A method for preparing a nickel-iron battery and a nickel-iron battery

Abstract

The present invention provides a preparation method for a nickel-iron battery, which specifically includes the following steps: S1, designing a three-dimensional structure, stirring a 3D printing slurry evenly, and then sequentially performing digital light processing printing, degreasing sintering, and high-temperature reduction to obtain a 3D porous nickel template; S2, depositing graphene on the surface of the 3D porous nickel template obtained in step S1, and obtaining nitrogen-doped graphene foam after acid etching and freeze-drying; S3, preparing a positive electrode; S4, preparing a negative electrode; S5, preparing a nickel-iron battery: the positive electrode of the nickel-iron battery obtained in step S3 and the negative electrode of the nickel-iron battery obtained in step S4 are respectively placed in a gel electrolyte for immersion, then taken out, and laminated to each other to obtain a nickel-iron battery. The present invention also provides a nickel-iron battery prepared by the above preparation method. Compared with the prior art, the present invention utilizes the technical advantages of 3D printing and the microscopic porous structure to give the electrode structure flexibility while also giving the nickel-iron battery good flexibility, thereby meeting more application scenarios and actual needs.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method for preparing a nickel-iron battery and the nickel-iron battery. Background Art

[0002] With the rapid development of wearable electronics, there is a strong market demand for energy storage devices with advantages such as high energy density, high power density, long cycle life, and mechanical flexibility. Lithium batteries have been widely studied due to their high energy density, but their poor safety and proneness to organic electrolyte leakage have also limited their wider application.

[0003] Aqueous batteries, as their electrolyte is water, have solved the safety problem very well. Among them, nickel-iron batteries, as a typical aqueous battery, have attracted widespread attention due to their relatively high theoretical specific capacity, high safety, abundant raw materials and environmental protection. In order to obtain nickel-iron batteries with high energy density and high power, researchers have mainly made two attempts. One is to prepare high-specific-capacity electrode materials through sophisticated nanomaterial design to achieve high specific capacity and good rate performance, but there is a disadvantage of low active material loading (1 mg cm -2 ), which results in the mass of the current collector, electrolyte and diaphragm dominating, and the device performance decreases by an order of magnitude. The second is to increase the thickness of the electrode, that is, to increase the active material loading, which leads to an increase in the ion-electron transmission distance of the traditional two-dimensional electrode, an increase in internal resistance, and then a decrease in power density and rate performance. How to achieve high active material utilization under high load through reasonable structural design and preparation methods is one of the important issues in the current preparation of high energy density and high power nickel-iron batteries. At the same time, the iron negative electrode usually has poor conductivity and poor structural stability during charging and discharging, resulting in poor cycle stability of the nickel-iron battery, which is also a key factor affecting the service life and number of uses of the nickel-iron battery. Moreover, due to the sturdy shell of the traditional button battery, or the electrode material is coated on the current collector such as nickel foam, it cannot meet the needs of flexible electric wearable electronics. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a nickel-iron battery, which has a simple and environmentally friendly preparation process. The nickel-iron battery prepared has the advantages of high active material loading of the process electrode, good flexibility, high energy density, high power density and good cycle performance. The battery structure is highly customized and has broad application prospects.

[0005] To solve the above problems, the present invention provides a method for preparing a nickel-iron battery, which specifically comprises the following steps:

[0006] S1. Design a three-dimensional structure, stir the 3D printing slurry evenly, and then perform digital light processing printing, degreasing sintering, and high-temperature reduction to obtain a 3D porous nickel template;

[0007] S2, depositing graphene on the surface of the 3D porous nickel template obtained in step S1, and obtaining nitrogen-doped graphene foam after acid etching and freeze drying;

[0008] S3, positive electrode preparation: electroplating nickel cobalt hydroxide on the surface of the nitrogen-doped graphene foam obtained in step S2 to obtain a positive electrode for a nickel-iron battery;

[0009] S4, preparing the negative electrode: pyrolyzing the positive electrode of the nickel-iron battery obtained in step S3 and depositing iron oxide on the surface to obtain the negative electrode of the nickel-iron battery;

[0010] S5. Preparation of nickel-iron battery: The positive electrode of the nickel-iron battery obtained in step S3 and the negative electrode of the nickel-iron battery obtained in step S4 are respectively immersed in gel electrolyte, taken out, and laminated to each other to obtain a nickel-iron battery.

[0011] Preferably, in step S1, the 3D printing slurry comprises nickel nitrate, Variquat CC42NS, hexanediol diacrylate and diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide.

[0012] Preferably, in step S1, the conditions for degreasing and sintering are as follows: the sintering atmosphere is air, the sintering temperature is 600-1200°C, the heating rate is 0.5-5°C / min, and the sintering time is 30-72h; the conditions for high-temperature reduction are as follows: the reaction temperature is 400-800°C, the heating rate is 2-20°C / min, the reaction time is 5-10h, the reducing gas is 10% argon hydrogen, and the reducing gas flow rate is 50-500sccm.

[0013] Preferably, in step S2, the deposition method adopts chemical vapor deposition, and the chemical vapor deposition method specifically includes the following steps: at a heating rate of 10-40°C / min, the 3D porous nickel template is heated to 600-1000°C and kept warm for 1 hour, and then carbon and nitrogen sources N,N-dimethylformamide are bubbled into the template, followed by reaction for 10-210 minutes, and finally rapid cooling.

[0014] Preferably, in step S3, the conditions for electroplating nickel cobalt hydroxide on the surface of nitrogen-doped graphene foam are as follows: the electrolyte solution is an aqueous solution containing 0.05M nickel nitrate and 0.05M cobalt nitrate, a saturated calomel electrode is used as the reference electrode, a platinum sheet is used as the counter electrode, the voltage window is -1.2V-0V, the scan rate is 100mV / s, and the number of cycles is 100 times.

[0015] Preferably, in step S4, the specific steps of pyrolyzing the positive electrode of the nickel-iron battery are as follows: the positive electrode of the nickel-iron battery obtained in step S3 and dicyandiamide are placed in front and behind, and the temperature is raised to 800-1000°C for reaction for 3 hours at a heating rate of 10°C / min, a nitrogen atmosphere, and an air flow of 100sccm.

[0016] Preferably, in step S4, the conditions for depositing iron oxide on the surface of the positive electrode of the pyrolyzed nickel-iron battery are as follows: the deposition liquid is an aqueous solution containing 0.2M sodium acetate, 0.1M sodium sulfate and 0.1M ammonium ferrous sulfate, the current density is 0.2mA, and the deposition time is 5-20h.

[0017] Preferably, in step S4, after iron oxide is deposited on the surface of the positive electrode of the pyrolyzed nickel-iron battery, a thermal annealing process is further performed, and the conditions of the thermal annealing process are as follows: temperature is 400° C., and time is 2 hours.

[0018] Preferably, in step S5, the preparation method of the gel electrolyte is as follows: PVA is added to deionized water, vigorously stirred in a 90° C. water bath, and then potassium hydroxide solution is slowly added and stirred until the solution becomes transparent.

[0019] Another object of the present invention is to provide a nickel-iron battery prepared by the above-mentioned preparation method.

[0020] Compared with the existing technology, the present invention has the following advantages: 1. Utilizing the technical advantages of 3D printing and the microscopic porous structure, the electrode structure is given flexibility while also giving the nickel-iron battery good flexibility, meeting more application scenarios and practical needs;

[0021] 2. The hierarchical porous structure gives it a large specific surface area, which can load more active materials and thus improve the energy density of the device. At the same time, the good conductivity of the current collector graphene foam and carbon nanotubes ensures that the active materials have a high power density;

[0022] 3. The microporous structure ensures full penetration of the electrolyte, shortens the ion transmission distance, reduces resistance, and improves battery performance;

[0023] 4. Due to the ultra-low density of hollow graphene foam, the prepared battery is lightweight and has a high proportion of active materials, which is conducive to practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is one of the electron microscope scanning images of the positive electrode of the nickel-iron battery prepared in Example 1;

[0025] Figure 2 This is the second electron microscope scanning image of the positive electrode of the nickel-iron battery prepared in Example 1;

[0026] Figure 3 This is a scanning electron microscope image of the positive electrode of the nickel-iron battery prepared in Example 2 after pyrolysis;

[0027] Figure 4 This is a scanning electron microscope image of the negative electrode of the nickel-iron battery prepared in Example 1;

[0028] Figure 5 This is a scanning electron microscope image of the negative electrode of the nickel-iron battery prepared in Example 4. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0030] Example 1

[0031] A nickel-iron battery is prepared by the following method:

[0032] S1. Prepare 3D printing slurry: 40g nickel nitrate, 6mL dispersant Variquat CC42NS, 30mL monomer hexanediol diacrylate, 0.5g photoinitiator diphenyl-(2,4,6-trimethylbenzoyl) phosphine, ball mill for 24h to obtain a uniform 3D printing slurry, design the three-dimensional structure of the 3D porous nickel template, in this embodiment, the length, width and height of the 3D porous nickel template are 20*15*5mm, and the 3D printing slurry is stirred evenly and then subjected to digital light processing printing, degreasing sintering and high-temperature reduction in sequence to obtain a 3D porous nickel template, wherein the degreasing and sintering conditions are as follows: the sintering atmosphere is air, the sintering temperature is 1000℃, the heating rate is 2℃ / min, and the sintering time is 24h; the high-temperature reduction conditions are as follows: the reaction temperature is 800℃, the heating rate is 15℃ / min, the reaction time is 10h, the reducing gas is 10% argon hydrogen, and the reducing gas flow rate is 100sccm;

[0033] S2. Graphene is deposited on the surface of the 3D porous nickel template obtained in step S1 by chemical vapor deposition, and nitrogen-doped graphene foam is obtained after acid etching and freeze-drying. The chemical vapor deposition conditions are as follows: the 3D porous nickel template is heated to 800° C. at a heating rate of 20° C. / min, and then N,N-dimethylformamide, a carbon and nitrogen source, is bubbled into the template, followed by reaction for 30 minutes, and finally rapid cooling.

[0034] S3. Positive electrode preparation: Nickel cobalt hydroxide was electroplated on the surface of the nitrogen-doped graphene foam obtained in step S2 to obtain a positive electrode for a nickel-iron battery. The electroplating conditions were as follows: the electrolyte solution was an aqueous solution containing 0.05 M nickel nitrate and 0.05 M cobalt nitrate, a saturated calomel electrode was used as the reference electrode, a platinum sheet was used as the counter electrode, the voltage window was -1.2 V to 0 V, the scan rate was 100 mV / s, and the number of cycles was 100;

[0035] S4, negative electrode preparation: the positive electrode of the nickel-iron battery obtained in step S3 and dicyandiamide are placed in front and behind, and the temperature is raised to 1000°C for reaction for 3 hours at a heating rate of 10°C / min, a nitrogen atmosphere, and an air flow of 100 sccm, and then iron oxide is deposited on the surface. The conditions for depositing iron oxide are as follows: the deposition liquid is an aqueous solution containing 0.2M sodium acetate, 0.1M sodium sulfate and 0.1M ammonium ferrous sulfate, the current density is 0.2 mA, the deposition time is 10 hours, and then thermal annealing is performed at 400°C for 2 hours to obtain the negative electrode of the nickel-iron battery;

[0036] S5. Preparation of nickel-iron battery: Add 4 g of PVA to 20 ml of deionized water, stir vigorously in a 90° C. water bath, slowly add 20 mL of potassium hydroxide solution, and continue stirring until the solution becomes transparent to obtain a gel electrolyte. The positive electrode of the nickel-iron battery obtained in step S3 and the negative electrode of the nickel-iron battery obtained in step S4 are respectively placed in the gel electrolyte for immersion, taken out, and laminated to each other to obtain a nickel-iron battery.

[0037] Example 2

[0038] The only difference from Example 1 is that the length, width and height of the 3D porous nickel template in this embodiment are 20*15*10 mm, and the rest are the same as Example 1 and will not be repeated here.

[0039] Example 3

[0040] The only difference from Example 1 is that the length, width and height of the 3D porous nickel template in this embodiment are 20*15*2.5 mm, and the rest are the same as in Example 1 and will not be repeated here. In the negative electrode of the nickel-iron battery obtained in Example 3, nano-sheet iron oxide grows evenly around the carbon nanotubes, greatly increasing the active material loading. At the same time, due to the high electrical conductivity of the nanotubes and graphene, the effective transmission of electrons is guaranteed, thereby improving the battery energy density while ensuring high power density.

[0041] Example 4

[0042] The only difference from Example 1 is that in step S4 of this embodiment, the deposition time is 5 hours. The rest is the same as Example 1 and will not be repeated here.

[0043] The inventors tested the intermediate products of Examples 1 to 4. Figure 1 and Figure 2 The following are electron microscope scans of the positive electrode of the nickel-iron battery prepared in Example 1. Figure 1 and Figure 2 It can be seen that the positive electrode material of the nickel-iron battery prepared by the preparation method of the present invention is a sheet material, and is evenly and densely distributed on the outside of the graphene. The porous microstructure of the graphene can also be clearly seen, which is conducive to the full penetration of the gel electrolyte and reduces the interface resistance.

[0044] Figure 3 The electron microscope scanning image of the positive electrode of the nickel-iron battery after pyrolysis in Example 2 is shown. Figure 3 Evenly distributed elongated carbon nanotube arrays can be seen in the figure, which increases the specific surface area and is conducive to the growth of more iron oxide.

[0045] Figure 4 and Figure 5 These are the electron microscope scanning images of the negative electrode of the nickel-iron battery obtained by deposition for 10 hours and 5 hours in Example 1 and Example 5, respectively. It can be seen that as the electroplating time becomes shorter, the number and thickness of the nanosheets will decrease, and the active material loading of the electrode can also be controlled by the electroplating time, thereby achieving good control of the electrode performance.

[0046] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing a nickel-iron battery, characterized in that: The preparation method specifically comprises the following steps: S1. Design a three-dimensional structure, stir the 3D printing slurry evenly, and then perform digital light processing printing, degreasing sintering, and high-temperature reduction to obtain a 3D porous nickel template; S2, depositing graphene on the surface of the 3D porous nickel template obtained in step S1, and obtaining nitrogen-doped graphene foam after acid etching and freeze drying; S3, positive electrode preparation: electroplating nickel cobalt hydroxide on the surface of the nitrogen-doped graphene foam obtained in step S2 to obtain a positive electrode for a nickel-iron battery; S4, preparing the negative electrode: pyrolyzing the positive electrode of the nickel-iron battery obtained in step S3 and depositing iron oxide on the surface to obtain the negative electrode of the nickel-iron battery; S5, preparing a nickel-iron battery: soaking the positive electrode of the nickel-iron battery obtained in step S3 and the negative electrode of the nickel-iron battery obtained in step S4 in a gel electrolyte, taking them out, and laminating them to each other to obtain a nickel-iron battery; In step S2, the deposition method adopts chemical vapor deposition, and the chemical vapor deposition method specifically includes the following steps: heating the 3D porous nickel template to 600-1000°C at a heating rate of 10-40°C / min, then bubbling carbon and nitrogen sources N,N-dimethylformamide, then reacting for 10-210 minutes, and finally rapidly cooling; In step S4, the specific steps of pyrolyzing the positive electrode of the nickel-iron battery are as follows: the positive electrode of the nickel-iron battery obtained in step S3 and dicyandiamide are placed in front of each other in a nitrogen atmosphere, and then heated to 800-1000° C. for reaction.

2. The method for preparing a nickel-iron battery according to claim 1, wherein In step S1, the 3D printing slurry includes nickel nitrate, Variquat CC42NS, hexanediol diacrylate and diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide.

3. The method for preparing a nickel-iron battery according to claim 1, wherein In step S1, the conditions for degreasing and sintering are as follows: the sintering atmosphere is air, the sintering temperature is 600-1200°C, the heating rate is 0.5-5°C / min, and the sintering time is 30-72h; the conditions for high-temperature reduction are as follows: the reaction temperature is 400-800°C, the heating rate is 2-20°C / min, the reaction time is 5-10h, the reducing gas is 10% argon hydrogen, and the reducing gas flow rate is 50-500sccm.

4. The method for preparing a nickel-iron battery according to claim 1, wherein In step S3, the conditions for electroplating nickel cobalt hydroxide on the surface of nitrogen-doped graphene foam are as follows: the electrolyte solution is an aqueous solution containing 0.05M nickel nitrate and 0.05M cobalt nitrate, a saturated calomel electrode is used as the reference electrode, a platinum sheet is used as the counter electrode, the voltage window is -1.2V-0V, the scan rate is 100mV / s, and the number of cycles is 100 times.

5. The method for preparing a nickel-iron battery according to claim 1, wherein: In step S4, the conditions for depositing iron oxide on the positive electrode surface of the pyrolyzed nickel-iron battery are as follows: the deposition liquid is an aqueous solution containing 0.2M sodium acetate, 0.1M sodium sulfate and 0.1M ammonium ferrous sulfate, the current density is 0.2mA, and the deposition time is 5-20h.

6. The method for preparing a nickel-iron battery according to claim 5, wherein: In the step S4, after iron oxide is deposited on the surface of the positive electrode of the pyrolyzed nickel-iron battery, a thermal annealing process is performed. The conditions of the thermal annealing process are as follows: temperature is 400° C. and time is 2 hours.

7. The method for preparing a nickel-iron battery according to claim 1, wherein: In step S5, the preparation method of the gel electrolyte is as follows: PVA is added to deionized water, vigorously stirred in a 90° C. water bath, and then potassium hydroxide solution is slowly added and stirred until the solution becomes transparent.

8. A nickel-iron battery, characterized in that: Prepared by any one of the preparation methods of claims 1-7.

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