Tab forming device for electrode assemblies

Abstract

A forming apparatus according to one embodiment of the present invention is a forming apparatus for radially bending an electrode tab in an electrode assembly in which a first electrode, a separator, and a second electrode are stacked and wound around a central axis, the first electrode of which is exposed extending further axially than the separator, the forming apparatus includes a forming jig for bending the electrode tab, the forming jig includes a facing surface facing the electrode assembly, the facing surface having a recess depth in the direction opposite to the pressing direction.

Description

[Technical Field]

[0001] The present invention relates to a tab forming apparatus for electrode assemblies.

[0002] This application claims priority based on Korean Patent Application No. 10-2023-0115853, filed on 31 August 2023, and all contents disclosed in the specification and drawings of said application are incorporated herein by reference. [Background technology]

[0003] Rechargeable batteries, which are easily adaptable to different product groups and possess electrical characteristics such as high energy density, are universally applied not only to portable devices but also to electric vehicles (EVs) and hybrid electric vehicles (HEVs) powered by electrical drive sources. Such rechargeable batteries not only have the primary advantage of dramatically reducing the use of fossil fuels, but also the advantage of producing no by-products associated with energy use, making them a promising new energy source for environmental friendliness and improved energy efficiency.

[0004] Currently widely used types of rechargeable batteries include lithium-ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries. The operating voltage of a single rechargeable battery cell is approximately 2.5V to 4.5V. Therefore, when a higher output voltage is required, multiple battery cells are connected in series to form a battery pack. Depending on the required charge and discharge capacity of the battery pack, multiple battery cells may also be connected in parallel to form a battery pack. Therefore, the number of battery cells included in the battery pack can be set in various ways depending on the required output voltage and / or charge and discharge capacity.

[0005] On the other hand, conventional cylindrical rechargeable batteries typically have a structure in which tabs connecting the jelly roll and external terminals are welded to the foil of the jelly roll. However, in cylindrical rechargeable batteries with this structure, the current path is limited, and the resistance of the jelly roll itself inevitably becomes extremely high. Attempts were also made to reduce resistance by increasing the number of tabs connecting the jelly roll and external terminals, but simply increasing the number of tabs in this way has limitations in reducing the resistance to the desired level and ensuring a sufficient current path.

[0006] As a result of the increase in the current applied to the secondary battery, efforts are being made to develop a new jelly roll structure in which the plain portion exposed at the axial end of the jelly roll is folded radially to flatten it, and then connected to the current collector plate by welding or other methods, and the current collector plate is connected to the external terminal, in order to reduce the aforementioned resistance.

[0007] To produce electrode assemblies with this structure, a processing step is required to expose plain sections at both axial ends of the electrode assembly and then bend them radially. This bending process is usually carried out using a forming jig.

[0008] Conventionally, a primary processing step was performed using an iris shutter type jig to bring together the ends of the plain sections that extend straight in the axial direction so that they are tilted radially. Next, a secondary processing step was performed using a jig that rotates with respect to the axis of rotation of the electrode assembly as a reference, to bring together and press the radially tilted plain sections a little more. Finally, a tertiary processing step was performed using a flat jig to press the tilted electrodes as flat as possible.

[0009] If the secondary processing is performed without the primary processing, which involves gathering the edges of the plain section so that they are angled radially, the deformation of the plain section becomes abrupt, making buckling, which causes significant deflection, unavoidable. For this reason, the primary processing, which involves gathering the edges of the plain section radially, was an indispensable step.

[0010] Furthermore, even during secondary processing, if the plain area was pressed while keeping the jig still, the frictional force between the jig and the edge of the plain area caused the deformation of the plain area to become rapid, resulting in a buckling phenomenon with significant deflection. For this reason, even during secondary processing, it was essential to press the plain area while rotating the jig.

[0011] Thus, the conventional jelly roll method for bending and forming the plain portion of electrode assemblies involved many steps, and the equipment required at each step also had to have a complex structure.

[0012] Due to these multi-stage processing steps and complex processing equipment, there were limitations to reducing the processing cycle and the size of the equipment.

[0013] On the other hand, in order to solve these problems, efforts have been made to develop tab forming devices that can reduce the number of processing steps required to flatten the plain portion exposed at the axial end of the electrode assembly by bending it radially, thereby simplifying the processing method for each processing step. However, even such forming devices do not take into account the amount of overlap of the plain portion, so buckling of the plain portion occurs. In this way, when buckling of the plain portion occurs, the possibility of a short circuit occurring inside the battery and leading to thermal events could not be ruled out. [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] Therefore, one objective of the present invention is to effectively prevent short circuits inside the battery.

[0015] In another aspect, one objective of the present invention is to provide a jig that takes into account the overlap amount of the plain portion of the electrode assembly, thereby preventing buckling of the plain portion.

[0016] However, the technical problems to be solved by the present invention are not limited to the above-mentioned problems at all, and other problems not mentioned should be clearly understood by those skilled in the art from the description of the invention described below.

Means for Solving the Problems

[0017] A forming device according to an embodiment of the present invention for solving the above problems is a forming device that bends an electrode tab in the radial direction, where the first electrode of an electrode assembly formed by laminating a first electrode, a separator, and a second electrode and winding it around a central axis extends further axially than the separator and is exposed, and the forming device includes a forming jig for bending the electrode tab, the forming jig includes a facing surface facing the electrode assembly, and the facing surface has a recess depth of the facing surface recessed in a direction opposite to the pressing direction.

[0018] For example, the facing surface may have a shape that is curved in a direction opposite to the pressing direction.

[0019] In one aspect of the present invention, the recess depth of the facing surface recessed in a direction opposite to the pressing direction may be configured to increase as it approaches the central axis.

[0020] In another aspect of the present invention, the recess depth of the facing surface recessed in a direction opposite to the pressing direction may be configured to increase and then decrease as it goes from the center side to the outer peripheral side.

[0021] In still another aspect of the present invention, the recess depth of the facing surface recessed in a direction opposite to the pressing direction may be configured to increase as it goes from the center side to the outer peripheral side, then maintain a certain length, and then decrease.

[0022] Preferably, the recess depth of the facing surface recessed in a direction opposite to the pressing direction may be configured to increase linearly as it goes from the center side to the outer peripheral side, then maintain a certain length, and then decrease linearly.

[0023] In one embodiment of the present invention, at least a portion of the electrode tab of the electrode assembly can be divided into a plurality of independently bendable segments.

[0024] Here, the electrode assembly may include, in the folded electrode assembly, a folded surface region of the electrode assembly, a uniform layering section in the radial direction where the number of layers of the divided pieces is equal to or greater than a predetermined number of layers, and a decreasing layering section located adjacent to the uniform layering section, where the number of layers of the divided pieces decreases as it moves away from the uniform layering section.

[0025] Preferably, the electrode assembly may include a layer-increasing section in the bent surface region of the bent electrode assembly where the number of layers of the divided pieces increases along the radial direction.

[0026] In another embodiment of the present invention, the recess depth may be configured to be even greater than the stacking thickness of the divided pieces.

[0027] In yet another embodiment of the present invention, the recess depth may be configured to be the same as the stacking thickness of the divided pieces.

[0028] In one embodiment of the present invention, the recess depth may be configured to be between 100 μm and 875 μm.

[0029] In another embodiment of the present invention, the recess depth may be configured to be between 50 μm and 700 μm.

[0030] In yet another embodiment of the present invention, the forming jig may be configured to include a steel material. [Effects of the Invention]

[0031] This invention can effectively prevent short circuits inside the battery.

[0032] In another embodiment, the present invention provides a jig that takes into account the overlap amount of the plain portion of the electrode assembly, thereby effectively preventing buckling of the plain portion.

[0033] However, the effects obtained through the present invention are not limited in any way to those described above, and other technical effects not mentioned should be clearly understood by an ordinary person from the description of the invention below.

[0034] The drawings accompanying this specification illustrate preferred embodiments of the present invention and are intended to further illustrate the technical idea of ​​the invention along with the content of the invention; therefore, the present invention shall not be construed as being limited only to what is shown in the drawings. [Brief explanation of the drawing]

[0035] [Figure 1] This is a plan view of a first embodiment of a first electrode having a plain portion and a textured portion. [Figure 2] This is a side view showing the stacked state of electrodes and separators for winding into a jelly roll-shaped electrode assembly. [Figure 3] This is a front view showing the process of stacking current collector plates by bending the electrode portions exposed at both axial ends of the electrode assembly radially, using them as electrode tabs. [Figure 4] This is a plan view of a second embodiment of a first electrode having a plain portion and a textured portion. [Figure 5] This is a front view showing a jelly roll-shaped electrode assembly to which the electrodes shown in Figure 4 are applied. [Figure 6] This graph shows the results of counting the number of stacked divided pieces along the radial direction in a bent surface region formed on the upper part of an electrode assembly according to one embodiment of the present invention. [Figure 7] This figure shows the bending results of an electrode assembly using a conventional flattening jig. [Figure 8]This is a plan view of an electrode assembly according to one embodiment of the present invention and a forming jig for a forming device for bending an electrode tab provided at the axial end of the electrode assembly. [Figure 9] This figure shows a cross-section of the forming jig in Figure 8. [Figure 10] This figure illustrates a forming jig according to another embodiment of the present invention. [Figure 11] This is a schematic diagram showing a cross-section of a bent surface region formed as the divided pieces are bent toward the core side of the electrode assembly. [Modes for carrying out the invention]

[0036] Preferred embodiments of the present invention will now be described in detail based on the attached drawings. Prior to this, terms and words used in this specification and in the claims shall not be interpreted in their ordinary or dictionary sense, but rather in the sense and concept corresponding to the technical idea of ​​the present invention, in accordance with the principle that the inventor may appropriately define the concept of terms in order to best describe the invention.

[0037] Therefore, the embodiments described herein and the configurations shown in the drawings represent only preferred embodiments of the present invention and do not represent the entire technical concept of the invention. It should be understood that there are various equivalent and modified embodiments that can be substituted for these at the time of filing this application.

[0038] Furthermore, to aid in understanding the invention, the attached drawings may not be shown to actual scale, and the dimensions of some components may be exaggerated.

[0039] Figure 1 is a plan view of a first embodiment of a first electrode having a plain portion and a textured portion.

[0040] Figure 2 is a side view showing the stacked state of the electrodes and separator 16 for winding onto the jelly roll-shaped electrode assembly 10.

[0041] Figure 3 is a front view showing the process of stacking current collector plates by bending the electrode portions exposed at both axial ends of the electrode assembly 10 into electrode tabs 11 in the radial direction.

[0042] Figure 4 is a plan view of a second embodiment of a first electrode having a plain portion and a textured portion.

[0043] Figure 5 is a front view showing a jelly roll-shaped electrode assembly 10 to which the electrodes shown in Figure 4 are applied.

[0044] Hereinafter, with reference to Figures 1 to 5, an embodiment of an electrode assembly 10 to which a forming device according to one embodiment of the present invention can be used will be described. However, the forming device of the present invention is not necessarily limited to electrode assemblies 10 having the structure described below.

[0045] An electrode assembly 10 to which a forming device according to one embodiment of the present invention is to be applied is formed by stacking a sheet-like first electrode 15, separator 16, and second electrode 17, which have a predetermined width in the width direction Y and extend in a long length direction X, at least once in the order of first electrode 15, separator 16, second electrode 17, and separator 16, and winding them around a winding shaft Y.

[0046] The first electrode 15 and / or the second electrode 17 are manufactured in a form in which an active material is coated onto a metal foil. The first electrode 15 and / or the second electrode 17 include a textured region where the active material is coated onto the metal foil and a plain region where the surface of the metal foil is exposed without the active material coating. At one end of the first electrode 15 in the width direction Y, i.e., in the axial direction Y, there is a first electrode tab 11 region which is a plain region not coated with the active material. And (or), at the other end of the second electrode 17 in the width direction Y, i.e., in the axial direction Y, there is a second electrode tab 12 region which is a plain region not coated with the active material. The electrode tabs 11 can be electrically connected to electrode terminals provided in a battery can (not shown) in which the electrode assembly 10 is to be housed, via a current collector plate.

[0047] In order to wind the electrode assembly 10 into a jelly roll shape, when stacking the first electrode 15, separator 16, second electrode 17, and separator 16, the first electrode tab 11 and the second electrode tab 12 are stacked such that they are further exposed (protrude) from one end and the other end of the separator 16 in the width direction Y, i.e., the axial direction Y, respectively. Then, the electrode assembly 10 can be manufactured by winding the stacked material in the X-axis direction with the Y-axis as the center.

[0048] An electrode assembly 10 applied to one embodiment of the present invention may be of the jelly roll type. In this case, an additional separator 16 may be provided on the outer surface of the electrode assembly 10 for insulation from the battery can.

[0049] The first electrode 15 includes a first electrode current collector (metal foil) and a first electrode active material 151 coated on one or both sides of the first electrode current collector. One end of the first electrode current collector in the width direction Y has a blank area where the first electrode active material is not coated. This blank area functions as a first electrode tab 11. The first electrode tab 11 is provided at the top of the electrode assembly 10 in the height direction Y.

[0050] The second electrode includes a second electrode current collector (metal foil) and a second electrode active material coated on one or both sides of the second electrode current collector. At the other end of the second electrode current collector in the width direction Y, there is a blank area where the second electrode active material is not coated. This blank area functions as a second electrode tab 12. The second electrode tab 12 is provided at the lower part of the electrode assembly 10 in the height direction.

[0051] The first electrode tab 11 and the second electrode tab 12 may be, for example, a positive electrode tab and a negative electrode tab, or vice versa.

[0052] 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 can be used without limitation as long as they are known active materials in the art.

[0053] In one example, the positive electrode active material may include an alkali metal compound represented by 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, Al, Mo, Sc, Zr, Ru, and Cr; x ≧ 0, 1 ≦ x + y ≦ 2, -0.1 ≦ z ≦ 2; the stoichiometric coefficients x, y, and z are selected so that the compound maintains electrical neutrality).

[0054] In another example, the positive electrode active material may be an alkali metal compound xLiM 1 O2-(1-x)Li2M 2 O3 (M 1 includes at least one element having an average oxidation state of 3; M 2 includes at least one element having an average oxidation state of 4; 0 ≦ x ≦ 1).

[0055] In still 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 includes at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, and Al; M 2 includes at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, Al, As, Sb, Si, Ge, V, and S; M3 contains a halogen group element selectively containing F; 0 < a ≤ 2, 0 ≤ x ≤ 1, 0 ≤ y < 1, 0 ≤ z < 1; the stoichiometric coefficients a, x, y, and z 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, Al, Mg, and Al].

[0056] Preferably, the positive electrode active material may contain primary particles and / or secondary particles in which the primary particles are aggregated.

[0057] 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 of 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.

[0058] The separator 16 can be used alone or in a laminated form of a porous polymer film, for example, a porous polymer film made from polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, etc. As another example, as the separator 16, a normal porous non-woven fabric, for example, a non-woven fabric made from high-melting-point glass fibers, polyethylene terephthalate fibers, etc. can be used.

[0059] The surface of at least one side of the separator 16 may contain a coating layer of inorganic particles. Also, the separator 16 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 bonded with a binder so that an interstitial volume exists between adjacent particles.

[0060] Inorganic particles may consist of inorganic materials with a dielectric constant of 5 or more. As an unrestricted example, the inorganic particles may be Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT), PB(Mg3Nb) 2 / 3 It may contain at least one substance selected from the group consisting of O3-PbTiO3(PMN-PT), BaTiO3, hafnia(HfO2), SrTiO3, TiO2, Al2O3, ZrO2, SnO2, CeO2, MgO, CaO, ZnO, and Y2O3.

[0061] The first electrode tab 11 and the second electrode tab 12 can be electrically connected to current collector plates 21 and 22, respectively. The first electrode tab 11 and the second electrode tab 12 can be joined to the first current collector plate 21 and the second current collector plate 22 by welding or other means, respectively, while bent radially as shown in Figure 3.

[0062] A forming apparatus according to one embodiment of the present invention is a processing apparatus for bending the first electrode tab 11 and the second electrode tab 12 in the radial direction.

[0063] The forms of the first electrode tab 11 and the second electrode tab 12 to which the forming device can be applied are not limited to the structures described above. The first electrode tab 11 shown in Figure 1 has a shape in which the first electrode tab 11 extends continuously in the winding direction (longitudinal direction) X. However, the first electrode tab 11 may also have a shape that is not continuous in the winding direction (longitudinal direction) X.

[0064] Referring to Figure 4, the first electrode tab 11 provided on the first electrode 15 may have a shape in which it is cut in the axial direction (height direction) Y at predetermined intervals along the longitudinal direction. Due to such cut lines, the first electrode tab 11 may have a shape in which a plurality of divided pieces 111 are arranged along the longitudinal direction.

[0065] The shape of the divided piece 111 formed by the cutting line may be an equilateral trapezoid, a rectangle, or a variety of other shapes such as a semicircle or a semiellipse, as shown in the figure. Various shapes of divided pieces 111 may be used in combination, and the width and height of the divided pieces 111, as well as the spacing between the divided pieces 111, may be constant or may vary under a predetermined rule.

[0066] On the other hand, as shown in Figure 4, the bottom line BL, which is a hypothetical line connecting the bottoms of the divided pieces 111, can be defined. The bottom line BL may be, for example, a straight line or a curved line.

[0067] Furthermore, as shown in Figures 4 and 5, the segmented piece 111 may be omitted in a predetermined section B1 near the core, and within section B2 where the segmented piece 111 is provided, the segmented piece 111 may have a shape in which the height of the axial projection increases gradually or in steps as it moves from the core toward the outer circumference. Although not shown, the segmented piece 111 may also be removed in the last turn section B3 for ease of processing, etc. Alternatively, in another embodiment, unlike in Figures 4 and 5, the segmented piece 111 may have a shape in which the height of the axial projection is the same within section B2 where the segmented piece 111 is provided.

[0068] If the electrode tab 11 is formed in the shape of the segmented piece 111 as described above, the lower end of the segmented piece 111 can be bent when the electrode tab 11 is bent radially. For example, the segmented piece 111 can be bent along the bottom line BL shown in Figure 4. Alternatively, the segmented piece 111 can be bent at a position above the bottom line BL shown in Figure 4.

[0069] Figure 6 is a graph showing the result of counting the number of stacked divided pieces along the radial direction in the bent surface region formed on the upper part of the electrode assembly 10 according to one embodiment of the present invention, and Figure 7 is a diagram showing the bending result of the electrode assembly 10 to which a conventional flattening jig was applied.

[0070] Referring to Figure 6, a uniform layering interval b1 of the divided pieces appears. The uniform layering interval b1 is the radius interval of the flat region in each graph. Outside the uniform layering interval b1, a decreasing layering interval b2 appears where the number of layered divided pieces decreases as the radius increases. The decreasing layering interval b2 is the radius interval where the number of layered divided pieces decreases as the radius of the electrode assembly 10 increases. The uniform layering interval b1 and the decreasing layering interval b2 are adjacent in the radial direction. On the other hand, inside the uniform layering interval b1, a increasing layering interval b3 appears where the number of layered divided pieces increases as the radius increases. The increasing layering interval b3 is the radius interval where the number of layered divided pieces increases as the radius of the electrode assembly 10 increases. Thus, the change in the number of layers in the electrode assembly 10 is due to the height of the divided pieces, the starting position of the divided pieces, the ending position of the divided pieces, etc. As a result, depending on the number of stacked segments, the axial height of the bent surface region of the electrode assembly 10 may differ in the radial direction.

[0071] On the other hand, conventional flattening jigs were configured as jigs having a flat shape on the surface facing the electrode tab 11. Such conventional flattening jigs have a flat shape that does not take into account this overlap thickness, and therefore press the electrode assembly 10 into a planar shape.

[0072] As a result, as shown in Figure 7, multiple electrode tabs 11 buckle. In this case, the buckled electrode tab 11 is more likely to come into contact with an adjacent electrode tab 11 that has the opposite electrode. Therefore, the likelihood of a short circuit occurring inside the battery increases, which in turn is more likely to lead to a thermal event.

[0073] One embodiment of the present invention was created to solve these problems, and will be described in detail below with reference to Figures 8 to 11.

[0074] Figure 8 is a plan view of an electrode assembly 10 according to one embodiment of the present invention and a forming jig 100 of a forming device for bending an electrode tab 11 provided at the axial end of the electrode assembly 10.

[0075] Referring to Figures 8 and 9, the forming apparatus may be configured to radially bend the electrode tab 11 of the electrode assembly 10, which is formed by stacking the first electrode, the separator 16, and the second electrode and winding them around a central axis, so that the first electrode extends further axially than the separator 16 and is exposed.

[0076] The forming jig 100 and the flattening jig 50 may be made of steel. The forming jig 100 extends straight in the axial direction and can bend the spirally arranged electrode tabs 11 radially inward without buckling.

[0077] More specifically, the forming apparatus may include a forming jig 100 for bending the electrode tab 11. The forming jig 100 may include a facing surface S that faces the electrode assembly 10. In particular, the forming jig 100 may face the electrode tab 11 of the electrode assembly 10. Here, the facing surface S may be configured to have a recess depth that is recessed in the direction opposite to the pressing direction D.

[0078] With this structure, it becomes possible to perform bending that takes into account the different overlap thickness of the electrode tab 11 at each bending position of the electrode tab 11. In other words, even if there is a region where the overlap thickness of the electrode tab 11 is large, buckling of the electrode tab 11 can be prevented because the recess depth of the opposing surface S is set to a predetermined depth.

[0079] Figure 9 is a cross-sectional view of the forming jig 100 shown in Figure 8.

[0080] In one embodiment, the opposing surface S may be configured to have a shape that is curved in the direction opposite to the pressing direction D. For example, the opposing surface S may have a curved shape that is convex in the direction opposite to the pressing direction D. For example, as shown in the embodiment of Figure 9, the depth of the recess of the opposing surface S, which is recessed in the direction opposite to the pressing direction D, may have a shape that increases toward the central axis.

[0081] In another embodiment, the opposing surface S may be configured to have a generally parabolic shape. That is, it may be configured to have the deepest recess depth at the central axis, and the depth may decrease towards the outer circumference.

[0082] This structure makes it possible to perform bending while taking into account the profile of the layer count reduction section b2. That is, since the shape of the opposing surface S is configured to correspond to the profile of the layer count reduction section b2 located on the outer circumference of the electrode assembly 10, buckling of the electrode tab 11 located in the layer count reduction section b2 can be prevented. In addition, the shape of the jig is simple, which is advantageous from the standpoint of jig manufacturing.

[0083] Figure 10 is a diagram illustrating a forming jig 100 according to another embodiment of the present invention.

[0084] In another embodiment of the present invention, the depth of the recess of the opposing surface S, which is recessed in the direction opposite to the pressing direction D, may be configured to increase from the center to the outer circumference before decreasing.

[0085] For example, referring to Figure 10, the recess depth of the opposing surface S is configured to increase from the center towards the outer circumference before decreasing.

[0086] This structure makes it possible to perform bending while taking into account the profiles of the layer count reduction section b2 and the layer count increase section b3. That is, the shape of the opposing surface S is configured to correspond to the profile of the layer count reduction section b2 located on the outer circumference side of the electrode assembly 10 and the profile of the layer count increase section b3 located on the central side of the electrode assembly 10, respectively, so that buckling of the electrode tabs 11 located in the layer count reduction section b2 and the layer count increase section b3 can be effectively prevented.

[0087] In yet another embodiment of the present invention, the recess depth of the opposing surface S, which is recessed in the direction opposite to the pressing direction D, may be configured to be constant from the center to the outer circumference, then increase and then decrease.

[0088] For example, unlike in Figure 10, the recess depth of the opposing surface S may be configured to increase from the center towards the outer periphery before decreasing, starting from the point where the electrode tab 11 begins to form.

[0089] This structure makes it possible to perform bending with more accurate consideration of the profiles of the layer count reduction section b2 and the layer count increase section b3. In other words, since the shape of the opposing surface S is configured to correspond to the profile of the layer count reduction section b2 located on the outer circumference side of the electrode assembly 10 and the profile of the layer count increase section b3 located on the central side of the electrode assembly 10, buckling of the electrode tabs 11 located in the layer count reduction section b2 and the layer count increase section b3 can be effectively prevented.

[0090] In yet another embodiment of the present invention, the depth of the recess of the opposing surface S, which is recessed in the direction opposite to the pressing direction D, may increase from the center towards the outer circumference, then maintain a constant length before decreasing.

[0091] For example, returning to Figure 6, as you move from the center towards the outer edge, you will see, in order, a section b3 where the number of layers increases, a section b1 where the number of layers is uniform, and a section b2 where the number of layers decreases.

[0092] Therefore, according to this embodiment, it becomes possible to perform bending while considering the profiles of the layer count increase section b3, the layer count uniform section b1, and the layer count decrease section b2 all together. That is, the shape of the opposing surface S is configured to correspond to the profile of the layer count decrease section b2 located on the outer circumference side of the electrode assembly 10, the profile of the layer count increase section b3 located on the center side of the electrode assembly 10, and the layer count uniform section b1 located between the layer count decrease section b2 and the layer count increase section b3, respectively. As a result, buckling of the electrode tabs 11 located in the layer count increase section b3, the layer count uniform section b1, and the layer count decrease section b2 can be effectively prevented. Furthermore, since the electrode tabs 11 are bent by an amount corresponding to the thickness of the laminated layer at all radial positions, a result is achieved in which the electrode tabs 11 make firm contact with each other without buckling.

[0093] More preferably, the depth of the recess of the opposing surface S, which is recessed in the direction opposite to the pressing direction D, may be configured to increase linearly from the center to the outer circumference, then maintain a constant length, and then decrease linearly.

[0094] For example, as can be clearly seen from Figure 6, the number of stacked electrode tabs 11 can be increased and decreased linearly. Therefore, a structure in which the recess depth of the opposing surface S increases linearly from the center to the outer circumference, then maintains a constant length before decreasing linearly, can be achieved in which the electrode tabs 11 make firm contact with each other without buckling at any radial position.

[0095] On the other hand, as mentioned above, the stacking profile of the electrode tab 11 may differ depending on the height of the divided piece, the starting position of the divided piece, and the ending position of the divided piece. For example, the number of stacks of the electrode tab 11 may increase and / or decrease in a curved manner. In this way, it goes without saying that the shape of the jig can be changed to match the different stacking profile.

[0096] On the other hand, at least a portion of the electrode tab 11 of the electrode assembly 10 may be divided into a plurality of independently bendable segments.

[0097] For example, returning to Figure 4, at least a portion of the electrode tab 11 of the electrode assembly 10 is divided into a plurality of independently bendable segments, and the bent surface region of the bent electrode assembly 10 may include a uniform layer count section b1 along the radial direction where the number of layers of the segments is equal to or greater than a predetermined number of layers, and a decreasing layer count section b2 located adjacent to the uniform layer count section b1, where the number of layers of the segments decreases as it moves away from the uniform layer count section b1. Furthermore, the bent surface region of the bent electrode assembly 10 may include an increasing layer count section b3 along the radial direction where the number of layers of the segments increases.

[0098] In one embodiment of the present invention, the recess depth may be configured to be even greater than the stacking thickness of the divided piece. If the recess depth is configured to be even smaller than the stacking thickness of the divided piece, the electrode tab 11 will be excessively pressed by the forming jig 100, making it impossible to avoid buckling of the electrode tab 11.

[0099] Therefore, according to the structure of the present invention described above, the recess depth is configured to be greater than the stacking thickness of the divided pieces, thereby effectively preventing excessive pressing and buckling of the electrode tab 11.

[0100] In another embodiment of the present invention, the recess depth may be configured to be the same as the stacking thickness of the segmented pieces. With such a structure, the recess depth is configured to be even greater than the stacking thickness of the segmented pieces, so that excessive pressing and buckling of the electrode tabs 11 can be effectively prevented. At the same time, the electrode tabs 11 can be firmly in contact with each other and overlap without buckling.

[0101] In one embodiment of the present invention, the depth of the depression can be determined as follows.

[0102] Depth of depression ≤ thickness of foil × maximum number of foil layers

[0103] In other words, the depth of the depression may be less than or equal to the maximum thickness of the foil at a specific point in the radial direction.

[0104] Specifically, the electrode may be a first electrode 15. In this case, the thickness of the positive electrode current collector (foil) constituting the first electrode 15 may be 10 μm or more and 25 μm or less. As a result, the folded surface region F of the positive electrode may include a region where the total stacking thickness of the divided pieces is 100 μm or more and 875 μm or less.

[0105] In one embodiment of the present invention, the recess depth may be configured to fall within the range of 100 μm to 875 μm. For example, if the electrode tab 11 is a positive electrode tab, the total stacking thickness of the divided pieces may be 100 μm to 875 μm. Therefore, if the recess depth is such that the total stacking thickness of the divided pieces is 100 μm to 875 μm, unnecessary buckling and short circuits can be prevented.

[0106] On the other hand, the electrode may be a second electrode 17. In this case, the thickness of the negative electrode current collector (foil) constituting the second electrode 17 may be 5 μm or more and 20 μm or less. As a result, the folded surface region F of the negative electrode may include a region where the total laminate thickness of the divided pieces is 50 μm or more and 700 μm or less.

[0107] In another embodiment of the present invention, the recess depth may be configured to fall within the range of 50 μm to 700 μm. For example, if the electrode tab 11 is a negative electrode tab, the total stacking thickness of the segmented pieces may be 50 μm to 700 μm. Therefore, if the recess depth or the total stacking thickness of the segmented pieces is 50 μm to 700 μm, unwanted buckling and short circuits can be prevented.

[0108] Figure 11 is a schematic diagram showing a cross-section of a bent surface region formed when a divided piece is bent toward the core side of the electrode assembly 10.

[0109] Referring to Figure 11, the folded surface region F has a structure in which the segmented pieces 111 overlap as multiple layers in the winding axis direction. The overlap direction is the winding axis direction Y. Section circle 1 is a section without segmented pieces (first part B1), and sections circle 2 and 3 are sections where winding turns containing segmented pieces 111 are located (second part B2). More specifically, section circle 2 is a uniform height section in which the height of the segmented pieces is kept uniform, and section circle 3 is a variable height section in which the height of the segmented pieces 111 is variable. Here, the radial lengths of sections circle 2 and section circle 3 may be variable depending on the embodiment.

[0110] As a result of applying the forming apparatus shown in Figures 8 to 10 to press the electrode tabs 11 of the electrode assembly 10, as shown in Figure 11, the electrode tabs 11 were able to firmly contact and overlap each other while maintaining the electrode stacking thickness profile without buckling.

[0111] In other words, one embodiment of the present invention can effectively prevent internal short circuits in a battery through the various embodiments described above. Furthermore, according to one embodiment of the present invention, a jig that takes into account the overlap amount of the plain portion of the electrode assembly 10 can be provided, thereby effectively preventing buckling of the plain portion.

[0112] On the other hand, while directional terms such as "up" and "down" have been used in this specification, these terms are used merely for the sake of ease of explanation, and it will be obvious to those skilled in the art that they may vary depending on the position of the object in question, the observer's position, etc.

[0113] Although the present invention has been described above with limited embodiments and drawings, it goes without saying that the present invention is not limited in any way, and that it can be implemented by persons with ordinary skill in the art to which the present invention pertains, with various modifications and variations within the equivalent scope of the technical idea and the appended claims. [Explanation of symbols]

[0114] 10 Electrode assembly r radius 11 Electrode tab (first electrode tab) 111 Split piece 12 Electrode tabs (second electrode tabs) 15 First electrode 151 First electrode active material 16 Separators 17. Second electrode H1 Winding hole (hollow section) X Longitudinal direction, circumferential direction, winding direction Y-direction (width), winding shaft, axial direction, central axis, height direction Z radial direction, normal direction 21 Current collector plate (first current collector plate) 22 Current collector plate (second current collector plate) 100 forming jigs S Opposite side D. Direction of pressure

Claims

1. A forming device for radially bending an electrode tab in an electrode assembly, which is formed by stacking a first electrode, a separator, and a second electrode and winding them around a central axis, and in which the first electrode extends further axially than the separator and is exposed, The forming apparatus includes a forming jig for bending the electrode tab, the forming jig includes a facing surface that faces the electrode assembly, the facing surface having a recess depth such that it is recessed in the direction opposite to the pressing direction.

2. The forming apparatus according to claim 1, wherein the opposing surface has a shape that is curved in the direction opposite to the pressing direction.

3. The forming apparatus according to claim 1 or 2, wherein the depth of the recess of the opposing surface, which is recessed in the direction opposite to the pressing direction, increases toward the central axis.

4. The forming apparatus according to claim 1 or 2, wherein the depth of the recess of the opposing surface, which is recessed in the direction opposite to the direction of pressing, increases from the center side to the outer circumference side and then decreases.

5. The forming apparatus according to claim 1 or 2, wherein the depth of the recess of the opposing surface, which is recessed in the direction opposite to the direction of pressing, increases from the center to the outer circumference, then maintains a constant length before decreasing.

6. The forming apparatus according to claim 1 or 2, wherein the depth of the recess of the opposing surface, which is recessed in the direction opposite to the direction of pressing, increases linearly from the center to the outer circumference, then maintains a constant length and then decreases linearly.

7. At least a portion of the electrode tab of the electrode assembly is divided into a plurality of independently bendable segments, The forming apparatus according to claim 1 or 2, wherein the bent surface region of the bent electrode assembly includes a uniform stacking section in the radial direction where the number of stacked division pieces is equal to or greater than a predetermined number of stacks, and a decreasing stacking section located adjacent to the uniform stacking section where the number of stacked division pieces decreases as it moves away from the uniform stacking section.

8. The electrode assembly is The forming apparatus according to claim 7, wherein the bent surface region of the bent electrode assembly includes a layer number increasing section along the radial direction in which the number of layers of the divided pieces increases.

9. The forming apparatus according to claim 7, wherein the recess depth is even greater than the stacking thickness of the divided pieces.

10. The forming apparatus according to claim 7, wherein the recess depth is the same as the stacking thickness of the divided pieces.

11. The forming apparatus according to claim 1 or 2, wherein the recess depth is 100 μm or more and 875 μm or less.

12. The forming apparatus according to claim 1 or 2, wherein the recess depth is 50 μm or more and 700 μm or less.

13. The forming apparatus according to claim 1 or 2, wherein the forming jig is made of steel.

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