Enhancing Reaction Kinetics of Sulfur-Containing Species in Li-S Batteries by Quantum Dot-Level Tin Oxide Hydroxide Catalysts

The application of Li-S batteries is hampered by some unresolved issues, including the severe polysulfides shuttle effects and sluggish reaction kinetics. Hence, we designed and prepared tin oxide hydroxide quantum dots (TOH) anchored on a honeycomb porous carbon (HPC) matrix as multifunctional sulfur hosts, and deeply studied the enhancement of TOH on the reaction kinetics of Li-S battery referred to as the apparent activation energy, Li+ ion diffusion coefficient, and reaction barrier. It is proved by density functional theory that the HPC@TOH hosts have a higher binding energy to polysulfides than the simplex carbon matrix. Meanwhile, the catalytic TOH can decrease the surface active energy of the redox reaction and accelerate the conversion of sulfur-containing species. Consequently, by means of the synergistic effects of physical capture and chemical adsorption together with catalytic conversion, the comprehensive performances of Li-S batteries are distinctly promoted. In particular, a Li-S battery using HPC@TOH as a host delivers a good reversible specific capacity of 1342.95 mAh g–1 at 0.1 C. Moreover, with the current increased to 1 C, it shows a relatively satisfactory specific capacity of 918.05 mAh g–1. After 400 cycles, a competitive specific capacity of 688.54 mAh g–1 can still be maintained with a very low fading rate of 0.06% per cycle. Most importantly, when the sulfur areal loading reaches as high as 4.25 mg cm–2 and electrolyte/sulfur ratio is controlled to be as low as 7 μL mg–1, and the Li-S battery using HPC @TOH as a host can still cycle steadily more than 50 cycles at 0.2 C. Therefore, this work provides an effective manner to boost the comprehensive performance of Li-S batteries by virtue of optimizing and designing the host material with synergistic effects of physical capture, chemical adsorption, and catalytic conversion.