Electrolytes Ageing in Lithium-ion Batteries: A Mechanistic Study from Picosecond to Long Timescales

• Published in: ChemSusChem Vol. 8; no. 21; pp. 3605 - 3616
• Main Authors: Ortiz, Daniel, Jiménez Gordon, Isabel, Baltaze, Jean-Pierre, Hernandez-Alba, Oscar, Legand, Solène, Dauvois, Vincent, Si Larbi, Gregory, Schmidhammer, Uli, Marignier, Jean-Louis, Martin, Jean-Frédéric, Belloni, Jacqueline, Mostafavi, Mehran, Le Caër, Sophie
• Format: Journal Article
• Language: English
• Published: Germany Blackwell Publishing Ltd 01.11.2015; Wiley Subscription Services, Inc
• Subjects: ageing; Aging; batteries; Electric Power Supplies; Electrolysis; Electrolytes - chemistry; Lithium Compounds - chemistry; Mass Spectrometry; Pulse Radiolysis; radiolysis; reaction mechanisms; Solutions; Time Factors; Viscosity; reaction mechanisms; electrolysis; ageing; batteries; radiolysis
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201500641

The ageing phenomena occurring in various diethyl carbonate/LiPF6 solutions are studied using gamma and pulse radiolysis as a tool to generate similar species as the ones occurring in electrolysis of Li‐ion batteries (LIBs). According to picosecond pulse radiolysis experiments, the reaction of the electron with (Li+, PF6−) is ultrafast, leading to the formation of fluoride anions that can then precipitate into LiF(s). Moreover, direct radiation‐matter interaction with the salt produces reactive fluorine atoms forming HF(g) and C2H5F(g). The strong Lewis acid PF5 is also formed. This species then forms various R1R2R3P=O molecules, where R is mainly −F, −OH, and −OC2H5. Substitution reactions take place and oligomers are slowly formed. Similar results were obtained in the ageing of an electrochemical cell filled with the same model solution. This study demonstrates that radiolysis enables a description of the reactivity in LIBs from the picosecond timescale until a few days. Accelerated Ageing! Radiolysis is used as a tool to study the ageing phenomena occurring in various diethyl carbonate/LiPF6 solutions. The degradation products obtained by radiolysis are similar to the ones occurring in electrolysis of Li‐ion batteries (LIBs) (see scheme). The research validates the use of steady‐state and pulse radiolysis as tools to quickly investigate the reactivity of newly developed electrolytes.