Hui Xiaobin, Zhao Danyang, Wang Peng, Di Haoxiang, Ge Xiaoli, Zhang Peng, Yin Longwei
Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, School of Materials Science and Engineering, Shandong University, Jinan, 250061, P. R. China.
Small. 2022 Feb;18(5):e2104439. doi: 10.1002/smll.202104439. Epub 2021 Nov 23.
The commercialization of MXenes as anodes for lithium-ion batteries is largely impeded by low initial coulombic efficiency (ICE) and unfavorable cycling stability, which are closely associated with defects such as Ti vacancies (V ) in Ti C MXenes. Herein, an effective strategy is developed to deactivate V defects by in situ growing Al O nanoclusters on MXenes to alleviate the irreversible electrolyte decomposition and Li dendrites formation trend induced by defects, improving ICE and cycling stability. Furthermore, it is revealed that excessively lithiophilic V defects would impede Li ions diffusion due to their strong adsorption, leading to a locally nonuniform Li flux to these "hot spots," setting scene for the formation of Li dendrites. The Al O nanoclusters anchored on V sites can not only improve Li diffusion kinetics but also promote the homogeneous solid electrolyte interphase formation with small charge transfer resistance, achieving uniform Li deposition in a smaller overpotential without formation of Li dendrites. As expected, Ti C @Al O -11 electrode delivers a high ICE of 76.6% and an outstanding specific capacity of 285.5 mAh g after 500 cycles, which is much higher than that of pristine Ti C sample. This work sheds light on modulating defects for high-performance energy storage materials.
MXenes作为锂离子电池负极的商业化在很大程度上受到低初始库仑效率（ICE）和不良循环稳定性的阻碍，这与Ti₃C₂ MXenes中的Ti空位（V）等缺陷密切相关。在此，开发了一种有效的策略，通过在MXenes上原位生长Al₂O₃纳米团簇来钝化V缺陷，以减轻由缺陷引起的不可逆电解质分解和锂枝晶形成趋势，提高ICE和循环稳定性。此外，研究表明，过度亲锂的V缺陷由于其强烈吸附会阻碍锂离子扩散，导致局部锂离子通量向这些“热点”不均匀，为锂枝晶的形成创造了条件。锚定在V位点上的Al₂O₃纳米团簇不仅可以改善锂扩散动力学，还可以促进具有小电荷转移电阻的均匀固体电解质界面形成，在较小的过电位下实现均匀的锂沉积而不形成锂枝晶。正如预期的那样，Ti₃C₂@Al₂O₃-11电极在500次循环后具有76.6%的高ICE和285.5 mAh g的出色比容量，远高于原始Ti₃C₂样品。这项工作为高性能储能材料的缺陷调控提供了思路。
