SYNTHESIS AND ELECTROCHEMICAL PERFORMANCES OF Γ-KCOPO4 NANOCRYSTALS AS PROMISING ELECTRODE FOR AQUEOUS SUPERCAPATTERIES

Abstract

Herein, discrete γ-KCoPO4 nanocrystals were prepared by a facile, green and fast sol-gel route. The lattice parameters as well as positional and displacement parameters of atoms in the average γ-KCoPO4 structure with a space group of P21/n were calculated using full profile Rietveld refinement. Monodispersed quadrangular γ-KCoPO4 nanocrystals with improved phase purity and crystallinity were found through XRD patterns and HRTEM images. Subsequently, the prepared γ-KCoPO4 nanocrystals were tested as electrode material for supercapatteries in aqueous electrolytes. The γ-KCoPO4 electrode shows superior specific charge capacity of 309 C g−1 at 1 mV s−1 in 1 M KOH, compared to 1 M NaOH (222 C g−1) and 1 M LiOH (77 C g−1). Further, it exhibits improved electrochemical activity by delivering an impressive specific charge capacity of 100 C g−1 at a current of 0.6 mA cm−2 in an aqueous electrolyte medium with acceptable capacity retention. A lab-scale supercapattery was assembled resembling the commercial device. The fabricated device delivered an enhanced specific energy of 28 W h kg−1 and a specific power of 1600 W kg−1 and prolonged cycle life of about 5000 cycles.