Accordingly, the discharge/charge (D/C) profiles of the SnO2@C and SnO2@C/Cu electrodes in the first two cycles at a current density of 200 mA g_1 between 0.05 V and 3.00 V are presented in Fig. 5c and d, respectively. The first two D/C profiles for SnO2 electrode were also shown in Fig. S6b. Those voltage plateaus shown in D/C profiles for the SnO2, SnO2@C and SnO2@C/Cu electrodes are consistent with the CVs observation. It is found that the first coulombic efficiency for SnO2, SnO2@C and SnO2@C/Cu are about _58 % (i.e., 1060/1760), _63 % (i.e., 1040 /1650) and _66 % (i.e., 960 /1375), respectively. The improvement for the first coulombic efficiency should benefit from the carbon coating and Cu particles. In addition, the lower initial discharged capacity for SnO2@C/Cu is obtained, which may be resulted from the additional weight of Cu element in SnO2@C/Cu composites.In other words, this large capacity loss in the first cycle corresponded to the formation of the SEI layer, which was consistent with the CV observation.