Membrane based on fast ion conductor and preparation method and application thereof

Abstract

The invention belongs to the technical field of diaphragms, and particularly relates to a diaphragm based on a fast ion conductor as well as a preparation method and application. The diaphragm comprises a base membrane, a coating and a polymer glue layer, and the coating layer comprises Mg and Lu doped lithium aluminum titanium phosphate LATP. The method comprises the following steps: carrying out ion doping modification on LATP to prepare a modified LATP material, further preparing the modified LATP material into diaphragm coating slurry, and coating the diaphragm coating slurry on a diaphragm by adopting a gravure roller coating method. The coating diaphragm not only can effectively and rapidly conduct lithium ions, but also can effectively inhibit lithium dendrites, and when the coating diaphragm is applied to a battery, the electrical performance and the safety performance of a battery cell can be improved at the same time.

Description

Technical Field

[0001] The present application belongs to the field of membrane technology, and specifically relates to a membrane based on a fast ion conductor and its preparation method and application. Background Art

[0002] With the widespread application of lithium-ion batteries in electric vehicles, energy storage systems, and portable electronic devices, the requirements for their energy density, cycle life, and safety performance are increasing. As one of the key components of lithium-ion batteries, the separator must not only have good mechanical strength and chemical stability, but also excellent ion conductivity to reduce the internal resistance of the battery and improve its electrochemical performance. Although traditional polyolefin separators (such as polyethylene and polypropylene) have good mechanical properties and electrochemical stability, they have low ionic conductivity and are prone to thermal shrinkage at high temperatures, leading to battery short circuits and even thermal runaway. In order to solve these problems, it is necessary to explore the application of functional coatings on the surface of traditional separators to improve the performance of the separators.

[0003] Fast ion conductor materials (such as lithium aluminum titanium phosphate, Li 1.3 Al 0.3 Ti 1.7 (PO4)3, referred to as LATP) has become an ideal candidate material for separator coating due to its high ionic conductivity, wide electrochemical window and excellent thermal stability. However, the ionic conductivity of pure LATP material is still insufficient to meet the needs of high-performance batteries, and its interfacial compatibility with the electrolyte is poor, which limits its performance in practical applications. In order to further improve the performance of LATP, researchers have proposed a variety of modification methods, among which ion doping is an effective strategy. By introducing suitable doping ions (such as F - 、Eu 3+ CN 117458082A discloses a method of doping LATP with Eu2O3 and coating it on a diaphragm base film. By modifying the LATP in the coating layer on the diaphragm surface, the ion conductivity of the diaphragm is improved. However, Eu 3+ Its stability in high temperatures or electrochemical environments is poor, and the rare earth element europium is expensive. Furthermore, doping can improve the hydrophobicity and interfacial compatibility of LATP, further enhancing its performance in batteries. CN 118693332A discloses a method for modifying LATP by doping with fluorine, which significantly improves the ionic conductivity of LATP, broadens its electrochemical window, and is beneficial for improving its hydrophobicity. However, the fluorine doping process may introduce new impurities or defect states, thereby affecting the crystallinity and uniformity of the material.

[0004] In summary, although some studies have reported the modification of LATP and its application in batteries, the following problems still exist: 1. Limited improvement in ionic conductivity: The existing technology has limited effect on the modification of LATP, which makes it difficult to meet the needs of high-energy-density batteries. 2. Insufficient interface compatibility: The interface impedance between LATP and the electrolyte or electrode material is high, which affects the cycle performance and rate performance of the battery. 3. Complex process: The existing LATP coating preparation process is complex and difficult to achieve large-scale production. Therefore, the development of a membrane based on ion-doped modified LATP and its preparation method to solve the above problems and improve the comprehensive performance of the battery has important research significance and application value. Summary of the Invention

[0005] To overcome the limitations of existing separators in high-capacity, long-cycle lithium-ion batteries, including their low ionic conductivity, poor safety, inability to suppress dendrite penetration, and poor interfacial compatibility, the present invention provides a separator based on a fast ion conductor and a method for preparing the same. This material is prepared by ion-doping LATP into a modified LATP material, which is then further prepared into a separator coating slurry and applied to the separator using a gravure roller coating method.

[0006] In a first aspect, the present invention provides a fast ion conductor-based diaphragm, the diaphragm comprising a base film, a coating layer, and a polymer adhesive layer arranged in sequence; The coating comprises Mg and Lu doped lithium aluminum titanium phosphate LATP.

[0007] The coating of the present invention can not only effectively and quickly conduct lithium ions, but also effectively suppress lithium dendrites. Applying it to batteries can simultaneously improve the electrical performance and safety performance of the battery core.

[0008] Through the polymer glue layer: mechanical reinforcement is achieved: the flexibility and fracture resistance of the composite electrolyte are improved, compensating for the brittleness of the ceramic; interface optimization: the adhesion performance between the diaphragm and the electrode is increased, the interface of the battery cell is smoothed, and the contact impedance between LATP and the electrode is reduced; dendrite suppression: the elastic modulus prevents lithium dendrites from puncturing and uniformizes lithium deposition; Modified LATP (lithium aluminum titanium phosphate) solid electrolyte can improve ionic conductivity, interface stability and electrochemical performance by doping Mg and Lu to meet the application requirements of high-power batteries. + Can replace Li + or Ti 4+ sites, introducing lithium vacancies through the charge compensation mechanism, promoting the + migration, thus improving bulk ionic conductivity. At the same time, Mg doping can inhibit Ti 4+ Reduction (Ti 4+ →Ti³ +), reducing electronic conductivity, enhancing the stability of LATP on the lithium metal negative electrode side, and reducing interface side reactions. 3+ Usually occupies Al 3+ or Ti 4+ sites, whose high valence state stabilizes the crystal structure and reduces the risk of decomposition under high voltage. The introduction of Lu can also form an inert interface layer (such as Lu2O3), reducing the interfacial impedance between LATP and the electrode, widening the electrochemical window and making it suitable for high-voltage cathode materials (such as lithium cobalt oxide and NCM). In general, Mg and Lu co-doping can optimize the lattice defects and microstructure of LATP, balance ionic conductivity and chemical stability, while inhibiting lithium dendrite growth and improving the cycle life and safety of solid-state batteries.

[0009] As a specific embodiment of the present invention, the Mg and Lu doped LATP includes Li 1.3 Al 0.3-x Mg x Lu y Ti 1.7-y (PO4)3, where 0<x≤0.2; 0<y≤0.5.

[0010] As a specific embodiment of the present invention, the base film includes one of polyethylene film (PE), polypropylene film (PP), polyester film (PET), cellulose film, polyimide film (PI), polyamide film (PA), spandex and aramid film.

[0011] The base film in the present invention can be made in-house or commercially available, and the present invention does not impose any particular limitation thereto.

[0012] As a specific embodiment of the present invention, the polymer adhesive layer includes at least one of PVDF, PMMA, polyvinyl alcohol, and acrylate.

[0013] As a specific embodiment of the present invention, the base film has a thickness of 7 μm to 12 μm.

[0014] As a specific embodiment of the present invention, the thickness of the coating is 1 to 4 μm.

[0015] The base film provides mechanical strength to resist stress changes during battery charge and discharge (such as lithium dendrite puncture), while maintaining low porosity to reduce interface side reactions. A thickness of 7 to 12 μm can ensure structural integrity while avoiding excessive thickness that leads to a long ion transmission path. A base film that is too thin (<7 μm) is prone to pinhole defects, increasing the risk of short circuits; a base film that is too thick (>12 μm) will significantly increase the Li + Transmission impedance reduces battery rate performance. This thickness range can balance electrical conductivity and mechanical stability.

[0016] The coating doped with Mg and Lu can improve the compatibility of LATP with electrodes (such as lithium metal or high-voltage cathode). The thickness of 1-4 μm is sufficient to form a continuous protective layer to inhibit the side reactions at the interface (such as Ti 4+ Reduction and electrolyte decomposition), while also avoiding the additional impedance introduced by excessively thick coatings. Modified coatings prepared by sol-gel, magnetron sputtering, or atomic layer deposition (ALD) with a thickness of 1 to 4 μm can achieve uniform coverage and match the thermal expansion coefficient of the base film to avoid cracking or delamination during sintering. As a specific embodiment of the present invention, the raw materials of the coating include Dispersant: 0-5 parts by weight; preferably 2-5 parts by weight; Mg and Lu doped LATP: 10-50 parts by weight; Ceramic material: 0-50 parts by weight; preferably 20-50 parts by weight; Binder: 1-8 parts by weight; Wetting agent: 0.2-3 parts by weight; Thickener: 1-10 parts by weight; The rest is water.

[0017] As a specific embodiment of the present invention, the dispersant includes at least one of polyamide, polyvinyl alcohol, calcium carbonate, silica powder, sodium phosphate, sodium silicate, sodium carbonate, polyacrylamide, polyacrylic acid and its sodium salt, sodium dodecylbenzene sulfonate and sodium hexametaphosphate.

[0018] As a specific embodiment of the present invention, the ceramic material is alumina fiber or boehmite.

[0019] As a specific embodiment of the present invention, the size of the alumina fiber is 100-2000 nm; the size of the boehmite is 50-800 nm.

[0020] As a specific embodiment of the present invention, the binder is at least one of polyacrylamide, polyvinylamide, polyvinylidene fluoride, polyvinyl pyrrolidone, polymethyl methacrylate, polycarboxylic acid, polyacrylic acid, polyurethane acrylate, polyacrylate copolymer emulsion, butadiene rubber, styrene-butadiene rubber and polyurethane.

[0021] As a specific embodiment of the present invention, the wetting agent is polyether-modified silicone and / or polyol.

[0022] As a specific embodiment of the present invention, the thickener is selected from one or more of hydroxymethyl cellulose, sodium carboxymethyl cellulose and water-soluble biopolysaccharides.

[0023] The above raw materials in the present invention can be prepared in-house or purchased commercially, and the present invention is not particularly limited thereto.

[0024] In a second aspect, the present invention provides a method for preparing the above-mentioned fast ion conductor-based diaphragm, comprising the following steps: (1) preparing a coating slurry by uniformly mixing the coating raw materials to obtain a coating slurry; (2) Coating: coating the coating slurry and polymer adhesive layer on one side or both sides of the base film.

[0025] As a specific embodiment of the present invention, the preparation method of the Mg- and Lu-doped LATP in the coating adopts a solid-phase synthesis method, specifically comprising: S1 Weigh raw materials including lithium salt, aluminum oxide, titanium oxide, phosphorus source, lutetium oxide, and magnesium oxide, mix them by ball milling, and dry them; S2: The precursor after drying in step S1 is subjected to a first sintering treatment, and the sample is cooled and ground, and then subjected to a second sintering treatment; thus, the product is obtained.

[0026] As a specific embodiment of the present invention, the phosphorus source is at least one of NH4H2PO4, (NH4)2HPO4, H3PO4, KH2PO4, K2HPO4, NaH2PO4 and Na2HPO4.

[0027] As a specific embodiment of the present invention, the lithium salt includes at least one of lithium carbonate, lithium hydroxide, lithium chloride, lithium bromide, lithium sulfate, lithium fluoride, lithium phosphate, lithium perchlorate and lithium nitrate; preferably, the lithium salt includes lithium carbonate and lithium hydroxide.

[0028] As a specific embodiment of the present invention, the organic peptide is (C4H9O)4Ti.

[0029] As a specific embodiment of the present invention, the sintering conditions include sintering in a ceramic crucible at 300-600° C. for 4-10 hours.

[0030] As a specific embodiment of the present invention, the conditions of the second sintering include a pressure of 5-12 MPa and sintering at 600-800° C. for 3-8 hours.

[0031] The reactions that occur during sintering include: Precursor pre-reaction and decomposition of organic components: The phosphorus source (such as NH4H2PO4) and organic peptide ((C4H9O)4Ti) in the raw materials are decomposed at low temperature to avoid violent outgassing during direct high-temperature sintering, which may lead to excessive porosity or uneven composition of the material.

[0032] Preliminary solid-phase reaction: promoting Li + 、Al 3+ 、Ti 4+ PO4 3-The initial combination of plasma forms an amorphous or partially crystallized intermediate phase (such as an amorphous phosphate complex), which provides a uniform precursor for subsequent crystallization.

[0033] Function: To avoid loosening or cracking of materials caused by rapid escape of raw material decomposition gas (such as NH3, H2O) during high-temperature one-step sintering. Through low-temperature and long-term heat treatment, Mg² + and Lu³ + The uniformity of the initial doping distribution.

[0034] The reactions that occur during sintering include: Crystal phase formation and doping stabilization: NASICON-type LATP (Li 1+ x Al x Ti 2- x (PO4)3) crystallization, promoting Mg 2+ He Lu 3+ into the lattice site (Mg 2+ Replace Li + / Ti 4+ , Lu 3+ Replace Al 3+ / Ti 4+ ), forming a stable solid solution.

[0035] Densification and performance optimization: Sintering under pressure (5-12 MPa) can significantly reduce grain boundary porosity, increase material density (>90%), and reduce grain boundary resistance. Controlling the temperature (600-800°C) prevents excessive temperatures from causing lithium volatilization (e.g., Li2O sublimates easily at temperatures above 800°C) or excessive grain growth.

[0036] Function: To obtain high-purity, high-density LATP ceramics with ionic conductivity up to 10 -4 ~10 -3 Pressure-assisted sintering can compensate for the poor particle contact inherent in solid-phase sintering and improve mechanical strength (such as resistance to lithium dendrite penetration).

[0037] As a specific embodiment of the present invention, the preparation method of the Mg- and Lu-doped LATP in the coating is prepared by a hydrothermal method, specifically comprising: M1 lithium salt, aluminum Salt Add to the solvent for reaction, add lutetium salt and magnesium salt and stir; M2 is then added with a phosphorus source and an organic peptide and stirred to form a sol; dried and calcined to obtain a precursor; M3: Grind the precursor of step M2, calcine twice, and then ball mill to obtain the product.

[0038] As a specific embodiment of the present invention, the calcination conditions include sintering in a ceramic crucible at 300-500° C. for 3-8 hours.

[0039] As a specific embodiment of the present invention, the conditions of the second calcination include calcination at 800-1000° C. and 5-10 MPa for 1-5 hours.

[0040] The purpose of calcination: Removal of organic components: Organic peptides (such as citric acid, EDTA, etc.) are added in step M2 as complexing agents or templates. The main function of calcination is to pyrolyze these organic substances to avoid residual carbon impurities affecting the purity of the material.

[0041] Initial crystallization: At a lower temperature, the precursor is prompted to form an amorphous or partially crystallized intermediate phase (such as amorphous phosphate), laying the foundation for subsequent high-temperature crystallization.

[0042] Function: Prevents particle agglomeration caused by direct high-temperature sintering. Rapid decomposition of organic matter during direct high-temperature treatment can cause explosions or damage the pore structure. Ensures uniform material composition and prevents impurities (such as free carbon) from interfering with ion conduction. Provides a structurally stable precursor for high-temperature crystallization during calcination.

[0043] Calcination has two purposes: Complete the crystal phase transformation: High temperature promotes the transformation of the precursor into the target crystal phase (NASICON type LATP), Mg² + and Lu³ + Entering the lattice site (Li + or Ti 4+ bit), to achieve effective doping.

[0044] Improve density: Sintering under pressure (5-10 MPa) can reduce grain boundary pores, enhance inter-particle contact, and improve bulk ionic conductivity.

[0045] Optimize grain size: High temperature calcination promotes grain growth, but excessive growth leading to increased brittleness can be avoided by controlling the calcination time (1-5 h).

[0046] Function: To obtain high purity and high crystallinity LATP materials, ensuring ionic conductivity (usually >10 -4 S / cm). High-pressure sintering can reduce interfacial impedance and is suitable for the densification requirements of solid-state batteries.

[0047] As a specific embodiment of the present invention, the phosphorus source is at least one of NH4H2PO4, (NH4)2HPO4, H3PO4, KH2PO4, K2HPO4, NaH2PO4 and Na2HPO4.

[0048] As a specific embodiment of the present invention, the lithium salt includes at least one of lithium carbonate, lithium hydroxide, lithium chloride, lithium bromide, lithium sulfate, lithium fluoride, lithium phosphate, lithium perchlorate and lithium nitrate; preferably, the lithium salt includes lithium carbonate and lithium hydroxide.

[0049] As a specific embodiment of the present invention, the aluminum salt includes at least one of aluminum trichloride, aluminum sulfate and aluminum nitrate.

[0050] As a specific embodiment of the present invention, the lutetium salt includes at least one of lutetium fluoride, lutetium chloride, lutetium bromide, lutetium hydroxide and lutetium iodide.

[0051] As a specific embodiment of the present invention, the magnesium salt includes at least one of magnesium oxide, magnesium carbonate, magnesium hydroxide, magnesium chloride and magnesium bromide.

[0052] As a specific embodiment of the present invention, the organic peptide includes (C4H9O)4Ti.

[0053] In a third aspect, the present invention provides the use of the above-mentioned fast ion conductor-based diaphragm or the fast ion conductor-based diaphragm prepared by the above-mentioned method in lithium ion batteries.

[0054] Beneficial effects of the present invention 1. Modified LATP material is prepared by ion doping LATP, which is then further prepared into a separator coating slurry and coated on the separator using a gravure roller coating method. This coated separator not only effectively and rapidly conducts lithium ions but also effectively suppresses lithium dendrites. Its application in batteries can simultaneously improve the electrical performance and safety of the battery cell.

[0055] 2. Through the polymer adhesive layer: mechanical enhancement: improve the flexibility and fracture resistance of the composite electrolyte, and compensate for the brittleness of the ceramic; interface optimization: increase the adhesion performance between the diaphragm and the electrode, make the battery interface smooth, and reduce the contact impedance between LATP and the electrode; dendrite suppression: the elastic modulus prevents lithium dendrites from piercing and homogenizes lithium deposition.

[0056] 3. Through double sintering or double calcination, high-purity and high-density LATP ceramics are obtained, and the ionic conductivity can reach 10 -4 ~10 -3 Pressure-assisted sintering can compensate for the poor particle contact inherent in solid-phase sintering and improve mechanical strength (such as resistance to lithium dendrite penetration). BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of the structure of the diaphragm prepared in the present invention. DETAILED DESCRIPTION

[0058] The present invention will be further described below with reference to specific examples, but they do not constitute any limitation to the present invention.

[0059] Example 1 A method for preparing a diaphragm comprises the following steps: (1) Base film selection: PE base film with a thickness of 9um; (2) Preparation of LATP-Mg-Lu: Solid-phase synthesis of Li 1.3 Al 0.3-x Mg x Lu y Ti 1.7-y (PO4)3 (x=0.1, y=0.4) material. Li2CO3 (0.026 kg), Al2O3 (0.014 kg), TiO2 (0.035 kg), NH4H2PO4 (0.012 kg) and Lu2O3 (0.067 kg) and MgO (0.024 kg) were weighed according to the stoichiometric ratio and thoroughly mixed in acetone solvent by planetary ball milling for 10 hours. In addition, in order to compensate for the loss of lithium during high-temperature sintering, an additional 0.01 kg of Li2CO3 was added as compensation. The mixture was then dried in a vacuum drying oven for 24 hours to evaporate the acetone solvent. The dried precursor was sintered in a ceramic crucible at 500°C for 6 hours. After the sample was cooled and fully ground, it was sintered in a muffle furnace at a pressure of 8 MPa and 900°C for 5 hours. Finally, Li 1.3 Al 0.2 Mg 0.1 Lu 0.4 Ti 1.3 Finally, the obtained LATP-Mg-Lu material was ground by planetary ball milling to obtain LATP-Mg-Lu powder with uniform particles.

[0060] (3) Preparation of coating slurry: First, 20 parts of LATP-Mg-Lu powder, 30 parts of alumina fiber (size 100-2000 nm) and 3 parts of dispersant polyacrylic acid were dissolved in 60 parts of ultrapure water according to the mass ratio, and stirred at 300 rpm for 30 minutes. Then, 7 parts of thickener sodium carboxymethyl cellulose were added and stirred for 30 minutes. Finally, 0.5 parts of wetting agent sodium dodecylbenzene sulfate and 2 parts of adhesive polyvinylidene fluoride were added and stirred for 60 minutes. Finally, the coating solution was prepared and the solution was passed through a 200-mesh sieve to obtain a coating slurry with uniform particle size.

[0061] (4) Preparation of polymer adhesive layer: The solvent dichloromethane was mixed with PVDF powder, stirred and dispersed for 60 minutes, and then methyl methacrylate was added as a binder and stirred for 30 minutes to obtain an ultra-high dispersion PVDF slurry, wherein the solvent was dichloromethane, and the ratio of solvent, PVDF powder and methyl methacrylate was 95:5:5 by mass. The molecular weight (number average) of the PVDF powder was 1.5 million.

[0062] (5) Preparation of diaphragm: The coating slurry made of modified LATP material is evenly coated on one side of the PE base film with a thickness of 9 μm by gravure roller. After drying, a polymer adhesive layer is coated on the coating by gravure roller. After drying, a single-sided modified LATP-polymer coating diaphragm is obtained.

[0063] Example 2 A method for preparing a diaphragm comprises the following steps: (1) Base film selection: PE base film with a thickness of 9um; (2) Synthesis of Li by hydrothermal method 1.3 Al 0.3-x Mg x Lu y Ti 1.7-y (PO4)3 material, x=0.1, y=0.5.

[0064] According to the stoichiometric ratio, LiOH·H2O (0.085 kg) and Al(NO3)3·9H2O (0.013 kg) were added to (200 ml) of anhydrous ethanol at the same time, mixed and stirred in a reaction tank at 100℃ for 2h, and then LuCl3·6H2O (0.042 kg) and MgCl (0.05 kg) were added and stirred for 1h. Then, NH4H2PO4 (0.014 kg) and (C4H9O)4Ti (0.026 kg) were added to react with LiOH·H2O and stirred for 2h to form a sol. The sol was dried in a vacuum oven at 80℃ for 12h, and then placed in a muffle furnace for calcination. The precursor was calcined at 400℃ for 5h. After grinding the precursor in a ball mill, it was transferred to a muffle furnace and calcined at 700℃ and 8mpa for 3h to finally form Li 1.3 Al 0.2 Mg 0.1 Lu 0.5 Ti 1.2 (PO4)3 calcined product, the obtained LATP-Mg-Lu calcined product was ground using a planetary ball mill and sieved to finally obtain LATP-Mg-Lu powder with uniform particles.

[0065] (3) Preparation of coating slurry: First, 20 parts of LATP-Mg-Lu powder, 30 parts of alumina fiber (size 100-2000 nm) and 3 parts of dispersant polyacrylic acid were dissolved in 60 parts of ultrapure water according to the mass ratio, and stirred at 300 rpm for 30 minutes. Then, 7 parts of thickener sodium carboxymethyl cellulose were added and stirred for 30 minutes. Finally, 0.5 parts of wetting agent sodium dodecylbenzene sulfate and 2 parts of adhesive polyvinylidene fluoride were added and stirred for 60 minutes. Finally, the coating solution was prepared and the solution was passed through a 200-mesh sieve to obtain a coating slurry with uniform particle size.

[0066] (4) Preparation of polymer adhesive layer: Mix the solvent dichloromethane with PMMA powder, stir and disperse for 60 minutes, then add methyl methacrylate as a binder and stir for 30 minutes to obtain an ultra-high dispersion PVDF slurry, wherein the solvent is dichloromethane, and the ratio of solvent, PMMA powder and methyl methacrylate is 95:5:5 by mass. The molecular weight (number average) of PVDF powder is 1.5 million.

[0067] (5) Preparation of diaphragm: The coating slurry made of modified LATP material is evenly coated on one side of the PE base film with a thickness of 9 μm by gravure roller. After drying, a polymer adhesive layer is coated on the coating by gravure roller. After drying, a single-sided modified LATP-Mg-Lu-polymer coating diaphragm is obtained. Example 3 A method for preparing a diaphragm comprises the following steps: (1) The preparation method of LATP-modified (LATP-Mg-Lu) powder is the same as that in Example 1.

[0068] (2) Preparation of coating slurry: Add 30 parts of boehmite (size 50-800 nm) to 50 parts of ultrapure water according to mass fraction and stir for 30 minutes; then add 0.8 parts of dispersant (polyacrylamide) and 25 parts of LATP modified (LATP-Mg-Lu) powder and stir for 30 minutes; then add 4 parts of thickener (carboxymethyl cellulose) and stir for 30 minutes; finally, add 3 parts of binder (polybutyl acrylate) and 0.3 parts of wetting agent (sodium lauryl sulfate) and stir for 30 minutes; finally, pass the mixture through a 200 mesh sieve to form a finished slurry; (3) Preparation of diaphragm: The modified LATP-Mg-Lu slurry was evenly coated on both sides of the PE base film with a thickness of 9 μm by extrusion coating. After drying, PVDF and PMMA were dot-coated in a matrix and coated on the coating. After drying, a double-sided modified LATP-Mg-Lu-polymer coating diaphragm was obtained.

[0069] Comparative Example 1 Different from Example 1, Lu2O3 (0.067 kg) was not added.

[0070] Comparative Example 2 Different from Example 1, no MgO (0.024 kg) was added.

[0071] Comparative Example 3 The diaphragm is a PE-based film without coating material.

[0072] Comparative Example 4 Different from Example 1, the separator is not coated with a polymer glue layer.

[0073] The composite diaphragm materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were installed in lithium-ion button batteries (CR2430) and tested. The negative electrode was a metal lithium sheet with a thickness of 1 mm and a diameter of 18 mm, the positive electrode used a commercial lithium iron phosphate electrode with a diameter of 14 mm, and the diaphragm was cut into a disc with a diameter of 20 mm. It was assembled in a glove box, and the oxygen and water vapor were both below 0.1 ppm during assembly. The electrochemical test used the CHI760e electrochemical workstation of Shanghai Chenhua Company and the LAND-CT2001C battery testing system of Wuhan Landian Company. The impedance value of each battery was tested and the ionic conductivity value of the diaphragm was calculated, and the rate performance and cycle performance of the half-cell were tested. The results are shown in Table 1.

[0074] Table 1 Performance of batteries prepared with the separators obtained in Examples 1 to 3 and Comparative Examples 3 to 4

[0075] The separators produced in Examples 1-3 and Comparative Examples 3-4 were tested for peel strength and puncture strength using a high-speed rail testing instrument. Adhesion strength was tested according to GB / T 2792-2014, "Test Method for Peel Strength of Adhesive Tapes," and puncture strength was tested according to GB / T 36363-2018, "Polyolefin Separators for Lithium-ion Batteries."

[0076] The peel strength test involves performing a 180-degree peel on the separator and the positive electrode at a rate of 50 mm / min and a 20 mm electrode width. A separator with greater peel strength can create a smoother cell interface. The puncture test uses a standard probe to penetrate the separator at a rate of 25 mm / min. The greater the puncture strength, the less likely the separator is to be broken down by voltage in the cell, resulting in better cell safety. The test results are as follows: Table 2 Peeling force and puncture strength test of the separators prepared in Examples 1 to 3 and Comparative Examples 3 to 4

[0077] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A fast ion conductor-based diaphragm, characterized in that: The diaphragm includes a base film, a coating layer, and a polymer adhesive layer arranged in sequence; The coating comprises Mg and Lu doped lithium aluminum titanium phosphate LATP.

2. The fast ion conductor-based diaphragm according to claim 1, wherein The Mg and Lu doped LATP includes Li 1.3 Al 0.3-x Mg x Lu y Ti 1.7-y (PO4)3, where 0<x≤0.2; 0<y≤0.5; and / or, the base film comprises one of a polyethylene film, a polypropylene film, a polyester film, a cellulose film, a polyimide film, a polyamide film, a spandex film and an aramid film; And / or, the polymer adhesive layer includes at least one of PVDF, PMMA, polyvinyl alcohol and acrylate.

3. The fast ion conductor-based diaphragm according to claim 1, characterized in that The base film has a thickness of 7 μm to 12 μm; And / or, the coating has a thickness of 1 to 4 μm.

4. The fast ion conductor-based diaphragm according to any one of claims 1 to 3, characterized in that: The raw materials of the coating include: Dispersant: 0-5 parts by weight; preferably 2-5 parts by weight; Mg and Lu doped LATP: 10-50 parts by weight; Ceramic material: 0-50 parts by weight; preferably 20-50 parts by weight; Binder: 1-8 parts by weight; Wetting agent: 0.2-3 parts by weight; Thickener: 1-10 parts by weight; The rest is water.

5. The fast ion conductor-based diaphragm according to claim 4, characterized in that The dispersant comprises at least one of polyamide, polyvinyl alcohol, calcium carbonate, silica powder, sodium phosphate, sodium silicate, sodium carbonate, polyacrylamide, polyacrylic acid and its sodium salt, sodium dodecylbenzene sulfonate and sodium hexametaphosphate; And / or, the ceramic material is alumina fiber and / or boehmite; preferably, the size of the alumina fiber is 100-2000 nm; the size of the boehmite is 50-800 nm; and / or, the binder is at least one of polyacrylamide, polyvinylamide, polyvinylidene fluoride, polyvinyl pyrrolidone, polymethyl methacrylate, polycarboxylic acid, polyacrylic acid, polyurethane acrylate, polyacrylate copolymer emulsion, butadiene rubber, styrene-butadiene rubber, and polyurethane; And / or, the wetting agent is polyether-modified silicone and / or polyol; And / or, the thickener is selected from at least one of hydroxymethyl cellulose, sodium carboxymethyl cellulose and water-soluble biopolysaccharides.

6. A method for preparing a fast ion conductor-based diaphragm according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) preparing a coating slurry by uniformly mixing the raw materials of the coating to obtain a coating slurry; (2) Coating: coating the coating slurry and polymer adhesive layer on one side or both sides of the base film.

7. The preparation method according to claim 6, characterized in that The preparation method of the Mg- and Lu-doped LATP in the coating adopts a solid-phase synthesis method, which specifically includes: S1 Weigh raw materials including lithium salt, aluminum oxide, titanium oxide, phosphorus source, lutetium oxide, and magnesium oxide, mix them by ball milling, and dry them; S2: The precursor dried in step S1 is subjected to a first sintering process, and the sample is cooled and ground, and then subjected to a second sintering process; Preferably, the phosphorus source is at least one of NH4H2PO4, (NH4)2HPO4, H3PO4, KH2PO4, K2HPO4, NaH2PO4 and Na2HPO4; Preferably, the lithium salt includes at least one of lithium carbonate, lithium hydroxide, lithium chloride, lithium bromide, lithium sulfate, lithium fluoride, lithium phosphate, lithium perchlorate and lithium nitrate; preferably, the lithium salt includes lithium carbonate and lithium hydroxide.

8. The preparation method according to claim 7, characterized in that The sintering step includes: sintering in a ceramic crucible at 300-600° C. for 4-10 hours; And / or, the second sintering comprises: sintering at a pressure of 5-12 MPa and 600-800° C. for 3-8 hours.

9. The preparation method according to claim 6, characterized in that The preparation method of the Mg- and Lu-doped LATP in the coating is prepared by a hydrothermal method, which specifically includes: M1: Add lithium salt and aluminum salt to the solvent for reaction, then add lutetium salt and magnesium salt and stir; M2 is then added with a phosphorus source and an organic peptide and stirred to form a sol; dried and calcined to obtain a precursor; M3: Grind the precursor of step M2, calcine twice, and ball mill to obtain; Preferably, the calcination step includes: sintering in a ceramic crucible at 300-500° C. for 3-8 hours; Preferably, the second calcination comprises: calcining at 800-1000°C and 5-10 MPa for 1-5 hours; Preferably, the phosphorus source is at least one of NH4H2PO4, (NH4)2HPO4, H3PO4, KH2PO4, K2HPO4, NaH2PO4 and Na2HPO4; Preferably, the lithium salt includes at least one of lithium carbonate, lithium hydroxide, lithium chloride, lithium bromide, lithium sulfate, lithium fluoride, lithium phosphate, lithium perchlorate and lithium nitrate; preferably, the lithium salt includes lithium carbonate and lithium hydroxide; Preferably, the aluminum salt comprises at least one of aluminum chloride, aluminum sulfate and aluminum nitrate; Preferably, the lutetium salt comprises at least one of lutetium fluoride, lutetium chloride, lutetium bromide, lutetium hydroxide and lutetium iodide; Preferably, the magnesium salt comprises at least one of magnesium oxide, magnesium carbonate, magnesium hydroxide, magnesium chloride and magnesium bromide; Preferably, the organic peptide comprises (C4H9O)4Ti.

10. Use of the fast ion conductor-based diaphragm according to any one of claims 1 to 5 or the fast ion conductor-based diaphragm prepared by the preparation method according to any one of claims 6 to 9 in a lithium ion battery.

Images