Extraction liquid for extracting lithium ion battery electrolyte and extraction method of lithium ion battery electrolyte

Abstract

The invention relates to the technical field of batteries, in particular to extract liquor for extracting a lithium ion battery electrolyte and an extraction method of the lithium ion battery electrolyte. The extraction liquid comprises a component A and a component B, the component A comprises acetonitrile; the component B comprises fluorobenzene and / or fluorobenzene derivatives. By utilizing the characteristics of low viscosity of the component A and high wettability of the component B, the mixing effect of the extract and the lithium ion battery electrolyte is improved; secondly, the component A and the component B also have certain chemical inertness and cannot chemically react with byproducts in a battery cell, and the component A and the component B are not components originally existing in the lithium ion battery electrolyte and do not influence peak test results of the components, so that the measurement results of the components of the electrolyte cannot be influenced, and the measurement accuracy is improved. And the mixing uniformity of the extraction liquid and the lithium ion battery electrolyte is improved, and the universality and the accuracy of the extraction method are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an extracting solution for extracting lithium ion battery electrolyte and a method for extracting lithium ion battery electrolyte. Background Art

[0002] Lithium-ion batteries stand out from many battery types due to their high specific energy density and long cycle life. They are now widely used in electric vehicles, energy storage power stations and portable electronic devices. The study of battery cycle life mechanism has become increasingly important. The content of components in the electrolyte is a key factor affecting the cycle life. Therefore, studying the changes in the content of each component of the battery throughout its life cycle has important guiding significance for the study of battery cycle life mechanism and the optimization of electrolyte formulation.

[0003] In order to accurately detect the composition of the electrolyte in the battery under different cycle states, there are currently three main methods for extracting battery electrolytes, namely centrifugation, extrusion and extraction. Among them, the centrifugation method is to use the centrifugal force generated by the centrifuge to extract the electrolyte by throwing out the electrolyte in the battery cell; the extrusion method is to extract the electrolyte by applying mechanical pressure to the battery cell to squeeze out the electrolyte in the cell; the extraction method is to inject the extraction liquid into the battery cell, fully mix the extraction liquid and the remaining electrolyte in the battery cell, and then collect the mixed liquid to extract the electrolyte. Among the above-mentioned methods for extracting electrolytes, the centrifugation method and the extrusion method have limited extraction capabilities, and the remaining electrolyte can no longer be effectively collected for batteries with less electrolyte remaining in the later stages of the cycle. The extraction method can effectively extract the remaining electrolyte of the battery cell throughout its life cycle, but the selection and configuration of the extraction liquid have an impact on the accuracy of the test of the electrolyte components extracted by the extraction method that cannot be ignored.

[0004] In the method of extracting battery electrolyte by extraction, dimethyl carbonate, ethyl acetate and dichloromethane are currently commonly used as extractants. However, these existing extractants all have certain defects. For example, the viscosity of dimethyl carbonate is relatively high, which makes it difficult to mix evenly with the electrolyte, and it will affect the test of the dimethyl carbonate component of the electrolyte itself; ethyl acetate has high chemical activity and may react with by-products in the battery cell in the late stage of circulation; dichloromethane has a strong corrosive effect on anion chromatography columns, which limits the determination of the lithium salt content of the electrolyte.

[0005] Therefore, it is urgent to develop an extraction solution to improve the universality and accuracy of the extraction method. Summary of the invention

[0006] In view of this, the present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the present invention provides an extraction solution for extracting lithium ion battery electrolyte and a method for extracting lithium ion battery electrolyte, which can meet the testing requirements of all components of lithium ion battery electrolyte and effectively improve the universality and accuracy of extracting electrolyte by extraction method.

[0007] In order to solve the above technical problems, this application is implemented as follows:

[0008] According to one aspect of the present application, an embodiment of the present application provides an extraction solution for extracting electrolyte of a lithium-ion battery, wherein the extraction solution comprises component A and component B;

[0009] The component A comprises acetonitrile;

[0010] The component B includes fluorobenzene and / or fluorobenzene derivatives.

[0011] In addition, the extract according to the present application may also have the following additional technical features:

[0012] In some embodiments, the mass fraction of component A is x, and the value of x satisfies: 80%≤x<100%.

[0013] In some embodiments, the mass fraction of component B is y, and the value of y satisfies: 0%<y≤20%.

[0014] In some embodiments, x and y further satisfy x+y=100%.

[0015] In some embodiments, the fluorobenzene includes at least one of 1-fluorobenzene, 1,2-difluorobenzene or 1,3,5-trifluorobenzene.

[0016] In some embodiments, the fluorobenzene derivative includes an alkyl derivative of fluorobenzene, and the alkyl derivative of fluorobenzene includes at least one of 1-methyl-3,5-difluorobenzene, 1-ethyl-3,5-difluorobenzene or 1-n-propyl-3,5-difluorobenzene.

[0017] In some embodiments, the purity of component A and component B is greater than or equal to 99.9%, and the water content is less than or equal to 20 ppm.

[0018] According to another aspect of the present application, an embodiment of the present application provides a method for extracting electrolyte from a lithium-ion battery, comprising the following steps: injecting an extraction solution into a lithium-ion battery to be analyzed and tested, allowing the extraction solution to stand and perform ultrasonic treatment, and then extracting the electrolyte from the lithium-ion battery;

[0019] The extract comprises the above-mentioned extract.

[0020] In some embodiments, the dew point temperature of the environment when the extract is injected is -80°C to -10°C.

[0021] In some embodiments, the dew point temperature of the environment when extracting the electrolyte in the lithium-ion battery is -80°C to -10°C.

[0022] In some embodiments, the injection amount of the extracting solution is based on the initial capacity of the lithium-ion battery, and the injection coefficient of the extracting solution is 0.1 to 10 g / Ah.

[0023] In some embodiments, the standing and ultrasonic treatment specifically include a first standing, ultrasonication and a second standing performed sequentially.

[0024] In some embodiments, the temperature of the first standing still is 0° C. to 80° C., and the time of the first standing still is 4 h to 24 h.

[0025] In some embodiments, the temperature of the ultrasound is 0°C to 60°C, the power of the ultrasound is 24W to 120W, and the time of the ultrasound is 0.5h to 4h.

[0026] In some embodiments, the second standing temperature is 0°C to 60°C, and the second standing time is 4h to 48h.

[0027] In some embodiments, the lithium-ion battery includes one of a battery before formation, a battery after formation but before capacity division, a battery after capacity division, or a battery after cycling.

[0028] In some embodiments, the cycled battery is a battery that has been cycled for any number of times.

[0029] In some embodiments, when the lithium-ion battery is a battery after formation but before capacity division, a battery after formation and capacity division, or a battery after cycling, before injecting the extraction liquid into the lithium-ion battery to be analyzed and tested, a step of discharging the lithium-ion battery to be analyzed and tested is also included.

[0030] In some embodiments, the discharging step includes discharging the lithium-ion battery to a lower voltage limit of the battery, and the discharge current of the discharging is 0.05 to 0.5C, preferably 0.05 to 0.1C.

[0031] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0032] In an embodiment of the present application, an extracting solution for extracting lithium-ion battery electrolyte is provided, which comprises two components, component A and component B, wherein component A comprises acetonitrile, and component B comprises fluorobenzene and its fluorobenzene derivatives. Thus, the low viscosity of component A and the high wettability of component B are utilized to improve the effect of mixing the extracting solution with the battery electrolyte; secondly, component A is chemically inert, and component B also has a certain degree of chemical inertness, and neither will react chemically with the by-products in the battery core, and component A and component B are not components originally existing in the battery electrolyte, and do not affect the results of the peak test of each component, and therefore will not affect the determination results of the electrolyte components; furthermore, component A, as the main component in the extracting solution, can be well mixed with the organic components in the battery electrolyte, and at the same time has a strong solubility for lithium salts, thereby improving the universality and accuracy of the extraction method for extracting the battery electrolyte; in addition, component A and component B are not corrosive to the chromatographic column and will not damage the detection instrument.

[0033] Additional aspects and advantages of the present application will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0034] The present application is further described below in conjunction with specific embodiments. It should be understood that these embodiments of the present application are only used to illustrate the present application and are not used to limit the scope of the present application.

[0035] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0036] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0037] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0038] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0039] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0040] Generally, the extraction method is based on the difference in the distribution coefficients of different substances between two immiscible solvents for separation. By selecting a suitable extraction liquid, the target substance can be transferred from the original solution (such as battery electrolyte) to the extraction liquid, thereby achieving separation. Therefore, the selection and configuration of the extraction liquid has a significant impact on the accuracy of the test of the electrolyte components extracted by the extraction method.

[0041] In order to ensure the accuracy of the extraction method test, the extraction liquid should have the following characteristics: first, it has excellent miscibility with the organic components of the electrolyte; second, it has good solubility for the lithium salt components of the electrolyte; third, it has low viscosity and can quickly and fully wet the battery cell; fourth, it does not chemically react with the battery cell components and by-products; fifth, the extraction agent does not affect the test peaks of the electrolyte components; and sixth, the extraction agent does not damage the detection instrument.

[0042] Currently, dimethyl carbonate, ethyl acetate and dichloromethane are commonly used as extraction liquids, but they all have certain defects. Dimethyl carbonate has a relatively high viscosity, making it difficult to mix evenly with the electrolyte, and will affect the test of the dimethyl carbonate component of the electrolyte itself; ethyl acetate has a high chemical activity and may react with by-products in the battery cell in the later stage of the cycle; dichloromethane has a strong corrosive effect on anion chromatography columns, limiting the determination of the lithium salt content of the electrolyte.

[0043] In view of this, the present invention provides an extracting solution for extracting lithium-ion battery electrolyte and a method for extracting lithium-ion battery electrolyte using the extracting solution. The extracting solution can meet the testing requirements of organic components and all anion components in lithium-ion battery electrolyte, broadening the testing capabilities of lithium-ion batteries; it also further improves the mixing effect of the extracting solution and the lithium-ion battery electrolyte, thereby improving the universality and accuracy of the extraction method for extracting lithium-ion battery electrolyte. At the same time, the extracting solution does not chemically react with the battery cell components and by-products, and has no effect on the peak test of each component of the electrolyte, and will not damage the detection instrument. The specific technical solution is described below.

[0044] In some embodiments, the present application provides an extraction solution for extracting lithium-ion battery electrolyte, the extraction solution comprising component A and component B;

[0045] Wherein, component A comprises acetonitrile;

[0046] Component B includes fluorobenzene and / or fluorobenzene derivatives.

[0047] In the embodiment of the present application, the extract includes component A and component B, wherein component A is acetonitrile (CAS number: 75-05-8), and component B includes fluorobenzene and / or fluorobenzene derivatives, such as component B can be fluorobenzene, can be or fluorobenzene derivatives, or can be a mixture of fluorobenzene and fluorobenzene derivatives. Preferably, component B is 1-fluorobenzene (CAS number: 462-06-6). Acetonitrile can be well mixed with the organic components in the lithium ion battery electrolyte, and has a strong solubility for lithium salts. At the same time, acetonitrile itself also has the characteristic of low viscosity, which can quickly infiltrate the lithium ion battery and fully mix with the remaining electrolyte in the lithium ion battery. Therefore, the composition of the extracted electrolyte can better represent the actual composition of the remaining electrolyte inside the lithium ion battery, and the test deviation is lower.

[0048] Furthermore, acetonitrile itself is chemically inert, and fluorobenzene and fluorobenzene derivatives are also relatively inert, that is, the components of the extract do not react with the by-products in the battery cell at the later stage of the cycle; and acetonitrile, fluorobenzene and fluorobenzene derivatives are not originally components in the lithium-ion battery electrolyte, and do not affect the results of the peak test of each component, and therefore will not affect the determination results of the electrolyte components. In addition, the components in the extract are not corrosive to the chromatographic column and will not damage the detection instrument.

[0049] Therefore, based on the above, the extract mainly utilizes the low viscosity and chemical inertness of acetonitrile, as well as the characteristics of fluorobenzene and its derivatives to improve wettability, to achieve the testing requirements of organic components and all anion components, that is, it can meet the testing requirements of organic components and all anion components in lithium-ion battery electrolytes, broadening the testing capabilities of lithium-ion batteries; it also further improves the mixing effect of the extract and lithium-ion battery electrolyte, thereby improving the universality and accuracy of the extraction method for lithium-ion battery electrolytes. At the same time, the extract does not chemically react with the battery components and by-products of the lithium-ion battery, and has no effect on the peak test of each component of the electrolyte, and will not damage the detection instrument.

[0050] In the embodiment of the present application, the mass fraction of component A is x, and the value of x satisfies: 80%≤x<100%;

[0051] The mass fraction of component B is y, and the value of y satisfies: 0%<y≤20%;

[0052] x and y also satisfy x+y=100%.

[0053] Particularly, in the embodiment of the present application, the mass fraction x of component A in the extract satisfies: 80% ≤ x < 100%; as an example, the value of x can be 80%, 81%, 83%, 84%, 85%, 89%, 90%, 91%, 92%, 95%, etc.; the mass fraction y of component B satisfies: 0% < y ≤ 20%; as an example, the value of y can be 0.5%, 0.6%, 0.8%, 0.9%, 1%, 2%, 5%, 6%, 7%, 9%, 11%, 13%, 15%, 17%, 18%, 19%, 19.5%, etc.; there is no special requirement for the values ​​of x and y, as long as the above range limits are met, and the values ​​of x and y also need to satisfy x + y = 100%. The extract has acetonitrile as the main component. Since the viscosity of acetonitrile is 0.35 cP (20°C), which is lower than that of ethyl acetate (viscosity: 0.45 cP@20°C) and dimethyl carbonate (viscosity: 0.91 cP@25°C), the extract and the electrolyte can be mixed better. At the same time, the addition of fluorobenzene or fluorobenzene derivatives improves the overall wettability of the extract, which can make the extract diffuse better in the lithium-ion battery, accelerate the mixing of the extract and the remaining electrolyte inside the lithium-ion battery, and thus improve the accuracy of the test. When the values ​​of x and y exceed the above-mentioned specified range, the test deviation of the organic component of the electrolyte will increase, especially the test deviation of the concentration of lithium salts such as LiPF6 will increase significantly. This is because the mixing ability of component B itself and the organic components in the electrolyte is general, especially the solubility of lithium salts is poor. Therefore, when the content of component A decreases and the content of component B increases, the lithium salt cannot be well dissolved in the mixed solution, resulting in its test content deviating from the actual value.

[0054] In the embodiment of the present application, fluorobenzene includes at least one of 1-fluorobenzene, 1,2-difluorobenzene, and 1,3,5-trifluorobenzene. Preferably, fluorobenzene is selected from 1-fluorobenzene, which is used in combination with acetonitrile, has a better application effect, is widely available, is easy to obtain, and has a low cost.

[0055] In the embodiments of the present application, the fluorobenzene derivative includes an alkyl derivative of fluorobenzene, and the alkyl derivative of fluorobenzene includes, but is not limited to, at least one of 1-methyl-3,5-difluorobenzene, 1-ethyl-3,5-difluorobenzene or 1-n-propyl-3,5-difluorobenzene.

[0056] The above-mentioned selection of fluorobenzene and fluorobenzene derivatives can bring excellent wettability to the extracting solution, thereby facilitating better mixing of the extracting solution and the lithium-ion battery electrolyte.

[0057] In the embodiment of the present application, the purity of component A and component B is ≥99.9%. As an example, the purity of component A can be 99.9%, 99.92%, 99.99%, etc., and the purity of component B can be 99.9%, 99.95%, 99.99%, etc. By limiting component A and component B to a higher purity range, the influence of impurities in the reagent on the test of the lithium-ion battery electrolyte composition can be eliminated, thereby avoiding affecting the test results.

[0058] In the embodiment of the present application, the water content of component A and component B is ≤20ppm. As an example, the water content of component A can be 20ppm, 19ppm, 18ppm, 17ppm, 16ppm, 15ppm, 10ppm, and the water content of component B can be 20ppm, 19ppm, 18ppm, 17ppm, 16ppm, 15ppm, 10ppm; by controlling the water content of component A and component B, it is possible to prevent water from being brought into the electrolyte and causing decomposition. There is no requirement for the method of removing water from component A and component B, as long as the water content range specified in the present application can be reached. For example, molecular sieves can be used to remove water to control the water content in component A and component B.

[0059] Thus, based on the above scheme, the present application provides an extracting solution for extracting lithium-ion battery electrolyte, comprising two components, component A and component B, and utilizing the low viscosity of component A and the high wettability of component B to improve the mixing effect of the extracting solution and the lithium-ion battery electrolyte; secondly, component A is chemically inert, and component B also has a certain degree of chemical inertness, and neither will chemically react with the by-products in the battery cell, and component A and component B are not components originally existing in the lithium-ion battery electrolyte, and do not affect the results of the peak test of each component, and therefore will not affect the measurement results of the electrolyte components; furthermore, component A, as the main component in the extracting solution, can be well mixed with the organic components in the lithium-ion battery electrolyte, and at the same time has a strong solubility for lithium salts, thereby improving the universality and accuracy of the extraction method for extracting lithium-ion battery electrolytes; in addition, component A and component B are not corrosive to the chromatographic column and will not damage the detection instrument.

[0060] Based on the same inventive concept, the present application also provides a method for preparing an extract, which comprises preparing the above-mentioned component A and component B in proportion.

[0061] In the embodiment of the present application, the preparation environment is an inert gas atmosphere, the water content in the environment is less than or equal to 0.1ppm, and the oxygen value is less than or equal to 50ppm. As an example, the water content in the preparation environment can be 0.1ppm, 0.09ppm, 0.08ppm, 0.05ppm, 0.01ppm, etc., and the oxygen value in the preparation environment can be 50ppm, 49ppm, 48ppm, 35ppm, 31ppm, etc. Preferably, when preparing the extract, in order to meet the requirements of the preparation environment, it can be carried out in a glove box.

[0062] The contents of component A and component B here refer to the first aspect and will not be described in detail here.

[0063] Based on the same inventive concept, the present application also provides a method for extracting electrolyte from a lithium-ion battery, comprising the following steps: injecting a lithium-ion battery to be analyzed and tested into an extraction solution, allowing the solution to stand and undergo ultrasonic treatment, and then extracting the electrolyte from the lithium-ion battery;

[0064] The extract comprises the extract provided by any one of the above embodiments.

[0065] The method for extracting the lithium-ion battery electrolyte of the embodiment of the present application uses the above-mentioned extraction solution containing acetonitrile and fluorobenzene and its derivatives for extraction, thereby utilizing the low viscosity and chemical inertness of acetonitrile and the property of fluorobenzene to improve wettability, thereby meeting the testing requirements of organic components and all anion components, broadening the testing capabilities for lithium-ion batteries, improving the universality of the extraction method, and at the same time improving the uniformity of mixing the extraction solution with the lithium-ion battery electrolyte, effectively improving the accuracy of the extraction.

[0066] Specifically, in an embodiment of the present application, the ambient dew point temperature when the extract is injected is -80 to -10°C, and the ambient dew point temperature is preferably -80 to -40°C; as an example, the ambient dew point temperature can be any point value among -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, and -10°C, or a range value between any two of them.

[0067] In the embodiment of the present application, when the liquid inside the lithium-ion battery is removed, such as when the electrolyte in the lithium-ion battery is extracted, the ambient dew point temperature is -80 to -10°C, and the ambient dew point temperature is preferably -80 to -40°C; as an example, the ambient dew point temperature can be any one of -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, and -10°C, or a range value between any two of them.

[0068] By controlling the ambient humidity when the extraction liquid is injected and the ambient humidity when the internal liquid is removed after the lithium-ion battery electrolyte extraction is completed, it is possible to prevent certain components in the electrolyte from decomposing when exposed to water, thereby ensuring the accuracy of the test results.

[0069] In the embodiment of the present application, the injection amount of the extracting liquid is based on the initial capacity of the lithium-ion battery, and the injection amount of the extracting liquid is adjusted according to the initial capacity of the lithium-ion battery. The injection coefficient of the extracting liquid is 0.1-10 g / Ah, preferably 0.5-5 g / Ah. As an example, the injection coefficient of the extracting liquid can be any one of 0.1 g / Ah, 0.2 g / Ah, 0.3 g / Ah, 1 g / Ah, 1.5 g / Ah, 2 g / Ah, 3 g / Ah, 4 g / Ah, 5 g / Ah, 6 g / Ah, 7 g / Ah, 8 g / Ah, 9 g / Ah, and 10 g / Ah, or a range between any two of them.

[0070] The amount of the extract added can be adjusted according to the capacity of the lithium-ion battery. For example, if the initial capacity of the lithium-ion battery is relatively large, more extract can be injected, or if the capacity of the lithium-ion battery is relatively small, less extract can be injected. Usually, the injection coefficient of the extract can be adjusted in the range of 0.1 to 10 g / Ah.

[0071] It should be understood that battery capacity refers to the amount of electricity stored in the battery, which is the amount of electricity released by the battery under certain conditions. How much energy a battery can provide depends on its capacity. Capacity is a material-specific variable that can be calculated directly from material data using simple equations. In other words, battery capacity is affected by active substances and utilization. For a battery system composed of specific materials, there will be an initial capacity at the beginning. The initial capacity of the battery is the maximum capacity of the battery system. As the battery is used for a longer time, the battery capacity will decrease accordingly.

[0072] In the embodiment of the present application, the standing and ultrasonic treatment specifically include a first standing, ultrasonic and a second standing performed in sequence.

[0073] As an example, the method for extracting the electrolyte of a lithium-ion battery in an embodiment of the present application specifically includes:

[0074] First, inject the extraction liquid into the lithium-ion battery to be analyzed and tested. For example, first fully discharge the lithium-ion battery in a specified state to the lower limit voltage, inject the prepared extraction liquid into the lithium-ion battery, and seal it;

[0075] After sealing, the first static state is performed, and then the lithium-ion battery is placed in an ultrasonic device for ultrasonication. After the ultrasonication, the second static state is performed, and finally the liquid inside the lithium-ion battery is extracted, thus completing the extraction of the electrolyte.

[0076] It should be understood that the amount of liquid extracted from the lithium-ion battery after the second standing should be sufficient to complete subsequent analysis requirements such as organic component analysis and lithium salt concentration testing.

[0077] In the embodiment of the present application, the temperature of the first standing is 0-80°C, and the temperature of the first standing is preferably 30-70°C; as an example, the temperature of the first standing can be any point value of 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 65°C, 70°C, 80°C or any range value between two of them. Theoretically, the higher the temperature of the first standing, the faster the extraction liquid and the electrolyte can be mixed evenly, but the temperature during the first standing should not be higher than the upper limit of the temperature during the first standing specified in the present application. If the temperature is higher than 80°C, the lithium salt in the electrolyte will decompose, causing the electrolyte to decompose during the extraction process, affecting the accuracy of the test. By limiting the temperature of the first standing, the extraction liquid and the lithium-ion battery electrolyte can be better mixed without affecting the accuracy of the test results.

[0078] In an embodiment of the present application, the first standing time is 4 to 24 hours, and the first standing time is preferably 6 to 12 hours; as an example, the first standing time can be any one of 4h, 6h, 8h, 10h, 11h, 12h, 15h, 16h, 20h, 24h or a range value between any two of them.

[0079] In the embodiment of the present application, the temperature of ultrasound is 0 to 60°C, and the temperature of ultrasound is preferably 40 to 60°C; as an example, the temperature of ultrasound can be any point value of 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C or a range value between any two of them. The higher the temperature of ultrasound, the faster the extraction liquid and the electrolyte can be mixed evenly, but the temperature of ultrasound should not be higher than the upper temperature limit of ultrasound specified in the present application. If the temperature is higher than 60°C, the lithium salt in the electrolyte will decompose, causing the electrolyte to decompose during the extraction process, affecting the test accuracy. By limiting the temperature of ultrasound, the extraction liquid and the lithium-ion battery electrolyte can be better mixed without affecting the accuracy of the test results.

[0080] In the embodiment of the present application, the power of ultrasound is 24 to 120 W, and the power of ultrasound is preferably 30 to 100 W. As an example, the power of ultrasound can be any point value among 24 W, 30 W, 40 W, 50 W, 60 W, 70 W, 80 W, 90 W, 100 W, 110 W, 120 W, or a range value between any two of them.

[0081] In the embodiment of the present application, the ultrasonic time is 0.5 to 4 hours, and the ultrasonic time is preferably 1 to 2 hours; as an example, the ultrasonic time can be any point value of 0.5 hours, 0.8 hours, 1 hour, 1.2 hours, 1.5 hours, 2 hours, 3 hours, 3.5 hours, and 4 hours, or a range value between any two of them. The ultrasonic time within this range can achieve the effect of uniform mixing of the extract and the electrolyte, and a longer ultrasonic time will reduce the extraction efficiency of the electrolyte.

[0082] By limiting the above-mentioned ultrasonic parameters, during the ultrasonic process, the extraction liquid will fully infiltrate the lithium-ion battery and can be fully mixed with the remaining electrolyte inside the lithium-ion battery. At the same time, it can also accelerate the transfer of organic matter and lithium salts in the electrolyte to the extraction liquid, thereby accelerating the extraction process of the electrolyte.

[0083] In the embodiment of the present application, the temperature of the second standing is 0-60°C, preferably 10-40°C; as an example, the temperature of the second standing can be any point value of 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C or a range value between any two of them. The effect that can be achieved by limiting the temperature range of the second standing in the present application is the same as the temperature limitation of the first standing, and will not be repeated here.

[0084] In an embodiment of the present application, the second standing time is 4 to 48 hours, and the second standing time is preferably 12 to 36 hours; as an example, the second standing time can be any one of 4h, 6h, 8h, 10h, 11h, 12h, 15h, 16h, 20h, 24h, 26h, 30h, 36h, 40h, and 48h, or a range value between any two of them.

[0085] In the embodiment of the present application, the lithium-ion battery includes one of a battery before formation, a battery before capacity division after formation, a battery after capacity division, or a battery after cycling.

[0086] In the embodiment of the present application, the battery after capacity division includes a battery before circulation after capacity division, a battery before storage after capacity division, or a battery stored after capacity division; preferably, there is no limit to the storage time.

[0087] In the embodiments of the present application, the cycled battery is a battery that has been cycled any number of times.

[0088] That is, the lithium-ion battery to be analyzed and tested may be a lithium-ion battery in a specified state, wherein the specified state may be a state after liquid injection but before formation, a state after formation but before capacity division, a state after capacity division but before circulation / storage, a state after circulation for a certain number of times, wherein the number of circulations is not limited, or a state after storage for a certain number of days, wherein the number of storage days is not limited.

[0089] In the embodiment of the present application, when the lithium-ion battery is a battery before capacity splitting, a battery after capacity splitting or a battery after cycling, before injecting the lithium-ion battery to be analyzed and tested into the extraction liquid, the step of discharging the lithium-ion battery to be analyzed and tested is also included.

[0090] In the embodiment of the present application, the discharge step includes discharging to the lower limit voltage of the lithium-ion battery, wherein the discharge current is 0.05-0.5C, and the discharge current is preferably 0.05-0.1C; as an example, the discharge current is any one of 0.5C, 0.3C, 0.1C, 0.05C or a range between any two of them. Preferably, the discharge current is less than or equal to 0.1C, such as the discharge current can be 0.1C or 0.05C, so that the voltage rebound caused by polarization can be reduced.

[0091] It should be noted that the above discharge current is calculated based on the initial capacity of the battery.

[0092] The lithium-ion battery electrolyte extraction method, by using the extraction solution of this embodiment, can complete the extraction of lithium-ion battery electrolyte in a simple manner, and at the same time has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0093] In the embodiments of the present application, the specific type of the lithium-ion battery is not limited. As an example, the lithium-ion battery can be a cylindrical lithium-ion battery, a soft-pack lithium-ion battery, or an aluminum-shell lithium-ion battery.

[0094] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this area or the product instructions are used. If the manufacturer of the reagents, materials or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0095] Battery Preparation

[0096] The lithium-ion battery uses a soft-pack cell with a capacity of 3Ah after injection and before formation. After injection, the lithium-ion battery undergoes a normal high-temperature static process. Because the battery has not yet been formed and charged, the step of discharging the battery to the lower limit voltage is skipped and it can be directly used for subsequent electrolyte extraction. The electrolyte configuration process is as follows: in a glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are uniformly mixed in a weight ratio of 3:6:1, and LiPF6 is added and stirred evenly, wherein the mass fraction of LiPF6 in the total electrolyte is 12.5%, and finally additives are added, wherein the mass fractions of ethylene carbonate (VC) and vinyl sulfate (DTD) in the total electrolyte are 4% and 1% respectively, to obtain an injection electrolyte.

[0097] Example 1

[0098] 1. Extraction solution preparation

[0099] In a glove box with an argon atmosphere, acetonitrile (purity 99.9%, water content 15 ppm) and 1-fluorobenzene (purity 99.9%, water content 15 ppm) were mixed in proportion to prepare an extract. The mass fractions of acetonitrile and 1-fluorobenzene in the extract are shown in Table 1.

[0100] Among them, the water content in the glove box is 0.09ppm and the oxygen value is 48ppm.

[0101] 2. Extraction of Lithium-ion Battery Electrolyte

[0102] Transfer the lithium-ion battery and the extract to an environment with a dew point temperature below -50°C. Cut the lithium-ion battery from one corner and slowly inject the extract into the battery cell with a syringe. By weighing the weight of the battery cell before and after, ensure that the amount of extract injected is 6g (the injection coefficient is 2g / Ah). After injection, seal the battery to ensure that the seal strength is sufficient. Then place the battery in a 60°C oven for 8h for the first static. After the first static, transfer the battery to an ultrasonic pool, set the ultrasonic power to 80W, set the ultrasonic time to 1h, and use a thermometer to monitor the water temperature in the ultrasonic pool. Control the water temperature at 50±5°C by changing the water in the pool. After the ultrasound is finished, place the battery in a 25°C environment for a second static 24h, then transfer the battery to an environment with a dew point temperature below -50°C, cut the diagonal of the initial opening of the battery, collect the liquid released from the opening, and complete the electrolyte extraction process.

[0103] Example 2

[0104] The difference between Example 2 and Example 1 is that the component ratios of the extract are different. The specific component ratios are shown in Table 1. The rest are the same as Example 1.

[0105] Example 3

[0106] The difference between Example 3 and Example 1 is that the component ratios of the extract are different. The specific component ratios are shown in Table 1. The rest are the same as Example 1.

[0107] Example 4

[0108] The difference between Example 4 and Example 1 is that the component ratios of the extract are different. The specific component ratios are shown in Table 1. The rest are the same as Example 1.

[0109] Example 5

[0110] The difference between Example 5 and Example 1 is that in the extract component, 1-fluorobenzene is replaced by 1-methyl-3,5-difluorobenzene; the rest is the same as Example 1.

[0111] Example 6

[0112] The difference between Example 6 and Example 1 is that the injection coefficient is different. The injection coefficient of Example 6 is 5 g / Ah; the rest is the same as Example 1.

[0113] Example 7

[0114] The difference between Example 7 and Example 1 is that the temperature of the first standing is 40° C.; the rest is the same as Example 1.

[0115] Example 8

[0116] The difference between Example 8 and Example 1 is that the ultrasonication time is 1.5 h; the rest is the same as Example 1.

[0117] Comparative Example 1

[0118] The difference between Comparative Example 1 and Example 1 is that the extract contains only one component, acetonitrile, and the rest is the same as Example 1.

[0119] Comparative Example 2

[0120] The difference between Comparative Example 2 and Example 1 is that the extract contains only ethyl acetate as a component, and the rest is the same as Example 1.

[0121] Comparative Example 3

[0122] The difference between Comparative Example 3 and Example 1 is that the extract contains only 1-fluorobenzene, and the rest is the same as Example 1.

[0123] Comparative Example 4

[0124] The difference between Comparative Example 4 and Example 1 is that the component ratios of the extract are different. The specific component ratios are shown in Table 1. The rest are the same as Example 1.

[0125] Comparative Example 5

[0126] The difference between Comparative Example 5 and Example 1 is that the component ratios of the extract are different. The specific component ratios are shown in Table 1. The rest are the same as Example 1.

[0127] Comparative Example 6

[0128] The difference between Comparative Example 6 and Example 1 is that the acetonitrile in Example 1 is replaced by ethyl acetate, and the rest is the same as Example 1.

[0129] Lithium-ion battery electrolyte composition testing

[0130] The liquid extracted from the above embodiments and comparative examples was tested for organic component content and anion concentration, specifically including:

[0131] (1) Organic ingredient content test

[0132] The content of organic components was determined by gas chromatography. The gas chromatography column model was GC-2014AT. The carrier gas was selected from a mixture of hydrogen and air. The hydrogen flow rate was set to 50 ml / min, the air flow rate was set to 400 ml / min, the starting temperature was 50°C for 2 min, the heating rate was 15°C / min, and the ending temperature was 250°C for 2 min. The response factor correction normalization method was used to achieve quantification of organic components such as EC, EMC, DMC, VC and DTD.

[0133] (2) Anion concentration test

[0134] The anion concentration was determined by ion chromatography. The chromatographic column was Swiss Metrohm Supp-5-250, the eluent was 10 mmol / L sodium carbonate aqueous solution, the regeneration liquid was 0.5% sulfuric acid aqueous solution, the column temperature was 40°C, the injection volume was 20 μL, and the flow rate was 0.7 ml / min.

[0135] Test Results

[0136] The compositions of the extracts of the above-mentioned embodiments and comparative examples, and the test deviations of EC, EMC, DMC, VC, DTD and LiPF6 in the lithium-ion battery electrolyte are shown in Table 1;

[0137] Wherein, taking the electrolyte formula as a reference, test deviation = (test result of the embodiment or comparative example - electrolyte formula) / electrolyte formula × 100%, and the closer the test deviation is to 0, the higher the test accuracy is.

[0138] Table 1

[0139]

[0140]

[0141] As shown in Examples 1-5 and Comparative Examples 1-3 and Comparative Example 6 in Table 1, acetonitrile can be used as the main extractant of the extract, and a lower test deviation can be achieved, and a higher test accuracy can be achieved. This is because acetonitrile can be well blended with organic components such as EC and DMC in the electrolyte, and has a strong solubility for lithium salts such as LiPF6. Compared with the commonly used extractant ethyl acetate, acetonitrile has a lower viscosity, can quickly infiltrate lithium-ion batteries, and fully mix with the remaining electrolyte in the lithium-ion battery, so the composition of the extracted electrolyte can better represent the actual composition of the remaining electrolyte inside the lithium-ion battery, and the test deviation is lower. In addition, acetonitrile has a lower chemical activity than ethyl acetate, is not easy to react with by-products such as lithium analysis of lithium ion batteries, affects the electrolyte composition test, and can effectively expand the scope of application of the extraction method to extract lithium-ion battery electrolytes, and improves the universality of the test. When acetonitrile is compounded with 1-fluorobenzene as an extractant, the accuracy of component tests such as VC, DTD and LiPF6 can be effectively improved, and the effect of 1-fluorobenzene is better than that of 1-methyl-3,5-difluorobenzene. Because the fluorobenzene structure can reduce the surface tension of the mixed solution and improve the wettability of the mixed solution, the addition of 1-fluorobenzene can improve the wettability of the mixed solution injected into the battery cell and accelerate the mixing of the extract and the remaining electrolyte inside the lithium-ion battery. Compared with 1-methyl-3,5-difluorobenzene, 1-fluorobenzene has a smaller molecular weight and can more effectively reduce the surface tension, thereby achieving higher test accuracy.

[0142] It can be seen from Examples 1-4 and Comparative Examples 4-5 in Table 1 that when the acetonitrile content x and the 1-fluorobenzene content y in the extract exceed the set range of the present invention, the test deviation of the organic component of the electrolyte increases, especially the test deviation of the concentration of lithium salts such as LiPF6 increases significantly. This is because 1-fluorobenzene itself has general miscibility with organic components in the electrolyte, especially its solubility in lithium salts is poor. Therefore, when the acetonitrile content decreases and the 1-fluorobenzene content increases, the lithium salt cannot be well dissolved in the mixed solution, causing its test content to deviate from the actual value.

[0143] It can be seen from Example 1 and Examples 6-8 in Table 1 that, within the scope of the claims, increasing the injection coefficient of the extractant can improve the test accuracy, reducing the first standing temperature will reduce the test accuracy, and extending the extraction ultrasonic time can improve the test accuracy. The specific extraction process parameters need to balance the test accuracy requirements and the extraction experiment efficiency.

[0144] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0145] The basic principle of the present invention is described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, strengths, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. must be possessed by each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of illustration and facilitation of understanding, rather than limitation, and the above details do not limit the present invention to being implemented by adopting the above specific details.

[0146] It should be noted that the term "and / or" or " / " used in this document is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The singular forms of "a", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0147] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A, B are listed, the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, C are listed, the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An extracting solution for extracting lithium ion battery electrolyte, characterized in that: The extract comprises component A and component B; The component A comprises acetonitrile; The component B includes fluorobenzene and / or fluorobenzene derivatives.

2. The extracting solution for extracting electrolyte of lithium ion batteries according to claim 1, characterized in that: The mass fraction of component A is x, and the value of x satisfies: 80%≤x<100%; The mass fraction of component B is y, and the value of y satisfies: 0%<y≤20%; Preferably, x and y also satisfy x+y=100%.

3. The extracting solution for extracting electrolyte of lithium ion batteries according to claim 1, characterized in that: The fluorobenzene includes at least one of 1-fluorobenzene, 1,2-difluorobenzene or 1,3,5-trifluorobenzene; And / or, the fluorobenzene derivative includes an alkyl derivative of fluorobenzene, and the alkyl derivative of fluorobenzene includes at least one of 1-methyl-3,5-difluorobenzene, 1-ethyl-3,5-difluorobenzene or 1-n-propyl-3,5-difluorobenzene.

4. The extracting solution for extracting electrolyte of lithium ion batteries according to any one of claims 1 to 3, characterized in that: The purity of the component A and the component B are both greater than or equal to 99.9%, and the water content is both less than or equal to 20 ppm.

5. A method for extracting lithium ion battery electrolyte, characterized in that: The following steps are involved: The lithium-ion battery to be analyzed and tested is injected into the extraction solution, allowed to stand and subjected to ultrasonic treatment, and then the electrolyte in the lithium-ion battery is extracted; Wherein, the extract comprises the extract according to any one of claims 1 to 4.

6. The extraction method according to claim 5, characterized in that The ambient dew point temperature when the extract is injected is -80°C to -10°C; And / or, the ambient dew point temperature when extracting the electrolyte from the lithium-ion battery is -80°C to -10°C.

7. The extraction method according to claim 5, characterized in that The injection amount of the extracting solution is based on the initial capacity of the lithium-ion battery, and the injection coefficient of the extracting solution is 0.1 to 10 g / Ah.

8. The extraction method according to claim 5, characterized in that The standing and ultrasonic treatment specifically include a first standing, ultrasonic treatment and a second standing performed sequentially; Preferably, the temperature of the first standing is 0°C to 80°C, and the time of the first standing is 4h to 24h; Preferably, the temperature of the ultrasound is 0°C to 60°C, the power of the ultrasound is 24W to 120W, and the time of the ultrasound is 0.5h to 4h; Preferably, the temperature of the second standing is 0°C to 60°C, and the time of the second standing is 4h to 48h.

9. The extraction method according to any one of claims 5 to 8, characterized in that The lithium ion battery comprises one of a battery before formation, a battery before capacity division after formation, a battery after capacity division, or a battery after cycling; Preferably, the cycled battery is a battery that has been cycled an arbitrary number of times.

10. The extraction method according to claim 9, characterized in that When the lithium-ion battery is a battery before capacity division after formation, a battery after capacity division after formation, or a battery after circulation, before injecting the lithium-ion battery to be analyzed and tested into the extraction liquid, the step of discharging the lithium-ion battery to be analyzed and tested is also included; The discharging step includes discharging the lithium ion battery to a lower voltage limit of the battery, and the discharging current is 0.05 to 0.5C, preferably 0.05 to 0.1C.

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