Horizontal oscillation processed large MXene with Low Ti–Ti coordination for fast sodium storage

MXene stands out as a rising family of transition metal carbides/nitrides with exceptional size-dependent properties and versatile potential applications. However, the realization of large MXene with a controllable surface at atomic level remains challenging to keep the balance among the conductivity, stability and activity. Herein, the horizontal oscillation-induced delamination (HOD) strategy is proposed to acquire Ti₃C₂ flakes with large size and low Ti–Ti coordination (HO-Ti₃C₂). The average size of the as-obtained flakes can reach 6.48 µm to keep the overall conductive skeleton and merits from large size. Simultaneously, metal atoms at surface can be partially removed due to the enhanced local vibrational turbulence during the reciprocating horizontal oscillation process. Such MXenes with clear and unique surface states exhibit high potentials in ion adsorption together with satisfied electric conductivity and stability. As proof of concept, HO-Ti₃C₂ anode exhibits remarkable rate capability and long-term stability during sodium storage. A capacity of 100.5 mAh g⁻¹ with a long-life cycle (4,500 cycles) at a high rate of 1.0 A g⁻¹ originates from the increased s-d interaction between Na and Ti. Therefore, the HOD strategy provides a controllable surface design to promote the clear criteria into size-dependent research on MXene.