Résumé
An innovative approach to electrolyte engineering in carbonate electrolytes is introduced by incorporating high donor number dual anion additives into the conventional electrolyte system (1 M NaPF6 EC:PC). The active engagement of anions in the primary solvation shell effectively hinders the reduction of solvent molecules by reducing the Lowest Unoccupied Molecular Orbital (LUMO) of Na+-solvent-anion complex as compared to the LUMO of pure solvents or Na+-solvent complex. The participation of anions leads to the formation of a thinner and an inorganic-rich Solid Electrolyte Interphase on the hard carbon anode enhancing Initial Coulombic Efficiency and significantly improving its kinetics. Moreover, the system with dual anion additives exhibits oxidative stability up to 4.5 V, effectively mitigating the undesired side reactions at high voltage operation of the layered sodium nickel manganese oxide cathode. The addition of dual anion additives proves instrumental in suppressing structural degradation and transition metal dissolution during the long cycling performance of the layered oxide cathode in a sodium-ion full cell. The synergistic effects of this dual anion additive added electrolyte on both the anode and the cathode ultimately ensured prolonged cycling of the sodium-ion full cell. The electrolyte engineering approach outlined in this study opens the door to advancing next-generation high-voltage sodium batteries.
This study presents an innovative method to modify electrolyte composition by integrating anion additives, forming thin and durable electrode-electrolyte interfaces on both anode and cathode surfaces, thereby enhancing the initial coulombic efficiency of the negative electrode and prolonging the lifespan of sodium-ion batteries using high-voltage layered oxide cathodes. image