Efficient Synergy\nof Sea Urchin-like Graded Structure\nSupercapacitor Electrodes by Modulating the Morphology of Layered\nDouble Hydroxide Composites

Rational design of the multidimensional structure of\nself-supporting\ncomposite electrode materials is an effective way to maintain the\nstructural stability of supercapacitors and the efficient energy storage\nperformance of ion and electron transport. Here, layered double hydroxide\n(LDH) composite electrodes (CoMn LDH@CoNi LDH/NF, CM@CN LDH) with\ngraded structure and unique sea urchin-like distribution are prepared\non nickel foam (NF) by the solvothermal method. The synergistic effect\nof the dual-LDH leads to increased layer spacing and provides more\nelectrochemically accessible surfaces together with short and effective\nion transport paths, which helps to accommodate a large number of\nactive sites to achieve a rapid Faraday oxidation–reduction\nreaction. The results show that the CM@CN LDH-S1 in the three-electrode\nsystem exhibits an excellent specific capacitance of 2381.3 F·g<sup>–1</sup> at a current density of 1 A·g<sup>–1</sup>. The assembled asymmetric supercapacitor device has a high specific\ncapacitance of 240.8 F·g<sup>–1</sup> at 1 A·g<sup>–1</sup>, a high energy density of 75.3 Wh·kg<sup>–1</sup>, and an excellent cycling performance (85.2% initial retention after\nmore than 5000 cycles at 5 A·g<sup>–1</sup>), indicating\nthat the graded nanostructure dual-LDH material has excellent application\npotential.