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EP-4353714-B1 - GAS CHROMATOGRAPHY ANALYSIS METHODS BASED ON ETHYLENE CARBONATE SPLIT INJECTION

EP4353714B1EP 4353714 B1EP4353714 B1EP 4353714B1EP-4353714-B1

Inventors

  • YOKOYAMA, MASAKO

Dates

Publication Date
20260506
Application Date
20220316

Claims (14)

  1. A gas chromatography analytical method based on an ethylene carbonate split injection technique, comprising: injecting ethylene carbonate to be analyzed into a gas chromatography analyzer, vaporizing the injected ethylene carbonate in a single taper liner not packed with wool, introducing a part of the vaporized ethylene carbonate into a capillary column with an inert gas flowing and allowing the ethylene carbonate to pass through the capillary column, and detecting the ethylene carbonate having passed through the capillary column with a detector.
  2. A gas chromatography analytical method based on an ethylene carbonate split injection technique, comprising: injecting molten ethylene carbonate to be analyzed into a gas chromatography analyzer, vaporizing the injected ethylene carbonate in a liner, introducing a part of the vaporized ethylene carbonate into a capillary column with an inert gas flowing and allowing the ethylene carbonate to pass through the capillary column, and detecting the ethylene carbonate having passed through the capillary column with a detector.
  3. The gas chromatography analytical method according to claim 2, wherein the liner is a single taper liner not packed with wool.
  4. The gas chromatography analytical method according to any one of claims 1 to 3, wherein a water content of the ethylene carbonate to be analyzed is 100 ppm or less.
  5. The gas chromatography analytical method according to any one of claims 1 to 4, wherein a purity of the ethylene carbonate to be analyzed is 99.5% by mass or more.
  6. The gas chromatography analytical method according to any one of claims 1 to 5, wherein a carrier gas pressure during injection of the ethylene carbonate to be analyzed into the gas chromatography analyzer is set to 1.5 to 30 times a common operating pressure, and after injection, the carrier gas pressure is set to the common operating pressure.
  7. The gas chromatography analytical method according to any one of claims 1 to 6, further comprising collecting the ethylene carbonate to be analyzed into a syringe for injection in a gas chromatograph, under a dry inert gas.
  8. The gas chromatography analytical method according to any one of claims 1 to 6, further comprising introducing the ethylene carbonate to be analyzed into a vial for an autoinjector of a gas chromatograph and capping the vial, under a dry inert gas.
  9. The gas chromatography analytical method according to any one of claims 1 to 8, further comprising sampling the ethylene carbonate to be analyzed under dry air, under a dry inert gas, or under vacuum.
  10. The gas chromatography analytical method according to any one of claims 1 to 9, wherein a liquid phase in the capillary column contains at least one component selected from the group consisting of cyanopropyl- and phenyl-substituted polysiloxane, cyanopropyl- and methyl-substituted polysiloxane, trifluoropropyl-substituted polysiloxane, phenyl-substituted polysiloxane, and polyethylene glycol.
  11. The gas chromatography analytical method according to any one of claims 1 to 10, wherein an injection port temperature in the gas chromatography analyzer is 250 to 290°C.
  12. The gas chromatography analytical method according to any one of claims 1 to 11, wherein a detector temperature in the gas chromatography analyzer is 240 to 300°C.
  13. The gas chromatography analytical method according to any one of claims 1 to 12, wherein the inert gas allowed to flow in the capillary column is nitrogen or helium.
  14. The gas chromatography analytical method according to any one of claims 1 to 13, wherein a split ratio (flow rate of inert gas discharged out of capillary column vs flow rate of inert gas introduced into capillary column) is 5:1 to 50:1.

Description

Technical Field The present invention relates to a gas chromatography analytical method. Background Art In recent years, interest in lithium-ion secondary batteries (LiB) has been growing increasingly because they contribute to reduction of global environmental burden, such as energy saving or resource saving. The range of use of recent LiB is continually expanding up to not only batteries for mobile devices, such as smartphones and tablets, but also in-vehicle batteries for hybrid electric vehicles (HEV), electric vehicles (EV), etc., and further, batteries for energy storage. LiB is a secondary battery in which lithium ions move between a positive electrode and a negative electrode to carry out electrical charge and discharge, and it is composed of a positive electrode, a negative electrode, a separator, and an electrolyte. Highly polar ethylene carbonate is a typical electrolyte solvent because it has features (advantages) that it dissolves a lithium salt at a high concentration to cause dissociation, and in addition, it forms a coating film of nanometer order on the negative electrode surface of a carbon material to stabilize the carbon material of the negative electrode. However, there are concerns that impurities of ethylene carbonate have an influence on the battery performance during the battery charge and discharge cycle, and therefore, for the electrolyte applications, high-purity ethylene carbonate is used. Regarding the lithium-ion battery manufacturing field, a variety of methods for measuring a hetero-alcohol content in ethylene carbonate particularly in a lithium-ion battery electrolyte has been proposed (e.g., Patent Literature 1). EP 2 374 803 A1 discloses an analytical method comprising injecting ethylene carbonate to be analyzed into a gas chromatography analyzer. Citation List Patent Literature Patent Literature 1: CN105319303A Summary of Invention Technical Problem In the analysis of a purity of high-purity ethylene carbonate, it has become apparent that by decomposition of ethylene carbonate in gas chromatography analyzer, impurities, such as ethylene oxide (EO), ethylene glycol (EG), and diethylene glycol (DEG), are formed in amounts that are non-negligible as accuracy of the measurement results. On that account, an analytical method for ethylene carbonate with higher accuracy has been desired. That is to say, it is an object of the present invention to provide a gas chromatography analytical method in which a purity of high-purity ethylene carbonate can be accurately analyzed by gas chromatography analysis. Solution to Problem In order to solve the above-mentioned problem, the present inventor has earnestly studied, and as a result, he has found that a purity of high-purity ethylene carbonate can be accurately analyzed by introducing a sample into a capillary column using a single taper liner that is not packed with wool in a gas chromatography analytical method based on a split technique, and he has arrived at the present invention. Furthermore, the present inventor has earnestly studied in order to solve the above-mentioned problem, and as a result, he has found that a purity of high-purity ethylene carbonate can be accurately analyzed by injecting molten ethylene carbonate into a gas chromatography analyzer in a gas chromatography analytical method based on a split technique, and he has arrived at the present invention. The present invention is defined in the appended claims. Advantageous Effect of Invention According to the present invention, a gas chromatography analytical method in which a purity of high-purity ethylene carbonate can be accurately analyzed by gas chromatography analysis can be provided. Brief Description of Drawings [Figure 1] Figure 1 is a schematic block diagram of gas chromatography analyzer 1.[Figure 2] Figure 2 is a schematic block diagram showing one example of a single taper liner. Description of Embodiment Hereinafter, an embodiment of the present invention (also referred to as the "present embodiment" hereinafter) will be described in detail. The present invention is not limited to the present embodiment below, and can be carried out by variously modifying it within the range of the gist thereof. The gas chromatography analytical method according to the present embodiment is a gas chromatography analytical method based on an ethylene carbonate split injection technique, including: injecting ethylene carbonate to be analyzed into a gas chromatography analyzer,vaporizing the injected ethylene carbonate in a single taper liner not packed with wool,introducing a part of the vaporized ethylene carbonate into a capillary column with an inert gas flowing and allowing the ethylene carbonate to pass through the capillary column, anddetecting the ethylene carbonate having passed through the capillary column with a detector. According to the present embodiment, the above-mentioned constitution is included, and therefore, a purity of high-purity ethylene carbonate