JP2017069169A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack in which, even if there are variations in thickness of an assembled battery, applied pressure is adequately adjusted to obtain stable products with no variation (individual difference) between products.SOLUTION: A battery pack includes: an assembled battery in which a plurality of flat-shaped single cells 4 are laminated in a thickness direction, each of the single cells housing a power generating element therein and having a film outer package; a box 1 housing the assembled battery therein and having an opening; a pressing spring 5 arranged above the assembled battery; a lid 2 pressing the assembled battery via the pressing spring 5 to close the opening of the box 1; and a pressurizing force adjustment member 3 provided between the box 1 and the lid 2 and abutting against the lid 2 to adjust a compression amount of the assembled battery by the pressing spring 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a battery pack, and more particularly to a battery pack having a plurality of single cells covered by a film outer package.

  The battery pack is a combination of a plurality of single cells and is accommodated as an assembled battery so that a predetermined voltage and capacity can be obtained. There are roughly two types of outer casings for single cells: metal cans and films (laminate films). A battery having a laminate film outer package (hereinafter referred to as a laminate battery) is characterized in that the outer package is lighter than a metal can and can be easily built into a predetermined capacity by increasing the number of stacked current collectors.

On the other hand, as a problem that arises due to the flexible exterior of the laminated battery, there are cases where the variation in thickness among the single cells is large and the characteristics must be stabilized by appropriate pressure.
Regarding the thickness variation, in the laminated battery, the current collector is laminated and covered with a flexible laminate film, so the thickness variation of the current collector (component variation), the lamination state (assembly variation) and the component Two variations of assembly work factors are likely to appear as thickness variations.
On the other hand, in the battery of the metal can package, since the current collector is inserted into a metal rigid body having a predetermined size, there is little variation in shape.

  By the way, in a laminated battery, it is common to obtain target battery characteristics by appropriately applying pressure. For example, the internal resistance related to the input / output characteristics of the battery decreases according to the applied pressure as shown in FIG. This is because in a laminated battery, the distance between the electrodes can be kept constant and stable by applying pressure.

Here, when the patent document is seen, as a pressurizing method of the laminated battery, Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-339032) discloses that the temperature variation between the single cells in the battery pack is reduced and the box body is used. Describes a battery pack in which a unit cell is housed and the unit cell is pressurized with a lid.
However, according to this method, since the lid is attached at the same position even when individual differences occur in the thickness of the assembled battery, the pressure generated between the box and the lid varies for each battery pack. Therefore, there is a problem that the product variation becomes large.

In addition, a laminate battery provided with a pressure adjusting means is also known (Patent Document 2; JP-A-2015-115313).
This pressurizing pressure adjusting method enables a part of a plurality of pressurizing means to be adjusted in order to adjust the pressure when gas is generated. That is, according to this method, the pressure can be partially adjusted, and the pressure at the fixed pressurization point is constant even when the thickness of the assembled battery varies. Therefore, there is a problem that the variation as a product cannot be reduced.

  The present invention has been made in view of the above-described conventional problems, and its purpose is to appropriately adjust the pressure applied to the laminated battery even if the thickness of the laminated battery varies, and between products. The aim is to obtain a stable product without variations (individual differences).

  The present invention provides an assembled battery in which a plurality of unit cells that contain a power generation element and have a film outer package are stacked in a thickness direction, a box having an opening that accommodates the assembled battery, and the assembled battery. A pressure member, a lid that closes an opening of the box that pressurizes the assembled battery via the pressure member, and a lid that is provided between the box and the lid, and is in contact with the lid And a pressure adjusting member that adjusts the compression amount of the assembled battery by the pressure member.

  According to the present invention, even if the thickness of the laminated battery varies in the battery pack, the pressure applied to the laminated battery is appropriately adjusted to obtain a stable product free from variations (individual differences) between products. It is done.

It is a perspective view which shows the external appearance of the laminated battery pack of the battery pack which concerns on the 1st Embodiment of this invention. It is a side view of the assembled battery shown in FIG. It is sectional drawing of the assembled battery in FIG. 1 in the arrow direction of the line XX. It is a side view of the cell shown in FIG. It is a disassembled perspective view of the electric power generation element shown in FIG. It is a figure which shows the relationship between the applied pressure of a power generation element on a horizontal axis, and the internal resistance on a vertical axis | shaft about the internal resistance which is one of the characteristics of a laminated battery. It is sectional drawing of the assembled battery of FIG. 1 in the arrow XX direction explaining the effect of the battery pack of this embodiment. It is sectional drawing similar to FIG. 7, Comprising: It is a figure which shows the adjustment method of a pressurization adjustment member. It is a flowchart which shows the work procedure at the time of the assembly of an assembled battery. It is a perspective view which shows the external appearance of the assembled battery which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows the external appearance of the assembled battery which concerns on the 2nd Embodiment of this invention. In 2nd Embodiment, sectional drawing of the assembled battery in the arrow XX direction of FIG. 10 which shows adjusting the thickness of a pressurization adjustment member appropriately with respect to the dispersion | variation in the height of an assembled battery. It is. It is a top view of the assembled battery explaining the 3rd Embodiment of this invention. FIG. 14A is an enlarged view of a pressure adjusting member used in the assembled battery, FIG. 14A is a perspective view of the pressure adjusting member as viewed obliquely, and FIG. 14B is a diagram showing a cross-sectional shape of the pressure adjusting member.

First Embodiment A laminated battery pack of a battery pack according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view showing an appearance of a laminated battery pack of a battery pack according to the first embodiment of the present invention.
The battery pack according to the first embodiment comprises a plurality of unit cells (laminated unit cells; hereinafter referred to as unit cells) covered with a laminated film outer case, in this case, an elastic body, for example, a laminated film outer case. A method of applying pressure with a pressure spring is adopted.
That is, in FIG. 1, reference numeral 1 denotes a lower frame (box) having an open top, and a plurality of single cells 4 (three in the illustrated example) are stacked and accommodated in the lower frame 1. On the stacked unit cells 4, a plate body 6 having substantially the same size as the unit cells 4 is placed, and a plurality of pressurizing springs 5, for example, coil springs, which are pressurizing members, are placed thereon. They are arranged side by side.

Here, the upper frame 2 is placed on the plurality of pressure springs 5, but the upper frame 2 (lid body) and the lower frame (box body having an opening at an abutting portion between the upper frame) 1. A pressure adjusting member 3 is interposed therebetween. Specifically, the pressure adjusting member 3 is arranged at the upper end of the lower frame. The assembled battery configured as described above is housed in a resin case (not shown) to obtain a battery pack product.
In the assembled battery according to the present embodiment, the lower frame 1 is closed by the upper frame 2, and at that time, the pressure spring 5 is compressed by a predetermined length to generate pressure on the unit cell 4. Here, at this time, for example, a washer-shaped member interposed between the lower frame 1 and the upper frame 2, the pressure adjusting member 3 made of resin or metal appropriately adjusts the compression amount of the pressure spring 5. Then, the pressure applied to the unit cell 4 and, therefore, the amount of compression is adjusted.

2 is a side view of the battery pack shown in FIG. 1, and FIG. 3 is a cross-sectional view of the battery pack in the direction of the arrow XX in FIG.
The plurality of single cells 4 can obtain predetermined voltages and capacities by being connected in series or in parallel. Here, an example in which the cells are connected in series is shown.
The pressure adjusting member 3 is fixed to a flange-like portion formed by bending the upper end portion of the lower frame 1 inward. In addition, a separator 7 made of a metal such as aluminum having good thermal conductivity is sandwiched between the single cells 4 for the purpose of releasing heat generated from the single cells 4 during charging and discharging.
The lower frame (box body) 1 and the upper frame (lid body) 2 are preferably formed of, for example, a sheet metal material so as not to be deformed by pressure.

FIG. 4 is a side view of the unit cell 4 shown in FIG.
Here, the cell 4 is a secondary battery such as a lithium ion battery, and has a flat shape as shown in the figure. The unit cell 4 includes a power generation element 41, a laminate 42 that is an exterior body that covers the power generation element 41, and positive and negative electrodes 43 and 44 installed on the laminate 42.
The positive and negative electrodes 43 and 44 are derived from the same side surface, but may be derived from the opposing side surface. By doing so, the width of the electrode can be made wider, and the heat generation with respect to the current can be reduced.

FIG. 5 is an exploded perspective view of the power generation element 41 shown in FIG.
The power generation element is formed by laminating a positive electrode 51, a separator 52, and a negative electrode 53 in this order. The number of stacked layers is appropriately set according to a predetermined specification value such as a capacity.
The laminated power generation element 41 including an electrolyte solution (not shown) is sealed with a laminate film to form a laminate type single cell. For the laminate film, a composite of resin and metal is used. The resin is made of, for example, polypropylene or polyethylene, and a metal such as aluminum or stainless steel is used for the metal layer.

In the unit cell having the above structure, since the laminate film as the outer package is flexible, the variation in stacking the current collector, the variation in the thickness of the positive and negative electrode materials and the separator becomes the thickness of the battery as it is. appear.
Therefore, the variation in thickness at the time of manufacture is larger than that of a dry battery having a metal case. Therefore, when the battery pack is assembled, the variation is amplified in order to stack a plurality of the batteries, and the variation in the thickness (herein referred to as height) in which the plurality of single cells are stacked between the battery packs increases.

FIG. 6 is a diagram showing the relationship between the internal pressure (Pa) of the power generation element 41 on the horizontal axis and the internal resistance (Ω) on the vertical axis for the internal resistance which is one of the characteristics of the laminated battery.
That is, FIG. 6 shows that the internal resistance is reduced by pressurizing the laminated battery. This is because the laminated battery has a flexible exterior, so that the distance between the electrodes increases or varies before pressurization, and the distance between the cells becomes closer and more stable by pressurization. is there. As described above, it is necessary to apply a predetermined pressure to the laminated battery.

FIG. 7 is a cross-sectional view of the assembled battery in the direction of arrows XX in FIG. 1 for explaining the effect of the battery pack of the present embodiment.
That is, if the upper and lower limits are gathered when the unit cells 4 are stacked, the heights may be greatly different as shown on the left and right in FIG. In this case, if the height is different, the amount of compression of the pressure spring 5 is different. Therefore, if the pressure spring 5 is simply uniformly compressed by the upper frame (lid body) 2, the applied pressure differs.

FIG. 8 is a cross-sectional view similar to FIG. 7 and shows a method for adjusting the pressure adjusting member 3.
In this embodiment, as shown in FIG. 8, the thickness of the pressure adjusting member 3, that is, the height when fixed to the upper end of the lower frame is determined according to the height of the stacked unit cells 4, By adjusting the lowering amount of the upper frame (lid body) 2, the compression amount of the pressure spring 5 is adjusted to obtain an appropriate pressing force. Thereby, even when the height of the assembled battery varies, the applied pressure is appropriate, so that it is possible to supply a battery pack having the same characteristics of the assembled battery. That is, a battery pack with little characteristic variation can be provided by assembling the assembled battery with an appropriate pressure.

FIG. 9 is a flowchart showing an operation procedure when assembling the assembled battery.
That is, a predetermined number of unit cells 4 are stacked in the lower frame (box) 1 (S101), and when they are stacked, the height is measured by an arbitrary height measuring means (S102). According to the result, the thickness of the pressure adjusting member 3 that can obtain an appropriate pressure is determined (S103). Here, a plurality of types of pressure adjusting members 3 having different thicknesses are prepared in advance, and the determined thickness is supplied at the time of assembly (S104). Assembly is performed (S105).
Note that it is also preferable that the pressure adjusting member 3 is formed on demand by 3D modeling. By calculating an appropriate thickness from the height measurement result of the assembled battery and shaping the shape (thickness) of the pressure adjusting member 3 according to the thickness, it is possible to eliminate inventory reduction and component supply errors. .

Second Embodiment FIGS. 10 and 11 are perspective views showing the appearance of an assembled battery according to a second embodiment of the present invention. The same parts as those in FIG.
In the battery pack of the battery pack according to the first embodiment, the laminated battery is pressurized by a plurality of pressure springs 5, but in this embodiment, the pressure springs 5 are not used, that is, they are configured as rigid pressure members. As the pressure member, a box-shaped member 5a (FIG. 10) formed by bending a sheet metal into a box shape, a resin box-shaped member 5a (FIG. 11), or the like is used. Note that the box-shaped member referred to here does not necessarily form a box body, but can be provided with a flat surface that comes into contact with the laminated battery and a push-in allowance by the upper frame when arranged on the laminated battery. Good.
According to the present embodiment, since the number of parts can be reduced as compared with the pressurizing means using the plurality of pressurizing springs 5, it is possible to reduce the parts cost and the number of assembling steps, thereby obtaining a lower cost battery pack.

In the present embodiment, pressure is obtained by pressing the box-shaped member 5 a until the upper frame (lid body) 2 (FIG. 10) contacts the pressure adjusting member 3.
FIG. 12 is a cross-sectional view taken along line XX in FIG. 10 of the assembled battery showing that the thickness of the pressure adjusting member 3 is appropriately adjusted with respect to the variation in the height of the assembled battery in the present embodiment. FIG.
Also in the present embodiment, when the upper frame (lid body) 2 is pushed into contact with the pressure adjusting member 3 by the gap (pressure gap in the drawing) between the pressure adjusting member 3 and the box-shaped member 5a, Pressure is applied to the assembled battery. In order to appropriately adjust the pressing force, the thickness of the pressing force adjusting member 3 is also adjusted here.

Third Embodiment In the present embodiment, the pressure adjusting member 3 having a thickness corresponding to each height is used by measuring the height at a plurality of locations by the height measuring means.
FIG. 13 is a plan view of an assembled battery for explaining the third embodiment.
In FIG. 13, the height is measured at four points, and the thickness of the appropriate pressure adjusting member 3 corresponding to each height is calculated from the result. By using the pressure adjusting member 3 having the calculated thickness, it is possible to cope with the variation in the height of the assembled battery caused by the variation in the thickness of the single cell more finely. As a result, the product variation of the battery pack can be further reduced. Here, four height measurement points and eight pressure adjustment points are shown, but the combination is naturally not limited to this.

Fourth Embodiment In the fourth embodiment of the present invention, the pressure adjusting member 3 described above is configured to be hollow.
By making the pressure adjusting member 3 have a hollow structure, the battery pack can be reduced in weight.

Fifth Embodiment FIG. 14 is an enlarged view of the pressure adjusting member 3 used in the assembled battery described above, FIG. 14A is a perspective view of the pressure adjusting member 3 as viewed obliquely, and FIG. FIG. 3 is a view showing a cross-sectional shape of an adjustment member 3.
In particular, when the pressure adjusting member 3 is obtained by 3D modeling, the strength can be increased by having the lattice-like structure 3a inside as shown in FIG. In addition, by making the inside of the lattice-like structure 3a in this way, the moving amount of the 3D printer head can be reduced and the molding speed can be increased because of the linear pattern compared to the honeycomb shape, and the cost due to shortening the assembly tact time Reduction is possible.

As mentioned above, although embodiment of this invention was described, according to this,
(1) A battery pack with little variation in characteristics can be obtained by obtaining a pressing force that matches the height of the assembled battery.
(2) Since the unit cells have a flat shape in plan view, the applied pressure can be made uniform even when the stacked height is not uniform.
(3) By making the pressure adjusting member hollow, the weight of the member can be reduced, and the weight of the battery pack can be reduced.
(4) By making the cross-sectional shape of the pressure adjusting member a lattice shape, for example, the path when forming a part by molten resin lamination processing becomes linear, and the processing cost is reduced because the processing time is shortened. Cost reduction is possible.

  DESCRIPTION OF SYMBOLS 1 ... Lower frame, 2 ... Upper frame, 3 ... Pressure adjusting member, 4 ... Single cell, 5 ... Pressure spring, 5a ... Box-shaped member, 6 ... Plate, 7 ... separator.

JP 2006-339032 A JP, 2015-115313, A

Claims (9)

An assembled battery in which a plurality of unit cells containing a power generation element and having a film exterior body are stacked in the thickness direction;
A box having an opening for accommodating the assembled battery;
A pressure member disposed on the assembled battery;
A lid that closes the opening of the box that pressurizes the assembled battery via the pressure member;
A battery pack comprising: a pressure adjusting member provided between the box and the lid, wherein the pressure adjusting member adjusts a compression amount of the assembled battery by the pressure member in contact with the lid. The battery pack according to claim 1,
The said pressurizing force adjustment member is a battery pack which adjusts the pressurization force which acts on the said assembled battery when the said cover body is covered on the said box according to the different height of the said assembled battery. In the battery pack according to claim 1 or 2,
The pressure member is a battery pack including a plurality of elastic bodies. In the battery pack according to claim 1 or 2,
The pressure member is a battery pack configured by a box-shaped member. In the battery pack according to claim 2 or 4,
The battery pack according to claim 1, wherein the pressure adjusting member has a thickness corresponding to a height of the assembled battery. In the battery pack according to claim 2 or 4,
A battery pack having the pressure adjusting member having a different thickness according to a difference in height at a plurality of locations of the assembled battery. The battery pack according to any one of claims 1 to 6,
The pressure adjusting member is a battery pack having a hollow structure. The battery pack according to claim 7, wherein
The hollow structure is a battery pack having a lattice structure. The battery pack according to any one of claims 1 to 8,
The unit cell is a flat battery pack.

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