Preparation And Lithium Storage Property Of Three Dimensional ZnO/C Nanoarrays

Zinc oxide has attracted a lot of attention as anode material for lithium ion batteries owing to its abundance, low cost, good safety performance and high theoretical capacity(978 m Ah/g). However, the poor electronic conductivity, as well as the huge volume change during lithiation-delithiation process, leads to poor cycling performance and rate capability. The main way to improve the electrochemical performance of Zn O anode is to design special structure and combine with other material. In this study, Zn O nanoarrays were grown on the surface of nickel foam substrates. Core-shell Zn O/C and sholk-shell Zn O/C nanoarrays were prepared to improve the electrochemical performance of Zn O nanoarrays.Core-shell Zn O/C nanoarrays were synthesized by coating Zn O nanorods with polypyrrole(Ppy) via vapor deposition and following thermal treatment. The SEM and TEM images of Zn O/C nanocomposite indicated that foam substrate was covered with core-shell nanorods with a diameter around 100 nm and shell thickness of 10 nm. The as-prepared core-shell Zn O/C electrode delivered an initial lithiation and delithiation capacity of 1171.7 m Ah/g and 884.6 m Ah/g at a current density of 100 m A/g, corresponding to an initial coulombic efficiency of 75.5%. A reversible delithiation capacity of 544.3 m Ah/g can be obtained even after 100 cycles with a capacity retention of 61.53% which was four times as large as those of Zn O nano arrays and Zn O/Ppy composite, offering a high reversible capacity and good cycling stability. The electrochemical performance of coreshell Zn O/C nanorods with a carbon layers derived from polydopamine, electrodeposited Ppy and vapor deposited Ppy were investigated, among which the vapor deposited Ppy exhibited the best.The TEM images showed yolk-shell structured by etching part of Zn O with KOH solution, leaving voids between the Zn O-nanorod core and carbon shell. The reversible capacity of yolk-shell Zn O/C nanocomposite decreased when the degree of etching increased. After 100 cycles at a current density of 100 m A/g, the delithiation capacity of etched Zn O/C composites with an active mass fraction of 10 % is 496.7 m Ah/g, when the active mass fraction increased to 50 %, it only showed reversible capacity of 381.3 m Ah/g. Even at high current density of 400 m A/g, the etched Zn O/C composites with an active mass fraction of 10 % sti ll exhibited reversible capacity of 242.2 m Ah/g, showing a high reversible capacity and good rate capability.