Doubling the Capacity of Lithium Manganese Oxide Spinel by a Flexible Skinny Graphitic Layer**

Abstract

By coating nanoparticular lithium manganese oxide (LMO) spinel with a few layers of graphitic basal planes, the capacity of the material reached up to 220mAhg(-1) at a cutoff voltage of 2.5V. The graphitic layers 1)provided a facile electron-transfer highway without hindering ion access and, more interestingly, 2)stabilized the structural distortion at the 3V region reaction. The gain was won by a simple method in which microsized LMO was ball-milled in the presence of graphite with high energy. Vibratory ball milling pulverized the LMO into the nanoscale, exfoliated graphite of less than 10layers and combined them together with an extremely intimate contact. Abinitio calculations show that the intrinsically very low electrical conductivity of the tetragonal phase of the LMO is responsible for the poor electrochemical performance in the 3V region and could be overcome by the graphitic skin strategy proposed.