Ternary lithium salts assisted room-temperature succinonitrile-based polymer electrolyte for lithium metal battery

Solid polymer electrolyte with high room-temperature ionic conductivity and safety is a potential solution to the application of lithium metal batteries. Succinonitrile (SN) is a promising candidate due to its non-flammability and good ionic conductivity. However, the high reactivity between SN and lithium limits the application. Herein, a ternary-lithium-salt (LiTFSI-LiDFOB-LiNO 3 ) system is proposed to regulate the behavior of SN-based electrolyte. SN is anchored in the polymer network generated by crosslinking ethoxylate trimethylolpropane triacrylate through in-situ thermal polymerization. The SN-based ternary-lithium-salt electrolyte (TSE) possesses high room-temperature ionic conductivity and excellent flame retardancy. The ternary lithium salts promote the formation of stable heterostructured composite SEI with enhanced mechanical strength and flexibility, which effectively inhibits SN-Li side reactions, improves interfacial compatibility, and ensures stable lithium plating/stripping. The Li|TSE|Li symmetric cell can stably cycle for 1800 h with small polarization of ∼10 mV. The LiCoO 2 |TSE|Li full cell delivers high capacity retention of 88.4 % at 4.4 V after 200 cycles. TSE is also suitable for various high-voltage cathodes, showing great promise in high-performance and high-safety solid-state lithium metal batteries. The excellent stability and electrochemical performance brought by ternary lithium salts provides a promising perspective into the development of room-temperature SN-based polymer electrolytes.