JP6232213B2 - Secondary battery and manufacturing method thereof - Google Patents

Description

  The present invention relates to a secondary battery and a manufacturing method thereof, and more particularly, to a high-capacity flat wound secondary battery for in-vehicle use and the like and a manufacturing method thereof.

  In recent years, as a power source for electric vehicles and the like, development of a lithium ion secondary battery having a high energy density has been progressing, which includes an electrode group produced by winding a separator between a positive electrode and a negative electrode. ing. Lithium ion secondary batteries have been used for more applications as performance is improved, and there has been a demand for simplification of the manufacturing process and cost reduction.

  As such a lithium ion secondary battery, a secondary battery that can reduce the internal resistance and can be miniaturized has been proposed and put into practical use (for example, see Patent Document 1 below). The secondary battery of patent document 1 is equipped with the electric power generation element group arrange | positioned in the space defined by the battery can and the battery cover. The power generation element group has a positive and negative electrode plate that is wound or laminated and has an uncoated portion of the active material mixture formed on opposite sides, and the uncoated portion of the positive and negative electrode plate penetrates the battery can They are positioned so as to face the hole formation surfaces.

  The secondary battery of Patent Document 1 further includes a connection member that is electrically and mechanically connected to an uncoated portion of the positive and negative electrode plates and is electrically connected to the outside of the battery through a through hole of the battery can. Thereby, the current path from the power generation element group to the outside of the battery is shortened, the internal resistance can be reduced, the inside of the battery can is made compact, and the battery can be downsized.

JP 2010-103027 A

  However, in the conventional technique, when the positive and negative electrode plates are wound to form the power generation element group, there is a problem that the positive and negative electrode plates may be loosened or wound in the winding axis direction. .

  That is, in the secondary battery of Patent Document 1, the elastic force of the positive and negative electrode plates, that is, the spring back, in the curved portion of the wound positive and negative plates such as the corner portion of the power generation element group formed flat. As a result, a force that expands the stacking interval of the positive and negative electrode plates is generated. On the other hand, on the axial center side of the power generation element group, that is, in the vicinity of the winding shaft, a force that reduces the stacking interval of the positive and negative electrode plates is generated by the weight of the positive and negative electrode plates.

  Therefore, until the uncoated portion of the positive and negative electrode plates is joined to the connection member connected to the external terminal by, for example, ultrasonic welding, a deviation in the winding direction occurs between the positive and negative plates, for example. Winding slack may occur in the rotated positive and negative plates. Alternatively, for example, there is a possibility that winding deviation in the winding axis direction may occur due to the influence of vibration during conveyance. The loosening of the winding causes a non-uniform distance between the electrode electrodes and may deteriorate the battery characteristics. Moreover, the winding deviation causes a decrease in the area where the positive electrode and the negative electrode face each other, which may reduce the yield of the secondary battery.

  The present invention has been made in view of the above problems, and the object of the present invention is to prevent winding slack or winding deviation of the wound electrode group and to stabilize characteristics and improve yield. A secondary battery and a manufacturing method thereof are provided.

  In order to achieve the above object, a secondary battery according to the present invention includes a wound electrode group having a metal foil exposed portion in which a metal foil of an electrode is exposed at an end in a winding axis direction, and the wound electrode. A battery can that accommodates the group, a battery lid that seals the opening of the battery can, an external terminal disposed on the battery lid, and the metal foil exposed portion of the wound electrode group that is electrically connected A first battery welded to each other in the stacking direction, the metal foil exposed portion, and the metal foil exposed portion, And a second welded portion that joins the current collector plate.

  According to the secondary battery of the present invention, the metal foils of the electrodes stacked in the metal foil exposed portion of the wound electrode group are joined to each other in the stacking direction by the first welded portion, and the metal foil exposed portion of the wound electrode group Is connected to the current collector plate by the second welded portion, so that winding and loosening of the wound electrode can be prevented, and the characteristics can be stabilized and the yield can be improved.

1 is an external perspective view of a lithium ion secondary battery according to Embodiment 1 of the present invention. The disassembled perspective view of the lithium ion secondary battery shown in FIG. The disassembled perspective view of the electric power generation element assembly shown in FIG. FIG. 3 is an exploded perspective view of the wound electrode group shown in FIG. Sectional view of the power generation element assembly shown in FIG. The top view which shows the other example of the winding electrode group shown in FIG. The disassembled perspective view of the electric power generation element assembly which concerns on Embodiment 2 of this invention. Sectional drawing of the electric power generation element assembly shown in FIG. The perspective view of the winding electrode group which concerns on Embodiment 3 of this invention. Sectional drawing of the electric power generation element assembly which concerns on Embodiment 3 of this invention. Sectional drawing of the electric power generation element assembly which concerns on Embodiment 4 of this invention. FIG. 12 is a plan view illustrating another example of the wound electrode group illustrated in FIG. 11. The flowchart which shows an example of the manufacturing process of the lithium ion secondary battery which concerns on embodiment of this invention.

  Hereinafter, a secondary battery according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is an external perspective view of a lithium ion secondary battery according to Embodiment 1. FIG. FIG. 2 is an exploded perspective view of the lithium ion secondary battery shown in FIG. The lithium ion secondary battery 1 is mainly composed of a battery container 2 and a wound electrode group 3 accommodated in the battery container 2.

  The battery container 2 includes a battery can 11 having an opening 11 a and a battery lid 21 that seals the opening 11 a of the battery can 11. The battery container 2 of this embodiment is formed in a rectangular parallelepiped shape. That is, in the battery container 2, the pair of wide side surfaces PW, the pair of narrow side surfaces PN, the bottom surface PB, and the battery lid 21 constitute a rectangular parallelepiped flat rectangular container. The battery can 11 and the battery lid 21 are made of, for example, an aluminum alloy.

  The battery container 2 accommodates the wound electrode group 3 inside the battery can 11 such that a sheet-like insulating protective film 41 is interposed between the inner surface of the battery can 11 and the wound electrode group 3. The wound electrode group 3 is accommodated by joining the outer edge of the battery lid 21 to the opening portion 11a of 11 by, for example, laser welding.

  The battery lid 21 is provided with a positive electrode terminal 51 and a negative electrode terminal 61 as a pair of electrode terminals via an insulating member (not shown). The positive electrode terminal 51 and the negative electrode terminal 61 are disposed at positions separated from each other in the longitudinal direction of the battery lid 21. Further, the battery lid 21 is opened when the pressure in the battery container 2 rises above a predetermined value, and a gas discharge valve 71 that discharges the gas in the battery container 2 and an electrolyte solution into the battery container 2. The liquid injection port 72 is provided. The liquid injection port 72 is closed by a liquid injection plug 73 after the injection of the electrolytic solution. The battery lid 21, the positive electrode terminal 51, the negative electrode terminal 61, the gas discharge valve 71, and the like constitute the lid assembly 4, and the lid assembly 4 and the wound electrode group 3 constitute the power generation element assembly 5. Yes.

  FIG. 3 is an exploded perspective view of the power generation element assembly 5 shown in FIG. The positive electrode terminal 51 and the negative electrode terminal 61 are external terminals 52 and 62 disposed outside the battery container 2, and current collectors that are electrically connected to the external terminals 52 and 62 and disposed inside the battery container 2. (Connection terminals) 53 and 63. The positive-side external terminal 52 and the current collecting plate 53 are made of an aluminum alloy, and the negative-side external terminal 62 and the current collecting plate 63 are made of a copper alloy. The current collecting plates 53 and 63 and the external terminals 52 and 62 are electrically insulated from the battery lid 21 by interposing an insulating member (not shown) between the current collector plates 53 and 63 and the external terminals 52 and 62.

  The current collecting plates 53 and 63 extend downward from the lower surface of the battery lid 21 serving as the inner surface of the battery container 2 toward the bottom surface PB of the battery can 11. The wound electrode group 3 has metal foil exposed portions 3a and 3b in which the metal foil of the electrode is exposed at the end in the winding axis direction (X-axis direction in the figure). It is joined to the metal foil exposed portions 3 a and 3 b of the rotating electrode group 3. Thereby, the current collecting plates 53 and 63 electrically connect the external terminals 52 and 62 disposed on the battery lid 21 and the metal foil exposed portions 3 a and 3 b of the wound electrode group 3. The joining of the metal foil exposed portions 3a and 3b and the current collector plates 53 and 63 will be described in detail later.

  4 is a developed perspective view of the wound electrode group 3 shown in FIG. The wound electrode group 3 is configured by stacking the separator 35, the negative electrode plate 32, the separator 33, and the positive electrode plate 34 in this order and winding them around the winding core of a winding device that is a winding shaft. That is, the wound electrode group 3 is wound around the winding axis in a state where separators 33 and 35 that are insulators are interposed between the positive electrode plate 34 and the negative electrode plate 32 that are electrodes, and these are overlapped. Thereafter, it has a structure molded into a flat shape.

  In the wound electrode group 3, the separator 35 is wound on the outermost periphery, the negative electrode plate 32 is wound on the inner side, and the separator 33 and the positive electrode plate 34 are wound on the inner side. The separators 33 and 35 electrically insulate the positive electrode plate 34 and the negative electrode plate 32.

  The positive electrode plate 34 that is a positive electrode has a positive electrode metal foil 34b that is a positive electrode current collector, and a positive electrode coating portion 34a that is formed by applying a positive electrode active material mixture on both surfaces of the positive electrode metal foil 34b. ing. A positive electrode uncoated portion where the positive metal foil 34b is exposed is provided at one end in the width direction of the positive electrode plate 34, that is, the winding axis direction (X-axis direction in the drawing).

  The negative electrode plate 32, which is a negative electrode, has a negative electrode metal foil 32b, which is a negative electrode current collector, and a negative electrode coating portion 32a formed by applying a negative electrode active material mixture on both surfaces of the negative electrode metal foil 32b. ing. In the width direction of the negative electrode plate 32, that is, in the winding axis direction, a negative electrode uncoated portion where the negative electrode metal foil 32b is exposed is provided at the end of the positive electrode plate 34 opposite to the uncoated portion.

  In the winding axis direction of the wound electrode group 3, the width of the negative electrode coating portion 32 a of the negative electrode plate 32 is wider than the width of the positive electrode coating portion 34 a of the positive electrode plate 34. Thereby, the positive electrode coating part 34a is comprised so that it may be always pinched | interposed into the negative electrode coating part 32a.

  The positive electrode uncoated portion and the negative electrode uncoated portion are regions where the metal foil 32b of the negative electrode plate 32 and the metal foil 34b of the positive electrode plate 34 are exposed at one end and the other end of the wound electrode group 3 in the winding axis direction. It is. As described above, the uncoated portion of the negative electrode plate 32 and the uncoated portion of the positive electrode plate 34 are arranged at one end and the other end in the winding axis direction, respectively, and wound around the winding axis. Metal foil exposed portions 3a and 3b in which the metal foils 32b and 34b are exposed are formed at one end and the other end of the group 3 in the winding axis direction.

  In the winding axis direction, the widths of the separators 33 and 35 are wider than the width of the negative electrode coating portion 32a. However, the separators 33 and 35 are disposed at positions where the uncoated portions of the negative electrode plate 32 and the positive electrode plate 34 are exposed at one end and the other end in the winding axis direction, respectively. Thereby, the metal foil 32b of the negative electrode plate 32 and the metal foil 34b of the positive electrode plate 34 are exposed without being covered by the separators 33 and 35 at one end and the other end of the wound electrode group 3 in the winding axis direction, Foil exposed portions 3a and 3b are formed.

  As described above, the wound electrode group 3 includes the separator 33, the negative electrode plate 32, the separator 35, and the positive electrode plate 34, which are stacked in this order and wound around the winding axis. It is formed into a flat shape. That is, the wound electrode group 3 is wound into a flat shape having a pair of flat portions 3c and a pair of curved portions 3d. The flat portion 3c is a region where the negative electrode plate 32 and the positive electrode plate 34 are stacked in a substantially flat state. The curved portion 3 d is an area where the negative electrode plate 32 and the positive electrode plate 34 are stacked in a curved state, located on both sides of the flat surface portion 3 c, and includes a corner portion of the wound electrode group 3.

  When the wound electrode group 3 is accommodated in the battery case 2, the pair of flat portions 3 c are opposed to the pair of wide side surfaces PW of the battery can 11, and the upper and lower portions between the battery lid 21 and the bottom surface PB of the battery can 11. It extends in the direction (Y-axis direction in FIG. 3). Of the pair of curved portions 3 d, the upper curved portion 3 d is disposed in the vicinity of the battery lid 21, and the lower curved portion 3 d is disposed in the vicinity of the bottom surface PB of the battery can 11.

  In the secondary battery 1 of the present embodiment, the metal foil 32b of the laminated negative electrode plate 32 is laminated in the lamination direction at the negative electrode side metal foil exposed portion 3a provided at one end of the winding electrode group 3 in the winding axis direction. It has the 1st welding part 32c joined mutually. Further, in the secondary battery 1, the metal foil 34 b of the laminated positive electrode plate 34 is also arranged in the laminating direction at the metal foil exposed part 3 b on the positive electrode side provided at the other end in the winding axis direction of the wound electrode group 3. It has the 1st welding part 34c joined mutually. Here, the stacking direction is a direction in which the negative electrode plate 32 and the positive electrode plate 34 wound around the winding axis are stacked in a cross section perpendicular to the winding axis direction, in other words, the negative electrode plate 32 and the positive electrode plate 34. This is the thickness direction.

  The first welded portion 32c on the negative electrode side is formed by, for example, resistance welding or ultrasonic welding of the metal foil 32b of the negative electrode plate 32 wound and laminated in the exposed metal foil exposed portion 3a on the negative electrode side of the wound electrode group 3. It is the part which was welded by and integrated in the thickness direction. Similarly, the first welded portion 34c on the positive electrode side is the metal foil exposed portion 3b on the positive electrode side of the wound electrode group 3, and the metal foil 34b of the stacked positive electrode plate 34 is formed by, for example, resistance welding or ultrasonic welding. It is a part welded and integrated in the thickness direction.

  FIG. 5 is a schematic cross-sectional view of the power generation element assembly 5 as viewed from the A direction of FIG. 3, that is, the winding axis direction of the wound electrode group 3. The first welded portion 32c bundles the metal foils 32b of the negative electrode plate 32 laminated at the metal foil exposed portion 3a on the negative electrode side of the wound electrode group 3 together in the laminating direction to bundle them together. Yes. Note that the secondary battery 1 has the same configuration as that of the metal foil exposed portion 3 a on the negative electrode side shown in FIG. 5 in the metal foil exposed portion 3 b on the positive electrode side of the wound electrode group 3. That is, the first welded portion 34c is formed by joining together the metal foils 34b of the positive electrode plate 34 laminated in the metal foil exposed portion 3b on the positive electrode side of the wound electrode group 3 in the thickness direction and bundling them together. Yes.

  Further, in the secondary battery 1 of the present embodiment, the metal foil exposed portions 3a and 3b of the wound electrode group 3 and the current collector plates 63 and 53 are joined, and the second welded portion 32d that electrically connects them. , 34d. The second welded portion 32d on the negative electrode side is composed of a metal foil 32b of the negative electrode plate 32 laminated at the metal foil exposed portion 3a on the negative electrode side of the wound electrode group 3, and a current plate 64 and a current collecting plate 63 made of a copper alloy. And are integrally joined by, for example, ultrasonic welding. The second welded portion 34d on the positive electrode side is composed of a metal plate 34b of the positive electrode plate 34 laminated on the metal foil exposed portion 3b on the positive electrode side of the wound electrode group 3, and a current plate 54 and a current collecting plate 53 made of an aluminum alloy. And are integrally joined by, for example, ultrasonic welding.

  In the present embodiment, the first welded portions 32 c and 34 c and the second welded portions 32 d and 34 d are provided on the flat surface portion 3 c of the wound electrode group 3.

  Moreover, in this embodiment, the 1st welding parts 32c and 34c are formed by resistance welding, and the 2nd welding parts 32d and 34d are formed by ultrasonic welding. And the area of the 2nd welding parts 32d and 34d is larger than the area of the 1st welding parts 32c and 34c. Here, the areas of the first welded portions 32 c and 34 c are areas of individual welding spots in a plan view of the flat surface portion 3 c of the wound electrode group 3. The area of the second welded portions 32d and 34d is a current collector plate that is joined to the metal foil exposed portions 3a and 3b of the wound electrode group 3 in a plan view of the flat portion 3c of the wound electrode group 3. This means the area of the regions 63 and 53.

  Moreover, in this embodiment, the 1st welding parts 32c and 34c are formed so that it may overlap with the 2nd welding parts 32d and 34d.

  In addition, you may form the 1st welding parts 32c and 34c by ultrasonic welding similarly to the 2nd welding parts 32d and 34d. Moreover, you may make it a part of 1st welding parts 32c and 34c overlap with the 2nd welding parts 32d and 34d. An example of this is shown in FIG.

  FIG. 6 is a schematic plan view of the wound electrode group 3 and shows a relationship between the first welded portions 32c and 34c and the second welded portions 32d and 34d in a plan view of the plane portion 3c. In FIG. 6, the components other than the wound electrode group 3 and the current collecting plates 53 and 63 are not shown. In the figure, the regions indicated by the broken-line hatching rising to the right are the first welded portions 32c and 34c, and the regions indicated by the dotted-line hatching falling to the right are the second welded portions 32d and 34d.

  In the example shown in FIG. 6, the first welded portions 32c and 34c partially overlap the second welded portions 32d and 34d. However, also in this example, the first welded portions 32c and 34c and the second welded portions 32d and 34d may be completely overlapped or may be adjacent so that the outer edges are in contact with each other. When a part of the first welds 32c and 34c overlaps with the second welds 32d and 34d, for example, the area of 50% or more and 100% or less of the area of the first welds 32c and 34c is You may make it overlap with the 2nd welding parts 32d and 34d.

  Further, as in the example shown in FIG. 6, the area of the second welded portions 32 d and 34 d is equal to the area of the first welded portions 32 c and 34 c in the plan view of the planar portion 3 c of the wound electrode group 3. It may be formed as follows. In the example shown in FIG. 6, the first welds 32c and 34c are also formed by ultrasonic welding in the same manner as the second welds 32d and 34d. Here, the areas of the first welded portions 32c and 34c are the areas of individual regions where the metal foils 32b and 34b are joined to each other in the stacking direction, that is, the plane portions of the wound electrode group 3 shown in FIG. In the plan view of 3c, it means the area of each region indicated by dashed hatching. Similarly, in FIG. 6, the areas of the second welds 32 d and 34 d mean the areas of individual regions indicated by dotted hatching.

  In the wound electrode group 3, the metal foil exposed portions 3a and 3b are supported and fixed to the current collecting plates 63 and 53 of the lid assembly 4 shown in FIG. 3 by the second welded portions 32d and 34d. Thus, the power generation element assembly 5 is configured together with the lid assembly 4.

  Next, the effect | action of the secondary battery 1 of this embodiment is demonstrated. In the wound electrode group 3 included in the secondary battery 1 of the present embodiment, the negative electrode plate 32 and the positive electrode plate 34 are wound around the winding axis, and the negative electrode plate 32 and the positive electrode plate 34 in the curved portion 3d including the corner portion. Is curved. Therefore, in the bending portion 3d, a force that expands the stacking interval between the negative electrode plate 32 and the positive electrode plate 34 is generated by the elastic force of the negative electrode plate 32 and the positive electrode plate 34, that is, the spring back. On the other hand, on the axial center side of the wound electrode group 3, that is, a portion close to the wound axis, a force that reduces the stacking interval between the negative electrode plate 32 and the positive electrode plate 34 is generated by the dead weight of the negative electrode plate 32 and the positive electrode plate 34. To do.

  Therefore, for example, as described in Patent Document 1, in the conventional secondary battery having the wound positive and negative plates, the uncoated portion of the positive and negative plates is connected to the connection member connected to the external terminal. For example, there is a possibility that a deviation in the winding direction occurs between the positive and negative electrode plates before joining by ultrasonic welding, and winding and slackening may occur in the wound positive and negative electrode plates. Alternatively, for example, there is a risk that winding of the wound positive and negative electrode plates in the winding axis direction may occur due to vibration during transportation.

  The loosening of the winding may cause an event that the wound positive and negative plates are lifted in the stacking direction, causing a non-uniform distance between the electrode electrodes and degrading battery characteristics. In addition, the above-described winding deviation causes, for example, an event that the wound positive and negative plates are unwound in a spiral shape or a bamboo shoot shape, which causes a reduction in the area where the positive electrode and the negative electrode face each other, and the secondary There is a concern of lowering the yield of the battery.

  On the other hand, the lithium ion secondary battery 1 of the present embodiment includes the negative electrode plate 32 and the metal foil 32b of the positive electrode plate 34 that are stacked on the metal foil exposed portions 3a and 3b of the wound electrode group 3 as described above. It has the 1st welding parts 32c and 34c which join 34b mutually in the lamination direction. Therefore, even if a force that increases the stacking interval between the negative electrode plate 32 and the positive electrode plate 34 is generated as described above, the stacking interval is maintained by the first welded portions 32c and 34c, thereby preventing the stacking interval from increasing. be able to.

  Thereby, for example, the negative electrode plate 32 and the positive electrode plate 34 are prevented from being displaced in the winding direction until the metal foil exposed portions 3a and 3b of the wound electrode group 3 are joined to the current collector plates 63 and 53. In addition, it is possible to prevent the winding slack and winding deviation. Therefore, the distance between the electrode electrodes of the wound electrode group 3 can be kept uniform, and the battery characteristics can be improved as compared with the conventional case. Moreover, the area where the negative electrode plate 32 and the positive electrode plate 34 face each other can be maintained, and the yield of the secondary battery can be improved as compared with the conventional case.

  Further, in the secondary battery 1 of the present embodiment, the wound electrode group 3 is wound into a flat shape having a pair of flat portions 3c, and the first welded portions 32c and 34c and the second welded portions 32d and 34d are Are provided on the flat surface portion 3c. Thereby, welding becomes easier than the case where the first welded portions 32c and 34c and the second welded portions 32d and 34d are provided in the curved portion 3d, and the productivity is improved and the reliability of welding is improved. .

  Further, in the secondary battery 1 of the present embodiment, at least a part of the first welded portions 32c and 34c and the second welded portions 32d and 34d is a plan view of the planar portion 3c of the wound electrode group 3. It is provided so that it may overlap. Thereby, compared with the case where the 1st welding parts 32c and 34c and the 2nd welding parts 32d and 34d do not overlap, the current collection plates 63 and 53 and the winding electrode by the 2nd welding parts 32d and 34d Bonding with the metal foil exposed portions 3a and 3b of the group 3 is easier and more reliable.

  Further, by overlapping the first welded portions 32c and 34c and the second welded portions 32d and 34d, for example, even when the height of the wound electrode group 3 is reduced and the area of the plane portion 3c is reduced. The welding area of each of the first welds 32c and 34c and the second welds 32d and 34d can be ensured. Therefore, a desired effect can be obtained without being restricted by the dimensions of the wound electrode group 3.

  Further, in the secondary battery 1 of the present embodiment, the area of the second welded portions 32d and 34d is greater than or equal to the area of the first welded portions 32c and 34c in a plan view of the flat portion 3c of the wound electrode group 3. It is an area. Thereby, joining with respect to the current collector plates 63 and 53 of the metal foil exposure parts 3a and 3b of the wound electrode group 3 can be made more reliable. In addition, when the second welded portions 32d and 34d are formed so as to overlap at least a part of the first welded portions 32c and 34c after the first welded portions 32c and 34c are formed, the second welded portion 32d is formed. , 34d are formed so as not to overlap with the first welds 32c, 34c. Thereby, damage to the metal foils 32b and 34b can be prevented, and the current collector plates 63 and 53 and the metal foil exposed portions 3a and 3b of the wound electrode group 3 can be more easily and reliably joined.

(Embodiment 2)
Next, a secondary battery according to another embodiment of the present invention will be described with reference to FIGS. 7 and 8 with reference to FIGS. FIG. 7 is an exploded perspective view of the power generation element assembly 5A of the lithium ion secondary battery according to the present embodiment. FIG. 8 is a schematic cross-sectional view of the power generation element assembly 5A viewed from the direction A shown in FIG.

  The lithium ion secondary battery of the present embodiment is different from the lithium ion secondary battery 1 of the first embodiment in the configuration of the power generation element assembly 5A. Specifically, the power generation element assembly 5A of the present embodiment is different from the power generation element assembly 5 of the first embodiment in that the first welding portions 32c and 34c and the second welding portions 32d and 34d do not overlap. Is different. The power generation element assembly 5A of the present embodiment is different from the power generation element assembly of Embodiment 1 in the configuration of the wound electrode group 3A. Specifically, the wound electrode group 3A of the present embodiment is different from the wound electrode group 3 of the secondary battery 1 of the first embodiment in that a plurality of first welds 32c and 34c are provided. ing. Since the other points of the lithium ion secondary battery of the present embodiment are the same as those of the lithium ion secondary battery 1 of the first embodiment, the same parts are denoted by the same reference numerals and description thereof is omitted.

  The wound electrode group 3A is provided with a plurality of first welds 32c and 34c, respectively, in the vertical direction (Y-axis direction in the figure) of the flat surface part 3c. Thereby, the laminated negative electrode plate 32 and positive electrode plate 34 can be more reliably held, and the winding slack and winding deviation can be more effectively prevented. Therefore, the distance between the electrode electrodes of the wound electrode group 3A can be kept uniform, and the battery characteristics can be improved as compared with the conventional case. Moreover, the area where the negative electrode plate 32 and the positive electrode plate 34 face each other can be maintained, and the yield of the secondary battery can be improved as compared with the conventional case.

  Further, in the power generation element assembly 5A of the present embodiment, the first welded portions 32c and 34c and the second welded portions 32d and 34d are provided so as not to overlap each other. That is, the first welded portions 32c and 34c and the second welded portions 32d and 34d are provided so as to be separated from each other in a plan view of the planar portion 3c of the wound electrode group 3A. Thereby, even if it is a case where the 1st welding parts 32c and 34c and the 2nd welding parts 32d and 34d are formed, the negative electrode plate 32 and the positive electrode plate 34 in the metal foil exposure parts 3a and 3b of the wound electrode group 3A. It can be avoided that the metal foils 32b and 34b are double-welded. Therefore, even when a material having a relatively low strength is used for the metal foils 32b and 34b of the negative electrode plate 32 and the positive electrode plate 34, the metal foils 32b and 34b can be prevented from being damaged. In other words, the negative electrode plate 32 and the positive electrode plate 34 can be formed by using thinner metal foils 32b and 34b, and the winding amount of the negative electrode plate 32 and the positive electrode plate 34 is increased to increase the capacity of the secondary battery. Can be made. Therefore, the battery characteristics of the secondary battery can be improved and the yield can be improved.

(Embodiment 3)
Next, a secondary battery according to another embodiment of the present invention will be described with reference to FIGS. 9 and 10 with reference to FIGS. FIG. 9 is a perspective view of the wound electrode group 3B of the lithium ion secondary battery according to the present embodiment. FIG. 10 is a schematic cross-sectional view of the power generation element assembly 5B of the lithium ion secondary battery according to the present embodiment when the wound electrode group 3B shown in FIG. 9 is viewed from the A direction.

  The lithium ion secondary battery of this embodiment differs from the lithium ion secondary battery 1 of Embodiment 1 in the configuration of the lid assembly 4B. More specifically, as shown in FIG. 10, the lid assembly 4B of the present embodiment includes a pair of current collector plates 63A facing each other so as to sandwich the metal foil exposed portion 3a on the negative electrode side of the wound electrode group 3B. 63B and a pair of current collector plates 53A and 53B facing each other so as to sandwich the metal foil exposed portion 3b on the positive electrode side. The current collector plates 63A and 63B on the negative electrode side have the same configuration as that of the current collector plate 63 of the first embodiment, and are electrically connected to the external terminal 62. The current collector plates 53 </ b> A and 53 </ b> B on the positive electrode side have the same configuration as that of the current collector plate 53 of Embodiment 1 and are electrically connected to the external terminal 52.

  Further, the lithium ion secondary battery of the present embodiment is different from the lithium ion secondary battery 1 of the first embodiment in the configuration of the wound electrode group 3B. More specifically, as shown in FIG. 9, in the wound electrode group 3B of the present embodiment, the metal foils 32b and 34b are respectively wound around the winding axis in the metal foil exposed portions 3a and 3b on the negative electrode side and the positive electrode side. It is divided and bundled in two in the thickness direction across the hollow part along. And it has the 1st welding parts 32c and 34c in each part bundled by the negative electrode side and the positive electrode side. In addition, each portion of the metal foil 32b that is divided and bundled into two on the negative electrode side is sandwiched between the abutting plates 64A and 64B and the current collecting plates 63A and 63B similar to the abutting plate 64 of the first embodiment, respectively. For example, they are integrally joined by ultrasonic welding. Similarly, each portion of the metal foil 34b that is divided and bundled in two on the positive electrode side is sandwiched between the same plates 54A and 54B and the current collector plates 53A and 53B, respectively, similar to the plate 54 of the first embodiment. For example, they are integrally joined by ultrasonic welding. Since the other points are the same as those of the first embodiment, the same parts are denoted by the same reference numerals and description thereof is omitted.

  In the present embodiment, as described above, the metal foils 32b and 34b are divided into two pieces and bundled in the metal foil exposed portions 3a and 3b on the negative electrode side and the positive electrode side of the wound electrode group 3B. Welding portions 32c and 34b. Therefore, the negative electrode plate 32 and the positive electrode plate 34 are held by the first welded portions 32c and 34b in each portion where the metal foils 32b and 34b are bundled. Thereby, the laminated negative electrode plate 32 and positive electrode plate 34 can be more reliably held, and the winding slack and winding deviation can be more effectively prevented.

  Therefore, the distance between the electrode electrodes of the wound electrode group 3B can be kept uniform, and the battery characteristics can be improved as compared with the conventional case. Moreover, the area where the negative electrode plate 32 and the positive electrode plate 34 face each other can be maintained, and the yield of the secondary battery can be improved as compared with the conventional case. In addition, according to the present embodiment, even in a large-sized lithium ion battery in which the metal foils 32b and 34b need to be collected and collected in the metal foil exposed portions 3a and 3b of the wound electrode group 3B, the above-described effect is obtained. Can be effectively obtained.

  In the present embodiment, the first welded portions 32c and 34c are formed on both of the divided portions of the metal foil exposed portions 3a and 3b of the wound electrode group 3B. Alternatively, the first welds 32c and 34c may be provided on one of them.

(Embodiment 4)
Next, a secondary battery according to another embodiment of the present invention will be described with reference to FIGS. FIG. 11 is a schematic cross-sectional view of the power generation element assembly 5C of the lithium ion secondary battery according to the present embodiment.

  The lithium ion secondary battery of this embodiment differs from the lithium ion secondary battery 1 of Embodiment 1 in the configuration of the power generation element assembly 5C. More specifically, the power generating element assembly 5C of the present embodiment is different from the wound electrode group 3 and the lid assembly 4 of the first embodiment in the configuration of the wound electrode group 3C and the lid assembly 4C.

  Specifically, the cover assembly 4C has a length that the current collector plate 63 extends from the lower surface of the battery lid 21 toward the bottom surface PB of the battery can 11 as compared with the cover assembly 4 of the first embodiment. The lower ends 63a and 53a of the current collector plates 63 and 53 are positioned near or above the middle portion in the vertical direction of the flat surface portion 3c of the wound electrode group 3C.

  The first welds 32 c and 34 c of the wound electrode group 3 are provided below the lower ends 63 a and 53 a of the current collector plates 63 and 53. As a result, the second welded portions 32d and 34d are positioned so as not to overlap the first welded portions 32c and 34c in the plan view of the flat surface portion 3c of the wound electrode group 3C. They are spaced apart. Since the other structure of the lithium ion battery of this embodiment is the same as the structure of the lithium ion secondary battery 1 of Embodiment 1, the same code | symbol is attached | subjected to the same part and description is abbreviate | omitted.

  According to the lithium ion secondary battery of the present embodiment, the same effects as those of the first embodiment can be obtained by forming the first welds 32c and 34c. Further, since the first welded portions 32c and 34c are provided below the lower ends of the current collector plates 63 and 53 and are provided apart from the second welded portions 32d and 34d, the same effects as in the second embodiment are provided. Can be obtained.

  Furthermore, since the current collector plates 63 and 53 of the lithium ion secondary battery of this embodiment are shorter than the lithium ion secondary battery 1 of Embodiment 1, it is easy to insert the power generation element assembly 5C into the battery can 11. can do.

  Further, in the so-called teardrop type in which the current collector plates 63 and 53 are short, the lower end of the wound electrode group 3C is likely to swell after the charging / discharging of the lithium ion secondary battery, so that winding slack is likely to occur. However, according to the lithium ion secondary battery of the present embodiment, the first welds 32c and 34c are provided below the lower ends of the current collector plates 63 and 53, so that the lower end of the wound electrode group 3C is wound. It becomes possible to prevent loosening effectively.

  In the example shown in FIG. 11, the first welds 32c and 34c are formed by resistance welding, and the second welds 32d and 34d are formed by ultrasonic welding. However, the first welds 32c and 34c may be formed by ultrasonic welding. An example of this is shown in FIG.

  FIG. 12 is a schematic plan view of the wound electrode group 3C of the present embodiment. In FIG. 12, the components other than the wound electrode group 3 </ b> C and the current collecting plates 53 and 63 are not shown. As shown in FIG. 12, when the first welds 32c and 34c are formed by ultrasonic welding, the areas of the first welds 32c and 34c are equal to the areas of the second welds 32d and 34d. Area.

(Method for manufacturing secondary battery)
Next, a method for manufacturing the lithium ion secondary battery 1 described in the first embodiment will be described. FIG. 13 is a flowchart showing an example of a manufacturing process of a lithium ion secondary battery.

First, as a preparation stage, the negative electrode plate 32 and the positive electrode plate 34 are manufactured. Regarding the negative electrode plate 32, 10 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) is added as a binder to 100 parts by weight of amorphous carbon powder as a negative electrode active material, and N as a dispersion solvent. -A negative electrode mixture in which methylpyrrolidone (hereinafter referred to as NMP) is added and kneaded is prepared. This negative electrode mixture is applied on both sides of a 10 μm thick copper foil (negative electrode electrode foil) leaving a current collecting portion (negative electrode uncoated portion). Thereafter, drying, pressing, and cutting are performed to obtain a negative electrode plate 32 having a negative electrode active material application portion that does not include a copper foil and has a thickness of 70 μm. The case where amorphous carbon is used as the negative electrode active material is exemplified, but the present invention is not limited to this, and natural graphite capable of inserting and removing lithium ions, various artificial graphite materials, carbon such as coke, etc. It may be a porous material, a compound such as Si or Sn (for example, SiO, TiSi ₂ or the like), or a composite material thereof, and the particle shape is not particularly limited, such as a scale shape, a spherical shape, a fibrous shape, or a massive shape. .

Regarding the positive electrode plate 34, 10 parts by weight of flaky graphite as a conductive material and 10 parts by weight of PVDF as a binder are added to 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) as a positive electrode active material. Then, a positive electrode mixture in which NMP is added and kneaded as a dispersion solvent is prepared. This positive electrode mixture is applied on both surfaces of an aluminum foil (positive electrode foil) having a thickness of 20 μm, leaving a solid current collecting part (positive electrode uncoated part). Thereafter, drying, pressing, and cutting are performed to obtain a positive electrode plate 34 having a positive electrode active material application portion that does not include an aluminum foil and has a thickness of, for example, 90 μm. Illustrated when lithium manganate is used as the positive electrode active material, but other lithium manganate having a spinel crystal structure, lithium manganese composite oxide partially substituted or doped with a metal element, and cobalt acid having a layered crystal structure Lithium, lithium titanate, or a lithium-metal composite oxide obtained by substituting or doping a part thereof with a metal element may be used. Moreover, although the case where PVDF was used as a binder of the coating part in the positive electrode plate 34 and the negative electrode plate 32 was illustrated, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene butadiene rubber, Polymers such as polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and acrylic resins, and mixtures thereof can be used.

  Next, as a first step, the separator 35, the negative electrode plate 32, the separator 33, and the positive electrode plate 34 are stacked in this order and wound by flatly winding around the winding core of a winding device that is a winding shaft. The electrode group 3 is produced. Next, the negative electrode plate 32 and the metal foils 32b and 34b of the positive electrode plate 34 laminated by the metal foil exposed portions 3a and 3b of the wound electrode group 3 are converged and joined together in the thickness direction by, for example, resistance welding. First welds 32c and 34c are formed.

  Next, as a second step, the positive electrode terminal 51 and the negative electrode terminal 61 are attached to the battery lid 21 via an insulating member, and the lid assembly 4 is produced. After that, the metal foil exposed portions 3a and 3b of the wound electrode group 3 are joined to the current collecting plate 63 of the negative electrode terminal 61 and the current collecting plate 53 of the positive electrode terminal 51 of the lid assembly 4 by, for example, ultrasonic welding, and are conducted. By connecting, the second welds 32d and 34d are formed, and the power generation element assembly 5 is produced.

  Next, as a third step, the power generation element assembly 5 in which the wound electrode group 3 and the lid assembly 4 are integrated is assembled into a battery can with an insulating protective film 41 interposed between the inner surface of the battery can 11. 11 is inserted. Thereafter, the battery lid 21 is joined to the opening 11a of the battery can 11 by laser welding. Then, the lithium ion secondary battery 1 is manufactured by injecting an electrolytic solution from the injection port 72, sealing the injection plug 73 and the injection port 72 by welding with a laser, and charging with external generated power. To do.

  According to the method for manufacturing the lithium ion secondary battery 1, the metal foils 32 b and 34 b of the negative electrode plate 32 and the positive electrode plate 34 laminated on the metal foil exposed portions 3 a and 3 b of the wound electrode group 3 as described above. First welds 32c and 34c that are joined to each other in the stacking direction are formed. Therefore, even if a force that increases the stacking interval between the negative electrode plate 32 and the positive electrode plate 34 is generated as described above, the stacking interval is maintained by the first welded portions 32c and 34c, thereby preventing the stacking interval from increasing. be able to.

  Thereby, for example, the negative electrode plate 32 and the positive electrode plate 34 are prevented from being displaced in the winding direction until the metal foil exposed portions 3a and 3b of the wound electrode group 3 are joined to the current collector plates 63 and 53. In addition, it is possible to prevent the winding slack and winding deviation. Therefore, the distance between the electrode electrodes of the wound electrode group 3 can be kept uniform, and the battery characteristics can be improved as compared with the conventional case. Moreover, the area where the negative electrode plate 32 and the positive electrode plate 34 face each other can be maintained, and the yield of the secondary battery can be improved as compared with the conventional case.

  As described above, according to the lithium ion secondary battery 1 and the manufacturing method thereof according to the above-described embodiment, winding and loosening of the wound negative electrode plate 32 and positive electrode plate 34 are prevented, and the characteristics are stabilized. In addition, the yield can be improved.

  In addition, this invention is not limited to the above-mentioned embodiment, Various modifications are included. The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

  For example, in the above-described embodiment, the case where the wound electrode group has the left and right flat portions opposed to the pair of wide side surfaces of the battery can has been described, but the battery lid and the bottom surface of the battery can are arranged above and below the wound electrode group. You may further have a pair of plane part which opposes. In this case, a curved portion including a corner portion is formed between the left and right plane portions and the upper and lower plane portions of the wound electrode group.

  In the above-described embodiment, the case where the first welded portion and the second welded portion are provided on the flat surface portion of the wound electrode group has been described. However, at least the first welded portion and the second welded portion are described. One may be provided in addition to the plane portion of the wound electrode group. For example, at least one of the first welded portion and the second welded portion may be provided on the curved portion of the wound electrode group.

  In the above-described embodiment, the configuration in which only the first welded portion is provided in the vertical direction of the planar portion has been described. However, even if only the second welded portion is provided in the vertical direction of the planar portion. In addition, both the first welded portion and the second welded portion may be provided in the vertical direction of the plane portion.

DESCRIPTION OF SYMBOLS 1 Secondary battery 3, 3A, 3B, 3C Winding electrode group 3a, 3b Metal foil exposure part 3c Plane part 11 Battery can 11a Opening part 21 Battery cover 32 Negative electrode plate (electrode)
34 Positive electrode (electrode)
32b, 34b Metal foils 32c, 34c First welded portions 32d, 34d Second welded portions 52, 62 External terminals 53, 53A, 63, 63A Current collector plate 63a Lower end PB Bottom surface

Claims (4)

A wound electrode group having a metal foil exposed portion in which the metal foil of the electrode is exposed at an end in the winding axis direction, a battery can that accommodates the wound electrode group, and a battery that seals the opening of the battery can A secondary battery comprising: a lid; and a current collector that electrically connects an external terminal disposed on the battery lid and the metal foil exposed portion of the wound electrode group;
A first weld formed by joining the metal foil of the electrode laminated at the exposed portion of the metal foil in the lamination direction;
A second weld portion formed by the the collector plate and the said metal foil exposed portion first weld is formed is bonded by ultrasonic welding,
Have
The wound electrode group is wound into a flat shape having at least a pair of flat portions,
The first welded portion and the second welded portion are provided on the planar portion,
In a plan view of the flat portion, the area of the second welded portion is an area equal to or larger than the area of the first welded portion,
The secondary battery, wherein at least a part of the first welded portion and the second welded portion overlap in a plan view of the flat portion.   2. The secondary battery according to claim 1, wherein the first welded portion overlaps with the second welded portion in a plan view of the flat portion. The flat portion extends in a vertical direction between the battery lid and the bottom surface of the battery can,
At least one of the first welded portion and the second welded portion is provided with a plurality in the vertical direction of the planar portion,
The secondary battery according to claim 1. A wound electrode group having a metal foil exposed portion in which the metal foil of the electrode is exposed at an end in the winding axis direction, a battery can that accommodates the wound electrode group, and a battery that seals the opening of the battery can A method for producing a secondary battery comprising: a lid; and a current collector plate that electrically connects an external terminal disposed on the battery lid and the metal foil exposed portion of the electrode group,
Winding the electrode around the winding axis to obtain the wound electrode group wound in a flat shape having at least a pair of flat portions; and
Joining the metal foils of the electrodes laminated in the metal foil exposed portion of the planar portion of the wound electrode group to each other in the thickness direction, and forming a first welded portion;
The metal foil exposed portion of the planar portion of the wound electrode group and the current collector plate of the battery lid are joined by ultrasonic welding in an area equal to or greater than the area of the first welded portion, and at least a part of the Forming a second weld so as to overlap the first weld;
Accommodating the wound electrode group having the first welded portion and the second welded portion in the battery can;
Bonding the battery lid to the opening of the battery can and sealing the battery can;
A method for producing a secondary battery, comprising:

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