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• A facile method of directly converting electroplating sludge into nickel-based energy storage composites. • The unique embedded multilevel nanostructure improves the effective reaction of active substances with electrolyte. • Fe-Al co-doped α-Ni(OH) 2 and Ni(HCO 3) 2 composites show high specific capacitance and good cycling stability. The recovery of heavy metals from electroplating sludge is an important technology, which can not only reduce environmental pollution, but also serve as a secondary source of metals. However, the current techniques are either non-selective or difficult to operate, which limits its applications in recovery technologies. Herein, based on the existence of multiple metal ions in electroplating sludge, Fe and Al co-doped ultrathin α-Ni(OH) 2 nanosheets embedded in Ni(HCO 3) 2 nanowire assembly spheres were prepared by adjusting the ratio of urea under hydrothermal condition. Under the optimum conditions, the recovery of Ni, Fe, and Al are 92.58%, 81.52%, and 61.19% respectively. In addition, at the current density of 1 A g−1, the specific capacitance of the spherical composite electrode is as high as 495.6 C g−1, and the retention rate of the initial capacity is 55.58% after 3500 cycles in 6 M KOH electrolyte, showing good cycling stability. Furthermore, the ASC device (NN-4//AC) achieved a high energy density of 30.27 Wh kg−1 at a power density of 0.37 kW kg−1. A new method for converting electroplating sludge into nickel-based energy storage materials was developed, which provided a new strategy and idea for the harmless and resourceful treatment of electroplating sludge. [ABSTRACT FROM AUTHOR]