Non-interpenetrating three-dimensional covalent organic framework material, application thereof, lithium metal negative electrode coated with protective layer and lithium metal-based battery

Abstract

The invention belongs to the technical field of lithium batteries, and discloses a non-interpenetrating three-dimensional covalent organic framework material, application, a lithium metal negative electrode coated with a protective layer and a lithium metal-based battery. The non-interpenetrating three-dimensional covalent organic framework material is prepared from a monomer 1 containing more than or equal to 4 ethyoxyl repeating units and aldehyde groups and a monomer 2 containing amino groups through a Schiff base reaction under the conditions of a regulator, a first organic solvent and a catalyst. The non-interpenetrating three-dimensional COF material disclosed by the invention has the advantages of more sufficient exposure of active sites, higher stability of a molecular skeleton structure, easiness in regulation and control of pore size and space structure and the like. The artificial solid electrolyte interface layer based on the non-interpenetrating three-dimensional COF is a leading-edge normal form of lithium negative electrode interface engineering, uniform deposition of Li < + > can be more effectively achieved, growth of lithium dendrites is effectively inhibited, and a promising solution is provided for development of a high-performance lithium metal battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium batteries, and more particularly, relates to a non-interpenetrated three-dimensional covalent organic framework material and application and a lithium metal anode and a lithium metal-based battery with a protective layer. BACKGROUND

[0002] Since the 1970s, the invention of lithium-ion batteries has been a major breakthrough in the history of rechargeable batteries. Lithium-ion batteries have completely changed the landscape of portable electronic products, electric vehicles and energy storage systems, and have promoted the widespread application of portable electronic devices and electric vehicles. Compared with the last generation of widely used lead-acid batteries, lithium-ion batteries have made significant progress in energy density and size compactness, and these advantages have ensured that it is still the preferred power source for most mobile electronic devices. However, with the rapid expansion of the market for portable electronic devices and electric vehicles, traditional lithium-ion batteries with graphite anodes have been unable to meet the growing demand. In contrast, lithium metal has attracted much attention due to its ultra-high theoretical capacity (3860 mAh·g -1 ) and is considered an ideal electrode for the next generation of high-energy-density batteries.

[0003] Lithium metal is a highly potential battery anode material due to its intrinsic properties and exhibits significant application value in the field of energy storage. However, the inherent high reactivity of lithium metal leads to complex electrochemical behavior at the electrode / electrolyte interface, with dynamic instability of the solid-state electrolyte interface layer (SEI) being particularly prominent. The non-uniformity of this interface layer triggers continuous interfacial side reactions, leading to irreversible consumption of active lithium and electrolyte; at the same time, the anisotropic growth of lithium dendrites easily penetrates the separator, leading to internal short circuits of the battery and causing safety hazards. The above interface problems not only severely restrict the practical application of lithium metal batteries, but also become a key technical bottleneck hindering the practical application process of lithium metal batteries.

[0004] Current strategies to protect lithium metal anodes include:

[0005] 1) Optimizing electrolyte composition, optimizing the original SEI by adding inhibitors or catalysts to extend the cycle life of the battery;

[0006] 2) Three-dimensional current collector to reduce local current density and guide uniform deposition of lithium metal;

[0007] 3) Modification of the separator to accelerate ion migration and inhibit the continuous growth of lithium dendrites through surface modification;

[0008] 4) Artificial SEI layer, using artificial protective layer to inhibit the continuous reaction between lithium metal and electrolyte;

[0009] 5) Solid-state electrolyte has non-flammable characteristics and excellent mechanical strength, which can inhibit the growth and penetration of lithium dendrites.

[0010] In addition, in recent years, COF has shown excellent Li + transport and lithium deposition regulation ability, but conventional layered two-dimensional COF (2D-COF) has a π-π stacking structure between layers, which limits the full exposure of active sites, reduces the utilization rate, and inhibits the performance of the electrochemical performance. In contrast, three-dimensional COF (3D-COF) with full covalent bonding has a stable full interconnection network structure and high porosity, which can significantly improve the channel utilization, increase the Li + flux and relieve the volume expansion of the electrode. However, traditional 3D-COF often has a self-interpenetrating framework structure, and the interpenetrating part of the active site is shielded, thereby weakening the charge transport dynamics and limiting its function. Therefore, the reasonable design of 3D-COF with low interpenetration or non-interpenetration structure for constructing an efficient charge regulation interface layer is an important research direction to realize high-energy density lithium metal batteries. SUMMARY

[0011] The purpose of the present application is to provide a non-interpenetrating three-dimensional covalent organic framework material and application and a coated lithium metal anode and lithium metal-based battery in combination with the prior art. The non-interpenetrating three-dimensional COF material of the present application has the advantages of more fully exposed active sites, higher stability of molecular framework structure, and easy regulation of pore size and spatial structure. The artificial solid-state electrolyte interface layer based on the non-interpenetrating three-dimensional COF of the present application is a frontier paradigm of lithium anode interface engineering, which can more effectively realize the uniform deposition of Li + and effectively inhibit the growth of lithium dendrites, providing a promising solution for the development of high-performance lithium metal batteries.

[0012] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a non-interpenetrating three-dimensional covalent organic framework material, which is prepared by Schiff base reaction of monomer 1 containing ≥4 ethoxy repeating units and aldehyde groups and monomer 2 containing amino groups under the condition of adjusting agent, first organic solvent and catalyst.

[0013] In the present application, the non-interpenetrating three-dimensional COF material with a regular octahedral structure is prepared by Schiff base reaction of monomer 1 containing ≥4 ethoxy repeating units and aldehyde groups and monomer 2 containing amino groups, as shown in Figure 1 、 2b The non-interpenetrating three-dimensional COF material of the present application is highly concerned due to its high structural stability, high porosity and easy regulation of spatial structure.

[0014] As shown in Figure 2aThe non-interpenetrated three-dimensional COF material of the present application has a completely interconnected network structure system, which is different from the stacking mode of two-dimensional materials. For the non-interpenetrated three-dimensional COF material of the present application, the three-dimensional completely interconnected network structure provides a large number of continuous pores, significantly improves the channel utilization, plays an important role in increasing the lithium ion flux and relieving the volume expansion of the electrode, and the completely interconnected structure can provide more exposed lithiumophilic active sites. Therefore, the non-interpenetrated three-dimensional COF material of the present application can be used as an artificial solid-state electrolyte interface film (SEI) to realize long-term stable cycling of lithium metal batteries.

[0015] In addition, the non-interpenetrated three-dimensional COF material prepared by the present application has a large number of -C=N- groups (formed by the Schiff base reaction of the aldehyde group in the monomer 1 containing ≥4 ethoxy repeating units and aldehyde group and the amino group in the monomer 2 containing amino group) and -O- groups, which have a strong attraction to lithium ions, promote the uniform deposition of metal lithium, and relieve the occurrence of electrode interface side reactions.

[0016] Meanwhile, the non-interpenetrated three-dimensional COF material of the present application has an ether chain structure based on the -O- group. The linear long ether chain structure of the present application has a steric hindrance effect on the one hand, effectively inhibiting the interpenetration of the structural framework, and on the other hand, the -O- groups are distributed on the ether chain, significantly increasing the lithiumophilic active sites in the molecular structure, which can accelerate lithium ion migration through inter-chain transmission, increase lithium ion migration channels, and significantly enhance the charge transfer kinetics within the molecule.

[0017] According to the present application, preferably, the monomer 1 containing ≥4 ethoxy repeating units and aldehyde group is 2,5-bis(2-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}ethoxy) benzene-1,4-dialdehyde (CAS No.: 1246398-04-8).

[0018] In the present application, when the monomer 1 containing ≥4 ethoxy repeating units and aldehyde group is 2,5-bis(2-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}ethoxy) benzene-1,4-dialdehyde, the preparation method comprises: mixing and stirring the monomer 3, the monomer 4, the second organic solvent and the base and performing the Williamson reaction, and after the reaction is completed, performing extraction and purification (such as using column chromatography) to obtain the 2,5-bis(2-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}ethoxy) benzene-1,4-dialdehyde.

[0019] The monomer 3 is triethylene glycol 2-bromoethyl methyl ether;

[0020] The monomer 4 is 2,5-dihydroxy benzene-1,4-dialdehyde;

[0021] The molar ratio of the monomer 3 to the monomer 4 is 1:(1-2);

[0022] the second organic solvent is N,N-dimethylformamide;

[0023] the base is anhydrous potassium carbonate;

[0024] the Williamson reaction is carried out under a nitrogen atmosphere, at a temperature of 60-90℃, for a time of 8-12h.

[0025] According to the present application, preferably, the amino-containing monomer 2 is at least one of tetrakis(4-aminophenyl)methane (CAS No.: 60532-63-0), tetra-(4-aminophenyl)ethylene (CAS No.: 78525-34-5) and 1,3,5,7-tetraaminoadamantane (CAS No.: 16004-77-6).

[0026] According to the present application, preferably, the molar ratio of the monomer 1 containing ≥4 ethoxyl repeat units and aldehyde group and the amino-containing monomer 2 is 1:(1-2).

[0027] According to the present application, preferably, the modulator is aniline, the molar ratio of the monomer 1 containing ≥4 ethoxyl repeat units and aldehyde group and the modulator is 1:(1-6). In the present application, the modulator is used to adjust the rate of Schiff base reaction, so as to ensure that the non-interpenetrated three-dimensional covalent organic framework material is obtained.

[0028] According to the present application, preferably, the first organic solvent is at least one of 1,4-dioxane, anhydrous ethanol and N,N-dimethylacetamide.

[0029] According to the present application, preferably, the catalyst is aqueous acetic acid, the concentration of the aqueous acetic acid is 3-17.5 mol / L, and the molar ratio of the amino-containing monomer 2 and acetic acid is 1:(200-600).

[0030] According to the present application, preferably, the temperature of the Schiff base reaction is 15-30℃, and the time is 24-96h.

[0031] According to the present application, preferably, the preparation method of the non-interpenetrated three-dimensional covalent organic framework material comprises: mixing and ultrasonic dispersing the monomer 1 containing ≥4 ethoxyl repeat units and aldehyde group, the amino-containing monomer 2, the modulator and the first organic solvent, adding the catalyst, carrying out the Schiff base reaction, and obtaining the non-interpenetrated three-dimensional covalent organic framework material through centrifugation, washing and drying.

[0032] In the present application, the solvent used for washing is an ether and / or an alcohol solvent.

[0033] According to the application, preferably, the operating conditions of the ultrasonic dispersion include that the temperature of the ultrasonic dispersion is kept at 15-30 DEG C for 5-30 min.

[0034] The second aspect of the application provides application of the non-interpenetrated three-dimensional covalent organic framework material in preparation of a protective layer of a lithium metal negative electrode.

[0035] The third aspect of the application provides a lithium metal negative electrode coated with a protective layer, wherein the protective layer is prepared by mixing an adhesive, a protective solvent and the non-interpenetrated three-dimensional covalent organic framework material into a protective dispersion liquid, coating the protective dispersion liquid on the surface of the lithium metal negative electrode and drying.

[0036] According to the application, preferably, the adhesive is at least one of polyvinylidene fluoride, butadiene rubber emulsion and carboxymethyl cellulose.

[0037] According to the application, preferably, the protective solvent is at least one of anhydrous acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide and 1,4-dioxane.

[0038] According to the application, preferably, the mass ratio of the non-interpenetrated three-dimensional covalent organic framework material, the adhesive and the protective solvent is 1:(0.1-0.4):(80-120); and the concentration of the non-interpenetrated three-dimensional covalent organic framework material in the protective dispersion liquid is 1-2 wt%.

[0039] According to the application, preferably, the coating amount of the protective dispersion liquid on the surface of the lithium metal negative electrode is 1-60 muL·cm -2 .

[0040] According to the application, preferably, the coating method is at least one of blade coating, spray coating, spin coating and drop coating.

[0041] According to the application, preferably, the drying temperature is 15-35 DEG C and the drying time is 3-12 h.

[0042] The fourth aspect of the application provides a lithium metal-based battery, wherein the negative electrode of the battery is the lithium metal negative electrode coated with a protective layer.

[0043] According to the application, preferably, the electrolyte of the battery is at least one of a lithium salt-containing carbonate electrolyte, a lithium salt-containing ether electrolyte, a lithium salt-containing sulfone electrolyte and a lithium salt-containing carboxylate electrolyte; and the lithium salt is at least one of lithium nitrate, lithium bis-trifluoromethanesulfonimide, lithium perchlorate, lithium hexafluorophosphate and lithium hexafluoroarsenate.

[0044] According to the application, preferably, the lithium metal-based battery is a lithium-lithium symmetric battery, a lithium-copper half-cell, a lithium-ion battery, a lithium solid-state battery, a lithium-sulfur battery, a lithium-oxygen battery, a lithium-nitrogen battery or a lithium-carbon dioxide battery.

[0045] The beneficial effects of the technical solution of the present application are as follows: The present application adopts steric hindrance occupation principle, proposes a synthesis strategy of pre-modified 3D-COF with ethoxy chain segment to construct non-interpenetrated structure, effectively inhibits the interpenetration degree, maximizes the exposure of lithiumophilic sites, and uniformly coats the lithium negative electrode surface, significantly improves the interface electrochemical stability of the lithium metal electrode.

[0046] The present application utilizes the steric hindrance exclusion principle, covalently pre-grafting linear methoxy polyethylene glycol segments to aldehyde ligands, and then synthesizing non-interpenetrated 3D-COF materials through Schiff base condensation reaction with amino ligands with diamond-shaped tetrahedral structure. Compared with 2D-COF with π-π stacking, the all-covalent bond connection system and tetrahedral amino ligand structure of non-interpenetrated 3D-COF on the one hand endow the molecular structure with high stability, and on the other hand, the non-interpenetrated structure promotes the full exposure of lithiumophilic active sites, and the connected ion conduction network maximizes the mass transfer utilization, greatly promotes the interface charge transfer and reaction kinetics. In addition, grafting of methoxy polyethylene glycol segments with different chain lengths can flexibly regulate the pore size of the 3D-COF molecular structure, providing sufficient pores and space for lithium ion conduction and lithium deposition. Finally, the present application is synthesized at room temperature, which has the advantages of mild conditions, simple steps, easy-to-obtain raw materials, green environmental protection and suitability for industrial promotion.

[0047] The present application coats non-interpenetrated three-dimensional COF materials as an artificial protective layer on the surface of the lithium metal negative electrode, on the one hand, realizes all-around Li + flux, dissipates Li + concentration gradient and suppresses electrode interface polarization, on the other hand, fully exposed lithiumophilic sites improve lithium ion migration number and reduce migration energy barrier. The test batteries assembled by modifying the electrode all exhibit excellent rate performance and long-term cycle stability under high current density, realize uniform Li + deposition and inhibit dendrite growth, providing a promising solution for the development of high-performance lithium metal batteries.

[0048] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0049] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the several views, in which exemplary embodiments of the present application are shown.

[0050] Figure 1 A structure diagram of a non-interpenetrated three-dimensional covalent organic framework material provided by the embodiment 1 of the present application is shown.

[0051] Figure 2a A structure diagram of the two-dimensional COF material of the comparative example 1 and a structure diagram of a non-interpenetrated three-dimensional covalent organic framework material provided by the embodiment 1 of the present application are shown. Figure 2a 2D-COF for the COF material of the comparative example 1; Figure 2b 3D-COF for the non-interpenetrated three-dimensional covalent organic framework material of the embodiment 1.

[0052] Figure 3 An XRD diagram (Intensity is intensity, 2θ (degree) is test angle) of a non-interpenetrated three-dimensional covalent organic framework material provided by the embodiment 1 of the present application is shown.

[0053] Figure 4 An FT-IR diagram (Transmittance is light transmittance, Wavenumbers is wave number) of a non-interpenetrated three-dimensional covalent organic framework material provided by the embodiment 1 of the present application is shown.

[0054] Figure 5 An SEM diagram of a non-interpenetrated three-dimensional covalent organic framework material provided by the embodiment 1 of the present application is shown.

[0055] Figure 6 A TEM diagram of a non-interpenetrated three-dimensional covalent organic framework material provided by the embodiment 1 of the present application is shown.

[0056] Figure 7 A galvanostatic charge-discharge test result of a lithium metal-based battery provided by the embodiment 2 of the present application and a battery of the control group 1 is shown (Bare Li is a lithium-lithium symmetric battery (control group 1) assembled by a blank lithium metal anode without protection; “TDP4-COF@Li” is a lithium-lithium symmetric battery assembled by a lithium metal anode protected by the octahedral three-dimensional COFs material prepared by the embodiment 1 of the present application; Voltage is voltage, Time is time).

[0057] Figure 8 A coulombic efficiency performance diagram of a lithium metal-based battery provided by the embodiment 3 of the present application and a battery of the control group 2 is shown (Bare Cu is a lithium-copper half battery assembled by a blank lithium metal anode without protection (control group 2); TDP4-COF@Cu is a lithium-copper half battery assembled by a lithium metal anode protected by the octahedral three-dimensional COFs material prepared by the embodiment 1 of the present application; Coulombic Effciency is coulombic efficiency; Cycle number is cycle number).

[0058] Figure 9 An SEM image of the COF material of Inventive Comparative Example 1 is shown.

[0059] Figure 10A A reaction equation for preparing 2,5-bis(2-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}ethoxy)terephthalaldehyde according to the present application is shown.

[0060] Figure 10B A reaction equation for preparing a non-interpenetrated three-dimensional covalent organic framework material provided in Example 1 according to the present application is shown. DETAILED DESCRIPTION

[0061] The preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it is understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0062] In each of the following examples:

[0063] The method for preparing 2,5-bis(2-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}ethoxy)terephthalaldehyde (CAS No.: 1246398-04-8) is as follows: 110 mg of 2,5-dihydroxyterephthalaldehyde and 0.45 mL of triethylene glycol 2-bromoethyl methyl ether are added to a reaction bottle, followed by the addition of 10 mL of N,N-dimethylformamide and 500 mg of anhydrous potassium carbonate, and the reaction is stirred at 80°C under a nitrogen atmosphere for 12 hours. After the reaction is completed, the reaction mixture is diluted with water, extracted by adding a small amount of ethyl acetate several times, and the upper organic phase is collected. The organic phase is dried with anhydrous magnesium sulfate, filtered, and evaporated to concentrate to obtain a crude product. Finally, the crude product is separated and purified using a silica gel chromatographic column to obtain the 2,5-bis(2-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}ethoxy)terephthalaldehyde as a yellow-green oily liquid with a purity of 95%, and the specific reaction equation is as follows: Figure 10A .

[0064] Tetrakis(4-aminophenyl)methane is purchased from Shanghai McLean Biochemical Science and Technology Co., Ltd.;

[0065] Aniline is purchased from Shanghai McLean Biochemical Science and Technology Co., Ltd.

[0066] Example 1

[0067] This embodiment provides a non-penetrating three-dimensional covalent organic framework material, which is prepared by a Schiff base reaction of 2,5-bis(2-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}ethoxy)terephthalaldehyde and tetra(4-aminophenyl)methane in the presence of aniline, 1,4-dioxane and an aqueous solution of acetic acid.

[0068] The Schiff base reaction comprises: in a glass bottle, dissolving 34.3 mg of 2,5-bis(2-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}ethoxy)terephthalaldehyde and 21 μL of aniline in 0.3 mL of 1,4-dioxane, and ultrasonically dispersing the solution at 25 °C for 5 min, yielding solution 1. Simultaneously, in another glass bottle, dissolving 12 mg of tetra(4-aminophenyl)methane in 0.3 mL of 1,4-dioxane, and ultrasonically dispersing the solution under the same conditions, yielding solution 2. All of solution 2 is transferred to solution 1 and ultrasonically dispersed at 25 °C for 5 min, yielding a mixture. 354 μL of 6M acetic acid aqueous solution is added to the mixture. Upon addition of acetic acid, a yellow solid immediately precipitates, yielding a suspension. The suspension is stored at room temperature (25 °C) for 3 days. Three days later, the reaction solution was removed, and the yellow powder was collected by centrifugation and washed with 1,4-dioxane, acetone, and n-hexane. Finally, the washed product was vacuum dried overnight at 70°C to obtain a yellow-green powder, which is the non-penetrating three-dimensional covalent organic framework material. The specific reaction equation is as follows: Figure 10B .

[0069] like Figure 3 The image shown is the XRD pattern of the non-penetrating three-dimensional covalent organic framework material prepared in this embodiment. Figure 3 It can be seen that there is a strong diffraction peak at 2θ=4.3°, corresponding to the (101) crystal plane, and only a single peak appears.

[0070] like Figure 4 The image shown is the FT-IR spectrum of the non-interpenetrating three-dimensional covalent organic framework material prepared in this embodiment. Figure 4 As can be seen from the data, the amino groups (-NH2, 3392.1 cm⁻¹) of the two monomers (Dha-PEG4 as monomer 1 and TAPM as monomer 2) are... -1 and 3153.8cm -1 ) and aldehyde group (-CHO, 1678.2cm) -1 The stretching vibration peak disappeared, and at the same time, the peak at 1610 cm⁻¹ disappeared. -1 The presence of a distinct imine bond (-C=N-) stretching vibration peak indicates that the non-interpenetrating three-dimensional covalent organic framework material of this embodiment was successfully synthesized.

[0071] like Figure 5 andFigure 6 SEM and TEM images of the non-interpenetrated three-dimensional covalent organic framework material prepared in this embodiment are shown, respectively, from which it can be seen that the non-interpenetrated three-dimensional covalent organic framework material has a regular octahedral structure and a particle size of about 700 nm. Figure 5 and Figure 6 As can be clearly seen from the SEM and TEM images, the non-interpenetrated three-dimensional covalent organic framework material has a regular octahedral structure and a particle size of about 700 nm.

[0072] Example 2

[0073] This embodiment provides a lithium metal negative electrode coated with a protective layer, which uses an artificial protective layer to protect the lithium metal negative electrode.

[0074] The binder polyvinylidene fluoride, the protective solvent N-methyl pyrrolidone, and the non-interpenetrated three-dimensional covalent organic framework material described in Example 1 are mixed into a protective dispersion liquid; the mass ratio of the non-interpenetrated three-dimensional covalent organic framework material, the binder, and the protective solvent is 1:0.1:100; the concentration of the non-interpenetrated three-dimensional covalent organic framework material in the protective dispersion liquid is 1 wt%;

[0075] 45 μL of the protective dispersion liquid is taken out using a pipette and is dropped onto the surface of a lithium metal negative electrode with a diameter of 16 mm in three times (the coating amount is 2.8152 μL·cm -2 ), and drying treatment is performed under vacuum at room temperature of 25℃ (the temperature of the drying treatment is 25℃, and the time is 8 h), to obtain the lithium metal negative electrode coated with a protective layer.

[0076] This embodiment also provides a lithium metal-based battery, in particular:

[0077] The lithium metal negative electrode coated with a protective layer of this embodiment is assembled into a lithium-lithium symmetric battery, a polypropylene separator is used, the electrolyte is LiTFSI / DME-DOL (a mixed solution is formed by dimethyl ether (DME) and 1,3-dioxolane (DOL) at a volume ratio of 1:1; lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is added to the mixed solution, the concentration of LiTFSI in the electrolyte solution is 1.0 M, anhydrous lithium nitrate is added to the above electrolyte, and the concentration of anhydrous lithium nitrate in the electrolyte solution is 2 wt%), and a CR2032 button cell is assembled.

[0078] Example 3

[0079] This embodiment provides a lithium metal-based battery, and the difference between this embodiment and Example 2 is only that this embodiment is a lithium-copper half-cell.

[0080] Comparative Example 1

[0081] This comparative example provides a preparation method of a three-dimensional spherical covalent organic framework material:

[0082] Take 938.3 mg of 1,3,5-tris(4-aminophenyl)benzene and 776 mg of 2,5-dimethoxy-p-phenylenediformaldehyde, add 1000 mL of acetonitrile (AR, 99.0%), ultrasonic mixing, add 50 mL of glacial acetic acid (17.5M), stir at room temperature 25℃ for 12h, after the reaction is completed, add 40μL of benzaldehyde to quench the reaction, wash with acetonitrile after 1h, centrifuge to collect the solid material, wash with acetonitrile three times, and dry at 120℃ overnight to obtain a yellow solid powder, which is a three-dimensional spherical COFs material, and the specific reaction equation is as follows:

[0083] As can be seen from Figure 9 , the three-dimensional spherical COFs material prepared in Comparative Example 1 is a three-dimensional spherical morphology in macroscopic view. As can be seen from Figure 2a , the three-dimensional spherical COFs material prepared in Comparative Example 1 still belongs to a two-dimensional layered COF (2D-COF) in molecular structure, the interlayer is π-π stacking, the embedding of the lithiumophilic site is limited, and there is only ether bond lithiumophilic structure, and the lithiumophilic site is insufficient, while Figure 2b The non-interpenetrated three-dimensional covalent organic framework material of the present application belongs to a three-dimensional framework (3D-COF) in molecular structure, is fully covalently linked, the channel is open and through, and the pore and lithiumophilic site are fully exposed, so that the non-interpenetrated three-dimensional covalent organic framework material of Example 1 of the present application has a congenital deficiency in structure compared with Comparative Example 1. The structural defects of 2D-COF not only reduce the transmission efficiency of Li + , but also limit the role of COF material in inhibiting lithium dendrite and relieving volume expansion. Unlike 2D-COF, 3D-COF has a fully interconnected network structure system. This three-dimensional network structure provides a large number of continuous pores, significantly improves the channel utilization rate, and is beneficial to the rapid transmission of Li + and the relief of volume expansion. In addition, the open structure of 3D-COF fully exposes the lithiumophilic site, which can accelerate the migration of Li + in the interfacial double layer, further optimize the lithium deposition behavior, and thus synergistically inhibit the electrode volume expansion and dendrite penetration problem. In addition, Figure 9 As shown in the spherical structure 2D-COF material as an artificial SEI layer verification process, lithium deposition will be affected by conformal growth, i.e. lithium metal deposition preferentially grows along the spherical surface to form a lithium deposition layer of many spherical particles, which is more likely to induce the generation of lithium dendrites. In contrast Figure 5The 3D-COF material of the octahedral morphology of the application shown has a more compact packing degree, and lithium ions are more likely to grow along the particle plane during lithium deposition, thereby reducing the trend of lithium dendrite formation to a certain extent. Therefore, from the perspectives of micro-molecular structure, lithiumophilic site transmission, particle size and morphology, and the like, the non-interpenetrated 3D-COF material proposed in the application has more distinct progressiveness as a lithium negative electrode artificial SEI layer for regulating the stability of the lithium metal interface.

[0084] Test Example 1

[0085] In this test example, the battery device assembled according to Example 2 (a blank lithium metal negative electrode without protection was set as a control group 1 (Bare Li), and a CR2032 button cell was assembled according to the method of Example 2) was placed in a constant temperature box at 25°C for 8 hours, and then constant current charge-discharge test was performed on a blue light test system (test conditions included: current density was 20 mA·cm -2 , and discharge depth was 10 mAh·cm -2 ). The test results are as follows:

[0086] As shown in Figure 7 , it can be seen that the deposition / extraction behavior of the lithium metal battery modified by the non-interpenetrated three-dimensional covalent organic framework material assembled according to Example 2 and the battery of the control group 1 showed significant differences; the modified battery of Example 2 showed excellent cycle stability, and the cycle life was more than 4600 hours, and the polarization voltage was stably maintained at about 32 mV without obvious fluctuation; the control group 1 showed a lower voltage in the initial stage, but the voltage gradually increased as the cycle proceeded. After 600 hours of cycle, the voltage fluctuated sharply, and the battery finally short-circuited after 1000 hours of cycle.

[0087] Test Example 2

[0088] In this test example, the battery device assembled according to Example 3 (a blank lithium metal negative electrode without protection was set as a control group 2 (Bare Cu), and a CR2032 button cell was assembled according to the method of Example 3) was subjected to constant current charge-discharge cycle test (test conditions included: current density was 1 mA·cm -2 , and discharge depth was 1 mAh·cm -2 ). The test results are as follows:

[0089] As shown in Figure 8As shown, the lithium metal battery modified by the non-interpenetrated three-dimensional covalent organic framework material prepared in Example 1 (Example 3) has a lower nucleation overpotential, and maintains a coulombic efficiency of more than 95% after 100 cycles, while the lithium metal battery of Control Group 2 has poorer cycle stability. For the lithium-copper battery without protection by the non-interpenetrated three-dimensional covalent organic framework material (Bare Cu), the coulombic efficiency begins to decrease when cycled to 50 cycles, and falls to less than 90% after 72 cycles, which is much less than the coulombic efficiency of the lithium metal battery protected by the COFs material prepared in Example 1.

[0090] In summary, the non-interpenetrated three-dimensional covalent organic framework material with a regular octahedral structure prepared from the Schiff base reaction of monomer 1 containing ≥4 ethoxy repeat units and an aldehyde group and monomer 2 containing an amino group protects the lithium metal anode, greatly reduces the occurrence of lithium metal interface side reactions, makes the morphology of lithium deposition more flat, greatly slows the growth of lithium dendrites, and significantly improves the electrochemical performance of the lithium metal battery. In addition, the non-interpenetrated three-dimensional organic framework network structure prepared by full covalent bond crosslinking gives it higher rigidity and structural stability, provides higher mechanical strength in inhibiting the penetration of lithium dendrites through the SEI layer and avoiding the rupture and failure of the SEI. The non-interpenetrated three-dimensional covalent organic framework material provided by the present application opens up a new way for the structural design and optimization of high-performance lithium metal batteries, and has a broad application prospect.

[0091] The above has described various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A non-interpenetrating three-dimensional covalent organic framework material, characterized in that, The non-penetrating three-dimensional covalent organic framework material is prepared by a Schiff base reaction of monomer 1 containing ≥4 ethoxy repeating units and aldehyde groups and monomer 2 containing amino groups under the conditions of a regulator, a first organic solvent and a catalyst.

2. The non-interpenetrating three-dimensional covalent organic framework material according to claim 1, wherein, The monomer 1 containing ≥4 ethoxy repeating units and an aldehyde group is 2,5-bis(2-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}ethoxy)terephthalaldehyde; The amino-containing monomer 2 is at least one selected from tetrakis(4-aminophenyl)methane, tetrakis(4-aminophenyl)ethylene, and 1,3,5,7-tetraaminoadamantane.

3. The non-interpenetrating three-dimensional covalent organic framework material according to claim 1, wherein, The molar ratio of monomer 1 containing ≥4 ethoxy repeating units and aldehyde groups to monomer 2 containing amino groups is 1:(1-2).

4. The non-interpenetrating three-dimensional covalent organic framework material according to claim 1, wherein, The regulator is aniline, and the molar ratio of monomer 1 containing ≥4 ethoxy repeating units and aldehyde groups to the regulator is 1:(1-6); The first organic solvent is at least one of 1,4-dioxane, anhydrous ethanol, and N,N-dimethylacetamide; The catalyst is an aqueous solution of acetic acid, the concentration of which is 3-17.5 mol / L, and the molar ratio of the amino-containing monomer 2 to acetic acid is 1:(200-600). The Schiff base reaction is carried out at a temperature of 15-30℃ for a time of 24-96 hours.

5. The non-interpenetrating three-dimensional covalent organic framework material according to claim 1, wherein, The preparation method of the non-penetrating three-dimensional covalent organic framework material includes: mixing and ultrasonically dispersing the monomer 1 containing ≥4 ethoxy repeating units and aldehyde groups, the amino-containing monomer 2, the regulator and the first organic solvent, adding the catalyst, carrying out the Schiff base reaction, and centrifuging, washing and drying to obtain the non-penetrating three-dimensional covalent organic framework material. Preferably, the ultrasonic dispersion operating conditions include: maintaining the ultrasonic dispersion temperature at 15-30℃ for 5-30 minutes.

6. The application of the non-penetrating three-dimensional covalent organic framework material according to any one of claims 1-5 in the preparation of a lithium metal anode protective layer.

7. A lithium metal anode with a protective coating, characterized in that, The protective layer is prepared by mixing an adhesive, a protective solvent, and the non-penetrating three-dimensional covalent organic framework material as described in any one of claims 1-5 into a protective dispersion, coating the protective dispersion onto the surface of a lithium metal anode, and then drying it.

8. The lithium metal anode with a protective coating according to claim 7, wherein, The adhesive is at least one of polyvinylidene fluoride, styrene-butadiene rubber latex and carboxymethyl cellulose; The protective solvent is at least one of anhydrous acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide and 1,4-dioxane; The mass ratio of the non-penetrating three-dimensional covalent organic framework material, the binder, and the protective solvent is 1:(0.1-0.4):(80-120); the concentration of the non-penetrating three-dimensional covalent organic framework material in the protective dispersion is 1-2 wt%. The protective dispersion is coated on the surface of the lithium metal anode at an amount of 1-60 μL·cm. -2 ; The coating method is at least one of scraping, spraying, spin coating and drip coating; The drying process is carried out at a temperature of 15-35℃ for 3-12 hours.

9. A lithium metal-based battery, characterized in that, The negative electrode of the battery is a lithium metal negative electrode with a protective coating as described in claim 7 or 8.

10. The lithium metal-based battery according to claim 9, wherein, The electrolyte of the battery is at least one of lithium salt carbonate electrolyte, lithium salt ether electrolyte, lithium salt sulfone electrolyte, and lithium salt carboxylic acid ester electrolyte; the lithium salt is at least one of lithium nitrate, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, and lithium hexafluoroarsenate. The lithium metal-based battery is a lithium-lithium symmetric battery, a lithium-copper half-cell, a lithium-ion battery, a lithium solid-state battery, a lithium-sulfur battery, a lithium-oxygen battery, a lithium-nitrogen battery, or a lithium-carbon dioxide battery.

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