Needle punched nonwoven zinc-air battery flexible electrolyte membrane and method of making

Abstract

The application discloses a needled non-woven zinc-air battery flexible electrolyte film, which comprises a support body formed by interwinding PP fibers and PVA fibers and an alkaline aqueous solution in interwinding pores of the two fibers. 2 The thickness of the support body is 25-50 mm, the surface density of the support body is 200-210 g / m 2. The length of the PP fiber is 38±5 mm, the diameter is 1.2-2.0D, the length of the PVA fiber is 51±5 mm, and the diameter is 12-13D. The alkaline aqueous solution is composed of potassium hydroxide KOH and zinc acetate Zn(Ac)2. The application further discloses a preparation method of the needled non-woven zinc-air battery flexible electrolyte film. The application solves the problems of complex preparation process and poor mechanical property of the conventional electrolyte film in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of zinc-air battery electrolyte membrane technology, specifically relating to a needle-punched nonwoven flexible electrolyte membrane for zinc-air batteries. This invention also relates to a method for preparing the needle-punched nonwoven flexible electrolyte membrane for zinc-air batteries. Background Technology

[0002] With increasing public concern about the energy crisis and environmental issues, the high energy density and environmentally friendly characteristics of zinc-air batteries have attracted considerable attention from researchers. A zinc-air battery generally consists of four parts: a positive electrode, a negative electrode, an alkaline electrolyte, and a separator. The separator material directly affects the battery's electrical performance. Furthermore, with the development of flexible zinc-air batteries, some gel electrolyte materials not only act as a separator to isolate the positive and negative electrodes but also serve as ion transporters.

[0003] Traditional separators are installed into the battery after being impregnated with electrolyte during battery fabrication. Even though the separators possess high porosity and hydrophilicity, their limited liquid absorption and retention rates hinder their application in flexible zinc-air batteries. Flexible solid electrolytes typically use hydrogels as electrolyte materials, but the inherent drawbacks of hydrogels—such as easy water loss, low strength, and complex manufacturing processes—significantly impede their further development. Therefore, this invention leverages the ultra-high liquid absorption rate and simple, rapid manufacturing process of needle-punched nonwoven fabrics, using them as the electrolyte membrane for flexible zinc-air batteries to achieve flexible zinc-air batteries with excellent mechanical properties. Summary of the Invention

[0004] The purpose of this invention is to provide a flexible electrolyte membrane for needle-punched nonwoven zinc-air batteries, which solves the problems of complex preparation process and poor mechanical properties of traditional electrolyte membranes in the prior art.

[0005] The first technical solution adopted in this invention is a needle-punched nonwoven zinc-air battery flexible electrolyte membrane, comprising a support formed by intertwining PP fibers and PVA fibers, and an alkaline aqueous solution in the intertwined pores of the two fibers.

[0006] The first technical solution of the present invention is further characterized in that,

[0007] The thickness of the support is 25-50mm, and the surface density of the support is 200-210g / m³. 2 .

[0008] The length of PP fiber is 38±5mm and the diameter is 1.2-2.0D, while the length of PVA fiber is 51±5mm and the diameter is 12-13D.

[0009] The mass ratio of PP fiber to PVA fiber is 9:1 to 1:9.

[0010] The transverse breaking strength of the support is 200-225N, and the longitudinal breaking strength is 350-450N.

[0011] The alkaline aqueous solution is composed of potassium hydroxide (KOH) and zinc acetate (Zn(Ac)2), with a molar mass ratio of 3:1 to 1:1. The molar concentration of potassium hydroxide (KOH) is 1-6 mol / L, and the molar concentration of zinc acetate (Zn(Ac)2) is 0.1-0.2 mol / L.

[0012] The second technical solution adopted in this invention is a method for preparing a flexible electrolyte membrane for a needle-punched nonwoven zinc-air battery, which is implemented according to the following steps:

[0013] Step 1: Manually mix PP fibers and PVA fibers, then open and loosen the clusters of the two fibers, mix them together, and remove short fibers and impurities between the fibers to form fiber clusters of PP fibers and PVA fibers mixed together.

[0014] Step 2: The fibers are combed into a web, and the individual PP fibers and PVA fibers are evenly mixed and intertwined to form blocky flocs;

[0015] Step 3: The blocky flocs are laid through a netting process and cross-laid to form flocs;

[0016] Step 4: The wadding is repeatedly punctured by the needle of the needle punching machine. The fibers perpendicular to the surface of the wadding become entangled with each other, and the fluffy wadding gradually shrinks. The needle punching process is divided into two steps: pre-needling and barbed punching. After the needle punching process, a support is prepared.

[0017] Step 5: After the support is soaked in an alkaline aqueous solution for 24-25 hours, the final needle-punched nonwoven zinc-air battery flexible electrolyte membrane is obtained.

[0018] The second technical solution of the present invention is further characterized in that,

[0019] In step 2, the cylinder speed during the combing process is 1010-1020 m / min. -1 The speed of the dolphin is 8-10 m / min. -1 .

[0020] In step 3, the mesh laying method is cross-laying.

[0021] In step 4, the pre-puncture and barb puncture depth is 8-10 mm, and the puncture density is 350-380 punctures / cm². 2 In the barbed process, the flakes need to be reversed before entering the needle punching machine so that both sides of the flakes are evenly penetrated by the needles.

[0022] The beneficial effects of this invention are that, utilizing the high porosity of the three-dimensional porous structure of needle-punched nonwoven fabric, it can absorb as much alkaline electrolyte as possible as a support. Furthermore, the needle-punched nonwoven fabric maintains excellent mechanical properties even after absorbing a large amount of alkaline electrolyte. More importantly, it also features simple processing and high preparation efficiency. Therefore, unlike the low liquid absorption rate of traditional separators and the complex preparation process of gel electrolyte membranes, this invention introduces a flexible zinc-air battery electrolyte membrane with a simple and rapid process, high electrolyte absorption rate, and the ability to be bent and stretched at will, while also providing its preparation process. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a needle-punched nonwoven flexible zinc-air battery electrolyte membrane according to the present invention;

[0024] Figure 2 This is a flowchart of the preparation process of the present invention;

[0025] Figure 3 This is the electrical performance test result of comparison sample 2.

[0026] In the diagram, 1: PP fiber, 2: PVA fiber, 3: alkaline aqueous solution. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0028] This invention relates to a needle-punched nonwoven flexible electrolyte membrane for zinc-air batteries, such as... Figure 1 As shown, it includes a support structure formed by the intertwining of PP fiber 1 and PVA fiber 2, and an alkaline aqueous solution 3 in the pores of the intertwined fibers.

[0029] The thickness of the support is 25-50mm, and the surface density of the support is 200-210g / m³. 2 .

[0030] PP fiber 1 has a length of 38±5mm and a diameter of 1.2-2.0D, while PVA fiber 2 has a length of 51±5mm and a diameter of 12-13D.

[0031] The mass ratio of PP fiber 1 to PVA fiber 2 is 9:1 to 1:9. PVA fiber has a large number of hydroxyl groups on its surface, resulting in excellent hydrophilicity, while PP fiber lacks hydrophilic groups and has poor affinity for electrolytes. Therefore, adding a certain amount of PVA fiber allows alkaline aqueous solutions to quickly wet the fibers and then penetrate the pores between the fiber interlocking strands.

[0032] The transverse breaking strength of the support is 200-225N, and the longitudinal breaking strength is 350-450N.

[0033] The alkaline aqueous solution 3 is composed of potassium hydroxide (KOH) and zinc acetate (Zn(Ac)2), with a molar mass ratio of 3:1 to 1:1. The molar concentration of potassium hydroxide (KOH) is 1-6 mol / L, and the molar concentration of zinc acetate (Zn(Ac)2) is 0.1-0.2 mol / L.

[0034] A method for preparing a flexible electrolyte membrane for needle-punched nonwoven zinc-air batteries, combined with Figure 2 The specific steps are as follows:

[0035] Step 1: Manually mix PP fiber 1 and PVA fiber 2, then loosen and break up the clusters of the two fibers, mix them together, and remove short fibers and impurities between the fibers to form fiber clusters of PP fiber 1 and PVA fiber 2 mixed together.

[0036] Step 2: The fibers are carded into a web, and the individual PP fibers 1 and PVA fibers 2 are uniformly mixed and intertwined to form blocky flocs; the cylinder speed in the carding process of Step 2 is 1010-1020 m·min. -1 The speed of the dolphin is 8-10 m / min. -1 .

[0037] Step 3: The blocky flocs are laid out in a cross-laying pattern in a certain direction to form flocs of a certain thickness; the laying pattern in Step 3 is cross-laying.

[0038] Step 4: The wadding is repeatedly punctured by the needles of the needle punching machine. The fibers perpendicular to the surface of the wadding become entangled with each other, and the fluffy wadding gradually shrinks. Because the initial needle punching density is too high, it will damage and break the fibers. Therefore, the needle punching process is divided into two steps: pre-needling and barbed punching. After the needle punching process, a support is prepared.

[0039] In step 4, the pre-puncture and barb puncture depth is 8-10 mm, and the puncture density is 350-380 punctures / cm². 2 In the barbed process, the flakes need to be reversed before entering the needle punching machine so that both sides of the flakes are evenly penetrated by the needles.

[0040] Step 5: After the support is soaked in alkaline aqueous solution 3 for 24-25 hours, the final needle-punched nonwoven zinc-air battery flexible electrolyte membrane is obtained.

[0041] In this embodiment, to test the absorption capacity and mechanical properties of the electrolyte membrane of the needle-punched nonwoven zinc-air battery with different fiber ratios to alkaline aqueous solution, a 6 mol / L KOH and a 0.2 mol / L Zn(Ac)2 solution were used. The liquid absorption capacity was calculated using the following formula:

[0042]

[0043] E - Liquid absorption rate (%), M1 - Diaphragm mass before liquid absorption (g), M2 - Diaphragm mass after liquid absorption (g).

[0044] In accordance with the requirements of the national standard FZ / T 60005—1991 "Determination of breaking strength and elongation at break of nonwoven fabrics", parallel sampling method was adopted to take five samples in each direction. Considering that it is used in battery separators, the size of the cut samples was selected as 10mm*5mm. The samples were pre-conditioned according to the regulations. At the same time, the clamping distance of the strength testing machine was set to 50±1mm and the tensile speed was set to 100mm / min.

[0045] The results of liquid absorption capacity and tensile strength tests for samples with different proportions are shown in Table 1.

[0046] Table 1 Performance test results of samples with different proportions

[0047]

[0048] PVA fibers have better hydrophilicity than PP fibers, therefore, the support's ability to absorb electrolyte increases with the increase of PVA fiber proportion. However, all support comparison samples exhibited very good liquid absorption capacity. Meanwhile, as the PVA fiber proportion increased, the tensile strength of the support showed a trend of first decreasing and then increasing. With other parameters remaining constant, it can be inferred that this is related to the entanglement structure between the fibers.

[0049] Figure 2 In the process, the fiber ratio remains unchanged, with the mass ratio of PP fiber to PVA fiber ranging from 9:1 to 1:9. In step S5, the pre-needling density is usually set in advance, and then the remaining needled density is allocated, which is carried out in two steps.

[0050] The formula for converting acupuncture density to acupuncture frequency of the acupuncture machine is as follows:

[0051]

[0052] D n —Needle density (number of needles / cm²), n—number of needles on a one-meter-long needle plate, N—needle frequency (number of needles / min), V—fiber web output speed (meters / min).

[0053] The pre-needling machine has 1400 needles on a one-meter-long needle plate, while the barbed needle machine has 2461 needles on a one-meter-long needle plate. The acupuncture frequency is 1Hz = 20rpm, and the output speed is 1Hz = 0.085m / min.

[0054] Based on the tensile strength standards mentioned above, the tensile strengths for different needle-punching parameters are shown in Table 2.

[0055] Table 2 Mechanical properties of different needle penetration densities

[0056]

[0057] The S4 step cross-laying process inherently exhibits a significant difference in strength between the longitudinal and transverse directions, with the longitudinal strength being much greater than the transverse strength. As the needle-punching density increases, the strength of the support increases accordingly. This is because a higher needle-punching density leads to a greater degree of fiber entanglement; however, excessive needle-punching density can damage the fiber structure, and beyond a certain value, the mechanical properties of the support will decrease.

[0058] In step S6, the negative electrode material is zinc foil, the positive electrode catalyst is Pt / C particles, and the support is carbon cloth. The positive electrode material preparation involves ultrasonically dispersing 12 mg of Pt / C particles, 3 ml of anhydrous ethanol, and 75 μL of Nafion dispersion for 15 min, followed by spraying onto the carbon cloth surface on an 80°C heating platform. The positive electrode material preparation is then complete. The zinc foil thickness for the negative electrode material is 0.8 mm.

[0059] Testing the electrical performance of the flexible electrolyte membrane in needle-punched nonwoven zinc-air batteries, such as... Figure 3 As shown.

[0060] The needle density of the support is 380 needles / cm². -2 The mass ratio of PP fiber to PVA fiber is 9:1 to 5:5.

[0061] When the mass ratio of PP fiber to PVA fiber is between 9:1 and 7:3, it exhibits good cycle performance.

[0062] Figure 3 The electrical performance was tested under different fiber ratios. It can be seen that both the discharge voltage plateau and the charging voltage plateau can remain stable within a certain time range. Therefore, the needle-punched nonwoven flexible electrolyte membrane of this invention can be used in flexible zinc-air batteries.

[0063] In summary, this invention provides a needle-punched nonwoven flexible electrolyte membrane for zinc-air batteries and its preparation process. A nonwoven fabric interwoven with PP and PVA fibers serves as the support, and an alkaline aqueous solution is absorbed internally. The fibers exhibit high strength and superior electrical properties due to purely physical entanglement. The invention also provides the aforementioned preparation process for the needle-punched nonwoven flexible electrolyte membrane for zinc-air batteries.

Claims

1. A needle-punched nonwoven flexible electrolyte membrane for zinc-air batteries, characterized in that, The support consists of a PP fiber (1) and a PVA fiber (2) intertwined, and an alkaline aqueous solution (3) in the intertwined pores of the two fibers. The thickness of the support body is 25-50 mm, and the areal density of the support body is 200-210 g / m³. 2 ; The PP fiber (1) has a length of 38±5mm and a diameter of 1.2-2.0D, and the PVA fiber (2) has a length of 51±5mm and a diameter of 12-13D. The mass ratio of the PP fiber (1) to the PVA fiber (2) is 7:3; The needle-punched nonwoven zinc-air battery flexible electrolyte membrane is prepared through the following steps: Step 1: Manually mix PP fiber (1) and PVA fiber (2) and then loosen and break up the clusters of the two fibers, mix them together, and remove short fibers and impurities between the fibers to form a fiber cluster of PP fiber (1) and PVA fiber (2) mixed together. Step 2: The fibers are combed into a web, and the single PP fiber (1) and PVA fiber (2) are evenly mixed and intertwined to form blocky flocs; Step 3: The blocky flocs are laid in a cross-laid mesh to form flocs; the mesh laying method in step 3 is cross-laid mesh. Step 4: The wadding is repeatedly pierced by the needles of a needle punching machine. The fibers perpendicular to the surface of the wadding become entangled, and the loose wadding gradually shrinks. The needle punching process is divided into two steps: pre-needling and barbed punching. After the needle punching process, a support is prepared. In step 4, the pre-needling and barbed punching depth is 8-10 mm, and the needle punching density is 350-380 needles / cm. 2 In the barbed process, the flakes need to be reversed before entering the needle punching machine so that both sides of the flakes are evenly penetrated by the needles. Step 5: After the support is soaked in an alkaline aqueous solution (3) for 24-25 hours, the final needle-punched nonwoven zinc-air battery flexible electrolyte membrane is obtained.

2. The needle-punched nonwoven zinc-air battery flexible electrolyte membrane according to claim 1, characterized in that, The transverse breaking strength of the support is 200-225N, and the longitudinal breaking strength is 350-450N.

3. The needle-punched nonwoven zinc-air battery flexible electrolyte membrane according to claim 1, characterized in that, The alkaline aqueous solution (3) is composed of potassium hydroxide (KOH) and zinc acetate (Zn(Ac)2), with a molar mass ratio of 3:1 to 1:

1. The molar concentration of potassium hydroxide (KOH) is 1-6 mol / L, and the molar concentration of zinc acetate (Zn(Ac)2) is 0.1-0.2 mol / L.

4. The needle-punched nonwoven zinc-air battery flexible electrolyte membrane according to claim 1, characterized in that, In step 2, the cylinder speed during the combing process is 1010-1020 m·min. -1 The speed of the dolphin is 8-10 m / min. -1 .

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