Lithium storage performance and mechanism of nano-sized Ti₂InC MAX phase

Fine powders of MAX phases (a family of layered carbides/nitrides) have been showing great promise in energy storage applications. A feasible method of obtaining nano-sized MAX phase particles is critical to realizing the practical application of the vast MAX phase family in more technologically important fields. Herein, ball milling, a commercial and feasible method, is employed to prepare nano-sized Ti₂InC, which delivers a high specific capacity of 590 mA h g^-1 after 500 cycles and maintains 574.4 mA h g^-1 after 600 cycles at 0.1 A g^-1 when used as a lithium storage anode. Compared with other methods (e.g., partial etching), decreasing the size of Ti₂InC particles by ball milling can preserve the exfoliated indium (In) atoms, which have great volumetric and gravimetric capacities. In situ XRD analysis indicates that the capacity of the nano-sized Ti₂InC primarily comes from the lithiation of elemental In exfoliated from Ti₂InC, and in particular, the exfoliated In atoms by ball milling can increase the initial capacity. The lithiation/delithiation cycle can effectively activate and even exfoliate the Ti₂InC grains, which accounts for the increasing capacity upon cycling.