Method for detecting lithium metal negative electrode composition

Abstract

This application relates to the field of fluorescence detection technology, and in particular to 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. The method includes the following steps: using flavonoids as fluorescent probes to detect the composition on the surface of the lithium metal anode. Using flavonoids as probes enables the visual observation and quantitative detection of deposited lithium, lithium dendrites, byproducts, dead lithium, and the solid electrolyte interface film on the surface of the lithium metal anode.

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] Theoretically, metal anodes can be used to construct high-energy-density rechargeable batteries, and have received widespread attention in recent years. However, lithium metal anodes consistently face problems such as uneven lithium deposition (lithium dendrites), decreased coulombic efficiency, and loss of active materials in the electrode and electrolyte due to side reactions during long-term cycling. On the one hand, the solid electrolyte interphase (SEI) film formed between the lithium metal anode and the electrolyte through chemical and electrochemical reactions is considered a key factor determining the long-term stability of the battery. The structure, chemical, and thermodynamic properties of the SEI play a crucial role in achieving high levels of electrode reversibility in rechargeable batteries, especially in battery systems with high energy density and low cost, including metal anodes. On the other hand, lithium dendrites are dendritic lithium crystals formed by the irregular electrodeposition of highly reactive lithium atoms at nucleation sites. They not only lead to battery performance degradation, such as low coulombic efficiency and rapid capacity decay, but also cause internal short circuits, resulting in thermal runaway and posing serious safety hazards. Due to the complexity of battery systems and the unique properties of lithium metal, the nucleation and growth behavior of lithium dendrites is also affected by various factors, making in-depth characterization and direct observation difficult. Therefore, studying the distribution, morphology, and relative abundance of lithium dendrites on the surface of lithium metal anodes is key to preparing next-generation lithium metal batteries with high energy density and safety.

[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), and transmission electron microscopy (TEM). These techniques can detect the morphology, interface properties, chemical composition, and microstructure of the anode surface material. 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), atomic Raman spectroscopy, and in-situ nuclear magnetic resonance (in-situ NMR), can obtain information about the electrode surface through specific signals, but direct observation is not possible.

[0004] Researchers proposed using a solid-state fluorescent molecule (catechol tetraphenylethylene, CAS No. 2113665-30-6) to analyze the surface composition of a cycled lithium metal anode, achieving visualization of the surface composition. While this method is helpful in analyzing battery failure mechanisms, selecting optimal cycling conditions, and predicting uneven lithium deposition, the synthesis of this type of fluorescent probe molecule is cumbersome and costly; furthermore, the high reagent concentrations (above 3.0 mg / mL) result in significant losses per use, thus limiting its commercial application potential. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for detecting the components of lithium metal anodes. Using flavonoids as probes can enable the visual observation and quantitative detection of deposited lithium, lithium dendrites, by-products, dead lithium, and solid electrolyte interface films 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. The method includes the following steps: using flavonoids as fluorescent probes to detect the composition on the surface of the lithium metal anode.

[0007] In some embodiments, the flavonoid 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 flavonoids include one or more of myricetin, luteolin, apigenin, quercetin, and kaempferol.

[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 flavonoids;

[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 change in fluorescence color.

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

[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 flavonoid compound in the probe solution is 0.5 mg / mL to 5 mg / mL.

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

[0026] The flavonoids provided in this application, as fluorescent probes, exhibit a "shift" response mode, capable of reacting with active lithium, uneven lithium deposition, and lithium dendrites on the lithium metal anode surface. The flavonoids show fluorescence changes (the shift of the fluorescence spectral peak changes) before and after the reaction. Conversely, byproducts, the SEI film, and dead lithium surrounded by byproducts on the lithium metal anode surface do not react with the flavonoids and show no fluorescence change. This allows for visual detection based on fluorescence changes, enabling qualitative analysis of the composition of the lithium metal anode surface. Therefore, the flavonoids provided in this application, as probes, can accurately detect the surface conditions of lithium metal anodes. Furthermore, the response shift (Δλ) of the flavonoids as fluorescent molecules can reach at least 150 nm, offering advantages such as high detection efficiency, high sensitivity and accuracy, fast response, good stability, and wide applicability.

[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 flavonoids before and after their interaction with the lithium metal anode surface in Examples 1-4 are shown.

[0031] Figure 6 The images show the fluorescence stability spectra of the flavonoids in Examples 1-4 after they interact with the lithium metal anode surface. 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 flavonoid compounds as fluorescent probes to detect the composition of the lithium metal anode surface.

[0042] The flavonoids provided in this application, as fluorescent probes, exhibit a "shift" response mode, capable of reacting with active lithium, uneven lithium deposition, and lithium dendrites on the lithium metal anode surface. The flavonoids show fluorescence changes (the shift of the fluorescence spectral peak changes) before and after the reaction. Conversely, byproducts, the SEI film, and dead lithium surrounded by byproducts on the lithium metal anode surface do not react with the flavonoids and show no fluorescence change. This allows for visual detection based on fluorescence changes, enabling qualitative analysis of the composition of the lithium metal anode surface. Therefore, the flavonoids provided in this application, as probes, can accurately detect the surface conditions of lithium metal anodes. Furthermore, the response shift (Δλ) of the flavonoids as fluorescent molecules can reach at least 150 nm, offering advantages such as high detection efficiency, high sensitivity and accuracy, fast response, good stability, and wide applicability.

[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] It can be understood that the "displacement" response mode refers to the change in the fluorescence signal of the fluorescent probe before and after the flavonoids react with the lithium metal surface.

[0045] In some embodiments, the flavonoid 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 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.

[0049] Furthermore, R2, R4, and R8 are all selected from hydroxyl groups, and R1, R3, R6, and R... 10 All are selected from hydrogen atoms, and R5, R7 and R9 are independently selected from hydrogen atoms or hydroxyl groups, respectively.

[0050] In some embodiments, the flavonoid compounds include one or more of myricetin, luteolin, apigenin, quercetin, and kaempferol. The structural formulas of myricetin (CAS No. 529-44-2), luteolin (CAS No. 491-70-3), apigenin (CAS No. 520-36-5), kaempferol (CAS No. 520-18-3), and quercetin (CAS No. 117-39-5) are shown in Formulas 1 to 5, 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. Among these, the groups (such as hydroxyl groups) in flavonoids can react with active lithium, unevenly deposited lithium, and lithium dendrites, causing drastic changes in the molecular structure and electronic effects of the flavonoids, resulting in fluorescence changes before and after the reaction. However, byproducts on the lithium metal anode surface, dead lithium surrounded by byproducts, and the SEI film do not react and maintain intrinsic fluorescence emission. Therefore, different components on the lithium metal anode surface can be distinguished based on the different fluorescence colors (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, 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 flavonoids;

[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 flavonoids 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 flavonoids 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 flavonoid 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 was irradiated with excitation light, and the composition of the lithium metal anode surface was qualitatively analyzed based on the change in fluorescence color.

[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 signal distribution on the lithium metal anode surface and the fluorescence intensity differences in different distribution areas.

[0065] Specifically, by observing the fluorescence color of the lithium metal anode surface, different components on the lithium metal anode surface can be distinguished, enabling visual analysis of the lithium metal anode surface. Using a fluorescence spectrometer to measure the fluorescence intensity and wavelength of 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) Dissolve myricetin in ether to prepare a solution with a concentration of 0.5 mg / mL to obtain myricetin probe solution.

[0071] (3) Spray the myricetin 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).

[0072] Example 2

[0073] Example 2 uses the same detection method as Example 1, except that luteolin is used instead of myricetin to prepare a luteolin 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).

[0074] Example 3

[0075] Example 3 uses the same detection method as Example 1, except that kaempferol is used instead of myricetin to prepare a kaempferol probe solution with a concentration of 0.5 mg / mL. The fluorescence pattern obtained in this example under ultraviolet light at a wavelength of 365 nm is shown below. Figure 1 As shown in (c).

[0076] Example 4

[0077] Example 4 uses the same detection method as Example 1, except that apigenin is used instead of myricetin to prepare a apigenin probe solution with a concentration of 0.5 mg / mL. The fluorescence pattern obtained in this example under ultraviolet light at a wavelength of 365 nm is shown below. Figure 1 As shown in (d).

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

[0079] Table 1

[0080]

[0081] like Figure 1As shown, when flavonoids come into contact with the surface of a lithium metal anode, the groups (phenolic hydroxyl groups) in the flavonoids react with the active lithium, uneven lithium deposition, and lithium dendrites on the surface to form anionic lithium salts (such as myricetin lithium salt, luteolin lithium salt, kaempferol lithium salt, apigenin lithium salt, etc.). This causes drastic changes in the molecular structure and electronic effects of the flavonoids, resulting in a significant difference in fluorescence signals before and after the reaction (yellow fluorescence after the reaction). However, the flavonoids do not react with the SEI film and byproducts on the lithium metal anode surface, and can maintain intrinsic fluorescence emission (dark red fluorescence). Therefore, different chemical components can be identified based on the changes in fluorescence color on the lithium metal anode surface, and the distribution area of ​​each component on the lithium metal anode surface can be determined based on the fluorescence signal distribution.

[0082] The fluorescence emission intensity of flavonoids 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, myricetin exhibits dark red solid-state fluorescence under 365 nm UV excitation, with an emission wavelength of 697 nm; while the product after reaction with lithium metal (lithium myricetin) exhibits orange solid-state fluorescence, with an emission wavelength of 633 nm and a response shift of 64 nm. Lutein exhibits dark red solid-state fluorescence, with an emission wavelength of 701 nm; lithium lutein exhibits yellow solid-state fluorescence, with an emission wavelength of 541 nm and a response shift of 160 nm. Kaempferol exhibits dark red solid-state fluorescence, with an emission wavelength of 692 nm; lithium kaempferol exhibits yellow-green solid-state fluorescence, with an emission wavelength of 514 nm and a response shift of 178 nm. Apigenin exhibits dark red solid-state fluorescence, with an emission wavelength of 695 nm; lithium apigenin exhibits yellow solid-state fluorescence, with an emission wavelength of 521 nm and a response shift of 174 nm.

[0083] like Figure 6 As shown in Table 1, lithium myricetin, lithium luteolin, lithium kaempferol, and lithium apigenin all exhibit good fluorescence stability and resistance to photobleaching. After 1 hour of continuous UV excitation, the fluorescence intensity of lithium myricetin at 633 nm remained at 75.9%, lithium luteolin at 541 nm at 60.2%, lithium kaempferol at 514 nm at 38.8%, and lithium apigenin at 521 nm at 30.7%. This demonstrates that the flavonoids 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 for detecting the composition of a lithium metal anode, characterized in that, The lithium metal anode is a lithium metal anode in a lithium battery after charge-discharge cycles. The method includes the following steps: using flavonoids as fluorescent probes to detect the components on the surface of the lithium metal anode; the detection items include one or more of the following on the surface of the lithium metal anode: deposited lithium, by-products, lithium dendrites, dead lithium, and solid electrolyte interface film. The flavonoids have the structural formula shown in formula (I): （I） 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.

2. The method for detecting the composition of lithium metal anode as described in claim 1, characterized in that, R1~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.

3. The method for detecting the composition of lithium metal anode as described in claim 2, characterized in that, R2, R4, and R8 are all selected from hydroxyl groups, and R1, R3, R6, and R... 10 All are selected from hydrogen atoms, and R5, R7 and R9 are independently selected from hydrogen atoms or hydroxyl groups, respectively.

4. The method for detecting the composition of lithium metal anode as described in claim 3, characterized in that, The flavonoids include one or more of myricetin, luteolin, apigenin, quercetin, and kaempferol.

5. The method for detecting the composition of lithium metal anodes as described in claim 1, characterized in that, 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.

6. The method for detecting the composition of lithium metal anode as described in claim 1, characterized in that, 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 for detecting the composition of lithium metal anodes as described in any one of claims 1 to 6, characterized in that, The detection steps include: Preparation of probe solutions containing flavonoids; 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.

8. The method for detecting the composition of lithium metal anode as described in claim 7, characterized in that, The steps for performing the fluorescence test include: 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 change in fluorescence color. And / or, the surface of the lithium metal anode is irradiated with excitation light, and the composition of the lithium metal anode surface is quantitatively analyzed based on the fluorescence signal distribution and fluorescence intensity differences in different distribution areas.

9. The method for detecting the composition of lithium metal anode as described in claim 8, characterized in that, It has at least one of the following characteristics: 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; 2) The excitation light is ultraviolet light with a wavelength of 300 nm to 365 nm.

10. The method for detecting the composition of a lithium metal anode as described in claim 7, characterized in that, The concentration of the flavonoids in the probe solution is 0.5 mg / mL to 5 mg / mL.

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