Despite the high theoretical capacity, the practical use of this type of material is greatly hampered by their quick capacity fading over an extended number of cycles, which is believed to be caused by the alloy/de-alloy process shown in [Eq. (2)]. Several strategies have been proposed to resolve this problem and improve the lithium storage performance. In addition to the well-known method of designing hollow and/or porous nanostructures, another widelypracticed strategy is to improve the conductivity of SnO2based materials by combining them with electronically conductive agents, such as CNTs and noble metals. However, despite the sound concept, most previous CNTs@SnO2 composites exhibit relatively low capacities, because the weight fraction of active SnO2 is generally below 40%, and poor capacity retention because the SnO2 nanoparticles are loosely attached to CNTs. The third strategy is to introduce a flexible buffering matrix to prevent the collapse of SnO2 materials during discharge–charge cycling. [12,15] Of the buffering matrices reported thus far, carbon has been considered as a good candidate because of its highly flexible nature. Herein, we propose a new anode nanostructure: CNTs@SnO2@carbon coaxial nanocables with a sandwich structure, in which the SnO2 content is about 80 wt%. The subsequent electrochemical measurements confirm that through combining the highly conductive CNTs support and the flexible carbon nanolayer, the as-prepared CNTs@SnO2@carbon nanocables demonstrate greatly improved lithium-storage properties. The synthetic process is illustrated in Scheme 1. In the first step, mediated by a bifunctional molecule (mercaptoacetic acid), SnO2 is efficiently deposited on the surface of CNTs to form an intermediate layer. Afterwards, a layer of glucose-derived polysaccharide (PS) is coated on the outer surface of CNTs@SnO2 to give rise to the sandwich structure. Finally, PS is converted into carbon by heat treatment under an inert atmosphere. Figure 1 shows the morphologies of the respective samples. The CNT templates are quite smooth and are about 60–80 nm in diameter (Figure 1a,b). After being coated with SnO2, the surface of the CNTs become much rougher and the diameter has increased to 110–130 nm (Figure 1c,d), thus indicating that the thickness of the SnO2 layer is approximately 25 nm. Figure 1e,f show the morphology of CNT@SnO2@carbon, and a thin layer of carbon can be clearly observed as the outer-most layer of the sandwich structure with a thickness of about 5 nm (Figure 1 f). The crystal structure of the as-prepared samples was determined by X-ray diffraction (XRD), with the results shown in Figure 2a. In curve I, the diffraction peaks at 26.38 and 43.08 can be assigned to the (002) and (100) of CNTs. In curve II, the peaks at 26.38, 33.88, 37.78, and 51.78 can be assigned to tetragonal SnO2 (JCPDS card no.41-1445, SG: P42/mnm, ao=4.738 , co=3.187 ). [12] It is obvious from the Figure that after carbonization, better crystallinity is achieved in the SnO2 phase as the intensity of its diffraction peaks increases significantly by comparing curve III with curve II. The carbon content in each sample was determined using thermogravimetric analysis (TGA). Figure 2b shows the weight losses of CNTs, CNTs@SnO2, and CNTs@SnO2@carbon. It can be seen from curve I that the decomposition of CNTs takes place between 500 and 700 8C. [a] S. Ding, J. S. Chen, X. W. Lou School of Chemical and Biomedical Engineering Nanyang Technological University 70 Nanyang Drive, Singapore 637457 (Singapore) Fax: (+65)6791-1761 E-mail : xwlou@ntu.edu.sg