Urchin-Like Ni_1/3Co_2/3(CO₃)_1/2(OH)·0.11H₂O for Ultrahigh-Rate Electrochemical Supercapacitors: Structural Evolution from Solid to Hollow

Abstract

Portable electronics and electric or hybrid electric vehicles are developing in the trend of fast charge and long electric mileage, which ask us to design a novel electrode with sufficient electronic and ionic transport channels at the same time. Herein, we fabricate a uniform hollow-urchin-like Ni_1/3Co_2/3(CO₃)_1/2(OH)·0.11H₂O electrode material through an easy self-generated and resacrificial template method. The one-dimensional chain-like crystal structure unit containing the metallic bonding and the intercalated OH^- and H₂O endow this electrode material with abundant electronic and ionic transport channels. The hollow-urchin-like structure built by nanorods contributes to the large electrode-electrolyte contact area ensuring the supply of ions at high current. CNTs are employed to transport electrons between electrode material and current collector. The as-assembled NC-CNT-2//AC supercapacitor device exhibits a high specific capacitance of 108.3 F g^-1 at 20 A g^-1, a capacitance retention ratio of 96.2% from 0.2 to 20 A g^-1, and long cycle life. Comprehensive investigations unambiguously highlight that the unique hollow-urchin-like Ni_1/3Co_2/3(CO₃)_1/2(OH)·0.11H₂O electrode material would be the right candidate for advanced next-generation supercapacitors.