Recently, many efforts have been deployed to develop new electrode materials for lithium ion batteries (LIBs) in order to meet the growing demand for higher energy density and stronger cyclic stability. Among these materials, zinc oxide (ZnO) as anode has attracted a particular attention due to the natural abundance, low cost, facile preparation and chemical stability. Besides, it has a theoretical capacity of 987 mAh/g, much higher than that of the conventional graphite anode (370 mAh/g). However, ZnO suffers from large volume variations during charge/discharge processes resulting on a severe capacity degradation and reduced cycle life  [1]. To overcome these limitations, metal doping and composite synthesis with highly conductive matrix such as graphene have been used to improve the electrochemical performances of ZnO anode [2,3].

In this study, zinc oxide (ZnO), ZnO/Graphene composite (ZnO/G), aluminium doped ZnO (AZO) and AZO/Graphene composites (AZO/G) were prepared by sol gel method and utilized as anode material for lithium-ion batteries. Samples were characterized by several methods such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron spectroscopy (SEM), and transmission electron microscopy (TEM). Electrochemical properties were investigated by cyclic voltammetry and galvanostatic cycling tests.

The effect on the ZnO structure by aluminium doping with different concentrations is observed in the figure attached. This results in an advanced performance with reversible lithium storage capacities compared to the pure ZnO. Moreover, to improve its electrochemical performances, AZO was uniformly dispersed on graphene sheets and the electrochemical properties exhibit higher reversible capacities, better cycle performances and rate capabilities than ZnO, ZnO/G and AZO. The higher performances of this composite may be attributed to the graphene encapsulation, which enhances the electrical conductivity, avoids the aggregation and stabilizes the structure of AZO nanoparticles during cycling.

This communication will compare results obtained from the four samples and evidence the effect of aluminium and graphene added to ZnO anode material.  

References

[1] J.P. Liu, Y.Y. Li, R.M. Ding, J. Jiang, Y.Y. Hu, X.X. Ji, Q.B. Chi, Z.H. Zhu, X.T. Huang, J. Phys. Chem. C 113 (2009) 5336-5339.


[2] G.L. Xu, Y. Li, T. Ma, Y. Ren, H.H. Wang, L. Wang, J. Wen, D. Miller, K. Amine, Z. Chen, PEDOT-PSS coated ZnOC hierarchical porous nanorods as ultralong-life anode material for lithium ion batteries, Nano Energy, 18 (2015) 253–264.

[3] L. Zhang, J. Zhang, Y. Liu, S. Guo, Effect of aluminium doping amount on the electrochemical properties of ZnO nanoparticles as anode for lithium ion batteries, Micro & Nano Letters, IET, 10 (2015) 217-219.