First Principles Calculations of Novel Binary Transition Metal Oxides NaCr0.5X0.5O2 (X = Y, Tc, Rh) for Na-Ion Batteries

Recently, layered transition metal oxides have demonstrated voltage windows favorable for use as cathodes in sodium-ion batteries, leading to increased specific capacity and energy density. Here, NaCr 0.5 Y 0.5 O 2 , NaCr 0.5 Tc 0.5 O 2 , and NaCr 0.5 Rh 0.5 O 2 were studied by using first-principles calculations to elucidate their properties. There is a trigonal arrangement in the structure of both pure and substituted NaCrO 2 . Structural characteristics reveal the ferromagnetic behavior of these compounds (NaCr 0.5 X 0.5 O 2 ; X = Y, Tc, Rh). We calculated the density of states and spin-polarized electronic band structures for the three compounds tested. NaCr 0.5 Y 0.5 O 2 and NaCr 0.5 Rh 0.5 O 2 exhibit diluted magnetic semiconductor (DMS) behavior, while NaCr 0.5 Tc 0.5 O 2 has half-metallic (HM) behavior. The substitutional material’s ferromagnetic nature is confirmed by the negative values of the exchange constants (N օ α and N օ β ). The fractional value of the magnetic moment also confirms the DMS nature of NaCr 0.5 Y 0.5 O 2 and NaCr 0.5 Rh 0.5 O 2 , while the HM behavior is confirmed by the integral value of the magnetic moment for NaCr 0.5 Tc 0.5 O 2 . The thermoelectric characteristics were computed using the BoltzTraP code. Alectrochemical analysis of NaCr 0.5 Y 0.5 O 2 showed a theoretical discharge capacity of 400 mhAg −1 and an average intercalation voltage of 4.87 V, calculated from the total energies of the optimized compounds and their de-sodianted phases. These theoretical computations demonstrate that the binary layered TM oxides studied are appropriate substances to employ in coin cell fabrication as cathodes.