JP6810886B2 - Batteries - Google Patents

Description

The present invention relates to an assembled battery. More specifically, the present invention relates to an assembled battery in which a secondary battery is a single battery and a plurality of the single batteries are connected.

Lithium-ion secondary batteries, nickel-hydrogen batteries and other secondary batteries or storage elements such as capacitors are used as single batteries, and assembled batteries in which multiple such single batteries are connected in series or in parallel are power supplies for vehicles, personal computers, mobile terminals, etc. It is becoming more important as a power source for batteries. Each cell constituting such an assembled battery is generally formed by accommodating an electrode body and an electrolytic solution in a square battery case.

For example, Patent Document 1 has a plurality of cells arranged side by side in one direction and a plate-shaped spacer arranged between adjacent cells, and the directions in which adjacent cells approach each other. A battery pack (battery assembly) that is restrained by the force of the battery is disclosed. The spacer of the assembled battery described in Patent Document 1 has a plurality of protrusions arranged aligned on one surface, and has a spacer flat surface portion parallel to the battery facing surface on the other surface. .. Further, other techniques for arranging spacers between arranged cells are disclosed in Patent Documents 2 and 3.

Japanese Unexamined Patent Publication No. 2014-238924 Japanese Unexamined Patent Publication No. 2012-230837 Japanese Unexamined Patent Publication No. 2016-4724

However, in the above-mentioned assembled battery, when charging and discharging are repeated at a high current value, the electrolytic solution in the cell may be biased and the electrolytic solution that has permeated into the electrode body may be discharged.
Specifically, when the battery is repeatedly charged and discharged at a high current value, the electrode body and the electrolytic solution in the battery case may expand. However, in the case of an assembled battery, since each cell is restrained by a predetermined pressure, the expansion of the electrode body and the electrolytic solution inside the battery case is restricted, and the electrode body to expand depends on the electrode body. The electrolytic solution that has permeated the inside is pushed out to the outside of the electrode body and discharged.
Since the electrolytic solution is unevenly distributed on the lower side of the battery case due to gravity in the battery case, the discharge of the electrolytic solution due to the expansion of the electrode body tends to occur in the lower part of each cell, and the discharged electrolytic solution It is difficult for the liquid to permeate the inside of the electrode body again. For this reason, a portion where the electrolytic solution is insufficient is generated inside the electrode body, an increase in battery resistance occurs due to uneven charging / discharging reaction, which causes a decrease in high rate characteristics.

The present invention has been made in view of this point, and a main object thereof is to allow an electrolytic solution to move to the outside of the electrode body in the battery case of each cell when charging / discharging is repeated at a high current value. It is an object of the present invention to provide an assembled battery capable of suppressing discharge and maintaining high high-rate characteristics.

The assembled battery disclosed here includes a plurality of cell cells in which an electrode body and an electrolytic solution are housed in a battery case, and the electrode terminals of the cell cells are connected in series to each other. The cells are arranged along a predetermined direction so that the side walls of the plurality of cells face each other, and each of the plurality of cells is constrained along the arrangement direction.
Then, in such an assembled battery, when each of the cells is arranged with the electrode terminals facing upward, the surface pressure applied to the lower region of the side wall of the cell is the surface pressure applied to the upper region of the side wall of the cell. Each of the plurality of cells is constrained so as to be smaller than.

In the assembled battery disclosed here, as described above, when each of the cells is arranged with the electrode terminals facing upward, the surface pressure applied to the lower region of the side wall of the cell is the side wall of the cell. Each of the plurality of cells is constrained so as to be smaller than the surface pressure applied to the upper region. In this way, the surface pressure applied to the lower region where the electrolytic solution is likely to be unevenly distributed due to gravity is relatively reduced, and the electrode body and the electrolytic solution are allowed to expand in the lower region, thereby penetrating into the electrode body. It is possible to prevent the electrolytic solution that has been used from being pushed out to the outside of the electrode body and discharged. As a result, an increase in battery resistance due to uneven charging / discharging reaction can be suppressed, and the high rate characteristics of the assembled battery can be maintained in a high state.

It is a perspective view which shows typically the assembled battery which concerns on 1st Embodiment of this invention. It is a side view which shows typically the assembled battery which concerns on 1st Embodiment of this invention. It is a side view which shows typically the spacer used for the assembled battery which concerns on 1st Embodiment of this invention. It is a front view which shows typically the spacer used for the assembled battery which concerns on 1st Embodiment of this invention. It is a side view which shows typically the spacer used for the assembled battery which concerns on 2nd Embodiment of this invention. It is a front view which shows typically the spacer used for the assembled battery which concerns on 3rd Embodiment of this invention. It is a side view which shows typically the spacer used for the assembled battery which concerns on 3rd Embodiment of this invention. It is a graph which shows the measurement result of the resistance increase rate in a test example, the vertical axis shows the resistance increase rate (%), and the horizontal axis shows the number of cycles.

Hereinafter, as the assembled battery according to the embodiment of the present invention, a lithium ion secondary battery is used as a single battery, and an assembled battery formed by connecting a plurality of the lithium ion secondary batteries will be described as an example. In the assembled battery disclosed here, the battery used as the cell is not limited to the lithium ion secondary battery, and for example, a nickel hydrogen battery or the like can be used.

1. 1. First Embodiment First, the overall configuration of the assembled battery 10 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view schematically showing the assembled battery 10 of the present embodiment, and FIG. 2 is a side view schematically showing the assembled battery 10 of the present embodiment. In FIG. 2, for convenience of explanation, the restraint plates 70A and 70B and the tightening beam material 72 in FIG. 1 are omitted.

The assembled battery 10 according to the present embodiment includes four cell cells 20 in which an electrode body and an electrolytic solution (not shown) are housed in a battery case 50, and each electrode terminal (positive electrode terminal) of the cell cell 20 is provided. 60 and the negative electrode terminal 62) are connected in series. Hereinafter, each configuration will be specifically described.

In the present embodiment, as the electrode body, the same electrode body as that conventionally used for the lithium ion secondary battery can be used without particular limitation. For example, a positive electrode sheet and a negative electrode sheet are laminated via a separator. A wound electrode body or the like formed by winding the laminated body can be used.
Further, as the electrolytic solution, the same one as that conventionally used for a lithium ion secondary battery can be used without particular limitation. For example, a non-aqueous solvent (non-aqueous solvent) containing a supporting salt can be used. An electrolytic solution or the like can be used.

Further, the cell 20 in the present embodiment is a square cell 20 using a flat square battery case 50, and electrode terminals (positive electrode terminal 60 and negative electrode terminal 62) are formed on the upper surface 54 of the battery case 50. Is provided. The positive electrode terminal 60 is electrically connected to the positive electrode of the electrode body in the battery case 50, and the negative electrode terminal 62 is electrically connected to the negative electrode.

In the assembled battery 10 according to the present embodiment, the side walls 20a of each cell 20 are arranged along a predetermined direction so as to face each other. Specifically, in the assembled battery 10 according to the present embodiment, the side wall of the battery case 50 (that is, a flat square battery case) so that the positive electrode terminal 60 and the negative electrode terminal 62 are adjacent to each other between the cell 20s. The flat surfaces of 50) 20a are opposed to each other, and each cell 20 is inverted and arranged one by one.
Then, between the adjacent cells 20, one cell 20, the positive electrode terminal 60, and the negative terminal 62 of the other cell 20 are electrically connected by a connector 64. As a result, each of the plurality of cell cells 20 is electrically connected in series.

Then, the assembled battery 10 is constructed by restraining each of the cell cells 20 arranged as described above along the arrangement direction y. In the present embodiment, a restraining member for restraining a plurality of the cells 20 is attached around the arranged cells 20. The restraint member is composed of a pair of restraint plates 70A and 70B and a tightening beam material 72, and each of the pair of restraint plates 70A and 70B is arranged on the outermost side of the cell 20 in the arrangement direction y. A tightening beam material 72 extending along the arrangement direction y of the cell 20 is attached so as to bridge the pair of restraint plates 70A and 70B, and the end portions of the tightening beam material 72 are bound by screws 74 to the restraint plates 70A and 70B. By tightening to, each of the arranged cell batteries 20 is restrained so that a predetermined load is applied along the arrangement direction y. At this time, a surface pressure (constraint load) along the tightening direction (that is, the arrangement direction y) is applied to the side wall 20a of each cell 20 according to the tightening condition of the tightening beam material 72.

When using the assembled battery 10 constructed as described above, as shown in FIGS. 1 and 2, the surface opposite to the surface on which the positive electrode terminal 60 and the negative electrode terminal 62 are provided is the ground plane. Arrange so that In the following description, in the height direction z of the cell 20, the direction in which the positive electrode terminal 60 and the negative electrode terminal 62 are provided is above the height direction z, and the direction in which the ground contact surface is provided is the height direction z. Downward.

Then, in the assembled battery 10 according to the present embodiment, as shown in FIG. 2, when each of the cell 20 is arranged with the positive electrode terminal 60 and the negative electrode terminal 62 facing upward, the lower side of the side wall 20a of the cell 20 Each of the plurality of cell cells 20 is constrained so that the surface pressure applied to the region B of the cell 20 is smaller than the surface pressure applied to the area A above the side wall 20a of the cell 20.
In this way, by relatively reducing the surface pressure applied to the lower region B where the electrolytic solution is likely to be unevenly distributed due to gravity and allowing the electrode body and the electrolytic solution to expand in the lower region B, the inside of the electrode body. It is possible to prevent the electrolytic solution permeating the electrode body from being discharged to the outside of the electrode body.

Specifically, in the present embodiment, in order to make the surface pressure applied to the lower region B of the side wall 20a of the cell 20 smaller than that of the upper region A, the spacer having the structure shown in FIGS. 40 is used. Hereinafter, the spacer 40 used in the assembled battery 10 according to the present embodiment will be specifically described. FIG. 3 is a side view schematically showing a spacer used for the assembled battery according to the present embodiment, and FIG. 4 is a front view schematically showing a spacer used for the assembled battery according to the present embodiment.

As shown in FIG. 2, the spacer 40 of the present embodiment is arranged between the respective cell cells 20 arranged so that the side walls 20a face each other, and the cell cells 20 are arranged from the surface of the plate-shaped spacer body 41. It has a plurality of ridges 42a and 42b protruding toward the side wall 20a of the ridge. As shown in FIG. 4, the plurality of ridges 42a and 42b extend along the width direction x of the cell 20 and are arranged in parallel at a predetermined interval in the height direction z of the cell 20. There is. As shown in FIG. 2, by arranging the spacer 40 provided with the ridges 42a and 42b between the cell 20s, a refrigerant such as air can flow between the cell 20s. The gap 44 can be formed.

Then, in the present embodiment, the protrusion height t2 of the ridge 42b corresponding to the lower region B is compared with the protrusion height t1 of the ridge 42a that abuts on the upper region A of the side wall 20a of the cell 20. Is configured to be low. When the spacer 40 having such a structure is arranged between the cells 20 and each cell 20 is constrained along the arrangement direction y of the cell 20, the spacer 40 and the region B on the lower side of the side wall 20a of the cell 20 A gap is formed between the ridges 42b of 40 and the ridges 42b. As a result, the surface pressure applied to the lower region B of the side wall 20a of the cell 20 can be made smaller than the surface pressure applied to the upper region A of the side wall 20a of the cell 20.
In this way, the surface pressure applied to the lower region B where the electrolytic solution is likely to be unevenly distributed in the battery case 50 is relatively reduced, and the expansion of the electrode body and the electrolytic solution in the lower region B is allowed. Therefore, it is possible to prevent the electrolytic solution that has permeated into the electrode body from being discharged to the outside of the electrode body. As a result, an increase in battery resistance due to uneven charging / discharging reaction can be suppressed, and the high rate characteristics of the assembled battery can be maintained in a high state.

In FIG. 2, when the arranged cells 20 are restrained, a gap is formed between the lower region B of the side wall 20a of the cells 20 and the protrusions 42b of the spacer 40, but the cells Whether or not the ridge 42b is in contact with the lower region B of the side wall 20a of 20 is not particularly limited.
Specifically, when the protrusion height t2 of the ridge 42b is made lower than the protrusion height t1 of the ridge 42a, even if the ridge 42b is in contact with the region B below the side wall 20a, it is below the side wall 20a. Since the surface pressure applied to the side region B becomes relatively small, it is possible to prevent the electrolytic solution permeating into the electrode body from being discharged to the outside of the electrode body.

Further, the dimension L2 (see FIG. 3) of the lower region where the ridge 42b having the relatively lower protrusion height is formed is 25% to 75% of the total length dimension L1 of the spacer 40 in the height direction z. It is preferably set to%, and more preferably set to about 50%. When the dimension L2 of such a region is less than 25% of the total length dimension L1 of the spacer 40, the area of the lower region B that can tolerate the expansion of the electrode body and the electrolytic solution becomes small, and the discharge of the electrolytic solution is prevented. There is a risk that the effect of On the other hand, if it exceeds 75%, the area of the upper region A that restrains the cell 20 with a relatively large surface pressure becomes small, and the durability and safety of the assembled battery 10 after construction may decrease.

In the above embodiment, the assembled battery 10 is constructed by arranging four cell batteries 20, but the number of cell cells is not particularly limited as long as it is two or more.
Further, in the above-described embodiment, the spacer 40 having the structure shown in FIG. 3 is used for all the spacers arranged between the cells 20, but this point is not particularly limited. For example, among the plurality of spacers arranged between the cell 20s, the spacer 40 having the structure shown in FIG. 3 may be used only for a part of the spacers. Even in this case, the surface pressure applied to the lower region B of the side wall 20a of the cell 20 can be made smaller than the surface pressure applied to the upper region A of the side wall 20a of the cell 20.

Further, it is also possible to use a spacer in which no ridge is formed at a position corresponding to the lower region B of the side wall 20a (that is, a spacer in which the lower ridge 42b in FIG. 3 is not formed). However, considering the durability and safety of the assembled battery 10 after construction, it is preferable that the lower ridge 42b corresponding to the lower region B is formed as in the above-described embodiment. Considering the durability and safety of the assembled battery 10 after construction and the prevention of discharge of the electrolytic solution, the protruding height t2 of the ridge 42b is about half of the protruding height t1 of the ridge 42a. Is preferable.

The protruding heights t1 and t2 of the ridges 42a and 42b are not particularly limited as long as the relationship of t1> t2 is satisfied. However, by increasing the protruding height t1 of the ridge 42a, the gap 44 between the spacer 40 and the cell 20 becomes large, and the cooling performance of each cell 20 can be improved, but the strength of the spacer 40 is increased. There is a risk that the durability and safety of the assembled battery 10 after construction will be reduced, and therefore it is preferable to appropriately adjust the height in consideration of these factors.

2. 2. Second Embodiment In the first embodiment described above, as shown in FIG. 2, the surface pressure applied to the lower region B of the side wall 20a of the cell 20 is made smaller than the surface pressure applied to the upper region A. Therefore, the spacer 40 having the structure shown in FIG. 3 is used, but the assembled batteries disclosed here use each assembled battery so that the surface pressure applied to the lower region B becomes relatively small. The structure of the spacer 40 is not particularly limited as long as it can be constrained, and a spacer other than the spacer 40 having the structure shown in FIG. 3 may be used.

Specifically, in the present embodiment, instead of the spacer 40 having the structure shown in FIG. 3, the protruding height is small from above to below in the height direction z of the cell as shown in FIG. A spacer 40A in which a plurality of ridges 42c, 42d, 42e are formed so as to be used is used.
Even when such a spacer 40A is used, the surface pressure applied to the lower region of the side wall of the cell is made smaller than the surface pressure applied to the upper region, and the electrolytic solution is discharged to the outside of the electrode body. It can be prevented from being done.

3. 3. Third Embodiment In the spacer 40 used in the first and second embodiments described above, as shown in FIG. 4, a plurality of ridges 42a and 42b are formed along the width direction x of the cell 20. Along with the extension, they are arranged in parallel with a predetermined interval in the height direction z of the cell 20.
However, the direction in which the ridges extend is not limited to the present invention. For example, as shown in FIG. 6, a plurality of ridges 43 extending along the height direction z of the cell are in the width direction of the cell 20. Spacers 40B that are formed in parallel at predetermined intervals may be used in x.
When a spacer 40B having a ridge 43 extending along the height direction z of such a cell is used, as shown in FIG. 7, the protruding height of the upper portion of the ridge 43 in the height direction z is used. The protrusion height t4 of the lower portion is made lower than that of t3. As a result, the surface pressure applied to the lower region of the side wall of the cell can be relatively reduced, and the discharge of the electrolytic solution can be prevented.

4. Fourth Embodiment In the first to third embodiments described above, the protrusion height of the ridges of the spacer corresponding to the region below the side wall of the cell is relatively low, so that the cell is a cell. The surface pressure applied to the lower region of the side wall is smaller than the surface pressure applied to the upper region.
However, the means for reducing the surface pressure applied to the lower region of the side wall of the cell is smaller than the upper region is not limited to the means using the spacer described above. Even in this case, the surface pressure applied to the region below the side wall of the cell can be relatively reduced.

Specifically, as shown in FIG. 1, in a normal assembled battery 10, a restraint plate that covers the outermost side wall of the cell 20 so that a uniform surface pressure is applied to the side wall of each cell 20. Using 70A and 70B, a tightening beam material 72 is attached near the center of the restraint plates 70A and 70B in the height direction z to restrain each cell 20.
On the other hand, in the assembled battery according to the fourth embodiment, the dimensions of the restraint plates 70A and 70B in the height direction z are made smaller than before, and the restraint plates 70A and 70B are on the upper side of the side wall of the cell 20. Arrange so as to cover only the area. Then, the tightening beam material 72 is attached to the restraint plates 70A and 70B to restrain each of the cell 20. As a result, the surface pressure applied to the side wall of the cell 20 can be concentrated in the upper region of the side wall, and the surface pressure applied to the lower region can be relatively reduced. Similar to the embodiment, it is possible to prevent the electrolytic solution from being discharged from the inside of the electrode body in the battery case 50.

The means for changing the restraint position by the restraint member as in the present embodiment can be implemented together with the means for changing the structure of the spacer in the first to third embodiments described above. That is, as shown in FIG. 2, the spacer 40 is arranged between the cells 20 and the restraining member is arranged at a position where the surface pressure is concentrated in the upper region A, so that the spacer 40 is applied to the lower region B. Since the surface pressure can be sufficiently reduced, it is possible to more preferably prevent an increase in battery resistance due to discharge of the electrolytic solution.

[Test example]
Hereinafter, test examples relating to the present invention will be described, but the following test examples are not intended to limit the present invention.

1. 1. Test Example 1 and Test Example 2
(1) Test Example 1
After manufacturing a lithium ion secondary battery (cell cell) by storing the wound electrode body in which the positive electrode sheet, the negative electrode sheet, and the separator are wound together with the electrolytic solution in a square battery case, four cell cells Are adjacent to each other so that the side walls face each other, and the positive electrode terminal and the negative electrode terminal of each cell are electrically connected by a connector. Then, after arranging a spacer between each cell, the assembled battery was constructed by restraining along the arrangement direction using a restraining member composed of a restraining plate and a tightening beam material.
Then, in Test Example 1, as shown in FIGS. 2 and 3, the protruding height t2 of the ridge 42b corresponding to the lower region B of the side wall 20a of the cell 20 corresponds to the upper region A. Spacers 40 configured to be lower than the protrusion height t1 of the ridges 42a were arranged between the respective cell batteries 20.
The protrusion height t2 of the ridge 42b corresponding to the lower region B was set to 1/2 of the protrusion height t1 of the ridge 42a corresponding to the upper region A. Further, the dimension L2 of the region where the ridge 42b having the relatively lower protrusion height t2 is formed is set to 50% of the total length dimension L1 of the spacer 40 in the height direction z.

(2) Test Example 2
Test examples, except that spacers with the same protrusion height were placed between each cell, and each cell was restrained so that a uniform surface pressure was applied to the side wall of each cell. The assembled battery was constructed under the same conditions as in 1.

2. 2. Evaluation Test Each of the above-mentioned assembled batteries was subjected to a charge / discharge cycle test in which charging / discharging was repeated under a temperature condition of 25 ° C., and the resistance increase rate (%) in the cycle test was calculated. The specific test conditions are as follows.
First, under a temperature condition of 25 ° C., a constant current charge is performed at a charge rate of 2C to a charge state of SOC 100%, and then a constant current discharge is performed at a discharge rate of 2C to a charge state of SOC 0%. did. Then, the battery resistance (IV resistance) (mΩ) of each assembled battery is measured every time the charge / discharge cycle is performed 100 times, and the battery resistance (battery resistance at the 0th cycle) before the charge / discharge cycle test is 100. %, And the resistance increase rate (%) of the battery resistance with respect to the battery resistance in the 0th cycle was calculated. The results are shown in FIG.
In Test Example 1, the above charge / discharge cycle was performed 3000 times to measure the battery resistance 30 times, and in Test Example 2, the charge / discharge cycle was performed 2000 times to measure the battery resistance 20 times.

3. 3. Evaluation Results As shown in FIG. 8, in Test Example 2, the battery resistance increased sharply from around the 1000th cycle, and when the 2000th cycle was reached, the resistance increase rate exceeded 120%. It is understood that this is because the electrode body expands by repeating charging and discharging, and the electrolytic solution immersed in the electrode body is discharged.
On the other hand, in Test Example 1 using a spacer having a structure as shown in FIG. 3, the increase in battery resistance is gradual, the resistance increase rate is 110% or less at 2000 cycles, and the charge / discharge reaches 3000 cycles. Even in this case, the resistance increase rate was 115% or less.
For this reason, a spacer having a structure as shown in FIG. 3 is used to restrain each cell so that the surface pressure applied to the lower region of the side wall of the cell is smaller than the surface pressure applied to the upper region. As a result, it was confirmed that the electrolytic solution in the electrode body could be prevented from being discharged to the outside, the increase in battery resistance could be suppressed, and the high rate characteristics of the assembled battery could be maintained in a high state.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

10 sets Battery 20 Single battery 20a Side wall of single battery 40, 40A, 40B Spacer 41 Spacer body 42a, 42b, 42c, 42d, 42e, 43 Convex 44 Gap 50 Battery case 54 Upper surface of battery case 60 Positive terminal 62 Negative terminal 64 Connector 70A, 70B Restraint plate 72 Tightening beam material 74 Screw A Upper area B Lower area L1 Total length of spacer in the height direction L2 Lower area dimensions t1, t2, t3, t4 Protrusion height of ridges X Single cell width direction y Single cell arrangement direction z Single cell height direction

Claims (1)

It is an assembled battery in which a plurality of cell cells in which an electrode body and an electrolytic solution are housed in a battery case are provided, and the electrode terminals of the cell cells are connected in series.
The cells are arranged along a predetermined direction so that the side walls of the plurality of cells face each other, and each of the plurality of cells is constrained along the arrangement direction.
A spacer is arranged between each of the cells arranged so that the side walls face each other.
The spacer is
A plate-shaped spacer body arranged along the side wall of one of the pair of facing cells,
With a plurality of ridges protruding from the surface of the spacer body toward the side wall of the other cell.
Have,
Each of the plurality of ridges extends along a predetermined first direction in the front view of the spacer, and is arranged at a predetermined interval in a second direction intersecting the first direction. A gap for refrigerant flow is formed between adjacent ridges in the second direction, and
When each of the cells is arranged with the electrode terminals facing upward, the protrusions corresponding to the lower region are compared with the protruding height of the protrusions abutting on the upper region of the side wall of the cell. The protrusion height of each of the plurality of convex shapes is set so that the protrusion height is low, and the surface pressure applied to the region below the side wall of the cell is applied to the region above the side wall of the cell. Each of the plurality of cells is restrained so as to be smaller than the applied surface pressure .
The assembled battery, wherein the height dimension of the lower region is 25% to 75% of the total length dimension 1 of the spacer in the height direction .

Images