Highly thermally conductive lithium-ion battery separator and process for its preparation

Abstract

The application relates to the technical field of battery diaphragm, in particular to a high-heat-conducting lithium ion battery diaphragm and a preparation process thereof. The preparation process comprises the following steps: step 1: a solvent is pre-stirred, a binder is added, stirring and mixing are conducted, and a colloidal solution is obtained; step 2: the colloidal solution is subjected to first vacuum stirring, a heat-conducting material is added, second vacuum stirring is conducted, shearing dispersion is conducted, and sieving is conducted, so that a slurry is obtained; step 3: the slurry is coated on a base film, drying is conducted, a heat-conducting coating layer is obtained, winding is conducted, and the high-heat-conducting lithium ion battery diaphragm is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery separator, in particular to a high-thermal-conductivity lithium ion battery separator and a preparation process thereof. BACKGROUND

[0002] Lithium ion battery is a kind of secondary battery, which has the advantages of high voltage, long cycle life, high specific energy, high safety performance, less environmental pollution, etc., and is widely used in portable electronic devices, space technology, electric vehicles, national defense industry and other technical fields.

[0003] Most of the traditional lithium ion batteries use polyolefin porous base film as the isolation film. However, the pure polyolefin isolation film will produce a large shrinkage when heated, which can easily lead to short circuit of the positive and negative electrodes of the battery, thereby causing safety accidents. At the same time, due to the poor thermal conductivity of the polyolefin separator, the problem of heat accumulation in the battery exists, which affects the performance of the battery and increases the hidden danger of the safety of the battery. In order to solve this problem, some researches use adhesive to coat inorganic particles on the porous substrate to make organic / inorganic composite porous isolation film containing inorganic coating. The thermal stability of inorganic particles is used to reduce the thermal shrinkage of the isolation film, and the organic material is used to increase the adhesion between the separator and the positive and negative electrode interfaces, so as to improve the hardness of the battery cell while effectively preventing the positive and negative short circuit of the lithium ion battery.

[0004] However, these newly developed isolation films still have different degrees of defects, only the heat resistance is improved, and the heat transfer is not optimized. For example, a polymer lithium ion battery separator including a porous base film, an inorganic coating and an organic coating is disclosed in the prior art, wherein the organic coating is coated on the surface of the porous base film and / or the inorganic coating, and is distributed in island and linear shapes. However, this composite isolation film needs to use N-methyl pyrrolidone, ethanol and other organic substances as solvents for multiple coating during coating, which is complex in process and increases the cost. More importantly, its adhesion is not strong, which cannot meet the requirements of the battery on hardness. In addition, an oily coating isolation film with a porous active coating is disclosed in another prior art, which coats a mixture of oily polymers on the porous base film to form a porous active coating. However, the coating speed is slow, the production efficiency is low, and the use of a large amount of organic solvents will cause serious environmental pollution and greatly increase the manufacturing cost.

[0005] Therefore, it is of important application value to solve the above problems and realize excellent interface adhesion performance to prepare a high-thermal-conductivity lithium ion battery separator. SUMMARY

[0006] The purpose of the present application is to provide a high-thermal-conductivity lithium ion battery separator and a preparation process thereof to solve the problems raised in the background.

[0007] To solve the above technical problems, the present application provides the following technical solutions:

[0008] A preparation process of high-thermal-conductivity lithium ion battery diaphragm, comprising the following steps:

[0009] Step 1: The solvent is pre-stirred, the binder is added, and stirring and mixing are performed to obtain a colloidal solution;

[0010] Step 2: The colloidal solution is subjected to primary vacuum stirring, the thermal conductive material is added, and secondary vacuum stirring, shear dispersion and sieving are performed to obtain a slurry;

[0011] Step 3: The slurry is coated on a base film, dried to obtain a thermal conductive coating layer, and wound to obtain the high-thermal-conductivity lithium ion battery diaphragm.

[0012] More preferably, the slurry comprises the following raw materials in terms of percentage by weight: 1.5-20% of the binder, 3-15% of the thermal conductive material, and the rest of the solvent.

[0013] More preferably, the binder is polyvinylidene fluoride (PVDF) with a characteristic viscosity of 0.2-2.5 g / mL and a crystallinity of ≥60%; the thermal conductive material is one or more of silicon nitride, aluminum nitride, silicon nitride, aluminum oxide, boehmite and zirconium dioxide, and the particle size of the thermal conductive material is 0.1-3 μm; the solvent is one or more of N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMAC) and acetone; and the base film is one of a PP diaphragm, a PE diaphragm, a non-woven PET diaphragm, a non-woven PP diaphragm and a non-woven PE diaphragm.

[0014] More preferably, in Step 2, during the primary vacuum stirring, the revolution speed is 20-25 r / min and the rotation speed is 1000-1500 r / min; during the secondary vacuum stirring, the revolution speed is 10 r / min and the rotation speed is 50 r / min; the shear dispersion time is 1-1.5 hours, and the sieve mesh for sieving is 150-220 meshes; and in Step 3, the coating speed is 5-180 m / min.

[0015] In Step 2, the temperature is always controlled to be ≤50℃, and the vacuum degree is in the range of -0.05 Mpa to 0.01 Mpa.

[0016] More preferably, the slurry further comprises 0.3-0.4% of a photoinitiator, the binder is polyvinylidene fluoride, ethoxylated pentaerythritol tetraacrylate and lysine acrylate in a mass ratio of (8-8.5):0.5:(1-1.5), and the thermal conductive material is styrene nanoparticle modified boron nitride.

[0017] More preferably, the preparation method of the lysine acrylate is: adding hydroxyethyl methacrylate and a catalyst into a solvent, setting the temperature to 0-5℃, and stirring uniformly; adding L-lysine diisocyanate, the dropping time is 2-2.5 hours, stirring at room temperature for 20-22 hours, evaporating the solvent, washing, filtering and drying to obtain lysine acrylate.

[0018] More preferably, the preparation method of the styrene nanoparticle modified boron nitride is: (1) mixing boron nitride, cysteine and sodium hydroxide solution uniformly, placing in a ball milling device, wet milling for 6-8 hours, washing, drying to obtain pretreated boron nitride; (2) dispersing the pretreated boron nitride, styrene, acrylic acid and polyethylene glycol diacrylate in deionized water in sequence, ultrasonic dispersion, adding azobisisobutyronitrile, setting the temperature to 50-60℃ under nitrogen atmosphere, stirring for 6-8 hours, washing and drying to obtain styrene nanoparticle modified boron nitride.

[0019] More preferably, in step (1), the mass ratio of boron nitride, cysteine and sodium hydroxide solution is 1:2:12, and the concentration of sodium hydroxide solution is 1 mol / L; during the ball milling process, the ratio of zirconium oxide microspheres is 8mm:5mm:3mm=1:2:1; in step (2), the styrene nanoparticle modified boron nitride comprises the following raw materials: 10 parts of pretreated boron nitride, 3-3.5 parts of styrene, 1-1.2 parts of acrylic acid, 0.05-0.06 parts of polyethylene glycol diacrylate, 0.2-0.3 parts of azobisisobutyronitrile and 65-70 parts of deionized water.

[0020] More preferably, in step 3, the drying process is irradiation under a UV lamp with a wavelength of 365nm for 5-10 seconds, and the oven drying temperature is 80-100℃.

[0021] More preferably, the preparation process of the high-thermal-conductivity lithium ion battery separator is used to prepare the high-thermal-conductivity lithium ion battery separator; the high-thermal-conductivity lithium ion battery separator comprises a base film and a thermal conductive coating layer, the thickness of the base film is 3-20μm, and the thickness of the thermal conductive coating layer is 0.5-6μm (single side or double sides).

[0022] The beneficial effects of the technical solution are:

[0023] (1) In the scheme, the thermal conductive coating layer is prepared by using an oily slurry, which can effectively reduce the bubbles of the slurry and improve the processing performance. At the same time, the solvent is pre-stirred, which is beneficial to the dispersion of the adhesive and effectively improves the dispersion efficiency of the slurry.

[0024] (2) In the scheme, during the dispersion of the slurry, the means of one-time vacuum stirring, second-time vacuum stirring and then high-efficiency fluid dynamic shearing, which is "shear cavitation", is beneficial to the uniform dispersion of the nanoscale thermal conductive material and improves the slurry preparation efficiency.

[0025] (3) The heat-conducting coating prepared in this scheme can replace the lithium ion battery separator aluminum foil current collector, increase the adhesion of the separator material and the current collector, thereby effectively improving the heat conductivity of the battery, which is beneficial to the capacity of the battery, thereby effectively improving the specific capacity, specific power and cycle performance of the battery.

[0026] (4) Since polyvinylidene fluoride (PVDF) is introduced as a binder alone, its adhesion to the base film is weak and the interface stability is poor, so during battery assembly, the coating is prone to falling off and other phenomena, and the expansion stress during charging and discharging also causes the coating to fall off, and the durability is not high. Moreover, the heat-conducting material is directly introduced, which has poor dispersibility, increases the heat transfer resistance, reduces the heat-conducting performance, and increases the expansion stress, thereby reducing the durability of the coating. Therefore, in order to further improve the interface adhesion, enhance the heat conductivity, and improve the durability of the lithium ion battery separator.

[0027] In the scheme, ethoxylated pentaerythritol tetraacrylate and lysine acrylate are further introduced as binders. The acrylate network formed by the two and the polyvinylidene fluoride network form a semi-interpenetrating network under the action of photo-crosslinking, effectively improving the adhesion of the heat-conducting coating. At the same time, among the substances of ethoxylated pentaerythritol tetraacrylate and lysine acrylate, there are polar groups such as carbonyl, ether bond and amino group, which not only enhance the dispersibility of the heat-conducting material, but also have good miscibility with the electrolyte, which can effectively improve the lithium ion migration. The introduction amount of ethoxylated pentaerythritol tetraacrylate with four crosslinking groups and lysine acrylate with two crosslinking groups relates to the density of the crosslinking network. If the content changes, the crosslinking degree will change, thereby affecting the porosity and reducing the average pore size, affecting the lithium ion migration. Therefore, the introduction amount needs to be determined.

[0028] In the scheme, the heat-conducting material is further optimized and modified. First, cysteine is used to wet mill and treat boron nitride, effectively glassing the sheet layer, and the residual cysteine on the surface also helps to increase the dispersibility; finally, free radical polymerization of styrene is used to form carboxylated styrene nanoparticles in situ between the sheet layers and the surface, which are further intercalated in the sheet layers to form a nanocomposite. Due to the non-covalent interaction between the modified sheet layer and the nanoparticles, the interface electrons are reduced and the heat transfer is increased. The crosslinking is between the semi-interpenetrating networks, so that the separator has excellent mechanical properties.

[0029] In this way, the modification of the heat-conducting material and the introduction of the acrylate binder effectively enhance the durability of the lithium ion battery separator. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described 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 work fall within the protection scope of the present application.

[0031] In the following examples, HSV900, KYNAR PVDF 761A and Solef 5130 are several models of PVDF, KYNAR PVDF 761A and HSV900 are two models produced by Arkema Company in France, and Solef 5130 is a model of Solvay Company in the United States. NMP is electronic grade NMP. Alumina, boehmite and zirconium dioxide are analytical grade, the article number of alumina is 1344-28-1, and the manufacturer is Meilan Industry (Shanghai) Co., Ltd.; the article number of boehmite is B302379, and the manufacturer is Shanghai Aladdin Biochemical Technology Co., Ltd.; the article number of zirconium dioxide is C006151023, and the manufacturer is Hubei Chengfeng Chemical Co., Ltd. The molecular weight of polyethylene glycol diacrylate is 200, the CAS number is 26570-48-9, the CAS number of acrylic acid is 79-10-7, the CAS number of styrene is 100-42-5, the CAS number of hydroxyethyl methacrylate is 868-77-9, and the CAS number of L-lysine diisocyanate is 45172-15-4, which are all commercially available.

[0032] The preparation method of the styrene nanoparticle modified boron nitride is as follows: (1) 10 g of boron nitride, 20 g of cysteine and 120 g of 1 mol / L sodium hydroxide solution are uniformly mixed and placed in a ball milling device (the ratio of zirconium oxide microspheres is 8 mm:5 mm:3 mm=1:2:1), wet milling is performed at a stirring speed of 400 r / min for 8 hours, and then washing and drying are performed to obtain pretreated boron nitride; (2) 10 g of the pretreated boron nitride, 3.2 g of styrene, 1.08 g of acrylic acid and 0.06 g of polyethylene glycol diacrylate are sequentially dispersed in 70 g of deionized water, ultrasonic dispersion is performed, 0.25 parts of azobisisobutyronitrile is added, a nitrogen atmosphere is set, the temperature is set to 60°C, and stirring is performed for 8 hours, and then washing and drying are performed to obtain the styrene nanoparticle modified boron nitride.

[0033] The preparation method of the lysine acrylate is as follows: 26 g of hydroxyethyl methacrylate and 0.5 g of dibutyltin dilaurate are added to 150 g of acetone, the temperature is controlled to be 3°C, and stirring is uniformly performed; 22.6 g of L-lysine diisocyanate is added, the dropping time is 1 hour, stirring is performed at room temperature for 20 hours, the solvent is evaporated, and then washing, filtering and drying are performed to obtain the lysine acrylate.

[0034] Example 1: Step 1: NMP is stirred at high speed using a planetary mixer, the revolution speed is 20 r / min, the rotation speed is 1500 r / min, stop stirring when the temperature reaches 40℃, add the binder (PVDF-Solef5130), first low-speed revolution, the speed is 10 r / min, start rotation after 5 min, the speed is 500 r / min, 10 min later, scrape the wall to get a colloidal solution;

[0035] Step 2: The colloidal solution is vacuumed to a vacuum degree of -0.05 Mpa, revolution, the speed is 15 r / min, high-speed rotation, the speed is 1500 r / min, connect the cold circulating water, control the slurry temperature below 50℃, stirring time is 1 hour, vacuum to a vacuum degree of 0.01 Mpa, add the thermal conductive material, revolution, the speed is 10 r / min, start rotation after 5 min, the speed is 50 r / min, scrape the wall after 5 min, vacuum to a vacuum degree of -0.05 Mpa, stir for 1 hour, vacuum to a vacuum degree of 0.01 Mpa; transfer it to a high-efficiency fluid power shear slurry mixer for shear dispersion, dispersion time is 1 hour, sieve to get the slurry;

[0036] Step 3: The slurry is coated using a coating machine, coated on a dry-made PP separator, the thickness of the PP separator is 12 μm, the coating thickness is controlled at 1 μm, the coating speed is 5 m / min, the coating oven temperature is set at 80℃, to get a high-thermal-conductive lithium ion battery separator;

[0037] In the technical solution, the slurry includes the following raw materials: 1.5% binder, 3wt% thermal conductive material, and the rest is NMP by weight percentage.

[0038] Example 2: Step 1: NMP is stirred at high speed using a planetary mixer, the revolution speed is 25 r / min, the rotation speed is 2000 r / min, stop stirring when the temperature reaches 45℃, add the binder (PVDF-HSV900), first low-speed revolution, the speed is 15 r / min, start rotation after 10 min, the speed is 1000 r / min, 15 min later, scrape the wall to get a colloidal solution;

[0039] Step 2: the colloidal solution is vacuumed to a vacuum degree of -0.05 Mpa, rotation is at a speed of 20 r / min, high-speed rotation is at a speed of 1500 r / min, cold circulating water is connected, the slurry temperature is controlled below 50 DEG C, the stirring time is 1 hour, vacuuming is performed to a vacuum degree of 0.01 Mpa, the heat-conducting material is added, rotation is at a speed of 10 r / min, 5 min later, rotation is started, the speed is 50 r / min, 5 min later, the wall is scraped, vacuuming is performed to a vacuum degree of -0.05 Mpa, stirring is performed for 2 hours, vacuuming is performed to a vacuum degree of 0.01 Mpa; it is transferred to a high-efficiency fluid power shearing slurry mixer for shearing and dispersing, the dispersing time is 1.5 hours, screening is performed, and the slurry is obtained;

[0040] Step 3: the slurry is coated by using a coating machine, is coated on a wet-prepared PE separator, the PE separator thickness is 9 um, the coating thickness is controlled to be 1.5 um, the coating speed is 10 m / min, the coating oven temperature is set to be 80 DEG C, and double-sided coating is carried out, and the high-heat-conducting lithium ion battery separator is obtained;

[0041] In the technical solution, the slurry comprises the following raw materials in percentage by weight: 2% binder, 5wt% heat-conducting material, and the rest is NMP.

[0042] Example 3: Step 1: acetone is stirred by using a planetary mixer at high speed, rotation is at a speed of 25 r / min, rotation is at a speed of 2000 r / min, stirring is stopped when the temperature reaches 45 DEG C, the binder (PVDF-Solef5130) is added, low-speed rotation is at a speed of 15 r / min, 10 min later, rotation is started, the speed is 1000 r / min, 15 min later, the wall is scraped, and the colloidal solution is obtained;

[0043] Step 2: the colloidal solution is vacuumed to a vacuum degree of -0.05 Mpa, rotation is at a speed of 20 r / min, high-speed rotation is at a speed of 1500 r / min, cold circulating water is connected, the slurry temperature is controlled below 50 DEG C, the stirring time is 1 hour, vacuuming is performed to a vacuum degree of 0.01 Mpa, the heat-conducting material is added, rotation is at a speed of 10 r / min, 5 min later, rotation is started, the speed is 50 r / min, 5 min later, the wall is scraped, vacuuming is performed to a vacuum degree of -0.05 Mpa, stirring is performed for 2 hours, vacuuming is performed to a vacuum degree of 0.01 Mpa; it is transferred to a high-efficiency fluid power shearing slurry mixer for shearing and dispersing, the dispersing time is 1.5 hours, screening is performed, and the slurry is obtained;

[0044] Step 3: the slurry is coated by using a coating machine, is coated on a non-woven PET separator, the PET separator thickness is 9 um, the coating thickness is controlled to be 2 um, the coating speed is 15 m / min, the coating oven temperature is set to be 80 DEG C, and the high-heat-conducting lithium ion battery separator is obtained;

[0045] The slurry includes the following raw materials: 2% binder, 5wt% heat-conducting material, and the rest is acetone.

[0046] Example 4: Step 1: Acetone is stirred at high speed using a planetary mixer, with a revolution speed of 25 r / min and a rotation speed of 2000 r / min. When the temperature reaches 45℃, stop stirring, add the binder (PVDF-KYNAR PVDF761A), first at low speed revolution, at a speed of 15 r / min, then start rotation, at a speed of 1000 r / min, after 15 minutes, scrape the wall, to obtain a colloidal solution;

[0047] Step 2: Vacuumize the colloidal solution to a vacuum degree of -0.05 Mpa, with revolution at a speed of 20 r / min and high-speed rotation at a speed of 1500 r / min, connect to cold circulating water, control the slurry temperature below 50℃, stirring time is 1 hour, vacuumize to a vacuum degree of 0.01 Mpa, add heat-conducting material, revolution at a speed of 10 r / min, start rotation after 5 minutes, at a speed of 50 r / min, scrape the wall after 5 minutes, vacuumize to a vacuum degree of -0.05 Mpa, stir for 2 hours, vacuumize to a vacuum degree of 0.01 Mpa; transfer it to a high-efficiency fluid power shearing slurry mixer for shearing dispersion, dispersion time is 1.5 hours, sieve to obtain the slurry;

[0048] Step 3: Use a coating machine for coating, coat on a non-woven PP membrane, the thickness of the PP membrane is 16μm, the coating thickness is controlled at 2.5μm, the coating speed is 20m / min, the coating oven temperature is set at 90℃, to obtain a high-heat-conducting lithium ion battery separator;

[0049] The slurry includes the following raw materials: 2% binder, 5wt% heat-conducting material, and the rest is acetone.

[0050] Example 5: Step 1: Stir DMAC at high speed using a planetary mixer, with a revolution speed of 25 r / min and a rotation speed of 2000 r / min. When the temperature reaches 45℃, stop stirring, add the binder (PVDF-HSV900), first at low speed revolution, at a speed of 15 r / min, then start rotation, at a speed of 1000 r / min, after 15 minutes, scrape the wall, to obtain a colloidal solution;

[0051] Step 2: the colloidal solution is vacuumed to a vacuum degree of -0.05 Mpa, rotation is at a speed of 20 r / min, high-speed rotation is at a speed of 1500 r / min, cold circulating water is connected, the slurry temperature is controlled below 50 DEG C, the stirring time is 1 hour, vacuuming is performed to a vacuum degree of 0.01 Mpa, the heat-conducting material is added, rotation is at a speed of 10 r / min, 5 min later, rotation is started, the speed is 50 r / min, 5 min later, the wall is scraped, vacuuming is performed to a vacuum degree of -0.05 Mpa, stirring is performed for 2 hours, vacuuming is performed to a vacuum degree of 0.01 Mpa; it is transferred to a high-efficiency fluid power shearing slurry mixer for shearing and dispersing, the dispersing time is 1.5 hours, screening is performed, and the slurry is obtained;

[0052] Step 3: coating is performed by using a coating machine, the coating is performed on a non-woven PE separator, the PE separator thickness is 16 um, the coating thickness is controlled to be 3 um, the coating speed is 50 m / min, the coating oven temperature is set to be 100 DEG C, and a high-thermal-conductivity lithium ion battery separator is obtained.

[0053] In the technical scheme, the slurry comprises the following raw materials in percentage by weight: 10% binder, 15 wt% heat-conducting material, and the rest is DMAC.

[0054] Example 6: Step 1: DMAC is stirred at a high speed by using a planetary stirrer, rotation is at a speed of 25 r / min, rotation is started, the speed is 2000 r / min, when the temperature reaches 45 DEG C, the stirring is stopped, the binder (PVDF-HSV900) is added, first, low-speed rotation is at a speed of 15 r / min, 10 min later, rotation is started, the speed is 1000 r / min, 15 min later, the wall is scraped, and a colloidal solution is obtained;

[0055] Step 2: the colloidal solution is vacuumed to a vacuum degree of -0.05 Mpa, rotation is at a speed of 20 r / min, high-speed rotation is at a speed of 1500 r / min, cold circulating water is connected, the slurry temperature is controlled below 50 DEG C, the stirring time is 1 hour, vacuuming is performed to a vacuum degree of 0.01 Mpa, the heat-conducting material is added, rotation is at a speed of 10 r / min, 5 min later, rotation is started, the speed is 50 r / min, 5 min later, the wall is scraped, vacuuming is performed to a vacuum degree of -0.05 Mpa, stirring is performed for 2 hours, vacuuming is performed to a vacuum degree of 0.01 Mpa; it is transferred to a high-efficiency fluid power shearing slurry mixer for shearing and dispersing, the dispersing time is 1.5 hours, screening is performed, and the slurry is obtained;

[0056] Step 3: coating is performed by using a coating machine, the coating is performed on a non-woven PE separator, the PE separator thickness is 16 um, the coating thickness is controlled to be 3 um, the coating speed is 50 m / min, the coating oven temperature is set to be 100 DEG C, and a high-thermal-conductivity lithium ion battery separator is obtained.

[0057] The slurry includes the following raw materials: 20% binder, 15wt% heat-conducting material, and the rest DMAC.

[0058] Example 7: The parameters of the scheme are the same as those of Example 6, except that the heat-conducting material is boron nitride.

[0059] Example 8: Step 1: DMAC is stirred at high speed with a planetary mixer, the revolution speed is 25 r / min, and the rotation speed is 2000 r / min, until the temperature reaches 45℃, then stop stirring, add the binder (PVDF-HSV900, ethoxylated pentaerythritol tetraacrylate, and lysine acrylate with a mass ratio of 8.2:0.5:1.3), first low-speed revolution, the speed is 15 r / min, then start rotation, the speed is 1000 r / min, after 15 min, scrape the wall, and obtain a colloidal solution;

[0060] Step 2: The colloidal solution is vacuumed to a vacuum degree of -0.05 Mpa, revolution, the speed is 20 r / min, high-speed rotation, the speed is 1500 r / min, connect the cold circulating water, control the slurry temperature below 50℃, and stir for 1 hour, vacuum to a vacuum degree of 0.01 Mpa, add the heat-conducting material, revolution, the speed is 10 r / min, start rotation after 5 min, the speed is 50 r / min, scrape the wall after 5 min, vacuum to a vacuum degree of -0.05 Mpa, stir for 2 hours, and vacuum to a vacuum degree of 0.01 Mpa; then transfer it to a high-efficiency fluid power shearing slurry mixer for shearing dispersion, the dispersion time is 1.5 hours, sieve, and obtain the slurry;

[0061] Step 3: Use a coating machine for coating, coat on a PE separator prepared by a wet method, the PE separator thickness is 9 μm, the single-side coating thickness is controlled at 1.5 μm, the coating speed is 80 m / min, irradiate under a UV lamp with a wavelength of 365 nm for 10 seconds (single-side time), the coating oven temperature is set at 100℃, and perform double-side coating, and obtain a high-heat-conducting lithium ion battery separator;

[0062] The slurry includes the following raw materials: 20% binder, 15wt% heat-conducting material, and the rest DMAC.

[0063] Example 9: The parameters of the scheme are the same as those of Example 8, except that the binder is PVDF-HSV900, ethoxylated pentaerythritol tetraacrylate, and lysine acrylate with a mass ratio of 8:0.5:1.5.

[0064] Example 10: The parameters of the scheme are the same as those of Example 8 except for the adhesive, which is PVDF-HSV900, ethoxylated pentaerythritol tetraacrylate and lysine acrylate in a mass ratio of 8.5:0.5:1.

[0065] Example 11: The parameters of the scheme are the same as those of Example 8, except that the thermally conductive material is different, which is boron nitride.

[0066] Example 12: The parameters of Example 8 are the same except for the thermally conductive material, which is not pretreated. The difference is that 10g of boron nitride, 3.2g of styrene, 1.08g of acrylic acid, and 0.06g of polyethylene glycol diacrylate are dispersed sequentially in 70g of deionized water and ultrasonically dispersed evenly. Then, 0.25 parts of azobisisobutyronitrile are added, and the mixture is stirred and reacted at 60°C for 8 hours under a nitrogen atmosphere. After washing and drying, styrene nanoparticles modified boron nitride are obtained.

[0067] Example 13: The parameters of the scheme are the same as those of Example 8, except that the adhesive is PVDF-HSV900 and ethoxylated pentaerythritol tetraacrylate with a mass ratio of 8.2:1.8.

[0068] Experiment 1: The high thermal conductivity lithium-ion battery separator prepared in the examples was subjected to performance testing, and the data obtained are shown in the table below:

[0069] Table 1:

[0070]

[0071]

[0072] Table 2:

[0073]

[0074] Conclusion: Data from Tables 1 and 2 show that the lithium-ion battery separators prepared in Examples 1-7 exhibit good adhesion strength, durability, and capacity retention, with Example 7 being the most optimized. Examples 8-10, representing further improvements, show significant performance enhancements compared to Example 7, with substantial improvements in adhesion strength, thermal conductivity, and capacity retention. Comparing the data from Examples 9-11 with Example 8 reveals that in Example 11, the lack of modification to the thermally conductive material resulted in a significant decrease in thermal conductivity, leading to a reduction in the capacity retention after 500 cycles. In Example 12, the absence of pretreatment of boron nitride resulted in decreased thermal conductivity, reduced durability, and a lower capacity retention. In Example 13, the introduction of four crosslinking groups into ethoxylated pentaerythritol tetraacrylate increased the degree of crosslinking and decreased porosity, leading to increased charge / discharge resistance and consequently reduced cycle capacity retention.

[0075] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for preparing a high thermal conductive lithium-ion battery separator, characterized in that: The method comprises the following steps: Step 1: Pre-stir the solvent, add the binder, stir and mix to obtain a colloidal solution; Step 2: Stir the colloidal solution once under vacuum, add the heat-conducting material, stir again under vacuum, shear and disperse, sieve to obtain a slurry; Step 3: Apply the slurry to a base film, dry to obtain a heat-conducting coating layer; Roll up to obtain a high-heat-conducting lithium ion battery separator; The slurry comprises the following raw materials: 1.5-20% of the binder, 3-15% of the heat-conducting material, 0.3-0.4% of the photoinitiator, and the rest is the solvent; The binder is polyvinylidene fluoride, ethoxylated pentaerythritol tetraacrylate and lysine acrylate at a mass ratio of (8-8.5):0.5:(1-1.5); and the heat-conducting material is styrene nanoparticle modified boron nitride; The preparation method of the lysine acrylate comprises the following steps: adding hydroxyethyl methacrylate and a catalyst into a solvent, setting the temperature to 0-5 DEG C, stirring uniformly, adding L-lysine diisocyanate, dropping for 2-2.5 hours, stirring at room temperature for 20-22 hours, evaporating the solvent, washing, filtering and drying to obtain the lysine acrylate.

2. The process for preparing a high thermal conductive lithium-ion battery separator according to claim 1, characterized in that: The polyvinylidene fluoride has a characteristic viscosity of 0.2-2.5 g / mL and a crystallinity of greater than or equal to 60%; the heat-conducting material has a particle size of 0.1-3 microns; the solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide and acetone; and the base film is one of a PP separator, a PE separator, a non-woven PET separator, a non-woven PP separator and a non-woven PE separator.

3. The process for preparing a high thermal conductive lithium-ion battery separator according to claim 1, characterized in that: In step 2, the revolution speed is 20-25 r / min and the rotation speed is 1000-1500 r / min during the first vacuum stirring; the revolution speed is 10 r / min and the rotation speed is 50 r / min during the second vacuum stirring; the shear and dispersion time is 1-1.5 hours; and the sieve mesh is 150-220 meshes; and in step 3, the coating speed is 5-180 m / min.

4. The process of claim 1, wherein the process is characterized by: The preparation method of the styrene nanoparticle modified boron nitride comprises the following steps: (1) uniformly mixing boron nitride, cysteine and a sodium hydroxide solution, placing in a ball milling device, wet milling for 6-8 hours, washing, drying to obtain pretreated boron nitride; (2) sequentially dispersing the pretreated boron nitride, styrene, acrylic acid and polyethylene glycol diacrylate in deionized water, ultrasonic dispersion, adding azobisisobutyronitrile, setting the temperature to 50-60 DEG C under a nitrogen atmosphere, stirring and reacting for 6-8 hours, washing, drying to obtain the styrene nanoparticle modified boron nitride.

5. The process of claim 4, wherein the process further comprises: In step (1), the mass ratio of boron nitride, cysteine, and sodium hydroxide solution is 1:2:12, and the concentration of the sodium hydroxide solution is 1 mol / L; during the ball milling process, the ratio of the zirconium oxide microspheres is 8 mm:5 mm:3 mm=1:2:1; in step (2), the styrene nanoparticle modified boron nitride comprises the following raw materials: 10 parts of pretreated boron nitride, 3-3.5 parts of styrene, 1-1.2 parts of acrylic acid, 0.05-0.06 parts of polyethylene glycol diacrylate, 0.2-0.3 parts of azobisisobutyronitrile, and 65-70 parts of deionized water.

6. The process of claim 1, wherein the process is characterized by: In step 3, the drying process is irradiation under a UV lamp with a wavelength of 365 nm for 5-10 seconds, and the oven drying temperature is 80-100°C.

7. A high-thermal-conductivity lithium-ion battery separator prepared by the preparation process according to any one of claims 1-6; the high-thermal-conductivity lithium-ion battery separator comprises a base film and a thermal-conductivity coating layer, the thickness of the base film is 3-20 μm, and the thickness of the thermal-conductivity coating layer is 0.5-6 μm.

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