Poly-1,3-dioxolane anchoring graphitic carbon nitride to achieve high-energy–density solid-state Li metal batteries.

[Display omitted] • A novel composite polymer electrolyte is prepared via a coupling reaction. • Li/Li cells stably cycle beyond 300 h with small overpotential of 13 mV. • Li/LiFePO 4 cells deliver high capacity of 89.7 % after 150 cycles. • A stable solid electrolyte interphase is formed on Li anode surface upon cycling. Solid-state Li metal batteries (SSLMBs) are promising solutions for the next-generation energy storage devices with high energy densities and safety. Accordingly, the advanced solid-state electrolytes are further needed to address the challenges-low ionic conductivity, poor interfacial compatibility and uncontrollably Li dendrites, boosting the electrochemical and safety performances of SSLMBs. Herein, a "flexible and rigid" strategy is proposed to enhance the electrochemical and mechanical properties of polyethylene oxide (PEO)-based electrolytes. Specifically, the flexible poly-1,3-dioxolane (poly-DOL) and rigid graphitic carbon nitride (g-C 3 N 4) are coordinated by a coupling reaction to prepare g-C 3 N 4 -poly-DOL, which is further employed as the filler for the PEO matrix to fabricate a composite polymer electrolyte g-C 3 N 4 -pDOL-PEO. The flexible poly-DOL and rigid g-C 3 N 4 together endow the PEO-based electrolyte with good interfacial stability, high ion-conductivity and strong mechanical strength. Consequently, the Li/g-C 3 N 4 -pDOL-PEO/LiFePO 4 cell delivers high cyclability with a capacity retention ratio of 89.7 % after 150 cycles and an average Coulombic efficiency over 99.9 %, and, the Li/g-C 3 N 4 -pDOL-PEO/Li cell can stably cycle beyond 300 h at 0.2 mAh cm−2 with small polarization (13 mV). The "flexible and rigid" strategy coupling the polymer with the filler provides an effective electrolyte design for high-performance SSLMBs. [ABSTRACT FROM AUTHOR]