SnO 2 hollow nanospheres were synthesized from glucose and SnCl 2 solution under hydrothermal environment and calcinations. The carbon layer was then deposited as a buffer layer via hydrothermally treated glucose solution. The thickness of the SnO 2 shell in the hollow structures could be adjusted by changing the concentration of the SnCl 2 coating solution. The crystalline structure and morphological observation of the as-synthesized hollow structures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thickness of SnO 2 under 0.1 and 1 M SnCl 2 coating solution was 15 and 60 nm, respectively. It was demonstrated that the electrochemical performance was significantly improved by the hollow structure and strongly affected by the shell thickness of SnO 2 . The hollow structure with 15 nm in SnO 2 thickness exhibited an outstanding reversible capacity of 500 mA hg -1 at 5 C. The extraordinary performance should be associated with the ultrathin SnO 2 shell and the carbon layer, which could accommodate the volume changes and prevent the agglomeration of Sn particles during cycling.

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The cycle life of LiCoO 2 cathodes cycled at a high cutoff voltage can be largely improved by surface modification with ZnO coating. The bright-field transmission electron microscopy ͑TEM͒ images and selected area diffraction patterns of as-coated LiCoO 2 particles reveal the existence of continuous ZnO films with a 10-nm thickness deposited on LiCoO 2 surfaces, indicating a Li-Zn-O phase formed on the surface region. Besides high-voltage cycleability, cycle-life degradation caused by inappropriate conductive carbon can also be moderated by ZnO coating. Furthermore, the rate capability at high current density can also be notably improved. The role ZnO coating played in the charge-discharge process is discussed from the viewpoint of surface chemistry with the aid of data from scanning electron microscopy, TEM, energy-dispersive X-ray, and impedance spectra. Moreover, the correlation between electrochemical performance and surface properties of ZnO-coated LiCoO 2 is explored.

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