Defect Engineering of Hexagonal MAB Phase Ti2InB2 as Anode of Lithium‐Ion Battery with Excellent Cycling Stability

Hexagonal MAB phases （h‐MAB） have attracted attention due to their potential to exfoliate into MBenes, similar to MXenes, which are predicted to be promising for Li‐ion battery applications. However, the high cost of synthesizing MBenes poses challenges for their use in batteries. This study presents a novel approach where a simple ball‐milling treatment is employed to enhance the purity of the h‐MAB phase Ti2InB2 and introduce significant indium defects, resulting in improved conductivity and the creation of abundant active sites. The synthesized Ti2InB2 with indium defects (VIn‐Ti2InB2) exhibits excellent electrochemical properties, particularly exceptional long‐cycle stability at current densities of 5 A g−1 (5000 cycles, average capacity decay of 0.0018%) and 10 A g−1 (15 000 cycles, average capacity decay of 0.093%). The charge storage mechanism of VIn‐Ti2InB2, involving a dual redox reaction, is proposed, where defects promote the In‐Li alloy reaction and a redox reaction with Li in the TiB layer. Finally, a Li‐ion full cell demonstrates cycling stability at 0.5 A g−1 after 350 cycles. This work presents the first accessible and scalable application of VIn‐Ti2InB2 as a Li‐ion anode, unlocking a wealth of possibilities for sustainable electrochemical applications of h‐MAB phases. This work presents a simple and effective approach to introducing indium defects into the h‐MAB phase Ti2InB2, which exhibits exceptional long‐term cycling stability. This study highlights the novel functionality of h‐MAB phases in lithium‐ion batteries, shedding light on their potential applications in energy storage and beyond.