. Preparation process of NiCo₂S₄@ACF composite electrode material

2. SEM images of raw materials and composite electrode material
(a-b) Pretreatment ACF; (c) NiCo₂S₄ microspheres; (d) NiCo₂S₄@ACF precursor; (e-f) NiCo₂S₄@ACF

. XRD pattern of NiCo₂S₄@ACF composites

. (a) CV characteristics of NiCo₂S₄@ACF composite electrode materials at different scan rates, (b) GCD curves of NiCo₂S₄@ACF composite electrodes at various current densities, (c) specific capacitance and (d) Nyquist plots of NiCo₂S₄@ACF, NiCo₂S₄@ACF, NiS@ACF and CoS@ACF composite electrodes with inset in (d) showing magnified curves and equivalent circuit

. CV curves (a) of NiCo₂S₄@ACF electrode and ACF electrode at scan rate of 20 mV/s; and (b) ASC device in different voltage window at 20 mV/s and (c) ASC device in a voltage window of 0-1.6 V at different scan rates, (d) GCD curves and (e) specific capacitance of ASC device at various current densities, and (f) cycling performance of ASC device at current density of 7 A/g

. Ragon plots of the ASC device

Table 1. Energy densities and powder densities of different ASC in an aqueous system