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

Abstract

The nickel sulfide, Ni 3S 2, was examined as a potential cathode material of the all-solid-state-lithium-batteries using thio-LISICON, Li 2S–GeS 2–P 2S 5, as the solid-electrolyte. Ni 3S 2and Li 2S–GeS 2–P 2S 5 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 × 1 0 − 3 S cm −1 was observed for a sample prepared at 700 °C with 10% of excess P 2S 5, and bear comparison with the maximum conductivity reported for the thio-LISICON, Li 3.35Ge 0.35P 0.65S 4. An all-solid-state-lithium-battery based on, Ni 3S 2/Li 3.35Ge 0.35P 0.65S 4/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 Ni 3S 2/thio-LISICON compositions in the cathode mixture, with a cell containing 60 wt.% of Ni 3S 2 exhibiting the most stable reversible capacities. As the depth of the first discharge capacity also influences the cycling properties, Ni 3S 2 consumed during the discharge reaction may play an important role in the nickel reduction mechanism.