Manufacturing Method of Electrode for Secondary Battery Including Pressing Process of Wet Electrode Active Material Slurry and Manufacturing Apparatus

Abstract

In the present invention, as a method for manufacturing an electrode for a secondary battery, The above method for manufacturing an electrode for a secondary battery includes a rolling process in which a load is applied to an electrode active material slurry when the solid content of the un-dried electrode active material slurry is 70 wt% to 98 wt% during the process of drying an electrode active material slurry coated in one or more layers on a current collector, and an apparatus for manufacturing the same is provided.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing an electrode for a secondary battery, comprising a process of rolling an undried electrode active material slurry, and a manufacturing apparatus. Background Technology

[0002] Due to the rapid increase in the use of fossil fuels, there is a growing demand for alternative and clean energy. As part of this effort, the fields of power generation and energy storage utilizing electrochemistry are the most actively researched.

[0003] Currently, a representative example of an electrochemical device utilizing such electrochemical energy is the secondary battery, and its scope of application is steadily expanding.

[0004] Recently, as technology development and demand for portable devices such as portable computers, mobile phones, and cameras have increased, the demand for secondary batteries as an energy source has been rapidly increasing. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, have been the subject of much research and have been commercialized and widely used.

[0005] Furthermore, as interest in environmental issues grows, extensive research is being conducted on electric vehicles and hybrid electric vehicles to replace fossil fuel-powered vehicles, such as gasoline and diesel cars, which are major causes of air pollution. While nickel-metal hydride batteries are primarily used as the power source for these electric and hybrid vehicles, research utilizing lithium-ion batteries, which offer high energy density and discharge voltage, is actively underway and is already in the commercialization stage.

[0006] The electrode, which is a component of a lithium secondary battery, is manufactured by coating and drying an electrode active material slurry, in which an active material is mixed with a conductive material, a binder, and a thickener in a solvent, onto a current collector.

[0007] At this time, the solvent is removed during the drying process and an electrode mixture is formed with the active material and the other components, and the structural characteristics of the electrode mixture are determined only by the composition of the slurry or the target loading amount.

[0008] Meanwhile, the electrode, after the drying process is completed, is too thick to be suitable for constructing secondary batteries requiring high energy density, so it undergoes a rolling process to densify the electrode to a target thickness.

[0009] Generally, this rolling process is performed such that the rolling reduction rate, which indicates the change in thickness before and after rolling, is at a level of 20 to 40%, and a load of about 10 tons is applied to the electrode to achieve this rolling reduction rate. However, as the load applied to the electrode increases, various defect issues such as active material breakage, electrode fracture, and wave phenomena occur.

[0010] Therefore, there is an urgent need to develop secondary battery electrode manufacturing technology that can solve these problems, reduce the probability of defect issues occurring during the rolling process, and improve processability. The problem to be solved

[0011] The present invention aims to solve the aforementioned problems by manufacturing an electrode that is more densified than the structure naturally formed by a drying process, and thereby minimizing the rolling load required to roll the electrode to a target thickness during the rolling process, with the goal of minimizing the probability of defect issues occurring. means of solving the problem

[0012] Terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0013] According to one embodiment of the present invention, a method for manufacturing an electrode for a secondary battery is provided below.

[0014] A method for manufacturing an electrode for a secondary battery is provided, comprising a rolling process of applying a load to an electrode active material slurry when the solid content of the un-dried electrode active material slurry is 70 wt% to 98 wt% during the process of drying an electrode active material slurry coated with one or more layers on a current collector.

[0015] At this time, the rolling process can be performed when the solid content of the undried electrode active material slurry is 80 wt% to 90 wt%.

[0016] The above rolling process can be performed by a press roll that applies linear pressure to an undried electrode active material slurry.

[0017] Specifically, the above rolling process can be performed with a linear pressure of 0.5 kgf / cm to 0.1 ton / cm.

[0018] In addition, the method for manufacturing the electrode for the secondary battery described above may additionally perform drying after the rolling process until the solid content of the electrode active material slurry reaches 99 to 100 wt%.

[0019] The above method for manufacturing an electrode for a secondary battery is, more specifically,

[0020] (a) A coating step of coating one or more layers of electrode active material slurry onto a current collector;

[0021] (b) a drying step of drying the electrode active material slurry so that the solid content is 70 wt% to 98 wt%;

[0022] (c) a wetting rolling step of applying a load onto an electrode active material slurry having a solid content of 70 wt% to 98 wt%;

[0023] (d) an additional drying step of forming an electrode composite by further drying until the solid content of the electrode active material slurry becomes 99 to 100 wt%; and

[0024] (e) may include a dry rolling step for rolling the electrode mixture after drying is complete.

[0025] In addition, according to another embodiment of the present invention, as an apparatus for manufacturing an electrode for a secondary battery,

[0026] A roller-shaped unwinder on which a sheet-type current is wound;

[0027] A conveying unit that continuously conveys the above sheet-type collector;

[0028] A coating portion for applying one or more layers of electrode active material slurry to at least one surface of the above-mentioned sheet-type current collector;

[0029] A drying unit for drying the above electrode active material slurry to form an electrode mixture on at least one surface of a sheet-type current collector; and

[0030] It includes a roller-shaped rewinder for rewinding an electrode sheet on which an electrode composite is formed on the sheet-type current collector, and

[0031] An electrode manufacturing apparatus for a secondary battery is provided, comprising a drying section that applies a load to the electrode active material slurry when the solid content of the undried electrode active material slurry is 70 wt% to 98 wt%.

[0032] At this time, the coating part may be a coating die, a coating roll, or a slide-slot.

[0033] Meanwhile, the drying unit may include a hot air nozzle that generates hot air inside a drying oven, an IR lamp, or both, and the wetting rolling unit may be a press roll and may be formed in a section inside or outside the drying oven where the solid content of the electrode active material slurry is 70 wt% to 98 wt%.

[0034] Here, the hot air nozzle and the IR lamp may be arranged alternately. Effects of the invention

[0035] According to the present invention, when a wet rolling process is performed to apply a load to an undried electrode active material slurry when the solid content satisfies specific conditions before the electrode active material slurry is completely dried, a structurally more densified structure can be secured when drying is completed compared to when rolling is not performed. Subsequently, after drying is completed, the target rolling rate is reduced in the dry rolling process, and accordingly, the rolling load required to roll the electrode to the target thickness can be reduced, thereby minimizing defect issues such as active material breakage, fracture, and wave phenomena. Brief explanation of the drawing

[0036] FIG. 1 is a schematic diagram of an electrode manufacturing apparatus for a secondary battery according to one embodiment of the present invention. Specific details for implementing the invention

[0037] The present invention will be described in more detail below.

[0038] According to one embodiment of the present invention, as a method for manufacturing an electrode for a secondary battery,

[0039] The above method for manufacturing an electrode for a secondary battery includes a rolling process in which a load is applied to an electrode active material slurry when the solid content of the un-dried electrode active material slurry is 70 wt% to 98 wt% during the process of drying an electrode active material slurry coated in one or more layers on a current collector.

[0040] In addition, according to another embodiment of the present invention,

[0041] As an apparatus for manufacturing electrodes for secondary batteries,

[0042] A roller-shaped unwinder on which a sheet-type current is wound;

[0043] A conveying unit that continuously conveys the above sheet-type collector;

[0044] A coating portion for applying one or more layers of electrode active material slurry to at least one surface of the above-mentioned sheet-type current collector;

[0045] A drying unit for drying the above electrode active material slurry to form an electrode mixture on at least one surface of a sheet-type current collector; and

[0046] It includes a roller-shaped rewinder for rewinding an electrode sheet on which an electrode composite is formed on the sheet-type current collector, and

[0047] An electrode manufacturing apparatus for a secondary battery is provided, comprising a drying section that applies a load to the electrode active material slurry when the solid content of the undried electrode active material slurry is 70 wt% to 98 wt%.

[0049] Hereinafter, the apparatus for manufacturing an electrode for a secondary battery and the method for manufacturing an electrode for a secondary battery based thereon according to the present invention will be described in detail with reference to the drawings so that those skilled in the art to which the present invention pertains can easily implement it. However, the following drawings are merely examples, and the present invention may be implemented in various different forms within the scope of the present invention and is not limited to the drawings.

[0051] Specifically, FIG. 1 schematically illustrates an electrode manufacturing apparatus for a secondary battery according to one embodiment of the present invention. The electrode manufacturing apparatus for a secondary battery according to the present invention comprises a roller-shaped unwinder (110) on which a sheet-shaped current collector (101) is wound, a conveying unit (120) for continuously conveying the sheet-shaped current collector (101), a coating unit (130) for applying one or more layers of electrode active material slurry (102) to at least one surface of the sheet-shaped current collector (101), a drying unit (140) for drying the electrode active material slurry (102) to form an electrode composite (103) on at least one surface of the sheet-shaped current collector (101), and a roller-shaped winder (150) for rewinding the electrode sheet on which the electrode composite (103) is formed on the sheet-shaped current collector (101).

[0052] At this time, the drying section (140) includes a wetting rolling section (143) that applies a load to the electrode active material slurry (102) when the solid content of the undried electrode active material slurry (102) is 70 wt% to 98 wt%.

[0053] In the following, the components of the electrode manufacturing apparatus described above will be explained in detail, and a method for manufacturing an electrode for a secondary battery according to the present invention will also be explained.

[0054] First, the unwinder (110) is structured to wind a sheet-type current collector (101) onto a roll.

[0055] This unwinding device (110) unwinds the sheet-type current collector (101) and allows the sheet-type current collector (101) to be transported by the transport unit (120).

[0056] The transfer unit (120) receives the sheet-type current collector (101) unwound from the unwinder (110) and performs the role of transferring the sheet-type current collector (101) to the winder (150) via the coating unit (130) and the drying unit (140).

[0057] Here, the conveying part (120) can be a roll.

[0058] Next, the sheet-type current collector (101), which is unwound from the unwound unit (110) and transported by the transport unit (120), is transported to the coating unit (130) by the transport unit (120).

[0059] The coating portion (130) coats one or more layers of electrode active material slurry (102) on the sheet-type current collector (101).

[0060] At this time, the coating portion (130) is not limited to a shape capable of coating the electrode active material slurry (101), and can be coated by a conventionally known coating device such as a coating die, a coating roll, or a slide-slot, and can be determined according to the number of layers of the electrode active material slurry (102), and there are differences in the specific configuration depending on whether it is double-sided coating or single-sided coating. However, since various coating forms are disclosed in the art, FIG. 1 only shows a structure in which the electrode active material slurry is coated through a coating die as one example.

[0061] Specifically, the coating portion (130) may be structured to include a coating die (131) having an outflow slot so that an electrode active material slurry (102) is discharged to the outside toward a sheet-type current collector (101), and a coater roll (132) spaced apart from the outflow slot of the die (131) at a predetermined distance and transporting the sheet-type current collector (101) by rotation so that the electrode active material slurry (102) can be applied to the sheet-type current collector (101) by the coating die (131).

[0062] Afterwards, the sheet-type current collector (101) coated with the electrode active material slurry (102) is transferred to the drying section (140) by the transfer section (120).

[0063] The drying unit (140) according to the present embodiment is not limited to any device capable of evaporating a solvent from an electrode active material slurry (102) to form an electrode composite (103), and may have any structure known in the prior art, and may be performed, for example, by heating and / or hot air.

[0064] Accordingly, the drying section (140) includes a hot air nozzle (141) that generates hot air inside the drying oven (144) and an IR lamp (142). Meanwhile, in FIG. 1, the electrode manufacturing device (100) for a secondary battery according to the present invention includes a wetting rolling section (143) as a press roll inside the drying oven (144).

[0065] Meanwhile, Figure 1 below illustrates a configuration in which a wetting rolling section (143) is formed within a drying oven (144), but is not limited thereto. Even if the wetting rolling section (143) is included in the drying section (140), it is not formed within the drying oven (144). Alternatively, the drying oven (144) may be formed with two or more units, each unit may include a hot air nozzle (141) and an IR lamp (142), and the wetting rolling section (143) may be included between units with a solid content of 70 wt% to 98 wt%.

[0066] The drying process of the electrode active material slurry (102) in the drying section (140) is carried out as follows.

[0067] First, when drying of the electrode active material slurry (102) begins in the drying section (140), the electrode active material slurry (102) is dried to a solid content of 70 wt% to 98 wt%. Afterwards, wetting rolling is performed to apply a load to the electrode active material slurry (102) with a solid content of 70 wt% to 98 wt%, and then additional drying is performed until the solid content of the electrode active material slurry (102) becomes 99 to 100 wt% to form an electrode composite (103).

[0068] To this end, the wetting rolling section (143) may be formed in a section where the solid content of the electrode active material slurry (102) is 70 wt% to 98 wt% inside or outside the drying oven (144), and more specifically, the wetting rolling section (143) according to the present embodiment may be formed in a section where the solid content of the undried electrode active material slurry (102) is 80 wt% to 90 wt%.

[0069] The above solid content can be expressed as solid content by measuring the change in weight of the slurry before and after drying, or by measuring the moisture content within the electrode through inline measurement using an NIR moisture measurement sensor, etc.

[0070] At this time, the wetting rolling process is performed by a press roll that applies linear pressure to the undried electrode active material slurry.

[0071] Specifically, the above wetting rolling process can be performed with a linear pressure load of 0.5 kgf / cm or more, more specifically 0.8 kgf / cm or more, 5 ton / cm or less, more specifically 1 ton / cm, and more specifically 0.1 ton / cm or less.

[0072] If the process is performed with a line pressure that is too small, outside the above range, the benefits of performing wetting rolling cannot be obtained, and thus the effects of the present invention cannot be achieved. If the process is performed with a line pressure that is too large, breakage of the active material may occur even during wetting rolling, which is undesirable.

[0073] Meanwhile, as another component included within the drying section (140), the configuration of the hot air nozzle (141) and IR lamp (142) for performing drying is not limited, and may include only one component or both components, and may have a configuration such as including the hot air nozzle (141) on one side and the IR lamp (142) on the other side based on the wetting rolling section (143), but the hot air nozzle (141) and the IR lamp (142) may be arranged alternately so that hot air and heating drying can be performed together.

[0074] When passing through such a drying section (140), the solvent is almost completely evaporated on the sheet-type current collector (101) to form an electrode composite (103) with a solid content of 99 to 100 wt%, and the electrode sheet formed on the sheet-type current collector with the electrode composite (103) is subsequently wound onto a roller-shaped winder (150).

[0075] The winder (150) is structured to wind the electrode sheet onto a roll, just like the unwinder (110).

[0076] Although not shown in the drawing, the electrode sheet may subsequently be wound again for rolling and rolled through a dry rolling section to have an appropriate porosity and electrode density.

[0077] The dry rolling section is also not limited in its device, structure, etc. as long as it is in a form capable of rolling the electrode composite, but, for example, it may be in a form that rolls by adjusting the spacing between a pair of rollers.

[0078] At this time, according to the present invention, a wet rolling process is performed once while the electrode active material slurry is in an undried state that has not been completely dried, and subsequently, the rolling rate is relatively low during the dry rolling process performed after the drying is completely completed.

[0079] More specifically, when wetting rolling is not performed, the reduction rate in the dry rolling stage cannot generally be set high. However, when wetting rolling is performed according to the present invention, since drying is completed with the electrode composite already having reduced thickness, rolling can be performed with a lower load, and the desired thickness and porosity of the electrode composite can be obtained even without a high reduction rate.

[0080] Here, the above rolling reduction ratio refers to the ratio of the difference in thickness of the electrode mixture before and after rolling to the thickness of the electrode mixture before rolling. Therefore, a smaller rolling reduction ratio means that the difference in thickness before and after dry rolling is smaller.

[0081] Various electrode materials included in the above electrode active material slurry, such as active materials, conductive materials, binders, fillers, etc., are known in the art, and all of these are included within the scope of the present invention, and the present invention is not limited to the composition of the electrode active material slurry.

[0082] Meanwhile, the sheet-type current collector coated with the electrode active material slurry is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surfaces treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the sheet-type current collector may have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0084] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0086] <Example 1>

[0087] Using synthetic graphite as the active material, SBR as the binder, carbon black as the conductive agent, and CMC as the additive, an electrode active material slurry with a solid content of 48 wt%, added to water such that the weight ratio of electrode active material: binder: conductive agent: additive is 96:0.5:2.5:1, has a loading amount of 266 mg / 25 cm² after complete drying. 2 After coating on a current collector of Cu foil (thickness: 20㎛) to achieve the desired result, it was dried at 100°C. When the solid content of the electrode active material slurry reached 90wt%, it was removed from the drying oven and rolled at a linear pressure of 0.8kgf / cm through a roll press process, and then further dried at 100°C until the solid content reached approximately 100wt% to manufacture the electrode.

[0088] The above solid content was measured by the change in weight of the slurry before and after drying.

[0090] <Example 2>

[0091] In the above Example 1, an electrode was manufactured in the same manner as in Example 1, except that the time at which the roll press process was performed was when the solid content of the electrode active material slurry was 80 wt%.

[0093] <Comparative Example 1>

[0094] In the above Example 1, an electrode was manufactured in the same manner as in Example 1, except that the time at which the roll press process was performed was when the solid content of the electrode active material slurry was 60 wt%.

[0096] <Comparative Example 2>

[0097] In the above Example 1, an electrode was manufactured in the same manner as in Example 1, except that the roll press process was performed at a linear pressure of 0.2 kgf / cm.

[0099] <Comparative Example 3>

[0100] In the above Example 1, an electrode was manufactured in the same manner as Example 1, except that the roll press process was not performed.

[0102] <Experimental Example 1>

[0103] The thickness of the electrode mixture of the electrodes prepared in Examples 1 to 4 and Comparative Examples 1 to 3 was measured using a thickness gauge. Specifically, the measurement was performed using TESA’s u-Hite height gauges as the thickness gauge.

[0104] The value obtained by subtracting the thickness of the Cu foil as a current collector from the value measured by this thickness gauge was taken as the thickness of the electrode mixture, and the results are shown in Table 1 below.

[0105] Electrode thickness Example 1 113 um Example 2 114 um Comparative Example 1 Electrode layer destroyed during rolling Comparative Example 2 118 µm (no rolling effect during drying) Comparative Example 3 118 µm (electrode thickness after typical drying process)

[0106] Referring to Table 1 above, it can be seen that when wet rolling according to the present invention is performed, the electrode thickness dried before the dry rolling process is reduced by a certain amount compared to Comparative Example 3, which is not. On the other hand, when drying is not performed, i.e., when the solid content is less than 70 wt% (Comparative Example 1), the electrode layer is destroyed during rolling, and when the linear pressure of wet rolling is too weak (Comparative Example 2), there is no rolling effect, so it is undesirable. Explanation of the symbols

[0108] 100: Electrode manufacturing device, 101: Sheet-type whole house, 102: Electrode active material slurry, 110: Kwon Chul-gi, 120: Transfer section, 130: Coating section, 140: Drying section, 150: Winder.

Claims

Claim 1 A method for manufacturing an electrode for a secondary battery, wherein the method for manufacturing an electrode for a secondary battery comprises drying an electrode active material slurry coated in one or more layers on a current collector so that the solid content is 70 wt% to 98 wt%, and a rolling process of applying a load to the electrode active material slurry when the solid content of the un-dried electrode active material slurry is 70 wt% to 98 wt%, and performing additional drying after the rolling process. Claim 2 A method for manufacturing an electrode for a secondary battery according to claim 1, wherein the rolling process is performed when the solid content of the undried electrode active material slurry is 80 wt% to 90 wt%. Claim 3 A method for manufacturing an electrode for a secondary battery according to claim 1, wherein the rolling process is performed by a press roll that applies linear pressure to an undried electrode active material slurry. Claim 4 A method for manufacturing an electrode for a secondary battery according to claim 3, wherein the rolling process is performed under a linear pressure load of 0.5 kgf / cm to 0.1 ton / cm. Claim 5 In claim 1, the method for manufacturing an electrode for a secondary battery comprises additionally performing drying after the rolling process until the solid content of the electrode active material slurry becomes 99 to 100 wt%. Claim 6 In claim 1, the method for manufacturing an electrode for a secondary battery comprises: (a) a coating step of coating an electrode active material slurry in one or more layers on a current collector; (b) a drying step of drying the electrode active material slurry so that the solid content is 70 wt% to 98 wt%; (c) a wetting rolling step of applying a load to the electrode active material slurry having a solid content of 70 wt% to 98 wt%; (d) an additional drying step of forming an electrode composite by performing additional drying until the solid content of the electrode active material slurry is 99 to 100 wt%; and (e) a dry rolling step of rolling the electrode composite after drying is completed. Claim 7 An apparatus for manufacturing an electrode for a secondary battery, comprising: a roller-shaped unwinder on which a sheet-shaped current collector is wound; a conveying unit for continuously conveying the sheet-shaped current collector; a coating unit for applying one or more layers of an electrode active material slurry to at least one surface of the sheet-shaped current collector; a drying unit for drying the electrode active material slurry to form an electrode composite on at least one surface of the sheet-shaped current collector; and a roller-shaped rewinder for rewinding an electrode sheet on which the electrode composite is formed on the sheet-shaped current collector, wherein the drying unit dries the electrode active material slurry so that its solid content is 70 wt% to 98 wt%, and the wetting rolling unit for applying a load to the electrode active material slurry when the solid content of the un-dried electrode active material slurry is 70 wt% to 98 wt%. Claim 8 In claim 7, the coating part is a coating die, a coating roll, or a slide-slot, forming an electrode manufacturing apparatus for a secondary battery. Claim 9 An electrode manufacturing apparatus for a secondary battery according to claim 7, wherein the drying unit comprises a hot air nozzle that generates hot air inside a drying oven, an IR lamp, or both, and the wetting rolling unit is a press roll formed in a section inside or outside the drying oven where the solid content of the electrode active material slurry is 70 wt% to 98 wt%. Claim 10 In claim 9, the above-mentioned hot air nozzle and IR lamp are arranged alternately in a secondary battery electrode manufacturing apparatus.

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