Na3CoZr(PO4)3 as high-voltage cathode material for sodium-ion batteries

Phosphate-based electrode materials are sustainable, abundant, low cost and exhibit stable structures. We report Na3ZrCo(PO4)3 cathode material synthetized through a sol-gel method, that shows high electrochemical per-formances. The electrochemical activity of Co3+/Co+2 redox couple is reversibly accessed in Na3ZrCo(PO4)3, providing thus high discharge voltage plateaus at 4.05 V. Furthermore, a discharge capacity of 85 mAh g-1 was measured, which is about 80% of the theoretical capacity (106 mAh g-1). These results were obtained with small variations of the lattice parameters and a small volume change of 3.8%, as was confirmed by Operando XRD. These results provide guidelines to improve the electrochemical performance of high-voltage Na3ZrCo(PO4)3 cathode materials for the next generation sodium-ion batteries.