Electrochemically activated 3D Mn doped NiCo hydroxide electrode materials toward high-performance supercapacitors

Metal doping and electrochemical reconstruction had been demonstrated to play a significant role in the preparation of advanced electrode materials, which is helpful to achieve high-performance supercapacitors. However, there was no report about the combination of two technologies to construct electrode materials and their applications in supercapacitors. Herein, a rational Mn doped NiCo sulfide compound with open structure composed of 2D ultra-thin nanosheets was designed via a Mn doping route. In order to further improve the energy storage performance of the resulted product, we adopted a simple electrochemical activation strategy to reconstruct it. It was found that the reconstructed sample not only exhibited an irreversible evolution of structure (from 2D sheet to 3D channel), but also the phase transformation (from metal sulfide to metal hydroxide). Benefiting from the stable 3D curved structure with numerous channels, multitudinous charge transfer provided by numerous valence states of metals and copious active sites by low crystalline state, the in-situ self-reconstructed sample exhibited superior capacitance. In details, the optimized product delivered excellent specific capacitance of 1462C g^-1 (3655F/g) at 1 A g^-1 and high rate capability of 66 % even at 5 A g^-1. Moreover, the corresponding assembled asymmetric supercapacitor exhibited an excellent energy density of 141.8 Wh kg^-1 at a power density of 850.1 W kg^-1, and the capacitance retention rate was 96.6 % even after 5000 cycles, which was distinctly superior than thoseofthe previous similarmaterialsreported. In a word, this work provided a feasible and effective strategy to construct 3D Mn doped NiCo hydroxide electrode materials toward high-performance supercapacitors.