Coated separator, manufacturing method of coated separator, and battery

Abstract

A coated separator, a manufacturing method for a coated separator, and a battery in which first nanofibers (21) of similar size are mixed in a first coating layer (20) and second nanofibers (31) of similar size are mixed in a second coating layer (30), thereby avoiding the problem that nanofibers of similar surface energy tend to aggregate due to the large difference in surface energy caused by the large difference in size between different nanofibers, and greatly improving the uniformity of mixing between the nanofibers. Furthermore, by making the first coating layer (20) a mixture of large-sized first nanofibers (21) and large-particle-diameter first ceramic particles (22), and by making the second coating layer (30) a mixture of small-sized second nanofibers (31) and small-particle-diameter second ceramic particles (32), the first coating layer (20) has a large pore size and a strong skeletal structure, and the coated separator can be maintained to maintain high heat resistance and high permeability. The second coating layer with a small pore size can improve the conductivity of lithium ions, and the risk of electrochemical stability due to high-temperature exposure or long-term cycles is reduced.

Description

[Technical Field]

[0001] The present invention relates to the field of battery separator technology, and more particularly to coated separators, methods for manufacturing coated separators, and batteries. [Background technology]

[0002] The separator is one of the main components of a lithium battery, and its performance has a significant impact on the overall performance of the battery, making it one of the key technologies that restrict the development of lithium batteries. As the application fields of lithium batteries continue to expand and the impact of lithium battery products on people's lives continues to become more profound, people's requirements for the performance of lithium batteries are also increasing. To meet the development requirements of lithium batteries, the separator, as an important component of lithium batteries, not only must have good chemical stability and low manufacturing costs, but further improving the safety performance of lithium-ion batteries is also an important trend in the current development of lithium batteries.

[0003] In the related art, a coated separator may include a base membrane and a coating layer coated on at least one surface of the base membrane, and a ceramic layer may be coated on the surface of the coated separator to improve the heat resistance of the separator. However, the two-phase interface between the ceramic layer and the separator has a weak bond, and separation easily occurs at high temperatures, causing the ceramic layer to peel off, melting the separator substrate, and reducing heat resistance. Meanwhile, the surface ceramic layer increases the conduction distance of lithium ions, further reducing the conductivity of lithium ions, and the large pores make it difficult to maintain the liquid electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a coated separator, a method for manufacturing the coated separator, and a battery in order to improve the performance of the separator. [Means for solving the problem]

[0005] According to a first aspect of the present invention, a coated separator is provided, the coated separator comprising a base membrane and a coating layer structure disposed on at least one surface of the base membrane, the coating layer structure comprising at least a first coating layer and a second coating layer, wherein the first coating layer is a surface of the base membrane. At least one a second coating layer disposed on a surface of the first coating layer away from the base membrane, the first coating layer comprising a first nanofiber material and first ceramic particles, and the second coating layer comprising a second nanofiber material and second ceramic particles; the first nanofiber material comprises a number of first nanofibers and the second nanofiber material comprises a number of second nanofibers; The difference in length between some of the first nanofibers is 500 nm or less, the difference in length between some of the second nanofibers is 200 nm or less, the length of the first nanofibers is greater than the length of the second nanofibers, and the average particle diameter of the first ceramic particles is greater than the average particle diameter of the second ceramic particles.

[0006] Optionally, the first nanofibers have a length of 500 to 1000 nm, and the first ceramic particles have an average particle size of 100 to 600 nm.

[0007] Optionally, the mass ratio of the first nanofiber material to the first ceramic particles is 5:1 to 1:5.

[0008] Optionally, the second nanofibers have a length of 100 to 300 nm, and the second ceramic particles have an average particle size of 10 to 60 nm.

[0009] Optionally, the mass ratio of the second nanofiber material to the second ceramic particles is 5:1 to 1:5.

[0010] Optionally, the diameter of the first nanofibers is 5 to 50 nm, and the diameter of the second nanofibers is 5 to 50 nm.

[0011] Optionally, the ratio of the thickness of the first coating layer to the thickness of the second coating layer is greater than two.

[0012] Optionally, at least one additional coating layer is further included between the first coating layer and the second coating layer.

[0013] Optionally, fast lithium ion conducting functional groups are grafted onto the surface of the second ceramic particles; Furthermore, the high-speed lithium ion conducting functional group includes any one of hydroxyl (-OH), carbonyl (-C=O), fluorine (-F), and carboxyl (-COOH).

[0014] Optionally, the first ceramic particles and Before The second ceramic particles At least one of is an inorganic compound that has a melting point of 200°C or higher, is electrically insulating, and is electrochemically stable within the range of use of lithium batteries.

[0015] Optionally, the coating separator comprises at least: a) ionic conductivity ≥ 1.2 mS / cm; b) Capacity maintenance rate ≧98%, c) Thermal shrinkage at 180℃ / h ≦ 5%; Satisfy one of the following conditions.

[0016] According to a second aspect of the present invention, there is provided a method for manufacturing a coated separator for manufacturing the coated separator according to the first aspect and its alternative solutions, the method comprising the steps of: producing a paste; and forming a film by coating the paste; In preparing the paste, a first paste including first ceramic particles and a first nanofiber material is prepared, and a second paste including second ceramic particles and a second nanofiber material is prepared; In the film formation by coating, the first paste is coated on at least one surface of the base film to form a first coating layer, and the second paste is coated on the side of the first coating layer away from the base film to form a second coating layer; moreover, preparing the first paste includes dispersing first ceramic particles in a first solvent to obtain a first ceramic dispersion, dispersing a first nanofiber material in a second solvent to obtain a first nanofiber dispersion, and mixing the first ceramic dispersion and the first nanofiber dispersion to obtain the first paste; The preparation of the second paste includes dispersing second ceramic particles in a third solvent to obtain a second ceramic dispersion, dispersing a second nanofiber material in a fourth solvent to obtain a second nanofiber dispersion, and mixing the second ceramic dispersion and the second nanofiber dispersion to obtain the second paste.

[0017] Optionally, prior to the preparation of the paste, the method further comprises sorting ceramics; In the selection of the ceramics, first ceramic particles and second ceramic particles having different particle sizes are selected, wherein the first ceramic particles have an average particle size of 100 to 600 nm, and the second ceramic particles have an average particle size of 10 to 60 nm; The method further includes a pretreatment of the ceramic, in which the second ceramic particles are subjected to a grafting reaction with a grafting target to graft high-speed lithium ion conductive functional groups onto the surfaces of the second ceramic particles.

[0018] Optionally, the grafting object includes any one of polycarbonate, polylactic acid, polyurethane, perfluoropropyl vinyl ether, and methyl isopropyl ketone.

[0019] According to a third aspect of the present invention, there is provided a battery, the battery comprising a coated separator according to the first aspect and its alternative solutions, or a coated separator produced by the method for producing a coated separator according to the second aspect and its alternative solutions, Furthermore, the battery is a lithium battery.

[0020] In the coated separator, the method for manufacturing the coated separator, and the battery provided by the present invention, first nanofibers of similar size are mixed in the first coating layer, and second nanofibers of similar size are mixed in the second coating layer, thereby avoiding the problem of nanofibers with similar surface energies easily agglomerating due to the large difference in surface energy caused by the large difference in size between different nanofibers, and significantly improving the uniformity of the mixture among the nanofibers. Furthermore, by making the first coating layer a mixture of large-sized first nanofibers and large-sized first ceramic particles, a first mixed material layer with large and uniform pores is formed. This first mixed material layer is disposed on the surface of the base membrane, and its large pores and strong skeletal structure allow the coated separator to maintain high heat resistance and high permeability. By making the second coating layer a mixture of small-sized second nanofibers and small-sized second ceramic particles, a second mixed material layer with small and uniform pores is formed. ,hair Due to tubular action The small pore size allows the coated separator to It has a strong adsorption ability for the electrolyte, which can improve the conductivity of lithium ions, thereby reducing the possibility of lithium dendrite formation and reducing the risk of electrochemical stability when left at high temperatures or cycled for long periods of time. [Brief explanation of the drawings]

[0021] In order to more clearly describe the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative efforts. [Figure 1] FIG. 2 is a schematic diagram of the local structure of a coating separator in one embodiment of the present invention. [Figure 2] 1 is a flowchart of a method for manufacturing a coated separator in one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, the technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings according to the embodiments of the present invention, and it is obvious that the described embodiments are only some of the embodiments of the present invention, and not all of the embodiments thereof. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any creative efforts shall fall within the protection scope of the present invention.

[0023] In describing the specification of the present invention, it should be understood that the orientations or positional relationships indicated by terms such as "upper," "lower," "top," "bottom," "lower surface," "top," etc. are based on the orientations or positional relationships shown in the drawings, and are intended merely to facilitate and simplify the description of the present invention, and are not intended to indicate or suggest that the devices or elements shown have a particular orientation or must be constructed and operated in a particular orientation, and therefore should not be understood as limiting the present invention.

[0024] In describing the present specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying the relative importance or the number of technical features indicated, whereby a feature qualified by "first" or "second" may explicitly or implicitly include one or more of the said features.

[0025] In the description of the present invention, "plurality" means more than one, for example, two, three, four, etc., unless otherwise clearly and specifically limited.

[0026] In the description of the present invention, the term "connection" and the like should be understood in a broad sense unless otherwise clearly specified or limited, and may mean, for example, a fixed connection, a detachable connection, or an integrated structure, a mechanical connection, an electrical connection or a structure capable of communicating with each other, a direct connection, an indirect connection via an intermediate medium, internal communication between two elements, or an interactive relationship between two elements. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to specific circumstances.

[0027] The technical solutions of the present invention will be described in detail below using specific embodiments, and some of the following specific embodiments may be combined with each other, and some of the same or similar concepts or processes may be omitted in some embodiments.

[0028] Before proposing the present invention, the applicant conducted a series of studies and experiments on conventional separators, To solve the problem of the ceramic layer easily peeling off, this field proposes that one-dimensional nanomaterials can be added to the coating layer.

[0029] In order to solve problems such as the messy and irregular deposition method of one-dimensional nanomaterials in the coating layer, too many gaps, and few contact points, the applicant proposes a corresponding solution, which is to reduce the length of the one-dimensional nanomaterials layer by layer according to the coating layer (embodied in the reduction of the described value of the length of the one-dimensional nanomaterials in each material layer). By doing so, the pores when long nanomaterials are deposited are large, so the lower the layer, the larger the gaps become. The shorter nanomaterials in the upper layer can fill these gaps to a certain extent. By depositing them layer by layer, there are not too many gaps inside the coating layer and there are more contact points. Therefore, when heat is applied, the dense structure of the coating layer can suppress the occurrence of thermal deformation of the separator, thereby improving the heat resistance of the coated separator. Regarding this solution, the applicant has also proposed a patent application (application number: PCT / CN2022 / 077087, filing date: 2022.02.21), and this application incorporates the entire contents of PCT / CN2022 / 077087 into this specification, i.e., the entire contents of PCT / CN2022 / 077087 can be used as support for this application.

[0030] To solve the problem that the deposition density of 1D nanofibers is too high due to the layer-by-layer reduction of the 1D nanofibers, which blocks the lithium ion conduction channels and affects the lithium ion conductivity, limiting the separator performance, the applicant has proposed a corresponding solution, which is to introduce ceramic particles into the 1D nanomaterial coating layer, which can effectively increase the ion conduction rate. Regarding this solution, the applicant has also filed a patent application (application number: PCT / CN2022 / 108551, filing date: 2022.07.28), the entire contents of which are incorporated herein by reference, i.e., the entire contents of PCT / CN2022 / 108551 can be used as support for this application.

[0031] However, through further research, the applicant discovered that while the above solution can avoid excessive stacking density of one-dimensional nanomaterials by using ceramic particles, thereby forming effective lithium ion conduction channels and improving lithium ion conductivity, the overall performance of the separator is still not fully ideal. Through research and testing, the applicant discovered that when the size difference between different nanofibers is too large, the difference in surface energy is large, making nanofibers with similar surface energies more likely to aggregate. This means that the surface energy of small-sized nanofibers is high, making them more likely to aggregate and form aggregates, which are then mixed with larger-sized nanofibers. This results in the small-sized nanofibers being unable to fully demonstrate their intended performance, and the ceramic particles are not properly separated according to the size of the nanofibers, limiting the performance of the separator.

[0032] Based on this discovery, the applicant has obtained the technical solution of the present application through a series of research, testing and verification. Since the orderly arrangement of one-dimensional nanofibers is one of the applicant's major technical innovations, the problems further investigated and the resulting solutions based on the orderly arrangement are also major technical innovations, and the entire research process should be an integral part of the solution and should be considered as a whole when assessing the inventive step of the present application.

[0033] Referring to FIG. 1, an embodiment of the present invention provides a coated separator, which includes a base membrane 10 and a coating layer structure disposed on the base membrane 10, the coating layer structure including a first coating layer 20 and a second coating layer 30, wherein the first coating layer 20 is disposed on the surface of the base membrane 10, the second coating layer 30 is disposed on the side of the first coating layer 20 away from the base membrane 10, the first coating layer 20 includes a first nanofiber material and a first ceramic particle 22, and the second coating layer 30 is disposed on the surface ... The coating layer 30 comprises a second nanofiber material and second ceramic particles 32, the first nanofiber material comprising several first nanofibers 21, the second nanofiber material comprising several second nanofibers 31, the difference in length between each of the first nanofibers 21 being 500 nm or less, the difference in length between each of the second nanofibers 31 being 200 nm or less, the length of the first nanofibers 21 being greater than the length of the second nanofibers 31, and the average particle diameter of the first ceramic particles 22 being greater than the average particle diameter of the second ceramic particles 32.

[0034] In the embodiment of the present invention, when the difference in size of different nanofibers is too large, the difference in surface energy is large, and nanofibers with similar surface energies tend to aggregate, i.e., the surface energy of small-sized nanofibers becomes large, and they tend to aggregate with each other to form aggregates, and then come into contact and mix with large-sized nanofibers. In view of this, nanofibers with small sizes cannot fully demonstrate their intended performance, by mixing nanofibers with similar sizes, the uniformity of the mixture is greatly improved, The uniformity of distribution of nanofibers (due to differences in length) due to their aggregationThe first coating layer is a mixture of large-sized first nanofibers and large-sized first ceramic particles, forming a first mixed material layer with large and uniform pore sizes. This first mixed material layer is placed on the surface of the base membrane, and its large pore size and strong skeletal structure enable the coated separator to maintain high heat resistance and high permeability. The second coating layer is a mixture of small-sized second nanofibers and small-sized second ceramic particles, forming a second mixed material layer with small and uniform pore sizes. Such small pores have strong adsorption ability for the electrolyte due to their capillary action, thereby improving the conductivity of lithium ions. As a result, the possibility of lithium dendrite formation is reduced, and the risk of electrochemical stability due to high-temperature storage or long-term cycling is reduced. This effectively improves the performance of the separator.

[0035] In a preferred embodiment, the length of the first nanofibers 21 is 500 to 1000 nm, and may be, for example, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc., and the average particle diameter of the first ceramic particles 22 is 100 to 600 nm, and may be, for example, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, etc. By forming a first coating layer containing the first nanofibers and the first ceramic particles on the surface of the base membrane to form a large pore size and a strong skeletal structure, the coated separator can maintain high heat resistance and high permeability.

[0036] In a preferred embodiment, the mass ratio of the first nanofiber material to the first ceramic particles 22 is 5:1 to 1:5. By setting the mass ratio of the first nanofiber material to the first ceramic particles 22 within this range, the coating layer can be maintained with excellent heat resistance and lithium ion conductivity. As a specific example, the mass ratio of the first nanofiber material to the first ceramic particles 22 may be, for example, any one or any two of 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, and 1:5. Naturally, the mass ratio of the first nanofiber material to the first ceramic particles 22 may be, for example, any one or any two of 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, and 1:5. fiber The mass ratio of the material to the first ceramic particles may be other values, and the specific numerical value does not limit the present invention, and any ratio between 5:1 and 1:5 is within the scope of protection of the present invention.

[0037] In a preferred embodiment, the length of the second nanofibers 31 is 100 to 300 nm, and may be, for example, 100 nm, 150 nm, 200 nm, 250 nm, or 300 nm, and the average particle diameter of the second ceramic particles 32 is 10 to 60 nm, and may be, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, or 60 nm. The second coating layer is disposed on the side of the first coating layer away from the base membrane and is a mixture of second nanofibers and second ceramic particles. Such small pore diameters provide strong adsorption ability for the electrolyte due to capillary action, improving the conductivity of lithium ions. As a result, the possibility of lithium dendrite formation is reduced, and the risk of electrochemical stability due to high-temperature storage or long-term cycling is reduced.

[0038] In a preferred embodiment, the mass ratio of the second nanofiber material to the second ceramic particles 32 is 5:1 to 1:5. By setting the mass ratio of the second nanofiber material to the second ceramic particles 32 within this range, the coating layer has excellent battery capacity retention and lithium ion conductivity. As a specific example, 32The mass ratio of the second nanoparticles to the second nanoparticles may be, for example, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, or any one of the ranges between any two of the ranges. fiber The mass ratio of the material to the second ceramic particles may be other values, and the specific numerical value does not limit the present invention, and any ratio between 5:1 and 1:5 is within the scope of protection of the present invention.

[0039] In a preferred embodiment, the diameter of the first nanofibers is 5 to 50 nm, and the diameter of the second nanofibers is 5 to 50 nm.

[0040] In a preferred embodiment, the ratio of the thickness of the first coating layer 20 to the thickness of the second coating layer 30 is set to be greater than 2, so that the heat resistance of the coated separator can be more effectively improved.

[0041] In a preferred embodiment, at least one additional coating layer is further included between the first coating layer 20 and the second coating layer 30. For example, one additional coating layer, such as a third coating layer, may be further included between the first coating layer 20 and the second coating layer 30, or two additional coating layers, such as a third coating layer and a fourth coating layer, may be further included. Of course, other numbers of additional coating layers may also be included. Here, the additional coating layer may be selected to be the same material and size as the first coating layer or the second coating layer, or may be selected to be a different material and size. That is, a third coating layer is disposed between the first and second coating layers, the third coating layer comprising third ceramic particles having an average particle size of 100-600 nm and third nanofibers having a length-to-diameter ratio of ≦200, the third ceramic particles and third nanofibers being different in material and size from those in the second coating layer, or a third coating layer is disposed between the first and second coating layers, the third coating layer comprising third ceramic particles having an average particle size of 10-60 nm and third nanofibers having a length-to-diameter ratio of ≦60, the third ceramic particles and third nanofibers being different in material and size from those in the first coating layer. Note that the number of coating layers in the coated separator, the selection of different interlayer materials, and size settings can be adjusted according to actual requirements and should not be construed as limiting the present invention.

[0042] In a preferred embodiment, fast lithium ion conducting functional groups are grafted onto the surfaces of the second ceramic particles 32. The fast lithium ion conducting functional groups contained in large quantities on the surfaces of the second ceramic particles 32 can significantly improve the lithium ion conduction capability. Furthermore, the fast lithium ion conducting functional groups include any one of hydroxyl (-OH), carbonyl (-C=O), fluorine (-F), and carboxyl (-COOH).

[0043] In a preferred embodiment, the first ceramic particles 22 and / or the second ceramic particles 32 are inorganic compounds having a melting point of 200° C. or higher, electrical insulation, and electrochemical stability within the range of use of a lithium battery. Examples of ceramics include oxide ceramics such as alumina, silica, titanium oxide, zirconia, magnesia, ceria, yttria, and zinc oxide; nitride ceramics such as silicon nitride, titanium nitride, and boron nitride; silicon carbide, calcium carbonate, magnesium sulfate, aluminum sulfate, basic alumina (aluminum hydroxide oxide), potassium titanate, talc, kaolinite, kaolin, nacrite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand. These may be used alone or in combination.

[0044] In a preferred embodiment, the coating separator comprises at least: a) ionic conductivity ≥ 1.2 mS / cm; b) Capacity maintenance rate ≧98% c) Thermal shrinkage at 180℃ / h ≦ 5%; Satisfy one of the following conditions.

[0045] Furthermore, referring to FIG. 2, an embodiment of the present invention further provides a method for manufacturing a coated separator according to the first aspect and its alternative solution, the method including: manufacturing a first paste, manufacturing a second paste, and forming a film by coating; S1, in the preparation of a first paste, a first paste including first ceramic particles and a first nanofiber material is prepared; S2, in the preparation of a second paste, a second paste containing second ceramic particles and a second nanofiber material is prepared; S3: In film formation by coating, the first paste is coated on at least one surface of the base film to form a first coating layer, and the second paste is coated on the side of the first coating layer away from the base film to form a second coating layer.

[0046] Specifically, producing the first paste includes dispersing first ceramic particles in a first solvent to obtain a first ceramic dispersion, dispersing a first nanofiber material in a second solvent to obtain a first nanofiber dispersion, and mixing the first ceramic dispersion and the first nanofiber dispersion to obtain the first paste; The preparation of the second paste includes dispersing second ceramic particles in a third solvent to obtain a second ceramic dispersion, dispersing a second nanofiber material in a fourth solvent to obtain a second nanofiber dispersion, and mixing the second ceramic dispersion and the second nanofiber dispersion to obtain the second paste.

[0047] Here, it goes without saying that the first solvent, second solvent, third solvent, and fourth solvent may be the same type of solvent or may be different, and the present invention is not limited thereto.

[0048] Here, the present invention does not limit the order of producing the first paste and the second paste, and the second paste may be produced first, and then the first paste.

[0049] In one example, the first solvent and the third solvent The medium is , each Water, N-methylpyrrolidone, ethanol, acetone, etc. At least one of the following is selected: The first ceramic particles and the second ceramic particles are dispersed by high-speed stirring, high-pressure homogenization, sand mill dispersion, etc. each The mass concentrations of the first ceramic particles and the second ceramic particles in the dispersion liquid are uniformly dispersed in the solvent. both It ranges from 2% to 40%.

[0050] In one example, the second solvent and the fourth solvent The medium is , each Water, N-methylpyrrolidone, ethanol, acetone, etc. At least one of the following is selected: The first nanofiber material and the second nanofiber material were dispersed using high-speed stirring, high-pressure homogenization, sand mill dispersion, etc. Solvents The first nanofibers are uniformly dispersed in the and Second nanofiber dispersion liquid The mass concentration at both It is 2% to 30%.

[0051] where: Multiple The length of the first nanofiber is such that the difference in length is 500 nm or less, i.e. Suitable They may be different as long as they are within the size range. Multiple The length of the second nanofiber is determined as long as the difference in length is 200 nm or less, i.e. Suitable They may be different as long as they are within the size range.

[0052] Here, nanofibers of different lengths are realized based on the selection of the nanofiber raw material; for example, when nanofiber materials of different materials are selected, nanofibers of different lengths may be formed.

[0053] In other examples, nanofibers of different lengths may be formed by corresponding technical solutions.

[0054] The raw nanofiber material or the cut nanofiber material is cut into nanofibers of different lengths by one or more cuts.

[0055] Here, by cutting the nanofiber material, a short nanofiber material can be formed based on a raw material of nanofiber material of one length. For example, the nanofiber material can be cut in half of the raw material, and in other examples, this can be achieved without adopting the half-cutting method.

[0056] Any existing or improved means for achieving cutting of nanofiber material may be used as an embodiment of the present invention, including by etching the nanofiber material, for example, by etching the nanofiber to half its original length.

[0057] Depending on the desired layering, a single cut or multiple cuts can be made to the feedstock, for example, by first etching the nanofiber material to half the length of the feedstock, and then Part Half the length of the nanofiber material is retained, and the other part of the nanofiber material is cut to half the length to obtain a nanofiber material of one-quarter the length; in other examples, a portion of the nanofiber material of one-quarter the length may be further cut, and the number of cuts can be set as desired.

[0058] Naturally, One Other raw materials for nanofiber materials Nanofiber materials Joining to one end of the raw material, One of the bonded nanofiber material; Nanofiber materials Joining to one end of the raw material, One At least one joining step may be performed, joining one end of a joined nanofiber material to one end of another joined nanofiber material, and one or more joinings may be performed to form nanofiber materials of different lengths.

[0059] In this way, the objects of joining are: Nanofiber materials One end of the raw material and the other Nanofiber materials It may be a part of the raw material, Nanofiber materials It may be one end of a raw material and one end of a joined nanofiber material, or one end of a joined nanofiber material and one end of another joined nanofiber material.

[0060] Here, by bonding to the nanofiber material, a long nanofiber material can be formed based on a raw material of one length of nanofiber material, for example, two Nanofiber materials By joining the feedstocks together, a double length nanofiber material may be formed, and in other instances, different lengths may be formed. Nanofiber materials This may be achieved using raw (or grafted nanofiber) materials.

[0061] Any existing or modified means by which bonding of nanofiber materials can be achieved may be embodied in an embodiment of the present invention.

[0062] For example, the conjugation of nanofiber materials may be achieved based on materials with a high content of hydroxyl functional groups (e.g., polyethylene glycol PEG), and the conjugation mentioned above may be achieved by: mixing the nanofiber material to be conjugated and a material containing a large amount of hydroxyl functional groups (e.g., PEG) in a solution; adding molecular sieve particles to the solution as a catalyst; heating the solution and cooling it, and filtering to remove the molecular sieves to obtain the grafted nanofiber material.

[0063] Take nanocellulose as an example. The ends of nanocellulose have a significantly higher hydroxyl content than the middle region. To increase the length of nanocellulose, the activity of hydroxyls can be fully utilized. This can be done by: (1) Nanocellulose was mixed with polyethylene glycol (PEG), and the molecular weight of PEG was 50,000 to 1,000,000 g / mol. Mass ratio of accounts for 1% of the nanocellulose, and the two are thoroughly and uniformly stirred to form the corresponding solution. (2) adding 13A molecular sieve particles to the solution, the particle size being 1 mm to 10 mm, and the molecular sieve is a catalyst; (3) 80 over 1-2 hours ℃ to water bathHeat with (4) After cooling to room temperature and filtering out the 13A molecular sieve particles, the grafted nanocellulose is obtained.

[0064] In the above solution, nanocellulose can be crosslinked by adding a material containing a large amount of hydroxyl functional groups (e.g., PEG). The polymerization reaction between PEG and nanocellulose can be accelerated by using a molecular sieve (e.g., 13A molecular sieve) as a catalyst, ultimately forming a nanocellulose-PEG-nanocellulose structure. Depending on the desired layering, the raw material can be bonded once or multiple times. For example, the raw nanofiber material can be bonded twice as long as the raw material, and some of the double-length nanofiber material can be reserved and bonded to the other double-length nanofiber material or to the raw material or the double-length nanofiber material to obtain a nanofiber material that is three or four times longer. In other cases, further bonding can be performed. The number of bonding times can be freely set as needed.

[0065] Here, mixing a first ceramic dispersion with a first nanofiber dispersion to obtain a first paste and mixing a second ceramic dispersion with a second nanofiber dispersion to obtain a second paste both involve the following: mixing the first ceramic dispersion with the first nanofiber dispersion to obtain a first mixed solution, and mixing the second ceramic dispersion with the second nanofiber dispersion to obtain a second mixed solution, using a mixing method such as high-speed stirring, high-pressure homogenization, or sand mill dispersion. Then, adding an adhesive to both the first mixed solution and the second mixed solution, respectively, to obtain a first paste and a second paste. Here, the adhesive is at least one of polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, styrene butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, and polyimide. The adhesive accounts for 1% to 10% of the solid mass in the first mixed solution and the second mixed solution, respectively.

[0066] In one example, the coating method for film formation is to first coat the first paste on a base film and dry it to obtain a first coating layer, and then coat the first coating layer with a second paste and dry it to obtain the coated separator. Coating methods include spray coating, dip coating, microgravure roll coating, print coating, extrusion coating, and wire bar coating. At least one of The base film is, for example, a polyolefin base film, the thickness of which is 3 to 30 microns, and the drying temperature is 40 to 130°C. ℃ The coating speed is 10 to 200 m / min.

[0067] Naturally, drying is the first paste and / or Second paste to first coating layer and / or It is just one method of forming a second coating layer, and the first paste and / or The second paste is then transferred to the first coating layer through a phase transition process. and / or A second coating layer may be formed. and / or How to make the first coating layer from the second paste and / or The present invention does not impose any limitations on the method of forming the second coating layer.

[0068] Here, a preferred embodiment further includes selection of ceramics and pretreatment of ceramics before dispersion of ceramics, specifically as follows. Specifically, the selection of ceramics involves selecting first ceramic particles and second ceramic particles having different particle sizes, where the first ceramic particles have an average particle size of 100 to 600 nm and the second ceramic particles have an average particle size of 10 to 60 nm; Specifically, the ceramic pretreatment involves adding the second ceramic particles to a reactor, adding a grafting material, and carrying out a grafting reaction to graft fast lithium ion conductive functional groups onto the surfaces of the second ceramic particles. Specifically, the second ceramic particles are added to a solvent and then placed in a reactor, followed by adding the grafting material, and the fast lithium ion conductive functional groups are grafted onto the second ceramic particles under a certain reaction temperature, pressure, and time.

[0069] The second ceramic particles are not particularly limited, but are preferably a material having a melting point of 200°C or higher, high electrical insulation, and electrochemical stability within the range of use of a lithium battery. Examples include oxide ceramics such as alumina, silica, titanium oxide, zirconia, magnesia, ceria, yttria, and zinc oxide, nitride ceramics such as silicon nitride, titanium nitride, and boron nitride, silicon carbide, calcium carbonate, magnesium sulfate, aluminum sulfate, basic alumina (aluminum hydroxide oxide), potassium titanate, talc, kaolinite, kaolin, nacrite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand. These may be used alone or in combination.

[0070] The first ceramic particles are not particularly limited, and are preferably made of an inorganic material having a melting point of 200°C or higher, high electrical insulation, and electrochemically stable within the range of use of a lithium battery, and may be the same or different from the second ceramic particles. The solvent may be water, ethanol, acetone, NMP, etc. At least one of The grafting target may be polycarbonate, polylactic acid, polyurethane, perfluoropropyl vinyl ether, methyl isopropyl ketone, etc. At least one ofThe reaction temperature is 100-200°C, the reaction pressure is 0.1-0.5 MPa, and the reaction time is 10-50 min. After the reaction is complete, the liquid solvent is removed, leaving a solid, yielding second ceramic particles grafted with high-speed lithium ion conductivity.

[0071] Based on this, the dispersion of ceramics is specifically The first ceramic particles and the pretreated second ceramic particles are dispersed in a first solvent and a third solvent, respectively, to obtain a first ceramic dispersion and a second ceramic dispersion, respectively.

[0072] Furthermore, embodiments of the present invention further provide a battery including a coated separator according to the first aspect of the present invention and its alternative solutions or a coated separator manufactured using the second aspect of the present invention and its alternative solutions, wherein the battery is, for example, a lithium battery.

[0073] The product performance of several embodiments of the present invention will be analyzed through experiments below. [Example]

[0074] In this example, the coated separator is manufactured by the following steps.

[0075] In selecting ceramics, first ceramic particles and second ceramic particles having different particle sizes are selected, wherein the average particle size of the first ceramic particles is 300 nm, the average particle size of the second ceramic particles is 40 nm, and both the first ceramic and the second ceramic are alumina.

[0076] In dispersing the ceramics, the first ceramic particles and the second ceramic particles are uniformly dispersed in N-methylpyrrolidone using high-speed stirring to obtain a first ceramic dispersion and a second ceramic dispersion, where the mass concentration of the first ceramic particles in the first ceramic dispersion and the mass concentration of the second ceramic particles in the second ceramic dispersion are both 20%.

[0077] In the nanomaterial dispersion, first and second nanofibers of different lengths were dispersed in N-methylpyrrolidone to obtain a first nanofiber dispersion and a second nanofiber dispersion, respectively, where the length L50 of the first nanofiber was 600 nm and the length L50 of the second nanofiber was 300 nm, the dispersion method was high-speed stirring, and the mass concentrations of the first and second nanofibers in the dispersant were both 15%.

[0078] In preparing the paste by mixing, a first ceramic dispersion and a first nanofiber dispersion are mixed to obtain a first mixed solution, and a second ceramic dispersion and a second nanofiber dispersion are mixed to obtain a second mixed solution. The mixing method is high-speed stirring, and then an adhesive is added to the first mixed solution and the second mixed solution to obtain a first paste and a second paste, respectively. The adhesive is polyvinyl alcohol, and it accounts for 8% of the solid mass in the first mixed solution and the second mixed solution, respectively. The mass ratio of the first nanofibers to the first ceramic particles is 1:1, and the mass ratio of the second nanofibers to the second ceramic particles is 1:1.

[0079] In the coating method, a first paste is coated on one surface of the base film and dried to form a first coating layer on the surface of the base film, thereby obtaining a semi-finished coated separator. The second paste is coated on the first coating layer and dried to form a second coating layer on the surface of the first coating layer, thereby obtaining a coated separator. Here, the base film is a polyethylene base film, the thickness of which is 9 microns, and the drying temperature is 100 ℃ and the coating speed is 100 m / min. The thickness of the resulting first coating layer is 0.8 microns, and the thickness of the second coating layer is 0.3 microns.

[0080] Here, the first and second nanofibers are specifically one-dimensional nanofibers that deposit on the surface of the base film, forming a layered structure (i.e., hierarchical nanomaterials of different lengths). During the deposition process on the base film, due to surface energy, the longest one-dimensional nanomaterial (which has the highest surface energy, is the most unstable, and is most likely to adhere once it comes into contact with an interface with low surface energy) deposits first, followed by the second-longest, and the shortest nanofiber deposits last, thus forming a layered structure gradually deposited in order of length. The present invention significantly improves the uniformity of the mixture and reduces size differences by mixing nanofibers of similar sizes.

[0081] Using the same method, Examples 2 to 12 and Comparative Examples 1 to 5 were obtained, and the performance of the corresponding separators obtained in Examples 1 to 12 and Comparative Examples 1 to 5 can be seen in Table 1. Except for the differences in the manufacturing parameters shown in Table 1, all the Examples and Comparative Examples are identical to Example 1 in other respects, and therefore, further explanations are omitted here.

[0082] Example 12, shown in Table 1, differs from Example 1 only in that a ceramic pretreatment step was performed on the second ceramic particles before dispersing the S2 ceramic. The second ceramic particles were added to a solvent and then placed in a reactor. The grafting material was then added, and high-speed lithium-ion conductive functional groups were grafted onto the second ceramic particles by maintaining a constant reaction temperature, pressure, and time. The solvent was acetone, and the grafting material was polycarbonate. The reaction temperature was 150°C, the pressure was 0.3 MPa, and the reaction time was 20 minutes. After the reaction was completed, the liquid solvent was removed, leaving a solid, yielding second ceramic particles grafted with high-speed lithium-ion conductive functional groups.

[0083] [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4]

[0084] As can be seen from Table 1 and a comparison of Examples 1 to 12, when the first nanofibers were mixed with the first ceramic particles and when the second nanofibers were mixed with the second ceramic particles, the thermal shrinkage at 180°C was less than 5%, the lithium ion conductivity was greater than 1.2 mS / cm, and the battery capacity retention rate over 30 days was 98% or more. As the thickness of the first coating layer decreased and the thickness of the second coating layer increased (Examples 1, 2, and 3), the heat resistance decreased. This is mainly because the first nanofibers and first ceramic particles are the main skeleton and are in direct contact with the base film. Therefore, the heat resistance of the first coating layer composed of the first nanofibers and first ceramic particles is directly improved, and as the thickness of the first coating layer decreased, the heat resistance was directly reduced. The second coating layer, consisting of the second nanofibers and the second ceramic particles, is in direct contact with the electrode plate, and its uniformity directly determines the capacity retention rate of the battery; the higher the uniformity, the higher the capacity retention rate of the battery. The thickness of the second coating layer can greatly improve the uniformity of the entire coating layer structure, so as the thickness of the second coating layer increases, the capacity retention rate of the battery improves (Examples 1, 2, and 3).

[0085] As can be seen from a comparison between Example 1, Example 5, and Comparative Example 3, if the particle size of the second ceramic particles in the second coating layer is too large, the capacity retention rate of the battery left at high temperatures decreases (Comparative Example 3), and if the particle size of the second ceramic particles in the second coating layer is small, the lithium ion conductivity decreases (Examples 1 and 5). As can be seen from a comparison between Example 1 and Example 7, if the length of the second nanofibers in the second coating layer decreases, the lithium ion conductivity decreases. This phenomenon is caused by the fact that, as the length of the second nanofibers increases, the irregularity of the pore size distribution in the second coating layer increases, resulting in a decrease in the capacity retention rate of the battery, and, as the length of the second nanofibers decreases, the pore size narrows and the lithium ion conduction channel becomes smaller. However, as shown in Example 12, if the particle size of the second ceramic particles in the second coating layer decreases, the lithium ion conductivity decreases. particleThe conductivity of lithium ions can be further improved by grafting fast lithium ion conducting functional groups onto the surface.

[0086] As can be seen from the comparison between Example 1, Comparative Example 2, and Comparative Example 4, as the diameter of the first ceramic particles in the first coating layer increases, the heat resistance of the separator decreases, and as the length of the first nanofibers in the first coating layer increases, the heat resistance of the separator also decreases. The main causes of this phenomenon are: Ceramic particle size and nanofiber If the size increases too much, the gaps between the coating layer materials will increase, limiting the contact points with the base membrane, which will manifest as an inability to effectively suppress shrinkage when heat is applied to the separator.

[0087] As can be seen from a comparison of Example 1, Comparative Example 1, and Comparative Example 5, when the nanofibers and ceramic particles are irregularly distributed, the capacity retention rate of the battery left at high temperatures is only 95%, which is much lower than in the case of layering. When the first nanofibers and the second ceramic particles, or the second nanofibers and the first ceramic particles are mixed, the lithium ion conductivity, the capacity retention rate of the battery left at high temperatures, and the heat resistance are further reduced. The cause of this phenomenon is the nanofibers and ceramic particles. particle When the first coating layer is irregularly distributed, the pore size of the coating layer becomes less uniform and the pore size varies, resulting in a decrease in the capacity retention rate of the battery when left at high temperatures. Nanofiber materials The second nanofiber Made up of , second coating layer Nanofiber materials The first nanofiber Consists of In this case, the size difference between the nanofibers and the ceramics becomes large, which reduces the compatibility of the mixture, while increasing the adhesion of the first coating layer to the second coating layer. 1 The introduction of nanofibers into the first coating layer significantly increases the pore size and its inconsistency, which significantly reduces the capacity retention rate of the battery when left at high temperatures. 2 The introduction of nanofibers reduces the rigidity of the skeleton, resulting in a decrease in heat resistance at high temperatures.

[0088] In the description herein, the use of terms such as "one embodiment," "one example," "specific implementation," or "one example" means that the specific feature, structure, material, or characteristic described with reference to that example or embodiment is included in at least one example or embodiment of the present invention. In the description herein, the exemplary use of the term does not necessarily refer to the same example or embodiment. Furthermore, the specific feature, structure, material, or characteristic described may be combined in any suitable manner in any one or more examples or embodiments.

[0089] Finally, the above embodiments are only used to explain the technical solutions of the present invention, and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still understand that the technical solutions described in the above embodiments can be modified or equivalently substituted for part or all of the technical features therein, and such modifications or substitutions will not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present invention. [Explanation of symbols]

[0090] 10. Base membrane 20, first coating layer 21. The first nanofiber 22. First ceramic particles 30, second coating layer 31. Second nanofiber 32. Second ceramic particles

Claims

1. A coated separator comprising a base membrane and a coating layer structure disposed on at least one surface of the base membrane, the coating layer structure includes at least a first coating layer and a second coating layer, wherein the first coating layer is disposed on at least one surface of the base membrane, the second coating layer is disposed on a side of the first coating layer away from the base membrane, the first coating layer includes a first nanofiber material and first ceramic particles, and the second coating layer includes a second nanofiber material and second ceramic particles; the first nanofiber material comprises a number of first nanofibers, and the second nanofiber material comprises a number of second nanofibers; the difference in length between the several first nanofibers is 500 nm or less, the difference in length between the several second nanofibers is 200 nm or less, the length of the first nanofibers is greater than the length of the second nanofibers, and the average particle size of the first ceramic particles is greater than the average particle size of the second ceramic particles; A coated separator, characterized in that the first nanofibers have a length of 500 to 600 nm, the first ceramic particles have an average particle size of 100 to 300 nm, the second nanofibers have a length of 100 to 300 nm, and the second ceramic particles have an average particle size of 10 to 60 nm.

2. 2. The coated separator according to claim 1, wherein a mass ratio of the first nanofiber material to the first ceramic particles is 5:1 to 1:

5.

3. 2. The coated separator according to claim 1, wherein a mass ratio of the second nanofiber material to the second ceramic particles is 5:1 to 1:

5.

4. 2. The coated separator according to claim 1, wherein the first nanofibers have a diameter of 5 to 50 nm, and the second nanofibers have a diameter of 5 to 50 nm.

5. A coated separator as described in claim 1, characterized in that the thickness of the first coating layer is greater than the thickness of the second coating layer, and the ratio of the thicknesses of the first coating layer and the second coating layer is greater than 2.

6. fast lithium ion conducting functional groups are grafted onto the surfaces of the second ceramic particles; The coated separator according to claim 1, wherein the high-speed lithium ion conductive functional group includes any one of hydroxyl (-OH), carbonyl (-C=O), fluorine (-F), and carboxyl (-COOH).

7. 2. The coated separator according to claim 1, wherein at least one of the first ceramic particles and the second ceramic particles is an inorganic compound that has a melting point of 200°C or higher, is electrically insulating, and is electrochemically stable within the range of use of a lithium battery.

8. The coating separator comprises at least a) ionic conductivity ≥ 1.2 mS / cm; b) Capacity retention rate ≧98%, c) thermal shrinkage at 180 ° C / h ≦ 5%; 2. The coated separator according to claim 1, which satisfies any one of the following conditions:

9. 2. A method for producing the coated separator according to claim 1, the method comprising the steps of: producing a paste; and forming a film by coating. In preparing the paste, a first paste including first ceramic particles and a first nanofiber material is prepared, and a second paste including second ceramic particles and a second nanofiber material is prepared; In the film formation by coating, the first paste is coated on at least one surface of the base film to form a first coating layer, and the second paste is coated on the side of the first coating layer away from the base film to form a second coating layer; moreover, preparing the first paste includes dispersing first ceramic particles in a first solvent to obtain a first ceramic dispersion, dispersing a first nanofiber material in a second solvent to obtain a first nanofiber dispersion, and mixing the first ceramic dispersion and the first nanofiber dispersion to obtain the first paste; A method for producing a coated separator, characterized in that the production of the second paste includes dispersing second ceramic particles in a third solvent to obtain a second ceramic dispersion, dispersing a second nanofiber material in a fourth solvent to obtain a second nanofiber dispersion, and mixing the second ceramic dispersion and the second nanofiber dispersion to obtain the second paste.

10. Prior to producing the paste, the method further comprises sorting ceramics; 10. The method for producing a coated separator according to claim 9, wherein in the selection of ceramics, first ceramic particles and second ceramic particles having different particle sizes are selected, and wherein the average particle size of the first ceramic particles is set to 100 to 300 nm, and the average particle size of the second ceramic particles is set to 10 to 60 nm.

11. 10. The method for producing a coated separator according to claim 9, further comprising a ceramic pretreatment, wherein the ceramic pretreatment involves a graft reaction between the second ceramic particles and a grafting target, thereby grafting high-speed lithium ion conductive functional groups onto the surfaces of the second ceramic particles.

12. The method for manufacturing a coated separator according to claim 11, wherein the grafting object includes any one of polycarbonate, polylactic acid, polyurethane, perfluoropropyl vinyl ether, and methyl isopropyl ketone.

13. A battery comprising the coated separator according to any one of claims 1 to 8 or a coated separator produced by the method for producing a coated separator according to any one of claims 9 to 12, The battery is further characterized in that the battery is a lithium battery.

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