The development and study of Na ion batteries are expanding. This study employs the hydrothermal technique to produce single-phase, well-crystallized, fluorine-added O3-type NaFe1-xMgxO2. Using XRD, FESEM, and HRTEM, the sample’s phase structure and morphological information were characterized. Initially, without adding fluorine the electrode suffers from poor stability at high voltage ranges and also during long-term cycling. So, fluorine was added to the structure and the electrochemical performance of the material was greatly increased. The electrochemical performance of O3-type positive electrode materials for rechargeable Na ion batteries is evaluated. The capacity of fluorine-added O3-type NaFe1-xMgxO2 is approximately 163 mAh g−1 (50 mA g−1). Adding fluorine to the host structure increases the stability of the electrode, leading to improved electrochemical performance during long-term cycling. The electrochemical results indicate that fluorine-added O3-type NaFe1-xMgxO2 cathode material for cost-effective and environmentally friendly sodium-ion batteries is promising. Fluorine-based electrodes will be a future for Na ion energy storage devices