A br-cofs material, a preparation method thereof and a preparation method of a lithium metal battery covalent organic framework material interface film

Abstract

The application discloses a Br-COFs material, a preparation method thereof and a preparation method of a lithium metal battery covalent organic framework material interface film. The Br-COFs material is prepared by dissolving 1,3,5-tri(4-aminophenyl)benzene and 2,5-dibromobenzene-1,4-diformaldehyde in an organic solvent, adding acetic acid dropwise into the solution, stirring the reaction mixture, filtering, washing and drying to obtain the covalent organic framework material; the obtained Br-COFs material is dissolved in an organic solvent together with a PVdF adhesive to obtain a mixed solution, the mixed solution is coated on the surface of a copper foil with a certain thickness, and after the solvent is volatilized, a Br-COFs artificial interface film is formed on the surface of the copper foil electrode. The preparation method is simple, the preparation process is green and environment-friendly, the prepared product has high purity, the structure is controllable, the mechanical strength is high, and the product can be directly used as an artificial interface film of a lithium metal battery, and when the product is used in a Li / Cu battery, excellent stability is exhibited.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of artificial interface film preparation of lithium metal battery, and particularly relates to a preparation method of covalent organic framework material and application thereof in lithium metal battery interface film. BACKGROUND

[0002] With the rapid development of artificial intelligence technology and electronic equipment, and the shortage of fossil resources and the arrival of energy crisis, developing new energy can alleviate energy crisis and meet the demand for energy in various industries. At the same time, energy storage devices also need to accelerate the pace of development to obtain more excellent energy storage properties. Since the commercialization of lithium ion batteries in the 1990s, they have long dominated the energy storage field with their high safety, long cycle life, environmental friendliness and high energy density. Today's hot market of Xiaomi, BYD and Tesla new energy vehicles all use lithium ion batteries. The negative electrode materials of lithium ion batteries mainly include graphite (-372 mAh / g), lithium titanate (-175 mAh / g), metal lithium (-3860 mAh / g), silicon-based alloy (-2500 mAh / g), metal lithium (-3860 mAh / g), tin-based alloy (-850 mAh / g), graphite material is easy to prepare, has good stability and low price but low specific capacity. Lithium titanate material can be discharged at high power and has good stability, but the specific capacity is also low. The specific capacity of silicon-based alloy is high, but the material is prone to volume expansion. The specific capacity of metal lithium is the highest, but the growth of lithium dendrites will cause some safety problems. The specific capacity of tin-based alloy is high, but the stability is poor. In summary, although the negative electrode materials of lithium ion batteries have certain disadvantages, the specific capacity of lithium metal electrode is as high as -3860 mAh / g, and if the problem of lithium dendrite growth can be solved, the lithium metal electrode can greatly improve the energy density of the battery.

[0003] Lithium metal batteries and lithium-ion batteries are similar, both using carbonate, ether, ionic liquid and other solvents as electrolyte solvents. From the development history and current research status of lithium metal batteries, most of the research focuses on obtaining excellent solid electrolyte interface film (SEI) by adjusting the electrolyte components and solvation structure. The excellent solid electrolyte interface film obtained by electrolyte design can also inhibit the growth of lithium dendrites, making the lithium-lithium symmetric battery stable deposition / peeling. However, it is difficult for us to accurately control the thickness and component distribution of the interface film produced by electrolyte decomposition. In order to promote the development of artificial SEI film and achieve the goal of accurately controlling SEI thickness, component, physical / chemical properties, there have been some reports about the synthesis of artificial SEI, such as Xiulin Fan team synthesized a kind of polyimide covalent organic framework (COFs) material and used it as artificial SEI film for lithium metal battery, after coating COFs material, the coulombic efficiency of lithium-copper battery remained above 99% after 400 cycles [Wu X, Zhang S, Xu X, Wen F, Wang H, Chen H, Fan X, Huang N. Lithiophilic Covalent Organic Framework as Anode Coating for High-Performance Lithium Metal Batteries. Angew Chem Int Ed Engl. 2024, 63, e202319355]. Shanlin Qiao team prepared a kind of high crystalline spherical COFs material and used it as SEI film for lithium metal electrode, the lithium metal electrode coated with this material can make lithium ions deposit uniformly and densely, and the lithium-lithium symmetric battery can almost not increase the overpotential after 2400 hours of cycle at a current density of 4mA / cm 2 [Wenbo Wang, Zehua Yang, Yantao Zhang, Aiping Wang, Yunrui Zhang, Liling Chen, Qing Li, Shanlin Qiao, Highly stable lithium metal anode enabled by lithiophilic and spatial-confined spherical-covalent organic framework, Energy Storage Materials, 2022, 46, 374-383]. Xunhui Xiong team synthesized a kind of dynamic gel containing reversible imine groups, which can be used as artificial SEI film protective layer on the surface of lithium metal, the lithium-lithium symmetric battery cycled by the lithium metal electrode treated by the gel can be cycled at a current density of 6mA / cm2 Stable cycling for 3000 hours at current density [Dynamic gel as artificial interphase layer for ultrahigh-rate and large-capacity lithium metal anode, Chen C, Zhang J, Hu B, Liang Q, Xiong X. Dynamic gel as artificial interphase layer for ultrahigh-rate and large-capacity lithium metal anode. Nat Commun. 2023, 14, 4018].

[0004] The preparation methods of COFs materials or other functional materials mainly include chemical vapor deposition (CVD) method, solvothermal synthesis method, mechanical synthesis method, microwave synthesis method, ionothermal synthesis method and hydrothermal synthesis method, etc.

[0005] In this work, the COFs material is synthesized by dissolving 2,5-dibromobenzene-1,4-diformaldehyde and 1,3,5-tris(4-aminophenyl)benzene in an organic solvent and continuously stirring and reacting. The synthesized COFs material and the adhesive PVdF are dissolved in N-methyl pyrrolidone (NMP) according to a certain mass ratio to prepare a slurry. Then, the above slurry is coated on the surface of a copper foil as an artificial solid electrolyte interface film of a lithium metal battery by a traditional battery material coating method. The copper electrode sheet coated with the COFs material prepared is applied to the lithium metal battery for electrochemical performance test. Compared with the traditional solid electrolyte interface film, the material and the artificial interface film prepared by the method are more stable and uniform. SUMMARY

[0006] The purpose of the present application is to prepare a covalent organic framework material that can be stably used as an artificial interface film of a lithium metal battery. The material is spherical, uniform, structurally ordered and does not chemically react with lithium metal and organic electrolyte components, is heat and corrosion resistant, and a copper electrode coated with Br-COFs material can be stably cycled for more than 200 hours when assembled into a half battery in an electrolyte, with better cycle stability than ordinary lithium / copper batteries.

[0007] The present application is realized by the following technical solutions.

[0008] The present application provides a preparation method of a covalent organic framework material for an artificial interface film of a lithium metal battery, which adopts a simple preparation method to obtain spherical COFs materials with uniform size, which are coated on a copper electrode to form a stable and uniform artificial interface film.

[0009] A method for preparing a covalent organic framework material, comprising the following steps:

[0010] Dissolving 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 2,5-dibromobenzene-1,4-diformaldehyde (BBDD) in an organic solvent, and adding acetic acid dropwise to the above solution, continuously stirring the reaction mixture at a suitable temperature for a required time, after the reaction is completed, filtering, washing, and centrifugally separating and drying to obtain Br-COFs.

[0011] Preferably, the specific steps for synthesizing Br-COFs are as follows: mixing 1,3,5-tris(4-aminophenyl)benzene and 2,5-dibromobenzene-1,4-diformaldehyde with an organic solvent in a flat-bottomed flask, magnetically stirring for 10-20 min, then adding acetic acid to the above flask, and stirring the obtained mixture vigorously at 25-40℃ for 20-26 h, and then filtering, washing, and centrifugally separating and drying the reaction solution to obtain Br-COFs.

[0012] Preferably, the organic solvent is one of acetonitrile, acetone, and N,N-dimethylformamide.

[0013] Preferably, the concentration of acetic acid is 16-18 mol / L.

[0014] Preferably, the reaction temperature is 25-40℃, and the time is 20-26 h.

[0015] Preferably, the organic solvent is one of acetonitrile, acetone, and N,N-dimethylformamide.

[0016] Preferably, the washing is centrifugal washing with acetonitrile, acetone, and anhydrous ethanol for 2-3 times in sequence.

[0017] Preferably, the drying is vacuum drying, the drying temperature is 100-150℃, and the time is 6-24 h.

[0018] The Br-COFs material prepared by the above method is spherical with uniform size, the diameter is 960 nm, and the pore size is 3.15 nm.

[0019] Further, the Br-COFs material prepared above is mixed and dispersed in an organic solvent according to a certain proportion with a PVdF adhesive to obtain a uniformly dispersed slurry, and then a Br-COFs film covered Cu electrode is obtained by coating the slurry on the surface of a copper foil according to a conventional coating method and according to a certain thickness.

[0020] Preferably, the proportion of the Br-COFs material and the PVdF adhesive is 8.5:1.5 to 9.5:0.5.

[0021] Preferably, the coating thickness of the Br-COFs interface film is 5-15 microns.

[0022] Preferably, the organic solvent for dispersing the Br-COFs material and the PVdF adhesive is one of N-methylpyrrolidone, dimethyl sulfoxide and N,N-dimethylformamide.

[0023] The Br-COFs material prepared by the present application is uniform and orderly, and the size is about 0.9-1 micron. The Br-COFs material is coated on the surface of a copper electrode as an artificial interface film of a lithium metal battery. Compared with a traditional solid electrolyte interface film, the artificial interface film can make the lithium / copper battery stably cycle for more than 200 hours. The Br-COFs material has great application potential in the field of artificial interface films of lithium metal batteries.

[0024] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0025] (1) The present application first proposes to use the Br-COFs material as an artificial interface film of a lithium metal battery. The Br-COFs material is a spherical particle with a size of 0.9-1 micron, and is rich in Br groups in structure. The pore size is 3.15 nm, which belongs to mesoporous and is beneficial to the diffusion and migration of lithium ions at the interface, thereby improving the dynamic performance of the battery.

[0026] (2) The Br-COFs material prepared by the present application as an artificial interface film of a lithium metal battery does not chemically react with the components of an organic electrolyte and a lithium metal electrode. Compared with a traditional solid electrolyte interface film, the Br-COFs material can improve the cycle stability of the lithium metal battery. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The figure is a synthetic path of the Br-COFs material prepared in Example 1 of the present application, and the molecular structure diagrams of the corresponding reactants and products.

[0028] Figure 2 The figure is a scanning electron microscope image and a particle size distribution diagram of the Br-COFs material prepared in Example 1 of the present application.

[0029] Figure 3 The figure is an infrared characterization diagram of the Br-COFs material prepared in Example 1 of the present application, and the infrared spectra of the reactants TAPB and BBDD obtained after optimization by theoretical calculation.

[0030] Figure 4 The figure is a nitrogen adsorption-desorption curve and a pore size distribution curve diagram of the Br-COFs material prepared in Example 1 of the present application.

[0031] Figure 5 The figure is an X-ray diffraction diagram of the Br-COFs material prepared in Example 1 of the present application.

[0032] Figure 6 Time-voltage performance comparison chart of lithium copper batteries of Example 3 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0033] The specific embodiments of the present application are further described in conjunction with the accompanying drawings and examples, but the embodiments of the present application are not limited thereto.

[0034] Example 1

[0035] Preparation of Br-COFs material, including the following steps:

[0036] First, 30 mg of 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 30 mg of 2,5-dibromobenzene-1,4-diformyl (BBDD) were added to a flask containing 30 mL of acetonitrile. Then the mixture was stirred at room temperature while 1.6 mL of 17.5 mol / L acetic acid was added dropwise to the flask. After stirring for 12 hours, the reaction product was filtered and washed with acetonitrile and acetone in sequence. Finally, Br-COFs powder was obtained after vacuum drying at 120°C overnight.

[0037] 17.5 mol / L acetic acid was added dropwise to the flask. After stirring for 12 hours, the reaction product was filtered and washed with acetonitrile and acetone in sequence. Finally, Br-COFs powder was obtained after vacuum drying at 120°C overnight.

[0038] Example 2

[0039] Preparation of Br-COFs material artificial interface film, including the following steps:

[0040] The Br-COFs material and PVdF binder were dissolved in 1-2 mL of N-methyl pyrrolidone solvent to obtain a mixed slurry at a mass ratio of 9:1 (0.09 g of Br-COFs:0.01 g of PVdF). The slurry was uniformly dispersed using a defoaming machine, and the obtained slurry was coated onto the surface of a copper foil using an automatic coating machine to obtain a coated Br-COFs-Cu electrode. The Br-COFs-Cu electrode was transferred to a 120°C vacuum oven to volatilize the N-methyl pyrrolidone solvent in the electrode.

[0041] Example 3

[0042] The Br-COFs-Cu electrode obtained in step (1) of Example 2 was assembled with a lithium metal electrode to form a Br-COFs-Cu / Li coin-type half-battery, and the electrochemical performance thereof was tested.

[0043] Comparative Example 1

[0044] A Cu / Li coin-type half-battery was assembled using a lithium metal electrode and a common copper electrode using the same electrolyte as in Example 3, and the electrochemical performance thereof was tested.

[0045] Figure 2SEM characterization of the morphology of Br-COFs material, from the figure can be seen that the Br-COFs material is spherical, uniform size, particle size distribution graph shows that the particle size is mostly distributed at about 960nm.

[0046] Figure 3 Br-COFs material is tested by infrared to characterize its structure and composition, Br-COFs material at 1550cm -1 ~1660cm -1 The peak of -C=N appears, which indicates that the Schiff base crosslinking reaction occurs between the amine group of the reactant TAPB and the aldehyde group of BBDD, and only weak -CHO and -NH2 peaks can be detected in the product, in addition, the Br-COFs material detects the stretching vibration peak of -C-Br at 800~1060, which further indicates that BBDD participates in the reaction.

[0047] Figure 4 The specific surface adsorption and pore size distribution of Br-COFs material, from the figure can be seen that the pore size of Br-COFs material is about 3.15nm.

[0048] Figure 5 The X-ray diffraction pattern of Br-COFs material, the XRD diffraction peak of Br-COFs is relatively wide, which indicates that the material is not necessarily a single crystal and the crystallinity is weak.

[0049] Figure 6 The electrochemical test performance evaluation results of Br-COFs-Cu / Li battery in Example 3 and Cu / Li in Comparative Example 1 in the application. It can be seen that the Br-COFs-Cu / Li battery has excellent cycle stability, and the battery can be stably cycled for more than 200 hours, while the Cu / Li battery has obvious increase in battery polarization after 150 hours of cycle, indicating that the cycle stability and interface impedance of the system are large. The performance of Br-COFs-Cu electrode is obviously better than that of ordinary Cu electrode, which shows that Br-COFs material is beneficial to the normal deposition of lithium ions and the stability of the electrode interface.

[0050] It should be understood that the above detailed description of the technical solutions of the application by means of the optimization examples is illustrative but not limiting, and the specific embodiments of the application cannot be limited to this, for ordinary skilled persons in the technical field to which the application belongs, on the premise of not departing from the concept of the application, modifying the technical solutions recorded in each embodiment, or equivalently replacing some technical features, should be regarded as belonging to the patent protection scope determined by the claims submitted by the application.

[0051] The above embodiments of the present application are merely used for clearly illustrating the present application, but not for limiting the present application. Based on the above description, any modification, equivalent replacement and improvement made by those skilled in the art should be included in the protection scope of the present application.

Claims

1. Use of a Br-COFs material in the preparation of a copper-based artificial interphase film for lithium metal batteries, characterized in that, The Br-COFs material is prepared by using 1,3,5-tri(4-aminophenyl)benzene and 2,5-dibromobenzene-1,4-diformaldehyde as the only polymerization monomer, under the condition of room temperature 25-40 DEG C, in acetonitrile solvent, under the catalysis of 16-18 mol / L acetic acid, and by Schiff base reaction for 20-26 hours. The Br-COFs material is spherical with uniform size, with a diameter of 960 nm and a pore size of 3.15 nm, and is rich in Br groups. The application is that the Br-COFs material is mixed with PVdF adhesive in a mass ratio of 8.5:1.5 to 9.5:0.5, dispersed in N-methylpyrrolidone to obtain a slurry, the slurry is coated on the surface of a copper foil with a coating thickness of 5-15 microns, and a Br-COFs artificial interface film is formed after drying.

2. A lithium metal battery interface film, characterized in that, A slurry is prepared by dispersing the Br-COFs material and PVdF adhesive in an organic solvent in a mass ratio of 8.5:1.5 to 9.5:0.5, and is coated on the surface of a copper foil to form a Br-COFs artificial interface film. The Br-COFs material is prepared by using 1,3,5-tri(4-aminophenyl)benzene and 2,5-dibromobenzene-1,4-diformaldehyde as the only polymerization monomer, under the condition of room temperature 25-40 DEG C, in acetonitrile solvent, under the catalysis of 16-18 mol / L acetic acid, and by Schiff base reaction for 20-26 hours; the Br-COFs material is spherical with uniform size, with a diameter of 960 nm and a pore size of 3.15 nm, and is rich in Br groups.

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