Synergistic electrolyte design for dual-interface stability in sodium-ion batteries

Abstract

Layered oxide materials are widely recognized as promising cathode materials for sodium-ion batteries; however, their unstable interface under high-current conditions leads to a decline in electrochemical performance, significantly impeding their application. A highly effective and straightforward approach to address these issues involves introducing trace additives to modulate the solid electrolyte interface (SEI) and cathode electrolyte interface (CEI) on the anode and cathode, respectively. In this study, we report the novel introduction of a 2-FP and FEC additive combination, which synergistically facilitates the formation of a SEI and CEI rich in F/N components. As expected, the NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM)‖Na cell with this dual additive system retained a capacity of 97.7 mA h g⁻¹ at a high current density of 5C after 500 cycles, with a retention rate of 73.13%. Moreover, the NFM‖hard carbon (HC) pouch cell achieved a remarkable 90.8% capacity retention after 300 cycles.