Electrode assembly and secondary battery including same

Abstract

The present invention relates to an electrode assembly in which a first electrode, a separator, and a second electrode are stacked and wound, the first electrode including a current collector and an electrode active material layer provided on the current collector, an edge portion of the current collector provided on one end side of a winding shaft of the electrode assembly includes an uncoated portion where no electrode active material layer is provided, and the uncoated portion of the first electrode is folded one or more times from a winding center of the electrode assembly toward the outer periphery of the electrode assembly.

Description

[Technical field]

[0001] The present specification relates to an electrode assembly and a secondary battery including the same.

[0002] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0160355, filed with the Korean Intellectual Property Office on November 19, 2021, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] In recent years, there has been an increasing need for batteries with high capacity and high output. The electric vehicle market has grown rapidly due to environmentally friendly policies, and as a result, the performance requirements for batteries have increased significantly.

[0004] In the case of cylindrical secondary batteries, optimization is being carried out by changing the thickness of the current collector and separator, as well as the size and shape of the can and top cap, in order to fit a large number of electrodes into a limited space, but this has reached a limit within the limited size.

[0005] In the case of conventional cylindrical capacitors, one or two taps were used on the anode and cathode to act as conductive paths, but this had the disadvantage that the resistance increased as the physical distance from the tap increased, limiting the improvement of resistance.

[0006] To remedy this, there is a method of creating uncoated areas (uncoated areas) of electrode active material on the top and bottom of the electrode collector, and stacking them after the notching process to use them as taps. However, in this case, as shown in Figure 2, some of the anode uncoated areas 110 may break and penetrate inside, hitting the cathode 130 and causing a short circuit, so a solution to this is needed. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to eliminate the possibility of short circuit occurrence caused by the conventional folding method of the uncoated portion of the electrode by changing the folding method of the uncoated portion of the electrode of the electrode assembly. [Means for solving the problem]

[0008] One embodiment of the present specification provides an electrode assembly in which a first electrode, a separator, and a second electrode are stacked and wound, the first electrode including a current collector and an electrode active material layer provided on the current collector, an edge portion of the current collector provided on one end of a winding shaft of the electrode assembly includes an uncoated portion where no electrode active material layer is provided, and the uncoated portion of the first electrode is folded one or more times from a winding center of the electrode assembly toward the outer periphery of the electrode assembly.

[0009] In addition, in one embodiment of the present specification, the uncoated portion of the first electrode may include a plurality of segment pieces, and the plurality of segment pieces may be folded one or more times from a winding center of the electrode assembly toward an outer periphery of the electrode assembly.

[0010] In one embodiment of the present specification, a segment of the uncoated portion of the first electrode present at least on the outermost periphery of the electrode assembly may be folded twice to face a side surface of the electrode assembly.

[0011] In one embodiment of the present specification, at least a part of a bent portion of the uncoated portion of the first electrode is in contact with at least a part of a bent portion of an adjacent uncoated portion.

[0012] In one embodiment of the present specification, the length from the first bent portion to the end of the uncoated portion of the first electrode may be 1 mm or more.

[0013] Furthermore, in one embodiment of the present specification, a segment of the uncoated portion of the twice folded first electrode may contact a side surface of the electrode assembly at a height of 1% to 30% of the total height of the electrode assembly.

[0014] In addition, in one embodiment of the present specification, the first electrode may be an anode, the second electrode may be a cathode, and the first electrode may be formed to be exposed to the outside based on an upper surface of the electrode assembly.

[0015] In addition, in one embodiment of the present specification, the first electrode may further include an insulating tape provided on a surface opposite to a surface facing the side of the electrode assembly.

[0016] Also, one embodiment of the present specification provides a secondary battery including the above-mentioned electrode assembly, a battery can containing the electrode assembly, and a cap assembly coupled to an upper portion of the battery can. Effect of the Invention

[0017] In an electrode assembly according to one embodiment of the present specification, the uncoated portion of the electrode is folded one or more times from the winding center of the electrode assembly toward the outer periphery of the electrode assembly, thereby preventing an internal short circuit from occurring due to the uncoated portion of the anode coming into contact with the cathode. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic diagram showing a direction in which a conventional anode uncoated portion is bent from the outside of an electrode assembly to the winding center of the electrode assembly. [Diagram 2] This is a schematic diagram showing that when the anode uncoated portion is folded from the outside of the electrode assembly toward the center of the winding of the electrode assembly, the anode uncoated portion is folded inward due to the load from above and hits the cathode, causing a short circuit. [Diagram 3] 4 is a schematic diagram showing the folding form and direction of a positive electrode uncoated portion in an electrode assembly according to an embodiment of the present specification. [Figure 4] 13 is a schematic diagram illustrating that the uncoated portion of the first electrode includes a plurality of segment pieces. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present specification will be explained in further detail below.

[0020] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that correspond to the technical ideas of the present invention, based on the principle that the inventor can appropriately define the concepts of the terms in order to best describe his / her invention.

[0021] Therefore, it should be understood that the embodiment 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 therefore there may be various equivalents and modifications that can be substituted for them at the time of this application.

[0022] Furthermore, in order to facilitate understanding of the present invention, the accompanying drawings may not be drawn to scale, and the dimensions of some components may be exaggerated. Also, the same reference numerals may be used to refer to the same components in different embodiments.

[0023] As used herein, "on" does not mean physically on top of a layer, but rather on or above a position, i.e., a layer that is on top of any layer may have other layers between them.

[0024] In this specification, when a part is said to "comprise" a certain component, this means that it may further include other components, rather than excluding other components, unless specifically stated to the contrary.

[0025] The electrode assembly 10 according to the present specification is a jelly-roll type electrode assembly having a structure in which a first electrode and a second electrode having a sheet shape and a separator interposed between them are wound in one direction.

[0026] In one embodiment of the present specification, the electrode assembly 10 is an electrode assembly in which a first electrode 110, a separator 120, and a second electrode 130 are stacked and wound up, the first electrode 110 includes a current collector 111 and an electrode active material layer 112 provided on the current collector 111, an edge portion of the current collector 111 provided on one end side of a winding shaft of the electrode assembly 10 includes an uncoated portion 113 where the electrode active material layer 112 is not provided, and the uncoated portion 113 of the first electrode is folded one or more times from the winding center of the electrode assembly 10 toward the outer edge direction P of the electrode assembly 10.

[0027] In one embodiment of the present specification, the uncoated portion 113 of the first electrode is bent at an angle of 30° to 90° at least once from the winding center of the electrode assembly toward the outer periphery direction P of the electrode assembly.

[0028] FIG. 3 shows a direction P from the winding center of the electrode assembly to the outer periphery of the electrode assembly.

[0029] The region of the current collector where the electrode active material layer is not formed is a non-coated portion (not shown), which means a region where the anode or cathode current collector is exposed.

[0030] In this case, a separate electrode tap may not be coupled to the uncoated portion of the first electrode, and at least a portion of the uncoated portion may be used as an electrode tap by itself.

[0031] In one embodiment of the present specification, the first electrode 110 may be an anode, the second electrode 130 may be a cathode, and the first electrode 110 may be formed to be exposed to the outside based on the top surface of the electrode assembly.

[0032] In one embodiment of the present specification, the first electrode 110 and the second electrode 130 include a current collector 111 and an electrode active material layer 112 provided on the current collector 111, and the electrode active material layer 112 includes an electrode active material.

[0033] In this case, the electrode active material may be any active material known in the art without any limitations.

[0034] In one example, the positive electrode active material may include lithium cobalt oxide having a high operating voltage and excellent capacity characteristics, lithium nickel oxide having a high reversible capacity and easily realizing a large-capacity battery, lithium nickel cobalt oxide in which part of nickel is substituted with cobalt, lithium nickel cobalt metal oxide in which part of nickel is substituted with manganese, cobalt, or aluminum, lithium manganese-based oxide which is excellent in thermal stability and inexpensive, and lithium iron phosphate which is excellent in stability.

[0035] The negative electrode active material may be, for example, a carbon material such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, silicon, lithium metal or lithium alloy, and the like.

[0036] The separation membrane 120 is located between the anode and the cathode while maintaining a certain mechanical strength, and is made of a porous material to facilitate the movement of ions between the electrodes. For example, the separation membrane 120 may be formed from any base material selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene (PP), and a copolymer of polyethylene (PE) and polypropylene (PP).

[0037] In one embodiment of the present specification, the method of folding the uncoated portion of the first electrode of the electrode assembly may be performed by applying pressure using a folding device.

[0038] Specifically, the bending device may be used to wind and bend the uncoated portion of the first electrode from a winding direction of the electrode assembly toward an outer periphery of the electrode assembly. By using the bending device, the uncoated portion of the first electrode that is present at least on the outermost periphery of the electrode assembly may also be folded by inertia.

[0039] More specifically, after folding the uncoated portion of the first electrode once using the folding device, the uncoated portion of the first electrode present at least at the outermost periphery of the electrode assembly may be additionally folded together with a process of taping an insulating tape, or the electrode assembly may be attached to a hollow cylindrical holder having an open bottom and a closed top to induce additional folding and then taping an insulating tape.

[0040] FIG. 3 is a diagram illustrating the folding form and direction of the positive electrode uncoated portion in the electrode assembly, and the positive electrode 110 shown in FIG. 3 includes an electrode active material layer (not shown), an insulating coating layer (not shown), and a non-coated portion (not shown).

[0041] As shown in FIG. 3, an electrode assembly according to an embodiment of the present disclosure includes an anode 110, a separator 120, and a cathode 130, and an uncoated portion of the anode 110 is folded from the winding center of the electrode assembly toward the outer periphery of the electrode assembly. In particular, the uncoated portion of the anode located at the outermost periphery of the electrode assembly is folded twice to face a side of the electrode assembly.

[0042] Uncoated areas are formed on the top and bottom of the electrode current collector, and are stacked after the notching process to be used as a tap. In a conventional method, the folding direction of the anode uncoated area is toward the winding center of the electrode assembly as shown in FIG. 1 of this specification. In this case, however, there is a problem that some of the anode uncoated areas may bend and get inward and touch the cathode, causing a short circuit, as shown in the dotted circle in FIG. 2 of this specification.

[0043] In the present invention, the uncoated portion of the anode is bent from the winding center of the electrode assembly toward the outer edge of the electrode assembly as shown in FIG. 3, which has the effect of preventing an internal short circuit caused by the uncoated portion of the anode coming into contact with the cathode.

[0044] In one embodiment of the present specification, the uncoated portion of the first electrode includes a plurality of segment pieces 113, and the plurality of segment pieces 113 may be folded one or more times from the winding center of the electrode assembly toward the outer periphery direction P of the electrode assembly.

[0045] In one embodiment of the present specification, the uncoated portion of the first electrode may include a plurality of segment pieces 113 that are notched. That is, the uncoated portion of the first electrode may be formed in the shape of a gear. FIG. 4 is a diagram showing that the uncoated portion 113 of the first electrode includes a plurality of segment pieces, and shows that the uncoated portion 113 where the electrode active material layer 112 is not provided is divided to form a gear shape. FIG. 4 is a diagram showing that each segment piece is formed separately, and the shape, length, and spacing distance of the segment pieces are not limited thereto.

[0046] In one embodiment of the present disclosure, the plurality of segment pieces 113 may have the same or different heights, widths, and spacings.

[0047] In one embodiment herein, the length of each of the plurality of segments 113 may be between 4 mm and 20 mm.

[0048] The length of the segment 113 means the vertical distance from the boundary between the electrode active material layer 112 and the uncoated portion 113 of the current collector 111 to the end of the uncoated portion.

[0049] When the length range is satisfied, it is possible to prevent a phenomenon in which the segment pieces are short in length and enter the inside of the electrode assembly when bent, causing a short circuit.

[0050] In one embodiment herein, the length of each of the plurality of segments 113 may be between 4 mm and 15 mm.

[0051] In one embodiment herein, the length of each of the plurality of segments 113 may be between 6 mm and 10 mm.

[0052] In one embodiment of the present specification, any one of the plurality of segment pieces 113 may be spaced apart from the adjacent segment piece by a distance of 1 mm to 150 mm.

[0053] When the distance range is satisfied, gas can be easily discharged when the electrolyte is injected while the electrode resistance is appropriately maintained, and gas trapping during use after activation of the battery is unlikely to occur.

[0054] In one embodiment of the present specification, any one segment piece 113 of the plurality of segment pieces may be spaced apart from another adjacent segment piece by a distance of 1 mm to 48 mm.

[0055] In one embodiment of the present specification, any one segment piece 113 of the plurality of segment pieces may be spaced apart from another adjacent segment piece by a distance of 5 mm to 36 mm.

[0056] In one embodiment of the present specification, the width of the segment piece 113 may be 2 mm to 30 mm.

[0057] When the above range is satisfied, welding and bending can be facilitated.

[0058] In one embodiment of the present specification, a segment of the uncoated portion of the first electrode 115 present at least on the outermost periphery of the electrode assembly may be folded twice to face a side of the electrode assembly.

[0059] In one embodiment of the present specification, a segment of the uncoated portion of the first electrode 115 present at least at the outermost periphery of the electrode assembly may be bent twice to face the side of the electrode assembly 10 as shown in FIG. 3, to have a C-shape or a U-shape.

[0060] Since the uncoated portion of the first electrode 115 at least at the outermost portion of the electrode assembly has a twice-folded shape, when the first electrode 110 is used as an anode, it is possible to prevent shots caused by the anode uncoated portion hitting the cathode and to enhance structural stability.

[0061] In one embodiment of the present specification, at least a portion of the folded portion of the plain portion may be in contact with at least a portion of the folded portion of an adjacent plain portion.

[0062] The term "adjacent" may refer to a positional relationship between the plain part and another plain part close to the plain part, and does not necessarily mean a physical contact. Specifically, the term "adjacent" may refer to a positional relationship between the plain part and another plain part closest to the plain part.

[0063] When at least a portion of the folded portion of the non-coated portion is in contact with at least a portion of the folded portion of the adjacent non-coated portion, it does not come into contact with the cathode, thereby preventing an internal short circuit.

[0064] In one embodiment of the present specification, a width a of an area in contact with at least a portion of a folded portion of an adjacent plain part may be longer than a width b of the first electrode, thereby further enhancing structural stability.

[0065] In one embodiment of the present specification, the length from the first bend to the end of the non-coated portion may be 1 mm or more. When the length is satisfied, it is possible to prevent short circuits caused by electrodes coming into contact with each other.

[0066] In one embodiment of the present specification, the length from the first folding position to the end of the plain portion may be 2 mm or more.

[0067] In one embodiment of the present specification, the length from the first folding position to the end of the plain portion may be 4 mm or more.

[0068] In one embodiment of the present specification, the length from the first folding position to the end of the plain portion may be 5 mm or more.

[0069] In one embodiment of the present specification, the length from the first folding position to the end of the plain portion may be 10 mm or more.

[0070] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a portion of 1% or more of the total height of the electrode assembly.

[0071] In this specification, the overall height of the electrode assembly means the maximum length of the electrode assembly in the winding axis direction, that is, the length in the y direction in FIG.

[0072] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a portion that is 2% or more of the total height of the electrode assembly.

[0073] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a portion of 3% or more of the total height of the electrode assembly.

[0074] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a portion that is 4% or more of the total height of the electrode assembly.

[0075] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a portion that is 5% or more of the total height of the electrode assembly.

[0076] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a position equal to or less than 30% of the total height of the electrode assembly.

[0077] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a position equal to or less than 25% of the total height of the electrode assembly.

[0078] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a position that is 20% or less of the total height of the electrode assembly.

[0079] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a position equal to or less than 15% of the total height of the electrode assembly.

[0080] In one embodiment of the present specification, the twice folded uncoated portion may contact a side surface of the electrode assembly at a position equal to or less than 10% of the total height of the electrode assembly.

[0081] In one embodiment of the present specification, a height of a portion of the twice-folded uncoated portion facing a side surface of the electrode assembly may be 1% to 30% of an overall height of the electrode assembly.

[0082] In one embodiment of the present specification, the first electrode 110 may further include an insulating tape 140 provided on a surface opposite to a surface facing the side of the electrode assembly. The provision of the insulating tape 140 can prevent a non-coated portion of the twice-folded first electrode exposed to the side of the electrode assembly from coming into contact with a battery can, thereby preventing a short circuit from occurring. Although the position where the insulating tape 140 is provided on the twice-folded non-coated portion is shown in FIG. 3, the position where the insulating tape is provided is not limited thereto.

[0083] In one embodiment of the present specification, the insulating tape 140 may be provided to surround the area from the twice folded portion to the end of the uncoated portion of the first electrode.

[0084] In one embodiment of the present disclosure, the insulating tape 140 may be provided to surround both the twice folded portion of the uncoated portion of the first electrode and the adjacent separator.

[0085] The material of the insulating tape 140 may be any insulating material known in the art without limitation, and may include, for example, polyamide, polyacetal, polycarbonate, polyethylene terephthalate, or rubber.

[0086] In one embodiment of the present specification, the first electrode 110 and the second electrode 130 may further include an insulating coating layer 114 covering the boundary between the electrode active material layer 112 and the uncoated portion 113, as shown in Fig. 4. The insulating coating layer 114 includes an insulating polymer resin, and may optionally further include an inorganic filler.

[0087] The insulating coating layer 114 prevents the end of the electrode active material layer 112 from contacting the active material layer of the opposite polarity facing the separator, and serves to structurally support the folding of the segment pieces 113 .

[0088] In one embodiment of the present specification, the second electrode 130 includes a current collector and an electrode active material layer provided on the current collector, and an edge portion of the current collector provided on the other end side of the winding shaft of the electrode assembly may include a plain portion where no electrode active material layer is provided.

[0089] In one embodiment herein, the second electrode 130 may be a cathode.

[0090] The electrode active material used in the electrode active material layer of the second electrode is the same as the negative electrode active material described above.

[0091] Another embodiment of the present specification provides a secondary battery including the above-mentioned electrode assembly, a battery can containing the electrode assembly, and a cap assembly coupled to an upper portion of the battery can.

[0092] The electrode assembly may be inserted into a battery can in the form of a wound jelly roll.

[0093] The battery can accommodates the electrode assembly therein and may be made of stainless steel, aluminum, etc., but is not limited thereto. The battery can may be made of a material that accommodates the electrode assembly and the electrolyte therein, has low reactivity, and can protect the battery can from external impact.

[0094] The battery can may be cylindrical, and its size may be a circular diameter of 30 mm to 55 mm at both ends and a height of 60 mm to 120 mm. For example, the circular diameter x height of the cylindrical battery can may be 40 mm x 60 mm, 40 mm x 80 mm, 40 mm x 90 mm, or 40 mm x 120 mm.

[0095] The cap assembly may include a circuit board and an insulating gasket, and is coupled to the top of the battery can to seal the inside.

[0096] In one embodiment of the present disclosure, the secondary battery may further include an upper current collecting plate disposed on the electrode assembly, and in this case, the upper current collecting plate may be welded and coupled to the electrode assembly.

[0097] In one embodiment herein, the current collector of the secondary battery may be coupled to the cap assembly.

[0098] In one embodiment of the present specification, the secondary battery may further include a lower current collecting plate provided at a lower portion of the electrode assembly, and the lower current collecting plate may be electrically connected to a battery can, that is, the lower current collecting plate may be provided between the electrode assembly and the battery can.

[0099] In one embodiment of the present specification, the lower current collecting plate may be electrically coupled to an uncoated portion of a second electrode of the electrode assembly.

[0100] Other embodiments of the present invention provide a battery module and a battery pack including the secondary battery according to the above-mentioned embodiments.

[0101] Those skilled in the art will appreciate that the present invention can be applied in various ways and modified within the scope of the present invention based on the above content. [Explanation of symbols]

[0102] 110: First electrode, anode 111: Current collector 112: Electrode active material layer 113: Plain part, segmented piece 114: Insulating coating layer 115: First electrode located at the outermost periphery of the electrode assembly 120: Separation membrane 130:Second electrode, cathode 140: Insulating tape a: The width of the area in contact with at least a portion of the folded portion of the plain part and at least a portion of the folded portion of the adjacent plain part b: width of the first electrode P: from the winding center of the electrode assembly to the outer periphery of the electrode assembly

Claims

1. An electrode assembly in which a first electrode, a separator, and a second electrode are stacked and wound, the first electrode includes a current collector and an electrode active material layer provided on the current collector, and an edge portion of the current collector provided on one end side of a winding shaft of the electrode assembly includes a plain portion where no electrode active material layer is provided, the uncoated portion of the first electrode is bent at least once from a winding center of the electrode assembly toward an outer periphery of the electrode assembly, At least a part of the folded portion of the first electrode is in contact with at least a part of the folded portion of the adjacent plain portion, The uncoated portion of the first electrode includes a plurality of segment pieces, The plurality of segment pieces are folded at least once from a winding center of the electrode assembly toward an outer side of the electrode assembly, A segment of the uncoated portion of the first electrode that is present at least at the outermost edge of the electrode assembly is folded twice to face a side surface of the electrode assembly, The side of the electrode assembly is the separator. Electrode assembly.

2. The length from the first bend to the end of the uncoated portion of the first electrode is 1 mm or more. The electrode assembly of claim 1 .

3. the segment of the uncoated portion of the first electrode that is folded twice contacts a side surface of the electrode assembly at a height of 1% to 30% of the total height of the electrode assembly; The electrode assembly of claim 1 .

4. the first electrode is an anode, the second electrode is a cathode, and the first electrode is formed to be exposed to the outside based on an upper surface of the electrode assembly; The electrode assembly of claim 1 .

5. The first electrode further includes an insulating tape provided on a surface opposite to a surface facing the side of the electrode assembly. The electrode assembly of claim 1 .

6. The electrode assembly of claim 1 ; a battery can that houses the electrode assembly therein; and a cap assembly coupled to an upper portion of the battery can;

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