阅读说明：本技术 一种硫酸乙烯酯的水分检测方法 (Method for detecting moisture of vinyl sulfate ) 是由 侯涛 张天祥 李兴涛 付文博 梁丽莹 于 2021-08-12 设计创作，主要内容包括：本发明公开了一种硫酸乙烯酯的水分检测方法。该检测方法采用卡尔费休容量滴定法测量硫酸乙烯酯的水分,该检测方法中配置滴定剂和溶剂,检测时：首先,采用水分仪,进行滴定度进行标定,得到滴定剂的滴定度T,其次,对待测硫酸乙烯酯样品的水分进行测定,得到硫酸乙烯酯样品的水分含量W。本发明的技术方案是采用卡尔费休容量滴定法测量硫酸乙烯酯的水分,滴定剂和溶剂中都不含甲醇,滴定剂为碘、二氧化硫、氯代醇、咪唑组成,在反应溶剂中加入卤代醇、助溶剂,即可以保证卡尔费休反应所需要的羟基,让反应正常进行,又可以减缓硫酸乙烯酯与醇的反应,即使有轻微的酸性反应物生成,也可以通过溶剂中大量的咪唑进行中和,缓冲滴定溶液的PH值,减缓副反应,最终实现硫酸乙烯酯的水分滴定。(The invention discloses a method for detecting moisture of vinyl sulfate. The detection method adopts a Karl Fischer volume titration method to measure the moisture of the vinyl sulfate, a titrant and a solvent are configured in the detection method, and during detection: firstly, calibrating the titrimeter by adopting a moisture meter to obtain the titrimeter T of the titrimeter, and secondly, measuring the moisture of the to-be-measured vinyl sulfate sample to obtain the moisture content W of the vinyl sulfate sample. The invention adopts the technical scheme that a Karl Fischer volume titration method is adopted to measure the moisture of the vinyl sulfate, methanol is not contained in a titrant and a solvent, the titrant consists of iodine, sulfur dioxide, chlorohydrin and imidazole, halogenated alcohol and a cosolvent are added into a reaction solvent, so that the hydroxyl required by the Karl Fischer reaction can be ensured, the reaction can be normally carried out, the reaction of the vinyl sulfate and the alcohol can be slowed down, even if a slight acidic reactant is generated, the vinyl sulfate can be neutralized by a large amount of imidazole in the solvent, the PH value of the titration solution is buffered, the side reaction is slowed down, and finally the moisture titration of the vinyl sulfate is realized.)

1. A method for detecting the moisture of vinyl sulfate adopts a Karl Fischer volume titration method to measure the moisture of the vinyl sulfate, and is characterized in that:

preparing a titrant and a solvent in the detection method, wherein the titrant consists of iodine, sulfur dioxide, chlorohydrin and imidazole, halogenated alcohol and a cosolvent are added into the solvent, and the titrant and the solvent do not contain methanol;

the detection method comprises the following steps: firstly, calibrating the titrimeter by adopting a moisture meter to obtain the titrimeter T of the titrant, and specifically comprising the following steps of:

the first step is as follows: drying the moisture meter, the titrant, the solvent and the to-be-detected vinyl sulfate sample,

the second step is that: filling the titrant into a moisture meter, and connecting a burette; putting the prepared solvent in a titration cup, putting the titration cup into a moisture meter with the dosage of A ml, titrating until the solvent is anhydrous, and balancing the drift of the moisture meter;

the third step: a ul of deionized water is absorbed by a microsyringe, the weight is weighed by a decrement method to be accurate to 0.00001g, and a moisture meter is started to calibrate the titrimetric degree of the titrant;

calibrating a calculation formula: m ═ T_{Water (W)}/V_{Sign board}*1000；

Wherein T- - -the titer of Karl Fischer reagent mg/ml;

M_{water (W)}-the sample amount of water g at calibration;

V_{sign board}- -titration volume in ml at calibration of water;

secondly, measuring the moisture of the to-be-measured vinyl sulfate sample to obtain the moisture content W of the vinyl sulfate sample, and the specific steps are as follows: feeding vinyl sulfate into the sample by about 5-10g (to the accuracy of 0.0001 g); and (3) calculating the result after the instrument reaches the end point, wherein the calculation formula of the water content of the sample is as follows: w ═ T ═ V_{Sample (A)}/M_{Sample (A)}1000, wherein W is the sample moisture content ppm.

2. The method for detecting moisture in vinyl sulfate according to claim 1, wherein: the titrant comprises the following components in percentage by mass:

3. the method for detecting moisture in vinyl sulfate according to claim 2, wherein: the preparation method of the titrant comprises the following steps:

adding imidazole into chlorohydrin at normal temperature, fully stirring for dissolving, adding iodine, fully stirring for dissolving, placing the solution in an ice bath at the temperature of 0-10 ℃, introducing sulfur dioxide gas or adding liquid sulfur dioxide while stirring until the weight is increased to the content of the sulfur dioxide, and standing in a dark place to obtain the titrant.

4. The method for detecting moisture in vinyl sulfate according to claim 1, wherein: the solvent comprises the following components in percentage by mass:

50-80% of chlorohydrin

20 to 50 percent of cosolvent.

5. The method for detecting moisture in vinyl sulfate according to claim 4, wherein: the chlorohydrin is as follows: any one or combination of 2-chloroethanol and 2,2, 2-trichloroethanol; the cosolvent is: any one or combination of propylene carbonate, diethyl carbonate and acetonitrile.

6. The method for detecting moisture in vinyl sulfate according to claim 5, wherein: the preparation method of the solvent comprises the following steps: and mixing chlorohydrin and cosolvent at normal temperature, and fully stirring to obtain the solvent.

7. The method for detecting moisture in vinyl sulfate according to any one of claims 1 to 6, wherein: in the process of calibrating the titrimetry, the moisture meter, the titrant, the solvent and the to-be-tested vinyl sulfate sample are placed in a drying room with a dew point of-50 ℃ for drying treatment.

Technical Field

The invention relates to the technical field of a moisture detection method of an additive for lithium ion battery electrolyte, in particular to a moisture detection method of vinyl sulfate.

Background

The vinyl sulfate is an additive for lithium ion battery electrolyte, is widely applied as an important additive for battery film formation, and generally requires the water concentration to be lower than 200ppm in the use process. Therefore, when the lithium ion battery electrolyte is prepared, the moisture content of the vinyl sulfate needs to be measured, and currently, there are several ways for detecting the moisture content of the vinyl sulfate:

a Ka's furnace moisture meter detection method. This method has disadvantages in that: the melting point of the vinyl sulfate is only 99 ℃, and the temperature of the Karl Fischer furnace is set to be over 100 ℃, so that a detected sample is liquefied, and the test cannot be continued. If the temperature is set to be lower than 100 ℃, moisture cannot be completely gasified and enters the titration cell, so that the detection result is low and inaccurate.

A coulometric method direct sample introduction or a sample introduction analysis and measurement method after solvent dilution. The detection method has the following defects: the vinyl sulfate can slowly react with methanol in the Coulomb-method Karl-Fischer reagent to generate acid, so that the PH value in the Coulomb-method Karl-Fischer reagent is reduced, the buffer solution of the Coulomb-method Karl-Fischer reagent is invalid, the drift value of an instrument is increased, and the test cannot be continued.

The currently used karl fischer titrators can be divided into two methods, the volume method and the coulometry method, wherein,

the principle of the Capacity method of a Karl Fischer titrator is as follows: the Karl Fischer volumetric method is based primarily on electrochemical reactions for determining water content. The Karl Fischer's reagent contains active ingredients such as pyridine and iodine, and can be measured and dropped into a reaction tank. Water consumption was complete until the end of the reaction was titrated. At this point, the solution between the two platinum electrodes began conducting, and the end point was reached as indicated by the current, and the titration was stopped. Thus, the water content in the solution can be calibrated by measuring the volume (volume) of reagent consumed.

The coulometric method (electric measurement method) measurement principle of the Karl Fischer titrator is as follows: the coulometry is based on the consumption of iodine in water after the sample is dissolved in an electrolyte containing a specific iodine-containing solvent, but the required iodine is no longer titrated with a calibrated iodine-containing reagent, but is oxidized to iodine in solution by an electrolytic process. The iodine reacts with the water in the sample. The endpoint is represented by a double platinum electrode. When the iodine concentration in the electrolyte is restored to the original concentration, the electrolysis is stopped. And then, calculating the water content of the sample to be measured according to a Faraday's law of electrolysis.

In the current production process of lithium ion batteries, no improvement is provided for a method for detecting the moisture of vinyl sulfate, and only the improvement is generally provided for reducing the moisture of the vinyl sulfate, for example, the method is disclosed in Chinese patent numbers: 201610651817.4, which proposes a method for removing water and reducing acid of vinyl sulfate, the technical proposal of the patent application is that: and adding a water and acid removing agent into the purifying column, connecting the water and acid removing tank and the purifying column in a sealing way by using a stainless steel pipeline, and starting a circulating system to continuously circulate the mixed solution for water and acid removal.

In order to improve the manufacturing accuracy of the lithium battery and determine the moisture content of the vinyl sulfate, the inventor provides the following technical scheme through continuous experiments.

Disclosure of Invention

The invention aims to provide a method for detecting moisture in vinyl sulfate.

In order to solve the technical problems, the invention adopts the following technical scheme: a method for detecting the moisture content of vinyl sulfate adopts a Karl Fischer volume titration method to measure the moisture content of the vinyl sulfate, and a titrant and a solvent are prepared in the method, wherein the titrant consists of iodine, sulfur dioxide, chlorohydrin and imidazole, halogenated alcohol and a cosolvent are added into the solvent, and the titrant and the solvent do not contain methanol; the detection method comprises the following steps: firstly, calibrating the titrimeter by adopting a moisture meter to obtain the titrimeter T of the titrant, and specifically comprising the following steps of: the first step is as follows: drying a moisture meter, a titrant, a solvent and a to-be-detected vinyl sulfate sample, and a second step of: filling the titrant into a moisture meter, and connecting a burette; putting the prepared solvent in a titration cup, putting the titration cup into a moisture meter with the dosage of A ml, titrating until the solvent is anhydrous, and balancing the drift of the moisture meter; the third step: sucking A ul deionized water by a microsyringe, weighing by a decrement method to 0.00001g, and starting a moisture meter for calibrationThe titrimetric of the titrant is obtained; calibrating a calculation formula: m ═ T_{Water (W)}/V_{Sign board}1000; secondly, measuring the moisture of the to-be-measured vinyl sulfate sample to obtain the moisture content W of the vinyl sulfate sample, and the specific steps are as follows: feeding vinyl sulfate into the sample by about 5-10g (to the accuracy of 0.0001 g); and (3) calculating the result after the instrument reaches the end point, wherein the calculation formula of the water content of the sample is as follows: w ═ T ═ V_{Sample (A)}/M_{Sample (A)}1000, wherein W is the sample moisture content ppm.

Further, in the above technical scheme, the components and mass ratio of the titrant are as follows:

further, in the above technical solution, the configuration method of the titrant includes: adding imidazole into chlorohydrin at normal temperature, fully stirring for dissolving, adding iodine, fully stirring for dissolving, placing the solution in an ice bath at the temperature of 0-10 ℃, introducing sulfur dioxide gas or adding liquid sulfur dioxide while stirring until the weight is increased to the content of the sulfur dioxide, and standing in a dark place to obtain the titrant.

Further, in the above technical scheme, the solvent comprises the following components in parts by mass:

50-80% of chlorohydrin

20 to 50 percent of cosolvent.

Further, in the above technical solution, the chlorohydrin is: any one or combination of 2-chloroethanol and 2,2, 2-trichloroethanol; the cosolvent is: any one or combination of propylene carbonate, diethyl carbonate and acetonitrile.

Further, in the above technical solution, the solvent preparation method comprises: and mixing chlorohydrin and cosolvent at normal temperature, and fully stirring to obtain the solvent.

Further, in the above technical scheme, in the process of performing titrimetric calibration, the moisture meter, the titrant, the solvent and the to-be-measured vinyl sulfate sample are placed in a drying room with a dew point of-50 ℃ for drying treatment.

The invention adopts the technical scheme that a Karl Fischer volume titration method is adopted to measure the moisture of the vinyl sulfate, methanol is not contained in a titrant and a solvent, the titrant consists of iodine, sulfur dioxide, chlorohydrin and imidazole, halogenated alcohol and a cosolvent are added into a reaction solvent, so that the hydroxyl required by the Karl Fischer reaction can be ensured, the reaction can be normally carried out, the reaction of the vinyl sulfate and the alcohol can be slowed down, even if a slight acidic reactant is generated, the vinyl sulfate can be neutralized by a large amount of imidazole in the solvent, the PH value of the titration solution is buffered, the side reaction is slowed down, and finally the moisture titration of the vinyl sulfate is realized.

Detailed Description

The present invention will be described in detail with reference to specific examples.

The invention relates to a method for detecting the moisture of vinyl sulfate, which adopts a Karl Fischer volume titration method to measure the moisture of the vinyl sulfate.

In the detection method, a titrant and a solvent are required to be prepared, wherein the titrant consists of iodine, sulfur dioxide, chlorohydrin and imidazole, halogenated alcohol and a cosolvent are added into the solvent, and the titrant and the solvent do not contain methanol.

The titrant comprises the following components in percentage by mass:

the preparation method of the titrant comprises the following steps:

adding imidazole into chlorohydrin at normal temperature, stirring to dissolve, adding iodine, stirring to dissolve, and cooling in ice bath at 0-10 deg.C. While stirring, slowly introducing sulfur dioxide gas or adding liquid sulfur dioxide until the weight is increased to the required weight percent of sulfur dioxide. Standing for 24 hours in dark. The reagent was filled in a titration flask of a volumetric Karl Fischer moisture meter as a titrant.

The solvent comprises the following components in percentage by mass:

50-80% of chlorohydrin

20 to 50 percent of cosolvent.

The chlorohydrin is as follows: any one or combination of 2-chloroethanol and 2,2, 2-trichloroethanol; the cosolvent is: any one or combination of propylene carbonate, diethyl carbonate and acetonitrile.

The preparation method of the solvent comprises the following steps: and mixing chlorohydrin and cosolvent at normal temperature, and fully stirring to obtain the solvent.

The detection method comprises the following steps: firstly, calibrating the titrimeter by adopting a moisture meter to obtain the titrimeter T of the titrant, and specifically comprising the following steps of:

the first step is as follows: putting a volumetric method moisture meter, a Karl Fischer reagent and a sample of the to-be-detected vinyl sulfate into a drying room with a dew point of-50 ℃ for operation;

the second step is that: firstly, filling a prepared titration agent of a Karl Fischer volumetric method into a titration bottle of a moisture meter, and connecting a titration tube; taking 50-100ml of prepared solvent for the Karl Fischer volumetric method in a titration cup, loading into an instrument, and titrating until the solvent is anhydrous and the instrument drift reaches balance;

the third step: weighing about 5mg of pure water (accurate to 0.01mg) by using a 5ul micro-injection needle, and calibrating the titer of the titrant;

calibrating a calculation formula: m ═ T_{Water (W)}/V_{Sign board}*1000；

Wherein T- - -the titer of Karl Fischer reagent mg/ml;

M_{water (W)}-the sample amount of water g at calibration;

V_{sign board}- -titration volume in ml at calibration of water;

secondly, measuring the moisture of the to-be-measured vinyl sulfate sample to obtain the moisture content W of the vinyl sulfate sample, and the specific steps are as follows: vinyl sulfate esterInjecting about 5-10g (to the precision of 0.0001 g); and (3) calculating the result after the instrument reaches the end point, wherein the calculation formula of the water content of the sample is as follows: w ═ T ═ V_{Sample (A)}/M_{Sample (A)}1000, wherein W is the sample moisture content ppm.

Two different batches of samples of vinyl sulfate were tested as follows.

In the detection, the components and the mass ratio of the titrant are as follows:

in the detection, the solvent comprises the following components in percentage by mass:

50 percent of 2,2, 2-trichloroethanol

50 percent of propylene carbonate

Firstly, putting a moisture meter, a Karl Fischer reagent and a sample to be detected into a drying room with the dew point of-50 ℃ for operation, firstly, filling a prepared Karl Fischer volumetric method titrant into the instrument, and connecting a burette at the same time; 50ml of prepared solvent for Karl Fischer volumetric method is put into a titration cup, an instrument is put into the titration cup, the titration is carried out until the solvent is anhydrous, the instrument drift is balanced, 5ul of deionized water is absorbed by a 5ul microsyringe, the weighing is carried out by a decrement method until the weight is accurate to 0.00001g, and the instrument is started to calibrate the titre of the titrant.

According to a calibration calculation formula: m ═ T_{Water (W)}/V_{Sign board}1000 the titre of the titrant was calculated.

The following are the titer values obtained after six tests, respectively.

Next, the sample is tested.

Detecting after the instrument is stable, and respectively testing the two batches of the vinyl sulfate for 6 times, wherein in the testing process, the sample introduction of each time of the vinyl sulfate is about 5-10g (accurate to 0.0001 g); and (3) calculating according to the water content of the sample after the instrument reaches the end point:

W＝T*V_{sample (A)}/M_{Sample (A)}1000 ppm sample moisture content.

The following are the water content values obtained after six tests on two batches of samples.

Through the test experiments, for test samples of different batches, the deviation value of the test result for six times is within a reasonable range, the test result is stable, and the accuracy is high.

Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.