KR100881641B1 - Middle or Large-sized Battery Pack Having Safety System - Google Patents

Abstract

The present invention relates to a physical change of a battery cell when an electrical connection member of at least one of the electrical connection members of the battery pack components in a battery pack including two or more battery cells expands above a threshold of the battery cell. Provides a medium-large battery pack that is configured to be mechanically disconnected by.

According to the present invention, the electrical connection member is mechanically expanded when the battery cell expands due to abnormal operation such as overcharge, over discharge, over current, and when the battery cell expands due to deterioration of battery components due to continuous use. By powering down, the safety of the battery pack can be secured. In particular, expansion of a battery cell due to deterioration of the battery is a phenomenon that cannot be controlled by a conventional safety system in a battery pack.

Description

Middle or Large-sized Battery Pack Having Safety System}

1 is a schematic view of a battery module having a structure in which an electrode terminal and a bus bar of a unit cell in a battery pack according to an embodiment of the present invention can be separated;

FIG. 2 is a schematic diagram of an expanded state of all unit cells in the battery module of FIG. 1; FIG.

3 and 4 are partial schematic views illustrating a connection relationship between a bus bar and an electrode terminal in a normal connection state and a disconnection state due to expansion of a battery cell in the battery module of FIG. 1;

5 is a schematic view of a battery module having a structure in which a cable and a terminal tab can be separated in a battery pack according to another embodiment of the present invention;

FIG. 6 is a schematic view of some unit cells expanded in the battery module of FIG. 5; FIG.

7 is a partial schematic view of a battery module having a structure in which a cable itself may be separated from a battery pack according to another embodiment of the present invention;

FIG. 8 is a partial schematic view illustrating an expanded state of unit cells in the battery module of FIG. 7.

The present invention relates to a medium-large battery pack having a safety system, and more particularly, in a medium-large battery pack composed of two or more battery cells, abnormal operation or long-term charging of a battery pack such as overcharge, overdischarge, and overcurrent The present invention provides a technology for securing the safety of a battery pack by mechanically disconnecting an electrical connection portion of the battery pack by physical change when the battery cell expands due to deterioration due to discharge.

As the development and demand for mobile devices increases, the demand for secondary batteries as energy sources is increasing rapidly. Among them, many researches have been conducted and commercialized and widely used for lithium secondary batteries with high energy density and discharge voltage. It is used.

Rechargeable batteries are not only mobile phones, digital electronics such as mobile phones, digital cameras, PDAs, notebooks, etc., but also energy sources for power devices such as electric bicycles (EVs), electric vehicles (EVs), and hybrid electric vehicles (HEVs). It is attracting a lot of attention.

Small battery packs with one battery cell are used for small devices such as mobile phones and cameras, while two or more battery cells (hereinafter sometimes referred to as "multi-cells") are used for medium and large devices such as notebooks and electric vehicles. Medium or large battery packs packed with battery modules connected in parallel and / or in series are used.

As described above, the lithium secondary battery has a problem of low safety while having excellent electrical characteristics. For example, lithium secondary batteries cause decomposition reactions of battery components, such as active materials and electrolytes, under abnormal operating conditions such as overcharge, overdischarge, exposure to high temperatures, and electrical short circuits to generate heat and gas, resulting in high temperature and high pressure. The condition of may further accelerate the decomposition reaction, resulting in an air ignition or explosion.

Therefore, the lithium secondary battery includes a protection circuit that blocks current during overcharge, over discharge, and overcurrent, a PTC element (Positive Temperature Coefficient Element) that blocks current by increasing resistance when temperature rises, and a current when pressure rises due to gas generation. Safety systems are provided, such as safety vents to shut off or vent the gases. For example, in a cylindrical small secondary battery, a PCT element and a safety vent are usually installed on an electrode assembly (power generation element) of a cathode / separation membrane / cathode embedded in a cylindrical can, and in a rectangular or pouch type small secondary battery, The protection circuit module and the PCT element are generally mounted on the top of the square can or pouch case in which the generator is sealed.

The safety problem of the lithium secondary battery is more serious in the medium-large battery pack of the multi-cell structure. In the battery pack of the multi-cell structure, because a large number of battery cells are used, a malfunction in some battery cells may cause a chain reaction to other battery cells, and the resulting fire and explosion may cause a large accident. Accordingly, safety systems such as fuses, bimetals, and battery management systems (BMSs) for protecting battery cells from overdischarge, overcharge, and overcurrent are provided in medium and large battery packs.

However, lithium secondary batteries are deteriorated gradually during continuous use, that is, during continuous charging and discharging, such as power generators, electrical connection members, and the like. This causes the battery cells (cans, pouch cases) to expand slowly. In addition, in a normal normal state, the safety system BMS detects overdischarge, overcharge, overcurrent, and the like and controls / protects the battery pack. However, when the BMS is inoperative in an abnormal situation, it becomes difficult to control the battery pack for danger and safety. Since medium and large battery packs generally have a structure in which a plurality of battery cells are fixedly mounted in a predetermined case, each expanded battery cell is further pressurized in a limited case, and there is a risk of fire and explosion under abnormal operating conditions. This greatly increases.

Therefore, there is a very high need for a technology capable of fundamentally securing the safety of medium and large battery packs.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

That is, an object of the present invention is that the electrical connection of the battery pack is mechanically disconnected by the physical change when the battery cell is expanded due to abnormal operation of the battery pack such as overcharge, overdischarge, overcurrent or deterioration due to prolonged charge and discharge. It is to provide a battery pack to ensure safety.

In the medium-to-large battery pack according to the present invention for achieving the above object, at least one of the electrical connection member of the battery pack components of the battery pack including two or more battery cells, the threshold value of the battery cell In the expansion above, the battery cell is mechanically disconnected by the physical change of the battery cell.

Therefore, in the medium-large battery pack according to the present invention, in the battery pack of a so-called multi-cell structure including two or more battery cells, the electrical connection member is automatically adapted to the physical change caused by the expansion of the battery cell (unit battery). Safety is ensured by powering off.

The battery cells as unit cells constituting the battery pack are not particularly limited as long as they are rechargeable batteries capable of charging and discharging. Preferably, the battery cells may be rectangular secondary batteries or pouch secondary batteries. Pouch type secondary battery with a relatively small weight is more preferable. The pouch type secondary battery may be charged with high density due to its small volume and weight, thereby making the overall size and weight of the battery pack smaller or providing higher output and capacity than the same standard.

The positive electrode, the negative electrode, the separator, and the electrolyte constituting the unit cell may be used as they are known in the art. For example, in the case of the active material constituting the positive electrode, lithium cobalt oxide, lithium manganese oxide, lithium nickel Oxides in lithium transition metals such as oxides and complex oxides thereof may be used.

The charging state of the unit cell in the battery pack is preferably made of a laminated structure to provide a high density. The stacked structure refers to a structure in which square or pouch type secondary batteries as unit cells are continuously arranged such that their can or case surfaces face each other. In such a stacked structure, the unit cells may face each other in direct contact or may face each other at regular intervals. In the latter case, for example, in order to stabilize the stacking structure, the cartridges may be connected to each other through an adhesive member such as a double-sided tape, or the cartridges may be stored in one or more unit cells in a separate cartridge. It may be a laminated structure.

The unit cells are electrically connected to each other in series and / or parallel according to the desired output and capacity, and also to the main board assembly for controlling the entire battery pack, and to FET devices for controlling overcharge and overdischarge. . In addition, a plurality of components are electrically connected to the battery pack to perform a necessary function. This electrical connection is achieved by electrical connection members such as bus bars, wires, cables and the like.

The present invention is characterized in that the electrical connection member is configured to be automatically disconnected in accordance with the volume change of the individual or multiple unit cells. In general, the medium-large battery pack includes safety systems such as protection circuits, fuses, and FET devices, but a system that seeks mechanical safety based on physical changes caused by changes in volume of battery cells is not known.

For example, when a pouch type secondary battery is used as a unit cell, in normal conditions, the thickness of the battery may swell within the maximum range of 10%, but if an abnormal state persists, the battery swells beyond the maximum range, and deterioration in the electrode may occur. Power generation to accelerate the risk of explosion. Therefore, it is possible to ensure the safety of the battery pack by setting the threshold value below the thickness range, which greatly increases the risk of explosion, to achieve electrical disconnection of the electrical connection member. Since the rectangular secondary battery as the unit cell has a smaller volume change than the pouch type secondary battery due to the mechanical properties of the rectangular can, the threshold of the thickness change may be set in consideration of this point.

The portion of the connection member which is mechanically disconnected when the volume of the unit cell changes may be varied. For example, the electrode terminal and the connection part of the bus bar or wire, the tab terminal to which the cable is connected to the cable, the cable itself, etc. can do.

Specifically, since the connection between the electrode terminals and the bus bar (or wire) is mainly made by welding, soldering, screwing, etc., when the unit cell is expanded, stress is applied to the connecting member between them so that an intended short circuit occurs. The length of the connecting member may be defined to be constant or the coupling portion may be cut in one direction.

The cable and the tab terminal are preferably of a fastening structure that can be separated and combined, and the cable is connected to the fastening tab terminal in a direction surrounding the thickness of the at least one unit cell so as to correspond directly to the change in thickness of the unit cells. It may be a structure.

Cables are generally manufactured to have a tensile force that does not break even when a significant external force is applied, so that when the cable itself is cut, the cable includes a fastening member that can be separated and joined in the middle of the cable, and the cable includes at least one unit cell. It may be a structure that is mounted in a direction surrounding the thickness of.

Preferably, based on both ends (a, b) of the unit cell, when the electrical connection member for inducing short-circuit is located in one end (a) direction of the unit cell, by fixing the opposite end (b) of the unit cell As a result, the thickness expansion of the unit cell mainly appears toward the end (a), thereby facilitating the electrical disconnection of the electrical connection member.

In general, the battery pack has a structure in which the unit cells are mounted inside the pack case in one piece or in a separate form together with other components. In the present invention, since the change in the thickness direction during the expansion of the unit cells induces electrical breakdown of the electrical connection member, preferably, a top and bottom split pack case may be used. In addition, in the vertically separate pack case, a structure in which the fastening portion of the pack case may be variably changed so that a change in the thickness direction of the unit cells may be reflected. However, even in the case of an integrated pack case, the present invention may be implemented if a vertically variable portion exists in the space in which the unit cells are mounted, and thus is not particularly limited.

In the following, some embodiments of the present invention will be described in more detail, but the scope of the present invention is not limited thereto.

FIG. 1 schematically illustrates a battery module having a structure in which an electrode terminal and a bus bar of a unit cell may be separated in a battery pack according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a battery module 100 for constructing a medium-large battery pack is a unit battery in which a plurality of battery cells 110 are stacked with their terminals 112 and 114 oriented in the same direction. In some cases, the terminals 112 and 114 of each battery cell 110 may be stacked to be oriented at 90 degrees or 180 degrees, and details thereof are disclosed in Korean Patent Application No. 2004-92887 of the applicant. It is. Accordingly, this application is incorporated by reference in the context of the present invention.

The battery cells 110 are stacked to be in direct contact with each other, or stacked at regular intervals as shown in FIG. 1. Since the battery cell 110, which is a secondary battery, generates heat during charging and discharging, and accumulates such heat, abnormal operation or deterioration of the battery is promoted, so that the battery cell 110 is spaced apart from each other to achieve effective heat dissipation. Such a heat dissipation stacked structure, for example, after interposing a specific medium between the battery cells 110 or after mounting each of the battery cells 110 or some combination of battery cells 110 in a separate cartridge. By lamination.

Terminals 112 and 114 are connected in series by bus bar 120, and terminals 112 and 114 and bus bar 120 are coupled by laser welding, spot welding, soldering, screws, and the like.

Some or all of the battery cells 110 may expand due to deterioration due to abnormal operation or continuous charging and discharging.

FIG. 2 is a schematic view of the expanded state of all the unit cells constituting the battery module. For the sake of understanding, the degree of expansion is somewhat exaggerated.

As shown in FIG. 2, when the battery cell 110 is expanded by various causes, the electrode terminals 112 and 114 are further spaced apart from the electrode terminals of adjacent battery cells due to the expansion of the cell body. In the present invention, the bus bar 120 as the electrical connection member during the volume expansion of the battery cell 110 is configured to be easily disconnected mechanically by the physical change of the battery cell 110.

3 and 4 schematically show a connection relationship between a bus bar and an electrode terminal in a normal connection state and a disconnection state due to expansion of a battery cell.

Referring to these drawings, the bus bar 120 is spot welded to the electrode terminals 112, 112 'of the battery cells 110, 110' as a plate-shaped conductive member. Since the welding point 130 is formed at one electrode terminal 112 more, the bus bar 120 has a higher coupling force with respect to the specific electrode terminal 112.

In addition, the locking protrusion 140 is formed at one end of the electrode terminal 112 at the lower end of the bus bar 120. The locking protrusion 140 facilitates positioning of the bus bar 120 on the electrode terminal 112, and the bus bar 120 is identified when the battery cells 110 and 110 ′ are inflated. The role of helping to be easily separated from the other electrode terminal 112 'while maintaining the state of engagement with the electrode terminal 112 is also parallel. In some cases, the locking protrusion 141 may be formed at the lower end of the bus bar 120 in contact with the electrode terminal 112 ′ in the same direction.

Referring back to FIG. 1, since the short circuit of the bus bars 120 is induced among the electrical connection members of the battery pack when the volume of the battery cell 110 is expanded, the battery that is opposite to the electrode terminals 112 and 114. When fixing the lower end of the cell 110, the volume change of the battery cell 110 is mainly concentrated toward the electrode terminals 112 and 114, so that separation from the bus bar 120 may occur more easily.

5 schematically illustrates a battery module having a structure in which a cable and a terminal tab may be separated from the battery pack according to another embodiment of the present invention.

Referring to FIG. 5, in the battery module 200, the plurality of battery cells 210 are stacked at high density with the electrode terminal 212 connected to the connecting board 220. The connecting board 220 electrically and physically connects the battery cells 210 as a PCB, for example, and also senses a voltage, a temperature, and the like of each battery cell 210. Current from the connecting board 220 is sent through the cable 230 to another PCB 240 located at the rear of the battery cell 210. The rear PCB 240 may be a main board that controls the operation of the entire battery pack, or may be a safety board equipped with an FET device. In some cases, an external input / output terminal may be included.

The connecting board 220 and the rear PCB 240 are fixed to the lower case 250, and the cable 230 is wired in a structure surrounding the outer surface of the battery cell 210. Therefore, when the battery cell 210 expands as shown in FIG. 6, tension is applied upward. 6 schematically illustrates a case in which some of the battery cells 210 are inflated. However, even when all of the battery cells 210 are inflated, tension is applied upward with respect to the cable 240. Since the electrode terminals 212 of the battery cell 210 are mechanically connected to the connecting board 220, the volume expansion of the battery cell 210 is concentrated to the battery cell 210.

While the end 232 of the cable 230 is coupled with a strong fastening force against the connecting board 220, the opposite end 234 is a fastening that can be detached and coupled to the terminal tab 242 of the rear PCB 240. Are combined into structures. In particular, the terminal tab 242 to which the cable end 234 is fastened has a coupling structure that protrudes upward, so that the terminal tab 242 is separated from the cable end 234 when upward tension is applied. The volume expansion threshold condition of the battery cell 210 for the cable end 234 and the terminal tab 242 to be separated is the length of the cable 230 relative to the length of the battery cell 210 and the cable end 234 and the terminal tab. It is mainly determined by the binding force of (242). Thus, by appropriate setting of these conditions, it is possible to determine the threshold condition for disconnection of the cable 230 as the electrical connecting member.

FIG. 7 schematically illustrates a battery module having a structure in which a cable itself may be separated from a battery pack according to another embodiment of the present invention.

Referring to FIG. 7, the battery module 300 has a structure in which a fastening member 330 that is detachable and coupled to an intermediate portion of the cable 320 that is wired to surround the outer surface of the battery cell 310 is included. have.

The cable 320 is wired to surround the surface and the bottom of the battery cell 310 at the same time, so that the cable 320 receives tension when the volume of the battery cell 310 changes. Since the battery cell 310 has the largest length (thickness) in the width direction during volume expansion, upward tension is mainly applied to the cable 320.

The fastening member 330 included in the middle portion of the cable 320 is composed of a detachable and joinable structure coupled by mechanical contact, and an insulating member is coated on its outer surface. Therefore, as shown in FIG. 8, when the volume of the battery cell 310 expands, the battery cell 310 is separated. Since the fastening member 330 has contact sizes at both ends thereof in contact with the inside thereof, disconnection may occur only when the battery cell 310 is expanded to a predetermined size or more. Therefore, according to the structure of the fastening member 330, it is possible to determine the expansion size of the battery cell 310 in which power failure may occur.

The fastening member 330 may be formed on the cable 320 positioned on the surface of the battery cell 310 as shown in FIGS. 7 and 8, but may be positioned on the bottom surface of the battery cell 310 in some cases. In the latter case, when the electrode tab direction of the battery cell 310 is fixed as shown in FIG. 6, the volume expansion of the battery cell 310 is concentrated toward the bottom surface, thereby making it easier to separate the fastening member 330.

The present invention has been described above with reference to the drawings according to some embodiments of the present invention. However, those skilled in the art to which the present invention pertains have various applications and modifications within the scope of the present invention. It will be possible.

As described above, the medium-to-large battery pack according to the present invention has a case in which a battery cell expands due to abnormal operation such as overcharge, overdischarge, overcurrent, and the like, and the battery cell expands due to deterioration of battery components due to continuous use. In this case, the electrical connection member can be mechanically disconnected according to such physical change, thereby ensuring the safety of the battery pack. In particular, the expansion of the battery cell due to the deterioration of the battery is a phenomenon that can not be controlled by the conventional safety system in the battery pack can be controlled only by the safety system according to the present invention. Such medium and large battery packs may be preferably used as a power source of an electric bicycle (E-bike), an electric motorcycle, an electric vehicle, or a hybrid electric vehicle.

Claims (10)

In a battery pack including two or more battery cells, at least one of the electrical connection members of the battery pack components is mechanically disconnected by the physical change of the battery cell when the electrical connection member expands above the threshold of the battery cell. Consisting of; The electrical connection member is a bus bar, wire or cable; The portion of the electrical connection member which is mechanically disconnected during the volume expansion of the battery cell may be a connection portion between electrode terminals and a bus bar or a wire, a connection portion between a cable and a tab terminal to which the cable is connected, or a connection portion in the middle of a cable. Medium and large battery pack characterized by. The medium-large battery pack according to claim 1, wherein the battery cell is a rectangular secondary battery or a pouch secondary battery. delete The medium-large battery pack according to claim 1, wherein the battery cells (unit cells) are stacked in a heat dissipation stacked structure. delete The medium and large battery pack of claim 1, wherein the cable is wired in a direction surrounding the thickness of at least one unit battery so as to directly receive a tension in response to a change in thickness of the battery cells. The opposite end of the unit cell according to claim 1, wherein when the electrical connection member for inducing short-circuit is located in the direction of one end (a) of the unit cell, based on both ends (a, b) of the battery cell (unit cell), (B) is fixed, the medium-large battery pack, characterized in that the electrical expansion of the electrical connection member is easily performed because the expansion of the thickness of the unit cell mainly appears toward the end (a) direction. The method of claim 1, wherein the battery pack is a medium-large battery pack, characterized in that the battery cells (unit cells) are built in the upper and lower separate pack case. The medium and large battery pack according to claim 8, wherein the fastening portion of the pack case is variably changed so that a change in thickness direction may be reflected when the battery cells (unit cells) are expanded. The medium and large battery pack of claim 1, wherein the battery pack is used as a power source of an electric bicycle, an electric motorcycle, an electric vehicle, or a hybrid electric vehicle.

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