Nickel sulfides as a cathode for all-solid-state ceramic lithium batteries

The nickel sulfide, Ni3S2, was examined as a potential cathode material of the all-solid-state-lithium-batteries using thio-LISICON, Li2S–GeS2–P2S5, as the solid-electrolyte. Ni3S2and Li2S–GeS2–P2S5 system, was synthesized with a new sintering system, which proceed under a flowing argon in the reusable quartz tube. The highest ionic conductivity 2.39×10−3 S cm−1 was observed for a sample prepared at 700 °C with 10% of excess P2S5, and bear comparison with the maximum conductivity reported for the thio-LISICON, Li3.35Ge0.35P0.65S4. An all-solid-state-lithium-battery based on, Ni3S2/Li3.35Ge0.35P0.65S4/Li–Al alloy, showed electrochemical capacities of greater than 300 mAh g−1 after 30 cycles. The cycling performances of the cells were found to be dependent on the Ni3S2/thio-LISICON compositions in the cathode mixture, with a cell containing 60 wt.% of Ni3S2 exhibiting the most stable reversible capacities. As the depth of the first discharge capacity also influences the cycling properties, Ni3S2 consumed during the discharge reaction may play an important role in the nickel reduction mechanism.