Multifunctional battery diaphragm, preparation method thereof, electrochemical device and application

Abstract

The invention discloses a multifunctional battery diaphragm, a preparation method thereof, an electrochemical device and application, and belongs to the technical field of battery diaphragms. The multifunctional battery diaphragm comprises a base membrane and functional coatings coated on the two sides of the base membrane, the functional coatings comprise microsphere binders, inorganic particles and functional auxiliaries, and the microsphere binders are composed of acrylate monomers, divinyl benzene monomers, 4, 4 '-divinyl benzene monomers, 2, 4'-divinyl benzene monomers, 2, 4 '-divinyl benzene monomers, 2, 4'-divinyl benzene monomers and 2, 4 '-divinyl benzene monomers. The polymer is prepared from 4, 4 '-biphenyl diacrylate and 1-(3-sulfo propyl)-2-vinylpyridine inner salt through emulsion copolymerization reaction. The two sides of the base membrane are coated with the functional coatings, the functional coatings comprise the microsphere binder, the inorganic particles and the functional additive, and the quadripolymer serves as the microsphere binder and acts together with the inorganic particles and the functional additive, so that the diaphragm has excellent peel strength, electrolyte wettability and high temperature resistance.

Description

Technical Field

[0001] This application relates to a multifunctional battery separator, its preparation method, electrochemical device, and application, belonging to the field of battery separator technology. Background Technology

[0002] As a key internal component of lithium-ion batteries, the separator's unique microporous structure allows for ion transport while isolating electrons, thus enabling the charging and discharging of lithium-ion batteries. Its performance directly affects the battery's interface structure, internal resistance, capacity, cycle life, and safety performance. Currently, commercially available polyolefin separators are prone to shrinkage at high temperatures and lack sufficient mechanical strength. During long-term cycling, they are easily punctured by lithium dendrites, leading to short circuits and significant thermal safety hazards. Especially under thermal runaway conditions, traditional separators cannot effectively block ion conduction, exacerbating reaction propagation and seriously threatening battery safety. Therefore, developing separators that combine high mechanical strength with excellent heat resistance and fire resistance has become an urgent need in the field of lithium-ion battery safety.

[0003] To address the risk of thermal runaway caused by high energy density, coating the surface of polyolefin separators with functional coatings has become one of the more effective ways to improve the mechanical strength and heat resistance of the separators. Chinese Patent CN114582813A discloses an alumina ceramic-coated separator and its preparation method, illustrating the role of inorganic particles in providing dimensional stability at high temperatures. Its strengthening principle mainly lies in the fact that the functional coating constructs a robust framework, maintaining the initial shape of the separator during the thermal melting and shrinkage of the polyolefin-based membrane, thereby preventing direct contact between the positive and negative electrodes. Furthermore, to achieve active suppression of thermal runaway, Chinese Patent CN119481572A describes a method for preparing a battery separator with thermal runaway prevention function, describing a functional coating that uses microspheres to melt and block pores to achieve battery thermal protection. Its working principle is that in the early stages of thermal runaway, the microspheres melt and flow upon heating, promptly blocking the pores between the electrodes, cutting off ion transport, and thus inhibiting the further expansion of the thermal runaway reaction.

[0004] Although the above methods have achieved initial success, existing functional coating structures still have significant shortcomings in the following aspects, which seriously restrict the further improvement of their overall performance: Ⅰ) Simple microsphere structure design: Most technologies use polymer microspheres with a single function, focusing only on their thermal melting characteristics, while ignoring the influence of the microspheres' affinity for electrolytes and the synergistic effect of inorganic fillers. Ⅱ) Uneven dispersion of inorganic particles: High content of inorganic particles is prone to agglomeration, forming local stress concentration points, which not only reduces the uniformity and mechanical integrity of the coating, but may also puncture the separator substrate, causing the risk of internal short circuit in the battery.

[0005] Therefore, there is a need to provide a battery separator that has good heat resistance and mechanical strength, as well as good electrolyte wettability and long-term interfacial cycle stability. Summary of the Invention

[0006] To address the aforementioned issues, this application provides a multifunctional battery separator, its preparation method, electrochemical device, and applications. The present application discloses that a functional coating is applied to both sides of a base membrane, specifically including a microsphere binder, inorganic particles, and functional additives in the functional coating. The quaternary copolymer acts as the microsphere binder, working in conjunction with the inorganic particles and functional additives to give the separator excellent peel strength, electrolyte wettability, and high-temperature resistance.

[0007] According to one aspect of this application, a multifunctional battery separator is provided, comprising a base film and a functional coating coated on both sides of the base film, the functional coating comprising a microsphere binder, inorganic particles and functional additives, wherein the microsphere binder is prepared by emulsion copolymerization of acrylate monomers, divinylbenzene monomers, 4,4′-biphenyl diacrylate and 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt.

[0008] Specifically, the base film includes PP base film, PE base film, or PP / PE / PP three-layer composite film.

[0009] Preferably, the base film is a PE base film.

[0010] Optionally, the mass ratio of the microsphere binder, inorganic particles and functional additives is (3~5):(90~95):(1~3).

[0011] Preferably, the mass ratio of the microsphere binder, inorganic particles, and functional additives is 3:95:2.

[0012] Optionally, the molar ratio of the acrylate monomer, the divinylbenzene monomer, 4,4′-biphenyl diacrylate and the 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt is (9~6):(0.5~2):(0.1~1):(0.1~1).

[0013] Preferably, the molar ratio of the acrylate monomer, the divinylbenzene monomer, 4,4′-biphenyl diacrylate and the 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt is 8:1:0.5:0.5.

[0014] Optionally, the preparation method of the microsphere binder includes the following steps: S1 Pre-emulsification stage: Under an argon atmosphere, the emulsifier is dissolved in water to obtain an emulsifier solution. A homogeneous oil phase mixture of acrylate monomer, divinylbenzene monomer, 4,4′-diphenyl acrylate and 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt is slowly added dropwise to the emulsifier solution at a speed of 300-500 rpm to prepare a water-oil mixture with a solid content of 10-30%. The speed is increased to 800-1000 rpm and stirred at room temperature for 0.5-1.5 h to emulsify until a bluish-white emulsion is obtained, thus obtaining a pre-emulsion. S2 Seed Polymerization Stage: Dissolve 20-40 wt% of pre-emulsion and 20-40 wt% of initiator in water, heat to 60-70℃ and react for 0.5-1 h to form seed emulsion; S3 main polymerization stage: Keep the S2 temperature constant, add the remaining pre-emulsion and initiator dropwise. After the addition is complete, raise the temperature to 80~90℃ and react for 24~48h to mature. Then lower the temperature to 40℃ and discharge through a 100-mesh sieve to obtain microsphere binder.

[0015] Optionally, the emulsifier comprises one or more of sodium dodecyl sulfate, sodium stearate, sodium α-olefin sulfonate, soybean lecithin, Tween 20, PEG-40 hydrogenated castor oil, decyl glucoside, and polyoxyethylene stearate, wherein the amount of the emulsifier is 1-20% of the total mass of acrylate monomers, divinylbenzene monomers, 4,4′-diphenyl acrylate, and 1-(3-sulfopropyl)-2-vinylpyridine inner salt; and / or The initiator includes one or more of potassium persulfate, ammonium persulfate, sodium persulfate, azobisisobutyramidine hydrochloride, and azobiscyanopentanoic acid; the amount of the initiator is 0.1 to 0.8% of the total mass of acrylate monomers, divinylbenzene monomers, 4,4′-diacrylate biphenyl ester, and 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt.

[0016] Preferably, the emulsifier is sodium dodecyl sulfate; the initiator is ammonium persulfate.

[0017] Optionally, the acrylate monomer is selected from one or more of butyl acrylate, ethyl acrylate, isooctyl acrylate and methyl methacrylate; The divinylbenzene monomers are selected from one or more of divinyltoluene, divinylxylene, p-stilbene, and heterocyclic stilbene derivatives.

[0018] Preferably, the acrylate monomer is butyl acrylate; Preferably, the divinylbenzene monomer is divinylbenzene and biphenyl 4,4′-diacrylate.

[0019] Optionally, the inorganic particles include one or more of alumina, aluminum hydroxide, silicon dioxide, zirconium oxide, titanium oxide, boehmite, boron nitride, aluminum nitride, silicon carbide, aluminosilicate, and barium sulfate; and / or The functional additives include one or more of lithium hexametaphosphate, fatty alcohol polyoxyethylene ether, carboxymethyl cellulose, trioctyl trimellitate, polyaniline, polypyrrole, and Si-69.

[0020] Preferably, the inorganic particles are boehmite.

[0021] Preferably, the functional additive is carboxymethyl cellulose.

[0022] According to another aspect of this application, a method for preparing the above-mentioned multifunctional battery separator is also provided, comprising the following steps: mixing microsphere binder, inorganic particles and functional additives uniformly according to a mass ratio, coating them on both sides of a base film using a coating machine, drying in a forced air at 60~80℃ for 18~24h, vacuum drying at 100~120℃ for 24~48h, and finally rolling them multiple times under a roller press at 15~20 MPa until the surface is smooth, thereby obtaining a multifunctional battery separator.

[0023] Specifically, this application employs a combination of dual-stage drying and high-pressure roller pressing, which makes the functional coating dense and enhances the interfacial adhesion, making it less likely for the functional coating to detach from the base film or delaminate, thus providing a stable ion transport environment and cycle stability for the electrochemical device.

[0024] Specifically, the coating machine used for coating includes one or more of the following: transfer coating machine, slot extrusion coating machine, double-sided coating machine, or microgravure coating machine.

[0025] Preferably, the coating machine used for coating is a transfer coating machine.

[0026] According to another aspect of this application, an electrochemical device is also provided, comprising the multifunctional battery separator described above or the multifunctional battery separator prepared by the above preparation method. The electrochemical device includes a lithium-ion battery, a sodium-ion battery, a lithium metal battery, a sodium metal battery, a lithium supercapacitor, or a sodium supercapacitor.

[0027] Specifically, the lithium-ion battery includes lithium iron phosphate battery, lithium cobalt oxide battery, lithium manganese iron phosphate battery, lithium manganese oxide battery, lithium nickel manganese oxide battery, lithium nickel cobalt aluminum oxide battery, or lithium nickel cobalt manganese oxide battery.

[0028] According to another aspect of this application, the above-described electrochemical device is also provided for use in consumer electronics, electric transportation, power tools, or stationary energy storage.

[0029] The beneficial effects of this application include, but are not limited to: 1. The multifunctional battery separator according to this application, by coating both sides of the base film with a functional coating, specifically discloses that the functional coating includes a microsphere binder, inorganic particles and functional additives, and the quaternary copolymer acts as the microsphere binder, working together with the inorganic particles and functional additives, so that the separator has excellent peel strength, electrolyte wettability and high temperature resistance, and is suitable for various types of lithium batteries, with broad prospects for industrial application.

[0030] 2. According to the multifunctional battery separator of this application, the microsphere binder is prepared by emulsion copolymerization of acrylate monomers, divinylbenzene monomers, 4,4′-diacrylate biphenyl ester, and 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt. The acrylate monomers provide flexible segments, which improve the interfacial adhesion between the functional coating and the base film and prevent peeling or delamination. The 4,4′-diacrylate biphenyl ester further enhances the crosslinking density, increases the thermal weight loss temperature, and reduces the thermal shrinkage rate. The 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt provides polar functional groups, while improving the wettability of the electrolyte and reducing the interfacial impedance, thereby helping to improve the battery power.

[0031] 3. According to the preparation method of the multifunctional battery separator of this application, the preparation of the microsphere binder adopts three stages: pre-emulsification, seed polymerization, and main polymerization, which are initiated in stages. On the one hand, this is conducive to achieving uniform microsphere particle size and ensuring the porous structure of the coating and unobstructed ion channels. On the other hand, it is conducive to improving the dispersion stability of inorganic particles, avoiding their agglomeration, forming local stress concentration points, which would reduce the uniformity and mechanical integrity of the coating, and may also puncture the separator substrate, causing the risk of internal short circuit in the battery. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a SEM image of the multifunctional battery separator in Embodiment 1 of this application; Figure 2 This is a graph showing the peel strength test results of the multifunctional battery separator in Embodiment 1 of this application; Figure 3a Figure showing the results of electrolyte wettability test for commercially available PP battery separators; Figure 3b This is a graph showing the electrolyte wettability test results of the multifunctional battery separator in Example 5 of this application; Figure 4 This is a graph showing the heat resistance test results of the multifunctional battery separator in Embodiment 2 of this application; Figure 5This is a schematic diagram of the rate performance of the multifunctional battery separator assembled lithium battery at room temperature in Embodiment 4 of this application; Figure 6 This is a schematic diagram of the long-cycle performance of the multifunctional battery separator assembled lithium battery at room temperature in Embodiment 4 of this application. Detailed Implementation

[0033] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0035] Example 1 Preparation method of microsphere binder A: S1 Pre-emulsification stage: Under an argon atmosphere, 5 wt% sodium dodecyl sulfate of the total monomer mass was dissolved in water to obtain an emulsifier solution, and 0.5 wt% ammonium persulfate of the total monomer mass was dissolved in water to obtain an initiator solution. 8 mol butyl acrylate, 1 mol divinyl xylene, 0.5 mol biphenyl 4,4′-diacrylate and 0.5 mol 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt homogeneous oil phase mixture were slowly added dropwise to the emulsifier solution at 300 rpm to prepare a water-oil mixture with a solid content of 20%. The stirring speed was increased to 1000 rpm and stirred at room temperature for 1 hour to emulsify to a blue-white emulsion, thus obtaining a pre-emulsion. S2 Seed Polymerization Stage: Dissolve 30wt% of pre-emulsion and 25wt% of initiator ammonium persulfate in water, heat to 60℃ and react for 1 hour to form seed emulsion; S3 main polymerization stage: Keep the S2 temperature constant, add the remaining pre-emulsion and initiator ammonium persulfate dropwise. After the addition is complete, raise the temperature to 80℃ and react for 48 hours to mature. Then lower the temperature to 40℃ and discharge through a 100-mesh sieve to obtain microsphere binder A.

[0036] A method for preparing a multifunctional battery separator: Microsphere binder A, boehmite, and carboxymethyl cellulose were mixed evenly at a mass ratio of 3:95:2 and coated onto both sides of a PE base film using a transfer coating machine. The film was then dried at 60°C with forced air for 24 hours, followed by vacuum drying at 120°C for 48 hours. Finally, the film was rolled multiple times at 20 MPa using a roller press until the surface was smooth, thus obtaining a multifunctional battery separator.

[0037] Example 2 Preparation method of microsphere binder B: S1 Pre-emulsification stage: Under an argon atmosphere, 5 wt% of the total monomer mass of polyoxyethylene stearate was dissolved in water to obtain an emulsifier solution. 0.5 wt% of the total monomer mass of azobisacrylonitrile valerate was dissolved in water to obtain an initiator solution. 7 mol of ethyl acrylate, 2 mol of divinyltoluene, 0.5 mol of biphenyl 4,4′-diacrylate, and 0.5 mol of 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt homogeneous oil phase mixture were slowly added dropwise to the emulsifier solution at 500 rpm to prepare a water-oil mixture with a solid content of 30%. The stirring speed was increased to 800 rpm, and the mixture was stirred at room temperature for 0.5 h to emulsify into a bluish-white emulsion, thus obtaining a pre-emulsion. S2 Seed Polymerization Stage: 30 wt% of pre-emulsion and 40 wt% of initiator azodiacetic acid valerate are dissolved in water and heated to 70 ℃ for 1 h to form seed emulsion; S3 main polymerization stage: Keep the S2 temperature constant, add the remaining pre-emulsion and initiator azodiacetic acid valerate dropwise. After the addition is complete, raise the temperature to 90℃ and react for 48 hours to mature. Then lower the temperature to 40℃ and discharge through a 100-mesh sieve to obtain microsphere binder B.

[0038] A method for preparing a multifunctional battery separator: Microsphere binder B, aluminum hydroxide and lithium hexametaphosphate were mixed evenly in a mass ratio of 4:93:3 and coated on both sides of a PP base film using a slot extrusion coating machine. The film was dried at 80°C for 24 hours and then vacuum dried at 120°C for 48 hours. Finally, it was rolled multiple times at 15 MPa using a roller press until the surface was smooth, thus obtaining a multifunctional battery separator.

[0039] Example 3 Preparation method of microsphere binder C: S1 Pre-emulsification Stage: Under an argon atmosphere, 10 wt% of Tween 20 (total monomer mass) was dissolved in water to obtain an emulsifier solution. 0.5 wt% of potassium persulfate (initiator) (total monomer mass) was dissolved in water to obtain an initiator solution. 9 mol of isooctyl acrylate, 1 mol of p-diphenylvinylbenzene, 0.5 mol of biphenyl 4,4′-diacrylate, and 0.5 mol of 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt were slowly added dropwise to the emulsifier solution at 500 rpm to prepare a homogeneous oil phase mixture with a solid content of 10%. The stirring speed was increased to 900 rpm, and the mixture was stirred at room temperature for 0.5 h to emulsify into a bluish-white emulsion, thus obtaining a pre-emulsion. S2 Seed Polymerization Stage: Dissolve 20wt% of pre-emulsion and 25wt% of initiator potassium persulfate in water, heat to 70℃ and react for 0.5h to form seed emulsion; S3 main polymerization stage: Keep the temperature of S2 constant, add the remaining pre-emulsion and initiator potassium persulfate dropwise. After the addition is complete, raise the temperature to 80℃ and react for 24 hours to mature. Then lower the temperature to 40℃ and discharge through a 100-mesh sieve to obtain microsphere binder C.

[0040] A method for preparing a multifunctional battery separator: Microsphere binder C, zirconium oxide and polyaniline were mixed evenly at a mass ratio of 5:90:5 and coated on both sides of a PP / PE / PP three-layer composite film using a slot extrusion coating machine. The film was dried at 60°C with forced air for 18 hours and then vacuum dried at 100°C for 24 hours. Finally, it was rolled multiple times at 15MPa with a roller press until the surface was smooth, thus obtaining a multifunctional battery separator.

[0041] Example 4 Preparation method of microsphere binder D: S1 Pre-emulsification stage: Under an argon atmosphere, 5 wt% of soybean lecithin (total monomer mass) was dissolved in water to obtain an emulsifier solution. 0.5 wt% of azobisisobutyramidine hydrochloride (total monomer mass) was dissolved in water to prepare an initiator solution. 7 mol of ethyl acrylate, 1 mol of divinyltoluene, 1 mol of biphenyl 4,4′-diacrylate, and 1 mol of 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt were slowly added dropwise to the emulsifier solution at 300 rpm to prepare a homogeneous oil phase mixture, resulting in a water-oil mixture with a solid content of 20%. The stirring speed was increased to 800 rpm, and the mixture was stirred at room temperature for 0.5 h to emulsify into a bluish-white emulsion, thus obtaining a pre-emulsion. S2 Seed Polymerization Stage: 30 wt% of pre-emulsion and 25 wt% of initiator azobisisobutyramidine hydrochloride are dissolved in water, and the mixture is heated to 60℃ and reacted for 0.5 h to form a seed emulsion; S3 main polymerization stage: Keep the S2 temperature constant, add the remaining pre-emulsion and initiator azobisisobutyramidine hydrochloride dropwise. After the addition is complete, raise the temperature to 80℃ and react for 24 hours to mature. Then lower the temperature to 40℃ and discharge through a 100-mesh sieve to obtain microsphere binder D.

[0042] A method for preparing a multifunctional battery separator: Microsphere binder D, barium sulfate and polypyrrole were mixed evenly at a mass ratio of 3:95:2 and coated on both sides of a PP / PE / PP three-layer composite film using a microgravure coating machine. The film was dried at 60°C with forced air for 18 hours and then vacuum dried at 100°C for 24 hours. Finally, it was rolled multiple times under 20 MPa with a roller press until the surface was smooth, thus obtaining a multifunctional battery separator.

[0043] Example 5 Preparation method of microsphere binder E: S1 Pre-emulsification stage: Under an argon atmosphere, 10 wt% of sodium stearate (total monomer mass) was dissolved in water to obtain an emulsifier solution. 0.5 wt% of azodicyanovalerate (total monomer mass) was dissolved in water to prepare an initiator solution. 6 mol of methyl methacrylate, 2 mol of heterocyclic divinylbenzene derivative, 1 mol of 4,4′-diacrylate biphenyl ester, and 1 mol of 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt were slowly added dropwise to the emulsifier solution at 400 rpm to prepare a homogeneous oil phase mixture, resulting in a water-oil mixture with a solid content of 20%. The stirring speed was increased to 1000 rpm, and the mixture was stirred at room temperature for 1.5 h to emulsify into a bluish-white emulsion, thus obtaining a pre-emulsion. S2 Seed Polymerization Stage: 30 wt% of pre-emulsion and 25 wt% of initiator azodicyanovalerate are dissolved in water and heated to 60℃ for 0.5 h to form seed emulsion; S3 main polymerization stage: Keep the S2 temperature constant, add the remaining pre-emulsion and initiator azodicyanovalerate dropwise. After the addition is complete, raise the temperature to 85℃ and react for 36 hours to mature. Then lower the temperature to 40℃ and discharge through a 100-mesh sieve to obtain microsphere binder E.

[0044] A method for preparing a multifunctional battery separator: Microsphere binder E, boron nitride, and trioctyl trimellitate were mixed evenly at a mass ratio of 4:93:3 and coated onto both sides of a PE base film using a double-sided coating machine. The film was then dried at 80°C with forced air for 24 hours, followed by vacuum drying at 120°C for 48 hours. Finally, the film was rolled multiple times at 18 MPa using a roller press until the surface was smooth, thus obtaining a multifunctional battery separator.

[0045] Example 6 Preparation method of microsphere binder F: S1 Pre-emulsification Stage: Under an argon atmosphere, 10 wt% of PEG-40 hydrogenated castor oil (total monomer mass) was dissolved in water to obtain an emulsifier solution. 0.5 wt% of azobis(cyanopentanoic acid) (total monomer mass) was dissolved in water to prepare an initiator solution. At 500 rpm, 8 mol of butyl acrylate monomer, 0.5 mol of divinyl xylene, 0.5 mol of 4,4′-diacrylate biphenyl ester, and 1 mol of 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt homogeneous oil phase mixture were slowly added dropwise to the emulsifier solution to prepare a water-oil mixture with a solid content of 20%. The rotation speed was increased to 900 rpm, and the mixture was stirred at room temperature for 1 hour to emulsify into a blue-white emulsion, thus obtaining a pre-emulsion. S2 Seed Polymerization Stage: Dissolve 40 wt% of pre-emulsion and 40 wt% of initiator azodicyanovalerate in water, heat to 70℃ and react for 1 h to form seed emulsion; S3 main polymerization stage: Keep the temperature of S2 constant, add the remaining pre-emulsion and initiator azodicyanovalerate dropwise. After the addition is complete, raise the temperature to 90℃ and react for 48 hours to mature. Then lower the temperature to 40℃ and discharge through a 100-mesh sieve to obtain microsphere binder F.

[0046] A method for preparing a multifunctional battery separator: Microsphere binder F, titanium dioxide and Si-69 were mixed evenly in a mass ratio of 5:92:3 and coated on both sides of a PP base film using a transfer coating machine. The film was dried at 80°C for 24 hours and then vacuum dried at 110°C for 36 hours. Finally, it was rolled multiple times under 20MPa with a roller press until the surface was smooth, thus obtaining a multifunctional battery separator.

[0047] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not include 4,4′-biphenyl diacrylate and 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt, but all other aspects are the same.

[0048] Experimental Example 1 The membranes obtained in Examples 1-6 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 1.

[0049] Table 1. Test results of diaphragm performance

[0050] As shown in Table 1, the multifunctional battery separator provided in this application exhibits advantages such as a peel strength of 5–6 N / cm, high-temperature resistance of 250–300 °C, and electrolyte wettability of 0–5 °C. It can effectively suppress lithium dendrite penetration caused by thermal shrinkage of the separator under high-temperature conditions and improve the peel strength of the coating. This enhances the safety performance of the battery and extends its cycle life.

[0051] Figure 1 The image shown is a SEM image of the multifunctional battery separator in Example 1 of this application. It can be seen that the separator matrix has no obvious defects and the pores are evenly distributed. This indicates that the separator has good process consistency during preparation, which helps to ensure the interface stability of the battery during charging and discharging.

[0052] Figure 2 This is a graph showing the peel strength test results of the multifunctional battery separator in Embodiment 1 of this application. Figure 2 The measured peel strength was 5 N / cm, which reflects the strong adhesion between the separator coating and the base film, as well as the internal adhesion of the coating. This ensures that the functional coating is not easily detached from the base film or delaminated, providing a stable ion transport environment and cycle stability for the battery.

[0053] Figure 3aThe image shows the electrolyte wettability test results for commercially available PP battery separators. It can be seen that the electrolyte contact angle of commercially available PP separators is 45°. Figure 3b The figure shows the test results of electrolyte wettability of the multifunctional battery separator in Example 5 of this application. The electrolyte contact angle is 0°, which reflects good electrolyte wettability. The significant improvement in the contact angle is beneficial to reducing interfacial impedance and improving battery power characteristics.

[0054] Figure 4 The graph shows the heat resistance test results of the multifunctional battery separator in Embodiment 2 of this application. It can be seen that the thermal weight loss temperature is 280°C, indicating that it has excellent high temperature resistance. This ensures that the separator maintains dimensional stability and structural integrity at high temperatures, effectively blocking the positive and negative electrodes and avoiding short circuits.

[0055] Using the multifunctional separator of Example 4 of this application as a key functional component of the lithium battery, a lithium battery was assembled and its electrochemical performance was tested. The test results are as follows: Figure 5 and Figure 6 ,in Figure 5 This is a schematic diagram illustrating the rate performance of the multifunctional battery separator assembled lithium battery at room temperature in Embodiment 4 of this application. It can be seen that the separator exhibits excellent rate performance, with a reversible capacity of up to 50.98 mAh g⁻¹ at 5 C rate. -1 When the current density returns to the initial current density, its capacity can also be effectively restored. Figure 6 This is a schematic diagram of the long-cycle performance of the multifunctional battery separator assembled lithium battery at room temperature in Embodiment 4 of this application. It can be seen that the initial specific capacity is 98.10 mAh g⁻¹. -1 After 500 cycles, the specific capacity was 89.94 mAh g. -1 It has a capacity retention rate of up to 91.68% and excellent cycle stability.

[0056] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A multifunctional battery separator, characterized in that, The invention includes a base film and a functional coating applied to both sides of the base film. The functional coating includes a microsphere binder, inorganic particles, and functional additives. The microsphere binder is prepared by emulsion copolymerization of acrylate monomers, divinylbenzene monomers, 4,4′-biphenyl diacrylate, and 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt.

2. The multifunctional battery separator according to claim 1, characterized in that, The mass ratio of the microsphere binder, inorganic particles and functional additives is (3~5):(90~95):(1~3).

3. The multifunctional battery separator according to claim 1, characterized in that, The molar ratio of the acrylate monomers, divinylbenzene monomers, 4,4′-biphenyl diacrylate and 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt is (9~6):(0.5~2):(0.1~1):(0.1~1).

4. The multifunctional battery separator according to claim 1, characterized in that, The preparation method of the microsphere binder includes the following steps: S1 Pre-emulsification stage: Under an argon atmosphere, the emulsifier is dissolved in water to obtain an emulsifier solution. A homogeneous oil phase mixture of acrylate monomer, divinylbenzene monomer, 4,4′-diphenyl acrylate and 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt is slowly added dropwise to the emulsifier solution at a speed of 300-500 rpm to prepare a water-oil mixture with a solid content of 10-30%. The speed is increased to 800-1000 rpm and stirred at room temperature for 0.5-1.5 h to emulsify until a bluish-white emulsion is obtained, thus obtaining a pre-emulsion. S2 Seed Polymerization Stage: Dissolve 20-40 wt% of pre-emulsion and 20-40 wt% of initiator in water, heat to 60-70℃ and react for 0.5-1 h to form seed emulsion; S3 main polymerization stage: Keep the S2 temperature constant, add the remaining pre-emulsion and initiator dropwise. After the addition is complete, raise the temperature to 80~90℃ and react for 24~48h to mature. Then lower the temperature to 40℃ and discharge through a 100-mesh sieve to obtain microsphere binder.

5. The multifunctional battery separator according to claim 4, characterized in that, The emulsifier comprises one or more of sodium dodecyl sulfate, sodium stearate, sodium α-olefin sulfonate, soybean lecithin, Tween 20, PEG-40 hydrogenated castor oil, decyl glucoside, and polyoxyethylene stearate, wherein the amount of the emulsifier is 1-20% of the total mass of acrylate monomers, divinylbenzene monomers, 4,4′-biphenyl diacrylate, and 1-(3-sulfopropyl)-2-vinylpyridine inner salt; and / or The initiator includes one or more of potassium persulfate, ammonium persulfate, sodium persulfate, azobisisobutyramidine hydrochloride, and azobiscyanopentanoic acid; the amount of the initiator is 0.1 to 0.8% of the total mass of acrylate monomers, divinylbenzene monomers, 4,4′-diacrylate biphenyl ester, and 1-(3-sulfonylpropyl)-2-vinylpyridine inner salt.

6. The multifunctional battery separator according to claim 4, characterized in that, The acrylate monomers are selected from one or more of butyl acrylate, ethyl acrylate, isooctyl acrylate, and methyl methacrylate; The divinylbenzene monomers are selected from one or more of divinyltoluene, divinylxylene, p-stilbene, and heterocyclic stilbene derivatives.

7. The multifunctional battery separator according to claim 1, characterized in that, The inorganic particles include one or more of the following: alumina, aluminum hydroxide, silicon dioxide, zirconium oxide, titanium oxide, boehmite, boron nitride, aluminum nitride, silicon carbide, aluminosilicate, and barium sulfate; and / or The functional additives include one or more of lithium hexametaphosphate, fatty alcohol polyoxyethylene ether, carboxymethyl cellulose, trioctyl trimellitate, polyaniline, polypyrrole, and Si-69.

8. The method for preparing a multifunctional battery separator according to any one of claims 1 to 7, characterized in that, The process includes the following steps: mixing microsphere binder, inorganic particles and functional additives evenly according to the mass ratio, coating them on both sides of the base film using a coating machine, drying at 60~80℃ for 18~24h with forced air, drying at 100~120℃ under vacuum for 24~48h, and finally rolling them multiple times under 15~20 MPa with a roller press until the surface is smooth, thus obtaining a multifunctional battery separator.

9. An electrochemical device, characterized in that, The multifunctional battery separator includes any one of claims 1 to 7 or the multifunctional battery separator prepared by the preparation method described in claim 8; The electrochemical device includes a lithium-ion battery, a sodium-ion battery, a lithium metal battery, a sodium metal battery, a lithium supercapacitor, or a sodium supercapacitor.

10. The application of the electrochemical device of claim 9 in the fields of consumer electronics, electric transportation, power tools or stationary energy storage.

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