Tailoring the Perovskite Structure to Acquire an Inorganic La₂NiCrO₆ Double Perovskite as an Efficient Energy Storage Application by Varying Molar Concentrations of Citric Acid

Abstract

Owing to the high power density and long cycle stability, supercapacitors are promising energy storage devices instead of electrochemical batteries. In recent years, perovskite materials have received good attention in the research community for pseudocapacitive electrode material. Especially, these materials, having a high oxygen vacancy concentration, exhibit ultra-high capacitance due to oxygen-anion intercalations. In this study, La2NiCrO6 (LNC) double perovskites are successfully synthesized using the sol–gel method followed by the solid–state reaction at different concentrations of citric acid. The interconnected spherical granular-structured LNC is an efficient supercapacitor electrode material because of its stress-free octahedron lattice and inherent oxygen vacancies. In a three-electrode system, LNC@Ni-foam reveals a specific capacity of 529 C g–1 (147 mA h g–1) at a current density of 1 A g–1. To exhibit a real-time application, a device is fabricated with LNC@Ni-foam as a positive electrode and activated carbon (AC) AC@Ni-foam as a negative electrode. This asymmetric device can achieve the specific capacity of 227 C g–1 (63 mA h g–1) at a current density of 1 A g–1. The fabricated device exhibits an energy density of 49.17 W h kg–1 at a power density of 779.79 W kg–1. In addition, the as-fabricated device has a cycle stability of 97% even after 10,000 cycles at a current density of 10 A g–1. These superior electrochemical performances promise the application of this LNC electrode in pseudocapacitors.

Investigation of the Role of 3d-4d Elements in a Disordered Double Perovskite toward Efficient Photocatalytic Energy Conversion and Electrochemical Energy-Storage Behaviors

“…On the other hand, to obtain information about the long-term stability and durability of the present three composite electrodes, the GCD measurements were also carried out within the same potential window of 0 to 1.2 V at a controlled current density of 0.2 A/g in 0.5 M H 3 PO 4 and 0.5 M H 2 SO 4 electrolytes (Figure ). The nonlinear triangular shape of the GCD plots further confirms both EDLC and pseudocapacitance contributions of the present electrode materials and is well harmonized with their CV results. ,,− ,,,, The specific capacitance of the active composite materials can also be derived from the charge/discharge (GCD plots) experiments using eq ,,, : C sp = I 0.25em normald t / m 0.25em normald V where C sp is the specific capacitance based on the mass of electroactive materials (F/g), I is the response current (A), d V is the sweep potential window (V), m is the mass of the electroactive materials deposited on to the electrode surface (g), and d t is the discharge time (s).…”

“…The maximum specific capacitance value is 176.3 F/g at 25 mV/s. The reason is that metal oxides are poor conductors, and the addition of conductive carbon (∼9%) is not sufficient enough to get good conductivity; hence, the capacitance value is low. − ,− Importantly, all three present compounds exhibit better capacitance in 0.5 M H 3 PO 4 compared to 0.5 M H 2 SO 4 electrolyte. On the other hand, to obtain information about the long-term stability and durability of the present three composite electrodes, the GCD measurements were also carried out within the same potential window of 0 to 1.2 V at a controlled current density of 0.2 A/g in 0.5 M H 3 PO 4 and 0.5 M H 2 SO 4 electrolytes (Figure ).…”

“…In the specified potential window range (from 0 to 1.2 V) with sweep of scan rates, the peak current gradually shifted toward higher positive and negative potential areas of the present electrode materials as represented in Figure . It may be due to the internal diffusion along with polarization effect of the electrodes in both 0.5 M H 2 SO 4 and 0.5 M H 3 PO 4 electrolytes. ,,− ,,, Importantly, the quasi-rectangular shape of each CV curve is still well maintained even at a higher scan rate, indicating that the material possesses excellent rate capability and reversibility. ,,− ,,, …”

“…Further, a flat round shape redox peak signal is also associated with all of the present composite materials from their respective cyclic voltammogram plots in both electrolytes, confirming the major EDLC combined with pseudocapacitance behaviors present in the current composite compounds (Figure ). ,,− ,,,, Furthermore, the specific capacitance values of all three compounds were calculated from the CV curves using eq , ,,,, and the values are given in Table S4 (Supporting Information). C s = ∫ I 0.25em normald V 2 × v × normalΔ V × m where I (A) is the constant current, V is the applied voltage, v (mV/s) is the scan rate, and m represents mass loading of the active electrode material.…”

“…Over a couple of years, researchers have also paid much effort to design efficient and compact energy-storage devices with balanced power and energy densities. − Supercapacitors known as electrochemical capacitors, are the most favorable choice for energy-storage systems due to their very high power density, large capacitance, long cycle life, quick charge–discharge rates, and capabilities to bridge the gap between energy density and power density as compared to conventional batteries. − Particularly, supercapacitors can be classified as electrical double-layer capacitors (EDLCs) and pseudocapacitors depending upon the charge-storage mechanism. − In EDLCs, charge can be stored by simple ion intercalation, while pseudocapacitors can possess charge storage via reversible Faradic charge-transfer pathway. − Although several merits of progress have been made by researchers to develop the energy density of supercapacitors, among them utilization of metal oxide-based composites as electroactive materials as one of the suitable ingredients not only for achieving high energy and power densities but also for superior stability during long life cycles. − Most of the commercial supercapacitors available in the market are based on activated carbon (AC)/inorganic oxide-based electrodes that are separated by an ion permeable polymeric membrane. − ,− Despite various carbon allotropes (i.e., AC, carbon nanotube, etc.) that are being generally used for EDLC-based electrode materials, now-a-days covalent modification of reduced graphene oxide (rGO) and related composite materials has opened up extensive opportunities to tailor supercapacitor performances. − The higher intrinsic electronic conductivity, tunable surface area, and greater stability of rGO can exhibit unpredicted electrochemical performance in energy-storage devices. − …”