Method for monitoring dry state of electrode substrate

Abstract

The present invention relates to an apparatus and method for monitoring a dry state of an electrode substrate in which electrode slurry is applied to a collector. The monitoring method comprises emitting light onto a surface of the electrode substrate; receiving the light reflected by the surface of the electrode substrate; and analyzing a luminous intensity or spectrum of the received light to estimate a drying rate of the electrode substrate. The apparatus includes a light emitting part emitting light from a light source onto a surface of the electrode substrate; a light receiving part receiving the light reflected by the surface of the electrode substrate; and a computing device analyzing a luminous intensity or spectrum of the received light and comparing analyzed characteristics of the light with the reference data of the reflected light to the drying rate of the electrode substrate.

Claims

1. A method for monitoring a dry state of an electrode substrate in which electrode slurry having a solid content is applied to a collector, comprising: emitting light onto a surface of the electrode substrate; receiving light reflected by the surface of the electrode substrate; and analyzing a luminous intensity or a spectrum of the received light to estimate a drying rate of the electrode substrate based on the solid content of the electrode substrate, wherein the light emitted onto the surface of the electrode substrate is light having a visible ray band wherein the electrode slurry comprises a reference material that is changed in a reflection characteristic according to the dry state.

2. The method of claim 1, wherein, when the electrode slurry reaches a drying rate within a specific range, the reflection characteristic of the reference material has a section in which the electrode slurry is more sharply changed than that when the electrode slurry is in a drying rate within a different range.

3. The method of claim 1, wherein the reference material is graphite.

4. The method of claim 1, wherein, the reflection characteristic of the received light is compared with reference data to estimate the drying rate, wherein the reference data is previously written data exhibiting characteristics of the reflected light according to the drying rate of the electrode substrate.

5. The method of claim 1, further comprising drying the electrode substrate in a drying device by passing the electrode substrate through a drying chamber of the drying device to which heat is applied, and controlling a temperature of the drying chamber based on data of the estimated drying rate of the electrode substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a simplified projective view of a drying device for drying an electrode substrate.

(2) FIG. 2 is a simplified view of a monitoring apparatus according to an embodiment of the present invention.

(3) FIG. 3 is a perspective view of a device for stirring a solvent and an electrode active material and a view of an inner blade.

(4) FIG. 4 is a graph illustrating a variation in torque required for a blade of FIG. 3 according to a variation in solid content (%) of electrode slurry applied to the electrode substrate and a view illustrating stirred states of a solvent and an electrode active material.

(5) FIG. 5 is a view illustrating a state in which a luminous intensity is changed on a surface of the electrode substrate according to the variation in solid content (%) of the electrode slurry applied to the electrode substrate.

MODE FOR CARRYING OUT THE INVENTION

(6) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings in such a manner that the technical idea of the present invention may easily be carried out by a person with ordinary skill in the art to which the invention pertains. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein.

(7) In order to clearly illustrate the present invention, parts that are not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

(8) Also, terms or words used in this specification and claims should not be restrictively interpreted as ordinary meanings or dictionary-based meanings, but should be interpreted as meanings and concepts conforming to the scope of the present invention on the basis of the principle that an inventor can properly define the concept of a term to describe and explain his or her invention in the best ways.

(9) The present invention provides an apparatus and method for monitoring a dry state of an electrode substrate in which electrode slurry is applied to a collector.

(10) According to an embodiment of the present invention, an electrode is a negative electrode, and the collector manufactured as the negative electrode is provided as a copper or aluminum thin plate. The electrode slurry has a structure in which a solvent and a negative electrode active material are mixed with each other and is applied to one surface or both surfaces of the collector. Also, while a drying process is performed on the electrode slurry, the solvent is vaporized to cure the negative electrode active material on a surface of the collector so that the electrode slurry adheres to the collector. Here, although the explanation is made based on the negative electrode, the same or similar principle may be applied in the process of manufacturing a positive electrode.

(11) Hereinafter, preferred embodiments according to the present invention will be described with reference to the accompanying drawings.

Embodiment 1

(12) In this embodiment, a method for monitoring a dry state of an electrode substrate is provided. This embodiment will be considered and described to be performed in a drying device 4 through which the electrode substrate continuously passes. As described above, the drying device 4 is a device in which a collector 2a is unwound from a unwinding roller 1a, and an electrode substrate 2, on which electrode slurry is applied to a surface thereof, is dried, and then the electrode slurry injected or applied to a surface of the collector 2a is heated and dried while the electrode substrate 2 is wound around a winding roller 1b. At least one or more drying chambers 4a, 4b, and 4c are provided between and inlet and an outlet.

(13) In this embodiment, the method for monitoring the dry state of the electrode substrate comprises a step of emitting light onto a surface of the electrode substrate 2 coated with the electrode slurry, a step of receiving the light reflected by the surface of the electrode substrate 2 (the light reflected by the electrode slurry), and a step of analyzing a luminous intensity or spectrum of the received light to estimate a drying rate of the electrode substrate.

(14) That is, as illustrated in FIG. 2, a probe 3 is disposed in one or more of the drying chambers 4a, 4b, and 4c. Here, a light receiving part 20 and a light emitting part 10 are built in an end of the probe 30 to emit light onto the surface of the collector coated with the electrode slurry and receive the light through the light receiving part 20. The received light is analyzed by a computing device 40 to determine reflection characteristics.

(15) The electrode slurry according to the present invention contains a reference material having a variable reflection characteristic according to the dry state. Preferably, the reference material is contained to constitute a main component of the active material. When reaching a drying rate within a specific range, the reflection characteristic of the reference material has a section in which the electrode slurry is relatively changed more sharply than that when the electrode slurry is in a drying rate within a different range.

(16) For example, in an embodiment of the present invention, the reference material may be graphite, preferably, artificial graphite, and the light emitted onto the surface of the electrode substrate 2 is light having a visible ray band.

(17) For reference, as described above, the electrode slurry is prepared by dissolving the electrode active material in an organic solvent. The electrode active material is prepared by being stirred in a mixer 50 as illustrated in FIG. 3. Here, as a content of the electrode active material increases, a state of particles S of the electrode active material and the organic solvent are changed into (a) a pendular state (liquid and particles are discontinuously present), (b) a funicular state (a state in which liquid and particles are continuous), (c) a capillary state (a state in which particles and liquid are well combined with each other in a moist state), and (d) a slurry state (a thick state).

(18) FIG. 4 is a graph illustrating a magnitude of torque according to a solid content (%) of the electrode slurry. The torque means torque required while the blade 51 of the mixer 50 stirs the solvent and the electrode active material. As illustrated in the graph, the torque is highest at a solid content of 72% to 73%. Here, as illustrated in FIG. 5, it is seen that a change in luminous intensity of the electrode slurry is largest when the solid content is 72% to 73% (between iii and iv).

(19) That is, in this embodiment, it is seen that a reflection characteristic of the electrode slurry is most rapidly changed in the vicinity of the solid content at which the torque is the largest when the electrode slurry is stirred. In FIG. 5, lines ‘A’, ‘B’, and ‘C’ indicate characteristics of electrode slurry containing different reference materials. However, it is confirmed that all of the above materials commonly exhibit that the reflection characteristic is most rapidly changed in the vicinity of the solid content at which the torque is the largest when the electrode slurry is stirred.

(20) Thus, in a state of knowing the luminous intensity and/or the reflection characteristic of the electrode slurry according to the drying rate of the electrode substrate 2, when the luminous intensity and/or the reflection characteristic of the electrode slurry being dried are compared, it is possible to estimate a drying rate.

(21) That is, the present invention provides a method of estimating a dry state by utilizing a phenomenon that a change in surface gloss according to drying of the electrode slurry is similar to a change in solid content of the electrode slurry. When the electrode slurry has the highest torque during the stirring, bonding force between the solvent and the solute (the electrode active material) is maximized. Here, the electrode slurry may more efficiently adheres to the surface of the collector. Thus, the method according to the present invention may provide monitoring data in real time to control the drying device so as to secure maximum adhesion.

(22) Reference data showing characteristics of reflected light according to the drying rate of the electrode substrate 2 may be obtained through repeated experiments according to various reference materials, and a computing device 40 may estimate a drying rate by comparing and analyzing measured values and the reference data of received light in a state in which data is previously secured. Furthermore, error correction of the estimated values of the drying rate may also be performed to approach an actual drying rate according to control conditions, variables, and types of the reference material through repetitive experiments.

(23) Also, the monitoring method as described above may be performed in real time at selected one position or at various positions of the drying device 4 having the plurality of drying chambers 4a, 4b and 4c as illustrated in FIG. 1. That is, in the drying device 4 in which the electrode substrate 2 is dried by passing therethrough, a temperature control of each of the drying chambers 4a, 4b and 4c to which heat is applied may be performed based on data of the estimated drying rate of the electrode substrate 2.

Embodiment 2

(24) Also, the present invention additionally provides an apparatus 100 for monitoring a dry state of an electrode substrate 2. At least a portion of the monitoring apparatus 100 provided in this embodiment may be detachably mounted in the drying chamber of the above-described drying device 4 (more particularly, a probe may be mounted inside the drying chamber, and a computing device may be mounted outside the drying chamber) and be manufactured to have sufficient heat resistance against an internal temperature of the drying chamber.

(25) The apparatus 100 is an apparatus for monitoring a drying state of the electrode substrate 2 on which electrode slurry is applied to a collector and comprises a light emitting part 10 emitting light generated in a light source onto a surface of an electrode substrate, a light receiving part 20 receiving the light reflected by the surface of the electrode substrate 2, and a computing device 40 analyzing a luminous intensity and/or a spectrum of the received light and comparing the analyzed characteristics of the light with the reference data of the reflected light to estimate the drying rate of the electrode substrate.

(26) Each of the light emitting part 10 and the light receiving part 20 is made of an optical fiber, through which light is capable of passing, and configured to transmit the light reflected from the light source 11 or transmit the reflected light to the computing device 40. The light emitting part 10 and the light receiving part 20 may be mounted to be built together in the probe 30. That is, the probe 30 has an inner hollow pipe shape, and the light receiving part 20 and the light emitting part 10 are inserted together into the probe.

(27) As illustrated in FIG. 2, in this embodiment, the light receiving part 20 is disposed at a center within the probe 30, and a plurality of light emitting parts 10 are disposed along a circumference of the light receiving part 20. The light emitting part 10 may be configured to emit light having a visible ray band and also configured to selectively emit light having other wavelengths. The probe 30 is disposed so that an end of the probe 30 is spaced a predetermined distance (preferably, 1 mm to 5 mm) from the surface of the electrode substrate 2.

(28) Thus, the light generated in the light source 11 is emitted to the surface of the electrode substrate 2 (in more detail, a surface of the electrode slurry applied to the surface of the collector) through the light emitting part 10, and the reflected light is transmitted to the computing device 40 through the light receiving part 20. Here, the computing device 40 analyzes characteristics of the reflected light to estimate a drying rate.

(29) Since the present invention having the above-described constituents may grasp the dry state without directly contacting the surface of the electrode substrate, the electrode substrate may be prevented from being damaged or scratched on the surface thereof. In addition, since the electrode substrate is not affected by the internal conditions of the drying chamber, the measured result may be improved in reliability.

(30) While the embodiments of the present invention have been described with reference to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.