Electrode for rechargeable battery and electrode assembly including the same

Abstract

An electrode according to one embodiment of the present invention comprises an electrode active portion, a substrate having a tab-free portion protruding from the electrode active portion, and an active material layer formed on the electrode active portion of the substrate, wherein the substrate of the electrode active portion comprises an opening formed of a plurality of openings.

Description

Technology Field

[0001] The present invention relates to an electrode and an electrode assembly for a secondary battery. Background Technology

[0002] Unlike primary batteries, rechargeable batteries are batteries that repeatedly perform charging and discharging.

[0003] Small-capacity rechargeable batteries are used in portable small electronic devices such as mobile phones, laptop computers, and camcorders. Large-capacity and high-density rechargeable batteries are used as power sources for driving motors in hybrid and electric vehicles or for energy storage.

[0004] As the applications of secondary batteries expand and capacities increase, requirements regarding performance changes during operation are becoming more diverse. Recently, silicon-containing cathodes are being developed to secure battery energy density. However, silicon exhibits greater swelling compared to conventional graphite electrodes.

[0005] Furthermore, while high-nickel cathode active materials are used to achieve high capacity, local temperature non-uniformity due to the thermal properties of the material itself leads to local electrochemical non-uniformity. In particular, temperature non-uniformity further accelerates the swelling of the anode and shortens the battery life.

[0006] The information described above disclosed in the background technology of this invention is intended only to enhance understanding of the background of the present invention and may therefore include information that does not constitute prior art. The problem to be solved

[0007] The present invention provides an electrode and an electrode assembly including the same, which use a high-capacity active material to increase the battery life and have stable battery characteristics even when heat generation and swelling occur. means of solving the problem

[0008] An electrode according to one embodiment of the present invention comprises an electrode active portion, a substrate having a tab-free portion protruding from the electrode active portion, and an active material layer formed on the electrode active portion of the substrate, wherein the substrate of the electrode active portion comprises an opening formed of a plurality of openings.

[0009] The above opening can be filled with the active material of the active material layer.

[0010] The above-mentioned tab-free portion is located on one side of the electrode active portion, and the width of the opening can be formed to be 50% or less of the length of the electrode active portion in the direction from one side to the other side of the electrode active portion.

[0011] The area of ​​the above opening may be 50% or less of the area of ​​the electrode active part.

[0012] The planar shape of the above opening may be circular or polygonal.

[0013] The above opening may be located on the opposite side of the tab-less portion.

[0014] The above opening can gradually change in size as it moves in one direction.

[0015] The spacing between adjacent openings can change gradually in one direction.

[0016] The above active material layer may include silicon.

[0017] An electrode tab for drawing current to the outside can be electrically connected to the above-mentioned tab portion.

[0018] An electrode assembly according to another embodiment of the present invention comprises an anode substrate having a first tab-free portion and a first electrode active portion, an anode having an anode active material layer formed on the first electrode active portion of the anode substrate, a cathode substrate having a second tab-free portion and a second electrode active portion, a cathode having a cathode active material layer formed on the second electrode active portion of the cathode substrate, and a separator located between the anode and the cathode, and includes an opening formed on the cathode substrate of the second electrode active portion and comprising a plurality of openings, wherein the opening may be located relatively adjacent to the first tab-free portion.

[0019] The first tab-free section and the second tab-free section may protrude in opposite directions from each other, centered on the first electrode active section or the second electrode active section.

[0020] An electrode tab for drawing current to the outside can be connected to each of the first tap-free section and the second tap-free section.

[0021] The width of the above opening may be formed to be 50% or less of the length of the second electrode active portion in the direction from the first tab-free portion to the second tab-free portion.

[0022] The first temperature of the area adjacent to the first tab-free section is higher than the second temperature of the area adjacent to the second tab-free section, and the opening may overlap with the area with a relatively higher temperature.

[0023] The above positive active material layer includes a nickel-based active material, and the negative active material layer may include silicon.

[0024] The above opening can be filled with the active material of the active material layer.

[0025] The planar shape of the above opening may be circular or polygonal.

[0026] The above opening can gradually change in size as it moves in one direction.

[0027] The spacing between adjacent openings can change gradually in one direction. Effects of the invention

[0028] By forming an opening as in the present invention, swelling is reduced even if a region with a locally high temperature occurs, thereby increasing the battery life and improving electrical characteristics, and an electrode for a secondary battery and an electrode assembly including the same can be provided. Brief explanation of the drawing

[0029] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. FIG. 1 is a schematic perspective view of another secondary battery according to one embodiment of the present invention. Figure 2 is a schematic plan view of the electrode and separator included in Figure 1. Figure 3 is a cross-sectional view taken along the line III-III' of Figure 2. FIG. 4 is a schematic plan view of an electrode according to another embodiment of the present invention. FIGS. 5 to 8 are plan views of an electrode according to another embodiment of the present invention. FIG. 9 is a schematic perspective view of a secondary battery according to another embodiment of the present invention. Figure 10 is a cross-sectional view taken along the line X-X' of Figure 9. Figure 11 is a schematic plan view of the cathode included in Figure 10. FIG. 12 is a diagram illustrating swelling displacement according to the temperature distribution of a battery formed according to the prior art. FIG. 13 is a diagram illustrating swelling displacement according to the temperature distribution of a battery formed according to the present invention. Specific details for implementing the invention

[0030] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe their invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. It should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0031] Additionally, as used herein, “comprise, include” and / or “comprising, including” specify the presence of the mentioned features, numbers, steps, actions, parts, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, numbers, actions, parts, elements, and / or groups.

[0032] Additionally, to aid in understanding the invention, the attached drawings are not drawn to actual scale, and the dimensions of some components may be exaggerated. Furthermore, the same reference numerals may be assigned to identical components in different embodiments.

[0033] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may also be the second component.

[0034] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0035] Spatial relative terms such as "beneath," "below," "lower," "above," and "upper" may be used herein for ease of explanation to describe the relationship between one element or feature and another element(s) or feature(s) as illustrated in the drawings. Spatially relative positions are to be understood as encompassing different orientations of the device in use or operation, in addition to the orientations depicted in the figures. For example, if the device in the drawing is inverted, an element described as "below" or "below" is understood as "above" or "upper" of another element. Thus, the term "below" may encompass both upward and downward directions.

[0036] Furthermore, where one component is described as being "connected to" or "coupled to" another component, it should be understood that while the components may be directly connected or coupled to each other, another component may be "interposed" between each component, or each component may be "connected," "coupled," or "coupled" through another component.

[0037] The terms used in this specification are intended to describe embodiments of the present disclosure and are not intended to limit the present disclosure.

[0038] FIG. 1 is a schematic perspective view of a secondary battery according to one embodiment of the present invention, FIG. 2 is a schematic plan view of an electrode and a separator included in FIG. 1, FIG. 3 is a cross-sectional view taken along the line III-III' of FIG. 2, and FIG. 4 is a schematic plan view of an electrode according to another embodiment of the present invention.

[0039] As illustrated in FIGS. 1 to 3, a secondary battery (1000) according to one embodiment of the present invention includes an electrode assembly (400) and a case (500) that accommodates the electrode assembly (400) and an electrolyte (not shown).

[0040] The electrode assembly (400) is a stacked assembly in which an anode (100) and a cathode (200) are repeatedly stacked with a separator (300) in between. For convenience of explanation, only one anode, cathode, and separator are shown in FIGS. 2 and 3.

[0041] The positive electrode (100) includes a positive electrode substrate (10) and an active material layer (12) formed on the positive electrode substrate (10). The positive electrode substrate (10) is formed from a thin conductive metal foil and used as a current collector, and may be, for example, aluminum.

[0042] The positive electrode substrate (10) includes an electrode active portion (DA1) in which a positive electrode active material layer (12) is formed, and an electrode non-active portion in which the positive electrode substrate (10) is exposed because the active material layer (12) is not formed. The positive electrode substrate (10) provides a path for the movement of charges generated in the positive electrode active material layer (12) and supports the positive electrode active material layer (12).

[0043] The electrode non-electrode portion may be located around the electrode active portion (DA1) and may have a shape extended from the electrode active portion (DA1).

[0044] As shown in FIGS. 1 and 2, a protruding portion on one side of the electrode active portion (DA1) among the electrode non-existent portions may be connected to an anode tab (91) for drawing current out to the outside, and the anode tab (91) may be made of a material such as the substrate, for example, aluminum. For convenience of explanation, the protruding electrode non-existent portion to which the anode tab (91) is connected is referred to as a tab non-existent portion (DA2). The tab non-existent portions (DA2) of the repeatedly stacked anode (100) may be electrically connected through welding, etc.

[0045] The positive active material layer (12) may be formed on one side (not shown) or both sides, respectively, centered on the positive substrate (10). The positive active material layer (12) may include a positive active material and may further include a binder and / or a conductive material.

[0046] The content of the positive active material in the positive active material layer is 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer, and the content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the positive active material layer.

[0047] positive electrode active material

[0048] As a positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0049] The above composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0050] As an example, a compound represented by any one of the following chemical formulas may be used. 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 Mn 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 O 2-α D α(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤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); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0051] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al, or a combination thereof.

[0052] For example, the above-mentioned positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of the metal excluding lithium in the lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. The high-nickel positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density lithium secondary batteries.

[0053] bookbinder

[0054] The binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0055] Challenge

[0056] A conductive material is used to impart conductivity to an electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0057] The cathode (200) includes a cathode substrate (20) and a cathode active material layer (22) formed on the cathode substrate (20). The cathode substrate (20) is formed from a thin conductive metal foil and used as a current collector, and may be selected from, for example, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0058] The cathode substrate (20) includes an electrode active portion (DB1) in which a cathode active material layer (22) is formed, and an electrode non-active portion in which the cathode substrate (20) is exposed because the cathode active material layer (22) is not formed. The cathode substrate (20) provides a path for the movement of charges generated in the cathode active material layer (22) and supports the cathode active material layer (22).

[0059] The electrode non-electrode portion may be located around the electrode active portion (DB1) and may have an extended shape from the electrode active portion (DB1).

[0060] As shown in FIGS. 1 and 2, a portion protruding from one side of the electrode active portion (DB1) among the electrode non-electrode portions may be connected to a negative electrode tab (92) for drawing current out to the outside. For convenience of explanation, the protruding electrode non-electrode portion to which the negative electrode tab (92) is connected is referred to as the tab non-electrode portion (DB2).

[0061] The tab-free portions (DB2) of the repeatedly stacked cathodes (200) can be electrically connected through welding or the like.

[0062] The tab-free portions (DA2, DB2) of the positive and negative electrodes are shown protruding in opposite directions, but are not limited thereto, and the positive and negative electrodes may be spaced apart from each other and protrude in the same direction (not shown).

[0063] The negative electrode active material layer may be formed on one side (not shown) or both sides, respectively, centered on the substrate. The content of the negative electrode active material in the negative electrode active material layer may be 95% to 99% by weight with respect to the total weight of the negative electrode active material layer.

[0064] cathode active material

[0065] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0066] A material capable of reversibly intercalating / deintercalating the above lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0067] As the above lithium metal alloy, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0068] As a material capable of doping and undoping the above lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (wherein Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0069] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include a secondary particle (core) assembled from silicon primary particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particle. The amorphous carbon may also be located between the silicon primary particles, so that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0070] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

[0071] The above Si-based or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0072] bookbinder

[0073] The binder serves to effectively bond the negative electrode active material particles to each other and also to effectively bond the negative electrode active material to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used.

[0074] Examples of the above-mentioned non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, or combinations thereof.

[0075] The above-mentioned water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylenepropylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0076] When a water-based binder is used as the above-mentioned cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. As this cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. Na, K, or Li may be used as the alkali metal.

[0077] The above dry binder is a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0078] Challenge

[0079] A conductive material is used to impart conductivity to an electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjenblack, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0080] The separator (300) is a polymer film that allows lithium ions to pass through, and may be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof. In addition, mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0081] The separator (300) may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0082] The porous substrate may be a polymer membrane formed from any one of the following: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyacetal; polyamide; polyimide; polycarbonate; polyetherketone; polyaryletherketone; polyetherimide; polyamideimide; polybenzimidazole; polyethersulfone; polyphenylene oxide; cyclic olefin copolymer; polyphenylene sulfide; polyethylene naphthalate; glass fiber; Teflon; and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0083] The above organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0084] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include, but is not limited to, inorganic particles selected from SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0085] The above organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0086] Meanwhile, the cathode substrate (20) includes an opening (SD) in which a plurality of openings are formed. The opening (SD) is an area in which a plurality of openings (S) are formed, and may be an area formed by connecting the outer boundary lines of the openings located at the outermost edge. For better understanding, in FIG. 2, the boundary line of the opening located at the outermost edge is shown as a dotted line. Also, although the boundary between the two active material layers (22) formed on one side and the other side centered on the substrate (20) is shown as being located within the opening (S), if the active material layers (22) formed on the one side and the other side are formed from the same material, the boundary between the two active material layers (22) located within the opening (S) may be unclear. Furthermore, if the active material layer formed first, for example, the active material layer located at the top in the drawing, is formed first, the bottom boundary surface of the upper active material layer may be at the same position as the bottom surface of the substrate.

[0087] The opening (SD) is located in the electrode active portion (DB1) and may be located adjacent to one side opposite the tapless portion (DB2). Thus, the opening (SD) may be adjacent to the tapless portion (DA2) of the anode (100).

[0088] Due to the flow of charge, resistance increases and heat may be generated as it gets closer to the tab-free portion (DA2) to which the positive electrode tab (91) is attached. Therefore, the temperature increases as it gets closer to the positive electrode tab-free portion (DA2) where heat is generated within the electrode, and the temperature may decrease as it gets relatively farther from the tab-free portion (DA2). For convenience of explanation, the region where the temperature rises and is relatively high is referred to as the heat-generating portion (FA). If the positive electrode active material includes a high-capacity nickel-based material, the amount of heat generated may be even greater.

[0089] The heat generation increases as it is adjacent to the tapless portion (DA2) of the anode, and the heat generation portion (FA) can be formed locally. That is, the heat generation portion (FA) can be located adjacent to the tapless portion (DA2) of the anode and can be an area that is at least 2 degrees higher than the lowest temperature in the electrode assembly. The width (W1) of the heat generation portion (FA) can be 50% or less of the length (L1) of the anode electrode active portion (DA1), and preferably 30% or less.

[0090] Meanwhile, when a heating element (FA) with increased temperature is formed, heat can be transferred to the cathode overlapping with the heating element (FA), which can increase the swelling phenomenon of the cathode active material layer (22).

[0091] Generally, the energy density of silicon-based active materials included in negative electrode active materials is approximately 10 times higher than that of carbon-based active materials, but silicon-based active materials have a larger volume change than carbon-based active materials during the charging and discharging process, and the volume change can be even greater due to heat.

[0092] Accordingly, in the present invention, by placing an opening (SD) in the cathode substrate (20) corresponding to the heating portion (FA), the swelling phenomenon is prevented from becoming excessive locally, thereby ensuring that the volume change occurs uniformly throughout the cathode. At this time, the width (W2) of the opening (SD) may be 50% or less of the length (L2) of the cathode electrode active portion (DB1), and preferably 30% or less. Also, the area of ​​the opening (SD) may be equal to or smaller than the area of ​​the heating portion (FA), and may be 50% or less of the area of ​​the cathode electrode active portion (DB1). Preferably 30% or less.

[0093] The active material of the negative active material layer (22) located at the opening (SD) can fill the opening (S). Therefore, the diameter (D) of the opening (S) may be larger than the size of the particles forming the active material. For example, if the size of the negative active material is mixed from 0.4 μm to 40 μm, the diameter (D) of the opening may be 40 μm or more. The planar shape of the opening (S) may be a polygon such as a square as in FIG. 2, but is not limited thereto; it may be circular as in the negative (201) of FIG. 4, or have a shape of a slit (not shown) with a long length in one direction. In this case, the diameter of the polygon is the length of the longest diagonal.

[0094] The negative electrode active material filled in the opening (S) increases the bonding strength between the negative electrode active material layer (22) and the substrate (20), and mitigates volume change during charging and discharging, thereby allowing the volume change to occur uniformly throughout the negative electrode.

[0095] Meanwhile, the tensile strength of the opening (SD) may be lower than that of the negative electrode substrate (20) in which the opening (SD) is not formed. Therefore, the opening (S) is formed so that the tensile strength of the opening (SD) is at least 80% of the tensile strength of the negative electrode substrate (20) in which the opening (SD) is not formed, so that the negative electrode active material layer (22) can be stably supported by the substrate (20).

[0096] The opening (SD) may be formed along one side of the cathode corresponding to the heating element (FA) or over the entire heating element (FA), as in FIGS. 2 and 4, but is not limited thereto and may be formed in various shapes as in FIGS. 5 to 8.

[0097] FIGS. 5 to 8 are plan views of an electrode according to another embodiment of the present invention.

[0098] Since the anode (100) and cathode (202, 203, 204, 205) of FIGS. 5 to 8 are mostly identical to the anode and cathode of FIGS. 1 to 3, only the different parts will be described in detail.

[0099] In FIGS. 2 and 4, an opening (S) is placed across the entire area corresponding to the heating element (FA), so that the opening (SD) occupies an area roughly equal to that of the heating element (FA).

[0100] On the other hand, the openings (SD) of FIGS. 5 to 8 may have a plurality of openings (S) arranged in various ways according to the temperature distribution of the heating element (FA).

[0101] Referring to the cathode (202) illustrated in FIG. 5, the opening (S) is concentrated only in the area adjacent to the tab-free portion of the anode (100). The heating portion (FA) of the present invention is an area approximately 2 degrees higher than the lowest temperature of the electrode assembly, but the temperature distribution may vary depending on the location within the heating portion (FA). In particular, the closer it is to the tab-free portion of the anode, the greater the temperature difference from the lowest temperature may be. Additionally, the size and range of the swelling phenomenon according to temperature may vary depending on the size and design of the electrode assembly.

[0102] Accordingly, considering the temperature distribution and swelling phenomenon as shown in FIG. 5, an opening (S) can be formed only in the area adjacent to the tapless portion of the anode (100), which has a relatively higher temperature even within the heating portion (FA).

[0103] Referring to the cathode (203) illustrated in FIG. 6, the size of the opening (S) can gradually change according to the temperature distribution within the heating element (FA).

[0104] Referring to FIG. 6, the size of the opening (S) can be reduced as it moves away from the area adjacent to the tapless portion of the anode (100) and toward the first direction (X1) adjacent to the tapless portion of the cathode (203). At this time, the spacing between adjacent openings (S) in the first direction (X1) can be the same.

[0105] Additionally, as the size of the opening (S) decreases, the area occupied by the opening (S) in the second direction (X2) decreases, so the opening (SD) may be in a trapezoidal shape with a width that decreases as it approaches the center of the electrode.

[0106] Referring to the cathode (204) illustrated in FIG. 7, the spacing (L) between adjacent openings (S) in the first direction (X1) can gradually change according to the temperature distribution within the heating element (FA). At this time, the size of all openings (S) may be the same.

[0107] In addition, by reducing the number of openings (S) in the second direction (X2), the opening (SD) can have a trapezoidal or triangular shape in which the width decreases as it approaches the center of the electrode.

[0108] Additionally, referring to the cathode (205) illustrated in FIG. 8, the anode (100) may have a tab-free section protruding in multiple directions from the electrode active section. In this way, by forming a tab-free section protruding in multiple directions, a heating section (FA) may be formed in multiple directions.

[0109] Accordingly, an opening (SD) can be formed within each heating element (FA), as in the cathode (205) of FIG. 8. Of course, as in FIG. 2 and FIG. 4, an opening (SD) can be formed over a wide area regardless of the number of heating elements (FA).

[0110] Again, referring to FIGS. 1 and 2, the electrode assembly (400) can be housed in a pouch or can-shaped rectangular case (not shown) together with an electrolyte and used as a secondary battery, and the electrolyte includes a non-aqueous organic solvent and a lithium salt.

[0111] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0112] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0113] The above carbonate-based solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc.

[0114] Ester-based solvents such as methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, and caprolactone may be used.

[0115] Dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used as ether-based solvents.

[0116] In addition, cyclohexanone and the like may be used as ketone-based solvents. Ethyl alcohol and isopropyl alcohol and the like may be used as alcohol-based solvents, and as aprotic solvents, nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes may be used.

[0117] The above-mentioned non-aqueous organic solvent can be used alone or in a mixture of two or more types.

[0118] In addition, when using a carbonate-based solvent, a mixture of cyclic carbonates and chain carbonates can be used, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0119] The above lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and facilitating the movement of lithium ions between the anode and cathode. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 It may include one or more selected from SO2)(x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0120] The case (500) can be formed as a pouch-type laminated outer material, and the laminated outer material can be formed as a multilayer structure having, for example, a first insulating layer (2), a metal layer (3), and a second insulating layer (4). Of course, various adhesive layers or functional layers may also be added.

[0121] The first insulating layer (2) is formed on the inner surface of the laminate exterior material using a material having insulating and heat-sealing properties, so that the edges can be heat-sealed and sealed while the electrode assembly (400) is housed therein. Additionally, the first insulating layer (2) is formed on one surface of the metal layer (3) and forms the inner surface of the laminate exterior material facing the electrode assembly (400). The first insulating layer (2) may be formed from casted polypropylene (CPP) or an equivalent that does not react with the electrolyte.

[0122] FIG. 9 is a schematic perspective view of a secondary battery according to another embodiment of the present invention, FIG. 10 is a cross-sectional view taken along the line X-X' of FIG. 9, and FIG. 11 is a schematic plan view of a negative electrode included in FIG. 10.

[0123] As illustrated in FIGS. 9 to 11, a secondary battery (1001) according to one embodiment of the present invention includes an electrode assembly (95), a case (27) that accommodates the electrode assembly (95), and a cap assembly (310) installed in an opening of the case (27).

[0124] The electrode assembly (95) includes an anode (100) and a cathode (206) stacked sequentially, and a separator (300) located between them. The separator (300) is placed between the anode (100) and the cathode (206) and insulates them from each other.

[0125] The electrode assembly (95) may be a jelly roll type that is flattened and pressed after being wound or stacked around a winding axis (X) with a separator (300) interposed between the positive electrode (100) and the negative electrode (206).

[0126] The positive electrode (100) and the negative electrode (206) include an electrode active portion (DA1, DB1) and an electrode non-active portion, and the positive electrode substrate and the negative electrode substrate may be in the form of a long strip in one direction. Among the electrode non-active portions, the electrode active portion (DA1, DB1) is located around the electrode active portion (DA1, DB1) and may have a shape that extends from the electrode active portion (DA1, DB1). The electrode non-active portion located at the edge of the electrode active portion (DA1, DB1) and continuously formed along the length direction (or winding direction) is called the tab portion (DA2, DB2).

[0127] The tap-free portion (DA2) of the positive electrode (100) and the tap-free portion (DB2) of the negative electrode (206) can be located on opposite sides of each other with respect to the electrode active portions (DA1, DB1).

[0128] The negative electrode substrate of the negative electrode (206) includes an opening (SD) consisting of a plurality of openings (S) as shown in FIG. 2. The opening (SD) can overlap with the heating portion (FA) of the positive electrode.

[0129] Referring to FIGS. 10 and 11, the opening (SD) is located in the electrode active portion (DB1) of the cathode and can be formed lengthwise along a first direction (X1), which is a winding direction perpendicular to the winding axis of the electrode assembly.

[0130] The opening (SD) according to the present invention may be positioned corresponding to the heating portion (FA) of the positive electrode, where heat is generated as a result of the movement of electric charge. Accordingly, it may be located on one side opposite the tab-free portion (DB2) of the negative electrode and adjacent to the tab-free portion (DA2) of the positive electrode.

[0131] FIG. 12 is a diagram illustrating swelling displacement according to the temperature distribution of a battery formed according to the prior art, and FIG. 13 is a diagram illustrating swelling displacement according to the temperature distribution of a battery formed according to the present invention.

[0132] Referring to FIG. 12 according to the prior art, it can be seen that as the distance from the tapless portion (DA2) decreases, the temperature rises and a heat-generating portion is formed, and accordingly, it can be seen that the swelling displacement of the part adjacent to the distance from the tapless portion (DA2) is greater than that of other parts.

[0133] Referring to FIG. 13 according to the present invention, as the distance from the tapless portion (DA2) decreases, the temperature rises and a heat-generating portion can be formed, but it can be seen that the swelling displacement of the portion adjacent to the distance from the tapless portion (DA2) is significantly reduced compared to the swelling displacement according to the prior art of FIG. 12.

[0134] In this way, by placing an opening (SD) at a position corresponding to the heat source (FA), the local temperature rise and the increase in swelling in the corresponding area can be reduced. Therefore, the size of the swelling is reduced, and the effect of the swelling occurring uniformly in the electrode assembly can be expected.

[0135] Again, referring to FIGS. 9 and 10, the electrolyte can be injected in liquid form through the inlet (32), and the electrolyte can move through the tab-free portion located at the edge of the electrode assembly to the center of the electrode assembly. That is, the electrolyte can move in a direction parallel to the winding axis (X).

[0136] Meanwhile, the electrode assembly (95) can be accommodated in the case (27) together with the electrolyte.

[0137] The case (27) may be made of a metal such as aluminum and may be approximately rectangular. One side of the case (27) may be open, and a cap assembly (310) may be installed on the open side of the case (27).

[0138] The cap assembly (310) includes a cap plate (31) that is coupled to the case (27) and blocks the opening of the case (27), a positive terminal (21) that protrudes outward from the cap plate (31) and is electrically connected to the positive electrode (100), and a negative terminal (23) that is electrically connected to the negative electrode (206).

[0139] The cap plate (31) is formed in the shape of an elongated plate extending in one direction and is connected to the opening of the case (27).

[0140] The cap plate (31) has an injection port (32) that penetrates the interior. The injection port (32) is for injecting an electrolyte and is equipped with a sealing plug (38). Additionally, the cap plate (31) has a vent plate (39) with a notch (39a) formed therein installed in the vent hole (34) so ​​that it can be opened at a set pressure.

[0141] The positive terminal (21) and the negative terminal (23) are installed to protrude above the cap plate (31). The positive terminal (21) is electrically connected to the tap-unatted portion (DA2) of the positive electrode (100) via a current collection tap (41), and the negative terminal (23) is electrically connected to the tap-unatted portion (DB2) of the negative electrode (206) via a current collection tap (42).

[0142] A terminal connecting member (25) is installed between the positive terminal (21) and the current collection tap (41) to electrically connect the positive terminal (21) and the current collection tap (41). The terminal connecting member (25) is inserted into a hole formed in the positive terminal (21), and its upper end is fixed to the positive terminal (21) by welding, and its lower end is fixed to the current collection tap (41) by welding.

[0143] Between the terminal connecting member (25) and the cap plate (31), a gasket (59) for sealing is inserted into a hole through which the terminal connecting member (25) passes, and a lower insulating member (43) into which the lower part of the terminal connecting member (25) is inserted is installed below the cap plate (31). Between the positive terminal (21) and the cap plate (31), a connecting plate (58) that electrically connects them is installed. The terminal connecting member (25) is fitted into the connecting plate (58). Accordingly, the cap plate (31) and the case (27) are charged as positive (100).

[0144] A terminal connecting member (26) is installed between the negative terminal (23) and the current collection tap (42) to electrically connect the negative terminal (23) and the current collection tap (42). The terminal connecting member (26) is inserted into a hole formed in the negative terminal (23), and its upper end is fixed to the negative terminal (23) by welding, while its lower end is fixed to the current collection tap (42) by welding.

[0145] A gasket (59) for sealing is inserted and installed in a hole through which a terminal connecting member (26) penetrates between the negative terminal (23) and the cap plate (31), and an upper insulating member (54) is installed to insulate between the negative terminal (23) and the cap plate (31). The terminal connecting member (26) can be installed by being fitted into the hole of the upper insulating member (54), and the upper insulating member (54) can be formed to surround the end of the negative terminal (23).

[0146] And below the cap plate (31), a lower insulating member (45) is installed to insulate the negative terminal (23) and the current collection tap (42) from the cap plate (31).

[0147] A shorting hole (37) is formed in the cap plate (31), and a shorting member (56) is installed in the shorting hole (37). The shorting member (56) includes a curved portion that is bent downward in a convex arc shape and a rim portion formed on the outer side of the curved portion and fixed to the cap plate (31). The upper insulating member (54) may have an incision that overlaps with the shorting hole (37), and the shorting member (56) overlaps with the negative terminal (23) exposed through the aforementioned incision.

[0148] The short-circuit member (56) is electrically connected to the cap plate (31) and deforms when the internal pressure of the secondary battery (1001) rises, causing a short circuit between the positive and negative electrodes. That is, when gas is generated due to an abnormal reaction inside the secondary battery, the internal pressure of the secondary battery rises. When the internal pressure of the secondary battery rises above a preset pressure, the curved portion deforms to become convex upward, and at this time, the negative terminal (23) and the short-circuit member (56) come into contact, causing a short circuit.

[0149] To facilitate short-circuiting between the negative terminal (23) and the short-circuit member (56), the negative terminal (23) may further include at least one projection (not shown) protruding toward the short-circuit member (56), and the projection may be spaced apart from the short-circuit member (56).

[0150] In the above embodiments, a secondary battery including a rectangular case has been described, but it is not limited thereto and may include a cylindrical case.

[0151] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention. Explanation of the symbols

[0152] 10, 20: Entry 12, 22: Active material layer 95, 400: Electrode assembly 100: Anode 200, 201, 202, 203, 204, 205, 206: Cathode 300: Separator 310: Cap assembly 500: Case 1000, 1001: Secondary battery

Claims

Claim 1 An electrode comprising an electrode active portion, a substrate having a tab-free portion protruding from the electrode active portion, and an active material layer formed on the electrode active portion of the substrate, wherein the substrate of the electrode active portion includes an opening formed of a plurality of openings. Claim 2 In claim 1, the electrode in which the opening is filled with the active material of the active material layer. Claim 3 An electrode according to claim 1, wherein the tab-free portion is located on one side of the electrode active portion, and the width of the opening is formed to be 50% or less of the length of the electrode active portion in the direction from the one side toward the other side of the electrode active portion. Claim 4 In paragraph 3, the electrode in which the area of ​​the opening is 50% or less of the area of ​​the electrode active portion. Claim 5 In claim 1, the electrode in which the planar shape of the opening is circular or polygonal. Claim 6 In claim 1, the opening is an electrode located on the opposite side of the tab blank portion. Claim 7 In claim 1, the opening is an electrode whose size gradually changes as it moves in one direction. Claim 8 In claim 1, the gap between adjacent openings is an electrode that gradually changes in one direction. Claim 9 In claim 1, the active material layer is an electrode comprising silicon. Claim 10 In claim 1, the electrode to which an electrode tab for drawing current to the outside is electrically connected to the above-mentioned tab-free portion. Claim 11 An electrode assembly comprising: an anode having a first tab-free portion and a first electrode active portion; an anode having an anode active material layer formed on the first electrode active portion of the anode substrate; a cathode having a second tab-free portion and a second electrode active portion; a cathode having a cathode active material layer formed on the second electrode active portion of the cathode substrate; a separator located between the anode and the cathode; and an opening formed on the cathode substrate of the second electrode active portion and comprising a plurality of openings, wherein the opening is located relatively adjacent to the first tab-free portion. Claim 12 In claim 11, the first tab-free portion and the second tab-free portion are electrode assemblies protruding in opposite directions from each other, centered on the first electrode active portion or the second electrode active portion. Claim 13 In paragraph 12, an electrode assembly in which an electrode tab for drawing current to the outside is connected to each of the first tap-free portion and the second tap-free portion. Claim 14 In claim 12, the electrode assembly is formed such that the width of the opening is 50% or less of the length of the second electrode active portion in the direction from the first tab-free portion toward the second tab-free portion. Claim 15 In claim 11, the first temperature of the region adjacent to the first tap-free portion is higher than the second temperature of the region adjacent to the second tap-free portion, and the opening overlaps with a region of relatively high temperature in an electrode assembly. Claim 16 In claim 11, the positive electrode active material layer comprises a nickel-based active material, and the negative electrode active material layer comprises silicon, forming an electrode assembly. Claim 17 In claim 11, the electrode assembly in which the opening is filled with the active material of the active material layer. Claim 18 In paragraph 11, the electrode assembly in which the planar shape of the opening is circular or polygonal. Claim 19 In paragraph 11, the above opening is an electrode assembly whose size gradually changes as it moves in one direction. Claim 20 In claim 11, an electrode assembly in which the spacing between adjacent openings gradually changes in one direction.

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