A water-based composite coating for lithium battery separators, coating, and preparation method and application thereof

Abstract

The present invention belongs to the field of lithium-ion battery materials technology, specifically relating to a water-based organic-inorganic composite coating and composite coating for lithium battery separators. The invention further discloses a preparation method thereof, as well as uses thereof for preparing lithium battery separators and lithium batteries. The water-based organic-inorganic composite coating for lithium battery separators described herein comprises a solid electrolyte, an inorganic powder, and an organic emulsion as the main polymers, with a thickener, a pH adjuster, and a binder added to form a water-based organic-inorganic polymer system. By controlling the degree of dispersion during the polymerization reaction and combining a dispersion treatment, high-speed emulsification dispersion treatment, and sand milling, the coating system's stability and performance are effectively improved and guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and specifically relates to a water-based organic-inorganic composite coating and a composite coating for lithium battery separators. The invention further discloses a preparation method thereof, and uses thereof in preparing lithium battery separators and lithium batteries. Background Art

[0002] In recent years, with growing environmental awareness and pressure on the living environment, the importance of green and clean energy in the power energy sector has gradually increased. As a key direction and product in the energy conversion and storage fields, lithium-ion batteries occupy a key position. Lithium-ion batteries are a type of chemical battery that relies on the shuttle of lithium ions between positive and negative electrodes to achieve discharge. They have the characteristics and advantages of high energy density, high operating voltage, long cycle life, low self-discharge rate, and environmental protection. As a result, they are widely used in electronic products, electric vehicles, energy storage batteries, and other fields. In particular, the demand for lithium-ion batteries in the new energy vehicle field is increasing year by year.

[0003] Lithium-ion batteries, in terms of their structural composition, primarily consist of positive electrode materials, negative electrode materials, electrolytes, and separators. The separator, as one of the key internal components of a lithium-ion battery, is a crucial component. Its fundamental function is to separate the positive and negative electrodes to prevent short circuits, while ensuring that lithium ions can flow through microporous channels during charging and discharging to ensure proper battery operation. The performance of the separator determines parameters such as the battery's interface structure and internal resistance, and directly impacts battery characteristics such as capacity, cycling, and safety. A separator with excellent performance plays a crucial role in improving the battery's overall performance.

[0004] In recent years, the continuous development of lithium-ion batteries as power vehicles and energy storage battery products has placed more stringent requirements on the performance of lithium-ion battery separators. As a result, the heat resistance and liquid absorption properties of traditional lithium-ion battery separators have become difficult to meet the application requirements of power batteries. In order to further meet the market's performance requirements for lithium-ion battery separators, the modification and optimization of lithium-ion battery separators has become an effective method.

[0005] For example, Chinese patent CN112563660A discloses a method for preparing a lithium battery separator for solid-state electrolytes. This method uses modified polyvinyl alcohol (PVA) as a film-forming agent by grafting and modifying polyvinyl alcohol. The modified polyvinyl alcohol is then used as a film-forming agent. The film-forming effect of the modified polyvinyl alcohol is utilized to achieve uniform distribution and fixation of nano-titanium dioxide and yttrium hydride on the base film. The pore size of the diaphragm is simultaneously controlled to prevent conventional film-forming agents from affecting the permeability of the diaphragm. The resulting diaphragm is suitable for use as a solid-state electrolyte lithium battery separator. The diaphragm has high ionic conductivity and enhances the safety of lithium batteries. However, this lithium battery separator solution requires a large amount of solvent during implementation, which can easily cause environmental pollution. Furthermore, a single organic coating cannot improve the thermal shrinkage of the lithium battery separator, affecting the overall performance of the subsequent battery. Furthermore, a single inorganic coating has poor adhesion, resulting in a large contact angle between the separator and the electrolyte.

[0006] Another example is the conductive ceramic composite diaphragm disclosed in Chinese patent CN108878751A, which includes a porous base membrane and a conductive ceramic composite coating coated on one or both sides of the porous base membrane; wherein the conductive ceramic composite coating includes an organic polymer, a nano-inorganic solid electrolyte, a polymer grafted modified ceramic, a binder, and a wetting agent; and the polymer grafted modified ceramic is a ceramic particle grafted and modified with an acrylic polymer. In this solution, by introducing polymer grafted modified ceramic into the nano-inorganic solid electrolyte, the mechanical and electrochemical properties of the solid electrolyte are improved. The conductive ceramic composite diaphragm has excellent thermal stability and mechanical strength, and improves lithium-ion cycling performance. However, in this solution, the added ceramic particles must undergo grafting modification pretreatment before they can function, which increases the number of process operations. Moreover, the mechanical properties of the diaphragm material are not ideal.

[0007] In view of this, the development of a lithium battery separator composite coating with thermal stability, better mechanical properties and simpler preparation process has positive significance for improving the electrochemical stability and application performance of lithium batteries. Summary of the Invention

[0008] To this end, the technical problem to be solved by the present invention is to provide a water-based organic-inorganic composite coating for lithium battery separators, the composite coating having the advantages of simple and easy preparation process and green and environmentally friendly synthesis system, and further discloses its preparation method;

[0009] The second technical problem to be solved by the present invention is to provide an aqueous organic-inorganic composite coating for lithium battery separators, which has the characteristics of better thermal stability and mechanical strength, effectively improves the lyophilic properties of the electrolyte, and thus improves the ionic conductivity of the lithium battery, electrochemical stability and application performance.

[0010] The second technical problem to be solved by the present invention is to provide a lithium ion battery separator and a lithium ion battery.

[0011] To solve the above technical problems, the present invention provides a method for preparing a water-based composite coating for a lithium battery separator, comprising the following steps:

[0012] (1) Mix the raw material components according to the following weight ratio: 30-70 parts of water, 0.1-1 parts of thickener, 5-25 parts of solid electrolyte, 20-60 parts of organic emulsion, 0-1 parts of pH regulator, 1-10 parts of binder, and 1-10 parts of wetting agent;

[0013] (2) mechanically dispersing the obtained mixture to obtain a first composite slurry;

[0014] (3) emulsifying and dispersing the first composite slurry to obtain a second composite slurry;

[0015] (4) The second composite slurry is subjected to sand grinding to obtain.

[0016] Specifically, in the method for preparing the water-based composite coating for lithium battery separators, in the step (1):

[0017] The solid electrolyte comprises one or a mixture of garnet-type solid electrolyte material, NASCION-type solid electrolyte material, LISCION-type solid electrolyte material or perovskite-type solid electrolyte material;

[0018] The chemical composition of the LISICON solid electrolyte is specifically Li 14 A(BO4)4, wherein A is one or more elements selected from Zr, Cr, and Sn, and B is one or more elements selected from Si, S, and P; the chemical composition of the NASICON solid electrolyte is specifically Li 1+x A x B 2+x (PO4)3, wherein x is between 0.01 and 0.5, A is one or more elements selected from the group consisting of Al, Y, Ga, Cr, In, Fe, Se, and La, and B is one or more elements selected from the group consisting of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf; the chemical composition of the perovskite-type solid electrolyte is specifically Li 3x A 2 / 3-x BO3, wherein x is between 0.01 and 0.5, A is one or more elements selected from La, Al, Mg, Fe, and Ta, and B is one or more elements selected from Ti, Nb, Sr, and Pr; the chemical composition of the garnet-type solid electrolyte is specifically Li7A3B2O 12, wherein A is one or more elements selected from La, Ca, Sr, Ba, and K, and B is one or more elements selected from Zr, Ta, Nb, and Hf;

[0019] Preferably, the particle size D50 of the solid electrolyte is 100 nm-5 μm;

[0020] The organic emulsion comprises one or a mixture of polyvinylidene fluoride, polyperfluoroethylene, polymethyl methacrylate, and polyacrylonitrile aqueous slurry, preferably a mixture of one or two of the above; preferably, the solid content of the aqueous slurry is 10-50wt%;

[0021] The thickener includes one or a mixture of methyl cellulose, hydroxyethyl cellulose, methyl hydroxypropyl cellulose, guar gum, polyvinyl alcohol or polyethylene wax; preferably, the thickener is methyl cellulose, including but not limited to sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, etc., more preferably methyl cellulose with a molecular weight distribution between 1000-30000;

[0022] The pH regulator includes one or a mixture of ammonia, sodium hydroxide, aluminum hydroxide or alkanolamine;

[0023] The binder includes one or a mixture of several resin binders; preferably, the binder includes a PAA binder or an SBR binder;

[0024] The wetting agent includes one or a mixture of alkylphenol polyoxyethylene ether or acrylic wetting agents; preferably, the wetting agent includes an alkylphenol polyoxyethylene ether wetting agent, including but not limited to OP-4, OP-7, OP-10, OP-15 or OP-20.

[0025] Specifically, the method for preparing the water-based composite coating for lithium battery separators, in the step (1), further comprises the step of adding 5-25 parts by weight of inorganic powder;

[0026] Preferably, the inorganic powder comprises one or a mixture of alumina or boehmite;

[0027] Preferably, the particle size D50 of the inorganic fraction is 100 nm-5 μm.

[0028] Specifically, in the method for preparing the water-based composite coating for lithium battery separators, in the step (2), the mechanical dispersion treatment step includes the step of using a conventional high-speed disperser or a high-speed magnetic stirrer for high-speed dispersion;

[0029] Preferably, the rotation speed of the mechanical dispersion treatment step is controlled to be 1000-4000 r / min, and the dispersion time is 3-10 min.

[0030] Specifically, in the method for preparing the water-based composite coating for lithium battery separators, in the step (3), the emulsification and dispersion treatment step includes the step of dispersing using an emulsifier;

[0031] Preferably, the rotation speed of the emulsification and dispersion treatment step is 7000-14000 r / min, and the dispersion time is 3-10 min.

[0032] Specifically, in the method for preparing the water-based composite coating for lithium battery separators, in the step (4), the sanding step includes the step of sanding using zirconium beads as a sanding medium;

[0033] Preferably, the diameter of the zirconium beads is 0.1 mm to 0.5 mm, and the dispersion time is 10 to 30 minutes.

[0034] The invention also discloses a water-based organic-inorganic composite coating for lithium battery diaphragms prepared by the method.

[0035] The present invention also discloses a lithium battery diaphragm composite coating, wherein the coating is formed by the lithium battery diaphragm water-based organic-inorganic composite coating.

[0036] The present invention also discloses a method for preparing the lithium battery separator composite coating, comprising the steps of applying the lithium battery separator water-based organic-inorganic composite coating on the surface of a selected base film, and drying the coating to obtain the coating;

[0037] Preferably, the coating comprises at least one of blade coating, roller coating, slit coating, and spin coating, preferably micro-concave roller coating;

[0038] Preferably, the coating thickness is 1 μm-30 μm, more preferably 0.5 μm-30 μm.

[0039] Preferably, the drying method includes but is not limited to forced air drying or vacuum drying, and the drying temperature is preferably 50-100°C.

[0040] The present invention also discloses a lithium battery separator, comprising a base film and a composite coating coated on at least one side of the base film;

[0041] The composite coating is the above composite coating, or a composite coating formed by the lithium battery separator water-based organic-inorganic composite coating according to the method.

[0042] Specifically, the lithium battery separator, the base film includes at least one of a PE film, a PP film, a PMMA film, a PVDF film or a PTFE film;

[0043] Preferably, the base film has a thickness of 2 μm-30 μm.

[0044] Preferably, the coating layer can be a single layer coating or a double layer coating, and a reasonable selection can be made according to the performance requirements of the lithium battery.

[0045] The invention also discloses a lithium ion battery, comprising a positive electrode, a negative electrode, and the lithium battery separator.

[0046] The water-based organic-inorganic composite coating that can be used for lithium battery separators described in the present invention uses solid electrolyte, inorganic powder and organic emulsion as the polymerization main body, and adds thickener, pH regulator and binder to form a water-based organic-inorganic polymerization system. The water-based organic-inorganic composite coating described in the present invention effectively improves and ensures the stability of the coating system by controlling the degree of dispersion during the polymerization reaction, combined with the treatment method of dispersion treatment-high-speed emulsification dispersion treatment-sand grinding, and especially improves the defects of traditional coating systems that result in insufficient performance such as coating ion conductivity due to the addition of ceramic particles. At the same time, the present application scheme does not require grafting modification pretreatment of ceramic particles to achieve the purpose of improving coating conductivity, and the entire synthesis method is simple and easy to implement, with high synthesis efficiency, and the water-based slurry system also effectively ensures the environmental friendliness of the production process, which is suitable for expanded production and industrial promotion.

[0047] The lithium battery separator described in the present invention forms a composite coating based on the aqueous organic-inorganic composite coating. Compared with traditional lithium battery separators, the scheme of the present invention optimizes the performance of the lithium battery separator by using an aqueous organic-inorganic composite coating, thereby effectively improving the thermal performance, lyophilicity with the electrolyte, and mechanical properties of the overall separator of the traditional single lithium battery, thereby improving the ionic conductivity, electrochemical stability and electrical performance of the lithium battery. DETAILED DESCRIPTION

[0048] Example 1

[0049] The water-based organic-inorganic composite coating for lithium battery separators described in this embodiment includes the following raw material components in parts by weight:

[0050] 46 parts of water, 0.1 parts of thickener, 5 parts of alumina inorganic powder, 5 parts of lithium lanthanum zirconium oxide powder, 40 parts of PVDF organic emulsion (solid content 30wt%), 0.2 parts of pH regulator, 3.5 parts of binder, 0.3 parts of wetting agent; wherein,

[0051] The particle size D50 of the inorganic powder and the solid electrolyte powder is 300 nm;

[0052] The thickener is CMC with a molecular weight of 10,000;

[0053] The pH regulator is aqueous ammonia;

[0054] The binder is a PAA binder;

[0055] The wetting agent is OP-10.

[0056] The preparation method of the water-based organic-inorganic composite coating for lithium battery separators described in this embodiment comprises the following steps:

[0057] (1) mixing the water, thickener, alumina inorganic powder, solid electrolyte powder, PVDF organic emulsion, pH regulator, binder and wetting agent according to the above selected ingredient amounts to obtain a mixture;

[0058] (2) The obtained mixture is preliminarily dispersed by high-speed mechanical dispersion using a conventional high-speed disperser, with the speed controlled at 3000 r / min and the dispersion time being 5 min to obtain a first composite slurry;

[0059] (3) further dispersing the first composite slurry using an emulsifier at a speed of 12,000 r / min for 5 min to obtain a second composite slurry;

[0060] (4) The second composite slurry was sand-milled for 20 minutes, and 0.3 mm zirconium beads were used as the medium.

[0061] The lithium battery separator described in this embodiment includes a base film and a composite coating coated on one surface of the base film; wherein, the base film is a PE film (9 μm thickness), and the composite coating is a composite coating formed by the water-based organic-inorganic composite coating of the lithium battery separator described in this embodiment.

[0062] Take the water-based organic-inorganic composite coating described in this embodiment and apply it to one side of the base film using a conventional micro-concave roller coating method. The coating thickness of the coating is controlled to be 5 μm. The coated base film is subjected to a blast drying treatment at 80° C. until it is completely dry.

[0063] Example 2

[0064] The water-based organic-inorganic composite coating for lithium battery separators described in this embodiment includes the following raw material components in parts by weight:

[0065] 46 parts of water, 0.1 parts of thickener, 5 parts of alumina inorganic powder, 5 parts of lithium lanthanum zirconium oxide powder, 40 parts of PMMA aqueous emulsion (solid content 30wt%), 0.2 parts of pH regulator, 3.5 parts of binder, 0.3 parts of wetting agent; wherein,

[0066] The particle size D50 of the inorganic powder and the solid electrolyte powder is 300 nm;

[0067] The thickener is CMC with a molecular weight of 10,000;

[0068] The pH regulator is aqueous ammonia;

[0069] The binder is a PAA binder;

[0070] The wetting agent is OP-10.

[0071] The preparation method of the water-based organic-inorganic composite coating for lithium battery separators described in this embodiment comprises the following steps:

[0072] (1) mixing the water, thickener, alumina inorganic powder, PVDF organic emulsion, pH regulator, binder and wetting agent according to the above selected ingredient amounts to obtain a mixture;

[0073] (2) The obtained mixture is preliminarily dispersed by high-speed mechanical dispersion using a conventional high-speed disperser, with the speed controlled at 3000 r / min and the dispersion time being 5 min to obtain a first composite slurry;

[0074] (3) further dispersing the first composite slurry using an emulsifier at a speed of 12,000 r / min for 5 min to obtain a second composite slurry;

[0075] (4) The second composite slurry was sand-milled for 20 minutes using 0.3 mm zirconium beads as the grinding medium.

[0076] The lithium battery separator described in this embodiment includes a base film and a composite coating coated on one surface of the base film; wherein, the base film is a PE film (9 μm thickness), and the composite coating is a composite coating formed by the water-based organic-inorganic composite coating of the lithium battery separator described in this embodiment.

[0077] Take the water-based organic-inorganic composite coating described in this embodiment and apply it to one side of the base film using a conventional micro-concave roller coating method. The coating thickness of the coating is controlled to be 5 μm. The coated base film is subjected to a blast drying treatment at 80° C. until it is completely dry.

[0078] Example 3

[0079] The water-based organic-inorganic composite coating for lithium battery separators described in this embodiment includes the following raw material components in parts by weight:

[0080] 46 parts of water, 0.1 parts of thickener, 5 parts of lithium lanthanum zirconium oxide powder, 45 parts of PVDF organic emulsion (solid content 30wt%), 0.2 parts of pH regulator, 3.5 parts of binder, 0.3 parts of wetting agent; wherein,

[0081] The particle size D50 of the solid electrolyte powder is 300 nm;

[0082] The thickener is CMC with a molecular weight of 10,000;

[0083] The pH regulator is aqueous ammonia;

[0084] The binder is a PAA binder;

[0085] The wetting agent is OP-10.

[0086] The preparation method of the water-based organic-inorganic composite coating for lithium battery separators described in this embodiment comprises the following steps:

[0087] (1) mixing the water, thickener, alumina inorganic powder, PVDF organic emulsion, pH regulator, binder and wetting agent according to the above selected ingredient amounts to obtain a mixture;

[0088] (2) The obtained mixture is preliminarily dispersed by high-speed mechanical dispersion using a conventional high-speed disperser, with the speed controlled at 3000 r / min and the dispersion time being 5 min to obtain a first composite slurry;

[0089] (3) further dispersing the first composite slurry using an emulsifier at a speed of 12,000 r / min for 5 min to obtain a second composite slurry;

[0090] (4) The second composite slurry was sand-milled for 20 minutes using 0.3 mm zirconium beads as the grinding medium.

[0091] The lithium battery separator described in this embodiment includes a base film and a composite coating coated on one surface of the base film; wherein, the base film is a PE film (9 μm thickness), and the composite coating is a composite coating formed by the water-based organic-inorganic composite coating of the lithium battery separator described in this embodiment.

[0092] Take the water-based organic-inorganic composite coating described in this embodiment and apply it to one side of the base film using a conventional micro-concave roller coating method. The coating thickness of the coating is controlled to be 5 μm. The coated base film is subjected to a blast drying treatment at 80° C. until it is completely dry.

[0093] Example 4

[0094] The water-based organic-inorganic composite coating for lithium battery separators described in this embodiment includes the following raw material components in parts by weight:

[0095] 46 parts of water, 0.1 parts of thickener, 10 parts of lithium lanthanum zirconium oxide powder, 40 parts of PVDF organic emulsion (solid content 30wt%), 0.2 parts of pH regulator, 3.5 parts of binder, 0.3 parts of wetting agent; wherein,

[0096] The particle size D50 of the solid electrolyte powder is 300 nm;

[0097] The thickener is CMC with a molecular weight of 10,000;

[0098] The pH regulator is aqueous ammonia;

[0099] The binder is a PAA binder;

[0100] The wetting agent is OP-10.

[0101] The preparation method of the water-based organic-inorganic composite coating for lithium battery separators described in this embodiment comprises the following steps:

[0102] (1) mixing the water, thickener, alumina inorganic powder, PVDF organic emulsion, pH regulator, binder and wetting agent according to the above selected ingredient amounts to obtain a mixture;

[0103] (2) The obtained mixture is preliminarily dispersed by high-speed mechanical dispersion using a conventional high-speed disperser, with the speed controlled at 3000 r / min and the dispersion time being 5 min to obtain a first composite slurry;

[0104] (3) further dispersing the first composite slurry using an emulsifier at a speed of 12,000 r / min for 5 min to obtain a second composite slurry;

[0105] (4) The second composite slurry was sand-milled for 20 minutes using 0.3 mm zirconium beads as the grinding medium.

[0106] The lithium battery separator described in this embodiment includes a base film and a composite coating coated on one surface of the base film; wherein, the base film is a PE film (9 μm thickness), and the composite coating is a composite coating formed by the water-based organic-inorganic composite coating of the lithium battery separator described in this embodiment.

[0107] Take the water-based organic-inorganic composite coating described in this embodiment and apply it to one side of the base film using a conventional micro-concave roller coating method. The coating thickness of the coating is controlled to be 5 μm. The coated base film is subjected to a blast drying treatment at 80° C. until it is completely dry.

[0108] Example 5

[0109] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, with the only difference being that the water-based organic-inorganic composite coating comprises the following raw material components in parts by weight:

[0110] 30 parts of water, 0.1 parts of thickener, 25 parts of lithium lanthanum zirconium oxide powder, 60 parts of PVDF organic emulsion (solid content 30wt%), 0.1 parts of pH regulator, 10 parts of binder, and 1 part of wetting agent.

[0111] Example 6

[0112] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, with the only difference being that the water-based organic-inorganic composite coating comprises the following raw material components in parts by weight:

[0113] 70 parts of water, 1 part of thickener, 5 parts of boehmite inorganic powder, 5 parts of lithium lanthanum zirconium oxide powder, 20 parts of PVDF organic emulsion (solid content 30wt%), 1 part of pH regulator, 1 part of binder, and 10 parts of wetting agent.

[0114] Example 7

[0115] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, with the only difference being that the water-based organic-inorganic composite coating comprises the following raw material components in parts by weight:

[0116] 70 parts of water, 1 part of thickener, 5 parts of boehmite inorganic powder, 5 parts of lithium aluminum titanium phosphate powder, 20 parts of PVDF organic emulsion (solid content 30wt%), 1 part of pH regulator, 1 part of binder, and 10 parts of wetting agent.

[0117] Example 8

[0118] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, with the only difference being that the water-based organic-inorganic composite coating comprises the following raw material components in parts by weight:

[0119] 70 parts of water, 1 part of thickener, 10 parts of inorganic alumina powder, 40 parts of PVDF organic emulsion (solid content 30wt%), 0.2 parts of pH regulator, 3.5 parts of binder, and 0.3 parts of wetting agent.

[0120] Example 9

[0121] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, the only difference being that in the preparation method of the composite emulsion described in this embodiment, in step (2), the rotation speed of the mechanical dispersion treatment step is 500 r / min.

[0122] Example 10

[0123] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, the only difference being that in the preparation method of the composite emulsion described in this embodiment, in step (2), the rotation speed of the mechanical dispersion treatment step is 4500 r / min.

[0124] Example 11

[0125] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, the only difference being that in the preparation method of the composite emulsion described in this embodiment, in step (3), the rotation speed of the emulsification and dispersion treatment step is 3000 r / min.

[0126] Example 12

[0127] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, with the only difference being that in the preparation method of the composite emulsion described in this embodiment, in step (3), the rotation speed of the emulsification and dispersion treatment step is 4000 r / min.

[0128] Example 13

[0129] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, with the only difference being that in the preparation method of the composite emulsion described in this embodiment, in step (3), the dispersion treatment step adopts mechanical high-speed dispersion, and the speed is controlled to be 12000 r / min.

[0130] Example 14

[0131] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, with the only difference being that in the preparation method of the composite emulsion described in this embodiment, in step (4), the diameter of the zirconium bead sanding medium in the sanding treatment step is 0.6 mm.

[0132] Example 15

[0133] The structure and preparation method of the lithium battery separator described in this embodiment are the same as those in Example 1, with the only difference being that in the preparation method of the composite emulsion described in this embodiment, in step (4), the diameter of the zirconium bead sanding medium in the sanding treatment step is 1 mm.

[0134] Comparative Example 1

[0135] The structure and preparation method of the lithium battery separator described in this comparative example are the same as those in Example 1, with the only difference being the preparation method of the emulsion used to form the composite coating. The preparation method of the composite emulsion described in this comparative example only performs the dispersion treatment of step (2), and does not perform steps (3) and (4).

[0136] Comparative Example 2

[0137] The structure and preparation method of the lithium battery separator described in this comparative example are the same as those in Example 1, the only difference being the preparation method of the emulsion used to form the composite coating. The preparation method of the composite emulsion described in this comparative example only performs the dispersion treatments of steps (2) and (3), and does not perform the treatment of step (4).

[0138] Comparative Example 3

[0139] The structure and preparation method of the lithium battery separator described in this comparative example are the same as those in Example 1, the only difference being the preparation method of the emulsion used to form the composite coating. The preparation method of the composite emulsion described in this comparative example only performs the dispersion treatments of steps (2) and (4), and does not perform the treatment of step (3).

[0140] Comparative Example 4

[0141] This comparative example scheme prepares the required lithium battery separator according to the scheme of Example 3 in Chinese patent CN108878751A.

[0142] Comparative Example 5

[0143] This comparative example scheme directly uses PE film as the blank control group.

[0144] Experimental example

[0145] 1. Mechanical properties

[0146] The lithium battery separators prepared in Examples 1-15 and Comparative Examples 1-5 were respectively subjected to mechanical property tests according to the national standard GB-36363-2018 and compared with blank control aluminum foil. The test results are shown in Table 1 below.

[0147] Table 1 Test results of mechanical properties of lithium battery separators

[0148]

[0149] The data in Table 1 demonstrates that the mechanical properties of PE membranes coated with the water-based organic-inorganic composite coating described herein are significantly improved. Of particular note, the coating prepared using the method described herein exhibits superior mechanical properties. Furthermore, adjustments to the preparation method effectively address the drawback of conventional coating systems, where the addition of ceramic particles can negatively impact membrane performance.

[0150] 2. Thermal stability

[0151] The lithium battery separators prepared in Examples 1-15 and Comparative Examples 1-5 were respectively subjected to thermal stability tests according to the national standard GB36363-2018 and compared with blank control aluminum foil. The test results are shown in Table 2 below.

[0152] The test method is a heat shrinkage test, the test temperature is 140° C., and the test time is 30 minutes.

[0153] Table 2 Lithium battery separator thermal stability test results

[0154] Thermal shrinkage (%) Example 1 5.2 Example 2 9.1 Example 3 7.5 Example 4 11.2 Example 5 6.7 Example 6 4.9 Example 7 7.2 Example 8 13.6 Example 9 6.5 Example 10 4.8 Example 11 12.7 Example 12 10.4 Example 13 15.7 Example 14 17.3 Example 15 4.5 Comparative Example 1 22.9 Comparative Example 2 15.9 Comparative Example 3 18.2 Comparative Example 4 20.5 Comparative Example 5 55.3

[0155] It can be seen from the data in Table 2 that the thermal shrinkage of the PE film coated with the water-based organic-inorganic composite coating of the present invention is significantly lower, indicating that its thermal stability is enhanced.

[0156] 3. Lyophilic properties

[0157] The lithium battery separators prepared in Examples 1-15 and Comparative Examples 1-5 were respectively subjected to contact angle test using a contact angle tester, porosity test using a water boiling method, and liquid absorption test using a weighing method to evaluate their lyophilic effect, and compared with blank control aluminum foil. The test results are shown in Table 3 below.

[0158] Table 3 Lithium battery separator lyophilicity test results

[0159]

[0160]

[0161] It can be seen from the data in Table 3 that the PE film coated with the water-based organic-inorganic composite coating of the present invention has better lyophilic properties.

[0162] 4. Ionic conductivity

[0163] The lithium battery separators prepared in Examples 1-15 and Comparative Examples 1-5 were respectively subjected to ion conductivity tests using an electrochemical workstation and compared with blank control aluminum foil. The test results are shown in Table 4 below.

[0164] Table 4 Lithium battery separator lyophilicity test results

[0165]

[0166]

[0167] It can be seen from the data in Table 4 that the ionic conductivity of the PE membrane coated with the water-based organic-inorganic composite coating of the present invention is significantly improved.

[0168] 5. Dispersion effect test

[0169] The lithium battery slurries prepared in Examples 1-15 and Comparative Examples 1-5 were respectively tested for particle size using a particle size analyzer. After standing, the absolute value of the difference in solid content between the upper and lower layers was tested to determine the dispersion effect. The slurries were compared with blank control aluminum foil. The test results are shown in Table 5 below.

[0170] Table 5 Dispersion effect test

[0171]

[0172]

[0173] It can be seen from the data in Table 5 that the aqueous organic-inorganic composite coating of the present invention has a good dispersion effect on the lithium battery slurry.

[0174] In summary, the aqueous coating and separator composite of the present invention, when applied to lithium batteries, can effectively improve the thermal stability of a single separator and reduce its thermal shrinkage. It significantly enhances the electrolyte's lyophilicity and the separator's mechanical properties, thereby improving the battery's ionic conductivity, electrochemical stability, and electrical performance. Furthermore, the use of a pure aqueous emulsion and aqueous solvent ensures an environmentally friendly production process. The preparation method is simple, instruments and equipment are readily available, and the preparation is highly efficient, making it suitable for scaled-up production. This is of great significance for the further development of the lithium battery industry.

[0175] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a water-based composite coating for a lithium battery separator, characterized in that: The steps include: (1) Mix the raw materials according to the following weight ratio: 30-70 parts of water, 0.1-1 parts of thickener, 5-25 parts of solid electrolyte, 20-60 parts of organic emulsion, 0-1 parts of pH adjuster, 1-10 parts of binder, 1-10 parts of wetting agent, and 5-25 parts of inorganic powder; The solid electrolyte comprises one or a mixture of garnet-type solid electrolyte material, NASCION-type solid electrolyte material, LISCION-type solid electrolyte material or perovskite-type solid electrolyte material; The organic emulsion includes one or a mixture of polyvinylidene fluoride, polymethyl methacrylate, and polyacrylonitrile aqueous slurry; (2) mechanically dispersing the obtained mixture to obtain a first composite slurry; (3) dispersing the first composite slurry with an emulsifier at a speed of 7000-14000 r / min for 3-10 min to obtain a second composite slurry; (4) The second composite slurry is sanded using zirconium beads as a grinding medium to obtain the obtained composite slurry.

2. The method for preparing the water-based composite coating for lithium battery separator according to claim 1, characterized in that: In the step (1): the particle size D50 of the solid electrolyte is 100 nm-5 μm.

3. The method for preparing the water-based composite coating for lithium battery separator according to claim 1, characterized in that: In the step (1): the solid content of the aqueous slurry is 10-50wt%; The thickener includes one or a mixture of methyl cellulose, hydroxyethyl cellulose, methyl hydroxypropyl cellulose, guar gum, polyvinyl alcohol or polyethylene wax; The pH regulator includes one or a mixture of ammonia, sodium hydroxide, aluminum hydroxide or alkanolamine; The binder includes a resin binder; The wetting agent includes one or a mixture of alkylphenol polyoxyethylene ether or acrylic acid wetting agents.

4. The method for preparing the water-based composite coating for lithium battery separator according to claim 1, characterized in that: In the step (1), the inorganic powder includes one or a mixture of alumina or boehmite.

5. The method for preparing the water-based composite coating for lithium battery separator according to claim 4, characterized in that: In the step (1), the particle size D50 of the inorganic powder is 100 nm-5 μm.

6. The method for preparing the water-based composite coating for lithium battery separator according to any one of claims 1 to 5, characterized in that: In the step (2), the mechanical dispersion treatment includes the step of using a high-speed disperser or a high-speed magnetic stirrer for high-speed dispersion.

7. The method for preparing the water-based composite coating for lithium battery separator according to claim 6, characterized in that: In the step (2), the rotation speed of the mechanical dispersion treatment is controlled to be 1000-4000 r / min, and the dispersion time is 3-10 min.

8. The method for preparing the water-based composite coating for lithium battery separator according to any one of claims 1 to 5, characterized in that: In the step (4), the diameter of the zirconium beads is 0.1 mm to 0.5 mm, and the dispersion time is 10 to 30 minutes.

9. A water-based organic-inorganic composite coating for lithium battery separators prepared by the method according to any one of claims 1 to 8.

10. A lithium battery separator composite coating, characterized in that: The coating is formed by the water-based organic-inorganic composite coating for lithium battery separators according to claim 9.

11. A method for preparing the lithium battery separator composite coating according to claim 10, characterized in that: The method comprises the steps of applying the water-based organic-inorganic composite coating for lithium battery separators according to claim 9 on the surface of a selected base film, and obtaining the coating by drying.

12. The method for preparing a lithium battery separator composite coating according to claim 11, characterized in that: The coating includes at least one of blade coating, roller coating, slit coating, and spin coating.

13. The method for preparing a lithium battery separator composite coating according to claim 12, characterized in that: The coating thickness is 1 μm-30 μm.

14. A lithium battery separator, characterized in that: It comprises a base film and a composite coating applied on at least one side of the base film; The composite coating is the composite coating according to claim 10, or a composite coating formed by the water-based organic-inorganic composite coating for lithium battery separators according to any one of the methods according to claims 11-13.

15. The lithium battery separator according to claim 14, characterized in that The base film includes at least one of a PE film, a PP film, a PMMA film, a PVDF film or a PTFE film.

16. The lithium battery separator according to claim 15, characterized in that The base film has a thickness of 2 μm-30 μm.

17. A lithium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode, and a lithium battery separator according to any one of claims 14 to 16.

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