A bipolar organic material, its preparation method and use in sodium-ion batteries

Abstract

This invention relates to a bipolar organic material, its preparation method, and its application in sodium-ion batteries, belonging to the field of organic electrode materials technology. The bipolar organic material is prepared from 4,4-dibromoazobenzene, 5,10-dihydrophenazine, 2-bicyclohexylphosphine-2',6'-diisopropoxybiphenyl (Ruphos), [2'-(amino)[1,1'-biphenyl]-2-yl][[2',6'-di(1-methylethoxy)[1,1'-biphenyl]-2-yl]dicyclohexylphosphine]palladium chloride (Ruphos Pd G2), and sodium tert-butoxide. Because the chemical structure of this material simultaneously contains substances that can react with sodium... + Azo units for reversible storage and for ClO4 ‑ The phenazine unit stores anions, thus exhibiting bipolar characteristics. When used as a cathode material in coin cells, it demonstrates excellent electrochemical performance. Its preparation method is simple, easy to operate, and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of organic electrode materials technology, and relates to a bipolar organic material, its preparation method, and its application in sodium-ion batteries. Background Technology

[0002] With the rapid development of electronic products, electric vehicles, and energy storage power stations, the demand for batteries has surged, leading to the development of lithium-ion batteries such as lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium titanate. However, nickel salts, cobalt salts, manganese salts, and lithium salts are scarce and expensive, resulting in high manufacturing costs for lithium-ion batteries. Compared to lithium-ion batteries, sodium-ion batteries (SIBs) have abundant and inexpensive sodium salt raw materials, making them a promising alternative and supplement to lithium-ion batteries in the future, applicable to new battery systems for large-scale energy storage. Therefore, more and more researchers are focusing on the research and development of sodium-ion batteries. In sodium-ion batteries, the cathode material is one of the key factors affecting energy density, specific capacity, rate performance, and cycle performance. To maximize the overall performance of the battery, it is urgent to find suitable cathode materials.

[0003] Currently, the cathode materials for sodium-ion batteries mainly include inorganic electrode materials such as transition metal layered oxides, polyanionic compounds, and Prussian blue analogues. However, these inorganic electrode materials suffer from problems such as the high cost of transition metals, structural instability caused by the insertion and extraction of large-radius sodium ions, and potential harm to human health, thus limiting their practical application. Compared to inorganic materials, organic materials have the following advantages: ① Organic materials are composed of abundant elements such as C, H, O, and N, making them readily available, inexpensive, and environmentally friendly; ② Organic materials exhibit smaller structural changes during charging and discharging, and their large molecular spacing can accommodate ions of various sizes (Li). + Na + Mg 2+ The p-type organic materials exhibit high redox potentials (>3V), promising high energy density. In SIBs composed of p-type organic materials, both cations and anions act as charge carriers, hence the name dual-ion batteries. Common p-type organic materials include phenothiazine, thiathracene, polythiophene, dihydrophenazine derivatives, and nitryl derivatives. Despite their high operating voltages, they suffer from several drawbacks: ① low specific capacity; ② excessively high voltages easily cause electrolyte decomposition, leading to irreversible capacity and low coulombic efficiency; ③ easy solubility in electrolytes and poor conductivity. Therefore, to address the problems associated with p-type organic materials as cathode materials in sodium-ion batteries, it is necessary to provide a novel organic polymer electrode material with high specific capacity and stable cycle performance. Summary of the Invention

[0004] In view of this, one objective of the present invention is to provide a bipolar organic material; a second objective of the present invention is to provide a method for preparing a bipolar organic material; and a third objective of the present invention is to provide the application of the bipolar organic material in the preparation of cathode materials for sodium-ion batteries.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] 1. A bipolar organic material, wherein the structural formula of the bipolar organic material is as follows:

[0007]

[0008] In the formula, n is an integer and n = 3 to 20.

[0009] 2. The method for preparing the bipolar organic material, wherein the method is as follows:

[0010] In a glove box, 4,4-dibromoazobenzene, 5,10-dihydrophenazine, 2-bicyclohexylphosphine-2',6'-diisopropoxybiphenyl, [2'-(amino)[1,1'-biphenyl]-2-yl][[2',6'-di(1-methylethoxy)[1,1'-biphenyl]-2-yl]dicyclohexylphosphine]palladium chloride and sodium tert-butoxide are mixed to form a mixture. Then, xylene is added to the mixture under an argon atmosphere, and the reaction is carried out at 140-145°C for 3-4 days. After the reaction is stopped, the mixture is cooled and filtered under reduced pressure to obtain a solid product. The product is washed successively with toluene, deionized water, methanol, dichloromethane and acetone, and then dried under vacuum to obtain a bipolar organic material.

[0011] Preferably, the molar ratio of 4,4-dibromoazobenzene, 5,10-dihydrophenazine, 2-bicyclohexylphosphine-2',6'-diisopropoxybiphenyl, [2'-(amino)[1,1'-biphenyl]-2-yl][[2',6'-di(1-methylethoxy)[1,1'-biphenyl]-2-yl]dicyclohexylphosphine]palladium chloride and sodium tert-butoxide is 1:1:0.03~0.05:0.03~0.05:5.

[0012] 3. The application of the bipolar organic material in the preparation of cathode materials for sodium-ion batteries.

[0013] The beneficial effects of this invention are as follows: This invention provides a bipolar organic material. This bipolar organic material is prepared from 4,4-dibromoazobenzene, 5,10-dihydrophenazine, 2-bicyclohexylphosphine-2',6'-diisopropoxybiphenyl (Ruphos), [2'-(amino)[1,1'-biphenyl]-2-yl][[2',6'-di(1-methylethoxy)[1,1'-biphenyl]-2-yl]dicyclohexylphosphine]palladium chloride (Ruphos Pd G2), and sodium tert-butoxide. Infrared spectroscopy results show that the chemical structure of this material simultaneously contains electrochemically active azo units and phenazine units, i.e., the material exhibits bipolar characteristics. The azo units can react with Na... + Reversible storage is possible; the phenazine unit can store ClO4. - The material is reversibly stored as anion. When used as a cathode material in coin cells, the initial discharge specific capacity reaches 260 mAh / g at a current density of 125 mA / g, and the capacity retention rate is 94% after 300 cycles. This demonstrates that the bipolar organic material exhibits excellent discharge specific capacity, rate performance, and cycle stability.

[0014] This invention also provides a method for preparing bipolar organic materials. This method is low-cost, simple, easy to operate, and suitable for large-scale production.

[0015] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0017] Figure 1 The infrared spectrum of the bipolar organic material in Example 1;

[0018] Figure 2 This is a thermal field emission scanning electron microscope image of the bipolar organic material (ABPZ) in Example 1;

[0019] Figure 3 This is a thermogravimetric curve of the bipolar organic material (ABPZ) in Example 1;

[0020] Figure 4 A schematic diagram of the energy storage mechanism when the bipolar organic material in this application is used as the cathode material;

[0021] Figure 5Cyclic test results of a coin cell using the bipolar organic material from Example 2 as the cathode material at a current density of 125 mA / g.

[0022] Figure 6 Cyclic voltammetry curves of coin cells using the bipolar organic material (ABPZ) from Example 2 as the cathode material at a scan rate of 0.2 mV / s; Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] Example 1

[0025] Preparation of bipolar organic materials

[0026] In a glove box, 170 mg of 4,4-dibromoazobenzene, 137 mg of 5,10-dihydrophenazine, 20 mg of 2-bicyclohexylphosphine-2',6'-diisopropoxybiphenyl (Ruphos), and 31 mg of [2'-(amino)[1,1'-biphenyl]-2-yl][[2',6'-di(1-methylethoxy)[1,1'-biphenyl]-2-yl]dicyclohexylphosphine]palladium chloride (Ruphos Pd) were added sequentially in a molar ratio of 1:1:0.05:0.05:5. G2) and 360 mg of sodium tert-butoxide were placed in a 200 mL dry Schlenk flask and mixed thoroughly. Then, 80 mL of xylene was added to the flask using a syringe under an Ar2 atmosphere. The mixture was reacted at 140 °C for 3 days. After the reaction was stopped, the mixture was cooled and filtered under reduced pressure to obtain a solid product. The product was washed successively with toluene, deionized water, methanol, dichloromethane, and acetone. After vacuum drying, a reddish-brown solid bipolar organic material (ABPZ) was obtained.

[0027] Figure 1 The image shows the infrared spectrum of the bipolar organic material in Example 1. Figure 1 It can be seen from this that at a wavelength of 536cm -1 No characteristic C-Br absorption peak was observed at 1585 cm⁻¹, indicating that the starting material 4,4-dibromoazobenzene was completely consumed in the synthesis; -1 A characteristic absorption peak of N=N appears at a wavelength of 1263 cm⁻¹. -1The presence of a CN characteristic absorption peak indicates that a bipolar organic material containing both azo and phenazine units has been successfully prepared.

[0028] Figure 2 This is a thermal field emission scanning electron microscope (SEM) image of the bipolar organic material (ABPZ) from Example 1. Figure 2 As can be seen from the data, the bipolar organic material (ABPZ) in Example 1 does not have a fixed crystal form, indicating that it is amorphous.

[0029] Figure 3 This is a thermogravimetric curve of the bipolar organic material (ABPZ) in Example 1. From... Figure 3 As can be seen from the data, when the temperature is 472℃, the weight loss of the bipolar organic material (ABPZ) in Example 1 is only 5%, indicating that the material has good thermal stability.

[0030] Example 2

[0031] A coin cell was prepared using the bipolar organic material from Example 1 as the positive electrode and metallic sodium as the negative electrode.

[0032] (1) Preparation of working electrode: Weigh the bipolar organic material, conductive carbon black and binder in Example 1 in a mass ratio of 6.5:2:1.5, then place them in a mortar and grind them evenly. Add N-methylpyrrolidone and continue grinding to form a slurry. Coat the slurry onto carbon-coated aluminum foil with a scraper and dry it overnight at 60°C in a vacuum drying oven to obtain the working electrode.

[0033] (2) Preparation of button cell: In a glove box filled with argon gas, the working electrode, separator, 1 mol / L sodium perchlorate electrolyte (the solvent is tetraethylene glycol dimethyl ether), sodium sheet, gasket, spring sheet and negative electrode shell are placed on the positive electrode shell in sequence to form a CR2032 type button cell.

[0034] The schematic diagram of the energy storage mechanism when the bipolar organic material is used as the cathode material in this application is shown below. Figure 4 As shown. From Figure 4 It can be seen that the -N=N- functional group in the azo unit can affect Na. + The N atom in the phenazine unit can perform insertion / extraction operations on A. - (where A) - It involves reversible insertion / extraction of anions such as perchlorate, hexafluorophosphate, or bis(trifluoromethanesulfonyl)imide. Specifically, during charging, Na-N loses sodium ions to become N=N, and then the phenazine nitrogen is oxidized to nitrogen free radicals to store anions; during discharging, the nitrogen free radicals disappear and the anions are released, and then N=N is reduced to N-Na to store sodium ions.

[0035] The coin cell in Example 2 was subjected to cycle performance testing at a current density of 125 mA / g. The experimental results are as follows: Figure 5 As shown. From Figure 5 As can be seen, the initial discharge specific capacity reaches 260 mAh / g at a current density of 125 mA / g, and the capacity retention rate is 94% after 300 cycles. This demonstrates that the bipolar organic material exhibits high discharge specific capacity and good cycle stability.

[0036] The coin cell in Example 2 was tested using cyclic voltammetry (scan rate of 0.2 mV / s), and the experimental results are as follows: Figure 6 As shown. From Figure 6 As can be seen, within the voltage window of 1.0–4.0 V, there are three pairs of redox peaks at 1.67 / 1.6 V, 3.22 / 3.15 V, and 3.83 / 3.77 V, which correspond to the storage of sodium ions by the azo group (1.67 / 1.6 V) and the storage of perchlorate ions by the phenazine unit (3.22 / 3.15 V and 3.83 / 3.77 V), respectively. This indicates that the bipolar organic material can function as both an n-type and p-type material, exhibiting bipolar characteristics.

[0037] In summary, this invention provides a bipolar organic material. The material's chemical structure simultaneously contains both azo and phenazine units. Based on its bipolar nature, this material can simultaneously react with Na... + and ClO4 - When the material is used as a cathode material in coin cells for reversible storage of anions, its initial discharge specific capacity reaches 260 mAh / g at a current density of 125 mA / g, and its capacity retention rate is 94% after 300 cycles. This demonstrates that the bipolar organic material exhibits excellent electrochemical performance.

[0038] This invention also provides a method for preparing bipolar organic materials. This method is low-cost, simple, easy to operate, and suitable for large-scale production.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A bipolar organic material characterized in that: The structural formula of the bipolar organic material is as follows: In the formula, n is an integer and n = 3 to 20.

2. The method of claim 1, wherein the method is characterized by: The method is as follows: In a glove box, 4,4-dibromoazobenzene, 5,10-dihydrophenazine, 2-bicyclohexylphosphine-2',6'-diisopropoxybiphenyl, [2'-(amino)[1,1'-biphenyl]-2-yl][[2',6'-di(1-methylethoxy)[1,1'-biphenyl]-2-yl]dicyclohexylphosphine]palladium chloride and sodium tert-butoxide are mixed to form a mixture. Then, xylene is added to the mixture under an argon atmosphere, and the reaction is carried out at 140-145°C for 3-4 days. After the reaction is stopped, the mixture is cooled and filtered under reduced pressure to obtain a solid product. The product is washed successively with toluene, deionized water, methanol, dichloromethane and acetone, and then dried under vacuum to obtain a bipolar organic material.

3. The preparation method according to claim 2, characterized in that: The molar ratio of 4,4-dibromoazobenzene, 5,10-dihydrophenazine, 2-bicyclohexylphosphine-2',6'-diisopropoxybiphenyl, [2'-(amino)[1,1'-biphenyl]-2-yl][[2',6'-di(1-methylethoxy)[1,1'-biphenyl]-2-yl]dicyclohexylphosphine]palladium chloride and sodium tert-butoxide is 1:1:0.03~0.05:0.03~0.05:

5.

4. The application of the bipolar organic material according to claim 1 in the preparation of cathode materials for sodium-ion batteries.

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