As we know, carbon shell has been demonstrated to offer residual buffer space to accommodate the large volume change and weaken secondary agglomeration of SnO2 particles during cycling. TEM images of SnO2@C and SnO2@C/Cu were conducted to characterize their structure. Meanwhile, the TEM images of SnO2 have been presented in Fig. S4 for comparison. From Fig. 4, almost all the samples are sphere-like and core-shell morphology. Hereinto, the element mapping test for SnO2@C shown in Fig. S5 displayed that the C-shell and Sn-O-core are clearly distinguished. For SnO2@C/Cu, the irregular Cu particles signed by arrow were also presented in the Fig. 4b. Furthermore, the insets of HR-TEM image shown in both of Fig. 4a and b revealed the interplanar spacing of 0.335 and 0.264 nm, corresponding to the (110) and (10 1) planes of SnO2 in both samples. It is noted that the surface contact between C shells and the contact between C shells and Cu particles should be both considered to be beneficial to enhance electronic conductivity and improve electrochemical performance of their electrodes for LIBs.