Advanced Characterization of Lithium‐Ion Battery Electrolytes Using Ultra‐high Resolution Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy

Electricity storage is one of the key elements in the transition to renewable energy sources. Nowadays, the most common technology to meet this demand is the lithium‐ion battery (LIB). The electrolytic solution composing these batteries is crucial for their good performance, as it determines the charging capacity and the lifetime through passivation processes. Among salts, additives and solvents that make up the electrolyte solution of LIBs, additional species can be present in a non‐negligible amount. Such species may originate from impurities of added substances or from chemical reactions occurring during the operation of the batteries. All these components need to be characterized and quantified precisely to ensure good performances. However, electrolytic solutions are extremely sensitive to water and need to be manipulated under inert conditions. This constraint, together with their exotic molecular composition (numerous heteroatoms), increases the difficulty of the monitoring procedure. In the present work, we combine a molecular characterization and quantification approach using ultra‐high resolution mass spectrometry and nuclear magnetic resonance to decipher a solution containing the most used electrolytes nowadays. The advantages and disadvantages of the used instruments are discussed.