Fig. 2. Thermogravimetric analysis of the GA–S hybrids in nitrogen with heating rate of 10 °C min−1.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 3. Low and high magnification SEM images of (a and b) GA–S-120, (c and d) GA–S-150 and (e and f) GA–S-180 hybrids. (g) Digital images of as-prepared GA–S hybrids. (h) The EDS spectrum (h6) and Cyclosporin A mapping of sulfur (h6) for GA–S hybrid.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 4. Raman spectra of GA–S hybrids with its characteristic D band (1335 cm−1) and G band (1580 cm−1) that are characteristic of graphene.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 5. TEM images of (a) GA–S-120, (b) GA–S-150 and (c) GA–S-180 hybrids. (d) HRTEM image of GA–S-180 hybrid.Figure optionsDownload full-size imageDownload as PowerPoint slide
The unique structure of the GA–S nanocomposite can improve the overall electrochemical performance when it is used as a cathode material for Li/S batteries. First, the small characteristic dimension of the sulfur particles generally means low volume expansion/contraction and reduction of pulverization during charge/discharge cycling. In addition, the partially reduced graphene with its large surface area along with ubiquitous cavities can establish more intimate electronic contact with S and avoid aggregation and loss of electrical contact with the current collector. Second, the low temperature hydrothermal-treated GA still contains various kinds of oxygen-containing functional groups. These functional groups have strong adsorbing ability to anchor S atoms and to effectively prevent the subsequently formed Li polysulfides from dissolving in the electrolyte, improving the utilization of active materials and suppressing shuttle effect .