Electrode assembly and secondary battery containing the same

Abstract

To provide an electrode assembly capable of preventing discoloration of a ceramic layer for improving safety of a secondary battery, and provide a secondary battery including the same.SOLUTION: An electrode assembly is a winding type electrode assembly including a first electrode, a separator film, and a second electrode. The first electrode includes: a first substrate; a front surface first active material layer and a rear surface first active material layer respectively provided on at least a front surface and a rear surface of the first substrate; a first termination functional layer and a second termination functional layer respectively formed on the front surface and the rear surface of the first substrate at a predetermined distance from the front surface first active material layer and the rear surface first active material layer; and a step compensation layer disposed on the second terminal functional layer, and corresponding to a gap between the front first active material layer and the first terminal functional layer. The first termination functional layer is wrapped around the electrode assembly at least one time or more.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an electrode assembly, and more particularly to an electrode assembly for a secondary battery and a secondary battery including the same.

Background Art

[0002] A secondary battery is a power storage system that provides excellent energy density capable of storing electrical energy in the form of chemical energy. Compared with a primary battery that cannot be recharged, a secondary battery can be recharged, and thus is widely used in IT devices such as smartphones, notebook computers, and tablet PCs.

[0003] In recent years, due to environmental problems and the depletion of fossil fuels, interest in electric vehicles has increased, and there is a tendency to use the battery of an electric vehicle as a secondary battery.

[0004] Due to such a tendency, secondary batteries are required to have characteristics such as high density, high output, and safety.

[0005] In particular, since the risk of ignition, rupture, and explosion of a secondary battery increases due to external impact or charge and discharge, the installation of an appropriate safety device is required.

[0006] On the other hand, in order to increase the safety of a secondary battery, a ceramic layer is additionally formed on the longitudinally seamless portion of the electrode assembly.

[0007] However, as the usage time of the secondary battery increases, deposits are generated on the ceramic layer, and as a result, a phenomenon occurs in which a part of the ceramic layer discolors.

[0008] The above-described information disclosed in the background art of such an invention is for improving the understanding of the background of the present invention, and thus may include information that does not constitute the prior art.

Summary of the Invention

Problems to be Solved by the Invention

[0009] One embodiment is to provide an electrode assembly capable of preventing discoloration of a ceramic layer for improving the safety of a secondary battery, and a secondary battery including the same.

[0010] However, the technical problems to be solved by the present invention are not limited to the above problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description of the invention.

Means for Solving the Problems

[0011] In a wound electrode assembly including a first electrode, a separator, and a second electrode according to an embodiment, the first electrode includes a first substrate, a front first active material layer and a rear first active material layer respectively provided on at least the front and rear surfaces of the first substrate, a first terminal functional layer and a second terminal functional layer respectively formed on the front and rear surfaces of the first substrate at a certain distance from the front first active material layer and the rear first active material layer, and a step compensation layer located on the second terminal functional layer and corresponding to the gap between the front first active material layer and the first terminal functional layer. The first terminal functional layer is wound around the electrode assembly at least once.

[0012] The step compensation layer may be made of the same material as the second terminal functional layer.

[0013] The first terminal functional layer and the second terminal functional layer may include a ceramic material.

[0014] The thickness of the step compensation layer is the same as or smaller than the thickness of the front first active material layer.

[0015] An intermediate functional layer respectively formed between the first substrate and the front first active material layer, and between the first substrate and the rear first active material layer may be further included.

[0016] The intermediate functional layer is formed larger than the front first active material layer and the rear first active material layer, respectively, and can extend from the front first active material layer and the rear first active material layer toward the first terminal functional layer and the second terminal functional layer.

[0017] The step compensation layer can be formed in multiple stages.

[0018] The separation membrane can be wound around the electrode assembly at least once together with the second terminal functional layer and can be positioned between the gap and the step compensation layer.

[0019] The electrode bare portion of the second electrode can be wound around the electrode assembly at least once together with the second terminal functional layer and the separation membrane and can be positioned between the gap and the step compensation layer.

[0020] The step compensation layer becomes narrower as it gets farther from the first base material.

[0021] The first electrode may be a positive electrode and the second electrode may be a negative electrode.

Advantages of the Invention

[0022] When a step compensation layer is formed as in the embodiment, it is possible to provide an electrode assembly that reduces the generation of deposits in the ceramic layer and the resulting discoloration phenomenon, and a secondary battery including the same.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Best Mode for Carrying Out the Invention

[0024] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings. The inventor should interpret them in accordance with the meanings and concepts that conform to the technical idea of the present invention based on the principle that the concept of the terms can be appropriately defined in order to explain his invention in the best way. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, at the time of this application, it should be understood that there are various equivalents and modifications that can replace these.

[0025] Also, as used in this specification, "comprise" and / or "comprising" and / or "include" and / or "including" are used to specify the presence of the recited shape, number, step, operation, member, element, and / or group thereof, and do not preclude the presence or addition of one or more other shapes, numbers, operations, members, elements, and / or groups.

[0026] Also, for the purpose of understanding the invention, the attached drawings may be illustrated such that the dimensions of some components are exaggerated rather than shown at actual scale. Also, the same reference numerals may be given to the same components in different embodiments.

[0027] For example, although first, second, etc. are used to describe various components, these components are of course not limited by these terms. These terms are merely used to distinguish one component from another, and of course, the first component may be the second component as long as there is no negative description.

[0028] Throughout the specification, unless otherwise negatively stated, each component may be in the singular or plural.

[0029] As shown in the drawings, for the purpose of facilitating the description of the relationship between an element or feature and another element or feature, spatially relative terms such as "beneath", "below", "lower", "above", "upper", etc. may be used in this specification. The spatially relative positions are understood to include directions other than those depicted in the figures and different directions of the device during use or operation. For example, if the device in the drawing is turned upside down, an element described as "below" or "beneath" another element is understood to be "above" or "upper" of the other element. Therefore, the term "below" can include both upward and downward directions.

[0030] Also, when a component is described as "connected to" or "coupled to" another component, it should be understood that the components are directly connected or joined to each other, but other components may be "interposed" between the components, or each component may be "connected", "coupled" or "joined" through other components.

[0031] The terms used in this specification are for the purpose of describing embodiments of the present disclosure and are not intended to limit the present disclosure.

[0032] Hereinafter, a secondary battery according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

[0033] FIG. 1 is a schematic exploded perspective view of a secondary battery according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of the electrode assembly of FIG. 1, FIG. 3 is a (a) plan view seen from a first direction for explaining the first electrode of the electrode assembly shown in FIG. 2, (b) a plan view seen from a direction opposite to the first plan view, and (c) a cross-sectional view, and FIGS. 4 and 5 are cross-sectional views showing an enlarged part (F) of FIG. 2.

[0034] The plan view seen from the first direction in FIG. 3(a) shows one surface of the first electrode, FIG. 3(b) is a plan view of the other surface seen from a direction opposite to the first plan view, and the cross-sectional view of FIG. 3(c) is a cross-sectional view taken along the line C1-C1' of FIGS. 3(a) and (b).

[0035] As shown in FIG. 1, a secondary battery 1000 according to an embodiment of the present invention includes an electrode assembly 100 and a pouch 200.

[0036] Referring to FIGS. 1 and 2, the electrode assembly 100 includes a first electrode 121, a second electrode 122, and a separator 123 positioned between the first electrode and the second electrode. The separator 123 is for insulation, and the first electrode 121, the separator 123, the second electrode 122, and the separator 123 may be laminated in this order.

[0037] The electrode assembly 100 may be in the form of a jelly roll wound around a winding axis (XL) with the first electrode 121, the separator 123, and the second electrode 122 laminated. If necessary, after the electrode assembly 100 is wound, it may be pressed flat, and the cross-section cut in the vertical direction across the winding axis (XL) may be an ellipse elongated in one direction.

[0038] Therefore, when viewed in cross-section, the electrode assembly 100 includes a relatively flat flat portion (P1) and a relatively round curved portion (P2). The flat portion (P1) is the portion that is pressed after being wound around the electrode assembly 100, and the curved portion (P2) can connect between two facing flat portions (P1). In the electrode assembly 100, one rotation can include a pair of facing flat portions and a pair of curved portions connected to the ends of the flat portions.

[0039] Specifically, referring to FIGS. 2, 3, and 6, the first electrode 121 includes a first electrode active portion (LA1), a first electrode blank portion (LA2) and a first finishing portion (LA3) respectively located on the opposite sides centered on the first electrode active portion (LA1), and the second electrode 122 includes a second electrode active portion (LB1) and a second electrode blank portion (LB2) respectively located on the opposite sides centered on the second electrode active portion (LB1).

[0040] Hereinafter, when winding the strip-shaped first electrode and second electrode around the winding axis (XL), the end adjacent to the winding axis (XL) is referred to as the tip, and the end located relatively far away is referred to as the terminal.

[0041] Referring to FIG. 3, the first electrode active portion (LA1) includes a first substrate 11, an intermediate functional layer 12 formed on the first substrate 11, and a first active material layer 13 formed on the intermediate functional layer 12.

[0042] The intermediate functional layer 12 and the first active material layer 13 are formed on one or both sides of the substrate, and the lengths of the first electrode active portions (LA1) formed on one side (A) and the other side (B) of the substrate 11 may be different from each other.

[0043] The first substrate 11 provides a charge transfer path generated in the first active material layer 13 and supports the first active material layer 13.

[0044] The first electrode 121 may be a positive electrode, and the first substrate 11 may be a metal thin plate with excellent conductivity, such as aluminum foil, or may have a mesh structure.

[0045] The intermediate functional layer 12 may contain a compound represented by the following [Chemical Formula 1], a compound represented by the following [Chemical Formula 2], or a substance containing a combination thereof: [Chemical Formula 1] Li a1 M 1 x1 Fe (1-x1) PO4

[0046] In Chemical Formula 1, 0.90 ≦ a1 ≦ 1.5, 0 ≦ x1 ≦ 0.4, and M 1 is Mg, Co, Ni, or a combination thereof. [Chemical Formula 2] Li a2 Mn x2 Fe (1-x2) PO4

[0047] In Chemical Formula 2, 0.90 ≦ a2 ≦ 1.5, 0.1 ≦ x2 ≦ 1.

[0048] The compound represented by Chemical Formula 1 may be a lithium iron phosphate compound.

[0049] In Chemical Formula 1, the molar fraction of lithium is appropriately adjusted between approximately 0.9 and 1.5, for example, 0.90 ≦ a1 ≦ 1.2, or 0.95 ≦ a1 ≦ 1.1. In Chemical Formula 1, Mn may be present in addition to Fe, and its molar fraction may be 0 ≦ x1 ≦ 0.7, 0 ≦ x1 ≦ 0.5, 0 ≦ x1 ≦ 0.3, 0 ≦ x1 ≦ 0.1, or 0 ≦ x1 ≦ 0.05.

[0050] The compound represented by Chemical Formula 2 may be a lithium manganese iron phosphate compound (lithium manganese iron phosphate). In Chemical Formula 2, the molar fraction of lithium may be 0.90 ≦ a2 ≦ 1.2 or 0.95 ≦ a2 ≦ 1.1, similar to Chemical Formula 1. In Chemical Formula 2, the molar fraction of manganese may be 0.2 ≦ x2 ≦ 0.9, 0.3 ≦ x2 ≦ 0.9, or 0.4 ≦ x2 ≦ 0.8. In particular, when 0.5 ≦ x2 ≦ 0.9, the lithium ion conduction ability is high.

[0051] For example, the intermediate functional layer 12 may contain, as a lithium transition metal phosphate, LiFePO4, LiMn 0.5 Fe 0.5 PO4, LiMnPO4, and the like.

[0052] The intermediate functional layer 12 contains the above substances and may further contain a binder and / or a conductive agent. Here, the content of the above substances may be 80% to 97% by weight based on the total weight of the first functional layer 12, the content of the binder may be 1% to 10% by weight, and the content of the conductive material may be 0.5% to 10% by weight.

[0053] The binder can make the substance particles in the first functional layer adhere well to each other and make the substance particles adhere well to the substrate. The binder can include a water-insoluble binder, a water-soluble binder, or a combination thereof.

[0054] Examples of the water-insoluble binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, an ethylene-propylene copolymer, polystyrene, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0055] Examples of the water-soluble binder include rubber-based binders or polymer resin binders. The rubber-based binder is selected from styrene-butadiene rubber (SBR), acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber (ABR), acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0056] When a water-soluble binder is used as the binder, a cellulose-based compound capable of imparting viscosity can be further included. As this cellulose-based compound, one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof can be mixed and used. As the alkali metal, Na, K, or Li can be used.

[0057] The conductive material is used to impart conductivity to the electrode, and the conductive material can include carbon-based substances, metal-based substances, conductive polymers, or mixtures thereof.

[0058] The conductive material contained in the intermediate functional layer 12 can be any material as long as it is an electron conductive material that does not cause a chemical change in the battery containing it. For example, carbon-based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based substances in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof can be used.

[0059] The first active material layer 13 can be formed by dispersing an electrode composite material containing a positive electrode active material, a binder, a conductive material, etc. in a solvent to form a slurry, applying this slurry to at least one surface of the first substrate 11, and then drying and compressing it.

[0060] The first active material layer 13 contains a positive electrode active material, and as the positive electrode active material, a compound capable of reversible insertion and desorption of lithium (lithium - ion intercalation compound) can be used.

[0061] Examples of the positive electrode active material include compounds represented by any of the following chemical formulas: Li a A 1-b X b D2(0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5); Li a A 1-b X b O 2-c D c (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li a E 1-b X b O 2-c D c (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li a E 2-b X b O 4-c D c (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li a Ni 1-b-c Co b X c D α (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.5, 0 < α ≦ 2); Li a Ni 1-b-c Co b X c O 2-α T α (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 < α < 2); Li a Ni1-b-c Co b X c O 2-α T2(0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b X c D α (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 < α ≦ 2); Li a Ni 1-b-c Mn b X c O 2-α T α (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b X c O 2-α T2(0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 < α < 2); Li a Ni b E c G d O2(0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0.001 ≦ d ≦ 0.1); Li a Ni b Co c Mn d G e O2(0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.5, 0.001 ≦ e ≦ 0.1); Li a NiG b O2(0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); Li a CoG b O2(0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); Li a Mn 1-b G b O2(0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); Li a Mn2G bO4 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-g G g PO4 (0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5); QO2; QS2; LiQS2; V2O5; LiV2O5; LiZO2; LiNiVO4; Li (3-f) J2(PO4)3 (0 ≤ f ≤ 2; Li (3-f) Fe2(PO4)3 (0 ≤ f ≤ 2; Li a FePO4 (0.90 ≤ a ≤ 1.8.

[0062] In the above chemical formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

[0063] Of course, those having a coating layer on the surface of the compound can also be used, or the compound and the compound having a coating layer can be mixed and used. This coating layer can contain at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compounds forming these coating layers may be amorphous or crystalline. Examples of the coating elements contained in the coating layer include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or combinations thereof. The coating layer forming process can use a method that does not adversely affect the physical properties of the active material in the active material layer, such as spray coating, dipping method, etc.

[0064] As an example of the positive electrode active material, a positive electrode active material represented by the following chemical formula A1 can be included: [Chemical formula A1] Li a11 Ni x11 M 11 y11 M 12 1-x11-y12 O2

[0065] In chemical formula A1, 0.9 ≦ a11 ≦ 1.8, 0.3 ≦ x11 ≦ 1, 0 ≦ y11 ≦ 0.7, and M 11 and M 12 are each independently selected from Al, B, Ce, Co, Cr, F, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, and combinations thereof.

[0066] In Chemical Formula A1, 0.4 ≦ x11 ≦ 1 and 0 ≦ y11 ≦ 0.6 may hold, or 0.5 ≦ x11 ≦ 1 and 0 ≦ y11 ≦ 0.5, or 0.6 ≦ x11 ≦ 1 and 0 ≦ y11 ≦ 0.4, or 0.7 ≦ x11 ≦ 1 and 0 ≦ y11 ≦ 0.3, or 0.8 ≦ x11 ≦ 1 and 0 ≦ y11 ≦ 0.2, or 0.9 ≦ x11 ≦ 1 and 0 ≦ y11 ≦ 0.1 may hold.

[0067] As a specific example, the positive electrode active material may include a lithium nickel cobalt composite oxide represented by the following Chemical Formula A2. [Chemical Formula A2] Li a12 Ni x12 Co y12 M 13 1-x12-y12 O2

[0068] In Chemical Formula A2, 0.9 ≦ a12 ≦ 1.8, 0.3 ≦ x12 < 1, 0 < y12 ≦ 0.7, and M 13 is selected from Al, B, Ce, Cr, F, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, and combinations thereof.

[0069] In Chemical Formula A2, 0.3 ≦ x12 ≦ 0.99 and 0.01 ≦ y12 ≦ 0.7 may hold, or 0.4 ≦ x12 ≦ 0.99 and 0.01 ≦ y12 ≦ 0.6, or 0.5 ≦ x12 ≦ 0.99 and 0.01 ≦ y12 ≦ 0.5, or 0.6 ≦ x12 ≦ 0.99 and 0.01 ≦ y12 ≦ 0.4, or 0.7 ≦ x12 ≦ 0.99 and 0.01 ≦ y12 ≦ 0.3, or 0.8 ≦ x12 ≦ 0.99 and 0.01 ≦ y12 ≦ 0.2, or 0.9 ≦ x12 ≦ 0.99 and 0.01 ≦ y12 ≦ 0.1 may hold.

[0070] As a specific example, the positive electrode active material may include a lithium nickel cobalt composite oxide represented by the following Chemical Formula A3. [Chemical Formula A3] Li a13 Ni x13 Co y13 M 14z13 M 15 1-x13-y13-z13 O2

[0071] In Chemical Formula A3, 0.9 ≦ a13 ≦ 1.8, 0.3 ≦ x13 ≦ 0.98, 0.01 ≦ y13 ≦ 0.69, 0.01 ≦ z13 ≦ 0.69, and M 14 is selected from Al, Mn, and combinations thereof, and M 15 is selected from B, Ce, Cr, F, Mg, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, and combinations thereof.

[0072] In Chemical Formula A3, it may be that 0.4 ≦ x13 ≦ 0.98, 0.01 ≦ y13 ≦ 0.59, and 0.01 ≦ z13 ≦ 0.59, or 0.5 ≦ x13 ≦ 0.98, 0.01 ≦ y13 ≦ 0.49, and 0.01 ≦ z13 ≦ 0.49, or 0.6 ≦ x13 ≦ 0.98, 0.01 ≦ y13 ≦ 0.39, and 0.01 ≦ z13 ≦ 0.39, or 0.7 ≦ x13 ≦ 0.98, 0.01 ≦ y13 ≦ 0.29, and 0.01 ≦ z13 ≦ 0.29, or 0.8 ≦ x13 ≦ 0.98, 0.01 ≦ y13 ≦ 0.19, and 0.01 ≦ z13 ≦ 0.19, or 0.9 ≦ x13 ≦ 0.98, 0.01 ≦ y13 ≦ 0.09, and 0.01 ≦ z13 ≦ 0.09.

[0073] The first active material layer 13 contains the positive electrode active material and may further contain a binder and / or a conductive material. Here, the content of the positive electrode active material is 90% to 98% by weight based on the total weight of the positive electrode active material layer, and may be, for example, 90% to 95% by weight. The contents of the binder and the conductive material may each be 1% to 5% by weight based on the total weight of the positive electrode active material layer.

[0074] The binder can make the positive electrode active material particles adhere well to each other and also make the positive electrode active material adhere well to the functional layer or the substrate, and is the same as the binder constituting the intermediate functional layer 12.

[0075] The conductive material is used to impart conductivity to the electrode and is the same as the conductive material constituting the first functional layer 12.

[0076] The first electrode blank part (LA2) is located at the tip of the first electrode 121. Since a separate material layer was formed on the first base material 11, the surface of the first base material 11 is exposed, and the first electrode tap 14 for drawing current to the outside can be connected onto the first base material 11.

[0077] The first electrode tap 14 can be connected to the first electrode blank part (LA2) by ultrasonic welding, laser welding, or resistance welding methods and can protrude outside the first electrode blank part (LA2).

[0078] The first electrode tap 14 can contain aluminum similar to the first base material 11, and the thickness of the first electrode tap 14 may be 12 μm or less.

[0079] A protective tape 70 for protecting the first electrode tap 14 is attached onto the first electrode tap 14. The protective tape 70 is also formed together on the other surface (B) of the base material 11 where the first electrode tap 14 is not formed and can extend to cover one side end of the first functional layer 12 and the first active material layer 13. Additionally, a protective tape 74 may be formed to cover the exposed base material 11 between the first active material layer 13 and the first electrode tap 14 so as not to be short-circuited with the second electrode 122.

[0080] The first finishing part (LA3) is located at the terminal of the first electrode 121 that is relatively far from the winding shaft and includes the first base material 11 and the terminal functional layer 15 formed on the first base material 11. The terminal functional layers 15, 16 contain an insulating ceramic material, are located at a certain distance from one end of the first active material layer 13, and are respectively located on one surface (A) and the other surface (B) of the first base material. The terminal functional layer 15 formed on one surface (A) of the first base material 11 is formed relatively longer than the terminal functional layer 15 formed on the other surface (B), and the first finishing part (LA3) on the other surface (B) may be wound around the electrode assembly at least once or more.

[0081] The terminal functional layers 15 and 16 are made of materials with relatively higher resistance than the base material 11. When an external impact occurs, the terminal functional layers 15 and 16 are located between the base materials, which can prevent the battery from short-circuiting due to the external impact.

[0082] The terminal functional layers 15 and 16 can contain ceramics and binders.

[0083] The ceramics can include endothermic ceramics such as pseudoboehmite and boehmite; general ceramics such as aluminum oxide (AlO3, Al2O3, etc.), silicon dioxide (SiO2), magnesium oxide (MgO), titanium dioxide (TiO2), hafnium oxide (HfO2), tin oxide (SnO), cerium (IV) oxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), silicon carbide (SiC); or combinations thereof.

[0084] General ceramics are insulating materials with only insulating properties, and endothermic ceramics are endothermic materials with insulating and endothermic properties.

[0085] The binder can include a water-insoluble binder, a water-soluble binder, or a combination thereof.

[0086] The binder makes the substances in the ceramic layer adhere well to each other and enables the ceramic layer to adhere well to the base material.

[0087] Examples of the water-insoluble binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, ethylene-propylene copolymer, polystyrene, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0088] Examples of the water-soluble binder include a rubber-based binder or a polymer resin binder. The rubber-based binder may be selected from styrene-butadiene rubber (SBR), acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber (ABR), acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0089] When a water-soluble binder is used as the binder, a cellulose-based compound capable of imparting viscosity can be further included. As this cellulose-based compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof can be mixed and used. As the alkali metal, Na, K, or Li can be used.

[0090] On the other hand, since the terminal functional layer 15 is formed by being wound around the electrode assembly at least once or more, the first terminal functional layer 15 formed on one surface and the second terminal functional layer 16 formed on the other surface can face each other. As shown in FIGS. 2 and 4, the gap (S) between the first active material layer 13 formed on one surface and the first terminal functional layer 15 and the second terminal functional layer 16 formed on the other surface can face each other (F in FIG. 2).

[0091] A step compensation layer 80 can be further formed on the second terminal functional layer 16. The first terminal functional layer 15 and the first active material layer 13 are spaced apart from each other, and the step compensation layer 80 can correspond to the gap (S) between the first terminal functional layer 15 and the first active material layer 13.

[0092] Therefore, in the winding type electrode assembly, the step compensation layer 80 can be in a form inserted into the gap (S). The step compensation layer 80 can be formed by additionally applying a ceramic for forming the second terminal functional layer 16 at a position corresponding to the gap (S) after forming the second terminal functional layer 16.

[0093] By being formed by applying the ceramic, the step compensation layer 80 becomes narrower from the lower part to the upper part.

[0094] The electrolyte filled in the empty space formed by the gap (S) contacts the second terminal functional layer 16 and reacts with the ceramic contained in the second terminal functional layer 16 to generate ceramic precipitates, whereby the second terminal functional layer 16 can be discolored.

[0095] In the present invention, the step compensation layer 80 can fill the empty space formed by the gap (S) to minimize the penetration of the electrolyte. Therefore, the reaction between the electrolyte and the ceramic can be minimized, and discoloration of the terminal functional layer can be prevented.

[0096] In FIG. 4, the step compensation layer 80 is shown as a cross section, but it is not limited thereto. In order to fill the empty space having different widths due to the difference in the sizes of the lower functional layer 12 and the first active material layer 13, the step compensation layer 80 can have a stepped structure as shown in FIG. 5.

[0097] FIGS. 6(a) to (c) are (a) a plan view seen from a first direction for explaining the second electrode of the electrode assembly shown in FIG. 2, (b) a plan view seen from a direction opposite to the first plan view, and (c) a cross-sectional view.

[0098] The plan view seen from the first direction in FIG. 6(a) shows one side of the second electrode, FIG. 6(b) is a plan view of the other side seen from a direction opposite to the first plan view, and the cross-sectional view in FIG. 6(c) is a cross-sectional view shown by cutting along the line C2-C2' in FIGS. 6(a) and (b).

[0099] Referring to FIGS. 6(a) to 6(c), the second electrode active part (LB1) includes a second substrate 21 and a second active material layer 22 formed on the second substrate 21.

[0100] The second active material layer 22 is formed on one or both surfaces of the substrate, and the lengths of the second electrode active parts (LB1) formed on one surface (A) and the other surface (B) of the substrate 21 may be different from each other.

[0101] The second non-coated electrode part (LB2) is located at the tip and the end of the second electrode, respectively. No separate material layer is formed on the second substrate 21, the surface of the second substrate 21 is exposed, and a second electrode tap 23 for drawing current to the outside can be connected.

[0102] The second electrode tap 23 can be connected to the second non-coated electrode part (LB2) by ultrasonic welding, laser welding or resistance welding methods, and can protrude outside the second non-coated electrode part (LB2). The second electrode tap 23 may be made of nickel.

[0103] A protective tape 70 is formed on the second electrode tap 23, and the protective tape 70 can also be formed together on the other surface (B) of the substrate 21 where the second electrode tap 23 is not formed. In the wound state, a protective tape 75 can also be attached to the part where the substrates of different polarities can contact each other to prevent short circuit.

[0104] The second substrate 21 provides a charge transfer path generated in the second active material layer 22 and supports the second active material layer 22.

[0105] The second electrode 122 may be a negative electrode, and the second substrate 21 may be a metal thin plate with excellent conductivity, such as copper foil or nickel foil, or may have a mesh structure. The second active material layer 22 can be formed by dispersing a solvent in an electrode composite material composed of a negative electrode active material, a binder, a conductive material, etc. to form a slurry, and then applying this to at least one surface of the second substrate 21, and then drying and compressing.

[0106] The negative electrode active material of the second active material layer 22 can use a material capable of reversibly inserting / desorbing lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

[0107] Examples of the material capable of reversibly inserting / desorbing the lithium ions include carbon materials, that is, carbon-based negative electrode active materials generally used in lithium secondary batteries. Representative examples of the carbon-based negative electrode active materials include crystalline carbon, amorphous carbon, or these can be used together. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0108] As the alloy of the lithium metal, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn is used.

[0109] Examples of the material capable of doping and undoping lithium include Si, SiO x(0 < x < 2), Si-Q alloy (where Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Si-carbon composite, Sn, SnO2, Sn-R (where R is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), Sn-carbon composite, etc. may be mentioned, and at least one of these and SiO2 can also be mixed and used. As the elements Q and R, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof can be used.

[0110] As the transition metal oxide, lithium titanate can be used.

[0111] Referring again to FIGS. 1 and 2, the separation membrane 123 is located between the first electrode 121 and the second electrode 122 and prevents a short circuit between them.

[0112] The separation membrane 123 can be formed of a porous film having high ion permeability and mechanical strength. For example, it can be formed of an olefin-based polymer such as polyethylene or polypropylene. The separation membrane is formed to extend more than the first electrode active part (LA1) or the second electrode active part (LB1) along the length direction or the width direction, and can prevent a short circuit from occurring between the first electrode active part (LA1) and the second electrode active part (LB1) due to thermal shrinkage.

[0113] The electrode assembly 100 can be placed in a pouch-type case 200 together with an electrolyte. The pouch-type case can be formed of a laminated exterior material, and the exterior material can include a lower exterior material 201 and an upper exterior material 202. After placing the electrode assembly 100 between them, they are heat-sealed by heat fusion.

[0114] The laminated exterior material can be formed, for example, in a multilayer structure having a first insulating layer 2, a metal layer 3, and a second insulating layer 4. Of course, various adhesive layers and functional layers may be further added in addition to this.

[0115] The first insulating layer 2 is formed of a material having insulating and thermally adhesive properties on the inner surface of the laminated exterior material, and in a state where the electrode assembly 100 is accommodated, the edges can be heat-sealed to be sealed. Further, the first insulating layer 2 is formed on one surface of the metal layer 3 and forms the inner surface of the laminated exterior material facing the electrode assembly 100. The first insulating layer 2 can be formed of non-stretched polypropylene (casted polypropylene: CPP) or its equivalent that does not react with the electrolyte.

[0116] In the above embodiments, an example was described in which there is no separator and a second electrode in the outermost shell of the electrode assembly, and the first electrode is wound one or more times, but it is not limited to this. As shown in FIGS. 7 and 9, a separator or a second electrode can be located.

[0117] FIGS. 7 and 9 are cross-sectional views of an electrode assembly according to another embodiment of the present invention, FIG. 8 is an enlarged cross-sectional view showing a part of FIG. 7, and FIG. 10 is an enlarged cross-sectional view showing a part of FIG. 9.

[0118] Since FIGS. 7 to 10 are the same as the electrode assemblies of FIGS. 1 to 3, only the different parts will be specifically described.

[0119] As shown in FIGS. 7 to 10, a separator and a non-patterned portion of the first electrode are wound one or more times around the outermost shell of the electrode assembly, and the step compensation layer 80 can be inserted into the gap (S) between the first terminal functional layer 15 and the first active material layer 13.

[0120] At this time, as shown in FIGS. 7 and 8, the separation film 123 located between the step compensation layer 80 and the gap (S) is inserted into the gap (S) together, or as shown in FIGS. 9 and 10, the separation film 123 and the second electrode blank portion (LB2) located between the step compensation layer 80 and the gap (S) are inserted together.

[0121] Therefore, as shown in FIGS. 7 to 10, when the separation film 123 or the second electrode blank portion (LB2) is located between the step compensation layer 80 and the gap (S), the step compensation layer 80 may not be completely inserted into the gap (S) due to the thickness of the separation film 123 or the second electrode blank portion (LB2).

[0122] In this way, even if the step compensation layer 80 is not completely inserted, the separation film 123 or the second electrode blank portion (LB2) fills the empty space due to the gap (S), so that the electrolyte can be prevented from staying in the empty space. Therefore, it is possible to prevent the electrolyte filled in the empty space from reacting with the ceramic in the second terminal functional layer 16 and discoloring.

[0123] As shown in FIGS. 7 to 10, when the separation film 123 or the second electrode blank portion (LB2) is located between the step compensation layer 80 and the gap (S), the height of the step compensation layer 80 can be reduced by the thickness of the separation film 123 or the second electrode blank portion (LB2) so that the step compensation layer 80 can be completely inserted into the gap (S).

[0124] As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited thereto, and various modifications can be made and implemented within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and it is natural that these also belong to the scope of the present invention.

Description of Reference Numerals

[0125] 11: First base material 12: First functional layer 13: First active material layer 14: First electrode tab 15: Second functional layer 21: Second base material 22: Second active material layer 23: Second electrode tab 70: Protection tape 100: Electrode assembly 121: First electrode 122: Second electrode 200: Pouch 1000: Secondary battery

Claims

1. In a wound-type electrode assembly including a first electrode, a separator, and a second electrode, the first electrode includes a first substrate, a front first active material layer and a rear first active material layer respectively provided on at least the front surface and the rear surface of the first substrate, a first terminal functional layer and a second terminal functional layer respectively formed on the front surface and the rear surface of the first substrate at a certain distance from the front first active material layer and the rear first active material layer, a step compensation layer positioned above the second terminal functional layer and corresponding to the gap between the front first active material layer and the first terminal functional layer and includes the first terminal functional layer is wound around the electrode assembly at least once or more.

2. The electrode assembly according to claim 1, wherein the step compensation layer is made of the same material as the second terminal functional layer.

3. The electrode assembly according to claim 1, wherein the first terminal functional layer and the second terminal functional layer contain a ceramic material.

4. The electrode assembly according to claim 1, wherein the thickness of the step compensation layer is the same as or smaller than the thickness of the front first active material layer.

5. An intermediate functional layer respectively formed between the first substrate and the front first active material layer and between the first substrate and the rear first active material layer The electrode assembly according to claim 1, further comprising.

6. The electrode assembly according to claim 5, wherein the intermediate functional layer is formed larger than the front first active material layer and the rear first active material layer respectively, and extends from the front first active material layer and the rear first active material layer toward the first terminal functional layer and the second terminal functional layer.

7. The electrode assembly according to claim 6, wherein the step compensation layer is formed in multiple stages.

8. The electrode assembly according to claim 1, wherein the separator is wound around the electrode assembly at least once or more together with the second terminal functional layer and is positioned between the gap and the step compensation layer.

9. The electrode assembly according to claim 8, wherein the electrode blank portion of the second electrode is wound around the electrode assembly at least once or more together with the second terminal functional layer and the separator and is positioned between the gap and the step compensation layer.

10. The electrode assembly according to claim 1, wherein the step compensation layer becomes narrower as it is farther from the first substrate.

11. The first electrode is a positive electrode, The second electrode is a negative electrode. The electrode assembly according to claim 1.

12. The electrode assembly according to any one of claims 1 to 11, a case containing the electrode assembly and an electrolytic solution A secondary battery comprising.

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