Electrochemical performance of cauliflower like binder-free magnesium-sulphide-electrodes for supercapacitor application

Abstract

Herein, magnesium sulphide (MgS) electrode material (EM) is deposited on nickel-foam (NF) placed at 16 and 17 cm away from the raw material by simple powder vapour transport method. The increasing source to substrate distance (SSD) not only changed the structural parameters but also changed the nanofibers to cauliflowers like surface morphology. The cauliflowers like MgS/NF EM exhibited high specific capacitance (6339 F/g) as compared to the specific capacitance (1677 F/g) of nanofibers like MgS/NF EM. The cauliflowers like EM is showed high energy density of 220–99 Wh/kg, power density of 250–2500 W/kg, equivalent series resistance of 0.95 O and capacitance-stability of 93 % even for 10,000 cycles. The increasing SSD is fruitful for the increment in diffusion rate as confirmed by shifting of electrochemical impedance spectrum to y-axis, Dunn’s model and power law simulations. The diffusive contribution is 88/82 % at 5 mV/s which become 63/50 % at 100 mV/s for the cauliflower/nanofibers like EM. Moreover, the cauliflowers like EM have both battery and capacitive nature as 0.5 < b < 1 predicted by power law simulations. Additionally, the configured asymmetric supercapacitive (ASC) device is presented the specific capacitance of 834 F/g, energy density of 354–247 Wh/kg and power density of 2625–26250 W/kg. The ASC device could maintain the Coulombic-efficiency of 99 % and capacitance stability of 93 % even for 10,000 cycles. The excellent pseudocapacitive behaviour of MgS/NF EM enables them to use in the lithium ion battery and supercapacitor devices.