Versatile Inorganic/Polymer Composite Electrolyte Added with 2‑Methylsuccinic Anhydride via a Solvent-Free Preparation Method for High-Performance All-Solid-State Li-Metal Batteries: High Voltage, Long Cycle Life, and Room-Temperature Operation

Solid-state Li-metal batteries (LMBs) with a high room-temperature energy density, long cycle life, and remarkable flexibility and safety are necessary for practical energy-storage applications. In this study, 2-methylsuccinic anhydride was used as a novel additive to fabricate a series of all-solid-state inorganic/polymer composite electrolytes (IPCEs) using a completely solvent-free hot-pressing process instead of the conventional solution-casting method. This electrolyte comprises a poly(ethylene oxide) framework that is hybridized with a Li6.4Al0.24La3Zr2O12 inorganic filler. The freestanding IPCE membrane exhibited long-term stability against Li metal and a high ion conductivity of 2.4 × 10–4 S cm–1 at 25 °C, showing an appreciable transference number of 0.87. All-solid-state LMBs (ASSLBs) fabricated using this IPCE, high-voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode, and lithium foil anode achieved a specific capacity of 163 mA h g–1 at 0.5C and 25 °C. The IPCE inhibited lithium dendrite growth and eventually delivered an excellent battery cycling performance beyond 400 cycles. Moreover, this ASSLB performed well even at 15 °C and showed notable rate performance at 35 °C, at which a capacity of 143 mA h g–1 at 2C was realized for 133 cycles. Remarkably, a pouch cell based on this system exhibited good electrochemical performance, flexibility, and safety. This ASSLB holds great promise for practical energy-storage applications.