Effect of strontium doping on the electrochemical pseudocapacitance of Y_1-SrMnO_3- perovskites

Grid-scale bulk energy storage solutions are needed to utilize the full potential of renewable energy technologies. Pseudocapacitive electrochemical energy storage can play a vital role in developing efficient energy storage solutions. The use of perovskites as anion intercalation-type pseudocapacitor electrodes has received significant attention in recent years. In this study, Sr-doped YMnO₃i.e. Y_1-SrMnO_3- perovskite was prepared by the solid-state ceramic route and studied for electrochemical pseudocapacitance in aqueous KOH electrolyte. Microstructures, morphologies, and electrochemical properties of these materials were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance method. The formation of the mostly cubic phase, with 50% strontium doped YMnO₃ (YSMO-50) provides an equivalent three-dimensional network and superior conductivity due to Mn³⁺-O^2--Mn⁴⁺ hopping conduction. YSMO-50 exhibited low intrinsic resistance, 1.45 Ω cm^-2, and the highest specific capacity, 259.83 F g^-1 at a current density of 1 A g^-1 in 2 M KOH aqueous electrolyte. Redox-mediated interconversion of oxide to hydroxide (M²⁺O^2- + H₂O + e^- ↔ M⁺OH^- + OH^-) in aqueous media is shown to be the reason behind the high capacitance of YSMO-50. The excellent electrochemical performance of YSMOs was attributed to the reversible interconversion of oxide-ion into hydroxide ion coupled with surface redox reaction of Mn²⁺/Mn³⁺ and Mn³⁺/Mn⁴⁺ occurring during the charge-discharge process. The maximum energy density of 65.13 W h kg^-1 was achieved at a power density of 0.45 kW kg^-1 for an asymmetric mode, in which YSMO serves as a negative electrode and Activated carbon (AC) as a positive electrode in the PVA-KOH gel electrolyte. Our study reveals that the doping of low valence atom (Sr) at the A-site in perovskite manganites (YMnO₃) may be an effective tool to enhance the pseudocapacitive performance of perovskite-based electrodes.