As the "blood" of lithium batteries, electrolyte is the carrier of ion transport in lithium batteries, which is generally prepared by mixing lithium salts, solvents, and additives in a certain proportion. Lithium salt, as an important component of lithium-ion battery electrolyte, largely determines the power density, energy density, cycling, and safety performance of the battery. Lithium hexafluorophosphate (LiPF6) is the most widely used lithium salt due to its relatively optimal comprehensive performance in carbonate mixed solvent electrolytes. In addition, in order to improve the overall performance of the battery, some lithium salt additives will be added to the electrolyte, such as lithium difluorophosphate (LiPO2F2), lithium tetrafluoroborate (LiBF4), lithium bis (trifluoromethylamide) imine () Lithium bis (fluorosulfonyl) imide (LiTSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorooxalate borate (LiODFB), lithium difluorooxalate borate (LiBOB), lithium tetrafluorooxalate phosphate (LiTFOP), and lithium difluorobis (oxalate) phosphate (LiBODFP). The type, properties, and content of lithium salts in the electrolyte directly affect the performance of the battery, so content monitoring becomes very important. Ion chromatography can effectively separate and retain anions, and can be used for the detection of known lithium salts, but cannot perform qualitative analysis of unknown lithium salts and related degradation products. High resolution mass spectrometry, due to its high quality and accuracy, can achieve more in-depth qualitative analysis of unknown substances.