In-situ constructed solid composite cathode electrode enables poly (ethylene oxide) based solid-state lithium batteries to stably operate at high-voltage

Solid polymer electrolytes (SPEs) are promising candidates for the application of solid-state batteries (SSBs). However, the narrow electrochemical window and inadequate electrode-electrolyte interfacial contact restrict the practical application of SPEs. To address these issues, the solid composite cathode electrode (SCCE) is designed through in-situ polymerization in the LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode electrode. The in-situ polymerized electrolyte exhibits high ionic conductivity (0.133 mS cm −1 at 30 °C and 1.1 mS cm −1 at 60 °C) and a wide electrochemical window (>4.8 V). The poly (ethylene oxide) (PEO) based SSB using the constructed NCM811-SCCE shows superior cycling stability with a capacity retention ratio of 74.14 % after 500 cycles (2.8–4.2 V). Moreover, the PEO solid-state pouch cell employing the NCM811-SCCE can operate under bending or cutting conditions, demonstrating its high safety and reliability. Therefore, this work presents an effective design of SCCE, enabling the PEO-based SSB to be compatible with the high-voltage cathode. This is a practical approach for the applications of SSBs with high energy density and safety.