Electrode for secondary battery and secondary battery including the same

Abstract

To provide an electrode enabling prevention of short circuit between the electrodes in a secondary battery.SOLUTION: The present invention relates to an electrode for a secondary battery and the secondary battery including the same, and the present disclosure includes a first surface 11 and a second surface 12 that is positioned to the side opposite to the first surface. The first surface includes : a first active part in which an electrode active material layer is formed on an electrode collector body 1; and a first solid color part in which the electrode active material layer is not formed. The second surface includes: a second active part in which the electrode active material layer is formed, on the electrode collector body without depending from the first surface; and a second solid color part in which the electrode active material layer is not formed. The first surface includes: a first active part insulation layer 351 formed on the first active part; and a first solid color insulation layer 451 formed on the first solid color part. The second surface includes: a second active part insulation layer 352 formed on the second active part; and a second solid color part insulation layer 452 formed to the second solid color part. A position of an end terminal 3511 of the first active part insulation layer and a position of an end terminal 3522 of the second active part insulation layer are different from each other.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to an electrode for a secondary battery and a secondary battery including the same.

Background Art

[0002] An electrode used in a lithium secondary battery is manufactured by applying a slurry-like electrode binder containing an electrode active material onto an electrode current collector, drying to form an electrode active material layer, and rolling the electrode active material layer so as to have a predetermined electrode density.

[0003] The electrode thus manufactured includes a coated portion where the electrode active material layer is formed and an uncoated portion where 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 with a separator interposed therebetween. Therefore, the positive electrode and the negative electrode are separated by the separator, so that direct contact is blocked. However, in a lithium secondary battery, for example, when an uncoated portion of the positive electrode comes into contact with a part of the negative electrode, a short circuit may occur, and as a result, an abnormal situation such as ignition may occur.

[0005] On the other hand, the process of manufacturing the electrode as described above includes a rolling process of pressing the electrode active material layer to adjust it to a predetermined electrode density. Since the physical properties of the coated portion and the uncoated portion are different due to the difference in the presence or absence of the electrode active material layer, different pressures are applied to the coated portion and the uncoated portion during the rolling process in electrode manufacturing, and as a result, 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

Problems to be Solved by the Invention

[0006] As one embodiment, the present disclosure provides an electrode capable of preventing a short circuit between electrodes in a secondary battery.

[0007] As yet another example, the present disclosure prevents a short circuit between the positive electrode and the negative electrode to improve the safety of the battery. **Means for Solving the Problems**

[0008] As one example, the present disclosure 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 opposite to the first surface, the first surface including a first active portion on which an electrode active material layer is formed and a first blank portion on which no electrode active material layer is formed on an electrode current collector, the second surface independently of the first surface including a second active portion on which an electrode active material layer is formed and a second blank portion on which no electrode active material layer is formed on an electrode current collector, the first surface including a first active portion insulating layer formed on the first active portion and a first blank portion insulating layer formed on the first blank portion, the second surface including a second active portion insulating layer formed on the second active portion and a second blank portion insulating layer formed on the second blank portion, and positions of ends of the first active portion insulating layer and positions of ends of the second active portion insulating layer may be different from each other.

[0009] The first active portion insulating layer and the first blank portion insulating layer are continuous layers, the second active portion insulating layer and the second blank portion insulating layer are continuous layers, and a length of the first active portion insulating layer, which is a length from a boundary between the first active portion and the first blank portion to an end of the first active portion insulating layer, and a length of the second active portion insulating layer, which is a length from a boundary between the second active portion and the second blank portion to an end of the second active portion insulating layer, may be different from each other.

[0010] The length of the first active portion insulating layer, which is a length from a boundary between the first active portion and the first blank portion to an end 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, which is a length from a boundary between the second active portion and the second blank portion to an end of the second active portion insulating layer.

[0011] Also, the length of the first active-region insulating layer, which is the length from the boundary between the first active region and the first non-patterned region to the end of the first active-region insulating layer, may be 1.5 times or more and 7.5 times or less the length of the second active-region insulating layer, which is the length from the boundary between the second active region and the second non-patterned region to the end of the second active-region insulating layer.

[0012] The length of the first active-region insulating layer, which is the length from the boundary between the first active region and the first non-patterned region to the end of the first active-region insulating layer, may be 2 times or more and 9 times or less the length of the second active-region insulating layer, which is the length from the boundary between the second active region and the second non-patterned region to the end of the second active-region insulating layer.

[0013] The distance between the end of the first active-region insulating layer and the end of the second active-region insulating layer may be 0.2 mm or more and 0.9 mm or less.

[0014] Also, the distance between the end of the first active-region insulating layer and the end of the second active-region insulating layer may be 0.3 mm or more and 0.8 mm or less.

[0015] Also, the distance between the end of the first active-region insulating layer and the end of the second active-region insulating layer may be 0.4 mm or more and 0.7 mm or less.

[0016] The first active-region insulating layer and the second active-region insulating layer may each independently be 0.1 mm or more and 1.2 mm or less.

[0017] The length of the first active-region insulating layer may be 0.3 to 1.2 mm, and the length of the second active-region insulating layer may be 0.1 to 1.0 mm.

[0018] The positions of the ends of the first non-patterned-region insulating layer and the second non-patterned-region insulating layer may be the same or different.

[0019] The distance between the end of the first non-patterned-region insulating layer and the end of the second non-patterned-region insulating layer may be 0.5 mm or less.

[0020] The above-mentioned first non-coated insulating layer and second non-coated insulating layer can each independently have a length of 1 to 12 mm.

[0021] The above-mentioned first active insulating layer, first non-coated insulating layer, second active insulating layer, and second non-coated insulating layer can each independently have a thickness of 3 to 40 μm.

[0022] The above-mentioned electrode can have an electrode tab including a first non-coated part or a second non-coated part.

[0023] The above-mentioned electrode may be a negative electrode or a positive electrode.

[0024] The above-mentioned electrode includes grooves respectively independently formed in regions where the ends of the first active insulating layer and the ends of the second active insulating layer are present, and the positions of the grooves on the first surface and the second surface may be different from each other.

[0025] As another implementation example of the present disclosure, a secondary battery including at least one positive electrode and at least one negative electrode is provided, where the positive electrode, negative electrode, or a combination thereof is any one of the above-mentioned electrodes.

Advantages of the Invention

[0026] According to one implementation example of the present disclosure, during the rolling process of manufacturing the electrode, it is possible to suppress the phenomenon that the electrode breaks at the boundary between the coated part and the non-coated part, and the phenomenon that disconnection occurs during the tap welding process.

[0027] According to another implementation example of the present disclosure, the yield of electrode manufacturing can be improved (the defective rate of the electrode can be reduced), and the operating rate of the electrode manufacturing equipment can be improved.

[0028] According to still another implementation example of the present disclosure, it is possible to suppress the occurrence of short circuit due to the contact between the positive electrode and the negative electrode.

[0029] The electrodes of the present disclosure can be widely applied in the fields of green technologies such as electric vehicles, battery charging stations, and solar and wind power generation that utilize batteries. In addition, the electrodes of the present disclosure can be used in eco-friendly electric vehicles, hybrid vehicles, etc. that suppress air pollution and greenhouse gas emissions and prevent climate change.

Brief Description of the Drawings

[0030]

Figure 1

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Figure 11

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Embodiments for Carrying Out the Invention

[0031] Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings. However, this is merely exemplary, and the present disclosure is not limited to the specific embodiments described exemplarily.

[0032] As one implementation example, the present disclosure provides an electrode for a lithium secondary battery that can prevent short circuits between the positive electrode and the negative electrode.

[0033] In a lithium secondary battery, in order to prevent direct contact between the negative electrode and the positive electrode, a porous separator or a solid electrolyte membrane is interposed between the positive electrode and the negative electrode. However, when a phenomenon occurs in which the plain part of the positive electrode is pushed during the process of manufacturing the electrode assembly or the electrode manufacturing process, a short circuit may occur due to the direct contact between the plain part of the positive electrode and the negative electrode.

[0034] For example, an example in which the plain part of the positive electrode is pushed and a short circuit occurs is schematically shown in FIG. 1. FIG. 1 is a diagram schematically showing an example in which the plain part of the positive electrode in the battery is pushed, the plain part of the positive electrode approaches the electrode assembly, and finally a short circuit occurs due to the direct contact between the plain part of the positive electrode and the negative electrode.

[0035] When the components of the positive electrode and the negative electrode come into contact in this way, there is a risk such as a fire due to a short circuit, so a safety device for preventing a short circuit between the positive electrode and the negative electrode is required.

[0036] For example, FIG. 2 shows an example of an electrode with an insulating layer formed to prevent a short circuit between the positive electrode and the negative electrode. As shown in FIG. 2, the electrode 10 includes an electrode active material layer 3 containing an electrode active material formed on an electrode current collector 1.

[0037] Specifically, the electrode includes a first surface 11 and a second surface 12 which is the opposite of the first surface. The first surface and the second surface each independently have an active portion 13 where an electrode active material layer is formed and a plain portion 14 where no electrode active material layer is formed on the electrode current collector. The first surface can include a first active portion where an electrode active material layer is formed on the electrode current collector and a first plain portion where no electrode active material layer is formed. The second surface, independently of the first surface, can include a second active portion where an electrode active material layer is formed on the electrode current collector and a second plain portion where no electrode active material layer is formed. Also, the first surface can include a first active portion insulating layer formed on the first active portion and a first plain portion insulating layer formed on the first plain portion. The second surface can include a second active portion insulating layer formed on the second active portion and a second plain portion insulating layer formed on the second plain portion.

[0038] An insulating layer 5 is formed on at least a part of the plain portion of the electrode. When the negative electrode and the positive electrode are stacked to form an electrode assembly, the insulating layer can be included as a part of a tab of the first electrode (for example, the positive electrode). Even if the plain portion comes into contact with a component of the negative electrode such as a negative electrode active material layer of the second electrode (for example, the negative electrode), the electrical connection is interrupted, and the occurrence of a short circuit phenomenon can be prevented.

[0039] Although not limited thereto, the insulating layer may be a continuous layer formed continuously without interruption. Specifically, as shown in FIG. 2, the first blank portion insulating layer formed on the first blank portion of the electrode and the first active portion insulating layer formed on the first active portion may be a continuous layer, or a continuous layer may also be formed continuously between the first blank portion insulating layer and the first active portion insulating layer. Similarly, the second blank portion insulating layer formed on the second blank portion of the electrode and the second active portion insulating layer formed on the second active portion may be a continuous layer, or a continuous layer may also be formed continuously between the second blank portion insulating layer and the second active portion insulating layer.

[0040] As shown in FIG. 2, FIG. 3 conceptually shows that in a battery including an electrode having a blank portion insulating layer formed on the blank portion of the electrode, a short circuit can be prevented under the condition that the positive electrode blank portion and the negative electrode are in direct contact. Generally, the electrode surface of the negative electrode can be formed larger than that of the positive electrode, and on the side surface of the electrode assembly, the negative electrode can protrude more than the positive electrode. As shown in FIG. 1, even if the positive electrode blank portion approaches the side surface of the electrode current collector due to the phenomenon that the positive electrode blank portion is pushed, when an insulating layer is formed on the positive electrode blank portion, as shown in FIG. 3, the electrical contact between the positive electrode and the negative electrode can be blocked, thereby preventing a short circuit.

[0041] The blank portion insulating layer formed on the blank portion may be formed over the entire region of the blank portion or may be formed on a part of the blank portion. When the blank portion insulating layer is formed in a partial region of the blank portion, as shown in FIG. 2, the blank portion insulating layer can be partially formed in the blank portion of the region adjacent to the boundary 15 between the blank portion and the active portion.

[0042] In the blank portion insulating layer, the first blank portion insulating layer 451 formed on the blank portion of the first surface 11 and the second blank portion insulating layer 452 formed on the blank portion of the second surface 12 may have the same or different positions of the end 4511 of the first blank portion insulating layer and the end 4522 of the second blank portion insulating layer.

[0043] The end of the above-mentioned non-active part insulating layer is the end of the insulating layer located on the non-active part, and can be located on the non-active part side from the boundary between the non-active part and the active part. For example, as shown in FIG. 2, the ends of the above-mentioned non-active part insulating layer may have the same position as each other, or the positions of the ends of the non-active part insulating layer may be different from each other. Specifically, the end 4511 of the first non-active part insulating layer can be located further away from the boundary 15 between the non-active part and the active part than the end 4522 of the second non-active part insulating layer, and as shown in FIG. 4, the end 4522 of the second non-active part insulating layer can be located further away from the boundary 15 between the non-active part and the active part than the end 4511 of the first non-active part insulating layer.

[0044] At this time, the interval ΔL1 between the end of the first non-active part insulating layer and the end of the second non-active part insulating layer is not particularly limited, but may be 0.5 mm or less.

[0045] The length from the boundary between the active part and the non-active part to the end 4511 of the first non-active part insulating layer (i.e., the length of the first non-active part insulating layer) and the length to the end 4522 of the second non-active part insulating layer (i.e., the length of the second non-active part insulating layer) are not particularly limited. As an example, they may be 1 to 12 mm independently of each other, and more specifically, may be 3 to 10 mm or 5 to 7 mm.

[0046] The above-mentioned insulating layer may be formed to overlap a partial region of the above-mentioned electrode active material layer. In this case, the above-mentioned insulating layer can include the first non-active part insulating layer 451 and the second non-active part insulating layer 452 on the non-active part, and the first active part insulating layer 351 and the second active part insulating layer 352 on the above-mentioned electrode active material layer.

[0047] By forming the active part insulating layer on the above electrode active material layer, the efficiency of the coating process for forming the above insulating layer can be improved. By including the active part insulating layer on the above electrode active material layer, the insulating performance of the insulating layer can be improved. When the above insulating layer is formed only on the non-patterned part and the above insulating layer is separated from the end of the above electrode active material layer, wrinkles are likely to be formed in the non-patterned part during the process of the electrode running by a roller or the like during the electrode manufacturing process, and there is a possibility that the electrode may be easily broken during the rolling process.

[0048] The above active part insulating layer may be formed in the same region on the first surface and the second surface of the electrode. Specifically, as shown in FIGS. 2 and 4, the positions of the end 3511 of the first active part insulating layer and the end 3522 of the second active part insulating layer may be the same as each other. The end of the above active part insulating layer is the end of the insulating layer located on the active part, and can be located on the active part side from the boundary between the non-patterned part and the active part.

[0049] As an electrode according to an embodiment of the present disclosure, the above active part insulating layer may be formed in different regions on the first surface and the second surface of the electrode. As an embodiment, as shown in FIGS. 5 and 6, the positions of the end 3511 of the first active part insulating layer and the end 3522 of the second active part insulating layer may be different from each other.

[0050] In the present disclosure, when rolling an electrode in which the above insulating layer and the electrode active material layer overlap, the above insulating layer and the electrode active material layer may have differences in physical properties such as elongation. Such differences in physical properties may, in some cases, cause stress to concentrate at the boundary between the non-patterned part and the active part during the rolling process in the electrode manufacturing process, leading to electrode breakage.

[0051] For example, an electrode mixture slurry containing an electrode active material is applied to a part of a current collector to form an active part, and an insulating liquid is applied over the non-coated part and a part of the active part to form an insulating layer. Then, an electrode having the insulating layer can be manufactured through a drying and rolling process. At this time, in the active part insulating layer region where the insulating layer and the active part overlap, the thickness is greater than that of the adjacent non-coated part insulating layer and the electrode active material layer (i.e., the electrode active material layer where no insulating layer is formed). Therefore, a groove may be formed between the active part insulating layer and the adjacent region (e.g., the electrode active material layer where no insulating layer is formed). Throughout this specification, the thickness can mean the width up to the surface of the first surface or the second surface with reference to the surface of the electrode current collector 1 that the electrode active material layer of the first surface or the second surface abuts against.

[0052] For example, the thickness distribution with respect to the electrode in the active part insulating layer and the adjacent non-coated part insulating layer and electrode active material layer is schematically shown in FIG. 7. (a) of FIG. 7 schematically shows a cross-section after applying the insulating liquid after coating the electrode mixture slurry, and (b) of FIG. 7 shows a cross-section of the electrode manufactured by drying and rolling.

[0053] As shown in Fig. 7(a), in the first active part insulating layer 351 and the second active part insulating layer 352, which are regions where the coating layer of the electrode mixture slurry and the coating layer of the insulating liquid overlap, in the coating layer 3 (or the electrode active material layer) of the electrode mixture slurry adjacent to them, fine grooves are formed near the end 3511 of the first active part insulating layer and the end 3522 of the second active part insulating layer. As shown in Fig. 7(b), after the drying and rolling processes are performed, the formation of the above grooves may appear more significantly. In both Fig. 7(a) and (b), in the regions where the first active part insulating layer 351 and the second active part insulating layer 352 are formed, the coating layer of the electrode mixture slurry and the coating layer of the insulating liquid overlap, but they are shown as one region without distinguishing each coating layer. The above grooves can be formed at the ends of each active part insulating layer. In the part where the above grooves are formed, an insulating layer and an electrode active material layer with different elongation rates are located with the above grooves as the boundary. Therefore, when exposed to severe conditions such as rolling during the electrode manufacturing process or manufacturing an electrode tab by converging and welding a plurality of non-patterned parts of the electrode, the part where the above grooves are formed acts as a vulnerable part and forces such as pressure concentrate, and finally, the electrode may break.

[0054] According to an embodiment of the present disclosure, by shifting the positions of the grooves generated on the first surface and the second surface of the electrode when forming the above insulating layer, the problem of electrode breakage occurring in the region where the grooves 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 arranged at different positions from each other.

[0055] For example, Fig. 8 schematically shows the thickness distribution with respect to the electrode in the active part insulating layer and the non-patterned part insulating layer and the electrode active material layer adjacent to it, as an electrode in which the end positions of the active part insulating layer on the first surface and the second surface of the electrode are different from each other. In Fig. 8, in the regions where the first active part insulating layer 351 and the second active part insulating layer 352 are formed, the coating layer of the electrode mixture slurry and the coating layer of the insulating liquid overlap, but they are shown as one region without distinguishing each coating layer.

[0056] As shown in Fig. 8, a fine groove is formed in a region between the coating layers of the electrode mixture slurry adjacent to the region where the coating layer of the electrode mixture slurry and the coating layer of the insulating liquid overlap, that is, in the region where the end of the active part insulating layer exists, and a deep groove is also formed in the rolled electrode. However, the grooves may be formed at different positions on the first surface and the second surface. At this time, among the regions where the active part insulating layer is formed, the thickness decreases from the thickest part toward the end of the active part insulating layer, and increases from the end of the active part insulating layer toward the electrode active material layer where the insulating layer is not formed. As a result, a groove can be formed in the region where the end of the active part insulating layer exists, and the positions of the grooves on the first surface and the second surface may be different from each other. Specifically, the grooves independently formed in the region where the end of the first active part insulating layer exists and the region where the end of the second active part insulating layer exists may be included, and the positions of the grooves on the first surface and the second surface may be different from each other.

[0057] In the electrode according to one embodiment of the present disclosure, the positions of the ends of the first active part insulating layer and the second active part insulating layer may be different. In this way, in the electrode, the respective ends of the active part insulating layers on the first surface and the second surface exist at different positions from each other and have an interval, so that the grooves on the first surface and the second surface can exist at different positions from each other. Therefore, by dispersedly arranging the vulnerable parts of the electrode, the force applied to the electrode when manufacturing the electrode tab by rolling or welding can be dispersed, and even if the electrode is exposed to harsh conditions, the breakage phenomenon of the electrode at the position where the groove is formed can be prevented or suppressed.

[0058] In one embodiment, in the electrode of the present disclosure, the interval ΔL2 between the end of the first active part insulating layer and the end of the second active part insulating layer 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 interval 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.

[0059] In one implementation example, the electrode has the first and second active part insulating layers as the length of the first active part insulating layer from the boundary 15 to the end of the first active part insulating layer and the length of the second active part insulating layer from the boundary 15 to the end of the second active part insulating layer, and is not particularly limited as long as the difference between the two lengths satisfies the interval, ΔL2, as described above.

[0060] In one implementation example, the lengths of the first active part insulating layer, which is the length of the first active part insulating layer from the boundary 15 between the first active part and the first blank part to the end of the first active part insulating layer, and the second active part insulating layer, which is the length of the second active part insulating layer from the boundary 15 between the second active part and the second blank part to the end of the second active part insulating layer, may be different from each other. The positions of the boundary 15 on the first surface and the second surface of the electrode may not coincide. In this case, the reference for measuring the length of the active part insulating layer may be the boundary with the shorter length among the boundary on the first surface (the first boundary) and the boundary on the second surface (the second boundary). For example, when the positions of the first boundary and the second boundary are different from each other, if 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 can be measured based on the second boundary.

[0061] As one implementation example, 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 may be 1.3 times or more and 9 times or less the length of the second active part insulating layer, for example, 1.5 times or more and 7.5 times or less, or 2 times or more and 9 times or less. 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 yet another implementation example, 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. By forming the positions of the ends of the first and second active part insulating layers not to coincide in this way, the pressure applied to the electrode in the rolling process, welding process, etc. can be dispersed, thereby preventing the electrode from being damaged.

[0062] As an implementation example, 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 may be 0.3 to 1.2 mm, and the length of the second active part insulating layer may be 0.1 to 1.0 mm.

[0063] In the active part insulating layer, a side ring defect having a convex mountain shape may occur at the end of the overlapping part due to the interaction between the insulating liquid and the electrode binder slurry. Such a side ring may cause pressure concentration during the rolling process, and as a result, may cause breakage of the electrode.

[0064] The insulating layer formed on the plain part and the active part is not particularly limited, but may have a thickness of 3 μm or more. If the thickness of the insulating layer is small, the insulating properties may be insufficient. The upper limit of the thickness of the insulating layer is not particularly limited as long as it does not inhibit the performance of the electrode. For example, the insulating layer can have a thickness of 40 μm or less. Specifically, the first active part insulating layer, the first plain part insulating layer, the second active part insulating layer, and the second plain part insulating layer can each independently have a thickness of 3 to 40 μm.

[0065] The above-mentioned insulating layer can be manufactured from an insulating material, and the insulating material is not particularly limited. 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), acrylonitrile-butadiene rubber, styrene-butadiene rubber (SBR), poly(meth)acrylic acid, carboxymethyl cellulose (CMC), hydroxyethyl cellulose, polyvinyl alcohol, and the like. As the above-mentioned insulating material, any one of these can be used alone, or two or more thereof can be used in combination. Further, carboxymethyl cellulose and the like can also be used in the form of salts such as sodium salts.

[0066] The above-mentioned insulating layer can be formed by applying an electrode binder slurry containing an electrode active material onto the active part of the electrode current collector, applying the insulating liquid for forming the insulating layer before drying, and then drying. Further, the above-mentioned insulating layer can be rolled together with the electrode active material layer in a rolling process.

[0067] The above-mentioned insulating liquid may be a resin contained in the formation of the above-mentioned insulating layer dissolved in an organic solvent. The above-mentioned organic solvent can be preferably used here as long as it is usually used as a solvent for organic resins. As an example, N-methyl-2-pyrrolidone (NMP), cyclohexanone, and the like can be used as the above-mentioned organic solvent.

[0068] The amount of the above-mentioned organic solvent used is not particularly limited, but it can be added so that the viscosity of the above-mentioned insulating liquid has a range of 1,000 to 9,000 cp at room temperature (25°C). If the viscosity of the above-mentioned insulating liquid is outside the above range, the workability may decrease. More specifically, the organic solvent can be added so that the viscosity of the above-mentioned insulating liquid has a range of 4,000 to 7,000 cp.

[0069] The above-mentioned 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., but is not limited thereto.

[0070] The electrode according to the present disclosure may be a negative electrode or a positive electrode.

[0071] When the above-mentioned electrode is a positive electrode, the positive electrode may include a positive electrode current collector and positive electrode active material layers disposed on both sides of the positive electrode current collector.

[0072] 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. Further, the positive electrode current collector may be a polymer substrate coated with a conductive metal such as nickel, aluminum, titanium, or silver.

[0073] The positive electrode current collector may be in various forms such as, as non-limiting examples, foil, foam, net, porous body, non-woven fabric body, etc. Also, although not limited thereto, the positive electrode current collector may have a thickness of 10 to 50 μm.

[0074] The positive electrode active material layer may include a positive electrode active material. The above-mentioned positive electrode active material may include a compound capable of reversibly intercalating and de-intercalating lithium ions.

[0075] According to an exemplary embodiment, the above-mentioned positive electrode active material may include a lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0076] In some embodiments, the cathode active material or the lithium-nickel metal oxide may include a layered structure or a crystal structure represented by the following Chemical Formula 1.

[0077] [Chemical Formula 1] Li x Ni a M b O 2+z

[0078] 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 may be satisfied. As described above, M may include Co, Mn, and / or Al.

[0079] The chemical structure represented by Chemical Formula 1 shows the bonding relationship included in the layered structure or the crystal structure of the cathode active material and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn can be provided as the main active element of the cathode active material together with Ni. Chemical Formula 1 is provided to represent the bonding relationship of the main active element and should be understood as an expression including the introduction and substitution of additional elements.

[0080] In one embodiment, in order to enhance the chemical stability of the cathode active material or the layered structure / crystal structure, the cathode active material may further include an auxiliary element. The auxiliary element can be mixed together in the layered structure / crystal structure to form a bond, and in this case, it should also be understood that it is included within the range of the chemical structure represented by Chemical Formula 1.

[0081] The above auxiliary element can 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 above auxiliary element can also act as an auxiliary active element that contributes to the capacity / output activity of the positive electrode active material together with Co or Mn, such as Al.

[0082] For example, the above positive electrode active material or the above lithium-nickel metal oxide can include a layered structure or a crystal structure represented by the following Chemical Formula 1-1.

[0083] [Chemical Formula 1-1] Li x Ni a M1 b1 M2 b2 O 2+z

[0084] In Chemical Formula 1-1, M1 can include Co, Mn, and / or Al. M2 can include the above auxiliary element. Among 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 may be satisfied.

[0085] The above positive electrode active material can further include a coating element or a doping element. For example, an element substantially the same as or similar to the above auxiliary element may be used as the coating element or the doping element. For example, among the above-described elements, they can be used alone or in combination of two or more as the coating element or the doping element.

[0086] The above coating element or doping element can 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 the above Chemical Formula 1 or Chemical Formula 1-1.

[0087] The above positive electrode active material can include nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, an NCM-based lithium oxide with an increased nickel content may be used.

[0088] Ni can be provided as a transition metal related to the output and capacity of a lithium secondary battery. Therefore, by adopting the high-content (High-Ni) composition in the above positive electrode active material as described above, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0089] However, as the Ni content increases, the long-term storage stability and life stability of the positive electrode or the secondary battery may relatively decrease, and the side reaction with the electrolyte may also increase. However, according to an exemplary embodiment, by including Co, the electrical conductivity can be maintained while the life stability and capacity retention characteristics can be improved by Mn.

[0090] The Ni content (for example, the molar fraction of nickel in the total number of moles of nickel, cobalt, and manganese) in the above NCM-based lithium oxide may be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the Ni content may 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.

[0091] In some embodiments, the above positive electrode active material can also 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-based (LFP) active material (for example, LiFePO4).

[0092] In some embodiments, the above positive electrode active material can include, for example, an Mn-rich active material having a chemical structure or crystal structure represented by Chemical Formula 2, an LLO (Li rich layered oxide) / OLO (Over Lithiated Oxide)-based active material, or a Co-less active material.

[0093] [Chemical Formula 2] p[Li2MnO3]·(1-p)[Li q JO2]

[0094] In Chemical Formula 2, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J can contain at least one element among Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0095] The positive electrode can be produced, for example, by mixing the positive electrode active material in a solvent to produce a positive electrode slurry. After coating the positive electrode slurry on a positive electrode current collector, it is dried, and the insulating liquid is coated before or after the drying, and then rolled to produce a positive electrode active material layer.

[0096] The positive electrode may be a multilayer positive electrode. In the case of a multilayer positive electrode, for example, a first positive electrode binder slurry is coated on a positive electrode current collector to form a first positive electrode binder layer, a second positive electrode binder slurry is coated on the first positive electrode binder layer to form a second positive electrode binder layer, and then the insulating liquid can be coated. The first positive electrode binder slurry and the second positive electrode binder slurry can be dried simultaneously, and the second positive electrode binder slurry can be coated and dried after the first positive electrode binder slurry is dried.

[0097] The coating process can be carried out by methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc., but is not limited thereto.

[0098] The positive electrode active material layer can further contain a binder, and optionally can further contain a conductive material, a thickening agent, etc.

[0099] Examples of the solvent used in the production of the above-mentioned positive electrode slurry include, but are not limited to, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, and the like.

[0100] The above-mentioned binder can include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (Poly(vinylidene fluoride-co-hexafluoropropylene)), polyacrylonitrile, polymethylmethacrylate, acrylonitrile-butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), and the like. In one embodiment, a PVDF-based binder can be used as the positive electrode binder.

[0101] The above-mentioned conductive material can 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 above-mentioned conductive material can include carbon-based conductive materials such as graphite, carbon black, acetylene black, ketjen black, graphene, carbon nanotubes, VGCF (vapor-grown carbon fiber), carbon fibers, etc. and / or metal-based conductive materials including perovskite substances such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc., but is not limited thereto.

[0102] If necessary, the above-mentioned positive electrode binder can further include a thickener and / or a dispersant, etc. As one embodiment, the above-mentioned positive electrode binder can include a thickener such as carboxymethyl cellulose (CMC).

[0103] When the above electrode is a negative electrode, the negative electrode may include a negative electrode current collector and negative electrode active material layers disposed on both surfaces of the negative electrode current collector.

[0104] 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. Further, the negative electrode current collector may be a polymer substrate coated with a conductive metal such as nickel, aluminum, titanium, or silver.

[0105] The negative electrode current collector may be in various forms such as, by way of non-limiting example, foil, foam, net, porous body, non-woven fabric body, etc. Also, although not limited thereto, the negative electrode current collector may have a thickness of 10 to 50 μm.

[0106] The negative electrode active material layer may contain a negative electrode active material. As the negative electrode active material, a material capable of adsorbing and desorbing lithium ions can be used. For example, as the negative electrode active material, carbon-based materials such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber; lithium metal; lithium alloy; silicon (Si)-containing substances or tin (Sn)-containing substances can be used.

[0107] Examples of the amorphous carbon include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc.

[0108] Examples of the crystalline carbon include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0109] Examples of the lithium metal include pure lithium metal or lithium metal with a protective layer formed thereon for suppressing dendrite growth. In one embodiment, a lithium metal-containing layer vapor-deposited or coated on a negative electrode current collector can be used as the negative electrode active material layer. In one embodiment, a thin lithium film layer may be used as the negative electrode active material layer.

[0110] Examples of the elements included in the lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, or the like.

[0111] The silicon-containing material can provide more enhanced capacity characteristics. The silicon-containing material can include Si, SiOx (0 < x < 2), metal-doped SiOx (0 < x < 2), a silicon-carbon composite, or the like. The metal includes lithium and / or magnesium, and the metal-doped SiOx (0 < x < 2) can include a metal silicate.

[0112] For example, the negative electrode active material can be mixed in a solvent to produce a negative electrode slurry. The negative electrode active material layer can further include a binder, and optionally can further include a conductive material, a thickener, or the like.

[0113] After coating / vapor-depositing the negative electrode slurry on the negative electrode current collector, it can be dried and rolled to produce a negative electrode active material layer. The coating process can be performed by methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, or the like, but is not limited thereto.

[0114] In some embodiments, the negative electrode can also include a negative electrode active material layer in the form of lithium metal formed by a vapor deposition / coating process.

[0115] 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 active material slurry is applied onto a negative electrode current collector to form a first negative electrode active material layer, a second negative electrode active material slurry is applied onto the first negative electrode active material layer to form a second negative electrode active material layer, and then the insulating liquid can be coated. The first negative electrode active material slurry and the second negative electrode active material slurry can be dried simultaneously, or the second negative electrode active material slurry can be applied and dried after the first negative electrode active material slurry is dried.

[0116] Non-limiting examples of the solvent for the negative electrode active material include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, t-butanol, and the like.

[0117] The binder may include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (Poly(vinylidene fluoride-co-hexafluoropropylene)), polyacrylonitrile, polymethylmethacrylate, acrylonitrile butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), and the like. In one embodiment, a styrene-butadiene rubber (SBR)-based binder, carboxymethyl cellulose (CMC), a polyacrylic acid-based binder, a poly(3,4-ethylenedioxythiophene) (PEDOT)-based binder, or the like can be used as the negative electrode binder.

[0118] The binder may be contained in an amount of about 1.5% to about 5% by weight based on the total weight of the negative electrode active material layer.

[0119] The above 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 above conductive material can include carbon-based conductive materials such as graphite, carbon black, acetylene black, ketjen black, graphene, carbon nanotubes, VGCF (vapor-grown carbon fiber), carbon fibers, etc. and / or metal-based conductive materials including perovskite substances such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc., but is not limited thereto.

[0120] In one embodiment, the above conductive material may be included in an amount of about 0.05% to about 0.2% by weight based on the total weight of the negative electrode active material layer.

[0121] If necessary, the above negative electrode active material layer can further include a thickening agent and / or a dispersant, etc. As one embodiment, the above negative electrode active material layer can include a thickening agent such as carboxymethyl cellulose (CMC).

[0122] The above positive electrode and negative electrode can be alternately laminated, and an electrode assembly can be manufactured by interposing a separator between the positive electrode and the negative electrode.

[0123] The above separator can be configured to prevent an electrical short circuit between the positive electrode and the negative electrode and allow an ion flow to occur. As one embodiment, the thickness of the above separator is not limited thereto, but for example, it may be 10 μm to 20 μm.

[0124] For example, the separation membrane can include a porous polymer film or a porous non-woven fabric. The porous polymer film can include polyolefin-based polymers such as an ethylene polymer, a propylene polymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer. The porous non-woven fabric can include high-melting-point glass fibers, polyethylene terephthalate fibers, and the like. The separation membrane may include a ceramic-based material. For example, inorganic particles can be coated on the polymer film or dispersed in the polymer film to improve heat resistance.

[0125] The separation membrane can have a single-layer or multi-layer structure including the above-described polymer film and / or non-woven fabric.

[0126] 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.

[0127] In the present disclosure, the electrode assembly may be a winding type electrode assembly. The manufacturing process of the winding type electrode assembly is schematically shown in FIG. 9. As shown in FIG. 9, the winding type electrode assembly can be manufactured, for example, by laminating a long positive electrode in one direction and a long negative electrode in one direction, and interposing a long separation membrane in one direction between the positive electrode and the negative electrode and on one surface of the positive electrode or the negative electrode, and then winding it in one direction.

[0128] As the long electrode in one direction used for the above winding type electrode assembly, the electrode according to the present disclosure as described above can be used. Therefore, it can include an active portion in which an electrode active material layer is formed on both surfaces of the electrode current collector, and can include a non-patterned portion at one end portion in the above one direction. Further, the long electrode in the above one direction can include an active portion insulating layer and a non-patterned portion insulating layer in a region near the boundary between the active portion and the non-patterned portion. Furthermore, the end of the first active portion insulating layer on the first surface and the end of the second active portion insulating layer on the second surface can be different in position from each other.

[0129] The long electrode in the above one direction can include an active portion insulating layer at one end portion including the non-patterned portion, a non-patterned portion insulating layer and a non-patterned portion, and can have a step in the above one direction. Further, although not shown, the non-patterned portion may be formed at both end portions of the electrode.

[0130] In the long electrode in one direction used for the above winding type electrode assembly, the above one direction may be a winding direction or a step direction. Here, the step direction may be a direction from the center portion of the electrode toward the step formed in the electrode, and the above step may be provided by forming an active portion insulating layer, a non-patterned portion insulating layer and a non-patterned portion at one end portion of the electrode. Also, the step direction may indicate a direction opposite to the winding direction.

[0131] An example of an electrode laminate in which a long electrode in one direction and a separator used for manufacturing the above winding type electrode assembly are laminated is schematically shown in FIG. 10. Also, as shown in FIG. 10, the long electrode in the above one direction can be joined to the electrode leads 23 and 24 in a direction perpendicular to the above one direction (winding direction or step direction) by methods such as ultrasonic welding or laser welding, respectively. Also, as an example, in the above winding type electrode assembly, the negative electrode lead 24 and the positive electrode lead 23 may be joined in opposite directions to each other.

[0132] In the present disclosure, the electrode assembly may be a stacked electrode assembly. An example of the stacked electrode assembly and its manufacturing process is schematically shown in FIG. 11. As shown in FIG. 11(a), for example, the stacked electrode assembly is provided with a plurality of positive electrodes, a plurality of negative electrodes, and a plurality of separator membranes having a predetermined size, and as shown in FIG. 11(b), a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked, and a separator membrane is inserted between the positive electrode and the negative electrode for manufacturing. The stacked electrode assembly thus manufactured can include a stacking order such as positive electrode / separator membrane / negative electrode / separator membrane as shown in FIG. 11(c).

[0133] A secondary battery including the stacked electrode assembly is schematically shown in FIG. 12. The secondary battery shown in FIG. 12 can be obtained by housing the stacked electrode assembly as shown in FIG. 11 in a battery case such as a pouch case and sealing it.

[0134] As shown in FIG. 12, the obtained secondary battery can have the same planar shape as the planar shape of the stacked electrode assembly housed inside the battery case, and can also have the same planar shape as the planar shape of the electrodes used in the manufacture of the stacked electrode assembly.

[0135] The manufacturing process of the electrodes used in the manufacture of the stacked electrode assembly and the electrodes thus obtained are schematically shown in FIG. 13. Although not particularly limited, the electrodes used in the formation of the stacked electrode assembly are, as shown in FIG. 13, a slurry is coated on one or both surfaces of the electrode current collector to form an active part and a blank part, dried and rolled to manufacture an electrode plate long in one direction (step (a)), and a slitting step (b) of cutting the electrode plate so as to have the same shape as the length of the battery to be obtained, and a notching step ((c) and (d)) of notching the slit electrode plate so as to have the width of the battery and have an electrode tab, whereby an electrode having the same or similar shape as the plane of the battery can be manufactured.

[0136] In the above electrode, the above length can be represented based on the direction in which the electrode tab is formed, and the width can be represented based on the direction perpendicular to the formation direction of the electrode tab.

[0137] The electrode having the planar shape of the above battery and used in the above stacked electrode assembly may be the electrode according to the present disclosure as described above. Therefore, it may include an active portion in which an electrode active material layer is formed on both surfaces of the electrode current collector, and may include a non-patterned portion at one end portion of the above electrode. The above non-patterned portion may be a part of the electrode tab. For example, two or more of the above non-patterned portions may converge and be provided as an electrode tab by being mutually welded. Further, the above electrode may include an active portion insulating layer and a non-patterned portion insulating layer in a region near the boundary between the above active portion and the non-patterned portion. Furthermore, the end of the first active portion insulating layer on the first surface and the end of the second active portion insulating layer on the second surface may have different positions from each other.

[0138] The electrode having the planar shape of the above battery may sequentially include an active portion insulating layer, a non-patterned portion insulating layer, and a non-patterned portion at one end portion including the above non-patterned portion. Therefore, the above electrode may have a step at one end.

[0139] In the above electrode included in the above stacked electrode assembly, the electrode tab extends in the step direction having the above step, and the electrode lead can be joined by a method such as ultrasonic welding or laser welding in the direction in which the electrode tab extends. Therefore, in the above electrode, the step direction and the extension direction of the electrode tab may coincide, and may also be the same as the extension direction of the electrode lead. In the above stacked electrode assembly, the extension direction of the above electrode lead may be the same in the positive electrode and the negative electrode, or may be opposite to each other.

[0140] In the present disclosure, the electrode assembly may be a stack-folding type electrode assembly. The stack-folding type electrode assembly and its manufacturing process are schematically shown in FIG. 14. As shown in FIG. 14, the stack-folding type electrode assembly can be manufactured, for example, by alternately inserting a plurality of positive electrodes and a plurality of negative electrodes having a predetermined size while folding a separator that is long in one direction in a zigzag direction. The electrode assembly thus manufactured has a laminated sequence such as positive electrode / separator / negative electrode / separator as shown in FIG. 14 in terms of cross-sectional shape, and the separator is folded in a zigzag and can be interposed between the positive electrode and the negative electrode.

[0141] A secondary battery can be manufactured by housing and sealing the stack-folding type electrode assembly in a battery case such as a pouch case.

[0142] The secondary battery manufactured using the stack-folding type electrode assembly is substantially the same as the secondary battery manufactured using the stack type electrode assembly, except that a separator that is long in one direction is used, and the electrodes used in the stack type electrode assembly can be used.

[0143] An electrolytic solution can be housed in the battery case together with the electrode assembly to define a lithium secondary battery. According to one embodiment, the electrolytic solution can use a non-aqueous electrolytic solution.

[0144] The non-aqueous electrolytic solution contains a lithium salt as an electrolyte and an organic solvent. The lithium salt is represented by, for example, 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. can be exemplified.

[0145] The above organic solvent can contain an organic compound that has sufficient solubility in the above lithium salt and additives and has no reactivity in the battery. Examples of the above organic solvent can include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, and aprotic solvents.Examples of the organic solvent include 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), fluoroethyl acetate (FEA), difluoroethyl acetate (DFEA), trifluoroethyl acetate (TFEA), dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), 2-methyltetrahydrofuran, ethyl alcohol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, diethoxyethane, sulfolane, gamma-butyrolactone, and propylene sulfite. These can be used alone or in combination of two or more.

[0146] The above non-aqueous electrolyte can further contain an additive. The additive can include, for example, cyclic carbonate compounds, fluorine-substituted carbonate compounds, sultone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, and borate compounds.

[0147] The above cyclic carbonate compounds can include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and the like.

[0148] The above fluorine-substituted carbonate compounds can include fluoroehtylene carbonate (FEC), and the like.

[0149] The above sultone compounds can include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, and the like.

[0150] The above cyclic sulfate compounds can include 1,2-ethylene sulfate, 1,2-propylene sulfate, and the like.

[0151] The above cyclic sulfite compounds can include Ethylene sulfite, Buthylene sulfite, and the like.

[0152] The above phosphate compounds can include Lithium difluoro bis-oxalato phosphate, Lithium difluoro phosphate, and the like.

[0153] The above borate compound can include lithium bis(oxalate) borate and the like.

[0154] As one implementation example, the above electrode can have an electrode tab including a first plain part or a second plain part.

[0155] As one implementation example, the above electrode may be a negative electrode or a positive electrode.

[0156] As one implementation example, the above secondary battery can include at least one positive electrode and at least one negative electrode, and the above positive electrode, negative electrode, or a combination thereof can be the electrode of the present disclosure.

[0157] For the above secondary battery, for example, electrode tabs (a positive electrode tab and a negative electrode tab) can 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 above battery case may be a pouch type case, a square case, a cylindrical case, a coin type case, etc. The above electrode tab can extend or be exposed to the outside from the above one side of the battery case and be connected to an electrode lead (a positive electrode lead and a negative electrode lead). When the above battery case is a pouch type case, the electrode tab extending to the outside from one side of the battery case can be welded together with the battery case.

[0158] Examples Hereinafter, the embodiments of the present invention will be further described with reference to specific experimental examples. The examples and comparative examples included in the experimental examples are only illustrative of the present invention and do not limit the appended claims. It is obvious to those skilled in the art that various changes and modifications to the examples are possible within the scope of the present invention and the scope of the technical idea, and it is natural that such deformations and modifications belong to the appended claims.

[0159] Example 1 On both active parts of an aluminum foil (thickness: 12 μm) divided into an active part and a plain part, a positive electrode active material slurry containing 96% by weight of NCM622, 1.5% by weight of carbon black conductive material, and 2.5% by weight of PVDF (polyvinylidene fluoride) binder was applied to form a positive electrode active material layer, and the length of the plain part where the slurry was not coated was made 15 mm.

[0160] An insulating liquid in which polyimide (PI) was dissolved in NMP was used to apply 5 mm of the insulating liquid from the boundary between the active part and the plain part to the plain part side on both sides of the positive electrode, forming a plain part insulating layer.

[0161] Also, the insulating liquid was applied so as to overlap the positive electrode active material slurry on the active part side from the boundary between the plain part and the active part. At this time, the first side of the positive electrode was applied so as to overlap the active part by 1 mm, and the second side was applied so as to overlap by 0.5 mm, and the first and second active part insulating layers were respectively formed so that the interval ΔL2 between the ends of the first active part insulating layer and the ends of the second active part insulating layer was 0.5 mm and they were separated from each other.

[0162] After that, after drying the positive electrode active material slurry and the insulating liquid, it was rolled at a pressure of 3.6 g / cm 3 to manufacture a positive electrode.

[0163] For the manufactured positive electrode, a voltage was applied for 0.5 seconds between the plain part and the plain part insulating layer, between the plain part insulating layer and the positive electrode active material layer, and between the plain part and the positive electrode active material layer using a resistance measuring instrument (measurement range: 0.1 MΩ to 5,000 MΩ), and the resistance between two points was measured respectively.

[0164] Between the plain part and the plain part insulating layer and between the plain part insulating layer and the positive electrode active material layer, the resistance value (5,000 MΩ) of the maximum measurement limit of the resistance measuring instrument was shown. On the other hand, between the plain part and the positive electrode active material layer, a resistance value of 0.1 MΩ was shown.

[0165] From such results, it was found that the above-mentioned plain part insulating layer acts as a resistor between the plain part and the positive electrode active material layer, and even if the positive electrode and the negative electrode come into direct contact, it can be electrically interrupted by the above-mentioned insulating layer, preventing the occurrence of a short circuit.

[0166] The obtained positive electrode was cut so as to include both the plain part and the active part, and five test pieces were obtained.

[0167] For one of the above test pieces, the thickness profile of the first surface was analyzed with a 3D microscope, and the results are shown in FIG. 15. As shown in FIG. 15, a groove is formed at the end of the active part insulating layer 351. On the other hand, although not shown, it was confirmed that on the second surface of the test piece, the position of the groove was formed at a position different from the groove on the first surface. At this time, the groove formed on the first surface and the groove formed on the second surface were separated from each other by 0.5 mm (ΔL2 = 0.5 mm).

[0168] For the five prepared test pieces, the tensile strength in the TD (Transverse Direction) was measured using a universal testing machine (UTM, Universal Test Machine), and the average values are shown in Table 1. The above tensile strength represents the value when the test piece breaks. As shown in Table 1, an average value of 2,240 kgf / mm 2 showed a high value. This is evaluated to be because the ends of the active part insulating layer are formed at different positions on the first surface and the second surface, so that the force applied to the electrode during rolling is dispersed, reducing the decrease in tensile strength.

[0169] Also, in the measurement of the above tensile strength, as shown in FIG. 16(a), it was confirmed that breakage occurred in the plain part and no decrease in tensile strength occurred at the end of the active part insulating layer.

[0170] Furthermore, a tensile strength measurement test was further conducted on the other test pieces manufactured above, but breakage occurred in the plain part in the same way, or breakage occurred in the active part as shown in Fig. 16(b). From this, it was found that the end of the active part insulating layer does not act as a fragile part.

[0171] In addition, when manufacturing a positive electrode tab by welding the plain part of the positive electrode by pre-treatment welding and main welding with respect to the manufactured positive electrode above, the positive electrode tab (a) after pre-treatment welding and the positive electrode tab (b) after main welding were each photographed and shown in Fig. 17. From Fig. 17, it was found that the welding quality of the electrode tab is good.

[0172] Furthermore, with respect to the welded part, the welding strength was measured with a UTM in the same manner as the above-described tensile strength measurement method, and the results are shown in Table 1. As shown in Table 1, the welding strength was also an average of 65.91 kgf and a minimum of 53.89 kgf, showing excellent values.

[0173] Example 2 In Example 1, except that the first plain part insulating layer on the first surface was applied 4.5 mm from the boundary between the plain part and the active part, and the interval ΔL1 between the end of the first plain part insulating layer and the end of the second plain part insulating layer was 0.5 mm and they were formed so as not to coincide with each other, a positive electrode was manufactured in the same manner as in Example 1.

[0174] For the above test pieces, the tensile strength in the TD direction was measured in the same manner as in Example 1, and the results are shown in Table 1. As can be seen from Table 1, the tensile strength showed excellent values of an average of 2,317 kgf / mm 2 This is evaluated that because the ends of the active part insulating layer are formed at different positions on the first surface and the second surface, the force applied to the electrode during rolling is dispersed and the decrease in tensile strength can be reduced.

[0175] Furthermore, the welding strength was also an average of 64.79 kgf and a minimum of 52.89 kgf, showing excellent values.

[0176] Comparative Example 1 A positive electrode was manufactured in the same manner as in Example 1, except that first and second active part insulating layers were formed on the first and second surfaces of the positive electrode so as to overlap the active part by 1 mm as well.

[0177] In the same manner as in Example 1 above, a voltage was applied between the ground part and the ground part insulating layer, between the ground part insulating layer and the positive electrode active material layer, and between the ground part and the positive electrode active material layer for 0.5 seconds to measure the resistance between two points respectively.

[0178] Between the ground part and the ground part insulating layer and between the ground part insulating layer and the positive electrode active material layer, a resistance value (5,000 MΩ), which is the maximum value within the measurement limit of the resistance measuring instrument, was shown. On the other hand, a resistance value of 0.1 MΩ was shown between the ground part and the positive electrode active material layer.

[0179] From such results, it was found that the ground part insulating layer acts as a resistor between the ground part and the positive electrode active material layer, and even if the positive electrode and the negative electrode come into direct contact, they can be electrically blocked by the insulating layer, preventing the occurrence of a short circuit.

[0180] The obtained positive electrode was cut so as to include both the ground part and the active part, and five test pieces were obtained.

[0181] For one of the above test pieces, the thickness profile of the first surface was analyzed with a 3D microscope, and the results are shown in Fig. 18. In Fig. 18, (a) is the electrode before rolling, and (b) is the electrode after rolling. As shown in Fig. 18, fine grooves were formed at the ends of the active part insulating layer (inside the circles) from before rolling, and it was confirmed that the grooves became deeper in the electrode after rolling.

[0182] The cross-section of the same test piece was photographed using a scanning electron microscope (SEM), and the results are shown in Fig. 19. As shown in Fig. 19, it can be confirmed that the current collector is broken in the region where the first active part insulating layer 351 on the first surface and the second active part insulating layer 352 on the second surface of the positive electrode are formed. This can be evaluated as follows: since the ends of the active part insulating layers on both sides are formed at similar positions, the pressure cannot be dispersed during the rolling process, and the pressure is concentrated in the groove formed near the ends of the active part insulating layers, resulting in this situation.

[0183] On the other hand, in Fig. 19, although it is shown that the positions of the first and second active part insulating layers do not exactly match, this is due to errors in the manufacturing process. The interval between the ends of the two active part insulating layers is an extremely small difference of less than 100 μm, and it can be evaluated as being substantially the same.

[0184] For the above-prepared 5 test pieces, the tensile strength in the TD (Transverse Direction) was measured using a universal testing machine (UTM, Universal Test Machine), and the average values are shown in Table 1. The above tensile strength represents the value when the test piece breaks and is shown in Table 1. As shown in Table 1, the average value is 1,562 kgf / mm 2 showed a value.

[0185] On the other hand, in the measurement of the above tensile strength, the test piece broke in the region where the ends of the active part insulating layer were located. From such results, it can be evaluated that the concentration of pressure during the rolling process at the ends of the active part insulating layer led to a decrease in the tensile strength of the current collector.

[0186] Also, when manufacturing a positive electrode tab by welding the plain part of the positive electrode through pre-treatment welding and main welding for the above-produced positive electrode, the positive electrode tab (a) after pre-treatment welding and the positive electrode tab (b) after main welding were photographed respectively, and these are shown in Fig. 20 (a) and (b) respectively.

[0187] It can be seen from (b) of FIG. 20 above that the welding state is poor. This is considered to show the result that the impact applied to the electrode during this welding was transmitted to the boundary between the active part insulating layer and the positive electrode active material layer (that is, the end of the active part insulating layer), electrode breakage occurred, and due to this, shaking of the electrode occurred and the welding state became poor.

[0188] Furthermore, the welding strength of the welded part was measured, and the results are shown in Table 1. As shown in Table 1, the welding strength had an average value of 46.47 kgf and a minimum value of 23.54 kgf, showing a relatively low value. This can be evaluated as being due to the presence of a vulnerable part at the end of the active part insulating layer as described above.

[0189] Comparative Example 2 A positive electrode was manufactured in the same manner as in Example 1, except that an insulating layer was not formed using an insulating liquid.

[0190] The positive electrode obtained above was cut to obtain a test piece so as to include both the non-coated part and the active part. The tensile strength in the TD direction of the above test piece was measured in the same manner as in Example 1, and the results are shown in Table 1.

[0191] As can be seen from Table 1, the tensile strength showed an average value of 2,446 kgf / mm 2 , which was higher than that of Comparative Example 1 and slightly higher than those of Examples 1 and 2. This can be evaluated as being because no vulnerable part was generated due to the formation of grooves by not forming an insulating layer. Therefore, breakage occurred in the non-coated part during the measurement of the tensile strength, and it was evaluated that the welding strength also showed the highest value.

[0192] However, the non-coated part does not contain an insulating layer, and there is a possibility that the above non-coated part comes into contact with the negative electrode and a short circuit occurs. Therefore, there is a risk of hindering the safety of the battery.

[0193]

Table 1

[0194] Further, when the manufactured positive electrode was welded to produce a positive electrode tab by pre-welding and main welding on the plain part of the positive electrode, the positive electrode tab (a) after pre-welding and the positive electrode tab (b) after main welding were respectively photographed and shown in FIGS. 21(a) and 21(b). From FIG. 21, it was found that the welding quality of the electrode tab was good because it did not include a separate insulating layer and thus did not affect the tensile strength.

[0195] The above-described content is merely an example applying the principle of the present disclosure, and other configurations can be further included without departing from the scope of the present invention.

Explanation of Reference Numerals

[0196] 1: Current collector of electrode 3: Electrode active material layer 5: Insulating layer 10: Electrode 11: First surface 12: Second surface 13: Active part 14: Plain part 15: Boundary 16: Electrode plate 17: Positive electrode 18: Negative electrode 19: Separator 20: Electrode tab 21: Positive electrode tab 22: Negative electrode tab 23: Positive electrode lead 24: Negative electrode lead 25: Electrode lead 30: Pouch case 351: First active part insulating layer 352: Second active part insulating layer 3511: End of the first active part insulating layer 3522: End of the second active part insulating layer 451: First plain part insulating layer 452: Second plain part insulating layer 4511: End of the first plain part insulating layer 4522: End of the second plain part insulating layer ΔL1: Spacing between the ends of the first and second plain part insulating layers ΔL2: Spacing between ends of the first and second active part insulating layers

Claims

1. An electrode for a secondary battery including a first surface and a second surface located opposite to the first surface, wherein the first surface includes a first active part on which an electrode active material layer is formed and a first plain part on which no electrode active material layer is formed on an electrode current collector, the second surface independently of the first surface includes a second active part on which an electrode active material layer is formed and a second plain part on which no electrode active material layer is formed on an electrode current collector, the first surface includes a first active part insulating layer formed on the first active part and a first plain part insulating layer formed on the first plain part, the second surface includes a second active part insulating layer formed on the second active part and a second plain part insulating layer formed on the second plain part, and an electrode for a secondary battery, wherein positions of ends of the first active part insulating layer and positions of ends of the second active part insulating layer are different from each other.

2. The first active part insulating layer and the first plain part insulating layer are continuous layers, the second active part insulating layer and the second plain part insulating layer are continuous layers, and the electrode for a secondary battery according to Claim 1, wherein a length of the first active part insulating layer, which is a length from a boundary between the first active part and the first plain part to an end of the first active part insulating layer, and a length of the second active part insulating layer, which is a length from a boundary between the second active part and the second plain part to an end of the second active part insulating layer, are different from each other.

3. The electrode for a secondary battery according to Claim 2, wherein the length of the first active part insulating layer is 1.3 times or more and 9 times or less the length of the second active part insulating layer.

4. The electrode for a secondary battery according to Claim 2, wherein a distance between an end of the first active part insulating layer and an end of the second active part insulating layer is 0.2 mm or more and 0.9 mm or less.

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

6. The electrode for a secondary battery according to Claim 2, wherein the length of the first active part insulating layer is 0.3 to 1.2 mm and the length of the second active part insulating layer is 0.1 to 1.0 mm.

7. The electrode for a secondary battery according to Claim 1, wherein positions of ends of the first plain part insulating layer and positions of ends of the second plain part insulating layer are the same or different.

8. The electrode for a secondary battery according to Claim 1, wherein a distance between an end of the first plain part insulating layer and an end of the second plain part insulating layer is 0.5 mm or less.

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

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

11. The electrode for a secondary battery according to claim 1, having an electrode tab including the first non-active portion or the second non-active portion.

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

13. including grooves respectively and independently formed in regions where the ends of the first active-portion insulating layer and the ends of the second active-portion insulating layer are present, The electrode for a secondary battery according to claim 1, wherein the positions of the grooves on the first surface and the second surface are different from each other.

14. including at least one positive electrode and at least one negative electrode, The secondary battery, wherein 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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