KR101467640B1 - Method and apparatus for drying electrode - Google Patents

Abstract

The present invention provides an electrode drying method and an electrode drying apparatus capable of setting desirable drying conditions while grasping a continuous drying state of an electrode layer.
An electrode drying method for drying an electrode layer (40) formed by applying an electrode slurry (20) containing a solvent (21) to a current collecting foil (30) in a drying furnace (50) The drying reference value A1 or A2 defined by the trajectory of the evaporation amount of the solvent 21 is set in advance and the drying factor including the temperature, wind speed and solvent concentration in the drying furnace 50 is detected and based on the drying factor The heating section 80 and the drying furnace 50 which heat the inside of the drying furnace 50 so as to calculate the solvent evaporation amount M and follow the drying reference values A1 and A2, The electrode layer 40 is dried while controlling the blowing part 70.

Description

TECHNICAL FIELD [0001] The present invention relates to an electrode drying method,

The present invention relates to an electrode drying method and an electrode drying apparatus.

Lithium ion secondary batteries are widely used as power sources for automobiles and household electric appliances because they have a large storage density and maintain good storage performance even after repeated charging and discharging.

In the electrode forming process of a lithium ion secondary battery, first, an electrode layer is formed by applying an electrode slurry in a slurry state including a solvent on an electrode foil such as an aluminum foil of a positive electrode and a copper foil of a negative electrode at a constant weight. Subsequently, in the drying furnace, the solvent contained in the electrode layer is evaporated and dried to fix the solid portion of the electrode layer and the electrode foil. In the electrode drying step, hot air is sprayed to the electrode layer on the electrode foil in a drying furnace (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2006-107780

If the evaporation rate of the solvent in the electrode drying step is too high, the movement of the binder contained in the electrode slurry becomes remarkable along with the movement of the solvent in the electrode layer, and the binder is localized in the upper layer of the electrode layer. If such binder segregation occurs, the amount of the binder between the solid content of the electrode layer and the electrode foil is reduced, and the adhesion strength is lowered, the resistance value in the battery is increased, and the electrode performance is lowered.

Further, if the evaporation rate of the solvent in the electrode drying step is low, the adhesion strength is increased, but there is a possibility that the material is liable to occur in the material in the electrode slurry. As a result, the resistance value in the battery becomes high, .

Therefore, it is preferable to appropriately maintain the evaporation rate of the solvent. However, since the amount of the solvent in the electrode layer varies depending on the evaporation of the solvent, it is not easy to maintain the desired evaporation rate. Thus, for example, in Patent Document 1, the electrode drying process is divided into a plurality of regions according to the degree of drying, and the drying conditions (temperature and wind speed) in the respective regions are changed, .

However, in the method described in Patent Document 1, since the evaporation rate of the solvent can not be measured, the drying conditions are initially set based on experience and trial and error, and the set conditions are fixed. Therefore, the point of arrival of the dry state at the end of the electrode drying step in each region is defined, and the continuous dry state affecting the quality is not grasped.

An object of the present invention is to provide an electrode drying method and an electrode drying apparatus capable of setting desirable drying conditions while grasping a continuous drying state of an electrode layer.

The electrode drying method according to the present invention is an electrode drying method in which an electrode layer formed by applying an electrode slurry containing a solvent to a current collector is dried in a drying furnace. In the electrode drying method, a drying reference value defined by a locus of evaporation amount of a solvent from the electrode layer with respect to time is set in advance, a drying factor including a temperature, a wind speed and a solvent concentration in the drying furnace is detected, The amount of evaporation of the solvent is calculated. Then, the electrode layer is dried while controlling the heating section for heating the inside of the drying furnace and the blowing section for blowing air into the drying furnace such that the evaporation amount of the solvent follows the drying reference value.

According to the electrode drying method of the present invention, since the heating unit and the blowing unit are controlled so that the evaporation amount of the solvent calculated on the basis of the drying factor follows the drying reference value, it is possible to set the preferable drying condition .

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic configuration diagram showing an electrode drying apparatus according to an embodiment. Fig.
Fig. 2 is a schematic diagram showing a state in which the electrode layer is dried by the drying method of the embodiment. Fig.
3 is a schematic structural view showing one of the drying zones provided in the electrode drying apparatus according to the embodiment.
4 is a schematic sectional view along line 4-4 of Fig.
5 is a graph showing the amount of solvent evaporation relative to the passage time of the drying furnace.
6 is a graph showing the amount of solvent evaporation relative to the passage time of the drying furnace after changing the drying conditions.
FIG. 7 is a schematic sectional view showing a case where a solvent evaporated by the air discharged from a collecting nozzle is guided to a collecting tube. FIG. 7A shows a case where laminar flow is generated, and FIG. 7B shows a case where a vortex is generated .
8 is a schematic structural view showing one of the drying zones when the additional heating unit is operated.
9 is a schematic cross-sectional view showing another example of the solvent concentration detecting portion.
10 is a schematic structural view showing another example of the additional heating section.
11 is a schematic structural view showing still another example of the additional heating section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. The dimensional ratios in the drawings are exaggerated for convenience of explanation, and are different from actual ratios.

1 to 3, the electrode drying apparatus 10 includes an electrode layer 40 formed by applying an electrode slurry 20 including a solvent 21 to an electrode foil 30 (corresponding to a current collector) ) Is dried in the drying furnace (50). The electrode drying apparatus 10 includes a transfer section 60 for transferring the electrode foil 30 on which the electrode layer 40 is formed in the drying furnace 50 and a heating section A blowing unit 70 for blowing the heated air into the drying furnace 50 and an additional heating unit 90 different from the heating unit 80. The electrode drying apparatus 10 includes a plurality of measuring means and includes an electrode temperature detecting unit 100 for measuring the temperature of the electrode layer 40 and a wind speed detecting unit 110 for measuring the wind speed in the drying furnace 50, An in-furnace temperature detecting section 120 for measuring the atmospheric temperature in the furnace, and a solvent concentration detecting section 130 for measuring the concentration of the evaporated solvent. The constituent parts of the electrode drying apparatus 10 are controlled by the control unit 160 in a general manner. This will be described in detail below.

The electrode foil 30 is used as a current collector. The electrode foil 30 may be made of any suitable material, for example, aluminum, copper, nickel, iron, and stainless steel. Specifically, for example, an electrode foil 30 made of aluminum or the like may be used for the positive electrode current collector, and an electrode foil 30 made of copper or the like may be used for the negative electrode collector. The specific thickness of the electrode foil 30 is not particularly limited. For example, it is a thin film of about 20 占 퐉 for aluminum and about 10 占 퐉 for copper.

The electrode slurry 20 has a positive electrode slurry used for forming a positive electrode and a negative electrode slurry used for forming a negative electrode.

The positive electrode slurry has, for example, a positive electrode active material 22, a conductive auxiliary agent 24, and a binder 23, and a predetermined viscosity is obtained by adding the solvent 21. The positive electrode active material 22 is, for example, lithium manganese oxide. The conductive auxiliary agent 24 is, for example, acetylene black. The binder 23 is, for example, PVDF (polyvinylidene fluoride). The solvent 21 is, for example, NMP (normal methylpyrrolidone). The positive electrode active material 22 is not particularly limited to lithium manganese oxide, but it is preferable to use a lithium-transition metal composite oxide from the viewpoints of capacity and output characteristics. As the conductive auxiliary agent 24, carbon black or graphite may be used, for example. The binder 23 and the solvent 21 are not limited to PVDF and NMP. Water may also be used as the solvent (21).

The negative electrode slurry has, for example, a negative electrode active material 22, a conductive auxiliary agent 24, and a binder 23, and a predetermined viscosity is obtained by adding the solvent 21. The negative electrode active material 22 is, for example, graphite. The conductive auxiliary agent 24, the binder 23, and the solvent 21 are, for example, acetylene black, PVDF, and NMP. The negative electrode active material 22 is not particularly limited to graphite, and hard carbon or a lithium-transition metal composite oxide may be used. As the conductive auxiliary agent 24, carbon black or graphite may be used, for example. The binder 23 and the solvent 21 are not limited to PVDF and NMP. Water may also be used as the solvent (21).

The electrode layer 40 of the positive electrode formed by applying the positive electrode slurry to the electrode foil 30 and the negative electrode electrode layer 40 formed by applying the negative electrode slurry are dried in the drying furnace 50 to form the positive electrode and the negative electrode. At this time, the NMP as the solvent 21 contained in the electrode slurry 20 is removed from the electrode slurry 20 by evaporation.

The drying furnace 50 of the electrode drying apparatus 10 has a casing 140 which forms a hot air passage and a conveying path of the electrode foil 30. The drying furnace 50 is composed of drying zones 51 to 56 partitioned by a plurality (six in the illustrated example). For convenience of explanation, the first drying zone 51, the second drying zone 51, the second drying zone 51, the second drying zone 51, and the second drying zone 51 are sequentially (sequentially from the left in Fig. 1) from the upstream side in the direction of transporting the electrode foil 30 2 drying zone 52, the third drying zone 53, the fourth drying zone 54, the fifth drying zone 55, and the sixth drying zone 56, respectively. By providing the partition wall 141 in the casing 140, the first to sixth drying zones 51 to 56 are formed. An opening is formed in the end face of the casing 140 and in the partition wall 141 in order to arrange the carry section 60. Each of the first to sixth drying zones 51 to 56 is provided with an upper nozzle 142 for supplying hot wind from an upper position of the electrode foil 30 to be conveyed and a lower nozzle And an exhaust port 144 for discharging the exhaust gas from the inside of the drying zones 51 to 56 through the exhaust pipe 190 are provided.

The heating section 80, the blowing section 70, and the additional heating section 90 are provided for each of the drying zones 51 to 56. The electrode temperature detecting unit 100, the wind speed detecting unit 110, the furnace temperature detecting unit 120, and the solvent concentration detecting unit 130 are provided for each of the drying zones 51 to 56.

A hot air supply pipe 150 is connected to the upper nozzle 142 and the lower nozzle 143 and a heating unit 80 and a blower unit 70 are connected to the hot air supply pipe 150. The heating unit and the blowing unit 70 are connected to the control unit 160 so that the heating temperature and the blowing amount can be arbitrarily controlled. An air intake pipe 170 for introducing air from the outside and a circulation pipe 180 for reusing the air in the drying zones 51 to 56 are connected to the blowing unit 70 and installed in the circulation pipe 180 The air discharged from the circulation pipe 180 can be mixed with air from the intake pipe 170 at an arbitrary ratio and used again. By reusing the exhaust gas, mass production at low cost becomes possible.

The blowing-out portion 70 has a fan 71 for blowing air. The heating unit 80 is a heat exchanger and performs heat exchange between the heat medium (for example, steam or steam reflux water) to heat the air. The temperature of the hot air is not particularly limited because it varies in various ways depending on the environmental temperature and the kind of the electrode slurry 20. For example, it is 100 占 0 占 폚.

The additional heating section 90 includes an irradiation section 91 for irradiating the electrode layer 40 with infrared light from an upper position of the electrode foil 30 to be transported and a shutter 92 capable of covering the irradiation section 91. The shutter 92 can be opened and closed by a drive source such as a motor and the infrared ray from the irradiation unit 91 is not irradiated onto the electrode layer 40 in the closed state, (Depth direction of the paper surface of Figs. 1 and 3). (Hereinafter sometimes referred to as " width direction ") (see Fig. 8). The infrared ray irradiated through the slit 93 heats the electrode layer 40. At this time, a uniform irradiation rate is obtained in the direction (width direction) in which the slit 93 extends, In the conveying direction), the irradiation rate decreases in both directions with the central portion as a vertex.

The solvent concentration detecting unit 130 includes a collecting pipe 131 (exhaust path) for collecting the evaporated solvent, a collecting nozzle 132 for forming a flow toward the collecting pipe 131 in the drying furnace 50, And a solvent concentration meter 134 installed in the collecting pipe 131. The collecting tube 131 and the collecting nozzle 132 are disposed so as to face each other in the width direction so as to sandwich the electrode layer 40 therebetween. The collecting nozzle 132 is connected to the hot air supply pipe 150 having the valve 151 to discharge the heated air and form a flow of air along the upper surface of the electrode layer 40, ). The collecting pipe 131 guides the collected air to the exhaust pipe 190. The solvent concentration meter 134 detects the concentration of the solvent contained in the collected air, and transmits the detected signal to the control unit 160.

The electrode temperature detector 100 detects the temperature of the electrode layer 40 from a position spaced apart from the radiant thermometer and transmits the detected signal to the controller 160. [

The wind speed detection unit 110 detects the wind speed in the drying furnace and transmits the detected signal to the control unit 160. [

The in-furnace temperature detecting unit 120 detects an atmospheric temperature in the drying furnace 50 and transmits the detected signal to the control unit 160, for example, a thermocouple or a resistance thermometer.

The transport section 60 includes a supply roll 61 for supplying the electrode foil 30 before application of the electrode slurry 20 and a winding roll 62 for winding up the electrode foil 30 after drying the electrode layer 40 And a plurality of support rolls 63 that are disposed between the supply roll 61 and the winding roll 62 and hold the lower surface of the electrode foil 30. In the supply roll 61, the electrode foil 30 is wound beforehand. The winding roll 62 is connected to a motor M for driving the winding roll 62 to rotate. The electrode foil 30 is unwound from the supply roll 61 and is conveyed in the drying furnace 50 to be wound around the winding roll 62 do. In this way, the carry section 60 continuously transports the elongated electrode foil 30 by the roll-to-roll method.

The application of the electrode slurry 20 is performed by the application unit 145 while the electrode foil 30 is being conveyed. The application section 145 has a coater 146 for applying an electrode slurry 20 on the slurry containing the solvent 21 to the electrode foil 30. The coater 146 opposes the electrode foil 30 and applies the electrode slurry 20 intermittently while conveying the electrode foil 30. Thereby, the electrode slurry 20 is intermittently arranged with a gap of a constant interval. In the intermittent application method using the coater 146, the electrode slurry 20 is applied uniformly to the current collecting foil supplied in a roll-to-roll system at a thickness of about 30 to 300 mu m, and continuous production is performed.

The control unit 160 is configured mainly by a CPU and a memory, and a program for controlling the operation is stored in the memory. The control unit 160 controls the operation of the application unit 145 and adjusts the application amount and the coating thickness of the electrode slurry 20 and controls the heating unit 80 and the blowing unit 70, and adjusts the temperature, air flow rate, etc. of the supply air. The control unit 160 also controls the operation of the motor M and adjusts the conveying speed of the electrode foil 30.

The control unit 160 calculates the solvent evaporation amount M from signals transmitted from the solvent concentration detection unit 130, the in-furnace temperature detection unit 120, the wind speed detection unit 110, and the electrode temperature detection unit 100. That is, since the solvent evaporation amount M in the furnace is determined by the conditions of the solvent concentration in the atmosphere, the furnace temperature, the wind speed in the furnace, and the temperature of the electrode layer 40, And the solvent evaporation amount M, which is the total amount of the solvent 21 evaporated from the electrode layer 40, is calculated. The solvent evaporation amount M increases as the solvent concentration in the atmosphere is low, the furnace temperature is high, the wind speed in the furnace is fast, and the temperature of the electrode layer 40 is high. The solvent evaporation amount (M) based on these drying factors can be obtained experimentally.

5, the control unit 160 stores in advance a drying reference value A1 defined by the trajectory of the solvent evaporation amount with respect to time. The control unit 160 controls the heating unit 80, the additional heating unit 90, and the blowing unit 70 so that the solvent evaporation amount M calculated from the measured drying factor is always within the range of the drying reference value A1. Automatically. The solvent evaporation amount M increases as the heating amount by the heating unit 80 and the additional heating unit 90 is increased and the blowing amount by the blowing unit 70 is increased.

In this embodiment, the drying reference value A1 is defined as a band-shaped range in which the solvent evaporation amount has a width as shown in Fig. 5, but is defined as a line having no width, and the calculated evaporation amount of solvent (M) may be controlled so as to follow the line as much as possible. The drying reference value A1 is determined by an experiment or the like.

The drying reference value is provided in a plurality (two in this embodiment) depending on the time required for drying. FIG. 6 shows the drying reference value A2 when drying is performed for a longer time than the drying reference value A1 shown in FIG.

Before describing the operation of the present embodiment, a problem that occurs when the temperature and the air flow rate of the supply air supplied to the drying furnace 50 are not appropriate will be described.

In order to improve the drying speed in the drying furnace 50 using hot air, the hot air temperature is increased and the air volume is increased, and the amount of the solvent in the interface portion between the surface of the electrode layer 40 and the atmosphere 57 (21) (NMP) is increased. In such a case, drying is accelerated and the binder 23 (PVDF) segregates near the surface of the electrode layer 40. This makes it impossible to obtain a coating film strongly adhered to the electrode foil 30, that is, the electrode layer 40 with a strong adhesion.

The reason why the binder 23 segregates when the hot air temperature is increased is as follows. That is, since the electrode layer 40 contains the binder 23 dissolved in the solvent 21 at the time of drying, if the electrode layer 40 is exposed under a high temperature environment, It causes convection itself. As a result, the binder 23 which is dissolved is segregated.

Further, as the cause of segregation of the binder 23 when the air volume is increased, the following can be cited. That is, only the solvent 21 (NMP) in the vicinity of the surface of the electrode layer 40 is preferentially evaporated and only the vicinity of the surface is dried first (front surface drying), and the surface of the capillary By the development, the NMP is sucked from the deep portion toward the surface. As a result, the binder 23 that is dissolved becomes segregated.

The contact amount or the contact area between the electrode foil 30 and the electrode layer 40 is reduced because the surface roughness is large and the adhesion force is weak under the drying conditions that can cause segregation of the binder 23 at the time of drying. As a result, not only the resistance value in the battery at the initial stage but also the resistance value in the battery after repetition of charging and discharging increases, resulting in deterioration of electrode performance.

To solve segregation of the resulting binder 23, there is a method of compressing the dried electrode by a roll press machine or the like. However, since the drying is completed and the structure is forcibly changed after the electrode layer 40 is fixed, the adhesion strength of the electrode layer 40 is not improved so much. In addition, from the viewpoint of realizing mass production at low cost, it is preferable to avoid adding a compression step after the drying step.

Next, the operation of the present embodiment will be described.

The motor M is driven to rotate the winding roll 62 and the electrode foil 30 is unwound from the supply roll 61 and wound around the winding roll 62. [ The coater 146 intermittently applies the electrode slurry 20 to the surface of the moving electrode foil 30. The control unit 160 controls the operation of the application unit 145 to adjust the application amount of the electrode slurry 20, the coating thickness, and the like. The heating section 80 and the blowing section 70 supply hot air from the upper and lower nozzles 142 and 143 into the hot air passage. The electrode slurry 20 containing the solvent 21 is coated on the surface of the electrode foil 30 and the electrode layer 40 is successively transferred from the first drying zone 51 to the sixth drying zone 56, The solvent 21 contained in the electrode layer 40 is evaporated in the drying furnace 50 of each of the drying zones 51 to 56.

In each drying furnace 50, heated air supplied from the hot air supply pipe 150 is discharged from the collecting nozzle 132 to form a flow of air along the upper surface of the electrode layer 40 , And introduces air into the collecting pipe (131). As shown in Fig. 7A, the flow of air can be made into a laminar flow along the electrode layer 40, or a swirling state with linearity as shown in Fig. 7B, for example. have. The collection pipe 131 guides the collected air to the solvent concentration meter 134, and then discharges the air to the exhaust pipe 190. By providing the collecting nozzle 132 and the collecting tube 131 in this manner, the solvent evaporated from the electrode layer 40 can be effectively collected and the vicinity of the electrode layer 40, which affects the evaporation of the solvent 21 Can be accurately measured by the solvent concentration meter 134.

The solvent concentration detection unit 130, the in-furnace temperature detection unit 120, the wind speed detection unit 110 and the electrode temperature detection unit 100 in the drying zones 51 to 56 determine the solvent concentration in the atmosphere, The temperature in the furnace, and the temperature of the electrode layer 40 in that order, and transmits the detected signal to the control unit 160. The control unit 160 sequentially calculates the solvent evaporation amount M from the electrode layer 40 during transportation from the received signal. Since the solvent evaporation amount M in the drying furnace 50 is determined by the conditions of the solvent concentration in the atmosphere, the furnace temperature, the wind speed in the furnace, and the temperature of the electrode layer 40, The evaporation amount M of the solvent evaporated from the electrode layer 40 can be calculated. Further, it is also possible to approximate the temperature in the furnace and the temperature of the electrode layer 40 to approximately the same value, and use it in the calculation of the evaporation amount M of the solvent.

The control unit 160 controls the heating unit 80 and the blowing unit 70 so that the solvent evaporation amount M calculated from the measured drying factor is always contained within the range of the predetermined drying reference value A1 Adjust automatically.

The electrode layer 40 is successively transferred from the first drying zone 51 to the sixth drying zone 56 and the amount of solvent evaporated from the drying furnace 50 in each drying zone 51 to 56 M) is always contained within the range of the predetermined drying reference value A1, the solvent 21 contained in the electrode layer 40 is evaporated. Thus, by constantly monitoring the solvent concentration in the atmosphere, the furnace temperature, the wind speed in the furnace, and the temperature of the electrode layer 40 in the atmosphere as the drying factor and adjusting the solvent evaporation amount M within the drying reference value A1, The desired solvent evaporation amount M can be maintained so as to follow the changing drying reference value A1. As a result, it is possible to stably produce an electrode having strong peeling strength and high performance.

If it is necessary to change the drying time, the drying reference value A1 is switched to another drying reference value A2 shown in Fig.

The electrode manufacturing process includes the steps of dispersing the solid content of the electrode slurry 20 in the solvent 21, applying the electrode slurry 20 to the electrode foil, drying the electrode slurry 20, And a step of cutting the electrode into a predetermined shape. By continuously performing these steps, the electrode exhibits a high production rate. However, each process has its own production rate, and between the processes, latency and cleaning time associated with the delivery of the material or product occur. However, it is preferable that the electrode drying apparatus 10 has a capability of absorbing an increase / decrease of the production time without stopping the electrode drying apparatus 10 because it takes time to restart the electrode drying apparatus 10 once it is stopped. By providing a plurality of drying reference values A1 and A2 having different drying times, it is possible to freely change the drying time, thereby making it possible to absorb increase or decrease in the production time between before and after the drying step.

Therefore, for example, when replacing the container of the electrode slurry 20 supplied in a predetermined amount by putting it in a container, the electrode drying apparatus 10 is switched to the drying reference value A2 without stopping, Can change the time to earn the time to exchange the container.

After switching to the drying reference value A2, the control unit 160 controls the motor M to change the conveying speed.

The control unit 160 controls the heating unit 80 and the blowing unit 70 so that the solvent evaporation amount M calculated from the measured drying factor is always contained within the range of the predetermined drying reference value A2 And adjust it automatically. The electrode layer 40 is successively transferred from the first drying zone 51 to the sixth drying zone 56 and the amount of solvent evaporated from the drying furnace 50 in each drying zone 51 to 56 M) is evaporated so that the solvent 21 contained in the electrode layer 40 is always accommodated within the range of the changed drying reference value A2.

When it is necessary to raise the furnace temperature in one of the drying zones 51 to 56 in accordance with the switching to the drying reference value A2, the heating by the heating section 80 is performed by the drying furnace 50 , The additional heating section 90 is also operated while raising the amount of heating by the heating section 80. As a result, The additional heating section 90 operates the irradiation section 91 with the shutter 92 closed so that the shutter 92 is opened and the electrode layer 40 is rapidly heated can do. When the shutter 92 is opened, the infrared rays are irradiated from the slit 93. At this time, since the irradiation rate is uniform in the extending direction (width direction) of the slit 93, It can be uniformly heated. Since the infrared ray radiated from the slit 93 reduces the irradiation rate in both directions (the upstream direction and the downstream direction in the transport direction) with the central portion as the apex in the direction of gap (transport direction) of the slit 93, When the electrode layer 40 moving in the carrying direction enters the irradiation range of the infrared ray, it is not rapidly heated and the drying of the solvent can be maintained well. Thereafter, as the temperature in the drying furnace 50 is entirely raised by the heating by the heating unit 80, the amount of heating by the additional heating unit 90 is reduced, and finally the additional heating unit 90 is stopped .

Thus, by constantly monitoring the solvent concentration in the drying agent, the furnace temperature, the wind speed in the furnace, and the temperature of the electrode layer 40, and adjusting the solvent evaporation amount M within the drying reference value A2, , It is possible to maintain the preferable solvent evaporation amount (M) so as to follow the drying reference value (A2). Therefore, it is possible to maintain the desirable dry state at all times, and therefore it is possible to prevent the occurrence of segregation of the binder 23. The adhesion between the electrode foil 30 and the electrode layer 40 is improved and the amount of contact between the electrode foil 30 and the electrode layer 40 Or the contact area is sufficiently large. As a result, not only the resistance value in the battery at the initial stage, but also the resistance value in the battery after repetition of charging and discharging are lowered, and the electrode performance can be improved.

When the replacement of the container of the electrode slurry 20 is completed, the electrode is returned to the original drying reference value A1 having a shorter drying time (faster drying speed), and drying of the electrode is performed. At this time, when it is necessary to raise the furnace temperature in any of the drying zones 51 to 56, the heating amount by the heating unit 80 is increased and the additional heating unit 90 is operated . As the temperature in the drying furnace 50 is entirely raised by the heating by the heating unit 80, the amount of heating by the additional heating unit 90 is reduced, and finally the additional heating unit 90 is stopped .

<Experimental Example>

Drying experiments were carried out at a conveying speed of 0.5X (m / min) using a drying furnace having a length X (m) in the conveying direction in the furnace. The drying furnace is divided into a plurality of drying zones, and the temperature and wind speed can be individually set for each drying zone. In each of the drying zones, a solvent concentration detecting section, an in-furnace temperature detecting section, a wind speed detecting section and an electrode temperature detecting section were provided and the solvent concentration in the atmosphere, the furnace temperature, the wind speed in the furnace and the temperature of the electrode layer were monitored and recorded. Then, the solvent evaporation amount was calculated based on the measured drying factor, and the locus of the time variation of the solvent evaporation amount was obtained. At this time, the equipment conditions were changed so as to change the drying factor, and traces of time variation of the evaporation amounts of a plurality of solvents were obtained as shown in Experimental Examples 1 to 5 in Table 1. Then, an electrode was manufactured under the conditions of Experimental Examples 1 to 5, and the peel strength and the resistance value in the battery after charging and discharging were repeated 100 times were evaluated. The results are shown in Table 1.

As a result, in Experimental Examples 1 and 5, the peel strength was low and the resistance value was high, so that the quality as a battery was not satisfied. On the other hand, in Experimental Examples 2 to 4, the peel strength was high and the resistance value was low, so that the quality as a battery was satisfied. Thus, it was possible to obtain a plurality of traces of the amount of solvent evaporation, in which the battery to be manufactured exhibited good performance. Therefore, it became possible to set the drying reference value for establishing the quality of the battery in the range of the conditions of Experimental Examples 2 to 4.

Subsequently, the same drying furnace was used to conduct the drying test at a conveying speed of 0.25X (m / min) which is half of the above-mentioned experiment. The drying conditions were the same as those in the experiment except for the conveying speed. Then, the temperature and wind speed were controlled for each drying zone so that the amount of solvent evaporation in each drying zone was the same as in Experimental Examples 1 to 5, and the results of Experimental Examples 6 to 10 were obtained. That is, in Experimental Examples 6 to 10, the locus of the solvent evaporation amount obtained from Experimental Examples 1 to 5 was used as a drying reference value to produce an electrode. The results are shown in Table 2.

As a result, in Experimental Example 6 and Experimental Example 10 corresponding to Experimental Example 1 and Experimental Example 5, the peel strength was low and the resistance value was high, so that the quality as a battery was not satisfied. On the other hand, in Examples 7 to 9 corresponding to Experimental Examples 2 to 4, the peeling strength was high and the resistance value was low, thereby satisfying the quality of the battery. As described above, it was confirmed that a desirable electrode can be obtained by using the drying reference value at which the quality is established even when the conveying speed changes and the time passing through each drying zone in the furnace changes.

As described above, according to the present embodiment, the drying reference values A1 and A2 defined by the locus of the evaporation amount of the solvent 21 from the electrode layer 40 with respect to time are set in advance, , The wind speed and the solvent concentration, and calculates the solvent evaporation amount (M) based on the drying factor. The electrode layer 40 is dried while controlling the heating section 80 and the blowing section 70 so that the solvent evaporation amount M follows the drying reference values A1 and A2. Therefore, desirable drying conditions can be set while grasping the continuous drying state of the electrode layer 40. This makes it possible to prevent the binder 23 from segregating because the electrode layer 40 is dried under the preferable drying conditions continuously provided. The adhesion between the electrode foil 30 and the electrode layer 40 is improved and the resistance value in the battery at the initial stage is increased as well as the charge / The resistance value in the battery after the repetition of the above-described steps is also lowered, and it is possible to improve the electrode performance.

When the drying time for holding the electrode layer 40 in the drying furnace 50 is changed, the evaporation amount M of the solvent calculated on the basis of the drying factor is changed from a predetermined drying reference value A1 corresponding to the drying time after the change , And A2, the heating unit 80 and the blowing unit 70 are controlled. Therefore, it is possible to freely change the drying time, and it becomes possible to absorb increase or decrease in the production time between before and after the process.

The electrode layer 40 is heated using the additional heating portion 90 other than the heating portion 80 in addition to the heating portion 80 when the drying time for holding the electrode layer 40 in the drying furnace 50 is changed do. As a result, the electrode layer 40 can be rapidly heated, and the operation can be rapidly performed under the changed drying conditions.

When the drying time for holding the electrode layer 40 in the drying furnace 50 is changed, the additional heating portion 90 is operated while increasing the heating amount by the heating portion 80, and then the additional heating portion 90 ) Is gradually reduced. As a result, the heating by the additional heating section 90 can be reduced as the heating by the heating section 80 becomes effective after quickly coping with the changed drying conditions by using the additional heating section 90, It is possible to maintain desirable drying conditions.

A dedicated collecting pipe 131 (exhaust path) for discharging the solvent 21 evaporated from the electrode layer 40 is provided and the solvent concentration detecting unit 130 is disposed in the collecting pipe 131 to detect the concentration of the solvent do. This makes it possible to effectively collect the solvent 21 evaporated from the electrode layer 40 and more accurately detect the concentration of the solvent in the vicinity of the electrode layer 40 that affects the evaporation of the solvent 21. [

Since the flow of the fluid toward the dedicated collecting pipe 131 (exhaust path) is generated in the drying furnace 50 and the solvent 21 evaporated in the collecting pipe 131 is guided, Can be effectively collected.

A collecting nozzle 132 for generating a flow of the fluid toward the dedicated collecting pipe 131 (exhaust path) is provided and the solvent 21 evaporated to the collecting pipe 131 by the collecting nozzle 132 The desired flow can be easily formed, and the vaporized solvent 21 can be collected more effectively.

(Modification example)

The embodiment has been described in which the inside of the drying furnace 50 is divided into a plurality of (six) drying zones 51 to 56. However, the present invention can be applied to a drying furnace having only one drying zone, .

Since the drying speed is likely to rise sharply only within the irradiation range when the irradiation range of the infrared ray is linear, the additional heating section 90 sets the infrared ray transmittance so that the irradiation rate gradually changes toward the carrying direction of the electrode layer 40 The infrared ray may be irradiated through the infrared ray reflecting film. Alternatively, as the material constituting the shutter 92, an infrared reflective film may be used.

9, the solvent concentration detecting portions 200 and 201 may be provided at a plurality of positions in the drying furnace 50 where the distance from the electrode layer 40 is different from each other, May be disposed. At this time, the solvent concentration detecting section 200 is located above the gas-liquid boundary layer formed above the electrode layer 40, and the solvent concentration detecting section 201 is located below the gas-liquid boundary layer of the electrode layer 40. Thus, by accurately averaging the detection results by the plurality of solvent concentration detection units 200 and 201, it is possible to calculate the accurate solvent evaporation amount M without depending on the deviation of the concentration of the solvent depending on the place. It is of course possible to use only one solvent concentration detection section which is not provided in the collection tube.

Further, the additional heating unit is not limited to the configuration for irradiating infrared rays. 10, the support roll 211 is provided with a heating source 212 for heating the support roll 211 itself and a support roll 211 by circulating the coolant in the support roll 211. [ The heating unit 210 may be provided with a cooling unit 213 for cooling the heating unit 210. The configuration of the heating source 212 is not limited as long as it can be heated, and for example, an electric heating line, an infrared ray, a heat exchanger, or an electromagnetic induction heating can be used. With this configuration, the electrode layer 40 can be heated through the electrode foil 30 directly contacting the support roll 211. [ Further, by providing the cooling means 213, when the heating by the additional heating portion 210 becomes unnecessary, the support roll 211 can be cooled quickly, and the followability to a desired temperature is improved. When the electromagnetic induction heating is used for the heating source 212, the metal foil 30 may be heated directly instead of heating the support roll 211. [

11, an additional heating unit 220 installed in parallel with the heating unit 80 and heating the air blown into the drying furnace 50 may be provided in the same manner as the heating unit 80 . The additional heating unit 220 can switch supply and stop of hot air to the hot air supply pipe 150 by opening and closing the valve 221 by the control unit 160. [

Further, the drying zones 51 to 56 are provided with additional heating sections 90 of the same configuration, but additional drying sections having different configurations may be provided in the drying zones 51 to 56, respectively.

Although the electrode foil 30 is continuously transported, it may be transported in a batch manner.

Further, the present invention is not limited to the case where the electrode slurry 20 is intermittently applied, and it goes without saying that the present invention is also applicable to the case where the electrode slurry 20 is continuously applied.

10: Electrode drying device
20: Electrode slurry
21: Solvent
40: electrode layer
50: drying furnace
51 to 56: first to second drying zones,
60:
70:
80:
90, 210: additional heating section
100: electrode temperature detector
110:
120: No-temperature sensor
130, 200, 201: solvent concentration detector
131: Collecting pipe (dedicated exhaust path)
132: collecting nozzle
134: solvent concentration meter
145:
160:
A1, A2: Drying reference value
M: Solvent Evaporation Rate

Claims (15)

An electrode drying method for drying an electrode layer formed by applying an electrode slurry containing a solvent to a current collector in a drying furnace,
A drying reference value defined by the trajectory of the evaporation amount of the solvent from the electrode layer with respect to time is previously set and a drying factor including the temperature, the wind speed, the solvent concentration, and the temperature of the electrode layer in the drying furnace is detected, And drying the electrode layer while controlling a heating unit for heating the inside of the drying furnace and an air blowing unit for blowing air into the drying furnace so as to calculate the evaporation amount of the solvent so that the evaporation amount of the solvent follows the drying standard value . The method according to claim 1,
Wherein when the drying time for holding the electrode layer in the drying furnace is changed, the evaporation amount of the solvent calculated on the basis of the drying factor is controlled so as to follow a predetermined drying reference value corresponding to the drying time after the change, And the air blowing section. 3. The method according to claim 1 or 2,
Wherein when the drying time for holding the electrode layer is changed in the drying furnace, the electrode layer is heated by using an additional heating section different from the heating section in addition to the heating section. The method of claim 3,
Wherein when the drying time for holding the electrode layer is changed in the drying furnace, an amount of heating by the additional heating portion is gradually reduced after the additional heating portion is operated while increasing the heating amount by the heating portion, Drying method. 3. The method according to claim 1 or 2,
Wherein a dedicated exhaust path for exhausting the solvent evaporated from the electrode layer is provided and a solvent concentration detecting section for detecting the concentration of the solvent is disposed in the exhaust path to detect the concentration of the solvent. 6. The method of claim 5,
Wherein a flow of fluid toward the dedicated exhaust path is generated in the drying furnace to induce the solvent evaporated in the dedicated exhaust path. The method according to claim 6,
Wherein a collecting nozzle for generating a flow of the fluid toward the dedicated exhaust path is provided and the solvent vaporized by the dedicated exhaust path is guided by the collecting nozzle. 3. The method according to claim 1 or 2,
Wherein a solvent concentration detecting section for detecting the concentration of a solvent evaporated from the electrode layer is disposed at a plurality of positions different in distance from the electrode layer in the drying furnace and a concentration of the solvent is calculated by averaging a plurality of detection results, Way. An electrode drying apparatus for drying an electrode layer formed by applying an electrode slurry containing a solvent on a current collector in a drying furnace,
An in-furnace temperature detector for detecting a temperature in the drying furnace,
A wind speed detection unit for detecting the wind speed in the drying furnace,
A solvent concentration detecting section for detecting a solvent concentration of the atmosphere in the drying furnace;
An electrode temperature detector for measuring the temperature of the electrode layer,
A heating unit for heating the inside of the drying furnace,
A blowing section for blowing air into the drying furnace,
And a controller for receiving a signal detected from the in-furnace temperature detector, the wind speed detector, the solvent concentration detector, and the electrode temperature detector, calculating the evaporation amount of the solvent on the basis of the detected value, And a control section for controlling the heating section and the blowing section so as to follow a predetermined drying reference value defined by the trajectory of the evaporation amount of the solvent of the drying section. 10. The method of claim 9,
And the electrode temperature detection section, the control section controls the drying time of the electrode layer in the drying furnace so as to change the drying time of the electrode layer in the drying furnace, To control the heating unit and the blowing unit so as to follow a predetermined drying reference value corresponding to the drying time after the change. 11. The method according to claim 9 or 10,
And an additional heating unit different from the heating unit,
And the control section operates the additional heating section in addition to the heating section when the drying time for holding the electrode layer in the drying furnace is changed. The method of claim 11, wherein
Wherein the control unit controls the heating unit to increase the amount of heating by the heating unit and to gradually decrease the heating amount by the additional heating unit when the drying time for holding the electrode layer in the drying furnace is changed, The electrode drying device. 11. The method according to claim 9 or 10,
And an exhaust path dedicated for exhausting the solvent evaporated from the electrode layer, in which the solvent concentration detecting section is disposed. 14. The method of claim 13,
And a collecting nozzle for generating a flow of the fluid toward the dedicated exhaust path. 11. The method according to claim 9 or 10,
Wherein the solvent concentration detecting section is provided at a plurality of locations in the drying furnace where the distance from the electrode layer is different.

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