Aromatic heterocycle and fat heterocycle connected piperidine nitroxide free radical compound and synthesis method thereof, positive electrode electrolyte based on same and application of piperidine nitroxide free radical compound in flow battery

Abstract

The invention discloses a synthetic method of a piperidine nitroxide free radical compound formed by connecting an aromatic heterocyclic ring and an aliphatic heterocyclic ring, a derivative of the piperidine nitroxide free radical compound, a positive electrode electrolyte based on the piperidine nitroxide free radical compound and application of the piperidine nitroxide free radical compound in a flow battery. A series of TEMPO nitroxide free radical derivatives in which aromatic heterocycles and fat heterocycles are connected in a substituted manner are prepared and tested by adjusting amino or hydroxyl chains on the 4-site of cyclic nitroxide free radicals to be connected with different aromatic heterocycles and fat heterocycles, the connected substituted heterocycles form extended TEMPO compounds, the conjugation degree of the extended TEMPO compounds is increased, the molecular structure can be well stabilized, and the molecular structure can be used for preparing the TEMPO nitroxide free radical derivatives. Disproportionation-dimerization and secondary ring-opening reaction of a cyclic nitroxide free radical structure are inhibited, and the stability is improved, namely the cycle life of the battery is prolonged and the capacity of the battery is increased. The invention provides a new strategy for constructing a high-performance neutral aqueous organic flow battery, and can be suitable for large-scale energy storage.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid flow battery electrode materials, and specifically relates to a type of piperidine nitroxide free radical compound in which an aromatic heterocycle and an aliphatic heterocycle are connected, a preparation method thereof, the preparation of a positive electrode electrolyte based thereon, and an application in a liquid flow battery. Background Art

[0002] With the rapid development of modern industry, the global environment is gradually warming due to excessive carbon emissions. The use of clean and efficient energy has become a trend in the world, and the development of new energy and renewable energy technologies has also flourished accordingly. Among them, solar energy and wind energy are expected to become the main energy sources in the future. However, solar energy and wind energy have strong intermittent, random and uneven geographical distribution, which greatly limits their application. Therefore, it is urgent to develop new and efficient large-scale power storage and transportation technologies. Large-scale storage and transportation need to meet the requirements of high safety, long life and low cost. Compared with traditional electrochemical energy storage devices such as lithium batteries, sodium sulfur batteries and supercapacitors, the battery safety issues of the former two are still to be solved, and the high cost of the latter restricts its large-scale use. Based on the characteristics of high safety and long life, aqueous organic flow batteries stand out among many energy storage technologies and are considered to be very suitable for the storage and transportation of solar energy and wind energy. Because of its rich structure, cheap raw materials and high safety, it has become one of the best candidates for large-scale energy storage technology.

[0003] The positive and negative electrolytes of neutral aqueous organic flow batteries are composed of earth-abundant elements such as C, H, O, N, and S. The electrolyte is a cheap sodium chloride / potassium chloride aqueous solution, which has the advantages of high safety, green environmental protection, and low cost. In addition, the electrochemical properties of organic molecules can be adjusted through molecular engineering. The organic active molecules of the negative electrode electrolyte are generally selected from viologen, anthraquinone, phenazine, and azobenzene derivatives. The positive electrode electrolyte materials include 2,2,6,6-tetramethylpiperidinyl nitroxide free radical (TEMPO), tetrathiafulvalene (TTF) derivatives, metallocene derivatives, etc.

[0004] At present, many negative electrode electrolyte materials with excellent structural stability have been developed. In comparison, positive electrode electrolytes are relatively few in variety and slightly less stable, and also have disadvantages such as cross-penetration of electrolytes through the diaphragm due to small molecular volume. Therefore, the development of new organic molecules as active materials is of great significance for the application of aqueous organic flow batteries. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a type of piperidine nitroxide free radical compound in which an aromatic heterocycle and an aliphatic heterocycle are connected, and a preparation method thereof, a positive electrode electrolyte based thereon, and an application in a liquid flow battery, so as to solve the defect problem of cross-penetration caused by a small number of positive electrode electrolytes, low stability and small molecular volume.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention discloses a piperidine nitroxide free radical compound in which an aromatic heterocycle and an aliphatic heterocycle are connected. The main body of the piperidine nitroxide free radical compound is a piperidine nitroxide free radical molecule, and the structural formula is shown in one of the following formulas:

[0008]

[0009] Wherein, R is any one of nitrogen-oxygen heterocycles or their derivatives; X=Cl or Br; and n=1-4.

[0010] Preferably, R includes a five-membered heterocycle, a six-membered heterocycle, a benzoheterocycle, a heterocycloheterocycle, and derivatives of the aforementioned heterocycles.

[0011] Further preferably, R comprises the following structure:

[0012]

[0013] The present invention also discloses a method for synthesizing the piperidine nitroxide free radical compound in which the aromatic heterocycle and the aliphatic heterocycle are connected, comprising:

[0014] Take the reaction materials 1,3-dicyclohexylcarbodiimide, 4-dimethylaminopyridine, 4-NH2-TEMPO and monochloroacetic acid, add dichloromethane, and synthesize the chloroacetylamide-substituted piperidine nitroxide free radical molecule;

[0015] According to the equivalent ratio, an aromatic heterocyclic / aliphatic heterocyclic molecule is added to a piperidine nitroxide free radical molecule substituted with chloroacetylamide, the mixture is stirred in a solvent for reaction, and then washed, filtered and dried to obtain a piperidine nitroxide free radical compound.

[0016] Preferably, the solvent is acetonitrile, acetone or tetrahydrofuran.

[0017] Preferably, the equivalent ratio of the chloroacetamide-substituted piperidine nitrogen oxide free radical to the aromatic heterocyclic / aliphatic heterocyclic molecule is 1:1.5.

[0018] The aromatic heterocyclic molecules referred to in the present invention are heterocyclic rings with planar structural characteristics, and the atoms in the rings form a closed conjugated system. The ring system of the aromatic heterocyclic ring has certain stability and aromaticity, and the ring is not easy to break in general chemical reactions. Common aromatic heterocyclic rings include pyridine, furan, thiophene, pyrrole, etc.

[0019] The aliphatic heterocyclic molecules referred to in the present invention refer to heterocyclic compounds whose heterocyclic rings in the molecular skeleton cannot embody aromaticity. The chemical properties of aliphatic heterocyclic rings are similar to those of corresponding chain compounds, but due to the presence of the rings, their reactivity and selectivity may be different. Common aliphatic heterocyclic rings include oxirane, aziridine, ethylene sulfide, tetrahydrofuran, etc.

[0020] In short, aromatic heterocyclic / aliphatic heterocyclic molecules have their own characteristics in structure, properties and applications. Aromatic heterocyclic compounds are usually more stable than aliphatic heterocyclic compounds and have a more uniform distribution of electrons.

[0021] Preferably, the reaction temperature is room temperature, and the stirring reaction time is 24 to 48 hours.

[0022] The invention also discloses the application of the piperidine nitrogen oxide free radical compound in which the aromatic heterocycle and the aliphatic heterocycle are connected to prepare the positive electrode electrolyte.

[0023] The invention also discloses a piperidine nitroxide free radical positive electrode electrolyte, which is prepared from the piperidine nitroxide free radical compound.

[0024] The invention also discloses the application of the piperidine nitroxide free radical positive electrode electrolyte in the preparation of a neutral aqueous liquid flow battery.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The piperidine nitroxide free radical compound in which an aromatic heterocycle and an aliphatic heterocycle are connected is disclosed in the present invention. After hydrophilic modification at the 4-position structure and conjugation extension strategy, a series of TEMPO nitroxide free radical derivatives in which an aromatic heterocycle and an aliphatic heterocycle are connected are successfully prepared and tested. The connected substituted nitrogen heterocycle forms an extended TEMPO compound, and its conjugation degree is increased, which can better increase the electron donation potential, that is, increase the battery voltage, and is beneficial to the battery voltage management. The groups with positive or negative charges in the redox active molecules improve their solubility in water and increase the battery capacity. At the same time, the middle chloroacetyl group can form an extended conjugated system with the aromatic heterocycle in the single-electron reduced state, effectively delocalize electrons, and improve the stability of the molecule. The branched structure increases the molecular volume, effectively prevents the problem of interpenetration and penetration of positive and negative electrode electrolytes, and ensures a high battery cycle stability.

[0027] The present invention also designs and develops a 4-dimethylaminopyridine functionalized 4-acetylamino-2,2,6,6-tetramethylpiperidin-N-oxyl derivative (DMA-TEMPO) cathode electrolyte with better performance, which can be applied to high-performance AORFBs and achieves a breakthrough in high stability during the charge and discharge process. The present invention provides a new strategy for building high-performance neutral aqueous organic flow batteries, which can be applied to large-scale energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a neutral aqueous organic redox flow battery composed of piperidine nitroxide radicals connected by aromatic heterocycles and aliphatic heterocycles;

[0029] Figure 2 Cyclic voltammetry curves of the molecules prepared in the present invention (scanning rates are 0.01, 0.02, 0.05, 0.1, 0.2, 0.5 and 1 V / s, respectively); wherein a) and b) are Example 2; c) and d) are Example 3; e) and f) are Example 4;

[0030] Figure 3 Cyclic voltammetry curves of the molecules prepared in the present invention (scanning rates are 0.01, 0.02, 0.05, 0.1, 0.2, 0.5 and 1 V / s, respectively); wherein a) and b) are from Example 5; c) and d) are from Example 1;

[0031] Figure 4 The EPR diagrams of the piperidine nitroxide free radical compounds prepared in the examples of the present invention; wherein a) is MPA-TEMPO; b) is MMA-TEMPO; c) is PyrA-TEMPO; d) is PA-TEMPO; e) is DMA-TEMPO;

[0032] Figure 5 The cyclic charge-discharge curve of 0.1M molecule (5mL) / 0.1M diol-Vi (7ml) prepared in Example 1 in 2M sodium chloride aqueous solution;

[0033] Figure 6 The cyclic charge-discharge curve of the symmetrical battery of the 1M DMA-TEMPO cathode electrolyte system prepared in Example 1;

[0034] Figure 7 The cyclic charge-discharge curve of the symmetrical battery with 0.1M DMA-TEMPO positive electrolyte system prepared in Example 1; wherein a) is the cyclic charge-discharge curve of the symmetrical battery with 0.1M DMA-TEMPO at 40mA cm -2 The cycle curve b) below is a representative charge and discharge curve of the half-cell between -0.35V and +0.40V. Figure; c) is a representative voltage-current curve during charge and discharge. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings: 1. Specific embodiments

[0039] Example 1

[0040] DMA-TEMPO, i.e., compound 1, was synthesized as follows:

[0041] In a 500mL round-bottom flask, add 250mL dichloromethane (DCM), 14.95g 1,3-dicyclohexylcarbodiimide (DCC), 2.25g 4-dimethylaminopyridine (DMAP), 12.5g 4-NH2-TEMPO, and 6.85g monochloroacetic acid, respectively, and stir at room temperature for 18h under argon. When weighing the ingredients, 4-NH2-TEMPO and monochloroacetic acid can be separated in time to avoid rapid acid-base neutralization reaction in the air. In addition, since the acid-base neutralization reaction releases a lot of heat, the addition of dry DCM should be carried out in an ice bath. After the reaction is completed, wash three times with deionized water, collect the organic phase, dry it with anhydrous sodium sulfate, and distill it under reduced pressure to obtain a red liquid. The product is purified by silica gel column chromatography (ethyl acetate: petroleum ether = 2:1) to obtain the primary product ClAcNH-TEMPO, and the reaction formula is as follows:

[0042]

[0043] Synthesis of DMA-TEMPO: 12 g ClAcNH-TEMPO, 6 g DMAP and 50 mL dried MeCN were added to a 100 mL round-bottom flask, stirred at room temperature for 36 h, then distilled under reduced pressure, washed 3 times with 30 mL MeCN (3 times with 10 mL), collected the aqueous phase, and distilled under reduced pressure to obtain orange solid DMA-TEMPO. Yield: 16.1 g (90%). The reaction formula is as follows:

[0044]

[0045] Example 2

[0046] MPA-TEMPO, i.e., compound 2, was synthesized as follows:

[0047] 12g ClAcNH-TEMPO, 5g N-methylpiperidine and 50mL dried MeCN were added to a 100mL round-bottom flask, stirred at room temperature for 36h, then distilled under reduced pressure, washed 3 times with 30mL MeCN (3 times with 10mL), and the aqueous phase was collected and distilled under reduced pressure to obtain a light orange solid MPA-TEMPO. Yield: 12.86g (80%). The reaction formula is as follows:

[0048]

[0049] Example 3

[0050] MMA-TEMPO, i.e. compound 3, was synthesized as follows:

[0051] 12g ClAcNH-TEMPO, 5g N-methylmorpholine and 50mL dried MeCN were added to a 100mL round-bottom flask, stirred at room temperature for 36h, then distilled under reduced pressure, washed 3 times with 30mL MeCN (3 times with 10mL), and the aqueous phase was collected and distilled under reduced pressure to obtain light orange solid MMA-TEMPO. Yield: 13.7g (81%). The reaction formula is as follows:

[0052]

[0053] Example 4

[0054] PyrA-TEMPO, i.e., compound 4, was synthesized as follows:

[0055] Synthesis of PyrA-TEMPO: 12 g ClAcNH-TEMPO, 5 g N-methylpyrrolidine and 50 mL dried MeCN were added to a 100 mL round-bottom flask, stirred at room temperature for 36 h, then distilled under reduced pressure, washed 3 times with 30 mL MeCN (3 times with 10 mL), and the aqueous phase was collected and distilled under reduced pressure to obtain a light orange solid PyrA-TEMPO. Yield: 12.6 g (79%). The reaction formula is as follows:

[0056]

[0057] Example 5

[0058] PA-TEMPO, i.e. compound 5, was synthesized as follows:

[0059] Synthesis of PA-TEMPO: 12 g ClAcNH-TEMPO, 4 g pyridine and 50 mL dried MeCN were added to a 100 mL round-bottom flask, stirred at room temperature for 36 h, then distilled under reduced pressure, washed 3 times with 30 mL MeCN (3 times with 10 mL), and the aqueous phase was collected and distilled under reduced pressure to obtain a light orange solid PA-TEMPO. Yield: 12.86 g (80%). The reaction formula is as follows:

[0060]

[0061] 2. Structural analysis

[0062] The physical properties and structure of the piperidine nitroxide free radicals prepared in the examples of the present invention were analyzed to prove that the above process indeed synthesized these compounds. The specific hydrogen spectrum data are as follows:

[0063] Compound 1: 1 H NMR(400MHz,D2O)δ7.61(d,J=7.6Hz,2H),6.62(d,J=7.7Hz,2H),4.63(d,J=6.6Hz,2H),3.99( t,J=14.1Hz,1H),2.97(s,6H),1.75(d,J=12.6Hz,2H),1.37(t,J=12.7Hz,2H),1.04(s,12H).

[0064] Compound 2: 1H NMR(400MHz,D2O)δ7.26,7.24,7.17,7.13,6.79,6.75,6.70,6.32,6.29,4.70,4.03,4.00,3. 96,3.71,3.33,3.31,3.19,3.17,2.97,1.75,1.72,1.65,1.45,1.43,1.36,1.32,1.07,1.06.

[0065] Compound 3: 1 H NMR(400MHz,D2O)δ7.27,7.18,7.16,6.84,6.80,6.78,4.70,4.04,4.03,3. 99,3.84,3.52,3.42,3.39,3.15,1.78,1.75,1.40,1.37,1.34,1.08,1.06.

[0066] Compound 4: 1 H NMR(400MHz,D2O)δ7.29,7.21,7.19,7.17,6.83,6.81,4.70,4.06,4.03,4.00,3.87 ,3.86,3.50,3.48,3.46,2.99,2.05,2.04,1.79,1.75,1.40,1.37,1.34,1.09,1.07.

[0067] Compound 5: 1 H NMR (400MHz, D2O) δ7.62,7.60,6.63,6.61,4.63,4.62,4.02,3.99,3.95,2.97,1.76,1.73,1.40,1.37,1.34,1.04.

[0068] 3. Application of organic flow battery preparation

[0069] The DMA-TEMPO neutral aqueous organic redox flow battery electrode material prepared in Example 1 can be prepared by the following steps:

[0070] Step 1: Assemble the core fixture;

[0071] The neutral aqueous organic redox flow battery used in the test is a single cell structure. The positive terminal plate, positive insulating plate, positive conductive plate, positive flow frame, positive graphite felt, positive gasket, anion exchange membrane, negative gasket, negative graphite felt, negative flow frame, negative conductive plate, negative insulating plate, and negative terminal plate are fixed with bolts in turn, and external pipes are connected. Check whether the bolts are loose. If they are loose, they can be reinforced again. Before the test, a sealing and pressure test should be performed. On the basis of the above-mentioned fixture, two liquid storage bottles and a peristaltic pump are connected. After 2 hours of circulation, if there is no leakage and no change in liquid volume, it can be retained for use. If the above-mentioned leaks occur, readjustment is required.

[0072] Step 2: Preparation of electrode materials,

[0073] Prepare a sufficient amount of 1M NaCl solution in a volumetric flask. The negative electrode electrolyte is diol-Vi, and the positive electrode electrolyte is the above-mentioned piperidine nitroxide free radical DMA-TEMPO.

[0074] Preparation of 0.1 M DMA-TEMPO:

[0075] Take 184mg DMA-TEMPO and 263mg diol-Vi and dissolve them in 5mL and 7mL of 1M NaCl solution respectively, stir or ultrasonicate to make them completely dissolved, the concentration of both in NaCl solution is 0.1M, and the volume ratio of the mixed solution formed by the two is 1:1.4 to ensure that the DMA-TEMPO on the positive electrode side is fully charged and discharged. Bubble Ar for 10 minutes, DMA-TEMPO and diol-Vi are used as the positive electrode electrolyte and negative electrode electrolyte of the battery respectively, referred to as 0.1M DMA-TEMPO / diol-Vi AORFB.

[0076] Step 3: Assemble the neutral aqueous organic redox flow battery and perform performance testing;

[0077] Place the fixture prepared in step 1 and the solution in step 2 in the glove box, use DMA-TEMPO as the positive electrolyte and diol-Vi solution as the negative electrolyte. Connect the external power supply, peristaltic pump, and Xinwei tester, set the program, and then you can perform the charge and discharge test.

[0078] After the above steps, the 0.1M DMA-TEMPO system was in the voltage range of 0.3-1.5V, 40mA / cm 2 At a current density of , the system capacity reaches a maximum of 12.1 mAh (specific capacity of 26.8 Ah / L). After 2060 cycles, the total capacity retention rate is 98.1%, the single-cycle capacity retention rate is 99%, the overall coulombic efficiency is around 98%, and the energy efficiency is 67%.

[0079] Therefore, the above battery tests confirm that DMA-TEMPO is an excellent cathode electrolyte material in neutral aqueous organic redox flow batteries. The solubility of piperidine nitroxide derivatives ionized with aromatic heterocycles and aliphatic heterocycles increases. The introduction of multiple ionization sites also increases the redox potential of piperidine nitroxide derivatives, and the entire voltage range is 0.865V (vs. NHE), proving that piperidine nitroxide derivatives are a class of efficient cathode electrolytes, thereby achieving high solubility, high capacity, less intercalation, and long life battery performance.

[0080] 4. Flow battery performance test

[0081] In order to verify the effect of the present invention, the piperidine nitroxide derivative synthesized in Example 1 was used to prepare the positive electrolyte of the flow battery. The test results are shown in Figure 1 to Figure 7 The results are analyzed as follows:

[0082] Figure 1 The schematic diagram of a neutral aqueous organic redox flow battery composed of piperidine nitroxide radicals connected by aromatic heterocycles and aliphatic heterocycles is shown, wherein the positive electrode electrolyte is the piperidine nitroxide radical molecule described in the present invention, the negative electrode electrolyte is diol-Vi molecule, and the supporting electrolyte is 1M NaCl solution. The system is charged and discharged by an external power supply. During the charging process, based on the piperidine nitroxide radical molecule as the positive electrode electrolyte, 1e - After that, the +1-valent cation is converted into a +2-valent cation containing a free radical; diol-Vi is used as the negative electrode electrolyte to obtain 1e - After that, the +2-valent cation is converted into a +1-valent cation containing a free radical, and the monopyridine structure undergoes conjugation transformation. The discharge process is opposite to the charging process and is highly reversible.

[0083] Figure 2 and Figure 3 , which shows the cyclic voltammetry curves of the molecules prepared in the embodiments of the present invention (scan rates are 0.01, 0.02, 0.05, 0.1, 0.2, 0.5 and 1 V / s, respectively). Specifically, it is the cyclic voltammetry curve of the piperidine nitroxide free radical solution with a concentration of 10 mM aromatic heterocycles and aliphatic heterocycles connected, and the scan rates are 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1 V / s, respectively. It can be clearly seen from the figure that the redox potential of the derivative DMA-TEMPO is as high as 0.865 V Vs NHE, which means that this type of viologen derivative can be used as a type of efficient positive electrode electrolyte in neutral aqueous organic liquid flow batteries.

[0084] Figure 4This is the EPR diagram of the piperidine nitroxide free radical positive electrode electrolyte prepared in the embodiment of the present invention. It can be seen from the figure that the substance is in a stable free radical state in the air state.

[0085] Figure 5 The cyclic charge-discharge curve of 0.1M molecule (5mL) / 0.1M diol-Vi (7mL) in 2M sodium chloride aqueous solution prepared in Example 1 of the present invention. The electrolyte molecule can stably cycle for more than 2000 cycles at a concentration of 0.1M, and the capacity retention rate is still greater than 98%.

[0086] Figure 6 This is a single electron cycle charge-discharge curve of 1M DMA-TEMPO (5mL) / diol-Vi AORFB (7mL) prepared in Example 1 in 1M NaCl aqueous solution. Figure 6 It can be seen that when the current density is 40mA / cm 2 When the cut-off voltage is 1.5V, the battery system shows 560 cycles of charge and discharge capacity and the relationship between coulombic efficiency and cycle number. The total capacity retention rate is 99.96%, the overall coulombic efficiency is around 99%, and the energy efficiency is 73%, indicating that the system has high stability and is very suitable for use as an electrode material for neutral aqueous flow batteries.

[0087] Figure 7 The cyclic charge-discharge curve of the symmetrical battery with 0.1M DMA-TEMPO positive electrolyte prepared in Example 1 of the present invention. In the voltage range of -0.35V to +0.4V, the DMA-TEMPO was evaluated by symmetrical battery cycle experiment. 1+· / DMA-TEMPO 2+ The redox couple is at a current density of 40 mA cm -2 The study focused specifically on evaluating the stability of the redox couple itself, excluding any interference from the negative electrode electrolyte material that could cause capacity degradation. The battery showed excellent performance over more than 2,000 cycles, with a total capacity retention of 93.35%.

[0088] In summary, the present invention discloses a type of piperidine nitroxide free radical redox flow battery positive electrode electrolyte molecule connected with an aromatic heterocycle and an aliphatic heterocycle, with a highly water-soluble piperidine nitroxide free radical compound as the positive electrode electrolyte active molecule of the flow battery, with viologen or naphthalene anhydride derivatives as the negative electrode electrolyte active molecule, NaCl or KCl as the supporting electrolyte, DSVN membrane as the anion exchange membrane, 3×3 cm carbon felt as the electrode material, copper sheet and graphite plate as the positive and negative electrode current collectors. The DMA-TEMPO of the present invention has the advantages of reversible redox potential, high water solubility, fast electron transfer rate, excellent reversibility, etc. It is matched with viologen or naphthalene anhydride derivatives and applied to neutral aqueous flow batteries, and has high electrochemical stability, high energy efficiency and capacity utilization. It is produced in neutral aqueous flow batteries for large-scale energy storage.

[0089] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A piperidine nitroxide free radical compound in which an aromatic heterocycle and an aliphatic heterocycle are connected, characterized in that: Its main body is a piperidine nitrogen oxide free radical molecule, and its structural formula is shown in one of the following formulas: Wherein, R is any one of nitrogen-oxygen heterocycles or their derivatives; X=Cl or Br; and n=1-4.

2. The piperidine nitroxide free radical compound of a type of aromatic heterocycle and aliphatic heterocycle connected in succession according to claim 1, characterized in that: R includes a five-membered heterocycle, a six-membered heterocycle, a benzoheterocycle, a heterocycloheterocycle, and derivatives of the aforementioned heterocycles.

3. The piperidine nitroxide free radical compound of a type of aromatic heterocycle and aliphatic heterocycle connected together according to claim 2, characterized in that: R includes the following structure:

4. The method for synthesizing the piperidine nitroxide free radical compound having an aromatic heterocycle and an aliphatic heterocycle connected thereto according to any one of claims 1 to 3, characterized in that: include: Take the reaction materials 1,3-dicyclohexylcarbodiimide, 4-dimethylaminopyridine, 4-NH2-TEMPO and monochloroacetic acid, add dichloromethane, and synthesize the chloroacetylamide-substituted piperidine nitroxide free radical molecule; According to the equivalent ratio, an aromatic heterocyclic / aliphatic heterocyclic molecule is added to a piperidine nitroxide free radical molecule substituted with chloroacetylamide, the mixture is stirred in a solvent for reaction, and then washed, filtered and dried to obtain a piperidine nitroxide free radical compound.

5. The method for synthesizing the piperidine nitroxide free radical compound in which an aromatic heterocycle and an aliphatic heterocycle are connected according to claim 4, characterized in that: The solvent is acetonitrile, acetone or tetrahydrofuran.

6. The method for synthesizing the piperidine nitroxide free radical compound according to claim 4, characterized in that: The equivalent ratio of the piperidine nitrogen oxide free radical substituted with chloroacetamide and the aromatic heterocyclic / aliphatic heterocyclic molecules is 1:1.

5.

7. The method for synthesizing the piperidine nitroxide free radical compound having an aromatic heterocycle and an aliphatic heterocycle connected thereto according to claim 4, characterized in that: The reaction temperature is room temperature, and the stirring reaction time is 24 to 48 hours.

8. Use of the piperidine nitroxide free radical compound having an aromatic heterocycle and an aliphatic heterocycle connected thereto as claimed in any one of claims 1 to 3 in preparing a positive electrode electrolyte.

9. A piperidine nitroxide free radical positive electrode electrolyte in which an aromatic heterocycle and an aliphatic heterocycle are connected, characterized in that: The invention is prepared from the piperidine nitrogen oxide free radical compound according to any one of claims 1 to 3.

10. Use of the piperidine nitroxide free radical positive electrode electrolyte containing aromatic heterocycles and aliphatic heterocycles as claimed in claim 9 in the preparation of neutral aqueous liquid flow batteries.

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