A Robust Route to Co₂(OH)₂CO₃ Ultrathin Nanosheets with Superior Lithium Storage Capability Templated by Aspartic Acid-Functionalized Graphene Oxide

Two-dimensional (2D) nanomaterials are widely recognized as an important class of functional materials possessing superior electrochemical reaction kinetics. Herein, an L-aspartic acid (AA)-modified graphene oxide (GO) templating strategy is developed to in situ yield ultrathin (i.e., ≈5 nm) cobalt carbonate hydroxide (Co₂(OH)₂CO₃) nanosheets as advanced anode materials of lithium ion batteries. Notably, the covalent tethering of AA on the GO surface renders a high density of carboxyl groups that impart effective loading of Co-containing precursors and subsequent growth into Co₂(OH)₂CO₃ nanosheets bridging adjacent GO layers. The lasagna-like Co₂(OH)₂CO₃-GO nanocomposites exhibit an ultrahigh lithium storage capacity of 1770 mAh g⁻¹ after 500 cycles at 100 mA g⁻¹. It is noteworthy that the cycled Co₂(OH)₂CO₃ phase separates into homogeneously dispersed Co(OH)₂ and CoCO₃ phases with two different charge plateaus at ≈1.2 and 2.0 V, respectively, which effectively inhibit large-scale homophase coarsening of Co, Li₂CO₃, and LiOH. The much shortened Li⁺/e⁻ transfer distance enabled by individual ultrathin Co₂(OH)₂CO₃ nanosheet together with robust layer-by-layer assembled nanostructure of Co₂(OH)₂CO₃-GO confers the superior electrochemical reactivity and mechanical stability. As such, the amino acid-modified GO templating strategy may represent a simple yet robust means of crafting a variety of 2D nanostructured composites of interest for energy storage applications.