Conductivity Enhancement of MgMxOy (M=Co, Ni) Oxide Cathodes for Mg Battery Applications

Wednesday, 8 October 2014
Expo Center, 1st Floor, Center and Right Foyers (Moon Palace Resort)
S. Y. Tsai (Dept. of Materials Science and Engineering, National Cheng Kung University, Taiwan), K. Z. Fung (Research Center for Energy Technology and Strategy, Dept. of Materials Science and Engineering, National Cheng Kung University, Taiwan, Research Center for Energy Technology and Strategy, National Cheng Kung University), and C. T. Ni (Dept. of Materials Science and Engineering, National Cheng Kung University)
Mg batteries have received a lot of interest due to its improved safety of handling, abundance and low cost of magnesium. Furthermore, Mg is more stable in air than Li and may provide capacity as high as 2200 mAh/g or 3830 mAh cm−3. Thus, Mg battery is known to have great potential for many practical applications and becomes one of post LIB technologies. Unfortunately, divalent Mg ions are expected to exhibit slow diffusion in Mg compounds. Thus, to find appropriate cathode materials for Mg battery has been difficult. Recently, MgCo2O4 Spinel Oxide and Mg0.67Ni1.33O2 were found to be potential high voltage (~3V) cathode for Mg batteries based on the work of Tetsu Ichitsubo’s group. The conductivity of MgCo2O4 is in the order of 10-1S/cm. On the other hand, the conductivity of Mg-doped NiO is much lower than that of MgCo2O4 spinel. The electronic conduction of semi-conducting oxides is highly dependent on the hole jumping in between those cations occupying the tetrahedral and/or octahedral sites of oxygen sublattice. Thus, the conductivity of these oxide cathodes may be enhanced by proper substitution of aliovalent cations. Therefore, the objective of this work is to enhance the electrical conductivity of Mg-containing transition metal oxides with either spinel or rock salt structure by the substitution of aliovalent cations with proper valence and ionic radius in the cation sublattice. After the electrical conductivity of cathode materials is improved, the electrochemical property such as capacity, charge/discharge cycles of Mg batteries is expected to be enhanced as well. The conductivity and crystal structure of prepared samples will be examined by using AC-impedance spectroscopy and XRD. The electrochemical properties including CV and cell testing will be conducted after cell assembly using the obtained cathode and Mg anode.