Nickel battery positive pole piece suitable for three-electrode test and preparation method of nickel battery positive pole piece

Abstract

The invention belongs to the technical field of battery pole pieces, and particularly discloses a nickel battery positive pole piece suitable for a three-electrode test and a preparation method of the nickel battery positive pole piece. The method comprises the following steps: carrying out surface pretreatment on a foamed nickel base material, and cutting the foamed nickel base material according to requirements to obtain a conductive substrate; mixing an active substance, a conductive agent, an adhesive (polyvinylidene fluoride), an additive (yttrium oxide) and a solvent to obtain electrode slurry; and then coating a conductive substrate with the electrode slurry, drying and removing floating powder on the surface to obtain the nickel battery positive pole piece suitable for the three-electrode test. The preparation process of the nickel battery positive plate is simple, feasible and novel, and the prepared nickel battery positive plate is relatively high in capacity, good in adhesiveness of active substances and long in service life.

Description

Technical Field

[0001] This invention relates to the field of battery electrode technology, and in particular to a nickel battery positive electrode suitable for three-electrode testing and its preparation method. Background Technology

[0002] Nickel batteries, as a mature traditional battery product, have long relied on a wet slurry-forming and sheet-pulling process for their positive electrode preparation. This method first mixes solid powders such as active materials and conductive agents with liquid components such as binders and deionized water. After thorough stirring, a uniform slurry is formed. This slurry is then coated or filled onto a nickel foam substrate, followed by a series of processes including drying, rolling, and cutting to finally produce the positive electrode sheet of the required specifications.

[0003] For analyzing reaction mechanisms, assessing actual potential and polarization, and accurately pinpointing the cause of battery failure, three-electrode systems should be prioritized for testing. In the flooded electrolyte environment after three-electrode battery assembly and testing, the repeated volume changes and gas evolution during electrolyte immersion and battery charging / discharging continuously impact and weaken the bonding interface between the active material and the substrate. Over the long term, the active material is still prone to peeling and detaching from the substrate, leading to powder shedding from the positive electrode. This phenomenon not only causes loss of active material, directly reducing battery capacity and energy density, but also accelerates battery performance degradation and premature failure, severely impacting battery reliability, cycle life, and safety.

[0004] Therefore, how to provide a nickel battery positive electrode sheet suitable for three-electrode testing and its preparation method, to ensure the capacity of the nickel battery positive electrode sheet is fully utilized and to improve the capacity qualification rate; at the same time, to avoid positive electrode sheet powdering, reduce battery short circuit and low voltage rate, improve battery electrical performance and safety performance, and extend battery life are urgent problems to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a nickel battery positive electrode sheet suitable for three-electrode testing and its preparation method, aiming to provide a simple, feasible, novel method for manufacturing a nickel battery positive electrode sheet with high capacity and better adhesion of active materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a nickel-cadmium battery positive electrode suitable for three-electrode testing includes the following steps: 1) Pre-treat the surface of the nickel foam substrate and cut it according to requirements to obtain a conductive substrate; 2) The active material, conductive agent, binder, additives and solvent are mixed to obtain the electrode paste; 3) The electrode slurry is coated onto the conductive substrate, dried, and the surface powder is removed to obtain a nickel battery positive electrode suitable for three-electrode testing; The additive is yttrium oxide, and the adhesive is polyvinylidene fluoride. There is no specific order requirement for steps 1) and 2).

[0007] Preferably, the surface pretreatment includes sequential ultrasonic cleaning in citric acid solution and acetone; The citric acid solution has a mass concentration of 40~60g / L, and the ultrasonic conditions in the citric acid solution are: temperature 25~35℃, time 15~25min, and power 100~200W. The conditions for sonication in acetone are a temperature of 25-35℃, a time of 10-20 minutes, and a power of 100-200W.

[0008] Preferably, the mass ratio of the active substance, conductive agent, binder and additive in step 2) is 100:0.01~5:8~20:1~10; The mass-to-volume ratio of the adhesive to the solvent is 5~15:100.

[0009] Preferably, the active material comprises nickel hydroxide particles coated with cobalt. The conductive agent includes one or more of nickel powder, acetylene black, graphite powder, and Co(OH)2; The solvent includes one or more of N-methylpyrrolidone, polyvinyl alcohol, dipropylene glycol dimethyl ether, and dipropylene glycol methyl ether.

[0010] Preferably, the conductive agent is Co(OH)2; The mass ratio of the active substance, conductive agent, and additive is 100:2:5.

[0011] Preferably, the electrode paste coating amount on the conductive substrate surface in step 3) is 100~120 mg / cm². 2 .

[0012] Another object of the present invention is to provide a nickel battery positive electrode sheet prepared by the above preparation method that is suitable for three-electrode testing.

[0013] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: The method for manufacturing the nickel-ion battery positive electrode sheet of this invention is simple, feasible, and novel. By employing a coating process to fill the positive electrode slurry within a nickel foam matrix, and using polyvinylidene fluoride (PVDF) as a binder in the slurry, the adhesion of the active material to the nickel foam matrix is ​​improved. This results in a nickel-ion battery positive electrode sheet that is less prone to powdering during battery use, ensuring optimal capacity utilization and improving capacity yield. Simultaneously, the reduced powdering reduces battery short circuits and low voltage rates, improving battery electrical and safety performance and extending battery life. Furthermore, the introduction of yttrium oxide as a functional additive into the slurry further enhances the high-temperature and cycle stability of the electrode. During battery charging and discharging, the positive electrode active material β-NiOOH readily transforms into γ-NiOOH, which expands significantly in volume, leading to electrode deformation and weakening the electrical contact between the active material and the current collector, causing capacity decay. The incorporation of yttrium oxide effectively inhibits the formation of γ-NiOOH, reducing electrode expansion and deformation at high temperatures, thereby improving the structural stability and cycle charge / discharge capability of the electrode. When evaluating the high-temperature electrochemical performance of electrodes, the difference between the oxygen evolution potential and the oxidation potential of the nickel active material is a key indicator. The larger this difference, the stronger the battery's charging efficiency and charge acceptance. Adding yttrium oxide can significantly increase the oxygen evolution overpotential, effectively suppressing the occurrence of oxygen evolution side reactions at high temperatures, thereby improving the battery's charging efficiency and energy utilization efficiency under high-temperature environments. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0015] Figure 1 The cyclic voltammetry curves of the three-electrode test system corresponding to Embodiment 1 of the present invention are shown below. Figure 2 This is a constant current charge-discharge curve corresponding to Embodiment 1 of the present invention. Detailed Implementation

[0016] This invention provides a method for preparing a nickel battery positive electrode suitable for three-electrode testing, comprising the following steps: 1) Pre-treat the surface of the nickel foam substrate and cut it according to requirements to obtain a conductive substrate; 2) The active material, conductive agent, binder, additives and solvent are mixed to obtain the electrode paste; 3) The electrode slurry is coated onto the conductive substrate, dried, and the surface powder is removed to obtain a nickel battery positive electrode suitable for three-electrode testing.

[0017] In this invention, the surface pretreatment includes ultrasonic cleaning in citric acid solution and acetone in sequence.

[0018] In this invention, the mass concentration of the citric acid solution is 40~60 g / L, specifically 42 g / L, 45 g / L, 48 g / L, 50 g / L, 52 g / L, 55 g / L, or 58 g / L; the ultrasonic conditions in the citric acid solution are: temperature 25~35℃, specifically 26℃, 28℃, 30℃, 32℃, or 34℃; time 15~25 min, specifically 16 min, 18 min, 20 min, 22 min, or 24 min; and power 100~200 W, specifically 120 W, 140 W, 150 W, 160 W, or 180 W.

[0019] In this invention, the conditions for ultrasonication in acetone are: temperature of 25~35℃, specifically 26℃, 28℃, 30℃, 32℃, and 34℃; time of 10~20min, specifically 12min, 14min, 15min, 16min, and 18min; and power of 100~200W, specifically 120W, 140W, 150W, 160W, and 180W.

[0020] In this invention, the mass ratio of the active substance, conductive agent, binder and additive in step 2) is 100:0.01~5:8~20:1~10, preferably 100:0.05~4:10~18:2~8; more preferably 100:0.1~2:12~16:4~6, and even more preferably 100:1:15:5.

[0021] In this invention, the mass-volume ratio of the adhesive to the solvent is 5~15:100, preferably 6~12:100, and even more preferably 8~10:100.

[0022] In this invention, the active material comprises nickel hydroxide particles coated with cobalt; the conductive agent comprises one or more of nickel powder, acetylene black, graphite powder, and Co(OH)2; the additive is yttrium oxide; the binder is polyvinylidene fluoride; and the solvent comprises one or more of N-methylpyrrolidone, polyvinyl alcohol, dipropylene glycol dimethyl ether, and dipropylene glycol methyl ether.

[0023] In this invention, the conductive agent is preferably Co(OH)2; the mass ratio of the active substance, the conductive agent and the additive is 100:2:5.

[0024] In this invention, the coating amount of the electrode paste on the conductive substrate surface in step 3) is 100~120 mg / cm². 2 Specifically, it can be 112 mg / cm³ 2 115mg / cm 2 118mg / cm 2 110mg / cm 2 112mg / cm 2 115mg / cm 2 118mg / cm 2 .

[0025] In this invention, the drying temperature in step 3) is 80~110℃, specifically 85℃, 90℃, 95℃, 100℃, or 105℃; the drying time is 2~4h, specifically 2.2h, 2.5h, 2.8h, 3h, 3.2h, 3.5h, or 3.8h.

[0026] The present invention also provides a nickel battery positive electrode sheet prepared by the above preparation method, suitable for three-electrode testing.

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for manufacturing a positive electrode sheet for a nickel-metal hydride battery, comprising the following steps: A 0.05mm thick nickel foam substrate with a PPI of 110 underwent surface pretreatment. First, it was ultrasonically cleaned in a 50g / L citric acid solution (30℃, 20 minutes, 150W) to effectively remove surface oxides and inorganic contaminants. Then, it was ultrasonically cleaned with acetone (30℃, 15 minutes, 150W) to thoroughly remove oil, organic residues, and adsorbed particles, ensuring a clean substrate surface with good wettability and adhesion, providing an ideal interface for subsequent positive electrode slurry coating. The 0.05mm thick nickel foam substrate with a PPI of 110 was then cut to the predetermined length and width of the electrode.

[0030] First, the active material (cobalt-coated nickel hydroxide particles, manufactured by Youke New Energy, type III spherical nickel), conductive agent (cobalt(II) hydroxide), and additive (yttrium oxide) are weighed at a mass ratio of 9.9:0.01:0.1. A 10% PVDF solution is prepared, with N-methylpyrrolidone as the solvent. The weighed active material, conductive agent, and additive are mixed with the PVDF solution to obtain an electrode slurry (active material:PVDF = 100:12, g / g). Then, the prepared electrode slurry is coated onto a nickel foam substrate (coating amount 110 mg / cm³). 2 Dry at 100℃ for 3 hours, scrape off surface powder, and cut into electrode sheets to obtain nickel battery positive electrode sheets.

[0031] The nickel-cadmium battery positive electrode sheet prepared above was assembled into a three-electrode test system for capacity testing. The counter electrode was a high-purity platinum sheet (Pt), the reference electrode was a mercury oxide electrode (Hg / HgO), and the working electrode was the prepared positive electrode sheet. The electrolyte used was 6 mol / L potassium hydroxide + 15 g / L lithium hydroxide. To further verify its performance under the actual operating voltage window, a cyclic test was conducted: charging at a 0.2C rate for 5.5 hours to ensure complete activation, followed by constant current discharge at a 0.2C rate to the cutoff voltage of 0.0V (relative to the Hg / HgO reference electrode). The test results show that under the rich electrolyte working environment after the three-electrode battery assembly test, the positive electrode material exhibits excellent electrochemical performance, with a specific capacity as high as 210 mAh / g, showing extremely high utilization of active materials; at the same time, its coulombic efficiency reaches 98% (from...). Figure 2 This indicates that the charge-discharge process is highly reversible, has very few side reactions, and possesses excellent electrochemical stability and cycle reliability.

[0032] The cyclic voltammetry curve of the three-electrode test system is as follows: Figure 1 As shown, through Figure 1 It can be seen that in an alkaline system, the nickel hydroxide electrode undergoes a reversible redox reaction: Charging (oxidation process): Ni(OH)2 + OH → NiOOH + H2O + e - Discharge (reduction process): NiOOH + H₂O + e - →Ni(OH)2+OH - The potential is scanned positively from 0.0V: At this time, the electrode is in the reduced state (Ni(OH)2). When the potential is scanned to about 0.45V, the current begins to rise significantly and an anodic peak appears, corresponding to the process of Ni(OH)2 being oxidized to NiOOH. A cathode peak will appear at about 0.24V, corresponding to NiOOH being reduced back to Ni(OH)2.

[0033] Constant current charge-discharge curve as shown Figure 2 As shown, the electrode was charged at a 0.2C rate for 5.5 hours to ensure complete activation, followed by constant current discharge at a 0.2C rate to a cutoff voltage of 0.0V (relative to the Hg / HgO reference electrode). The curve shows a typical discharge plateau between approximately 0.2 and 0.35V (slow voltage change, significant capacity increase), indicating good reversibility and low polarization of the electrode material, providing a stable discharge voltage. The four curves almost overlap, indicating excellent capacity retention and high stability of the electrode during these cycles. The constant current charge-discharge curves yielded a specific capacity as high as 210 mAh / g (discharge capacity divided by the mass of the active material). Figure 2 (as given in the text), will Figure 2 The Coulomb efficiency is obtained by dividing the discharge capacity by the charge capacity × 100%, and the Coulomb efficiency is 98%.

[0034] Example 2

[0035] A method for manufacturing a positive electrode sheet for a nickel-metal hydride battery, comprising the following steps: A 0.05mm thick nickel foam substrate with a PPI of 110 underwent surface pretreatment. First, it was ultrasonically cleaned in a 40g / L citric acid solution (25℃, 25 minutes, 200W) to effectively remove surface oxides and inorganic contaminants. Then, it was ultrasonically cleaned with acetone (35℃, 12 minutes, 200W) to thoroughly remove oil, organic residues, and adsorbed particles, ensuring a clean substrate surface with good wettability and adhesion, providing an ideal interface for subsequent positive electrode slurry coating. The 0.05mm thick nickel foam substrate with a PPI of 110 was then cut to the predetermined length and width of the electrode sheet.

[0036] First, the active material (cobalt-coated nickel hydroxide particles, manufactured by Youke New Energy, type III spherical nickel), conductive agent (cobalt(II) hydroxide), and additive (yttrium oxide) are weighed at a mass ratio of 10:0.1:0.8. A 10% PVDF solution is prepared, with N-methylpyrrolidone as the solvent. The weighed active material, conductive agent, and additive are mixed with the PVDF solution to obtain an electrode slurry (active material:PVDF = 100:10, g / g). Then, the prepared electrode slurry is coated onto a nickel foam substrate (coating amount 100 mg / cm³). 2 Dry at 100℃ for 3 hours, scrape off surface powder, and cut into electrode sheets to obtain nickel battery positive electrode sheets.

[0037] Example 3

[0038] A method for manufacturing a positive electrode sheet for a nickel-metal hydride battery, comprising the following steps: A 0.05mm thick nickel foam substrate with a PPI of 110 underwent surface pretreatment. First, it was ultrasonically cleaned in a 60g / L citric acid solution (35℃, 25 minutes, 120W) to effectively remove surface oxides and inorganic contaminants. Then, it was ultrasonically cleaned with acetone (28℃, 20 minutes, 160W) to thoroughly remove oil, organic residues, and adsorbed particles, ensuring a clean substrate surface with good wettability and adhesion, providing an ideal interface for subsequent positive electrode slurry coating. The 0.05mm thick nickel foam substrate with a PPI of 110 was then cut to the predetermined length and width of the electrode sheet.

[0039] First, the active material (cobalt-coated nickel hydroxide particles, manufactured by Youke New Energy, type III spherical nickel), conductive agent (acetylene black), and additive (yttrium oxide) are weighed at a mass ratio of 9.9:0.3:0.5. A 10% PVDF solution is prepared, with polyvinyl alcohol as the solvent. The weighed active material, conductive agent, and additive are mixed with the PVDF solution to obtain an electrode slurry (active material:PVDF = 100:20, g / g). Then, the prepared electrode slurry is coated onto a nickel foam substrate (coating amount 120 mg / cm³). 2 Dry at 100℃ for 3 hours, scrape off surface powder, and cut into electrode sheets to obtain nickel battery positive electrode sheets.

[0040] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0041] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a nickel battery positive electrode suitable for three-electrode testing, characterized in that, Includes the following steps: 1) Pre-treat the surface of the nickel foam substrate and cut it according to requirements to obtain a conductive substrate; 2) The active material, conductive agent, binder, additives and solvent are mixed to obtain the electrode paste; 3) The electrode slurry is coated onto the conductive substrate, dried, and the surface powder is removed to obtain a nickel battery positive electrode suitable for three-electrode testing; The additive is yttrium oxide, and the adhesive is polyvinylidene fluoride. There is no specific order requirement for steps 1) and 2).

2. The method for preparing a nickel battery positive electrode sheet suitable for three-electrode testing according to claim 1, characterized in that, The surface pretreatment includes sequential ultrasonic cleaning in citric acid solution and acetone; The citric acid solution has a mass concentration of 40~60g / L, and the ultrasonic conditions in the citric acid solution are: temperature 25~35℃, time 15~25min, and power 100~200W. The conditions for sonication in acetone are a temperature of 25-35℃, a time of 10-20 minutes, and a power of 100-200W.

3. The method for preparing a nickel battery positive electrode sheet suitable for three-electrode testing according to claim 2, characterized in that, The mass ratio of the active substance, conductive agent, binder, and additives in step 2) is 100:0.01~5:8~20:1~10; The mass-to-volume ratio of the adhesive to the solvent is 5~15:

100.

4. A method for preparing a nickel battery positive electrode sheet suitable for three-electrode testing according to any one of claims 1 to 3, characterized in that, The active material includes nickel hydroxide particles with cobalt coated on the surface; The conductive agent includes one or more of nickel powder, acetylene black, graphite powder, and Co(OH)2; The solvent includes one or more of N-methylpyrrolidone, polyvinyl alcohol, dipropylene glycol dimethyl ether, and dipropylene glycol methyl ether.

5. The method for preparing a nickel battery positive electrode sheet suitable for three-electrode testing according to claim 4, characterized in that, The conductive agent is Co(OH)2; The mass ratio of the active substance, conductive agent, and additive is 100:2:

5.

6. The method for preparing a nickel battery positive electrode sheet suitable for three-electrode testing according to claim 5, characterized in that, In step 3), the electrode paste is coated on the conductive substrate surface at a rate of 100-120 mg / cm². 2 .

7. The nickel battery positive electrode sheet suitable for three-electrode testing prepared by the preparation method according to any one of claims 1 to 6.

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