Thermal lithiation of manganese dioxide: effect of low lithium concentration (x ≤ 0.3 in Li xMnO 2) on structure and electrochemical performance

The effect of lithium concentration on LixMnO2 (x ≤ 0.3) materials prepared by co-precipitation/heating is investigated. Lithium concentration determines the phase formed, with three different phases identified in the concentration range. Low levels of lithiation (x = 0.08) leads to the formation of a γ/β type MnO2 material. As the lithium concentration is increased to x = 0.15, a lithiated γ−MnO2 like phase is formed. Finally, at x = 0.28 tunnel structured monoclinic MnO2 is obtained. Increasing the concentration of lithium inhibits the formation of the undesired inactive Mn2O3 phase, which is formed upon heat-treatment of MnO2. At a 5 mA/g charge/discharge rate the monoclinic Li0.28MnO2 material gave the best performance, while at 30 mA/g the Li0.08MnO2 material proved superior.