Neutral zinc slurry battery negative electrode system and preparation method and application thereof

Abstract

The invention discloses a flowing type neutral zinc slurry battery negative electrode system and a preparation method thereof. A flowing type neutral zinc slurry battery negative electrode system is characterized in that neutral zinc slurry is composed of a zinc salt aqueous solution, a conductive agent, a dispersing agent, an organic ligand and nano-zinc according to the mass ratio of 100: (10-60): (5-50): (5-50): (5-50), the nano-zinc and the conductive agent form a solid compound in the neutral zinc slurry battery negative electrode system, and the solid compound is a mixture of the zinc salt aqueous solution, the conductive agent, the dispersing agent, the organic ligand and the nano-zinc. The zinc / conductive agent solid compound is suspended in a neutral zinc slurry battery negative electrode system. According to the flowing type neutral zinc slurry battery negative electrode system, monodisperse zinc nanoparticle electrodeposition with uniform particle size distribution, limited overpotential and charge transfer resistance and ultrahigh coulombic efficiency can be realized, and the flowing type neutral zinc slurry battery negative electrode system has practical application value in the field of long-time fixed energy storage.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical energy storage, and relates to a flow-type neutral zinc slurry battery negative electrode system and a preparation method thereof, as well as an application in long-term zinc-based stationary energy storage. Background Art

[0002] Electrochemical energy storage has become the most ideal energy storage technology due to its advantages such as environmental friendliness, high efficiency, and low cost. Currently, lead-acid batteries and lithium-ion batteries that dominate the mainstream market have problems such as environmental pollution, poor safety, or scarce raw material reserves. The two-electron transfer characteristic of zinc not only provides a sufficiently high theoretical specific capacity (5851 Ah·L -1 ), but also the surface reserves of zinc are extremely rich (about 230 million tons globally), the price is low, the battery assembly conditions based on neutral electrolytes are loose, and it is safe and environmentally friendly. These favorable conditions make neutral zinc metal batteries more promising to be widely promoted to various fixed energy storage application scenarios compared with other energy storage technologies.

[0003] Currently, in the research of neutral zinc metal batteries, zinc foils / plates are generally directly used as the negative electrode to form a negative electrode interface with the electrolyte. In this case, on the one hand, after repeated charge and discharge, the electroplated zinc at the interface tends to grow in a dendritic manner, various adverse side reactions occur, and there is even a risk of piercing the diaphragm and causing battery failure. On the other hand, the performance degradation of traditional aqueous zinc batteries is mainly due to side reactions such as hydrogen evolution and surface passivation at the negative electrode. Although a large number of improvement measures have been proposed in the academic community (including electrolyte regulation, zinc negative electrode surface protection, bulk alloying, etc.), these solutions cannot truly eliminate the interface side reactions. The irreversible changes at the interface will accumulate with cycling, and the influence degree of the side reactions on the system also increases exponentially as the battery device is enlarged, greatly reducing the cycle life of fixed aqueous zinc batteries. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a flow-type neutral zinc slurry battery negative electrode system, a preparation method thereof, and its application in long-term fixed energy storage.

[0005] The neutral zinc slurry battery negative electrode system of the present invention is characterized in that the neutral zinc slurry is composed of an aqueous zinc salt solution, a conductive agent, a dispersant, an organic ligand, and nano zinc in a mass ratio of 100:(10 - 60):(5 - 50):(5 - 50):(5 - 50), and the nano zinc and the conductive agent form a solid complex and are suspended in the neutral zinc slurry battery negative electrode system.

[0006] The aqueous zinc salt solution is one or a combination of two or more of an aqueous zinc sulfate solution, an aqueous zinc chloride solution, an aqueous zinc tetrafluoroborate solution, an aqueous zinc perchlorate solution, an aqueous zinc trifluoromethanesulfonate solution, an aqueous zinc nitrate solution, and an aqueous zinc acetate solution.

[0007] The conductive agent is one or a combination of two or more of conductive carbon black, Ketjen black, acetylene black, conductive graphite powder, carbon nanotubes, and graphene.

[0008] The dispersant is one or a combination of two or more of polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, carboxymethyl cellulose, polyethylene oxide, polyacrylamide, and polyacrylic acid.

[0009] The organic ligand is one or a combination of two or more of cysteine, cystine, glutamic acid, glycine, methionine, mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, mercaptoethanol, mercaptopropanol, mercaptobutanol, glutathione, mercaptoethylamine, mercaptopropylamine, and mercaptobutylamine.

[0010] The nano zinc is monodispersed zinc metal nanoparticles with an average particle size of 10 - 500 nm.

[0011] The present invention also provides a preparation method of a negative electrode system for a neutral zinc slurry battery, which is obtained by uniformly mixing and grinding the components in the negative electrode system for the neutral zinc slurry battery.

[0012] The viscosity of the negative electrode system for the neutral zinc slurry battery is 5 - 50 Pa·s.

[0013] The present invention also provides an aqueous zinc battery, which includes the negative electrode system for the neutral zinc slurry battery.

[0014] The present invention also provides the application of the negative electrode system for the neutral zinc slurry battery in an aqueous zinc battery.

[0015] Invention Effect

[0016] Through the flow-type negative electrode system for the neutral zinc slurry battery and its preparation method of the present invention, during the charge and discharge process, monodispersed zinc nanoparticles with uniform particle size distribution can be achieved for electrodeposition, with limited overpotential and charge transfer resistance, as well as ultra-high Coulomb efficiency, and the dendrite problem is completely eliminated, having practical application value in the field of long-term fixed energy storage. Description of the Drawings

[0017] Figure 1 In (a) is a wide-angle transmission electron microscope photo of the neutral zinc slurry of the present invention; Figure 1 In (b) is a partial high-resolution transmission electron microscope photo of the neutral zinc slurry of the present invention.

[0018] Figure 2 is a schematic structural diagram of the flow-type neutral zinc slurry - manganese dioxide battery of the present invention.

[0019] Figure 3Schematic diagram of the organic ligand restricting the overgrowth and agglomeration of electrodeposited zinc during the charging of the negative electrode of the flow-through neutral zinc slurry battery of the present invention.

[0020] Figure 4 Specific capacity-voltage polarization curve of charge and discharge of the flow-through neutral zinc slurry-manganese dioxide battery of the present invention.

[0021] Figure 5 High-resolution transmission electron microscope photo of the morphology of the deposited zinc product after charging of the flow-through neutral zinc slurry of the present invention.

[0022] Figure 6 Scanning electron microscope photo of the electrode interface morphology of the existing zinc plate electrode after charging.

[0023] Explanation of reference numerals in the drawings

[0024] 1 Positive electrode

[0025] 2 Negative electrode system of the neutral zinc slurry battery

[0026] 3 Diaphragm

[0027] 4 Current collector

[0028] 5 Pump

[0029] 6 Storage tank Detailed description of the specific implementation

[0030] The following is a detailed description of the present invention.

[0031]

Negative electrode system of neutral zinc slurry battery

[0032] The flow-through negative electrode system of the neutral zinc slurry battery of the present invention (hereinafter sometimes simply referred to as the slurry system) contains an aqueous zinc salt solution, a conductive agent, a dispersant, an organic ligand, and nano zinc in a mass ratio of 100:(10 - 60):(5 - 50):(5 - 50):(5 - 50). In this negative electrode system, nano zinc and the conductive agent form a solid complex (hereinafter referred to as the nano zinc-conductive agent complex), which is suspended in the negative electrode system of the neutral zinc slurry battery.

[0033] The mass ratio is the ratio when the mass fraction of the aqueous zinc salt solution is set to 100 parts.

[0034] "Neutral" in the negative electrode system of the neutral zinc slurry battery means that the pH of the negative electrode system of the zinc slurry battery is 4 - 7.

[0035] The zinc salt aqueous solution is a solution formed by dissolving a zinc salt in water. The water is water commonly used in the battery field such as ultrapure water and deionized water. Preferably, the zinc salt aqueous solution is one or a combination of two or more of zinc sulfate aqueous solution, zinc chloride aqueous solution, zinc tetrafluoroborate aqueous solution, zinc perchlorate aqueous solution, zinc trifluoromethanesulfonate aqueous solution, zinc nitrate aqueous solution, and zinc acetate aqueous solution.

[0036] Preferably, the conductive agent is one or a combination of two or more of conductive carbon black, Ketjen black, acetylene black, conductive graphite powder, carbon nanotubes, and graphene. Relative to 100 parts by mass of the zinc salt aqueous solution, the content of the conductive agent is 10 - 60 parts by mass. The network formed by the conductive agent forms a solid composite with nano zinc in the negative electrode system of the neutral zinc slurry battery.

[0037] Preferably, the dispersant is one or a combination of two or more of polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, carboxymethyl cellulose, polyethylene oxide, polyacrylamide, and polyacrylic acid. Relative to 100 parts by mass of the zinc salt aqueous solution, the content of the dispersant is 5 - 50 parts by mass. The viscosity of the slurry system presented when the dispersant content is in this range helps the solid products to be stably suspended during the initial static process and the charge and discharge process, avoiding agglomeration or sedimentation.

[0038] Preferably, the organic ligand is one or a combination of two or more of cysteine, cystine, glutamic acid, glycine, methionine, mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, mercaptoethanol, mercaptopropanol, mercaptobutanol, glutathione, mercaptoethylamine, mercaptopropylamine, and mercaptobutylamine.

[0039] Relative to 100 parts by mass of the zinc salt aqueous solution, the content of the organic ligand in the present invention is 5 - 50 parts by mass. When the content of the organic ligand is in this range, in the flowable neutral zinc slurry battery negative electrode system of the present invention, the organic ligand can avoid the coalescence sedimentation caused by excessive growth during the electrodeposition of zinc species, and instead electrodeposit in the form of monodispersed nanoparticles between the conductive networks of the slurry system. In addition, as Figure 3 shown, the hydrogen bond regulation effect of the organic ligand can effectively slow down the water decomposition and parasitic side reactions such as basic zinc sulfate during the electrodeposition process. However, when the content of the organic ligand exceeds the above range, it is instead unfavorable for the transport of zinc ions in the system, and the charge transfer resistance increases.

[0040] Regarding nano zinc, relative to 100 parts by mass of the zinc salt aqueous solution, the content of nano zinc is 5 - 50 parts by mass. A nano zinc-conductive agent composite is formed between the nano zinc and the conductive agent network. The nano zinc-conductive agent composite is suspended in the slurry system.

[0041] Preferably, the nano zinc is monodispersed zinc metal nanoparticles with an average particle size of 10 - 500 nm. The average particle size is the number average particle size, which can be measured using a nano particle size analyzer. The high specific surface area of nano zinc itself also solves the problems such as low discharge depth and small released current density of the zinc plate type negative electrode. When the diameter of nano zinc is within the above range, it will not affect the suspension stability of the solid complex in the negative electrode system of the neutral zinc slurry battery during static state or charge-discharge process, and will not cause the settlement of solid components.

[0042] The nano zinc material can use commercial products, such as the nano zinc powder of type Z433469 sold by Shanghai Aladdin Biochemical Technology Co., Ltd., or can be self-synthesized by chemical methods, such as using the method of thermal reduction of organic zinc salts with sodium borohydride.

[0043] The viscosity of the negative electrode system of the neutral zinc slurry battery is 5 - 50 Pa·s. The viscosity is the dynamic viscosity, which can be measured using a rotational viscometer, etc. When the viscosity of the negative electrode system of the neutral zinc slurry battery is within the above range, it helps the solid products to be stably suspended during the initial static process and charge-discharge process, and avoids agglomeration or settlement.

[0044]

Preparation method of negative electrode system of neutral zinc slurry battery

[0045] For the preparation method of the flow-type negative electrode system of the neutral zinc slurry battery, the components of the negative electrode system of the neutral zinc slurry battery can be mixed and ground evenly to obtain it. Specifically, it can include the following steps:

[0046] S1. Weigh 10 - 60 parts by mass of conductive agent, 5 - 50 parts by mass of dispersant, 5 - 50 parts by mass of organic ligand, 5 - 50 parts by mass of nano zinc, 5 - 80 parts by mass of zinc salt, and 20 - 95 parts by mass of water, and stir until evenly mixed to obtain a preliminary mixed dispersion liquid;

[0047] S2. Transfer the preliminary mixed dispersion liquid prepared in step S1 to a ball mill tank, and grind it at a rotation speed of 100 - 1000 rpm for 2 - 48 h to obtain a uniformly mixed neutral zinc slurry. The viscosity of the neutral zinc slurry is measured to be 5 - 50 Pa·s, and the pH range is 4 - 7.

[0048] In the above preparation method of the flow-type negative electrode system of the neutral zinc slurry battery, preferably, the nano zinc in step S1 is monodispersed zinc metal nanoparticles with an average particle size of 10 - 500 nm.

[0049] Let the total content of the zinc salt and water be 100 parts by mass.

[0050] Preferably, in step S1, the conductive agent is one or a combination of two or more of conductive carbon black, Ketjen black, acetylene black, conductive graphite powder, carbon nanotubes, and graphene.

[0051] Preferably, in step S1, the dispersant is one or a combination of two or more of polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, carboxymethyl cellulose, polyethylene oxide, polyacrylamide, and polyacrylic acid.

[0052] Preferably, in step S1, the zinc salt is one or a combination of two or more of zinc sulfate, zinc chloride, zinc tetrafluoroborate, zinc perchlorate, zinc trifluoromethanesulfonate, zinc nitrate, and zinc acetate.

[0053] Preferably, in step S1, the organic ligand is one or a combination of two or more of cysteine, cystine, glutamic acid, glycine, methionine, mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, mercaptoethanol, mercaptopropanol, mercaptobutanol, glutathione, mercaptoethylamine, mercaptopropylamine, and mercaptobutylamine.

[0054]

Aqueous Zinc Battery

[0055] The negative electrode system of the neutral zinc slurry battery can be used in an aqueous zinc battery. As Figure 2 shown, the aqueous zinc battery includes a positive electrode 1, the negative electrode system 2 of the neutral zinc slurry battery of the present invention, a separator 3, an electrolyte, etc. The negative electrode system 2 of the neutral zinc slurry battery of the present invention acts as the negative electrode and can be matched with the positive electrode 1 (such as a neutral air positive electrode, a vanadium positive electrode, a manganese positive electrode, etc.) to form a full battery for testing.

[0056] The present invention also provides the application of the negative electrode system of the neutral zinc slurry battery in an aqueous zinc battery. The neutral zinc slurry obtained by the preparation method of the above-mentioned negative electrode system of the neutral zinc slurry battery can be pumped into the negative electrode electrolytic cell of the battery at a certain flow rate (such as 1 - 100 mL·min -1 ) through a pump 5 and circulated back to the storage tank 6. A current collector 4 is inserted into the negative electrode electrolytic cell, a separator 3 is inserted between the positive and negative electrodes, and then discharging or charging is carried out at a certain current density (such as 1 - 500 mA / cm 2 ).

[0057] Preferably, the current collector 4 can be one or a combination of two or more of a stainless steel mesh, carbon cloth, carbon paper, carbon felt, copper foil, and aluminum foil.

[0058] The positive electrode material may include materials commonly used as positive electrode materials in the art, such as carbon black, manganese dioxide, vanadium pentoxide, polyaniline, molybdenum oxide, and zinc vanadate.

[0059] Preferably, the separator 3 can be one or a combination of two or more of a polyethylene separator, a polypropylene separator, filter paper, a cellulose separator, a glass fiber separator, and a synthetic resin separator.

[0060] The above manufacturing method, as well as equipment and materials such as the electrolyte, ball milling tank, negative electrode electrolytic cell, and storage tank 6 used in the aqueous zinc battery, can be common equipment and substances in the art.

[0061] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0062] Embodiment

[0063] The present invention will be described below with reference to embodiments. The embodiments are merely illustrative examples of preferred specific implementation manners and do not limit the protection scope of the present invention. Information on the reagents used in the embodiments and comparative examples is as follows.

[0064] Carbon black: manufactured by Cabot Corporation, USA, model: XC-72R

[0065] Carboxymethyl cellulose: manufactured by Huazhong Chemical Factory, model: 348

[0066] Cysteine: manufactured by Shanghai Aladdin Reagent Co., Ltd., model: C163514

[0067] Zinc trifluoromethanesulfonate: manufactured by Shanghai Aladdin Reagent Co., Ltd., model: Z100682

[0068] Nano zinc 1: self-synthesized, average particle size: 10 - 30 nm

[0069] Nano zinc 2: self-synthesized, average particle size: 400 - 450 nm

[0070] The synthesis method of nano zinc is as follows:

[0071] Nano zinc 1: Measure 20 mL of octadecylamine, 1 mmol of zinc acetate, and 5 mmol of sodium stearate. Under argon protection, heat and stir to 110 °C for 10 min to dissolve into a transparent light yellow solution. Add 2 mmol of sodium borohydride, and quickly raise the temperature to 180 °C under vigorous stirring, and maintain the reaction for 2 h. Cool to room temperature, and successively add petroleum ether and methanol for washing, centrifuge, and dry to obtain nano zinc 1.

[0072] Nano zinc 2: Measure 20 mL of octadecylamine, 1 mmol of zinc acetate, and 5 mmol of sodium stearate. Under argon protection, heat and stir to 110 °C for 10 min to dissolve into a transparent light yellow solution. Add 2 mmol of sodium borohydride, and quickly raise the temperature to 260 °C under vigorous stirring, and maintain the reaction for 12 h. Cool to room temperature, and successively add petroleum ether and methanol for washing, centrifuge, and dry to obtain nano zinc 2.

[0073] The average particle size of nano zinc was measured using an NS-90Z Plus nano particle size analyzer (Omec Instrument Co., Ltd.).

[0074] Micron zinc powder: manufactured by Shanghai Aladdin Reagent Co., Ltd., model: Z683800, average particle size: 2.9 μm

[0075] Carbon cloth current collector: manufactured by Carbon Energy Technology Co., Ltd., model: WOS1011

[0076] Example 1

[0077] The manufacturing method of the negative electrode system of the neutral zinc slurry battery in this example is as follows.

[0078] (1) Preparation of neutral zinc slurry: Weigh 20 g of conductive carbon black, 12 g of carboxymethyl cellulose, 10 g of cysteine, 22.8 g of zinc trifluoromethanesulfonate, and 30 g of nano zinc 1 and add them to 77.2 g of ultrapure water. Stir until completely and evenly mixed to obtain a preliminary mixed dispersion. Then transfer this preliminary mixed dispersion to a 200 mL ball mill jar, set the rotation speed to 400 rpm, and continuously ball mill for 24 h to obtain a completely and evenly mixed negative electrode system of the neutral zinc slurry battery. Use a rotary viscometer (manufactured by Shanghai Lichen Instrument Co., Ltd., model: LC-DV-HB) to measure the viscosity at room temperature as 22.6 Pa·s, and use a pH detector (manufactured by Japan Sanli Instrument Co., Ltd., model: PH220) to measure the pH at room temperature as 5.8.

[0079] (2) Operating scheme for charge and discharge energy storage using the neutral zinc slurry negative electrode system: Pump the above-prepared neutral zinc slurry negative electrode system into a 20 mL negative electrode electrolytic cell at a flow rate of 1 mL·min -1 and circulate it back to the negative electrode storage tank. Insert a carbon cloth current collector with an area of 12 cm 2 into the negative electrode electrolytic cell. In addition, insert a carbon cloth current collector with a manganese dioxide positive electrode active material coated on its surface at 3 mg / cm 2 into the positive electrode electrolytic cell to construct a full cell, or a copper foil to construct a half cell. Insert an NKK TF45 type aqueous diaphragm between the two electrodes, then connect the electrode tabs and copper wires, and use a LANDdt CT3004A battery test system to charge and discharge the assembled flow battery at a current density of 50 mA / cm 2 for 2 h. Electrochemically deposited zinc nanocrystals confined by organic ligands with good monodispersity were obtained on the negative electrode electrolytic cell side. In addition, use an electrochemical workstation (manufactured by Shanghai Chenhua Instrument Co., Ltd., model: CHI660E) and corresponding program parameters (open circuit voltage, frequency range: 0.01 - 100 kHz, bias voltage: 5 mV) to perform AC impedance analysis on the flow battery and collect experimental data.

[0080] The neutral zinc slurry battery anode system prepared in step (1) was analyzed by high-resolution transmission electron microscopy. The results are as Figure 1 (a) and (b) show that nano-zinc forms a complex with the conductive agent and is suspended in the slurry. As shown in Figure 1 (b), a high-resolution image of the corresponding magnified nano-zinc particles can be seen, showing clear lattice fringes corresponding to the pure zinc crystal phase.

[0081] The device of the flow-through neutral zinc slurry battery is as shown in Figure 2 . The zinc slurry is pumped into the electrolysis chamber at a flow rate of 2 mL·min -1 for an electrochemical reaction and then circulated back to the storage tank. During discharge, the zinc slurry anode continuously transfers zinc ion carriers to the cathode and delivers electrons through the external circuit load. During charging, as shown in the mechanism diagram of Figure 3 , the organic ligand enables the zinc species to grow uniformly and monodispersed in the form of quantum dot nanocrystals, preventing excessive aggregation and sedimentation between bulk particles under the electric field. Figure 5 It also intuitively shows the monodispersed morphology of the quantum dot nanocrystals formed by electrodeposition under the regulation of the organic ligand.

[0082] The charge-discharge specific capacity-voltage polarization curve of the full battery based on the neutral zinc slurry anode in step (2) was recorded using a Blue-Energy battery test system. As shown in Figure 4 , the discharge curve has a specific capacity close to the theoretical value, extremely high Coulomb efficiency, reversibility, and a stable voltage plateau.

[0083] Example 2

[0084] The preparation method is the same as that of Example 1, except that 20 g of cysteine was added to 77.2 g of ultrapure water in step (1). The viscosity of the obtained zinc slurry was 24.5 Pa·s and the pH was 5.4.

[0085] Example 3

[0086] The preparation method is the same as that of Example 1, except that 30 g of cysteine was added to 77.2 g of ultrapure water in step (1). The viscosity of the obtained zinc slurry was 26.7 Pa·s and the pH was 5.1.

[0087] Example 4

[0088] The preparation method is the same as that of Example 1, except that 40 g of cysteine was added to 77.2 g of ultrapure water in step (1). The viscosity of the obtained zinc slurry was 28.4 Pa·s and the pH was 4.9.

[0089] Example 5

[0090] The preparation method is the same as that of Example 1, except that 50 g of cysteine is added to 77.2 g of ultrapure water in step (1). The viscosity of the obtained zinc paste is 29.8 Pa·s and the pH is 4.6.

[0091] Example 6

[0092] The preparation method is the same as that of Example 1, except that 30 g of mercaptoacetic acid is added to 77.2 g of ultrapure water in step (1), conductive carbon black is used as the conductive agent with a content of 60 g, and polyvinyl alcohol is used as the dispersant with a content of 50 g. The viscosity of the obtained zinc paste is 16.4 Pa·s and the pH is 4.7.

[0093] Example 7

[0094] The preparation method is the same as that of Example 6, except that 30 g of mercaptopropanol is added to 77.2 g of ultrapure water in step (1). The viscosity of the obtained zinc paste is 46.3 Pa·s and the pH is 5.9.

[0095] Example 8

[0096] The preparation method is the same as that of Example 6, except that 30 g of mercaptobutylamine is added to 77.2 g of ultrapure water in step (1). The viscosity of the obtained zinc paste is 28.8 Pa·s and the pH is 6.4.

[0097] Example 9

[0098] The preparation method is the same as that of Example 6, except that 30 g of glutathione is added to 77.2 g of ultrapure water in step (1). The viscosity of the obtained zinc paste is 26.4 Pa·s and the pH is 5.7.

[0099] Example 10

[0100] The preparation method is the same as that of Example 4, except that 30 g of nano-zinc 1 is replaced by 30 g of nano-zinc 2 in step (1). The viscosity of the obtained zinc paste is 25.2 Pa·s and the pH is 4.9.

[0101] Comparative Example 1

[0102] The preparation method is the same as that of Example 1, except that cysteine is not added to the ultrapure water in step (1). The viscosity of the zinc paste is 9.4 Pa·s and the pH is 7.6.

[0103] Comparative Example 2

[0104] The preparation method is the same as that of Example 1, except that 70 g of excessive cysteine is added to 77.2 g of ultrapure water in step (1). The viscosity of the obtained zinc paste is 66.4 Pa·s and the pH is 3.7.

[0105] Comparative Example 3

[0106] The preparation method was the same as that of Example 3, except that micron-sized zinc powder was used instead of nano zinc. The viscosity of the obtained zinc slurry was 55.1 Pa·s and the pH was 5.0.

[0107] Comparative Example 4

[0108] A traditional aqueous zinc plate battery negative electrode and an example of its preparation were provided as a comparative example to the flow-through neutral zinc slurry battery negative electrode system disclosed in the present invention, including the following steps.

[0109] (1) Preparation of the traditional aqueous zinc plate negative electrode: Weigh 22.8 g of zinc trifluoromethanesulfonate and add it to 77.2 g of ultrapure water. Stir until completely dissolved to obtain the battery electrolyte; wipe the surface of a 1 mm thick zinc plate with ethanol, and then cut it into a 15 mm diameter disc with a tablet press for later use.

[0110] (2) Operating scheme for charge and discharge energy storage using the traditional aqueous zinc plate negative electrode: Use the above-prepared zinc plate as the negative electrode side, and the manganese dioxide / carbon cloth or copper foil (12 mm 2 ) coated in Example 1 as the positive electrode. Insert an NKK TF45 type aqueous separator in the middle, then drop 75 μL of the battery electrolyte, encapsulate it in a CR2032 button battery case, and let it stand for 4 hours. Use the LANDdt CT3004A battery test system to perform constant current charging and discharging on the assembled button battery at current densities of 2 and 50 mA / cm 2 ) respectively. Additionally, use a CHI660E electrochemical workstation and corresponding program parameters to perform AC impedance analysis on the button battery, and collect experimental data. 2

[0111] Observe the surface morphology of the zinc negative electrode after charging the half-cell in step (2) using a scanning electron microscope. As shown in Figure 6 (a), it was clearly found that there was a lot of dendritic deposited zinc on the surface of the zinc electrode. These dendrites may fall off to form dead zinc, reducing the Coulomb efficiency of the battery and even piercing the separator, resulting in battery failure. In addition, as shown in Figure 6 (b), a lot of by-products were also found on the surface of the zinc. The formation of these by-products also consumed a large amount of zinc species and electrolyte.

[0112] Perform transmission electron microscopy analysis and full-cell electrochemical performance testing on the electrodeposited zinc slurry products of the battery negative electrodes prepared in Examples 1-9 and Comparative Examples 1-4. The result parameters are shown in Table 1.

[0113] After testing, the performance parameters of the neutral zinc slurry battery negative electrode systems made from the above examples and comparative examples are as shown in Table 1 below.

[0114] Table 1. Electrochemical performance tests of the flow-type neutral zinc slurry battery negative electrode systems of Examples 1-9 and the battery negative electrodes of Comparative Examples 1-4

[0115]

[0116] The average particle size of the electrodeposited zinc particles in the above table was obtained by reasonably counting no less than 100 particles on the transmission electron microscope (JEOL JEM 2100F type) pictures of the products after charging the flow-type zinc slurry negative electrode systems of Examples 1-9 and the negative electrodes of Comparative Examples 1-4, and then performing arithmetic averaging.

[0117] Regarding the overpotential, first assemble copper foil-zinc half-cells based on different flow-type slurry negative electrodes and zinc plate negative electrodes according to the schemes in the above examples and comparative examples, and use the LANDdt CT3004A battery test system to perform cyclic stripping deposition according to a specific current density and capacity. The value of the overpotential (mV) can be directly read from the obtained discharge curve.

[0118] Regarding the charge transfer resistance, also assemble copper foil-zinc half-cells according to the above examples and comparative examples, and use a CHI660E electrochemical workstation and corresponding program parameters to perform AC impedance analysis on the button cells, collect the measured Nyquist plots, and then perform fitting to obtain the charge transfer resistance (Ω) represented by the semicircle diameter.

[0119] The Coulombic efficiency of the battery is a key indicator to measure the charge transfer efficiency during the charge and discharge process of the battery. Specifically defined as: the ratio of the amount of electricity released during discharge (i.e., the discharge capacity) to the amount of electricity input during charging (i.e., the charge capacity) in a complete charge-discharge cycle of the battery, usually expressed in percentage form. This ratio directly reflects the effectiveness of charge conversion inside the battery and the energy utilization efficiency. In the present invention, the Coulombic efficiency value can be directly measured by assembling copper foil-zinc half-cells according to the above examples and comparative examples and using the LANDdt CT3004A battery test system under the conditions of 8 mA·cm -2 and 5.12 mAh·cm -2 to perform cyclic stripping deposition.

[0120] As can be seen from the test results in Table 1 above, in Examples 1 to 5, as the content of the organic ligand gradually increases, the overpotential and charge transfer resistance of the slurry system begin to decrease, indicating that the added organic ligand regulates the morphology of electrodeposited zinc and electroplates in the form of monodisperse zinc quantum dots. This nano-scale electrodeposition method reduces the barrier of interfacial electron transfer, thereby reducing energy loss, which is also consistent with the continuously increasing Coulomb efficiency. It is found through testing that after adding the organic ligand, the charge-discharge of this neutral zinc slurry battery negative electrode system can achieve reversible and efficient zinc electrodeposition / stripping behavior, and the generation of zinc dendrites is eliminated.

[0121] In Examples 6 to 9, when different types of organic ligands are added to the slurry system, their battery Coulomb efficiencies are all above 92%.

[0122] In Example 10, nano-zinc with different particle sizes from those in Examples 1 to 9 was used, and all electrochemical properties are excellent.

[0123] For Comparative Example 1 without adding cysteine, it is poor in terms of overpotential, charge transfer resistance, and Coulomb efficiency.

[0124] In Comparative Example 2 containing an excessive amount of organic ligand, as the organic ligand is introduced, the average particle size of zinc particles gradually decreases, the charge transfer resistance increases, and the Coulomb efficiency decreases.

[0125] In Comparative Example 3 using zinc powder with a large particle size as the zinc active species, it can be found that electrodeposited zinc is directly electroplated on the initial large-particle zinc powder, resulting in a risk of zinc aggregation, thereby causing a large polarization potential and charge transfer resistance.

[0126] On the other hand, in Comparative Example 4 using a traditional zinc plate negative electrode, due to the formation of dead zinc caused by dendritic growth of zinc and the generation of zinc salt by-products, a large amount of zinc source and electrolyte are consumed. Therefore, both the overcharge and charge transfer resistance increase, seriously inhibiting the Coulomb efficiency of its charge-discharge process.

[0127] Therefore, the flow-type neutral zinc slurry battery negative electrode system of the present invention can achieve monodisperse zinc nanoparticles with a uniform particle size distribution, limited overpotential and charge transfer resistance, and ultra-high Coulomb efficiency, and has practical application value in the field of long-term fixed energy storage. The charge-discharge Coulomb efficiency of the present invention reaches up to 98.6%. This design of the flow-type slurry system also allows the battery to have the potential for decoupled design of energy density and power density, which is far superior to the negative electrode structure of traditional zinc plate batteries, thereby greatly improving the electrochemical energy storage efficiency.

[0128] Those skilled in the art should understand that the above are only several specific embodiments of the present invention, rather than all embodiments. It should be noted that many variations and improvements can be made by those of ordinary skill in the art, and all variations or improvements that do not exceed the claims should be regarded as the protection scope of the present invention.

Claims

1. A negative electrode system for a neutral zinc slurry battery, characterized in that, The neutral zinc slurry is composed of an aqueous zinc salt solution, a conductive agent, a dispersant, an organic ligand, and nano zinc in a mass ratio of 100:(10 - 60):(5 - 50):(5 - 50):(5 - 50). The nano zinc and the conductive agent form a solid complex and are suspended in the negative electrode system of the neutral zinc slurry battery.

2. The negative electrode system of the neutral zinc slurry battery according to claim 1, wherein The aqueous zinc salt solution is one or a combination of two or more of an aqueous zinc sulfate solution, an aqueous zinc chloride solution, an aqueous zinc tetrafluoroborate solution, an aqueous zinc perchlorate solution, an aqueous zinc trifluoromethanesulfonate solution, an aqueous zinc nitrate solution, and an aqueous zinc acetate solution.

3. The negative electrode system of the neutral zinc paste battery according to claim 1 or 2, characterized in that, The conductive agent is one or a combination of two or more of conductive carbon black, Ketjen black, acetylene black, conductive graphite powder, carbon nanotubes, and graphene.

4. The negative electrode system of the neutral zinc paste battery according to claim 1 or 2, characterized in that, The dispersant is one or a combination of two or more of polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, carboxymethyl cellulose, polyethylene oxide, polyacrylamide, and polyacrylic acid.

5. The negative electrode system of the neutral zinc paste battery according to claim 1 or 2, characterized in that, The organic ligand is one or a combination of two or more of cysteine, cystine, glutamic acid, glycine, methionine, mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, mercaptoethanol, mercaptopropanol, mercaptobutanol, glutathione, mercaptoethylamine, mercaptopropylamine, and mercaptobutylamine.

6. The negative electrode system of the neutral zinc paste battery according to claim 1 or 2, characterized in that, The nano zinc is monodisperse zinc metal nanoparticles with an average particle size of 10 - 500 nm.

7. The negative electrode system of the neutral zinc paste battery according to claim 1 or 2, characterized in that, The viscosity of the negative electrode system of the neutral zinc slurry battery is 5 - 50 Pa·s.

8. A method for preparing a negative electrode system of a neutral zinc slurry battery, which is obtained by uniformly mixing and grinding the components in the negative electrode system of the neutral zinc slurry battery according to any one of claims 1 to 7.

9. A water-based zinc battery, characterized in that, Comprising the negative electrode system of the neutral zinc slurry battery according to any one of claims 1 to 7.

10. Application of the negative electrode system of the neutral zinc slurry battery according to any one of claims 1 to 7 in an aqueous zinc battery.

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