Patent Publication Number: US-2013252037-A1

Title: Battery and battery system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a battery, and particularly, to a safety valve which is provided in the battery. 
     Priority is claimed on Japanese Patent Application No. 2012-065229, filed on Mar. 22, 2012, the content of which is incorporated herein by reference. 
     2. Description of Related Art 
     As batteries, there are primary batteries which perform only discharge and secondary batteries which perform discharge and charge. Particularly, in recent years, attention has been paid to lithium secondary batteries having features such as a high energy density, a high output, and a long lifespan as secondary batteries. Generally, the lithium secondary batteries have a configuration in which a laminated electrode body having a positive electrode plate and a negative electrode plate laminated with a separator interposed therebetween is sealed in a battery container together with an electrolyte and the like. 
     In batteries such as lithium secondary batteries, for example, there are concerns that when problems such as a short or an overcharge occur, a large amount of high-temperature gas is generated in the battery container due to the rapid evaporation of the electrolyte and the like and an internal pressure of the battery container rapidly increases, whereby a battery container body explodes. 
     Therefore, generally, a lid of the battery container is provided with a safety valve for discharging the gas in the battery container to the outside when the internal gas pressure of the battery container increases to a predetermined value or greater, to prevent the battery container from exploding (for example, see Japanese Unexamined Patent Application, First Publication No. 2005-332700). 
     However, since conventional batteries such as the battery described in Japanese Unexamined Patent Application, First Publication No. 2005-332700 have a safety valve provided according to the surface shape of the lid, the discharge direction of the gas when a problem occurs in the battery is determined as a direction facing the surface of the lid. That is, the battery container generally has a rectangular parallelepiped or cylindrical object shape, the bottom surface and the upper surface thereof are parallel to each other with respect to the horizontal plane, and the lid positioned on the upper surface of the battery container is provided with a safety valve. In addition, the gas generated in the battery container is discharged in a normal direction of the horizontal plane (for example, direction of gravity) from the safety valve. Therefore, for example, in the case in which batteries which are provided with a safety valve on a lid positioned on the upper surface of the battery container are disposed on each shelf in a container to constitute one large-capacity electric storage device, when a safety valve of a battery on a certain shelf operates, a high-temperature gas is directly discharged to an upper shelf above the battery. As a result, there is a possibility that a chain reaction may be caused in which a battery disposed on the upper shelf is also heated and the internal pressure thereof also increases, whereby a safety valve operates. 
     SUMMARY OF THE INVENTION 
     The invention provides a battery which takes the discharge direction of a gas discharged from a safety valve into account. 
     According to a first aspect of the present invention, a battery includes: a valve unit which is disposed on a first surface of a battery container to be broken when the gas pressure in the battery container increases to a predetermined value or greater, so as to guide a gas in the battery container in a direction inclined at a predetermined angle with respect to a normal direction of the first surface to discharge the gas to the outside. 
     According to such a configuration, the battery has the valve unit (safety valve) which guides the gas generated in the battery container in a direction inclined at a predetermined angle with respect to a normal direction of the first surface of the battery container to discharge the gas to the outside. Accordingly, even when various objects are present in a direction facing the first surface provided with the safety valve of the battery when the battery is disposed, it is possible to avoid direct discharge of the gas to the objects. As a result, for example, as described above, in the case in which batteries which are provided with a safety valve on a lid positioned on the upper surface of the battery container are disposed on each shelf in a container to constitute one large-capacity electric storage device, even when a safety valve of a battery on a certain shelf operates, a high-temperature gas is not directly discharged to an upper shelf above the battery. As a result, it is possible to prevent a chain reaction in which a battery disposed on the upper shelf is also heated and the internal pressure thereof also increases, whereby a safety valve is caused to operate. 
     According to a second aspect of the present invention, the valve unit includes a break part which seals a through hole formed on the first surface and is broken when the gas pressure in the battery container increases to a predetermined value or greater, and a guide which is formed into a tubular shape, protruding from a peripheral edge of the break part toward the outside of the battery container, in which an angle between central axes of both end surfaces is inclined at a predetermined angle, and guides the gas in the direction inclined at a predetermined angle to discharge the gas to the outside when the break part is broken. 
     According to a third aspect of the present invention, the guide is detachably joined to the break part. 
     According to a fourth aspect of the present invention, the guide is rotatable around the central axis of the first end surface. 
     According to a fifth aspect of the present invention, a battery system includes: a battery module which is constituted by a plurality of batteries, each of which is provided with a valve unit which is disposed on a first surface of a battery container to be broken when the gas pressure in the battery container increases to a predetermined value or greater, so as to guide a gas in the battery container in a direction inclined at a predetermined angle with respect to a normal direction of the first surface to discharge the gas to the outside; and a fireproof plate which is disposed on a side of the battery module. The respective valve units of the plurality of batteries guide the gas generated in the battery container in a direction inclined at a predetermined angle toward the fireproof plate to discharge the gas to the outside. 
     According to a sixth aspect of the present invention, the respective valve units of the plurality of batteries are different from each other in terms of the direction in which the gas is discharged to the outside according to a distance to the fireproof plate. 
     According to the battery constituted as described above, it is possible to avoid direct discharge of a gas to various objects positioned in a direction facing a battery lid provided with a safety valve even when the gas is generated from the safety valve of the battery. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic perspective view of a battery according to an embodiment. 
         FIG. 2  is a diagram for illustrating elements constituting a valve unit in the battery according to the embodiment. 
         FIG. 3A  is a cross-sectional view of the valve unit in the battery according to the embodiment, illustrating a cross-section taken along the line A-A′ of  FIG. 1 . 
         FIG. 3B  is a cross-sectional view of the valve unit in the battery according to the embodiment, illustrating a cross-section taken along the line B-B′ of  FIG. 1 . 
         FIG. 4A  is a reference diagram for the case in which a battery module with a plurality of conventional batteries combined together is disposed on each shelf 
         FIG. 4B  is a reference diagram for the case in which a battery module with a plurality of batteries according to the embodiment combined together is disposed on each shelf. 
         FIG. 5  is a reference diagram for the case in which a battery module with a plurality of batteries having different valve units combined together is disposed on each shelf. 
         FIG. 6  illustrates a cross-sectional view of Modified Example 1 of the valve unit of the battery according to the embodiment. 
         FIG. 7  illustrates a cross-sectional view of Modified Example 2 of the valve unit of the battery according to the embodiment.  FIG. 8A  is a schematic view of Modified Example 3 of the valve unit of the battery according to the embodiment, and is a front view of the valve unit viewed from a break surface. 
         FIG. 8B  is a schematic view of Modified Example 3 of the valve unit of the battery according to the embodiment, and is a cross-sectional view in a direction perpendicular to the break surface of the valve unit. 
         FIG. 9  illustrates a cross-sectional view of Modified Example 4 of the valve unit of the battery according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, preferred embodiments for carrying out the present invention will be described referring to the drawings. In the following embodiments, a lithium secondary battery will be described as an example of a battery. In addition, in the respective drawings, from the viewpoint of clarity, the dimensions and scale of the shapes of units constituting the battery may be different from the actual dimensions and scale thereof. 
     First Embodiment 
       FIG. 1  illustrates a schematic perspective view of a battery  1  according to a first embodiment of the present invention. 
     The battery  1  according to the first embodiment of the present invention is as shown in  FIG. 1 , and is constituted by a battery container body  10  and a battery lid  20  which covers an opening of the battery container body  10  and has two electrode terminals  21  (positive electrode terminal  21 A and negative electrode terminal  21 B) and a safety valve (valve unit)  22  disposed thereon. Hereinafter, the battery container body  10  formed integrally with the battery lid  20  will be referred to as the “battery container”. 
     The battery container body (body of the battery container)  10  is an angular container which accommodates an electrode plate, that is, a laminated electrode body (not shown) having a positive electrode plate and a negative electrode plate laminated with a separator interposed therebetween, together with an electrolyte and the like. The battery container body is made of, for example, a metallic material such as an aluminum alloy. A positive electrode tab is formed at one end of the positive electrode plate, and a positive electrode lead electrically connects the positive electrode tab and the positive electrode terminal  21 A to each other. In addition, a negative electrode tab is formed at one end of the negative electrode plate, and a negative electrode lead electrically connects the negative electrode tab and the negative electrode terminal  21 B to each other. By virtue of the above-described configuration, the battery  1  can take a current out of the positive electrode terminal  21 A and the negative electrode terminal  21 B. 
     As shown in  FIG. 1 , the battery lid  20  is a flat plate-shaped lid for covering and sealing the battery container body  10 . Similarly to the battery container body  10 , the battery lid is made of, for example, a metallic material such as an aluminum alloy. In addition, the battery lid  20  is provided with through holes, each of which is for passing the positive electrode terminal  21 A and the negative electrode terminal  21 B therethrough. An insulating resin (sealing member)  23  is provided to fill in the gaps of the positive electrode terminal  21 A and the negative electrode terminal  21 B which pass through the through holes so as not to be brought into contact therewith, respectively, and to seal the gaps. The laminated electrode body and the like are accommodated in the battery container body  10 , and then the outer edge of the battery lid  20  is welded to the peripheral edge of the opening of the battery container body  10  (for example, laser welding) to seal the battery container body  10 . 
     Here, referring to  FIGS. 2 ,  3 A, and  3 B, the structure of a valve unit  22  in the embodiment will be described in detail.  FIG. 2  is a diagram for illustrating elements (break part  30  and guide  40 ) constituting the valve unit  22 , and  FIG. 3A  illustrates a cross-sectional view (cross-sectional view taken along the line A-A′ of  FIG. 1 ) for the case in which the valve unit  22  is formed integrally with the battery lid  20 . In the following embodiments, descriptions will be provided appropriately using an XYZ orthogonal coordinate system. In the battery  1 , a direction perpendicular from the bottom surface of the battery container body  10  (surface opposed to the battery lid  20 ) shown in  FIG. 1  toward the battery lid  20  is set as a Z-axis direction, a direction along a side of the battery lid  20  in a longitudinal direction, which is perpendicular to the Z-axis direction, is set as a X-axis direction, and a direction which is perpendicular to the X-axis direction and the Z-axis direction (direction along a side perpendicular to the horizontal direction of the battery lid  20 ) is set as a Y-axis direction. 
     The valve unit  22  is a rupturing-type safety valve for preventing the battery container itself from exploding by the generation of a large amount of a high-temperature gas in the battery container due to the rapid evaporation of the electrolyte and the like, and by a rapid increase of an internal pressure when a short or an overcharge occur in the battery  1 . 
     As shown in  FIG. 2 , the valve unit  22  is constituted by a break part  30  for sealing a through hole  24  formed on a surface (on a first surface) of the battery lid  20  and to break when the gas pressure in the battery container increases to a predetermined value or greater, and a guide  40  which protrudes from the peripheral edge of the break part  30  toward the outside of the battery container and guides a gas in a direction inclined at a predetermined angle to discharge the gas to the outside when the break part  30  is broken. 
     The break part  30  has a break surface  31  which is broken when the gas pressure in the battery container increases to a predetermined value or greater, a first joining unit  32  for joining to the battery lid  20 , and a second joining unit  33  for joining to the guide  40 . 
     The break surface  31  is a part which covers the through hole  24  of the battery lid  20  and is broken when the gas pressure in the battery container increases to a predetermined value or greater. The material, shape, and break conditions of the break surface  31  may be the same as those of a break surface of a conventional safety valve. 
     The first joining unit  32  is a part which is provided along the outer periphery of the break surface  31  to be joined to a protrusion  25 , protruding from the peripheral edge of the through hole  24  of the battery lid  20  to the outside of the battery container (+Z direction), by welding. In this part, the joining by welding can be performed using various kinds of methods such as laser welding and ultrasonic welding. 
     The second joining unit  33  is a part which is provided along the outer periphery of the first joining unit  32  to be joined to the guide  40 , and has a recess (notch)  331  at a predetermined position on the outer periphery. The recess  331  allows a height  41  of the guide  40  provided at a position corresponding to the recess  331  to be passed therethrough in the Z-axis direction when the second joining unit  33  of the break part  30  and the height (joining unit)  41  of the guide  40  are joined to each other. 
     As shown in  FIGS. 2 and 3A , the guide  40  is formed into a tubular shape in which a first end surface  42  facing and being open to the break part  30  and a second end surface  43  facing and being open to the outside communicate with each other, and has the height  41  at a predetermined position at the inner peripheral edge of the first end surface  42  so as to correspond to the recess  331  of the second joining unit  33 . The guide  40  is preferably made of a material capable of withstanding the gas temperature at the time of discharging the gas, such as a steel plate or ceramic. In addition, the guide  40  is formed so that the area of the opening of the first end surface  42 , the area of the gas flow channel in the body part of the tubular shape communicating the first end surface with the second end surface, and the area of the opening of the second end surface  43  are substantially the same as each other so as to easily discharge the gas generated in the battery container to the outside when the break part  30  is broken. When the guide  40  is formed as described above, the gas can be smoothly discharged to the outside and the gas discharged to the outside has directivity, and thus the gas can be discharged toward a desired position in a desired direction. The embodiment is not limited to the case in which the area of the opening of the first end surface  42 , the area of the gas flow channel, and the area of the opening of the second end surface  43  are substantially the same as each other, and for example, the area of the opening of the second end surface  43  may be greater than the area of the opening of the first end surface  42  and the area of the gas flow channel may be increased from the first end surface  42  toward the second end surface  43 . 
     In joining to the break part  30 , the guide  40  can be joined thereto by passing the height  41  through the notch  331  of the second joining unit  33  of the break part  30  in the Z-axis direction and by then rotating the guide  40  around the Z axis (that is, the guide is rotated so that the height  41  and the second joining section  33  are positioned at different positions on the X-Y plane as shown in  FIG. 3B ). The protrusion  25  is provided at the peripheral edge of the through hole  24  of the battery lid  20  to provide the break part  30  and the guide  40  as described above, whereby the guide  40  itself can be detachable from the break part  30 . When the guide  40  is detachable from the break part  30 , that is, the battery lid  20 , it is possible to appropriately judge the necessity for the attachment of the guide according to various causes such as a position at which the battery  1  is disposed and a space for providing the guide  40 . 
     In addition, since the guide  40  guides the gas in a direction inclined at a predetermined angle to discharge the gas to the outside when the break part  30  is broken, the angle between a central axis (Z axis) of the first end surface  42  and a central axis of the second end surface  43  is inclined at a predetermined angle θ as shown in  FIG. 3A . The predetermined angle θ can be appropriately set in the range of, for example, 0°&lt;θ≦90° so that the gas is not directly discharged in a direction (Z-axis direction) facing the battery lid according to the position at which the battery  1  is disposed. 
     According to the battery  1  of the embodiment constituted as described above, the battery has the valve unit (safety valve)  22  which guides the gas generated in the battery container in a direction inclined at a predetermined angle with respect to a normal direction of the surface (first surface) of the battery lid  20  of the battery container to discharge the gas to the outside. Accordingly, even when various objects are present in a direction facing the surface of the battery lid  20  of the battery  1  when the battery  1  is disposed, it is possible to avoid direct discharge of the gas to the objects. 
     Specifically, for example, the invention is effective for the case in which a battery module constituted by a plurality of batteries  1  is disposed on each shelf of a container to constitute one large-capacity electric storage device as shown in  FIG. 4B . That is, in the case in which a break surface of a safety valve is provided parallel to a surface of a battery lid  20  as in the case of the conventional batteries, when a safety valve (valve unit) of a battery  1  constituting a battery module on a lower shelf operates, a high-temperature gas is directly discharged to an upper shelf above the battery as shown in  FIG. 4A . However, according to the battery  1  of the embodiment, when a safety valve (valve unit) of a battery  1  constituting a battery module on a lower shelf operates, a valve unit  22  guides the gas in a direction inclined at a predetermined angle θ with respect to a normal direction of a surface of a battery lid  20  of a battery container to discharge the gas to the outside as shown in  FIG. 4B . Accordingly, the high-temperature gas is not directly discharged to an upper shelf above the battery  1 , and as a result, it is possible to suppress a battery  1  disposed on the upper shelf from being heated to thus suppress the battery container made of aluminum from being melted. In addition, it is possible to prevent a chain reaction in which due to the heated battery  1 , the internal pressure thereof increases, and thus the valve unit (safety valve) is caused to operate. 
     In addition, a fireproof plate  50  may be disposed on a side of a battery module constituted by a plurality of batteries  1  and valve units  22  of the plurality of batteries  1  may guide a gas generated in the battery container in a direction inclined at a predetermined angle toward the fireproof plate  50  to discharge the gas to the outside. When the fireproof plate  50  is provided in the gas discharge direction, the frame itself which forms the container is not directly heated, and deformation thereof and the like can be prevented. As the fireproof plate  50 , for example, a steel plate having a thickness of 1.6 mm or greater can be used. However, the thickness and the material are not limited thereto, and may be appropriately selected as long as the fireproof plate has a fire-resistant property with respect to the gas. 
     Furthermore, when a distance to the fireproof plate  50  of each of the batteries  1  varies depending on the disposition of the battery module, the respective valve units  22  of the batteries  1  may be designed so that the direction in which the gas is discharged to the outside may vary according to the distance to the fireproof plate  50 . Specifically, when a battery la and a battery lb which are different in terms of the distance to the fireproof plate  50  are present (in the case of the battery  1   a , a distance d 1  to a fireproof plate  50 , and in the case of the battery  1   b , a distance d 2  to a fireproof plate  50  (d 1 &lt;d 2 )), the gas discharge directions of a valve unit  22   a  of the battery la and a valve unit  22   b  of the battery  1   b  can be inclined at 45° and 60°, respectively, as shown in  FIG. 5 . When the valve unit is designed so that the direction in which the gas is discharged to the outside varies according to the distance to the fireproof plate  50 , it is possible to securely prevent the high-temperature gas from being directly discharged to the upper shelf. 
     Modified Examples 
     As described above, the preferred embodiments of the battery and the battery system of the invention have been described. However, the invention is not limited to the above-described embodiments, and various modifications, additions, and omissions can be made by those skilled in the art without departing from the spirit and scope represented in the claims. 
     For example, in the above-described embodiments, the case in which the second joining section  33  of the break part  30  and the height  41  of the guide  40  are joined to each other, and thus the break part  30  and the guide  40  are joined to each other has been described as an example. However, the invention is not limited thereto, and the guide  40  may be directly joined to the battery lid  20 . For example, as shown in  FIG. 6 , in a columnar protrusion which protrudes from the peripheral edge of the through hole  24  of the battery lid  20  to the outside of the battery container (+Z direction), a joining section (for example, male screw)  26  may be formed on an outer peripheral surface of the protrusion and a joining section (for example, female screw)  44  may be formed on an inner peripheral surface of a first end surface  42  of a guide  40 A to join the guide  40 A to the battery lid  20 . 
     In addition, in the above-described embodiments, the case in which the protrusion  25  is provided from the peripheral edge of the through hole  24  of the battery lid  20  to the outside of the battery container to constitute the valve unit  22  has been described as an example. However, the invention is not limited thereto, and the guide  40  according to the embodiment may be directly joined and attached to the peripheral edge of the safety valve provided on a conventional battery to provide the valve unit of the invention. That is, as shown in  FIG. 7 , a joining section  45  for joining to the battery lid  20  may be provided at the peripheral edge of the first end surface  42  of a guide  40 B to be joined to the peripheral edge of the safety valve of the battery lid  20  in the joining section  45 . Even in the case of a conventional battery, when the valve unit can be constituted as described above, this is useful from the viewpoint of appropriate attachment according to the position of the battery. 
     Furthermore, in the above-described embodiments, the case in which the break part  30  is provided parallel (or substantially parallel) to the surface of the battery lid  20  has been described as an example. However, the invention is not limited thereto. For example, as shown in  FIGS. 8A and 8B , a guide  40 C may be joined to the battery lid  20  and a break surface  31 ′ may be provided on the second end surface  43  facing the outside of the guide  40 C. 
     Furthermore, as shown in  FIG. 9 , in the battery  1  according to the above-described embodiments, a guide  40 D may be constituted by a fixing unit  46  fixed to the battery lid  20  and a rotation unit  47  rotatable with respect to the fixing unit, and for example, the guide may be rotatable around the central axis of the first end surface  42 . In this case, this is useful from the viewpoint of setting the gas discharge direction to an appropriate direction according to the circumstances such as a change of the position of the battery  1 . 
     Furthermore, in the above-described embodiments, the case in which the battery lid  20  is provided with the break part  30  has been described as an example. However, the invention is not limited thereto. For example, the break part  30  may not be provided on the battery lid  20 , but on a side surface of the battery container. 
     In the above-described embodiments, the lithium secondary battery has been described as an example of the battery. However, the invention is not limited thereto, and it is obvious to apply the invention to other batteries as long as the batteries are provided with a safety valve.