Solvation regulation and interphase stabilization enabled by a BiF3-MOF composite electrolyte for high-performance lithium metal anodes.

Despite their high energy density, lithium metal batteries (LMBs) remain hindered in practical applications by the intrinsic instability of the lithium metal anode. Owing to its high reactivity, lithium readily forms a fragile and heterogeneous solid electrolyte interphase (SEI), leading to nonuniform Li deposition, dendrite growth, and consequent safety risks and rapid capacity decay. In this work, a quasi-solid-state electrolyte (QSE) incorporating a BiF3-decorated metal-organic framework (MOF) is developed to stabilize lithium metal anodes. The BiF3 nanoparticles confined within the MOF regulate the Li+ solvation sheath through interactions with solvent molecules, thereby facilitating Li+ transport and delivering an ionic conductivity of 2.0 mS cm-1 with an enhanced Li+ transference number of 0.48. In addition, the QSE promotes the in-situ formation of a LiF/Li3Bi-rich SEI, which accelerates Li+ diffusion, lowers the Li nucleation barrier, and enables uniform and smooth lithium deposition. As a result, lithium metal anodes exhibit markedly improved reversibility and interfacial kinetics. Li||Li symmetric cells achieve a high critical current density of 2.5 mA cm-2 and maintain stable cycling for over 4600 h at 0.2 mA cm-2. Furthermore, Li||LiFePO4 full cells demonstrate excellent rate capability and long-term cycling stability, retaining 92.2% of the initial capacity after 1500 cycles at 1C and delivering 72.6 mAh g-1 at 20C.