Ternary Electrolyte Enables High-Voltage and High-Temperature Na-Ion Batteries

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Extending the voltage and temperature range for Na-ion batteries (NIBs) is crucial for enhancing energy densities and practical applications. Stabilizing electrode–electrolyte interphases under extreme conditions is challenging. Here, we present a high-performance electrolyte with delicate regulation of ternary solvent–solvent interactions, which augments the chemical and electrochemical stability of the electrolyte. The competition of solvation forces and solvent–solvent interactions in the ternary electrolyte promotes Na+ transport and leads to robust interphases. Compared to the conventional carbonate electrolyte, the ternary electrolyte effectively hinders structural phase transitions and transition metal dissolution in the layered oxide cathode. This enables oxide cathodes to perform under 4.2 V with 99.95% Coulombic efficiency for 1000 cycles and stable operation from −35 to 80 °C. Ah pouch cells demonstrate good cycling stability under various temperatures. This work provides valuable insights for developing high-performance NIB electrolytes without increasing costs or sacrificing kinetics.