Method for detecting lithium metal negative electrode composition

Abstract

The application relates to the technical field of fluorescence detection, in particular to a method for detecting the composition of a lithium metal negative electrode, wherein the lithium metal negative electrode is a lithium metal negative electrode after charge-discharge cycle in a lithium battery, and the method comprises the following steps: adopting an isoflavone compound as a fluorescent probe to detect the composition on the surface of the lithium metal negative electrode. Adopting the isoflavone compound as the probe can realize visual observation and quantitative detection of deposited lithium, lithium dendrites, by-products, dead lithium and a solid electrolyte interface film on the surface of the lithium metal negative electrode.

Description

Technical Field

[0001] This application relates to the field of fluorescence detection technology, and in particular to a method for detecting the composition of lithium metal anodes. Background Technology

[0002] Lithium metal, with its advantages of high specific capacity and low electrode potential, is considered a key anode material for further breakthroughs in battery specific energy. However, the large-scale commercialization of lithium metal anodes is still hampered by numerous technical challenges, such as: 1) the high reactivity of lithium metal, which repeatedly interacts with electrolyte components to form a discontinuous solid electrolyte interphase (SEI) layer, consuming and eventually depleting a limited amount of electrolyte; 2) uneven lithium deposition gradually develops into vigorous lithium dendrites that break off at the root, forming isolated "dead lithium," reducing lithium utilization; 3) unstable SEI and the shedding of "dead lithium" cause battery safety hazards and significant volume changes.

[0003] To address the accumulation of lithium dendrites and by-reaction products on the surface of lithium metal anodes, several characterization and detection techniques exist, such as optical microscopy, digital imaging (DIC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and cryo-electron microscopy (Cryo-SEM). These techniques can detect the morphology, interface properties, chemical composition, and microstructure of the anode surface. However, for early lithium deposition, the resolution of methods like optical microscopy and DIC is insufficient for observation, while methods like electron microscopy are limited by expensive experimental equipment and complex sample preparation procedures. Other methods, such as X-ray diffraction (XRD), Raman spectroscopy, infrared absorption spectroscopy, and in-situ nuclear magnetic resonance (in-situ NMR), can obtain partial physicochemical data of the electrode surface through specific signals, but direct observation is not possible.

[0004] Researchers have proposed using solid-state fluorescent molecules (such as catechol tetraphenylethylene, o-phenol benzoxazole, and hydroxychalcone) to analyze the surface composition of lithium metal anodes after cycling. While this method helps in analyzing battery failure mechanisms, selecting optimal cycling conditions, and predicting uneven lithium deposition, the synthesis steps of these fluorescent probe molecules are cumbersome and the preparation cost is high. Furthermore, the high concentration of reagents used (above 3.0 mg / mL) results in high consumption per use, thus limiting their potential for commercial application. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for detecting the components of lithium metal anodes. Using isoflavone compounds as probes, it is possible to achieve visual observation and quantitative detection of deposited lithium, lithium dendrites, by-products, dead lithium, and solid electrolyte interface film on the surface of lithium metal anodes.

[0006] This application provides a method for detecting the composition of a lithium metal anode, wherein the lithium metal anode is a lithium metal anode in a lithium battery after charge-discharge cycles, and the method includes the following steps: using isoflavone compounds as fluorescent probes to detect the composition on the surface of the lithium metal anode.

[0007] In some embodiments, the isoflavone compound has the structural formula shown in formula (I):

[0008]

[0009] Among them, R1~R 10 Each is independently selected from one or more of hydrogen atom, hydroxyl, alkyl, alkoxy, amino, aryl and halogen, and at least one of them is hydroxyl.

[0010] In some implementations, R1 to R 10 Each is independently selected from one or more of hydrogen atoms, hydroxyl groups, and alkoxy groups, with at least one being a hydroxyl group.

[0011] In some embodiments, the isoflavone compounds include one or more of chickpea stigmata extract A, gentiopicrin, soy isoflavone, genistein, and isochorin.

[0012] In some embodiments, the detection items include one or more of the following: deposited lithium, by-products, lithium dendrites, dead lithium, and solid electrolyte interface film on the surface of the lithium metal anode.

[0013] The byproducts include lithium salts and / or polymers, wherein the lithium salts include one or more of lithium fluoride, lithium chloride, lithium acetate, lithium carbonate, lithium hydroxide, lithium oxide, and lithium alkoxide, and the polymers include one or more of polyvinyl carbonate, polycarbonate, and polypropylene.

[0014] In some embodiments, the lithium battery is a lithium-oxygen battery, a lithium-sulfur battery, a lithium-oxide battery, a lithium-air battery, or a lithium-lithium battery.

[0015] In some implementations, the detection step includes:

[0016] Prepare probe solutions containing isoflavone compounds;

[0017] The probe solution is brought into contact with the surface of the lithium metal anode, and a fluorescence test is performed on the surface of the lithium metal anode to detect the composition of the surface of the lithium metal anode.

[0018] In some embodiments, the step of performing the fluorescence test includes:

[0019] The surface of the lithium metal anode is irradiated with excitation light, and the composition of the lithium metal anode surface is qualitatively analyzed based on the fluorescence signal distribution on the surface of the lithium metal anode.

[0020] And / or, by irradiating the surface of the lithium metal anode with excitation light, the composition of the lithium metal anode surface is quantitatively analyzed based on the fluorescence intensity differences in different distribution areas of the lithium metal anode surface.

[0021] In some embodiments, the method for detecting the composition of the lithium metal anode has at least one of the following features:

[0022] 1) The solvent used in the probe solution includes one or more of the following: ether solvents, furan solvents, alkane solvents, ketone solvents, and chloroform;

[0023] 2) The excitation light is ultraviolet light with a wavelength of 300nm to 365nm.

[0024] In some embodiments, the concentration of the isoflavone compound in the probe solution is 0.5 mg / mL to 5 mg / mL.

[0025] This application uses isoflavones as probes for lithium metal anode detection. Isoflavones are natural products widely distributed in plants, characterized by their wide availability and the abundance of derivatives obtained through various chemical modifications. Therefore, using isoflavones as probes greatly expands the sources of fluorescent molecules.

[0026] The isoflavone compounds provided in this application, as fluorescent probes, exhibit an "open" response mode. This means that the isoflavone compounds react with components on the lithium metal anode surface, such as active lithium, uneven lithium deposition, and lithium dendrites. After the reaction, the isoflavone compounds exhibit new fluorescent signals and a change in fluorescence color (new signal peaks appear in the fluorescence spectrum). However, byproducts, the SEI film, and dead lithium surrounded by byproducts on the lithium metal anode surface do not react with the isoflavone compounds, resulting in weakened or even completely absent fluorescence signals. This allows for visual detection of the fluorescence changes, enabling qualitative analysis of the components on the lithium metal anode surface. In other words, this application uses isoflavone compounds as fluorescent probes, achieving a complete transformation of fluorescence signal from non-existent to present before and after the reaction, resulting in a more intuitive and precise difference in fluorescence change. Therefore, the isoflavone compounds provided in this application, as probes, can accurately detect the surface conditions of lithium metal anodes.

[0027] Furthermore, by combining fluorescence observation and fluorescence intensity detection, this application can semi-quantitatively and visually identify active lithium and lithium dendrites on the surface of lithium metal anodes, as well as their abundance, and identify uneven lithium deposition, by-products and their accumulation. It can also further link battery performance degradation and failure with the amount of lithium dendrites, uneven lithium deposition, and by-product accumulation, which is expected to provide a feasible method for analyzing the causes of battery failure and early prevention and warning of battery performance failure. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 The Li|Li button cells in Examples 1-4 were subjected to 25 charge-discharge cycles (charge-discharge current of 2.5 mAh / cm²). 2 After that, the fluorescence image of the lithium negative electrode sheet after its interaction with the probe solution;

[0030] Figures 2-5 The fluorescence spectra of isoflavone compounds in Examples 1-4 before and after their interaction with the lithium metal anode surface are shown.

[0031] Figure 6 The fluorescence stability spectra of isoflavone compounds in Examples 1-4 after their interaction with the lithium metal anode surface are shown. Detailed Implementation

[0032] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0035] The term "alkyl" refers to a saturated hydrocarbon containing a primary (normal) carbon atom, or a secondary carbon atom, or a tertiary carbon atom, or a quaternary carbon atom, or a combination thereof. Phrases containing this term, such as "C1-C9 alkyl," refer to alkyl groups containing 1 to 9 carbon atoms, and each occurrence can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, or C9 alkyl. Suitable examples include, but are not limited to: methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(C H3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (- CH2CH2CH(CH3)2), 2-methyl-1-butyl(-CH2CH(CH3)CH2CH3), 1-hexyl(-CH2CH2CH2CH2CH2CH3), 2-hexyl(-CH(CH3)CH2CH2CH2CH3), 3-hexyl(-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl(-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl(-CH(CH3)CH( CH3)CH2CH3), 4-methyl-2-pentyl (-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3 and octyl (-(CH2)7CH3).

[0036] The term "aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by losing one or more hydrogen atoms. Aryl groups can be monocyclic aryl, fused-ring aryl, two or more monocyclic aryl groups conjugated by carbon-carbon bonds, monocyclic aryl and fused-ring aryl groups conjugated by carbon-carbon bonds, or two or more fused-ring aryl groups conjugated by carbon-carbon bonds.

[0037] "Amino" refers to a derivative of ammonia, possessing the structural characteristic of the formula -N(X)2, where each "X" is independently H, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted heterocyclic group, etc. Non-limiting types of amino groups include -NH2, -N(alkyl)2, -NH(alkyl), -N(cycloalkyl)2, -NH(cycloalkyl), -N(heterocyclic)2, -NH(heterocyclic), -N(aryl)2, -NH(aryl), -N(alkyl)(aryl), -N(alkyl)(heterocyclic), -N(cycloalkyl)(heterocyclic), -N(aryl)(heteroaryl), -N(alkyl)(heteroaryl), etc.

[0038] "Halogen" or "halogen group" refers to F, Cl, Br or I.

[0039] The term "hydroxyl group" has the chemical formula -OH and mainly includes alcohol hydroxyl groups and phenolic hydroxyl groups.

[0040] The term "alkoxy" is usually represented by RO- and consists of an alkyl group and an oxygen atom. Specific examples, without limitation, include methoxy (CH3O-), ethoxy (C2H5O-), propoxy (C3H7O-), etc.

[0041] Currently used solid-state fluorescent molecules, such as catechol tetraphenylethylene, for detecting and analyzing the composition of lithium metal anode surfaces after cycling, can achieve visual detection of electrode surface components. However, the synthesis of these fluorescent probe molecules is cumbersome and costly. Furthermore, the detection process requires high-concentration probe solutions, typically above 3.0 mg / mL, resulting in significant losses. Therefore, this application provides a method for detecting the composition of lithium metal anodes, where the lithium metal anode is a lithium metal anode that has undergone charge-discharge cycles in a lithium battery. The method includes the following steps: using isoflavone compounds as fluorescent probes to detect the composition of the lithium metal anode surface.

[0042] The isoflavone compounds provided in this application, as fluorescent probes, exhibit an "open" response mode. This means that the isoflavone compounds react with components on the lithium metal anode surface, such as active lithium, uneven lithium deposition, and lithium dendrites. After the reaction, the isoflavone compounds exhibit new fluorescent signals and a change in fluorescence color (new signal peaks appear in the fluorescence spectrum). However, byproducts, the SEI film, and dead lithium surrounded by byproducts on the lithium metal anode surface do not react with the isoflavone compounds, resulting in weakened or even completely absent fluorescence signals. This allows for visual detection of the fluorescence changes, enabling qualitative analysis of the components on the lithium metal anode surface. In other words, this application uses isoflavone compounds as fluorescent probes, achieving a complete transformation of fluorescence signal from non-existent to present before and after the reaction, resulting in a more intuitive and precise difference in fluorescence change. Therefore, the isoflavone compounds provided in this application, as probes, can accurately detect the surface conditions of lithium metal anodes.

[0043] Furthermore, by combining fluorescence observation and fluorescence intensity detection, this application can semi-quantitatively and visually identify active lithium and lithium dendrites on the surface of lithium metal anodes, as well as their abundance, and identify uneven lithium deposition, by-products and their accumulation. It can also further link battery performance degradation and failure with the amount of lithium dendrites, uneven lithium deposition, and by-product accumulation, which is expected to provide a feasible method for analyzing the causes of battery failure and early prevention and warning of battery performance failure.

[0044] The "open" response mode can be understood as follows: before the isoflavone compound reacts with the lithium metal surface, or if it does not react at all, the fluorescent probe will not produce a fluorescent signal or will produce a very weak fluorescent signal; after the reaction, the fluorescent probe will produce a new fluorescent signal, achieving a transition from no fluorescence to presence. The "closed" response mode refers to the fluorescent probe producing a fluorescent signal before the isoflavone compound reacts with the lithium metal surface, or if it does not react at all; after the reaction, the fluorescent signal weakens or disappears, achieving a transition from presence to absence. The "displacement" response mode refers to the change in the fluorescent probe's fluorescence signal before and after the isoflavone compound reacts with the lithium metal surface. The "open" response mode offers a more intuitive and precise effect compared to the "closed" and "displacement" response modes.

[0045] In some embodiments, the isoflavone compound has the structural formula shown in formula (I):

[0046]

[0047] Among them, R1~R 10 Each is independently selected from one or more of hydrogen atom, hydroxyl, alkyl, alkoxy, amino, aryl and halogen, and at least one of them is hydroxyl.

[0048] In some implementations, R1 to R10 Each is independently selected from one or more of hydrogen atoms, hydroxyl groups, and alkoxy groups, with at least one being a hydroxyl group.

[0049] Furthermore, R2 is selected from hydroxyl groups, R1, R3, R5, R6, R7, R9, and R 10 All are selected from hydrogen atoms, R4 is selected from hydrogen atoms or hydroxyl groups, and R8 is selected from hydroxyl groups or methoxy groups (-OMe).

[0050] In some embodiments, the isoflavone compounds include one or more of chickpea seed extract A, gentiopicrin, soy isoflavone, genistein, succinoside, and isochorin. The structural formulas of chickpea seed extract A (CAS No. 491-80-5), gentiopicrin (CAS No. 485-72-3), soy isoflavone (CAS No. 486-66-8), genistein (CAS No. 446-72-0), succinoside (CAS No. 152-95-4), and isochorin (CAS No. 4569-98-6) are shown in Formulas 1 to 6, respectively.

[0051]

[0052] It is understood that the byproducts are the products of side reactions occurring on the surface of the lithium metal anode. When the battery is charged and discharged with different numbers of cycles and different charge and discharge currents, the method provided in this application can visualize and semi-quantitatively analyze the battery condition under different conditions.

[0053] In some embodiments, the detection items include one or more of the following on the lithium metal anode surface: deposited lithium, byproducts, lithium dendrites, dead lithium, and the solid electrolyte interphase (SEI) film. Specifically, isoflavone groups (such as hydroxyl groups) can react with active lithium, unevenly deposited lithium, and lithium dendrites, causing drastic changes in the molecular structure and electronic effects of the isoflavones, resulting in new fluorescence signals after the reaction. Byproducts on the lithium metal anode surface, dead lithium surrounded by byproducts, and the SEI film do not react, and the fluorescence signals weaken or even disappear. Therefore, based on the distribution of fluorescence signals, different components on the lithium metal anode surface can be distinguished (e.g., active lithium, unevenly deposited lithium, and lithium dendrites exhibit orange fluorescence, while byproducts exhibit dark red fluorescence), enabling visual analysis of the lithium metal anode surface. Differences in fluorescence intensity can visually reflect the abundance of unevenly deposited lithium or lithium dendrites in different regions, the distribution of lithium dendrites, dead lithium, the degree of byproduct accumulation, the growth degree and distribution area of ​​the SEI film, etc., and quantitative analysis of different components can be achieved using a fluorescence spectrometer. Specifically, the byproducts include lithium salts and / or polymers, wherein the lithium salts include one or more of lithium fluoride, lithium chloride, lithium acetate, lithium carbonate, lithium hydroxide, lithium oxide, and lithium alkoxide, and the polymers include one or more of polyvinyl carbonate, polycarbonate, and polypropylene.

[0054] In some implementations, the lithium battery is a lithium-oxygen battery, a lithium-sulfur battery, a lithium-oxide battery, a lithium-air battery, or a lithium-lithium battery.

[0055] In some implementations, the detection step includes:

[0056] Prepare probe solutions containing isoflavone compounds;

[0057] The probe solution is brought into contact with the surface of the lithium metal anode, and a fluorescence test is performed on the surface of the lithium metal anode to detect the composition of the surface of the lithium metal anode.

[0058] In this application, the choice of solvent for the probe solution is not limited; any volatile solvent may be used. In some embodiments, the solvent used for the probe solution includes one or more of ether solvents, furan solvents, alkane solvents, ketone solvents, and chloroform. Specifically, the ether solvent may be diethyl ether; the furan solvent may be tetrahydrofuran; the alkane solvent may be n-hexane and / or cyclohexane; and the ketone solvent may be acetone.

[0059] In some embodiments, the concentration of isoflavone compounds in the probe solution is 0.5 mg / mL to 5 mg / mL, for example, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 3 mg / mL, and 4 mg / mL. That is, the concentration of isoflavone compounds in this application can be as low as 0.5 mg / mL, thereby minimizing the interference of probe molecules on the inherent morphology of the lithium metal anode interface and obtaining better detection results; at the same time, it can reduce detection costs.

[0060] In some implementations, bringing the probe solution into contact with the surface of the lithium metal anode to be tested specifically means spraying the probe solution onto the surface of the lithium metal anode.

[0061] In this application, the excitation light is specifically a light wave capable of exciting isoflavone compounds to emit fluorescence. In some embodiments, the excitation light is ultraviolet light with a wavelength of 300 nm to 365 nm. Preferably, the excitation light is ultraviolet light with a wavelength of 365 nm.

[0062] In some implementations, the steps of performing fluorescence testing include:

[0063] The surface of the lithium metal anode is irradiated with excitation light, and the composition of the lithium metal anode surface is qualitatively analyzed based on the fluorescence signal distribution on the surface of the lithium metal anode.

[0064] And / or, by irradiating the surface of the lithium metal anode with excitation light, the composition of the lithium metal anode surface is quantitatively analyzed based on the fluorescence intensity differences in different distribution areas of the lithium metal anode surface.

[0065] Specifically, by observing the fluorescence signal distribution on the surface of the lithium metal anode, different components on the surface can be distinguished, enabling visual analysis of the lithium metal anode surface. Using a fluorescence spectrometer to measure the fluorescence intensity and wavelength on the lithium metal anode surface allows for semi-quantitative analysis of the aforementioned detection items.

[0066] The present application will be further described in detail below with reference to specific embodiments.

[0067] Example 1

[0068] The lithium metal battery used in this embodiment is a Li||Li symmetrical coin cell, with lithium sheets as both the positive and negative electrodes. The electrolyte is 1 mol / L LiPF6 / (EC+DEC+EMC) (the mass ratio of EC, DEC, and EMC is 1:1:1), and the separator is Celgard 2500. The specific method for detecting the lithium metal negative electrode is as follows:

[0069] (1) The battery was charged and discharged using a blue-chip device. The charge and discharge program was: rest for 2 hours, 1.0 mAh / cm³. 2Charge for 1 hour, discharge for 1 hour, repeat 25 times to simulate the battery's condition after use. Then, disassemble the battery and remove the negative lithium electrode.

[0070] (2) Chickpea seed A was dissolved in ether to prepare a solution with a concentration of 0.5 mg / mL, thus obtaining a chickpea seed A probe solution.

[0071] (3) Spray the chickpea stigmata A probe solution prepared in step (2) onto the surface of the negative lithium electrode in step (1). After the ether evaporates (within 10 seconds), a fluorescence image can be obtained under ultraviolet light with a wavelength of 365 nm. See Figure 1 (a). By Figure 1 (a) It is known that when isoflavones come into contact with the surface of the lithium metal anode, the groups (phenolic hydroxyl groups) in the isoflavones react with the active lithium, uneven lithium deposition, and lithium dendrites on the surface to form chickpea seed A lithium salt. This causes a drastic change in the molecular structure and electronic effects of the isoflavones, resulting in indigo fluorescence from the active lithium, lithium dendrites, and unevenly deposited lithium on the lithium metal anode surface. The isoflavones do not react with the SEI film or the byproducts on the lithium metal anode surface; the fluorescence signal in the areas where the byproducts and SEI film are located is weak, dim, or even absent. Therefore, the distribution area of ​​each component on the lithium metal anode surface can be determined based on the fluorescence signal distribution, enabling qualitative detection.

[0072] Example 2

[0073] Example 2 uses the same detection method as Example 1, except that genistein is used instead of chickpea seed extract A to prepare a genistein probe solution with a concentration of 0.5 mg / mL. The fluorescence pattern obtained in this example under 365 nm ultraviolet light is shown below. Figure 1 As shown in (b). Figure 1 (b) It is known that when isoflavones come into contact with the surface of the lithium metal anode, the groups (phenolic hydroxyl groups) in the isoflavones react with the active lithium, uneven lithium deposition, and lithium dendrites on the surface to form gentianin lithium salt. This causes a drastic change in the molecular structure and electronic effects of the isoflavones, resulting in blue fluorescence from the active lithium, lithium dendrites, and unevenly deposited lithium on the lithium metal anode surface. However, the isoflavones do not react with the SEI film or the byproducts on the lithium metal anode surface; the fluorescence signal in the areas where the byproducts and SEI film are located is weak, dim, or even absent. Therefore, the distribution area of ​​each component on the lithium metal anode surface can be determined based on the fluorescence signal distribution, enabling qualitative detection.

[0074] Example 3

[0075] Example 3 uses the same detection method as Example 1, except that soy isoflavones are used instead of chickpea stigmata A to prepare a soy isoflavone probe solution with a concentration of 0.5 mg / mL. The fluorescence pattern obtained in this example under 365 nm ultraviolet light is shown below. Figure 1 As shown in (c). Figure 1 (c) It is evident that when isoflavones come into contact with the surface of the lithium metal anode, the groups (phenolic hydroxyl groups) in the isoflavones react with the active lithium, uneven lithium deposition, and lithium dendrites on the surface to form soy isoflavone lithium salts. This causes a drastic change in the molecular structure and electronic effects of the isoflavones, resulting in blue fluorescence from the active lithium, lithium dendrites, and unevenly deposited lithium on the lithium metal anode surface. However, the isoflavones do not react with the SEI film or byproducts on the lithium metal anode surface; the fluorescence signal in the areas where the byproducts and SEI film are located is weak, dim, or even absent. Therefore, the distribution area of ​​each component on the lithium metal anode surface can be determined based on the fluorescence signal distribution, enabling qualitative detection.

[0076] Example 4

[0077] Example 4 uses the same detection method as Example 1, except that genistein is used instead of chickpea styracin A to prepare a genistein probe solution with a concentration of 0.5 mg / mL. The fluorescence pattern obtained in this example under 365 nm ultraviolet light is shown below. Figure 1 As shown in (d). Figure 1 (d) It is evident that when isoflavones come into contact with the surface of the lithium metal anode, the groups (phenolic hydroxyl groups) in the isoflavones react with the active lithium, uneven lithium deposition, and lithium dendrites on the surface to form genistein lithium salt. This causes a drastic change in the molecular structure and electronic effects of the isoflavones, resulting in indigo fluorescence from the active lithium, lithium dendrites, and unevenly deposited lithium on the lithium metal anode surface. However, the isoflavones do not react with the SEI film or byproducts on the lithium metal anode surface; the fluorescence signal in the areas where the byproducts and SEI film are located is weak, dim, or even absent. Therefore, the distribution area of ​​each component on the lithium metal anode surface can be determined based on the fluorescence signal distribution, enabling qualitative detection.

[0078] The molecular structure parameters and fluorescence properties of the isoflavone compounds used in Examples 1-4 are shown in Table 1 below:

[0079] Table 1

[0080]

[0081]

[0082] The fluorescence emission intensity of isoflavones before and after interaction with the lithium metal anode surface can directly reflect the abundance of unevenly deposited lithium or lithium dendrites in different regions, the degree of byproduct accumulation, etc. After measuring the fluorescence intensity using a fluorescence spectrometer, quantitative analysis of various components can be performed. For example... Figures 2-5 As shown in Table 1, chickpea seed extract A showed no obvious fluorescence emission under 365 nm UV excitation; however, the product after reaction with lithium metal (lithium chickpea seed extract A) exhibited indigo blue solid fluorescence with an emission wavelength of 496 nm. Strigolide showed no obvious fluorescence emission; strigolide lithium salt exhibited blue solid fluorescence with an emission wavelength of 436 nm. Soy isoflavones showed no obvious fluorescence emission; soy isoflavone lithium salt exhibited blue solid fluorescence with an emission wavelength of 457 nm. Gentian isoflavones showed no obvious fluorescence emission; gentian isoflavone lithium salt exhibited indigo blue solid fluorescence with an emission wavelength of 495 nm.

[0083] like Figure 6 As shown in Table 1, lithium salts of chickpea arvense A, gentianin, soy isoflavones, and genistein all exhibit good fluorescence stability and resistance to photobleaching. After 1 hour of continuous UV excitation, the fluorescence intensity of lithium salt of chickpea arvense A remained at 53.3% at an emission wavelength of 496 nm, that of lithium gentianin remained at 74.2% at an emission wavelength of 436 nm, that of lithium soy isoflavones remained at 88.0% at an emission wavelength of 457 nm, and that of lithium genistein remained at 35.5% at an emission wavelength of 495 nm. This demonstrates that the isoflavone compounds provided in this application exhibit excellent stability as probes for detecting lithium metal anode surfaces.

[0084] As can be seen from the detection results of Examples 1 to 4, excellent detection results can be achieved using a very low concentration (0.5 mg / mL) of probe solution, indicating that the detection method provided in this application can achieve better detection results while minimizing the interference of probe molecules on the inherent morphology of the lithium metal anode interface.

[0085] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the scope of the claims.

Claims

1. A method of detecting a lithium metal negative electrode composition, characterized by, The lithium metal negative electrode is a lithium metal negative electrode after charge-discharge cycle in a lithium battery, and the method comprises the following steps: adopting an isoflavone compound as a fluorescent probe to detect components on the surface of the lithium metal negative electrode; the detection items of the detection include one or more of deposited lithium, by-products, lithium dendrites, dead lithium and solid electrolyte interface film on the surface of the lithium metal negative electrode. The isoflavone compound has a structural formula shown in formula (I): （I） wherein R1~R 10 each is independently selected from one or more of a hydrogen atom, a hydroxyl group, an alkyl group, an alkoxy group, an amino group, an aryl group, and a halogen, and at least one is a hydroxyl group.

2. The method of detecting lithium metal negative electrode composition of claim 1, wherein, R1~R 10 each is independently selected from one or more of a hydrogen atom, a hydroxyl group, and an alkoxy group, and at least one is a hydroxyl group.

3. The method of detecting lithium metal negative electrode composition of claim 2, wherein, R2is selected from the group consisting of hydrogen atom, R1, R3, R5, R6, R7, R9and R 10 R4is selected from the group consisting of hydrogen atom or hydroxyl group, and R8is selected from the group consisting of hydroxyl group or methoxyl group.

4. The method of detecting lithium metal negative electrode composition of claim 3, wherein, The isoflavone compound includes one or more of glycitein A, calyxoside, soy isoflavone, genistein, sophoricoside and isosakuranin.

5. The method for detecting components of a lithium metal negative electrode according to claim 1, wherein, The by-products include lithium salts and / or polymers, the lithium salts include one or more of lithium fluoride, lithium chloride, lithium acetate, lithium carbonate, lithium hydroxide, lithium oxide and lithium alcoholate, and the polymers include one or more of polyvinyl carbonate, polycarbonate and polypropylene.

6. The method of detecting lithium metal negative electrode composition of claim 1, wherein, The lithium battery is a lithium-oxygen battery, a lithium-sulfur battery, a lithium oxide battery, a lithium-air battery or a lithium-lithium battery.

7. The method of detecting components of a lithium metal negative electrode according to any one of claims 1 to 6, wherein The detection step comprises: Preparation of a probe solution containing an isoflavone compound; Contacting the probe solution with the surface of the lithium metal negative electrode, and performing fluorescence testing on the surface of the lithium metal negative electrode to detect the components on the surface of the lithium metal negative electrode.

8. The method of detecting lithium metal negative electrode composition of claim 7, wherein, The fluorescence testing step comprises: Irradiating the surface of the lithium metal negative electrode with excitation light, and qualitatively analyzing the components on the surface of the lithium metal negative electrode according to the fluorescence signal distribution on the surface of the lithium metal negative electrode; And / or, irradiating the surface of the lithium metal negative electrode with excitation light, and quantitatively analyzing the components on the surface of the lithium metal negative electrode according to the fluorescence intensity difference of different distribution regions on the surface of the lithium metal negative electrode.

9. The method of detecting lithium metal negative electrode composition of claim 8, wherein, At least one of the following characteristics is possessed: 1) The solvent used in the probe solution includes one or more of ether solvents, furan solvents, alkane solvents, ketone solvents and chloroform; 2) The excitation light is ultraviolet light with a wavelength of 300 nm to 365 nm.

10. The method of detecting lithium metal negative electrode composition of claim 7, wherein, The concentration of the isoflavone compound in the probe solution is 0.5 mg / mL to 5 mg / mL.

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