Electrolyte Engineering via Nucleophilic Anion Design: Lithium Pentafluoropropionate Enabling Dendrite-Free High-Performance Lithium Metal Batteries

To address the challenges of low Coulombic efficiency and uncontrolled lithium dendrite growth on lithium metal anodes in lithium metal batteries (LMBs), we design and synthesize a lithium salt, lithium pentafluoropropionate (LiPFP), as an additive salt for LMB electrolytes. Unlike conventional lithium salts, the anion of LiPFP is designed to be strongly nucleophilic. Consequently, when introduced into the electrolyte, PFP^- preferentially enters the inner Li⁺ solvation sheath and undergoes prior decomposition, participating in the formation of inorganic components (Li₂O, LiF, Li₂CO₃) within the solid electrolyte interphase (SEI). The LiPFP-containing electrolyte forms a bilayer-like SEI structure on the lithium anode. This structure effectively enhances the stability of the lithium anode/electrolyte interface and mitigates dendrite formation and dead lithium generation. Cycle evaluations of high-loading full cells and pouch cells under lean electrolyte conditions demonstrated that LiPFP significantly improved the cycling lifespan and rate capability of LMBs. Specifically, a 360 mAh Li||LiNi_0.91Co_0.045Mn_0.045O₂ pouch cell achieved stable operation for 100 cycles at a high current rate (0.5C, 2.045 mA·cm^-2) with a capacity retention of 95.2%. These results comprehensively validate the effectiveness of this approach, offering a viable pathway for developing carbonate-based electrolytes toward the commercial application of LMBs.