KR101550487B1 - Method for drying electrode and apparatus for drying electrode - Google Patents

Abstract

An object of the present invention is to provide an electrode drying method and an electrode drying apparatus capable of efficiently evaporating a solvent contained in an electrode layer in a slurry state without reducing the electrode performance and shortening the drying time .
The electrode drying apparatus 10 dries the electrode layer 40 formed by applying the electrode slurry 20 containing the solvent 21 to the electrode foil 30 in the drying furnace 50. The electrode drying apparatus includes an evaporation speed adjusting member 70 for reducing the concentration difference between the solvent concentration remaining in the electrode layer and the solvent concentration in the atmosphere 57 in the drying furnace by increasing the solvent concentration in the atmosphere, And a heater unit 80 for applying heat to dry the substrate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [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 high storage density and maintain good storage performance even when they are repeatedly charged and discharged.

In the process of forming the electrode of the lithium ion secondary battery, firstly, a slurry-like electrode slurry containing a solvent is applied to the electrode foil such as the aluminum foil of the positive electrode (positive electrode) and the copper foil of the negative electrode . Next, during the drying furnace of the electrode drying apparatus, the solvent contained in the electrode layer is volatilized and dried to fix the solid portion of the electrode layer and the electrode foil.

In the electrode drying step, hot air is sprayed from the upper and lower surfaces of the electrode foil in the drying furnace (see, for example, Patent Documents 1 and 2). The main conditions of the drying conditions in the case of hot air are the temperature of hot air, the amount of hot air spray, and the drying time.

Japanese Patent Application Laid-Open No. 2003-272612 Japanese Patent Application Laid-Open No. 2006-73234

In order to increase the productivity of the electrode, it is required to reduce the drying time of the electrode drying apparatus. For such a request, if the drying conditions (the temperature of the hot air in the case of hot air and the amount of hot air blowing) are changed greatly, the fine structure inside the electrode may be influenced and the electrode performance may be lowered. The drying conditions must be changed within a range that does not cause deterioration of the electrode performance. Therefore, effective measures can not be taken against shortening of the drying time.

The reason for influencing the microstructure of the inside of the electrode is that when the drying temperature is increased or the amount of hot air is increased, the rate of volatilization of the solvent on the surface and the rate of diffusion of the solvent from the deep portion The larger the difference is, and the binder in the electrode slurry is segregated. If such binder segregation occurs, sufficient adhesion between the electrode foil and the electrode layer as a coating film can not be obtained. If a strong adhesion coating film can not be obtained, not only the resistance value in the battery at the initial stage but also the resistance value in the battery after repeated charging and discharging increases, resulting in deterioration of the electrode performance.

Accordingly, an object of the present invention is to provide an electrode drying method and an electrode drying apparatus capable of efficiently evaporating a solvent contained in an electrode layer in a slurry state without causing deterioration of electrode performance and shortening a drying time I have to.

An electrode drying method for achieving the above object is a 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. The electrode layer is dried by applying heat while reducing the concentration difference between the solvent remaining in the electrode layer and the solvent concentration in the atmosphere (air) in the drying furnace by increasing the solvent concentration in the atmosphere .

An electrode drying apparatus for achieving the above object is an electrode drying apparatus for drying an electrode layer formed by applying an electrode slurry containing a solvent to a current collector in a drying furnace. The electrode drying apparatus includes an evaporation rate adjusting member for reducing the concentration difference between the solvent concentration remaining in the electrode layer and the solvent concentration in the atmosphere in the drying furnace by increasing the solvent concentration in the atmosphere, And a heater unit for applying heat to the heater.

According to the present invention, since the difference in the concentration of the solvent remaining in the electrode layer and the concentration of the solvent in the atmosphere in the drying furnace is reduced by increasing the solvent concentration in the atmosphere, heat is applied to dry the electrode layer, It is possible to prevent the occurrence of segregation of the binder by drying slowly. The adhesion between the current collector and the electrode layer is improved and the resistance value in the battery after repeated charging and discharging is lowered as well as the resistance value in the battery at the initial stage, Can be improved. Accordingly, it is possible to provide an electrode drying method and an electrode drying apparatus capable of efficiently volatilizing a solvent contained in an electrode layer in a slurry state without shortening the electrode performance and shortening the drying time.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic structural view showing an electrode drying apparatus according to an embodiment; Fig.
2 is a schematic diagram showing a state in which an electrode layer is dried by the drying method of the embodiment;
3 is a schematic diagram showing a state in which an electrode layer is dried by a drying method of a contrast example.
4 is a graph showing changes in the NMP vapor concentration in the furnace in each of the embodiment in which the electrode layer is dried while increasing the solvent concentration in the atmosphere and the comparative example in which the electrode layer is dried without increasing the solvent concentration in the atmosphere .

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 differ from actual ratios.

1 and 2, the electrode drying apparatus 10 includes an electrode layer (electrode) 30 formed by applying an electrode slurry 20 containing a solvent 21 to an electrode foil 30 (corresponding to a current collector) 40 are dried in the drying furnace 50. The electrode drying apparatus 10 includes a transfer section 60 for transferring the electrode foil 30 in which the electrode layer 40 is formed in the drying furnace 50 and a transfer section 60 for transferring the solvent concentration remaining in the electrode layer 40 to the drying furnace An evaporation speed adjusting member 70 for reducing the concentration difference of the solvent concentration in the atmosphere 57 in the atmosphere 57 by decreasing the solvent concentration in the atmosphere 57, And a heater portion 80 for heating the heater. The heater unit 80 uses hot air as a heat source. The difference between the concentration of the solvent remaining in the electrode layer 40 and the concentration of the solvent in the atmosphere 57 in the drying furnace 50 is reduced by increasing the concentration of the solvent in the atmosphere 57, The electrode layer 40 is dried. Hereinafter, this will be described in detail.

The electrode foil 30 is used as a current collector. The electrode foil 30 may be made of a suitable material, for example, aluminum, copper, nickel, iron, or stainless steel. Specifically, for example, an electrode foil 30 made of aluminum or the like is used for the positive electrode current collector, and an electrode foil 30 made of copper or the like is used for the negative electrode collector. There is no particular limitation on the specific thickness of the electrode foil 30, but it is, for example, 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 manganate. 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 in view of capacity and output characteristics. As the conductive auxiliary agent 24, for example, carbon black or graphite may be used. 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, for example, carbon black or graphite may be used. 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 volatilization.

The drying furnace 50 of the electrode drying apparatus 10 has a casing 90 for forming a hot air passage and a conveying path for the electrode foil 30. The drying furnace 50 is constituted by drying zones 51 to 56 partitioned into a plurality (six in the illustrated example). For each of the drying zones 51 to 56, the evaporation speed adjusting member 70 and the heater unit 80 are provided. The first drying zone 51, the second drying zone 52, and the third drying zone 53 (in this order from the left side in Fig. 1) in order from the upstream side in the direction in which the electrode foil 30 is conveyed The fourth drying zone 54, the fifth drying zone 55 and the sixth drying zone 56, respectively. By providing the partition wall 91 in the casing 90, the first to sixth drying zones 51 to 56 are formed. An opening is formed in the end surface of the casing 90 and in the partition wall 91 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 92 for supplying hot wind from an upper position of the electrode foil 30 to be conveyed, And an exhaust port 94 for exhausting the inside of the drying zones 51 to 56 are formed. The upper nozzle 92, the lower nozzle 93 and the exhaust port 94 are set to positions where the hot air flows uniformly in the passage by stirring the hot air in the drying zones 51 to 56.

The evaporation speed adjusting member 70 in the illustrated example is provided with a piping system 100 for supplying the exhaust gas discharged from the drying furnace 50 into the atmosphere 57. And the exhaust gas discharged from the drying furnace 50 is reused to increase the solvent concentration in the atmosphere 57. The evaporation speed adjusting member 70 also supplies the inside of the atmosphere 57 without lowering the temperature of the exhaust to the dew condensation temperature. Since the exhaust gas is reused, mass production can be realized at a low cost.

The piping system 100 is provided with a first piping 101 for connecting the respective exhaust ports 94 and the solvent recovery apparatus 110, a heat exchanger 120 formed for each outlet of the solvent recovery apparatus 110 and the drying zones 51 to 56, A third pipe 103 for connecting the outlet of the heat exchanger 105 to the upper and lower nozzles 92 and 93 and a third pipe 103 for bypassing the solvent recovery device 110 And a bypass pipe 104 for discharging the exhaust gas. The solvent recovery device 110 includes a solvent recovery device 111 and a blowing fan 112. The solvent recovery device 110 recovers excess NMP as a liquid and recovers a part of the recovered solvent 21 into the atmosphere 57 (Air supply). The bypass pipe 104 is provided with a heat exchanger 105 for exchanging heat with a heating medium (for example, steam or steam reflux water) to heat the air and a valve 106 for adjusting the amount of exhaust to be bypassed Is installed. The first pipe 101 is provided with a temperature sensor 107 for measuring the exhaust temperature at the inlet side of the solvent recovery apparatus 110 and the second pipe 102 is provided with a temperature sensor 107 for measuring the temperature of the exhaust gas at the outlet side of the solvent recovery apparatus 110 And a temperature sensor 108 for measuring the supply air temperature. The temperature sensor 108 on the outlet side measures the supply air temperature at a position after the bypass pipe 104 is joined to the second pipe 102. The second pipe 102 is provided with a concentration sensor 109 for measuring the solvent concentration of the supply air. The solvent recovery apparatus 110 controls the amount of the solvent to be mixed again with the supply air so that the solvent concentration of the supply air becomes a predetermined concentration.

The amount of exhaust air flowing down the bypass pipe 104 is controlled based on the measured supply air temperature so as to supply the exhaust air into the atmosphere 57 without lowering the temperature of the exhaust to the condensation temperature. Since exhaust discharged by bypassing the solvent recovery apparatus 110 is higher in temperature than air that has passed through the solvent recovery apparatus 110, the supply air temperature can be raised to keep the supply air temperature constant. The temperature of the supply air can be kept constant even when the supply air temperature is further lowered by heating the exhaust flowing down the bypass pipe 104 by the heat exchanger 105 provided in the bypass pipe 104. [ A special measure for preventing condensation in the piping system 100, for example, the placement of a heat insulating material, etc., is not required by supplying the exhaust gas into the atmosphere 57 without lowering the temperature of the exhaust to the dew condensation temperature. With this, it is possible to contribute to the reduction of the equipment cost.

The first to third pipes 101 to 103 are not provided with a damper flow. It is to prevent condensation.

The heat exchanger 120 provided for each of the drying zones 51 to 56 performs heat exchange with the heating medium (for example, steam or vapor reflux water) to heat the air. A temperature sensor 121 for measuring the temperature of the atmosphere 57 is provided for each of the drying zones 51 to 56. [ The temperature of the hot air blown out from the upper and lower nozzles 92 and 93 can be controlled by heating the supply air with each heat exchanger 120 so that the temperature of each drying zone 51 to 56 can be maintained at the set temperature. The temperature of the hot air differs depending on the environmental temperature, the type of the electrode slurry 20, and the like, and is not particularly limited, but is, for example, 100 占 폚 to 40 占 폚.

The solvent 21 contained in the exhaust gas to be reused and the solvent 21 volatilized from the electrode layer 40 are contained in the atmosphere 57 of each of the drying zones 51 to 56 during drying. The solvent concentration in the atmosphere 57 at the time of drying can be appropriately set. However, in order to obtain the electrode layer 40 having a strong adhesion, it is preferable to control the solvent concentration to be, for example, 1000 PPM or less.

The electrode layer 40 is dried until the residual NMP becomes 200 ppm or less. Since the use of steam as a heat source is an easily available heat source and the use of NMP (melting point -24 캜, boiling point 204 캜) is used for the solvent 21, continuous drying at a relatively low temperature of around 100 캜 is possible Because.

The evaporation speed adjusting member 70 is constituted by a piping system 100, a solvent recovery apparatus 110, and the like. The heater unit 80 is a member for adjusting the temperature and the flow rate of the heat medium supplied to the piping system 100, the solvent recovery apparatus 110, the heat exchangers 105 and 120 and the heat exchangers 105 and 120 And the like.

The transport section 60 includes a supply roll 61 for supplying the electrode foil 30 before applying the electrode slurry 20 and a winding roll 60 for winding the electrode foil 30 after drying the electrode layer 40 And a plurality of support rolls 63 which are disposed between the supply roll 61 and the winding roll 62 and which hold the lower surface of the electrode foil 30. In the supply roll 61, the electrode foil 30 is wound in advance. The winding roll 62 is connected to a motor M for driving the winding roll 62 to rotate. When the motor M is driven to rotate the winding roll 62, the electrode foil 30 is fed from the supply roll 61 and is conveyed in the drying furnace 50 to be wound around the winding roll 62 do. In this manner, 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 95 while the electrode foil 30 is being conveyed. The application unit 95 has a coater 96 for applying an electrode slurry 20 in a slurry state including the solvent 21 to the electrode foil 30. The coater 96 intermittently applies the electrode slurry 20 while conveying the electrode foil 30 against 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 96, a slurry having a viscosity of about 10,000 to 300,000 cps (solid content 63.4 ± 10%) is applied to the current collector supplied by the roll-to-roll method, A method of uniformly applying coatings on one side (Wet film thickness 130 占 10 占 퐉, Dry film thickness 87 占 10 占 퐉) and performing continuous production is general.

The electrode drying apparatus 10 includes a controller for controlling the operation of the solvent recovery apparatus 110, the valve 106 of the bypass pipe 104, the heater unit 80, the motor M and the application unit 95 130). The controller 130 is constituted mainly by a CPU and a memory, and a program for controlling the operation is stored in the memory. The controller 130 controls the operation of the application unit 95 to adjust the application amount and the coating thickness of the electrode slurry 20 and controls the operation of the heater unit 80 to adjust the temperature, Adjust. The controller 130 also controls the operation of the motor M to adjust the conveying speed of the electrode foil 30.

Before explaining 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 largely changed will be described.

As one of the quality indicators that change in the drying process, there is adhesion between the electrode layer 40 and the electrode foil 30. In general, in the drying process, it is known that the adhesion is improved by gradually evaporating the NMP as the solvent 21 and slowly drying the electrode layer 40 according to the following equations (1), (2) and (3).

3 is a diagram showing a problem that occurs when the temperature and the air flow rate of the supply air supplied to the drying furnace 50 are largely changed.

In order to improve the drying speed in the drying furnace 50 using hot air, the hot air temperature is increased and the air flow rate is increased so that the solvent [ 21 (NMP)]. In such a case, the drying is accelerated and the binder 23 (PVDF) is segregated near the surface of the electrode layer 40. This makes it impossible to obtain a coated film strongly adhered to the electrode foil 30, that is, the strongly adhered electrode layer 40.

The reason why the binder 23 segregates when the hot air temperature is raised is as follows. That is, when the electrode layer 40 is exposed to the environment at a high temperature, since the electrode layer 40 contains the binder 23 dissolved in the solvent 21 at the time of drying, the solvent 21 ) Itself causes convection. As a result, the dissolved binder 23 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 volatilized and only the vicinity of the surface is first dried (surface dry), and cracks By capillary phenomenon caused by holes and the like, NMP is sucked from the deep portion toward the surface. As a result, the dissolved binder 23 is 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 is weak under the drying conditions capable of causing 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 charge and discharge increases, resulting in deterioration of electrode performance.

In order 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 of the electrode layer 40 is forcibly changed after it is fixed, the adhesion strength of the electrode layer 40 is not improved so much. From the viewpoint of realizing mass production at low cost, it is desirable 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 fed out from the feeding roll 61 and wound around the winding roll 62. [ The coater 96 intermittently applies the electrode slurry 20 to the surface of the moving electrode foil 30. The controller 130 controls the operation of the application unit 95 to adjust the application amount of the electrode slurry 20, the coating thickness, and the like. The heater unit 80 supplies hot air from the upper and lower nozzles 92 and 93 into the hot air passage. The electrode slurry 20 containing the solvent 21 is coated on the surface of the electrode foil 30 and then the solvent 21 contained in the electrode layer 40 is volatilized in the drying furnace 50. [ While the electrode foil 30 is being conveyed, the application of the electrode slurry 20 and the drying of the coated electrode layer 40 are continued.

When the electrode layer 40 is dried in the drying furnace 50, the evaporation speed adjusting member 70 supplies the exhaust gas discharged from the drying furnace 50 into the atmosphere 57 through the piping system 100. The difference in the concentration of the solvent remaining in the electrode layer 40 and the concentration of the solvent in the atmosphere 57 in the drying furnace 50 becomes small as the solvent concentration in the atmosphere 57 increases. Further, the heater portion 80 applies heat to dry the electrode layer 40.

In this way, when the solvent concentration is increased in the atmosphere 57, the NMP as the solvent 21 is gradually evaporated to increase the airflow temperature and to increase the air flow rate in order to improve the drying speed, Can be slowly dried. Although the electrode layer 40 is gradually dried, since the hot air temperature can be increased and the air volume can be increased, the drying time can be shortened as a whole, and the productivity can be increased. The drying time can be shortened, so that the length of the drying furnace 50 can be shortened. Therefore, it is possible to reduce the investment required for drying the electrode.

It is necessary to increase the solvent concentration in the atmosphere 57 to a concentration not exceeding the solvent concentration remaining in the electrode layer 40. This is to avoid a state in which the drying of the electrode layer 40 does not proceed.

As shown in Fig. 2, since the electrode layer 40 is gradually dried, segregation of the binder 23 can be prevented. 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 is increased by the drying of the electrode layer 40 under the condition that the binder 23 is not segregated 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 repeated charging and discharging are lowered, and the electrode performance can be improved.

The evaporation speed adjusting member 70 and the heater unit 80 are provided for each of the first to sixth drying zones 51 to 56. Thus, the electrode layer 40 can be dried by applying heat while reducing the concentration difference by increasing the solvent concentration in the atmosphere 57 for each of the first to sixth drying zones 51 to 56. [ It is possible to prevent the occurrence of segregation of the binder 23 for each of the drying zones 51 to 56 even when it is divided into a plurality of drying zones 51 to 56 and it is possible to manufacture an electrode have.

The binder 23 does not segregate, so that it is not necessary to compress the dried electrode by a roll press machine or the like. It is not necessary to add a compression step after the drying step, so mass production can be realized at low cost.

4 shows an embodiment in which the electrode layer 40 is dried while increasing the solvent concentration in the atmosphere 57 and a comparative example in which the electrode layer 40 is dried without increasing the solvent concentration in the atmosphere 57 Fig. 5 is a graph showing changes in the NMP vapor concentration in the furnace. The abscissa represents the drying furnace passage time (sec), and the ordinate represents the NMP vapor concentration in the furnace. Further, the value of the present embodiment is obtained by subtracting the value obtained by increasing the solvent concentration in the atmosphere 57. In the drawings, the embodiments are shown by solid lines, and the contrast examples are shown by broken lines.

The first drying zone 51 is a preheating zone, and the solvent 21 is not volatilized from the electrode layer 40.

In the comparative example, in the second drying zone 52, the volatilization of the solvent 21 starts abruptly, and the NMP vapor concentration in the furnace is suddenly increased. In the third and fourth drying zones 53 and 54, fluctuations in NMP vapor concentration in the furnace are large. At the outlet of the fifth drying zone 55, the drying of the electrode layer 40 is almost completed, and the NMP vapor concentration in the furnace becomes zero.

In the embodiment, in the second drying zone 52, the change in the NMP vapor concentration in the furnace is gentler than that in the comparative example, and it is found that the drying of the electrode layer 40 is gradually started. In the third to fifth drying zones 53 to 55, fluctuation of the NMP vapor concentration in the furnace is relatively small and falls within the range of the solvent concentration range? C. It can be seen that the variation of the NMP vapor concentration in the furnace is more uniform than that in the comparative example, and the drying of the electrode layer 40 is progressing gradually. In the outlet portion of the sixth drying zone 56, the drying of the electrode layer 40 is almost completed, and the NMP vapor concentration in the furnace becomes zero.

The adhesion of the electrode layer 40 in the contrast example was NG level as a product, but the adhesion of the electrode layer 40 in the embodiment satisfied the OK level as a product.

The concentration of the solvent remaining in the electrode layer 40 and the concentration of the solvent in the atmosphere 57 in the drying furnace 50 are large because the solvent concentration in the atmosphere 57 is not increased under the drying conditions of the comparative example, As the drying of the electrode layer 40 is almost completed at the outlet portion of the fifth drying zone 55, the drying speed is accelerated. However, the adhesive force of the electrode layer 40 can not satisfy the demand as a product.

On the other hand, in the drying condition of the embodiment, since the solvent concentration in the atmosphere 57 is increased, the difference in concentration of the solvent remaining in the electrode layer 40 and the solvent concentration in the atmosphere 57 in the drying oven 50 So that the electrode layer 40 is gradually dried. The drying speed is slower than that in the comparative example, but since the hot air temperature can be increased and the air volume can be increased, the drying time as a whole can be shortened. Further, the adhesion of the electrode layer 40 can sufficiently satisfy the demand as a product.

As described above, according to the present embodiment, the evaporation speed adjusting member 70 and the heater unit 80 are provided in the electrode drying apparatus 10, and the concentration of the solvent remaining in the electrode layer 40 and the concentration of the solvent remaining in the drying furnace 50 The electrode layer 40 is dried by applying heat while reducing the concentration difference of the solvent concentration in the atmosphere 57 in the atmosphere 57 by increasing the solvent concentration in the atmosphere 57. This makes it possible to prevent the binder 23 from segregating because the electrode layer 40 is gradually dried. 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 improved as well as the charge / The resistance value in the battery after the repetition of the above steps is also lowered, and the electrode performance can be improved. Since the temperature in the furnace can be set to a high value, the solvent 21 contained in the slurry-like electrode layer 40 can be efficiently volatilized, and the drying time can be shortened as a whole.

The inside of the drying furnace 50 is divided into a plurality of drying zones 51 to 56 and an evaporation speed adjusting member 70 and a heater section 80 are provided for each of the drying zones 51 to 56, To 56, the electrode layer 40 is dried by increasing the solvent concentration in the atmosphere 57 and applying heat while reducing the difference in concentration. This makes it possible to prevent the binder 23 from segregating for each of the drying zones 51 to 56 even when it is divided into a plurality of drying zones 51 to 56, Can be manufactured.

The solvent concentration in the atmosphere 57 is increased to a concentration that does not exceed the solvent concentration remaining in the electrode layer 40. This makes it possible to avoid a state in which the drying of the electrode layer 40 does not proceed.

The evaporation speed adjusting member 70 is provided with a piping system 100 for supplying the exhaust gas discharged from the drying furnace 50 into the atmosphere 57 so that the concentration of the solvent in the atmosphere 57 is controlled by the drying furnace 50 Is reused and increased. Since the exhaust gas is reused, mass production can be realized at a low cost.

The evaporation speed adjusting member 70 is supplied into the atmosphere 57 without lowering the temperature of the exhaust to the dew condensation temperature. Therefore, it is not necessary to take a special countermeasure for preventing condensation in the piping system 100, for example, the arrangement of the heat insulating material, etc., so that the equipment cost can be reduced.

(Modification example)

The embodiment has been described in which the inside of the drying furnace 50 is divided into a plurality of drying zones 51 to 56. However, the present invention can also be applied to a drying furnace having only one drying zone. The supply air of the same solvent concentration is supplied to the atmosphere 57 of each of the drying zones 51 to 56. However, it is also possible to supply the supply air of the different solvent concentration to the atmosphere 57 of each of the drying zones 51 to 56 You can.

The embodiment has been described in which the solvent concentration in the atmosphere 57 is increased by reusing the exhaust gas discharged from the drying furnace 50. However, the present invention is not limited to this case. For example, the solvent concentration in the atmosphere 57 may be increased by spraying the solvent 21 such as NMP.

As the carrier gas for the solvent, an inert gas such as nitrogen may be used.

Although the embodiments using hot air as the heat source of the heater unit 80 are shown, an infrared heater may be used. Hot air or an infrared heater as a heat source may be used in combination.

The electrode foil 30 is continuously conveyed, but the electrode foil 30 may be conveyed in a batch manner.

Needless to say, the present invention is not limited to the case where the electrode slurry 20 is intermittently applied, but can also be applied to the case where the electrode slurry 20 is continuously applied.

10: Electrode drying device
20: Electrode slurry
21: Solvent
22: active material
23: Binder
24: Conducting preparation
30: Electrode foil (collector)
40: electrode layer
50: drying furnace
51 to 56: Dry zone
57: Atmosphere
60:
70: evaporation rate adjusting member
80:
90: Casing
91: compartment wall
92: upper nozzle
93: Lower nozzle
94: Exhaust
95:
96: Coater
100: Piping system
101: first piping
102: Second piping
103: Third piping
104: Bypass pipe
105: heat exchanger
106: Valve
107, 108: Temperature sensor
109: Concentration sensor
110: solvent recovery device
111: solvent recovery machine
112: blowing fan
120: heat exchanger
121: Temperature sensor
130: controller

Claims (9)

A method for drying an electrode layer formed by applying an electrode slurry containing a solvent to a current collector in a drying furnace,
The difference between the concentration of the solvent remaining in the electrode layer and the concentration of the solvent in the air in the drying furnace is reduced by increasing the solvent concentration in the air,
The solvent concentration in the air is increased to a concentration not exceeding the solvent concentration remaining in the electrode layer,
Hot air having a solvent concentration higher than the solvent concentration in the air in the drying furnace is supplied into the drying furnace for each drying zone in which the inside of the drying furnace is divided into a plurality of drying zones, Is dried. delete delete The electrode drying method according to claim 1, wherein the concentration of the solvent in the air is increased by reusing the exhaust gas discharged from the drying furnace. 5. The electrode drying method according to claim 4, wherein the temperature of the exhaust gas is supplied into the air without lowering to the dew condensation temperature. An electrode drying apparatus for drying an electrode layer formed by applying an electrode slurry containing a solvent to a current collector in a drying furnace,
An evaporation speed adjusting member for reducing the concentration difference between the solvent concentration remaining in the electrode layer and the solvent concentration in the air in the drying furnace by increasing the solvent concentration in the air,
And a heater for applying heat to dry the electrode layer,
The evaporation rate adjusting member raises the solvent concentration in the air to a concentration not exceeding the solvent concentration remaining in the electrode layer,
Wherein the drying furnace is constituted by a plurality of drying zones, wherein the evaporation speed adjusting member and the heater unit are provided for each drying zone,
Hot air having a solvent concentration higher than the solvent concentration in the air in the drying furnace is supplied into the drying furnace for each drying zone in which the inside of the drying furnace is divided into a plurality of drying zones, Is dried. delete 7. The electrode drying apparatus according to claim 6, wherein the evaporation speed adjusting member includes a piping system for supplying exhaust air discharged from the drying furnace into the air. 9. The electrode drying apparatus according to claim 8, wherein the evaporation speed adjusting member supplies the exhaust air into the air without lowering the temperature of the exhaust to a dew condensation temperature.

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