# Thiokol with Excellent Restriction on the Shuttle Effect in Lithium-Sulfur Batteries
## 3 Results and Discussion  
The CV curves of the Li-S battery with the Thiokol and PVDF binder at a scan rate of 0.1 mV/s are shown in Figure 1a,b, respectively. Both curves show three distinct peaks at similar positions including two reduction peaks and one oxidation peak. One slight oxidation shoulder appears near the main oxidation peak for the battery with the Thiokol binder. According to the previous studies, the reduction peak around 2.3 V could be assigned to the transition of element sulfur to the long-chain polysulfides (Li\({}_{2}\)S\({}_{x}\), 4 \(\leq x\leq\) 8), while the reduction peak around 2.0 V be attributed to the further conversion into the short-chain polysulfides such as Li\({}_{2}\)S\({}_{2}\) and/or Li\({}_{2}\)S [20; 21; 22; 23]. Conversely, the main oxidation peak in the lower potential represents the conversion of Li\({}_{2}\)S and/or Li\({}_{2}\)S\({}_{2}\) to long-chain polysulfides and the shoulder at higher potential represents the further oxidation to elemental sulfur [24]. In addition, a small reduction peak between 1.7 and 1.5 V can be seen if carefully checked, which might originate from the lithiation of Thiokol. Comparison of the three cycles shows that the cyclic voltammograms almost coincided with each other, indicating a high electrochemical reversibility of the battery with the Thiokol binder. Figure 1: The first three cycles of the battery with the Thiokol binder and first cycle of the battery with the polyvinylidene fluoride (PVDF) binder at a sweep rate of 0.1 mV/s. Figure 2a compares the discharge capacity of the Li-S batteries with the binders of Thiokol and PVDF, respectively. It could be seen from Figure 2a that the battery with the Thiokol binder delivered an initial discharge capacity of 819 mAh/g at 0.1 C while the battery with PVDF binder only delivered an initial value of 578 mAh/g. In addition, the discharge capacity of the Thiokol binder remained 501 mAh/g after 200 cycles, indicating a capacity retention rate of 61.1%; while the discharge capacity of the PVDF binder dropped to 166 mAh/g, with a capacity retention rate of only 28.7%. That is to say, compared to the battery with conventional PVDF binder, the initial discharge capacity for the battery with the Thiokol binder were increased by 42%--that is from 578 to 819 mAh/g--while the capacity after 200 cycles were increased by 201%--which is from 166 to 501 mAh/g. This suggested that the Thiokol binder improved not only the initial discharge capacity but also the capacity retention rate, compared to PVDF. Besides, the coulombic efficiency of the two kinds of batteries remain at a high level, indicating high utilization of active materials. The cycling performance of the battery with the Thiokol binder at 0.5 C is shown in Figure 2b. With an initial discharge capacity of 751 mAh/g, the capacity slowly dropped to 597 mAh/g after 100 cycles, indicating a capacity retention of 79.5%. The coulombic efficiency also kept as high as 96.4%. The result is encouraging since it suggested the Thiokol binder in this work could maintain the structural stability of the sulfur cathode during the long charge-discharge cycles. That is to say, it would not collapse, even as the charge and discharge occurs rapidly due to the increase of current density, consequently leading to a long cycle life of the Li-S battery at high current density. Figure 2c presents the rate performance of the Li-S batteries with the Thiokol and PVDF binder.