Oxide Nanoclusters on Ti3C2 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-Ti) in Ti3C2 MXenes. Herein, an effective strategy is developed to deactivate V-Ti defects by in situ growing Al2O3 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-Ti 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 Al2O3 nanoclusters anchored on V-Ti 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, Ti3C2@Al2O3-11 electrode delivers a high ICE of 76.6% and an outstanding specific capacity of 285.5 mAh g(-1) after 500 cycles, which is much higher than that of pristine Ti3C2 sample. This work sheds light on modulating defects for high-performance energy storage materials.