Oxide Nanoclusters on Ti C MXenes to Deactivate Defects for Enhanced Lithium Ion Storage Performance.

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.