KR20180037802A - Device for Preparing Electrode Comprising Electrode Active Material Particles Having Different Diameters Dependent on Distance from Current Collector and Method of Manufacturing Electrode Using The Same - Google Patents

Abstract

The present invention relates to an apparatus for producing an electrode on which an electrode mixture layer containing electrode active material particles having different particle diameter is formed on a collector. Moreover, provided is an electrode production apparatus which comprises: an electrode mixture coating part spraying, toward the top, electrode mixture slurry containing the electrode active material particles to the lower side of the collector so as to form the electrode mixture layer on the lower side of the collector on the basis of the ground surface; a drying part drying the collector coated with the electrode mixture slurry to the lower side; a first roller applying pressure to an upper side of the collector while being in contact with the upper side of the collector; and a second roller supporting pressure applied from the first roller while being in contact with the lower side of the electrode mixture layer by facing the first roller.

Description

TECHNICAL FIELD [0001] The present invention relates to a device for manufacturing an electrode including electrode active material particles having different particle diameters according to a distance from a current collector, and an electrode manufacturing method using the electrode active material particle. Electrode Using The Same}

The present invention relates to an apparatus for manufacturing an electrode including electrode active material particles having different particle sizes according to a distance from a current collector, and a method of manufacturing an electrode using the same.

In recent years, the demand for environmentally friendly alternative energy sources has become an indispensable factor for the future, as the increase in the price of energy sources due to depletion of fossil fuels and the interest in environmental pollution are amplified. Various researches on power generation technologies such as nuclear power, solar power, wind power, and tidal power have been continuing, and electric power storage devices for more efficient use of such generated energy have also been attracting much attention.

Particularly, as technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries that can meet various demands have been conducted.

Typically, in terms of the shape of a battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery which can be applied to products such as mobile phones with a small thickness, and has advantages such as high energy density, discharge voltage, There is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries.

The secondary battery includes a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch type battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet .

Also, the secondary battery is classified according to the structure of the electrode assembly having the positive electrode, the negative electrode, and the separator interposed between the positive electrode and the negative electrode. Typically, the long battery- A stacked (stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in a predetermined size unit are sequentially stacked with a separator interposed therebetween, the jelly-roll type (wound type) electrode assembly having a structure in which a separator is interposed; In recent years, in order to solve the problems of the jelly-roll type electrode assembly and the stack type electrode assembly, an electrode assembly having an advanced structure, which is a combination of the jelly-roll type and the stack type, A stack / folding type electrode having a structure in which unit cells stacked with a separator interposed between an anode and a cathode are sequentially wound while being placed on a separation film Developed body lip.

Generally, such an electrode assembly is produced by applying an electrode mixture slurry on a current collector for a long sheet-like electrode, drying the electrode assembly slurry, drying the electrode sheet, cutting the electrode sheet into a desired size and shape, .

1 is a schematic view schematically showing the structure of a conventional electrode manufacturing apparatus.

Referring to FIG. 1, the electrode manufacturing apparatus 100 includes a slot die 110 for coating an electrode mixture slurry, drying units 121 and 122, and a rolling roller 130.

The current collector 140 is in the form of a long sheet, wound in the form of a roll 141, and conveyed continuously or discontinuously in the opposite direction.

The slot die 110 is configured such that the coating liquid is discharged to the slot 111 which is the gap between the two ends of the slot die 110 as the ink flows from the fountain pen to the tip of the pen tip, The electrode assembly slurry is applied onto the current collector 140 as the electrode assembly 140 moves. Since the coating method using the slot die 110 is superior to other coating methods in terms of maintenance and productivity, it is possible to apply the electrode mixture slurry to the current collector 140 of the secondary battery electrode up to now, And the like.

The current collector 140 coated with the electrode mixture slurry is transferred (103) to the drying units 121 and 122.

The drying units 121 and 122 are configured to dry one side and the other side of the current collector 140 coated with the electrode mixture slurry by a high-temperature hot air or a light source.

The rolling roller 130 is composed of two rollers 131 and 132. In the course of the two rollers 131 and 132 rotating in opposite directions 101 and 102, The adhesive force of the electrode slurry to the current collector 140 is improved and the thickness of the slurry of the electrode slurry is uniformly formed by applying pressure to both surfaces of the electrode slurry 140.

Fig. 2 is a schematic view schematically showing the rolling structure of the electrode mixture slurry by the rolling roller of Fig.

Referring to FIG. 2, the electrode mixture slurry applied on the top surface of the current collector 140 has electrode active material particles 211 and 212 having different particle diameters dispersed therein.

Accordingly, in the case of manufacturing the electrode using the electrode manufacturing apparatus, in the electrode active material particles 211 and 212 dispersed in the electrode mixture slurry applied on the upper surface of the collector 140 in the drying process by the drying unit, The electrode active material particles 211 having a large particle diameter are positioned at a portion adjacent to the current collector 140 by gravity while the electrode active material particles 212 having a relatively small particle diameter are positioned apart from the current collector 140 Surface area.

Therefore, in the electrode mix layer 210 formed by the electrode mixture slurry, a high porosity is formed due to the relatively large particle size of the electrode active material particles 211 in the vicinity of the current collector 140, A low porosity is formed due to the relatively small particle size of the electrode active material particles 212 on the surface portion of the electrode mix layer 210 spaced from the electrode assembly layer 140, Impregnation property of the lithium ion is lowered and the mobility of the lithium ion is lowered during charging and discharging of the battery.

The electrode active material particles 212 coated on the current collector 140 are rolled by a rolling roller 131 having a large hardness so that the electrode active material particles 212 having a small diameter on the surface portion are rolled 131, the particles are broken or deformed, resulting in rearrangement. As a result, the porosity at the surface portion is further lowered, and problems such as deterioration of electrolyte impregnability and deterioration of mobility of lithium ions Which results in a further deterioration of the image quality.

Therefore, there is a high need for a technique capable of fundamentally solving such problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have configured to include an electrode material mixture coating portion for spraying an electrode mixture slurry upward by spraying on the lower surface of a collector as described later, The electrode active material particles having relatively large particle diameters are located on the surface portion separated from the current collector by the gravity in the course of drying the slurry for the electrolyte to improve the electrolyte impregnability at the surface portion, The first roller that applies pressure to the upper surface of the current collector in a state of being in contact with the upper surface of the current collector has a hardness that is relatively larger than that of the second roller which is in contact with the lower surface portion of the electrode mixture layer, It is possible to prevent the electrode mixture layer from being damaged when the roller directly contacting the electrode material mixture layer has a large hardness It is possible to effectively prevent the deterioration of the electrolyte impregnation property and the lowering of the mobility of the lithium ion which may occur on the surface of the electrode compound mixture layer. And the present invention has been accomplished.

According to an aspect of the present invention,

There is provided an apparatus for manufacturing an electrode in which an electrode mixture layer containing electrode active material particles having different particle diameters is formed on a current collector,

An electrode material mixture coating part for upward spraying an electrode mixture slurry containing electrode active material particles on the lower surface of the current collector so as to form an electrode mixture layer on the lower surface of the current collector on the basis of the ground;

A drying unit for drying the current collector coated with the slurry for the electrode material mixture on the lower surface;

A first roller for applying pressure to an upper surface of the current collector in contact with the upper surface of the current collector; And

A second roller for supporting a pressure applied from the first roller in a state of being in contact with the lower surface of the electrode mixture layer facing the first roller;

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Therefore, in the drying process of the slurry for electrode mixture, the electrode active material particles having a relatively large particle diameter are located on the surface portion separated from the current collector by gravity, thereby improving the electrolyte impregnability at the surface portion, The mobility of lithium ions can be improved during charging and discharging, and breakage, shape change and rearrangement of electrode active material particles, which may occur when the roller directly contacting the electrode mix layer has a large hardness, can be effectively suppressed Thus, it is possible to effectively prevent the problem of deterioration of electrolyte impregnability and reduction of mobility of lithium ions that may occur on the surface of the electrode mixture layer.

In one specific example, the electrode compound coating portion comprises: It may be a structure in which the electrode mixture slurry in which the electrode active material particles are mixed with the solvent is sprayed upward against the lower surface of the current collector.

That is, the slurry for the electrode material mixture may be a structure in which electrode active material particles are injected upward in the form of a liquid or an aerosol mixed with a solvent to the lower surface of the current collector.

At this time, the content of the solvent may be 40 wt% to 80 wt% based on the total weight of the slurry.

If the content of the solvent in the slurry for the electrode material mixture is too small, the viscosity of the slurry for the electrode material mixture becomes excessively high and the spraying on the bottom surface of the current collector may not be easy. On the contrary, When the content of the solvent of the slurry for the electrode mixture is excessively higher than the above range, the viscosity of the slurry for electrode mixture becomes excessively low and the adhesion to the lower surface of the current collector becomes weak, You may not be able to keep it.

It is preferable that the current collector coated with the slurry for the electrode material mixture is such that the particles of the electrode active material having a relatively large particle size are distributed at a portion spaced from the current collector by gravity during the drying process through the drying portion, The slurry can be dried while being positioned on the bottom side with respect to the paper surface.

Accordingly, the electrode active material particles having a relatively large particle diameter can be more easily distributed by gravity to a portion spaced apart from the current collector, without any additional processing or processing, during the drying process through the drying portion, The impregnation of the electrolyte solution on the surface of the layer and the mobility of lithium ions can be further improved.

In such a case, the electrode mix layer may be formed such that the average particle diameter of the electrode active material particles increases continuously or discontinuously as the distance from the current collector increases on a vertical section.

Therefore, a high porosity can be formed by the electrode active material particles having a relatively large particle size at the surface portion of the electrode mixture layer, which is distant from the current collector, and the electrolyte impregnability and the lithium ion mobility can be further improved .

On the other hand, the first roller may have a structure having a relatively large hardness as compared with the second roller.

As described above, when the electrode active material particles are rolled by a roller having a large hardness, they are broken or deformed to cause rearrangement. This degrades the impregnation of the electrolyte solution on the surface of the electrode mixture layer and the deterioration of the mobility of lithium ions It can act as a factor to deteriorate.

Accordingly, among the first roller and the second roller, the first roller in contact with the upper surface of the collector has a structure having a relatively large hardness at the lower surface of the electrode mixture layer as compared with the second roller in contact with the electrode mixture layer , It is possible to improve the adhesive force of the electrode mixture layer and to form the surface of the electrode mixture layer uniformly while preventing the problems caused by the rolling.

In one specific example, the first roller may have a structure in which the vertical section has a diameter smaller than that of the second roller.

Accordingly, when the first roller applies pressure in a state of being in contact with the upper surface of the current collector, the lower surface portion of the electrode mixture layer opposing the first roller contacts the second roller supporting the pressure in a relatively large area, The pressure applied to the electrode active material particles constituting the electrode mixture layer is dispersed and the pressure applied to the electrode active material particles can be greatly reduced as compared with the conventional electrode active material particles.

Therefore, it is possible to prevent the electrode active material particles from being rearranged due to breakage or deformation of the electrode active material particles on the surface of the electrode mixture layer by the pressure applied by the first roller, It is possible to effectively prevent the problems such as deterioration of electrolyte impregnability due to deterioration and lowering of mobility of lithium ion.

Further, the present invention provides a method of manufacturing an electrode using the above electrode manufacturing apparatus,

a) a step of spraying an electrode mixture slurry upward by spraying an electrode mixture slurry on a lower surface of the current collector from an electrode mixture coating portion located at a lower portion of the current collector with respect to the ground;

b) drying the current collector coated with the slurry for the electrode material mixture on the lower surface by a drying unit; And

c) rolling the electrode mixture layer while rotating a first roller for applying a pressure to the upper surface of the current collector and a second roller for supporting a lower surface portion of the electrode mixture layer facing the first roller, Process;

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That is, the electrode according to the present invention may be formed on one surface and the other surface sequentially, rather than a structure in which the electrode mixture layer is formed on both surfaces of the current collector at the same time.

At this time, the slurry for the electrode material mixture in the step a) may be injected upward to the lower surface of the current collector in the form of a slurry in which the electrode active material particles are mixed with the solvent.

That is, the slurry for the electrode material mixture may be a structure in which electrode active material particles are injected upward in the form of a liquid or an aerosol mixed with a solvent to the lower surface of the current collector.

In this case, the slurry for the electrode material mixture may be sprayed at a pressure of 4 MPa to 20 MPa.

If the slurry for the electrode material mixture is injected at an excessively low pressure beyond the above range, it may be difficult to maintain a stable application state of the slurry for the electrode material mixture sprayed upward in liquid or aerosol form on the lower surface of the current collector, On the other hand, when the slurry for the electrode mixture is out of the range and is sprayed at an excessively high pressure, the surface of the electrode mixture layer may not be uniformly formed, or the slurry for the electrode mixture may not be applied in a desired thickness .

Also, drying in the step b) may be performed in a state where the coated slurry is positioned at the bottom of the ground so that the electrode active material particles having a relatively large particle size are distributed at a portion separated from the current collector by gravity.

Therefore, among the electrode active material particles of the slurry for the electrode material mixture applied to the lower surface of the current collector, the electrode active material particles having a relatively large particle size are easily separated from the current collector by gravity in the drying process, And a separate apparatus or process for forming a specific distribution structure according to the particle diameters of the electrode active material particles is not necessary, so that the cost required for the process can be saved.

At this time, drying in the step b) may be performed at a drying rate of 30 m / min to 50 m / min in a temperature range of 40 to 140 degrees Celsius.

If the drying is carried out at an excessively low temperature beyond the above range or if the drying is carried out for an excessively short time, the slurry for the electrode material mixture applied on the lower surface of the current collector can not be sufficiently dried, The electrode active material particles having relatively large particle diameters may not be sufficiently distributed to the portion separated from the current collector by the gravity, and conversely, the drying may be performed at an excessively high temperature outside the range, Cracks may be generated on the surface of the electrode material mixture layer or deformation and damage of the current collector coated with the slurry for the electrode material mixture may occur and the electrode mixture to the lower surface of the current collector may be damaged due to an excessively long drying time, There is a problem that the adhesive force of the slurry for use may be lowered.

Meanwhile, in step c), the pressure applied to the top surface of the current collector by the first roller may be 4 psi to 20 psi.

If the pressure applied to the upper surface of the current collector by the first roller exceeds the above range and is excessively small in the step c), the surface of the electrode compound mixture layer may be uniformed or the adhesion of the electrode mixture layer to the bottom surface of the current collector It may not be possible to sufficiently exhibit the desired effect by the rolling, such as the increase.

On the contrary, if the pressure applied to the upper surface of the current collector by the first roller in the step c) is too large beyond the above range, the electrode active material particles may be broken or deformed as in the case of the conventional electrode , Rearrangement occurs, and voids on the surface of the electrode material mixture layer can not be formed so large that the desired effect may not be exhibited.

The present invention also provides an electrode manufactured using the electrode manufacturing apparatus or the electrode manufacturing method,

An electrode material mixture layer containing electrode active material particles having different particle diameters; And

A current collector having the electrode mixture layer formed on one surface or both surfaces thereof;

And,

The electrode mix layer may have a structure in which the average particle diameter of the electrode active material particles is continuously or discontinuously increased as the distance from the current collector increases in a vertical section.

Therefore, since the electrode active material particles having relatively large particle diameters are located on the surface portion separated from the current collector by gravity, the electrolyte impregnability at the surface portion can be improved and the lithium ion mobility can be improved during charging and discharging of the battery .

At this time, the porosity of the electrode mix layer spaced apart from the current collector is preferably 101% to 250% of the porosity of the electrode mix layer adjacent to the current collector, Lt; / RTI >

If the porosity of the electrode mix layer adjacent to the current collector is outside of the above range and is too small, the desired effect according to the present invention is not exerted On the contrary, if the electrode is excessively large, the performance of the battery including the electrode may be deteriorated due to an excessive difference in the porosity.

As described above, the electrode manufacturing apparatus according to the present invention includes the electrode mixture coating portion for spraying the electrode mixture slurry upward by spraying on the lower surface of the current collector, so that in the drying process of the slurry for electrode mixture, The electrode active material particles having relatively large particle diameters are located on the surface portion separated from the current collector by gravity to improve the electrolyte impregnation property at the surface portion and improve the mobility of lithium ions during charging and discharging of the battery And the first roller for applying pressure to the upper surface of the current collector in contact with the upper surface of the current collector has a relatively greater hardness than the second roller adjacent to the lower surface portion of the electrode mixture layer facing the electrode, Cracking of the electrode active material particles that may occur when the roller directly contacting the composite layer has a large hardness The shape change and the rearrangement thereof can be effectively suppressed. Thus, it is possible to effectively prevent problems such as lowering of electrolyte impregnation property and lowering of mobility of lithium ions that may occur on the surface of the electrode compound mixture layer.

1 is a schematic diagram schematically showing a structure of a conventional electrode manufacturing apparatus;
Fig. 2 is a schematic view schematically showing a rolling structure of an electrode mixture slurry by the rolling roller of Fig. 1; Fig.
3 is a schematic view schematically showing a structure of an electrode manufacturing apparatus according to one embodiment of the present invention;
Fig. 4 is a schematic view schematically showing a rolling structure of an electrode mixture slurry by the rolling roller of Fig. 3; Fig.

Hereinafter, the present invention will be described in detail with reference to the drawings according to the embodiments of the present invention, but the scope of the present invention is not limited thereto.

3 is a schematic view schematically showing the structure of an electrode manufacturing apparatus according to one embodiment of the present invention.

Referring to FIG. 3, the electrode manufacturing apparatus 300 includes an electrode compound coating portion 310 for coating a slurry 311 for an electrode mixture, drying portions 321 and 322, and a rolling roller 330.

The current collector 340 is in the form of a long sheet, wound in the form of a roll 341, and conveyed continuously or discontinuously in the opposite direction.

The electrode assembly coating portion 310 is disposed on the lower surface of the current collector 340 with respect to the ground surface and is formed on the lower surface of the current collector 340 so as to form an electrode mixture layer on the lower surface of the current collector 340, The slurry 311 for slurry in which the particles are mixed with the solvent is sprayed upward.

Therefore, the slurry for electrode mixture 311 is sprayed in a liquid or aerosol form and applied to the lower surface of the current collector 340.

The current collector 340 coated with the slurry for electrode mixture 311 is transferred 303 to the drying units 321 and 322.

The drying units 321 and 322 are configured to dry one side and the other side of the current collector 340 coated with the slurry for electrode mixture 311 by hot air or a light source at a high temperature.

The current collector 340 is formed by coating the coated slurry 311 so that the electrode active material particles having a relatively large particle size are distributed in a region separated from the current collector 340 by gravity in the drying process by the drying units 321 and 322. [ ) Is placed on the ground with reference to the ground.

The rolling roller 330 is composed of a first roller 331 and a second roller 332 which are respectively disposed on the upper surface and the lower surface of the current collector 340.

The two rollers 331 and 332 apply a pressure in a state in which the first roller 331 is in contact with the upper surface of the current collector 340 in the process of rotating in opposite directions 301 and 302, The electrode assembly slurry 332 supports the pressure applied from the first roller 331 in contact with the lower surface of the current collector 340 coated with the slurry for electrode mixture 311, The adhesion force of the electrode slurry 311 is improved and the thickness and the surface of the slurry for electrode mixture 311 are uniformly formed.

The first roller 331 has a structure in which the diameter on the vertical section is relatively small as compared with the second roller 332.

Accordingly, when the first roller 331 applies pressure in a state of being in contact with the upper surface of the current collector 340, the lower surface portion of the electrode mixture layer opposite to the first roller 331 faces the upper surface of the current collector 340, By contacting the roller 332, the pressure applied to the electrode active material particles constituting the electrode mixture layer is dispersed, and the pressure applied to the electrode active material particles can be greatly reduced as compared with the conventional electrode active material particles.

Therefore, the electrode active material layer is prevented from being rearranged due to breakage or deformation of the electrode active material particles on the surface of the electrode mix layer by the pressure applied by the first roller 331, It is possible to effectively prevent problems such as lowering of the electrolyte impregnability due to lowering of the electrolyte and lowering of the mobility of lithium ions.

Fig. 4 is a schematic view schematically showing the rolling structure of the electrode mixture slurry by the rolling roller of Fig.

Referring to FIG. 4, the slurry for the electrode material mixture applied on the lower surface of the current collector 340 is formed by dispersing electrode active material particles 411 and 412 having different particle sizes.

Accordingly, when the electrode is manufactured using the electrode manufacturing apparatus, in the electrode active material particles 411 and 412 dispersed in the slurry for the electrode material mixture applied on the lower surface of the current collector 340 in the drying process by the drying unit, The electrode active material particles 411 having a relatively large particle diameter are located on the surface portion separated from the current collector 340 by gravity and the electrode active material particles 412 having a relatively small particle diameter are positioned on the current collector 340, As shown in FIG.

Therefore, in the electrode mix layer 410 formed by the slurry for electrode mixture, a high porosity is formed due to the relatively large particle size of the electrode active material particles 411 on the surface portion remote from the current collector 340, It is possible to improve the impregnation property with respect to the electrolytic solution at the surface portion of the electrode mixture layer 410 and improve the mobility of the lithium ion during charging and discharging of the battery.

The upper surface of the current collector 340 is rolled by the first roller 331 having a smaller diameter on the vertical section and the surface of the electrode mixture layer 410 formed on the lower surface of the current collector 340 has a diameter The electrode active material particles 411 on the surface portion are increased in area in contact with the second roller 331 so that the pressure applied from the first roller 331 is dispersed .

Therefore, the electrode active material particles 411 having a relatively large particle diameter are cracked or deformed and rearrangement occurs, so that deterioration of the electrolyte impregnation performance or deterioration of the lithium ion mobility due to the decrease of porosity at the surface portion of the electrode mixture layer 410 The same problem can be effectively prevented.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention.

Claims (15)

There is provided an apparatus for manufacturing an electrode in which an electrode mixture layer containing electrode active material particles having different particle diameters is formed on a current collector,
An electrode material mixture coating part for upward spraying an electrode mixture slurry containing electrode active material particles on the lower surface of the current collector so as to form an electrode mixture layer on the lower surface of the current collector on the basis of the ground;
A drying unit for drying the current collector coated with the slurry for the electrode material mixture on the lower surface;
A first roller for applying pressure to an upper surface of the current collector in contact with the upper surface of the current collector; And
A second roller for supporting a pressure applied from the first roller in a state of being in contact with the lower surface of the electrode mixture layer facing the first roller;
Wherein the electrode assembly includes an electrode assembly. The electrode assembly according to claim 1, wherein the electrode material mixture coating portion comprises: Wherein an electrode mixture slurry in which electrode active material particles are mixed with a solvent is sprayed upward against a lower surface of the current collector. The electrode manufacturing apparatus according to claim 2, wherein the slurry for the electrode mixture has a solvent content of 40 to 80 wt% based on the total weight of the slurry. The method according to claim 1, wherein the current collector coated with the slurry for the electrode material mixture is coated on the surface of the current collector such that the electrode active material particles having a relatively large particle size are distributed at a portion separated from the current collector by gravity, Wherein the slurry for electrode assemblies is dried while being positioned on the bottom surface with respect to the ground surface. 5. The electrode manufacturing apparatus according to claim 4, wherein the electrode material mixture layer has a distribution such that the average particle diameter of the electrode active material particles increases continuously or discontinuously as the distance from the current collector increases on a vertical cross- . The apparatus of claim 1, wherein the first roller has a relatively greater hardness than the second roller. 2. The electrode manufacturing apparatus according to claim 1, wherein the first roller has a vertical cross-sectional diameter smaller than that of the second roller. A method of manufacturing an electrode using the electrode manufacturing apparatus according to claim 1,
a) a step of spraying an electrode mixture slurry upward by spraying an electrode mixture slurry on a lower surface of the current collector from an electrode mixture coating portion located at a lower portion of the current collector with respect to the ground;
b) drying the current collector coated with the slurry for the electrode material mixture on the lower surface by a drying unit; And
c) rolling the electrode mixture layer while rotating a first roller for applying a pressure to the upper surface of the current collector and a second roller for supporting a lower surface portion of the electrode mixture layer facing the first roller, Process;
Wherein the first electrode and the second electrode are electrically connected to each other. [9] The method of claim 8, wherein the slurry for the electrode mixture in the step a) is injected upward in the form of a slurry in which the electrode active material particles are mixed with the solvent. The method according to claim 9, wherein the slurry for electrode mixture is sprayed at a pressure of 4 MPa to 20 MPa. The method according to claim 8, wherein drying in step b) is performed in a state in which the coated slurry is positioned on the ground surface so that the electrode active material particles having a relatively large particle size are distributed at a portion separated from the current collector by gravity Wherein the first electrode and the second electrode are formed on the substrate. The method of claim 8, wherein the drying of step b) is performed at a drying rate of 30 m / min to 50 m / min in a temperature range of 40 to 140 degrees Celsius. The method of claim 8, wherein the pressure applied to the top surface of the current collector by the first roller in step c) is 4 psi to 20 psi. An electrode material mixture layer containing electrode active material particles having different particle diameters; And
A current collector having the electrode mixture layer formed on one surface or both surfaces thereof;
And,
Wherein the electrode material mixture layer has a distribution such that the average particle diameter of the electrode active material particles increases continuously or discontinuously as the distance from the current collector increases on a vertical section. 15. The electrode assembly according to claim 14, wherein a porosity of a portion of the electrode mixture layer spaced apart from the current collector from a portion of the electrode mixture layer that is 50% % ≪ / RTI > to 250%.

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