context: The high-rate performance of 3Mg/Mg2Sn was mainly attributed to a low RCT. EIS spectra revealed that the RCT in 3Mg/Mg2Sn is significantly smaller than that in Mg2Sn (Fig. S5†). While the RCT values in 3Mg/Mg2Sn varied between 77 and 140 Ω, those in Mg2Sn varied in the range of 500–2500 Ω. This was not surprising because the apparent RCT is dependent on the surface area that is accessible by electrolytes. The larger BET surface area and micro-to-macroporosity of 3Mg/Mg2Sn, therefore, resulted in a significantly low RCT, which eventually contributed to the high-rate performance.