Pristine Ni-Sn layered-double-hydroxide and NiO/SnO₂ hierarchical nanocomposites as high-performance electrode materials for supercapacitor applications

Abstract

Cost effective and complication-free wet chemical co precipitation protocal was employed to prepar Ni-Sn-layered double hydroxide and NiO/SnO₂ nanocomposites. Fundamental characterizations were done to evaluate structural, optical, morphological and dielectric behaviours. Cubic and tetragonal structures were witnessed for NiO and SnO₂ via XRD analysis respectively. Allowed direct band gap nature was revealed from the optical absorption study and the calculated bandgap values were 3.29, 3.39, 3.09 and 3.20 eV for NiO. SnO₂, NiO/SnO₂, and Ni-Sn-LDH respectively. Surface features, stacked layered nanosheet arrangements and textural properties of the high-performance electrode materials were witnessed from SEM and HRTEM analyses. The composite materials, NiO/SnO₂ and Ni-Sn-LDH nanosheet, demonstrate an enhanced capacitance per unit area and superior capacitance retainable nature with numerical values of 821 F/g for 5mV/s scanning for NiO/SnO₂ sample. For 1 A per gram electric current density NiO/SnO₂ exhibited a capacitance of 99.2 % retentively beyond 300 consecutive cycles. High surface area and large active site densities of this electrode material enabled it to exhibit such performance with respect to charge storage, enhanced charge/discharge rates and long-term stability. The Ni-Sn-LDH electrode exhibited 315 F/g of capacitance per unit area at 5 mV/s scan rate. Appreciable retentive capacitance (98.01 %) and one ampere per gram beyond 300 cycles was shown by Ni-Sn LDH. Morphological dependent (granular structured layers) carbon-free stain less steel electrode supercapacitance properties were revealed from the present work.