Organic coating slurry for ceramic affinity type lithium battery diaphragm as well as preparation method and application of organic coating slurry

Abstract

The invention relates to the technical field of lithium battery diaphragms, and provides ceramic affinity type lithium battery diaphragm organic coating slurry and a preparation method and application thereof.The ceramic affinity type lithium battery diaphragm organic coating slurry is prepared from, by weight, 10-12 parts of deionized water, 1-3 parts of ceramic microcapsule particles, 0.1-0.3 part of hydroxymethyl cellulose lithium and 0.5-1 part of solid electrolyte; core materials of the ceramic microcapsule particles are ceramic particles, and wall materials of the ceramic microcapsule particles are organic polymers; the preparation method of the ceramic microcapsule particles comprises the following steps: S1, dispersing deionized water, ceramic particles and a dispersing agent, uniformly stirring, introducing nitrogen, sequentially adding a lithium salt, a coating agent and a pore forming agent, then adding PVDF powder and PMMA powder, and mixing to obtain a pre-agglomerated solution; and S2, carrying out spray drying granulation on the pre-agglomerated liquid to obtain the ceramic microcapsule particles. According to the technical scheme, the problems of insufficient heat resistance and safety of the lithium battery diaphragm in related technologies are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery separator, in particular to a ceramic affinity type lithium battery separator organic coating slurry, a preparation method and application thereof. BACKGROUND

[0002] With the continuous growth of demand for portable electronic devices, new energy vehicles and large-scale energy storage systems in modern society, lithium ion batteries have become the current mainstream electrochemical energy storage devices due to their high energy density, small size, no memory effect and other advantages. However, with the expansion of application scenarios and the improvement of life quality, the market has put forward more stringent requirements for the core performance indicators of lithium ion batteries, which are embodied in three key dimensions: first, fast charging efficiency, which needs to meet the use demand of rapid energy supplement in a short time; second, cycle life, which needs to ensure stable capacity output after long-term charge and discharge cycles; third, safety and reliability, which needs to avoid the risk of thermal runaway caused by uncontrolled internal reaction.

[0003] The charging and discharging process of lithium ion battery is essentially the dynamic cycle of lithium ion (Li + ) directional migration between the positive electrode and the negative electrode driven by the potential difference between the electrodes. In this process, lithium ions need to be first deintercalated from the positive electrode active material, then cross the barrier of the battery internal separator, and finally be intercalated into the negative electrode active material; the discharging process is carried out in reverse. The smoothness of this series of migration behavior directly determines the charging and discharging efficiency and overall performance of the battery. As the core medium for lithium ion transmission, the wettability of electrolyte in the electrode and separator system is crucial. On the one hand, the electrolyte needs to fully wet the active material pores of the positive electrode and the negative electrode to provide sufficient transmission channels for lithium ion deintercalation; on the other hand, the electrolyte needs to effectively penetrate the porous structure of the separator to ensure that lithium ions can efficiently cross the separator to complete migration. If the electrolyte reserve is insufficient or its wettability to the electrode / separator is poor, it will directly lead to two problems: one is to restrict the deintercalation rate of lithium ions from the positive electrode material, reducing the deintercalation efficiency of lithium ions; the other is to slow down the transmembrane transport kinetics of lithium ions, increasing the migration resistance of lithium ions. The above problems will eventually cause rapid capacity decay, charging and discharging efficiency decline, cycle life shortening of the battery, and even may induce safety hazards due to local ion concentration imbalance, becoming the key technical bottleneck restricting the performance improvement of lithium ion batteries.

[0004] In the above-mentioned performance optimization requirements of lithium ion batteries, the safety and heat resistance of the separator as a key component have become a prominent shortcoming. Currently, in order to improve the heat resistance and safety of traditional separators, the industry generally adopts a "two-step coating" process: in the first step, a conventional ceramic inorganic layer is coated on the surface of the base film by roll coating, and in the second step, an organic coating layer is covered by spraying; this traditional process has obvious technical defects: on the one hand, the interface compatibility of the organic coating layer and the inorganic ceramic layer is poor, and the synergistic enhancement effect of "1+1>2" cannot be achieved; on the other hand, the adhesion of the two coating layers is insufficient, which easily leads to the loss of adhesion to the electrode of the separator in subsequent processing or use. This not only causes the interruption of battery cell production process, directly affecting the stability of production capacity, but also may cause micro-short circuit risk due to interlayer peeling, thereby restricting the improvement of battery safety performance.

[0005] Therefore, it is necessary to develop a lithium battery separator with good heat resistance and high safety performance. SUMMARY

[0006] The present application provides a ceramic affinity type lithium battery separator organic coating slurry, its preparation method and application, which solves the problem of insufficient heat resistance and safety of lithium battery separator in related technology.

[0007] The technical scheme of the present application is as follows: the present application provides a ceramic affinity type lithium battery separator organic coating slurry, which comprises the following components by weight: deionized water 10-12 parts, ceramic microcapsule particles 1-3 parts, hydroxymethyl cellulose lithium 0.1-0.3 parts, and solid electrolyte 0.5-1 part; the core material of the ceramic microcapsule particles is ceramic particles, and the wall material is organic polymer; the preparation method of the ceramic microcapsule particles comprises the following steps: S1, uniformly disperse, stir, and pass nitrogen into deionized water, ceramic particles, and dispersant, then add lithium salt, coating agent, and pore former in sequence, and then add PVDF powder and PMMA powder, and mix to obtain a pre-agglomeration liquid; S2, the pre-agglomeration liquid is granulated by spray drying to obtain the ceramic microcapsule particles.

[0008] As a further technical solution, the mass ratio of the deionized water, the ceramic particles, the dispersant, the lithium salt, the coating agent, the pore former, the PVDF powder and the PMMA powder is 15:(1.2-1.8):(0.005-0.008):(0.1-0.3):(0.2-0.6):(0.2-0.6):(1.2-1.8):(0.6-0.9).

[0009] As a further technical solution, the ceramic particles are composed of small-diameter ceramic particles, medium-diameter ceramic particles and large-diameter ceramic particles in a mass ratio of 1:(0.1~0.3):(0.1~0.5).

[0010] As a further technical solution, the ceramic particles are porous alumina.

[0011] As a further technical solution, the small-diameter ceramic particles have a particle size of 0.1~0.2μm and a specific surface area of ​​15~18m². 2 / g, wherein the medium-sized ceramic particles have a particle size of 0.35~0.45μm and a specific surface area of ​​20~38m². 2 / g, wherein the large-diameter ceramic particles have a particle size of 1.15~1.95μm and a specific surface area of ​​50~68m². 2 / g.

[0012] In the organic coating slurry of the ceramic-affinity lithium-ion battery separator of this invention, spherical porous ceramic particles with a three-level particle size distribution (large, medium, and small) are used for gradient composite to construct a functional separator with a hierarchical pore structure. Large-diameter particles serve as a mechanical support framework, providing excellent dimensional stability; medium-diameter particles form a transition layer, enabling stepwise control of pore size; and small-diameter particles fill the gaps to form a dense surface layer. This multidimensional pore network significantly optimizes electrolyte wetting kinetics, increasing the electrolyte absorption rate and enhancing the electrolyte retention capacity, while simultaneously shortening the lithium-ion transport path and reducing electrode polarization.

[0013] As a further technical solution, the pore-forming agent is an inorganic pore-forming agent, and the inorganic pore-forming agent is ammonium bicarbonate.

[0014] In the organic coating slurry of the ceramic-affinity lithium battery separator of this invention, the pore-forming agent is the inorganic pore-forming agent ammonium bicarbonate, which can form pores inside the ceramic microcapsules. Its decomposition process is mild and stable, and the pore size is appropriate, which can avoid insufficient separator strength due to excessively large pores or obstructed ion transport due to excessively small pores. As a solid powder pore-forming agent, ammonium bicarbonate can mix more evenly with ceramic particles, PVDF and other components in the pre-agglomeration liquid, and will not exhibit local aggregation or stratification as in liquids. The pores formed after decomposition are more regularly distributed in space, reducing the situation of local non-pores or pore congestion, ensuring uniform porosity of the separator coating, and thus stabilizing lithium ion transport efficiency.

[0015] As a further technical solution, the dispersant includes one or both of polyvinylpyrrolidone and polyethylene glycol.

[0016] As a further technical solution, the coating agent includes one or both of polyether-type waterborne polyurethane and polyether nitrile-type cationic waterborne polyurethane.

[0017] As a further technical solution, when the coating agent is a polyether-type waterborne polyurethane, the number-average molecular weight of the polyether-type waterborne polyurethane is 8000~10000g / mol.

[0018] As a further technical solution, when the coating agent is a polyether nitrile-type cationic waterborne polyurethane, the polyether nitrile-type cationic waterborne polyurethane is prepared from hydroxyl-terminated polyether nitrile, toluene diisocyanate, 1,4-butanediol, and triethanolamine as main raw materials, and is a transparent viscous liquid with a density of 1.25 g / cm³. 3 (25℃).

[0019] As a further technical solution, the lithium salt includes one or more of lithium sulfate, lithium chloride, and dilithium oxalate, preferably lithium chloride.

[0020] As a further technical solution, the solid electrolyte includes one or more of NASICON-type solid electrolyte, perovskite-type solid electrolyte, and garnet-type oxide solid electrolyte, preferably NASICON-type solid electrolyte.

[0021] As a further technical solution, in step S1, the dispersion speed is 800~1000 r / min, the dispersion time is 5~10 min, the stirring speed is 50~60 r / min, the stirring time is 5~10 min, and the mixing time is 60~70 min.

[0022] As a further technical solution, in step S1, the step of sequentially adding lithium salt, coating agent and pore-forming agent, and then adding PVDF powder and PMMA powder includes: adding lithium salt, adjusting the rotation speed to 2000 r / min, mixing for 20 min, adding coating agent, mixing for another 20 min, adding pore-forming agent, mixing for another 20 min, and then adding PVDF powder and PMMA powder.

[0023] As a further technical solution, in step S2, the inlet air temperature of the spray drying is 80~85℃, the outlet air temperature of the spray drying is 45~50℃, the pressure of the spray drying is 1.0Mpa, and the spray drying time is 3~4h.

[0024] As a further technical solution, in step S2, the frequency of the atomizer in the spray dryer is 300Hz.

[0025] This invention also proposes a method for preparing a ceramic affinity lithium battery separator organic coating slurry, which includes the following steps: adding deionized water and ceramic microcapsule particles to a synthesis reactor, introducing nitrogen gas, dispersing and stirring, then sequentially adding lithium hydroxymethyl cellulose and solid electrolyte, and dispersing and stirring a second time to obtain the ceramic affinity lithium battery separator organic coating slurry.

[0026] As a further technical solution, the dispersion speed is 1600 r / min, the dispersion time is 30 min, the stirring speed is 50 r / min, and the stirring time is 30 min.

[0027] As a further technical solution, the sequential addition of lithium hydroxymethyl cellulose and solid electrolyte includes the following steps: adding lithium hydroxymethyl cellulose, dispersing at 1000 r / min for 30 min, stirring at 50 r / min for 30 min, and adding solid electrolyte.

[0028] As a further technical solution, the rotation speed of the secondary dispersion is 1000 r / min, the secondary dispersion time is 30 min, the rotation speed of the secondary stirring is 50 r / min, and the secondary stirring time is 30 min.

[0029] Application of the ceramic affinity lithium battery separator organic coating slurry prepared according to the method described above in lithium battery separators.

[0030] As a further technical solution, the preparation method of the lithium battery separator includes the following steps: coating the ceramic affinity lithium battery separator organic coating slurry onto one side of the base film, and drying it to obtain the lithium battery separator.

[0031] As a further technical solution, the base film is a polyolefin base film, which includes one or two of polyethylene film and polypropylene film, preferably polyethylene film.

[0032] As a further technical solution, the coating method includes one of dot coating and roller coating.

[0033] As a further technical solution, the drying temperature is 80°C and the drying time is 10 minutes.

[0034] The working principle and beneficial effects of this invention are as follows: In this invention, the organic coating slurry for a ceramic-affinity lithium-ion battery separator utilizes the intrinsic properties of porous ceramic materials combined with a three-dimensional interpenetrating network structure design to effectively suppress thermally induced deformation under high-temperature conditions. Compared to traditional single-particle-size ceramic coatings, this composite structure exhibits a lower separator thermal shrinkage rate. Through dispersion and spray drying granulation, organic matter is coated onto the surface of inorganic ceramic particles, forming ceramic-affinity spray particles with a microcapsule structure. This significantly improves the inorganic-organic interface affinity, enabling stable chemical bonding between the ceramic layer and the polymer matrix, thus endowing the separator with excellent cold-pressing adhesion strength and flexibility. Based on the high specific surface area of ​​porous materials, the coating surface density is effectively reduced while maintaining the same barrier performance. Compared to traditional solid ceramic particles, the reduced increase in coating mass for the same thickness results in a lower surface density for the separator of this invention, which is more conducive to the lightweighting of the separator. The addition of coating agents allows organic matter to better coat the surface of inorganic particles. Pore-forming agents, decomposed by heat during spraying, create pores on the surface of the spray-dried granulated particles, facilitating electrolyte wetting. Embedding lithium salts within the granulated particles allows the separator to replenish lithium sources and reduces lithium dendrites. The addition of solid electrolytes improves the uniformity of the slurry, resulting in higher ionic conductivity and better wettability of the separator. The synergistic effect of these components promotes cell rigidity, good compatibility, and strong cold-pressing adhesion in lithium battery separators; it also extends battery cycle life, reduces capacity decay, and improves the temperature resistance and safety performance of the lithium battery separator. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] In the following examples and comparative examples: PMMA powder: average particle size is 2.2 μm, number average molecular weight is 541207; PVDF powder: average particle size is 6.0 μm, number average molecular weight is 885231; Small-particle-size porous alumina: particle size of 0.1~0.2μm, specific surface area of ​​80~100m² 2 / g; Medium-sized porous alumina: particle size 0.35~0.45μm, specific surface area 22~38m² 2 / g; Large-particle-size porous alumina: particle size 1.15~1.95μm, specific surface area 10~15m² 2 / g; Polyether-based waterborne polyurethane: number average molecular weight is 10000 g / mol; Polyethylene glycol: Model number PEG-600.

[0037] Example 1 A method for preparing a ceramic-affinity lithium battery separator organic coating slurry includes the following steps: adding 10 parts of deionized water and 1 part of ceramic microcapsule particles to a synthesis reactor, purging with nitrogen to replace the air, dispersing at 1600 r / min for 30 min and stirring at 50 r / min for 30 min, adding 0.1 parts of lithium hydroxymethyl cellulose, dispersing at 1000 r / min for 30 min and stirring at 50 r / min for 30 min, adding 0.5 parts of solid electrolyte, dispersing at 1000 r / min for 30 min and stirring at 50 r / min for 30 min, and obtaining the ceramic-affinity lithium battery separator organic coating slurry; The preparation method of ceramic microcapsule particles includes the following steps: S1. Deionized water, ceramic particles, and polyethylene glycol are dispersed in a synthesis reactor. Nitrogen gas is introduced to replace the air. The mixture is dispersed at 1000 r / min for 10 min and stirred at 50 r / min for 10 min. Lithium chloride is added, and the mixture is dispersed at 2000 r / min for 20 min. Polyether-type waterborne polyurethane is added and mixed for another 20 min. Ammonium bicarbonate is added and mixed for another 20 min. PVDF powder and PMMA powder are then added and mixed for 60 min to obtain a pre-agglomerated liquid. The mass ratio of deionized water, ceramic particles, polyethylene glycol, lithium chloride, polyether-type waterborne polyurethane, ammonium bicarbonate, PVDF powder, and PMMA powder is 15:1.2:0.005:0.1:0.2:0.2:1.2:0.6. S2. The pre-agglomerated liquid is spray-dried and granulated. The inlet air temperature of the spray dryer is 80℃, the outlet air temperature is 45℃, the spray dryer pressure is 1.0 MPa, the spray dryer time is 3 hours, and the frequency of the atomizer used for spray drying is 300 Hz, to obtain ceramic microcapsule particles. The ceramic particles consist of small-diameter porous alumina, medium-diameter porous alumina, and large-diameter porous alumina in a mass ratio of 1:0.1:0.1.

[0038] Example 2 The preparation method of the ceramic affinity lithium battery separator organic coating slurry includes the following steps: adding 11 parts of deionized water and 2 parts of ceramic microcapsule particles to a synthesis reactor, purging with nitrogen to replace the air, dispersing at 1600 r / min for 30 min and stirring at 50 r / min for 30 min, adding 0.2 parts of lithium hydroxymethyl cellulose, dispersing at 1000 r / min for 30 min and stirring at 50 r / min for 30 min, adding 0.8 parts of solid electrolyte, dispersing at 1000 r / min for 30 min and stirring at 50 r / min for 30 min, and obtaining the ceramic affinity lithium battery separator organic coating slurry; The preparation method of ceramic microcapsule particles includes the following steps: S1. Deionized water, ceramic particles, and polyethylene glycol are dispersed in a synthesis reactor. Nitrogen gas is introduced to replace the air. The mixture is dispersed at 1000 r / min for 10 min and stirred at 50 r / min for 10 min. Lithium chloride is added, and the mixture is dispersed at 2000 r / min for 20 min. Polyether-type waterborne polyurethane is added and mixed for another 20 min. Ammonium bicarbonate is added and mixed for another 20 min. PVDF powder and PMMA powder are then added and mixed for 60 min to obtain a pre-agglomerated liquid. The mass ratio of deionized water, ceramic particles, polyethylene glycol, lithium chloride, polyether-type waterborne polyurethane, ammonium bicarbonate, PVDF powder, and PMMA powder is 15:1.5:0.006:0.2:0.4:0.4:1.5:0.8. S2. The pre-agglomerated liquid is spray-dried and granulated. The inlet air temperature of the spray dryer is 80℃, the outlet air temperature is 45℃, the spray dryer pressure is 1.0 MPa, the spray dryer time is 3 hours, and the frequency of the atomizer used for spray drying is 300 Hz, to obtain ceramic microcapsule particles. The ceramic particles consist of small-diameter porous alumina, medium-diameter porous alumina, and large-diameter porous alumina in a mass ratio of 1:0.2:0.3.

[0039] Example 3 A method for preparing a ceramic-compatible lithium-ion battery separator organic coating slurry includes the following steps: adding 12 parts of deionized water and 3 parts of ceramic microcapsule particles to a synthesis reactor, purging with nitrogen to replace the air, dispersing at 1600 r / min for 30 min, stirring at 50 r / min for 30 min, adding 0.3 parts of lithium hydroxymethyl cellulose, dispersing at 1000 r / min for 30 min, stirring at 50 r / min for 30 min, adding 1 part of solid electrolyte, dispersing at 1000 r / min for 30 min, stirring at 50 r / min for 30 min, and obtaining the ceramic-compatible lithium-ion battery separator organic coating slurry; The preparation method of ceramic microcapsule particles includes the following steps: S1. Deionized water, ceramic particles, and polyethylene glycol are dispersed in a synthesis reactor. Nitrogen gas is introduced to replace the air. The mixture is dispersed at 1000 r / min for 10 min and stirred at 50 r / min for 10 min. Lithium chloride is added, and the mixture is dispersed at 2000 r / min for 20 min. Polyether-type waterborne polyurethane is added and mixed for another 20 min. Ammonium bicarbonate is added and mixed for another 20 min. PVDF powder and PMMA powder are then added and mixed for 60 min to obtain a pre-agglomerated liquid. The mass ratio of deionized water, ceramic particles, polyethylene glycol, lithium chloride, polyether-type waterborne polyurethane, ammonium bicarbonate, PVDF powder, and PMMA powder is 15:1.8:0.008:0.3:0.6:0.6:1.8:0.9. S2. The pre-agglomerated liquid is spray-dried and granulated. The inlet air temperature of the spray dryer is 80℃, the outlet air temperature is 45℃, the spray dryer pressure is 1.0 MPa, the spray dryer time is 3 hours, and the frequency of the atomizer used for spray drying is 300 Hz, to obtain ceramic microcapsule particles. The ceramic particles consist of small-diameter porous alumina, medium-diameter porous alumina, and large-diameter porous alumina in a mass ratio of 1:0.3:0.5.

[0040] Example 4 Compared with Example 2, Example 4 differs in that medium-sized porous alumina (particle size of 0.35~0.45μm) is replaced with an equal amount of porous alumina with an average particle size of 0.5μm.

[0041] Example 5 Compared with Example 2, Example 5 differs in that the medium-sized porous alumina (particle size of 0.35~0.45μm) is replaced with an equal amount of porous alumina with an average particle size of 1μm.

[0042] Example 6 Compared with Example 2, Example 6 differs in that the medium-sized porous alumina (particle size of 0.35~0.45μm) is replaced with an equal amount of porous alumina with an average particle size of 3μm.

[0043] Example 7 The difference between Example 7 and Example 2 is that the ceramic particles are composed of small-particle-size porous alumina and large-particle-size porous alumina in a mass ratio of 1:0.3.

[0044] Example 8 The difference between Example 2 and Example 8 is that all ceramic particles are large-diameter porous alumina.

[0045] Example 9 The difference between Example 2 and Example 9 is that ammonium bicarbonate is replaced with an equal amount of ethanol.

[0046] Comparative Example 1 A method for preparing an organic coating slurry for a ceramic-compatible lithium-ion battery separator includes the following steps: adding 11 parts of deionized water and 17 parts of pre-agglomerated liquid to a synthesis reactor, purging with nitrogen to replace the air, dispersing at 1600 r / min for 30 min and stirring at 50 r / min for 30 min, adding 0.2 parts of lithium hydroxymethyl cellulose, dispersing at 1000 r / min for 30 min and stirring at 50 r / min for 30 min, adding 0.8 parts of solid electrolyte, dispersing at 1000 r / min for 30 min and stirring at 50 r / min for 30 min, and obtaining the organic coating slurry for a ceramic-compatible lithium-ion battery separator; The preparation method of ceramic microcapsule particles includes the following steps: S1. Deionized water, ceramic particles, and polyethylene glycol are dispersed in a synthesis reactor. Nitrogen gas is introduced to replace the air. The mixture is dispersed at 1000 r / min for 10 min and stirred at 50 r / min for 10 min. Lithium chloride is added, and the mixture is dispersed at 2000 r / min for 20 min. Polyether-type waterborne polyurethane is added and mixed for another 20 min. Ammonium bicarbonate is added and mixed for another 20 min. PVDF powder and PMMA powder are then added and mixed for 60 min to obtain a pre-agglomerated liquid. The mass ratio of deionized water, ceramic particles, polyethylene glycol, lithium chloride, polyether-type waterborne polyurethane, ammonium bicarbonate, PVDF powder, and PMMA powder is 15:1.5:0.006:0.2:0.4:0.4:1.5:0.8. The ceramic particles consist of small-diameter porous alumina, medium-diameter porous alumina, and large-diameter porous alumina in a mass ratio of 1:0.2:0.3.

[0047] Comparative Example 2 Compared with Example 2, Comparative Example 2 differs in that ammonium bicarbonate is not added in the preparation method of ceramic microcapsule particles in this comparative example.

[0048] The ceramic-affinity lithium-ion battery separator organic coating slurries prepared in Examples 1-9 and Comparative Examples 1-2 were pumped into a matrix dot-coating structure. The slurry was applied to one side of a polyethylene film using a dot-coating method. The base film thickness was 5.1 μm, and the air permeability was 109 sec / 100 ml. The film was then dried at 80°C for 10 min to obtain the lithium-ion battery separator. The resulting lithium-ion battery separator had a thickness increase of 1.2 μm and a coating amount of 1.3 g / m² per micrometer. 2 The lithium battery separators prepared in Examples 1-9 and Comparative Examples 1-2 were tested as follows.

[0049] The ceramic-affinity lithium-ion battery separator organic coating slurry prepared in Example 2 was applied using a textured roller coating method, resulting in a lithium-ion battery separator thickness increase of 1.2 μm and a coating amount of 1.3 g / m² per micrometer. 2 This is referred to as Example 10, and the following tests were performed; The thickness increment is calculated as follows: thickness of battery separator - thickness of base film. The coating amount per micrometer = (battery separator surface density - base film surface density) / coating thickness increment. The surface density of the polyethylene base film is 3.56 g / m². 2 .

[0050] 1. Liquid absorption rate and liquid retention rate: Cut a 50mm×50mm lithium battery separator sample, weigh the sample and record the mass as m1. Immerse the weighed separator in the electrolyte at 25℃ for 30 minutes, remove it and place it on industrial wiping paper (size > 150mm×150mm). Use another piece of industrial wiping paper to gently press and wipe the free electrolyte on the surface of the lithium battery separator sample. Weigh the dried separator sample and record the mass as m2. After 1 hour, weigh it again and record the mass as m3. Calculate the liquid absorption rate and liquid retention rate of the separator according to the following formulas: Liquid absorption rate (%) = (m2-m1) / m1×100%, Liquid retention rate (%) = (m3-m1) / m1×100%. 2. Wettability: The electrolyte used in the test is a mixture of electrolyte and solvent. The electrolyte is lithium hexafluorophosphate, and the solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (the volume ratio of EC to DEC is 1:1). The concentration of the electrolyte in the electrolyte is 1 mol / L. The wettability v is calculated by the formula: v = h / t, where h is the wetting height (the height of the electrolyte penetrating the membrane in the vertical direction) in mm, and t is the wetting time in min. 3. Cold-pressed electrode adhesion strength: The electrode is either a positive or negative electrode. The adhesion strength is determined when the electrode is a positive electrode and vice versa. Positive electrode adhesion strength is measured when the electrode is a negative electrode. Positive electrode adhesion strength: The diaphragm and positive electrode are cut to 25*150mm. The hot press temperature is set to 25℃ and the pressure to 1000KG. The diaphragm and positive electrode are preheated for 1 second and then cold-pressed for 1 second. The adhesion strength of the cold-pressed positive electrode is tested using an electronic tensile testing machine. The diaphragm and positive electrode are then peeled... The tensile distance from the electronic tensile testing machine is 50mm, the speed of the electronic tensile testing machine is 300mm / min, and the peel angle is 180°. The bonding strength of the positive electrode sheet is calculated as the peel force divided by the tensile distance of the electronic tensile testing machine. The peel force is the average force collected by the electronic tensile testing machine during the peeling process between the separator and the positive electrode sheet. The bonding strength of the cold-pressed positive electrode sheet is calculated based on data with a tensile distance between 10 and 40mm, i.e., the bonding strength of the positive electrode sheet = the peel force between 10 and 40mm divided by 30mm. The positive electrode sheet is a ternary lithium nickel cobalt aluminum oxide with the chemical formula LiNi. 0.8 Co 0.15 Al 0.05 The O2 electrode is a carbon-based graphite electrode (containing 91% carbon). 4. Heat shrinkage: The heat shrinkage performance of the lithium battery separator was tested according to the test method specified in GB / T 36363-2018, at 150℃ for 1 hour. 5. Ionic conductivity: The ionic conductivity of the lithium battery separator was tested according to the test method specified in GB / T 36363-2018. The test temperature was 40℃ and the relative humidity was 50%.

[0051] The test results are shown in Table 1: Table 1 Performance test results of Examples 1-10 and Comparative Examples 1-2

[0052] As shown in Table 1, comparing Example 2 with Examples 4-8, it can be seen that when the ceramic particles are composed of small-diameter ceramic particles, medium-diameter ceramic particles, and large-diameter ceramic particles, and when the average particle size of the small-diameter ceramic particles is 0.1-0.2 μm, the average particle size of the medium-diameter ceramic particles is 0.35-0.45 μm, and the average particle size of the large-diameter ceramic particles is 1.15-1.95 μm, the temperature resistance and safety performance of the lithium battery separator can be improved.

[0053] A comparison of Examples 2 and 9 shows that when the pore-forming agent is the inorganic pore-forming agent ammonium bicarbonate, the resulting lithium battery separator has better temperature resistance and safety performance.

[0054] The lithium battery separators prepared in Examples 3 and 8 were used to assemble batteries. The assembled batteries were subjected to 500 charge-discharge cycles to test the cell capacity retention rate. The cell capacity retention rate of Example 3 was 97.2%, and that of Example 8 was 91.9%.

[0055] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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 ceramic-compatible lithium battery separator organic coating slurry, characterized in that, The raw materials include the following components by weight: 10-12 parts deionized water, 1-3 parts ceramic microcapsule particles, 0.1-0.3 parts lithium hydroxymethyl cellulose, and 0.5-1 parts solid electrolyte; the core material of the ceramic microcapsule particles is ceramic particles, and the wall material is an organic polymer; the preparation method of the ceramic microcapsule particles includes the following steps: S1. Disperse and stir deionized water, ceramic particles and dispersant evenly, introduce nitrogen gas, add lithium salt, coating agent and pore-forming agent in sequence, then add PVDF powder and PMMA powder, and mix to obtain pre-agglomerate liquid. S2. The pre-agglomerated liquid is spray-dried and granulated to obtain the ceramic microcapsule particles.

2. The ceramic affinity lithium battery separator organic coating slurry according to claim 1, characterized in that, The mass ratio of the deionized water, the ceramic particles, the dispersant, the lithium salt, the coating agent, the pore-forming agent, the PVDF powder, and the PMMA powder is 15:(1.2~1.8):(0.005~0.008):(0.1~0.3):(0.2~0.6):(0.2~0.6):(1.2~1.8):(0.6~0.9).

3. The ceramic-affinity lithium battery separator organic coating slurry according to claim 1, characterized in that, The ceramic particles consist of small-diameter ceramic particles, medium-diameter ceramic particles, and large-diameter ceramic particles in a mass ratio of 1:(0.1~0.3):(0.1~0.5).

4. The ceramic affinity lithium battery separator organic coating slurry according to claim 3, characterized in that, The small-diameter ceramic particles have a particle size of 0.1~0.2μm, the medium-diameter ceramic particles have a particle size of 0.35~0.45μm, and the large-diameter ceramic particles have a particle size of 1.15~1.95μm.

5. The ceramic affinity lithium battery separator organic coating slurry according to claim 1, characterized in that, The pore-forming agent is an inorganic pore-forming agent, and the inorganic pore-forming agent is ammonium bicarbonate.

6. The ceramic affinity lithium battery separator organic coating slurry according to claim 1, characterized in that, The dispersant includes one or both of polyvinylpyrrolidone and polyethylene glycol; The coating agent includes one or both of polyether-type waterborne polyurethane and polyether nitrile-type cationic waterborne polyurethane. The lithium salt includes one or more of lithium sulfate, lithium chloride, and dilithium oxalate. The solid electrolyte includes one or more of the following: NASICON-type solid electrolyte, perovskite-type solid electrolyte, and garnet-type oxide solid electrolyte.

7. The ceramic affinity lithium battery separator organic coating slurry according to claim 1, characterized in that, In step S1, the dispersion speed is 800~1000 r / min, the dispersion time is 5~10 min, the stirring speed is 50~60 r / min, the stirring time is 5~10 min, and the mixing time is 60~70 min.

8. The ceramic affinity lithium battery separator organic coating slurry according to claim 1, characterized in that, In step S2, the inlet air temperature of the spray drying is 80~85℃, the outlet air temperature of the spray drying is 45~50℃, the pressure of the spray drying is 1.0 MPa, and the spray drying time is 3~4 hours.

9. A method for preparing a ceramic affinity lithium-ion battery separator organic coating slurry, used to prepare the ceramic affinity lithium-ion battery separator organic coating slurry according to any one of claims 1 to 8, characterized in that, Includes the following steps: Deionized water and ceramic microcapsule particles were added to the synthesis reactor, nitrogen gas was introduced, and after dispersion and stirring, lithium hydroxymethyl cellulose and solid electrolyte were added in sequence. After secondary dispersion and secondary stirring, the organic coating slurry of the ceramic affinity lithium battery separator was obtained.

10. The application of the ceramic affinity lithium battery separator organic coating slurry prepared by the preparation method of the ceramic affinity lithium battery separator organic coating slurry according to any one of claims 1 to 8 or claim 9 in lithium battery separators.

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