Positive electrode slurry, preparation method, positive electrode plate and battery

Abstract

The invention relates to positive electrode slurry, a preparation method, a positive electrode plate and a battery. The positive electrode slurry comprises an active substance, a conductive agent, a metal compound additive and a binder, and the metal compound additive comprises bismuth hydroxide and calcium nitrite. According to the positive electrode slurry, the performance of the zinc-nickel battery is remarkably optimized through the synergistic effect of bismuth hydroxide and calcium nitrite. Gas produced in the battery is greatly reduced, the problems of gas expansion and liquid spraying of the battery are solved, the conductivity is obviously improved, the anode current is uniformly distributed, active substances are efficiently utilized, and the cycle stability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of zinc-nickel battery positive electrode additives, in particular to a positive electrode slurry, a preparation method, a positive electrode sheet and a battery. BACKGROUND

[0002] Nowadays, aqueous zinc-nickel batteries stand out due to their main advantage of high safety, and are widely studied by experts and scholars due to their good cycle stability, high specific capacity, good rate performance and excellent wide-temperature thermal stability. However, there are also certain technical problems, such as hydrogen evolution problem of the negative electrode, serious self-discharge of the battery, rapid capacity attenuation, low battery coulomb efficiency caused by hydrogen and oxygen evolution corrosion, and the like, which increase the difficulty of commercialization of zinc-nickel batteries.

[0003] ①In the aqueous alkaline electrolyte system, water participates in the charging and discharging of the battery during the charging and discharging process, and a large amount of hydrogen and oxygen is generated in the battery, resulting in low battery coulomb efficiency and serious battery swelling.

[0004] ②During the cycle process of the battery, due to serious gas production, the battery shell is severely deformed, and electrolyte is sprayed out, which causes certain safety problems during use and increases the difficulty of commercialization of the battery.

[0005] ③The poor conductivity of the positive electrode active material leads to large internal resistance of the battery during charging and discharging, resulting in uneven current distribution. During charging, the poor conductivity also leads to low utilization rate of the positive electrode active material, resulting in a large difference between the actual capacity and the theoretical capacity.

[0006] In summary, in the research and development process of aqueous zinc-nickel batteries, how to effectively suppress the battery swelling phenomenon and simultaneously improve the cycle stability has become a core problem that needs to be solved by technical personnel in the industry. SUMMARY

[0007] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a positive electrode slurry that can effectively suppress battery swelling and improve cycle stability. In addition, the present application also provides a preparation method of the positive electrode slurry, a positive electrode sheet modified by the positive electrode slurry and a battery.

[0008] The purpose of the present application is achieved by the following technical solutions: The present application provides a positive electrode slurry, which comprises an active material, a conductive agent, a metal compound additive and a binder, and the metal compound additive comprises bismuth hydroxide and calcium nitrite.

[0009] Preferably, the positive electrode slurry comprises, by weight percentage: Active material 60%-70% Conductive agent 1.5%-5% Bismuth hydroxide 1%-5% Calcium nitrite 0.1%-0.4% First adhesive 0.4%-1.5% Second adhesive 2%-6%, Highly conductive carbon materials: 1%-5%; The first binder is carboxymethyl cellulose, the second binder is polytetrafluoroethylene, and the remainder is water.

[0010] Preferably, the active material is spherical nickel hydroxide.

[0011] Preferably, the conductive agent comprises 1%-3% nickel powder and 0.5%-2% cobalt hydroxyoxide by weight percentage.

[0012] Preferably, the highly conductive carbon material is A66 graphite.

[0013] Secondly, the present invention also provides a method for preparing the above-mentioned positive electrode slurry, wherein the binder includes carboxymethyl cellulose and polytetrafluoroethylene, and the preparation method includes: Carboxymethyl cellulose solution, polytetrafluoroethylene solution, and calcium nitrite aqueous solution were prepared separately. Weigh out spherical nickel hydroxide, nickel powder, cobalt hydroxide and bismuth hydroxide respectively, mix them to obtain a mixed powder; A carboxymethyl cellulose solution was mixed thoroughly with a calcium nitrite aqueous solution to obtain a colloid. A66 graphite was added to the colloid to obtain an intermediate slurry; The mixed powder was added to the intermediate slurry in several batches and stirred. Polytetrafluoroethylene was then added and stirred to obtain the positive electrode slurry.

[0014] Preferably, in the step of "adding the mixed powder to the intermediate slurry in several batches", the mixed powder is added to the intermediate sauce in three batches, and stirred after each batch.

[0015] Thirdly, the present invention also provides a positive electrode sheet, which is obtained by the following steps: uniformly coating the above-mentioned positive electrode slurry or the positive electrode slurry obtained by the above-mentioned preparation method onto a nickel current collector, scraping off the excess slurry on the surface, and vacuum drying.

[0016] Preferably, the thickness of the positive electrode slurry on the nickel current collector is 0.2-0.4 mm.

[0017] Fourthly, the present invention also provides a battery comprising the above-described positive electrode.

[0018] Compared with the prior art, the present invention has at least the following advantages: This invention provides a positive electrode slurry with bismuth hydroxide and calcium nitrite as key components, which significantly optimize the performance of zinc-nickel batteries through their synergistic effect. Specifically, during the battery charging and discharging process, calcium nitrite plays a dual role: on the one hand, it can actively adsorb oxygen generated in the electrolyte, promoting the oxidation-reduction reaction between oxygen and nitrite to generate nitrate, thereby achieving efficient elimination of oxygen production in the battery; calcium nitrite, in combination with bismuth hydroxide, utilizes bismuth hydroxide to inhibit hydrogen evolution to further improve the conductivity of the positive electrode, greatly reducing gas production inside the battery.

[0019] On the other hand, the released calcium ions can enhance the structural stability of the battery during cycling. Bismuth hydroxide has good conductivity, forming a dense conductive network in the slurry, enhancing the conductivity of the positive electrode and reducing the internal resistance of the battery during charging and discharging. Due to the improved conductivity of the positive electrode, the positive electrode active material can effectively undergo redox reactions during battery charging and discharging, thereby improving the utilization rate of the positive electrode active material.

[0020] The synergistic effect of bismuth hydroxide and calcium nitrite greatly reduces gas production inside the battery, overcomes the problems of battery swelling and liquid spraying, significantly improves conductivity, makes the positive electrode current distribution uniform, makes efficient use of active materials, and improves cycle stability. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart illustrating the steps of a method for preparing a positive electrode slurry according to an embodiment of the present invention. Figure 2 This is a line graph showing the changes in coulombic efficiency and discharge capacity of the battery tested in Example 1 of the present invention as a function of the number of cycles.

[0023] Figure 3 This is a line graph showing the changes in coulombic efficiency and discharge capacity of the battery tested in Example 2 of the present invention as a function of the number of cycles.

[0024] Figure 4 This is a line graph showing the changes in coulombic efficiency and discharge capacity of the battery tested in Example 3 of the present invention as a function of the number of cycles.

[0025] Figure 5 This is a line graph showing the coulombic efficiency and discharge capacity of the test battery in Comparative Example 1 of this invention as a function of the number of cycles.

[0026] Figure 6This is a line graph showing the coulombic efficiency and discharge capacity of the test battery in Comparative Example 2 of this invention as a function of the number of cycles.

[0027] Figure 7 This is a line graph showing the coulombic efficiency and discharge capacity of the test battery in Comparative Example 3 of this invention as a function of the number of cycles.

[0028] Figure 8 This is a line graph showing the coulombic efficiency and discharge capacity of the test battery in Comparative Example 4 of this invention as a function of the number of cycles. Detailed Implementation

[0029] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] This invention provides a positive electrode slurry, comprising an active material, a conductive agent, a metal compound additive, and a binder, wherein the metal compound additive includes bismuth hydroxide and calcium nitrite.

[0032] The positive electrode slurry is evenly distributed behind the positive electrode sheet. By utilizing the synergistic effect between bismuth hydroxide and calcium nitrite, the stability of battery cycle is effectively improved, the coulombic efficiency is increased, and problems such as battery gas swelling are overcome.

[0033] Preferably, the cathode slurry comprises, by weight percentage: 60%-70% active ingredients Conductive agent 1.5%-5% Bismuth hydroxide 1%-5% Calcium nitrite 0.1%-0.4% First adhesive 0.4%-1.5% Second adhesive 2%-6%, Highly conductive carbon materials: 1%-5%; The first binder is carboxymethyl cellulose, the second binder is polytetrafluoroethylene, and the remainder is water.

[0034] Preferably, the active material is spherical nickel hydroxide.

[0035] Preferably, based on the weight percentage of the positive electrode slurry, The conductive agent consists of 1%-3% nickel powder and 0.5%-2% cobalt hydroxyl oxide.

[0036] Preferably, the highly conductive carbon material is A66 graphite.

[0037] Secondly, the present invention also provides a method for preparing the above-mentioned positive electrode slurry, wherein the binder includes carboxymethyl cellulose and polytetrafluoroethylene, and the preparation method includes: The adhesive comprises a first adhesive and a second adhesive, and the preparation method comprises: Prepare the first binder solution and the calcium nitrite aqueous solution separately; Weigh out spherical nickel hydroxide, nickel powder, cobalt hydroxide and bismuth hydroxide respectively, mix them to obtain a mixed powder; The first binder solution was mixed evenly with the calcium nitrite aqueous solution to obtain a colloid; A66 graphite was added to the colloid to obtain an intermediate slurry; The mixed powder is added to the intermediate slurry in several batches, stirred, and then the second binder is added and stirred to obtain the positive electrode slurry.

[0038] Preferably, in the step of "adding the mixed powder to the intermediate slurry in stages," the mixed powder is added to the intermediate sauce in three stages, with stirring after each addition. This step helps to ensure that the mixed powder in the colloid is evenly dispersed, ensuring that there are no large solid particles.

[0039] The preparation method is simple, greatly reducing the difficulty of industrialization. Moreover, the prices of the two bismuth hydroxides and calcium nitrite are relatively low, significantly reducing the cost of industrialization.

[0040] The present invention also provides a positive electrode sheet, which is obtained by the following process: uniformly coating the above-mentioned positive electrode slurry or the positive electrode slurry obtained by the above-mentioned preparation method onto a nickel current collector, scraping off the excess slurry on the surface, and vacuum drying.

[0041] Preferably, the thickness of the positive electrode slurry on the nickel current collector is 0.2-0.4 mm.

[0042] The present invention also provides a battery comprising the above-described positive electrode.

[0043] The following is a detailed implementation plan.

[0044] Example 1 Weigh out deionized water and carboxymethyl cellulose in a mass percentage ratio of 97wt%:3wt%. Use a stirrer to completely dissolve the carboxymethyl cellulose in the deionized water to obtain an aqueous solution of carboxymethyl cellulose.

[0045] Weigh out deionized water and calcium nitrite in a mass percentage ratio of 94wt%:6wt%, stir with a magnetic stirrer for 5-10 minutes until completely dissolved to obtain a precursor solution. Seal and store the precursor solution for later use.

[0046] Spherical nickel hydroxide, nickel powder, cobalt hydroxide and bismuth hydroxide were weighed out according to the following proportions: 64wt%: 3wt%: 1wt%: 4wt% of the positive electrode slurry mass, and then mixed to obtain a mixed powder.

[0047] Weigh out 17% of the carboxymethyl cellulose aqueous solution by weight of the positive electrode slurry, and weigh out 5% of the precursor solution by weight of the slurry. Add both to a stirrer and stir for 15-30 minutes until they are evenly mixed to obtain the colloid.

[0048] Weigh 3% of A66 graphite by mass of the positive electrode slurry, add it to the colloid obtained above, stir under a stirrer for 5-10 minutes until it is evenly mixed, and obtain the intermediate slurry.

[0049] Add the above-mentioned mixed powder to the intermediate slurry in three batches, adding 1 / 3 of the powder each time. Stir for 15-20 minutes after each addition to ensure the slurry is uniformly mixed and free of large solid particles. The stirring speed should be 500-1200 r / min. After the mixed powder is completely and uniformly dispersed in the slurry, add 3% (by weight) of polytetrafluoroethylene (PTFE) to the positive electrode slurry and stir for 6-10 minutes to ensure it is uniformly incorporated into the slurry. The stirring speed should be 400-800 r / min. The positive electrode slurry is now obtained.

[0050] The positive electrode slurry was uniformly coated onto a pre-pressed 0.9mm thick nickel foam current collector. Excess slurry was then scraped off using a scraper with a 0.93mm gap, resulting in a positive electrode slurry thickness of 0.03mm. The electrode was then stretched. The stretched electrode was then vacuum-dried in a 140-170℃ vacuum drying oven for 2 hours.

[0051] The dried modified positive electrode sheet is rolled to a thickness of 0.58mm-0.65mm. After rolling, the electrode sheet is cut, cleaned, and the tabs are welded. The separator is then made into a bag and assembled into a single cell with the unmodified negative electrode sheet.

[0052] In this embodiment, the main components of the negative electrode sheet include: the binder is polyvinyl alcohol, styrene-butadiene rubber and polytetrafluoroethylene, the conductive agent is zinc powder, the active material is zinc oxide, and the surfactant is sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide.

[0053] Example 2 Weigh out deionized water and carboxymethyl cellulose in a mass percentage ratio of 97wt%:3wt%. Use a stirrer to completely dissolve the carboxymethyl cellulose in the deionized water to obtain an aqueous solution of carboxymethyl cellulose.

[0054] Weigh out deionized water and calcium nitrite in a mass percentage ratio of 98wt%:2wt%, stir with a magnetic stirrer for 5-10 minutes until completely dissolved to obtain a precursor solution. Seal and store the precursor solution for later use.

[0055] Spherical nickel hydroxide, nickel powder, cobalt hydroxide and bismuth hydroxide were weighed out according to the following proportions: 67wt%: 3wt%: 1wt%: 1wt% of the positive electrode slurry mass, and then mixed to obtain a mixed powder.

[0056] Weigh out 17% of the carboxymethyl cellulose aqueous solution by weight of the positive electrode slurry, and weigh out 5% of the precursor solution by weight of the slurry. Add both to a stirrer and stir for 15-30 minutes until they are evenly mixed to obtain the colloid.

[0057] Weigh 3% of A66 graphite by mass of the positive electrode slurry, add it to the colloid obtained above, stir under a stirrer for 5-10 minutes until it is evenly mixed, and obtain the intermediate slurry.

[0058] Add the above-mentioned mixed powder to the intermediate slurry in three batches, adding 1 / 3 of the powder each time. Stir for 15-20 minutes after each addition to ensure the slurry is uniformly mixed and free of large solid particles. The stirring speed should be 500-1200 r / min. After the mixed powder is completely and uniformly dispersed in the slurry, add 3% (by weight) of polytetrafluoroethylene (PTFE) to the positive electrode slurry and stir for 6-10 minutes to ensure it is uniformly incorporated into the slurry. The stirring speed should be 400-800 r / min. The positive electrode slurry is now obtained.

[0059] The positive electrode slurry was uniformly coated onto a pre-pressed 0.9mm thick nickel foam current collector. Excess slurry was then scraped off using a scraper with a 0.93mm gap, resulting in a positive electrode slurry thickness of 0.03mm. The electrode was then stretched. The stretched electrode was then vacuum-dried in a 140-170℃ vacuum drying oven for 2 hours.

[0060] The dried modified positive electrode sheet is rolled to a thickness of 0.58mm-0.65mm. After rolling, the electrode sheet is cut, cleaned, and the tabs are welded. The separator is then made into a bag and assembled into a single cell with the unmodified negative electrode sheet.

[0061] In this embodiment, the main components of the negative electrode sheet include: the binder is polyvinyl alcohol, styrene-butadiene rubber and polytetrafluoroethylene, the conductive agent is zinc powder, the active material is zinc oxide, and the surfactant is sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide.

[0062] Example 3 Weigh out deionized water and carboxymethyl cellulose in a mass percentage ratio of 97wt%:3wt%. Use a stirrer to completely dissolve the carboxymethyl cellulose in the deionized water to obtain an aqueous solution of carboxymethyl cellulose.

[0063] Weigh out deionized water and calcium nitrite in a mass percentage ratio of 92wt%:8wt%, stir with a magnetic stirrer for 5-10 minutes until completely dissolved to obtain a precursor solution. Seal and store the precursor solution for later use.

[0064] Spherical nickel hydroxide, nickel powder, cobalt hydroxide and bismuth hydroxide were weighed out according to the following proportions: 63wt%: 3wt%: 1wt%: 5wt% of the positive electrode slurry mass, and then mixed to obtain a mixed powder.

[0065] Weigh out 17% of the carboxymethyl cellulose aqueous solution by weight of the positive electrode slurry, and weigh out 5% of the precursor solution by weight of the slurry. Add both to a stirrer and stir for 15-30 minutes until they are evenly mixed to obtain the colloid.

[0066] Weigh 3% of A66 graphite by mass of the positive electrode slurry, add it to the colloid obtained above, stir under a stirrer for 5-10 minutes until it is evenly mixed, and obtain the intermediate slurry.

[0067] Add the above-mentioned mixed powder to the intermediate slurry in three batches, adding 1 / 3 of the powder each time. Stir for 15-20 minutes after each addition to ensure the slurry is uniformly mixed and free of large solid particles. The stirring speed should be 500-1200 r / min. After the mixed powder is completely and uniformly dispersed in the slurry, add 3% (by weight) of polytetrafluoroethylene (PTFE) to the positive electrode slurry and stir for 6-10 minutes to ensure it is uniformly incorporated into the slurry. The stirring speed should be 400-800 r / min. The positive electrode slurry is now obtained.

[0068] The positive electrode slurry was uniformly coated onto a pre-pressed 0.9mm thick nickel foam current collector. Excess slurry was then scraped off using a scraper with a 0.93mm gap, resulting in a positive electrode slurry thickness of 0.03mm. The electrode was then stretched. The stretched electrode was then vacuum-dried in a 140-170℃ vacuum drying oven for 2 hours.

[0069] The dried modified positive electrode sheet is rolled to a thickness of 0.58mm-0.65mm. After rolling, the electrode sheet is cut, cleaned, and the tabs are welded. The separator is then made into a bag and assembled into a single cell with the unmodified negative electrode sheet.

[0070] In this embodiment, the main components of the negative electrode sheet include: the binder is polyvinyl alcohol, styrene-butadiene rubber and polytetrafluoroethylene, the conductive agent is zinc powder, the active material is zinc oxide, and the surfactant is sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide.

[0071] Comparative Example 1 Weigh out deionized water and carboxymethyl cellulose in a mass percentage ratio of 97wt%:3wt%. Use a stirrer to completely dissolve the carboxymethyl cellulose in the deionized water to obtain an aqueous solution of carboxymethyl cellulose.

[0072] Spherical nickel hydroxide, nickel powder, and cobalt hydroxyl oxide were weighed out according to the mass percentages of the positive electrode slurry: 70wt%: 3wt%: 1wt%, and then mixed to obtain a mixed powder.

[0073] Weigh out 3% of A66 graphite according to the mass percentage of the positive electrode slurry, add it to the above-mentioned carboxymethyl cellulose aqueous solution, wherein the mass of the carboxymethyl cellulose aqueous solution is 20% of the total mass of the final slurry, stir under a stirrer for 5-10 minutes, mix evenly, and obtain an intermediate slurry.

[0074] The above-mentioned mixed powder is added to the intermediate slurry in three batches, with 1 / 3 added each time. After each addition, the mixture is stirred for 15-20 minutes to ensure uniform mixing and the absence of large solid particles. The stirring speed is 500-1200 r / min. After the mixed powder is completely and uniformly dispersed in the slurry, 3% PTFE (by weight of the final slurry) is added, and the mixture is stirred for 6-10 minutes to ensure uniform integration into the slurry. The stirring speed is 400-800 r / min to obtain the positive electrode slurry.

[0075] The positive electrode slurry was uniformly coated onto a pre-pressed 0.9mm thick nickel foam current collector. Excess slurry was then scraped off using a scraper with a 0.93mm gap, and the slurry was then stretched. The thickness of the positive electrode slurry was 0.03mm. The stretched electrode was then vacuum dried in a vacuum drying oven at 140-170℃ for 2 hours.

[0076] The dried positive electrode sheet is rolled to a thickness of 0.58mm-0.65mm. After rolling, the electrode sheet is cut, cleaned, the tabs are welded, the separator is made into a bag, and then assembled into a single cell with the negative electrode sheet.

[0077] In this embodiment, the main components of the negative electrode sheet are: the binder is polyvinyl alcohol, styrene-butadiene rubber and polytetrafluoroethylene, the conductive agent is zinc powder, the active material is zinc oxide, and the surfactant is sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide.

[0078] Comparative Example 2 Weigh out deionized water and carboxymethyl cellulose in a mass percentage ratio of 97 wt%: 3 wt%. Use a stirrer to completely dissolve the carboxymethyl cellulose in the deionized water to obtain a carboxymethyl cellulose aqueous solution.

[0079] Weigh out deionized water and calcium nitrite in a mass percentage ratio of 94wt%:6wt%, stir with a magnetic stirrer for 5-10 minutes until completely dissolved to obtain a precursor solution. Seal and store the precursor solution for later use.

[0080] Spherical nickel hydroxide, nickel powder, and cobalt hydroxyl oxide were weighed according to the following ratios: 68wt%: 3wt%: 1wt% of the positive electrode slurry, and then mixed to obtain a mixed powder.

[0081] Weigh out 17% of the carboxymethyl cellulose aqueous solution by weight of the positive electrode slurry, and weigh out 5% of the precursor solution by weight of the slurry. Stir in a stirrer for 15-30 minutes until the mixture is homogeneous to obtain a colloid.

[0082] Weigh 3% of A66 graphite by mass of the positive electrode slurry, add it to the colloid obtained above, stir under a stirrer for 5-10 minutes until it is evenly mixed, and obtain the intermediate slurry.

[0083] Add the mixed powder to the intermediate slurry in three batches, adding 1 / 3 of the powder each time. Stir for 15-20 minutes after each addition to ensure the slurry is uniformly mixed and free of large solid particles. The stirring speed should be 500-1200 r / min. After the mixed powder is completely and uniformly dispersed in the slurry, add 3% PTFE (by weight of the slurry) and stir for 6-10 minutes to ensure it is uniformly incorporated into the slurry. The stirring speed should be 400-800 r / min. The positive electrode slurry is now obtained.

[0084] The positive electrode slurry was uniformly coated onto a pre-pressed 0.9mm thick nickel foam current collector. Excess slurry was then scraped off using a scraper with a 0.93mm gap, and the slurry was then stretched. The thickness of the positive electrode slurry was 0.03mm. The stretched electrode was then vacuum dried in a vacuum drying oven at 140-170℃ for 2 hours.

[0085] The dried positive electrode sheet is rolled to a thickness of 0.58mm-0.65mm. After rolling, the electrode sheet is cut, cleaned, the tabs are welded, the separator is made into a bag, and then assembled into a single cell with the negative electrode sheet.

[0086] In this embodiment, the main components of the negative electrode sheet are: the binder is polyvinyl alcohol, styrene-butadiene rubber and polytetrafluoroethylene, the conductive agent is zinc powder, the active material is zinc oxide, and the surfactant is sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide.

[0087] Comparative Example 3 Weigh out deionized water and carboxymethyl cellulose in a mass percentage ratio of 97wt%:3wt%. Use a stirrer to completely dissolve the carboxymethyl cellulose in the deionized water to obtain an aqueous solution of carboxymethyl cellulose.

[0088] Spherical nickel hydroxide, nickel powder, cobalt hydroxide, and bismuth hydroxide were weighed out in proportions of 66wt%, 3wt%, 1wt%, and 4wt% of the positive electrode slurry, respectively, and then mixed to obtain a mixed powder.

[0089] Weigh 3% of A66 graphite by mass of the positive electrode slurry, add the above-mentioned carboxymethyl cellulose aqueous solution, wherein the mass of the carboxymethyl cellulose aqueous solution is 20% of the total mass of the positive electrode slurry, stir under a stirrer for 5-10 minutes, mix evenly, and obtain an intermediate slurry.

[0090] Add the mixed powder to the intermediate slurry in three batches, one-third of the powder each time. Stir for 15-20 minutes after each addition to ensure the slurry is uniformly mixed and free of large solid particles. The stirring speed should be 500-1200 r / min. After the mixed powder is completely and uniformly dispersed in the slurry, add 3% PTFE (by weight of the slurry) and stir for 6-10 minutes to ensure it is evenly incorporated. The stirring speed should be 400-800 r / min. This yields the positive electrode slurry.

[0091] The positive electrode slurry was uniformly coated onto a pre-pressed 0.9mm thick nickel foam current collector. Excess slurry was then scraped off using a scraper with a 0.93mm gap, and the slurry was then stretched. The thickness of the positive electrode slurry was 0.03mm. The stretched electrode was then vacuum dried in a vacuum drying oven at 140-170℃ for 2 hours.

[0092] The dried positive electrode sheet is rolled to a thickness of 0.58mm-0.65mm. After rolling, the electrode sheet is cut, cleaned, the tabs are welded, the separator is made into a bag, and then assembled into a single cell with the negative electrode sheet.

[0093] In this embodiment, the main components of the negative electrode sheet are: the binder is polyvinyl alcohol, styrene-butadiene rubber and polytetrafluoroethylene, the conductive agent is zinc powder, the active material is zinc oxide, and the surfactant is sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide.

[0094] Comparative Example 4 Weigh out deionized water and carboxymethyl cellulose in a mass percentage ratio of 97wt%:3wt%. Use a stirrer to completely dissolve the carboxymethyl cellulose in the deionized water to obtain an aqueous solution of carboxymethyl cellulose.

[0095] Weigh out deionized water and calcium nitrite in a mass percentage ratio of 90wt%:10wt%, stir with a magnetic stirrer for 5-10 minutes until completely dissolved to obtain a precursor solution. Seal and store the precursor solution for later use.

[0096] Spherical nickel hydroxide, nickel powder, cobalt hydroxide and bismuth hydroxide were weighed out according to the following proportions: 60wt%: 3wt%: 1wt%: 8wt% of the positive electrode slurry mass, and then mixed to obtain a mixed powder.

[0097] Weigh out 17% of the carboxymethyl cellulose aqueous solution by weight of the positive electrode slurry, and weigh out 5% of the precursor solution by weight of the slurry. Add both to a stirrer and stir for 15-30 minutes until they are evenly mixed to obtain the colloid.

[0098] Weigh 3% of A66 graphite by mass of the positive electrode slurry, add it to the colloid obtained above, stir under a stirrer for 5-10 minutes until it is evenly mixed, and obtain the intermediate slurry.

[0099] Add the above-mentioned mixed powder to the intermediate slurry in three batches, adding 1 / 3 of the powder each time. Stir for 15-20 minutes after each addition to ensure the slurry is uniformly mixed and free of large solid particles. The stirring speed should be 500-1200 r / min. After the mixed powder is completely and uniformly dispersed in the slurry, add 3% (by weight) of polytetrafluoroethylene (PTFE) to the positive electrode slurry and stir for 6-10 minutes to ensure it is uniformly incorporated into the slurry. The stirring speed should be 400-800 r / min. The positive electrode slurry is now obtained.

[0100] The positive electrode slurry was uniformly coated onto a pre-pressed 0.9mm thick nickel foam current collector. Excess slurry was scraped off using a scraper with a 0.93mm gap, resulting in a positive electrode slurry thickness of 0.03mm. The electrode was then stretched. The stretched electrode was vacuum dried in a 140-170℃ vacuum drying oven for 2 hours.

[0101] The dried modified positive electrode sheet is rolled to a thickness of 0.58mm-0.65mm. After rolling, the electrode sheet is cut, cleaned, and the tabs are welded. The separator is then made into a bag and assembled into a single cell with the unmodified negative electrode sheet.

[0102] In this embodiment, the main components of the negative electrode sheet include: the binder is polyvinyl alcohol, styrene-butadiene rubber and polytetrafluoroethylene, the conductive agent is zinc powder, the active material is zinc oxide, and the surfactant is sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide.

[0103] Performance testing The modified positive electrode sheets obtained in Examples 1 to 3 and the positive electrode sheets in Comparative Examples 1 to 4 were assembled into single-cell batteries with negative electrode sheets from the same batch. The electrolyte was a 6 mol / L potassium hydroxide electrolyte with saturated zinc oxide. Charge-discharge tests were conducted, with a voltage range of 1.3-1.9V and a charge-discharge rate of 0.5C. The battery test results are shown in Table 1 below. Table 1. Charge and discharge test results of different test batteries ; at the same time, Figures 2 to 8 Line graphs showing the coulombic efficiency and discharge capacity of different test batteries as a function of cycle number are presented.

[0104] Referring to Table 1, Figures 2 to 8 It can be seen that after 65 cycles in Comparative Example 1, the discharge capacity retention rate drops below 80%. After 101 cycles, the capacity retention rate drops below 60%, and after 89 cycles, the coulombic efficiency drops to 93%, indicating severe hydrogen and oxygen evolution inside the battery.

[0105] Comparative Example 2 is a positive electrode sheet with only calcium nitrite added to the positive electrode slurry. Its cycle life is improved compared to Comparative Example 1. The capacity retention is above 80% and above 60% for 82 cycles and 148 cycles respectively. The coulombic efficiency is also improved to a certain extent.

[0106] Comparative Example 3 is a single-cell battery with only bismuth hydroxide added to the positive electrode slurry. Its cycle stability is better than that of Comparative Example 2. The capacity retention is above 80% and above 60% for 103 cycles and 205 cycles respectively. The coulombic efficiency is also around 98%, indicating that the addition of bismuth hydroxide can effectively improve the coulombic efficiency of the battery.

[0107] In Comparative Example 4, the amounts of calcium nitrite and bismuth hydroxide were increased. Comparisons of Comparative Examples 1-4 and Example 1 show that, although the unreasonable addition of calcium nitrite and bismuth hydroxide still improves the battery coulombic efficiency to over 99% and suppresses gas generation and side reactions, its cycle resistance is greater than that of Example 1 and Comparative Example 3, its specific capacity is lower than that of Comparative Example 3, and its conductivity also shows a decreasing trend. This is because the unreasonable addition of calcium nitrite and bismuth hydroxide affects the discharge of the active material and its conductivity, and reduces the cycle stability of the battery. In Comparative Example 4, the number of cycles with over 80% capacity retention is 57 fewer than in Example 1, and it also shows a decreasing trend compared to Comparative Examples 2 and 3. This demonstrates that unreasonable addition can have side effects on the battery.

[0108] However, the modified positive electrode single cell of Example 1 performed the best, maintaining a capacity retention of over 80% for 157 cycles and over 60% for 303 cycles, with slow discharge capacity decay. The modified positive electrode exhibited stable charge-discharge performance, and its cycle life was significantly improved compared to Comparative Examples 1 to 4. The coulombic efficiency remained stable above 99% during cycling, with an average coulombic efficiency of 99.45%. Compared to Comparative Examples 1 to 4, the coulombic efficiency of Example 1 was higher, approaching 100%, indicating that hydrogen and oxygen evolution corrosion inside the battery was effectively mitigated during cycling, and gas production was significantly reduced.

[0109] Examples 2 and 3 differ from Example 1 in the additive addition ratio, but both remain within a reasonable range. Cyclic data graphs show that despite the different addition ratios, the cyclic performance is highly similar. Compared to Example 1, Examples 2 and 3 show only a difference of less than 8 cycles in retention rate, consistent coulombic efficiency, and minimal differences in cyclic discharge internal resistance and specific capacity. This demonstrates that within this additive ratio range, the battery performance is significantly improved, exhibiting reliability and indicating a high degree of consistency and repeatability in this experiment.

[0110] It is worth noting that Example 1 exhibited the best overall performance, with an average discharge internal resistance of 29.83 mΩ, lower than that of Comparative Examples 1 to 4, indicating good conductivity of the modified electrode. The specific capacity after activation was 239.19 mAh / g, 24-29 mAh / g higher than that of Comparative Examples 1 and 2, significantly improving the utilization rate of the positive electrode active material. It achieved a capacity retention of over 80% for 157 cycles and over 60% for 303 cycles. All values ​​were superior to those of Comparative Examples 1 to 4.

[0111] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A positive electrode slurry, characterized in that, It includes active substances, conductive agents, metal compound additives, and binders, wherein the metal compound additives include bismuth hydroxide and calcium nitrite.

2. The positive electrode slurry according to claim 1, characterized in that, The positive electrode slurry comprises, by weight percentage: 60%-70% active ingredients Conductive agent 1.5%-5% Bismuth hydroxide 1%-5% Calcium nitrite 0.1%-0.4% First adhesive 0.4%-1.5% Second adhesive 2%-6%, Highly conductive carbon materials: 1%-5%; The first binder is carboxymethyl cellulose, the second binder is polytetrafluoroethylene, and the remainder is water.

3. The positive electrode slurry according to claim 2, characterized in that, The active substance is spherical nickel hydroxide.

4. The positive electrode slurry according to claim 2, characterized in that, Based on the weight percentage of the positive electrode slurry, The conductive agent comprises 1%-3% nickel powder and 0.5%-2% cobalt hydroxyl oxide.

5. The positive electrode slurry according to claim 2, characterized in that, By weight percentage The highly conductive carbon material is A66 graphite.

6. A method for preparing a positive electrode slurry according to any one of claims 1-5, characterized in that, The adhesive comprises a first adhesive and a second adhesive, and the preparation method comprises: Prepare the first binder solution and the calcium nitrite aqueous solution separately; Weigh out spherical nickel hydroxide, nickel powder, cobalt hydroxide and bismuth hydroxide respectively, mix them to obtain a mixed powder; The first binder solution was mixed evenly with the calcium nitrite aqueous solution to obtain a colloid; A66 graphite was added to the colloid to obtain an intermediate slurry; The mixed powder is added to the intermediate slurry in several batches, stirred, and then the second binder is added and stirred to obtain the positive electrode slurry.

7. The method for preparing the positive electrode slurry according to claim 6, characterized in that, In the phrase "adding the mixed powder to the intermediate slurry in several batches", the mixed powder is added to the intermediate slurry in three batches, and stirred after each batch.

8. A positive electrode sheet, characterized in that, The positive electrode sheet is obtained through the following process: uniformly coating the positive electrode slurry according to any one of claims 1-5 or the positive electrode slurry obtained by any one of the preparation methods according to claims 6-7 onto the nickel current collector, scraping off the excess slurry on the surface, and vacuum drying.

9. A positive electrode sheet according to claim 8, characterized in that, The thickness of the positive electrode slurry on the nickel current collector is 0.05-0.3 mm.

10. A battery, characterized in that, Includes the positive electrode sheet as described in claim 8 or 9.

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