Nickel-based battery positive active compound, nickel-based battery positive plate as well as preparation method and application of nickel-based battery positive active compound and nickel-based battery positive plate

Abstract

The invention relates to the field of nickel-based batteries, and discloses a nickel-based battery positive active compound, a nickel-based battery positive plate and a preparation method and application of the nickel-based battery positive active compound and the nickel-based battery positive plate. The nickel-based battery positive electrode active compound comprises a positive electrode active substance, a conductive agent, potassium polyacrylate and an adhesive, and the content of the potassium polyacrylate in the positive electrode active compound is 0.01-4.00 wt%. The nickel-based battery positive plate provided by the invention comprises a positive electrode substrate and the positive electrode active compound provided by the invention. The preparation method of the nickel-based battery positive plate comprises the following steps: preparing positive slurry containing the positive active compound; and distributing the positive electrode slurry on a positive electrode substrate or in pores of a positive electrode substrate, drying, tabletting and forming. An electrode prepared from the nickel-based battery positive electrode active compound is good in stability and good in electrode performance.

Description

Technical Field

[0001] The present invention relates to energy storage technology, and particularly to a nickel-based battery positive electrode active composite, a nickel-based battery positive electrode sheet, and a preparation method and application thereof. Background Art

[0002] In recent years, due to its characteristics of safety, stability, low cost and simple maintenance, the zinc-nickel single-flow battery has been widely discussed in the field of large-scale energy storage technology. The positive and negative electrodes of the zinc-nickel single-flow battery use the same electrolyte, eliminating the problem of cross-contamination of the solution. At the same time, there is no need to use expensive ion exchange membranes, and the battery materials are relatively inexpensive. Its unique advantages make it have good application prospects.

[0003] The main active material of the nickel positive electrode of the zinc-nickel battery is Ni(OH)2, and the nickel positive electrode is mainly divided into a sintered type and a foam type (non-sintered type). The currently used zinc-nickel single-flow battery positive electrode usually uses the sintered type, which has strong support, less powder falling, and high capacity retention rate, but also has problems of large volume and low capacity, and cannot meet the high-capacity requirements of energy storage. Compared with the sintered positive electrode, the foam positive electrode has the characteristics of high capacity, high activity and low energy consumption. Generally, a fiber nickel or foam nickel material with a relatively high porosity is used as a support, and spherical nickel hydroxide is coated to obtain the nickel positive electrode. However, the structural stability of the foam electrode is not as good as that of the sintered type. When the ordinary foam nickel electrode is applied to the flow battery, the electrode material is easily detached under the scouring of the electrolyte, resulting in the loss of active substances. Moreover, the positive electrode powder of the foam nickel electrode will expand and contract during the cycle, which will cause the positive electrode powder to fall off and separate from the conductive matrix, further affecting the battery performance. Summary of the Invention

[0004] In the preparation process of the foam nickel positive electrode slurry, a thickening agent needs to be used to improve the dispersibility and stability of the slurry. Usually, sodium carboxymethyl cellulose CMC is selected as the thickening agent, but sodium carboxymethyl cellulose CMC has poor chemical stability in a high-concentration alkaline electrolyte, and the viscosity is significantly reduced, thereby causing the collapse of the electrode skeleton, seriously damaging the performance and life of the electrode. Therefore, the preparation of a highly stable foam nickel positive electrode is of great significance for the application of high-capacity nickel-based batteries.

[0005] The purpose of the present invention is to provide a nickel-based battery positive electrode active composite, a nickel-based battery positive electrode sheet, and a preparation method and application thereof, aiming at the problems of the existing nickel-based battery positive electrode.

[0006] To achieve the above purpose, the present invention provides a nickel-based battery positive electrode active composite, including a positive electrode active material, a conductive agent, potassium polyacrylate and a binder. Among them, in the positive electrode active composite, the content of potassium polyacrylate is 0.01-4.00 wt%. By adopting the foregoing technical solution, the obtained electrode has good stability and good electrode performance.

[0007] In the present invention, the optional range of the positive electrode active material is relatively wide, and commonly used positive electrode active materials can all be used in the present invention. The following is a demonstration, but it does not limit the scope of the present invention. For example, it is selected from one or more of nickel hydroxide, nickel oxide, nickel hydroxide doped with zinc and / or cobalt elements.

[0008] In the present invention, the optional range of the conductive agent is relatively wide, and commonly used conductive agents can all be used in the present invention. The following is a demonstration, but it does not limit the scope of the present invention. For example, the conductive agent is selected from one or more of superconducting carbon black, carbon nanotubes, graphite powder, and graphene.

[0009] In the present invention, the optional range of the binder is relatively wide, and commonly used binders can all be used in the present invention. The following is a demonstration, but it does not limit the scope of the present invention. For example, the binder is selected from one or more of polytetrafluoroethylene, gum arabic, and acrylate. Polytetrafluoroethylene and gum arabic used in the present invention are all commercially available products, and commonly used ones include 60wt% polytetrafluoroethylene emulsion, 10wt% gum arabic solution, etc.

[0010] In the present invention, the optional range of the number average molecular weight of potassium polyacrylate is relatively wide. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the number average molecular weight of the potassium polyacrylate is 5000 - 10000000.

[0011] According to a preferred embodiment of the present invention, the potassium polyacrylate includes potassium polyacrylate with a number average molecular weight of 10000 - 100000 and potassium polyacrylate with a number average molecular weight of 500000 - 5000000. Based on the total weight of the potassium polyacrylate, the mass content of each is not less than 15wt%, and preferably each content is 20 - 80wt%. By adopting the foregoing technical solution, the electrode has good stability and good electrode performance, and avoids the problem of collapse of the traditional foam-type nickel positive electrode skeleton; the positive electrode has excellent water absorption and water retention properties, can significantly increase the viscosity of the slurry, maintain the stability of the slurry, and improve the consistency of the preparation of the positive electrode; the positive electrode has strong wettability, and its good ductility can better adapt to the expansion of the positive electrode powder during the cycling process.

[0012] In the present invention, as long as the object of the present invention can be achieved, the content range of potassium polyacrylate in the positive active complex is relatively wide. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, in the positive active complex, the content of potassium polyacrylate is 0.05 to 4.00 wt%, such as 0.08 wt%, 0.10 wt%, 0.30 wt%, 0.80 wt%, 1.00 wt%, 1.50 wt%, 2.00 wt%, 2.50 wt%, 3.00 wt%, 3.50 wt%. By adopting the foregoing technical solution, the electrode has good stability and good electrode performance, and avoids the problem of the collapse of the traditional foam nickel positive electrode skeleton; the positive electrode has excellent water absorption and water retention properties, can significantly increase the viscosity of the slurry, maintain the stability of the slurry, and improve the consistency of the preparation of the positive electrode; the positive electrode has strong wettability, and its good ductility can better adapt to the expansion of the positive electrode powder during the cycle.

[0013] In the present invention, as long as the object of the present invention can be achieved, there are no special requirements for the content of the positive active material in the positive active complex. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, in the positive active complex, the content of the positive active material is 60 to 95 wt%, preferably 65 to 90 wt%.

[0014] In the present invention, as long as the object of the present invention can be achieved, there are no special requirements for the content of the conductive agent in the positive active complex. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, in the positive active complex, the content of the conductive agent is 3 to 20 wt%, preferably 5 to 16 wt%.

[0015] In the present invention, as long as the object of the present invention can be achieved, there are no special requirements for the content of the binder in the positive active complex. According to a preferred embodiment of the present invention, in the positive active complex, the content of the binder is 1 to 10 wt%, preferably 2 to 8 wt%.

[0016] In the present invention, the role of the positive active additive is to improve the conductivity of positive active materials such as Ni(OH)2, increase the electron transport channels and improve the electron transport rate, and reduce the polarization resistance; inhibit the volume expansion of the positive electrode and extend the cycle life. According to a preferred embodiment of the present invention, the positive active complex contains a positive active additive, and the optional range of the additive is relatively wide. A demonstration of an embodiment is given, but it does not limit the scope of the present invention. For example, the positive active additive is selected from one or more of cobalt hydroxide, cobaltous oxide, manganese dioxide, and zinc powder, preferably cobalt hydroxide and zinc powder. By adopting the foregoing technical solution, the positive electrode structure of the alkaline zinc-nickel single flow battery is stable and has a long cycle life.

[0017] In the present invention, as long as the object of the present invention can be achieved, there is no special requirement for the content of the positive active additive in the positive active composite. According to a preferred embodiment of the present invention, in the positive active composite, the content of the positive active additive is 1 to 15 wt%, preferably 2 to 11 wt%. By adopting the foregoing technical solution, the positive electrode structure of the alkaline zinc-nickel single-flow battery is stable and has a long cycle life.

[0018] The present invention provides a positive electrode sheet for a nickel-based battery, which includes a positive electrode substrate and the positive active composite of the present invention.

[0019] The present invention provides a method for preparing a positive electrode sheet for a nickel-based battery, which method includes: preparing a positive electrode slurry containing the positive active composite of the present invention; distributing the positive electrode slurry on the positive electrode substrate or in the pores of the positive electrode substrate, and drying and pressing into a sheet.

[0020] In the present invention, as long as the object of the present invention can be achieved, the optional range of the drying temperature is relatively wide. An embodiment is demonstrated for illustrative purposes, but this does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the drying temperature is 70 to 130 °C. By adopting the foregoing technical solution, the positive electrode structure is stable and has a long cycle life.

[0021] In the present invention, as long as the object of the present invention can be achieved, the optional range of the drying time is relatively wide. An embodiment is demonstrated for illustrative purposes, but this does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the drying time is 5 to 10 h.

[0022] In the present invention, as long as the object of the present invention can be achieved, there is no special requirement for the material selection of the positive electrode substrate. An embodiment is demonstrated for illustrative purposes, but this does not limit the scope of the present invention. For example, the positive electrode substrate is selected from one or more of nickel foam, fibrous nickel, nickel mesh, and punched steel strip.

[0023] Nickel foam has advantages such as good electrical conductivity and high porosity. According to a preferred embodiment of the present invention, the positive electrode substrate is nickel foam. By adopting the foregoing technical solution, it has the advantage of improving the mass specific capacity of the battery.

[0024] In the present invention, as long as the object of the present invention can be achieved, the optional range of the amount of the positive electrode slurry is relatively wide, and it is generally selected and determined according to the specific composition to be obtained. For example, the target composition is achieved by means of excessive immersion of the positive electrode slurry.

[0025] In the present invention, as long as the object of the present invention can be achieved, the optional range of the content of the positive active composite in the positive electrode sheet for the nickel-based battery is relatively wide. An embodiment is demonstrated for illustrative purposes, but this does not limit the scope of the present invention. According to a preferred embodiment of the present invention, in the positive electrode sheet for the nickel-based battery, the content of the positive active composite is 100 to 250 mg / cm2 , preferably 120 - 240 mg / cm 2 .

[0026] According to a preferred embodiment of the present invention, in the positive electrode paste, the mass concentration of the positive electrode active complex is 40 - 80 wt%, and the mass concentration of the solvent is 20 - 60 wt%. Adopting the foregoing technical solution has the advantages of uniform dispersion of the paste and good consistency.

[0027] In the present invention, the optional range of the solvent is relatively wide. One embodiment is demonstrated, but it does not limit the scope of the present invention. For example, the solvent includes one or more of water, ethanol, and isopropanol. According to a preferred embodiment of the present invention, the solvent is a mixed solution of isopropanol and water, and based on the total weight of the solvent, the amount of isopropanol used is 5 - 15 wt%. Adopting the foregoing technical solution has the advantage of improving the mass specific capacity of the battery.

[0028] In the present invention, there is no special requirement for the method of preparing the positive electrode paste containing the positive electrode active complex described in the present invention. One embodiment is demonstrated, but it does not limit the scope of the present invention. For example, the method of preparing the positive electrode paste of the positive electrode active complex includes: uniformly mixing the positive electrode active material, the conductive agent, potassium polyacrylate, and the binder in the solvent.

[0029] More specifically, the method of preparing the positive electrode paste of the positive electrode active complex includes: in the solvent, first add the binder and stir evenly, then add potassium polyacrylate and stir evenly, and finally add the uniformly mixed positive electrode active material, conductive agent, and additive powder and stir evenly.

[0030] In the present invention, during the process of preparing the positive electrode paste of the positive electrode active complex, there is no special requirement for the stirring time. One embodiment is demonstrated, but it does not limit the scope of the present invention. For example, adding the binder to the solvent and stirring evenly for 10 - 150 min to prepare a uniform emulsion, and the time is preferably 10 - 100 min; then adding potassium polyacrylate and stirring for 30 min - 180 min to prepare a gel-like viscous liquid, and the time is preferably 30 - 120 min; finally, stirring the positive electrode active material, conductive agent, and additive powder evenly and adding them to the foregoing gel-like viscous liquid, and stirring for 60 - 180 min, preferably 90 - 180 min.

[0031] In the present invention, as long as the object of the present invention can be achieved, there is no special requirement for the method of distributing the positive electrode paste on the positive electrode substrate or in the pores of the positive electrode matrix. One embodiment is demonstrated, but it does not limit the scope of the present invention, including using methods such as impregnation, coating, or doctor blading to distribute the positive electrode paste on the positive electrode substrate or in the pores of the positive electrode matrix.

[0032] Specifically, for example, using the impregnation method, the substrate is immersed in a sufficient amount of nickel positive electrode slurry, such as 2 L of nickel positive electrode slurry.

[0033] In the present invention, there are no special requirements for tablet pressing. For example, tablet pressing is carried out under a pressure of 15 - 25 MPa for 2 - 5 min by hot pressing to obtain the positive electrode sheet.

[0034] Specifically, for example, using the impregnation method, a 12*9 cm 2 foamed nickel substrate is immersed in a sufficient amount of nickel positive electrode slurry, such as 2 L of nickel positive electrode slurry, for 5 min. After impregnation and drying, hot pressing is carried out under a pressure of 15 - 25 MPa for 2 - 5 min by a hot press to obtain the positive electrode sheet.

[0035] The present invention provides a nickel-based battery positive electrode sheet obtained by the preparation method of the nickel-based battery positive electrode sheet described in the present invention.

[0036] The present invention provides the application of the nickel-based battery positive electrode sheet described in the present invention in a zinc-nickel single-flow battery, a zinc-nickel solid-state battery, a nickel-metal hydride battery or a nickel-cadmium battery.

[0037] According to a preferred embodiment of the present invention, the nickel-based battery positive electrode sheet described in the present invention is particularly suitable for application in a zinc-nickel single-flow battery.

[0038] According to a preferred embodiment of the present invention, in a zinc-nickel single-flow battery, the negative electrode is selected from one or more of carbon felt, graphite felt, carbon cloth and zinc sheet, the electrolyte is a potassium hydroxide solution dissolved with zinc ions, and no ion exchange membrane is used in battery assembly, which can reduce the battery cost and reduce battery polarization.

[0039] The liquid storage tank, pump and pipeline in the zinc-nickel single-flow battery can be selected according to the prior art, which does not affect the performance of the zinc-nickel single-flow battery of the present invention, and the present invention will not elaborate.

[0040] The electrode prepared by using the nickel-based battery positive electrode active composite of the present invention has good stability and good electrode performance. It is speculated that the reason is that the nickel-based battery positive electrode active composite of the present invention uses potassium polyacrylate as a thickener, overcoming the disadvantage that the electrode skeleton collapses due to instability in a strong alkaline electrolyte when using sodium carboxymethyl cellulose CMC as a thickener. At the same time, potassium polyacrylate has excellent water retention, can enhance the wettability of the positive electrode during the battery cycle, enhance ion transport, and its good ductility can better adapt to the expansion of the positive electrode powder during the cycle, maintaining the stability of the electrode structure and further improving the electrode performance. Description of the Drawings

[0041] Figure 1 is the cycle efficiency diagram of the zinc-nickel single-flow battery in Example 1 at a current density of 35 mA cm -2 Current density.

[0042] Figure 2 is the cycle efficiency graph of the zinc-nickel single flow battery of Comparative Example 1 at a current density of 35 mA cm -2 ².

[0043] Figure 3 is the cycle efficiency graph of the zinc-nickel single flow battery of Comparative Example 2 at a current density of 35 mA cm -2 ². Detailed implementation manners

[0044] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0045] The present invention will be described in detail below through examples. In the following examples, wt% represents mass fraction; polytetrafluoroethylene emulsion, gum arabic solution, potassium polyacrylate, graphite powder, carbon nanotubes, conductive carbon black, graphene, cobalt hydroxide, zinc powder, cobalt oxide, nickel hydroxide, zinc sheet, nickel foam, etc. are all commercially available products.

[0046] Example 1

[0047] Use a vacuum mixer to prepare the slurry. Disperse 1.8 kg of water, 333.3 g of 60 wt% polytetrafluoroethylene emulsion, and 250 g of 10 wt% gum arabic solution for 30 min; add 0.875 kg of potassium polyacrylate solution containing 25 g of potassium polyacrylate (the number average molecular weight of potassium polyacrylate is 1,250,000) and disperse for 1 h to obtain a viscous solution; slowly add the stirred solid powder. The solid powder composition is 4 kg of nickel hydroxide powder, 400 g of graphite powder, 100 g of carbon nanotubes, 200 g of cobalt hydroxide, and 50 g of zinc powder, and disperse for 2 h to obtain a uniform nickel positive electrode slurry; immerse a 12*9 cm 2 nickel foam substrate in 2 L of the nickel positive electrode slurry for 5 min, dry at 90 °C for 8 h, and then use a hot press to hot press for 3 min at a pressure of 20 MPa to form a sheet. After weighing, subtract the mass of the nickel foam to obtain the content of the positive electrode active complex in the electrode sheet. In the obtained electrode sheet, the content of the positive electrode active complex is 182 mg / cm 2 .

[0048] Assemble a zinc-nickel single flow battery with the formed nickel positive electrode as the positive electrode material. The negative electrode is a zinc sheet, and the electrolyte is a 7 M potassium hydroxide solution containing 0.5 M zinc ions, without a separator. The obtained zinc-nickel single flow battery at a current density of 35 mA cm -2Under the condition that the charging time is 30 min and the discharging is to 0.8 V, the cyclic efficiency diagram is shown in Figure 1 , and the results of Coulomb efficiency and energy efficiency are shown in Table 1. It can be seen that the zinc-nickel single-flow battery assembled with the electrode using potassium polyacrylate as the thickener exhibits stable Coulomb efficiency and energy efficiency.

[0049] Example 2

[0050] Use a vacuum mixer to prepare the slurry. Disperse 0.2 kg of water, 541.7 g of 60 wt% polytetrafluoroethylene emulsion, and 500 g of 10 wt% gum arabic solution for 100 min; add 0.5 kg of a potassium polyacrylate solution containing 2.5 g (the number-average molecular weight of potassium polyacrylate is 10,000,000) and disperse for 2 h to obtain a viscous solution; slowly add the well-stirred solid powder. The solid powder composition is 3.35 kg of nickel hydroxide, 750 g of graphite powder, and 500 g of cobalt oxide, and disperse for 3 h to obtain a uniform nickel positive electrode slurry; immerse a 12*9 cm 2 foamed nickel substrate in 2 L of the nickel positive electrode slurry for 5 min, dry it at 90 °C for 8 h, and then use a hot press to hot-press for 3 min at a pressure of 20 MPa to form a tablet. After weighing, subtract the mass of the foamed nickel to obtain the content of the positive electrode active complex in the electrode sheet. In the obtained electrode sheet, the content of the positive electrode active complex is 237 mg / cm 2 .

[0051] Use the same method as in Example 1 to assemble the zinc-nickel single-flow battery and test the battery performance. The cyclic efficiency diagram of Example 2 is similar to that of Example 1. The results of Coulomb efficiency and energy efficiency are shown in Table 1. It can be seen that the zinc-nickel single-flow battery assembled with the electrode using potassium polyacrylate as the thickener exhibits stable Coulomb efficiency and energy efficiency.

[0052] Example 3

[0053] Use a vacuum mixer to prepare the slurry. Disperse 3.5 kg of water, 1.0 kg of ethanol, and 250 g of 60 wt% polytetrafluoroethylene emulsion for 10 min; add 2.5 kg of a potassium polyacrylate solution with a solid content of 200 g (the number-average molecular weight of potassium polyacrylate is 5000) and disperse for 30 min to obtain a viscous solution; slowly add the well-stirred solid powder. The solid powder composition is 4.3 kg of nickel hydroxide powder, 150 g of conductive carbon black, 100 g of graphene, 50 g of cobalt oxide, and 50 g of zinc powder, and disperse for 90 min to obtain a uniform nickel positive electrode slurry; immerse a 12*9 cm 2 foamed nickel substrate in 2 L of the nickel positive electrode slurry for 5 min, dry it at 90 °C for 8 h, and then use a hot press to hot-press for 3 min at a pressure of 20 MPa to form a tablet. After weighing, subtract the mass of the foamed nickel to obtain the content of the positive electrode active complex in the electrode sheet. In the obtained electrode sheet, the content of the positive electrode active complex is 125 mg / cm2 。

[0054] The zinc-nickel single-flow battery was assembled and the battery performance was tested using the same method as in Example 1. The cycle efficiency graph of Example 3 obtained was similar to that of Example 1. The results of Coulombic efficiency and energy efficiency are shown in Table 1. It can be seen that the zinc-nickel single-flow battery assembled with the electrode using potassium polyacrylate as the thickener exhibits stable Coulombic efficiency and energy efficiency.

[0055] Example 4

[0056] The preparation method of the nickel positive electrode material was the same as that in Example 1, except that in the same mass of potassium polyacrylate solution added, there were 12.5 g of potassium polyacrylate with a number average molecular weight of 100,000 and 12.5 g of potassium polyacrylate with a number average molecular weight of 3,000,000.

[0057] The zinc-nickel single-flow battery was assembled and the battery performance was tested using the same method as in Example 1. The cycle efficiency graph was similar to that of Example 1. The results of Coulombic efficiency and energy efficiency are shown in Table 1.

[0058] Example 5

[0059] The preparation method of the nickel positive electrode material was the same as that in Example 1, except that in the same mass of potassium polyacrylate solution added, there were 5.0 g of potassium polyacrylate with a number average molecular weight of 50,000 and 20.0 g of potassium polyacrylate with a number average molecular weight of 500,000.

[0060] The zinc-nickel single-flow battery was assembled and the battery performance was tested using the same method as in Example 1. The cycle efficiency graph was similar to that of Example 1. The results of Coulombic efficiency and energy efficiency are shown in Table 1.

[0061] Example 6

[0062] The preparation method of the nickel positive electrode material was the same as that in Example 1, except that in the same mass of potassium polyacrylate solution added, there were 20.0 g of potassium polyacrylate with a number average molecular weight of 10,000 and 5.0 g of potassium polyacrylate with a number average molecular weight of 5,000,000.

[0063] The zinc-nickel single-flow battery was assembled and the battery performance was tested using the same method as in Example 1. The cycle efficiency graph was similar to that of Example 1. The results of Coulombic efficiency and energy efficiency are shown in Table 1.

[0064] Example 7

[0065] The preparation method of the nickel positive electrode material was the same as that in Example 1, except that 1.8 kg of water was replaced with 1.5 kg of water and 0.3 kg of isopropanol.

[0066] The zinc-nickel single-flow battery was assembled and the battery performance was tested using the same method as in Example 1. The obtained cycle efficiency diagram was similar to that of Example 1. The results of Coulomb efficiency and energy efficiency are shown in Table 1.

[0067] Comparative Example 1

[0068] The preparation method of the nickel positive electrode material was the same as that in Example 1, except that 0.875 kg of a polyacrylate potassium solution containing 25 g of polyacrylate potassium (the number-average molecular weight of polyacrylate potassium was 1,250,000) was replaced with 0.875 kg of a sodium carboxymethylcellulose solution containing 25 g of sodium carboxymethylcellulose.

[0069] The zinc-nickel single-flow battery was assembled and the battery performance was tested using the same method as in Example 1. The obtained cycle efficiency diagram is shown in Figure 2 , and the results of Coulomb efficiency and energy efficiency are shown in Table 1. It can be seen from Figure 2 that when a zinc-nickel single-flow battery is assembled with a positive electrode using sodium carboxymethylcellulose as a thickener, after only a few cycles, the Coulomb efficiency and energy efficiency show obvious attenuation. The main reason is that sodium carboxymethylcellulose is unstable in a strong alkaline solution, and the flushing of the flowing electrolyte in the zinc-nickel single-flow battery further aggravates the collapse of the electrode skeleton, resulting in serious shedding of the positive electrode powder in a short time, which is not suitable for the zinc-nickel single-flow battery system.

[0070] Comparative Example 2

[0071] The preparation method of the nickel positive electrode was the same as that in Example 1, except that 0.875 kg of a polyacrylate potassium solution was replaced with 0.875 kg of water.

[0072] The zinc-nickel single-flow battery was assembled and the battery performance was tested using the same method as in Example 1. The obtained cycle efficiency diagram is shown in Figure 3 , and the results of Coulomb efficiency and energy efficiency are shown in Table 1. The slurry prepared without adding polyacrylate potassium in Comparative Example 2 has obvious particle sense, poor slurry consistency, and poor performance of the prepared nickel positive electrode.

[0073] Comparative Example 3

[0074] The preparation method of the nickel positive electrode was the same as that in Example 1, except that 250 g of polyacrylate potassium was added to the same mass of polyacrylate potassium solution (the number-average molecular weight of polyacrylate potassium was 1,250,000). The viscosity of the obtained nickel positive electrode slurry was too high to penetrate into the nickel foam substrate, and the foam-type nickel positive electrode required by the present invention could not be obtained.

[0075] Table 1 Performance of zinc-nickel single-flow battery

[0076] Coulomb efficiency (%) Energy efficiency (%) Example 1 96.1 79.8 Example 2 95.7 78.9 Example 3 96.8 80.8 Example 4 97.1 81.4 Example 5 96.4 80.7 Example 6 96.7 80.9 Example 7 97.2 81.6 Comparative Example 1 70.3 50.1 Comparative Example 2 92.6 72.6 Comparative Example 3 / /

[0077] The electrode prepared by using the nickel-based battery cathode active composite of the present invention has good stability and good electrode performance. It avoids the problem of framework collapse of the traditional foam nickel cathode when applied to the zinc-nickel single-flow battery; and potassium polyacrylate has excellent water absorption and water retention properties, which can significantly increase the slurry viscosity to maintain the stability of the slurry and improve the consistency of the cathode preparation; at the same time, its outstanding hydrophilic and water retention ability significantly enhances the hydrophilic property of the electrode, accelerates the ion transport between the electrode and the electrolyte, and reduces the ohmic resistance of the electrode.

[0078] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A nickel-based battery positive electrode active composite, characterized in that: The invention comprises a positive electrode active material, a conductive agent, potassium polyacrylate and a binder, wherein the content of potassium polyacrylate in the positive electrode active composite is 0.01-4.00wt%.

2. The composite according to claim 1, wherein The number average molecular weight of the potassium polyacrylate is 5000-10000000; preferably, the potassium polyacrylate comprises potassium polyacrylate with a number average molecular weight of 10000-100000 and potassium polyacrylate with a number average molecular weight of 500000-5000000, and the mass content of the two is not less than 15wt% respectively, based on the total weight of the potassium polyacrylate; and / or In the positive electrode active composite, the content of potassium polyacrylate is 0.05-4.00wt%.

3. The composite according to claim 1 or 2, wherein: In the positive electrode active composite, The positive electrode active material content is 60 to 95 wt%, preferably 65 to 90 wt%; and / or Conductive agent 3-20wt%, preferably 5-16wt%; and / or Binder 1-10wt%, preferably 2-8wt%; Preferably, The positive electrode active composite contains a positive electrode active additive, and the positive electrode active additive is selected from one or more of cobalt hydroxide, cobaltous oxide, manganese dioxide, and zinc powder, preferably cobalt hydroxide and zinc powder; More preferably, in the positive electrode active composite, the content of the positive electrode active additive is 1 to 15 wt %, preferably 2 to 11 wt %.

4. A nickel-based battery positive electrode sheet, comprising a positive electrode substrate and the positive electrode active composite according to any one of claims 1 to 3.

5. A method for preparing a nickel-based battery positive electrode sheet, characterized in that: The method includes: Preparing a positive electrode slurry containing the positive electrode active composite according to any one of claims 1 to 3; The positive electrode slurry is distributed on the positive electrode substrate or in the pores of the positive electrode substrate, dried, and pressed into tablets.

6. The method according to claim 5, wherein: The drying temperature is 70-130°C; and / or The positive electrode substrate is selected from one or more of foamed nickel, fibrous nickel, nickel mesh, and perforated steel strip, preferably foamed nickel; and / or In the nickel-based battery positive electrode sheet, the content of the positive electrode active composite is 100-250 mg / cm 2 , preferably 120 to 240 mg / cm 2 .

7. The method according to claim 5 or 6, wherein: In the positive electrode slurry, the mass concentration of the positive electrode active composite is 40-80wt%, and the mass concentration of the solvent is 20-60wt%; Preferably, the solvent comprises one or more of water, ethanol and isopropanol, preferably a mixed solution of isopropanol and water, and the amount of isopropanol used is 5-15wt% based on the total weight of the solvent.

8. A nickel-based battery positive electrode sheet prepared by the method according to any one of claims 5 to 7.

9. Use of the nickel-based battery positive electrode sheet described in claim 4 or 8 in a zinc-nickel single-flow battery, a zinc-nickel solid-state battery, a nickel-hydrogen battery or a nickel-cadmium battery, preferably in a zinc-nickel single-flow battery.

10. The use according to claim 9, wherein: In the zinc-nickel single-flow battery, the negative electrode is selected from one or more of carbon felt, graphite felt, carbon cloth and zinc sheet; the electrolyte is a potassium hydroxide solution containing zinc ions.

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