Dane Morgan

LI CONDUCTIVITY IN LIX MPO 4 ( M = MN , FE , CO , NI ) OLIVINE MATERIALS

Materials with the olivine structure form an important class of rechargeable battery cathodes. Using first-principles methods, activation barriers to Li ion motion are calculated and an estimate for Li diffusion constants, in the absence of electrical conductivity constraints, is made. Materials with Fe, Co, Ni are considered. Li diffuses through one-dimensional channels with high energy barriers to cross between the channels. Without electrical conductivity limitations the intrinsic Li diffusivity is high.

First-principles alloy theory in oxides

The physical mechanisms which may contribute to the energy and entropy of mixing in oxide systems are identified and discussed. Ionic size, magnetism and electrostatics can all contribute to the configurational energy dependence of transition-metal oxides. While the many sources of substitutional disorder make configurational entropy an essential contribution to the free energy of oxides, electronic and magnetic entropy may be of the same order of magnitude. This is illustrated with some first-principles results on LiCoO2 and LiMnO2.

Phase Separation Tendencies of Aluminum-Doped Transition-Metal Oxides (LiAl 1-x M x O 2 ) in the a-NaFeO 2 Crystal Structure

First-principles methods are used to calculate the miscibility of eight aluminum-doped transition-metal oxides in the layered α-NaFeO 2 structure. This study finds that for all Li(Al,M)O 2 compounds investigated (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu) the enthalpy of mixing is positive. In addition, detailed analyses were performed on LiAl 1- xCoxO2 and LiAl 1-x Cr x O 2 by calculating full temperature-composition phase diagrams. For the Li(Al,Co)O 2 system, we find regions of immiscibility below - 173°C and above 600°C. For both Li(Al,Co)O 2 and Li(Al,Cr)O 2 above 600°C, Al-doping is limited by the formation of γ-LiAlO 2 .

Phase separation tendencies of aluminum-doped transition-metal oxides (LiAl{sub 1{minus}x}M{sub x}O{sub 2}) in the {alpha}-NaFeO{sub 2} crystal structure

First-principles methods are used to calculate the miscibility of eight aluminum-doped transition-metal oxides in the layered α-NaFeO 2 structure. This study finds that for all Li(Al,M)O 2 compounds investigated (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu) the enthalpy of mixing is positive. In addition, detailed analyses were performed on LiAl 1- xCoxO2 and LiAl 1-x Cr x O 2 by calculating full temperature-composition phase diagrams. For the Li(Al,Co)O 2 system, we find regions of immiscibility below - 173°C and above 600°C. For both Li(Al,Co)O 2 and Li(Al,Cr)O 2 above 600°C, Al-doping is limited by the formation of γ-LiAlO 2 .