Alkaline battery isolation tube processing and forming process and extrusion die

Abstract

The invention provides an alkaline battery isolation tube processing and forming process and an extrusion die, and the process comprises the following steps: coating titanium-based or silicon-based coating slurry on the surface of a sheet-shaped diaphragm before a cutting process, and carrying out existing alkaline battery diaphragm processing processes such as winding and the like; the tubular composite diaphragm is tightly held by using an extrusion die and a reel together and then is subjected to hot pressing, the temperature of the tubular composite diaphragm is controlled to be 240-270 DEG C in the hot pressing process, the pressure is controlled to be 0.5-2 Mpa, the coating slurry layer is pressurized in a plastic state, and the coating slurry layer is uniformly distributed on the surface of the tubular alkaline battery diaphragm. The process provided by the invention can change the surface state of the diaphragm of the alkaline battery and adjust the aperture distribution of the diaphragm, so as to prevent pulverized manganese powder particles from penetrating through the pores of the diaphragm and prevent zinc dendrites from puncturing the diaphragm to cause perforation in the later discharge period of the alkaline battery, thereby being beneficial to prolonging the service life of the battery, reducing the gas production rate in the battery and improving the safety performance of the battery.

Description

Technical Field

[0001] The invention relates to the field of batteries, and in particular to a processing and forming process and an extrusion die for an alkaline battery isolation tube. Background Art

[0002] Alkaline batteries are also called alkaline zinc-manganese batteries. They use manganese dioxide as the positive electrode, zinc as the negative electrode, and potassium hydroxide as the electrolyte. The diaphragm structure composed of non-woven fiber paper isolates the positive and negative electrodes of the battery to prevent direct contact between the positive and negative electrodes, and the diaphragm stores a certain amount of electrolyte required for the reaction. In the battery structure, the diaphragm only allows conducting ions, usually sodium ions or hydroxide ions, to move freely between the positive and negative electrodes through the diaphragm, thereby maintaining the current circulation of the battery.

[0003] With the development of the market, alkaline batteries are more widely used in scenarios of low-current continuous discharge or intermittent discharge, especially remote controls, clocks, wireless mouse and keyboards, etc. In low-current discharge scenarios, consumers will pay more attention to battery durability and safety. As alkaline batteries are discharged for a long time at low current, the positive electrode structure (positive electrode ring) will gradually crack, or even pulverize into fine manganese powder particles, and the pulverized manganese powder particles may pass through the diaphragm pores, reach the surface of the negative electrode zinc paste and react with it, which is equivalent to the "self-discharge phenomenon", resulting in rapid consumption of battery capacity, affecting battery durability. At the same time, the battery is prone to over-discharge, which intensifies the gas evolution reaction inside the battery, increases the amount of gas inside the battery, brings the risk of battery leakage, and poses a safety hazard. In addition, during the deep discharge of the battery, zinc dendrites will be generated near the negative electrode surface of the diaphragm. The zinc dendrites have a sharp crystal structure. The generation of this crystal structure is easy to puncture the surface of the diaphragm, forming a direct contact short circuit between the positive and negative electrodes, causing battery failure and affecting battery durability. It can be seen that the stability of the battery diaphragm plays a very important role in improving battery durability and battery safety performance.

[0004] Therefore, improving the durability and safety of batteries used by consumers in small and medium current modes and designing and producing diaphragms with stable performance and not easily punctured are issues that major battery manufacturers need to address. Summary of the invention

[0005] The first object of the present invention is to provide an alkaline battery isolation tube processing and forming process, which can change the surface state of the alkaline battery diaphragm and adjust the diaphragm pore size distribution to prevent pulverized manganese powder particles from passing through the diaphragm pores and zinc dendrites appearing in the late stage of alkaline battery discharge from piercing the diaphragm and causing perforation, which is beneficial to extending the battery life, and can also reduce the gas production inside the battery and improve the battery safety performance.

[0006] A processing and forming process for an alkaline battery isolation tube comprises the following steps: (1) Coating and drying: A layer of coating slurry with a thickness of 5 to 20 μm is uniformly coated on the surface of an existing non-woven fabric separator for alkaline batteries, and the coating slurry is solidified by drying to obtain a sheet-like composite separator; wherein the coating slurry comprises nano-scale inorganic particles, a binder and an organic solvent; the nano-scale inorganic particles are any one of titanate, silicate, titanium oxide and silicon oxide or a mixture of two or more in any proportion; wherein the ratio of the inorganic particles: binder: organic solvent in the coating slurry is 10 to 56: 5 to 20: 30 to 50; (2) Winding: The sheet-shaped composite diaphragm obtained in step (1) is wound around a reel into a tube to obtain a tubular composite diaphragm; (3) Suppression: The tubular composite diaphragm obtained in step (2) is tightly held by an extrusion die and then hot-pressed. During the hot-pressing process, the temperature of the tubular composite diaphragm is controlled at 240-270° C., and the pressure applied by the extrusion die to the outer surface of the tubular composite diaphragm is controlled at 0.5-2 MPa. After the hot-pressing is completed, an alkaline battery isolation tube is obtained.

[0007] The alkaline battery isolation tube processing and forming process of the present invention is to coat the surface of the sheet-like diaphragm with a titanium-based or silicon-based coating slurry before the cutting process, and after the existing alkaline battery diaphragm processing processes such as winding, the tubular composite diaphragm is clamped and hot-pressed together with an extrusion die and a reel, so that the coating slurry layer is pressurized in a plastic state, so that the coating slurry layer is evenly distributed on the surface of the tubular alkaline battery diaphragm. On the one hand, the inorganic particles (titanium-based or silicon-based materials) in the coating slurry can significantly improve the surface state of the alkaline battery diaphragm and prevent the zinc dendrites that appear in the late stage of alkaline battery discharge; another invention, by coating the coating slurry on the surface and pressing after winding, the titanium-based and silicon-based material particles with a spatial structure can be evenly covered on the curved surface of the diaphragm, thereby improving the originally uneven pore structure of the diaphragm, and after winding, the diaphragm is pressurized and pressed in an embracing manner, so that the diaphragm is pressurized while maintaining the shape required by the alkaline battery, and the uniformity and integrity of the distribution of the coating slurry layer on the curved surface of the alkaline battery isolation tube are maintained to the greatest extent; during the discharge process of the alkaline battery, the uniform pore structure can improve the stability of ion transmission, prevent the powdered manganese powder particles from passing through the pores of the diaphragm and the zinc dendrites that appear in the late stage of alkaline battery discharge from piercing the diaphragm to cause perforation, reduce the generation of gas inside the battery, and improve the safety and life of the battery.

[0008] Furthermore, in step (1), the coating slurry is dried and solidified until the moisture content of the coating slurry is 1-3%, and the drying temperature is controlled at 80-120°C.

[0009] Furthermore, the particle size of the nanoscale inorganic particles is 200 to 500 nm.

[0010] Furthermore, the binder in the coating slurry is one or a mixture of two or more of polyvinylidene fluoride (PVDF), polyurethane (PU), and polytetrafluoroethylene (PTFE) in any proportion.

[0011] Furthermore, the organic solvent is: one or a mixture of two or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF), and acetone in any proportion.

[0012] Furthermore, the coating slurry further includes a dispersant; the ratio of the inorganic particles: binder: dispersant: organic solvent in the coating slurry is 10-56: 5-20: 0-5: 30-50. The dispersant is one or a mixture of any proportion of sodium dodecyl sulfate (SDS), triethanolamine (TEA), and polymethyl methacrylate (PMMA).

[0013] The second object of the present invention is to provide an extrusion die specifically used for the alkaline battery isolation tube processing and forming process described in the first object of the present invention, including at least two arc-shaped dies distributed along the circumference of the reel on the outside of the reel; these arc-shaped dies are close to each other and enclose a ring structure to tightly embrace the tubular composite diaphragm wound on the reel; the inner surface shape of each of the arc-shaped dies matches the outer surface shape of the tubular composite diaphragm.

[0014] Furthermore, the arc-shaped mold is a heating mold, and heat is transferred to the tubular composite diaphragm through the heating mold to make it reach the temperature required for hot pressing.

[0015] Furthermore, a displacement mechanism is connected to the back of the arc-shaped mold to drive the arc-shaped molds to move closer to each other. The arc-shaped mold is also equipped with a pressure detection device to monitor the pressing force between the arc-shaped mold and the tubular composite diaphragm (i.e., the pressure applied by the extrusion mold to the outer surface of the tubular composite diaphragm). In the specific implementation process, the displacement mechanism can be a gas cylinder or an oil cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a simplified schematic diagram of the three-dimensional structure of the extrusion die of the present invention, wherein the dot-dashed line is the central axis of the reel, and the direction indicated by the arrow is the rotation direction of the reel; Figure 2 It is a simplified schematic diagram of the top view structure of the extrusion die of the present invention. DETAILED DESCRIPTION

[0017] The following is a detailed description of the preferred embodiments of the alkaline battery isolation tube processing and forming process and the extrusion die of the present invention in conjunction with the accompanying drawings.

[0018] A processing and forming process for an alkaline battery isolation tube comprises the following steps: (1) Coating and drying: A layer of coating slurry with a thickness of 5 to 20 μm is uniformly coated on the surface of an existing non-woven fabric separator for alkaline batteries, and the coating slurry is solidified by drying to obtain a sheet-like composite separator; wherein the coating slurry comprises nano-scale inorganic particles, a binder and an organic solvent; the nano-scale inorganic particles are one or a mixture of any proportion of titanate, silicate, titanium oxide and silicon oxide; wherein the ratio of the inorganic particles, the binder and the organic solvent in the coating slurry is 10 to 56:5 to 20:30 to 50; (2) Winding: like Figure 1 As shown, the sheet-shaped composite diaphragm obtained in step (1) is wound around a reel 10 into a tubular shape to obtain a tubular composite diaphragm 30; (3) Suppression: like Figure 1 As shown, the tubular composite diaphragm 30 obtained in step (2) is held tightly by an extrusion die 20 for hot pressing. During the hot pressing process, the temperature of the tubular composite diaphragm 30 is controlled at 240-270° C., and the pressure applied by the extrusion die 20 to the outer surface of the tubular composite diaphragm 30 is controlled at 0.5-2 MPa. After the hot pressing is completed, an alkaline battery isolation tube is obtained.

[0019] Among them, the extrusion die 20 used in the alkaline battery isolation tube processing and forming process of the present invention is as follows: Figure 1 As shown, it includes at least two arc-shaped molds 21 distributed along the circumference of the reel 10 on the outside of the reel 10; these arc-shaped molds 21 are close to each other and enclose a ring structure to tightly embrace the tubular composite diaphragm 30 wound on the reel 10; the inner surface shape of each arc-shaped mold 21 matches the outer surface shape of the tubular composite diaphragm 30; the arc-shaped mold 21 is also equipped with a pressure detection device 50 for monitoring the clamping force between the arc-shaped mold 21 and the tubular composite diaphragm 30 (that is, the pressure applied by the extrusion mold 20 to the outer surface of the tubular composite diaphragm 30).

[0020] The coating slurry may further include a dispersant; the ratio of the inorganic particles: the binder: the dispersant: the organic solvent in the coating slurry is 10-56: 5-20: 0-5: 30-50.

[0021] During the experimental stage, the inventors mixed the various raw materials according to the composition formula of the coating slurry in Table 1 below and stirred them at high speed to obtain the coating slurry; and under the process conditions such as the coating thickness, pressing time and pressing conditions of the coating slurry in Table 1, an alkaline battery isolation tube was obtained.

[0022] Table 1

[0023] The surface physical properties (including average pore size, maximum pore size and air permeability) of the alkaline battery isolation tubes prepared in various embodiments and comparative examples were tested, and the test results are shown in Table 2 below.

[0024] Table 2

[0025] It can be seen from the test results of the physical properties of the diaphragm surfaces of Examples 1 to 4 and Comparative Example 1 in Table 2 that the pore size change of the alkaline battery isolation tube (Examples 1 to 4) produced by the alkaline battery isolation tube processing and molding process of the present invention is small, especially the adjustment of the maximum pore size, so that the overall pore size of the diaphragm is more uniform and the air permeability is significantly reduced. At the same time, the pore size will not be too low, which will not cause the ion conduction in the battery reaction to be blocked and affect the discharge performance of the battery; and it can be seen from the comparison between Comparative Example 2 and Example 1 that: under the same coating slurry formula and pressing parameters, the maximum pore size and average pore size of the alkaline battery isolation tube obtained by first winding and then pressing are smaller, indicating that the pore size is more uniform and the air permeability is also lower, and the effect of preventing the powdered manganese powder particles from passing through the pores of the diaphragm and the zinc dendrites appearing in the late stage of alkaline battery discharge from piercing the diaphragm to cause perforation is better.

[0026] The alkaline battery isolation tubes prepared in the embodiments and comparative examples were used to prepare finished alkaline batteries. After the batteries were over-discharged in a 48h constant resistance 10Ω discharge mode, they were aged at room temperature for 1 day, 3 days, 7 days, and 14 days. The gas production inside the batteries corresponding to different aging days was tested, and the test results are shown in Table 3.

[0027] Table 3

[0028] The finished alkaline batteries obtained by using Examples 1 and 2 and Comparative Examples 1 and 2 were discharged in two modes, namely, "24Ω; 24h / d; EV: 0V" and "15mA; 1h / 2h; 24h / d; EV: 0.6V", and then aged at high temperature (60°C). The leakage of the batteries was monitored during the aging process, as shown in Table 4.

[0029] Table 4

[0030] It can be seen from the data in Table 3 and Table 4 that the battery prepared by using the coated diaphragm has a large initial internal gas volume after over-discharge in the 48h constant resistance 10Ω discharge mode, but the gas volume increase rate decreases with the extension of aging time. After the aging time is greater than 3 days, the internal gas volume is lower than that of the comparative example, and the internal gas volume of the battery tends to be stable after aging for 7 days. The gas production inside the battery is highly correlated with the battery leakage rate. Therefore, the alkaline battery isolation tube processing and molding process of the present invention can effectively reduce the gas evolution of the battery when it is placed for a long time after over-discharge, and the safety performance is improved.

[0031] In step (1), the coating slurry is dried and cured until the moisture content is 1-3%, and the drying temperature is controlled at 80-120° C. In each embodiment and comparative example in Table 1, the drying and curing conditions of step (1) are specifically: drying and curing at 120° C. for 15 minutes.

[0032] Furthermore, the particle size of the nanoscale inorganic particles is 200 to 500 nm.

[0033] Furthermore, the binder in the coating slurry is one or a mixture of two or more of polyvinylidene fluoride (PVDF), polyurethane (PU), and polytetrafluoroethylene (PTFE) in any proportion.

[0034] Furthermore, the organic solvent is: one or a mixture of two or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF), and acetone in any proportion.

[0035] Furthermore, the dispersant is one or a mixture of any proportion of two or more of sodium dodecyl sulfate (SDS), triethanolamine (TEA), and polymethyl methacrylate (PMMA).

[0036] The sheet-shaped composite membrane obtained in step (1) of the present invention can be cut into fixed lengths before the composite membrane of fixed length is wound in step (2); or the composite membrane can be wound in step (2) and then cut when wound to a fixed length.

[0037] The arc-shaped die 21 of the extrusion die 20 can be a heating die, and the tubular composite diaphragm can be heated by the heating die to reach the required temperature during hot pressing. Of course, the tubular composite diaphragm can also be directly heated to reach the required temperature during hot pressing.

[0038] The back of the arc-shaped mold 21 of the extrusion mold 20 is also connected to a shift mechanism 40 for driving the arc-shaped molds 21 to move closer to each other, thereby realizing automatic closing and automatic separation of the arc-shaped molds 21 (such as Figure 2In the specific implementation process, the shifting mechanism 40 can be a gas cylinder or an oil cylinder.

[0039] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A process for processing and forming an alkaline battery isolation tube, characterized in that: The following steps are involved: (1) Coating and drying: A layer of coating slurry with a thickness of 5 to 20 μm is uniformly coated on the surface of an existing non-woven fabric separator for alkaline batteries, and the coating slurry is solidified by drying to obtain a sheet-like composite separator; wherein the coating slurry comprises nano-scale inorganic particles, a binder and an organic solvent; the nano-scale inorganic particles are any one of titanate, silicate, titanium oxide and silicon oxide or a mixture of two or more in any proportion; wherein the ratio of the inorganic particles: binder: organic solvent in the coating slurry is 10 to 56: 5 to 20: 30 to 50; (2) Winding: The sheet-shaped composite diaphragm obtained in step (1) is wound around a reel into a tube to obtain a tubular composite diaphragm; (3) Suppression: The tubular composite diaphragm obtained in step (2) is tightly held by an extrusion die and then hot-pressed. During the hot-pressing process, the temperature of the tubular composite diaphragm is controlled at 240-270° C., and the pressure applied by the extrusion die to the outer surface of the tubular composite diaphragm is controlled at 0.5-2 MPa. After the hot-pressing is completed, an alkaline battery isolation tube is obtained.

2. The alkaline battery isolation tube processing and forming process according to claim 1, characterized in that: In step (1), the coating slurry is dried and solidified until the moisture content of the coating slurry is 1-3%, and the drying temperature is controlled at 80-120°C.

3. The alkaline battery isolation tube processing and forming process according to claim 1, characterized in that: The particle size of the nano-scale inorganic particles is 200-500 nm.

4. The alkaline battery isolation tube processing and forming process according to claim 1, characterized in that: The binder in the coating slurry is one or a mixture of two or more of polyvinylidene fluoride, polyurethane and polytetrafluoroethylene in any proportion.

5. The alkaline battery isolation tube processing and forming process according to claim 1, characterized in that: The organic solvent is one of N-methylpyrrolidone, dimethylformamide and acetone or a mixture of two or more of them in any proportion.

6. The alkaline battery isolation tube processing and forming process according to claim 1, characterized in that: The coating slurry further comprises a dispersant; the ratio of the inorganic particles: the binder: the dispersant: the organic solvent in the coating slurry is 10-56: 5-20: 0-5: 30-50.

7. The alkaline battery isolation tube processing and forming process according to claim 6, characterized in that: The dispersant is one or a mixture of two or more of the following in any proportion: sodium lauryl sulfate, triethanolamine, and polymethyl methacrylate.

8. An extrusion die for use in the alkaline battery isolation tube processing and forming process as claimed in any one of claims 1 to 7, comprising at least two arc-shaped dies distributed along the circumference of the reel on the outside of the reel; these arc-shaped dies are close to each other and enclose a ring structure to tightly embrace the tubular composite diaphragm wound on the reel; the inner surface shape of each of the arc-shaped dies matches the outer surface shape of the tubular composite diaphragm.

9. The extrusion die according to claim 8, characterized in that: The arc-shaped mold is a heating mold.

10. The extrusion die according to claim 8, characterized in that: The back of the arc-shaped mold is connected with a displacement mechanism for driving the arc-shaped molds to move closer to each other; the arc-shaped mold is also equipped with a pressure detection device for monitoring the pressing force between the arc-shaped mold and the tubular composite diaphragm.

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