High-Efficacy and Polymeric Solid-Electrolyte Interphase for Closely Packed Li Electrodeposition.

The industrial application of lithium metal anode requires less side reaction between active lithium and electrolyte, which demands the sustainability of the electrolyte-induced solid-electrolyte interface. Here, through a new diluted lithium difluoro(oxalato)borate-based (LiDFOB) high concentration electrolyte system, it is found that the oxidation behavior of aggregated LiDFOB salt has a great impact on solid-electrolyte interphase (SEI) formation and Li reversibility. Under the operation window of Cu/LiNiCoMnO full cells (rather than Li/Cu configuration), a polyether/coordinated borate containing solid-electrolyte interphase with inner LiO crystalline can be observed with the increasing concentration of salt, which can be ascribed to the reaction between aggregated electron-deficient borate species and electron-rich alkoxide SEI components. The high Li reversibility (99.34%) and near-theoretical lithium deposition enable the stable cycling of LiNiCoMnO/Li cells (/ < 2, 350 Wh kg) under high cutoff voltage condition of 4.6 V and lean electrolyte condition (/ ≈ 3.2 g Ah).