Electrode assembly and secondary battery including the same

Abstract

Disclosed are an electrode assembly and a secondary battery including the same. The electrode assembly comprises a first electrode, a diaphragm and a second electrode, the first electrode includes a first substrate having a front surface and a rear surface, a front first active material layer on the front surface, and a rear first active material layer on the rear surface, a first end functional layer on the front surface and spaced apart from the front first active material layer, a second end functional layer on the rear surface and spaced apart from the rear first active material layer, and a step compensation layer on the second end functional layer and corresponding to a gap between the front first active material layer and the first end functional layer, the first end functional layer is wound around the electrode assembly at least once.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to an electrode assembly, for example, an electrode assembly for a secondary battery and a secondary battery including the same. Background Art

[0002] A secondary battery (e.g., a lithium battery) is an electric power storage system that provides excellent or desired (e.g., relatively high) energy density by converting electrical energy into chemical energy. Compared with a primary battery that cannot be recharged, a secondary battery can be recharged and is widely used in Internet technology (IT) devices such as smart phones, laptop computers, and / or tablet PCs.

[0003] Recently, due to environmental problems and fossil fuel depletion problems, interest in electric vehicles has increased, and thus, there is a trend to use secondary batteries in electric vehicles.

[0004] According to this trend, it is desirable and / or required that secondary batteries have characteristics such as relatively high density (e.g., energy density), high power, and safety.

[0005] However, secondary batteries have an increased risk of fire, rupture, and explosion due to external shock or charge and discharge, and thus, it is also desirable and / or required to install an appropriate safety device.

[0006] To improve the safety of secondary batteries, a ceramic layer may be additionally formed on an uncoated area at a distal end of the electrode assembly.

[0007] However, as the usage time of the secondary battery increases, precipitates may be generated on the ceramic layer, resulting in discoloration of a part of the ceramic layer.

[0008] The above-disclosed information is only intended to enhance the understanding of the background of the described technology, and thus it may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0009] Aspects of one or more embodiments of the present disclosure relate to an electrode assembly and a secondary battery including the electrode assembly, the electrode assembly being capable of preventing or reducing discoloration of a ceramic layer to improve the safety of the secondary battery.

[0010] Additional aspects will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the presented embodiments of the disclosure.

[0011] A wound or wound-type electrode assembly according to one or more embodiments of the present disclosure includes a first electrode, a separator, and a second electrode, wherein the first electrode includes a first substrate including a front surface and a rear surface, a front first active material layer on the front surface, a rear first active material layer on the rear surface, a first distal functional layer on the front surface and spaced apart from the front first active material layer, a second distal functional layer on the rear surface and spaced apart from the rear first active material layer, and a step compensation layer disposed on the second distal functional layer and corresponding to the gap between the front first active material layer and the first distal functional layer, wherein the first distal functional layer winds (e.g., wraps) around the electrode assembly at least once.

[0012] In one or more embodiments, the step compensation layer may be made of the same material as the second distal functional layer.

[0013] In one or more embodiments, the first distal functional layer and the second distal functional layer may include a ceramic material.

[0014] In one or more embodiments, the thickness of the step compensation layer may be equal to or less than the thickness of the front first active material layer.

[0015] In one or more embodiments, the electrode assembly may further include intermediate functional layers between the first substrate and the front first active material layer and between the first substrate and the rear first active material layer, respectively.

[0016] In one or more embodiments, the intermediate functional layers may be larger than the front first active material layer and the rear first active material layer, respectively, and may extend (e.g., stretch) from the front first active material layer and the rear first active material layer toward the first distal functional layer and the second distal functional layer, respectively.

[0017] In one or more embodiments, the step compensation layer may be formed in multiple levels (e.g., may have a stepped structure).

[0018] In one or more embodiments, the separator may wind around the electrode assembly at least once together with the second distal functional layer, and the separator may be disposed between the gap and the step compensation layer.

[0019] In one or more embodiments, the uncoated electrode region of the second electrode may wind around the electrode assembly at least once together with the second distal functional layer and the separator, and the uncoated electrode region of the second electrode may be disposed between the gap and the step compensation layer.

[0020] In one or more embodiments, as the step compensation layer moves away from the first substrate (e.g., extends), the width of the step compensation layer may decrease.

[0021] In one or more embodiments, the first electrode may be a positive electrode and the second electrode may be a negative electrode.

[0022] By forming a step compensation layer as in one or more embodiments of the present disclosure, an electrode assembly capable of reducing the generation of precipitates in the ceramic layer and the resulting discoloration phenomenon can be provided, and a secondary battery including the electrode assembly can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic exploded perspective view of a secondary battery according to one or more embodiments of the present disclosure.

[0024] Figure 2 is according to one or more embodiments of the present disclosure Figure 1 schematic cross-sectional view of the electrode assembly.

[0025] Figure 3 shows a plan view and a cross-sectional view of a first electrode of an electrode assembly shown in Figure 2 for describing the electrode assembly according to one or more embodiments of the present disclosure.

[0026] Figure 4 and Figure 5 are both enlarged cross-sectional views of part F of Figure 2 according to one or more embodiments of the present disclosure.

[0027] Figure 6 is for describing Figure 2 a plan view and a cross-sectional view of a second electrode of the electrode assembly shown in

[0028] Figure 7 is a cross-sectional view of an electrode assembly according to one or more embodiments of the present disclosure.

[0029] Figure 8 is according to one or more embodiments of the present disclosure Figure 7 enlarged cross-sectional view of part F of

[0030] Figure 9 is a cross-sectional view of an electrode assembly according to one or more embodiments of the present disclosure.

[0031] Figure 10 is according to one or more embodiments of the present disclosure Figure 9 enlarged cross-sectional view of part F of DETAILED DESCRIPTION

[0032] The present disclosure may be modified in many alternative forms, and specific embodiments will be shown in the drawings and described in more detail. However, it should be understood that this is not intended to limit the present disclosure to the specific forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure.

[0033] Hereinafter, example embodiments will be described in more detail with reference to the drawings. However, the present disclosure may be implemented in various different forms and should not be construed as limited to the embodiments shown herein. Instead, these embodiments are provided as examples so that the present disclosure will be thorough and complete, and will fully convey the aspects and features of the present disclosure to those skilled in the art. Accordingly, processes, elements, and techniques that are not necessary for those of ordinary skill in the art to fully understand the aspects and features of the present disclosure may not be described.

[0034] It will also be understood that when used in this specification, the terms "comprises", "comprising", "has", "having", and variations thereof specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0035] In addition, for ease of understanding the present disclosure, the drawings may not be drawn to scale, but some component dimensions may be exaggerated for clarity. Additionally, unless otherwise stated, the same reference numerals represent the same elements throughout the drawings and the written description, and thus, their repeated description may not be provided.

[0036] It will be understood that although the terms "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, the first element, component, region, layer, or part described below may be referred to as the second element, component, region, layer, or part without departing from the scope of the present disclosure.

[0037] As used herein, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" are also intended to include the plural forms.

[0038] For ease of explanation, spatial relative terms such as "on", "under", "below", "beneath", "above", "over", "front", "rear", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to another (other) element or feature. It will be understood that the spatial relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings. For example, if the device in the drawings is flipped, an element described as "under" or "beneath" or "below" another element or feature will then be positioned "above" the said other element or feature. Thus, the example terms "under" and "beneath" and "below" can include both an orientation of above and below. The device may be otherwise positioned (e.g., rotated 90 degrees or at other orientations), and the spatial relative descriptors used herein should be interpreted accordingly.

[0039] It will be understood that when an element such as a region, layer, film, zone, or portion is referred to as being "on", "connected to", or "bonded to" another element, the element may be directly on, directly connected to, or bonded to the other element, or there may be one or more intervening elements. Additionally, it will also be understood that when an element is referred to as being "between" two elements, the element may be the only element between the two elements, or there may also be one or more intervening elements.

[0040] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the disclosure.

[0041] As used herein, the term "and / or" includes any combination and all combinations of one or more of the associated listed items.

[0042] The description of features or aspects within each embodiment should generally be considered applicable to other similar features or aspects in other embodiments. Additionally, as used herein, the terms "use" and its variants may be considered to be synonymous with the terms "utilize" and its variants, respectively.

[0043] Hereinafter, a secondary battery according to one or more embodiments of the present disclosure will be described in more detail with reference to the drawings.

[0044] Figure 1 is a schematic exploded perspective view of a secondary battery according to one or more embodiments of the present disclosure, Figure 2 is according to one or more embodiments of the present disclosure Figure 1 a schematic cross-sectional view of an electrode assembly of Figure 3 including a plan view and a cross-sectional view of a first electrode of an electrode assembly for describing Figure 2 shown inFigure 4 and Figure 5 are both enlarged cross-sectional views of part F according to one or more embodiments of the present disclosure Figure 2 of the secondary battery 1000.

[0045] According to one or more embodiments of the present disclosure, Figure 3 a plan view of each of a surface A and another surface B of the first electrode is shown, and the cross-sectional view is a cross-sectional view taken along line C1-C1' in Figure 3 .

[0046] As shown in Figure 1 , a secondary battery 1000 according to one or more embodiments of the present disclosure includes an electrode assembly 100 and a housing 200.

[0047] Referring to Figure 1 and Figure 2 , the electrode assembly 100 includes a first electrode 121, a second electrode 122, and a separator 123 disposed between the first electrode and the second electrode. The separator 123 is for insulation, and the electrode assembly 100 may be stacked in the following order: the first electrode 121, the separator 123, the second electrode 122, and the separator 123.

[0048] The electrode assembly 100 may be in the form of a pole core in which the first electrode 121, the separator 123, and the second electrode 122 are stacked and wound around a winding axis XL. If desired and / or necessary, the electrode assembly 100 may be wound and flattened, and a cross-section cut in a vertical direction intersecting the winding axis XL may have an elliptical shape that is long in one direction.

[0049] Therefore, the electrode assembly 100 may include a relatively flat flat portion P1 in a cross-sectional view (e.g., along the thickness direction of the electrode assembly) and a relatively circular curved portion P2 in a cross-sectional view (e.g., along the thickness direction of the electrode assembly). The flat portion P1 may be a portion where the electrode assembly 100 is pressed after being wound, and the curved portion P2 may connect two opposite flat portions P1. In the electrode assembly 100, one turn may include a pair of opposite flat portions and a pair of curved portions connecting to the ends of the flat portion P1.

[0050] For example, referring to Figure 2 , Figure 3 and Figure 6 , the first electrode 121 includes a first electrode active portion LA1, and a first electrode uncoated region LA2 and a first termination portion LA3 disposed on opposite sides of the first electrode active portion LA1. The second electrode 122 includes a second electrode active portion LB1 and a second electrode uncoated region LB2 disposed on opposite sides of the second electrode active portion LB1.

[0051] In the following, if (for example, when) a strip-shaped (for example, formed in a rectangular or oval shape, where the length of the rectangle or oval is substantially longer than the width) first electrode and a second electrode are wound around a winding axis XL, the end adjacent to the winding axis XL is referred to as the front end and the end arranged relatively far (for example, at the end opposite to the front end) is referred to as the distal end.

[0052] Referring to Figure 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.

[0053] The intermediate functional layer 12 and the first active material layer 13 are formed on the surface (for example, one surface or two surfaces (for example, opposite surfaces)) of the first substrate such that the lengths of the first electrode active portions LA1 formed on one surface A and the other surface B of the first substrate 11 can be different. For example, on one surface A, the intermediate functional layer 12 is formed larger (for example, longer) than the first active material layer 13 and extends from the first active material layer 13 toward the distal functional layer 15, and on the other surface B, the intermediate functional layer 12 is formed larger (for example, longer) than the first active material layer 13 and extends from the first active material layer 13 toward the distal functional layer 16.

[0054] The first substrate 11 provides a channel for the movement of charges generated in the first active material layer 13 and supports the first active material layer 13.

[0055] The first electrode 121 can be a positive electrode, and the first substrate 11 can have a metal thin plate (for example, aluminum foil) or a mesh structure having excellent or suitable conductivity.

[0056] The intermediate functional layer 12 can include a material containing a compound represented by the following Chemical Formula 1, a compound represented by the following Chemical Formula 2, and / or a combination thereof (for example, any suitable combination): Chemical Formula 1 Li a1 M 1 x1 Fe 1-x1 PO4 In Chemical Formula 1, 0.90 ≤ a1 ≤ 1.5, 0 ≤ x1 ≤ 0.4, M 1 is Mg, Co, Ni, and / or a combination thereof (for example, any suitable combination).

[0057] Chemical Formula 2 Li a2 Mn x2 Fe 1-x2 PO4 In Chemical Formula 2, 0.90 ≤ a2 ≤ 1.5 and 0.1 ≤ x2 ≤ 1.

[0058] The compound represented by Chemical Formula 1 can be a lithium iron phosphate compound. The molar fraction of lithium in Chemical Formula 1 can be appropriately or suitably adjusted between about 0.9 and 1.5 - for example, 0.90 ≤ a1 ≤ 1.2 or 0.95 ≤ a1 ≤ 1.1. In Chemical Formula 1, Mn can be present in addition to Fe, and the molar fraction of Mn can be 0 ≤ x1 ≤ 0.7, 0 ≤ x1 ≤ 0.5, 0 ≤ x1 ≤ 0.3, 0 ≤ x1 ≤ 0.1, or 0 ≤ x1 ≤ 0.05.

[0059] The compound represented by Chemical Formula 2 can be a lithium manganese iron phosphate compound. In Chemical Formula 2, the molar fraction of lithium can be 0.90 ≤ a2 ≤ 1.2 or 0.95 ≤ a2 ≤ 1.1 as in Chemical Formula 1. In Chemical Formula 2, the molar fraction of manganese can be 0.2 ≤ x2 ≤ 0.9, 0.3 ≤ x2 ≤ 0.9, or 0.4 ≤ x2 ≤ 0.8. Specifically, if (for example, when) 0.5 ≤ x2 ≤ 0.9, the lithium ion conduction ability is high.

[0060] For example, the intermediate functional layer 12 is a lithium transition metal phosphate and can include LiFePO4, LiMn 0.5 Fe 0.5 PO4 and / or LiMnPO4, etc.

[0061] The intermediate functional layer 12 can include one or more of the above materials and can also include a binder and / or a conductive material. Here, based on the total weight of the intermediate functional layer 12, the content (for example, amount) of the above materials can be 80 wt% to 97 wt%, the content (for example, amount) of the binder can be 1 wt% to 10 wt%, and the content (for example, amount) of the conductive material is 0.5 wt% to 10 wt%.

[0062] The binder that can easily adhere the material particles in the intermediate functional layer to each other and adhere the material particles to the substrate can include a water-insoluble binder, a water-soluble binder, and / or a combination thereof (for example, any suitable combination).

[0063] The water-insoluble binder can be selected from polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide, polyimide, and / or a combination thereof (for example, any suitable combination).

[0064] The water-soluble binder can be a rubber-based binder or a polymer resin binder. The rubber-based binder can be selected from styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber (ABR), acrylic rubber, butyl rubber, fluororubber, and / or a combination thereof (e.g., any suitable combination). The polymer resin binder can be selected from polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin polymer, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and / or a combination thereof (e.g., any suitable combination).

[0065] When the water-soluble binder is used as a binder, a cellulose compound can also be used to provide viscosity. The cellulose compound includes one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and / or their alkali metal salts. The alkali metal can be Na, K, or Li.

[0066] The conductive material is used to provide conductivity to the electrode, and the conductive material can include carbon materials, metal materials, conductive polymers, and / or a mixture thereof (e.g., any suitable mixture).

[0067] The conductive material included in the intermediate functional layer 12 can be any electron-conducting material that does not cause a chemical change in the battery containing the conductive material. For example, the conductive material can include carbon materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and / or carbon fiber; metal materials of metal powder or metal fiber, including copper, nickel, aluminum, and / or silver; conductive polymers such as polyphenylene derivatives; or any mixture thereof.

[0068] The first active material layer 13 can be formed by dispersing an electrode mixture containing a positive electrode active material, a binder, and / or a conductive material in a solvent to form a slurry, then applying the slurry to at least one surface of the first substrate 11, and subsequently drying and pressing.

[0069] The first active material layer 13 includes a positive electrode active material, and a compound capable of reversibly inserting and extracting lithium (reversible insertion compound) can be used as the positive electrode active material.

[0070] Examples of the positive electrode active material include compounds represented by any one or more (e.g., at least one) selected from 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 bO 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 Ni 1-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 O2-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 b O4 (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); and / or Li a FePO4 (0.90 ≤ a ≤ 1.8).

[0071] In the above chemical formula, A is selected from the group consisting of Ni, Co, Mn, and their (e.g., any suitable) combinations; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and their (e.g., any suitable) combinations; D is selected from the group consisting of O, F, S, P, and their (e.g., any suitable) combinations; E is selected from the group consisting of Co, Mn, and their (e.g., any suitable) combinations; T is selected from the group consisting of F, S, P, and their (e.g., any suitable) combinations; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and their (e.g., any suitable) combinations; Q is selected from the group consisting of Ti, Mo, Mn, and their (e.g., any suitable) combinations; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and their (e.g., any suitable) combinations; and J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and their (e.g., any suitable) combinations.

[0072] The compound may have a coating layer on its surface or may be mixed with another compound having a coating layer. The coating layer may include at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides of coating elements, hydroxyoxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compound for the coating layer may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, and / or their (e.g., any suitable) combinations. The coating layer forming process may use methods that have no adverse effects on the properties of the active material - such as spraying, dipping, etc.

[0073] Examples of the positive electrode active material may include a positive electrode active material represented by the following chemical formula A1: Chemical formula A1 Li a11 Ni x11 M 11 y11 M 12 1-x11-y11 O2 In chemical formula A1, 0.9 ≤ a11 ≤ 1.8, 0.3 ≤ x11 ≤ 1, 0 ≤ y11 ≤ 0.7, and M 11 and M 12 may each independently be selected from Al, B, Ce, Co, Cr, F, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, and / or their (e.g., any suitable) combinations.

[0074] In Chemical Formula A1, the ranges can be: 0.4 ≤ x11 ≤ 1 and 0 ≤ y11 ≤ 0.6, 0.5 ≤ x11 ≤ 1 and 0 ≤ y11 ≤ 0.5, 0.6 ≤ x11 ≤ 1 and 0 ≤ y11 ≤ 0.4, 0.7 ≤ x11 ≤ 1 and 0 ≤ y11 ≤ 0.3, 0.8 ≤ x11 ≤ 1 and 0 ≤ y11 ≤ 0.2, or 0.9 ≤ x11 ≤ 1 and 0 ≤ y11 ≤ 0.1.

[0075] As a specific example, the positive electrode active material can include a lithium nickel cobalt composite oxide represented by the following Chemical Formula A2.

[0076] Chemical Formula A2 Li a12 Ni x12 Co y12 M 13 1-x12-y12 O2 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 / or a combination thereof (e.g., any suitable combination).

[0077] In Chemical Formula A2, the ranges can be: 0.3 ≤ x12 ≤ 0.99 and 0.01 ≤ y12 ≤ 0.7, 0.4 ≤ x12 ≤ 0.99 and 0.01 ≤ y12 ≤ 0.6, 0.5 ≤ x12 ≤ 0.99 and 0.01 ≤ y12 ≤ 0.5, 0.6 ≤ x12 ≤ 0.99 and 0.01 ≤ y12 ≤ 0.4, 0.7 ≤ x12 ≤ 0.99 and 0.01 ≤ y12 ≤ 0.3, 0.8 ≤ x12 ≤ 0.99 and 0.01 ≤ y12 ≤ 0.2, or 0.9 ≤ x12 ≤ 0.99 and 0.01 ≤ y12 ≤ 0.1.

[0078] As a specific example, the positive electrode active material can include a lithium nickel cobalt composite oxide represented by the following Chemical Formula A3.

[0079] Chemical Formula A3 Li a13 Ni x13 Co y13 M 14 z13 M 15 1-x13-y13-z13 O2 In Chemical Formula A3, 0.9 ≤ a13 ≤ 1.8, 0.3 ≤ x13 ≤ 0.98, 0.01 ≤ y13 ≤ 0.69, 0.01 ≤ z13 ≤ 0.69, M 14 is selected from Al, Mn, and / or a combination thereof (e.g., any suitable combination), and M15 Selected from B, Ce, Cr, F, Mg, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, and / or a combination thereof (e.g., any suitable combination).

[0080] In chemical formula A3, the ranges can be: 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.

[0081] The first active material layer 13 may include a positive electrode active material and may further include a binder and / or a conductive material. Here, based on the total weight of the positive electrode active material layer (i.e., the first active material layer), the amount of the positive electrode active material may be 90 wt% to 98 wt% - for example, 90 wt% to 95 wt%. Based on the total weight of the positive electrode active material layer, the amount of each of the binder and the conductive material may be 1 wt% to 5 wt%.

[0082] The binder may be used to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the functional layer or the substrate, and may be the same as the binder constituting the intermediate functional layer 12 (included in the intermediate functional layer 12).

[0083] A conductive material (e.g., a conductor) may be included to provide conductivity (e.g., electron conductivity) to the electrode, and may be the same as the conductive material constituting the intermediate functional layer 12 (included in the intermediate functional layer 12).

[0084] The first electrode uncoated region LA2 is disposed at the front end of the first electrode 121. Since no separate material layer is formed on the first substrate 11, the surface of the first substrate 11 may be exposed, and the first electrode tab 14 for leading current to the outside may be connected to the first substrate 11.

[0085] The first electrode tab 14 may be connected to the first electrode uncoated region LA2 by ultrasonic welding, laser welding, or resistance welding, and may protrude from the first electrode uncoated region LA2. The first electrode tab 14 may include aluminum like the first substrate 11, and the thickness of the first electrode tab 14 may be 12 μm or less.

[0086] The protective tape 70 adheres to the first electrode tab 14 to protect the first electrode tab 14. The protective tape 70 is also formed on the other surface B of the first substrate 11 where the first electrode tab 14 is not formed. Additionally, the protective tape 74 can be formed to cover the exposed first substrate 11 between the first active material layer 13 and the first electrode tab 14, and can extend to cover one end of the intermediate functional layer 12 and one end of the first active material layer 13 to prevent or reduce a short circuit with the second electrode 122 (e.g., protect the intermediate functional layer 12 and the first active material layer 13 from short circuiting with the second electrode 122).

[0087] The first termination portion LA3 is disposed at the distal end of the first electrode 121 relatively far from the winding axis XL, and includes the first substrate 11 and distal functional layers (or referred to as "end functional layers") 15, 16 formed on the first substrate 11. The distal functional layers 15, 16 include a ceramic material having insulating properties, are disposed at a certain distance from one end of the first active material layer 13, and are respectively disposed on one surface A and the other surface B of the first substrate. The distal functional layer 15 formed on one surface A of the first substrate 11 is formed to be relatively longer than the distal functional layer 16 formed on the other surface B, and the first termination portion LA3 of the other surface B can be wound around the electrode assembly at least once.

[0088] The distal functional layers 15, 16 are materials having a resistance relatively greater than that of the first substrate 11, such that the distal functional layers 15, 16 can be disposed between the first substrates, so that in the case of an external impact, the possibility of a battery short circuit caused by the external impact can be prevented or reduced.

[0089] The distal functional layers 15, 16 can include ceramics and a binder.

[0090] The ceramics can include: endothermic ceramics such as pseudoboehmite and boehmite; common ceramics such as alumina (AlO3 and / or Al2O3, etc.), silica ((SiO2), magnesia (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), and silicon carbide (SiC); and / or a combination thereof (e.g., any suitable combination).

[0091] The common ceramics are insulating materials having only insulating properties, and the endothermic ceramics are endothermic materials having insulating properties and endothermic properties.

[0092] The binder can include a water-insoluble binder, a water-soluble binder, and / or a combination thereof (e.g., any suitable combination).

[0093] The binder ensures that the materials in the ceramic layer adhere to each other and that the ceramic layer adheres to the first substrate.

[0094] The water-insoluble binder may be selected from polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, ethylene-propylene copolymers, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamides, polyimides, and / or combinations thereof (e.g., any suitable combination).

[0095] The water-soluble binder may be a rubbery binder or a polymeric resin binder. The rubbery binder may be selected from styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber (ABR), acrylic rubber, butyl rubber, fluororubber, and / or combinations thereof (e.g., any suitable combination). The polymeric 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 / or combinations thereof (e.g., any suitable combination).

[0096] When the water-soluble binder is used as the binder, a cellulose-based compound may also be used to provide adhesiveness. The cellulose-based compound includes one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and / or their alkali metal salts. The alkali metal may be Na, K, or Li.

[0097] In one or more embodiments, since the distal functional layer 15 is formed by winding around the electrode assembly at least once, the first distal functional layer 15 formed on one surface A and the second distal functional layer 16 formed on the other surface B may face each other. As Figure 2 and Figure 4 shown, the gap S between the first active material layer 13 and the first distal functional layer 15 formed on one surface and the second distal functional layer 16 formed on the other surface may face each other (see, for example Figure 2 F in

[0098] A step compensation layer 80 may be further formed on the second distal functional layer 16. The first distal functional layer 15 and the first active material layer 13 may be arranged spaced apart and / or separated (e.g., spaced or separated), and the step compensation layer 80 may correspond to the gap S between the first distal functional layer 15 and the first active material layer 13.

[0099] Accordingly, in a wound or wound-type electrode assembly, the step compensation layer 80 may be inserted into the gap S and may have a thickness equal to that of the first active material layer 13. The step compensation layer 80 may be formed by the following steps: forming the second distal functional layer 16, and then applying the ceramic forming the second distal functional layer 16 to a position corresponding to the gap S.

[0100] By applying the ceramic to form the step compensation layer 80, the width of the step compensation layer 80 may narrow from the bottom (e.g., the surface adjacent to the second distal functional layer 16) to the top (e.g., the surface opposite to the bottom and spaced apart from the second distal functional layer 16).

[0101] The electrolyte solution filled in the empty space formed by the gap S may contact the second distal functional layer 16 and react with the ceramic included in the second distal functional layer 16 to produce ceramic precipitates, which may cause the second distal functional layer 16 to change color.

[0102] In the present disclosure, the empty space formed by the gap S is filled with the step compensation layer 80, thereby minimizing or reducing the penetration of the electrolyte solution. Therefore, it is possible to prevent or reduce the discoloration of the distal functional layer by minimizing or reducing the reaction between the electrolyte solution and the ceramic.

[0103] Although Figure 4 the step compensation layer 80 is shown as a single layer, it is not limited thereto, and in order to fill the blank spaces having different widths due to the dimensional difference between the intermediate functional layer 12 and the first active material layer 13, the step compensation layer 80 may have a stepped structure as shown in, for example, Figure 5 as shown.

[0104] Figure 6 A plan view and a cross-sectional view of a second electrode including an electrode assembly according to one or more embodiments of the present disclosure. Figure 2 as shown.

[0105] According to one or more embodiments of the present disclosure, Figure 6 the plan view includes a plan view of one surface A and another surface B of the second electrode, and the cross-sectional view is a cross-sectional view taken along the line C2-C2' of Figure 6 as shown.

[0106] Referring to Figure 6 , the second electrode active portion LB1 includes a second substrate 21 and a second active material layer 22 formed on the second substrate 21.

[0107] The second active material layer 22 is formed on the surface of the second substrate (e.g., one surface or two surfaces (e.g., opposite surfaces)) such that the lengths of the second electrode active portions LB1 formed on one surface A and another surface B of the second substrate 21 may be different.

[0108] The uncoated regions LB2 of the second electrode are respectively arranged at the front end and the distal end of the second electrode, and no separate material layer is formed on the second substrate 21, so that the surface of the second substrate 21 can be exposed, and the second electrode tab 23 for leading current to the outside can be connected to the second substrate 21.

[0109] The second electrode tab 23 can be connected to the uncoated region LB2 of the second electrode by ultrasonic welding, laser welding or resistance welding, and can protrude beyond the uncoated region LB2 of the second electrode. The second electrode tab 23 can be made of nickel.

[0110] The protective tape 70 can be formed on the second electrode tab 23, and the protective tape 70 can also be formed on the other surface B of the second substrate 21 where the second electrode tab 23 is not formed. The protective tape 75 can also be attached to the portion where the substrates of different polarities may come into contact in the wound state, thereby preventing or reducing short circuits (for example, protecting the substrates of different polarities to prevent short circuits).

[0111] The second substrate 21 provides a channel for the movement of charges generated in the second active material layer 22 and supports the second active material layer 22.

[0112] The second electrode 122 can be a negative electrode, and the second substrate 21 can have a thin metal plate (for example, copper foil, nickel foil) or a mesh structure with excellent or suitable conductivity. The second active material layer 22 can be formed by the following steps: dispersing an electrode mixture containing a negative electrode active material, a binder, and / or a conductive material, etc. in a solvent to form a slurry, then applying it to at least one surface of the second substrate 21, and then drying and pressing.

[0113] The negative electrode active material of the second active material layer 22 can be a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, and / or a transition metal oxide.

[0114] The material capable of reversibly intercalating / deintercalating lithium ions can be, for example, a carbon material - that is, a carbon-based negative electrode active material commonly used in lithium secondary batteries. Representative examples of carbon-based negative electrode active materials include crystalline carbon, amorphous carbon, and / or a combination thereof (for example, any suitable combination). Examples of crystalline carbon include graphite, such as natural graphite or artificial graphite in the form of flakes, sheets, spherical or fibrous shapes without a fixed shape, and examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, and / or calcined coke, etc.

[0115] The lithium metal alloy can be an alloy of lithium and a metal, and the metal is selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn, and combinations thereof.

[0116] The material capable of doping and de-doping lithium can be 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 / or combinations thereof (e.g., any suitable combination), but not Si), Si-carbon composite, Sn, SnO x (0 < x ≤ 2) (e.g., 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 / or combinations thereof (e.g., any suitable combination), but not Sn), and / or Sn-carbon composite, etc., and at least one of these materials can be mixed with SiO2. The element Q and the element R can be selected from the group consisting of 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, either individually or in combination.

[0117] Lithium titanium oxide can be used as a transition metal oxide.

[0118] Referring again to Figure 1 and Figure 2 , the separator 123 is disposed between the first electrode 121 and the second electrode 122, and prevents or reduces the possibility of short circuit between the first electrode 121 and the second electrode 122.

[0119] The separator 123 can be formed of a porous membrane having high ion permeability and mechanical strength. For example, the separator 123 can be formed of an olefin polymer such as polyethylene or polypropylene. The separator can extend in the length direction or the width direction, longer than the active part LA1 of the first electrode or the active part LB1 of the second electrode, which can prevent or reduce the possibility of short circuit between the active part LA1 of the first electrode and the active part LB1 of the second electrode due to thermal shrinkage.

[0120] The electrode assembly 100 can be contained in a pouch-type or bag-like housing 200 together with an electrolyte. The pouch-type or bag-like housing can be formed of a laminated outer material. For example, as Figure 1As shown, the outer materials include a lower outer material 201 and an upper outer material 202, and the electrode assembly 100 is disposed between the lower outer material 201 and the upper outer material 202, and then sealed by heat fusion.

[0121] The laminated outer material may be formed into a multi-layer structure having, for example, a first insulating layer 2, a metal layer 3, and a second insulating layer 4. Various other adhesive layers or functional layers may be added.

[0122] The first insulating layer 2 may be formed of a material having insulating properties and heat-bonding properties on the inner surface of the laminated outer material, and may be sealed by heat-bonding the edges while accommodating the electrode assembly 100. In addition, the first insulating layer 2 is formed on one surface of the metal layer 3 and forms the inner side of the laminated outer material facing the electrode assembly 100. The first insulating layer 2 may be formed of cast polypropylene (CPP) or its equivalent that does not react with the electrolyte solution.

[0123] In the above embodiment, the first electrode is wound at least once on the outermost part of the electrode assembly without a separator and a second electrode, but the present disclosure is not limited thereto, and as shown in, for example, Figure 7 and Figure 9 the separator or the second electrode may be disposed on the outermost part of the electrode assembly.

[0124] Figure 7 and Figure 9 are cross-sectional views of electrode assemblies according to one or more embodiments of the present disclosure, Figure 8 is according to one or more embodiments of the present disclosure Figure 7 partial enlarged cross-sectional view of part F, and Figure 10 is Figure 9 partial enlarged cross-sectional view of part F.

[0125] Figures 7 to 10 may all be independently the same as the Figures 1 to 3 electrode assembly, and thus only the different parts will be described in more detail.

[0126] As shown in Figures 7 to 10 the uncoated area LB2 of the separator 123 and / or the second electrode may be wound at least once on the outermost part of the electrode assembly, and the step compensation layer 80 may be inserted into the gap S between the first distal functional layer 15 and the first active material layer 13, and may have a thickness smaller than the thickness of the first active material layer 13.

[0127] At this time, as shown in, for example, Figure 7 and Figure 8 the separator 123 disposed between the step compensation layer 80 and the gap S may be inserted into the gap S together, or as shown in, for example, Figure 9 and Figure 10As shown, the diaphragm 123 disposed between the step compensation layer 80 and the gap S and the uncoated region LB2 of the second electrode of the second substrate 21 can be inserted into the gap S together.

[0128] Therefore, if (for example, when) the diaphragm 123 and / or the uncoated region LB2 of the second electrode are arranged as Figures 7 to 10 shown between the step compensation layer 80 and the gap S, due to the thickness of the diaphragm 123 and / or the uncoated region LB2 of the second electrode, the step compensation layer 80 may not be fully inserted into the gap S.

[0129] In this way, even if the step compensation layer 80 is not fully inserted, the diaphragm 123 and / or the uncoated region LB2 of the second electrode fill the empty space caused by the gap S, thereby preventing or reducing the possibility of the electrolyte solution remaining in the empty space. Therefore, discoloration caused by the reaction between the electrolyte solution filled in the empty space and the ceramic in the second distal functional layer 16 can be prevented or reduced.

[0130] As Figures 7 to 10 shown, if (for example, when) the diaphragm 123 and / or the uncoated region LB2 of the second electrode are arranged between the step compensation layer 80 and the gap S, the height of the step compensation layer 80 can be reduced by as much as the thickness of the diaphragm 123 and / or the uncoated region LB2 of the second electrode, so that the step compensation layer 80 can be fully inserted into the gap S.

[0131] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will also be understood that terms (such as those defined in a general dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and / or the context of this disclosure, and should not be interpreted in an idealized or overly formal sense unless clearly so defined herein.

[0132] As used herein, the terms "substantially", "about" and similar terms are used as approximate terms and not as terms of degree, and are intended to account for the inherent deviations of measured or calculated values that would be recognized by one of ordinary skill in the art. Considering the measurements discussed and the errors associated with the measurement of a particular quantity (i.e., the limitations of the measurement system), "substantially" as used herein includes the stated value and represents within an acceptable deviation range of the particular value as determined by one of ordinary skill in the art. For example, "substantially" may mean within one or more standard deviations, or within ±30%, ±20%, ±10%, ±5% of the stated value.

[0133] In addition, any numerical range stated herein is intended to include all sub-ranges of the same numerical precision that are included within the stated range. For example, the range of "1.0 to 10.0" is intended to include all sub-ranges between the stated minimum value of 1.0 and the stated maximum value of 10.0 (including the stated minimum value of 1.0 and the stated maximum value of 10.0), that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limit stated herein is intended to include all smaller numerical limits contained therein, and any minimum numerical limit stated in this specification is intended to include all larger numerical limits contained therein. Accordingly, the applicant reserves the right to amend this specification (including the claims) to expressly state any sub-range that is included within the ranges expressly stated herein.

[0134] In addition, in describing embodiments of the present disclosure, the use of "may" refers to "one or more embodiments of the present disclosure".

[0135] A portable device, vehicle, and / or battery (e.g., a battery controller) and / or any other relevant device or component according to embodiments of the present disclosure described herein may be implemented using any suitable hardware, firmware (e.g., an application specific integrated circuit), software, or a combination of software, firmware, and hardware. For example, various components of the device may be formed on one integrated circuit (IC) chip or on separate IC chips. In addition, various components of the device may be implemented on a flexible printed circuit film, tape carrier package (TCP), printed circuit board (PCB), or formed on a substrate. Further, various components of the device may be processes or threads running on one or more processors in one or more computing devices that execute computer program instructions and interact with other system components to perform the various functions described herein. The computer program instructions are stored in a memory that may be implemented in a computing device using a standard memory device (such as, for example, random access memory (RAM)). The computer program instructions may also be stored in other non-transitory computer-readable media (such as, for example, CD-ROMs, flash drives, etc.). In addition, those skilled in the art should recognize that, without departing from the scope of the embodiments of the present disclosure, the functions of various computing devices may be combined or integrated into a single computing device, or the functions of a particular computing device may be distributed across one or more other computing devices.

[0136] Although embodiments of the present disclosure have been described, it should be understood that the present disclosure should not be limited to these embodiments, but rather one or more suitable changes and modifications may be made by those of ordinary skill in the art within the scope of the present disclosure defined by the appended claims and their equivalents.

[0137] Reference numeral 11: First substrate 12: Intermediate functional layer 13: First active material layer 14: First electrode tab 15: Distal functional layer 21: Second substrate 22: Second active material layer 23: Second electrode tab 70: Protection tape 100: Electrode assembly 121: First electrode 122: Second electrode 200: Housing 1000: Secondary battery.

Claims

1. An electrode assembly, the electrode assembly comprising: A first electrode; A separator; And A second electrode, Wherein, the first electrode includes: a first substrate including a front surface and a rear surface; a front first active material layer and a rear first active material layer, the front first active material layer being on the front surface, and the rear first active material layer being on the rear surface; a first end functional layer and a second end functional layer, the first end functional layer being on the front surface and spaced apart from the front first active material layer, the second end functional layer being on the rear surface and spaced apart from the rear first active material layer; and a step compensation layer, on the second end functional layer and corresponding to the gap between the front first active material layer and the first end functional layer, and Wherein, the second end functional layer winds around the electrode assembly at least once.

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

3. The electrode assembly according to claim 1, wherein, The first end functional layer and the second end functional layer include ceramic materials.

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

5. The electrode assembly according to claim 1, the electrode assembly further comprising an intermediate functional layer, Among them, The intermediate functional layer is between the first substrate and the front first active material layer, and is also between the first substrate and the rear first active material layer.

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

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

8. The electrode assembly according to claim 1, wherein, The separator winds around the electrode assembly at least once together with the second end functional layer, and the separator is located between the gap and the step compensation layer.

9. The electrode assembly according to claim 8, wherein, The uncoated electrode region of the second electrode winds around the electrode assembly at least once together with the second end functional layer and the separator, and the uncoated electrode region of the second electrode is located between the gap and the step compensation layer.

10. The electrode assembly according to claim 1, wherein, As the step compensation layer extends away from the first substrate, the width of the step compensation layer decreases.

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

12. The electrode assembly according to claim 1, wherein, The step compensation layer has a stepped structure.

13. A secondary battery, the secondary battery comprising: The electrode assembly according to claim 1, A housing for accommodating the electrode assembly; And An electrolyte.

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