A two-dimensional assembly of ultrafine cobalt oxide nanocrystallites anchored on single-layer Ti3C2Tx nanosheets with enhanced lithium storage for Li-ion batteries

Abstract

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 Ti₃C₂T_x (s-Ti₃C₂T_x) hybrids, where numerous homogeneous Co₃O₄ nanocrystallites (NCs), serving both as a spacer and electroactive phase, are anchored uniformly on the surface of s-Ti₃C₂T_x 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-Ti₃C₂T_x NSs. Thanks to the structural and compositional merits, the 2D Co₃O₄@s-Ti₃C₂T_x 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.