A quantitative detection method for water content of lithium aluminum chloride

Abstract

The application provides a quantitative detection method of water content of lithium tetrachloroaluminate, which comprises the following steps: (1) mixing 1,3-dioxolane and deionized water to obtain a mixed solution in a dry environment; (2) mixing part of the mixed solution obtained in step (1) and / or 1,3-dioxolane to obtain at least six organic solutions with different water contents; (3) adding the same mass of lithium tetrachloroaluminate into the organic solutions obtained in step (2), and then standing and shaking to obtain parallel samples; (4) measuring the viscosity of the parallel samples obtained in step (3), and drawing a standard curve; and (5) calculating the water content of lithium tetrachloroaluminate according to the standard curve obtained in step (4) and the viscosity of the sample to be measured. The quantitative detection method provided by the application can qualitatively judge the relative high and low of the water content of lithium salt, and can also preliminarily and roughly quantitatively judge, which plays a guiding role in the research of the influence of water on the performance of the battery and the method and process for reducing the introduction of water.

Description

Technical Field

[0001] This invention belongs to the field of chemical analysis technology and relates to a method for detecting the water content of lithium salts in lithium-ion battery electrolytes, and more particularly to a quantitative method for detecting the water content of lithium tetrachloroaluminate. Background Technology

[0002] Lithium-thionyl chloride (LTC) batteries are liquid lithium primary batteries and currently boast the highest energy density and widest operating temperature range among commercially available battery products. Furthermore, the characteristics of liquid batteries ensure that their voltage remains stable for over 90% of their total capacity. Today, LTC batteries are widely used in various smart meters such as electricity meters, water meters, and gas meters, and their applications in transportation, security, and the Internet of Things (IoT) are continuously expanding, placing even higher demands on their performance.

[0003] The electrolyte of a lithium-ion battery mainly consists of two parts: the electrolyte solute, lithium tetrachloroaluminum salt, and the electrolyte solvent, thionyl chloride. Thionyl chloride acts as the cathode active material, undergoing a reduction reaction; lithium tetrachloroaluminum dissolves in thionyl chloride, providing lithium ions for charge conduction. In addition, some additives are added to the electrolyte to improve the battery's electrical performance.

[0004] For lithium-ion batteries, the most significant factor affecting battery performance is the moisture introduced during the battery manufacturing process. Excessive moisture can cause severe damage to the battery, and the principle behind this is as follows:

[0005] LiAlCl4+H2O→LiAlCl3OH+HCl;

[0006] AlCl3 + H2O → AlCl2OH + HCl;

[0007] LiAlCl3OH+SOCl2→LiAlCl4+SO2+HCl;

[0008] AlCl2OH+SOCl2→AlCl3+SO2+HCl.

[0009] The introduction of moisture generates hydrogen chloride, which acts as a catalyst in the battery, causing the aforementioned reactions to continue. This leads to the continuous consumption of active materials and capacity loss. Furthermore, the reaction products accelerate the hysteresis of lithium-ion batteries, resulting in a decrease in battery load capacity. In short, moisture, especially in lithium salts, is arguably the biggest enemy of batteries.

[0010] Lithium tetrachloroaluminate (LCA) is produced by melting lithium chloride and aluminum trichloride at high temperatures. It is a highly hygroscopic substance and must be stored in an extremely dry, sealed environment after melting. Poor storage conditions or inadequate sealing will cause the lithium salt to absorb a large amount of moisture before use. Furthermore, LCA is volatile and decomposes upon heating. Currently, it cannot be further dried through other processes before lithium-ion battery manufacturing, making the moisture content requirements for raw materials before use extremely stringent. Moisture detection of LCA raw materials is crucial for lithium-ion battery manufacturers. However, there is currently no effective method in the technology to detect the water content in LCA.

[0011] In conclusion, the detection of water content in lithium aluminum tetrachlorois is of great practical significance and is currently a research challenge in the field of chemical analysis. Summary of the Invention

[0012] The purpose of this invention is to provide a quantitative detection method for the water content of lithium aluminum tetrachloro. This quantitative detection method can qualitatively determine the relative level of water content in lithium salt water, and can also make a preliminary quantitative judgment. It plays a guiding role in the research on the impact of water on battery performance, as well as methods and processes for reducing the introduction of water.

[0013] To achieve this objective, the present invention adopts the following technical solution:

[0014] This invention provides a method for quantitatively detecting the water content of lithium aluminum tetrachloro, the method comprising the following steps:

[0015] (1) Mix 1,3-dioxolane with deionized water in a dry environment to obtain a mixed solution;

[0016] (2) Mix the partial mixed solution obtained in step (1) and / or 1,3-dioxolane to obtain at least 6 organic solutions with different water contents;

[0017] (3) Add the same mass of lithium aluminum tetrachloroto the organic solvent obtained in step (2), and then let it stand and shake to obtain parallel samples.

[0018] (4) Measure the viscosity of the parallel samples obtained in step (3) and plot the standard curve;

[0019] (5) Calculate the water content of lithium tetrachloroaluminate based on the standard curve obtained in step (4) and the viscosity of the sample to be tested.

[0020] The purpose of preparing the mixed solution in step (1) of this invention is to obtain a 1,3-dioxolane solution with a certain water content.

[0021] The 1,3-dioxolane described in this invention is a cyclic organic compound that is liquid at room temperature and is commonly used as an organic solvent. In the reaction of lithium aluminum tetrachlorohydrate with water (LiAlCl4 + H2O → LiAlCl3OH + HCl), the 1,3-dioxolane undergoes ring-opening polymerization under the action of hydrogen chloride, gradually transforming into a high-molecular-weight organic compound with increased viscosity. The amount of hydrogen chloride added determines the rate of the reaction.

[0022] Preferably, the temperature in the drying environment described in step (1) is 20-30℃, for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the relative humidity in the dry environment described in step (1) is <1%, for example, it can be 0.99%, 0.95%, 0.9%, 0.85%, 0.8%, 0.75%, 0.7%, 0.65% or 0.6%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the purity of the 1,3-dioxolane is ≥99.8%, for example, it can be 99.8%, 99.82%, 99.84%, 99.86%, 99.88%, 99.9%, 99.92%, 99.94%, 99.96%, or 99.98%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the water content of the organic solution in step (2) is 0-1000 ppm, for example, it can be 0 ppm, 60 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm or 1000 ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the amount of lithium aluminum tetrachlorotri ...

[0027] The lithium aluminum tetrachloroethylene described in this invention is pure lithium aluminum tetrachloroethylene that is sealed immediately after high-temperature melting and has a production date within one month.

[0028] Preferably, the water content in the parallel samples in step (3) varies in a gradient.

[0029] Preferably, the settling time in step (3) is 8-12 hours, for example, it can be 8 hours, 8.4 hours, 8.8 hours, 9.2 hours, 9.6 hours, 10 hours, 10.4 hours, 10.8 hours, 11.2 hours, 11.6 hours or 12 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the interval time of the shaking in step (3) is 1-2 hours, for example, it can be 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the viscosity detection tool in step (4) is a rotational viscometer.

[0032] Preferably, the rotor used in the rotary viscometer is rotor No. 3.

[0033] Preferably, in step (4), the independent variable of the standard curve is the viscosity of the parallel samples, and the dependent variable is the ratio of water to lithium tetrachloroaluminate in the organic solution.

[0034] Preferably, the viscosity determination method for the sample to be tested in step (5) includes:

[0035] The test sample was obtained by mixing lithium aluminum tetrachloro and 1,3-dioxolane; the viscosity of the test sample was then measured using a rotational viscometer.

[0036] Preferably, the mass ratio of the lithium tetrachloroaluminate to be tested and 1,3-dioxolane is (1-15):100, for example, it can be 1:100, 3:100, 5:100, 7:100, 9:100, 11:100, 13:100 or 15:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the general formula for calculating the water content of lithium aluminum tetrachlorotri ...

[0038]

[0039] Where x is the viscosity of the sample to be tested, and y0, A, x0 and t are calculated based on the standard curve obtained in step (4).

[0040] As a preferred embodiment of the present invention, the method for quantitatively detecting the water content of lithium aluminum tetrachloroethylene provided by the present invention includes the following steps:

[0041] (1) Mix 1,3-dioxolane with deionized water at a purity ≥99.8% in a dry environment with a temperature of 20-30℃ and a relative humidity of <1% to obtain a mixed solution;

[0042] (2) Mix the partial mixed solution obtained in step (1) and / or 1,3-dioxolane with a purity ≥99.8% to obtain at least 7 organic solutions with different water contents;

[0043] (3) Add the same mass of lithium aluminum tetrachloroethylene to the organic solvent obtained in step (2), and then let it stand for 8-12 hours, shaking it once every 1-2 hours to obtain parallel samples; the amount of lithium aluminum tetrachloroethylene added is 5-15% of the 1,3-dioxolane content in the organic solvent.

[0044] (4) Measure the viscosity of the parallel samples obtained in step (3) using a rotational viscometer and plot a standard curve;

[0045] (5) Calculate the water content of lithium aluminum tetrachloroethylene based on the standard curve obtained in step (4) and the viscosity of the sample to be tested. The general formula for calculating the water content of lithium aluminum tetrachloroethylene is:

[0046]

[0047] Where x is the viscosity of the sample to be tested, and y0, A, x0 and t are calculated based on the standard curve obtained in step (4).

[0048] The present invention can determine whether the lithium aluminum tetrachloroethylene is qualified based on the viscosity of the sample to be tested. When the viscosity of the sample to be tested is greater than 6000 mPa·s, the sample to be tested is a non-qualified product and is not suitable for production.

[0049] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) The quantitative detection method for water content of lithium aluminum tetrachlorosilane provided by the present invention can qualitatively determine the relative level of water content in lithium salt water, and can also preliminarily quantitatively determine the impact of water content on battery performance; it can also play a guiding role in the research of methods and processes to reduce the introduction of water.

[0052] (2) The quantitative detection method for water content of lithium tetrachloroaluminate provided by the present invention can detect the viscosity of the lithium tetrachloroaluminate. For lithium tetrachloroaluminate with a viscosity higher than the set value, it can be directly judged as unqualified, thereby reducing the loss caused by quality factors after production. Attached Figure Description

[0053] Figure 1 This is a standard curve diagram in the quantitative detection method for the water content of lithium aluminum tetrachloroethylene provided in Embodiment 1 of the present invention. Detailed Implementation

[0054] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0055] Example 1

[0056] This embodiment provides a method for quantitatively detecting the moisture content of lithium aluminum tetrachloroethylene, which includes the following steps:

[0057] (1) Mix 300g of 1,3-dioxolane with a purity ≥99.8% with 30μL of deionized water in a dry environment with a temperature of 25±3℃ and a relative humidity of <1% to obtain a mixed solution;

[0058] (2) Mix the partial mixed solution obtained in step (1) and / or 1,3-dioxolane with a purity ≥99.8% to obtain 7 organic solutions with different water contents;

[0059] Take 100g of the mixed solution obtained in step (1) and label it as organic solution A;

[0060] Mix 75g of the mixed solution obtained in step (1) with 25g of 1,3-dioxolane with a purity ≥99.8%, and label it as organic solution B;

[0061] Mix 50g of the mixed solution obtained in step (1) with 50g of 1,3-dioxolane with a purity ≥99.8%, and label it as organic solution C;

[0062] Mix 25g of the mixed solution obtained in step (1) with 75g of 1,3-dioxolane with a purity ≥99.8%, and label it as organic solution D;

[0063] Mix 12.5g of the mixed solution obtained in step (1) with 87.5g of 1,3-dioxolane with a purity ≥99.8%, and label it as organic solution E;

[0064] Mix 6g of the mixed solution obtained in step (1) with 94g of 1,3-dioxolane with a purity ≥99.8%, and label it as organic solution F;

[0065] Take 100g of 1,3-dioxolane with a purity ≥99.8% and label it as organic solution G;

[0066] (3) Add 10g of lithium aluminum tetrachloro to the organic solvent AG obtained in step (2), and then let it stand for 12h, shaking it once every 2h to obtain parallel sample AG.

[0067] (4) The viscosity of the parallel sample AG obtained in step (3) was measured using a rotational viscometer, as shown in Table 1, and plotted as follows. Figure 1 The standard curve shown;

[0068] (5) Calculate the water content of lithium aluminum tetrachloroethylene based on the standard curve obtained in step (4) and the viscosity of the sample to be tested. The general formula for calculating the water content of lithium aluminum tetrachloroethylene is:

[0069]

[0070] Where x is the viscosity of the sample to be tested, and y0, A, x0 and t are calculated according to the standard curve obtained in step (4): y0 = -397.408, A = 291.089, x0 = -954.675, t = 10286.517;

[0071] The viscosity of the sample to be tested in this embodiment was measured as follows: 10g of lithium aluminum tetrachloroethylene and 100g of 1,3-dioxolane were mixed and allowed to stand for 12 hours. During this period, the mixture was shaken every 2 hours and a rotational viscometer with rotor No. 3 was used to measure the viscosity of the sample to be tested, which was 6025mPa·s. The water content of the sample to be tested in this embodiment was calculated to be 176.4ppm.

[0072] Therefore, the sample provided in this embodiment has a high water content and is a substandard product, unsuitable for production.

[0073] Table 1

[0074] Water content / ppm Viscosity / mPa·s Parallel Sample A 1000 15205 Parallel Sample B 750 13056 Parallel Samples C 500 10785 Parallel Samples D 250 7039 Parallel Sample E 125 5034 Parallel Samples F 60 4069 Parallel Samples G 0 2054

[0075] Example 2

[0076] This embodiment provides a quantitative detection method for the water content of lithium aluminum tetrachloro. The only difference between this quantitative detection method and Embodiment 1 is that the sample to be tested is changed in this embodiment. The viscosity of the sample to be tested in this embodiment is 8098 mPa·s.

[0077] The water content of the sample provided in this embodiment is 304 ppm.

[0078] Therefore, the sample provided in this embodiment has a high water content and is a substandard product, unsuitable for production.

[0079] In summary, the quantitative detection method for the water content of lithium tetrachloroaluminate provided by this invention can qualitatively determine the relative level of water content in lithium salt water, and can also make a preliminary quantitative judgment. It plays a guiding role in the research on the impact of water on battery performance, as well as methods and processes for reducing the introduction of water.

[0080] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for quantitatively detecting the water content of lithium aluminum tetrachloro, characterized in that, The quantitative detection method includes the following steps: (1) Mix 1,3-dioxolane with deionized water in a dry environment to obtain a mixed solution; (2) Take the mixed solution obtained in step (1), or take 1,3-dioxolane, or mix part of the mixed solution obtained in step (1) with 1,3-dioxolane to obtain at least 6 organic solutions with different water contents; (3) Add the same mass of lithium aluminum tetrachloroto the organic solution obtained in step (2), and then let it stand and shake to obtain parallel samples; the amount of lithium aluminum tetrachloroto the organic solution is 5-15% of the 1,3-dioxolane content in the organic solution; (4) Measure the viscosity of the parallel samples obtained in step (3) and plot the standard curve; (5) Calculate the water content of lithium aluminum tetrachlorobased samples based on the standard curve obtained in step (4) and the viscosity of the sample to be tested; The viscosity determination method for the sample to be tested includes: The test sample was obtained by mixing lithium aluminum tetrachloro and 1,3-dioxolane; the viscosity of the test sample was then measured using a rotational viscometer; the mass ratio of the test lithium aluminum tetrachloro and 1,3-dioxolane was (1-15):

100. The general formula for calculating the water content of lithium tetrachloroaluminate is: Where x is the viscosity of the sample to be tested, and y0, A, x0 and t are calculated based on the standard curve obtained in step (4).

2. The quantitative detection method according to claim 1, characterized in that, The temperature in the drying environment described in step (1) is 20-30℃.

3. The quantitative detection method according to claim 1, characterized in that, The relative humidity in the dry environment described in step (1) is <1%.

4. The quantitative detection method according to claim 1, characterized in that, The purity of the 1,3-dioxolane is ≥99.8%.

5. The quantitative detection method according to claim 1, characterized in that, The water content of the organic solution in step (2) is 0-1000 ppm.

6. The quantitative detection method according to claim 1, characterized in that, The water content in the parallel samples in step (3) varies in a gradient.

7. The quantitative detection method according to claim 1, characterized in that, The settling time in step (3) is 8-12 hours.

8. The quantitative detection method according to claim 1, characterized in that, The interval between the shaking in step (3) is 1-2 hours.

9. The quantitative detection method according to claim 1, characterized in that, The viscosity testing tool in step (4) is a rotational viscometer.

10. The quantitative detection method according to claim 9, characterized in that, The rotary viscometer uses rotor number 3.

11. The quantitative detection method according to claim 1, characterized in that, Step (4) The independent variable of the standard curve is the viscosity of the parallel samples, and the dependent variable is the ratio of water to lithium tetrachloroaluminate in the organic solution.

12. The quantitative detection method according to claim 1, characterized in that, The quantitative detection method includes the following steps: (1) Mix 1,3-dioxolane with a purity ≥99.8% with deionized water in a dry environment with a temperature of 20-30℃ and a relative humidity of <1% to obtain a mixed solution; (2) Take the mixed solution obtained in step (1), or take 1,3-dioxolane with a purity ≥99.8%, or mix part of the mixed solution obtained in step (1) and 1,3-dioxolane with a purity ≥99.8% to obtain at least 7 organic solutions with different water contents; (3) Add the same mass of lithium aluminum tetrachloroethylene to the organic solution obtained in step (2), and then let it stand for 8-12 hours, shaking it once every 1-2 hours to obtain parallel samples; the amount of lithium aluminum tetrachloroethylene added is 5-15% of the 1,3-dioxolane content in the organic solution; (4) Measure the viscosity of the parallel samples obtained in step (3) using a rotational viscometer and plot a standard curve; (5) Calculate the water content of lithium aluminum tetrachlorobased samples based on the standard curve obtained in step (4) and the viscosity of the sample to be tested. The general formula for calculating the water content of lithium aluminum tetrachlorobased samples is: Where x is the viscosity of the sample to be tested, and y0, A, x0 and t are calculated based on the standard curve obtained in step (4); The viscosity determination method for the sample to be tested includes: The test sample was obtained by mixing lithium aluminum tetrachloro and 1,3-dioxolane; the viscosity of the test sample was then measured using a rotational viscometer; the mass ratio of the test lithium aluminum tetrachloro and 1,3-dioxolane was (1-15):100.

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