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 (V-In-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 V-In-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 V-In-Ti2InB2 as a Li-ion anode, unlocking a wealth of possibilities for sustainable electrochemical applications of h-MAB phases.