Electrode for secondary battery and secondary battery including same

Abstract

The present invention relates to an electrode for a secondary battery and a secondary battery comprising the same, the electrode comprising a first surface and a second surface on the opposite side of the first surface, the first surface comprises a first active part in which an electrode active material layer is formed on the electrode current collector and a first uncoated part in which the electrode active material layer is not formed, and the second surface comprises a second active part in which an electrode active material layer is formed on the electrode current collector and a second uncoated part in which the electrode active material layer is not formed. The first surface includes a first active portion insulating layer formed on the first active portion and a first uncoated portion insulating layer formed on the first uncoated portion. The second surface includes a second active portion insulating layer formed on the second active portion and a second uncoated portion insulating layer formed on the second uncoated portion, and a position of an end of the first active portion insulating layer and a position of an end of the second active portion insulating layer are different from each other.

Description

Technical Field

[0001] The present invention relates to an electrode for a secondary battery and a secondary battery including the electrode. Background Art

[0002] The electrodes used in lithium secondary batteries are manufactured by the following method: an electrode mixture containing an electrode active material is coated on an electrode current collector in a slurry state and dried to form an electrode active material layer, and the electrode active material layer is rolled to a specified electrode density to manufacture an electrode.

[0003] The electrode thus manufactured includes a coated portion on which the electrode active material layer is formed and an uncoated portion on which the electrode active material layer is not coated, and the uncoated portion can be provided as an electrode tab.

[0004] The lithium secondary battery is manufactured by alternately laminating a negative electrode and a positive electrode and disposing a separator between the positive electrode and the negative electrode. Therefore, the positive electrode and the negative electrode are separated by the separator, thereby preventing direct contact. However, in a lithium secondary battery, for example, if the uncoated portion of the positive electrode comes into contact with a part of the negative electrode, a short circuit occurs, and abnormal situations such as fire may occur.

[0005] In addition, the process of manufacturing the electrode as described above includes a rolling process of pressing the electrode active material layer to adjust to a specified electrode density. Due to the difference in the presence or absence of the electrode active material layer, the coated portion and the uncoated portion have different physical properties, so the pressures applied to the coated portion and the uncoated portion are different during the rolling process of manufacturing the electrode, and finally problems such as breakage of the electrode at the boundary between the coated portion and the uncoated portion or disconnection during the process of welding the electrode tab may occur. Summary of the Invention

[0006] (I) Technical Problems to be Solved

[0007] An object of a specific embodiment of the present invention is to provide an electrode that can prevent a short circuit between electrodes in a secondary battery.

[0008] Another object of a specific embodiment of the present invention is to improve the safety of the battery by preventing a short circuit between the positive electrode and the negative electrode.

[0009] (II) Technical Solutions

[0010] A specific embodiment of the present invention provides an electrode for a lithium secondary battery, the electrode being an electrode for a secondary battery including a first surface and a second surface located on the opposite side of the first surface. Among them, the first surface may include a first active portion where an electrode active material layer is formed on an electrode current collector and a first uncoated portion where no electrode active material layer is formed. The second surface may be independent of the first surface. The second surface may include a second active portion where an electrode active material layer is formed on an electrode current collector and a second uncoated portion where no electrode active material layer is formed. The first surface may include a first active portion insulating layer formed on the first active portion and a first uncoated portion insulating layer formed on the first uncoated portion. The second surface may include a second active portion insulating layer formed on the second active portion and a second uncoated portion insulating layer formed on the second uncoated portion. The position of the end of the first active portion insulating layer and the position of the end of the second active portion insulating layer may be different from each other.

[0011] The first active portion insulating layer and the first uncoated portion insulating layer may be continuous layers. The second active portion insulating layer and the second uncoated portion insulating layer may be continuous layers. The length of the first active portion insulating layer and the length of the second active portion insulating layer may be different from each other. The length of the first active portion insulating layer is the length from the boundary between the first active portion and the first uncoated portion to the end of the first active portion insulating layer. The length of the second active portion insulating layer is the length from the boundary between the second active portion and the second uncoated portion to the end of the second active portion insulating layer.

[0012] The length of the first active portion insulating layer may be 1.3 times or more and 9 times or less the length of the second active portion insulating layer. The length of the first active portion insulating layer is the length from the boundary between the first active portion and the first uncoated portion to the end of the first active portion insulating layer. The length of the second active portion insulating layer is the length from the boundary between the second active portion and the second uncoated portion to the end of the second active portion insulating layer.

[0013] In addition, the length of the first active portion insulating layer may be 1.5 times or more and 7.5 times or less the length of the second active portion insulating layer. The length of the first active portion insulating layer is the length from the boundary between the first active portion and the first uncoated portion to the end of the first active portion insulating layer. The length of the second active portion insulating layer is the length from the boundary between the second active portion and the second uncoated portion to the end of the second active portion insulating layer.

[0014] The length of the first active part insulating layer can be more than 2 times to less than 9 times the length of the second active part insulating layer. The length of the first active part insulating layer is the length from the boundary between the first active part and the first uncoated part to the end of the first active part insulating layer. The length of the second active part insulating layer is the length from the boundary between the second active part and the second uncoated part to the end of the second active part insulating layer.

[0015] The distance between the end of the first active part insulating layer and the end of the second active part insulating layer can be 0.2 mm or more and 0.9 mm or less.

[0016] In addition, the distance between the end of the first active part insulating layer and the end of the second active part insulating layer can be 0.3 mm or more and 0.8 mm or less.

[0017] In addition, the distance between the end of the first active part insulating layer and the end of the second active part insulating layer can be 0.4 mm or more and 0.7 mm or less.

[0018] The first active part insulating layer and the second active part insulating layer can each independently have a length of 0.1 mm or more and 1.2 mm or less.

[0019] The length of the first active part insulating layer can be 0.3 - 1.2 mm, and the length of the second active part insulating layer can be 0.1 - 1.0 mm.

[0020] The position of the end of the first uncoated part insulating layer and the position of the end of the second uncoated part insulating layer can be the same or different.

[0021] The distance between the end of the first uncoated part insulating layer and the end of the second uncoated part insulating layer can be 0.5 mm or less.

[0022] The first uncoated part insulating layer and the second uncoated part insulating layer can each independently have a length of 1 - 12 mm.

[0023] The first active part insulating layer, the first uncoated part insulating layer, the second active part insulating layer, and the second uncoated part insulating layer can each independently have a thickness of 3 - 40 μm.

[0024] The electrode can have an electrode tab including the first uncoated part or the second uncoated part.

[0025] The electrode can be a negative electrode or a positive electrode.

[0026] Regions where the ends of the first active portion insulating layer of the electrode are present and regions where the ends of the second active portion insulating layer are present may include valleys formed independently of each other, and the positions of the valleys at the first surface and the second surface may be different from each other.

[0027] Another specific embodiment of the present invention provides a secondary battery including at least one positive electrode and at least one negative electrode, wherein the positive electrode, the negative electrode, or a combination thereof is any one of the above electrodes.

[0028] (III) Advantageous Effects

[0029] According to a specific embodiment of the present invention, it is possible to suppress the phenomenon that the electrode breaks at the boundary between the coated portion and the uncoated portion during the calendering process of manufacturing the electrode, or it is possible to suppress the phenomenon of disconnection during the tab welding process.

[0030] According to another specific embodiment of the present invention, it is possible to improve the yield rate of electrode manufacturing (reduce the defect rate of the electrode), and it is possible to improve the operation rate of the electrode manufacturing equipment.

[0031] According to another specific embodiment of the present invention, it is possible to suppress the occurrence of a short circuit caused by the contact between the positive electrode and the negative electrode.

[0032] The electrode of the present invention can be widely applied to green technology fields such as electric vehicles, battery charging stations, other battery-utilizing solar power generation, and wind power generation. In addition, the electrode of the present invention can be used for eco-friendly electric vehicles and hybrid vehicles that prevent climate change by suppressing air pollution and greenhouse gas emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a diagram schematically showing the mechanism of a short circuit occurring in a battery due to the pushing phenomenon of the uncoated portion of the positive electrode.

[0034] Figure 2 is a diagram schematically showing a cross-section of an electrode having an insulating layer formed on the surfaces of the uncoated portion and the active portion, and schematically showing an example in which the first active portion insulating layer and the second active portion insulating layer match each other on both sides of the electrode.

[0035] Figure 3 is a diagram schematically showing the mechanism of preventing a short circuit even when the uncoated portion of the positive electrode and the negative electrode are in direct contact by forming an insulating layer.

[0036] Figure 4FIG. is a cross-sectional view schematically showing an electrode having an insulating layer formed on the surfaces of an uncoated portion and an active portion, and schematically showing an embodiment in which a first uncoated portion insulating layer and a second uncoated portion insulating layer do not match each other on both sides of the electrode.

[0037] Figure 5 FIG. is a cross-sectional view schematically showing an electrode having an insulating layer formed on the surfaces of an uncoated portion and an active portion, and schematically showing an embodiment in which a first active portion insulating layer and a second active portion insulating layer do not match each other on both sides of the electrode.

[0038] Figure 6 FIG. is a cross-sectional view schematically showing an electrode having an insulating layer formed on the surfaces of an uncoated portion and an active portion, and schematically showing an embodiment in which a first active portion insulating layer and a second active portion insulating layer and a first uncoated portion insulating layer and a second uncoated portion insulating layer do not match each other on both sides of the electrode, respectively.

[0039] Figure 7 FIG. schematically shows Figure 2 a thickness profile of the electrode, where (a) is the thickness profile before rolling and (b) is the thickness profile after rolling.

[0040] Figure 8 FIG. schematically shows Figure 5 a thickness profile of the electrode after rolling.

[0041] Figure 9 FIG. is a diagram schematically showing a wound electrode assembly and a manufacturing process thereof.

[0042] Figure 10 FIG. is a diagram schematically showing an electrode laminate for manufacturing a wound electrode assembly.

[0043] Figure 11 FIG. is a diagram schematically showing a stacked electrode assembly and a manufacturing process thereof.

[0044] Figure 12 FIG. is a diagram schematically showing a secondary battery including a stacked electrode assembly.

[0045] Figure 13 FIG. is a diagram schematically showing a manufacturing process of an electrode for manufacturing the stacked electrode assembly and the electrode obtained thereby.

[0046] Figure 14 FIG. is a diagram schematically showing a stacked-folded electrode assembly and a manufacturing process thereof.

[0047] Figure 15 FIG. is a diagram showing a thickness profile of a first surface of an electrode obtained in Example 1 observed using a three-dimensional (3D) microscope.

[0048] Figure 16 This is a photograph of the positive electrode that broke when measuring the tensile strength of the positive electrode obtained in Measurement Example 1. (a) shows the state of breakage occurring in the uncoated portion, and (b) shows the state of breakage occurring in the active portion.

[0049] Figure 17 This is a photograph of an electrode tab manufactured by welding the uncoated portion of the electrode obtained in Example 1. (a) is a photograph of the electrode tab before pre-welding, and (b) is a photograph of the electrode tab after main welding.

[0050] Figure 18 This is a thickness profile obtained by analyzing the thickness of the first side of the electrode obtained in Comparative Example 1 before ((a)) and after ((b)) rolling using a three-dimensional (3D) microscope.

[0051] Figure 19 This is a photograph of the cross-section of the rolled electrode obtained in Comparative Example 1 taken using a scanning electron microscope (SEM).

[0052] Figure 20 This is a photograph of an electrode tab manufactured by welding the uncoated portion of the electrode obtained in Comparative Example 1. (a) is a photograph of the electrode tab before pre-welding, and (b) is a photograph of the electrode tab after main welding.

[0053] Figure 21 This is a photograph of an electrode tab manufactured by welding the uncoated portion of the electrode obtained in Comparative Example 2. (a) is a photograph of the electrode tab before pre-welding, and (b) is a photograph of the electrode tab after main welding.

[0054] Explanation of reference numerals:

[0055] 1: Electrode current collector

[0056] 3: Electrode active material layer

[0057] 5: Insulating layer

[0058] 10: Electrode

[0059] 11: First side

[0060] 12: Second side

[0061] 13: Active portion

[0062] 14: Uncoated portion

[0063] 15: Boundary

[0064] 16: Electrode plate

[0065] 17: Positive electrode

[0066] 18: Negative electrode

[0067] 19: Separator

[0068] 20: Electrode tab

[0069] 21: Positive electrode tab

[0070] 22: Negative electrode tab

[0071] 23: Positive electrode lead

[0072] 24: Negative electrode lead

[0073] 25: Electrode lead

[0074] 30: Soft package type housing

[0075] 351: First active part insulating layer

[0076] 352: Second active part insulating layer

[0077] 3511: End of the first active part insulating layer

[0078] 3522: End of the second active part insulating layer

[0079] 451: First uncoated part insulating layer

[0080] 452: Second uncoated part insulating layer

[0081] 4511: End of the first uncoated part insulating layer

[0082] 4522: End of the second uncoated part insulating layer

[0083] ΔL1: Spacing between the end of the first uncoated part insulating layer and the end of the second uncoated part insulating layer

[0084] ΔL2: Spacing between the end of the first active part insulating layer and the end of the second active part insulating layer Detailed implementation mode

[0085] Hereinafter, with reference to the drawings, the present invention will be described in detail. However, this is merely an exemplary implementation scheme, and the present invention is not limited to the specific implementation schemes described exemplarily.

[0086] A specific implementation scheme of the present invention provides an electrode for a lithium secondary battery that can prevent short - circuit between the positive electrode and the negative electrode.

[0087] In a lithium secondary battery, a porous separator or a solid electrolyte membrane is disposed between the positive electrode and the negative electrode to prevent direct contact between the negative electrode and the positive electrode. However, when the pushing phenomenon of the uncoated portion of the positive electrode occurs during the process of manufacturing the electrode assembly or during the process of manufacturing the electrode, the uncoated portion of the positive electrode may come into direct contact with the negative electrode, thereby causing a short circuit to occur.

[0088] For example, Figure 1 An example of a short circuit occurring due to the pushing of the uncoated portion of the positive electrode is schematically shown. Figure 1 FIG. schematically shows an example in which, due to the pushing of the uncoated portion of the positive electrode in the battery, the uncoated portion of the positive electrode approaches the electrode assembly, and finally the uncoated portion of the positive electrode comes into direct contact with the negative electrode, thereby causing a short circuit.

[0089] As described above, when the constituent components of the positive electrode and the negative electrode come into contact, there is a risk such as a fire caused by a short circuit. Therefore, a safety device for preventing a short circuit between the positive electrode and the negative electrode is required.

[0090] For example, Figure 2 An example of an electrode in which an insulating layer is formed to prevent a short circuit between the positive electrode and the negative electrode is shown. As Figure 2 shown, the electrode 10 includes an electrode active material layer 3, and the electrode active material layer 3 contains an electrode active material formed on the electrode current collector 1.

[0091] Specifically, the electrode includes a first surface 11 and a second surface 12, and the second surface 12 is the other surface opposite to the first surface. The first surface and the second surface independently have an active portion 13 on which an electrode active material layer is formed and an uncoated portion 14 on which no electrode active material layer is formed. The first surface may include a first active portion on which an electrode active material layer is formed on the electrode current collector and a first uncoated portion on which no electrode active material layer is formed. The second surface may be independent of the first surface, and the second surface may include a second active portion on which an electrode active material layer is formed on the electrode current collector and a second uncoated portion on which no electrode active material layer is formed. In addition, the first surface may include a first active portion insulating layer formed on the first active portion and a first uncoated portion insulating layer formed on the first uncoated portion, and the second surface may include a second active portion insulating layer formed on the second active portion and a second uncoated portion insulating layer formed on the second uncoated portion.

[0092] In the electrode, an insulating layer 5 is formed on at least a part of the uncoated portion. When the negative electrode and the positive electrode are laminated to form an electrode assembly, the insulating layer may be included as a part of the tab of the first electrode (for example, the positive electrode), and even if the uncoated portion comes into contact with a component of the negative electrode such as the negative electrode active material layer of the second electrode (for example, the negative electrode), the electrical connection can be blocked, thereby preventing the occurrence of a short circuit phenomenon.

[0093] Although not limited thereto, the insulating layer may be a continuous layer formed without interruption. Specifically, as Figure 2 shown, the first uncoated portion insulating layer formed on the first uncoated portion of the electrode and the first active portion insulating layer formed on the first active portion may be continuous layers, and a continuous layer may also be continuously formed between the first uncoated portion insulating layer and the first active portion insulating layer. Similarly, the second uncoated portion insulating layer formed on the second uncoated portion of the electrode and the second active portion insulating layer formed on the second active portion may be continuous layers, and a continuous layer may also be continuously formed between the second uncoated portion insulating layer and the second active portion insulating layer.

[0094] Figure 3 is a diagram schematically showing a battery of an electrode on which an uncoated portion insulating layer is formed on an uncoated portion of an electrode as shown in Figure 2 shown, in which short circuit can be prevented when the uncoated portion of the positive electrode and the negative electrode are in direct contact. Generally, compared with the positive electrode, the electrode surface of the formed negative electrode may be larger, and on the side of the electrode assembly, the negative electrode may protrude more compared with the positive electrode. Even as Figure 1 shown, due to the pushing phenomenon of the uncoated portion of the positive electrode, the uncoated portion of the positive electrode approaches the side of the electrode current collector, when an insulating layer is formed on the uncoated portion of the positive electrode, as Figure 3 shown, the electrical contact between the positive electrode and the negative electrode can be blocked, thereby preventing short circuit.

[0095] The uncoated portion insulating layer formed on the uncoated portion may be formed over the entire area of the uncoated portion, or may be formed on a part of the uncoated portion. When the uncoated portion insulating layer is formed on a partial area of the uncoated portion, as Figure 2 shown, the uncoated portion insulating layer may be partially formed on the uncoated portion from the boundary 15 between the uncoated portion and the active portion to the adjacent area.

[0096] In the uncoated portion insulating layer, among the first uncoated portion insulating layer 451 formed on the uncoated portion of the first surface 11 and the second uncoated portion insulating layer 452 formed on the uncoated portion of the second surface 12, the positions of the end 4511 of the first uncoated portion insulating layer and the end 4522 of the second uncoated portion insulating layer may be the same or different from each other.

[0097] The end of the uncoated portion insulating layer is the end of the insulating layer located on the uncoated portion, and may be located on the uncoated portion side of the boundary between the uncoated portion and the active portion. For example, with respect to the end of the uncoated portion insulating layer, as Figure 2As shown, the positions of the ends of the uncoated portion insulating layers may be the same as each other, and the positions of the ends of the uncoated portion insulating layers may also be different from each other. Specifically, the end 4511 of the first uncoated portion insulating layer may be located at a position farther from the boundary 15 between the uncoated portion and the active portion than the end 4522 of the second uncoated portion insulating layer, and as Figure 4 shown, the end 4522 of the second uncoated portion insulating layer may be located at a position farther from the boundary 15 between the uncoated portion and the active portion than the end 4511 of the first uncoated portion insulating layer.

[0098] At this time, the distance ΔL1 between the end of the first uncoated portion insulating layer and the end of the second uncoated portion insulating layer is not particularly limited, but may be 0.5 mm or less.

[0099] The length from the boundary between the active portion and the uncoated portion to the end 4511 of the first uncoated portion insulating layer (i.e., the length of the first uncoated portion insulating layer) and the length from the boundary between the active portion and the uncoated portion to the end 4522 of the second uncoated portion insulating layer (i.e., the length of the second uncoated portion insulating layer) are not particularly limited. As an example, the lengths may be independently 1 - 12 mm, more specifically, may be 3 - 10 mm or 5 - 7 mm.

[0100] The insulating layer may be formed in a manner that overlaps a partial region of the electrode active material layer. In this case, the insulating layer may include the first uncoated portion insulating layer 451 and the second uncoated portion insulating layer 452 on the uncoated portion and the first active portion insulating layer 351 and the second active portion insulating layer 352 on the electrode active material layer.

[0101] By forming the active portion insulating layer on the electrode active material layer, the efficiency of the coating process for forming the insulating layer can be improved. By including the active portion insulating layer on the electrode active material layer, the insulating performance brought by the insulating layer can be improved. When the insulating layer is only formed on the uncoated portion such that the insulating layer is spaced apart from the end of the electrode active material layer, wrinkles may be easily formed on the uncoated portion during the process of the electrode moving through a roller or the like during electrode manufacturing, and breakage of the electrode may be likely to occur during the calendering process.

[0102] The active portion insulating layer may be formed in the same region on the first surface and the second surface of the electrode. Specifically, as Figure 2 and Figure 4 shown, the positions of the end 3511 of the first active portion insulating layer and the end 3522 of the second active portion insulating layer may be the same as each other. The end of the active portion insulating layer is the end of the insulating layer located on the active portion, and may be located on the active portion side of the boundary between the uncoated portion and the active portion.

[0103] In an electrode according to a specific embodiment of the present invention, the active part insulating layer may be formed in different regions of the first and second surfaces of the electrode. As a specific embodiment, as Figure 5 and Figure 6 shown, the positions of the ends 3511 of the first active part insulating layer and the ends 3522 of the second active part insulating layer may be different from each other.

[0104] In the present invention, when rolling an electrode in which the insulating layer and the electrode active material layer are overlapped, the insulating layer and the electrode active material layer may have differences in physical properties, such as elongation. Regarding such differences in physical properties, in the rolling process in the electrode manufacturing process, depending on the situation, stress may concentrate at the boundary between the uncoated part and the active part, which may cause the electrode to break.

[0105] For example, an electrode mixture slurry containing an electrode active material may be coated on a part of the current collector to form an active part, and an insulating liquid may be coated in a manner overlapping with a part of the uncoated part and the active part to form an insulating layer, and then a drying and rolling process may be performed to manufacture an electrode with an insulating layer. At this time, the thickness of the active part insulating layer region where the insulating layer and the active part overlap is thicker than the thickness of the adjacent uncoated part insulating layer and the electrode active material layer (i.e., the electrode active material layer where the insulating layer is not formed), so that a valley may be formed between the active part insulating layer and the adjacent region (for example, the electrode active material layer where the insulating layer is not formed). Throughout this specification, the thickness of any surface of the electrode may refer to the distance from the surface of the electrode current collector 1 in contact with the electrode active material layer on the first or second surface to the surface of the first or second surface.

[0106] For example, Figure 7 schematically shows the thickness profiles of the active part insulating layer in the electrode, the adjacent uncoated part insulating layer, and the electrode active material layer. In Figure 7 , (a) schematically shows a cross-section after coating the electrode mixture slurry and then coating the insulating liquid, and (b) shows a cross-section of the electrode manufactured by drying and rolling.

[0107] As Figure 7 shown in (a), in the first active part insulating layer 351 and the second active part insulating layer 352 in the region where the coating of the electrode mixture slurry and the coating of the insulating liquid overlap, and the adjacent coating of the electrode mixture slurry (or the electrode active material layer 3), fine valleys are formed near the ends 3511 of the first active part insulating layer and the ends 3522 of the second active part insulating layer, and as Figure 7 shown in (b), after the drying and rolling process, the formation of the valleys may become more obvious. In Figure 7In (a) and (b) thereof, in the regions where the first active part insulating layer 351 and the second active part insulating layer 352 are formed, the coating of the electrode mixture paste and the coating of the insulating liquid overlap, but each coating is represented as one region without distinction. The valley can be formed at the end of each active part insulating layer. In the part where the valley is formed, there are insulating layers and electrode active material layers with different elongation rates with the valley as the boundary. Therefore, when exposed to the harsh conditions such as calendering in the electrode manufacturing process or concentrating and welding multiple uncoated parts of the electrode to manufacture electrode tabs, etc., the part where the valley is formed becomes a vulnerable part, and forces such as pressure concentrate here, and ultimately the electrode may break.

[0108] According to a specific embodiment of the present invention, when forming the insulating layer, the positions of the valleys formed at the first surface and the second surface of the electrode can be staggered from each other, so that the problem of electrode breakage occurring in the region where the valleys are formed can be prevented or reduced. Specifically, the positions of the ends of the first active part insulating layer and the second active part insulating layer of the electrode can be set at different positions from each other.

[0109] For example, Figure 8 schematically shows the thickness profiles of the active part insulating layer, the uncoated part insulating layer adjacent thereto, and the electrode active material layer in the electrode where the positions of the ends of the active part insulating layer at the first surface and the second surface of the electrode are different from each other. In Figure 8 the regions where the first active part insulating layer 351 and the second active part insulating layer 352 are formed, the coating of the electrode mixture paste and the coating of the insulating liquid overlap, but each coating is represented as one region without distinction.

[0110] As Figure 8 shown, in the part indicated by the dotted line between the region where the coating of the electrode mixture paste and the coating of the insulating liquid overlap and the adjacent coating of the electrode mixture paste, that is, in the region where the end of the active part insulating layer exists, fine valleys are formed, so that deeper valleys are also formed in the calendered electrode, but the valleys can be formed at different positions on the first surface and the second surface. At this time, the thickness decreases from the thickest part in the region where the active part insulating layer is formed to the end of the active part insulating layer, and the thickness increases from the end of the active part insulating layer to the electrode active material layer where the insulating layer is not formed. Therefore, the valleys can be formed in the region where the end of the active part insulating layer exists, and the positions of the valleys at the first surface and the second surface can be different from each other. Specifically, the regions where the ends of the first active part insulating layer exist and the regions where the ends of the second active part insulating layer exist can include valleys formed independently of each other, and the positions of the valleys at the first surface and the second surface can be different from each other.

[0111] The positions of the ends of the first active part insulating layer and the second active part insulating layer of the electrode according to a specific embodiment of the present invention may be different. As described above, in the electrode, the ends of the active part insulating layers on the first surface and the second surface exist at different positions from each other and have a spacing, so that the valleys on the first surface and the second surface may exist at different positions from each other. Therefore, by dispersing the vulnerable parts of the electrode, the force applied to the electrode during the manufacture of the electrode tab by rolling or welding can be dispersed, and even if the electrode is exposed to harsh conditions, the phenomenon of electrode fracture at the position where the valley is formed can be prevented or suppressed.

[0112] In a specific embodiment, the spacing ΔL2 between the end of the first active part insulating layer and the end of the second active part insulating layer of the electrode of the present invention may be 0.2 mm to 0.9 mm, 0.3 mm or more to 0.8 mm or less, or 0.4 mm or more to 0.7 mm or less. More specifically, the spacing may be 0.2 mm or more, 0.3 mm or more, 0.4 mm or more, or 0.5 mm or more, and may be 0.9 mm or less, 0.8 mm or less, or 0.7 mm or less.

[0113] In a specific embodiment, the electrode has a first active part insulating layer and a second active part insulating layer. The length of the first active part insulating layer is the length from the boundary 15 to the end of the first active part insulating layer, and the length of the second active part insulating layer is the length from the boundary 15 to the end of the second active part insulating layer. As long as the difference between the length of the first active part insulating layer and the length of the second active part insulating layer satisfies the spacing ΔL2 as described above, there is no particular limitation.

[0114] In a specific embodiment, the lengths of the first active part insulating layer and the second active part insulating layer of the electrode may be different from each other. The length of the first active part insulating layer is the length from the boundary 15 between the first active part and the first uncoated part to the end of the first active part insulating layer, and the length of the second active part insulating layer is the length from the boundary 15 between the second active part and the second uncoated part to the end of the second active part insulating layer. The positions of the boundary 15 on the first surface and the second surface of the electrode may not match. At this time, the reference for measuring the length of the active part insulating layer may be the boundary (the first boundary) on the first surface and the boundary (the second boundary) on the second surface that makes the length shorter. For example, when the positions of the first boundary and the second boundary are different from each other, and the relationship between the distance (D1) from the first boundary to the end of the first active part insulating layer and the distance (D2) from the second boundary to the end of the first active part insulating layer is D1 > D2, the length of each active part insulating layer may be measured based on the second boundary.

[0115] As a specific implementation, when the length of the first active part insulating layer is longer than that of the second active part insulating layer, the length of the first active part insulating layer can be more than 1.3 times to less than 9 times the length of the second active part insulating layer. For example, it can be more than 1.5 times to less than 7.5 times, and can be more than 2 times to less than 9 times. As an example, the first active part insulating layer can be formed to be 1.0 mm, and the second active part insulating layer can be formed to be 0.5 mm. As another specific implementation, the first active part insulating layer can be formed to be 0.9 mm, and the second active part insulating layer can be formed to be 0.1 mm. As described above, by making the positions of the ends of the first active part insulating layer and the second active part insulating layer not match, the pressure applied to the electrode in the calendering process or welding process, etc. can be dispersed, thereby preventing the fracture of the electrode.

[0116] As a specific implementation, the length of the first active part insulating layer and the length of the second active part insulating layer can each independently be 0.1 mm or more, 0.3 mm or more, or 0.5 mm or more, and can be 1.2 mm or less, 1 mm or less, or 0.9 mm or less. Specifically, the first active part insulating layer and the second active part insulating layer can each independently have a length of 0.1 mm or more to 1.2 mm or less. More specifically, the length of the first active part insulating layer can be 0.3 - 1.2 mm, and the length of the second active part insulating layer can be 0.1 - 1.0 mm.

[0117] In the active part insulating layer, due to the interaction between the insulating liquid and the electrode mixture slurry, a convex mountain-shaped side ring defect may occur at the end of the overlapping part. Such a side ring may cause pressure concentration in the calendering process and may ultimately lead to electrode fracture.

[0118] The insulating layer formed on the uncoated part and the active part is not particularly limited, but the thickness of the insulating layer can be 3 μm or more. When the thickness of the insulating layer is small, the insulating properties may be insufficient. Within the range that does not damage the performance of the electrode, the upper limit of the thickness of the insulating layer is not particularly limited. For example, the insulating layer can have a thickness of 40 μm or less. Specifically, the first active part insulating layer, the first uncoated part insulating layer, the second active part insulating layer, and the second uncoated part insulating layer can each independently have a thickness of 3 - 40 μm.

[0119] The insulating layer can be made of an insulating material, which is not particularly limited, but examples thereof include fluororesins, polyimide resins, acrylic resins such as polymethyl acrylate (PMA) and polymethyl methacrylate (PMMA), polyvinyl acetate, polyamide (PA), polyvinyl chloride (PVC), polyether nitrile (PEN), polyethylene (PE), polypropylene (PP), polyacrylonitrile (PAN), nitrile rubber, styrene-butadiene rubber (SBR), poly(meth)acrylic acid, carboxymethyl cellulose (CMC), hydroxyethyl cellulose, polyvinyl alcohol, etc. The insulating material can be used alone or in combination of two or more of the above substances. In addition, carboxymethyl cellulose and the like can also be used in the form of salts such as sodium salts.

[0120] The insulating layer can be formed by the following method: coating an electrode mixture slurry containing an electrode active material on the active part of an electrode current collector, coating an insulating liquid for forming the insulating layer before drying, and drying to form the insulating layer. In addition, the insulating layer can be added to a calendering process together with the electrode active material layer and calendered.

[0121] The insulating liquid can be an insulating liquid in which the resin contained in the insulating layer is dissolved in an organic solvent. As long as the organic solvent is generally used as a solvent for organic resins, it can also be suitably used here. As an example, N-methyl-2-pyrrolidone (NMP), cyclohexanone, etc. can be used as the organic solvent.

[0122] The amount of the organic solvent used is not particularly limited, but the organic solvent can be added so that the viscosity of the insulating liquid ranges from 1000 to 9000 cp at room temperature (25°C). When the viscosity of the insulating liquid is not within the above range, the workability may be reduced. More specifically, the organic solvent can be added so that the viscosity of the insulating liquid ranges from 4000 to 7000 cp.

[0123] The insulating liquid can be applied by methods such as gravure coating, slot die coating, multi-layer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc., and is not limited thereto.

[0124] The electrode according to the present invention can be a negative electrode or a positive electrode.

[0125] When the electrode is a positive electrode, the positive electrode can include a positive electrode current collector and positive electrode active material layers provided on both surfaces of the positive electrode current collector.

[0126] The positive electrode current collector may include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector may also include aluminum surface-treated with carbon, nickel, titanium, and silver or stainless steel surface-treated with carbon, nickel, titanium, and silver. Additionally, the positive electrode current collector may be a polymer substrate coated with a conductive metal such as nickel, aluminum, titanium, silver, etc.

[0127] As a non-limiting example, the positive electrode current collector may be in various forms such as foil, foam, mesh, porous body, non-woven fabric, etc. Additionally, the positive electrode current collector is not limited thereto, but the thickness of the positive electrode current collector may be 10 - 50 μm.

[0128] The positive electrode active material layer may contain a positive electrode active material. The positive electrode active material may contain a compound that allows lithium ions to be reversibly intercalated and deintercalated.

[0129] According to an exemplary embodiment, the positive electrode active material may contain a lithium-nickel metal oxide. The lithium-nickel metal oxide may further contain at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0130] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may contain a layered structure or crystal structure represented by the following Chemical Formula 1.

[0131] [Chemical Formula 1]

[0132] Li x Ni a M b O 2+z

[0133] In Chemical Formula 1, 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.4, and -0.5 ≤ z ≤ 0.1. As described above, M may contain Co, Mn, and / or Al.

[0134] The chemical structure represented by Chemical Formula 1 represents the bonding relationship contained in the layered structure or crystal structure of the positive electrode active material, and does not exclude other additional elements. For example, M may contain Co and / or Mn, and Co and / or Mn may be provided together with Ni as the main active element of the positive electrode active material. Chemical Formula 1 is provided to represent the bonding relationship of the main active element, and it should be understood that Chemical Formula 1 is a formula including the introduction and substitution of additional elements.

[0135] In one embodiment, the positive electrode active material may further include an auxiliary element to enhance the chemical stability of the positive electrode active material or the layered structure / crystalline structure. The auxiliary element may be incorporated together into the layered structure / crystalline structure to form a bond, and it should be understood that this case is also included within the chemical structure represented by Chemical Formula 1.

[0136] The auxiliary element may include at least one of, for example, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Zr. The auxiliary element may act as an auxiliary active element that contributes to the capacity / power activity of the positive electrode active material together with Co or Mn, such as Al.

[0137] For example, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or a crystalline structure represented by the following Chemical Formula 1-1.

[0138] [Chemical Formula 1-1]

[0139] Li x Ni a M1 b1 M2 b2 O 2+z

[0140] In Chemical Formula 1-1, M1 may include Co, Mn, and / or Al. M2 may include the above-mentioned auxiliary element. In Chemical Formula 1-1, 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b1 + b2 ≤ 0.4, and -0.5 ≤ z ≤ 0.1.

[0141] The positive electrode active material may further include a coating element or a doping element. For example, an element that is substantially the same as or similar to the above-mentioned auxiliary element may be used as the coating element or the doping element. For example, one or a combination of two or more of the above elements may be used as the coating element or the doping element.

[0142] The coating element or the doping element may be present on the surface of the lithium-nickel metal oxide particles or penetrate through the surface of the lithium-nickel metal oxide particles and be included in the bonding structure represented by Chemical Formula 1 or Chemical Formula 1-1.

[0143] The positive electrode active material may include a nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, an NCM-based lithium oxide with an increased nickel content may be used.

[0144] Ni can be provided as a transition metal related to the power and capacity of a lithium secondary battery. Thus, as described above, by using a high-content (high-Ni) composition for the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0145] However, as the Ni content increases, the long-term storage stability and life stability of the positive electrode or the secondary battery may be relatively reduced, and side reactions with the electrolyte may also increase. However, according to exemplary embodiments, conductivity can be maintained by including Co, and life stability and capacity retention characteristics can be improved by Mn.

[0146] The content of Ni in the NCM-based lithium oxide (e.g., the mole fraction of Ni in the total moles of nickel, cobalt, and manganese) can be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni can be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0147] In some embodiments, the positive electrode active material may further include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0148] In some embodiments, the positive electrode active material may include, for example, a Mn-rich-based active material, a Li rich layered oxide (LLO) / Over Lithiated Oxide (OLO)-based active material, or a Co-less-based active material having a chemical structure or crystal structure represented by Chemical Formula 2.

[0149] [Chemical Formula 2]

[0150] p[Li2MnO3]·(1-p)[Li q JO2]

[0151] In Chemical Formula 2, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J may include at least one element among Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0152] For the positive electrode, for example, the positive electrode active material can be mixed in a solvent to prepare a positive electrode slurry. The positive electrode slurry can be coated on a positive electrode current collector and then dried, and an insulating liquid can be coated before or after the drying, and then calendered to manufacture a positive electrode active material layer.

[0153] The positive electrode may be a multi-layer positive electrode. In the case of a multi-layer positive electrode, for example, a first positive electrode mixture slurry may be coated on a positive electrode current collector to form a first positive electrode mixture layer, and a second positive electrode mixture slurry may be coated on the first positive electrode mixture layer to form a second positive electrode mixture layer, and then the insulating liquid is coated. The first positive electrode mixture slurry and the second positive electrode mixture slurry may be dried simultaneously, or the second positive electrode mixture slurry may be coated and dried after the first positive electrode mixture slurry is dried.

[0154] The coating process may be carried out by methods such as gravure coating, slot die coating, multi-layer simultaneous die coating, imprinting, blade coating, dip coating, rod coating, casting, etc., and is not limited thereto.

[0155] The positive electrode active material layer may further include a binder, and may optionally further include a conductive material, a thickener, etc.

[0156] The solvent used for preparing the positive electrode slurry is not limited thereto, but for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. may be cited.

[0157] The binder may include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (Poly(vinylidene fluoride-co-hexafluoropropylene)), polyacrylonitrile, polymethyl methacrylate, nitrile rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. In one embodiment, a PVDF-based binder may be used as the positive electrode binder.

[0158] The conductive material may be added to enhance the conductivity of the positive electrode active material layer and / or the mobility of lithium ions or electrons. For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber, etc. and / or metal-based conductive materials containing perovskite substances such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc., but is not limited thereto.

[0159] As needed, the positive electrode mixture may further include a thickening agent and / or a dispersing agent, etc. As an embodiment, the positive electrode mixture may include a thickening agent such as carboxymethyl cellulose (CMC).

[0160] When the electrode is a negative electrode, the negative electrode may include a negative electrode current collector and negative electrode active material layers provided on both surfaces of the negative electrode current collector.

[0161] The negative electrode current collector may include stainless steel, copper, nickel, titanium, or an alloy thereof. The negative electrode current collector may also include copper surface-treated with carbon, nickel, titanium, and silver or stainless steel surface-treated with carbon, nickel, titanium, and silver. Additionally, the negative electrode current collector may be a polymer substrate coated with a conductive metal such as nickel, aluminum, titanium, or silver.

[0162] As a non-limiting example, the negative electrode current collector may be in various forms such as a foil, foam, mesh, porous body, non-woven fabric, etc. Additionally, the negative electrode current collector is not limited thereto, but the thickness of the negative electrode current collector may be 10 - 50 μm.

[0163] The negative electrode active material layer may contain a negative electrode active material. The negative electrode active material may be a material that allows lithium ions to be intercalated and deintercalated. For example, the negative electrode active material may use carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers; lithium metal; lithium alloys; silicon (Si)-containing substances or tin (Sn)-containing substances, etc.

[0164] As an example of the amorphous carbon, hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc. may be cited.

[0165] As an example of the crystalline carbon, graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc. may be cited.

[0166] The lithium metal may be cited as pure lithium metal or lithium metal formed with a protective layer for suppressing dendrite growth, etc. In one embodiment, a lithium metal-containing layer deposited or coated on the negative electrode current collector may be used as the negative electrode active material layer. In one embodiment, a lithium thin film layer may be used as the negative electrode active material layer.

[0167] As elements included in the lithium alloy, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium, etc. may be cited.

[0168] The silicon-containing substance may provide further increased capacity characteristics. The silicon-containing substance may include Si, SiO x(0 < x < 2), SiO doped with metal x (0 < x < 2), silicon-carbon composite, etc. The metal may include lithium and / or magnesium, and the SiO doped with metal x (0 < x < 2) may include metal silicate.

[0169] For example, the negative electrode active material may be mixed in a solvent to prepare a negative electrode paste. The negative electrode active material layer may further contain a binder, and may optionally further contain a conductive material, a thickening agent, etc.

[0170] The negative electrode paste may be coated / deposited on the negative electrode current collector and then dried and calendered to form the negative electrode active material layer. The coating process may be carried out by methods such as gravure coating, slot die coating, multi-layer simultaneous die coating, imprinting, knife coating, dip coating, rod coating, casting, etc., and is not limited thereto.

[0171] In some embodiments, the negative electrode may further include a negative electrode active material layer in the form of lithium metal formed by a deposition / coating process.

[0172] The negative electrode may be a multi-layer negative electrode. In the case of a multi-layer negative electrode, for example, a first negative electrode mixture paste may be coated on the negative electrode current collector to form a first negative electrode mixture layer, and a second negative electrode mixture paste may be coated on the first negative electrode mixture layer to form a second negative electrode mixture layer, and then the insulating liquid is coated. The first negative electrode mixture paste and the second negative electrode mixture paste may be dried simultaneously, or the first negative electrode mixture paste may be dried and then the second negative electrode mixture paste is coated and dried.

[0173] Non-limiting examples of the solvent for the negative electrode mixture may include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, tert-butanol, etc.

[0174] The binder may include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (poly(vinylidene fluoride-co-hexafluoropropylene) copolymer), polyacrylonitrile, polymethyl methacrylate, nitrile rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. In one embodiment, the negative electrode binder may use a styrene-butadiene rubber (SBR)-based binder, carboxymethyl cellulose (CMC), a polyacrylic acid-based binder, a poly(3,4-ethylenedioxythiophene) (PEDOT)-based binder, etc.

[0175] Based on the total weight of the negative electrode active material layer, the content of the binder can be about 1.5 wt% to about 5 wt%.

[0176] The conductive material can be added to enhance the conductivity of the negative electrode active material layer and / or the mobility of lithium ions or electrons. For example, the conductive material can include carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fibers (VGCF), carbon fibers, etc. and / or metal-based conductive materials including perovskite minerals such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc., but is not limited thereto.

[0177] In one embodiment, based on the total weight of the negative electrode active material layer, the content of the conductive material can be about 0.05 wt% to about 0.2 wt%.

[0178] As needed, the negative electrode active material layer can further include a thickener and / or a dispersant, etc. As one embodiment, the negative electrode active material layer can include a thickener such as carboxymethyl cellulose (CMC).

[0179] The electrode assembly can be manufactured by alternately laminating the positive electrode and the negative electrode and disposing a separator between the positive electrode and the negative electrode.

[0180] The separator can be arranged to prevent short circuits between the positive electrode and the negative electrode and to allow the flow of ions. As one embodiment, the thickness of the separator is not limited thereto, but for example, the thickness of the separator can be 10 μm to 20 μm.

[0181] For example, the separator can include a porous polymer membrane or a porous non-woven fabric. The porous polymer membrane can include polyolefin-based polymers such as ethylene polymers, propylene polymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers. The porous non-woven fabric can include high-melting-point glass fibers, polyethylene terephthalate fibers, etc. The separator can also include a ceramic-based material. For example, inorganic particles can be coated on or dispersed in the polymer membrane to improve heat resistance.

[0182] The separator can have a single-layer or multi-layer structure including the above polymer membrane and / or non-woven fabric.

[0183] As an example, the electrode assembly may be a winding type electrode assembly, a stacking type electrode assembly, or a stack-folding type electrode assembly.

[0184] In the present invention, the electrode assembly may be a winding type electrode assembly. Figure 9 The manufacturing process of the winding type electrode assembly is schematically shown. As Figure 9 shown, the winding type electrode assembly can be manufactured, for example, by the following method: laminating a positive electrode that is long in one direction and a negative electrode that is long in one direction, respectively disposing a separator that is long in one direction between the positive electrode and the negative electrode and on one surface of the positive electrode or the negative electrode and laminating them, and winding them in one direction to manufacture a winding type electrode assembly.

[0185] The electrode that is long in one direction used in the winding type electrode assembly can use the electrode according to the present invention as described above. Therefore, it may include an active part in which an electrode active material layer is formed on both surfaces of an electrode current collector, and may include an uncoated part at one end in the one direction. In addition, the electrode that is long in one direction may include an active part insulating layer and an uncoated part insulating layer in a region near the boundary between the active part and the uncoated part, and the positions of the ends of the first active part insulating layer on the first surface and the ends of the second active part insulating layer on the second surface may be different from each other.

[0186] The electrode that is long in one direction may include an active part insulating layer, an uncoated part insulating layer, and an uncoated part at one end including the uncoated part, and may have a step difference in the one direction. In addition, although not shown, the uncoated part may also be formed at both ends of the electrode.

[0187] In the electrode that is long in one direction used in the winding type electrode assembly, the one direction may be the winding direction, or may be the step difference direction. Among them, the step difference direction may be the direction from the central part of the electrode toward the step difference formed in the electrode, and the step difference may be formed by forming an active part insulating layer, an uncoated part insulating layer, and an uncoated part at one end of the electrode. In addition, the step difference direction may refer to the direction opposite to the winding direction.

[0188] Figure 10 An example of an electrode laminate formed by laminating an electrode that is long in one direction and a separator for manufacturing the winding type electrode assembly is schematically shown. In addition, as described Figure 10As shown, the electrodes elongated in one direction can be joined to electrode leads (23, 24) in a direction perpendicular to the one direction (winding direction or step difference direction) by methods such as ultrasonic welding or laser welding. Additionally, as an example, in the wound electrode assembly, the negative electrode lead 24 and the positive electrode lead 23 can be joined in opposite directions.

[0189] In the present invention, the electrode assembly can be a stacked electrode assembly. Figure 11 An example of the stacked electrode assembly and its manufacturing process is schematically shown. The stacked electrode assembly can be manufactured, for example, by the following method: As shown in (A) of Figure 11 , prepare a plurality of positive electrodes, a plurality of negative electrodes, and a plurality of separators having predetermined dimensions, and as shown in (B) of Figure 11 , alternately stack a plurality of positive electrodes and a plurality of negative electrodes, and insert a separator between the positive electrode and the negative electrode to manufacture a stacked electrode assembly. The stacked electrode assembly thus manufactured can include a stacking order of positive electrode / separator / negative electrode / separator as shown in (C) of Figure 11 .

[0190] Figure 12 A secondary battery including the stacked electrode assembly is schematically shown. Figure 12 The secondary battery shown can be obtained by accommodating the stacked electrode assembly shown in Figure 11 in a battery case such as a pouch-type case and sealing it.

[0191] As shown in Figure 12 , the obtained secondary battery can have the same planar shape as the planar shape of the stacked electrode assembly accommodated inside the battery case, and can have the same planar shape as the planar shape of the electrodes used when manufacturing the stacked electrode assembly.

[0192] Figure 13 A manufacturing process of the electrodes for manufacturing the stacked electrode assembly and the electrodes thus obtained are schematically shown. Although not particularly limited, for the electrodes for forming the stacked electrode assembly, as shown in Figure 13 , electrodes having a shape the same as or similar to the plane of the battery can be manufactured by the following steps: Step (A), coat a slurry on one or both surfaces of an electrode current collector to form an active portion and an uncoated portion, and perform drying and calendering to manufacture an electrode plate elongated in one direction; a slitting step (B), cut the electrode plate to have the same shape as the length of the battery desired to be obtained; and steps (C) and (D), cut the slit electrode plate to have the width of the battery and electrode tabs.

[0193] In the electrode, the length may be represented based on the direction in which the electrode tab is formed, and the width may be represented based on the direction perpendicular to the direction in which the electrode tab is formed.

[0194] The electrode having the planar shape of the battery used in the stacked electrode assembly may be the electrode according to the present invention as described above. Accordingly, an active portion in which an electrode active material layer is formed on both surfaces of an electrode current collector may be included, and one end portion of the electrode may include an uncoated portion, and the uncoated portion may be a part of the electrode tab. For example, the electrode tab may be provided by gathering and welding two or more of the uncoated portions together. In addition, the electrode may include an active portion insulating layer and an uncoated portion insulating layer in a region near the boundary between the active portion and the uncoated portion, and the positions of the ends of the first active portion insulating layer on the first surface and the ends of the second active portion insulating layer on the second surface may be different from each other.

[0195] The electrode having the planar shape of the battery may sequentially include an active portion insulating layer, an uncoated portion insulating layer, and an uncoated portion at one end portion including the uncoated portion. Accordingly, the electrode may have a step difference at one end.

[0196] In the electrode included in the stacked electrode assembly, the electrode tab may extend along the step difference direction having the step difference, and the electrode lead may be joined along the direction in which the electrode tab extends by a method such as ultrasonic welding or laser welding. Accordingly, in the electrode, the step difference direction may be the same as the extension direction of the electrode tab, and may also be the same as the extension direction of the electrode lead. In the stacked electrode assembly, the extension direction of the electrode lead may be the same in the positive electrode and the negative electrode, or may be opposite to each other.

[0197] In the present invention, the electrode assembly may be a stacked-folded type electrode assembly. Figure 14 Schematically shows the stacked-folded type electrode assembly and its manufacturing process. As Figure 14 shown, the stacked-folded type electrode assembly may be manufactured, for example, by the following method: folding a separator that is long in one direction in a zigzag direction while alternately inserting a plurality of positive electrodes and a plurality of negative electrodes having a predetermined size to manufacture a stacked-folded type electrode assembly. The electrode assembly thus manufactured may include a stacking order of a positive electrode / separator / negative electrode / separator having a cross-sectional shape as Figure 14 shown, and the separator may be folded in a zigzag and interposed between the positive electrode and the negative electrode.

[0198] The stacked-folded type electrode assembly may be accommodated in a battery case such as a pouch type case and sealed to manufacture a secondary battery.

[0199] In a secondary battery manufactured using the stacked-folded type electrode assembly, compared with a secondary battery manufactured using the stacked type electrode assembly, except for using a separator that is long in one direction, it is substantially the same, so the electrodes used in the stacked type electrode assembly can be used.

[0200] The electrode assembly can be accommodated in a battery case together with an electrolytic solution, thereby defining a lithium secondary battery. According to one embodiment, the electrolytic solution can use a non-aqueous electrolytic solution.

[0201] The non-aqueous electrolytic solution can contain a lithium salt as an electrolyte and an organic solvent. The lithium salt can be represented, for example, by Li + X - . As the anion (X - ) of the lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - etc.

[0202] The organic solvent may contain an organic compound that has sufficient solubility for the lithium salt and the additive and is non-reactive in the battery. The organic solvent may include, for example, at least one of a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, and an aprotic solvent. The organic solvent may be used, for example, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, vinylene carbonate, methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), ethyl fluoroacetate (FEA), ethyl difluoroacetate (DFEA), ethyl trifluoroacetate (TFEA), dibutyl ether, tetraethylene glycol dimethylether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), 2-methyltetrahydrofuran, ethyl alcohol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, diethoxyethane, sulfolane, γ-butyrolactone, and propylene sulfite. These may be used alone or in combination of two or more.

[0203] The non-aqueous electrolyte may further contain an additive. The additive may include, for example, a cyclic carbonate-based compound, a fluorine-substituted carbonate-based compound, a sultone-based compound, a cyclic sulfate-based compound, a cyclic sulfite-based compound, a phosphate-based compound, and a borate-based compound.

[0204] The cyclic carbonate-based compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), etc.

[0205] The fluorine-substituted carbonate-based compound may include fluoroethylenecarbonate (FEC), etc.

[0206] The sultone-based compound may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc.

[0207] The cyclic sulfate-based compound may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc.

[0208] The cyclic sulfite-based compound may include Ethylene sulfite, Butylene sulfite, etc.

[0209] The phosphate-based compound may include Lithium difluoro bis-oxalato phosphate, Lithium difluoro phosphate, etc.

[0210] The borate-based compound may include Lithium bis(oxalate) borate, etc.

[0211] As a specific embodiment, the electrode may have an electrode tab including a first uncoated portion or a second uncoated portion.

[0212] As a specific embodiment, the electrode may be a negative electrode or a positive electrode.

[0213] As a specific embodiment, the secondary battery may include at least one positive electrode and at least one negative electrode, and the positive electrode, the negative electrode, or a combination thereof may be the electrode of the present invention.

[0214] In the secondary battery, for example, electrode tabs (a positive electrode tab and a negative electrode tab) may protrude from a positive electrode current collector and a negative electrode current collector, respectively, and extend to one side of the battery case. For example, the battery case may be a pouch-type case, a prismatic case, a cylindrical case, a coin-type case, or the like. The electrode tabs may extend from the one side of the battery case to the outside or be exposed to the outside and connected to electrode leads (a positive electrode lead and a negative electrode lead). When the battery case is a pouch-type case, the electrode tabs extending from the one side of the battery case may be fused to the battery case.

[0215] Example

[0216] Hereinafter, with reference to specific experimental examples, the examples of the present invention will be further described. The examples and comparative examples included in the experimental examples are only for illustrating the present invention and are not used to limit the claims. Various changes and modifications can be made to the examples within the scope and technical idea of the present invention, which will be obvious to those skilled in the art, and such variations and modifications are naturally within the scope of the claims.

[0217] Example 1

[0218] A positive electrode mixture slurry was coated on the active portions on both sides of an aluminum foil (thickness: 12 μm) divided into an active portion and an uncoated portion. The positive electrode mixture slurry contained 96% by weight of a positive electrode active material of NCM 622, 1.5% by weight of a carbon black conductive material, and 2.5% by weight of a PVDF (polyvinylidene fluoride) binder, thereby forming a positive electrode active material layer, and the length of the uncoated portion where the slurry was not coated was 15 mm.

[0219] On both sides of the positive electrode, an insulating liquid in which polyimide (PI) was dissolved in NMP was used to coat the insulating liquid from the boundary between the active portion and the uncoated portion to 5 mm on the uncoated portion side, thereby forming an uncoated portion insulating layer.

[0220] In addition, starting from the boundary between the uncoated portion and the active portion, the insulating liquid was coated in a manner overlapping the positive electrode mixture slurry on the active portion side. At this time, for the first side of the positive electrode, it was coated in a manner overlapping the active portion by 1 mm, and for the second side of the positive electrode, it was coated in a manner overlapping the active portion by 0.5 mm, thereby forming a first active portion insulating layer and a second active portion insulating layer separated from each other, such that the distance ΔL2 between the ends of the first active portion insulating layer and the ends of the second active portion insulating layer was 0.5 mm.

[0221] Then, the positive electrode mixture slurry and the insulating liquid were dried, and then calendered at a pressure of a positive electrode density of 3.6 g / cm 3 to manufacture a positive electrode.

[0222] For the obtained positive electrode, using a resistance measuring instrument (measurement range: 0.1 MΩ to 5000 MΩ), a voltage is applied for 0.5 seconds between the uncoated portion and the uncoated portion insulating layer, between the uncoated portion insulating layer and the positive electrode active material layer, and between the uncoated portion and the positive electrode active material layer, and the resistance between two positions is measured respectively.

[0223] The resistance value (5000 MΩ), which is the maximum value of the measurement limit of the resistance measuring instrument, is shown between the uncoated portion and the uncoated portion insulating layer and between the uncoated portion insulating layer and the positive electrode active material layer. In addition, a resistance value of 0.1 MΩ is shown between the uncoated portion and the positive electrode active material layer.

[0224] From these results, it can be seen that the uncoated portion insulating layer acts as a resistor between the uncoated portion and the positive electrode active material layer. Even if the positive electrode and the negative electrode are in direct contact, resistance break can be achieved through the insulating layer, thereby preventing the occurrence of short circuit.

[0225] For the obtained positive electrode, it is cut in such a way that it entirely includes the uncoated portion and the active portion, thereby obtaining five samples.

[0226] For one of the samples, the thickness profile of the first surface is analyzed using a three-dimensional (3D) microscope, and the result is shown in Figure 15 as follows. As Figure 15 shown, a valley is formed at the end of the first active portion insulating layer 351. In addition, although not shown in the figure, it can be confirmed that the position of the valley on the second surface of the sample is formed at a position different from the valley on the first surface. At this time, the valley formed on the first surface is separated from the valley formed on the second surface by 0.5 mm (ΔL2 = 0.5 mm).

[0227] For the five prepared samples, the tensile strength in the transverse (TD) direction is measured respectively using a universal testing machine (UTM, Universal Test Machine), and their average values are shown in Table 1. The tensile strength is the value when the sample breaks and is shown in Table 1. As shown in Table 1, the tensile strength shows a relatively high value, and the average value is 2240 kgf / mm 2 . This is evaluated as follows. Since the ends of the active portion insulating layers are formed at different positions on the first surface and the second surface, the force applied during calendering to the electrode is dispersed, thereby reducing the decrease in tensile strength.

[0228] In addition, during the measurement of the tensile strength, it can be confirmed that as shown in (a) of Figure 16 , fracture occurs in the uncoated portion, and no decrease in tensile strength occurs at the end of the active portion insulating layer.

[0229] In addition, additional tensile strength measurement tests were conducted on the other samples prepared above. Similarly, fractures occurred in the uncoated portion, or as shown in (b) of Figure 16 , fractures occurred in the active portion. From this, it can be seen that the ends of the active portion insulating layer did not become fragile portions.

[0230] In addition, for the positive electrode prepared, when manufacturing the positive electrode tab by welding the uncoated portion of the positive electrode through pre-welding and main welding, the positive electrode tab (a) after pre-welding and the positive electrode tab (b) after main welding were respectively photographed and shown in Figure 17 . It can be seen from Figure 17 that the welding quality of the electrode tab is good.

[0231] In addition, for the welded portion, the welding strength was measured using the same method as the measurement method of the tensile strength and using a UTM, and the results are shown in Table 1. As shown in Table 1, the welding strength also showed excellent values, with an average value of 65.91 kgf and a minimum value of 53.89 kgf.

[0232] Example 2

[0233] A positive electrode was manufactured by the same method as in Example 1, except that for the first uncoated portion insulating layer on the first surface, coating was started 4.5 mm from the boundary between the uncoated portion and the active portion, thereby forming a first uncoated portion insulating layer and a second uncoated portion insulating layer that do not match each other, such that the distance ΔL1 between the ends of the first uncoated portion insulating layer and the second uncoated portion insulating layer is 0.5 mm.

[0234] For the sample, the tensile strength in the TD direction was measured by the same method as in Example 1, and the results are shown in Table 1. It can be seen from Table 1 that the tensile strength showed excellent values, with an average value of 2317 kgf / mm 2 . This is evaluated as follows: Since the ends of the active portion insulating layer are formed at different positions on the first surface and the second surface, the force applied to the electrode during pressing is dispersed, thereby reducing the decrease in tensile strength.

[0235] In addition, the welding strength also showed excellent values, with an average value of 64.79 kgf and a minimum value of 52.89 kgf.

[0236] Comparative Example 1

[0237] A positive electrode was manufactured by the same method as in Example 1, except that a first active portion insulating layer and a second active portion insulating layer were respectively formed on the first surface and the second surface of the positive electrode, such that the first active portion insulating layer and the second active portion insulating layer overlapped by 1 mm in the same manner as the active portion.

[0238] By the same method as in Embodiment 1, a voltage was applied for 0.5 seconds between the uncoated portion and the uncoated portion insulating layer, between the uncoated portion insulating layer and the positive electrode active material layer, and between the uncoated portion and the positive electrode active material layer, and the resistance between two positions was measured respectively.

[0239] Between the uncoated portion and the uncoated portion insulating layer and between the uncoated portion insulating layer and the positive electrode active material layer, a resistance value (5000 MΩ) which is the maximum value of the measurement limit of the resistance measuring instrument was shown. In addition, a resistance value of 0.1 MΩ was shown between the uncoated portion and the positive electrode active material layer.

[0240] From these results, it can be seen that the uncoated portion insulating layer functions as a resistor between the uncoated portion and the positive electrode active material layer. Even if the positive electrode and the negative electrode are in direct contact, resistance breaking can be performed through the insulating layer, thereby preventing the occurrence of a short circuit.

[0241] The obtained positive electrode was cut in such a way as to entirely include the uncoated portion and the active portion, thereby obtaining five samples.

[0242] For one of the samples, the thickness profile of the first surface was analyzed using a three-dimensional (3D) microscope, and the results are shown in Figure 18 In Figure 18 , (a) is the electrode before rolling, and (b) is the electrode after rolling. As Figure 18 shown, it can be seen that fine valleys have been formed at the ends (inside the circles) of the active portion insulating layer before rolling, and in the electrode after rolling, the valleys become deeper.

[0243] Using a scanning electron microscope (SEM), the cut surface of the same sample was photographed, and the results are shown in Figure 19 In Figure 19 shown, it can be confirmed that in the region formed by the first active portion insulating layer 351 on the first surface and the second active portion insulating layer 352 on the second surface of the positive electrode, the current collector is bent. This can be evaluated as follows: Since the ends of the active portion insulating layers on both surfaces are formed at similar positions, the pressure cannot be dispersed during the rolling process, and the pressure is concentrated in the valleys formed near the ends of the active portion insulating layers, resulting in this phenomenon.

[0244] In addition, in Figure 19 , the positions of the first active portion insulating layer and the second active portion insulating layer do not exactly match, but this is due to manufacturing process errors. The distance between the ends of the two active portion insulating layers is a very small difference of less than 100 μm, so it can be evaluated as substantially the same.

[0245] For the five prepared samples, the tensile strength in the transverse direction (TD) was measured using a universal testing machine (UTM), and their average values are shown in Table 1. The tensile strength is the value at which the sample breaks and is shown in Table 1. As shown in Table 1, the tensile strength shows an average value of 1562 kgf / mm 2 .

[0246] In addition, in the measurement of the tensile strength, the sample broke in the region where the end of the active part insulating layer was located. From these results, it can be evaluated that due to the pressure concentrating at the end of the active part insulating layer during the calendering process, the tensile strength of the current collector decreased.

[0247] In addition, for the prepared positive electrode, when manufacturing the positive electrode tab by welding the uncoated part of the positive electrode through pre-welding and main welding, the positive electrode tab (a) after pre-welding and the positive electrode tab (b) after main welding were photographed respectively, and they are shown in Figure 20 (a) and (b) of

[0248] From Figure 20 (b) of

[0249] it can be seen that the welding state is poor. This seems to be because the impact applied to the electrode during main welding is transmitted to the boundary between the active part insulating layer and the positive electrode active material layer (i.e., the end of the active part insulating layer), resulting in the fracture of the electrode, and thus the shaking of the electrode, showing the result of poor welding state.

[0250] Comparative Example 2

[0251] A positive electrode was manufactured by the same method as in Example 1, except that no insulating liquid was used to form the insulating layer.

[0252] For the obtained positive electrode, it was cut in a way that included all the uncoated part and the active part to obtain samples. For the samples, the tensile strength in the TD direction was measured by the same method as in Example 1, and the results are shown in Table 1.

[0253] As can be seen from Table 1, the tensile strength of Comparative Example 2 shows 2446 kgf / mm 2The average value shows a value higher than that of Comparative Example 1 and slightly higher than those of Example 1 and Example 2. This can be evaluated as follows: Since the insulating layer is not formed, the weak part caused by the formation of valleys is not generated. Therefore, when measuring the tensile strength, fracture occurs at the uncoated part, and the welding strength is also evaluated to show the highest value.

[0254] However, since the uncoated part does not include an insulating layer, the uncoated part may come into contact with the negative electrode and cause a short circuit, thereby posing a risk of compromising the safety of the battery.

[0255] [Table 1]

[0256]

[0257] In addition, when manufacturing the positive electrode tab by welding the uncoated part of the positive electrode through pre-welding and main welding for the obtained positive electrode, the positive electrode tab (a) after pre-welding and the positive electrode tab (b) after main welding are respectively photographed and shown in Figure 21 (a) and (b) of Figure 21 It can be seen that since the separate insulating layer is not included and the tensile strength is not affected, the welding quality of the electrode tab is good.

[0258] The content described above is merely an example of applying the principle of the present invention, and other configurations may be further included without departing from the scope of the present invention.

Claims

1. A secondary battery electrode, comprising a first surface and a second surface located on the opposite side of the first surface, in, The first surface includes a first active portion where an electrode active material layer is formed on the electrode current collector and a first uncoated portion where no electrode active material layer is formed. The second surface is independent of the first surface, and the second surface includes a second active portion on which an electrode active material layer is formed on the electrode current collector and a second uncoated portion on which an electrode active material layer is not formed. The first surface includes a first active portion insulating layer formed on the first active portion and a first uncoated portion insulating layer formed on the first uncoated portion. The second surface includes a second active portion insulating layer formed on the second active portion and a second uncoated portion insulating layer formed on the second uncoated portion. A position of an end of the first active portion insulating layer and a position of an end of the second active portion insulating layer are different from each other.

2. The secondary battery electrode according to claim 1, wherein The first active portion insulating layer and the first uncoated portion insulating layer are continuous layers, The second active portion insulating layer and the second uncoated portion insulating layer are continuous layers, The length of the first active portion insulating layer and the length of the second active portion insulating layer are different from each other. The length of the first active portion insulating layer is the length from the boundary between the first active portion and the first uncoated portion to the end of the first active portion insulating layer, and the length of the second active portion insulating layer is the length from the boundary between the second active portion and the second uncoated portion to the end of the second active portion insulating layer.

3. The secondary battery electrode according to claim 2, wherein: The length of the first active portion insulating layer is 1.3 to 9 times greater than the length of the second active portion insulating layer.

4. The secondary battery electrode according to claim 2, wherein: A distance between an end of the first active portion insulating layer and an end of the second active portion insulating layer is greater than or equal to 0.2 mm and less than or equal to 0.9 mm.

5. The secondary battery electrode according to claim 2, wherein The first active portion insulating layer and the second active portion insulating layer each independently have a length of 0.1 mm or more and 1.2 mm or less.

6. The secondary battery electrode according to claim 2, wherein: The length of the first active portion insulating layer is 0.3-1.2 mm, and the length of the second active portion insulating layer is 0.1-1.0 mm.

7. The secondary battery electrode according to claim 1, wherein The position of the end of the first uncoated portion insulating layer is the same as or different from the position of the end of the second uncoated portion insulating layer.

8. The secondary battery electrode according to claim 1, wherein A distance between an end of the first uncoated portion insulating layer and an end of the second uncoated portion insulating layer is 0.5 mm or less.

9. The secondary battery electrode according to claim 1, wherein The lengths of the first uncoated portion insulating layer and the second uncoated portion insulating layer are each independently 1-12 mm.

10. The secondary battery electrode according to claim 1, wherein The first active portion insulating layer, the first uncoated portion insulating layer, the second active portion insulating layer, and the second uncoated portion insulating layer each independently have a thickness of 3-40 μm.

11. The secondary battery electrode according to claim 1, wherein The secondary battery electrode has an electrode tab including the first uncoated portion or the second uncoated portion.

12. The secondary battery electrode according to claim 1, wherein The electrode is a negative electrode or a positive electrode.

13. The secondary battery electrode according to claim 1, wherein The region where the end of the first active portion insulating layer exists and the region where the end of the second active portion insulating layer exists include valleys that are independently formed, and the positions of the valleys on the first surface and the second surface are different from each other.

14. A secondary battery comprising at least one positive electrode and at least one negative electrode, in, The positive electrode, the negative electrode, or a combination thereof is the electrode for a secondary battery according to any one of claims 1 to 13.

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