CoNi‐Layered Double Hydroxides Electrodes with Hierarchical Structure and Dual‐Ion Doping for High‐Performance Asymmetric Supercapacitors

The agglomeration caused by high loading and the blockage of electrolyte ion transport are the main bottleneck problems that limit the application of layered double hydroxide (LDH) materials. Here, a hierarchically structured CuO@CoNi‐LDH composite is constructed on a copper foam (CF) scaffold, with alkali/halogen dual‐ion codoping employed to synergistically enhance its electrochemical performance. The CF/CuO core provides a conductive backbone for high‐loading LDH, while Li + optimizes the electronic structure. The Br − ion with multiple effects can reduce the OH − adsorption energy and strengthen the covalent characteristics of Co/Ni‐O in the LDH, thereby improving reaction activity. The hierarchical architecture combined with the ionic size effect facilitates charge transport and ion diffusion, enabling the LDH (Li,Br) electrode to deliver a high areal capacitance of 45.9 F cm −2 at 5 mA cm −2 and still retain 56% of its initial capacitance after 14 000 cycles under a high mass loading of 16 mg cm −2 . An asymmetric supercapacitor using CF/CuO@CoNi‐LDH(LiBr)//AC exhibits excellent performance (1.87 F cm −2 at 5 mA cm −2 , 55.6% retention at 30 mA cm −2 ), stable cycling (89.15% after 6400 cycles), and high energy density (0.67 mWh cm −2 ), highlighting the practical potential of dual‐ion doping and hierarchical design.