LAAN-A-LC-E181

High Performance Liquid Chromatography No.L403

Analysis of Electrolytic Solvents for Lithium-Ion Rechargeable Battery

Lithium-ion rechargeable batteries are widely used in types of : cyclic carbonates, which are high- notebook computers, cellular phones and other permittivity, high-boiling-point solvents, and short-chain portable electronic equipment because of their high ester carbonates, which are low-viscosity solvents. In efficiency and high energy density features. addition, both types usually contain additives for They are also expected to be widely used as a source enhancing battery performance, as well. of power for electric vehicles, which are just now Here, we introduce an example of analysis of becoming more widespread. The electrolytic solution electrolytic solvents used in lithium-ion rechargeable used in these batteries is typically a mixture of two batteries by HPLC.

n Analysis of Standard Solution Table 1 Analytical Conditions A total of 6 substances typically used in lithium-ion Column : Shim-pack FC-ODS (150 mm L. × 4.6 mm I.D.) rechargeable batteries were selected as analytical Mobile Phase : Water/ = 80/20 (v/v) targets: 5 electrolytic solvents (ethylene , Flow Rate : 1.2 mL/min , dimethyl carbonate, ethyl methyl Column Temp. : 40 °C carbonate, and diethyl carbonate) and one additive Injection Volume : 2 µL (vinylene carbonate). The structural formulae are Detection : RID-10A shown in Fig. 1. Fig. 2 shows the chromatogram obtained from analysis of a standard solution of the substances each at 10 g/L (except for vinylene carbonate, at 4 g/L), and Table 1 shows the analytical conditions used.

uRIU 20 O O O ■ Peaks 1. (10 g/L) 2. Vinylene Carbonate (4 g/L) O O O O O O 3. Propylene Carbonate (10 g/L) 15 4. Dimethyl Carbonate (10 g/L) 5. Ethyl Methyl Carbonate (10 g/L) Ethylene Carbonate Vinylene Carbonate 6. Diethyl Carbonate (10 g/L) 1 Propylene Carbonate 3

O O 10

OO OO 4 Dimethyl CarbonateEthyl Methyl Carbonate 5 2 5 O 6

OO 0 Diethyl Carbonate

0.0 2.5 5.07.5 10.0 12.5 15.017.520.022.5min

Fig. 1 Structures of Electrolytic Solvents Used in Lithium-Ion Fig. 2 Chromatogram of a Standard Mixture of Electrolytic Solvents Rechargeable Batteries No.L403

n Linearity Fig. 3 shows the calibration curves obtained using Excellent linearity was obtained for all the substances, standard solution concentrations from 0.5-50 g/L with R2 values greater than 0.9999. (except for vinylene carbonate, with 0.2-20 g/L).

350000 Ethylene 140000 Vinylene 350000 Dimethyl Carbonate Carbonate Carbonate 300000 300000 Propylene 120000 Ethyl Methyl Carbonate Carbonate 250000 100000 250000 Diethyl 200000 80000 200000 Carbonate Are a Are a Are a

150000 60000 150000 Peak Peak Peak

100000 40000 100000

50000 20000 50000

0 0 0 0204060002040 20 40 60 Concentration (g/L) Concentration (g/L)Concentration (g/L)

Fig. 3 Linearity

n Repeatability n Analysis of Electrolytic Solution for Lithium-Ion Rechargeable Battery Table 2 shows the relative standard deviations (n = 6) of the retention times and peak areas obtained from Table 2 shows the relative standard deviations (n = 6) analysis of standard solutions each at 10 g/L (except of the retention times and peak areas obtained from for vinylene carbonate, at 4 g/L). analysis of standard solutions each at 10 g/L (except for vinylene carbonate, at 4 g/L).

Table 2 Repeatability of Retention Time and Peak Area uRIU 50 Retention Time Peak Area Compounds ■ Peaks %RSD %RSD 1. Ethylene Carbonate 40 2. Vinylene Carbonate Ethylene Carbonate 0.05 0.27 4. Dimethyl Carbonate 5. Ethyl Methyl Carbonate

30 Vinylene Carbonate 0.04 0.30

Propylene Carbonate 0.04 0.38 20 4

Dimethyl Carbonate 0.03 0.39 10 1

Ethyl Methyl Carbonate 0.02 0.35 5 2 0

Diethyl Carbonate 0.02 0.59 0.0 2.55.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5min

Fig.4 Chromatogram of Electrolytic Solution for Lithium-ion Rechargeable Battery

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