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/LiNi(0.8)Co(0.1)Mn(0.1)O(2) full cells (rather than Li/Cu configuration), a polyether/coordinated borate containing solid‐electrolyte interphase with inner Li(2)O 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 LiNi(0.8)Co(0.1)Mn(0.1)O(2)/Li cells (N/P < 2, 350 Wh kg(−1)) under high cutoff voltage condition of 4.6 V and lean electrolyte condition (E/C ≈ 3.2 g Ah(−1)).