Efficient Lithium Metal Cycling at a Wide Range of Pressures from an Anion-Derived Solid-Electrolyte Interphase Framework

Abstract

Novel electrolytes have been developed to improve the cyclability of lithium (Li) metal anodes, yet their working mechanisms remain unclear. The dependence of the performance on the operational pressure can provide valuable insights on the Li plating mechanisms in different electrolytes. Here, we study Li cycling performance evolution against pressure in 1 M LiFSI/fluorinated 1,4-dimethoxylbutane (FDMB) electrolyte, one of the highest-performing electrolytes for Li metal to date. We show that it enables excellent Coulombic efficiency (CE) in a pouch cell format under a wide range of initial pressures (30-600 psi). We discover that this is due to a completely different Li plating mode with superior deposition morphologies compared to that in a conventional carbonate electrolyte, which exhibits increasing cycle stability with increased pressure. We show that this is enabled by the properties of an anion-derived residual solid-electrolyte interphase (rSEI) framework on the electrode surface, an undercharacterized structure with profound implications for Li metal cycling. The plating morphology enabled by this anion-derived rSEI chemistry is likely the key to a prolonged cycle life in high performance electrolytes for Li metal.