Preparation method of SnPc-COF used as negative electrode material of lithium ion battery

Abstract

This invention discloses a method for preparing SnPc-COF as a negative electrode material for lithium-ion batteries. The method includes: S1: uniformly mixing tin and pyromellitic tetracarbonyl to obtain a mixed powder; S2: placing the mixed powder in a heat-resistant glass tube and sealing it under vacuum to obtain a reaction COF tube; S3: placing the reaction COF tube in a tubular annealing furnace, heating it to 210°C under a vacuum atmosphere, holding it at that temperature for 2 days, then heating it to 400°C, holding it at that temperature for 4 hours, and then cooling it to room temperature to obtain SnPc-COF; the molar ratio of tin to pyromellitic tetracarbonyl is 1~2:1. The lithium-ion battery negative electrode material prepared by this invention not only greatly improves the cycle life of lithium batteries, but also has superior charge-discharge efficiency and reversible capacity, showing excellent potential as a high-performance lithium-ion battery negative electrode material, and can be further used as an energy storage device.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a method for preparing SnPc-COF as a negative electrode material for lithium-ion batteries. Background Technology

[0002] With the rapid increase in fossil fuel consumption, the greenhouse effect is becoming increasingly severe. Therefore, the development of efficient energy storage materials with excellent electrochemical performance, low cost, environmental friendliness, and sustainability is urgently needed. Lithium-ion batteries (LIBs) have become the most widely used energy storage technology due to their high energy density. However, using graphite as the anode material in lithium-ion batteries presents some problems, such as its relatively low theoretical capacity (372 mAh g⁻¹). -1 This limitation restricts the further development of lithium-ion batteries in the energy storage field. Therefore, there is an urgent need to develop high-energy-density energy storage materials. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing SnPc-COF as a negative electrode material for lithium-ion batteries, so as to solve the problem of low theoretical capacity of existing lithium battery negative electrode materials.

[0004] This invention provides a method for preparing SnPc-COF as a negative electrode material for lithium-ion batteries, the method comprising:

[0005] S1: Tin and pyromellitic nitrile are uniformly mixed to obtain a mixed powder;

[0006] S2: The mixed powder is placed in a heat-resistant glass tube and sealed under vacuum to obtain a COF reaction tube;

[0007] S3: The reaction COF tube is placed in a tube annealing furnace, heated to 210°C under vacuum, held for 2 days, then heated to 400°C, held for 4 hours, and then cooled to room temperature to obtain SnPc-COF.

[0008] The molar ratio of tin to pyromellitic nitrile is 1~2:1.

[0009] The above-mentioned method for preparing SnPc-COF as a negative electrode material for lithium-ion batteries produces a composite material that not only greatly improves the cycle life of lithium batteries, but also has superior charge-discharge efficiency and reversible capacity. Specifically, it has excellent potential as a high-performance negative electrode material for lithium-ion batteries and can be further used as an energy storage device.

[0010] Furthermore, the method for preparing the mixed powder is one or more of grinding, ball milling, and stirring.

[0011] Furthermore, the method for preparing the mixed powder includes:

[0012] S11, mix tin and pyromellitic tetranitrile in a mortar and pestle at a molar ratio of 1:1 until homogeneous.

[0013] Further, step S2 includes:

[0014] S21, the mixed powder is placed in a single-sided sealed heat-resistant glass tube, vacuumed and sealed with a flame to obtain the reaction COF tube;

[0015] S22, the reaction COF tube is placed in a tube furnace and heated under vacuum to obtain polytin phthalocyanine COF.

[0016] Further, in step S22, the heating rate is 5℃ / min, the temperature is 210℃, the reaction time is 2 days to obtain tin phthalocyanine monomer, and then the temperature is raised to 400℃ and the polymerization reaction is carried out for 4 hours to obtain the polytin metal phthalocyanine COF.

[0017] Further, step S3 includes:

[0018] S31, the glass tube that has completed the reaction in step S22 is opened with a ring cutter, the polytin metal phthalocyanine COF is ground and placed in a mixed solution of methanol and ethanol and ultrasonically washed to obtain a mixed solution;

[0019] S32, after filtering the mixed solution to obtain a solid, it is washed with ethanol 3-5 times to remove unreacted pyromellitic nitrile, then washed with 55 ml of a mixed solution of hydrochloric acid and hydrogen peroxide to remove unreacted tin metal; then washed with deionized water 3-5 times to remove excess hydrochloric acid and hydrogen peroxide solution, and dried overnight in a vacuum drying oven at 60-80°C to finally obtain the SnPc-COF.

[0020] Furthermore, the hydrochloric acid and hydrogen peroxide mixed solution is 50 ml of 6 mol / L solution. -1 Hydrochloric acid and 5 ml of 30% hydrogen peroxide.

[0021] Furthermore, the ratio of methanol to ethanol in the methanol-ethanol mixed solution is 1:1. Attached Figure Description

[0022] Figure 1 This is a front view of the cell structure of the SnPc-COF composite anode material prepared by the invention.

[0023] Figure 2 This is a side view of the cell structure of the SnPc-COF composite anode material prepared by the invention.

[0024] Figure 3 This is the XRD-Pawley refinement image of the SnPc-COF composite anode material prepared by the invention.

[0025] Figure 4 This is a SEM image of the SnPc-COF composite anode material prepared by the invention.

[0026] Figure 5 This is a TEM image of the SnPc-COF composite anode material prepared by the invention.

[0027] Figure 6 This is a charge-discharge curve of the SnPc-COF composite anode material prepared by the invention.

[0028] Figure 7 This is the specific capacity cycling diagram of the SnPc-COF composite anode material prepared by the invention.

[0029] Figure 8 This is a rate capability diagram of the SnPc-COF composite anode material prepared by the invention.

[0030] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0032] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] Covalent organic frameworks (COFs) are a class of crystalline porous materials. COFs possess robust and extended framework structures, which result in low solubility in electrolytes, high specific surface areas that promote interfacial contact between electrodes and electrolytes, and tunable pore sizes that accelerate ion insertion / extraction processes, thereby improving lithium-ion storage performance. Among these, two-dimensional covalent organic frameworks (2D-COFs) have attracted considerable attention from researchers due to their π-π stacked layered structure, which endows them with better conductivity, facilitating charge transport and accelerating lithium-ion insertion / extraction.

[0035] Tin (Sn) compounds are alloy materials used in lithium-ion batteries, possessing extremely high specific capacity (994 mAh g⁻¹). -1 The relatively low lithium storage potential of tin-based materials has made them a popular alternative to graphite anodes. However, tin-based materials exhibit significant volume changes (approximately 260%) during lithium alloying and dealloying. This often leads to problems such as mechanical fracture, particle expansion, and unstable solid electrolyte interface (SEI), thereby reducing the cycle stability and other performance characteristics of lithium batteries. Constructing tin-based polyphthalocyanines with Sn–N4 coordination bonds can overcome the problem of drastic volume changes of tin during charge and discharge, as coordination interactions can uniformly anchor or release Sn atoms into the organic matrix and inhibit particle growth and aggregation. Furthermore, nitrogen-rich organic ligands can provide additional lithium storage active sites. Based on this, the present invention provides the following embodiments to address the problems existing in the prior art.

[0036] Example 1

[0037] Please see Figures 1 to 8 The present invention provides a method for preparing SnPc-COF as a negative electrode material for lithium-ion batteries, comprising the following steps:

[0038] Synthesis of SnPc-COF: S1: Tin and pyromellitic nitrile are uniformly mixed to obtain a mixed powder; S2: The mixed powder is placed in a heat-resistant glass tube and sealed under vacuum to obtain a reaction COF tube; S3: The reaction COF tube is placed in a tube annealing furnace, heated to 210°C under vacuum, held for 2 days, then heated to 400°C, held for 4 hours, and then cooled to room temperature to obtain SnPc-COF.

[0039] Specifically: 50 mg of 0.28 mmol of 1,2,4,5-phenyltetrafluoronitrile (TCB, pyromellitic nitrile) and 16.6 mg of 0.14 mmol of tin powder (50 nm particle size) were mixed in a mortar and placed in a single-sided sealed heat-resistant glass tube (20 cm * 8 mm * 1 mm). The mixture was then evacuated and ultrasonically sealed with a flame. The sealed glass tube was placed in a tube furnace under vacuum (<0.1 MPa), with a heating rate of 5 °C / min at 210 °C for 2 days. The temperature was then increased to 400 °C for 4 hours of polymerization. After the reaction, the mixture was cooled to room temperature. The glass tube was opened with a ring cutter, and the reacted material was ground in a mortar and placed in a 1:1 methanol and ethanol mixture and ultrasonically washed for 30 minutes. The mixture was filtered to obtain a solid, which was then washed 3–5 times with ethanol. Finally, the solid was washed with a 55 ml 6 mol / L hydrochloric acid and hydrogen peroxide mixture. -1 Wash with HCl and 5 ml of 30% H2O2; wash 3-5 times with deionized water, and dry overnight in a vacuum drying oven at 60-80℃ to obtain the blue-green to purplish-black powder SnPc-COF.

[0040] Example 2

[0041] Synthesis of SnPc-COF

[0042] 50 mg, 0.28 mmol 1,2,4,5-benzenetetracarbononitrile (TCB) and 33 mg, 0.28 mmol tin powder (50 μm particle size) were mixed in a mortar and placed in a single-sided sealed heat-resistant glass tube (20 cm * 8 mm * 1 mm). The mixture was then evacuated and ultrasonically sealed with a flame. The sealed glass tube was placed in a tube furnace under vacuum (<0.1 MPa), with a heating rate of 5 °C / min at 210 °C for 2 days. The temperature was then increased to 400 °C for 4 hours of polymerization. After the reaction, the mixture was cooled to room temperature. The glass tube was opened with a ring cutter, and the reacted material was ground in a mortar and placed in a 1:1 methanol and ethanol mixture and ultrasonically washed for 30 minutes. The mixture was filtered to obtain a solid, which was then washed 3–5 times with ethanol. Finally, the solid was washed with a 55 ml 6 mol / L hydrochloric acid and hydrogen peroxide mixture. -1 Wash with HCl and 5 ml of 30% H2O2; wash 3-5 times with deionized water, and dry overnight in a vacuum drying oven at 60-80℃ to obtain the blue-green to purplish-black powder SnPc-COF.

[0043] Example 3

[0044] Synthesis of SnPc-COF

[0045] 50 mg, 0.28 mmol 1,2,4,5-benzenetetracarbonyl nitrile (TCB) and 66.5 mg, 0.56 mmol tin powder (50 nm particle size) were mixed in a mortar and placed in a single-sided sealed heat-resistant glass tube (20 cm * 8 mm * 1 mm). The mixture was then evacuated and ultrasonically sealed with a flame. The sealed glass tube was placed in a tube furnace under vacuum (<0.1 MPa), with a heating rate of 5 °C / min at 210 °C for 2 days. The temperature was then increased to 400 °C for 4 hours. After the reaction, the mixture was cooled to room temperature. The glass tube was opened with a ring cutter, and the reacted material was ground in a mortar and placed in a 1:1 methanol and ethanol mixture and ultrasonically washed for 30 minutes. The mixture was filtered to obtain a solid, which was then washed 3–5 times with ethanol. Finally, the solid was washed with a 55 ml 6 mol / L hydrochloric acid and hydrogen peroxide mixture. -1 Wash with HCl and 5 ml of 30% H2O2; wash 3-5 times with deionized water, and dry overnight in a vacuum drying oven at 60-80℃ to obtain the blue-green to purplish-black powder SnPc-COF.

[0046] The SnPc-COF samples from Examples 1-3 of this invention exhibit similar performance and parallel effects when used as anode materials for lithium-ion batteries. The following study uses Example 1 as an example, with specific research methods and results shown below:

[0047] The SnPc-COF anode material prepared in Example 1 was assembled into a coin cell, and its electrochemical performance was tested. The coin cell assembly steps were as follows: the active material SnPc-COF anode material, conductive carbon black, and polyvinylidene fluoride were added to N-methylpyrrolidone in a mass ratio of 7:2:1 and mixed evenly to form an electrode slurry; the slurry was coated onto a 9 μm thick copper foil and dried in a vacuum oven at 60 °C for 12 h to form an electrode sheet; the electrode sheet and lithium metal were assembled into a coin cell in an argon-filled glove box; and the electrochemical performance was tested using a LAND battery testing system at 0.2 A g. -1 Performance tests were conducted on coin cells at current density.

[0048] Figure 1-8 The images show the XRD pattern, XRD Pawley refinement image, SEM image, TEM image, charge-discharge curve, cycle chart, and rate curve of the SnPc-COF anode material prepared in Example 1. Figure 3It can be seen that the SnPc-COF structure exhibits a granular rod-like structure with numerous active sites. The results show that the SnPc-COF anode material from Example 1, when subjected to coin cell testing, exhibits the highest capacity during the first discharge. The irreversible capacity loss is mainly attributed to the formation of the SEI film and the continuous decomposition of the electrolyte during the first cycle. Afterward, it begins to stabilize, demonstrating excellent electrochemical lithium storage stability. The specific capacity is 750 mAh g⁻¹ after 100 cycles. -1 From the perspective of the magnification chart, it exhibits good reversibility from low to high and then back to low magnification.

[0049] The SnPc-COF material prepared in this application comprises a covalent organic framework (COFs), a type of crystalline porous material. COFs possess a robust and extended framework structure, resulting in low solubility in electrolytes, high specific surface area promoting interfacial contact between the electrode and electrolyte, and adjustable pore size accelerating ion insertion / extraction processes, thereby improving lithium-ion storage performance. Two-dimensional covalent organic frameworks (2D-COFs), with their π-π stacked layered structure, exhibit better conductivity, facilitating charge transport and accelerating lithium-ion insertion / extraction, attracting significant research attention. Furthermore, the SnPc-COF material obtained in this invention can be used as a negative electrode material for lithium-ion batteries, improving cycle stability and cycle life. When used as a negative electrode material, it shortens the lithium-ion transport path and enhances material conductivity. This results in lithium-ion batteries with advantages such as high stability, long cycle life, high rate performance, simple preparation process, readily available and inexpensive raw materials, low cost, and environmental friendliness, effectively meeting the practical application requirements of high-energy-density lithium-ion batteries.

[0050] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for the preparation of SnPc-COF for use as a negative electrode material for lithium-ion batteries, characterized by, The method comprises: S1: uniformly mixing tin and melamine to obtain a mixed powder; S2: placing the mixed powder in a heat-resistant glass tube to obtain a reaction COF tube by vacuumizing and sealing; S3: placing the reaction COF tube in a tube furnace, heating to 210 DEG C under a vacuum atmosphere, keeping warm for 2 days, then heating to 400 DEG C, keeping warm for 4 hours, and then reducing to room temperature to obtain SnPc-COF; The molar ratio of the tin and melamine is 1-2:

1.

2. A method for the preparation of SnPc-COF for use as a negative electrode material for lithium ion batteries according to claim 1, characterized in that, The preparation method of the mixed powder is one or more of grinding, ball milling and stirring.

3. A method for the preparation of SnPc-COF for use as a negative electrode material for lithium-ion batteries according to claim 2, characterized in that, The preparation method of the mixed powder comprises: S11: mixing tin and melamine in a mortar at a molar ratio of 1:

1.

4. The method for preparing SnPc-COF as a negative electrode material for lithium ion batteries according to claim 3, characterized by, The step S2 comprises: S21: placing the mixed powder in a single-sided sealing heat-resistant glass tube, vacuumizing and sealing by flame to obtain the reaction COF tube; S22: placing the reaction COF tube in a tube furnace, heating under a vacuum environment to obtain poly-tin metal phthalocyanine COF.

5. A method for the preparation of SnPc-COF for use as a negative electrode material for lithium ion batteries according to claim 4, characterized in that, In the step S22, the heating rate is 5 DEG C / min, the temperature is 210 DEG C, the reaction time is 2 days, tin phthalocyanine monomer is obtained, then the temperature is increased to 400 DEG C, and the polymerization reaction is carried out for 4 hours to obtain the poly-tin metal phthalocyanine COF.

6. A method for the preparation of SnPc-COF as a negative electrode material for lithium ion batteries according to claim 4, characterized by, The step S3 comprises: S31: opening the glass tube in which the reaction is completed in the step S22 by using a ring-shaped cutter, grinding the poly-tin metal phthalocyanine COF, and then placing the poly-tin metal phthalocyanine COF in a mixed solution of methanol and ethanol to wash by ultrasonic wave to obtain a mixed solution; S32: after the solid is obtained by suction filtration from the mixed solution, the unreacted melamine is removed by washing with ethanol for 3-5 times, then the unreacted tin metal is removed by washing with a mixed solution of 55 ml of hydrochloric acid and hydrogen peroxide, then the mixed solution of excess hydrochloric acid and hydrogen peroxide is removed by washing with deionized water for 3-5 times, and the SnPc-COF is finally obtained by drying in a vacuum drying oven at 60-80 DEG C overnight.

7. The method for preparing SnPc-COF as a negative electrode material for lithium ion batteries according to claim 6, characterized by, The mixed solution of hydrochloric acid and hydrogen peroxide is 50 ml 6 mol / L -1 hydrochloric acid and 5 ml 30% hydrogen peroxide.

8. The method for preparing SnPc-COF as a negative electrode material for lithium ion batteries according to claim 6, characterized by, The ratio of methanol to ethanol in the mixed solution of methanol and ethanol is 1:1.

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