A separator coating material, a method for preparing the same, and a battery separator

Abstract

The application provides a diaphragm coating material, a preparation method thereof and a battery diaphragm using the diaphragm coating material. The diaphragm coating material can effectively adsorb acidic substances and transition metals in a lithium battery electrolyte by using nitrogen-containing functional groups in a covalent organic framework material, so that the battery diaphragm using the diaphragm coating material has good lithium battery electrolyte adsorption, infiltration and retention capacity, thereby effectively improving the service life, safety and high-low temperature cycle stability of the lithium battery using the battery diaphragm.

Description

Technical Field

[0001] This application relates to the field of porous organic polymer application technology, specifically to a membrane coating material, its preparation method, and a battery separator using the membrane coating material. Background Technology

[0002] With the widespread application of lithium-ion batteries in high-energy-density energy storage, their stability and safety issues have become increasingly prominent. Commonly used lithium salts in lithium battery electrolytes, such as lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI), readily react with trace amounts of moisture to generate HF, leading to electrode interface corrosion, transition metal dissolution, and damage to the solid electrolyte interphase (SEI), significantly reducing battery cycle life and causing safety hazards. The corrosive effect of HF is particularly severe in high-nickel cathode and lithium metal anode systems, exacerbating capacity decay and dendrite growth.

[0003] Traditional solutions typically employ physical adsorption or chemical additives to indirectly reduce HF formation by adsorbing moisture. However, moisture itself plays a positive role in the formation of LiF in the SEI, and LiF is a key component for inhibiting dendrite formation. Therefore, the core challenge of current research is how to directly eliminate HF while retaining moisture, and simultaneously inhibit the dissolution of transition metal ions. Summary of the Invention

[0004] This application provides a membrane coating material and its preparation method, as well as a battery separator prepared using the membrane coating material. The membrane coating material can effectively filter out HF and transition metals in lithium battery electrolyte, effectively solving the problems of HF corrosion of electrode interfaces and dissolution of transition metals in lithium battery electrolyte. Furthermore, the battery separator prepared using the membrane coating material has good lithium battery electrolyte wetting and retention capabilities.

[0005] To achieve the above-mentioned objectives, the present invention provides a diaphragm coating material comprising 50-90 wt% solvent, 2-30 wt% dispersant, 0-10 wt% stabilizer, 0-10 wt% defoamer, and 0-10 wt% binder.

[0006] The membrane coating material also includes a covalent organic framework material; the covalent organic framework material is prepared using an organic monomer containing nitrogen-containing functional groups.

[0007] As a further improvement of the present invention, the nitrogen-containing functional group is one or more of the following: pyridine group, pyrazine group, pyrrole group, amino group, imine group, imidazole group, triazine group, piperazine group, quaternary ammonium group, and guanidine group.

[0008] As a further improvement of the present invention, the nitrogen content of the covalent organic framework material is greater than 2 mol / kg.

[0009] As a further improvement of the present invention, an acidic substance is added during the preparation of the covalent organic framework material. The addition of the acidic substance causes pores to form on the covalent organic framework material, and the pore size is adjusted in the range of 0.1-10 nm; the specific surface area of ​​the covalent organic framework material is in the range of 0-3000 m². 2 / g.

[0010] As a further improvement of the present invention, the covalent organic framework material is an unmodified or modified porous or non-porous powder material.

[0011] To achieve the above-mentioned objectives, the present invention also provides a method for preparing a diaphragm coating material, comprising the following steps:

[0012] S1. Take a covalent organic framework material containing nitrogen-containing functional groups as a membrane additive, and pulverize the membrane additive into ultrafine powder to obtain membrane additive powder with a particle size of 10-100 μm.

[0013] S2. Add solvent and grinding aid to the diaphragm additive powder and perform sand milling to prepare a diaphragm coating pre-slurry with an average particle size of 0.1-5μm;

[0014] S3. Add 50-90wt% solvent, 2-30wt% dispersant, 0-10wt% stabilizer, 0-10wt% defoamer and 0-10wt% binder to the pre-prepared slurry of the diaphragm coating to prepare a diaphragm coating material.

[0015] As a further improvement of the present invention, the covalent organic framework coating material is structurally modified and altered during the preparation process. The covalent organic framework coating material is obtained by modification or thermal treatment synthesis methods such as covalent chemical grafting, small molecule impregnation, ion adsorption and exchange, carbonization, etc.

[0016] As a further improvement of the present invention, in step S2, the solvent is one or more of ultrapure water, ethanol, N-methylpyrrolidone and cyclohexanone; the grinding aid is one or more of ethylene glycol, triisopropanolamine, polyether alcoholamine, polymeric alcoholamine, polymeric polyol, and propylene glycol.

[0017] As a further improvement of the present invention, in step S3, the solvent is one or more of ultrapure water, ethanol, N-methylpyrrolidone and cyclohexanone; the binder is one or more of polyvinylidene fluoride, polyvinylpyrrolidone, carboxymethyl cellulose, hydroxyethyl cellulose and polyacrylic acid.

[0018] To achieve the above-mentioned objectives, the present invention further provides a battery separator, comprising:

[0019] basal layer;

[0020] A diaphragm coating is disposed on at least one side of the substrate layer; the diaphragm coating is obtained by coating the aforementioned diaphragm coating material onto the substrate layer and then drying it under vacuum.

[0021] As a further improvement of the present invention, the base layer is any one of polyethylene film, polypropylene film, polyester film, polyamide film, and polyimide film.

[0022] Compared with the prior art, the beneficial effects of this application are as follows:

[0023] The membrane coating material provided in this application uses a covalent organic framework material containing nitrogen-containing functional groups as a membrane additive, making the membrane coating material a Lewis base with adjustable polarity, porosity, and functional properties. This allows for the rapid and effective adsorption of HF and transition metals generated during lithium battery operation. Furthermore, the battery separator prepared using this membrane coating material effectively utilizes the porosity of the coating material to enhance the wetting and retention capacity of the battery separator for lithium battery electrolyte. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This invention relates to a partial structural example of the covalent organic framework material;

[0026] Figure 2 This is a flowchart illustrating the preparation method of the diaphragm coating material of the present invention.

[0027] Figure 3 The X-ray diffraction pattern of the diaphragm coating YK1 in Embodiment 1 of the present invention;

[0028] Figure 4 The diagram shows the nitrogen isotherm adsorption-desorption curves (black circular curves represent adsorption, and white circular curves represent desorption) and pore size distribution of the membrane coating YK1 in Example 1 of this invention at 77 K.

[0029] Figure 5 This is a scanning electron microscope image of the diaphragm coating YK1 in Embodiment 1 of the present invention;

[0030] Figure 6The X-ray diffraction patterns of the diaphragm coating YK4 in Examples 1-3 of this invention are shown below.

[0031] Figure 7 The nitrogen isotherm adsorption-desorption curves of the membrane coating YK4 in Examples 1-3 of this invention at 77 K (black circular curves represent adsorption, and white circular curves represent desorption).

[0032] Figure 8 The contact angles between the battery separator coated with the YK4 separator coating and the battery separator substrate in Embodiment 3 of the present invention and the lithium battery electrolyte are shown. Detailed Implementation

[0033] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0034] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0035] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0036] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood as each intermediate value between the upper and lower limits of the specifically disclosed range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] This invention provides a separator coating material comprising 50-90 wt% solvent, 2-30 wt% dispersant, 0-10 wt% stabilizer, 0-10 wt% defoamer, and 0-10 wt% binder; the separator coating material further comprises a covalent organic framework material; the covalent organic framework material is prepared using an organic monomer containing nitrogen-containing functional groups. The separator coating material of this application, by using a covalent organic framework material containing nitrogen-containing functional groups as a separator additive, gives the separator coating material good polarity and coordination ability, thereby enabling the battery separator using this separator coating material to have good adsorption of HF and transition metals generated during lithium battery operation; simultaneously, the separator coating material can form pores with adjustable pore size, thereby giving the separator coating material a large specific surface area, effectively improving the wetting and retention capacity of the battery separator using this separator coating material for lithium battery electrolyte.

[0039] In this application, the nitrogen-containing functional group is one or more selected from pyridine, pyrazine, pyrrole, amino, imine, imidazole, triazine, piperazine, quaternary ammonium, and guanidine groups; and the content of the nitrogen-containing functional group is 0.1~10 mol / kg. Preferably, the nitrogen content of the covalent organic framework material is greater than 2 mol / kg.

[0040] Preferably, the covalent organic framework material is one or more of NKCOF-41, NKCOF-13, NKCOF-10, NKCOF-62, DPZ-COF, COF-366, NH2-Th-Tz COF, TPPA-NH2, LZU-1, TPPA-COF, LZU-520, TMT-BPA-COF, V-COF-3, KUF-2, and KUF-3, and more preferably, such as Figure 1 As shown, the membrane additive is any one of NKCOF-41, NKCOF-10, COF-366, NH2-Th-Tz COF, V-COF-3, and KUF-2.

[0041] In a preferred embodiment of this application, the covalent organic framework material is prepared using organic monomers containing nitrogen-containing functional groups (pyridyl, pyrazinyl, etc.), organic monomers containing aldehydes, and acidic substances to prepare a covalent organic framework material with porous surfaces. The pores are hexagonal, quadrilateral, irregular, through-hole, or non-through two-dimensional or three-dimensional channels. Preferably, the pore size of the covalent organic framework material is adjusted within the range of 0.1-10 nm; and the specific surface area of ​​the covalent organic framework material is in the range of 0-3000 m². 2 / g.

[0042] In another preferred embodiment of this application, the covalent organic framework material is prepared by using organic monomers containing nitrogen-containing functional groups (pyridyl, pyrazinyl, etc.) and organic monomers containing aldehydes to obtain a non-porous covalent organic framework material. That is, in this application, whether the covalent organic framework material has pores can be selected based on user needs and is not limited in this application.

[0043] Please see Figure 2 As shown, the present invention also provides a method for preparing a diaphragm coating material, the method comprising the following steps:

[0044] S1. Using covalent organic framework materials containing nitrogen-containing functional groups as membrane additives, the membrane additives are ultra-finely pulverized to obtain membrane additive powder with a particle size of 10-100 μm.

[0045] S2. Add solvent and grinding aid to the diaphragm additive powder and perform sand milling to obtain a diaphragm coating pre-slurry with an average particle size of 0.1-5μm;

[0046] S3. Add 50-90wt% solvent, 2-30wt% dispersant, 0-10wt% stabilizer, 0-10wt% defoamer and 0-10wt% binder to the pre-prepared slurry of the diaphragm coating to prepare a diaphragm coating material.

[0047] Furthermore, in S2, the solvent is one or more of ultrapure water, ethanol, N-methylpyrrolidone, and cyclohexanone; the grinding aid is one or more of ethylene glycol, triisopropanolamine, polyether alcoholamine, polymeric alcoholamine, polymeric polyol, and propylene glycol.

[0048] In step S3, the solvent is one or more of ultrapure water, ethanol, N-methylpyrrolidone, and cyclohexanone; the binder is one or more of polyvinylidene fluoride, polyvinylpyrrolidone, carboxymethyl cellulose, hydroxyethyl cellulose, and polyacrylic acid.

[0049] Furthermore, this application also provides a battery separator. The battery separator includes:

[0050] basal layer;

[0051] A separator coating is disposed on at least one side of the substrate layer; the separator coating is obtained by coating the aforementioned separator coating material onto the substrate layer and then vacuum drying; in this configuration, the separator coating material can be used to filter out metal ions and / or acidic substances in the battery electrolyte, and improve the wetting and retention capacity of the electrolyte.

[0052] In this application, the base layer is any one of polyethylene film, polypropylene film, polyester film, polyamide film, and polyimide film.

[0053] To further verify the filtering effect of the battery separator using the separator coating material of this application on HF and transition metals in lithium battery electrolyte, as well as its wetting and retention capabilities in the electrolyte, this invention tested the filtering performance of the battery separator provided in this application and the wetting and retention performance of the battery separator in lithium battery electrolyte by preparing lithium battery electrolytes containing HF and transition metals respectively.

[0054] Example 1

[0055] In this embodiment, membrane coating materials YK1~YK6 are prepared respectively, wherein membrane coating materials YK1, YK2 and YK3 are prepared by using pyridine groups as nitrogen-containing functional groups as covalent organic framework materials as membrane additives.

[0056] Specifically, the preparation processes of diaphragm coating materials YK1, YK2, and YK3 are as follows:

[0057] S1. Using a covalent organic framework material containing pyridine groups as a membrane additive, 50 mg of the membrane additive was ultra-finely pulverized to obtain membrane additive powder with a particle size of 10-100 μm.

[0058] S2. Add solvent and grinding aid to the diaphragm additive powder and perform sand milling to obtain a diaphragm coating pre-slurry with an average particle size of 0.1-5μm;

[0059] S3. Add 50-90wt% solvent, 2-30wt% dispersant, 0-10wt% stabilizer, 0-10wt% defoamer and 0-10wt% binder to the pre-prepared slurry of the diaphragm coating to prepare a diaphragm coating material.

[0060] Specifically, in S1, the weight of the organic monomer containing the pyridine group, the type of organic monomer, and the use of acidic substances are controlled to prepare the following:

[0061] The membrane coating material YK1 is a covalent organic framework material NKCOF-41.

[0062] The membrane coating material YK2 is a non-porous covalent organic framework material NKCOF-41; and,

[0063] The diaphragm coating material YK3 is a non-porous covalent organic framework material NKCOF-13.

[0064] Furthermore, the preparation processes of membrane coating materials YK4, YK5, and YK6 are basically the same as those of membrane coating materials YK1, YK2, and YK3. The only difference is that in S1, membrane coating material YK4 is prepared using a covalent organic framework material with pyridine and pyrrole groups as nitrogen-containing functional groups as a membrane additive; membrane coating material YK5 is prepared using a covalent organic framework material with pyrazine groups as nitrogen-containing functional groups as a membrane additive; and membrane coating material YK6 is prepared using a covalent organic framework material with pyrazine and pyrrole groups as nitrogen-containing functional groups as a membrane additive.

[0065] Similarly, by controlling the weight of the organic monomer containing nitrogen groups, the type of organic monomer, and the use of acidic substances in S1, the following preparations were made:

[0066] The membrane coating material YK4 is a hybrid covalent organic framework material NKCOF-13 and COF-366.

[0067] The membrane coating material YK5 is a covalent organic framework material NKCOF-10; and,

[0068] The membrane coating material YK6 is a hybrid covalent organic framework material NKCOF-10 and COF-366.

[0069] Furthermore, two portions of battery separators were prepared using commercial electrolytes with HF contents of 5500 mg / L and 400 mg / L, respectively, and using separator coating materials YK1-YK6. The loading of separator coating materials YK1-YK6 in each portion of the battery separator was 0.1-50 wt%. The two portions of battery separators using the same separator coating materials YK1-YK6 were respectively immersed in 10 mL of commercial electrolyte with 5500 mg / L HF and commercial electrolyte with 400 mg / L HF. It should be noted that the commercial electrolyte used in this application is the LBE01 type lithium-ion electrolyte produced by Nanjing Mojes Energy Technology Co., Ltd.

[0070] HF in commercial electrolyte was adsorbed under ambient temperature and pressure conditions. Each battery separator was fully impregnated in a closed environment, and the adsorption capacity of each battery separator for HF was tested by potentiometric titration.

[0071] Table 1. Explanation of Group Content and HF Adsorption Data

[0072]

[0073] Table 2. Explanation of Pore Type and HF Adsorption Data

[0074]

[0075] Please see Figure 3 The image shows the X-ray diffraction pattern of the diaphragm coating material YK1. It can be seen that the diaphragm coating material YK1 has strong diffraction peaks, indicating an ordered structure and good crystallinity.

[0076] Please see Figure 4 The figure shows the nitrogen isotherm adsorption-desorption curve and pore size distribution of the membrane coating material YK1 at 77 K. It can be seen that its BET specific surface area is approximately 1600 m². 2 / g, with a high surface area. As shown in Table 2, the pore distribution diagram shows that the material has a microporous structure of 1.8 nm, with uniform pore size and high porosity.

[0077] Please see Figure 5 The image shown is a scanning electron microscope image of the diaphragm coating material YK1. It can be seen that the diaphragm coating material YK1 has relatively regular morphological features at the microscale, and the material size is at the micrometer level.

[0078] Please see Figure 6 The image shows the X-ray diffraction pattern of the diaphragm coating material YK4. It can be seen that the diaphragm coating material YK4 has strong diffraction peaks, indicating that it has an ordered structure and a certain degree of crystallinity.

[0079] Please see Figure 7 The figure shows the nitrogen isotherm adsorption-desorption curve of the diaphragm coating material YK4 at 77 K, indicating that its BET specific surface area is approximately 350 m². 2 / g, and simultaneously possesses a hierarchical porous structure of micropores and mesopores.

[0080] As shown in Tables 1 and 2 above, membrane coating materials YK1 and YK3, which incorporate strongly polar nitrogen-containing pyridine functional groups, exhibit good adsorption capacity for 5500 mg / L HF. However, the adsorption capacity for 5500 mg / L HF is improved when using pyridine-based membrane coating material YK2 with a nitrogen content of 4.1 mol / kg. This demonstrates that the content of strongly polar pyridine groups significantly affects the adsorption capacity for high-concentration HF. It should be noted that the polarity of the nitrogen-containing functional groups in this application is determined based on the adsorption capacity of the nitrogen-containing functional groups for 1 mol / L hydrochloric acid.

[0081] Furthermore, for a low concentration of HF of 400 mg / L, the porous membrane coating material YK1 showed the highest adsorption capacity compared to the non-porous membrane coating materials YK2 and YK3. The adsorption capacity of membrane coating material YK2 was higher than that of membrane coating material YK3. This indicates that among membrane coating materials with the same nitrogen-containing functional groups and similar nitrogen content, the porous structure and high specific surface area of ​​the material are beneficial to the adsorption of low concentration HF.

[0082] Furthermore, for nitrogen-containing functional groups of different polarities, since the polarity of pyridine groups is greater than that of pyrazine groups, which are greater than that of pyrrole groups, membrane coating materials YK1 and YK4, which contain strongly polar pyridine groups, show a greater adsorption increase for HF of different concentrations compared to membrane coating materials YK5 and YK6, which contain weakly polar pyrazine and pyrrole groups. This indicates that membrane coating materials with strongly polar nitrogen-containing functional groups adsorb more HF than those with weakly polar functional groups. Comparing the low-concentration HF adsorption of membrane coating materials YK1, YK4, YK5, and YK6, membrane coatings with the same nitrogen functional group polarity and similar nitrogen content show a greater adsorption capacity for low-concentration HF with larger pore sizes, demonstrating that the pore size of the membrane coating material has a significant impact on the low-concentration HF adsorption capacity.

[0083] Example 2

[0084] In this embodiment, the membrane coating materials YK1 and YK4~YK6 from the previous embodiment were used as membrane coatings to prepare battery separators, wherein the amount of covalent organic framework material added to each battery separator was 20 mg.

[0085] Furthermore, FeCl3, MnCl2, NiCl2, and CoCl2 were dissolved in commercial electrolytes respectively to prepare Fe... 3+ Transition metal ion solutions with concentrations of 50 mg / L and 1000 mg / L, respectively; Mn 2+ Ni 2+ or Co 2+ Five battery separators were prepared using transition metal ion solutions with a concentration of 50 mg / L, and five portions of each separator were prepared using separator coating materials YK1 and YK4-YK6, with each portion containing 0.1-50 wt% of separator coating materials YK1 and YK4-YK6. The five battery separators using the same separator coating materials YK1 and YK4-YK6 were then immersed in 10 mL of 50 mg / L Fe solution. 3+ Transition metal ion solution, 1000 mg / L Fe 3+Transition metal ion solution, 50 mg / LMn 2+ Transition metal ion solution, 50 mg / L Ni 2+ Transition metal ion solutions and 50 mg / L Co 2+ In transition metal ion solutions.

[0086] Adsorption of transition metals from a solution of transition metal ions was performed at room temperature and atmospheric pressure. The battery separator was then thoroughly impregnated in a sealed environment. Atomic absorption spectrometry was used to test the adsorption of transition metal Fe on the battery separators coated with separator coating materials YK1 and YK4~YK6. 3+ Mn 2+ Ni 2+ and Co 2+ Adsorption capacity.

[0087] Table 3. Explanation of Group Content, Pore Type, and Transition Metal Adsorption Data

[0088]

[0089] As shown in the table above, for membrane coating materials YK1 and YK4, which incorporate strongly polar nitrogen-containing pyridine functional groups, and membrane coating materials YK5 and YK6, which contain weakly polar nitrogen-containing pyrazine and pyrrole functional groups, the effect on 50 mg / L Fe 3+ Transition metal ion solution, 50 mg / L Co 2+ Transition metal ion solution, 50 mg / L Ni 2+ The membrane coatings exhibit good adsorption capacity for low concentrations of transition metal ions, demonstrating that different polarities of nitrogen-containing functional groups in the membrane coatings effectively adsorb low concentrations of transition metal Fe. 3+ Co 2+ Ni 2+ The filtration performance difference was not significant; however, for 50 mg / L Mn 2+ The adsorption properties of transition metals are compared with those of membrane coating materials YK4 and YK6, which contain pyrrole groups, and membrane coating materials YK1 and YK5, which do not contain pyrrole groups.

[0090] Specifically, the membrane coating material YK1 contains pyridine groups, YK4 contains pyridine and pyrrole groups, YK5 contains pyrazine groups, and YK6 contains pyrazine and pyrrole groups. By comparing the adsorption levels of metal ions on battery membranes coated with membrane coating materials YK1 and YK4 with the adsorption levels on battery membranes coated with membrane coating materials YK5 and YK6, it can be seen that the membrane coating material with added pyrrole groups has a stronger Mn adsorption capacity. 2+Adsorption performance. Furthermore, by comparing the adsorption levels of metal ions on battery separators coated with membrane coating materials YK1 and YK5, it is evident that the membrane coating material containing pyrazine groups adsorbs Mn more readily than the membrane coating material containing pyridine groups. 2+ .

[0091] Example 3

[0092] In this embodiment, YK4 is provided as a membrane coating material to prepare a battery separator, wherein the amount of covalent organic framework material added as a separator additive in the battery separator is 100 mg.

[0093] Furthermore, commercial electrolyte was dropped onto the YK4 battery separator coated with separator coating material and the substrate layer without separator coating material, respectively, and the wetting ability of the battery separator and the battery separator substrate layer to commercial electrolyte was tested using a contact angle meter.

[0094] Please see Figure 8 As shown, the contact angles of the battery separator coated with YK4 and the substrate without the coating material to the commercial electrolyte are as follows: The contact angle between the substrate without the coating material and the commercial electrolyte is 33.4°, while the contact angle between the battery separator coated with YK4 and the commercial electrolyte is 20.9°. This demonstrates that coating the substrate with a separator containing a covalent organic framework material can significantly reduce the contact angle between the substrate and the commercial electrolyte. In other words, coating the substrate with a separator containing a covalent organic framework material can effectively improve the wettability of the battery separator to the commercial electrolyte.

[0095] Example 4

[0096] In this embodiment, the membrane coating materials YK1 and YK5 used in the embodiment, as well as commercial alumina coating materials, are used as membrane coatings to prepare battery separators. Each battery separator has the same mass, and the amount of coating material added to each battery separator is 1000 mg.

[0097] Furthermore, battery separators coated with YK1, YK5, and commercial alumina coating materials were respectively immersed in commercial electrolyte. After saturation immersion for 30 minutes, the electrolyte on the surface of the three battery separators was wiped off. The mass of the three battery separators after saturation electrolyte adsorption was weighed, and the electrolyte absorption rate of the battery separators coated with YK1, YK5, and commercial alumina coating materials was calculated.

[0098] Table 4. Explanation of Pore Type and Electrolyte Adsorption Data

[0099]

[0100] As shown in the table above, for membrane coating materials YK1 and YK4, which have organic porous structures and high specific surface areas, their electrolyte absorption rates are much higher than those of non-porous inorganic alumina coating materials. This proves that coating membrane materials containing covalent organic framework materials can effectively improve the electrolyte retention capacity of battery membranes for commercial electrolytes.

[0101] Example 5

[0102] Diaphragm coating materials YK1~YK6 were prepared separately. Diaphragm coating materials YK1, YK4 and YK5 were prepared by using unmodified covalent organic framework materials as diaphragm additives, while diaphragm coating materials YK2, YK3 and YK6 were prepared by using modified covalent organic framework materials as diaphragm additives.

[0103] Specifically, the preparation process of the diaphragm coating materials YK1~YK6 is as follows:

[0104] S1. Using a covalent organic framework material containing pyridine groups or pyrazine and pyrrole groups as a membrane additive, take 500 mg of the membrane additive and pulverize it into ultrafine powder to obtain membrane additive powder with a particle size of 10-100 μm.

[0105] S2. Add solvent and grinding aid to the diaphragm additive powder and perform sand milling to obtain a diaphragm coating pre-slurry with an average particle size of 0.1-5μm;

[0106] S3. Add 50-90wt% solvent, 2-30wt% dispersant, 0-10wt% stabilizer, 0-10wt% defoamer and 0-10wt% binder to the pre-prepared slurry of the diaphragm coating to prepare a diaphragm coating material.

[0107] Among them, the membrane coating material YK1 is the unmodified covalent organic framework material NKCOF-41;

[0108] The membrane coating material YK2 is a modified non-porous covalent organic framework material NKCOF-41;

[0109] The membrane coating material YK3 is a modified non-porous covalent organic framework material NKCOF-13;

[0110] The membrane coating material YK4 is an unmodified hybrid covalent organic framework material NKCOF-13 and COF-366;

[0111] The membrane coating material YK5 is the unmodified covalent organic framework material NKCOF-10;

[0112] The membrane coating material YK6 is a modified hybrid covalent organic framework material NKCOF-10 and COF-366.

[0113] In S2, S1 also includes structural modification treatment of covalent organic framework materials NKCOF-41, NKCOF-13, and mixed covalent organic framework materials NKCOF-10 and COF-366, respectively. Specifically, in S1, the synthesis method of membrane coating material YK2 is as follows: terephthalaldehyde (40.2 mg, 0.3 mmol), 2,4,6-trimethylpyridine (26 mg, 0.2 mmol), and benzoic acid (0.6 mg, 0.005 mmol) are added to a reaction vessel, heated to 220℃ and reacted for 5 days. The mixture is then washed with N,N-dimethylformamide and methanol, respectively. Finally, after drying, membrane coating material YK2 is obtained.

[0114] Specifically, the synthesis method of the membrane coating material YK3 in S1 is as follows: pyromellitic aldehyde (48.6 mg, 0.3 mmol), 2,4,6-trimethylpyridine (36.4 mg, 0.3 mmol), and benzoic acid (0.6 mg, 0.005 mmol) are added to a reaction vessel, heated to 220℃ and reacted for 5 days. The mixture is then washed with N,N-dimethylformamide and methanol, respectively. Finally, after drying, the membrane coating material YK3 is obtained.

[0115] Specifically, the synthesis method of the membrane coating material YK6 in S1 is as follows: pyromellitic aldehyde (27.4 mg, 0.18 mmol), 2,5-dimethylpyrazine (16 μL, 0.15 mmol), tetraaminophenylporphyrin (27 mg, 0.04 mmol), and benzoic acid (1.2 mg, 0.01 mmol) are added to a reaction vessel, heated to 200℃ and reacted for 5 days. The mixture is then washed with N,N-dimethylformamide and methanol, respectively. Finally, after drying, the membrane coating material YK6 is obtained.

[0116] Furthermore, diaphragm coating materials YK2, YK3, and YK6 are used as diaphragm additives and subjected to ultrafine grinding to obtain diaphragm additive powder with a particle size of 10-100 μm.

[0117] Then, the membrane coating material was prepared according to S2 and S3; the membrane coating materials YK2, YK3 and YK6 after structural modification were used as membrane additives to prepare the membrane coating material, which can also rapidly and effectively adsorb HF and transition metals generated during the operation of lithium battery.

[0118] Table 5. Explanation of the modified structure of the diaphragm coating material and HF adsorption data.

[0119]

[0120] Table 5 shows that the unmodified membrane coating materials all have porous structures with micropore sizes, while the modified membrane coating materials have non-porous or low surface area structures. Regarding HF adsorption performance, compared to the porous membrane coating material YK6 modified with the covalent organic framework NKCOF-10, the non-porous membrane coating materials YK2 and YK3 modified with the covalent organic frameworks NKCOF-41 and NKCOF-13, respectively, exhibit superior HF adsorption performance. Furthermore, compared to the unmodified membrane coating material YK1, the membrane coating material YK2 modified with the covalent organic framework NKCOF-41 shows a significant improvement in HF adsorption capacity even after the membrane coating material becomes non-porous. This is attributed to the adsorption effect of the strongly polar nitrogen-containing pyridine functional group in the membrane coating material YK2, demonstrating that this material modification method is beneficial for the efficient adsorption of HF in the electrolyte.

[0121] Example 6

[0122] Diaphragm coating materials YK7 and YK8 were prepared respectively. Diaphragm coating materials YK7 and YK8 were prepared by using pyridine groups as nitrogen-containing functional groups as covalent organic framework materials as diaphragm additives.

[0123] Specifically, the preparation processes of diaphragm coating materials YK7 and YK8 are as follows:

[0124] S1. Using a covalent organic framework material containing pyridine groups as a membrane additive, 500 mg of the membrane additive was ultra-finely pulverized to obtain membrane additive powder with a particle size of 10-100 μm.

[0125] S2. Add solvent and grinding aid to the diaphragm additive powder and perform sand milling to obtain a diaphragm coating pre-slurry with an average particle size of 0.1-5μm;

[0126] S3. Add 50-90wt% solvent, 2-30wt% dispersant, 0-10wt% stabilizer, 0-10wt% defoamer and 0-10wt% binder to the pre-prepared slurry of the diaphragm coating to prepare a diaphragm coating material.

[0127] Specifically, in S1, the weight of the organic monomer containing the pyridine group, the type of organic monomer, and the use of acidic substances are controlled to prepare the following:

[0128] The membrane coating material YK7 is a modified covalent organic framework material NKCOF-10;

[0129] The diaphragm coating material YK8 is a modified covalent organic framework material NKCOF-13.

[0130] In S2, S1 also includes structural modification and amino modification treatment of covalent organic framework materials NKCOF-10 and NKCOF-13, respectively; specifically, in S1, a Tris-HCl buffer solution with a concentration of 10 mg / mL is prepared for the membrane coating material, 5 mg / L of dopamine hydrochloride is added and stirred evenly, and the pH value of the suspension is adjusted to 8.5 with 0.1 M NaOH solution, filtered and washed with pure water; finally, the membrane coating material is obtained after drying.

[0131] Furthermore, diaphragm coating materials YK7 and YK8 were used as diaphragm additives and subjected to ultrafine grinding to obtain diaphragm additive powder with a particle size of 10-100 μm.

[0132] Then, the membrane coating material was prepared according to S2 and S3; the membrane coating materials YK7 and YK8, which were treated with structural modification and amino modification, were used as membrane additives to prepare the membrane coating material, which can also quickly and effectively adsorb HF and transition metals generated during the operation of lithium batteries.

[0133] In summary, the separator coating provided in this application utilizes nitrogen-containing functional groups to prepare a covalent organic framework material with diverse porous environments. The nitrogen-containing functional groups in this material can form hydrogen bonds with HF in the lithium-ion battery electrolyte and coordinate bonds with transition metals, thus enabling rapid and effective adsorption of HF and transition metals generated during lithium-ion battery operation. Furthermore, the battery separator prepared using this coating effectively utilizes its porous nature and pore confinement effect to enhance the separator's wetting and retention capabilities for the lithium-ion battery electrolyte. This novel separator possesses numerous functions, significantly improving the lifespan, safety, and high / low temperature cycling stability of lithium-ion batteries.

[0134] It should be noted that this application has been described in detail in this specification with general descriptions and specific embodiments. However, some modifications or improvements can be made to this application, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of this application are within the scope of protection claimed in this application.

Claims

1. A diaphragm coating material, comprising 50-90 wt% solvent, 2-30 wt% dispersant, 0-10 wt% stabilizer, 0-10 wt% defoamer and 0-10 wt% binder; Its features are: The membrane coating material also includes a covalent organic framework material; the covalent organic framework material is prepared using an organic monomer containing nitrogen-containing functional groups.

2. The diaphragm coating material according to claim 1, characterized in that: The nitrogen-containing functional group is one or more of the following: pyridine group, pyrazine group, pyrrole group, amino group, imine group, imidazole group, triazine group, piperazine group, quaternary ammonium group, and guanidine group.

3. The diaphragm coating material according to claim 1, characterized in that, The nitrogen content of the covalent organic framework material is greater than 2 mol / kg.

4. The diaphragm coating material according to claim 1, characterized in that, The covalent organic framework material is prepared by adding an acidic substance, which creates pores in the material. The pore size is adjusted from 0.1 to 10 nm. The specific surface area of ​​the covalent organic framework material is 0 to 3000 m². 2 / g.

5. The diaphragm coating material according to claim 1, characterized in that, The covalent organic framework material is an unmodified or modified porous or non-porous powder material.

6. A method for preparing a diaphragm coating material, used to prepare the diaphragm coating material according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Take a covalent organic framework material containing nitrogen-containing functional groups as a membrane additive, and pulverize the membrane additive into ultrafine powder to obtain membrane additive powder with a particle size of 10-100 μm. S2. Add solvent and grinding aid to the diaphragm additive powder and perform sand milling to prepare a diaphragm coating pre-slurry with an average particle size of 0.5-5 μm; S3. Add 50-90wt% solvent, 2-30wt% dispersant, 0-10wt% stabilizer, 0-10wt% defoamer and 0-10wt% binder to the pre-prepared slurry of the diaphragm coating to prepare a diaphragm coating material.

7. The method for preparing the diaphragm coating material according to claim 6, characterized in that: In step S2, the solvent is one or more of ultrapure water, ethanol, N-methylpyrrolidone, and cyclohexanone; the grinding aid is one or more of ethylene glycol, triisopropanolamine, polyether alcoholamine, polymeric alcoholamine, polymeric polyol, and propylene glycol.

8. The method for preparing the diaphragm coating material according to claim 6, characterized in that: In step S3, the solvent is one or more of ultrapure water, ethanol, N-methylpyrrolidone, and cyclohexanone; the binder is one or more of polyvinylidene fluoride, polyvinylpyrrolidone, carboxymethyl cellulose, hydroxyethyl cellulose, and polyacrylic acid.

9. A battery separator, characterized in that, include: basal layer; A diaphragm coating is disposed on at least one side of the substrate layer; The diaphragm coating is obtained by coating the diaphragm coating material of any one of claims 1 to 5 onto the substrate layer and then drying it under vacuum.

10. The battery separator according to claim 9, characterized in that: The base layer is any one of polyethylene film, polypropylene film, polyester film, polyamide film, and polyimide film.

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