Post lithium ion battery is highly demanding energy storage for smaller scale as stationary use to greater scale as grid storage, and vehicle use as well. Magnesium ion battery with metal magnesium as an anode has been investigated over decades because of its high theoretical capacity of magnesium (3833 mAh cm³) and relatively lower potential (0.7 V vs lithium) for naturally abundant mineral resources in “multivalent” metals with less risk on forming dendritic deposits [1]. After over a decade of finding of stable and reversible electrolyte based on Grignard agent such as APC [2], our finding of magnesium monocarborane [3] opened next door toward high energy density by its wider potential window up to 3.7 V and high current density more than 1mS cm^-1, without corrosive issue which is intrinsic to conventional electrolytes containing chlorine.

Although of many efforts for electrolytes and electrodes, the battery system has lack of cathode capable of providing high potential and / or capacity with stable performance over numbers of cycles in charge and discharge, to takeover Li ion battery. Recently some challenges proved custom approach for magnesium ion effective to certain extent; eg. C₆₀ [4] works as a mimic of cluster aspect of highly reversible Chevrel Mo₆S₈, and spinel Ti₂S₄ [5] presents the design of host framework with “soft” anion and ionic path.

In this study we approach to new insights into active materials by means of charge transfer. Interfacial analysis such as electrochemical impedance, XPS, etc., to the most established cathode, Chevrel phase Mo₆S₈ [1] in contact with MMC electrolyte gives some key factors of highly reversible cathode. Besides, our new approach for a cathode active material and its battery performance will be introduced for the next step of the reaction design.

References:

[1] J. Muldoon, C. B. Bucur, and Th. Gregory, Chem. Rev. 2014, 114, 11683.

[2] D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature 2000, 407, 724.

[3] O. Tutusaus, R. Mohtadi, T. S. Arthur, F. Mizuno, E. G. Nelson, Y. V. Sevryugina, Angew. Chem. Int. Ed. 2015, 54, 7900.

[4] R. Zhang, F. Mizuno, L. Chen,, Chem. Commn.. 2015, 51, 1108.

[5] X. Sum, P. Bonnick, V. Duffort, M. Liu, Z. Rong, K. A. Persson, G. Ceder, an L. F. Nazer, Energy Environ. Sci. 2016, 9, 2273.