Preparation method and application of high-temperature-resistant lithium ion battery coating diaphragm

Abstract

The invention discloses a preparation method and application of a high-temperature-resistant lithium ion battery coating diaphragm, and relates to the technical field of lithium batteries. The upper surface and the lower surface of the polyolefin diaphragm are coated with high-temperature-resistant slurry to endow the diaphragm with high-temperature resistance, attapulgite is added into the slurry to enhance the puncture resistance and the tensile strength of the slurry, sodium citrate is added to enhance the dispersity of materials, polyacrylic acid is added to be compounded as a binder, and the diaphragm has the high-temperature-resistant performance. The thickening agent sodium carboxymethyl cellulose and the alkynol wetting agent are added, so that the viscosity of the slurry is adjusted, sedimentation is prevented, the uniformity of the coating is guaranteed, meanwhile, the interface bonding force between the high-temperature-resistant coating and the polyolefin diaphragm is enhanced, uneven coating and bubble residue are avoided, and heat-resistant irregular granular aluminum oxide is added, so that the heat-resistant shrinkage performance of the slurry is improved. Due to the characteristics of high specific surface area, low density and multistage pores, the structural collapse at high temperature is inhibited, and the thermal stability of the diaphragm is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery, and particularly relates to a preparation method of a high-temperature-resistant lithium ion battery coated diaphragm and application thereof. BACKGROUND

[0002] In a lithium ion battery system, a diaphragm is a key component, which bears the important functions of isolating positive and negative electrodes, preventing short circuit and guaranteeing ion conduction, and its performance has a significant influence on battery safety, stability and cycle life. At present, the industry generally adopts a method of coating a ceramic coating on the surface of a polyethylene diaphragm to improve the heat resistance of the diaphragm. The ceramic material has high thermal stability, and the coating can enhance the heat protection ability of the diaphragm to a certain extent. However, at a higher temperature, the diaphragm appears to be broken, which can cause the positive and negative electrodes of the battery to be short-circuited, instantaneously generate a large current, and cause serious safety problems such as battery overheating, fire and even explosion, and at the same time, aggravate the internal polarization of the battery, damage the charge and discharge performance, and greatly shorten the battery capacity and cycle life.

[0003] The existing ceramic coating technology cannot meet the severe requirements of the battery in a high-temperature environment, and the problem of easy diaphragm breakage at high temperature seriously restricts the application and performance improvement of the lithium ion battery in a high-temperature environment. Therefore, the present application develops a preparation method of a high-temperature-resistant lithium ion battery coated diaphragm to solve the above problems. SUMMARY

[0004] The present application aims to provide a preparation method of a high-temperature-resistant lithium ion battery coated diaphragm and application thereof to solve the problems in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] A high-temperature-resistant lithium ion battery coated diaphragm comprises a base film and a coating layer arranged on the upper surface and the lower surface of the base film.

[0007] Further, the base film is a polyolefin diaphragm, the thickness is 3-18 μm, and the porosity is 33.5%-40.5%.

[0008] Further, the coating layer comprises the following components: inorganic fillers, inorganic fiber powder, dispersants, thickening agents, binders and wetting agents.

[0009] Further, the thickness of the coating layer is 1-8 μm, the bulk density is 1-1.9 g / m 2 / μm, and the coating speed is 10-200 m / min.

[0010] Further, the inorganic fillers are one or more of alumina, boehmite, magnesium hydroxide and barium sulfate, and the inorganic fillers are preferably irregular granular heat-resistant alumina.

[0011] Further, the inorganic fiber powder is one or more of attapulgite, zeolite, fibrous boehmite, silicon carbide fiber, carbon fiber, boron nitride fiber, and preferably attapulgite.

[0012] Further, the dispersant is one or more of sodium citrate, sodium lactate, sodium hexametaphosphate, polyacrylic acid, polyacrylic acid ammonium salt, and polyacrylic acid sodium salt, and preferably sodium citrate.

[0013] Further, the thickening agent is sodium carboxymethyl cellulose.

[0014] Further, the binder is one or more of polyacrylic acid, polyacrylate, acrylonitrile, and polyacrylamide, and preferably a mixture of polyacrylic acid emulsion and solvent-based polyacrylic acid.

[0015] Further, the wetting agent is one or more of acetylenic alcohol, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, and cetyltrimethylammonium bromide, and preferably an acetylenic alcohol wetting agent.

[0016] Further, the wetting agent is 2,4,7,9-tetramethyl-5-decyne-4,7-diol and its oxirane adduct.

[0017] Further, the irregularly granular heat-resistant aluminum oxide has a particle size of D10>0.2 μm, D50: 0.6-1.0 μm, D90<2.5 μm, and D99<4.3 μm.

[0018] Further, the attapulgite has a single fiber longitudinal length of 0.1-3 μm, a radial length of 0.01-0.1 μm, and an aspect ratio (longitudinal length / radial length) of (3-55):1.

[0019] In the above technical solution, the attapulgite has the advantages of low cost, fibrous porous structure, good dispersibility, and large specific surface area, and its special fibrous porous structure can build a firm three-dimensional network structure inside the coating; sodium citrate enhances the dispersibility of the material through the synergistic effect of electrostatic repulsion, steric hindrance, metal ion chelation, and pH adjustment, and is non-toxic and easy to degrade; the solvent-based polyacrylic acid binder has good heat resistance and can improve the heat shrinkage resistance of the coated separator, but using the solvent-based polyacrylic acid binder alone can cause problems such as high coating hardness and poor air permeability of the coated separator, so mixing the polyacrylic acid emulsion with the solvent-based polyacrylic acid binder can reduce the coating hardness and improve the air permeability.

[0020] A preparation method of a high-temperature-resistant lithium ion battery coated separator includes the following steps:

[0021] S1: mixing inorganic cellulose powder, dispersant, and ultrapure water, and stirring to obtain an inorganic fiber dispersion liquid;

[0022] S2: adding inorganic filler into inorganic fiber dispersion liquid, stirring, to obtain mixed dispersion liquid;

[0023] S3: adding thickening agent into mixed dispersion liquid, stirring, grinding, adding binder, wetting agent, continuing stirring, to obtain slurry;

[0024] S4: taking base film, coating slurry on upper surface and lower surface of base film, drying, forming coating layer, to obtain high-temperature-resistant lithium ion battery coated separator.

[0025] Further, in steps S1 and S3, the process conditions for stirring are: stirring speed 600-1500 r / min, stirring time 60-120 min.

[0026] Further, in step S2, the process conditions for stirring are: stirring speed 600-1500 r / min, stirring time 20-60 min.

[0027] Further, in step S3, the process conditions for grinding and dispersing are: speed 500-1000 r / min, grinding flow 900-1700 L / h, grinding 1-4 times.

[0028] Further, in step S2, the process conditions for continuing stirring are: stirring speed 100-500 r / min, stirring time 20-60 min.

[0029] Further, in step S3, the slurry comprises the following components: inorganic fiber powder 0.5-6% by mass, dispersant 0.5-6%, inorganic filler 25-45%, thickening agent 0.1-1%, binder 0.5-5%, wetting agent 0.1-0.9%, and the balance is ultrapure water.

[0030] Further, in step S4, the coating is performed by micro-concave roller coating, and the coating speed is 10-200 m / min.

[0031] Further, in step S4, the process conditions for drying are: at a temperature of 50-90°C, drying for 1-2 h.

[0032] In the above technical solution, the inorganic fiber powder provides the puncture resistance and tensile strength of the separator, prevents the deformation or damage of the separator during the charging and discharging process of the battery, improves the high-temperature dimensional stability of the separator, inhibits thermal shrinkage, and avoids the risk of short circuit; the dispersant ensures that the solid particles such as inorganic fibers and fillers are uniformly dispersed in the slurry, avoids sedimentation or local accumulation, improves the surface flatness and density of the coating, reduces pinholes and cracks, improves the flowability of the slurry, and facilitates process control; the addition of inorganic fillers improves thermal stability, enhances mechanical properties, and controls porosity; the thickening agent adjusts the viscosity of the slurry, prevents sedimentation (assists the dispersant to maintain particle suspension stability), and adjusts the uniformity and thickness consistency of the coating through viscosity; the binder bonds the inorganic fibers, fillers, and other materials to the separator substrate, prevents the coating from falling off, maintains the bonding force between the coating and the substrate during the charging and discharging cycle of the battery, avoids delamination, and needs to be chemically compatible with the substrate and electrolyte; the wetting agent reduces the surface tension of the slurry, promotes the spreading of the slurry on the separator substrate, improves the coating coverage, and prevents uneven coating or bubble residue (cooperates with the dispersant to improve particle dispersion effect).

[0033] Further, the inorganic filler is subjected to organic modification treatment.

[0034] Further, the modified inorganic filler is prepared by the following steps:

[0035] Step one: add inorganic fillers to a buffer solution, ultrasonic dispersion, add dopamine hydrochloride, heat reaction, centrifugation, drying, grinding, and obtain organic inorganic fillers;

[0036] Step two: mix the organic inorganic fillers with trichlorophosphazene, add a solvent and an acid binding agent, ultrasonic dispersion, heat reaction, filtration and drying, and obtain modified inorganic fillers.

[0037] In the above technical solution, the modified alumina has the effects of flame retardation and enhancement of material toughness, irregular granular alumina is used, the irregular granular characteristics of which can form a porous structure, and the characteristics of high specific surface area, low density and multi-level porosity are combined, local stress concentration is reduced, and structural collapse under high temperature is inhibited, the bond energy of Al-O bond in alumina is significantly higher than that of C-C bond in polyolefin separator. At high temperature, Al-O bond absorbs heat and forms a stable silicate protective layer, inhibits thermal decomposition of the separator matrix, improves the complexity of the heat conduction path, and delays the temperature rise rate, but it has poor compatibility with polymers and is not easy to disperse, thereby affecting the stability of the polymer, dopamine can form polydopamine (PDA) through autoxidative polymerization, and exhibits high adhesion, therefore, dopamine is grafted on the surface of alumina to form polydopamine-coated alumina, and trichlorophosphazene is added to introduce flame retardant groups (P / N), thereby enhancing the thermal stability, mechanical properties and flame retardancy of the slurry.

[0038] The present application introduces nitrogen and phosphorus sources by functionalizing the polydopamine surface with trichloro phosphazene, the chlorine atoms on the phosphazene ring have high reactivity and are easily replaced by the nucleophilic amino group on the polydopamine; phosphorus (P) provides flame retardance, and nitrogen (N) promotes carbonization, thereby endowing the slurry with flame retardant properties.

[0039] Secondly, the abundant phenolic hydroxyl and amino groups on the polydopamine surface can physically adsorb palygorskite, sodium citrate, aluminum oxide, sodium carboxymethyl cellulose and alkyne alcohol in the slurry, thereby enhancing the interfacial bonding capacity of the slurry and the polyolefin separator, and thus enhancing the stability and heat resistance of the material.

[0040] Further, in step one, the grinding process conditions are as follows: using a ball mill to grind at a speed of 300-450 r / min, grinding for 3-6 times, and each time for 15-30 min.

[0041] Further, in step one, the buffer solution is Tris-HCl (3-hydroxymethyl-aminomethane-hydrochloric acid) solution.

[0042] Further, in step one, the mass ratio of the inorganic filler, the buffer solution and hydrochloric acid dopamine is (1-3) : 50: 5.

[0043] Further, in step two, the mass ratio of the organic inorganic filler, trichloro phosphazene, solvent and acid binding agent is (1-3) : 5: 50: 0.1.

[0044] Further, the solvent is tetrahydrofuran.

[0045] Further, the acid binding agent is triethylamine.

[0046] Further, the ultrasonic dispersion process conditions are as follows: a frequency of 28-40 kHz and a time of 30-40 min.

[0047] Further, the heating reaction process conditions are as follows: a temperature of 80-90℃ and a reaction time of 5-6 h.

[0048] Further, the centrifugation process conditions are as follows: a speed of 2400-3000 r / min and a time of 30-40 min.

[0049] Further, the drying process conditions are as follows: a temperature of 60-70℃ and a time of 1-2 h.

[0050] Further, the polyolefin separator is subjected to plasma pretreatment.

[0051] Further, the plasma pretreatment process conditions are as follows:

[0052] The polyolefin diaphragm is put into the acetone solution for 30-40 min, taken out at a temperature of 60-70 DEG C, dried for 1-2 h, and plasma treated at room temperature with a power of 200-300 W, a vacuum degree of 20-50 Pa, and a time of 3-5 min.

[0053] Further, the concentration of the acetone solution is 30-35% aqueous solution.

[0054] Further, the carrier gas is a mixed gas of argon and oxygen with a volume ratio of (18-19) : 1 and a flow rate of 100-200 sccm.

[0055] In the above technical solution, the surface of the polyolefin diaphragm is treated by plasma, so that the surface energy and wettability are improved, and the mechanical combination and adhesion strength of the diaphragm and the slurry are enhanced.

[0056] A high-temperature-resistant lithium ion battery comprises the coated diaphragm for lithium ion batteries.

[0057] Compared with the prior art, the present application has the following beneficial effects:

[0058] 1. The coated diaphragm can maintain structural integrity after baking at high temperature, and has a small thermal shrinkage rate.

[0059] 2. The excellent heat shrinkage resistance of the coated diaphragm can ensure the stability of the internal structure of the battery under high-temperature working conditions, and significantly reduce the internal short circuit risk caused by diaphragm shrinkage.

[0060] 3. The coated diaphragm has a lower bulk density than ordinary ceramic coatings, and is lighter.

[0061] 4. The coated diaphragm of the present application, by modifying the heat-resistant irregular granular alumina, grafting dopamine on the surface of the alumina, and introducing a flame-retardant group (P / N), thereby enhancing the thermal stability, mechanical properties and flame retardancy of the slurry. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 Sample picture after oven baking at 180℃ for 1h;

[0063] Figure 2 Sample picture after oven baking at 180℃ for 1h for Comparative Example 1; DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0065] In the following detailed description, the solid components of the following slurries are in mass percentage;

[0066] The thickness of the coating layer is the total thickness of the coating layers on the upper surface and the lower surface of the base film, and the total thickness is 2.4μm, and the thickness of the coating layer on the upper surface and the lower surface of the base film is the same;

[0067] The label "broken film" means that the coated polyethylene film is melted and broken under the test conditions, and the test cannot be performed;

[0068] The inorganic cellulose powder is attapulgite, the dispersing agent is sodium citrate, the inorganic filler is heat-resistant irregular granular alumina, the thickening agent is sodium carboxymethyl cellulose, the binder is a mixture of polyacrylic acid emulsion and solvent-based polyacrylic acid, the mass ratio is 3:1, the wetting agent is alkyne alcohol (2,4,7,9-tetramethyl-5-decyne-4,7-diol and its oxirane adduct), model TEGO surten 228E, content 99.99%;

[0069] Base film: polyethylene film, thickness 9μm;

[0070] Attapulgite, average longitudinal length of single fiber 0.5μm, average radial length 0.05μm;

[0071] Heat-resistant irregular granular alumina, particle size requirements: D10>0.2μm, D50:0.6-1.0μm, D90<2.5μm, D99<4.3μm;

[0072] Sodium carboxymethylcellulose, model DSL-1220, 1% aqueous solution viscosity 15 mPa·s, 1% aqueous solution pH 6.0-8.0;

[0073] Polyacrylic acid emulsion, model GR401, solid content 30%;

[0074] Solvent type polyacrylic acid, model GR506, solid content 15%;

[0075] Tris-HCl (3-hydroxymethyl-aminomethane-hydrochloric acid) solution: the mass ratio of Tris to HCl solution is 1:5.8, the pH is 7.4, and the HCl solution concentration is 1 mol / L;

[0076] Example 1: a preparation method of a high-temperature-resistant lithium ion battery coated separator, comprising the following steps:

[0077] S1: adding inorganic cellulose powder, dispersant and ultrapure water into a double-star row stirrer, stirring for 80 min at a stirring speed of 700 r / min to obtain an inorganic fiber powder dispersion liquid;

[0078] S2: adding inorganic filler into the inorganic fiber powder dispersion liquid and continuing to stir for 30 min at a stirring speed of 700 r / min to obtain a mixed dispersion liquid;

[0079] S3: adding thickening agent into the mixed dispersion liquid and continuing to stir for 70 min at a stirring speed of 850 r / min; after stirring is completed, grinding dispersion is carried out at a grinding dispersion speed of 700 r / min and a grinding flow of 1500 L / h, and the grinding dispersion is carried out twice; after the grinding dispersion is completed, a binder and a wetting agent are added and stirred at a stirring speed of 300 r / min for 40 min to obtain a slurry; the slurry comprises the following components in mass percentage: 2% of inorganic fiber powder, 2% of dispersant, 33.5% of inorganic filler, 0.3% of thickening agent, 1.8% of binder, 0.25% of wetting agent, and the balance of ultrapure water;

[0080] S4: taking a base film, coating the slurry on the upper surface and the lower surface of the 9 μm base film by means of roll coating, drying in an oven at a temperature of 65 ℃ to form a coating layer, and obtaining a high-temperature-resistant lithium ion battery coated separator; the thickness of the single-side coating layer is 1.2 μm, and the coating speed is 100 m / min.

[0081] Example 2: a preparation method of a high-temperature-resistant lithium ion battery coated separator, comprising the following steps:

[0082] S1: adding inorganic cellulose powder, dispersant and ultrapure water into a double-star row stirrer, stirring for 80 min at a stirring speed of 700 r / min to obtain an inorganic fiber powder dispersion liquid;

[0083] S2: The inorganic filler is added to the inorganic fiber dispersion liquid for continuous stirring, the stirring time is 30 min, and the stirring speed is 700 r / min, to obtain a mixed dispersion liquid;

[0084] S3: The thickening agent is added to the mixed dispersion liquid for continuous stirring, the stirring time is 70 min, and the stirring speed is 850 r / min; after the stirring is completed, grinding dispersion is performed, the grinding dispersion speed is 1300 r / min, the grinding flow is 900 L / h, and the grinding is performed once; after the grinding dispersion is completed, the binder and the wetting agent are added for stirring, the stirring speed is 300 r / min, the stirring time is 40 min, and a slurry is obtained; the slurry comprises the following components: 6% of inorganic fiber powder, 6% of dispersant, 25% of inorganic filler, 0.3% of thickening agent, 1.8% of binder, and 0.25% of wetting agent, and the balance is ultrapure water;

[0085] S4: A base film is taken, the slurry is coated on the upper surface and the lower surface of the 9 μm base film in a manner of roller coating, drying is performed in an oven with a temperature of 65 ℃, a coating layer is formed, and a high-temperature-resistant lithium ion battery coated separator is obtained; the single-side coating layer thickness is 1.2 μm, and the coating speed is 100 m / min.

[0086] Embodiment 3: A preparation method of a high-temperature-resistant lithium ion battery coated separator, comprising the following steps:

[0087] S1: The inorganic fiber powder, the dispersant, and the ultrapure water are added to a double-star row stirrer for stirring, the stirring time is 80 min, and the stirring speed is 700 r / min, to obtain an inorganic fiber powder dispersion liquid;

[0088] S2: The inorganic filler is added to the inorganic fiber powder dispersion liquid for continuous stirring, the stirring time is 30 min, and the stirring speed is 700 r / min; the stirring time is 70 min, and the stirring speed is 850 r / min; after the stirring is completed, grinding dispersion is performed, the grinding dispersion speed is 500 r / min, the grinding flow is 1600 L / h, and the grinding is performed three times; after the grinding dispersion is completed, the binder and the wetting agent are added for stirring, the stirring speed is 300 r / min, the stirring time is 40 min, and a slurry is obtained; the slurry comprises the following components: 1% of inorganic fiber powder, 1% of dispersant, 40% of inorganic filler, 0.4% of thickening agent, 0.9% of binder, and 0.4% of wetting agent, and the balance is ultrapure water;

[0089] S4: A base film is taken, the slurry is coated on the upper surface and the lower surface of the 9 μm base film in a manner of roller coating, drying is performed in an oven with a temperature of 65 ℃, a coating layer is formed, and a high-temperature-resistant lithium ion battery coated separator is obtained; the single-side coating layer thickness is 1.2 μm, and the coating speed is 100 m / min.

[0090] Embodiment 4: A method for preparing a high-temperature-resistant lithium-ion battery coated separator, comprising the following steps:

[0091] S1: adding inorganic fiber powder, dispersant and ultrapure water into a double-star stirring machine, stirring for 80 min at a stirring speed of 700 r / min to obtain an inorganic fiber powder dispersion liquid;

[0092] S2: adding inorganic filler into the inorganic fiber powder dispersion liquid and continuing to stir for 30 min at a stirring speed of 700 r / min to obtain a mixed dispersion liquid;

[0093] S3: adding thickening agent into the mixed dispersion liquid and continuing to stir for 70 min at a stirring speed of 850 r / min; after the stirring is completed, grinding and dispersion are carried out at a grinding and dispersion speed of 500 r / min and a grinding flow of 1600 L / h for 3 times; after the grinding and dispersion is completed, a binder and a wetting agent are added and stirred at a stirring speed of 300 r / min for 40 min to obtain a slurry; the slurry comprises the following components: 1.2% of inorganic fiber powder, 1.2% of dispersant, 40% of inorganic filler, 0.8% of thickening agent, 1.8% of binder, 0.4% of wetting agent, and the balance of ultrapure water;

[0094] S4: taking a base film, coating the slurry on the upper surface and the lower surface of the 9 μm base film by means of roll coating, drying in an oven at a temperature of 65 ℃ to form a coating layer, and obtaining a high-temperature-resistant lithium-ion battery coated separator; the single-side coating layer has a thickness of 1.2 μm and a coating speed of 100 m / min.

[0095] The inorganic filler is subjected to organic modification treatment, and the modified inorganic filler comprises the following steps:

[0096] Step one: adding inorganic filler into Tris-HCl solution, ultrasonic dispersion for 35 min at a frequency of 30 kHz, adding dopamine hydrochloride, reacting for 5 h at a temperature of 85 ℃, centrifuging for 40 min at a speed of 2400 r / min, drying for 1 h at a temperature of 60 ℃, grinding by using a ball mill at a speed of 300 r / min for 3 times, each time for 15 min, and obtaining organic inorganic filler;

[0097] Step two: mixing the organic inorganic filler with phosphonitrilic chloride trimer, adding tetrahydrofuran and triethylamine, ultrasonic dispersion for 35 min at a frequency of 30 kHz, reacting for 5 h at a temperature of 80 ℃, drying for 2 h at a temperature of 70 ℃, and obtaining modified inorganic filler.

[0098] Embodiment 5: A preparation method of a high-temperature-resistant lithium ion battery coated separator, comprising the following steps: steps S1, S2, S3, S4 are the same as Embodiment 4.

[0099] The inorganic filler is subjected to organic modification treatment, and the modified inorganic filler comprises the following steps:

[0100] Step one: add the inorganic filler to the Tris-HCl solution, ultrasonic dispersion at a frequency of 29 kHz for 31 min, add dopamine hydrochloride, react at a temperature of 82°C for 5 h, centrifuge at a speed of 2400 r / min for 32 min, dry at a temperature of 60°C for 1 h, use a ball mill to grind at a speed of 300 r / min for 3 times, each time for 15 min, to obtain the organic inorganic filler;

[0101] Step two: mix the organic inorganic filler with the trichloro phosphazene, add tetrahydrofuran and triethylamine, ultrasonic dispersion at a frequency of 30 kHz for 35 min, react at a temperature of 80°C for 5 h, dry at a temperature of 70°C for 2 h, to obtain the modified inorganic filler.

[0102] Embodiment 6: A preparation method of a high-temperature-resistant lithium ion battery coated separator, comprising the following steps: steps S1, S2, S3, S4 are the same as Embodiment 4.

[0103] The inorganic filler is subjected to organic modification treatment, and the modified inorganic filler comprises the following steps:

[0104] Step one: add the inorganic filler to the Tris-HCl solution, ultrasonic dispersion at a frequency of 40 kHz for 40 min, add dopamine hydrochloride, react at a temperature of 89°C for 6 h, centrifuge at a speed of 3000 r / min for 40 min, dry at a temperature of 80°C for 2 h, use a ball mill to grind at a speed of 450 r / min for 6 times, each time for 30 min, to obtain the organic inorganic filler;

[0105] Step two: mix the organic inorganic filler with the trichloro phosphazene, add tetrahydrofuran and triethylamine, ultrasonic dispersion at a frequency of 40 kHz for 40 min, react at a temperature of 90°C for 5 h, dry at a temperature of 70°C for 2 h, to obtain the modified inorganic filler.

[0106] Comparative Example 1: A preparation method of a lithium ion battery coated separator, comprising the following steps: steps S1, S2, S3, S4 are the same as Embodiment 1, and the slurry comprises the following components: 0.3% inorganic fiber powder, 0.3% dispersant, 33.5% inorganic filler, 0.3% thickening agent, 1.8% binder, 0.25% wetting agent, and the balance is ultrapure water.

[0107] Comparative Example 2: A preparation method of a lithium ion battery coated separator, comprising the following steps: steps S1, S2, S3, S4 are the same as those of Example 1, and the slurry comprises the following components: 8% inorganic fiber powder, 8% dispersing agent, 33.5% inorganic filler, 0.3% thickening agent, 1.8% binder, 0.25% wetting agent, and the balance is ultrapure water.

[0108] Comparative Example 3: A preparation method of a lithium ion battery coated separator, comprising the following steps: steps S1, S2, S3, S4 are the same as those of Example 1, and the slurry comprises the following components: 2% inorganic fiber powder, 2% dispersing agent, 23% inorganic filler, 0.3% thickening agent, 1.8% binder, 0.25% wetting agent, and the balance is ultrapure water.

[0109] Comparative Example 4: A preparation method of a lithium ion battery coated separator, comprising the following steps: steps S1, S2, S3, S4 are the same as those of Example 1, and the slurry comprises the following components: 2% inorganic fiber powder, 2% dispersing agent, 47% inorganic filler, 0.3% thickening agent, 1.8% binder, 0.25% wetting agent, and the balance is ultrapure water.

[0110] Comparative Example 5: A preparation method of a lithium ion battery coated separator, comprising the following steps: in step S3, the grinding process is: after stirring is completed, grinding and dispersion is performed, the grinding and dispersion rotation speed is 300 r / min, the grinding flow rate is 1800 L / h, and grinding is performed once; steps S1, S2, S4 are the same as those of Example 1.

[0111] Comparative Example 6: A preparation method of a lithium ion battery coated separator, comprising the following steps: in step S3, the grinding process is: after stirring is completed, grinding and dispersion is performed, the grinding and dispersion rotation speed is 1100 r / min, the grinding flow rate is 1000 L / h, and grinding is performed once; steps S1, S2, S4 are the same as those of Example 1.

[0112] Comparative Example 7: The polyolefin separator in this comparative example is not coated with a slurry.

[0113] Comparative Example 8: In this comparative example, the inorganic filler is treated with dopamine hydrochloride, but not with trichloro-phosphine triazole, and the other steps are the same as those of Example 4.

[0114] Experiment:

[0115] The coated separator obtained in Examples 1-6 and Comparative Examples 1-8 is made into a sample, and the performance thereof is detected and the detection results are recorded.

[0116] Tensile strength: with GB / T 1040.3-2006 as the reference standard, using a tensile testing machine, testing the tensile strength of the sample in the longitudinal direction (MD) and the transverse direction (TD) at a speed of 250 mm / min.

[0117] Puncture strength: with GB / T 36363-2018 as the reference standard, a 100x100mm square is cut, a puncture strength tester is used, a 1.0mm diameter spherical probe is used, and the puncture strength is tested at a speed of 100mm / min.

[0118] Bulk density: with ASTM D2873 as the reference standard, a 100x100mm square is cut, weighed, and the porosity is measured by a mercury porosimeter, and the bulk density is calculated by combining the mass.

[0119] Heat shrinkage: with GB / T 36363-2018 as the reference standard, a 100x100mm square is cut in the longitudinal direction, the sample is placed in a constant temperature oven at 180℃ for 1h, and after cooling, the longitudinal (MD) and transverse (TD) shrinkage is measured with a vernier caliper.

[0120] Performance comparison table

[0121]

[0122]

[0123] According to the data in the above table, the following conclusions can be clearly obtained:

[0124] Comparing Examples 1-6 with Comparative Examples 1 and 2, it can be seen that when the mass ratio of attapulgite to sodium citrate in the slurry is too low or too high, the bulk density of the coated separator increases, and the tensile strength, puncture strength and heat shrinkage resistance performance are all poor.

[0125] Comparing Examples 1-6 with Comparative Example 3, it can be seen that when the mass ratio of alumina in the slurry is too low, the bulk density of the coated separator decreases, and the tensile strength, puncture strength and heat shrinkage resistance performance are all poor.

[0126] Comparing Examples 1-6 with Comparative Example 4, it can be seen that when the mass ratio of alumina in the slurry is too high, the bulk density of the coated separator increases, and the tensile strength, puncture strength and heat shrinkage resistance performance are all poor.

[0127] Comparing Examples 1-6 with Comparative Example 5, it can be seen that when the slurry is not ground sufficiently, the bulk density of the coated separator decreases, and the tensile strength, puncture strength and heat shrinkage resistance performance are all poor.

[0128] Comparing examples 1-6 with comparative example 6, it can be seen that when the slurry is excessively ground, the coated separator corresponding to the slurry has increased bulk density, poor tensile strength, poor puncture strength and poor heat shrinkage resistance.

[0129] Comparing examples 1-6 with comparative example 7, it can be seen that the coating can improve the tensile strength, puncture strength and heat shrinkage resistance of the separator.

[0130] Comparing examples 1-6 with comparative example 8, it can be seen that when the inorganic filler is organically modified by dopamine hydrochloride without trimerization of phosphorus chloride, the coated separator corresponding to the slurry has increased bulk density, poor tensile strength, poor puncture strength and poor heat shrinkage resistance, and cannot meet the requirements of high temperature resistance, high tensile strength and high puncture resistance.

[0131] In summary, compared with the existing lithium ion coated separator technology, the high temperature resistant lithium ion battery coated separator prepared by the present application has low bulk density, high tensile strength and puncture strength, and excellent heat resistance, and has good application prospect in the field of separators.

[0132] It is apparent for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all aspects as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and range of the equivalent elements of the claims are intended to be included in the present application.

Claims

1. A method for preparing a high-temperature resistant lithium-ion battery coated diaphragm, characterized in that: The following steps are involved: S1: mixing inorganic cellulose powder, dispersant, and ultrapure water, and stirring to obtain an inorganic fiber dispersion; S2: adding the inorganic filler to the inorganic fiber dispersion and stirring to obtain a mixed dispersion; S3: adding a thickener to the mixed dispersion, stirring, grinding, adding a binder and a wetting agent, and continuing stirring to obtain a slurry; S4: Take a polyolefin separator as a base membrane, apply the slurry on the upper and lower surfaces of the base membrane, dry it, form a coating layer, and obtain a high-temperature resistant lithium-ion battery coated separator.

2. The method for preparing a high-temperature resistant lithium-ion battery coating diaphragm according to claim 1, characterized in that: The slurry comprises the following components: by mass percentage, 0.5-6% of inorganic fiber powder, 0.5-6% of dispersant, 25-45% of inorganic filler, 0.1-1% of thickener, 0.5-5% of binder, 0.1-0.9% of wetting agent, and the balance is ultrapure water.

3. The method for preparing a high-temperature resistant lithium-ion battery coating diaphragm according to claim 2, characterized in that: The inorganic fiber powder is attapulgite; the dispersant is sodium citrate; the inorganic filler is heat-resistant irregular granular aluminum oxide; the thickener is sodium carboxymethyl cellulose; the binder is a mixture of polyacrylic acid emulsion and solvent-based polyacrylic acid; and the wetting agent is an acetylene alcohol wetting agent.

4. The method for preparing a high-temperature resistant lithium-ion battery coating diaphragm according to claim 1, characterized in that: The coating layer has a thickness of 1 to 8 μm and a bulk density of 1 to 1.9 g / m 2 / μm, coating speed is 10~200m / min.

5. The method for preparing a high-temperature resistant lithium-ion battery coating diaphragm according to claim 3, characterized in that: The particle size of the heat-resistant irregular granular aluminum oxide is D10>0.2μm, D50: 0.6-1.0μm, D90<2.5μm, and D99<4.3μm.

6. The method for preparing a high-temperature resistant lithium-ion battery coating diaphragm according to claim 1, characterized in that: The attapulgite has a single fiber with a longitudinal length of 0.1 to 3 μm, a radial length of 0.01 to 0.1 μm, and an aspect ratio of (3 to 55):

1.

7. The method for preparing a high-temperature resistant lithium-ion battery coating diaphragm according to claim 1, characterized in that: In steps S1 and S3, the stirring process conditions are: stirring speed 600-1500 r / min, stirring time 60-120 min; in step S2, the stirring process conditions are: speed 600-1500 r / min, time 20-60 min, and the process conditions for continued stirring are: speed 100-500 r / min, time 20-60 min; in step S3, the grinding and dispersion process conditions are: speed 500-1000 r / min, grinding flow rate 900-1700 L / h, and grinding 1-4 times.

8. The method for preparing a high-temperature resistant lithium-ion battery coating diaphragm according to claim 1, characterized in that: The inorganic filler is subjected to organic modification treatment, and the modified inorganic filler is prepared by the following steps: Step 1: adding the inorganic filler to the buffer solution, ultrasonically dispersing, adding dopamine hydrochloride, heating for reaction, centrifuging, drying, and grinding to obtain the organic inorganic filler; Step 2: Mixing the organized inorganic filler with tripolyphosphazene chloride, adding a solvent and an acid-binding agent, performing ultrasonic dispersion, heating for reaction, filtering and drying to obtain a modified inorganic filler.

9. The method for preparing a high-temperature resistant lithium-ion battery coating diaphragm according to claim 8, characterized in that: The solvent is tetrahydrofuran; the acid binding agent is triethylamine; in step 2, the mass ratio of the organized inorganic filler, tripolyphosphazene chloride, solvent, and acid binding agent is (1-3):5:50:0.

1.

10. Use of a high-temperature resistant lithium-ion battery coating diaphragm prepared by the preparation method according to any one of claims 1 to 9, characterized in that: Application in high temperature resistant lithium ion batteries.

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