A high lithium ion transport ceramic slurry and coated separator

Abstract

The application discloses a high lithium ion transmission ceramic slurry and a coated diaphragm thereof, and relates to the technical field of ceramic diaphragms, which comprises a dopant composed of ceramic particles, MXenes, a dispersing agent and sodium carboxymethyl cellulose in a mass ratio of 1:0.1-0.5:0.005-0.02:0.005-0.03; a bonding agent; a wetting agent; and solution water as a balance; wherein the solution water accounts for 55-65 wt% of the total mass, the mass ratio of the dopant, the bonding agent and the wetting agent is 1.11-1.54:0.1-0.5:0.0005-0.002, and the viscosity of the ceramic slurry is greater than 20 cp. The application improves the chemical compatibility of MXenes and organic polymers, improves the ion conduction efficiency, and maintains the effective electrode physical barrier effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic separator, in particular to a high lithium ion transmission ceramic slurry and a coated separator thereof. BACKGROUND

[0002] Lithium ion batteries (LIB) have become the mainstream choice for electric vehicles due to their high energy density, high operating voltage and good cycle performance. Ceramic coated separators are key components of LIBs, which can isolate the anode and cathode of the battery to avoid their mutual contact, while absorbing and retaining a large amount of electrolyte, promoting the transmission of lithium ions. The hydrophobicity and relatively low porosity of conventional separators hinder the wettability of electrolyte. Therefore, it is crucial to modify the ceramic separator to improve the wettability and lithium ion transmission performance of the separator.

[0003] However, when MXenes are used as direct additive materials for ceramic coated separators, due to the rich polar functional groups on the surface of MXenes, it is easy to cause side reactions with lithium salts in the electrolyte, resulting in increased interfacial impedance or electrolyte decomposition, thus causing the pores of the separator to be blocked, reducing ion conduction efficiency, and affecting the battery charge and discharge rate. In addition, when MXenes are combined with the substrate, due to the poor chemical compatibility of the metal-carbon structure of MXenes with organic polymers, the coating layer is prone to fall off or delaminate, and further lose the physical barrier effect on the electrode, increasing the risk of dendrite puncture. Therefore, there is room for improvement. SUMMARY

[0004] Therefore, the first object of the present application is to provide a high lithium ion transmission ceramic slurry to improve ion conduction efficiency and maintain effective electrode physical barrier. The specific scheme is as follows:

[0005] A high lithium ion transmission ceramic slurry, comprising:

[0006] a dopant composed of ceramic particles, MXenes, a dispersing agent and sodium carboxymethyl cellulose in a mass ratio of 1:0.1-0.5:0.005-0.02:0.005-0.03;

[0007] a binder;

[0008] a wetting agent;

[0009] and a solution water as the balance;

[0010] wherein:

[0011] the solution water accounts for 55-65wt% of the total mass, the mass ratio of the dopant, the binder and the wetting agent is 1.11-1.54:0.1-0.5:0.0005-0.002, and the viscosity of the ceramic slurry is greater than 20cp;

[0012] The MXenes are modified composite MXenes materials, which are obtained by sequentially grafting dopamine hydrochloride and CNT compounding from MXenes raw materials.

[0013] Preferably, the particle size D50 of the ceramic particles is 0.4-2.0 μm, and the ceramic particles are selected from at least one of alpha alumina, boehmite and magnesium hydroxide.

[0014] Preferably, the binder is an emulsion type polyacrylic acid binder, and the solid content is 20-50%, and the viscosity is greater than 50 cp.

[0015] Preferably, the wetting agent is a siloxane wetting agent.

[0016] Preferably, the preparation method of the modified composite MXenes material comprises the following steps: ① dispersing MXenes raw materials in a Tris-HCl buffer solution, adding dopamine hydrochloride, stirring at room temperature for grafting, centrifugal washing, and vacuum drying to obtain polydopamine grafted MXenes; ② dispersing the polydopamine grafted MXenes in ethanol, adding polyethylene glycol and a crosslinking agent, and stirring to obtain PEG functionalized MXenes; and ③ mixing the PEG functionalized MXenes with CNT at a mass ratio of 5-10:1, adding an ethanol aqueous solution, and performing ultrasonic dispersion treatment and suction filtration to obtain the finished modified composite MXenes material.

[0017] Preferably, in step ①, the pH of the Tris-HCl buffer solution is 8.5, the concentration is 10 mM, and the mixing ratio of the MXenes raw materials, the Tris-HCl buffer solution and the dopamine hydrochloride is 1 g:80-120 ml:80-120 mg; in step ②, the mixing ratio of the ethanol, the polyethylene glycol, the crosslinking agent and the MXenes raw materials is 50 ml:1.8-2.2 g:0.4-0.55 g:1 g; and in step ③, the length of the CNT is 1-2 μm.

[0018] A second object of the present application is to provide a coated separator of high lithium ion transmission ceramic slurry, which comprises a high lithium ion transmission ceramic slurry as described above, and comprises a breathable isolation film and a high lithium ion transmission ceramic layer, and the preparation method of the high lithium ion transmission ceramic layer comprises the following steps: ① putting a dispersant into solution water, stirring uniformly to obtain a dispersion solution; ② putting ceramic particles and MXenes into the dispersion solution, adding sodium carboxymethyl cellulose after high-speed dispersion, and obtaining a doped solution by high-speed sand mill dispersion; ③ adding a binder to the doped solution, and obtaining a bonding solution after high-speed dispersion; ④ adding a wetting agent to the bonding solution, and obtaining a coating slurry after uniform dispersion; and ⑤ putting the coating slurry into a coating machine, and obtaining a finished coated separator by coating and oven drying through a coating die and winding.

[0019] Preferably: in step ①, a double planetary mixer is used, and the linear speed is controlled to be 15-20 m / s, and the stirring time is 30-60 min; in step ②, a double planetary mixer and a grinder are used, and the linear speed of the double planetary mixer is controlled to be 20-25 m / s, and the stirring time is 60-120 min, and the flow rate of the grinder is controlled to be 10-20 L / min; in step ③, a double planetary mixer is used, and the linear speed is controlled to be 15-20 m / s, and the stirring time is 30-60 min; in step ④, a double planetary mixer is used, and the linear speed is controlled to be 5-10 m / s, and the stirring time is 20-30 min.

[0020] Preferably: in step ⑤, the coating machine comprises a feeding unit, an unwinding unit, a coating unit, a drying unit and a winding unit; the feeding speed of the feeding unit is controlled to be 5-15 L / min; the unwinding tension of the unwinding unit is controlled to be 20-40 N / m, the coating tension of the coating unit is controlled to be 50-80 N / m, the drying unit is provided with four drying zones, and the temperature of the four drying zones is controlled to be 60-70℃, 80-90℃, 80-90℃ and 50-60℃ in sequence; the winding tension of the winding unit is controlled to be 10-25 N / m.

[0021] Preferably: the thickness of the coated separator is 3-20 μm, the air permeability value is 10-500 s / 100 ml, the high-temperature resistance is 130℃ / 30 min, and the thermal shrinkage MD and TD are both less than 3%.

[0022] It can be known from the above scheme that the application provides a high lithium ion transmission ceramic slurry and a coated separator thereof. The high lithium ion transmission ceramic slurry is obtained by mixing dopants, adhesives, wetting agents and water as the balance, so as to provide a channel for fast ion transmission between the two-dimensional layered structure of MXenes and the formed interlayer spacing, and improve the wettability of the electrolyte in the ceramic separator in combination with various functional groups on the surface thereof. Since the modified composite MXenes material is used, the fraction single stability is further improved, the ion conductivity at 25℃ and the tensile lightness are improved, the conductivity is significantly improved, and the compatibility and durability of the organic polymer are improved. The coated separator of the high lithium ion transmission ceramic slurry improves the chemical compatibility of MXenes and the organic polymer, improves the ion conduction efficiency, and maintains the effective electrode physical barrier effect. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only 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 of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0024] It should be noted that the raw material of MXenes in the embodiments of the present application is single / few-layer colloidal solution TI3C2Tx, and the size is 1-5 μm. In the preparation method of the modified composite MXenes material, the crosslinking agent used is DCC.

[0025] The following will specifically describe a high lithium ion transmission ceramic slurry and a coated separator according to the present application.

[0026] A high lithium ion transmission ceramic slurry includes a dopant, a binder, a wetting agent, and solution water as a balance. In the embodiments of the present application, the binder is an emulsion type polyacrylic acid binder, and the solid content is 20-50%, and the viscosity is greater than 50 cp. The wetting agent is a silicon ether type wetting agent. The dopant is composed of ceramic particles, MXenes, dispersants and sodium carboxymethyl cellulose in a mass ratio of 1:0.1-0.5:0.005-0.02:0.005-0.03. Among them, the particle size D50 of the ceramic particles is 0.4-2.0 μm, and is selected from at least one of α-alumina, boehmite and magnesium hydroxide. The solution water accounts for 55-65 wt% of the total mass, and the mixing mass ratio of the dopant, the binder and the wetting agent is controlled to be 1.11-1.54:0.1-0.5:0.0005-0.002. It has been tested that the viscosity of the high lithium ion transmission ceramic slurry obtained in the embodiments of the present application is greater than 20 cp.

[0027] It needs to be mentioned that the MXenes in the embodiments of the present application are modified composite MXenes materials. The preparation method of the modified composite MXenes material comprises the following steps: ① 1 g of MXenes raw material is dispersed in 80-120 ml of Tris-HCl buffer solution with a pH of 8.5 and a concentration of 10 mM, and ultrasonic treatment is performed for 30-60 min, then 80-120 mg of dopamine hydrochloride is added, stirring at room temperature is performed for 20-28 h to complete grafting, and then centrifugal washing is performed, the centrifugal speed is controlled to be 8000 rpm, and the treatment time is 10 min, and then vacuum drying treatment is performed at 60 ℃ for 12 h to obtain polydopamine grafted MXenes; ② the polydopamine grafted MXenes are dispersed in 50 ml of ethanol, 1.8-2.2 g of polyethylene glycol and 0.4-0.55 g of a crosslinking agent are added, and then stirring treatment is performed at 50 ℃ for 12 h to obtain PEG functionalized MXenes; ③ the PEG functionalized MXenes are mixed with CNT with a length of 1-2 μm at a mass ratio of 5-10:1, then an ethanol aqueous solution with a mass ratio of 1 is added, ultrasonic dispersion treatment is performed for 1 h, and then vacuum filtration is performed to obtain the finished modified composite MXenes material.

[0028] The second object of the present application is to provide a coated separator of high lithium ion transmission ceramic slurry, comprising a high lithium ion transmission ceramic slurry as described above, comprising a breathable isolation film and a high lithium ion transmission ceramic layer, and the preparation method of the high lithium ion transmission ceramic layer comprises the following steps: step 1, adding a dispersing agent into a solution of water, stirring with a double planetary mixer, and controlling the linear speed to be 15-20 m / s, the stirring time is 30-60 min, and the uniform stirring obtains a dispersion solution; step 2, ceramic particles and MXenes are added into the dispersion solution, and the double planetary mixer is used for stirring, the linear speed of the double planetary mixer is controlled to be 20-25 m / s, the stirring time is 60-120 min, after high-speed dispersion, sodium carboxymethyl cellulose is added, and then a grinder is used for grinding, the flow rate of the grinder is controlled to be 10-20 L / min, high-speed sanding dispersion is carried out, and a doped solution is obtained; step 3, an adhesive is added into the doped solution, a double planetary mixer is used for stirring, the linear speed is controlled to be 15-20 m / s, the stirring time is 30-60 min, after high-speed dispersion, an adhesive solution is obtained; step 4, a wetting agent is added into the adhesive solution, a double planetary mixer is used for stirring, the linear speed is controlled to be 5-10 m / s, the stirring time is 20-30 min, after dispersion, a coating slurry is obtained; step 5, the coating slurry is put into a coating machine, the coating machine comprises a feeding unit, an unwinding unit, a coating unit, a drying unit and a winding unit, the feeding speed of the feeding unit is controlled to be 5-15 L / min, the unwinding tension of the unwinding unit is controlled to be 20-40 N / m, the coating tension of the coating unit is controlled to be 50-80 N / m, the drying unit is provided with four drying zones, and the temperature of the four drying zones is controlled to be 60-70℃, 80-90℃, 80-90℃ and 50-60℃ in sequence, and the winding tension of the winding unit is controlled to be 10-25 N / m, so that the product coated separator is obtained after coating through a coating die and heating and drying in an oven. The thickness of the coated separator of high lithium ion transmission ceramic slurry obtained in the embodiment of the present application is 3-20 μm, the air permeability value is 10-500 s / 100 ml, the high temperature resistance is 130℃ / 30min, and the heat shrinkage MD is less than 3%, and the heat shrinkage TD is less than 3%.

[0029] Of course, in order to better test and compare, the thickness of the coated separator in the following examples is 2 μm, and the thickness of the breathable isolation film is controlled to be 7 μm. That is, the formed coated separator is a breathable isolation film with a thickness of 7 μm in the middle, and a coated separator with a thickness of 2 μm on both sides of the breathable isolation film.

[0030] Example 1

[0031] The high lithium ion transmission ceramic slurry comprises dopant, adhesive, wetting agent and solution water as the balance. In the embodiment of the application, the adhesive is an emulsion type polyacrylic acid adhesive, and the solid content is 40% and the viscosity is greater than 50 cp. The wetting agent is a silicon ether type wetting agent. The dopant is composed of ceramic particles, MXenes, dispersants and sodium carboxymethyl cellulose in a mass ratio of 75:25:1:2. The sodium carboxymethyl cellulose is provided by 160 kg of sodium carboxymethyl cellulose aqueous solution with a solid content of 5%. Among them, the ceramic particles are alpha aluminum oxide with a particle size D50 of 0.6 microns. The solution water accounts for 60% of the total mass, and the mixing mass ratio of the dopant, adhesive and wetting agent is controlled to be 412:80:0.54.

[0032] It should be noted that the MXenes in the embodiment of the application are modified composite MXenes materials. The preparation method of the modified composite MXenes material comprises the following steps: ① dispersing 1 g of MXenes raw material in 100 ml of Tris-HCl buffer solution with pH of 8.5 and concentration of 10 mM, and ultrasonic treatment for 30 min, then adding 100 mg of dopamine hydrochloride, stirring at room temperature for 24 h to complete the grafting, centrifugal washing, controlling the centrifugal speed to be 8000 rpm for 10 min, and then vacuum drying at 60 DEG C for 12 h to obtain polydopamine grafted MXenes; ② dispersing the polydopamine grafted MXenes in 50 ml of ethanol, adding 2 g of polyethylene glycol and 0.5 g of crosslinking agent, stirring at 50 DEG C for 12 h to obtain PEG functionalized MXenes; ③ mixing the PEG functionalized MXenes with CNT with a length of 1-2 microns in a mass ratio of 5:1, then adding an ethanol aqueous solution with a mass ratio of 1, ultrasonic dispersion for 1 h, and then vacuum filtration to obtain the finished modified composite MXenes material.

[0033] A second object of the present application is to provide a coated separator of high lithium ion transmission ceramic slurry, comprising a high lithium ion transmission ceramic slurry as described above, comprising a breathable isolation film and a high lithium ion transmission ceramic layer, and the preparation method of the high lithium ion transmission ceramic layer comprises the following steps: step 1, put the dispersant into the solution water, stir with a double planetary mixer, control the linear speed to be 20 m / s, and stir for 50 min, and obtain a dispersion solution after uniform stirring; step 2, put the ceramic particles and MXenes into the dispersion solution, stir with a double planetary mixer, control the linear speed of the double planetary mixer to be 25 m / s, and stir for 100 min, add sodium carboxymethyl cellulose after high-speed dispersion, and then grind with a grinder, control the flow rate of the grinder to be 16 L / min, and obtain a doped solution after high-speed sanding dispersion; step 3, add the binder to the doped solution, stir with a double planetary mixer, control the linear speed to be 20 m / s, and stir for 50 min, and obtain a bonding solution after high-speed dispersion; step 4, add the wetting agent to the bonding solution, stir with a double planetary mixer, control the linear speed to be 10 m / s, and stir for 25 min, and obtain a coating slurry after dispersion; step 5, put the coating slurry into a coating machine, the coating machine comprises a feeding unit, an unwinding unit, a coating unit, a drying unit and a winding unit, the feeding speed of the feeding unit is controlled to be 8 L / min, the unwinding tension of the unwinding unit is controlled to be 30 N / m, the coating tension of the coating unit is controlled to be 60 N / m, the drying unit is provided with four drying zones, and the temperatures of the four drying zones are controlled to be 65℃, 85℃, 85℃ and 55℃ in sequence, and the winding tension of the winding unit is controlled to be 15 N / m, so as to obtain a finished product coated separator after coating and drying through a coating die and an oven.

[0034] Example two

[0035] A high lithium ion transmission ceramic slurry, comprising a dopant, a binder, a wetting agent and a solution water as a balance. In the embodiment of the present application, the binder is an emulsion type polyacrylic acid adhesive, and the solid content is 20%, and the viscosity is greater than 50 cp. The wetting agent is a silicon ether type wetting agent. The dopant is composed of ceramic particles, MXenes, dispersants and sodium carboxymethyl cellulose in a mass ratio of 1:0.1:0.005:0.005. Among them, the ceramic particles are boehmite with a particle size D50 of 2.0 μm. The solution water accounts for 65 wt% of the total mass, and the mixed mass ratio of the dopant, the binder and the wetting agent is 1.11:0.1:0.0005.

[0036] It needs to be mentioned that the MXenes in the embodiments of the present application are modified composite MXenes materials. The preparation method of the modified composite MXenes material includes the following steps: ① 1 g of MXenes raw material is dispersed in 80 ml of Tris-HCl buffer solution with a pH of 8.5 and a concentration of 10 mM and ultrasonic treatment for 45 min, then 80 mg of dopamine hydrochloride is added, stirring at room temperature for 20 h to complete the grafting, and then centrifugal washing is performed at a centrifugal speed of 8000 rpm for 10 min, and vacuum drying at 60℃ for 12 h to obtain polydopamine grafted MXenes; ② the polydopamine grafted MXenes are dispersed in 50 ml of ethanol, 1.8 g of polyethylene glycol and 0.4 g of crosslinking agent are added, and stirring treatment at 50℃ for 12 h to obtain PEG functionalized MXenes; ③ the PEG functionalized MXenes are mixed with CNT with a length of 1-2 μm at a mass ratio of 7:1, and then an ethanol aqueous solution with a mass ratio of 1 is added, and ultrasonic dispersion treatment is performed for 1 h, and then vacuum filtration to obtain the finished modified composite MXenes material.

[0037] A second object of the present application is to provide a coated separator of high lithium ion transmission ceramic slurry, which comprises a high lithium ion transmission ceramic slurry as described above, and comprises a breathable isolation film and a high lithium ion transmission ceramic layer, and the preparation method of the high lithium ion transmission ceramic layer comprises the following steps: ① a dispersing agent is put into a solution of water, a double planetary mixer is used for stirring, the linear speed is controlled to be 15 m / s, and the stirring time is 60 min, and then a dispersion solution is obtained after uniform stirring; ② ceramic particles and MXenes are put into the dispersion solution, a double planetary mixer is used for stirring, the linear speed of the double planetary mixer is controlled to be 20 m / s, and the stirring time is 120 min, carboxymethyl cellulose sodium is added after high-speed dispersion, a grinder is used for grinding, the flow rate of the grinder is controlled to be 10 L / min, and high-speed sand mill dispersion is performed to obtain a doped solution; ③ an adhesive is added to the doped solution, a double planetary mixer is used for stirring, the linear speed is controlled to be 15 m / s, and the stirring time is 60 min, and then an adhesive solution is obtained after high-speed dispersion; ④ a wetting agent is added to the adhesive solution, a double planetary mixer is used for stirring, the linear speed is controlled to be 5 m / s, and the stirring time is 30 min, and then a coating slurry is obtained after dispersion; ⑤ the coating slurry is put into a coating machine, the coating machine comprises a feeding unit, an unwinding unit, a coating unit, a drying unit and a winding unit, the feeding speed of the feeding unit is controlled to be 5 L / min, the unwinding tension of the unwinding unit is controlled to be 20 N / m, the coating tension of the coating unit is controlled to be 50 N / m, the drying unit is provided with four drying zones, and the temperatures of the four drying zones are controlled to be 60℃, 80℃, 80℃ and 50℃ in sequence, and the winding tension of the winding unit is controlled to be 10 N / m, so that the finished coated separator is obtained after coating by a coating die and heating and drying in an oven.

[0038] Example Three

[0039] A high lithium ion transmission ceramic slurry includes a dopant, a binder, a wetting agent, and solution water as a balance. In the embodiment of the present application, the binder is an emulsion type polyacrylic acid binder, and the solid content is 50%, and the viscosity is greater than 50 cp. The wetting agent is a silicon ether type wetting agent. The dopant is composed of ceramic particles, MXenes, a dispersant, and sodium carboxymethyl cellulose in a mass ratio of 1:0.5:0.02:0.03. Among them, the ceramic particles are magnesium hydroxide with a particle size D50 of 0.4 μm. The solution water accounts for 55wt% of the total mass, and the mixed mass ratio of the dopant, the binder, and the wetting agent is controlled to be 1.54:0.5:0.002.

[0040] It needs to be mentioned that the MXenes in the embodiment of the present application are modified composite MXenes materials. The preparation method of the modified composite MXenes material includes the following steps: ① 1g of MXenes raw material is dispersed in 120ml of Tris-HCl buffer solution with pH of 8.5 and concentration of 10mM for ultrasonic treatment for 60min, then 120mg of dopamine hydrochloride is added, and after stirring at room temperature for 28h, centrifugal washing is performed, the centrifugal speed is controlled to be 8000rpm for 10min, and then vacuum drying treatment is performed at 60℃ for 12h to obtain polydopamine grafted MXenes; ② the polydopamine grafted MXenes are dispersed in 50ml of ethanol, 2.2g of polyethylene glycol and 0.55g of crosslinking agent are added, and after stirring treatment at 50℃ for 12h, PEG functionalized MXenes are obtained; ③ the PEG functionalized MXenes and CNT with a length of 1-2 μm are mixed in a mass ratio of 10:1, then an ethanol aqueous solution with a mass ratio of 1 is added, ultrasonic dispersion treatment is performed for 1h, and then vacuum filtration is performed to obtain the finished modified composite MXenes material.

[0041] A second object of the present application is to provide a coated separator of high lithium ion transmission ceramic slurry, comprising a high lithium ion transmission ceramic slurry as described above, comprising a breathable isolation film and a high lithium ion transmission ceramic layer, the preparation method of the high lithium ion transmission ceramic layer comprising the following steps: step 1, adding a dispersing agent into a solution of water, stirring with a double planetary mixer, and controlling the linear speed to be 20 m / s, the stirring time is 30 min, after uniform stirring, a dispersion solution is obtained; step 2, ceramic particles and MXenes are added into the dispersion solution, stirring with a double planetary mixer, controlling the linear speed of the double planetary mixer to be 25 m / s, the stirring time is 60 min, after high-speed dispersion, sodium carboxymethyl cellulose is added, and then a grinder is used for grinding, controlling the flow rate of the grinder to be 20 L / min, high-speed sanding dispersion is carried out, and a doped solution is obtained; step 3, adding a bonding agent to the doped solution, stirring with a double planetary mixer, controlling the linear speed to be 20 m / s, the stirring time is 30 min, after high-speed dispersion, a bonding solution is obtained; step 4, adding a wetting agent to the bonding solution, stirring with a double planetary mixer, controlling the linear speed to be 10 m / s, the stirring time is 20 min, after dispersion, a coating slurry is obtained; step 5, the coating slurry is put into a coating machine, the coating machine comprises a feeding unit, an unwinding unit, a coating unit, a drying unit and a winding unit, the feeding speed of the feeding unit is controlled to be 15 L / min, the unwinding tension of the unwinding unit is controlled to be 40 N / m, the coating tension of the coating unit is controlled to be 80 N / m, the drying unit is provided with four drying zones, and the temperature is controlled to be 70℃, 90℃, 90℃ and 60℃ in turn, the winding tension of the winding unit is controlled to be 25 N / m, and the finished product coated separator is obtained after coating through a coating die and heating and drying in an oven.

[0042] Comparative Example 1

[0043] The difference between Comparative Example 1 and Example 1 is that the MXenes in Comparative Example 1 are MXenes raw materials.

[0044] Comparative Example 2

[0045] The difference between Comparative Example 2 and Example 1 is that the preparation method of the modified composite MXenes material in Comparative Example 2 does not have step ③.

[0046] The DCR / mΩ and ACR / mΩ are determined based on the national standard battery internal resistance test method GB / T 31467.3-2015 "Lithium ion power battery pack and system for electric vehicles Part 3: Safety requirements and test methods", and the test results are shown in Table 1 as follows:

[0047] Table 1 Test results

[0048]

[0049] It can be seen from the above table that by introducing amino and catechol groups through dopamine grafting, the chemical cross-linking effect of MXenes and PAA can be effectively enhanced, and the conductive network of carbon nanotubes (CNT) is constructed to improve the ion channel and achieve the purpose of accelerating ion transmission. When only the chemical cross-linking effect is enhanced, it has the effect of prolonging the service life by improving the chemical compatibility of MXenes and organic polymers, but the speed of ion conduction efficiency is not significantly enhanced. If CNT is added to construct a core-shell / sandwich structure, the surface properties of MXenes raw materials will be improved, and the interface bonding effect with PAA will be improved. At the same time, the interlayer spacing stability of MXenes will be improved by CNT compounding, thereby providing a stable channel for lithium ion transmission and achieving the effect of inhibiting the aggregation of MXenes.

[0050] In summary, the present application provides a high lithium ion transmission ceramic slurry and a coated separator thereof. The high lithium ion transmission ceramic slurry is obtained by mixing dopants, adhesives, wetting agents and water as the balance, thereby providing a channel for fast ion transmission for the two-dimensional layered structure of MXenes and the interlayer spacing formed, and improving the wettability of the electrolyte in the ceramic separator by combining various functional groups on the surface thereof. Since the modified composite MXenes material is used, the fraction single stability is further improved, the ion conductivity at 25°C and the tensile lightness are improved, the conductivity is significantly improved, and the compatibility and durability with organic polymers are improved. The coated separator of the high lithium ion transmission ceramic slurry improves the chemical compatibility of MXenes and organic polymers, improves the ion conduction efficiency, and maintains the effective electrode physical barrier effect.

[0051] The terms "first", "second", "third", "fourth" and the like, if any, used in the present application are used to distinguish similar objects, and do not necessarily have to be used to describe a particular order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods or devices.

[0052] It should be noted that the terms "first", "second", and the like in the description and in the claims do not denote any particular importance, but are merely used to distinguish one element from another. Thus, a "first" and "second" feature can be presented explicitly or implicitly, and can include at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, nor is it within the scope of protection required by the present application.

[0053] The principles and implementation manners of the present application are described by applying specific examples herein, and the above description of the examples is only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application, and in view of the above, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A coating membrane for a high lithium-ion transport ceramic slurry, characterized in that, This includes using a high lithium-ion transport ceramic slurry, wherein the high lithium-ion transport ceramic slurry comprises: The dopant consists of ceramic particles, MXenes, dispersant, and sodium carboxymethyl cellulose in a mass ratio of 1:0.1-0.5:0.005-0.02:0.005-0.03; Adhesive; wetting agent; And the remaining amount of water solution; in: The solution contains 55-65 wt% water, the mass ratio of the dopant, binder and wetting agent is 1.11-1.54:0.1-0.5:0.0005-0.002, and the ceramic slurry viscosity is greater than 20 cp; the binder is an emulsion-type polyacrylic acid binder. The MXenes are modified composite MXenes materials. The preparation method of the modified composite MXenes material includes: Step ① dispersing MXenes raw materials in Tris-HCl buffer solution, adding dopamine hydrochloride, stirring and grafting at room temperature, centrifuging and washing, and then vacuum drying to obtain polydopamine-grafted MXenes; Step ② dispersing polydopamine-grafted MXenes in ethanol, adding polyethylene glycol and a crosslinking agent, and stirring to obtain PEG-functionalized MXenes; Step ③ mixing PEG-functionalized MXenes with CNTs at a mass ratio of 5-10:1, and then... The modified composite MXenes material is obtained by adding an aqueous ethanol solution, followed by ultrasonic dispersion and filtration. In step ①, the pH of the Tris-HCl buffer solution is 8.5, the concentration is 10 mM, and the mixing ratio of MXenes raw material, Tris-HCl buffer solution and dopamine hydrochloride is 1 g: 80-120 ml: 80-120 mg. In step ②, the mixing ratio of ethanol, polyethylene glycol and crosslinking agent with MXenes raw material is 50 ml: 1.8-2.2 g: 0.4-0.55 g: 1 g. In step ③, the CNT length is 1-2 μm.

2. The coating membrane of a high lithium-ion transport ceramic slurry according to claim 1, characterized in that: The ceramic particles have a particle size D50 of 0.4-2.0 μm and are selected from at least one of α-alumina, boehmite, and magnesium hydroxide.

3. The coating membrane of a high lithium-ion transport ceramic slurry according to claim 1, characterized in that: The emulsion-type polyacrylic acid adhesive has a solid content of 20-50% and a viscosity greater than 50 cp.

4. The coating membrane of a high lithium-ion transport ceramic slurry according to claim 1, characterized in that: The wetting agent is a silicone ether wetting agent.

5. The coating membrane of a high lithium-ion transport ceramic slurry according to claim 1, characterized in that: The invention comprises a breathable separator and a high lithium-ion transport ceramic layer. The preparation method of the high lithium-ion transport ceramic layer includes the following steps: Step 1: Add a dispersant to a solution of water and stir until homogeneous to obtain a dispersion solution; Step 2: Add ceramic particles and MXenes to the dispersion solution, disperse at high speed, add sodium carboxymethyl cellulose, and disperse at high speed to obtain a doped solution; Step 3: Add a binder to the doped solution and disperse at high speed to obtain a binder solution; Step 4: Add a wetting agent to the binder solution and disperse until homogeneous to obtain a coating slurry; Step 5: Put the coating slurry into a coating machine, coat it with a coating die, dry it in an oven, and then roll it up to obtain the finished coated separator.

6. The coating membrane of a high lithium-ion transport ceramic slurry according to claim 5, characterized in that: In step one, a double planetary mixer is used, with the linear velocity controlled at 15-20 m / s and the mixing time at 30-60 min. In step two, a double planetary mixer and a grinder are used, with the linear velocity of the double planetary mixer controlled at 20-25 m / s and the mixing time at 60-120 min, and the flow rate of the grinder controlled at 10-20 L / min. In step three, a double planetary mixer is used, with the linear velocity controlled at 15-20 m / s and the mixing time at 30-60 min. In step four, a double planetary mixer is used, with the linear velocity controlled at 5-10 m / s and the mixing time at 20-30 min.

7. The coating membrane of a high lithium-ion transport ceramic slurry according to claim 5, characterized in that: In step five, the coating machine includes a feeding unit, an unwinding unit, a coating unit, a drying unit, and a rewinding unit; the feeding speed of the feeding unit is controlled at 5-15 L / min; the unwinding tension of the unwinding unit is controlled at 20-40 N / m; the coating tension of the coating unit is controlled at 50-80 N / m; the drying unit is provided with four drying zones, and the temperatures are controlled sequentially at 60-70℃, 80-90℃, 80-90℃, and 50-60℃; the rewinding tension of the rewinding unit is controlled at 10-25 N / m.

8. The coating membrane of a high lithium-ion transport ceramic slurry according to claim 5, characterized in that: The coating membrane has a thickness of 3-20 μm, an air permeability of 10-500 s / 100 ml, a high temperature resistance of 130℃ / 30 min, and a heat shrinkage MD < 3% and TD < 3%.

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