A Polyanion Host as a Prospective High Voltage Cathode Material for Sodium Ion Batteries

It is essential to develop efficient electrode materials for sodium in batteries, which are currently being considered as a promising alternative to lithium-ion batteries. In this work, we are presenting NaMnBO3 nanoparticles with conductive carbon matrix (C-NMB) synthesized by urea-assisted hydrothermal method used as a potential cathode material in sodium ion batteries. The C-NMB electrode delivered discharge capacities of 116 mAh g−1, 97 mAh g−1, and 52 mAh g−1 at 0.2 C, 0.5 C, and 2 C rates, respectively and exhibited excellent cyclic behavior at all current densities. Further, the C-NMB electrode demonstrated the best electrochemical stability among other polyanion cathodes, with a capacity fade of 0.06% per cycle at 2 C after 250 cycles with more than 99% coulombic efficiency. X-ray photoelectron spectroscopy revealed that the reduction in oxygen containing surface functionalities (carboxyl groups) further increased the electrical conductivity of the NMB materials. The ex-situ XRD studies after first initial charge and discharge steps reveals that the hexagonal C-NMB electrode displays a topotactic sodium storage mechanism. These outcomes will contribute to the progress of developing low cost, eco-friendly electrode materials for sodium-ion batteries.