Investigation of the enhanced sodium ion storage properties of sphere-like NiS in ethers-based electrolyte

Sodium ion batteries (SIBs) with rich abundance and similar chemical properties with that of lithium-ion batteries have attracted plenty attentions. Transition metal sulfides anodes with high energy density and relatively good conductivity show promising application potential but severely hinder by unsatisfied performance. In the present study, sphere-like NiS was prepared by solvothermal method using L-tryptophan as template. When severed as anode in SIBs, NiS displays distinguished electrochemical performances in esters-based and ethers-based electrolytes. A low initial coulombic efficiency of 65% is shown; meanwhile a cliff descent of capacity is emerged after 20 cycles in esters-based electrolyte. Surprisingly, a high coulombic efficiency of 95.4% with enhanced cycling stability is obtained with ethers-based electrolyte. The thin and even distributed SEI film with F-rich inorganic component that formed in the ethers-based electrolyte is the key factor to promote the electrochemical performance.