Stable lithium storage behavior observed in Mn-doped MgCo2O4 anode materials

Abstract

Cation substitution strategy is considered to be an effective way to create defect structure in the spinel structure for improving the performance of Li-ion batteries. In this work, a series of MgMnxCo2-xO4 (x = 0, 0.5, 1, 1.5, 2) materials with Mn ions replacing Co ions were synthesized by a facile hydrothermal method. The collected X-ray diffraction and scanning electron microscope results show that the lattice parameters and particle size of the materials increase with the increase of Mn doping concentration. The O 1s X-ray photoelectron spectra results show that there are more oxygen vacancies and interstitial hydroxyl groups in MgMn0.5Co1.5O4 samples, which is conducive to the improvement of conductivity of the material. Analyses of XPS spectra of Mg 1s, Mn 2p and Co 2p reveal that magnesium exists as Mg2+ ions, manganese and cobalt exist in multivalent states (Mn2+/3+/4+ and Co2+/3+), and these ions are mixed and distributed in the spinel structure. The effect of Mn doping on the inversion degree of spinel and electrochemical performance of materials is discussed. Compared with pure MgCo2O4 material, Mn-doped MgCo2O4 anode materials exhibit good cycle stability. When x = 0.5, MgMn0.5Co1.5O4 anode material has the highest cycle capacity with an initial discharge capacity of 1165.2 mAh g−1, and a capacity of 427.6 mAh g−1 after 100 cycles. Mn-doped MgCo2O4 can significantly improve the cycle stability of the material while maintaining a high specific capacity.