Wang Yatong, Shen Jiale, Xu Li-Chun, Yang Zhi, Li Rong, Liu Ruiping, Li Xiuyan
College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan, 030024, China.
Phys Chem Chem Phys. 2019 Aug 28;21(34):18559-18568. doi: 10.1039/c9cp03419f.
The development of lithium-sulfur (Li-S) batteries is hindered by capacity loss due to lithium polysulfide (LIPS) dissolution into electrolyte solutions (known as the "shuttle effect"). MXenes with excellent electrical conductivity, high mechanical strength and multiple possible active two-dimensional surface terminations are attracting much attention as anchoring materials of Li-S batteries. Here, the S-functionalized V2C (V2CS2) is designed and demonstrated to have not only dynamic and thermal stability, but also metallic character. Compared with bare V2C and V2CO2, V2CS2 exhibits a moderate adsorption effect to suppress the "shuttle effect" and can preserve the structure of LIPSs without any decomposition. Moreover, the metallic properties of V2CS2 are maintained after LIPSs are adsorbed, which can promote the electrochemical activity during the charge and discharge process. The low energy barriers of Li2S decomposition and Li diffusion on the V2CS2 surface promise the phase transformation of LIPSs and assist the electrochemical process. Based on these remarkable results, we can conclude that V2CS2 is a promising anchoring material for lithium-sulfur batteries. Our work may also inspire the exploration of other MXenes and new surface functionalization methods to improve the performance of MXenes as host materials for high performance Li-S batteries.
锂硫（Li-S）电池的发展受到多硫化锂（LIPS）溶解到电解质溶液中导致的容量损失（即“穿梭效应”）的阻碍。具有优异导电性、高机械强度和多种可能的活性二维表面终端的MXenes作为Li-S电池的锚定材料正受到广泛关注。在此，设计并证明了S功能化的V2C（V2CS2）不仅具有动态和热稳定性，还具有金属特性。与裸V2C和V2CO2相比，V2CS2表现出适度的吸附作用以抑制“穿梭效应”，并且能够保持LIPS的结构而不发生任何分解。此外，在吸附LIPS后，V2CS2的金属特性得以保持，这可以促进充放电过程中的电化学活性。Li2S在V2CS2表面分解和Li扩散的低能垒保证了LIPS的相变并辅助电化学过程。基于这些显著结果，我们可以得出结论，V2CS2是一种有前途的锂硫电池锚定材料。我们的工作也可能激发对其他MXenes和新的表面功能化方法的探索，以提高MXenes作为高性能Li-S电池主体材料的性能。
