Solid-state electrolyte-modified material for a separator and method for preparing the same

Abstract

The application discloses a solid electrolyte modified material for a diaphragm and a preparation method thereof. 50 The first powder is between 100 nm and 10 microns; the first powder is subjected to high-temperature baking to obtain second powder with water content less than or equal to 200 ppm; in a low-moisture environment, the second powder, a high-molecular polymer, an additive, a non-aqueous solvent are placed in a dispersing machine for dispersing treatment, and a second dispersion liquid is obtained after uniform dispersion; the second dispersion liquid is subjected to low-temperature vacuum drying treatment, and then is placed in a crushing device for crushing treatment to obtain the solid electrolyte modified material with water content less than or equal to 200 ppm.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery materials, in particular to a solid electrolyte modified material for coating a separator and a preparation method thereof. BACKGROUND

[0002] The existing oil-based coating technology does not take into account the characteristics that the solid electrolyte is more prone to water absorption than the traditional ceramic material, and the initial powder is not subjected to water removal treatment after nanocrystallization. In addition, the traditional oil-based coating slurry has the characteristics of not easy to store (the slurry will have obvious sedimentation) and preserve (short shelf life, already deteriorated), and generally needs to be made and coated immediately. The preparation of the slurry takes a long time and the addition of each party is inconsistent, which to some extent limits the popularization and application of solid electrolyte materials.

[0003] Although the existing water-based coating slurry needs to be prepared under water conditions later, it does not take into account that a part of the electrolyte material has a higher binding water binding energy during nanocrystallization, and the water content of the separator coated with the untreated water-based solid electrolyte slurry will be high, which will affect the performance of the battery.

[0004] For example, Chinese patent CN109148794A (published on January 4, 2019) discloses a separator oil-based ceramic slurry, a preparation method thereof and a separator. The separator oil-based ceramic slurry is beneficial to reduce the water content of the separator and improve the cycle performance of the lithium ion battery, but this patent only uses an oil-based solvent to replace a water-based solvent to achieve the purpose of reducing the water content, and mixes polyvinylidene fluoride to improve the adhesion, without controlling the combined water of the ceramic powder itself, and the performance improvement of the lithium ion battery is limited. SUMMARY

[0005] The present application aims to provide a solid electrolyte modified material for coating a separator and a preparation method thereof. The solid electrolyte modified material provided by the present application has more uniform particle size and more complete removal of combined water compared to the solid electrolyte material obtained by conventional preparation methods. This is because the semi-finished powder material is obtained by first spray drying and then high-temperature baking the solid electrolyte material after sanding, which reduces the water content of the solid electrolyte material. The spray drying is for granulation and preliminary drying, and the high-temperature baking is for reducing the combined water in the material. Then, the oil-based coating slurry is prepared using the semi-finished powder material, and the oil-based coating slurry is subjected to low-temperature vacuum drying to completely remove the combined water in the material. After crushing, a self-adhesive solid electrolyte modified material with a water content of less than or equal to 200 ppm is obtained.

[0006] The solid-state electrolyte modification material can be mixed with an oil-based solvent according to requirements, and the solid-state electrolyte modification material can be used to prepare an oil-based coating separator, so that the problem of long preparation time of an oil-based coating slurry and inconsistent addition ratio of each household in the prior art is avoided, and the prepared slurry is not easy to settle and is not easy to store, so that the popularization and application of the solid-state electrolyte material are limited to a certain extent.

[0007] The solid-state electrolyte modification material is used to prepare a separator and assemble a lithium ion battery, so that the stability of the lithium ion battery can be effectively improved.

[0008] Therefore, in a first aspect, a preparation method of a solid-state electrolyte modification material for a separator is provided, and the preparation method comprises the following steps:

[0009] In step S1, a solvent, a dispersing agent and a solid-state electrolyte material are added to a sand mill, and a first dispersion liquid is obtained after sand milling.

[0010] In step S2, the first dispersion liquid is granulated by spray drying to obtain a second powder with a particle size D 50 The first powder has a particle size of 100 nm-10 μm.

[0011] In step S3, the first powder is high-temperature baked to obtain a second powder with a water content of less than or equal to 200 ppm.

[0012] In step S4, the second powder, a high-molecular polymer and an additive are placed in a dispersing machine in a low-water environment, and a non-aqueous solvent is added for dispersion treatment, and a second dispersion liquid is obtained after uniform dispersion.

[0013] In step S5, the second dispersion liquid is subjected to low-temperature vacuum drying treatment, and then is subjected to crushing treatment in a crushing device to obtain a solid-state electrolyte modification material with a water content of less than or equal to 200 ppm.

[0014] The particle size D 50 of the solid-state electrolyte modification material is 100 nm-5 μm.

[0015] Preferably, the solvent comprises one or more of deionized water, alcohol, N-methyl pyrrolidone, dimethylformamide and isopropyl alcohol.

[0016] The dispersing agent comprises one or more of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium dodecyl phosphate, sodium hexametaphosphate, polyethylene glycol, polyvinyl pyrrolidone, polyacrylate, polymethacrylate and maleic anhydride-styrene copolymer.

[0017] The solid-state electrolyte material comprises one or more of lithium oxide, lithium sulfide, lithium hydride, and lithium halide; the original particle size D 50 Between 1 μm and 20 μm;

[0018] The mass ratio of the solid-state electrolyte material to the dispersant is [95-99.99]: [0.01-5];

[0019] The solid content of the first dispersion is between 1% and 60%.

[0020] Preferably, the lithium oxide comprises garnet-type solid-state electrolyte, perovskite-type solid-state electrolyte, NASICON-type solid-state electrolyte, LISICON-type solid-state electrolyte.

[0021] Preferably, the rotation speed of the sand mill main machine is 400 rpm-3000 rpm; the particle size D 50 Between 50 nm and 5 μm;

[0022] The inlet temperature of the spray drying is between 160°C and 230°C, the outlet temperature is between 50°C and 150°C, and the rotation speed of the spray centrifugal disc is 10000 rpm-30000 rpm.

[0023] Preferably, the temperature of the high-temperature baking is between 250°C and 500°C, and the baking time is 4 hours-24 hours.

[0024] Preferably, the high molecular polymer comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate;

[0025] The auxiliary agent comprises one or more of polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, polydimethylsiloxane, polyoxyethylene ether;

[0026] The mass ratio of the second powder to the high molecular polymer is [80-99]: [1-20];

[0027] The mass ratio of the second powder to the auxiliary agent is [70-99]: [1-30];

[0028] The non-aqueous solvent comprises one or more of alcohol, N-methylpyrrolidone, tetrahydrofuran, dimethylacetamide, isopropyl alcohol, ethyl acetate, or acetone;

[0029] The solid content in the second dispersion is between 1% and 60%;

[0030] The dew point of the low-moisture environment is between -10°C and -60°C;

[0031] The rotation speed of the disperser is between 1000 rpm and 3000 rpm, and the dispersion treatment time is between 30 minutes and 5 hours.

[0032] Preferably, the drying temperature of the low-temperature vacuum drying treatment is between 50°C and 120°C, the drying time is between 5 hours and 24 hours, and the vacuum degree is less than or equal to 150 Pa.

[0033] The pulverizing device is an air flow pulverizer, the frequency of the air flow pulverizer is between 50 Hz and 100 Hz, and the pulverizing time is between 1 hour and 2 hours.

[0034] In a second aspect, an embodiment of the present application provides a solid-state electrolyte modified material prepared by the preparation method of the first aspect, and the solid-state electrolyte modified material comprises 80wt%-97wt% of a solid-state electrolyte material, 1wt%-5wt% of a dispersant, 1wt%-20wt% of a high molecular polymer, and 1wt%-30wt% of an auxiliary agent.

[0035] The solid-state electrolyte material comprises one or more of an oxide of lithium, a sulfide of lithium, a hydride of lithium, and a halide of lithium; wherein the oxide of lithium comprises a garnet-type solid-state electrolyte, a perovskite-type solid-state electrolyte, a NASICON-type solid-state electrolyte, and a LISICON-type solid-state electrolyte.

[0036] The high molecular polymer comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polymethyl methacrylate.

[0037] The auxiliary agent comprises one or more of polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, polydimethylsiloxane, and polyoxyethylene ether.

[0038] The particle size D 50 of the solid-state electrolyte modified material is between 100 nm and 5 μm, and the moisture content of the solid-state electrolyte modified material is less than or equal to 200 ppm.

[0039] In a third aspect, an embodiment of the present application provides a separator, which comprises the solid-state electrolyte modified material of the second aspect.

[0040] In a fourth aspect, an embodiment of the present application provides a lithium ion battery, which comprises the separator of the third aspect.

[0041] The embodiment of the present application provides a preparation method of a solid electrolyte modified material for a diaphragm, first, the solid electrolyte material is ground to a specified particle size through a wet sanding method, granulation is performed through spray drying at a certain temperature, all bound water in the material is removed through high-temperature baking, and then the solid electrolyte material with removed bound water and a high-molecular polymer are uniformly dispersed in a non-aqueous solvent at a certain proportion in a low-moisture environment, and then the solid electrolyte modified material with a content of less than or equal to 200 ppm is obtained through low-temperature vacuum drying treatment and crushing treatment; the preparation method provided by the embodiment of the present application is simple to operate, can be applied to large-scale production, and has practical significance for industrial application.

[0042] Compared with the solid electrolyte material obtained through a conventional preparation method, the solid electrolyte modified material provided by the present application has more uniform particle size and more thorough removal of bound water, because the semi-finished powder material is obtained through the treatment of first spray drying and then high-temperature baking on the solid electrolyte material after sanding, so as to reduce the moisture content of the solid electrolyte material, the spray drying is for granulation and preliminary drying, the high-temperature baking is for reducing the bound water in the solid electrolyte material, and then the semi-finished powder material is used to prepare an oil-based coating slurry, the oil-based coating slurry is subjected to low-temperature vacuum drying to completely remove the bound water in the material, and the self-adhesive solid electrolyte modified material with a moisture content of less than or equal to 200 ppm is obtained after crushing.

[0043] The solid electrolyte modified material can be directly mixed with an oil-based solvent to obtain a slurry for the preparation of an oil-based coated diaphragm according to the fixed ratio, so that the problems, such as long preparation time of the oil-based coating slurry in the existing oil-based coating technology, inconsistent addition ratio of each party, and slurry prepared is prone to sedimentation and difficult to preserve, which to some extent limit the popularization and application of the solid electrolyte material, are avoided.

[0044] The solid electrolyte modified material is used to prepare a diaphragm and assemble a lithium ion battery, so that the stability of the lithium ion battery can be effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0045] The technical solutions of the embodiments of the present application are further described in detail below through the drawings and examples.

[0046] Figure 1 The figure is a flow chart of the preparation method of the solid electrolyte modified material provided by the embodiment of the present application. DETAILED DESCRIPTION

[0047] The present application is further described in detail below through the drawings and specific examples, but it should be understood that these examples are only used for more detailed description, and should not be understood as limiting the present application in any form, that is, the protection scope of the present application is not intended to be limited.

[0048] The embodiment of the present application provides a preparation method of a solid electrolyte modified material for a diaphragm, as shown in the following formula I: Figure 1 The preparation method comprises the following steps:

[0049] In step S1, a solvent, a dispersant and a solid electrolyte material are added into a sand mill, and a first dispersion liquid is obtained after sand milling;

[0050] The solvent comprises one or more of deionized water, alcohol, N-methyl pyrrolidone, dimethylformamide and isopropyl alcohol.

[0051] The dispersant comprises one or more of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium dodecyl phosphate, sodium hexametaphosphate, polyethylene glycol, polyvinyl pyrrolidone, polyacrylate, polymethacrylate and maleic anhydride-styrene copolymer.

[0052] The solid electrolyte material comprises one or more of lithium oxide, lithium sulfide, lithium hydride and lithium halide; the original particle size D 50 of the solid electrolyte material is between 1 μm and 20 μm; the lithium oxide comprises a garnet-type solid electrolyte, a perovskite-type solid electrolyte, a NASICON-type solid electrolyte and a LISICON-type solid electrolyte.

[0053] The mass ratio of the solid electrolyte material to the dispersant is [95-99.99]:[0.01-5].

[0054] The solid content of the first dispersion liquid is between 1% and 60%.

[0055] The main machine rotation speed of sand milling is between 400 rpm and 3000 rpm; and the particle size D 50 of the solid electrolyte material in the first dispersion liquid after sand milling is between 50 nm and 5 μm.

[0056] In step S2, the first dispersion liquid is granulated by spray drying to obtain a first powder with a particle size D 50 between 100 nm and 10 μm.

[0057] The inlet temperature of spray drying is between 160°C and 230°C, the outlet temperature is between 50°C and 150°C, and the spray centrifugal disc rotation speed is between 10000 rpm and 30000 rpm.

[0058] In step S3, the first powder is high-temperature baked to obtain a second powder with a moisture content less than or equal to 200 ppm.

[0059] The high-temperature baking temperature is between 250°C and 500°C, and the baking time is between 4 hours and 24 hours.

[0060] The moisture content of the second powder obtained in this step is less than or equal to 200 ppm. When the second powder obtained in this step is used to prepare a slurry for water-based coating of a separator, the moisture content of the water-based coating separator can be effectively reduced, and the performance of the second powder is verified to be superior to that of ordinary solid electrolyte materials. Preparing the second powder with a moisture content of less than or equal to 200 ppm is beneficial to the preparation of a solid electrolyte modified material with low moisture content in the subsequent step.

[0061] In step S4, the second powder, the high molecular polymer, and the additive are placed in a dispersing machine, and a non-aqueous solvent is added for dispersion treatment, and a second dispersion liquid is obtained after uniform dispersion.

[0062] The high molecular polymer includes one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polymethyl methacrylate (PMMA).

[0063] The additive includes one or more of polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, polydimethylsiloxane, and polyoxyethylene ether.

[0064] The mass ratio of the second powder to the high molecular polymer is [80-99]:[1-20].

[0065] The mass ratio of the second powder to the additive is [70-99]:[1-30].

[0066] The non-aqueous solvent includes one or more of alcohol, N-methyl pyrrolidone, tetrahydrofuran, dimethylacetamide, isopropyl alcohol, ethyl acetate, or acetone.

[0067] The solid content in the second dispersion liquid is between 1% and 60%.

[0068] The dew point of the low-moisture environment is between -10°C and -60°C.

[0069] The rotational speed of the dispersing machine is between 1000 rpm and 3000 rpm, and the dispersion treatment time is between 30 minutes and 5 hours.

[0070] In step S5, the second dispersion liquid is subjected to low-temperature vacuum drying treatment, and then is placed in a crushing device for crushing treatment to obtain a solid electrolyte modified material with a moisture content of less than or equal to 200 ppm.

[0071] The drying temperature of the low-temperature vacuum drying treatment is between 50°C and 120°C, the drying time is between 5 hours and 24 hours, and the vacuum degree is less than or equal to 150 Pa.

[0072] The pulverizing device is an air flow pulverizer, the frequency of the air flow pulverizer is 50Hz-100Hz, and the pulverizing time is 1 hour-2 hours.

[0073] The particle size D of the prepared solid electrolyte modified material 50 Between 100nm-5um, preferably 300nm-800nm.

[0074] In the preparation of the separator coating slurry, the sanding nanometerization process of the preparation method of the application is used, and in the sanding process, the solid electrolyte material forms a high-energy hydrate with water, and if the high-energy hydrate is directly prepared into a coating slurry with a conductive agent, a binder and an additive and coated to prepare a separator, the moisture content of the separator will be high, and even if the separator is baked, the bound water in the solid electrolyte material cannot be removed, thereby affecting the stability of the lithium ion battery.

[0075] The solid electrolyte modified material prepared by the preparation method of the embodiment of the application includes 80wt%-97wt% of a solid electrolyte material, 1wt%-5wt% of a dispersant, 1wt%-20wt% of a high molecular polymer and 1wt%-30wt% of an additive.

[0076] The solid electrolyte material includes one or more of lithium oxide, lithium sulfide, lithium hydride and lithium halide; the lithium oxide includes garnet-type solid electrolyte, perovskite-type solid electrolyte, NASICON-type solid electrolyte and LISICON-type solid electrolyte.

[0077] The high molecular polymer includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and polymethyl methacrylate.

[0078] The additive includes one or more of polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, polydimethylsiloxane and polyoxyethylene ether.

[0079] The particle size D of the solid electrolyte modified material 50 Between 100nm-5um, preferably 300nm-800nm; the moisture content of the solid electrolyte modified material is less than or equal to 200ppm.

[0080] The solid electrolyte modifying material can be directly mixed with an oily solvent or an aqueous solvent to prepare a slurry for coating a separator. Since the solid electrolyte material in the solid electrolyte modifying material does not form hydrates with water and the water content of the solid electrolyte modifying material itself is low during the preparation of the slurry, the water content of the prepared separator is low. Assembling the separator containing the solid electrolyte modifying material of the present application into a lithium ion battery can improve the stability of the lithium ion battery.

[0081] In order to better understand the technical solutions provided by the present application, the preparation process and properties of the solid electrolyte modifying material of the present application are described in the following specific examples.

[0082] Example 1

[0083] This example provides a preparation process and performance test of a solid electrolyte modifying material, and the specific process is as follows:

[0084] (1) Add 2 kg of deionized water, 5 g of dispersant polymethacrylate and 0.5 kg of solid electrolyte material Li 1.3 Al 0.3 Ti 1.7 (PO4) with a particle size of 4 μm into a sand mill, and set the rotation speed of the sand mill to 2200 rpm. After sand milling for 2 hours, a first dispersion liquid is obtained, and the average particle size of the solid material in the first dispersion liquid is 400 nm.

[0085] (2) The first dispersion liquid is granulated by spray drying, and the parameters of the spray dryer are set as follows: the inlet temperature is 180℃, the outlet temperature is between 130℃, and the rotation speed of the spray centrifugal disc is 15000 rmp. After spray drying, a first powder with a particle size D 50 of 450 nm is obtained.

[0086] (3) The first powder is high-temperature baked in an oven at 380℃ for 8 hours to obtain a second powder with a water content of 90 ppm.

[0087] (4) In a dew point-40 environment, 0.5 kg of the second powder, 80 g of PVDF-HFP and 5 g of polyvinylpyrrolidone are placed in a disperser, and 2 kg of N-methylpyrrolidone (NMP) is added for dispersion treatment at a rotation speed of 2000 r / min for 4 hours. After uniform dispersion, a second dispersion liquid is obtained.

[0088] (5) The second dispersion liquid is subjected to low-temperature vacuum drying treatment, the temperature of the low-temperature vacuum drying treatment is set to 80°C, the drying time is 10 hours, the vacuum degree is 130 Pa, after drying, the solid electrolyte modified material with a moisture content of 110 ppm is obtained by crushing in a crushing device, the frequency of the crushing machine is 80 Hz, and the particle size D 50 500 nm.

[0089] The second powder of step (3) prepared from the intermediate product of the present example is used to prepare a water-based coating separator, specifically: 0.5 kg of the second powder obtained in step (3), 2 kg of deionized water, 3 g of sodium carboxymethyl cellulose (CMC), 60 g of styrene-butadiene rubber (SBR), 3 g of polyethylene glycol, and 10 g of polyether-modified siloxane are dispersed in a dispersing machine for 4 hours at a speed of 2000 rpm, and the obtained water-based coating slurry is coated on a 9 μm polyethylene (PE) film at a coating thickness of 2 μm, and the coating drying temperature is 65°C, to obtain a water-based coating separator. The moisture content of the water-based coating separator prepared in the present example is tested at 150°C, 180°C, and 200°C, respectively, and the test environment dew point is -40°C. The test data are shown in Table 1.

[0090] The solid electrolyte modified material prepared in the present example is used to prepare an oil-based coating separator, specifically: 0.5 kg of the crushed solid electrolyte modified material and 2 kg of NMP are dispersed in a dispersing machine for 0.5 hours to obtain an oil-based coating slurry, which is coated on a 9 μm PE base film at a coating thickness of 1 μm, and the coating drying temperature is 80°C, to obtain an oil-based coating separator. The moisture content of the oil-based coating separator prepared in the present example is tested at 150°C, 180°C, and 200°C, respectively, and the test environment dew point is -40°C. The moisture content and film surface flatness test data are shown in Table 2.

[0091] The oil-based coating separator prepared in the present example is used to prepare a lithium ion battery, and the specific process is as follows:

[0092] Preparation of positive electrode sheet: after the active material lithium cobaltate, conductive carbon black, binder polyvinylidene fluoride, and solvent NMP are uniformly mixed and stirred in a mass ratio of 64:3:3:30, they are coated on an aluminum foil, and then dried, cold-pressed, and slitted to obtain a positive electrode sheet;

[0093] Preparation of negative electrode sheet: after the active material graphite, binder styrene-butadiene rubber, thickening agent sodium carboxymethyl cellulose, and deionized water are uniformly mixed and stirred in a mass ratio of 62:2:1:35, they are coated on a copper foil, and then dried, cold-pressed, and slitted to obtain a negative electrode sheet;

[0094] The positive electrode sheet, the oil-based coated separator prepared in the embodiment (wherein the side containing the solid electrolyte modifying material faces the negative electrode), and the negative electrode sheet are sequentially stacked and wound to obtain a bare battery cell. The bare battery cell is placed in a shell, an electrolyte is injected, and the shell is sealed to obtain a lithium ion battery. The electrolyte is a 1 mol / L LiPF6 solution of ethylene carbonate EC / dimethyl carbonate DEC (volume ratio of EC to DEC is 1:1).

[0095] The test cycle process is as follows: at 25°C, constant current charging to 4.4V at 1C, then constant voltage charging to 0.05C at 4.4V, then discharging to 2.0V at 1C, and then repeating the above process. The first week coulombic efficiency and the cycle capacity retention rate after 500 cycles are tested. The test data are shown in Table 3.

[0096] Example 2

[0097] The embodiment provides a preparation process and performance test of a solid electrolyte modifying material. The specific process is as follows:

[0098] (1) 2 kg of alcohol, 3 g of dispersant polyvinylpyrrolidone, and 0.5 kg of solid electrolyte material Li 0.33 La 0.57 TiO3 with a particle size of 5 μm are added to a sand mill. The rotation speed of the sand mill is set to 2000 rpm. After sand milling for 3 hours, a first dispersion liquid is obtained. The average particle size of the solid material in the first dispersion liquid is 350 nm.

[0099] (2) The first dispersion liquid is granulated by spray drying. The parameters of the spray dryer are set as follows: the inlet temperature is 150°C, the outlet temperature is between 125°C, and the rotation speed of the spray centrifugal disc is 16000 rpm. After spray drying, a first powder with a particle size D 50 of 400 nm is obtained.

[0100] (3) The first powder is subjected to high-temperature baking in an oven at 350°C for 10 hours to obtain a second powder with a moisture content of 100 ppm.

[0101] (4) 0.5 kg of the second powder, 80 g of PVDF-HFP, and 5 g of polyvinyl alcohol are placed in a disperser together under a dew point of -40. 2 kg of dimethylacetamide is added for dispersion treatment at a rotation speed of 2200 rpm for 4 hours. After uniform dispersion, a second dispersion liquid is obtained.

[0102] (5) The second dispersion liquid is subjected to low-temperature vacuum drying treatment, the temperature of the low-temperature vacuum drying treatment is set to 85°C, the drying time is 8 hours, the vacuum degree is 135 Pa, after drying, the solid electrolyte modified material with a water content of 100 ppm is obtained by crushing in a crushing device, the frequency of the crushing machine is 75 Hz, and the particle size D 50 is 500 nm.

[0103] The water-based coated separator prepared from the second powder of step (3) of the intermediate product prepared in this example is tested for moisture content at 150°C, 180°C and 200°C respectively, the test environment dew point is -40°C, and the test data are shown in Table 1.

[0104] The oil-based coated separator prepared from the solid electrolyte modified material prepared in this example is tested for moisture content at 150°C, 180°C and 200°C respectively, the test environment dew point is -40°C, and the test data of moisture content and film surface flatness are shown in Table 2.

[0105] The lithium ion battery is prepared using the oil-based coated separator prepared in this example, and the test is performed, the specific process is the same as that of Example 1, and the test data are shown in Table 3.

[0106] To better illustrate the effect of the embodiment of the present application, the water-based coated separators prepared in Comparative Examples 1-2 and Example 1-2 are compared, and the oil-based coated separators prepared in Comparative Examples 3-6 and Example 1-2 are compared.

[0107] Comparative Example 1

[0108] The water-based coated separator is prepared directly using the first dispersion liquid with a solid material average particle size of 400 nm prepared in step (1) of Example 1, and the specific preparation process is as follows: 2.5 kg of the first dispersion liquid, 3 g of CMC, 60 g of SBR, 3 g of polyethylene glycol, and 10 g of polyether modified siloxane are placed in a dispersing machine and dispersed for 4 hours, the dispersing machine speed is 2000 rpm, the obtained water-based coating slurry is coated on a PE base film at 9 μm, the coating thickness is 2 μm, the coating drying temperature is 65°C, and the water-based coated separator is obtained.

[0109] The moisture content of the water-based coated separator prepared in this comparative example is tested at 150°C, 180°C and 200°C respectively, the test environment dew point is -40°C, and the test data are shown in Table 1.

[0110] The lithium ion battery is assembled using the oil-based coated separator prepared in this comparative example, the specific assembly process and test process are the same as those of Example 1, and the test data are shown in Table 3.

[0111] Comparative Example 2

[0112] The water-based coated separator was prepared by directly using the first dispersion liquid with an average particle size of 350 nm of the solid material prepared in step (1) of Example 2, and the preparation process was as follows: 2.5 kg of the first dispersion liquid, 3 g of CMC, 60 g of SBR, 3 g of polyethylene glycol, and 10 g of polyether-modified siloxane were placed in a dispersing machine and dispersed for 4 hours at a speed of 2000 rpm, and the obtained water-based coating slurry was coated on a PE base film at 9 μm, the coating thickness was 2 μm, the coating and drying temperature was 65℃, and the water-based coated separator was obtained.

[0113] The moisture content of the water-based coated separator prepared in the comparative example was tested at 150℃, 180℃, and 200℃, respectively, and the test environment was at a dew point of -40℃, and the test data are shown in Table 1.

[0114] The oil-based coated separator prepared in the comparative example was assembled into a lithium ion battery, and the assembly process and test process were the same as those of Example 1, and the test data are shown in Table 3.

[0115] Comparative Example 3

[0116] The comparative example provides a solid-state electrolyte dispersion liquid, and an oil-based coated separator is prepared, and the difference from Example 1 is that the preparation process of the solid-state electrolyte dispersion liquid of the present application does not go through the steps (2) of spray granulation at a certain temperature, step (3) of high-temperature baking, and step (4) of low-temperature vacuum drying treatment in Example 1, and the specific preparation process of the solid-state electrolyte dispersion liquid is as follows:

[0117] The solid-state electrolyte material Li 1.3 Al 0.3 Ti 1.7 (PO4) with a particle size of 4 μm was baked in an oven at 150℃ for 8 hours to obtain a powder with a moisture content of 350 ppm; the powder was added to a sand mill together with 5 g of polyvinylpyrrolidone and 2 kg of N-methylpyrrolidone, and the speed of the sand mill was set to 2200 rpm, and the sand milling treatment was performed for 2 hours to obtain a first dispersion liquid, and the average particle size of the solid material in the first dispersion liquid was 450 nm; the first dispersion liquid was added to a dispersing machine together with 80 g of PVDF-HFP at a speed of 2000 rpm at a dry room environment of -40℃, and dispersed for 2 hours to obtain a solid-state electrolyte dispersion liquid.

[0118] The oil-based coated separator prepared by the present comparative example was used to prepare a lithium ion battery, and the specific assembly process and test process were the same as those of Example 1. The test data are shown in Table 3.

[0119] The oil-based coated separator prepared by the present comparative example was used to prepare a lithium ion battery, and the specific assembly process and test process were the same as those of Example 1. The test data are shown in Table 3.

[0120] Comparative Example 4

[0121] The present comparative example provides a solid-state electrolyte dispersion liquid, and an oil-based coated separator is prepared. The difference between the present example and Example 1 is that the preparation process of the solid-state electrolyte dispersion liquid of the present example does not go through the steps of spraying granulation at a certain temperature, high-temperature baking and low-temperature vacuum drying treatment in Example 1. The specific preparation process of the solid-state electrolyte dispersion liquid is as follows:

[0122] The solid-state electrolyte material Li 1.3 Al 0.3 Ti 1.7 (PO4) with a particle size of 4 μm was baked in an oven at 150°C for 8 hours to obtain a powder with a moisture content of 350 ppm; the powder was added to a sand mill together with 5 g of polyvinylpyrrolidone and 2 kg of N-methylpyrrolidone, and the sand mill was set to a speed of 2200 rpm. The sand milling treatment was carried out for 2 hours to obtain a first dispersion liquid, and the average particle size of the solid material in the first dispersion liquid was 450 nm; the first dispersion liquid was added to a dispersing machine together with 80 g of PVDF-HFP at -40°C in a dry room environment, and the dispersing machine was operated at a speed of 2000 rpm for 4 hours to obtain a solid-state electrolyte dispersion liquid.

[0123] The oil-based coated separator prepared by the present comparative example was used to prepare a lithium ion battery, and the specific assembly process and test process were the same as those of Example 1. The test data are shown in Table 3.

[0124] The oil-based coated separator prepared by the present comparative example was used to prepare a lithium ion battery, and the specific assembly process and test process were the same as those of Example 1. The test data are shown in Table 3.

[0125] Comparative Example 5

[0126] The comparative example provides a solid-state electrolyte dispersion liquid, and an oil-based coated separator is prepared. Different from example 2, the preparation process of the solid-state electrolyte dispersion liquid of the present application does not go through the steps (2) spray granulation at a certain temperature, step (3) high-temperature baking and step (4) low-temperature vacuum drying treatment of example 2. The specific solid-state electrolyte dispersion liquid preparation process is as follows:

[0127] In the environment of dew point-40℃, the solid-state electrolyte material Li 0.33 La 0.57 TiO3 with a particle size of 5μm is baked in an oven at 150℃ for 8 hours to obtain a powder with a moisture content of 330ppm; the powder is added to a sand mill together with 5g of polyvinyl alcohol and 2kg of N-methyl pyrrolidone, and the rotation speed of the sand mill is set to 2000rpm. The sand milling treatment is carried out for 3 hours to obtain a first dispersion liquid. The average particle size of the solid material in the first dispersion liquid is 350nm. The first dispersion liquid is added to a dispersing machine together with 80g of PVDF-HFP at-40℃ in a dry room environment, and the rotation speed is set to 2200rpm. The dispersion is carried out for 2 hours to obtain a solid-state electrolyte dispersion liquid.

[0128] The solid-state electrolyte dispersion liquid prepared by the comparative example is used to prepare an oil-based coated separator. Specifically, 2.5kg of the solid-state electrolyte dispersion liquid is coated on a 9μm PE-based film with a coating thickness of 1μm. The coating and drying temperature is 80℃, and an oil-based coated separator is obtained. The moisture content of the oil-based coated separator prepared by the comparative example is tested at 150℃, 180℃ and 200℃, respectively. The dew point of the test environment is-40℃. The moisture content and film surface flatness test data are shown in Table 2.

[0129] The oil-based coated separator prepared by the comparative example is used to assemble a lithium ion battery. The specific assembly process and test process are the same as those of example 1. The test data are shown in Table 3.

[0130] Comparative example 6

[0131] The comparative example provides a solid-state electrolyte dispersion liquid, and an oil-based coated separator is prepared. Different from example 2, the preparation process of the solid-state electrolyte dispersion liquid of the present application does not go through the steps (2) spray granulation at a certain temperature, step (3) high-temperature baking and step (4) low-temperature vacuum drying treatment of example 2. The specific solid-state electrolyte dispersion liquid preparation process is as follows:

[0132] In the environment of dew point-40℃, the solid-state electrolyte material Li 0.33 La 0.57The TiO3 was baked in an oven at 150°C for 8 hours to obtain a powder with a moisture content of 330 ppm; the powder was added to a sand mill together with 5 g of polyvinyl alcohol and 2 kg of N-methylpyrrolidone, the rotation speed of the sand mill was set to 2000 rpm, and the sand milling treatment was performed for 3 hours to obtain a first dispersion liquid, the average particle size of the solid material in the first dispersion liquid was 350 nm; the first dispersion liquid was added to a disperser together with 80 g of PVDF-HFP in a dry room environment at -40°C, and the dispersion was performed at a rotation speed of 2200 rpm for 4 hours to obtain a solid-state electrolyte dispersion liquid.

[0133] An oil-based coated separator was prepared using the solid-state electrolyte dispersion liquid prepared in the present comparative example, specifically: 2.5 kg of the solid-state electrolyte dispersion liquid was coated on a 9 μm PE base film, the coating thickness was 1 μm, the coating drying temperature was 80°C, and an oil-based coated separator was obtained. The moisture content of the oil-based coated separator prepared in the present comparative example was tested at 150°C, 180°C and 200°C, respectively, the dew point of the test environment was -40°C, and the moisture content and film flatness test data are shown in Table 2.

[0134] A lithium ion battery was assembled using the oil-based coated separator prepared in the present comparative example, and the test process was the same as that of Example 1, and the test data are shown in Table 3.

[0135] Table 1 is a summary of the moisture content test data of the water-based coated separators prepared in Examples 1-2 and Comparative Examples 1-2:

[0136]

[0137] Table 1

[0138] As can be seen from the test data in Table 1, the moisture content of the water-based coated separators of Examples 1-2 was below 1000 ppm when tested at 150°C, while the moisture content of Comparative Examples 1-2 was above 1500 ppm, and as the test temperature increased, the moisture content of the separators of Comparative Examples 1-2 increased significantly, while the moisture content of the samples of Examples 1-2 changed little with the test temperature, indicating that the combined water in Examples 1-2 had been removed, and high-energy combined water would not be introduced into the material during the conventional water-based dispersion process, verifying that the performance of the powder obtained by two baking processes of spray drying and high-temperature baking in the preparation process of the present application is superior to that of ordinary solid-state electrolyte materials that do not undergo two baking processes, the two processes of spray drying and high-temperature baking in the preparation process of the present application have advantages, and the second powder obtained can be directly used as a solid-state electrolyte material for the preparation of water-based coated separators, and is also beneficial to the preparation of low-moisture solid-state electrolyte modified materials in subsequent steps.

[0139] Table 2 is a summary of the moisture content and flatness test data of the oil-based coated separators prepared in Examples 1-2 and Comparative Examples 3-6 at different temperatures:

[0140]

[0141] Table 2

[0142] From the test data of Table 2, it can be seen that the oil-based coated separators prepared in Examples 1-2 have lower winding moisture at 150℃ test, but the moisture of the separators of Comparative Examples 3-4 increases significantly as the test temperature increases, indicating that part of the bound water in the solid electrolyte material is only baked out at high temperature, verifying the obvious advantages of the secondary baking method of the present application.

[0143] In the field pulping process, the pulp of Examples 1-2 only needs to be dispersed for 0.5 hours, while the pulp of Comparative Example 3 and Comparative Example 5 is dispersed for 2 hours, the film surface is uneven, with scratches and missed coating points. The film surface of Comparative Example 3 and Comparative Example 5 dispersed for 4 hours is flawless, which is comparable to that of Examples 1-2 dispersed for 0.5 hours, indicating that the solid electrolyte modified material prepared by applying the examples of the present application can greatly improve the production efficiency.

[0144] Table 3 is a summary of test data of lithium ion batteries assembled with oil-based coated separators prepared in Examples 1-2 and Comparative Examples 3-6:

[0145]

[0146]

[0147] Table 3

[0148] From the test data of Table 3, it can be seen that the first cycle coulombic efficiency and the cycle capacity retention rate after 500 cycles of the lithium ion batteries assembled with the separators containing the solid electrolyte modified material of Examples 1-2 of the present application are better than those of the lithium ion batteries assembled with Comparative Examples 3-6, indicating that the solid electrolyte modified material provided by the examples of the present application can improve the stability of the lithium ion battery.

[0149] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for the preparation of a solid-state electrolyte-modified material for a separator, characterized by, The preparation method comprises: Step S1, adding a solvent, a dispersing agent and a solid electrolyte material in a sand mill, and obtaining a first dispersion liquid after sand milling; the solvent comprises one or more of deionized water, alcohol, N-methyl pyrrolidone, dimethylformamide and isopropyl alcohol; the dispersing agent comprises one or more of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium dodecyl phosphate, sodium hexametaphosphate, polyethylene glycol, polyvinyl pyrrolidone, polyacrylate, polymethacrylate and maleic anhydride-styrene copolymer; Step S2, the first dispersion liquid is granulated by spray drying to obtain granules with a particle size D 50 from 100 nm to 10 μm; Step S3, high-temperature baking the first powder to obtain a second powder with a moisture content less than or equal to 200 ppm; Step S4, placing the second powder, a high-molecular polymer and an additive in a dispersing machine in a low-moisture environment, adding a non-aqueous solvent for dispersion treatment, and obtaining a second dispersion liquid after uniform dispersion; the high-molecular polymer comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and polymethyl methacrylate; the additive comprises one or more of polyacrylonitrile, polyvinyl alcohol, polyvinyl pyrrolidone, polydimethylsiloxane and polyoxyethylene ether; Step S5, low-temperature vacuum drying treatment of the second dispersion liquid, and then crushing treatment in a crushing device to obtain a solid electrolyte modified material with a moisture content less than or equal to 200 ppm; The particle size D of the solid electrolyte modified material 50 It is 100nm-5μm.

2. The production method according to claim 1, characterized by, The solid-state electrolyte material includes one or more of: an oxide of lithium, a sulfide of lithium, a hydride of lithium, and a halide of lithium; an original particle diameter D 50 is 1 μm - 20 μm; The mass ratio of the solid electrolyte material to the dispersing agent is [95-99.99]: [0.01-5]; The solid content of the first dispersion liquid is 1%-60%.

3. The preparation method according to claim 2, characterized in that, The oxide of lithium comprises a garnet-type solid electrolyte, a perovskite-type solid electrolyte, a NASICON-type solid electrolyte and a LISICON-type solid electrolyte.

4. The method of claim 1, wherein, The main speed of the sand mill is 400 rpm-3000 rpm; the particle size D 50 of the solid electrolyte material after sand milling in the first dispersion is 50 nm-5 μm; The inlet temperature of the spray drying is 160-230 DEG C, the outlet temperature is 50-150 DEG C, and the rotation speed of the spray centrifugal disc is 10,000-30,000 rpm.

5. The preparation method according to claim 1, characterized in that, The high-temperature baking temperature is 250-500 DEG C, and the baking time is 4-24 hours.

6. The preparation method according to claim 1, wherein, The mass ratio of the second powder to the high-molecular polymer is [80-99]: [1-20]; The mass ratio of the second powder to the additive is [70-99]: [1-30]; The non-aqueous solvent comprises one or more of alcohol, N-methyl pyrrolidone, tetrahydrofuran, dimethylacetamide, isopropyl alcohol, ethyl acetate or acetone; The solid content of the second dispersion liquid is 1%-60%; The dew point of the low-moisture environment is -10 DEG C to -60 DEG C; The rotation speed of the dispersing machine is 1,000-3,000 rpm, and the dispersion treatment time is 30 minutes-5 hours.

7. The preparation method according to claim 1, characterized in that, The drying temperature of the low-temperature vacuum drying treatment is 50-120 DEG C, the drying time is 5-24 hours, and the vacuum degree is less than or equal to 150 Pa; The crushing device is an air flow crusher, the frequency of the air flow crusher is 50-100 Hz, and the crushing time is 1-2 hours.

8. The solid-state electrolyte-modified material prepared by the method according to any one of claims 1 to 7, characterized in that, The solid-state electrolyte modification material comprises 80wt%-97wt% of a solid-state electrolyte material, 1wt%-5wt% of a dispersant, 1wt%-20wt% of a high molecular polymer, and 1wt%-30wt% of an auxiliary agent; The solid-state electrolyte material comprises one or more of an oxide of lithium, a sulfide of lithium, a hydride of lithium, and a halide of lithium; wherein the oxide of lithium comprises a garnet-type solid-state electrolyte, a perovskite-type solid-state electrolyte, a NASICON-type solid-state electrolyte, and a LISICON-type solid-state electrolyte; The high molecular polymer comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polymethyl methacrylate; The auxiliary agent comprises one or more of polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, polydimethylsiloxane, and polyoxyethylene ether; The particle size D of the solid electrolyte modified material 50 The size is 100nm-5μm; the moisture content of the solid electrolyte modified material is less than or equal to 200ppm.

9. A diaphragm characterized by, The separator comprises the solid-state electrolyte modification material of claim 8.

10. A lithium-ion battery, characterized by, The lithium ion battery comprises the separator of claim 9.

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