Patent Description:
The electrode assembly is classified into a jelly-roll type in which a positive electrode and a negative electrode which are long sheet-shaped and are coated with active materials are wound with a separator interposed therebetween, and a stack type in which a plurality of positive electrodes and negative electrodes of a predetermined size are sequentially stacked while a separator is interposed therebetween.

Further, the electrode included in the secondary battery may be manufactured by coating an electrode slurry including an electrode active material on a current collector, and a metal foil made of aluminum or copper may be used as the current collector.

Such a metal foil may go through the rolling process in order to planarize the surface. In this process, rolling oil is used for lubrication. As such, rolling oil elements remain on the metal foil after the rolling process. Likewise, when there is remaining oil on the metal foil, a collapsed or disconnected phenomenon of the electrode slurry may occur during the coating of the electrode slurry.

Conventionally, a dyne test was performed to measure the remaining oil level on the metal foil used as the current collector. This is a scheme of a broken degree of a liquid film by coating a reagent like <NUM>-ethoxyethanol on a metal foil. However, in a conventional dyne test scheme, there may be an error in the measured remaining oil level due to the difference in the reagent or contamination of the reagent.

Therefore, there is a need for a technology for accurately recognizing the remaining oil level.

<CIT> discloses coating of an aluminum foil current collector using a roll coater.

The present invention is believed to solve at least some of the above problems. For example, an aspect of the present invention provides an electrode slurry coating apparatus and method for accurately recognizing the remaining oil level on the surface of a metal foil used as a current collector.

An apparatus for coating an electrode slurry according to the present invention includes: a coater which coats an electrode slurry on a metal foil; a remaining oil level measuring unit which measures a remaining oil level on a surface of the metal foil before coating the electrode slurry; and a controller which determines whether the remaining oil level is excessive from a measurement value of the remaining oil level, and determines whether to coat the electrode slurry therefrom.

The remaining oil level measuring unit measures at least one of a spread degree and a contact angle of the electrode slurry dropped on the metal foil.

More specifically, the remaining oil level measuring unit may include: a syringe which drops an electrode slurry on a metal foil; and a vision camera which photographs shapes of the electrode slurry dropped by the syringe, collects images obtained by photographing the shapes of the electrode slurry, and measures a spread degree or a contact angle of the dropped electrode slurry from the photographed images.

At this time, the vision camera senses the metal foil shown on an image and at least one of color, brightness, and chroma of the dropped electrode slurry, and measures a diameter or a contact angle of the electrode slurry dropped by the syringe.

In a specific example, the syringe and the vision camera are positioned on the upper side of the coater on the basis of the coating direction, and the syringe is positioned on the upper side of the vision camera on the basis of the coating direction.

In a specific example, the controller compares the measured spread degree or contact angle of the electrode slurry with a reference value, and when the spread degree is less than the reference value or the contact angle exceeds the reference value, it may be determined that the remaining oil level is excessive.

At this time, when the remaining oil level on the surface of the metal foil is within a predetermined range, the controller may control the coater to discharge the electrode slurry.

Further, the electrode slurry coating apparatus according to the present invention may further include a cleaning unit which cleans the metal foil.

The controller may transfer the metal foil, which has been determined to have an excessive remaining oil level on the surface, to the cleaning unit to allow the metal foil to be cleaned.

As such, the remaining oil level measuring unit may remeasure the remaining oil level for the cleaned metal foil, and the controller may redetermine whether to coat an electrode slurry on the cleaned metal foil.

Further, the present invention provides a method of coating an electrode slurry.

The method of coating an electrode slurry according to the present invention includes: preparing a metal foil for an electrode current collector; measuring a remaining oil level on the metal foil; and determining whether the remaining oil level is excessive from a measurement value of the remaining oil level, and determining whether to coat the electrode slurry therefrom.

During the measuring of remaining oil level on the metal foil, the measuring unit measures at least one of a spread degree and a contact angle of the electrode slurry dropped on the metal foil.

At this time, the measuring of the remaining oil level on the metal foil may be performed right before coating the electrode slurry.

In a specific example, the measuring of the remaining oil level on the metal foil may be performed by dropping an electrode slurry on the metal foil by a syringe, photographing shapes of the electrode slurry dropped by the syringe using a vision camera, collecting images obtained by photographing the shapes of the electrode slurry, and then measuring at least one of a spread degree and a contact angle of the electrode slurry from the images.

The vision camera may sense the metal foil and at least one of color, brightness, and chroma of the dropped electrode slurry, and measure a diameter or a contact angle of the electrode slurry dropped by the syringe.

Further, when the spread degree is less than the reference value or the contact angle exceeds the reference value, it may be determined that the remaining oil level is excessive.

When it is determined that the remaining oil level on the surface of the metal foil is excessive, the method may further include cleaning the metal foil.

Further, the electrode slurry coating method according to the present invention may further include remeasuring the remaining oil level for the cleaned metal foil, and redetermining whether to coat an electrode slurry on the cleaned metal foil.

According to the present invention, it is possible to more accurately recognize the remaining oil level on the metal foil by dropping an electrode slurry on a metal foil before coating the electrode slurry and measuring the spread degree and a contact angle of the dropped electrode slurry.

<FIG> is a block diagram showing a configuration of an electrode slurry coating apparatus according to the present invention.

Referring to <FIG>, an electrode slurry coating apparatus <NUM> according to the present invention includes: a coater <NUM> which coats an electrode slurry on a metal foil; a remaining oil level measuring unit <NUM> which measures a remaining oil level on a surface of the metal foil before coating the electrode slurry; and a controller <NUM> which determines whether the remaining oil level is excessive from a measurement value of the remaining oil level, and determines whether to coat the electrode slurry therefrom.

<FIG> is a schematic diagram showing an electrode slurry coating apparatus according to an embodiment of the present invention.

Referring to <FIG> together with <FIG>, the electrode slurry coating apparatus <NUM> according to the present invention includes a coater <NUM> which coats an electrode slurry <NUM> on a metal foil <NUM>. The coater <NUM> may be positioned to be spaced apart from the metal foil <NUM> by a predetermined distance. Various types of coater <NUM> may be used. Specifically, a slot die type, in which a discharge port, through which an electrode slurry is discharged, is formed in a slit shape along the coating width, may be used. In this case, the coater may include a main body and a tip formed on the lower surface of the main body. A discharge path, on which the supplied electrode slurry may be moved, is formed at the main body, and a discharge port, through which the electrode slurry is discharged, may be formed at the end of the tip. The discharge port may have a slit shape extended in the width direction along the end of the tip, and the thickness may be adjusted according to the thickness of the electrode slurry coated on the metal foil. Further, the electrode slurry <NUM> is stored in a separate slurry supply tank (not shown), and the electrode slurry <NUM> may be supplied to the coater <NUM> through a supply pipe connected to the coater <NUM>. Other details about the coater <NUM> are known to those of ordinary skill in the art, and thus detailed description thereof will be omitted.

Further, the metal foil <NUM> may be in a state that has been wound on a separate roll or has gone through a rolling process, and when the coating is started, the metal foil <NUM> is unwound and is supplied to the coater.

The metal foil <NUM> may be what is used as a positive electrode current collector or a negative electrode current collector.

In the present invention, the positive electrode collector generally has a thickness of <NUM> to <NUM> micrometers. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel of which the surface has been treated with carbon, nickel, titanium, silver, or the like. The current collector may have fine irregularities on the surface thereof to increase the adhesion of the positive electrode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The negative electrode collector generally has a thickness of <NUM> to <NUM> micrometers. The negative electrode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel of which the surface has been treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like. In addition, like the positive electrode current collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

Further, the electrode slurry <NUM> includes an electrode active material and a solvent and may further include a conductive material and a binder in addition to an electrode active material.

In the present invention, the positive electrode active material is a material capable of causing an electrochemical reaction and a lithium transition metal oxide, and contains two or more transition metals. Examples thereof include: layered compounds such as lithium cobalt oxide (LiCoO<NUM>) and lithium nickel oxide (LiNiO<NUM>) substituted with one or more transition metals; lithium manganese oxide substituted with one or more transition metals; lithium nickel oxide represented by the formula LiNi<NUM>-yMyO<NUM> (wherein M = Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn or Ga and contains at least one of the above elements, <NUM> ≦ y ≦ <NUM>); lithium nickel cobalt manganese composite oxide represented by the formula Li<NUM>+zNibMncCo<NUM>-(b+c+d)MdO(<NUM>-e)Ae such as Li<NUM>+zNi<NUM>/<NUM>Co<NUM>/<NUM>Mn<NUM>/<NUM>O<NUM>, Li<NUM>+zNi<NUM>Mn<NUM>Co<NUM>O<NUM> etc. (wherein - <NUM>≤z≤<NUM>, <NUM>≤b≤<NUM>, <NUM>≤c≤<NUM>, <NUM>≤d≤<NUM>, <NUM>≤e≤<NUM>, b+c+d<<NUM>, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl); olivine-based lithium metal phosphate represented by the formula Li<NUM>+xM<NUM>-yM'yPO<NUM>-zXz (wherein M = transition metal, preferably Fe, Mn, Co or Ni, M'= Al, Mg or Ti, X = F, S or N, and -<NUM>≤x≤<NUM>, <NUM>≤y≤<NUM>, <NUM>≤z≤<NUM>).

Examples of the negative electrode active material include carbon such as non-graphitized carbon and graphite carbon; metal complex oxide such as LixFe<NUM>O<NUM>(<NUM>≤x≤<NUM>), LixWO<NUM>(<NUM>≤x≤<NUM>), SnxMe<NUM>-xMe'yOz (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, groups <NUM>, <NUM>, and <NUM> of the periodic table, halogen; <NUM><x≤<NUM>; <NUM>≤y≤<NUM>; <NUM>≤z≤<NUM>); lithium alloy; silicon alloy; tin alloy; metal oxides such as SnO, SnO<NUM>, PbO, PbO<NUM>, Pb<NUM>O<NUM>, Pb<NUM>O<NUM>, Sb<NUM>O<NUM>, Sb<NUM>O<NUM>, Sb<NUM>O<NUM>, GeO, GeO<NUM>, Bi<NUM>O<NUM>, Bi<NUM>O<NUM>, and Bi<NUM>O<NUM>; conductive polymers such as polyacetylene; and Li-Co-Ni-based materials.

The conductive material is usually added in an amount of <NUM> to <NUM>% by weight based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum and nickel powder; conductive whiskey such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives and the like.

The binder is added in an amount of <NUM> to <NUM>% by weight, on the basis of the total weight of the mixture containing the positive electrode active material, as a component that assists in bonding between the active material and the conductive material and bonding to the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylenepropylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers and the like.

The type of the solvent is not particularly limited as long as it is capable of dispersing an electrode active material, and either an aqueous solvent or a non-aqueous solvent may be used. For example, the solvent may be a solvent generally used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP ), acetone, or water, and one of them alone or a mixture of two or more may be used. The amount of the solvent used may be such that the slurry can be adjusted to have an appropriate viscosity in consideration of the coating thickness, production yield, and workability of the slurry, and is not particularly limited.

Further, in the present invention, the metal foil <NUM> may be made of aluminum as what is used as a positive electrode current collector. Likewise, the electrode slurry <NUM> is obtained as a positive electrode active material, a conductive material and a binder are dispersed in a solvent. Herein, for example, NMP may be used as the solvent.

Further, referring to <FIG> and <FIG> together with <FIG>, the remaining oil level measuring unit <NUM> measures a remaining oil level on a surface of the metal foil <NUM> before coating the electrode slurry <NUM>.

In one example, the remaining oil level measuring unit <NUM> measures the spread degree of the electrode slurry <NUM> dropped on the metal foil <NUM>. The spread degree means a degree to which a liquid phase material is spread on a solid phase material when the liquid phase material contacts the solid phase material. The spread degree is related with the affinity between the liquid phase material and the solid phase material. For example, when the affinity between a liquid phase material and a solid phase material is high, the liquid phase material is widely spread on the solid phase material, which means that the surface free energy level of the solid phase material is high. On the other hand, when the affinity between the liquid phase material and the solid phase material is low, the contact area between the liquid phase material and the solid phase material is small, which means that the surface free energy level of the solid phase material is low.

In the present invention, a non-aqueous solvent having a little polarity like NMP is used as a solvent in the electrode slurry <NUM>. Further, oil remaining on the metal foil <NUM> is generally non-polar. As such, when the remaining oil level on the surface of the metal foil <NUM> is large, the affinity between the electrode slurry <NUM> and the metal foil <NUM> is low, and accordingly, the spread degree becomes relatively small. On the contrary, when the remaining oil level on the surface of the metal foil <NUM> is large, the affinity between the electrode slurry <NUM> and the metal foil <NUM> becomes large and accordingly, the spread degree also increases. Likewise, according to the present invention, it is possible to recognize and control the remaining oil level on the surface of the metal foil <NUM> from the affinity between the electrode slurry <NUM> and the metal foil <NUM>.

Referring to <FIG>, in the electrode slurry coating apparatus <NUM> according to the present invention, the remaining oil level measuring unit <NUM> includes a syringe <NUM> and a vision camera <NUM>.

The syringe <NUM> drops an electrode slurry <NUM> on a metal foil <NUM>. There is no limitation to the shape and the size of the syringe <NUM> as long as it can drop the electrode slurry <NUM>. Herein, when the size of the syringe is too large, control is difficult, and when the diameter of the tip portion, at which an electrode slurry is discharged at the end portion of the syringe, becomes large, the size of the electrode slurry becomes large, which may form a step at the dropped portion at the time of coating an electrode slurry by a coater. Hence, a size, at which the spread degree can be observed, is sufficient. For example, the volume of the syringe may be in the range of <NUM> to <NUM> and specifically <NUM> to <NUM>.

Likewise, the distance between the syringe <NUM> and the metal foil <NUM> may be appropriately designed by one of ordinary skill in the art. If the distance between the syringe and the metal foil is too large, the electrode slurry is dropped in a contorted form due to the impact generated as the electrode slurry falls on the metal foil. On the other hand, if the distance between the syringe and the metal foil is too small, there may be an error in measurement as the electrode slurry is pressed down by the syringe. For example, the distance between the syringe and the metal foil may correspond to <NUM> to <NUM> times and specifically <NUM> to <NUM> times of the thickness of the electrode slurry, but the present invention is not limited to these examples.

The vision camera <NUM> photographs shapes of the electrode slurry <NUM> dropped by the syringe <NUM>, collects images obtained by photographing the shapes of the electrode slurry <NUM>, and measures a spread degree of the dropped electrode slurry <NUM> from the photographed images. There is no limitation to the vision camera <NUM> as long as it can visually sense the shape of the electrode slurry <NUM> dropped on the metal foil <NUM> like a CCD camera. The vision camera <NUM> senses the metal foil shown on an image and at least one of color, brightness, and chroma of the dropped electrode slurry, and measures spread degree of the electrode slurry dropped by the syringe.

Specifically, referring to <FIG>, the electrode slurry <NUM> dropped on the metal foil <NUM> has a circular shape when looked down at the metal foil <NUM>. When the vision camera <NUM> measures the spread degree of the electrode slurry <NUM>, the vision camera <NUM> is positioned on the upper surface of the metal foil <NUM>, specifically the upper surface of the portion where the electrode slurry <NUM> has been dropped on the metal foil <NUM>, to thereby measure the diameter (d) of the dropped electrode slurry. At this time, the angle between the vision camera <NUM> and the metal foil may be <NUM>°.

As shown in <FIG>, the vision camera <NUM> converts the photographed image into visual data. To this end, the vision camera <NUM> may include a predetermined program storage unit for data conversion and calculation, a calculation unit which converts an actual photographing screen into visual data based on the program and calculates the spread degree (diameter) of the electrode slurry from the visual data as a numerical value, and a display unit which displays the visual data and the spread degree on a screen. The vision camera may transmit such visual data and spread degree measurement values to a controller to be described later. The program storage unit, the calculation unit and the display unit may be installed in the controller.

<FIG> and <FIG> each are a schematic diagram showing an electrode slurry coating apparatus <NUM> according to another embodiment of the present invention.

Referring to <FIG> and <FIG> together with <FIG> and <FIG>, the remaining oil level measuring unit <NUM> measures the contact angle of the electrode slurry <NUM> dropped on the metal foil <NUM>. The contact angle is an angle at which a liquid is thermodynamically in equilibrium on the surface of a solid, and means an angle (θ) at a side including liquid among angles between a solid surface and a tangent line at a contact point of three phases of air, a metal foil and an electrode slurry when an electrode slurry is dropped on a metal foil in the air as shown in <FIG>.

As in the above-described spread degree, the contact angle also becomes the criterion for evaluating affinity or wettability of a solid phase material (metal foil) and a liquid phase material (electrode slurry). As described above, when the affinity between the solid phase material and the liquid phase material is high, the liquid phase material is widely spread on the solid phase material. In this case, the contact angle becomes small. On the other hand, when the affinity between the solid phase material and the liquid phase material is low, the liquid phase material is aggregated on a small region, and the contact angle becomes large.

Namely, when the remaining oil level on the surface of the metal foil <NUM> is large, the affinity between the electrode slurry <NUM> and the metal foil <NUM> is low, and accordingly, the contact angle becomes relatively large. On the contrary, when the remaining oil level on the surface of the metal foil <NUM> is low, the affinity between the electrode slurry <NUM> and the metal foil <NUM> becomes large and accordingly, the contact angle decreases. Likewise, according to the present invention, it is possible to recognize and control the remaining oil level on the surface of the metal foil from the affinity between the electrode slurry and the metal foil.

Referring to <FIG> and <FIG>, in the electrode slurry coating apparatus <NUM> according to the present invention, the remaining oil level measuring unit <NUM> includes a syringe <NUM> and a vision camera <NUM>. The syringe <NUM> drops an electrode slurry <NUM> on a metal foil <NUM> as described above.

The vision camera <NUM> photographs shapes of the electrode slurry <NUM> dropped by the syringe, collects images obtained by photographing the shapes of the electrode slurry <NUM>, and measures a contact angle of the dropped electrode slurry <NUM> from the photographed images. The vision camera <NUM> senses at least one of color, brightness, and chroma of the dropped electrode slurry <NUM> and the metal foil <NUM> shown on an image, and measures spread degree of the electrode slurry dropped by the syringe.

Specifically, referring to <FIG>, the electrode slurry <NUM> dropped on the metal foil <NUM> has an arc or chord shape when observed in the side surface direction of the metal foil <NUM>. When the vision camera <NUM> measures the contact angle of the electrode slurry <NUM>, the vision camera <NUM> is positioned on the side surface of the metal foil <NUM> and measures the contact angle of the dropped electrode slurry. At this time, the vision camera <NUM> may be parallel to the surface formed by the metal foil <NUM>.

As shown in <FIG>, the vision camera <NUM> converts the photographed image into visual data. To this end, the vision camera <NUM> may include a predetermined program storage unit for data conversion and calculation, a calculation unit which converts an actual photographing screen into visual data based on the program and calculates the contact angle of the electrode slurry from the visual data as a numerical value, and a display unit which displays the visual data and the spread degree on a screen. The vision camera <NUM> may transmit such visual data and contact angle measurement values to a controller to be described later.

Further, in the present invention, the remaining oil level measuring unit <NUM> measures at least one of the spread degree and the contact angle of the electrode slurry <NUM> dropped on the metal foil <NUM>. At this time, the remaining oil level measuring unit <NUM> may measure one or both of the spread degree and the contact angle of the electrode slurry <NUM>. In this case, the vision camera <NUM>, which photographs the shape of the electrode slurry, is positioned on the upper surface and the side surface of the metal foil <NUM>, respectively, to thereby measure the spread degree and contact angle of the electrode slurry <NUM>.

Further, in the present invention, the measuring of the remaining oil level of the metal foil may be performed right before coating the electrode slurry. This is because the remaining oil level on the surface may change during the process of storing, transferring and processing the metal foil before coating the electrode slurry. Namely, in the present invention, the measurement of the remaining oil level and the coating of the electrode slurry may be performed as consecutive processes in one device. For example, in a state that the metal foil <NUM> is fixed, as the syringe <NUM>, the vision camera <NUM>, and the coater <NUM> are moved in a coating direction, the remaining oil level is measured by the syringe <NUM> and the vision camera <NUM>, and the electrode slurry may then be coated by the coater <NUM>. Alternatively, in a state that the syringe <NUM>, the vision camera <NUM> and the coater <NUM> are fixed, as the metal foil <NUM> is transferred in the coating direction, the measurement of the remaining oil level and the coating of the electrode slurry may be sequentially performed. To this end, the syringe <NUM> and the vision camera <NUM> are positioned on the upper side of the coater <NUM> on the basis of the coating direction, and the syringe <NUM> is positioned on the upper side of the vision camera <NUM> on the basis of the coating direction. Herein, being positioned on the upper side on the basis of the coating direction means being positioned close to the side where the coating of the electrode slurry has not been relatively formed, based on the transfer direction of the metal foil or the moving direction of the coater, etc..

Likewise, if the remaining oil level on the surface of the metal foil before coating an electrode slurry is measured by the remaining oil level measuring unit <NUM>, the controller <NUM> determines whether the remaining oil level is excessive.

As explained above, The higher the remaining oil level of the metal foil, the lower the above-described the affinity between the electrode slurry and the metal foil. Hence, as the remaining oil level increases, the contact angle of the electrode slurry increases, and the spread degree decreases. Hence, the controller <NUM> compares the measured spread degree or contact angle of the electrode slurry with a reference value, and when the spread degree is less than the reference value or the contact angle exceeds the reference value, it is determined that the remaining oil level is excessive. To this end, the controller <NUM> includes a storage unit which stores a database about preset reference values, a comparison-calculation unit which comparison-calculates values extracted from the database with the measured spread degree or contact angle, and a determination unit which determines a remaining oil level according to the calculation result and determines whether to coat an electrode slurry. Specifically, when the spread degree is less than the reference value or the contact angle exceeds the reference value, the controller <NUM> determines that the remaining oil level is excessive.

As a result of determination, when the remaining oil level on the surface of the metal foil is within a predetermined range, the controller <NUM> controls the coater <NUM> to discharge the electrode slurry. At this time, the controller <NUM> may order a predetermined moving means (not shown) connected to the coater <NUM> to move the coater <NUM>.

On the other hand, if the remaining oil level on the surface of the metal foil is excessive as a result of determination, the controller <NUM> may control the metal foil to be cleaned.

<FIG> is a block diagram showing the configuration of an electrode slurry coating apparatus according to further another embodiment of the present invention.

Referring to <FIG>, the electrode slurry coating apparatus <NUM> according to the present invention further includes a cleaning unit <NUM>. There is no particular limitation to the structure of the cleaning unit <NUM> as long as it can clean the metal foil. The cleaning unit <NUM>, for example, may include a washing tank for accommodating cleaning liquid, a nozzle for spraying cleaning liquid to a metal foil, a cleaning part for washing off the cleaning liquid, and a drying part for drying the metal foil.

The controller <NUM> may transfer the metal foil, which has been determined to have an excessive remaining oil level on the surface, to the cleaning unit <NUM> to allow the metal foil to be cleaned, thereby removing the remaining oil on the surface.

Likewise, the same process is repeated for the metal foil from which the remaining oil on the surface has been removed. Namely, the remaining oil level measuring unit <NUM> remeasures the remaining oil level for the cleaned metal foil, and the controller <NUM> redetermines whether to coat an electrode slurry on the cleaned metal foil. When the remaining oil level on the surface of the metal foil is within a predetermined range, the controller <NUM> controls the coater <NUM> to discharge the electrode slurry, and transfers the metal foil, which has been determined to have an excessive remaining oil level on the surface, to the cleaning unit <NUM> to allow the metal foil to be cleaned.

Likewise, according to the present invention, it is possible to more accurately recognize the remaining oil level on the metal foil by dropping an electrode slurry on a metal foil before coating the electrode slurry and measuring the spread degree and a contact angle of the dropped electrode slurry. Through this, it is possible to prevent the decrease of the quality of the electrode mixture layer formed after the coating of the electrode slurry.

Further, the present invention provides a method of coating an electrode slurry. This may be performed by the above-described electrode slurry coating apparatus.

<FIG> is a flowchart illustrating an order of an electrode slurry coating method according to the present invention.

Referring to <FIG>, an electrode slurry coating method according to the present invention includes: preparing a metal foil for an electrode current collector (S10); measuring a remaining oil level of the metal foil (S20); and determining whether the remaining oil level is excessive from a measurement value of the remaining oil level (S30) and determining whether to coat the electrode slurry therefrom (<NUM>).

First, a metal foil is prepared (S10). What has been described above may be used as the metal foil. For example, aluminum may be used. Such a metal foil may be manufactured by a known scheme such as electroplating. The surface of the manufactured metal foil may be planarized through rolling.

When the metal foil is prepared, the remaining oil level on the surface of the metal foil is measured (S20). As described above, during the measuring of remaining oil level of the metal foil, the measuring unit measures at least one of a spread degree and a contact angle of the electrode slurry dropped on the metal foil.

Further, since the measuring of the remaining oil level of the metal foil is performed right before coating the electrode slurry, the error of the remaining oil level may be reduced. This is because the remaining oil level on the surface may change during the process of storing, transferring and processing the metal foil.

At this time, the remaining oil level of the metal foil may be measured by the remaining oil level measuring unit. Specifically, the measuring of the remaining oil level of the metal foil may be performed by dropping an electrode slurry on the metal foil by the syringe, photographing shapes of the electrode slurry dropped by the syringe using a vision camera, collecting images obtained by photographing the shapes of the electrode slurry, and then measuring at least one of a spread degree and a contact angle of the electrode slurry from the images.

At this time, the vision camera may sense the metal foil and at least one of color, brightness, and chroma of the dropped electrode slurry, and measure a diameter or a contact angle of the electrode slurry dropped by the syringe. The specific process of measuring the spread degree and the contact angle of the electrode slurry is as described above.

When the remaining oil level of the metal foil is measured, it is determined whether the remaining oil level is excessive therefrom (S30). As described above, the higher the remaining oil level on the surface of the metal foil, the higher the contact angle of the electrode slurry, and the lower the spread degree. As such, when the spread degree is less than the reference value or the contact angle exceeds the reference value, it may be determined that the remaining oil level is excessive.

Thereafter, if it is determined whether the remaining oil level is excessive, it is determined whether to coat the electrode slurry therefrom. If the remaining oil level is good, it is determined that an electrode slurry is to be coated, and accordingly, the controller controls the coater to coat an electrode slurry on the metal foil (S40).

On the other hand, if it is determined that the remaining oil level is excessive, the process of cleaning the metal foil (S50) is performed. As such, the metal foil is transferred to the cleaning unit to clean the remaining oil on the surface.

After the cleaning of the metal foil is completed, the process of remeasuring the remaining oil level for the cleaned metal foil and redetermining whether to coat an electrode slurry on the cleaned metal foil is performed. If the remaining oil level is good as a result of remeasurement, the electrode slurry is coated, and if it is determined that the remaining oil level is excessive, the process of cleaning the metal foil is reperformed.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the drawings disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these drawings. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claim 1:
An apparatus (<NUM>, <NUM>, <NUM>) for coating an electrode slurry, the apparatus comprising:
a coater (<NUM>) which coats an electrode slurry (<NUM>) on a metal foil (<NUM>);
a remaining oil level measuring unit (<NUM>) which measures a remaining oil level on a surface of the metal foil (<NUM>) before coating the electrode slurry (<NUM>); and
a controller (<NUM>) which determines whether the remaining oil level is excessive from a measurement value of the remaining oil level, and determines whether to coat the electrode slurry (<NUM>) therefrom,
characterised in that:
the remaining oil level measuring unit (<NUM>) measures at least one of a spread degree and a contact angle of the electrode slurry (<NUM>) dropped on the metal foil (<NUM>).