Fig. 1

(a) Schematic diagram of the synthesis of coal-based graphene oxide (GO); (b) Scanning electron microscope (SEM) diagram of coal; (c) Schematic diagram of lithium-sulfur batteries cathode material synthesis; (d) Physical picture of coal-based GO and schematic diagram of slurry synthesis route"

Fig. 2

(a)—(c) Scanning electron microscope (SEM) images of coal-based graphene oxide (GO) with corresponding sizes of 1 μm, 5 μm, and 20 μm, respectively; (d) Transmission electron microscopy (TEM) image of coal-based graphene oxide (GO); (e) Magnification high-power transmission electron microscope (HRTEM) images at (d) marks; (f) X-ray diffraction (XRD) diagram of coal-based GO; (g) Raman spectra of coal-based graphene (G) and coal-based graphene oxide (GO); (h) and (i) are nitrogen adsorption/desorption ratio surface (BET) and pore size profiles of coal-based GO, respectively"

Fig. 3

Electrochemical performance test of lithium sulfur batteries: (a) CV curves of lithium-sulfur batteries at GO@S and G@S cathodes at 0.1 mV/s scan rate; (b) and (c) CV curves of lithium-sulfur batteries with cathodes containing GO@S and G@S under different voltage windows. The insets are Tafel curves corresponding to (b) peaks 1 and (c) peaks 2; (d) Comparison of charge and discharge curves of lithium-sulfur batteries with GO@S and G@S cathodes at 0.1 C; (e) and (f) EIS curves of lithium-sulfur batteries with cathodes containing GO@S and G@S before and after cycling, respectively"

Fig. 4

(a) and (b) are the CV curves of G@S and GO@S lithium-sulfur batteries at different scan rates (0.1—0.5 mV/s), respectively; (c) Anodic oxidation process (peak 1); (d) The first cathodic reduction process (peak 2); (e) The second cathodic reduction process (peak 3), the relationship between CV peak current and the square root of scanning rate"

Fig. 5

(a) Schematic diagram of Lithium-sulfur batteries structure; (b) Performance comparison of lithium-sulfur batteries with cathodes containing GO@S and G@S at different magnifications from 0.1 C to 3 C; (c) Comparison of cycle performance of lithium-sulfur batteries with cathodes containing GO@S and G@S at 0.2 C; (d) and (f) The cathode contains lithium sulfur electricity GO@S and G@S comparison of charging and discharging curves of the cell at different rates of 0.1—3 C; (e) The lithium-sulfur batteries containing GO@S and G@S were compared 500 times at a rate of 3 C; (g) The lithium-sulfur batteries with cathodes containing GO@S and G@S were compared 1000 times at a rate of 0.5 C"