Synthesis, characterization and electrochemical performances of nanocrystalline FeVO4 as negative and LiCoPO4 as positive electrode for asymmetric supercapacitor

Iron vanadate, FeVO4 nanoparticles are synthesized by simple co-precipitation method and explored as the pseudocapacitor negative electrode for the first time. The structural analysis shows the highly crystalline nature and phase purity of the material. The morphological features of FeVO4 particles are polyhedral in shape and are in the range of 100–200 nm. The well defined lattice fringes corroborate the highly crystalline nature of FeVO4. The FeVO4 electrode exhibits a pronounced supercapacitive performance in 1 M KOH electrolyte than 1 M NaOH and 1 M LiOH electrolytes due to its smaller hydration sphere radii, increased mobility and ionic conductivity. The obtained higher specific capacitance of 972 F g−1 at 2 mV s−1 and 922 F g−1 at 2 mA cm−2, inferred that it could be utilized as a suitable negative electrode. On the other hand, LiCoPO4 is tested as the positive electrode (0 to 0.5 V) for the first time and delivers a specific capacitance of 320 F g−1 at 5 mV s−1. Finally, an asymmetric supercapacitor is fabricated using FeVO4 as negative and LiCoPO4 as positive electrodes. The device exhibits an excellent energy density of 21 Wh kg−1 with a power density of 1326 W kg−1 in the potential range between 0 to 1.6 V.