Electrode assembly and secondary battery including the same

Abstract

To provide an electrode assembly and a secondary battery including the same, in particular, an electrode assembly capable of improving the safety of secondary batteries even under a high-temperature and heat-shrinkage environment of a separator, and a secondary battery.SOLUTION: The electrode assembly includes a cathode plate, an anode plate corresponding to the cathode plate, and first and second separators that are positioned adjacent to each other with the cathode plate or the anode plate interposed therebetween. At least one end of the first separator adheres to at least one end of the second separator along the longitudinal direction of the cathode plate and the anode plate. At least one end of the first and second separators is folded so as to wrap the cathode plate or the anode plate. The electrode assembly further includes an insulating tape covering the folded part of the first and second separators.SELECTED DRAWING: Figure 3a

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0036922, filed on March 22, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly and a secondary battery including the same, and more particularly to an electrode assembly and a secondary battery that can improve the safety of the secondary battery even in a high-temperature thermal shrinkage environment of a separator. [Background technology]

[0003] With technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. As a result, much research is being conducted on secondary batteries that can meet various requirements. Secondary batteries are attracting much attention not only for mobile devices such as mobile phones, digital cameras, and laptops, but also as an energy source for power devices such as electric bicycles, electric cars, and hybrid electric vehicles.

[0004] Small devices such as mobile phones and cameras use small battery packs containing a single battery cell, while medium- to large-sized devices such as laptops and electric vehicles use medium- to large-sized battery packs containing two or more battery cells connected in parallel and / or series.

[0005] Lithium secondary batteries have excellent electrical properties but suffer from poor safety. For example, when lithium secondary batteries are subjected to abnormal operating conditions such as overcharging, overdischarging, exposure to high temperatures, or electrical short circuits, decomposition reactions of the active materials and electrolytes, which are components of the battery, are induced, generating heat and gas. The resulting high temperature and pressure conditions can further accelerate the decomposition reactions, potentially resulting in fire or explosion.

[0006] In a more specific example, in existing electrode assemblies and prismatic or pouch-type secondary batteries including the same, the separator included in the electrode assembly often undergoes thermal shrinkage when exposed to a high-temperature environment. This thermal shrinkage of the separator causes the positive and negative electrodes to come into direct contact with each other, resulting in an electrical short circuit, which can lead to fire or explosion of the lithium secondary battery.

[0007] In particular, as lithium secondary batteries have recently become higher in capacity and voltage, positive electrode active materials containing high amounts of nickel, for example, 60 wt % or more, have been widely used. Such positive electrode active materials containing high amounts of nickel have high heat generation, low structural collapse temperatures, and relatively low thermal stability, which has led to growing concerns about the safety of the secondary batteries, particularly their high-temperature safety.

[0008] Due to these disadvantages of conventional electrode assemblies, there is a continuing demand for the development of technology that can improve the safety of secondary batteries even in a high-temperature heat shrinkage environment of the separator. Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, the present invention provides an electrode assembly that can improve the safety of a secondary battery even in a high-temperature thermal shrinkage environment of a separator, and a secondary battery including the same.

[0010] However, the problems to be solved by the embodiments of the present invention are not limited to the above problems, and can be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0011] The present invention comprises a positive electrode plate and a negative electrode plate corresponding to the positive electrode plate; and first and second separators positioned adjacent to each other with the positive electrode plate or the negative electrode plate sandwiched therebetween, At least one end of the first separator is bonded to at least one end of the second separator along the longitudinal direction of the positive electrode plate and the negative electrode plate, At least one end of the first and second separators is folded so as to surround the positive electrode plate or the negative electrode plate, The electrode assembly further includes an insulating tape covering the folded portions of the first and second separators.

[0012] The present invention also provides a semiconductor device comprising the electrode assembly, and a battery case that houses the electrode assembly. [Effects of the Invention]

[0013] In the electrode assembly of the present invention, a separator film is attached between the stacked positive and negative electrode plates, and is folded to surround the positive and negative electrode plates, with insulating tape covering the periphery.

[0014] As a result, even if the electrode assembly and secondary battery are exposed to a high-temperature environment, the separator can minimize thermal contraction that can cause an electrical short circuit between the positive and negative electrode plates. Therefore, even if a positive electrode active material containing a high content of nickel is used, fire or explosion of the secondary battery can be minimized, thereby maximizing the safety of the lithium secondary battery.

[0015] In addition, since the separators bonded to each other are folded to surround the positive and negative electrode plates, the process of inserting the electrode assembly into a pouch-type battery case can be performed more smoothly.

[0016] Therefore, the present invention can provide a high-capacity, high-energy-density secondary battery by applying a cathode active material containing a high content of nickel, while improving the safety and processability of the secondary battery, thereby making a significant contribution to the provision of a high-quality secondary battery. [Brief explanation of the drawings]

[0017] [Figure 1]1 is a perspective view schematically illustrating an electrode assembly according to an embodiment of the present invention. [Figure 2] 1 is a plan view schematically illustrating an electrode-separator stack for manufacturing an electrode assembly according to an embodiment of the present invention. [Figure 3A] 1 is a plan view schematically illustrating an electrode assembly according to an embodiment of the invention. [Figure 3B] 1 is a plan view schematically illustrating an electrode assembly according to an embodiment of the invention. [Figure 4A] 1 is a cross-sectional view schematically illustrating an electrode assembly according to an embodiment of the invention. [Figure 4B] 4A is an enlarged cross-sectional view showing the folded portions of the first and second separation membranes indicated by circles in FIGS. 3A, 3B, and 4A. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will now be described in detail with reference to the accompanying drawings, in which various embodiments of the present invention can be easily implemented by those skilled in the art. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0019] For clarity of explanation, parts unnecessary for explanation are omitted, and the same reference numerals are used throughout the specification to refer to the same or similar components.

[0020] Furthermore, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the invention is not necessarily limited to those shown in the drawings. In the drawings, thicknesses are exaggerated to clearly show various layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for the convenience of explanation.

[0021] Furthermore, throughout the specification, when a part "comprises" a certain element, this means that it can further include other elements, but not excluding other elements, unless specifically stated to the contrary.

[0022] Furthermore, throughout the specification, when we say "on a plane (or plan view)," this means when the subject part is viewed from above, and when we say "on a cross section (or cross section)," this means when the subject part is cut vertically and viewed from the side.

[0023] 1, 3A, 3B and 4A show a perspective view, a plan view and a cross-sectional view, respectively, of an electrode assembly according to an embodiment of the invention.

[0024] As shown in these Figures 1, 3A, 3B and 4A, according to one embodiment of the invention: A positive electrode plate 110, a negative electrode plate 130 corresponding to the positive electrode plate 110; The positive electrode plate 110 or the negative electrode plate 130 is sandwiched between first and second separators 120a and 120b, and the first and second separators 120a and 120b are adjacent to each other. At least one end of the first separator 120a is bonded to at least one end of the second separator 120b along the longitudinal direction of the positive electrode plate 110 and the negative electrode plate 130, At least one end of the first and second separators 120a and 120b is folded to surround the positive electrode plate 110 or the negative electrode plate 130, The electrode assembly 100 further includes an insulating tape 140 covering the folded portions of the first and second separators 120a and 120b.

[0025] The electrode assembly 100 of the embodiment basically includes a stacked electrode-separator stack in which positive electrode plates 110 and negative electrode plates 130 are alternately stacked, and first and second separators 120a and 120b are formed between the alternately stacked positive electrode plates 110 and negative electrode plates 130. Referring to FIG. 2, in this stacked electrode-separator stack, the first and second separators 120a and 120b are formed / positioned to have widths greater than the positive electrode plates 110 and negative electrode plates 130 (shown by squares on the right of FIG. 2).

[0026] Also, as shown in Figures 3A, 3B, and 4A, the first separator 120a and the second separator 120b, which are arranged adjacent to each other, have at least one end bonded to each other along the longitudinal direction of the positive electrode plate 110 and the negative electrode plate 130, and the bonded portion of the first and second separators 120a, 120b is folded to surround the positive electrode plate 110 and / or the negative electrode plate 130 (circular portions in Figures 3A, 3B, and 4A).

[0027] In addition, an insulating tape 140 is formed to surround the periphery of the positive electrode plate 110 and the negative electrode plate 130 along the width direction perpendicular to the longitudinal direction while covering the folded portions of the first and second separators 120a and 120b.

[0028] Thus, in one embodiment of the electrode assembly 100, at least one end of the first and second separators 120a, 120b adjacent to each other are bonded to each other and folded around the positive electrode plate 110 and the negative electrode plate 130, and three separator fixing structures are provided in which insulating tape 140 is formed around the folded portions of the first and second separators 120a, 120b and around the electrode plates 110, 130.

[0029] Due to the fixing structure and fixing force of the first and second separators 120a, 120b, even if the electrode assembly 100 and the secondary battery are exposed to a high-temperature environment or heat is generated from the positive electrode active material, the thermal contraction forces of the first and second separators 120a, 120b are offset, preventing the first and second separators 120a, 120b from thermally contracting.

[0030] As a result, it is possible to minimize the occurrence of electrical short circuits caused by contact between the positive electrode plate 110 and the negative electrode plate 130 due to thermal contraction of the separators. In particular, compared to an electrode assembly in which the first and second separators are simply formed to be wider than the electrode plates in order to improve battery safety, the electrode assembly of the embodiment having the separator fixing structure described above can further significantly reduce thermal contraction of the separators and the resulting electrical short circuits of the electrode plates.

[0031] Therefore, by applying the electrode assembly of one embodiment, it is possible to minimize the risk of fire or explosion in a secondary battery, thereby significantly improving the safety of a secondary battery, particularly a high-capacity, high-energy-density lithium secondary battery that uses a high-nickel-containing positive electrode active material. In addition, because the first and second separators 120a and 120b bonded to each other are folded to surround the positive electrode plate 110 and the negative electrode plate 130, a process of inserting the electrode assembly 100 into a pouch-type battery case can be performed more smoothly.

[0032] Meanwhile, in the electrode assembly 100 according to the above-described embodiment, the positive electrode plate 110 and the negative electrode plate 130 may each include an electrode current collector, an electrode active material layer formed on the electrode current collector, and electrode tabs 115, 135 formed to protrude from the electrode current collector.

[0033] Among these, the electrode current collector (i.e., positive electrode current collector) included in the positive electrode plate 110 may generally have a thickness of 3 to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity and does not induce chemical changes in the secondary battery including the electrode assembly 100 according to an embodiment of the invention, and examples thereof include stainless steel, aluminum, nickel, titanium, baked carbon, and aluminum or stainless steel surfaces that have been surface-treated with carbon, nickel, titanium, silver, etc.

[0034] The electrode active material layer (i.e., the positive electrode active material layer) of the positive electrode plate 110 includes a positive electrode active material, and examples of the positive electrode active material include layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), compounds substituted with one or more transition metals, and compounds represented by the chemical formula Li 1+y Mn 2-y O4 (where y is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2, lithium copper oxide (Li2CuO2), vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7, and vanadium oxides with the chemical formula LiNi 1-y M yO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and y = 0.01 to 0.3), Ni-site type lithium nickel oxide, chemical formula LiMn 2-y M y Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides expressed as Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn), LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion, disulfide compounds, and Fe2(MnO4)3.

[0035] However, when a lithium transition metal composite oxide-based positive electrode active material containing 60 wt % or more, or 60 to 99 wt %, of nickel is used, safety issues such as ignition, heat generation, or explosion of the secondary battery may occur more severely. Therefore, the structure of the electrode assembly according to the embodiment of the present invention is more preferably applicable to electrode assemblies and secondary batteries containing such positive electrode active materials.

[0036] Meanwhile, the positive electrode active material layer can be manufactured by applying a positive electrode mixture containing a mixture of the positive electrode active material, a conductive agent, and a binder to the remaining area of ​​the positive electrode current collector except for the area where the positive electrode tab 115 is formed, followed by drying and rolling, and a filler can be further added to the mixture if necessary. However, the composition and method of forming such a positive electrode active material layer can be the same as those of active material layers contained in general lithium secondary batteries, and therefore further description thereof will be omitted.

[0037] Meanwhile, the electrode current collector (i.e., negative electrode current collector) included in the negative electrode plate 130 may generally have a thickness of 3 to 500 micrometers. The negative electrode current collector is not particularly limited as long as it has high conductivity and does not induce chemical changes in the battery including the electrode assembly, and examples of the negative electrode current collector include copper, stainless steel, and aluminum-cadmium alloy.

[0038] The electrode active material layer (i.e., the negative electrode active material layer) of the negative electrode plate 130 includes a negative electrode active material, and the negative electrode active material is, for example, carbon such as non-graphitizable carbon or graphite-based carbon; Li x FeO3(0≦x≦1), Li x WO2(0≦x≦1), Sn x Me 1-x Me' y O z Examples of materials that can be used include metal composite oxides such as (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Groups 1, 2, and 3 of the periodic table, and halogens; 0≦x≦1; 1≦y≦3; 1≦z≦8), lithium metal, lithium alloys, silicon-based alloys, tin-based alloys, metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5, conductive polymers such as polyacetylene, and Li-Co-Ni-based materials.

[0039] The negative electrode active material layer can be manufactured by applying a negative electrode mixture containing a mixture of the negative electrode active material, a conductive agent, and a binder to the remaining area of ​​the negative electrode current collector except for the area where the negative electrode tab 135 is to be formed, followed by drying and rolling, and a filler can be further added to the mixture as needed. The composition and method of forming the negative electrode active material layer can also be any of the commonly used compositions and methods.

[0040] As shown in FIG. 2 , in a manufacturing process of the electrode assembly 100 according to one embodiment, the positive electrode plates 110 and the negative electrode plates 130 are alternately stacked, and first and second separators 120 a and 120 b having larger widths are formed between the alternately stacked positive electrode plates 110 and the negative electrode plates 130, respectively, to form a stacked electrode-separator laminate that electrically insulates the positive electrode plates 110 and the negative electrode plates 130.

[0041] In this electrode-separator stack, the adjacent positive electrode plate 110 and negative electrode plate 130 and the first and second separators 120a, 120b therebetween are in physical contact with each other (for reference, although the positive electrode plate 110, negative electrode plate 130, and first and second separators 120a, 120b are shown spaced apart in FIG. 2 for convenience of illustration). In this case, the first and second separators 120a, 120b may only be in physical contact with the opposing positive electrode plate 110 or negative electrode plate 130, or may be bonded to the opposing positive electrode plate 110 or negative electrode plate 130. Therefore, when the electrode assembly 100 and secondary battery are exposed to a high-temperature environment, the thermal contraction forces of the first and second separators 120a, 120b can be further offset, further minimizing the thermal contraction of the separators.

[0042] In the electrode-separator laminate and the electrode assembly 100 manufactured therefrom, the first and second separators 120a and 120b may be thin insulating membranes having high ion permeability, mechanical strength, low shrinkage, etc. For example, sheets or nonwoven fabrics made of chemically resistant and hydrophobic olefin polymers such as polypropylene, glass fiber, or polyethylene may be used.

[0043] Meanwhile, in the electrode-separator stack, at least one or both ends of the adjacent first separator 120a and second separator 120b may be bonded to each other along the longitudinal direction of the positive electrode plate 110 and negative electrode plate 130 (the square on the right in FIG. 2, and the circular portions in FIGS. 3A, 3B, and 4). In this case, it is more preferable that both ends of the first and second separators 120a and 120b be bonded to each other along the longitudinal direction of the electrode plates 110 and 130 to more effectively suppress thermal contraction of the first and second separators 120a and 120b.

[0044] To bond the first and second separators 120a, 120b to each other, a binder contained in the first and second separators 120a, 120b may be heat-sealed, or, in another optional embodiment, an adhesive may be applied to the contact portion of the adjacent first and second separators 120a, 120b. Examples of such adhesives include, but are not limited to, hot melt adhesives containing ethylene vinyl acetate, polyurethane, or a mixture thereof.

[0045] In addition, in one embodiment of the electrode assembly 100, at least one or both ends of the first and second separators 120a, 120b bonded to each other are folded to surround the positive electrode plate 110 and / or the negative electrode plate 130 (circular portions in FIGS. 3A, 3B, and 4A). In this case, one or both ends of the bonded first and second separators 120a, 120b may be folded only once to surround the positive electrode plate 110 and / or the negative electrode plate 130, or may be folded twice as shown in FIG. 4B.

[0046] This double-folded structure can more effectively prevent the separator from thermally shrinking at high temperatures, making the shape of the electrode assembly 100 more compact and facilitating the process of inserting it into a pouch-type battery case, etc.

[0047] Meanwhile, in the above-described electrode assembly 100, insulating tapes 140 are formed on the folded portions of the first and second separators 120a and 120b, covering the folded portions of the separators and surrounding the peripheries of the positive electrode plate 110 and the negative electrode plate 130 along a width direction perpendicular to the longitudinal direction. As shown in FIGS. 1, 3A, and 3B, multiple insulating tapes 140 may be attached at regular intervals to surround the folded portions of the separators and the peripheries of the positive electrode plate 110 and the negative electrode plate 130. Also, referring to FIG. 3B, in addition to the insulating tapes 140, additional insulating tapes 140 may be attached to further surround the peripheries of the positive electrode plate 110 and the negative electrode plate 130 around the protruding portions of the electrode tabs 115 and 135.

[0048] By adding the insulating tape 140, the high temperature thermal shrinkage of the separator can be further suppressed, and the safety of the secondary battery can be further improved.

[0049] The type of the insulating tape 140 is not particularly limited, but for example, a polyimide insulating tape or a polyester insulating tape (for example, a PET or PEN insulating tape) can be used.

[0050] The electrode assembly may be impregnated with an electrolyte and housed in a battery case to form a secondary battery. The electrode assembly may include a stacked electrode-separator laminate and is typically housed in a pouch-type or prismatic battery case.

[0051] In this case, the battery case may be a general battery case that has been applied to a pouch-type or square-type secondary battery.

[0052] In addition, the electrode assembly and the secondary battery including the same can be applied to various devices, including, but not limited to, transportation means such as electric bicycles, electric cars, and hybrid cars, and the electrode assembly and the secondary battery including the same can be used in various devices, which also fall within the scope of the invention.

[0053] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0054] 100: Electrode assembly 110: Electrode plate (positive electrode plate) 115: Electrode tab (positive electrode tab) 120a, 120b: first and second separation membranes 130: Electrode plate (negative electrode plate) 135: Electrode tab (negative electrode tab) 140:Insulating tape

Claims

1. A positive electrode plate; a negative electrode plate corresponding to the positive electrode plate; and first and second separators positioned adjacent to each other with the positive electrode plate or the negative electrode plate sandwiched therebetween, At least one end of the first separator is bonded to at least one end of the second separator along the longitudinal direction of the positive electrode plate and the negative electrode plate, At least one end of the first and second separators is folded so as to surround the positive electrode plate or the negative electrode plate, The electrode assembly further includes an insulating tape covering the folded portions of the first and second separators.

2. The positive electrode plate and the negative electrode plate each include an electrode current collector and an electrode active material layer formed on the electrode current collector; The electrode assembly according to claim 1 , further comprising an electrode tab formed protruding from the electrode current collector.

3. The electrode assembly according to claim 1 or 2, wherein the first and second separators have a width greater than that of the positive and negative electrode plates.

4. The electrode assembly according to claim 1 , wherein the first and second separators are bonded to the opposing positive electrode plate or negative electrode plate.

5. Both ends of the first separator are bonded to both ends of the second separator along the longitudinal direction of the positive electrode plate and the negative electrode plate, The electrode assembly according to claim 1 , wherein both ends of the first and second separators are folded so as to surround the positive electrode plate or the negative electrode plate.

6. 6. The electrode assembly according to claim 1, wherein at least one end of the first and second separators bonded to each other is double-folded.

7. 3. The electrode assembly according to claim 1, wherein the insulating tape is formed to surround the peripheries of the positive electrode plate and the negative electrode plate along a width direction perpendicular to the longitudinal direction while covering the folded portions of the first and second separators.

8. The electrode assembly according to claim 2 , wherein the insulating tape is formed to further surround the periphery of the positive electrode plate and the negative electrode plate around the protruding portion of the electrode tab.

9. The electrode assembly according to any one of claims 1 to 8; a battery case that houses the electrode assembly.

10. The secondary battery according to claim 9 , wherein the battery case is a pouch-type battery case or a prismatic battery case.

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