Battery manufacturing method

Abstract

The present invention provides a battery manufacturing method that enables uniform thickness and properties of the coated film after drying. [Solution] The method for manufacturing this battery comprises the steps of applying a coating film onto an electrode body and drying the coating film by irradiating it with a laser. The step of drying the coating film involves drying the coating film by irradiating it with a laser from a laser irradiation device having a plurality of laser light-emitting elements arranged in the width direction of the electrode body. The plurality of laser light-emitting elements comprises a first element group that irradiates laser light onto the width direction ends of the electrode body, a second element group located inward in the width direction from the first element group, and a third element group located inward in the width direction from the second element group. The output energy of the first element group is smaller than the output energy of the second element group, and the output energy of the third element group is smaller than the output energy of the second element group.

Description

Technical Field

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[0001] The present invention relates to a method for manufacturing a battery.

Background Art

[0002] For example, an electrode of a battery such as a lithium-ion battery is formed by applying a coating film on a base material and drying the coating film by performing a drying process. The drying process is performed, for example, by blowing hot air toward the base material on which the coating film is applied by a heater (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The coating film on the base material after the drying process is required to have a uniform thickness and properties on the base material. However, in the conventional drying process using hot air, it is difficult to uniformly transfer heat to the coating film. For example, burning occurs in some coating films, or sagging occurs at the ends of the coating film, resulting in a thinner thickness. It has been difficult to make the thickness and properties of the coating film after drying uniform.

[0005] In view of the above problems, the present invention provides a method for manufacturing a battery capable of making the thickness and properties of the coating film after drying uniform.

Means for Solving the Problems

[0006] <00A method for manufacturing a battery according to the present invention comprises the steps of applying a coating film onto an electrode body and drying the coating film by irradiating it with a laser. The step of drying the coating film involves drying the coating film by irradiating it with a laser from a laser irradiation device having a plurality of laser light-emitting elements arranged in the width direction of the electrode body. The plurality of laser light-emitting elements include a first element group that irradiates laser light onto the width direction ends of the electrode body, a second element group located inward in the width direction from the first element group, and a third element group located inward in the width direction from the second element group. The output energy of the first element group is smaller than the output energy of the second element group, and the output energy of the third element group is smaller than the output energy of the second element group.

[0007] According to this manufacturing method, the output energy of the second element group is greater than that of the first and third element groups. As a result, the heat generated by the laser light is dispersed towards the center of the electrode body corresponding to the third element group, as well as towards the edges corresponding to the first element group. Therefore, the heat generated by the laser can be uniformly dispersed in the width direction, making it possible to dry the coated film uniformly in thickness and properties without causing foil burning or other damage.

[0008] In this method, the output energy of the laser light-emitting element of the first element group can be less than the average value of the output energies of the multiple laser light-emitting elements, the output energy of the laser light-emitting element of the second element group can be greater than the average value, and the output energy of the laser light-emitting element of the third element group can be less than the average value. Such settings make it possible to dry the coated film more uniformly.

[0009] Furthermore, the third element group may be located in the center of the plurality of laser light-emitting elements. In addition, the second element group may be located on both sides of the third element group and arranged symmetrically with respect to the center in the width direction.

[0010] In the above manufacturing method, the sum of the output energies of the third element group can be made to be less than a reference value by a first amount, the sum of the output energies of the second element group can be made to be more than a reference value by a second amount, and the first amount can be made to be greater than the second amount. By setting in this way, the output energies of the third element group can be optimized, and the drying process of the coated film by the third element group can be performed more appropriately while avoiding foil burning and the like. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view illustrating the structure of a lithium-ion secondary battery used as a power source in vehicles. [Figure 2] This is a perspective view illustrating the structure of a lithium-ion secondary battery used as a power source in vehicles. [Figure 3] This is a cross-sectional view illustrating the structure of a lithium-ion secondary battery used as a power source in vehicles. [Figure 4] This is a schematic diagram illustrating the coating and drying processes for the negative electrode body 40 or the positive electrode body 50. [Figure 5] The configuration of the laser irradiation device 130 used in the drying process will be described. [Figure 6] This graph shows the distribution of the output energy of the laser irradiation device 130. [Figure 7] The effects of this embodiment will now be explained. [Modes for carrying out the invention]

[0012] This embodiment will be described below with reference to the attached drawings. In the attached drawings, functionally identical elements may be indicated by the same number. The attached drawings show embodiments and implementation examples in accordance with the principles of this disclosure, but they are for the purpose of understanding this disclosure and are not to be used in any way to restrict the interpretation of this disclosure. The descriptions in this specification are merely typical examples and do not limit the claims or applications of this disclosure in any way.

[0013] While this embodiment is described in sufficient detail for those skilled in the art to implement the disclosure, it is important to understand that other implementations and forms are possible, and that the configuration and structure can be modified and various elements replaced without departing from the scope and spirit of the technical idea of ​​this disclosure. Therefore, the following description should not be construed as limiting to this.

[0014] Hereinafter, a manufacturing method according to an embodiment of the present invention will be described with reference to the drawings. The battery manufactured by the manufacturing method of this embodiment is, for example, a lithium-ion secondary battery. The lithium-ion secondary battery constitutes a battery pack used as an on-board power source for vehicles such as electric vehicles and hybrid vehicles.

[0015] Referring to Figures 1 to 3, an example of the structure of a lithium-ion secondary battery used as an in-vehicle power source will be explained. In each figure, arrow D indicates the longitudinal direction D of the lithium-ion secondary battery 10, arrow E indicates the depth direction E of the lithium-ion secondary battery 10, arrow F indicates the vertical direction F of the lithium-ion secondary battery 10, and arrow T indicates the thickness direction T of the winding body 30. The longitudinal direction D of the lithium-ion secondary battery 10 coincides with the width direction G of the winding body 30, with one side of the width direction G of the winding body 30 being the positive electrode and the other side of the width direction G of the winding body being the negative electrode.

[0016] As shown in Figure 1, the lithium-ion secondary battery 10 includes a lid assembly 20, a winding body 30, and a battery case 70.

[0017] The battery case 70 is made of aluminum, for example, and is formed in the shape of a rectangular box with an open top and a long longitudinal direction D. The lid assembly 20 includes a lid member 21, a positive current collection terminal 22 as a current collection terminal, a negative current collection terminal 23 as a current collection terminal, a positive external terminal 24 as an external terminal, and a negative external terminal 25 as an external terminal.

[0018] The lid member 21 is made of, for example, aluminum and is formed in a rectangular plate shape extending in the longitudinal direction D. The lid member 21 includes a safety valve 21A and a cap 26 that closes the injection port 21B. The safety valve 21A opens when the value of the internal pressure of the battery case 70 reaches a predetermined pressure, and discharges the gas generated inside the battery case 70. The injection port 21B is formed as a through-hole penetrating in the plate thickness direction of the lid member 21 and is used when injecting electrolyte into the battery case 70. A cap 26 is airtightly sealed and attached to the injection port 21B, for example, by laser welding.

[0019] The battery case 70 houses a wound body 30, a positive electrode current collector terminal 22, and a negative electrode current collector terminal 23. The lid member 21 is attached, for example, by laser welding, so as to close the opening of the battery case 70.

[0020] The positive electrode current collector terminal 22 and the positive electrode external terminal 24 are made of, for example, aluminum and are arranged on one end side in the longitudinal direction D of the battery case 70. The positive electrode current collector terminal 22 is formed in a rectangular plate shape with the depth direction E as the plate thickness direction. The positive electrode current collector terminal 22 is joined to the positive electrode current collecting portion 32 of the wound body 30, for example, by resistance welding. The positive electrode external terminal 24 is electrically connected to the positive electrode current collector terminal 22 and is exposed outside the lid member 21.

[0021] The negative electrode current collector terminal 23 is made of, for example, copper and is arranged on the other end side in the longitudinal direction D of the battery case 70 and is formed in a rectangular plate shape with the depth direction E as the plate thickness direction. The negative electrode current collector terminal 23 is joined to the negative electrode current collecting portion 33 of the wound body 30, for example, by ultrasonic welding. The negative electrode external terminal 25 is electrically connected to the negative electrode current collector terminal 23 and is exposed outside the lid member 21.

[0022] As shown in Figure 2, the wound body 30 is wound with a negative electrode body 40, a positive electrode body 50, and a separator 60 stacked on top of each other, and as an example, its cross-section is formed to be flattened and housed in the battery case 70. The power generation unit 31 of the wound body 30 is formed by stacking the region of the positive electrode body 50 to which the positive electrode active material is coated, the region of the negative electrode body 40 to which the negative electrode active material is coated, and the separator 60. The power generation unit 31 has the function of storing electrical energy of the lithium-ion secondary battery 10.

[0023] The positive electrode current collector portion 32 of the wound body 30 is not coated with active material and is formed by winding the positive electrode body 50. The negative electrode current collector portion 33 is not coated with active material and is formed by winding the negative electrode body 40.

[0024] As shown in Figure 3, the negative electrode body 40 has a long, strip-shaped negative electrode body 41 on both sides coated with a negative electrode active material 42. The negative electrode active material 42 has an outer peripheral negative electrode active material 42A that is located on the outer peripheral side and an inner peripheral negative electrode active material 42B that is located on the inner peripheral side. The other end of the negative electrode body 40 in the width direction G is not coated with the negative electrode active material 42, and the negative electrode body 41 is exposed.

[0025] The positive electrode body 50 has a positive electrode active substance 52 coated on both sides of a long, strip-shaped positive electrode body 51. The positive electrode active substance 52 has an outer peripheral positive electrode active substance 52A that is arranged on the outer peripheral side and an inner peripheral positive electrode active substance 52B that is arranged on the inner peripheral side. At one end of the positive electrode body 50 in the width direction G, the positive electrode active substance 52 is not coated, and the positive electrode body 51 is exposed.

[0026] The separator 60 is made of an insulating material. The separator 60 is placed between the positive electrode body 50 and the negative electrode body 40, and insulates the positive electrode body 50 from the negative electrode body 40.

[0027] The wound body 30 shown in Figure 3 is formed by stacking a negative electrode body 40, a positive electrode body 50, and a separator 60 and winding them into a roughly cylindrical shape. Subsequently, the roughly cylindrical wound body 30 is pressed in a pressing process to flatten it. After that, a lithium-ion secondary battery as shown in Figure 1 is formed through a terminal welding process, a cell drying process, electrolyte injection, a sealing process, and a high-temperature aging process.

[0028] The manufacturing process for the negative electrode body 40 and the positive electrode body 50 will be explained with reference to Figures 4 to 6. Figure 4 is a schematic diagram illustrating the coating and drying process of the negative electrode body 40 or the positive electrode body 50, and Figure 5 shows the laser irradiation device 130 used in the drying process. The graph in Figure 6 shows an example of the output energy distribution of the laser irradiation device 130 (the horizontal axis represents the distance G in the width direction, and the vertical axis represents the output energy).

[0029] As described above, the negative electrode body 40 has negative electrode active material 42 (42A, 42B) coated on both sides of the negative electrode body 41, and the positive electrode body 50 has positive electrode active material 52 (52A, 52B) coated on both sides of the positive electrode body 51. Since the manufacturing process is the same for the negative electrode body 40 and the positive electrode body 50, the manufacturing process for the negative electrode body 40 will be described below.

[0030] The negative electrode body 41 is wound around a roll section (not shown) and is fed by the roller 110 in the direction of the arrow in Figure 4. The negative electrode active substance 42 is discharged from the coating section 120 and applied onto the negative electrode body 41 (step S1).

[0031] When the negative electrode active substance 42 is applied to the negative electrode body 41, a laser irradiation device 130 located downstream of the application section 120 irradiates the negative electrode active substance 42 with laser light, thereby performing a drying process (step S2) for the negative electrode active substance 42. In this embodiment, a laser irradiation device 130 is used for the drying process. Since the drying process is performed by the heat generated by the laser irradiation, it is possible to dry the thin film without causing it to flutter, compared to devices that perform a drying process by blowing hot air, such as those described in Patent Document 1.

[0032] As shown in Figure 5, the laser irradiation device 130 is configured by arranging a plurality of laser diodes LD (laser light-emitting elements) along the width direction G of the negative electrode body 40. The plurality of laser diodes LD include a first element group LDe that irradiates the ends of the negative electrode body 40 in the width direction G with laser light, a second element group LDm that is located inside the width direction G of the first element group LDe and irradiates the intermediate part between the ends and the center with laser light, and a third element group LDc that is located inside the width direction G of the second element group LDm and irradiates the center with laser light. The second element group LDm is arranged symmetrically on either side of the third element group LDc.

[0033] The laser diodes LD in the first to third element groups LDe, LDm, and LDc have different output energies. Specifically, as shown in Figure 6, the output energy of the laser diode LD in the first element group LDe, which corresponds to the ends, is lower than that of the laser diode LD in the second element group LDm, which corresponds to the middle section. Also, the output energy of the laser diode LD in the third element group LDc, which corresponds to the center section, is lower than that of the laser diode LD in the second element group LD.

[0034] Preferably, when the average output energy of the laser diodes LD in the laser irradiation device 130 is Ea, the output energy of each laser diode LD in the first element group LDe is set to be less than the average value Ea, the output energy of each laser diode LD in the second element group LDm is set to be greater than the average value Ea, and the output energy of each laser diode LD in the third element group LDc is set to be less than the average value Ea.

[0035] Furthermore, it is preferable that the sum of the output energies in the first element group Lde be 10-20% lower than the reference value (integral value of the average value). Also, it is preferable that the sum of the output energies in the second element group LDm be 10-20% higher than the reference value. Furthermore, it is preferable that the sum of the output energies in the third element group LDc be 10-20% lower than the reference value.

[0036] As described above, in the laser irradiation device 130 of this embodiment, the output energy (amount of light irradiation) from the laser diode LD is set to be greater than the average value Ea in the middle part of the width direction G of the negative electrode body 40 or positive electrode body 50, and less than the average value Ea at the ends and center. This suppresses heat concentration at the ends of the negative electrode body 40 or positive electrode body 50, and prevents non-uniformity of the film due to foil burning of the coated film. Furthermore, by setting the output energy of the laser diode in the center to be less than the average value Ea, excessive heat input in the center is prevented, and non-uniformity of the film due to foil burning of the center can be suppressed.

[0037] Furthermore, it is preferable to adjust the output energy of the laser diode LD such that the decrease in output energy in the central part is greater than the increase in output energy in the left and right intermediate parts. The decrease in output energy in the central part is represented by the area Ac shown in Figure 6. The increase in output energy in the intermediate part is represented by the area Am shown in Figure 6. The decrease in output energy at the ends is represented by the area Ae shown in Figure 6.

[0038] Area Ac is equal to the sum of the output energies of the multiple laser diodes LD in the central region, minus the value obtained by multiplying the average output energy of all laser diodes LD (Ea) by the number of laser diodes LD in the central region. Area Am is equal to the sum of the output energies of the multiple laser diodes LD in the middle region, minus the value obtained by multiplying the average output energy of all diodes LD by the number of laser diodes LD in the middle region. Area Ae is equal to the sum of the output energies of the multiple laser diodes LD at the edges, minus the value obtained by multiplying the average output energy of all diodes LD by the number of laser diodes LD at the edges.

[0039] By adjusting the output energy of the laser diode LD so that area Ac is larger than area Am, excess thermal energy generated in the middle can be absorbed in the center, and the transfer of excess thermal energy to the edges can be suppressed. If excess thermal energy is absorbed at the edges, foil burning of the coating film (negative electrode active material 42, positive electrode active material 52) at the edges may occur, which may degrade the properties of the coating film. According to this embodiment, the coating film can be dried while maintaining uniform thickness and properties, while preventing the occurrence of such foil burning.

[0040] The effects of this embodiment will be explained with reference to Figure 7. Figure 7(a) shows the heat distribution of the negative electrode body 40 or the positive electrode body 50 when the output energy of all laser diodes LD of the laser irradiation device 130 is the same. Figure 7(b) shows the heat distribution when the laser irradiation device 130 is configured as in this embodiment.

[0041] When the output energy of all laser diodes (LDs) is the same, as shown in Figure 7(a), heat concentration occurs at the edges, resulting in a large temperature difference between the edges and the center (for example, 113.7°C compared to 200.6°C). In contrast, when the output energy distribution as in this embodiment is applied, the temperature difference between the edges and the center becomes smaller (for example, 126.8°C compared to 165.8°C). By reducing the temperature difference between the edges and the center, foil burning of the coating film is suppressed, and the properties of the coating film can be further improved. Since the drying process can be performed while suppressing foil burning due to uneven heat transfer, the drying process can be completed in a shorter time according to this embodiment. For example, in a hot air drying process such as that described in Patent Document 1, drying takes about 9 seconds to complete, but according to this embodiment, it can be completed in about 3 seconds.

[0042] This disclosure is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are described in detail for the purpose of explaining this disclosure clearly, and are not necessarily limited to having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. [Explanation of Symbols]

[0043] 10…Lithium-ion rechargeable battery 20…Lid Assembly 21... Lid component 21A…Safety valve 21B…Inlet 22... Positive current collection terminal 23... Negative current collection terminal 24…Positive external terminal 25... Negative external terminal 26…Cap 30...Wound body 31...Power generator 32... Positive electrode current collector 33... Negative electrode current collector 40... Negative electrode body 41... Negative electrode body 42...Negative electrode active material 42A…Outer peripheral side negative electrode active material 42B…Inner circumferential negative electrode active material 50…Positive electrode body 51…Positive electrode body 52...Cathode active material 52A…Outer positive electrode active material 52B…Inner circumferential positive electrode active material 60... Separator 70...Battery case 110...Laura 120...Coating area 130…Laser irradiation device

Claims

1. The steps include applying a coating film onto the electrode body, The steps include drying the coated film by irradiating it with a laser and Equipped with, The step of drying the coating film involves drying the coating film by irradiating it with a laser from a laser irradiation device having a plurality of laser light-emitting elements arranged in the width direction of the electrode body. The plurality of laser light-emitting elements comprises a first group of elements that irradiates laser light to the widthwise ends of the electrode body, a second group of elements located further inward in the widthwise direction than the first group of elements, and a third group of elements located further inward in the widthwise direction than the second group of elements. The output energy of the laser light-emitting element of the first element group is smaller than the output energy of the laser light-emitting element of the second element group. The output energy of the laser light-emitting element of the third element group is smaller than the output energy of the laser light-emitting element of the second element group. A method for manufacturing a battery, characterized by the following features.

2. The output energy of the laser light-emitting element of the first element group is smaller than the average value of the output energies of the plurality of laser light-emitting elements. The output energy of the laser light-emitting element of the second element group is greater than the average value. The method for manufacturing a battery according to claim 1, wherein the output energy of the laser light-emitting element of the third element group is smaller than the average value.

3. The method for manufacturing a battery according to claim 1 or 2, wherein the third group of elements is located in the center of the plurality of laser light-emitting elements.

4. The method for manufacturing a battery according to claim 3, wherein the second group of elements is located on both sides of the third group of elements and is arranged symmetrically with respect to the center in the width direction.

5. The sum of the output energies of the third group of elements is less than the reference value by a first amount. The sum of the output energies of the second group of elements is greater than the reference value by a second amount. The method for manufacturing a battery according to claim 1, wherein the first amount is greater than the second amount.

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