Magnetic responsive electrode paste, low tortuosity magnetic field assisted coating preparation method and battery

Abstract

This invention discloses a magnetically responsive electrode slurry, a low-torsion magnetic field-assisted coating preparation method, and a battery, belonging to the field of battery electrode manufacturing technology. The magnetic slurry comprises active materials, magnetic alignment agents, solvents, and binders. The core of the preparation method is to coat the magnetic slurry onto a current collector, then apply a uniform magnetic field perpendicular to the current collector during the wet film leveling stage to induce the magnetic alignment agent to stand vertically. After in-situ curing and drying, a low-torsion thick electrode is obtained. This invention constructs a vertical transport channel through magnetic field-assisted technology, effectively solving the problems of labyrinth effect, low ion / electron transport efficiency, and fast-charging failure in ultra-thick electrodes. The electrode tortuosity can be reduced to 1.2-1.4, and the 5C discharge capacity retention rate is ≥88%.

Description

Technical Field

[0001] This application relates to the field of battery electrode technology, and in particular to magnetically responsive electrode slurry, low-torsivity magnetic field-assisted coating preparation method, and battery. Background Technology

[0002] With the rapid development of new energy battery technology, improving battery energy density and reducing manufacturing costs have become core R&D directions in the industry. In the field of electrode manufacturing, increasing electrode thickness from the traditional 50μm to 200-500μm is a key path to achieve high energy density, reduce current collector usage, and thus lower costs, and has become the mainstream development trend in the industry.

[0003] However, the large-scale application of ultra-thick electrodes faces severe limitations in kinetic performance, which has become a core bottleneck restricting their industrialization. Traditional electrodes are prepared using a blade coating process. During coating and drying, the flaky particles (such as graphite and hard carbon) and conductive agents in the electrode slurry tend to align horizontally parallel to the current collector due to the slurry's flow characteristics and gravity, forming a randomly distributed microstructure. This structure leads to two major problems: First, a significant "maze effect" occurs, where ions must navigate through layers of particle barriers to reach the surface from the bottom of the electrode, resulting in an actual transport path length that can be 3-5 times the straight-line distance, with extremely high tortuosity. Second, ion transport efficiency drops sharply, leading to a severe degradation in the rate performance of thick electrodes. Even at a 1C charging rate, significant polarization occurs, greatly increasing the risk of hydrogen evolution and failing to meet the fast-charging performance requirements of power batteries.

[0004] To address these issues, the industry has attempted various technical solutions, but all have insurmountable limitations, failing to balance performance, cost, and the demands of large-scale production. Laser drilling technology, by creating vertical channels on dried electrodes, can reduce tortuosity to some extent; however, this technology is a subtractive processing method, resulting in the loss of active material and a decrease in battery energy density. Furthermore, the purchase and operation costs of laser equipment are high, and the processing efficiency is low, making it difficult to adapt to roll-to-roll mass production lines. Cryocasting technology, which uses ice crystal growth to induce vertical channel structures, can produce low-torque electrodes in a laboratory environment, but the process is complex and requires stringent temperature and humidity control, making continuous roll-to-roll production impossible and lacking prospects for industrial application.

[0005] Therefore, there is an urgent need in this field for a non-subtractive, low-cost, thick electrode fabrication technology that can be adapted to existing production lines, effectively constructing vertically oriented ion transport channels, significantly reducing electrode tortuosity, improving the rate performance of thick electrodes while ensuring energy density and production efficiency, and meeting the high-performance and large-scale production requirements of power batteries. Summary of the Invention

[0006] To address at least one of the aforementioned technical problems, and to develop a non-subtractive, low-cost, and adaptable thick electrode to existing production lines, this application provides a magnetically responsive electrode slurry, a low-torsivity magnetic field-assisted coating preparation method, and a battery.

[0007] In a first aspect, the magnetic response electrode paste provided in this application comprises, by mass percentage, 65 wt% to 90 wt% of solid components and 10 wt% to 35 wt% of solvent; The solid components, based on a total mass of 100%, include the following components: Active substance 75 wt%~92 wt%; Magnetic orientation agent 1 wt%~8 wt%; Adhesive 1 wt%~5 wt%; Dispersant or thickener 0.5 wt%~5 wt%; The magnetic orientation agent is one or more of the following: magnetic conductive agent, magnetic emulsion template, or chain nickel powder. The magnetic conductive agent is a carbon material with a surface-modified magnetic nanolayer. The magnetic emulsion template uses micron-sized oil droplets containing magnetic fluid. Optionally, the carbon material is selected from at least one of carbon nanotubes, carbon fibers, or graphene; the magnetic nanolayer is made of Fe3O4 or Ni.

[0008] Optionally, the magnetic fluid is an oleic acid-coated Fe3O4 kerosene-based magnetic fluid, and the magnetic emulsion template accounts for 3%-8% of the volume of the slurry.

[0009] Optionally, the active material is selected from at least one of Prussian blue, hard carbon, graphite, NCA, NMC, and LFP; The adhesive is selected from at least one of styrene-butadiene rubber, carboxymethyl cellulose, and polyvinylidene fluoride.

[0010] Secondly, this application provides a low-torsivity magnetic field-assisted coating preparation method, comprising the following steps: S1. Slurry preparation: The active material, magnetic orientation agent, solvent, binder and dispersant are mixed and dispersed to obtain the magnetic response electrode slurry as described in claim 1; S2. Coating operation: The magnetic response electrode slurry is uniformly coated on the surface of the current collector to form a wet film; S3. Magnetic field orientation treatment: The current collector coated with wet film is conveyed to the leveling area, and a uniform magnetic field perpendicular to the plane of the current collector is applied in the leveling area, so that the magnetic orientation agent overcomes the viscosity resistance of the slurry under the action of magnetic torque and rotates to an upright state perpendicular to the current collector. S4. In-situ curing and shaping: Maintain the uniform magnetic field until the wet film is surface dry and shaped, freezing the vertical orientation structure inside the electrode. S5. Subsequent processing: The shaped electrode is sent into an oven to be completely dried, resulting in a thick electrode with low tortuosity and vertical orientation.

[0011] Optionally, the magnetic field strength of the uniform magnetic field described in S3 can be adjusted according to the type of magnetic alignment agent: when the magnetic alignment agent is a magnetic conductive agent, the magnetic field strength is 100-200 mT; when the magnetic alignment agent is a nickel nanochain, the magnetic field strength is 40-60 mT; when the magnetic alignment agent is a magnetic emulsion template, the magnetic field strength is 80-150 mT.

[0012] Optionally, the wet film temperature of the slurry in the leveling zone in S3 is controlled at 25-40℃, the viscosity is controlled at 5000-20000mPa·s, and the vertical orientation completion time of the magnetic orientation agent is 1-5 seconds.

[0013] Optionally, the in-situ curing and shaping described in S4 uses infrared lamp irradiation to achieve rapid surface drying, with a drying time of 5-15 seconds, and the moisture content of the electrode wet film after surface drying is ≤10%.

[0014] Optionally, the current collector is a copper foil or an aluminum foil, the current collector thickness is 8-20 μm, and the coating process adopts a roll-to-roll continuous coating method with a coating speed of 3-10 m / min.

[0015] Thirdly, this application provides a battery including a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode and / or the negative electrode are low-torsion vertically oriented thick electrodes prepared by the preparation method described above.

[0016] In summary, the present invention has at least one of the following beneficial technical effects: 1. It can significantly reduce the tortuosity of ultra-thick electrodes of 200-500μm, effectively breaking through the kinetic bottleneck of severe polarization and high hydrogen evolution risk of traditional thick electrodes during fast charging, so that the electrode 5C discharge capacity retention rate is stable at more than 88%, ensuring the high rate performance of thick electrodes.

[0017] 2. The vertical transmission channel is constructed using a non-subtractive material method, which does not require the loss of active materials and can maximize the battery energy density; at the same time, it can be directly adapted to existing roll-to-roll mass production lines without the need for large-scale equipment modification, thus reducing the production threshold and cost of thick electrode industrialization.

[0018] 3. It is compatible with various active materials such as hard carbon, Prussian blue, and NCM811, and is compatible with various battery systems such as lithium-ion, sodium-ion, and aqueous systems. It can flexibly optimize ion or electron transport performance according to needs, and its technology has a wide range of applications.

[0019] 4. The vertically oriented structure induced by the magnetic field has excellent stability after in-situ solidification. It can effectively reduce the stress and volume expansion inside the electrode during battery charging and discharging, inhibit the shedding of active materials, and significantly improve the cycle stability and service life of the battery. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram comparing the microstructures (ion pathways); Figure 2 This is a schematic diagram of a magnetic field-assisted coating production line. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] This embodiment aims to provide a method for preparing an ultra-thick hard carbon anode based on the vertical orientation of magnetic carbon nanotubes (m-CNTs). The core objective is to solve the ion transport bottleneck and fast charging failure problem of the ultra-thick anode (300μm), achieve stable charge and discharge at 5C rate, and at the same time ensure the structural integrity and energy density of the electrode.

[0024] The technical solution of this application is as follows.

[0025] In a first aspect, the magnetic response electrode paste provided in this application comprises, by mass percentage, 65 wt% to 90 wt% of solid components and 10 wt% to 35 wt% of solvent; The solid components, based on a total mass of 100%, include the following components: Active substance 75 wt%~92 wt%; Magnetic orientation agent 1 wt%~8 wt%; Adhesive 1 wt%~5 wt%; Dispersant or thickener 0.5 wt%~5 wt%; The magnetic orientation agent is one or more of the following: magnetic conductive agent, magnetic emulsion template, or chain nickel powder. The magnetic conductive agent is a carbon material with a surface-modified magnetic nanolayer. The magnetic emulsion template uses micron-sized oil droplets containing magnetorheological fluid.

[0026] The technical solution of this application significantly reduces the solvent content in the slurry, which can reduce the energy consumption and time of the subsequent drying process and improve the coating production efficiency; at the same time, it supports the preparation of thick electrodes with higher loading capacity, directly improving the volumetric energy density and gravimetric energy density of the battery. It ensures the core electrochemical capacity of the electrode, providing sufficient magnetic responsiveness to achieve effective orientation while avoiding excessive occupation of the active material volume; the ratio of binder to dispersant or thickener ensures both the dispersion stability and coating adaptability of the slurry, and also ensures the mechanical strength and flexibility of the electrode after drying. Magnetic alignment agents offer three options: magnetic conductive agents, magnetic emulsion templates, and chain nickel powder, allowing for flexible selection based on different battery systems and performance requirements. Magnetic conductive agents retain the high conductivity of carbon nanotubes, carbon fibers, and graphene while imparting magnetic response characteristics. After alignment, they can form a vertical conductive network that runs through the electrode, significantly reducing electron transport resistance. Magnetic emulsion templates, after alignment, can construct continuous vertical ion channels inside the electrode, significantly reducing the tortuosity of lithium / sodium ion transport. Furthermore, the template can be completely removed during subsequent drying, leaving no residual impurities. Chain nickel powder combines magnetism and high conductivity. Its chain structure is more easily oriented under a magnetic field, rapidly forming a continuous conductive pathway, and the raw material cost is low.

[0027] Optionally, the carbon material is selected from at least one of carbon nanotubes, carbon fibers, or graphene; the magnetic nanolayer is made of Fe3O4 or Ni.

[0028] Optionally, the magnetic fluid is an oleic acid-coated Fe3O4 kerosene-based magnetic fluid, and the magnetic emulsion template accounts for 3%-8% of the volume of the slurry.

[0029] Optionally, the active material is selected from at least one of Prussian blue, hard carbon, graphite, NCA, NMC, and LFP; The adhesive is selected from at least one of styrene-butadiene rubber, carboxymethyl cellulose, and polyvinylidene fluoride.

[0030] Secondly, this application provides a low-torsivity magnetic field-assisted coating preparation method, comprising the following steps: S1. Slurry preparation: The active material, magnetic orientation agent, solvent, binder and dispersant are mixed and dispersed to obtain the magnetic response electrode slurry as described in claim 1; S2. Coating operation: The magnetic response electrode slurry is uniformly coated on the surface of the current collector to form a wet film; S3. Magnetic field orientation treatment: The current collector coated with wet film is conveyed to the leveling area, and a uniform magnetic field perpendicular to the plane of the current collector is applied in the leveling area, so that the magnetic orientation agent overcomes the viscosity resistance of the slurry under the action of magnetic torque and rotates to an upright state perpendicular to the current collector. S4. In-situ curing and shaping: Maintain the uniform magnetic field until the wet film is surface dry and shaped, freezing the vertical orientation structure inside the electrode. S5. Subsequent processing: The shaped electrode is sent into an oven to be completely dried, resulting in a thick electrode with low tortuosity and vertical orientation.

[0031] Optionally, the magnetic field strength of the uniform magnetic field described in S3 can be adjusted according to the type of magnetic alignment agent: when the magnetic alignment agent is a magnetic conductive agent, the magnetic field strength is 100-200 mT; when the magnetic alignment agent is a nickel nanochain, the magnetic field strength is 40-60 mT; when the magnetic alignment agent is a magnetic emulsion template, the magnetic field strength is 80-150 mT.

[0032] Optionally, the wet film temperature of the slurry in the leveling zone in S3 is controlled at 25-40℃, the viscosity is controlled at 5000-20000mPa·s, and the vertical orientation completion time of the magnetic orientation agent is 1-5 seconds.

[0033] Optionally, the in-situ curing and shaping described in S4 uses infrared lamp irradiation to achieve rapid surface drying, with a drying time of 5-15 seconds, and the moisture content of the electrode wet film after surface drying is ≤10%.

[0034] Optionally, the current collector is a copper foil or an aluminum foil, the current collector thickness is 8-20 μm, and the coating process adopts a roll-to-roll continuous coating method with a coating speed of 3-10 m / min.

[0035] A uniform magnetic field perpendicular to the current collector plane is applied, causing the magnetic alignment agent to spontaneously rotate to an upright position under the influence of magnetic torque. This allows for the construction of a highly ordered vertical conductive network and ion channels within the electrode. Different magnetic field strengths are set for different types of magnetic alignment agents, ensuring sufficient alignment while avoiding problems such as slurry disturbance and wet film deformation caused by excessively strong magnetic fields. The wet film temperature is controlled at 25–40℃, and the viscosity at 5000–20000 mPa. This method enables the magnetic alignment agent to overcome the viscosity resistance of the slurry to achieve rotational alignment without causing wet film sagging or uneven thickness. Utilizing a rapid surface drying method with infrared lamps, the moisture content of the wet film is reduced to below 10% within 5-15 seconds, while maintaining a uniform magnetic field throughout. This instantly "freezes" the vertically aligned structure inside the electrode, avoiding the collapse and disorder of the alignment structure caused by solvent evaporation and particle sedimentation during traditional drying processes. This method can prepare thick electrodes with a thickness of 100-300 μm while maintaining excellent ion and electron transport properties.

[0036] Thirdly, this application provides a battery including a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode and / or the negative electrode are low-torsion vertically oriented thick electrodes prepared by the preparation method described above.

[0037] The specific preparation steps are as follows: Example 1 Multi-walled carbon nanotubes (MWCNTs) with a diameter of 20–50 nm and a length of 5–10 μm were selected as the matrix material. MWCNTs were first placed in anhydrous ethanol and ultrasonically dispersed at a power of 200–300 W for 20–30 min to remove impurities and agglomerates on the surface of MWCNTs, thereby obtaining a uniformly dispersed MWCNTs ethanol dispersion with a concentration controlled at 2–5 mg / mL.

[0038] Fe3O4 nanoparticle precursor was slowly added to the above MWCNTs ethanol dispersion. Ferric nitrate and ferrous sulfate were mixed in a molar ratio of 2:1. Ammonia was added to adjust the pH of the system to 8-9. The reaction temperature was controlled at 60-70℃ and the mixture was stirred at a constant temperature for 1.5-2 h at a speed of 300-400 r / min to ensure that Fe3O4 nanoparticles were uniformly deposited on the surface of MWCNTs.

[0039] After the reaction was completed, the mixture was centrifuged at 8000-10000 r / min for 10-15 min. The precipitate was collected and washed 3-4 times with anhydrous ethanol and deionized water to remove unreacted precursors and impurities. The precipitate was then placed in a vacuum oven and dried at 80-100℃ for 4-6 h to obtain magnetic carbon nanotubes with a uniform Fe3O4 magnetic layer on the surface. The thickness of the Fe3O4 magnetic layer was 5-10 nm, and the saturation magnetization of the m-CNTs reached 8-12 emu / g.

[0040] Hard carbon with a particle size of 10-20 μm was used as the active material, styrene-butadiene rubber as the binder, carboxymethyl cellulose as the thickener, and the above-prepared m-CNT as the core magnetic conductive agent. Deionized water was used as the solvent. The active material, m-CNT, CMC, SBR, and solvent were added to the mixing tank in a mass ratio of 85:3:2:2:18.

[0041] First, stir at a low speed of 500~800 r / min for 30 min to make the components initially mixed evenly. Then, increase the speed to 1500~2000 r / min for high-speed dispersion for 2~3 h. During the process, control the slurry temperature at 25~35℃. Finally, obtain a hard carbon anode base slurry with a viscosity of 8000~15000 mPa·s, uniform dispersion, and no obvious agglomeration.

[0042] A roll-to-roll continuous coating process is used to uniformly coat the above-mentioned hard carbon negative electrode base slurry onto the surface of a copper foil current collector with a thickness of 8~12 μm. The wet film thickness is controlled at 450~500 μm to match the final electrode thickness of 300 μm after drying. The coating speed is 3~5 m / min to ensure that the wet film surface is flat and free of scratches and bubbles.

[0043] A copper foil coated with a wet film is conveyed to a leveling zone. A permanent magnet array perpendicular to the current collector plane is placed in the leveling zone, and a uniform magnetic field is applied vertically. The magnetic field strength is precisely controlled at 150 mT. Simultaneously, the ambient temperature in the leveling zone is controlled at 25–40°C, the wet film viscosity at 10,000–20,000 mPa·s, and the magnetic field duration is controlled at 2–3 s. Under these conditions, the m-CNTs rapidly overcome the viscosity resistance of the slurry under the action of the magnetic torque, rotating to an upright position perpendicular to the copper foil current collector, forming a vertical CNT array that penetrates the thickness of the wet film.

[0044] While maintaining the uniform magnetic field, the wet film is rapidly dried and shaped using an infrared lamp. The infrared lamp temperature is controlled at 70~90℃ and the drying time is 8~12 s, which reduces the surface moisture content of the wet film to below 10%. This stabilizes the vertical orientation structure of m-CNTs inside the electrode, preventing structural collapse or orientation shift during subsequent drying.

[0045] After surface drying, the magnetic field is removed, and the electrode is sent into a tunnel oven for complete drying. The oven adopts a segmented temperature control mode: the first segment (inlet) temperature is 80℃, the second segment temperature is 100℃, and the third segment (outlet) temperature is 120℃. The total drying time is 3~4 hours to ensure that the final moisture content of the electrode is ≤1%, and an ultra-thick hard carbon anode with a thickness of 300 μm is obtained.

[0046] The dried, ultra-thick hard carbon anode is subjected to roll pressing, with the pressing pressure controlled at 10~15 MPa to ensure that the electrode compaction density is 1.2~1.4 g / cm³, while ensuring that the vertical CNT array structure is not damaged. Subsequently, the electrode is cut into sheets, the tabs are welded, and assembled into a coin cell.

[0047] Performance testing of the assembled battery and electrodes showed that the tortuosity of the ultra-thick hard carbon anode decreased from 4.2 in the traditional process to 1.35, and the effective ionic conductivity reached 8.5 mS / cm; the 5C discharge capacity retention rate was 92.0%, which is far superior to the electrode prepared by the traditional non-magnetic field process; after 100 cycles of 5C fast charging, the capacity retention rate was still ≥88%, the polarization degree was significantly reduced, and there was no obvious hydrogen evolution phenomenon, which fully meets the requirements for high-rate ultra-thick anode use.

[0048] Example 2 First, Fe3O4 nanoparticles coated with oleic acid were synthesized: Fe3O4 nanoparticles with a particle size of 10~20 nm were selected as the magnetic response core. Oleic acid was added as a surfactant at a mass ratio of 1:5~1:8 to Fe3O4. The mixture was placed in an environment of 80~90℃ and stirred at a speed of 500~800 r / min for 2~3 h to ensure that oleic acid was uniformly modified on the surface of Fe3O4 nanoparticles, thus obtaining superparamagnetic Fe3O4 particles with good dispersibility.

[0049] Subsequently, a kerosene-based magnetic fluid was prepared: the modified Fe3O4 particles were added to industrial-grade kerosene to form a dispersion system with a mass-volume ratio of 5% to 10%. The system was ultrasonically treated with a power of 300 to 500 W for 30 to 60 minutes, and the system was kept uniformly dispersed during the ultrasonic process. Finally, a kerosene-based magnetic fluid with a saturation magnetization of 10 to 15 emu / g and no obvious sedimentation was obtained. After the magnetic fluid was prepared, it was stored away from light to prevent the Fe3O4 particles from oxidizing.

[0050] Prussian blue was used as the active material, carboxymethyl cellulose as the binder, conductive carbon black as the auxiliary conductive agent, and deionized water as the solvent. The materials were mixed in a mass ratio of active material: binder: auxiliary conductive agent: solvent = 80:3:2:15, and then stirred and dispersed in a stirring device. The basic viscosity of the slurry after stirring was controlled to be 3000~8000 mPa·s, so as to obtain a uniform and stable aqueous Prussian blue base slurry.

[0051] The kerosene-based magnetic fluid prepared above was added to the water-based Prussian blue base slurry at a volume ratio of 3% to 8%, and Span-80 and Tween-80 compound emulsifiers were added at the same time to ensure that the emulsifiers were compatible with the CMC binder and did not affect the stability of the slurry.

[0052] The mixed system was placed in a high-speed shear emulsification device and sheared at 8000-12000 r / min for 10-15 min at an environment of 25-30℃, with the emulsification temperature controlled to not exceed 30℃ and not fall below 25℃, ultimately forming a magnetic emulsion template slurry with an oil droplet size of 1-5μm and a particle size distribution variation coefficient ≤15%. Stability testing of the emulsion slurry showed no obvious stratification after standing for 24 hours, meeting the requirements for coating application.

[0053] Using a roll-to-roll continuous coating method, the above-mentioned magnetic emulsion template slurry is uniformly coated on the surface of an aluminum foil current collector with a thickness of 8~20 μm to form a wet electrode with a wet film thickness adapted to the final electrode thickness.

[0054] The aluminum foil coated with a wet film is conveyed to the leveling zone. A uniform magnetic field perpendicular to the plane of the collector is applied in the leveling zone. The magnetic field strength is controlled at 80~150 mT, while the viscosity of the wet film in the leveling zone is controlled at 5000~20000 mPa·s. The magnetic field is applied for 2~5 s. This causes the magnetic oil droplets in the slurry to overcome the viscosity resistance of the slurry under the action of the magnetic torque, move rapidly along the direction perpendicular to the collector, converge and connect in series to form a continuous oil column that runs through the entire thickness of the wet film.

[0055] While maintaining the uniform magnetic field, use an infrared lamp at 60~80℃ to quickly dry the wet film. The drying time is controlled at 5~15 s to ensure that the moisture content of the wet film is ≤10%, thus freezing the vertically arranged oil column structure and the initial shape of the channels inside the electrode.

[0056] After surface drying, the electrodes are sent to an oven for final drying. The oven temperature is controlled at 100~120℃ and the drying time is 2~3 hours. Normal pressure air is used for drying to completely evaporate the kerosene and other oil phase components in the oil column, and the space originally occupied by the oil column forms a vertical cylindrical channel.

[0057] The performance of the prepared Prussian blue cathode thick electrode was tested. The results showed that the electrode tortuosity was as low as 1.2, the effective ionic conductivity reached 9.2 mS / cm, and the 5C discharge capacity retention rate was 90.5%. The electrode porosity was controlled at 25%~35%, the pore structure was intact and there was no collapse. The ion transport path inside the electrode was significantly shortened, which completely solved the maze effect problem of traditional thick electrodes. Moreover, no active material was lost, and the battery energy density was effectively guaranteed.

[0058] Example 3 Commercially available chain-like nickel powder was selected as the core magnetic orientation agent. Its particle size is 50~100 nm and chain length is 2~5 μm. It has ferromagnetism and shape anisotropy and does not require additional magnetic modification. The active material is NCM811 ternary material with a particle size of 15~25 μm. The binder is polyvinylidene fluoride, the dispersant is N-methylpyrrolidone, and the current collector is aluminum foil with a thickness of 12~20 μm.

[0059] Pretreatment of nickel nanochains: The nickel nanochains were placed in NMP and ultrasonically dispersed for 20-30 min at a power of 400-600 W with an ultrasonic speed of 10000-12000 r / min to remove the oxide layer and agglomerates on the surface of the nickel nanochains, and a uniform nickel nanochain NMP dispersion with a concentration of 3-6 mg / mL was obtained for later use.

[0060] According to the mass ratio of active material NCM811: nickel nanochains: PVDF: conductive carbon black: solvent NMP = 88:2:3:2:15, NCM811 and conductive carbon black were added to a mixing tank in sequence. The mixture was first stirred at a low speed of 600~800 r / min for 30 min to achieve preliminary mixing. Then, the pretreated nickel nanochain NMP dispersion was added and the mixture was stirred for another 1 h. Finally, the dissolved PVDF binder solution was added and the speed was increased to 1800~2200 r / min for high-speed dispersion for 2~3 h. During the process, the slurry temperature was controlled at 25~30℃ and the final viscosity was 10000~20000 mPa·s to obtain a uniformly dispersed and non-agglomerated NCM811 positive magnetic slurry.

[0061] A roll-to-roll continuous coating process is used to uniformly coat the above-mentioned NCM811 positive electrode magnetic paste onto the surface of the aluminum foil current collector. The wet film thickness is controlled at 400~450 μm, which is adapted to the final dried electrode thickness of 300 μm. The coating speed is 5~8 m / min to ensure that the wet film surface is flat and free of bubbles and scratches.

[0062] Aluminum foil coated with a wet film is conveyed to a leveling zone. A uniform magnetic field perpendicular to the plane of the current collector is applied in the leveling zone. Because nickel nanochains have strong magnetic responsiveness, the magnetic field strength only needs to be controlled at 40~60 mT. At the same time, the ambient temperature of the leveling zone is controlled at 25~35℃, the viscosity of the wet film is controlled at 12000~18000 mPa·s, and the magnetic field action time is controlled at 1~2 s. This will cause the nickel nanochains to rotate rapidly under the action of the magnetic torque and stand vertically perpendicular to the current collector, forming a vertical nickel nanochain conductive network that runs through the thickness of the wet film.

[0063] While maintaining the aforementioned weak magnetic field, an infrared lamp is used to rapidly surface dry and shape the wet film. The infrared lamp temperature is controlled at 60~80℃, and the surface drying time is 6~10 s, so that the moisture content of the wet film is reduced to below 10%, thus stabilizing and freezing the vertical orientation structure of the nickel nanochains and preventing orientation shift during subsequent drying.

[0064] After surface drying, the magnetic field is removed, and the electrode is sent into an oven for complete drying. The oven temperature is controlled at 110~130℃, and the drying time is 2.5~3.5 h. A vacuum drying environment is used to ensure that the final moisture content of the electrode is ≤0.5%, and an NCM811 ultra-thick cathode with a thickness of 300 μm is obtained.

[0065] The dried ultra-thick positive electrode is subjected to roll pressing, with the rolling pressure controlled at 12~18 MPa to ensure that the electrode compaction density is 3.8~4.0 g / cm³, while ensuring that the vertical nickel nanochain conductive network is not damaged; then the electrode is cut, the tabs are welded, and assembled into a pouch cell.

[0066] Performance testing of the electrode and battery revealed that the electronic conductivity of this NCM811 ultra-thick cathode reached 120 S / m, far exceeding that of electrodes prepared by traditional processes; the tortuosity was reduced to 1.4, and the 5C discharge capacity retention rate was 89.2%; after 200 cycles of 3C fast charging and 5C discharge, the battery capacity retention rate was still ≥86%, and the electrode exhibited good stability in alkaline and weakly acidic electrolytes, with no nickel nanochain dissolution. This effectively solved the electronic transport bottleneck of high-resistivity ternary thick electrodes, while also reducing the energy consumption and control difficulty of the magnetic field-assisted process.

[0067] To further verify the superiority of the magnetic field-assisted coating technique for preparing low-torsion vertically oriented thick electrodes of the present invention, the following three comparative examples were set up. Unless otherwise specified below, the experimental conditions of each comparative example are consistent with the basic experimental conditions of Example 1 of the present invention.

[0068] Comparative Example 1 1. Preparation of magnetic slurry: According to the formula and process of Example 1 of this invention, a hard carbon negative electrode magnetic slurry containing magnetic CNTs was prepared. The slurry viscosity, dispersibility and other parameters were completely consistent with those of Example 1.

[0069] 2. Coating operation: The above magnetic paste is uniformly coated on the surface of the copper foil current collector using a roll-to-roll continuous coating process, and the wet film thickness is the same as in Example 1.

[0070] 3. Natural drying and curing: After coating, without applying any external magnetic field, the wet film is directly sent into the leveling area for natural leveling, and then put into the oven to complete the drying and shaping according to the drying process of Example 1 to obtain a 300μm thick hard carbon anode.

[0071] 4. Performance Testing Results: Microstructural observation and electrochemical performance testing of the electrode revealed that the m-CNTs inside the electrode were randomly and disordered, without forming a vertically oriented structure. The core performance indicators were: electrode thickness 300 μm, tortuosity 4.50, effective ionic conductivity 2.1 mS / cm, and 5C discharge capacity retention rate of only 25.0%. After being assembled into a coin cell, the electrode exhibited extremely poor high-rate performance, severe polarization during charging, and significant hydrogen evolution, failing to meet the requirements for power battery use.

[0072] Comparative Example 2 1. Preparation of ordinary slurry: The magnetic CNTs in Example 1 were replaced with ordinary multi-walled carbon nanotubes without Fe3O4 magnetic layer modification. The proportions and mixing processes of the remaining slurry components were completely consistent with those in Example 1 to prepare ordinary hard carbon anode slurry.

[0073] 2. Magnetic field-assisted coating: The slurry was coated according to the coating process of Example 1. A vertical uniform magnetic field of the same intensity was applied to the leveling zone. The magnetic field application time, the temperature of the leveling zone, the viscosity and other parameters were the same as those in Example 1.

[0074] 3. Subsequent processing: The electrode was prepared according to the drying and rolling process in Example 1 to obtain a 300μm thick hard carbon anode.

[0075] 4. Performance Testing Results: Microstructural observation shows that ordinary MWCNTs do not respond to external magnetic fields and remain randomly distributed within the electrode, failing to form a vertically oriented conductive network. The core performance indicators are: electrode thickness 300 μm, tortuosity 4.45, effective ionic conductivity 2.3 mS / cm, and 5C discharge capacity retention rate of only 28.0%. Electrochemical testing shows that its rate performance is similar to Comparative Example 1, only slightly better than the non-magnetic field process, fully demonstrating that the "magnetic modification" of the conductive agent is the core prerequisite for achieving magnetic field-induced vertical orientation and improving electrode performance. Conductive agents without magnetic modification cannot optimize the electrode structure through magnetic field action.

[0076] Comparative Example 3 This comparative example aims to compare the advantages and disadvantages of the technology of this invention with existing laser drilling technology. The specific steps are as follows: 1. Preparation of ordinary thick electrode: According to the traditional scraping process, a hard carbon anode slurry without magnetic orientation agent was prepared. The formula was the same as in Example 1, except that m-CNTs were removed. After coating, the slurry was naturally dried and rolled to obtain a 300μm thick ordinary hard carbon anode.

[0077] 2. Laser drilling process: Using existing laser drilling equipment, the dried ordinary electrode sheet is vertically drilled. The diameter and density of the holes are adapted to the spacing of the m-CNT vertical array in Example 1.

[0078] 3. Performance Testing Results: Tests showed that although the electrode improved some ion transport paths due to the presence of vertical holes, and its core performance indicators were: electrode thickness 300μm, tortuosity 1.5, effective ionic conductivity 7.8mS / cm, and 5C discharge capacity retention rate 88.00%, it had two major defects: First, some active material was removed during the drilling process, resulting in a lower battery energy density than in Example 1 of this invention; second, active material detachment and pulverization occurred at the laser-drilled edges, leading to poor electrode structural stability. After 100 5C charge-discharge cycles, the capacity retention rate was far lower than that of Example 1, fully demonstrating the significant advantages of the "non-material-reducing hole-making" method of this invention in ensuring energy density and structural stability.

[0079] Table 1: Performance Comparison of Examples and Comparative Examples

[0080] The technical solution of this application achieves precise control of electrode structure through the synergy of magnetic orientation agent and vertical magnetic field, which significantly reduces the tortuosity of electrode ion transport from the traditional 4.2~4.5 to 1.2~1.4, and increases the effective ionic conductivity by 3~4 times, so that the 300μm ultra-thick electrode can still maintain excellent rate performance. This invention provides a magnetic carbon nanotube solution, which combines high conductivity and magnetic responsiveness. After orientation, it forms a vertical conductive network that runs through the electrode, while optimizing electron and ion transport, resulting in optimal overall performance. It is suitable for the negative electrode of power batteries with extremely high rate performance requirements. A magnetic emulsion template solution achieves "non-subtractive pore creation" through in-situ pore creation induced by a magnetic field, avoiding the loss of active material caused by traditional pore-forming techniques such as laser drilling. It constructs continuous vertical ion channels while maintaining high energy density, making it particularly suitable for positive electrode materials such as Prussian blue. A chain-like nickel powder solution possesses natural ferromagnetism and shape anisotropy, requiring no additional magnetic modification. It exhibits extremely strong magnetic responsiveness, requiring only a weak magnetic field of 40-60 mT for rapid orientation, significantly reducing the energy consumption and equipment cost of magnetic field-assisted processes. Simultaneously, it significantly improves the electronic conductivity of ternary materials, making it suitable for large-scale industrial production.

[0081] The in-situ curing process, combining continuous magnetic field application with rapid infrared surface drying, reduces the moisture content of the wet film to below 10% within 5-15 seconds. This stabilizes the vertical orientation structure of the magnetic alignment agent within the electrode before solvent evaporation and particle settling. This solves the problems of orientation structure collapse and conductive agent re-agglomeration caused by capillary forces resulting from solvent evaporation during traditional drying processes, ensuring a high degree of orderliness in the final electrode's internal structure.

[0082] In Comparative Example 1, only a magnetic orientation agent was added without applying a magnetic field. The conductive agent was still randomly and disordered, the electrode tortuosity was as high as 4.50, the ion transport path was tortuous and long, resulting in a capacity retention rate of only 25.0% at 5C rate, severe polarization and obvious hydrogen evolution, and the 300μm thick electrode could not be used normally at all.

[0083] Comparative Example 2: Conductive agents without magnetic modification applied only by a magnetic field cannot generate magnetic torque to drive orientation. Ordinary carbon nanotubes remain randomly distributed in the magnetic field, and the electrode performance is almost indistinguishable from that of the process without a magnetic field.

[0084] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0085] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0086] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A magnetically responsive electrode paste, characterized in that, By mass percentage, it comprises 65 wt% to 90 wt% solid components and 10 wt% to 35 wt% solvent. The solid components, based on a total mass of 100%, include the following components: Active substance 75 wt%~92 wt%; Magnetic orientation agent 1 wt%~8 wt%; Adhesive 1 wt%~5 wt%; Dispersant or thickener 0.5 wt%~5 wt%; The magnetic orientation agent is one or more of the following: magnetic conductive agent, magnetic emulsion template, or chain nickel powder. The magnetic conductive agent is a carbon material with a surface-modified magnetic nanolayer. The magnetic emulsion template uses micron-sized oil droplets containing magnetorheological fluid.

2. The magnetically responsive electrode paste according to claim 1, characterized in that, The carbon material is selected from at least one of carbon nanotubes, carbon fibers, or graphene; the magnetic nanolayer is made of Fe3O4 or Ni.

3. The magnetically responsive electrode paste according to claim 1, characterized in that, The magnetic fluid is an oleic acid-coated Fe3O4 kerosene-based magnetic fluid, and the magnetic emulsion template accounts for 3%-8% of the volume of the slurry.

4. The magnetically responsive electrode paste according to claim 1, characterized in that, The active substance is selected from at least one of Prussian blue, hard carbon, graphite, NCA, NMC, and LFP; The adhesive is selected from at least one of styrene-butadiene rubber, carboxymethyl cellulose, and polyvinylidene fluoride.

5. A method for preparing low-torsivity magnetic field-assisted coating, characterized in that, Includes the following steps: S1. Slurry preparation: The active material, magnetic orientation agent, solvent, binder and dispersant are mixed and dispersed to obtain the magnetic response electrode slurry as described in claim 1; S2. Coating operation: The magnetic response electrode slurry is uniformly coated on the surface of the current collector to form a wet film; S3. Magnetic field orientation treatment: The current collector coated with wet film is conveyed to the leveling area, and a uniform magnetic field perpendicular to the plane of the current collector is applied in the leveling area, so that the magnetic orientation agent overcomes the viscosity resistance of the slurry under the action of magnetic torque and rotates to an upright state perpendicular to the current collector. S4. In-situ curing and shaping: Maintain the uniform magnetic field until the wet film is surface dry and shaped, freezing the vertical orientation structure inside the electrode. S5. Subsequent processing: The shaped electrode is sent into an oven to be completely dried, resulting in a thick electrode with low tortuosity and vertical orientation.

6. The preparation method according to claim 5, characterized in that, The magnetic field strength of the uniform magnetic field described in S3 is adjusted according to the type of magnetic alignment agent: when the magnetic alignment agent is a magnetic conductive agent, the magnetic field strength is 100-200 mT; when the magnetic alignment agent is chain nickel powder, the magnetic field strength is 40-60 mT; when the magnetic alignment agent is a magnetic emulsion template, the magnetic field strength is 80-150 mT.

7. The preparation method according to claim 5, characterized in that, The wet film temperature of the slurry in the leveling zone described in S3 is controlled at 25-40℃, the viscosity is controlled at 5000-20000mPa·s, and the vertical orientation completion time of the magnetic orientation agent is 1-5 seconds.

8. The preparation method according to claim 5, characterized in that, The in-situ curing and shaping described in S4 uses infrared lamp irradiation to achieve rapid surface drying, with a drying time of 5-15 seconds. After surface drying, the moisture content of the electrode wet film is ≤10%.

9. The preparation method according to claim 5, characterized in that, The current collector is made of copper foil or aluminum foil, with a thickness of 8-20 μm. The coating process adopts a roll-to-roll continuous coating method with a coating speed of 3-10 m / min.

10. A battery, characterized in that, It includes a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode and / or the negative electrode are low-torsional vertically oriented thick electrodes prepared by the preparation method of claim 5.

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