<p>Spinel LiCuFe₂O₄ was synthesized by a co-precipitation method and investigated as a cathode material for aqueous rechargeable lithium-ion batteries. Powder X-ray diffraction confirmed that the synthesized product was predominantly composed of the cubic spinel LiCuFe₂O₄ phase. Scanning electron microscopy revealed aggregated microcrystalline particles, while SEM–EDX analysis qualitatively verified the presence of Fe, Cu, and O in the annealed sample. The electrochemical properties of LiCuFe₂O₄ were studied in saturated Li₂SO₄ aqueous electrolyte using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy in a three-electrode configuration. The cyclic voltammograms exhibited a well-defined Fe²⁺/Fe³⁺ redox couple, and the linear dependence of peak current on the square root of scan rate indicated that lithium storage is predominantly diffusion-controlled. In half-cell measurements, the LiCuFe₂O₄ electrode delivered an initial discharge capacity of 136 mAh g⁻¹ and retained 121 mAh g⁻¹ after 200 cycles at a current density of 0.005&#xa0;mA/cm2, demonstrating stable lithium-storage behavior in aqueous electrolyte. A full cell assembled with LiCuFe₂O₄ as the cathode and carbon black as the anode also showed stable cycling with good coulombic efficiency over extended operation. Impedance analysis revealed a relatively low charge-transfer resistance together with a distinct Warburg-type diffusion response, indicating favorable Li⁺ transport at the electrode–electrolyte interface. These results suggest that co-precipitation-derived spinel LiCuFe₂O₄ is a promising cathode material for safe aqueous rechargeable lithium-ion batteries.</p>