Magnesium Storage Performance and Surface Film Formation Behavior of Tin Anode Material

Abstract Electrochemical cycling performance of microsize bulk and thin film Sn electrodes up to 50 cycles in Mg half‐cell configuration, as well as Mg diffusivity and interfacial reaction behavior in a phenylmagnesium chloride (PhMgCl)/THF electrolyte are studied. The bulk Sn electrode delivers capacities of 321–289 mAh g −1 with capacity retention of 90 % and coulombic efficiencies higher than 99 % over 30 cycles, and thus demonstrates the potential of Sn anodes. The Sn film electrode shows good cycling ability. Surface analysis by XPS reveals that the surface of cycled electrodes is composed of a mixture of various inorganic salts of Sn and Mg formed by interfacial reactions between Sn and PhMgCl, and organic functionality produced by decomposition of THF, indicating surface film formation. The Mg 2+ diffusivity of Sn is on the order of 10 −11 cm 2 s −1 , which is four orders of magnitude lower than the Li + diffusivity of Sn in Li‐ion batteries. Advanced material design for enhanced electronic conductivity and control of the interfacial chemistry for formation of a surface protective film are believed to be the keys to overcome such sluggish kinetics, increase the capacity, and improve the cycling performance.