Constructing hierarchical lanthanum-doped nickel hydroxidenitrate nanoflowers with dilated lattice spacing for improving asymmetric supercapacitors

Abstract

The novel lanthanum-doped nickel hydroxidenitrate (LaNiHN) nanoflowers are prepared by a facile one-step solvothermal growth method. The doping of La ions into the lattice of the NiHN nanoflowers can effectively increase the electrical conductivity, lattice volume and c-axis spacing of NiHN nanosheets and lead to rapid transfer of electrolyte ions and electrons between the nanosheet channels, resulting in a high specific capacity of 154 mAh g−1 (at 1 A g−1) and high rate performance for supercapacitor positive electrode. Moreover, the Fe2O3 supported on graphene nanosheets (Fe2O3/GNS) with high specific capacity and excellent stability is selected as negative electrode to match the LaNiHN nanoflowers positive electrode for assembly of a novel LaNiHN//Fe2O3/GNS asymmetric supercapacitor (ASC). By virtue of their excellent electrochemical properties and complementary working voltage, the as-assembled ASC possesses a wide operating voltage of 1.65 V, high energy density of 51 Wh kg−1 at a power density of 825 W kg−1, as well as the acceptable cycling stability of 87% capacity retention after 5000 cycles.