Two-Dimensional Cobalt-/Nickel-Based Oxide Nanosheets for High-Performance Sodium and Lithium Storage

Two-dimensional (2D) nanomaterials are one of the most promising types of candidates for energy-storage applications due to confined thicknesses and high surface areas, which would play an essential role in enhanced reaction kinetics. Herein, a universal process that can be extended for scale up is developed to synthesise ultrathin cobalt-/nickel-based hydroxides and oxides. The sodium and lithium storage capabilities of Co₃ O₄ nanosheets are evaluated in detail. For sodium storage, the Co₃ O₄ nanosheets exhibit excellent rate capability (e.g., 179 mA h g^-1 at 7.0 A g^-1 and 150 mA h g^-1 at 10.0 A g^-1 ) and promising cycling performance (404 mA h g^-1 after 100 cycles at 0.1 A g^-1 ). Meanwhile, very impressive lithium storage performance is also achieved, which is maintained at 1029 mA h g^-1 after 100 cycles at 0.2 A g^-1 . NiO and NiCo₂ O₄ nanosheets are also successfully prepared through the same synthetic approach, and both deliver very encouraging lithium storage performances. In addition to rechargeable batteries, 2D cobalt-/nickel-based hydroxides and oxides are also anticipated to have great potential applications in supercapacitors, electrocatalysis and other energy-storage-/-conversion-related fields.