Complexing agent, solid-phase bromine positive electrode active material, preparation method of solid-phase bromine positive electrode active material, solid-phase bromine positive electrode and zinc-bromine battery

Abstract

The invention provides a complexing agent, a solid-phase bromine positive electrode active material, a preparation method of the solid-phase bromine positive electrode active material, a solid-phase bromine positive electrode and a zinc-bromine battery, and belongs to the technical field of energy storage batteries. The complexing agent has a structure as shown in a formula (I): (CnH2n + 2-mXm) Rm (I), wherein 1 < = n < = 8, 2 < = m < = 4, and m and n are integers; in the presence of a plurality of X, each X is independently selected from any one of chlorine, bromine and iodine; and in the presence of a plurality of R, each R is independently selected from any one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring.

Description

Technical Field

[0001] The invention belongs to the technical field of energy storage batteries, and specifically relates to a complexing agent, a solid-phase bromine positive electrode active material and a preparation method thereof, a solid-phase bromine positive electrode, and a zinc-bromine battery. Background Art

[0002] Renewable energy, such as wind power and solar energy, plays an important role in the future smart grid. They can effectively alleviate the pollution caused by traditional fossil fuels and their own energy shortage. However, renewable energy is subject to environmental restrictions and has certain intermittent and random characteristics, requiring energy storage devices to adjust its frequency and store energy. As an energy storage device, rechargeable batteries have the characteristics of low price, no geographical restrictions, and short investment cycle, so they have attracted much attention in large-scale energy storage.

[0003] Aqueous zinc-bromine batteries are the strongest contenders for the next generation of large-scale energy storage batteries due to their low cost, pollution-free, high safety and stability. However, there are many problems in traditional zinc-bromine flow batteries, which limit their large-scale use. For example, the diffusion of bromide ions leads to cross-infection between the positive and negative electrodes of the battery, the use of expensive ion exchange membranes increases the cost of the battery, and the zinc negative electrode is prone to some side reactions, resulting in poor stability, which reduces the efficiency and cycle stability of the battery. At the same time, it also increases the maintenance cost of the liquid circulation device, thereby increasing the cost of the battery. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a complexing agent, a solid-phase bromine positive electrode active material and a preparation method thereof, a solid-phase bromine positive electrode, and a zinc-bromine battery, in order to at least partially solve the above technical problems. The specific technical solutions provided by the present invention are as follows.

[0005] As a first aspect of the present invention, a complexing agent is provided, having a structure shown in formula (1):

[0006] (C n H 2n+2-m X m )R m (one);

[0007] Wherein, 1≤n≤8, 2≤m≤4, m and n are both integers; when there are multiple Xs, each is independently selected from any one of chlorine, bromine and iodine; when there are multiple Rs, each is independently selected from any one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring.

[0008] As a second aspect of the present invention, a method for preparing the above-mentioned complexing agent is provided, comprising: mixing a nitrogen-containing heterocyclic compound and a halogenated alkane and performing a first complexing reaction to obtain a complexing agent; wherein the nitrogen-containing heterocyclic compound comprises at least one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring; and the halogenated alkane comprises a C substituted with chlorine, bromine or iodine. 1-8 at least one of the alkanes.

[0009] As a third aspect of the present invention, a solid-phase bromine positive electrode active material is provided, which is prepared using the above-mentioned complexing agent and has a structure shown in formula (II):

[0010] [(C n H 2n+2-m X m )R m ]Br a m (two);

[0011] Wherein, 1≤n≤8, 2≤m≤4, m and n are both integers, a is 2 or 4 or 6; when there are multiple Xs, each is independently selected from any one of chlorine, bromine and iodine; when there are multiple Rs, each is independently selected from any one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring; the nitrogen-containing five-membered ring includes one or more of pyrrole, methylpyrrole, ethylpyrrole, pyrrolidine, methylpyrrolidine, ethylpyrrolidine, imidazole, methylimidazole, ethylimidazole, pyrazole, methylpyrazole and ethylpyrazole; the nitrogen-containing six-membered ring includes one or more of pyridine, methylpyridine, ethylpyridine, piperidine, methylpiperidine, ethylpiperidine, pyrimidine, methylpyrimidine and ethylpyrimidine.

[0012] As a fourth aspect of the present invention, a method for preparing the above-mentioned solid-phase bromine positive electrode active material is provided, comprising: mixing the above-mentioned complexing agent with bromine element or a first bromine salt and then performing a second complexing reaction to obtain a solid-phase bromine positive electrode active material.

[0013] As the fifth aspect of the present invention, a solid-phase bromine positive electrode is provided, comprising: the above-mentioned solid-phase bromine positive electrode active material, a conductive agent, a binder, and a current collector; wherein the solid-phase bromine positive electrode active material, the conductive agent, and the binder are evenly mixed and loaded on the surface of the current collector; the mass ratio of the solid-phase bromine positive electrode active material, the conductive agent, and the binder is 7:1-2:0.5-1.

[0014] As a sixth aspect of the present invention, a zinc-bromine battery is provided, comprising: the above-mentioned solid-phase bromine positive electrode, a zinc negative electrode, and an aqueous electrolyte located between the solid-phase bromine positive electrode and the zinc negative electrode; wherein the zinc negative electrode is any one of a zinc foil, a pre-galvanized zinc-philic current collector, and a zinc powder-loaded current collector; and the aqueous electrolyte is a second bromine salt, a zinc salt, or a mixed electrolyte of a second bromine salt, a zinc salt and the above-mentioned complexing agent.

[0015] Based on the above technical scheme, the complexing agent, solid-phase bromine positive electrode active material and preparation method thereof, solid-phase bromine positive electrode and zinc-bromine battery provided by the present invention have at least one of the following beneficial effects.

[0016] (1) In the embodiments of the present invention, the complexing agent provided by the present invention has a high symmetry, and its peripheral charge distribution is more uniform, and it is easier to complex with bromine molecules in the subsequent process to form a stable solid-phase bromine positive electrode active material. At the same time, the number of main chain carbons in the complexing agent does not exceed 8, the molecular structure is relatively simple, and the relative molecular mass of the complexing agent is small, so that not only the subsequently synthesized solid-phase bromine positive electrode has a higher specific capacity, but also it has better diffusivity, so the synthesized solid-phase bromine positive electrode has excellent reaction kinetics.

[0017] (2) In the embodiment of the present invention, a nitrogen-containing heterocyclic compound and a halogenated alkane are used as raw materials to react by a hot solvent method, and multiple nitrogen-containing heterocyclic compounds are complexed on the halogenated alkane to obtain a complexing agent with better symmetry and more uniform peripheral charge distribution. The preparation method of the synthetic complexing agent provided by the present invention does not require solvents or other additives, the preparation method is simple, the requirements for equipment and reaction environment are low, and it is suitable for industrial production.

[0018] (3) In the embodiment of the present invention, the present invention obtains a solid-phase bromine positive electrode active material by complexing multiple bromine molecules on a complexing agent, wherein the complexing agent has multiple active adsorption sites for bromine and can simultaneously bind multiple bromine molecules, thereby increasing the mass proportion of active bromine elements in the solid-phase bromine positive electrode active material, which is beneficial to improving the specific capacity of the bromine positive electrode. At the same time, the preparation method of the solid-phase bromine positive electrode active material provided by the present invention is simple and easy to implement, and is suitable for large-scale promotion.

[0019] (4) In the embodiment of the present invention, the solid-phase bromine positive electrode active material is mixed with a conductive agent and a binder and then directly loaded on a current collector to obtain a solid-phase bromine positive electrode. Since multiple bromine molecules are complexed in the solid-phase bromine positive electrode active material, the solid-phase bromine positive electrode has a higher bromine loading amount, so the battery prepared using the solid-phase bromine positive electrode has a higher specific capacity, surface capacity and energy density.

[0020] (5) In an embodiment of the present invention, the zinc-bromine battery provided by the present invention comprises a solid-phase bromine positive electrode, a zinc negative electrode and an electrolyte therebetween. The positive electrode of the zinc-bromine battery undergoes a solid / liquid phase conversion reaction, and the charging product in the positive electrode exists in a complexed form and will not diffuse to the negative electrode to cause corrosion of the zinc negative electrode, thereby improving the cycle stability of the zinc-bromine battery. At the same time, the solid-phase bromine positive electrode in the zinc-bromine battery provided by the present invention enables the zinc-bromine battery to have a higher specific capacity, surface capacity and energy density. In addition, since the solid-phase bromine positive electrode active material in the solid-phase bromine positive electrode utilizes a new type of complexing agent, the charging material in the zinc-bromine battery is solid, thereby avoiding the use of ion exchange membranes, breaking the monopoly of ion exchange membranes, and the cost of the zinc-bromine battery provided by the present invention will be one-tenth of that of the traditional liquid flow zinc-bromine battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the reaction mechanism of zinc-bromine battery in an embodiment of the present invention;

[0022] Figure 2 The positive electrode loading of the zinc-bromine battery in Example 1 of the present invention is 68 mg / cm 2 The discharge curve diagram when

[0023] Figure 3 The positive electrode loading of the zinc-bromine battery in Example 1 of the present invention is 68 mg / cm 2 Cycle curve diagram when

[0024] Figure 4 The positive electrode loading of the zinc-bromine battery in Example 1 of the present invention is 136 mg / cm 2 The discharge curve diagram when

[0025] Figure 5 The positive electrode loading of the zinc-bromine battery in Example 2 of the present invention is 67 mg / cm 2 The discharge curve diagram when

[0026] Figure 6 The positive electrode loading of the zinc-bromine battery in Example 3 of the present invention is 67 mg / cm 2 The discharge curve diagram when

[0027] Figure 7 The zinc-bromine battery in Example 4 of the present invention has a positive electrode loading of 25 mg / cm 2 The discharge curve diagram when

[0028] Figure 8 The discharge curve of the zinc-bromine battery in Comparative Example 1 of the present invention;

[0029] Fig. 9 This is a cycle curve diagram of the zinc-bromine battery in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0031] In view of the pollution of zinc negative electrode caused by the diffusion of bromine positive electrode active material in traditional zinc flow zinc-bromine battery, and the high cost of battery caused by the use of expensive Nafion membrane, researchers have developed static zinc-bromine battery by using complexing agent in recent years. However, the complexing agent currently used in static zinc-bromine battery has a large molecular weight, resulting in low specific capacity and poor reversibility of the battery. Accordingly, the present invention provides a complexing agent with high symmetry and uniform peripheral charge distribution. At the same time, the main chain carbon number of the complexing agent provided by the present invention does not exceed 8, and the relative molecular mass is small.

[0032] As a first aspect of the present invention, a complexing agent is provided, having a structure shown in formula (1):

[0033] (C n H 2n+2-m X m )R m (one);

[0034] Wherein, 1≤n≤8, 2≤m≤4, m and n are both integers; when there are multiple Xs, each is independently selected from any one of chlorine, bromine and iodine; when there are multiple Rs, each is independently selected from any one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring.

[0035] In the embodiment of the present invention, the complexing agent provided by the present invention has high symmetry, and its peripheral charge distribution is more uniform, and it is easier to complex with bromine molecules in the subsequent process to form a stable solid-phase bromine positive electrode active material. At the same time, the main chain carbon number in the complexing agent does not exceed 8, the molecular structure is relatively simple, and the relative molecular mass of the complexing agent is small, so that not only the solid-phase bromine positive electrode synthesized in the subsequent process has a higher specific capacity, but also it has better diffusivity and better electrode reaction kinetics in the subsequent reaction.

[0036] Specifically, the complexing agent provided by the present invention has any one of the structures of formula (1) to formula (3):

[0037] Formula (1);

[0038] Formula (2);

[0039] Formula (3);

[0040] Wherein, n is an integer between 1 and 8, X1, X2, X3, and X4 are each independently selected from any one of chlorine, bromine, and iodine; R1, R2, R3, and R4 are each independently selected from any one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring.

[0041] According to an embodiment of the present invention, the nitrogen-containing five-membered ring includes one or more of pyrrole, methylpyrrole, ethylpyrrole, pyrrolidine, methylpyrrolidine, ethylpyrrolidine, imidazole, methylimidazole, ethylimidazole, pyrazole, methylpyrazole, and ethylpyrazole; the nitrogen-containing six-membered ring includes one or more of pyridine, methylpyridine, ethylpyridine, piperidine, methylpiperidine, ethylpiperidine, pyrimidine, methylpyrimidine, and ethylpyrimidine.

[0042] Specifically, the complexing agent having formula (1) provided by the present invention includes but is not limited to any one of the following specific structures:

[0043] Formula (1-1);

[0044] Formula (1-2);

[0045] Formula (1-3);

[0046] Formula (1-4);

[0047] Formula (1-5);

[0048] Formula (1-6);

[0049] Formula (1-7);

[0050] Formula (1-8).

[0051] Specifically, the complexing agent having formula (2) provided by the present invention includes but is not limited to any one of the following specific structures:

[0052] Formula (2-1);

[0053] Formula (2-2);

[0054] Formula (2-3).

[0055] Specifically, the complexing agent having formula (3) provided by the present invention includes but is not limited to any one of the following specific structures:

[0056] Formula (3-1);

[0057] Formula (3-2);

[0058] Formula (3-3);

[0059] Formula (3-4).

[0060] As a second aspect of the present invention, a method for preparing the above-mentioned complexing agent is provided, comprising: mixing a nitrogen-containing heterocyclic compound and a halogenated alkane and performing a first complexing reaction to obtain a complexing agent; wherein the nitrogen-containing heterocyclic compound comprises at least one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring; and the halogenated alkane comprises a C substituted with chlorine, bromine or iodine. 1-8 at least one of the alkanes.

[0061] In an embodiment of the present invention, a nitrogen-containing heterocyclic compound and a halogenated alkane are used as raw materials and reacted by a hot solvent method, and multiple nitrogen-containing heterocyclic compounds are complexed on the halogenated alkane to obtain a complexing agent with good symmetry and more uniform peripheral charge distribution. The preparation method of the synthetic complexing agent provided by the present invention does not require solvents or other additives, the preparation method is simple, the requirements for equipment and reaction environment are low, and it is suitable for industrial production.

[0062] According to an embodiment of the present invention, the molar ratio of the nitrogen-containing heterocyclic compound to the halogenated alkane is 2-4:1; the first complexation reaction temperature is 60-120°C, and the first complexation reaction time is 6-72h; the nitrogen-containing five-membered ring includes one or more of pyrrole, methylpyrrole, ethylpyrrole, pyrrolidine, methylpyrrolidine, ethylpyrrolidine, imidazole, methylimidazole, ethylimidazole, pyrazole, methylpyrazole, and ethylpyrazole; the nitrogen-containing six-membered ring includes one or more of pyridine, methylpyridine, ethylpyridine, piperidine, methylpiperidine, ethylpiperidine, pyrimidine, methylpyrimidine, and ethylpyrimidine.

[0063] Specifically, the preparation method of the complexing agent provided by the present invention can be: mixing the nitrogen-containing heterocyclic compound and the halogenated alkane at a molar ratio of 2-4:1, reacting at 60-120°C for 6-72h after sealing, washing 2-6 times with one or more of ethyl acetate, ethanol, methanol, and deionized water after sufficient reaction to remove unreacted salts and impurities, and then drying in an oven at 60-100°C for 2-12h to obtain the complexing agent.

[0064] In an embodiment of the present invention, a complexing agent is prepared by a hot solvent method using a nitrogen-containing heterocyclic compound and a halogenated alkane. The halogenated alkane can combine with a corresponding number of nitrogen-containing heterocyclic compound molecules to form a complexing agent having a quaternary ammonium salt compound structure, and the structure of the complexing agent molecule maintains excellent symmetry. This is conducive to the subsequent formation of a solid bromine positive electrode active material after the complexing agent combines with the bromine molecule. The position corresponding to the quaternary ammonium salt compound in the above-mentioned complexing agent contains a bromine active site, and each active site can complex one XBr2 - 、XBr4 - or XBr6 - The group, wherein X is a halogen, including Cl, Br, and I, can increase the mass proportion of bromine in the entire solid-phase bromine positive electrode active material by complexing multiple bromine atoms, thereby increasing the specific capacity of the subsequent solid-phase bromine positive electrode active material.

[0065] As a third aspect of the present invention, a solid-phase bromine positive electrode active material is provided, which is prepared using the above-mentioned complexing agent and has a structure shown in formula (II):

[0066] [(C n H 2n+2-m X m )R m ]Br a m (two);

[0067] Wherein, 1≤n≤8, 2≤m≤4, m and n are both integers, a is 2 or 4 or 6; when there are multiple Xs, each is independently selected from any one of chlorine, bromine and iodine; when there are multiple Rs, each is independently selected from any one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring; the nitrogen-containing five-membered ring includes one or more of pyrrole, methylpyrrole, ethylpyrrole, pyrrolidine, methylpyrrolidine, ethylpyrrolidine, imidazole, methylimidazole, ethylimidazole, pyrazole, methylpyrazole and ethylpyrazole; the nitrogen-containing six-membered ring includes one or more of pyridine, methylpyridine, ethylpyridine, piperidine, methylpiperidine, ethylpiperidine, pyrimidine, methylpyrimidine and ethylpyrimidine.

[0068] In an embodiment of the present invention, the present invention obtains a solid-phase bromine positive electrode active material by complexing multiple bromine molecules on a complexing agent, wherein the complexing agent has multiple active adsorption sites for bromine and can simultaneously combine multiple bromine molecules to form XBr2 - 、XBr4 - 、XBr6 - , increasing the mass proportion of active bromine element in the solid phase bromine positive electrode active material.

[0069] Specifically, the solid-phase bromine positive electrode active material provided by the present invention has any one of the structures of formula (4) to formula (6):

[0070] Formula (4);

[0071] Formula (5);

[0072] Formula (6);

[0073] Wherein, n is an integer between 1 and 8, a is 2 or 4 or 6; X1, X2, X3, and X4 are each independently selected from any one of chlorine, bromine, and iodine; R1, R2, R3, and R4 are each independently selected from any one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring.

[0074] Specifically, the solid-phase bromine positive electrode active material having the formula (4) provided by the present invention includes but is not limited to any one of the following specific structures:

[0075] Formula (4-1);

[0076] Formula (4-2);

[0077] Formula (4-3);

[0078] Formula (4-4);

[0079] Formula (4-5);

[0080] Formula (4-6);

[0081] Formula (4-7);

[0082] Formula (4-8).

[0083] Specifically, the solid-phase bromine positive electrode active material having the formula (5) provided by the present invention includes but is not limited to any one of the following specific structures:

[0084] Formula (5-1);

[0085] Formula (5-2);

[0086] Formula (5-3).

[0087] Specifically, the solid-phase bromine positive electrode active material having the formula (6) provided by the present invention includes but is not limited to any one of the following specific structures:

[0088] Formula (6-1);

[0089] Formula (6-2);

[0090] Formula (6-3);

[0091] Formula (6-4).

[0092] As a fourth aspect of the present invention, a method for preparing the above-mentioned solid-phase bromine positive electrode active material is provided, comprising: mixing the above-mentioned complexing agent with bromine element or a first bromine salt and then performing a second complexing reaction to obtain a solid-phase bromine positive electrode active material.

[0093] In the embodiments of the present invention, the preparation method of the solid-phase bromine positive electrode active material provided by the present invention is simple and easy to implement, and is suitable for large-scale promotion.

[0094] According to an embodiment of the present invention, the second complexing reaction after mixing the above-mentioned complexing agent with bromine element or the first bromine salt includes: mixing the above-mentioned complexing agent and bromine element in a molar ratio of 1:2-12 and adding them to a solvent, reacting at room temperature for 5-60 minutes to obtain a solid-phase bromine positive electrode active material; or mixing the above-mentioned complexing agent and the first bromine salt in a molar ratio of 1:2-24 and adding them to water, electroplating in a two-electrode system, to obtain a solid-phase bromine positive electrode active material; wherein the solvent includes at least one of water, acetonitrile, ethanol, methanol, and N-methylpyrrolidone; and the first bromine salt includes at least one of ZnBr2, KBr, NaBr, NH4Br, and CaBr2.

[0095] Specifically, the solid-phase bromine cathode active material can be obtained by the following solvent reaction method: the complexing agent and the bromine element are mixed in a molar ratio of 1:2-12 and added to the solvent, reacted at room temperature for 5-60 minutes, washed 2-6 times with the same solvent as in the reaction, filtered and dried, and the solid-phase bromine cathode active material is obtained. The solvent includes at least one of water, acetonitrile, ethanol, methanol, and N-methylpyrrolidone; the concentration of the complexing agent is 0.1-10 mol / L; the concentration of the bromine element is 0.1-10 mol / L.

[0096] Specifically, the solid-phase bromine positive electrode active material can be obtained by the following electroplating method: the complexing agent and the first bromine salt are mixed in a molar ratio of 1:2-24 and added to water, and electroplated in a two-electrode system to obtain the solid-phase bromine positive electrode active material. Wherein, the working electrode and the counter electrode in the two-electrode system are independently selected from any one of graphite plate, graphite felt, platinum sheet, and gold platinum; the concentration of the complexing agent is 0.1-10 mol / L; the first bromine salt includes at least one of ZnBr2, KBr, NaBr, NH4Br, CaBr2, and the concentration is 0.1-20 mol / L. The electroplating current is 0.1-1000 mA / cm 2 . The electroplating time is 5-120 min.

[0097] As the fifth aspect of the present invention, a solid-phase bromine positive electrode is provided, comprising: the above-mentioned solid-phase bromine positive electrode active material, a conductive agent, a binder, and a current collector; wherein the solid-phase bromine positive electrode active material, the conductive agent, and the binder are evenly mixed and loaded on the surface of the current collector; the mass ratio of the solid-phase bromine positive electrode active material, the conductive agent, and the binder is 7:1-2:0.5-1.

[0098] In an embodiment of the present invention, the solid-phase bromine positive electrode active material is mixed with a conductive agent and a binder and then directly loaded on a current collector to obtain a solid-phase bromine positive electrode. Since a plurality of bromine molecules are complexed in the solid-phase bromine positive electrode active material, the solid-phase bromine positive electrode has a higher bromine loading, so the battery prepared using the solid-phase bromine positive electrode has a higher specific capacity, surface capacity and energy density.

[0099] Specifically, the solid-phase bromine positive electrode is obtained by the following method: the solid-phase bromine positive electrode active material, the conductive agent, and the binder are mixed in a proper solvent at a mass ratio of 7:1-2:0.5-1, and then coated or dripped onto the current collector, and the solid-phase bromine positive electrode is obtained after drying. Among them, the conductive agent includes at least one of Ketjen black, activated carbon, multi-walled carbon tubes, nanocarbon balls, amorphous carbon, and graphene; the binder includes at least one of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), and polyoxyethanol (PEO); the solvent includes at least one of water, methanol, ethanol, acetonitrile, and 1-methyl-2-pyrrolidone; the current collector includes at least one of carbon felt, carbon cloth, carbon paper, carbon fiber, and titanium foil. The loading amount of the solid-phase bromine positive electrode active material on the current collector can be controlled at 5-300 mg / cm 2 , different load capacities can be obtained according to different requirements.

[0100] As a sixth aspect of the present invention, a zinc-bromine battery is provided, comprising: the above-mentioned solid-phase bromine positive electrode, a zinc negative electrode, and an aqueous electrolyte located between the solid-phase bromine positive electrode and the zinc negative electrode; wherein the zinc negative electrode is any one of a zinc foil, a pre-galvanized zinc-philic current collector, and a zinc powder-loaded current collector; and the aqueous electrolyte is a second bromine salt, a zinc salt, or a mixed electrolyte of a second bromine salt, a zinc salt and the above-mentioned complexing agent.

[0101] In an embodiment of the present invention, the zinc-bromine battery provided by the present invention comprises a solid-phase bromine positive electrode, a zinc negative electrode and an electrolyte therebetween. The positive electrode of the zinc-bromine battery undergoes a solid / liquid phase conversion reaction, and the charging product in the positive electrode exists in a complexed form and will not diffuse to the negative electrode to cause corrosion of the zinc negative electrode, thereby improving the cycle stability of the zinc-bromine battery. At the same time, the solid-phase bromine positive electrode in the zinc-bromine battery provided by the present invention enables the zinc-bromine battery to have a higher specific capacity, surface capacity and energy density. In addition, since the solid-phase bromine positive electrode active material in the solid-phase bromine positive electrode utilizes a complexing agent, the charging material in the zinc-bromine battery is solid, thereby avoiding the use of an ion exchange membrane, breaking the monopoly of the ion exchange membrane, and the cost of the zinc-bromine battery provided by the present invention will be one-tenth of that of a traditional liquid flow zinc-bromine battery.

[0102] Specifically, the aqueous electrolyte in the zinc-bromine battery is a second bromine salt, a zinc salt, or a mixed electrolyte of a second bromine salt, a zinc salt and the above-mentioned complexing agent. The second bromine salt includes ZnBr2, KBr, NaBr, MnBr2, BaBr2, CuBr2, MgBr2C4H 12 BrN、C8H 10 BrN、C 12 H 28 BrN、C 16 H 36 At least one of BrN; zinc salts include ZnSO4, ZnCl2, Zn(NO3)2, ZnBr2, ZnI2, Zn(CH3COO) 2、 At least one of Zn(CF3SO3)2; the concentrations of the second bromine salt and the zinc salt are both 0.01-20 mol / L; when the aqueous electrolyte contains the above-mentioned complexing agent, the concentration of the complexing agent is 0.001-20 mol / L.

[0103] In the embodiments of the present invention, the zinc-bromine battery provided by the present invention can draw on the processes of lithium-ion batteries and lead-acid batteries, which are relatively mature in the current industrial production, thereby reducing the manufacturing cost. In addition, the aqueous zinc-bromine battery has the characteristics of intrinsic safety, which can simplify the cost of the safety management system and is conducive to its subsequent large-scale production and application.

[0104] According to an embodiment of the present invention, the zinc-bromine battery includes any one of a button battery, a cylindrical battery, a soft-pack battery, a square battery, and a flow battery.

[0105] The present invention is further described below by examples and related test experiments. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments may also be implemented without these specific details. And, in the absence of conflict, the details in the following embodiments may be combined into other feasible embodiments at will. All instruments, consumables and reagents in the following examples, if not otherwise specified, may be obtained from commercial sources.

[0106] Example 1

[0107] In this Example 1, a complexing agent 1,4-di(pyridin-1-yl)butane dibromide (PCPBr2) was prepared, and a solid-phase bromine positive electrode active material 1,4-di(pyridin-1-yl)butane hexabromide (PCPBr6) and a solid-phase bromine positive electrode were prepared using the complexing agent. The solid-phase bromine positive electrode was assembled into a zinc-bromine battery, and the electrochemical performance of the zinc-bromine battery was tested.

[0108] (1) Preparation of complexing agent 1,4-di(pyridin-1-yl)butane dibromide (PCPBr2).

[0109] Take 1,4-dibromobutane and pyridine with a total volume of 10 mL and put them into a round-bottom flask (the molar ratio of 1,4-dibromobutane to pyridine is 1:2.5), stir with a glass rod for 2 minutes, and then put the round-bottom flask into a thermostat at 80°C for 48 hours. Then take out the round-bottom flask, transfer the reaction product to a mortar, grind it, add ethyl acetate to the ground sample and stir it thoroughly, then centrifuge it in a high-speed centrifuge for 10 minutes, and repeat the washing operation 3 times. Then put the obtained pure sample into an oven at 80°C for 10 hours for drying to obtain 1,4-di(pyridin-1-yl)butane dibromide (PCPBr2) as shown in formula (I), that is, the complexing agent PCPBr2.

[0110] Formula (I).

[0111] (2) Preparation of solid-phase bromine positive electrode active material 1,4-di(pyridin-1-yl)butane hexabromide (PCPBr6) and solid-phase bromine positive electrode.

[0112] PCPBr2 is complexed with bromine in an acetonitrile solution (the molar ratio of PCPBr2 to bromine is 1:2) to obtain 1,4-di(pyridin-1-yl)butane hexabromide (PCPBr6) as shown in formula (II), i.e., solid-phase bromine positive electrode active material PCPBr6.

[0113] Formula (II).

[0114] Then, polyethylene oxide (PEO) and carbon black were added to the above solution and stirred for 8 hours, wherein the mass ratio of PCPBr6:carbon black:PEO was 7:2:1. The stirred slurry was coated on the carbon felt current collector and placed in an oven for drying for 6 hours to obtain a solid-phase bromine positive electrode.

[0115] (3) Preparation of zinc-bromine batteries.

[0116] The above solid-phase bromine positive electrode and the zinc sheet negative electrode are assembled into a static zinc-bromine battery, and the electrolyte is: 0.5 mol / L ZnBr2 and 0.1 mol / L PCPBr2.

[0117] (4) Electrochemical performance test of zinc-bromine battery.

[0118] Figure 1 Schematic diagram of the reaction mechanism of zinc-bromine battery in an embodiment of the present invention.

[0119] The schematic diagram of the reaction mechanism of preparing a solid-phase bromine cathode using PCPBr6 as the solid-phase bromine cathode active material and assembling a zinc-bromine battery using the solid-phase bromine cathode active material PCPBr6 is shown in the figure. Figure 1 As shown; and the reaction equations of the positive and negative electrodes and their standard electrode potentials are as follows:

[0120] Cathode: 6Br - +PCP 2+ -4e - PCPBr6(E 0 =1.08V),

[0121] Negative electrode: Zn 2+ +2e - Zn(E 0 =-0.76V),

[0122] Overall reaction: 6Br - +PCP 2+ +2Zn 2+ PCPBr6+2Zn(E=1.84V).

[0123] The charge-discharge and cycle performance tests of the aqueous zinc-bromine battery assembled with the solid-phase bromine positive electrode, zinc sheet negative electrode and electrolyte were carried out at a current density of 10 mA / cm 2 .

[0124] Figure 2 The positive electrode loading of the zinc-bromine battery in Example 1 of the present invention is 68 mg / cm 2 The discharge curve diagram when Figure 3 The positive electrode loading of the zinc-bromine battery in Example 1 of the present invention is 68 mg / cm 2 Cycle curve diagram when Figure 4 The positive electrode loading of the zinc-bromine battery in Example 1 of the present invention is 136 mg / cm 2 The discharge curve diagram when .

[0125] Combination Figure 2 and Figure 3 It can be seen that the solid-phase bromine positive electrode prepared in Example 1 has a specific capacity of 147 mAh / g and has high cycle stability. Under long-cycle conditions, the coulomb efficiency is maintained at about 98%, and the average discharge voltage reaches 1.7 V. In addition, the battery has a high surface capacity (10 mAh / cm 2 ) can stably cycle more than 1400 times. Figure 4 It can be seen that when the loading amount of PCPBr6 on the solid phase bromine positive electrode is increased to 130 mg, its surface capacity is close to 19 mAh / cm 2 Therefore, the solid-phase bromine cathode prepared in Example 1 has high specific capacity, surface capacity, coulombic efficiency and cycle stability in static aqueous zinc-bromine batteries.

[0126] Example 2

[0127] In this Example 2, a complexing agent 1,4-di(pyridin-1-yl)butane dibromide (PCPBr2) as shown in formula (III) is prepared. The specific preparation method is the same as that in Example 1, except that the reaction temperature in this Example 2 is 60°C and the reaction time is 72 hours. Similarly, in this Example 2, the obtained complexing agent PCPBr2 is used to prepare a solid-phase bromine positive electrode active material 1,4-di(pyridin-1-yl)butane hexabromide (PCPBr6) as shown in formula (IV) and a solid-phase bromine positive electrode, the solid-phase bromine positive electrode is assembled into a zinc-bromine battery, and the electrochemical performance of the zinc-bromine battery is tested. The specific preparation method, assembly method and test method are the same as those in Example 1.

[0128] Formula (III);

[0129] Formula (IV).

[0130] Figure 5 The positive electrode loading of the zinc-bromine battery in Example 2 of the present invention is 67 mg / cm 2 The discharge curve diagram when .

[0131] Combination Figure 5 It can be seen that the zinc-bromine battery in Example 2 can be used at 67 mg / cm 2 A specific capacity of about 138 mAh / g was obtained at a loading of , indicating that the complexing agent PCPBr2 was successfully synthesized under this condition. Compared with Example 1, the slightly reduced specific capacity indicates that a small amount of impurities exist in the complexing agent PCPBr2 synthesized under the reaction conditions of Example 2 and in the solid-phase bromine positive electrode.

[0132] Example 3

[0133] In this embodiment 3, a complexing agent 1,4-di(imidazol-1-yl)butane dichloride complexing agent (ICICl2) as shown in formula (V) is prepared. The specific preparation method is the same as that in embodiment 1, except that the raw materials used in this embodiment 3 are 1,4 dichlorobutane and imidazole, the reaction temperature is 100°C, and the reaction time is 6 hours. Similarly, in this embodiment 3, the solid phase bromine positive electrode active material 1,4-di(imidazol-1-yl)butane dichlorotetrabromide (ICICl2Br4) and the solid phase bromine positive electrode as shown in formula (VI) are prepared using the obtained complexing agent ICICl2, and the solid phase bromine positive electrode is assembled into a static zinc-bromine battery, wherein the electrolyte is: 0.5 mol / LZnBr2 and 0.1 mol / L ICICl2. The electrochemical performance of the zinc-bromine battery is tested, and the specific preparation method, assembly method and test method are the same as those in embodiment 1.

[0134] Formula (V);

[0135] Formula (VI).

[0136] Figure 6 The positive electrode loading of the zinc-bromine battery in Example 3 of the present invention is 67 mg / cm 2 The discharge curve diagram when .

[0137] Combination Figure 6 It can be seen that the zinc-bromine battery in this embodiment 3 can be used at 67 mg / cm 2 A specific capacity of about 170 mAh / g was obtained at a loading amount of , indicating that chlorine-substituted alkanes can also be successfully used to synthesize the complexing agent ICICl2 with a higher specific capacity.

[0138] Example 4

[0139] In this Example 4, a complexing agent 1,2,3,4-tetra(pyridin-1-yl)butane tetrabromide (PCPBr4) as shown in formula (VII) was prepared. The specific preparation method is the same as that in Example 1, except that the raw materials used in this Example 4 are 1,2,3,4-tetrabromobutane and pyridine, and the molar ratio of 1,2,3,4-tetrabromobutane to pyridine is 1:4, the reaction temperature is 90°C, and the reaction time is 72 hours. Similarly, in this Example 4, the obtained complexing agent PCPBr4 was used to prepare a solid-phase bromine positive electrode active material 1,2,3,4-tetra(pyridin-1-yl)butane 20-bromide (PCPBr) as shown in formula (VIII) 20) and a solid-phase bromine positive electrode, the solid-phase bromine positive electrode is assembled into a zinc-bromine battery, and the electrochemical performance of the zinc-bromine battery is tested. The specific preparation method, assembly method and testing method are the same as those in Example 1, except that: in this Example 4, when preparing the solid-phase bromine positive electrode active material, the molar ratio of PCPBr4 to bromine element is 1:8, and the electrolyte is: 0.5 mol / L ZnBr2 and 0.1 mol / L PCPBr4.

[0140] Formula (VII);

[0141] Formula (VIII).

[0142] Figure 7 The zinc-bromine battery in Example 4 of the present invention has a positive electrode loading of 25 mg / cm 2 The discharge curve diagram when .

[0143] Combination Figure 7 It can be seen that the polybromine ion Br5 - Formed on a solid-phase bromine cathode, loading 25 mg / cm 2 The solid-phase bromine positive electrode obtained a specific capacity of 206 mAh / g, indicating that the complexing agent PCPBr4 successfully complexed multiple bromine molecules and obtained a higher specific capacity.

[0144] Comparative Example 1

[0145] In this comparative example 1, a traditional solid-phase bromine positive electrode active material tetrapropylammonium tribromide (TPABr3) was prepared, and a solid-phase bromine positive electrode was prepared using the TPABr3. The solid-phase bromine positive electrode was assembled into a zinc-bromine battery, and the electrochemical performance of the zinc-bromine battery was tested.

[0146] (1) Preparation of solid-phase bromine cathode active material TPABr3 and solid-phase bromine cathode

[0147] Tetrapropylammonium bromide (TPABr) and bromine element are complexed in an acetonitrile solution (the molar ratio of TPABr to bromine element is 1:1) to obtain tetrapropylammonium tribromide (TPABr3) as shown in formula (IX), i.e., solid-phase bromine active material TPABr3. Then, PEO and carbon black are added to the above solution and stirred for 8 hours, wherein the mass ratio of TPABr3:carbon black:PEO is 7:2:1, and the stirred slurry is applied to a carbon felt current collector and placed in an oven for 6 hours for drying to obtain a solid-phase bromine positive electrode.

[0148] Formula (IX).

[0149] (2) Preparation of zinc-bromine batteries.

[0150] The above solid-phase bromine positive electrode and the zinc sheet negative electrode were assembled into a static zinc-bromine battery, and the electrolyte was: 0.5 mol / L ZnBr2 and 0.25 mol / L TPABr.

[0151] (3) Electrochemical performance test of zinc-bromine battery.

[0152] The reaction equations of the zinc-bromine battery positive electrode and negative electrode assembled using solid-phase bromine positive electrode active material TPABr3 and its standard electrode potential are as follows:

[0153] Cathode: 3Br - +TPA + -2e - TPABr3(E 0 =1.08V),

[0154] Negative electrode: Zn 2+ +2e - Zn(E 0 =-0.76V),

[0155] Overall reaction: 3Br - +TPA + +Zn 2+ TPABr+Zn(E=1.84V).

[0156] The charge-discharge and cycle performance tests of the aqueous zinc-bromine battery assembled with the solid-phase bromine positive electrode, zinc sheet negative electrode and electrolyte were carried out at a current density of 10 mA / cm 2 .

[0157] Figure 8 The discharge curve of the zinc-bromine battery in Comparative Example 1 of the present invention; Fig. 9 This is a cycle curve diagram of the zinc-bromine battery in Comparative Example 1 of the present invention.

[0158] contrast Figure 8 and Figure 2 It can be seen that the solid-phase bromine cathode prepared in this comparative example 1 has a specific capacity of only 96 mAh / g and an average voltage of 1.55 V, which are lower than the 147 mAh / g and the average voltage of 1.7 V of the solid-phase bromine cathode prepared in Example 1. Fig. 9 and Figure 3 By comparison, it can be seen that the zinc-bromine battery assembled with the solid-phase bromine positive electrode in Comparative Example 1 can only 2 The surface capacity of the zinc-bromine battery can be stably cycled for 550 cycles, which is lower than the 1400 cycles of the zinc-bromine battery in Example 1. The comparative example illustrates that the solid-phase bromine positive electrode prepared in Example 1 of the present invention has high specific capacity, surface capacity, coulombic efficiency and cycle stability.

[0159] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A complexing agent, wherein The complexing agent has a structure shown in formula (1): (C n H 2n+2-m X m )R m (one); Wherein, 1≤n≤8, 2≤m≤4, m and n are both integers; When there are multiple Xs, each of them is independently selected from any one of chlorine, bromine and iodine; When there are plural Rs, each R is independently selected from any one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring.

2. The complexing agent according to claim 1, wherein The nitrogen-containing five-membered ring includes one or more of pyrrole, methylpyrrole, ethylpyrrole, pyrrolidine, methylpyrrolidine, ethylpyrrolidine, imidazole, methylimidazole, ethylimidazole, pyrazole, methylpyrazole, and ethylpyrazole; The nitrogen-containing six-membered ring includes one or more of pyridine, methylpyridine, ethylpyridine, piperidine, methylpiperidine, ethylpiperidine, pyrimidine, methylpyrimidine, and ethylpyrimidine.

3. A method for preparing the complexing agent according to claim 1, comprising: The nitrogen-containing heterocyclic compound and the halogenated alkane are mixed and subjected to a first complexation reaction to obtain a complexing agent; Wherein, the nitrogen-containing heterocyclic compound includes at least one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring; The halogenated alkanes include C 1-8 at least one of the alkanes.

4. The method for preparing a complexing agent according to claim 3, wherein: The molar ratio of the nitrogen-containing heterocyclic compound to the halogenated alkane is 2-4:1; The first complexation reaction temperature is 60-120°C, and the first complexation reaction time is 6-72h; The nitrogen-containing five-membered ring includes one or more of pyrrole, methylpyrrole, ethylpyrrole, pyrrolidine, methylpyrrolidine, ethylpyrrolidine, imidazole, methylimidazole, ethylimidazole, pyrazole, methylpyrazole, and ethylpyrazole; The nitrogen-containing six-membered ring includes one or more of pyridine, methylpyridine, ethylpyridine, piperidine, methylpiperidine, ethylpiperidine, pyrimidine, methylpyrimidine, and ethylpyrimidine.

5. A solid-phase bromine positive electrode active material prepared using the complexing agent as claimed in claim 1, wherein: The solid-phase bromine positive electrode active material has a structure shown in formula (II): [(C n H 2n+2-m X m )R m Br a m (II); Wherein, 1≤n≤8, 2≤m≤4, m and n are both integers, and a is 2 or 4 or 6; When there are multiple Xs, each of them is independently selected from any one of chlorine, bromine and iodine; When there are multiple Rs, each is independently selected from any one of a nitrogen-containing five-membered ring and a nitrogen-containing six-membered ring; The nitrogen-containing five-membered ring includes one or more of pyrrole, methylpyrrole, ethylpyrrole, pyrrolidine, methylpyrrolidine, ethylpyrrolidine, imidazole, methylimidazole, ethylimidazole, pyrazole, methylpyrazole, and ethylpyrazole; The nitrogen-containing six-membered ring includes one or more of pyridine, methylpyridine, ethylpyridine, piperidine, methylpiperidine, ethylpiperidine, pyrimidine, methylpyrimidine, and ethylpyrimidine.

6. A method for preparing a solid-phase bromine positive electrode active material as claimed in claim 5, comprising: The complexing agent as claimed in claim 1 is mixed with bromine element or the first bromine salt and then subjected to a second complexing reaction to obtain a solid-phase bromine positive electrode active material.

7. The method for preparing a solid-phase bromine positive electrode active material according to claim 6, wherein: The second complexing reaction after mixing the complexing agent as claimed in claim 1 with bromine element or the first bromine salt comprises: The complexing agent as claimed in claim 1 and the bromine element are mixed in a molar ratio of 1:2-12 and added to a solvent, and reacted at room temperature for 5-60 minutes to obtain a solid phase bromine positive electrode active material; or The complexing agent according to claim 1 and the first bromine salt are mixed in a molar ratio of 1:2-24 and added into water, and electroplated in a two-electrode system to obtain a solid-phase bromine positive electrode active material; Wherein, the solvent includes at least one of water, acetonitrile, ethanol, methanol, and N-methylpyrrolidone; The first bromine salt includes at least one of ZnBr2, KBr, NaBr, NH4Br, and CaBr2.

8. A solid phase bromine positive electrode comprising: The solid-phase bromine positive electrode active material, conductive agent, binder and current collector as claimed in claim 5; The solid-phase bromine positive electrode active material, the conductive agent and the binder are uniformly mixed and loaded on the surface of the current collector; The mass ratio of the solid-phase bromine positive electrode active material, the conductive agent and the binder is 7:1-2:0.5-1.

9. A zinc-bromine battery comprising: The solid-phase bromine positive electrode, the zinc negative electrode, and the aqueous electrolyte located between the solid-phase bromine positive electrode and the zinc negative electrode as claimed in claim 8; Wherein, the zinc negative electrode is any one of zinc foil, pre-galvanized zinc-philic current collector, and zinc powder-loaded current collector; The aqueous electrolyte is a second bromine salt, a zinc salt, or a mixed electrolyte of a second bromine salt, a zinc salt and a complexing agent as described in any one of claims 1-2.

10. The zinc-bromine battery according to claim 9, wherein: The zinc-bromine battery includes any one of a button battery, a cylindrical battery, a soft-pack battery, a square battery, and a flow battery.

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