Cerium oxide-sulfur nanohybrids: Combining the robust adsorption of polysulfides with enhanced redox kinetics to improve the energy Storage capabilities of Li-S batteries

An in-depth investigation of the physical and chemical parameters that affect Li-sulfur batteries is imperative to optimize their performances. Here, we report promising [CeO2](100-x)-[S-8](x) nanohybrids for anchoring lithium polysulfides (LiPSs) that are generated during cycling. The composition of [CeO2](100-x)-[S-8](x) (x = 30, 50 and 70%) could be simply controlled by varying the CeO2/S-8 mass ratio added in each reaction. Our results indicated that the [CeO2](100-x)-[S-8](x) nanohybrids displayed a crystalline structure composed of both phases (CeO2 and S-8), indicating an efficient impregnation process of S-8 on the CeO2 nanowire surface. The surface area of CeO2 nanowires decreased as the amount of S-8 was increased, and the [CeO2](70)-[S-8](30) nanohybrid maintained a uniform distribution of S-8 over the entire CeO2 nanowires. Remarkably, the [CeO2](70)-[S-8](30) nanohybrid showed the best Li-storage performance, leading to specific capacities of approximately 600 mA h g(-1) over 160 cycles and a Coulombic efficiency of approximately 100%. Moreover, this sample showed excellent rate capability performance (even discharging at 10 A g(-1)). Additionally, the chemical interaction of CeO2 with LiPS was demonstrated by a visual experiment through the addition of pure CeO2 in a solution of Li2S6. The solution containing CeO2 nanowires became completely colorless after 30 min. To further investigate these improvements, density functional theory (DFT) calculations revealed the formation of strong interactions between the CeO2 nanowire surface and different sulfur species. For instance, the adsorption energies between the CeO2 nanowires and S-8,Li2S4, and Li4S8 were -3.95, -5.84 and -7.31 eV, respectively, suggesting that the [CeO2](70)-[S-8](30) nanohybrid provided an appropriate surface to anchor LiPS by electrostatic interactions, leading to faster redox kinetics in Li-sulfur battery applications. (C) 2021 Elsevier Ltd. All rights reserved.