Engineering Oxygen-Terminated Hexagonal MBene for Accelerated Lithium Migration and Exceptional Lithium-Ion Battery...

Ultrathin 2D hexagonal transition metal borides (h-MBenes) hold significant promise for advancing energy storage technologies. Herein, with cost-effective methods and earth-abundant metals, the experimental feasibility of atomically thin Ti-based 2D h-MBenes (TiBT_x) for lithium-ion battery application is reported for the first time. These thin-layer nanosheets are synthesized by using ZnCl₂ molten salt as Ti₂InB₂ etchant, followed with a delaminated intercalation of tetrabutylammonium hydroxide (denoted as d-TiBT_x). The formation of disorderly low-boiling-point Zn-In intermediate phase is revealed to significantly reduce the In migration energy barrier and accelerate the lattice-In release from parent Ti₂InB₂ under low-temperature. Moreover, in-depth analyses reveal that the formation of O-termination on the atomic d-TiBT_x surface endows d-TiBT_x h-MBene with exceptional lithium-ion migration, achieving an impressive specific capacity of 530 mAh g^-1 at 0.1 A g^-1 and an exceptional rate capability of 120 mAh g^-1 at 10 A g^-1. Notably, a lithium full-cell paired with a LiFePO₄ cathode achieves an impressive energy density of 425 Wh kg^-1 and retains 94.3% of its capacity after 100 cycles, sufficient to power a toy car under normal operation. This work confirms the usefulness of ultrathin Ti-based 2D MBenes, paving the way for innovatively harnessing the potential application of h-MBenes.