Coating slurry, coating separator, method for manufacturing a separator, and battery

Abstract

The present invention provides a coating slurry, a coated separator, a method for producing the same, and a battery. The coating slurry includes a solvent, a binder polymer resin, and a photoinitiator as main components, and the weight ratio of the photoinitiator in the slurry is 0.08-1.0wt%, and the binder polymer resin includes any one of PVDF-based binder resin polymer, polyimide, polyetherimide, and polymethyl methacrylate, or a combination thereof. By setting the weight ratio of the photoinitiator in the slurry to 0.08-1.0wt%, within this weight ratio range, after the slurry is coated on the base film, the photoinitiator can reliably penetrate into the substrate layer and generate sufficient active radicals in the base film, ceramic layer, and their bonding interface layer, thereby ensuring sufficient photoinitiation efficiency and crosslinking degree, ensuring the complete crosslinking effect of the entire separator, and greatly increasing the film rupture temperature of the product. In addition, the content of the photoinitiator remaining in the adhesive layer is not large, so that it does not affect the sheet resistance of the separator and does not affect the interface impedance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separators, and particularly to a coating slurry for coating a battery separator, a separator coated with the slurry, a method for manufacturing a separator, and a battery.

Background Art

[0002] The separator of a lithium-ion battery is one of the four important components of a lithium-ion battery. In a lithium-ion battery, it separates the positive electrode and the negative electrode, allows lithium ions to pass through, and insulates electrons. The quality of the separator's performance directly affects the performance of the lithium-ion battery and is one of the important technologies that limit the development of lithium-ion batteries.

[0003] The separators of lithium-ion batteries applied in hybrid electric vehicles (HEV: Hybrid Electric Vehicle), electric vehicles (EV: Electric Vehicle), and the energy storage field need to have performance such as high heat resistance, low impedance, and high adhesiveness.

[0004] However, since the current heat resistance of the separator is not yet ideal, how to effectively improve the heat resistance of the separator has become a technical problem to be solved in the industry.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention provides a coating slurry for improving the heat resistance of a battery separator, a coated separator, methods for manufacturing them, and a battery.

Means for Solving the Problems

[0006] According to the first aspect of the present invention, there is provided a coating slurry containing a solvent, a binder polymer resin, and a photoinitiator as main components, wherein the weight ratio of the photoinitiator in the slurry is 0.08 to 1.0 wt%, and the binder polymer resin includes any one or a combination of a PVDF-based binder resin polymer, polyimide, polyetherimide, and polymethyl methacrylate.

[0007] In some embodiments, the PVDF-based binder resin polymer includes any one or a combination of a PVDF homopolymer, a vinylidene fluoride - hexafluoropropylene copolymer, a polyvinylidene fluoride - tetrafluoroethylene - propylene terpolymer, and a polyvinylidene fluoride - trifluoroethylene - chlorotrifluoroethylene terpolymer.

[0008] In some embodiments, the photoinitiator includes any one or a combination of ITX and benzophenone.

[0009] According to the second aspect of the present invention, there is provided a coated separator including a base film, a ceramic layer, and an adhesive layer, wherein the ceramic layer is coated on one or both sides of the base film, the adhesive layer is coated on the ceramic layer, and the adhesive layer is formed by coating the coating slurry described in the first aspect and its possible forms.

[0010] In some embodiments, the weight ratio of the photoinitiator in the adhesive layer is 0.05 to 0.3 wt%.

[0011] In some embodiments, the entire surface of the ceramic layer is coated with the adhesive layer.

[0012] In some embodiments, the adhesive layer is distributed on the ceramic layer at intervals.

[0013] In some embodiments, the area ratio of the long adhesive layer to the gap is 1:1 to 5:1, and the gap is the gap between two adjacent adhesive layers.

[0014] In some embodiments, the material of the ceramic layer includes an inorganic material, an acrylate-based adhesive, a polyacrylic acid-based adhesive, a dispersant, a wetting agent, a thickening agent, and an antifoaming agent.

[0015] In some embodiments, the inorganic material may be one or more of silica, alumina, boehmite, titanium oxide, magnesium oxide, and nanofibers.

[0016] In some embodiments, the base film is a PP base film, a PE base film, or a PP / PE / PP composite base film. According to a third aspect of the present invention, it includes a base film, a ceramic layer, and an adhesive layer. The ceramic layer is coated on one or both sides of the base film, and the adhesive layer is coated on the ceramic layer, with an adhesive strength of 15 gf / 25 mm or more, a film breaking temperature higher than 180°C, and a sheet resistance of 1.4 Ω·cm 2 A coated separator is provided as follows.

[0017] According to a fourth aspect of the present invention, (1) providing a base film coated with a ceramic layer on one or both sides; (2) Manufacturing a slurry: adding 5 to 3 0 wt% or less of a binder polymer resin and 0.08 to 1.0 wt% of a photoinitiator to a solvent and dissolving well to obtain a coating slurry; (3) Coating: coating the coating slurry manufactured above on the ceramic layer to form an adhesive layer on the ceramic layer; (4) UV crosslinking: A step of subjecting the base film after coating to a crosslinking reaction by irradiating with ultraviolet rays to obtain a corresponding coated separator, and a method for manufacturing a coated separator according to the above second aspect and its possible forms, or the third aspect is provided.

[0018] In some embodiments, the coating in step (3) is specifically a full-surface coating in which the coating slurry manufactured above is coated on the entire surface of the ceramic layer to form an adhesive layer on the entire surface of the ceramic layer.

[0019] In some embodiments, the coating in step (3) is specifically a gap coating in which the coating slurry manufactured above is gap-coated on the ceramic layer on which the adhesive layer is formed at intervals.

[0020] In some embodiments, the wavelength of the ultraviolet ray used is in the range of 210 nm to 420 nm, the UV crosslinking time is 0.001 s to 10 s, and the irradiation light intensity is 50 mj / cm 2 or more.

[0021] According to a fifth aspect of the present invention, a battery is provided, which includes the coated separator according to the above second aspect and its possible aspects or the third aspect, a positive electrode, a negative electrode, and an electrolyte.

Effects of the Invention

[0022] Compared with the prior art, the present invention has at least the following technical effects.

[0023] In the coating slurry and the coated separator according to the present invention, by setting the weight ratio of the photoinitiator in the slurry to 0.08 to 1.0 wt%, within this weight ratio range, after the slurry is coated on the base film, the photoinitiator can surely penetrate into the base material layer (ceramic layer and base film), thereby ensuring that the photoinitiator generates sufficient active radicals in the base film, ceramic layer and their bonding interface layer, making the photoinitiation efficiency and crosslinking degree sufficient, ensuring the complete crosslinking effect of the entire separator, greatly increasing the breakdown temperature of the product, while the content of the photoinitiator remaining in the adhesive layer is not much, so it does not affect the sheet resistance of the separator and does not affect the interfacial impedance of the battery.

[0024] In a more preferred embodiment, the present invention provides a coated separator in which, by setting the weight ratio of the photoinitiator in the adhesive layer to 0.05 to 0.3 wt%, even if the product raises the breakdown temperature, it hardly affects the sheet resistance of the separator.

[0025] In a more preferred embodiment, in the coated separator according to the present invention and the manufacturing method of the coated separator, the adhesive layer is gap-coated on the ceramic layer, that is, the adhesive layer is distributed at intervals in a long strip shape on the ceramic layer. Compared with full-surface coating, gap coating utilizes capillary action to achieve a better penetration effect, enabling the photoinitiator to penetrate more surely into the base material layer (ceramic layer and base film) after the slurry is coated on the base film.

Brief Description of the Drawings

[0026] Hereinafter, the present invention will be further described with reference to the drawings and specific embodiments.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 7

Mode for Carrying Out the Invention

[0027] Hereinafter, the technical solutions in the embodiments of the present invention will be clearly and completely described. It is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by those skilled in the art without creative labor based on the embodiments of the present invention belong to the protection scope of the present invention.

[0028] Before submitting this application, the applicant conducts a series of research and experiments on existing separators.

[0029] Here, in order to ensure heat resistance, first, heat resistance is ensured by coating a ceramic layer on both sides or one side of a PP, PE or PP / PE / PP base film. Next, a manufacturing process by CCS+NIPS laminated coating is adopted in which a binder resin is coated on the ceramic layer so as to satisfy adhesiveness. However, the breakdown temperature of the obtained product is still limited.

[0030] Another method is an oil-based mixed coating in which a high heat-resistant binder resin (e.g., polyetherimide) and a photoinitiator are coated on a base film and UV-crosslinked. However, in the conventional oil-based mixed coating process, the overall performance of the product is not good.

[0031] In order to solve the problem of poor heat resistance of the separator, the applicant conducted a series of theoretical studies and experimental verifications, such as changing the conventional high heat-resistant binder resin to an ultra-high heat-resistant binder resin (e.g., polyetherimide), but the improvement in heat resistance was not significant.

[0032] As a further research means, an attempt was made to change the content of the binder polymer resin, but the improvement in heat resistance was not significant.

[0033] Therefore, the technical solution of this application is obtained through a series of research and experiments on the above problems existing in the laminated coating manufacturing process and the oil-based mixed coating process, aiming to solve the problem of how to improve the heat resistance of the separator.

[0034] Through experimental verification and analysis, the Applicant innovatively discovered a new manufacturing process for coated separators. As a result of combining the advantages of the CCS+NIPS laminated coating manufacturing process and the oil-based mixed coating process, first, a ceramic layer is coated on both sides or one side of a PP, PE, or PP / PE / PP base film. Then, a binder polymer resin slurry containing a photoinitiator is coated on the ceramic layer, and a cross-linking reaction is initiated by ultraviolet irradiation to obtain the corresponding coated separator. This process combines the advantages of the CCS+NIPS laminated coating manufacturing process and the oil-based mixed coating process, improving the heat resistance and film-breaking temperature of the separator. However, even in this process, the improvement in the heat resistance of the separator was not very apparent. As a result of further research and development and testing by the Applicant, it was found that the amount of photoinitiator added has a very important impact on the performance of the product. If the amount of photoinitiator added is too much, side reactions will occur during the operation of the obtained separator, affecting the performance of the product. If the amount of photoinitiator added is too little, the amount of photoinitiator penetrating into the ceramic layer is not sufficient, the cross-linking reaction is insufficient, and the heat resistance is affected. On the other hand, it was found that the coating method (such as full-surface coating, gap coating, etc.) of the binder polymer resin slurry also affects the production cost and the overall performance of the product.

[0035] Therefore, the Applicant optimized the content of the photoinitiator and the coating method on the basis of combining the advantages of the CCS+NIPS laminated coating manufacturing process and the oil-based mixed coating process. It should be noted that the process of discovering and researching the above technical problems should also be one of the elements having the inventiveness of the invention.

[0036] Hereinafter, the technical solution embodiments of the present invention will be described in detail using specific examples. Some of the following specific examples may be combined with each other. In some examples, the same or similar concepts or processes may not be described again.

[0037] In the embodiments of the present invention, it mainly contains a solvent, a binder polymer resin, and a photoinitiator. The weight ratio of the photoinitiator in the slurry is 0.08 to 1.0 wt%, and the binder polymer resin includes any one or a combination thereof of PVDF-based binder resin polymers, polyimide, polyetherimide, and polymethyl methacrylate, to provide a coating slurry.

[0038] Here, the PVDF-based binder resin polymer includes any one or a combination thereof of PVDF homopolymer, vinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-tetrafluoroethylene-propylene terpolymer, and polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer.

[0039] The addition amount of the binder polymer resin is 5 to 3 0 wt%. For example, the addition amount of the binder polymer resin may be any point value among 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 28 wt%, 30 wt % of %, and may also be in the range between any two point values. Of course, the present invention is not limited thereto, and the addition amounts of other binder polymer resins are also within the protection scope of the present invention, as long as the weight ratio of the photoinitiator in the slurry is 0.08 to 1.0 wt%.

[0040] In addition, the binder polymer resin of the present application selects polymers such as polyimide, polyetherimide, and polymethyl methacrylate as the binder polymer resin in addition to the conventional PVDF-based binder resin polymer. These polymers have extremely strong adhesiveness, and moreover, have ultra-high heat resistance and good electrochemical performance, which are helpful for improving the comprehensive performance of the product.

[0041] The photoinitiator includes any one kind or a combination of ITX and benzophenone. The addition amount of the photoinitiator is closely related to the performance of the separator. If the addition amount of the photoinitiator is too small, the degree of crosslinking and curing is insufficient, and the improvement of the film breaking temperature does not meet expectations. If the addition amount of the photoinitiator is too large, the photoinitiator will remain excessively in the separator, leading to an increase in cost. In the existing process, the actual addition amount of the photoinitiator is usually 1.0 wt% or more. As a result of studying the mechanism of the photoinitiator and combining it with the performance of the product, the present invention has revealed that when the weight ratio of the photoinitiator in the slurry is in the range of 0.08 to 1.0 wt%, the weight ratio of the photoinitiator in the adhesive layer obtained by coating such a slurry is 0.05 to 0.3 wt%, and in this case, the performance of the product is optimal.

[0042] For example, the addition amount of the photoinitiator to the slurry is any point value among 0.08 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, and the range between any two point values.

[0043] In some embodiments, the solvent is an NMP solvent.

[0044] As shown in FIGS. 1 to 4, the present invention also provides a coated separator including a base film 10, a ceramic layer 20, and an adhesive layer 30, wherein the ceramic layer 20 is coated on one side (shown in FIGS. 1 and 3) or both sides (shown in FIGS. 2 and 4) of the base film, the adhesive layer 30 is coated on the ceramic layer 20, and the adhesive layer 30 is formed by coating the coating slurry in the first aspect and its possible aspects.

[0045] Here, the weight ratio of the photoinitiator in the adhesive layer 30 is 0.05 to 0.3 wt%. The photoinitiator can rapidly and uniformly penetrate into the substrate layers (ceramic layer 20 and base film 10) together with the solvent at the moment when the slurry is coated on the ceramic layer, thereby ensuring that the photoinitiator generates sufficient active radicals within the base film layer, ceramic layer, and their bonding interface layer, making the photoinitiation efficiency and crosslinking degree sufficient, ensuring the complete crosslinking effect of the entire separator, and maximizing the breakdown temperature of the product. Also, the amount of the photoinitiator in the entire adhesive layer is maintained in the range of 0.05 to 0.3 wt% (for example, the content of the photoinitiator in the adhesive layer may be any point value of 0.05%, 0.15%, 0.18%, 0.25%, 0.29%, 0.3% and the range between any two point values). As a result of research, the applicant found that the photoinitiator at a ratio within this range can not only generate sufficient radicals, enhance the photoinitiation efficiency and crosslinking degree, and maximize the breakdown temperature of the product, but also has no effect on the sheet resistance of the separator. Beyond this usage amount range, the sheet resistance of the separator will increase significantly, affecting the interface impedance of the battery. Below this range, the crosslinking degree of the product is insufficient and the breakdown temperature is not improved.

[0046] Also, the applicant notes that when the weight ratio of the photoinitiator in the adhesive layer 30 is 0.05 to 0.3 wt%, there is a close relationship between the coating rate of the adhesive layer and the physical properties of the product. The higher the coating rate, the higher the adhesion strength of the surface layer of the product, the more the amount of the photoinitiator introduced, the lower the porosity, the greater the ventilation increment, and the slower the infiltration rate of the electrolyte. Therefore, the influence brought by the coating method of the slurry is also very important. It is necessary to comprehensively consider the individual physical properties of the product and the control of the initiator introduction amount.

[0047] Based on this, in one specific embodiment, as shown in FIGS. 1 and 2, the adhesive layer 30 is coated over the entire surface of the ceramic layer 20.

[0048] In one specific embodiment, as shown in FIGS. 3 and 4, the adhesive layers 30 that are distributed at intervals in a long strip shape on the ceramic layer 20 are gap-coated on the ceramic layer 20.

[0049] As one specific embodiment, the area ratio of the long-strip adhesive layer to the gap is 1:1 to 5:1, and the gap is the gap between two adjacent long-strip adhesive layers. Specifically, the area ratio of the long-strip adhesive layer to the gap may be, for example, 1:1, 2:1, 3:1, 4:1, 5:1. By distributing the adhesive layer 30 on the ceramic layer 20 at intervals in a long strip shape, the capillary phenomenon can be fully utilized to enhance the wettability of the solvent and improve the permeability of the solvent into the base material layer. Also, the usage amount of the coating raw material can be reduced, and the production cost can be lowered. The adhesive strength meets the design requirements, such as the adhesive strength being 15 gf / 25 mm or more.

[0050] The material of the ceramic layer 20 includes inorganic materials, acrylic ester adhesives, polyacrylic acid adhesives, dispersants, wetting agents, thickeners, and defoaming agents. Specifically, the inorganic material is any one or a combination of silica, alumina, boehmite, titanium oxide, magnesium oxide, and nanofibers.

[0051] The base film is a PP base film, a PE base film, or a PP / PE / PP composite base film. The thickness of the base material is 5 to 20 μm. As one possible embodiment, the thickness of the ceramic layer 20 is, for example, 1 to 6 μm, the thickness of the adhesive layer 30 is, for example, 0.5 to 3 μm, and when the adhesive layer 30 is distributed at intervals in a long strip shape on the ceramic layer 20, the thickness of the adhesive layer 30 is preferably 0.5 to 2 μm, whereby a considerable amount of photoinitiator penetrates into the base material layer.

[0052] Of course, in the case of gap coating, the adhesive layers being distributed at intervals in a long strip shape on the ceramic layer is only one embodiment of the present invention. The gap coating is not limited to the long strip-shaped gap coating. In other embodiments, it may be a dot-shaped gap coating. That is, the adhesive layer 30 may be distributed in a dot shape on the ceramic layer 20. The SEM topography of the surface of the separator obtained by the dot-shaped gap coating is shown in FIG. 6C.

[0053] In the coating slurry and the coated separator according to the present invention, by setting the weight ratio of the photoinitiator in the slurry to 0.08 - 1.0 wt%, within this weight ratio range, after coating the slurry on the base film, the photoinitiator can surely penetrate into the base material layer (ceramic layer and base film), thereby ensuring that the photoinitiator generates sufficient active radicals in the base film, ceramic layer, and their bonding interface layer, making the photoinitiation efficiency and crosslinking degree sufficient, ensuring the complete crosslinking effect of the entire separator, greatly increasing the film breakage temperature of the product. On the other hand, since the content of the photoinitiator remaining in the adhesive layer is not much, it does not affect the sheet resistance of the separator and does not affect the interface impedance of the battery.

[0054] As shown in FIG. 5, the present invention also provides a method for manufacturing the aforementioned coated separator, which includes the following steps. S1: Provide a base film coated with a ceramic layer on one side or both sides. S2: Manufacture of the slurry: Add 5 - 30 wt% or less of a binder polymer resin and 0.08 - 1.0 wt% of a photoinitiator to a solvent and dissolve thoroughly to obtain a coating slurry. S3: Coating: Coat the coating slurry manufactured above on the ceramic layer to form an adhesive layer on the ceramic layer. S4: Ultraviolet crosslinking: Subject the base film after coating to a crosslinking reaction by ultraviolet irradiation to obtain the corresponding coated separator.

[0055] In some embodiments, the coating in step (3) is specifically a full-surface coating in which the coating slurry manufactured above is coated on the entire surface of the ceramic layer to form an adhesive layer on the entire surface of the ceramic layer.

[0056] In some embodiments, the coating in step (3) is specifically a gap coating in which the coating slurry manufactured above is gap-coated on the ceramic layer on which a long-strip-shaped adhesive layer or dot-shaped adhesive layers are formed at intervals. By gap-coating the adhesive layer on the ceramic layer, that is, by the adhesive layer being distributed on the ceramic layer with long-strip-shaped intervals or dot-shaped intervals, the gap coating achieves a better penetration effect by utilizing capillary action compared to full-surface coating, and after coating on the base film, enables the photoinitiator to penetrate better into the base material layer (ceramic layer and base film).

[0057] The ultraviolet cross-linked separator for lithium-ion batteries by gap coating in the present invention has an ultra-high heat resistance with a heat shrinkage rate of less than 5% at 150 °C * 30 min and an ultra-high film-breaking temperature exceeding 180 °C, further improving the safety of the product.

[0058] In some embodiments, the wavelength of the ultraviolet light used is in the range of 210 nm to 420 nm, the ultraviolet cross-linking time is 0.001 s to 10 s, and the irradiation light intensity is 50 mj / cm 2 as above. The photoinitiator or its combined photoinitiator rapidly generates radicals under ultraviolet excitation, and the radicals cause the active groups in the base film layer, ceramic layer, binder polymer resin layer, and the interface layer binding them to generate reactive groups, pendant bonds, and radicals, initiating graft reactions and cross-linking reactions to generate a polymer network structure. The grafts and polymer networks generated by the cross-linking reaction provide a strong support frame for the separator, giving it a higher film-breaking temperature and heat resistance.

[0059] Since the wavelength of ultraviolet light varies within a certain range, in other embodiments, the ultraviolet light may have range values such as 210 - 310 nm, 250 - 390 nm, 280 - 420 nm, etc. When the wavelength range value is constant, the influence of the ultraviolet cross-linking time and the irradiation light intensity on the cross-linking effect is significant. Because the formulation contains inorganic particles that have a certain shielding effect on ultraviolet light, when the intensity of ultraviolet light is less than 50 mj / cm 2 the cross-linking effect is poor.

[0060] In FIGS. 6A - 6B, the SEM topography of the surface of the separator obtained by gap coating is shown using the method for manufacturing a coated separator in an embodiment of the present invention. As is clear from FIG. 6A, the adhesive layers 30 are distributed at intervals in a long shape on the ceramic layer 20. As is clear from FIG. 6B, the adhesive layer is a surface adhesive layer with holes across the surface. In this way, the liquid absorption rate of the electrolyte can be increased, the air permeability can be decreased, and the permeability of the electrolyte and the passing rate of lithium ions can be improved.

[0061] Furthermore, the present invention provides a battery including the coated separator, a positive electrode, a negative electrode, and an electrolyte.

[0062] Hereinafter, the performance of the products of some embodiments of the present invention will be analyzed experimentally.

[0063] Example 1 S1: Provide a base film coated with a ceramic layer on one or both sides. Specifically, add a ceramic material to a solvent, dissolve it sufficiently to obtain a ceramic slurry, and then coat the ceramic slurry on one or both sides of the base film. S2: Preparation of slurry: Add 5 - 30 wt% or less of a binder polymer resin and 0.4 wt% of a photoinitiator to a solvent, dissolve it sufficiently to obtain a coating slurry. S3: Coating: The coating slurry manufactured above is gap-coated onto the ceramic layer to form a long-strip adhesive layer distributed at intervals on the ceramic layer. The content of the photoinitiator in the adhesive layer is 0.25 wt%, and the area ratio of the long-strip adhesive layer to the gap is 5:1. S4: UV Crosslinking: The base film after coating is subjected to a crosslinking reaction by UV irradiation to obtain the corresponding coated separator. In this example, the base film used is a PP base film with a thickness of 10.4 μm, the ceramic material used is alumina, and ceramic layers are coated on both sides of the base film. ITX is used as the photoinitiator.

[0064] Example 2 Compared with Example 1, in Example 2, the area ratio of the long-strip adhesive layer to the gap is 4:1, and the content of the photoinitiator in the adhesive layer is 0.18 wt%. Since other aspects of Example 2 are the same as those of Example 1, they will not be mentioned further here.

[0065] Example 3 Compared with Example 1, in Example 3, the area ratio of the long-strip adhesive layer to the gap is 3:1, and the content of the photoinitiator in the adhesive layer is 0.11 wt%. Since other aspects of Example 3 are the same as those of Example 1, they will not be mentioned further here.

[0066] Example 4 Compared with Example 1, in Example 4, the area ratio of the long-strip adhesive layer to the gap is 2:1, and the content of the photoinitiator in the adhesive layer is 0.1 wt%. Since other aspects of Example 4 are the same as those of Example 1, they will not be mentioned further here.

[0067] Example 5 Compared with Example 1, in Example 5, the area ratio of the long adhesive layer to the gap is 1:1, and the content of the photoinitiator in the adhesive layer is 0.06 wt%, which are different. Since other aspects of Example 5 are the same as those of Example 1, they will not be mentioned further here.

[0068] Example 6 Compared with Example 1, in Example 6, the content of the photoinitiator in the slurry is 0.8 wt%, and the content of the photoinitiator in the adhesive layer is 0.29 wt%, which are different. Since other aspects of Example 6 are the same as those of Example 1, they will not be mentioned further here.

[0069] Example 7 Compared with Example 1, in Example 7, the area ratio of the long adhesive layer to the gap is 1:1, the content of the photoinitiator in the slurry is 0.9 wt%, and the content of the photoinitiator in the adhesive layer is 0.12 wt%, which are different. Since other aspects of Example 7 are the same as those of Example 1, they will not be mentioned further here.

[0070] Example 8 Compared with Example 1, in Example 8, the gap coating is changed to a full-surface coating, that is, the adhesive layer covers the entire surface of the ceramic layer, that is, the area ratio of the long adhesive layer to the gap is 1:0, the content of the photoinitiator in the slurry is 0.10 wt%, and the content of the photoinitiator in the adhesive layer is 0.08 wt%, which are different. Since other aspects of Example 8 are the same as those of Example 1, they will not be mentioned further here.

[0071] Example 9 Compared with Example 1, in Example 9, the gap coating is changed to a full-surface coating, that is, the adhesive layer covers the entire surface of the ceramic layer, that is, the area ratio of the long adhesive layer to the gap is 1:0, and the content of the photoinitiator in the adhesive layer is 0.39 wt%, which are different. Since other aspects of Example 9 are the same as those of Example 1, they will not be mentioned further here.

[0072] Example 10 Compared with Example 6, in Example 10, the gap coating was changed to a full-surface coating, that is, the adhesive layer covered the entire surface of the ceramic layer, that is, the area ratio of the long-strip adhesive layer to the gap was 1:0. The difference lies in that the content of the photoinitiator in the adhesive layer is 0.78 wt%. Since other aspects of Example 10 are the same as those of Example 6, they will not be mentioned further here.

[0073] Example 11 Compared with Example 7, in Example 11, the gap coating was changed to a full-surface coating, that is, the adhesive layer covered the entire surface of the ceramic layer, that is, the area ratio of the long-strip adhesive layer to the gap was 1:0. The difference lies in that the content of the photoinitiator in the adhesive layer is 0.85 wt%. Since other aspects of Example 11 are the same as those of Example 7, they will not be mentioned further here.

[0074] Comparative Example 1 Compared with Example 1, in Comparative Example 1, the gap coating was changed to a full-surface coating, that is, the adhesive layer covered the entire surface of the ceramic layer, that is, the area ratio of the long-strip adhesive layer to the gap was 1:0. The difference lies in that the content of the photoinitiator in the adhesive layer is 0.38 wt%. Since other aspects of Comparative Example 1 are the same as those of Example 1, they will not be mentioned further here.

[0075] Comparative Example 2 Compared with Example 1, in Comparative Example 2, the area ratio of the long-strip adhesive layer to the gap is 1:1. The difference lies in that the content of the photoinitiator in the slurry is 0.04 wt% and the content of the photoinitiator in the adhesive layer is 0.03 wt%. Since other aspects of Comparative Example 2 are the same as those of Example 1, they will not be mentioned further here.

[0076] Comparative Example 3 Compared with Example 1, in Comparative Example 3, the area ratio of the long adhesive layer to the gap is 1:1, the content of the photoinitiator in the slurry is 3.0 wt%, and the content of the photoinitiator in the adhesive layer is 2.80 wt%, which are different. Since the other aspects of Comparative Example 3 are the same as those of Example 1, they will not be mentioned further here.

[0077] Table 1 shows the performance of the corresponding separators obtained in the above Examples 1 to 11 and Comparative Examples 1 to 3. Among them, the test method for the loading amount is specifically to perform a loading amount test with an electronic balance. Specifically, First, test the areal density of the separator coated with the ceramic layer, that is, cut the coated ceramic film into test pieces with a size of 297 mm * width 210 mm, roll the test piece film into a ball and then place it on the weighing platform for weighing, record the weight m1, and calculate the areal density M1 (unit: g / m 2 ) by the formula Ps = M / (length * width * 10 -6 ). Measure the areal density M2 of the separator after coating in the same manner as above. Calculation of the loading amount: M2 - M1.

[0078] The test method for the heat shrinkage rate at 150°C for 30 minutes is specifically as follows. First, cut the separator along the horizontal and vertical directions into test samples with a size of 50 mm × 50 mm. Next, sandwich the cut samples between A4 papers, and lay 5 A4 papers on top and bottom respectively. Subsequently, set the oven temperature to 150°C, raise the temperature to the set temperature, preheat sufficiently, and stably maintain the internal temperature at the set temperature. Furthermore, place the sample sandwiched between the A4 papers quickly into the oven together with the A4 papers, making sure the sample is placed in the middle of the upper layer of the oven and not in the lower layer, and then close the oven door immediately after putting it in. After closing the oven door, set the test time of 30 minutes according to the test requirements. When the time is up, take out the sample film from the oven, cool it to room temperature, then gently flatten the film, measure the distance between the edges of the separator in the horizontal / vertical direction, record the data, and calculate the heat shrinkage rate. The calculation formula for the heat shrinkage rate: Heat shrinkage rate % = (Initial length between the marks - Length after heating between the marks) / Initial length between the marks × 100%. Liquid absorption represents the performance of the adsorption amount of the separator to the electrolyte. Liquid absorption test method: Cut the separator sample to be measured with a size of 150 mm × 150 mm (s = 0.0225 m 2 ), weigh and record the weight m1. Immerse the separator sample to be measured in the electrolyte for 1 hour. Take out the separator immersed in the electrolyte and wipe off the excess electrolyte with a paper towel. Weigh the separator sample after wiping and record the weight m2, and calculate the liquid absorption rate (unit: g / m 2 ). Liquid absorption rate = (m2 - m1) / s.

[0079] The test method for the adhesion force is as follows. Make the sample of the coating film to be measured into a standard test piece (coating film (25 mm × 180 mm), electrode plate (20 mm × 150 mm)), and bond the coating surface of the separator and the electrode plate with a certain pressure at a temperature of 60°C using a hot press forming machine. Next, clamp the other end of the electrode plate and the sample with a jig and apply a tensile force until the stroke of the tensile machine ends. Tensile machine parameter settings: Fixed displacement: 150 mm, test speed: 300 mm / min.

[0080] The breakdown temperature was measured by a TMA test in which the separator was tensioned with a constant force (simulating the state when inside the battery) and then the temperature was gradually increased until breakdown.

[0081] In the test method for the sheet resistance of the separator, the sheet resistance test of the separator is carried out using an electrochemical workstation. Specifically, it includes the following steps. 1 Sample preparation: Neatly fold the separator sample to be measured and cut 4 circular sheets with a diameter of 47 mm. 2 Place the circular sheet into the electrolyte, seal it, and soak it for 1 h. 3 Connect the test module to the electrochemical workstation, open the impedance spectrum test software of the electrochemical workstation, perform an impedance test R1, and obtain the impedance of the first layer. 4 Put the second layer, the third layer, and the fourth layer in sequence, measure their impedance spectra, and obtain the resistance values R2, R3, and R4 respectively. 5 Plot the horizontal axis as the number of layers and the vertical axis as the resistance value corresponding to each number of layers, obtain the slope A of the curve and the linear fitting degree. When the linear fitting degree is greater than 0.999, the test result is valid; otherwise, retest. An example of the fitting curve is shown in Figure 7. Here, the calculation formula for the sheet resistance value R of the separator is R = A * S.

[0082] In the formula, R is the sheet resistance of the test piece (Ω·cm 2 ), A is the slope of the curve, and S is the test area of the separator (cm 2 ), and the test area of the separator is the effective electrode area = 9.616 cm 2 .

[0083] The calculation formula for the ionic conductivity σ is σ = d / R.

[0084] In the formula, σ is the ionic conductivity (S / cm), and d is the thickness of the separator (cm).

[0085]

Table 1

[0086] As can be seen from Table 1, the present application significantly improves the heat resistance of the entire separator. In Examples 1 to 8, the heat shrinkage rate at 150°C * 30 min is less than 4%, and the film breakage temperature is all 200°C or higher. Therefore, the product as a whole has excellent performance.

[0087] Also, when comparing Examples 1 to 7 with Examples 8 to 11, when the content of the photoinitiator in the slurry is within the range of the content of the present application, the separator obtained by full-surface coating has almost a liquid absorption property (wettability) of 6.2 g / m 2 ~6.5 g / m 2 and a sheet resistance of 1.2 Ω·cm 2 ~2.3 Ω·cm 2 On the other hand, the separator obtained by gap coating has almost a liquid absorption property (wettability) of 6.3 g / m 2 ~7.0 g / m 2 and a sheet resistance of 1.0 Ω·cm 2 ~1.4 Ω·cm 2 In particular, from the comparison between Example 6 and Example 10 and between Example 7 and Example 11, it was found that gap coating shows a higher liquid absorption property (wettability) at a lower production cost compared with full-surface coating. At the same time, the sheet resistance of the separator is significantly reduced, and it shows better adhesiveness, indicating that the overall performance of the product is more excellent.

[0088] Moreover, when comparing Examples 1 to 8 with Comparative Example 2, when the content of the photoinitiator in the slurry is below the minimum content range of the present application and the content of the photoinitiator in the adhesive layer is below the minimum content range of the present application, the film-breaking temperature of the separator significantly decreases. For example, in Comparative Example 2, the film-breaking temperature decreased to about 150 °C. On the other hand, from the comparison between Examples 1 to 8 and Comparative Example 3, when the content of the photoinitiator in the slurry exceeds the maximum content range of the present application and the content of the photoinitiator in the adhesive layer exceeds the maximum content range of the present application, the adhesive strength significantly decreases, and the sheet resistance of the separator clearly increases. For example, in Comparative Example 2, the adhesive strength of the A side decreased to 30 gf / 25 mm or less, the adhesive strength of the B side decreased to 20.1 gf / 25 mm, and the sheet resistance of the separator reached 2.4 Ω·cm 2 Therefore, within the content range of the photoinitiator in the slurry of the present application and the content range of the photoinitiator in the adhesive layer, the performance of the separator product is optimal.

[0089] In the description of this specification, the description referring to terms such as "one embodiment", "one example", "specific implementation process", "one example", etc. means that the specific features, structures, materials, or characteristics described with reference to the said embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the described specific features, structures, materials, or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0090] It should be noted that each of the above embodiments is only used to explain the technical solution of the present invention and is not intended to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can modify the technical solutions described in the above embodiments or equivalently replace some or all of their technical features. These modifications or replacements do not deviate from the spirit of the corresponding technical solutions from the scope of the technical solutions of each embodiment of the present invention.

Claims

1. A base film, a ceramic layer, and an adhesive layer, wherein the ceramic layer is formed on one or both sides of the base film, the adhesive layer is formed on the ceramic layer, the adhesive layer contains a binder polymer resin and a photoinitiator as main components, the binder polymer resin is any one or a combination of PVDF-based binder resin polymers, polyimide, polyetherimide, and polymethyl methacrylate, the weight ratio of the photoinitiator in the adhesive layer is 0.05 to 0.3 wt%, the adhesive layer is a coating separator distributed at intervals on the ceramic layer.

2. The coating separator according to claim 1, characterized in that the area ratio of the adhesive layer to the gap is 1:1 to 5:1, and the gap is the gap between two adjacent adhesive layers.

3. The coating separator according to claim 1, characterized in that the ceramic layer contains an inorganic material, and the inorganic material is any one or a combination of silica, alumina, boehmite, titanium oxide, magnesium oxide, and nanofibers.

4. A method for manufacturing a coating separator including a base film, a ceramic layer, and an adhesive layer, comprising forming the ceramic layer on one or both sides of the base film, forming the adhesive layer on the ceramic layer, the adhesive layer contains a solvent, a binder polymer resin, and a photoinitiator as main components, the weight ratio of the photoinitiator in the slurry is 0.08 to 1.0 wt%, and the binder polymer resin contains any one or a combination of PVDF-based binder resin polymers, polyimide, polyetherimide, and polymethyl methacrylate, and is formed by a coating slurry, (1) providing a base film coated with a ceramic layer on one or both sides; (2) manufacturing a slurry: adding 5 to 30 wt% or less of a binder polymer resin and 0.08 to 1.0 wt% of a photoinitiator to a solvent and dissolving well to obtain a coating slurry; (3) coating: coating the coating slurry on the ceramic layer to form an adhesive layer on the ceramic layer. (4) UV crosslinking: A step of subjecting the base film after coating to a crosslinking reaction by UV irradiation to obtain a corresponding coated separator, The coating in step (3) is a gap coating in which the coating slurry is gap-coated on the ceramic layer on which the adhesive layer is formed at intervals, and the method for manufacturing a coated separator is characterized by this.

5. The coating in step (3) is specifically an all-over coating in which the coating slurry manufactured above is coated on the entire surface of the ceramic layer to form an adhesive layer on the entire surface of the ceramic layer, and the method for manufacturing a coated separator according to claim 4 is characterized by this.

6. The wavelength of the ultraviolet ray used is in the range of 210 nm to 420 nm, the ultraviolet crosslinking time is from 0.001 s to 10 s, and the irradiation light intensity is 50 mj / cm ２ or more, and the method for manufacturing a coated separator according to claim 4, characterized in that.

7. A battery comprising the coated separator according to claim 1, a positive electrode, a negative electrode, and an electrolytic solution, and the battery is characterized by this.

8. The PVDF-based binder resin polymer includes any one kind or a combination thereof of a PVDF homopolymer, a vinylidene fluoride-hexafluoropropylene copolymer, a polyvinylidene fluoride-tetrafluoroethylene-propylene terpolymer, and a polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer, and the coated separator according to any one of claims 1 to 3 is characterized by this.

9. The photoinitiator includes any one kind or a combination thereof of ITX and benzophenone, and the coated separator according to any one of claims 1 to 3 is characterized by this.

10. The PVDF-based binder resin polymer includes any one kind or a combination thereof of a PVDF homopolymer, a vinylidene fluoride-hexafluoropropylene copolymer, a polyvinylidene fluoride-tetrafluoroethylene-propylene terpolymer, and a polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer, and the method for manufacturing a coated separator according to any one of claims 4 to 6 is characterized by this.

11. The photoinitiator includes any one kind or a combination thereof of ITX and benzophenone, and the method for manufacturing a coated separator according to any one of claims 4 to 6 is characterized by this.

12. The PVDF-based binder resin polymer includes any one or a combination thereof of a PVDF homopolymer, a vinylidene fluoride-hexafluoropropylene copolymer, a polyvinylidene fluoride-tetrafluoroethylene-propylene terpolymer, and a polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer. The battery according to claim 7 is characterized by this.

13. The photoinitiator includes any one or a combination thereof of ITX and benzophenone. The battery according to claim 7 is characterized by this.

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