Diaphragm and preparation method thereof, battery and electric equipment

Abstract

The invention discloses a diaphragm, a preparation method, a battery and electric equipment. The diaphragm comprises a base film and a gluing layer located on at least one side surface of the base film; the gluing layer comprises dye; the color of the dye is different from that of the base film. According to the diaphragm, the preparation method, the diaphragm and the gluing layer, the color difference is large, the diaphragm gluing area in unit area can be conveniently detected, detection can be conducted through CCD detection equipment, the uniformity of the diaphragm gluing layer can be easily controlled, and therefore the electrochemical performance of a battery and the bonding performance of the gluing layer are guaranteed.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a diaphragm and a preparation method thereof, a battery and an electrical device. Background Art

[0002] As a new type of secondary battery, lithium battery has the advantages of high energy density and long cycle life. As the scope of application continues to expand, lithium batteries are widely used in portable electronic devices, energy storage equipment, power vehicles and other fields, and especially in the context of the rapid development of the new energy industry, the application of lithium batteries in power vehicles is becoming more and more extensive.

[0003] As an important component of lithium batteries, the diaphragm plays a key role in preventing the positive and negative electrodes from directly contacting each other and causing a short circuit, and has an important impact on the safety of lithium batteries. Regarding the problem of the adhesion of the diaphragm to the electrode, the current main solution is to coat a rubber layer on one or both sides of the diaphragm. This rubber layer can effectively improve the adhesion of the diaphragm and has good wettability with the electrolyte.

[0004] However, there are many problems in the existing glue coating technology. The traditional glue coating diaphragm cannot detect the glue coating area per unit area. Taking the water-based PVDF (polyvinylidene fluoride) glue coating technology as an example, since it is impossible to effectively detect the glue coating area per unit area of ​​the diaphragm, it is difficult to control the coating uniformity, which is easy to affect the electrochemical performance of the battery and the bonding performance of the glue coating layer. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one purpose of the present application is to propose a diaphragm and a preparation method, a battery and an electrical device. The diaphragm and the preparation method of the present application have a large color difference between the diaphragm and the coating layer, which is convenient for detecting the diaphragm coating area per unit area, and can be detected by a CCD (charge-coupled device) detection device, which is conducive to controlling the uniformity of the diaphragm coating layer, thereby ensuring the electrochemical performance of the battery and the bonding performance of the coating layer.

[0006] The first aspect of the present application provides a diaphragm. According to an embodiment of the present application, the diaphragm includes a base film and a coating layer located on at least one side of the base film; the coating layer includes a dye; and the color of the dye is different from the color of the base film.

[0007] The present application adds a dye to the coating layer, and the color of the dye is different from the color of the base film. The color contrast between the coating layer and the base film is high, so that the coating area is clearly distinguished from the uncoated area, the coating recognition is high, and the recognition error is small. Therefore, the coating area of ​​the diaphragm within a unit area can be fully detected by CCD online and the equipment can be fully detected under existing conditions, intercepting unevenly coated diaphragms. In addition, the present application can be applied to coating layers of various thicknesses.

[0008] The second aspect of the present application provides a method for preparing a diaphragm, comprising the steps of:

[0009] mixing the dye with the glue coating slurry to obtain a mixed slurry;

[0010] The mixed slurry is coated on the base film to form a coating layer to obtain a separator; the color of the dye is different from the color of the base film.

[0011] The method for preparing the diaphragm provided in the embodiment of the present application is a method for preparing a glue-coated diaphragm. The existing glue-coating preparation process is not changed, and a dye is directly added to the glue-coating slurry. The preparation method is simple and is conducive to industrial production.

[0012] The present application adds a dye to the coating layer, and the color of the dye is different from the color of the base film. The color contrast between the coating layer and the base film is high, so that the coating area is clearly distinguished from the uncoated area, the coating recognition is high, and the recognition error is small. Therefore, the coating area of ​​the diaphragm within a unit area can be fully detected by CCD online and the equipment can be fully detected under existing conditions, intercepting unevenly coated diaphragms. In addition, the present application can be applied to coating layers of various thicknesses.

[0013] The third aspect of the present application provides a battery, comprising the above-mentioned diaphragm, or comprising the diaphragm obtained by the above-mentioned preparation method.

[0014] The battery provided in the present application has the above-mentioned diaphragm, which is convenient for detecting the diaphragm coating area per unit area during the preparation process, controlling the uniformity of the coating layer, and is beneficial to improving the electrochemical performance of the battery and the adhesion of the coating layer.

[0015] The fourth aspect of the present application proposes an electrical device, comprising the above-mentioned battery.

[0016] The electrical equipment provided in the present application has the above-mentioned battery, which is used to provide electrical energy supply and has high safety performance.

[0017] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. DETAILED DESCRIPTION

[0018] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0019] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0020] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this application.

[0021] In the present application, the terms "comprise" or "include" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0022] As an important component of lithium batteries, the diaphragm plays a key role in preventing the positive and negative electrodes from directly contacting each other and causing a short circuit, and has an important impact on the safety of lithium batteries. Regarding the problem of the adhesion of the diaphragm to the electrode, the current main solution is to coat a rubber layer on one or both sides of the diaphragm. This rubber layer can effectively improve the adhesion of the diaphragm and has good wettability with the electrolyte.

[0023] At present, in order to improve the wettability of the diaphragm and the electrolyte, enhance the thermal stability of the diaphragm, and improve the ion mobility, the coating layer on the surface of the diaphragm is usually not 100% fully covered, and the coating area of ​​the diaphragm per unit area is less than 100%. The traditional coating diaphragm cannot detect the coating area of ​​the diaphragm per unit area. Taking the water-based PVDF (polyvinylidene fluoride) coating technology as an example, since it is impossible to detect the coating area of ​​the diaphragm per unit area for effective detection, the coating amount of the coating diaphragm is too much or too little. Too much leads to an increased probability of diaphragm pore blockage and reduced battery electrical performance; too little leads to insufficient adhesion of the coating diaphragm, which fails to achieve the purpose of bonding the coating diaphragm. The CCD detection equipment has been further upgraded. Since the coating layer and the diaphragm are usually white, transparent or nearly transparent, the contrast difference between the two is low, and full online inspection cannot be achieved.

[0024] To this end, a first aspect of an embodiment of the present application proposes a diaphragm, comprising a base film and a coating layer located on at least one surface of the base film; the coating layer comprises a dye; the color of the dye is different from the color of the base film.

[0025] In the embodiment of the present application, a dye is added to the coating layer, and the color of the dye is different from the color of the base film. The color contrast between the coating layer and the base film is high, so that the coating area is clearly distinguished from the uncoated area, the coating recognition is high, and the recognition error is small. Therefore, the coating area of ​​the membrane within a unit area can be fully detected by CCD online and the equipment can be fully detected under existing conditions, intercepting unevenly coated membranes. In addition, the present application can be applied to coating layers of various thicknesses.

[0026] According to an embodiment of the present application, the raw material of the adhesive layer includes a hot-melt adhesive, and the starting volatilization temperature of the dye is less than or equal to the melting temperature of the hot-melt adhesive.

[0027] In the embodiments of the present application, the starting volatilization temperature of the dye added to the coating layer meets the above conditions. In addition to improving the color contrast between the coating layer and the base film, the dye is volatilized by heat during the hot melting process of the raw materials of the coating layer, and only a small amount of dye components remain in the final coating layer, which can greatly reduce the impact of the addition of the dye on the battery performance and help maintain the stability of the battery system. In a specific embodiment, a dye with a starting volatilization temperature suitable for the present application can be selected based on the raw material composition of the coating layer, the preparation process of the battery, etc.

[0028] According to an embodiment of the present application, the dye includes at least one of formaldehyde blue, citrulline and methylene blue.

[0029] In some embodiments, at least one dye selected from formaldehyde blue, citrulline and methylene blue is added to the coating layer to improve the color contrast between the coating layer and the base film, thereby realizing the detection of the coating area of ​​the diaphragm within a unit area, and achieving full online inspection through CCD detection equipment.

[0030] In some embodiments, at least one dye selected from formaldehyde blue, citrulline and methylene blue is added to the adhesive layer. These dyes have a relatively low starting volatilization temperature. During the hot melt treatment of the raw materials of the adhesive layer, the dye disappears or weakens due to heat, which can maintain the stability of the separator in the battery and reduce the impact of the dye addition on the battery performance.

[0031] Formaldehyde blue (Methyl Violet): Formaldehyde blue is a volatile dye, commonly used in biological staining, histology and microscopy. The temperature at which volatilization begins is about 150℃~180℃, and the temperature at which volatilization is completed is about 200℃~230℃.

[0032] Cresol Red: Cresol Red is a volatile dye that changes color in acid and alkali, and is widely used in biochemical analysis in chemical laboratories. The temperature at which volatilization begins is about 130℃~150℃, and the temperature at which volatilization is completed is about 180℃.

[0033] According to the embodiments of the present application, the color difference between the base film and the adhesive layer is 0.2NBS to 15NBS.

[0034] In the embodiment of the present application, dye is added during the preparation of the adhesive layer. During the preparation of the adhesive diaphragm, there is a large color difference between the base film and the adhesive layer (uncured) coated with the adhesive slurry, and the adhesive area of ​​the diaphragm per unit area can be detected to effectively control the uniformity of the adhesive. After the adhesive layer is cured, although the dye may be lost, there is still excess or residual, and at this time there is still a certain color difference between the base film and the adhesive layer. In a specific example, the color difference between the base film and the coating layer is 0.2NBS, 0.3NBS, 0.4NBS, 0.5NBS, 0.6NBS, 0.7NBS, 0.8NBS, 0.9NBS, 1NBS, 1.1NBS, 1.2NBS, 1.3NBS, 1.4NBS, 1.5NBS, 1.6NBS, 1.7NBS, 1.8NBS, 1.9NBS, 2NBS, 2.1NBS, 2.2NBS, 2.5NBS, 2.6NBS, 2.7NBS, 2.8NBS, 2.9NBS, 3NBS, 3.1NBS, 3.2NBS, 3 .3NBS, 3.4NBS, 3.5NBS, 3.6NBS, 3.7NBS, 3.8NBS, 3.9NBS, 4NBS, 4.1NBS, 4.2NBS, 4.3NBS, 4.4NBS, 4.5NBS, 4.6NBS, 4.7NBS, 4.8NB S, 4.9NBS, 5NBS, 5.1NBS, 5.2NBS, 5.3NBS, 5.4NBS, 5.5NBS, 5.6NBS, 5.7NBS, 5.8NBS, 5.9NBS, 6NBS, 6.1NBS, 6.2NBS, 6.3NBS, 6.4NB S, 6.5NBS, 6.6NBS, 6.7NBS, 6.8NBS, 6.9NBS, 7NBS, 7.1NBS, 7.2NBS, 7.3NBS, 7.4NBS, 7.5NBS, 7.6NBS, 7.7NBS, 7.8NBS, 7.9NBS, 8N BS, 8.1NBS, 8.2NBS, 8.3NBS, 8.4NBS, 8.5NBS, 8.6NBS, 8.7NBS, 8.8NBS, 8.9NBS, 9NBS, 9.1NBS, 9.2NBS, 9.3NBS, 9.4NBS, 9.5NBS, 9. 6NBS, 9.7NBS, 9.8NBS, 9.9NBS, 10NBS, 10.1NBS, 10.2NBS, 10.3NBS, 10.4NBS, 10.5NBS, 10.6NBS, 10.7NBS, 10.8NBS, 10.9NBS, 11N BS, 11.1NBS, 11.2NBS, 11.3NBS, 11.4NBS, 11.5NBS, 11.6NBS, 11.7NBS, 11.8NBS, 11.9NBS, 12NBS, 12.1NBS, 12.2NBS, 12.3NBS, 12.4NBS, 12.5NBS, 12.6NBS, 12.7NBS, 12.8NBS, 12.9NBS, 13NBS, 13.1NBS, 13.2NBS, 13.3NBS, 13.4NBS, 13.5NBS, 13.6NBS, 13.7NBS, 13.8NBS, 13.9NBS, 14NBS or 15NBS, or any other value between 0.2NBS and 15NBS. .

[0035] Furthermore, the color difference between the base film and the adhesive layer is 0.2NBS to 8NBS.

[0036] According to the embodiments of the present application, before the glue layer is cured, the color difference between the base film and the glue layer is 2NBS to 15NBS; a dye is added during the preparation of the glue layer. During the preparation of the glued diaphragm, there is a large color difference between the base film and the glue layer (uncured) coated with the glue slurry, and the glue coating area of ​​the diaphragm per unit area can be detected, effectively controlling the uniformity of the glue coating. During the curing process of the glue layer, dye loss may occur. If a volatile dye is selected to be added to the glue layer, the glue layer will volatilize during the preparation process, and most of the dye will evaporate from the glue layer for hours, reducing the impact on battery performance. In the end, there may be a small amount of dye residue in the glue layer, and the color difference between the base film and the coating will still be detected. Therefore, after the glue layer is cured, the color difference between the base film and the glue layer is 0.2NBS to 8NBS. Furthermore, the color difference between the base film and the glue layer is 0.2NBS to 3NBS.

[0037] According to an embodiment of the present application, the coating area of ​​the adhesive layer on the surface of the base film is 5% to 95% of the area of ​​the base film.

[0038] At present, in order to improve the wettability of the diaphragm and the electrolyte, enhance the thermal stability of the diaphragm, and improve the ion mobility, the coating layer on the surface of the diaphragm is usually not 100% fully covered, and the coating area of ​​the diaphragm per unit area is less than 100%. The traditional coating diaphragm cannot detect the coating area of ​​the diaphragm per unit area. However, the present application can improve the color contrast between the coating layer and the base film by adding a dye whose color is different from that of the base film to the coating layer, thereby realizing the detection of the coating area of ​​the diaphragm per unit area. Based on the current coverage of the coating layer, the present application can be applied to the case where the coating area of ​​the coating layer on the base film surface is 5% to 95% of the base film area. In a specific example, the coating area of ​​the adhesive layer on the surface of the base film is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc. of the area of ​​the base film.

[0039] According to an embodiment of the present application, the coating area of ​​the adhesive layer on the surface of the base film is 10% to 50% of the area of ​​the base film.

[0040] At present, the lower the coating area of ​​the adhesive layer on the surface of the base film is, the more difficult it is to identify, detect, and control the uniformity of the coating. However, the present application can improve the color contrast between the adhesive layer and the base film by adding a dye whose color is different from that of the base film to the adhesive layer. When the coating area on the surface of the base film is small, the randomly distributed small adhesive particles are thin and have low color contrast, and the coverage detection accuracy is low. The method of the present application can still effectively detect the adhesive coating area of ​​the diaphragm per unit area when the coating area on the surface of the base film is less than 50% of the base film area, which is of great significance for the preparation of the adhesive-coated diaphragm and improving battery performance.

[0041] In specific examples, the coating area of ​​the glue layer on the surface of the base film is 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50% of the area of ​​the base film.

[0042] Furthermore, the coating area of ​​the adhesive layer on the surface of the base film is 15% of the area of ​​the base film.

[0043] According to an embodiment of the present application, the coating layer further includes rubber particles, and the rubber particles include at least one of polyvinylidene fluoride rubber particles, polyvinyl alcohol rubber particles, polymethyl methacrylate rubber particles and AFL rubber particles.

[0044] In the embodiment of the present application, a hot melt adhesive can be used as the raw material of the adhesive layer, and the hot melt adhesive includes rubber particles. In the present application, the type of rubber particles used in the adhesive layer is not limited, as long as the requirements of the battery separator are met, and the rubber particles for the adhesive layer known in the art can be used.

[0045] In a specific example, the colloid particles of the present application may include at least one of polyvinylidene fluoride (PVDF) colloid particles, polyvinyl alcohol (PVA) colloid particles, polymethyl methacrylate (PMMA) colloid particles, and AFL colloid particles.

[0046] The AFL particles are "acrylic acid and polyacrylic acid modified particles", such as modified acrylic acid particles or polyacrylic acid modified particles.

[0047] According to an embodiment of the present application, the dye is soluble in the solvent or insoluble in the solvent.

[0048] The solubility of the dye selected to be added to the coating layer in the embodiment of the present application is not limited, and the dye may be soluble in a solvent (such as water or an organic solvent) or insoluble in a solvent.

[0049] Furthermore, the dye is insoluble in the solvent or the solubility of the dye in the solvent is low.

[0050] In the embodiments of the present application, insoluble or low-solubility dyes are added to the coating slurry, and the dyes exist in the coating slurry in the form of particles. Later, during the desolventizing process, the solvent evaporates, and pores are formed in the coating layer after evaporation, which is conducive to air permeability and serves as a lithium ion channel, thereby reducing the probability of pore blockage in the coating layer.

[0051] A second aspect of the embodiment of the present application provides a method for preparing a diaphragm, comprising the steps of:

[0052] mixing the dye with the glue coating slurry to obtain a mixed slurry;

[0053] The mixed slurry is coated on the base film to form a coating layer to obtain a separator; the color of the dye is different from the color of the base film.

[0054] The method for preparing the diaphragm provided in the embodiment of the present application is a method for preparing a glue-coated diaphragm. The existing glue-coating preparation process is not changed, and a dye is directly added to the glue-coating slurry. The preparation method is simple and is conducive to industrial production.

[0055] In the embodiment of the present application, a dye is added to the coating layer, and the color of the dye is different from the color of the base film. The color contrast between the coating layer and the base film is high, so that the coating area is clearly distinguished from the uncoated area, the coating recognition is high, and the recognition error is small. Therefore, the coating area of ​​the membrane within a unit area can be fully detected by CCD online and the equipment can be fully detected under existing conditions, intercepting unevenly coated membranes. In addition, the present application can be applied to coating layers of various thicknesses.

[0056] According to the embodiments of the present application, the dye satisfies at least one of the following:

[0057] The raw material of the adhesive layer includes a hot-melt adhesive, and the starting volatilization temperature of the dye is less than or equal to the melting temperature of the hot-melt adhesive;

[0058] The dye comprises at least one of formaldehyde blue, citrulline and methylene blue.

[0059] In the embodiments of the present application, the starting volatilization temperature of the dye added to the coating layer meets the above conditions. In addition to improving the color contrast between the coating layer and the base film, the dye is volatilized by heat during the hot melting process of the raw materials of the coating layer, and only a small amount of dye components remain in the final coating layer, which can greatly reduce the impact of the addition of the dye on the battery performance and help maintain the stability of the battery system. In a specific embodiment, a dye with a starting volatilization temperature suitable for the present application can be selected based on the raw material composition of the coating layer, the preparation process of the battery, etc.

[0060] In some embodiments, at least one dye selected from formaldehyde blue, citrulline and methylene blue is added to the coating layer to improve the color contrast between the coating layer and the base film, thereby realizing the detection of the coating area of ​​the diaphragm within a unit area, and achieving full online inspection through CCD detection equipment.

[0061] In some embodiments, at least one dye selected from formaldehyde blue, citrulline and methylene blue is added to the adhesive layer. These dyes have a relatively low starting volatilization temperature. During the hot melt treatment of the raw materials of the adhesive layer, the dye disappears or weakens due to heat, which can maintain the stability of the separator in the battery and reduce the impact of the dye addition on the battery performance.

[0062] According to an embodiment of the present application, the preparation method further includes: the step of coating the mixed slurry on the base film to form a coating layer includes: coating the mixed slurry on the base film and then performing a heat melting treatment.

[0063] In the method for preparing the glue-coated diaphragm, after the glue-coating slurry is coated on the base film, it needs to be subjected to a heat melting treatment to achieve solidification and finally form a glue-coating layer.

[0064] If the dye is a volatile dye and the starting volatilization temperature of the dye is less than or equal to the melting temperature of the hot-melt adhesive, the dye will volatilize during the hot melting process of the raw materials of the coating layer, which can maintain the stability of the separator in the battery and reduce the impact of the dye addition on the battery performance.

[0065] When the diaphragm is used in the process of preparing batteries, the coated diaphragm is rolled into the pole core. In the middle of the battery core preparation, the pole core enters the baking process. The dye on the diaphragm is volatilized after high-temperature baking, thereby reducing the influence of the dye on the battery performance.

[0066] According to an embodiment of the present application, the coating area of ​​the mixed slurry on the surface of the base film is 5% to 95% of the area of ​​the base film.

[0067] At present, in order to improve the wettability of the diaphragm and the electrolyte, enhance the thermal stability of the diaphragm, and improve the ion mobility, the coating layer on the surface of the diaphragm is usually not 100% fully covered, and the coating area of ​​the diaphragm per unit area is less than 100%. The traditional coating diaphragm cannot detect the coating area of ​​the diaphragm per unit area. However, the present application can improve the color contrast between the coating layer and the base film by adding a dye whose color is different from that of the base film to the coating layer, thereby realizing the detection of the coating area of ​​the diaphragm per unit area. Based on the current coverage of the coating layer, the present application can be applied to the case where the coating area of ​​the coating layer on the base film surface is 5% to 95% of the base film area. In a specific example, the coating area of ​​the adhesive layer on the surface of the base film is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc. of the area of ​​the base film.

[0068] According to an embodiment of the present application, the coating area of ​​the adhesive layer on the surface of the base film is 10% to 50% of the area of ​​the base film. In a specific example, the coating area of ​​the adhesive layer on the surface of the base film is 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, etc. of the area of ​​the base film. Furthermore, the coating area of ​​the adhesive layer on the surface of the base film is 15% of the area of ​​the base film.

[0069] According to an embodiment of the present application, the added amount of the dye is within 3% of the mass of the glue slurry.

[0070] In the embodiment of the present application, the more dye is added to the coating slurry, the greater the color contrast between the coating layer and the base film, but it may affect the electrochemical performance of the battery separator, reduce the electrochemical performance of the battery, and increase the preparation cost. In addition, the amount of coating has a strong correlation with the depth of color.

[0071] In the embodiment of the present application, the amount of dye added to the glue slurry meets the above conditions, which is beneficial to balance the color contrast between the glue layer and the base film, battery performance and preparation cost, and realizes effective detection of the glue area of ​​the diaphragm per unit area. In a specific example, the amount of dye added accounts for within 3%, within 2.8%, within 2.6%, within 2.4%, within 2.2%, within 2.0%, within 1.8%, within 1.6%, within 1.4%, within 1.2%, within 1%, within 0.8%, within 0.6%, within 0.4%, within 0.2%, within 0.1%, within 0.08%, within 0.06%, within 0.04%, within 0.02%, within 0.01%, within 0.005%, etc. of the mass of the glue slurry.

[0072] According to the embodiment of the present application, the amount of dye added accounts for 0.01% to 1% of the mass of the glue slurry.

[0073] In the embodiment of the present application, the amount of dye added is 0.01% to 1% of the mass of the glue slurry, which can effectively balance the color contrast between the glue layer and the base film, battery performance and preparation cost, and realize the effective detection of the diaphragm glue area per unit area, which is beneficial to improve the electrochemical performance of the battery and ensure the bonding performance of the glue layer. In the specific example, the amount of dye added is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc. of the mass of the glue slurry.

[0074] According to an embodiment of the present application, the preparation method further satisfies at least one of the following:

[0075] The coating slurry includes rubber particles and a solvent; the rubber particles include at least one of polyvinylidene fluoride rubber particles, polyvinyl alcohol rubber particles, polymethyl methacrylate rubber particles and AFL rubber particles; the solvent includes water or an organic solvent;

[0076] The material of the base film includes at least one of polyolefin, polyvinylidene fluoride, aramid, cellulose and polyimide.

[0077] In the present application, the type of the colloid particles used in the coating layer is not limited, as long as the requirements of the battery separator are met, and the colloid particles for the coating layer known in the art can be used. The material of the base film is not limited, and the material of the base film known in the art can be used.

[0078] In a specific example, the colloid particles of the present application may include at least one of polyvinylidene fluoride (PVDF) colloid particles, polyvinyl alcohol (PVA) colloid particles, polymethyl methacrylate (PMMA) colloid particles, and AFL colloid particles.

[0079] The AFL particles are "acrylic acid and polyacrylic acid modified particles", such as modified acrylic acid particles or polyacrylic acid modified particles.

[0080] The material of the base film includes at least one of polyolefin, polyvinylidene fluoride, aramid, cellulose and polyimide, and in specific examples, at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, cellulose and polyimide.

[0081] According to an embodiment of the present application, the organic solvent includes at least one of acetone, N-methylpyrrolidone (NMP), n-hexane, dimethylformamide (DMF), dimethylacetamide (DMAC) and dimethyl sulfoxide (DMSO).

[0082] According to an embodiment of the present application, the coating slurry also includes other additives, and the other additives include at least one of a dispersant, a wetting agent and a binder.

[0083] The dispersant, wetting agent and binder can be selected based on the additives for the diaphragm coating layer known in the art.

[0084] Furthermore, the dispersant includes an organic dispersant and / or an inorganic dispersant.

[0085] Furthermore, the organic dispersant includes, but is not limited to, at least one of aliphatic amides, triethylhexyl phosphate, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide, guar gum and polyethylene glycol esters of fatty acids.

[0086] Furthermore, the inorganic dispersant includes but is not limited to at least one of silicates and alkali metal phosphates. The alkali metal phosphates include but are not limited to at least one of sodium tripolyphosphate, sodium hexametaphosphate and sodium pyrophosphate.

[0087] Furthermore, the wetting agent includes but is not limited to: at least one of anionic and nonionic surfactants. The wetting agent is mainly used to solve the problem of excessive surface tension of the slurry, facilitate coating on the base film to form a lithium battery separator, and also improve the adhesion between the slurry and the separator.

[0088] Furthermore, the adhesive includes but is not limited to an acrylic adhesive.

[0089] According to an embodiment of the present application, the raw materials of the slurry include colloid particles, a dispersant, a wetting agent, a binder and water; the mass ratio of the raw materials of the slurry and the dye satisfies:

[0090] The mass ratio of the colloid particles, dispersant, wetting agent, binder, water and dye is 1:(0.05-0.1):(0.005-0.009):(0.1-0.5):(2-15):(0.05-1).

[0091] The composition formula of the water-based glue slurry provided in the embodiment of the present application meets the above requirements. By using the water-based glue coating technology, a large color contrast between the glue layer and the base film can be obtained, which is convenient for detecting the glue coating area of ​​the diaphragm per unit area. During the preparation process, the CCD detection equipment can be used for full online and full equipment detection to intercept unevenly coated diaphragms, improve coating uniformity, and improve the electrochemical properties of the battery and the bonding properties of the glue layer. In the specific example, the mass ratio of the colloid particles, dispersant, wetting agent, binder, water, and dye is 1: (0.05-0.1): (0.005-0.009): (0.1-0.5): (2-15): 0.05, 1: (0.05-0.1): (0.005-0.009): (0.1-0.5): (2-15): 0.08, 1: (0.05-0.1): (0.005-0.0 09):(0.1~0.5):(2~15):0.1, 1:(0.05~0.1):(0.005~0.009):(0.1~0.5):(2~15):0.2, 1:(0.05~0.1):(0.005~0.009):(0.1~0.5):(2~15):0.3, 1:(0.05~0.1):(0.005~0.009):(0.1 ~0.5):(2~15):0.4、1:(0.05~0.1):(0.005~0.009):(0.1~0.5):(2~15):0.5、1:(0.05~0.1):(0.005~0.009):(0.1~0.5):(2~15):0.6、1:(0.05~0.1):(0.005~0.009):(0.1~0.5):(2 ~15):0.7, 1:(0.05~0.1):(0.005~0.009):(0.1~0.5):(2~15):0.8, 1:(0.05~0.1):(0.005~0.009):(0.1~0.5):(2~15):0.9, 1:(0.05~0.1):(0.005~0.009):(0.1~0.5):(2~15):1, etc.

[0092] Furthermore, the mass ratio of the colloid particles, the dispersant, the wetting agent, the binder, the water and the dye is 1:0.08:0.007:0.3:10:0.5.

[0093] A third aspect of the embodiments of the present application provides a battery, comprising the above-mentioned diaphragm, or comprising the diaphragm obtained by the above-mentioned preparation method.

[0094] The battery provided in the embodiment of the present application has the above-mentioned diaphragm, which is convenient for detecting the diaphragm coating area per unit area during the preparation process, controlling the uniformity of the coating layer, and is beneficial to improving the electrochemical performance of the battery and the adhesion of the coating layer.

[0095] The isolation membrane is set between the positive electrode sheet and the negative electrode sheet. Its main function is to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0096] According to an embodiment of the present application, the battery further includes a positive electrode sheet, a negative electrode sheet and an electrolyte.

[0097] During the battery charging and discharging process, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0098] According to an embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material. The raw materials of the positive electrode current collector and the positive electrode active material layer (including the positive electrode active material) can be materials for batteries known in the art.

[0099] According to an embodiment of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material. Alternatively, the negative electrode sheet uses a lithium metal sheet. The raw materials of the negative electrode current collector and the negative electrode active material layer (including the negative electrode active material) can use materials for batteries known in the art.

[0100] According to the embodiments of the present application, the electrolyte may be an electrolyte known in the art.

[0101] A fourth aspect of the embodiments of the present application provides an electrical device, comprising the above-mentioned battery.

[0102] The electrical equipment provided in the embodiment of the present application has the above-mentioned battery, which is used to provide electrical energy supply and has high safety and long service life.

[0103] Electrical devices may include mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0104] As another embodiment, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

[0105] It should be noted that the features and advantages described above for the diaphragms of the first and second aspects of the present application are also applicable to the battery of the third aspect and the electrical equipment of the fourth aspect of the present application, and will not be repeated here.

[0106] The scheme of the present application will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the literature in this area or the product specification are carried out. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0107] Example 1

[0108] 1. Preparation of positive electrode

[0109] The positive electrode active material lithium iron phosphate, the conductive agent conductive carbon black, the binder polyvinylidene fluoride (PVDF), and the solvent N-methylpyrrolidone (NMP) are stirred and mixed in a mass ratio of 100:8:2.5:60 to obtain a positive electrode slurry, and the positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained after drying, rolling and sheeting.

[0110] 2. Preparation of negative electrode sheet

[0111] The negative electrode active material graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), conductive graphite, N-methylpyrrolidone (NMP) and water are stirred and mixed in a mass ratio of 100:3:1.5:1:2:115 to obtain a negative electrode slurry, and the negative electrode slurry is applied to both sides of the negative electrode current collector copper foil, and the negative electrode sheet is obtained after drying, rolling and sheeting.

[0112] 3. Preparation of electrolyte

[0113] Electrolyte (the electrolyte consists of 13wt% LiPF6, 26wt% ethylene carbonate (EC), and 61wt% diethyl carbonate (DEC))

[0114] 4. Preparation of diaphragm

[0115] The mass ratio of colloid particles (polyvinylidene fluoride (PVDF) colloid particles), dispersant (vinyl bisstearamide), wetting agent (sodium dodecyl sulfate), binder (methyl acrylate), water and dye (methylene blue dye) is 1:0.08:0.007:0.3:10:0.5, which are mixed to form slurry; the slurry is applied to a layer of polypropylene diaphragm by water-based spraying with a coverage rate of 25% to form a colored coated diaphragm.

[0116] 5. Lithium-ion battery preparation

[0117] The negative electrode sheet, separator and positive electrode sheet prepared above are placed in order and wound to obtain a battery cell. After the battery cell is placed in an outer packaging foil, the battery is baked at 120°C for 10 hours, and an electrolyte is injected (the electrolyte consists of 13wt% LiPF6, 26wt% EC, and 61wt% DEC), and a lithium-ion battery is obtained under a restraining pressure of 0.3MPa.

[0118] Example 2-3

[0119] Example 2 adopts the method of Example 1, except that citrulline is used to replace the methylene blue in Example 1.

[0120] Example 3 adopts the method of Example 1, except that formaldehyde blue is used to replace the methylene blue in Example 1.

[0121] Embodiment 4-6

[0122] Example 4 adopts the method of Example 1, except that the mass ratio of the colloid particles, dispersant, wetting agent, binder, water and dye is 1:0.08:0.007:0.3:10:0.05.

[0123] Example 5 adopts the method of Example 1, except that the mass ratio of the colloid particles, the dispersant, the wetting agent, the binder, the water, and the dye is 1:0.08:0.007:0.3:10:0.1.

[0124] Example 6 adopts the method of Example 1, except that the mass ratio of the colloid particles, dispersant, wetting agent, binder, water and dye is 1:0.08:0.007:0.3:10:1.

[0125] Embodiment 7-9

[0126] Example 7 adopts the method of Example 1, except that the coating area of ​​the slurry on the surface of the base film accounts for 5% of the area of ​​the base film.

[0127] Example 8 adopts the method of Example 1, except that the coating area of ​​the slurry on the surface of the base film accounts for 50% of the area of ​​the base film.

[0128] Example 9 adopts the method of Example 1, except that the coating area of ​​the slurry on the surface of the base film accounts for 95% of the area of ​​the base film.

[0129] Example 10

[0130] The method of Example 1 is adopted, except that the material of the base film is replaced by aramid.

[0131] Embodiment 11

[0132] The method of Example 1 is adopted, except that the drying temperature is replaced with 80°C.

[0133] Comparative Example 1

[0134] The method of Example 1 is adopted, except that no dye is added to the glue slurry during the preparation of the diaphragm.

[0135] Performance Testing

[0136] 1. Detection method:

[0137] 1. Color difference: Take the samples provided in the embodiments and comparative examples as samples and measure them using a colorimeter. The specific steps are as follows:

[0138] (1) Turn on the device: First, turn on the colorimeter. Press the power button and wait for the device to complete the self-test.

[0139] (2) Select calibration mode: Switch to calibration mode and perform white standard calibration on a blank plate, followed by black standard calibration.

[0140] (3) Select measurement mode: Select the color measurement mode in the device, select the sample to be measured, and place it on the test bench.

[0141] (4) Setting conditions: The tester is placed vertically to measure the sample.

[0142] (5) Measurement: Press the measurement button to measure the color and record the data △E.

[0143] 2. Performance test results:

[0144] 1. Color difference detection results.

[0145] The color difference test results of the samples provided in the embodiments and comparative examples are shown in Table 1.

[0146] As can be seen from Table 1, in the solution provided in the embodiment of the present application, in the process of preparing the battery diaphragm, a dye is added to the coating layer. The color of the dye is different from the color of the base film. The color contrast between the coating layer and the base film is high, and the color difference is large, so that the coated area is obviously different from the uncoated area, the coating recognition is high, and the recognition error is small. Therefore, for the diaphragm coating area per unit area, CCD online full and equipment full detection can be achieved under existing conditions to intercept unevenly coated diaphragms.

[0147] Table 1 Color difference detection results

[0148] Sample Before drying △E(NBS) After drying △E(NBS) Example 1 6.27 0.30 Example 2 6.30 3.0 Example 3 6.77 2.2 Example 4 3.10 0.21 Example 5 4.93 0.23 Example 6 7.98 0.42 Example 7 3.24 0.22 Example 8 7.24 0.61 Example 9 10.34 1.34 Example 10 6.32 0.33 Embodiment 11 6.27 5.98 Comparative Example 1 0.11 0.11

[0149] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A diaphragm, characterized in that: It comprises a base film and a coating layer located on at least one side of the base film; The coating layer includes a dye; The color of the dye is different from the color of the base film.

2. The diaphragm according to claim 1, characterized in that: The raw material of the adhesive layer includes a hot-melt adhesive, and the starting volatilization temperature of the dye is less than or equal to the melting temperature of the hot-melt adhesive.

3. The diaphragm according to claim 1 or 2, characterized in that: The dye comprises at least one of formaldehyde blue, citrulline and methylene blue.

4. The diaphragm according to any one of claims 1 to 3, characterized in that: The color difference between the base film and the adhesive layer is 0.2NBS to 15NBS.

5. The diaphragm according to any one of claims 1 to 4, characterized in that: The coating area of ​​the adhesive layer on the surface of the base film is 5% to 95% of the area of ​​the base film.

6. The diaphragm according to any one of claims 4 to 5, characterized in that The coating area of ​​the adhesive layer on the surface of the base film is 10% to 50% of the area of ​​the base film.

7. The diaphragm according to any one of claims 4 to 6, characterized in that The coating layer includes rubber particles, and the rubber particles include at least one of polyvinylidene fluoride rubber particles, polyvinyl alcohol rubber particles, polymethyl methacrylate rubber particles and AFL rubber particles.

8. A method for preparing a diaphragm, characterized in that: Includes steps: mixing the dye with the glue coating slurry to obtain a mixed slurry; The mixed slurry is coated on a base film to form a coating layer to obtain a separator; the color of the dye is different from the color of the base film.

9. The method for preparing the diaphragm according to Example 8 of the present application is characterized in that: The dye satisfies at least one of the following: The raw material of the adhesive layer includes a hot-melt adhesive, and the starting volatilization temperature of the dye is less than or equal to the melting temperature of the hot-melt adhesive; The dye comprises at least one of formaldehyde blue, citrulline and methylene blue.

10. The method for preparing a diaphragm according to claim 8 or 9, characterized in that: The step of coating the mixed slurry on the base film to form a coating layer includes: coating the mixed slurry on the base film and then performing a heat melting treatment.

11. The method for preparing a diaphragm according to any one of claims 8 to 10, characterized in that: The coating area of ​​the mixed slurry on the surface of the base film is 5% to 95% of the area of ​​the base film.

12. The method for preparing a diaphragm according to any one of claims 8 to 11, characterized in that: The added amount of the dye is within 3% of the mass of the glue slurry.

13. The method for preparing a diaphragm according to any one of claims 8 to 12, characterized in that: The added amount of the dye accounts for 0.01% to 1% of the mass of the glue slurry.

14. The method for preparing a diaphragm according to any one of claims 8 to 13, characterized in that: Also meet at least one of the following: The coating slurry comprises colloid particles and a solvent; the colloid particles comprise at least one of polyvinylidene fluoride colloid particles, polyvinyl alcohol colloid particles, polymethyl methacrylate colloid particles and AFL colloid particles; the solvent comprises water or an organic solvent; The material of the base film includes at least one of polyolefin, polyvinylidene fluoride, aramid, cellulose and polyimide.

15. The method for preparing a diaphragm according to any one of claims 8 to 14, characterized in that: The raw materials of the slurry include colloid particles, a dispersant, a wetting agent, a binder and water; the mass ratio of the raw materials of the slurry and the dye satisfies: The mass ratio of the colloid particles, dispersant, wetting agent, binder, water and dye is 1:(0.05-0.1):(0.005-0.009):(0.1-0.5):(2-15):(0.05-1).

16. A battery, characterized in that: A diaphragm comprising any one of claims 1 to 7, or a diaphragm obtained by the preparation method according to any one of claims 8 to 15.

17. An electrical equipment, characterized in that: Comprising the battery of claim 16.