JP7321204B2 - Electrode plate manufacturing method - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a method for manufacturing an electrode plate.

2. Description of the Related Art Conventionally, as an electrode plate in a battery or the like, one having a collector foil and an electrode layer on the surface thereof has been used. An electrode plate is generally manufactured by coating an electrode layer on a collector foil. A portion of the current collector foil is a non-coated portion having no electrode layer. This is due to the current collecting structure in the battery. In some cases, the electrode plate coated with the electrode layer is pressed for charge/discharge performance when assembled in a battery.

As the technology of the press, the one described in Patent Document 1 can be mentioned. In the technique of the same document, a wrinkle prevention device is installed on the entry side of the roll press machine that presses the coated part. The wrinkle prevention device is a device that prevents the occurrence of wrinkles and warpage in the electrode plate by pressing the non-coated portion. This is because uneven elongation of the current collector foil caused by pressing with a roll press acting only on the coated portion causes wrinkles and warping.

JP 2019-102172 A

The conventional techniques described above have the following problems. Even with a wrinkle prevention device, there are cases where wrinkles and warping cannot be completely prevented. The reason is that the position in the width direction of the conveyed electrode plate may deviate from its original position. This is because, in the state in which this positional deviation occurs, part of the non-coated portion remains unpressed by neither the wrinkle prevention device nor the roll press machine, and uneven elongation remains. Although the wrinkle prevention device disclosed in Patent Document 1 performs meandering detection to deal with misalignment, it cannot completely correct the misalignment.

The disclosed technology has been made to solve the problems of the conventional technology described above. That is, it is an object of the present invention to provide a method of manufacturing an electrode plate which can prevent the occurrence of wrinkles and warpage while manufacturing the electrode plate.

A method for manufacturing an electrode plate according to one aspect of the disclosed technology has a collector foil and an electrode layer on the surface thereof, and a part in the width direction is a coated part having both the collector foil and the electrode layer. In addition, a method of manufacturing an electrode plate in which the remainder in the width direction is a non-coated portion having a current collecting foil and no electrode layer, comprising this pressing step of pressing the coated portion in the thickness direction; Straightening that reduces the difference in elongation between the coated and uncoated current collector foils after the pressing process by pressing the uncoated current collector foil before or after the pressing process. Prior to the pressing process, whichever of the main pressing process and the straightening pressing process is performed later, only the boundary between the coated and non-coated parts of the current collector foil is subjected to the temperature of the current collector foil. and a heating step of heating with an IH heater within a range that does not reach its melting point.

In the electrode plate manufacturing method of the above aspect, the electrode plate is subjected not only to the main pressing step but also to the correction pressing step. Either of the two pressing processes may be performed first, but the heating process is performed before the pressing process which is performed later. By performing the heating process, the current collector foil at the boundary is softened and its extensibility is improved. As a result, warpage and breakage of the current collector foil at the boundary where stress is applied due to the difference in elongation rate due to the pressing process can be prevented. On the other hand, by not subjecting the portion of the current collector foil away from the coated portion to the heating process, the generation of wrinkles in the non-coated portion of the current collector foil as a whole is prevented.

According to the technology disclosed herein, there is provided a method of manufacturing an electrode plate that can manufacture an electrode plate while preventing the occurrence of wrinkles and warpage.

1 is a perspective view of an electrode plate manufactured in an embodiment; FIG. It is a schematic diagram which shows this press process. It is a schematic diagram which shows a straightening press process. It is a top view which shows the object location of a heating process. It is sectional drawing which shows the heating process in this form. It is sectional drawing which shows the heating process in a comparative example. FIG. 4 is a plan view showing a state in which wrinkles are generated in the entire non-coated portion. FIG. 4 is a plan view showing a state in which wrinkles are not generated in most of the non-coated portion. FIG. 3 is a plan view showing a state in which a test for confirming easiness to break is carried out; FIG. 10 is a plan view showing a state in which no breakage occurred due to the heating process; FIG. 10 is a plan view showing a state in which breakage occurs due to not performing a heating step; FIG. 4 is a plan view showing a state of cutting out a test piece for a tensile test; It is a graph which shows the result of a tensile test.

Embodiments embodying the disclosed technology will be described in detail below with reference to the accompanying drawings. This embodiment embodies the disclosed technique as a method of manufacturing the electrode plate 1 shown in FIG. The electrode plate 1 of FIG. 1 has a collector foil 2 and an electrode layer 3 on its surface. In the electrode plate 1, a part in the width direction is a coating part 4 having both the current collector foil 2 and the electrode layer 3, and the remaining part in the width direction has the current collector foil 2 and the electrode layer 3. The non-coated portion 5 is not coated. There are non-coated portions 5 near both ends in the width direction of the electrode plate 1 , and the rest including the center is the coated portion 4 .

In this embodiment, the case where the electrode plate 1 is a positive electrode plate of a lithium ion battery will be described. Therefore, the collector foil 2 is aluminum foil, and the main component of the electrode layer 3 is nickel-cobalt-lithium-manganese oxide. In this embodiment, the electrode plate 1 is completed by performing the following two pressing processes on the starting material, which is the state in which the electrode layer 3 has been formed on the surface of the current collecting foil 2. . An electrode plate that has not undergone these two pressing processes is sometimes called an electrode plate 1, but it is incomplete in the technology of the present disclosure.
1. Main pressing process2. Straightening press process

This pressing step is a step of pressing the coating portion 4 of the electrode plate 1 in the thickness direction (FIG. 2). This is done to improve the charge/discharge performance of the electrode plate 1 by increasing the density of the electrode layer 3 . The straightening press process is a process of pressing the collector foil 2 in the non-coated portion 5 of the electrode plate 1 in the thickness direction (FIG. 3). Either the main pressing step or the straightening pressing step may be performed first.

The reason why the straightening press process is performed in addition to the main press process is to alleviate the non-uniform elongation of the current collector foil 2 . In this pressing step, as described above, the coated portion 4 is pressed in the thickness direction. It is mainly the electrode layer 3 that is compressed by this. The stiffer collector foil 2 compresses less than the electrode layer 3 . However, it is not compressed at all, but compressed somewhat. Therefore, there is a difference in elongation rate between the collector foil 2 in the non-coated portion 5 that is not compressed at all and the collector foil 2 in the coated portion 4 that is slightly compressed. In order to prevent the collector foil 2 from being damaged or deformed due to the difference in elongation rate, a straightening press process is performed.

In this embodiment, a heating process is also performed in addition to the above two pressing processes. In the heating step of this embodiment, the boundary portion 7 between the coated portion 4 and the non-coated portion 5 is heated, as shown in FIG. 4, instead of heating the entire electrode plate 1 . The purpose of the heating process is to soften the collector foil 2 at the boundary portion 7 . This is because damage or deformation can be prevented if the current collecting foil 2 at the location is already softened when the above-described difference in elongation rate between the non-coated portion 5 and the coated portion 4 is determined. For this reason, the pressing process must be performed earlier than the later one of the above two pressing processes. Therefore, the order of performing the three steps including the heating step can be the following four types.
・Main press process→→heating process→→→→correction press process ・correction press process→heating process→→→→main press process・heating process→→→→main press process→→correction press process・heating process→→→ → straightening press process → main press process

The present inventor conducted a test to verify the softening effect of the current collector foil 2 by the heating process, and the results will be described. The following three tests were conducted.
・Confirmation test for wrinkles ・Confirmation test for easiness to break ・Tensile test

First, the confirmation test of wrinkle occurrence conditions will be explained. In this test, when the electrode plate 1 was subjected to the heating process and then the main pressing process, wrinkles of the collector foil 2 at the boundary portion 7 after the main pressing process were confirmed. At that time, there are two heating steps, one for the boundary portion 7 only (see FIG. 5, corresponding to this embodiment) and the other for the entire non-coated portion 5 (see FIG. 6, comparative example). We went through the streets and compared. An IH heater 8 was used for heating.

The heating conditions in this test were as follows.
・Heating temperature: 250℃
・Heating time: 1.2 seconds

The heating temperature is obtained by measuring the temperature of the current collector foil 2 immediately after leaving the heating area by the IH heater 8 with a radiation thermometer, and adjusting the output of the IH heater 8 so that the measured value becomes the above temperature. controlled. It goes without saying that the heating temperature should not be so high as to melt the current collector foil 2, so the above temperature was used in this test. If the upper limit temperature at which the electrode layer 3 can maintain charge/discharge performance is lower than the melting point of the current collector foil 2, the heating temperature must be lower than the upper limit temperature, but there is no problem if the temperature is within the above range. The heating time was adjusted as described above by changing the transport speed of the electrode plate 1 in the direction perpendicular to the paper surface of FIGS.

The press conditions in this test were as follows.
・Press load (linear pressure): 20 kN/cm
・Roll diameter: 300mm
・Through speed: 1.0m/min

The state of wrinkling of the current collector foil 2 in the non-coated portion 5 after the test was different depending on the heating position. In the case where the entire non-coated portion 5 was heated as shown in FIG. 6, wrinkles 9 were generated in the entire current collector foil 2 of the non-coated portion 5 as shown in FIG. This is probably because the entire non-coated portion 5 was softened during the heating process. On the other hand, in the case where only the boundary portion 7 is heated as shown in FIG. There has occurred. A portion of the current collector foil 2 distant from the coated portion 4 was slightly undulated, but no wrinkles 9 were formed. This is probably because only the boundary portion 7 was softened during the heating process.

In this test, the straightening press process was not performed, so the manufacturing method of this embodiment was not entirely reproduced, but the difference in the occurrence of the wrinkles 9 mentioned above shows the significance of appropriately selecting the heating position. ing. This is because if the wrinkles 9 are generated in the entire non-coated portion 5 as shown in FIG. 7, it is expected that the subsequent winding process and the mounting process of the collector terminal member will be hindered. In this case, if the straightening press process is performed after the heating process, the straightening press process itself will also be troubled. On the other hand, by heating only the boundary portion 7 as in the present embodiment, most of the non-coated portion 5 can be kept wrinkle-free even after the heating process.

Next, we will explain the test for confirming the fragility. In this test, the occurrence of breakage of the current collector foil 2 after the pressing process was confirmed in the case where the heating process was performed as shown in FIG. compared ease. As shown in FIG. 9, this test was performed in a state in which the collector foil 2 of the non-coated portion 5 was cut off leaving a width of 2 mm. The reason for this is that by narrowing the width of the non-coated portion 5, the tensile stress during the main pressing process is concentrated there, and the difference in elongation at the boundary portion is emphasized. The heating conditions and pressing conditions in this test were the same as those in the aforementioned confirmation test of wrinkle formation.

In the case where the heating process was performed, the non-coated portion 5 (current collector foil 2) was not broken as shown in FIG. 10 even after the pressing process. On the other hand, as shown in FIG. 11, after the press process was performed on the material that had not been subjected to the heating process, a fracture portion 10 occurred in the non-coated portion 5 (collector foil 2).

In this test, the straightening press process was not performed and the manufacturing method of this embodiment was not completely reproduced, but the difference in the occurrence of breakage mentioned above shows the significance of performing the heating process. 11, it can be seen that the conditions of this test are quite severe with respect to the tensile stress applied to the boundary portion 7, since the breakage point 10 occurs in FIG. The reason why no breakage occurs in FIG. 10 is that the collector foil 2 at the boundary 7 is softened in advance in the heating process so that breakage will not occur even under severe tensile stress. It means that you can

Next, the tensile test will be explained. In this test, a tensile test was performed on the current collecting foil 2 of the non-coated portion 5 of the electrode plate 1 after the heating process as shown in FIG. 5, and the elongation rate was measured. The heating conditions in the heating process were the same as the conditions in each test described above. In this tensile test, as shown in FIG. 12, test pieces 11 were cut from two positions in the non-coated portion 5 of the electrode plate 1 after the heating process. One is immediately adjacent to the coating 4 and belongs to the boundary 7, which is the area heated during the heating process. The other is a position closer to the edge away from the coating portion 4, which has not been heated during the heating process. Five test pieces 11 were cut out from both of them and used for the test.

In this test, the test pieces 11 cut out from these two positions were pulled by a tensile tester, and the elongation rates up to just before breakage were compared. The results are shown in FIG. In FIG. 13, the "non-heated part" shows the elongation rate of the test piece 11 from the position near the edge, and the "heated part" shows the elongation rate of the test piece 11 from the boundary part 7. is. All are average values of the results of five test pieces 11 . Comparing the two, it can be seen that the elongation rate of the "heated part" is about 1.5 times that of the "non-heated part".

In this test, only the heating process was performed, and the manufacturing method of this embodiment was not entirely reproduced. It is significant in that it is possible to know changes in the material. The current collecting foil 2 in the area affected by the heating process clearly has higher elongation than the current collecting foil 2 before being affected by the heating process. Damage or deformation of the current collecting foil 2 is prevented by preliminarily applying a heating process to the boundary portion 7, which is likely to be subjected to strong stress if both the main pressing step and the straightening pressing step are performed. can do.

As described in detail above, according to the present embodiment, the main pressing for pressing the coated portion 4 against the electrode plate 1 in a state where the electrode layer 3 on the surface of the current collecting foil 2 has been formed. and a straightening pressing step of pressing the non-coated portion 5. As shown in FIG. Then, the heating process is performed on the boundary portion 7 prior to the later one of the two pressing processes. By doing so, the extensibility of the collector foil 2 at the boundary portion 7 is improved in advance.

As a result, the collector foil 2 is prevented from being damaged or deformed even at the boundary portion 7 where the difference in elongation rate due to both pressing processes concentrates. On the other hand, the portion of the current collector foil 2 away from the coating portion 4 is not subjected to the heating process. As a result, most of the collector foil 2 in the non-coated portion 5 is prevented from being excessively wrinkled.

Making the boundary portion 7 the target of the heating process is particularly significant when there is a slight shift in the target position of the pressing between the main pressing process and the straightening pressing process. In such a case, at one of the left and right boundary portions 7 of the electrode plate 1, there is a slight area that is not pressed in either the main pressing step or the corrective pressing step. In that region, after both the main pressing process and the corrective pressing process are performed, a remarkable difference in elongation is concentrated within a very narrow range. Since the extensibility of the current collecting foil 2 in the boundary portion 7 is improved in advance, even in such a case, damage or deformation of the current collecting foil 2 in that region can be prevented. Thus, a method of manufacturing an electrode plate is realized that can manufacture an electrode plate while preventing the occurrence of wrinkles and warpage.

The present embodiments and examples are merely examples, and do not limit the disclosed technology in any way. Therefore, the disclosed technique can naturally be improved and modified in various ways without departing from the gist thereof. For example, the type of target electrode plate is not limited to the positive electrode plate of the lithium ion battery, and may be other types .

1 Electrode plate 2 Current collector foil 3 Electrode layer 4 Coated part 5 Non-coated part 7 Boundary part 8 IH heater

Claims (1)

It has a collector foil and an electrode layer on its surface, and a part in the width direction is a coating part having both the collector foil and the electrode layer, and the rest in the width direction is the collector foil. A method for manufacturing an electrode plate, which is a non-coated portion having no electrode layer, comprising:
A main pressing step of pressing the coated portion in the thickness direction;
By pressing the current collector foil of the non-coated portion before or after the main pressing step, the current collector foil of the coated portion and the current collector of the non-coated portion after the main pressing step A straightening press process that reduces the difference in elongation with the foil,
Only the boundary portion between the coated portion and the non-coated portion of the current collector foil is removed prior to the latter one of the main pressing step and the straightening pressing step. and a heating step of heating with an IH heater within a range in which the temperature of the electrode plate does not reach its melting point.

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