Entropy-Driven Highly Chaotic MXene-Based Heterostructures as an Efficient Sulfur Redox Electrocatalysts for Li-S Battery

Both the sluggish sulfur redox reaction (SRR) kinetics and lithium polysulfides (LiPSs) shuttle effect limit the practical application of Li-S batteries. Designing heterostructure sulfur hosts has emerged as an effective way to address these two issues with one material. However, the principles of heterostructures reinforced Li-S batteries remain inadequately understood. Here, it is demonstrated for the first time that increasing the entropy of heterostructure can promote its SRR catalytic activity and alleviate the LiPSs shuttling. By a simple solution-based strategy, a highly chaotic MXene-based heterostructure (HCMH, TiS₂/TiN/TiO₂/Ti₃C₂T_x) is fabricated. The smart integration of “high entropy”, heterostructure, and MXene endow the HCMH catalyst with significantly improved performance, demonstrated by a much smaller Tafel slope of 62.9 mV dec⁻¹ and a higher electron transfer number of 7.10, compared with the moderately chaotic MXene-based heterostructure (MCMH, TiO₂/TiN/Ti₃C₂T_x) and MXene. DFT theoretical calculations reveal that introducing new phases lowers the Gibbs energy barriers of both rate-limiting Li₂S₂/Li₂S reduction and Li₂S decomposition. Upon the addition of only 5 wt.% HCMH to the sulfur cathode, both the reversible capacity and rate capability of Li-S cells are greatly improved, which further highlights the importance of the high entropy “cocktail effect” in the design of SRR electrocatalysts in the future.