Method for testing residual volume of electrolyte

Abstract

The invention provides a method for testing the residual volume of electrolyte, which comprises the following steps: 1) preparing an internal standard solution with gradient mass concentration, and constructing a mass concentration-test response value standard curve of the internal standard solution; 2) injecting an internal standard solution with the mass of m1 and the mass percentage of C1 into the battery to be detected, and mixing the internal standard solution with the residual electrolyte in the battery to be detected to obtain a detection electrolyte; 3) testing the detection electrolyte, and obtaining the mass concentration C2 of the internal standard substance in the detection electrolyte according to the test response value of the internal standard substance in the detection electrolyte and the mass concentration-test response value standard curve of the internal standard solution; and 4) obtaining the mass m < residual > of the residual electrolyte according to m1, C1, C2 and the density rho of the detection electrolyte. The test method provided by the invention can accurately and efficiently measure the residual amount of the electrolyte in the battery after the charge and discharge test.

Description

Technical Field

[0001] This invention relates to a method for testing electrolyte residue, belonging to the field of battery technology. Background Technology

[0002] Lithium-ion batteries possess advantages such as high specific energy, no memory effect, and long cycle life, and have been gradually applied in the electric vehicle field. However, the development of this field necessitates continuous improvements in battery energy density. Electrolyte is a crucial component of lithium-ion batteries, and the amount of electrolyte used significantly impacts the energy density of the cell.

[0003] During battery use, the electrolyte is consumed. When the electrolyte consumption reaches a certain level, the battery performance will significantly decline due to insufficient electrolyte. Therefore, to ensure that the battery performance does not plummet due to insufficient electrolyte within its lifespan, it is necessary to analyze the remaining electrolyte level in the battery.

[0004] However, it is difficult to determine the residual amount of electrolyte in a battery cell after formation, storage, and cycling. Traditional methods for determining residual electrolyte require centrifugation to remove a certain amount of electrolyte, but after cycling and storage, most battery cells may not be able to remove electrolyte by centrifugation, resulting in poor practicality.

[0005] Therefore, how to accurately and efficiently determine the residual amount of electrolyte is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention provides a method for testing the residual amount of electrolyte. This method can accurately and efficiently determine the residual amount of electrolyte in a battery, which is beneficial for predicting the cycle life of the battery.

[0007] This invention provides a method for testing the residual amount of electrolyte, comprising the following steps:

[0008] 1) Prepare internal standard solutions with gradient concentrations and construct a standard curve of internal standard solution concentration versus test response value;

[0009] 2) Inject an internal standard solution with a mass of m1 and a mass percentage of C1 into the battery to be tested. The internal standard solution is mixed with the residual electrolyte in the battery to be tested to obtain the test electrolyte.

[0010] 3) Test the detection electrolyte and obtain the mass concentration C2 of the internal standard in the detection electrolyte based on the test response value of the internal standard in the detection electrolyte and the standard curve of the mass concentration of the internal standard solution versus the test response value.

[0011] 4) Based on m1, C1, C2 and the density ρ of the detected electrolyte, obtain the mass m of the residual electrolyte.残 .

[0012] The method for testing the residual electrolyte as described above, wherein step 4) involves calculating the mass m of the residual electrolyte according to Equation 1. 残 :

[0013]

[0014] Where, m 残 The units of m1, C1, C2, and ρ are g, g, %, g / L, and g / L, respectively.

[0015] The method for testing electrolyte residue as described above, wherein step 2) further includes:

[0016] Prepare the electrolyte; inject the initial electrolyte into the cell, and after standing, obtain the battery to be tested; the initial electrolyte is absorbed and consumed by the cell to obtain the residual electrolyte;

[0017] The electrolyte consumption of the battery under test is obtained by the difference between the initial mass of the electrolyte and the residual amount of the electrolyte.

[0018] The method for testing electrolyte residue as described above further includes the following steps:

[0019] 1) Prepare standard solutions for each electrolyte component and construct the response relationship between the mass concentration of each electrolyte component and the measured loudness value;

[0020] The detection electrolyte is tested, and the mass concentration C of each component in the detection electrolyte is obtained based on the test response values ​​of each component and the single-standard calibration area normalization method. i ';

[0021] 2) Based on m1, C1, C2, ρ, and C i ', obtain the residual amount m of each component in the residual electrolyte. i ;

[0022] Where i represents the number of components in the electrolyte, i = 1, 2, 3, ..., n, and n is a positive integer.

[0023] The method for testing electrolyte residue as described above, wherein step 2) further includes: according to

[0024] Equation 2 calculates the residual amount m of each component in the residual electrolyte. i :

[0025]

[0026] Where, m i Ci The units for ' are g and %.

[0027] The method for testing electrolyte residue as described above, wherein step 2) further includes:

[0028] An electrolyte is prepared by mixing electrolyte components; the initial electrolyte is injected into the battery cell and allowed to stand to obtain the battery to be tested; the initial electrolyte is absorbed and consumed by the battery cell to obtain the residual electrolyte;

[0029] The consumption of each component in the electrolyte of the battery under test is obtained by the difference between the mass of each component in the initial electrolyte and the residual amount of each component in the residual electrolyte.

[0030] The method for testing electrolyte residue as described above, wherein the internal standard includes one of biphenyl, cyclohexylbenzene, methyl acetate, toluene, ethyl acetate, lithium tetrafluoroborate, bis(trifluoromethaneamide)imine, lithium, lithium bis(fluorosulfonyl)imine, lithium difluorophosphate, rubidium, and cesium.

[0031] The method for testing electrolyte residue as described above, wherein the solvent of the internal standard solution includes a carbonate solvent; and / or,

[0032] The carbonate solvent includes at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl acetate, diethyl carbonate, ethyl methyl carbonate, and propylene carbonate.

[0033] The method for testing electrolyte residue as described above, wherein C1 is 0.1-50%.

[0034] The method for testing residual electrolyte as described above, wherein the test response values ​​for detecting internal standards and each component in the electrolyte are obtained by at least one of the following methods: inductively coupled plasma optical emission spectrometry, ion chromatography, gas chromatography, and gas chromatography-mass spectrometry.

[0035] This invention involves adding an internal standard solution to the battery under test, then testing the detection electrolyte (including both the electrolyte and the internal standard solution) and its density. Finally, the residual amount of electrolyte in the battery is calculated. This invention fully considers the density change of the residual electrolyte after adding the internal standard solution, enabling a more accurate determination of the residual electrolyte amount and facilitating a more accurate prediction of the battery's cycle life. Furthermore, this invention eliminates the need for battery disassembly, offering advantages such as simplicity and efficiency. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] This invention provides a method for testing the residual amount of electrolyte, the method comprising the following steps:

[0038] 1) Prepare internal standard solutions with gradient concentrations and construct a standard curve of internal standard solution concentration versus test response value;

[0039] 2) Inject an internal standard solution with a mass of m1 and a mass percentage of C1 into the battery to be tested. The internal standard solution is mixed with the residual electrolyte in the battery to be tested to obtain the test electrolyte.

[0040] 3) Test the detection electrolyte and obtain the mass concentration C2 of the internal standard in the detection electrolyte based on the test response value of the internal standard in the detection electrolyte and the standard curve of the mass concentration of the internal standard solution versus the test response value.

[0041] 3) Based on m1, C1, C2, and the density ρ of the electrolyte being tested, obtain the mass m of the residual electrolyte. 残 .

[0042] Specifically, in step 1), a series of internal standard solutions with gradient mass concentrations are first prepared, and then the internal standard solutions with gradient mass concentrations are tested to obtain the test response values ​​of the internal standard solutions. Subsequently, a curve is plotted with the mass concentration of the internal standard solution as the abscissa and the test response value of the corresponding internal standard solution as the ordinate, thus obtaining the standard curve of internal standard mass concentration-test response value.

[0043] The internal standard solution of this invention refers to a solution with an internal standard as the solute. This invention does not limit the specific selection of the internal standard; it can be selected according to actual needs, as long as it does not react with any components in the electrolyte, has good compatibility with the electrolyte, and the electrolyte does not contain the substance. For example, biphenyl can be selected. This invention does not limit the selection of the solvent for the internal standard solution; it can be selected according to actual needs, as long as it can dissolve the internal standard and has good compatibility with the electrolyte.

[0044] The mass concentration of the internal standard solution in this invention refers to the mass of the internal standard in a unit volume of internal standard solution.

[0045] Step 2) Add a certain amount of internal standard solution to the battery to be tested, seal and let stand so that the residual electrolyte in the battery to be tested mixes with the internal standard solution. Centrifuge the battery to be tested with the added internal standard solution to obtain a portion of the mixture and obtain the test electrolyte. The added mass of the internal standard solution is m1 and the mass percentage is C1.

[0046] The present invention does not limit the specific selection of the battery to be tested. For example, the battery can be tested after being stored for a period of time, the battery can be tested after formation, or the battery can be tested after a certain number of charge-discharge cycles.

[0047] The present invention does not limit the specific parameters of sealing and standing treatment, and can be selected according to actual needs. For example, it can be left to stand at room temperature for 96 hours to allow the residual electrolyte in the battery to be tested to mix with the internal standard solution.

[0048] This invention does not limit the specific parameters of centrifugation treatment, and can be selected according to actual needs.

[0049] This invention does not limit m1 and C1, and can be selected according to actual needs.

[0050] Step 3) Test the detection electrolyte to obtain the test response value of the internal standard in the detection electrolyte. Then, according to the standard curve of the mass concentration of the internal standard solution and the test response value, obtain the mass concentration C2 of the internal standard in the detection electrolyte.

[0051] This invention does not limit the testing method for the electrolyte; the method can be selected according to actual needs, such as gas chromatography testing.

[0052] Step 4) Perform a density test on the electrolyte to obtain the density ρ of the electrolyte. Then, calculate the mass of the residual electrolyte in the electrolyte to be tested based on the m1, C1, C2 and ρ obtained above.

[0053] This invention does not limit the method for testing the density of the electrolyte; it can be selected according to actual needs, for example, a densitometer can be used for testing.

[0054] This invention involves adding an internal standard solution to the battery under test, then testing the electrolyte, which includes both the electrolyte and the internal standard solution. Based on the test response value and a standard curve of the internal standard's mass concentration versus the test response value, the mass concentration of the internal standard in the electrolyte is obtained, and the density of the electrolyte is tested. Finally, the mass of the residual electrolyte in the battery under test is calculated. Since the internal standard solution does not contain lithium salts, while the residual electrolyte contains a certain amount of lithium salts, the density of the residual electrolyte in the battery changes after the addition of the internal standard solution. When testing the electrolyte, a constant volume of solution is used. Solutions with different densities have different masses of the analyte, leading to large errors in the test results. Therefore, this invention fully considers the density change before and after adding the internal standard solution and tests the density of the residual electrolyte, enabling a more accurate determination of the electrolyte mass in the battery and thus a more accurate prediction of the battery's cycle life. Furthermore, the method provided by this invention uses the internal standard method, which does not require disassembly of the battery or other processes, and uses instruments to test the electrolyte, thereby enabling a simple and efficient determination of the residual amount of electrolyte in the battery.

[0055] In one specific embodiment, step 4) further includes: calculating the mass m of the residual electrolyte according to Equation 1. 残 :

[0056]

[0057] Where, m 残 The units of m1, C1, C2, and ρ are g, g, % (%), g / L, and g / L, respectively. Based on Equation 1 and the measured m1, C1, C2, and ρ, the mass of the residual electrolyte in the battery under test can be calculated. This formula can accurately obtain the mass data of the residual electrolyte.

[0058] In one specific embodiment, step 2) further includes: preparing an electrolyte; injecting an initial electrolyte into a battery cell and allowing it to stand to obtain a battery under test; obtaining a residual electrolyte after the initial electrolyte is absorbed and consumed by the battery cell; and obtaining the electrolyte consumption amount of the battery under test by the difference between the mass of the initial electrolyte and the mass of the residual electrolyte. Specifically, an initial electrolyte is injected into a battery cell and allowed to stand to obtain a battery under test; the battery under test is then formed, stored, or subjected to charge-discharge cycles, and a residual electrolyte is obtained after the initial electrolyte in the battery under test is absorbed and consumed by the battery cell; the electrolyte consumption amount of the battery under test is obtained by calculating the difference between the mass of the initial electrolyte and the residual amount of the residual electrolyte calculated by Equation 1. This invention does not limit how the mass of the initial electrolyte of the battery under test is obtained; for example, the amount of electrolyte injected during battery preparation can be recorded. By calculating the electrolyte consumption of the present invention, the electrolyte consumption of the battery under test during formation, storage or cycling can be accurately understood, thereby enabling accurate analysis of the changes inside the battery during formation, storage or cycling, and thus enabling reasonable prediction of the battery's formation, storage or cycling performance.

[0059] In one specific embodiment, the method further includes the following steps: 1) preparing standard solutions for each electrolyte component, and establishing a response relationship between the mass concentration of each electrolyte component and the test response value; testing the detection electrolyte, and obtaining the mass concentration C of each component in the detection electrolyte based on the test response value of each component in the detection electrolyte and the single-standard calibration area normalization method. i ';2) Based on m1, C1, C2, ρ and C i ', Obtain the residual amount m of each component in the residual electrolyte. i Where i represents the number of components in the electrolyte, i = 1, 2, 3, ..., n, and n is a positive integer.

[0060] Specifically, in step 1), a standard solution of an electrolyte component is prepared, and then the component solution with a known mass concentration is tested to obtain the test response value of the component solution, thus acquiring the response relationship between the electrolyte component and the test response value. This invention constructs the above-mentioned response relationship between the mass concentration of each component and the test response value for each component in the electrolyte. Subsequently, the electrolyte is tested to obtain the test response value of each component in the electrolyte. The response relationship is then subjected to a single-standard calibration area normalization method to obtain the mass concentration C of each component in the electrolyte. i '.

[0061] The mass concentration of each component in this invention refers to the mass of the corresponding component per unit volume of each component solution.

[0062] The present invention does not limit the selection of the mass concentration of the electrolyte component standard solution; for example, a mass concentration close to that of the electrolyte being tested can be selected.

[0063] This invention does not limit the testing method for the electrolyte; the method can be selected according to actual needs, such as gas chromatography testing.

[0064] Step 2), based on m1, C1, C2, ρ and C i 'Calculate the residual amount m of each component in the residual electrolyte. i .

[0065] This invention tests each component in the electrolyte and obtains the mass concentration of each component based on the test response values ​​and a standard curve of mass concentration versus test response value. Finally, the residual amount of each component in the battery under test is calculated. This testing method accurately determines the residual amount of each component in the battery under test, enabling precise analysis of changes in each component during battery formation, storage, or cycling. This, in turn, provides guidance for optimizing and selecting battery electrolyte formulations.

[0066] In one specific embodiment, step 2) further includes: calculating the mass m of each component in the residual electrolyte according to Equation 2. i :

[0067]

[0068] Where, m i C i The units of ' are g and % respectively. This invention utilizes Equation 2 and the measured m1, C1, ρ, C i By calculating C2, the mass of each component in the residual electrolyte can be obtained. This formula can accurately obtain the mass data of each component.

[0069] In one specific embodiment, step 2) further includes: preparing an electrolyte by distributing the electrolyte components; injecting the initial electrolyte into a battery cell and allowing it to stand to obtain a battery under test; obtaining a residual electrolyte after the initial electrolyte is absorbed and consumed by the battery cell; and obtaining the consumption amount of each component in the electrolyte of the battery under test by the difference between the mass of each component in the initial electrolyte of the battery under test and the residual amount of each component in the residual electrolyte. Specifically, the electrolyte is prepared by distributing the electrolyte components according to their proportions; the initial electrolyte is injected into a battery cell and allowed to stand to obtain a battery under test; the battery under test is then formed, stored, or cycled for charge and discharge; the initial electrolyte is absorbed and consumed by the battery cell to obtain a residual electrolyte; the consumption amount of the electrolyte in the battery under test is obtained by calculating the difference between the mass of each component in the initial electrolyte of the battery under test and the residual amount of each component in the residual electrolyte calculated by Equation 1. This invention does not limit how the mass of each component in the initial electrolyte of the battery under test is obtained; for example, the amount of each component in the electrolyte during battery preparation can be recorded. By calculating the consumption of each component in the electrolyte of this invention, the consumption of each component during formation, storage, or recycling can be accurately understood, thereby enabling effective optimization of the electrolyte formulation.

[0070] In one specific embodiment, the internal standard includes one of biphenyl, cyclohexylbenzene, methyl acetate, toluene, ethyl acetate, lithium tetrafluoroborate, bis(trifluoromethaneamide)imide, lithium, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, rubidium, and cesium. When the internal standard is selected from the above compounds, it will not react with the electrolyte and has good compatibility with it, thereby avoiding the formation of other substances by reacting with the electrolyte, which could lead to large errors in the test results. Moreover, the above compounds are all conventional compounds, making the test simple and safe.

[0071] In one specific embodiment, the solvent of the internal standard solution includes a carbonate solvent; and / or, the carbonate solvent includes at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl acetate, diethyl carbonate, ethyl methyl carbonate, and propylene carbonate. When the solvent of the internal standard solution includes the above-mentioned organic solvents, the organic solvents can fully dissolve the internal standard to form a stable internal standard solution, and the above-mentioned solvents have good compatibility with the electrolyte, which can avoid problems such as incompatibility or side reactions with the electrolyte, thereby improving the accuracy of the test.

[0072] In one specific embodiment, C1 is 0.1-50%, for example, C1 is 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. When the mass percentage of the internal standard solution is within the above range, the internal standard solution can be fully mixed with the electrolyte, and the low test response value caused by an excessively low concentration of the internal standard solution can be avoided, thereby greatly improving the accuracy of the test method.

[0073] In one specific embodiment, the test response values ​​of the internal standard and each component in the electrolyte are obtained by at least one of the following methods: inductively coupled plasma optical emission spectrometry (ICP-OES), ion chromatography, gas chromatography, and gas chromatography-mass spectrometry (GC-MS). When metal cations are used as the internal standard and electrolyte components, the test response values ​​can be obtained by ICP-OES; when anions are used, the test response values ​​can be obtained by ion chromatography; and when organic compounds are used, the test response values ​​can be obtained by gas chromatography or GC-MS. Choosing different test methods to obtain test response values ​​based on the selection of different internal standards and electrolyte components allows for more accurate determination of the test response values, thereby improving the accuracy of the test methods by obtaining more accurate information about the residual electrolyte mass and the residual amounts of each component.

[0074] In one specific embodiment, the present invention verifies the accuracy of the electrolyte quality testing method provided by the present invention through the following steps:

[0075] 1) Prepare the electrolyte, and then inject a known mass m of the electrolyte into the cell to obtain a battery;

[0076] 2) Inject an internal standard solution with a mass of m1 and a mass percentage of C1 into the battery to obtain the test electrolyte;

[0077] 3) Based on the test response value of the internal standard in the electrolyte and the standard curve of the mass concentration of the internal standard solution versus the test response value, the mass concentration C2 of the internal standard in the electrolyte is obtained;

[0078] 4) Based on m1, C1, C2, and the density ρ of the electrolyte, obtain the mass m of the electrolyte in the battery. 残 .

[0079] 5) The mass of the electrolyte in the battery is obtained by calculation using Equation 3:

[0080]

[0081] 6) The accuracy of the test method for calculating the residual electrolyte amount using Equation 4:

[0082]

[0083] The present invention will be further described in detail below through specific embodiments.

[0084] Example 1

[0085] This embodiment tests the accuracy of the method for testing electrolyte residue through the following steps:

[0086] 1. Prepare the electrolyte, and then inject the electrolyte with a known mass m of 7.2964g into the cell to obtain the battery.

[0087] 2. Prepare an internal standard solution, wherein the internal standard is biphenyl, the solvent is diethyl carbonate, and the mass percentage of the internal standard C1 is 9.905%.

[0088] 3. Inject a known mass m1 of 3.3283 g of internal standard solution into the battery to be tested, seal it, and let it stand at 25°C for 96 h to obtain the test electrolyte including the internal standard solution and the electrolyte.

[0089] 4. The mass concentration C2 of the internal standard in the electrolyte was determined to be 3.676 g / L by gas chromatography, and the density ρ of the electrolyte was determined to be 1.0761 g / L by hydrometer.

[0090] 5. Calculate the mass m of the electrolyte in the battery. 残 The amount is 7.2709g, therefore, the error w of the method for testing the residual amount of electrolyte is -0.34%.

[0091] The accuracy testing methods provided in Examples 2-9 are basically the same as those in Example 1, and the specific parameters are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] Comparative Example 1

[0096] This comparative example tests the accuracy of the method for determining electrolyte residue using the following steps:

[0097] 1. Prepare the electrolyte, and then inject the electrolyte with a known mass m of 7.2964g into the cell to obtain the battery.

[0098] 2. Prepare an internal standard solution, wherein the internal standard is biphenyl, the solvent is diethyl carbonate, and the mass percentage of the internal standard C1 is 9.9%.

[0099] 3. Inject a known mass m1 of 3.8283 g of internal standard solution into the battery to be tested, seal it, and let it stand at 25°C for 96 h to obtain the test electrolyte including the internal standard solution and the electrolyte.

[0100] 4. The mass concentration C2 of the internal standard in the electrolyte was determined to be 3.5764% by gas chromatography.

[0101] 5. Calculate the mass m of the electrolyte in the battery using Equation 5. 残 :

[0102]

[0103] The mass m of the electrolyte in the battery was calculated. 残 The amount is 6.7743g, therefore, the accuracy w of the method for testing the residual amount of electrolyte is 7.16%.

[0104] The accuracy testing methods provided in Comparative Examples 2-9 are basically the same as those in Comparative Example 1, and the specific parameters are shown in Table 2.

[0105] Table 2

[0106]

[0107]

[0108] Example 10

[0109] This embodiment tests the accuracy of the method for testing electrolyte residue through the following steps:

[0110] 1. Prepare the electrolyte, and then inject the electrolyte with a known mass m of 7.051g into the cell to obtain the battery.

[0111] 2. Prepare an internal standard solution, wherein the internal standard is cyclohexylbenzene, the solvent is diethyl carbonate, and the mass percentage of the internal standard C1 is 9.4987%.

[0112] 3. Inject a known internal standard solution with a mass m1 of 2.5339 g into the battery to be tested, seal it, and let it stand at 25°C for 96 h to obtain a test electrolyte including the internal standard solution and the electrolyte.

[0113] 4. The mass concentration C2 of the internal standard in the electrolyte was determined to be 2.8691 g / L by gas chromatography and ion chromatography, and the density ρ of the electrolyte was determined to be 1.1367 g / L by a densitometer.

[0114] 5. Calculate the mass m of the electrolyte in the battery. 残The amount is 7.0018g, therefore, the error w of the method for testing the residual amount of electrolyte is 0.70%.

[0115] The accuracy testing methods provided in Examples 10-19 are basically the same as those in Example 10, and the specific parameters are shown in Table 3.

[0116] Table 3

[0117]

[0118]

[0119] Example 20

[0120] This embodiment tests the residual amounts of each component in the residual electrolyte through the following steps:

[0121] 1. Prepare the electrolyte, wherein the electrolyte comprises, by mass percentage, 26% ethylene carbonate, 25% dimethyl carbonate, 33% ethyl methyl carbonate, 3% vinylene carbonate, 1% ethylene sulfate, and 12% lithium hexafluorophosphate.

[0122] 2. Inject 7.15g of electrolyte into the cell to obtain a battery. Perform 1500 charge-discharge cycles on the battery to obtain the battery to be tested.

[0123] 3. Prepare an internal standard solution, wherein the internal standard is biphenyl, the solvent is diethyl carbonate, and the mass percentage of the internal standard is 10%.

[0124] 4. Inject 3.0560g of internal standard solution into the battery to be tested, seal it, and let it stand at 25°C for 96 hours to obtain the test electrolyte including the internal standard solution and the residual electrolyte.

[0125] 5. The mass concentrations of the internal standard and each component in the electrolyte were tested by gas chromatography and ion chromatography. The concentration of the internal standard was 4.8885 g / L, and the density of the electrolyte was 1.1767 g / L. The specific results are shown in Table 4.

[0126] 6. The residual amount and consumption of the residual electrolyte, as well as the residual amount and consumption of each component, are obtained through calculation using Equations 1 and 2. The specific results are shown in Table 4.

[0127] Table 4

[0128]

[0129] In summary, the electrolyte residual amount test method provided by this invention can accurately and efficiently determine the residual amount of electrolyte in the battery, which is beneficial for predicting the battery's cycle life. Furthermore, it can accurately determine the residual amount of each component in the residual electrolyte, which is beneficial for accurately analyzing the changes of each component during battery formation, storage, or cycling. In this way, it can provide guidance for the optimization and screening of battery electrolyte formulations.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of testing the residual amount of electrolyte, characterized by, The method comprises the following steps: 1) preparing a gradient mass concentration internal standard solution, and constructing a mass concentration-test response value standard curve of the internal standard solution; 2) injecting the internal standard solution with a mass of m1 and a mass percentage of C1 into the battery to be measured, mixing the internal standard solution with residual electrolyte in the battery to be measured to obtain a detection electrolyte; 3) testing the detection electrolyte, and obtaining the mass concentration C2 of the internal standard in the detection electrolyte according to the test response value of the internal standard in the detection electrolyte and the mass concentration-test response value standard curve of the internal standard solution. 4) obtaining the mass m of the residual electrolyte as a function of ml, Cl, C2 and the density p of the detection electrolyte 残 .

2. The method of testing the residual amount of electrolyte according to claim 1, wherein Step 4) is the calculation of the mass m of the residual electrolyte according to formula 1 残 : wherein m 残 , ml, Cl, C2, p are in g, g, %, g / L, g / L, respectively.

3. The method for testing electrolyte residue according to claim 2, characterized in that, Step 2) further comprises: configuring an electrolyte; injecting an initial electrolyte into the battery cell to obtain a battery to be measured after standing; and obtaining residual electrolyte after the initial electrolyte is absorbed and consumed by the battery cell; obtaining the consumption amount of the electrolyte of the battery to be measured by the difference between the mass of the initial electrolyte of the battery to be measured and the mass of the residual electrolyte.

4. The method of testing the residual amount of electrolyte according to any one of claims 1 to 3, characterized in that, The method further comprises the following steps: 1) configuring a standard solution of each electrolyte component, and constructing a response relationship between the mass concentration of each electrolyte component and the test response value; The detection electrolyte is tested, and according to the test response values of each component in the detection electrolyte and the single-standard correction area normalization method, the mass concentration C of each component in the detection electrolyte is obtained i ’; 2) according to m1, C1, C2, p and C i ’, the residual amount m of each component in the residual electrolyte is obtained i ; wherein i represents the number of components in the electrolyte, i = 1, 2, 3, …, n, and n is a positive integer.

5. The method for testing electrolyte residue according to claim 4, characterized in that, Step 2) also comprises calculating the mass m of each component in the residual electrolyte according to formula 2 i : wherein m i , C i The units of m , C , and m ’ are g, %, and g, respectively.

6. The method for testing electrolyte residue according to claim 5, characterized in that, Step 2) further comprises: configuring an electrolyte by taking electrolyte components; injecting an initial electrolyte into the battery cell to obtain a battery to be measured after standing; and obtaining residual electrolyte after the initial electrolyte is absorbed and consumed by the battery cell; obtaining the consumption amount of each component in the electrolyte of the battery to be measured by the difference between the mass of each component in the initial electrolyte of the battery to be measured and the residual amount of each component in the residual electrolyte.

7. The method of testing the residual amount of electrolyte according to any one of claims 1 to 6, characterized in that, The internal standard comprises one of biphenyl, cyclohexylbenzene, methyl acetate, toluene, ethyl acetate, lithium tetrafluoroborate, bis(trifluoromethaneamide) imide, lithium, lithium bis(fluorosulfonyl) imide, lithium difluorophosphate, rubidium, and cesium.

8. The method of testing the residual amount of electrolyte according to any one of claims 1 to 7, characterized in that, The solvent of the internal standard solution comprises a carbonate solvent; and / or, The carbonate solvent comprises at least one of vinyl carbonate, dimethyl carbonate, methyl ethyl carbonate, ethyl acetate, propyl acetate, diethyl carbonate, methyl ethyl carbonate, and propylene carbonate.

9. The method of testing the residual amount of electrolyte according to any one of claims 1 to 8, characterized in that, C1 is 0.1-50%.

10. The method of testing the residual amount of electrolyte according to any one of claims 1 to 9, characterized in that, The test response values of the internal standard and each component in the detection electrolyte are obtained by at least one of inductively coupled plasma emission spectrometry, ion chromatography, gas chromatography, and gas chromatography-mass spectrometry.

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