Electrolyte consumption testing method

Abstract

The invention relates to the technical field of batteries, in particular to a method for testing electrolyte consumption. The electrolyte consumption testing method comprises the following steps: injecting an internal standard agent into a to-be-tested battery to obtain the to-be-tested battery containing the internal standard agent; performing a first shallow charge-discharge cycle on the to-be-tested battery containing the internal standard agent; disassembling the to-be-tested battery after the first shallow charge-discharge cycle, taking out the electrolyte, testing or calculating to obtain a first consumption amount of the electrolyte, and recording the first consumption amount as m1; according to the standard curve, the second consumption amount of the electrolyte in the first shallow charge-discharge cycle process is obtained and recorded as m2, according to m1 and m2, the consumption amount of the electrolyte in the to-be-tested battery is obtained and recorded as m, and m = m1-m2. According to the invention, the internal standard agent and the electrolyte in the battery cell can be uniformly mixed by carrying out shallow charge-discharge cycle on the battery, so that the accuracy of the detection result is improved; and by drawing a standard curve, the electrolyte consumed in the shallow charge-discharge cycle process can be compensated, and the result accuracy can be further improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method for testing electrolyte consumption. Background Art

[0002] As an important component of batteries (such as lithium batteries), electrolyte has a great impact on life. Usually, electrolyte, as an ion transmission carrier in the battery, is mainly composed of lithium salts, organic solvents and a small amount of additives. The electrolyte mainly plays the role of conducting ions between the positive and negative electrodes of the lithium battery. It is the guarantee for lithium-ion batteries to obtain advantages such as high voltage and high specific energy. Therefore, the influence of electrolyte on battery reliability is crucial. By studying the mechanism of action of electrolyte in lithium batteries and optimizing the electrolyte formula, it is helpful to improve the performance of the battery cell. In actual application, the amount of lithium battery electrolyte is not constant. As the operating conditions are running, the electrolyte is constantly consumed. When the electrolyte is consumed to a certain value, the battery capacity will decay faster, affecting the battery life. Therefore, the change in the amount of electrolyte is very important for electrolyte design and is an important factor affecting the reliability of battery life.

[0003] In the related art, the internal standard method is used to test the consumption of electrolyte. However, the traditional internal standard method adds an internal standard substance to the battery and obtains the electrolyte consumption through the content of the internal standard substance. It uses the extrusion / centrifugation method combined with the internal standard method for testing. Since the extrusion cannot squeeze out all the electrolyte in the core, and the centrifugation cannot obtain all the electrolyte, the test results are not accurate enough and the operation is difficult. Therefore, the traditional internal standard method has inaccurate results.

[0004] Therefore, it is necessary to develop a more accurate and effective method to analyze and test the consumption of electrolyte in a battery. In view of this, the present invention is proposed. Summary of the invention

[0005] In view of this, the present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the present invention provides a method for testing electrolyte consumption, which can improve the accuracy of the test result.

[0006] In order to solve the above technical problems, this application is implemented as follows:

[0007] According to one aspect of the present application, an embodiment of the present application provides a method for testing electrolyte consumption, the method comprising:

[0008] Injecting an internal standard agent into the battery to be tested to obtain a battery to be tested containing the internal standard agent;

[0009] Subjecting the battery to be tested containing the internal standard agent to a first shallow charge-discharge cycle, wherein the first shallow charge-discharge cycle is charging each time until the state of charge of the battery is less than 100%;

[0010] Disassembling the battery to be tested after the first shallow charge and discharge cycle, taking out the electrolyte to test or calculate to obtain a first consumption of the electrolyte, recorded as m1;

[0011] According to the standard curve, the second consumption of the electrolyte during the first shallow charge-discharge cycle is obtained, recorded as m2,

[0012] According to the m1 and the m2, the consumption of the electrolyte in the battery to be tested is obtained, which is recorded as m, wherein m=m1-m2.

[0013] In addition, the electrolyte consumption test method according to the present application may also have the following additional technical features:

[0014] In some embodiments, drawing of the standard curve includes: subjecting the battery to a second shallow charge and discharge cycle, and then injecting an internal standard agent into the battery to obtain a battery containing the internal standard agent; subjecting the battery containing the internal standard agent to a third shallow charge and discharge cycle; disassembling the battery after the third shallow charge and discharge cycle, taking out the electrolyte and calculating the consumption of the electrolyte; drawing a standard curve with the number of cycles as the horizontal coordinate and the consumption of the electrolyte as the vertical coordinate; wherein the operating conditions of the first shallow charge and discharge cycle, the operating conditions of the second shallow charge and discharge cycle and the operating conditions of the third shallow charge and discharge cycle are all the same.

[0015] In some embodiments, the operating conditions of the first shallow charge and discharge cycle include: the charge and discharge temperature is 25-60° C., the charge and discharge rate is 0.5C-3C, and the upper limit voltage of charge and discharge is greater than the reduction voltage of the internal standard agent.

[0016] In some embodiments, the operating conditions of the second shallow charge and discharge cycle include: the charge and discharge temperature is 25-60° C., the charge and discharge rate is 0.5C-3C, and the upper limit voltage of charge and discharge is greater than the reduction voltage of the internal standard agent.

[0017] In some embodiments, the operating conditions of the third shallow charge and discharge cycle include: the charge and discharge temperature is 25-60° C., the charge and discharge rate is 0.5C-3C, and the upper limit voltage of charge and discharge is greater than the reduction voltage of the internal standard agent.

[0018] In some embodiments, the first shallow charge and discharge cycle is charging to 50% to 80% of the state of charge of the battery each time.

[0019] In some embodiments, the second shallow charge and discharge cycle is charging to 50% to 80% of the state of charge of the battery each time.

[0020] In some embodiments, the third shallow charge and discharge cycle is charging to 50% to 80% of the state of charge of the battery each time.

[0021] In some embodiments, after injecting the internal standard agent into the battery and before performing the third shallow charge and discharge cycle, the method further includes the step of ultrasonically treating the battery containing the internal standard agent.

[0022] In some embodiments, after injecting the internal standard agent into the battery to be tested and before performing the first shallow charge and discharge cycle, the method further includes the step of ultrasonically treating the battery to be tested containing the internal standard agent.

[0023] In some embodiments, the internal standard agent includes at least one of nitriles, carboxylates, carbonates, tetrahydrofuran, ethers, amides, alkanes, halides, ketones, alcohols, benzene and its derivatives, or carbon disulfide, whose main chain contains more than 2 carbon atoms.

[0024] In some embodiments, the m1 is calculated according to formula (1):

[0025] m1= m0- m 内 / w 内 +m 内 (1);

[0026] Where m0 is the total mass of electrolyte injection, in g; m 内 is the injection volume of the internal standard agent, in g; w 内 It is the content of internal standard agent in the electrolyte sample taken out after disassembly, in %.

[0027] In some embodiments, the consumption of any additive in the electrolyte is recorded as m 添 , the m 添 Calculate according to formula (2):

[0028] m 添 =m0*w0-w 添 *(m 内 +m0') (2);

[0029] Among them, m 添 The unit is g; w0 is the content of any additive in the initial electrolyte, the unit is %; w 添 is the content of additives in the electrolyte sample taken out after disassembly, in %; m0' is the mass of the remaining electrolyte in the battery, in g.

[0030] In some embodiments, the method further includes: taking the number of cycles as the horizontal coordinate and the consumption of electrolyte in the battery to be tested as the vertical coordinate to obtain a curve showing that the consumption of electrolyte varies with the number of cycles; or, taking SOH as the horizontal coordinate and the consumption of electrolyte in the battery to be tested as the vertical coordinate to obtain a curve showing that the consumption of electrolyte varies with SOH.

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

[0032] In an embodiment of the present application, a method for testing electrolyte consumption is provided which uses an internal standard method combined with shallow charge and discharge to measure electrolyte consumption. This method injects an internal standard agent into a battery such as a battery that has completed working conditions, and then performs shallow charge and discharge cycles (at high temperature or room temperature). The electrolyte is made to flow by shallow charge and discharge. In addition, high temperature will also increase the activity space of the electrolyte inside the winding core, thereby allowing the internal standard agent to be evenly mixed with the electrolyte in the winding core. The battery is then disassembled and the free electrolyte is taken to test the content of the internal standard agent and other components. Therefore, compared with the traditional internal standard method, the internal standard method combined with the shallow charge and discharge method produces more accurate results.

[0033] That is, by subjecting the battery to shallow charge and discharge cycles at high or room temperature, the internal standard agent is mixed evenly with the electrolyte in the core, thereby improving the accuracy of the test results. Furthermore, by drawing a standard curve, the electrolyte consumed during the shallow charge and discharge cycle can be determined to compensate for the electrolyte consumed in the previous steps, thereby further improving the accuracy of the results.

[0034] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Shown is a schematic flow chart of a method for testing electrolyte consumption provided in some embodiments of the present invention.

[0036] Figure 2 Another schematic flow chart of a method for testing electrolyte consumption provided in some embodiments of the present invention is shown.

[0037] Figure 3 Shown is a schematic diagram of the operation of the electrolyte consumption testing method provided in some embodiments of the present invention.

[0038] Figure 4 It is a schematic diagram of a standard curve (45° C., 0.5C / 0.5C, 0-50% SOC consumption standard curve) of the test method of electrolyte consumption provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0039] 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.

[0040] 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.

[0041] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0042] 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.

[0043] Electrolyte plays a vital role in batteries. After the battery undergoes processes such as formation, storage or circulation, the electrolyte is continuously consumed, which directly affects the actual performance of the battery. Therefore, the accurate analysis of the electrolyte composition and its content after the actual working conditions in the battery has important guiding significance for the design of the battery cell. At the same time, accurately analyzing the consumption of the electrolyte is also of great significance for studying the mechanism of action of the electrolyte in the battery, optimizing the electrolyte formula, and thus improving the performance of the battery cell. The present application provides an analytical test method for the consumption of the electrolyte, which can more accurately analyze and detect the consumption of the electrolyte, has the advantages of high accuracy, simple operation, low analysis cost, safety and reliability, etc., and can be widely used in the design or use of different secondary batteries, which helps to improve the performance of secondary batteries.

[0044] See also Figure 1 As shown, in some embodiments, the present application provides a method for testing electrolyte consumption, the method comprising the following steps:

[0045] Injecting an internal standard agent into the battery to be tested to obtain a battery to be tested containing the internal standard agent;

[0046] The battery to be tested containing the internal standard agent is subjected to a first shallow charge-discharge cycle, wherein the first shallow charge-discharge cycle is charging each time until the state of charge (SOC) of the battery is less than 100%;

[0047] After the first shallow charge and discharge cycle, the battery to be tested is disassembled, and the electrolyte is taken out for testing or calculation to obtain the first consumption of the electrolyte, which is recorded as m1;

[0048] According to the standard curve, the second consumption of electrolyte in the first shallow charge-discharge cycle is obtained, recorded as m2,

[0049] According to m1 and m2, the consumption of electrolyte in the battery to be tested is obtained, which is recorded as m, wherein m=m1-m2.

[0050] It should be pointed out that in the present application, the electrolyte consumption test method provided has a wide range of applications and can be suitable for any type of battery, such as lithium batteries, sodium batteries, magnesium batteries and other types of batteries, or various types of batteries such as soft-pack batteries, square-shell batteries, power batteries, etc. For the sake of simplicity, the electrolyte consumption test method of the present invention is further described below mainly using lithium batteries as an example. It should be understood that other types of batteries have the same principle and will not be described in detail one by one.

[0051] In addition, the battery system of the present invention, such as the lithium battery system, can be various types of battery systems, and their structures, raw materials, and preparation processes, except for special limitations of the present invention, are all conventional technical means, and those skilled in the art can make adaptive choices based on actual needs.

[0052] It should also be pointed out that the method of the present invention adopts the internal standard method combined with (high temperature or room temperature) shallow charge and discharge cycle (shallow charge and discharge cycle) to measure the electrolyte consumption. Among them, usually, conventional charge and discharge refers to charging the battery from 0% SOC (State of Charge, i.e. the remaining power of the battery, also known as the state of charge) to 100% SOC, discharging the battery from 100% SOC to 0% SOC, and the standard cycle is also a full charge and discharge cycle; compared with the conventional charge and discharge cycle, shallow charge and discharge refers to charging the battery from 0% SOC to a specified SOC (preset SOC, less than 100%, such as 50%-60%, 70%-80%, etc.), and then discharging the battery from the specified SOC to 0% SOC. Such a cycle is a shallow charge and discharge cycle.

[0053] Thus, the above-mentioned first shallow charge and discharge cycle can be charging to a state of charge of less than 100% each time, for example, charging to a specified SOC each time, as long as it is less than 100% SOC, such as 50% to 90% SOC, or 60% to 80% SOC, etc., the present application does not limit the specific numerical value, and then, the battery is discharged from the specified SOC to 0% SOC, thus performing a shallow charge and discharge cycle.

[0054] The test method for electrolyte consumption of the present application requires injecting an internal standard agent into the battery to be tested, and then performing a shallow charge and discharge cycle, and then disassembling the battery after the shallow charge and discharge cycle, taking out the electrolyte therein and calculating to obtain the first consumption of the electrolyte; it should be pointed out that since a certain amount of electrolyte will be consumed during the shallow charge and discharge cycle, it is necessary to draw a standard curve first in the actual analysis and testing process. According to the standard curve, the amount of electrolyte consumed during the shallow charge and discharge cycle can be obtained, which can be recorded as the second consumption. The amount of electrolyte consumed in the actual operating condition of the battery to be tested is the first consumption minus the second consumption.

[0055] The above-mentioned shallow charge and discharge cycle can be carried out at room temperature or high temperature. If it is carried out at high temperature, the mixing uniformity of the internal standard agent and the electrolyte can be further improved.

[0056] Therefore, based on the above settings, the provided method for testing electrolyte consumption, compared with the traditional internal standard method which adopts the method of adding an internal standard (internal standard agent) and then letting it stand for a period of time, has the problem that the internal standard can basically not be evenly mixed with the electrolyte in the core, resulting in inaccurate measured consumption. The present invention uses high temperature (or room temperature) shallow charging and discharging combined with the internal standard method to measure the electrolyte consumption more accurately. That is, the present invention adds a high temperature shallow charging and discharging step after the internal standard method, which can make the internal standard agent and the electrolyte inside the core mix evenly, and the measured result is more accurate.

[0057] In other words, the present invention injects an internal standard agent into the battery after the working condition is completed, and then performs shallow charge and discharge cycles at high temperature (or room temperature). The shallow charge and discharge causes the electrolyte to flow, so that the internal standard agent and the electrolyte in the core are mixed more evenly, thereby improving the accuracy of the test results; in addition, high temperature will also increase the activity space of the electrolyte inside the core, which is conducive to a more uniform mixing of the internal standard agent and the electrolyte. In addition, the present invention can determine the electrolyte consumed during the shallow charge and discharge cycle by drawing a standard curve to compensate for the electrolyte consumed in the previous steps, thereby further improving the accuracy of the results.

[0058] The method provided by the present invention is simple in operation and highly practical, and can accurately obtain the consumption of each component in the electrolyte of the used battery. In addition, it can also provide strong data support for the amount of electrolyte required to be injected when preparing the battery, and also provide the relationship between the electrolyte consumption and the number of charge / discharge cycles, indirectly verifying the reaction mechanism of each component in the electrolyte, such as additives, and the role played by the additives.

[0059] In addition, the used battery can be understood as a prepared battery that has undergone at least one charge / discharge cycle, wherein the number of charge / discharge cycles is not subject to specific restrictions as long as there is still electrolyte in the used battery.

[0060] See also Figures 2 to 3 As shown, in some specific embodiments, the method for testing the electrolyte consumption specifically includes the following steps:

[0061] S100, draw a standard curve.

[0062] In the present application, in order to obtain the amount m2 of electrolyte consumed during the first shallow charge and discharge cycle, a standard curve needs to be drawn first.

[0063] Specifically, drawing of the standard curve includes: subjecting the battery to a second shallow charge and discharge cycle, and then injecting an internal standard agent into the battery to obtain a battery containing the internal standard agent; subjecting the battery containing the internal standard agent to a third shallow charge and discharge cycle; disassembling the battery after the third shallow charge and discharge cycle, taking out the electrolyte and calculating the consumption of the electrolyte; drawing a standard curve with the number of cycles as the horizontal coordinate and the consumption of the electrolyte as the vertical coordinate; wherein the operating conditions of the first shallow charge and discharge cycle, the operating conditions of the second shallow charge and discharge cycle, and the operating conditions of the third shallow charge and discharge cycle are all the same.

[0064] Optionally, after injecting the internal standard agent into the battery and before performing the third shallow charge and discharge cycle, the method further includes the step of ultrasonically treating the battery containing the internal standard agent. Specifically, step S100 specifically includes:

[0065] S101. In the present application, in order to obtain the amount of electrolyte consumed in the shallow charge and shallow discharge steps after the injection of the internal standard agent, it is necessary to first cycle the battery under operating conditions (consistent with the operating conditions performed after the subsequent injection of the internal standard agent, for example, 45°C, 0-50% SOC, 0.5C / 0.5C), select several offline points (such as 5 cycles, 10 cycles, 20 cycles, 30 cycles, 40 cycles, 50 cycles, 60 cycles, 70 cycles and 80 cycles, etc.), and perform the following steps on the offline battery to obtain the electrolyte consumption of the corresponding number of cycles.

[0066] It should be noted here that the unloading point refers to the unloading of the battery after it has completed the corresponding required working conditions. For example, you can choose to test 9 batteries at the same time, unload one battery after 5 cycles, unload another battery after 10 cycles... and so on. Of course, the number of batteries to be tested at the same time can be adjusted according to actual conditions, and the number of cycles to be unloaded can also be adjusted according to actual conditions. This application does not limit the specific values.

[0067] In the test process of the present application, the operating conditions of the shallow charge and discharge cycles of the battery need to be consistent. Optionally, the operating conditions of the first shallow charge and discharge cycle, the operating conditions of the second shallow charge and discharge cycle, and the operating conditions of the third shallow charge and discharge cycle may include: the charge and discharge temperature is 25-60°C, the charge and discharge rate is 0.5C-3C, and the upper limit voltage of charge and discharge is greater than the reduction voltage of the internal standard agent.

[0068] Preferably, the charge and discharge temperature is 45-60° C. Performing a shallow charge and discharge cycle test at a high temperature such as 45-60° C. will increase the activity space of the electrolyte inside the winding core, which is conducive to more uniform mixing of the internal standard agent and the electrolyte.

[0069] Of course, the operating temperature range of the present application is not limited to 45-60°C, and can be room temperature and high temperature, such as 25-60°C. Moreover, it is worth noting that the temperature selection needs to ensure that the internal standard agent does not chemically react with the electrolyte, positive and negative electrode materials at this temperature; and 25-60°C is only a rough temperature selection range, and the specific temperature depends on the internal standard agent, the battery system, and the electrolyte composition.

[0070] S102. After the second shallow charge and discharge cycle, it is necessary to inject an internal standard agent into the battery to obtain a battery containing the internal standard agent. Specifically: a certain mass of the internal standard agent is injected into the battery, and ultrasound is applied for a certain period of time to mix the internal standard agent and the electrolyte inside the battery evenly. The internal standard agent can be a reagent that does not react with the electrolyte at room temperature and high temperature (high temperature such as 45-60°C), does not undergo chemical changes at high temperature, and does not participate in the film-forming reaction of the battery. In addition, the peak position detected by the electrolyte GC (gas chromatography: can analyze organic matter in a mixed liquid sample and detect the content of each organic matter) is required not to coincide with the peak position of the electrolyte component.

[0071] In the present application, ultrasound is applied for a period of time after the internal standard agent is injected, so that the internal standard agent can be pre-mixed with the free electrolyte in the battery, and the subsequent shallow charge and discharge steps can make the mixing effect better. Of course, in some embodiments, the ultrasound step can also be omitted; the specific time and power of the ultrasound step can be adjusted according to actual conditions, and there is no special requirement for this.

[0072] In some embodiments, the internal standard agent includes, but is not limited to, any one or more combinations of nitriles, carboxylates, carbonates, tetrahydrofuran, ethers, amides, alkanes, halides, ketones, alcohols, benzene and its derivatives (such as benzene and its homologues or halides) or carbon disulfide, whose main chain contains more than 2 carbon atoms.

[0073] It should be understood that the selection of the internal standard agent requires that the internal standard agent does not chemically react with the electrolyte and other components in the battery during all test steps.

[0074] As an example, the internal standard agent can be selected from ester substances such as EA (ethyl acetate) and DMC (dimethyl carbonate). EA can be used alone, or can be added to a mixture internal standard agent, such as EA / DMC. DMC has a higher polarity and better wettability, which helps the internal standard agent to mix with the electrolyte inside the core.

[0075] S103. After obtaining the battery containing the internal standard agent, a third shallow charge and discharge cycle is required. Specifically: the battery is subjected to shallow charge and discharge cycles at high temperature. Shallow charge and discharge can make the electrolyte flow, and the internal standard agent can enter the core, thereby being evenly mixed with all the electrolytes: the temperature can be selected to be 45-60°C. High temperature can make the core expand, and the internal standard agent can enter the core more easily, but the temperature cannot cause chemical changes in the internal standard agent; the charging SOC interval can be selected from any interval of 0-100%, such as the interval of 50%-80%. The upper limit voltage of charging (the negative electrode voltage of the battery at this moment) needs to be greater than the reduction voltage of the internal standard agent. For example, EA (ethyl acetate) is used as the internal standard agent (test method: the reference electrode is generally a standard hydrogen electrode; the working electrode is generally a platinum carbon electrode to form a battery, the internal standard agent EA is a solution, the potential difference between the working electrode and the reference electrode is measured, and the cyclic voltammetry curve is tested to obtain the hydrogen standard reduction potential of the internal standard agent). During the charging process of the battery, the positive electrode potential gradually increases and the negative electrode potential gradually decreases. Therefore, the substance with high reduction potential in the electrolyte will react first at the negative electrode. The upper limit voltage of shallow charging and discharging (the negative electrode voltage of the battery at this moment) needs to be greater than the reduction voltage of EA, otherwise it will cause the internal standard agent to react at the electrode during charging and discharging. The charge and discharge rate can be determined according to the battery capacity. Assuming that 104Ah is used for the experiment, it takes 1 hour to charge from 0% SOC to 50% SOC at 0.5C. In this way, 10 cycles of charge and discharge at 0.5C plus the rest time in between take a total of 30 hours. The higher the rate, the faster the cycle and the shorter the experimental time. However, some types of batteries have the problem of lithium deposition during high-rate charge and discharge. For example, 104Ah will deposit lithium when it exceeds 0.5C. In order to save experimental time and prevent lithium deposition in the battery, the maximum rate of the corresponding type of battery that will deposit lithium is generally selected; the more cycles, the more evenly the internal standard agent and the electrolyte are mixed, and the more accurate the calculation results. In addition, the process steps must be consistent: that is, the temperature and the specified SOC of shallow charge and discharge are consistent.

[0076] In the present application, the first shallow charge and discharge cycle, the second shallow charge and discharge cycle, and the third shallow charge and discharge cycle may all be charged to 50% to 80% of the state of charge of the battery each time.

[0077] It should be understood that all conditions during the internal standard test, that is, the working conditions involved in each step, including temperature, rate, etc., need to be completely consistent, because the shallow charge and discharge step itself consumes electrolyte, and the purpose of making a standard curve is to quantify this part of the electrolyte consumption. The consumption rate of electrolyte is different at different temperatures, and the standard curves made at different temperatures will also deviate, so it is necessary to keep the temperature and other working conditions consistent.

[0078] In this application, different internal standard agents are used, and the voltage range during the cycle test will also be different. Taking the commonly used internal standard agent ethyl acetate (EA) as an example, experiments show that the reduction potential of EA is 0.15V vs Li + / Li, according to the voltage curve of the battery during charging and the reference potential change curve of the positive and negative electrodes (at room temperature), when the negative electrode reference potential is 0.15V, the corresponding battery voltage (taking the ternary battery as an example, the full voltage range is 2.8V-4.3V) is 3.61V, and the voltage range of the shallow charge and discharge of the ternary battery using EA as the internal standard agent is 2.8V-3.61V. Of course, in other embodiments, when different internal standard agents are used, the voltage range can also be adaptively adjusted.

[0079] S104. After the third shallow charge and discharge cycle, the battery is disassembled, and the electrolyte is taken out to measure and calculate the consumption of the electrolyte. Specifically, the battery is disassembled, and the free electrolyte is collected to test the content of the internal standard agent such as EA and other organic components therein.

[0080] The above calculation method includes: defining the total mass of the electrolyte injection of the battery (the total amount of electrolyte added when manufacturing the battery) as m0, in g, and the amount of the internal standard agent (injection amount) as m 内 , the unit is g, the content of internal standard in the electrolyte liquid sample taken out after disassembly is w 内 , in %, the amount of remaining electrolyte in the battery is m0', in g, then w 内 (%) = m 内 / (m 内 +m0'), that is, the amount of remaining electrolyte in the battery m0'(g) = m 内 / w 内 -m 内 , then the consumption of electrolyte m1(g)=m0-m0'=m0-m 内 / w 内 +m 内 .

[0081] Then, according to each solvent and the added content, the consumption of organic solvent and additive in the electrolyte is calculated, and the content of additive in the liquid sample is defined as w 添 , the unit is %, the remaining mass of additive is M 剩添加剂 , in g, then w 添 (%) = M 剩添加剂 / (m+m0'), that is, M 剩添加剂 (g) = w 添 *(m+m0'); Assume that the content of a certain additive in the initial electrolyte is w0 additive, then the mass of a certain additive in the initial electrolyte is m0*w0(g), then the consumption of a certain additive is M 耗添加剂 (g) = m0*w0-M 剩添加剂 =m0*w0-w 添 *(m 内 +m0'). That is, similarly, the additive consumption can be calculated using the same method.

[0082] S105. After injecting the internal standard agent and shallow charging and discharging the battery in step S101, the electrolyte consumption corresponding to the corresponding number of cycles will be obtained. With the number of cycles as the horizontal coordinate (the number of cycles in the early stage + the number of shallow charging and discharging in the later stage), and the electrolyte consumption as the vertical coordinate, a curve showing the change of electrolyte consumption with the number of cycles under the corresponding working conditions will be obtained, which is defined as the standard curve. Therefore, according to the obtained standard curve, the number of shallow charging and discharging in the later stage is brought into this curve, that is, the amount of electrolyte consumed in the shallow charging and discharging steps in the later stage can be set as m2 (g); similarly, the amount of a certain additive in the electrolyte consumed in the shallow charging and discharging steps in the later stage can be obtained, which is set as m 耗添加剂 (or m 添 , unit is g).

[0083] It should be pointed out that in this application, the consumption of electrolyte (the sum of all components, including solvent, electrolyte lithium salt, additives) and the consumption of each additive can be calculated. Among them, the consumption of solvent can also be calculated, for example, the battery after shallow charge and discharge is disassembled, and the free electrolyte is sent to IC (ion chromatography, which can test the mass percentage of lithium salt). Suppose the measured lithium salt content is w 锂盐 %, assuming that the remaining lithium salt mass in the electrolyte is m 剩锂盐 , then w 锂盐 % = m 剩锂盐 / m0', then m 剩锂盐 =m0'*w 锂盐 %,m 剩溶剂 =m0'-m 剩锂盐 -M 剩添加剂 , assuming that the mass of the initial added solvent is m 始溶剂 , then the solvent consumption m 耗溶剂 =m 始溶剂 -m 剩溶剂 The standard curves of lithium salt consumption and solvent consumption can be drawn in the same way. The amount of lithium salt and solvent consumed in the shallow charge and discharge step of the internal standard can be obtained from the standard curves. 耗溶剂 ', the solvent consumption needs to be subtracted from m 耗溶剂 ', that is, the solvent consumption of the battery when it is operating in this condition can be obtained.

[0084] Step S200, injecting an internal standard agent into the battery to be tested, specifically comprising:

[0085] Inject the internal standard agent into a battery after the working condition through the battery explosion-proof valve through a syringe, seal the explosion-proof valve with AB glue, and ultrasonicate the battery for a period of time for preliminary mixing.

[0086] In the present application, after injecting the internal standard agent into the battery to be tested and before performing the first shallow charge and discharge cycle, the step of ultrasonically treating the battery to be tested containing the internal standard agent can be performed for preliminary mixing to improve the mixing effect.

[0087] Step S300 , subjecting the battery to be tested containing the internal standard agent to a first shallow charge and discharge cycle.

[0088] As an example, the battery is subjected to high-temperature shallow charge and shallow discharge cycles, such as placing it in an oven at 45°C (or 50°C, 55°C, 60°C, etc.) for a period of time (such as 4h, 3h, or 5h, etc.), charging and discharging at 0% to 50% SOC, with a rate of 0.5C, and cycling for 10 times.

[0089] It should be understood that the operating conditions when drawing the standard curve should be consistent with the operating conditions of shallow charging and shallow discharging after injecting the internal standard agent, so that the amount of electrolyte consumed in the shallow charging and shallow discharging cycle can be obtained from the standard curve.

[0090] Step S400, disassemble the battery and collect free electrolyte for testing. The electrolyte consumption can be calculated by the formula and recorded as the first electrolyte consumption m1. Then, the electrolyte consumed by high-temperature shallow charging and discharging is obtained according to the above standard curve, that is, the second electrolyte consumption m2 (that is, the amount of electrolyte consumed by the battery in this working condition). The electrolyte consumption of the battery to be tested can be obtained by subtracting m2 from m1.

[0091] Optionally, the method of the present invention also includes: taking the number of cycles as the horizontal coordinate and the consumption of electrolyte in the battery to be tested as the vertical coordinate to obtain a curve showing that the consumption of electrolyte varies with the number of cycles; or, taking SOH as the horizontal coordinate and the consumption of electrolyte in the battery to be tested as the vertical coordinate to obtain a curve showing that the consumption of electrolyte varies with SOH.

[0092] It should be understood that in the present application, after drawing the standard curve, in order to detect the electrolyte consumption of the battery to be tested, the off-line point can be set after the battery has completed the cycle or storage condition (the different off-line points are set to establish an electrolyte consumption model, not limited to these off-line points, and the number of cycles can be used as the off-line point, such as 200 cycles, 400 cycles, 600 cycles, 800 cycles, 1000 cycles, etc.; SOH can also be selected as the off-line point, such as 95%, 90%, 85%, 80%, 75% SOH, depending on customer requirements). After the off-line, the battery is injected with an internal standard agent and subjected to shallow charge and discharge cycles at high temperature (or room temperature), and then the battery is disassembled to detect the internal standard agent content and the content of other organic components in the free electrolyte, and the electrolyte consumption of the battery at each off-line point can be calculated (combined with the above standard curve, the electrolyte consumption obtained by m1-m2). Furthermore, SOH can be used as the horizontal axis and the electrolyte consumption as the vertical axis (Note: the electrolyte consumption needs to be reduced by m2 at this time). Finally, a curve of electrolyte consumption changing with SOH can be obtained, which can be used to understand the consumption rate of electrolyte during circulation and storage; similarly, the consumption of battery additives at each off-line point can be calculated, with SOH as the horizontal axis and the additive consumption as the vertical axis (Note: the additive consumption needs to be reduced by m2 at this time). 耗添加剂 ), and finally a curve showing the variation of the consumption of each additive with SOH can be obtained, which can help us understand the consumption rate of each additive during circulation and storage.

[0093] In this application, m1 can be calculated according to the following formula: m1 = m0 - m 内 / w 内 +m 内 ;

[0094] Where m0 is the total mass of electrolyte injection, in g; m 内 is the injection volume of the internal standard agent, in g; w 内 It is the content of internal standard agent in the electrolyte sample taken out after disassembly, in %.

[0095] In addition, the consumption of any additive in the electrolyte is recorded as m 添 , m 添 Calculated according to the following formula:

[0096] m 添 =m0*w0-w 添 *(m 内 +m0');

[0097] Among them, m 添 The unit is g; w0 is the content of any additive in the initial electrolyte, the unit is %; w 添 is the content of additives in the electrolyte sample taken out after disassembly, in %; m0' is the mass of the remaining electrolyte in the battery, in g.

[0098] The following is an illustration of an example of analyzing and testing the electrolyte using the electrolyte consumption test method proposed in this application.

[0099] Example

[0100] Step S100, draw a standard curve and calculate m2.

[0101] In order to determine the standard curve, first take 11 formed batteries and perform 45°C 0.5C / 0.5C 0-50% SOC cycles. After 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 cycles, take a certain mass of internal standard agent EA (ethyl acetate) and inject it into the battery through the explosion-proof valve using a syringe. Seal the explosion-proof valve with AB glue (such as Figure 3 As shown), the battery was placed in an ultrasonic machine for 1 h to allow the EA and electrolyte to be preliminarily mixed.

[0102] Then, the battery was subjected to shallow charge and discharge cycles at high temperature, and the operating conditions included: 45° C., 0-50% SOC, and 0.5C / 0.5C charge and discharge cycles for 10 weeks (10 circles).

[0103] Then, the battery was disassembled, the free electrolyte was collected, GC was tested, and the content of EA and other organic components was tested;

[0104] Then, the calculation is performed: Assume that the total mass of the electrolyte injection is m0, in g, the amount of internal standard agent (injection amount) is m, in g, and the content of internal standard agent in the electrolyte liquid sample taken out after disassembly is w 内 , in %, the amount of remaining electrolyte in the battery is m0', in g, then w 内 (%) = m 内 / (m 内 +m0'), that is, the amount of remaining electrolyte in the battery m0'(g) = m 内 / w 内 -m 内 , then the consumption of electrolyte m1(g)=m0-m0'=m0-m 内 / w 内 +m 内 Then, according to each solvent and the added content, the consumption of organic solvent and additive in the electrolyte is calculated. Assume that the content of additive in the liquid sample is w 添 , the unit is %, the remaining mass of additive is M 剩添加剂 , in g, then w 添 (%) = M 剩添加剂 / (m+m0'), that is, M 剩添加剂 (g) = w 添*(m+m0'); Assume that the content of a certain additive in the initial electrolyte is w0 additive, then the mass of a certain additive in the initial electrolyte is m0*w0(g), then the consumption of a certain additive is M 耗添加剂 (g) = m0*w0-M 剩添加剂 =m0*w0-w 添 *(m 内 +m0'). That is, similarly, the additive consumption can be calculated using the same method.

[0105] The above formula calculates that the electrolyte consumption of 11 batteries is 0.31g, 0.62g, 1.01g, 1.37g, 1.82g, 2.23g, 2.67g, 3.05g, 3.46g, 3.82g, and 4.25g, respectively. The number of cycles (5+10, 10+10, 20+10, 30+10, 40+10, 50+10, 60+10, 70+10, 80+10, 90+10, and 100+10) is used as the abscissa and the electrolyte consumption is used as the ordinate. A standard curve is made and the curve fitting equation (such as Figure 4 As shown), 10 cycles are brought in, and the amount of electrolyte consumed for 10 cycles at 45°C, 0.5C / 0.5C, and 0-50% SOC is 0.17g. That is, according to the standard curve drawn, it can be known that m2 is 0.17g.

[0106] Step S200, injecting an internal standard agent into the battery to be tested, specifically comprising:

[0107] The battery under any working condition (eg, 45°C, 100% SOC storage for 90 days) was injected with EA, sealed and ultrasonicated for 1 hour for preliminary mixing.

[0108] Step S300, subjecting the battery to be tested containing the internal standard agent to shallow charge and discharge cycles, specifically comprising:

[0109] The battery obtained in step S200 is subjected to high temperature shallow charge and shallow discharge cycles, and the cycle operating conditions include: 45° C., 0.5C / 0.5C, 0-50% SOC, and 10 charge and discharge cycles.

[0110] It should be understood that the operating conditions when drawing the standard curve should be consistent with the operating conditions of shallow charging and shallow discharging after injecting the internal standard agent, so that the amount of electrolyte consumed in the shallow charging and shallow discharging cycle can be obtained from the standard curve.

[0111] Step S400, disassemble the battery, collect the free electrolyte to detect the EA and other organic matter content therein, and calculate the electrolyte consumption of the battery at this time by the formula, which is recorded as the first electrolyte consumption m1, and m1 is 40.05g.

[0112] Then, the consumption of electrolyte of this battery (battery to be tested) after being stored at 45° C. and 100% SOC for 90 days is m, where m=m1-m2=40.05g-0.17g=39.88g.

[0113] In order to further verify the accuracy of the detection method provided by the present invention, the following groups of comparative experiments were carried out.

[0114] Test the first group (blank group): weigh 15g EA, inject it into the aluminum shell battery (formation only) by syringe, seal it with AB glue and ultrasonicate the battery for 1h; disassemble the battery, collect the free electrolyte and detect the EA content.

[0115] Test the second group (stationary group): weigh 15g EA, inject it into the aluminum shell battery (formation only) by syringe, seal it with AB glue and let the battery stand for 24h; disassemble the battery, collect the free electrolyte and detect the EA content.

[0116] The third group was tested (the shallow charge and discharge group provided by the present invention): 15 g of EA was weighed and injected into an aluminum shell battery (formed only) by a syringe. After sealing with AB glue, the battery was ultrasonicated for 1 hour to allow the EA and the electrolyte to be preliminarily mixed; the battery was subjected to shallow charge and discharge cycles at high temperature: 45°C, 0-50% SOC, 0.5C / 0.5C charge and discharge cycles for 10 weeks; the battery was disassembled to collect the free electrolyte and test the EA content.

[0117] The test results are shown in Table 1:

[0118] Table 1

[0119]

[0120] Among them, the theoretical content of EA = EA injection amount / (liquid retention amount + EA injection amount), the measured value is to disassemble the battery to collect the free electrolyte, send it to GC for inspection (gas chromatography: it can analyze the organic matter in the mixed liquid sample and detect the content of each organic matter), and the measured EA content, the initial state of the two batteries is the same. If EA is evenly mixed with the electrolyte in the battery, and the electrolyte loss in the 45℃ 0-50% SOC 0.5C / 0.5C charge and discharge cycle for 10 weeks is very small, then the measured value should be close to the theoretical content of EA. It can be seen from the measured results that the numerical deviation measured by the traditional internal standard method is large. The deviation is caused by the electrolyte not being evenly mixed with EA. The high-temperature shallow charge and discharge method can also mix the internal standard agent with the electrolyte in the core evenly, and the test results are more accurate. Further, if the EA measured value is accurate, the electrolyte consumption determined by EA will also improve the accuracy simultaneously. This shows that the method of the present invention can effectively improve the accuracy of the test.

[0121] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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. A method for testing electrolyte consumption, characterized in that: The method comprises: Injecting an internal standard agent into the battery to be tested to obtain a battery to be tested containing the internal standard agent; Subjecting the battery to be tested containing the internal standard agent to a first shallow charge-discharge cycle, wherein the first shallow charge-discharge cycle is charging each time until the state of charge of the battery is less than 100%; Disassembling the battery to be tested after the first shallow charge and discharge cycle, taking out the electrolyte to test or calculate to obtain a first consumption of the electrolyte, recorded as m1; According to the standard curve, the second consumption of the electrolyte during the first shallow charge-discharge cycle is obtained, recorded as m2, According to the m1 and the m2, the consumption of the electrolyte in the battery to be tested is obtained, which is recorded as m, wherein m=m1-m2.

2. The method for testing electrolyte consumption according to claim 1, characterized in that: The drawing of the standard curve comprises: The battery is subjected to a second shallow charge-discharge cycle, and then an internal standard agent is injected into the battery to obtain a battery containing the internal standard agent; Subjecting the battery containing the internal standard agent to a third shallow charge-discharge cycle; Disassembling the battery after the third shallow charge and discharge cycle, taking out the electrolyte and measuring and calculating the consumption of the electrolyte; Draw a standard curve with the number of cycles as the horizontal axis and the consumption of electrolyte as the vertical axis; Among them, the operating conditions of the first shallow charge and discharge cycle, the operating conditions of the second shallow charge and discharge cycle and the operating conditions of the third shallow charge and discharge cycle are all the same.

3. The method for testing electrolyte consumption according to claim 2, characterized in that: The operating conditions of the first shallow charge and discharge cycle include: the charge and discharge temperature is 25-60° C., the charge and discharge rate is 0.5C-3C, and the upper limit voltage of the charge and discharge is greater than the reduction voltage of the internal standard agent; And / or, the operating conditions of the second shallow charge and discharge cycle include: the charge and discharge temperature is 25-60° C., the charge and discharge rate is 0.5C-3C, and the upper limit voltage of charge and discharge is greater than the reduction voltage of the internal standard agent; And / or, the operating conditions of the third shallow charge and discharge cycle include: the charge and discharge temperature is 25-60° C., the charge and discharge rate is 0.5C-3C, and the upper limit voltage of charge and discharge is greater than the reduction voltage of the internal standard agent.

4. The method for testing electrolyte consumption according to claim 2, characterized in that: The first shallow charge and discharge cycle is charging to 50% to 80% of the battery's state of charge each time; And / or, the second shallow charge and discharge cycle is charging to 50% to 80% of the state of charge of the battery each time; And / or, the third shallow charge and discharge cycle is charging to 50% to 80% of the state of charge of the battery each time.

5. The method for testing electrolyte consumption according to claim 2, characterized in that: After injecting the internal standard agent into the battery and before performing the third shallow charge and discharge cycle, the method further includes the step of ultrasonically treating the battery containing the internal standard agent.

6. The method for testing electrolyte consumption according to claim 1, characterized in that: After injecting the internal standard agent into the battery to be tested and before performing the first shallow charge and discharge cycle, the method further includes a step of ultrasonically treating the battery to be tested containing the internal standard agent.

7. The method for testing electrolyte consumption according to any one of claims 1 to 6, characterized in that: The internal standard agent includes at least one of nitriles, carboxylates, carbonates, tetrahydrofuran, ethers, amides, alkanes, halogenated alkanes, ketones, alcohols, benzene and its derivatives or carbon disulfide, the main chain of which has a carbon number greater than 2.

8. The method for testing electrolyte consumption according to any one of claims 1 to 6, characterized in that: The m1 is calculated according to formula (1): m1= m0- m 内 / w 内 +m 内 (1); Wherein, m0 is the total mass of electrolyte injection, in g; m 内 is the injection amount of the internal standard agent, in g; w 内 It is the content of internal standard agent in the electrolyte sample taken out after disassembly, in %.

9. The method for testing electrolyte consumption according to claim 8, characterized in that: The consumption of any additive in the electrolyte is recorded as m 添 , the m 添 Calculate according to formula (2): m 添 =m0*w0-w 添 *(m 内 +m0’) (2); Among them, m 添 The unit is g; w0 is the content of any additive in the initial electrolyte, in %; w 添 It is the content of additives in the electrolyte sample taken out after disassembly, in %; m0' is the mass of the remaining electrolyte in the battery, in g.

10. The method for testing electrolyte consumption according to any one of claims 1 to 6, characterized in that: The method further comprises: The number of cycles is taken as the horizontal axis, and the consumption of electrolyte in the battery to be tested is taken as the vertical axis, to obtain a curve showing the change of electrolyte consumption with the number of cycles; Alternatively, a curve showing the variation of electrolyte consumption with SOH is obtained by taking SOH as the horizontal coordinate and the consumption of electrolyte in the battery to be tested as the vertical coordinate.

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