A Multifunctional Silicon‐Doped Polyether Network for Double Stable Interfaces in Quasi‐Solid‐State Lithium Metal Batteries

Polymer-based quasi-solid-state electrolyte (QSE) is an effective means to solve the safety problem of lithium (Li) metal batteries, and stable solid-electrolyte-interface (SEI) layers between electrolyte and anode/cathode are highly required for their long-term stability. Herein, it is demonstrated that a silicon-doped polyether functions as a multifunctional unit, which can induce the formation of stable and robust SEI layers with rich Lix SiOy on both the surfaces of cathode and anode. It simultaneously solves the compatibility of electrolyte and electrodes in the quasi-solid-state Li-metal battery. Moreover, the robust polymer skeleton with a cross-linked network is beneficial to inhibit liquid volatilization and improve battery safety. The assembled Li|QSE|LiFePO4 batteries show a capacity retention rate as high as 97.5% after 400 cycles at 1 C (30 °C), and reach 78.1% after 1000 cycles. Furthermore, there is almost no attenuation of reversible capacity after 100 cycles for the assembled Li|QSE|LiNi0.8 Mn0.1 Co0.1 O2 batteries. The concept of silicon-doped polymer with a crosslinking structure provides an important strategy for designing solid-state or quasi-solid-state polymer electrolytes for the stable long-term operation of both anode and cathode.