Self-Assembly of NiO-Coated ZnO Nanorod Electrodes with Core-Shell Nanostructures as Anode Materials for Rechargeable Lithium-Ion Batteries

A porous nickel hydroxide shell was self-assembled by hydrolysis of aqueous nickel chloride in the presence of hexagonal ZnO nanorod template at room temperature. The nickel hydroxide shell converted to cubic NiO after heat treatment at 500 degrees C. Galvanostatic charge and discharge results indicated that the NiO-coated ZnO nanorod electrode is capable of delivering a higher capacity than the bare ZnO nanorod and carbon-coated ZnO nanorod electrodes especially in high-rate charge and discharge processes. The presence of porous NiO shell might prevent the disintegration of ZnO nanorods because of the large volume change during charge and discharge. In addition, the porous NiO shell ensured good electrical contact of ZnO with the current collector and facilitated the charge transfer and transport of lithium ions. The amount of NiO coated on ZnO nanorods significantly affected the electrochemical performance of ZnO electrode toward lithium. Insufficient NiO shell would not provide enough electrical conductivity and protection against disintegration. When the NiO content was higher than 32.6 wt %, the electrode performance could be significantly improved.