A two-dimensional assembly of ultrafine cobalt oxide nanocrystallites anchored on single-layer Ti3C2Tx nanosheets with enhanced lithium storage for Li-ion batteries
Recently, Ti-based MXenes were expected to compete with graphene and other carbonaceous materials towards Li-ion batteries (LIBs) due to their two-dimensional (2D) open structure, cost efficiency, superior conductivity and low Li+ diffusion barrier. However, the relatively moderate capacity and aggregation tendency hamper their practical applications in next-generation LIBs. Herein, we explore for the first time a scalable bottom-up approach to fabricate a series of Co3O4@single-layer Ti3C2Tx (s-Ti3C2Tx) hybrids, where numerous homogeneous Co3O4 nanocrystallites (NCs), serving both as a spacer and electroactive phase, are anchored uniformly on the surface of s-Ti3C2Tx nanosheets (NSs) through the Co–O–Ti interfacial bonds. Furthermore, detailed experimental analyses clearly shed light upon the formation mechanism of the hybrid Co3O4@s-Ti3C2Tx NSs. Thanks to the structural and compositional merits, the 2D Co3O4@s-Ti3C2Tx NSs even exhibit a remarkable high-rate capacity of ∼223 mA h g−1 at an ultra-high current density of 10 A g−1, and a long-span cycle life with a high reversible capacity of 550 mA h g−1 at 1 A g−1 after 700 consecutive cycles. Corresponding density functional theory calculation further confirms that the Co–O–Ti interfacial function leads to an even higher pseudocapacitive contribution and faster lithium storage behavior due to the enhanced interfacial electron transfer.