Effect of Ti modification on Structural, Electronic and Electrochemical properties of Li2FeSiO4-A DFT study using FPLAPW approach

We report the effect of Ti modification on structural, electronic and electrochemical properties of Li+ ion battery cathode material Li2FeSiO4. A density functional theory (DFT) study based on full potential linearized augmented plane wave (FPLAPW) approach has been performed on Li2FeSiO4 of Pmn21 polymorphic phase. Simulation of geometric, electronic structure and electrochemical characteristics of Li2FeSiO4 are performed prior to Ti modification. Ti doping is done by replacing either 50% Fe or 50% Si in Li2FeSiO4 with Ti. The optimized Ti-doped geometric structures are used to evaluate electronic structure and electrochemical properties in terms of density of states (DOS), and Li de-intercalation voltage. Effect of de-intercalation on structural stability, density of states and hence band-gaps are also analyzed. Feasibility of de-lithiation of more than one Li+ ion per formula unit of Li2FeSiO4 of Pmn21 polymorphic phase without and with Ti modification is estimated using FPLAPW approach. It is observed that, Ti doping by replacing 50% Fe would be suitable for more than one (1.5 Li ion) Li+ ion de-intercalation from Pmn21 polymorphic phase of Li2Fe0.5Ti0.5SiO4.