Manufacturing method of battery separator

Abstract

The battery, battery separator, and manufacturing method thereof belong to the field of batteries. The battery separator has a composite structure consisting of a first member and a second member. The first member is a layered nanowire stack manufactured from a modifying material used to improve the thermal stability of the separator. The second member is manufactured from a base material that constitutes the main body of the separator, and the first member is placed on and supported by the second member. The battery separator has good thermal stability. [Selected Figure] Figure 1

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority based on a Chinese application bearing application number 2018104718423 and entitled “Battery, battery separator and manufacturing method thereof” filed with the State Intellectual Property Office of the People's Republic of China on May 16, 2018, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to the field of batteries, and more particularly to electric Pond separator Ta's It relates to a manufacturing method. [Background technology]

[0003] Lithium-ion batteries are widely used secondary batteries. Lithium-ion batteries work mainly by the movement of lithium ions between the positive and negative electrodes. During the charging and discharging process, Li+ is inserted and removed back and forth between the two electrodes. During charging, Li+ is removed from the positive electrode and inserted into the negative electrode through the electrolyte, making the negative electrode lithium-rich; the more lithium ions inserted into the negative electrode, the higher the charge capacity. Conversely, during discharging, lithium ions inserted into the carbon layer of the negative electrode are removed and returned to the positive electrode through the electrolyte; the more lithium ions returned to the positive electrode, the higher the discharge capacity.

[0004] Lithium-ion batteries have the advantages of a high working voltage for a single battery, large specific energy, long cycle life, small self-discharge, non-pollution, and no memory effect, and are therefore widely used in modern electrical fields such as mobile phones, portable devices, automobiles, aviation, scientific research, entertainment, and the military, replacing traditional batteries.

[0005] Lithium-ion batteries are mainly composed of four materials: positive electrode material, negative electrode material, separator, and electrolyte. The separator plays an important role in the performance of the battery as an important component. The term battery separator refers to the layer of separator material between the positive and negative electrodes of a battery, and is usually called battery separator. The main role of the battery separator is to separate the positive and negative electrodes, preventing the free passage of electrons in the battery, while allowing the ions in the electrolyte to pass freely between the positive and negative electrodes.

[0006] The ion conduction ability of the battery separator is directly related to the performance of the whole battery. By isolating the positive and negative electrodes, it can suppress the increase in current when the battery is overcharged or the temperature rises, and prevent the explosion caused by the short circuit of the battery. In addition, it has a protective effect by blocking the micropores, and plays a role in safety protection for battery users and equipment. Polyolefin materials are widely used as microporous separators because of their advantages such as low cost, good mechanical strength and chemical stability, excellent comprehensive performance, and low cost. However, their poor thermal stability limits their further application in batteries.

[0007] The information disclosed in the Background section is intended only to facilitate understanding of the overall background of the present disclosure, and is not intended to acknowledge or otherwise imply that the information is prior art known to those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0008] The objective is to innovate the conventional battery separator by providing a composite structure in the battery separator, improving its thermal stability by using a modified material, and utilizing the modified material in the form of nanowires to avoid the problem of increased thickness and weight of the separator caused by the use of the modified material, thereby maintaining the thermal stability of the battery separator while suppressing the increase in thickness and weight. [Means for solving the problem]

[0009] The present disclosure provides a battery separator, which has a composite structure consisting of a first member and a second member, in which the first member is a stack of nanowires distributed in layers, made of a modifying material used to improve the thermal stability of the battery separator, and the second member is made of a base material constituting the main body of the battery separator, and the first member is placed on and supported by the second member.

[0010] In one or more examples, the first component has a thickness on the order of microns and / or sub-microns.

[0011] In one or more embodiments, the first component has a thickness of 0.01 to 1 μm.

[0012] In one or more examples, the nanowires have a length to diameter ratio of greater than 50.

[0013] In one or more examples, the nanowires have a diameter of 1-100 nm and a length of 0.1-100 μm.

[0014] In one or more examples, the modifying material includes one or more of carbon nanotubes, silver nanowires, boron carbide nanowires, nanocellulose, copper hydroxide nanowires, silicon monoxide nanowires, and hydroxyapatite nanowires.

[0015] In one or more examples, the base material is an organic polymeric material.

[0016] In one or more examples, the organic polymeric material includes a polyolefin.

[0017] In one or more examples, the polyolefin includes polyethylene.

[0018] In one or more examples, the first component has a porous structure.

[0019] The present disclosure further provides a method for producing the above battery separator.

[0020] The method for producing a battery separator is used to produce a battery separator having the following configuration.

[0021] The battery separator includes a first member and a second member, the first member being placed on the second member in a layered form and being composed of nanowires; The manufacturing method includes the steps of preparing a dispersion in which nanowires are dispersed in a dispersant, transferring the dispersion to a surface of the second component so as to deposit the nanowires in a layer on the surface of the second component, and removing the dispersant in the dispersion on the surface of the second component.

[0022] In one or more examples, the dispersant includes one or more of water, ethanol, acetone, N-methylpyrrolidone, and further includes an adhesive.

[0023] In one or more examples, the adhesive includes one or more of polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, styrene butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, and polyimide.

[0024] In one or more examples, the dispersion further comprises an adjuvant.

[0025] In one or more examples, the mass concentration of the nanowires in the dispersion is between 0.01 and 50%, and the mass concentration of the adhesive is between 0.01 and 49%.

[0026] In one or more examples, the dispersion is transferred to the surface of the second component by painting.

[0027] In one or more examples, the application is accomplished by spin coating, doctor blade coating, or dip coating.

[0028] In one or more examples, the dispersion is transferred to the surface of the second component by dip coating, which includes immersing the second component in the dispersion at a first predetermined speed while under tension, and removing the second component from the dispersion at a second predetermined speed.

[0029] In one or more examples, the second member is tensioned by a tensioning system consisting of multiple rolls, the tensioning system including at least one dip roll for immersing the second member in the dispersion, with some or all of the dip roll entering the dispersion.

[0030] In one or more examples, the dip roll has a cavity and an air vent passage communicating with the cavity and extending to the surface, and a second member is in surface contact with the surface of the dip roll and has a predetermined vacuum within the cavity.

[0031] In one or more embodiments, the degree of vacuum is 0.01 to 0.1 MPa.

[0032] A battery according to the present disclosure has the above-described battery separator. Effect of the Invention

[0033] The battery separator according to the present disclosure has a composite structure, innovates the conventional battery separator, and improves its thermal stability by using a modified material. Furthermore, by utilizing the modified material in the form of nanowires, the problem of the increase in thickness and weight of the separator caused by the use of the modified material can be avoided, and the thermal stability of the battery separator can be maintained while suppressing the increase in thickness and weight. [Brief description of the drawings]

[0034] [Figure 1] FIG. 2 is a schematic diagram showing the configuration of a first type of battery separator according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of a second type of battery separator according to an embodiment of the present disclosure. [Diagram 3]FIG. 2 is a schematic diagram showing the configuration of a film-forming apparatus for producing a second type of battery separator according to an embodiment of the present disclosure. [Figure 4] 4 is a schematic diagram showing a configuration of a first direction of a dip roll in the film forming apparatus shown in FIG. 3. FIG. [Diagram 5] 4 is a schematic diagram showing a configuration of a dip roll in a second direction in the film forming apparatus shown in FIG. 3. FIG. [Figure 6] 4 is a schematic diagram showing a cross-sectional configuration along the axial direction of a dip roll in the film forming apparatus shown in FIG. 3. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] In order to make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings of the embodiments of the present disclosure. Of course, the described embodiments are only some of the embodiments of the present disclosure, and not all of the embodiments. Usually, the parts of the embodiments of the present disclosure described and shown here with the drawings can be arranged and designed in their own combination. Therefore, the detailed description of the embodiments of the present disclosure shown in the drawings below only shows selected embodiments of the present disclosure, and does not limit the scope of the present disclosure to be protected. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without using inventive ability belong to the protection scope of the present disclosure.

[0036] In addition, since like symbols indicate like things in the drawings, if a definition is made in one drawing, it is unnecessary to further define and interpret it in the other drawings.

[0037] In the description of the present disclosure, directions or positional relationships expressed by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the drawings or are normal arrangement directions or positional relationships of the products of the disclosure, and are merely for the purpose of conveniently and simply describing the present disclosure, and do not necessarily express or imply that the relevant devices or elements have a fixed direction, or are constructed or operated in a fixed direction, and therefore should not be understood as limiting the present disclosure. In addition, terms such as "first", "second", "third", etc. are merely for the purpose of distinction and description, and do not express or imply relative importance.

[0038] In the description of the present disclosure, unless otherwise clearly specified or limited, the terms "installation", "attachment", "association" and "connection" should be understood in a broad sense. For example, they may be fixedly connected, detachably connected, or integrally connected. They may be mechanically connected or electrically connected. They may be directly connected, indirectly connected via an intermediate object, or the insides of two elements may communicate with each other. Those skilled in the art can understand the specific meanings of the above terms in the present disclosure according to the specific circumstances.

[0039] In this disclosure, unless otherwise clearly specified or limited, a first feature being located "above" or "below" a second feature means that the first feature and the second feature may be in direct contact with each other, or that the first feature and the second feature may not be in direct contact with each other but may be in contact with each other through another feature between them. And, a first feature being located "above," "above," or "on the upper surface" of a second feature includes the first feature being located directly above and diagonally above the second feature, or only means that the height of the first feature is higher than the height of the second feature. A first feature being located "below," "below," or "on the lower surface" of a second feature includes the first feature being located directly below and diagonally below the second feature, or only means that the height of the first feature is smaller than the height of the second feature.

[0040] In this disclosure, all examples, embodiments and features of this disclosure can be combined or combined unless there is a contradiction or conflict. In this disclosure, commonly used equipment, devices, parts, etc. may be commercially available or may be manufactured with reference to the contents disclosed in this disclosure. In this disclosure, some commonly used operations and equipment, devices, parts are omitted or briefly described in order to highlight the main points of this disclosure.

[0041] In the prior art, battery separators, especially polyolefin separators used in lithium ion batteries (including primary and secondary batteries), have poor thermal stability and must be modified to improve thermal stability. The inventors have found through practice that the thermal stability of a conventional (battery) separator can be improved simply and effectively by coating the surface of the separator with an inorganic material such as alumina.

[0042] However, the inventors have found that in the case of conventional coating means, some of the properties of the prepared separator are impaired, for example, the thickness and weight are significantly increased, and the separator's usability is deteriorated.

[0043] In this embodiment, in order to achieve both the thermal stability of the separator and a surface that does not significantly increase the thickness and weight, a material that can improve the thermal stability of the separator is placed on the separator material in the form of nanowires. In this embodiment, one-dimensional nanowires are used as the coating layer (for example, realized by coating). One-dimensional nanowires are much smaller in size and density than inorganic materials, and the thickness can be reduced.

[0044] Moreover, due to their unique structural features and interfacial effects, one-dimensional nanowires have the potential to impart new properties to the separator or improve its existing properties.

[0045] Please refer to Figures 1 to 6.

[0046] As shown in Fig. 1, the battery separator according to this embodiment has a multi-layer composite structure. The battery separator has a composite structure consisting of a first member 100 and a second member 200. Furthermore, the above battery separator structure can be modified as necessary. For example, as shown in Fig. 2, the battery separator has a composite structure consisting of a first member 100 and a second member 200, and the first member further includes a porous structure 300 having a plurality of holes.

[0047] 1 and 2 are merely schematic diagrams of the configuration of the battery separator, and the absolute thickness of the first member, the absolute thickness of the second member, and their magnitude and proportional relationships cannot be determined by the dimensions and proportions shown in the drawings, although the thickness of the first member in the battery separator is significantly smaller than the thickness of the second member.

[0048] For example, in some examples, the first member has a thickness on the order of submicrons or microns, and the second member has a thickness on the order of millimeters or centimeters. In some specific, selectable examples, the thickness of the first member may be 0.01 to 1 micron (μm). Furthermore, it may be any value among 0.03 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.4 μm, 0.6 μm, 0.8 μm, and 1 μm, or any value within a range specified by any two values. The thickness of the first member may be specified according to specific product specifications and experimental effects, and is not specifically limited in the examples of the present disclosure.

[0049] Furthermore, in this embodiment, since the first member is composed of nanowires, the specifications of the nanowires can be limited as follows based on the difference in performance between the first member and the nanowires, the difficulty of the manufacturing method thereof, and the performance of the battery separator. For example, the length-to-diameter ratio of the nanowires may be greater than 50. Furthermore, the length-to-diameter ratio may be, for example, 146, 138, 127, etc. Furthermore, the length-to-diameter ratio can be adjusted by appropriately controlling the length and diameter of the nanowires. For example, the diameter of the nanowires is set to 1 to 100 nm, and the length is set to 0.1 to 100 μm. In some specific, selectable examples, the diameter of the nanowires is 100 nm, and the length is 5 μm.

[0050] There are several options for the materials of the battery separator, which can be selected according to the specific actual situation.

[0051] The first component is a stack of nanowires distributed in layers, made of a modifying material used to improve the thermal stability of the separator. Typically, the first component is in the form of a macroscopically thin film (membrane layer) and has a thickness of the submicron or micron order as described above.

[0052] The first member is a nanowire deposit, but the nanowire deposit may have various forms. For example, the first member is a single-layer deposit structure having a thickness equivalent to the diameter of the nanowire, and the nanowires are arranged in an array. In the vertical direction, the nanowires in the same row are arranged in a row, and in the horizontal direction, multiple rows are arranged in parallel. Or, in some examples, the nanowires are deposited crossing vertically and horizontally. Or, in other examples, the nanowires are deposited crossing irregularly. The deposition method of the nanowires may be specified according to the manufacturing method of the battery separator, and is not specifically limited in the examples of the present disclosure. Furthermore, the deposit made of nanowires may be composed of two layers, three layers, or more layers. Also, the manufacturing method and deposition method of each layer may be similar or different.

[0053] The first component, which is a stack of nanowires arranged in a suitable manner, has high porosity, uniform pore size, light weight and high strength, so the nanowire coating layer can solve the thermal stability problem of polyolefin separators, and is thin and light, which is suitable for the development trend of lightweight and high energy batteries.

[0054] The first member having the above-mentioned holes may be formed by depositing nanowires on the second member. In other words, the holes may be formed unintentionally in the manufacturing process of the battery separator, or may be formed by intentional control (distribution density, distribution method, hole size). By controlling the configuration of the holes (e.g., hole size, porosity, etc.), it is possible to adjust the effect on the movement of ions when a battery separator having the first member and the second member is applied to a battery.

[0055] In addition, there are multiple options for the modifying material, and for example, one or more of carbon nanotubes, silver nanowires, boron carbide nanowires, nanocellulose, copper hydroxide nanowires, silicon monoxide nanowires, and hydroxyapatite nanowires can be selected.

[0056] The second member is made of a base material that constitutes the separator body, and the first member is placed on the second member and supported by the second member. The separator body may be a battery separator in the prior art. In this embodiment, a separator that can stop electrons and pass ions is provided and used as the separator body, and plays a role corresponding to electrons and ions, respectively.

[0057] As described above, there are multiple options for the modifying material used to manufacture the first component, and similarly, there are multiple options for the base material used to manufacture the second component, and these can be selected appropriately according to specific performance and process requirements.

[0058] In this embodiment, the second member is preferably made of a polyolefin such as polyethylene, polypropylene, or the like.

[0059] Based on the above battery separator, an embodiment of the present disclosure further provides a battery, which may be a primary battery or a secondary battery, for example a rechargeable lithium ion battery. The battery has a housing in which the above battery separator is built-in, and a positive electrode and a negative electrode separated by the battery separator. A positive electrode part is formed between the positive electrode and the battery separator, and a negative electrode part is formed between the negative electrode and the battery separator. The positive electrode part and the negative electrode part are filled with the same electrolyte.

[0060] Corresponding to the above battery separator, an embodiment in the present disclosure further provides a method for manufacturing the battery separator. The manufacturing method includes the following steps. In step S101, a dispersion liquid in which nanowires are dispersed in a dispersant is prepared.

[0061] The nanowires are preferably well dispersed in the dispersant, and in order to preserve the structure of the nanowires, the dispersant is generally a poor solvent for the nanowires, i.e., the dispersant does not significantly dissolve the nanowires and destroy their nanostructure.

[0062] In addition, it is preferable that the nanowires are uniformly dispersed in the dispersant, rather than concentrating and sinking in the dispersant. In some cases, a dispersion in the form of a suspension, a suspension liquid, or an emulsion can be selected and used.

[0063] In some embodiments of the present disclosure, for example, the dispersant is water, and the nanowires are carbon nanotubes. The carbon nanotubes can be uniformly dispersed in water by ultrasonication, high-speed stirring, or other vibration methods. In general, in order to avoid the problem of uneven distribution of the nanowires in the dispersion, it is preferable to prepare the dispersion on the spot and use it on the spot. However, when there is not much demand or when a stable dispersion with relatively excellent dispersion uniformity is used, the dispersion may be prepared or purchased in advance and used. The concentration of the nanowires in the dispersion is 0.01 to 50 wt%, and may be, for example, 0.1 to 43 wt%, 3 to 36 wt%, 14 to 29 wt%, etc.

[0064] Regarding the selection of the material of the nanowire, please refer to the above, and the explanation will be omitted here.

[0065] In some improvement schemes, in order to improve the bonding reliability between the first and second components, an adhesive is usually added to the dispersant, which is usually compatible with the dispersant, i.e., does not cause significant stratification or the like, which impairs the uniformity of the nanowire distribution.

[0066] For example, in this embodiment, the dispersant may be one or more selected from water, ethanol, acetone, and N-methylpyrrolidone. The adhesive may be one or more selected from polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, styrene butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, and polyimide. The mass concentration of the adhesive may be 0.01 to 49%, 5 to 37%, 11 to 27%, 16 to 20%, etc.

[0067] In addition, the dispersion may contain the auxiliary agents glycerol, sodium butylbenzenesulfonate, propylene glycol, polyoxyethylene-thioether to provide a wetting effect.

[0068] Step S102 transfers the dispersion onto a surface of the second component, so as to place the nanowires on the surface of the second component in a layer, and removes the dispersant in the dispersion on the surface of the second component.

[0069] The method of transferring the dispersion may be, for example, coating such as spin coating, doctor blade coating, or dip coating. Removal of the dispersant in the dispersion is achieved by evaporation. For example, the second member on which the dispersion is placed is heated to evaporate the dispersant (e.g., water). Radiation heating can be used as the heating method. In addition, the evaporation rate of the dispersion is appropriately controlled to avoid impairing the reliability of the bond between the formed first member and the second member due to the irrationality of the evaporation method.

[0070] In a preferred refinement of the present disclosure, the dispersion is transferred to the surface of the second component by dip coating. For example, dip coating is carried out as follows. The second member is immersed in the dispersion at a first predetermined speed under tension and removed from the dispersion at a second predetermined speed. As the second member passes through the dispersion, the nanowires or an optional adhesive in the dispersion are bonded to the second member by chemical action, adsorption, capillary action, or the like. The dispersant in the dispersion is then removed from the surface of the second member in an appropriate manner so as to leave the nanowires on the surface of the second member.

[0071] Particularly, in this embodiment, the dispersion liquid is transferred to the second member by the film forming device. As shown in FIG.

[0072] The film forming apparatus has a liquid storage tank 401 for storing the dispersion liquid.

[0073] The film forming apparatus further includes a tensioning system 402. The tensioning system includes a plurality of rolls. As shown in FIG. 3, the tensioning system includes three rolls, one of which is disposed between the other two rolls, and a triangle can be formed by a line connecting the center points of the projected images of the three rolls on a plane. The second member in the battery separator is tensioned by the tensioning system. The tensioning system includes at least one dip roll 403 (i.e., a roll located in the above-mentioned middle portion) for immersing the second member 200 in the dispersion liquid, and a part or the whole of the dip roll enters the dispersion liquid (as an example, the immersion depth is 1 / 4 to the whole of its radius).

[0074] The depth to which the dip roll enters can be adjusted by a movement mechanism (not shown) for driving the dip roll in an appropriate manner, such as a vertical movement, relative to the dispersion liquid. The tension system is also configured to be able to appropriately drive the second member so that the depth to which the dip roll enters can be adjusted without changing the positions of the two rolls other than the dip roll. Alternatively, in some examples, any of the three rolls constituting the tension system can be moved so that the adjustment of the dip roll's depth can be more easily controlled.

[0075] More preferably, the dip roll 403 has a hollow portion 4031 and an air hole passage 4032 that communicates with the hollow portion and extends to the surface. The second member is in surface contact with the surface of the dip roll. A predetermined degree of vacuum is provided within the hollow portion, for example, the degree of vacuum is 0.01 to 0.1 MPa. A vacuum generator (not shown) for generating a desired degree of vacuum in the dip roll can be a commercially available vacuum pump or other equipment.

[0076] In this way, when the second component passes through the dispersion, the dispersion can be better adsorbed and bonded to the surface of the second component under the effect of negative pressure. Also, by controlling the air hole passage of the dip roll, the porosity, hole diameter, and hole distribution pattern of the first component can be adjusted to obtain the desired effect.

[0077] In addition, the thickness of the first component can be adjusted by adjusting the concentration of nanowires in the dispersion, the depth to which the dip roll penetrates the dispersion, and the degree of vacuum of the dip roll. The inventors discovered that the higher the concentration of the solution, the thicker the coating layer, the deeper the penetration depth, and the higher the degree of vacuum, the thicker the coating layer.

[0078] In the embodiment of the present disclosure, the battery separator has a layered structure, and is a multi-layer membrane structure. Among them, the second member is a base membrane, and the first member is a surface membrane. The surface membrane may be one layer or may be multi-layered. When the surface membrane is multi-layered, it can be disposed on two sides in the thickness direction of the base membrane, or on only one of the two sides in the thickness direction. When the surface membrane is disposed on two sides in the thickness direction of the base membrane, the number of layers of the surface membrane disposed on each side may be the same or different.

[0079] Table 1 below lists several examples of battery separators, including their manufacturing materials, processes, and performance.

[0080] [Table 1] Batteries were manufactured using the battery separators according to Examples 1 to 4 above, and their electrical performance was measured. The measurement results are shown in Table 2 below.

[0081] [Table 2] In Examples 1 to 4 and Comparative Examples 1 to 6 shown in Table 2, the batteries have the same structure and include a positive electrode, a negative electrode, an electrolyte, and a separator. The main difference is that the battery separators in Examples 1 to 4 are manufactured by the method according to the examples of the present disclosure and are provided with a nanowire coating layer. The battery separators in Comparative Examples 1 to 4 are made of a commercially available product and are provided with a coating layer made of a granular material on the order of millimeters. The battery separators in Comparative Examples 5 and 6 are made of a commercially available product and are not provided with a material for forming a coating layer. The polyethylene film and polypropylene film, for example, used as the base of the battery separators in each Example and Comparative Example, are commercially available products. The polyethylene film and polypropylene film can be manufactured by, for example, a wet non-woven method.

[0082] As can be seen from Tables 1 and 2 above, when the battery separator according to the embodiment of the present disclosure is used, the thermal stability of the battery separator is significantly improved, and the battery capacity retention rate of the battery is improved to a certain extent. In Tables 1 and 2 above, TD represents the thermal stability (thermal shrinkage rate) of the separator in the transverse direction, and MD represents the thermal stability (thermal shrinkage rate) in the longitudinal direction.

[0083] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Industrial Applicability]

[0084] The battery separator according to the present disclosure has a composite structure, innovates the conventional battery separator, and improves its thermal stability by using a modified material. Furthermore, by utilizing the modified material in the form of nanowires, the problem of the increase in thickness and weight of the separator caused by the use of the modified material can be avoided, and the thermal stability of the battery separator can be maintained while suppressing the increase in thickness and weight. [Explanation of symbols]

[0085] 100...first member, 200...second member, 300...porous structure, 401...storage tank, 402...tension system, 403...dip roll, 4031...cavity, 4032...vent passage, 200...second member.

Claims

1. A battery separator, comprising: A two-layer composite structure comprising a first member and a second member, the first component is a stack of nanowires made of a modified material and distributed in layers; the modified material comprises one or more of boron carbide nanowires, nanocellulose, copper hydroxide nanowires, silicon monoxide nanowires; The second member is made of a base material constituting a main body of the battery separator, and the first member is placed on a surface of the second member and supported by the second member; The first member has a thickness of 0.01 to 1 μm, preparing a dispersion in which the nanowires are dispersed in a dispersant; transferring the dispersion onto a surface of the second member so as to deposit the nanowires onto the surface of the second member in a layer, and removing the dispersant in the dispersion on the surface of the second member; The dispersion is transferred to the surface of the second member by dip coating; The dip coating includes immersing the second member in the dispersion liquid at a first predetermined speed while the second member is tensioned by tension, and removing the second member from the dispersion liquid at a second predetermined speed; The second member is tensioned by a tension system consisting of a plurality of rolls, the tension system includes at least one dip roll for immersing the second member in the dispersion liquid, and a part or all of the dip roll is immersed in the dispersion liquid; The dip roll has a cavity and an air hole passage communicating with the cavity and extending to the surface, the second member is in surface contact with the surface of the dip roll and has a predetermined vacuum degree within the cavity, The degree of vacuum is 0.01 to 0.1 MPa. A method for producing a battery separator comprising the steps of:

2. The method of claim 1 , wherein the nanowires have a length-to-diameter ratio of greater than 50.

3. 3. The method for producing a battery separator according to claim 2, wherein the nanowires have a diameter of 1 to 100 nm and a length of 0.1 to 100 μm.

4. 2. The method for producing a battery separator according to claim 1, wherein the base material is an organic polymer material, and the organic polymer material includes a polyolefin.

5. 5. The method for producing a battery separator according to claim 4, wherein the polyolefin comprises polyethylene.

6. The method for producing a battery separator according to claim 1 , wherein the first member has a porous structure.

7. 2. The method for producing a battery separator according to claim 1, wherein the dispersant contains one or more of water, ethanol, acetone, and N-methylpyrrolidone.

8. 8. The method for producing a battery separator according to claim 7, wherein the dispersion further contains an adhesive, and the adhesive contains one or more of polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, styrene-butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, and polyimide.

9. 8. The method for manufacturing a battery separator according to claim 7, wherein the dispersion further comprises an auxiliary agent, the auxiliary agent comprising glycerol, sodium butylbenzenesulfonate, propylene glycol, and polyoxyethylene-thioether.

10. 9. The method for producing a battery separator according to claim 8, wherein the mass concentration of the nanowires in the dispersion is 0.01 to 50%, and the mass concentration of the adhesive is 0.01 to 49%.

Images