Roll press equipment for secondary battery manufacturing

Abstract

The disclosed invention relates to a roll press device that performs hot rolling on an electrode coated with an electrode active material, and in one example, a preheater is disposed upstream of a rolling unit that performs rolling on an electrode transported by a roll-to-roll method, and the preheater irradiates the electrode surface with an infrared laser along the width direction to heat it as radiant heat.

Description

[Technical Field]

[0001] The present invention relates to a roll press device for hot rolling electrodes for secondary batteries.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0173935, dated December 5, 2023, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference. [Background technology]

[0003] As technological development and demand for mobile devices increases, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, much research is being conducted on secondary batteries that can meet various requirements.

[0004] Typically, in terms of battery shape, there is a high demand for prismatic secondary batteries and pouch-type secondary batteries that are thin and can be applied to products such as mobile phones, and in terms of materials, there is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries that have advantages such as high energy density, discharge voltage, and output stability.

[0005] Such secondary batteries are manufactured by coating an electrode sheet with an electrode mixture, which is a mixture of an active material, a conductive material, a binder, etc., and then laminating the electrodes manufactured through processes such as rolling, drying, slitting, and notching with a separator interposed therebetween, and then housing the formed electrode assembly in a battery case, injecting an electrolyte, and sealing it.

[0006] Many processes performed during the manufacture of such secondary batteries are carried out in a roll-to-roll manner, in which an electrode roll having electrodes wound around a bobbin is unwound using an unwinder and various processes are carried out, while at the same time, a rolling process, drying process, etc. are carried out by rewinding the processed electrode roll on the opposite side using a rewinder.

[0007] The rolling process uses a roll press device to transfer the electrode between two rolls and apply pressure. Hot rolling with the roll press device increases the temperature of the electrode and reduces the surface hardness, achieving high rolling density with low rolling force. The current electrode heating method uses an electric heating rod to directly heat the roll, which then applies conductive heat to the electrode surface.

[0008] However, the conduction heating method has a slow heating response speed, residual heat remains even when the power supply to the heating rod is cut off, the cooling speed is slow, and it takes time for heat to be conducted to the electrode, making it difficult to increase the electrode roll transfer speed.Increasing the roll transfer speed can reduce the tack time, but there are limits to such process improvements with the conduction heating method. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to provide a roll press device that uses radiant heat to improve the heating and cooling response of the electrode surface and selectively heats the electrode active material, thereby preventing quality problems such as wrinkles in non-coated areas caused by foil expansion.

[0010] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the description of the invention described below. [Means for solving the problem]

[0011] The present invention relates to a roll press device that performs hot rolling on an electrode to which an electrode active material has been applied. In one example, a preheater is disposed upstream of a rolling unit that performs rolling on an electrode being transported by a roll-to-roll method, and the preheater irradiates the surface of the electrode with an infrared laser along the width direction to heat it as radiant heat.

[0012] In one embodiment of the present invention, the wavelength of the infrared laser irradiated by the preheater is in a range that has an absorptivity of at least 10% or less for copper or aluminum, which are the materials of the electrode, and at the same time has an absorptivity of at least 70% or more for the electrode active material.

[0013] For example, the wavelength of the infrared laser may be in the range of 1064±100 nm.

[0014] The output of the infrared laser may be controlled to maintain the temperature of the electrode active material in the range of 80±5°C.

[0015] In one embodiment, the output of the infrared laser may be controlled as an output per unit time that varies depending on the transport speed of the electrode.

[0016] The preheater can irradiate an infrared laser in the form of a line beam or a square beam across the direction of movement of the electrode being moved in a roll-to-roll manner.

[0017] On the other hand, the present invention provides a hot rolling method for electrodes for secondary batteries, in which an electrode coated with an electrode active material is transported by a roll-to-roll method, and a preheater arranged upstream of a rolling unit that rolls the electrode irradiates an infrared laser along the width direction of the surface of the electrode to heat it as radiant heat.

[0018] Preferably, the wavelength of the infrared laser irradiated by the preheater can be in a range that has an absorption rate of at least 10% or less for copper or aluminum, which are the materials of the electrode, and at the same time has an absorption rate of at least 70% or more for the electrode active material.

[0019] For example, the wavelength of the infrared laser may be in the range of 1064±100 nm.

[0020] The output of the infrared laser may be controlled as an output per unit time that varies depending on the transport speed of the electrode so that the temperature of the electrode active material is maintained within the range of 80±5°C. [Effects of the Invention]

[0021] In the roll press device of the present invention having the above-described configuration, the surface of the electrode is heated by the infrared laser emitted by the preheater, i.e., the electrode is heated in the form of radiant heat transfer rather than conductive heat transfer.

[0022] Therefore, according to the roll press device of the present invention, the heating response speed is fast due to radiant heat, the preheater is cooled immediately without residual heat when the power supply is cut off, and the fast heat transfer makes it easy to increase the transport speed of the electrode roll.

[0023] Furthermore, since radiant heat selectively heats the electrode active material rather than the electrode, which is made of a metal material, problems such as wrinkles caused by expansion of non-coated portions where there is no electrode active material do not occur.

[0024] However, the technical effects that can be obtained by the present invention are not limited to the effects described above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the invention described below.

[0025] The drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention below, serve to facilitate a better understanding of the technical concept of the present invention; therefore, the present invention should not be interpreted as being limited solely to the matters depicted in such drawings. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a view schematically illustrating a roll press device according to an embodiment of the present invention. [Figure 2]1 is a graph showing infrared absorptance for copper and aluminum according to wavelength; [Figure 3] 1 is a diagram schematically showing an example of infrared absorption in an electrode to which an electrode active material is applied. [Figure 4] 1 is a diagram showing an example of irradiating an infrared laser onto an electrode surface coated with an electrode active material. [Figure 5] 1 is a flowchart of a hot rolling method for a secondary battery electrode. DETAILED DESCRIPTION OF THE INVENTION

[0027] Because the present invention can be modified in various ways and can have various embodiments, specific embodiments will be described in detail below.

[0028] However, this is not to be construed as limiting the invention to any particular embodiment, but rather as including all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0029] In the present invention, the terms "comprise" and "have" are understood to mean the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification, without precluding the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0030] In addition, in the present invention, when an element such as a layer, film, region, or plate is described as being "on" another element, this includes not only the case where it is "directly on" the other element, but also the case where there is another element between them. Conversely, when an element such as a layer, film, region, or plate is described as being "under" another element, this includes not only the case where it is "directly under" the other element, but also the case where there is another element between them. Furthermore, in this application, being arranged "on" can include not only the case where it is arranged on the top, but also the case where it is arranged on the bottom.

[0031] The present invention relates to a roll press device that performs hot rolling on an electrode coated with an electrode active material. In one example, a preheater is disposed upstream of a rolling unit that performs rolling on an electrode transported by a roll-to-roll method, and the preheater irradiates the electrode surface with an infrared laser along the width direction to heat it as radiant heat.

[0032] According to the roll press device of the present invention having the above-described configuration, the surface of the electrode is heated by the infrared laser irradiated by the preheater, i.e., the electrode is heated in the form of radiative heat conduction rather than conductive heat transfer.

[0033] Therefore, according to the roll press device of the present invention, the heating response speed is fast due to radiant heat, the preheater is cooled immediately without residual heat when the power supply is cut off, and the fast heat transfer makes it easy to increase the transport speed of the electrode roll.

[0034] Hereinafter, a specific embodiment of a roll press apparatus 10 according to the present invention will be described in detail with reference to the accompanying drawings. The directions of front, back, up, down, left, and right used in the following description to specify relative positions are intended to aid in understanding the invention, and unless otherwise specified, are based on the directions shown in the drawings.

[0035] (First embodiment) FIG. 1 is a diagram schematically illustrating a roll press apparatus 10 according to one embodiment of the present invention.

[0036] The roll press device 10 is a device that performs a rolling process to apply pressure to the surface of the electrode 300 coated with the electrode active material 310, thereby increasing the density of the electrode active material 310 and making the thickness of the electrode active material 310 uniform. For the rolling process that is performed using a roll-to-roll method, the electrode 300 coated with the electrode active material 310 is wound around a bobbin, and the bobbin around the electrode 300 is attached to an unwinder 100. The electrode 300 attached to the unwinder 100 is unwound, and the unwound electrode 300 is rewound by a rewinder 140 located downstream to return to a roll shape. Appropriate tension is applied to the electrode 300 being transported using the roll-to-roll method, preventing various problems such as bending or undulation of the electrode 300.

[0037] A rolling unit 120 is disposed between the unwinder 100 and the rewinder 140. The rolling unit 120 applies a set pressure to the electrode 300 as it passes between a pair of rotating rollers. The pressure increases the density of the active material 310 of the electrode 300 and makes the thickness uniform. The roll press apparatus 10 also includes an infeed 110 and an outfeed 130. The infeed 110 is disposed between the unwinder 100 and the rolling unit 120, and the outfeed 130 is disposed between the rolling unit 120 and the rewinder 140. The infeed 110 and the outfeed 130 adjust the tension applied to the electrode 300 or align the electrode 300 so that the electrode 300 is transported smoothly. For example, the infeed 110 and the outfeed 130 can correct the meandering phenomenon, in which the electrode 300 is transported at an angle.

[0038] The roll press apparatus 10 of the present invention includes a preheater 200 for hot rolling. Hot rolling increases the temperature of the electrode 300 to reduce the surface hardness, thereby achieving a high rolling density with a low rolling force. Therefore, the preheater 200 is disposed upstream of the rolling unit 120, which rolls the electrode 300 transported by a roll-to-roll method. The electrode 300 is appropriately heated by the preheater 200, allowing hot rolling to be performed in the rolling unit 120.

[0039] In the roll press apparatus 10 of the present invention, the preheater 200 irradiates the surface of the transported electrode 300 with an infrared laser along the width direction to heat it as radiant heat. The infrared heat of the electrode 300 is selectively absorbed by the electrode 300, which is a metal material, and the electrode active material 310 applied thereon. In other words, there is a significant difference in the absorbance of the infrared light between the electrode 300 and the electrode active material 310.

[0040] FIG. 2 is a graph showing the infrared absorptance of copper and aluminum at different wavelengths. Copper and aluminum are typical electrode 300 (positive and negative electrode) materials, and as shown in FIG. 2, copper or aluminum has an infrared absorption rate of at least 10%. On the other hand, a nearly black electrode active material 310 has an infrared absorption rate of at least 70%. Therefore, when an infrared laser with the same output power is irradiated along the width direction of the surface of the electrode 300, the temperature of the electrode active material 310 rises significantly compared to the temperature of the electrode 300 due to the significant difference in absorptance.

[0041] For example, the wavelength of the infrared laser may be within the range of 1064±100 nm. In this wavelength range, the absorption rate of copper is less than about 1%, and the absorption rate of aluminum is less than about 5%. Meanwhile, the absorption rate of the electrode active material 310 reaches a level of about 80% or more. That is, at the reference wavelength of 1064 nm, the electrode active material 310 absorbs most of the infrared light, while copper and aluminum reflect almost all of the infrared light.

[0042] 3 is a diagram schematically illustrating an example of infrared absorption in an electrode 300 coated with an electrode active material 310. The electrode active material 310 is coated on the surface of the electrode 300, and a laser irradiator 210 provided in a preheater 200 irradiates the electrode with an infrared laser. The infrared laser is first irradiated onto the electrode active material 310 on the surface, and as a result, some of the infrared light is reflected from the surface, but most of the infrared energy is absorbed by the electrode active material 310. Furthermore, some of the infrared light reaches the surface of the electrode 300, but most of it is reflected from the surface of the electrode 300 and reabsorbed by the electrode active material 310.

[0043] When the electrode 300 is heated by the radiant heat of an infrared laser, most of the energy is absorbed by the electrode active material 310, and only a small portion is absorbed by the copper or aluminum electrode 300. Heating by radiant heat has a fast response, and energy transfer is immediately cut off when infrared irradiation is stopped. This selective heating by infrared radiation prevents a significant rise in the temperature of the electrode 300. Therefore, the temperature rise of the electrode 300 where the electrode active material 310 is not applied is significantly lower than when conventional conductive heat is applied, and problems such as wrinkling of the uncoated portion 320 due to expansion of the electrode 300 are also eliminated.

[0044] 4 is a diagram illustrating an example of irradiating an infrared laser onto the surface of an electrode 300 coated with an electrode active material 310. In the exemplary embodiment illustrated in FIG. 4, the preheater 200 includes two laser irradiators 210. Each laser irradiator 210 irradiates infrared light in a wavelength band of 1064±100 nm, and can irradiate the infrared laser in the form of a line beam or square beam across the transport direction of the electrode 300 transported in a roll-to-roll manner.

[0045] The driving of the laser irradiator 210 is controlled by a preheater controller 220. The preheater controller 220 can also adjust the output of the laser light. By adjusting the output of the infrared laser, the heating temperature to which the electrode 300 is heated can be adjusted. For example, the output of the infrared laser can be controlled so that the temperature of the electrode active material 310 is maintained within a range of 80±5°C.

[0046] For feedback control, a temperature sensor 230 for measuring the temperature of the electrode active material 310 may be disposed downstream of the preheater 200. The temperature sensor 230 may measure the temperature of the electrode active material 310, for example, in a non-contact manner. Based on the measured temperature of the electrode active material 310, the output of the infrared laser may be variably adjusted.

[0047] Furthermore, since the preheater 200 heats the electrode 300 that is transported in a roll-to-roll manner, it is preferable to change the output of the infrared laser according to the transport speed of the electrode 300. In other words, since the time it takes for radiant heat to be transmitted varies depending on the transport speed, it is appropriate to control the output of the laser by taking into consideration the transport speed of the electrode 300. Therefore, the output of the infrared laser can be controlled as an output per unit time that changes according to the transport speed of the electrode 300.

[0048] As a result, when the transport speed of the electrode 300 increases, the temperature of the electrode active material 310 can be raised to a required value, for example, within a range of 80±5°C, by irradiating it with an infrared laser having a higher output per unit time. This is made possible by the high responsiveness of the radiant heat and the instantaneous output control of the laser irradiator 210. In other words, the roll-to-roll transport speed can be increased within the range of the allowable output per unit time of the infrared laser. Therefore, the roll press apparatus 10 of the present invention is advantageous for increasing the roll transport speed and correspondingly shortening the tack time.

[0049] (Second embodiment) Meanwhile, the present invention provides a hot rolling method for secondary battery electrodes, in which an electrode 300 coated with an electrode active material 310 is transported in a roll-to-roll manner, and a preheater 200 arranged upstream of a rolling unit 120 that rolls the electrode 300 irradiates an infrared laser along the width direction of the surface of the electrode 300 to heat it as radiant heat. The main components of this hot rolling method for secondary battery electrodes are summarized in the flowchart of FIG.

[0050] As described in the first embodiment, it may be preferable that the wavelength of the infrared laser irradiated by the preheater 200 has an absorptivity of at least 10% or less for copper or aluminum, which is the material of the electrode 300, and at the same time has an absorptivity of at least 70% or more for the electrode active material 310.

[0051] For example, the wavelength of the infrared laser emitted by the preheater 200 may be within the range of 1064±100 nm.

[0052] The output of the infrared laser may be controlled as an output per unit time that varies depending on the transport speed of the electrode 300 so that the temperature of the electrode active material 310 is in the range of 80±5° C. As described above, a temperature sensor 230 for measuring the temperature of the electrode active material 310 may be disposed downstream of the preheater 200 for feedback control.

[0053] The present invention has been described in more detail above with reference to the drawings and embodiments, etc. However, the configurations shown in the drawings or embodiments in this specification are merely one embodiment of the present invention and do not represent all of the technical ideas of the present invention, and therefore, there may be various equivalents and modifications that can replace them at the time of filing this application. [Explanation of symbols]

[0054] 10: Roll press device 100: Unwinder 110: Infeed 120: Rolling unit 130: Outfeed 140: Rewinder 200: Preheater 210: Laser irradiator 220: Preheater controller 230: Temperature sensor 300: Electrode 310: Electrode active material 320: Non-coated area

Claims

1. A roll press device that performs hot rolling on an electrode to which an electrode active material is applied, a preheater is disposed upstream of a rolling unit that rolls the electrode being transported by a roll-to-roll method; The preheater irradiates the surface of the electrode with an infrared laser along the width direction thereof to heat the surface as radiant heat.

2. 2. The roll press device according to claim 1, wherein the wavelength of the infrared laser irradiated by the preheater is in a range that has an absorption rate of at least 10% or less for copper or aluminum, which is a material of the electrode, and at the same time has an absorption rate of at least 70% or more for the electrode active material.

3. The roll press apparatus according to claim 2 , wherein the wavelength of the infrared laser is within a range of 1064±100 nm.

4. 4. The roll press device according to claim 3, wherein the output of the infrared laser is controlled so as to maintain the temperature of the electrode active material within a range of 80±5°C.

5. 5. The roll press device according to claim 4, wherein the output of the infrared laser is controlled as an output per unit time that varies in accordance with the transport speed of the electrode.

6. 6. The roll press apparatus according to claim 1, wherein the preheater irradiates the infrared laser in a line beam or square beam manner across a transfer direction of the electrode being transferred in a roll-to-roll manner.

7. The electrode coated with the electrode active material is transferred using a roll-to-roll method. A hot rolling method for electrodes for secondary batteries, in which a preheater located upstream of a rolling unit that rolls the electrode irradiates an infrared laser along the width direction of the surface of the electrode to heat it as radiant heat.

8. 8. The hot rolling method for a secondary battery electrode according to claim 7, wherein the wavelength of the infrared laser irradiated by the preheater is in a range that has an absorptivity of at least 10% or less for copper or aluminum that is a material of the electrode, and at the same time has an absorptivity of at least 70% or more for the electrode active material.

9. 9. The hot rolling method for a secondary battery electrode according to claim 8, wherein the wavelength of the infrared laser is within a range of 1064±100 nm.

10. 10. The hot rolling method for a secondary battery electrode according to claim 9, wherein the output of the infrared laser is controlled as an output per unit time that changes according to a transport speed of the electrode so that the temperature of the electrode active material is maintained in a range of 80±5°C.

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