JP2017004710A - Electrode assembly and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode assembly and a power storage device capable of improving battery capacity.SOLUTION: An electrode assembly 20 includes an electrode body 21 in which a negative electrode 30 and a positive electrode 40 are alternately arranged between a pair of strip-shaped separators 50. The pair of separators 50 are coupled to each other by a welded portion 70 formed around the negative electrode 30 and the positive electrode 40 so as to partition the adjacent negative electrode 30 and positive electrode 40. The electrode body 21 has a zigzag shape in which the negative electrode 30 and the positive electrode 40 are alternately laminated by folding the pair of separators 50 in a folding line 80 along the boundary between the negative electrode 30 and the welded portion 70.SELECTED DRAWING: Figure 3

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-shaped separators. In this electrode assembly, the pair of separators are bonded to each other by welded portions formed so as to surround the periphery of each of the negative electrode and the positive electrode. The electrode body has a zigzag shape in which the negative electrode and the positive electrode are alternately stacked by folding a pair of separators in a folding line passing through the center of the region between the negative electrode and the positive electrode.

JP 7-335244 A

  The electrode assembly as described above is housed in, for example, a case to constitute a power storage device. In the power storage device, in order to ensure battery capacity, it is preferable to increase the area of the portion contributing to charging / discharging within the predetermined case width, that is, the area of the facing portion between the negative electrode and the positive electrode as much as possible. In this regard, the electrode assembly described in Patent Document 1 has a portion that does not contribute to charge and discharge, and there is room for improvement in terms of improving battery capacity.

  Therefore, an object of the present invention is to provide an electrode assembly and a power storage device that can improve battery capacity.

  An electrode assembly according to an aspect of the present invention includes an electrode body in which negative electrodes and positive electrodes are alternately arranged between a pair of strip-shaped separators, and the pair of separators separate adjacent negative electrodes and positive electrodes. The electrode body is bonded to each other by the welded portions formed around the negative electrode and the positive electrode, and the electrode body is alternately laminated with the negative electrode and the positive electrode by folding back a pair of separators at a folding line along the boundary between the negative electrode and the welded portion. It has a folded shape.

  In this electrode assembly, the pair of separators are folded at a folding line along the boundary between the negative electrode and the welded portion. As a result, the length between the folded lines is substantially the same as the length of the negative electrode, and the welded portion that does not contribute to charging / discharging is not disposed between the negative electrode and the folded line. It is arranged only between. As a result, the length of the negative electrode can be maximized within a 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 welding part 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 of the negative electrode is positioned so as to overlap with one edge of the pair of separators in the width direction. The portion of the negative electrode that overlaps one edge of the main body may be opened without forming a welded portion. In this case, since one edge portion of the main body portion of the negative electrode overlaps with one edge portion in the width direction of the pair of separators, the length of the negative electrode is maximized on one edge side of the width direction of the pair of separators. Battery capacity can be further improved.

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

  The other edge part of the main body part in the negative electrode may be located closer to the other edge part side in the width direction of the pair of separators than the other edge part of the main body part 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, the other edge of the main body of the positive electrode is located on the inner side of the other edge of the main body of the negative electrode, and the positive electrode is located on the inner side of the negative electrode when viewed from the stacking direction. can do.

  A power storage device according to one aspect of the present invention includes the electrode assembly housed in a case.

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

  ADVANTAGE OF THE INVENTION According to this invention, the electrode assembly and electrical storage apparatus which can aim at the improvement of battery capacity can be provided.

It is sectional drawing of the electrical storage apparatus which concerns on 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 being folded. It is a top view of the electrode body which concerns on the reference example before being folded. It is a top view of the electrode body concerning a reference example after being folded up. 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 reference numerals are used for the same or corresponding elements, and duplicate descriptions are omitted.

  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 is a lithium ion secondary battery in the present embodiment. The case 10 is a rectangular box-shaped housing, for example. The case 10 has a main body portion 12 opened on one side and a lid portion 14 that closes the opening of the main body portion 12.

  The electrode assembly 20 is accommodated in the case 10. As shown in FIG. 2, the electrode assembly 20 includes electrode bodies 21 in which negative electrodes 30 and positive electrodes 40 are alternately arranged between a pair of strip-shaped separators 50. The electrode body 21 is folded by a pair of separators 50 being folded back at a predetermined interval, and has a zigzag shape in which the negative electrodes 30 and the positive electrodes 40 are alternately stacked. The zigzag fold shape refers to a shape formed by folding a long belt-like body at regular intervals so that mountain folds and valley folds are alternately repeated. The electrode body 21 is formed in a zigzag shape and then 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 bonded to each surface at a plurality of locations using, for example, a tape.

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

  The positive electrode 40 includes, for example, a rectangular main body portion 41 and a rectangular tab portion 42 that is formed integrally with the main body portion 41 and protrudes from the main body portion 41 to one side. The positive electrode 40 is made 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 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 a positive electrode terminal 67 arranged so as to penetrate the lid portion 14 of the case 10. The lid 14 and the positive terminal 67 are insulated by an insulating member 63 and an insulating member 64. The main body 41 of the positive electrode 40 is shorter in both length and breadth (long side and short side) than the main body 31 of the negative electrode 30 and has a smaller area. The setting regarding the size of the positive electrode 40 and the negative electrode 30 is a technique for suppressing lithium deposition in the lithium ion secondary battery.

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

  The pair of separators 50 are, for example, resin microporous films, and the pair of separators 50 are 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 electrodes 30 and the positive electrodes 40 are alternately arranged in the longitudinal direction D1 of the pair of separators 50 at a predetermined interval. The one edge 34 of the main body 31 in the negative electrode 30 is positioned so as to substantially overlap the one edge 51 of the pair of separators 50 in the width direction D2. The other edge 35 of the main body 31 in the negative electrode 30 is located on the inner side of the other edge 52 of the pair of separators 50 in the width direction D2 (the one edge 34 of the main body 31 in the negative electrode 30). The tab portion 32 of the negative electrode 30 extends from the other edge portion 35. One edge 44 of the main body 41 in the positive electrode 40 is located on the inner side of the one edge 51 of the pair of separators 50 in the width direction D2. 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 portion 35.

  The pair of separators 50 are connected to each other by a welded portion 70. The welded portion 70 is formed around the negative electrode 30 and the positive electrode 40 so as to separate the adjacent negative electrode 30 and positive electrode 40. Thereby, 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 region of the pair of separators 50 other than the region where the negative electrode 30 and the positive electrode 40 are located.

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

  In the present embodiment, for example, the welded portion 70 is formed as a region in which a large number of dot-like welded portions formed by thermal welding are formed in a predetermined arrangement. Such a welding portion 70 can be formed by using an apparatus including 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 in consideration of errors such as 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 active material layers on both surfaces of the main body portion, the electrode body 21 is pressed against the pair of separators 50 in the stacked direction as described above. It is hard to slip, and thereby, displacement of the negative electrode 30 and the positive electrode 40 with respect to the pair of separators 50 is suppressed.

  The electrode body 21 is folded by folding the pair of separators 50 along a folding line 80 along the boundary between the negative electrode 30 and the welded portion 70. The folding line 80 is an imaginary straight line set as the 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. In this example, the folding line 80 passes through a gap S formed between the negative electrode 30 and the welded portion 70. 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, an electrode body 21A according to a reference example compared with the electrode body 21 according to the embodiment will be described with reference to FIG. FIG. 4 is a plan view of the electrode body 21A before being 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 that in the electrode body 21 according to the embodiment.

  In the electrode body 21 </ b> A, the one edge portion 34 </ b> A of the main body portion 31 </ b> A in the negative electrode 30 </ b> A is located inside the one edge portion 51 of the pair of separators 50 in the width direction D <b> 2. And in one edge part 51 of the width direction D2 in a pair of separator 50, 70 A of welding parts are formed in the part along the one edge part 34A of the main-body part 31A in the negative electrode 30A.

  Also in the electrode body 21A, as in the electrode body 21 according to the embodiment, the other edge portion 35A of the main body 31A in the negative electrode 30A is located on the inner side of the other edge portion 52 in the width direction D2 in the pair of separators 50. Yes. Further, the one edge portion 44A of the main body portion 41A in the positive electrode 40A is located inside the one edge portion 34A of the main body portion 31A in the negative electrode 30A. Further, the other edge portion 45A of the main body portion 41A in the positive electrode 40A is located inside the other edge portion 35A of the main body portion 31A in the negative electrode 30A.

  In the electrode body 21A, a folding line 80A is set at a position passing through a welded portion 70A formed between the negative electrode 30A and the positive electrode 40A. More specifically, the folding line 80A passes through a position slightly closer to the negative electrode 30A than the center between the negative electrode 30A and the positive electrode 40A. In the electrode body 21, the welded portion 70 </ b> A is continuous on a return line 80 </ b> A described later. That is, the welded portion 70 </ b> A is formed in a region including the fold line 80.

  With reference to FIG.5 and FIG.6, the electrode body 21A which concerns on a reference example and the state after the electrode body 21 which concerns on embodiment are folded are demonstrated and contrasted. 5 and 6, a part of the welded portions 70A and 70 is omitted.

  In the electrode body 21A according to the reference example, the pair of separators 50 are folded at a folding line 80A passing through a 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. A welded portion 70A is disposed in a region between the return line 80A and the negative electrode 30A, and the region is a portion that does not contribute to charging / discharging.

  On the other hand, in the electrode body 21 according to the embodiment, the pair of separators 50 are folded at the folding line 80 along the boundary between the negative electrode 30 and the welded portion 70. As a result, 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 line 80. These are disposed only between the positive electrode 40 and the folding line 80. As a result, the area of the facing portion between the negative electrode 30 and the positive electrode 40 that contributes to charging / discharging (in this example, the area of the main body 31 in the positive electrode 40) is larger than that of the electrode body 21A according to the reference example. It has become. Thus, in the electrode body 21 according to the embodiment, the length of the negative electrode 30 is maximized within a predetermined product width, and the battery capacity is improved.

  Further, in the electrode body 21A according to the reference example, a 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 back and to be folded back on the folding line 80A with high accuracy. As a method for facilitating the folding, it is 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 width of the welded portion. On the other hand, in the electrode body 21 according to the embodiment, the welded portion 70 is not formed on the folding line 80. Since the unwelded region is not newly set but the gap S set for suppressing manufacturing errors and the like is used, it is not necessary to expand the welded portion. Thereby, a pair of separator 50 becomes easy to return | fold. As a result, the workability of the folding operation of the electrode body 21 is improved, and as a result, the workability of the manufacturing operation of the electrode assembly 20 is improved.

  Further, in the electrode body 21A according to the reference example, as illustrated in FIG. 5, in the one edge portion 51 of the pair of separators 50 in the width direction D2, the portion along the one edge portion 34A of the main body portion 31A in the negative electrode 30A A welded portion 70A is formed. The region where the welded portion 70A is formed is a portion that does not contribute to charging / 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 in the width direction D2 of the pair of separators 50. In the one edge portion 51 of the separator 50 in the width direction D2, a portion overlapping the one edge portion 34 of the main body portion 31 in the negative electrode 30 is opened without forming the welded portion 70. Thereby, the length of the negative electrode 30 is maximized on the one edge portion 51 side in the width direction D2 of the pair of separators 50, and the battery capacity is further improved. Further, in the one edge portion 51 of the pair of separators 50 in the width direction D2, the formation of the welded portion 70 can be omitted for the portion overlapping the one edge portion 34 of the main body portion 31 in the negative electrode 30. As a result, it is possible to suppress deterioration of the welding equipment and reduce power consumption in the welding work.

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

  Further, in the electrode body 21 according to the embodiment, as illustrated 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. Yes. More specifically, the one edge 44 of the main body 41 in the positive electrode 40 is located on the inner side of 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 the negative electrode. 30 is located inside the other edge 35 of the main body 31. Further, the edge 46 in the longitudinal direction D1 of the pair of separators 50 in the main body 41 is located on the inner side of the edge 36 in the longitudinal direction D1 of the pair of separators 50 in the main body 31. Thereby, it is suppressed that lithium (metal component) in electrolyte solution precipitates. This also applies to the electrode body 21A according to the reference example.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention can be modified without departing from the scope described in the claims or applied to other embodiments. 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, the one edge 34 of the main body 31 in the negative electrode 30 may be located inside the one edge 51 of the pair of separators 50 in the width direction D2. In this case, a welded portion 70 may be formed in a portion of the edge 51 of the longitudinal direction D1 in the pair of separators 50 that overlaps the edge 34 of the main body 31 of the negative electrode 30.

  Further, the portion along the one edge 44 of the main body 41 in the positive electrode 40 may be opened without forming the welded portion 70. However, as in the above-described embodiment, when the welded portion 70 is formed in the portion along the one edge portion 44 of the main body 41 in the positive electrode 40, for example, the electrode body 21 in the course of manufacturing or the like is pressed and adhered in the stacking direction. This is preferable from the viewpoint of suppressing the displacement of the positive electrode 40 in the state before the operation.

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

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

Claims (6)

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

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