Fig. 6 and S7 compared the cycling performance of SnO2, SnO2@C and SnO2@C/Cu electrodes. The SnO2@C anode exhibits much better cyclic stability than that of bare SnO2 anode with reversible capacity of SnO2 only remained at _50 mAh g_1 after 50 cycles. The quick capacity fading of bare SnO2 should be resulted from severe aggregation and pulverization of SnO2 nanoparticles in the charge and discharge processes. Importantly, the LIB perfor- mance for SnO2@C anode can be further enhanced by introducing metal Cu particles. It is observed from Fig. 6a that the reversible capacity of SnO2@C/Cu can remain at _740 mAh g_1 tested at 200 mA g_1 after 60 cycles, being larger than that of only 450 mAh g_1 for the SnO2@C anode. Similarly, the SnO2@C and SnO2@C/Cu electrodes were cycled under a relatively high current density of 600 mA g_1 after being activated at 200 mA g_1 in the first three cycles. As displayed in Fig. 6b, the specific capacity and cycling performance of the SnO2@C/Cu composite was improved by adding Cu particles compared with SnO2@C electrode. The improved electrochemical performance for the SnO2@C/Cu elec-trodes can be attributed to the adding of the Cu particles, which may contribute positively to the conductance and SnO2@C stabilization. According to the EIS result shown in Fig. S8, the good performance of SnO2@C/Cu electrodes is also ascribed to the good conductivity and electronic contact between SnO2@C and Cu particles.