An Inorganic-Rich Solid Electrolyte Interphase for Advanced Lithium-Metal Batteries in Carbonate Electrolytes

In carbonate electrolytes, the organic–inorganic solid electrolyte interphase (SEI) formed on the Li-metal anode surface is strongly bonded to Li and experiences the same volume change as Li, thus it undergoes continuous cracking/reformation during plating/stripping cycles. Here, an inorganic-rich SEI is designed on a Li-metal surface to reduce its bonding energy with Li metal by dissolving 4m concentrated LiNO₃ in dimethyl sulfoxide (DMSO) as an additive for a fluoroethylene-carbonate (FEC)-based electrolyte. Due to the aggregate structure of NO₃⁻ ions and their participation in the primary Li⁺ solvation sheath, abundant Li₂O, Li₃N, and LiN_xO_y grains are formed in the resulting SEI, in addition to the uniform LiF distribution from the reduction of PF₆⁻ ions. The weak bonding of the SEI (high interface energy) to Li can effectively promote Li diffusion along the SEI/Li interface and prevent Li dendrite penetration into the SEI. As a result, our designed carbonate electrolyte enables a Li anode to achieve a high Li plating/stripping Coulombic efficiency of 99.55 % (1 mA cm⁻², 1.0 mAh cm⁻²) and the electrolyte also enables a Li||LiNi_0.8Co_0.1Mn_0.1O₂ (NMC811) full cell (2.5 mAh cm⁻²) to retain 75 % of its initial capacity after 200 cycles with an outstanding CE of 99.83 %. © 2020 Wiley-VCH GmbH