Method for in-situ electro-synthesizing perylene hexacarboxylate sodium electrode with regular morphology

Abstract

The invention discloses a method for in-situ electro-synthesizing a trisodium carboxylate hexaazaphenanthrene electrode with a regular morphology, belonging to the technical field of organic electrode materials. First, a trisodium carboxylate hexaazaphenanthrene electrode is prepared from trisodium carboxylate hexaazaphenanthrene. Then, using an NaOH solution as the electrolyte, an electrochemical reaction is carried out. The trisodium carboxylate hexaazaphenanthrene in the trisodium carboxylate hexaazaphenanthrene electrode undergoes deprotonation to form trisodium carboxylate hexaazaphenanthrene. By utilizing the conjugated structure of trisodium carboxylate hexaazaphenanthrene, the electrode is induced to undergo highly oriented growth on the surface under the action of an electric current, and thus a trisodium carboxylate hexaazaphenanthrene electrode with a regular, dense, and high aspect ratio needle-like structure is obtained. Experimental results show that the trisodium carboxylate hexaazaphenanthrene electrode prepared by the method provided by the invention has a dense needle-like structure with a high aspect ratio and excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of organic electrode materials, and particularly relates to a method for in-situ electro-synthesizing a trisodium carboxylate hexaazaphenanthrene electrode with a regular morphology. Background Art

[0002] Aqueous sodium-ion batteries have the characteristics of high safety, pollution-free, long life, low cost, environmental friendliness, and easy assembly, and can meet the requirements of large-scale energy storage systems. However, the limited potential window of water restricts the selection range for developing suitable electrode materials. Therefore, there is an urgent need to find potential electrode materials with excellent aqueous sodium-ion storage performance.

[0003] The inorganic electrode materials commonly used in aqueous sodium-ion batteries are mainly divided into insertion-type (such as Na2Ti3O7), conversion-type (metal oxides and sulfides), and alloy-type (Sn, Sb, Bi, etc.). Among them, although the conversion-type and alloy-type electrode materials have a relatively high sodium storage specific capacity, the sodium storage kinetics is slow, and phase transformation occurs during the sodium insertion process, and the volume is prone to expansion, resulting in the collapse or damage of their structure and the decline of cycle stability, which is not conducive to the construction of high-rate and long-life aqueous sodium-ion batteries. The insertion-type electrode materials have characteristics such as stable structure, but have disadvantages such as poor conductivity, low theoretical capacity, and poor rate performance.

[0004] In order to overcome the above-mentioned disadvantages of inorganic materials in sodium-ion storage, organic electrode materials have received extensive attention. Among them, phenazine, as an important N-containing heteroatom π-conjugated aromatic organic molecule, has been highly regarded by the physics, chemistry, and materials science communities since its emergence. It has the advantages of rich C=N redox active groups, high electrochemical activity, strong ability to coordinate and chelate sodium ions through coordination reactions, and flexible structure design. However, the organic electrode materials prepared by traditional methods generally do not have a regular morphology, and most of the active substances are embedded in the carbon matrix and cannot be better utilized. Therefore, how to prepare organic electrode materials with a regular morphology to effectively utilize the active substances has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] Object of the Invention: In order to solve the technical problems existing in the prior art, the present invention aims to provide a method for in-situ electro-synthesizing a trisodium carboxylate hexaazaphenanthrene electrode with excellent electrochemical performance and a regular morphology.

[0006] Technical Solution: The method for in-situ electro-synthesizing a trisodium carboxylate hexaazaphenanthrene electrode with a regular morphology according to the present invention includes the following steps:

[0007] (1) Prepare a slurry by mixing tris-carboxy hexaazaphenanthrene, a conductive agent, a binder, and a solvent, and then coat it on a current collector to obtain a tris-carboxy hexaazaphenanthrene electrode;

[0008] (2) Under a three - electrode system, using the NaOH solution as the electrolyte, the above - mentioned tri - carboxy hexaazaphenalene electrode undergoes an electrochemical reaction to obtain a sodium tri - carboxylate hexaazaphenalene electrode with a regular morphology.

[0009] Further, in step (1), the synthesis method of the tri - carboxy hexaazaphenalene is as follows: under an inert atmosphere, mix di - aminobenzoic acid, cyclohexanehexone octahydrate and an organic solvent, and then carry out reflux heating to obtain it.

[0010] Further, the inert gas is nitrogen, the molar ratio of di - aminobenzoic acid to cyclohexanehexone octahydrate is 2 - 4:1, preferably 3 - 4:1, the organic solvent is acetic acid, for every 2 - 4 mmol of di - aminobenzoic acid added, 30 - 35 mL of the organic solvent is added; the temperature of the reflux heating is 100 - 150 °C, preferably 110 - 125 °C, and the reflux heating time is 8 - 12 h, preferably 10 h.

[0011] Further, the product obtained after the reflux heating also includes centrifugation, washing, purification and drying treatments. The washing method is: wash successively with hot ethanol at 30 - 40 °C, acetone and ethanol for 2 - 3 times; the reagent used for purification is nitric acid solution; the concentration of the nitric acid solution is 30 - 35 wt%; the amount of the nitric acid solution used is 50 - 60 mL; the purification temperature is 120 - 140 °C; the purification time is 3 - 4 h.

[0012] Further, in step (1), the mass ratio of the tri - carboxy hexaazaphenalene, the conductive agent and the binder is 5:4:1 - 8:1:1. Controlling the mass ratio of the tri - carboxy hexaazaphenalene, the conductive agent and the binder within the above range is beneficial to ensuring the content of the active material in the electrode, thereby improving the electrochemical performance of the electrode; the ratio of the volume of the solvent to the mass of the tri - carboxy hexaazaphenalene is 10 - 20 mL:6 - 7 g; the method of making a slurry from the tri - carboxy hexaazaphenalene, the conductive agent, the binder and the solvent is grinding and mixing.

[0013] Further, the conductive agent is one or more of acetylene black, Ketjen black and carbon nanotubes, the binder is one or more of PVDF, CMC and SBR; the solvent is N - methylpyrrolidone; the current collector is one of graphite paper, aluminum foil and copper foil, and the coating thickness is 0.3 - 0.5 mm.

[0014] Further, in step (2), the concentration of the NaOH solution is 5-10 mol / L, preferably 8-10 mol / L. The NaOH solution can provide Na ions for the preparation of hexazine tricarboxylate sodium while serving as an electrolyte; the electrochemistry reaction method is cyclic voltammetry or galvanostatic charge-discharge method, preferably cyclic voltammetry; the scanning rate of the cyclic voltammetry is 1-5 mV s -1 , preferably 1-2 mV s -1 , the voltage range is -1.4 to 0 V, preferably -1.2 to 0 V, the reaction time is 1-5 cycles, preferably 4-5 cycles; the current density of the galvanostatic charge-discharge method is 1-5 A g -1 , and the voltage range is -1.4 to 0 V.

[0015] Further, the product of the electrochemistry reaction also includes washing and drying treatments, and the washing reagent is ethanol.

[0016] Further, in step (2), the aspect ratio of the hexazine tricarboxylate sodium electrode with regular morphology is 20-5:1, preferably 20-15:1.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0018] (1) In the present invention, a hexazine tricarboxylate electrode is first prepared from hexazine tricarboxylic acid, and then an electrochemistry reaction is carried out using the NaOH solution as an electrolyte. The hexazine tricarboxylic acid in the hexazine tricarboxylate electrode will be deprotonated to form hexazine tricarboxylate sodium. Utilizing the conjugated structure of hexazine tricarboxylate sodium, the electrode is promoted to have a highly oriented surface through the action of current, and then a hexazine tricarboxylate sodium electrode with a regular, dense, and high aspect ratio needle-like structure is obtained; the experimental results show that the hexazine tricarboxylate sodium electrode prepared by the method provided by the present invention has a dense needle-like structure with a high aspect ratio and excellent electrochemical performance;

[0019] (2) The prepared hexazine tricarboxylate sodium electrode with regular morphology has a unique needle-like structure, and the aspect ratio is 20-5:1. Thanks to the electrochemical synthesis, the active substances originally embedded in the carbon matrix are exposed on the electrode surface, in full contact with the electrolyte, and the charge transfer resistance is significantly reduced, only 0.56-0.83 Ω, thereby optimizing the reaction kinetics. At a current density of 1 A g -1 , a specific capacity of 195.7-231.9 mAh g -1 can be obtained. A long-term cycle stability test of 10,000 cycles is carried out at a current density of 10 A g -1 , and the cycle retention rate is as high as 83.3-98.6%. Description of the Drawings

[0020] Figure 1 This is the chemical structure diagram of tricarboxyhexazine (HATNTC) in Example 1 of the present invention;

[0021] Figure 2 This is the SEM image of tricarboxyhexazine (HATNTC) prepared in Example 1 of the present invention;

[0022] Figure 3 SEM image of the surface of the tricarboxyhexazine (HATNTC) electrode prepared in Example 1;

[0023] Figure 4 This is the chemical structure diagram of trisodium carboxyhexazine (Na3HATNC) in Example 1 of the present invention;

[0024] Figure 5 This is the SEM image of the surface of the trisodium carboxyhexazine (Na3HATNC) electrode in Example 1 of the present invention;

[0025] Figure 6 This is the SEM image of the surface of the trisodium carboxyhexazine (Na3HATNC-CS) electrode in Comparative Example 1 of the present invention. Detailed implementation manners

[0026] Next, the present invention will be further described in conjunction with specific embodiments and the accompanying drawings.

[0027] Example 1: The method for in-situ electro-synthesizing a trisodium carboxyhexazine electrode with a regular morphology according to the present invention includes the following steps:

[0028] (1) Under nitrogen protection, add 0.456 g (3 mmol) of 3,4-diaminobenzoic acid, 0.312 g (1 mmol) of hexaketocyclohexane octahydrate, and 30 mL of acetic acid into a reactor, carry out reflux heating at 120 °C, after reacting for 10 h, stop heating, cool to room temperature, centrifuge and wash the solid product, then wash it twice with hot acetic acid, acetone, and ethanol at 40 °C respectively. The obtained product is stirred in 50 mL of 30 wt% HNO3 solution at 140 °C for 3 h, and finally washed with deionized water and ethanol, and dried to obtain tricarboxyhexazine. Its chemical structure diagram is as shown in Figure 1 shown, and the electron microscopy image is as shown in Figure 2 shown. The tricarboxyhexazine organic material has no specific morphology and presents an irregular block structure;

[0029] (2) The tricarboxyhexaazanaphthylene obtained in step (1) is mixed with acetylene black, PVDF, and N-methylpyrrolidone, and the mixture is ground into a slurry, which is then evenly coated on graphite paper with a coating thickness of 0.5 mm to prepare a tricarboxyhexaazanaphthylene electrode; wherein the mass ratio of tricarboxyhexaazanaphthylene to acetylene black and bonding PVDF is 7:2:1, and the mass ratio of the volume of N-methylpyrrolidone to the mass ratio of tricarboxyhexaazanaphthylene is 10 mL:6 g; the electron microscope image of the tricarboxyhexaazanaphthylene electrode is as follows: Figure 3 As shown in the figure, it can be seen that tricarboxyhexaazanaphthalene is disorderly stacked on the electrode surface.

[0030] (3) The tricarboxyhexaazine electrode obtained in step (2) was placed in a three-electrode system with an electrolyte of 10 mol / L NaOH solution at 1 mVs -1 Cyclic voltammetry was performed at a scan rate of -1.2 to -0.4 V. After two cycles of cyclic voltammetry, the sodium tricarboxylate hexaazine electrode was obtained after ethanol washing and drying. The chemical structure is shown in the figure below. Figure 4 As shown in the electron microscope image Figure 5 As shown by Figure 5 It can be seen that after in situ electrochemical synthesis, Figure 3 The disordered accumulation of tricarboxyhexaazanaphthalene organic matter in the electrode is transformed into sodium tricarboxyhexaazanaphthalene, which is highly oriented on the electrode surface and presents a dense needle-like structure with a high aspect ratio (length: width = 20-15:1).

[0031] Example 2: The method for in-situ electrosynthesis of a sodium tricarboxylate hexaazine electrode having a regular morphology according to the present invention comprises the following steps:

[0032] (1) Under nitrogen protection, 0.304 g (2 mmol) of 3,4-diaminobenzoic acid, 0.312 g (1 mmol) of hexacyclohexane octahydrate and 30 mL of acetic acid were added to a reactor, and refluxed at 120° C. for 10 h. After the reaction, the heating was stopped, the mixture was cooled to room temperature, and the solid product was washed by centrifugation. The solid product was washed twice with 40° C. hot acetic acid, acetone and ethanol respectively. The obtained product was stirred in 50 mL of 30 wt% HNO3 solution at 140° C. for 3 h, and finally washed with deionized water and ethanol, and dried to obtain tricarboxyhexaazanaphthalene;

[0033] (2) The tricarboxyhexaazanaphthalene obtained in step (1) is mixed with acetylene black, PVDF, and N-methylpyrrolidone, and the mixture is ground into a slurry, which is then evenly coated on graphite paper with a coating thickness of 0.5 mm to prepare a tricarboxyhexaazanaphthalene electrode; wherein the mass ratio of tricarboxyhexaazanaphthalene to acetylene black and PVDF is 7:2:1, and the mass ratio of the volume of N-methylpyrrolidone to the mass ratio of tricarboxyhexaazanaphthalene is 10 mL:6 g;

[0034] (3) The tricarboxy hexaazaphenanthrene electrode obtained in step (2) is placed in a three - electrode system with an electrolyte of 5 mol / L NaOH solution. At a scanning rate of 5 mV / s -1 and a voltage range of - 1.2 V to - 0.4 V, cyclic voltammetry is performed. After 5 cycles of cyclic voltammetry, it is washed with ethanol and then dried to obtain the sodium tricarboxylate hexaazaphenanthrene electrode.

[0035] Example 3: The method for in - situ electro - synthesizing a sodium tricarboxylate hexaazaphenanthrene electrode with a regular morphology according to the present invention comprises the following steps:

[0036] (1) Under nitrogen protection, 0.608 g (4 mmol) of 3,4 - diaminobenzoic acid, 0.312 g (1 mmol) of hexaketocyclohexane octahydrate and 30 mL of acetic acid are added to a reactor. It is refluxed and heated at 120 °C. After reacting for 10 h, the heating is stopped and cooled to room temperature. The solid product is centrifuged and washed, and washed twice with hot acetic acid, acetone and ethanol at 40 °C respectively. The obtained product is stirred in 50 mL of 30 wt% HNO3 solution at 140 °C for 3 h, and finally washed with deionized water and ethanol and dried to obtain tricarboxy hexaazaphenanthrene;

[0037] (2) The tricarboxy hexaazaphenanthrene obtained in step (1) is mixed with acetylene black, PVDF, and N - methylpyrrolidone, ground into a slurry, and then uniformly coated on graphite paper with a coating thickness of 0.5 mm to prepare a tricarboxy hexaazaphenanthrene electrode; wherein, the mass ratio of tricarboxy hexaazaphenanthrene, acetylene black, and PVDF is 7:2:1, and the volume ratio of N - methylpyrrolidone to the mass of tricarboxy hexaazaphenanthrene is 10 mL:6 g;

[0038] (3) The tricarboxy hexaazaphenanthrene electrode obtained in step (2) is placed in a three - electrode system with an electrolyte of 10 mol / L NaOH solution. At a scanning rate of 5 mV / s -1 and a voltage range of - 1.2 V to - 0.4 V, cyclic voltammetry is performed. After 5 cycles of cyclic voltammetry, it is washed with ethanol and then dried to obtain the sodium tricarboxylate hexaazaphenanthrene electrode.

[0039] Example 4: The method for in - situ electro - synthesizing a sodium tricarboxylate hexaazaphenanthrene electrode with a regular morphology according to the present invention comprises the following steps:

[0040] (1) Under nitrogen protection, 0.456 g (3 mmol) of 3,4-diaminobenzoic acid, 0.312 g (1 mmol) of hexaketocyclohexane octahydrate and 30 mL of acetic acid were added to a reactor, and reflux heating was carried out at 120 °C. After reacting for 10 h, the heating was stopped, and it was cooled to room temperature. The solid product was centrifuged and washed, and washed twice with hot acetic acid, acetone and ethanol at 40 °C each. The obtained product was stirred in 50 mL of 30 wt% HNO3 solution at 140 °C for 3 h, and finally washed with deionized water and ethanol and dried to obtain tricarboxyhexazine;

[0041] (2) The tricarboxyhexazine obtained in step (1) was mixed with acetylene black, PVDF, and N-methylpyrrolidone, ground to form a slurry, and then uniformly coated on graphite paper with a coating thickness of 0.5 mm to prepare a tricarboxyhexazine electrode; among them, the mass ratio of tricarboxyhexazine, acetylene black, and PVDF is 7:2:1, and the volume ratio of N-methylpyrrolidone to the mass of tricarboxyhexazine is 10 mL:6 g;

[0042] (3) The tricarboxyhexazine electrode obtained in step (2) was under a three-electrode system, with the electrolyte being 10 mol / L NaOH solution, and constant current charge and discharge were carried out at a current density of 1 A g -1 and a voltage of -1.2 to -0.4 V. After 5 cycles of constant current charge and discharge, it was washed with ethanol and then dried to obtain a sodium tricarboxyhexazine electrode.

[0043] Comparative Example 1: The preparation method of the sodium tricarboxyhexazine electrode in this comparative example is as follows:

[0044] (1) Under nitrogen protection, 0.456 g (3 mmol) of 3,4-diaminobenzoic acid, 0.312 g (1 mmol) of hexaketocyclohexane octahydrate and 30 mL of acetic acid were added to a reactor, and reflux heating was carried out at 120 °C. After reacting for 10 h, the heating was stopped, and it was cooled to room temperature. The solid product was centrifuged and washed, and then washed twice with hot acetic acid, acetone and ethanol at 40 °C each. The obtained product was stirred in 50 mL of 30 wt% HNO3 solution at 140 °C for 3 h, and finally washed with deionized water and ethanol and dried to obtain tricarboxyhexazine;

[0045] (2) The tricarboxyhexazine obtained in step (1) was reacted in a mixed solution of NaOH and ethanol for 24 h to obtain sodium tricarboxyhexazine;

[0046] (3) Mix the sodium tricarboxylate perylene diimide obtained in step (2) with acetylene black, PVDF, and N-methylpyrrolidone, grind them to form a slurry, and then uniformly coat it on the graphite paper with a coating thickness of 0.5 mm to obtain a sodium tricarboxylate perylene diimide electrode; wherein, the mass ratio of sodium tricarboxylate perylene diimide, acetylene black, and PVDF is 7:2:1, and the volume ratio of N-methylpyrrolidone to the mass of sodium tricarboxylate perylene diimide is 10 mL:6 g; the SEM image of sodium tricarboxylate perylene diimide is as shown in Figure 6 shown. It can be seen from Figure 6 that the sodium tricarboxylate perylene diimide organic material synthesized by the traditional chemical method in Comparative Example 1 also has no specific morphology and presents an irregular block structure.

[0047] Use SEM analysis, cyclic voltammetry, galvanostatic charge-discharge method, and constant voltage scanning frequency impedance method to test the aspect ratio, redox peak current, specific capacity, charge transfer impedance, and cycle retention rate of the sodium tricarboxylate perylene diimide electrodes prepared in Examples 1 to 4 and Comparative Example 1. The test results are shown in Table 1.

[0048] It can be seen from Table 1 that from the aspect ratios of sodium tricarboxylate perylene diimide in Examples 1, 2, and 3, by selecting a 10 mol / L NaOH solution with a higher electrolyte concentration and a lower scanning rate of 1 mV s -1 , a larger aspect ratio can be obtained, thereby obtaining better electrochemical performance. It can be seen from Examples 1 and 4 that whether cyclic voltammetry or galvanostatic charge-discharge method is selected, a large aspect ratio and excellent electrochemical performance can be obtained. At a scanning rate of 1 mV s -1 , the peak current of the sodium tricarboxylate perylene diimide electrode prepared in Example 1 is higher than that of Comparative Example 1, indicating that the sodium tricarboxylate perylene diimide electrode prepared by the method of Example 1 undergoes a more complete redox reaction during the charge-discharge process. At a current density of 1 A g -1 , the specific capacity of the sodium tricarboxylate perylene diimide electrode prepared in Example 1 is much higher than that of Comparative Example 1, indicating that the needle-like structure prepared in Example 1 helps to more fully and efficiently utilize the active material to obtain a higher capacity. The charge transfer impedance is measured by the constant voltage scanning frequency impedance method. The sodium tricarboxylate perylene diimide electrode prepared in Example 1 has a lower impedance, which is beneficial to the rapid transfer of charges and improves the ion diffusion rate. A long-term cycle stability test of 10,000 cycles was carried out at a current density of 10 A g -1 . The cycle retention rate of Comparative Example 1 is only 34.2%. On the contrary, the sodium tricarboxylate perylene diimide electrode prepared in Example 1 shows almost no capacity decay during the cycle, indicating its potential as a next-generation electrode material.

[0049] Table 1 Performance of tricarboxylate hexaazaphenanthrene electrodes prepared in Examples 1 to 4 and Comparative Example 1

[0050]

[0051] As can be seen from the above examples, the tricarboxylate hexaazaphenanthrene electrode prepared by the method provided by the present invention has a regular morphology, presents a dense needle-like structure with a high aspect ratio, and improves the electrochemical performance of the electrode.

Claims

1. A method for in-situ electro-synthesizing a trisodium carboxylate perylene diimide electrode with a regular morphology, characterized in that, It includes the following steps: (1) Prepare a slurry by mixing tricarboxyhexazine, a conductive agent, a binder, and a solvent, and then coat it on a current collector to obtain a tricarboxyhexazine electrode; (2) Under a three - electrode system, use the NaOH solution as the electrolyte which can also provide Na ions for the preparation of sodium tricarboxyhexazine, and carry out an electrochemical reaction. The tricarboxyhexazine electrode as the cathode is prepared into a sodium tricarboxyhexazine electrode with a regular morphology through a reduction reaction; the way of the electrochemical reaction is cyclic voltammetry or galvanostatic charge - discharge method, and the voltage range is - 1.4~0V.

2. The method according to claim 1, characterized in that, In step (1), the synthesis method of the tricarboxyhexazine is: under an inert atmosphere, mix diaminobenzoic acid, hexaketocyclohexane octahydrate, and an organic solvent and then carry out reflux heating to obtain it.

3. The method according to claim 1, wherein In step (1), the mass ratio of the tricarboxyhexazine, the conductive agent, and the binder is 5:4:1~8:1:

1.

4. The method according to claim 1, wherein In step (1), the ratio of the volume of the solvent to the mass of the tricarboxyhexazine is 10~20mL:6~7g.

5. The method according to claim 1, characterized in that In step (2), the concentration of the NaOH solution is 5~10mol / L.

6. The method according to claim 1, wherein In step (2), the scanning rate of the cyclic voltammetry is 1 to 5 mV / s -1 , the voltage range is -1.4 to 0 V, and the reaction time is 1 to 5 cycles.

7. The method according to claim 1, wherein In step (2), the current density of the constant current charge-discharge method is 1~5 A g -1 , and the voltage range is -1.4~0V.

8. The method according to claim 1, characterized in that In step (2), in the sodium tricarboxyhexazine electrode with a regular morphology, the sodium tricarboxyhexazine is highly oriented on the electrode surface, presenting a dense needle - like structure with an aspect ratio of 20~15:

1.

9. A sodium tricarboxyhexazine electrode with a regular morphology prepared by the method according to any one of claims 1~8.

Images