Electrolyte consumption testing method

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a method for testing electrolyte consumption, and aims to solve the problem that an existing method for testing the electrolyte consumption is too long in testing time. Therefore, according to the electrolyte consumption testing method, the internal standard substance with the known mass is added into the extraction solution, and the extraction efficiency of the extraction solution is calculated according to the mass of the internal standard substance before extraction, the mass percentage content of the internal standard substance after extraction and the total mass of the extraction solution after extraction. The mass of the to-be-detected component in the permeated residual electrolyte in the disassembled battery is calculated according to the extraction efficiency, and then the consumption of the to-be-detected component is calculated according to the initial mass of the to-be-detected component in the electrolyte and the mass of the to-be-detected component in the free electrolyte. The battery does not need to be extracted for many times, and the test time can be effectively shortened.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, and specifically provides a method for testing electrolyte consumption. Background Art

[0002] For energy storage batteries, whether they have a long service life is an important criterion for evaluating the performance of batteries. The amount of electrolyte in lithium-ion batteries has an important impact on the cycle life. Therefore, it is necessary to evaluate the electrolyte consumption during the battery cycle to determine whether the battery life meets the requirements.

[0003] At present, most of the detection methods for electrolyte consumption are to disassemble the battery, obtain part of the pole piece in the core, put the pole piece in a centrifuge, collect the electrolyte by centrifugation, and calculate the electrolyte consumption by testing the organic components in the centrifuged electrolyte. Or soak the pole piece in the extract for a long time to obtain the extract. By testing the electrolyte components in the extract, the electrolyte consumption is calculated.

[0004] However, the above test methods all have the problem of long test time. Accordingly, the art needs a new technical solution to solve the above technical problem. Summary of the invention

[0005] The present invention aims to solve the above technical problem, that is, to solve the problem that the existing method for testing electrolyte consumption has a long testing time.

[0006] The present invention provides a method for testing electrolyte consumption, the method comprising the following steps: S1, obtaining the initial mass M of the component to be tested of the electrolyte injected into the battery to be tested 初始 ; S2, dismantling the battery to be tested, collecting the free electrolyte, and determining the free mass M1 of the component to be tested in the free electrolyte; S3, extracting the disassembled battery using an extraction solvent, wherein the extraction solvent is added with a mass of M x1 internal standard; record the mass M of the extraction solution after extraction 萃取2 , testing the concentration of the internal standard substance in the extraction solution after extraction and the concentration of the component to be tested; S4, according to M 萃取2 、M x1 and the concentration of the internal standard, calculating the extraction efficiency α of the extraction solution; S5, according to α, M 萃取2 、M 初始 , M1 and the concentration of the component to be tested, and calculate the consumption ΔM of the component to be tested in the battery to be tested.

[0007] In the preferred technical solution of the above-mentioned method for testing the electrolyte consumption, the concentration of the internal standard substance is the mass percentage content w of the internal standard substance. x2In step S4, the extraction efficiency α is calculated by the following formula: α=M 萃取2 × x2 ÷M x1 ; and / or, the concentration of the component to be detected is the mass percentage content w2 of the component to be detected. In step S5, the consumption ΔM of the component to be detected is calculated by the following formula: ΔM=M 初始 -M1-M2, where M2=M 萃取2 ×w2÷α, M2 is the mass of the component to be detected remaining in the disassembled battery.

[0008] In the preferred technical scheme of the above-mentioned test method for electrolyte consumption, in step S3, the extraction solvent is acetonitrile and / or dimethyl carbonate, and the extraction solvent does not contain the components in the electrolyte; and / or, in step S3, the internal standard substance includes an ester substance, and the internal standard substance does not contain the components in the electrolyte.

[0009] In the preferred technical solution of the above-mentioned method for testing the electrolyte consumption, the electrolyte comprises a lithium salt, a solvent and an additive and does not contain methyl acetate, and the internal standard substance is methyl acetate.

[0010] In the preferred technical scheme of the above-mentioned test method for electrolyte consumption, the extraction system is subjected to water bath ultrasonic treatment during the extraction process, the water bath ultrasonic treatment time is 1 to 2 hours, and the water bath temperature is 45°C to 60°C.

[0011] In the preferred technical solution of the above-mentioned method for testing the electrolyte consumption, in step S2, the step of "determining the free mass M1 of the component to be detected in the free electrolyte" specifically includes: performing a component test on the free electrolyte to obtain the free concentration of the component to be detected in the free electrolyte; according to M 游 and the free concentration of the component to be detected, and calculate the free mass M1 of the component to be detected in the free electrolyte, where M 游 is the mass of free electrolyte.

[0012] In the preferred technical scheme of the above-mentioned test method for electrolyte consumption, the free concentration of the component to be detected is the free mass percentage w1 of the component to be detected. In step S2, the free mass M1 of the component to be detected is calculated by the following formula: M1=M 游 ×w1.

[0013] In the preferred technical scheme of the above-mentioned electrolyte consumption test method, step S1 specifically includes: S11, obtaining the injection mass M0 of the electrolyte in the battery to be tested and the initial mass percentage w0 of the component to be detected in the electrolyte; S12, calculating the initial mass M0 of the component to be detected in the injected electrolyte according to M0 and w0. 初始 .

[0014] In the preferred technical solution of the above-mentioned electrolyte consumption test method, in step S12, the initial mass M of the component to be detected is 初始 It is calculated by the following formula: M 初始 =M0×w0.

[0015] In the preferred technical solution of the above-mentioned method for testing the electrolyte consumption, the component to be detected is any one or more components of the lithium salt, additive or solvent of the electrolyte.

[0016] Compared with the prior art, the electrolyte consumption test method of the present application has the following advantages: Beneficial effects:

[0017] The test method for electrolyte consumption of the present application adds an internal standard of known mass to the extraction solution, calculates the extraction efficiency of the extraction solution according to the mass of the internal standard before extraction, the mass percentage of the internal standard after extraction, and the total mass of the extraction solution after extraction, and calculates the mass of the component to be detected in the residual electrolyte that has permeated into the disassembled battery according to the extraction efficiency, and then calculates the consumption of the component to be detected in combination with the initial mass of the component to be detected in the electrolyte and the mass of the component to be detected in the free electrolyte. The test method for electrolyte consumption of the present application does not require multiple extractions of the battery, and can effectively shorten the test time.

[0018] In addition, when methyl acetate is used as the internal standard in the non-methyl acetate electrolyte system, the calculated extraction efficiency of the extraction solvent is closer to the actual extraction efficiency than that of other internal standards, and the error between the calculated consumption of the component to be detected in the electrolyte and its actual consumption is small, which can improve the test accuracy of the final test result. DETAILED DESCRIPTION

[0019] The preferred embodiments of the present invention are described below. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0020] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0021] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0022] It should be understood that in various embodiments of the present application, the above-mentioned order of steps does not mean the order of execution, and some or all of the steps can be executed in parallel or sequentially. For example, step S1 can be executed at any node before executing step S5. The execution order of each step should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0023] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0024] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0025] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0026] The experimental methods in the following examples are conventional methods unless otherwise specified, and the materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

[0027] The existing electrolyte consumption test method mentioned in the background art has the problem of too long test time.

[0028] The present application provides a method for testing electrolyte consumption, by adding an internal standard of known mass into an extraction solution, calculating the extraction efficiency of the extraction solution according to the mass of the internal standard before extraction, the mass percentage of the internal standard after extraction, and the total mass of the extraction solution after extraction, and calculating the mass of the component to be detected in the residual electrolyte that has permeated into the disassembled battery according to the extraction efficiency, and then calculating the actual consumption of the component to be detected in combination with the initial mass of the component to be detected in the electrolyte and the mass of the component to be detected in the free electrolyte. The method for testing electrolyte consumption of the present application does not require multiple extractions of the battery, and can effectively shorten the test time.

[0029] Specifically, the test method of the electrolyte consumption of the present application specifically includes the following steps:

[0030] S1. Obtaining the initial mass Minitial of the component to be detected of the electrolyte injected into the battery to be tested.

[0031] Specifically, since the composition ratio of the electrolyte is known before injection, the mass of each component in the electrolyte can be obtained by the injection mass and the ratio of each component. Therefore, the initial mass M of any component to be detected in the electrolyte is 初始 The components to be detected are any one or more components in the composition of the electrolyte, and the consumption of each electrolyte component can be detected by the test method of the present application.

[0032] Preferably, step S1 specifically includes:

[0033] S11, obtaining the injection mass M0 of the electrolyte in the battery to be tested and the initial mass percentage w0 of the component to be tested in the electrolyte.

[0034] S12, calculate the initial mass M of the component to be detected in the injected electrolyte according to M0 and w0 初始 .

[0035] In step S12, the initial mass M of the component to be detected 初始 It is calculated by the following formula: M 初始 =M0×w0.

[0036] Specifically, the injection amount M0 can be obtained by subtracting the mass of the battery before and after the injection.

[0037] Wherein, the component to be detected is any one or more components in the electrolyte composition.

[0038] S2. Disassemble the battery to be tested, collect the free electrolyte, and determine the free mass M1 of the component to be tested in the free electrolyte.

[0039] Specifically, the step of "determining the free mass M1 of the component to be detected in the free electrolyte" specifically includes: performing a component test on the free electrolyte to obtain the free concentration of the component to be detected in the free electrolyte, and determining the free mass M1 of the component to be detected in the free electrolyte according to M1. 游 and the free concentration of the component to be detected, calculate the free mass M1 of the component to be detected in the free electrolyte, where M 游 is the mass of the free electrolyte. The free concentration may be mass concentration, molar concentration or mass percentage. In one embodiment, the free concentration of the component to be detected is the free mass percentage w1 of the component to be detected, wherein the free mass M1 of the component to be detected is calculated by the following formula: M1 = M 游 ×w1.

[0040] S3, extracting the disassembled batteries using an extraction solvent, specifically, putting all the disassembled batteries into an aluminum-plastic film bag, adding an extraction solvent into the aluminum-plastic film bag and completely immersing the batteries, wherein a substance with a mass of M is added to the extraction solvent. x1 internal standard; record the mass M of the extraction solution after extraction 萃取2 , testing the concentration of the internal standard and the concentration of the component to be detected in the extraction solution after extraction, wherein the extraction solution is a mixed solution of the extraction solvent and the electrolyte.

[0041] Preferably, the extraction system is subjected to water bath ultrasonic treatment during the extraction process. Specifically, the aluminum-plastic film bag is sealed and placed in a water bath for ultrasonic treatment. The purpose is to promote the flow of the extraction solvent under ultrasonic conditions, to infiltrate the battery particles more quickly and fully, and to fully extract the electrolyte in the pole piece. The time for water bath ultrasonic treatment is 1 to 2 hours, and the water bath temperature is 45°C to 60°C. Controlling the water bath temperature within the temperature range of 45°C to 60°C can not only make the extraction solvent more miscible with the electrolyte faster, but also ensure that the temperature is not higher than 60°C, which can avoid volatilization of the electrolyte when it is higher than 60°C, resulting in a reduction in the amount of extracted electrolyte and errors. After the water bath ultrasonic treatment is completed, all the extraction solution is sucked out, and the mass of the extracted extraction solution is recorded as M 萃取2 .

[0042] S4. According to M 萃取2 、M x1 and the concentration of the internal standard, calculate the extraction efficiency α of the extraction solution.

[0043] In one embodiment, the concentration of the internal standard is the mass percentage of the internal standard w x2 , where the extraction efficiency α is calculated by the following formula: α=M 萃取2 × x2 ÷M x1 .

[0044] In another embodiment, the concentration of the internal standard is the mass concentration of the internal standard, and the mass percentage of the internal standard can be calculated by the mass concentration of the internal standard and the detected volume. x2 , where the extraction efficiency α is calculated by the following formula: α=M 萃取2 × x2 ÷M x1 .

[0045] In another embodiment, the concentration of the internal standard is the molar concentration of the internal standard, and the mass percentage of the internal standard can be calculated by the molar concentration of the internal standard and the detected volume. x2 , where the extraction efficiency α is calculated by the following formula: α=M 萃取2 × x2 ÷M x1 .

[0046] S5, according to α, M 萃取2 、M 初始 , M1 and the concentration of the component to be tested, calculate the consumption ΔM of the component to be tested in the battery to be tested.

[0047] In one embodiment, the concentration of the component to be detected is the mass percentage content w2 of the component to be detected, wherein the consumption ΔM of the component to be detected is calculated by the following formula: ΔM=M 初始 -M1-M2, where M2=M 萃取2 ×w2÷α, M2 is the mass of the component to be detected remaining in the disassembled battery.

[0048] In another embodiment, the concentration of the component to be detected is the mass concentration of the component to be detected. The mass percentage w2 of the component to be detected can be calculated by the mass concentration of the component to be detected and the detected volume. The consumption ΔM of the component to be detected is calculated by the following formula: ΔM=M 初始 -M1-M2, where M2=M 萃取2 ×w2÷α, M2 is the mass of the component to be detected remaining in the disassembled battery.

[0049] In another embodiment, the concentration of the component to be detected is the molar concentration of the component to be detected. The mass percentage w2 of the component to be detected can be calculated by the molar concentration of the component to be detected and the detected volume. The consumption ΔM of the component to be detected is calculated by the following formula: ΔM=M 初始-M1-M2, where M2=M 萃取2 ×w2÷α, M2 is the mass of the component to be detected remaining in the disassembled battery.

[0050] The test method for electrolyte consumption of the present application adds an internal standard of known mass to the extraction solution, calculates the extraction efficiency of the extraction solution according to the mass of the internal standard before extraction, the mass percentage of the internal standard after extraction and the total mass of the extraction solution after extraction, and calculates the mass of the component to be detected in the residual electrolyte permeated in the disassembled battery according to the extraction efficiency, and then calculates the consumption of the component to be detected in combination with the initial mass of the component to be detected in the electrolyte and the mass of the component to be detected in the free electrolyte. Such a test method does not require multiple extractions of the battery. The mass of the component to be detected in the extraction solution can be calculated according to the extraction efficiency through one extraction operation, and then the consumption of the component to be detected can be obtained, which can effectively shorten the time required for the test.

[0051] It should be noted that, the battery to be tested is a battery that has been cycled a certain number of times and discharged to the lower limit window of the use voltage. During the discharge process, those skilled in the art can choose the corresponding rate for discharge according to actual needs, for example, the battery to be tested is discharged at 1 / 3C, or the battery to be tested is discharged at 1 / 2C. The specific adjustments and changes to the discharge operation do not deviate from the basic principles of this application and should be limited to the protection scope of this application. The number of cycles can be determined according to actual needs. For example, it can be a battery after 200 cycles, or it can be a battery after 500 cycles, or it can be a battery after 1000 cycles. The test method of the present application is suitable for detection and use of batteries with different numbers of cycles. The adjustment and change of the number of cycles of the battery to be tested does not deviate from the basic principles of this application and should be limited to the protection scope of this application.

[0052] It should be noted that in the above steps S2 and S3, when the component to be detected is a lithium salt, the mass percentage of the lithium salt in the free electrolyte and the extraction solution is tested by an ion liquid chromatograph. Specifically, the solution to be tested is treated by dilution, pH adjustment and other steps, and the treated solution to be tested is injected into the ion chromatograph, and the ion exchange resin in the ion liquid chromatograph is passed through, and the F in the solution to be tested is separated according to the different affinity between the ions in the solution to be tested and the exchange resin. - PF6 - Plasma separation, through PF6 - The response intensity of the characteristic ion peak is tested to obtain the mass percentage of the lithium salt.

[0053] It should be noted that in the above steps S2 and S3, when the components to be detected are additives and solvents, the mass percentage of the solvents and additives in the free electrolyte and the extract is tested by gas chromatography-mass spectrometry (GC-MS). Specifically, when the solution sample to be tested enters the chromatographic column, it is separated by the chromatographic column, and each gaseous molecule separated by gas chromatography is bombarded by an ion source and electrolytically decomposed into ions. Under the action of the electric field and the magnetic field, they are separated according to the mass-to-charge ratio m / z, and the appropriate organic components of the electrolyte are matched according to the mass-to-charge ratio value, that is, the mass percentage of each organic component is calculated.

[0054] It should be noted that the present application does not impose any restrictions on the specific components of the extraction solvent, as long as the extraction solvent can dissolve and extract the lithium salt, solvent and additives. In practical applications, those skilled in the art can select the specific components of the extraction solvent according to actual needs. For example, the extraction solvent can be acetonitrile, or the extraction solvent can also be dimethyl carbonate, or the extraction solvent can also be DMC, etc. The adjustment and change of the specific components of the extraction solvent do not deviate from the basic principles of the present application and should be limited within the scope of protection of the present application.

[0055] Preferably, in step S3, the extraction solvent is acetonitrile and / or dimethyl carbonate, and the extraction solvent does not contain components in the electrolyte.

[0056] The extraction solvent is set to acetonitrile and dimethyl carbonate, and the extraction solvent does not contain the components in the electrolyte, can be distinguished from the solvent components in the electrolyte, does not affect the test results of the solvent in the electrolyte, and its test results are more accurate. Specifically, the selection of the extraction solvent is determined according to the components of the electrolyte. When the electrolyte does not contain acetonitrile and does not contain dimethyl carbonate, the extraction solvent can be selected as any one or a combination of acetonitrile and dimethyl carbonate; when the electrolyte contains dimethyl carbonate but does not contain acetonitrile, the extraction solvent is set to acetonitrile, and when the electrolyte contains acetonitrile but does not contain dimethyl carbonate, the extraction solvent is set to dimethyl carbonate.

[0057] Preferably, in step S3, the internal standard substance includes an ester substance, and the internal standard substance does not contain components in the electrolyte.

[0058] In a preferred embodiment, the electrolyte includes a lithium salt, a solvent and an additive, and the electrolyte does not contain methyl acetate, and the internal standard is methyl acetate. Methyl acetate is selected as the internal standard, and the substance has a peak time of about 3 minutes in GC-MS, and the peak is early, which will not affect the peak position and intensity of the organic component in the electrolyte. The mass percentage content measured is more accurate, and the extraction efficiency of the extraction solvent calculated by the mass percentage content is closer to the actual extraction efficiency.

[0059] The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethanesulfonyl imide), and lithium difluorobis(oxalatophosphate).

[0060] The solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0061] The additive includes one or more of vinylene carbonate, vinyl sulfite, fluoroethylene carbonate, vinylethylene carbonate, succinonitrile, adiponitrile, 1,3-propane sultone, propenyl-1,3-sultone, and phenyl trifluoromethyl sulfide.

[0062] When the components to be detected are lithium salt, solvent and additive, the test method of electrolyte consumption of the present application specifically includes the following steps:

[0063] S11, obtaining the injection mass M0 of the electrolyte in the battery to be tested, as well as the initial lithium salt mass percentage w1, the initial solvent mass percentage w2, and the initial additive mass percentage w3 in the electrolyte;

[0064] S12, calculate the lithium salt mass M of the injected electrolyte according to M0, w1, w2, and w3 初始锂盐 , Solvent quality M 初始溶剂 and additive mass M 初始添加剂 Among them, M 初始锂盐 =M0×w1;M 初始溶剂 =M0×w2;M 初始添加剂 =M0×w3.

[0065] S2. Disassemble the battery to be tested, collect the free electrolyte, and test the composition of the free electrolyte to obtain the mass percentage of free lithium salt in the free electrolyte w. 11 , free solvent mass percentage w 21 And free additive mass percentage w 31 According to M 游 、w 11 、w 21 and w 31 Calculate the mass M of free lithium salt in the free electrolyte 锂盐1 , the mass of free solvent M 溶剂1 and the mass of free additives M 添加剂1 Among them, M 锂盐1 =M 游 × 11 ;M 溶剂1 =M 游 × 21 ;M 添加剂1 =M游 × 31 , M 游 is the mass of free electrolyte.

[0066] S3, extracting the disassembled batteries using an extraction solvent, specifically, putting all the disassembled batteries into an aluminum-plastic film bag, adding an extraction solvent into the aluminum-plastic film bag and completely immersing the batteries, wherein a substance with a mass of M is added to the extraction solvent. x1 internal standard; record the mass M of the extraction solution after extraction 萃取2 , test the mass percentage of the internal standard in the extraction solution after extraction w x2 , mass percentage of lithium salt w 12 , mass percentage of solvent w 22 , mass percentage of additives w 32 The extraction solution is a mixed solution of an extraction solvent and an electrolyte.

[0067] S4. According to M 萃取2 、M x1 and w x2 Calculate the extraction efficiency α of the extraction solution. Where α=M 萃取2 × x2 ÷M x1 .

[0068] S5, according to α, M 萃取2 、w 12 、M 初始锂盐 、M 锂盐1 Calculate the lithium salt consumption ΔM of the battery under test 锂盐 , ΔM 锂盐 =M 初始锂盐 -M 锂盐1 -M 锂盐2 , where M 锂盐2 =M 萃取2 × 12 ÷α,M 锂盐2 It is the mass of lithium salt remaining in the disassembled battery.

[0069] S6, according to α, M 萃取2 、w 22 、M 初始溶剂 、M 溶剂1 , calculate the solvent consumption ΔM of the battery to be tested 溶剂 , ΔM 溶剂 =M 初始溶剂 -M 溶剂1 -M 溶剂2 , where M 溶剂2 =M 萃取2 × 22 ÷α,M 溶剂2 It is the mass of the extraction solvent remaining in the disassembled battery.

[0070] S7, according to α, M 萃取2 、w 32 、M 初始添加剂 、M 添加剂1 Calculate the additive consumption ΔM of the battery under test 添加剂 , ΔM 添加剂 =M 初始添加剂 -M 添加剂1 -M 添加剂2 , where M 添加剂2 =M 萃取2 × 32 ÷α,M 添加剂2 It is the mass of additives remaining in the disassembled battery.

[0071] The following is a detailed description of the electrolyte consumption test method of the present application through a specific example. In the following examples, comparative examples and test examples, the reagents, materials and instruments used are conventional reagents, conventional materials and conventional instruments, unless otherwise specified, and can all be commercially available.

[0072] The lithium-ion batteries of the following embodiments and comparative examples are all self-made lithium iron phosphate graphite system square wound batteries, wherein the positive electrode material is LFP, the negative electrode material is graphite, the size of the square battery cell is 71mm*173mm*204mm, and the capacity is about 314Ah. The electrolyte injected is a matching lithium iron phosphate electrolyte, and specifically, the design parameters of the electrolyte are shown in Table 1.

[0073] Table 1 Design parameters of electrolytes for lithium-ion batteries of embodiments and comparative examples

[0074] Example

[0075] The electrolyte injection amount of the lithium ion battery in this embodiment is M0=1005g. 初始锂盐 =M0×w 10 =1005g×12.5%=125.625g; Solvent EMC mass M 初始溶剂(EMC) =M0×w 20(EMC) =1005g×50%=502.5g; Solvent EC mass M 初始溶剂(EC) =M0×w 20(EC) =1005g×34%=341.7g; additive VC mass M 初始添加剂 =M0×w 30 =1005g×3.5%=35.175g.

[0076] After the prepared lithium-ion battery was cycled for 2000 times, it was discharged at 1 / 3C to the lower voltage limit window, disassembled, and the consumption of various components in its electrolyte was tested according to the following steps.

[0077] (1) Disassemble the battery and collect the free electrolyte during disassembly. Record the mass of the free electrolyte as M. 游 , test the composition of the free electrolyte to obtain the mass percentage of free lithium salt in the free electrolyte w 11 , free solvent EMC mass percentage w 21(EMC) 、Free solvent EC mass percentage w 21(EC) And free additive mass percentage w 31 ; and calculate the mass M of free lithium salt in the free electrolyte 锂盐1 =M 游 × 11 、Free solvent EMC quality M 溶剂1(EMC) =M 游 × 21(EMC) 、Free solvent EC mass M 溶剂1(EC) =M 游 × 21(EC) and free additive mass M 添加剂1 =M 游 × 31 The detected and calculated data are shown in Table 2.

[0078] Table 2 Composition of free electrolyte

[0079] As shown in Table 2, the free electrolyte mass M1 is 30g, and the free lithium salt mass percentage w 11 9%, free solvent EMC mass percentage w 21(EMC) is 50%, the free solvent EC mass percentage w 21(EC) The free additive mass percentage is 40%. 31 1%, the mass of free lithium salt M 锂盐1 The mass of free solvent EMC is 2.7g. 溶剂1(EMC) The free solvent EC mass is 15g. 溶剂1(EC) 12g and free additive mass M 添加剂1 It is 0.3g.

[0080] (2) Put all the disassembled batteries into an aluminum-plastic film bag, add extraction solvent into the aluminum-plastic film bag and completely immerse the batteries. Record the mass of the extraction solvent as M 萃取1 300g, and add mass M to the extraction solvent x1The first internal standard is 10 g and the mass M x1 ' is 10g of the second internal standard; wherein the extraction solvent is acetonitrile, the first internal standard is methyl acetate, and the second internal standard is ethyl acetate.

[0081] (3) The aluminum-plastic film bag was sealed and placed in a water bath for water bath ultrasonic treatment, wherein the water bath ultrasonic treatment time was 2 h and the water bath temperature was 55° C.

[0082] (4) After the ultrasonic treatment is completed, all the extraction solution is sucked out, and the mass of all the extraction solution sucked out is recorded as M 萃取2 =1110 g, wherein the extraction solution is a mixed solution of electrolyte and acetonitrile, and the composition of the extraction solution is tested to obtain the mass percentage content of the extracted lithium salt in the extraction solution w 12 、Extraction solvent EMC mass percentage w 22(EMC) 、Extraction solvent EC mass percentage w 22(EC) And the mass percentage of extraction additives w 32 , mass percentage of the first internal standard w x2 And the mass percentage of the second internal standard w x2 '; Among them, the detected data are shown in Table 3.

[0083] Table 3 Components in the extraction solution

[0084] It can be seen from Table 3 that the mass percentage of extracted lithium salt w 12 The mass percentage of EMC in the extraction solvent is 6.5%. 22(EMC) The mass percentage of the extraction solvent EC is 33.5%. 22(EC) The mass percentage of the extraction additive is 13.5%. 32 The first internal standard mass percentage is 0.1%. x2 The mass percentage of the second internal standard is 0.8%. x2 ' is 0.64%.

[0085] (5) Calculating the extraction efficiency α of the extraction solution, wherein the first extraction efficiency α calculated from the first internal standard is =M 萃取2 × x2 ÷M x1 =1110 g×0.8%÷10 g=88.8%, the second extraction efficiency α' calculated by the second internal standard is =M 萃取2 × x2 '÷M x1 '=1110g×0.75%÷10g=83.25%.

[0086] (6) Calculate the mass M of the extracted lithium salt in the extraction solution 锂盐2 and the battery's lithium salt consumption ΔM 锂盐 ; Wherein, M is calculated according to the first extraction efficiency α 锂盐2 =M 萃取2 × 12 ÷α=1110g×6.5%÷88.8%=81.25g, ΔM 锂盐1 =M 初始锂盐 -M 锂盐1 -M 锂盐2 =125.625g-2.7g-81.25g=41.675g; M is calculated based on the second extraction efficiency α' 锂盐2 '=M 萃取2 × 12 ÷α'=1110g×6.5%÷83.25%=86.67g, ΔM 锂盐1 '=M 初始锂盐 -M 锂盐1 -M 锂盐2 '=125.625g-2.7g-86.67g=36.255g.

[0087] (7) Calculate the EMC mass M of the extraction solvent in the extraction solution 溶剂2(EMC) and the solvent EMC consumption of the battery ΔM 溶剂(EMC) ; Wherein, M is calculated according to the first extraction efficiency α 溶剂2(EMC) =M 萃取2 × 22(EMC) ÷α=1110g×33.5%÷88.8%=418.75g, ΔM 溶剂1(EMC) =M 初始溶剂(EMC) -M 溶剂1(EMC) -M 溶剂2(EMC) =502.5g-15g-418.75g=68.75g; M is calculated based on the second extraction efficiency α' 溶剂2(EMC) '=M 萃取2 × 22(EMC) ÷α'=1110g×33.5%÷83.25%=446.67g, ΔM 溶剂1(EMC) '=M 初始溶剂(EMC) -M 溶剂1(EMC) -M 溶剂2(EMC) '=502.5g-15g-446.67g=40.83g.

[0088] (8) Calculate the mass M of the extraction solvent EC in the extraction solution 溶剂2(EC) and the solvent EC consumption of the battery ΔM 溶剂(EC) ; Wherein, M is calculated according to the first extraction efficiency α 溶剂2(EC) =M 萃取2 × 22(EC)÷α=1110g×13.5%÷88.8%=168.75g, ΔM 溶剂1(EC) =M 初始溶剂(EC) -M 溶剂1(EC) -M 溶剂2(EC) =341.7g-12g-168.75g=160.95g; M is calculated based on the second extraction efficiency α' 溶剂2(EC) '=M 萃取2 × 22(EC) ÷α'=1110g×13.5%÷83.25%=180g, ΔM 溶剂1(EC) '=M 初始溶剂(EC) -M 溶剂1(EC) -M 溶剂2(EC) '=341.7g-12g-180g=149.7g.

[0089] (9) Calculate the mass M of the extraction additive in the extraction solution 添加剂2 and battery additive consumption ΔM 添加剂 ; Wherein, M is calculated according to the first extraction efficiency α 添加剂2 =M 萃取2 × 32 ÷α=1110g×0.1%÷88.8%=1.25g, ΔM 添加剂1 =M 初始添加剂 -M 添加剂1 -M 添加剂2 =35.175g-0.3g-1.25g=33.625g; M is calculated based on the second extraction efficiency α' 添加剂2 '=M 萃取2 × 32 ÷α'=1110g×0.1%÷83.25%=1.33g, ΔM 添加剂1 '=M 初始添加剂 -M 添加剂1 -M 添加剂2 '=35.175g-0.3g-1.33g=33.515g.

[0090] Comparative Example

[0091] The battery after the extraction solution is sucked out in step (4) of Example 1 is subjected to multiple second extraction operations again until the mass percentage of lithium salt, additive and solvent in the extraction solution of the last second extraction operation is 0% and then the second extraction operation is stopped.

[0092] The steps of the second extraction operation are as follows: put the battery into an aluminum-plastic film bag, add the extraction solvent (acetonitrile) into the aluminum-plastic film bag and completely immerse the battery. Seal the aluminum-plastic film bag and put it into a water bath for water bath ultrasonic treatment. The water bath ultrasonic treatment time is 2 hours and the water bath temperature is 55°C. After the ultrasonic treatment is completed, all the extraction solution is sucked out, and the mass of all the extraction solution sucked out is recorded as M 萃取n+2 The extraction solution is a mixed solution of electrolyte and acetonitrile. The composition of the extraction solution is tested to obtain the mass percentage of extracted lithium salt in the extraction solution. n2 、Extraction solvent EMC mass percentage w n2(EMC) 、Extraction solvent EC mass percentage w n2(EC) And the mass percentage of extraction additives w n2 . Wherein n is the number of times the second extraction operation is performed.

[0093] The mass of each component in the extraction solution of the first extraction operation and each second extraction operation is calculated, and based on the mass of each component in the extraction solution of each extraction operation, the consumption of each component is calculated. The specific process is as follows:

[0094] (A) Record the mass M of the extraction solution sucked out in step (4) of Example 1 萃取2 =1110g, and according to M 萃取2 , Extracted lithium salt mass percentage w 12 、Extraction solvent EMC mass percentage w 22(EMC) 、Extraction solvent EC mass percentage w 22(EC) And the mass percentage of extraction additives w 32 Calculate the mass M of extracted lithium salt in the extraction solution 锂盐3 、Extraction solvent EMC quality M 溶剂3(EMC) 、Extraction solvent EC quality M 溶剂3(EC) and extraction additive mass M 添加剂3 .

[0095] Among them, M 锂盐3 =M 萃取2 × 12 =1110g×6.5%=72.15g, M 溶剂3(EMC) =M 萃取2 × 22(EMC) =1110g×33.5%=371.85g, M 溶剂3(EC) =M 萃取2 × 22(EC) =1110g×13.5%=149.85g, M 添加剂3 =M 萃取2 × 32 =1110g×0.1%=1.11g.

[0096] (B) The battery in step (4) of Example 1 is subjected to a second extraction operation, i.e., a secondary extraction, and the mass M of the extracted solution is recorded. 萃取3 =500g, at the same time, the mass percentage of extracted lithium salt in the extraction solution is detected 13 、Extraction solvent EMC mass percentage w 23(EMC) 、Extraction solvent EC mass percentage w 23(EC) And the mass percentage of extraction additives w 33 ; Among them, the detected data are shown in Table 4.

[0097] Table 4 Components in the secondary extraction solution

[0098] It can be seen from Table 4 that the mass percentage of extracted lithium salt w 13 The mass percentage of EMC in the extraction solvent is 1.7%. 23(EMC) The mass percentage of the extraction solvent EC is 8.8%. 23(EC) The mass percentage of the extraction additive is 3.5%. 33 It is 0.03%.

[0099] (C) According to M 萃取3 , Extracted lithium salt mass percentage w 13 、Extraction solvent EMC mass percentage w 23(EMC) 、Extraction solvent EC mass percentage w 23(EC) And the mass percentage of extraction additives w 33 Calculate the mass M of extracted lithium salt in the secondary extraction solution 锂盐4 、Extraction solvent EMC quality M 溶剂4(EMC) 、Extraction solvent EC quality M 溶剂4(EC) and extraction additive mass M 添加剂4 .

[0100] Among them, M 锂盐4 =M 萃取3 × 13 =500g×1.7%=8.5g, M 溶剂4(EMC) =M 萃取3 × 23(EMC) =500g×8.8%=44g, M 溶剂4(EC) =M 萃取3 × 23(EC) =500g×3.5%=17.5g, M 添加剂4 =M 萃取3 × 33 =500g×0.03%=0.15g.

[0101] (D) The battery extracted in step (B) is subjected to a second extraction operation again, i.e., three extractions are performed, and the mass M of the extracted solution is recorded. 萃取4 =350g, at the same time, the mass percentage of extracted lithium salt in the extraction solution is detected 14 、Extraction solvent EMC mass percentage w 24(EMC) 、Extraction solvent EC mass percentage w 24(EC) And the mass percentage of extraction additives w 34 ; Among them, the detected data are shown in Table 5.

[0102] Table 5 Components of the three extraction solutions project Mass percentage (%) Lithium salts 0.7％ EMC 2.4％ EC 1.5％ VC 0％

[0103] It can be seen from Table 5 that the mass percentage of extracted lithium salt in the three extraction solutions is w 14 The mass percentage of EMC in the extraction solvent is 0.7%. 24(EMC) The mass percentage of the extraction solvent EC is 6.8%. 24(EC) The mass percentage of the extraction additive is 1.5%. 34 is 0%.

[0104] (E) According to M 萃取4 , Extracted lithium salt mass percentage w 14 、Extraction solvent EMC mass percentage w 24(EMC) 、Extraction solvent EC mass percentage w 24(EC) And the mass percentage of extraction additives w 34 Calculate the mass M of extracted lithium salt in the secondary extraction solution 锂盐5 、Extraction solvent EMC quality M 溶剂5(EMC) 、Extraction solvent EC quality M 溶剂5(EC) and extraction additive mass M 添加剂5 .

[0105] Among them, M 锂盐5 =M 萃取4 × 14 =350g×0.7%=2.45g, M 溶剂5(EMC) =M 萃取4 × 24(EMC) =350g×2.4%=8.4g, M 溶剂5(EC) =M 萃取4 × 24(EC) =350g×1.5%=5.25g, M 添加剂5 =M 萃取4 × 34 =350g×0%=0g.

[0106] (F) The battery extracted in step (D) is subjected to a second extraction operation again, i.e., four extractions are performed, and the mass M of the extracted solution is recorded. 萃取5 =320g, at the same time, the mass percentage of extracted lithium salt in the extraction solution is detected w 15 、Extraction solvent EMC mass percentage w 25(EMC) 、Extraction solvent EC mass percentage w 25(EC) And the mass percentage of extraction additives w 35 ; Among them, the detection data is shown in Table 6.

[0107] Table 6 Components in the four extraction solutions project Mass percentage (%) Lithium salts 0％ EMC 0％ EC 0％ VC 0％

[0108] It can be seen from Table 6 that the four extraction solutions no longer contain the components of the electrolyte, so all the components of the electrolyte have been extracted.

[0109] (G) According to M 初始锂盐 、M 锂盐1 、M 锂盐3 、M 锂盐4 、M 锂盐5 Calculate the battery's lithium salt consumption ΔM 锂盐2 ; where ΔM 锂盐2 =M 初始锂盐 -M 锂盐1 -M 锂盐3 -M 锂盐4 -M 锂盐5 =125.625g-2.7g-72.15g-8.5g-2.45g=39.825g.

[0110] (H) According to M 初始溶剂(EMC) 、M 溶剂1(EMC) 、M 溶剂3(EMC) 、M 溶剂4(EMC) 、M 溶剂5(EMC) Calculate the solvent EMC consumption ΔM of the battery 溶剂2(EMC) ; where ΔM 溶剂2(EMC) =M 初始溶剂(EMC) -M 溶剂 1(EMC)-M 溶剂3(EMC)) -M 溶剂4(EMC)) -M 溶剂5(EMC) =502.5g-15g-371.85g-44g-8.4g=63.25g.

[0111] (I) According to M 初始溶剂(EC) 、M 溶剂1(EC) 、M 溶剂3(EC) 、M 溶剂4(EC) 、M 溶剂5(EC) Calculate the solvent EC consumption ΔM of the cell 溶剂2(EC); where ΔM 溶剂2(EC) =M 初始溶剂(EC) -M 溶剂1(EC) -M 溶剂3(EC) -M 溶剂4(EC) -M 溶剂5(EC) =341.7g-12g-149.85g-17.5g-5.25g=157.1g.

[0112] (J) According to M 初始添加剂 、M 添加剂1 、M 添加剂3 、M 添加剂4 、M 添加剂5 Calculate the battery additive consumption ΔM 添加剂2 ; where ΔM 添加剂2 =M 初始添加剂 -M 添加剂1 -M 添加剂3 -M 添加剂4 -M 添加剂5 =35.175g-0.3g-1.11g-0.15g-0g=33.69g.

[0113] (I) Calculate the relative error E of the electrolyte consumption calculated with the first internal standard based on the data of the examples and comparative examples:

[0114] (11) Absolute error ΔX of lithium salt 锂盐 =ΔM 锂盐1 -ΔM 锂盐2 =41.675g-39.825g=1.85g; relative error of lithium salt E 锂盐 =ΔX 锂盐 ÷ΔM 锂盐2 =1.85÷39.825=4.65%.

[0115] (12) Absolute error of solvent EMC ΔX 溶剂(EMC) =ΔM 溶剂1(EMC) -ΔM 溶剂2(EMC) =68.75-63.25g=5.5g; relative error of solvent EMC E 溶剂(EMC) =ΔX 溶剂(EMC) ÷ΔM 溶剂2(EMC) =5.5÷63.25=8.7%.

[0116] (13) Absolute error ΔX of solvent EC 溶剂(EC) =ΔM 溶剂 -ΔM 溶剂2(EC)1(EC) =168.75g-157.1g=11.65g; relative error E of solvent EC 溶剂(EC) =ΔX 溶剂(EC) ÷ΔM 溶剂2(EC) =11.65÷157.1=7.42%.

[0117] (14) Absolute error ΔX of additive VC 添加剂 =ΔM 添加剂1 -ΔM 添加剂2 =33.625-33.615=0.01g; Relative error E of additive VC 添加剂 =ΔX 添加剂 ÷ΔM 添加剂2 =0.01÷33.615=0.03%.

[0118] (ii) Calculate the relative error E' of the electrolyte consumption calculated with the second internal standard based on the data of the embodiment and the comparative example:

[0119] (21) Absolute error ΔX of lithium salt 锂盐 '=ΔM 锂盐1 '-ΔM 锂盐2 =36.255g-39.825g=-3.57g; relative error of lithium salt E 锂盐 '=ΔX 锂盐 '÷ΔM 锂盐2 '=-3.57÷39.825=-8.96%.

[0120] (22) Absolute error of solvent EMC ΔX 溶剂(EMC) '=ΔM 溶剂1(EMC) '-ΔM 溶剂2(EMC) =40.83g-63.28g=-23.25g; relative error EMC of solvent 溶剂(EMC) '=ΔX 溶剂(EMC) '÷ΔM 溶剂2(EMC) '=-23.25÷63.28=-36.74%.

[0121] (23) Absolute error of solvent EC ΔX 溶剂(EC) '=ΔM 溶剂1(EC) '-ΔM 溶剂2(EC) =149.7g-157.1g=-8g; relative error E of solvent EC 溶剂(EC) '=ΔX 溶剂(EC) '÷ΔM 溶剂2(EC ' ) =-8÷157.1=-5.09%.

[0122] (24) Absolute error ΔX of additive VC 添加剂 '=ΔM 添加剂1 '-ΔM 添加剂2 =33.515g-33.615=-0.1g; relative error E of additive VC 添加剂 '=ΔX 添加剂 '÷ΔM 添加剂2'=-0.1÷33.615=-0.3%.

[0123] It can be seen from the experimental data of the embodiments and comparative examples that the consumption of the electrolyte measured by the test method for the consumption of the electrolyte of the present application, when the internal standard is methyl acetate, the consumption of lithium salts, solvents, and additives calculated are slightly higher than the actual consumption obtained by multiple extractions in the comparative example, and the relative errors are small, all not higher than 9%; in addition, when the internal standard is ethyl acetate, the consumption of lithium salts, solvents, and additives measured are less than the actual consumption obtained by multiple extractions in the comparative example, and the relative errors are large. It can be seen that when the internal standard is ethyl acetate, the error of the calculated extraction efficiency is large, and the error of the calculated consumption of each component is also large. When the internal standard is methyl acetate, the calculated extraction efficiency is closer to the actual extraction efficiency of the extraction solvent, and the calculated consumption of each component is also closer to the actual consumption of each component, with a small error. It can be seen from this that when the internal standard is methyl acetate, using the electrolyte consumption test method of the present application to test the electrolyte consumption can effectively shorten the time required for the test while ensuring the accuracy of the test results, is more convenient to use, and has practical application significance.

[0124] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments, but it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for testing electrolyte consumption, characterized in that: The following steps are involved: S1. Obtain the initial mass M of the component to be tested of the electrolyte injected into the battery to be tested 初始 ; S2, disassembling the battery to be tested, collecting free electrolyte, and determining the free mass M1 of the component to be tested in the free electrolyte; S3, extracting the disassembled battery using an extraction solvent, wherein the extraction solvent is added with a mass of M x1 internal standard; record the mass M of the extraction solution after extraction 萃取2 , testing the concentration of the internal standard substance in the extraction solution after extraction and the concentration of the component to be tested; S4. According to M 萃取2 、M x1 and the concentration of the internal standard, calculating the extraction efficiency α of the extraction solution; S5, according to α, M 萃取2 、M 初始 , M1 and the concentration of the component to be tested, and calculate the consumption ΔM of the component to be tested in the battery to be tested.

2. The method for testing electrolyte consumption according to claim 1, characterized in that: The concentration of the internal standard is the mass percentage of the internal standard w x2 In step S4, the extraction efficiency α is calculated by the following formula: α=M 萃取2 × x2 ÷M x1 ; And / or, the concentration of the component to be detected is the mass percentage content w2 of the component to be detected. In step S5, the consumption ΔM of the component to be detected is calculated by the following formula: ΔM=M 初始 -M1-M2, where M2=M 萃取2 ×w2÷α, M2 is the mass of the component to be detected remaining in the disassembled battery.

3. The method for testing electrolyte consumption according to claim 1, characterized in that: In step S3, the extraction solvent is acetonitrile and / or dimethyl carbonate, and the extraction solvent does not contain components in the electrolyte; And / or, in step S3, the internal standard substance includes an ester substance, and the internal standard substance does not contain components in the electrolyte.

4. The method for testing electrolyte consumption according to claim 3, characterized in that: The electrolyte comprises a lithium salt, a solvent and an additive and does not contain methyl acetate, and the internal standard substance is methyl acetate.

5. The method for testing electrolyte consumption according to claim 1, characterized in that: During the extraction process, the extraction system is subjected to water bath ultrasonic treatment, the water bath ultrasonic treatment time is 1 to 2 hours, and the water bath temperature is 45° C. to 60° C.

6. The method for testing electrolyte consumption according to claim 1, characterized in that: In step S2, the step of "determining the free mass M1 of the component to be detected in the free electrolyte" specifically includes: Conducting a component test on the free electrolyte to obtain the free concentration of the component to be detected in the free electrolyte; According to M 游 and the free concentration of the component to be detected, and calculate the free mass M1 of the component to be detected in the free electrolyte, where M 游 is the mass of free electrolyte.

7. The method for testing electrolyte consumption according to claim 6, characterized in that: The free concentration of the component to be detected is the free mass percentage w1 of the component to be detected. In step S2, the free mass M1 of the component to be detected is calculated by the following formula: M1=M 游 ×w1.

8. The method for testing electrolyte consumption according to claim 1, characterized in that: Step S1 specifically includes: S11, obtaining the injection mass M0 of the electrolyte in the battery to be tested and the initial mass percentage w0 of the component to be tested in the electrolyte; S12, calculate the initial mass M of the component to be detected in the injected electrolyte according to M0 and w0 初始 .

9. The method for testing electrolyte consumption according to claim 8, characterized in that: In step S12, the initial mass M of the component to be detected is 初始 It is calculated by the following formula: M 初始 =M0×w0.

10. The method for testing electrolyte consumption according to any one of claims 1 to 9, characterized in that: The component to be detected is any one or more components in the composition of the electrolyte.

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