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.
Keywords: cobalt; electrochemistry; energy storage; nanostructures; transition metals.
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