An unwanted guest in the electrochemical oxidation of high-voltage Li-ion battery electrolytes : the life of highly reactive protons

Ilić, Stefan (author), Genorio, Boštjan (author), Cabana, Jordi (author), Strmčnik, Dušan (author)

Lithium-ion batteries (LIBs) are central to the urgent societal need to decarbonize both transportation and energy storage on the grid. Unfortunately, despite their attractive energy/power density, as well as high coulombic and energy efficiencies, further improvement of this technology – especially their durability – is desperately needed. To support these efforts, our study focuses on fundamental understanding of the decomposition pathways for LIB electrolytes at the cathode–electrolyte interface (CEI), as the nature of these reactions directly controls the extent to which cell capacity and voltage decays in these systems. In this study, we employ electrochemical methods, coupled with product analysis using NMR spectroscopy and mass spectrometry, to determine the decomposition mechanisms in both model and technologically relevant electrolytes. Remarkably, we discovered the electrochemical formation of protons with high chemical activity, comparable to known superacids, at potentials relevant to practical Li-ion batteries. Their reactivity toward every individual component of the CEI provides a unified thermochemical origin for a myriad of side reactions that are commonly associated with the electrochemical reaction. In particular, electrochemically generated protons react with intact EC molecules to form CO$_2$ and other short and long chain ethers. They also undergo an acid–base reaction with LiPF$_6$, to form the weaker acid HF, and with the cathode active material, leaching transition metals into the electrolyte. Collectively, the results of this study all point to the urgent need to either mitigate this proton formation or introduce benign harvesting additives via new electrolyte design strategies.

• Language: English
• Keywords: electrochemistry, lithium-ion batteries, energy storage, electrolytes
• 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: Str. 8303-8312
• Numbering: Vol. 18, iss. 17
• PID: 20.500.12556/RUL-178398
• UDC: 544.5/.6
• ISSN on article: 1754-5706
• DOI: 10.1039/D5EE02403J
• COBISS.SI-ID: 250361859
• Publication date in RUL: 26.01.2026

Record is a part of a journal

• Title: Energy & environmental science
• Publisher: Royal Society of Chemistry
• ISSN: 1754-5706
• COBISS.SI-ID: 519833369

Licences

• License: CC BY-NC 3.0, Creative Commons Attribution-NonCommercial 3.0 Unported
• Link: http://creativecommons.org/licenses/by-nc/3.0/
• Description: You are free to reproduce and redistribute the material in any medium or format. You are free to remix, transform, and build upon the material. You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. You may not use the material for commercial purposes. You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.

Secondary language

• Language: Slovenian
• Keywords: elektrokemija, litij-ionske baterije, shranjevanje energije, elektroliti

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: J7-50227
• Name: Izboljšava učinkovitosti sistemov za pretvorbo in shranjevanje energije s pomočjo 2D modificiranih elektrokemijskih faznih mej