Figure 1.Schematic of the role of DCBQ in Li-S redox reactions. (a) Photographs showing the formation of solid organosulfur polymer after adding Li2S6 in the electrolyte with DCBQ. (b) Illustration of the nucleophilic substitution reactions between polysulfides and DCBQ. (c) The molecular structure of the S-DCBQ organosulfur polymer. (d, e) Schematics of sulfur reduction process (d) without and (e) with DCBQ.
Figure 2. Verification of the nucleophilic substitution reactions between polysulfides and DCBQ. C 1s XPS spectra of (a) DCBQ and (b) S-DCBQ organosulfur polymer. ATR-FTIR spectra of (c) DCBQ and (d) S-DCBQ organosulfur polymer.
Figure 3. Demonstration of the effect of DCBQ on the Li-S redox kinetics. (a) The relationships between the cathodic peak current Ip at the lower potential and square root of scan rate (mV/s)1/2 of the cells with and without DCBQ based on CV curves recorded at different scan rates. (b) The adsorption configuration of Li2S4 and DCBQ. (c) Potential energy diagram during the Li2S4 reduction process.
电化学性能测试表明，加入DCBQ后，电池极化降低，活性物质利用率提升，循环稳定性增加，尤其在高倍率下的性能提升明显，放电比容量为622 mAh g-1，是不加添加剂电池比容量的3.5倍。
Figure 4. Electrochemical properties of the Li-S cells with and without DCBQ. (a, b) Charge/discharge curves at different rates. (c) Voltage polarizations at different cycle rates (calculations of polarization were calculated as indicated in Figures 4a and 4b). (d) Rate capabilities. (e, f) Charge/discharge curves at different number of cycles at 1 C rate. (g) Discharge capacities during the lower discharge plateau. (h) Cycling performance and Coulombic efficiency at 1 C rate.
Figure 5. Investigations of the polysulfide-blocking effect enabled by the DCBQ.SEM images and corresponding EDS elemental maps of the sulfur cathode at a discharge voltage of 2.1 V. Cyan is for C, and yellow is for S. (a-c) with DCBQ, (d-f) without DCBQ. (g) UV-Vis absorption spectra of dimethoxyethane (DME) solution soaking the sulfur cathodes at discharge voltage of 2.1 V with and without DCBQ. Inset shows the corresponding photograph.