JP6852308B2 - Batteries - Google Patents

Description

The present invention relates to an assembled battery in which a plurality of square battery cells in which an electrode winding body is housed and a plurality of spacers are alternately laminated in the thickness direction.

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

The square battery cell is configured by accommodating an electrode winding body and an electrolytic solution that function as a non-aqueous electrolyte secondary battery in a square cell case. It is known that a battery cell made of such a non-aqueous electrolyte secondary battery cannot undergo a uniform battery reaction in the electrode winding body unless an appropriate pressure is applied to the surface thereof, and wear deterioration is likely to occur. Therefore, conventionally, it has been proposed that square battery cells and spacers made of resin or the like are alternately laminated to form an assembled battery, and further, a force of compression in the stacking direction is applied to the assembled battery. For example, Patent Document 1 discloses a power storage device (battery assembly) in which square power storage elements (battery cells) and spacers are alternately laminated. In Patent Document 1, a plurality of ribs abutting on the surface of the power storage element are formed on the surface of the spacer. Then, the space between the plurality of ribs serves as a flow path through which cooling air flows. Further, in this case, since the battery cells are evenly pressed via the ribs, wear deterioration of the battery cells is effectively suppressed.

JP-A-2016-091665

However, it is known that a non-aqueous electrolyte secondary battery causes not only wear deterioration but also high rate deterioration. High-rate deterioration is deterioration caused by repeated charging and discharging at a high rate. It is considered that such high-rate deterioration occurs when the electrolytic solution expanded due to charging / discharging at a high rate leaks to the outside of the electrode winding body. Leakage of the electrolytic solution to the outside of the electrode winding body causes non-uniform salt (ion) concentration distribution in the electrode winding body and salt deficiency in the electrode winding body, resulting in deterioration of battery cell performance. It causes so-called high rate deterioration.

When the entire surface of the battery cell is evenly pressed via the ribs on the surface of the spacer as in Patent Document 1, the expansion of the electrode winding body is suppressed. In this case, since the electrode winding body cannot completely hold the expanded electrolytic solution, the electrolytic solution tends to leak to the outside of the electrode winding body, and high-rate deterioration tends to proceed. That is, in the prior art such as Patent Document 1, although 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 capable of further suppressing high-rate deterioration while suppressing wear deterioration of the battery cell.

Assembled battery of the present invention is a battery assembly having a plurality of prismatic battery cell in which the electrode winding body and electrolyte are accommodated functioning as a non-aqueous electrolyte secondary battery therein, and a plurality of spacers, the The electrode winding body is housed in the battery cell in a posture in which the winding axis direction is substantially orthogonal to the gravity direction, and the plurality of the battery cells and the plurality of spacers are housed in the winding axis direction. It is laminated alternately in a direction orthogonal to the direction of gravity and substantially orthogonal to the direction of gravity, and a plurality of ribs arranged in a comb-tooth shape and abutting on the surface of the battery cell are formed on the surface of the spacer. the ribs, of the surface of the spacer, only a substantially U-shaped region facing the direction of gravity upper and the winding axial direction both ends of the electrode winding body or gravity of the electrode winding body It is characterized in that it is arranged only in a substantially E-shaped range facing the upper part of the direction, both ends in the winding axis direction, and the center in the winding axis direction.

According to the present invention, expansion of the electrode winding body is allowed in the lower part where the electrolytic solution tends to accumulate, so that high-rate deterioration is suppressed. Further, since the upper portion of the electrode winding body and both ends in the width direction are pressed by the ribs, wear deterioration of the battery cell is suppressed.

It is a schematic perspective view of the assembled battery which is an 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 permissible range in the resin frame of FIG. It is a figure which shows the expansion permissible range in the resin frame of FIG. It is a figure which shows the experimental result of deterioration resistance according to the shape of a rib. It is a schematic front view of the conventional resin frame.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view of the assembled battery 10 according to the 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 the present embodiment is installed so that the terminals 22p and 22n of the square battery cell 16 are "upper".

The assembled battery 10 includes a battery laminate 12 and a pair of end plates 14 arranged on both sides of the battery laminate 12 in the stacking direction. Further, the battery laminate 12 is configured by alternately laminating the battery cell 16 and the spacer 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 rechargeable secondary battery, for example, a lithium ion secondary battery, a sodium ion secondary battery, or the like. The battery cell 16 is a square battery in which a flat electrode winding body 20 is housed together with an electrolytic solution inside a flat rectangular parallelepiped cell case. The electrode winding body 20 is formed by laminating a sheet-shaped positive electrode, a separator, and a negative electrode, winding the electrode winding body 20 in a spiral shape, and then molding the electrode winding body 20 into a flat shape. The electrode winding body 20 is housed in the cell case in a posture in which the winding axis R is substantially orthogonal to the direction of gravity (vertical direction). Further, the electrode winding body 20 is impregnated with the electrolytic solution. In the following, the direction of the winding axis R will be referred to as a "width direction".

A substantially cylindrical positive electrode terminal 22p and a negative electrode terminal 22n project from the upper end surface of the battery cell 16. The positive electrode terminal 22p and the negative electrode terminal 22n are arranged at intervals in the width direction. A gas release valve 24 is provided at the center of the upper end surface of the battery cell 16 in the width direction, that is, between the positive electrode terminal 22p and the negative electrode terminal 22n. The gas release valve 24 is a valve that releases the gas generated inside the battery cell 16 when the battery cell 16 reacts abnormally. The gas release valve 24 is closed when the internal pressure of the battery cell 16 is less than a certain level, but is opened when the internal pressure becomes a certain level or more, and the gas is discharged to the outside. The gas release valve 24 is configured, for example, by forming a part of the case of the battery cell 16 into a thin wall so as to break when a certain pressure or more is applied. 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 in alternating directions so that the positive electrode terminals 22p and the negative electrode 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. Then, by sequentially connecting the positive electrode terminals 22p and the negative electrode terminals 22n adjacent to each other in the stacking direction with a bus bar (not shown), the plurality of battery cells 16 are electrically connected in series.

A spacer 18 is arranged between the battery cell 16 and the battery cell 16. In other words, the battery laminate 12 is formed by alternately laminating a plurality of battery cells 16 and a plurality of spacers 18. The spacer 18 is made of an insulating material, has a substantially flat base portion 26 (not visible in FIG. 1), a frame portion 28 projecting from the peripheral edge of the base portion 26 in the thickness direction, and a duct protruding from the upper end of the base portion. It is equipped with a piece 30 and.

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, the frame portion 28 and the duct piece 30 are not shown for the sake of clarity. Further, in FIG. 3, the portion where the black hatching is applied is the rib 32. As is clear from FIG. 3, in the present embodiment, the ribs 32 are concentrated on both sides and the upper portion in the width direction of the base portion 26, while the ribs 32 are provided in the lower portion and the central portion in the width direction of the base portion 26. Not provided. This configuration is for preventing wear deterioration and high rate deterioration of the battery cell 16, which will be described later.

To explain again with reference to FIG. 1, the frame portion 28 has a shape along the peripheral surface of the battery cell 16 and restricts the 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 is formed so as to project 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 discharge valve 24 of the battery cell 16. Further, the duct piece 30 projects 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 laminate 12. This tunnel serves as a smoke exhaust duct through which the gas released from the gas discharge valve 24 flows.

A pair of end plates 14 are arranged on both sides of the battery laminate 12 including the battery cell 16 and the spacer 18 in the stacking direction. The end plate 14 is a plate material made of a material having sufficient rigidity, for example, aluminum, hard plastic, or the like. The laminated body composed of the battery laminated body 12 and the pair of end plates 14 is the assembled battery 10. A force of compression in the stacking direction (hereinafter, referred to as "binding force") is applied to the assembled battery 10. By applying the binding force, the movements of the battery cells 16, the spacer 18, and the end plate 14 constituting the assembled battery 10 are restricted and restrained. Further, by applying the binding force, the surface of the battery cell 16 and the rib 32 formed on the surface of the spacer 18 are brought into close contact with each other, and an appropriate pressure is applied to the battery cell 16.

Such binding force is applied, for example, by using a metal band called a restraining band. Specifically, when a binding force is applied to the assembled battery 10, a pair of end plates 14 are fixed to both ends of a binding band made of metal and having an invariant length. As a result, 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 laminate 12 in the no-load state, the battery The laminated body 12 receives a binding force of compression in the stacking direction from the end plate 14.

Further, as another form, the size of the case accommodating the assembled battery 10 may be adjusted to impart a binding force. Specifically, the length of the accommodation space provided in the case in the stacking direction is made shorter than the length of the assembled battery 10 in the no-load state in the stacking direction. Then, the assembled battery 10 in the contracted state may be accommodated in this accommodation space by the force of compression in the stacking direction. In any case, by applying the binding force of compression in the stacking direction, the surface of each battery cell 16 comes into contact with the rib 32 formed on the spacer 18.

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 portion where the black hatching is applied is the rib 32. However, the portion of the rib 32 that has been hatched with dark ink is a contact portion that comes into contact with the surface of the battery cell 16 when restraint is applied. Further, among the ribs 32, the portion where the light ink hatching is applied is in contact with a gradient portion that gradually rises from the surface of the base portion 26 to the height of the contact portion, in other words, the surface of the battery cell 16. It is the part that does not. Further, in FIG. 3, the rectangle illustrated by the alternate long and short dash line indicates a region of the battery cell 16 facing the electrode winding body 20 when assembled as the assembled battery 10.

As is clear from FIG. 3, the plurality of ribs 32 are arranged in a comb-teeth shape with a predetermined distance from the adjacent ribs 32. From another point of view, 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 comes into contact with the surface of the battery cell 16, and 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 in the width direction of the base portion 26, and when approaching the center of the base portion 26, the rib 32 bends in an arc shape and extends downward. The cooling air that cools the battery cell 16 flows in from the lower side of the base portion 26, spreads on both sides in the width direction along the groove 34, and is finally discharged to the outside from the width direction end portion of the base portion 26. The thick arrow in FIG. 3 indicates the flow of the cooling air.

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

The battery cell 16 gradually deteriorates with its use, and the types of this deterioration are known to be wear deterioration and high rate deterioration. Abrasion deterioration means that the materials constituting the battery cell 16, for example, electrodes and separators, deteriorate. In order to prevent this wear deterioration, it is effective to prevent deformation (waviness) of the electrode winding body 20 in the cell case. Then, in order to prevent the swell of the electrode winding body 20, it is effective to evenly press the surface of the battery cell 16 with an appropriate 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 diagram showing an example of the conventional spacer 18. Ribs 32 are evenly provided on the entire surface of the base portion 26 of the conventional spacer 18. 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. It is considered that this high-rate deterioration occurs when the electrolytic solution expanded due to charging / discharging at a high rate leaks to the outside of the electrode winding body 20. Leakage of the electrolytic solution to the outside of the electrode winding body 20 causes non-uniformity of the salt (ion) concentration distribution in the electrode winding body 20 and salt deficiency in the electrode winding body 20. The performance of the cell 16 deteriorates.

As shown in FIG. 8, when the rib 32 is provided so as to evenly press the entire electrode winding body 20, the electrode winding body 20 expands even if the electrolytic solution expands due to charging and discharging at a high rate. Is regulated. As a result, the electrode winding body 20 cannot hold the expanded electrolytic solution, and the electrolytic solution tends to leak to the outside from both ends in the width direction (both ends in the winding axis R direction) of the electrode winding body, resulting in high rate deterioration.

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

Here, the electrolytic solution tends to collect in the lower part of the electrode winding body 20 due to gravity. Therefore, the amount of expansion of the electrolytic solution when charged and discharged at a high rate is larger in the lower part than in the upper part of the electrode winding body 20. Further, the electrolytic 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 the leakage of the electrolytic solution, it is desirable to press both ends of the electrode winding body 20 in the width direction so as to prevent the leakage of the electrolytic solution. Further, in the lower part of the electrode winding body 20 having a large expansion amount, it is desirable that the electrode winding body 20 can also expand following the expansion of the electrolytic solution.

Therefore, in the present embodiment, the rib 32 is not provided in the lower portion of the electrode winding body 20 and in the range facing the center in the width direction of the base portion 26, and the electrode winding body 20 is allowed to expand. Thereby, high rate deterioration can be effectively prevented. On the other hand, in the base portion 26, ribs 32 are provided in a comb-teeth shape in a substantially U-shaped range facing both ends in the width direction and the upper portion of the electrode winding body 20. By providing the ribs 32 at appropriate intervals in this way, wear deterioration of the battery cell 16 can be suppressed. 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 can be prevented and high rate deterioration can be suppressed.

Further, according to the present embodiment, the flow velocity of the cooling air for cooling the battery cell 16 can be made uniform. As a result, the 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 cell 16 flows in from the lower part of the base portion 26. In the prior art shown in FIG. 8, since a plurality of ribs 32 are also formed in the lower part of the base portion 26, the flow velocity of the cooling air flowing in from the lower part is temporarily high because the flow path is sharply narrowed. Become. In FIG. 8, the shaded hatched portion indicates the portion where the flow velocity suddenly increases. When the refrigerant flow path is rapidly throttled and the flow velocity is rapidly increased in this way, the pressure loss increases, so that the cooling efficiency of the battery cell 16 decreases.

On the other hand, in the present embodiment, the rib 32 is not provided in the lower part which is the inlet of the cooling air. Therefore, the cooling air flowing in from the lower part is gradually throttled, so that a sudden 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 number of ribs 32 pressing the lower portion of the electrode winding body 20 is 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 portion, and the center in the width direction of the electrode winding body 20. In FIG. 4, in addition to the configuration of FIG. 3, a rib 32 extending vertically in the center in the width direction is further provided. Even in this case, expansion at the lower part of the electrode winding body 20 is allowed, so that high rate deterioration is effectively prevented.

5 and 6 are views showing the expandable range of the electrode winding body 20. In FIGS. 5 and 6, the cross-hatched portion indicates the range in which the electrode winding body 20 can be expanded. As is clear from FIGS. 5 and 6, expansion is possible in both cases where the ribs 32 are arranged in a substantially U-shaped range (FIG. 5) and the ribs 32 are arranged in a substantially E-shaped range (FIG. 6). A sufficient range can be secured. In particular, it is possible to secure a wide expandable 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 ribs 32 are provided in the upper portion of the electrode winding body 20 and in the range facing both ends in the width direction, wear deterioration can be effectively suppressed.

FIG. 7 is a diagram showing experimental results of deterioration resistance according to the shape of the rib 32. In FIG. 7, the horizontal axis represents the number of charge / discharge cycles at a high rate, and the vertical axis represents 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 set to 100%. Further, in FIG. 7, the solid line and triangular 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 with 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 the spacers 18 of FIGS. 3 and 4 that do not have or have few ribs 32 that press the lower center of the electrode winding body 20 are used, the spacer 18 of FIG. 8 that evenly presses the entire electrode winding body 20 is used. It can be seen that the increase in resistance is significantly suppressed as compared with the case of using it. Specifically, even when 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 forms of FIGS. 3 and 4. That is, according to the modes of FIGS. 3 and 4, the deterioration of the battery cell 16 can be suppressed to about 1/3 to 1/7 as compared with the conventional technique.

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 ends of the electrode winding body 20 in the width direction and the upper portion, or both ends in the width direction of the electrode winding body 20. By arranging only in a substantially E-shaped range facing the upper part and the center in the width direction, it is possible to suppress wear deterioration of the battery cell 16 and also suppress high rate deterioration. Further, with such an arrangement, the flow velocity of the cooling air flowing through the refrigerant passage formed between the ribs 32 can be made uniform, and the battery cell 16 can be cooled more efficiently.

The configuration described so far is an example, and is provided only in a substantially U-shaped range facing both ends and the upper portion of the electrode winding body 20 in the width direction, or both ends and the upper portion in the width direction of the electrode winding body 20. If the rib 32 is provided only in a substantially E-shaped range facing the center in the width direction, other configurations may be changed as appropriate. For example, in the present embodiment, the number and configuration 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 positions. Further, in the present embodiment, a plurality of battery cells 16 are connected in series, but the plurality of battery cells 16 may be connected in parallel.

10 sets of batteries, 12 battery laminate, 14 end plate, 16 battery cell, 18 spacer, 20 electrode winding body, 22n negative electrode terminal, 22p positive electrode terminal, 24 gas discharge valve, 26 base part, 28 frame part, 30 duct pieces , 32 ribs, 34 grooves.

Claims (1)

A battery assembly having a plurality of prismatic battery cell in which the electrode winding body and electrolyte are accommodated functioning as a non-aqueous electrolyte secondary battery therein, and a plurality of spacers, and
The electrode winding body is housed in the battery cell in a posture in which the winding axis direction is substantially orthogonal to the gravity direction.
The plurality of battery cells and the plurality of spacers are alternately laminated in a direction orthogonal to the winding axis direction and substantially orthogonal to the gravity direction.
On the surface of the spacer, a plurality of ribs are formed which are arranged in a comb-teeth shape and abut on the surface of the battery cell.
The ribs, of the surface of the spacer, only a substantially U-shaped region facing the direction of gravity upper and the winding axial direction both ends of the electrode winding body, or gravity direction of the electrode winding body It is arranged only in a substantially E-shaped range facing the upper part, both ends in the winding axis direction, and the center in the winding axis direction.
An assembled battery characterized by that.

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