Masahiro Yoshizawa-Fujita

Abstract:

Lithium-ion batteries (LIBs) have been widely used in power devices. For further expanding the usage of LIBs, safety and energy densities must be improved. We have focused on zwitterions, which have positive charge and negative charge in the same molecule [1]. Lithium-ion transport was improved by adding a zwitterion to polymer gel electrolytes [2]. Recently, we found that adding a small amount of zwitterion improved not only the electrochemical stability of oligo-ether electrolytes up to about 5 V [3], but also the charge-discharge cycle stability of cells with oligo-ether electrolytes [4]. We also investigated the effect of zwitterions on electrochemical properties of ionic liquid (IL) electrolytes. Zwitterions showed positive effects in IL electrolytes containing Li salts. Li/LiCoO₂ cells containing the IL/zwitterion electrolyte system exhibited high capacities as compared with those of IL electrolytes without zwitterions [5,6]. The increase in the interfacial resistance between the electrolyte and cathode with cycling was suppressed.
Recently, we have focused on the magnesium secondary battery, which has been attracting much attention as a next generation secondary battery. Magnesium metal has a high theoretical capacity density and low electrode potential, so it is expected to have high energy density. It is, however, difficult to control stripping and plating of Mg because of the formation of the passivation film. We will add zwitterions into IL/Mg electrolytes. The effect of zwitterions on the properties of IL/Mg electrolytes will be introduced.

[1] H. Ohno, M. Yoshizawa-Fujita, Y. Kohno, Phys. Chem. Chem. Phys. 20 (2018) 10978.
[2] C. Tiyapiboonchaiya, J. M. Pringle, J. Sun, N. Byrne, P. C. Howlett, D. R. MacFarlane, M. Forsyth, Nat. Mater. 3 (2004) 29.
[3] M. Suematsu, M. Yoshizawa-Fujita, H. Zhu, M. Forsyth, Y. Takeoka, M. Rikukawa, Electrochim. Acta 175 (2015) 209.
[4] S. Yamaguchi, M. Yoshizawa-Fujita, H. Zhu, M. Forsyth, Y. Takeoka, M. Rikukawa, Electrochim. Acta 186 (2015) 471.
[5] S. Yamaguchi, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa, J. Power Sources 331 (2016) 308.
[6] S. Horiuchi, H. Zhu, M. Forsyth, Y. Takeoka, M. Rikukawa, M. Yoshizawa-Fujita, Electrochim. Acta 241 (2017) 272.