In situ co-growth LiF-Li3N rich dual-protective layers enable high interface stability for solid-state lithium-metal batteries

Lithium metal anodes hold promise for next-generation high-energy-density batteries. However, serious dendrite formation and unstable solid electrolyte interphase (SEI) impede their practical implementation. Herein, a novel gel polymer electrolyte (GPE) integrated design is exploited to in situ co-growth Li3N and LiF rich SEI by improving electron transfer kinetics and enhancing mechanical properties. Specifically, a polyethylene glycol diacrylate is used as GPE matrix to form a robust crosslinked network. Meanwhile, the high electron transport capacity of acrylonitrile promotes the generation of Li3N. The polyfluorinated polymer introduction boosts electron transfer kinetics, facilitating C-F bond cleavage to form LiF. Finally, the in situ co-growth Li3N and LiF rich dual-protective SEI is constructed, which regulates the ion flux and achieves dendrite-free lithium deposition. Impressively, the SEI treated symmetrical cell demonstrates excellent plating/stripping cycling for 1000 h at 0.5 mA cm−2 with notably reduced overpotentials (50 mV). Moreover, the obtained GEL@F matched with LiFePO4 displays good cycling stability over 400 cycles with 91.8 % capacity retention at 1 C. Concurrently, paired with LiCoO2 drives a good capacity retention of over 82.8 % after 200 cycles. This study introduces a rational SEI design from the structural composition of GPE to optimize the chemical activity/physical properties of lithium metal interfaces.