Oriented Assembly of Anisotropic Nanosheets into Ultrathin Flowerlike Superstructures for Energy Storage

The hierarchical ultrathin nanostructures are excellent electrode materials for supercapacitors because of their large surface area and their ability to promote ion and electron transport. Herein, we investigated nine l-amino acids (LAs) as inductive agents to synthesize a series of CoNi-OH/LAs materials for energy storage. With the different amino acids, the assembled CoNi-OH/LAs form a lamellar, flower-shaped, and bulk structure. Among all materials, the ultrathin flowerlike CoNi₂-OH/l-asparagine (CoNi₂-OH/l-Asn) exhibits an excellent specific capacity of 405.4 mAh g^-1 (2608 F g^-1) and a 100% retention rate after 3000 cycles. We also assembled asymmetrical supercapacitor CoNi₂-OH/l-Asn//N-rGO devices, which demonstrated an energy density of 64.9 Wh kg^-1 at 799.9 W kg^-1 and superlong cycling stability (82.4% at 10 A g^-1) over 5000 cycles.