One-pot solvothermal synthesis of Co_1-xMn_xC₂O₄ and their application as anode materials for lithium-ion batteries

A facile one-pot solvothermal route has been developed to synthesize phase pure M_xC₂O₄·2H₂O (M = Mn, Co; 0 < x ≤ 1) microstructures without employing any hard/soft template and their electrochemical performance in lithium-ion batteries has been systematically investigated. Morphology, microstructure and composition of the synthesized materials are characterized by field emission-scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. Anhydrous micron-sized MnC₂O₄ and CoC₂O₄ exhibits specific reversible discharge capacity of ∼800 and 950 mA h g^-1 respectively, at 1 C-rate. MnC₂O₄ exhibited good cycling stability while CoC₂O₄ showed severe capacity fading phenomenon after 40 cycles, thereafter attaining 400-600 mA h g^-1 for all C-rates. Interestingly, mixed solid solution having Co_0.52Mn_0.48C₂O₄ composition improved the specific reversible discharge capacity to a stable value of ∼1000 mA h g^-1 (1 C-rate), which is one of the highest reported values for such oxalates. The cycling stability of this mixed metal oxalate is remarkably better than its individual constituents at most C-rates. The Mn²⁺ substitution into CoC₂O₄ lattice has led to the synergistic modification of the electrochemical performances, thus making it a promising anode candidate for future LIBs.