The polyanionic compound Na 2 MnSiO 4 is regarded as one of the promising cathode materials for Na ion batteries due to good specific capacity with its attractive prospect of utilization of two electrons in the redox processes. Therefore, in this study, we have performed the thermodynamic and electronic structure analysis of Na 2 MnSiO 4 using first-principles density functional theory calculations. The intermediate ground state configurations for Na 2 MnSiO 4 of Na deintercalation were found by using the cluster expansion method and are used to obtain the 0 K voltage profile as a function of Na concentration. This material shows an average voltage of 4.2 V, and the finite temperature analysis at 300 K using Monte Carlo simulations indicates that this material undergoes two-phase mixing when it desodiates beyond 1.5 Na/formula unit. The chemical bonding interactions between the constituents were analyzed with various bond analysis tools. The involvement of oxygen in the redox reaction apart from the transition metal is identified by using Bader charge analysis. Relevant Na diffusion pathways and their corresponding calculated energy barriers are compared with the those for partially Fe substituted Na 2 MnSiO 4 to understand the effect of Mn site substitution on the process of Na migration through this material.

The increasing relevance of energy storage technologies demands high-capacity cathode materials for Li-ion batteries. Recently, Li-rich defect anti-fluorite Li5FeO4 has emerged as a high-capacity cathode material exhibiting simultaneous anionic and...

In order to understand the role of W-site substitution on properties of cubic tungsten carbide (β-WC), we have investigated the structural, mechanical, and electronic properties of WXC 2 (X = Si,

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Li-rich materials with simultaneous anionic and cationic reductions are one among the most promising class of cathode materials for high−capacity Li-ion batteries. The recent studies on the Li-rich Li 5 FeO 4 with defect antifluorite-type structure show that Li 5 FeO 4 can generate high capacity by simultaneous reduction of Fe and O atoms without any obvious release of oxygen gas. But, the poor cyclability as well as electrical conductivity of Li 5 FeO 4 makes it a less attractive cathode for Li-ion batteries in practical applications. In the present study, we have substituted the Fe sites with Ti in different concentrations (Li 5 Fe 1−x Ti x O 4 with x = 0.125, 0.250, 0.375, 0.500, 0.625, 0.750, 0.875, 1.00) and investigated the structural, electronic and Li-diffusion properties using density functional theory calculations. The total energy calculations show that all the Ti substituted systems have negative enthalpy of formation and this implies that the Ti substituted materials are also stable. The analysis of the calculated density of states indicates that Ti substitution reduces the bandgap and thereby improves the electronic conductivity of these materials. Similarly, the analysis of Li migration in Ti substituted Li 5 FeO 4 shows lower barrier height compared to that in the parent compound indicating the possibility of fast diffusion of Li-ions by Ti substitution.