Method for manufacturing electrode by using dry electrode process, and electrode manufactured using same

Abstract

The present invention relates to a method for manufacturing an electrode by using a dry electrode process, and an electrode manufactured using same. Fibrillation of a polytetrafluoroethylene (PTFE) binder is used to uniformly couple a conductive material and an active material and both the mechanical stability and electrical conductivity of an electrode are improved such that a solvent use problem of a wet process is solved, and an electrode with high-speed charging / discharging performance and a high energy density can be implemented and, particularly, efficient and eco-friendly battery performance is provided in high-power applications.

Description

Method for manufacturing an electrode using a dry electrode process and an electrode using the same

[0001] The present invention relates to a method for manufacturing an electrode using a dry electrode process and an electrode using the same, and more specifically, to a method for manufacturing an electrode using a dry electrode process including a mixing step, a kneading step, a grinding step and an electrode film forming step, and an electrode manufacturing technology using the same.

[0002] Lithium-ion batteries have established themselves as essential energy storage devices for various electronic devices and industries, such as electric vehicles, smartphones, and laptops, and there is a continuous demand for improvements in energy density and safety. In particular, while technology using thick electrodes to increase the energy density of lithium-ion batteries is advancing, there are various limitations in the existing wet electrode process.

[0003] Currently, the manufacture of electrodes for commercially available lithium-ion batteries is generally carried out through a wet process using organic solvents. The wet process is a method of forming an electrode by applying a mixture in the form of a slurry, comprising a conductive material, an active material, and a binder, onto a metal foil and drying it. However, when fabricating thick electrodes, the distribution of the binder and conductive material becomes uneven due to solvent evaporation. This leads to instability in the physical structure of the electrode and degrades electrochemical performance, thereby limiting the ability to manufacture thick electrodes that are stable and have high energy density.

[0004] To address this, solvent-free dry electrode processes are attracting attention. Dry processes can fundamentally resolve the problem of solvent evaporation that occurs in wet processes and are environmentally friendly as they do not require solvent treatment. Furthermore, they can improve the physical and electrical performance of electrodes by enabling the fabrication of electrodes with a more uniform distribution of binders and conductive materials. However, current dry electrode processes are limited to laboratory-level research, resulting in low potential for practical commercialization and insufficient technological development for mass production.

[0005] In particular, in dry processes, it is crucial to use a binder to form a uniform structure within the electrode. The binder must immobilize the conductive material and active material within the electrode and form a structure capable of ensuring electrical conductivity. However, optimizing various variables such as the type and content of the binder and the injection ratio is necessary; since electrode performance varies significantly depending on specific process conditions, detailed evaluation and optimization are required.

[0006] The purpose is to solve the problems of the conventional technology described above, to resolve environmental and cost issues associated with the use of solvents in existing wet processes, to resolve the problem of non-uniform distribution of binder and conductive material when fabricating thick electrodes, and to achieve material optimization for improved electrode performance.

[0007] The technical problems that the invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the invention belongs from the description below.

[0008] To achieve the above objectives, a method for manufacturing an electrode using a dry electrode process according to one embodiment of the present invention may include: a mixing step of dry-mixing an electrode mixture comprising an electrode active material, a conductive material, and a binder to form a powder; a kneading step of introducing the powder formed in the mixing step into a kneader to produce an electrode dough; a grinding step of grinding the electrode dough produced in the kneading step to form an electrode powder; and an electrode film forming step of applying and pressing the electrode powder formed in the grinding step onto a substrate to form an electrode film.

[0009] In addition, the binder of the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention may be characterized as polytetrafluoroethylene (PTFE) having an extrusion ratio of 1,000 or more.

[0010] In addition, the electrode kneaded in the kneading step of the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention may be characterized in that the binder is fiberized and includes the form of fibrils.

[0011] In addition, the conductive material of the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention has a specific surface area of ​​500 m² 2 / g to 5,000 m 2 It can be characterized as carbon black having an internal porosity of 50% to 100% and a g / g.

[0012] In addition, the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention may be characterized in that the content of the binder is 0.5 to 2 weight% based on 100 weight% of the total electrode, and the average particle size of the electrode powder is 100 to 500 μm.

[0013] In addition, the kneading step of the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention may include terminating the kneading step within three times the point at which maximum kneading torque occurs.

[0014] Meanwhile, an electrode using a dry electrode process according to one embodiment of the present invention provides an electrode using a dry electrode process manufactured by an electrode manufacturing method using any one of the dry electrode processes described above.

[0015] By means of the solution to the above problem, the electrode manufacturing method using the dry electrode process of the present invention is environmentally friendly as it applies a dry electrode process that does not use organic solvents, and can improve performance by realizing a uniform distribution of the conductive material and binder within the electrode by using a PTFE binder with a high injection ratio, and has the effect of realizing a high-performance battery by realizing a uniformly thick electrode.

[0016] FIG. 1 is a figure showing a method for manufacturing an electrode using a dry electrode process according to one embodiment of the present invention.

[0017] FIG. 2 is a graph showing the mechanical properties measured according to the semi-finished product state according to one embodiment of the present invention.

[0018] Figure 3 is a TEM image of a conductive material (Super P, Li-435, EC-300J, EC-600JD) according to one embodiment of the present invention.

[0019] Figure 4 is an SEM image showing a cross-section of a lithium-ion battery electrode according to one embodiment of the present invention.

[0020] FIG. 5 is a graph showing the electrical performance of an electrode according to the type of conductive material according to one embodiment of the present invention.

[0021] Figure 6 is a graph showing physical properties according to the content of PTFE binder and the size of electrode powder particles according to one embodiment of the present invention.

[0022] Figure 7 is a photograph showing edge non-uniformity due to an increase in the content of PTFE binder according to one embodiment of the present invention.

[0023] FIG. 8 is a graph showing the change in torque according to the fiberization process and kneading time of a PTFE binder according to one embodiment of the present invention.

[0024] FIG. 9 is a graph showing the performance evaluation according to the type and content of the PTFE binder according to one embodiment of the present invention.

[0025] FIG. 10 is a graph showing the effect of various types of carbon black conductive materials according to one embodiment of the present invention on the electrochemical performance of an electrode.

[0026] Figure 11 is a photograph and graph showing electrochemical performance according to electrode thickness and capacity (aerial capacity) according to one embodiment of the present invention.

[0027] FIG. 12 is a graph showing the kneading torque according to the type of conductive material according to one embodiment of the present invention.

[0028] FIG. 13 is a photograph showing a cross-section of an electrode manufactured according to a type of conductive material according to one embodiment of the present invention.

[0029] Specific embodiments of the present invention will be described in detail below with reference to the drawings. However, the concept of the present invention is not limited to the presented embodiments. Those skilled in the art who understand the concept of the present invention may easily propose other inventions that are inferior or other embodiments included within the scope of the concept of the present invention by adding, changing, or deleting other components within the same scope of the concept, and such are also to be considered to be included within the scope of the concept of the present invention.

[0030] Additionally, components with the same function within the scope of the same concept appearing in the drawings of each embodiment are described using the same reference numeral.

[0031]

[0032] FIG. 1 is a figure showing a method for manufacturing an electrode using a dry electrode process according to one embodiment of the present invention.

[0033] The electrode manufacturing method using the dry electrode process of the present invention and the electrode using the same relate to a dry electrode unit process for a lithium-ion battery, which can improve battery performance and help protect the environment without using harmful solvents.

[0034] Lithium-ion battery electrodes are traditionally fabricated using a wet process. However, using thick electrodes leads to performance degradation due to the uneven distribution of binders and conductive materials. On the other hand, the dry electrode process does not use organic solvents, allowing for the production of uniform electrodes, but it remains at the laboratory level where commercialization is difficult.

[0035] The electrode manufacturing method using the dry electrode process according to the present invention and the electrode using the same have increased the potential for commercialization by introducing a solvent-free dry process based on a polytetrafluoroethylene (PTFE) binder.

[0036] The electrode manufacturing method using a dry electrode process according to the present invention comprises: a mixing step of dry-mixing an electrode mixture comprising an electrode active material, a conductive material, and a binder to form a powder; a kneading step of introducing the powder formed in the mixing step into a kneader to produce an electrode dough; a grinding step of grinding the electrode dough produced in the kneading step to form an electrode powder; and an electrode film forming step of applying and pressing the electrode powder formed in the grinding step onto a substrate to form an electrode film.

[0037] The present invention indicates optimal process conditions by evaluating the physical, electrical, and electrochemical properties of semi-finished products produced at each stage.

[0038]

[0039] The mixing step is a step of dry-mixing an electrode mixture containing an electrode active material, a conductive material, and a binder to form a powder.

[0040] This is a step of creating a uniform composite using a powder mixer or the like so that the electrode active material, conductive material, and binder are uniformly distributed.

[0041] Electrode active materials are materials that generate capacity by participating in electrochemical reactions during charging and discharging; lithium nickel-cobalt-manganese oxide is primarily used for the positive electrode of lithium-ion batteries, while graphite is mainly used for the negative electrode.

[0042] Conductive materials are materials that form electron transport pathways within the composite layer; since lithium nickel-cobalt-manganese oxide, the positive electrode active material, has low electron conductivity, carbon-based conductive materials are mixed in to fabricate the electrode.

[0043] A binder is a material that acts as an adhesive to physically bond the active material and the conductive material.

[0044] The electrode mixture includes an electrode active material, a conductive material, and a binder, and is mixed dry to form a powder.

[0045]

[0046] The kneading step is a step of preparing electrode dough by introducing the powder formed in the mixing step into a kneader.

[0047] Kneading is a process in which binder particles are fiberized through a kneader to create a network structure in which electrode active material and conductive material are integrated, thereby producing a semi-finished product called 'electrode dough'.

[0048]

[0049] The grinding step is a step of grinding the electrode dough prepared in the kneading step to form electrode powder.

[0050] Grinding is a process of grinding the electrode paste into 'electrode granules' using a powder mill or the like to improve process speed and produce an electrode film with uniform thickness. The size can be adjusted according to the required characteristics, but in the present invention, a size of about 200 μm is preferred. At this time, the smaller the granules, the less binder with a high extrusion ratio is used.

[0051]

[0052] The electrode film formation step is a step of forming an electrode film by applying and pressing the electrode powder formed in the grinding step onto a substrate.

[0053] A thin electrode film of uniform thickness is produced using a roll mill or similar equipment. The tensile strength and other physical properties of the electrode film can be evaluated using a universal testing machine. To increase composite density and improve the electrical contact of the material, a rolling mill can be used to press the film thinly, thereby reducing the thickness and increasing the composite density. Unlike the wet electrode process, this can be performed as a two-step process in which the electrode film is first rolled without a current collector, followed by the bonding of a current collector. Through the evaluation of semi-finished product characteristics, it can be found that using less binder with a high extrusion ratio improves the microstructure of the electrode and enhances output characteristics.

[0054]

[0055] In the following, an experiment is performed on an electrode manufacturing method using a dry electrode process according to one embodiment of the present invention and on an electrode using the same, and the experimental results are explained in detail using examples.

[0056]

[0057] 1. Ingredients

[0058] Active material: A material that generates capacity by participating in electrochemical reactions during charging and discharging. In the case of commercial lithium-ion batteries, lithium nickel-cobalt-manganese oxide is primarily used for the positive electrode, and graphite for the negative electrode. In this experiment, single-crystal LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811, SML83-L15U, SMLab, d 50 = 5.4㎛) was used as an active material.

[0059] Binder: Two types of Daikin PTFE powders (F-104 and F-208) were used as binders.

[0060] Conductive agent: Four types of carbon black (Super P (Imerys), Li-435 (Denka), EC-300J & EC-600JD (Nouryon)) and carbon nanotubes (Tuball (OCSiAl)) were used as conductive agents.

[0061] Current collector: Carbon-coated aluminum foil (Al 15㎛ + C 1㎛) was used as the current collector.

[0062] All ingredients were used as is, without any additional refining.

[0063]

[0064] 2. Dry Electrode Manufacturing Experimental Procedure

[0065] The powder formation process included mixing, kneading, and grinding, and was performed in 100g batches. Prior to mixing, the conductive materials composed of CNT and CB were pre-mixed at ratios of 0 / 100, 5 / 95, 10 / 90, and 25 / 75, and mixed for 9 minutes using a powder mixer at 5000 / 10 rpm. The PTFE content was adjusted to 2%, 3%, and 5% by weight, and accordingly, the compositional ratios of the active material, binder, and conductive material (A / B / C) were formed as 96 / 2 / 2, 95 / 3 / 2, and 93 / 5 / 2, respectively. The equipment used in the dry electrode manufacturing process includes a powder mixer (LS-300, KMTech), a kneader (NEP-0.5 K, KMTech), a roll mill (KRM-80D, KMTech), a roll press (MP-230H, Rohtec), etc.

[0066]

[0067] 3. Intermediate Product Characteristics Analysis Experiment

[0068] The electrical resistivity of the electrodes was measured using an electrode resistance measurement system (RM2610, Hioki), and the reciprocal value was interpreted as the electronic conductivity. The microstructure of the intermediate products was investigated using a scanning electron microscope (SEM, SU7000, Hitachi). The kneading torque of each electrode dough was monitored in real time within a dough mixer (NEP-0.5 K, KMTech). The powder size distribution was determined by sieving using five sieves with mesh sizes of 100, 200, 300, 400, and 500 μm (TS-F0100, TS-F0200, TS-F0300, TS-F0400, TS-F0500, Glenammer). Tensile strength was evaluated using a universal testing machine (AGX-100NX, Shimadzu) at a cross rate of 1 mm / min.

[0069]

[0070] 4. Electrochemical Characterization Experiment

[0071] A symmetric CR2032 coin cell was fabricated to determine the electrode tortuosity. Each electrode was formed with a diameter of 14 mm, and a separator (Celgard 2320, Celgard) was prepared with a diameter of 19 mm. The cell was tested under cutoff conditions with a lithium-free electrolyte (100 mM TBACIO4 in ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (v / v). The bulk conductivity (K) of the electrolyte bulk ) was 2.25 mS / cm and was measured using a conductivity meter (FiveEasy Plus FP30, Mettler Toledo). Electrochemical impedance spectroscopy (EIS) analysis covering a frequency range of 5 MHz to 20 MHz was performed by applying a 5 mV AC signal using a potentiometer (VSP-300, BioLogic).

[0072] A CR2032 kinetic half-cell was assembled to evaluate electrochemical performance. The electrode and polyethylene (PE, SKIET, 15 μm) separator were punched to diameters of 14 mm and 19 mm, respectively. A lithium foil (1 mm, Wuxi) was used as the counter electrode and was cut to a diameter of 16 mm. The kinetic half-cell was filled with 6 g / Ah of liquid electrolyte containing 1.1 M LiPF6; the electrolyte consisted of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) in a ratio of 25 / 35 / 40 (v / v), with 1 wt% vinylene carbonate (VC) and 10 wt% fluoroethylene carbonate (FEC) added. EIS analysis was performed using a potentiometer (VSP-300, BioLogic) by applying a 5 mV AC signal in a frequency range from 5 MHz to 20 mHz. The electrochemical evaluation of the coin-type half-cell was performed at 25°C in a battery cycler (PESC05-0.1, WONIK PNE) and included a formation cycle at 0.1C and a standard cycle at 0.2C. Rate capacity tests were performed at a charge / discharge ratio of 0.1C, and the charge / discharge cycles designed for capacity recovery are not described in the drawings.

[0073]

[0074] FIG. 2 is a graph showing the mechanical properties measured according to the semi-finished product state according to one embodiment of the present invention.

[0075] The binder of the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention may be characterized as polytetrafluoroethylene (PTFE) having an extrusion ratio of 1,000 or more.

[0076] The electrode kneaded in the kneading step of the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention may be characterized in that the binder is fiberized and includes the form of fibrils.

[0077] Polytetrafluoroethylene (PTFE) has the property of easily becoming fiberized by shear force due to the strong repulsive force of fluorine (F) attached to carbon (C) chains. It can stretch like chewing gum to intertwine electrode active materials and conductive materials like a spiderweb, creating an electrode paste with properties similar to an eraser. This fiberization process is a characteristic of polytetrafluoroethylene molecules, and it is utilized to perform kneading, acting as a binder for the electrode.

[0078] The injection ratio and content of the polytetrafluoroethylene (PTFE) used affect the entire dry electrode process. The higher the injection ratio, the easier it is to mold thin products.

[0079] A binder according to one embodiment of the present invention is characterized by being polytetrafluoroethylene with an injection ratio of 1,000 or more. When the injection ratio is less than 1,000, high energy is required during electrode mixing, an electrode film with low tensile strength is formed, and the microstructure of the electrode is not improved, resulting in high flexibility and low effective ion conductivity, making it difficult to utilize for electrode fabrication. Conversely, when polytetrafluoroethylene with an injection ratio of 1,000 or more is used according to the present invention, an electrode film with high tensile strength can be formed with less energy during electrode mixing, and a high-power electrode having low flexibility and high effective ion conductivity can be fabricated by improving the microstructure of the electrode. Since it is impossible to realize such a high-power electrode at a low injection ratio of less than 1,000, it is preferable that the injection ratio be 1,000 or more.

[0080]

[0081] d 50 (Particle size, μm) Bulk density (g / cc) Specific tensile strength (MPa) Elongation at break (%) Recommended injection ratio F-10 4500 0.46 2.17 45400 36 (20~100) F-20 86 100 0.49 2.17 37 560 1500 (100~4,000)

[0082] According to Table 1 above, among polytetrafluoroethylenes, F-208 has a slightly larger particle size compared to F-104, a slightly higher bulk density, the same specific gravity, lower tensile strength, higher elongation, and a higher recommended injection ratio.

[0083] The recommended injection ratio is a value indicating the appropriate process conditions for PTFE provided by the material manufacturer, guaranteeing that PTFE can be injected stably while maintaining optimal physical properties within that range. For example, PTFE with a recommended injection ratio range of 20 to 100 is suitable for low pressure and simple processes, while PTFE with a range of 100 to 4,000 is used in high-pressure or complex injection processes. Using the material outside the recommended ratio may result in reduced fiberization efficiency, injection process instability, or loss of physical properties. Failure to adhere to the recommended injection ratio significantly increases the likelihood of problems such as cracking during injection, reduced injection speed, or decreased strength and flexibility of the molded product.

[0084] Applying PTFE with a high injection ratio, such as F-208 used in this invention, facilitates the fiberization of PTFE particles during the electrode process, thereby enabling the formation of a more flexible electrode paste. The high injection ratio of PTFE reduces resistance to flow during the paste process, which lowers the paste torque. Consequently, even with the same amount of PTFE, using PTFE with a higher extrusion ratio results in a reduction in equipment load, manifested as paste torque, leading to a decrease in process energy.

[0085] Therefore, since F-208 has a high elongation and injection ratio, it possesses characteristics that allow for better fiberization. This indicates that it is advantageous for strengthening the bonding force by intertwining the active material and the conductive material like a spiderweb within the electrode.

[0086] F-208 has the characteristic of being injected thinly due to its high injection ratio, so in the production of the electrode of the present invention, due to its soft physical properties, it is possible to form a low kneading torque and a small electrode powder, and the electrode film after rolling has greater tensile strength, which is because the thin strands of polytetrafluoroethylene fibers are more intertwined due to the high injection ratio.

[0087] In addition, according to Figure 2, tortuosity is a value representing the ion movement path relative to the electrode thickness, and the lower the value, the better the microstructure of the electrode. Compared to F-104, F-208 exhibits a superior microstructure in the electrode due to its lower tortuosity.

[0088]

[0089] Figure 3 is a TEM image of a conductive material (Super P, Li-435, EC-300J, EC-600JD) according to one embodiment of the present invention.

[0090] The conductive material of the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention has a specific surface area of ​​500 m² 2 / g to 5,000 m 2 It can be characterized as carbon black having an internal porosity of 50% or more and a g / g.

[0091]

[0092] Super-PDenka Black Ketjen Black Product Name: Super PLi-435EC-300JEC-600JDD 50 (Particle size, nm) 40 23 35 35 Specific surface area (m² 2 / g)621338001270 Porosity(%)006080

[0093] In conventional wet mixing, the binder had to be used in proportion to the specific surface area of ​​the conductive material and the active material. In the case of conductive materials with a large specific surface area, a large amount of binder is required, which results in a reduced amount of active material and a decrease in capacity (reduction in energy density). Furthermore, there were problems that made it difficult to use due to the tendency for dispersion and clumping. In the dry process according to the present invention, since no solvent is used, the above-mentioned problems do not occur, making it easier to use materials with internal pores and a large specific surface area.

[0094]

[0095] FIG. 5 is a graph showing the electrical performance of an electrode according to the type of conductive material according to one embodiment of the present invention.

[0096] Referring to Fig. 5, the specific surface area is 500 m² 2 EC-300J, 1,000 m² or more / g 2 It can be observed that the reduction ratio becomes very low at EC-600JD values ​​greater than / g, which indicates that the specific surface area is 500 m² 2 / g to 5,000 m 2 / g, it can be said that such an effect occurs in materials with an internal porosity of 50 or higher. Also, 5,000 m 2 If it exceeds / g, it is difficult for carbon materials to stably maintain an ultrafine pore structure, which complicates the manufacturing process and degrades mechanical strength and chemical stability, making synthesis and use as battery conductive materials difficult. Therefore, a specific surface area of ​​500 m² 2 / g to 5,000 m 2 / g is appropriate.

[0097]

[0098] Figure 4 is an SEM image showing a cross-section of a lithium-ion battery electrode.

[0099] FIG. 5 is a graph showing the electrical performance of an electrode according to the type of conductive material according to one embodiment of the present invention.

[0100] The bright areas represent the NCM electrode active material, and the dark areas represent the binder and conductive material regions. The binder and conductive material regions are labeled as CBD (carbon-binder domain). As the content of the conductive material increased, the proportion of CBD also increased.

[0101] Graph a compares the electrical conductivity of various conductive materials (Super P, Li-435, EC-300J, EC-600JD, CNT), and presents the conductivity by dividing it into C (conductive material alone), PTFE+C (mixture of binder and conductive material), and NCM+PTFE+C (mixture of electrode active material, binder, and conductive material). In the NCM+PTFE+C group, EC-600JD exhibits the second highest electrical conductivity after CNT, indicating that it is advantageous for electron transport within the electrode.

[0102] b. Graph shows the resistance reduction rate (the rate of reduction in electrical conductivity when a material is added) in the conductive agent and electrode states. The upper graph shows the resistance reduction rate during the process of converting from the conductive agent alone state to CBD, and the lower graph shows the resistance reduction rate during the process of converting from CBD to the electrode state. KB (EC-600JD) had a low resistance reduction rate, indicating that when porous carbon black with a large specific surface area is used, the electrical conductivity of the electrode is high and the resistance is low.

[0103] The graph c represents tortuosity, indicating tortuosity according to the type of conductive material. When using porous carbon black with a large specific surface area, such as KB (EC-600JD), electrodes with excellent microstructures can be fabricated. In particular, it was possible to fabricate electrodes with very low tortuosity of less than 2, and this effect is [due to] 500 m 2 Since this is a feature not found in ordinary carbon black with a specific surface area of ​​less than 1g and a porosity of less than 50%, the specific surface area is 500 m² 2 / g to 5,000 m2 It is preferable to use carbon black with an internal porosity of 50% to 100% and a particulate matter of / g.

[0104] Based on the above, the conductive material can be selected through the ratio of the electrical conductivity of the 'conductive material' and the 'mixed material of binder and conductive material', and the ratio of the electrical conductivity of the 'mixed material of binder and conductive material' and the 'electrode'.

[0105] As shown in Fig. 5b, there may be a method of manufacturing an electrode by selecting a conductive material with the lowest reduction ratio, or an electrode may be manufactured by selecting a conductive material with a reduction ratio of 98 to 99% to the 2 wt% standard electrode.

[0106]

[0107] Figure 6 is a graph showing physical properties according to the content of PTFE binder and the size of electrode powder particles according to one embodiment of the present invention.

[0108] Based on 100% by weight of the total electrode of the electrode in a method for manufacturing an electrode using a dry electrode process according to one embodiment of the present invention, the electrode comprises an active material, a binder, and a conductive material, wherein the content of the binder is 0.5 to 2% by weight, the conductive material is 0.5 to 5% by weight, and the active material is 93% to 99% by weight. Additionally, the electrode powder may be characterized by having an average particle size of 100 to 500 μm.

[0109] If the binder is added at less than 0.5%, the physical strength of the electrode becomes very weak, making electrode film formation difficult; if it is added at 5% or more, the microstructure of the electrode deteriorates, significantly hindering the movement of lithium ions. Furthermore, if the conductive material is added at less than 0.5%, electron transport pathways within the electrode are not sufficiently formed, causing it to act as an insulator and rendering it unusable; if it is added at 5% or more, the unnecessarily excessive amount of conductive material not only hinders ion conduction but also leads to a problem of reduced cell energy density due to a decrease in the fraction of active material. The content of the active material can be determined by the content of the binder and conductive material, and in terms of energy density, a higher content of the active material is preferable.

[0110]

[0111] Graph 6a shows the mass fraction of electrode powders by size according to the type of PTFE binder (F-104, F-208) and PTFE content (2%, 3%, 5%). F-208 mainly has an average particle size of 100 to 500 μm, which is advantageous for forming a uniform electrode structure. This means that a uniform distribution can be achieved by maintaining a relatively small particle size.

[0112] Graph b of Fig. 6 shows the distribution density of electrode powder particle sizes according to the PTFE content of F-104. As the PTFE content increases, the distribution shifts to the right, forming larger particles, and since the particle size is largest at 5% content, it tends to be difficult to maintain a uniform distribution.

[0113] Graph c of Fig. 6 shows the particle size distribution density of the electrode powder according to the PTFE content of F-208. Similarly, as the PTFE content increases, the particle size increases, but the distribution is located to the left compared to F-104, indicating that it maintains a relatively small particle size. Therefore, since F-208 has a relatively uniform particle distribution even when the PTFE content increases, it can be said that it is advantageous for ensuring the uniformity of the electrode.

[0114] Graph d of Fig. 6 shows the ideal electrode structure according to the particle size of the electrode powder. Large particles (too large) of 600 μm or more indicate that the electrode is formed unevenly and requires additional grinding time, while particles of about 200 μm (desired) are ideal, enabling uniform electrode formation and reducing edge roughness. Small particles (too small) of 100 μm or less may cause the PTFE fibers to break, weakening the bonding strength, which can reduce the mechanical strength of the electrode.

[0115] Figure 7 is a photograph showing edge non-uniformity due to an increase in the content of PTFE binder according to one embodiment of the present invention.

[0116] When electrode powder becomes large, the edges of the electrode film are formed unevenly and very unevenly when manufacturing the electrode film using a roll mill. In this case, the edges must be cut off, which results in losses during the process and is an uneconomical problem.

[0117] Accordingly, the binder content is preferably 0.5 to 2 weight%, and if it is less than 0.5 weight%, there is a problem that the electrode film is not formed, and if it exceeds 2 weight%, the average particle size of the electrode powder increases, causing the edges to become uneven when manufacturing the electrode film.

[0118] Likewise, when the size of the electrode powder after grinding is 100 μm, the binder is excessively ground, and the problem arises that it does not perform the role of physically interlocking and connecting the electrode active material and the conductive material, and when it exceeds 500 μm, the problem arises that the edges of the electrode film are produced very unevenly.

[0119]

[0120] FIG. 8 is a graph showing the change in torque according to the fiberization process and kneading time of a PTFE binder according to one embodiment of the present invention.

[0121] The kneading step of the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention may include terminating the kneading step within three times the point at which maximum kneading torque occurs.

[0122] The kneading step is terminated within three times the point at which the maximum kneading torque occurs. By determining the point at which the kneading step is terminated, the quality of the electrode dough can be consistently maintained, and the degradation of electrode performance due to excessive kneading can be prevented. Preferably, the kneading process can be operated by detecting changes in torque occurring during the kneading process in real time and terminating the kneading process when it reaches three times the point at which the maximum torque occurs.

[0123] When the kneader rotates at the same RPM, the kneading torque increases if a large number of unfibrized PTFE particles are present inside. When using PTFE with a high injection ratio, fiberization can be induced with less force, resulting in a lower overall kneading torque. During the initial stages of the process, as PTFE particles fiberize into PTFE fibrils, the kneading torque rises; however, once it reaches a maximum point, the number of remaining PTFE particles decreases, causing the kneading torque to decline.

[0124] Excessive kneading time breaks the fibrotic PTFE fibers, preventing the formation of electrode paste and causing it to turn back into powder.

[0125]

[0126] Meanwhile, an electrode using a dry electrode process according to one embodiment of the present invention provides an electrode using a dry electrode process manufactured by an electrode manufacturing method using any one of the dry electrode processes described above.

[0127]

[0128] Meanwhile, the electrode film manufactured by the manufacturing method according to one embodiment of the present invention includes maintaining a tensile strength of 1 MPa or more after rolling.

[0129] When the tensile strength is less than 1 MPa, the mechanical strength of the electrode film is very weak, and there is a problem of it breaking.

[0130]

[0131] FIG. 9 is a graph showing the performance evaluation according to the type and content of the PTFE binder according to one embodiment of the present invention.

[0132] Through Figure 9, graphs a and b relate to the impedance spectrum, which indicates that the ion transport resistance increases as the PTFE content increases. Therefore, it can be seen that the higher the injection ratio and the lower the PTFE content (F-208 2%), the lower the ion resistance and tortuosity, indicating an excellent electrode microstructure.

[0133] Graph c represents ionic resistance and curvature. It can be seen that F-208 has lower ionic resistance compared to F-104, indicating smoother ion movement within the electrode. Additionally, the lower curvature implies better ion mobility because the ion movement path is simpler.

[0134] Graph d represents the charge-discharge curve, and as the C-rate increases, the voltage drops faster, which means that the capacity decreases during high-speed charging and discharging. The electrode using F-208 showed less capacity degradation even as the C-rate increased, thus demonstrating more stable performance even during high-speed charging and discharging.

[0135] Graph e shows the capacity retention rate according to the C-rate, and the electrode using F-208 maintained a higher capacity during high-speed charging and discharging compared to F-104. The lower the PTFE content, the better the capacity is maintained even at higher C-rates, and in particular, F-208 2% showed the highest capacity retention rate.

[0136] In conclusion, the electrode manufacturing method using a dry electrode process according to one embodiment of the present invention uses an F-208 binder and optimizes the PTFE content to maximize the electrical performance and charge / discharge efficiency of the electrode.

[0137]

[0138] FIG. 10 is a graph showing the effect of various types of carbon black conductive materials according to one embodiment of the present invention on the electrochemical performance of an electrode.

[0139] Graph c represents the impedance spectrum, where the size of the semicircle indicates the ionic resistance of the electrode; a smaller semicircle signifies lower ion mobility resistance. The EC-600JD exhibited the smallest semicircle, indicating low ionic resistance and excellent electrical conductivity.

[0140] Graph d relates to aerial capacity and C-rate performance; as current density increases, capacity decreases, which implies that capacity degradation occurs during high-speed charging and discharging. The EC-600JD maintains high capacity even at high current densities, indicating excellent high-speed charging and discharging performance. It also exhibits the lowest curvature, which simplifies the ion transport pathway, facilitates smooth ion movement, and contributes to improved electrochemical performance.

[0141]

[0142] Figure 11 is a photograph and graph showing electrochemical performance according to electrode thickness and capacity (aerial capacity) according to one embodiment of the present invention.

[0143] Photograph a shows a cross-sectional image of an electrode and aerial capacity, indicating that aerial capacity increases as the thickness increases. This is because the inclusion of more electrode active material provides higher capacity.

[0144] Graph b shows the voltage-capacity curve according to aerial capacity. It indicates a tendency for the voltage range to decrease as aerial capacity increases, and demonstrates that while thicker electrodes provide high capacity, the voltage drops more rapidly due to increased ion migration resistance. This suggests that as capacity increases (as thickness increases), significant voltage drop may occur during the charge-discharge process.

[0145] Graph c shows a comparison of aerial capacity according to C-rate (dry vs. wet). The dry electrode maintains aerial capacity well even at higher current densities (higher C-rates), indicating that its uniformly formed structure tends to maintain performance even during high-speed charging and discharging. The aerial capacity of the wet electrode decreases more rapidly as the C-rate increases. This is because the ion migration pathways in thick electrodes can become non-uniform due to the solvent-containing process characteristics. While there is no significant difference between the two processes at low current densities, as the current density increases (above 0.5 C), the electrode fabricated by the dry process maintains a higher capacity.

[0146]

[0147] FIG. 12 is a graph showing the kneading torque according to the type of conductive material according to one embodiment of the present invention.

[0148] FIG. 13 is a photograph showing a cross-section of an electrode manufactured according to a type of conductive material according to one embodiment of the present invention.

[0149] In the graph of the kneading torque measured in Fig. 12, there was a difference in kneading torque initially, but the kneading torque appeared to be almost similar around 10 minutes.

[0150] Figure 13 compares Super P and EC-600JD, and the left photo of Figure 13 shows a cross-section of an electrode using Super P, and the right photo shows a cross-section of an electrode using EC-600JD.

[0151] Although the specific surface area of ​​the two conductive materials differs by more than 20 times, unlike the wet process where slurry viscosity increases or dispersion deteriorates, the kneading torque is almost similar in the dry process, and as can be seen from the electrode cross-section, it was confirmed that there are no process disadvantages. Even when compared to the widely used Super P, as shown in the photograph, there is no significant difference in the distribution or size of the active material and conductive material, indicating that they are similar in physical properties.

[0152] The electrode manufacturing method using the dry electrode process according to the present invention and the electrode using the same can be utilized in battery fields such as lithium-ion batteries.

Claims

1. A mixing step of dry-mixing an electrode mixture comprising an electrode active material, a conductive material, and a binder to form a powder; A kneading step of preparing electrode dough by feeding the powder formed in the mixing step above into a kneader; A grinding step for forming electrode powder by grinding the electrode dough prepared in the above kneading step; and an electrode film forming step comprising applying and pressing the electrode powder formed in the above grinding step onto a substrate to form an electrode film; Electrode manufacturing method using a dry electrode process.

2. In Paragraph 1, The above binder is, Characterized as polytetrafluoroethylene (PTFE) having an extrusion ratio of 1,000 or more, Electrode manufacturing method using a dry electrode process.

3. In Paragraph 1, The electrode kneaded in the above kneading step is characterized by containing the binder in the form of fibrils, wherein the binder is fiberized. Electrode manufacturing method using a dry electrode process.

4. In Paragraph 1, The above conductive material is, Specific surface area is 500 m² 2 / g to 5,000 m 2 Characterized as carbon black having an internal porosity of 50% or more and a g / g Electrode manufacturing method using a dry electrode process.

5. In Paragraph 1, Based on 100 weight% of the total electrode, the content of the binder is 0.5 to 2 weight%, and Characterized by the average particle size of the electrode powder being 100 to 500 μm, Electrode manufacturing method using a dry electrode process.

6. In Paragraph 1, The above kneading step is, Includes terminating the kneading step within three times the point at which maximum dough torque occurs. Electrode manufacturing method using a dry electrode process.

7. An electrode using a dry electrode process characterized by being manufactured according to the manufacturing method of any one of claims 1 to 6.

Images