Determining Factor on the Polarization Behavior of Magnesium Deposition for Magnesium Battery Anode

Feilure Tuerxun; Kentaro Yamamoto; Masashi Hattori; Toshihiko Mandai; Koji Nakanishi; Ashu Choudhary; Yoshitaka Tateyama; Keitaro Sodeyama; Aiko Nakao; Tomoki Uchiyama; Masaki Matsui; Kazuki Tsuruta; Yusuke Tamenori; Kiyoshi Kanamura; Yoshiharu Uchimoto

doi:10.1021/acsami.0c03696

Determining Factor on the Polarization Behavior of Magnesium Deposition for Magnesium Battery Anode

ACS Appl Mater Interfaces. 2020 Jun 10;12(23):25775-25785. doi: 10.1021/acsami.0c03696. Epub 2020 May 27.

Authors

Affiliations

¹ Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsucho, Sakyo-ku, Kyoto 606-8316, Japan.
² Center for Green Research on Energy and Environmental Materials and International Center for Materials Nanoarchitectonics, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan.
³ Laboratory of Advanced Science and Technology for Industry, Hyogo University, 3-1-2 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1205, Japan.
⁴ Research and Services Division of Materials Data and Integrated System, NIMS, Tsukuba, Ibaraki 305-0047, Japan.
⁵ Bioengineering Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
⁶ Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 651-8501, Japan.
⁷ Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo 679-5198, Japan.
⁸ Department of Applied Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachioji, Tokyo 192-0397, Japan.

PMID: 32395982
DOI: 10.1021/acsami.0c03696

Abstract

To clarify the origin of the polarization of magnesium deposition/dissolution reactions, we combined electrochemical measurement, operando soft X-ray absorption spectroscopy (operando SXAS), Raman, and density functional theory (DFT) techniques to three different electrolytes: magnesium bis(trifluoromethanesulfonyl)amide (Mg(TFSA)₂)/triglyme, magnesium borohydride (Mg(BH₄)₂)/tetrahydrofuran (THF), and Mg(TFSA)₂/2-methyltetrahydrofuran (2-MeTHF). Cyclic voltammetry revealed that magnesium deposition/dissolution reactions occur in Mg(TFSA)₂/triglyme and Mg(BH₄)₂/THF, while the reactions do not occur in Mg(TFSA)₂/2-MeTHF. Raman spectroscopy shows that the [TFSA]^- in the Mg(TFSA)₂/triglyme electrolyte largely does not coordinate to the magnesium ions, while all of the [TFSA]^- in Mg(TFSA)₂/2-MeTHF and [BH₄]^- in Mg(BH₄)₂/THF coordinate to the magnesium ions. In operando SXAS measurements, the intermediate, such as the Mg⁺ ion, was not observed at potentials above the magnesium deposition potential, and the local structure distortion around the magnesium ions increases in all of the electrolytes at the magnesium electrode|electrolyte interface during the cathodic polarization. Our DFT calculation and X-ray photoelectron spectroscopy results indicate that the [TFSA]^-, strongly bound to the magnesium ion in the Mg(TFSA)₂/2-MeTHF electrolyte, undergoes reduction decomposition easily, instead of deposition of magnesium metal, which makes the electrolyte inactive electrochemically. In the Mg(BH₄)₂/THF electrolyte, because the [BH₄]^- coordinated to the magnesium ions is stable even under the potential of the magnesium deposition, the magnesium deposition is not inhibited by the decomposition of [BH₄]^-. Conversely, because [TFSA]^- is weakly bound to the magnesium ion in Mg(TFSA)₂/triglyme, the reduction decomposition occurs relatively slowly, which allows the magnesium deposition in the electrolyte.

Keywords: anode/electrolyte interface; coordination structure; magnesium deposition; magnesium rechargeable battery; operando soft X-ray absorption spectroscopy; passivation layer.