JP6520429B2 - Electrode assembly and power storage device - Google Patents

Description

  The present invention relates to an electrode assembly and a power storage device.

  For example, Patent Document 1 describes an electrode assembly including an electrode body in which a negative electrode and a positive electrode are alternately arranged between a pair of strip-like separators. In this electrode assembly, the pair of separators are connected to each other by welding portions formed to surround the negative electrode and the positive electrode. The electrode body has a serpentine shape in which the negative electrode and the positive electrode are alternately stacked by folding back the pair of separators at a folding line passing through the center of the region between the negative electrode and the positive electrode.

JP-A-7-335244

  The electrode assembly as described above is housed, for example, in a case to constitute a power storage device. In the power storage device, in order to secure the battery capacity, it is preferable that the area of the portion contributing to charge and discharge, that is, the area of the opposing portion between the negative electrode and the positive electrode be as large as possible. In this respect, in the electrode assembly described in Patent Document 1, there is a portion that does not contribute to charge and discharge, and there is room for improvement in terms of improvement in battery capacity.

  Then, an object of this invention is to provide the electrode assembly which can aim at the improvement of a battery capacity, and an electrical storage apparatus.

  An electrode assembly according to one aspect of the present invention includes an electrode assembly in which a negative electrode and a positive electrode are alternately disposed between a pair of strip-like separators, and the pair of separators separate adjacent negative electrodes and positive electrodes. The negative electrode and the positive electrode are alternately stacked by folding back a pair of separators along a folding line along the boundary between the negative electrode and the welded portion, which are connected to each other by the welded portion formed around the negative electrode and the positive electrode. It has a folded shape.

  In this electrode assembly, the pair of separators is folded at a folding line along the boundary between the negative electrode and the welded portion. As a result, the length between the folding lines and the length of the negative electrode are substantially the same, and the welded portion that does not contribute to charge and discharge is not disposed between the negative electrode and the folding line, and the positive electrode and the folding line It is arranged only between and. As a result, the length of the negative electrode can be maximized within the predetermined case width, and the battery capacity can be improved.

  The welded portion may be discontinuous on the folding line. In this case, since the welded portion is not formed on the folding line, the pair of separators can be easily folded, and the workability of the manufacturing operation of the electrode assembly can be improved.

  The negative electrode has a rectangular main body, and one edge of the main body in the negative electrode is positioned to overlap with one edge in the width direction of the pair of separators, and at one edge in the width direction of the pair of separators The portion of the negative electrode overlapping the one edge of the main body portion may be open without forming the welded portion. In this case, since one edge of the main body in the negative electrode overlaps one edge in the width direction of the pair of separators, the length of the negative electrode is maximized to one edge of the pair of separators in the width direction. The battery capacity can be further improved.

  The positive electrode has a rectangular main body, and one edge of the main body in the positive electrode is positioned inward of one edge in the width direction of the pair of separators, and in the edge of the pair of separators in the width direction A welded portion may be formed in a portion along one edge of the main body portion in the positive electrode. When the electrode assembly is incorporated into a power storage device and used, it is preferable that the positive electrode be located inside the negative electrode as viewed from the stacking direction in order to suppress the deposition of the metal component. In this point, in this electrode assembly, one edge portion of the main body portion in the positive electrode is positioned inward of one edge portion in the width direction of the pair of separators (one edge portion of the main body portion in the negative electrode) Since the positive electrode is located inside the negative electrode, the deposition of the metal component can be suppressed.

  The other edge of the main body in the negative electrode may be located closer to the other edge in the width direction of the pair of separators than the other edge of the main body in the positive electrode. In this case, the length of the negative electrode can be increased on the other edge side in the width direction of the pair of separators, and the battery capacity can be further improved. In addition, since the other edge of the main body in the positive electrode is positioned inward of the other edge of the main body in the negative electrode, and the positive electrode is positioned inward of the negative electrode as viewed from the stacking direction, precipitation of metal components is suppressed. can do.

  In the power storage device according to one aspect of the present invention, the electrode assembly is housed in a case.

  In this power storage device, the pair of separators is folded at a folding line along the boundary between the negative electrode and the welded portion. As a result, the length between the folding lines and the length of the negative electrode are substantially the same, and the welded portion that does not contribute to charge and discharge is not disposed between the negative electrode and the folding line, and the positive electrode and the folding line It is arranged only between and. As a result, the length of the negative electrode can be maximized within a predetermined product width, and the battery capacity can be improved.

  According to the present invention, it is possible to provide an electrode assembly and a storage device capable of improving the battery capacity.

1 is a cross-sectional view of a power storage device according to an embodiment. It is sectional drawing of the electrode assembly in the II-II line | wire of FIG. It is a top view of the electrode body before it is folded. It is a top view of the electrode body concerning a reference example before it is folded. It is a top view of the electrode body concerning the reference example after being folded. It is a top view of the electrode body after being folded.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements will be denoted by the same reference symbols, without redundant description.

  As shown in FIG. 1, the power storage device 1 includes a case 10 and an electrode assembly 20. The power storage device 1 is a non-aqueous electrolyte secondary battery, and in the present embodiment, a lithium ion secondary battery. The case 10 is, for example, a rectangular box-like housing. The case 10 has a main body 12 opened to one side and a lid 14 closing the opening of the main body 12.

  The electrode assembly 20 is housed in the case 10. As shown in FIG. 2, the electrode assembly 20 includes an electrode body 21 in which a negative electrode 30 and a positive electrode 40 are alternately disposed between a pair of strip separators 50. The electrode body 21 is folded by folding back a pair of separators 50 at predetermined intervals, and has a serpentine shape in which the negative electrode 30 and the positive electrode 40 are alternately stacked. The serpentine shape refers to a shape formed by folding a long strip at regular intervals so that mountain folds and valley folds are alternately repeated. After the electrode body 21 is formed into a serpentine shape, the electrodes 21 are pressed in the stacking direction so that the surfaces are in close contact with each other. The electrode body 21 is fixed in that state by being pasted together in multiple places, for example, with a tape on each surface.

  As shown in FIG. 1, the negative electrode 30 is formed integrally with, for example, a rectangular main body portion 31 and the main body portion 31, and a rectangular tab portion 32 which protrudes from one edge 34 of the main body portion 31 to one side. And. The negative electrode 30 is formed of, for example, a copper foil. A negative electrode active material layer is provided on the entire surface of both surfaces of the main body portion 31. The tab portion 32 protrudes from the pair of separators 50, and is electrically connected to the conductive member 61 at the protruding portion. The conductive member 61 is electrically connected to the negative electrode terminal 62 disposed so as to penetrate the lid 14 of the case 10. The lid 14 and the negative electrode terminal 62 are insulated by the insulating member 63 and the insulating member 64.

  The positive electrode 40 has, for example, a rectangular main body portion 41 and a rectangular tab portion 42 which is integrally formed with the main body portion 41 and protrudes from the main body portion 41 to one side. The positive electrode 40 is formed of, for example, an aluminum foil. A positive electrode active material layer is provided on the entire surface of both surfaces of the main body portion 41. The tab portion 42 protrudes from the pair of separators 50 and is electrically connected to the conductive member 66 at the protruding portion. The conductive member 61 is electrically connected to the positive electrode terminal 67 disposed to penetrate the lid 14 of the case 10. The cover 14 and the positive electrode terminal 67 are insulated by the insulating member 63 and the insulating member 64. The main body portion 41 of the positive electrode 40 is shorter in length and width (long side and short side) as compared with the main body portion 31 of the negative electrode 30, and the area is smaller. The setting regarding the size of the positive electrode 40 and the negative electrode 30 is a technique for suppressing lithium deposition in a lithium ion secondary battery.

  In the longitudinal direction D1 of the pair of separators 50, the length L1 of the main portion 31 of the negative electrode 30 is substantially the same as the width of the electrode body 21 (the interval at which the pair of separators 50 is folded back) 41 is greater than the length L2. Further, in the width direction D2 of the pair of separators 50, the length L3 of the main body portion 31 is smaller than the width of the pair of separators 50 and larger than the length L4 of the main body portion 41.

  The pair of separators 50 is, for example, a microporous film made of resin, and the pair of separators 50 is impregnated with an electrolytic solution. The electrolytic solution is, for example, an organic solvent-based or non-aqueous electrolytic solution, and is also impregnated in the negative electrode active material layer and the positive electrode active material layer.

  The electrode body 21 before being folded will be described with reference to FIG. As shown in FIG. 3, in the electrode body 21 before being folded, the negative electrode 30 and the positive electrode 40 are alternately disposed at predetermined intervals in the longitudinal direction D1 of the pair of separators 50. One edge 34 of the main body 31 in the negative electrode 30 is positioned so as to substantially overlap with one edge 51 of the width direction D2 of the pair of separators 50. The other edge 35 of the main body 31 of the negative electrode 30 is positioned more inside than the other edge 52 (one edge 34 of the main body 31 of the negative electrode 30) of the width direction D2 of the pair of separators 50. The tab portion 32 of the negative electrode 30 extends from the other edge 35. One edge portion 44 of the main body portion 41 in the positive electrode 40 is positioned inside the one edge portion 51 of the width direction D2 of the pair of separators 50. The other edge 45 of the main body 41 in the positive electrode 40 is located inside the other edge 35 of the main body 31 in the negative electrode 30. The tab portion 42 of the positive electrode 40 extends from the other edge 35.

  The pair of separators 50 are coupled to each other by the welded portion 70. Welded portion 70 is formed around negative electrode 30 and positive electrode 40 so as to separate adjacent negative electrode 30 and positive electrode 40. Thus, each of the negative electrode 30 and the positive electrode 40 is held by the pair of separators 50. In this example, the welded portion 70 is formed over the entire area of the pair of separators 50 except the area where the negative electrode 30 and the positive electrode 40 are located.

  At one edge 51 of the width direction D2 of the pair of separators 50, a welded portion 70 is formed and closed at a portion along the one edge 44 of the main body 41 of the positive electrode 40. On the other hand, at one edge 51 of the width direction D2 of the pair of separators 50, a portion overlapping the one edge 34 of the main body 31 of the negative electrode 30 is opened without forming the welded portion 70.

  For example, in the present embodiment, the welding portion 70 is formed as a region in which a plurality of spot welding portions formed by heat welding are formed in a predetermined arrangement. Such a welding portion 70 can be formed by using a device provided with a heater (heating head) having a large number of protrusions as a welding machine. In this example, a gap S is formed between the welded portion 70, the main body portion 31 and the tab portion 32 in the negative electrode 30, and the main body portion 41 and the tab portion 42 in the positive electrode 40. The gap S is provided, for example, in consideration of errors in the positions of the negative electrode 30 and the positive electrode 40 placed between the pair of separators 50 before welding. In addition, since the negative electrode 30 and the positive electrode 40 are provided with the active material layers on both sides of the main body, as described above, the electrode body 21 is pressed against and closely adhered to the pair of separators 50. It is hard to slip, and, thereby, the positional offset with respect to a pair of separator 50 of the negative electrode 30 and the positive electrode 40 is suppressed.

  The electrode body 21 is folded by folding back the pair of separators 50 at a folding line 80 along the boundary between the negative electrode 30 and the welded portion 70. The folding line 80 is a virtual straight line set as a folding position of the pair of separators 50. The folding line 80 is set substantially parallel to the width direction D2 of the pair of separators 50. The folded line 80 passes through a gap S formed between the negative electrode 30 and the welding portion 70 in this example. The welded portion 70 is discontinuous on the folding line 80. That is, the welded portion 70 is formed in a region other than the folding line 80.

  Next, with reference to FIG. 4, an electrode assembly 21A according to a reference example to be compared with the electrode assembly 21 according to the embodiment will be described. FIG. 4 is a plan view of the electrode body 21A before it is folded. As shown in FIG. 4, in the electrode body 21A, the distance between the negative electrode 30A and the positive electrode 40A in the longitudinal direction D1 of the pair of separators 50 is wider than in the case of the electrode body 21 according to the embodiment.

  In the electrode body 21A, one edge 34A of the main body 31A of the negative electrode 30A is positioned inward of one edge 51 of the pair of separators 50 in the width direction D2. Then, a welded portion 70A is formed at a portion along one edge 34A of the main body 31A of the negative electrode 30A at one edge 51 of the pair of separators 50 in the width direction D2.

  Also in the electrode body 21A, similarly to the electrode body 21 according to the embodiment, the other edge 35A of the main body 31A of the negative electrode 30A is positioned inside the other edge 52 of the width direction D2 of the pair of separators 50 There is. In addition, one edge 44A of the main body 41A in the positive electrode 40A is positioned inside the one edge 34A of the main body 31A in the negative electrode 30A. Further, the other edge 45A of the main body 41A of the positive electrode 40A is located inside the other edge 35A of the main body 31A of the negative electrode 30A.

  In the electrode body 21A, a folding line 80A is set at a position passing through the welded portion 70A formed between the negative electrode 30A and the positive electrode 40A. More specifically, the folding line 80A passes a position slightly closer to the negative electrode 30A than the center between the negative electrode 30A and the positive electrode 40A. Further, in the electrode body 21, the welded portion 70A is continuous on a folding line 80A described later. That is, welding part 70A is formed in the field including the folding line 80 top.

  With reference to FIG.5 and FIG.6, the state after the electrode body 21A which concerns on a reference example and the electrode body 21 which concerns on embodiment are folded is contrasted and demonstrated. In FIG.5 and FIG.6, one part of welding part 70A, 70 is abbreviate | omitted and shown.

  In the electrode body 21A according to the reference example, the pair of separators 50 is folded back at a folding line 80A passing through the welded portion 70A formed between the negative electrode 30A and the positive electrode 40A. Thereby, as shown in FIG. 5, in the longitudinal direction D1 of the pair of separators 50, the length of the negative electrode 30A is smaller than the length between the folding lines 80A. The welded portion 70A is disposed in a region between the folding line 80A and the negative electrode 30A, and the region is a portion that does not contribute to charging and discharging.

  On the other hand, in the electrode body 21 according to the embodiment, the pair of separators 50 is folded at the folding line 80 along the boundary between the negative electrode 30 and the welded portion 70. Thereby, as shown in FIG. 6, the length between the folding lines 80 and the length of the negative electrode 30 are substantially the same, and the welded portion 70 is not disposed between the negative electrode 30 and the folding lines 80. , And between the positive electrode 40 and the folding line 80. As a result, the area of the facing portion of the negative electrode 30 and the positive electrode 40 (the area of the main portion 31 in the positive electrode 40 in this example), which is a portion contributing to charge and discharge, is larger than that of the electrode assembly 21A according to the reference example. It has become. As described above, in the electrode body 21 according to the embodiment, the length of the negative electrode 30 is maximized in the predetermined product width, and the battery capacity is improved.

  Further, in the electrode body 21A according to the reference example, the welded portion 70A is formed on the folding line 80A. For this reason, it is difficult for the pair of separators 50 to be folded easily and to be accurately folded on the folding line 80A. As a method of facilitating the folding, it is also conceivable to provide an unwelded region along the folding line 80A in the middle of the welded portion. However, in that case, it is necessary to widen the welded portion. In contrast, in the electrode body 21 according to the embodiment, the welding portion 70 is not formed on the folding line 80. Since the gap S set for suppressing a manufacturing error or the like is used instead of setting a new unwelded region, it is not necessary to expand the welded portion. Thereby, the pair of separators 50 is easily folded. As a result, the workability of the folding operation of the electrode assembly 21 is improved, and the workability of the manufacturing operation of the electrode assembly 20 is thus improved.

  In addition, in the electrode body 21A according to the reference example, as shown in FIG. 5, in the one edge 51 of the width direction D2 of the pair of separators 50, the portion along the one edge 34A of the main body 31A in the negative electrode 30A. , Weld portion 70A is formed. The region where the welded portion 70A is formed is a portion that does not contribute to charging and discharging.

  On the other hand, in the electrode body 21 according to the embodiment, as shown in FIG. 6, one edge 34 of the main body 31 in the negative electrode 30 overlaps with one edge 34 of the width direction D2 in the pair of separators 50. In the one edge 51 of the width direction D2 in the separator 50, the portion overlapping the one edge 34 of the main body 31 in the negative electrode 30 is opened without forming the welded portion 70. As a result, the length of the negative electrode 30 is maximized at the side of one edge 51 of the pair of separators 50 in the width direction D2, and the battery capacity is further improved. In addition, in the one edge 51 of the width direction D2 of the pair of separators 50, the formation of the welded portion 70 can be omitted in a portion overlapping the one edge 34 of the main body 31 in the negative electrode 30. As a result, it is possible to suppress the deterioration of the welding facility and to reduce the power consumption in the welding operation.

  Further, in the electrode body 21 according to the embodiment, as shown in FIG. 6, the other edge 35 of the main body 31 in the negative electrode 30 is more in the pair of separators 50 than the other edge 45 of the main body 41 in the positive electrode 40. It is located in the other edge 52 side of width direction D2. As a result, the length of the negative electrode 30 is increased on the other edge 52 side in the width direction D2 of the pair of separators 50, and the battery capacity is further improved. This point is the same as in the electrode body 21A according to the reference example.

  Further, in the electrode body 21 according to the embodiment, as shown in FIG. 6, the main body portion 41 of the positive electrode 40 is positioned inside the main body portion 31 of the negative electrode 30 when viewed from the stacking direction of the negative electrode 30 and the positive electrode 40. There is. More specifically, one edge 44 of the main body 41 in the positive electrode 40 is positioned inside the one edge 34 of the main body 31 in the negative electrode 30, and the other edge 45 of the main body 41 in the positive electrode 40 is negative It is located inside the other edge 35 of the main body 31 at 30. Further, the edge 46 in the longitudinal direction D1 of the pair of separators 50 in the main body portion 41 is positioned inside the edge 36 in the longitudinal direction D1 of the pair of separators 50 in the main body portion 31. Thereby, precipitation of lithium (metal component) in the electrolytic solution is suppressed. This point is the same as in the electrode body 21A according to the reference example.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the invention as set forth in the claims. May be

  For example, in the above embodiment, the welded portion 70 is discontinuous on the folding line 80, but may be continuous on the folding line 80. Further, one edge 34 of the main body 31 in the negative electrode 30 may be located inside the one edge 51 of the width direction D2 of the pair of separators 50. In this case, a welded portion 70 may be formed at a portion overlapping with one edge 34 of the main body 31 in the negative electrode 30 at one edge 51 of the pair of separators 50 in the longitudinal direction D1.

  Further, the portion along the one edge portion 44 of the main body portion 41 in the positive electrode 40 may be opened without the welded portion 70 being formed. However, if the welded portion 70 is formed along the one edge 44 of the main body 41 in the positive electrode 40 as in the above embodiment, the electrode body 21 is pressurized in the laminating direction, for example, in the middle of manufacturing It is preferable from the viewpoint of suppressing the displacement of the positive electrode 40 in the state before the step.

  Further, from the viewpoint of improving the battery capacity, the folded line 80 is preferably close to the edge 46 of the main body 31 of the negative electrode 30, and ideally it should ideally be coincident with the edge 46 of the main body 31 of the negative electrode 30. preferable. If it is difficult to fold the pair of separators 50 on the edge 46, it may be folded at a position as close as possible to the edge 46.

DESCRIPTION OF SYMBOLS 1 ... Storage device, 10 ... Case, 20 ... Electrode assembly, 21 ... Electrode body, 30 ... Negative electrode, 31 ... Main body part, 34 ... One edge, 35 ... Other edge part, 40 ... Positive electrode, 41 ... Main body part, 44: One edge, 45: other edge, 50: pair of separators, 51: one edge, 52: other edge, 70: welded portion, 80: folding line.

Claims (6)

An electrode assembly in which a negative electrode and a positive electrode are alternately disposed between a pair of strip-like separators;
The pair of separators are coupled to each other by a welded portion formed around the negative electrode and the positive electrode so as to separate the adjacent negative electrode and the positive electrode,
The electrode assembly has a zigzag shape in which the negative electrode and the positive electrode are alternately stacked by folding the pair of separators along a folding line along the boundary between the negative electrode and the welded portion. Three-dimensional.   The electrode assembly according to claim 1, wherein the welding portion is discontinuous on the folding line. The negative electrode has a rectangular main body,
One edge of the main body in the negative electrode is positioned to overlap with one edge in the width direction of the pair of separators,
The electrode assembly according to claim 1 or 2, wherein at one edge in the width direction of the pair of separators, a portion overlapping the one edge of the main body in the negative electrode is opened without forming the welded portion. Three-dimensional. The positive electrode has a rectangular main body,
One edge of the main body in the positive electrode is positioned inward of one edge in the width direction of the pair of separators,
The electrode assembly according to claim 3, wherein the welded portion is formed at a portion along one edge of the main body in the positive electrode at one edge in the width direction of the pair of separators.   The electrode according to claim 3 or 4, wherein the other edge of the main body in the negative electrode is positioned on the other edge side in the width direction of the pair of separators than the other edge of the main body in the positive electrode. Assembly.   The electrical storage apparatus by which the electrode assembly of any one of Claims 1-5 is accommodated in a case.

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