JP2020087747A - Double side coating applicator and double side coating method - Google Patents

Abstract

To provide a double side coating applicator capable of applying mixture slurry to both front and back surfaces of a base material at the coating them if flexure variations occurs, and forming an electrode plate at high accuracy.SOLUTION: A double side coating applicator 20 includes a front surface coating die 3 that forms a front surface mixture layer 4 by applying mixture slurry onto a front surface of a base material 1 supported by a backup roll 2; a first displacement meter 10 that measures displacement of the base material 1 before formation of the front surface mixture layer 4 and displacement of the same after formation in a width direction intersecting a conveying direction at at least two points; a back surface coating die 6 that applies slurry onto a back surface of the base material 1 to be conveyed by a conveying roll 5 and thereby forming a back surface mixture layer 7; and a second displacement meter 11 that is provided so as to be opposite to the back surface coating die 6 across the base material 1, and measures the displacement of the base material 1 before the formation of the front surface mixture layer 4 and the back surface mixture layer 7 and the displacement of the front surface mixture layer 4 that includes flexure of the base material 1 after the formation in the width direction at at least two points. The thickness is calculated from the displacement and the flexure, and a discharge amount of the slurry are controlled on the basis of this information.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method of applying an electrode mixture slurry to both surfaces of an electrode plate used in a lithium secondary battery or the like.

A lithium secondary battery is generally used as a power source for portable electronic devices and the like. In this lithium secondary battery, a positive electrode plate using a lithium-containing composite oxide such as lithium cobalt oxide as a positive electrode active material, a negative electrode plate using a graphite material as a negative electrode active material, a separator that electrically insulates between the electrode plates, It is composed of an electrolytic solution filled between the electrode plates. As a result, a lithium secondary battery with high potential and high discharge capacity is realized.
However, in recent years, there has been a demand for multifunctional electronic devices and communication devices, as well as for higher capacity and improved charge/discharge cycle characteristics of lithium secondary batteries as power sources for electric vehicles.

On the other hand, cost reduction, that is, improvement in productivity, is an issue for further popularization of lithium secondary batteries, and various technologies have been developed. For example, as a conventional method of manufacturing an electrode plate, there is a method of sequentially applying and drying the front surface and the back surface. In this case, first, the mixture slurry is applied to the surface of the base material, dried in a drying oven, and then the electrode plate is wound around a winding core. Then, after transporting the electrode plate together with the winding core, the electrode plate is unwound, the mixture slurry is applied to the back surface of the base material, dried in a drying oven, and then the electrode plate is wound. On the other hand, the mixture slurry is applied to the surface of the base material, dried in a drying oven, and then folded back without winding to apply the mixture slurry to the back surface of the base material and dried in a drying oven before the electrode. There is a manufacturing method for winding a plate. In this method, the winding and unwinding operations and the transportation of the electrode plate between the front and back steps can be omitted, and the electrode plate can be efficiently manufactured. However, compared to the conventional method, the equipment cost and the equipment space are the same, and there is a limit to the reduction of the production cost.

As a method for solving the above problems, for example, as in Patent Document 1, the die discharge ports are opposed to each other so as to sandwich the base material, and the mixture slurry is simultaneously discharged from both sides to form a mixture layer on both surfaces of the base material. A method has been proposed in which the front and back surfaces of the electrode plate are simultaneously formed by forming and drying in a drying oven.

Further, as another form, a method has been proposed, for example, as in Patent Document 2, in which only the front surface and the back surface are applied in this order and then dried. In this case, the surface is coated with the mixture slurry by a surface coating die while supporting the substrate with a backup roll. Next, the base material is conveyed in the horizontal direction, the end portion of the base material is held by the rotating body unit, and then the mixture slurry is applied by the back surface coating die installed on the lower side of the base material. Then, the front and back surfaces of the electrode plate are formed by drying in a drying furnace.

Japanese Patent No. 4354598 WO2011/001648

However, in the method described in Patent Document 1, since the base material position is not fixed, when the discharge amount is different for each of the two dies, the base material position is easily affected by the influence, and the front surface and the back surface are affected. However, there is a problem that the weight of the mixture layer differs.

Further, in the method described in Patent Document 2, flapping of the base material is alleviated by gripping both ends of the base material by the rotary unit during back surface coating, but bending of the base material in the width direction cannot be eliminated. .. Therefore, there is a problem in that the backside mixture weight becomes unstable in the width direction due to the variation in the amount of the flexure of the base material caused by the variation in the mixture weight on the surface and the variation in the weight depending on the coating length.

The present invention is to solve the above-mentioned conventional problems, and even when the amount of flexure of the base material changes, application can be performed with reduced mixture weight variation, and a highly accurate electrode plate can be obtained. The purpose is to provide.

In order to achieve the above object, the simultaneous coating device according to the present invention, a backup roll supporting the substrate,
A surface coating die for forming a surface mixture layer by coating a mixture slurry on the surface of the base material supported by the backup roll,
Displacement of the base material before forming the surface mixture layer supported by the backup roll, and displacement of the surface mixture layer after forming the surface mixture layer in the width direction intersecting the transport direction A first displacement meter that measures at least two points,
A transport roll for transporting the base material coated with the mixture slurry on the surface,
A back surface coating die that forms a back surface material mixture layer by applying a material mixture slurry to the back surface of the base material that is being transported by the transport roll,
Displacement of the base material before the formation of the front surface mixture layer and the back surface mixture layer, and the front surface mixture layer and the back surface mixture are provided so as to face the back surface coating die with the base material interposed therebetween. A second displacement meter that measures the displacement of the surface mixture layer including the bending of the base material after the formation of the agent layer at at least two points in the width direction;
The thickness of the surface mixture layer is calculated from the displacement of the base material and the displacement of the surface mixture layer measured by the first displacement meter, and the displacement of the base material measured by the second displacement meter and the The thickness of the surface mixture layer including the deflection of the substrate is calculated from the displacement of the surface mixture layer including the deflection of the substrate, and the surface mixture including the thickness of the surface mixture layer and the deflection of the substrate. Based on the thickness of the agent layer, the deflection of the base material in the width direction is calculated, and the width from the back surface coating die is opposite to the calculated deflection of the base material in the width direction. A discharge amount adjusting mechanism for controlling the discharge amount of the mixture slurry in the direction,
A drying oven for drying the base material having the front surface mixture layer and the back surface mixture layer,
Equipped with.

Further, the double-sided coating method according to the present invention comprises a step of measuring the displacement of the base material before forming the surface mixture layer supported by the backup roll at at least two points in the width direction intersecting the transport direction,
Measuring the displacement of the base material before forming the front surface mixture layer and the back surface mixture layer at at least two points in the width direction from a position facing the back surface coating die with the base material interposed therebetween;
Forming a surface mixture layer by applying a mixture slurry with a surface coating die on the surface of the base material supported by the backup roll;
Measuring the displacement of the surface mixture layer after forming the surface mixture layer supported by the backup roll at least at two points in the width direction intersecting the transport direction;
Forming a back surface mixture layer by applying a material mixture slurry to the back surface of the base material by a back surface coating die,
From the position facing the back surface coating die with the base material sandwiched, the displacement of the front surface mixture layer including the deflection of the base material after the formation of the front surface mixture layer and the back surface mixture layer is performed in the width direction. Measuring at least two points,
The thickness of the surface mixture layer is calculated from the displacement of the base material and the displacement of the surface mixture layer before and after forming the surface mixture layer supported by the backup roll, and the back surface is sandwiched between the base materials. From the displacement of the surface mixture layer including the displacement of the base material and the deflection of the base material before and after the formation of the front surface mixture layer and the back surface mixture layer measured from the position facing the coating die of the base material Calculate the thickness of the surface mixture layer including bending, based on the thickness of the surface mixture layer and the thickness of the surface mixture layer including the bending of the base material, of the base material in the width direction. A step of calculating the deflection, and controlling the discharge amount of the mixture slurry in the width direction from the back surface coating die so as to conflict with the calculated deflection of the base material in the width direction,
Drying the substrate having the front surface mixture layer and the back surface mixture layer,
including.

As described above, according to the double-sided coating device and the double-sided coating method according to the present invention, even when the deflection amount of the base material changes due to the change in the mixture weight of the electrode plate surface or the change in the electrode plate weight due to the coating length, It is possible to reduce the variation in the mixture weight on the back surface and obtain a highly accurate electrode plate.

1 is a schematic diagram showing an overall configuration of a double-sided coating device according to a first embodiment. FIG. 3 is a block diagram showing an example of a configuration of a double-sided coating device 20 according to the first embodiment. It is a schematic side view which shows arrangement|positioning of the back coating die and the 2nd displacement meter in the double-sided coating apparatus of FIG. It is a schematic sectional drawing seen from the AA direction of FIG. 3A. It is a flow chart regarding the amount of deflection of the base material and the adjustment of the discharge amount. 3 is a flowchart of a double-sided coating method according to the first embodiment.

The double-sided coating device according to the first aspect includes a backup roll that supports a base material,
A surface coating die for forming a surface mixture layer by coating a mixture slurry on the surface of the base material supported by the backup roll,
Displacement of the base material before forming the surface mixture layer supported by the backup roll, and displacement of the surface mixture layer after forming the surface mixture layer in the width direction intersecting the transport direction A first displacement meter that measures at least two points,
A transport roll for transporting the base material having a surface mixture layer formed on the surface,
A back surface coating die that forms a back surface material mixture layer by applying a material mixture slurry to the back surface of the base material that is being transported by the transport roll,
Displacement of the base material before the formation of the front surface mixture layer and the back surface mixture layer, and the front surface mixture layer and the back surface mixture are provided so as to face the back surface coating die with the base material interposed therebetween. A second displacement meter that measures the displacement of the surface mixture layer including the bending of the base material after the formation of the agent layer at at least two points in the width direction;
The thickness of the surface mixture layer is calculated from the displacement of the base material and the displacement of the surface mixture layer measured by the first displacement meter, and the displacement of the base material measured by the second displacement meter and the The thickness of the surface mixture layer including the deflection of the substrate is calculated from the displacement of the surface mixture layer including the deflection of the substrate, and the surface mixture including the thickness of the surface mixture layer and the deflection of the substrate. Based on the thickness of the agent layer, the deflection of the base material in the width direction is calculated, and the width from the back surface coating die is opposite to the calculated deflection of the base material in the width direction. A discharge amount adjusting mechanism for controlling the discharge amount of the mixture slurry in the direction,
A drying oven for drying the base material having the front surface mixture layer and the back surface mixture layer,
Equipped with.

With the above structure, it is possible to form an electrode plate with little weight variation even when the base material is bent or when the bending amount is changed.

In the double-sided coating device according to the second aspect, in the first aspect, the first and second displacement meters measure the total thickness at at least three points including the center and both ends in the width direction. Good.

In the double-sided coating device according to the third aspect, in the first or second aspect, the discharge amount adjusting mechanism has a difference between the maximum value and the minimum value of the bending of the base material in the width direction of 20 μm or more. In this case, the discharge amount of the mixture slurry from the back surface coating die may be controlled.

The double-sided coating method according to the fourth aspect, a step of measuring the displacement of the base material before forming the surface mixture layer supported by the backup roll at at least two points in the width direction intersecting the transport direction,
Measuring the displacement of the base material before forming the front surface mixture layer and the back surface mixture layer at at least two points in the width direction from a position facing the back surface coating die with the base material interposed therebetween;
Forming a surface mixture layer by applying a mixture slurry with a surface coating die on the surface of the base material supported by the backup roll;
Measuring the displacement of the surface mixture layer after forming the surface mixture layer supported by the backup roll at least at two points in the width direction intersecting the transport direction;
Forming a back surface mixture layer by applying a material mixture slurry to the back surface of the base material by a back surface coating die,
From the position facing the back surface coating die with the base material sandwiched, the displacement of the front surface mixture layer including the deflection of the base material after the formation of the front surface mixture layer and the back surface mixture layer is performed in the width direction. Measuring at least two points,
The thickness of the surface mixture layer is calculated from the displacement of the base material and the displacement of the surface mixture layer before and after forming the surface mixture layer supported by the backup roll, and the back surface is sandwiched between the base materials. From the displacement of the surface mixture layer including the displacement of the base material and the deflection of the base material before and after the formation of the front surface mixture layer and the back surface mixture layer measured from the position facing the coating die of the base material Calculate the thickness of the surface mixture layer including bending, based on the thickness of the surface mixture layer and the thickness of the surface mixture layer including the bending of the base material, of the base material in the width direction. A step of calculating the deflection, and controlling the discharge amount of the mixture slurry in the width direction from the back surface coating die so as to conflict with the calculated deflection of the base material in the width direction,
Drying the substrate having the front surface mixture layer and the back surface mixture layer,
Double-sided coating method including.

The double-sided coating method according to a fifth aspect is the fourth aspect, wherein the displacement of the base material and the displacement of the surface mixture layer before and after the formation of the surface mixture layer are measured at the center and both ends in the width direction. Measure the total thickness at least 3 points including
The displacement of the surface mixture layer including the displacement of the base material and the deflection of the base material before and after the formation of the front surface mixture layer and the back surface mixture layer is at least three points including the center and both ends in the width direction. You may measure.

A double-sided coating method according to a sixth aspect is the mixture slurry from the backside coating die according to the fourth or fifth aspect, when the difference between the maximum value and the minimum value of the bending of the base material is 20 μm or more. May be controlled.

Hereinafter, a double-sided coating device and a double-sided coating method according to embodiments will be described with reference to the accompanying drawings. In the drawings, substantially the same members are designated by the same reference numerals.

(Embodiment 1)
<Double-sided coating device>
FIG. 1 is a schematic diagram showing an overall configuration of a double-sided coating device 20 for coating a mixture slurry on both front and back surfaces of a base material according to the first embodiment. FIG. 2 is a block diagram showing an example of the configuration of the double-sided coating device 20 according to the first embodiment. Note that, in FIG. 1, for convenience, the width direction of the substrate 1 is shown as the X direction, the conveying direction of the substrate 1 to the drying furnace 8 is shown as the Y direction, and the vertically upward direction is shown as the Z direction.
The double-sided coating device 20 according to the first embodiment includes a backup roll 2 that supports the substrate 1, a surface coating die 3, a first displacement meter 10, and a transport roll 5 that transports the substrate 1. A back surface coating die 6, a second displacement meter 11, a discharge amount adjusting mechanism 12, and a drying furnace 8 are provided. The mixture slurry is applied to the surface of the substrate 1 supported by the backup roll 2 by the surface coating die 3 to form the surface mixture layer 4. With the first displacement meter 10, the displacement of the base material 1 supporting the surface mixture layer 4 with the backup roll 2 before and after the formation and the displacement of the surface mixture layer are crossed in the width direction (Y direction). Measure at least two points in the (X direction). The substrate 1 having the surface mixture layer 4 formed on the surface thereof is conveyed by the conveying rolls 5. The mixture slurry is applied to the back surface of the substrate 1 being conveyed by the conveying roll 5 by the back surface coating die 6 to form the back surface material mixture layer 7. The second displacement meter 11 is provided so as to face the back surface coating die 6 with the base material 1 interposed therebetween. The displacement of the surface mixture layer including the displacement of the substrate 1 and the deflection of the substrate 1 before and after the formation of the front surface mixture layer 4 and the back surface mixture layer 7 is measured by the second displacement meter 11 in the width direction (X direction). Is measured at at least two points. The discharge amount adjusting mechanism 12 calculates the thickness of the surface mixture layer 4 from the displacement of the base material 1 and the displacement of the surface mixture layer measured by the first displacement meter 10. Further, the thickness of the surface mixture layer including the deflection of the base material is calculated from the displacement of the base material measured by the second displacement meter 11 and the displacement of the surface mixture layer including the deflection of the base material 1. Further, the bending of the base material 1 in the width direction (X direction) is calculated based on the thickness of the surface material mixture layer and the thickness of the surface material mixture layer including the bending of the base material. Then, the discharge amount of the mixture slurry in the width direction (X direction) from the back surface coating die 6 is controlled so as to conflict with the calculated bending of the base material 1 in the width direction (X direction). The substrate 1 having the front surface mixture layer 4 and the back surface mixture layer 7 is dried by a drying oven 8.

According to the double-sided coating device according to the first embodiment, even if the amount of flexure of the base material changes due to a change in the mixture weight on the surface of the electrode plate or a change in the weight of the electrode plate due to the coating length, the mixture weight on the back surface varies. It is possible to reduce the number of electrodes and obtain a highly accurate electrode plate.

Below, each member which comprises this double-sided coating device 20 is demonstrated.

<First displacement gauge>
The first displacement meter 10 is installed at a position where the surface mixture layer 4 is coated by the surface coating die 3. The first displacement meter 10 measures the displacement of the base material 1 and the displacement of the surface mixture layer 4 in the width direction (X direction) before and after the formation of the surface mixture layer. In order to measure the displacement of the base material in the width direction (X direction), the first displacement meter 10 has at least two locations, the center and one end, in the case of line symmetry across the center. Just install it. Preferably, it is installed at three or more places.
The first displacement gauge 10 may be a non-contact displacement gauge, and for example, a laser displacement gauge can be used. The displacement is not limited to the laser displacement meter, and may be any one that can measure the displacement of the base material and the displacement of the surface mixture layer 4 without contact.
When there is a portion where the surface mixture layer is not formed on a part of the base material 1, the displacement of the substrate and the surface mixture after the formation of the surface mixture layer at the portion where the surface mixture layer is not formed. The displacement of layers can be measured simultaneously. In this case, only the measurement after forming the surface mixture layer should be performed.

<Second displacement meter>
The second displacement meter 11 is provided so as to face the back surface coating die 6 with the base material 1 interposed therebetween. By the second displacement meter 11, displacement of the base material layer in the width direction (X direction) before and after formation of the front surface mixture layer and the back surface mixture layer and displacement of the front surface mixture layer 4 including bending of the base material 1 are measured. measure. The second displacement meter 11 measures the displacement of the base material and the displacement of the surface mixture layer in the width direction (X direction). It may be installed at least at two places. Preferably, it is installed at three or more places.
The second displacement gauge 11 may be a non-contact displacement gauge, and for example, a laser displacement gauge can be used. Note that the displacement is not limited to the laser displacement meter and may be any one that can measure the displacement of the base material without contact. Further, it is preferable that the plurality of second displacement gauges to be installed are arranged so that the distances to the back surface coating die 6 are substantially the same.
In addition, when there is a part where the surface mixture layer and the back surface mixture layer are not formed on a part of the base material 1, particularly on the end portion, the edge part is not formed even after the surface mixture layer and the back surface mixture layer are formed. The front surface mixture layer and the back surface mixture layer are not formed. Therefore, the displacement of the base material is measured at the ends after the surface mixture layer and the back surface mixture layer are formed, and the surface mixture including the bending of the base material at the position where the surface mixture layer and the back surface mixture layer are formed. The displacement of the layer may be measured. In this case, it suffices to perform only the measurement after forming the front surface mixture layer and the back surface mixture layer.

<Discharge rate adjustment mechanism>
Displacement of the base material 1 in the width direction (X direction) measured by the first displacement meter 10 and the base material 1 in the width direction (X direction) measured by the second displacement meter 11 by the discharge amount adjusting mechanism 12. The amount of bending of the base material 1 when the back surface material mixture layer 7 is formed is calculated based on the displacement including the bending. Then, the discharge amount of the mixture slurry in the width direction (X direction) from the back surface coating die 6 is controlled according to the calculated bending of the base material 1.
The ejection amount adjusting mechanism 12 may be realized as hardware, or may be realized as a program as described later.

When the discharge amount adjusting mechanism 12 is implemented as a program, for example, the double-sided coating device 20 includes a control unit (computer device) 30 including the discharge amount adjusting mechanism 12 as a program as shown in FIG.

<Control unit (computer device)>
The control unit 30 is, for example, a computer device. A general-purpose computer device can be used as this computer device, and includes, for example, a processing unit 31, a storage unit 32, and a display unit 33, as shown in FIG. Further, an input device, a storage device, an interface, etc. may be included.
The controller 30 controls the back surface coating die 6. The control unit 30 may control the backup roll 2, the front surface coating die 3, the first displacement meter 10, the transport roll 5, the back surface coating die 6, the second displacement meter 11, and the drying oven 8. ..

<Processing unit>
The processing unit 31 may be, for example, a central processing operator (CPU), a microcomputer, or a processing device that can execute computer-executable instructions.

<Memory>
The storage unit 32 may be, for example, at least one of ROM, EEPROM, RAM, flash SSD, hard disk, USB memory, magnetic disk, optical disk, magneto-optical disk, and the like.
The storage unit 32 includes a program 35. When the control unit 30 is connected to the network, the program 35 may be downloaded from the network as needed.

<Program>
The program 35 includes the ejection amount adjusting mechanism 12. The discharge amount adjusting mechanism 12 is read from the storage unit 32 and executed by the processing unit 31 at the time of execution.

Here, the amount of bending of the substrate 1 in the width direction (X direction) and calculation of the amount of bending in the discharge amount adjusting mechanism 12 will be described with reference to FIGS. 3A and 3B. FIG. 3A is a schematic side view showing the arrangement of the back surface coating die 6 and the second displacement meter 11 when the mixture slurry is applied to the back surface. FIG. 3B is a schematic cross-sectional view seen from the visual field A (the AA direction) in FIG. 3A. When the back surface coating die is applied to the back surface of the base material 1 by the back surface coating die 6, the base material 1 is bent in the width direction into a concave shape due to the weight of the front surface mixture layer 4, as shown in FIG. 3B. Due to this bending, a difference occurs in the width direction (X direction) between the discharge port of the back surface coating die 6 and the substrate 1 (hereinafter referred to as the coating gap). The present inventor has confirmed through previous studies that there is a strong correlation between the coating gap and the coating weight, and it is possible to stabilize the coating gap in the width direction (X direction) of the substrate 1. They have found that this leads to an improvement in coating accuracy and have completed the present invention.

Therefore, in the first embodiment, in order to quantitatively grasp the coating gap, that is, the bending amount of the base material 1, the second displacement gauges 11a, 11b, 11c are provided directly above the back surface coating die 6. I have it. In addition, in order to measure the displacement of the base material and the displacement of the surface mixture layer in the width direction (X direction), in the case of line symmetry across both ends with respect to the center, at least two locations, the center and one end The first and second displacement gauges 10 and 11 may be installed in the. Preferably, it is installed at three or more places. Although it is installed at three locations in FIG. 3B, it is not limited to this form as long as the displacement of the base material and the displacement of the surface mixture layer in the width direction can be measured.

Since the displacement of the surface mixture layer obtained by the second displacement meter 11 includes the bending of the base material 1 and the thickness of the surface mixture layer 4, it is not possible to directly measure only the bending of the base material 1. It is impossible. Therefore, the present inventor uses the first displacement meter 10 installed immediately after the formation of the surface mixture layer 4 to form the base material 1 in the width direction (X direction) before and after the formation of the surface mixture layer 4. And the displacement of the surface mixture layer 4 are measured. Thereby, the thickness of the surface mixture layer 4 can be calculated. Further, before and after the formation of the front surface mixture layer 4 and the back surface mixture layer 7, the front surface mixture including the displacement of the base material in the width direction (X direction) and the flexure of the base material 1 by the second displacement meter 11 The displacement of layer 4 is measured. Thereby, the thickness of the surface mixture layer including the bending of the base material can be calculated. Then, the amount of bending of the base material 1 in the width direction (X direction) is calculated by the difference between the thickness of the surface material mixture layer and the thickness of the surface material mixture layer including the bending of the base material. In addition, it was confirmed that the amount of flexure of the base material 1 in the width direction (X direction) can be calculated accurately even on an undried coating film surface, regardless of the influence of the coating speed and the flapping of the base material 1. is doing.

Next, the flexure amount of the base material 1 is calculated in the same manner at least at three or more locations in the width direction (X direction), thereby varying the flexure amount (from the maximum value to the minimum value of the flexure amount in the width direction (X direction)). The value obtained by subtracting is obtained. Since this variation leads to variation in the coating gap and variation in the mixture weight, the ejection rate is adjusted by the ejection rate adjusting mechanisms 12a, 12b, 12c provided in the back surface coating die 6. For example, the base material 1 is lifted by increasing the discharge quantity by widening the discharge gap of the die by the discharge quantity adjusting mechanism 12b installed at a position where the base material 1 has a large deflection amount, and the base material 1 is moved in the width direction (X direction). Adjust so that the amount of deflection is uniform. That is, the discharge amount is adjusted so as to be opposite to the bending of the base material.

Here, the threshold value of the bending amount using the ejection amount adjusting mechanism 12 will be described. This adjusting mechanism is for reducing the variation in the mixture weight, and it is not necessary to use it if the amount of deflection of the base material 1 and the coating gap are stable. Good. This time, the present inventor set a threshold value of 4% as the back surface mixture weight variation (value obtained by dividing the average value of the mixture weight in the width direction by the value obtained by subtracting the minimum value from the maximum value of the mixture weight in the width direction). Set. This is an actual value of the variation in weight of the surface mixture layer, and the high-quality electrode plate 9 can be obtained by forming the back surface mixture layer with the same accuracy as the surface. The threshold value is not limited to 4% as long as the highly accurate electrode plate 9 can be obtained. Then, as a result of verifying the relationship between the variation in the mixture weight and the bending amount of the base material, it was found that the variation in the bending amount needs to be suppressed to 20 μm or less to satisfy the variation 4% in the mixture weight.
Therefore, the threshold value of the variation in the bending amount of the base material using the discharge amount adjusting mechanism is set to 20 μm or more. The target value is not limited to 20 μm or more as long as the electrode plate 9 with high accuracy can be obtained.

FIG. 4 is a flowchart regarding the calculation of the amount of bending of the base material 1 and the adjustment of the discharge amount.
(1) The displacement (Z1a) of the base material 1 before application of the mixture is measured by the first displacement meter 10 (S01). Since the surface mixture layer is not yet formed, the displacement of the base material 1 itself is measured.
(2) The displacement (Z1b) of the surface mixture layer 4 after application of the mixture is measured by the first displacement meter 10 (S02).
(3) The thickness T1 of the surface mixture layer 4 is calculated by the formula (Z1b-Z1a) (S03).
(4) The displacement (Z2a) of the base material 1 before application of the mixture is measured by the second displacement meter 11 (S04).
(5) The displacement (Z2b) of the surface mixture layer 4 after the mixture is applied is measured by the second displacement meter 11 (S05).
(6) The thickness T2 of the surface mixture layer 4 including the bending of the base material 1 is calculated by the formula (Z2b-Z2a) (S06).
(7) The flexure amount (D) of the base material is calculated by the formula (T2-T1) (S07). In addition, it is preferable to calculate the bending of the base material at least at three or more positions in the width direction (X direction) of the base material.
(8) It is determined whether or not the difference (DMax-Dmin) between the maximum value and the minimum value of the bending amount of the base material 1 in the width direction (X direction) is 20 μm or more (S08). The difference (DMax-Dmin) between the maximum value and the minimum value of the bending amount is called the bending amount variation.
(9) When the variation of the deflection amount is 20 μm or more, the mixture amount slurry is ejected by the ejection amount adjusting mechanism 12 provided in the back surface coating die 6 according to the difference in the deflection amount in the width direction (X direction). The amount is adjusted (S09).
(10) After that, the process returns to displacement measurement and discharge amount adjustment (S10). In this case, the process returns to steps S01 and S04.
(11) On the other hand, if the variation in the deflection amount is less than 20 μm, the adjustment is completed (S11). In this case, the displacement measurement and the ejection amount adjustment may be returned to.
As described above, it is possible to reduce variations in the amount of bending of the base material 1 in the width direction (X direction) and variations in the weight of the mixture on the front and back surfaces of the base material 1.

<Double-sided coating method>
FIG. 5 is a flowchart of the double-sided coating method according to the first embodiment. The double-sided coating method according to the first embodiment will be described with reference to FIG.
(A) The displacement of the base material 1 before forming the surface mixture layer supported by the backup roll 2 is measured at at least two points in the width direction intersecting the transport direction (S21).
(B) From the position facing the back surface coating die 6 with the base material 1 interposed therebetween, the displacement of the base material 1 before the formation of the front surface mixture layer and the back surface mixture layer is measured at at least two points in the width direction (S22). ).
(C) The surface mixture die 4 is applied to the surface of the substrate 1 supported by the backup roll 2 to form the surface mixture layer 4 (S23). The base material 1 is supplied from an unwinder (not shown).
(D) At least two displacements of the surface mixture layer of the base material 1 after forming the surface mixture layer 4 supported by the backup roll 2 in the width direction (X direction) intersecting the transport direction (Y direction). Is measured (S24). In this case, since the base material 1 is supported by the backup roll 2, the bending of the base material 1 need not be considered. Therefore, the thickness of the surface mixture layer 4 can be calculated from the displacement of the base material 1 measured before the formation of the surface mixture layer and the displacement of the surface mixture layer 4 measured after the formation of the surface mixture layer 4.
(E) The back surface mixture layer 7 is formed by applying the material mixture slurry to the back surface of the substrate 1 by the back surface coating die 6 (S25). In this case, as shown in FIG. 3B, since the base material 1 cannot be supported, the weight of the surface mixture layer 4 causes the base material 1 to bend in a concave shape. Therefore, when the discharge amount of the mixture slurry is not adjusted in the width direction, the back surface mixture layer 7 is formed according to the concave shape of the base material 1.
(F) From the position facing the back surface coating die 6 with the base material 1 interposed therebetween, the displacement of the front surface material mixture layer 4 including the bending of the base material 1 after the formation of the front surface material mixture layer 4 and the back surface material mixture layer 7 is performed. At least two points are measured in the width direction (X direction) (S26). In this case, by measuring the displacement of the surface mixture layer 4 including the displacement of the base material and the deflection of the base material before and after the formation of the front surface mixture layer 4 and the back surface mixture layer 7, the surface including the deflection of the base material 1 is measured. The thickness of the mixture layer 4 can be calculated.
(G) The surface in the width direction (X direction) based on the displacement of the base material 1 measured before and after the formation of the surface mixture layer 4 supported by the backup roll 2 and the displacement of the surface mixture layer 4. The thickness of the mixture layer is calculated (S27).
(H) Based on the displacement of the base material 1 measured before and after the formation of the front surface mixture layer 4 and the back surface mixture layer 7 and the displacement of the front surface mixture layer 4 including the bending of the base material 1, the width direction (X The thickness of the surface mixture layer including the bending of the base material 1 in the (direction) is calculated (S28).
(I) The deflection of the substrate 1 in the width direction (X direction) is calculated based on the thickness of the surface mixture layer and the thickness of the surface mixture layer including the deflection of the substrate 1, and the calculated width direction is calculated. The discharge amount of the mixture slurry in the width direction (X direction) from the back surface coating die 6 is controlled so as to conflict with the bending of the base material 1 (S29).
(F) The base material 1 having the front surface mixture layer 4 and the back surface mixture layer 7 is dried (S30).
As described above, the electrode plate 9 which is the base material 1 having the front surface mixture layer 4 and the back surface mixture layer 7 can be formed. In this case, since the discharge amount of the mixture slurry can be adjusted according to the variation in the bending amount of the base material 1 in the width direction (X direction), it is possible to reduce the variation in the mixture weight on the front surface and the back surface of the base material 1. .

Hereinafter, it will be described in more detail with reference to examples.

(Example 1)
As a mixture slurry, 100 parts by weight of artificial graphite and 2.5 parts by weight of a styrene-butadiene copolymer rubber particle dispersion as a binder per 100 parts by weight of the negative electrode active material (1 part by weight in terms of binder solid content). Then, carboxymethyl cellulose as a thickener was prepared by stirring and kneading with 1 part by weight of 100 parts by weight of the negative electrode active material and an appropriate amount of water in a double-arm type kneader.

Using this mixture slurry and a copper foil base material having a base material width of 300 mm and a thickness of 10 μm, the double-sided coating device shown in FIG. 1 has a wet thickness of 200 μm, a coating width of 280 mm, and a coating speed of 5 m/min. And the mixture slurry was applied to the back surface. Further, after the bending amount of the base material shown in the flowchart of FIG. 3 was calculated and the discharge amount was adjusted, the base material was dried to obtain an electrode plate. A laser displacement meter (LK-G30, manufactured by Keyence Corporation) was used for the displacement measurement, and the measurement was carried out by installing the laser displacement meter at a total of 3 positions of 10 mm from the center of the base material in the width direction and the end of the mixture layer.

In the produced electrode plate, after punching the same position as the above-mentioned displacement gauge installation place into 30 mm in diameter, the backside mixture weight was measured by an electronic balance to calculate the weight variation in the width direction (X direction).

(Comparative Example 1)
An electrode plate was prepared in the same manner as described in Example 1 except that the discharge amount was not adjusted, and the weight variation in the width direction (X direction) was evaluated.

Table 1 below shows the results of variations in the amount of bending in the width direction (X direction) of the base materials of Example 1 and Comparative Example 1 and variations in the weight of the back surface material mixture layers of the manufactured electrode plates.

As is clear from Table 1, in Example 1 and Comparative Example 1, there is a clear difference in the mixture weight variation. This is because in Example 1, the discharge amount of the die is adjusted according to the variation in the bending amount of the base material, the coating gap that is the distance between the die discharge port and the base material is stabilized, and the width is uniform in the width direction (X direction). It is considered that the coating was realized.

It should be noted that the present disclosure includes appropriate combination of any of the various embodiments and/or examples described above, and each of the embodiments and/or The effects of the embodiment can be achieved.

According to the double-sided coating device and the double-sided coating method according to the present invention, it is possible to form a mixture layer on both front and back surfaces of a base material with high precision and at the same time, and it is possible to reduce the cost of an electrode plate for a lithium secondary battery. ..

1 Base Material 2 Backup Roll 3 Surface Coating Die 4 Surface Mixing Layer 5 Conveying Roll 6 Backside Coating Die 7 Backside Mixing Layer 8 Drying Oven 9 Electrode Plate 10 First Displacement Meter 11, 11a, 11b, 11c 2 displacement gauges 12, 12a, 12b, 12c Discharge amount adjusting mechanism

Claims (6)

A backup roll that supports the base material,
A surface coating die for forming a surface mixture layer by coating a mixture slurry on the surface of the base material supported by the backup roll,
Displacement of the base material before forming the surface mixture layer supported by the backup roll, and displacement of the surface mixture layer after forming the surface mixture layer in the width direction intersecting the transport direction A first displacement meter that measures at least two points,
A transport roll for transporting the base material coated with the mixture slurry on the surface,
A back surface coating die that forms a back surface material mixture layer by applying a material mixture slurry to the back surface of the base material that is being transported by the transport roll,
Displacement of the base material before the formation of the front surface mixture layer and the back surface mixture layer, and the front surface mixture layer and the back surface mixture are provided so as to face the back surface coating die with the base material interposed therebetween. A second displacement meter that measures the displacement of the surface mixture layer including the bending of the base material after the formation of the agent layer at at least two points in the width direction;
The thickness of the surface mixture layer is calculated from the displacement of the base material and the displacement of the surface mixture layer measured by the first displacement meter, and the displacement of the base material measured by the second displacement meter and the The thickness of the surface mixture layer including the deflection of the substrate is calculated from the displacement of the surface mixture layer including the deflection of the substrate, and the surface mixture including the thickness of the surface mixture layer and the deflection of the substrate. Based on the thickness of the agent layer, the deflection of the base material in the width direction is calculated, and the width from the back surface coating die is opposite to the calculated deflection of the base material in the width direction. A discharge amount adjusting mechanism for controlling the discharge amount of the mixture slurry in the direction,
A drying oven for drying the base material having the front surface mixture layer and the back surface mixture layer,
A double-sided coating device equipped with. The double-sided coating device according to claim 1, wherein the first and second displacement gauges measure the total thickness at at least three points including the center and both ends in the width direction. The discharge amount adjusting mechanism controls the discharge amount of the mixture slurry from the back surface coating die when the difference between the maximum value and the minimum value of the bending of the base material in the width direction is 20 μm or more. Item 3. The double-sided coating device according to Item 1 or 2. Measuring the displacement of the base material before forming the surface mixture layer supported by the backup roll at at least two points in the width direction intersecting the transport direction;
Measuring the displacement of the base material before forming the front surface mixture layer and the back surface mixture layer at at least two points in the width direction from a position facing the back surface coating die with the base material interposed therebetween;
Forming a surface mixture layer by applying a mixture slurry with a surface coating die on the surface of the base material supported by the backup roll;
Measuring the displacement of the surface mixture layer after forming the surface mixture layer supported by the backup roll at least at two points in the width direction intersecting the transport direction;
Forming a back surface mixture layer by applying a material mixture slurry to the back surface of the base material by a back surface coating die,
From the position facing the back surface coating die with the base material sandwiched, the displacement of the front surface mixture layer including the deflection of the base material after the formation of the front surface mixture layer and the back surface mixture layer is performed in the width direction. Measuring at least two points,
The thickness of the surface mixture layer is calculated from the displacement of the base material and the displacement of the surface mixture layer before and after forming the surface mixture layer supported by the backup roll, and the back surface is sandwiched between the base materials. From the displacement of the surface mixture layer including the displacement of the base material and the deflection of the base material before and after the formation of the front surface mixture layer and the back surface mixture layer measured from the position facing the coating die of the base material Calculate the thickness of the surface mixture layer including bending, based on the thickness of the surface mixture layer and the thickness of the surface mixture layer including the bending of the base material, of the base material in the width direction. A step of calculating the deflection, and controlling the discharge amount of the mixture slurry in the width direction from the back surface coating die so as to conflict with the calculated deflection of the base material in the width direction,
Drying the substrate having the front surface mixture layer and the back surface mixture layer,
Double-sided coating method including. Before and after the formation of the surface mixture layer, the displacement of the substrate and the displacement of the surface mixture layer are measured at a total thickness of at least three points including the center and both ends in the width direction,
The displacement of the surface mixture layer including the displacement of the base material and the deflection of the base material before and after the formation of the front surface mixture layer and the back surface mixture layer is at least three points including the center and both ends in the width direction. The double-sided coating method according to claim 4, which is measured. The control of the discharge amount controls the discharge amount of the mixture slurry from the back surface coating die when the difference between the maximum value and the minimum value of the bending of the base material in the width direction is 20 μm or more. The double-sided coating method according to 4 or 5.