A DA polymer coating for modifying lithium battery separator, preparation method thereof, lithium battery separator and application thereof

Abstract

The present application discloses a D-A polymer coating for modifying lithium battery separators, a preparation method thereof, a lithium battery separator and its application. The modified separator used in the lithium battery is selected to be a polymer separator as the main body, and a coating is applied on both sides of the polymer separator, and the coating is a lithium-philic D-A polymer material. The above-mentioned D-A polymer material coating contains a lithium-philic triazine structure, and the enriched triazine group has a high affinity not only for lithium, but also for solvent molecules. This synergistic effect promotes desolvation and enhances the lithium ion (Li + ) transport, promoting the uniform deposition of lithium, thereby inhibiting the growth of dendrites, thereby improving the charge and discharge capacity and cycle stability of lithium batteries, giving them fast reaction kinetics and excellent electrochemical stability.

Description

Technical Field

[0001] The present application relates to the field of battery material technology, and more specifically, to a DA polymer coating for modifying a lithium battery separator, and a preparation method and application thereof. Background Art

[0002] Since their introduction, lithium-ion batteries (LIBs) have become essential electrochemical devices in everyday life due to their exceptional energy storage and conversion capabilities. Lithium metal batteries (LMBs) replace the negative electrode with lithium metal, which is considered a key next-generation energy storage material due to its extremely high theoretical specific capacity (3860 mAh g-1) and low electrochemical potential. Separators are a crucial component of both lithium-ion and lithium metal batteries, serving as a barrier between the positive and negative electrodes and absorbing the electrolyte.

[0003] The separator plays an important role in preventing direct contact between the positive and negative electrodes. + The transfer provides a channel to avoid direct contact between the positive and negative electrodes. Many characteristics of the separator are closely related to the internal resistance, cycle performance, rate capacity, safety and commercial prospects of lithium-ion batteries.

[0004] Polyolefin separators (polyethylene (PE), polypropylene (PP)) are widely used in commercial lithium-ion batteries due to their electrochemical stability. However, commercial polyolefin separators with poor thermal stability and wettability cannot meet the growing energy demand. Since lithium-ion batteries operate in harsh environments, the separators experience thermal shrinkage, which can cause short circuits, leading to catastrophic failure of lithium-ion batteries due to their flammability and poor thermal stability. Polyolefin separators have poor absorption of electrolytes, and incomplete filling of the electrolyte in the separator pores leads to blockage of ion pathways, resulting in Li-ion battery failure between the anode and cathode. + The transfer is uneven and irreversible. Consequently, polyolefin separators have poor compatibility with the positive and negative electrodes. Furthermore, poorly compatible interfaces easily form unstable solid electrolyte interfaces (SEIs), which are associated with uneven lithium dendrite growth. These uneven lithium dendrites can pierce the separator, posing a safety hazard.

[0005] Application Contents

[0006] To overcome at least one problem with the prior art, this application provides a DA polymer coating for modifying lithium battery separators, as well as its preparation method and application. Using the method provided herein, a thin, lithium-philic DA organic polymer coating is modified on both sides of a commercial polypropylene (PP) separator. The customized functional groups of the lithium-philic DA organic polymer coating for modifying lithium battery separators exhibit lithium ion affinity and solvent anchoring, facilitating lithium ion desolvation and significantly promoting lithium ion transfer.

[0007] In order to solve the above technical problems, the technical solution adopted in this application is:

[0008] A DA polymer coating for modifying a lithium battery separator, wherein the DA polymer coating contains a lithium-philic triazine structure, the structural formula of which is shown below:

[0009] .

[0010] The present application also provides a method for preparing the above-mentioned DA polymer coating for modifying a lithium battery separator, which comprises the following steps:

[0011] S1. Melamine and trimesic acid were dissolved in dimethyl sulfoxide solvent to obtain a transparent clear solution, mixed and heated to react, and poured into deionized water to obtain a white suspension;

[0012] S2. The white suspension obtained in step S1 was centrifuged, washed with deionized water and dried to obtain a precursor;

[0013] S3. The precursor obtained in step S2 is calcined to obtain a DA polymer;

[0014] S4. The DA polymer obtained in step S3 is mixed with a second polymer and an organic solvent to obtain a DA polymer slurry;

[0015] S5. The DA polymer slurry obtained in step S4 is coated on the surface of the base film, and then vacuum dried to form a DA polymer coating on the surface of the base film, and obtain a DA polymer coated separator, wherein the base film is a separator for lithium metal batteries / lithium ion batteries.

[0016] Preferably, in step S1, the heating reaction temperature is 50-150° C., the heating reaction time is 0.5-4 h, and the dimethyl sulfoxide solvent is an ultra-dry dimethyl sulfoxide solvent.

[0017] Preferably, in step S2, the centrifugal speed is 6000-9000 ppm, and the centrifugal time is 5-20 min.

[0018] Preferably, in step S3, the calcination temperature is 30-450° C., and the calcination time is 1-8 hours.

[0019] Preferably, in step S4, the second polymer is one or more of polyvinylidene fluoride, polyacrylate, and lithiated polyacrylic acid.

[0020] More preferably, in step S4, the mass ratio of the DA polymer to the second polymer is (0-10):1.

[0021] Preferably, in step S5, the vacuum drying temperature is 30-100° C., and the vacuum drying time is 4-24 hours.

[0022] The present application also provides a lithium battery separator, which is provided with a lithium-philic DA polymer coating for modifying the lithium battery separator prepared by the above-mentioned preparation method, and the thickness of the coating is 23~26um.

[0023] The present application also provides the use of the above-mentioned lithium battery separator containing the modified DA polymer coating in lithium metal batteries and / or lithium ion batteries.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This application applies DA polymer to LMBs. DA polymer materials have many excellent physical and chemical properties, such as high porosity, good thermal stability, high chemical stability and high active site exposure rate. Applying them to lithium batteries will further facilitate the migration of lithium ions. The material of this application is a π-conjugated system that facilitates electron transfer, thereby reducing polarization and accelerating the reaction kinetics of the battery. A DA polymer coating is applied on both sides of a commercial polypropylene (PP) separator, and its surface also has abundant lithium-philic triazine groups that can interact with lithium ions and anchor solvent molecules, helping to simplify the lithium ion solvation structure and significantly promote lithium ion transfer. At the same time, the preparation method of this application is simple to operate, has good controllability, short preparation time, and is easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the infrared spectrum of the ArMT material prepared in Example 1 of the present application.

[0027] Figure 2 HAADF and corresponding EDS graphs of the ArMT material prepared in Example 1 of the present application.

[0028] Figure 3 This is the thermogravimetric diagram of the ArMT material prepared in Example 1 of the present application.

[0029] Figure 4 This is the top surface SEM image of the ArMT@PP modified diaphragm prepared in Example 1 of the present application.

[0030] Figure 5 This is a cross-sectional SEM image of the ArMT@PP modified diaphragm prepared in Example 1 of the present application.

[0031] Figure 6 The voltage-time curve of the Li|membrane|Li symmetric battery assembled with the DA polymer coated membrane and the 2400 type PP membrane prepared in Example 1 of the present application.

[0032] Figure 7 Performance diagram of an LFP|membrane|Li (LFP||Li full battery (negative electrode: 100 μmLi) assembled with a DA polymer-coated separator and a PP separator prepared in Example 1 of the present application at a charge and discharge rate of 1C.

[0033] Figure 8 Rate performance diagram of LFP|membrane|Li (LFP||Li full battery (negative electrode: 100um Li) assembled with the DA polymer coated separator and PP separator prepared in Example 1 of the present application.

[0034] Figure 9 Performance diagram of an NCM811|membrane|Li (NCM811|Li full battery (negative electrode: 100 μm Li) assembled with a DA polymer-coated separator and a PP separator prepared in Example 1 of the present application at a charge and discharge rate of 1C.

[0035] Figure 10 The infrared spectra of the NCM811|membrane|Li (NCM811|Li full battery (negative electrode: 100 μmLi) assembled with the DA polymer coated membrane prepared in Example 1 of the present application before and after cycling are shown. DETAILED DESCRIPTION

[0036] The embodiments of the present application will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are merely illustrative of the present application and should not be construed as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. Reagents or instruments not specified by manufacturer are conventional products that can be purchased commercially. In the following examples, the term XRD, a term specific to this area, refers to an X-ray diffractometer. The sodium source and organic reducing agent used are conventional materials commonly used in the art and are not particularly limited herein.

[0037] It should be noted that:

[0038] In this application, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0039] In this application, unless otherwise stated, each reaction or operation step can be carried out sequentially or in a sequential manner. Preferably, the reaction method herein is carried out sequentially.

[0040] Unless otherwise indicated, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to this application.

[0041] This application provides a DA polymer coating for modifying lithium battery separators. The DA polymer coating contains a lithium-philic triazine structure, the structural formula of which is shown below:

[0042] .

[0043] The present application provides a method for preparing the above-mentioned DA polymer coating for modifying a lithium battery separator, the method comprising the following steps:

[0044] S1. Melamine and trimesic acid were dissolved in dimethyl sulfoxide solvent to obtain a transparent clear solution, mixed and heated to react, and poured into deionized water to obtain a white suspension;

[0045] S2. The white suspension obtained in step S1 was centrifuged, washed with deionized water and dried to obtain a precursor MT;

[0046] S3. The precursor obtained in step S2 is calcined to obtain a DA polymer;

[0047] S4. The DA polymer ArMT obtained in step S3 is mixed with a second polymer and an organic solvent to obtain a DA polymer slurry;

[0048] S5. The DA polymer slurry obtained in step S4 is coated on the surface of the base film, and then vacuum dried to form a DA polymer coating on the surface of the base film, and obtain a DA polymer coated separator, wherein the base film is a separator for lithium metal batteries / lithium ion batteries.

[0049] Further technical solutions of the present application: In step S1, the heating temperature is preferably 50-150°C, more preferably 90-110°C, and even more preferably 100°C. In the present application, the heating reaction time is preferably 0.5-4h, more preferably 0.5-2h, and even more preferably 1h. The temperature and time of the heating reaction in the present application are within the above ranges, which is conducive to the subsequent successful preparation of DA polymer for modifying lithium battery separators. In the present application, the dimethyl sulfoxide solvent is an ultra-dry dimethyl sulfoxide solvent.

[0050] A further technical solution of the present application: in step S2, the centrifugal speed is 6000-9000 ppm, more preferably 7000-8500 ppm; further preferably 8000 ppm; the centrifugal time is 5-20 min, more preferably 8-15 min; further preferably 12 min.

[0051] There is no particular restriction on the centrifugal separation method in this application, as long as solid-liquid separation is achieved. There is no particular restriction on the number of deionized water washings in this application, as long as the pH of the washing liquid is 7 to 8. In this application, the drying temperature is preferably 85 to 95°C. There is no particular restriction on the drying time in this application, as long as residual reagents are removed.

[0052] A further technical solution of the present application: In step S3, the calcination temperature is preferably 30-450° C., more preferably 350-450° C., and further preferably 400° C. In the present application, the calcination time is preferably 1-8 hours, more preferably 2-6 hours, and further preferably 4 hours.

[0053] A further technical solution of the present application: in step S4, the second polymer is one or more of polyvinylidene fluoride, polyacrylate, and lithiated polyacrylic acid.

[0054] A further technical solution of the present application: In step S4, the mass ratio of the DA polymer to the second polymer is (0-10):1, more preferably (3-8):1, and further preferably (4-5):1.

[0055] In the present application, the organic solvent in step S4 is preferably N-methylpyrrolidone, and the ratio of the mass of the DA polymer to the volume of the organic solvent is 160 mg: (0.5-1.0) mL.

[0056] A further technical solution of the present application: In step S5, the vacuum drying temperature is 30-100°C, more preferably 50-80°C; the vacuum drying time is preferably 4-24 hours, more preferably 12 hours. The present application controls the vacuum drying temperature and time within the above ranges to achieve complete removal of the organic solvent.

[0057] In step S5 of the present application, the DA polymer slurry is coated on the surface of the base film and then vacuum dried. Preferably, a scraper is used to evenly coat the DA polymer slurry on one side of the base film, and then vacuum dried. The same operation is repeated on the other side of the base film to achieve double-sided coating, thereby forming a DA polymer coating on both sides of the base film.

[0058] In step S5 of the present application, the base film is a separator for lithium metal batteries and / or lithium ion batteries, more preferably a PP film.

[0059] The thickness of the DA polymer coating described in the present application is preferably adjusted by adjusting the height of the doctor blade.

[0060] The present application also provides a lithiophilic DA polymer coating prepared by the above preparation method for modifying a lithium battery separator.

[0061] The present application also provides a battery separator, which is provided with a lithium-philic DA polymer coating prepared by the above-mentioned preparation method for modifying the lithium battery separator.

[0062] In some preferred embodiments, the thickness of the DA polymer coating used to modify the lithium battery separator in this application is preferably 23-26 μm. The thickness of the DA polymer coating used to modify the lithium battery separator in this application is controlled within the above range to facilitate shortening the mass transfer path and reducing the overall impedance. Lighter loads are beneficial for increasing the energy density of the battery.

[0063] The preparation method of the DA polymer coating for modifying the lithium battery separator provided in the present application is simple to operate, has mild reaction conditions, and is suitable for large-scale production.

[0064] The present application also provides the use of the above-mentioned lithium battery separator containing the modified DA polymer coating in lithium metal batteries and / or lithium ion batteries.

[0065] This application applies DA polymer to LMBs. DA polymer materials have many excellent physical and chemical properties, such as high porosity, good thermal stability, high chemical stability and high active site exposure rate. Applying them to lithium batteries is more conducive to the migration of lithium ions. The material of this application is a π-conjugated system that helps electron transfer, thereby reducing polarization and accelerating the reaction kinetics of the battery. A DA polymer coating is applied on both sides of a commercial polypropylene (PP) separator, and its surface also has abundant lithium-philic triazine groups that can interact with lithium ions and anchor solvent molecules, helping to simplify the lithium ion solvation structure and significantly promote lithium ion transfer. At the same time, the preparation method of this application is simple to operate, has good controllability, short preparation time, and is easy to mass produce. In this way, the performance of the modified separator for lithium batteries of this application can show obvious superiority. At a current density of 1C (C = 170mAh g -1 ) can still maintain 125.5 mAh g after 240 cycles -1 , which is much better than the original PP membrane (74.9 mAh g -1 ); and this coating process is simple, saving a lot of costs.

[0066] Next, the DA polymer coating for modifying the lithium battery separator and the preparation method of the sodium ion battery in this application are described in detail with specific examples.

[0067] Explanation of terms

[0068] 2D: two-dimensional structure, such as nanosheet structure;

[0069] SEM: scanning electron microscope;

[0070] TEM: Transmission electron microscope

[0071] LFP: lithium iron phosphate

[0072] NCM811: lithium nickel cobalt manganese oxide (nickel:cobalt:manganese = 8:1:1)

[0073] Super P: Conductive carbon black

[0074] PVDF: polyvinylidene fluoride

[0075] EC: Ethylene carbonate

[0076] DEC: Diethyl carbonate

[0077] FEC: Fluoroethylene carbonate

[0078] LFP|Separator|Li (LFP||Li): Lithium Iron Phosphate|Separator|Lithium

[0079] NCM811 | diaphragm | Li: lithium nickel cobalt manganese oxide | diaphragm | lithium

[0080] Li|Separator|Li Symmetric Cell: Lithium Symmetric Cell

[0081] Example 1 Preparation of DA polymer coating for modifying lithium battery separator

[0082] The preparation method of the DA polymer coating for modifying the lithium battery separator comprises the following steps:

[0083] S1. Equimolar amounts of melamine (MA) and trimesic acid (TMA) were dissolved in dimethyl sulfoxide (DMSO) to form transparent solutions A and B, respectively. Solution B was then added to solution A and stirred thoroughly at 100°C for 1 hour to obtain a clear solution C. Polymerization between MA and TMA then occurred via hydrogen bonding. Solution C was then added to deionized water (DIW) and stirred continuously for 1 hour to form a white suspension.

[0084] S2. The white suspension obtained in step S1 was centrifuged to remove the solvent, the white precipitate was separated, and vacuum dried to obtain a precursor named MT;

[0085] S3. The MT precursor obtained in step S2 was placed in a tube furnace and calcined at 400°C for 4 hours in an argon atmosphere at a heating rate of 2°C min -1 , a DA polymer was obtained and named ArMT;

[0086] S4. The DA polymer ArMT obtained in step S3 and the second polymer polyvinylidene fluoride (PVDF) were thoroughly mixed in an organic solvent, N-methylpyrrolidone (NMP), at a mass ratio of 4:1 to obtain a DA polymer slurry; the mass of the DA polymer to the volume of the organic solvent NMP was 160 mg:0.7 mL;

[0087] S5. Use a scraper to evenly coat the DA polymer slurry obtained in step S4 on one side of a PP membrane (25 μm, Celgard 2400). The coating thickness can be adjusted by adjusting the scraper height. Then, dry the membrane in a vacuum oven at 60°C for 6 h to remove NMP. After coating on one side, repeat the same operation on the other side of the PP membrane to achieve double-sided coating, forming a DA polymer coating on both sides of the base membrane to obtain a DA polymer coated membrane, named ArMT@PP. The thickness of the DA polymer coating on the surface of ArMT@PP is 24 μm.

[0088] The present application conducted performance tests on the DA polymer ArMT material and the ArMT@PP modified diaphragm prepared in Example 1, and the results are as follows: Figure 1-5 shown. Figure 1 The test results are obtained by infrared testing the samples obtained after drying. Figure 1 In the infrared spectrum shown, at 1599 cm -1 A clear -CONH- absorption peak is seen at 2236 cm -1 There is a -C≡N absorption peak at , which indicates the accurate synthesis of ArMT.

[0089] Figure 2 This is the high-angle annular dark field imaging HAADF transmission electron microscope image and the corresponding energy dispersion spectrum EDS image of the ArMT material prepared in Example 1 of the present application. Figure 2 The morphology of the prepared DA polymer was directly observed using HAADF. The ArMT exhibited a porous nanorod-like morphology. The corresponding mapping image revealed a uniform distribution of carbon, nitrogen, and oxygen elements. This unique porous nanorod-like morphology facilitates the full exposure of functional group sites within the structure. These uniformly distributed functional groups interact effectively with solvent molecules and lithium ions, thereby ensuring uniform lithium ion flux, reducing ion channel obstruction, and improving battery performance.

[0090] Figure 3 This is the thermogravimetric diagram of the ArMT material prepared in Example 1 of the present application. Figure 3 Thermogravimetric analysis in the results showed that ArMT exhibited significant mass loss only at 455 °C, indicating its good thermal stability.

[0091] Figure 4This is the top surface SEM image of the ArMT@PP modified diaphragm prepared in Example 1 of this application. Figure 4 The SEM image shows that the nanorod-like DA polymer material ArMT and the binder are evenly distributed on the surface of the PP separator. The pores in the membrane help promote electrolyte wettability, allowing the solvent molecules in the electrolyte and the lithium ions to fully interact with the DA polymer coating on the separator.

[0092] Figure 5 This is a cross-sectional SEM image of the ArMT@PP modified diaphragm prepared in Example 1 of this application. Figure 5 The SEM image in the middle shows the thickness of the modified layer of the prepared modified membrane.

[0093] At the same time, the present application also applies the modified DA polymer coating prepared in Example 1 above to a lithium battery separator, and tests the electrical properties of the lithium battery using the modified DA polymer coating lithium battery separator, as follows:

[0094] The coin cell assembly process involved cutting the DA polymer-coated separator prepared in Example 1 into 19 mm diameter discs as separators, then installing them into CR2025 coin cell batteries (LFP|diaphragm|Li and NCM811|diaphragm|Li) for testing. The battery performance (cyclability and rate capability) of the DA polymer-coated separator prepared in Example 1 was investigated in full cells at room temperature and in two potential ranges, 2.8–4.2 V and 3.0–4.5 V. The LFP and NCM811 cathodes consisted of LFP / NCM811, Super P, and PVDF in a mass ratio of 8:1:1, with active material loadings of approximately 2.3 mg·cm -2 , High loading capacity: 11 mg·cm -2 , and 2.8 mg·cm -2 ; The working electrolyte composition was 1M LiPF6in EC / DEC=1:2 vol% with 10% FEC; All battery assemblies were carried out in an argon-filled glove box with water and oxygen levels below 0.1 ppm.

[0095] In this application, a Li|diaphragm|Li symmetric cell was used to test the repeated shuttling of lithium ions through the separator, explaining the interfacial stability. Compared with the PP separator, the DA polymer-coated separator exhibited faster polarization voltage stabilization, lower overpotential, and longer stable deposition and desorption times, indicating that the rapid evolution of the SEI hindered side reactions between the lithium metal anode and the electrolyte.

[0096] The primary focus is on full LFP / diaphragm / Li cells. Full-cell testing under identical current conditions reveals that the increased specific capacity of cells assembled with DA polymer-coated separators directly demonstrates improved electrochemical performance. High-load LFP batteries require higher stability, while batteries with DA polymer-coated separators significantly unleash greater capacity.

[0097] The NCM811|Separator|Li battery replaces the LFP cathode with the NCM811 ternary lithium cathode material. This material is a lower-cost, lower-theoretical-specific-capacity, high-voltage material with greater commercial value. This battery was assembled primarily to demonstrate the suitability of the DA polymer separator for high-voltage environments.

[0098] According to the same method as above, the DA polymer-coated separator prepared in Example 1 was used as a separator to assemble Li|separator|Li symmetric cells (2025 type button cells) and study the cycling stability of the lithium metal electrode.

[0099] This application uses Land CT2001 produced by Wuhan Landian Electronics Co., Ltd. to perform constant current charge and discharge performance tests.

[0100] In order to evaluate the effect of the DA polymer coating used to modify the lithium battery separator on lithium deposition / stripping, the Li|diaphragm|Li symmetric cells (i.e., lithium symmetric cells) assembled with the DA polymer coating separator prepared in Example 1 and the ordinary PP separator were tested. The Li|diaphragm|Li symmetric cells (100 μm Li) were tested at a current density of 1 mA cm -2 , the surface capacity is 1 mAh·cm -2 The voltage-time curve under the conditions of , the voltage-time curve of the Li|membrane|Li symmetric battery assembled with the DA polymer coating membrane and PP membrane prepared in Example 1 was obtained. Figure 6 As shown, Figure 6 (b) is the DA polymer coating membrane prepared in Example 1, Figure 6 (a) in the figure is a PP separator. In a symmetrical battery system, overpotential and cycle life are important evaluation criteria. Figure 6 It can be seen that compared with the PP separator, ArMT@PP containing a DA polymer coating exhibits a smaller overpotential and polarization angle under the same cycling conditions, indicating that ArMT@PP has higher lithium ion flux and cycling performance. This shows that the DA polymer coated separator prepared in Example 1 provides a higher and more uniform lithium ion flux, and can achieve a lower overpotential and a longer cycle life in a symmetric battery.

[0101] The performance of LFP|membrane|Li(LFP||Li full battery (negative electrode: 100 μm Li) assembled with the DA polymer coating separator prepared in Example 1 and the ordinary PP separator at different charge and discharge rates is shown in the figure below. Figure 7 and Figure 8 As shown, Figure 7 The medium charge and discharge rate is 1C (the initial 10 cycles charge and discharge rate is 0.1C). Figure 9 It is shown that the battery composed of the ArMT@PP modified membrane of the present application has fast reaction kinetics and excellent electrochemical stability, and improves the charge and discharge capacity of the lithium battery.

[0102] The results show that the NCM811|membrane|Li full battery (negative electrode: 100 μm Li) assembled with the DA polymer coating membrane prepared in Example 1 and the ordinary PP membrane has a high capacity at 1C (C = 200 mAh g -1 ) performance diagram as shown in Figure 9 As shown in the figure (the initial 3 cycles of charge and discharge rate is 0.1C), the DA polymer coated separator and the ArMT@PP modified separator show improved electrochemical performance. Figure 9 It can be seen that at high loading (loading: ~11 mg.cm -2 Under the harsh conditions of 240 cycles at 1C, the performance of the DA polymer coated separator ArMT@PP showed obvious superiority, with a specific capacity of 125.5 mAh g after 240 cycles at 1C. -1 , which is much better than the original PP diaphragm (74.9mAh g -1 ), indicating that the ArMT@PP modified separator of the present application significantly improves the charge-discharge capacity and cycle stability of the lithium battery.

[0103] Figure 10 It shows that after 1000 cycles under 1C conditions (NCM811|membrane|Li full electricity), the infrared spectrum of the modified membrane has almost no change, which shows that the chemical stability of the DA polymer material ArMT prepared in this application is very high.

[0104] Control group (using PP diaphragm)

[0105] According to the method of Example 1, the electrical performance of the battery of the control group with the PP separator (25 μm, Celgard 2400) without the DA polymer coating was also tested, as follows:

[0106] The coin cell assembly process involved cutting the PP separator prepared in Example 1 into 19 mm diameter discs as separators, then installing them into CR2025 coin cells (LFP|diaphragm|Li (LFP||Li) and NCM811|diaphragm|Li) for testing. The battery performance (cyclability and rate capability) of the PP separator prepared in Example 1 was investigated in full cells at room temperature and in two potential ranges, 2.8–4.2 V and 3.0–4.5 V. The LFP and NCM811 cathodes consisted of LFP (NCM811), Super P, and PVDF in a mass ratio of 8:1:1, with active material loadings of approximately 2.3 mg cm-3. -2 and 2.8 mg·cm -2 The working electrolyte composition was 1M LiPF6in EC / DEC=1:2 vol% with 10% FEC. All battery assemblies were performed in an argon-filled glove box with water and oxygen levels below 0.1 ppm.

[0107] Following the same method as above, Li|diaphragm|Li symmetric batteries (2025 type button cells) were assembled using the PP separator prepared in the control group as the separator, and the cycling stability of the lithium metal electrode was studied.

[0108] This application uses Land CT2001 produced by Wuhan Landian Electronics Co., Ltd. to perform constant current charge and discharge performance tests.

[0109] The experimental data obtained in this control group has been compared with the data in Example 1, and the performance of Example 1 is better.

[0110] In summary, the modified separator used in the present application is a polymer separator as the main body, and a coating is applied on both sides of the polymer separator, wherein the coating is a lithium-philic DA polymer material. The above-mentioned DA polymer material coating contains a lithium-philic triazine structure, and the enriched triazine group has a high affinity not only for lithium but also for solvent molecules. This synergistic effect promotes desolvation and enhances the lithium ion (Li + ) transport, promoting the uniform deposition of lithium, thereby inhibiting the growth of dendrites, thereby improving the charge and discharge capacity and cycle stability of lithium batteries, giving them fast reaction kinetics and excellent electrochemical stability.

[0111] Specifically, this application incorporates DA polymer into LMBs. DA polymer materials possess numerous excellent physical and chemical properties, such as high porosity, excellent thermal stability, high chemical stability, and high active site exposure. Their application in lithium batteries further facilitates lithium ion migration. The material's π-conjugated system facilitates electron transfer, thereby reducing polarization and accelerating battery reaction kinetics.

[0112] A DA polymer coating is applied on both sides of a commercial polypropylene (PP) separator. The surface of the DA polymer coating has abundant lithium-philic triazine groups that can interact with lithium ions and anchor solvent molecules, helping to simplify the lithium ion solvation structure and significantly promote lithium ion transfer. The preparation method of the present application is simple to operate, has good controllability, and a short preparation time, making it easy to mass-produce. This allows the modified separator for lithium batteries of the present application to demonstrate significant superiority in performance. At a current density of 1C (C = 170 mAh g -1 ) can still maintain 125.5 mAh g after 240 cycles -1 , which is much better than the original PP membrane (74.9 mAh g -1 ); and this coating process is simple, saving a lot of costs.

[0113] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0114] Although several embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and purpose of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A DA polymer coating for modifying a lithium battery separator, characterized in that: The DA polymer coating contains a lithium-philic triazine structure, the structural formula of which is shown below: 。 2. The method for preparing the DA polymer coating for modifying the lithium battery separator according to claim 1, characterized in that: The following steps are involved: S1. Melamine and trimesic acid were dissolved in dimethyl sulfoxide solvent to obtain a transparent clear solution, mixed and heated to react, and poured into deionized water to obtain a white suspension; S2. The white suspension obtained in step S1 was centrifuged, washed with deionized water and dried to obtain a precursor; S3. The precursor obtained in step S2 is calcined to obtain a DA polymer; S4. The DA polymer obtained in step S3 is mixed with a second polymer and an organic solvent to obtain a DA polymer slurry; S5. The DA polymer slurry obtained in step S4 is coated on the surface of the base film, and then vacuum dried to form a DA polymer coating on the surface of the base film, and obtain a DA polymer coated separator, wherein the base film is a separator for lithium metal batteries / lithium ion batteries.

3. The method for preparing a DA polymer coating for modifying a lithium battery separator according to claim 2, wherein: In step S1, the heating reaction temperature is 50-150° C., the heating reaction time is 0.5-4 h, and the dimethyl sulfoxide solvent is an ultra-dry dimethyl sulfoxide solvent.

4. The method for preparing a DA polymer coating for modifying a lithium battery separator according to claim 2, wherein: In step S2, the centrifugal speed is 6000-9000 ppm, and the centrifugal time is 5-20 minutes.

5. The method for preparing a DA polymer coating for modifying a lithium battery separator according to claim 2, wherein: In step S3, the calcination temperature is 350-450° C., and the calcination time is 1-8 hours.

6. The method for preparing a DA polymer coating for modifying a lithium battery separator according to claim 2, wherein: In step S4, the second polymer is one or more of polyvinylidene fluoride, polyacrylate, and lithiated polyacrylic acid.

7. The method for preparing a DA polymer coating for modifying a lithium battery separator according to claim 6, wherein: In step S4, the mass ratio of the DA polymer to the second polymer is (0-10):1, and the mass of the DA polymer is not 0.

8. The method for preparing a DA polymer coating for modifying a lithium battery separator according to claim 2, wherein: In step S5, the vacuum drying temperature is 30-100° C., and the vacuum drying time is 4-24 hours.

9. A lithium battery separator, characterized in that: The separator is provided with a lithium-philic DA polymer coating for modifying a lithium battery separator, which is prepared by the preparation method according to any one of claims 2 to 8, and the thickness of the coating is 23 to 26 microns.

10. Use of the lithium battery separator according to claim 9 in lithium metal batteries and / or lithium ion batteries.

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