Doubling the capacity of lithium manganese oxide spinel by a flexible skinny graphitic layer.
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.
School of Energy and Chemical Engineering, UNIST, Ulsan, 689-798 (Korea). hknoh21@gmail.com.
Hyun Kuk
HK
Noh
Han-Saem
HS
Park
Hu Young
HY
Jeong
Sang Uck
SU
Lee
Hyun-Kon
HK
Song
ab initio calculations; graphitic layers; lithium manganese oxide; lithium-ion batteries; spinel