Structural, Thermal, and Electrochemical Studies of Novel Li2CoxMn1–x(SO4)2 Bimetallic Sulfates

A novel high-voltage solid solution of Li2CoxMn1–x(SO4)2 (x = 0–1) was synthesized using a simple solid-state reaction. Single-phase monoclinic crystal structure was identified, and there was no evidence for the presence of an orthorhombic polymorph at a sample preparation temperature of 450 °C. Interestingly, the bimetallic sulfates were found to be thermally stable up to 550 °C, and it was validated through various characterization techniques. Beyond 550 °C, the materials start to decompose and form Li2SO4 and α-CoSO4 in the case of Li2Co(SO4)2, while Li2Mn(SO4)2 decomposes to form Li2Mn2(SO4)3. In addition, an important property called sensitivity toward moisture was also characterized, which plays a critical role in the handling of the sulfate-based cathode during the cell fabrication. Thus, the reaction mechanism involved during the absorption of the atmospheric moisture was also investigated carefully. Finally, for the first time electrochemical activity of both Co and Mn systems was discovered wher...