JP2018049823A - Power storage module having vibration-proof connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage module excellent in vibration resistance at a connection part, maintaining low resistance, and also improved in weight energy density.SOLUTION: A power storage module (7) includes: a cell stack (2) including a plurality of flat-shaped power storage elements (1) stacked therein; and a connection part where a plurality of electrode tabs (5) individually projecting from the power storage elements (1) adjacent to each other are connected via an L-shape or U-shape connection terminal (4 or 6), the electrode tabs (5) adjacent to each other being in almost parallel to each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage module.

  In power storage systems such as load leveling devices such as solar power generation or wind power generation, instantaneous voltage drop countermeasure devices, energy recovery devices for electric vehicles or hybrid vehicles, etc. A device is needed.

  In recent years, power storage modules using power storage elements such as lithium ion secondary batteries, nickel metal hydride batteries, electric double layer capacitors, or lithium ion capacitors have been developed. These power storage modules include a power storage unit in which a plurality of power storage elements are connected in series or in parallel, and can be charged and discharged in a high voltage or large capacity state, and thus are used for various applications as a power supply device. .

  Such a power storage module is attracting attention as a vehicle-mounted application such as a hybrid vehicle, and not only has a good performance as a power storage element contained therein, but also a higher level of performance and durability as a power storage module. Is required.

  Furthermore, since the power storage module has a metal connection portion that connects a plurality of power storage elements, increasing the performance of this connection portion leads to improving the performance and durability of the power storage module. In particular, an in-vehicle application requires a power storage module having a connection portion having low resistance and vibration resistance.

JP 2013-012458 A

  According to the power storage module described in Patent Document 1, the positive and negative tabs of a plurality of secondary batteries are connected in series via a bus bar having a rectangular parallelepiped shape. Since the electrical storage module described in Patent Document 1 uses a rectangular parallelepiped bus bar, the weight of the joint is large, which is disadvantageous in terms of weight energy density. In addition, the width of the bus bar is shorter than the distance between the positive and negative tabs when the bus bar is arranged substantially perpendicular to the battery end surface, so the direction of taking out the positive and negative tabs substantially perpendicular to the battery end surface cannot be maintained. The positive and negative tabs are curved in a letter C (see paragraph 0042 of FIG. 8 and FIG. 8B). For this reason, in the power storage module described in Patent Document 1, when external vibration is applied, stress tends to concentrate on the positive and negative tabs, and there is a risk of tab breakage.

  Therefore, the problem to be solved by the present invention is to provide a power storage module that is excellent in vibration resistance of a connection portion, maintains low resistance, and has improved weight energy density.

The problems described above are solved by the following technical means.
[1]
A cell stack formed by laminating a plurality of storage elements having a flat shape;
A plurality of electrode tabs individually protruding from a plurality of adjacent power storage elements are connected to each other substantially in parallel via L-shaped or U-shaped connection terminals;
A power storage module having
[2]
The electrical storage module according to [1], wherein a distance between a plurality of adjacent electrode tabs is substantially equal to a length of one side of the L-shaped or U-shaped connection terminal.
[3]
The electrical storage module according to [1] or [2], wherein the electrode tab connected to the L-shaped or U-shaped connection terminal has a sheet shape.
[4]
In any one of [1] to [3], a joint surface between the electrode tab and the L-shaped or U-shaped connection terminal is substantially parallel to a plane perpendicular to the stacking direction of the plurality of power storage elements. The electricity storage module described.
[5]
The power storage module includes the cell stack, the electrically connected portion, and a non-connected portion in which the plurality of electrode tabs are not electrically connected, and a space of the non-connected portion. The energy storage module according to any one of [1] to [4], in which a cushioning material is inserted.
[6]
The energy storage module according to [5], wherein the buffer material has a weight density of 80 g / L or more and 300 g / L or less.
[7]
The energy storage module according to [5] or [6], wherein the buffer material has a Young's modulus of 0.2 MPa or more and 100 MPa or less.

In the power storage module according to the present invention, a bonding portion that is resistant to vibration from the outside can be formed by fixing the plurality of adjacent electrode tabs while maintaining the direction in which they are taken out. In addition, by maintaining the direction in which the electrode tab is taken out, the stress on the joint is reduced, and a low resistance can be maintained without an increase in the electrical resistance value due to distortion of the joint. Furthermore, by using an L-shaped or U-shaped connection terminal between a plurality of adjacent electrode tabs, it is possible to contribute to weight reduction of the connection portion.
That is, according to the present invention, it is possible to provide a power storage module that is excellent in vibration resistance of the connection portion, maintains low resistance, and has improved weight energy density.

1 (a) is a perspective view of an L-shaped connection terminal, FIG. 1 (b) is a side view of the L-shaped connection terminal, FIG. 1 (c) is a perspective view of a U-shaped connection terminal, and FIG.1 (d) is a side view of a U-shaped connection terminal. FIG. 2 is a side view of a connection portion when a pair of electrode tabs are connected via L-shaped connection terminals in a plurality of adjacent power storage elements. FIG. 3 is a side view of a connection portion when a pair of electrode tabs are connected via a U-shaped connection terminal in a plurality of adjacent power storage elements. FIG. 4 shows a side view of a power storage module configured by a connection method using L-shaped connection terminals. FIG. 5 shows a side view of a power storage module configured by a connection method using a U-shaped connection terminal. FIG. 6 shows a side view of a power storage module configured by a connection method using L-shaped connection terminals and inserting a buffer into a non-connection portion between electrode tabs. FIG. 7 shows a side view of a power storage module configured by a connection method using a U-shaped connection terminal and inserting a buffer into a non-connection portion between electrode tabs.

  Hereinafter, although an embodiment of the present invention is described in detail, the present invention is not limited to the following embodiment.

<Embodiment 1>
Embodiment 1 demonstrates the detail about an electrical storage module at the time of connecting at least one pair of electrode tabs via an L-shaped connection terminal.
The power storage module according to Embodiment 1 includes the following components:
A cell stack formed by laminating a plurality of flat storage elements;
A plurality of electrode tabs individually protruding from a plurality of adjacent power storage elements are connected to each other substantially in parallel via L-shaped connection terminals;
Have

  In general, the power storage module is also referred to as a battery module, a capacitor module, a capacitor module, a battery pack or a battery assembly, and the power storage element is also referred to as a capacitor, a power storage cell, or a battery storage.

FIG. 4 is a side view of the power storage module according to the first embodiment.
The cell stack (2) is formed by laminating a plurality of storage elements (1) having a flat shape, with a holding plate or a spacer (8) disposed between them as necessary. Of the plurality of electrode tabs (5) protruding from the plurality of adjacent power storage elements (1), a pair of adjacent electrode tabs (5) are arranged between the L-shaped connection terminals (4). The connection part according to the first embodiment is formed by connecting so as to be substantially parallel to each other. The connecting portion can be further connected to an external circuit board connector (not shown) in order to perform voltage measurement, temperature measurement, or state monitoring of the storage element (1) or the cell stack (2).

  In the power storage module (7) shown in FIG. 4, the cell stack (2) formed by a plurality of power storage elements (1) is protected by a pair of end plates (3) disposed at both ends thereof. The number of end plates that protect the cell stack (2) is not limited, and the power storage module (7) may have an exterior case (not shown) that houses one or more end plates. . Such an end plate and an exterior case may be formed of a resin material or a metal material.

  If desired, the cell stack has a holding plate between the plurality of power storage elements in order to suppress misalignment between the plurality of power storage elements, and a spacer to control the outer shape or dimensions of the cell stack. You may have. The holding plate and the spacer can be formed of a known material that operates as described above, for example, an adhesive resin, an insulating resin, or the like.

In FIG. 4, for convenience of explanation, the cell stack (2) is shown as a stacked body of eight power storage elements (1), but the number of stacked power storage elements (1) is not limited.
In addition, depending on the use of the power storage module, the cell stack is an element arrangement (FIG. 4) formed by stacking surfaces having a relatively large surface area of a plurality of power storage elements, or a relatively surface area of a plurality of power storage elements. You may have the element arrangement | positioning (not shown) formed by overlapping small surfaces (what is called an edge part).
Details of the storage element, the L-shaped connection terminal, the junction between the electrode tab and the L-shaped connection terminal, and the storage module will be described below.

[Storage element]
The power storage element has, for example, an airtight flexible packaging material of a metal laminated resin film in which an organic electrolyte containing lithium ions and an electrode laminate are sealed, for example, an aluminum foil laminated with a resin film. Moreover, it has the electrode tab electrically connected to the electrode laminated body.

  The electrode tab is preferably made of a metal having copper or aluminum having excellent conductivity as a main component. In the present embodiment, the main component refers to a component constituting 90% or more of the metal.

  A plating layer may be present on the surface of the electrode tab. A metal mainly composed of nickel, tin, gold or the like is suitable for the plating layer.

The electrode tab can protrude in an arbitrary direction from an arbitrary part of the electric storage element.
From the viewpoint of joining the electrode tab and the L-shaped connection terminal, which will be described later, the electrode tab is preferably from the power storage element in a direction substantially parallel to the surface having the largest surface area of the power storage element, more preferably other than the thickness direction of the power storage element. It is preferable that the protrusion protrudes in a direction substantially parallel to a plane perpendicular to the stacking direction of the plurality of power storage elements.

[L-shaped connection terminal]
The shape of the L-shaped connection terminal is shown in FIGS. The L-shaped connection terminal is characterized by being L-shaped when viewed from the side, and the length of the L-shaped in the depth direction (x) is not particularly limited. However, in the L-shaped plane, it is desirable that the length of at least one side is substantially equal to the distance between a plurality of adjacent electrode tabs when the power storage module is configured. By connecting the portion having one side described above of the L-shaped connection terminal so as to match the distance between the electrode tabs, it is possible to fix the electrode tab while maintaining the direction in which the electrode tab is taken out. It can be reduced, and a connection portion that is resistant to vibration from the outside can be formed. Moreover, since the strain of the electrode tab is reduced and the change in the cross-sectional area of the electrode tab can be suppressed to the minimum by reducing the stress, an increase in resistance can be prevented. In general, there is a correlation between the strain of a metal material and the rate of change in electrical resistance, and this characteristic is applied to strain gauges and the like. However, since the present invention relates to a power storage module, it is desirable that the change in resistance can be suppressed. Therefore, the idea of maintaining the electrode tab extraction direction as described above becomes important.

  The L-shaped connection terminal is preferably made of a metal whose main component is copper or aluminum. Since copper or aluminum is a material having high electrical conductivity, it is possible to realize a joint portion in which an increase in resistance is suppressed. In addition, since the strength of the material itself is high, it is possible to provide a joint portion in consideration of vibration resistance.

  Further, a plating layer may be present on the surface of the L-shaped connection terminal. For the plating layer, a metal mainly composed of nickel, tin, gold or the like is suitable.

  When the L-shaped connection terminal is interposed between the electrode tabs, for example, as shown in FIG. 2, the joining portion is constructed by overlapping the two L-shaped connection terminals (4) facing each other. The two L-shaped connection terminals are preferably joined by using one or more methods among laser welding, ultrasonic welding, resistance welding, and screwing. When joining by screwing, it is desirable to have one or more through holes in the L-shaped connection terminal as shown in FIG.

  Since the L-shaped connection terminal has a simple shape and is lightweight, it can also contribute to weight reduction of the power storage module. That is, the L-shaped connection terminal can be said to be a useful connection component because it can improve the weight energy density and weight power density of the power storage module.

[Junction of electrode tab and L-shaped connection terminal]
Both the electrode tabs provided in the storage elements and the L-shaped connection terminals that serve to connect the storage elements are components that assume that a large current flows, and the quality of the joining state directly affects the performance of the storage module, for example. Affect it.

  In order to sufficiently exhibit the performance of the power storage element constituting the power storage module, the joint portion between the electrode tab and the L-shaped connection terminal needs to have a low resistance. If the resistance of the junction portion is low, current or voltage loss can be suppressed, and energy and power inherent in the power storage element can be exhibited.

  In addition, since the joint portion described above also has a role of connecting and fixing each power storage element, stress due to vibration from the outside may be concentrated. For this reason, it is necessary to have a strength that cannot be easily removed.

  As a result of the above, it is considered desirable to use welding such as laser welding, ultrasonic welding, or resistance welding for joining the electrode tab and the L-shaped connection terminal. If it is welding, it is possible to realize low-resistance and high-strength bonding.

  In general, the joint obtained by welding has a higher strength when pulled in a direction perpendicular to the joint surface and when pulled in a direction parallel to the joint surface. Show. This is because the tensile strength of the material is higher than the shear strength. In the present invention, by assembling the module so that the joint surface is substantially parallel to a plane perpendicular to the stacking direction of the plurality of power storage elements, durability against vibrations in the stacking direction of the power storage elements that are likely to resonate. It is possible to realize a joint having a thickness. The same applies to the U-shaped connection terminal described below.

[Power storage module]
With the above bonding method, as shown in FIG. 4, the power storage module (7) according to Embodiment 1 can be configured.

<Embodiment 2>
Embodiment 2 demonstrates the detail about an electrical storage module at the time of connecting at least a pair of electrode tabs via a U-shaped connection terminal.
The power storage module according to Embodiment 2 has the same configuration as that of Embodiment 1 except that at least a pair of electrode tabs are connected to each other via a U-shaped connection terminal instead of an L-shaped connection terminal. Can have.
In the second embodiment, details of the power storage element, the U-shaped connection terminal, the connection between the U-shaped connection terminal and the electrode tab, and the power storage module will be described below.

[Storage element]
The power storage element is the same as that of the first embodiment.

[U-shaped connection terminal]
The shape of the U-shaped connection terminal is shown in FIGS. 1 (c) and 1 (d). The U-shaped connection terminal is characterized by a U-shape when viewed from the side, and the length of the U-shape in the depth direction (x) is not particularly limited. However, in the U-shaped plane, it is desirable that the length of at least one side is substantially equal to the distance between a plurality of adjacent electrode tabs when the power storage module is configured. By forming a connection so that the portion having the one side described above of the U-shaped connection terminal matches the distance between the electrode tabs, it is possible to maintain and fix the electrode tab take-out direction. The applied stress can be reduced, and a connection portion resistant to external vibration can be formed. Moreover, since the strain of the electrode tab is reduced and the change in the cross-sectional area of the electrode tab can be suppressed to the minimum by reducing the stress, an increase in resistance can be prevented.

  The U-shaped connection terminal is preferably made of a metal mainly composed of copper or aluminum for the same reason as the L-shaped connection terminal. Moreover, the plating layer may exist in the surface similarly to the L-shaped connection terminal. For the plating layer, a metal mainly composed of nickel, tin, gold or the like is suitable.

  When the U-shaped connection terminal is interposed between the electrode tabs, it is desirable to arrange the U-shaped connection terminal (6) between a pair of opposed electrode tabs (5) as shown in FIG. For the connection of the U-shaped connection terminals, it is desirable to use one or a plurality of methods among laser welding, ultrasonic welding, resistance welding, and screwing.

  Since the U-shaped connection terminal has a simple shape and is lightweight, it can also contribute to weight reduction of the power storage module. That is, the U-shaped connection terminal can be said to be a useful connection component because it can improve the weight energy density and weight power density of the power storage module.

[Join U-shaped connection terminal and electrode tab]
For the same reason as described in the section of joining the L-shaped connection terminal and the electrode tab of the first embodiment, laser welding, ultrasonic welding, resistance welding is used for joining the electrode tab and the connecting terminal of the second embodiment. It is considered desirable to use welding. If it is welding, low resistance and high strength joining can be realized.

[Power storage module]
With the above bonding method, as shown in FIG. 5, the power storage module according to Embodiment 2 can be configured.

<Improvement of vibration resistance of unconnected parts>
In Embodiment 1 or 2, since the L-shaped terminal or the U-shaped terminal exists in the connection portion where the electrode tabs of the adjacent power storage elements are electrically connected, the electrode tabs can be taken out in parallel. On the other hand, since there is a space in the non-connected portion where the plurality of electrode tabs are not electrically connected, and there is room for the electrode tab to shake, the electrode tabs in the non-connected portion may not be maintained in parallel. In Embodiment 1 or 2, it is possible to further improve the vibration resistance by inserting a cushioning material into the space of the non-connecting portion.
FIG. 6 is a side view of the power storage module according to Embodiment 1 configured by inserting a cushioning material into the space of the non-connection portion. For example, as shown in FIG. 6, the storage module (7) includes a cell stack (2) and a connection portion in which a plurality of electrode tabs (5) are electrically connected via an L-shaped connection terminal (4). And a plurality of electrode tabs (5) are not electrically connected, and a buffer (9) is inserted in the space of the non-connected parts.
FIG. 7 is a side view of the power storage module according to Embodiment 2 configured by inserting a buffer material into the space of the non-connection portion. For example, as shown in FIG. 7, the storage module (7) is connected to the cell stack (2) and the plurality of electrode tabs (5) are electrically connected via the U-shaped connection terminal (6). Part and a non-connection part which is not electrically connected between a plurality of electrode tabs (5), and buffer (9) is inserted in the space of the non-connection part.

[Insulation properties of cushioning material]
A material that can be electrically insulated may be used as the buffer material. The buffer material is preferably a material having a resistance value of 10 MΩ or more at a direct current of 500 V, and more preferably 100 MΩ or more at a direct current of 500 V. If the buffer material has a direct current of 500 V and a resistance value of 10 MΩ or more, an electrical short circuit between adjacent power storage elements can be prevented.

[Weight density of cushioning material]
The weight density of the buffer material is preferably 80 g / L or more and 300 g / L or less, more preferably 100 g / L or more and 200 g / L or less, and further preferably 110 g / L or more and 180 g / L or less. is there. If the weight density of the buffer material is 80 g / L or more, the strength of the buffer material can be maintained, and if it is 300 g / L or less, a decrease in the weight energy density of the power storage module can be suppressed.
[Young's modulus of cushioning material]
The Young's modulus of the buffer material is preferably 0.2 MPa or more and 100 MPa or less, more preferably 10 MPa or more and 80 MPa or less, and further preferably 20 MPa or more and 50 MPa or less. If the Young's modulus of the buffer material is 0.2 MPa or more, the buffer material has sufficient rigidity, and the resonance point of the power storage module can be shifted to the high frequency side. Resonance can be avoided within the range, and vibration resistance is improved. If the Young's modulus is 100 MPa or less, it has flexibility to allow welding marks generated in the electrode tab or distortion of the electrode tab, and locally prevents pressure from being applied to the electrode tab.
Examples of the material of the buffer material include a resin material, a foamable resin material, or a mixed material thereof.

<Other embodiments>
A power storage module in which a plurality of electrode tabs individually protruding from a plurality of adjacent power storage elements are connected to be substantially parallel to each other using an L-shaped connection terminal and a U-shaped connection terminal is also provided. It is another embodiment (not shown). In this embodiment, one connection part may be formed by interposing both the L-shaped connection terminal and the U-shaped connection terminal between a pair of electrode tabs, or a specific pair of electrode tabs may be L-shaped. It is also possible to connect via a terminal and connect another pair of electrode tabs via a U-shaped connection terminal to form at least two connecting portions.

  Embodiments of the present invention will be described in detail in the following examples, but the present invention is not limited to these examples and can be variously modified.

<Embodiment 1>
[Example 1]
[Production of power storage module]
When the power storage module (7) is configured as shown in FIG. 4, the direct current internal resistance of the power storage module (7) is 30.1 mΩ, and the total internal resistance of the plurality of stacked power storage elements (1) is 30. Since the resistance was 0.0 mΩ, the rate of increase in resistance due to the joint portion was less than 1%, and the resistance was low. In addition, when an internal resistance was measured after applying vibrations of 1 G and 50 Hz for 3 hours in the stacking direction of a plurality of power storage elements in this power storage module, the resistance value was 30.2 mΩ and the resistance increase rate was less than 1%. Met.
On the other hand, the length of one side of the L-shaped connection terminal was reduced by 10%, and a test similar to the above was performed in a joined state in which the tab take-out direction was not parallel. When applying vibrations of 1 G and 50 Hz, The resistance value was 31.0 mΩ, and the resistance increase rate exceeded 1%.
[Vibration test of power storage module]
The state of the electrode tab after inserting a buffer material (mixture of foamed polyethylene and polyester) with a Young's modulus of 0.3 MPa and a weight density of 120 g / L into the non-connected portion of the electricity storage module and applying vibrations of 10 G and 100 Hz for 3 hours As a result of visual observation, it was confirmed that there was no dislodging or cracking.

[Examples 2 to 5, Comparative Examples 1 to 5]
Vibration tests were performed using buffer materials with different Young's modulus and weight density. However, in Comparative Example 1, the vibration test was performed without inserting the cushioning material.
The results of Examples 1 to 5 and Comparative Examples 1 to 5 are shown in Table 1 below.

<Embodiment 2>
[Examples 6 to 10, Comparative Examples 6 to 10]
[Production of power storage module]
When the power storage module is configured as shown in FIG. 5, the direct current internal resistance of the power storage module (7) is 30.1 mΩ, and the total internal resistance of the plurality of stacked power storage elements (1) is 30.0 mΩ. Therefore, the rate of increase in resistance due to the joint portion was less than 1%, and the resistance was low. Further, when the internal resistance was measured while applying vibrations of 1 G and 50 Hz in the stacking direction of the power storage elements of this power storage module, the resistance value was 30.2 mΩ and the resistance increase rate was less than 1%.
On the other hand, when a test similar to the above was performed in a joined state in which the length of one side of the U-shaped connection terminal was shortened by 10% and the tab take-out direction was not parallel, when vibrations of 1 G and 50 Hz were applied. The resistance value was 31.3 mΩ, and the resistance increase rate exceeded 1%.
[Vibration test of power storage module]
The buffer material similar to the buffer material used in Examples 1 to 5 was used for the power storage modules produced in Examples 6 to 10, respectively, and after applying vibration of 10 G and 100 Hz for 3 hours, the state of the electrode tab Was visually observed. The results are shown in Table 2 below.
In Comparative Example 6, a vibration test was performed without inserting a buffer material into the power storage module produced above. The buffer material similar to the buffer material used in Comparative Examples 2 to 5 was used for the power storage modules prepared in Comparative Examples 7 to 10, respectively, and after applying vibration of 10 G and 100 Hz for 3 hours, the state of the electrode tab Was visually observed.
The results of Examples 6 to 10 and Comparative Examples 6 to 10 are shown in Table 2 below.

  From the comparison between Table 1 and Table 2, it can be seen that the power storage module according to the second embodiment also obtained the same result as the power storage module according to the first embodiment.

  The power storage element and the power storage module of the present invention are suitable, for example, in the field of a hybrid drive system in which an internal combustion engine, a fuel cell, or a motor in a car and a power storage element are combined; Can be used.

DESCRIPTION OF SYMBOLS 1 Power storage element 2 Cell stack 3 End plate 4 L-shaped connection terminal 5 Electrode tab 6 U-shaped connection terminal 7 Power storage module 8 Holding plate or spacer 9 Buffer material x Depth direction

Claims (7)

A cell stack formed by laminating a plurality of storage elements having a flat shape;
A plurality of electrode tabs individually protruding from a plurality of adjacent power storage elements are connected to each other substantially in parallel via L-shaped or U-shaped connection terminals;
A power storage module having   The power storage module according to claim 1, wherein a distance between a plurality of adjacent electrode tabs is substantially equal to a length of one side of the L-shaped or U-shaped connection terminal.   The power storage module according to claim 1 or 2, wherein the electrode tab connected to the L-shaped or U-shaped connection terminal has a sheet shape.   The joint surface of the said electrode tab and the said L-shaped or U-shaped connection terminal is substantially parallel to the plane perpendicular | vertical to the lamination direction of several said electrical storage element. Power storage module.   The power storage module includes the cell stack, the electrically connected portion, and a non-connected portion in which the plurality of electrode tabs are not electrically connected, and a space of the non-connected portion. The power storage module according to any one of claims 1 to 4, wherein a buffer material is inserted into the battery module.   The power storage module according to claim 5, wherein the buffer material has a weight density of 80 g / L or more and 300 g / L or less.   The power storage module according to claim 5 or 6, wherein the buffer material has a Young's modulus of 0.2 MPa to 100 MPa.

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