.73 V) and superior interfacial stability with Li metal. Thus, high performance Li metal batteries can be achieved. The Li|PMI|Li symmetric cell displays stable cycling for 1600 h at 0.1 mA cm−2/0.1 mAh cm−2, and the solid-state LFP|PMI|Li cells exhibit a reversible capacity of 136.95 mAh g−1 after 300 cycles with a high capacity retention of 96.97 % at 0.5C under room temperature. This work provides the feasibility of using environmental-friendly SiO2 submicro-spheres in realizing high-performance PEO-based electrolytes for Li metal batteries.