Constructing Anion Solvation Microenvironment Toward Durable High-Voltage Sodium-Based Batteries.

Sodium-based rechargeable batteries are some of the most promising candidates for electric energy storage with abundant sodium reserves, particularly, sodium-based dual-ion batteries (SDIBs) perform advantages in high work voltage (≈5.0 V), high-power density, and potentially low cost. However, irreversible electrolyte decomposition and co-intercalation of solvent molecules at the electrode interface under a high charge state are blocking their development. Herein, a high-salt concentration microenvironment is created and proposed by tailoring the solvation structures of charge carriers including both cations and anions, which maintains highly oxidation-resistant contact ion pairs and ion aggregates and provides a high ion conductivity. The tailored solvation structure makes a great contribution to protecting the graphite cathode from electrolyte oxidation, solvent co-intercalation, and structural degradation by constructing a robust cathode-electrolyte interphase with standout electrochemical stability. Based on this, the SDIBs achieved an excellent high-voltage cycling stability with 81% capacity retention after 10 000 cycles and the battery showed an improved rate performance with 97.4 mAh g maintained at 100 C. It is identified that regulating anion solvation structure is responsible for the stable interface chemistry and enhanced reaction kinetics, which provides deep insight into the compatibility design between the electrolyte and specialized charge storage in electrodes.