Double-Layered Multifunctional Composite Electrolytes for High-Voltage Solid-State Lithium-Metal Batteries

The need for safe storage systems with a high energy density has increased the interest in high-voltage solid-state Li-metal batteries (LMBs). Solid-state electrolytes, as a key material for LMBs, must be stable against both high-voltage cathodes and Li anodes. However, the weak interfacial contact between the electrolytes and electrodes poses challenges in the practical applications of LMBs. In this study, a double-layered solid composite electrolyte (DLSCE) was synthesized by introducing an antioxidative poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)-10 wt % Li1.3Al0.3Ti1.7(PO4)3 (LATP) to the cathode interface, whereas a lithium-friendly poly(oxyethylene) (PEO)-5 wt % LATP was made to come into contact with Li metal. Owing to the heterogeneous double-layered structure of the DLSCE, a high ionic transfer number (0.43), high ionic conductivity (1.49 × 10–4 S/cm), and a wide redox window (4.82 V) were obtained at ambient temperature. Moreover, the DLSCE showed excellent Li-metal stability, thereby enabling the Li–Li symmetric cells to stably run for over 600 h at 0.2 mA/cm2 with effective lithium dendrite inhibition. When paired with a high-voltage LiNi1/3Co1/3Mn1/3O2 cathode, the Li/DLSCE/NCM111 cell exhibited excellent electrochemical performance: long-term cyclability with 85% capacity retention could be conducted at 0.2C after 100 cycles corresponding to 100% Coulombic efficiencies.