Li-Ion Storage Performance of Carbon-Coated Mn–Al–O Composite Oxides

The composites of manganese oxide and alumina (Mn–Al–O) with varied Mn/Al molar ratios were fabricated by a simple coprecipitation method and subsequently sintered at different temperatures. Carbon-coated oxides were prepared at 550 °C using pyrrole as the carbon source. Compared with the carbon-coated MnO prepared under the same conditions, the carbon-coated Mn–Al–O exhibits greatly enhanced electrochemical performance which is associated with both the Mn/Al molar ratio and sintering temperature. The carbon-coated composites with a ratio of 2:1 sintered at 600 °C could deliver a stable reversible capacity of 450 mAh g^–1 after 100 cycles at a current density of 100 mA g^–1 and the capacities of 373, 309, 245, and 175 mAh g^–1 at the densities of 200, 400, 800, and 1600 mA g^–1, respectively. The enhanced cycling and rate performance is attributed to the improved Li-ion conductivity owing to the formation of LiAlO₂ and the smaller particle size of MnO due to the dispersion effect of Al₂O₃