Enhanced Electrochemical Performance of LaNiO ₃ Through Mn and Co‐Doping for High‐Energy‐Density Next‐Generation Supercapacitors

Perovskite oxides are regarded as attractive electrode materials for use in supercapacitors. Here, we present the sol–gel synthesis of Mn‐Co co‐doped LaNiO 3 , formulated as LaMn x Co y Ni 1‐(x + y) O 3, with compositions (0, 0), (0.02, 0.08), and (0.08, 0.02). In this work, LaMn x Co y Ni 1‐(x + y) O 3 electrodes were fabricated on nickel foam via a simple drop‐casting method for efficient and highly stable supercapacitor applications. XRD confirmed the hexagonal crystal structure in all three samples, while XPS spectroscopy confirmed the presence of La 3+ species, and the transition metals exhibit mixed valence states, including Ni 2+ /Ni 3+ , Mn 3+ /Mn 4+ , and Co 2+ /Co 3+ . Electrochemical measurements in 6 M KOH reveal that increasing the cobalt content enhances specific capacitance, LaMn 0.02 Co 0.08 Ni 0.9 O 3 delivering the best electrochemical performance. The optimized electrode exhibited an exceptional specific capacitance of 1085 F/g at 0.5 A/g. An asymmetric device assembled with LaMn 0.02 Co 0.08 Ni 0.9 O 3 //AC delivered an energy density of 24.78 Wh/kg. These results demonstrate that Mn‐Co co‐doping is an effective and cost‐efficient technique for optimizing charge‐storage properties in LaNiO 3 ‐based perovskite oxides, positioning LaMn 0.02 Co 0.08 Ni 0.9 O 3 as a strong candidate for supercapacitors.