Saccharin Sodium Coupling Fluorinated Solvent Enabled Stable Interface for High‐Voltage Li‐Metal Batteries

Abstract Optimizing the electrode/electrolyte interface structure is the key to realizing high‐voltage Li‐metal batteries (LMBs). Herein, a functional electrolyte is introduced to synergetically regulate the interface layer structures on the high‐voltage cathode and the Li‐metal anode. Saccharin sodium (NaSH) as a multifunctional electrolyte additive is employed in fluorinated solvent‐based electrolyte (FBE) for robust interphase layer construction. On the one hand, combining the results of ex‐situ techniques and in‐situ electrochemical dissipative quartz crystal microbalance (EQCM‐D) technique, it can be seen that the solid electrolyte interface (SEI) layer constructed by NaSH‐coupled fluoroethylene carbonate (FEC) on Li‐metal anode significantly inhibits the growth of lithium dendrites and improves the cyclic stability of the anode. On the other hand, the experimental results also confirm that the cathode‐electrolyte interface (CEI) layer induced by NaSH‐coupled FEC effectively protects the active materials of LiCoO 2 and improves their structural stability under high‐voltage cycling, thus avoiding the material rupture. Moreover, theoretical calculation results show that the addition of NaSH alters the desolvation behavior of Li + and enhances the transport kinetics of Li + at the electrode/electrolyte interface. In this contribution, the LiCoO 2 ǁLi full cell containing FBE+NaSH results in a high capacity retention of 80% after 530 cycles with a coulombic efficiency of 99.8%.