Electrode group three-dimensional

Abstract

The present invention relates to an electrode assembly including a stack and a second separator. The stack includes a first electrode, a second electrode, and a first separator folded in a zigzag pattern, the first separator including a stacking portion and a folding portion. The first and second electrodes are alternately arranged between spacer portions of the first separator, and the second separator extends along the upper surface, the lower surface, and at least a pair of opposing side surfaces of the stack. Side portions of the first separator define portions of the sides of the stack where the first and second electrodes are not disposed. The second separator is bonded to at least one of the side portions.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0090590 filed with the Korean Intellectual Property Office on July 9, 2021, and Korean Patent Application No. 10-2021-0090591 filed with the Korean Intellectual Property Office on July 9, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly, and more particularly, to an electrode assembly in which the size of a separator included in the electrode assembly is reduced to increase the electrode density of the electrode assembly. [Background technology]

[0003] Secondary batteries, unlike primary batteries, are rechargeable and have the potential to be small and have large capacities. As technological development and demand for mobile devices increases, the demand for secondary batteries as an energy source is rapidly increasing.

[0004] Secondary batteries are classified into coin-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries depending on the shape of the battery case. The electrode assembly attached to the inside of the battery case in a secondary battery is a power generating element that can be charged and discharged and is made up of a laminated structure of electrodes and a separator.

[0005] Electrode assemblies are generally classified into sheet types in which a separator is interposed between an anode and a cathode and the active material is coated on the electrode, rolled-up jellyroll types, and stack types in which multiple anodes and cathodes are stacked. There are two types: a type in which the electrodes are stacked one after the other with a separator sandwiched between them, and a stack-and-fold type in which stacked unit cells are wound up in a long separator film.

[0006] In a conventional manufacturing process of a stack-and-fold type electrode assembly, electrodes and a separator are stacked, and the stack in which the electrodes and the separator are bonded is heated and compressed to manufacture the electrode assembly. At this stage of the electrode assembly process, the separator is folded, but the electrodes are exposed to the outside.

[0007] To overcome certain drawbacks of conventional electrode assemblies, the electrodes and separators are heated and stacked, and the layers are stacked and compressed so that they adhere to each other at the same time, and the outer side of the separator is wrapped around the outermost edge of the electrode stack, so that the stack is wrapped around the outer side of the separator to form the electrode assembly.

[0008] However, in this electrode assembly, because a separator envelops the outermost periphery of the laminate, a space may be formed between the side of the separator located on the side of the electrode assembly and the side electrode of the electrode assembly, which may cause wrinkles in the side separator of the electrode assembly. This configuration may result in a problem of reduced energy density of the electrode assembly.

[0009] Therefore, it is necessary to take measures against the space formed between the side of the separator and the side of the electrode assembly. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention provides an electrode assembly that can reduce the width of an electrode assembly by enclosing the outermost edge of a stack formed by stacking a separator or an electrode and an edge of another separator with the outermost edge separator. A portion of the outermost edge separator located along the side of the stack can be shrunk by heating and compressing the side of the stack, thereby shrinking the stack. [Means for solving the problem]

[0011] One embodiment of the present invention provides an electrode assembly including a first electrode, a stack including a first separator folded in a zigzag configuration and including a folding portion on each side between stacked portions, and a second electrode arranged alternately with the first electrode between the stacked portions of the first separator, and a second separator extending along the upper surface, lower surface, and at least a pair of opposing side surfaces of the stack, wherein the folding portions of the first separator are positioned on the sides of the stacked portion and include areas where the first electrode and the second electrode are not arranged, and the second separator is adhered to at least one of the folding portions.

[0012] In one embodiment of the present invention, there is provided an electrode assembly, wherein each of the folding portions includes a folding portion of the first separator.

[0013] In one embodiment of the present invention, an electrode assembly is provided in which folding portions are alternately positioned on the sides of the first electrode and the second electrode of the laminate.

[0014] In one embodiment of the present invention, there is provided an electrode assembly, wherein the number of folding portions of the first separator attached to the second separator is 30% or more of the total number of folding portions.

[0015] In one embodiment of the present invention, there is provided an electrode assembly, wherein each of the laminated portions of the first separator has the same length as the first and second electrodes of the laminate, and each of the folding portions extends between each adjacent pair of the laminated portions.

[0016] In one embodiment of the present invention, there is provided an electrode assembly, wherein two or more of the folding portions are adhered to each other, and the second separator is adhered to at least a portion of the folding portions.

[0017] In one embodiment of the present invention, an area of ​​the second separator attached to the folded portion of the first separator is 30% or more of the total area of ​​the inner separator surface of the second separator located on the opposite side of the laminate.

[0018] In one embodiment of the present invention, there is provided an electrode assembly, wherein the folding portion is folded one or more times in a direction parallel to the stacking direction of the laminate.

[0019] In one embodiment of the present invention, there is provided an electrode assembly, wherein the length of one of the folding portions is 0.1% to 1% of the overall length of the stacked portion to which the folding portion is attached.

[0020] In one embodiment of the present invention, an electrode assembly is provided, in which the first separator is adhered to at least one of the first electrodes. In one embodiment of the present invention, an electrode assembly is provided, in which the first separator is adhered to at least one of the second electrodes. In one embodiment of the present invention, an electrode assembly is provided, in which the first separator is adhered to at least one of the first electrodes and at least one of the second electrodes. In one embodiment of the present invention, an electrode assembly is provided, in which the second separator is adhered to at least one of the second electrodes. In one embodiment of the present invention, an electrode assembly is provided, in which the second separator is adhered to at least one of the first electrodes and at least one of the second electrodes. In one embodiment of the present invention, an electrode assembly is provided, in which both the first separator and the second separator are adhered to at least one of the first electrodes and the second electrodes.

[0021] In one embodiment of the present invention, there is provided an electrode assembly, wherein the wet adhesive strength of at least one of the second separator and the folding portion adhered to the second separator is 40 gf / 25 mm to 70 gf / 25 mm.

[0022] In one embodiment of the present invention, there is provided an electrode assembly in which the second separator is a continuation of the first separator, and an end of the first separator is shared with an end of the second separator. In another embodiment of the present invention, there is provided an electrode assembly in which the ends of the first separator and the second separator do not overlap. [Effects of the Invention]

[0023] According to an electrode assembly according to an embodiment of the present invention, the electrode density and therefore the energy density of the electrode assembly can be increased compared to conventional electrode assemblies by constricting the space between the outermost separator surrounding the outermost part of the laminate in which the electrodes and separators are stacked and the laminate.

[0024] In one embodiment, the electrode assembly may be manufactured with dimensions that correspond to the interior space of a pouch, such as the interior space of a can for use in a pouch-type battery or a cylindrical battery. In this way, the size of the pouch or can can be easily varied as desired without concern for the manufacturability of the electrode assembly. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view showing an electrode assembly according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing a stack of the electrode assembly of FIG. [Figure 3] 1 is a plan view showing an apparatus for manufacturing an electrode assembly according to an embodiment of the present invention; [Figure 4] FIG. 4 is a front view showing a manufacturing apparatus for the electrode assembly of FIG. 3. [Figure 5] 4 is a cross-sectional view of an electrode assembly in a side sealing portion of the electrode assembly manufacturing apparatus of FIG. 3 according to an embodiment of the present invention. [Figure 6] FIG. 2 is a process flow diagram of a manufacturing process of an electrode assembly according to an embodiment of the present invention. [Figure 7] 2 is a pair of photographs taken with an optical microscope showing an enlarged cross section of the electrode assembly generally along line AA' of FIG. 1. [Figure 8] 1 is an enlarged photograph showing an enlarged cross section of an electrode assembly taken with an optical microscope after cutting the cross section of Comparative Examples 1 and 2, which are further described in the present invention. [Figure 9] 10 is a photograph of an electrode assembly according to Comparative Example 3. [Explanation of symbols]

[0026] S ···Laminate 1...1st electrode 2...Second electrode 4...1st separation membrane 4a...Laminated part 4b Folding section 5...Second separation membrane 100 Electrode assembly manufacturing apparatus 10 Stack Table 20...Separation membrane supply section 21 Separation membrane roll 22 Separation membrane heating section 30...First electrode supply section 31 First electrode placement table 32 First transfer head 33 First electrode roll 34 First cutter 35 No. 1 Conveyor 36 First electrode supply head 37 First moving part 40...Second electrode supply section 41 Second electrode placement table 42 Second transfer head 43 Second electrode roll 44 Second cutter 45 Second conveyor 46 Second electrode supply head 47 Second moving part 50 Press Department 50a, 50b: A pair of pressure blocks 60 Side sealing part 60a, 60b Heating bar DETAILED DESCRIPTION OF THE INVENTION

[0027] The detailed description of the present invention is intended to fully explain the present invention to those skilled in the art. Throughout this specification, when a part is described as "comprising" a certain element or "featuring" a certain structure and shape, this means that other elements, structures, and shapes may be included, without excluding other elements or other structures and shapes, unless otherwise specified to the contrary.

[0028] Since the present invention can be modified in various ways and can have various embodiments, specific embodiments will be presented and described in detail in the detailed description, but this is not intended to limit the content of the invention to the embodiments, and it should be understood that the present invention includes all modifications, equivalents, or alternatives that fall within the spirit and technical scope of the present invention.

[0029] The present invention will be described in detail below with reference to the drawings. However, the drawings are for illustrative purposes only and the scope of the present invention is not limited by the drawings.

[0030] 1 and 2, the electrode assembly may include a laminate S and a second separator 5 surrounding the laminate S.

[0031] As shown, in the laminate S, the first electrodes 1 and the second electrodes 2 may be alternately arranged between the laminated portions 4a of the first separator 4. Furthermore, as shown, the first separator 4 may be folded in a zigzag pattern to form the laminated portions 4a.

[0032] 3 to 5, the electrode assembly manufacturing apparatus 100 includes a stack table 10, a separation membrane supply unit 20, a first electrode supply unit 30, a second electrode supply unit 40, and a side sealing unit 60.

[0033] The stack table 10 may have a single support surface on which the first electrode 1, the stacked portions of the first separator 4, and the second electrode 2 are stacked in this order. A stack S, which includes the first electrode 1, the second electrode 2, and the stacked portions of the first separator 4 located between the first and second electrodes, may be attached to a first combination of the first electrode 1, the stacked portions 4a, and the second electrode 2. The first separator 4 may be folded in a zigzag pattern to form the stacked portions 4a and folding portions 4b on opposing sides of each stacked portion 4a. In this manner, the stacked portions 4a of the first separator 4 may be disposed between each of the first electrodes 1 and each of the second electrodes 2 in the stack S.

[0034] The stack table 10 can rotate in one direction toward each stack portion 4a of the first separator 4 supported by the stack table 10 and each first electrode 1 supplied to be stacked on the previously stacked electrode and separator stack portion 4a, and can rotate in the opposite direction toward each second electrode 2 supplied to be stacked on each of the stack portions 4a of the first separator 4 supported by the stack table 10 and the previously stacked electrode and separator stack portion 4a. Therefore, the electrode assembly manufacturing apparatus 100 may further include a rotating unit (not shown) that rotates the stack table 10. For details regarding such a rotating unit, see Korean Patent Publication No. 10-2020-0023853, which is incorporated herein by reference.

[0035] In the electrode assembly manufacturing apparatus 100, the first electrode supply unit 30 may be located on one side of the stack table 10, and the second electrode supply unit 40 may be located on the other side of the stack table 10. In the configuration of the electrode assembly manufacturing apparatus 100 shown in the figure, the rotation unit can rotate the stack table 10 alternately in the direction of the first electrode supply unit 30 and the direction of the second electrode supply unit 40.

[0036] For example, the separation membrane supplier 20 may be located above the stack table 10, i.e., along the stacking direction of the stack S. In this configuration, the first electrode supplier 30 may be located on the left side of the stack table 10, and the second electrode supplier 40 may be located on the right side of the stack table 10 based on the stacking direction of the stack S.

[0037] In the configuration of the electrode assembly manufacturing apparatus 100 shown in the figures, the rotating unit can rotate the stack table 10 so that, when stacking the first electrode 1, the stack table 10 faces the first transfer head 32 or another first mounting device for temporarily holding the first electrode 1. When stacking the second electrode 2, the rotating unit can rotate the stack table 10 so that the stack table 10 faces the second mounting device or second transfer head 42 for temporarily holding the second electrode 2.

[0038] When using the electrode assembly manufacturing apparatus 100, the stacking unit 4a and folding unit 4b of the first separator 4 may be supplied by the separator supply unit 20 and placed on the stack table 10 in a partial array. The rotating unit may rotate the stack table 10 to the left, and the first electrode 1 supplied from the first electrode supply unit 30 may be supplied onto the first separator 4. The rotating unit may also rotate the stack table 10 to the right, and this rotation may occur simultaneously with the supply of the first separator 4. In this rotation configuration of the rotating unit, the first separator 4 may form a first pocket in the form of a left pocket covering the lower, right, and upper surfaces of the first electrode 1 of the stack S. Here, the first electrode 1 of the stack S may be placed on the stack table 10 so that the upper surface of the first electrode 1 is partially covered by the first separator 4. In this case, the second electrode 2 may be supplied from the second electrode supply unit 40 to the portion of the first separator 4 covering the upper surface of the first electrode 1.

[0039] By repeating the above process, the first separator 4 may be placed on the stack table 10 from the separator supply unit 20 in the form of a left pocket and a right pocket facing the left pocket. In this configuration, when each portion of the first separator 4 is positioned on the stack table 10, the left and right pockets alternately form left and right openings, respectively, and these left and right openings may be configured to accommodate the first electrode 1 and the second electrode 2 supplied by the first electrode supply unit 30 and the second electrode supply unit 40, respectively. Furthermore, when the first separator 4 is folded, the folded portion 4b of the first separator 4, which may be in the form of a folded portion, may be provided in a position facing the left and right openings (see FIG. 2). In some alternative arrangements, which may be mirror arrangements with respect to the arrangement of the electrode assembly manufacturing apparatus 100, the first separator 4 may form a first pocket in the form of a right pocket covering the lower surface, left surface, and upper surface of the second electrode 2. In such a mirror arrangement, the second electrode 2 may be the first electrode of the laminate S placed on the stack table 10.

[0040] The stack table 10 may further include a table body (not shown) that determines the shape of the stack table 10 and a table heater (not shown), and the table heater may be, for example, a resistance coil embedded above, below, or inside the body of the stack table 10. The table heater can heat the table body to heat the stack S placed on the stack table 10.

[0041] The table heater can heat the laminate S before the laminate S is heated and compressed by the press unit 50 of the electrode assembly manufacturing apparatus 100. Preheating the laminate S with such a table heater can shorten the time it takes for heat to be conducted to the center of the laminate S, and can reduce the pressing time required for sufficient pressure to be applied by the press unit 50.

[0042] In one embodiment, the first electrode 1 and the second electrode 2 may be an anode and a cathode. When the first electrode 1 is an anode, the second electrode 2 may be a cathode, and when the first electrode 1 is a cathode, the second electrode 2 may be an anode.

[0043] In one embodiment, the positive electrode can be prepared by, for example, coating a positive electrode current collector with a positive electrode coating mixture containing a positive electrode active material, a conductive material, and a binder, followed by drying. A filler may be added to the mixture as needed. Such materials may be any suitable material used in the relevant field, particularly a material commonly used in a particular application field.

[0044] Specifically, the positive electrode active material is, for example, a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; 1+x Mn 2-x Lithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3) 2-x M x Examples of such compounds include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and x 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(MoO4)3.

[0045] There are no particular limitations on the materials that can be used for the anode current collector. The anode current collector preferably has relatively high conductivity without undergoing chemical changes when used in a battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like may be used. The anode current collector is preferably aluminum. The surface of the current collector that comes into contact with the coating mixture preferably has fine irregularities to enhance adhesion between the current collector and the anode coating mixture. Various forms are possible, including films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics. The anode current collector generally has a thickness of 3 μm to 500 μm.

[0046] The conductive material contained in the anode coating mixture may generally be contained in an amount of 1 to 50 wt % of the total weight of the mixture including the anode active material. For example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; conductive fiber such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum powder, and nickel powder; conductive whiskey such as zinc oxide and potassium titanate; conductive metal oxide such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0047] The binder in the anode coating mixture aids in bonding between the active material and the conductive material and in binding the coating mixture to the current collector. Such binders may generally be present in an amount of 1 to 50% by weight of the total weight of the mixture, including the anode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butylene rubber, fluororubber, and various copolymers.

[0048] The filler optionally added to the anode coating mixture may be used as a component to suppress anode expansion. Such fillers are not particularly limited and may include fibrous materials that do not undergo chemical changes when used in a battery. Examples of fibrous materials that can be used include olefin polymers such as polyethylene and polypropylene; glass fiber; and carbon fiber.

[0049] In one embodiment, the cathode may be prepared by applying a cathode active material to a cathode current collector, drying, and pressing the applied material. The cathode may further contain, as needed, a conductive material, a binder, a filler, and the like. In this case, materials commonly used in the art may be used. Specifically, the cathode active material may be, for example, carbon, such as non-graphitizable carbon or graphite-based carbon; Li x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1), Sn x Me 1-x Me' y O zMetal composite oxides such as (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8); lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials, etc. may be used.

[0050] The material that can be used for the cathode current collector is not particularly limited. The cathode current collector preferably does not undergo a chemical change when used in a battery and has a relatively high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those surface-treated with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used.

[0051] Also, similar to the anode current collector, fine irregularities can be formed on the surface to strengthen the binding force of the cathode active material. It may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven bodies, etc. Further, the cathode current collector may generally have a thickness of 3 μm to 500 μm.

[0052] In one embodiment of the present invention, the separator may be an organic / inorganic composite porous SRS (Safety-Reinforcing Separators) separator. The SRS separator may have a structure in which a coating layer component containing inorganic particles and a binder polymer is applied on a polyolefin-based separator substrate.

[0053] Such an SRS separator does not undergo high-temperature thermal shrinkage due to the heat resistance of the inorganic particles, so even if the electrode assembly penetrates through a needle-shaped conductor, the elongation rate of the safety separator can be maintained.

[0054] The SRS separator may have a uniform pore structure formed by the pore structure contained in the separator substrate itself and the interstitial volume between the inorganic particles that make up the coating layer. The pores not only significantly reduce external impacts on the electrode assembly, but also allow for smooth movement of lithium ions through the pores, allowing for a high impregnation rate due to the large amount of electrolyte that is filled, thereby improving battery performance.

[0055] In one embodiment of the present invention, the separator may have a width dimension (perpendicular to the longitudinal dimension of the separator) that extends outward from both sides beyond the edges corresponding to the adjacent anode and cathode (hereinafter, the "excess portions" of the separator). Furthermore, the separator may have a structure in which a coating layer thicker than the separator is formed on one or both sides of the excess portions to prevent the separator from shrinking. For details regarding the thick coating layer on the excess portions extending outward from the separator, see Korean Patent Publication No. 10-2016-0054219, the entire contents of which are incorporated herein by reference. In one embodiment of the present invention, the excess portions of the separator may each be 5% to 12% of the width of the separator. Furthermore, in another embodiment of the present invention, the coating layer may be coated on both sides of the separator with a size that is 50% to 90% of the width of the excess portion of the separator. Furthermore, the widths of the coating layers on both sides may be the same or different.

[0056] In one embodiment of the present invention, the coating layer may contain inorganic particles and a binder polymer.

[0057] In one embodiment of the present invention, examples of the polyolefin-based separation membrane component include high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high-molecular-weight polyethylene, polypropylene, or derivatives thereof.

[0058] In one embodiment of the present invention, the thickness of the coating layer may be smaller than the thickness of the first electrode or the second electrode. In a specific example, the thickness of the coating layer may be 30% to 99% of the thickness of the first electrode or the second electrode.

[0059] In one embodiment of the present invention, the coating layer may be formed by wet coating or dry coating.

[0060] In one embodiment of the present invention, the substrate and coating layer are present in a form where the pores on the surface of the polyolefin-based separator substrate and the coating layer are intertwined (anchoring), thereby allowing the separator substrate and the active layer to be physically strongly bonded. In this case, the thickness ratio of the separator substrate to the active layer may be 9:1 to 1:9. Preferably, the thickness ratio may be 5:5.

[0061] In one embodiment of the present invention, the inorganic particles may be inorganic particles commonly used in the art. The inorganic particles interact with each other to form micropores in the form of void spaces between the mineral particles, and at the same time, they can help maintain the physical structure of the coating layer. In addition, the inorganic particles generally have physical properties that do not change even at high temperatures of 200°C or higher, so the formed organic / inorganic composite porous film has excellent heat resistance.

[0062] In addition, the materials that can be used for the inorganic particles are not particularly limited, but are preferably electrochemically stable materials. That is, the inorganic particles that can be used in the present invention are those that are within the operating voltage range of the applied battery (for example, Li / Li +There are no particular limitations on the inorganic particles, as long as they do not undergo oxidation and / or reduction reactions at a voltage (0 to 5 V relative to the reference voltage). In particular, the use of inorganic particles with ion-transfer ability can increase the ionic conductivity in the electrochemical device, thereby improving performance. Therefore, it is desirable to use inorganic particles with as high an ionic conductivity as possible. Furthermore, if the inorganic particles have a high density, it becomes difficult to disperse the inorganic particles during coating, which increases the weight of the battery during battery manufacture. Therefore, it is preferable to use inorganic particles with as low a density as possible. Furthermore, inorganic particles with a high dielectric constant can contribute to increasing the degree of dissociation of electrolyte salts, such as lithium salts, in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte solution.

[0063] For the reasons mentioned above, the inorganic particles may be at least one type selected from the group consisting of inorganic particles having piezoelectricity and inorganic particles having lithium ion transport ability.

[0064] The piezoelectric inorganic particles are non-conductors under normal pressure, but when a certain pressure is applied, they change their internal structure to allow electricity to pass through. They also have a high dielectric constant of 100 or more. When a certain pressure is applied to the piezoelectric inorganic particles, they generate electric charges, and one side becomes positively charged and the other side becomes negatively charged, generating a potential difference between the two sides (e.g., a separator).

[0065] When inorganic particles having the above characteristics are used as a coating layer component, if an internal short circuit occurs between the electrodes due to an external impact such as a needle-shaped conductor, the inorganic particles coated on the separator may prevent the anode and cathode from coming into direct contact. In addition, the piezoelectricity of the inorganic particles generates a potential difference within the particles, which causes electron transfer (i.e., the flow of a minute current) between the electrodes, resulting in a gradual decrease in the battery voltage and thereby improved safety.

[0066] Examples of inorganic particles having piezoelectricity include BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT), PB(Mg3Nb 2 / 3 )O3-PbTiO3 (PMN-PT) and hafnia (HfO2), but is not limited thereto.

[0067] The inorganic particles having lithium ion transport ability refer to inorganic particles that contain lithium but have the function of transporting lithium ions instead of storing lithium. The inorganic particles having lithium ion transport ability can transport lithium ions through a type of defect present within the particle structure. As a result, lithium ion conductivity within the battery can be improved, thereby improving battery performance.

[0068] Examples of inorganic particles having lithium ion transfer ability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3,0 <x<2、0<y<3)、リチウムアルミニウムチタニウムホスフェート(Li x Al y Ti z (PO4)3,0 <x<2、0<y<1、0<z<3)、(LiAlTiP) x O y Type glass(0 <x<4、0<y<13)、リチウムランタンチタネート(Li x La y TiO3, 0 <x<2、0<y<3)、リチウムゲルマニウムチオホスフェート(Li x Ge y P z S w , 0 <x<4、0<y<1、0<z<1、0<w<5)、リチウムナイトライト(Li x N y , 0 <x<4、0<y<2)、SiS2(Li x Siy S z ., 0 < x < 3, 0 < y < 2, 0 < z < 4) series glass and P2S5 (Li x P y S z ., 0 < x < 3, 0 < y < 3, 0 < z < 7) series glass, and may be one or more selected from the group consisting of, but is not limited thereto.

[0069] The composition ratio of the inorganic particles and the binder polymer constituting the coating layer of the separation membrane is not particularly limited, but can be adjusted within the range of 10:90 to 99:1% by weight, and the range of 80:20 to 99:1% by weight is preferred. When the composition ratio is less than 10:90% by weight, the content of the polymer becomes excessively large, and the pore size and porosity due to the reduction of the empty space formed between the inorganic particles decrease, which may cause a decrease in the performance of the final battery. On the other hand, when it exceeds 99:1% by weight, the polymer content is too small, so the adhesive force between the inorganics weakens, and the mechanical properties of the final organic / inorganic composite porous separation membrane may decrease.

[0070] In one embodiment of the present invention, as the binder polymer, a binder polymer generally used in the industry may be used.

[0071] Among the above organic / inorganic composite porous separation membranes, the coating layer may further contain other commonly known additives in addition to the aforementioned inorganic particles and binder polymer.

[0072] In one embodiment of the present invention, the coating layer can also be said to be an active layer.

[0073] Referring to FIGS. 1 and 2 again, the first separation membrane 4 may include a folding portion 4b that is connected and extends between a plurality of stacked portions 4a located between the first electrode 1 and the second electrode 2 and the side surface of the adjacent stacked portion 4a. In this specification, the side surface of the stacked portion 4a means one side in a direction perpendicular to the stacking direction of the laminate S. Therefore, the side surface of the stacked portion 4a is a position corresponding to the side surface of the laminate S.

[0074] In the stack S, the folded portions 4b may be alternately positioned on the side surfaces of each layer of the stack. Adjacent stack portions 4a and the folded portions 4b attached to the adjacent stack portions 4a may have openings formed in the first separator 4. Here, the side surfaces of the stack S facing the folded portions 4b may be defined by first and second electrodes received in the openings of the first separator 4. In this way, the stack S may have openings defined by the first separator 4 and folded portions 4b alternately on a pair of opposing side surfaces for each layer of the stack.

[0075] The first electrode 1 and the second electrode 2 do not have to be disposed inside or on top of the folding portion 4b.

[0076] 1, the second separation membrane 5 may be positioned on the upper surface, the lower surface, and at least one pair of opposing side surfaces of the laminate S. That is, as further shown in FIG. 1, the end of the second separation membrane 5 may be connected to the end of the first separation membrane 4 and may be wound around the laminate S at least once.

[0077] Therefore, the surfaces of the internal separation membranes of the second separation membranes 5 located on a pair of opposing side surfaces of the laminate S may face the folding portions 4b. Furthermore, the second separation membranes 5 located on at least a pair of both side surfaces of the laminate S may contact at least one folding portion 4b.

[0078] The electrode assembly 10 may be manufactured by heating or heat-compressing the sides of the laminate S when the second separator 5 is wound around the outermost periphery of the laminate. For example, the electrode assembly 10 may be manufactured by heating or heat-compressing both sides of the laminate S with a side sealing unit 60 (see FIG. 3 and related descriptions) including a pair of pressure blocks 60a, 60b when the second separator 5 is wound around it. The space formed between the folding portions 4b on both sides of the laminate S and the surface of the inner separator of the second separator 5 facing the folding portions 4b may be condensed by heat-sealing one or more of the side portions and the surface of the inner separator. Such heat-sealing between the folding portions 4b and the second separator 5 may be formed by heat-compressing the opposing sides of the laminate S with the side sealing unit 60 when the second separator 5 is wound around the outermost periphery of the laminate S.

[0079] The electrode assembly 10 may be manufactured by heat-compressing the top, bottom, and part or all of both side surfaces of the laminate S, which has the second separator 5 wound around the outermost periphery of the laminate S. For example, the electrode assembly 10 may be manufactured by heat-compressing the top and bottom surfaces of the laminate S in a press unit 50 (see FIG. 3 and related descriptions herein) and then separately or simultaneously heat-compressing both side surfaces of the laminate S using a side-sealing unit 60.

[0080] The press unit 50 may include a pair of pressure blocks 50a, 50b. The space between the first electrode 1, the first separator 4, and the second electrode 2 may be condensed by heat-sealing the top and bottom surfaces of the laminate S to the inner separator surface of the second separator 5. In this manner, the top and bottom heat-sealing bonding with the second separator 5 may be formed by heating and compressing the laminate S with the pair of pressure blocks 50a, 50b while the second separator 5 is wrapped around the outermost region of the laminate S. Here, the top and bottom surfaces of the laminate S refer to the outer surfaces of the laminate S located at the top and bottom in the stacking direction.

[0081] Therefore, in one embodiment of the electrode assembly 10, the first electrode 1 and the first separator 4, and the first separator 4 and the second electrode 2 may be bonded together. Furthermore, the top and bottom surfaces of the laminate S may be heated and compressed, compressing the folded portions 4b and heat-sealing adjacent folded portions 4b to each other. That is, two or more folded portions 4b may be bonded together. In this regard, unlike the schematic representation shown in FIG. 1, the folded portions 4b may extend outward a relatively large distance past the ends of the electrodes 1 and 2, as seen in the examples of FIGS. 5 and 6. In this way, the folded portions 4b may be biased and bonded to each other through either one or any combination of the heated compression of the side sealing portion 60 and the press portion 50.

[0082] In one embodiment, the two or more joined folded portions 4b of the first separation membrane 4 and the inner surface of the second separation membrane 5 positioned to face the folded portions 4b of the laminate S may be joined to each other.

[0083] In one embodiment, the folding portions 4b may be attached to the inner surface of the second separation membrane 5, with adjacent folding portions 4b not being attached to each other. In this case, the folding portions 4b may be attached to the second separation membrane 5 in a folded state without being bent in a direction parallel to the stacking direction of the laminate S, or the folding portions 4b may be folded one or more times in any direction parallel to the stacking direction of the laminate S.

[0084] The length of each folding portion 4b may be in the range of 0.1% to 1% of the total length of the stacked portion 4a to which the folding portion 4b is attached (100%). In this case, the length of the folding portion 4b may refer to the length of the folding portion 4b in an unbent state.

[0085] If the length of the folding portion 4b exceeds 1% of the total length of the laminated portion 4a to which the folding portion 4b is attached, the electrode density and energy density of the electrode assembly 10 may be reduced. Here, the total length of the laminated portion 4a means the length from the folding portion 4b to the opening on the opposite side of the folding portion 4b.

[0086] Furthermore, the number of folding portions 4b bonded to the inner surface of the second separation membrane 5 may be 30% or more of the total number of folding portions 4b. Preferably, the number of folding portions 4b may be 40% or more, and more preferably 50% or more.

[0087] In a state where adjacent folding portions 4b are joined to each other, a certain folding portion 4b may be joined to the inner surface of the second separation membrane 5. When a folding portion 4b of the first separation membrane 4 is joined to an adjacent folding portion 4b, the area of ​​the second separation membrane 5 joined to a certain folding portion 4b may be 30% or more of the total area of ​​the second separation membrane 5 located on a pair of opposing side surfaces of the laminate S. Preferably, the area of ​​the second separation membrane is 40% or more, and more preferably 50% or more.

[0088] In an electrode assembly 10 in which the number of joined folding portions 4b and the joining area between the folding portions 4b and the second separator 5 are less than the above-mentioned 30%, the side of the laminate S may have folding portions 4b that are not sufficiently fixed. In this case, it may be difficult to place the electrode assembly 10 into a pouch or can. Furthermore, in an electrode assembly 10 in which the number of joined folding portions 4b and the area of ​​the second separator 5 satisfy the above-mentioned 30%, the folding portions 4b may protrude from the sealed portion of the pouch, resulting in an undesirable situation in which the electrode assembly 10 is sealed together with the pouch.

[0089] Furthermore, since the difference between the size of the pouch or can and the size of the electrode becomes large, there is a limit to how much the size of the pouch or can can be minimized.

[0090] In one embodiment, when adjacent folded portions 4b are bonded to each other, 50% or more of the total number of folded portions 4b may be bonded to each other. In one embodiment, the width of the first electrode 1 and the second electrode 2 may be provided to be smaller than the width of the laminate S. In other words, the electrode assembly 10 may be positioned such that the ends of the first electrode 1 and the second electrode 2 in the folded portion 4b and in the layer adjacent to such folded portion 4b do not overlap or lie underneath each other. In this case, the first electrode 1 or the second electrode 2 is not located between the adjacent folded portions 4b, so that the adjacent folded portions 4b can be bonded to each other.

[0091] For example, if the electrode assembly 10 includes 10 folding portions 4b and 50% of the total number of folding portions 4b are adhered to each other, the electrode assembly 10 may include five folding portions 4b, two of which are adhered to each other, three of which are adhered to each other, and one of which is not adhered to an adjacent folding portion 4b.

[0092] 3 and 4, as illustrated in the electrode assembly manufacturing apparatus 100, the separation membrane supply unit 20 may be configured to supply the first separation membrane 4 to the stack table 10. For details regarding the separation membrane supply unit 20, see Korean Patent Publication No. 10-2020-0023853. For example, as shown in FIG. 4, the separation membrane supply unit 20 may be located above the stack table 10. The separation membrane supply unit 20 may also include a separation membrane roll 21 around which the first separation membrane 4 can be wound. The first separation membrane 4 wound around the separation membrane roll 21 can be gradually unwound by gravity and supplied to the stack table 10.

[0093] A passage through which the first separation membrane 4 passes is formed in the separation membrane supply unit 20. The separation membrane supply unit 20 may include a separation membrane heating unit (not shown) to heat the passing first separation membrane 4. For details regarding such a separation membrane heating unit, refer to Korean Patent Publication No. 10-2020-0023853.

[0094] The separation membrane heating unit may include a pair of bodies (not shown) and a separation membrane heater (separation membrane heating unit 22) that heats the bodies. The pair of bodies may be located on both sides of the first separation membrane 4, spaced apart by a predetermined distance so that the first separation membrane 4 can pass through. For example, the first separation membrane 4 may pass through the separation membrane heating unit without contact so that the first separation membrane 4 is heated in a contactless manner. In one embodiment, the pair of bodies of the separation membrane heating unit may be formed, for example, in the shape of a rectangular block.

[0095] As illustrated in the electrode assembly manufacturing apparatus 100, the first electrode supply unit 30 may be configured to supply the first electrodes 1 to the stack table 10 and stack the first electrodes 1 on the stack table 10. The first electrode supply unit 30 may include a first electrode placement table 31 on which the first electrodes 1 are placed before being stacked on the stack table 10. The first electrode supply unit 30 may also include a first electrode roll 33, a first cutter 34, a first conveyor 35, and a first electrode supply head 36. While supplying one of the first electrodes 1 to the first electrode placement table 31, the first electrode supply unit 30 gradually winds and unwinds the first electrode sheet on which the first electrodes 1 are formed around the first electrode roll 33. The first cutter 34 can cut the first electrodes 1 from the first electrode sheet supplied from the first electrode roll 33 to a predetermined length. The first cutter 34 can cut the first electrode sheet so that a first electrode tab 1a protrudes from an end of the first electrode 1.

[0096] The first electrode 1 cut by the first cutter 34 may be fed to a first conveyor 35, which may be in the form of a belt as shown, and the first conveyor 35 can move the first electrode 1 to the first electrode placement table 31. A first electrode feed head 36 (e.g., via a vacuum fitting, suction cup, or similar fitting or other temporary attachment such as a magnetic attachment) can pick up the first electrode 1 placed on the first conveyor 35 and place it on the first electrode placement table 31.

[0097] As shown, the first electrode supply unit 30 may include a first transfer head 32 and a first moving unit 37 from which the first transfer head 32 extends and is capable of vibrating. The first transfer head 32 can pick up the first electrode 1 placed on the first electrode placement table 31 (e.g., via a vacuum fitting, a suction cup or similar fitting, or other temporary attachment such as a magnetic attachment). In one embodiment, the first transfer head 32 may include a vacuum suction unit (not shown) on the bottom surface of the transfer head configured to suck the first electrode 1 through the vacuum suction port to attach the first electrode 1 to the bottom surface of the first transfer head 32. A channel formed in the first transfer head 32 can connect the vacuum suction port to the vacuum suction device (not shown).

[0098] The first moving unit 37 can be configured to pick up the first electrode 1 placed on the first electrode placement table 31 and move the first transfer head 32 to a position where it can be placed on the stack table 10, where the first transfer head 32 can be released, for example, by reducing or removing vacuum suction or other force applied to the first electrode 1 to hold the first electrode 1 against the transfer head. In this manner, the first transfer head 32 can transfer the first electrode 1 from the first electrode placement table 31, via the other electrodes 1, 2, to a section of the first separation membrane 4 that is to be placed on or placed on the stack table 10.

[0099] The second electrode supply unit 40 may have a mirror configuration of the first electrode supply unit 30, or may essentially have such a configuration. In this way, the second electrode supply unit 40 can supply the second electrode 2 to a portion of the stack S placed on the stack table 10, and stack the second electrode 2 on such a portion of the stack S on the stack table 10.

[0100] The second electrode supply unit 40 may include a second electrode placement table 41 on which the second electrode 2 is placed before being moved to the portion of the stack S on the stack table 10 and stacked.

[0101] The second electrode supply unit 40 may include a second electrode roll 43 on which a second electrode sheet having a second electrode 2 formed thereon is wound up, a second cutter 44 that cuts the second electrode sheet at regular intervals while unwinding the second electrode sheet from the second electrode roll 43 to form second electrodes 2 of a predetermined size, a second conveyor 45 that moves the second electrodes 2 cut by the second cutter 44, and a second electrode supply head 46 that picks up the second electrodes 2 moved by the second conveyor 45 and places them on the second electrode placing table 41.

[0102] The second cutter 44, like the first cutter 34, can cut the second electrode sheet so that the formed second electrode 2 includes a second electrode tab 2a protruding from the end of the second electrode 2.

[0103] The second electrode supply unit 40 may also include a second transfer head 42 that picks up the second electrode 2 placed on the second electrode placement table 41, and a second transfer unit 47 configured to move to an upper portion of the stack table 10 from which the second transfer head 42 can be released, for example, by reducing or eliminating vacuum suction or other force applied to the second electrode 2 to hold the second electrode 2 against the second transfer head 42. At this time, the second transfer head 42 can stack the second electrode 2 on a portion of the stack S on the stack table 10. The second transfer head 42 may be formed in the same manner as the first transfer head 32, such that the second electrode 2 is temporarily attached to the bottom surface of the second transfer head 42.

[0104] The side sealing unit 60 can heat at least one side of the laminate S while surrounding the outermost periphery of the laminate S with the first separator 4. That is, the side sealing unit 60 can apply heat to at least one side of the laminate S to impart or increase adhesive strength to the coating layer components that are applied to one side of the first separator 4 and face the electrodes 1 and 2.

[0105] The direction of pressure application of the side sealing portion 60 may be perpendicular to the direction of pressure application of the press portion 50, which will be further described herein.

[0106] In one embodiment, the side sealing unit 60 may include a pair of heating bars 60a, 60b. The pair of heating bars 60a, 60b can be moved toward or away from each other to compress the laminate S from the sides toward the center of the stack. That is, the side sealing unit 60 can heat and compress the laminate S at the sides of the laminate S.

[0107] The side of the stack S is the side that includes the folded portion P of the stack S. Preferably, the side of the stack is not located on the same side of the electrodes 1, 2 where the electrode tab 1a is located.

[0108] The laminate S may be provided in a structure in which one or more first electrodes 1, first separators 4, and second electrodes 2 are stacked in order, with the outermost periphery being wrapped in the first separator 4. The side sealing unit 60 heats and compresses the outermost portion of the first separator 4 (hereinafter referred to as the outermost separator) surrounding the outermost periphery of the laminate S, thereby heat-compressing the side of the laminate S and the folded portions P included in the laminate S. Thus, the side sealing unit 60 heats and compresses the side of the laminate S to bond the multiple folded portions P included in the laminate S, thereby bonding the inner surface of the outermost first separator 4 to the folded portions of the first separator 4 facing the outermost first separator 4, the first electrode 1, and the second electrode 2.

[0109] The electrode assembly manufacturing apparatus 100 may further include a press unit 50. The press unit 50 is heated to compress the laminate S. The first electrode 1, the first separator 4, and the second electrode 2 can be joined together by pressing the press unit 50.

[0110] The press unit 50 may include a pair of pressure blocks 50a, 50b that can be positioned adjacent to the upper and lower surfaces of the laminate S. The pair of pressure blocks 50a, 50b can move toward each other to compress the upper and lower surfaces of the laminate S, and then move away from each other in response to such compression.

[0111] When the first separator 4 is configured to enclose the outer surface of the laminate S, the space between the inner surface of the outermost first separator 4 and the side surfaces of the first electrode 1 and the second electrode 2 and the outermost first separator 4 facing the inner surface of the first separator 4 may be bonded. In this configuration, the outermost first separator 4 may include an upper surface and a lower surface of the laminate S, and two side surfaces facing between the upper surface and the lower surface of the outermost first separator 4 surrounding the laminate S.

[0112] As a result, when the first electrode 1, the first separation membrane 4, and the second electrode 2 are stacked to form the electrode assembly 10, the press section 50 separates the positions of the first and second electrodes 1, 2, and the first separation membrane 4, preventing the stacked configuration from coming undone.

[0113] The press unit 50 may further include a press heater (not shown) for heating the pair of pressure blocks 50a, 50b so that the pair of pressure blocks 50a, 50b can heat the laminate S while compressing the laminate. In this manner, when the press unit 50 compresses the laminate S, heat fusion can be more effectively performed between the first electrode 1 and the section of the first separator 4 adjacent to the first electrode 1, and between the second electrode and the section of the first separator 4 adjacent to the second electrode 2.

[0114] As shown in FIG. 4, each of the pair of pressure blocks 50a, 50b may be formed with a pressure surface whose length and width are longer than the length and width of the laminate S, and may be formed with a flat pressure surface.

[0115] The pair of pressure blocks 50a, 50b may be rectangular blocks having a rectangular parallelepiped shape.

[0116] In one embodiment, the electrode assembly manufacturing apparatus 100 may further include a third moving part (not shown) attached to the third moving head (not shown) and configured to rotate or otherwise move. The third moving part and the third moving head may be the same as or similar to the first moving part 37 and the second moving part 47 and the first moving head 32 and the second moving head 42, respectively.

[0117] In one embodiment, the third transfer head can suck the stack S placed on the stack table 10. The third transfer head has a vacuum suction part on its bottom surface, and the stack S can be temporarily attached to the bottom surface of the third transfer head by sucking it through the vacuum suction port. The third transfer head may have a passage formed therein that connects the vacuum suction port to the vacuum suction device.

[0118] The third moving section can move the third transfer head to the side sealing section 60, for example, through one or both of translation and rotation, so as to move the stack S placed on the stack table 10 to the side sealing section 60.

[0119] In one embodiment, the third transfer head may be temporarily attached to the stack S in the manner described above when the stack is placed in the press section 50. In one embodiment, the third moving section may be configured to move the third transfer head to the side sealing section 60 so that the stack S placed in the press section 50 can be moved to the side sealing section 60.

[0120] Referring to FIG. 6, the method for manufacturing the electrode assembly may include a step of manufacturing a laminate (S10) and a side sealing step (S30).

[0121] In the step of manufacturing a laminate (S10), a first electrode (e.g., first electrode 1), a separator (e.g., first separator 4), and a second electrode (e.g., second electrode 2) can be supplied to an in-process stack of a stack table (e.g., stack table 10) to manufacture the laminate.

[0122] In step (S11) of step (S10) of manufacturing a stack, a portion of the separation membrane is supplied to the stack table. In one embodiment, the portion of the separation membrane is attached to the stack table by a holding mechanism, such as, but not limited to, a clamp, a clamp set, or other clamping mechanism. In step (S12), the stack table may rotate toward a first electrode supply unit, e.g., first electrode supply unit 30. In step (S13), the first electrode may be supplied and then attached to the stack table or stacked on the portion of the separation membrane otherwise stacked on the stack table. In step (S14), the stack table may rotate toward a second electrode supply unit, e.g., second electrode supply unit 40, so that an additional portion of the separation membrane may be folded and superimposed on the first electrode. In step (S15), the second electrode may be supplied and then stacked on the additional portion of the separation membrane. In step (S16), steps (S12), (S13), (S14), and (S15) may be repeated to sequentially add one or more first electrodes, portions of the separator, and one or more second electrodes. When step (S12) is repeated, another portion of the separator may be folded and superimposed on the second electrode by rotating the stack table, and a next first electrode may be supplied, which may then be stacked on the additional portion of the separator. By alternately rotating the stack table, the separator may be stacked in a zigzag pattern between the first and second electrodes.

[0123] In step (S17) of the step (S10) of preparing the laminate, the outermost periphery of the laminate may be surrounded by the separator by rotating the separator in one direction. Here, the outermost periphery of the laminate includes the upper surface, the lower surface, and both opposing side surfaces of the laminate. Each side surface may extend in a plane parallel to the stacking direction of the laminate. Each of the side surfaces may exclude all surfaces on which electrode tabs, e.g., electrode tab 1a, are located. The upper and lower surfaces of the laminate each include a surface perpendicular to one or both of the side surfaces of the laminate.

[0124] The side sealing step (S30) may heat at least one side of the laminate. This operation may heat and compress one or both of the opposite sides of the laminate, thereby compressing the laminate. In this step, the pair of heating bars, e.g., heating bars 60a and 60b, may press the separator along the side of the laminate for 10 seconds or less while the heating bars are at a side sealing temperature of 100°C to 200°C.

[0125] If the side sealing temperature is less than 100°C, the binder applied to the separator may not exhibit sufficient adhesive strength. If the side sealing temperature is more than 200°C or the pressing time is more than 10 seconds, the increase in adhesive effect may be small compared to the energy supplied to heat the pair of heating bars.

[0126] In the side sealing step (S30), at least one side of the laminate may be compressed at a pressure in the range of 0.1 MPa to 1.5 MPa. Preferably, the one or more sides may be compressed at a pressure in the range of 0.1 MPa to 1 MPa, more preferably at a pressure in the range of 0.1 MPa to 0.5 MPa.

[0127] That is, in the side sealing step (S30), both sides of the laminate can be compressed in a direction perpendicular to the sides and toward the center of the laminate while simultaneously heating both sides of the laminate.

[0128] When the pressure applied to the side of the covered laminate is within the above pressure range, damage to the first and second electrodes can be prevented or at least suppressed due to contact and bonding between the outermost separator and the folded portion.

[0129] The method for manufacturing an electrode assembly may further include steps (S20, S30) of heating and pressing the laminate. In these steps, a pair of heating and pressing blocks, e.g., a pair of pressing blocks 50a, 50b, may compress the laminate downward and selectively upward toward the sides of the laminate that are generally parallel to the laminate. Heat conducted from the pair of pressing blocks may improve adhesion between the binder and the separator coated with the binder, further bonding the separator to the first and second electrodes by pressure.

[0130] 7, each folding portion 4b may be folded one or more times in a direction parallel to the stacking direction of the laminate S. In this manner, in an electrode assembly 10 in which the second separator 5 is wound around the laminate S, the distance between the end of the first electrode 1 and the surface of the inner separator of the second separator 5 facing the end of the first electrode 1 and the distance between the end of the second electrode 2 and the portion of the surface of the inner separator of the second separator 5 facing the end of the second electrode 2 are reduced, thereby reducing the overall width of the electrode assembly 10.

[0131] The distance between the first electrode 1 or the second electrode 2 and the surface of the inner separator of the second separator 5 adjacent to the end of the first electrode 1 or the second electrode 2 of the electrode assembly 10 may be reduced by 50% to 95% based on the total length of the folding portion 4b being 100%. The total length of the folding portion 4b is the distance from the end of the first electrode 1 or the second electrode 2 to the end of the folding portion 4b that contacts the second separator 5 when the folding portion 4b is in an unbent state.

[0132] By reducing the length of the folding portion 4b by 50% to 95% compared to the overall length of the folding portion 4b, the portion of the folding portion 4b that does not include the first electrode 1 and the second electrode 2 is reduced, thereby increasing the electrode density and energy density of the electrode assembly 10.

[0133] The wet adhesive strength between the folded portion 4b of the electrode assembly 10 and the second separator 5 bonded to the folded portion 4b may be in the range of 40 gf / 25 mm to 70 gf / 25 mm.

[0134] While the present invention has been described above with reference to preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as set forth in the following claims.

[0135] Experimental example The following experiment was conducted to measure battery characteristics depending on the adhesion rate and adhesion area between the side edge of the separator, which serves as the second separator of the laminate included in the electrode assembly, and the inner separator surface of the outermost part.

[0136] Example The separator was folded in a zigzag pattern, anodes and cathodes were alternately arranged between the edges of the folded separator, and the outermost edge of the stack was surrounded by the separator to prepare an electrode assembly. The electrode assembly was prepared by compressing the top and bottom surfaces of the stack using a heated press to bond the entire stack, and then compressing the opposing side surfaces of the stack using a heated side sealing unit to side-seal the stack.

[0137] Example 1 Example 1 includes an electrode assembly in which the stack is compressed at a pressure of 0.15 MPa using a side sealing portion, and the folding portion of the separator is bonded to an area of ​​30% of the total area of ​​the inner surface of the separator located on the side of the stack opposite the folding portion.

[0138] Example 2 In Example 2, the stack was compressed at a pressure of 0.25 MPa using a side sealing portion, and the side portion of the separator included an electrode assembly bonded to an area of ​​80% of the total area of ​​the inner separator surface of the separator located on the side of the stack facing the side portion.

[0139] Comparative Example 1 Comparative Example 1 includes an electrode assembly in which the laminate is compressed at a pressure of 0.05 MPa using side sealing portions.

[0140] Comparative Example 2 Comparative Example 2 includes an electrode assembly in which the side portion of the separator is bonded to an area of ​​20% of the total area of ​​the inner separator surface located on the side of the stack facing the side portion by compressing the stack at a pressure of 0.10 MPa using a side sealing portion.

[0141] Comparative Example 3 Comparative Example 3 includes an electrode assembly in which the side portion of the separator is bonded to 90% of the total area of ​​the inner separator surface of the separator located on the side of the stack facing the side portion by compressing the stack at a pressure of 0.30 MPa using a side sealing portion.

[0142] [Table 1]

[0143] [Table 2]

[0144] Table 2 shows the results of measuring damage to the cathode of the electrode assembly, including the degree of adhesion between the folding part and the portion of the separator located at the folding part, and the degree of lifting of the outermost corner of the separator located on the side of the electrode assembly. The degree of side sealing was visually observed based on the degree of adhesion between the folding part of the separator and the outermost part of the separator functioning as the second separator. The degree of lifting of the second or side separator means that the second separator is pressed against the top or bottom of the electrode assembly, meaning that parts of the separator located on the top and bottom of the electrode assembly are not in close contact with the electrode.

[0145] Referring to Table 2, in Comparative Example 1, the pressure applied by the side seal was low, so the electrode assembly could not be compressed, and damage to the cathode, the extent of the side seal, or the degree of lifting of the second separator could not be measured (see (a) of Figure 8).

[0146] In the case of Comparative Example 2, the side seal portion presses against the side of the electrode assembly, but the second separator located on the side of the electrode assembly does not move to the folding portion due to the low pressure, and therefore the adhesive strength between the folding portion and the second separator is reduced (see (b) of Figure 8).

[0147] In Comparative Example 3, the pressure applied to the side of the electrode assembly by the side seal was large. As a result, the second separator located on the side of the electrode assembly rose above the cathode, and the cathode pressed against the separator located on the top or bottom of the electrode assembly. It was visually confirmed that the separator located on the top or bottom of the electrode assembly was folded (see Figure 9).

Claims

1. a stack including a first electrode, a first separator folded in a zigzag pattern and including a folding portion on each side between stacked portions, and a second electrode alternately disposed with the first electrode between the stacked portions of the first separator; a second separator extending along the upper surface, the lower surface, and at least a pair of opposing side surfaces of the laminate; Including, the folded portion of the first separator is positioned on a side surface of the laminate and includes an area where the first electrode and the second electrode are not disposed; the second separation membrane is bonded to at least one of the folding portions, two or more of the folding parts are adhered to each other, and the second separator is adhered to at least a portion of the folding parts; an area of ​​the second separator attached to the folded portion of the first separator is 30% to 80% of a total area of ​​an inner separator surface of the second separator located on an opposite side of the stack.

2. The electrode assembly of claim 1 , wherein the folding portions are alternately positioned on the sides of the first electrode and the second electrode of the laminate.

3. The electrode assembly of claim 1 , wherein the number of the folded portions of the first separator attached to the second separator is 30% or more of the total number of the folded portions.

4. 4. The electrode assembly of claim 3, wherein each of the laminations of the first separator has a length equal to the length of the first electrode and the second electrode of the lamination, and each of the folding portions extends between adjacent pairs of the laminations.

5. The electrode assembly of claim 1 , wherein the folding portion is folded one or more times in a direction parallel to a stacking direction of the laminate.

6. The electrode assembly of claim 1 , wherein the length of one of the folding portions is 0.1% to 1% of the overall length of the stacked portion to which the one of the folding portions is attached.

7. The electrode assembly of claim 1 , wherein the first separator is adhered to at least one of the first electrodes and at least one of the second electrodes.

8. The electrode assembly of claim 1 , wherein the second separator is adhered to at least one of the first electrodes and at least one of the second electrodes.

9. The electrode assembly of claim 1, wherein at least one of the second separator and the folding portion bonded to the second separator has a wet adhesive strength of 40 gf / 25 mm to 70 gf / 25 mm.

10. The electrode assembly of claim 1 , wherein the second separator is a continuation of the first separator, and an end of the first separator is shared with an end of the second separator.

11. The electrode assembly of claim 1 , wherein the first separator and the second separator do not overlap at their ends.

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