Secondary batteries

Abstract

The present invention provides a secondary battery comprising an electrode assembly manufactured by a stack-and-fold method and a case for housing the electrode assembly, wherein the electrode assembly includes six or more unit cells bonded to a folded separator membrane, each of the six or more unit cells having one side surface bonded to the folded separator membrane, and the unit cells are arranged such that when the electrode assembly is unfolded, the number of negative electrodes among the electrodes on the other side surface of the unit cells not bonded to the folded separator membrane is minimized.

Description

Technical Field

[0001] The present invention relates to a secondary battery, and more specifically, to a secondary battery with an extended lifespan.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0045248 filed on April 3, 2024, and all contents disclosed in the documents of the said Korean patent application are included as part of the present specification.

Background Art

[0003] A secondary battery refers to a battery capable of charging and discharging, unlike a non-rechargeable primary battery, and is widely used in electronic devices such as mobile phones, notebook computers, camcorders, or electric vehicles and the like. In particular, a lithium secondary battery has a larger capacity than a nickel-cadmium battery or a nickel-hydrogen battery, and has a high energy density per unit weight, so the degree of its utilization tends to increase rapidly.

[0004] Various structures and / or manufacturing methods have been proposed and applied for manufacturing secondary batteries, and various efforts have been made to extend the lifespan of secondary batteries.

Summary of Invention

Problems to be Solved by the Invention

[0005] The technical problem to be achieved by the present invention is to provide a secondary battery with an extended lifespan.

Means for Solving the Problems

[0006] To achieve the above technical objectives, the present invention provides a secondary battery comprising an electrode assembly manufactured by a stack-and-fold method and a case for housing the electrode assembly, wherein the electrode assembly includes six or more unit cells bonded to a folded separator membrane, each of the six or more unit cells having one side surface bonded to the folded separator membrane, and the unit cells are arranged such that when the electrode assembly is unfolded, the number of negative electrodes among the electrodes on the other side surface of the unit cell that is not bonded to the folded separator membrane is minimized.

[0007] In some embodiments, the outermost unit cells on both sides of the electrode assembly may each have a stacked structure of single positive electrode / separator membrane / negative electrode / separator membrane / positive electrode.

[0008] In some embodiments, the electrode assembly may be configured such that the polarities of the electrodes of a pair of unit cells facing each other with the folding separation membrane in between are different.

[0009] In some embodiments, the electrode assembly may include at least one monocell.

[0010] In some embodiments, the electrode assembly includes eight or more unit cells, and the number of monocells may be less than half the total number of unit cells.

[0011] In some embodiments, the electrode assembly may be manufactured by arranging six or more unit cells on a folding separation membrane, then adhering one side surface of the unit cells to the folding separation membrane, and folding it.

[0012] In some embodiments, a unit cell in which a positive electrode is provided on each side of the negative electrode and a separation membrane is included between the electrodes is defined as type A; a unit cell in which a negative electrode is provided on each side of the positive electrode and a separation membrane is included between the electrodes is defined as type C; a unit cell in which a single positive electrode and a positive electrode are provided on each side of the negative electrode and a separation membrane is included between the electrodes, with the tab of the single positive electrode positioned on the right side is defined as type R; a unit cell in which a single positive electrode and a positive electrode are provided on each side of the negative electrode and a separation membrane is included between the electrodes, with the tab of the single positive electrode positioned on the left side is defined as type L; a unit cell in which a negative electrode and a positive electrode are provided on each side of the separation membrane and the tab of the positive electrode is positioned on the right side is defined as type MR; and a unit cell in which a negative electrode and a positive electrode are provided on each side of the separation membrane and the tab of the positive electrode is positioned on the left side is defined as type ML.

[0013] In some embodiments, the electrode assembly is composed of 12 unit cells, and the arrangement of the unit cells when the electrode assembly is unfolded may be one of the following arrangements.

[0014] RLC-MR-A-MR-C-MR-ACCA; RL-ML-C-ML-A-ML-CCAAC.

[0015] In some embodiments, the electrode assembly is composed of 11 unit cells, and the arrangement of the unit cells when the electrode assembly is unfolded may be one of the following arrangements.

[0016] RLC-MR-A-MR-CCAAC; RL-ML-C-ML-ACCAAC; RL-ML-C-ML-ML-ML-ACCa; RLC-MR-MR-MR-A-MR-CCA.

[0017] In some embodiments, the electrode assembly may consist of 10 unit cells, and when the electrode assembly is unfolded, the unit cells may be arranged in the order RL-ML-C-ML-A-ML-CCA.

[0018] In some embodiments, the electrode assembly described above is composed of 9 unit cells, and when the electrode assembly is unfolded, the arrangement of the unit cells may be one of the following arrangements.

[0019] R-L-C-MR-A-MR-C-C-A; R-L-ML-C-ML-A-C-C-A; R-L-ML-C-ML-ML-ML-A-C.

[0020] In some embodiments, the electrode assembly described above is composed of 7 unit cells, and when the electrode assembly is unfolded, the unit cells may be arranged in the order of R-L-ML-MR-ML-MR-C. ADVANTAGEOUS EFFECTS OF INVENTION

[0021] The secondary battery of the present invention, which is a secondary battery manufactured by a stack-and-folding method, has the effect of extending the service life of the secondary battery by maximally suppressing the deposition of lithium in a fingerprint-like pattern.

[0022] The effects obtained from the exemplary embodiments of the present invention are not limited to the effects described above, and other effects not mentioned can be clearly derived and understood from the following description by those having ordinary skill in the art to which the exemplary embodiments of the present disclosure pertain. That is, unintended effects associated with practicing the exemplary embodiments of the present disclosure can also be derived from the exemplary embodiments of the present disclosure by those having ordinary skill in the art. BRIEF DESCRIPTION OF DRAWINGS

[0023] [Figure 1] It is an exploded perspective view showing a secondary battery according to an embodiment of the present invention. [Figure 2] It is a conceptual diagram showing a method of manufacturing an electrode assembly by a stack-and-folding method. [Figure 3] It is a side view showing side surfaces of various unit cells that may be included in the unit cell described above. [Figure 4] It is a side view showing aspects of various unit cells that may be included in the above unit cell. [Figure 5] It is a side view showing aspects of various unit cells that may be included in the above unit cell. [Figure 6] It is a side view showing aspects of various unit cells that may be included in the above unit cell. [Figure 7] It is a side view showing aspects of various unit cells that may be included in the above unit cell. [Figure 8] It is a side view showing aspects of various unit cells that may be included in the above unit cell. [Figure 9] When the number of stacked unit cells is 6, this is an image showing the number of possible arrangements of unit cells when the electrode assembly is unfolded. [Figure 10] When the number of stacked unit cells is 7, this is an image showing the possible arrangements of unit cells when the electrode assembly is unfolded. [Figure 11] When the number of stacked unit cells is 8, this is an image showing the possible arrangements of unit cells when the electrode assembly is unfolded. [Figure 12] When the number of stacked unit cells is 9, this is an image showing the possible arrangements of unit cells when the electrode assembly is unfolded. [Figure 13] When the number of stacked unit cells is 10, this is an image showing the possible arrangements of unit cells when the electrode assembly is unfolded. [Figure 14] When the number of stacked unit cells is 11, this is an image showing the possible arrangements of unit cells when the electrode assembly is unfolded. [Figure 15] When the number of stacked unit cells is 12, this is an image showing the possible arrangements of unit cells when the electrode assembly is unfolded. [Mode for Carrying Out the Invention]

[0024] Preferred embodiments of the concept of the present invention will be described in detail below with reference to the accompanying drawings. However, embodiments of the concept of the present invention may be modified into various different forms, and the scope of the concept of the present invention should not be construed as being limited by the embodiments described below. It is preferable that embodiments of the concept of the present invention be construed as being provided to more fully explain the concept of the present invention to a person of average skill in the art. The same reference numerals mean the same element throughout. Furthermore, various elements and areas in the drawings are depicted schematically. Therefore, the concept of the present invention is not limited by the relative sizes or spacings depicted in the accompanying drawings.

[0025] Terms such as "first," "second," etc., may be used to describe various components, but these components are not limited by these terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the concept of the present invention, the first component may be named the second component, and conversely, the second component may be named the first component.

[0026] The terms used herein are used solely to describe specific embodiments and are not intended to limit the concepts of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, expressions such as “includes” or “has” are intended to specify the presence of features, quantities, steps, operations, components, parts, or combinations thereof described in the specification, and are understood not to preemptively exclude the presence or possibility of adding one or more other features, quantities, steps, operations, components, parts, or combinations thereof.

[0027] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those commonly understood by those of ordinary skill in the art to which the concepts of this invention pertain. Furthermore, terms defined in commonly used dictionaries may be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an overly formal sense unless explicitly defined herein.

[0028] Where a particular embodiment can be otherwise realized, a specific sequence of steps may be performed in a different order than that described. For example, two steps described consecutively may be performed substantially simultaneously, or in the reverse order of the description.

[0029] In the accompanying drawings, deformation of the shown shapes may be expected, for example, due to manufacturing techniques and / or tolerances. Therefore, embodiments of the present invention should not be construed as being limited to specific shapes of the regions shown herein, and may include, for example, changes in shape resulting from the manufacturing process. All terms used herein, "and / or," include each of the components mentioned and all combinations of one or more of them. The term "substrate" as used herein may mean the substrate itself or a laminated structure including a predetermined layer or film formed on the substrate. The term "surface of the substrate" as used herein may mean the exposed surface of the substrate itself or an outer surface including a predetermined layer or film formed on the substrate.

[0030] Figure 1 is an exploded perspective view showing a secondary battery 10 according to one embodiment of the present invention.

[0031] Referring to Figure 1, the secondary battery 10 includes an electrode assembly 12 to which electrode leads 11 are attached and a case 13.

[0032] The case 13 comprises a storage section 13a for housing the electrode assembly 12 and a sealing section 13b formed to seal the electrode assembly 12. The sealing section 13b contains a sealant resin, and the sealant resin can be welded along the outer surface of the storage section 13a to seal the electrode assembly 12.

[0033] Case 13 described above may be provided in the form of a multilayer film comprising an outer layer for protection against external impacts, a metal barrier layer for blocking moisture, and a sealant layer for sealing the case. The outer layer may include other polyester films such as poly(ethylene terephthalate) (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, polycarbonate, and nylon, and may consist of a single layer or multiple layers. The metal barrier layer may include aluminum, copper, etc. The sealant layer may include a sealant resin and may consist of a single layer or multiple layers. The sealant resin may include polypropylene (PP), acid-modified polypropylene (PPa), random polypropylene, ethylene propylene copolymer, or two or more of these. The ethylene propylene copolymer may include, but is not limited to, ethylene-propylene rubber and ethylene-propylene block copolymer.

[0034] In some embodiments, the case 13 may be a pouch case. If the case 13 is a pouch case, it may include an upper pouch and a lower pouch. If the case 13 includes an upper pouch and a lower pouch, it may have a structure in which the upper pouch and the lower pouch are positioned so that the sealant resins face each other, and then the opposing sealant resins fuse together by heat and pressure to seal the battery.

[0035] The sealing portion 13b may be fused by heat, ultrasonic welding, etc., but is not particularly limited as long as the sealing portion 13b can be fused. The sealing portion 13b may be sealed on four sides or three sides at the edge of the case 13. The three-sided sealing structure means that after the upper pouch and lower pouch are formed into a single pouch sheet, the interface between the upper pouch and the lower pouch is folded so that the housing portion 13a of the electrode assembly formed in the upper pouch and the lower pouch overlap, and the edges of the remaining three sides excluding the folded portion are sealed.

[0036] The electrode leads 11 can be housed inside the case 13 such that a portion of them is exposed to the outside of the case 13. The secondary battery 10 may further include a lead film 14 on the electrode leads 11.

[0037] The lead film 14 surrounds a portion of the outer surface of the electrode lead 11 and is interposed between the electrode lead 11 and the sealing portion 13b. The lead film 14 is interposed between the electrode lead 11 and the sealing portion 13b and helps to bond the electrode lead 11 and the sealing portion 13b.

[0038] However, the case 13 of the present invention is not limited to a pouch case, and any case suitable for manufacturing rectangular or cylindrical batteries may be used.

[0039] The electrode assembly 12 described above includes a negative electrode (anode), a positive electrode (cathode), and a separator membrane. The electrode assembly 12 is a stack-and-folding type electrode assembly.

[0040] Figure 2 is a conceptual diagram showing a method for manufacturing the electrode assembly 12 using a stack-and-fold method.

[0041] Referring to Figure 2, the electrode assembly 12 can be obtained by aligning and adhering unit cells 121 onto the folding separation membrane 122, and then continuously folding the folding separation membrane 122. Such a stack-and-fold electrode assembly 12 has high stability because the movement of the unit cells 121 can be restricted by the folding separation membrane.

[0042] The above-mentioned unit cell 121 may be a monocell and / or bicell, and a pair of unit cells 121 may be adjacent to each other with the folding separation membrane 122 in between. In this case, the polarities of the electrodes facing each other with the folding separation membrane 122 in between in an adjacent pair of unit cells 121 may be different.

[0043] The above unit cell 121 can be of various types.

[0044] Figures 3 to 8 are side views showing various aspects of the unit cells that may be included in the above-mentioned unit cell 121.

[0045] Referring to Figure 3, a negative electrode AA is provided on both sides of a positive electrode AC, with a separator membrane AS provided between the negative electrode AA and the positive electrode AC. The negative electrode AA includes negative electrode active material layers on both sides of the current collector, and the positive electrode AC includes positive electrode active material layers on both sides of the current collector. A unit cell of this form may be called an A-type.

[0046] Referring to Figure 4, a negative electrode CA is provided on both sides of a positive electrode CC, and a separator membrane CS is provided between the positive electrode CC and the negative electrode CA. The negative electrode CA includes a negative electrode active material layer on both sides of the current collector, and the positive electrode CC includes a positive electrode active material layer on both sides of the current collector. A unit cell of this form may be called a C-type.

[0047] Referring to Figure 5, a positive electrode RC is provided on one side of a negative electrode RA, and a single positive electrode RSC is provided on the other side. A separator membrane RS is provided between the negative electrode RA and the positive electrode RC, and between the negative electrode RA and the single positive electrode RSC. The negative electrode RA includes negative electrode active material layers on both sides of the current collector, and the positive electrode RC includes positive electrode active material layers on both sides of the current collector. The single positive electrode RSC includes a positive electrode active material layer on only one side of the current collector facing the separator membrane RS, and the tab of the single positive electrode RSC is positioned on the right side. A unit cell of this form may be called an R-type.

[0048] Referring to Figure 6, a positive electrode LC is provided on one side of a negative electrode LA, and a single positive electrode LSC is provided on the other side. A separator membrane LS is provided between the negative electrode LA and the positive electrode LC, and between the negative electrode LA and the single positive electrode LSC. The negative electrode LA includes negative electrode active material layers on both sides of the current collector, and the positive electrode LC includes positive electrode active material layers on both sides of the current collector. The single positive electrode LSC includes a positive electrode active material layer on only one side of the current collector facing the separator membrane LS, and the tab of the single positive electrode LSC is positioned on the left side. A unit cell of this form may be called an L-type.

[0049] The A-type, C-type, R-type, and L-type unit cells described above are all bicells.

[0050] Referring to Figure 7, a negative electrode MRA and a positive electrode MRC are provided on either side of the separator membrane MRS, with the tab of the positive electrode MRC positioned on the right side. The negative electrode MRA includes negative electrode active material layers on both sides of the current collector, and the positive electrode MRC includes positive electrode active material layers on both sides of the current collector. A unit cell of this form may be called an MR-type.

[0051] Referring to Figure 8, a negative electrode MLA and a positive electrode MLC are provided on either side of the separator membrane MLS, with the tab of the positive electrode MLC positioned on the right side. The negative electrode MLA includes negative electrode active material layers on both sides of the current collector, and the positive electrode MLC includes positive electrode active material layers on both sides of the current collector. A unit cell of this form may be called an ML-type.

[0052] The MR-type and ML-type unit cells described above are all monocells.

[0053] The folding separation membrane 122 described above can be any porous polymer substrate commonly used in this field, for example, a polyolefin-based porous membrane or nonwoven fabric can be used, but is not particularly limited to these.

[0054] Examples of the above-mentioned polyolefin-based porous membranes include membranes formed from polyethylene such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, as well as polyolefin polymers such as polypropylene, polybutylene, and polypentene, either individually or as mixtures thereof.

[0055] The above-mentioned nonwoven fabrics include, in addition to polyolefin-based nonwoven fabrics, nonwoven fabrics formed from polymers such as polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfide, and polyethylene naphthalate, either individually or as mixtures thereof. The structure of the nonwoven fabric may be a spunbond nonwoven fabric or a meltblown nonwoven fabric composed of long fibers.

[0056] The thickness of the porous polymer substrate described above is not particularly limited, but may be approximately 5 μm to approximately 50 μm. The pore size and pore density of the porous polymer substrate are also not particularly limited, but may be approximately 0.01 μm to approximately 50 μm and approximately 10% to approximately 95%, respectively. In this case, the porous polymer substrate may be formed as a single layer or as two or more layers laminated together.

[0057] The unit cells shown in Figures 3 to 8 can be aligned and bonded to the folding separation membrane 122, as shown in Figure 2. In this case, the electrode forming one side surface of the unit cell 121 is bonded to the folding separation membrane 122, while the electrode forming the other side surface of the unit cell 121 is not bonded to the folding separation membrane 122. The electrode that is not bonded to the folding separation membrane 122 will face the folding separation membrane 122 after folding, but it will not be bonded to the folding separation membrane 122.

[0058] If the electrode on the other side surface that is not adhered to the folding separation membrane 122 is the negative electrode, lithium tends to precipitate in a fingerprint-like pattern as the charge-discharge cycle is repeated, which can be one of the causes of limiting the lifespan of the secondary battery. This is understood to be because, when the electrode that is not adhered to the folding separation membrane 122 is the negative electrode, the unadhered surface tends to act as an interfacial diffusion resistance, promoting chemical side reactions and accelerating the consumption of the electrolyte.

[0059] Therefore, the inventors of the present invention have found it important to reduce the number of unit cells 121 in which the electrode on the exposed other side surface that is not adhered to the folding separation membrane 122 is the negative electrode.

[0060] Incidentally, when the number of stacked unit cells 121 is 5 or less, we found that the number of unit cells 121 with exposed electrodes that are not adhered to the folding separation membrane 122 and are negative electrodes remains constant, even when considering all possible arrangements of the unit cells 121. Therefore, we found that when the number of stacked unit cells 121 is 5 or less, it is difficult to minimize the number of unit cells 121 with exposed electrodes that are not adhered to the folding separation membrane 122 and are negative electrodes.

[0061] However, when the number of stacked unit cells 121 is six or more, we found that when considering all possible arrangements of the unit cells 121, there is a case where the number of unit cells 121 with exposed electrodes that are not adhered to the folding separation membrane 122 is minimized.

[0062] When there are 6 stacked unit cells 121, the number of possible arrangements of the unit cells 121 when the electrode assembly is unfolded is shown in Figure 9. Of these, the case with an RL-ML-MR-ML-C arrangement (i.e., Case 2) minimizes the number of unit cells 121 whose exposed electrodes, not adhered to the folding separation membrane 122, are negative electrodes.

[0063] As shown in Figure 2, the unit cell 121 from which folding begins is the rightmost unit cell 121, and a blank area corresponding to the width of one unit cell 121 may be placed between the two rightmost unit cells 121. Such a rule can also be applied when the number of stacked unit cells 121 is greater than six.

[0064] Furthermore, the last two unit cells 121 at which folding is completed are R-type and L-type. In the R-type and L-type unit cells 121, the electrode that is not adhered to the folding separation membrane 122 is the positive electrode.

[0065] When there are seven stacked unit cells 121, the possible arrangements of the unit cells 121 when the electrode assembly is unfolded are as shown in Figure 10. Of these, the case with an RL-ML-MR-ML-MR-C arrangement (i.e., case 6) minimizes the number of unit cells 121 whose exposed electrodes, not adhered to the folding separation membrane 122, are negative electrodes.

[0066] When there are 8 stacked unit cells 121, the possible arrangements of the unit cells 121 when the electrode assembly is unfolded are as shown in Figure 11. In Case 1, there are 4 unit cells 121 with exposed negative electrodes, while in the other cases, there are 3 unit cells 121 with exposed negative electrodes. Therefore, when there are 8 stacked unit cells 121, one of the arrangements from Case 2 to Case 5 can be adopted.

[0067] When there are nine stacked unit cells 121, the possible arrangements of the unit cells 121 when the electrode assembly is unfolded are as shown in Figure 12. Of these, the case in which the number of unit cells 121 with exposed negative electrodes is minimized is one of the following three cases.

[0068] RLC-MR-A-MR-CCA (Case 3); RL-ML-C-ML-ACCA (Case 5); RL-ML-C-ML-ML-ML-AC (Case 6).

[0069] When there are 10 stacked unit cells 121, the possible arrangements of the unit cells 121 when the electrode assembly is unfolded are as shown in Figure 13. Of these, the case with the RL-ML-C-ML-A-ML-CCA arrangement (i.e., case 8) minimizes the number of unit cells 121 whose exposed electrodes, not adhered to the folding separation membrane 122, are negative electrodes.

[0070] When there are 11 stacked unit cells 121, the possible arrangements of the unit cells 121 when the electrode assembly is unfolded are as shown in Figure 14. Of these, the case in which the number of unit cells 121 with exposed negative electrodes is minimized is one of the following four cases.

[0071] RLC-MR-A-MR-CCAAC (Case 5); RL-ML-C-ML-ACCAAC (Case 6); RL-ML-C-ML-ML-ML-ACCA (Case 10); RLC-MR-MR-MR-A-MR-CCA (Case 11).

[0072] When there are 12 stacked unit cells 121, the possible arrangements of the unit cells 121 when the electrode assembly is unfolded are as shown in Figure 15. Of these, the case in which the number of unit cells 121 with exposed negative electrodes is minimized is one of the following two cases.

[0073] RLC-MR-A-MR-C-MR-ACCA (Case 10); RL-ML-C-ML-A-ML-CCAAC (Case 11).

[0074] A typical engineer can consider all possible cases even when the number of stacked unit cells 121 is 13 or more, following the method described above, and find the case that minimizes the number of unit cells 121 whose exposed electrode is the negative electrode.

[0075] The above unit cell 121 may include at least one monocell. In some embodiments, the number of monocells may be less than half (1 / 2) of the total number of unit cells 121.

[0076] The secondary battery 10 according to an embodiment of the present invention minimizes the number of unit cells 121 in which the electrode on the exposed other side surface that is not adhered to the folding separation membrane 122 is the negative electrode, thereby maximally suppressing the tendency for lithium to precipitate in a fingerprint-like pattern as the charge-discharge cycle is repeated. This contributes to extending the lifespan of the secondary battery.

[0077] Although embodiments of the present invention have been described in detail above, any person with ordinary skill in the art to which the present invention pertains can modify and implement the present invention in various ways without departing from the spirit and scope of the invention as defined in the appended claims. Therefore, any future modifications to embodiments of the present invention will not depart from the art of the present invention. [Explanation of symbols]

[0078] 10: Secondary battery 11: Electrode Leads 12: Electrode assembly 13: Case 13a: Electrode assembly storage section 13b: Sealing section 14: Lead film 121: Unit cell 122: Folding Separation Membrane

Claims

1. An electrode assembly manufactured using a stack-and-fold method, A case for housing the electrode assembly, A secondary battery that includes, The electrode assembly includes six or more unit cells bonded to a folded separation membrane, and each of the six or more unit cells has one side surface bonded to the folded separation membrane. A secondary battery in which the unit cell is arranged such that, when the electrode assembly is unfolded, the number of negative electrodes is minimized among the electrodes on the other side surface of the unit cell that is not adhered to the folded separator membrane.

2. The secondary battery according to claim 1, wherein the outermost unit cells on both sides of the electrode assembly each have a stacked structure of single positive electrode / separator membrane / negative electrode / separator membrane / positive electrode.

3. The secondary battery according to claim 1, wherein the electrode assembly is configured such that the polarities of the electrodes of a pair of opposing unit cells, separated by the folded separator membrane, are different from each other.

4. The secondary battery according to claim 1, wherein the electrode assembly includes at least one monocell.

5. The secondary battery according to claim 1, wherein the electrode assembly includes eight or more unit cells, and the number of monocells is less than half the total number of unit cells.

6. The secondary battery according to claim 1, wherein the electrode assembly is manufactured by arranging six or more unit cells on a folded separator membrane, then adhering one side surface of the unit cells to the folded separator membrane, and folding the assembly.

7. A unit cell in which a positive electrode is provided on each side of the negative electrode, and a separation membrane is included between the electrodes, is defined as type A. A unit cell in which negative electrodes are provided on both sides of the positive electrode, and a separation membrane is included between the electrodes, is defined as a C-type. A unit cell is defined as an R-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the right side. A unit cell is defined as an L-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the left side. A unit cell in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, with the positive electrode tab positioned on the right side, is defined as an MR-type. When a unit cell is defined as an ML-type, in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, and the tab of the positive electrode is positioned on the left side, The secondary battery according to claim 1, wherein the electrode assembly is composed of 12 unit cells, and the arrangement of the unit cells when the electrode assembly is unfolded is one of the following arrangements. R-L-C-MR-A-MR-C-MR-A-C-C-A; R-L-ML-C-ML-A-ML-C-C-A-A-C.

8. A unit cell in which a positive electrode is provided on each side of the negative electrode, and a separation membrane is included between the electrodes, is defined as type A. A unit cell in which negative electrodes are provided on both sides of the positive electrode, and a separation membrane is included between the electrodes, is defined as a C-type. A unit cell is defined as an R-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the right side. A unit cell is defined as an L-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the left side. A unit cell in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, with the positive electrode tab positioned on the right side, is defined as an MR-type. When a unit cell is defined as an ML-type, in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, and the tab of the positive electrode is positioned on the left side, The secondary battery according to claim 1, wherein the electrode assembly is composed of 11 unit cells, and the arrangement of the unit cells when the electrode assembly is unfolded is one of the following arrangements. R-L-C-MR-A-MR-C-C-A-A-C; R-L-ML-C-ML-A-C-C-A-A-C; R-L-ML-C-ML-ML-ML-A-C-C-A; R-L-C-MR-MR-MR-A-MR-CCA.

9. A unit cell in which a positive electrode is provided on each side of the negative electrode, and a separation membrane is included between the electrodes, is defined as type A. A unit cell in which negative electrodes are provided on both sides of the positive electrode, and a separation membrane is included between the electrodes, is defined as a C-type. A unit cell is defined as an R-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the right side. A unit cell is defined as an L-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the left side. A unit cell in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, with the positive electrode tab positioned on the right side, is defined as an MR-type. When a unit cell is defined as an ML-type, in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, and the tab of the positive electrode is positioned on the left side, The secondary battery according to claim 1, wherein the electrode assembly is composed of eight unit cells, and the arrangement of the unit cells when the electrode assembly is unfolded is one of the following arrangements. R-L-ML-C-C-A-A-C; R-L-C-MR-A-C-C-A; R-L-C-MR-MR-MR-A-C; R-L-ML-C-ML-ML-CA.

10. A unit cell in which a positive electrode is provided on each side of the negative electrode, and a separation membrane is included between the electrodes, is defined as type A. A unit cell in which negative electrodes are provided on both sides of the positive electrode, and a separation membrane is included between the electrodes, is defined as a C-type. A unit cell is defined as an R-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the right side. A unit cell is defined as an L-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the left side. A unit cell in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, with the positive electrode tab positioned on the right side, is defined as an MR-type. When a unit cell is defined as an ML-type, in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, and the tab of the positive electrode is positioned on the left side, The secondary battery according to claim 1, wherein the electrode assembly is composed of 10 unit cells, and when the electrode assembly is unfolded, the unit cells are arranged in the order R-L-ML-C-ML-A-ML-C-C-A.

11. A unit cell in which a positive electrode is provided on each side of the negative electrode, and a separation membrane is included between the electrodes, is defined as type A. A unit cell in which negative electrodes are provided on both sides of the positive electrode, and a separation membrane is included between the electrodes, is defined as a C-type. A unit cell is defined as an R-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the right side. A unit cell is defined as an L-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the left side. A unit cell in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, with the positive electrode tab positioned on the right side, is defined as an MR-type. When a unit cell is defined as an ML-type, in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, and the tab of the positive electrode is positioned on the left side, The secondary battery according to claim 1, wherein the electrode assembly is composed of nine unit cells, and the arrangement of the unit cells when the electrode assembly is unfolded is one of the following arrangements. R-L-C-MR-A-MR-CC-A; R-L-ML-C-ML-A-C-C-A; R-L-ML-C-ML-ML-ML-A-C.

12. A unit cell in which a positive electrode is provided on each side of the negative electrode, and a separation membrane is included between the electrodes, is defined as type A. A unit cell in which negative electrodes are provided on both sides of the positive electrode, and a separation membrane is included between the electrodes, is defined as a C-type. A unit cell is defined as an R-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the right side. A unit cell is defined as an L-type, in which a single positive electrode and a positive electrode are provided on each side of the negative electrode, a separator membrane is included between the electrodes, and the tab of the single positive electrode is positioned on the left side. A unit cell in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, with the positive electrode tab positioned on the right side, is defined as an MR-type. When a unit cell is defined as an ML-type, in which a negative electrode and a positive electrode are provided on both sides of the separation membrane, and the tab of the positive electrode is positioned on the left side, The secondary battery according to claim 1, wherein the electrode assembly is composed of seven unit cells, and when the electrode assembly is unfolded, the unit cells are arranged in the order R-L-ML-MR-ML-MR-C.

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