Design of ultrafast lithium ion channel for solid-state lithium metal batteries by in-situ polymerization induced phase separation

• A bicontinuous structured SN-based deep eutectic polymer electrolyte was synthesized by in situ polymerization-induced phase separation method. • PDMAA exhibits ultrafast conduction pathway (PDMAA—[SN—Li + ]). • The amide group of DMAA with a high donor number promote formation of stable SEI. • PDSLF-based lithium metal batteries exbibit excellent cycling performance at −10 °C and rate performance. • PDSLF-based lithium metal batteries possess excellent safety. Lithium ion transport in succinonitrile-based deep eutectic electrolyte is hindered due to its high viscosity. Meanwhile, weak reductive stability of α-H in free succinonitrile(SN) molecules can result in unfavorable interfacial reactions. Herein, we introduce a method combining advantages of polymerization-induced phase separation and in situ polymerization, which enables deep eutectic polymer electrolytes (PDSLF) of bicontinuous nanostructure consisting of two chemically independent domains. Significantly, in situ formation of poly (N, N-dimethylacrylamide) (PDMAA) phase can anchor and modulate SN molecules by electronegativity difference in bicontinuous structure, resulting in ultrafast conduction pathway (PDMAA − [SN − Li + ]). Additionally, as diluent, N, N-dimethylacrylamide (DMAA) attributes to the formation of organic/inorganic composite SEI consisting of organic N−(C) 3 with Li affinity to homogenize ion distribution, rich LiF with high surface energies to render dendrite-free morphology and high ionic conductive Li 3 N to guide rapid Li + transport. As a result, PDSLF exhibits ionic conductivity of 1.47 mS cm −1 , wide electrochemical window of 5.1 V, high Li-ion transfer number (t Li+ ) of 0.866. The Li symmetrical cells using PDSLF display stable plating/stripping for over 600 h at a constant current of 0.2 mA cm −2 . The Li||LFP cell maintains an excellent capacity retention of 98.29 % at 0.5C after 300 cycles, and even at −10 °C can maintain a discharge capacity of 123.73 mAh g −1 at 0.1C. The study introduces a novel approach to achieving commercial utilization of solid-state lithium metal batteries with enhanced energy density and safety.