This study presents a systematic, characterization of electrolytes from commercial lithium-ion batteries (LIB), encompassing 90 batteries from leading global manufacturers across diverse formats and application sectors. An integrated, complementary mass spectrometric workflow combining LC–MS/MS, GC–MS, and high-resolution MS was employed. To ensure robust structural annotation, molecular identifications were assigned confidence levels following Schymanski et al. (2014). Across all formats, PF6− was confirmed as the dominant Li+ counterion, frequently coexisting with BF4−, PO2F2−, and bis(fluorosulfonyl)imide (FSI−), forming binary and ternary salt systems optimized for both conductivity and safety. Solvent systems revealed the widespread use of propylene carbonate (PC) combined with diverse carbonate mixtures, demonstrating trends in performance optimization specific to cell format. A variety of additives were identified, reflecting a clear shift towards multifunctional, synergistic additive packages and the gradual replacement of fluorinated species with environmentally safer alternatives. Cycling studies demonstrated that electrolyte degradation mechanisms are strongly influenced by electrode composition and additive chemistry, with oxidative degradation pathways dominating. Together, these findings provide rare empirical insight into the evolving formulation strategies of electrolytes in commercial LIB, still employing classic carbonates and LiPF6, but highlighting a trend toward safer, more robust, and sustainable electrolyte architectures by using synergistic multifunctional systems.
Scholl et al. (Thu,) studied this question.