Pseudocapacitive contributions to enhanced electrochemical energy storage in hybrid perovskite-nickel oxide nanoparticles composites electrodes

Composite materials of metal halide hybrid perovskites (MBI and MPI) and nickel oxide (NiO) nanoparticles, synthesized by a wet chemical route, were used to fabricate a supercapacitor by solution process spin coating technique. Films of the nanocomposite materials were characterized with different techniques to study their morphology, crystal nature, surface analysis and elemental composition. Charge storage due to surface faradaic and diffusion-controlled proton intercalation processes were distinguished, both qualitatively and quantitatively, by analyzing the cyclic voltammetric (CV) sweep data. With addition of the perovskites, pseudocapacitive contributions become increasingly important and lead to greater amounts of total stored charge. The electrochemical performance of the pristine NiO, MBI@NiO and MPI@NiO based devices were investigated as well as the two composite electrodes and exhibit specific capacitances of 407 Fg⁻¹ and 368 Fg⁻¹, respectively, at 10 mVs⁻¹, with corresponding energy densities of 56.5 Whkg⁻¹ and 51.1 Whkg⁻¹. The devices also show capacitance retention efficiencies of more than 90% after 3000 CV cycles. The device were further investigated by electrochemical impedance spectroscopy and the results are in agreement with CV analysis. Besides the charge storage, the stability benefits derived from decorating perovskites with metal oxide provide an interesting direction for the design of materials that offer both high energy density and power density.