A method for evaluating the density of a lithium battery electrolyte

Abstract

This application provides a method for evaluating the density of a lithium battery electrolyte, comprising the following steps: the electrolyte to be tested comprises the following raw material components: n liquids and A solids; in the electrolyte to be tested, the A solids are dissolved in the n liquids; one liquid is selected from the n liquids as a reference liquid, and the rest are the liquids to be tested; concentration-density fitting lines are obtained for each of the n-1 liquids to be tested, and the density contribution coefficient of the n-1 liquids to be tested is obtained; concentration-density fitting lines are obtained for each of the A solids to be tested, and the density contribution coefficient of the A solid is obtained; the density ρ of the electrolyte to be tested at 25°C is... 待测 , ρ 待测 =. The electrolyte density assessment method provided in this application can pinpoint the actual amount of abnormal materials fed in one go, increasing the speed of anomaly investigation by 3-5 times and ensuring the continuity of on-site production rhythm; at the same time, the accuracy of this assessment method is high (controlled within 0.5%), avoiding material waste during the investigation process.

Description

Technical Field

[0001] This invention belongs to the field of electrolyte density assessment technology, and specifically relates to a method for assessing the density of lithium battery electrolyte. Background Technology

[0002] The density of lithium-ion battery electrolytes requires specialized instruments for measurement. On the electrolyte production line, if errors occur in the feeding process, such as excessive or insufficient addition of a single additive, or incorrect additive addition, the existing methods for troubleshooting electrolyte feeding anomalies are as follows: frequently prepare intermediate-control electrolyte samples with different concentrations of the material, measure the density of these samples, and compare the results with those of the production line samples to determine the actual amount of material to be fed. However, this process is not only time-consuming and labor-intensive but also significantly slows down production and increases electrolyte preparation costs. Therefore, there is an urgent need to develop a simple and rapid method for assessing electrolyte density to quickly determine the actual amount of material fed in case of feeding anomalies during production, ensuring the continuity of production. Summary of the Invention

[0003] To address the problem that in the existing electrolyte preparation and production process, it is necessary to prepare semi-finished products in the central control system multiple times to determine the content of each component in abnormal samples when troubleshooting anomalies, which is time-consuming, labor-intensive, and seriously slows down the production rhythm, this application provides a method for evaluating the density of lithium battery electrolyte.

[0004] The technical solution adopted in this application to solve the above-mentioned technical problems is as follows: On the one hand, this application provides a method for evaluating the density of lithium battery electrolyte, including the following steps: The electrolyte to be tested comprises the following raw material components: n liquids and A solids, wherein the A solids are dissolved in the n liquids. Choose one liquid from n liquids as the reference liquid, and the rest are the liquids to be tested; The concentration-density fitting lines for each of the n-1 test liquids are obtained, and the density contribution coefficient of each of the n-1 test liquids is obtained. The concentration-density fitting lines for solid A are obtained respectively, and the density contribution coefficient of solid A is obtained. The density ρ of the electrolyte to be tested at 25℃ 待测 , ρ 待测 = Wherein, ρ0 is the density of the reference liquid at 25℃, in g / cm³. 3 ; The mass content of the i-th liquid among n-1 test liquids is expressed as % (%). The density contribution coefficient of the i-th liquid among n-1 test liquids, in g / cm³. 3 ; The mass content of the s-th solid in type A in the electrolyte to be tested is expressed as % (%). The density contribution coefficient of the s-th solid in solid A, expressed in g / cm³. 3 .

[0005] Preferably, the concentration-density fitting lines for each of the n-1 test liquids are obtained, and the density contribution coefficients of the n-1 test liquids are obtained, including the following steps: Dissolve n-1 test liquids into the reference liquid to obtain n-1 sets of mixed solutions. Configure each set of mixed solutions into sub-solutions with gradually increasing or decreasing concentrations. Use the sub-solutions to establish a concentration-density fitting line to obtain n-1 fitting lines. The slope of the n-1 fitting lines is the density contribution coefficient of the n-1 test liquids.

[0006] Preferably, the concentration-density fitting straight line of solid A is obtained to obtain the density contribution coefficient of solid A, including the following steps: Solid A is dissolved in the reference liquid to obtain a group of mixed solutions. Each group of mixed solutions is prepared into sub-solutions with gradually increasing or decreasing concentrations. Concentration-density fitting lines are established using the sub-solutions to obtain A fitting lines. The slope of the A fitting lines is the density contribution coefficient of solid A.

[0007] Preferred, =m i / (m1+m2+...+m n ), m i Let m1 + m2 + ... + m be the mass of the i-th liquid among n-1 types of liquids to be tested, where i ≥ 1. n Let be the total mass of n liquids.

[0008] Preferably, the n liquids include non-aqueous organic solvents, which include at least one of carbonate solvents, carboxylic acid ester solvents, sulfone solvents, ether solvents, and nitrile solvents.

[0009] Preferably, the reference liquid includes at least one of carbonate solvents and carboxylic acid ester solvents.

[0010] Preferably, in the step of obtaining the concentration-density fitting line of solid A, in the step of dissolving solid A into the reference liquid, ethylene carbonate is added as a co-solvent, and the amount of the co-solvent added is X of the mass of the reference liquid, where X ranges from 0 to 5%.

[0011] Preferably, the solid A comprises a lithium salt, including LiPF6, LiBF4, LiAsF6, LiClO4, LiBOB, LiDFOB, LiFSI, LiTFSI, LiPO2F2, LiCH3SO3, LiSbF6, LiCF3SO3, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiCl, LiBr, LiI, and LiB. 10 Cl 10 At least one of the following: LiAlCl4, lithium chloroborane, lithium difluorodioxazophosphate, lithium difluorophosphate, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, lithium tetraphenylborate, and lithium imino.

[0012] Preferably, the n liquids further include a first additive, which includes at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds.

[0013] Preferably, the solid A further includes a second additive, which includes at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds.

[0014] The lithium battery electrolyte density evaluation method provided in this application has the following advantages: 1) It can evaluate the density of abnormal electrolytes on the production line by substituting the density into the formula ρ. 待测 = The method allows for the reverse calculation of the actual quality of the added abnormal material, saving manpower and resources, reducing costs, and significantly accelerating the investigation of abnormal material input, thus speeding up the production pace. 2) The electrolyte density assessment method provided in this application can pinpoint the actual amount of abnormal material input in one step, increasing the anomaly investigation speed by 3-5 times and ensuring the continuity of on-site production. At the same time, the accuracy of this assessment method is high (controlled within 0.5%), avoiding material waste during the investigation process. Detailed Implementation

[0015] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] This invention provides a method for evaluating the density of lithium battery electrolyte, comprising the following steps: The electrolyte to be tested comprises the following raw material components: n liquids and A solids, wherein the A solids are dissolved in the n liquids in the electrolyte to be tested; Choose one liquid from n liquids as the reference liquid, and the rest are the liquids to be tested; The concentration-density fitting lines for each of the n-1 test liquids are obtained, and the density contribution coefficient of each of the n-1 test liquids is obtained. The concentration-density fitting lines for solid A are obtained respectively, and the density contribution coefficient of solid A is obtained. The density ρ of the electrolyte to be tested at 25℃ 待测 , ρ 待测 = Wherein, ρ0 is the density of the reference liquid at 25℃, in g / cm³. 3 ; The mass content of the i-th liquid among n-1 test liquids is expressed as % (%). The density contribution coefficient of the i-th liquid among n-1 test liquids, in g / cm³. 3 ; The mass content of the s-th solid in type A in the electrolyte to be tested is expressed as % (%). The density contribution coefficient of the s-th solid in solid A, expressed in g / cm³. 3 .

[0017] Specifically, in electrolyte formulations, different components such as additives, lithium salts, and solvents contribute differently to the electrolyte density, and the overall density can be calculated by weighting them proportionally. During electrolyte production, the accuracy range for electrolyte density is generally ±0.01 g / cm³. 3 A small portion has an accuracy range of ±0.004 g / cm³. 3 However, when troubleshooting errors in material feeding on the production line, the accuracy requirements for the electrolyte density assessment method are not high. Therefore, the physical equations and theoretical models that require fine precision can be ignored, and a simpler empirical method of mathematical fitting can be used to establish the calculation formula for electrolyte density assessment and determine the weighting coefficient of materials in the electrolyte density calculation.

[0018] The density of a mixed solution cannot be directly calculated by the ratio of the sum of the masses to the sum of the volumes of the components before mixing. This is due to the excess volume phenomenon during mixing—the actual volume of the mixed solution is not simply the sum of the volumes of the components, leading to a deviation from the linear prediction of the density. Many factors contribute to this phenomenon, with two main influencing factors: one is the influence of intermolecular forces, such as solvent-solute and solute-solute hydrogen bonds, dipole interactions, and ion association. These forces alter molecular packing efficiency, thus affecting the overall volume of the mixed system. The other is the ion solvation effect; after the dissociation of lithium salts, cations (such as Li)... + It can form a solvation shell with solvent molecules, compressing the free volume of the system (such as Li in a high-concentration electrolyte). + Strong coordination with EC leads to volume shrinkage.

[0019] Induction coefficients can also effectively assess electrolyte density. To reduce the mutual influence between solute and mixed solvent, the liquid can be dissolved in the solvent to form mixed solutions with different concentration gradients, resulting in different densities. A concentration-density fitting line can be established, and the density weighting coefficient of the liquid in the solvent can be obtained from the slope of the fitted line. Similarly, a solid solute can be dissolved in the solvent to form mixed solutions with different concentration gradients, resulting in different densities. A concentration-density fitting line can be established, and the density weighting coefficient of the solid solute in the solvent can be obtained from the slope of the fitted line.

[0020] In the newly developed electrolyte evaluation method, it is necessary to first convert the mass ratio of liquid material in the electrolyte into its mass ratio in the mixed solvent, and then use this as a basis to further estimate the density of the electrolyte to be tested.

[0021] The lithium battery electrolyte density assessment method provided in this application is mainly used for troubleshooting abnormal feeding during the electrolyte production process. The specific operation is as follows: first, take a sample of the abnormal electrolyte from the production process and test its actual density; then, substitute the obtained density of the abnormal electrolyte into the formula ρ. 待测 = The density of the abnormal electrolyte is ρ. 待测 The actual feed mass of abnormal materials is calculated based on the formula. When conducting anomaly investigation, it is not necessary to prepare intermediate control semi-finished products with different concentrations of abnormal materials to compare the density one by one to determine the mass of abnormal materials in the abnormal sample.

[0022] The lithium battery electrolyte density evaluation method provided in this application has the following advantages: 1) It can substitute the density of abnormal electrolytes on the production line into ρ 待测 = The method allows for the reverse calculation of the actual quality of the added abnormal material, saving manpower and resources, reducing costs, and significantly accelerating the investigation of abnormal material input, thus speeding up the production pace. 2) The electrolyte density assessment method provided in this application can pinpoint the actual amount of abnormal material input in one step, increasing the anomaly investigation speed by 3-5 times and ensuring the continuity of on-site production. At the same time, the accuracy of this assessment method is high (controlled within 0.5%), avoiding material waste during the investigation process.

[0023] In some embodiments, the concentration-density fitting lines for n-1 types of test liquids are obtained respectively, and the density contribution coefficients of the n-1 test liquids are obtained, including the following steps: Dissolve n-1 test liquids into the reference liquid to obtain n-1 sets of mixed solutions. Configure each set of mixed solutions into sub-solutions with gradually increasing or decreasing concentrations. Use the sub-solutions to establish a concentration-density fitting line to obtain n-1 fitting lines. The slope of the n-1 fitting lines is the density contribution coefficient of the n-1 test liquids.

[0024] Specifically, the electrolyte includes n types of liquids, and one of them is selected as the reference liquid. The reference liquid is used to facilitate the calculation of the density contribution coefficients of the remaining n-1 types of liquids to be tested.

[0025] The remaining n-1 test liquids are dissolved in the reference liquid to obtain n-1 sets of mixed solutions. Then, each of the n-1 sets of mixed solutions is further prepared into sub-solutions with gradually increasing or decreasing concentrations. Next, a concentration-density fitting line is established based on the sub-solutions with gradually increasing or decreasing concentrations to obtain n-1 fitting lines. The slope of the n-1 fitting lines is calculated, and the obtained slope is the density contribution coefficient of the corresponding n-1 test liquids.

[0026] For example, when n=4, one liquid is selected as the reference liquid, and the remaining three liquids are recorded as the first liquid, the second liquid, and the third liquid, respectively. The first liquid is dissolved in the reference liquid to obtain the first mixed solution. Then, the first mixed solution is prepared into a first sub-solution with gradually increasing or decreasing concentrations. A concentration-density fitting line is established based on the first sub-solution to obtain the first fitted line. The slope of the first fitted line is calculated, and the slope is the density contribution coefficient of the first liquid. Similarly, the second liquid is dissolved in the reference liquid to obtain the second mixed solution. Then, the second mixed solution is prepared into a second sub-solution with gradually increasing or decreasing concentrations. A concentration-density fitting line is established based on the second sub-solution to obtain the second fitted line. The slope of the second fitted line is calculated, and the slope is the density contribution coefficient of the second liquid. The third liquid is dissolved in the reference liquid to obtain the third mixed solution. Then, the third mixed solution is prepared into a third sub-solution with gradually increasing or decreasing concentration. A concentration-density fitting line is established based on the third sub-solution to obtain the third fitting line. The slope of the third fitting line is calculated, and the slope is the density contribution coefficient of the third liquid.

[0027] In the step of calculating the density contribution coefficient of n-1 kinds of test liquids, the n-1 kinds of test liquids are dissolved into the reference liquid to obtain n-1 sets of mixed solutions. The reference liquid contains relatively few kinds of liquids, which can reduce the mutual influence between mixed solvents and solutes (such as lithium salts) and further improve the estimation accuracy of the density of the electrolyte to be tested.

[0028] In some embodiments, the concentration-density fitting straight line of solid A is obtained to obtain the density contribution coefficient of solid A, including the following steps: Solid A is dissolved in the reference liquid to obtain a group of mixed solutions. Each group of mixed solutions is prepared into sub-solutions with gradually increasing or decreasing concentrations. Concentration-density fitting lines are established using the sub-solutions to obtain A fitting lines. The slope of the A fitting lines is the density contribution coefficient of solid A.

[0029] Specifically, the electrolyte includes n types of liquids, and one of them is selected as the reference liquid. The reference liquid is used to facilitate the dissolution of solid A.

[0030] Solid A is dissolved in a reference liquid to obtain a mixed solution A. Then, each mixed solution in the mixed solution A is further prepared into sub-solutions with gradually increasing or decreasing concentrations. Next, a concentration-density fitting line is established based on the sub-solutions with gradually increasing or decreasing concentrations to obtain A fitting lines. The slope of the A fitting lines is calculated, and the obtained slope is the density contribution coefficient of the corresponding solid A.

[0031] For example, if A=2, the two solids are recorded as solid 1 and solid 2. The specific steps include: dissolving solid 1 in a reference liquid to obtain a mixed solution A1; then preparing sub-solutions A1 with gradually increasing or decreasing concentrations; establishing a concentration-density fitting line based on sub-solutions A1 to obtain the A1th fitting line; and calculating the slope of the A1th fitting line, which is the density contribution coefficient of the corresponding solid 1. Similarly, dissolving solid 2 in a reference liquid to obtain a mixed solution A2; then preparing sub-solutions A2 with gradually increasing or decreasing concentrations; establishing a concentration-density fitting line based on sub-solutions A2 to obtain the A2th fitting line; and calculating the slope of the A2th fitting line, which is the density contribution coefficient of the corresponding solid 2.

[0032] In the step of calculating the density contribution coefficient of solid A, solid A is dissolved in a reference liquid to obtain a mixed solution of group A. Preferably, the reference liquid does not contain solutes such as lithium salts, which can reduce the mutual influence between the mixed solvent and the solute (such as lithium salts) and further improve the estimation accuracy of the density contribution coefficient of the solid.

[0033] It should be noted that the number of sub-solutions with gradually increasing or decreasing concentrations is not limited in this application, nor is the magnitude of the increase in concentration limited in this application, nor is the magnitude of the decrease in concentration limited in this application.

[0034] In some embodiments, ωi=m i / (m1+m2+...+m n ), m i Let m1 + m2 + ... + m be the mass of the i-th liquid among n-1 types of liquids to be tested, where i ≥ 1. n Let be the total mass of n liquids.

[0035] Specifically, It represents the mass content of the i-th liquid among n-1 types of liquids to be tested, expressed as a percentage. It is calculated by dividing the mass of the i-th liquid among n-1 types of liquids by the total mass of the n types of liquids.

[0036] It should be noted that, The calculation method can also be used as follows: = The mass content of the i-th liquid among n-1 test liquids in the electrolyte divided by the sum of the mass contents of the n liquids in the electrolyte. The appropriate calculation method can be selected based on actual needs.

[0037] In some embodiments, the n liquids include non-aqueous organic solvents, which include at least one of carbonate solvents, carboxylic acid ester solvents, sulfone solvents, ether solvents, and nitrile solvents.

[0038] In some embodiments, the ether solvent includes cyclic ethers or chain ethers, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms. The cyclic ether may be, but is not limited to, at least one of 1,3-dioxane (DOL), 1,4-dioxane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF). The chain ether may be, but is not limited to, at least one of dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, 1,3-dioxane, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. Because chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. One ether compound can be used alone, or two or more can be used in any combination and ratio. There are no particular restrictions on the amount of ether compound added; it is arbitrary as long as it does not significantly impair the lithium-ion battery effect of the present invention. Typically, the volume ratio is 1% or more, preferably 2% or more, and more preferably 3% or more, when the non-aqueous solvent volume ratio is 100%. Furthermore, the volume ratio is typically 30% or less, preferably 25% or less, and more preferably 20% or less. When two or more ether compounds are used in combination, the total amount of ether compounds should meet the above-mentioned range. When the amount of ether compound added is within the above-mentioned preferred range, it is easy to ensure the improved ionic conductivity effect resulting from the increased lithium-ion dissociation degree and reduced viscosity of the chain ether. In addition, when the negative electrode active material is a carbon material, the phenomenon of co-intercalation between chain ethers and lithium ions can be suppressed, thus enabling the input-output characteristics and charge-discharge rate characteristics to reach an appropriate range.

[0039] In some embodiments, the nitrile solvent may specifically include, but is not limited to, at least one of acetonitrile and malononitrile.

[0040] In some embodiments, carbonate solvents include cyclic carbonate solvents and chain carbonate solvents.

[0041] Cyclic carbonate solvents may specifically include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), butylene carbonate (BC), and butene carbonate.

[0042] In some embodiments, the chain carbonate solvent may be, but is not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC).

[0043] There are no particular restrictions on the content of cyclic carbonate solvents; it can be arbitrary as long as it does not significantly impair the performance of the lithium-ion battery of this invention. However, when using a single type, its content is typically 3% or more, preferably 5% or more, by volume relative to the total amount of solvent in the non-aqueous electrolyte. By setting this range, a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, making it easier to achieve good high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. Furthermore, the upper limit is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, thereby contributing to improved stability during high-temperature storage.

[0044] During battery charging and discharging, cyclic carbonate solvents partially decompose at the negative electrode interface to produce alkyl lithium carbonate, which participates in the formation of the SEI film.

[0045] The content of the chain carbonate solvent is not particularly limited, but relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 15% or more by volume, preferably 20% or more, and more preferably 25% or more. Furthermore, it is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. By keeping the chain carbonate content within the above range, it is easier to achieve an appropriate viscosity for the non-aqueous electrolyte, suppressing the decrease in ionic conductivity, and thus helping to achieve a good range of output characteristics for the non-aqueous electrolyte battery. When using two or more chain carbonates in combination, it is sufficient to ensure that the total amount of chain carbonates meets the above range.

[0046] In some embodiments, a chain carbonate solvent having fluorine atoms (hereinafter referred to as "fluorinated chain carbonate") may also be preferably used. There is no particular limitation on the number of fluorine atoms in the fluorinated chain carbonate as long as it is 1 or more, but it is generally 6 or less, preferably 4 or less. When the fluorinated chain carbonate has multiple fluorine atoms, these fluorine atoms may be bonded to the same carbon atom or to different carbon atoms. Examples of fluorinated chain carbonates include dimethyl fluorinated carbonate derivatives, methyl ethyl fluorinated carbonate derivatives, and diethyl fluorinated carbonate derivatives.

[0047] Carboxylic acid ester solvents include cyclic carboxylic acid esters and / or chain carbonates. Examples of cyclic carboxylic acid esters include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonates include at least one of methyl formate, methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, and ethyl trimethylacetate.

[0048] In some embodiments, the sulfone solvent includes cyclic sulfones and chain sulfones. Preferably, in the case of cyclic sulfones, it is typically a compound with 3 to 6 carbon atoms, more preferably 3 to 5 carbon atoms; in the case of chain sulfones, it is typically a compound with 2 to 6 carbon atoms, more preferably 2 to 5 carbon atoms. There are no particular limitations on the amount of sulfone solvent added, and it is arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of the present invention. Relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 0.3% or more by volume, preferably 0.5% or more by volume, more preferably 1% or more by volume. Furthermore, it is typically 40% or less by volume, preferably 35% or less by volume, more preferably 30% or less by volume. When using two or more sulfone solvents in combination, the total amount of sulfone solvent should satisfy the above range. When the amount of sulfone solvent added is within the above range, a non-aqueous electrolyte with excellent high-temperature storage stability is tended to be obtained.

[0049] In some embodiments, the reference liquid includes at least one of carbonate solvents and carboxylic acid ester solvents.

[0050] Specifically, the reference liquid is selected from the above types. The interaction between the solute, such as lithium salt, and the solvent is small, and the force is small. The solid density contribution coefficient obtained by the test is more accurate, which improves the accuracy of the electrolyte density under test.

[0051] In some embodiments, in the step of obtaining the concentration-density fitting line of n-1 test liquids, the reference liquid used includes at least one of carbonate solvents and carboxylic acid ester solvents.

[0052] Specifically, in the step of obtaining the concentration-density fitting line for n-1 test liquids, the reference liquid can be a carbonate solvent, a carboxylic acid ester solvent, or a mixture of carbonate and carboxylic acid ester solvents.

[0053] In some embodiments, in the step of dissolving solid A into the reference liquid, a co-solvent is added to the reference liquid, the mass of the co-solvent being X times the mass of the reference liquid, where X ranges from 0 to X ≤ 0.05; the co-solvent includes ethylene carbonate.

[0054] Specifically, when dissolving solid A separately in a reference liquid, some solids may not completely dissolve, leading to a decrease in the accuracy of the calculated density contribution coefficient. To address this issue, a co-solvent is added to the reference liquid. The resulting mixture, containing ethylene carbonate, facilitates the complete dissolution of the poorly soluble solid, thereby improving the accuracy of the solid density contribution coefficient. The mass of the co-solvent is X times the mass of the reference liquid, where X ranges from 0 to 0.05. The amount of co-solvent added is small and can be ignored when calculating the solid density contribution coefficient, thus not reducing its accuracy.

[0055] In some embodiments, the solid A comprises a lithium salt, including LiPF6, LiBF4, LiAsF6, LiClO4, LiBOB, LiDFOB, LiFSI, LiTFSI, LiPO2F2, LiCH3SO3, LiSbF6, LiCF3SO3, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiCl, LiBr, LiI, and LiB. 10 Cl 10 At least one of the following: LiAlCl4, lithium chloroborane, lithium difluorodioxazophosphate, lithium difluorophosphate, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, lithium tetraphenylborate, and lithium imino.

[0056] Type A solids include lithium salts, which are selected from the above types and can improve the conductivity of the electrolyte and enhance the electrical performance of the battery.

[0057] In some embodiments, the n liquids include a first additive, which includes at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds.

[0058] In some embodiments, the solid A further includes a second additive, the second additive comprising at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds.

[0059] In some embodiments, the cyclic sulfate compounds include at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate; The sulfonyl lactone compounds include at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate. The cyclic carbonate compound is selected from at least one of vinylene carbonate (VC), ethylene ethylene carbonate, or the compound shown in structural formula 4: Structural Formula 4 In structural formula 4, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 hydrocarbon group; The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphites or the compound shown in structural formula 5: Structural Formula 5 In structural formula 5, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, C1-C5 unsaturated hydrocarbon groups, and C1-C5 halohydrocarbon groups, and R 31 R 32 R 33 At least one of them is an unsaturated hydrocarbon group; The borate esters are selected from tri(triethylsilane) borate esters.

[0060] In a preferred embodiment, the unsaturated phosphate compound includes at least one of the following: triargyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate. The nitrile compounds include at least one of succinic anion, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octanilide, nonadionitrile, and sebaconitrile.

[0061] In other embodiments, the additive may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, such as flame retardant additives like fluorophosphates, or overcharge prevention additives like tert-amylbenzene and tert-butylbenzene.

[0062] The electrolyte to be tested comprises the following raw material components: n kinds of liquids and A kinds of solids. In the electrolyte to be tested, the A kinds of solids are dissolved in the n kinds of liquids. Specifically, the preparation process of the electrolyte to be tested involves raw materials containing n kinds of liquids and A kinds of solids, and the A kinds of solids are dissolved in the n kinds of liquids to form a homogeneous, stable, liquid electrolyte to be tested.

[0063] It should be noted that "Type A solid" refers to the solute being added to the liquid solvent or n liquids of the electrolyte to be tested in a solid state, and does not mean that it exists as a solid in the electrolyte to be tested.

[0064] In some embodiments, n liquids refer to substances with a melting point of less than or equal to 33°C, and A solids refer to substances with a melting point of greater than 33°C.

[0065] The present invention will be further illustrated by the following examples.

[0066] Example 1 This embodiment illustrates a method for evaluating the density of lithium battery electrolyte disclosed in this invention.

[0067] The electrolyte to be tested consists of 55.16 wt% dimethyl carbonate, 15.76 wt% ethylene carbonate, 7.88 wt% methyl ethyl carbonate, 1.20 wt% vinylene carbonate, 3.00 wt% fluoroethylene carbonate, 0.50 wt% lithium difluorooxalate borate, and 16.50 wt% lithium hexafluorophosphate.

[0068] The method for evaluating the density of the electrolyte to be tested includes the following steps: S1: Select reference liquid The composition of the electrolyte in the sample to be tested shows that it includes 5 liquids and 2 solids, i.e., n=5 and A=2. Ethyl methyl carbonate is used as the reference liquid.

[0069] S2: Find ωi The mass content of dimethyl carbonate in five liquids ω1; ω1=55.16% / (55.16%+15.76%+7.88%+1.2%+3.0%)=66.46%.

[0070] Mass content ω2 of ethylene carbonate in five liquids; ω2=15.76% / (55.16%+15.76%+7.88%+1.2%+3.0%)=18.99%.

[0071] The mass content of vinylene carbonate in five liquids ω3; ω3=1.2% / (55.16%+15.76%+7.88%+1.2%+3.0%)=1.45%.

[0072] Mass content of fluoroethylene carbonate in 5 liquids ω4; ω4=3.0% / (55.16%+15.76%+7.88%+1.2%+3.0%)=3.61%.

[0073] S3: Calculate the density contribution coefficient of the liquid. Dimethyl carbonate was dissolved in ethyl methyl carbonate to obtain the first mixed solution. The first mixed solution was then configured into a first sub-solution group with gradually increasing concentration. Using the first sub-solution group, a concentration-density fitting line was established to obtain the first fitting line. The slope of the first fitting line is the density contribution coefficient ρ1 of dimethyl carbonate, where ρ1 = 0.0516.

[0074] Ethylene carbonate was dissolved in methyl ethyl carbonate to obtain a second mixed solution. The second mixed solution was then configured into a second sub-solution group with gradually increasing concentrations. Using the second sub-solution group, a concentration-density fitting line was established to obtain a second fitting line. The slope of the second fitting line is the density contribution coefficient ρ2 of ethylene carbonate, where ρ2 = 0.2998.

[0075] Ethylene carbonate was dissolved in ethyl methyl carbonate to obtain the third mixed solution. The third mixed solution was then configured into a third sub-solution group with gradually increasing concentrations. Using the third sub-solution group, a concentration-density fitting line was established to obtain the third fitting line. The slope of the third fitting line is the density contribution coefficient ρ3 of ethylene carbonate, where ρ3 = 0.2833.

[0076] Fluoroethylene carbonate was dissolved in methyl ethyl carbonate to obtain the fourth mixed solution. The fourth mixed solution was then configured into a fourth sub-solution group with gradually increasing concentrations. Using the fourth sub-solution group, a concentration-density fitting line was established to obtain the fourth fitting line. The slope of the fourth fitting line is the density contribution coefficient ρ4 of fluoroethylene carbonate, where ρ4 = 0.3544.

[0077] S4: Calculate the density contribution coefficient of the solid. Lithium difluorooxalate borate was dissolved in methyl ethyl carbonate to obtain the second-1 group of mixed solutions. The second-1 group of mixed solutions was then configured into a second-1 sub-solution group with gradually increasing concentrations. Using the second-1 sub-solution group, a concentration-density fitting line was established to obtain the second-1 fitting line. The slope of the second-1 fitting line is the density contribution coefficient ρ'1 of lithium difluorooxalate borate, where ρ'1 = 0.4850.

[0078] Lithium hexafluorophosphate was dissolved in methyl ethyl carbonate to obtain the second-2 group of mixed solutions. The second-2 group of mixed solutions was then configured into a second-2 sub-solution group with gradually increasing concentrations. Using the second-2 sub-solution group, a concentration-density fitting line was established to obtain the second-2 fitting line. The slope of the second-2 fitting line is the density contribution coefficient ρ'2 of lithium hexafluorophosphate, where ρ'2 = 0.7934.

[0079] S5: Calculate the density of the electrolyte to be tested. Density ρ of the electrolyte to be tested at 25℃ 待测 ρ 待测 =ρ0 ω1×ρ1+ω2×ρ2+ω3×ρ3+ω4×ρ4+ω'1×ρ'1+ω'2×ρ'2 =1.006 + 66.46% × 0.0516 + 18.99% × 0.2998 + 1.45% × 0.2833 + 3.61% × 0.3544 + 0.50% × 0.4850 + 16.50% × 0.7934 =1.24746 g / cm³ 3 .

[0080] The density of the electrolyte to be tested, obtained according to the above formula, is 1.24746 g / cm³. 3 The actual measured density of the electrolyte to be tested was 1.2530 g / cm³. 3 The difference is 0.442%, which is small, and the electrolyte density obtained by the formula is within the standard density of 1.245 g / cm³. 3 -1.255 g / cm 3 Within the range.

[0081] Example 2 The electrolyte to be tested consists of 25.00% dimethyl carbonate, 25.00% ethylene carbonate, 4.16% propylene carbonate, 29.17% methyl ethyl carbonate, 2.50% vinylene carbonate, 0.50% fluoroethylene carbonate, 0.30% propane sulpholol, 4.62% lithium difluorosulfonyl imide, and 8.75% lithium hexafluorophosphate.

[0082] The method for evaluating the density of the electrolyte under test in this embodiment is the same as most of the steps in Embodiment 1. The differences in steps S2, S3, and S4, and the corresponding calculated values, are as follows: S2: Find ω i Mass content ω1 of dimethyl carbonate in 7 liquids; ω1=25% / (25%+25%+4.16%+29.17%+2.5%+0.5%+0.3%)=28.86%.

[0083] Mass content ω2 of ethylene carbonate in 7 liquids; ω2=25% / (25%+25%+4.16%+29.17%+2.5%+0.5%+0.3%)=28.86%.

[0084] Mass content of vinylene carbonate in 7 liquids ω3; ω3=2.5% / (25%+25%+4.16%+29.17%+2.5%+0.5%+0.3%)=2.89%.

[0085] Mass content of fluoroethylene carbonate in 7 liquids ω4; ω4=0.5% / (25%+25%+4.16%+29.17%+2.5%+0.5%+0.3%)=0.58%.

[0086] The mass content of propylene carbonate in 7 liquids ω5; ω5=4.16% / (25%+25%+4.16%+29.17%+2.5%+0.5%+0.3%)=4.80%.

[0087] Mass content of propanesulfonyl lactone in 7 liquids ω6; ω6=0.3% / (25%+25%+4.16%+29.17%+2.5%+0.5%+0.3%)=0.35%.

[0088] Step S3 adds a step to calculate the density contribution coefficient of propylene carbonate: dissolve propylene carbonate in methyl ethyl carbonate to obtain the fifth mixed solution; prepare the fifth mixed solution into a fifth sub-solution group with gradually increasing concentration; use the fifth sub-solution group to establish a concentration-density fitting line to obtain the fifth fitting line; the slope of the fifth fitting line is the density contribution coefficient ρ5 of propylene carbonate, where ρ5 = 0.1844.

[0089] Step S3 adds a step to determine the density contribution coefficient of propane sulfonyl lactone: dissolve propane sulfonyl lactone in methyl ethyl carbonate to obtain the sixth group of mixed solutions; prepare the sixth group of mixed solutions into a sixth sub-solution group with gradually increasing concentrations; use the sixth sub-solution group to establish a concentration-density fitting line to obtain the sixth fitting line; the slope of the sixth fitting line is the density contribution coefficient ρ6 of propane sulfonyl lactone, where ρ6 = 0.3570.

[0090] In step S4, lithium difluorooxalate borate is replaced with lithium bis(fluorosulfonyl)imide. The slope of the resulting (2-1)th fitted line is the density contribution coefficient ρ'1 of lithium bis(fluorosulfonyl)imide, where ρ'1 = 0.6617.

[0091] S5: Calculate the density of the electrolyte to be tested. Density ρ of the electrolyte to be tested at 25℃ 待测 ρ 待测 =ρ0 ω1×ρ1+ω2×ρ2+ω3×ρ3+ω4×ρ4+ω5×ρ5+ω6×ρ 6+ ω'1×ρ'1+ω'2×ρ'2 =1.006 + 28.86% × 0.0516 + 28.86% × 0.2998 + 2.89% × 0.2833 + 0.58% × 0.3544 + 4.80% × 0.1844 + 0.35% × 0.3570 + 4.62% × 0.6617 + 8.75% × 0.7934 =1.2277g / cm 3 .

[0092] The density of the electrolyte to be tested, obtained according to the above formula, is 1.2277 g / cm³. 3 The actual measured density of the electrolyte to be tested was 1.2270 g / cm³. 3 The difference is 0.058%, which is small, and the electrolyte density obtained by the formula is within the standard density range of 1.218-1.238 g / cm³. 3 Within the range.

[0093] Example 3 The electrolyte to be tested consists of 15.96% dimethyl carbonate, 29.56% ethylene carbonate, 38.04% methyl ethyl carbonate, 3.00% vinylene carbonate, 1.00% propane sulcolone, 0.60% ethylene sulfate, and 11.84% lithium hexafluorophosphate.

[0094] The method for evaluating the density of the electrolyte under test in this embodiment is the same as most of the steps in Embodiment 1. The differences in steps S2, S3, and S4, and the corresponding calculated values, are as follows: S2: Find ω i The mass content of dimethyl carbonate in five liquids ω1; ω1=15.96% / (15.96%+29.56%+38.04%+3%+1%)=18.23%.

[0095] Mass content ω2 of ethylene carbonate in five liquids; ω2=29.56% / (15.96%+29.56%+38.04%+3%+1%)=33.76%.

[0096] The mass content of vinylene carbonate in five liquids ω3; ω3=3% / (15.96%+29.56%+38.04%+3%+1%)=3.43%.

[0097] Mass content ω4 of propanesulfonyl lactone in 5 liquids; ω4=1% / (15.96%+29.56%+38.04%+3%+1%)=1.14%.

[0098] The density contribution coefficient of fluorinated ethylene carbonate in step S3 is ρ4.

[0099] In step S4, lithium difluorooxalate borate is replaced with vinyl sulfate. The slope of the 2-1 fitted line is the density contribution coefficient ρ'1 of vinyl sulfate, where ρ'1 = 0.4320.

[0100] S5: Calculate the density of the electrolyte to be tested. Density ρ of the electrolyte to be tested at 25℃ 待测 ρ 待测 =ρ0 ω1×ρ1+ω2×ρ2+ω3×ρ3+ω4×ρ4+ω'1×ρ'1+ω'2×ρ'2 =1.006 + 18.23% × 0.0516 + 33.76% × 0.2998 + 3.43% × 0.2833 + 1.14% × 0.3570 + 0.60% × 0.4320 + 11.84% × 0.7934 =1.2243g / cm 3 .

[0101] The density of the electrolyte to be tested, obtained according to the above formula, is 1.2243 g / cm³. 3 The actual measured density of the electrolyte to be tested was 1.2250 g / cm³. 3 The difference is 0.05%, which is small, and the electrolyte density obtained by the formula is within the standard density range of 1.215-1.235 g / cm³. 3 Within the range.

[0102] Example 4 The electrolyte to be tested consists of 23.91% dimethyl carbonate, 23.91% ethylene carbonate, 31.88% methyl ethyl carbonate, 1.80% vinylene carbonate, 1.00% fluoroethylene carbonate, 1.00% ethylene sulfate, 0.50% tris(trimethylsilane) phosphate, 10.50% lithium difluorosulfonylimide, and 5.50% lithium hexafluorophosphate.

[0103] The method for evaluating the density of the electrolyte under test in this embodiment is the same as most of the steps in Embodiment 1. The differences in steps S2, S3, and S4, and the corresponding calculated values, are as follows: S2: Find ω i The mass content ω1 of dimethyl carbonate in 6 liquids; ω1=23.91% / (23.91%+23.91%+31.88%+1.80%+1.00%+0.50%)=28.81%.

[0104] Mass content ω2 of ethylene carbonate in 6 liquids; ω2=23.91% / (23.91%+23.91%+31.88%+1.80%+1.00%+0.50%)=28.81%.

[0105] The mass content of vinylene carbonate in six liquids ω3; ω3=1.80% / (23.91%+23.91%+31.88%+1.80%+1.00%+0.50%)=2.17%.

[0106] Mass content of fluoroethylene carbonate in 6 liquids ω4; ω4=1% / (23.91%+23.91%+31.88%+1.80%+1.00%+0.50%)=1.2%.

[0107] Mass content ω5 of tris(trimethylsilane)phosphate in 6 liquids; ω5=0.5% / (23.91%+23.91%+31.88%+1.80%+1.00%+0.50%)=0.6%.

[0108] Step S3 adds a step to determine the density contribution coefficient of tris(trimethylsilane)phosphate: Dissolve tris(trimethylsilane)phosphate in methyl ethyl carbonate to obtain the fifth mixed solution; prepare the fifth sub-solution group with gradually increasing concentration using the fifth sub-solution group, establish a concentration-density fitting line using the fifth sub-solution group, and obtain the fifth fitting line. The slope of the fifth fitting line is the density contribution coefficient ρ5 of tris(trimethylsilane)phosphate, where ρ5 = -0.0840.

[0109] Step S4 is the step to increase the density contribution coefficient of vinyl sulfate: dissolve vinyl sulfate in methyl ethyl carbonate to obtain the second and third mixed solutions; prepare the second and third sub-solution groups with gradually increasing concentrations using the second and third sub-solution groups, establish a concentration-density fitting line to obtain the second and third fitting lines, and the slope of the second and third fitting lines is the density contribution coefficient ρ'3 of vinyl sulfate, where ρ'3 = 0.4320.

[0110] In step S4, lithium difluorooxalate borate is replaced with lithium bis(fluorosulfonyl)imide. The slope of the resulting (2-1)th fitted line is the density contribution coefficient ρ'1 of lithium bis(fluorosulfonyl)imide, where ρ'1 = 0.6617.

[0111] S5: Calculate the density of the electrolyte to be tested. Density ρ of the electrolyte to be tested at 25℃ 待测 ρ 待测 =ρ0 ω1×ρ1+ω2×ρ2+ω3×ρ3+ω4×ρ4+ω5×ρ5+ω'1×ρ'1+ω'2×ρ'2+ω'3×ρ'3 =1.006 + 28.81% × 0.0516 + 28.81% × 0.2998 + 2.17% × 0.2833 + 1.2% × 0.3544 + 0.6% × (-0.0840) + 10.50% × 0.6617 + 5.5% × 0.7934 + 1.0% × 0.4320 =1.2345g / cm 3 .

[0112] The density of the electrolyte to be tested, obtained according to the above formula, is 1.2345 g / cm³. 3 The actual measured density of the electrolyte to be tested was 1.2320 g / cm³. 3 The difference is 0.21%, which is small, and the electrolyte density obtained by the formula is within the standard density range of 1.227-1.237 g / cm³. 3 Within the range.

[0113] Example 5 The electrolyte to be tested consists of 13.16% ethylene carbonate, 7.18% propylene carbonate, 15.16% ethyl propionate, 32.89% propyl propionate, 7.00% fluoroethylene carbonate, 4.00% 1,3-propanesulfonyl lactone, 3.00% 1,3,6-hexanetrionitrile, 0.50% lithium difluorooxalate borate, and 17.11% lithium hexafluorophosphate.

[0114] The method for evaluating the density of the electrolyte in this embodiment is largely the same as that in Example 1, except that ethyl propionate is used as the reference liquid in step S1, and ethyl methyl carbonate is replaced with ethyl propionate in steps S3 and S4. The differences between steps S2, S3, and S4, and the corresponding calculated values, are as follows: S2: Find ω i Mass content ω1 of ethylene carbonate in 7 liquids; ω1=13.16% / (13.16%+7.18%+15.16%+32.89%+7.00%+4.00%+3.00%)=15.97%.

[0115] Mass content ω2 of propylene carbonate in 7 liquids; ω2=7.18% / (13.16%+7.18%+15.16%+32.89%+7.00%+4.00%+3.00%)=8.71%.

[0116] The mass content of propyl propionate in 7 liquids ω3; ω3=32.89% / (13.16%+7.18%+15.16%+32.89%+7.00%+4.00%+3.00%)=39.92%.

[0117] Mass content of fluoroethylene carbonate in 6 liquids ω4; ω4=7% / (13.16%+7.18%+15.16%+32.89%+7.00%+4.00%+3.00%)=8.50%.

[0118] The mass content ω5 of 1,3,6-hexanetrionitrile in 7 liquids; ω5=3.0% / (13.16%+7.18%+15.16%+32.89%+7.00%+4.00%+3.00%)=3.64%.

[0119] The mass content of 1,3-propanesulfonate lactone in 7 liquids ω6; ω6=4.0% / (13.16%+7.18%+15.16%+32.89%+7.00%+4.00%+3.00%)=4.85%.

[0120] S3: Calculate the density contribution coefficient of the liquid. Ethyl carbonate was dissolved in ethyl propionate to obtain the first mixed solution. The first mixed solution was then configured into a first sub-solution group with gradually increasing concentration. Using the first sub-solution group, a concentration-density fitting line was established to obtain the first fitting line. The slope of the first fitting line is the density contribution coefficient ρ1 of ethylene carbonate, where ρ1 = 0.3484.

[0121] Propylene carbonate was dissolved in ethyl propionate to obtain the second mixed solution. The second mixed solution was then configured into a second sub-solution group with gradually increasing concentration. Using the second sub-solution group, a concentration-density fitting line was established to obtain the second fitting line. The slope of the second fitting line is the density contribution coefficient ρ2 of propylene carbonate, where ρ2 = 0.2702.

[0122] Propyl propionate was dissolved in ethyl propionate to obtain the third mixed solution. The third mixed solution was then configured into a third sub-solution group with gradually increasing concentration. Using the third sub-solution group, a concentration-density fitting line was established to obtain the third fitting line. The slope of the third fitting line is the density contribution coefficient ρ3 of propyl propionate, where ρ3 = -0.0106.

[0123] Fluoroethylene carbonate was dissolved in ethyl propionate to obtain the fourth mixed solution. The fourth mixed solution was then configured into a fourth sub-solution group with gradually increasing concentrations. Using the fourth sub-solution group, a concentration-density fitting line was established to obtain the fourth fitting line. The slope of the fourth fitting line is the density contribution coefficient ρ4 of fluoroethylene carbonate, where ρ4 = 0.3829.

[0124] 1,3,6-hexanetrionitrile was dissolved in ethyl propionate to obtain the fifth mixed solution. The fifth mixed solution was then configured into a fifth sub-solution group with gradually increasing concentrations. Using the fifth sub-solution group, a concentration-density fitting line was established to obtain the fifth fitting line. The slope of the fifth fitting line is the density contribution coefficient ρ5 of 1,3,6-hexanetrionitrile, where ρ5 = 0.1463.

[0125] 1,3-propanesulfonate lactone was dissolved in ethyl propionate to obtain the sixth mixed solution. The sixth mixed solution was then configured into a sixth sub-solution group with gradually increasing concentrations. Using the sixth sub-solution group, a concentration-density fitting line was established to obtain the sixth fitting line. The slope of the sixth fitting line is the density contribution coefficient ρ6 of 1,3-propanesulfonate lactone, where ρ5 = 0.3530.

[0126] S4: Calculate the density contribution coefficient of the solid. Lithium difluorooxalate borate was dissolved in ethyl propionate to obtain the second-1 group of mixed solutions. The second-1 group of mixed solutions was then configured into a second-1 sub-solution group with gradually increasing concentrations. Using the second-1 sub-solution group, a concentration-density fitting line was established to obtain the second-1 fitting line. The slope of the second-1 fitting line is the density contribution coefficient ρ'1 of lithium difluorooxalate borate, where ρ'1 = 0.5150.

[0127] Lithium hexafluorophosphate was dissolved in ethyl propionate to obtain the second-2 group of mixed solutions. The second-2 group of mixed solutions was then configured into a second-2 sub-solution group with gradually increasing concentrations. Using the second-2 sub-solution group, a concentration-density fitting line was established to obtain the second-2 fitting line. The slope of the second-2 fitting line is the density contribution coefficient ρ'2 of lithium hexafluorophosphate, where ρ'2 = 0.6955.

[0128] S5: Calculate the density of the electrolyte to be tested. Density ρ of the electrolyte to be tested at 25℃ 待测 ρ 待测 =ρ0 ω1×ρ1+ω2×ρ2+ω3×ρ3+ω4×ρ4+ω5×ρ5+ω6×ρ 6+ ω'1×ρ'1+ω'2×ρ'2 =0.888 + 15.97% × 0.3484 + 8.71% × 0.2702 + 39.91% × (-0.0106) + 8.50% × 0.3829 + 3.64% × 0.1463 + 4.85% × 0.3530 + 0.5% × 0.515 + 17.11% × 0.6955 =1.1395g / cm 3 .

[0129] The calculation formula yielded a density of 1.1395 g / cm³ at 25℃, with a standard density range of 1.136-1.146 g / cm³. The actual measured density was 1.1424 g / cm³, a difference of 0.251%, which is small.

[0130] Example 6 The electrolyte to be tested consists of 9.54% ethylene carbonate, 15.89% propylene carbonate, 6.61% ethyl propionate, 32.29% propyl propionate, 10.00% fluoroethylene carbonate, 3.00% 1,3-propanesulfonyl lactone, 2.00% adiponitrile, 2.30% 1,3,6-hexanetrionitrile, 0.50% lithium bis(trifluoromethanesulfonylimide), 0.50% lithium difluorooxalateborate, and 17.37% lithium hexafluorophosphate.

[0131] The method for evaluating the density of the electrolyte under test in this embodiment is the same as most of the steps in Embodiment 5. The differences are as follows: the differences in steps S2, S3, and S4, and the corresponding calculated values ​​are as follows: S2: Find ω i Mass content ω1 of ethylene carbonate in 8 liquids; ω1=9.54% / (9.54%+15.89%+6.61%+32.29%+10.00%+3.00%+2.00%+2.30%)=11.69%.

[0132] Mass content ω2 of propylene carbonate in 8 liquids; ω2=15.89% / (9.54%+15.89%+6.61%+32.29%+10.00%+3.00%+2.00%+2.30%)=19.47%.

[0133] The mass content of propyl propionate in 8 liquids ω3; ω3=32.29% / (9.54%+15.89%+6.61%+32.29%+10.00%+3.00%+2.00%+2.30%)=39.56%.

[0134] Mass content of fluoroethylene carbonate in 8 liquids ω4; ω4=10% / (9.54%+15.89%+6.61%+32.29%+10.00%+3.00%+2.00%+2.30%)=12.25%.

[0135] The mass content ω5 of 1,3-propanesulfonate lactone in 8 liquids; ω5=3% / (9.54%+15.89%+6.61%+32.29%+10.00%+3.00%+2.00%+2.30%)=3.68%.

[0136] The mass content ω6 of 1,3,6-hexanetrionitrile in 8 liquids; ω6=2.3% / (9.54%+15.89%+6.61%+32.29%+10.00%+3.00%+2.00%+2.30%)=2.82%.

[0137] adiponitrile mass content ω7 in 8 liquids; ω7=2.0% / (9.54%+15.89%+6.61%+32.29%+10.00%+3.00%+2.00%+2.30%)=2.45%.

[0138] Step S3 adds a step to calculate the density contribution coefficient ρ6 of adiponitrile: adiponitrile is dissolved in ethyl propionate to obtain the sixth group of mixed solutions; the sixth group of mixed solutions is prepared into a sixth sub-solution group with gradually increasing concentrations; using the sixth sub-solution group, a concentration-density fitting line is established to obtain the sixth fitting line, and the slope of the sixth fitting line is the density contribution coefficient ρ6 of adiponitrile, where ρ6=0.0856.

[0139] Step S4 adds a step to calculate the density contribution coefficient ρ'4 of lithium bis(trifluoromethanesulfonylimide): Lithium bis(trifluoromethanesulfonylimide) is dissolved in ethyl propionate to obtain the second-fourth group of mixed solutions; the second-fourth group of mixed solutions is configured into the second-fourth sub-solution group with gradually increasing concentrations; using the second-fourth sub-solution group, a concentration-density fitting line is established to obtain the second-fourth fitting line, and the slope of the second-fourth fitting line is the density contribution coefficient ρ'4 of lithium bis(trifluoromethanesulfonylimide), where ρ'4 = 0.4688.

[0140] S5: Calculate the density of the electrolyte to be tested. Density ρ of the electrolyte to be tested at 25℃ 待测 =ρ0 ω1×ρ1+ω2×ρ2+ω3×ρ3+ω4×ρ4+ω5×ρ5+ω6×ρ6+ω7×ρ7+ω'1×ρ'1+ω'2×ρ'2+ω'3×ρ'3=0.888+11.69%×0 .3484+19.47%×0.2702+39.56%×(-0.0106)+12.25%×0.3829+3.68%×0.3530+2.45%×0.1463+2.82 %×0.0856+0.5%×0.515+17.37%×0.6955+0.5%×0.4688 =1.16894g / cm 3 .

[0141] The calculated density at 25℃ is 1.16894 g / cm³. 3 The standard density range is 1.162-1.172 g / cm³. 3 The actual measured density was 1.1645 g / cm³. 3 The difference is 0.382%, which is small.

[0142] Example 7 An error occurred during the production of the electrolyte: 1548.50 kg of dimethyl carbonate, 3687.50 kg of methyl ethyl carbonate, and ethylene carbonate were added, exceeding the standard amount. A control sample was taken and tested, revealing a density of 1.1247 g / cm³. 3Substituting the values ​​into the above formula, the actual amount of ethylene carbonate fed is calculated, and the calculation method is as follows.

[0143] Let the mass of ethylene carbonate be x, and methyl ethyl carbonate be the reference liquid. The calculation is as follows: The mass content of dimethyl carbonate in the three liquids ω1; ω1=1548.50 / (1548.50+3687.50+x).

[0144] The mass content ω2 of ethylene carbonate in the three liquids; ω2=x / (1548.50+3687.50+x).

[0145] S3: Calculate the density contribution coefficient of the liquid. Dimethyl carbonate was dissolved in ethyl methyl carbonate to obtain the first mixed solution. The first mixed solution was then configured into a first sub-solution group with gradually increasing concentration. Using the first sub-solution group, a concentration-density fitting line was established to obtain the first fitting line. The slope of the first fitting line is the density contribution coefficient ρ1 of dimethyl carbonate, where ρ1 = 0.0516.

[0146] Ethylene carbonate was dissolved in methyl ethyl carbonate to obtain a second mixed solution. The second mixed solution was then configured into a second sub-solution group with gradually increasing concentrations. Using the second sub-solution group, a concentration-density fitting line was established to obtain a second fitting line. The slope of the second fitting line is the density contribution coefficient ρ2 of ethylene carbonate, where ρ2 = 0.2998.

[0147] ρ 待测 =1.1247 g / cm 3 Substitute the values ​​into the equation to find x.

[0148] ρ 待测 = ρ0 ω1×ρ1+ω2×ρ2, which is 1.1247=1.006+1548.50 / (1548.50+3687.50+x)×0.0516+x / (1548.50+3687.50+x)×0.2998, so x=2990.67kg.

[0149] The above results show that the actual amount of ethylene carbonate fed was 2990.67 kg.

[0150] Verification: 1548.50 kg dimethyl carbonate, 3687.50 kg methyl ethyl carbonate, and 2990.67 kg ethylene carbonate were used to prepare the estimated formula. After preparing the control and standard samples, the actual density was measured to be 1.1249 g / cm³. 3 The results match the calculations, allowing for rapid anomaly detection.

[0151] Example 8 An error occurred during the production of the electrolyte: 2500.50 kg of dimethyl carbonate, 2501.50 kg of ethylene carbonate, 2918.50 kg of methyl ethyl carbonate, and 416.00 kg of propylene carbonate were added. The amount of vinylene carbonate added exceeded the standard. A control sample was taken and tested; the density was 1.1260 g / cm³. 3 Substituting the above formula, the actual amount of vinylene carbonate fed is calculated, and the calculation method is as follows.

[0152] Let the mass of vinylene carbonate be x, and methyl ethyl carbonate be the reference liquid. The calculation is as follows: The mass content of dimethyl carbonate in five liquids ω1; ω1=2500.50 / (2500.50+2501.50+2918.50 +416.00 +x).

[0153] Mass content ω2 of ethylene carbonate in five liquids; ω2=2501.50 / (2500.50+2501.50+2918.50 +416.00 +x).

[0154] The mass content of propylene carbonate in five liquids ω3; ω3=2501.50 / (2500.50+2501.50+2918.50 +416.00 +x).

[0155] The mass content of vinylene carbonate in five liquids ω4; ω4=x / (2500.50+2501.50+2918.50 +416.00 +x).

[0156] Step S3 calculates the density contribution coefficient of the liquid, as in Example 2.

[0157] ρ 待测 =1.126 g / cm 3 Substitute the values ​​into the equation to find x.

[0158] ρ 待测 = ρ0 ω1×ρ1+ω2×ρ2+ω3×ρ3+ω4×ρ4, That is, 1.126 = 1.006 + 2500.50 / (2500.50 + 2501.50 + 2918.50 + 416.00 + x) × 0.0516 + 2501.50 / (2500.50 + 2501.50 + 2918.50 + 416.00 + x) × 0.2998 + 2501.50 / (2500.50 + 2501.50 + 2918.50 + 416.00 + x) × 0.1844 + x / (2500.50 + 2501.50 + 2918.50 + 416.00 + x) × 0.2833, and we can find x = 273.69 kg.

[0159] The above results show that the actual amount of vinylene carbonate fed was 273.69 kg.

[0160] Verification: 2500.50 kg dimethyl carbonate, 2501.50 kg ethylene carbonate, 2918.50 kg methyl ethyl carbonate, 416.00 kg propylene carbonate, and 273.69 kg vinylene carbonate were used to prepare the estimated formula. After preparing the control and standard samples, the actual density was measured to be 1.1251 g / cm³. 3 The results match the calculations, allowing for rapid anomaly detection.

[0161] Example 9 An error occurred during the production of the electrolyte: 966.00 kg of ethylene carbonate, 966.50 kg of propylene carbonate, 1809.00 kg of ethyl propionate, 2899.50 kg of propyl propionate, and 50.00 kg of vinylene carbonate were already added. During subsequent additions, the flow meter malfunctioned, and the actual amount of fluoroethylene carbonate added is unknown. A control sample was taken, and its density was measured to be 1.0056 g / cm³. 3 Substituting the above formula, the actual amount of fluoroethylene carbonate fed is calculated as follows.

[0162] Let the mass of fluoroethylene carbonate be x, and ethyl propionate be the reference liquid. The calculation is as follows.

[0163] Mass content ω1 of ethylene carbonate in 6 liquids; ω1=966 / (966+966.5+1809+2899.50+50.00 +x).

[0164] Mass content ω2 of propylene carbonate in 6 liquids; ω2=966 / (966+966.5+1809+2899.50+50.00+x).

[0165] The mass content of propyl propionate in 6 liquids ω3; ω3=2899.50 / (966+966.5+1809+2899.50+50.00 +x).

[0166] The mass content of vinylene carbonate in six liquids ω4; ω4=50.00 / (966+966.5+1809+2899.50+50.00 +x).

[0167] Mass content ω5 of fluoroethylene carbonate in 6 liquids; ω5=x / (966+966.5+1809+2899.50+50.00 +x).

[0168] Step S3 calculates the density contribution coefficient of the liquid in the same way as in Example 5, except that the density contribution coefficient of vinylene carbonate is calculated using an additional method.

[0169] Step S3 adds the step of determining the density contribution coefficient ρ6 of vinylene carbonate: dissolve vinylene carbonate in ethyl propionate to obtain the sixth mixed solution; prepare the sixth sub-solution group with gradually increasing concentration using the sixth sub-solution group, establish a concentration-density fitting line to obtain the sixth fitting line, and the slope of the sixth fitting line is the density contribution coefficient ρ6 of vinylene carbonate, where ρ6 = 0.3315.

[0170] ρ 待测 =1.0056 g / cm 3 Substitute the values ​​into the equation to find x.

[0171] ρ 待测 = ρ0 ω1×ρ1+ω2×ρ2+ω3×ρ3+ω4×ρ4, That is, 1.0056 = 0.888 + 966 / (966 + 966.5 + 1809 + 2899.50 + 50.00 + x) × 0.3484 + 966 / (966 + 966.5 + 1809 + 2899.50 + 50.00 + x) × 0.2702 + 2899.50 / (966 + 966.5 + 1809 + 2899.50 + 50.00 + x) × -0.0106 + 50.00 / (966 + 966.5 + 1809 + 2899.50 + 50.00 + x) × 0.3315 + x / (966 + 966.5 + 1809 + 2899.50 + 50.00) (+x)×0.3829, we get x=761.54kg.

[0172] The above results show that the actual amount of fluoroethylene carbonate fed was 761.54 kg.

[0173] Verification: 966.00 kg ethylene carbonate, 966.50 kg propylene carbonate, 1809.00 kg ethyl propionate, 2899.50 kg propyl propionate, 50.00 kg vinylene carbonate, and 761.54 kg fluoroethylene carbonate were used to prepare the estimated formula. After preparing the control and standard samples, the actual density was measured to be 1.0086 g / cm³. 3 The results match the calculations, allowing for rapid anomaly detection.

[0174] Comparative Example 1 The electrolyte formulation is as follows: dimethyl carbonate 15.48%, ethylene carbonate 28.66%, methyl ethyl carbonate 36.88%, vinylene carbonate 5.00%, ethylene sulfate 1.00%, lithium difluorosulfonyl imide 6.17%, and lithium hexafluorophosphate 6.81%. An error occurred during production: 1548.50 g of dimethyl carbonate and 3687.50 g of methyl ethyl carbonate were added, exceeding the standard amount of ethylene carbonate. A control sample was taken and tested; the density was 1.1247 g / cm³. 3 Simulating on-site material feeding conditions, a control sample 1 was prepared: 15.4825 g of dimethyl carbonate, 36.8712 g of methyl ethyl carbonate, and 28.6583 g of ethylene carbonate. The density of the control sample was measured to be 1.1215 g / cm³. 3 The initial sample showed poor agreement with the control sample. Control sample 2 was prepared with 15.4773 g of dimethyl carbonate, 36.8726 g of methyl ethyl carbonate, and 29.0588 g of ethylene carbonate. The density of the control sample was measured to be 1.1228 g / cm³. 3 The match with the control sample was poor; control sample 3 was prepared with 15.4837 g of dimethyl carbonate, 36.8724 g of methyl ethyl carbonate, and 29.5553 g of ethylene carbonate, and the density of the control sample was measured to be 1.1239 g / cm³. 3 The results showed good agreement with the control sample. Further preparation of control sample 4 involved: 15.4782 g of dimethyl carbonate, 36.8845 g of methyl ethyl carbonate, and 30.0512 g of ethylene carbonate. The density of the control sample was measured to be 1.1251 g / cm³. 3 If the result is basically consistent with the control sample, then 3005.12 is taken as the actual amount of material fed, and the anomaly investigation is completed.

[0175] By comparing Examples 1-9 and Comparative Example 1, Comparative Example 1, using existing anomaly detection methods, prepared electrolyte samples with different ethylene carbonate contents, tested the sample density, and compared the sample density with the density detected by the central control system. The densities were basically close, thus determining the actual feed amount; this method was time-consuming and labor-intensive, severely slowing down the production pace. The lithium battery electrolyte density evaluation method provided in this application can, based on the density of abnormal electrolytes on the production line, substitute it into the formula ρ... 待测 = This method allows for the reverse calculation of the quality of the actual abnormal materials added, saving manpower and resources, reducing costs, significantly accelerating the investigation speed after abnormal material input, speeding up the production pace, and ensuring high accuracy (controlled within 0.5%), thus avoiding material waste during the investigation process.

[0176] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for evaluating the density of lithium battery electrolyte, characterized in that, Includes the following steps: The electrolyte to be tested comprises the following raw material components: n liquids and A solids, wherein the A solids are dissolved in the n liquids. Choose one liquid from n liquids as the reference liquid, and the rest are the liquids to be tested; The concentration-density fitting lines for each of the n-1 test liquids are obtained, and the density contribution coefficient of each of the n-1 test liquids is obtained. The concentration-density fitting lines for solid A are obtained respectively, and the density contribution coefficient of solid A is obtained. The density ρ of the electrolyte to be tested at 25℃ 待测 , r 待测 = Wherein, ρ0 is the density of the reference liquid at 25℃, in g / cm³. 3 ; The mass content of the i-th liquid among n-1 test liquids is expressed as % (%). The density contribution coefficient of the i-th liquid among n-1 test liquids, in g / cm³. 3 ; The mass content of the s-th solid in type A in the electrolyte to be tested is expressed as % (%). The density contribution coefficient of the s-th solid in solid A, expressed in g / cm³. 3 .

2. The method for evaluating the density of lithium battery electrolyte according to claim 1, characterized in that, Obtain the concentration-density fitting lines for each of the n-1 test liquids, and then obtain the density contribution coefficients for each of the n-1 test liquids. This process includes the following steps: Dissolve n-1 test liquids into the reference liquid to obtain n-1 sets of mixed solutions. Configure each set of mixed solutions into sub-solutions with gradually increasing or decreasing concentrations. Use the sub-solutions to establish a concentration-density fitting line to obtain n-1 fitting lines. The slope of the n-1 fitting lines is the density contribution coefficient of the n-1 test liquids.

3. The method for evaluating the density of lithium battery electrolyte according to claim 1, characterized in that, Obtain the concentration-density fitting straight line for solid A, and then obtain the density contribution coefficient of solid A. This includes the following steps: Solid A is dissolved in the reference liquid to obtain a group of mixed solutions. Each group of mixed solutions is prepared into sub-solutions with gradually increasing or decreasing concentrations. Concentration-density fitting lines are established using the sub-solutions to obtain A fitting lines. The slope of the A fitting lines is the density contribution coefficient of solid A.

4. The method for evaluating the density of lithium battery electrolyte according to claim 1, characterized in that, =m i / (m1+m2+...+m n ), m i Let m1 + m2 + ... + m be the mass of the i-th liquid among n-1 types of liquids to be tested, where i ≥ 1. n Let be the total mass of n liquids.

5. The method for evaluating the density of lithium battery electrolyte according to claim 1, characterized in that, The n liquids include non-aqueous organic solvents, which include at least one of carbonate solvents, carboxylic acid ester solvents, sulfone solvents, ether solvents, and nitrile solvents.

6. The method for evaluating the density of lithium battery electrolyte according to claim 1, characterized in that, The reference liquid includes at least one of carbonate solvents and carboxylic acid ester solvents.

7. The method for evaluating the density of lithium battery electrolyte according to claim 3, characterized in that, In the step of dissolving solid A into the reference liquid, a co-solvent is added to the reference liquid. The mass of the co-solvent is X times the mass of the reference liquid, and the value of X is in the range of 0 < X ​​≤ 0.

05. The co-solvent includes ethylene carbonate.

8. The method for evaluating the density of lithium battery electrolyte according to claim 1, characterized in that, The solid A includes lithium salts, including LiPF6, LiBF4, LiAsF6, LiClO4, LiBOB, LiDFOB, LiFSI, LiTFSI, LiPO2F2, LiCH3SO3, LiSbF6, LiCF3SO3, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiCl, LiBr, LiI, and LiB. 10 Cl 10 At least one of the following: LiAlCl4, lithium chloroborane, lithium difluorodioxazophosphate, lithium difluorophosphate, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, lithium tetraphenylborate, and lithium imino.

9. The method for evaluating the density of lithium battery electrolyte according to claim 1, characterized in that, The n liquids include a first additive, which includes at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds.

10. The method for evaluating the density of lithium battery electrolyte according to claim 1, characterized in that, The solid A further includes a second additive, which includes at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds.

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