Electrode assembly and secondary battery including the same

Abstract

Electrode assembly and secondary battery including the same. 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 a side of an end portion of a winding axis of the electrode assembly including a coating-free portion having no electrode active material layer, and the coating-free portion of the first electrode being bent one or more times in a direction from a winding center of the electrode assembly to an outer contour of the electrode assembly.

Description

Technical Field

[0001] This manual relates to electrode assemblies and the secondary batteries that include them.

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0160355, filed with the Korean Patent Office on November 19, 2021, the entire contents of which are included in this specification. Background Technology

[0003] In recent years, the need for high-capacity, high-power batteries has increased significantly. The rapid development of the electric vehicle market has also led to a substantial increase in the performance requirements for batteries.

[0004] In the case of cylindrical secondary batteries, in order to fit a large number of electrodes into a limited space, optimization can be achieved by changing the thickness of the current collector or separator, the size or shape of the can and top cover, etc., but the limit can only be reached within a limited size.

[0005] In the case of the existing cylindrical shape, one or two tabs are applied to the anode and cathode respectively to serve as conductive channels. However, in this case, the greater the physical distance from the tabs, the greater the resistance, thus limiting the improvement of resistance.

[0006] To improve this situation, a method exists where uncoated areas of electrode active material are formed above and below the electrode current collector (uncoated portions), and these areas are overlapped after a notching process to serve as electrode tabs. However, in this case, such as Figure 2 As shown, a portion of the uncoated anode portion 110 folds inward and contacts the cathode 130, causing a short circuit, which needs to be improved.

[0007] Existing technical documents

[0008] Patent documents

[0009] Korean Patent Application Publication No. 10-2015-0043016 (Publication Date: April 22, 2015) Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The purpose of this invention is to change the folding method of the uncoated portion of the electrode assembly to eliminate the possibility of short circuits caused by the folding method of the uncoated portion of the electrode, which was previously present.

[0012] Methods for solving problems

[0013] One embodiment of this specification provides an electrode assembly formed by stacking and winding a first electrode, a separation membrane, and a second electrode. The first electrode includes a current collector and an electrode active material layer disposed on the current collector. The edge portion of the current collector disposed at one end of the winding shaft of the electrode assembly includes an uncoated portion without the electrode active material layer. The uncoated portion of the first electrode is bent at least once from the winding center of the electrode assembly toward the outer contour of the electrode assembly.

[0014] In another embodiment of this specification, the uncoated portion of the first electrode includes a plurality of segments, which are bent at least once from the winding center of the electrode assembly toward the outer contour of the electrode assembly.

[0015] In another embodiment of this specification, the uncoated portion of at least the outermost first electrode of the electrode assembly is bent twice in a manner opposite to the side of the electrode assembly.

[0016] In another embodiment of this specification, at least a portion of the bent portion of the uncoated portion of the first electrode is in contact with at least a portion of the bent portion of an adjacent uncoated portion.

[0017] In addition, in one embodiment of this specification, the length from the initial bending portion of the uncoated portion of the first electrode to the end is 1 mm or more.

[0018] In another embodiment of this specification, the uncoated portion of the first electrode that is bent twice is connected to the side of the electrode assembly at a distance of 1% to 30% of the total height of the electrode assembly.

[0019] In another embodiment of this specification, the first electrode is an anode, the second electrode is a cathode, and the first electrode is formed to be exposed to the outside with reference to the upper surface of the electrode assembly.

[0020] In addition, in one embodiment of this specification, the first electrode further includes an insulating strip disposed on the opposite side of the side of the electrode assembly.

[0021] In addition, one embodiment of this specification provides a secondary battery comprising: the electrode assembly described above; a battery can housing the electrode assembly; and a cover assembly coupled to the upper part of the battery can.

[0022] Invention Effects

[0023] In one embodiment of the electrode assembly described in this specification, the uncoated portion of the electrode is bent at least once from the winding center of the electrode assembly toward the outer contour of the electrode assembly, thereby preventing the uncoated portion of the anode from contacting the cathode and causing an internal short circuit. Attached Figure Description

[0024] Figure 1 This is a schematic diagram showing the direction in which the existing uncoated anode portion folds from the outer contour of the electrode assembly toward the winding center of the electrode assembly.

[0025] Figure 2 This is a schematic diagram showing a situation where, when the uncoated anode portion is folded from the outer contour of the electrode assembly toward the winding center of the electrode assembly, the uncoated anode portion folds inward due to the upper load and comes into contact with the cathode, causing a short circuit.

[0026] Figure 3 This is a schematic diagram showing the folding shape and orientation of the uncoated anode portion in an electrode assembly according to one embodiment of this specification.

[0027] Figure 4 This is a schematic diagram showing the case where the uncoated portion of the first electrode includes multiple segments.

[0028] Explanation of reference numerals in the attached figures

[0029] 110: First electrode, anode

[0030] 111: Current collector

[0031] 112: Electrode active material layer

[0032] 113: Uncoated section

[0033] 114: Insulating coating

[0034] 115: The first electrode of the electrode assembly located at the outermost contour.

[0035] 120: Separation membrane

[0036] 130: Second electrode, cathode

[0037] 140: Insulating tape

[0038] a: The width of the area where at least a portion of the bent portion of the uncoated part contacts at least a portion of the bent portion of an adjacent uncoated part.

[0039] b: Width of the first electrode

[0040] P: The direction from the winding center of the electrode assembly towards the outer contour of the electrode assembly. Detailed Implementation

[0041] The following is a more detailed explanation of this instruction manual.

[0042] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Before proceeding, it should be noted that the terms and words used in this specification and claims should not be limited to their ordinary or dictionary meanings. Given the principle that inventors may appropriately define terms and concepts in order to best illustrate their invention, they should be interpreted as meanings and concepts consistent with the technical concept of the present invention.

[0043] Therefore, the embodiments described in this specification and the structures shown in the accompanying drawings are only one of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. It should be understood that at the time of filing this application, there may be various equivalents and multiple modifications that can replace these.

[0044] Furthermore, to aid in understanding the invention, the dimensions of some components in the drawings are sometimes enlarged, rather than shown at actual scale. Also, in different embodiments, the same symbols are used for the same components.

[0045] In this specification, "above" does not only refer to a situation where they are physically connected on a single layer, but also to a situation where they are located on top. That is, a layer located on any layer may have other layers in between.

[0046] In this specification, when a part is referred to as "including" a certain constituent element, it does not exclude other constituent elements unless otherwise stated, but rather indicates that other constituent elements may also be included.

[0047] The electrode assembly 10 in this specification is a jelly roll type electrode assembly having a sheet-like first electrode and a second electrode and a separation membrane sandwiched between them, rolled up in one direction.

[0048] In one embodiment of this specification, the electrode assembly 10 is an electrode assembly that is formed by stacking and winding a first electrode 110, a separation membrane 120 and a second electrode 130. The first electrode includes a current collector 111 and an electrode active material layer 112 disposed on the current collector 111. The edge portion of the current collector disposed at one end of the winding shaft of the electrode assembly includes an uncoated portion 113 that does not have the electrode active material layer 112. The uncoated portion 113 of the first electrode is bent at least once from the winding center of the electrode assembly toward the outer contour of the electrode assembly in the direction P.

[0049] In one embodiment of this specification, the uncoated portion 113 of the first electrode is bent at least once at an angle of 30° to 90° from the winding center of the electrode assembly toward the outer contour P of the electrode assembly.

[0050] Figure 3 The direction P is shown from the winding center of the electrode assembly to the outer contour of the electrode assembly.

[0051] The area of ​​the current collector where no electrode active material layer has been formed is called the uncoated part (not shown), indicating the area where the anode or cathode current collector is exposed.

[0052] At this time, no other electrode tab is attached to the uncoated portion of the first electrode, and at least a portion of the uncoated portion itself can be used as an electrode tab.

[0053] In one embodiment of this specification, the first electrode 110 is an anode and the second electrode 130 is a cathode. The first electrode 110 may be formed to be exposed to the outside with the upper surface of the electrode assembly as a reference.

[0054] In one embodiment of this specification, the first electrode 110 and the second electrode 130 include a current collector 111 and an electrode active material layer 112 disposed on the current collector 111.

[0055] At this point, any active material known in the art can be used arbitrarily regarding the aforementioned electrode active material.

[0056] In one example, the anode active material includes lithium cobalt oxide with high operating voltage and excellent capacity characteristics, lithium nickel oxide with high reversible capacity and easy to demonstrate large capacity, lithium nickel cobalt oxide with cobalt replacing part of the nickel, lithium nickel cobalt metal oxide with manganese, cobalt or aluminum replacing part of the nickel, lithium manganese oxide with excellent thermal stability and low price, and lithium iron phosphate with excellent stability.

[0057] Cathode active materials include, for example, carbon materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers, silicon, lithium metal, or lithium alloys.

[0058] The separation membrane 120 is located between the anode and the cathode while having a certain mechanical strength, and is made of a porous material to facilitate the movement of ions between the electrodes. For example, it is formed of any substrate selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene (PP) and copolymers of polyethylene (PE) and polypropylene (PP).

[0059] In one embodiment of this specification, the bending method of the uncoated portion of the first electrode of the above-described electrode assembly is performed by applying pressure using a bending device.

[0060] Specifically, the uncoated portion of the first electrode is bent by rolling it up from the winding direction of the electrode assembly toward the outer contour of the electrode assembly using the bending device described above. By using the bending device, at least the uncoated portion of the first electrode located at the outermost contour of the electrode assembly is also bent due to inertia.

[0061] More specifically, it is formed by the following steps: bending the uncoated portion of the first electrode once using the bending device, and then, while the uncoated portion of the first electrode at least on the outermost part of the electrode assembly is being wound with insulating tape, additional bending is performed, or the electrode assembly is combined with a hollow cylindrical support with an open bottom and a blocked top to guide the additional bending and the winding of insulating tape.

[0062] Figure 3 This is a diagram showing the folding shape and orientation of the uncoated anode portion in the electrode assembly. Figure 3 The anode 110 shown includes an electrode active material layer (not shown), an insulating coating (not shown), and an uncoated portion (not shown).

[0063] like Figure 3 As shown, an electrode assembly according to one embodiment of this specification includes an anode 110, a separation membrane 120, and a cathode 130. The uncoated portion of the anode 110 has a shape that bends from the winding center of the electrode assembly toward the outer contour of the electrode assembly. In particular, the uncoated portion of the anode located at the outermost contour of the electrode assembly is bent twice in a manner opposite to the side of the electrode assembly.

[0064] After forming uncoated portions on the top and bottom of the electrode current collector and performing a grooving process, they are overlapped to serve as electrode tabs, although this specification exists. Figure 1 The folding direction of the uncoated anode portion shown is the conventional method, which follows the winding center direction of the electrode assembly. However, in this case, as described in this specification... Figure 2 As shown in the dashed circle, a portion of the uncoated anode folds inward and contacts the cathode, causing a short circuit.

[0065] like Figure 3 As shown, the present invention has a shape in which the uncoated portion of the anode is bent from the winding center of the electrode assembly toward the outer contour of the electrode assembly, thereby preventing the uncoated portion of the anode from contacting the cathode and causing an internal short circuit.

[0066] In one embodiment of this specification, the uncoated portion of the first electrode includes a plurality of segments 113, which are bent at least once from the winding center of the electrode assembly toward the outer contour of the electrode assembly.

[0067] In one embodiment of this specification, the uncoated portion of the first electrode includes a plurality of slotted pieces 113. That is, the uncoated portion of the first electrode can be formed in a gear shape. Figure 4 This diagram schematically illustrates the case where the uncoated portion of the first electrode comprises multiple segments, showing a case where the uncoated portion, lacking an electrode active material layer, is cut into a gear shape. The above... Figure 4 The diagram is shown to illustrate the formation of individual segments, but the shape, length, and separation distance of the segments are not limited to this.

[0068] In one embodiment of this specification, the height, width, and separation distance of the plurality of segments 113 may be the same or different.

[0069] In one embodiment of this specification, the length of each of the plurality of segments 113 can be from 4 mm to 20 mm.

[0070] The length of the aforementioned section 113 refers to 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.

[0071] While meeting the above length range, the length of the cut piece is short, thereby preventing it from extending into the inside of the electrode assembly during bending and causing a short circuit.

[0072] In one embodiment of this specification, the length of each of the plurality of segments 113 can be from 4 mm to 15 mm.

[0073] In one embodiment of this specification, the length of each of the plurality of segments 113 may be 6 mm to 10 mm.

[0074] In one embodiment of this specification, the separation distance between any one of the plurality of segments 113 and another adjacent segment can be from 1 mm to 150 mm.

[0075] While maintaining the above separation distance range, it is easy to expel gas when injecting electrolyte while maintaining the resistance of the electrodes appropriately, thus reducing gas trapping when used after the battery is activated.

[0076] In one embodiment of this specification, the separation distance between any one of the plurality of segments 113 and another adjacent segment can be from 1 mm to 48 mm.

[0077] In one embodiment of this specification, the separation distance between any one of the plurality of segments 113 and another adjacent segment can be from 5 mm to 36 mm.

[0078] In one embodiment of this specification, the width of the above-mentioned cut-off piece 113 can be from 2 mm to 30 mm.

[0079] If the above conditions are met, welding and bending can be performed easily.

[0080] In one embodiment of this specification, a section of the uncoated portion of at least the outermost first electrode 115 of the electrode assembly is bent twice in a manner opposite to the side of the electrode assembly.

[0081] In one embodiment of this specification, as described above Figure 3 As shown, the uncoated portion of at least the first electrode 115 located at the outermost contour of the electrode assembly is bent twice in a manner opposite to the side of the electrode assembly 10 to have a "ㄷ" shape or a U-shape.

[0082] The uncoated portion of the first electrode 115 at least on the outermost edge of the electrode assembly has a shape that is bent twice, thereby preventing the uncoated portion of the anode from contacting the cathode and causing a short circuit when the first electrode 110 is used as the anode, and enhancing the stability of the structure.

[0083] In one embodiment of this specification, at least a portion of the bent portion of the uncoated portion is in contact with at least a portion of the bent portion of an adjacent uncoated portion.

[0084] The term "adjacent" refers to the positional relationship between the uncoated portion and another adjacent uncoated portion, and does not merely indicate physical contact. Specifically, it can refer to the positional relationship between the uncoated portion and the closest other uncoated portion.

[0085] When at least a portion of the bent portion of the uncoated portion is in contact with at least a portion of the bent portion of an adjacent uncoated portion, it does not come into contact with the cathode, thereby preventing internal short circuits.

[0086] In one embodiment of this specification, the length of the width 'a' of the area where at least a portion of the bent portion of the uncoated part contacts at least a portion of the bent portion of an adjacent uncoated part is longer than the length of the width 'b' of the first electrode. In this case, the stability of the structure can be further enhanced.

[0087] In one embodiment of this specification, the length from the initial bend of the uncoated portion to the end can be 1 mm or more. Meeting this length prevents the electrodes from coming into contact with each other and causing a short circuit.

[0088] In one embodiment of this specification, the length from the initial bending portion of the uncoated portion to the end can be 2 mm or more.

[0089] In one embodiment of this specification, the length from the initial bending portion of the uncoated portion to the end can be 4 mm or more.

[0090] In one embodiment of this specification, the length from the initial bend of the uncoated portion to the end can be 5 mm or more.

[0091] In one embodiment of this specification, the length from the initial bending portion of the uncoated portion to the end can be 10 mm or more.

[0092] In one embodiment of this specification, the uncoated portion that is bent twice is connected to the side of the electrode assembly at a height of 1% or more of the total height of the electrode assembly.

[0093] In this specification, the total height of the electrode assembly refers to the maximum length of the electrode assembly in the winding axis direction. Figure 3 The length in the y-direction.

[0094] In one embodiment of this specification, the uncoated portion that is bent twice is connected to the side of the electrode assembly at a height of 1% or more of the total height of the electrode assembly.

[0095] In one embodiment of this specification, the uncoated portion that is bent twice is connected to the side of the electrode assembly at a ratio of 2% or more of the total height of the electrode assembly.

[0096] In one embodiment of this specification, the uncoated portion that is bent twice is in contact with the side of the electrode assembly at a height of 3% or more of the total height of the electrode assembly.

[0097] In one embodiment of this specification, the uncoated portion that is bent twice is in contact with the side of the electrode assembly at a ratio of 4% or more of the total height of the electrode assembly.

[0098] In one embodiment of this specification, the uncoated portion that is bent twice is in contact with the side of the electrode assembly at a height of 5% or more of the total height of the electrode assembly.

[0099] In one embodiment of this specification, the uncoated portion that is bent twice is connected to the side of the electrode assembly at a distance of less than 30% of the total height of the electrode assembly.

[0100] In one embodiment of this specification, the uncoated portion that is bent twice is connected to the side of the electrode assembly at a distance of less than 25% of the total height of the electrode assembly.

[0101] In one embodiment of this specification, the uncoated portion that is bent twice is connected to the side of the electrode assembly at a distance of less than 20% of the total height of the electrode assembly.

[0102] In one embodiment of this specification, the uncoated portion that is bent twice is connected to the side of the electrode assembly at a height of less than 15% of the total height of the electrode assembly.

[0103] In one embodiment of this specification, the uncoated portion that is bent twice is connected to the side of the electrode assembly at a distance of less than 10% of the total height of the electrode assembly.

[0104] In one embodiment of this specification, in the uncoated portion that is bent twice, the height of the portion opposite to the side of the electrode assembly is more than 1% and less than 30% of the total height of the electrode assembly.

[0105] In one embodiment of this specification, the first electrode 110 further includes an insulating strip 140 disposed on the opposite side of the side facing the electrode assembly. With the insulating strip 140, it is possible to prevent the uncoated portion of the first electrode, which is exposed on the side of the electrode assembly and bent twice, from contacting the battery can and causing a short circuit. Figure 3 The diagram shows the location where the insulating strip 140 is provided in the uncoated portion after being bent twice, but the location of the insulating strip is not limited to this.

[0106] In one embodiment of this specification, the insulating tape 140 is formed to surround the area from the portion where the uncoated portion of the first electrode is bent twice to the end.

[0107] In one embodiment of this specification, the insulating tape 140 is formed to surround the portion of the uncoated portion of the first electrode that is bent twice together with the adjacent separation membrane.

[0108] Regarding the material of the aforementioned insulating tape 140, any insulating material known in the art may be used. For example, it may include polyamide, polyacetal, polycarbonate, polyethylene terephthalate, or rubber.

[0109] In one embodiment of this specification, such as Figure 4 As shown, the first electrode 110 and the second electrode 130 further include an insulating coating 114 covering the boundary between the electrode active material layer 112 and the uncoated portion 113. The insulating coating 114 includes an insulating polymer resin and optionally also includes inorganic fillers.

[0110] The aforementioned insulating coating 114 prevents the end of the electrode active material layer 112 from contacting the active material layer of opposite polarity that is opposite to it through the separation membrane, and structurally supports the bending of the segment 113.

[0111] In one embodiment of this specification, the second electrode 120 includes a current collector and an electrode active material layer disposed on the current collector, and the edge portion of the current collector disposed at the other end of the winding shaft of the electrode assembly includes an uncoated portion without the electrode active material layer.

[0112] In one embodiment of this specification, the second electrode 120 is a cathode.

[0113] The electrode active material used in the electrode active material layer of the second electrode is the same as the cathode active material described above.

[0114] Another embodiment of this specification provides a secondary battery, which includes the electrode assembly described above, a battery can housing the electrode assembly, and a cover assembly coupled to the upper part of the battery can.

[0115] The electrode assembly is inserted into the battery can in the form of a rolled-up gel roll.

[0116] The aforementioned battery canister houses the electrode assembly internally and can be made of materials such as stainless steel or aluminum, but is not limited to these. Materials that house the electrode assembly and electrolyte internally, have low reactivity, and can provide protection against external impacts can also be selected.

[0117] The aforementioned battery can is cylindrical, with the diameter of the circular ends ranging from 30mm to 55mm and the height from 60mm to 120mm. For example, the diameter x height of the cylindrical battery can is 40mm x 60mm, 40mm x 80mm, 40mm x 90mm, or 40mm x 120mm.

[0118] The aforementioned cover assembly includes a circuit board and insulating gaskets, which are attached to the upper part of the battery can to seal the interior.

[0119] In one embodiment of this specification, the secondary battery further includes an upper current collector plate disposed on the electrode assembly, wherein the upper current collector plate is welded to the electrode assembly for bonding.

[0120] In one embodiment of this specification, the current collector in the secondary battery is combined with the cover assembly.

[0121] In one embodiment of this specification, the secondary battery further includes a lower current collector plate disposed below the electrode assembly, wherein the lower current collector plate is electrically connected to the battery can. That is, the lower current collector plate is disposed between the electrode assembly and the battery can.

[0122] In one embodiment of this specification, the lower current collector is electrically coupled to the uncoated portion of the second electrode of the electrode assembly.

[0123] Another embodiment of the present invention provides a battery module and battery pack including the secondary battery of the above embodiments.

[0124] Those skilled in the art can make various applications and modifications within the scope of this invention based on the above content.

Claims

1. An electrode assembly comprising a first electrode, a separation membrane, and a second electrode stacked and wound together, characterized in that, The first electrode includes a current collector and an electrode active material layer disposed on the current collector. The edge portion of the current collector disposed at one end of the winding shaft of the electrode assembly includes an uncoated portion without the electrode active material layer. The uncoated portion of the first electrode is bent at least once from the winding center of the electrode assembly toward the outer contour of the electrode assembly. At least a portion of the bent portion of the uncoated part of the first electrode is in contact with at least a portion of the bent portion of an adjacent uncoated part. The uncoated portion of the first electrode includes multiple segments, which are bent at least once from the winding center of the electrode assembly toward the outer contour of the electrode assembly. The uncoated portion of at least the outermost first electrode of the aforementioned electrode assembly is bent twice in a manner opposite to the side of the aforementioned electrode assembly.

2. The electrode assembly according to claim 1, characterized in that, The length from the initial bend of the uncoated portion of the first electrode to its end is 1 mm or more.

3. The electrode assembly according to claim 1, characterized in that, The uncoated portion of the first electrode, which is bent twice, is connected to the side of the electrode assembly at a ratio of 1% to 30% of the total height of the electrode assembly.

4. The electrode assembly according to claim 1, characterized in that, The first electrode is the anode, the second electrode is the cathode, and the first electrode is formed to be exposed to the outside with the upper surface of the electrode assembly as a reference.

5. The electrode assembly according to claim 1, characterized in that, The first electrode further includes an insulating strip disposed on the opposite side of the side of the electrode assembly.

6. A secondary battery, characterized in that, It includes: The electrode assembly according to any one of claims 1 to 5; The battery canister houses the aforementioned electrode assembly. and The cover assembly is attached to the upper part of the aforementioned battery canister.

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