Sodium-ion batteries are sustainable alternatives to lithium-based systems. Among olivine-type cathodes, NaFePO4 (NFP) is often considered inferior to LiFePO4 (LFP) due to its metastability and sodium’s higher atomic weight. Here, we present a combined theoretical-experimental study to compare the electronic, structural, and electrochemical properties of NFP/C and LFP/C in sulfate-based aqueous electrolytes. LFP/C was synthesized via a hydrothermal route followed by carbon coating, while NFP/C w