Exploration of the Effect of Transition Metal on the Divergence of Orthorhombic Sodium Orthophosphate (NaXPO4) via the Polyol Process

Crystallization of olivine and maricite structures in polyanionic groups flourishing with splendid electrochemical performance is tedious, and the preparation of these materials involves ion exchange reaction. To mitigate these challenges, sodium orthophosphate (NaXPO4) is synthesized by a direct conventional polyol process in one step by vacillating the transition metals (X = manganese and iron) to analyze its behavior. Formulation of this material with different transition metals results in the crystallization of two different structures. Rietveld refinement endorses the configuration of maricite and olivine structures by employing manganese and iron precursors, respectively. The existence of the strong manganese–oxygen (Mn–O) bond appearing in maricite and phosphate–oxygen (P–O) in olivine signifies thermodynamic stability and electrochemical performance, respectively. Computational molecular structural dynamics validates the electrochemical reaction and the reduction in the conversion energy drift in the olivine system. The cyclic voltammetry behavior substantiates the disproportionation with poor faradaic reaction of maricite and the intrinsic kinetic faradaic redox reaction of olivine leading to better electrochemical performance. Subsequently, galvanostatic charge/discharge studies facilitate capacities of 102.6 and 120.7 mAh g–1 for maricite and olivine structures, respectively.