Sodium ion battery (SIB) technology is a promising technology for energy storage systems. Due to the abundance of sodium in nature and lower cost, it can be a viable alternative to the current Lithium ion battery (LIB) technology. In this research article P2-type layered sodium ion transition metal oxide Na0.7Ni0.3Mn0.59Co0.1Cu0.01O2 cathode material was synthesized using a citric acid assisted sol-gel method. It provided a very good reversible discharge capacity and better capacity retention than the state-of-the-art SIB. XRD pattern confirmed the successful insertion of copper ions in the lattice structure of Na-Ni-Co-Mn layered oxide. This material exhibited a high reversible capacity of 150 mAh/gm vs Na+ as the counter electrode when discharged through the voltage window of 4-1.5 V. The lesser polarization loss during cycling of the proposed cathode material helped to retain 94% of its maximum discharge capacity even after 80 cycles. (c) 2018 Elsevier Ltd. All rights reserved.