A method for detecting battery-grade lithium salt purity

Abstract

The application discloses a kind of detection methods for battery grade lithium salt purity, called lithium salt is placed in conical flask stirring dissolution;In the first solution to be measured, drop methyl red-bromocresol green indicator is added, and titrated with hydrochloric acid standard titration solution to wine red;Second solution to be measured, drop phenothalin indicator is added, and titrated with methyl red-bromocresol green indicator to wine red;Finally, the purity percentage of lithium salt is calculated.The detection method of the application can be effectively used for the analysis and detection of battery grade lithium carbonate, lithium hydroxide monohydrate and lithium oxide.Compared with the traditional method, the sample consumption is less, the hydrochloric acid consumption is less, and it is more environmentally friendly.Meanwhile, it can effectively solve the problem that the influence of carbonate ion consumption of hydrochloric acid is not considered in the traditional national standard, thereby improving the accuracy of detection.Meanwhile, the method can also be effectively used for the analysis and detection of battery grade lithium oxide.

Description

Technical Field

[0001] This invention relates to the field of battery material testing, and more specifically to a method for testing the purity of battery-grade lithium salts. Background Technology

[0002] In recent years, the market for high-tech, high-value-added products, such as lithium batteries, which are leading the green transformation, has been booming. According to relevant industry data, the demand for batteries will exceed 2TWh within two years and reach more than 6TWh by 2030. At that time, the requirements for product performance, cost, and technology will only continue to rise.

[0003] Lithium-ionization, energy conservation, and high-speed operation will be the future development trends of lithium batteries. As an important component of the new energy field, the lithium battery industry has developed rapidly and has become a new investment focus in the manufacturing sector. Lithium battery companies are increasing their investment in the construction of new factories, hoping to increase production capacity and leverage economies of scale to succeed. Energy conservation and high-speed operation in lithium battery manufacturing have become new industry trends. Battery-grade anhydrous lithium hydroxide, lithium hydroxide monohydrate, and lithium oxide are all lithium compounds, located in the midstream smelting and processing stage of the lithium battery industry chain. They are important lithium sources for lithium batteries, with a huge market potential. Therefore, quality control is particularly important. The purity indicators of battery-grade anhydrous lithium hydroxide, lithium hydroxide monohydrate, and lithium oxide are key factors in evaluating product quality and crucial testing items in the product acceptance process. The ability to quickly and accurately detect their purity is of great significance.

[0004] According to GB / T 1568-2022 "Battery Grade Anhydrous Lithium Hydroxide" and GB / T 26008-2020 "Battery Grade Lithium Hydroxide Monohydrate", its main contents are lithium hydroxide and lithium carbonate, with other impurities present in extremely small amounts, all at the ppm level. According to YS / T968-2014 "Battery Grade Lithium Oxide", its main contents are lithium oxide and lithium carbonate, with possible residual lithium hydroxide from unconverted processes during sintering or lithium hydroxide generated from moisture absorption during production. Other impurities are also present in extremely small amounts, all at the ppm level. Currently, the purity analysis method for anhydrous lithium hydroxide and lithium hydroxide monohydrate commonly uses GB / T 11064.2-2013 "Chemical Analysis Methods for Lithium Carbonate, Lithium Hydroxide Monohydrate and Lithium Chloride Part 2: Determination of Lithium Hydroxide Content by Acid-Base Titration". However, GB / T 11064.2-2013 does not consider the influence of carbonate ions, resulting in a higher consumption of hydrochloric acid during titration, often leading to higher results. There are no relevant industry or national standards for the purity testing of battery-grade lithium oxide. Therefore, the market urgently needs a testing method that can satisfy both supply and demand sides and improve testing accuracy. Summary of the Invention

[0005] To address the aforementioned problems, this invention aims to provide a method for detecting the purity of battery-grade lithium salts that can eliminate the influence of carbonate ions.

[0006] To achieve this technical objective, the present invention provides a method for detecting the purity of battery-grade lithium salts, comprising the following specific steps:

[0007] S1. Weigh out lithium salts of mass m1 and m2 into conical flasks, and perform parallel sample and blank experiments accordingly; add V0 mL of deionized water, stopper with a rubber stopper, and stir to dissolve, to obtain the first test solution and the second test solution;

[0008] S2. Add methyl red-bromocresol green indicator to the first test solution, and titrate with hydrochloric acid standard solution with a molar concentration of c1 until the solution changes from green to wine red; boil for two minutes to remove carbon dioxide, cool, and continue titrating until the solution turns wine red, which is the endpoint. Record the volume of hydrochloric acid standard titration solution consumed, V1; perform a blank experiment simultaneously and record the volume of hydrochloric acid standard titration solution consumed by the blank sample, V2.

[0009] S3. Add phenolphthalein indicator to the second test solution and titrate with hydrochloric acid solution of molar concentration c2 until a light red color is obtained under the condition of being isolated from air. Do not record the reading.

[0010] S4. Titrate with a standard hydrochloric acid solution with a molar concentration of c2 until colorless, without recording the reading;

[0011] S5. Add methyl red-bromocresol green indicator and continue titrating with a c2 hydrochloric acid standard titration solution until wine red; boil for two minutes, cool, and the wine red color is the endpoint. Record the volume V3 of the c2 hydrochloric acid standard titration solution consumed in this titration.

[0012] S6. Calculate the total alkalinity a of the first test solution based on the consumed volume V1 and the hydrochloric acid with a molar concentration of c1, which is the total amount of LiOH + Li2CO3 in the solution; calculate the carbonate ion content b of the second test solution based on the consumed volume V3 and the hydrochloric acid with a molar concentration of c2, which is the Li2CO3 content in the sample; and finally calculate the purity percentage of the lithium salt.

[0013] In step S1, the main components of the lithium salt used for testing are weighed, which contain anhydrous lithium hydroxide and lithium carbonate, or lithium hydroxide monohydrate and lithium carbonate, or lithium oxide and lithium carbonate.

[0014] The formulas for calculating the content of carbonate ions and lithium carbonate in step S6 are as follows:

[0015]

[0016] In the formula: c2--- is the hydrochloric acid standard titration solution in step S5, in mol / L;

[0017] m2 --- The mass of the sample in the second test solution, in grams;

[0018] ---Content of carbonate ions in the sample;

[0019] In step S2, the volume V of the standard hydrochloric acid titration solution of concentration c1 consumed by carbonate ions satisfies the following formula:

[0020] ;

[0021] The content of hydroxide ions can be calculated using the following formula:

[0022] .

[0023] When the main component is anhydrous lithium hydroxide, the calculation formula is:

[0024] .

[0025] When the main component is lithium hydroxide monohydrate, the calculation formula is:

[0026] .

[0027] When the main component is lithium oxide, the calculation formula is:

[0028] .

[0029] The beneficial effects of this invention are that the detection method of this application can be effectively used for the analysis and detection of battery-grade lithium carbonate, lithium hydroxide monohydrate, and lithium oxide. Compared with traditional methods, it requires less sample and less hydrochloric acid, making it more environmentally friendly. At the same time, it can effectively solve the problem that the traditional national standard does not take into account the impact of carbonate ions consuming hydrochloric acid, thereby improving the accuracy of detection. In addition, this method can also be effectively used for the analysis and detection of battery-grade lithium oxide. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating an embodiment of the present invention. Detailed Implementation

[0031] The following describes specific embodiments and appendices. Figure 1 The present invention will be further described below, but the invention is not limited to the following embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of protection of the invention. Unless otherwise specified, the reagents and materials described in the following embodiments are commercially available.

[0032] A method for detecting the purity of battery-grade lithium salts, wherein the main components of the lithium salts are anhydrous lithium hydroxide and lithium carbonate, or lithium hydroxide monohydrate and lithium carbonate, or lithium oxide and lithium carbonate. The specific steps are as follows:

[0033] (1) Place two samples of different masses into 300mL conical flasks, add 50mL of deionized water, stopper with a rubber stopper, and stir to dissolve the samples. When the sample is lithium oxide, the chemical reaction that occurs when dissolved in water is Li2O + H2O → LiOH.

[0034] (2) Add 10 drops of methyl red-bromocresol green indicator to the first sample to be tested, and titrate with 0.3 mol / L (c1) hydrochloric acid standard solution until the color changes from green to wine red; boil for two minutes to remove carbon dioxide, cool, and continue titrating until the color turns wine red, which is the endpoint. Record the volume V1 of hydrochloric acid standard titration solution consumed. The principle of this titration reaction is OH - +H + →H2O, CO3 2- +H + →HCO 3- HCO 3- +H + →CO2↑+H2O.

[0035] (3) Add 10 drops of phenolphthalein indicator to the second sample to be tested, and titrate with 2 mol / L hydrochloric acid solution until light red under the condition of being isolated from air.

[0036] (4) Titrate with 0.05 mol / L (CO) hydrochloric acid standard solution until colorless (do not record the reading). The purpose of steps (3) and (4) is to consume all hydroxide ions and convert carbonate ions into bicarbonate ions. The reaction principle is OH - +H + →H2O, CO3 2- +H + →HCO3 - .

[0037] (5) Perform a blank experiment and record the volume V2 of hydrochloric acid standard titration solution consumed by the blank sample; add 10 drops of methyl red-bromocresol green indicator and continue titrating with 0.05 mol / L hydrochloric acid (c2) standard titration solution until wine red; boil for two minutes, cool, and the wine red color is the endpoint. Record the volume V3 of 0.05 mol / L hydrochloric acid standard titration solution consumed. The principle of this reaction is HCO3 - +H + →CO2↑+H2O, and from this, the contents of carbonate ions and lithium carbonate can be obtained. The calculation formula is as follows:

[0038] ,

[0039] In the formula:

[0040] c2 --- The actual concentration of the hydrochloric acid standard titration solution (0.05 mol / L), in moles per liter (mol / L).

[0041] m2--- The mass of the sample in step (3), in grams (g);

[0042] ---Content of carbonate ions in the sample;

[0043] 30.00 / 36.94 --- Molar mass in terms of (1 / 2CO3, 1 / 2Li2CO3) basic units, in grams per mole (g / mol).

[0044] (6) When performing parallel and blank experiments, the volume of hydrochloric acid consumed by the blank sample should be subtracted from the volume of hydrochloric acid consumed in the calculation.

[0045] (7) Calculate the total alkalinity based on the 0.3 mol / L hydrochloric acid consumed by the first sample. The formula for calculating the volume of the standard hydrochloric acid titration solution with carbonate ion concentration c1 in step (2) is as follows:

[0046]

[0047] In the formula:

[0048] c1--- The actual concentration of the hydrochloric acid standard titration solution (0.3 mol / L), in moles per liter (mol / L).

[0049] m1--- The mass of the sample in step (2), in grams (g);

[0050] ---Calculate the carbonate content in step (5);

[0051] 30.00 --- Molar mass in terms of (1 / 2CO3) as the basic unit, expressed in grams per mole (g / mol).

[0052] Therefore, the hydroxide ion content can be calculated using the following formula: In the formula:

[0053] c1--- The actual concentration of the hydrochloric acid standard titration solution (0.3 mol / L), in moles per liter (mol / L).

[0054] m1--- The mass of the sample in step (2), in grams (g);

[0055] V1--- Step (2) The total volume of standard hydrochloric acid titration solution (0.3 mol / L) consumed in titrating hydroxide and carbonate is expressed in milliliters (mL).

[0056] V --- The volume of standard hydrochloric acid titration solution (0.3 mol / L) consumed by carbonate ions in step (6), in milliliters (mL);

[0057] 17.00 --- represents the molar mass of hydroxide ions, expressed in grams per mole (g / mol).

[0058] (8) Based on the consumption of 0.05 mol / L hydrochloric acid in the second sample, the carbonate ion content was calculated, and thus the contents of anhydrous lithium hydroxide, lithium hydroxide monohydrate, and lithium oxide were calculated. The calculation formulas are as follows:

[0059]

[0060] In the formula:

[0061] c1--- The actual concentration of the hydrochloric acid standard titration solution (0.3 mol / L), in moles per liter (mol / L).

[0062] m1--- The mass of the sample in step (2), in grams (g);

[0063] V1--- Step (2) The total volume of standard hydrochloric acid titration solution (0.3 mol / L) consumed in titrating hydroxide and carbonate is expressed in milliliters (mL).

[0064] V --- The volume of standard hydrochloric acid titration solution (0.3 mol / L) consumed by carbonate ions in step (6), in milliliters (mL);

[0065] 17.00 / 41.94 --- These are the molar masses of lithium hydroxide and lithium hydroxide monohydrate, respectively, in grams per mole (g / mol).

[0066]

[0067] In the formula:

[0068] 29.88 / 18.00 --- These are the molar masses of lithium oxide and water, respectively, in grams per mole (g / mol).

[0069] In summary, the detection method provided by this invention can be used for the purity of battery-grade anhydrous lithium hydroxide, lithium hydroxide monohydrate, and lithium oxide. The detection method of this invention is referred to as the "two-step method," which is based on the conventional acid-base titration method. Compared with the existing standard methods, the method is more effective, more efficient, and more accurate; and it can fill the gap in the detection method for lithium oxide purity.

[0070] Example 1:

[0071] Nine samples were obtained from three different manufacturers: battery-grade anhydrous lithium hydroxide, battery-grade lithium hydroxide monohydrate, and battery-grade lithium oxide. The lithium carbonate content was less than 1%, and other impurities were mostly at the ppm level. This embodiment studies the purity of these three lithium salts using the method of this invention, including the following steps (e.g., ...). Figure 1 ):

[0072] (1) First step: Quickly weigh 0.2g of lithium hydroxide, 0.3g of lithium hydroxide monohydrate and 0.1g of lithium oxide (accurate to 0.0001g) and place them in 300mL conical flasks (a total of 9 portions), add 50mL of deionized water, stopper with a rubber stopper, and stir to dissolve the sample;

[0073] (2) Add 10 drops of methyl red-bromocresol green indicator and titrate the solution with 0.3 mol / L hydrochloric acid standard solution until it changes from green to wine red; boil for two minutes to remove carbon dioxide, cool, and continue titrating until it turns wine red, which is the endpoint. Record the volume of hydrochloric acid standard titration solution consumed.

[0074] (3) Second step: Quickly weigh 1.0g lithium hydroxide, 1.0g lithium hydroxide monohydrate and 1.0g lithium oxide (accurate to 0.0001g) and place them in 300mL conical flasks (a total of 9 portions), add 50mL deionized water, stopper with rubber stopper, and stir to dissolve the sample;

[0075] (4) Add 10 drops of phenolphthalein indicator and titrate with 2 mol / L hydrochloric acid solution until pale red under air-isolated conditions;

[0076] (5) Titrate with 0.05 mol / L hydrochloric acid standard solution until colorless (do not record the reading);

[0077] (6) Add 10 drops of methyl red-bromocresol green indicator and continue titrating with 0.05 mol / L hydrochloric acid standard titration solution until wine red;

[0078] (7) Boil for another two minutes, cool, and continue titrating until the solution turns orange-red or wine-red, which is the endpoint. Record the volume of 0.05 mol / L hydrochloric acid standard titration solution consumed.

[0079] (8) Perform parallel sample and blank experiments simultaneously;

[0080] Comparative Example 1:

[0081] This comparative example uses the national standard GB / T 11064.2-2013 "Chemical Analysis Methods for Lithium Carbonate, Lithium Hydroxide Monohydrate and Lithium Chloride Part 2: Determination of Lithium Hydroxide Content by Acid-Base Titration" to test the purity of battery-grade anhydrous lithium hydroxide, battery-grade lithium hydroxide monohydrate and battery-grade lithium oxide in Example 1. The steps are as follows:

[0082] (1) Quickly weigh 0.5g of lithium hydroxide, 0.5g of lithium hydroxide monohydrate and 0.5g of lithium oxide (accurate to 0.0001g) and place them into 250mL Erlenmeyer flasks that have been pre-filled with 40.00mL of 0.25mol / L hydrochloric acid titration solution (a total of 9 portions);

[0083] (2) Add 10 drops of methyl red-bromocresol green indicator and titrate with 0.25 mol / L hydrochloric acid standard solution until the solution changes from green to wine red; boil for two minutes to remove carbon dioxide, cool, and continue titrating until the solution turns wine red, which is the endpoint. Record the volume of hydrochloric acid standard titration solution consumed.

[0084] Comparison table of results between Example 1 and Comparative Example 1

[0085]

[0086] As can be seen from the table above, the overall results are too high because the national standard GB / T 11064.2-2013 "Chemical Analysis Methods for Lithium Carbonate, Lithium Hydroxide Monohydrate and Lithium Chloride Part 2: Determination of Lithium Hydroxide Content by Acid-Base Titration" does not take into account the influence of carbonate ions consuming hydrochloric acid. Moreover, the sample weight in step (1) of Comparative Example 1 is too large, resulting in a huge amount of hydrochloric acid consumed, which is not environmentally friendly. The original national standard GB / T 11064.2-2013 does not involve the detection of lithium oxide, while the lithium oxide purity detection in Comparative Example 1 only refers to the steps of the national standard and is a test method derived by the inventor of this invention.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting the purity of battery-grade lithium salts, characterized in that, The specific steps are as follows: S1. Weigh out lithium salts of mass m1 and m2 into conical flasks, and perform parallel sample and blank experiments accordingly; add V0 mL of deionized water, stopper with a rubber stopper, and stir to dissolve, to obtain the first test solution and the second test solution; S2. Add methyl red-bromocresol green indicator to the first test solution, and titrate with hydrochloric acid standard solution with a molar concentration of c1 until the solution changes from green to wine red; boil for two minutes to remove carbon dioxide, cool, and continue titrating until the solution turns wine red, which is the endpoint. Record the volume of hydrochloric acid standard titration solution consumed, V1. S3. Add phenolphthalein indicator to the second test solution, and titrate with hydrochloric acid solution with a molar concentration of c0 until a light red color is obtained under the condition of being isolated from air. Do not record the reading. S4. Titrate with a standard hydrochloric acid solution with a molar concentration of c2 until colorless, without recording the reading; S5. Add methyl red-bromocresol green indicator and continue titrating with hydrochloric acid standard titration solution with a molar concentration of c2 until wine red; boil for two minutes, cool, and the wine red color is the endpoint. Record the volume V3 of hydrochloric acid standard titration solution with a molar concentration of c2 consumed in this titration. S6. Calculate the total alkalinity a of the first test solution based on the consumed volume V1 and the hydrochloric acid with a molar concentration of c1, which is the total amount of LiOH + Li2CO3 in the solution; calculate the carbonate ion content b of the second test solution based on the consumed volume V3 and the hydrochloric acid with a molar concentration of c2, which is the Li2CO3 content in the sample; and finally calculate the purity percentage of the lithium salt. In step S1, the main components of the lithium salt used for testing are weighed out as anhydrous lithium hydroxide and lithium carbonate, or lithium hydroxide monohydrate and lithium carbonate, or lithium oxide and lithium carbonate. The formulas for calculating the content of carbonate ions and lithium carbonate in step S6 are as follows: ， In the formula: c2 --- is the standard hydrochloric acid titration solution in step S5, in mol / L; m2 --- The mass of the sample in the second test solution, in grams; ---Content of carbonate ions in the sample; In step S2, the volume V of the standard hydrochloric acid titration solution of concentration c1 consumed by carbonate ions satisfies the following formula: ； The content of hydroxide ions can be calculated using the following formula: ； When the main component is anhydrous lithium hydroxide, the calculation formula is: ； When the main component is lithium hydroxide monohydrate, the calculation formula is: ； When the main component is lithium oxide, the calculation formula is: 。

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