Battery cell, battery, method of manufacture and device having high rate capability

Abstract

This invention discloses a high-rate-performance battery cell, battery, preparation method, and apparatus. The method involves coating the battery separator with a polymer material coating; assembling the separator containing the polymer material coating with a positive electrode containing positive electrode material and a negative electrode containing negative electrode material to form a semi-finished battery cell; injecting electrolyte; placing the cell between two clamping plates; and applying pressure to tightly bond the positive and negative electrode materials to the separator. During the first charge formation, the entire assembly formed by the two clamping plates undergoes thermal cross-linking and ultrasonic shearing. In this invention, the high-temperature formation process, after ultrasonic vibration, shearing, and compression, results in a state where the conductive agent is uniformly adhered to the material particles and evenly dispersed between the particle chains. This significantly reduces the possibility of excessively strong or weak local conductive agents, effectively lowering the film resistivity of the electrode sheets and improving the battery's rate performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and specifically to a battery cell, battery, preparation method and apparatus with high rate performance. Background Technology

[0002] With the widespread use of electronic products, the demand for longer battery life has been stimulated, making the improvement of battery energy density an urgent priority. Mainstream methods for increasing battery energy density primarily rely on advancements in materials technology, such as gradually increasing the voltage of the positive electrode and multi-lithium storage technology for the negative electrode, such as silicon-carbon anode materials. Simultaneously, other auxiliary materials in the battery are being further thinned to improve energy density. Alongside improving energy density, fast charging and discharging technologies have also been developed and applied to various electronic products. As electronic products become smaller and batteries thinner, high-rate performance requires support for fast charging and discharging to meet the demands of product usage.

[0003] The thinner the battery, the more prone it is to deformation during subsequent charge and discharge cycles when using aluminum-plastic film as the outer casing, due to the uneven expansion stress direction of the electrode materials caused by the winding structure. After a certain number of cycles, the coefficient of electrochemical expansion increases, making the deformation more pronounced. This deformation leads to increased spacing between layers and longer ion migration paths. Battery impedance increases significantly, ultimately resulting in rapid capacity decay. Severe deformation can even push up the packaging of electronic products, causing defects. The industry standard method involves coating the separator with a PVDF or PMMA-based gel. After electrolyte is injected, the electrolyte swells the gel. When the battery is placed in a high-temperature clamping fixture, the high temperature accelerates the swelling of the gel. The swollen gel cross-links with the PVDF in the positive electrode and the binder in the negative electrode, forming a unified structure of the positive electrode, separator, and negative electrode. During charge and discharge, this cross-linked bond overcomes most of the stress from the negative electrode expansion, making the battery less prone to deformation during subsequent cycles.

[0004] The demand for high-rate performance necessitates high-rate lithium-ion batteries, which are characterized by rapid charging and discharging within short timeframes. These batteries maintain good performance at high rates, withstand more charge-discharge cycles, reduce battery degradation, and extend battery life. They are widely used in various fields, including electric vehicles, drones, energy storage systems, consumer electronics, power tools, cleaning tools, and toys. Due to their high current density, high-rate batteries experience faster stress release during charge-discharge cycles. Without intervention, the expansion forces at the positive and negative electrodes can lead to severe deformation of the electrode assembly. Common solutions involve hardening the battery by coating the separator with PVDF or PMMA polymer colloids. These colloids swell at high temperatures in the electrolyte, cross-linking with the colloids in the positive and negative electrodes. This three-pronged approach effectively overcomes the expansion stress during charging and discharging, thus controlling cell expansion and deformation.

[0005] Meanwhile, in the demand for high-rate performance batteries, the dispersion of tiny conductive agents in the positive and negative electrodes is also a key consideration. The uniformity of conductive agent dispersion in the electrodes is crucial to battery performance. Uneven dispersion of conductive agents can lead to a series of problems. Uneven dispersion of conductive agents can result in uneven current distribution within the electrode, thereby affecting the SoC (State of Charge) state of different parts of the electrode and accelerating battery degradation. Uneven dispersion of conductive agents can deteriorate the battery's kinetic performance, such as reducing the battery's rate performance and long-term cycle performance. Conductive agent agglomeration can lead to a significant increase in electrode resistance at locations without conductive agents, thus affecting the overall battery performance. Generally, the main reasons affecting the uneven dispersion of conductive agents are that the smaller the carbon black particle size, the higher the carbon black oil absorption value, the lower the carbon black structure, the larger the carbon black specific surface area, the higher the viscosity in the product, and the worse the dispersion performance. The dispersion process also has a profound impact on uniformity. Improper use of grinding equipment or high-speed stirring dispersion equipment, inappropriate ratio of dispersant or auxiliary oil, feeding process sequence, and homogenization parameters can all affect the uniformity of dispersion. Typical improvement methods mainly involve optimizing the dispersion process, selecting appropriate dispersion equipment and process parameters such as stirring speed and dispersion time, using suitable dispersants and auxiliary oils to improve the dispersion performance of conductive agents, adjusting the particle size, structure, and oil absorption value of carbon black to enhance its dispersion performance, and strengthening the monitoring of parameters such as slurry viscosity, solid content, and coating quality during production, as well as using a diaphragm resistivity meter for resistivity control.

[0006] Based on the practical applications of the above two points, when PVDF or PMMA swells in the electrolyte, it cross-links with the polymers in the positive and negative electrodes, forming a unified structure of the positive electrode, negative electrode, and separator. This makes the battery harder and less prone to deformation. However, a negative effect is that the cross-linking area between PVDF and the positive or negative electrode after swelling is very large, which can easily cause severe blockage of some separator channels, affecting lithium-ion migration and leading to a decrease in the battery's rate performance. The same applies to PMMA. After absorbing electrolyte swelling, PMMA particles swell, and when these swollen particles form a single chain region, they affect lithium-ion migration. The resistivity of the electrode also has a profound impact on the battery's rate performance, and conventional optimization methods mainly focus on improving the electrode slurry and coating processes. Therefore, in this context, to prevent battery deformation, a gel coating on the separator is unavoidable. However, when the gel swells, it can clog the separator's pores, hindering lithium-ion migration and affecting the battery's rate performance. A balance needs to be struck between these two factors. The industry standard approach is to adjust the amount of gel coating on the separator and parameters such as temperature and pressure during high-temperature, high-pressure formation. By optimizing these two conditions, a balance can be struck between preventing battery deformation and meeting high-rate charge / discharge requirements. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned existing problems of batteries, especially polymer batteries using aluminum-plastic films, by providing a cell, battery, preparation method, and apparatus with high rate performance. During battery cycling, this invention enhances the rate characteristics of the battery without easily causing deformation, resulting in a significant increase in the charge and discharge rate of the battery.

[0008] This invention provides a high-rate battery, its preparation method, and apparatus. During the battery formation process, the high-temperature softening, cross-linking, and swelling properties of polymers are utilized; the conductive agent, acting as tiny particles in contact with the electrolyte, is also utilized. After high-temperature formation in a fixture for a certain time and with a specific charge, the colloidal material undergoes cross-linking and swelling. Ultrasonic waves under specific conditions are used to shear and process this cross-linking and swelling, controlling the dense cross-linking and sol-gel effect and creating voids that hinder lithium-ion transport. This reduces ion migration impedance, effectively improving the battery's rate performance while maintaining low battery hardness and cycle expansion rate. The cavitation effect of ultrasound shears and compresses the conductive agent particles upon contact with the electrolyte, playing a crucial role in ensuring uniform distribution of these particles, which is evident in the membrane resistivity and high-current-rate discharge characteristics.

[0009] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0010] This invention is achieved through the following technical solution:

[0011] The first aspect of this application provides a method for preparing a battery cell with high rate performance, comprising the following steps:

[0012] A polymer coating is applied to the battery separator;

[0013] A separator coated with a polymer material is assembled with a positive electrode containing a positive electrode material and a negative electrode containing a negative electrode material to form a semi-finished battery cell, and then an electrolyte is injected.

[0014] The semi-finished battery cell after being injected with electrolyte is placed between two clamping plates, and pressure is applied to the two clamping plates to make the positive electrode, negative electrode and separator stick together tightly.

[0015] The clamping plates have heating and ultrasonic functions. The two clamping plates heat the whole formed by the positive electrode, negative electrode and separator, and provide ultrasonic waves. When the semi-finished cell is charged and formed for the first time, the polymer material coating on the separator is cross-linked with the positive electrode material on the positive electrode and the negative electrode material on the negative electrode by heating. The products of the cross-linking reaction are ultrasonically sheared by applying ultrasonic waves.

[0016] After degassing, sealing, and aging, a finished battery cell with high rate performance is obtained.

[0017] To optimize the above technical solution, the specific measures also include:

[0018] The main component of the polymer coating is a polymer material, which is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-trifluorochloroethylene, polyacrylonitrile, or polymethyl methacrylate.

[0019] Furthermore, the polymer coating also contains an insulating material selected from alumina, silicon dioxide, hydrated alumina, or aramid.

[0020] Furthermore, in the polymer coating, the mass ratio of polymer to insulating material is 1-4:6-9.

[0021] Furthermore, the heating and ultrasonic waves provided to the entire assembly formed by the tight bonding of the positive electrode, negative electrode, and separator via two clamping plates are described, wherein:

[0022] The clamping plate heats the entire assembly formed by the close contact of the positive electrode, negative electrode and separator, at a temperature of 70-90°C.

[0023] Ultrasonic waves are provided during heating. The ultrasonic frequency is 25-100 kHz, the amplitude is 10-100 μm, the duration of a single ultrasonic wave is 0.5-15 s, the interval between ultrasonic waves is 0.5-1.5 min, and the number of cycles is 10-20.

[0024] The surface pressure of the two clamping plates is 8–22 kg / cm². 2 .

[0025] Furthermore, the provision of ultrasonic waves during heating specifically involves the clamping plate heating the semi-finished battery cell after the electrolyte has been injected, and ultrasonic waves being applied after the semi-finished battery cell has reached a charge of over 70% during heating.

[0026] Furthermore, by controlling the parameters of the ultrasonic waves, the shearing effect of the cross-linking products between the polymer coating on the diaphragm and the positive electrode material on the positive electrode and the negative electrode material on the negative electrode can be controlled.

[0027] The second aspect of this application provides an apparatus for preparing high-rate performance battery cells, including a first clamping plate and a second clamping plate for clamping a semi-finished battery cell after electrolyte injection, so that the positive electrode, negative electrode, and separator of the semi-finished battery cell are tightly attached together; the first clamping plate is provided with a heating device to heat the semi-finished battery cell; the second clamping plate is equipped with an ultrasonic transducer and an amplitude transformer, which transmits ultrasonic waves to the semi-finished battery cell when activated; the first clamping plate and the second clamping plate are connected to a pressure application device, so that the first clamping plate and the second clamping plate are brought closer together and clamp the semi-finished battery cell therebetween.

[0028] A third aspect of this application provides a battery cell prepared using the method described above.

[0029] A fourth aspect of this application provides a battery comprising the aforementioned battery cell.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] The key to this invention lies in solving the industry's dilemma of improving battery deformation and expansion.

[0032] Traditional methods involve coating the separator with a large amount of polymer colloid to improve battery deformation and expansion. However, this process can lead to problems. After the colloid swells at high temperatures, it cross-links with the polymers in the positive or negative electrode, causing the positive and negative electrodes to bond firmly together. Although this method can effectively improve battery deformation and expansion, it greatly sacrifices the kinetics of lithium-ion migration. The overly dense cross-linked structure reduces the migration path of ions, preventing them from quickly combining with electrons to react.

[0033] To improve this situation, the industry typically opts to apply a small amount of adhesive to the diaphragm or change the type of adhesive. However, reducing the amount of adhesive can affect the processing energy of the diaphragm during coating. The less adhesive applied, the more difficult it is to control the amount, and consistency cannot be guaranteed. Other types of polymers do not have good compatibility with the electrolyte in the early stages, making it difficult to quickly swell and crosslink.

[0034] The present invention solves the above-mentioned problems. It only requires placing the separator coated with polymer colloid in the device provided by the present invention after battery electrolyte filling. Pressure is applied by clamping to tightly adhere the positive electrode, negative electrode, and separator together. Heating and ultrasonic treatment are then performed using clamps. During the battery formation under heat and pressure, the polymer material coated on the separator cross-links with the polymer materials between the positive and negative electrodes. When the colloid softens due to heating, the vibration and cavitation effects of ultrasound shear the cross-linked colloid. By controlling the parameters of the ultrasound, the cross-linking ratio of the polymer can be effectively controlled.

[0035] The device of this invention has a heating device inside the first clamping plate to achieve temperature rise. The second clamping plate has an internal ultrasonic transducer and amplitude converter, which can provide ultrasonic waves to the battery at any time. When the ultrasonic waves propagate in the electrolyte liquid, they generate high-frequency vibrations, which act on the conductive agent particle clusters in contact with the liquid, breaking them apart through shear and compressive forces. At the same time, the high-pressure shock waves generated by the instantaneous collapse of bubbles formed by cavitation further promote the dispersion of conductive agent particles. The thermal effect also changes the surface properties of the particles. The two work together to enhance the dispersion effect. The uniform dispersion of the conductive agent helps to achieve uniform electron distribution, average current density distribution, and improve the electrochemical performance of the battery, especially significantly improving high-rate charge and discharge.

[0036] This invention fills a technological gap in the industry regarding this problem, particularly considering the high temperature and pressure characteristics during the formation of high-rate lithium-ion batteries, the properties of the separator coating material that hardens the battery, and the characteristics of the necessary conductive agents and electrolyte liquids in the electrode sheets. This invention optimizes and modifies the formation apparatus by incorporating an ultrasonic structural component, allowing for continuous or uninterrupted ultrasonic action when a certain charge level is reached during formation.

[0037] When the separator, positive electrode, and negative electrode with PVDF coating are subjected to ultrasonic shearing at high temperature, a cross-linking effect is produced. The cross-linking is loose, and the area of ​​the voids helps lithium ions migrate quickly, enhancing the rate performance of the battery.

[0038] When the separator, positive electrode, and negative electrode with polyacrylic coating are subjected to ultrasonic shearing at high temperature, the colloidal swelling and bonding occur, the swelling area decreases, the linkage between colloidal particles decreases, and the increased porosity facilitates rapid lithium ion migration, thereby enhancing the battery's rate performance.

[0039] In the preparation of the diaphragm coating material, this invention also mixes polymer materials with insulating materials. The polymer materials can cross-link with the polymer materials of the electrodes to form a polymer colloid, achieving an adhesion effect. Meanwhile, the insulating materials are uniformly distributed on the diaphragm surface and form a skeleton effect with the cross-linked colloid of the polymer materials, which significantly improves the thermal shrinkage performance of the diaphragm.

[0040] During high-temperature formation, the conductive agent undergoes ultrasonic vibration, shearing, and compression effects, resulting in a state where the conductive agent is uniformly adhered to the material particles and evenly dispersed between the particle chains. This significantly reduces the possibility of localized excessive or insufficient conductivity. The uniform dispersion of the conductive agent effectively reduces the film resistivity of the electrode, thereby improving the rate performance of the battery.

[0041] The present invention is simple in terms of process flow, does not require additional steps to process the battery, and is directly integrated into the formation device. It is simple in terms of cost and process, easy to promote, and the cost investment is not significant while the performance is significantly improved. Attached Figure Description

[0042] Figure 1 : Schematic diagram of battery and formation device placement.

[0043] Figure 2 : Schematic diagram of battery location and ultrasonic wave action.

[0044] Figure 3 Schematic diagram of the microscopic effects before and after cross-linking swelling and ultrasonic treatment.

[0045] Figure 4 Schematic diagram of the microscopic effects of conductive agent particles before and after ultrasonic treatment. Detailed Implementation

[0046] The present invention will be further described in detail below through embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0047] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0048] This invention provides a method for preparing a battery cell with high rate performance, comprising the following steps:

[0049] A polymer coating is applied to the battery separator;

[0050] A separator coated with a polymer material is assembled with a positive electrode containing a positive electrode material and a negative electrode containing a negative electrode material to form a semi-finished battery cell, and then an electrolyte is injected.

[0051] After the electrolyte is injected, the semi-finished cell is placed between two clamping plates, and pressure is applied to the two clamping plates to make the positive electrode, negative electrode and separator stick together tightly.

[0052] The clamping plates have heating and ultrasonic functions. The two clamping plates heat the whole formed by the positive electrode, negative electrode and separator, and provide ultrasonic waves. When the semi-finished cell is charged and formed for the first time, the polymer material coating on the separator is cross-linked with the positive electrode material on the positive electrode and the negative electrode material on the negative electrode by heating. The products of the cross-linking reaction are ultrasonically sheared by applying ultrasonic waves.

[0053] After degassing, sealing, and aging, a finished battery cell with high rate performance is obtained.

[0054] The main component of polymer coatings is polymer material, or a mixture of polymer material and insulating material. In polymer coatings, the mass ratio of polymer material to insulating material is 1–4:6–9.

[0055] The positive electrode, negative electrode, and separator are tightly bonded together by two clamping plates, which are then heated and subjected to ultrasonic waves.

[0056] The clamping plate heats the entire assembly formed by the close contact of the positive electrode, negative electrode, and separator, at a temperature of 70–90°C.

[0057] Ultrasonic waves are provided during heating. The ultrasonic waves in this invention are between 20 and 100 kHz, with a single continuous ultrasonic wave duration of 0.1 to 20 seconds, which can be cyclically spaced, and an amplitude range of 10 to 200 μm.

[0058] Preferably, the ultrasonic frequency provided is 25-100 kHz, the amplitude is 10-100 μm, the duration of a single ultrasonic wave is 0.5-15 s, the interval between ultrasonic waves is 0.5-1.5 min, and the number of cycles is 10-20.

[0059] The surface pressure of the two clamping plates is 8–22 kg / cm². 2 .

[0060] Ultrasonic waves are applied during heating. Specifically, the clamps heat the semi-finished battery cell after the electrolyte has been injected. Ultrasonic waves are applied after the semi-finished battery cell has reached more than 70% of its charge capacity.

[0061] By controlling the parameters of the ultrasonic waves, the shearing effect of the cross-linking products between the polymer coating on the diaphragm and the positive electrode material on the positive electrode and the negative electrode material on the negative electrode is controlled.

[0062] This application also provides an apparatus for preparing high-rate performance battery cells, including a first clamping plate and a second clamping plate for clamping a semi-finished battery cell after electrolyte injection, so that the positive electrode, negative electrode, and separator of the semi-finished battery cell are tightly attached together; the first clamping plate is equipped with a heating device to heat the semi-finished battery cell by raising the temperature through the heating device; the second clamping plate is equipped with an ultrasonic transducer and an amplitude transformer, and when turned on, ultrasonic waves are transmitted through the second clamping plate to act on the semi-finished battery cell; the first clamping plate and the second clamping plate are connected to a pressure application device, so that the first clamping plate and the second clamping plate are relatively close and clamp the semi-finished battery cell therebetween.

[0063] This application also provides a battery cell, which is prepared using the method described above.

[0064] This application also provides a battery comprising the aforementioned battery cell.

[0065] The technical solution of the present invention will be further described in detail below with reference to specific embodiments:

[0066] This invention first coats a polymer material onto a separator, and then uses this separator to form an electrode assembly by winding or stacking it with the positive and negative electrodes. The assembly is then encapsulated in an aluminum-plastic film or metal casing, and a semi-finished battery cell is obtained after injecting electrolyte. During the initial formation of the semi-finished battery cell, the device provided in this application is used for formation. Figure 1 As shown:

[0067] 1 is the transmission shaft of the device, which mainly provides pressure through a motor, cylinder, or pneumatic-hydraulic booster cylinder;

[0068] 2 is pressure plate A, whose main function is to press down the battery. It also contains an electric heating element that can raise the temperature.

[0069] 3 is pressure plate B, whose main function, in addition to pressing down the battery, is to house an ultrasonic transducer and amplitude converter. When the ultrasonic waves are activated, they are transmitted to the battery through this plate.

[0070] 4 is a semi-finished cell, 5 is the positive electrode, and 6 is the negative electrode. The battery polarity is introduced into the wires or contact metals by known methods to realize the voltage monitoring and current transmission of the battery, so as to use the battery for formation and charging and discharging.

[0071] 7 is the power supply and temperature controller for the heating plate;

[0072] 8 represents the ultrasonic controller;

[0073] 9 represents the power source for the ultrasonic waves.

[0074] This device sandwiches the semi-finished battery cell after liquid injection between two plates. In addition to bearing the pressure of the conduction shaft, plate A can also be heated to regulate the temperature during battery formation. Plate B mainly integrates the ultrasonic transducer and amplitude converter. When the battery is heated and pressurized for formation, the polymer material coated on the separator cross-links with the polymer material between the positive and negative electrodes. Under high temperature, the adhesive tape softens. At this time, the vibration and cavitation effects of ultrasonic waves can be used to shear the cross-linked adhesive.

[0075] Figure 2 Another implementation method:

[0076] 10 is pressure plate C, which mainly provides heating and applies pressure;

[0077] 12 is the pressure plate D, which mainly increases the applied pressure and the generation of ultrasonic waves;

[0078] 11 represents a semi-finished battery cell sandwiched between two boards;

[0079] Figure 13 shows a schematic diagram of the emission and reflection of ultrasonic waves;

[0080] 14 is a diagram showing the unfolded state, and 15 is a diagram showing the closed state.

[0081] During high-temperature formation, ultrasonic waves can be provided at regular intervals. These waves act on the battery, modifying the cross-linked polymer materials within the battery at high temperatures. This effectively controls the bonding and cross-linking effect. After passing through the battery body, the ultrasonic waves shear the cross-linked state, creating gaps in the sheared areas. These gaps facilitate electrolyte flow, increasing wetting and providing a larger channel for lithium-ion migration. Therefore, this method avoids significantly damaging the adhesion of the separator, positive electrode, and negative electrode while simultaneously increasing the number of channels to facilitate lithium-ion migration, thus improving the battery's rate performance.

[0082] Microscopic effect diagrams as follows Figure 3 :

[0083] 16 is a PVDF-type membrane coating, which, under high temperature conditions, exhibits a dense cross-linking state with the positive and negative electrodes.

[0084] 17 is a PVDF-based separator coating. Under high temperature conditions, the positive and negative electrodes undergo ultrasonic shearing, resulting in a cross-linking effect: the cross-linking is loose, and the increased porosity facilitates rapid lithium-ion migration, enhancing the battery's rate performance.

[0085] 18 is a polyacrylic acid-based membrane coating. Under high temperature conditions, the colloidal swelling and bonding effect of the positive and negative electrodes results in a larger swelling area and greater density.

[0086] 19 is a polyacrylic acid-based separator coating. The positive and negative electrodes are in a state of shearing after ultrasonic action at high temperature. The effect of colloidal swelling and bonding is: the swelling area is reduced, the linkage between colloidal particles is reduced, and the area of ​​the voids helps lithium ions migrate quickly, thus enhancing the rate characteristics of the battery.

[0087] During high-temperature formation, the device of this invention can provide ultrasonic waves to the battery at regular intervals. As the ultrasonic waves propagate in the electrolyte, they generate high-frequency vibrations that act on the conductive agent particles in contact with the liquid, breaking them apart through shear and compressive forces. Simultaneously, the high-pressure shock waves generated by the instantaneous collapse of bubbles due to cavitation further promote the dispersion of the conductive agent particles. The thermal effect also alters the particle surface properties, enhancing the dispersion effect. Uniform dispersion of the conductive agent contributes to uniform electron distribution, evenly distributing the current density and improving the battery's electrochemical performance, especially significantly improving high-rate charge and discharge performance. Figure 4 :

[0088] 20 represents the state of conductive agent particles in the positive and negative electrodes. The large gaps between electrode material particles can easily lead to the accumulation of conductive agent, resulting in localized excessive conductivity and localized insufficient conductivity when the same proportion of conductive agent is used. The high resistivity of the electrode film has a significant impact on the distribution of current density.

[0089] 21 represents the state after ultrasonic vibration, shearing, and compression effects during high-temperature formation. The conductive agent is uniformly attached to the material particles and evenly dispersed between the particle chains, greatly reducing the situation where the local conductive agent is too strong or too weak. The uniform dispersion of the conductive agent can effectively reduce the film resistivity of the electrode and improve the rate performance of the battery.

[0090] In some embodiments of this application, the positive electrode is mainly composed of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, ternary materials, binary materials, etc., prepared with polymer colloids (PVDF, etc.) and solvents (NMP, etc.), and coated onto aluminum foil. After rolling, it is cut into corresponding sizes according to the design of different battery dimensions to obtain the positive electrode sheet. The negative electrode mainly consists of carbon-based materials, such as natural graphite, artificial graphite, soft carbon, hard carbon, carbon fiber, etc., and non-carbon-based materials mainly include silicon-based materials, tin-based materials, lithium-containing transition metal nitrides, alloy negative electrode materials, nanoscale negative electrode materials, etc. It includes negative electrodes that are a mixture of carbon-based and non-carbon-based materials in a certain proportion. A slurry is prepared by preparing polymer colloids (CMC, etc.), adding binders (SBR, etc.), and homogenizing. The slurry is coated onto the surface of copper foil, baked, rolled, and cut into corresponding sizes according to the design of different battery dimensions to obtain the negative electrode sheet.

[0091] In some embodiments of this application, the compositions of the diaphragm substrate and the polymer slurry for the surface coating are as follows:

[0092] The membrane substrate is mainly composed of polyethylene (PE), polypropylene (PP), and PE / PP composite membrane.

[0093] The coating material mainly consists of a single polymer material or a polymer material mixed with other insulating materials. The polymer materials used in this invention include, but are not limited to, the following: polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA). The coating weight of the tape is 0.05–0.3 g / m².

[0094] The polymer material is mixed with the insulating material. The polymer material can cross-link with the polymer material of the electrode to form a polymer colloid to achieve a bonding effect. Meanwhile, the insulating material is uniformly distributed on the surface of the diaphragm and forms a skeleton effect with the cross-linked colloid of the polymer material, which significantly improves the thermal shrinkage performance of the diaphragm.

[0095] In some embodiments of this application, the insulating materials mainly include high heat-resistant polymers such as alumina (Al2O3), silicon dioxide (SiO2), hydrated alumina (γ-AlOOH), and aramid.

[0096] In some embodiments of this application, the electrolyte of the battery is mainly composed of a solvent and an electrolyte lithium salt. The solvent mainly includes ethylene carbonate (EC), diethyl carbonate (DEC), etc. In addition, functional additives such as film-forming stabilizers, ethylene sulfate (VEC), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), etc. are also added to the electrolyte.

[0097] In some embodiments of this application, the battery mainly uses a polymer-based aluminum-plastic composite film or a thin metal casing. The main function of the casing is to protect the electrode assembly and isolate impurities and moisture.

[0098] In some embodiments of this application, the battery manufacturing process mainly involves: mixing the main and auxiliary materials of the positive electrode together in a homogenized slurry, followed by coating, drying, rolling, and shearing processes to obtain a positive electrode sheet. Similarly, mixing the main and auxiliary materials of the negative electrode together in a homogenized slurry, followed by coating, drying, rolling, and shearing processes to obtain a negative electrode sheet. The obtained positive and negative electrode sheets, along with a coated separator, are then wound or stacked to form an electrode assembly. After casing, baking, and electrolyte injection, the electrode assembly yields a semi-finished battery cell. The semi-finished battery cell undergoes its first charge in a clamping, heating, and ultrasonic integration device provided by this invention. Finally, it undergoes degassing, sealing, aging, and sorting processes to obtain a finished battery cell.

[0099] For the sake of brevity, this article only discloses some numerical values ​​and the range of options. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range. Similarly, any upper limit can be combined with any other upper limit to form an unspecified range; the options in the range of options can also be combined arbitrarily.

[0100] Unless otherwise stated, the terms used in this application have the common meanings understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art. For example, the film resistivity testing method in this invention is as follows: take an electrode of a certain area, use aluminum foil or copper foil of the same thickness, measure the thickness, apply the same current for the same duration to the electrode, calculate the resistance, and then calculate the resistivity.

[0101] The method of shearing and dispersing cross-linking and aggregation in this invention is to utilize the swelling of polymer colloids in electrolyte, which changes with the increase of temperature and becomes soft, and then solidifies them through three processes: charging, heating, and ultrasound. Charging primarily causes the electrodes to fully expand, opening more channels and facilitating electrolyte wetting. Heating mainly accelerates the swelling of the polymer colloid in the separator coating by the electrolyte solvent, causing it to cross-link with the polymer colloid between the positive and negative electrodes. Simultaneous high-temperature heating increases the number of cross-linked and swollen states. Regular ultrasonic treatment at this time, followed by ultrasonic shearing, results in the following states: For separators, positive and negative electrodes with PVDF coatings, the cross-linking effect is achieved at high temperatures, and the cross-linking is loose, with the increased porosity facilitating rapid lithium-ion migration and enhancing the battery's rate performance. For separators, positive and negative electrodes with polyacrylic acid coatings, the colloid swells and bonds at high temperatures, reducing the swelling area and decreasing the linkage between colloid particles. The increased porosity also facilitates rapid lithium-ion migration and enhances the battery's rate performance.

[0102] During high-temperature formation, the conductive agent undergoes ultrasonic vibration, shearing, and compression effects, resulting in a state where it is uniformly adhered to the material particles and evenly dispersed between the particle chains. This significantly reduces the possibility of localized areas where the conductive agent is too strong or too weak. The uniform dispersion of the conductive agent effectively reduces the film resistivity of the electrode, thereby improving the rate performance of the battery.

[0103] The above-mentioned clamping plate heating method of the present invention includes, but is not limited to, the following methods: resistance heating, inductive heating, electric arc heating, and infrared heating, with the heating temperature between 70 and 90°C.

[0104] The ultrasonic waves in this invention are between 20 and 100 kHz, with a single continuous ultrasonic wave duration of 0.1 to 20 seconds, and can be cyclically spaced, with an amplitude range of 10 to 200 μm.

[0105] In some embodiments of the present invention, the positive electrode colloid is mainly PVDF-type colloid, accounting for 0.3% to 2%. The negative electrode colloid is mainly CMC and SBR-type colloid, accounting for 1% to 3% by weight.

[0106] In some embodiments of the present invention, lithium-ion batteries are used, and in other embodiments, sodium-ion batteries are used. The present invention is not limited to using the above types of batteries.

[0107] In the following examples and comparative examples, the positive electrode, negative electrode, and electrolyte inside the battery all use known lithium-ion battery materials.

[0108] Comparative Example 1:

[0109] The lithium-ion battery dimensions are: thickness 9.9mm, width 40mm, length 58mm, capacity 5Ah. The separator surface has a PVDF coating, which is mainly made by dissolving PVDF in solvents such as NMP to obtain an adhesive solution. The PVDF adhesive is applied to the separator surface by dip coating or roll coating. After coating, the separator is rolled and baked in an oven. After the solvent evaporates, the finished separator is obtained. The internal electrode structure is mainly produced by winding. After battery assembly and electrolyte injection, the semi-finished cells are aged by high-temperature static placement. After aging, the batteries undergo clamp pressure formation to activate the lithium-ion batteries. After degassing, edge sealing, edge trimming, aging, and testing of capacity, voltage, and internal resistance, the finished lithium-ion battery is obtained. The finished battery is disassembled and separated, and the peel strength between the separator and the positive and negative electrodes is measured. The resistivity data of the positive and negative electrodes are also measured. The internal resistance of the finished battery was measured, and the plateau voltage was confirmed by high-current charging and high-current discharging to confirm the discharge plateau voltage and retention rate data. The battery was also subjected to 500 high-current charge-discharge cycles, and the rate of increase in battery thickness expansion was measured during this period.

[0110] Examples 1-7:

[0111] The lithium-ion battery dimensions are: thickness 9.9mm, width 40mm, and length 58mm. The battery capacity is 5Ah. The positive and negative electrodes and electrolyte all use well-known lithium-ion battery materials. The separator surface has a PVDF coating, which is mainly prepared by dissolving PVDF in solvents such as NMP. The PVDF adhesive is applied to the separator surface through dip coating or roll coating. After coating, the separator is rolled and baked in an oven to evaporate the solvent, resulting in a coated separator. The internal electrode structure mainly uses a winding method. After assembly and electrolyte injection, the battery is allowed to stand at high temperature for electrolyte wetting.

[0112] The device of this invention is used to clamp semi-finished battery cells (surface pressure 12 kg / cm²). 2 The battery was formed to 90% total charge, then heated and charged at 80°C, with different states of charge (SOCs) as starting points: 60%, 70%, 75%, 80%, 85%, 90%, and 100%, corresponding to Examples 1-7 respectively. The battery was then treated with synchronous ultrasound: 0.5 seconds per ultrasound cycle, 25 kHz frequency, 10 μm amplitude, 1 min interval, and 10 cycles. This activated the lithium-ion battery. After degassing, sealing, trimming, aging, and testing of capacity, voltage, and internal resistance, the finished lithium-ion battery was obtained. The finished battery was disassembled and separated, and the peel strength between the separator and the positive and negative electrodes was measured. The resistivity of the positive and negative electrodes was measured. The internal resistance of the finished battery was measured. High-current charging was performed to confirm the plateau voltage, and high-current discharging was performed to confirm the discharge plateau voltage and retention rate. The battery was then subjected to 500 high-current charge-discharge cycles, and the battery thickness expansion rate was measured during this period.

[0113] Examples 8-12:

[0114] Examples 8-12 use the same starting point of battery charge (80%) as Example 4 to perform step verification of battery charging temperature, with other parameters the same as in Example 4.

[0115] The battery charging heating temperatures in Examples 8-12 were 60°C, 70°C, 85°C, 90°C, and 100°C, respectively.

[0116] Examples 13-16:

[0117] Examples 8-12 use the same starting point of charge state (80%) as Example 4 to perform step verification of ultrasonic frequency, and other parameters are the same as in Example 4.

[0118] Examples 13-16 show ultrasonic frequencies of 20KHz, 50KHz, 100KHz, and 110KHz, respectively.

[0119] Examples 17-21:

[0120] Examples 8-12 use the same starting point of charge state (80%) as Example 4 to perform step verification of ultrasonic amplitude, and other parameters are the same as in Example 4.

[0121] Examples 17-21 show ultrasonic amplitudes of 5µm, 30µm, 60µm, 100µm, and 110µm, respectively.

[0122] Examples 22-26:

[0123] Examples 22-26 use the same starting point of the battery state (80%) as in Example 4 to perform step verification on the single ultrasonic time, and other parameters are the same as in Example 4.

[0124] In Examples 22-26, the duration of a single ultrasound scan was 0.1s, 3s, 10s, 15s, and 20s, respectively.

[0125] Examples 27-29:

[0126] Examples 27-29 use the same starting point of charge state (80%) as in Example 4 to perform step verification on the number of ultrasonic cycles, with other parameters the same as in Example 4.

[0127] In Examples 27-29, the number of ultrasonic cycles was 15, 20, and 25, respectively.

[0128] Examples 30-31:

[0129] Examples 30-31 use the same charge state starting point (80%) as Example 4 to compare and verify the materials coated on the diaphragm, with other parameters the same as in Example 4.

[0130] In Examples 30 and 31, the membrane coating materials were PVDF-HFP coating and PMMA coating, respectively.

[0131] PVDF-HFP coating: The PVDF-HFP adhesive is prepared by dissolving PVDF-HFP in solvents such as NMP. The PVDF-HFP adhesive is coated onto the surface of the separator by dip coating or roll coating. After coating, the separator is rolled through an oven for baking. After the solvent evaporates during baking, the finished separator is obtained.

[0132] PMMA coating: PMMA is mixed with water to make a slurry. The water-soluble PMMA is then evenly roller-coated or sprayed onto the diaphragm. The diaphragm is then baked in a roller oven. After the water-soluble solvent evaporates, the finished diaphragm is obtained.

[0133] Examples 32-36

[0134] Examples 32-36 use the same charge state starting point (80%) as Example 4 to compare and verify the material ratio of the diaphragm coating, and other parameters are the same as in Example 4.

[0135] Examples 32-36 use a PVDF-γ-AlOOH coating: A slurry is prepared by dissolving PVDF and γ-AlOOH in solvents such as NMP. The slurry is coated onto its surface using dip coating, roller coating, or spray coating. After coating, the membrane is rolled through an oven for baking. The solvent evaporates during baking, resulting in the finished slurry. In Examples 32-36, the ratio of PVDF to γ-AlOOH is 1:9, 2:8, 3:7, 4:6, and 5:5, respectively.

[0136] Based on the above description, the resulting coating material, formation temperature, formation pressure, formation charge, ultrasonic initiation charge, ultrasonic time, ultrasonic frequency, ultrasonic amplitude, ultrasonic interval, and number of ultrasonic cycles are shown in Table 1.

[0137] Based on the methods described above, the test results of the finished battery are as follows: the bonding strength between the separator and the positive electrode, the bonding strength between the separator and the negative electrode, the resistivity of the positive electrode film, the resistivity of the negative electrode film, the internal resistance of the battery, the plateau voltage of 2C charging, the plateau voltage of 5C discharging, the retention rate of 5C discharge capacity, and the thickness expansion rate of the battery after 500 cycles, as shown in Table 2.

[0138]

[0139] Table 1

[0140]

[0141] Table 2

[0142] The experimental results of using the solution of this invention are as follows:

[0143] Examples 1-7 primarily employed the same ultrasonic parameters to verify the gradient of the initial charge level during formation. Compared to the comparative examples, the ultrasonically treated examples showed a significant reduction in the adhesion strength between the diaphragm and the positive electrode, and between the negative electrode and the diaphragm. The membrane resistance of both the positive and negative electrodes decreased, while the charging and discharging plateaus improved. The high-current discharge retention rate increased, but cyclic expansion did not show a significant increase. Initial charge levels below 60% did not significantly improve the adhesion strength between the positive and negative electrodes; the effect became apparent after the semi-finished cell reached a formation charge level of over 70%. From 90% to 100% charge level, the increase in effect became gradual and weaker. It is preferable to begin applying ultrasonic waves after the semi-finished cell has reached a formation charge level of over 70%.

[0144] Examples 8-12 were performed using the same formation and ultrasonic parameters as Example 4, with a gradient comparison of formation temperatures. Increasing the formation temperature helps soften the polymer colloid. The increased formation temperature significantly reduces the bonding strength between the positive and negative electrodes, significantly reduces the film resistance of the positive and negative electrode sheets, increases the charge / discharge plateau, and shows no significant change in the high-current discharge rate and post-cycle expansion rate. At 60 degrees Celsius, because the temperature has not yet reached the point of deep dissolution of the colloid, there is no significant improvement in bonding strength. Increasing the temperature to 100 degrees Celsius leads to a significant decrease in the bonding strength of the colloid due to overheating. The preferred battery charging heating temperature range is 70-90 degrees Celsius.

[0145] Examples 13-16 were performed using the same formation parameters as Example 4, but with different ultrasonic parameters and frequencies. Increasing the frequency resulted in slight changes in the bonding strength and the film resistance of the positive and negative electrodes, but significantly improved the performance of high-current discharge. The effect was not obvious at an ultrasonic frequency of 20 kHz, and the effect weakened above 100 kHz. The preferred ultrasonic frequency was 25-100 kHz.

[0146] Examples 17-21, using the same formation parameters as Example 4, verified different ultrasonic parameter frequencies and amplitude gradients. As the amplitude increased, the diaphragm resistance and battery internal resistance changed. At an amplitude as low as 5 μm, the change in bonding strength was not significant; after increasing the amplitude to 100 μm, the increase in rate capability was not significant. The optimal amplitude is between 10 and 100 μm.

[0147] Examples 22-26, compared with Example 4, verified different ultrasonic parameters and times. With increasing single ultrasonic time, the bonding strength of the positive and negative electrodes decreased, the resistance of the positive and negative electrode films decreased, the charge / discharge plateau increased, and the high-current discharge rate increased. Expansion decreased, mainly due to the longer ultrasonic time, which resulted in more thorough shearing of the cross-linked state and more uniform dispersion of the conductive agent. This led to a reduction in both ion migration impedance and electron movement impedance. A single ultrasonic time of 0.1 s was too short, resulting in minimal effect. However, after increasing the single ultrasonic time to 15 s, the effect gradually diminished; a single ultrasonic time of 0.5–15 s was preferred.

[0148] Examples 27-29 were performed using the same formation parameters and ultrasound parameters as Example 4, but with different numbers of ultrasound cycles. Increasing the number of cycles slightly increased the effectiveness of the ultrasound; however, after 20 cycles, the increase in effectiveness was not significant. The preferred conditions were 10-20 cycles.

[0149] Examples 30 and 31 were conducted with the same formation parameters and ultrasonic parameters as Example 4, and the differences in the membrane coating material were investigated. The membranes were coated with PVDF-HFP copolymer coating and PMMA colloidal coating, respectively. In both cross-linked and hot-melt states, they could be sheared by initial ultrasonication, which increased the channels for electrolyte flow, enhanced ion migration, and thus improved the rate performance of the battery.

[0150] Examples 32-36 were performed using the same formation and ultrasonic parameters as Example 4. The only difference was the membrane coating material and the varying ratio of membrane colloid to insulating material. Different ratios affected the bonding strength; too low a colloid ratio resulted in weak bonding, while too high a colloid ratio had little impact on the battery electrodes and battery test data due to its interaction with the insulator. The preferred ratio was a polymer material to insulating material mass ratio of 1-4:6-9.

[0151] In summary, the results show that using a separate separator coating without the treatment described in this invention results in significantly inferior high-rate characteristics compared to the ultrasonically treated solution. This invention is simple and practical, simultaneously satisfying battery bonding and initial formation activation. Furthermore, the device of this invention softens the colloids in the electrode and separator materials during heating, and ultrasonically shears the softened colloids, effectively controlling the bonding area and preventing battery deformation while simultaneously improving the battery's rate discharge performance. At high temperatures, the reduced electrolyte viscosity cavitation and compression effect on the fine conductive agents in the positive and negative electrode materials effectively disperses the conductive agents more uniformly, comprehensively enhancing electron migration capabilities and significantly improving the battery's rate discharge characteristics.

[0152] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for producing an electrode having high rate capability, characterized by, Includes the following steps: A polymer coating is applied to the battery separator; A separator coated with a polymer material is assembled with a positive electrode containing a positive electrode material and a negative electrode containing a negative electrode material to form a semi-finished battery cell, and then an electrolyte is injected. The semi-finished battery cell after being injected with electrolyte is placed between two clamping plates, and pressure is applied to the two clamping plates to make the positive electrode, negative electrode and separator stick together tightly. The clamping plates have heating and ultrasonic functions. The two clamping plates heat the whole formed by the positive electrode, negative electrode and separator, and provide ultrasonic waves. When the semi-finished cell is charged and formed for the first time, the polymer material coating on the separator is cross-linked with the positive electrode material on the positive electrode and the negative electrode material on the negative electrode by heating. The products of the cross-linking reaction are ultrasonically sheared by applying ultrasonic waves. After degassing, sealing, and aging, a finished battery cell with high rate performance is obtained. The process involves heating and providing ultrasonic waves to the entire assembly formed by tightly bonding the positive electrode, negative electrode, and separator using two clamping plates, wherein: The clamping plate heats the entire assembly formed by the close contact of the positive electrode, negative electrode and separator, at a temperature of 70~90℃. Ultrasonic waves are provided during heating. The ultrasonic frequency is 25~100KHz, the amplitude is 10~100um, the duration of a single ultrasonic wave is 0.5~15s, the interval between ultrasonic waves is 0.5~1.5min, and the number of cycles is 10~20. The surface pressure of the two clamps is 8-22 kg / cm 2 ; The provision of ultrasonic waves during heating specifically involves the clamping plate heating the semi-finished battery cell after the electrolyte has been injected, and ultrasonic waves being applied after the semi-finished battery cell has reached a charge level of over 70% during heating. Both the positive electrode material and the negative electrode material contain conductive agents.

2. The method of claim 1, wherein the method further comprises: The main component of the polymer coating is a polymer material, which is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-trifluorochloroethylene, polyacrylonitrile, or polymethyl methacrylate.

3. The method of claim 2, wherein the method further comprises: The polymer coating also contains an insulating material, which is selected from alumina, silicon dioxide, hydrated alumina, or aramid.

4. The method of claim 3, wherein the method further comprises: In the aforementioned polymer coating, the mass ratio of polymer material to insulating material is 1~4:6~9.

5. The method for preparing a battery cell with high rate performance according to claim 1, characterized in that: By controlling the parameters of the ultrasonic waves, the shearing effect of the cross-linking products between the polymer coating on the diaphragm and the positive electrode material on the positive electrode and the negative electrode material on the negative electrode is controlled.

6. A battery cell, characterized in that: The battery cell is prepared using the method described in any one of claims 1-5.

7. A battery, characterized in that: It contains the battery cell as described in claim 6.

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