Electrolyte decomposition and solid electrolyte interphase revealed by mass spectrometry

Non-aqueous electrolyte liquids such as carbonate solvents have been widely employed in the commercial lithium-ion batteries and in the development of next-generation rechargeable batteries. The decomposition products of the organic electrolyte and additive molecules contribute to the formation of solid electrolyte interphases (SEIs) on the electrode surface, which have key impacts on battery's electrochemical performance. The rational engineering of electrolyte systems demands precise understanding of the electrochemical reaction pathways as well as the decomposition products of the electrolytes. Mass spectrometry (MS) is a well-established molecular analytical approach that can provide critical information for unambiguous structure assignment based on its mass-resolving power. In recent years, the application of MS for battery research has been expanding rapidly, providing valuable insights about the chemical species generated during battery operation and electrolyte evolution. This review aims to summarize the recent advances of MS technique-based analysis of electrolyte decomposition products as well as SEIs, and thus to demonstrate the high utility of MS methods for characterization of battery systems.