The commonly used electrolytes for commercial lithium batteries are composed of lithium salts, organic solvents, and some additives. Organic solvents mainly include cyclic carbonates such as ethylene carbonate and propylene carbonate, as well as chain carbonates such as diethyl carbonate and ethyl methyl carbonate. The composition and proportion of these carbonates have a significant impact on the energy density, cycle life, and safety of lithium batteries. Therefore, studying the composition and content of carbonates in lithium-ion battery electrolytes plays an important role in the development and quality control of lithium-ion batteries.

This article usesPerkinElmer Clarus ® SQ 8 gas chromatograph/mass spectrometerA qualitative and quantitative method was established for the determination of nine carbonates in electrolytes using an electron bombardment ionization source (EI source). This method is simple, sensitive, and efficient. The experiment was conducted in EI mode using a Perkin Elmer Clarus SQ 8 gas chromatograph/mass spectrometer, and the experimental conditions are shown in Table 1. Separate all eluted compounds using a PerkinElmer Elite 35 MS column (30 meters x 0.25 millimeters x 0.25 micrometers).

Nine types of carbonates were purchased from Shanghai Anpu Experimental Technology Co., Ltd. Dilute the standard with ethyl acetate (HPLC grade, Honeywell brand) to obtain the desired concentration of calibration solution. Dilute the electrolyte sample with ethyl acetate in a ratio of 1:10000 (volume ratio) before sampling. The precision of the calculation method is based on the peak area of the 4th grade standard sample with six injections and the diluted sample. Calculate the detection limit of the method by analyzing the first level standard solution injected seven times. Add standard (4th grade standard) to the diluted electrolyte sample and calculate the recovery rate based on the peak area of the target compound.

The ion chromatogram of the selected standard for the results and discussion is shown in Figure 1. By using the ion scanning mode, all target compounds were separated. Draw a calibration curve graph with peak area and analyte content as the coordinate axes. The calibration coefficients (r2) of all compounds are greater than 0.999, indicating that the quantitative results are accurate and reliable within this range (1-100 mg/L). Tables 3 and 4 summarize the retention time, quantitative ions, qualitative ions, recovery rate, method detection limits (MDLs), and method quantification limits (MQLs) of each target compound. After calculation, the method detection limit for each target substance is 0.0800.176 milligrams per liter; The actual sample recovery rate is 92.40-104.45%; The precision of the standard sample is 1.02-2.16%, while the precision of the actual sample is 1.61-2.05%.

Summary of references: This article uses PerkinElmer Clarus ® A method for determining nine carbonates in lithium-ion battery electrolytes was established using an SQ 8 gas chromatograph/mass spectrometer with an electron bombardment ionization source. The results show that this method has good precision, recovery rate, linearity, and detection limit, meeting the monitoring needs of the lithium-ion battery industry.