KR20070092385A - Method of drying slurry for electrode of rechargeable battery and apparatus for the same - Google Patents

Abstract

A method and a device for drying electrode slurry for a secondary battery are provided to maintain a uniform drying process condition and prevent the occurrence of a drying process failure caused by a partial error of the device. A method for drying electrode slurry for a secondary battery comprises a step of coating a current collector with solvent-containing active material slurry, followed by heating the slurry-coated electrode current collector in a drying room to remove the solvent. Hot air is supplied to the slurry-coated electrode current collector and an infrared lamp(232) emits infrared rays from above the slurry at the same time. An indirect temperature measurement to measure the ambient temperature of the drying room and a direct temperature measurement to measure the surface temperature of the slurry applied onto the current collector are accomplished at the same time.

Description

Method and apparatus for drying electrode slurry of a secondary battery {Method of drying slurry for electrode of rechargeable battery and Apparatus for the same}

1 is a schematic perspective view for explaining a method of applying a slurry to an electrode current collector in the prior art,

2 is a schematic cross-sectional view showing the basic configuration of a conventional hot air drying apparatus;

Figure 3 is a schematic diagram showing an embodiment of a slurry drying apparatus of the present invention,

4 is a schematic structural diagram conceptually showing another embodiment of the slurry drying apparatus of the present invention;

5 is a flow diagram illustrating one embodiment of the method of the present invention.

The present invention relates to a method and apparatus for forming an electrode of a secondary battery, and more particularly, to a method for drying a slurry for forming an electrode active material layer of a secondary battery and an apparatus suitable for implementing the method.

The application method is often used to deposit another material layer on one material layer (substrate). For application, the stacked materials form a liquid phase with a solvent or a dispersion medium in the form of a solution or slurry. A die coater (DIE COATER) or the like may be used as a device for relatively thinly applying a solution or slurry to a large area, and a slot die formed in one direction may be used as the die coater. These slot dies allow for forming a layer of material on the substrate at a constant width.

Typically, the slot die moves the slot die itself by allowing the slurry (which is used in the broader sense of application liquid concept including the solution) to be discharged into the gap between the two ends of the slot die, as ink flows from the fountain pen to the tip of the pen. Alternatively, the slurry is applied to the surface corresponding to the substrate while the substrate is moved. The coating method using the slot die is superior to other coating methods in terms of maintenance and productivity, and can be used to manufacture active materials on current collectors in panels of flat panel display devices or electrodes of secondary batteries.

In the lithium secondary battery, the electrode assembly has to have a large amount of active material in a narrow space in order to have the maximum charging capacity, and even if the same amount of active material is embedded, the active material should be formed on the opposite side of the two electrodes in even thickness to increase the charge and discharge efficiency. do. On the other hand, there is a continuous demand for a method for improving efficiency in the production of lithium batteries. In order to increase the production efficiency, the slot die is enlarged and the application process is speeded up.

In lithium secondary batteries, electrodes are often formed by applying a slurry containing an electrode active material to the surface of a current collector made of metal foil or a metal mesh. The slurry is usually formed by mixing a solvent, a plasticizer, an electrode active material, a binder and the like. As the current collector, copper is used for the cathode, and aluminum is used for the anode. Polyvinylidene fluoride (PVDF) and stylene butadiene rubber (SBR) are used as binders, acetone and NMP (N-methylprolidone) as solvents. Etc. may be used, and water may be used.

In general, when the active material slurry is applied to the electrode substrate, the substrate to which the slurry is applied is stored again in a roll state, and is then in a state suitable for forming an individual electrode assembly through a slitting process.

However, since the slurry is a fluid state containing a large amount of solvent, after the slurry is applied, the solvent contained in the slurry should be removed so as not to damage the active material layer. Therefore, in order to apply the active material for producing the electrode at high speed, a drying process for efficiently removing the solvent component of the slurry in a short time should be performed.

In addition, in order to stably attach the active material layer to the current collector, reduce the internal resistance, improve the quality of the electrode, and improve the battery characteristics, a drying process of removing the solvent component from the applied slurry should be performed under appropriate conditions.

1 is a schematic perspective view illustrating a conventional method of applying a slurry to an electrode current collector, and FIG. 2 is a schematic cross-sectional view showing the basic configuration of a conventional hot air drying apparatus.

Referring to the drawings, the electrode current collector 10, which is wound in a roll shape in a unwinder (not shown) and is supplied with a predetermined width, is unwound in a plane, and the lower portion of the slot die 20 and the dryer 50 are removed. After rewinding in the winder (not shown). The slot die 20 receives the slurry from a slurry tank (not shown) and serves to evenly apply the slurry to the substrate through a slot formed in the die. Since the electrode current collector 10 constantly passes under the slot die 20, a slurry layer 30 having a predetermined thickness is attached to the surface of the electrode current collector 10.

Usually, the hot air drying method is used for drying an active material slurry. In the dryer 50, hot air is sent to volatilize and remove the solvent of the slurry, and the slurry adheres to the electrode current collector with considerable strength by the action of a binder. Hot air can be formed by making a flow of air to the blower 110 and installing a heater in the blower opening of the dryer. On the opposite side of the blower, an exhaust duct 120 for discharging the gas containing the evaporated solvent is installed.

The slurry drying method includes a hot air drying method and a method of irradiating light with an infrared lamp.

In hot air drying, the drying speed in a dryer may differ for each part according to the flow direction of hot air. In addition, hot air, which has transferred some heat to the surface of the current collector, is discharged together with the evaporated solvent and a considerable amount of heat energy, so that the energy efficiency of hot air drying is not high. In addition, a dryer installation space is required for sufficient slurry drying, and there is also a problem in that the process time is long.

When using a higher temperature hot air to reduce the drying time, the slurry tends to dry from the surface, so that the binder dissolved in the solvent concentrates on the slurry surface as the solvent moves. Therefore, the adhesive strength of an active material layer and an electrode collector falls, and a problem may arise that an active material layer peels from the surface of an electrical power collector.

In addition, when the slurry is dried from the surface, a solvent may not pass through the hardened surface well and may not be sufficiently dried due to confinement, or may cause a problem in that the drying time should be increased.

On the other hand, the infrared irradiation method is high energy efficiency, but the slurry temperature can be easily high temperature, for example, at 170 degrees Celsius or more, the quality of the active material layer is poor, it is difficult to continue the near-infrared irradiation of the continuous high output to the electrode plate. When the output of the infrared lamp is adjusted for each time position, the dryness for each part of the electrode may not be the same accordingly. In addition, as the high-capacity lamp is placed at a high density, there is a problem that the lamp is not sufficiently cooled, the life of the lamp is reduced, and the cost of equipment maintenance is high, and some lamps are frequently damaged during the process. When the process conditions are different, the reliability and effectiveness of the slurry drying process may be degraded.

The present invention is to alleviate the problems of the slurry drying method in the conventional secondary battery electrode forming process described above,

An object of the present invention is to provide a method and apparatus for drying an electrode slurry of a secondary battery capable of maintaining drying process conditions evenly.

It is an object of the present invention to provide a method and apparatus for drying electrode slurry of a secondary battery, which can prevent occurrence of a defective drying process due to partial abnormality of equipment.

The method of the present invention for achieving the above object, the electrode of the secondary battery comprising the step of applying an active material slurry containing a solvent to the current collector, and heating the electrode current collector with the slurry applied in a drying chamber space to remove the solvent. In the slurry drying method,

As the hot air is supplied to the electrode collector on which the slurry is applied, an infrared lamp irradiates infrared rays from above the slurry,

Indirect temperature measurement for measuring the ambient temperature of the drying chamber and direct temperature measurement for measuring the surface temperature of the slurry applied to the current collector is characterized in that it is made at the same time.

According to the method of the invention, the direct temperature measurement can be made by means of a non-contact temperature sensor.

According to the method of the present invention, the results of the indirect temperature measurement and the direct temperature measurement can be fed back to the infrared lamp module and the hot air fan operation by a predetermined program and used for managing the drying chamber atmosphere temperature and the slurry surface temperature.

The apparatus of the present invention for achieving the above object is provided with a drying chamber, a blower and a heater to pass through the current collector coated with the slurry, a hot air supply device configured to supply hot air to the slurry, infrared lamp module, vaporized solvent, etc. It is characterized by comprising an exhaust device to be discharged to the outside, a direct temperature sensor for measuring the surface temperature of the slurry and an indirect temperature sensor for measuring the air temperature inside the drying chamber.

In the device of the present invention, a controller for inputting the measurement results of the direct temperature sensor and the indirect temperature sensor is further provided, and the controller processes the measurement result values of each temperature sensor by a predetermined program to output the hot air supply device and the infrared lamp module. It can be made to adjust.

In the present invention, the infrared lamp module is formed by aligning a plurality of individual lamps, and in the present invention, a controller capable of adjusting each lamp module may be configured to detect whether each individual lamp is operated.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

Figure 3 is a schematic block diagram showing an embodiment of the slurry drying apparatus of the present invention, Figure 4 is a schematic block diagram conceptually showing another embodiment of the slurry drying apparatus of the present invention, Figure 5 is an embodiment of the method of the present invention It is a flow chart showing.

The slurry drying apparatus of the present invention is installed at the rear of the section for applying the slurry, based on the movement path of the electrode current collector conveyed by the roller in the electrode manufacturing equipment.

3 and 4, in embodiments of the present invention, the drying apparatus is a wall 260 for blocking the periphery except for the entrance and exit port for introducing and carrying out the slurry-coated electrode current collector, and the electrode current collector is withdrawn A hot air supply blower 210 installed to supply hot air toward the side where the electrode current collector is introduced into the side wall, an exhaust duct 220 which collects and discharges the hot air on the wall opposite to the hot air supply blower 210; Rear hot air supply nozzle 250 for supplying hot air toward the electrode plate from the opposite side to which the slurry to be dried is applied, the infrared lamp 232 arranged to irradiate infrared rays toward the electrode plate surface to which the slurry to be dried is applied, to the infrared lamp It is formed with an air shower unit 234 for supplying cooling air. The electrode plate formed by applying a slurry to the current collector may be moved through the roller 240.

Therefore, when the electrode current collector 10 coated with the slurry 30 enters through the inlet of the drying apparatus, heat is transmitted by the hot air supplied from the opposite wall. The wall 260 is preferably made of a heat insulator so as to prevent heat loss from being transferred to the inside through the heat energy.

 Hot air has a temperature of about 80 to 120 degrees Celsius. Slurry 30 of the initial electrode plate is brought into contact with the hot air is slightly lower temperature to reduce the evaporation of the internal solvent due to the surface hardening, and the slurry 30 of the discharge electrode plate is exposed to hot air of a higher temperature to the residual solvent To continue evaporation and discharge.

The blower 210 of the hot air supply device may be formed by installing a heater (not shown) for heating the air at an air outlet side of a general blower that supplies external air at a predetermined pressure by rotating a fan by a motor. A plurality of air pins 212 are installed in the air outlet 214, which is an air outlet of the blower, in parallel to control the direction of the hot air. The air fin 212 is inclined so as to pass through the slurry applied to the surface of the electrode current collector in a direction opposite to the direction in which the electrode current collector moves during the process while the hot air is slightly downward.

Since hot air has a relatively low specific gravity and rises slightly, the hot air flows almost parallel to the surface of the electrode current collector 10 on the surface of the slurry 30. In the process, the hot air raises the slurry temperature while transferring the retained heat to the slurry. The solvent in the slurry is vaporized by heat to be discharged out of the slurry in the form of steam, and at the same time, the solvent is included in the hot air air and moved together to be discharged out of the drying apparatus through the exhaust duct 220. Since the hot air rubs the surface of the slurry at a constant relative speed, the higher the relative speed, the lower the pressure, so that the evaporated solvent can be smoothly discharged from the slurry. In addition, the solvent component discharged out of the slurry 30 is continuously discharged out of the drying apparatus to lower the solvent partial pressure, thereby also helping the solvent to evaporate. On the other hand, in the state in which the infrared lamp 232 is arranged above the flow of the electrode plate hot air may serve to increase the temperature uniformity inside the drying apparatus according to the flow of air.

On the other hand, the back hot wind which improves the temperature uniformity inside a drying apparatus and supplies hot air through the back hot air supply nozzle 250 toward the back surface of the electrode plate in which the slurry to which it was dried was applied as a part of a means which supplies heat to a slurry. A supply device is also provided.

  The slurry also receives infrared light from infrared lamp 232. A plurality of infrared lamps are provided in rows, and may be arranged to maintain a predetermined distance and a distance from the electrode plate. In order to prevent overheating and breakage of the lamp, a case is installed around the air shower unit, and an air shower unit 234 for supplying cooling air is installed so that the infrared lamp 232 has a modular form.

In the embodiment of Fig. 3, a direct temperature sensor 321 for measuring the surface temperature of the slurry applied to the substrate is installed above the substrate, and an indirect temperature sensor 311 for measuring the ambient temperature in the air of the drying chamber in the interior space of the drying chamber. ) Is installed.

The direct temperature sensor may be attached to the infrared lamp module in the form of an infrared thermometer for measuring the amount of energy delivered to the substrate and the substrate temperature or the surface of the slurry. Direct contact of the sensor to the surface of the slurry is also undesirable for process quality, so various types of non-contact sensors can be used as direct temperature sensors.

Referring to the flowchart of FIG. 5 together, at the beginning of the slurry drying process, these sensors perform temperature measurement, and the temperature measurement results by these sensors are sent to the controller 330 via signal lines, and the controller is built-in. Program can detect the comparison with the appropriate temperature and the difference, and convert the power input to the heater of the infrared lamp module or the hot air supply through the signal lines (216,236) according to the value, and the temperature of the surface of the slurry or the temperature inside the drying chamber. Can change. This process is continuously performed during the period of time when the substrate is supplied into the drying chamber or during a predetermined time, and when the predetermined time elapses or when the substrate is not put into the drying chamber, the infrared lamp module or the hot air supply is activated by detecting it by a separate means. The process is finished.

While both the infrared lamp module and hot air supply contribute to the temperature of the slurry surface and the temperature inside the drying chamber, the infrared lamp module is highly thermally efficient and can make rapid temperature changes directly in the slurry, and the hot air supply indirectly It contributes a lot. Therefore, when the slurry surface temperature is higher or lower than the specified temperature, the power amount is first controlled through the controller supplied to the infrared lamp of the infrared lamp module, and when the drying chamber atmosphere temperature is higher or lower than the specified temperature, the heater of the hot air supply device is first applied. It is possible to use a method of adjusting the amount of power.

In this embodiment, the direct temperature sensor and the indirect temperature sensor are shown one by one, but each may be provided in plural. In this case, more delicate drying conditions can be temperature controlled. For example, by installing a direct temperature sensor for each lamp position, the drying efficiency is optimized by optimizing the drying conditions based on the slurry surface temperature which changes in real time from the wet state to the dry state based on the reference ambient temperature in the drying chamber. And drying speed.

As a specific method embodiment, a non-contact sensor and a thermocouple are installed in a combined drying chamber using both hot air and infrared rays to simultaneously measure the temperature of the atmosphere inside the drying chamber and the surface of the slurry. The slurry surface temperature is controlled through a temperature calculation algorithm that calculates the correlation between the slurry surface temperature and the ambient temperature. At the same time, the temperature of the atmosphere is raised (or cooled) by controlling the hot air temperature in order to suppress the increase in the surface temperature of the slurry due to the increase in the amount of heat through infrared rays.

On the other hand, in the embodiment of Figure 4 is provided with a signal line 238 for adjusting the output power for each lamp 232, a sensor (not shown) and a signal line 237 for detecting the operation of the lamp 232. If the controller has a means for detecting the amount of power input to the lamp, a separate motion detection sensor may not be necessary. In an embodiment having such a configuration, when any one of the lamps arranged in parallel with each other does not function during the process, the abnormality of the specific lamp is detected through the signal line 237, and the controller 330 ' By sending a signal to the alarm device, an alarm can be alarmed, and the amount of power that goes into the surrounding lamp can be increased to compensate for the amount of infrared radiation in the process to prevent process failure.

In the drying process, infrared light penetrates into the slurry and acts directly on the solvent, vibrating the solvent molecules, causing the solvent to evaporate by the heat. Thus, infrared lamp drying is highly efficient and also acts inside the slurry. As the lamps are arranged in all sections of the drying device, the solvent in the slurry continues to work with infrared light to evaporate and discharge out of the slurry while passing through the drying device. At this time, the cooling air of the infrared lamp may also serve as a kind of hot air.

As a result, the solvent of the slurry is energized by hot air and infrared light at the same time to be evaporated and discharged out of the slurry. Since the solvent is actively removed from the inside of the slurry mainly by the influence of infrared rays from the beginning of drying, unlike the high temperature hot air drying, the surface of the slurry is hardened and there is not much problem of preventing internal solvent discharge. In addition, the atmosphere in the drying apparatus can be adjusted to a constant temperature and pressure by the hot air, and the hot air acts to synergistically increase the slurry drying efficiency since the solvent component is smoothly moved out of the slurry and moved out of the drying apparatus. The hot air also acts to continuously remove the solvent components remaining in the slurry in the latter part of the drying apparatus, particularly from the slurry surface.

The slurry is dried in the inside and the surface layer, so that there is little residual solvent component within a short time, and there is no bias of the binder to maintain the active material layer on the surface of the current collector.

In order to smoothly discharge the hot air and the evaporated solvent in the drying apparatus, an exhaust fan having an appropriate capacity is usually installed. In the exhaust port 224 of the exhaust duct in which the hot air is sucked, there is a control plate 222 such as the air fin 212 of the blower 214, so that the exhaust flow can be adjusted to achieve a constant laminar flow and smoothly discharged.

According to the present invention, since the slurry temperature of the electrode plate and the drying chamber atmosphere temperature can be appropriately controlled at the same time, the quality of the secondary battery electrode made through the drying process can be increased, and the drying efficiency as well as the drying efficiency can be improved. .

In addition, according to one aspect of the invention, even if an error occurs in a part of the infrared lamp, the process can be prevented by adjusting the amount of infrared radiation while continuing without stopping the process, the problem is detected quickly, the next maintenance process is necessary It can be done immediately.

Claims (9)

A method of drying an electrode slurry of a secondary battery, comprising: applying an active material slurry containing a solvent to a current collector, and heating the electrode current collector to which the slurry is applied in a drying chamber space to remove the solvent. As the hot air is supplied to the electrode collector on which the slurry is applied, an infrared lamp irradiates infrared rays from above the slurry, An indirect temperature measurement for measuring the ambient temperature of the drying chamber and a direct temperature measurement for measuring the surface temperature of the slurry applied to the current collector are performed at the same time. The method of claim 1, The direct temperature measurement is an electrode slurry drying method of a secondary battery, characterized in that made by a non-contact temperature sensor. The method of claim 1, The results of the indirect temperature measurement and the direct temperature measurement are fed back to the operation of the module having the infrared lamp and the hot air fan to control the hot air by a predetermined program and used for managing the drying chamber atmosphere temperature and the slurry surface temperature. Electrode slurry drying method of a secondary battery. Drying chamber made to pass through the current collector with the slurry applied, Hot air supply device comprising a blower and a heater to supply hot air to the slurry, Infrared lamp module, An exhaust device configured to discharge vaporized solvent and the like out of the drying chamber, Direct electrode sensor for measuring the surface temperature of the slurry and an indirect temperature sensor for measuring the air temperature inside the drying chamber comprising the electrode slurry drying apparatus of a secondary battery. The method of claim 4, wherein The controller may further include a measurement result of the direct temperature sensor and the indirect temperature sensor. The controller is configured to process the measurement results of the direct temperature sensor and the indirect temperature sensor by a predetermined program to adjust the output of the hot air supply device and the infrared lamp module, the electrode slurry drying apparatus of the secondary battery . The method of claim 4, wherein The infrared lamp module is made of a plurality of individual infrared lamps are aligned, The electrode slurry drying apparatus of the secondary battery, characterized in that the controller for adjusting the infrared lamp module is made to detect the operation of the individual infrared lamp. The method of claim 6, Detection of the operation is made by a sensor installed for each individual infrared lamp, the sensor slurry drying apparatus of a secondary battery, characterized in that the sensor is connected by a signal line. The method of claim 6, The electrode slurry drying apparatus of the secondary battery, characterized in that the alarm device for warning the operation when the operation of the individual infrared lamp is not made. The method of claim 6, The controller of the secondary battery, characterized in that the controller to adjust the individual infrared lamp to increase the output of the other individual infrared lamp near the individual infrared lamp which is not operated when the operation of the individual infrared lamp is not made. Slurry drying apparatus.

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