Magnesium rechargeable batteries are deemed the next-generation secondary battery systems because of their high theoretical capacity and the terrestrial abundance of magnesium[1]. However, the Mg rechargeable battery research is still a very challenging field. One major problem is the slow diffusion of magnesium ions in cathode materials because coulombic interaction between the carrier ion and host material is strong [2]. In this study, we examined the electrochemical performance and reaction mechanism of MgCo2O4 spinel oxide cathode [3] under moderate temperature of 150 °C, using molten salts as the electrolyte and analyzed.
Experimental
MgCo2O4 cathode material was prepared by inverse coprecipitation. The electrochemical measurement was carried out using the three-electrodes cell. The electrolyte was mixed molten salts of 10 mol% magnesium bis(trifluolomehanesulfonyl)amide (Mg(TFSA)2) and 90 mol% CsTFSA. The composite cathode was prepared from a paste by mixing 80 wt% of as-prepared active materials, 10 wt% of acetylene black (as conductive agents) and 10 wt% of polyvinylidene difluoride (binder) in 1-methyl-2-pyrrolidone solvent and then this paste was coated on the Al foil collector. A Mg ribbon was used as the anode. The reference electrode was a Li ribbon immersed in a 0.5 M LiTFSA/N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis(trifluoromethanesulfonyl)amide electrolyte in a glass tube separated with a porous ceramic filter. Galvanostatic charge/discharge measurements were performed at 150 °C in the Ar-filled glove box.
Results and Discussion
The prepared MgCo2O4 was a single phase and the particle size was a few micrometers, which were confirmed by X-ray diffraction and scanning electron microscopy. The MgCo2O4 cathode exhibited about 250 mAh g-1 discharge capacity and about 120 mAh g-1 charge capacity during the 1st cycling at the C/10 rate. This material shows high capacity as the cathode for Mg rechargeable batteries at moderate temperature and the reaction mechanism will be discussed in the presentation.
References:
[1]D. Aurbach., Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich and E. Levi, Nature 2000, 407, 724.
[2] E. Levi, M. D. Levi, O. Chasid and D. Aurbach, J. Electroceram. 2009, 22, 13.
[3] S. Okamoto, T. Ichitsubo, T. Kawaguchi, Y. Kumagai, F. Oba, S.Yagi, K. Shimokawa, N. Goto, T. Doi, and E. Matsubara, Adv. Sci. 2015, 2, 1500072.
Acknowledgement:
This research was financially supported by the Japan Science and Technology Agency (JST), Advanced Low Carbon Technology Research and Development Program (ALCA), Specially Promoted Research for Innovative Next Generation Batteries (SPRING) Project.