Effect of Chemistry and Structure on Voltage of Li Intercalation Oxides

Abstract

With the aid of today’s powerful computers, quantum mechanical methods are becoming accurate enough to determine the properties of materials before going into laborious and expensive synthesis processes. These “computer experiments” do not require any input other than the atomic numbers of the constituent species. In addition, they allow full control over the “experimental” parameters. In this way the effect of any parameter on the materials properties can be investigated, which is usually not possible in traditional experiments.

We used theab initio pseudopotential method to study the effects of chemistry and structure on the voltage obtained from intercalating Li ions into transition metal oxides. The effect of transition metal and anion chemistry was systematically studied by changing M in LiMO₂, (M=Ti, V, Mn, Co, Ni, Cu and Zn) and X in LiCoX₂ (X=Se, S and O), keeping the structure fixed at α-NaFeO₂ layered structure. In addition, the effect of structure was studied by performing computer experiments on LiCoO₂ and LiMnO₂ in α-NaFeO₂, LiScO₂ and Al₂MgO₄(spinel) structures.

The computed voltages are in good agreement with experimental values. We found that, the electronic band structure and the extent of charge transfer between Li and O ions is correlated to the output voltage. We will explain how the output voltage is affected by the chemistry of the transition metal.