KR20230114814A - Method for manufacturing an electrode for a lithium secondary battery including solution coating process - Google Patents

Abstract

The present invention relates to a method for manufacturing an electrode for a lithium secondary battery, which includes a coating solution coating process. When manufacturing an electrode for a lithium secondary battery, a dehydration process is applied to maximize productivity by improving the drying speed without impairing electrode performance, and at the same time, a binder is used. It is possible to manufacture an electrode with improved life performance by improving the adhesion between the electrode active material and the copper foil by applying a process of applying the coating solution containing the present invention.

Description

Method for manufacturing an electrode for a lithium secondary battery including solution coating process}

The present invention relates to a method for manufacturing an electrode for a lithium secondary battery, and specifically, to a method for manufacturing an electrode for a lithium secondary battery to which a dehydration process and a coating solution coating process are applied.

A lithium secondary battery has a structure in which an electrolyte containing a lithium salt is impregnated in an electrode assembly composed of a positive electrode and a negative electrode, which are electrodes coated with an active material on a current collector, and a porous separator for separating them. The electrode is manufactured by coating a liquid slurry containing an active material, a conductive material, a binder, etc. on a foil-shaped current collector, drying it, and forming an electrode layer through a pressing process by roll pressing. The electrode manufacturing speed of is known at a level of 50 to 80 m/min.

On the other hand, as electronic devices are miniaturized, lightweight, thin, and portable according to the recent development of the information communication industry, demand for lithium secondary batteries used as power sources for electronic devices is rapidly increasing.

In particular, in recent years, there is a situation in which supply cannot keep up with demand due to the rapid spread of electric vehicles. Accordingly, recently, lithium secondary battery manufacturers have attempted to improve the electrode manufacturing speed, which occupies the largest portion of the lithium secondary battery manufacturing process, as a way to expand supply. Specifically, an attempt is being made to apply a drying process that does not use a solvent or to increase the hot air drying speed to increase the drying speed of the solvent.

However, since the dry process does not use a solvent, there is a problem that the electrode materials cannot be uniformly dispersed, and when the hot air drying speed is increased, the binder component in the slurry moves toward the surface and only the surface is dried. There is a problem that this may occur and cause degradation of electrode performance.

Accordingly, the inventors of the present invention, as an alternative to increasing the productivity of electrode manufacturing without impairing electrode performance, applied the dehydration process performed in the paper manufacturing process to electrode manufacturing and through the process of coating the coating solution on the current collector, Research was conducted focusing on the possibility of improving both productivity and overall performance of the battery.

The present inventors found a method that can efficiently apply the dehydration process used in paper manufacturing to the production of secondary battery electrodes, and based on this, maximized productivity by improving the drying speed in electrode production, and at the same time, the coating solution process The present invention was completed by implementing a method for further improving the performance of the electrode by coating.

Patent Document 1: Republic of Korea Patent Publication No. 10-2021-0006899 Patent Document 2: Republic of Korea Patent Publication No. 10-2018-0119158

The technical problem to be solved by the present invention is to maximize the productivity by improving the drying speed without impairing the electrode performance when manufacturing the electrode for a lithium secondary battery, and at the same time to improve the adhesion between the electrode active material and the current collector to improve the overall performance of the battery. It is to provide an electrode manufacturing method that can be improved.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention not mentioned above can be understood by the following description and will be more clearly understood by the examples of the present invention. It will also be readily apparent that the objects and advantages of the present invention may be realized by means of the instrumentalities and combinations indicated in the claims.

In order to solve the above technical problem, the present invention provides an electrode manufacturing method as follows.

(S100) forming an electrode layer by applying an electrode slurry containing an active material, a binder, a conductive material and a solvent to one side of a porous substrate, and then performing a dewatering process on the opposite side of the porous substrate;

(S200) applying a coating solution containing a binder on the electrode current collector;

(S300) laminating the electrode current collector on the electrode layer formed on the porous substrate to form a laminate in which the porous substrate, the electrode layer, and the electrode current collector are sequentially stacked, and pressurizing the laminate to perform additional dehydration; and

(S400) Provides a method for manufacturing an electrode comprising separating the porous substrate from the electrode layer and then drying the electrode layer formed on the current collector.

In the present invention, the porous substrate in step (S100) may be in the form of a mesh made of polymer, glass fiber, paper, metal or ceramic material, and in this case, the polymer includes PTFE (polytetrafluoroethylene), PES (polyethylsulfone), nylon etc. are available.

In the present invention, the average pore size of the porous substrate in step (S100) may range from 0.1 to 20 μm, or from 1 to 10 μm.

In the present invention, the porosity of the porous substrate in step (S100) may be in the range of 50 to 95%, or 70% to 90%.

According to the dehydration process of step (S100) in the present invention, a significant amount of the solvent in the electrode slurry, for example, 40% to 80%, specifically 50% to 70% of the used solvent content can be removed.

In the present invention, the coating solution in step (S200) may include one or more binders capable of improving adhesion between the electrode layer and the electrode current collector, and the coating solution containing the binder may be obtained by dispersing the binder in a solvent and stirring it. can At this time, the coating thickness of the coating solution containing the binder applied to the electrode current collector may be 5 to 50 μm.

In the present invention, the binder included in the coating solution of step (S200) is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidenefluoride, polyacrylonitrile ), polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid , styrene butyrene rubber (SBR), and fluorine-containing rubber may be one or more binder polymers selected from the group consisting of.

In the present invention, the binder in step (S200) may be included in an amount of 10 to 40 weight based on the total weight of the coating solution.

In the present invention, the pressurization of step (S300) may be performed at a pressure of 0.05 to 20,000 kPa, specifically 0.1 to 4,000 kPa.

In addition, the present invention provides an electrode manufactured by the method of the present invention and a lithium secondary battery including the same.

The solution to the above problems does not enumerate all the features of the present invention. Various features of the present invention and the advantages and effects thereof will be understood in more detail with reference to the following specific examples.

According to the present invention, a significant amount of the solvent in the electrode slurry is removed in advance by applying a dewatering process using a porous substrate to the manufacturing process of the electrode for a lithium secondary battery, and the porous substrate, the electrode layer, and the electrode current collector are pressurized and added After dehydration, the porous substrate is separated from the electrode layer, and then the electrode layer is dried to shorten the drying rate, thereby maximizing the productivity of the electrode without impairing electrode performance.

According to the present invention, by applying the coating solution containing the binder to the current collector in advance, it is possible to improve the overall performance of the battery by improving the adhesive strength between the active material and the electrode current collector due to the application of the dehydration process.

In addition to the above effects, specific effects of the present invention will be described together while explaining specific details for carrying out the present invention.

1 is a flowchart schematically illustrating a process of manufacturing an electrode for a lithium secondary battery including a coating solution coating process according to an embodiment of the present invention.
Figure 2 is a result of comparing the electrode adhesion between the lithium secondary battery electrodes of Examples 1 and 2 and Comparative Example 1 of the present invention.
Figure 3 is a result of comparing the porosity and void distribution between the electrodes of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention.
4 is a result of comparing capacity and lifetime performance between electrodes of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention.

Hereinafter, the present invention will be described in more detail.

The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "have" are intended to designate that the described feature, number, step, operation, component, part, or combination thereof exists, but one or more other features or numbers, It should be understood that the presence or addition of steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this specification, it should not be interpreted in an ideal or excessively formal meaning. don't

1 schematically illustrates an electrode manufacturing process in which a dehydration process according to an embodiment of the present invention is introduced.

Referring to FIG. 1, the electrode manufacturing method of the present invention includes (S100) dehydrating the electrode slurry to form an electrode layer; (S200) applying a coating solution containing a binder on the electrode current collector; (S300) forming a laminate of a porous substrate, an electrode layer, and an electrode current collector, and then applying pressure for additional dehydration; and (S400) a drying step after separating the porous substrate.

In the following, the electrode manufacturing method according to the present invention will be described step by step.

(S100) Dehydrating the electrode slurry to form an electrode layer

First, an electrode layer is formed by applying an electrode slurry to one side of a porous substrate and then performing a dewatering process on the opposite side of the porous substrate (S100).

The electrode slurry may be obtained by dispersing an active material in a solvent, mixing a binder, a conductive material, and the like, and then stirring them.

The active material is a material that causes an electrochemical reaction with lithium ions in an electrode. When the electrode manufactured according to the present invention is used as a positive electrode for a lithium secondary battery, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO ₄ , LiFePO ₄ , and LiNi _1-xyz Co _x M1 _y M2 _z O ₂ (M1 and M2 are each independently any one selected from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are independently oxides 0≤x<0.5, 0≤y<0.5, 0≤z<0.5, 0<x+y+z≤1 as the atomic fraction of the constituent elements) any one active material particle selected from the group consisting of, or two kinds thereof A mixture of the above may be included. On the other hand, when the electrode manufactured according to the present invention is used as a negative electrode for a lithium secondary battery, the active material is natural graphite, artificial graphite, carbonaceous material; lithium-containing titanium composite oxide (LTO), metals (Me) that are Si, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; alloys composed of the metals (Me); an oxide (MeO _x ) of the metal (Me); and any one active material particle selected from the group consisting of a composite of the metal (Me) and carbon, or a mixture of two or more of them. These electrode active materials may be used in an amount of 10 to 80% by weight based on the total weight of the electrode slurry.

The conductive material is a component that provides a conductive path for electrical connection in the electrode layer, and is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, carbon black, such as carbon black, acetylene black, Ketjen black, channel black, farnes black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used. The conductive material may be added in an amount of 0.1 to 10% by weight based on the total weight of the electrode slurry.

The binder is a component that is located between the active material and the conductive material in the electrode layer to connect and fix them while promoting bonding between the electrode layer and the electrode current collector, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP) , polyvinylidenefluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinyl Various types of binder polymers such as pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, styrene butyrene rubber (SBR), and fluorine-containing rubber may be used. The binder may be added in an amount of 0.1 to 10% by weight based on the total weight of the electrode slurry. N-methylpyrrolidone, acetone, water, etc. may be used as the solvent.

The content of the active material, binder, conductive material and solvent included in the electrode slurry may be selected within a range commonly used in the manufacture of electrodes for lithium secondary batteries, for example, a liquid electrode slurry having a solid content of 10 to 80% by weight or less can be obtained.

In addition, the electrode slurry may further include other additives such as a thickener and a filler, and the content of these other additives may be appropriately selected within a range that does not impair the performance of the electrode.

On the other hand, in the case of manufacturing a general electrode, a liquid slurry is applied uniformly on a current collector for an electrode, and then the solvent is dried and pressed.

In contrast, the electrode manufacturing method of the present invention is characterized in that the dehydration process performed in the paper manufacturing process is applied to the production of the electrode for a lithium secondary battery prior to applying the electrode slurry to the current collector for the electrode.

In the case of general paper production, raw materials are uniformly applied on a paper machine in the form of a wire mesh, dehydrated to obtain paper in the form of a sheet, and then dried by passing it through a high temperature. The paper raw material applied to the papermaking machine can be continuously transferred to the roll press and dryer while 95% or more of the water is removed through dehydration in a state where most of the paper raw material is water.

In order to apply this dehydration process to the production of secondary battery electrodes, a separate member corresponding to the paper machine is required, and through such a member, dehydration must be performed while preventing the release of solids from the electrode slurry having a higher solids content than paper.

Therefore, in the present invention, a porous substrate is used as a member for performing the dehydration process of the electrode slurry, and after applying the liquid electrode slurry thereon, a dehydration process is performed on the opposite side of the porous substrate to remove the solvent in the electrode slurry do. At this time, the coating thickness of the liquid electrode slurry applied to the current collector may be 200 to 500 μm, for example, 300 μm.

The porous substrate used in the dehydration process in the present invention may be in the form of a polymer, glass fiber, paper, metal or ceramic mesh, but there are no particular limitations on its shape and material. Polytetrafluoroethylene (PTFE), polyethylsulfone (PES), nylon, and the like can be used as the polymer, and these may be used in a surface-treated form if necessary.

Although the pore size of the porous substrate may vary depending on the type of material, the average size of the pores is 0.1 to 20 μm, such as 1 to 10 μm, in order to efficiently perform dehydration of the electrode slurry for secondary batteries containing particle-type solids. may be in the range of When the above pore range is satisfied, it is advantageous that only the solvent can pass through the porous substrate while suppressing the passage of materials constituting the electrode layer of the active material, the binder, and the conductive material.

In addition, the porous substrate may have a porosity in the range of 50 to 95%, for example, 70% to 90%, and the porosity may be measured by a method such as mercury intrusion porosimeter (MIP) or gas adsorption method (BET). there is.

In addition, the dehydration process may be performed by lowering the pressure to a negative pressure for more rapid and smooth dehydration.

According to this dehydration process, it is possible to remove a significant amount of the solvent in the electrode slurry, for example, 40% to 80%, specifically 50% to 70% of the solvent content used, thereby shortening the drying time of the electrode layer that proceeds afterwards. By shortening the length, the productivity of the electrode can be maximized.

(S200) Applying a coating solution containing a binder on the electrode current collector

In the electrode manufacturing method of the present invention, a coating solution containing a binder is applied on the electrode current collector (S200).

The electrode current collector serves as an intermediate medium for supplying electrons provided to the external conductor to the electrode active material or, on the contrary, serves as a transmitter to collect electrons generated as a result of the electrode reaction and flow them to the external conductor, thereby causing chemical changes in the battery It is not particularly limited as long as it has high conductivity without causing it. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, copper; stainless steel surface treated with carbon, nickel, titanium or silver; aluminum-cadmium alloy; Non-conductive polymer surface treated with a conductive material; non-conductive polymer surface treated with a metal such as aluminum; or a conductive polymer. In addition, the electrode current collector may have various forms such as a film, sheet, foil, net, porous material, foam, and nonwoven fabric, and may have a thickness ranging from 3 to 500 μm, but is not limited thereto.

Unlike a general electrode manufacturing method in which a liquid slurry is applied to a current collector for an electrode, bound to the current collector, and then pressurized again to manufacture an electrode, in the electrode manufacturing method of the present invention to which the dehydration process performed in the paper manufacturing process is applied, , Pressing an electrode layer in the form of a sheet already prepared using a porous substrate to the electrode current collector to physically bind the electrode layer and the electrode current collector.

Due to this, unlike the general electrode manufacturing method in which the electrode current collector is bound in the form of a liquid slurry, the electrode manufacturing method using the dehydration process performed in the paper manufacturing process improves the electrode manufacturing productivity, but the adhesive strength between the electrode layer and the electrode current collector There was a downside to being weak. Accordingly, a method was devised in which a coating solution containing a binder was applied onto an electrode current collector and then laminated on an electrode layer formed on a porous substrate.

The coating solution may include one or more types of binder capable of improving adhesion between the electrode layer and the electrode current collector, and the coating solution including the binder may be obtained by dispersing the binder in a solvent and stirring. At this time, the coating thickness of the coating solution containing the binder applied to the electrode current collector may be 5 to 50 μm.

The binder is, for example, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, Polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, styrene butyrene rubber (SBR), fluorine- It may be one or more binder polymers selected from the group consisting of containing rubber.

In one embodiment of the present invention, the coating solution is prepared by mixing the binder and a solvent, and N-methylpyrrolidone, acetone, water, or the like can be used as the solvent.

At this time, the binder may be included in an amount of 10 to 40 weight based on the total weight of the coating solution.

In one embodiment of the present invention, the coating solution is applied to the electrode current collector using a doctor blade, and it is sufficient if it can be uniformly applied on the electrode current collector using a known method, and is not limited to a specific method. .

(S300) Pressing for additional dehydration after forming a laminate of a porous substrate, an electrode layer, and an electrode current collector

In the electrode manufacturing method of the present invention, after the dehydration process, the electrode current collector coated with the coating solution is laminated on the electrode layer formed on the porous substrate to form a laminate in which the porous substrate, the electrode layer, and the electrode current collector are sequentially stacked, The laminate is pressed (S300).

The pressurization is a process for additional dehydration of the electrode slurry while increasing the capacity density of the electrode and increasing the adhesiveness between the electrode collector and the electrode layer, and the pressurization can be performed in a state in which the porous substrate, the electrode layer, and the electrode collector are sequentially stacked. there is. In addition, the pressing may be performed by way of roll pressing.

In one embodiment of the present invention, the pressurization may be performed at a pressure of 0.05 to 20,000 kPa, specifically 0.1 to 4,000 kPa, and when the pressurization range is satisfied, additional dehydration of the electrode slurry can be effectively performed. , it is advantageous in that it can increase the capacity density of the electrode and increase the adhesion between the electrode current collector and the electrode layer.

In one embodiment of the present invention, the pressing may be performed on the porous substrate side of the laminate, and in this case, the contact surface of the electrode layer with the current collector is increased compared to the porous substrate, so that the current collector is applied in a later step. It is believed that the porous substrate can be easily separated and removed from the adhered electrode layer.

(S400) Drying step after separation of the porous substrate

In the electrode manufacturing method of the present invention, after pressing, the porous substrate used for dehydration of the electrode slurry is separated and removed, and then the electrode layer formed on the electrode current collector is dried to manufacture an electrode (S400).

The drying is a process for removing the remaining solvent after a significant amount of the solvent is removed from the electrode slurry through the previously performed dehydration process, and is distinguished from drying in which all solvents included in the electrode slurry are removed during conventional electrode manufacturing. That is, in the present invention, since the dehydration process is performed in advance, drying can be performed at a faster rate than the drying process in conventional electrode manufacturing. Meanwhile, the drying temperature may vary depending on the type of solvent included in the electrode slurry.

This shortening of the drying speed not only maximizes the productivity of the electrode, but also causes problems caused by raising the temperature or increasing the hot air speed in order to speed up the drying speed in the existing electrode manufacturing process, that is, the binder component in the slurry moves toward the surface. It is possible to prevent degradation of electrode performance by suppressing a skinning phenomenon in which only the surface is dried.

In the electrode manufactured as described above, the binder and the conductive material are uniformly distributed along with the active material, and the average pore size between the conductive material particles is reduced, so that the pore size distribution is, for example, 0.005 to 60 μm, specifically 0.01 to 45 μm. ㎛, and an electrode having an average size of 0.25 to 0.29 ㎛, specifically 0.26 to 0.28 ㎛ can be manufactured.

Accordingly, the electrode manufactured by the method of the present invention exhibits excellent electrode performance in terms of adhesion and electrochemical properties, and thus can be usefully used as electrodes for various types of lithium secondary batteries such as stack type, winding type, stack and folding type, and cable type. can

For example, in a secondary battery including a positive electrode, a negative electrode, a separator interposed on the positive electrode and the negative electrode, and a non-aqueous electrolyte, at least one of the positive electrode and the negative electrode may be an electrode manufactured by the manufacturing method of the present invention.

In the secondary battery, the separator used to separate the negative electrode and the positive electrode can be any porous substrate commonly used in the field, for example, a polyolefin-based porous membrane or non-woven fabric can be used, In addition, a porous coating layer including inorganic particles and a binder polymer may be further provided on at least one surface of the porous substrate, but is not particularly limited thereto.

In addition, the non-aqueous electrolyte solution may include an organic solvent and an electrolyte salt, and the electrolyte salt is a lithium salt. As the lithium salt, those commonly used in non-aqueous electrolytes for lithium secondary batteries may be used without limitation.

Such a secondary battery can be used not only as a battery cell used as a power source for a small device, but also preferably used as a unit cell in a medium-large battery module including a plurality of battery cells. Preferable examples of the medium-to-large-sized device include an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system. In particular, it is useful for hybrid electric vehicles and batteries for renewable energy storage, which are areas where high power is required. can be used

Hereinafter, examples will be described in detail to aid understanding of the present invention. However, the embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the following examples. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example 1: Preparation of negative electrode using coating process (SBR 10)

40% by weight of natural graphite as an active material, 1.2% by weight of carbon black as a conductive material, 1.4% by weight of styrene-butadiene rubber as a binder, and 0.4% by weight of a thickener (CMC) were added to the remaining amount of distilled water to obtain an anode slurry (solid content) content: 43% by weight) was prepared.

A coating solution containing a binder was prepared by mixing 10 g of distilled water with 1.2 wt% of a thickener (CMC) and 10 wt% of styrene-butadiene rubber (SBR) for 2 hours using a magnetic stirrer.

As shown in FIG. 1, after applying the prepared cathode slurry to a thickness of 300 μm on a porous substrate made of PTFE (average pore size: 1 μm) treated with a hydrophilic surface, a dehydration process at room temperature on the opposite side of the porous substrate (dewatering) was performed to remove distilled water in the slurry.

Next, a coating solution containing a binder was coated on one surface of a copper (Cu) thin film to a thickness of 10 μm using a doctor blade.

Then, after the surface of the porous PTFE substrate coated with the slurry was laminated on one surface of the copper (Cu) thin film coated with the coating solution, an additional dehydration process was performed by pressurizing the laminate. At this time, the pressurization was performed by adjusting in the range of 0.1 to 4,000 kPa. Through these two dehydration processes, the weight of the slurry was reduced to about 65% of the initial weight before dewatering (about 60% of the distilled water used was removed) (see FIG. 2).

Thereafter, the porous PTFE substrate was separated from the surface (cathode layer) to which the slurry was applied, and drying was performed at 80° C., and drying was completed after about 2 minutes.

Thus, a negative electrode having a negative electrode layer formed on the copper current collector was manufactured.

Example 2: Preparation of negative electrode using coating solution coating process (SBR 20)

A negative electrode was prepared in the same manner as in Example 1, except that 20% by weight of styrene-butadiene rubber (SBR) was added in the method of preparing a coating solution containing a binder.

Comparative Example 1: Preparation of negative electrode without application of coating solution application process (Dewatering)

An anode was manufactured in the same manner as in Example 1, except that the coating solution containing the binder was not applied to one surface of the copper (Cu) thin film.

Comparative Example 2: Preparation of negative electrode without dehydration process (Blade coating)

40% by weight of natural graphite as an active material, 1.2% by weight of carbon black as a conductive material, 1.4% by weight of styrene-butadiene rubber as a binder, and 0.4% by weight of a thickener (CMC) were added to the remaining amount of distilled water to obtain an anode slurry (solid content) content: 43% by weight) was prepared. Thus, a negative electrode in which a negative electrode layer (thickness: 60 to 65 μm) was formed on the copper current collector was manufactured. The negative electrode slurry was applied to a thickness of 300 μm on one surface of a copper (Cu) thin film as a negative electrode current collector having a thickness of 10 μm and dried at 60 ° C. The drying was completed after about 6 minutes.

Thus, a negative electrode in which a negative electrode layer (thickness: 50 to 55 μm) was formed on the copper current collector was manufactured.

Experimental Example 1: Measurement of adhesion between current collector and electrode

In order to confirm the difference in adhesive strength of the anodes prepared according to Example 1, Example 2 and Comparative Example 1, a 90° peel test was performed to quantify mechanical properties.

The cathodes prepared in Example 1, Example 2, and Comparative Example 1 were made into specimens of 2.5 cm × 2.5 cm, adhered on glass using double-sided tape, and then, using UTM equipment (Comtech QC506B), per minute The force required to peel the electrode from the double-sided tape at a speed of 3 mm, that is, the peel strength was measured.

At this time, the advancing speed, which is the speed at which the electrode is detached from the copper foil, was set to 300 mm/s, and the results are shown in FIG. 2.

Referring to FIG. 2 , it can be seen that the adhesive performance of the electrodes prepared according to Examples 1 and 2 is higher than that of Comparative Example 1. Specifically, in the case of the negative electrode (Examples 1 and 2) subjected to the binder coating process, as the content of styrene butyrene rubber (SBR) in the binder coating solution increased, it was confirmed that the adhesive force between the current collector and the electrode greatly increased. .

Experimental Example 2: Porosity and Porosity Distribution in the Electrode Layer

The porosity and void distribution of the negative electrodes prepared according to Example 1 and Comparative Examples 1 and 2 were measured using a Mercury intrusion porosimeter (MIP). The results are shown in Figure 3.

The y-axis, LDI, is a unit used to indicate the pore distribution in the electrode. A high value means that there are many pores, and the x-axis, D _pore , means the diameter of the pores. Examining the results, there was no significant change in the degree of distribution in the voids in the unit of 100 nm, but in the case of the voids in the unit of 1 μm, which are voids between graphites, a difference in the degree of distribution can be confirmed. Specifically, the porosity (%) of Example 1 (SBR10) was (42.2 ± 1.4)%, Comparative Example 1 (Dewatering) (41.5 ± 2.0)%, Comparative Example 2 (Blade coating) was (47.3 ± 0.8)% You can check. This means that the porosity decreased by about 5% while being bonded to the copper foil through the dehydration process. Since the porosity reduction increases the tap density, it also affects the electrochemical increase of the electrode.

Experimental Example 3: Evaluation of capacity and lifetime performance

Lithium secondary battery cells including negative electrodes prepared according to Example 1 and Comparative Examples 1 and 2 were prepared, and capacity and life performance were measured under charging 0.1C, discharging 0.1C, and 30 °C conditions. The results are shown in FIG. 4 .

Referring to FIG. 4, the initial specific discharge capacity was measured in the order of Example 1 (SBR10), Comparative Example 1 (Dewatering), and Comparative Example 2 (Blade coating). It can be seen that the lifespan performance of the battery cell using the negative electrode of Example 1 is better.

That is, it can be confirmed that the electrode of Example 1 prepared by performing the coating process not only has improved adhesive strength, but also has excellent electrochemical performance compared to the electrodes of Comparative Examples 1 and 2.

Claims (10)

(S100) forming an electrode layer by applying an electrode slurry containing an active material, a binder, a conductive material and a solvent to one side of a porous substrate, and then performing a dewatering process on the opposite side of the porous substrate;
(S200) applying a coating solution containing a binder on the electrode current collector;
(S300) laminating the electrode current collector on the electrode layer formed on the porous substrate to form a laminate in which the porous substrate, the electrode layer, and the electrode current collector are sequentially stacked, and pressurizing the laminate to perform additional dehydration; and
(S400) comprising the step of separating the porous substrate from the electrode layer and drying the electrode layer formed on the current collector,
electrode manufacturing method.
According to claim 1,
The binder is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidenefluoride, polyacrylonitrile, polymethylmethacrylate, poly Vinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, styrene butyrene rubber (SBR), fluorine-containing At least one selected from the group consisting of rubber,
electrode manufacturing method.
According to claim 1,
The binder is included in 10 to 40 weight based on the total weight of the coating solution,
Method for manufacturing electrodes.
According to claim 1,
The porous substrate is in the form of a mesh of polymer, glass fiber, paper, metal or ceramic material,
electrode manufacturing method.
According to claim 1,
The dehydration process is carried out by reducing the pressure to negative pressure,
electrode manufacturing method.
According to claim 1,
The coating solution is applied at 5 to 50 μm,
electrode manufacturing method.
According to claim 1,
The active material is a positive electrode active material or a negative electrode active material for a lithium secondary battery,
electrode manufacturing method.
According to claim 7,
The cathode active material is LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO ₄ , LiFePO ₄ , and LiNi _1-xyz Co _x M1 _y M2 _z O ₂ (M1 and M2 are each independently Al, Ni, Co, Fe, It is any one selected from the group consisting of Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are independently atomic fractions of oxide composition elements, 0≤x<0.5, 0≤y< 0.5, 0≤z<0.5, 0<x+y+z≤1) comprising any one active material particle selected from the group consisting of or a mixture of two or more of them,
electrode manufacturing method.
According to claim 8,
The negative electrode active material is natural graphite, artificial graphite, carbonaceous material; lithium-containing titanium composite oxide (LTO), metals (Me) that are Si, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; alloys composed of the metals (Me); an oxide (MeOx) of the metal (Me); And any one active material particle selected from the group consisting of a composite of the metal (Me) and carbon, or a mixture of two or more thereof,
electrode manufacturing method.
An electrode manufactured by the method according to any one of claims 1 to 9, wherein the pore size distribution included in the electrode is 0.005 to 60 μm and the average pore size is 0.25 to 0.29 μm.