Closed system electrolyte repairing process based on membrane distillation technology

Abstract

The invention discloses a closed system electrolyte repairing process based on a membrane distillation technology. The closed system electrolyte repairing process comprises the following steps: step 1, preparing a composite membrane; step 2, preparing a deionized water sump; step 3, spraying a PVA (Polyvinyl Alcohol) strengthening layer on the outer wall of the deionized water sump; the deionized water sump is made of a composite membrane containing a super-hydrophobic layer, the super-hydrophobic layer is characterized in that the membrane distillation technology is used for isolating water from electrolyte, the vapor pressure difference on the two sides of the microporous hydrophobic membrane is used as pushing force, water, namely, the material hot side, in the membrane makes direct contact with the membrane, and the membrane is not damaged. Water in the membrane is evaporated into water vapor on the membrane surface and then enters the cold side through membrane holes to be condensed, other solute molecules cannot pass through the membrane, and therefore controllable transfer of deionized water is achieved.

Description

Technical Field

[0001] This invention relates to the field of battery electrolyte repair technology, specifically to a closed-system electrolyte repair process based on membrane distillation technology. Background Technology

[0002] Aqueous batteries include nickel-zinc, nickel-metal hydride, and lead-acid battery systems. Currently, the main causes of cell failure in aqueous batteries are hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) within the system, as well as internal micro-short circuits caused by dendrite formation. On the one hand, when the backup battery system is in operation, taking the aqueous nickel-zinc battery system as an example, the internal backup voltage is 1.6V-1.86V. At this time, a continuous and slow hydrogen evolution / oxygen evolution reaction occurs inside the battery, affecting the instantaneous battery activity. Activity can be restored through cycling, but the continuous hydrogen evolution / oxygen evolution reaction causes the electrolyte to be continuously consumed, thereby reducing the battery life. On the other hand, within the battery pack, due to the influence of cell consistency, there is a certain voltage difference between cells in the pack. When the system is in backup mode, some cells in the pack may exceed the full charge voltage. At this time, the cells with relatively higher voltage positions are in a long-term overcharged state relative to other cells, which further increases the rate of battery life reduction.

[0003] Current technology can effectively reduce dendrite formation by modifying the nucleation sites on the electrode surface. However, the hydrogen evolution reaction during high-rate discharge causes the alkalinity inside the battery (electrolyte concentration) to continuously increase, and the electrolyte volume to continuously decrease. The drying of the electrolyte will cause unstable temperature rise and voltage instability, thereby affecting the battery's lifespan. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems in the prior art and provide a closed-system electrolyte repair process based on membrane distillation technology. By setting up a membrane distillation water replenishment device with a chamber-like modification inside the battery cell, pure water is slowly released for replenishment. It has the characteristics of high dendrite prevention, can increase the electrolyte volume, slow down the electrolyte consumption, and will not damage the internal environment of the battery.

[0005] The specific technical solution is as follows: A closed-system electrolyte remediation process based on membrane distillation technology includes the following steps: Step 1: Preparation of composite membrane First, the PVDF base film was subjected to Fenton pretreatment. A mixed solution of ferrous sulfate heptahydrate, hydrogen peroxide, ethanol, and water was prepared. The PVDF base film was fully immersed in the mixed solution and heated to 30-50℃ for Fenton reaction for 1 hour. After the reaction, the PVDF base film was washed with 2% dilute hydrochloric acid and then vacuum dried to obtain the pretreated PVDF base film. Next, a superhydrophobic coating was prepared. SiO2 nanoparticles were dissolved in cyclohexane, magnetically stirred, and ultrasonically dispersed to obtain cyclohexane-SiO2. Then, 1H,1H,2H,2H-perfluorooctyltrichlorosilane was added dropwise to the cyclohexane-SiO2 solution, and ultrasonic dispersion was continued to obtain a PFTS / SiO2 solution. Finally, the pretreated PVDF base film was immersed in the PFTS / SiO2 solution and sealed for 12 hours. After removal, it was vacuum dried to obtain a composite film containing a superhydrophobic layer. Step 2: Preparation of deionized water tank First, cut the composite film obtained in step one into square pieces using a utility knife. Overlap the short edges and bend them into a cylindrical shape to form the main body of the deionized water tank. Next, prepare the adhesive: mix epoxy resin and co-solvent acetone in a beaker at a mass ratio of 100:5, stir with a stirring rod until the epoxy resin is diluted, place the bottom of the beaker in a 25°C water bath to cool, add curing agent ethylenediamine, and mix epoxy resin and curing agent ethylenediamine at a mass ratio of 100:1.5. Stir in a fume hood until the mixture is uniform and has stirring shear force. Use the prepared adhesive to seal the sides and bottom of the deionized water tank body, and let it cure for 6 hours. Then, inject deionized water into the deionized water tank body using a syringe, and then seal the top edge of the deionized water tank body with epoxy resin, and let it cure for 6 hours. A closed deionized water tank made of a composite film containing a superhydrophobic layer is obtained. Step 3: Spray a PVA reinforcement layer onto the outer wall of the deionized water tank. First, polyvinyl alcohol and deionized water are mixed and dissolved using a heated magnetic stirrer to obtain a mixed solution. The mixed solution is then mixed with anhydrous ethanol to obtain a PVA mixed solution. Next, the PVA mixed solution is evenly sprayed onto the outer wall surface of the deionized water tank using a spray gun at a spray pressure of 0.5±0.1 MPa. The spraying ensures that the outer wall surface of the deionized water tank is completely covered. After spraying, no solution drips from the outer wall surface of the deionized water tank. The tank is then suspended in a vacuum oven at 45°C for 4 hours to cure, resulting in a deionized water tank with a PVA reinforced layer. Step 4: Assembly of the deionized water tank and transfer of deionized water During the assembly stage of the aqueous battery, the deionized water tank is placed perpendicular to the electrode or plate, near the outer casing. Then, the battery is filled with electrolyte and assembled. When the electrolyte volume decreases, the battery storage environment temperature is controlled to 10-20℃ until the internal and external temperatures of the cell are equal. At this point, the internal environment of the battery is lowered, thus completing the membrane distillation cold-side temperature control. The battery is then transferred to an environment of 65-80℃, allowing the external environment to rapidly heat the deionized water tank near the casing, quickly establishing membrane distillation hot-side temperature control. This is maintained for 2-3 minutes. Due to the temperature difference, driven by the vapor pressure difference across the deionized water tank (made of a composite membrane containing a superhydrophobic layer), water in the deionized water tank evaporates into water vapor at the membrane surface and enters the cold side through the membrane pores, where it is condensed and transferred into the battery interior. This achieves controllable water transfer and completes electrolyte repair.

[0006] Furthermore, in step one, the mass ratio of ferrous sulfate heptahydrate, hydrogen peroxide, ethanol, and water is 3:12:100:100.

[0007] Furthermore, in step one, the mass ratio of SiO2 nanoparticles to cyclohexane is 1:50, and the mass ratio of cyclohexane-SiO2 solution to 1H,1H,2H,2H-perfluorooctyltrichlorosilane is 25:1.

[0008] Furthermore, in step two, the size of the square piece is 7*5cm.

[0009] Furthermore, in step three, the mass ratio of polyvinyl alcohol to deionized water is 1:9, and the mass ratio of the mixture to anhydrous ethanol is 5:1.

[0010] Furthermore, in step two, the amount of deionized water injected into the deionized water tank is adjusted according to the battery capacity, ranging from 50 to 100 mg / Ah.

[0011] Furthermore, in step one, the magnetic stirring is performed at 90-120 r / min for 30 min, and the ultrasonic dispersion power is 200-350 W.

[0012] Furthermore, the vacuum drying temperature in step one is 25-35℃.

[0013] The technical solution provided by this invention has the following beneficial effects: (1) The deionized water tank of the present invention is made of a composite membrane containing a superhydrophobic layer. The superhydrophobic layer is characterized by the use of membrane distillation technology to isolate water and electrolyte. The vapor pressure difference on both sides of the microporous hydrophobic membrane is used as the driving force. The water inside the membrane, i.e. the hot side of the material, is in direct contact with the membrane. The water inside the membrane evaporates into water vapor at the membrane surface and enters the cold side through the membrane pores and is condensed. Other solute molecules cannot pass through the membrane, thereby realizing the controllable transfer of deionized water. (2) The outer surface of the deionized water tank of the present invention is coated with a PVA reinforcement layer, which has the function of strengthening the outer surface to resist dendrites and alkaline crystallization, and the membrane distillation operation is not limited by the osmotic pressure of the solution.

[0014] (3) The present invention assembles a deionized water tank inside the battery cell to ensure that the system impurities caused by direct water addition are avoided, which will reduce the impact on battery performance caused by a sudden drop in solution concentration. It can introduce water replenishment capability without damaging the battery sealing and system safety. Compared with traditional battery water replenishment technology, it consumes less labor time and is convenient and simple. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the aqueous battery structure equipped with a deionized water tank according to an embodiment of the present invention; Figure 2 The figures show the test results of embodiments and comparative examples of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0017] This invention implements a 100Ah water-based zinc-based square-shell battery cell of model XNF50130230. The outer wall of the battery cell is made of ABS material, and there is a one-way valve for venting at the top. The battery cell is 130mm wide, and the width of the internal electrode plate is 90mm.

[0018] Example 1: A closed-system electrolyte remediation process based on membrane distillation technology includes the following steps: Step 1: Preparation of composite membrane First, the PVDF substrate membrane was pretreated with Fenton's solution. A mixed solution was prepared by mixing 6g of ferrous sulfate heptahydrate, 24g of hydrogen peroxide, 200g of ethanol, and 200g of water. The PVDF substrate membrane was then fully immersed in the mixed solution and heated to 30℃ for a Fenton reaction for 1 hour. After the reaction, the PVDF substrate membrane was washed with 2% dilute hydrochloric acid and then vacuum dried at 25℃ to obtain the pretreated PVDF substrate membrane. Next, a superhydrophobic coating was prepared by dissolving 2g of SiO2 nanoparticles in 50g of cyclohexane, stirring magnetically at 90r / min for 30min, and then ultrasonically dispersed until completely dispersed at a power of 200W to obtain a cyclohexane-SiO2 solution. Then, 2.08g of [unspecified substance] was added dropwise to the cyclohexane-SiO2 solution. 1H,1H,2H,2H-perfluorooctyltrichlorosilane was further ultrasonically dispersed to obtain a PFTS / SiO2 solution. Finally, the pretreated PVDF substrate was immersed in the PFTS / SiO2 solution and sealed for 12 hours. After being removed, it was vacuum dried at a temperature of 25°C to obtain a composite membrane containing a superhydrophobic layer. Step 2: Preparation of deionized water tank First, use a utility knife to cut the composite film obtained in step one into 7*5cm square pieces. Overlap the short edges and bend them into a cylindrical shape to form the main body of the deionized water tank. Next, prepare the adhesive: mix 200g of epoxy resin and 10g of acetone, the co-solvent, in a beaker and stir with a stirring rod until the epoxy resin is diluted. Place the bottom of the beaker in a 25°C water bath to cool it down. Add 3g of ethylenediamine, the curing agent, and stir in a fume hood until the mixture is uniform and has stirring shear force. Use the prepared adhesive to seal the sides and bottom of the deionized water tank body and let it cure for 6 hours. Then, use a syringe to inject 10mL of deionized water into the deionized water tank body. Finally, use epoxy resin to seal the top edge of the deionized water tank body and let it cure for 6 hours. A sealed deionized water tank made of a composite film containing a superhydrophobic layer is obtained. Step 3: Spray a PVA reinforcement layer onto the outer wall of the deionized water tank. First, mix 10g of polyvinyl alcohol and 90g of deionized water and stir with a heating magnetic stirrer to dissolve them, obtaining a mixed solution. Mix the mixed solution with 20g of anhydrous ethanol to obtain a PVA mixed solution. Then, use a spray gun to evenly spray the PVA mixed solution onto the outer wall surface of the deionized water tank at a spraying pressure of 0.4Mpa. Spray until the outer wall surface of the deionized water tank is completely covered. After spraying, no solution drips from the outer wall surface of the deionized water tank. Hang it in a vacuum oven at 45℃ for 4 hours to cure, and you will get a deionized water tank with a PVA reinforced layer. Step 4: Assembly of the deionized water tank and transfer of deionized water like Figure 1As shown, during the assembly stage of the aqueous battery, the deionized water tank is placed perpendicular to the electrode or plate, near the outer casing. Then, the battery is injected with electrolyte and assembled. When the electrolyte volume decreases, the battery storage environment temperature is controlled to 10°C until the internal and external temperatures of the cell are equal. At this point, the internal environment of the battery is lowered, thus completing the membrane distillation cold-side temperature control. The battery is then transferred to a 65°C environment, allowing the external environment to rapidly heat the deionized water tank near the casing, quickly establishing membrane distillation hot-side temperature control. This is maintained for 2 minutes. Due to the temperature difference, driven by the vapor pressure difference across the deionized water tank (made of a composite membrane containing a superhydrophobic layer), water in the deionized water tank evaporates into water vapor at the membrane surface and enters the cold side through the membrane pores, where it is condensed and transferred into the battery interior. This achieves controllable water transfer and completes electrolyte repair.

[0019] Example 2: Step 1: Preparation of composite membrane First, the PVDF substrate was pretreated with Fenton's solution. A mixed solution was prepared by mixing 6g of ferrous sulfate heptahydrate, 24g of hydrogen peroxide, 200g of ethanol, and 200g of water. The PVDF substrate was then fully immersed in the mixed solution and heated to 40℃ for a Fenton reaction for 1 hour. After the reaction, the PVDF substrate was washed with 2% dilute hydrochloric acid and then vacuum dried at 30℃ to obtain the pretreated PVDF substrate. Next, a superhydrophobic coating was prepared by dissolving 2g of SiO2 nanoparticles in 50g of cyclohexane, stirring magnetically at 110r / min for 30min, and then ultrasonically dispersed until completely dispersed at a power of 300W to obtain a cyclohexane-SiO2 solution. Then, 2.08g of [unspecified substance] was added dropwise to the cyclohexane-SiO2 solution. 1H,1H,2H,2H-perfluorooctyltrichlorosilane was further ultrasonically dispersed to obtain a PFTS / SiO2 solution. Finally, the pretreated PVDF base film was immersed in the PFTS / SiO2 solution and sealed for 12 hours. After being removed, it was vacuum dried at a temperature of 30°C to obtain a composite film containing a superhydrophobic layer. Step 2: Preparation of deionized water tank First, use a utility knife to cut the composite film obtained in step one into 7*5cm square pieces. Overlap the short edges and bend them into a cylindrical shape to form the main body of the deionized water tank. Next, prepare the adhesive: mix 200g of epoxy resin and 10g of acetone, the co-solvent, in a beaker and stir with a stirring rod until the epoxy resin is diluted. Place the bottom of the beaker in a 25°C water bath to cool it down. Add 3g of ethylenediamine, the curing agent, and stir in a fume hood until the mixture is uniform and has stirring shear force. Use the prepared adhesive to seal the sides and bottom of the deionized water tank body and let it cure for 6 hours. Then, use a syringe to inject 5mL of deionized water into the deionized water tank body. Finally, use epoxy resin to seal the top edge of the deionized water tank body and let it cure for 6 hours. A sealed deionized water tank made of a composite film containing a superhydrophobic layer is obtained. Step 3: Spray a PVA reinforcement layer onto the outer wall of the deionized water tank. First, mix 10g of polyvinyl alcohol and 90g of deionized water and stir with a heating magnetic stirrer to dissolve them, obtaining a mixed solution. Mix the mixed solution with 20g of anhydrous ethanol to obtain a PVA mixed solution. Then, use a spray gun to evenly spray the PVA mixed solution onto the outer wall surface of the deionized water tank at a spraying pressure of 0.5Mpa, ensuring that the outer wall surface of the deionized water tank is completely covered. After spraying, there should be no solution dripping from the outer wall surface of the deionized water tank. Hang the tank in a vacuum oven at 45℃ for 4 hours to cure, thus obtaining a deionized water tank with a PVA reinforced layer. Step 4: Assembly of the deionized water tank and transfer of deionized water During the assembly stage of the aqueous battery, the deionized water tank is placed perpendicular to the electrode or plate, near the outer casing. Then, the battery is filled with electrolyte and assembled. When the electrolyte volume decreases, the battery storage environment temperature is controlled to 15°C until the internal and external temperatures of the cell are equal. At this point, the internal environment of the battery is lowered, thus completing the membrane distillation cold-side temperature control. The battery is then transferred to a 72°C environment, allowing the external environment to rapidly heat the deionized water tank near the casing, quickly establishing membrane distillation hot-side temperature control. This is maintained for 2.5 minutes. Due to the temperature difference, driven by the vapor pressure difference across the deionized water tank (made of a composite membrane containing a superhydrophobic layer), water in the deionized water tank evaporates into water vapor at the membrane surface and enters the cold side through the membrane pores, where it is condensed and transferred into the battery interior. This achieves controllable water transfer and completes electrolyte repair.

[0020] Example 3: Step 1: Preparation of composite membrane First, the PVDF substrate was pretreated with Fenton's solution. 3g of ferrous sulfate heptahydrate, 12g of hydrogen peroxide, 100g of ethanol, and 100g of water were mixed to prepare a solution. The PVDF substrate was then fully immersed in the solution and heated to 50℃ for a Fenton reaction for 1 hour. After the reaction, the PVDF substrate was washed with 2% dilute hydrochloric acid and then vacuum dried at 35℃ to obtain the pretreated PVDF substrate. Next, a superhydrophobic coating was prepared. 2g of SiO2 nanoparticles were dissolved in 50g of cyclohexane, magnetically stirred at 120r / min for 30min, and ultrasonically dispersed until completely dispersed at a power of 350W to obtain a cyclohexane-SiO2 solution. Then, 1.04g of [unspecified substance] was added dropwise to the cyclohexane-SiO2 solution. 1H,1H,2H,2H-perfluorooctyltrichlorosilane was further ultrasonically dispersed to obtain a PFTS / SiO2 solution. Finally, the pretreated PVDF substrate was immersed in the PFTS / SiO2 solution and sealed for 12 hours. After being removed, it was vacuum dried at a temperature of 35℃ to obtain a composite membrane containing a superhydrophobic layer. Step 2: Preparation of deionized water tank First, cut the composite film obtained in step one into 7*5cm square pieces using a utility knife. Overlap the short edges and bend them into a cylindrical shape to form the main body of the deionized water tank. Next, prepare the adhesive: mix 200g of epoxy resin and 10g of acetone, the co-solvent, in a beaker and stir with a stirring rod until the epoxy resin is diluted. Place the bottom of the beaker in a 25°C water bath to cool it down. Add 3g of ethylenediamine, the curing agent, and stir in a fume hood until the mixture is uniform and has a stirring shearing force. Use the prepared adhesive to seal the sides and bottom of the deionized water tank body and let it cure for 6 hours. Then, use a syringe to inject 7.5mL of deionized water into the deionized water tank body. Finally, use epoxy resin to seal the top edge of the deionized water tank body and let it cure for 6 hours. This yields a sealed deionized water tank made of a composite film containing a superhydrophobic layer. Step 3: Spray a PVA reinforcement layer onto the outer wall of the deionized water tank. First, mix 10g of polyvinyl alcohol and 90g of deionized water and stir with a heating magnetic stirrer to dissolve them, obtaining a mixed solution. Mix the mixed solution with 20g of anhydrous ethanol to obtain a PVA mixed solution. Then, use a spray gun to evenly spray the PVA mixed solution onto the outer wall surface of the deionized water tank at a spraying pressure of 0.6Mpa. Spray until the outer wall surface of the deionized water tank is completely covered. After spraying, no solution drips from the outer wall surface of the deionized water tank. Hang it in a vacuum oven at 45℃ for 4 hours to cure, and you will get a deionized water tank with a PVA reinforced layer. Step 4: Assembly of the deionized water tank and transfer of deionized water During the assembly stage of the aqueous battery, the deionized water tank is placed perpendicular to the electrode or plate, near the outer casing. Then, the battery is filled with electrolyte and assembled. When the electrolyte volume decreases, the battery storage environment temperature is controlled to 20°C until the internal and external temperatures of the cell are equal. At this point, the internal environment of the battery is lowered, thus completing the membrane distillation cold-side temperature control. The battery is then transferred to an 80°C environment, allowing the external environment to rapidly heat the deionized water tank near the casing, quickly establishing membrane distillation hot-side temperature control. This is maintained for 3 minutes. Due to the temperature difference, driven by the vapor pressure difference across the deionized water tank (made of a composite membrane containing a superhydrophobic layer), water in the deionized water tank evaporates into water vapor at the membrane surface and enters the cold side through the membrane pores, where it is condensed and transferred into the battery interior. This achieves controllable water transfer and completes electrolyte repair.

[0021] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that in step two, 2.5 mL of deionized water is injected into the deionized water tank using a syringe.

[0022] Comparative Example 2: The comparative example uses a conventional water-based zinc battery cell system without a deionized water tank.

[0023] The batteries equipped with deionized water tanks prepared in Examples 1-3 and the batteries in Comparative Examples 1-2 were tested. Aqueous zinc cells that had been cycled 150 times were taken, and it was assumed that some water loss existed. After the repair process battery was replenished with water, it was subjected to high-temperature float charging aging. First, each battery was fully charged and float charged at 1.84V at 60°C for 30 days. The conventional batteries were not operated every 30 days. After the repair process battery was replenished with water, the discharge capacity was measured at 0.5C.

[0024] like Figure 2As shown, the water-based batteries that have undergone the repair process can maintain a better capacity retention rate in subsequent cycles. Based on experience, 30 days of high-temperature float charging is approximately equivalent to a calendar life of 9 months or 1 year. It can be seen that the cells in Examples 1-3 that have undergone the repair process have a significant advantage in capacity retention rate compared to the unrepaired cells, which is manifested in a reduction in discharge capacity decay after repair. Comparing different repair fluid volumes and water replenishment tank volumes, it can be seen that injecting 10 mL of deionized water into the deionized water tank is equivalent to a deionized water tank design of 100 mg / Ah, which performs best and can effectively extend the life by 1 year or show a better capacity retention level after water replenishment. When the deionized water volume is 7.5 mL and 5 mL, the equivalent deionized water tank design is 75-50 mg / Ah. The effect of the first two water replenishments is comparable to 10 mL. Subsequently, as membrane fouling causes a decrease in membrane flux, the effect of subsequent water replenishment decreases, but there is still a significant repair effect. When the deionized water volume is 2.5 mL, there is only an initial retention rate maintenance effect, and the performance is poor in subsequent cycles.

[0025] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A closed-system electrolyte remediation process based on membrane distillation technology, characterized in that, Includes the following steps: Step 1: Preparation of composite membrane First, the PVDF base film was subjected to Fenton pretreatment. A mixed solution of ferrous sulfate heptahydrate, hydrogen peroxide, ethanol, and water was prepared. The PVDF base film was fully immersed in the mixed solution and heated to 30-50℃ for Fenton reaction for 1 hour. After the reaction, the PVDF base film was washed with 2% dilute hydrochloric acid and then vacuum dried to obtain the pretreated PVDF base film. Next, a superhydrophobic coating was prepared. SiO2 nanoparticles were dissolved in cyclohexane, magnetically stirred, and ultrasonically dispersed to obtain cyclohexane-SiO2. Then, 1H,1H,2H,2H-perfluorooctyltrichlorosilane was added dropwise to the cyclohexane-SiO2 solution, and ultrasonic dispersion was continued to obtain a PFTS / SiO2 solution. Finally, the pretreated PVDF base film was immersed in the PFTS / SiO2 solution and sealed for 12 hours. After removal, it was vacuum dried to obtain a composite film containing a superhydrophobic layer. Step 2: Preparation of deionized water tank First, cut the composite film obtained in step one into square pieces using a utility knife. Overlap the short edges and bend them into a cylindrical shape to form the main body of the deionized water tank. Next, prepare the adhesive: mix epoxy resin and co-solvent acetone in a beaker at a mass ratio of 100:5, stir with a stirring rod until the epoxy resin is diluted, place the bottom of the beaker in a 25°C water bath to cool, add curing agent ethylenediamine, and mix epoxy resin and curing agent ethylenediamine at a mass ratio of 100:1.

5. Stir in a fume hood until the mixture is uniform and has stirring shear force. Use the prepared adhesive to seal the sides and bottom of the deionized water tank body, and let it cure for 6 hours. Then, inject deionized water into the deionized water tank body using a syringe, and then seal the top edge of the deionized water tank body with epoxy resin, and let it cure for 6 hours. A closed deionized water tank made of a composite film containing a superhydrophobic layer is obtained. Step 3: Spray a PVA reinforcement layer onto the outer wall of the deionized water tank. First, polyvinyl alcohol and deionized water are mixed and dissolved using a heated magnetic stirrer to obtain a mixed solution. The mixed solution is then mixed with anhydrous ethanol to obtain a PVA mixed solution. Next, the PVA mixed solution is evenly sprayed onto the outer wall surface of the deionized water tank using a spray gun at a spray pressure of 0.5±0.1 MPa. The spraying ensures that the outer wall surface of the deionized water tank is completely covered. After spraying, no solution drips from the outer wall surface of the deionized water tank. The tank is then suspended in a vacuum oven at 45°C for 4 hours to cure, resulting in a deionized water tank with a PVA reinforced layer. Step 4: Assembly of the deionized water tank and transfer of deionized water During the assembly stage of the aqueous battery, the deionized water tank is placed perpendicular to the electrode or plate, near the outer casing. Then, the battery is filled with electrolyte and assembled. When the electrolyte volume decreases, the battery storage environment temperature is controlled to 10-20℃ until the internal and external temperatures of the cell are equal. At this point, the internal environment of the battery is lowered, thus completing the membrane distillation cold-side temperature control. The battery is then transferred to an environment of 65-80℃, allowing the external environment to rapidly heat the deionized water tank near the casing, quickly establishing membrane distillation hot-side temperature control. This is maintained for 2-3 minutes. Due to the temperature difference, driven by the vapor pressure difference across the deionized water tank (made of a composite membrane containing a superhydrophobic layer), water in the deionized water tank evaporates into water vapor at the membrane surface and enters the cold side through the membrane pores, where it is condensed and transferred into the battery interior. This achieves controllable water transfer and completes electrolyte repair.

2. The closed-system electrolyte repair process based on membrane distillation technology according to claim 1, characterized in that: In step one, the mass ratio of ferrous sulfate heptahydrate, hydrogen peroxide, ethanol, and water is 3:12:100:

100.

3. The closed-system electrolyte repair process based on membrane distillation technology according to claim 1, characterized in that: In step one, the mass ratio of SiO2 nanoparticles to cyclohexane is 1:50, and the mass ratio of cyclohexane-SiO2 solution to 1H,1H,2H,2H-perfluorooctyltrichlorosilane is 25:

1.

4. The closed-system electrolyte repair process based on membrane distillation technology according to claim 1, characterized in that: The square piece in step two is 7*5cm in size.

5. The closed-system electrolyte repair process based on membrane distillation technology according to claim 1, characterized in that: In step three, the mass ratio of polyvinyl alcohol to deionized water is 1:9, and the mass ratio of the mixture to anhydrous ethanol is 5:

1.

6. The closed-system electrolyte repair process based on membrane distillation technology according to claim 1, characterized in that: In step two, the amount of deionized water injected into the main body of the deionized water tank is adjusted according to the battery capacity, 50-100 mg / Ah.

7. The closed-system electrolyte repair process based on membrane distillation technology according to claim 1, characterized in that: In step one, the magnetic stirring is performed at 90-120 r / min for 30 min, and the ultrasonic dispersion power is 200-350 W.

8. The closed-system electrolyte repair process based on membrane distillation technology according to claim 1, characterized in that: The temperature for vacuum drying in step one is 25-35℃.

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