context: 3Mg/Mg2Sn electrodes were subjected to galvanostatic C/D at various rates in Mg(HMDS)2/MgCl2. In addition to the unprecedented high capacity, the rate performance of 3Mg/Mg2Sn was also impressive. The stepwise increase in C/D rates resulted in a continuous decrease in reversible capacities, but the degree of reduction was not abrupt (Fig. 5A). For example, a reversible capacity of 805 mA h g−1 was delivered at 100 mA g−1 and as much as 87 and 53% (700 and 430 mA h g−1) of it was retained at 500 and 1500 mA g−1, respectively. Accordingly, the corresponding C/D profiles also showed a relatively small increase in overpotentials with an increase in the C/D rates (Fig. 5B). When compared with the plateau voltage at 100 mA g−1, the additional overpotential required at 1500 mA g−1 was only ca. ±50 mV. It should be stressed here that such excellence has never been reported for either alloy- or intercalation-type electrodes in MIBs. Most anode materials show a capacity of less than 400 mA h g−1 at a C/D rate lower than 100 mA g−1, which significantly decreases with increasing C/D rates (Table 1). A few materials can deliver reasonable capacities at high rates, but no performance has been comparable to that of 3Mg/Mg2Sn.