Application of benzoxazole compound probe in detection of lithium metal negative electrode

Abstract

The application relates to application of a benzoxazole compound as a probe in detection of a lithium metal negative electrode. The benzoxazole compound has a structural formula shown in the following formula (1), wherein R1-R8 are each independently selected from one or more of a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroalkyl group, a heterocyclic group, a heteroaryl group, an amino group, a nitro group, a cyano group, an isocyano group, a halogen, an alkylene group, an alkenylene group, an alkynylene group, a formyl group and an ester group. The benzoxazole compound provided by the application can realize visual observation and semi-quantitative detection of the lithium metal negative electrode, and the detection process is simple, efficient, accurate, fast in response, good in stability and wide in applicability.

Description

Technical Field

[0001] This application relates to the field of battery energy technology, and in particular to the application of a benzoxazole compound probe in the detection of lithium metal anodes. Background Technology

[0002] Human societal progress and productivity transformation are inseparable from energy sector reforms. In contemporary production and daily life, lithium-ion batteries, as one of the most important energy storage devices, are widely used in portable electronic products, electric transportation, and large-scale energy storage equipment. In addition to the currently mature and widely used lithium-ion batteries, lithium metal batteries, as the next-generation energy storage technology, are also attracting much attention from academia and industry.

[0003] Lithium metal batteries currently lack mature commercial applications, primarily due to the uncontrollable dendritic structures that frequently appear on the surface of lithium metal anodes. These dendrite structures can damage the solid electrolyte interphase (SEI) film, puncture the separator, and cause internal short circuits, ultimately leading to battery failure and even safety accidents. Uneven lithium deposition, uncontrolled dendrite growth, the continuous accumulation of by-reaction products, and the formation of dead lithium are serious obstacles hindering the practical application of lithium metal anodes. Visually observing and quantitatively detecting the distribution and morphology of lithium deposition, by-products, and lithium dendrites on the surface of lithium metal anodes is crucial for studying battery failure behavior and predicting cycle life.

[0004] In 2022, researchers first proposed using an AIE solid-state fluorescent molecule (catechol tetraphenylethylene, CAS No. 2113665-30-6) to analyze the surface composition of cycled lithium metal anodes. This method utilizes the reaction of catechol groups with lithium, resulting in a redshift in fluorescence wavelength and a decrease in emission intensity, while maintaining intrinsic fluorescence without reacting with byproducts. This enabled the visualization, tracking, and detection of surface components. However, the fluorescence intensity of the catechol tetraphenylethylene molecule decreases after reacting with lithium metal, weakening the imaging ability of this type of fluorescent probe for lithium dendrites. Furthermore, after deprotonation, the catechol groups are easily oxidized by air to quinones, causing fluorescence quenching and poor imaging timeliness. Summary of the Invention

[0005] Based on this, the present invention provides the application of benzoxazole compound probes in the detection of lithium metal anodes. Using benzoxazole compounds as probes, it is possible to achieve visual detection of lithium deposition, by-products, lithium dendrites, dead lithium, and solid electrolyte interface film on the surface of lithium metal anodes.

[0006] One aspect of this application provides the application of benzoxazole compounds as probes in the detection of lithium metal anodes, wherein the benzoxazole compounds have the structural formula shown in formula (1):

[0007]

[0008] In formula (1), R1 to R8 are each independently selected from one or more of the following: hydrogen atom, alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroalkyl, heterocyclic, heteroaryl, amino, nitro, cyano, isocyano, halogen, alkylene, alkenyl, alynyl, formyl, and ester.

[0009] In some embodiments, the benzoxazole compounds are selected from the structures described below:

[0010]

[0011] In some embodiments, the detection items include one or more of the following: deposited lithium, byproducts, lithium dendrites, dead lithium, and solid electrolyte interface film on the lithium metal anode surface.

[0012] In some embodiments, the byproducts include one or more of lithium fluoride, lithium chloride, lithium acetate, lithium carbonate, lithium hydroxide, lithium oxide, and lithium alkoxide.

[0013] In some embodiments, the lithium metal negative electrode is the lithium metal negative electrode in a lithium metal battery; the lithium metal battery is a lithium-oxygen battery, a lithium-sulfur battery, a lithium-oxide battery, a lithium-air battery, or a lithium-lithium battery.

[0014] A second aspect of this application provides a method for detecting lithium metal anodes, comprising the following steps:

[0015] Probe solutions are prepared by dissolving benzoxazole compounds in organic solvents.

[0016] The probe solution is brought into contact with the surface of the lithium metal anode to be tested. After the organic solvent has evaporated to dryness, the analysis is performed under excitation light irradiation.

[0017] The benzoxazole compounds have the structural formula shown in formula (1):

[0018]

[0019] In formula (1), R1 to R8 are each independently selected from one or more of the following: hydrogen atom, alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroalkyl, heterocyclic, heteroaryl, amino, nitro, cyano, isocyano, halogen, alkylene, alkenyl, alynyl, formyl, and ester.

[0020] In some embodiments, the benzoxazole compounds are selected from the structures described below:

[0021]

[0022] In some embodiments, the lithium metal negative electrode is the lithium metal negative electrode in a lithium metal battery; the lithium metal battery is a lithium-oxygen battery, a lithium-sulfur battery, a lithium-oxide battery, a lithium-air battery, or a lithium-lithium battery.

[0023] In some embodiments, the analysis steps include: visually observing the fluorescence of the lithium metal anode surface under test and / or using a fluorescence spectrometer to measure the fluorescence wavelength and fluorescence intensity.

[0024] In some embodiments, the concentration of benzoxazole compounds in the probe solution is 1–10 mg / mL, optionally 2 mg / mL–4 mg / mL.

[0025] Compared with the prior art, this application has at least the following beneficial effects:

[0026] The benzoxazole compounds provided in this application, when used as probes, can react with active lithium, unevenly deposited lithium, and lithium dendrites, respectively. The benzoxazole compounds exhibit fluorescence changes before and after the reaction, while byproducts, the SIE film, or dead lithium surrounded by byproducts do not react with the benzoxazole compounds and show no fluorescence change. Therefore, deposited lithium, lithium dendrites, byproducts, dead lithium, and the SEI film on the lithium metal anode surface can be visually detected and calibrated through fluorescence. Based on this, the benzoxazole compounds provided in this application, as probes, can accurately detect the surface conditions of lithium metal anodes. Furthermore, this detection process is simple, efficient, accurate, fast-responding, stable, and widely applicable.

[0027] Furthermore, by combining fluorescence observation and fluorescence intensity detection, this application can semi-quantitatively and visually identify active lithium, lithium dendrites and their abundance, uneven lithium deposition, by-products and their accumulation, etc. 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 1In one embodiment of this application, after 25 charge-discharge cycles (charge-discharge current: 2.5 mAh / cm2) of a Li|Li coin cell, the battery was disassembled, and an ether solution of o-phenol benzoxazole was sprayed onto the lithium metal anode. The surface fluorescence pattern showed that lithium metal, uneven lithium deposition, lithium dendrites, etc., exhibited yellow fluorescence, while the by-reaction products exhibited bright purple fluorescence. The fluorescence intensity was then measured using a fluorescence spectrometer to perform semi-quantitative analysis of various components.

[0030] Figure 2 The fluorescence change of the o-phenol benzoxazole described in this application before and after reaction with lithium metal is shown. This probe molecule exhibits significant fluorescence emission in both solution and solid states; its intrinsic emission is yellow, while the fluorescence emission after interaction with lithium metal is bright purple.

[0031] Figure 3 The photon nuclear magnetic resonance (NMR) spectrum of the orthophenol benzoxazole and its product after reaction with lithium metal described in this application is shown below.

[0032] Figure 4 The fluorescence micrographs are of the o-phenol benzoxazole described in this application after reacting with inorganic lithium salts or lithium metal.

[0033] Figure 5 The fluorescence spectrum of the o-phenol benzoxazole of the present invention after reaction with inorganic lithium salt or lithium metal;

[0034] Figure 6 The fluorescence stability test spectrum of the o-phenol benzoxazole described in this invention before and after its reaction with lithium metal is shown. Detailed Implementation

[0035] 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.

[0036] 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.

[0037] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0038] In this article, "one or more" refers to any one, two or more of the listed items.

[0039] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0040] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0041] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0042] 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(CH3)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 The groups are 2,3-dimethyl-2-butyl (-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). The term "alkylene" refers to a divalent group formed by losing a hydrogen atom from an alkyl group. For example, "C1-C5 alkylene" refers to a divalent group formed by losing a hydrogen atom from a C1-C5 alkyl group, including straight-chain C1-C5 alkylene and branched C3-C5 alkylene.

[0043] The term "cycloalkyl" refers to a non-aromatic hydrocarbon containing a ring of carbon atoms, which can be monocycloalkyl, spirocycloalkyl, or bridged cycloalkyl. Phrases containing this term, such as "C3-C9 cycloalkyl," refer to cycloalkyl compounds containing 3 to 9 carbon atoms, and each occurrence can independently be C3, C4, C5, C6, C7, C8, or C9 cycloalkyl. Suitable examples include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl. Additionally, "cycloalkyl" may contain one or more double bonds; representative examples of cycloalkyl compounds containing double bonds include cyclopentenyl, cyclohexenyl, cyclohexadienyl, and cyclobutadienyl.

[0044] The term "alkenyl" refers to a compound containing at least one unsaturated site, i.e., a carbon-carbon sp group. 2 Hydrocarbons with a double bond consisting of a positive, secondary, tertiary, or cyclic carbon atom. Phrases containing this term, such as "C2–C9 alkenyl," refer to alkenyl groups containing 2–9 carbon atoms, which, each time appearing, can independently be C2, C3, C4, C5, C6, C7, C8, or C9 alkenyl. Suitable examples include, but are not limited to: vinyl (-CH=CH2), allyl (-CH2CH=CH2), cyclopentenyl (-C5H7), and 5-hexenyl (-CH2CH2CH2CH2CH=CH2). The term "alkenyl" refers to a divalent group formed by further losing a hydrogen atom from an alkenyl group. For example, "C2–C9 alkenyl" refers to a divalent group formed by losing a hydrogen atom from a C2–C9 alkenyl group, including straight-chain alkenyl groups and branched alkenyl groups from C2–C9.

[0045] The term "alkynyl" refers to a hydrocarbon containing at least one unsaturated carbon atom, i.e., a carbon-carbon sp triple bond, consisting of a positive, secondary, tertiary, or cyclic carbon atom. Phrases containing this term, such as "C2–C9 alkenyl," refer to alkynyl groups containing 2–9 carbon atoms, and each occurrence can be independently C2-alkynyl, C3-alkynyl, C4-alkynyl, C5-alkynyl, C6-alkynyl, C7-alkynyl, C8-alkynyl, or C9-alkynyl. Suitable examples include, but are not limited to, ethynyl (-C≡CH) and propynyl (-CH2C≡CH). The term "ynynyl" refers to a divalent group formed by further losing a hydrogen atom from an alkynyl group. For example, "C2–C9 ynynyl" refers to a divalent group formed by losing a hydrogen atom from a C2–C9 alkynyl group, including straight-chain ynynyl groups and branched ynynyl groups from C2–C9.

[0046] 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.

[0047] The term "heteroaryl" refers to a group formed by replacing at least one carbon atom of an aryl group with a heteroatom. The heteroatom can be at least one of O, N, P, Si, Se, and S, and the number of heteroatoms in a heteroaryl group can be one or more. Heteroaryl groups can be monocyclic heteroaryl, fused-ring heteroaryl, two or more monocyclic heteroaryl groups conjugated by carbon-carbon bonds, monocyclic heteroaryl and fused-ring heteroaryl groups conjugated by carbon-carbon bonds, two or more fused-ring heteroaryl groups conjugated by carbon-carbon bonds, monocyclic aryl and fused-ring heteroaryl groups conjugated by carbon-carbon bonds, etc.

[0048] The term "heteroalkyl" refers to an alkyl group in which at least one carbon atom is replaced by a non-carbon atom, which can be an N atom, O atom, S atom, etc. For example, if the carbon atom in the alkyl group that is attached to the parent nucleus is replaced by a non-carbon atom, the resulting heteroalkyl group is an alkoxy group (e.g., -OCH3, etc.), an amine (e.g., -NHCH3, -N(CH3)2, etc.), or a thioalkyl group (e.g., -SCH3). If the carbon atom in the alkyl group that is not attached to the parent nucleus is replaced by a non-carbon atom, the resulting heteroalkyl group is an alkyl ether (e.g., -CH2CH2-O-CH3, etc.), an alkylamine (e.g., -CH2NHCH3, -CH2N(CH3)2, etc.), or a thioalkyl ether (e.g., -CH2-S-CH3). If the terminal carbon atom of the alkyl group is replaced by a non-carbon atom, the resulting heteroalkyl group is a hydroxyalkyl group (e.g., -CH2CH2-OH), an aminoalkyl group (e.g., -CH2NH2), or an alkyl mercapto group (e.g., -CH2CH2-SH). Phrases containing this term, such as “C1-C9 heteroalkyl”, refer to heteroalkyl groups containing 1 to 9 carbon atoms, and each time they appear, they can be independently C2 heteroalkyl, C3 heteroalkyl, C4 heteroalkyl, C5 heteroalkyl, C7 heteroalkyl, C8 heteroalkyl, or C9 heteroalkyl.

[0049] The term "heterocyclic group" refers to a cycloalkyl group in which at least one carbon atom is replaced by a non-carbon atom, which can be an N atom, O atom, S atom, etc., and can be a saturated ring or a partially unsaturated ring. Phrases containing this term, such as "C4-C9 heterocyclic group," refer to heterocyclic groups containing 4 to 9 carbon atoms, and each occurrence can be independently C4, C6, C7, C8, or C9 heteroalkyl. Suitable examples include, but are not limited to: dihydropyridyl, tetrahydropyridyl (piperidinyl), tetrahydrothiophenyl, sulfur-oxidized tetrahydrothiophenyl, tetrahydrofuranyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and dihydroindolyl.

[0050] The term "amino" refers to a derivative of ammonia, characterized by 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.

[0051] The term "halogen" or "halogen group" refers to F, Cl, Br, or I.

[0052] A first aspect of this application provides the application of a benzoxazole compound as a probe in the detection of lithium metal anodes. The benzoxazole compound has the structural formula shown in formula (1):

[0053]

[0054] In formula (1), R1 to R8 are each independently selected from one or more of the following: hydrogen atom, alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroalkyl, heterocyclic, heteroaryl, amino, nitro, cyano, isocyano, halogen, alkylene, alkenyl, alynyl, formyl, and ester.

[0055] Understandably, the lithium metal anode to be tested refers to the lithium metal anode of the battery after normal use (charge and discharge cycles).

[0056] In some specific examples, R1 to R8 are each independently selected from one or more of hydrogen atoms, triphenylamine groups, nitro groups, and maleimide groups. Further, at least four of R1 to R8 are selected from hydrogen atoms, and optionally at least five are selected from hydrogen atoms.

[0057] In some specific examples, the benzoxazole compounds are selected from the structures described in formula (1-1):

[0058]

[0059] In equation (1-1), R 1 R 2 Each of R1 to R8 is independently selected from one or more of the following groups: hydrogen atom, alkyl group, cycloalkyl group, alkenyl group, alkynyl group, aryl group, heteroalkyl group, heterocyclic group, heteroaryl group, amino group, nitro group, cyano group, isocyano group, halogen group, alkylene group, alkenylene group, alkynyl group, formyl group, and ester group. Optionally, R1 to R8 are each independently selected from one or more of the following groups: hydrogen atom, triphenylamine group, nitro group, and maleimide group.

[0060] In some specific examples, the benzoxazole compounds are selected from the structures described below:

[0061]

[0062] In some specific examples, the detected items include one or more of the following on the lithium metal anode surface: deposited lithium, byproducts, lithium dendrites, dead lithium, and SEI film. Benzoxazole compounds can react with active lithium, unevenly deposited lithium, and lithium dendrites, accompanied by fluorescence changes, but do not react with byproducts, the SIE film, or dead lithium surrounded by byproducts, and maintain unchanged fluorescence. The surface components (such as active lithium and byproducts) are distinguished based on different fluorescence colors; the intensity and distribution of fluorescence color indicate the uneven deposition of lithium, distribution of lithium dendrites, dead lithium, degree of byproduct accumulation, and the growth and distribution area of ​​the SEI film on the lithium metal anode surface, achieving visual analysis of the lithium metal surface. Specifically, the byproducts include one or more of lithium fluoride, lithium chloride, lithium acetate, lithium carbonate, lithium hydroxide, lithium oxide, and lithium alkoxide.

[0063] In some specific examples, the lithium metal anode is the lithium metal negative electrode in a lithium metal battery. Further, the lithium metal battery is a lithium-oxygen battery, a lithium-sulfur battery, a lithium-oxide battery, a lithium-air battery, or a lithium-lithium battery.

[0064] A second aspect of this application also provides a method for detecting lithium metal anodes, comprising the following steps:

[0065] Dissolve any of the benzoxazole compounds described above in an organic solvent to prepare a probe solution;

[0066] The probe solution is brought into contact with the surface of the lithium metal anode to be tested. After the organic solvent has evaporated to dryness, the analysis is performed under excitation light irradiation.

[0067] Understandably, the wavelength of the excitation light is the wavelength capable of exciting the benzoxazole compound to emit fluorescence, and can be any wavelength between 300 nm and 365 nm. In some specific examples, the excitation light is ultraviolet light, which can be ultraviolet light of 355 nm to 365 nm, and more specifically, ultraviolet light of 365 nm.

[0068] In some specific examples, the metal anode is the lithium metal anode in a lithium metal battery. Further, the lithium metal battery is a lithium-oxygen battery, a lithium-sulfur battery, a lithium-oxide battery, a lithium-air battery, or a lithium-lithium battery.

[0069] In some specific examples, the concentration of benzoxazole compounds in the probe solution is 1–10 mg / mL. Concentrations that are too high or too low will lead to decreased detection efficiency. Specifically, the concentration of benzoxazole compounds in the probe solution may include, but is not limited to: 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, and 10 mg / mL. Further, the concentration of benzoxazole compounds in the probe solution is between 2 mg / mL and 4 mg / mL. Better detection results are obtained within this concentration range.

[0070] In some specific examples, the organic solvent is selected from volatile solvents. Specific examples include, but are not limited to, one or more of diethyl ether, tetrahydrofuran, acetone, n-hexane, and cyclohexane.

[0071] In some specific examples, the analytical steps include: visually observing the fluorescence on the surface of the lithium metal anode to be tested and / or measuring the fluorescence wavelength and intensity using a fluorescence spectrometer. Measuring the fluorescence wavelength and intensity using a fluorescence spectrometer allows for semi-quantitative analysis of the aforementioned detection items.

[0072] The following are specific embodiments. They are intended to provide a more detailed description of this application to help those skilled in the art and researchers better understand it. The technical conditions described do not constitute any limitation on this application. Any modifications made within the scope of the claims of this application are protected by the claims of this application.

[0073] Unless otherwise stated, all raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. All instruments are conventionally selected in the art. Experimental methods not specifically described in the examples were performed under conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0074] Example 1

[0075] This embodiment describes a method for detecting the lithium metal anode in a lithium metal battery. The lithium metal battery used 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 (mass ratio 1:1:1), and the separator is Celgard 2500. The specific steps are as follows:

[0076] (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. 2 Charge 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.

[0077] (2) Dissolve o-phenol benzoxazole in diethyl ether to prepare a solution with a concentration of 3.0 mg / mL to obtain the probe solution.

[0078] (3) Spray the probe solution prepared in step (2) onto the surface of the negative lithium electrode after charge-discharge cycles. After the ether evaporates (within 10 seconds), a fluorescence image can be obtained under 365nm ultraviolet light. See Figure 1 .

[0079] In addition, such as Figure 2 As shown, a dimethyl sulfoxide solution of o-phenol-benzoxazole (concentration: 3.0 mg / mL) exhibits yellow fluorescence under 365 nm UV light. After directly immersing a lithium metal sheet in the solution for reaction, the product solution (lithium o-phenol-benzoxazole) exhibits bright purple fluorescence under 365 nm excitation. Simultaneously, o-phenol-benzoxazole and the reaction product (lithium o-phenol-benzoxazole) were characterized, and their 1H NMR spectra and 1H NMR spectra of o-phenol-benzoxazole are shown below. Figure 3 As shown, by Figure 3 It can be seen that after the reaction, the phenolic hydroxyl peak at a chemical shift of 11.2 ppm disappears. The specific reaction equation can be expressed as follows:

[0080]

[0081] Furthermore, fluorescence micrographs of a solution of o-phenol-benzoxazole in ether (concentration: 3.0 mg / mL) after contact with lithium acetate, lithium carbonate, lithium fluoride, and elemental lithium (see [link to image]). Figure 4 ) and fluorescence spectra (see Figure 5 As can be seen, the molecular structure of o-phenol benzoxazole remains unchanged after reacting with inorganic lithium salts, and it can still maintain its intrinsic yellow fluorescence emission (fluorescence wavelength of 533 nm). It can also visualize the crystal morphology of lithium acetate, the powder morphology of lithium carbonate, and the particulate morphology of lithium fluoride. However, after reacting with lithium metal, the fluorescence of o-phenol benzoxazole shifts from blue to bright purple (fluorescence wavelength of 411 nm), and it still has the function of interface imaging.

[0082] Combination Figures 1 to 5 Analysis shows that lithium metal, uneven lithium deposition, and lithium dendrites exhibit bright purple fluorescence, while byproducts (lithium acetate, lithium carbonate, lithium fluoride, etc.), SIE films, and dead lithium surrounded by byproducts exhibit yellow fluorescence. The two fluorescence signals are significantly different and can be directly observed with the naked eye. The intensity of the bright purple and yellow fluorescence can reflect the degree of uneven lithium deposition or lithium dendrite formation, and the degree of byproduct accumulation in different regions. Furthermore, fluorescence spectroscopy can determine that the bright purple fluorescence of lithium metal, uneven lithium deposition, and lithium dendrites is around 411 nm, while the yellow fluorescence of byproducts (lithium acetate, lithium carbonate, lithium fluoride, etc.), SIE films, and dead lithium surrounded by byproducts is around 533 nm. The fluorescence intensity can be measured to semi-quantitatively analyze the degree of uneven lithium deposition or lithium dendrite formation, and the degree of byproduct accumulation.

[0083] When the battery is charged and discharged with different numbers of cycles and different charge and discharge currents, the aforementioned steps can be applied to visualize and semi-quantitatively analyze the battery conditions under different conditions. Furthermore, a valuable scientific framework can be established between the detection of deposited lithium, byproducts, lithium dendrites, dead lithium, and solid electrolyte interfacial films on the lithium metal anode surface and various cycling conditions.

[0084] Stability test

[0085] The fluorescence intensity at 533 nm was measured using a fluorescence spectrometer after continuous irradiation of an ether solution of o-phenol-benzoxazole under a 365 nm UV lamp for one hour. After directly immersing a lithium metal sheet in the solution for reaction, the product solution (lithium salt of o-phenol-benzoxazole) was continuously irradiated under a 365 nm UV lamp for one hour, and the fluorescence intensity at 411 nm was measured using a fluorescence spectrometer. The results are as follows: Figure 6 As shown.

[0086] Depend on Figure 6 It was found that the fluorescence intensity of the ether solution of o-phenol-benzoxazole remained at 96.4% at 533 nm after one hour of continuous irradiation with a 365 nm UV lamp, while the fluorescence intensity of the product solution (lithium o-phenol-benzoxazole) remained at 62.3% at 411 nm after one hour of continuous irradiation with a 365 nm UV lamp. Therefore, the o-phenol-benzoxazole used in this application as a probe exhibits excellent stability for the detection of lithium metal anodes.

[0087] 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.

[0088] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection 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 scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. Application of a benzoxazole compound as a probe in the detection of a lithium metal negative electrode, characterized in that, The benzoxazole compounds have the structural formula shown in formula (1): （1） In formula (1), R1 to R8 are each independently selected from one or more of the following groups: hydrogen atom, alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroalkyl, heterocyclic, heteroaryl, amino, nitro, cyano, isocyano, halogen, alkylene, alkenylene, alkynyl, formyl, and ester. 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 lithium metal anode surface.

2. Use of the benzoxazole compound according to claim 1 as a probe in the detection of lithium metal negative electrodes, characterized in that, R1 to R8 are each independently selected from one or more of the following groups: hydrogen atom, triphenylamine group, nitro group, and maleimide group.

3. Use of the benzoxazole compound according to claim 1 as a probe in the detection of lithium metal negative electrodes, characterized in that, The benzoxazole compounds are selected from the structures described below: 。 4. Use of the benzoxazole compound according to claim 1 as a probe in the detection of a lithium metal negative electrode, characterized by, The byproducts include one or more of lithium fluoride, lithium chloride, lithium acetate, lithium carbonate, lithium hydroxide, lithium oxide, and lithium alkoxide.

5. The use of the benzoxazole compound according to any one of claims 1 to 4 as a probe in the detection of a lithium metal negative electrode, characterized in that, The lithium metal anode is the lithium metal anode in the lithium metal battery; the lithium metal battery is a lithium-oxygen battery, a lithium-sulfur battery, a lithium-oxide battery, a lithium-air battery, or a lithium-lithium battery.

6. A method of detecting a lithium metal anode, characterized by, Includes the following steps: Probe solutions are prepared by dissolving benzoxazole compounds in organic solvents; The probe solution is brought into contact with the surface of the lithium metal anode to be tested. After the organic solvent has evaporated to dryness, the analysis is performed under excitation light irradiation. The benzoxazole compounds have the structural formula shown in formula (1): （1） In formula (1), R1 to R8 are each independently selected from one or more of the following groups: hydrogen atom, alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroalkyl, heterocyclic, heteroaryl, amino, nitro, cyano, isocyano, halogen, alkylene, alkenylene, alkynyl, formyl, and ester. The detection items of the detection method include one or more of the following: deposited lithium, by-products, lithium dendrites, dead lithium, and solid electrolyte interface film on the surface of lithium metal anode.

7. The method of claim 6, wherein the detecting of the lithium metal anode is characterized by, The benzoxazole compounds are selected from the structures described below: 。 8. The method of claim 6, wherein the detecting of the lithium metal anode is characterized by, The lithium metal anode is the lithium metal anode in the lithium metal battery; the lithium metal battery is a lithium-oxygen battery, a lithium-sulfur battery, a lithium-oxide battery, a lithium-air battery, or a lithium-lithium battery.

9. The method of detecting a lithium metal anode according to any one of claims 6-8, wherein, The analytical steps include: visually observing the fluorescence on the surface of the lithium metal anode to be tested and / or using a fluorescence spectrometer to measure the fluorescence wavelength and fluorescence intensity.

10. The method of detecting a lithium metal negative electrode according to any one of claims 6 to 8, characterized in that, The concentration of benzoxazole compounds in the probe solution is 1~10 mg / mL.

11. The method of detecting a lithium metal anode according to any one of claims 6 to 8, wherein The concentration of benzoxazole compounds in the probe solution is 2 mg / mL to 4 mg / mL.

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