JP2011076967A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack capable of cooling uniformly every unit cell constituting the battery pack, and capable of restraining a battery from being locally deteriorated caused by dispersion of temperatures. <P>SOLUTION: This battery pack includes the plurality of unit cells, separators arranged respectively between the unit cells and having a flow channel for a cooling wind, a cooling wind introducing duct for introducing the cooling wind into the flow channel, and a cooling wind discharge duct for discharging the cooling wind from the flow channel, the flow channel is extended perpendicularly to cooling wind flow directions in insides of the cooling wind introducing duct and the cooling wind discharge duct, the separator has thermal conductivity, and the flow the channel is provided only in one face of the separator, in the battery pack. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lithium ion battery suitable for use in, for example, an automobile driving power source, and more particularly to a technique for suppressing variation in cooling of each battery in an assembled battery including a plurality of single batteries.

  In an in-vehicle lithium ion secondary battery, a plurality of cells each having a positive electrode, a negative electrode, and an electrolytic solution are arranged in series and housed in a casing, and a cell controller for charge / discharge control is connected to the battery. Is used as an assembled battery.

  In lithium-ion batteries, heat is generated due to the electrochemical reaction during charging and discharging, and the batteries deteriorate due to long-term exposure to this heat, so the batteries are cooled to improve battery durability. It is requested to do. In particular, in an assembled battery, since a plurality of single cells are arranged, it is difficult to exhaust heat, the temperature rises remarkably, and cooling of each single cell constituting the assembled battery is an issue.

  Conventionally, several methods for cooling such an assembled battery have been proposed. A separator is interposed between adjacent unit cells, and a flow path is formed on both sides of the separator so that cooling air (air) is circulated. Thus, a technique for cooling a single battery that is in contact with both surfaces of a separator has been disclosed (for example, see Patent Document 1).

JP 2006-252821 A

  However, due to the limitation of the storage space of the assembled battery, the thickness of the separator provided between the single cells must be extremely thin, and the flow paths formed on both sides of the thin separator are further narrowed, so It was difficult to circulate sufficiently, and an effective cooling effect could not be obtained.

  In addition, it has a structure in which flow paths are provided on both sides of each separator, that is, a structure in which two narrow flow paths are provided at close intervals, and cooling air is bent at a right angle from the introduction direction and flows into the flow paths. In this structure, as will be described later, since the flow velocity of the cooling air is fast in one of the flow passages located upstream with respect to the introduction direction of the cooling air, it is difficult for the cooling air to flow into the flow passage. In the other channel, the flow rate of the cooling air is slow, so that the cooling air easily flows into the channel. For this reason, there is a problem in that an equal amount of cooling air does not flow on both surfaces of one separator, cooling between batteries varies, and as a result, the battery deteriorates locally from a location where the battery is not sufficiently cooled.

  When a battery deteriorates locally, the charge / discharge characteristics of the battery decrease, but the charge / discharge of the entire assembled battery is controlled by the cell controller according to the battery with the lowest charge / discharge characteristics. The performance of other batteries cannot be fully utilized, and the capacity of the assembled battery as a whole is reduced.

  In addition, there is a problem that the entire portion is supported only by the protruding portion, the battery is deformed by tight binding, and a high-strength battery can is required.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and is a set capable of equalizing cooling for each unit cell constituting the assembled battery and suppressing local deterioration of the battery due to temperature variation. It aims to provide a battery.

  The assembled battery of the present invention includes a plurality of unit cells, a separator disposed between each unit cell and having a cooling air flow path, a cooling air introduction duct for introducing cooling air into the flow path, and cooling from the flow path. The battery pack includes a cooling air discharge duct that discharges wind, the flow path extending perpendicularly to the cooling air flow direction in the cooling air introduction duct and the cooling air discharge duct, and the separator It has conductivity, and the flow path is provided only on one surface of the separator.

  In the battery pack having the above-described configuration, interference between cooling airs that has conventionally occurred in the flow paths on both sides of one separator is reduced, and the cooling air flows smoothly through the flow paths. As a result, variation in cooling between one unit cell and another unit cell can be suppressed. In addition, the number of flow paths is halved compared to conventional separators with flow paths formed on both sides, so the flow path installation interval is widened to suppress pressure loss and variations, and the unit cell spacing is narrowed. Thus, the assembled battery can be reduced in size.

  In addition, on the surface where the separator channel is not formed, the cooling air does not directly hit the battery, but since the separator has thermal conductivity, heat is exchanged with this and indirectly cooled by the cooling air. The

  Furthermore, since the flow path only needs to be formed on one side of the separator, the thickness of the flow path on one side can be reduced as compared with the conventional separator in which the flow path is formed on both sides. Thereby, the space | interval between single cells can be narrowed and size reduction can be achieved as the whole assembled battery.

  In addition, since the flow path is not formed on one surface of the separator and is in contact with the unit cell in a plane, deformation of the battery due to binding can be suppressed on the contact surface.

  In the assembled battery of the present invention, it is preferable that the width of the flow path provided in the separator continuously decreases from the upstream side to the downstream side in the cooling air flow direction in the cooling air introduction duct. .

  As described above, it is difficult for the cooling air to flow into the flow path in the flow path located upstream with respect to the introduction direction of the cooling air, and the cooling air easily flows into the flow path in the flow path positioned downstream, In the battery pack having the configuration, the flow path is wide on the upstream side where the cooling air hardly flows, and the flow path is narrow on the downstream side where the cooling air easily flows. Ease of inflow becomes uniform, and variation in cooling for each unit cell can be further suppressed.

  According to the present invention, since the cooling air flows evenly for each flow path formed in the separator, the variation in cooling of each unit cell is suppressed, and as a result, the output limitation due to the local temperature rise of the battery, There is an effect of suppressing deterioration.

It is a perspective view which shows the cell and separator of this invention. It is a perspective view which shows the mounting state of the cell and separator of this invention. It is a perspective view which shows the state which arranged the several cell of this invention. It is a perspective view which shows the assembled battery of this invention. It is the sectional view on the AA line in FIG. (A) is sectional drawing which shows the conventional assembled battery, (b) is the figure which looked at the cross section along line segment OP in (a) from the viewpoint B, (c) is a line segment. It is a graph which shows the relationship between the position of the separator flow path in the cross section along OP, and the flow velocity of cooling air. (A) is sectional drawing which shows the assembled battery of this invention, (b) is the figure which looked at the cross section in alignment with line segment OP in (a) from the viewpoint C, (c) is a line It is a graph which shows the relationship between the position of the separator flow path in the cross section along a part OP, and the flow velocity of cooling air. It is a perspective view which shows the modification of the separator of this invention. It is a perspective view which shows the modification of the separator of this invention. It is a perspective view which shows the modification of the separator of this invention. It is a perspective view which shows the modification of the separator flow path of this invention. It is a perspective view which shows the modification of the cooling air introduction duct of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing a unit cell 10 and a separator (holder type) 20 used in the assembled battery of the present invention. The unit cell 10 is a known lithium ion secondary battery or the like having an electrolyte solution (not shown) inside and having a positive electrode 11 and a negative electrode 12. The separator 20 is made of a material having thermal conductivity such as a known metal material or resin material, and a projection 21 and a flow path 22 that is a relatively concave portion are formed on the surface. Moreover, the back surface which is not shown in figure is a smooth planar shape, hold | maintains the cell 10 and closely_contact | adheres. FIG. 2 shows a state where the separator 20 is attached to the unit cell 10. In order to improve the adhesion, an adhesive such as an adhesive or epoxy is inserted between the battery and the separator.

  As shown in FIG. 3, a plurality of single cells 10 equipped with the separator 20 are arranged to form a battery pack M in order to obtain a desired voltage. As shown in FIG. 4, the assembled battery M is fixed by a positioning member 40 and a casing 30, and connected to a cell controller 50 that controls charging / discharging of each unit cell. Reference numeral 31 denotes a cooling air introduction duct. Yes, the cooling air is introduced from the cooling air introduction port 33 and led to each cell. Reference numeral 32 denotes a cooling air discharge duct, which discharges the cooling air after cooling each unit cell from the cooling air discharge port 34.

  FIG. 5 is a cross-sectional view taken along line AA in the perspective view of FIG. As shown in FIG. 2, each separator 20 has a protrusion 21 and a flow path 22 on one surface, and the other surface is smooth. Therefore, in each portion indicated by a vertical thick line in FIG. A flow path is formed on one side of the battery, and the other side is in close contact with the unit cell 10.

  The cooling air is introduced from the cooling air introduction port 33 as shown by the right arrow in FIG. 5 and is bent at a right angle as shown by the downward arrow to flow the separator 20 provided between the single cells. The unit cell is cooled by passing through the road, and is then bent again at a right angle as indicated by the right arrow and discharged from the cooling air outlet 34.

  In the present invention, the flow path is formed only on one side of the separator, and of the two single cells sandwiching the separator, the single cell on the flow path side is directly cooled by the cooling air and is on the opposite side of the flow path. The cell is heat-exchanged by the thermal conductivity of the separator in contact, and is indirectly cooled by cooling air.

Here, in order to show the superiority of the present invention over the prior art, a conventional assembled battery in which channels are provided on both sides of the separator will be described. FIG. 6A is a cross-sectional view showing a conventional assembled battery in which flow paths are provided on both sides of such a separator, and FIG. 6B is a cross-sectional view taken along line O-P in FIG. It is the figure seen from. Also, FIG. 6 (c), of each channel, in each flow path in which the displacement from O points on the line segment OP is at a ₁ ~a _8, it is a graph showing the flow rate of the cooling air.

  The unit cell 10, the cooling air introduction duct 31, and the cooling air discharge duct 32 are components common to the present invention, and thus description thereof is omitted. In the assembled battery shown in FIGS. 6A and 6B, a protrusion 61 that supports the unit cell 10 and a flow path 62 that is a relatively concave portion therebetween are formed on both surfaces of the separator 60.

While the cooling air introduced from the cooling air introduction port 33 flows to the right in the drawing, the cooling air is bent at a right angle and passes through the flow paths 62 formed on both surfaces of the separator 60 sandwiched between the single cells, and again at a right angle. It is bent and discharged from the cooling air outlet 34. As shown in FIG. 6C, when the flow paths provided on both sides of one separator, for example, a ₁ and a ₂ are compared, in the flow path a ₁ on the upstream side of the cooling air, the downstream flow path a _The flow rate is lower than ₂ .

This is because, when the cooling air is bent at a right angle, the air (cooling air) between the flow paths has a high flow velocity on the upstream side when close to each other like the flow paths provided on both sides of the separator. There because on the downstream side relatively velocity is reduced, in order to flow towards the flow channel a ₂ on the downstream side. In addition, since fluids such as cooling air do not like to be bent at right angles and bend in an arc, it is difficult for the cooling air to flow into the upstream side where it is necessary to draw an arc at a steep angle when bending, and an arc is formed at a gentle angle. This is also caused by the phenomenon that the cooling air easily flows into the downstream side.

This tendency is the same in each of the combinations of a ₃ and a ₄ , a ₅ and a ₆ , and a ₇ and a ₈ , and more in each downstream flow path (a ₄ , a ₆ and a ₈ ). Cooling air flow rate is fast. Furthermore, among the four separators, there is a tendency that the flow velocity tends to be faster as it is located downstream (a ₁ , a ₃ , a ₅ , a ₇ comparison, and a ₂ , a ₄ , a ₆ , a ₈ Comparison between). As described above, in the conventional separator structure, there is a significant variation in the flow velocity of the cooling air. As a result, there is also a variation in the cooling of each surface of the unit cell, the temperature of the unit cell rises locally, and the output limit and Deterioration has occurred.

  Moreover, as shown in FIG.6 (b), since only the protrusion 61 is supporting the single cell 10, there existed a problem that a high pressure generate | occur | produced by binding and the container of the single cell 10 was dented.

On the other hand, FIG. 7A is a cross-sectional view showing the assembled battery of the present invention in which a flow path is provided only on one side of the separator, and FIG. 7B is an OP line in FIG. It is the figure which looked at the cross section from the viewpoint C. FIG. Further, FIG. 7 (c), of each channel, in each flow path in which the displacement from O points on the line segment OP is a b ₁ ~b _4, is a graph showing the flow rate of the cooling air. In the assembled battery shown in FIGS. 7A and 7B, the projections 21 that support the unit cell 10 and the flow path 22 that is a relatively concave portion therebetween are formed on both surfaces of the separator 20 (FIG. 7). 1).

While the cooling air introduced from the cooling air introduction port 33 flows to the right in the figure, it is bent at a right angle and passes through the flow paths 22 formed on both surfaces of the separator 20 sandwiched between the single cells, and then again at a right angle. It is bent and discharged from the cooling air outlet 34. In the present invention, since the flow path is provided only on one side of the separator, there is no variation that has occurred in the conventional flow paths a ₁ and a ₂ , and as shown in FIG. It indicates the flow rate b _1, it is possible to perform uniform cooling for each unit cell. Here, the unit cell facing the channel is directly cooled by the cooling air, and the unit cell not facing the channel is indirectly cooled through heat exchange of the separator. Thereby, the dispersion | variation in the cooling of the whole assembled battery is reduced.

  According to the present invention, by suppressing variation in cooling, local battery deterioration can be suppressed, and battery output can be stabilized by uniform temperature management. In addition, since the flow path only needs to be formed on one side, the thickness corresponding to the other flow path can be reduced, and the space between the batteries is clogged, so that the assembled battery is downsized to about 30% in module volume ratio. be able to.

  Further, as shown in FIG. 7B, the cell 10 is supported by the protrusions 21 on one surface, but is smooth on the other surface, so that the support by the protrusions of the flow path is 1 The surface can be reduced and the battery can be effectively held, so that the depression of the cell due to tight binding can be suppressed and the battery can be held more firmly.

  In addition, since the battery cell is covered with the resin parts, there is a heat retention effect, and it is possible to maintain a temperature with good output efficiency against a long signal waiting, temporary parking, and a rapid change in temperature.

Example of Change of Separator The separator used in the assembled battery of the present invention is not limited to the separator 20 having the protrusions and flow paths shown in FIG. 1, and can be arbitrarily changed within a range where the effects of the present invention can be obtained. For example, as shown in FIG. 8, a separator (holder type) 23 having linear protrusions and flow paths along the flow direction of the cooling air may be used.

  Further, the separator is not limited to the holder type that holds the unit cell shown in FIGS. 1 and 8, and may be fixed as a separator (plate-like) 24 as shown in FIG. 9 by a positioning member or a casing (not shown).

  Furthermore, as shown in FIG. 10, the separator 25 integrated with the unit cell 10 or the protrusion 21 and the flow path 22 may be directly formed on the surface of the unit cell 10. By integrally forming the separator on the battery surface, it is possible to improve heat conduction and assembly.

Example of changing separator channel spacing In the assembled battery of the present invention, the width of the channel provided between the single cells is not limited to that in which the intervals of all the channels are equal as shown in FIG. FIG. 11 shows an example in which the channel width between the cells is changed. In FIG. 11, the illustration of the separator is omitted, and only the flow paths C _{1 to} C ₅ are shown. As shown in FIG. 11, the flow path, the width of the upstream flow channel C ₁ of the cooling air is maximum, the width continuously decreases later, so that the width of the downstream-side passage C ₅ is minimum be able to. Cooling air is less likely to flow into the flow path as it goes upstream, and it is easier to flow into the flow path as it goes downstream, so if you narrow the flow path width from upstream to downstream to offset this trend, The flow rate of the cooling air in the flow path, that is, the variation in cooling between the single cells can be further suppressed.

To a modification 12 of the cooling air introduction duct shows an example of changing the cooling air introducing duct. Also in FIG. 12, illustration of the separator is omitted. As shown in FIG. 12, the cooling air introduction duct 35 has a maximum opening width at the cooling air introduction port 33 and has a structure that narrows toward the downstream side of the cooling air. The cooling air velocity increases as it goes upstream, and the flow velocity decreases as it goes downstream. Therefore, if the cooling air introduction duct 35 is narrowed from upstream to downstream so as to offset this tendency, the cooling air flows from upstream to downstream. And the degree of easiness of inflow of the cooling air in all the channels is made uniform, whereby the variation in cooling between the single cells can be further suppressed.

Cooling Control Method Lithium ion secondary batteries have poor charge / discharge characteristics at a remarkably low temperature. Therefore, the performance is improved when heated to a certain temperature. Therefore, in the present invention, when the surrounding environment is extremely low temperature or immediately after starting, the cooling air is not circulated and the temperature of the battery is increased by the heat generated by the assembled battery. It is preferable to control so as to start distribution. In order to control in this way, it is possible to use a known method such as providing a temperature sensor in the assembled battery and linking this sensor with the cooling air introducing means.

  According to the present invention, it is possible to suppress the local deterioration of each single cell by suppressing the variation in cooling of each single cell constituting the assembled battery, and to stably operate the assembled battery over a long period of time. Therefore, it is extremely promising when applied to an in-vehicle lithium ion secondary battery system that requires strict and stable operation.

10 ... single cell,
11 ... positive electrode,
12 ... negative electrode,
20: Separator (holder type),
21 ... protrusions,
22 ... flow path,
23 ... Separator (holder type),
24 ... separator (plate-like),
25 ... separator (integral type),
30 ... casing,
31 ... Cooling air introduction duct,
32. Cooling air discharge duct,
33 ... Cooling air inlet,
34 ... Cooling air outlet,
40: positioning member,
50 ... Cell controller,
60 ... Separator (conventional),
61 ... protrusion (conventional),
62 ... flow path (conventional),
a _{1 to} a ₈ ... conventional separator flow path coordinates,
b _{1 to} b ₄ ... the coordinates of the separator flow path of the present invention,
c _{1 to} c ₅ ...
M ... assembled battery.

Claims (2)

Multiple cells,
A separator having a cooling air flow path disposed between each of the unit cells;
A cooling air introduction duct for introducing cooling air into the flow path;
A battery pack comprising a cooling air discharge duct for discharging cooling air from the flow path,
The flow path extends perpendicular to the cooling air flow direction in the cooling air introduction duct and the cooling air discharge duct,
The separator has thermal conductivity,
The assembled battery, wherein the flow path is provided only on one surface of the separator. 2. The set according to claim 1, wherein the width of the flow path provided in the separator continuously decreases from the upstream side to the downstream side in the cooling air flow direction in the cooling air introduction duct. battery.

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