Synergistic Anion and\nSolvent-Derived Interphases\nEnable Lithium-Ion Batteries\nunder Extreme Conditions

Lithium-ion batteries (LIBs) face increasingly stringent\ndemands\nas their application expands into new areas, including extreme temperatures\nand fast charging. To meet these demands, the electrolyte should enable\nfast lithium-ion transport and form stable interphases on electrodes\nsimultaneously. In practice, however, improving one aspect often compromises\nanother. For instance, the trend toward electrolytes forming anion-derived\ninterphases typically reduces transport efficiency due to weak-solvating\nsolvents. We propose that instead of relying on anions to form the\ninterphase, leveraging both solvents and anions to form interphases\ncan potentially lead to a balancing point between robust interphase\nformation and effective ion transport. Guided by this design principle,\n2,2-difluoroethyl ethyl carbonate (DFDEC) was identified as the promising\nsolvent. With the new electrolyte using DFDEC as the major solvent\nand lithium bis(fluorosulfonyl) imide (LiFSI) as the salt, graphite||LiNi<sub>0.8</sub>Mn<sub>0.1</sub>Co<sub>0.1</sub>O<sub>2</sub> (NMC811) full\ncells are capable of fast charging and demonstrate long-term cycling\nstability with a cutoff voltage of 4.5 V. Notably, the battery shows\na capacity retention of 84.3% after 500 cycles with an average Coulombic\nefficiency (CE) as high as 99.93%. This new electrolyte also enables\nstable battery cycling across a wide temperature range (−20\nto 60 °C), with excellent capacity retention.