Jelly roll with excellent electrolyte impregnation, cylindrical battery cell including the same, battery pack, and automobile

Abstract

A jelly roll according to an embodiment of the present invention has a structure in which a laminate including a first electrode having a first electrode tab having a first polarity, a second electrode having a second electrode tab having a second polarity, and a separator interposed between the first and second electrodes is wound in one direction, and at least one of the first and second electrode tabs has a plurality of slits formed along the winding direction of the jelly roll, and the distance between the plurality of slits gradually increases from the core side to the outer periphery side of the jelly roll.

Description

[Technical Field]

[0001] The present invention relates to a jelly roll having excellent electrolyte impregnation properties, and a cylindrical battery cell, a battery pack, and an automobile each including the jelly roll.

[0002] This application claims priority based on Korean Patent Application No. 10-2021-0153452, filed on November 9, 2021, and the entire contents disclosed in the specification and drawings of that application are incorporated herein by reference. [Background technology]

[0003] Secondary batteries, which are easily applicable to various products and have electrical properties such as high energy density, are widely used not only in portable devices but also in electric vehicles (EVs) and hybrid electric vehicles (HEVs) that are driven by electrical sources. These secondary batteries are attracting attention as a new energy source because they not only have the primary advantage of dramatically reducing the use of fossil fuels, but also because they are environmentally friendly and improve energy efficiency by not producing any by-products associated with energy use.

[0004] Currently, widely used types of secondary batteries include lithium-ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries. The operating voltage of such unit secondary battery cells, i.e., unit battery cells, is approximately 2.5V to 4.5V. Therefore, if a higher output voltage is required, a battery pack is constructed by connecting multiple battery cells in series. Alternatively, a battery pack can be constructed by connecting multiple battery cells in parallel depending on the required charge / discharge capacity of the battery pack. Therefore, the number of battery cells included in the battery pack can be variously set depending on the required output voltage or charge / discharge capacity.

[0005] Meanwhile, in a typical secondary battery, an electrode assembly is impregnated with an electrolyte solution, which allows lithium ions to move smoothly and generate current. In this regard, electrolyte impregnation is a very important factor that affects the life and capacity of a battery, and a higher electrolyte impregnation rate is advantageous.

[0006] Meanwhile, as demand for cylindrical secondary batteries for electric vehicles has recently increased, the development of medium- to large-sized cylindrical battery cells, rather than the existing 18650 or 21700 sizes, has become increasingly important in order to improve energy density. However, as the size of cylindrical battery cells increases, the electrolyte impregnation characteristics at the center of the jelly-roll electrodes can deteriorate, which can lead to reduced battery performance. That is, the existing electrode assembly structure has limitations in improving the electrolyte impregnation characteristics of medium- to large-sized cylindrical battery cells.

[0007] Therefore, a solution is needed that can improve the electrolyte impregnation of the electrode assembly of a cylindrical battery cell. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above problems, and aims to improve the electrolyte impregnation of a cylindrical battery cell by forming slits in the electrode tabs of the cylindrical battery cell through which an electrolyte can pass, thereby uniformly impregnating the entire jelly-roll-shaped electrode assembly housed inside the cylindrical battery cell with the electrolyte.

[0009] Another object of the present invention is to reduce the internal resistance of a cylindrical battery cell by bending one end of the electrode tab to increase the contact area between the electrode tab and the current collecting plate of a jelly-roll-shaped electrode assembly.

[0010] Another object of the present invention is to improve the bonding strength between the jelly-roll type electrode assembly and the current collecting plate by ensuring a large contact area between the electrode tabs of the jelly-roll type electrode assembly and the current collecting plate.

[0011] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description of the invention. [Means for solving the problem]

[0012] To achieve the above object, a jelly roll according to one aspect of the present invention is a jelly roll having a structure in which a laminate including a first electrode having a first electrode tab with a first polarity, a second electrode having a second electrode tab with a second polarity, and a separator interposed between the first electrode and the second electrode is wound in one direction.

[0013] At least one of the first electrode tab and the second electrode tab may have a plurality of slits formed along the winding direction of the jelly roll, and the distance between the plurality of slits may gradually increase from the core side to the outer periphery side of the jelly roll.

[0014] Here, the plurality of slits may have a shape extending in a direction parallel to the winding direction.

[0015] Alternatively, the plurality of slits may be formed on the same line.

[0016] Meanwhile, the plurality of slits may be formed on a straight line parallel to the winding direction of the first electrode or the second electrode.

[0017] Meanwhile, the length of the slit in the winding direction may gradually increase from the core side to the outer periphery side of the jelly roll.

[0018] Meanwhile, among the plurality of slits, adjacent slits in a radial direction of the jelly roll may at least partially overlap each other to form an impregnation path through which an electrolyte can pass in the radial direction.

[0019] Here, the impregnation path may be formed to a predetermined depth along the radial direction from the outer circumferential surface of the jelly roll.

[0020] Meanwhile, at least one of the first electrode tab and the second electrode tab may be spaced apart from each other along the winding direction of the jelly roll and may include a plurality of bent portions defined by a plurality of incision lines formed at a predetermined depth from an end of the electrode tab.

[0021] Here, the plurality of bent portions may be bent in a direction toward the winding axis of the jelly roll and cover at least a portion of one side of the jelly roll that is perpendicular to the winding axis.

[0022] Alternatively, the plurality of folded portions may be folded in a direction toward the winding axis of the jelly roll to cover the entire side of the jelly roll that is perpendicular to the winding axis.

[0023] Meanwhile, among the plurality of slits, adjacent slits in the radial direction of the jelly roll may be at least partially overlapped with each other to form an impregnation path through which an electrolyte can pass in the radial direction, and the impregnation path may be formed to a predetermined depth in the radial direction from the outer circumferential surface of the jelly roll, and the depth of the impregnation path may be greater than or equal to the radial length of the area covered by the bent portion on one side of the jelly roll perpendicular to the winding shaft.

[0024] Meanwhile, the incision line and the slit may be spaced apart from each other by a predetermined distance.

[0025] A cylindrical battery cell according to an embodiment of the present invention includes a jelly roll according to the above-described embodiment.

[0026] Furthermore, the battery pack according to an embodiment of the present invention includes at least one cylindrical battery cell according to an embodiment of the present invention.

[0027] Meanwhile, a vehicle according to an embodiment of the present invention includes at least one battery pack according to an embodiment of the present invention. [Effects of the Invention]

[0028] According to the present invention, it is possible to improve the electrolyte impregnation of a jelly roll electrode assembly. More specifically, according to the present invention, it is possible to shorten the time required for impregnating a jelly roll electrode assembly with an electrolyte and improve the uniformity of the electrolyte impregnation. As a result, it is possible to achieve an increase in initial efficiency. In addition, it is possible to form a uniform SEI (Solid Electrolyte Interphase) layer at the electrode interface.

[0029] In particular, according to the present invention, a path through which the electrolyte can pass is formed in the electrode tab of the cylindrical battery cell, and the electrolyte is uniformly impregnated throughout the jelly roll electrode assembly housed inside the cylindrical battery cell, thereby improving the electrolyte impregnation of the cylindrical battery cell.

[0030] Furthermore, according to the present invention, the contact area between the electrode tabs of the jelly-roll-shaped electrode assembly and the current collecting plate can be increased, thereby reducing the internal resistance of the cylindrical battery cell.

[0031] Furthermore, according to the present invention, a large contact area between the electrode tabs of the jelly-roll-shaped electrode assembly and the current collecting plate can be ensured, thereby improving the bonding strength between the jelly-roll-shaped electrode assembly and the current collecting plate.

[0032] The present invention also provides various other effects, which will be explained in the respective embodiments, and explanations of effects that can be easily inferred by ordinary skilled artisans will be omitted.

[0033] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical concept of the present invention, so the present invention should not be interpreted as being limited to the matters described in the drawings. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a diagram illustrating a jelly roll according to an embodiment of the present invention. FIG. [Figure 2] 2 is a diagram illustrating a state in which the first electrode applied to the jelly roll of FIG. 1 is unfolded. FIG. [Figure 3] FIG. 2 is a plan view of the jelly roll of FIG. 1. [Figure 4] FIG. 4 is a diagram for explaining the impregnation path of the jelly roll of FIG. 3. [Figure 5] FIG. 10 is a diagram illustrating an impregnation path of a jelly roll according to another embodiment of the present invention. [Figure 6] FIG. 2 is a front cross-sectional view of the jelly roll of FIG. [Figure 7] FIG. 4 is a plan view of a jelly roll having a different configuration than the jelly roll shown in FIG. [Figure 8] FIG. 8 is a front cross-sectional view of the jelly roll of FIG. [Figure 9] 2 is a diagram illustrating a battery pack including at least one cylindrical battery cell including the jelly roll of FIG. 1. FIG. [Figure 10] FIG. 10 is a diagram illustrating a vehicle including the battery pack of FIG. 9. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in the specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best explain his invention.

[0036] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can be substituted for them at the time of this application.

[0037] In order to facilitate understanding of the invention, the accompanying drawings may be drawn not to scale but with some components exaggerated. The same reference numerals may be used to refer to the same components in different embodiments.

[0038] FIG. 1 is a diagram illustrating a jelly roll according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a state in which a first electrode applied to the jelly roll of FIG. 1 is unfolded.

[0039] 1 and 2, the electrode assembly is an electrode assembly having a jelly roll shape in which a laminate including a first electrode, a second electrode, and a separator is wound up. Hereinafter, the electrode assembly having a jelly roll shape will be referred to as a jelly roll 1.

[0040] The first electrode has a first electrode tab having a first polarity, and the second electrode has a second electrode tab having a second polarity, for example, the first electrode can be a positive or negative electrode and the second electrode can be an electrode having an opposite polarity to the first electrode.

[0041] A separator is interposed between the first and second electrodes. A laminate in which the first electrode, separator, second electrode, and separator are stacked in sequence at least once is wound around a winding center C extending in the width direction of the first and second electrodes, i.e., in the height direction of the jelly roll 1 (direction parallel to the Z axis), to form the jelly roll 1. That is, the jelly roll 1 has a structure in which a laminate including the first electrode, the second electrode, and the separator interposed between the first and second electrodes is wound in one direction.

[0042] The first electrode and the second electrode each include an electrode tab and an application portion.

[0043] The first electrode includes a first electrode current collector and a first electrode active material coated on one or both surfaces of the first electrode current collector. An uncoated portion where the first electrode active material is not coated exists at one end of the first electrode current collector in the width direction (direction parallel to the Z axis). The uncoated portion functions as a first electrode tab 10. That is, the first electrode tab 10 is the first uncoated portion. The first electrode tab 10 is provided at the upper portion in the height direction (direction parallel to the Z axis) of the electrode assembly housed in the battery can. A coated portion 20 where the first electrode active material is coated exists on the opposite side of the uncoated portion of the first electrode current collector.

[0044] Meanwhile, although not shown, the second electrode includes a second electrode current collector and a second electrode active material coated on one or both surfaces of the second electrode current collector. The other end of the second electrode current collector in the width direction has an uncoated portion where the second electrode active material is not coated. The uncoated portion functions as a second electrode tab. That is, the second electrode tab is the second uncoated portion. The second electrode tab is provided at a lower portion in the height direction of the electrode assembly housed in the battery can. The second electrode current collector has a coated portion coated with the second electrode active material on the opposite side of the uncoated portion.

[0045] Meanwhile, in one embodiment of the present invention, the positive electrode active material coated on the positive electrode plate and the negative electrode active material coated on the negative electrode plate may be any active material known in the art without any limitations.

[0046] In one example, the positive electrode active material has the general chemical formula A[A x M y ]O 2+z (A includes at least one element selected from Li, Na, and K; M includes at least one element selected from Ni, Co, Mn, Ca, Mg, Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, Mo, Sc, Zr, Ru, and Cr; x≧0, 1≦x+y≦2, −0.1≦z≦2; and the stoichiometric coefficients of x, y, z, and the components included in M ​​are selected so that the compound maintains electroneutrality.)

[0047] In another example, the positive electrode active material is an alkali metal compound xLiM disclosed in U.S. Pat. No. 6,677,082, U.S. Pat. No. 6,680,143, etc. 1 O2‐(1‐x)Li2M 2 O3(M 1 contains at least one element having an average oxidation state of 3; M 2 may contain at least one element having an average oxidation state of 4; 0≦x≦1).

[0048] In yet another example, the positive electrode active material has the general chemical formula Li a M 1 x Fe 1‐x M 2 y P 1‐y M 3 z O 4‐z (M 1 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Mg, and Al; M 2 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Mg, Al, As, Sb, Si, Ge, V, and S; M 3contains a halogen group element selectively containing F; 0 < a ≤ 2, 0 ≤ x ≤ 1, 0 ≤ y < 1, 0 ≤ z < 1; the stoichiometric coefficients of the components included in a, x, y, z, M1, M2 and M3 are selected so that the compound maintains electrical neutrality.), or can be a lithium metal phosphate represented by Li3M2(PO4)3 [M contains at least one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Mg and Al.].

[0049] Desirably, the positive electrode active material may contain primary particles and / or secondary particles formed by aggregation of primary particles.

[0050] In one example, as the negative electrode active material, a carbon material, a lithium metal or a lithium metal compound, silicon or a silicon compound, tin or a tin compound, etc. can be used. Metal oxides such as TiO2 and SnO2 with a potential less than 2V can also be used as the negative electrode active material. As the carbon material, both low-crystalline carbon and high-crystalline carbon can be used.

[0051] The separation membrane can be a porous polymer film, for example, a porous polymer film made from a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, etc., used alone or laminated. In another example, the separation membrane can be an ordinary porous non-woven fabric, for example, a non-woven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc.

[0052] At least one surface of the separation membrane may include a coating layer of inorganic particles. Also, the separation membrane itself can be composed of a coating layer of inorganic particles. The particles constituting the coating layer may have a structure in which they are bound to a binder so that an interstitial volume exists between adjacent particles.

[0053] The inorganic particles may be made of an inorganic material having a dielectric constant of 5 or more. Non-limiting examples of the inorganic particles include 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), BaTiO3, hafnia (HfO2), SrTiO3, TiO2, Al2O3, ZrO2, SnO2, CeO2, MgO, CaO, ZnO, and Y2O3.

[0054] The electrolyte is A + B - The salt may have the structure: + Li + , Na + , K. + or a combination thereof. - is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , BF2C2O4 - , BC4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO -, (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN- and (CF3CF2SO2)2N - The anion comprises one or more anions selected from the group consisting of:

[0055] Alternatively, the electrolyte may be dissolved in an organic solvent, such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone, or a mixture thereof.

[0056] In a jelly roll 1 according to an embodiment of the present invention, the first and second electrodes extend in opposite directions along the height direction (parallel to the Z-axis) of the jelly roll 1. In the following description, the structure of the first electrode will be specifically described. However, this is merely an example, and the structure of the first electrode described below can be applied to both the first and second electrodes, or can be applied only to the second electrode.

[0057] 1 and 2, the first electrode tab 10 includes a plurality of slits 10a. The first electrode tab 10 may further include a plurality of incision lines 10b and bent portions 10c defined by the incision lines 10b.

[0058] The plurality of slits 10a can be formed by, for example, punching with a die or laser notching.

[0059] The slits 10a are formed in the circumferential direction of the jelly roll 1, i.e., along the winding direction of the jelly roll 1. In this case, the slits 10a may be formed on the same line. For example, the slits 10a may be formed on a straight line parallel to the winding direction of the first electrode and / or the second electrode. That is, the extension lines of the length directions of adjacent slits 10a along the winding direction may overlap each other.

[0060] 1 and 2, the distance between the slits 10a may gradually increase from the core side to the outer periphery side of the jelly roll 1. That is, the slits 10a may be provided in a gradient pattern.

[0061] More specifically, referring to FIG. 2, the sheet-like first and / or second electrodes are wound in one direction. A plurality of slits 10a are formed along the winding direction. The slits 10a are relatively close to each other near the core of the first and / or second electrodes, and the distance between the slits 10a gradually increases toward the outer periphery. This is because the radius of the jelly roll 1 increases as the first and / or second electrodes are wound in one direction, and the circumferential length of the layers constituting the jelly roll 1 increases toward the outer periphery. That is, as the first and / or second electrodes are wound in one direction, the circumferential size of the outermost layer gradually increases. Therefore, when forming slits 10a in the sheet-like first electrode and / or second electrode, the distance between the slits 10a must be increased as one moves toward the outer periphery so that the slits 10a in the previous layer face the slits 10a in the next layer, forming the impregnation path IP. In other words, to form slits 10a at a specific angle on the jelly roll 1, the distance between the slits 10a must also increase as the number of windings increases. For example, if slits 10a are formed at approximately 90° intervals around the circumference of the jelly roll 1, the distance between the slits 10a should also increase as the number of windings increases. The exact location of the slits 10a to form the impregnation path IP may vary depending on the number of slits 10a per turn, the thickness of the first electrode, the thickness of the second electrode, the thickness of the separator, etc.

[0062] According to this structure of an embodiment of the present invention, the slits 10a are provided at specific angle points of the jelly roll 1, which allows for effective formation of the impregnation path IP, thereby improving the electrolyte impregnation characteristics at the center of the electrode of the jelly roll 1.

[0063] Furthermore, according to the above-described structure of one embodiment of the present invention, the size of the slit 10a does not need to be excessively large, and even if the size of the slit 10a is relatively small, the impregnation path IP is reliably formed, thereby minimizing weakening of the strength of the first electrode tab 10 and / or the second electrode tab.

[0064] That is, with the above-described structure, the strength of the first electrode tab 10 can be ensured at a certain level in one embodiment of the present invention.

[0065] For example, if the slits 10a are arranged at regular intervals or randomly rather than in a gradient pattern, the length of the slits 10a in the winding direction must be increased to form impregnation paths IP in the radial direction of the jelly roll 1. This is because increasing the length of the slits 10a in the winding direction increases the likelihood that the slits 10a in a previous layer will face the slits 10a in the next layer. This structure results from a design that does not take into account the increase in circumferential length that occurs with an increase in the number of windings. Therefore, this structure can significantly weaken the strength of the first electrode tab 10 at the locations where the slits 10a are formed. That is, the area of ​​the cross section of the first electrode tab 10 at the locations where the slits 10a are formed, i.e., the cross section cut along a direction perpendicular to the winding axis of the jelly roll 1 (a direction parallel to the XY plane), decreases. Therefore, the first electrode tab 10 may be damaged due to impacts or vibrations applied during use of the cylindrical battery cell, which may result in performance problems of the cylindrical battery cell and / or safety issues such as fire due to an internal short circuit.

[0066] In contrast, according to one embodiment of the present invention, the slits 10a formed in the previous layer face the slits 10a formed in the next layer, so that the impregnation path IP is reliably formed even if the length of the slits 10a in the winding direction is relatively short. This structure minimizes the reduction in the area of ​​the cross section of the first electrode tab 10 at the position where the slits 10a are formed, i.e., the cross section cut along a direction approximately perpendicular to the winding axis of the jelly roll 1 (a direction parallel to the XY plane). This improves the tensile strength of the first electrode tab 10 in the winding axis direction (a direction parallel to the Z axis). Therefore, in this case, the first electrode tab 10 is less likely to break even if an external force is applied to the first electrode tab 10.

[0067] Figure 3 is a plan view of the jelly roll of Figure 1. Figure 4 is a diagram illustrating the impregnation path of the jelly roll of Figure 3, and Figure 5 is a diagram illustrating the impregnation path of a jelly roll according to another embodiment of the present invention.

[0068] 4, in one embodiment of the present invention, the slit 10a may be formed to have a constant length in the winding direction regardless of the position of the slit 10a. With this structure, as can be seen from FIG. 4, the width of the impregnation path IP can be formed to be constant.

[0069] Meanwhile, referring to FIG. 5, in another embodiment of the present invention, the length of the slits 10a in the winding direction may gradually increase from the core side to the outer periphery of the jelly roll 1. As can be seen from FIG. 5, the width of the impregnation path IP may gradually increase toward the outer periphery of the jelly roll 1. In this case, the center of the length of the slits 10a in the winding direction of the previous layer may coincide with the center of the length of the slits 10a in the winding direction of the next layer. With this structure, the area of ​​the slits 10a in the outermost layer, where the electrolyte begins to impregnate the jelly roll 1, is large, thereby facilitating the impregnation of the electrolyte into the jelly roll 1. Furthermore, the area of ​​the slits 10a on the core side is small, thereby minimizing the reduction in the cross-sectional area of ​​the jelly roll 1 cut in a direction perpendicular to the winding axis (parallel to the XY plane). This improves the tensile strength of the first electrode tab 10 in the winding axis direction (parallel to the Z axis). Therefore, in this case, even if an external force is applied to the first electrode tab 10, the first electrode tab 10 is unlikely to break.

[0070] Meanwhile, in the same manner as minimizing the reduction in the cross-sectional area at the position where the slits 10a are formed as described above, the slits 10a may be arranged to be spaced apart from each other at a predetermined interval along the cutting line 10b (described below) and the extension direction of the winding shaft (direction parallel to the Z-axis), which may further reduce the possibility of the first electrode tab 10 being broken due to external forces such as impacts and vibrations applied during the manufacturing and use of the cylindrical battery cell.

[0071] Meanwhile, as mentioned above, for convenience, this specification has only described the case where the slit 10a is provided in the first electrode, but such slit 10a can also be provided in only the second electrode, or in both the first electrode and the second electrode.

[0072] 3 is a plan view of the jelly roll of FIG. 1, and FIG. 6 is a front cross-sectional view of the jelly roll of FIG.

[0073] 3 and 6, the first electrode tab 10 may have a plurality of bent portions 10c separated by a plurality of incision lines 10b formed at a predetermined depth from an end of the first electrode tab 10 and spaced apart from one another along the winding direction of the jelly roll 1. Thus, the bent portions 10c are provided at one end of the first electrode tab 10. That is, the first electrode tab 10 may have a plurality of segmented pieces divided along the circumferential direction of the jelly roll 1 by, for example, notching, and these segmented pieces may be folded along the radial direction of the jelly roll 1. Each of the bent segments becomes the above-mentioned bent portion 10c.

[0074] The plurality of folded portions 10c may be folded toward the winding axis of the jelly roll 1 to cover at least a portion of one side of the jelly roll 1 that is substantially perpendicular to the winding axis. For example, referring to Figures 3 and 6, the plurality of folded portions 10c may cover the entire one side of the jelly roll 1 that is perpendicular to the winding axis.

[0075] In this manner, the bent portion 10c provided at one end of the first electrode tab 10 is bent to cover one side of the jelly roll 1 perpendicular to the winding axis, thereby ensuring a wide contact area between the first electrode tab 10 and a current collecting plate (not shown) attached to one side of the jelly roll 1. This reduces the internal resistance of the cylindrical battery cell and improves the bonding strength between the jelly roll 1 and the current collecting plate.

[0076] Meanwhile, after the jelly roll 1 is placed in a battery can, the electrolyte may be injected through the opening at the top of the battery can. In this case, since the plurality of bent portions 10c entirely cover one side of the jelly roll 1 perpendicular to the winding axis, the electrolyte may not be smoothly impregnated through the top of the jelly roll 1. In particular, in the case of a medium- to large-sized cylindrical battery cell, the electrolyte may not be impregnated all the way to the center of the jelly roll 1.

[0077] Therefore, in one embodiment of the present invention, among the plurality of slits 10a, at least a portion of the slits 10a adjacent to each other along the radial direction of the jelly roll 1 may overlap with each other to form an impregnation path IP through which the electrolyte can pass along the radial direction. In this case, the impregnation path IP may be formed to a predetermined depth along the radial direction from the outer circumferential surface of the jelly roll 1.

[0078] For example, referring to FIG. 6, the plurality of bent portions 10c at one end of the first electrode tab 10 may be bent toward the winding shaft to cover the entire side of the jelly roll 1 perpendicular to the winding shaft. In this case, at least a portion of the adjacent slits 10a in the radial direction of the jelly roll 1 may overlap with each other, thereby forming an impregnation path IP through which the electrolyte can pass along the radial direction. In FIG. 6, the impregnation path IP is formed along the radial direction from the outer circumferential surface of the jelly roll 1 to the winding center C. This allows the electrolyte to move to the center of the jelly roll 1 through the impregnation path IP that penetrates the jelly roll 1. The electrolyte that flows into the impregnation path IP flows downward due to the force of gravity. Therefore, the jelly roll 1 according to one embodiment of the present invention can be uniformly impregnated with the electrolyte throughout its entire height (direction parallel to the Z axis) and its entire radial direction.

[0079] Meanwhile, in one embodiment of the present invention, when the first electrode tab 10 has the bent portion 10c as described above, the slits 10a may be formed in an area other than the area where the bent portion 10c is formed. Thus, the slits 10a may be formed on the outer circumferential surface of the jelly roll 1.

[0080] FIG. 7 is a plan view of a jelly roll having a different configuration from the jelly roll shown in FIG. 3, and FIG. 8 is a front cross-sectional view of the jelly roll of FIG.

[0081] 7 and 8, the plurality of bent portions 10c may be bent toward the winding axis of the jelly roll 1 and cover only a portion of one side of the jelly roll 1 perpendicular to the winding axis.

[0082] In this case, the length of the first electrode tab 10 in the region adjacent to the winding center C of the jelly roll 1 may be different from the length of the first electrode tab 10 in the region adjacent to the outer peripheral surface of the jelly roll 1. Specifically, the length of the first electrode tab 10 in the region adjacent to the winding center C of the jelly roll 1 may be shorter than the length of the first electrode tab 10 in the region adjacent to the outer peripheral surface of the jelly roll 1. In this case, the first electrode tab 10 in the region adjacent to the winding center C of the jelly roll 1 may not be provided with the incision lines 10b and the bends 10c. In other words, only the first electrode tab 10 in the region adjacent to the outer peripheral surface of the jelly roll 1 may be provided with multiple incision lines 10b and bends 10c.

[0083] Therefore, according to the above embodiment, the first electrode tab 10 may be unfolded and open upward in the region adjacent to the winding center C of the jelly roll 1. Hereinafter, the region not covered by the bent portion 10c above is referred to as the first region A1. Hereinafter, the radial length of the first region A1 is referred to as D1.

[0084] Meanwhile, the plurality of bent portions 10c of the first electrode tab 10 in the region adjacent to the outer circumferential surface of the jelly roll 1 are bent toward the winding shaft to cover only a portion of one side of the jelly roll 1 perpendicular to the winding shaft. Hereinafter, the region covered by the bent portions 10c is referred to as the second region A2. The radial length of the second region A2 is referred to as D2.

[0085] With this structure, the first region A1 is not covered by the bent portion 10c and is open upward, allowing the electrolyte solution flowing in from the opening at the top end of the battery can to smoothly flow into the first region A1, thereby further improving the electrolyte solution impregnation.

[0086] However, in this case, the impregnation rate of the second region A2, the upper portion of which is covered by the core-side folding of the plurality of folding portions 10c of the first electrode tab 10, may be slightly lower than the impregnation rate of the first region A1, the upper portion of which is not covered. Therefore, it is necessary to improve the impregnation rate of the second region A2. Therefore, in one embodiment of the present invention, the formation depth P of the impregnation path IP may be greater than or equal to the radial length D2 of the region covered by the folding portions 10c on one side of the jelly roll 1 perpendicular to the winding shaft. That is, referring to FIG. 8, the formation depth P of the impregnation path IP may be greater than or equal to the radial length D2 of the second region A2.

[0087] With this structure, the electrolyte impregnation path IP allows the electrolyte to move at least to the boundary between the second region A2 and the first region A1. Alternatively, the electrolyte may move beyond the second region A2 to the first region A1. The electrolyte may then flow downward due to the force of gravity. Therefore, the jelly roll 1 according to one embodiment of the present invention can be uniformly impregnated with the electrolyte even in its interior.

[0088] Meanwhile, as mentioned above, for convenience, this specification has only described the case where the first electrode has the incision line 10b and the bending portion 10c, but it is of course possible for such incision line 10b and the bending portion 10c to be provided only on the second electrode, or on both the first electrode and the second electrode.

[0089] <Impregnation and durability test> The electrolyte impregnation of the jelly roll according to the embodiment of the present invention was evaluated, and a drop test and a vibration test were also performed to evaluate the strength of the electrode tabs.

[0090] 1) Evaluation of electrolyte impregnation A jelly roll with slits for electrolyte impregnation was fabricated. The jelly roll was then placed into a battery can through the top or bottom opening, and the electrolyte was then injected into the battery can. After aging for 24 hours after the electrolyte injection, the electrolyte impregnation level (presence or absence of unimpregnated areas) was analyzed. ◯ (Pass): No unimpregnated areas present. × (fail): Unimpregnated areas present.

[0091] 2) Electrode tab strength evaluation - Drop test After welding the jelly roll and current collecting plate, they placed it in a battery can to create a cylindrical battery cell. After that, the cylindrical battery cell was fully charged to 4.2V and dropped from a height of 1.0m onto a concrete floor, and the cylindrical battery cell was checked for internal short circuit and / or fire. 〇 (Pass): No short circuit and / or fire occurred inside the battery. × (Fail): A short circuit and / or fire occurred inside the battery.

[0092] 3) Electrode tab strength evaluation - Vibration test After welding the jelly roll and current collecting plate, they were placed in a battery can to create a cylindrical battery cell. The cylindrical battery cell was then fully charged to 2.5V and vibrated. The vibration method was 7Hz to 200Hz, with the frequency changed every 15 minutes, and repeated 12 times in each of the X, Y, and Z directions. After the vibration test was completed, the cylindrical battery cell was checked for internal short circuits and / or fires. 〇 (Pass): No short circuit and / or fire occurred inside the battery. × (Fail): A short circuit and / or fire occurred inside the battery.

[0093] [Example 1] The jelly roll was fabricated so that the slits were formed on the same line and the distance between the slits gradually increased from the core side to the outer periphery of the jelly roll (gradient pattern type).

[0094] [Comparative Example 1] A jelly roll was fabricated under the same conditions as in Example 1, except that no slits were provided.

[0095] Comparative Example 2 A jelly roll was fabricated under the same conditions as in Example 1, except that multiple slits were provided at regular intervals.

[0096] Comparative Example 3 The jelly roll was manufactured so that the slits adjacent to each other in the winding direction were not formed on the same line but were positioned at offset positions (zigzag type).

[0097] The electrolyte impregnation and electrode tab strength of each jelly roll obtained as described above were evaluated, and the results are shown in Table 1.

[0098] [Table 1]

[0099] The following can be seen from Table 1:

[0100] In Example 1, the electrolyte impregnation was excellent, and there were no unimpregnated areas in the jelly roll. In addition, the jelly roll of Example 1 passed the drop test and the vibration test, confirming that the electrode tabs had excellent strength.

[0101] In Comparative Example 1, since no slits were provided, the electrolyte impregnation was poor and there were unimpregnated areas in the jelly roll.

[0102] In Comparative Example 2, although the electrolyte impregnation property was satisfied, the strength of the electrode tabs could not be ensured because the multiple slits, each long in the winding direction, were arranged at regular intervals on the same line. Specifically, the jelly roll of Comparative Example 2 suffered breakage in part of the electrode tabs as a result of drop tests and vibration tests. In other words, the jelly roll of Comparative Example 2 had low electrode tab strength, and the quality and safety of the battery could not be ensured.

[0103] In Comparative Example 3, although the electrolyte impregnation property was satisfied, the strength of the electrode tabs could not be ensured because the multiple slits, each long in the winding direction, were arranged in a zigzag pattern at offset positions. Specifically, the jelly roll of Comparative Example 3 suffered breakage in part of the electrode tabs as a result of drop tests and vibration tests. In other words, the jelly roll of Comparative Example 3 had poor electrode tab strength, and the quality and safety of the battery could not be ensured.

[0104] FIG. 9 is a diagram schematically illustrating the configuration of a battery pack according to an embodiment of the present invention.

[0105] 9, a battery pack 3 according to an embodiment of the present invention includes an assembly of electrically connected cylindrical battery cells and a pack housing 2 that accommodates the assembly. The cylindrical battery cells are the battery cells according to the above-described embodiment. For convenience, components such as bus bars for electrically connecting the cylindrical battery cells, a cooling unit, and external terminals are not shown in the drawing.

[0106] The battery pack 3 may be mounted on a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle may be a four-wheeled vehicle or a two-wheeled vehicle.

[0107] FIG. 10 is a diagram illustrating a vehicle including the battery pack of FIG.

[0108] 10, an automobile 5 according to an embodiment of the present invention includes a battery pack 3 according to an embodiment of the present invention. The automobile 5 operates by receiving power from the battery pack 3 according to an embodiment of the present invention.

[0109] Although terms indicating directions such as "up" and "down" are used in this specification, it will be obvious to those skilled in the art that these terms indicate relative positions and are used merely for convenience of explanation, and may vary depending on the position of the object in question, the position of the observer, etc.

[0110] Although the present invention has been described above with reference to limited examples and drawings, it goes without saying that the present invention is not limited thereto, and that various modifications and variations can be made by a person having ordinary skill in the art to which the present invention pertains within the technical spirit of the present invention and the equivalent scope of the claims set forth below. [Explanation of symbols]

[0111] 1 jelly roll 2-pack housing 3 Battery Pack 5. Automobiles 10 First electrode tab (non-coated portion) 10a Slit 10b Incision line 10c Bend part 20 Application section IP impregnation route P: Formation depth of impregnation path C Winding center A1 1st area A2 2nd area D1 Radial length of the first region D2 Radial length of the second region

Claims

1. A jelly roll having a structure in which a laminate including a first electrode having a first electrode tab with a first polarity, a second electrode having a second electrode tab with a second polarity, and a separator interposed between the first electrode and the second electrode is wound in one direction, At least one of the first electrode tab and the second electrode tab has a plurality of slits formed along the winding direction of the jelly roll, the distance between the slits gradually increases from the core side to the outer periphery side of the jelly roll, At least one of the first electrode tab and the second electrode tab is a plurality of bent portions formed along the winding direction of the jelly roll at intervals from each other and defined by a plurality of incision lines formed at a predetermined depth from the end of the electrode tab; Jelly roll.

2. The plurality of slits have a shape extending in a direction parallel to the winding direction.

2. The jelly roll of claim 1.

3. The plurality of slits are formed on the surface of the laminate on the same line along the winding direction.

3. A jelly roll according to claim 1 or 2.

4. The plurality of slits are formed on a straight line parallel to the winding direction of the first electrode or the second electrode.

3. A jelly roll according to claim 1 or 2.

5. The length of the slit in the winding direction gradually increases from the core side to the outer periphery side of the jelly roll.

3. A jelly roll according to claim 1 or 2.

6. Among the plurality of slits, slits adjacent to each other along the radial direction of the jelly roll are at least partially overlapped with each other to form an impregnation path through which an electrolyte can pass along the radial direction.

3. A jelly roll according to claim 1 or 2.

7. The impregnation path is formed from the outer circumferential surface of the jelly roll along the radial direction to a predetermined depth.

7. The jelly roll of claim 6.

8. The plurality of bent portions are The jelly roll is bent in a direction toward the winding shaft, covering at least a portion of one side of the jelly roll perpendicular to the winding axis 2. The jelly roll of claim 1.

9. The plurality of bent portions are The jelly roll is bent in a direction toward the winding shaft, Covering the entire side of the jelly roll that is perpendicular to the winding axis 2. The jelly roll of claim 1.

10. Among the plurality of slits, slits adjacent to each other along a radial direction of the jelly roll are at least partially overlapped with each other to form an impregnation path through which an electrolyte can pass along the radial direction; the impregnation path is formed from the outer peripheral surface of the jelly roll along the radial direction to a predetermined depth, The depth of the impregnation path is greater than or equal to the radial length of the area covered by the bent portion on one side of the jelly roll perpendicular to the winding axis.

9. The jelly roll of claim 8.

11. The incision line and the slit are spaced apart from each other by a predetermined distance.

2. The jelly roll of claim 1.

12. The jelly roll according to claim 1 or 2 is included. A cylindrical battery cell.

13. A battery comprising at least one cylindrical battery cell according to claim 12. A battery pack characterized by:

14. 14. A battery pack comprising at least one of the battery packs of claim 13. A vehicle characterized by:

Images