A polyetherimide-coated ceramic particle-coated diaphragm and its preparation method

Abstract

The present application discloses a polyetherimide-coated ceramic particle coating diaphragm in the technical field of lithium-ion battery materials. The steps include: S1, dissolving 4,4'-diaminodiphenyl ether and bisphenol A diether dianhydride in N,N-dimethylacetamide to obtain an ODA solution and a BPADA solution; dissolving 4-hydroxyphthalic anhydride in N,N-dimethylacetamide to obtain a 4-HP solution; S2, dropwise adding the BPADA solution to the ODA solution, and then dropwise adding the 4-HP solution to the ODA solution to obtain a polyetherimide solution; S3, adding water and an ethanol solvent to aluminum nitrate and ammonium bicarbonate to obtain an aluminum nitrate solution and an ammonium bicarbonate solution; adding polyethylene glycol to the ammonium bicarbonate solution, and then dropwise adding aluminum nitrate to the ammonium bicarbonate solution. The precipitate is washed and dried to obtain nano-Al2O3 particles; S4, preparing polyetherimide-coated nano-alumina; and S5, preparing a coating diaphragm. The lithium-ion battery (LCO / / HC) assembled with this separator still has a capacity retention rate of 64% at a rate of 100C, and a capacity retention rate of 91% after 1000 cycles.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery materials, and in particular to a polyetherimide-coated ceramic particle-coated diaphragm and a preparation method thereof. Background Art

[0002] Lithium-ion battery separators are a key component of lithium-ion batteries. They maintain the relative position of the battery cells during use, preventing direct contact between the positive and negative electrodes and creating a short circuit. They also provide a pathway for lithium ions to migrate smoothly during charging and discharging. The chemical stability, thermal stability, mechanical strength, and porosity of lithium-ion battery separators significantly impact the performance, safety, and lifespan of lithium-ion batteries.

[0003] Ceramic diaphragms are an improved type of diaphragm based on traditional lithium-ion battery diaphragms. They are produced by coating a layer of ceramic material (such as alumina, boehmite, etc.) on the surface of the diaphragm group (such as polyethylene, polypropylene, etc.). This structure gives the ceramic diaphragm better thermal stability and higher mechanical strength, improving the performance and safety of lithium-ion batteries. The traditional ceramic diaphragm preparation process includes: ceramic powder preparation, slurry preparation, coating, and drying. The main factor affecting the performance of ceramic diaphragms is the unevenness of the ceramic particle slurry. This is due to the interaction between the ceramic particles, such as electrostatic forces, causing smaller particles to agglomerate together and form many irregular agglomerates. As a result, after the ceramic particle slurry is coated on the base membrane, the coating effect is affected.

[0004] During the preparation process of ceramic separators, ceramic particles are prone to uneven distribution and agglomeration, which affects coating thickness and leads to separator defects. Weak bonding between the binder and the base film can also cause ceramic particles to fall off during long-term cycling. These problems can lead to uneven current density within lithium-ion batteries, poor rate performance, and poor cycling performance. Summary of the Invention

[0005] The present invention aims to provide a polyetherimide-coated ceramic particle coated diaphragm and a preparation method thereof, which can be more easily and evenly coated on a base membrane, increase the wetting properties and dielectric constant of the diaphragm, and significantly improve the electrochemical performance of the battery.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a polyetherimide-coated ceramic particle-coated diaphragm comprises the following steps:

[0008] S1. Under an inert gas atmosphere, 4,4'-diaminodiphenyl ether (ODA) and bisphenol A diether dianhydride (BPADA) are dissolved in N,N-dimethylacetamide (DMAc) to obtain an ODA solution and a BPADA solution, respectively; 4-hydroxyphthalic anhydride (4-HP) is dissolved in N,N-dimethylacetamide (DMAc) to obtain a 4-HP solution;

[0009] S2, BPADA solution is added dropwise to ODA solution, inert gas is introduced and stirred, and then 4-HP solution is added dropwise to ODA solution to obtain polyetherimide solution;

[0010] S3, adding aluminum nitrate and ammonium bicarbonate to a solvent consisting of water and ethanol, respectively, to obtain an aluminum nitrate solution and an ammonium bicarbonate solution; adding polyethylene glycol to the ammonium bicarbonate solution, and then adding aluminum nitrate dropwise to the ammonium bicarbonate solution; after continuous stirring, washing, drying, grinding, calcining, and then sieving to obtain nano-Al2O3 particles;

[0011] S4, adding toluene to obtain a suspension, adding KH570 silane coupling agent dropwise to the suspension for sufficient reaction, washing and drying the precipitate obtained by the reaction, and placing it in a container filled with ethanol, introducing an inert gas into the container, and adding a polyetherimide solution to the container; dissolving triethylamine and acetic anhydride in N,N-dimethylacetamide to obtain a triethylamine solution and an acetic anhydride solution, respectively, adding the triethylamine solution and the acetic anhydride solution to the container for stirring and reacting, and washing and drying the product obtained by the reaction to obtain a polyetherimide-coated nano-alumina material;

[0012] S5. Evenly mix polyetherimide-coated nano-aluminum oxide particles with sodium hydroxymethyl cellulose and styrene-butadiene rubber, add a mixed solvent of deionized water and ethanol, and stir until the mixture is evenly mixed to obtain a slurry; apply the obtained slurry on the front side of a commercial polyethylene diaphragm, then dry it, and apply the same method on the back side to obtain a polyetherimide-coated nano-aluminum oxide coated diaphragm.

[0013] Working principle and beneficial effects of the present invention:

[0014] The end-capping of the hydroxyl groups in S1 is an inventive point. The hydroxyl groups replace the heterogeneous groups at the end-capping of the polymer, which promotes the subsequent coating of nanoparticles. S2 uses polyethylene glycol PEG6000 with a molecular weight of 6000. Its surface activity reduces the agglomeration of nano-inorganic ceramic particles during nucleation, and obtains Al2O3 particles with an average particle size of 30nm. S4 uses KH570 silane coupling agent on the surface of the ceramic particles, which helps to form surface functional groups on the surface of the ceramic particles that are combined with the above-mentioned second step. For details, please inquire about the role of silane coupling agent modification. In the second step, only {C 37 H24 O6N2} polyetherimide molecular solution, generally the generated polyetherimide is {C 37 H 24 O6N2} molecule addition polymerization, that is, the chemical composition of the addition polymer is the same as the initial monomer, that is, {C 37 H 24 O6N2}n high molecular product. The formation of polymer is a continuous intensification reaction. The secondary end-capping mechanism here is that the polymer is {C 37 H 24 The hydroxyl groups of O6N2 react with the amino groups on the surface of nano-aluminum oxide to form chemical bonds, making {C 37 H 24 O6N2} is tightly connected with nano-aluminum oxide during the addition polymerization reaction to form a dense protective layer.

[0015] Polyetherimide is a type of polyimide with ether bonds in its molecular chain structure. It is widely used in aerospace, electronic instrumentation and other fields due to its high temperature resistance and low dielectric loss. Coating polyetherimide on the surface of inorganic nano-ceramic particles can reduce the agglomeration between inorganic ceramic particles. The specific principle can be referred to carbon-coated nano-lithium iron phosphate, which makes it easier for the particles to be evenly coated on the base membrane, increasing the permeability of the diaphragm. The improvement in wetting performance comes from the large number of functional groups remaining on the surface of the coated particles.

[0016] This application uses polyetherimide to coat nano-aluminum oxide particles. The polyetherimide forms a protective transition layer on the surface of the inorganic nanoparticles, increasing the strength and dielectric constant of the ceramic diaphragm. The polyetherimide is cross-linked and hydroxylated, increasing the diaphragm's breakdown strength and hydrophilicity, and improving electrolyte wettability. The polymer coating of the inorganic nanoparticles reduces nanoparticle agglomeration and ensures a more uniform dispersion of the nanoparticles.

[0017] The polyetherimide-coated ceramic particles coated diaphragm in this application has a uniform coating thickness, with a thickness range of less than 5% at five points. The diaphragm has a liquid absorption rate of 480%, and no shrinkage occurs after baking at 140°C for 6 hours. The electrochemical window can reach 5V, and the ionic conductivity reaches 2.05mS / cm. The lithium-ion battery (LCO / / HC) assembled using this diaphragm still has a capacity retention rate of 64% at a rate of 100C, and a capacity retention rate of 91% after 1000 cycles.

[0018] Optimally, the BPADA solution is added dropwise to the ODA solution at a rate of 1-2 ml / min.

[0019] Optimally, the solvent in S3 consists of water:ethanol in a volume ratio of 1:1.

[0020] Optimally, the molecular weight of the polyethylene glycol is 6000.

[0021] Preferably, S3 grinds the obtained powder and puts it into a microwave heating furnace for calcination at 1200°C for 2 hours. After cooling, it is ball-milled and sieved to obtain Al2O3 particles with an average particle size of 30 nm.

[0022] Preferably, KH570 silane coupling agent is added dropwise to the suspension at a rate of 1.5 ml / min, ultrasonication is continued for 1 h until uniform dispersion, and the suspension is reacted at 120° C. for 12 h.

[0023] Optimally, the volume ratio of ionized water and ethanol in the S5 mixed solvent is 1:1.

[0024] Optimally, S3 is washed with ethanol; the precipitate in S4 is washed with toluene, and the product obtained by the reaction is washed with ethanol.

[0025] Optimally, S5 bakes the solvent at 60°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the rate performance diagram of the diaphragm;

[0027] Figure 2 The cycle performance diagram is shown in Figure 2. DETAILED DESCRIPTION

[0028] The following is further described in detail through specific implementation methods:

[0029] Example 1: Al2O3 particles + diaphragm

[0030] 2.5 g of aluminum oxide particles were mixed with sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a mass ratio of 94:3:3, 25 ml of a mixed solvent of deionized water and ethanol in a volume ratio of 1:1 was added, and the mixture was stirred for 4 h until the mixture was uniformly mixed; the resulting slurry was coated on the front side of a commercial polyethylene (PE) diaphragm, and the solvent was then dried at 60°C, and the reverse side was coated in the same manner to obtain the diaphragm of Example 1.

[0031] Example 2: A nano-aluminum oxide particle diaphragm was prepared using the same method.

[0032] 20.02g aluminum nitrate (Al(NO3)3) and 60.07g ammonium bicarbonate (NH4HCO3) were added to 200ml of a solvent consisting of water and ethanol in a volume ratio of 1:1, and dissolved by ultrasonication for 1h.

[0033] Add 4.24g of polyethylene glycol (PEG6000, surfactant) with a molecular weight of 6000 to the NH4HCO3 solution and stir for 1h to fully dissolve. Add Al(NO3)3 solution to the NH4HCO3 solution at a rate of 1.5mL / min, ultrasonicate for 15min, and continue stirring for 30min. Then filter and separate the precipitate, wash it with a mixed solvent of water and ethanol for 3-5 times, and dry it in a vacuum drying oven at 80℃ for 2h. Grind the obtained powder and calcine it in a microwave heating furnace, keeping it warm at 1200℃ for 2h. After cooling, ball mill the sample and sieve it to obtain Al2O3 particles with an average particle size of 30nm.

[0034] 2.5g of Al2O3 particles were mixed evenly with sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a mass ratio of 94:3:3, 25ml of a mixed solvent of deionized water and ethanol in a volume ratio of 1:1 was added, and stirred for 4h until the mixture was uniform; the resulting slurry was coated on the front of a commercial polyethylene (PE) diaphragm, and then the solvent was dried at 60°C, and the back was coated in the same way to obtain a nano-alumina particle diaphragm.

[0035] Example 3: A method for preparing a polyetherimide-coated ceramic particle-coated diaphragm, comprising the following steps:

[0036] S1. Under an inert gas atmosphere (argon or helium), 4.42 g of 4,4'-diaminodiphenyl ether (ODA) and 10.39 g of bisphenol A diether dianhydride (BPADA) were dissolved in 100 ml of N,N-dimethylacetamide (DMAc) and sonicated for 1 h; 0.34 g of 4-hydroxyphthalic anhydride (4-HP) was dissolved in 5 ml of N,N-dimethylacetamide (DMAc) and sonicated for 1 h;

[0037] S2. At room temperature, add the dispersed ODA solution into a 500ml three-necked flask, introduce inert gas and stir for 1h; add the dispersed BPADA solution dropwise into the flask at a rate of 1ml / min, and continue stirring for 8h after the addition is completed (this process generates a polyetherimide solution); then add the 4-HP solution dropwise into the flask (this process caps the hydroxyl groups of the generated polyetherimide and increases the affinity of the polyetherimide with the nanoparticles).

[0038] S3, add 20.02g aluminum nitrate (Al(NO3)3)3) and 60.07g ammonium bicarbonate (NH4HCO3) into 200ml of a solvent consisting of water and ethanol in a volume ratio of 1:1, and dissolve them by ultrasonication for 1h;

[0039] 4.24 g of polyethylene glycol (PEG6000, a surfactant) with a molecular weight of 6000 was added to the NH4HCO3 solution and stirred for 1 hour to fully dissolve. The Al(NO3)3 solution was dripped into the NH4HCO3 solution at a rate of 1.5 mL / min. After ultrasonication for 15 minutes, stirring was continued for 30 minutes. The precipitate was then filtered and separated, washed 3-5 times with a mixed solvent of water and ethanol, and dried in a vacuum drying oven at 80°C for 2 hours. The resulting powder was ground and calcined in a microwave oven at 1200°C for 2 hours. After cooling, the sample was ball-milled and sieved to obtain Al2O3 particles with an average particle size of 30 nm.

[0040] S4, 10g of nano-Al2O3 particles were placed in a 1000ml flask, 650ml of toluene was added, and ultrasonic dispersion was performed for 1h to form a suspension; 11ml of KH570 silane coupling agent was added, and the addition rate was slowly dropped at 1.5ml / min, and ultrasonic dispersion was continued for 1h until uniform dispersion was achieved; the suspension was reacted at 120°C for 12h (surface amination); the precipitate was then washed 3-5 times with toluene, and after drying, the particles were placed in 150ml of ethanol in a three-necked flask with argon gas and ultrasonic dispersion was performed for 1h; the polyetherimide solution prepared above was added, 6.67g of triethylamine and 6.74g of acetic anhydride were dissolved in 20ml of N, N-dimethylacetamide (DMAc), ultrasonic dispersion was performed for 1h, the triethylamine solution and the acetic anhydride solution were added to the three-necked flask, and the reaction was terminated after stirring for 24h; the product was washed 3-5 times with ethanol and dried at 80°C to obtain a polyetherimide-coated nano-alumina material;

[0041] S5. Mix 2.5 g of polyetherimide-coated nano-aluminum oxide particles with sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a mass ratio of 94:3:3, add 25 ml of a mixed solvent of deionized water and ethanol in a volume ratio of 1:1, and stir for 4 hours until the mixture is uniform; apply the resulting slurry on the front of a commercial polyethylene (PE) diaphragm, then dry the solvent at 60°C, and apply the same method on the back to obtain a polyetherimide-coated nano-aluminum oxide coated diaphragm.

[0042] Example 4: PE original diaphragm.

[0043] The diaphragms prepared in Examples 1 to 4 were assembled into lithium-ion batteries and subjected to rate performance and cycle tests. Figure 1 and Figure 2 As shown, from Figure 1 and Figure 2 It can be seen that the polyetherimide-coated nano-aluminum oxide-coated diaphragm prepared in Example 3 is superior to Example 1, Example 2 and Example 4 in rate performance and number of cycles.

[0044] The polyetherimide-coated ceramic particles coated diaphragm in this application has a uniform coating thickness, with a thickness range of less than 5% at five points. The diaphragm has a liquid absorption rate of 480%, and no shrinkage occurs after baking at 140°C for 6 hours. The electrochemical window can reach 5V, and the ionic conductivity reaches 2.05mS / cm. The lithium-ion battery (LCO / / HC) assembled using this diaphragm still has a capacity retention rate of 64% at a rate of 100C, and a capacity retention rate of 91% after 1000 cycles.

Claims

1. A method for preparing a polyetherimide-coated ceramic particle-coated diaphragm, characterized in that: The following steps are included: S1. Under an inert gas atmosphere, 4,4'-diaminodiphenyl ether (ODA) and bisphenol A diether dianhydride (BPADA) are dissolved in N,N-dimethylacetamide (DMAc) to obtain an ODA solution and a BPADA solution, respectively; 4-hydroxyphthalic anhydride (4-HP) is dissolved in N,N-dimethylacetamide (DMAc) to obtain a 4-HP solution; S2, BPADA solution is added dropwise to ODA solution, inert gas is introduced and stirred, and then 4-HP solution is added dropwise to ODA solution to obtain polyetherimide solution; S3, adding aluminum nitrate and ammonium bicarbonate to a solvent consisting of water and ethanol, respectively, to obtain an aluminum nitrate solution and an ammonium bicarbonate solution; adding polyethylene glycol to the ammonium bicarbonate solution, and then adding aluminum nitrate dropwise to the ammonium bicarbonate solution; after continuous stirring, washing, drying, grinding, calcining, and then sieving to obtain nano-Al2O3 particles; S4, adding toluene to obtain a suspension, adding KH570 silane coupling agent dropwise to the suspension for sufficient reaction, washing and drying the precipitate obtained by the reaction, and placing it in a container filled with ethanol, introducing an inert gas into the container, and adding a polyetherimide solution to the container; dissolving triethylamine and acetic anhydride in N,N-dimethylacetamide to obtain a triethylamine solution and an acetic anhydride solution, respectively, adding the triethylamine solution and the acetic anhydride solution to the container for stirring and reacting, and washing and drying the product obtained by the reaction to obtain a polyetherimide-coated nano-alumina material; S5. Evenly mix polyetherimide-coated nano-aluminum oxide particles with sodium hydroxymethyl cellulose and styrene-butadiene rubber, add a mixed solvent of deionized water and ethanol, and stir until the mixture is evenly mixed to obtain a slurry; apply the obtained slurry on the front side of a commercial polyethylene diaphragm, then dry it, and apply the same method on the back side to obtain a polyetherimide-coated nano-aluminum oxide coated diaphragm.

2. The method for preparing a diaphragm coated with etherimide-coated ceramic particles according to claim 1, characterized in that: The BPADA solution was added dropwise to the ODA solution at a rate of 1-2 ml / min.

3. The method for preparing a diaphragm coated with etherimide-coated ceramic particles according to claim 2, characterized in that: S3 is a solvent consisting of water and ethanol in a volume ratio of 1:

1.

4. The method for preparing a diaphragm coated with etherimide-coated ceramic particles according to claim 3, characterized in that: The molecular weight of polyethylene glycol is 6000.

5. The method for preparing a diaphragm coated with etherimide-coated ceramic particles according to claim 4, characterized in that: S3 grinds the obtained powder and puts it into a microwave heating furnace for calcination at 1200°C for 2 hours. After cooling, it is ball-milled and sieved to obtain Al2O3 particles with an average particle size of 30 nm.

6. The method for preparing a diaphragm coated with etherimide-coated ceramic particles according to claim 5, characterized in that: KH570 silane coupling agent was added dropwise to the suspension at a rate of 1.5 ml / min, and ultrasonic treatment was continued for 1 h until the suspension was uniformly dispersed. The suspension was reacted at 120° C. for 12 h.

7. The method for preparing a diaphragm coated with etherimide-coated ceramic particles according to claim 6, characterized in that: The volume ratio of ionized water and ethanol in the S5 mixed solvent is 1:

1.

8. The method for preparing a diaphragm coated with etherimide-coated ceramic particles according to claim 7, characterized in that: S3 was washed with ethanol; the precipitate in S4 was washed with toluene, and the product obtained by the reaction was washed with ethanol.

9. The method for preparing a diaphragm coated with etherimide-coated ceramic particles according to claim 8, characterized in that: S5: drying the solvent at 60°C. 10 . A diaphragm prepared according to the method for preparing a diaphragm coated with etherimide-coated ceramic particles according to any one of claims 1 to 9 .

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