Dual-slit die coater having excellent insulating coating thickness uniformity, electrode manufacturing method using same, and electrode

Abstract

The present disclosure relates to a dual-slit die coater in which a width of an upper insulating liquid discharge flow path and a width of a lower insulating liquid discharge flow path are formed to be different, thereby preventing generation of a fat-edge at an end portion of an insulating layer and enabling formation of a uniform insulating layer.

Description

Technical Field

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0154675, filed on November 9, 2023, the disclosure of which is incorporated herein by reference.

[0002] This disclosure relates to a double-slit mold coating machine with improved uniformity of insulating coating thickness, an electrode manufacturing method using the double-slit mold coating machine, and an electrode; more specifically, it relates to a double-slit mold coating machine with a novel coating machine gasket design. Background Technology

[0003] Lithium-ion batteries are used as the energy source for various electronic devices. With the development of technology, there is an increasing need for batteries that can provide greater capacity than conventional batteries in the same space or design.

[0004] One of the main research challenges for these secondary batteries is improving safety. The primary cause of battery safety incidents is abnormally high temperatures resulting from a short circuit between the positive and negative electrodes. In other words, under normal circumstances, the separator, located between the positive and negative electrodes, maintains electrical insulation. However, conventional separators exhibit limitations under abnormal conditions such as overcharging or over-discharging, internal short circuits due to dendritic growth or foreign objects in the electrode material, penetration of the battery by sharp objects such as nails or screws, or excessive deformation of the battery due to external forces. Various methods have been explored to reduce the likelihood of electrode short circuits under such external shocks or high-temperature conditions. For example, to address internal short circuits in batteries, methods such as adhering insulating tape to uncoated portions of the electrodes and a portion of the active material layer, or forming an insulating layer by coating with an insulating liquid, have been proposed.

[0005] Furthermore, as a way to increase the loading of active material in the electrode, attempts have been made to form a double-layer electrode active material layer. In the process of forming the double-layer electrode active material layer on both sides of the current collector, the uniformity of the insulating layer has become an issue. Specifically, a top-side coating process for coating the front side of the current collector is followed by a back-side coating process for coating the back side. In particular, during the back-side coating process, thick edges are mainly generated in the insulating layer. Because the back-side coating process is performed by passing the current collector, whose front side is already coated with electrode active material, through a coating roller, the back-side coating process has the limitation of relatively inconsistent gap adjustment during coating. As a result, the insulation liquid application becomes uneven in the back-side coating process, and as the insulation liquid shrinks during the drying process, thick edges are caused in the insulating layer.

[0006] Therefore, there is a need to develop new technologies that can form a uniform insulating layer while forming a bilayer electrode active material. Summary of the Invention

[0007] Technical issues

[0008] Therefore, this disclosure aims to provide a double-slit mold coating machine capable of preventing the formation of a fat-edge at the end of the insulating layer, particularly at the end of the back-coated insulating layer, and forming a uniform insulating layer, an electrode manufacturing method using the double-slit mold coating machine, and an electrode.

[0009] Technical solution

[0010] To address the aforementioned issues, the dual-slit mold coating machine according to this disclosure has an average width of different structures for the discharge paths of insulating liquid formed in the upper and lower layers.

[0011] The double-slit mold coating machine according to this disclosure includes: a lower block, an intermediate block, and an upper block; a first coating pad located between the lower block and the intermediate block; and a second coating pad located between the intermediate block and the upper block. Each of the first and second coating pads includes: an electrode slurry discharge path for discharging electrode slurry; and an insulating liquid discharge path formed at a certain distance from the electrode slurry discharge path on one or both sides of the electrode slurry discharge path for discharging insulating liquid.

[0012] For example, the dual-slit mold coating machine satisfies the following condition 1:

[0013] [Condition 1]

[0014] 0.2≤D2 / D1≤0.8

[0015] Among the conditions mentioned above,

[0016] D1 represents the average width (mm) of the insulating liquid discharge path formed in the first coated gasket.

[0017] D2 represents the average width (mm) of the insulating liquid discharge path formed in the second coated gasket.

[0018] In this disclosure, the first coated pad and the second coated pad satisfy the following condition 2:

[0019] [Condition 2]

[0020] 1≤|D1-D2|≤10 (mm)

[0021] Among the conditions mentioned above, in condition 2,

[0022] D1 represents the average width (mm) of the insulating liquid discharge path formed in the first coated gasket.

[0023] D2 represents the average width (mm) of the insulating liquid discharge path formed in the second coated gasket.

[0024] In the specific example, D2 is in the range of 1 mm to 10 mm.

[0025] In this disclosure, each insulating liquid discharge path formed in the first and second coated pads is separated from the electrode slurry discharge path by a distance D on one or both sides. For example, the distance D is in the range of 1 mm to 5 mm.

[0026] Furthermore, this disclosure provides a method for manufacturing electrodes using the aforementioned dual-slit mold coating machine.

[0027] The electrode manufacturing method according to this disclosure includes: a top coating step of coating an electrode paste and an insulating liquid on one side of a current collector sheet; and a back coating step of coating an electrode paste and an insulating liquid on the opposite side of the current collector sheet.

[0028] At least one of the top coating step and the back coating step includes: a first layer forming step of discharging a first electrode paste and a first insulating liquid onto the current collector sheet through a first coating pad; and a second layer forming step of discharging a second electrode paste and a second insulating liquid onto the current collector sheet through a second coating pad.

[0029] In this disclosure, the average width (D1') of the first insulating layer formed by discharging the first insulating liquid and the average width (D2') of the second insulating layer formed by discharging the second insulating liquid satisfy the following condition 3:

[0030] [Condition 3]

[0031] 0.2≤D2' / D1'≤0.8

[0032] Among the conditions mentioned above, in condition 3...

[0033] D1' represents the average width (mm) of the first insulating layer.

[0034] D2' represents the average width (mm) of the second insulating layer.

[0035] The first layer forming step and the second layer forming step can be performed by a single process.

[0036] The electrode manufacturing method according to this disclosure includes: a top surface coating step of coating an electrode paste and an insulating liquid onto one side of a current collector sheet; and a back surface coating step of coating an electrode paste and an insulating liquid onto the opposite side of the current collector sheet. For example, the top surface coating step and the back surface coating step each independently include the first layer formation step and the second layer formation step described above.

[0037] In this disclosure, the average width (D1') of the first insulating layer formed by discharging the first insulating liquid and the average width (D2') of the second insulating layer formed by discharging the second insulating liquid satisfy the following condition 4:

[0038] [Condition 4]

[0039] 1≤|D1'-D2'|≤10 (mm)

[0040] Among the conditions mentioned above, in condition 4...

[0041] D1' represents the average width (mm) of the first insulating layer.

[0042] D2' represents the average width (mm) of the second insulating layer.

[0043] The insulating liquid used in the electrode manufacturing method according to this disclosure may contain inorganic particles. For example, the first insulating liquid may contain no inorganic particles or contain less than 30% by weight of inorganic particles based on solid content. The second insulating liquid may contain inorganic particles in the range of 30% to 95% by weight based on solid content.

[0044] Furthermore, this disclosure provides an electrode manufactured by the above-described manufacturing method. Specifically, the electrode is an electrode for a secondary battery. The electrode according to this disclosure includes: a top coating formed on one side of an electrode current collector, the top coating including a top surface electrode active material layer and a top surface insulating layer formed in the edge region of the top surface electrode active material layer; and a back coating formed on the opposite side of the electrode current collector, the back coating including a back surface electrode active material layer and a back surface insulating layer formed in the edge region of the back surface electrode active material layer. Here, the top surface insulating layer has a calculated value in the range of 1 to 1.15 according to the following condition 5, and the back surface insulating layer has a calculated value in the range of 1.15 to 1.5 according to the following condition 5.

[0045] [Condition 5]

[0046] H Edge / H Ever

[0047] Among the conditions mentioned above, in condition 5...

[0048] H Ever This represents the average height (μm) in the region of the insulating layer at a height of 25 μm or more from the electrode current collector.

[0049] H Edge The height (μm) represents the point in the end region of the insulating layer that has the highest height from the electrode current collector, and the end region is located on the opposite side of the region where the insulating layer contacts the electrode active material layer.

[0050] In one example, the top insulating layer and the back insulating layer satisfy the following condition 6:

[0051] [Condition 6]

[0052] 0.65≤S f Top / S f Back ≤0.95

[0053] Among the conditions mentioned above, in condition 6...

[0054] S f Top This indicates the uniformity of the coating of the top surface insulating layer.

[0055] S f Back This indicates the uniformity of the coating of the back insulating layer.

[0056] S f Top and S f Back Each is calculated according to the ratio shown in Formula 1 below:

[0057] [Formula 1]

[0058] H Edge / H Ever

[0059] In formula 1 above,

[0060] H Ever This represents the average height (μm) in the region of the insulating layer at a height of 25 μm or more from the electrode current collector.

[0061] H Edge The height (μm) represents the point in the end region of the insulating layer that has the highest height from the electrode current collector, and the end region is located on the opposite side of the region where the insulating layer contacts the electrode active material layer.

[0062] For example, the electrode active material layer of the top coating and the electrode active material layer of the back coating are both double-layer structures.

[0063] In one example, the electrode is a positive electrode. Specifically, the electrode is the positive electrode of a secondary battery. The secondary battery is a pouch battery. For example, the secondary battery is a pouch lithium secondary battery.

[0064] Beneficial effects

[0065] In the double-slit mold coating machine according to this disclosure, the widths of the upper insulating liquid discharge path and the lower insulating liquid discharge path are formed to prevent the formation of a fat-edge at the end of the insulating layer and to form a uniform insulating layer. Attached Figure Description

[0066] Figure 1 This is a schematic diagram illustrating an electrode manufacturing process according to one embodiment of the present disclosure.

[0067] Figure 2 This is a schematic diagram illustrating a top surface coating process according to one embodiment of the present disclosure.

[0068] Figure 3 This is a partial front view showing the discharge section of a double-slit mold coating machine according to conventional technology.

[0069] Figure 4 It is used according to Figure 3 A partial cross-sectional view of an electrode manufactured by a double-slit mold coating machine.

[0070] Figure 5 This is a partial front view showing the discharge section of a double slit mold coating machine according to one embodiment of the present disclosure.

[0071] Figure 6 It is used according to Figure 5 A partial cross-sectional view of an electrode manufactured by a double-slit mold coating machine.

[0072] Figure 7 It is a graph showing the thickness profile of the insulating layer of the electrode. Detailed Implementation

[0073] The dual-slit die coating machine according to this disclosure has a structure in which the average widths of the insulating liquid discharge channels formed in the upper and lower layers are designed to be different. Conventional dual-slit die coating machines have a structure in which the average widths of the insulating liquid discharge channels formed in the upper and lower layers are designed to be the same. In this disclosure, by designing the average widths of the insulating liquid discharge channels formed in the upper and lower layers to be different, this phenomenon of thick edges in the insulating layer can be prevented or reduced. In the process of manufacturing electrodes for secondary batteries, electrodes with a double-sided structure can be manufactured by forming electrode active material layers on the top and back surfaces of the electrode current collector. When the electrode active material layer is formed on the back surface of the electrode current collector, the dual-slit die coating machine according to this disclosure can be applied more effectively.

[0074] In one embodiment, the double-slit mold coating machine according to this disclosure includes: a lower block, an intermediate block, and an upper block; a first coating pad located between the lower block and the intermediate block; and a second coating pad located between the intermediate block and the upper block. Each of the first and second coating pads includes: an electrode slurry discharge path for discharging electrode slurry; and an insulating liquid discharge path formed at a distance from the electrode slurry discharge path on one or both sides for discharging insulating liquid.

[0075] The double-slit die coating machine meets the following condition 1:

[0076] [Condition 1]

[0077] 0.2≤D2 / D1≤0.8

[0078] Among the conditions mentioned above,

[0079] D1 represents the average width (mm) of the insulating liquid discharge path formed in the first coated gasket.

[0080] D2 represents the average width (mm) of the insulating liquid discharge path in the formation of the second coated gasket.

[0081] In condition 1 above, for example, D2 is in the range of 1 mm to 10 mm, in the range of 1 mm to 7 mm, or in the range of 1 mm to 5 mm.

[0082] Specifically, the calculated value according to condition 1 above can be in the range of 0.2 to 0.8, in the range of 0.4 to 0.8, in the range of 0.5 to 0.8, in the range of 0.2 to 0.6, or in the range of 0.4 to 0.6.

[0083] In this disclosure, by controlling the average width of the insulating liquid drainage path formed in the second coated gasket within the aforementioned range, thick edges can be prevented, and the thickness of the insulating layer can be formed more uniformly. For example, it has been found that it is more effective to form the average width (D2) of the insulating liquid drainage path formed in the second coated gasket to be shorter than the average width (D1) of the insulating liquid drainage path formed in the first coated gasket.

[0084] In this disclosure, the first coated gasket and the second coated gasket satisfy the following condition 2:

[0085] [Condition 2]

[0086] 1≤|D1-D2|≤10 (mm)

[0087] Among the conditions mentioned above, in condition 2,

[0088] D1 represents the average width (mm) of the insulating liquid discharge path formed in the first coated gasket.

[0089] D2 represents the average width (mm) of the insulating liquid discharge path formed in the second coated gasket.

[0090] Condition 2 above means that the average widths of the insulating liquid drainage paths formed in the first and second coated pads are different from each other. For example, the average width of the insulating liquid drainage path formed in the first coated pad can be designed to satisfy condition 1 in the range of 2 mm to 15 mm. Furthermore, the average width of the insulating liquid drainage path formed in the second coated pad is in the range of 1 mm to 10 mm, 1 mm to 7 mm, or 1 mm to 5 mm. In this case, the structure is such that the insulating liquid drainage path formed in the first coated pad has a longer average width in the transverse direction (Y-axis direction) from the electrode slurry drainage path, and the insulating liquid drainage path formed in the second coated pad has a shorter average width in the transverse direction (Y-axis direction) from the electrode slurry drainage path. Furthermore, the insulating liquid drainage paths formed in the first and second coated pads are formed to overlap on the side closer to the electrode slurry drainage path (Y-axis direction), while only the insulating liquid drainage path formed in the first coated pad is extended on the side farther from the electrode slurry drainage path.

[0091] As another example, the average width of the insulating liquid drainage path formed in the first coated pad is in the range of 1 mm to 10 mm, 1 mm to 7 mm, or 1 mm to 5 mm. Furthermore, the average width of the insulating liquid drainage path formed in the second coated pad can be designed to satisfy condition 1 above within the range of 2 mm to 15 mm. In this case, the structure is such that the average width of the insulating liquid drainage path in the first coated pad is shorter along the transverse direction (Y-axis direction) from the electrode slurry drainage path, while the average width of the insulating liquid drainage path in the second coated pad is longer along the transverse direction (Y-axis direction) from the electrode slurry drainage path. Furthermore, the insulating liquid drainage paths formed in the first and second coated pads overlap on the side closer to the electrode slurry drainage path (Y-axis direction), while only the extended insulating liquid drainage path formed in the second coated pad is formed on the side farther from the electrode slurry drainage path.

[0092] By controlling the average width of the insulating liquid discharge path in the formation of the first and second coated pads to meet the above range, the formation of thick edges can be minimized.

[0093] In the first and second coating pads, each insulating liquid discharge path is formed by separating it from the electrode slurry discharge path by a distance D on one or both sides. In specific examples, the distance D is in the range of 1 mm to 5 mm, 1 mm to 3 mm, 2 mm to 5 mm, or 1.5 mm to 2.5 mm. In this disclosure, the insulating liquid discharge path and the electrode slurry discharge path are separated by a certain distance D in the first and second coating pads. The electrode slurry discharged through the electrode slurry discharge path forms a sliding region at its end during the coating and drying processes. In the area where the sliding region overlaps with the insulating liquid discharge region, the problem of increased layer thickness may occur. In this disclosure, by separating the electrode slurry discharge path from the insulating liquid discharge path by a certain distance, this problem of increased thickness is prevented.

[0094] Furthermore, this disclosure provides an electrode manufacturing method using the aforementioned dual-slit mold coating machine. In one embodiment, the electrode manufacturing method according to this disclosure includes: a top surface coating step of coating an electrode slurry and an insulating liquid onto one side of a current collector sheet; and a back surface coating step of coating an electrode slurry and an insulating liquid onto the opposite side of the current collector sheet. One or both of the top surface coating step and the back surface coating step include: a first layer formation step of discharging a first electrode slurry and a first insulating liquid onto the current collector sheet respectively through a first coating pad; and a second layer formation step of discharging a second electrode slurry and a second insulating liquid onto the current collector sheet respectively through a second coating pad. Furthermore, the average width (D1') of the first insulating layer formed by discharging the first insulating liquid and the average width (D2') of the second insulating layer formed by discharging the second insulating liquid are controlled to satisfy the following condition 3:

[0095] [Condition 3]

[0096] 0.2≤D2' / D1'≤0.8

[0097] Among the conditions mentioned above, in condition 3...

[0098] D1' represents the average width (mm) of the first insulating layer.

[0099] D2' represents the average width (mm) of the second insulating layer.

[0100] Specifically, the calculated value according to condition 3 above can be in the range of 0.2 to 0.8, 0.4 to 0.8, 0.5 to 0.8, 0.2 to 0.6, or 0.4 to 0.6. For example, the calculated value according to condition 3 above is 0.5.

[0101] Specifically, the electrode manufacturing method according to this disclosure can be applied more effectively to the back coating step.

[0102] In this disclosure, by discharging the first electrode slurry and the second electrode slurry, the loading of the electrode active material can be significantly increased. The manufactured electrode has a structure in which a double-layer structure of electrode active material layer is formed, and compared with an electrode in which the electrode active material layer is a single-layer structure, the loading of the electrode active material can be increased by 30% or more by weight, 50% or more by weight, or 30% to 100% by weight.

[0103] In this disclosure, the first layer formation step and the second layer formation step can be performed in a single process. Conventionally, a bilayer electrode structure is manufactured by forming and drying the first layer, followed by forming and drying the second layer. However, this method involves performing the electrode slurry discharge and drying processes twice each, and the interfacial adhesion or interfacial resistance between the lower and upper layers must be controlled. In this disclosure, the first layer formation step and the second layer formation step can be performed as a single process using a dual-slit die coating machine.

[0104] Specifically, in this disclosure, in the first layer formation step, a first electrode slurry is discharged onto one side of the electrode sheet through a first coating pad to form a first electrode active layer, and a first insulating liquid is discharged from both sides of the first electrode slurry discharge area to form a first insulating layer. Furthermore, in the second layer formation step, a second electrode slurry is discharged onto the opposite side of the current collector sheet through a second coating pad to form a second electrode active layer, and a second insulating liquid is discharged from both sides of the second electrode slurry discharge area to form a second insulating layer. According to the electrode manufacturing method of this disclosure, two electrode active layers and two insulating layers are formed with one side of the current collector sheet as a reference.

[0105] Furthermore, the average width (D1') of the first insulating layer formed by discharging the first insulating liquid and the average width (D2') of the second insulating layer formed by discharging the second insulating liquid satisfy the following condition 4:

[0106] [Condition 4]

[0107] 1≤|D1'-D2'|≤10 (mm)

[0108] In condition 4,

[0109] D1' represents the average width (mm) of the first insulating layer, and D2' represents the average width (mm) of the second insulating layer.

[0110] Condition 4 above means that the average widths of the first insulating layer and the second insulating layer formed by the insulating liquid discharged through the first insulating liquid discharge path and the second insulating liquid discharge path formed in the first and second coated pads are different from each other. As an example, the average width (D1') of the first insulating layer is the average value of the width of the first insulating layer, and is in the range of 2 mm to 15 mm, satisfying condition 4 above. In addition, the average width (D2') of the second insulating layer is the average value of the width of the second insulating layer, and is in the range of 1 mm to 10 mm, 1 mm to 7 mm, or 1 mm to 5 mm. In this case, the structure is such that the average width of the first insulating layer is longer in the transverse direction (Y-axis direction) from the electrode active material layer formed through the electrode slurry discharge path, and the average width of the second insulating layer is shorter in the transverse direction (Y-axis direction) from the electrode active material layer. Furthermore, the first insulating layer and the second insulating layer are formed to overlap on the side (Y-axis direction) close to the electrode active material layer formed by the discharge electrode slurry, while only the first insulating layer is extended on the side away from the electrode active material layer.

[0111] As another example, the average width of the first insulating layer is in the range of 1 mm to 10 mm, 1 mm to 7 mm, or 1 mm to 5 mm. Furthermore, the average width of the second insulating layer is in the range of 2 mm to 15 mm, satisfying condition 4. In this case, the structure is such that the average width of the first insulating layer is shorter along the transverse direction (Y-axis direction) from the electrode active material layer formed through the electrode slurry discharge flow path, and the average width of the second insulating layer is longer along the transverse direction (Y-axis direction) from the electrode active material layer. Furthermore, the first and second insulating layers are formed to overlap on the side closer to the electrode active material layer (Y-axis direction), while only the second insulating layer is extended on the side farther from the electrode active material layer.

[0112] In one embodiment, the first insulating liquid and the second insulating liquid have different compositions. In a specific example, the first insulating liquid contains less than 30% by weight of inorganic particles based on solid content. For example, the first insulating liquid has a composition in which the inorganic particle content is in the range of 5% to 30% by weight, or contains no inorganic particles. Furthermore, the second insulating liquid contains inorganic particles in the range of 30% to 95% by weight based on solid content. For example, the second insulating liquid has an inorganic particle content in the range of 50% to 95% by weight or 80% to 95% by weight.

[0113] As an example of this disclosure, the first insulating liquid forming the lower insulating layer is composed of a low content of inorganic particles or contains no inorganic particles. This improves the adhesion between the insulating layer and the current collector. Conversely, the second insulating liquid forming the upper insulating layer is composed of a relatively high content of inorganic particles. This prevents thermal shrinkage of the insulating layer and improves electrical insulation performance. This disclosure does not exclude the possibility that the first and second insulating liquids are formed with the same composition.

[0114] In one embodiment, the electrode manufacturing method according to this disclosure includes: a top surface coating step of coating an electrode paste and an insulating liquid onto one side of a current collector sheet; and a back surface coating step of coating an electrode paste and an insulating liquid onto the opposite side of the current collector sheet. For example, the top surface coating step and the back surface coating step each independently include the first layer formation step and the second layer formation step described above. Specifically, in this disclosure, in the top surface coating step and / or the back surface coating step, a double-layer electrode active material layer and a double-layer insulating layer can be formed on both sides of the current collector by the above method.

[0115] Furthermore, this disclosure provides an electrode manufactured by the above-described manufacturing method. Specifically, the electrode is an electrode for a secondary battery. In one embodiment, the electrode according to this disclosure includes: a top coating formed on one side of an electrode current collector, the top coating including a top surface electrode active material layer and a top surface insulating layer formed in the edge region of the top surface electrode active material layer; and a back coating formed on the opposite side of the electrode current collector, the back coating including a back surface electrode active material layer and a back surface insulating layer formed in the edge region of the back surface electrode active material layer. Here, the top surface insulating layer has a calculated value in the range of 1 to 1.15 according to condition 5, and the back surface insulating layer has a calculated value in the range of 1.15 to 1.5 according to condition 5.

[0116] [Condition 5]

[0117] H Edge / H Ever

[0118] In condition 5 above, H Ever H represents the average height (μm) in the region of the insulating layer at a height of 25 μm or more from the electrode current collector. Edge The height (μm) represents the point in the end region of the insulating layer that has the highest distance from the electrode current collector, and the end region is located on the opposite side of the region where the insulating layer contacts the electrode active material layer.

[0119] In condition 5 above, H Edge This indicates the height of the thick edge formed in the insulation layer. Furthermore, if the calculation result according to condition 5 is 1, it means that no thick edge was formed.

[0120] In this disclosure, the top insulating layer of the electrode current collector is controlled to have a relatively low level of thick edge. Furthermore, this disclosure also has the effect of maximally suppressing the degree of thick edge formation in the back insulating layer of the electrode current collector. For example, the top insulating layer has a calculated value in the range of 1 to 1.1 according to condition 5, and the back insulating layer has a calculated value in the range of 1.15 to 1.3 according to condition 5.

[0121] In one embodiment, in the electrode for a secondary battery according to the present disclosure, the top insulating layer and the back insulating layer satisfy the following condition 6.

[0122] [Condition 6]

[0123] 0.65≤S f Top / S f Back ≤0.95

[0124] In condition 6, S f Top S indicates the uniformity of the top surface insulation layer coating. f Back This indicates the uniformity of the coating of the back insulation layer. Additionally, S f Top and S f Back Each is calculated according to the ratio shown in Formula 1 below:

[0125] [Formula 1]

[0126] H Edge / H Ever

[0127] In formula 1 above,

[0128] H Ever This represents the average height (μm) in the region of the insulating layer at a height of 25 μm or more from the electrode current collector.

[0129] H Edge The height (μm) represents the point in the end region of the insulating layer that has the highest distance from the electrode current collector, and the end region is located on the opposite side of the region where the insulating layer contacts the electrode active material layer.

[0130] Conventionally, this results in a higher level of thick edge in the back insulation layer, leading to a deterioration in the coating uniformity of the back insulation layer. This is due to condition S in condition 6 above. f BackThe value is increased to represent this. As a result, misalignment problems may occur in the electrode stack structure or the winding structure of the electrode rollers. This disclosure significantly reduces the degree of thick edges generated in the back insulation layer. Therefore, it is possible to solve the alignment defects of the electrode assembly while maintaining the thickness of the insulation layer at a certain level.

[0131] In one embodiment, the electrode active material layers of both the top coating and the back coating have a bilayer structure. This disclosure uses a double-slit die coating machine to manufacture the electrode. Therefore, the electrode according to this disclosure comprises a bilayer structured electrode active material layer on both sides, i.e., both the top coating and the back coating, with reference to the current collector. The electrode according to this disclosure can achieve high load capacity by including the bilayer structured electrode active material, while simultaneously achieving excellent safety by including a uniform insulating layer.

[0132] In one example, the electrode is the positive electrode. Specifically, the electrode is the positive electrode of a lithium secondary battery.

[0133] Model for implementing invention

[0134] The present disclosure will be described in more detail below with reference to the accompanying drawings, but the scope of the disclosure is not limited thereto.

[0135] Figure 1 This is a schematic diagram illustrating an electrode manufacturing process according to one embodiment of the present disclosure. (Refer to...) Figure 1 The current collector 20 substrate is supplied via the unwinder 10. A top surface coating step is performed, in which electrode slurry and insulating liquid are discharged onto the upper surface of the current collector 20 via a first double-slit die coating machine 30. Then, the top-surface coated current collector 20 is dried by a first heating section 40. The first heating section 40 may include multiple heaters 41, 42, and 43. The current collector 20, after the top surface coating and drying process, undergoes a back surface coating step. Electrode slurry and insulating liquid are discharged onto the lower surface of the top-surface coated current collector 20 via a second double-slit die coating machine 50. Then, the back-surface coated current collector 20 passes through a second heating section 60. The second heating section 60 may include multiple heaters 61, 62, and 63. The electrode substrate is formed through the top surface coating step and the back surface coating step, and the electrode substrate is wound onto the rewinder 70.

[0136] Figure 2 This is a schematic diagram illustrating a top surface coating process according to one embodiment of the present disclosure. (Refer to...) Figure 2The current collector 130 sheet, supplied along the Z-axis, passes over the coating roller 140. A double-slit die coating machine 100 is used to discharge electrode slurry and insulating liquid onto the upper surface of the current collector 130 passing over the coating roller 140. The double-slit die coating machine 100 includes a lower block 101, an intermediate block 102, and an upper block 103, with a first coating pad located between the lower block 101 and the intermediate block 102. Furthermore, a second coating pad is located between the intermediate block 102 and the upper block 103. The electrode slurry and insulating liquid are discharged through the slit formed by the first coating pad between the lower block 101 and the intermediate block 102 to form a first layer 110. The electrode slurry and insulating liquid are discharged through the slit formed by the second coating pad between the intermediate block 102 and the upper block 103 to form a second layer 120.

[0137] Figure 3 This is a partial front view showing the discharge section of a double-slit die coating machine according to conventional technology. (Refer to...) Figure 3 A conventional double-slit die coating machine 200 includes a lower block 201, an intermediate block 202, and an upper block 203. Furthermore, a first electrode slurry discharge path 211 is formed between the lower block 201 and the intermediate block 202, and a first insulating liquid discharge path 212 is formed to the side of the first electrode slurry discharge path 211. Additionally, a second electrode slurry discharge path 221 is formed between the intermediate block 202 and the upper block 203, and a second insulating liquid discharge path 222 is formed to the side of the second electrode slurry discharge path 221. Figure 3 In the conventional double-slit mold coating machine 200, the first insulating liquid discharge path 212 and the second insulating liquid discharge path 222 are formed with the same width.

[0138] When using according to Figure 3 When manufacturing electrodes using a double-slit mold coating machine 200, electrodes with the following characteristics are produced: Figure 4 Electrodes in the form shown. Figure 4 It is used according to Figure 3 A partial cross-sectional view of an electrode manufactured by a double-slit die coating machine. (Refer to...) Figure 4 The manufactured electrode has a structure in which an electrode active material layer 240 is formed on a current collector 230 and an insulating layer 250 is formed on the side surface of the electrode active material layer 240. The end of the insulating layer 250 is formed with a thick edge 251 having a relatively high height.

[0139] Figure 5 This is a partial front view showing the discharge section of a double-slit die coating machine according to one embodiment of the present disclosure. (Refer to...) Figure 5The dual-slit mold coating machine 300 according to this disclosure has a structure including a lower block 301, an intermediate block 302, and an upper block 303. Furthermore, a first electrode slurry discharge path 311 is formed between the lower block 301 and the intermediate block 302, and a first insulating liquid discharge path 312 is formed to the side of the first electrode slurry discharge path 311. Furthermore, a second electrode slurry discharge path 321 is formed between the intermediate block 302 and the upper block 303, and a second insulating liquid discharge path 322 is formed to the side of the second electrode slurry discharge path 321. Figure 5 In the present disclosure, the first insulating liquid discharge path 312 of the double-slit mold coating machine 300 has a width of 4 mm, and the second insulating liquid discharge path 322 has a width of 2 mm. Furthermore, a separation distance D (2 mm) is maintained between the first electrode slurry discharge path 311 and the first insulating liquid discharge path 312, and between the second electrode slurry discharge path 321 and the second insulating liquid discharge path 322.

[0140] When using according to Figure 5 When manufacturing electrodes using a 300-type double-slit mold coating machine, electrodes with the characteristics of... Figure 6 Electrodes in the form shown. Figure 6 It is used according to Figure 5 A partial cross-sectional view of an electrode manufactured by a double-slit die coating machine. (Refer to...) Figure 6 The manufactured electrode has a structure in which an electrode active material layer 340 is formed on a current collector 330 and an insulating layer 350 is formed on the side surface of the electrode active material layer 340. According to... Figure 6 In the electrode, the thick edge is almost invisible at the end of the insulating layer 350.

[0141] Figure 7 This is a graph showing the thickness profile of the insulating layer of the electrode. (Refer to...) Figure 7 The insulating layer is in a state where a flat surface of 2.3 mm is formed in the Y-axis direction, and the average thickness of the flat surface is 100 μm. Following the flat surface, the thickness of the insulating layer is confirmed to extend through a thicker edge section B. Edge The reduced section. In the thick-edge section B. Edge In the middle, the maximum height H Edge It is 120 μm. In this disclosure, H... Edge / H Ever The value is calculated to be 1.2.

[0142] As described above, this disclosure has been described in more detail with reference to the accompanying drawings and embodiments. However, since the configurations described in the drawings or embodiments herein are merely one embodiment of this disclosure and do not represent the overall technical spirit of this disclosure, it should be understood that this disclosure covers various equivalents, modifications, and substitutions made at the time of filing this application.

[0143] [Reference Symbol Explanation]

[0144] 10: Unwinder

[0145] 20, 130, 230, 330: Current collector

[0146] 30: The first double-slit mold coating machine

[0147] 40: First heating section

[0148] 41, 42, 43, 61, 62, 63: Heaters

[0149] 50: Second Double Slit Die Coating Machine

[0150] 60: Second heating section

[0151] 70: Rewinder

[0152] 100, 200, 300: Double-slit mold coating machine

[0153] 101, 201, 301: Next block

[0154] 102, 202, 302: Intermediate blocks

[0155] 103, 203, 303: Upper block

[0156] 110: First floor

[0157] 120: Second floor

[0158] 140: Coating roller

[0159] 211, 311: First electrode slurry discharge path

[0160] 212, 312: First insulating fluid discharge path

[0161] 221, 321: Second electrode slurry discharge path

[0162] 222, 322: Second insulating fluid discharge path

[0163] 240, 340: Electrode active material layer

[0164] 250, 350: Insulation layer

[0165] 251: Thick edge of the insulation layer

[0166] D: Separation distance

[0167] H Edge Height of the thick side in the insulation layer (μm)

[0168] H Ever Average height (μm) of the flat surface in the insulation layer.

[0169] B Edge Thick-edged sections in the insulation layer.

Claims

1. A double-slit mold coating machine, comprising: Bottom block, middle block, and top block; A first coated gasket is located between the lower block and the intermediate block; as well as The second coated pad is located between the middle block and the upper block. The first coating pad and the second coating pad each include: an electrode slurry discharge path for discharging electrode slurry; And an insulating liquid discharge path formed at a certain distance from the electrode slurry discharge path on one or both sides of the electrode slurry discharge path, for discharging insulating liquid. The double-slit mold coating machine meets the following condition 1: Among the conditions mentioned above, D1 represents the average width (mm) of the insulating liquid discharge path formed in the first coated gasket. D2 represents the average width (mm) of the insulating liquid discharge path formed in the second coated gasket.

2. The dual-slit mold coating machine according to claim 1, wherein the first coating pad and the second coating pad satisfy the following condition 2: Among the conditions mentioned above, in condition 2, D1 represents the average width (mm) of the insulating liquid discharge path formed in the first coated gasket. D2 represents the average width (mm) of the insulating liquid discharge path formed in the second coated gasket.

3. The double-slit mold coating machine according to claim 2, wherein the average width D2 of the insulating liquid discharge path formed in the second coating pad is in the range of 1 mm to 10 mm.

4. The double-slit mold coating machine according to claim 1, wherein each insulating liquid discharge path formed in the first coating pad and the second coating pad is separated from one or both sides of the electrode slurry discharge path by a distance D.

5. The double slit mold coating machine according to claim 4, wherein the distance D is in the range of 1 mm to 5 mm.

6. An electrode manufacturing method using a double-slit mold coating machine according to claim 1, comprising: Top surface coating step: coating one side of the current collector with electrode paste and insulating liquid; as well as The back coating step involves coating the electrode paste and insulating liquid onto the opposite side of the current collector. At least one of the top surface coating step and the back surface coating step includes: The first layer formation step involves discharging the first electrode slurry and the first insulating liquid onto the current collector sheet through the first coating pad; as well as The second layer formation step involves discharging the second electrode slurry and the second insulating liquid onto the current collector sheet via a second coating pad. The average width (D1') of the first insulating layer formed by draining the first insulating liquid and the average width (D2') of the second insulating layer formed by draining the second insulating liquid satisfy the following condition 3: Among the conditions mentioned above, in condition 3... D1' represents the average width (mm) of the first insulating layer. D2' represents the average width (mm) of the second insulating layer.

7. The electrode manufacturing method according to claim 6, wherein the first layer forming step and the second layer forming step are performed in one process.

8. The electrode manufacturing method according to claim 6, wherein the first layer forming step comprises: The first electrode slurry is discharged onto one side of the current collector through the first coating pad to form a first electrode active layer, and the first insulating liquid is discharged from both sides of the first electrode slurry discharge area to form the first insulating layer. The second layer forming step includes: discharging the second electrode slurry onto the opposite surface of the current collector through the second coating pad to form a second electrode active layer, and discharging the second insulating liquid on both sides of the second electrode slurry discharge area to form the second insulating layer.

9. The electrode manufacturing method according to claim 6, wherein the average width (D1') of the first insulating layer formed by discharging the first insulating liquid and the average width (D2') of the second insulating layer formed by discharging the second insulating liquid satisfy the following condition 4: [Condition 4] 1≤|D1'-D2'|≤10 (mm) Among the conditions mentioned above, in condition 4... D1' represents the average width (mm) of the first insulating layer. D2' represents the average width (mm) of the second insulating layer.

10. The electrode manufacturing method according to claim 6, wherein the first insulating liquid, based on solid content, contains no inorganic particles or contains less than 30% by weight of inorganic particles. The second insulating liquid contains inorganic particles ranging from 30% to 95% by weight, based on solid content.

11. An electrode for a secondary battery, comprising: A top coating is formed on one side of the electrode current collector, the top coating comprising a top surface electrode active material layer and a top surface insulating layer formed in the edge region of the top surface electrode active material layer; as well as A back coating is formed on the opposite side of the electrode current collector, the back coating comprising a back electrode active material layer and a back insulating layer formed in the edge region of the back electrode active material layer. The top insulating layer has a calculated value in the range of 1 to 1.15 according to condition 5 below, and the back insulating layer has a calculated value in the range of 1.15 to 1.5 according to condition 5 below. [Condition 5] H Edge / H Ever Among the conditions mentioned above, in condition 5... H Ever This represents the average height (μm) in the region of the insulating layer at a height of 25 μm or more from the electrode current collector. H Edge The height (μm) represents the point in the end region of the insulating layer that has the highest height from the electrode current collector, and the end region is located on the opposite side of the region where the insulating layer contacts the electrode active material layer.

12. The electrode for a secondary battery according to claim 11, wherein the top electrode active material layer and the back electrode active material layer are both double-layer structures.

13. The electrode for a secondary battery according to claim 11, wherein the secondary battery is a pouch cell.

14. The electrode for a secondary battery according to claim 11, wherein the electrode is a positive electrode.

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