Patent Publication Number: US-9413038-B2

Title: Battery module of improved stability

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/KR2012/005846 filed on Jul. 23, 2012, which claims the benefit of Patent Application No. 10-2011-0076741 filed in the Republic of Korea on Aug. 1, 2011, all of which are hereby expressly incorporated by reference into the present application. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a battery module with improved safety and, more particularly, to a battery module having a plurality of battery cells electrically connected to each other, the battery module including a voltage sensing unit including voltage sensing terminals electrically connected to electrode terminal connection portions of the battery cells and a conduction part connected to the voltage sensing terminals to transmit voltages detected by the voltage sensing terminals to a module control unit and a signal cutoff unit located between the voltage sensing terminals and the conduction part to interrupt transmission of the detected voltages when a short circuit occurs in the conduction part. 
     BACKGROUND ART 
     Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for devices which require high output and large capacity, such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels. 
     Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a battery module having a plurality of battery cells electrically connected to each other because high output and large capacity are necessary for the middle or large-sized devices. 
     Preferably, a battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of a middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight and the manufacturing cost of the pouch-shaped battery is low. 
     In addition, the battery module is configured to have a structure in which a plurality of battery cells is combined. In a case in which overvoltage is applied to some of the battery cells, overcurrent flows in some of the battery cells, or some of the battery cells overheat, therefore, safety and operation efficiency of the battery module are seriously concerned. For this reason, it is necessary to provide means to detect and control such overvoltage, overcurrent, or the overheating. 
     Consequently, voltage sensors are connected to the respective battery cells to check and control operation states of the battery cells in real time or at predetermined time intervals. However, installation or connection of such detection means very complicates a process for assembling the battery module. In addition, there is a possibility that a short circuit may occur due to a plurality of wires for the detection means. 
     In addition, as a secondary battery is used as a power source for vehicles as the result of extension in an application range of the secondary battery, it is necessary to provide fastening members to retain stable contact states of the detection means even when string impact or vibration is applied to the secondary battery. 
     In case of lithium ion secondary batteries, on the other hand, it is necessary to measure voltages of the respective batteries using a voltage sensing unit in order to check states of the respective batteries. For this reason, safety of the batteries is seriously concerned in a case in which a short circuit occurs in the voltage sensing unit. 
     In addition, protection of the voltage sensing unit when the safety of the batteries is seriously concerned is very important for a battery system. 
     Consequently, there is a high necessity for a battery module that is compact and exhibits improved safety while fundamentally solving the above problems. 
     DISCLOSURE 
     Technical Problem 
     Therefore, the present invention has been made to solve the above problems and other technical problems that have yet to be resolved. 
     It is an object of the present invention to provide a battery module configured to have a structure in which a signal cutoff unit is located between voltage sensing terminals and a conduction part to interrupt transmission of detected voltages when a short circuit occurs in the conduction part, thereby improving safety of the battery module. 
     It is another object of the present invention to prevent a conduction part from catching fire and to stop a voltage sensing operation of a battery module through the use of a signal cutoff unit. 
     Technical Solution 
     In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a battery module having a plurality of battery cells electrically connected to each other, the battery module including a voltage sensing unit including voltage sensing terminals electrically connected to electrode terminal connection portions of the battery cells and a conduction part connected to the voltage sensing terminals to transmit voltages detected by the voltage sensing terminals to a module control unit and a signal cutoff unit located between the voltage sensing terminals and the conduction part to interrupt transmission of the detected voltages when a short circuit occurs in the conduction part. 
     In the battery module according to the present invention, therefore, the signal cutoff unit is located between the voltage sensing terminals and the conduction part to interrupt transmission of detected voltages when a short circuit occurs in the conduction part, thereby greatly improving safety of the battery module. 
     In a preferred example, each of the voltage sensing terminals may be configured to have a receptacle structure such that the voltage sensing terminals can be easily fastened to the conduction part. 
     The conduction part may be configured to have a wire harness structure such that the voltages detected by the voltage sensing terminals can be easily transmitted to the module control unit. 
     Preferably, the wire harness is configured to have a structure in which one insulative member surrounds nine wires. 
     Specifically, in a case in which a short circuit occurs in the wires connected between the voltage sensing terminals and the module control unit due to external force, the signal cutoff unit is broken by instantaneously generated high current with the result that voltage signals detected by the voltage sensing terminals cannot be transmitted to the module control unit. 
     In addition, the battery module according to the present invention may prevent the voltage sensing terminals from catching fire and stop a voltage sensing operation of the battery module through the use of the signal cutoff unit. 
     The module control unit may control operation of the battery module based on the voltage signals detected by the voltage sensing terminals. For example, the module control unit may be a battery management system (BMS). However, the present invention is not limited thereto. 
     In a concrete example, the battery module may be configured to have a structure including a cell unit stack including two or more hexahedral cell units electrically connected to each other in a stacked state, a module case in which the cell unit stack is mounted in a state in which the cell unit stack is erected on a side thereof, and voltage sensing terminals electrically connected to the electrode terminal connection portions of the battery cells. 
     In the above structure, the signal cutoff unit may be mounted at a front or a rear of the module case. 
     In a preferred example, the signal cutoff unit may include a fuse box having fuses mounted therein. In a case in which the signal cutoff unit malfunctions, therefore, it is enough to replace only the fuse box, thereby improving maintenance of the signal cutoff unit. 
     The fuse box may have various structures, an example of which is as follows. 
     In an example, the fuse box may include a circuit board, at which the fuses are mounted, and a cover covering the circuit board to protect the circuit board. When the fuses are broken, therefore, it is enough to replace only the circuit board, thereby improving maintenance of the fuse box. 
     In the above structure, the fuses may be mounted on the circuit board, for example, by soldering to increase coupling force between the fuses and the circuit board. 
     According to circumstances, the fuses may be mounted on the circuit board in the shape of a receptacle terminal each, thereby improving assemblability of the fuse box. 
     The specification of each of the fuses may be changed based on the construction of the battery module. For example, each of the fuses may have a direct current voltage of 3 V to 500 V and a current of 1 A to 5 A. However, the present invention is not limited thereto. 
     Each of the battery cells is not particularly restricted so long as each of the battery cells is a secondary battery that can be charged and discharged. For example, each of the battery cells may be a lithium secondary battery, a nickel metal hydride (Ni-MH) secondary battery, or a nickel cadmium (Ni—Cd) secondary battery. Among such secondary batteries, the lithium secondary battery is preferably used because the lithium secondary battery exhibits a high output to weight ratio. 
     Each of the battery cells may be a plate-shaped secondary battery having a small thickness and a relatively large width and length so as to minimize the overall size of the battery module when the battery cells are stacked to constitute the battery module. A preferred example of the secondary battery may be a secondary battery configured to have a structure in which an electrode assembly is mounted in a battery case formed of a laminate sheet including a resin layer and a metal layer and electrode terminals protrude from upper and lower ends of the battery case. Specifically, the electrode assembly may be mounted in a pouch-shaped battery case formed of an aluminum laminate sheet. The secondary battery having the above structure may be referred to as a pouch-shaped battery cell. 
     Each of the battery cells may have electrode terminals formed at the upper end and the lower end thereof. 
     Meanwhile, the module case may include an upper case and a lower case, which are coupled each other by vertical assembly. Consequently, the assembly and disassembly between the upper case and the lower case may be easily achieved in a state in which the battery cell stack is mounted in the lower case. 
     In the above structure, the voltage sensing unit may include sensing unit frames mounted at a front and a rear of the lower case, voltage sensing terminals inserted into the sensing unit frames, and conduction part connected between the voltage sensing terminals. 
     In another example, the lower case may be provided inside the front and the rear thereof with fixing grooves, into which the electrical connection portions of the battery cells are inserted and mounted. 
     The lower case may be provided at the front thereof with a pair of slits, through which the outermost electrode terminals of the unit cell stack can be inserted. 
     The outermost electrode terminals may be bent to contact bus bars disposed at the rear of the lower case after the outermost electrode terminals are inserted through the slits. Preferably, upper ends of the bus bars may be formed in the shape of intended holes, through which external input and output terminals provided at a rear of the upper case are introduced when the upper case and the lower case are coupled to each other. 
     The lower case may be provided at the lower end of the front and/or the rear thereof with a fastening part, which protrudes from the lower case to fix the lower case to an external device, a through hole being formed at a middle part of the fastening part. 
     Meanwhile, each of the cell units may be configured to have a structure including two or more battery cells and a pair of plate-shaped sheathing members coupled to cover the outside of the battery cell stack excluding the electrode terminals. 
     Consequently, the sheathing members may protect the battery cells exhibiting low mechanical strength and restrain the repetitive expansion and contraction fluctuation during charge and discharge of the battery cells to prevent separation between sealed portions of the battery cells. 
     In the above structure, each of the cell units may further include a shock-absorbing member interposed at the interface between the battery cells to restrain movement of the battery cells and to absorb shock due to change in volume of the battery cells during charge and discharge of the battery cells. 
     Consequently, the shock-absorbing member absorbs shock due to change in volume of the battery cells caused by the repetitive expansion and contraction fluctuation during charge and discharge of the battery cells and increases frictional force between the battery cells to restrain movement of the battery cells. 
     The material for the shock-absorbing member interposed at the interface between the battery cells is not particularly restricted so long as the shock-absorbing member absorbs shock due to change in volume of the battery cells and increases frictional force between the battery cells to restrain movement of the battery cells. Preferably, the shock-absorbing member is formed of a polymer resin having a porous structure. The porous structure may include open pores or closed pores. 
     Kind of the polymer resin is not particularly restricted. For example, polyethylene, polypropylene, polybutylene, polystyrene, natural rubber, artificial rubber, NBR resin, ABS resin, etc. may be used. 
     Preferably, each of the sheathing members has an inner structure corresponding to an external shape of the battery cell stack. In particular, the sheathing members are coupled to each other by assembly and fastening without additional fastening members. 
     As a representative example of sectional coupling portions of the sheathing members, the sectional coupling portions of the sheathing members may be configured to have male and female fastening structures such that the sheathing members are engaged with each other through elastic coupling when the sheathing members are pushed in a state in which the sheathing members are in contact with each other such that the sheathing members face each other. 
     Meanwhile, heat is generated from the secondary battery during charge and discharge of the secondary battery. Effective dissipation of the generated heat is important to increase the lifespan of the battery. Consequently, each of the sheathing members may be formed of a metal sheet exhibiting high thermal conductivity to more easily dissipate heat generated from the battery cells in the sheathing members. 
     In a preferred example, each of the sheathing members may be provided at sides adjacent to upper and lower ends thereof with step parts having a predetermined size to easily fix the battery cells. According to circumstances, the step parts may be formed at sides adjacent to left and right ends of each of the sheathing members. More preferably, the step parts are formed at sides adjacent to the upper and lower ends and the left and right ends of each of the sheathing members to more securely fix the battery cells. 
     The battery cells may be fixed at the upper end and the lower end of each of the sheathing members in various forms. For more efficient fixing, depressed step parts are preferably provided while having a shape and size corresponding to sealed portions of the battery cells. 
     Movement of the battery cells is maximally restrained through a combination of the step parts formed at the sheathing members and the shock-absorbing member. 
     In a preferred example, each of the sheathing members according to the present invention may be provided at the outside thereof with a plurality of linear beads, which are spaced apart from each other in the lateral direction (horizontal direction), to provide a coolant flow space. In the above structure, each of the beads may be configured such that opposite ends of each of the beads reach corresponding ends of the sheathing member. In a state in which battery modules are stacked, therefore, a coolant (for example, air) may flow in the lateral direction of the sheathing members, thereby further improving cooling efficiency. 
     In addition, each of the sheathing members may be provided at the upper end and the lower end of the outside thereof with bars formed in shapes opposite to each other in the lateral direction (horizontal direction). When the battery modules are stacked, therefore, the sheathing member  200  has a shape corresponding to an adjacent one of the battery modules. Consequently, it is possible to prevent stacked positions between the battery modules from being reversed or deviating from each other. 
     In accordance with another aspect of the present invention, there is provided a battery pack configured to have a structure including two or more battery modules based on output and capacity. 
     The battery pack is manufactured by electrically and mechanically interconnecting a plurality of secondary batteries such that the battery pack can provide high output and large capacity. For example, the battery pack may be manufactured by mounting a stack of two or more battery modules in a pack frame in a state in which the battery module stack is erected in the lateral direction. 
     In accordance with a further aspect of the present invention, there is provided a vehicle using the battery pack as a power source. 
     In particular, the vehicle with the above structure may be used as an electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle in consideration of installation efficiency and structural stability based on desired output and capacity. 
     Effects of the Invention 
     As is apparent from the above description, the battery module according to the present invention is configured such that the signal cutoff unit is located between the voltage sensing terminals and the conduction part to interrupt transmission of detected voltages when a short circuit occurs in the conduction part, thereby increasing operation or lifespan characteristics of batteries and securing safety of the battery module. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view showing a battery module according to an embodiment of the present invention; 
         FIG. 2  is a perspective view showing a state in which a cover is removed from the battery module of  FIG. 1 ; 
         FIG. 3  is a perspective view showing a state in which the front and rear of the battery module of  FIG. 1  are rotated by 180 degrees; 
         FIG. 4  is an exploded perspective view of  FIG. 1 ; 
         FIG. 5  is an exploded perspective view of  FIG. 2 ; 
         FIG. 6  is an exploded perspective view showing the structure of a pouch-shaped secondary battery; 
         FIG. 7  is an exploded perspective view showing a cell unit according to another embodiment of the present invention; 
         FIG. 8  is a perspective view showing a sheathing member of  FIG. 7 ; and 
         FIG. 9  is an enlarged view showing coupling structures of the sheathing member of  FIG. 7 . 
     
    
    
     BEST MODE 
     Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted, however, that the scope of the present invention is not limited by the illustrated embodiments. 
       FIG. 1  is a perspective view typically showing a battery module according to an embodiment of the present invention and  FIG. 2  is a perspective view typically showing a state in which a cover is removed from the battery module of  FIG. 1 . 
     Referring to these drawings, a battery module  600  includes a voltage sensing unit (not shown), a battery management system (BMS) functioning as a module control unit, and a signal cutoff unit  610 . 
     The voltage sensing unit is connected to electrical connection portions of battery cells and the BMS controls operation of the battery module  600  based on a voltage signal detected by the voltage sensing unit. 
     In addition, the signal cutoff unit  610  is mounted between the voltage sensing unit and the BMS to cut off transmission of the detected voltage signal when a short circuit occurs in the voltage sensing unit. When transmission of the detected voltage signal is cut off, the BMS stops operation of the battery module  600 . 
     The battery module  600  includes a cell unit stack  620  including two hexahedral cell units electrically connected to each other in a stacked state, a module case in which the cell unit stack  620  is mounted in a state in which the cell unit stack  620  is erected on the side thereof, and voltage sensing terminals electrically connected to electrode terminal connection portions of battery cells. 
     The module case includes an upper case  630  and a lower case  640 , which are coupled each other by vertical assembly. The signal cutoff unit  610  is mounted to the front of the module case. 
     The signal cutoff unit  610  includes a fuse box having fuses  614  mounted therein. The fuse box includes a circuit board  612 , on which the fuses  614  are mounted by soldering, and a cover covering the circuit board to protect the circuit board. 
       FIG. 3  is a perspective view typically showing a state in which the front and rear of the battery module of  FIG. 1  are rotated by 180 degrees,  FIG. 4  is an exploded perspective view of  FIG. 1 , and  FIG. 5  is an exploded perspective view of  FIG. 2 . 
     Referring to these drawings, the battery module  600  includes the voltage sensing unit  650  and the signal cutoff unit  610 . 
     The voltage sensing unit  650  includes voltage sensing terminals  654  electrically connected to the electrode terminal connection portions of the battery cells and a conduction part  652  connected to the voltage sensing terminals  654  to transmit voltages detected by the voltage sensing terminals  654  to a module control unit. 
     The signal cutoff unit  610  is located between the voltage sensing terminals  654  and the conduction part  652  to interrupt transmission of the detected voltages when a short circuit occurs in the conduction part  652 . 
     Each of the voltage sensing terminals  654  is configured to have a receptacle structure and the conduction part  652  is configured to have a wire harness structure. 
     Specifically, the wire harness is configured to have a structure in which one insulative member surrounds nine wires. 
     The voltage sensing unit  650  includes sensing unit frames  656  mounted at the front and the rear of the lower case  640 , the voltage sensing terminals  654  inserted into the sensing unit frames  656 , and the conduction part  652  connected between the voltage sensing terminals  654 . 
     The lower case  640  is provided inside the front and the rear thereof with fixing grooves  642 , into which the electrical connection portions of the battery cells are inserted and mounted. The lower case  640  is provided at the front thereof with a pair of slits  644 , through which the outermost electrode terminals of the unit cell stack can be inserted. 
     After the outermost electrode terminals are inserted through the slits  644 , the outermost electrode terminals are bent to contact bus bars  624  disposed at the rear of the lower case  640 . The upper ends of the bus bars  624  are formed in the shape of intended holes  628 , through which external input and output terminals  626  provided at the rear of the upper case  630  are introduced when the upper case  630  and the lower case  640  are coupled to each other. 
     In addition, the lower case  640  is provided at the lower ends of the front and the rear thereof with fastening parts  648 , which protrude from the lower case  640  to fix the lower case to an external device. A through hole  646  is formed at the middle of each of the fastening parts  648 . 
       FIG. 6  is an exploded perspective view typically showing the structure of a pouch-shaped secondary battery. 
     Referring to  FIG. 6 , a pouch-shaped battery  100  is configured to have a structure in which two electrode leads  110  and  120  protrude from the upper end and the lower end of a battery body  130 , respectively, in a state in which the electrode leads  110  and  120  are opposite to each other. 
     A sheathing member  140  is a two-unit member. In a state in which an electrode assembly (not shown) is mounted in a receiving part formed in the sheathing member  140 , lateral sides  140   b , upper ends  140   a , and lower ends  140   c , which are contact regions, of the sheathing member  140  are bonded to each other, whereby the battery cell  100  is manufactured. The sheathing member  140  is configured to have a laminate structure of a resin layer/a metal foil layer/a resin layer. Consequently, it is possible to bond the lateral sides  140   b  and the upper and lower ends  140   a  and  140   c  of the sheathing member  140 , which are in contact with each other, to each other by applying heat and pressure to the lateral sides  140   b  and the upper and lower ends  140   a  and  140   c  of the sheathing member  140  so as to weld the resin layers thereof to each other. According to circumstances, the lateral sides  140   b  and the upper and lower ends  140   a  and  140   c  of the sheathing member  140  may be bonded to each other using a bonding agent. 
     In case of the lateral sides  140   b  of the sheathing member  140 , the same resin layers of upper and lower sheathing parts of the sheathing member  140  are in direct contact with each other, whereby uniform sealing at the lateral sides  140   b  of the sheathing member  140  is accomplished by welding. In case of the upper ends  140   a  and the lower ends  140   c  of the sheathing member  140 , on the other hand, the electrode leads  110  and  120  protrude from the upper ends  140   a  and the lower ends  140   c  of the sheathing member  140 , respectively. For this reason, the upper and lower ends  140   a  and  140   c  of the sheathing member  140  are thermally welded to each other, in a state in which film type sealing members  160  are interposed between the electrode terminals  110  and  120  and the sheathing member  140 , in consideration of the thickness of the electrode leads  110  and  120  and the difference in material between the electrode leads  110  and  120  and the sheathing member  140 , so as to improve sealability of the sheathing member  140 . 
       FIG. 7  is an exploded perspective view typically showing a cell unit according to another embodiment of the present invention. 
     Referring to  FIG. 7 , a cell unit  400  includes plate-shaped battery cells  100 , each of which has electrode terminals  110  and  120  formed at the upper end and the lower end thereof, respectively. A shock-absorbing member  300  is interposed at an interface between two battery cells  100 . A pair of sheathing members  200  is coupled to each other to cover the battery cells  100 . 
     The shock-absorbing member  300  is formed of a porous polymer resin. Consequently, the shock-absorbing member  300  absorbs shock due to change in volume of the battery cells caused by the repetitive expansion and contraction fluctuation during charge and discharge of the battery cells and increases frictional force between the battery cells to restrain movement of the battery cells. 
     The sheathing members  200  are coupled to each other to cover the outside of a stack of the battery cells  100  excluding the electrode terminals  110  and  120  formed. The sheathing members  200  protect the battery cells exhibiting low mechanical strength and restrain the repetitive expansion and contraction fluctuation during charge and discharge of the battery cells to prevent separation between sealed portions of the battery cells. 
       FIG. 8  is a perspective view typically showing the sheathing member of FIG.  7  and  FIG. 9  is an enlarged view typically showing coupling structures of the sheathing members of  FIG. 7 . 
     Referring to these drawings together with  FIG. 7 , the sheathing member  200  is provided at sides adjacent to left and right ends thereof with step parts  240  to easily fix a module. In addition, the sheathing member  200  is provided at the outside thereof with a plurality of linear beads  233 , which are spaced apart from each other in the lateral direction. Each of the beads  233  is configured such that opposite ends of each of the beads  233  reach corresponding ends of the sheathing member. In a state in which battery modules are stacked, therefore, a coolant (for example, air) may flow in the lateral direction of the sheathing member, thereby further improving cooling efficiency. 
     In addition, the sheathing member  200  is provided at the upper end and the lower end of the outside thereof with bars  235  formed in shapes opposite to each other in the lateral direction (horizontal direction). When the battery modules are stacked, therefore, the sheathing member  200  has a shape corresponding to an adjacent one of the battery modules. Consequently, it is possible to prevent stacked positions between the battery modules from being reversed or deviating from each other. 
     In addition, the sheathing member  200  includes a pair of left cell cover  211  and right cell cover  212 , which may be coupled to each other without using additional fastening members. 
     A coupling structure of the sheathing member  200  is shown in detail in  FIG. 7 . A sectional view and a partially enlarged view of the sheathing member  200  are shown in  FIG. 7 . Referring to  FIG. 7 , the sheathing members  211  and  212  are configured to have male and female fastening structures  221  and  222  such that the sheathing members  211  and  212  are engaged with each other through elastic coupling when the sheathing members  211  and  212  are pushed in a state in which the sheathing members  211  and  212  are in contact with each other such that the sheathing members  211  and  212  face each other. 
     Various fastening structures, such as hexahedral fastening structures  221   a  and  222   a  and cylindrical fastening structures  221   b  and  222   b , may be provided. During a fastening process, the fastening structures are engaged with each other to increase coupling force. 
     Consequently, strong mechanical coupling of the sheathing member  200  is achieved without additional coupling members or processes to assemble the sheathing member  200 . In particular, such a simple coupling method is preferably applied to mass production. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.