EIS analysis after 100, 200 and 300 cycles were conducted to investigate the decay of capacity (Fig. , Fig. , Fig. and Fig. ). The fitting of Si-SiOx@C after 300 cycles (Fig. ) consists of the resistances of the electrolyte solution (Rs), interfacial layer (Rsuf), and charge transfer (Rct). In Fig. , the resistances of the interfacial layer are shown. With the repeated lithiation and delithiation processes, the Rsuf gradually increases, which is caused by the thickening of the SEI layer and volume expansion. However, curly CNTs can provide conductive pathways and buffer regions, reducing the resistance compared with Si-SiOx@C. Si-SiOx@C-1.25 with optimal CNT content exhibits the lowest resistance, which is consistent with cycling performance.