CN115165812A - Method for testing degree of substitution of lithium carboxymethyl cellulose - Google Patents
Method for testing degree of substitution of lithium carboxymethyl cellulose Download PDFInfo
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- CN115165812A CN115165812A CN202210945263.4A CN202210945263A CN115165812A CN 115165812 A CN115165812 A CN 115165812A CN 202210945263 A CN202210945263 A CN 202210945263A CN 115165812 A CN115165812 A CN 115165812A
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Abstract
The invention relates to the technical field of substitution degree testing, in particular to a method for testing the substitution degree of lithium carboxymethyl cellulose. The method comprises the following steps: (1) Washing a lithium carboxymethyl cellulose sample by using a solvent, drying and weighing the washed sample, and recording the weight of the sample; (2) Preparing the sample dried in the step (1) into lithium oxide, adding water to the lithium oxide for dissolving to obtain a lithium hydroxide solution, and recording the volume; (3) Measuring the lithium ion concentration in the lithium hydroxide solution in the step (2), and calculating the millimole number of lithium contained in each gram of lithium carboxymethyl cellulose according to the weight, the volume and the lithium ion concentration of the sample; (4) And (4) calculating the substitution degree of the lithium carboxymethyl cellulose according to the millimole number of the lithium contained in each gram of the lithium carboxymethyl cellulose measured in the step (3). The method for testing the substitution degree of the lithium carboxymethyl cellulose can simply, conveniently and accurately test the substitution degree of the lithium carboxymethyl cellulose.
Description
Technical Field
The invention relates to the technical field of substitution degree testing, in particular to a method for testing the substitution degree of lithium carboxymethyl cellulose.
Background
The lithium ion battery has the characteristics of high working voltage, high energy density, long cycle life and the like, and is widely applied to the fields of consumer electronics, electric automobiles, energy storage power stations and the like.
In recent years, carboxymethyl cellulose lithium is beginning to be applied to a negative electrode plate of a lithium ion battery, and compared with sodium carboxymethyl cellulose, the carboxymethyl cellulose lithium as a thickening agent can effectively improve the number of lithium ions which freely move in the negative electrode plate, reduce the diffusion distance between the lithium ions and the surface of a negative electrode graphite material, and improve the efficiency of lithium intercalation and lithium deintercalation of the graphite material, so that the rate charge and discharge performance and the cycle life of the lithium ion battery are improved, and the more and more the carboxymethyl cellulose lithium is paid attention.
The technical indexes of the lithium carboxymethyl cellulose include degree of substitution, purity and viscosity. The most key index is the substitution degree, and the substitution degree of the carboxymethyl cellulose lithium refers to the condition that hydrogen on hydroxyl (-OH) on each cellulose macromolecular glucose ring is substituted by carboxymethyl (-CH) 2 COOLi), the degree of substitution determines the solubility of lithium carboxymethylcellulose, the greater the degree of substitution, the higher the solubility of lithium carboxymethylcellulose and the faster the rate of dissolution. However, few reports on the method for measuring the lithium substitution degree of carboxymethyl cellulose exist at present.
Disclosure of Invention
The invention provides a test method of a lithium carboxymethyl cellulose substitution degree, which is used for solving the defect that the measurement method of the lithium carboxymethyl cellulose substitution degree in the prior art is few and realizing accurate measurement of the lithium carboxymethyl cellulose substitution degree.
The invention provides a test method of a lithium substitution degree of carboxymethyl cellulose, which comprises the following steps:
(1) Washing a lithium carboxymethyl cellulose sample by using a solvent, drying and weighing the washed sample, and recording the weight of the sample;
(2) Preparing the sample dried in the step (1) into lithium oxide, adding water to the lithium oxide for dissolving to obtain a lithium hydroxide solution, and recording the volume;
(3) Determining the lithium ion concentration in the lithium hydroxide solution in the step (2), and calculating the millimole number of lithium contained in each gram of lithium carboxymethyl cellulose according to the weight, the volume and the lithium ion concentration of the sample;
(4) And (4) calculating the substitution degree of the lithium carboxymethyl cellulose according to the millimole number of lithium contained in each gram of the lithium carboxymethyl cellulose measured in the step (3).
In some embodiments, the test method for lithium substitution of carboxymethyl cellulose comprises the following steps:
(1) Washing a lithium carboxymethyl cellulose sample with a solvent, drying and weighing the washed sample, and recording the weight m (unit g) of the sample;
(2) Preparing the sample dried in the step (1) into lithium oxide, adding water to the lithium oxide for dissolving to obtain a lithium hydroxide solution, and recording the volume V (unit ml);
(3) Measuring the lithium ion concentration a (unit mmol/ml) in the lithium hydroxide solution in the step (2), and calculating the millimole number C (unit mmol/g) of lithium contained in each gram of lithium carboxymethyl cellulose according to the weight m, the volume V and the lithium ion concentration a of the sample measured in the step (2);
(4) And (4) calculating the substitution degree of the lithium carboxymethyl cellulose according to the millimole number C of the lithium carboxymethyl cellulose per gram measured in the step (3).
According to the test method of the lithium substitution degree of the carboxymethyl cellulose, provided by the invention, in the step (1), the solvent is one or more of methanol, ethanol, isopropanol, tert-butyl alcohol and acetone.
According to the test method for the lithium substitution degree of the carboxymethyl cellulose, provided by the invention, in the step (1), the solvent is any one of methanol, ethanol and isopropanol.
According to the test method of the lithium substitution degree of the carboxymethyl cellulose, provided by the invention, in the step (1), the mass fraction of the solvent is 75-95%.
According to the test method of the lithium substitution degree of the carboxymethyl cellulose, in the step (1), a washed sample is dried for 2-4h in vacuum at 115-125 ℃.
According to the test method of the lithium substitution degree of the carboxymethyl cellulose, provided by the invention, in the step (2), the carboxymethyl cellulose lithium sample obtained after drying in the step (1) is burned in a pure oxygen atmosphere to obtain lithium oxide.
Preferably, in the step (2), the lithium carboxymethyl cellulose sample is burned for 1 to 1.8 hours at 670 to 780 ℃ in a pure oxygen atmosphere to obtain the lithium oxide.
According to the test method of the lithium carboxymethyl cellulose substitution degree, provided by the invention, in the step (2), a lithium carboxymethyl cellulose sample is burned for 1-3h at 650-800 ℃ in a pure oxygen atmosphere to obtain lithium oxide.
According to the test method of the lithium substitution degree of the carboxymethyl cellulose, provided by the invention, in the step (3), the concentration of lithium ions in the lithium hydroxide solution is measured by using an inductively coupled plasma mass spectrometer.
According to the test method of the lithium substitution degree of the carboxymethyl cellulose, provided by the invention, in the step (3), the lithium ion concentration in the lithium hydroxide solution is diluted to be below 0.2mg/L, and then the lithium ion concentration in the lithium hydroxide solution is measured.
According to the test method of the lithium substitution degree of the carboxymethyl cellulose, provided by the invention, in the step (4), the formula for calculating the lithium substitution degree of the carboxymethyl cellulose is that the substitution degree DS = 0.162C/(1-0.064C).
The invention provides a method for testing the substitution degree of lithium carboxymethyl cellulose for a lithium ion battery, which comprises the following steps:
1. washing a sample of lithium carboxymethylcellulose with a solvent; the solvent can be one or more of methanol, ethanol, isopropanol, tert-butanol and acetone, and the mass fraction is 75-95%; vacuum drying the washed sample for 2-4h at 120 ℃; record the sample weight m (in g);
2.1, putting the lithium carboxymethyl cellulose sample in a muffle furnace, and burning the sample in pure oxygen atmosphere at the temperature of 650-800 ℃ for 1-3h to obtain lithium oxide; dissolving lithium oxide in water to obtain a lithium hydroxide solution, and recording the volume V (unit ml);
3. after the lithium hydroxide solution is diluted, an inductively coupled plasma mass spectrometer is adopted to measure the concentration of lithium ions in the solution, the concentration a (unit mmol/ml) of the lithium ions in the lithium hydroxide solution in 2 is calculated, and the millimole number C (unit mmol/g) of lithium contained in each gram of lithium carboxymethyl cellulose is calculated, wherein C = aV/m; the dilution multiple of lithium hydroxide is 200-2000 times, and the concentration of lithium ions in the solution is less than 0.2mg/L;
4. and calculating the lithium substitution degree of the carboxymethyl cellulose according to a formula, wherein the substitution degree DS = 0.162C/(1-0.064C). In the formula, 0.162 is the millimolar mass of one glucose unit in the cellulose, and the unit is (g/mmol); 0.064 is the millimolar mass (in g/mmol) of the carboxymethyl lithium group. The method directly uses the inductively coupled plasma mass spectrometer to measure the content of the lithium element, calculates the substitution degree through a formula, and has the advantages of simple operation, convenient calculation and higher accuracy of the test result.
The invention has the beneficial effects that:
(1) The method for measuring the lithium substitution degree of the carboxymethyl cellulose has the advantages of relatively small error, good repeatability, higher measuring precision and simple operation.
(2) The method comprises the steps of washing, drying, recording, washing and drying a lithium carboxymethyl cellulose sample, sequentially preparing lithium oxide and lithium hydroxide solution, calculating the lithium-containing millimole number per gram of lithium carboxymethyl cellulose by using the weight of the washed and dried sample, the volume of the lithium hydroxide solution and the concentration of lithium ions in the lithium hydroxide solution, and calculating the substitution degree according to the lithium-containing millimole number per gram of lithium carboxymethyl cellulose, so that the substitution degree of lithium carboxymethyl cellulose can be more accurately obtained.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
Example 1
The embodiment provides a method for testing a lithium substitution degree of carboxymethyl cellulose, which comprises the following steps:
1. weighing 1.5g of a sample of lithium carboxymethyl cellulose; washing with 95% ethanol solution for 10 times; drying the washed sample in vacuum for 2 hours at 120 ℃; record the sample weight m (in g);
2. putting the carboxymethyl cellulose lithium sample obtained in the step 1 into a muffle furnace, burning the sample in pure oxygen atmosphere at the temperature of 750 ℃ for 1h to obtain lithium oxide; dissolving lithium oxide in water to obtain a lithium hydroxide solution, and recording the volume V (unit ml);
3. after the lithium hydroxide solution is diluted by 250 times, the lithium ion concentration in the solution is measured by using an inductively coupled plasma mass spectrometer, the concentration a (unit mmol/ml) of lithium ions in the lithium hydroxide solution in the step 2 is calculated, and the millimole number C (unit mmol/g) of lithium contained in each gram of lithium carboxymethyl cellulose is calculated, wherein C = aV/m;
4. the degree of substitution of lithium carboxymethylcellulose is calculated according to the formula, wherein the degree of substitution DS = 0.162C/(1-0.064C). The final degree of substitution was 0.865.
Example 2
1. Weighing a 2.0g sample of lithium carboxymethyl cellulose; washing with isopropanol solution with mass fraction of 95% for 10 times; drying the washed sample for 3 hours in vacuum at 120 ℃; record the sample weight m (in g);
2. putting the lithium carboxymethyl cellulose sample obtained in the step 1 into a muffle furnace, and burning the sample in a pure oxygen atmosphere at the temperature of 750 ℃ for 1.5 hours to obtain lithium oxide; dissolving lithium oxide in water to obtain a lithium hydroxide solution, and recording the volume V (unit ml);
3. diluting the lithium hydroxide solution by 400 times, measuring the concentration of lithium ions in the solution by using an inductively coupled plasma mass spectrometer, calculating the concentration a (unit mmol/ml) of the lithium ions in the lithium hydroxide solution in the step 2, and calculating the millimole number C (unit mmol/g) of lithium contained in each gram of lithium carboxymethyl cellulose, wherein C = aV/m;
4. and calculating the lithium substitution degree of the carboxymethyl cellulose according to a formula, wherein the substitution degree DS = 0.162C/(1-0.064C). The final degree of substitution was 0.893.
Example 3
The embodiment provides a method for testing a lithium substitution degree of carboxymethyl cellulose, which comprises the following steps:
1. weighing a 2.0g sample of lithium carboxymethyl cellulose; washing with 90% methanol solution for 10 times; drying the washed lithium carboxymethyl cellulose sample for 3 hours in vacuum at 110 ℃; record the sample weight m (in g);
2. putting the lithium carboxymethyl cellulose sample subjected to vacuum drying in the step 1 into a muffle furnace, and burning the sample in pure oxygen atmosphere at the temperature of 700 ℃ for 1.0h to obtain lithium oxide; dissolving lithium oxide in water to obtain a lithium hydroxide solution, and recording the volume V (unit ml);
3. after the lithium hydroxide solution is diluted by 600 times, the lithium ion concentration in the solution is measured by using an inductively coupled plasma mass spectrometer, the concentration a (unit mmol/ml) of the lithium ions in the lithium hydroxide solution in the step 2 is calculated, and the millimole number C (unit mmol/g) of lithium contained in each gram of lithium carboxymethyl cellulose is calculated: c = aV/m;
4. and calculating the lithium substitution degree of the carboxymethyl cellulose according to a formula, wherein the substitution degree DS = 0.162C/(1-0.064C). The final degree of substitution was 0.887.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A test method for lithium substitution degree of carboxymethyl cellulose is characterized by comprising the following steps:
(1) Washing a lithium carboxymethyl cellulose sample by using a solvent, drying and weighing the washed sample, and recording the weight of the sample;
(2) Preparing the sample dried in the step (1) into lithium oxide, adding water to the lithium oxide for dissolving to obtain a lithium hydroxide solution, and recording the volume;
(3) Determining the lithium ion concentration in the lithium hydroxide solution in the step (2), and calculating the millimole number of lithium contained in each gram of lithium carboxymethyl cellulose according to the weight, the volume and the lithium ion concentration of the sample;
(4) And (4) calculating the substitution degree of the lithium carboxymethyl cellulose according to the millimole number C of the lithium carboxymethyl cellulose per gram measured in the step (3).
2. The method for testing the lithium substitution degree of carboxymethyl cellulose according to claim 1, wherein in the step (1), the solvent is one or more selected from methanol, ethanol, isopropanol, tert-butanol and acetone.
3. The method for testing degree of substitution of lithium carboxymethyl cellulose according to claim 1 or 2, wherein in the step (1), the solvent is any one of methanol, ethanol, and isopropanol.
4. The method for testing degree of substitution of lithium carboxymethyl cellulose according to any one of claims 1 to 3, wherein the mass fraction of the solvent in step (1) is 75 to 95%.
5. The method for measuring a degree of substitution of lithium carboxymethyl cellulose according to any one of claims 1 to 4, wherein, in the step (1), the washed sample is dried in vacuum at 115 to 125 ℃ for 2 to 4 hours.
6. The method for testing the degree of substitution with lithium carboxymethylcellulose according to any one of claims 1 to 5, wherein in the step (2), the lithium carboxymethylcellulose sample obtained after the drying in the step (1) is burned in a pure oxygen atmosphere to obtain lithium oxide.
7. The method for testing degree of substitution of lithium carboxymethyl cellulose according to any one of claims 1 to 6, wherein in step (2), a sample of lithium carboxymethyl cellulose is burned at 650 to 800 ℃ for 1 to 3 hours in a pure oxygen atmosphere to obtain lithium oxide.
8. The method for testing the degree of substitution with lithium carboxymethyl cellulose according to any one of claims 1 to 7, wherein in the step (3), the concentration of lithium ions in the lithium hydroxide solution is measured by using an inductively coupled plasma mass spectrometer.
9. The method for testing the degree of substitution with lithium carboxymethylcellulose according to any one of claims 1-8, wherein in the step (3), the concentration of lithium ions in the lithium hydroxide solution is measured after diluting the concentration of lithium ions in the lithium hydroxide solution to 0.2mg/L or less.
10. The method for testing the degree of substitution with lithium carboxymethyl cellulose according to any one of claims 1 to 9, wherein in the step (4), the degree of substitution with lithium carboxymethyl cellulose is calculated according to the formula of degree of substitution DS = 0.162C/(1-0.064C).
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