Effect of ligand variation on Mg alkoxyborate electrolytes : does more fluorine help?

Pavčnik, Tjaša (author), Radi, Muath (author), Lužanin, Olivera (author), Dedryvère, Rémi (author), Tchitchekova, Deyana S. (author), Ponrouch, Alexandre (author), Bitenc, Jan (author), Dominko, Robert (author)

Mg fluorinated alkoxyborate-based electrolytes are promising candidates for rechargeable Mg batteries. In this work, we investigate a series of Mg alkoxyborates with a different degree of anion fluorination in terms of their physicochemical properties, Mg metal anode, and organic cathode electrochemical performance, as well as Mg metal/electrolyte interphase. The results underscore the significant influence of the anion fluorination degree on the transport properties of electrolytes. Notably, the anion with the lowest degree of fluorination exhibits one order of magnitude lower ionic conductivity than electrolytes with more fluorinated anions. Interestingly, the same electrolyte demonstrates the second-best electrochemical performance, with the Mg plating/stripping efficiency close to 99 %. XPS analysis of the Mg metal deposit surface reveals that the high Coulombic efficiency is associated with a high amount of boron-containing species in the metal/electrolyte interphase of the best-performing electrolytes. Additionally, it has been noted that inorganic boron species result in a larger interfacial resistivity for Mg plating/stripping compared to boron species in an organic environment. Testing in combination with organic cathodes reveals the superior performance of the most fluorinated electrolyte in terms of cycling stability and Coulombic efficiency. The present work underlines the interplay of different phenomena affecting the overall electrochemical performance of electrolytes and strategies for the design of next-generation Mg electrolytes.

• Language: English
• Keywords: Mg fluorinated alkoxyborate electrolyte, ionic conductivity, plating, stripping, metal/electrolyte interphase, organic cathode
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 12 str.
• Numbering: Vol. 626, art. 235711
• PID: 20.500.12556/RUL-166512
• UDC: 66
• ISSN on article: 1873-2755
• DOI: 10.1016/j.jpowsour.2024.235711
• COBISS.SI-ID: 221893635
• Publication date in RUL: 16.01.2025

Record is a part of a journal

• Title: Journal of power sources
• Publisher: Elsevier BV
• ISSN: 1873-2755
• COBISS.SI-ID: 114431747

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: kemijska tehnologija, elektrokemija, magnezij, prevodnost