JP2006092828A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a battery pack from deforming by forming it into a structure, capable of preventing a tip of a sealing body of an adjacent cell from contacting a bottom part of a metallic exterior can, even if the cell internal pressure rises and each cell swells, and to allow a pressure valve to operate at a predetermined pressure to prevent the reliability from deteriorating. <P>SOLUTION: In this battery pack 100, a sealing body 18 of one-side cell E is welded to a metallic outer covering can 16 of the other-side cell D through a connection member 20 so as to form a space W, between a tip 18a of the sealing body 18 of the one-side cell E and the bottom part of the metallic outer covering can 16 of the other-side cell D. Even if the battery's internal pressure rises to cause valve opening in the cell and a battery bulge is generated, the tip 18a of the sealing body 18 of the one-side cell E is prevented from contacting the bottom part of the metallic armoring can 16 of the other-side cell D. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an assembled battery in which a plurality of unit cells each having a power generation element composed of an electrode group and an electrolyte solution, in which a positive electrode and a negative electrode are stacked via a separator, are connected in series. The present invention relates to an assembled battery in which a plurality of unit cells each having a sealing body that also serves as a terminal of the other electrode are connected in series to an opening of a metal outer can that also serves as a terminal of an electrode via an insulator.

  In general, alkaline storage batteries such as nickel-hydrogen storage batteries and nickel-cadmium storage batteries or lithium secondary batteries have a separator interposed between a positive electrode and a negative electrode, and after winding them in a spiral shape, A current collector is connected to form an electrode body, the electrode body is housed in a metal outer can, and a lead portion extending from the current collector is welded to the sealing body, and then the sealing body is attached to the opening of the outer can. It is configured to be hermetically sealed by attaching an insulating gasket. When such an alkaline storage battery is used for an electric vehicle such as HEV (Hybrid Electric Vehicles) or PEV (Pure Electric Vehicles), a high output is required. Therefore, a plurality of unit cells are connected in series to form an assembled battery. Generally, it is used.

  In such an assembled battery, it is necessary to connect a plurality of single cells in series, and various connection methods have been proposed. For example, in the assembled battery proposed in Patent Document 1, the cells 30 a and 30 b are connected in series by a connection body 31 as shown in FIG. In this case, the connection body 31 includes a cylindrical portion 34 that fits into the metal outer can 36 and a flat portion 35 that abuts against a metal electrode (sealing body) 37. Four projection projections 33 projecting in the direction of the metal outer can 36 to be fitted are formed on the cylindrical portion 34, and four projections 33 projecting in the direction of the metal electrode 37 in contact with the plane portion 35. A projection 32 is formed.

And when welding the connection body 31, the plane part 35 is first welded to the metal electrode (sealing body) 37 of the cell 30a. That is, the flat portion 35 is placed on the metal electrode (sealing body) 37, and the connecting portion 31 and the metal electrode (sealing body) 37 are pressed while pressing the flat portion 35 toward the metal electrode (sealing body) 37. A welding current is passed between them. Thereby, the connection body 31 is welded to the metal electrode (sealing body) 37 at the four positions of the projection protrusion 32. Next, the cylindrical portion 34 of the connection body 31 welded to the metal electrode (sealing body) 37 of the unit cell 30a is fitted into the metal exterior can 36 of the unit cell 30b, and the metal exterior can 36 and the connection body 31 are connected. A welding current is allowed to flow during Then, the connection body 31 is welded to the metal outer can 36 at four locations on the projection protrusion 33. Thereby, the unit cell 30 a and the unit cell 30 b are connected in series by the connection body 31. An assembled battery can be configured by connecting such inter-battery connections as many as a desired output voltage is obtained.
JP-A-10-106533

  However, when a plurality of unit cells are connected in series as described above, if the interval (W) between the front end portion of the sealing body 37 of the adjacent unit cell and the bottom portion of the metal outer can 36 is short, the battery is charged during charging. When the internal pressure rises and each cell expands, the tip of the sealing body 37 of the adjacent cell and the bottom of the metal outer can 36 come into contact. In this case, as shown in FIG. 4B, contact resistance is generated at the contact point X when the tip of the sealing body 37 of the adjacent unit cell contacts the bottom of the metal outer can 36. For this reason, in addition to the normal current path Y, an abnormal current path Z is formed at the contact point X, Joule heat is generated by the contact resistance at the contact point X, and the contact point X generates heat. In this case, when a large current flows through the contact point X, the contact point X generates heat abnormally, and this type of battery pack may be deformed or reliability may be impaired.

  Further, when the internal pressure of the battery rises and each unit cell expands and the tip of the sealing unit 37 of the adjacent unit cell comes into contact with the bottom of the metal outer can 36, the cell is disposed in the sealing unit 37. The operating pressure of the pressure valve 38 increases. Here, when the operating pressure of the pressure valve 38 increases, the pressure valve 38 does not operate unless the pressure is higher than a preset operating pressure, and thus each cell may be ruptured. .

  On the other hand, it is also known to directly weld the metal electrode 37 of the unit cell 30a and the bottom of the metal outer can 36 of the unit cell 30b without using such a connection body 31. In the case of this structure, since both are originally welded, abnormal heat generation is not caused by contact resulting from the swelling of each unit cell, but the entire length of the unit cell is increased by the swelling. As a result, the total length of the assembled battery becomes long, and in the structure in which the assembled battery is housed and held in the case, the case is broken or the assembled battery is bent, and between the single cells or between the assembled batteries. There was a problem that the connection of. Further, since welding is directly performed on the surface of the sealing body, which is a metal electrode, there is a problem that the operating pressure of the built-in safety valve 38 is changed due to the sealing body being pressed when the cell is swollen.

  Therefore, the present invention has been made to solve the above-described problems, and even if the cell internal pressure rises and each cell expands, the tip of the sealing body of the adjacent cell and the metal Make the structure so that the bottom of the outer can is not in contact so that this type of battery pack does not deform, or the pressure valve operates at a specified pressure so that reliability is not impaired. It is for the purpose.

  In order to achieve the above object, in the battery pack of the present invention, a gap (W) is formed between the tip of the sealing body of one unit cell and the bottom of the metal outer can of the other unit cell. The sealing body of one unit cell and the metal outer can of the other unit cell are welded by a connecting member. And even if a battery internal pressure rises until a valve opens in a single cell and a battery swells, the tip of the sealing body of one single cell does not contact the bottom of the metal outer can of the other single cell. It is characterized by being made. Thus, even if the battery internal pressure rises and the battery swells, the tip of the sealing body of one unit cell and the tip of the outer can bottom of the other unit cell are not in contact with each other. Current flows between the cells only through the connecting member. For this reason, since the battery temperature does not rise unnecessarily, the assembled battery is not deformed, the pressure valve does not operate at a predetermined pressure, and the reliability is not impaired.

  In this case, if the maximum expansion amount when the battery internal pressure rises and the battery expansion occurs until the valve opens in the unit cell is w, the interval (W) is 1.1 w to 1.5 w (1.1 w ≦ It is preferable that W ≦ 1.5w). This is because when the interval (W) is shorter than 1.1 w, when the battery internal pressure rises and the battery bulges, the tip of the sealing body of one unit cell and the outer can bottom of the other unit cell This is because the tip portion comes into contact with each other, and the temperature becomes high due to Joule heat resulting from contact resistance at the contact point, and deformation is likely to occur.

  On the other hand, when the interval (W) is larger than 1.5 w, the tip of the sealing body of the adjacent unit cell and the tip of the outer can bottom contact each other even if the battery internal pressure rises and the battery swells. There is no. However, since the length of the assembled battery becomes long, when it is necessary to store it in a certain volume, it becomes impossible to store it, and it is necessary to reduce the number of batteries. Furthermore, since it becomes necessary to enlarge the connecting member that connects between adjacent single cells, the resistance value of the connecting member increases, and high output cannot be obtained, and the bending strength of the assembled battery is weakened. This is because new problems will arise.

The Young's modulus of the material used for the metal outer can is preferably 15 × 10 ^{10 to} 25 × 10 ¹⁰ Pa. This is because the metal outer can whose Young's modulus is lower than 15 × 10 ¹⁰ Pa is easily deformed, and therefore the amount of battery swell increases as the battery internal pressure increases, and the tip of the sealing unit of the adjacent unit cell and the metal It is because it becomes easy to contact the front-end | tip part of the bottom part of an exterior can. On the other hand, a metal outer can having a Young's modulus of greater than 25 × 10 ¹⁰ Pa is less suitable for a metal outer can because it is difficult to process, while the amount of battery swelling associated with an increase in battery internal pressure is reduced.

  Below, although the embodiment at the time of applying the present invention to a nickel-hydrogen storage battery is described based on Drawing 1-Drawing 3, the present invention is not limited to this, and in the range which does not change the gist It can be implemented with appropriate changes. In addition, FIG. 1 is sectional drawing which shows typically the cross section of a nickel-hydrogen storage battery (unit cell). FIG. 2 is a diagram showing a state in which five nickel-hydrogen storage batteries (unit cells) are connected to form an assembled battery, FIG. 2 (a) is a plan view, and FIG. 2 (b) is a diagram of FIG. It is sectional drawing which expands and shows the A section of a), FIG.2 (c) is a perspective view which shows an example of the connection member for connecting between cells and making it an assembled battery. FIG. 3 is a plan view for explaining the relationship between the amount of swelling and the distance between the cells when the cells are expanded.

1. Nickel-hydrogen storage battery (single cell)
First, a nickel sintered porous body is formed on the surface of an electrode plate core made of punching metal, and then the nickel sintered porous body is filled with an active material mainly composed of nickel hydroxide by a chemical impregnation method. Subsequently, after drying this, it rolls until it becomes a predetermined thickness, and cut | disconnects so that it may become a predetermined dimension, and the nickel positive electrode plate 11 is produced. Also, the surface of the electrode plate core made of punching metal is filled with a paste-like negative electrode active material made of hydrogen storage alloy, dried, rolled to a predetermined thickness, and cut to a predetermined size. Thus, the hydrogen storage alloy negative electrode plate 12 is produced.

A separator 13 is interposed between the nickel positive electrode plate 11 and the hydrogen storage alloy negative electrode plate 12, and a spiral electrode group is produced by winding in a spiral shape. Thereafter, the positive electrode current collector 14 is welded to the electrode plate core body of the nickel positive electrode plate 11 exposed at the upper end surface of the spiral electrode group. Further, the negative electrode current collector 15 is welded to the electrode plate core body of the hydrogen storage alloy negative electrode plate 12 exposed at the lower end surface of the spiral electrode group to form an electrode body. After the cylindrical positive electrode lead 17 is welded to the upper part of the positive electrode current collector 14 of the obtained electrode body, a bottomed cylindrical outer can in which iron is nickel-plated (the outer surface of the bottom surface becomes a negative electrode external terminal) ) The negative electrode current collector 15 housed in 16 and welded to the hydrogen storage alloy negative electrode plate 12 is welded to the inner bottom surface of the outer can 16. The Young's modulus of the material used for the outer can 16 was 20 × 10 ¹⁰ Pa.

  Next, a vibration isolating ring 19a was inserted into the upper inner peripheral side of the outer can 16 and a groove was formed on the upper outer peripheral side of the outer can 16 to form a recess 16a at the upper end of the anti-vibration ring 19a. Thereafter, an electrolytic solution made of a 30 mass% potassium hydroxide (KOH) aqueous solution is injected into the outer can 16. Subsequently, it arrange | positions so that the bottom face of the sealing board 18a may contact the cylindrical part of the lead | read | reed 17 for positive electrodes on the upper part of the opening part of this exterior can 16. FIG. Here, a positive electrode cap (positive electrode external terminal) 18b is provided on the upper portion of the sealing plate 18a, and a valve body including a valve plate 18c and a spring 18d is provided in the positive electrode cap 18b. A vent hole is formed in the center, and the sealing body 18 is formed by the sealing plate 18a and the positive electrode cap 18b. An insulating gasket 19b is fitted in advance on the periphery of the sealing plate 18a of the sealing body 18.

  Next, one welding electrode (not shown) is arranged on the upper surface of the positive electrode cap (positive electrode external terminal) 18b, and the other welding electrode (not shown) is arranged on the lower surface of the bottom surface (negative electrode external terminal) of the outer can 16. Deploy. Thereafter, while applying a predetermined pressure between the pair of welding electrodes, a predetermined voltage was applied between the welding electrodes in the discharge direction of the battery, and an energization process was performed to flow a predetermined pulse current. By this energization process, the contact portion between the bottom surface of the sealing plate 18a and the peripheral side edge of the positive electrode lead 17 is welded.

  As described above, by applying a voltage between the welding electrodes while applying a predetermined pressure between the pair of welding electrodes and applying an energization process, the height dimension of the cylindrical positive electrode lead 17 varies. Even in such a case, a contact point can be formed between the peripheral edge of the cylindrical positive electrode lead 17 and the bottom surface of the sealing plate 18a. Thereby, the welding part excellent in welding strength can be formed now. If a small protrusion is provided on the lower surface of the sealing plate 18a, or if a small protrusion is provided on the peripheral edge that contacts the lower surface of the cylindrical positive electrode lead 17, current is concentrated on the small protrusion. As a result, a welded portion having higher welding strength is formed.

  Next, a pressure is applied to the sealing body 18 using a press machine, and the sealing body 18 is pushed into the outer can 16 until the lower end of the insulating gasket 19b is positioned at the recess 16a provided on the outer periphery of the upper portion of the outer can 16. . Thereafter, the nickel-hydrogen storage battery 10 (cells A, B, C, D, E) is obtained by sealing the battery by crimping the opening edge of the outer can 16 inward. The cylindrical positive electrode lead 17 is crushed by the applied pressure at the time of sealing, and the cross-sectional shape becomes an elliptical shape in which a circular shape is crushed.

2. Next, using the nickel-hydrogen storage battery 10 (single cells A, B, C, D, E) produced as described above, as shown in FIG. A connecting member 20 is interposed between B, C, D, and E, and the unit cells A, B, C, D, and E are connected in series to form an assembled battery. Here, as shown in FIG. 2C, the connecting member 20 is made of iron, copper, nickel, or an alloy thereof so that the cylindrical portion 22 is connected to the outer periphery of the stepped flat portion 21. It is formed by press molding of a metal plate with good conductivity.

  An opening 23 having a diameter larger than the outer diameter of the positive electrode cap 18b is formed at the center of the flat surface portion 21, and a plurality of protrusions projecting toward the positive electrode cap 18b are formed around the opening 23. Projection protrusions 24 are formed. On the other hand, the inner diameter of the cylindrical portion 22 is formed to be slightly larger than the outer diameter of the outer can 16 so that the cylindrical portion 22 is fitted to the bottom portion of the outer can 16. Projection projections 25 are formed. In this case, as shown in FIG. 2 (b), the stepped flat portion 21 is placed on the sealing plate 18a of the unit cell E, and the connecting member 20 is pressed while pressing the flat portion 21 toward the sealing plate 18a. When a welding current is passed between the sealing plate 18a and the projection projection (in this case, four locations) 24, the connecting member 20 is welded to the sealing plate 18a.

  Note that a short circuit occurs when the connection member 20 comes into contact with the caulking portion 16b of the metal outer can 16. Therefore, the cylindrical insulator 26 is disposed between the caulking portion 16b and the connection member 20. Next, after fitting the metal outer can 16 of the unit cell D in the cylindrical portion 22 of the connection member 20 welded to the unit cell E, the metal outer can 16 of the unit cell D and the connection member 20 are connected. When a welding current is passed through the connecting member 20, the connection member 20 is welded to the metal outer can 16 by projection projections (in this case, four locations) 25. By performing such a connection on a predetermined number of cells (5 in this embodiment), five cells A, B, C, D, as shown in FIG. The assembled battery 100 in which E is connected in series is obtained.

  Here, the inter-cell distance W (see FIG. 3A) is 1.0 times the maximum length w of the single cells when the internal pressure of the battery increases and expands to the maximum, as will be described later ( The assembled battery 100 formed so that W = 1.0w) was designated as an assembled battery A1. Similarly, an assembled battery 100 formed such that the inter-cell distance W is 1.1 times (W = 1.1 w) with respect to the maximum length w is referred to as an assembled battery A2, and 1.3 times (W = The assembled battery 100 formed to be 1.3 w) is referred to as an assembled battery A3, and the assembled battery 100 formed to be 1.5 times (W = 1.5 w) is referred to as an assembled battery A4, which is 1.6 times ( The assembled battery 100 formed so that W = 1.6w) was designated as assembled battery A5, and the assembled battery 100 formed so as to be 2.0 times (W = 2.0w) was designated as assembled battery A6.

Here, as shown in FIG. 3B, the maximum length w of the unit cell when the internal pressure of the battery rises and the battery expands to the maximum is the amount of swelling w1 on the side of the sealing body 18 and the outer can 16. As the sum (w = w1 + w2) of the bulging amount w2 on the bottom side, the following was obtained.
In this case, first, a hole having a diameter of 1 mm is formed in the center of the bottom of the outer can 16 of the unit cell 10, and then a gas inlet is connected to this hole. And nitrogen gas is inject | poured from this gas injection port, and the pressure which act | operates the valve body which consists of the valve plate 18c and the spring 18d is calculated | required previously. Next, nitrogen gas is injected from the gas injection port, and the position of the front end portion of the positive electrode cap 18b after one minute has elapsed after reaching the pressure at which the valve body determined in advance as described above is reached and pressurized. The difference from the previous position is obtained, and the swelling amount (w1) on the sealing body 18 side is obtained.

  On the other hand, after making a hole with a diameter of 1 mm in the sealing plate 18a of the sealing body 18 of the unit cell 10, a gas inlet is connected to this hole. Then, nitrogen gas is injected from this gas inlet, and the position of the tip of the bottom of the outer can 16 after one minute has elapsed after reaching the pressure at which the valve body determined in advance as described above is activated. Then, the difference from the position before pressurization is obtained, and the swelling amount (w2) on the outer can 16 side is obtained. By obtaining the sum (w = w1 + w2) of the obtained swollen amount w1 on the sealing body 18 side and the swollen amount w2 on the bottom side of the outer can 16, the battery internal pressure increases and the battery expands to the maximum The maximum length w of the single cell can be obtained.

3. Next, 10 assembled batteries A1 to A6 as described above were prepared, and each of these 10 assembled batteries A1 to A6 was used to charge the battery for 16 hours at a charging current of 1 It. After that, the battery was discharged at a discharge current of 1 It until the battery voltage became 0.9 V, and the initial discharge capacity C1 of each of the assembled batteries A1 to A6 was obtained from the discharge time. Next, after charging and discharging 10 times as described above at a current value of 1 It, charging is performed for 16 hours with a charging current of 1 It, and then discharging is performed until the battery voltage becomes 0.9 V with a discharging current of 10 It. The discharge capacity C10 after 10 It discharge of each of the assembled batteries A1 to A6 was determined from the discharge time. In this test, when the number of the assembled batteries whose temperature was increased, the results shown in Table 1 below were obtained. Next, when the ratio ((C10 / C1) × 100%) to the initial discharge capacity C1 is obtained from the obtained discharge capacity C10 as output characteristics (in this case, the average value of 10 assembled batteries), it is shown in Table 1 below. The results shown were obtained. However, the assembled battery A1 was excluded from the evaluation of the output characteristics because a battery with a rising temperature was recognized and the reliability was impaired.

  As is apparent from the results in Table 1, in the assembled battery A1 in which the interval (W) between the single cells is 1.0 times (W = 1.0 w) the amount of battery swelling (w), the assembled battery whose temperature has increased. Therefore, it is considered that there is a problem in the reliability of the assembled battery. In addition, the battery pack A5 in which the interval (W) between the single cells is 1.6 times (W = 1.6w) the battery swelling amount (w), and the battery pack having 2.0 times (W = 2.0w). In A6, it can be seen that the output characteristics are degraded. This is because it is necessary to increase the length of the connecting member 20 (the length of the cylindrical portion 22) by increasing the interval (W) of the single cells, and the resistance value at the connecting member 20 increases and outputs. It is considered that the characteristics have deteriorated. Moreover, it turned out that the bending strength as an assembled battery is also falling because the space | interval (W) between single cells becomes long.

  On the other hand, in the assembled batteries A2 to A4 in which the interval (W) of the single cells is 1.1 times (W = 1.1w) to 1.5 times (W = 1.5w) of the battery swelling amount (w), It can be seen that the temperature does not increase and the output characteristics are also good. Therefore, it is preferable that the interval (W) of the single cells is 1.1 times (W = 1.1w) to 1.5 times (W = 1.5w) the amount of battery swelling (w). Can do.

4). Examination of Young's modulus of outer can Next, the Young's modulus of the material used for the outer can was examined. Therefore, the single battery 10 was produced in the same manner as described above using the outer can 16 made of a material having a Young's modulus of 10 × 10 ¹⁰ Pa, and the assembled battery B1 was produced using the single battery 10 in the same manner as described above. Similarly, the assembled battery B2 is produced using the outer can 16 made of a material having a Young's modulus of 12 × 10 ¹⁰ Pa, and the assembled battery B3 is produced using an outer can 16 having a material having a Young's modulus of 15 × 10 ¹⁰ Pa. The assembled battery B4 (similar to A3 described above) is produced using the outer can 16 made of a material having a Young's modulus of 20 × 10 ¹⁰ Pa, and the outer can 16 made of a material having a Young's modulus of 23 × 10 ¹⁰ Pa is used. The assembled battery B5 is manufactured, the assembled battery B6 is manufactured using the outer can 16 made of a material having a Young's modulus of 25 × 10 ¹⁰ Pa, and the assembled battery B6 is manufactured using the outer can 16 made of a material having a Young's modulus of 28 × 10 ¹⁰ Pa. Battery B7 was produced.

  In this case, the material of the outer can 16 is 100% iron with nickel plating on the surface, but a mixture of materials with different Young's modulus is used as the iron material, and the mixing ratio is changed to change the Young The rate was adjusted. When an alloy containing a plurality of metals such as stainless steel is used for the outer can 16, the Young's modulus can also be adjusted by changing the alloy ratio of these metals.

  Next, using each of these assembled batteries B1 to B7, after charging for 16 hours with a charging current of 1 It, the battery is discharged until the battery voltage becomes 0.9 V with a discharging current of 1 It, and each assembled battery B1 is discharged from the discharging time. The initial discharge capacity C1 of ~ B7 was obtained. Next, after charging and discharging 10 times as described above at a current value of 1 It, charging is performed for 16 hours with a charging current of 1 It, and then discharging is performed until the battery voltage becomes 0.9 V with a discharging current of 10 It. The discharge capacity C10 after 10 It discharge of each of the assembled batteries B1 to B7 was determined from the discharge time.

Next, when the ratio ((C10 / C1) × 100%) to the initial discharge capacity C1 is obtained from the obtained discharge capacity C10 as output characteristics (in this case, the average value of 10 assembled batteries), it is shown in Table 2 below. The results shown were obtained. Further, in this test, when the total swelling amount of each of the assembled batteries B1 to B7 is obtained, the total swelling amount of the assembled battery B4 (A3) is set to 100, and the total swelling amount of the other assembled batteries is expressed as a ratio to the following. The results as shown in Table 2 were obtained.

As is apparent from the results in Table 2 above, the assembled batteries B3 to B7 manufactured using the outer can 16 made of a material having a Young's modulus of 15 × 10 ¹⁰ Pa or more have a small total swelling amount and improved output characteristics. You can see that However, a material having a large Young's modulus of 28 × 10 ¹⁰ Pa makes it difficult to process the outer can 16 and decreases the productivity. For this reason, since it is unsuitable as a material of the battery can, it is necessary to select and use a material having a Young's modulus of 25 × 10 ¹⁰ Pa or less. In this case, the assembled battery B1 produced using the outer can 16 made of a material having a Young's modulus of 10 × 10 ¹⁰ Pa and the assembled battery B2 made using an outer can 16 made of a material having a Young's modulus of 12 × 10 ¹⁰ Pa. It can be seen that the total amount of swelling is large and its output characteristics are degraded.

This is because an outer can made of a material having a Young's modulus of less than 15 × 10 ¹⁰ Pa has a large amount of swelling due to an increase in the internal pressure of the battery, so that the positive cap of the adjacent unit cell and the bottom of the outer can The space comes into contact. For this reason, it is considered that the contact portion becomes locally high in temperature, the resistance value thereof increases, and the output characteristics are deteriorated due to a resistance voltage drop. In this case, if the distance W between the adjacent unit cells is widened, the positive electrode cap of the adjacent unit cell and the bottom of the outer can can be prevented from contacting each other. An increase in the distance W is not preferable because it is necessary to reduce the number of single cells that can be accommodated in a certain volume.

  As described above, in the present invention, even if the cell internal pressure increases and each cell expands, the tip of the sealing body of the adjacent cell does not contact the bottom of the metal outer can. In addition, one sealing body of the adjacent unit cell and the other metal outer can are welded by the connecting member. For this reason, even if the cell internal pressure rises and each cell expands, current flows only between the cells through the connection member. As a result, the battery temperature does not rise unnecessarily, so that the assembled battery is not deformed, the pressure valve does not operate at a predetermined pressure, and the reliability is not impaired.

  In the embodiment described above, an example in which only five unit cells are used to form an assembled battery has been described. However, if the present invention is applied, it is possible to manufacture an assembled battery regardless of how many unit cells are connected. it is obvious. Moreover, in embodiment mentioned above, although the sealing body was used as the positive electrode terminal and the exterior can was used as the negative electrode terminal, the sealing body may be used as the negative electrode terminal and the exterior can may be used as the positive electrode terminal. Furthermore, in embodiment mentioned above, although the example which applies this invention to a nickel-hydrogen storage battery was demonstrated, this invention is not limited to nickel-hydrogen storage battery, but other nickel-cadmium storage battery, lithium secondary battery, etc. It is clear that the present invention can be applied to a storage battery.

  Further, the shape of the connecting member 20 can be changed. For example, the cylindrical part 22 may be eliminated, and a connection member in which projection protrusions protrude in opposite directions from the front and back surfaces of the flat part 21 may be sandwiched between the single cells. In this case, the interval between the single cells can be adjusted by the projection height of the projection protrusion.

It is sectional drawing which shows typically the cross section of a nickel-hydrogen storage battery (unit cell). It is a figure which shows the state which connected the five nickel-hydrogen storage batteries (unit cell) to make the assembled battery, FIG. 2 (a) is a top view, FIG.2 (b) is a figure of Fig.2 (a). It is sectional drawing which expands and shows A section, FIG.2 (c) is a perspective view which shows an example of the connection member for connecting between cells and making it an assembled battery. It is a top view explaining the relationship between the amount of swelling when a cell expands, and the distance between the cells. It is a figure which shows an example of the assembled battery of a prior art example.

Explanation of symbols

10 (A, A, C, D, E): single cell, 11: positive electrode plate, 12: negative electrode plate, 13: separator, 14 ... positive electrode current collector, 15 ... negative electrode current collector, 16 ... metal outer can , 16a ... concave portion, 16b ... caulking portion, 17 ... positive electrode lead, 18 ... sealing body, 18a ... sealing plate, 18b ... positive electrode cap, 18c ... valve plate, 18d ... spring, 19a ... vibration isolating ring, 19b ... insulating gasket , 20 ... connection member, 21 ... plane part, 22 ... cylindrical part, 23 ... opening, 24 ... projection protrusion, 25 ... projection protrusion, 26 ... cylindrical insulator, 100 ... assembled battery

Claims (4)

An assembled battery in which a plurality of unit cells having a sealing body that also serves as a terminal of the other electrode via an insulator are connected in series to an opening of a metal outer can that also serves as a terminal of one electrode that houses a power generation element. ,
The sealing unit of the one unit cell and the other unit cell so that a gap (W) is formed between the tip of the sealing unit of one unit cell and the bottom of the metal outer can of the other unit cell. The metal outer can is welded by the connecting member,
Even if the internal pressure of the battery rises and the battery bulges until the valve opens in the unit cell, the tip of the sealing body of the one unit cell does not contact the bottom of the metal outer can of the other unit cell. An assembled battery characterized by being configured as described above.   The contact portion between the connecting member and the sealing body of the one unit cell, and the contact portion of the outer can of the other unit cell are welded and connected, respectively. Battery pack. Assuming that the maximum swelling amount when the battery internal pressure rises and the battery bulges until the valve opens in the unit cell is w,
The assembled battery according to claim 1, wherein the interval (W) is 1.1 w to 1.5 w (1.1 w ≦ W ≦ 1.5 w). 4. The assembled battery according to claim 1, wherein the material used for the outer can has a Young's modulus of 15 × 10 ^{10 to} 25 × 10 ¹⁰ Pa. 5.

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