Synthesis of Synergistic Ni(OH)₂@ZnO Core–Shell Nanostructured Electrodes by a Hydrothermal Method and Atomic Layer Deposition for High‐Performance Supercapacitors

Abstract

A novel nanoporous Ni(OH)2@ZnO core–shell architecture is successfully synthesized via a hydrothermal reaction and atomic layer deposition (ALD). This hybrid material exhibited a well‐defined core–shell nanostructure with high purity and good crystallinity. The conductivity of the electrodes is obviously enhanced by the ALD ZnO thin film. Compared to the conventional Ni(OH)2, the Ni(OH)2 coated with 10 nm of ZnO exhibited significantly enhanced performance, with a maximum specific capacitance value of ≈1,400 F g−1 at a current density of 1 A g−1, which is attributed to the improved charge‐transfer resistance. The asymmetric Ni(OH)2@ZnO//graphene supercapacitor exhibited a good capacitance retention rate and an energy density of 32 Wh kg−1 at a power density of 480 W kg−1, which are higher than those of pure nanostructured Ni(OH)2 and ZnO‐based asymmetric supercapacitors. The remarkable electrochemical performance is contributed to the synergetic presence of the core–shell nanostructure with a high surface area and the highly conductive ZnO films with optimized thickness, which achieve appropriate mass ratio control of the active material. The design of the core–shell architectures demonstrated in this work is expected to be a new and promising approach to ALD for the development of hybrid electrode materials for high‐performance supercapacitor applications.