Enhanced Electrochemical Kinetics with Highly Dispersed Conductive and Electrocatalytic Mediators for Lithium-Sulfur Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 33987896.
- Also identified by DOI 10.1002/adma.202100810.
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Abstract
Lithium-sulfur (Li-S) batteries are promising energy-storage devices because of their high theoretical energy densities. However, the practical application of Li-S batteries is still impeded by the poor cycling performance and rate capability at practical conditions. In order to improve the performance of practical Li-S batteries, a hierarchical Mo<sub>2</sub> C nanocluster/carbon nanosheets hybrid based hollow spherical material (Mo<sub>2</sub> C/CHS) is designed and prepared. The hollow spheres composed of stacked carbon nanosheets can facilitate the infiltration of electrolyte. The ultrasmall and highly conductive Mo<sub>2</sub> C nanocrystals are confined in the carbon nanosheets and expose more active sites for anchoring and conversion of lithium polysulfides and increase the number of the nuclei for Li<sub>2</sub> S<sub>2</sub> /Li<sub>2</sub> S precipitation. Benefitting from the synergistic effects, Mo<sub>2</sub> C/CHS greatly promotes electrochemical kinetics in Li-S batteries with high sulfur loading (5 mg cm<sup>-2</sup> ). Even under lean electrolyte conditions (E/S = 7 μL mg<sub>sulfur</sub> <sup>-1</sup> ), the Li-S batteries with Mo<sub>2</sub> C/CHS added exhibit a discharge capacity of 904 mAh g<sup>-1</sup> at the high current rate of 0.5 C, and with 894 mAh g<sup>-1</sup> maintained after 200 cycles. This work provides a fundamental understanding of the electrochemical processes and guides the rational design of host and additive materials for practical Li-S batteries.