Novel MOF material and use thereof in negative electrode of lithium ion battery

Abstract

Disclosed in the present invention are a novel MOF material and the use thereof in a negative electrode of a lithium ion battery, which belong to the field of lithium ion batteries. Said MOF material is prepared by carrying out a self-assembly coordination reaction on tris(4-(pyridin-4-yl)phenyl)amine and copper nitrate The metal organic framework material (MOF) provided by the present invention will generate a large amount of pores during self-assembly, and thus can store a large amount of lithium ions; in addition, all the pores are mutually and tightly connected, so that ions and electrons can be conducted more quickly. Compared with other MOF negative electrode materials, the novel MOF material has longer cycle life and better stability.

Description

A new type of MOF material and its application in lithium-ion battery anode Technical Field

[0001] The present invention belongs to the field of lithium-ion batteries, and in particular relates to a novel MOF material and its application in the negative electrode of a lithium-ion battery. Background Art

[0002] With the rapid development of portable consumer electronics and electric vehicles, lithium-ion batteries have gradually entered people's field of vision. With the advantages of high energy density, no memory effect, high operating voltage, and low self-discharge, they have quickly become the mainstream commercial products. However, the negative electrode material of commercial lithium-ion batteries is graphite, which has a low theoretical capacity (372mAhg -1 ) cannot meet the market demand. Therefore, developing new negative electrode materials to replace graphite is the key to improving the overall performance of lithium-ion batteries.

[0003] Metal-organic frameworks (MOFs) have attracted numerous researchers due to their large surface area, rich porosity, and tunable structure. MOFs are porous crystalline materials formed by the self-assembly reaction of metal ions and organic ligands. They have found widespread application in electrochemical energy storage, electrocatalysis, drug delivery, adsorption and separation. The diversity of metal ions and organic ligands determines the diversity of MOF materials. Therefore, selecting the appropriate organic ligands and metal ions is crucial in determining the functionality of MOFs.

[0004] Patent CN 112708143 A discloses a method for preparing a novel MOFs lithium battery anode material, comprising the following steps: dissolving phenyl acid and nitrate in water to obtain a mixed solution, adding an alkaline reagent to adjust the mixed solution to a pH of 2-5; adding the mixed solution to a reactor for a hydrothermal reaction, cooling to room temperature after the reaction, and separating to obtain MOFs crystals; and drying and grinding the MOFs crystals to obtain the MOFs lithium battery anode material. This prior art MOFs material, prepared using carboxylic acid compounds as organic ligands, is a two-dimensional planar network with tetranuclear metals as nodes. When applied to lithium battery anode materials, this material demonstrated a specific capacity after 200 cycles at a current density of 500 mA / g at 25°C. The initial discharge specific capacity was 846 mAh / g, and the capacity after 200 cycles was 729 mAh / g, demonstrating its excellent electrical performance. However, to expand the application range of MOFs in batteries, further improvements in their electrical performance are necessary. From a production and preparation perspective, a more simplified MOFs material preparation method is also urgently needed in the field. Summary of the Invention

[0005] The present invention aims to provide a novel MOF material and its application in lithium-ion battery anodes to address the aforementioned problems of the prior art. The present invention selects copper as the metal center and triphenylamine tripyridine as the ligand. This is primarily due to the fact that Cu ions possess multiple valences and exhibit good redox activity, which facilitates redox reactions. Furthermore, the triphenylamine tripyridine ligand is highly stable. Combining the two to form a self-assembled Cu-MOF exhibits excellent electrochemical performance when used as a lithium-ion battery anode material. Its unique porous structure enables rapid ion conduction, significantly mitigating volume expansion. Furthermore, the four ligands on the Cu-MOF offer significant steric hindrance, resulting in excellent cycling performance for this novel MOF material.

[0006] One of the technical solutions provided by the present invention:

[0007] A new type of MOF material is prepared by a self-assembly coordination reaction between triphenylamine tripyridine and copper nitrate.

[0008] The second technical solution provided by the present invention is:

[0009] A novel method for preparing MOF material is characterized by comprising a solvent diffusion method and a precipitation method.

[0010] Preferably, the solvent diffusion method comprises the following steps: adding an intermediate layer dropwise onto the triphenylamine tripyridine solution, then adding a copper nitrate solution onto the intermediate layer, sealing, standing in the dark, taking out the precipitated green block crystals, washing, and drying to obtain the novel MOF material.

[0011] More preferably, the intermediate layer is a mixed solution of chloroform and methanol in equal volumes.

[0012] More preferably, the standing time is 3 weeks.

[0013] More preferably, the drying temperature is 60° C.-70° C., and the drying time is 6-10 hours.

[0014] Preferably, the precipitation method comprises the following steps: mixing a triphenylamine tripyridine solution and a copper nitrate solution, stirring, aging, filtering, and drying to prepare the novel MOF material.

[0015] More preferably, the solvent in the triphenylamine tripyridine solution is one or more of dichloromethane, chloroform and acetonitrile; the solvent in the copper nitrate solution is one or more of methanol, ethanol and water.

[0016] More preferably, the volume ratio of the triphenylamine tripyridine solution to the copper nitrate solution is (1:2)-(2:1); the molar ratio of the triphenylamine tripyridine to the copper nitrate is (3.5:1)-(4.5:1).

[0017] The molar ratio of triphenylamine tripyridine to copper nitrate is limited to (3.5:1)-(4.5:1) based on the following reasons: within this ligand range, the organic ligand reacts with the metal ion without generating impurities; when the molar ratio is greater than 4.5:1, an excess of organic ligand leads to the generation of triphenylamine tripyridine impurities; and when the ratio is less than 3.5:1, an excess of metal salt leads to the generation of copper nitrate impurities.

[0018] More preferably, the stirring time is 5-8 hours; the aging time is 6-10 hours.

[0019] More preferably, the drying temperature is 60° C.-70° C., and the drying time is 6-10 hours.

[0020] The third technical solution provided by the present invention is:

[0021] An application of the above-mentioned new MOF material in the preparation of lithium-ion battery negative electrode.

[0022] Beneficial effects of the present invention:

[0023] The present invention provides a novel MOF material with a porous structure that shortens the transport paths of ions and electrons, resulting in a larger diffusion coefficient. The ligand used in the present invention is triphenylamine tripyridine, which coordinates with copper ions to form a self-assembled Cu-MOF structure with good stability and exhibits excellent cycling performance.

[0024] The MOF material provided by the present invention has a novel structure and a simple synthesis method. More importantly, it has excellent electrochemical stability and economic value when used in the negative electrode of a lithium-ion battery.

[0025] The metal-organic frameworks (MOFs) provided by this invention generate numerous pores during self-assembly, which can store large quantities of lithium ions. Furthermore, the pores are tightly interconnected, allowing for faster ion and electron conduction. Compared to other MOF anode materials, this novel MOF material has a longer cycle life and better stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 is a single crystal X-ray diffraction measurement diagram of the novel MOF material prepared in Example 1 and an XRD pattern of the novel MOF materials prepared in Examples 1 and 2, wherein (a) is a coordination environment diagram, (b) is a one-dimensional plane diagram; (c) is an XRD pattern of the novel MOF materials prepared in Examples 1 and 2;

[0028] Figure 2 is the SEM and EDS characterization images of the new MOF material prepared in Example 2, wherein (a) is the SEM image, (b) is the EDS spectrum, and (c) is the mapping spectrum;

[0029] FIG3 is a graph showing the electrochemical performance of a lithium-ion battery negative electrode prepared from the novel MOF material in Example 2 when the electrolyte is LB063 solution;

[0030] Figure 4 shows the negative electrode of the lithium-ion battery prepared by the new MOF material in Example 2 at 0.1A g -1 The charge and discharge curves and cycle performance diagrams under current, where (a) is the charge and discharge curve and (b) is 0.1A g -1 Cycle performance diagram;

[0031] Figure 5 is a graph showing the cycle performance of the negative electrode of a lithium-ion battery prepared from the novel MOF material in Example 2 when the electrolyte is LB007 solution, where (a) is the cycle performance at 0.5 A g -1 Cycling performance diagram under current density; (b) is at 1Ag -1 Cycling performance at different current densities. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the present invention. The present description and examples are intended to be illustrative only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] The room temperature in the present invention refers to 25±2°C.

[0038] All raw materials in the examples of the present invention were purchased.

[0039] In the embodiments of the present invention, single crystals and powders of a novel MOF were synthesized using the solvent diffusion method and the precipitation method, respectively. The single crystal structure was analyzed using a single crystal X-ray diffractometer. The MOF powder was used as a negative electrode material and exhibited good electrochemical properties.

[0040] In order to characterize the crystal structure of the novel MOF material provided by the present invention, the novel MOF material was prepared by a solvent diffusion method, as shown in Example 1.

[0041] Example 1 Preparation method of a novel MOF material (solvent diffusion method)

[0042] 47.6 mg of triphenylamine tripyridine (0.1 mmol) was dissolved in 6 mL of chloroform and placed at the bottom of a test tube. 6 mL of a chloroform / methanol mixture (volume ratio 1:1) was added as an intermediate layer (to act as a buffer). 6 mL of a methanol solution of copper nitrate (18.8 mg, 0.1 mmol) was then added on top of the intermediate layer. The test tube was sealed with plastic wrap and placed in a dark place. After standing for three weeks, green block crystals suitable for X-ray structural analysis precipitated on the test tube wall. The solution was then washed three times with methanol and then three times with water, then dried in an oven (65°C) for 8 hours. The resulting green crystals were the novel MOF material.

[0043] The novel MOF material prepared by the solvent diffusion method in Example 1 and the novel MOF material prepared by the precipitation method are the same substance. The only difference between the two is the size of the crystal particles. This difference does not affect the performance of the MOF as a negative electrode material for lithium-ion batteries, because the factors that determine its electrochemical performance are the structure and composition of the MOFs material. The MOF materials prepared by the chemical precipitation method and the solvent diffusion method are the same in structure and composition. Considering the preparation time and preparation cost, the novel MOF material of the present invention is preferably prepared by the precipitation method.

[0044] Example 2 Preparation method of a new type of MOF material (precipitation method)

[0045] S1. Dissolve 190.4 mg of triphenylamine tripyridine (0.4 mmol) in 60 mL of chloroform, and dissolve 18.8 mg of copper nitrate (0.1 mmol) in 30 mL of methanol, and mix the two solutions.

[0046] S2. The mixed solution obtained in S1 was magnetically stirred at room temperature for 6 h, aged for 8 h, filtered, and then dried in an oven (65°C) for 8 h to obtain a green powder, which is the new MOF material.

[0047] Example 3 Preparation method of a new type of MOF material (precipitation method)

[0048] S1. Dissolve 166.6 mg of triphenylamine tripyridine (0.35 mmol) in 60 mL of dichloromethane, dissolve 18.8 mg of copper nitrate (0.1 mmol) in 60 mL of water, and mix the two solutions.

[0049] S2. The mixed solution obtained in S1 was magnetically stirred at room temperature for 5 h, aged for 6 h, filtered, and then dried in an oven (60°C) for 10 h to obtain a green powder, which is the new MOF material.

[0050] Example 4

[0051] S1. Dissolve 214.2 mg of triphenylamine tripyridine (0.45 mmol) in 60 mL of acetonitrile, and dissolve 18.8 mg of copper nitrate (0.1 mmol) in 120 mL of ethanol, and mix the two solutions.

[0052] S2. The mixed solution obtained in S1 was magnetically stirred at room temperature for 8 h, aged for 10 h, filtered, and then dried in an oven (70°C) for 6 h to obtain a green powder, which is the new MOF material.

[0053] Performance Testing

[0054] 1) Crystal structure determination of new MOF

[0055] The new MOF material prepared by the solvent diffusion method in Example 1 was analyzed using a single crystal X-ray diffractometer for its crystal structure. The results are shown in Figure 1: The new MOF material prepared in Example 1 is monoclinic and belongs to the P21 / c space group. Figure 1 (a) shows the coordination environment of the new MOF, with the central atom being a Cu atom. Four triphenylamine tripyridine molecules each remove a hydrogen atom and then bind to the Cu atom. Figure 1 (b) shows a one-dimensional plan view of the new MOF, showing relatively regular quadrilateral pores. Adjacent Cu-MOF molecules do not overlap, exhibiting a dispersed arrangement.

[0056] The new MOF materials prepared in Example 1 and Example 2 were characterized by XRD, respectively. Figure 1 (c) is the XRD diagram of the new MOF materials prepared in Example 1 and Example 2. The single crystal prepared in Example 1 (corresponding to simulated in Figure 1 (c)) and the powder sample prepared in Example 2 (corresponding to experimental in Figure 1 (c)) have similar diffraction peaks, proving that the two are the same substance and the powder sample has a high phase purity.

[0057] 2) SEM and EDS characterization experiments

[0058] The novel MOF material prepared in Example 2 was characterized by SEM and EDS. Figure 2 (a) shows an SEM image of the novel MOF prepared in Example 2, which shows that the product exhibits a regular brick-like structure with appropriate gaps between adjacent brick-like structures and a relatively smooth surface. Figure 2 (b) shows an EDS spectrum of the novel MOF prepared in Example 2, which shows that the elements C, N, O, and Cu are uniformly distributed. Figure 2 (c) shows a mapping spectrum, which also shows that the elements C, N, O, and Cu are uniformly distributed in the MOF.

[0059] Application Examples

[0060] (1) Preparation of lithium-ion battery negative electrode and battery assembly:

[0061] The new MOF material prepared in Example 2 was powdered and used as a raw material to prepare a lithium-ion battery negative electrode. The powdered new MOF material, acetylene black, and PVDF were mixed in a mass ratio of 6:3:1 (total mass 20 mg). 3 mL of N-methylpyrrolidone solvent was added to mix thoroughly to obtain a slurry. The resulting slurry was evenly coated on copper foil using an applicator, dried in a vacuum oven at 65°C for 12 hours, and then cut into negative electrode sheets with a diameter of 12 cm. This negative electrode sheet served as the working electrode, a PP / PE composite film served as the separator, a metal lithium sheet served as the counter electrode, and the electrolytes used were lithium electrolytes LB063 and LB007. A button-type half-cell was assembled in a glove box filled with high-purity argon.

[0062] (2) Testing the electrochemical properties of the new MOF powder: The electrochemical properties were measured using a Shanghai Chenhua CHI660E electrochemical workstation and a blue electrochemical system at room temperature; a series of electrochemical performance graphs were tested using LB063 solution as the electrolyte.

[0063] 0.1ms -1 The CV test results of the scanning rate of 0.1Ag are shown in Figure 3. As can be seen from Figure 3, except for the irreversible process of the electrode material in the first scan (mainly due to the formation of the SEI film and the initial decomposition of the electrolyte), there is no obvious change in the second and third cycles, showing good cycle stability and reversibility. Figure 4 is the negative electrode of the lithium ion battery prepared by the new MOF material in Example 2 at 0.1Ag -1 The charge and discharge curve and cycle performance diagram under current are shown in Figure 4 (a). It can be seen from the figure that the first discharge capacity is 727 mAh g -1 The first charge capacity is 218mA hg -1 , the first coulombic efficiency is 29.9%. Figure 4(b) is 0.1A g -1 The cycle performance diagram shows that the discharge capacity is basically maintained at 250mA hg -1 about.

[0064] (3) The electrolyte was LB007 solution, and the electrolyte was 0.5A g -1 and 1A g -1 The cycle performance diagram at the current density of 0.5A g is shown in Figure 5. It can be seen from the figure that the capacity increases slightly with the increase of the number of cycles. Figure 5 (a) is 0.5A g -1 Cycling performance under current density, after 500 cycles, the battery capacity increased from 129mAhg -1 Rising to 232mAhg -1 , the coulombic efficiency is close to 100%, showing good cycle stability. Figure 5 (b) shows the -1 Cycling performance under current density, after 762 cycles, the discharge capacity increased from 115mA hg -1 Rising to 238mA hg -1 , and still exhibits good fast charge and discharge performance under high current conditions.

[0065] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A new type of MOF material, characterized in that: It is prepared by the self-assembly coordination reaction of triphenylamine tripyridine and copper nitrate.

2. A novel method for preparing MOF materials, characterized in that: Including solvent diffusion method and precipitation method.

3. The preparation method according to claim 2, characterized in that The solvent diffusion method includes the following steps: adding an intermediate layer dropwise onto a triphenylamine-tripyridine solution, then adding a copper nitrate solution onto the intermediate layer, sealing the solution, standing the solution away from light, taking out the precipitated green block crystals, washing them, and drying them to obtain the novel MOF material.

4. The preparation method according to claim 3, characterized in that The middle layer is a mixed solution of chloroform and methanol in equal volumes.

5. The preparation method according to claim 3, characterized in that The standing time is 3 weeks.

6. The preparation method according to claim 2, characterized in that The precipitation method comprises the following steps: mixing a triphenylamine tripyridine solution and a copper nitrate solution, stirring, aging, filtering, and drying to prepare the novel MOF material.

7. The method for preparing the novel MOF material according to claim 6, characterized in that: The solvent in the triphenylamine tripyridine solution is one or more of dichloromethane, chloroform and acetonitrile; the solvent in the copper nitrate solution is one or more of methanol, ethanol and water.

8. The method for preparing the novel MOF material according to claim 6, characterized in that: The volume ratio of the triphenylamine tripyridine solution to the copper nitrate solution is (1:2)-(2:1); the molar ratio of the triphenylamine tripyridine to the copper nitrate is (3.5:1)-(4.5:1).

9. The method for preparing the novel MOF material according to claim 6, characterized in that: The stirring time is 5-8 hours; the aging time is 6-10 hours.

10. Use of the novel MOF material according to claim 1 in preparing a negative electrode of a lithium-ion battery.

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