Study of electrolytic cobalt sulfide Co9S8 as an electrode material in lithium accumulator prototypes

With the purpose to obtain a sulfide material for lithium and lithium-ionic thin-film batteries, cobalt sulfide Co 9 S 8 was synthesized on an aluminum foil or stainless steel by electrolysis of aqueous solutions containing cobalt sulfate, sodium thiosulfate and sodium sulfide. The surface morphology of electrolytic Co 9 S 8 is characterized by close packing of ball-like particles 8–12 μm in diameter, consisting of submicrometer structures 300–400 nm in size. It was found that e-Co 9 S 8 electrodes exhibit stable behavior during 100 lithiation-delithiation cycles in a voltage range of 2.8–1.1 V, providing a discharge capacity of ∼200 mAh/g. In a lithium cell with ethylene carbonate (EC)-dimethyl carbonate (DMC)-1M LiClO 4 electrolyte, a discharge capacity of the e-Co 9 S 8 -electrode was 250–450 mAh/g in a voltage range of 2.80–0.2 V. It was found that higher discharge capacities can be achieved for e-Co 9 S 8 -electrodes with a smaller active material mass.