Electrolyte-cleaning additive-driven inorganic-rich electrode/electrolyte interfaces enabling high-voltage and high-temperature lithium metal batteries

Lithium metal batteries (LMBs) have emerged as a prime candidate for high-energy storage due to their outstanding theoretical energy density. The practical application of LMBs is limited by cathode instability, lithium dendrite growth, and electrolyte decomposition at high voltages and temperatures. To address these issues, we developed a novel additive, N-(trimethylsilyl)bis-(trifluoromethanesulfonyl)imide (TFSNSi), to enhance the performance of carbonate-based electrolytes. The TFSNSi participates in Li+ solvation, reducing the coordination number of solvents. Additionally, it preferentially adsorbs on electrode surfaces, promoting the formation of an electrode-electrolyte interphase (EEI) abundant in inorganic components such as LiF, Li₃N, Li₂SO₃/Li₂SO₄, and Li₂S. Cathode stability is improved while lithium dendrite growth is restricted. The unique –Si–N– functional group in TFSNSi acts as an efficient “electrolyte cleaner” by scavenging harmful HF, which enhances the electrolyte stability. The Li||NCM622 battery employing the TFSNSi-contained electrolyte demonstrates stable cycling performance. The battery delivers reversible capacities of 185 mAh g−1 at 4.6 V and 196 mAh g−1 at 4.7 V, retaining 84.8% and 75.5% after 200 cycles, respectively. Even under harsh conditions (4.6 V, 60 °C), 80.6% of the initial capacity is preserved after 150 cycles, underscoring the superior stability imparted by the additive.