Coating process of carbon fiber positive electrode material, carbon fiber positive electrode material and application of carbon fiber positive electrode material

Abstract

The invention belongs to the technical field of preparation of new energy composite materials, and discloses a coating process of a carbon fiber positive electrode material, the carbon fiber positive electrode material and application of the carbon fiber positive electrode material. The coating process comprises the following steps: arranging carbon fiber positive electrode material slurry on carbon fibers subjected to surface treatment, and carrying out drying treatment; repeating the operation for 1-4 times to obtain intermediate carbon fibers; and sequentially carrying out drying and heat treatment on the intermediate carbon fiber to obtain the carbon fiber positive electrode material. According to the invention, the rheological property of the slurry is deeply coupled with the coating mode, and then a multi-step coating process is introduced, so that the required coating thickness and uniformity are realized, and a uniform, compact and well-attached positive active layer is formed on the carbon fiber. The carbon fiber positive electrode material prepared by the coating process can form a high-strength and high-energy-density composite structural member, and has a wide application prospect in structure-energy storage integrated composite materials in the fields of aerospace, electric automobiles, portable electronic equipment, energy storage infrastructures and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy composite material preparation, and particularly to a coating process for carbon fiber positive electrode materials, carbon fiber positive electrode materials and their applications. Background Art

[0002] In structural-energy storage integrated composite materials, directly depositing or coating lithium battery positive electrode materials on the surface of carbon fibers can achieve lightweight and multi-functional integration. However, there are certain difficulties in the existing coating processes. For example, when the positive electrode slurry is coated on the surface of carbon fibers, problems such as uneven distribution, inconsistent thickness, agglomeration and bubbles are likely to occur, affecting the quality of the electrode layer and electrochemical performance; insufficient adhesion causes the positive electrode layer to be easily detached or cracked during subsequent composite forming and long-term cycling; traditional coating methods (such as simple brushing) are difficult to ensure consistency and repeatability in large-scale production.

[0003] Currently, there is still a lack of a coating process that can achieve both uniform coating and stable adhesion, and is compatible with large-scale preparation processes. Summary of the Invention

[0004] The purpose of the present invention is to provide a coating process for carbon fiber positive electrode materials, carbon fiber positive electrode materials and their applications, and solve the defects that the existing coating processes are difficult to balance uniform coating, stable adhesion and large-scale preparation.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a coating process for carbon fiber positive electrode materials, including the following steps:

[0007] (1) Arrange the carbon fiber positive electrode material slurry on the surface-treated carbon fibers, and perform a drying treatment;

[0008] (2) Repeat the operation of step (1) 1 to 4 times to obtain intermediate carbon fibers;

[0009] (3) Sequentially dry and heat-treat the intermediate carbon fibers to obtain carbon fiber positive electrode materials;

[0010] Among them, the way of arranging in step (1) is impregnation or coating;

[0011] The coating includes spraying, spin coating or brushing.

[0012] Preferably, in the coating process, in step (1), the solid content of the carbon fiber positive electrode material slurry is 30 to 60 wt%, and the viscosity of the carbon fiber positive electrode material slurry is 1000 to 2000 mPa·s.

[0013] Preferably, in the coating process, in step (1), the surface-treated carbon fiber is obtained by subjecting carbon fiber to surface treatment;

[0014] The methods of surface treatment include: plasma treatment, chemical oxidation treatment, coupling treatment, or nanoparticle-assisted modification treatment.

[0015] Preferably, in the coating process, the conditions for dipping include: dipping time is 3 - 10 s, and the pulling rate is 0.1 - 1 cm / s.

[0016] Preferably, in the coating process, the conditions for spraying include: spraying pressure is 0.1 - 0.5 MPa, and the spraying distance is 10 - 25 cm;

[0017] The conditions for spin coating include: rotation speed is 1000 - 5000 rpm, and the time is 10 - 60 s;

[0018] The conditions for brush coating include: brush coating pressure is 0.05 - 0.3 N, brush coating speed is 10 - 50 mm / s, and the number of brush coating times is 1 - 5 times.

[0019] Preferably, in the coating process, in step (1), the conditions for drying treatment include: temperature is 20 - 80 °C, and the time is 10 - 30 min.

[0020] Preferably, in the coating process, in step (2), during the process of repeating the operation of step (1), the solid content of the carbon fiber positive electrode material slurry is greater than or equal to the solid content of the carbon fiber positive electrode material slurry used in the previous time;

[0021] Or, in step (2), during the process of repeating the operation of step (1), the viscosity of the carbon fiber positive electrode material slurry is greater than or equal to the viscosity of the carbon fiber positive electrode material slurry used in the previous time.

[0022] Preferably, in the coating process, in step (3), the conditions for drying include: temperature is 50 - 120 °C, and the time is 30 - 90 min;

[0023] The conditions for heat treatment include: carried out under a protective atmosphere, temperature is 150 - 250 °C, and the time is 1 - 4 h.

[0024] The present invention also provides a carbon fiber positive electrode material.

[0025] The present invention also provides the application of the carbon fiber positive electrode material in a structure - energy storage integrated composite material.

[0026] Through the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0027] The rheological properties of the slurry of the present invention (such as slurry viscosity and solid content) are deeply coupled with the coating method. By introducing a multi-step coating process, a low-concentration slurry can be first coated to form a bottom layer to improve the surface wettability and initial adhesion of the fibers, and then the slurry concentration and thickness can be gradually increased to achieve the required coating thickness and uniformity. Further controlling the parameters of the drying and heat treatment processes (temperature, humidity, atmosphere) can ensure the full curing of the binder and the reasonable distribution of the conductive agent, while avoiding the cracking or peeling of the coating caused by excessive stress, and forming a uniform, dense, and well-adhered positive electrode active layer on the carbon fiber. The carbon fiber positive electrode material prepared by this coating process can be directly combined with molding processes such as resins and prepregs to form high-strength and high-energy-density composite structural parts, and has broad application prospects in structural-energy integrated composite materials in the fields of aerospace, electric vehicles, portable electronic devices, and energy storage infrastructure. Moreover, the coating process of the present application can combine on-line quality inspection (such as optical inspection and coating thickness measurement) and an automated control system to ensure the consistency and repeatability of large-area and multi-batch production. Detailed Embodiment

[0028] The present invention provides a coating process for a carbon fiber positive electrode material, comprising the following steps:

[0029] (1) Arrange the carbon fiber positive electrode material slurry on the surface-treated carbon fiber and perform a drying treatment;

[0030] (2) Repeat the operation of step (1) 1 to 4 times to obtain an intermediate carbon fiber;

[0031] (3) Sequentially perform drying and heat treatment on the intermediate carbon fiber to obtain a carbon fiber positive electrode material;

[0032] Among them, the arrangement method in step (1) is impregnation or coating;

[0033] The coating includes spraying, spin coating, or brushing.

[0034] In the present invention, in step (1), the carbon fiber positive electrode material slurry preferably includes a conductive agent, a dispersion aid, a positive electrode active material, a binder, and a solvent.

[0035] In the carbon fiber positive electrode material slurry of the present invention, the conductive agent is preferably one or more of carbon nanotubes (CNT), graphene, and carbon black, more preferably a mixture of CNT, graphene, and carbon black, and even more preferably a mixture of CNT, graphene, and SuperP.

[0036] In the present invention, in the carbon fiber positive electrode material slurry, the dispersion aid is preferably a fluorosurfactant, an amphiphilic surfactant, polyvinylpyrrolidone (PVP) or carboxymethyl cellulose (CMC), more preferably a fluorosurfactant or PVP, and even more preferably a fluorosurfactant. The fluorosurfactant in the present invention is Capstone TM FS-10 of Chemours. The amphiphilic surfactant in the present invention is orafuor.

[0037] In the present invention, in the carbon fiber positive electrode material slurry, the positive electrode active material is preferably an NCM811 positive electrode material, an NCA positive electrode material, a lithium-rich layered positive electrode material, LiFePO 4 or one or more of them, more preferably an NCM811 positive electrode material or an NCA positive electrode material, and even more preferably an NCM811 positive electrode material.

[0038] In the present invention, in the carbon fiber positive electrode material slurry, the binder is preferably polyvinylidene fluoride (PVDF).

[0039] In the present invention, in the carbon fiber positive electrode material slurry, the solvent is preferably N-methylpyrrolidone (NMP).

[0040] In the present invention, the mass ratio of the conductive agent, the positive electrode active material, and the binder is preferably 0.1-1:7-9:0.1-1, more preferably 0.3-0.8:8-9:0.1-0.5, and even more preferably 0.7:9:0.3.

[0041] In the present invention, the mass fraction of the dispersion aid in the carbon fiber positive electrode material slurry is preferably 0.1-1%, more preferably 0.1-0.5%, and even more preferably 0.2%.

[0042] In the present invention, in step (1), the solid content of the carbon fiber positive electrode material slurry is preferably 30-60 wt%, more preferably 40-55 wt%, and even more preferably 50 wt%.

[0043] In the present invention, in step (1), the viscosity of the carbon fiber positive electrode material slurry is preferably 1000-2000 mPa·s, more preferably 1200-1800 mPa·s, and even more preferably 1500 mPa·s.

[0044] In the present invention, the preparation method of the carbon fiber positive electrode material slurry includes the following steps:

[0045] Pre-disperse the conductive agent in the solvent, then add the dispersion aid for dispersion, and then add the positive electrode active material and the binder for secondary dispersion to obtain the carbon fiber positive electrode material slurry;

[0046] Or, the conductive agent is pre-dispersed in a solvent, then the positive electrode active material and the binder are added for secondary dispersion, and then a dispersion aid is added for dispersion to obtain a carbon fiber positive electrode material slurry.

[0047] In the present invention, the method of pre-dispersion is preferably ultrasonic treatment and / or high-speed shear dispersion; the time of ultrasonic treatment is preferably 5 - 30 min, more preferably 10 - 25 min, and most preferably 20 min; the rotation speed of high-speed shear dispersion is preferably 5000 - 10000 rpm, more preferably 6000 - 9000 rpm, and most preferably 8000 rpm; the time of high-speed shear dispersion is preferably 10 - 60 min, more preferably 15 - 30 min, and most preferably 20 min.

[0048] In the present invention, the method of dispersion is preferably ultrasonic treatment and / or high-speed shear dispersion; the time of ultrasonic treatment is preferably 5 - 30 min, more preferably 10 - 25 min, and most preferably 20 min; the rotation speed of high-speed shear dispersion is preferably 5000 - 10000 rpm, more preferably 6000 - 9000 rpm, and most preferably 8000 rpm; the time of high-speed shear dispersion is preferably 10 - 60 min, more preferably 15 - 30 min, and most preferably 20 min.

[0049] In the present invention, the method of secondary dispersion is preferably high-speed shear dispersion and / or low-speed stirring dispersion; the rotation speed of high-speed shear dispersion is preferably 5000 - 10000 rpm, more preferably 8000 - 10000 rpm, and most preferably 10000 rpm; the time of high-speed shear dispersion is preferably 10 - 60 min, more preferably 20 - 40 min, and most preferably 30 min; the rotation speed of low-speed stirring dispersion is preferably 200 - 600 rpm, more preferably 300 - 500 rpm, and most preferably 500 rpm; the time of low-speed stirring dispersion is preferably 10 - 60 min, more preferably 10 - 30 min, and most preferably 20 min.

[0050] In the present invention, in step (1), the surface-treated carbon fiber is obtained by subjecting carbon fiber to surface treatment.

[0051] In the present invention, the method of surface treatment preferably includes: plasma treatment, chemical oxidation treatment, coupling treatment or nanoparticle-assisted modification treatment, more preferably includes: plasma treatment, chemical oxidation treatment or nanoparticle-assisted modification treatment, and most preferably is plasma treatment.

[0052] In the present invention, the conditions of plasma treatment preferably include: the gas is preferably O 2and / or N 2 , more preferably O 2 ; the radio frequency power is preferably 10-100 W, more preferably 30-80 W, and even more preferably 50 W; the processing pressure is preferably 0.01-0.1 Torr, more preferably 0.03-0.08 Torr, and even more preferably 0.05 Torr; the processing temperature is preferably 50-150 °C, more preferably 70-120 °C, and even more preferably 100 °C; the gas flow rate is preferably 10-50 sccm, more preferably 15-35 sccm, and even more preferably 20 sccm; the processing time is preferably 30-300 s, more preferably 50-180 s, and even more preferably 60 s.

[0053] In the present invention, the chemical oxidation treatment preferably includes the following steps: soaking the carbon fiber in an etching solution, and then washing and drying.

[0054] In the present invention, the etching solution preferably includes HF, HNO 3 , H 2 SO 4 or NaOH, more preferably includes HF, HNO 3 or NaOH, and even more preferably includes HNO 3 ; the concentration of the etching solution is preferably 1-10 wt%, more preferably 3-8 wt%, and even more preferably 5 wt%.

[0055] In the present invention, the conditions for soaking in the etching solution include: the temperature is preferably 20-80 °C, more preferably 20-40 °C, and even more preferably 25 °C; the time is preferably 1-30 min, more preferably 15-30 min, and even more preferably 30 min. The washing reagent is preferably water. The drying conditions include: the temperature is preferably 50-120 °C, more preferably 60-100 °C, and even more preferably 80 °C; the time is preferably 10-60 min, more preferably 20-40 min, and even more preferably 30 min.

[0056] In the present invention, the coupling treatment preferably includes the following steps: sequentially ultrasonically cleaning and drying the carbon fiber in acetone, then soaking it in a coupling agent solution, and drying it.

[0057] In the present invention, the coupling agent solution preferably includes amino silane, epoxy silane or fluoro silane, more preferably includes amino silane or epoxy silane, and even more preferably includes amino silane. The amino silane in the present invention is preferably KH550. The epoxy silane in the present invention is preferably KH560. The fluoro silane in the present invention is preferably FS-100. The concentration of the coupling agent solution is preferably 0.1-5 wt%, more preferably 0.4-2 wt%, and even more preferably 0.5 wt%.

[0058] In the present invention, the conditions for soaking in the coupling agent solution include: the temperature is preferably 20-80°C, more preferably 20-40°C, and still more preferably 25°C; the time is preferably 30-120 min, more preferably 40-80 min, and still more preferably 60 min. The conditions for drying include: the temperature is preferably 80-150°C, more preferably 100-140°C, and still more preferably 120°C; the time is preferably 1-4 h, more preferably 1.5-3 h, and still more preferably 2 h.

[0059] In the present invention, the nano-particle assisted modification treatment preferably includes the following steps: impregnating carbon fibers in the nano-particle dispersion liquid, and sequentially performing drying and heat treatment.

[0060] In the present invention, the nano-particle dispersion liquid preferably includes SiO 2 , TiO 2 , Al 2 O 3 or carbon nanotubes (CNT), more preferably includes SiO 2 or TiO 2 , and still more preferably includes SiO 2 . The concentration of the nano-particle dispersion liquid is preferably 0.1-10 wt%, more preferably 0.1-1 wt%, and still more preferably 0.1 wt%.

[0061] In the present invention, the conditions for impregnating in the nano-particle dispersion liquid include: the temperature is preferably 20-40°C, more preferably 20-30°C, and still more preferably 25°C; the time is preferably 5-30 min, more preferably 15-30 min, and still more preferably 30 min. The drying temperature is preferably room temperature. The conditions for heat treatment include: the temperature is preferably 100-200°C, more preferably 120-180°C, and still more preferably 150°C; the time is preferably 0.5-3 h, more preferably 0.8-1.5 h, and still more preferably 1 h.

[0062] In the present invention, the conditions for impregnation include: the immersion time is preferably 3-10 s, more preferably 4-7 s, and still more preferably 5 s; the pulling rate is preferably 0.1-1 cm / s, more preferably 0.3-0.7 cm / s, and still more preferably 0.5 cm / s.

[0063] In the present invention, the conditions for spraying include: the spraying pressure is preferably 0.1-0.5 MPa, more preferably 0.15-0.3 MPa, and still more preferably 0.2 MPa; the spraying distance is preferably 10-25 cm, more preferably 12-18 cm, and still more preferably 15 cm.

[0064] In the present invention, the conditions for spin coating include: the rotation speed is preferably 1000 - 5000 rpm, more preferably 1500 - 3000 rpm, and even more preferably 2000 rpm; the time is preferably 10 - 60 s, more preferably 20 - 40 s, and even more preferably 30 s.

[0065] In the present invention, the conditions for brush coating include: the brush coating pressure is preferably 0.05 - 0.3 N, more preferably 0.1 - 0.2 N, and even more preferably 0.15 N; the brush coating speed is preferably 10 - 50 mm / s, more preferably 15 - 30 mm / s, and even more preferably 20 mm / s; the number of brush coating times is preferably 1 - 5 times, more preferably 2 - 4 times, and even more preferably 3 times.

[0066] In the present invention, in step (1), the conditions for the drying treatment include: the temperature is preferably 20 - 80 °C, more preferably 20 - 50 °C, and even more preferably 20 °C; the time is preferably 10 - 30 min, more preferably 20 - 30 min, and even more preferably 20 min.

[0067] In the present invention, in step (2), during the process of repeating the operation of step (1), the solid content of the carbon fiber positive electrode material slurry is greater than or equal to the solid content of the carbon fiber positive electrode material slurry used in the previous time;

[0068] Alternatively, in step (2), during the process of repeating the operation of step (1), the viscosity of the carbon fiber positive electrode material slurry is greater than or equal to the viscosity of the carbon fiber positive electrode material slurry used in the previous time.

[0069] In the present invention, in step (3), the conditions for drying include: the temperature is preferably 50 - 120 °C, more preferably 80 - 120 °C, and even more preferably 120 °C; the time is preferably 30 - 90 min, more preferably 40 - 70 min, and even more preferably 60 min.

[0070] In the present invention, in step (3), the conditions for heat treatment include: it is carried out under a protective atmosphere; the protective atmosphere preferably includes nitrogen, argon or helium, more preferably nitrogen; the temperature is preferably 150 - 250 °C, more preferably 150 - 200 °C, and even more preferably 150 °C; the time is preferably 1 - 4 h, more preferably 1.5 - 3 h, and even more preferably 2 h.

[0071] The present invention also provides a carbon fiber positive electrode material.

[0072] The present invention also provides the application of the carbon fiber positive electrode material in a structure - energy storage integrated composite material.

[0073] In the present invention, the method for the application is not limited, and a scheme well - known to those skilled in the art can be adopted.

[0074] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0075] Example 1

[0076] This embodiment provides a coating process for a carbon fiber cathode material, including the following steps:

[0077] (1) Using a mixture of CNT (manufacturer: Shandong Dazhan Nano Materials Co., Ltd., model GT-300): graphene (manufacturer: Jiangsu Xianfeng Nano Materials Technology Co., Ltd., model XF002-1) with a mass ratio of 3:5 as the conductive agent, adding the conductive agent to NMP and ultrasonically treating for 20 min, adding 0.2 wt% fluorosurfactant Capstone TM FS-10 (Chemours), ultrasonically treating for 20 min first, and then high-speed shear dispersing at 8000 rpm for 20 min; subsequently adding NCM811 cathode material (manufacturer: Xiamen Tungsten Co., Ltd., model: NCM811-HV), PVDF (manufacturer: Arkema, model: Kynar HSV900), controlling the mass ratio of the conductive agent, NCM811 cathode material, and PVDF to be 0.7:9:0.3, and high-speed shear dispersing at 10000 rpm for 30 min to obtain carbon fiber cathode material slurries with solid contents of 48 wt% (viscosity 1500 mPa·s) and 50 wt% (viscosity 1600 mPa·s) respectively;

[0078] (2) Placing the T700 carbon fiber tow (manufacturer: Toray Industries, Inc., model: T700SC 1200050C) into a low-pressure oxygen plasma treatment system, treating at a radio frequency power of 50 W, a gas flow rate of O 2 of 20 sccm, a temperature of 100 °C, and a pressure of 0.05 Torr for 60 s to obtain surface-treated carbon fibers;

[0079] (3) Immersing the surface-treated carbon fibers into the carbon fiber cathode material slurry (solid content 48 wt%, viscosity 1500 mPa·s) at a pulling rate of 0.5 cm / s for an immersion time of 5 s to form a bottom thin coating, drying at 20 °C for 30 min; then spraying the carbon fiber cathode material slurry (solid content 50 wt%, viscosity 1600 mPa·s) on the thin coating twice by spraying method (air pressure 0.2 MPa, spraying distance 15 cm), and drying at 80 °C for 20 min after each spraying to obtain intermediate carbon fibers;

[0080] (4) Dry the middle carbon fiber at 80 °C for 60 min, and finally heat-treat it in a nitrogen atmosphere at 200 °C for 2 h to obtain a positive electrode layer with a uniform coating and good adhesion, that is, a carbon fiber positive electrode material.

[0081] Application Example 1

[0082] Assemble the carbon fiber positive electrode material prepared in Example 1 into a battery for performance testing. The preparation method is as follows:

[0083] Preparation of half-cell: Positive electrode sheet: Use the carbon fiber positive electrode material (12 mm round sheet) prepared in Example 1; Negative electrode: Use a lithium metal sheet (purity ≥ 99.9%, thickness 0.6 mm); Separator: Use Celgard 2400 separator; Electrolyte: 1M LiPF 6 Dissolved in EC / DMC (vt 1:1), add 2 wt% FEC; Assembly: Assemble into a CR2032 button cell in an argon glove box;

[0084] Testing method: Use a LAND CT2001A battery tester to perform constant current charge and discharge testing, and test the initial discharge capacity at a 1C rate; Perform 500 cycle tests and record the capacity changes every 100 cycles;

[0085] Performance test results: At 1C, the initial discharge capacity of the half-cell is 205 mAh / g, the retention rate of the half-cell after 100 cycles is 90%, and the retention rate of the half-cell after 200 cycles is 88%;

[0086] Preparation of full-cell: Positive electrode: Use the carbon fiber positive electrode material (50 mm × 50 mm sheet) prepared in Example 1; Negative electrode: Use a carbon fiber negative electrode coated with graphite slurry (50 mm × 50 mm sheet); Separator: Glass fiber cloth separator (50 μm); Electrolyte: Epoxy resin polymer electrolyte membrane (100 μm, the base resin is bisphenol A epoxy resin E51, the curing agent is a mixture of polyetheramine D230 and diaminodiphenylmethane MDA, the lithium salt is LiTFSI with an addition amount of 10 wt%, the plasticizer is EC and DMC = 1:1 volume ratio, and the filler is 5 wt% Al 2 O 3 nanoparticles. Mix the above components evenly, premix at room temperature, then put them into a mold, cure at 80 °C for 12 h, and then cure at 150 °C for 2 h to obtain an epoxy resin polymer electrolyte membrane); Assembly: Stack the positive electrode, separator, electrolyte and negative electrode in an anhydrous and oxygen-free environment, and use an aluminum-plastic film to encapsulate to form a full-cell;

[0087] Testing method: Use a LAND CT2001A to perform constant current charge and discharge testing, test at a 1C rate, and record the initial capacity and the capacity after cycling;

[0088] Performance test results: At 1C, the initial capacity of the full cell is 195 mAh / g, and the retention rate after 500 cycles of the full cell is 85%.

[0089] Preparation of soft-pack battery: Cathode: Use the carbon fiber cathode material of Example 1 (50 mm × 50 mm sheet); Anode: Use the carbon fiber anode treated by lithium plating (50 mm × 50 mm sheet); Separator: Glass fiber cloth separator (50 μm); Electrolyte: Epoxy resin polymer electrolyte (refer to the preparation process of the electrolyte in the full cell); Assembly: Stack the cathode, separator, electrolyte, and anode in an argon glove box, and encapsulate using the soft-pack battery encapsulation process, pre-cure for 24 h (60 °C), and post-cure for 2 h (150 °C);

[0090] Test method: Use LAND CT2001A for constant current charge and discharge test, and test the initial capacity and cycle performance at a rate of 1C (conduct 300 cycles); High-temperature aging test: Place the soft-pack battery in an incubator at 55 °C and test the capacity change after 100 h;

[0091] Performance test results: At 1C, the initial capacity of the soft-pack battery is 190 mAh / g, the retention rate after 300 cycles of the soft-pack battery is 87%, and the capacity decay during high-temperature aging at 55 °C is 8%.

[0092] Example 2

[0093] This example provides a coating process for a carbon fiber cathode material, including the following steps:

[0094] (1) Use a mixture of CNT (manufacturer: Shandong Dazhan Nano Materials Co., Ltd., model GT-300): graphene (manufacturer: Jiangsu Xianfeng Nano Materials Technology Co., Ltd., model XF002-2): SuperP (manufacturer: Timcal, model: SuperP Li) with a mass ratio of 1:4:2 as the conductive agent. Add the conductive agent to NMP and ultrasonically treat for 30 min. Add LiFePO 4 (manufacturer: Hebei Jinli New Energy Materials Technology Co., Ltd.), PVDF (manufacturer: Arkema, model: Kynar HSV900), and control the mass ratio of the conductive agent, LiFePO 4 , PVDF to be 0.5:9:0.5, and stir and disperse at 600 rpm for 40 min; Then add 0.5 wt% CMC (manufacturer: Changlin Chemical Industry, model: CMC203, weight average molecular weight: 250,000), ultrasonically treat for 10 min first, and then high-speed shear and disperse at 5000 rpm for 20 min to obtain carbon fiber cathode material slurries with solid contents of 30 wt% (viscosity of 1200 mPa·s) and 50 wt% (viscosity of 1800 mPa·s) respectively;

[0095] (2) Place the M55J carbon fiber (manufacturer: Toray Industries, Inc.) into a low-pressure oxygen plasma treatment system and treat it for 90 s at a radio frequency power of 60 W, a gas flow rate of 25 sccm, a temperature of 100 °C, and a pressure of 0.05 Torr to obtain the surface-treated carbon fiber; 2 After treatment for 90 s at a radio frequency power of 60 W, a gas flow rate of 25 sccm, a temperature of 100 °C, and a pressure of 0.05 Torr, the surface-treated carbon fiber is obtained;

[0096] (3) Spin-coat one layer of the carbon fiber cathode material slurry (solid content 30 wt%, viscosity 1200 mPa·s) on the surface-treated carbon fiber at a rotation speed of 2000 rpm for 30 s and dry it at 80 °C for 20 min; then spin-coat one more layer with the carbon fiber cathode material slurry (solid content 50 wt%, viscosity 1800 mPa·s) at a rotation speed of 2000 rpm for 30 s and dry it at 80 °C for 20 min; the slurry with a solid content of 50 wt% is spin-coated twice in total according to the above conditions to obtain the intermediate carbon fiber;

[0097] (4) Dry the intermediate carbon fiber at 120 °C for 60 min and finally heat-treat it in a nitrogen atmosphere at 150 °C for 1 h to obtain the cathode layer with a uniform coating (thickness 2 μm), that is, the carbon fiber cathode material.

[0098] Application Example 2

[0099] Referring to the battery preparation and testing method of Reference Application Example 1, assemble the carbon fiber cathode material prepared in Example 2 into a battery for performance testing:

[0100] Performance test results of the half-cell: At 1C, the initial discharge capacity of the half-cell is 207 mAh / g, the retention rate after 100 cycles of the half-cell is 91%, and the retention rate after 200 cycles of the half-cell is 89%;

[0101] Performance test results of the full cell: At 1C, the initial capacity of the full cell is 198 mAh / g, and the retention rate after 500 cycles of the full cell is 86%;

[0102] Performance test results of the soft-pack battery: At 1C, the initial capacity of the soft-pack battery is 192 mAh / g, the retention rate after 300 cycles of the soft-pack battery is 88%, and the capacity decay during high-temperature aging at 55 °C is 7%.

[0103] Example 3

[0104] This example provides a coating process for a carbon fiber cathode material, including the following steps:

[0105] (1) Using a mixture of CNT (manufacturer: Shandong Dazhan Nano Materials Co., Ltd., model: GT-300): graphene (manufacturer: Jiangsu Xianfeng Nano Materials Technology Co., Ltd., model: XF002-2): SuperP (manufacturer: Timcal, model: SuperP Li) with a mass ratio of 3:2:2 as the conductive agent, add the conductive agent to NMP and ultrasonically treat for 5 min. Then add 0.3 wt% PVP (weight average molecular weight 50,000), ultrasonically treat for 20 min first, and then perform high-speed shear dispersion at 8000 rpm for 20 min. Subsequently, add the NCA cathode material (manufacturer: Umicore, grade: eLNO) and PVDF (manufacturer: Arkema, model: Kynar HSV900), control the mass ratio of the conductive agent, NCA cathode material, and PVDF to be 1:8:1, perform high-speed shear dispersion at 8000 rpm for 20 min, and then perform stirring dispersion at 500 rpm for 10 min to obtain carbon fiber cathode material slurries with solid contents of 35 wt% (viscosity 1200 mPa·s) and 55 wt% (viscosity 1800 mPa·s) respectively;

[0106] (2) Place the T800 carbon fiber tow (manufacturer: Toray Industries, Inc., model: T800H) into a low-pressure nitrogen plasma treatment system and treat it at a radio frequency power of 70 W, a gas flow rate of N 2 of 30 sccm, a temperature of 90 °C, and a pressure of 0.06 Torr for 120 s to obtain surface-treated carbon fibers;

[0107] (3) Spray (at an air pressure of 0.3 MPa and a spraying distance of 20 cm) the carbon fiber cathode material slurry (solid content 35 wt%, low viscosity 1200 mPa·s) onto the surface-treated carbon fibers, dry at 80 °C for 30 min, and spray a total of 2 times according to the aforementioned conditions; then brush-coat the carbon fiber cathode material slurry (solid content 55 wt%, viscosity 1800 mPa·s) by the brush-coating method (pressure 0.15 N, brush-coating speed 25 mm / s, perpendicular cross 2 times), dry at 80 °C for 30 min, and brush-coat a total of 1 layer to obtain intermediate carbon fibers;

[0108] (4) Dry the intermediate carbon fibers at 120 °C for 90 min, and finally heat-treat them in a nitrogen atmosphere at 200 °C for 2 h to obtain a cathode layer with a uniform coating and good adhesion, that is, the carbon fiber cathode material.

[0109] Application Example 3

[0110] Referring to the battery preparation and testing method of Reference Application Example 1, assemble the carbon fiber cathode material prepared in Example 3 into a battery for performance testing:

[0111] Performance test results of the half-cell: At 1C, the initial discharge capacity of the half-cell is 210 mAh / g, the retention rate after 100 cycles of the half-cell is 94%, and the retention rate after 200 cycles of the half-cell is 92%.

[0112] Performance test results of the full cell: At 1C, the initial capacity of the full cell is 200 mAh / g, and the retention rate after 500 cycles of the full cell is 88%.

[0113] Performance test results of the soft-pack battery: At 1C, the initial capacity of the soft-pack battery is 195 mAh / g, the retention rate after 300 cycles of the soft-pack battery is 89%, and the capacity decay at 55°C high-temperature aging is 6%.

[0114] Example 4

[0115] This example provides a coating process for a carbon fiber positive electrode material, including the following steps:

[0116] (1) Using a mixture of CNT (manufacturer: Shandong Dazhan Nano Materials Co., Ltd., model: GT-300): graphene (manufacturer: Jiangsu Xianfeng Nano Materials Technology Co., Ltd., model: XF002-1): SuperP (manufacturer: Timcal, model: SuperP Li) with a mass ratio of 3:2:2 as the conductive agent, adding the conductive agent to NMP and ultrasonicating for 10 min, adding 0.1 wt% of orafuor, ultrasonicating for 10 min first, and then high-speed shear dispersing at 10000 rpm for 15 min; subsequently adding a lithium-rich layered positive electrode material (type: Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 , manufacturer: Dongsheng Technology Co., Ltd., grade: DSLM-01), PVDF (manufacturer: Arkema, model: Kynar HSV900), controlling the mass ratio of the conductive agent, lithium-rich layered positive electrode material, and PVDF to be 0.8:9:0.2, and high-speed shear dispersing at 8000 rpm for 30 min to obtain carbon fiber positive electrode material slurries with solid contents of 40 wt% (viscosity 1300 mPa·s), 45 wt% (viscosity 1400 mPa·s), 50 wt% (viscosity 1600 mPa·s), 55 wt% (viscosity 1800 mPa·s), and 60 wt% (viscosity 2000 mPa·s) respectively;

[0117] (2) Putting the T700 carbon fiber tow (manufacturer: Toray Industries, Inc., grade: T700SC 1200050C) into the nano-SiO 2 dispersion liquid (0.1 wt%, particle size 20 nm), impregnating at 30°C for 20 min, drying at room temperature for 12 h, and then heat-treating at 150°C for 1 h to make SiO 2Nanoparticles adhere to the fiber surface to form a micro-nano hierarchical structure, resulting in surface-treated carbon fibers;

[0118] (3) Immerse the surface-treated carbon fibers into the carbon fiber positive electrode material slurry at a pulling rate of 0.5 cm / s for 10 s, and dry at 80 °C for 10 min. Immerse a total of 5 times in slurries with different solid contents. The solid contents of the carbon fiber positive electrode material slurry are 40 wt% (viscosity 1300 mPa·s), 45 wt% (viscosity 1400 mPa·s), 50 wt% (viscosity 1600 mPa·s), 55 wt% (viscosity 1800 mPa·s), and 60 wt% (viscosity 2000 mPa·s) respectively to obtain intermediate carbon fibers;

[0119] (4) Dry the intermediate carbon fibers at 120 °C for 90 min, and finally heat-treat in a nitrogen atmosphere at 200 °C for 2 h to obtain a positive electrode layer with a coating thickness of 3 μm and a uniformity deviation of less than ±5%, that is, the carbon fiber positive electrode material.

[0120] Application Example 4

[0121] Referring to the battery preparation and testing method of Application Example 1, assemble the carbon fiber positive electrode material prepared in Example 4 into a battery for performance testing:

[0122] Performance test results of the half-cell: At 1C, the initial discharge capacity of the half-cell is 203 mAh / g, the retention rate after 100 cycles of the half-cell is 91%, and the retention rate after 200 cycles of the half-cell is 87%;

[0123] Performance test results of the full-cell: At 1C, the initial capacity of the full-cell is 192 mAh / g, and the retention rate after 500 cycles of the full-cell is 84%;

[0124] Performance test results of the soft-pack battery: At 1C, the initial capacity of the soft-pack battery is 188 mAh / g, the retention rate after 300 cycles of the soft-pack battery is 86%, and the capacity decay during high-temperature aging at 55 °C is 9%.

[0125] Example 5

[0126] This example provides a coating process for a carbon fiber positive electrode material, including the following steps:

[0127] (1) Use a mixture of CNT (manufacturer: Shandong Dazhan Nano Materials Co., Ltd., model: GT-300): graphene (manufacturer: Jiangsu Xianfeng Nano Materials Technology Co., Ltd., model: XF002-2) with a mass ratio of 3:5 as the conductive agent. Add the conductive agent to NMP and ultrasonically treat for 10 min, and add 0.2 wt% fluorinated surfactant Capstone TMFS-10 (Chemours), ultrasonic treatment for 20 min first, then high-speed shearing dispersion at 10000 rpm for 10 min; Subsequently, add NCM811 cathode material (manufacturer: Xiamen Tungsten Co., Ltd., model: NCM811-HV), PVDF (manufacturer: Arkema, model: Kynar HSV900), control the mass ratio of conductive agent, NCM811 cathode material, and PVDF to be 1:8:1, stir and disperse at 500 rpm for 60 min to obtain carbon fiber cathode material slurries with solid contents of 45 wt% (viscosity 1400 mPa·s) and 55 wt% (viscosity 1800 mPa·s) respectively;

[0128] (2) Put PAN-based carbon fiber (manufacturer: Toray Industries, Inc., grade: T800H-12K) into a low-pressure nitrogen-oxygen mixed plasma treatment system, at a radio frequency power of 60 W, gas flow rate of N 2 of 10 sccm, gas flow rate of O 2 of 15 sccm, temperature of 80 °C, pressure of 0.05 Torr for 90 s to obtain surface-treated carbon fiber;

[0129] (3) Spin-coat 1 layer of the carbon fiber cathode material slurry (solid content 45 wt%, viscosity 1400 mPa·s) on the surface-treated carbon fiber at a rotation speed of 2000 rpm for a spin-coating time of 30 s, and dry at 60 °C for 15 min. Spin-coat 2 layers in total under the above conditions; Then spray the carbon fiber cathode material slurry (solid content 55 wt%, viscosity 1800 mPa·s) on the thin coating by spraying method (air pressure 0.25 MPa, spraying distance 12 cm), and dry at 80 °C for 20 min. Spray 3 layers in total under the above conditions to obtain intermediate carbon fiber;

[0130] (4) Dry the intermediate carbon fiber at 100 °C for 90 min, and finally heat-treat it in a nitrogen atmosphere at 200 °C for 2 h to obtain the carbon fiber cathode material, realizing uniform coverage of the micro-convex and concave structure on the fiber surface. In Example 5, the coating consistency is controlled by an online laser thickness gauge, and the coefficient of variation of each batch of products is less than 5% in batch production, indicating that this coating process has good reproducibility in industrial production.

[0131] Application Example 5

[0132] Referring to the battery preparation and testing method of Application Example 1, assemble the carbon fiber cathode material prepared in Example 5 into a battery for performance testing:

[0133] Performance test results of the half-cell: At 1C, the initial discharge capacity of the half-cell is 200 mAh / g, the retention rate of the half-cell after 100 cycles is 90%, and the retention rate of the half-cell after 200 cycles is 88%;

[0134] Performance test results of the full cell: At 1C, the initial capacity of the full cell is 190 mAh / g, and the retention rate after 500 cycles of the full cell is 85%;

[0135] Performance test results of the soft-pack battery: At 1C, the initial capacity of the soft-pack battery is 186 mAh / g, the retention rate after 300 cycles of the soft-pack battery is 87%, and the capacity decay during high-temperature aging at 55°C is 8%.

[0136] The above embodiments verify the effectiveness and flexibility of the coating process of the present invention. It can be diversifiedly combined according to the material system and application requirements to improve the electrochemical performance and mechanical stability of the carbon fiber positive electrode material, so as to meet the requirements of the structure-energy storage integrated composite material. Online quality inspection and automatic control devices can also be used to realize real-time monitoring and optimization of the coating thickness and uniformity in mass production. The carbon fiber positive electrode material prepared by the present invention is assembled into a half cell, a full cell and a soft-pack battery for performance testing. The capacity retention rate is not less than 85% at a 1C rate, and the capacity retention rate is not less than 80% after 100 cycles, which proves that the carbon fiber positive electrode material of the present invention has excellent high-rate, long-cycle and high-temperature stable performance. Combining the obtained carbon fiber positive electrode material with a resin matrix or prepreg to form a composite structural component with both mechanical load-bearing and energy storage functions, the product is applicable to aerospace, electric vehicle body integrated batteries, portable electronic devices and household energy storage systems, realizing a multi-functional component with lightweight, high energy density and high cycle life.

[0137] The above is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A coating process for a carbon fiber positive electrode material, characterized in that: The following steps are involved: (1) arranging the carbon fiber positive electrode material slurry onto the surface treated carbon fiber and performing a drying process; (2) Repeating step (1) 1 to 4 times to obtain intermediate carbon fibers; (3) drying and heat treating the intermediate carbon fibers in sequence to obtain a carbon fiber positive electrode material; Wherein, the finishing method in step (1) is dipping or coating; The coating includes spray coating, spin coating or brush coating.

2. The coating process according to claim 1, characterized in that: In step (1), the solid content of the carbon fiber positive electrode material slurry is 30-60wt%, and the viscosity of the carbon fiber positive electrode material slurry is 1000-2000mPa·s.

3. The coating process according to claim 1 or 2, characterized in that: In step (1), the surface-treated carbon fiber is obtained by surface-treating carbon fiber; The surface treatment method includes: plasma treatment, chemical oxidation treatment, coupling treatment or nanoparticle-assisted modification treatment.

4. The coating process according to claim 1, characterized in that: The immersion conditions include: an immersion time of 3 to 10 seconds and a pulling rate of 0.1 to 1 cm / s.

5. The coating process according to claim 1 or 4, characterized in that: The spraying conditions include: spraying pressure of 0.1-0.5 MPa, spraying distance of 10-25 cm; The spin coating conditions include: a rotation speed of 1000 to 5000 rpm and a time of 10 to 60 s; The brushing conditions include: a brushing pressure of 0.05 to 0.3 N, a brushing speed of 10 to 50 mm / s, and a brushing number of times of 1 to 5.

6. The coating process according to claim 5, characterized in that: In step (1), the drying conditions include: temperature of 20 to 80° C. and time of 10 to 30 minutes.

7. The coating process according to claim 1, characterized in that: In step (2), during the process of repeating the operation of step (1), the solid content of the carbon fiber positive electrode material slurry is greater than or equal to the solid content of the carbon fiber positive electrode material slurry used last time; Alternatively, in step (2), during the process of repeating the operation of step (1), the viscosity of the carbon fiber positive electrode material slurry is greater than or equal to the viscosity of the carbon fiber positive electrode material slurry used last time.

8. The coating process according to claim 1, characterized in that: In step (3), the drying conditions include: a temperature of 50 to 120° C. and a time of 30 to 90 min; The heat treatment conditions include: being carried out under a protective atmosphere, at a temperature of 150 to 250° C., and for a time of 1 to 4 hours.

9. Carbon fiber positive electrode material, characterized in that: The invention is prepared by the coating process described in any one of claims 1 to 8.

10. Use of the carbon fiber positive electrode material according to claim 9 in a structure-energy storage integrated composite material.