Electrochemical properties of binder-free micro-blocks/sheets-based cadmium‑nickel-sulfide electrode materials for portable energy storage applications

The major goal of community is to synthesis the novel electrode materials for new energy storage sources to reduce the environmental pollution and to overcome the energy crises in developing countries. Herein, the authors synthesized a binder-free micro-blocks/sheets-based nickel sulfide, cadmium-sulfide‑nickel-sulfide (Ni-S, Cd-S-Ni-S) electrode materials (EMs) on nickel foam by home-made chemical vapor deposition technique. The XRD patterns reveals the development of polycrystalline Ni-S, Cd-S-Ni-S phases. The average crystallite size of Ni-S and Cd-Ni-S EMs are found to be ⁓32 to ⁓45 nm respectively. The microstructure of Ni-S is changed from cluster-of-nanoparticles/micro-blocks to nanosheets when a layer of Cd-S is condensed on Ni-S EMs. The EDX analysis confirms the presence of various wt% of Ni, Cd and S in Ni-S, Cd-S-Ni-S EMs. The molar ratios of Ni and S are found to be 1.46 and 0.46 in the synthesized Ni-S EMs. The molar ratios of Ni, Cd and S are found to be 0.459, 0.439 and 0.702 in the synthesized Cd-S-Ni-S EMs. The maximum values of specific capacitance, energy density and power density of Ni-S and Cd-S-Ni-S EMs are found to be 3305, 4086 F/g at 1 mV/s 25 Wh/kg and 1399 W/kg respectively. The capacitive contribution of Cd-S-Ni-S EMs is higher than Ni-S EMs, however, it is increased with increasing scan rates. The excellent capacity retention (75–92 %), good cyclic stability, impedance analysis show that the synthesized Ni-S, Cd-S-Ni-S EMs are suitable for energy storage devices like supercapacitor and batteries.