Mo2P2O11: A Potential Cathode Material for Rechargeable Sodium-Ion Batteries

Abstract

Due to the limiting lithium reserve and increasing price of lithium, alternatives to Li-ion batteries are growing rapidly. The world is now focusing on developing electrodes beyond Li-ion-based rechargeable batteries for portable electronics. Iron, nickel, and Co-based NASICON structured materials give stable capacity with reversible intercalation of almost one sodium in the host lattice. In the current work, we suggest a cathode material made of 3D framework-structured molybdenum polyanionic phosphate (Mo2P2O11) for a reversible sodium-ion battery. Mo2P2O11 was synthesized using the heat treatment of the MoO2HPO4·H2O precursor at 560 °C, having the morphology of stacked flakes. Characterization techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray were utilized for confirming the structure and morphology of the materials. For electrochemical performance, cyclic voltammetry, charge-discharge, and stability tests have been performed. Mo2P2O11 work through the active participation of the Mo6+/4+ redox couple with reversible intercalation of Na+ ions. The electrode exhibits reversible intercalation at 3.0 V versus Na and a steady capacity of ∼90 mA h/g, that is, ∼1.4 Na per formula unit, achieving a Coulombic efficiency of nearly 100%. The current finding opens up a new route for using transition-metal phosphates as efficient and stable charge storage cathode materials for sodium-ion batteries. © 2022 American Chemical Society.