RCoO3 {R=Pr, Nd and Sm} electrode-based for efficient solid-state symmetric supercapacitor

Tunable electrical conductivity and energy storage ability have been achieved by controllable rare earth substitution at the A-site in hydrothermally synthesized single perovskite oxides. Controlling the electrochemical performance of these electro-active materials has been attractive for futuristic energy storage devices. Crystallographic analysis confirmed a distorted orthorhombic Pnma structure for PrCoO3 (PCO), NdCoO3 (NCO) and SmCoO3 (SCO). The morphology of the materials showed significant changes in size, texture and porosity; with shape morphology varied from rectangular shaped crystallites in SCO and NCO to spherical shaped crystallites in PCO. The comparison of room temperature electrical conductivity shows good correlation with the structural features. A gradual decrease in the activation energies, obtained from the small polaron hopping (SPH) model, was observed as a function of the increasing ionic radii (Pr3+>Nd3+>Sm3+). The electrochemical properties are systematically investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectra (EIS) analysis. The charge storage mechanism in PCO, NCO and SCO is clearly demonstrated to be a diffusion controlled process. An effective correlation is drawn between the electrical and electrochemical parameters and their inherent structural disorder. PCO based materials show superior electrochemistry with a specific capacitance of ∼557 F/g at 1 A/g and ∼88% capacity retention even after 10,000 charging and discharging cycles. Based on its superior 3-electrode performance, a solid-state symmetric supercapacitor (SSC–P) was fabricated using PCO-based electrodes. It shows an energy and power densities of ∼40 W-h/Kg and ∼5574 W/kg respectively retaining 81% stability even after 5000 operational cycles. Finally, our fabricated solid-state symmetric supercapacitor (SSC–P) illuminated a LED for 3 min after 1 min charging, which shows its applicative potential for optimal smart energy storage device applications.