Series of Halogen Engineered Ni(OH)2 Nanosheet for Pseudocapacitive Energy Storage with High Energy Density

Abstract Ni(OH) 2 nanosheet, acting as a potential active material for supercapacitors, commonly suffers from sluggish reaction kinetics and low intrinsic conductivity, which results in suboptimal energy density and long cycle life. Herein, a convenient electrochemical halogen functionalization strategy is applied for the preparation of mono/bihalogen engineered Ni(OH) 2 electrode materials. The theoretical calculations and experimental results found that thanks to the extraordinarily high electronegativity, optimal reversibility, electronic conductivity, and reaction kinetics could be achieved through F functionalization . However, benefiting from the largest ionic radius, INi(OH) 2 contributes the best specific capacity and morphology transformation, which is a new finding that distinguishes it from previous reports in the literature. The exploration of the interaction effect of halogens (F, INi(OH) 2 , F, BrNi(OH) 2 , and Cl, INi(OH) 2 ) manifests that F, INi(OH) 2 delivers a higher specific capacity of 200.6 mAh g −1 and an excellent rate capability of 58.2% due to the weaker electrostatic repulsion, abundant defect structure, and large layer spacing. Moreover, the F, INi(OH) 2 //FeOOH@NrGO device achieves a high energy density of 97.4 Wh kg −1 and an extremely high power density of 32426.7 W kg −1 , as well as good cycling stability. This work develops a pioneering tactic for designing energy storage materials to meet various demands.