Layered CoS@NC in situ loaded onto Ti₃C₂T MXene as an efficient lithium-ion battery anode

Due to its large capacity and relatively high conductivity, cobalt sulfide has been considered an excellent electrode material for lithium-ion batteries, but its extreme volume change during charging and discharging and lower conductivity than graphite limits its development. In this work, composite nanosheets of MXene and N-doped carbon-confined cobalt sulfide nanosheets (CoS@NC/MXene) were synthesized by growing the Co metal-organic framework of ZIF-67 onto MXene sheets, followed by sulfidation treatment. Different from normal ZIF-67 generally prepared in methanol, this work fabricates ZIF-67 in aqueous solution, which induces ZIF-67 to undergo some degree of hydrolysis and form more dispersed Co layered hydroxides mounted onto MXene. Also, the MXene incorporation imparts better water stability to ZIF-67(Co) and helps maintain its morphology during the sulfidation. CoS@NC/MXene has a conductive network supported by MXene and enhanced by NC, as well as a 3D hierarchical porous structure offered by the rational combination of its components. These favorable characteristics allow CoS@NC/MXene to deliver a capacity of 691 mA h g^-1 at 200 mA g^-1 in the 100^th cycle and retain the specific capacity of 382 mA h g^-1 at a higher current density of 8000 mA g^-1.