*4.2.1 The SEM of anode and cathodes*

**Figure 7(a)** shows the SEM image of AC anode, which shows irregular structure and occupies the vast majority of space. Meanwhile, SP uniformly dispersed between gaps of AC particles can provide good conductivity. **Figure 7(b)** shows the SEM image of graphite cathode, and **Figure 7(c)** shows the SEM image of MWCNTs/graphite composite cathode; comparison shows that MWCNTs and graphite are well connected and present a web-like network structure and three-dimensional conduction system. This structure was applied to the negative electrode to shorten the diffusion path of lithium ions and improve the kinetics of lithium-ion intercalation.
