This application is a National Stage of International Application No. PCT/JP2013/069276 filed Jul. 16, 2013, claiming priority based on Japanese Patent Application No. 2012-173246 filed Aug. 3, 2012, the contents of all of which are incorporated herein by reference in their entirety.
The present application claims priority under Japanese Patent Application No. 2012-173246 filed on Aug. 3, 2012, the entire contents of which are incorporated herein by reference. A technology disclosed in this specification relates to an electric storage device.
An electric storage device may be mounted with a current interruption device to improve safety. Japanese Patent Application Publication No. H07-254401 A (1995) discloses an electric storage device mounted with a current interruption device configured to interrupt electric current when pressure inside an outer can rises. This electric storage device has an electrode group including a sheet-like positive electrode, a sheet-like separator, and a sheet-like negative electrode. The separator is disposed in such a state as to be sandwiched between the positive electrode and the negative electrode. A planar part of the positive electrode and a planar part of the negative electrode are in close contact with the separator. Contrary to this, each end of the positive electrode and the negative electrode is not in close contact with the separator, but are exposed to a space inside the outer can. The current interruption device of this electric storage device is provided on a conductive path between either the positive electrode or the negative electrode and a terminal plate serving as an external connection terminal. The current interruption device has a current interruption valve having conductivity. Electric current flows through this current interruption valve during charging or discharging. When pressure inside the outer can increases, the current interruption valve is actuated such that no electric current flows through the current interruption valve.
In the electric storage device of Japanese Patent Application Publication No. H7-254401 A (1995), the current interruption device and the electrodes are altogether disposed in the outer can. The current interruption device and the electrodes are placed in predetermined mounting positions in the outer can so that short circuit can be prevented from being caused by the current interruption device and the electrodes making contact with each other.
However, in the electric storage device of Japanese Patent Application Publication No. H07-254401 A, if inadvertent external force is applied to the outer can for example, there is a possibility that the outer can may deform thereby causing components inside thereof to be moved from the initial mounting positions. In this case, there is a possibility that the current interruption device connected to one of the electrodes and an end of the other electrode may make contact with each other and thus cause short circuit.
This specification provides a technology for reducing the possibility of a short circuit in an electric storage device.
This specification discloses an electric storage device. The electric storage device is a stacked type. The electric storage device includes a case. The electric storage device includes a sheet-like first electrode disposed within, the case and a sheet-like second electrode disposed within the case, wherein a polarity of the second electrode is different from that of the first electrode. The electric storage device includes a separator insulating the first electrode from the second electrode. The electric storage device includes a first electrode terminal and a second electrode terminal provided on the case. The electric storage device includes a first conductive path from the first electrode terminal to the first electrode and a second conductive path from the second electrode terminal to the second electrode. The electric storage device includes a current interruption device disposed between the second electrode terminal and the second electrode in the case, the current interruption device being configured to interrupt the second conductive path. In the electric storage device, one surface of the first electrode faces one surface of the second electrode. In the electric storage device, the separator includes a first surface part covering the one surface of the first electrode, a second surface part covering the other surface of the first electrode, and a connection part connected to both the first surface part and the second surface part. In the electric storage device, the connection part is disposed between the current interruption device and an end of the first electrode on a current interruption device side.
In the above-mentioned electric storage device, the connection part, which serves as an insulator, of the separator is disposed between the current interruption device electrically connected to the second electrode and the first electrode. For this reason, even if the first electrode and the current interruption device are moved from the initial mounting positions, the connection part, which serves as an insulator, can prevent the first electrode and the current interruption device from making contact with each other. This prevents the first electrode and the second electrode from being short-circuited via the second conductive path and the current interruption device.
The electric storage device disclosed herein makes it possible, to reduce the possibility of the electric storage device being short-circuited even when the case is subjected to inadvertent external force.
Hereinbelow, some of preferred technical aspects of below embodiments disclosed in the description will be listed. The features described individually have technical utility.
(Characteristic 1) In the electric storage device disclosed herein, a separator may cover a surface of a first electrode, and may be larger than the surface of the first electrode.
In the electric storage device, the first electrode is enclosed by the separator. This makes it possible to handle the first electrode and the separator as a single entity when the electric storage device is assembled. For this reason, the work of assembling the electric storage device can be made more efficient.
(Characteristic 2) In the electric storage device disclosed herein, the first electrode may include a sheet-like first metal foil. The second electrode may include a sheet-like second metal foil. In the electric storage device, the first metal foil may include a first tab protruding from an edge of the first metal foil toward an outside of the first metal foil. In the electric storage device, the second metal foil may include a second tab protruding from an edge of the second metal foil toward an outside of the second metal foil. In the electric storage device, the first tab and the second tab may be directed toward a same direction within the electric storage device.
In the electric storage device, the tabs of the first and second metal foils are directed toward a same direction in the electric storage device. For this reason, the volume of a space between an electrode assembly and a case can be made smaller than it is in a case where the tabs of the first and second metal foils are directed toward different directions with respect to the electrode assembly. This makes it possible to suppress an increase in size of the electric storage device.
(Characteristic 3) The electric storage device disclosed herein is a lithium-ion secondary battery and the first electrode may be a positive electrode and the second electrode may be a negative electrode. In the electric storage device, the second electrode may cover the first electrode, and may be larger than the first electrode.
In the electric storage device, an area of the negative electrode is larger than that of the positive electrode. For this reason, lithium ions having moved in a direction toward the negative electrode during charging are easily occluded by the negative electrode. This makes it possible to suppress a deposition of metal lithium at the negative electrode. Meanwhile, in the electric storage device, the positive electrode having a smaller area is covered by the separator. For this reason, a length by which the separator protrudes from an edge of the electrode can be made smaller than it is in a case where the negative electrode is covered by the separator, and thus an increase in size of the electric storage device can be suppressed. For these reasons, the electric storage device makes it possible to suppress the deposition of metal lithium while suppressing the increase in size of the electric storage device.
The case 4 is made of metal and is substantially rectangular parallelepiped in shape. The positive electrode terminal 12a is provided on an upper wall of the case 4 at a right-side edge of
As shown in
The negative electrode terminal 12b includes a bolt 24b made of metal, an inner nut 26b made of metal, and an outer nut 28b made of metal. The bolt 24b and the inner nut 26b hold the case 4 with a seal washer 32b put therebetween. The bolt 24b and the inner nut 26b are insulated from the case 4 by an insulator 30b. The outer nut 28b is used for wire connection with the wiring member.
As shown in
The electrode assembly 6 is immersed in an electrolyte. The electrolyte contains supporting salt including lithium salt in solvent. FEC (fluoroethylene carbonate) can be used for the solvent for example. LiPF6 (lithium hexafluorophosphate) can be used for the supporting salt for example.
As shown in
The current interruption device 40 is provided on the inner surface of the upper wall of the case 4. An insulator 34b is disposed between an upper surface of the second lead 10b and the inner surface of the upper wall of the case 4 and between a top end of the current interruption device 40 and the inner surface of the upper wall of the case 4. The current interruption device 40 is a pressure-sensitive current interruption device. In a case where the pressure inside the case 4 is less than a current interruption pressure value, the current interruption device 40 is in a state in which electric current flows through the conductive path between the negative electrodes 52b and the negative electrode terminal 12b. Further, in a case where the pressure inside the case 4 is equal to or greater than the current interruption pressure value, the current interruption device 40 is in a state in which no electric current flows through the conductive path between the negative electrodes 52b and the negative electrode terminal 12b.
In the following, the current interruption device 40 is described in detail. As shown in
That is, in a case where the pressure inside the case 4 is less than the current interruption pressure value, the diaphragm 38 is placed in such a state as to be bulged downward (
Next, the electrode assembly 6, the positive electrodes 52a, and the negative electrodes 52b are described in detail. The electrode assembly 6 is formed by stacking a plurality of positive electrode separator assemblies 50 and a plurality of negative electrodes 52b in sequence (
The positive electrode 52a is formed by a positive electrode metal foil 54a and positive electrode active material layers 58a. The positive electrode metal foil 54a is made, for example, of aluminum (Al). The positive electrode metal foil 54a has a rectangular body portion 56a and a positive electrode tab 55a extending in an upward direction of
The bag-like separator 60 is formed by two sheet-like separators 60c and 60d. The separators 60c and 60d are made of porous insulating resin. Usable examples of the insulating resin are polypropylene, polyethylene, a composite material thereof, etc. As shown in
The junction region 68 has welded regions 66 in which the separators 60c and 60d are welded and a non-welded region 67 in which the separators 60c and 60d are not welded. A usable example of a welding method herein is ultrasonic welding. As shown in
As shown in
The tabs 55a of the positive electrodes 52a and the tabs 55b of the negative electrodes 52b are disposed on a same side (on the upper side when viewed in
As shown in
When the electric storage device 2 is assembled, the electrode assembly 6 is formed by stacking a plurality of positive electrode separator assemblies 50 and a plurality of negative electrodes 52b in sequence. In the electric storage device 2 of the present embodiment, the positive electrode 52a is enclosed by the bag-like separator 60. This makes it possible to handle the positive electrode 52a and the separators 60c and 60d together as a single entity when the electric storage device 2 is assembled. The work of assembling the electric storage device 2 can be made more efficient than it is in a case where the positive electrode 52a and the separators 60c and 60d are handled separately.
In the electrode assembly 6, as shown in
In the electric storage device 2, the junction region 68 is disposed between the current interruption device 40 connected to one of the electrodes (i.e. to the negative electrode 52b) and an end 53a of the other electrode (positive electrode 52a) on a current interruption device 40 side (upper side). For this reason, even if the case 4 deforms and causes the current interruption device 40 and the other electrode (positive electrode 52a) to come close to each other, the current interruption device 40 and the positive electrode 52a can be prevented from making contact with each other. This allows the electric storage device 2 to reduce the possibility of short circuit in the electric storage device 2. That is, even if the areas of the positive electrode metal foil 54a and the positive electrode active material layers 58a in the positive electrode 52a are widened, the existence of the junction region 68 between the positive electrode 52a and the current interruption device 40 can reduce the possibility of short circuit when the positive electrode 52a makes contact with the current interruption device 40, which is a negative electrode potential. This makes it possible to increase battery capacity per unit volume.
The above mentioned effect achieved by the separators 60c and 60d forming the electrode assembly 6. The electric storage device 2 of the present embodiment makes it possible to reduce the possibility of short circuit in the electric storage device 2 without providing an insulator other than the separators 60c and 60d.
Correspondences between the terms used in the embodiment and those used in claims are explained. The bag-like separator 60 is an example of the “separator”. The junction region 68 is an example of the “connection part” in the claims, and parts other than the junction region 68 of the separators 60c and 60d are examples of the “first surface part” and the “second surface part”.
In the above embodiment, the bag-like separator 60 is formed by the two separators 60c and 60d being joined to each other at the junction region 68. However, the bag-like separator 60 may alternatively be formed by folding a single separator and joining one end thereof to another. In the above embodiment, the “first surface part” and the “second surface part” are parts other than the junction region 68 of the two separators 60c and 60d. However, the “first surface part” and the “second surface part” may alternatively be surface parts of a single separator that face each other across a folded portion formed by folding the single separator. In the embodiment, the “connection part” is the junction region 68 formed by the two separators 60c and 60d being joined to each other. However, the “connection part” may be a folded part formed by folding a single separator.
In the following, first and second modifications of the embodiment are described. In the electric storage device 2 of the embodiment, there is a clearance between the junction regions 68 and the current interruption device 40 (see
An electric storage device 202 of the second modification includes a current interruption device 240 (
Specific examples of the present invention have been described in detail, however, these are mere exemplary indications and thus do not limit the scope of the claims. The art described in the claims includes modifications and variations of the specific examples presented above. Technical features described in the description and the drawings may technically be useful alone or in various combinations, and are not limited to the combinations as originally claimed. Further, the art described in the description and the drawings may concurrently achieve a plurality of aims, and technical significance thereof resides in achieving any one of such aims.
Number | Date | Country | Kind |
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2012-173246 | Aug 2012 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2013/069276 | 7/16/2013 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2014/021094 | 2/6/2014 | WO | A |
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Number | Date | Country |
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102623740 | Aug 2012 | CN |
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07-105932 | Apr 1995 | JP |
07-254401 | Oct 1995 | JP |
2003-092100 | Mar 2003 | JP |
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Entry |
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Communication dated Feb. 3, 2015, issued by the International Searching Authority in counterpart Application No. PCT/JP2013/069276. |
International Search Report for PCT/JP2013/069276 dated Sep. 3, 2013 [PCT/ISA/210]. |
Written Opinion for PCT/JP2013/069276 dated Sep. 3, 2013 [PCT/ISA/237]. |
Number | Date | Country | |
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20150207124 A1 | Jul 2015 | US |