Rational synthesis of 3D ZnO-Cu-C yolk-shell hybrid microspheres and their high performance as anode material for zinc-nickel secondary batteries

The structural design and surface modification are recognized as an effective strategy to improve the performance of zinc electrode for zinc-nickel secondary batteries. Herein, 3D ZnO-Cu-C hybrid microspheres with controllable internal structures of solid, yolk-shell and hollow were prepared by electrostatic interplay and subsequent annealing treatment route. The decoration of the surface metallic Cu and interior in-situ carbon leads to form a 3D penetrating conductive framework as electronic pathway. Meanwhile, the external metallic Cu layer can also effectively inhibit the dissolution of the active ingredient. The structural architecture aims to provide large effective surface area for electrochemical reaction and facilitate the fast migration of ions. After a series of electrochemical tests, the ZnO-Cu-C microspheres with yolk-shell structure exhibit superior electrochemical performance in terms of high specific discharge capacity (maximum value of 654 mAh g(-1)) and excellent long-term cycling stability (610 mAh g(-1) over 710 cycles). The rational design of yolk-shell ZnO-Cu-C microsphere electrode paves new ways to develop the high-performance of zinc-nickel secondary batteries.