Reduction of Manganese Dioxide by Dissolved Lithium in Liquid Ammonia for Li-Mn-O Spinels

Spinel-structured Li-Mn-O compounds are considered as alternative cathode materials for high-power lithium ion batteries, which are the ideal power source for the electric vehicles in the near future. However, synthesizing Li-Mn-O spinels with good cycle performance is a difficult task. In this work, the lithium-ammonia solution is used to perform the reduction of manganese dioxide (MnO2), which demonstrates a new reaction process for preparing Li-Mn-O spinels. The whole processes for the formation of Li-Mn-O spinels are proposed and the Li-1.12 Mn1.88O4 spinel, as an example, is easily achieved via a simple annealing process. Galvanostatic charge/discharge results indicate that the resulting Li1.12Mn1.88O4 spinel exhibits both of high capacity (similar to 105 mAhg(-1) at 1C) and good cycling stability (500 cycles), even at the elevated temperature (similar to 55 degrees C). The present reaction conditions are interesting, especially, for preparing Li-contained compounds, which can be extended for other cathode materials.