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

Authors


  • This work was supported by MOTIE (Green: grant number 10042948 (KEIT)), MSIP (Mid: grant number 2013R1A2A2A04015706 (NRF), CRC: grant number 2013K000210) and MOE (BK21Plus: grant number 10Z20130011057), Korea. The authors thank for support from the Center for Computational Materials Science (Institute for Materials Research, Tohoku University; SR11000 supercomputing facilities).

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 220 mA h g−1 at a cutoff voltage of 2.5 V. The graphitic layers 1) provided a facile electron-transfer highway without hindering ion access and, more interestingly, 2) stabilized the structural distortion at the 3 V 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 10 layers and combined them together with an extremely intimate contact. Ab initio 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 3 V region and could be overcome by the graphitic skin strategy proposed.

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