Electrolyte Engineering on Performance Enhancement of Nico2s4 Anode for Sodium Storage

Abstract

Transition metal sulfides (TMSs) are attractive as anodes for sodium-ion batteries (SIBs) due to the high capacity, abundant resource, and excellent redox reversibility. Practical deployment of TMSs in SIBs, however, is still hindered by the inferior capacity and unsatisfactory cycling performance, which result from the mismatch between the electrolyte chemistry and electrode. Herein, we developed a functional electrolyte containing 1 M NaCF3SO3 in diethylene glycol dimethyl ether, which can be readily used for NiCo2S4 anode with enhanced cycling performance and boosted capacities (341.7 mA h g−1 after 250 continuous cycles at the current density of 200 mA g−1). Extensive experiments and theoretical calculation results on the electrode/electrolyte interfacial chemistry and the formation of sulfide intermediates indicate ester solvent suffers from a more severe decomposition than the ether solvent and the ether-electrolyte can form a better solvation structure. Our findings indicate that the electrolyte engineering would be an effective way in performance enhancement for sulfides in practical SIBs.

Keywords: ether-based electrolyte, NiCo2S4 electrode, electrode-electrolyte interface, mechanism understanding, Sodium ion batteries