Sono-chemical assisted synthesis of carbon nanotubes-nickel phosphate nanocomposites with excellent energy density and cyclic stability for supercapattery applications

Abstract

Nickel phosphate (NiP) was synthesized by sono-chemical synthesis followed by calcination at 400 °C for 5 h. Synthesized NiP was blended with various concentrations (10, 30 and 50 wt%) of multiwalled carbon nanotubes (MWCNTs) to prepare the nanocomposites that were then characterized in terms of microstructure, morphology, composition, and electrochemical performance. Microscopic analysis showed the presence of uniformly distributed MWCNTs in NiP matrix in case of nanocomposites containing 50 wt% MWCNTS (NiP50CNT50) resulting in its better electrochemical performance than the other compositions. X-ray diffraction and Fourier transformed infra-red spectroscopic analysis also confirmed the synthesis of MWCNTs/NiP nanocomposites by showing that the characteristics peaks becoming broader and intense due to incorporation of CNTs. The electrochemical analysis of all the prepared nanocomposites presented that NiP50CNT50 has demonstrated the better specific capacity of 845 Cg−1 at 0.6 Ag−1. This composition also presented better asymmetric supercapacitor (ASC) device performance with specific capacity of 400 Cg−1 at 0.4 Ag−1, excellent energy density of 94.4 Wh kg−1 (at 340 W kg−1 power density) that decreases to 24.82 Wh kg−1 (at 10,200 W kg−1) which might be attributed to its higher surface area (32.4 m2/g) and adsorbed gas volume (168 cm3 g−1). ASC device showed a capacity retention of 95.5 % at 12 Ag−1 after 5000 charge/discharge cycles.