Boehmite composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a boehmite composite material and a preparation method and application thereof. The boehmite composite material comprises a matrix layer and a coating layer located on at least part of the surface of the matrix layer, and the matrix layer comprises a boehmite matrix material and a grafting layer located on the surface of the boehmite matrix material; the grafting layer comprises a phosphate ester layer and an epoxy silane layer which are arranged in sequence; and the coating layer contains polydopamine. According to the boehmite composite material disclosed by the invention, the phosphate ester layer in the grafting layer can provide a stable inorganic-organic interface, and the epoxy silane layer can endow reaction active sites, so that Van der Waals' force can be generated with a binder to strengthen entanglement and enhance chemical bonding with a current collector; further, the structural stability of the coating containing the boehmite composite material and the binding force with the current collector are improved; the polydopamine coating layer can provide a physical anchoring point and buffer stress. The boehmite composite material disclosed by the invention has high stability and excellent interface performance.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a boehmite composite material and a preparation method and application thereof. Background Art

[0002] Boehmite (γ-AlOOH), a low-cost, highly thermally stable inorganic material, has a wide range of applications in lithium battery separator coatings, ceramic-reinforced composites, and functional fillers. However, its practical application faces the following key bottlenecks:

[0003] 1) Insufficient interfacial adhesion: The hydroxyl groups (Al-OH) on the surface of conventional boehmite are highly polar and incompatible with organic binders when used in polymer-based composites (such as PVDF-bonded electrode coatings), resulting in weak interfacial adhesion. During roll-forming or charge-discharge cycling of lithium-ion battery electrodes, the boehmite coating can easily peel from the current collector or active material surface, causing coating shedding, increased battery internal resistance, and even the risk of short circuits.

[0004] 2) The modification method is single and has poor stability: Current surface modification technologies for boehmite mostly rely on a single silane coupling agent, whose hydrolysis reaction depends on the ambient humidity. It is prone to self-condensation (such as Si-O-Si cross-linking) under dry or high humidity conditions, resulting in uneven coating on the boehmite surface. Moreover, when exposed to the electrolyte for a long time, the Si-O bond is easily hydrolyzed and broken, causing interface failure.

[0005] 3) Prominent electrochemical side effects: Some studies have attempted to use long-chain organic acids to hydrophobically modify boehmite to improve dispersibility, but these modifiers will increase interfacial impedance.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] One object of the present invention is to provide a boehmite composite material to solve the above-mentioned technical problems. The boehmite composite material of the present invention is conducive to enhancing the entanglement with the binder and the chemical bonding effect with the current collector, thereby improving the bonding force between the coating containing the boehmite composite material and the current collector; the polydopamine coating layer can provide physical anchor points and buffer stress, thereby improving interface performance.

[0008] Another object of the present invention is to provide a method for preparing a boehmite composite material, which is simple, easy to implement, and environmentally friendly, and the obtained boehmite composite material has excellent interface properties and structural stability.

[0009] Another object of the present invention is to provide a pole piece.

[0010] Another object of the present invention is to provide a battery.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0012] A boehmite composite material comprises a base layer and a coating layer located on at least a portion of the surface of the base layer, wherein the base layer comprises a boehmite base material and a graft layer located on the surface of the boehmite base material; the graft layer comprises a phosphate layer and an epoxy silane layer arranged in sequence; and the coating layer comprises polydopamine.

[0013] In some embodiments, the phosphate layer comprises P═O.

[0014] In some embodiments, the mass of the phosphate layer is 1% to 3% of the mass of the boehmite matrix material.

[0015] In some embodiments, the epoxy silane layer comprises O—Si—R, where R comprises an epoxy group.

[0016] In some embodiments, the weight of the epoxy silane layer accounts for 2% to 5% of the weight of the boehmite matrix material.

[0017] In some embodiments, the graft layer comprises

[0018] In some embodiments, the mass of the coating layer is 0.5% to 1% of the mass of the boehmite matrix material.

[0019] In some embodiments, the particle size D50 of the boehmite matrix material is 1 to 1.5 μm, and the specific surface area of ​​the boehmite matrix material is 75 to 90 m 2 / g.

[0020] In some embodiments, the surface of the boehmite matrix material contains hydroxyl groups, the boehmite matrix material forms a chemical bond with the phosphate layer, and the matrix layer comprises

[0021]

[0022] A method for preparing a boehmite composite material comprises the following steps:

[0023] The boehmite raw material is activated to obtain an activated boehmite system; the activated boehmite system is mixed with a phosphate ester and subjected to a first heat treatment to obtain a first boehmite material; a liquid phase system containing epoxy silane is mixed with a dispersion of the first boehmite material and subjected to a second heat treatment to obtain a base layer material; the base layer material is mixed with a dopamine hydrochloride solution to form a coating layer on the surface of the base layer material to obtain a boehmite composite material.

[0024] In some embodiments, the activation treatment specifically includes: drying the boehmite raw material, and then mixing it with an alcohol solvent and water to obtain a first system; using hydrochloric acid to adjust the pH of the first system to 3.5-4, and after stirring and ultrasonic treatment, obtaining an activated boehmite system.

[0025] In some embodiments, during the activation treatment, the mass ratio of the boehmite raw material, the alcohol solvent, and water is (100-200):(600-750):(100-250).

[0026] In some embodiments, during the activation treatment, the drying temperature is 100-130° C., and the drying time is 2-5 hours.

[0027] In some embodiments, during the activation treatment, the stirring speed is 800-1200 rpm, the stirring time is 2-6 hours, the ultrasonic treatment power is 300-500 W, the ultrasonic treatment temperature is 30-45° C., and the ultrasonic treatment time is 20-40 minutes.

[0028] In some embodiments, the phosphate ester includes at least one of diethyl vinyl phosphate and 1-(dimethoxyphosphine) diethyl vinyl phosphate.

[0029] In some embodiments, the mass of the phosphate ester accounts for 1% to 3% of the mass of the boehmite raw material.

[0030] In some embodiments, the temperature of the first heat treatment is 50-70° C., and the time of the first heat treatment is 1-3 hours.

[0031] In some embodiments, the mixed system after the first heat treatment is subjected to solid-liquid separation, and the solids are collected, washed, and dried to obtain the first boehmite material.

[0032] In some embodiments, the liquid phase system containing epoxy silane includes epoxy silane, a catalyst, an alcohol solvent and water, the volume ratio of the epoxy silane, the alcohol solvent and water is 1:(7-9):(1-2), and the mass percentage of the catalyst to the epoxy silane is 0.1% to 0.6%.

[0033] In some embodiments, in the liquid phase system containing epoxy silane, the epoxy silane comprises at least one of 3-glycidyloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and (3-glycidoxypropyl)methyldiethoxysilane.

[0034] In some embodiments, the dispersion of the first boehmite material includes the first boehmite material and an alcohol solvent, and the solid content of the first boehmite material is 8% to 12%.

[0035] In some embodiments, the mass of the epoxy silane accounts for 2% to 5% of the mass of the boehmite raw material.

[0036] In some embodiments, the temperature of the second heat treatment is 40-55° C., and the time of the second heat treatment is 2-5 hours.

[0037] In some embodiments, the mixed system after the second heat treatment is subjected to solid-liquid separation, and the solids are collected, washed, and dried to obtain the base layer material.

[0038] In some embodiments, the mass of the dopamine hydrochloride is 8% to 12% of the mass of the base layer material.

[0039] In some embodiments, the mixing treatment is performed by constant temperature oscillation treatment at a temperature of 20 to 30° C., an amplitude of 4 to 6 cm, and a frequency of 100 to 130 times / min.

[0040] In some embodiments, the mixing treatment time is 10 to 15 hours.

[0041] In some embodiments, the mixed system after the mixing treatment is subjected to solid-liquid separation, and the solids are collected and washed and dried.

[0042] A pole piece comprises an edge coating, wherein the edge coating comprises the boehmite composite material, or the boehmite composite material obtained by the preparation method of the boehmite composite material, and a binder.

[0043] A battery comprises the pole piece.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The boehmite composite material of the present invention has a phosphate layer in the grafted layer that can provide a stable inorganic-organic interface, and an epoxysilane layer that can provide reactive sites, which are conducive to generating van der Waals forces to strengthen entanglement with the binder and enhance chemical bonding with the current collector, thereby improving the structural stability of the coating containing the boehmite composite material and its binding force with the current collector; the polydopamine coating layer can provide physical anchoring points and buffer stress. The boehmite composite material of the present invention has high stability and excellent interfacial properties.

[0046] (2) The method for preparing the boehmite composite material of the present invention first activates the boehmite raw material to enrich its surface with hydroxyl groups, forming Al-OH and improving its surface reactivity. The activated boehmite system is mixed with a phosphate ester and subjected to a first heat treatment, whereupon the phosphate ester reacts with the Al-OH to form a first boehmite material (phosphate modified). A liquid phase system containing epoxy silane is mixed with a dispersion of the first boehmite material and subjected to a second heat treatment to form a three-dimensional covalent network matrix layer material (Al-OPO-Si≡). The surface of the matrix layer is then coated with a polydopamine layer to enhance the interfacial properties.

[0047] (3) The boehmite composite material of the present invention can form a better cross-linking effect with the binder and form a better chemical bond with the current collector, thereby improving the bonding performance between the edge coating and the current collector, and can improve the electrochemical performance of the electrode, thereby improving the structural stability, cycle performance, rate performance and safety performance of the battery. DETAILED DESCRIPTION

[0048] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0049] According to one aspect of the present invention, the present invention relates to a boehmite composite material, comprising a base layer and a coating layer located on at least a portion of the surface of the base layer, wherein the base layer comprises a boehmite base material and a grafted layer located on the surface of the boehmite base material; the grafted layer comprises a phosphate layer and an epoxy silane layer arranged in sequence; and the coating layer comprises polydopamine.

[0050] The boehmite composite material of the present invention comprises a phosphate layer in the grafted layer that provides a stable inorganic-organic interface, and an epoxysilane layer that provides reactive sites, which facilitate van der Waals force-enhanced entanglement with the binder and enhance chemical bonding with the current collector. This improves the structural stability of the coating containing the boehmite composite material and its binding strength with the current collector. The polydopamine coating layer provides physical anchoring points and buffers stress. The boehmite composite material of the present invention exhibits high stability and excellent interfacial properties.

[0051] In some embodiments, the phosphate layer comprises P=O. In some embodiments, the mass of the phosphate layer is 1% to 3% of the mass of the boehmite matrix material, for example, 1%, 2%, 3%, etc. The present invention grafts an appropriate proportion of the phosphate layer onto the surface of the boehmite matrix material, thereby further facilitating the grafting of the epoxy silane layer and improving the performance of the grafted layer.

[0052] In some embodiments, the epoxy silane layer comprises O-Si-R, where R comprises an epoxy group. In some embodiments, the mass of the epoxy silane layer accounts for 2% to 5% of the mass of the boehmite matrix material. The present invention further improves the interfacial properties of the boehmite matrix material by grafting an appropriate amount of epoxy silane onto the surface of the boehmite matrix material modified with the phosphate layer.

[0053] In some embodiments, the phosphate layer and the epoxy silane layer can form a bond to form a graft layer, and the graft layer includes

[0054] In some embodiments, the mass of the coating layer is 0.5% to 1% of the mass of the boehmite matrix material. A suitable coating layer is more conducive to ensuring that the surface has abundant physical anchoring and improving the effect of buffering stress.

[0055] In some embodiments, the particle size D50 of the boehmite matrix material is 1 to 1.5 μm, such as 1 μm, 1.1 μm, 1.2 μm, 1.3 μm or 1.5 μm, or any range therebetween. In some embodiments, the specific surface area of ​​the boehmite matrix material is 75 to 90 m 2 / g, for example 75m 2 / g、80m 2 / g、85m 2 / g or 90m 2 / g, etc. The boehmite matrix of the present invention has a suitable particle size D50 and specific surface area, which is beneficial to provide more sites for hydroxyl groups to ensure the grafting effect with the graft layer.

[0056] In some embodiments, the surface of the boehmite matrix material contains hydroxyl groups, the boehmite matrix material forms a bond with the phosphate layer, and the matrix layer comprises The grafted layer of the present invention has improved the performance of the boehmite matrix and provided more reactive sites through the bonding action of the above-mentioned chemical bonds.

[0057] According to another aspect of the present invention, the present invention also relates to a method for preparing a boehmite composite material, comprising the following steps:

[0058] The boehmite raw material is activated to obtain an activated boehmite system. The activated boehmite system is mixed with a phosphate ester and subjected to a first heat treatment to obtain a first boehmite material. A liquid phase system containing epoxy silane is mixed with a dispersion of the first boehmite material and subjected to a second heat treatment to obtain a base layer material. The base layer material is mixed with a dopamine hydrochloride solution to form a coating layer on the surface of the base layer material to obtain a boehmite composite material.

[0059] The present invention provides a method for preparing a boehmite composite material. First, the boehmite raw material is activated to enrich its surface with hydroxyl groups, forming Al-OH groups and improving its surface reactivity. The activated boehmite system is mixed with a phosphate ester and subjected to a first heat treatment, whereupon the phosphate ester reacts with the Al-OH groups to form a first boehmite material (phosphate-modified). A liquid phase system containing epoxy silane is mixed with a dispersion of the first boehmite material and subjected to a second heat treatment to form a three-dimensional covalent network matrix layer material (Al-OPO-Si≡). The surface of the matrix layer is then coated with a polydopamine layer to enhance interfacial properties.

[0060] In some embodiments, the activation treatment specifically includes: drying the boehmite raw material, then mixing it with an alcohol solvent and water to form a first system; adjusting the pH of the first system to 3.5-4 (e.g., 3.5, 3.7, or 4) using hydrochloric acid, and obtaining an activated boehmite system after stirring and ultrasonic treatment. During the activation treatment, the mass ratio of the boehmite raw material, the alcohol solvent, and the water is (100-200): (600-750): (100-250), for example, 100:600:100, 150:650:200, 200:700:250, etc. In some embodiments, during the activation treatment, the drying temperature is 100-130°C, for example, 100°C, 110°C, 130°C, etc., and the drying time is 2-5h, for example, 2h, 3h, 4h, or 5h, etc. In some embodiments, during the activation treatment, the stirring speed is 800 to 1200 rpm, such as 800 rpm, 1000 rpm, 1200 rpm, etc. The stirring time is 2 to 6 hours, such as 2 hours, 3 hours, 4 hours, 5 hours or 6 hours, etc. The power of the ultrasonic treatment is 300 to 500 W, such as 300 W, 350 W, 400 W, 500 W, etc. The temperature of the ultrasonic treatment is 30 to 45 ° C, such as 30 ° C, 35 ° C, 40 ° C or 45 ° C, etc. The ultrasonic treatment time is 20 to 40 minutes, such as 20 minutes, 30 minutes or 40 minutes, etc. The present invention adopts the above-mentioned suitable activation treatment conditions to make the surface of the boehmite raw material rich in hydroxyl groups, which is beneficial to the subsequent grafting reaction.

[0061] In some embodiments, the activated boehmite system is mixed with a phosphate ester (vinyl diethyl phosphate) and subjected to a first heat treatment to obtain a first boehmite material, and the bonding mechanism of the reaction includes: AlOOH-OH+(C2H5O)2P(O)CH2CH2→Al-OP(O)(OC2H5)2+H2O.

[0062] In some embodiments, covalently bonding the epoxy silane to the first boehmite material comprises:

[0063] ≡Si-OCH3+H2O→≡Si-OH+CH3OH

[0064] ≡Si-OH+Al-OP(O)(OC2H5)2→Al-OPO-Si≡.

[0065] In some embodiments, the phosphate ester includes at least one of diethyl vinyl phosphate and 1-(dimethoxyphosphine) vinyl diethyl phosphate. In some embodiments, the mass of the phosphate ester accounts for 1% to 3% of the mass of the boehmite raw material, for example, 1%, 1.5%, 2%, 3%, etc. The present invention controls the thickness of the phosphate-modified layer on the surface of the boehmite raw material by limiting the percentage of the mass of the phosphate ester to the mass of the boehmite raw material.

[0066] In some embodiments, the temperature of the first heat treatment is 50-70°C, for example, 50°C, 55°C, 60°C, 70°C, etc., and the time of the first heat treatment is 1-3 hours, for example, 1 hour, 2 hours, or 3 hours. By limiting the temperature and time of the first heat treatment, the present invention is more conducive to the bonding reaction between the phosphate ester and the activated boehmite raw material, thereby forming a phosphate ester chemical bonding layer.

[0067] In some embodiments, the mixed system after the first heat treatment is subjected to solid-liquid separation, and the solids are collected, washed, and dried to obtain the first boehmite material. Washing is performed sequentially with anhydrous ethanol, acetone, and distilled water, with the number of washes being 2 to 4. The drying temperature is 50 to 70° C., and vacuum drying can be used.

[0068] In some embodiments, the liquid phase system containing epoxy silane includes epoxy silane, a catalyst (including an aqueous ammonia solution), an alcohol solvent, and water. The volume ratio of the epoxy silane, the alcohol solvent, and water is 1:(7-9):(1-2), for example, 1:7:1, 1:7.5:1.5, 1:8:2, etc. The mass percentage of the catalyst to the epoxy silane is 0.1% to 0.6%, for example, 0.1%, 0.2%, 0.3%, 0.5%, or 0.6%. In some embodiments, in the liquid phase system containing epoxy silane, the epoxy silane includes 3-glycidyloxypropyltrimethoxysilane, the epoxy silane includes at least one of 3-glycidyloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and (3-glycidoxypropyl)methyldiethoxysilane. The components in the liquid phase system containing epoxy silane of the present invention have a suitable ratio to better achieve the condensation reaction between epoxy silane and the first boehmite material.

[0069] In some embodiments, the dispersion of the first boehmite material includes the first boehmite material and an alcohol solvent, and the solid content of the first boehmite material is 8% to 12%, for example, 8%, 9%, 10%, 11%, or 12%. In some embodiments, a liquid phase system containing epoxy silane is added dropwise to the dispersion of the first boehmite material.

[0070] In some embodiments, the mass of the epoxy silane accounts for 2% to 5% of the mass of the boehmite raw material, for example, 2%, 3%, 4%, 5%, etc. By limiting the mass percentage of the epoxy silane to the mass percentage of the boehmite raw material, the polymerization reaction of the epoxy silane with the phosphate layer of the first boehmite material is more favorable to form the epoxy silane molecular entanglement layer.

[0071] In some embodiments, the temperature of the second heat treatment is 40-55° C., for example, 40° C., 45° C., 50° C., 55° C., etc. The duration of the second heat treatment is 2-5 hours, for example, 2 hours, 3 hours, 4 hours, or 5 hours, etc. The present invention adopts appropriate second heat treatment conditions to ensure efficient reaction between the epoxy silane and the first boehmite material.

[0072] In some embodiments, the mixed system after the second heat treatment is subjected to solid-liquid separation, and the solids are collected, washed, and dried to obtain the substrate layer material. Washing is performed sequentially with anhydrous ethanol, acetone, and distilled water, with the number of washes being 2 to 4. The drying temperature is 50 to 65°C, and vacuum drying can be used.

[0073] In some embodiments, the mass of the dopamine hydrochloride is 8% to 12% of the mass of the base layer material, for example 8%, 9%, 10%, 11% or 12%. The present invention uses a suitable proportion of dopamine hydrochloride to form a uniform polydopamine coating layer of suitable thickness on the surface of the base layer material.

[0074] In some embodiments, the mixing treatment is performed by constant temperature oscillation treatment, with a temperature of 20-30°C, a flow rate of 20°C, 25°C, 30°C, etc.; an amplitude of 4-6 cm, such as 4 cm, 5 cm, or 6 cm; and a frequency of 100-130 times / min, such as 100 times / min, 120 times / min, or 130 times / min. The mixing treatment time is 10-15 hours, such as 10 hours, 11 hours, 12 hours, 13 hours, or 15 hours. The present invention adopts appropriate mixing treatment conditions to ensure that dopamine forms a uniform coating layer of appropriate thickness on the surface of the substrate material, thereby improving its surface properties.

[0075] In some embodiments, the mixed system after the mixing treatment is subjected to solid-liquid separation, and the solids are collected, washed, and dried. Washing is performed sequentially with anhydrous ethanol, acetone, and distilled water, with the number of washes being 2 to 4. The drying temperature is 50 to 70° C., and vacuum drying can be used.

[0076] According to another aspect of the present invention, the present invention also relates to a pole piece, comprising an edge coating, wherein the edge coating comprises the boehmite composite material, or the boehmite composite material obtained by the preparation method of the boehmite composite material, and a binder (such as PVDF).

[0077] The boehmite composite material of the present invention can form a better cross-linking effect with the binder, form a better chemical bond with the current collector, improve the bonding performance between the edge coating and the current collector, and improve the electrochemical performance of the pole piece.

[0078] According to another aspect of the present invention, the present invention also relates to a battery comprising the pole piece

[0079] The battery of the present invention has excellent structural stability, cycle performance and rate performance and good safety.

[0080] The following is further explained with reference to specific embodiments and comparative examples.

[0081] Example 1

[0082] A method for preparing a boehmite composite material comprises the following steps:

[0083] (1) Take 150g of boehmite powder (purchased from Shandong Guoci, D50 is 1.2μm, specific surface area is 2.5m 2 / g, pH 7.5), vacuum dried at 120°C for 4 h, 680 g of anhydrous ethanol and 170 g of deionized water were added thereto, 0.1 M hydrochloric acid was added to adjust the pH to 3.6, and mechanically stirred at 1000 rpm for 5 h. The mixture was then ultrasonically dispersed uniformly at an ultrasonic power of 400 W and a temperature of 40°C for 30 min to obtain an activated boehmite system.

[0084] (2) Under nitrogen protection, 4 g of vinyl diethyl phosphate was slowly added to the above-mentioned uniformly dispersed activated boehmite system, and the reaction was carried out at 60°C for 2 h. The resulting first system was centrifuged and the supernatant was discarded. The resulting solid was washed twice with anhydrous ethanol, acetone, and distilled water, respectively, and then vacuum-dried at 60°C to form a phosphate-modified boehmite, thereby obtaining a first boehmite material.

[0085] (3) Preparation of an epoxysilane liquid phase system: 3-glycidyloxypropyltrimethoxysilane (GPTMS); catalyst: 0.5 wt% ammonia solution (analytical grade); mixing ratio: GPTMS: ethanol: water = 1:8:1 (volume ratio). Hydrolysis-condensation reaction: The first boehmite material was redispersed in ethanol (solid content 10%), and the above-mentioned epoxysilane liquid phase system was added dropwise thereto, with the mass of epoxysilane accounting for 3% of the mass of the boehmite raw material; the reaction was carried out at a constant temperature of 50°C for 4 hours, the resulting mixture was centrifuged and the supernatant was discarded, and the resulting solid was washed twice with anhydrous ethanol, acetone, and distilled water, respectively. Vacuum drying was carried out at 60°C to form a cycloalkylsilane layer, thereby obtaining the substrate layer material.

[0086] (4) 1000 mL of dopamine hydrochloride solution (10 mg / mL) was added to 100 g of the matrix layer material, and the mixture was shaken at a constant temperature of 25°C (amplitude 5 cm, frequency 120 times / min) for 12 h. The mixed solution changed from colorless to brown-black. The obtained mixed solution was centrifuged and the supernatant was discarded. The obtained solid was washed twice with anhydrous ethanol, acetone and distilled water respectively and sequentially, and vacuum dried at 60°C to obtain a boehmite composite material.

[0087] Example 2

[0088] A method for preparing a boehmite composite material comprises the following steps:

[0089] (1) Take 150g of boehmite powder (purchased from Shandong Guoci, D50 is 1.2μm, specific surface area is 2.5m 2 / g, pH 7.5), vacuum dried at 110°C for 4.5 h, 700 g of anhydrous ethanol and 180 g of deionized water were added thereto, 0.1 M hydrochloric acid was added to adjust the pH to 3.8, and mechanical stirring was performed at 1100 rpm for 5 h. The mixture was then uniformly dispersed by ultrasonication at an ultrasonic power of 450 W and a temperature of 35°C for 35 min to obtain an activated boehmite system.

[0090] (2) Under nitrogen protection, 4.2 g of 1-(dimethoxyphosphine)vinyl diethyl phosphate was slowly added to the above-mentioned uniformly dispersed activated boehmite system, and the reaction was carried out at 65°C for 1.5 hours. The resulting first system was centrifuged and the supernatant was discarded. The resulting solid was washed twice with anhydrous ethanol, acetone, and distilled water, respectively, and then vacuum-dried at 60°C to form a phosphate-modified boehmite, thereby obtaining a first boehmite material.

[0091] (3) Preparation of an epoxysilane liquid phase system: 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane:(3-glycidoxypropyl)methyldiethoxysilane = 3:1; Catalyst: 0.5wt% ammonia solution (analytical grade); Mixing ratio: epoxysilane:ethanol:water = 1:8.5:1 (volume ratio). Hydrolysis-condensation reaction: The first boehmite material was redispersed in ethanol (solid content 10%), and the above-mentioned epoxysilane liquid phase system was added dropwise thereto, with the mass of epoxysilane accounting for 4% of the mass of the boehmite raw material; The reaction was carried out at a constant temperature of 45°C for 4.5 hours, and the resulting mixture was centrifuged and the supernatant was discarded. The resulting solid was washed twice with anhydrous ethanol, acetone, and distilled water, respectively. Vacuum drying was performed at 60°C to form a cycloalkanesilane layer, thereby obtaining a substrate layer material.

[0092] (4) 1000 mL of dopamine hydrochloride solution (10 mg / mL) was added to 100 g of the matrix layer material, and the mixture was shaken at a constant temperature of 30°C (amplitude 5.5 cm, frequency 125 times / min) for 10 h. The mixed solution changed from colorless to brown-black. The obtained mixed solution was centrifuged and the supernatant was discarded. The obtained solid was washed twice with anhydrous ethanol, acetone and distilled water respectively and sequentially, and then vacuum dried at 60°C to obtain a boehmite composite material.

[0093] Example 3

[0094] A method for preparing a boehmite composite material, which differs from Example 1 in that:

[0095] In step (2), the mass of diethyl vinyl phosphate is 3.5 g.

[0096] In step (3), the mass of epoxysilane accounts for 2.5% of the mass of the boehmite raw material.

[0097] In step (4), the volume of the dopamine hydrochloride solution is 800 mL.

[0098] Example 4

[0099] A method for preparing a boehmite composite material, which differs from Example 1 in that:

[0100] In step (2), the mass of diethyl vinyl phosphate is 4.5 g.

[0101] In step (3), the mass of epoxysilane accounts for 4.4% of the mass of the boehmite raw material.

[0102] In step (4), the volume of the dopamine hydrochloride solution is 1200 mL.

[0103] Example 5

[0104] A method for preparing a boehmite composite material comprises the following steps:

[0105] (1) Take 150g of boehmite powder (purchased from Shandong Guoci, D50 is 1.2μm, specific surface area is 2.5m 2 / g, pH 7.5), vacuum dried at 130°C for 2 h, 600 g of anhydrous ethanol and 200 g of deionized water were added thereto, 0.1 M hydrochloric acid was added to adjust the pH to 4, and mechanically stirred at 1200 rpm for 2 h. The mixture was then ultrasonically dispersed uniformly at an ultrasonic power of 300 W and a temperature of 30°C for 40 min to obtain an activated boehmite system.

[0106] (2) Under nitrogen protection, 4.5 g of vinyl diethyl phosphate was slowly added to the above-mentioned uniformly dispersed activated boehmite system, and the reaction was carried out at 70°C for 1 hour. The resulting first system was centrifuged and the supernatant was discarded. The resulting solid was washed twice with anhydrous ethanol, acetone, and distilled water, respectively, and then vacuum-dried at 60°C to form a phosphate-modified boehmite, thereby obtaining a first boehmite material.

[0107] (3) Preparation of an epoxysilane liquid phase system: 3-glycidyloxypropyltrimethoxysilane (GPTMS); catalyst: 0.5 wt% ammonia solution (analytical grade); mixing ratio: GPTMS: ethanol: water = 1:9:1 (volume ratio). Hydrolysis-condensation reaction: The first boehmite material was redispersed in ethanol (solid content 10%), and the above-mentioned epoxysilane liquid phase system was added dropwise thereto, with the mass of epoxysilane accounting for 5% of the mass of the boehmite raw material; the reaction was carried out at 55°C for 2 hours, the resulting mixture was centrifuged and the supernatant was discarded, and the resulting solid was washed twice with anhydrous ethanol, acetone, and distilled water, respectively. Vacuum drying was carried out at 60°C to form a cycloalkylsilane layer, thereby obtaining the substrate layer material.

[0108] (4) Add 800 mL of dopamine hydrochloride solution (10 mg / mL) to 100 g of the matrix layer material, and react at 30°C with constant temperature oscillation (amplitude 4 cm, frequency 130 times / min) for 15 h. The mixed solution changes from colorless to brown-black. The obtained mixed solution is centrifuged and the supernatant is discarded. The obtained solid is washed twice with anhydrous ethanol, acetone and distilled water respectively and sequentially, and then vacuum dried at 60°C to obtain a boehmite composite material.

[0109] Example 6

[0110] A method for preparing a boehmite composite material comprises the following steps:

[0111] (1) Take 150g of boehmite powder (purchased from Shandong Guoci, D50 is 1.2μm, specific surface area is 2.5m 2 / g, pH 7.5), vacuum dried at 100°C for 5 h, 750 g of anhydrous ethanol and 100 g of deionized water were added thereto, 0.1 M hydrochloric acid was added to adjust the pH to 3.8, and mechanically stirred at 800 rpm for 6 h. The mixture was then ultrasonically dispersed uniformly at an ultrasonic power of 300 W and a temperature of 45°C for 20 min to obtain an activated boehmite system.

[0112] (2) Under nitrogen protection, 1.5 g of 1-(dimethoxyphosphine)vinyl diethyl phosphate was slowly added to the above-mentioned uniformly dispersed activated boehmite system, and the reaction was carried out at 50°C for 3 h. The resulting first system was centrifuged and the supernatant was discarded. The resulting solid was washed twice with anhydrous ethanol, acetone, and distilled water, respectively, and then vacuum-dried at 60°C to form a phosphate-modified boehmite, thereby obtaining a first boehmite material.

[0113] (3) Preparation of an epoxysilane liquid phase system: 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; catalyst: 0.5 wt% ammonia solution (analytical grade); mixing ratio: GPTMS: ethanol: water = 1:8.5:1 (volume ratio). Hydrolysis-condensation reaction: The first boehmite material was redispersed in ethanol (solid content 10%), and the above-mentioned epoxysilane liquid phase system was added dropwise thereto, with the mass of epoxysilane accounting for 2% of the mass of the boehmite raw material; the reaction was carried out at 40°C for 5 hours, the resulting mixture was centrifuged and the supernatant was discarded, and the resulting solid was washed twice with anhydrous ethanol, acetone, and distilled water, respectively. Vacuum drying was carried out at 60°C to form a cycloalkylsilane layer, thereby obtaining a substrate layer material.

[0114] (4) 1200 mL of dopamine hydrochloride solution (10 mg / mL) was added to 100 g of the matrix layer material, and the mixture was shaken at a constant temperature of 30°C (amplitude 6 cm, frequency 100 times / min) for 10 h. The mixed solution changed from colorless to brown-black. The obtained mixed solution was centrifuged and the supernatant was discarded. The obtained solid was washed twice with anhydrous ethanol, acetone and distilled water respectively and sequentially, and vacuum dried at 60°C to obtain a boehmite composite material.

[0115] Comparative Example 1

[0116] The boehmite powder raw material (purchased from Shandong Guoci) was the same as that in Example 1 without modification.

[0117] Comparative Example 2

[0118] A method for preparing a boehmite powder modified material, comprising:

[0119] Preparation of silane-modified boehmite: Boehmite (γ-AlOOH) was dried at 110°C for 3 hours to remove physically adsorbed surface water. A silane coupling agent (KH-550) was then dissolved in an ethanol / water mixture (volume ratio 3:1). The pH was adjusted to 4.5 with hydrochloric acid, and the mixture was hydrolyzed for 60 minutes with stirring to generate silanol (Si-OH) reactive groups. The pretreated boehmite powder was slowly added to the hydrolyzed silane solution (boehmite:silane mass ratio 10:1) and ultrasonically dispersed for 30 minutes. The mixture was then mechanically stirred in a 70°C water bath for 6 hours to allow the silanol groups of the silane to condense with the hydroxyl groups (Al-OH) on the boehmite surface, forming Si-O-Al covalent bonds.

[0120] Experimental example

[0121] The boehmite powder composite materials of each embodiment, the boehmite powder raw materials and the boehmite powder modified materials of the comparative example were respectively prepared to obtain edge-coated electrodes, specifically comprising:

[0122] (1) 15 g of PVDF binder was added to 200 g of N-methylpyrrolidone (NMP) and stirred until completely dissolved. 85 g of the boehmite composite material of the example, the boehmite powder raw material of Comparative Example 1, or the boehmite powder modified material of Comparative Example 2 was then added while slowly stirring. Mechanical stirring was performed at 1000 rpm for 4 h to prepare a boehmite slurry. The boehmite slurry was coated onto 15 μm thick aluminum foil and dried at 100°C to obtain electrodes.

[0123] The boehmite electrodes obtained in the examples and comparative examples were subjected to a 180° peel strength test and an electrolyte immersion test.

[0124] 1.180° peel strength test

[0125] Cut the boehmite electrode into 150 mm long and 25 mm wide pieces, stick them on the double-sided tape in the center of the thin steel plate, use a 2 kg roller to roll back and forth 5 times, use a universal tensile testing machine, stretch them uniformly at an angle of 180° at a rate of 5 mm / s, and record the peel strength.

[0126] 2. Electrolyte immersion test

[0127] Place them in electrolyte respectively, soak them at 60℃ and compare the shedding time.

[0128] The test results are shown in Table 2.

[0129] Table 1 Test results

[0130]

[0131] As can be seen from Table 1, the edge-coated electrodes obtained from the boehmite powder composite materials of each embodiment of the present invention have better bonding performance between the edge-coated coating and the current collector, the 180° peel strength is above 165 N / m, and it can be maintained without falling off for more than 72 hours after immersion in an electrolyte at 60°C.

[0132] Comparative Example 1 uses untreated boehmite. The edge-coated electrode prepared therefrom has extremely poor bonding performance between the edge coating and the current collector, with a 180° peel strength of 65.4 N / m and falling off after being immersed in a 60°C electrolyte for 3 hours.

[0133] The boehmite in Comparative Example 2 was modified only with silane. The bonding performance between the edge coating and the current collector in the edge-coated electrode prepared therefrom was also poor, with a 180° peel strength of 89.3 N / m, and it fell off after being immersed in an electrolyte at 60°C for 18 hours.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A boehmite composite material, characterized in that: The invention comprises a base layer and a coating layer located on at least a portion of the surface of the base layer, wherein the base layer comprises a boehmite base material and a graft layer located on the surface of the boehmite base material; The graft layer comprises a phosphate layer and an epoxy silane layer arranged in sequence; The coating layer contains polydopamine.

2. The boehmite composite material according to claim 1, characterized in that Contains at least one of the following features (1) to (6): (1) The phosphate layer contains P=O; (2) The mass of the phosphate layer is 1% to 3% of the mass of the boehmite matrix material; (3) the epoxy silane layer comprises O—Si—R, where R comprises an epoxy group; (4) The mass of the epoxy silane layer accounts for 2% to 5% of the mass of the boehmite matrix material; (5) The graft layer contains (6) The mass of the coating layer is 0.5% to 1% of the mass of the boehmite matrix material.

3. The boehmite composite material according to claim 1, characterized in that Contains at least one of the following features (1) to (2): (1) The particle size D50 of the boehmite matrix material is 1 to 1.5 μm, and the specific surface area of ​​the boehmite matrix material is 75 to 90 m 2 / g; (2) The surface of the boehmite matrix material contains hydroxyl groups, the boehmite matrix material forms a chemical bond with the phosphate layer, and the matrix layer contains 4. A method for preparing a boehmite composite material, characterized in that: The following steps are involved: activating the boehmite raw material to obtain an activated boehmite system; mixing the activated boehmite system with a phosphate ester and performing a first heat treatment to obtain a first boehmite material; Mixing a liquid phase system containing epoxy silane with the dispersion of the first boehmite material, and performing a second heat treatment to obtain a base layer material; The base layer material is mixed with a dopamine hydrochloride solution to form a coating layer on the surface of the base layer material to obtain a boehmite composite material.

5. The method for preparing the boehmite composite material according to claim 4, wherein: Contains at least one of the following features (1) to (4): (1) The activation treatment specifically includes: drying the boehmite raw material, and then mixing it with an alcohol solvent and water to obtain a first system; adjusting the pH of the first system to 3.5-4 with hydrochloric acid, and obtaining an activated boehmite system after stirring and ultrasonic treatment; (2) During the activation treatment, the mass ratio of the boehmite raw material, the alcohol solvent, and water is (100-200):(600-750):(100-250); (3) During the activation treatment, the drying temperature is 100-130° C., and the drying time is 2-5 hours; (4) During the activation treatment, the stirring speed is 800-1200 rpm, the stirring time is 2-6 h, the ultrasonic power is 300-500 W, the ultrasonic temperature is 30-45 ° C, and the ultrasonic time is 20-40 min.

6. The method for preparing the boehmite composite material according to claim 4, characterized in that: Contains at least one of the following features (1) to (4): (1) The phosphate ester includes at least one of diethyl vinyl phosphate and 1-(dimethoxyphosphine) diethyl vinyl phosphate; (2) the mass of the phosphate ester accounts for 1% to 3% of the mass of the boehmite raw material; (3) The temperature of the first heat treatment is 50 to 70° C., and the time of the first heat treatment is 1 to 3 hours; (4) performing solid-liquid separation on the mixed system after the first heat treatment, collecting the solids, washing them, and drying them to obtain the first boehmite material.

7. The method for preparing the boehmite composite material according to claim 4, characterized in that: Contains at least one of the following features (1) to (6): (1) The liquid phase system containing epoxy silane comprises epoxy silane, a catalyst, an alcohol solvent and water, wherein the volume ratio of the epoxy silane, the alcohol solvent and the water is 1:(7-9):(1-2), and the mass percentage of the catalyst to the epoxy silane is 0.1% to 0.6%; (2) In the liquid phase system containing epoxy silane, the epoxy silane comprises at least one of 3-glycidyloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and (3-glycidoxypropyl)methyldiethoxysilane; (3) The dispersion of the first boehmite material comprises the first boehmite material and an alcohol solvent, and the solid content of the first boehmite material is 8% to 12%; (4) The mass of the epoxy silane accounts for 2% to 5% of the mass of the boehmite raw material; (5) The temperature of the second heat treatment is 40 to 55° C., and the time of the second heat treatment is 2 to 5 hours; (6) performing solid-liquid separation on the mixed system after the second heat treatment, collecting the solids, washing them, and drying them to obtain the base layer material.

8. The method for preparing the boehmite composite material according to claim 4, characterized in that: Contains at least one of the following features (1) to (4): (1) The mass of the dopamine hydrochloride is 8% to 12% of the mass of the base layer material; (2) The mixing treatment adopts a constant temperature oscillation treatment with a temperature of 20 to 30° C., an amplitude of 4 to 6 cm, and a frequency of 100 to 130 times / min; (3) The mixing treatment time is 10 to 15 hours; (4) performing solid-liquid separation on the mixed system after the mixing treatment, collecting the solids and washing and drying them.

9. A pole piece, characterized in that: The invention comprises an edge coating layer, wherein the edge coating layer comprises the boehmite composite material according to any one of claims 1 to 3, or the boehmite composite material obtained by the preparation method of the boehmite composite material according to any one of claims 4 to 8, and a binder.

10. A battery, characterized in that: Including the pole piece according to claim 9.

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