context: Herein, we report a new finding that 3Mg/Mg2Sn alloy can be a promising solution to the aforementioned issues in Sn-based alloy-type MIB anodes. It is shown that 3Mg/Mg2Sn, which is composed of ternary phases (crystalline Mg-rich (c-Mg), amorphous Mg-rich (a-Mg), and intermetallic Mg2Sn phases), reversibly magnesiates/de-magnesiates a significant amount of Mg2+ ions in a non-Grignard and Lewis acid-free electrolyte even under high rates of C/D. In Table 1, the unprecedented electrochemical performance of 3Mg/Mg2Sn is compared with that of other popular alloy-type anodes. The origin of high capacities and excellent rate-capabilities is also discussed in the context of structural features. Finally, we describe the compatibility of 3Mg/Mg2Sn with versatile conventional electrolytes and the optimality of using 3Mg/Mg2Sn with Mg2+-trapping cathodes (e.g., Mo6S8).
answer: Mo6S8