JP2018032581A - Assembled battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an assembled battery capable of further suppressing high rate deterioration while suppressing abrasion deterioration of a battery cell.SOLUTION: The assembled battery is formed by alternately stacking in a thickness direction a plurality of rectangular battery cells in which an electrode winding body 20 is housed and a plurality of spacers 18. On surfaces of the spacers 18, a plurality of ribs 32 arranged in a comb teeth shape and in contact with a surface of the battery cell are formed. The ribs 32 are arranged only in a substantially U-shaped range opposed to both ends in the width direction of the electrode winding body 20 of the surface of the spacer 18.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a battery pack in which a plurality of rectangular battery cells each having an electrode winding body accommodated therein and a plurality of spacers are alternately stacked in the thickness direction.

  Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries and sodium-ion secondary batteries are lighter and have higher energy density than existing batteries, so power sources for driving electric vehicles and power sources for portable electronic devices It is often used as.

  A rectangular battery cell is configured by accommodating an electrode winding body that functions as a non-aqueous electrolyte secondary battery and an electrolytic solution in a rectangular cell case. It is known that a battery cell composed of such a non-aqueous electrolyte secondary battery cannot be uniformly reacted with the wound electrode body and is subject to wear deterioration unless an appropriate pressure is applied to the surface thereof. Therefore, it has been conventionally proposed to form a battery pack by alternately stacking square battery cells and spacers made of resin or the like, and to apply a compressive force to the battery pack in the stacking direction. For example, Patent Document 1 discloses a power storage device (assembled battery) in which rectangular power storage elements (battery cells) and spacers are alternately stacked. In Patent Document 1, a plurality of ribs that are in contact with the surface of the electric storage element are formed on the surface of the spacer. A space between the plurality of ribs becomes a flow path through which cooling air flows. In this case, since the battery cells are pressed evenly through the ribs, the wear deterioration of the battery cells is effectively suppressed.

JP 2006-091665 A

  However, it is known that non-aqueous electrolyte secondary batteries cause not only wear deterioration but also high rate deterioration. High rate degradation is degradation caused by repeated charge and discharge at a high rate. Such high-rate deterioration is considered to be caused by leakage of the electrolyte that has expanded due to charge / discharge at a high rate to the outside of the electrode winding body. The electrolyte leaks out of the electrode winding body, resulting in non-uniform salt (ion) concentration distribution in the electrode winding body and insufficient salt in the electrode winding body, resulting in battery cell performance degradation, This causes so-called high rate deterioration.

  As in Patent Document 1, when the entire surface of the battery cell is pressed evenly through the ribs on the spacer surface, the expansion of the electrode winding body is suppressed. In this case, since the electrode winding body cannot hold the expanded electrolyte solution, the electrolyte solution easily leaks to the outside of the electrode winding body, and high-rate deterioration easily proceeds. That is, in the prior art such as Patent Document 1, even though the wear deterioration can be suppressed, the high rate deterioration cannot be sufficiently suppressed.

  Therefore, an object of the present invention is to provide an assembled battery that can further suppress high-rate deterioration while suppressing wear deterioration of battery cells.

  The assembled battery of the present invention is an assembled battery in which a plurality of rectangular battery cells each having an electrode winding body accommodated therein and a plurality of spacers are alternately stacked in the thickness direction, and the surface of the spacer Are formed with a plurality of ribs that are arranged in a comb shape and abut against the surface of the battery cell, and the ribs are opposed to both ends and an upper portion of the electrode winding body in the width direction on the surface of the spacer. It is arranged only in a substantially U-shaped range, or only in a substantially E-shaped range facing both ends in the width direction and the upper part and the center in the width direction of the electrode winding body.

  According to the present invention, since the electrode winding body is allowed to expand in the lower portion where the electrolytic solution easily accumulates, high-rate deterioration is suppressed. Moreover, since the upper part of the electrode winding body and both ends in the width direction are pushed by the ribs, wear deterioration of the battery cell is also suppressed.

It is a schematic perspective view of the assembled battery which is embodiment of this invention. It is a perspective view of a battery cell. It is a schematic front view of a resin frame. It is a schematic front view of the resin frame of another example. It is a figure which shows the expansion | swelling tolerance range in the resin frame of FIG. It is a figure which shows the expansion | swelling tolerance range in the resin frame of FIG. It is a figure which shows the experimental result of deterioration tolerance according to the shape of a rib. It is a schematic front view of the conventional resin frame.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic perspective view of an assembled battery 10 according to an embodiment of the present invention. In the present application, “lower” is the direction of action of gravity, and “upper” is the opposite side. The assembled battery 10 of this embodiment is installed so that the terminals 22p and 22n of the rectangular battery cell 16 are “up”.

  The assembled battery 10 includes a battery stack 12 and a pair of end plates 14 disposed on both sides in the stacking direction of the battery stack 12. Further, the battery stack 12 is configured by alternately stacking battery cells 16 and spacers 18 made of resin in the thickness direction.

  FIG. 2 is a perspective view of the battery cell 16. The battery cell 16 is a chargeable / dischargeable secondary battery, such as a lithium ion secondary battery or a sodium ion secondary battery. The battery cell 16 is a square battery in which a flat electrode winding body 20 is accommodated together with an electrolyte in a flat rectangular parallelepiped cell case. The electrode winding body 20 is configured by laminating a sheet-like positive electrode, a separator, and a negative electrode, then winding them in a spiral shape, and then forming them into a flat shape. This electrode winding body 20 is accommodated in the cell case in such a posture that its winding axis R is substantially orthogonal to the direction of gravity (vertical direction). Further, the electrode winding body 20 is impregnated with an electrolytic solution. Hereinafter, the direction of the winding axis R is referred to as a “width direction”.

  From the upper end surface of the battery cell 16, a substantially cylindrical positive electrode terminal 22 p and negative electrode terminal 22 n protrude. The positive electrode terminal 22p and the negative electrode terminal 22n are arranged at an interval in the width direction. A gas release valve 24 is provided in the center in the width direction of the upper end surface of the battery cell 16, that is, between the positive terminal 22p and the negative terminal 22n. The gas release valve 24 is a valve for releasing the gas generated inside the battery cell 16 when the battery cell 16 is abnormally reacted. The gas release valve 24 is closed when the internal pressure of the battery cell 16 is less than a certain value, but is opened when the internal pressure becomes equal to or greater than a certain value, and releases the gas to the outside. The gas release valve 24 is configured, for example, by forming a part of the case of the battery cell 16 to be thin so as to be broken when subjected to a certain pressure or more. However, the configuration of the gas release valve 24 is not limited to this, and may be changed as appropriate.

  The plurality of battery cells 16 are stacked in the thickness direction. At this time, the plurality of battery cells 16 are arranged with their orientations alternately changed so that the positive terminals 22p and the negative terminals 22n are alternately arranged in the stacking direction (see FIG. 1). That is, when a certain battery cell 16 is arranged so that the positive electrode terminal 22p is located on the right side, the next battery cell 16 is arranged so that the negative electrode terminal 22n is located on the right side. A plurality of battery cells 16 are electrically connected in series by sequentially connecting the positive electrode terminal 22p and the negative electrode terminal 22n adjacent in the stacking direction with a bus bar (not shown).

  Spacers 18 are disposed between the battery cells 16. In other words, the battery stack 12 is formed by alternately stacking a plurality of battery cells 16 and a plurality of spacers 18. The spacer 18 is made of an insulating material and has a substantially flat base portion 26 (not visible in FIG. 1), a frame portion 28 projecting in the thickness direction from the periphery of the base portion 26, and a duct protruding from the upper end of the base portion. And a piece 30.

  The base portion 26 is a portion arranged between the battery cells 16, and a plurality of ribs 32 for forming a refrigerant flow path are formed on the surface thereof at intervals. FIG. 3 is a schematic front view of the base portion 26. In FIG. 3, illustration of the frame portion 28 and the duct piece 30 is omitted for ease of viewing. Further, in FIG. 3, the portions where the black hatching is performed are the ribs 32. As is apparent from FIG. 3, in the present embodiment, the ribs 32 are concentrated on both sides and the upper portion of the base portion 26 in the width direction, while the ribs 32 are provided at the lower portion and the width direction central portion of the base portion 26. Not provided. The reason for this configuration is to prevent wear deterioration and high-rate deterioration of the battery cell 16, which will be described later.

  Referring again to FIG. 1, the frame portion 28 has a shape along the peripheral surface of the battery cell 16 and restricts movement of the battery cell 16 in the surface direction. A duct piece 30 is provided at the upper end of the spacer 18 and at the center in the width direction. The duct piece 30 protrudes from the upper end of the base portion of the spacer 18 and has a substantially U shape that opens toward the upper end surface of the battery cell 16. The upper surface of the duct piece 30 faces the gas release valve 24 of the battery cell 16. The duct piece 30 protrudes in the thickness direction from the base portion 26 of the spacer 18, and is in close contact with the duct piece 30 of another adjacent spacer 18. When the plurality of duct pieces 30 are in close contact with each other, a tunnel extending in the stacking direction is formed in the battery stack 12. This tunnel becomes a smoke exhaust duct through which the gas discharged from the gas discharge valve 24 flows.

  A pair of end plates 14 are disposed on both sides in the stacking direction of the battery stack 12 including the battery cells 16 and the spacers 18. The end plate 14 is a plate having a sufficient rigidity, for example, aluminum or hard plastic. The battery stack 12 and the stack formed by the pair of end plates 14 are the assembled battery 10. The assembled battery 10 is given a compression force in the stacking direction (hereinafter referred to as “binding force”). By applying the restraining force, the movement of the battery cell 16, the spacer 18, and the end plate 14 constituting the assembled battery 10 is restricted and restrained. Further, by applying the restraining force, the surface of the battery cell 16 and the rib 32 formed on the surface of the spacer 18 are in close contact with each other, and an appropriate pressure is applied to the battery cell 16.

  Such a restraining force is applied using, for example, a metal band called a restraining band. Specifically, when a restraining force is applied to the assembled battery 10, a pair of end plates 14 are fixed to both ends of a restraining band made of metal and having an invariable length. Thereby, the distance between the pair of end plates 14 is fixed. Here, if the length of the restraint band is adjusted in advance so that the distance between the end plates 14 fixed by the restraint band is shorter than the length in the stacking direction of the battery stack 12 in an unloaded state, the battery The laminated body 12 receives a restraining force of compression in the laminating direction from the end plate 14.

  Moreover, as another form, you may adjust the size of the case which accommodates the assembled battery 10, and may provide restraint force. Specifically, the stacking direction length of the accommodation space provided in the case is made shorter than the stacking direction length of the assembled battery 10 in the no-load state. And you may make it accommodate the assembled battery 10 of a contracted state by the force of the lamination direction compression in this accommodation space. In any case, the surface of each battery cell 16 comes into contact with the rib 32 formed on the spacer 18 by applying a binding force of compression in the stacking direction.

  Next, the arrangement of the ribs 32 provided on the spacer 18 will be described with reference to FIG. As described above, FIG. 3 is a front view of the base portion 26 of the spacer 18. In FIG. 3, the portions where the black hatching is applied are the ribs 32. However, the portion of the rib 32 that is darkly hatched is a contact portion that contacts the surface of the battery cell 16 when restraint is applied. Further, the portion of the rib 32 that has been subjected to light ink hatching is a slope portion that gradually rises from the surface of the base portion 26 to the height of the contact portion, that is, the surface of the battery cell 16. It is a part that does not. Furthermore, in FIG. 3, a rectangle illustrated by a two-dot chain line indicates a region facing the electrode winding body 20 of the battery cell 16 when assembled as the assembled battery 10.

  As is clear from FIG. 3, the plurality of ribs 32 are arranged in a comb-tooth shape with a predetermined interval between adjacent ribs 32. From another viewpoint, a groove 34 is formed between the rib 32 and the rib 32. When a binding force is applied to the assembled battery 10, the rib 32 contacts the surface of the battery cell 16. At this time, the groove 34 functions as a refrigerant path through which cooling air for cooling the battery cell 16 flows.

  The rib 32 extends in the width direction in the vicinity of both ends of the base portion 26 in the width direction. When the rib 32 approaches the center of the base portion 26, the rib 32 is bent in an arc shape and extends downward. Cooling air for cooling the battery cells 16 flows in from the lower side of the base portion 26, spreads on both sides in the width direction along the grooves 34, and is finally discharged to the outside from the width direction end portion of the base portion 26. Thick line arrows in FIG. 3 indicate the flow of cooling air.

  Here, as is apparent from FIG. 3, in this embodiment, the rib 32 is not provided in the lower portion of the base portion 26 and in the center in the width direction. In other words, in the present embodiment, the rib 32 is provided only in the substantially U-shaped range facing both ends and the upper portion of the electrode winding body 20. The reason for this configuration is to suppress wear deterioration and high rate deterioration of the battery cells 16. This will be described in comparison with the prior art.

  The battery cell 16 gradually deteriorates as the battery cell 16 is used, and wear deterioration and high-rate deterioration are known as types of the deterioration. The wear deterioration is a deterioration of the material constituting the battery cell 16, for example, an electrode or a separator. In order to prevent this wear deterioration, it is effective to prevent deformation (swell) of the electrode winding body 20 in the cell case. And in order to prevent the winding of the electrode winding body 20, it is effective to press the surface of the battery cell 16 equally with moderate pressure.

  Therefore, in the conventional spacer 18, the ribs 32 are evenly provided on the entire surface of the base portion 26. FIG. 8 is a view showing an example of a conventional spacer 18. In the base portion 26 of the conventional spacer 18, ribs 32 are evenly provided on the entire surface of the base portion 26. In this case, wear deterioration of the battery cell 16 can be effectively suppressed. However, in this case, since the entire surface of the electrode winding body 20 is pressed evenly, high-rate deterioration is likely to occur.

  High rate deterioration is deterioration that occurs when the battery cell 16 is charged and discharged at a high rate. This high-rate deterioration is considered to be caused by leakage of the electrolyte that has expanded due to charge / discharge at a high rate to the outside of the electrode winding body 20. When the electrolytic solution leaks to the outside of the electrode winding body 20, the salt (ion) concentration distribution in the electrode winding body 20 becomes non-uniform and the salt shortage in the electrode winding body 20 occurs. The performance of the cell 16 is degraded.

  As shown in FIG. 8, when the rib 32 is provided so as to press the entire electrode winding body 20 evenly, the expansion of the electrode winding body 20 is caused even if the electrolytic solution expands due to charge / discharge at a high rate. Is regulated. As a result, the electrode winding body 20 cannot hold the expanded electrolyte solution, and high-rate deterioration is likely to occur because the electrolyte solution leaks to the outside from both ends in the width direction (both ends in the winding axis R direction) of the electrode winding body.

  In order to suppress such high rate deterioration, it is desirable to allow the expansion of the electrode winding body 20 as much as possible. If the electrode winding body 20 can also expand along with the expansion of the electrolytic solution, the leakage of the electrolytic solution and, consequently, the high-rate deterioration can be effectively suppressed.

  Here, the electrolytic solution tends to accumulate in the lower part of the electrode winding body 20 due to gravity. Therefore, the amount of expansion of the electrolyte when charging / discharging at a high rate is larger in the lower part than in the upper part of the electrode winding body 20. Moreover, the electrolyte solution that could not be held by the electrode winding body 20 mainly leaks to the outside from both ends in the width direction (both ends in the winding axis R direction) of the electrode winding body 20. Therefore, in order to prevent leakage of the electrolytic solution, it is desirable to press both ends in the width direction of the electrode winding body 20 so as to block the leakage of the electrolytic solution. In addition, it is desirable that the electrode winding body 20 can expand at the lower part of the electrode winding body 20 having a large expansion amount following the expansion of the electrolytic solution.

  Therefore, in the present embodiment, the ribs 32 are not provided in a range of the base portion 26 that faces the lower part of the electrode winding body 20 and the center in the width direction, and the electrode winding body 20 is allowed to expand. Thereby, high rate deterioration can be prevented effectively. On the other hand, ribs 32 are provided in a comb-teeth shape in a substantially U-shaped range facing the both ends and the upper part of the electrode winding body 20 in the base portion 26. Thus, by providing the ribs 32 at appropriate intervals, it is possible to suppress wear deterioration of the battery cells 16. Further, by providing the ribs 32 so as to hold both ends of the electrode winding body 20 in the width direction, leakage of the electrolytic solution is blocked and high-rate deterioration can be suppressed.

  Furthermore, according to this embodiment, the flow velocity of the cooling air for cooling the battery cells 16 can be made uniform. And thereby, pressure loss can be reduced and the battery cell 16 can be cooled more efficiently. That is, as described above, the cooling air for cooling the battery cells 16 flows from the lower portion of the base portion 26. In the prior art shown in FIG. 8, since a plurality of ribs 32 are also formed at the lower portion of the base portion 26, the flow rate of the cooling air flowing in from the lower portion is rapidly reduced because the flow path is rapidly throttled. Become. In FIG. 8, the hatched areas indicate the areas where the flow velocity increases rapidly. As described above, when the refrigerant flow path is rapidly throttled and, as a result, when the flow velocity is rapidly increased, the pressure loss increases, and the cooling efficiency of the battery cell 16 is reduced.

  On the other hand, in this embodiment, the rib 32 is not provided in the lower part which is an inlet_port | entrance of cooling air. Therefore, since the cooling air flowing in from the lower part is gradually throttled, a rapid change in the flow velocity is unlikely to occur, and pressure loss can be effectively prevented.

  The arrangement of the ribs 32 shown in FIG. 3 is an example, and other forms may be used as long as the ribs 32 that hold down the lower part of the electrode winding body 20 are sufficiently small. For example, as shown in FIG. 4, the ribs 32 may be provided only in the substantially E-shaped range facing both ends, the upper part, and the center in the width direction of the electrode winding body 20. 4, in addition to the configuration of FIG. 3, a rib 32 extending vertically is provided at the center in the width direction. Even in this case, since expansion at the lower part of the electrode winding body 20 is allowed, high-rate deterioration is effectively prevented.

  5 and 6 are diagrams illustrating the expandable range of the electrode winding body 20. In FIGS. 5 and 6, the cross-hatched portion indicates a range where the electrode winding body 20 can be expanded. As is apparent from FIGS. 5 and 6, the rib 32 can be inflated both when it is disposed in a substantially U-shaped range (FIG. 5) and when the rib 32 is disposed in a substantially E-shaped range (FIG. 6). A sufficient range can be secured. In particular, it is possible to ensure a wide inflatable range in the lower part where the amount of expansion is large. As a result, high rate deterioration can be effectively suppressed. On the other hand, since the rib 32 is provided in the range which opposes the upper part of the electrode winding body 20, and the width direction both ends, wear deterioration can also be suppressed effectively.

  FIG. 7 is a diagram showing the experimental results of the deterioration resistance according to the shape of the rib 32. In FIG. 7, the horizontal axis indicates the number of charge / discharge cycles at a high rate, and the vertical axis indicates the rate of increase in the resistance of the battery cell 16. In FIG. 7, the resistance of the battery cell 16 in the initial state is 100%. In FIG. 7, the solid line and triangle markers are the spacer 18 shown in FIG. 3, the broken line and black circle markers are the spacer 18 shown in FIG. 4, and the alternate long and short dash line and square markers are the spacer 18 shown in FIG. The experimental result in the assembled battery 10 using (conventional spacer 18) is shown.

  As is clear from FIG. 7, the resistance value of the battery cell 16 gradually increases by repeating charging and discharging. However, when there is no rib 32 for pressing the lower center of the electrode winding body 20 or the spacer 18 shown in FIGS. 3 and 4 is used, the spacer 18 shown in FIG. It can be seen that the increase in resistance is significantly suppressed compared to the case of using it. Specifically, even if the resistance value increases by about 35% or more in the form of FIG. 8, the increase in resistance can be suppressed to about 5% to 10% in the form of FIGS. That is, according to the form of FIG. 3 and FIG. 4, the deterioration of the battery cell 16 can be suppressed to about 1/3 to 1/7 as compared with the prior art.

  As is clear from the above description, the ribs 32 provided on the spacer 18 are provided only in the substantially U-shaped range facing both the widthwise ends and the upper portion of the electrode winding body 20 or both ends of the electrode winding body 20 in the width direction. By disposing only in a substantially E-shaped range facing the upper part and the center in the width direction, high-rate deterioration can be suppressed while suppressing wear deterioration of the battery cells 16. Moreover, by setting it as this arrangement | positioning, the flow rate of the cooling air which flows through the refrigerant path formed between the ribs 32 can be equalize | homogenized, and the battery cell 16 can be cooled more efficiently.

  In addition, the structure demonstrated so far is an example, and only the width direction both ends and upper part of the width direction of the electrode winding body 20 are only in the substantially U-shaped range which opposes the width direction both ends and upper part of the electrode winding body 20. As long as the rib 32 is provided only in a substantially E-shaped range facing the center in the width direction, other configurations may be appropriately changed. For example, in the present embodiment, the numbers and configurations of the battery cells 16 and the spacers 18 are all examples, and other configurations may be appropriately changed as long as the ribs 32 are provided at appropriate locations. In the present embodiment, the plurality of battery cells 16 are connected in series, but the plurality of battery cells 16 may be connected in parallel.

10 battery packs, 12 battery stacks, 14 end plates, 16 battery cells, 18 spacers, 20 electrode winding bodies, 22n negative electrode terminals, 22p positive electrode terminals, 24 gas release valves, 26 base parts, 28 frame parts, 30 duct pieces , 32 ribs, 34 grooves.

Claims (1)

A battery pack in which a plurality of rectangular battery cells in which an electrode winding body is housed and a plurality of spacers are alternately stacked in the thickness direction,
On the surface of the spacer, a plurality of ribs are formed that are arranged in a comb shape and come into contact with the surface of the battery cell,
The rib is only in a substantially U-shaped range facing the both ends and the top of the electrode winding body on the surface of the spacer, or both ends and the top and the width direction of the electrode winding body. Arranged only in a substantially E-shaped range facing the center,
A battery pack characterized by that.