Effect of strontium doping on the electrochemical pseudocapacitance of Y 1- x Sr x MnO 3- δ 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 YMnO 3 i.e. Y 1- x Sr x MnO 3- δ 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 YMnO 3 (YSMO-50) provides an equivalent three-dimensional network and superior conductivity due to Mn 3+ -O 2- -Mn 4+ 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 (M 2+ O 2- + H 2 O + 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 Mn 2+ /Mn 3+ and Mn 3+ /Mn 4+ 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 (YMnO 3 ) may be an effective tool to enhance the pseudocapacitive performance of perovskite-based electrodes.