Self-reconstruction strategy to synthesis of Ni/Co-OOH nanoflowers decorated with N, S co-doped carbon for high-performance energy storage

•A facile activation strategy realizes the phase and structural self-reconstruction of transition metal materials.•The in-situ self-formed Ni/Co-OOH/NSCF has abundant pores and defective sites for faradaic reactions.•The device delivers a high energy density of 94.3 Wh kg−1 and power density of 18 kW kg−1.•This general method opens a new avenue for the structure regulating of electrode materials for energy storage. Well-designed structures with sufficient electroactive sites are vital for pseudocapacitive materials to yield high performances. Herein, we propose a facile electrochemical activation strategy to synthesize Ni/Co oxyhydroxides nanoflowers decorated with N, S co-doped carbon fragments (Ni/Co-OOH/NSCF). The applied-voltage can rapidly induce significant structural transformation of pristine Ni/Co sulfides particles into Ni/Co-OOH nanoflowers. Moreover, this evolution process endows the thin nanoflakes with abundant pores. Benefiting from the massively exposed active sites, rich mixed valences of bimetals, and high-speed electron/ion transport pathways, the Ni/Co-OOH/NSCF exhibits an excellent capacity of 237 mAh g−1 (equalling 853 C g−1) at 1 A g−1 and high rate capability of 61% at 20 A g−1 even at a high mass loading of 7 mg cm−2. The assembled asymmetric supercapacitor based on Ni/Co-OOH/NSCF delivers a superior energy density of 94.3 Wh kg−1 at the power density of 3.6 kW kg−1, and excellent stability of 90% capacitance retention after 5000 cycles, which outperforms most of reported transition metal compounds. This general synthetic method can be facilely realized without using any reagents and tedious procedures. Therefore, this work opens a new avenue for the structure manipulation of advanced materials toward energy storage.