Ternary stabilization strategies for succinonitrile-based in situ polymerized electrolyte enabling high-performance solid lithium metal batteries

Solid-state lithium metal batteries with high energy density and safety have gained increasing attention due to their potential applications. However, the practical use of solid electrolytes is hindered by several challenges. These include poor compatibility at the electrode–electrolyte interface, low ionic conductivity at room temperature, and fast capacity degradation. To address these issues, here we propose ternary strategies by in-situ cross-linked plastic crystal electrolyte (in-situ PCE) based on succinonitrile (SN). Through the in-situ polymerization of SN with polyacrylonitrile/poly(vinylidene difluoride) (PAN/PVDF) nanofibers separator, excellent mechanical strength and compatibility at the electrode–electrolyte interface are achieved. The cross-linked structure of thermally polymerized ethoxylated trimethylolpropane triacrylate (ETPTA) immobilizes the SN molecule, preventing its contact with the lithium metal and inhibiting irreversible side reactions. Additionally, a LiF-rich passivation layer is employed to further protect the SN at the electrolyte-lithium metal interface. The dual protection from ETPTA and LiF offers excellent stability to lithium. Hence, the in-situ PCE exhibits high ionic conductivity (0.79 mS cm−1 at 30 °C) and wide electrochemical window (4.56 V, vs Li+/Li). The cells exhibit excellent cycling stability and high-rate performance. LiFePO4//Li cells retain 96.6 % capacity after 1000 cycles at 10C rate. This study provides valuable insights into the development of high-performance solid-state electrolytes.