Fig. 4.

Electrochemical characterization of SnO₂@GCs. a Representative cyclic voltammetry curves (CVs) of SnO₂@GC-21 at a scan rate of 0.5 mV s^–1. b The gradient electrochemical performance change of SnO₂@GCs based on the different original sulfur contents when the gravimetric capacity became stable at around the 130^th–140^th cycles (100 mA g^–1). The overall cycling performance of SnO₂@GCs can be observed in Supplementary Fig. 17. c Rate performance of SnO₂@GCs. d Cycling performance of SnO₂@GC-0, 21 and 49 at a current density of 100 mA g^–1. e, f Comparison of the volumetric and gravimetric specific capacities of SnO₂@GC-21 with the referenced cases (based on the total active materials). e Comparison with SnO₂@GC-0 and SnO₂@GC-49. f Comparison with other reported anode materials (based on the total active materials), such as t-Si@G NW arrays⁵, Fe₂O₃-G₂⁶, PVP-Sn(IV)@Ti₂C⁷_, Sn/C nanocomposite⁸, SSG⁹, Si-C granule¹⁰_, Si-PANi¹³, NHGM¹⁵, SiNW fabric²², 3D Si membrane²³ and the bowl-like SnO₂@C²⁷, and Gr-Si-CNM⁴⁵, with a voltage it charged to (see details in Supplementary Table 1)