阅读说明：本技术 一种基于核磁共振定量测量双三氟甲基磺酰亚胺锂的方法 (Method for quantitatively measuring lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance ) 是由 耿谦 商洪涛 吕灵华 袁瑞玲 张明杰 郑艺 杨少飞 罗建志 于 2019-08-20 设计创作，主要内容包括：本发明涉及一种基于核磁共振定量测量双三氟甲基磺酰亚胺锂的方法,属于核磁共振检测方法技术领域。本发明所述方法是通过测定LiTFSI样品及内标物的定量目标峰在氘代试剂中的纵向弛豫时间,设定核磁共振仪的脉冲倾倒角和弛豫延迟时间,再测定LiTFSI样品及内标物的定量目标峰在氘代试剂中的积分值,从而获得LiTFSI样品中纯的LiTFSI相对于内标物的摩尔比,根据内标物的质量,计算纯的LiTFSI的质量,进而计算出LiTFSI样品的纯度,该方法能够准确、稳定、快速的测定双三氟甲基磺酰亚胺锂的纯度。(The invention relates to a method for quantitatively measuring lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance, and belongs to the technical field of nuclear magnetic resonance detection methods. The method comprises the steps of measuring the longitudinal relaxation time of quantitative target peaks of a LiTFSI sample and an internal standard substance in a deuterated reagent, setting a pulse dumping angle and relaxation delay time of a nuclear magnetic resonance spectrometer, measuring the integral value of the quantitative target peaks of the LiTFSI sample and the internal standard substance in the deuterated reagent, obtaining the molar ratio of pure LiTFSI in the LiTFSI sample relative to the internal standard substance, calculating the mass of the pure LiTFSI according to the mass of the internal standard substance, and further calculating the purity of the LiTFSI sample.)

1. A method for quantitatively measuring bis (trifluoromethyl) sulfimide lithium based on nuclear magnetic resonance is characterized by comprising the following steps: the steps of the method are as follows,

(1) measuring the longitudinal relaxation time of quantitative target peaks of a lithium bistrifluoromethylsulfonyl imide sample and an internal standard substance in a deuterated reagent under the resonance frequency of 377MHz by adopting a fluorine atom inversion-recovery longitudinal relaxation experimental method, and obtaining the maximum longitudinal relaxation time through comparison;

(2) setting detection parameters of the nuclear magnetic resonance apparatus: the resonance frequency is 377MHz, the spectrum width is 20 ppm-100 ppm, the test temperature is 23 ℃, the sampling accumulation times are not less than 16 times, the pulse flip angle is 30-90 degrees, and the relaxation delay time is not less than three times of the maximum longitudinal relaxation time;

(3) measuring the integral value of quantitative target peaks of a lithium bistrifluoromethylsulfonyl imide sample and an internal standard substance in a deuterated reagent;

(4) the purity of the lithium bistrifluoromethylsulfonimide sample was calculated according to formula (1):

W％＝(mIS×FIS×AS×MS×100％)/(MIS×AIS×FS×mS) (1)

w% -purity of the lithium bistrifluoromethylsulfonyl imide sample;

mS — mass of lithium bis (trifluoromethylsulfonyl) imide sample, g;

quantifying the fluorine atom number of a target peak by using an FS-bis (trifluoromethyl) sulfimide lithium sample;

MS-molar mass of pure lithium bis (trifluoromethylsulfonyl) imide, g/mol;

AS-integrated value of quantitative target peak of lithium bistrifluoromethylsulfonyl imide sample;

mIS mass of internal standard, g;

FIS-internal standard substance quantifies the fluorine atom number of the target peak;

MIS — molar mass of internal standard, g/mol;

AIS-integral value of quantitative target peak of internal standard substance;

wherein the chemical shift of a quantitative target peak of the lithium bis (trifluoromethylsulfonyl) imide sample is-79 ppm; the internal standard substance does not react with lithium bis (trifluoromethyl) sulfonyl imide, and the chemical shift of fluorine atom of the internal standard substance is in the range of 300ppm to-200 ppm and does not contain-79 ppm.

2. The method for quantitative measurement of lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance according to claim 1, wherein: the pulse flip angle is 30 ° or 90 °.

3. The method for quantitative measurement of lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance according to claim 1, wherein: the deuterated reagent is deuterium oxide, deuterated methanol, deuterated acetonitrile, deuterated chloroform or deuterated dimethyl sulfoxide.

4. The method for quantitative measurement of lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance according to claim 3, wherein: the deuterated reagent is deuterated dimethyl sulfoxide.

5. The method for quantitative measurement of lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance according to claim 1, wherein: the internal standard substance is 1, 4-bis (trifluoromethyl) benzene, trifluoromethyl benzene, hexafluorobenzene, trifluoroacetic acid, sodium fluoride, 4-fluoro cinnamic acid or 2-bromo-4-fluoro acetanilide.

6. The method for quantitative measurement of lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance according to claim 5, wherein: the internal standard substance is 1, 4-bis (trifluoromethyl) benzene.

7. The method for quantitative measurement of lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance according to claim 1, wherein: in the step (3), the concentration of the lithium bistrifluoromethylsulfonyl imide in the deuterated reagent is 10 mg/mL-20 mg/mL.

Technical Field

The invention relates to a method for quantitatively measuring lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance, and belongs to the technical field of nuclear magnetic resonance detection methods.

Background

Lithium bis (trifluoromethylsulfonyl) imide [ LiN (CF)₃SO₂)₂Hereinafter abbreviated as LiTFSI]Is an electrolyte substance with wide application prospect. The LiTFSI has proper conductivity, high thermal stability and electrochemical stability, small probability of side reaction, no generation of corrosive gases such as HF and the like, and is an indispensable high-tech product in the electrolyte of the current lithium ion secondary battery. With the continuous development of the lithium battery industry, the lithium battery can be used as an antistatic agent, an ionic liquid and other multiple purposes, and the market demand is increasing.

In the production process, various impurities exist due to the use of various chemical reagents, which affects the quality of the production of the LiTFSI, the difference of the application of different grades of LiTFSI is huge, and the LiTFSI needs to be quantitatively analyzed in production to test the main content, the impurity components and the content thereof. Nuclear magnetic resonance fluorine spectrum (¹⁹F NMR) technique is mainly used for structural determination of fluorine-containing compounds, and the basic principle is that¹⁹The area of the resonance peak in F NMR is proportional to the number of fluorine atoms contained in the resonance peak. At present, no report for quantitative determination of LiTFSI purity by adopting nuclear magnetic resonance fluorine spectrum exists.

Disclosure of Invention

In view of the above, the present invention provides a method for quantitatively measuring lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance, which comprises the steps of measuring longitudinal relaxation times of quantitative target peaks of a LiTFSI sample and an internal standard substance in a deuterated reagent, setting a pulse dump angle and a relaxation delay time of a nuclear magnetic resonance apparatus, and measuring an integral value of the quantitative target peaks of the LiTFSI sample and the internal standard substance in the deuterated reagent, thereby obtaining a molar ratio of pure LiTFSI in the LiTFSI sample relative to the internal standard substance, calculating a mass of pure LiTFSI according to the mass of the internal standard substance, and further calculating the purity of the LiTFSI sample.

The purpose of the invention is realized by the following technical scheme.

A method for quantitatively measuring lithium bistrifluoromethylsulfonyl imide based on nuclear magnetic resonance comprises the following steps:

(1) measuring the longitudinal relaxation time (T) of quantitative target peaks of a lithium bistrifluoromethylsulfonyl imide sample and an internal standard substance in a deuterated reagent under the resonance frequency of 377MHz by adopting a fluorine atom inversion-recovery longitudinal relaxation experimental method₁) The maximum longitudinal relaxation time (T) is obtained by comparison_1max)；

(2) Setting detection parameters of the nuclear magnetic resonance apparatus: the resonance frequency is 377MHz, the spectrum width is 20 ppm-100 ppm, the test temperature is 23 ℃, the sampling accumulation frequency is not less than 16 times, the pulse flip angle is 30-90 degrees, and the relaxation delay time (d)₁) Not less than 3T_1max；

(3) Measuring the integral value of quantitative target peaks of a lithium bistrifluoromethylsulfonyl imide sample and an internal standard substance in a deuterated reagent;

(4) the purity of the lithium bistrifluoromethylsulfonimide sample was calculated according to formula (1):

W％＝(mIS×FIS×AS×MS×100％)/(MIS×AIS×FS×mS) (1)

w% -purity of the lithium bistrifluoromethylsulfonyl imide sample;

mS — mass of lithium bis (trifluoromethylsulfonyl) imide sample, g;

quantifying the fluorine atom number of a target peak by using an FS-bis (trifluoromethyl) sulfimide lithium sample;

MS-molar mass of pure lithium bis (trifluoromethylsulfonyl) imide, g/mol;

AS-integrated value of quantitative target peak of lithium bistrifluoromethylsulfonyl imide sample;

mIS mass of internal standard, g;

FIS-internal standard substance quantifies the fluorine atom number of the target peak;

MIS — molar mass of internal standard, g/mol;

AIS-internal standard quantitates the integral value of the target peak.

Wherein the chemical shift of a quantitative target peak of the lithium bis (trifluoromethylsulfonyl) imide sample is-79 ppm; the internal standard substance does not chemically react with the lithium bis (trifluoromethyl) sulfonyl imide, the chemical shift of the fluorine atom of the internal standard substance is within the range of 300ppm to-200 ppm and does not overlap with the chemical shift of the fluorine atom in the lithium bis (trifluoromethyl) sulfonyl imide, namely-79 ppm

Further, the pulse flip angle is 30 ° or 90 °.

Further, the deuterated reagent is deuterium oxide, deuterated methanol, deuterated acetonitrile, deuterated chloroform or deuterated dimethyl sulfoxide, and is preferably deuterated dimethyl sulfoxide.

Further, the internal standard substance is 1, 4-bis (trifluoromethyl) benzene, trifluoromethyl benzene, hexafluorobenzene, trifluoroacetic acid, sodium fluoride, 4-fluorocinnamic acid or 2-bromo-4-fluoroacetanilide, preferably 1, 4-bis (trifluoromethyl) benzene.

Further, in the step (3), the concentration of the lithium bistrifluoromethylsulfonyl imide in the deuterated reagent is 10 mg/mL-20 mg/mL.

Has the advantages that:

(1) according to the invention, fluorine nuclear magnetic resonance is used for carrying out quantitative analysis on the bis-trifluoromethyl sulfonyl imide lithium for the first time, so that the interference of a small amount of organic compounds and lithium fluoride contained in the bis-trifluoromethyl sulfonyl imide lithium is overcome;

(2) the system of the invention determines the longitudinal relaxation time of the target signal which can be used for fluorine nuclear magnetic quantification, determines the pulse flip angle and the relaxation delay time on the basis, and ensures the accuracy of the detection method;

(3) according to the invention, the resonance peak with the chemical shift of-79 ppm is selected as the quantitative target peak of the lithium bistrifluoromethylsulfonyl imide sample, so that the detection result has higher accuracy, the calculation is simpler and more convenient, and the detection speed is higher;

(4) the method has the advantages of simple pretreatment of the lithium bis (trifluoromethyl) sulfonyl imide sample, short analysis time, no need of testing a reference substance of the lithium bis (trifluoromethyl) sulfonyl imide, good reproducibility, convenience in carrying out content analysis and quality control of lithium salt without ultraviolet absorption, and solves the technical problem of purity determination of the lithium bis (trifluoromethyl) sulfonyl imide;

(5) the method has the advantages that the test is carried out at 23 ℃, so that less liquid nitrogen consumption is ensured, the long-time operation of the nuclear magnetic resonance instrument is ensured, the resolution of the nuclear magnetic resonance spectrum is improved, and the accuracy of detecting the purity of the lithium bistrifluoromethylsulfonyl imide is improved;

(6) according to the invention, the detection concentration of the lithium bistrifluoromethylsulfonyl imide is 10 mg/mL-20 mg/mL, so that a nuclear magnetic resonance apparatus can accurately detect a resonance signal, and the accuracy of detecting the purity of the lithium bistrifluoromethylsulfonyl imide is further improved.

Drawings

FIG. 1 is a nuclear magnetic resonance fluorine spectrum of example 1.

FIG. 2 is a nuclear magnetic resonance fluorine spectrum of example 2.

FIG. 3 is a nuclear magnetic resonance fluorine spectrum of example 3.

Detailed Description

The invention is further illustrated by the following figures and detailed description, wherein the process is conventional unless otherwise specified, and the starting materials are commercially available from a public disclosure without further specification.

In the following examples, T_1maxDetermination of (maximum longitudinal relaxation time): a1.000 g sample of lithium bistrifluoromethylsulfonimide and 800mg of 1, 4-bistrifluoromethylbenzene were placed in a nuclear magnetic tube, and 0.5mL of DMSO-d was added₆(deuterated dimethyl sulfoxide) dissolution for¹⁹F NMR test; setting the resonance frequency of a nuclear magnetic resonance apparatus to be 377MHz, setting the relaxation delay time range to be 1-30 seconds, and adopting a fluorine atom inversion-recovery longitudinal relaxation time experimental method to determine the T of quantitative target peaks of a lithium bistrifluoromethylsulfonyl imide sample and 1, 4-bistrifluoromethylbenzene₁(longitudinal relaxation time) and using Bruker's T₁The calculation program calculates that the lithium bistrifluoromethylsulfonyl imide sample has a signal peak T at-79 ppm_1maxThe signal peak T is 10.218s, 1, 4-bistrifluoromethylbenzene-63 ppm_1maxIs 4.996;

the purity of the lithium bistrifluoromethylsulfonyl imide sample obtained in the following examples was 99.9% by impurity subtraction.