Nickel sulfide cathode in combination with an ionic liquid-based electrolyte for rechargeable lithium batteries

Nickel sulfides, pure Ni3S2 and a mixture of Ni7S6–NiS, were synthesized through a solvothermal process. The nickel sulfide powders were characterized by X-ray diffraction, scanning electron microscopy, and electrochemical testing. The results showed that the capacity of NiS–Ni7S6 is much higher than that of Ni3S2, when used as the cathode in a lithium cell with an organic solvent-based electrolyte, l M lithium bis(trifluoromethanesulfonyl)amide (LiNTf2) in poly(ethylene glycol) dimethyl ether 500. The NiS–Ni7S6 electrodes were also tested with an ionic liquid electrolyte consisting of 1 M LiNTf2 in N-methyl-N-propyl pyrrolidinium bis(trifluoromethanesulfonyl)amide ([C3mpyr][NTf2]) to compare with organic-solvent based electrolytes. The results revealed that the ionic liquid is a useful solvent for use with this cathode material.