Electrode coating device and method for manufacturing an electrode using the same

Abstract

The present invention relates to an electrode coating apparatus and a method for manufacturing an electrode using the same. The electrode coating apparatus induces static electricity on the back surface of an electrode current collector coated with an electrode slurry, so that the back surface has a charge opposite to the charge of an ionic binder contained in the electrode slurry as a binder. This prevents the binder from migrating to the surface of the electrode slurry even if the solvent volatilizes during the drying process of the electrode slurry, thereby providing an advantage of being highly effective in improving the adhesive strength between the electrode composite layer formed by drying the electrode slurry and the electrode current collector.

Description

Technical Field

[0001] The present invention relates to an apparatus for coating an electrode slurry on an electrode current collector and a method for manufacturing an electrode using the same.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0127327 filed on September 27, 2021, and all contents disclosed in the document of the Korean patent application are included as part of this specification.

Background Art

[0003] The electrodes of lithium secondary batteries are manufactured by mixing such active materials and a binder resin component, dispersing them in a solvent to form a slurry, applying this to the surface of a current collector, drying it, and then forming a composite layer.

[0004] In order to achieve a higher energy density of such lithium secondary batteries, as the loading of the active material loaded on the electrode using a high-capacity active material increases, the adhesive force between the active material and the electrode decreases, or as the resistance increases due to changes in the contact interface between the negative active materials, the capacity rapidly decreases as the charge-discharge cycle progresses, and there is a problem that the cycle life becomes short.

[0005] Generally, a polymer binder is widely used as a binder. By increasing the amount of such a polymer binder, the binding force can be enhanced not only between the active materials but also between the active material and the current collector, the detachment of the active material from the current collector can be reduced, and the effect of suppressing volume expansion due to charge and discharge of the battery can be enhanced. However, when an excessive amount of the polymer binder is used, the electrical resistance of the negative electrode increases due to the electrical insulation of the binder, and the amount of the active material relatively decreases, so problems such as a decrease in capacity have emerged.

[0006] In addition, in the drying process, the solvent in the slurry volatilizes, inducing a phenomenon in which the binder uniformly dispersed inside the slurry rises to the surface of the slurry and concentrates. As a result, it becomes difficult to induce a uniform chemical reaction within the electrode, and the longer the length of the binder, the higher the tendency for the binders to gather separately, which also affects the aging characteristics.

[0007] Therefore, there is a demand for the development of a technology that can prevent the separation between the electrode active materials or between the electrode active material and the current collector during the manufacture of the electrode with a strong adhesive force even in a small amount, control the volume expansion of the electrode active material that occurs during repeated charge and discharge with strong physical properties, and improve the structural stability of the electrode and thereby the performance of the battery.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, an object of the present invention is to provide a method capable of preventing the phenomenon in which the binder contained in the slurry rises to the surface and concentrates even in the electrode slurry drying process, and improving the adhesive force between the composite layer of the electrode and the electrode current collector.

Means for Solving the Problems

[0010] In order to solve the above problems, the present invention provides, in one embodiment, a transfer unit that moves an electrode current collector in a roll-to-roll manner, a coater that discharges an electrode slurry onto the surface of the electrode current collector moved by the transfer unit, and an electrostatic induction unit that induces static electricity on the back surface of the electrode current collector coated with the electrode slurry on the surface, and provides an electrode coating apparatus including the same.

[0011] Here, the electrostatic induction unit can induce static electricity by bringing the back surface of the electrode current collector coated with the electrode slurry into contact with the electrostatic induction material to cause contact electrification, or by using the charges formed by the frictional electrification of the friction member.

[0012] As an example, the electrostatic induction unit includes a roller including a charged region coated with an electrostatic induction material on the surface, and static electricity can be induced by the contact between the electrostatic induction material of the roller and the electrode current collector.

[0013] In this case, the electrostatic induction material may include ebonite, glass, nylon, wool, rayon, wool, silk, silk fabric, paper, iron, rubber, copper, silver, gold, platinum, polystyrene, acrylic, celluloid, polyvinyl chloride, polypropylene polyethylene, silicone or Teflon (registered trademark).

[0014] As another example, the electrostatic induction unit is composed of a motor and a motor unit composed of a power transmission shaft axially coupled to the motor shaft of the motor and having a gear formed on the outer peripheral surface, a circular rotary friction member that is gear-coupled to the power transmission shaft and has a gear formed on the outer peripheral surface so as to rotate by the rotation of the power transmission shaft, a fixed friction member installed so as to contact one side of the outer peripheral surface of the rotary friction member, and an arc-shaped electrostatic induction member installed at a certain distance from the rotary friction member and symmetric with the fixed friction member about the rotary friction member, and an electrostatic induction line installed on one side of the electrostatic induction member, and an electrostatic generation unit including an electrostatic plate connected to the electrostatic induction member by the electrostatic induction line, having a charge on the surface, and provided so as to face the back surface of the electrode current collector, and static electricity can be induced by bringing the charges induced by the rotary friction member close to the back surface of the electrode current collector.

[0015] At this time, the rotating friction member may have a structure in which a gear is formed on the upper or lower part of the outer peripheral surface, and the fixed friction member is in surface contact with the outer peripheral surface where the gear is not formed.

[0016] On the other hand, the electrode slurry applied to the surface of the electrode current collector can contain an ionic binder, and the electrostatic induction part can induce an opposite charge to the ionic binder of the electrode slurry applied to the surface of the electrode current collector on the back surface of the electrode current collector.

[0017] At this time, the ionic binder may contain one or more polymers selected from the group consisting of carboxymethyl cellulose (CMC), hydroxypropyl cellulose, regenerated cellulose, polyacrylic acid (PAA), polyacrylonitrile, polyacrylamide, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluororubber, polyvinyl alcohol, polyethylene glycol, and alginate.

[0018] Also, the transfer part may be operated at a speed of 20 to 100 m / min.

[0019] Moreover, in one embodiment of the present invention, a step of applying an electrode slurry to one surface of the electrode current collector; a step of inducing static electricity on the back surface of the electrode current collector coated with the electrode slurry, and provides a method for manufacturing an electrode including these steps.

[0020] At this time, the electrode slurry contains an ionic binder, and the static electricity induced on the back surface of the electrode current collector coated with the electrode slurry may have an opposite charge to the ionic binder.

[0021] Further, the ionic binder may contain one or more polymers selected from the group consisting of carboxymethyl cellulose (CMC), hydroxypropyl cellulose, regenerated cellulose, polyacrylic acid (PAA), polyacrylonitrile (PAN), polyacrylamide (PAM), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluoro rubber, polyvinyl alcohol (PVA), polyethylene glycol (PEG), and alginate.

[0022] Further, the step of inducing static electricity on the back surface of the electrode current collector may be performed by contact electrification between the back surface of the electrode current collector and the static electricity inducing substance, or by frictional electrification of the friction member.

[0023] Further, after the step of inducing static electricity, a step of drying the electrode slurry applied to one surface of the electrode current collector may be further included.

[0024] At this time, the step of drying the electrode slurry may be performed at a temperature of 50°C to 200°C.

Advantages of the Invention

[0025] The electrode coating apparatus according to the present invention induces static electricity on the back surface of the electrode current collector having the electrode slurry applied to its surface so that it has a charge opposite to the charge of the ionic binder contained as a binder in the electrode slurry. Thus, even when solvent evaporation occurs during the drying process of the electrode slurry, the binder can be prevented from moving to the surface of the electrode slurry. Therefore, there is an advantage in that it is excellent in the effect of improving the adhesive force between the electrode composite layer formed by drying the electrode slurry and the electrode current collector.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0027] The present invention can be subjected to various modifications and may have various embodiments, but specific embodiments will be described in detail below.

[0028] However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents or alternatives included in the spirit and technical scope of the present invention.

[0029] In the present invention, terms such as "comprising" or "having" are intended to specify the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and should not be construed as precluding the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0030] Also, in the present invention, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, plate, etc. is described as being "under" another part, this includes not only the case where it is "directly under" the other part, but also the case where there is another part in between. Also, in this application, being "disposed on" may include not only the upper part but also the case of being disposed in the lower part.

[0031] Hereinafter, the present invention will be described in more detail.

[0032] <Coating device for electrode manufacturing> In one embodiment, the present invention a transfer unit that moves the electrode current collector in the running direction through a roll-to-roll supply process, a coater that is located above the moving unit and discharges electrode slurry onto the surface of the electrode current collector that is moved by the moving unit, and an electrostatic induction unit that is disposed below the moving unit and induces static electricity on the back surface of the electrode current collector coated with the electrode slurry on the surface, and provides a coating device for electrode manufacturing including the same.

[0033] The coating device for electrode manufacturing according to the present invention includes, as shown in FIG. 1, transfer units 11 and 12 that move the electrode current collector, a coater 20 that supplies electrode slurry to the surface of the electrode current collector, and an electrostatic induction unit 30 that induces static electricity on the back surface of the electrode current collector coated with the electrode slurry.

[0034] At this time, the transfer units 11 and 12 can run the electrode assembly by a method commonly applied in the art. Specifically, the transfer units 11 and 12 may include a pair of rollers 11 and 12 disposed in front of and behind the running direction of the electrode current collector in a roll-to-roll manner.

[0035] Further, the transfer units 11 and 12 may be operated at a speed capable of uniformly applying the electrode slurry to the surface of the electrode assembly. Specifically, they may be operated at a speed of 20 to 100 m / min. More specifically, they may be operated at a speed of 30 to 90 m / min, 40 to 90 m / min, 50 to 100 m / min, 70 to 100 m / min, 20 to 80 m / min, 20 to 60 m / min, 20 to 40 m / min, 40 to 80 m / min, or 25 to 70 m / min. By controlling the operating speeds of the transfer units 11 and 12 as described above, the present invention can apply the electrode slurry to the surface of the electrode assembly with a constant thickness and provide the time required for the electrostatic induction unit to induce static electricity on the back surface of the electrode current collector coated with the electrode slurry.

[0036] Further, the coater 20 is a unit that supplies the electrode slurry to the surface of the moving electrode current collector, and may be applied in a manner commonly applied in the industry. Specifically, it may include a slot die coater.

[0037] The slot die coater forms an electrode composite layer by applying the electrode slurry onto the electrode current collector, and may have a structure that discharges the electrode slurry through a pair of discharge ports formed in the upper die and the lower die. Thereby, a two-layer electrode composite layer can be formed on the electrode current collector.

[0038] Further, the electrostatic induction unit 30 is located below the electrode current collector moved by the transfer unit, discharges the electrode slurry by the coater 20, and induces static electricity on the back surface of the electrode current collector coated with the discharged electrode slurry on the surface.

[0039] Here, the electrostatic induction unit 30 contains an ionic binder in which the electrode slurry applied to the surface of the electrode current collector has a charge, and the electrostatic induction unit 30 can induce static electricity so as to be charged with a charge opposite to the charge of the ionic binder on the back surface of the electrode current collector coated with the electrode slurry.

[0040] That is, when the electrostatic induction device applies an electrode slurry containing an ionic binder showing a (+) charge to an electrode current collector, the electrostatic induction device can induce a (-) charge on the back surface of the electrode current collector coated with the electrode slurry, or when applying an electrode slurry containing an ionic binder showing a (-) charge to the electrode current collector, the electrostatic induction device can induce a (+) charge on the back surface of the electrode current collector coated with the electrode slurry.

[0041] The type of the above-mentioned ionic binder is not particularly limited as long as it has a charge. However, considering the bonding force with the electrode active material and the electrical physical properties inside the composite material layer, hydroxypropyl cellulose, regenerated cellulose, polyacrylic acid (PAA), polyacrylonitrile (PAN: polyacrylonitrile), polyacrylamide (PAM: polyacryl amide), styrene butadiene rubber (SBR: styrene butadiene rubber), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluoro rubber, polyvinyl alcohol (PVA: polyvinyl alcohol), polyethylene glycol (PEG: polyethylene glycol), and one or more polymers selected from the group consisting of alginate may be included. The above-mentioned polymer contains a carboxyl group (-COOH), a sulfonic group (-SOOOH), etc., and a part thereof may have a (-) charge in the form of a salt with an alkali metal ion such as Na + or Li + etc.

[0042] In addition, as long as the electrostatic induction unit 30 can charge the surface of the electrode current collector to induce static electricity, its form and driving method are not limited. Specifically, it may have a structure that directly rubs against the moving electrode current collector to induce contact electrification, or may have a structure that is equipped with a separate friction member to induce frictional electrification.

[0043] Matter is composed of atomic nuclei and electrons. To maintain neutrality, the number of electrons and nuclei must be the same. However, since electrons (especially those in the outermost orbits farthest from the nucleus) move relatively freely, when two substances come into contact, one substance accepts electrons and becomes negatively charged, while the other substance loses electrons and becomes positively charged. At this time, the greater the contact pressure and the higher the electron separation rate (contact speed), the greater the amount of charge generated.

[0044] Charging methods that utilize such phenomena to impart charges to the surface of a substance include contact electrification, triboelectrification, and peeling electrification. Among them, "contact electrification" occurs when two different objects come into contact and then separate. When two different objects come into contact, charge transfer occurs in each object, forming an electric double layer, and static electricity is generated by charge separation. Also, even if the objects are of the same type, contact electrification may occur depending on surface conditions such as corrosion and smoothness. One such charging method is "triboelectrification". "Triboelectrification" refers to the phenomenon in which static electricity is generated when an object undergoes friction or the contact point moves due to friction and the charges are separated.

[0045] The electrostatic induction unit 30 of the present invention can impart charges to the surface of the electrode current collector that moves using such contact electrification and triboelectrification.

[0046] As an example, as shown in FIG. 2, the electrostatic induction unit includes a roller 30 that abuts against the back surface of the electrode current collector F on which the electrode slurry S is applied to the surface by applying the method of contact electrification. The roller 30 can be coated with an electrostatic induction substance on its surface so that the electrostatic induction substance directly abuts against the back surface of the region where the electrode slurry S is applied on the back surface of the electrode current collector F, that is, the back surface of the coating portion Fc.

[0047] The above roller 30 includes a charged area 31 coated with an electrostatic induction material on the back surface of the coated portion Fc with the electrode slurry S, and can directly induce charges on the back surface during the running of the electrode current collector F. At this time, as the usable electrostatic induction material, ebonite, glass, nylon, wool, rayon, wool, silk, silk fabric, paper, iron, rubber, copper, silver, gold, platinum, polystyrene, acrylic, celluloid, polyvinyl chloride, polypropylene, polyethylene, silicone or Teflon (registered trademark), etc. can be used.

[0048] For example, the above electrostatic induction material may include Teflon (registered trademark), polyvinyl chloride, celluloid or rubber.

[0049] Also, since the above electrostatic induction material is coated on the back surface of the coated portion Fc with the electrode slurry, it may be coated on the entire surface of the roller 30 or only on the central portion of the roller. When the electrostatic induction material is coated on the central portion of the roller 30, the above roller 30 may include a non-charged area 32 where the electrostatic induction material is not coated at both ends. At this time, the total area of the non-charged area 32 where the electrostatic induction material is not coated may be 25% or less of the entire surface of the roller 30.

[0050] As another example, the electrostatic induction unit 30 may have a configuration including a friction member by applying a friction electrification method. Specifically, as shown in FIG. 3, the electrostatic induction unit 30 includes a motor unit 320 composed of a motor 322 and a power transmission shaft 321 axially coupled to the motor shaft of the motor and having a gear formed on its outer peripheral surface; a circular rotary friction member 331 having a gear formed on its outer peripheral surface so as to be gear-coupled to the power transmission shaft 321 and rotate by the rotation of the power transmission shaft; a fixed friction member 332 installed so as to contact one side of the outer peripheral surface of the rotary friction member; an arcuate electrostatic induction member 333 installed at a certain distance from the rotary friction member 331 and symmetric with the fixed friction member 332 about the rotary friction member 331; and an electrostatic generation unit 330 composed of an electrostatic induction line 334 installed on one side of the electrostatic induction member 333; and an electrostatic plate 340 connected to the electrostatic induction member 333 by the electrostatic induction line 334, having an electric charge on its surface, and provided so as to face the back surface of the electrode current collector.

[0051] Here, the motor unit 320 is composed of a motor 322 supplied with power 323 from the outside or driven by a battery or the like, and a power transmission shaft 321 axially coupled to the motor shaft of the motor 322 and having a gear formed on its outer peripheral surface. The gear formed on the outer peripheral surface of the power transmission shaft 321 meshes with a rotary friction member described later and is formed to rotate the rotary friction member.

[0052] Also, the gear formed on the outer peripheral surface of the power transmission shaft 321 meshes with a rotary friction member 331 described later and is formed to rotate the rotary friction member 331.

[0053] The above-described electrostatic generation unit 330 is installed so as to be gear-coupled with the power transmission shaft 321. When the motor 322 rotates, a circular rotating friction member 331 having a gear formed on its outer peripheral surface so as to rotate by the rotation of the power transmission shaft 321, a fixed friction member 332 installed so as to contact one side of the outer peripheral surface of the rotating friction member 331, and an arcuate electrostatic induction member 333 installed at a certain distance from the rotating friction member 331 and symmetric with the fixed friction member 332 about the rotating friction member 331, and an electrostatic induction wire 334 installed on one side of the electrostatic induction member 333.

[0054] At this time, in order to reduce the loss of the generated static electricity, it is preferable that the rotating friction member 331 has a gear formed on the upper or lower part of the outer peripheral surface, and the fixed friction member 332 is formed to be in surface contact with the outer peripheral surface where no gear is formed.

[0055] The materials forming the rotating friction member 331 and the fixed friction member 332 are not particularly limited. However, in order to increase the amount of generated static electricity, it is preferable to use materials with a high charging rank, and materials that can be processed into respective shapes may also be used.

[0056] Also, the power transmission shaft 321 and the rotating friction member 331 are installed so as to mesh with each other in a worm gear manner. When the power transmission shaft 321 rotates, the rotating friction member 331 meshed with the gear of the power transmission shaft 321 rotates, and thereby, the rotating friction member 331 and the fixed friction member 332 rub against each other to generate static electricity.

[0057] The static electricity generated as described above has the strongest force to cancel the static electricity at the electrostatic generation site, that is, in the vicinity of the fixed friction member 332. Therefore, in order to transmit the static electricity generated on the electrostatic plate 340 without canceling it as much as possible, the electrostatic induction member 333 is installed adjacent to the rotating friction member 331 and at the farthest distance from the fixed friction member 332.

[0058] In addition, the fixed friction member 332 may be formed and used in various forms. Although not shown in the drawings, an integral pad may be fixed to the main body case 310 and used. For example, the fixed friction member may have a brush form.

[0059] When the static electricity generated in the rotating friction member 331 and the fixed friction member 332 is induced to the static electricity plate 340, it is preferable to use an electric wire coated with an insulating material so that no loss occurs.

[0060] In addition, the static electricity plate 340 is connected to the static electricity induction member 333 and is formed to discharge the induced static electricity over a wide area. Its shape is formed in a plate shape as shown in the drawings, having a wide area, and may be arranged to be separated from the back surface of the electrode current collector by a predetermined distance. At this time, the separation distance may be 1 to 30 cm, specifically, 1 to 20 cm, 1 to 10 cm, 1 to 5 cm, 5 to 10 cm, 10 to 20 cm, or 15 to 30 cm.

[0061] The static electricity plate 340 can indirectly induce charging on the back surface of the electrode current collector by being arranged at a predetermined distance from the back surface of the electrode current collector coated with the electrode slurry on the surface.

[0062] Moreover, the static electricity induction unit 30 can control the rotation speed of the rotating friction member 331 and the like in order to sufficiently induce static electricity on the back surface of the electrode current collector. For this purpose, a control unit 350 may be further included inside the case.

[0063] The electrode coating apparatus according to the present invention has the above-described configuration, and thus has the advantage of preventing the ionic binder of the electrode slurry applied to the surface of the electrode current collector from moving to the surface and increasing in concentration due to the influence of the solvent volatilized during the drying process of the electrode.

[0064] <Method for manufacturing an electrode> Moreover, in one embodiment of the present invention, Provided is a method for manufacturing an electrode using the above electrode coating device.

[0065] Specifically, the method for manufacturing the electrode includes a step of applying an electrode slurry on the surface of an electrode current collector, and a step of inducing static electricity on the back surface of the electrode current collector on which the electrode slurry has been applied.

[0066] In the method for manufacturing an electrode according to the present invention, an electrode slurry containing an ionic binder having a charge is applied on the surface of an electrode current collector, and the back surface of the electrode current collector on which the electrode slurry has been applied is charged with the opposite charge of the charge of the ionic binder to induce static electricity, so that when the electrode slurry dries, the solvent in the electrode slurry volatilizes, and it is possible to prevent the binder from concentrating on the surface of the electrode slurry.

[0067] Specifically, the above electrode slurry can contain an ionic binder showing a (+) charge. In this case, a (-) charge can be induced on the back surface of the electrode current collector on which the electrode slurry has been applied. Alternatively, the above electrode slurry can contain an electrode slurry containing an ionic binder showing a (-) charge. In this case, a (+) charge can be induced on the back surface of the electrode current collector on which the electrode slurry has been applied.

[0068] The above ionic binder is not particularly limited in terms of its type as long as it has a charge. However, considering the bonding force with the electrode active material and the electrical properties inside the composite layer, it may contain one or more polymers selected from the group consisting of hydroxypropyl cellulose, regenerated cellulose, polyacrylic acid (PAA), polyacrylonitrile (PAN: polyacrylonitrile), polyacrylamide (PAM: polyacryl amide), styrene butadiene rubber (SBR: styrene butadiene rubber), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluoro rubber, polyvinyl alcohol (PVA: polyvinyl alcohol), polyethylene glycol (PEG: polyethylene glycol), and alginate. The above polymers contain carboxyl groups (-COOH), sulfonic groups (-SOOOH), etc., and some are in the form of salts with alkali metal ions such as Na + or Li + and may have a (-) charge by having such forms of salts with alkali metal ions.

[0069] As an example, the ionic binder contained in the electrode slurry contains carboxymethyl cellulose (Na-CMC) partially substituted with Na + and the above electrostatic induction device can induce a (+) charge on the back surface of the electrode current collector coated with the above electrode slurry on its surface.

[0070] Also, the ionic binder may be contained in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the entire electrode slurry. Specifically, it may be contained in an amount of 0.5 to 5 parts by weight, or 1 to 4 parts by weight based on 100 parts by weight of the whole.

[0071] Also, the step of inducing static electricity on the back surface of the electrode current collector can be performed by contact electrification between the back surface of the electrode current collector and the electrostatic induction material; or can be performed by frictional electrification of the friction member.

[0072] Specifically, the above-mentioned electrostatic induction can be achieved by bringing an electrostatic induction material such as ebonite, glass, nylon, wool, rayon, wool, silk, silk fabric, paper, iron, rubber, copper, silver, gold, platinum, polystyrene, acrylic, celluloid, polyvinyl chloride, polypropylene, polyethylene, silicone, or Teflon (registered trademark) into contact with the back surface of the electrode current collector; or by preparing a separate friction member and bringing the charges generated by the friction of the prepared friction member close to the back surface of the electrode current collector.

[0073] On the other hand, the method for manufacturing an electrode according to the present invention may further include a step of drying the electrode slurry applied to one surface of the electrode current collector after the step of inducing static electricity on the back surface of the electrode current collector.

[0074] The above drying step is performed under high-temperature conditions. Even when the solvent of the electrode slurry volatilizes, the ionic binder uniformly dispersed in the electrode slurry is fixed to the lower part of the electrode slurry close to the electrode current collector by the static electricity induced on the back surface of the electrode current collector. Therefore, it is possible to prevent the ionic binder from moving to and concentrating on the surface of the electrode slurry.

[0075] At this time, the step of drying the electrode slurry can be performed at a temperature required to remove the solvent contained in the electrode slurry. Specifically, it may be 50°C to 200°C, and more specifically, it may also be 50°C to 200°C, 80°C to 200°C, 100°C to 200°C, 80°C to 150°C, or 110°C to 180°C.

[0076] The method for manufacturing an electrode according to the present invention can be performed using the above-described electrode coating device. Thereby, an electrode slurry containing an ionic binder having a charge is applied to the surface of the electrode current collector, and the back surface of the electrode current collector coated with the electrode slurry is charged with the opposite charge of the charge of the ionic binder to induce static electricity, so that when the electrode slurry dries, the solvent in the electrode slurry volatilizes, and it is possible to prevent the binder from concentrating on the surface of the electrode slurry.

[0077] Hereinafter, the present invention will be described in more detail based on examples and experimental examples. However, the following examples and experimental examples are illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0078] <Manufacture of negative electrodes for lithium secondary batteries in Examples 1 to 3 and Comparative Examples 1 to 3.> A copper thin plate was prepared to manufacture a negative electrode for a lithium secondary battery. Separately, water was poured into a homomixer, and natural graphite and silicon (Si)-containing particles as negative electrode active materials and styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) substituted with Na as binders were weighed at a weight ratio of 80:10:1:2, and were separately charged. After that, they were mixed at 3,000 rpm for 60 minutes to produce a negative electrode slurry.

[0079] The prepared copper thin plate was fixed to the transfer part 11 of the electrode coating apparatus having the structure as shown in FIG. 1, and the produced negative electrode slurry was charged into the coater 20. Next, the electrode coating apparatus was operated to apply the negative electrode slurry onto the surface of the copper thin plate as an electrode current collector.

[0080] The electrode current collector coated with the negative electrode slurry was transferred to the drying part to form a negative electrode composite layer in which the negative electrode slurry was dried, and this was rolled to manufacture a negative electrode for a lithium secondary battery. At this time, the total thickness of the negative electrode composite layer was 150 μm, and the total thickness of the manufactured negative electrode was about 200 μm. Also, as shown in FIG. 3, the electrostatic induction part induced static electricity on the back surface of the copper thin plate on which the negative electrode slurry was applied to the surface by the triboelectric charging method, and the traveling speed of the transfer part, the presence or absence of the operation of the electrostatic induction part before drying (that is, the presence or absence of + charge charging), and the drying temperature of the drying part were as shown in Table 1 below.

[0081]

Table 1

[0082] <Experimental Example> To evaluate the performance of the electrodes manufactured according to the present invention, the following experiments were conducted.

[0083] (A) Evaluation of the adhesion of the negative electrode composite layer The positive electrodes manufactured in the examples and comparative examples were cut so that the horizontal and vertical lengths were 25 mm and 70 mm, respectively, and a test piece was produced by pressing under the conditions of 70 °C and 4 MPa using a press. The prepared test piece was attached and fixed to a glass plate using double-sided tape, and at this time, the current collector was arranged so as to face the glass plate. Using a tensile tester, the second composite layer portion of the test piece was peeled at an angle of 90° at a speed of 100 mm / min at 25 °C, and the peeling force at this time was measured in real time, and the average value was defined as the adhesion of the negative electrode composite layer. The results are shown in Table 2 below.

[0084] (B) Evaluation of the electrode resistance The surface resistance of the negative electrodes manufactured in the examples and comparative examples was measured by a 4-point probe method, and the results are shown in Table 2 below.

[0085] (C) Evaluation of the electrode life N-methylpyrrolidone was injected into a homo mixer, and 96 parts by weight of LiNi0.6Co0.2Mn0.2O2 as a positive electrode active material, 2 parts by weight of carbon black as a conductive material, and 2 parts by weight of PVDF as a binder were weighed and added to 100 parts by weight of the positive electrode slurry solid content, and then mixed at 2,000 rpm for 30 minutes to produce a positive electrode slurry.

[0086] The produced positive electrode slurry was applied to one side of an aluminum current collector, dried at 100 °C, and rolled to produce a positive electrode. At this time, the total thickness of the positive electrode composite layer was 160 μm, and the total thickness of the produced positive electrode was about 200 μm.

[0087] A separator made of a porous polyethylene (PE) film (thickness: about 16 μm) was interposed between the produced positive electrode and the negative electrodes of the examples and comparative examples, and E2DVC was injected as an electrolytic solution to produce a full cell form cell. Here, "E2DVC" is a type of carbonate-based electrolyte solution, which means a solution obtained by mixing ethylene carbonate (EC): dimethyl carbonate (DMC): diethyl carbonate (DEC) = 1:1:1 (volume ratio) with lithium hexafluorophosphate (LiPF6, 1.0 M) and vinyl carbonate (VC, 2 wt%).

[0088] For each manufactured lithium secondary battery, while performing 200 charge-discharge cycles (n = 200) under the conditions of a charge cut-off voltage of 4.25 V, a discharge cut-off voltage of 2.5 V, and 0.33C / 0.33C at 25°C, the capacity retention rate (Capacity Retention [%]) was measured. The results are shown in Table 2 below.

[0089]

Table 2

[0090] It can be seen that the electrode manufactured according to the present invention has excellent adhesion between the electrode composite layer and the electrode current collector and excellent electrical performance.

[0091] Specifically, for the negative electrode for a lithium secondary battery of the example in which an electrode slurry was applied to the surface of the electrode current collector and static electricity was induced on the back surface of the electrode current collector to which the electrode slurry was applied, the adhesion between the negative electrode composite layer and the current collector showed a high adhesion exceeding 35 N / m, the electrode resistance was 2.2 Ω / sq. or less, and the capacity retention rate after 200 charge-discharge cycles was shown to exceed 95%.

[0092] On the other hand, for the negative electrode for a lithium secondary battery of the comparative example in which static electricity was not induced on the back surface of the electrode current collector to which the electrode slurry was applied, it was confirmed that not only was the adhesion between the negative electrode composite layer and the current collector weak, but also the electrical performance was low.

[0093] From such results, the electrode coating apparatus according to the present invention and the method for manufacturing an electrode using the same can prevent the binder from moving to the surface of the electrode slurry by inducing static electricity so that the back surface of the electrode current collector coated with the electrode slurry has a charge opposite to the charge of the ionic binder contained as a binder in the electrode slurry. Therefore, even when the solvent volatilizes during the drying process of the electrode slurry, there is an advantage that the adhesive force between the electrode composite layer formed by drying the electrode slurry and the electrode current collector is excellently improved.

[0094] As described above, the preferred embodiments of the present invention have been described. However, it can be understood that those skilled in the art or those having ordinary knowledge in the technical field can make various modifications and changes to the present invention without departing from the spirit and technical scope of the present invention described in the claims.

[0095] Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

Explanation of Reference Numerals

[0096] 1 Electrode coating apparatus 11 and 12 Transfer unit 20 Coater 30 Static electricity induction unit 31 Charged region 32 Non-charged region 40 Drying unit 50 Rolling unit 310 Main body case 320 Motor unit 321 Power transmission shaft 322 Motor 323 External power source 330 Static electricity generation unit 331 Rotating friction member 332 Fixed friction member 333 Static electricity induction member 334 Static electricity induction wire 340 Electrostatic plate 350 Control unit F Electrode current collector S Electrode slurry Fc Electrode slurry coating part of the electrode current collector Fn Plain part where the electrode slurry of the electrode current collector is not coated

Claims

1. A transfer unit that moves an electrode current collector in a roll-to-roll manner, A coater that discharges an electrode slurry onto the surface of the electrode current collector moved by the transfer unit, An electrostatic induction unit that induces static electricity on the back surface of the electrode current collector coated with the electrode slurry on the surface, and includes, The induction of the static electricity is performed by frictional electrification of a friction member, The electrostatic induction unit, A motor unit composed of a motor and a power transmission shaft axially coupled to the motor shaft of the motor and having a gear formed on the outer peripheral surface, A circular rotating friction member that is gear-coupled to the power transmission shaft and has a gear formed on the outer peripheral surface so as to rotate by the rotation of the power transmission shaft, a fixed friction member installed so as to contact one side of the outer peripheral surface of the rotating friction member, and a fixed friction member installed at a certain distance from the rotating friction member and symmetric with the fixed friction member about the rotating friction member. An electrostatic generation unit composed of an arcuate electrostatic induction member and an electrostatic induction wire installed on one side of the electrostatic induction member, An electrostatic plate that is connected to the electrostatic induction member by the electrostatic induction wire, is charged on the surface, and is provided so as to face the back surface of the electrode current collector, and includes, The electrode slurry contains an ionic binder, The electrostatic induction unit induces an opposite charge to the ionic binder of the electrode slurry coated on the surface of the electrode current collector on the back surface of the electrode current collector, An electrode coating device.

2. The rotating friction member has a gear formed on the upper or lower part of the outer peripheral surface, The electrode coating device according to claim 1, wherein the fixed friction member is in surface contact with the outer peripheral surface where no gear is formed.

3. The ionic binder includes one or more polymers selected from the group consisting of carboxymethyl cellulose (CMC), hydroxypropyl cellulose, regenerated cellulose, polyacrylic acid (PAA), polyacrylonitrile, polyacrylamide, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluororubber, polyvinyl alcohol, polyethylene glycol, and alginate. The electrode coating device according to claim 1.

4. The transfer unit operates at a speed of 20 to 100 m / min. The electrode coating device according to claim 1.

5. Applying an electrode slurry to one surface of the electrode current collector; Inducing static electricity on the back surface of the electrode current collector coated with the electrode slurry, and includes. The step of inducing static electricity on the back surface of the electrode current collector is performed using an electrostatic induction unit that induces static electricity on the back surface of the electrode current collector coated with the electrode slurry on its surface. The step of inducing static electricity on the back surface of the electrode current collector is performed by triboelectrification of a friction member. The electrostatic induction unit comprises a motor, and a motor unit composed of a power transmission shaft that is axially coupled to the motor shaft of the motor and has a gear formed on its outer peripheral surface. a circular rotating friction member that is gear-coupled to the power transmission shaft and has a gear formed on its outer peripheral surface so as to rotate by the rotation of the power transmission shaft, a fixed friction member installed so as to contact one side of the outer peripheral surface of the rotating friction member, an arcuate electrostatic induction member installed at a certain distance from the rotating friction member and symmetric with the fixed friction member about the rotating friction member, and an electrostatic generation unit composed of an electrostatic induction wire installed on one side of the electrostatic induction member. including an electrostatic plate that is connected to the electrostatic induction member by the electrostatic induction wire, has an electric charge on its surface, and is provided so as to face the back surface of the electrode current collector. The electrode slurry contains an ionic binder. The static electricity induced on the back surface of the electrode current collector coated with the electrode slurry has an opposite charge to the ionic binder. Method for manufacturing an electrode.

6. The method for manufacturing an electrode according to claim 5, wherein the ionic binder includes one or more polymers selected from the group consisting of carboxymethyl cellulose (CMC), hydroxypropyl cellulose, regenerated cellulose, polyacrylic acid (PAA), polyacrylonitrile, polyacrylamide, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluororubber, polyvinyl alcohol, polyethylene glycol, and alginate.

7. After the step of inducing the static electricity, The method for manufacturing an electrode according to claim 5, further comprising a step of drying the electrode slurry coated on one surface of the electrode current collector.

8. The method for manufacturing an electrode according to claim 7, wherein the step of drying the electrode slurry is performed at a temperature of 50°C to 200°C.

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