Stabilizing poly(vinylidene fluoride) solid-state electrolytes/lithium metal interface by constructing an ultrathin interface layer to inhibit the electron transfer

Residual N, N-dimethylformamide (DMF) enhances the conductivity of poly(vinylidene fluoride) (PVDF) solid-state polymer electrolytes (SPEs), but adversely impacts the SPEs/Li interface through electron transfer between DMF and Li. Herein, we developed a novel LiOH and LiNH₂ (LON) artificial solid electrolyte interface (SEI) layer with limited electronic conductivity to block such electron transfer. Unlike conventional SEI, which are unsuitable for integration with SPEs since their high thickness (1–30 μm) results in high interfacial resistance, the LON layer is ultrathin (∼30 nm), and more importantly, it facilitates the separation of Li ions from Li-DMF bound ions during Li plating, contributing to a notable reduction in interfacial impedance. As a result, the LON protected Li (Li@LON)-based symmetrical cell exhibits an ultra-long cycle life of 2100 h and survives even under 0.6 mAh cm⁻² at 25 °C, in stark contrast to the Bare Li-based symmetrical cell, which only maintains stable cycles for 806 h at 0.2 mAh cm⁻². Furthermore, the Li@LON//LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cell stably cycles over 3000 times at 0.5 C and 25 °C, significantly outperforming the Li//NCM811 cell with 880 times. This work paves a novel strategy for stabilizing SPEs-Li interface by constructing an ultrathin artificial SEI with low electronic conductivity.