CN117849247B

CN117849247B - Electrolyte detection method

Info

Publication number: CN117849247B
Application number: CN202410251391.8A
Authority: CN
Inventors: 王康纬; 周彤; 崔屹; 刘婵; 侯敏; 曹辉
Original assignee: Shanghai Ruipu Energy Co Ltd
Current assignee: Shanghai Ruipu Energy Co Ltd
Priority date: 2024-03-05
Filing date: 2024-03-05
Publication date: 2024-06-14
Anticipated expiration: 2044-03-05
Also published as: CN117849247A

Abstract

The invention provides a detection method of electrolyte, which aims at overcoming the defects existing in the prior art. The detection method comprises the following steps: s1, mixing electrolyte with an internal standard propylene carbonate to obtain a sample to be detected; s2, carrying out gas chromatography test on the sample to be detected; s3, injecting samples to be detected into a plurality of batteries, and performing gas chromatography test after the batteries after the liquid injection are respectively processed in different battery preparation stages; s4, calculating the contents of all components of the electrolyte after the treatment in different battery preparation stages. The detection method provided by the invention can accurately determine the content of each component of the electrolyte at different stages of battery preparation, is simple in operation and calculation process, does not need to be linked with a mass spectrometer, has no influence on analysis results due to impurities in a sample, and is good in repeatability and high in accuracy; the method is suitable for detecting a large number of analysis samples, and has the advantages of high detection speed, simple process and high accuracy.

Description

Electrolyte detection method

Technical Field

The invention belongs to the technical field of battery analysis and detection, and relates to a detection method of electrolyte.

Background

The secondary battery has the advantages of high working voltage, high energy and power density, long cycle life, small self-discharge, environmental friendliness and the like. Currently, the method is widely applied to mobile electronic equipment and is widely applied to electric automobiles. With the continuous upgrading of the market, the service life of electric vehicles is required to be prolonged in the market, the requirement on secondary batteries is greatly improved, and the long-cycle performance of the secondary batteries is increasingly important and urgent. The electrolyte is one of important main materials of the secondary battery, and has important influence on the cycle life and the charge-discharge rate performance of the secondary battery.

The electrolyte consists of lithium salt, solvent and additive, and common solvents include cyclic carbonate (PC, EC), chain carbonate (DEC, DMC, EMC) and carboxylic ester (MF, MA, EA, MA, MP, etc.). The lithium salt is typically LiPF ₆、LiClO₄、LiBF₄、LiAsF₆ or the like. The additives generally include film forming additives, conductive additives, flame retardant additives, overcharge protection additives, and the like. The composition of most electrolytes can be detected by gas chromatography. GC-MS (Gas chromatography-mass spectrometry) is fully called gas chromatography-mass spectrometry and is called gas chromatography-mass spectrometry for short. Is a technique of combining a Gas Chromatograph (GC) and a Mass Spectrometer (MS) through an appropriate interface, and performing a combined analysis by means of a powerful computer technique. When the multicomponent mixed sample enters the column, the components are separated from each other in the column due to differences in partition coefficients or adsorption coefficients of the components in the mobile phase and the stationary phase. Each gaseous molecule separated by gas chromatography is bombarded by an ion source, electrolyzed and cracked into ions, and the ions are separated according to the m/z size under the combined action of an electric field and a magnetic field, and then reach a detector for detection, recording and finishing, so that a mass spectrogram is obtained, and qualitative and quantitative analysis of a sample is realized. For example, CN110161133A discloses a method for detecting and analyzing components in lithium ion functional electrolyte by an external standard method; the method comprises the following steps: drawing standard curves of materials in the lithium ion functional electrolyte: selecting at least three electrolyte solvent samples to be detected; adding at least two additives into the at least three electrolyte solvent samples to prepare mixed liquid, taking a volumetric flask, respectively adding analytical grade ethanedinitrile into the volumetric flask as a diluent, diluting to 100mL scale marks, and detecting by a gas chromatograph to obtain a response value; measuring the content of each material in the lithium ion functional electrolyte; drawing a lithium salt standard curve in the lithium ion functional electrolyte; determination of the lithium salt content in the solvent.

Secondary batteries are a relatively complex system in which a series of complex chemical reactions occur between electrode materials and electrolyte, between electrolyte solvents and solutes, between impurities in the electrolyte and the electrolyte, and the electrolyte itself during charge and discharge. The existing gas chromatography direct sample injection detection technology can not accurately and quantitatively determine the component change of the secondary battery electrolyte.

Therefore, it is important to understand the variation in the content of each component of the electrolyte in each stage of the secondary battery.

Disclosure of Invention

Aiming at the defects existing in the prior art, the invention aims to provide a detection method of electrolyte. According to the method, PC is used as an internal standard substance, and the PC is added into the electrolyte to be detected, so that the content of each component of the electrolyte at different stages of battery preparation can be accurately measured; the method is suitable for detecting a large number of analysis samples, and has the advantages of high detection speed, simple process and high accuracy.

To achieve the purpose, the invention adopts the following technical scheme:

In a first aspect, the present invention provides a method for detecting an electrolyte, the method comprising the steps of:

s1, mixing electrolyte with an internal standard propylene carbonate to obtain a sample to be detected;

s2, carrying out gas chromatography test on the sample to be detected;

S3, injecting samples to be detected into a plurality of batteries, and performing gas chromatography test after the batteries after the liquid injection are respectively processed in different battery preparation stages;

S4, calculating the contents of all components of the electrolyte after the treatment in different battery preparation stages.

According to the detection method provided by the invention, the internal standard Propylene Carbonate (PC) is added, so that the PC and each component in the electrolyte have very similar physical and chemical properties and are completely dissolved in the electrolyte; PC is stable in the battery preparation process, can not be decomposed, and can not chemically react with each component in the electrolyte; PC can be completely separated from chromatographic peaks of each component in the electrolyte. Therefore, the method takes PC as an internal standard substance, and the content of each component of the electrolyte after treatment in different battery preparation stages is calculated by adding the PC into the electrolyte to be detected before the battery is injected; the method is simple to operate, simple in calculation process, free of linkage with a mass spectrometer, free of influence on analysis results by impurities in the sample, good in repeatability and high in accuracy; the method is suitable for detecting a large number of analysis samples, and has the advantages of high detection speed, simple process and high accuracy.

Preferably, the content of each component of the electrolyte after the treatment in the different battery preparation stages in the step S4 is recorded as A ₁, and the calculation formula of A ₁ is A ₁=X₁/X₂*Y₂;

Wherein A ₁ is the mass ratio of each component of the electrolyte after treatment in different battery preparation stages in a sample to be detected, namely the content of each component of the electrolyte after treatment in the different battery preparation stages;

X ₁ is the mass ratio of the internal standard substance in the sample to be detected, and is obtained from the chromatographic peak area of the internal standard substance in the S2;

X ₂ is the mass ratio of the internal standard substance in the sample to be detected after the treatment of different battery preparation stages, and is obtained from the chromatographic peak area of the internal standard substance in the S3;

Y ₂ is the mass ratio of each component of the electrolyte after the treatment in the different battery preparation stages in the sample to be detected after the treatment in the different battery preparation stages, and is obtained from the chromatographic peak area of each component of the electrolyte in the step S3.

The invention provides a calculation formula of the content A ₁ of each component of the electrolyte after treatment in different battery preparation stages, and the accurate value of A ₁ can be obtained simply and directly.

Preferably, the detection method further comprises:

S5, calculating consumption of each component of the electrolyte in different battery preparation stages.

Preferably, the consumption of each component of the electrolyte in the different battery preparation stages in S5 is denoted as a, and the calculation formula of a is a=y ₁-A₁;

Wherein A is the mass ratio of the reduced amount of each component of the electrolyte in different battery preparation stages in a sample to be detected, namely the consumption amount of each component of the electrolyte in the different battery preparation stages;

Y ₁ is the mass ratio of each component of the electrolyte in the sample to be detected, and is obtained from the chromatographic peak area of each component of the electrolyte in the step S2.

Furthermore, the invention can also obtain the consumption of each component in the corresponding electrolyte in different battery preparation stages, and realize the omnibearing knowledge of the component change of the electrolyte in each battery preparation stage, thereby being beneficial to the performance regulation and control of the battery.

Preferably, the negative electrode material in the battery containing the electrolyte comprises artificial graphite.

When the artificial graphite is selected as a negative electrode material system, the content of each component of the electrolyte after treatment in different battery preparation stages and the consumption of each component of the electrolyte in different battery preparation stages can be better obtained; if other negative electrode material systems are selected, such as a natural graphite system, the addition of an internal standard PC can co-intercalate natural graphite with lithium ions in a formation stage, so that the surface of the negative electrode is expanded and cracked, and a large amount of gas is produced, thereby causing irreversible damage to the battery; if the silicon-based anode system is adopted, PC participates in a film forming stage, and certain loss is caused, so that a test result is inaccurate; meanwhile, if the internal standard substance is added after the liquid injection, the consumption caused by vacuumizing and gas production in the formation process cannot be calculated.

Preferably, the mass ratio X ₁ of the internal standard propylene carbonate in the sample to be detected is 1-10%, for example 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.

The mass ratio of the internal standard propylene carbonate in the sample to be detected is X ₁ which is too large and exceeds 10%, so that the performance of the electrolyte is affected, and the lithium salt is consumed in a large amount to generate gas, so that the battery performance is affected; if PC addition is too small, below 1%, the accuracy of the test results is also reduced.

Preferably, the mass ratio X ₁ of the internal standard propylene carbonate in the sample to be detected is 3-7%, for example 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5% or 7%.

According to the invention, the mass ratio X ₁ of the internal standard propylene carbonate in the sample to be detected is within the numerical range of 3-7%, so that the accuracy of the detection result can be improved, and the influence on the performance of the electrolyte is avoided.

Preferably, the content of the internal standard is kept unchanged after the treatment of the different battery preparation stages, wherein the content of the internal standard is the mass ratio X ₁ of the internal standard in the sample to be detected.

In the present application, the definition of "content" and "consumption" refer to the mass ratio of the sample to be tested. In the technical field, after the treatment of different battery preparation stages, the total mass of the electrolyte and the mass of each component of the electrolyte are changed, so that it is not significant to pay attention to the mass ratio (i.e., Y ₂) of each component of the electrolyte after the treatment of different battery preparation stages in the sample to be detected after the treatment of different battery preparation stages, and it is actually the mass ratio in the sample to be detected because the mass of the sample to be detected is constant. Therefore, the content of the internal standard substance is the mass ratio X ₁ of the internal standard substance in the sample to be detected.

In the electrolyte containing PC, the energy of the solvation layer for removing one PC solvent molecule is similar to that of PF6 ^-, which indicates that part of solvation layer does not contain PF6 ^- in the desolvation process, and the content of the formed corresponding decomposition product LiF is lower than that of the electrolyte system; therefore, PC has no fluctuation in the production process of the battery on the basis of a certain content, and the consumption of each component is tested by the unchanged quantity.

Preferably, the different battery preparation stages include a formation stage, a capacity-dividing stage, and a charge-discharge cycle stage.

The detection method provided by the invention can detect the preparation stage and the charge-discharge use stage after the battery is injected, and realizes the multi-process coverage of the battery system.

As a preferred technical solution, the detection method includes the following steps:

S2, performing gas chromatography test on the sample to be detected to obtain the mass ratio Y ₁ of each component of the electrolyte in the sample to be detected and the mass ratio X ₁,X₁ of the internal standard in the sample to be detected as 1-10%;

S3, injecting a sample to be detected into a plurality of batteries, respectively carrying out gas chromatography test on the batteries after a plurality of liquid injection processes in a formation stage, a capacity-dividing stage and a charge-discharge cycle stage, obtaining the mass ratio X ₂ of an internal standard in the sample to be detected after the processes in the formation stage, the capacity-dividing stage and the charge-discharge cycle stage, and obtaining the mass ratio Y ₂ of each component of the electrolyte after the processes in the formation stage, the capacity-dividing stage and the charge-discharge cycle stage;

s4, calculating the contents A ₁ of each component of the electrolyte after treatment in the formation stage, the capacity-dividing stage and the charge-discharge cycle stage, wherein A ₁=X₁/X₂*Y₂;

s5, calculating consumption A of each component of the electrolyte in the formation stage, the capacity-dividing stage and the charge-discharge cycle stage, wherein A=Y ₁-A₁

The content of the internal standard substance is kept unchanged, wherein the content of the internal standard substance is the mass ratio X ₁ of the internal standard substance in a sample to be detected.

It should be noted that the electrolyte systems provided by the invention are all selected by conventional technologies, that is, the detection method provided by the invention is applicable to various electrolyte systems; the electrolyte can be electrolyte for sodium ion batteries or electrolyte for lithium ion batteries, wherein the organic solvent comprises one or more of chain carbonate organic solvents and cyclic carbonate organic solvents; preferably, the chain carbonate organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate and dipropyl carbonate; the cyclic carbonate organic solvent is selected from one or more of ethylene carbonate, vinylene carbonate and propylene carbonate.

It should be noted that the battery system provided by the invention is a battery system before liquid injection, and can be a plurality of types of battery systems, and the structure, the raw materials and the preparation process of the battery system are conventional technical means except the special limitations of the invention, so that a person skilled in the art can carry out adaptive selection according to actual requirements.

The battery comprises an anode plate, a diaphragm, a cathode plate and electrolyte.

The positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer positioned on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a conductive agent and a binder; the negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer positioned on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, a conductive agent and a binder.

Alternatively, the positive electrode active material includes, but is not limited to, a sodium ion battery positive electrode active material or a lithium ion battery positive electrode active material.

Alternatively, the positive electrode current collector is not particularly restricted so long as it has conductivity without causing chemical changes in the battery. In particular, copper, stainless steel, aluminum, nickel, titanium, or a metal current collector surface-treated with carbon or other substances may be used.

Optionally, the shape of the negative electrode current collector includes a foil shape, a plate shape, a mesh shape, or the like; the negative electrode current collector includes, but is not limited to, any of elemental aluminum, copper, nickel, or zinc.

Alternatively, the separator includes, but is not limited to, polyethylene films, polypropylene films, polyvinylidene fluoride films, and multilayer composite films composed of the above materials.

Alternatively, the binder includes, but is not limited to, poly (tetrafluoroethylene) (PTFE), sodium carboxymethyl cellulose (CMC), styrene Butadiene Rubber (SBR), polyvinylidene fluoride (PVDF), nitrile Butadiene Rubber (NBR), styrene ethylene butylene styrene copolymer (SEBS), styrene butadiene styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, and combinations thereof.

Alternatively, the conductive agent may comprise a carbon-based material, powdered nickel or other metal particles, or a conductive polymer. The carbon-based material may include, for example, particles of carbon black, graphite, superP, acetylene black (such as KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, and the like. Examples of the conductive polymer include polyaniline, polythiophene, polyacetylene, polypyrrole, poly (3, 4 ethylenedioxythiophene) polysulfstyrene, and the like.

Compared with the prior art, the invention has the following beneficial effects:

According to the detection method provided by the invention, the internal standard Propylene Carbonate (PC) is added, so that the PC and each component in the electrolyte have very similar physical and chemical properties and are completely dissolved in the electrolyte; PC is stable in the battery preparation process, can not be decomposed, and can not chemically react with each component in the electrolyte; PC can be completely separated from chromatographic peaks of each component in the electrolyte. Therefore, the method takes PC as an internal standard substance, and adds the PC into the electrolyte to be detected before the battery is injected, so as to calculate the contents of all components of the electrolyte after the treatment in different battery preparation stages; the method is simple to operate, simple in calculation process, free of linkage with a mass spectrometer, free of influence on analysis results by impurities in the sample, good in repeatability and high in accuracy; the method is suitable for detecting a large number of analysis samples, and has the advantages of high detection speed, simple process and high accuracy.

Detailed Description

The technical scheme of the invention is further described by the following specific examples. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.

Example 1

The embodiment provides a detection method of an electrolyte, which comprises the following steps:

S1, mixing electrolyte (the components and the content in the electrolyte are respectively EC 25%, EMC 24%, DMC 32%, VC 3%, DTD 0.5% and LiPF ₆:13%) with an internal standard substance propylene carbonate to obtain a sample to be detected;

S2, carrying out gas chromatography test on the sample to be detected, and obtaining the mass ratio Y ₁ of each component of the electrolyte in the sample to be detected according to the chromatographic peak area of each component, and obtaining the mass ratio X ₁,X₁ of the internal standard in the sample to be detected as 4%;

S3, injecting a sample to be detected into a plurality of batteries, performing chemical formation, capacity division and charge-discharge cyclic treatment on the batteries after the liquid injection respectively to perform gas chromatography test, obtaining the mass ratio X ₂ of an internal standard in the sample to be detected after the treatment of different battery preparation stages according to the chromatographic peak areas of the components, and obtaining the mass ratio Y ₂ of the components of the electrolyte after the treatment of different battery preparation stages in the sample to be detected after the treatment of different battery preparation stages;

The formation process comprises the following steps: the method sequentially comprises the steps of pre-forming a battery (charging the battery with small current of 0.05C after liquid injection), forming (charging the battery with relatively large current of 0.2C-0.5C after pre-forming), and aging (standing stage), so as to obtain the mass ratio X _{2- Formation into} of an internal standard PC after forming and the mass ratio Y _{2- Formation into} of each component of the electrolyte after forming;

The capacity-dividing process (after advanced formation treatment, capacity-dividing treatment is continued): fully charging the battery to 3.65V with a constant current and a constant voltage of 1/3C, discharging to 2.5V with 1/3C, and measuring the discharge capacity when the battery is fully charged to determine the capacity of the battery; obtaining the mass ratio X _{2- Capacity-dividing} of the internal standard PC after capacity division and the mass ratio Y _{2- Capacity-dividing} of each component of the electrolyte after capacity division;

And a charge-discharge cycle process (after formation and capacity division are sequentially carried out, charge-discharge cycle is continued): in the voltage range of 2.5-3.65V, charging and discharging are carried out by using charging and discharging current of 0.5C, and the cycle number is 100; obtaining the mass ratio X _{2- Circulation} of the internal standard PC after charge and discharge circulation and the mass ratio Y _{2- Circulation} of each component of the electrolyte after charge and discharge circulation;

S4, calculating the contents A ₁ (A _{1- Formation into}、A_{1- Capacity-dividing} and A _{1- Circulation} respectively) of all the components of the electrolyte after treatment in different battery preparation stages, wherein A ₁=X₁/X₂*Y₂;

S5, according to Y ₁ in S2 and A ₁ in S4, the consumption A of each component of the electrolyte of the battery in different preparation stages can be calculated, wherein A=Y ₁-A₁;

The preparation process of the battery (artificial graphite system) before liquid injection in the embodiment is as follows: preparing positive electrode slurry: lithium iron phosphate, polyvinylidene fluoride and conductive carbon black are mixed according to 98 percent: 1.5%: the slurry was prepared by mixing 0.5% in N-methylpyrrolidone solvent. Preparing a negative electrode slurry: artificial graphite, sodium carboxymethyl cellulose, styrene-butadiene rubber and conductive carbon black are mixed according to the ratio of 95 percent: 1%:2%:2% of the mixture was mixed to prepare a slurry. Coating: uniformly coating the stirred slurry on a metal foil, drying to prepare a positive plate and a negative plate, coating the positive plate on an aluminum foil, and coating the negative plate on a copper foil. And (3) rolling: and further compacting the coated pole piece, and improving the energy density of the battery. Cutting: continuously slitting the wider whole roll of pole piece into a plurality of narrow pieces. And (3) die cutting: and punching and forming the cut pole piece to form the pole lug. Winding/lamination: the pole pieces are wound or laminated into a cell. And (5) packaging in a shell: the coiled or laminated battery core is put into a shell, a square aluminum shell is used as a square shell battery, an aluminum plastic film is used as a soft package battery, and then a battery cover plate is welded and packaged.

The contents a ₁ of the components of the electrolyte in example 1 (initial stages Y ₁、A_{1- Formation into}、A_{1- Capacity-dividing} and a _{1- Circulation}, respectively) are shown in table 1.

TABLE 1

It can be derived from Table 1 that lithium salt, additives and solvents have different degree of loss after formation, and are mainly used for forming films on the surfaces of the anode and the cathode of the battery; the secondary liquid injection process is adopted in the battery during capacity division, so that the contents of the components are increased to different degrees; the main consumption in the circulation process is that film forming additives such as VC, DTD and the like are used for repairing the SEI film damaged on the surface of the negative electrode.

Example 2

The difference between this example and example 1 is that the mass ratio X ₁ of the internal standard in the sample to be tested in this example is 5%.

The remaining detection methods and procedures were consistent with example 1.

Table 2 shows the contents A ₁ of the components in example 2 (initial stages Y ₁、A_{1- Formation into}、A_{1- Capacity-dividing} and A _{1- Circulation}, respectively).

TABLE 2

Example 3

The difference between this example and example 1 is that the mass ratio X ₁ of the internal standard in the sample to be tested in this example is 6%.

The remaining detection methods and procedures were consistent with example 1.

Table 3 shows the contents A ₁ of the components in example 3 (initial stages Y ₁、A_{1- Formation into}、A_{1- Capacity-dividing} and A _{1- Circulation}, respectively).

TABLE 3 Table 3

Example 4

The difference between this example and example 1 is that the mass ratio X ₁ of the internal standard in the sample to be tested in this example is 2%.

The remaining detection methods and procedures were consistent with example 1.

Table 4 shows the contents A ₁ of the components in example 4 (initial stages Y ₁、A_{1- Formation into}、A_{1- Capacity-dividing} and A _{1- Circulation}, respectively).

TABLE 4 Table 4

Example 5

The difference between this example and example 1 is that the mass ratio X ₁ of the internal standard in the sample to be tested in this example is 8%.

The remaining detection methods and procedures were consistent with example 1.

Table 5 shows the contents A ₁ of the components in example 5 (initial stages Y ₁、A_{1- Formation into}、A_{1- Capacity-dividing} and A _{1- Circulation}, respectively).

TABLE 5

Example 6

The difference between this example and example 1 is that the mass ratio X ₁ of the internal standard in the sample to be tested in this example is 0.5%.

The remaining detection methods and procedures were consistent with example 1.

Table 5 shows the contents A ₁ of the components in example 6 (initial stages Y ₁、A_{1- Formation into}、A_{1- Capacity-dividing} and A _{1- Circulation}, respectively).

TABLE 6

Example 7

The difference between this example and example 1 is that the mass ratio X ₁ of the internal standard in the sample to be tested in this example is 12%.

The remaining detection methods and procedures were consistent with example 1.

Table 7 shows the contents A ₁ of the components in example 7 (initial stages Y ₁、A_{1- Formation into}、A_{1- Capacity-dividing} and A _{1- Circulation}, respectively).

TABLE 7

Example 8

The difference between this example and example 1 is that the electrolyte before the addition of the internal standard in this example is an electrolyte with 25% MA instead of EC.

The remaining detection methods and procedures were consistent with example 1.

Table 8 shows the contents A ₁ of the components in example 8 (initial stages Y ₁、A_{1- Formation into}、A_{1- Capacity-dividing} and A _{1- Circulation}, respectively).

TABLE 8

Comparative example 1

The difference between this embodiment and embodiment 1 is that the mass ratio X ₁ of the internal standard substance in the sample to be detected in this embodiment is 0%, i.e. no internal standard substance is added.

The remaining detection methods and procedures were consistent with example 1.

Table 9 shows the contents A ₁ (initial stages Y ₁、A_{1- Formation into}、A_{1- Capacity-dividing} and A _{1- Circulation}, respectively) of the components in comparative example 1.

TABLE 9

Combining tables 1-9, one can obtain:

As can be seen from the data results in tables 1-5, the detection method provided by the invention has higher accuracy on the content of each component of the electrolyte after treatment in different battery preparation stages and the detection result of the consumption of each component of the electrolyte in different battery preparation stages when the mass ratio of the internal standard in the sample to be detected is within the numerical range of 3-7%; and not in the range, but in the numerical range of 1-10%, the accuracy of the detection results of the content of each component of the electrolyte after treatment in different battery preparation stages and the consumption of each component of the electrolyte in different battery preparation stages is slightly poor.

As can be seen from the data results in tables 1 to 7, in the detection method provided by the invention, when the mass ratio of the internal standard substance to be detected is lower than 1%, the internal standard substance is excessively small, so that a relatively obvious error is easy to occur in the detection result; when the mass ratio of the internal standard substance to be detected is more than 10%, the performance of the electrolyte is affected due to the fact that the addition amount of the internal standard substance is too large, and the lithium salt is consumed in a large amount to generate gas, so that a relatively obvious error is easy to occur in the detection result.

From the data results in tables 1 and 8, the detection method provided by the invention is applicable to various electrolyte detection systems, and the detection results are rapid and accurate.

From the data in tables 1-9, it can be seen that if no internal standard is added before the injection, the variation of the components of the electrolyte at different stages of the battery preparation cannot be ensured to be compared in the same system.

In summary, according to the detection method provided by the invention, the internal standard Propylene Carbonate (PC) is added, so that the PC and each component in the electrolyte have very similar physical and chemical properties and are completely dissolved in the electrolyte; PC is stable in the battery preparation process, can not be decomposed, and can not chemically react with each component in the electrolyte; PC can be completely separated from chromatographic peaks of each component in the electrolyte. Therefore, the PC is used as an internal standard, and the content of each component of the electrolyte after treatment in different battery preparation stages is utilized by adding the PC into the electrolyte to be detected before the battery is injected; the method is simple to operate, simple in calculation process, free of linkage with a mass spectrometer, free of influence on analysis results by impurities in the sample, good in repeatability and high in accuracy; the method is suitable for detecting a large number of analysis samples, and has the advantages of high detection speed, simple process and high accuracy.

The applicant declares that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that are easily conceivable within the technical scope of the present invention disclosed by the present invention fall within the scope of the present invention and the disclosure.

Claims

1. A method for detecting an electrolyte, the method comprising the steps of:

s1, mixing electrolyte with an internal standard substance propylene carbonate to obtain a sample to be detected, wherein the mass ratio X1 of the internal standard substance propylene carbonate in the sample to be detected is 3-7%;

s2, carrying out gas chromatography test on the sample to be detected;

S4, calculating the contents of all components of the electrolyte after treatment in different battery preparation stages;

The content of each component of the electrolyte after the treatment in the different battery preparation stages in the step S4 is recorded as A ₁, and the calculation formula of A ₁ is A ₁=X₁/X₂*Y₂;

y ₂ is the mass ratio of each component of the electrolyte after the treatment in different battery preparation stages in the sample to be detected after the treatment in different battery preparation stages, and is obtained from the chromatographic peak area of each component of the electrolyte in the S3;

The negative electrode material in the battery containing the electrolyte includes artificial graphite;

The components and the content of the electrolyte in the step S1 are respectively 25% of EC; EMC 24%; 32% of DMC; VC is 3%; 0.5% of DTD; 13% of LiPF 6;

Or the combination and the content in the electrolyte in the step S1 are respectively 25 percent of MA; EMC 24%; 32% of DMC; VC is 3%; 0.5% of DTD; 13% of LiPF 6.

2. The method for detecting an electrolyte according to claim 1, further comprising:

3. The method for detecting electrolyte according to claim 2, wherein the consumption of each component of the electrolyte at the different battery preparation stages in S5 is denoted as a, and the calculation formula of a is a=y ₁-A₁;

Wherein A is the mass ratio of the reduced amount of each component of the electrolyte in different battery preparation stages in the sample to be detected;

y ₁ is the mass ratio of each component of the electrolyte in the sample to be detected, and is obtained from the chromatographic peak area of each component of the electrolyte in the S2.

4. The method according to claim 1, wherein the content of the internal standard substance is kept unchanged after the treatments of the different battery preparation stages, and wherein the content of the internal standard substance is the mass ratio X ₁ of the internal standard substance in the sample to be detected.

5. The method according to claim 1, wherein the different battery preparation stages include a formation stage, a capacity-dividing stage, and a charge-discharge cycle stage.

6. The method for detecting an electrolyte according to claim 1, characterized in that the method for detecting comprises the steps of: