Sodium ion batteries are considered as a cost effective and promising alternative to lithium-ion batteries for next generation large scale energy storage applications. However, the sluggish intercalation kinetics and poor stability plagues the efficient applications. Recently sodium rich cathode materials are emerging as a promising system to retain high specific energy with improved durability. Benefitting from the high Na ion mobility by sodium rich structure and reduced John-Teller active Mn site, improved stability have been examined. In this work, we developed a high performing Na rich cathode with Sodium Manganese Oxide (Na_xMn_1-xO₂) as a battery positive electrode. The stoichiometry of Na is varied from (X = 1.05-1.3) and corresponding structural and electrochemical performances are analysed. The highly favourable architecture as battery electrodes showed a high specific capacity of 161 mAh/g at 50 mA/g. To enhance its performance, the cathode materials were made disordered rocksalt by ball-milling and performance were evaluated. Also, it demonstrated an enhanced capability towards ion storage and same was demonstrated in full cell battery. A high energy retention at high power condition along with high stability have been achieved.