Li1.2(Mn0.32Ni0.32Fe0.16)O2 (LMNFO) nanoparticles with and without a chelating agent (adipic acid) were synthesized by sol–gel method. The supercapacitive behaviors of the synthesized materials as a cathode are evaluated with activated carbon (AC) as the anode in a hybrid supercapacitor (HSC) configuration utilizing a non-aqueous electrolyte. The structural, morphological and electrochemical features of the prepared materials are investigated using X-ray diffraction, scanning electron microscopy and cyclic voltammetry (CV) and charge–discharge studies, respectively. The results demonstrated that the LMNFO nanoparticles prepared with the chelating agent, adipic acid (AA), delivered an enhanced specific discharge capacitance (86Fg−1) and better cycling stability than the native compound. The CV studies also revealed the same conclusions, based on the stronger current response observed during various scan rates between 0 and 3V. Moreover, the AA-LMNFO/AC cell delivered maximum energy and power densities of 36Whkg−1 and 1.67Wkg−1, respectively, with a columbic efficiency of over 99% and excellent rate performance.