Electro-polymerization method was adopted to synthesize the Gel electrolyte, because it doesn’t need any other catalysts for polymerization, and it can be used directly without any further purify. LiTFSI was chosen as the lithium salt for saturation, and DOL monomer as the solvent for electropolymerisation. Figure 1a-c are typical photographs of the electrolyte with different forms which corresponding the prepared steps. It can be seen that the saturation electrolyte (LiTFSI/DOL) kept the characteristics of the liquid with its low viscosity (Figure 1a). After electro-induced polymerisation for several hours, the viscosity of the as-prepared electrolyte increased significantly compared to that of the saturation electrolyte, but it could slowly flow down the bottle wall when inverted (Figure 1b). Further self-polymerisation of the as-prepared electrolyte for more than two weeks at room-temperature produced a transparent solid polymer electrolyte which was immobile upon inversion of its container (Figure 1c).
Figure 2 show the typical scanning electron microscopy images (SEM) of metallic lithium anodes after long cycling experiments in Li-S cells. From these images, both of lithium anode with TEGDME and PIS electrolyte had an obvious change compared with fresh lithium, but the PIS electrolyte shows much the lower damage level of metallic lithium anode compared with the TEGDME.
The morphology of metallic lithium anodes which demonstrates that the gel electrolyte system can effectively inhibit the polysulfide diffusion, thus it can be reducing the corrosion. And also the ultrahigh lithium salt concentration and high viscosity can suppress the formation of lithium dendrites, and decrease the solubility of lithium polysulfide due to the common ion effect.
[i] J. F. Qian, W. A. Henderson,W. Xu, P. Bhattacharya, M. Engelhard, O. Borodin and J. G. Zhang. Nature Communications, 2015, 6, 6362.