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

Abstract

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.