Tailored interface composition improves the integrity of electrode/electrolyte interphases for high-voltage Ni-rich lithium metal batteries in a sulfolane-based electrolyte

High-voltage lithium metal batteries (LMBs) matched with Ni-rich cathodes can deliver high energy density to satisfy the rapid development of power battery systems. However, conventional solid electrolyte interphase (SEI) or cathode electrolyte interphase (CEI) composed of Li2CO3, Li2O, LiF and alkyl lithium carbonate cannot meet the requirements for high-voltage LMBs in terms of stability and mechanical performance. Herein, a sulfolane-based electrolyte assisted with co-solvent and dual-salt strategies is developed to realize tailored LiF-boride-sulfide-containing interphases on both electrodes, in which the decomposition product RSOx can combine various inorganic and organic components. The improved integrity of interphases can mitigate the continuous decomposition of the electrolyte, thereby promoting uniform and dense lithium deposition and protecting the structure of cathode materials. Thus, the prepared sulfolane-based electrolyte results in an average Coulombic efficiency of 99.1% for Li||Cu cells and enables 4.7 V Li||LiNi0.8Co0.1Mn0.1O2 cells to maintain 80.0% capacity retention after 200 cycles. Besides, Cu||LiNi0.8Co0.1Mn0.1O2 anode-free cells (3.5 mAh cm−2, capacity retention of 70.5% after 50 cycles) further confirm the practicality of the prepared electrolyte. This work offers a direct and efficient method to enhance the integrity and stability of interphases by optimizing the electrolyte composition.