LaCoO ₃ /Carbon Nanotubes Composite Electrodes for Advanced Hybrid Capacitors

Developing efficient energy storage solutions with ABO3-type perovskite oxide materials has long been a significant challenge due to their moderate conductivity, which severely limits fast electron and ion transport, and this needs improvement. In this context, an electrode series with different weight percentages (0, 3, 6, and 9%) of carbon nanotubes (CNTs) was incorporated with LaCoO3 and designated as PLCO, LCO-I, LCO-II, and LCO-III using sol–gel autocombustion and solvothermal synthesis techniques. FESEM and HRTEM analyses show that incorporating CNTs forms a strongly coupled LCO–CNT interface in certain regions, increasing electrochemically active sites and enhancing ion transport. The best electrode material (LCO-III) among all others exhibited the highest capacity of 1530 C/g, along with energy and power densities of approximately 102.01 Wh/kg and 1200 W/kg at 5 A/g, as observed in galvanostatic charge–discharge testing, using a 3-electrode configuration. Electrochemical impedance spectroscopy showed a low charge-transfer resistance of 5.28 Ω and a high ionic conductivity of 0.68 S cm–1, with a transference number (t+) of 0.40. An asymmetrically developed hybrid configuration of LCO-III delivered the highest energy and power densities of approximately 156.28 Wh/kg and 18000 W/kg, respectively, and exhibited a durability of 98.02% after 10,000 GCD cycles. These notable electrochemical features of the LCO-III-based perovskite electrode material highlight its potential for future supercapacitor applications.