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 Co9S8 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 Co9S8 is characterized by close packing of ball-like particles 8-12 mu m in diameter, consisting of submicrometer structures 300-400 nm in size. It was found that e-Co9S8 electrodes exhibit stable behavior during 100 lithiation-delithiation cycles in a voltage range of 2.8-1.1 V, providing a discharge capacity of similar to 200 mAh/g. In a lithium cell with ethylene carbonate (EC)-dimethyl carbonate (DMC)-1M LiClO4 electrolyte, a discharge capacity of the e-Co9S8-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-Co9S8-electrodes with a smaller active material mass.