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

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.