Synthesis and electrochemical study of CoNi₂S₄ as a novel cathode material in a primary Li thermal battery

In this work CoNi₂S₄ was investigated as a candidate cathode material for Li thermal batteries. The CoNi₂S₄ was synthesized by a solid state reaction at 550◦C in a sealed quartz tube. Neutron powder diffraction was utilized to confirm normal spinel structure up to 200◦C, however, there was cation disorder above this temperature. The electrochemical properties of the batteries were investigated at 500◦C by galvanostatic discharge to elucidate the mechanism and the products NiS, Co₃S₄ and Co₉S₈ of the discharge mechanism were confirmed using powder X-ray diffraction. CoNi₂S₄ exhibits two voltage plateaus vs Li₁₃Si₄ at 500◦C, one at 1.75 V and the second at 1.50 V. CoNi₂S₄ has an overall capacity of 318 mA h g−1 from OCV 2.58 V to 1.25 V vs Li1₃Si₄ which is comparable to that of the well-known metal disulfides