Nickel-hydrogen battery gel electrolyte and preparation method thereof

Abstract

The application discloses a kind of nickel-metal hydride battery colloidal electrolyte and preparation method thereof, wherein preparation method includes: the neutralization reaction is carried out by mixing olefinic acid solution and potassium hydroxide solution;After neutralization reaction is completed, it is cooled to room temperature, first, add NN-methylene bisacrylamide solution, then add ammonium persulfate solution, after stirring, seal, rest, obtain water-absorbing resin;The water-absorbing resin is scattered and placed in potassium hydroxide solution and soaked, to obtain nickel-metal hydride battery colloidal electrolyte.The application can avoid electrolyte loss, solve the problem of electrolyte drying, and effectively limit the self-discharge phenomenon caused by impurities in the electrolyte, prolong the service life of the battery.

Description

Technical Field

[0001] This invention belongs to the field of nickel-metal hydride battery technology, specifically relating to a nickel-metal hydride battery gel electrolyte and its preparation method. Background Technology

[0002] Electrolyte, spherical nickel hydroxide for the positive electrode, hydrogen storage alloy for the negative electrode, and polypropylene separator are known as the four core components of nickel-metal hydride batteries. The main function of the electrolyte is to provide a carrier for hydrogen ion transfer, so as to ensure the normal transport of hydrogen ions between the positive and negative electrodes during the charging and discharging process of nickel-metal hydride batteries.

[0003] Nickel-metal hydride battery electrolytes generally consist of three parts: solute, solvent, and a small amount of additives. The solute is a hydroxide such as potassium hydroxide, sodium hydroxide, or lithium hydroxide; the solvent is pure water with a pH of 7 and a conductivity of less than 1 μS / cm; and the additives are water-soluble compounds that improve certain performance characteristics.

[0004] During the charging process of a nickel-metal hydride (NiMH) battery, nickel hydroxide at the positive electrode reacts with hydroxide ions in the electrolyte to produce nickel hydroxide oxide and water. At the negative electrode, the hydrogen storage alloy reacts with hydrogen ions from the water produced at the positive electrode to form metal hydrides, generating hydroxide ions. From the overall reaction perspective, the electrolyte does not participate in the reaction itself, but both hydroxide ions and water in the electrolyte participate in the electrode reactions at both the positive and negative electrodes. However, in actual production and use, it has been observed that gas is produced during the charging process. Testing shows that this gas is mainly composed of hydrogen and oxygen. The main reasons for this gas production are twofold: first, the negative electrode fails to form metal hydrides with hydrogen ions in time, and excess hydrogen ions combine to form hydrogen gas; second, as the battery voltage continuously increases during charging, water in the electrolyte is electrolyzed to produce hydrogen and oxygen. The result of these phenomena is that after a period of use, the electrolyte will gradually dry out, eventually leading to battery damage.

[0005] To address these issues, most research focuses on improving the liquid absorption and retention properties of the diaphragm. While increasing the liquid absorption and retention capacity of the diaphragm can alleviate the rate of electrolyte drying, it cannot fundamentally solve the problem. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a nickel-metal hydride battery gel electrolyte and its preparation method, which can avoid electrolyte loss, solve the problem of electrolyte drying, and effectively limit the self-discharge phenomenon caused by impurities in the electrolyte, thereby extending the battery's service life.

[0007] This invention provides the following technical solution:

[0008] In a first aspect, a method for preparing a nickel-metal hydride battery gel electrolyte is provided, comprising:

[0009] A neutralization reaction is carried out by mixing an alkanoic acid solution and a potassium hydroxide solution.

[0010] After the neutralization reaction is completed and cooled to room temperature, N-N-methylenebisacrylamide solution is added first as a crosslinking agent, and then ammonium persulfate solution is added as an initiator. After stirring, the mixture is sealed and allowed to stand to obtain a water-absorbing resin.

[0011] After the water-absorbing resin is broken up, it is soaked in potassium hydroxide solution to obtain the nickel-hydrogen battery colloidal electrolyte.

[0012] Furthermore, the acrylate solution is either an ethylene glycol solution or an acrylic acid solution. Ethylene glycol and acrylic acid have short molecular chains, making subsequent polymerization reaction conditions easier to control; therefore, the viscosity of the resulting colloidal electrolyte is suitable for battery assembly.

[0013] Furthermore, the olefinic acid solution contains 50% olefinic acid by mass, the potassium hydroxide solution contains 15% potassium hydroxide by mass, the NN-methylenebisacrylamide solution contains 2% to 4% NN-methylenebisacrylamide by mass, and the ammonium persulfate solution contains 2% to 4% ammonium persulfate by mass.

[0014] Furthermore, the mass ratio of olefinic acid, potassium hydroxide, NN-methylenebisacrylamide, and ammonium persulfate in the olefinic acid solution, potassium hydroxide solution, NN-methylenebisacrylamide solution, and ammonium persulfate solution is (24.5–25):(7.075–7.5):1:1. This ratio results in a high proportion of olefinic acid solution, leading to a high final product yield, and the reduced neutralization reaction provides sufficient heat for the cross-linking reaction.

[0015] Furthermore, after adding the ammonium persulfate solution, stir at a speed of 60-80 r / min for 3 seconds to ensure that the mixed solution is fully and uniformly mixed, and then seal with plastic wrap to ensure that no air enters during the cross-linking reaction process.

[0016] Furthermore, the specific method for the settling process is as follows: place the container in a water bath at 60°C for 1 to 2 hours to ensure sufficient time for the cross-linking reaction to proceed fully.

[0017] Furthermore, the water-absorbing resin is broken down into powder using a high-speed pulverizer and then soaked in a 3-8 mol / L potassium hydroxide solution for 24-48 hours.

[0018] In a second aspect, a nickel-metal hydride battery gel electrolyte is provided, which is prepared using the method described in the first aspect.

[0019] Thirdly, a nickel-metal hydride battery is provided, comprising the nickel-metal hydride battery gel electrolyte described in the second aspect.

[0020] Fourthly, a method for preparing a nickel-metal hydride battery is provided, comprising: injecting the nickel-metal hydride battery gel electrolyte described in the second aspect into a nickel-metal hydride battery body, letting it stand for 1 to 2 hours, then evacuating the vacuum to a pressure of -0.08 MPa, letting it stand for 10 minutes, and completing the electrolyte filling.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] (1) In this invention, an olefinic acid solution and a potassium hydroxide solution are mixed and neutralized, then cooled to room temperature. An N-methylenebisacrylamide solution is added first, followed by an ammonium persulfate solution. After stirring, the mixture is sealed and allowed to stand to obtain a water-absorbing resin. This water-absorbing resin contains hydrophilic groups and a cross-linked polymer structure. The polymer chains are close together and entangled to form a network structure. The overall structure is firm and stable. The hydrophilic groups can absorb a large number of water molecules. The water molecules penetrate into the resin through capillary action and become a colloid, forming a "reservoir" in the middle of the battery electrode. This plays a role in preserving and protecting the water in the electrolyte and the water generated during the reaction.

[0023] (2) In this invention, the water-absorbing resin is dispersed and then soaked in potassium hydroxide solution. The water-absorbing resin can absorb tens of times its own weight of potassium hydroxide solution to obtain nickel-metal hydride battery gel electrolyte. After the gel electrolyte is injected into the nickel-metal hydride battery body, the water-absorbing resin in it comes into contact with the positive and negative electrodes of the nickel-metal hydride battery. Due to the presence of hydrophilic groups, there is a liquid electrolyte film between the electrode and the gel electrolyte. Therefore, during charging and discharging, the internal hydroxide ions and hydrogen ions can cross and diffuse through the solid-liquid interface between the electrode and the gel electrolyte, and move by attaching to the polymer chain. Water is not easily electrolyzed inside the resin, thereby avoiding electrolyte loss caused by water electrolysis during charging and discharging, solving the problem of electrolyte drying, and increasing the cycle life of the battery.

[0024] (3) The nickel-metal hydride battery gel electrolyte provided by the present invention utilizes the non-flowability of the gel electrolyte to effectively limit the self-discharge phenomenon caused by impurities in the electrolyte in the free state, and extend the service life of the nickel-metal hydride battery.

[0025] (4) The preparation method of nickel-hydrogen battery gel electrolyte provided by the present invention is simple, easy to implement, and low in cost, and can be applied in actual production. Attached Figure Description

[0026] Figure 1 This is a comparison chart of battery capacity loss after 300 cycles of testing in Examples 1-5 and Comparative Example 1 of the present invention.

[0027] Figure 2 This is a comparison chart of the self-discharge rates of batteries in Examples 1-5 and Comparative Example 1 after being charged and left to stand for 28 days. Detailed Implementation

[0028] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0029] Example 1

[0030] (1) Weigh 500g of ethylene acid and add it to 500g of distilled water to prepare an ethylene acid solution with a mass fraction of 50%; weigh 150g of potassium hydroxide and add it to 850g of distilled water to prepare a potassium hydroxide solution with a mass fraction of 15%; weigh 20g of NN-methylenebisacrylamide and add it to 980g of distilled water to prepare an NN-methylenebisacrylamide solution with a mass fraction of 2%; weigh 20g of ammonium persulfate and add it to 980g of distilled water to prepare an ammonium persulfate solution with a mass fraction of 2%.

[0031] (2) Mix ethylene acid solution and potassium hydroxide solution for neutralization reaction; after the neutralization reaction is completed, cool to room temperature, add NN-methylenebisacrylamide solution first, then add ammonium persulfate solution, stir at 80 r / min for 3 s, then seal with plastic wrap and place in a water bath at 60 ℃ for 1 h to obtain gel-like water-absorbing resin; finally, use a high-speed pulverizer to break the water-absorbing resin into powder state, place it in 6 mol / L potassium hydroxide solution for 24 h to obtain nickel-hydrogen battery gel electrolyte.

[0032] (3) Inject 180g of nickel-metal hydride battery gel electrolyte into a 40Ah square nickel-metal hydride battery body, let it stand for 2 hours, and then transfer it to a vacuum pump to evacuate the vacuum. The vacuum pressure is set to 0.08MPa. When the pressure reaches -0.08MPa, let it stand for 10 minutes, take it out, and complete the electrolyte filling.

[0033] Example 2

[0034] (1) Weigh 500g of ethylene acid and add it to 500g of distilled water to prepare an ethylene acid solution with a mass fraction of 50%; weigh 150g of potassium hydroxide and add it to 850g of distilled water to prepare a potassium hydroxide solution with a mass fraction of 15%; weigh 20g of NN-methylenebisacrylamide and add it to 980g of distilled water to prepare an NN-methylenebisacrylamide solution with a mass fraction of 2%; weigh 20g of ammonium persulfate and add it to 980g of distilled water to prepare an ammonium persulfate solution with a mass fraction of 2%.

[0035] (2) Mix ethylene acid solution and potassium hydroxide solution for neutralization reaction; after the neutralization reaction is completed, cool to room temperature, add NN-methylenebisacrylamide solution first, then add ammonium persulfate solution, stir at 80 r / min for 3 s, then seal with plastic wrap and place in a water bath at 60 ℃ for 2 h to obtain gel-like water-absorbing resin; finally, use a high-speed pulverizer to break the water-absorbing resin into powder state, place it in 6 mol / L potassium hydroxide solution for 36 h to obtain nickel-hydrogen battery gel electrolyte.

[0036] (3) Inject 180g of nickel-metal hydride battery gel electrolyte into a 40Ah square nickel-metal hydride battery body, let it stand for 2 hours, and then transfer it to a vacuum pump to evacuate the vacuum. The vacuum pressure is set to 0.08MPa. When the pressure reaches -0.08MPa, let it stand for 10 minutes, take it out, and complete the electrolyte filling.

[0037] Example 3

[0038] (1) Weigh 500g of ethylene acid and add it to 500g of distilled water to prepare an ethylene acid solution with a mass fraction of 50%; weigh 150g of potassium hydroxide and add it to 850g of distilled water to prepare a potassium hydroxide solution with a mass fraction of 15%; weigh 20g of NN-methylenebisacrylamide and add it to 980g of distilled water to prepare an NN-methylenebisacrylamide solution with a mass fraction of 2%; weigh 20g of ammonium persulfate and add it to 980g of distilled water to prepare an ammonium persulfate solution with a mass fraction of 2%.

[0039] (2) Mix ethylene acid solution and potassium hydroxide solution for neutralization reaction; after the neutralization reaction is completed, cool to room temperature, add NN-methylenebisacrylamide solution first, then add ammonium persulfate solution, stir at 80 r / min for 3 s, then seal with plastic wrap and place in a water bath at 60 ℃ for 2 h to obtain gel-like water-absorbing resin; finally, use a high-speed pulverizer to break the water-absorbing resin into powder state, place it in 6 mol / L potassium hydroxide solution for 48 h to obtain nickel-hydrogen battery gel electrolyte.

[0040] (3) Inject 180g of nickel-metal hydride battery gel electrolyte into a 40Ah square nickel-metal hydride battery body, let it stand for 2 hours, and then transfer it to a vacuum pump to evacuate the vacuum. The vacuum pressure is set to 0.08MPa. When the pressure reaches -0.08MPa, let it stand for 10 minutes, take it out, and complete the electrolyte filling.

[0041] Example 4

[0042] (1) Weigh 490g of ethylene acid and add it to 490g of distilled water to prepare an ethylene acid solution with a mass fraction of 50%; weigh 141.5g of potassium hydroxide and add it to 801.5g of distilled water to prepare a potassium hydroxide solution with a mass fraction of 15%; weigh 20g of NN-methylenebisacrylamide and add it to 666g of distilled water to prepare an NN-methylenebisacrylamide solution with a mass fraction of 3%; weigh 20g of ammonium persulfate and add it to 666g of distilled water to prepare an ammonium persulfate solution with a mass fraction of 3%.

[0043] (2) Mix ethylene acid solution and potassium hydroxide solution for neutralization reaction; after the neutralization reaction is completed, cool to room temperature, add NN-methylenebisacrylamide solution first, then add ammonium persulfate solution, stir at 70 r / min for 3 s, then seal with plastic wrap, place in a water bath at 60 ℃ and let stand for 1.5 h to obtain gel-like water-absorbing resin; finally, use a high-speed pulverizer to break the water-absorbing resin into powder state, place it in 3 mol / L potassium hydroxide solution and soak for 40 h to obtain nickel-hydrogen battery gel electrolyte.

[0044] (3) Inject 180g of nickel-metal hydride battery gel electrolyte into a 40Ah square nickel-metal hydride battery body, let it stand for 1.5h, and then transfer it to a vacuum pump to evacuate the vacuum. The vacuum pressure is set to 0.08MPa. When the pressure reaches -0.08MPa, let it stand for 10min, take it out, and complete the electrolyte filling.

[0045] Example 5

[0046] (1) Weigh 992g of ethylene acid and add it to 992g of distilled water to prepare an ethylene acid solution with a mass fraction of 50%; weigh 292g of potassium hydroxide and add it to 1655g of distilled water to prepare a potassium hydroxide solution with a mass fraction of 15%; weigh 40g of NN-methylenebisacrylamide and add it to 960g of distilled water to prepare an NN-methylenebisacrylamide solution with a mass fraction of 4%; weigh 40g of ammonium persulfate and add it to 960g of distilled water to prepare an ammonium persulfate solution with a mass fraction of 4%.

[0047] (2) Mix ethylene acid solution and potassium hydroxide solution for neutralization reaction; after the neutralization reaction is completed, cool to room temperature, add NN-methylenebisacrylamide solution first, then add ammonium persulfate solution, stir at 70 r / min for 3 s, then seal with plastic wrap, place in a water bath at 60 ℃ and let stand for 1.5 h to obtain gel-like water-absorbing resin; finally, use a high-speed pulverizer to break the water-absorbing resin into powder state, place it in 8 mol / L potassium hydroxide solution and soak for 40 h to obtain nickel-hydrogen battery gel electrolyte.

[0048] (3) Inject 180g of nickel-metal hydride battery gel electrolyte into a 40Ah square nickel-metal hydride battery body, let it stand for 1h, and then transfer it to a vacuum pump to evacuate the vacuum. The vacuum pressure is set to 0.08MPa. When the pressure reaches -0.08MPa, let it stand for 10min, take it out, and complete the electrolyte filling.

[0049] Comparative Example 1

[0050] (1) Weigh 342g of potassium hydroxide; weigh 22g of industrial grade sodium hydroxide with a purity of 90%; then add pure water to a volume of 1L to prepare a mixture of 5.5mol / L potassium hydroxide aqueous solution and 0.5mol / L sodium hydroxide aqueous solution. In addition, add 10g of industrial grade lithium hydroxide with a concentration of 99% to each liter of the above mixture to obtain the electrolyte.

[0051] (2) Inject 180g of electrolyte into a 40Ah square nickel-metal hydride battery, transfer it to a vacuum pump for vacuuming, set the vacuum pressure to 0.08MPa, and let it stand for 10 minutes after the pressure reaches -0.08MPa before taking it out.

[0052] Performance Comparison

[0053] 1. The batteries in Examples 1 to 5 and Comparative Example 1 were formed. After the formation was completed, they were weighed and then a charge-discharge cycle life test at 1C current was carried out. The weight of the batteries after 100, 200 and 300 cycles was weighed to examine the electrolyte loss. The test results are shown in Table 1 below.

[0054] Table 1

[0055]

[0056] As can be seen from Table 1, after 300 charge-discharge cycle tests, the electrolyte loss in the nickel-metal hydride battery using the colloidal electrolyte of the present invention is much lower than that using conventional electrolyte. This indicates that the nickel-metal hydride battery using the colloidal electrolyte of the present invention can effectively reduce electrolyte loss during charge and discharge, thereby reducing battery maintenance costs and extending battery life.

[0057] 2. The batteries in Examples 1-5 and Comparative Example 1 were subjected to 300 cycle tests to examine the battery capacity loss. The test results are as follows: Figure 1 .

[0058] from Figure 1It can be seen that, after 300 charge-discharge cycle tests, the nickel-metal hydride battery using the colloidal electrolyte described in this invention exhibits lower capacity loss than conventional electrolyte batteries. This indicates that the nickel-metal hydride battery using the colloidal electrolyte described in this invention can effectively reduce capacity loss caused by micro-short circuits during charge and discharge, thereby extending the battery's lifespan.

[0059] 3. Self-discharge tests were conducted on the batteries in Examples 1-5 and Comparative Example 1. The batteries were charged at 1C for 1 hour, then charged at 0.1C for 1 hour, and then left open-circuit at 25°C for 28 days. After the period, they were discharged to 1V at 1C. The self-discharge rate was calculated to examine the self-discharge behavior. The test results are as follows: Figure 2 .

[0060] from Figure 2 It can be seen that the self-discharge rate of nickel-metal hydride batteries using the colloidal electrolyte of the present invention is lower than that of conventional electrolyte batteries, indicating that nickel-metal hydride batteries using the colloidal electrolyte of the present invention can effectively reduce battery self-discharge.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a nickel-metal hydride battery gel electrolyte, characterized in that, include: A neutralization reaction is carried out by mixing an alkanoic acid solution and a potassium hydroxide solution. After the neutralization reaction is completed and cooled to room temperature, N-N-methylenebisacrylamide solution is added first, followed by ammonium persulfate solution. After stirring, the mixture is sealed and allowed to stand to obtain the water-absorbing resin. After the water-absorbing resin is broken up, it is soaked in a 3-8 mol / L potassium hydroxide solution for 24-48 hours to obtain a nickel-hydrogen battery gel electrolyte. The olefin solution contains 50% olefin by mass, the potassium hydroxide solution contains 15% potassium hydroxide by mass, the NN-methylenebisacrylamide solution contains 2%~4% NN-methylenebisacrylamide by mass, and the ammonium persulfate solution contains 2%~4% ammonium persulfate by mass. The mass ratio of olefinic acid, potassium hydroxide, NN-methylenebisacrylamide, and ammonium persulfate in the olefinic acid solution, potassium hydroxide solution, NN-methylenebisacrylamide solution, and ammonium persulfate solution is (24.5~25):(7.075~7.5):1:

1.

2. The method for preparing the nickel-metal hydride battery gel electrolyte according to claim 1, characterized in that, The acrylate solution is either an ethylene acrylate solution or an acrylic acid solution.

3. The method for preparing the nickel-metal hydride battery gel electrolyte according to claim 1, characterized in that, After adding the ammonium persulfate solution, stir at a speed of 60-80 r / min for 3 seconds, and then seal with plastic wrap.

4. The method for preparing the nickel-metal hydride battery gel electrolyte according to claim 1, characterized in that, The specific method for allowing the mixture to stand is as follows: place it in a water bath at 60°C for 1-2 hours.

5. A nickel-metal hydride battery gel electrolyte, characterized in that, It is prepared by the method described in any one of claims 1 to 4.

6. A nickel-metal hydride battery, characterized in that, Includes the nickel-metal hydride battery gel electrolyte as described in claim 5.

7. A method for preparing a nickel-metal hydride battery, characterized in that, include: The nickel-metal hydride battery gel electrolyte of claim 5 is injected into the nickel-metal hydride battery body and left to stand for 1-2 hours. Then, a vacuum is drawn until the pressure reaches -0.08 MPa and left to stand for 10 minutes to complete the electrolyte filling.

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