Fluorescent probe for detecting negative electrode lithium precipitation in lithium ion battery and detection method

Abstract

The invention relates to a fluorescent probe for detecting negative electrode lithium precipitation in a lithium ion battery and a detection method, and belongs to the technical field of lithium ion batteries. The fluorescent probe comprises a complex formed by coordination combination of 8-hydroxyquinoline-5-sulfonic acid and metal ions, the complex emits fluorescence under excitation of ultraviolet light, and the standard electrode potential of a metal simple substance corresponding to the metal ions is higher than that of lithium. The fluorescent probe can rapidly, simply and sensitively realize qualitative and quantitative detection of negative electrode lithium precipitation, and compared with large-scale instruments and visual inspection, the fluorescent probe can effectively simplify operation, reduce cost and improve detection efficiency and accuracy, meanwhile, a battery does not need to be disassembled under the condition of full charge, and detection safety is improved.

Description

Technical Field

[0001] This application relates to the technical field of lithium-ion batteries, and particularly to a fluorescence probe and a detection method for detecting lithium deposition on the negative electrode in a lithium-ion battery. Background Art

[0002] At present, detecting lithium deposition on the negative electrode in a lithium-ion battery mainly uses large-scale instruments (such as scanning electron microscopes, optical microscopes, atomic force microscopes, etc.) or methods such as visual observation. Among them, using large-scale instruments to detect lithium deposition in a lithium-ion battery is effective, but the detection cost is expensive, and professional instrument operators and professional preparation of detection samples are required in advance, which undoubtedly increases the detection time and cost; at the same time, since lithium dendrites are prone to oxidation, the detection difficulty is further increased. Moreover, only when there is a large amount of deposited lithium on the negative electrode surface can it be detected by the instrument, and it is difficult for the equipment to accurately detect trace amounts of deposited lithium. In addition, lithium dendrites can only be observed with the naked eye on the fully charged negative electrode plate with a golden yellow surface, but the fully charged negative electrode plate is extremely prone to catching fire, bringing danger to the disassembly work of lithium-ion batteries. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, this application provides a fluorescence probe and a detection method for detecting lithium deposition on the negative electrode in a lithium-ion battery, which can achieve convenient, accurate, low-cost, and high-safety detection of lithium deposition on the negative electrode in a lithium-ion battery.

[0004] In the first aspect, an embodiment of this application provides a fluorescence probe for detecting lithium deposition on the negative electrode in a lithium-ion battery, including a complex formed by the coordination binding of 8-hydroxyquinoline-5-sulfonic acid and a metal ion. The complex emits fluorescence under ultraviolet light excitation, and the standard electrode potential of the metal corresponding to the metal ion is higher than that of lithium.

[0005] In the above technical solution, by using the coordination binding of 8-hydroxyquinoline-5-sulfonic acid and a metal ion, the metal ion can sensitize 8-hydroxyquinoline-5-sulfonic acid to emit fluorescence under ultraviolet light excitation. Moreover, by controlling the standard electrode potential of the metal corresponding to the metal ion to be higher than that of lithium, the metal ion can undergo a displacement reaction with metallic lithium. After the displacement reaction, the sensitization effect of 8-hydroxyquinoline-5-sulfonic acid weakens, and the fluorescence intensity of the fluorescence probe decreases. Thus, the qualitative and quantitative detection of lithium deposition on the negative electrode in a lithium-ion battery can be quickly, simply, and sensitively realized by comparing the fluorescence intensities before and after the displacement reaction. Compared with using large-scale instruments and visual observation, using this fluorescence probe can effectively simplify the operation, reduce the cost, improve the detection efficiency and accuracy, and at the same time enable the battery to be disassembled without being fully charged, improving the detection safety.

[0006] In some embodiments, the metal ion includes Cd 2+ , Al 3+ or Zn2+ At least one of these. These metal ions can sensitize 8-hydroxyquinoline-5-sulfonic acid, coordinate with it to form a stable complex, and emit intense fluorescence under ultraviolet light irradiation. And these metal ions can also undergo an efficient displacement reaction with metallic lithium, which is beneficial to improving the detection rate and accuracy of the fluorescence probe.

[0007] In a second aspect, an embodiment of the present application provides a method for detecting lithium plating on the negative electrode in a lithium-ion battery, including the following steps:

[0008] Perform a coordination reaction between 8-hydroxyquinoline-5-sulfonic acid and a metal salt in an organic solution to obtain a fluorescence probe solution; wherein, the metal ions in 8-hydroxyquinoline-5-sulfonic acid and the metal salt coordinate and combine to form a complex, and the complex emits fluorescence under ultraviolet light excitation, and the standard electrode potential of the metal corresponding to the metal ion is higher than that of lithium;

[0009] Place the negative electrode plate to be detected in the fluorescence probe solution to allow the metal ions to undergo a displacement reaction with the metallic lithium deposited on the surface of the negative electrode plate;

[0010] Qualitatively and / or quantitatively analyze the lithium plating on the negative electrode by comparing the fluorescence intensities of the fluorescence probe solution before and after the displacement reaction.

[0011] In the above technical solution, a fluorescence probe is formed by the coordination reaction of 8-hydroxyquinoline-5-sulfonic acid and metal ions, and it is controlled that the metal ions can undergo a displacement reaction with metallic lithium. The negative electrode plate to be detected is placed in the fluorescence probe solution for the displacement reaction. After the displacement reaction, the sensitization effect of 8-hydroxyquinoline-5-sulfonic acid weakens, and the fluorescence intensity of the fluorescence probe decreases. Therefore, by comparing the fluorescence intensities before and after the displacement reaction, rapid quantitative and qualitative detection of lithium plating can be achieved. This detection method is simple to operate, low in cost, and fast and sensitive, avoiding the problems of high cost, long time, complex operation caused by using large instruments, high requirements for the amount of lithium plating, and solving the problem that the electrode plate cannot detect the lithium plating situation in time due to oxidation. At the same time, the lithium-ion battery does not need to be disassembled when fully charged, which can ensure the safety of the disassembling personnel and improve the detection safety.

[0012] In some embodiments, the metal salt is at least one of nitrates, sulfates, carbonates, acetates, halides or halates. These metal salts can all dissolve well in the organic solution.

[0013] In some embodiments, the metal ions include Cd 2+ , Al 3+ or Zn 2+At least one of these metal ions can sensitize 8-hydroxyquinoline-5-sulfonic acid in an organic solution, coordinate to form a stable complex, and produce high-intensity fluorescence under ultraviolet light irradiation. Moreover, these metal ions can also undergo an efficient displacement reaction with metallic lithium, which is beneficial to improving the detection rate and accuracy of the fluorescence probe.

[0014] In some embodiments, the material of the negative electrode plate is a carbon material, a silicon-based material, or a nitride. Lithium deposition may occur on the surface of the negative electrode plates made of these materials.

[0015] In some embodiments, the conditions for the coordination reaction include: stirring and reacting at 20 °C to 30 °C for 5 min to 30 min, and the molar ratio of 8-hydroxyquinoline-5-sulfonic acid to the metal ion is (1 to 1.5):(1 to 1.5). By controlling the conditions of the coordination reaction, 8-hydroxyquinoline-5-sulfonic acid and the metal ion can fully react to form a stable complex.

[0016] In some embodiments, the organic solution includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl acetate, or methyl propionate. These organic solvents can dissolve 8-hydroxyquinoline-5-sulfonic acid and metal salts well, and have good chemical stability, which can avoid chemical reactions with 8-hydroxyquinoline-5-sulfonic acid, metal salts, and the negative electrode plate material.

[0017] In some embodiments, the time for the displacement reaction is 0.5 h to 3 h. By controlling the time of the displacement reaction, the deposited lithium on the surface of the negative electrode plate can be fully reacted.

[0018] In some embodiments, it further includes: disassembling the lithium-ion battery to be detected, taking out the negative electrode plate and cleaning it to obtain the negative electrode plate to be detected. By disassembling and cleaning, a negative electrode plate with deposited lithium on the surface and high cleanliness can be obtained.

[0019] In some embodiments, after forming the fluorescence probe solution, it further includes: measuring the initial fluorescence intensity I0 of the fluorescence probe solution; adding lithium salt solutions with different concentrations to the fluorescence probe solution respectively, and measuring the fluorescence intensity I m after the displacement reaction respectively; using the lithium ion concentration in the lithium salt solution as the abscissa, and using the initial fluorescence intensity I0 and the fluorescence intensity I m as the abscissa to plot a standard curve. By making a standard curve with lithium salt solutions with different concentrations, it is convenient to quantitatively measure the deposited lithium according to the fluorescence intensity after the displacement reaction. Description of the Drawings

[0020] To more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a schematic diagram of the principle of using a fluorescence probe to detect lithium deposition on the negative electrode in a lithium-ion battery.

[0022] Figure 2 It is a schematic flowchart of the method for detecting lithium deposition on the negative electrode in the lithium-ion battery provided by the embodiment of the present application. Detailed implementation manners

[0023] Hereinafter, embodiments of the fluorescence probe and the preparation method of the fluorescence probe of the present application will be specifically disclosed with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0024] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise stated, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0025] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0026] Currently, the main methods for detecting lithium plating on the negative electrode in a lithium-ion battery are using large instruments (such as scanning electron microscopes, optical microscopes, atomic force microscopes, etc.) or visual observation. Among them, using large instruments to detect lithium precipitation on the negative electrode in a lithium-ion battery is effective, but the detection cost is expensive, and professional instrument operators and professional pre-preparation of detection samples are required, which undoubtedly increases the detection time and cost. At the same time, since lithium dendrites are prone to oxidation, the detection difficulty is further increased. Moreover, only when there is a large amount of precipitated lithium on the negative electrode surface can it be detected by the instrument, and it is difficult for the equipment to accurately detect trace amounts of precipitated lithium. In addition, lithium dendrites can only be observed with the naked eye on the fully charged negative electrode plate with a golden yellow surface, but the fully charged negative electrode plate is extremely prone to catching fire, bringing danger to the disassembly work of lithium-ion batteries.

[0027] Based on this, an embodiment of the present application provides a fluorescent probe for detecting lithium plating on the negative electrode in a lithium-ion battery, including a complex formed by the coordination of 8-hydroxyquinoline-5-sulfonic acid and a metal ion. The complex emits fluorescence under ultraviolet light excitation, and the standard electrode potential of the metal corresponding to the metal ion is higher than that of lithium.

[0028] Figure 1 For the schematic diagram of the principle of using the fluorescent probe to detect lithium plating on the negative electrode in a lithium-ion battery, please refer to Figure 1 , in the present application, 8-hydroxyquinoline-5-sulfonic acid (HQS) and a metal ion (M n+ ) are coordinated to form a complex. M n+ can sensitize HQS to emit fluorescence under ultraviolet light excitation. By controlling the standard electrode potential of the metal M corresponding to M n+ to be higher than that of Li, M n+ can undergo a displacement reaction with metallic Li. After the displacement reaction, the sensitization effect of 8-hydroxyquinoline-5-sulfonic acid weakens, and the fluorescence intensity of the fluorescent probe decreases. Thus, by comparing the fluorescence intensities before and after the displacement reaction, qualitative and quantitative detection of lithium plating on the negative electrode can be achieved quickly, simply, and sensitively. Compared with using large instruments and visual observation, using this fluorescent probe can effectively simplify the operation, reduce the cost, improve the detection efficiency and accuracy, and at the same time enable the battery to be disassembled without being fully charged, improving the detection safety.

[0029] The following specifically describes the fluorescent probe in the embodiment of the present application and the method for detecting lithium plating on the negative electrode in a lithium-ion battery with reference to the accompanying drawings.

[0030] Figure 2The following is a schematic flow chart of a method for detecting lithium plating on the negative electrode in a lithium-ion battery provided by an embodiment of the present application. Please refer to Figure 2 , the method for detecting lithium plating on the negative electrode in a lithium-ion battery includes the following steps:

[0031] S10: Perform a coordination reaction between 8-hydroxyquinoline-5-sulfonic acid and a metal salt in an organic solution to obtain a fluorescent probe solution; wherein, the metal ions in 8-hydroxyquinoline-5-sulfonic acid and the metal salt coordinate and combine to form a complex, and the complex emits fluorescence under ultraviolet light excitation, and the standard electrode potential of the metal corresponding to the metal ions is higher than that of lithium.

[0032] Among them, the molar ratio of 8-hydroxyquinoline-5-sulfonic acid to metal ions is (1-1.5):(1-1.5), such as 1:1, 1.2:1, 1:1.2, 1.5:1, 1:1.5, etc.

[0033] Furthermore, the molar concentration of 8-hydroxyquinoline-5-sulfonic acid and the metal salt in the organic solution are each independently 0.1 mol / L to 1 mol / L. For example, the molar concentration of 8-hydroxyquinoline-5-sulfonic acid is 0.4 mol / L, and the molar concentration of metal ions is 0.4 mol / L.

[0034] In some embodiments, the metal salt is at least one of nitrates, sulfates, carbonates, acetates, halides or halates.

[0035] In some embodiments, the metal ions include Cd 2+ , Al 3+ or Zn 2+ at least one of them. By way of example, the metal salt is cadmium nitrate, aluminum nitrate or zinc nitrate.

[0036] Among them, the complex obtained by the coordination reaction of 8-hydroxyquinoline-5-sulfonic acid and Cd 2+ (denoted as HQS-Cd) emits obvious green fluorescence under ultraviolet light excitation at 365 nm.

[0037] In some embodiments, the organic solution includes at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), methyl acetate (MA) or methyl propionate (MP).

[0038] In some embodiments, the conditions of the coordination reaction include: stirring and reacting at 20 °C to 30 °C for 5 min to 30 min. By way of example, stirring and reacting at 25 °C for 10 min.

[0039] S20: Place the negative electrode plate to be detected in the fluorescent probe solution to cause a displacement reaction between the metal ions and the metallic lithium deposited on the surface of the negative electrode plate.

[0040] The negative electrode sheet to be detected can be obtained by disassembling the lithium-ion battery to be detected, taking out the negative electrode sheet and cleaning it. The cleaning step may include: soaking the negative electrode sheet in an organic solvent 2 to 3 times, 30 minutes to 60 minutes each time.

[0041] In some embodiments, the material of the negative electrode sheet can be a carbon material, a silicon-based material or a nitride. Among them, the carbon material can be graphite, mesophase carbon microspheres, hard carbon, etc., the silicon-based material can be silicon, silicon oxide, silicon-carbon composite material, silicon-based alloy, etc., and the nitride can be MXene, etc.

[0042] In some embodiments, the time of the displacement reaction is 0.5 h to 3 h, such as 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, etc.

[0043] S30: Qualitatively and / or quantitatively analyze the lithium deposition by comparing the fluorescence intensities of the fluorescent probe solution before and after the displacement reaction.

[0044] When performing qualitative analysis, since the fluorescence intensity changes before and after the displacement reaction, the color depth under the corresponding ultraviolet light changes. By irradiating with an ultraviolet lamp and observing the fluorescence intensity with the naked eye, it can be determined whether lithium is deposited on the negative electrode in the lithium-ion battery.

[0045] When performing quantitative analysis, after step S10, it may further include: measuring the initial fluorescence intensity I0 of the fluorescent probe solution; adding lithium salt solutions with different concentrations to the fluorescent probe solution, and respectively measuring the fluorescence intensity I m ; taking the lithium ion concentration in the lithium salt solution as the abscissa, and taking the initial fluorescence intensity I0 and the fluorescence intensity I m as the abscissa to draw a standard curve. By making a standard curve with lithium salt solutions of different concentrations, the deposited lithium can be quantitatively determined according to the fluorescence intensity after the displacement reaction.

[0046] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified in the manufacturer are all conventional products that can be obtained by commercial purchase.

[0047] Example 1

[0048] This embodiment provides a method for detecting lithium deposition on the negative electrode in a lithium-ion battery, including the following steps:

[0049] (1) Subject the lithium cobalt oxide / graphite button cell to 1C overcharge and over-discharge cycling 3 times. When a plateau below 0V appears in the discharge curve, it is speculated that lithium is deposited on the negative electrode. Disassemble the fully discharged button cell to obtain the graphite electrode sheet for detecting lithium deposition on the negative electrode. Immerse the graphite negative electrode sheet in DMC solution 3 times, each time for 40 minutes.

[0050] (2) Dissolve dried 8-hydroxyquinoline-5-sulfonic acid (5 g) and cadmium nitrate (5 g) in 50 mL of DMC solution, and stir and react at 25°C for 10 minutes to obtain a fluorescent probe solution.

[0051] (3) Take out the immersed graphite negative electrode sheet from DMC, then put it into the fluorescent probe solution, and carry out a displacement reaction for 2 hours. After the displacement reaction ends, that is, after there is no change on the surface of the graphite negative electrode sheet, take it out.

[0052] (4) Take a part of the solutions obtained in steps (2) and (3) respectively, and observe the fluorescence intensity of the solutions under a 365 nm ultraviolet lamp. It is found that the fluorescence intensity of the solution obtained in step (3) becomes weaker, so it is proved that lithium is deposited on the graphite negative electrode sheet.

[0053] Example 2

[0054] This example provides a method for detecting lithium deposition on the negative electrode in a lithium-ion battery, including the following steps:

[0055] (1) Subject the lithium cobalt oxide / graphite button cell to 1C overcharge and over-discharge cycling 3 times. When a plateau below 0V appears in the discharge curve, it is speculated that lithium is deposited on the negative electrode. Disassemble the fully discharged button cell to obtain the graphite electrode sheet for detecting lithium deposition on the negative electrode. Immerse the graphite negative electrode sheet in DMC solution 3 times, each time for 40 minutes.

[0056] (2) Dissolve dried 8-hydroxyquinoline-5-sulfonic acid (10 g) and cadmium nitrate (10 g) in 100 mL of DMC solution, and stir and react at 25°C for 10 minutes to obtain a fluorescent probe solution. Measure the initial fluorescence intensity I0 of this solution, and calibrate the fluorescence intensity of the fluorescent probe solution with lithium nitrate solutions of different concentrations I m (1 mM, 3 mM, 5 mM, 7 mM, 9 mM, 10 mM). With the lithium ion concentration as the abscissa, and with the initial fluorescence intensity I0 and the fluorescence intensity I m as the abscissa, plot a standard curve.

[0057] (3) Take out the immersed graphite negative electrode sheet from DMC, then put it into the fluorescent probe solution, and carry out a displacement reaction for 2 hours. After the displacement reaction ends, that is, after there is no change on the surface of the graphite negative electrode sheet, take it out.

[0058] (4) Take a part of the solutions obtained in steps (2) and (3) respectively. Under the ultraviolet light of 365 nm, it is observed that the fluorescence intensity of the fluorescent probe solution becomes weaker. Then add the probe solution into a cuvette and put it into a fluorescence spectrophotometer to measure the fluorescence intensity. Calculate the lithium content precipitated through linear analysis.

[0059] The embodiments described above are some, but not all, of the embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application.

Claims

1. A fluorescence probe for detecting lithium deposition on the negative electrode in a lithium-ion battery, characterized in that, It includes a complex formed by the coordination binding of 8-hydroxyquinoline-5-sulfonic acid and a metal ion, and the complex emits fluorescence under ultraviolet light excitation, and the standard electrode potential of the metal corresponding to the metal ion is higher than that of lithium.

2. The fluorescent probe according to claim 1, wherein The metal ions include Cd 2+ , Al 3+ or Zn 2+ and at least one of them.

3. A method for detecting lithium deposition on the negative electrode in a lithium-ion battery, characterized in that, It includes the following steps: Carry out a coordination reaction of 8-hydroxyquinoline-5-sulfonic acid and a metal salt in an organic solution to obtain a fluorescent probe solution; wherein, the 8-hydroxyquinoline-5-sulfonic acid and the metal ion in the metal salt coordinate and combine to form a complex, the complex emits fluorescence under ultraviolet light excitation, and the standard electrode potential of the metal corresponding to the metal ion is higher than that of lithium; Place the negative electrode sheet to be detected in the fluorescent probe solution to enable the metal ion to undergo a displacement reaction with the metallic lithium precipitated on the surface of the negative electrode sheet; Qualitatively and / or quantitatively analyze the lithium precipitation by comparing the fluorescence intensities of the fluorescent probe solution before and after the displacement reaction.

4. The detection method according to claim 3, wherein The metal salt is at least one of nitrate, sulfate, carbonate, acetate, halide or halate.

5. The detection method according to claim 3, characterized in that The metal ions include Cd 2+ , Al 3+ or Zn 2+ and at least one of them.

6. The detection method according to claim 3, wherein The material of the negative electrode sheet is a carbon material, a silicon-based material or a nitride.

7. The detection method according to claim 3, characterized in that, The conditions of the coordination reaction include: stirring and reacting at 20 °C to 30 °C for 5 min to 30 min, and the molar ratio of the 8-hydroxyquinoline-5-sulfonic acid to the metal ion is (1 to 1.5):(1 to 1.5); Optionally, the organic solution includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl acetate or methyl propionate.

8. The detection method according to claim 3, wherein The time of the displacement reaction is 0.5 h to 3 h.

9. The detection method according to claim 3, wherein It also includes: Disassemble the lithium-ion battery to be detected, take out the negative electrode sheet and wash it with an organic solvent to obtain the negative electrode sheet to be detected.

10. The detection method according to claim 3, wherein After forming the fluorescent probe solution, it also includes: Measure the initial fluorescence intensity I0 of the fluorescent probe solution; Add lithium salt solutions with different concentrations to the fluorescent probe solution respectively, and measure the fluorescence intensity I after the displacement reaction respectively m ; Using the lithium ion concentration in the lithium salt solution as the abscissa and the initial fluorescence intensity I0 and the fluorescence intensity I m as the abscissa, a standard curve is plotted.

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