Carboxyl functionalized carbon incorporation of stacked ultrathin NiO nanosheets: topological construction and superior lithium storage.

Two-dimensional (2D) nanostructure engineering and surface modification with functional groups are of great importance to anode materials for rechargeable lithium-ion batteries. Herein, stacked NiO nanosheets@carbon (denoted as NiO@C) and 3 nm-ultrathin NiO nanosheets@functionalized carbon with surface functional groups NO3-, CO32-, OH-, and COOH- (denoted as NiO@FC) were prepared via a facile one-pot reaction and topotactic conversion. Specifically, NiO@FC exhibits excellent lithium storage performance: the capacity of NiO@FC is 489.2 mA h g-1, higher than that of NiO@C (1018.7 mA h g-1 at 0.2 A g-1), and maintains a capacity of 1133 mA h g-1 after 800 cycles, which exceed that of all previously reported NiO anodes. The enhanced lithium storage performance is attributed to the sufficient void space, which offers buffer space for volume change and speeds up the diffusion of Li+ ions. In addition, the surface functional groups were proved to not only hinder the agglomeration of nanosheets but also further donate active sites and improve storage capacity. These advantageous features achieved by designing such a stacked structure with functionalized carbon modification provide a promising strategy for the preparation of high-performance anode materials and other 2D functional materials.