JP2003346772A - Assembly type secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an assembly type secondary battery that can develop enough capacity at charge and discharge. <P>SOLUTION: When discharge reaction is carried out in the assembly type secondary battery 10, since the adjoining unit cells 40, 40 are electrically connected by the current collector coupling part 70, the electric current flows from the positive electrode side lead 46 of one unit cell 40 to the negative electrode side lead 47 of the other unit cell 40 through the current collector coupling part 70. At that time, the electric resistance, between each of the upper part, middle part, and lower part of the positive electrode side lead 46, and the current collector coupling part 70 through each of current collector elements 51, 52, and 53 of the positive electrode side current collector 50, is nearly equal, and the electric resistance between each of the upper part, middle part, and lower part of the negative electrode side lead 47 and the current collector coupling part 70 through each of current collector elements 61, 62, and 63 of the negative electrode side current collector 60 is also nearly equal. Thereby, the electric current flowing in the group of electrodes 45 becomes nearly uniform regardless of the upper part, middle part, and lower part, and the whole of the group of electrodes 45 can develop charge and discharge capacity nearly uniformly. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an assembled secondary battery.

[0002]

2. Description of the Related Art Conventionally, as a collective type secondary battery, a unit cell comprising an electrode group formed by laminating a structure in which a separator is sandwiched between a positive electrode plate and a negative electrode plate, and an alkaline electrolyte immersed in the electrode group. Are connected in series. For example, Japanese Patent Application Laid-Open No. 2001-93503 proposes an assembled secondary battery 100 as shown in FIG. In this assembled secondary battery 100, the inside of the case 110 is
The cells 140 are housed in each of a plurality of battery cases 123, 123,... Formed by partitioning by the cells 22, 122,..., And these cells 140, 140,. Each cell 140 has an electrode group 145 formed by stacking a structure in which a separator 143 is sandwiched between a positive electrode plate 141 and a negative electrode plate 142. In this assembled secondary battery 100, one of the unit cells 1 of the adjacent unit cells is
A current collector plate 150 is attached to an end surface of a positive electrode plate formed by aligning the ends of a plurality of positive electrode plates 141 included in the negative electrode plate 40, and an end surface of a negative electrode plate formed by aligning the ends of a plurality of negative electrode plates 142 included in another unit cell 140. A current collecting plate 160 is attached to the power supply.
Then, the protrusion formed on the upper part of the current collector plate 150 on the positive electrode side and the protrusion formed on the upper part of the current collector plate 160 on the negative electrode side,
They are connected so as to be conductive through a through hole formed in the upper part of the partition wall 122 to form a series connection portion 170. In this assembled secondary battery 100, the current collector 150 on the positive electrode side is in a state of contact from top to bottom of the positive electrode plate end surface, and the current collector plate 160 on the negative electrode side is in contact from top to bottom of the negative electrode plate end surface. Therefore, the current flowing through the electrode plate group 145 flows from the entire surface of each positive electrode plate 141 to the entire surface of each negative electrode plate 142 via the current collector 150 on the positive electrode side, the series connection point 170 and the current collector 160 on the negative electrode side. .

[0003]

However, the positive electrode plate 141 and the negative electrode plate 14
2, a large amount of current flows at a portion where the distance from the series connection point 170 is short, that is, at the upper part of the positive electrode plate 141 and the negative electrode plate 142 because the electric resistance is small, but the distance from the series connection point 170 is long Location, ie positive electrode plate 14
1 and a lower portion of the negative electrode plate 142, the electric resistance is large, so that only a small current flows. Here, the outlined arrows in FIG. 6 indicate the flow of current, and the width of the arrows indicates the amount of current.
When the distribution of the current flowing through the electrode group 145 becomes non-uniform, the entire electrode group 145 does not exhibit uniform charge / discharge capability, and cannot sufficiently exhibit the capability during charge / discharge. Note that Japanese Patent Application Laid-Open
JP-A-2001-325938 proposes a structure in which a current collector plate on the positive electrode side and a current collector plate on the negative electrode side are vertically divided into three. In this case, too, the distance from each divided current collector plate to the series connection point is increased. Accordingly, the distribution of current flowing through the electrode plate group becomes non-uniform, so that the capacity cannot be sufficiently exhibited during charge and discharge.

[0004] The present invention has been made in view of such problems, and has as its object to provide a collective secondary battery capable of sufficiently exhibiting its ability during charge and discharge.

[0005]

Means for Solving the Problems and Their Functions and Effects The present invention employs the following means to achieve the above object. That is, the present invention is an assembled secondary battery in which cells having an electrode group formed by laminating a plurality of positive electrodes and negative electrodes are connected in series, and ends of the plurality of positive electrodes included in the cells are provided. The end faces of the positive electrode plate in which the parts are aligned, the end faces of the negative electrode plate in which the ends of the plurality of negative electrodes included in the unit cell are aligned, and the plurality of locations of the end faces of the positive electrode plate and the connection points in series connection are electrically connected. A positive electrode-side current collector; and a negative electrode-side current collector that electrically connects a plurality of points on the negative electrode plate end face and a connection point in series connection, wherein the positive electrode-side current collector includes a plurality of points on the positive electrode plate end face. And the electrical resistance from each of the above to the connection point in the series connection is substantially the same, and the negative electrode current collector has substantially the same electrical resistance from each of the plurality of points on the end face of the negative electrode plate to the connection point in the series connection. It is.

[0006] In this assembled secondary battery, when the end face of the positive electrode plate is viewed from the connection point in the series connection as a base point, even if it is a part where the distance to the end face of the positive electrode plate is short or long, the electric resistance is high. Are substantially the same, so the flowing current is also substantially the same. In addition, when the end face of the negative electrode plate is viewed from the connection point in the series connection as a base point, the current flowing since the electric resistance is substantially the same even in a part where the distance to the negative electrode plate end face is short or in a long distance part is also large. It is almost the same. Therefore, the distribution of the current flowing through the electrode group during charging and discharging becomes substantially uniform, and the entire electrode group exhibits substantially uniform performance, and exhibits sufficient performance during charging and discharging.

Here, "connection points in series connection"
Means a place where adjacent cells are connected in series,
In addition to this, it may include a portion for connecting the external connection terminal and the cell. Further, in order to make the electric resistances substantially the same, for example, values of parameters relating to electric resistance such as length, cross-sectional area, and resistivity may be appropriately adjusted.

In the assembled secondary battery of the present invention, the positive electrode-side current collector or the negative electrode-side current collector is branched at its tip to form a plurality of branch ends, and the plurality of branch ends are formed at the positive electrode plate end face or The negative electrode plate may be joined to each of a plurality of locations on the end face, and a base end may form a connection location in the series connection. In this case, the positive electrode side current collector and the negative electrode side current collector can be relatively easily manufactured.

In the assembled secondary battery according to the present invention, the positive electrode-side current collector or the negative electrode-side current collector is bonded to different portions along the longitudinal direction of the positive electrode plate end surface or the negative electrode plate end surface. Is also good. In this case, when the end face of the positive electrode plate is viewed from the connection point in the series connection as a base point, the difference between the part where the distance to the end face of the positive electrode plate is short and the long part is relatively large, and the same applies to the end face of the negative electrode plate. The significance of applying the present invention is great. For example, the positive electrode-side current collector or the negative electrode-side current collector may be joined to two different places along the longitudinal direction of the positive electrode plate end face or the negative electrode plate end face, but three or more different places May be joined.

In the assembled secondary battery according to the present invention, the positive electrode-side current collector or the negative electrode-side current collector is formed by joining a plurality of current collector elements having different lengths so that the tip is branched to form a plurality of current collector elements. It may be formed in a shape forming a branch end. In this case, the positive electrode side current collector and the negative electrode side current collector can be relatively easily manufactured.

At this time, the plurality of current collector elements may have a cross-sectional area determined according to their lengths so that the electric resistance is substantially the same. In general, the electric resistance of a conductor is proportional to the length of the conductor and inversely proportional to the cross-sectional area. Therefore, the longer the length of the current collector element, the larger the cross-sectional area can be made to have substantially the same electric resistance.

Alternatively, the plurality of current collector elements may have a resistivity determined according to their lengths so that the electrical resistance is substantially the same. In general, the electrical resistance of a conductor is proportional to the length and resistivity of the conductor, so that the longer the current collector element, the lower the resistivity, the more the electrical resistance can be made substantially the same. To change the resistivity of each current collector element, for example, the material of each current collector element may be changed.

Alternatively, the contact area with the end face of the positive electrode plate or the end face of the negative electrode plate may be determined in accordance with the length of each of the plurality of current collector elements so that the electric resistance becomes substantially the same. Good. Generally, the electric resistance also changes depending on the contact area with the end face of the positive electrode plate or the end face of the negative electrode plate. For example, if the contact area is increased as the length of the current collector element increases, the electric resistance can be made substantially the same.

In the assembled secondary battery of the present invention, adjacent cells among the series-connected cells are housed in battery cases each having a case partitioned by a partition, and the adjacent cells are connected to each other. The part to be connected in series may be formed in a passage hole communicating the battery cases with the partition wall. This makes it possible to reduce the size of the assembled secondary battery as compared with a case where adjacent unit cells are connected in series outside the case.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to make the present invention more apparent, preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the appearance of the assembled secondary battery 10 of the present embodiment, FIG. 2 is a longitudinal sectional view of the assembled secondary battery 10, FIG. 3 is a partially enlarged view of FIG. 2, and FIG. A-
It is A sectional drawing.

The assembled secondary battery 10 of the present embodiment is shown in FIG.
As shown in FIG. 2, a plurality of battery cases 23, 23,...
This is a square sealed battery in which the plurality of unit cells 40 are connected in series. In the present embodiment, a nickel-hydrogen secondary battery will be described as an example of the unit cell 40.

As shown in FIG. 2, the case 20 is formed by sealing a resin case body 21 with a resin case cover 30. The case body 21 is formed in a rectangular parallelepiped shape having an open upper surface, and the inside thereof is
A plurality of battery cases 23, 23,... Are formed by being partitioned by 2,. Each partition wall 22 of the case main body 21 is provided with a through hole 24 (see FIG. 3) for connecting each cell 40 in series, and each end wall 25 of the case main body 21 exposes an external connection terminal 26. Are provided. The external connection terminal 26 on one end wall 25 is a positive terminal, and the external connection terminal 26 on the other end wall 25 is a negative terminal. The case lid 30 is provided with a top hole 31 above each battery case 23, and the adjacent top holes 31, 31 have the communication lid 3.
2 and a communication passage 33 formed in the communication lid 32.
The two top holes 31, 31 communicate with each other. Case lid 3
A safety valve 34 (see FIG. 1) for releasing the pressure when the internal pressure of the case 20 becomes equal to or higher than a predetermined pressure is attached to the zero. A sensor mounting portion 35 for mounting is formed. The battery cases 23 and 2 in the case 20
Since... Are communicated by the communication path 33, it is sufficient to provide only one safety valve.

The unit cell 40 has a positive electrode plate 41 mainly composed of nickel hydroxide, a negative electrode plate 42 mainly composed of a hydrogen storage alloy that reversibly stores and releases hydrogen, and a positive electrode plate 42 having high ion conductivity. A separator 43 for preventing a short circuit between the plate 41 and the negative electrode plate 42; and an alkaline electrolyte 44 for immersing the positive electrode plate 41 and the negative electrode plate 42 and transporting ions accompanying the electrochemical reaction between the positive and negative electrodes. I have. As shown in FIG. 4, a large number of positive electrode plates 41 and negative electrode plates 42 are stacked with a separator 43 interposed therebetween to form an electrode plate group 45. In the present embodiment, the separator 43 is a bag made of non-woven fabric, and is covered with the positive electrode plate 41. One end of each positive electrode plate 41 is a free end, and the other end is aligned so that the positive electrode plate end surface 41
The positive electrode plate end surface 41a has a positive electrode lead 46
Are joined. The positive electrode lead 46 is formed in a substantially rectangular plate shape with both side edges bent inward. One end of each negative electrode plate 42 is a free end, and the other end is aligned to form a negative electrode plate end surface 42a.
A negative electrode lead 47 is joined to 2a. The negative electrode lead 47 is formed in a substantially rectangular plate shape with both side edges bent inward. An outer peripheral separator 48 is provided outside the electrode plate group 45.

As shown in FIG. 2, a positive electrode side current collector 50 is welded to the positive electrode side lead 46. The positive current collector 50 includes a first current collector element 51 having a short length welded to an upper portion of the positive electrode lead 46 and a second current collector element 51 having a middle length welded to a middle portion of the positive electrode lead 46. It comprises a current collector element 52 and a long third current collector element 53 welded to the lower part of the positive electrode lead 46. As shown in FIG. 3, an insulating film 54 is inserted between the current collector elements 51, 52, and 53 except for the vicinity of the upper end. Each of the current collector elements 51, 52 and 53 is a conductive plate having a step, and has an end 50 opposite to the side welded to the positive electrode lead 46.
and are caulked and welded so as to be integrated at this end. As a result, when viewing the overall shape of the positive electrode-side current collector 50, the distal end (lower end) is branched to form a plurality of branched ends, and the base end (upper end) forms a non-branched end that is not branched. At the base end of the positive electrode side current collector 50, a convex portion 55 that can be inserted into the passage hole 24 provided in the partition wall 22 is provided. The projection 55 is provided on the third current collector element 53. Further, the positive current collector 50 includes a first current collector element 51.
The electric resistance from the joint surface between the positive electrode lead 46 to the convex portion 55, the electric resistance from the joint surface between the second current collector element 52 and the positive electrode lead 46 to the convex portion 55, and the third current collector. Element 5
Each of the current collector elements 51 and 5 is so arranged that the electrical resistance from the joint surface between the third element 3 and the positive electrode lead 46 to the convex 55 is substantially the same.
The cross-sectional area is determined according to the length of 2, 53.
Generally, since the electric resistance is proportional to the length and inversely proportional to the cross-sectional area, and since the first current collector element 51 is the shortest and the third current collector element 53 is the longest, disconnection of the first current collector element 51 is prevented. The area is set to be the smallest and the sectional area of the third current collector element 53 is the largest.

As shown in FIG. 2, a negative electrode current collector 60 is welded to the negative electrode lead 47. The negative current collector 60 includes a first current collector element 61 having a short length welded to the upper portion of the negative lead 47, and a second current collector element 61 having a middle length welded to the middle of the negative lead 47. It comprises a current collector element 62 and a long third current collector element 63 welded to the lower part of the negative electrode lead 47. As shown in FIG. 3, an insulating film 64 is inserted between the current collector elements 61, 62, and 63 except for the vicinity of the upper end. Each current collector element 6
1, 62, 63 are conductive plates having steps, and the end portions 60a on the opposite side to the side welded to the negative lead 47.
Are caulked and welded together at the end 60a. As a result, when the overall shape of the negative electrode side current collector 60 is viewed, the distal end (lower end) is branched to form a plurality of branched ends, and the base end (upper end) forms an unbranched end that is not branched. In addition, a partition wall 22 is provided on the upper end of the negative electrode side current collector 60.
Is provided with a protruding portion 65 that can be inserted into the passage hole 24 provided in the through hole. The protrusion 65 is provided on the third current collector element 63. Further, the negative-side current collector 60 has an electric resistance from the joint surface between the first current-collector element 61 and the negative-side lead 47 to the convex portion 65, and a resistance between the second current-collector element 62 and the negative-side lead 47. Each current collector element 61 is such that the electrical resistance from the joint surface to the convex portion 65 and the electrical resistance from the joint surface between the third current collector element 63 and the negative electrode lead 47 to the convex portion 65 are substantially the same. ,
The cross-sectional area is determined according to the lengths of 62 and 63. Generally, since the electric resistance is proportional to the length and inversely proportional to the cross-sectional area, and since the first current collector element 61 is the shortest and the third current collector element 63 is the longest, disconnection of the first current collector element 61 is prevented. The third current collector element 63 is set so as to have the smallest area and the largest sectional area.

The protrusion 55 of the positive electrode current collector 50 joined to one of the unit cells 40 and the protrusion of the negative electrode current collector 60 joined to the other unit cell 40 of the adjacent cells 40, 40. The part 65 is, as shown in FIG.
And is welded in a state where the current collectors are joined to each other to form a current collector connecting portion 70. The current collector connecting portion 70 corresponds to a connection point in a series connection. Further, as shown in FIG. 2, a unit cell 40 arranged at one end of the
The projection 55 of the positive electrode side current collector 50 is
7 and is welded to the external connection terminal 26. This welding location also corresponds to a connection location in the series connection. Although not shown, the unit cell 40 disposed at the other end of the collective secondary battery 10 also has a protrusion 65 of the negative electrode side current collector 60.
Are welded to the external connection terminals 26, and this welded portion also corresponds to a connection portion in a series connection.

Next, the operation of the assembled secondary battery 10 of the present embodiment will be described. When a load is connected between the connection terminals 26 and 26 to perform a discharge reaction inside the assembled secondary battery 10, the adjacent cells 40 and 40 are connected to the current collector connecting portion 70.
Therefore, a current flows from the positive electrode lead 46 of one cell 40 to the negative electrode lead 47 of the other cell 40 via the current collector connecting portion 70. At this time, the electric resistance from the upper, middle, and lower portions of the positive electrode lead 46 to the current collector connecting portion 70 via the current collector elements 51, 52, 53 of the positive electrode current collector 50 is all The current collector elements 61, 6 of the negative electrode current collector 60 extend from the upper, middle, and lower portions of the negative electrode lead 47, respectively.
The electrical resistance from the point 2 to the point 63 to the current collector connecting portion 70 is also substantially the same. On the other hand, the electric resistance from each of the upper, middle, and lower portions of the positive electrode lead 46 to the external connection terminal 26 serving as the positive electrode terminal through each of the current collector elements 51, 52, 53 of the positive electrode current collector 50 is increased. Is almost the same,
The electrical resistance from the upper, middle, and lower portions of the negative electrode lead 47 to the external connection terminal 26, which is the negative electrode terminal, through the current collector elements 61, 62, and 63 of the negative electrode current collector 60 is also substantially the same. Is the same. For this reason, the current flowing through the electrode plate group 45 becomes substantially uniform regardless of the upper part, the middle part, and the lower part. Note that the white arrows in FIG. 2 indicate the current flow, and the width of the arrows indicates the amount of the current. Also, when a charger (not shown) is connected between the two connection terminals 26 and 26 to perform a charging reaction, the current flowing through the electrode plate group 45 becomes substantially uniform, as in the case of discharging.

According to the assembled secondary battery 10 of this embodiment described in detail above, when the joining portion of the positive lead 46 and the joining portion of the negative lead 47 are viewed from the current collector connecting portion 70 as a base point, The electrical resistance is substantially the same regardless of whether the distance from the conductor connecting portion 70 is short or long, and the external connection terminal 26 as a positive terminal or the external connection terminal 26 as a negative terminal is used as a base point. When the joining portion of the positive lead 46 or the joining portion of the negative lead 47 is viewed, the electric resistance is substantially the same regardless of whether the distance from the external connection terminal 26 is short or long. The distribution of the current flowing through the electrode group 45 during discharge becomes substantially uniform, and the electrode group 4
5 can exhibit the charging / discharging ability substantially uniformly.

The positive-electrode-side current collector 50 is formed into a shape having a plurality of branched ends by joining a plurality of current collector elements 51, 52, 53 having different lengths. Therefore, it can be manufactured relatively easily. This is the same for the negative electrode current collector 60.

Further, the positive-electrode-side current collector 50 is designed such that the electrical resistance from the branch ends, ie, the lower ends of the current collector elements 51, 52, 53 to the base end, ie, the current collector connecting portion 70, is substantially the same. Since the cross-sectional area is determined according to the length of each of the current collector elements 51, 52, 53, the electric resistance can be relatively easily made substantially the same. This is the same for the negative electrode current collector 60.

Furthermore, in the positive electrode current collector 50, each branch end, that is, the lower end of each of the current collector elements 51, 52, 53 is joined to three different points along the longitudinal direction of the positive electrode lead 46. Since the distances from the lower ends of the current collector elements 51, 52, 53 to the current collector connecting portion 70 are relatively large, the application of the present invention is significant. This is the same for the negative electrode current collector 60.

Adjacent cells 40, 40 are separated from each other by battery cases 23, 2 in which case 20 is partitioned by partition walls 22.
, And the current collector connecting portion 70 is formed in the passage hole 24 that connects the battery cases 23, 23 with the partition wall 22, so that the adjacent cells 40, 40 are connected to the case 2.
The external appearance can be made more compact as compared with the case of connecting in series outside the 0.

It is needless to say that the present invention is not limited to the above-described embodiments, and can be implemented in various modes as long as they belong to the technical scope of the present invention.

For example, in the embodiment described above, the first to third current collector elements 51, 52,
53 is such that the longer the length is, the larger the cross-sectional area is so that the electric resistance from the front end to the base end is substantially the same, but the longer the length is, the larger the contact area with the positive electrode lead 46 becomes. Or the resistivity may decrease as the length increases. In this case, the resistivity may be changed by changing the type of the conductive material. Alternatively, the first to third current collector elements 51, 52, and 53 may have substantially the same cross-sectional area and resistivity and substantially the same length. In this case, the lengths of the first and second current collector elements 51 and 52 may be increased in accordance with the length of the third current collector element 53, and an extra portion may be appropriately folded or wound. These points are the same for the negative electrode current collector 60.

In the above-described embodiment, the first to third current collector elements 51, 52, 5
Although the insulating film 54 is sandwiched in the gap 3, a gap may be formed instead of sandwiching the insulating film 54. This is the same for the negative electrode current collector 60.

Further, in the above-described embodiment, the positive electrode side lead 46 covers the entire positive electrode plate end surface 41a.
The positive electrode lead 46 may be divided into upper, middle, and lower three parts, and each divided body may be joined to each of the current collector elements 51, 52, 53.
Alternatively, the current collector element 5
1, 52 and 53 may be directly joined to the end face 41a of the positive electrode plate. This is the same for the negative lead 47.

Further, in the above-described embodiment, the positive electrode current collector 50 is constituted by the first to third current collector elements 51, 52, and 53. However, as shown in FIG. It may be constituted by one element by performing cutting or the like. This is the same for the negative electrode current collector 60. In addition,
Also in this case, it is preferable to provide the insulating film 54 or a gap at the same position as in the above-described embodiment.

Further, in the above-described embodiment, the nickel-hydrogen secondary battery is exemplified as the secondary battery, but another secondary battery such as a nickel-cadmium secondary battery or a lithium-hydrogen secondary battery may be used. .

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an appearance of a collective secondary battery according to an embodiment.

FIG. 2 is a longitudinal sectional view of the collective secondary battery of the present embodiment.

FIG. 3 is a partially enlarged view of FIG. 2;

FIG. 4 is a sectional view taken along line AA of FIG. 2;

FIG. 5 is a cross-sectional view of a positive electrode side current collector of another embodiment.

FIG. 6 is a longitudinal sectional view of a conventional collective secondary battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Assembly type secondary battery, 20 ... Case, 21 ... Case main body, 22 ... Partition wall, 23 ... Battery case, 24 ... Passing hole, 25 ... End wall, 26 ... External connection terminal, 27 ... Passing hole, 30 ... Case Lid, 40: single cell, 41: positive electrode plate, 41a: positive electrode plate end surface, 42: negative electrode plate, 42a: negative electrode plate end surface, 43: separator, 44: alkaline electrolyte, 45: electrode plate group, 46: positive electrode side lead 47, a negative lead, 50, a positive current collector, 51 to 53, first to third current collector elements, 54, an insulating film, 55, a convex portion, 60, a negative current collector, 61 to 63
... first to third current collector elements, 64 ... insulating film, 65 ...
Convex part, 70 ... current collector connecting part,

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 5H011 AA04 CC02 DD01 DD07                 5H022 AA19 BB05 BB11 CC12 CC16                       CC21 CC22 CC25                 5H028 AA07 AA08 BB05 CC01 CC05                       CC07 CC08 FF02

Claims (9)

[Claims] 1. An assembled secondary battery in which unit cells each having an electrode group formed by laminating a plurality of positive electrode plates and negative electrode plates are connected in series, and end portions of the plurality of positive electrode plates included in the unit cells A positive electrode that electrically connects end faces of a positive electrode plate having the same arrangement, an end face of a negative electrode plate having the end portions of a plurality of negative electrodes included in the unit cell, and a plurality of locations on the end face of the positive electrode plate and a connection point in series connection A side current collector, comprising a negative electrode side current collector electrically connecting a plurality of locations on the end face of the negative electrode plate and a connection location in series connection, wherein the positive current collector is provided at a plurality of locations on the end face of the positive electrode plate. The electrical resistance from each to the connection point in the series connection is substantially the same, and the negative electrode current collector has substantially the same electrical resistance from each of the plurality of points on the end face of the negative electrode plate to the connection point in the series connection. A certain type of secondary battery. 2. The positive electrode-side current collector or the negative electrode-side current collector has a plurality of branched ends formed at a tip thereof to form a plurality of branch ends, and the plurality of branch ends are formed at a plurality of positions on the positive electrode plate end surface or the negative electrode plate end surface. The assembled secondary battery according to claim 1, wherein the secondary batteries are joined to each other, and a base end forms a connection portion in the series connection. 3. The assembly according to claim 1, wherein the positive electrode-side current collector or the negative electrode-side current collector is joined to different positions along a longitudinal direction of the positive electrode plate end surface or the negative electrode plate end surface. Type secondary battery. 4. The positive electrode-side current collector or the negative electrode-side current collector is joined to three or more different locations along the longitudinal direction of the positive electrode plate end surface or the negative electrode plate end surface.
An assembled secondary battery as described in the above. 5. The positive electrode-side current collector or the negative electrode-side current collector is formed into a shape having a plurality of branched ends by joining a plurality of current collector elements having different lengths. The assembled secondary battery according to any one of claims 1 to 4. 6. The collective secondary battery according to claim 5, wherein a cross-sectional area of each of the plurality of current collector elements is determined in accordance with a length of each of the current collector elements so as to have substantially the same electric resistance. 7. The collective secondary battery according to claim 5, wherein the plurality of current collector elements have a resistivity determined according to their lengths so as to have substantially the same electrical resistance. 8. A contact area with the end face of the positive electrode plate or the end face of the negative electrode plate according to the length of each of the plurality of current collector elements so that the electric resistance becomes substantially the same. Item 6. An assembled secondary battery according to Item 5. 9. Among the unit cells connected in series, adjacent unit cells are respectively housed in a battery case in which the inside of the case is partitioned by a partition, and a place where the adjacent unit cells are connected in series is located in the partition. The assembled secondary battery according to any one of claims 1 to 8, wherein the assembled secondary battery is formed in a passage hole that communicates both battery cases.