Harvesting enhanced electrochemical performance of mixed structured nickel cobalt phosphate for energy storage application

Abstract

The synergistic effect of two metals with a mixed crystal structure of an electrode material can enhance the electrochemical performance of the electrochemical energy storage device. Herein, mixed metal (nickel and cobalt) phosphates are synthesized by the facile sonochemical method followed by calcination. X-ray diffraction (XRD) confirmed the successful synthesis of pure and mixed metal phosphates with crystalline and amorphous phases, supplemented by Fourier transform infrared spectroscopy (FTIR). The field emission scanning electron microscopy (FESEM) micrograph revealed the flake-like morphology of mixed metal phosphates with a rough surface, confirmed by transmission electron microscopy (TEM). The surface area of mixed metal phosphate was estimated by Brunauer-Emmett-Teller (BET). The electrochemical performance of the prepared materials through a three-electrode cell revealed that 75:25 (Ni:Co) possesses excellent electrochemical performance compared to its counterparts. An asymmetric device (supercapattery) is fabricated to investigate the performance Ni:Co 75:25 used as a positive electrode. The supercapattery gave energy and power density values of 33.6 Wh/kg and 730 W/kg at 1 A/g, respectively. The cyclic stability test reveals high capacity retention of 84.1 % after 4000 cycles. The excellent electrochemical performance is ascribed to the two different metal phosphates with mixed crystalline phases.