Altered crystal structure of nickel telluride by selenide doping and a poly(N-methylpyrrole) coating amplify supercapacitor performance

Nickel telluride doped with selenide (NiTe:Se) flakes show remarkably enhanced charge storage response compared to undoped NiTe. Se doping induces a morphological transformation from fibrillar NiTe to flaky NiTe:Se thereby endowing a two times higher surface roughness and an eight-fold increment in electrical conductivity to the latter, thus allowing facile charge transport and transfer across the material. Free charge carrier density available for conduction for NiTe:Se is also found to be double of that of NiTe. These beneficial effects combinedly translate into a capacity of 565 C g(-1) (equivalent to a specific capacitance (SC) of 943 F g(-1)) for the single NiTe:Se electrode, which is 1.5 times greater than the NiTe electrode. The homogeneity of Se dispersion in the NiTe matrix is confirmed by magnetic force microscopy, where the prominent magnetic domains observed to be uniformly distributed across the surface of NiTe are obliterated homogeneously after Se doping. Asymmetric supercapacitor with activated carbon (AC//NiTe:Se) delivers a 300 C g(-1) and this performance is bettered by coating a poly(N-methylpyrrole) (PMP) layer at the electrodes, where the polymer also contributes to charge storage and also assists in preserving the structural integrity of the active materials. The ensuing PMP@AC//PMP@NiTe:Se supercapacitor delivers a capacity of 404 C g(-1), E-max and P-max of 90 Wh kg(-1), and 400 W kg(-1), superior to the AC//NiTe:Se cell. Practical demonstration of the PMP@AC//PMP@NiTe:Se with a 3S (series), 4.5 V configuration, coupled with the ease of fabrication and scale-up open up avenues to develop this cell as a commercial product. (C) 2020 Elsevier Ltd. All rights reserved.