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  • Cerium oxide-sulfur nanohyb...
    Chauque, Susana; da Silva, Anderson G.M.; Batista, Ana P. de Lima; de Oliveira-Filho, Antonio G.S.; Braga, Adriano H.; Torresi, Roberto M.

    Electrochimica acta, 06/2021, Letnik: 382
    Journal Article

    •CeO2100-x-S8x nanohybrids are prepared by a simple and rapid synthetic approach.•The CeO270-S830 nanohybrid presents a capacity of 600 mA h g–1 over 160 cycles.•CeO270-S830 promotes fast redox reactions, making the shuttle effect negligible.•DFT results reveal strong interactions between the CeO2 surface and sulfur species. 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 CeO2100-x-S8x nanohybrids for anchoring lithium polysulfides (LiPSs) that are generated during cycling. The composition of CeO2100- x-S8x (x = 30, 50 and 70%) could be simply controlled by varying the CeO2/S8 mass ratio added in each reaction. Our results indicated that the CeO2100- x-S8x nanohybrids displayed a crystalline structure composed of both phases (CeO2 and S8), indicating an efficient impregnation process of S8 on the CeO2 nanowire surface. The surface area of CeO2 nanowires decreased as the amount of S8 was increased, and the CeO270-S830 nanohybrid maintained a uniform distribution of S8 over the entire CeO2 nanowires. Remarkably, the CeO270-S830 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 S8, Li2S4, and Li4S8 were –3.95, –5.84 and –7.31 eV, respectively, suggesting that the CeO270-S830 nanohybrid provided an appropriate surface to anchor LiPS by electrostatic interactions, leading to faster redox kinetics in Li-sulfur battery applications. Display omitted