JP2015015102A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly cleave a cleavage groove formed in a plane part of an outer can of a battery case in a battery pack where multiple unit cells are laminated.SOLUTION: A battery case 11 of a unit cell 10 comprises an outer can 12 having a cup shape and a lid plate 13 which seals an opening of the outer can 12. A cleavage groove 17 is formed at a plane part 12a of the outer can 12. A positive electrode terminal 15 and a negative electrode terminal 14 are provided at the lid plate 13. The multiple unit cells 10 are arranged so that the lid plates 13 are located at the same side. Leads 22, 24 electrically connecting the multiple unit cells 10 are arranged at the side of the lid plate 13.

Description

  The present invention relates to a battery pack in which a plurality of unit cells are stacked.

  Generally, a battery pack includes a flat unit cell, a protection element, and a circuit board. In recent years, for battery packs used in electronic devices such as portable computers (for example, tablet terminals, notebook computers, etc.), electronic book terminals, digital cameras, etc., there has been a very high demand for an increase in battery capacity. In order to meet this demand, a battery pack in which a plurality of unit cells are stacked is known. In Patent Document 1, two unit cells are stacked so that the cover plate is on the same side, and the two unit cells are opposite to the negative electrode lead and the cover plate on the cover plate side (the bottom side of the outer can). The battery packs are connected in parallel so as to cross-link each of the positive electrode leads.

  On the other hand, in order to prevent the internal pressure of the unit cell from rising abnormally and rupturing the battery case, the battery case may be provided with a cleavage groove (sometimes referred to as a “vent”). Patent Document 2 describes that a cleavage groove is provided in a flat portion of a bottomed cylindrical outer can of a battery case. When the pressure in the battery case increases, the flat portion of the outer can expands, and when the amount of expansion exceeds a predetermined threshold, the cleavage groove is opened and the gas in the battery case is released.

JP 2008-166060 A JP 2013-98173 A

  In the battery pack of Patent Document 1, both ends of two unit cells are crosslinked and connected by a positive electrode lead and a negative electrode lead. Therefore, even if the internal pressure of the unit cell rises, there is a possibility that the swelling of the outer can of the battery case is limited by the positive electrode lead and the negative electrode lead. Even if the cleavage groove described in Patent Document 2 is formed in the outer can of the unit cell constituting such a battery pack, the amount of swelling of the outer can cannot reach a predetermined threshold value, so that the cleavage groove is broken. In the worst case, the battery case may burst.

  The present invention solves the above-described conventional problems, and in a battery pack in which a plurality of unit cells are stacked, the cleavage groove formed in the flat portion of the outer can of the battery case is appropriately cleaved, thereby improving the safety of the battery pack. The purpose is to improve.

  The battery pack of the present invention includes a plurality of flat unit cells stacked in the thickness direction. The unit cell includes a battery case including a bottomed cylindrical outer can and a cover plate that seals an opening of the outer can. A cleavage groove is formed in the flat portion of the outer can. The lid plate is provided with a positive terminal and a negative terminal. The plurality of unit cells are arranged such that the cover plate is on the same side. Leads for electrically connecting the plurality of unit cells are disposed on the lid plate side.

  According to the present invention, the plurality of unit cells are connected to each other by the lead on the cover plate side, but are not connected to the side opposite to the cover plate. Accordingly, when the pressure in at least one of the plurality of unit cells rises and the flat portion of the outer can expands, the plurality of unit cells may be displaced away from each other on the side opposite to the lid. it can. For this reason, the cleavage groove provided in the plane portion can be cleaved as intended. Therefore, a battery pack with improved safety can be provided.

FIG. 1A is a top view of a unit cell constituting a battery pack according to an embodiment of the present invention, and FIG. 1B is a front view thereof. FIG. 2 is a perspective view of the battery pack according to the embodiment of the present invention. FIG. 3 is an exploded perspective view of the battery pack according to the embodiment of the present invention. FIG. 4A is a perspective view of two unit cells connected in parallel by a positive electrode lead and a negative electrode lead, as viewed from the lid plate side, in one embodiment of the present invention. FIG. 4B is a perspective view of two unit cells connected in parallel with a positive electrode lead and a negative electrode lead, as viewed from the outer can side, in an embodiment of the present invention. FIG. 5 is a perspective view of two unit cells to which a circuit board is attached as viewed from the lid plate side in one embodiment of the present invention.

  In the battery pack of the present invention, when the internal pressure of at least one of the plurality of unit cells rises and the flat portion of the outer can expands, the plurality of unit cells are opposite to the lid plate. It is preferable that the side is displaced so as to be separated from each other on the side so that the cleavage groove is cleaved. Thereby, since the swelling of a plane part is not restrict | limited when the internal pressure of a unit cell rises, the battery pack with high safety | security which a cleavage groove | channel tears as intended can be provided.

  In the plurality of unit cells, the positive terminal is preferably disposed on the same side with respect to the negative terminal. Thereby, a some unit cell can be easily connected in parallel using a lead | read | reed.

  Below, this invention is demonstrated in detail, showing suitable embodiment. However, it goes without saying that the present invention is not limited to the following embodiments. In the following description, for convenience of explanation, among the members of the embodiment of the present invention, only the main members necessary for explaining the present invention are shown in a simplified manner. Therefore, the present invention can include any member not shown in the following drawings. Further, in the following drawings, the actual dimensions of members and the dimensional ratios of the members are not faithfully represented.

<Unit cell>
FIG. 1A is a top view of a unit cell 10 constituting a battery pack according to an embodiment of the present invention, and FIG. 1B is a front view of the unit cell 10. The unit cell 10 includes a battery case 11 having a bottomed cylindrical outer can 12 having one end opened and a lid plate 13 that seals the opening of the outer can 12. The unit cell 10 is a secondary battery that can be charged and discharged. The type of the secondary battery is not particularly limited, and for example, a lithium ion secondary battery can be used. The unit cell 10 has a flat shape (thin plate shape) that is smaller in the thickness direction (up and down direction in FIG. 1A) than in the vertical direction (up and down direction in FIG. 1B) and width direction (left and right direction in FIG. 1B). doing. In the battery case 11, a power generation element and an electrolytic solution (both not shown) are enclosed. The power generation element includes a positive electrode in which a positive electrode mixture layer containing a positive electrode active material is applied and formed on one or both sides of a sheet-like positive electrode current collector, and a negative electrode active material on one or both sides of the sheet-like negative electrode current collector A negative electrode on which a negative electrode mixture layer is formed by coating is a flat electrode body that is wound or laminated via a separator.

  The outer can 12 can be formed, for example, by deep drawing a metal plate made of aluminum or an alloy thereof. The lid plate 13 can be formed by, for example, pressing a metal plate made of an aluminum alloy or the like. The peripheral edge of the opening of the outer can 12 and the peripheral edge of the cover plate 13 are liquid-tightly sealed by, for example, seam welding using a laser beam.

  A negative electrode terminal 14 is provided at a substantially central position in the width direction of the lid plate 13. The negative electrode terminal 14 penetrates the lid plate 13 and is electrically connected to the negative electrode current collector of the power generation element housed in the battery case 11. Between the negative electrode terminal 14 and the cover plate 13, an insulating packing (not shown) for insulating the two is interposed. A positive electrode terminal 15 is provided on the lid plate 13 at a position slightly away from the negative electrode terminal 14 in the width direction. The positive terminal 15 is electrically connected to the positive current collector of the power generation element in the battery case 11. A sealing body 16 is provided on the opposite side of the positive electrode terminal 15 from the negative electrode terminal 14. The sealing body 16 seals the inlet (through hole) that penetrates the lid plate 13. After injecting the electrolytic solution into the battery case 11 through the injection port, the injection port is sealed with a sealing body 16.

  A tear groove 17 is formed in two substantially rectangular planar portions 12 a facing the thickness direction of the outer can 12. The cleavage groove 17 is thinner than the portion other than the cleavage groove 17 of the flat surface portion 12a. The method of forming the cleavage groove 17 is arbitrary, and for example, it can be formed simultaneously with the outer can 12 being press-molded. The shape, number, and position of the cleavage groove 17 are arbitrary. The broken cleavage groove 17 shown in FIG. 1B indicates the cleavage groove 17 formed in the flat surface portion 12a on the back surface side. In the present embodiment, two cleavage grooves 17 are formed in the outer can 12, and the two cleavage grooves 17 are rotationally symmetric with respect to the vertical axis passing through the negative electrode terminal 14. The cleavage groove 17 is designed so that the flat surface portion 12a expands when the pressure in the battery case 11 increases, and the flat surface portion 12a expands when the amount of expansion exceeds a predetermined threshold.

<Battery pack>
FIG. 2 is a perspective view of the battery pack 1 according to the embodiment of the present invention. FIG. 3 is an exploded perspective view of the battery pack 1.

  As shown in FIG. 3, the battery pack 1 includes the two unit cells 10 shown in FIGS. 1A and 1B. The two unit cells 10 are stacked such that the flat plates 12a face each other with the cover plate 13 facing the same side. The positive electrode terminal 15 is disposed on the same side of the two unit cells 10 with respect to the negative electrode terminal 14. A spacer 21 is provided between the two unit cells 10 in order to ensure a predetermined gap (for example, about 1 mm) between them.

  The positive terminals 15 of the two unit cells 10 stacked in the vertical direction are connected by a positive electrode lead 22 made of a strip-shaped thin metal plate curved in a substantially J shape. One end of the protection element 23 is connected to the negative electrode terminal 14 of each unit cell 10. The protection element 23 includes, for example, a polyswitch (PTC). The other ends of the two protective elements 23 are connected by a negative electrode lead 24 made of a strip-shaped thin metal plate curved in a substantially J shape. Thus, the two unit cells 10 are connected in parallel. 4A is a perspective view of two unit cells 10 connected in parallel as seen from the cover plate 13 side, and FIG. 4B is a perspective view of the outer can 12 as seen from the bottom surface 12b side. The two unit cells 10 are connected via the positive electrode lead 22 and the negative electrode lead 24 on the lid plate 13 side, but are not connected at all on the side opposite to the lid plate 13 (bottom surface 12b side). .

  Returning to FIG. 3, the positive terminal 26 p and the negative terminal 26 n of the circuit board 25 are connected to the positive lead 22 and the negative lead 24. The circuit board 25 includes electronic components that constitute a protection circuit (safety circuit). On the circuit board 25, a plurality of external connection terminals 27 are arranged in the width direction. FIG. 5 is a perspective view of the two unit cells 10 to which the circuit board 25 is attached as viewed from the cover plate 13 side.

  Returning to FIG. 3, the two unit cells 10 to which the circuit board 25 is attached are stored between the upper case 27a and the lower case 27b. Thus, the battery pack 1 shown in FIG. 2 is obtained. The two unit cells 10 are accommodated in a housing 27 that includes an upper case 27a and a lower case 27b. The external connection terminal 27 of the circuit board 25 is exposed to the outside.

<Action>
The operation of the battery pack 1 of the present embodiment configured as described above will be described.

  The two unit cells 10 constituting the battery pack 1 of the present embodiment are stacked such that the lid body 13 faces the same side, and the planar portions 12a face each other. A cleavage groove 17 is formed in the flat surface portion 12a. The lid body 13 is provided with a positive electrode terminal 15 and a negative electrode terminal 14, and leads 22 and 24 that electrically connect the two unit cells 10 are arranged only on the lid body 13 side. Therefore, since the two unit cells 10 are connected via the positive electrode lead 22 and the negative electrode lead 24 on the lid 13 side, it is difficult to displace the two unit cells 10 away from each other. On the other hand, since the two unit cells 10 are not connected on the side opposite to the lid 13 (the bottom surface 12b side of the outer can 12), it is relatively easy to displace the two unit cells 10 away from each other. It is. For this reason, when the pressure in the battery case 11 of at least one of the two unit cells 10 rises and the flat portion 12a swells, the two unit cells 10 have two unit cells on the side opposite to the lid 13. 10 can be displaced away from each other. Unlike the battery pack described in Patent Document 1 described above, in this embodiment, the battery case 11 can swell relatively freely. Therefore, when the amount of swelling of the flat surface portion 12a of the battery case 11 reaches a predetermined threshold value, the cleavage groove 17 is cleaved, and the gas in the battery case 11 is released to the outside.

  As described above, in the battery pack 1 of the present embodiment, the planar portions 12a of the plurality of battery cases 11 are connected only on the lid 13 side so that the planar portions 12a can swell freely. The cleavage groove 17 provided in 12a can be cleaved as intended. Therefore, the safety of the battery pack 1 is improved.

  The casing 27 is preferably designed so as not to limit the swelling of the battery case 11. For example, the inner dimension of the casing 27 in the thickness direction of the unit cell 10 is larger than the outer dimension in the thickness direction of the two stacked unit cells 10 in consideration of the amount of swelling of the battery case 11. Can be set. Alternatively, when the battery case 11 swells, the upper case 27a and the lower case 27b can be easily separated.

  The above embodiments are merely examples. The present invention is not limited to the above embodiment, and can be modified as appropriate.

  In said embodiment, although the several unit cell 10 was connected in parallel, this invention is not limited to this, The several unit cell 10 may be connected in series. In this case, the different polarity terminals (that is, the positive electrode terminal and the negative electrode terminal) of the adjacent unit cells 10 are connected by leads. The lead is disposed only on the cover plate 13 side as in the case of the leads 22 and 24 in the above embodiment.

  The number of unit cells 10 constituting the battery pack is not limited to two, and may be any number of three or more.

  The protection element and the circuit board may be composed of one component.

  The configuration of the casing 27 is not limited to the above embodiment. The housing 27 can be omitted.

  The application field of the present invention is not particularly limited, and can be widely used as a battery pack that requires a high capacity. In particular, it can be preferably used as a battery pack used in various portable devices such as a mobile phone, a portable computer (for example, a tablet terminal, a notebook computer, etc.), an electronic book terminal, and a digital camera.

DESCRIPTION OF SYMBOLS 1 Battery pack 10 Unit cell 11 Battery case 12 Outer can 12a Plane part 13 Cover plate 14 Negative electrode terminal 15 Positive electrode terminal 17 Cleavage groove 22 Positive electrode lead 23 Protection element 24 Negative electrode lead 25 Circuit board

Claims (3)

A battery pack in which a plurality of flat unit cells are stacked in the thickness direction,
The unit cell includes a battery case including a bottomed cylindrical outer can and a lid plate that seals the opening of the outer can.
A cleavage groove is formed in the flat portion of the outer can,
The lid plate is provided with a positive terminal and a negative terminal,
The plurality of unit cells are arranged so that the cover plate is on the same side,
A battery pack, wherein leads for electrically connecting the plurality of unit cells are arranged on the lid plate side.   When the planar portion of the outer can expands due to an increase in the internal pressure of at least one of the plurality of unit cells, the plurality of unit cells are displaced away from each other on the side opposite to the lid plate. The battery pack according to claim 1, wherein the cleavage groove is configured to be cleaved.   2. The battery pack according to claim 1, wherein in the plurality of unit cells, the positive electrode terminal is disposed on the same side with respect to the negative electrode terminal.

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