A Tip-Inhibitor Interphase Embedded with Soluble Polysulfides for High-Voltage Li Metal Batteries

The high-voltage battery has now become a goal in order to meet the demands for high energy density. However, the severe side reactions between Li metal and carbonate-based electrolytes in this system result in unstable interphase, leading to non-uniform Li-ion flux and thus aggravating the dendrite growth of Li. The protect interphase, traditional solid electrolyte interface (SEI), is a loose solid layer consisted of many components, which generally does not possess the function of preventing the lithium budding. Herein, based on polysulfide solubility in ester, we proposed a strategy to eliminate the dendrite by constructing a unique SEI in which the dynamic polysulfides were in situ formed and encapsuled. For this purpose, a 2-fluorophenylsulfur pentafluoride (2-FSPF) was employed as an additive in carbonate-based electrolyte that can be decomposed electrochemically during battery operation to form such a polysulfide-rich interphase. These polysulfides with certain fluidity can adhere to dynamically the budding tip of Li metal, as a so-called tip-inhibitor, when the local current density of the tip rising, thus to hinder Li⁺ diffusion toward the tip, resulting in inhibiting the further growth of Li dendrites and leveling the Li deposition. At the current density of 1 mA cm⁻², the average Coulombic efficiency of Li//Cu cells is as high as 98.39% during 600 cycles, and the stable cycling of Li//Li symmetric cell reaches 3500 h. Furthermore, due to the high anodic stability, the Li//high-voltage LiCoO₂ (LCO) full cells and Li–O₂ battery achieve excellent cycle performance with lean electrolyte.