Patent Application
20130108908
1. Field of the Invention
The present invention relates to a power supply apparatus having a plurality of battery cells.
2. Description of the Related Art
Power supply apparatuses used for hybrid automobiles, electric automobiles, large-sized electrical storage apparatuses, or the like are required to have a high-voltage output and a high-current capacity. Such power supply apparatuses include a power supply apparatus formed by laminating a plurality of battery cells. By connecting the battery cells in series, an output voltage of the power supply apparatus can be increased, whereas by connecting the battery cells in parallel, a current capacity of the power supply apparatus can be increased. A secondary battery cell is used as the battery cell of the power supply apparatus in order to allow a repetition of charging and discharging.
Since battery cells expand due to a repetition of charging and discharging, secondary battery cells deteriorate in performance (input-output characteristics) in accordance with the expansion. Therefore, the power supply apparatus formed by laminating a plurality of battery cells is provided in which the apparatus includes a faster for preventing expansion of the battery cells by fastening the battery cells under application of pressure, thereby suppressing the deterioration in battery performance in accordance with the expansion.
As this type of power supply apparatus, for example, known is a power supply apparatus including: a battery block formed by alternately laminating rectangular battery cells, as a battery cell, each having a rectangular parallelepiped outer can, and separators holding the rectangular battery cells; a pair of end plates provided at both ends of the battery block; and a binding bar fixed to the end plates for fastening the laminated rectangular battery cells in a direction of the lamination under application of pressure (Japanese Patent Laid-Open No. 2011-34775). According to the configuration, by fastening the battery block via the binding bar, the outer can of each rectangular battery cell is pressed by the adjacent separator, leading to suppression of expansion of the outer can. Specifically, a size of the rectangular battery cell is restricted by the binding bar fixed to the end plates. The expansion of the outer can is therefore prevented by the separator pressing a wide surface of the outer can even if an internal pressure of the outer can increases due to the repetition of charging and discharging.
The deterioration in battery performance is also influenced by a life of the battery cell (increase of an internal resistance due to aging, or the like). Specifically, a life of the battery cell is reduced due to usage under a high temperature. As for the power supply apparatus disclosed in JP 2011-34775-A, in addition to the above configuration, the outer can is made of metal for increasing heat dissipation performance of the battery cell, as well as each of the battery cells can be cooled via a cooling plate abutting on a lower part of the battery block.
In the case of using the outer can made of metal, adjacent battery cells need to be insulated each other because a potential difference between the outer cans of the adjacent battery cells is caused. The adjacent battery cells also need to be insulated each other in a power supply apparatus having a cooling mechanism such as a cooling plate. This is because condensed water may adhere to the outer can or the like due to a difference in temperature with surroundings.
In the power supply apparatus disclosed in JP 2011-34775-A, adjacent battery cells are insulated by providing a separator having an insulation property between the adjacent battery cells.
In the power supply apparatus disclosed in JP 2011-34775-A, the separator insulates the adjacent battery cells and prevents the expansion of the outer can by pressing the outer can of the battery cell via the binding bar.
In the configuration disclosed in JP 2011-34775-A, the separator uniformly presses the wide surface of the outer can. Sufficient study, however, has not been made on an optimal shape of the separator for efficiently suppressing the deterioration in battery performance of the rectangular battery cell due to the expansion. A power supply apparatus for efficiently preventing the expansion of the rectangular battery cell has therefore been desired.
The present invention has been made for solving such a problem. An object of the present invention is to provide a power supply apparatus formed by laminating a plurality of battery cells and capable of suppressing deterioration in battery performance.
A power supply apparatus according to the present invention includes: a plurality of battery cells each having a flat rectangular parallelepiped outer can, the battery cells provided so that wide surfaces of the outer cans are opposed to each other; a separator provided between the battery cells; and a fastener fastening the battery cells and the separator with the battery cells under application of pressure, wherein the wide surface of the outer can includes a circumference portion at a circumference of the wide surface and a central portion in a center of the wide surface, and wherein the separator includes an insulating portion insulating the adjacent battery cells and a pressing portion formed at a position corresponding to the central portion of the wide surface for pressing the central portion.
It is preferred that the outer can is a closed-end case for housing whose top surface is opened, the battery cell includes an electrode assembly provided in the outer can, a sealing body sealing an opening of the outer can, and output terminals fixed to the sealing body and electrically connected to the electrode assembly, and the separator is provided so as to have space between the circumference portion in the vicinity of the sealing body and the insulating portion.
It is preferred that the insulating portion is provided so as to protrude upward over an end surface of the sealing body of the outer can.
It is preferred that the battery cell includes a current blocking mechanism electrically blocking the output terminal and the electrode assembly when an internal pressure of the outer can increases, the current blocking mechanism provided in the vicinity of the sealing body.
It is preferred that the pressing portion includes a peak portion in a center of the pressing portion and a circumference portion at a circumference of the peak portion, and the pressing portion further includes a first inclined plane formed from the peak portion to the circumference portion on un upper side and a second inclined plane formed from the peak portion to the circumference portion on a lower side.
It is preferred that the first inclined plane has a gentler gradient than does the second inclined plane.
It is preferred that the electrode assembly is formed by winding a laminate including a positive electrode and an negative electrode to obtain a wound body, the wound body provided in the outer can with an axial direction of the wound body parallel to the wide surface and oriented toward a horizontal direction of the outer can, the pressing portion includes a third inclined plane and a fourth inclined plane formed from the peak portion to the circumference portion provided on both sides, and the pressing portion is further formed so that gradients of the third inclined plane and the fourth inclined plane become equal.
It is preferred that the current blocking mechanism is provided on one of the output terminals, the pressing portion includes a third inclined plane and a fourth inclined plane formed from the peak portion to the circumference portion provided on both sides, the third inclined plane is formed in the vicinity of the current blocking mechanism, and the pressing portion is further formed so that the third inclined plane has a steeper gradient than does the fourth inclined plane.
According to a configuration of claim 1, the adjacent battery cells can be insulated and the central portion of the outer can more likely to expand can be pressed. The expansion of the battery cell can therefore be efficiently suppressed, for example.
According to a configuration of claim 2, providing the space can perform insulation without pressing the circumference portion in the vicinity of the sealing body. Damage of a welded part between the sealing body and the outer can therefore be prevented, for example.
According to a configuration of claim 3, the insulating portion can be provided between the output terminals of the adjacent battery cells. A short circuit due to water condensation or the like can therefore be prevented, for example.
According to a configuration of claim 4, the current blocking mechanism operated depending on the internal pressure of the outer can is provided in the vicinity of the sealing body where a load is hard to be applied by the pressing portion. A malfunction of the current blocking mechanism can therefore be prevented, for example.
According to a configuration of claim 5, the inclined plane is formed from the peak portion to the circumference portion in the pressing portion. A contact area between the pressing portion and the wide surface of the outer can can therefore be gently changed depending on a fastening force by the fastener, for example.
According to a configuration of claim 6, the wide surface on a bottom side can be mainly pressed. A load applied to the sealing body or the like can therefore be reduced, for example.
According to a configuration of claim 7, the wide surface can be uniformly pressed in the axial direction of the electrode assembly, for example.
According to a configuration of claim 8, the third inclined plane close to the current blocking mechanism has a steeper gradient than does the fourth inclined plane. A load applied to the current blocking mechanism can therefore be reduced and the malfunction of the current blocking mechanism can be prevented, for example.
The above and further objects of the present invention as well as the features thereof will become more apparent from the following detailed description to be made in conjunction with the accompanying drawings.
An embodiment of the present invention will be described in detail below with reference to
The rectangular battery cells 2 of the battery block 4 are laminated so that output terminals 21 form a line on a top surface of the battery block 4. The rectangular battery cells 2 adjacent to each other are connected via a bus bar 8. The rectangular battery cells 2 are connected in series to increase an output voltage of the power supply apparatus 1. An outer shape of the end plates 5 provided at the both ends of the battery block 4 is a rectangular parallelepiped substantially similar to an outer shape of the rectangular battery cell 2. The end plate 5 is made of metal having relatively high strength such as aluminum and aluminum alloy, rigid plastic, or the like. Threaded holes for screwing and fixing a pair of binding bars 6 provided in parallel with each other in a vertical direction are formed at four corners of each of the end plates 5. This allows the binding bars 6 to be fixed to the end plates 5.
Although the rectangular battery cells 2 are connected in series in the above embodiment, the rectangular battery cells 2 may be connected in parallel. Connecting the rectangular battery cells 2 in parallel can increase a current capacity of the power supply apparatus 1. The battery block 4 may be formed by combining parallel connection and series connection depending on an intended output voltage or current capacity.
As illustrated in the cross-sectional views in
A topside of the diaphragm 71b is airtightly sealed in the inner case 72. The internal pressure of the outer can 22 does not act upon the topside of the diaphragm 71b by airtightly sealing the topside of the diaphragm 71b. The internal pressure of the outer can 22 acts upon an underside of the diaphragm 71b, so that a force pushing up the diaphragm 71b acts because of the internal pressure. The force pushing up the diaphragm 71b becomes larger in proportion to the internal pressure of the outer can 22. With the sufficiently small internal pressure of the outer can 22, the force pushing up the diaphragm 71b is also small, and therefore, deformation of the diaphragm 71b is prevented by sealed air on the topside of the diaphragm 71b. When increase of the internal pressure of the outer can 22 causes the force pushing up the diaphragm 71b to exceed a certain constant value, the deformation of the diaphragm 71b cannot be prevented, resulting in the deformation as illustrated in
The configuration allows the rectangular battery cell 2 to be electrically blocked from a load to which the power supply apparatus 1 is connected such as a motor for vehicle when the internal pressure of the outer can 22 extraordinarily increases, for example. Although the current blocking mechanism 7 is provided on a side of the positive electrode 251 in the above embodiment, the current blocking mechanism 7 may be provided on a side of the negative electrode 252.
When the end plate 5 is made of metal, the separator 3 is provided between the end plate 5 and the rectangular battery cell 2. The separator 3 provided at an end of the battery block 4 has only one surface opposed to the rectangular battery cell 2, and the pressing portion 32 is also formed on the surface opposed to the rectangular battery cell 2. The separator 3 at the end may be formed into such a shape as to fit the separator 3 into the end plate 5 for holding the end plate 5. Forming into such a shape can prevent displacement of the end plate 5 when the battery block 4 is fastened by the binding bars 6.
As for a separator 3 (3A) illustrated in
As described above, in the outer can 22 of the rectangular battery cell 2, the central portion 24b of the wide surface 24 particularly expands, while the circumference portion 24a of the wide surface 24 does not very expand. In such a configuration, if the circumference portion 24a of the outer can 22 is pressed, expansion of the outer can 22 cannot be prevented efficiently. This is because a part hardly expanding is pressed. Additionally, when an excessive force is applied to the circumference portion 24a of the outer can 22, particularly the circumference portion 24a in the vicinity of the sealing body 23, a welded part between the sealing body 23 and the outer can 22 may be cracked, or the weld may peel off.
According to the above configuration, the pressing portion 32 of the separator 3A mainly presses the central part of the wide surface 24 of the outer can 22 when the binding bars 6 fasten the battery block 4. The central portion 24b of the wide surface 24 with a large change in expansion can therefore be pressed, allowing the expansion of the outer can 22 to be efficiently suppressed. Additionally, in the configuration, a load is hard to be applied to the sealing body 23 and the like. The welded part between the sealing body 23 and the outer can 22 can therefore be prevented from being cracked and the weld can be prevented from peeling off, thereby being able to provide a safer power supply apparatus.
As for a separator 3 (3B) illustrated in
In a separator 3 (3C) in
As illustrated in
Since the current blocking mechanism 7 is provided in the vicinity of the sealing body 23 in the above embodiment, a load applied to the current blocking mechanism 7 can also be reduced. In particular, the current blocking mechanism 7 described in the above embodiment may have the diaphragm 71b deformed when an external force (such as a pressing force of the pressing portion pressing the outer can) is applied to the diaphragm 71b. This is because the current blocking mechanism 7 blocks the electrical connection between the output terminal 21 and the electrode assembly 25 by deforming the diaphragm 71b depending on the internal pressure of the outer can 22. Specifically, even if the internal pressure of the outer can 22 is not very high, the diaphragm 71b may be deformed to block a current, or the external force applied to the current blocking mechanism 7 with the electrical connection between the output terminal 21 and the electrode assembly 25 being blocked may deform the diaphragm 71b, causing the output terminal 21 and the electrode assembly 25 to be connected again. Since the configuration of the separator 3D illustrated in
As for a separator 3 (3E) illustrated in
As for a separator 3 (3F) illustrated in
Although various shapes of the separator 3 are illustrated in
Further, in the above embodiment, inclination of the inclined plane 33 (33a, 33b, 33c and 33d) is not necessarily to have a gradient with a certain angle of inclination. The inclination of the inclined plane 33 may be formed so that the angle of inclination successively changes as getting away from the peak portion 32a, that is, a cross section of the pressing portion 32 has an arc shape.
In the separators 3 illustrated in
The shape of the separator 3 and a change in a fasting force of the binding bar 6 will now be described. Specifically, as for a relationship between a pressing force and a cell width when the separator presses the outer can 22, a comparison will be made between a typical plate-like separator and the separator 3D in the embodiment illustrated in
In the expanded outer can 22, the wide surface 24 of the outer can 22 mainly expands. When the expanded outer can 22 is pressed, only an expanded part of the outer can 22 is pressed by the separator. On the other hand, the outer can 22 of the rectangular battery cell 2 pressed up to the original size has the same outer shape or substantially the same outer shape as the outer can 22 that does not expand. Therefore, when the outer can 22 in such a state is further pressed to reduce the cell width, compared with the case of pressing only an expanded part of the outer can 22, a contact area between the separator and the outer can 22 changes, thereby abruptly increasing a pressing force required for reducing the outer can 22 in size.
Additionally, the shape of the outer can 22 is formed so that the wide surfaces 24 are inclined to have wider space therebetween on the side of the sealing body 23, as described above. When the outer can 22 of the rectangular battery cell 2 pressed up to the original size is further pressed by the plate-like separator, the plate-like separator abuts on the circumference portion 24a on the side of the sealing body 23 of the outer can 22. The abutment part in the vicinity of the circumference portion 24a of the outer can 22 corresponds to a part of the outer can 22 hard to be deformed. Therefore, when the size of the outer can 22 is reduced in a state of the separator and the circumference portion 24a of the outer can 22 being abutted each other, the pressing force to be required abruptly increases.
As described above, since the space is provided between the circumference portion 24a and the insulating portion 31, the separator 3 can be formed so as not to abut on the vicinity of the circumference portion 24a regardless of the cell width of the outer can 22. Additionally, by providing an inclined plane on the pressing portion 32, the contact area between the separator 3 and the wide surface 24 of the outer can 22 can gently change.
In the meantime, outer cans vary in size at the time of production. Such a dimensional error cannot be completely eliminated. When a dimensional error occurs in the outer can 22, a relationship between the cell width of the outer can 22 and the pressing force F corresponds to one obtained by laterally translating the graphs in
As described above, when the plate-like separator presses the outer can 22, the dimensional error of the outer can 22 has a large influence. This is because the pressing force F significantly changes depending on the cell width of the outer can 22. On the other hand, according to the configuration of the separator 3 in the above embodiment, the pressing force F does not abruptly change. The influence of the dimensional error of the rectangular battery cell 2 to be laminated can therefore be reduced compared with the configuration in which the typical plate-like separator presses the outer can 22. Since variation of the load applied to the binding bar 6 can be reduced, rigidity of the binding bar 6 does not need to be increased more than necessary. The power supply apparatus 1 can also be downsized, for example, by reducing a thickness of the binding bar 6.
The battery block 4 is then formed by alternately laminating the rectangular battery cells 2 each having the rectangular parallelepiped outer can 22, and the separators 3 each having the pressing portions 32. The end plates 5 are provided at both ends of the battery block 4 in a direction of the lamination, and thereafter, the binding bars 6 are fixed to the end plates 5. Specifically, pressure is applied to the battery block 4 in the direction of the lamination with using a jig, and then, the binding bars 6 are screwed and fixed to the end plates 5. The battery block 4 having the binding bars 6 fixed thereto in such a manner is fastened by the binding bars 6 in a state of the pressure being applied in the direction of the lamination even if the jig is removed. The fastened battery block 4 is restrained in size and a fastening force changes depending on an expansion state of the rectangular battery cells 2 of the battery block 4.
The above power supply apparatus 1 can be used as a power supply for vehicles. Vehicles on which a power supply apparatus is mounted include electric vehicles such as hybrid automobiles or plug-in hybrid automobiles run and driven only by an engine and a motor, or electric automobiles run only by a motor. The power supply apparatus 1 is used as a power supply for these vehicles.
In addition to the power supply apparatus for vehicles, the power supply apparatus 1 can be appropriately used for various applications such as for a backup power supply apparatus mountable on a rack of a computer server, a backup power supply apparatus for a radio base station of a mobile phone or the like, a power supply for storage of electricity for household use or industrial use, a power supply for a street light or the like, an electrical storage apparatus in combination with a solar cell, and a backup power supply of a signal or the like.
The present invention can be widely used for power supply apparatuses.
It should be apparent to those with an ordinary skill in the art that while various preferred embodiments of the invention have been shown and described, it is contemplated that the invention is not limited to the particular embodiments disclosed, which are deemed to be merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the invention, and which are suitable for all modifications and changes falling within the scope of the invention as defined in the appended claims. The present application is based on Application No. 2011-237,006 filed in Japan on Oct. 28, 2011, the content of which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-237006 | Oct 2011 | JP | national |
