Patent Publication Number: US-2023155216-A1

Title: Pouch-Shaped Secondary Battery with Improved Safety and Battery Module Including the Same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national phase entry under 35 U.S.C. § 371 of International Applications No. PCT/KR2021/007778 filed on Jun. 22, 2021, which claims the benefit of priority to Korean Patent Application No. 10-2020-0087180 filed on Jul. 15, 2020, the disclosures of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a pouch-shaped secondary battery with improved safety and a battery module including the same. More particularly, the present invention relates to a pouch-shaped secondary battery including a danger sensing device including a gas pocket disposed on an electrode lead and a current sensing portion configured to move in response to an expansion or a contraction of the gas pocket and a battery module including the same. 
     BACKGROUND ART 
     With recent diversification of devices that use batteries, demand for high-capacity and high-density batteries has increased. In particular, concern about a pouch-shaped secondary battery configured such that the thickness of an aluminum laminate sheet is reduced to obtain a high-capacity and high-density battery has increased. 
     The pouch-shaped secondary battery is generally formed by shaping an aluminum laminate sheet to form a receiving portion and receiving an electrode assembly including a positive electrode, a separator, and a negative electrode in the receiving portion. The aluminum laminate sheet is easily deformed and thus manufactured in various forms, whereby it is possible to form pouch-shaped secondary batteries suitable for various electronic devices. In addition, since the aluminum laminate sheet is light, unlike a conventional cylindrical secondary battery or prismatic secondary battery, it is possible to increase energy density per weight of the pouch-shaped secondary battery. 
     When gas is generated in the pouch-shaped secondary battery during charging and discharging thereof, however, the battery may generate heat or may explode due to malfunction of the battery. In the case in which a battery case is broken, noxious gases or chemicals may be discharged therefrom. In particular, it is not possible to discharge gas generated when internal short circuit occurs, whereby there is a danger of explosion. 
       FIG.  1    is a plan view of a pouch-shaped secondary battery having a gas pocket. 
     As shown in  FIG.  1   , the pouch-shaped secondary battery having the gas pocket may include an electrode assembly  10  and a case  20  having a receiving portion  21  configured to receive the electrode assembly  10  and a gas pocket  22  configured to receive gas generated in the receiving portion  21 . The pouch-shaped secondary battery having the gas pocket  22  is provided with a separate space capable of receiving gas, whereby it is possible to prevent damage to the pouch-shaped secondary battery due to the gas, compared to a pouch-shaped secondary battery having no gas pocket  22 . However, the gas pocket  22  increases overall volume of the pouch-shaped secondary battery, and it is not possible to indicate interruption in function of the pouch-shaped secondary battery or damage to the pouch-shaped secondary battery in advance. 
       FIG.  2    is a plan view of a pouch-shaped secondary battery having a gas discharge induction portion. 
     The pouch-shaped secondary battery having the gas discharge induction portion includes an electrode assembly  10  and a case  20  having a receiving portion  21  configured to receive the electrode assembly  10 , similarly to the pouch-shaped secondary battery of  FIG.  1   . The gas discharge induction portion  23 , which induces discharge of gas, is located at the surface of the case  20  adjacent to the receiving portion. The gas discharge induction portion  23  is connected to the receiving portion  21 . A part of a sealed portion that seals the periphery of the receiving portion  21  is sealed with low sealing force, or a part of the sealed portion may not be sealed, as shown in  FIG.  2   . 
     In addition, a method of providing a safety device, such as a fuse or a protection circuit, outside a pouch or disposing a removal material in the pouch is considered in order to improve safety of the pouch-shaped secondary battery. However, there is no device that measures whether noxious gases have been generated in the battery before an accident occurs in order to assist in predicting the point in time at which a danger occurs, and therefore it is not possible to prevent occurrence of a problem or an accident due to malfunction of the pouch-shaped secondary battery. 
     Patent Document 1 discloses a battery module including a probe configured to sense swelling of a battery cell, wherein the sensing probe senses a change in local volumetric expansion of the battery cell and transmits a signal. However, there is a problem in that a measurement error may occur depending on a region of the battery cell that is expanded. 
     Therefore, there is a need to improve safety of a pouch-shaped secondary battery. 
     PRIOR ART DOCUMENT 
     (Patent Document 1) Korean Patent Application Publication No. 10-2017-0040919 
     DISCLOSURE 
     Technical Problem 
     The present invention has been made in view of the above problems, and it is an object of the present invention to measure the amount of gas in a receiving portion before a pouch-shaped secondary battery is broken. 
     It is another object of the present invention to indicate that a pouch-shaped secondary battery will break immediately before breakage of the pouch-shaped secondary battery in order to improve safety of the pouch-shaped secondary battery or a battery module and a battery pack including the same and to stably supply energy to a device that uses the battery. 
     Technical Solution 
     In order to accomplish the above objects, a pouch-shaped secondary battery according to the present invention includes an electrode assembly having an electrode lead protruding therefrom, a case including a receiving portion configured to receive the electrode assembly, and a danger sensing device including a gas pocket disposed on the electrode lead and a current sensing portion configured to move in response to expansion of the gas pocket. 
     The current sensing portion may include an electrode lead contact portion disposed in contact with the electrode lead and a gas pocket contact portion disposed abutting the gas pocket, the gas pocket contact portion being configured to move the current sensing portion using expansion force of the gas pocket. 
     The distance between the electrode lead contact portion and the electrode lead may be increased due to expansion of the gas pocket. 
     The gas pocket contact portion may come into contact with the gas pocket in the direction in which the gas pocket is expanded. 
     The gas pocket contact portion may have a larger sectional width than the electrode lead contact portion. 
     At least the electrode lead contact portion of the current sensing portion may be a conductor. 
     At least the outer surface of the gas pocket contact portion of the current sensing portion may be made of an insulation material. 
     The insulation material may be a material that has adhesive force. 
     One side of the current sensing portion may be connected to a voltage measurement device. 
     The portion at which the gas pocket and the receiving portion are connected to each other may be sealed with lower sealing force than the sealed portion. 
     When pressure in the receiving portion is equal to or higher than a predetermined range, the gas pocket may be expanded. 
     One surface of the gas pocket may be disposed in contact with the electrode lead, and the other surface of the gas pocket may be disposed in contact with the current sensing portion. 
     The gas pocket may be provided at each of opposite sides of the current sensing portion. 
     The gas pocket may be provided above a terraced portion formed by a sealed portion at a region at which the electrode lead protrudes or may be disposed at least on the electrode lead. 
     The present invention provides a battery module including the pouch-shaped secondary battery. 
     The pouch-shaped secondary battery may be connected in parallel. 
     The present invention provides a battery pack including the pouch-shaped secondary battery. In addition, the present invention provides a device in which the pouch-shaped secondary battery is mounted. 
     In the present invention, one or more constructions that do not conflict with each other may be selected and combined from among the above constructions. 
     Advantageous Effects 
     As is apparent from the above description, a pouch-shaped secondary battery according to the present invention is configured such that it is possible to determine whether gas is generated in a receiving portion and to prevent interruption in function of the pouch-shaped secondary battery or breakage of the pouch-shaped secondary battery due to the generated gas, whereby it is possible to improve safety of the battery. 
     Furthermore, the extent of gas generated in the receiving portion is directly converted into an electrical signal, which is transmitted, whereby it is possible to rapidly determine whether the pouch-shaped secondary battery is abnormal. 
     In addition, for a battery module including one or more pouch-shaped secondary batteries according to the present invention, it is possible to recognize malfunction of some of the pouch-shaped secondary batteries in advance. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a plan view of a pouch-shaped secondary battery having a gas pocket. 
         FIG.  2    is a plan view of a pouch-shaped secondary battery having a gas discharge induction portion. 
         FIG.  3    is a perspective view of a pouch-shaped secondary battery according to a first embodiment of the present invention. 
         FIG.  4    is a plan view of the pouch-shaped secondary battery of  FIG.  3   . 
         FIG.  5    is a side sectional view of the pouch-shaped secondary battery of  FIG.  3   . 
         FIG.  6    is a perspective view of a pouch-shaped secondary battery according to a second embodiment of the present invention. 
         FIG.  7    is a plan view of the pouch-shaped secondary battery of  FIG.  6   . 
         FIG.  8    is a plan view of a pouch-shaped secondary battery according to a third embodiment of the present invention. 
         FIG.  9    is a side sectional view of the pouch-shaped secondary battery of  FIG.  8   . 
         FIG.  10    is a schematic view showing a method to manufacture a pouch-shaped secondary battery according to the present invention. 
     
    
    
     BEST MODE 
     Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that the preferred embodiments of the present invention can be easily implemented by a person having ordinary skill in the art to which the present invention pertains. In describing the principle of operation of the preferred embodiments of the present invention in detail, however, a detailed description of known functions and configurations incorporated herein will be omitted when the same may obscure the subject matter of the present invention. 
     In addition, the same reference numbers will be used throughout the drawings to refer to parts that perform similar functions or operations. In the case in which one part is said to be connected to another part throughout the specification, not only may the one part be directly connected to the other part, but also, the one part may be indirectly connected to the other part via a further part. In addition, that a certain element is included does not mean that other elements are excluded, but means that such elements may be further included unless mentioned otherwise. 
     In addition, a description to embody elements through limitation or addition may be applied to all inventions, unless particularly restricted, and does not limit a specific invention. 
     Also, in the description of the invention and the claims of the present application, singular forms are intended to include plural forms unless mentioned otherwise. 
     Also, in the description of the invention and the claims of the present application, “or” includes “and” unless mentioned otherwise. Therefore, “including A or B” means three cases, namely, the case including A, the case including B, and the case including A and B. 
     In addition, all numeric ranges include the lowest value, the highest value, and all intermediate values therebetween unless the context clearly indicates otherwise. 
       FIG.  3    is a perspective view of a pouch-shaped secondary battery according to a first embodiment of the present invention,  FIG.  4    is a plan view of the pouch-shaped secondary battery according to the first embodiment of the present invention, and  FIG.  5    is a side sectional view of the pouch-shaped secondary battery according to the first embodiment of the present invention. 
     As shown in  FIGS.  3  to  5   , the pouch-shaped secondary battery according to the first embodiment of the present invention includes an electrode assembly  100  having electrode leads  110  protruding therefrom, a case  200  including a receiving portion  210  configured to receive the electrode assembly  100 , and a danger sensing device  300  including a gas pocket  310  disposed on each of the electrode leads  110  and a current sensing portion  320  configured to move in response to expansion of the gas pocket  310 . 
     The electrode assembly  100  may be a jelly-roll type assembly, which is configured to have a structure in which a long sheet type positive electrode and a long sheet type negative electrode are wound in the state in which a separator is interposed therebetween, a stacked type electrode assembly including unit cells, each of which is configured to have a structure in which a rectangular positive electrode and a rectangular negative electrode are stacked in the state in which a separator is interposed therebetween, a stacked and folded type assembly, which is configured to have a structure in which unit cells are wound using a long separation film, or a laminated and stacked type assembly, which is configured to have a structure in which unit cells are stacked in the state in which a separator is interposed therebetween and are then attached to each other. However, the present invention is not limited thereto. 
     The electrode leads  110  may be configured to have a structure in which the electrode leads are exposed out of the case after positive electrode tabs and negative electrode tabs of the electrode assembly  100  are electrically connected to the electrode leads or a structure in which the electrode leads  110  directly connect the electrode assembly  100  to the outside of the case  200  without positive electrode tabs and negative electrode tabs. However, the present invention is not limited thereto. The secondary battery described above is generally known, and therefore a more detailed description thereof will be omitted. 
     The case  200  is generally configured to have a laminate sheet structure including an inner layer, a metal layer, and an outer layer. The inner layer is disposed in direct contact with the electrode assembly, and therefore the inner layer must exhibit high insulation properties and high resistance to an electrolytic solution. In addition, the inner layer must exhibit high sealability in order to hermetically seal the case from the outside, i.e., a thermally-bonded sealed portion between inner layers must exhibit excellent thermal bonding strength. The inner layer may be made of a material selected from among a polyolefin-based resin, such as polypropylene, polyethylene, polyethylene acrylate, or polybutylene, a polyurethane resin, and a polyimide resin, which exhibit excellent chemical resistance and high sealability. However, the present invention is not limited thereto, and polypropylene, which exhibits excellent mechanical-physical properties, such as tensile strength, rigidity, surface hardness, and impact resistance strength, and excellent chemical resistance, is the most preferably used. 
     The metal layer, which is disposed so as to abut the inner layer, corresponds to a barrier layer configured to prevent moisture or various kinds of gas from permeating into the battery from the outside. An aluminum thin film, which is light and easily shapeable, may be used as a preferred material for the metal layer. 
     The outer layer is provided on the other surface of the metal layer. The outer layer may be made of a heat-resistant polymer that exhibits excellent tensile strength, resistance to moisture permeation, and resistance to air permeation such that the outer layer exhibits high heat resistance and chemical resistance while protecting the electrode assembly. As an example, the outer layer may be made of nylon or polyethylene terephthalate. However, the present invention is not limited thereto. 
     The receiving portion  210  may be formed in each of the upper part and the lower part of the case  200 , or may be formed in any one of the upper part and the lower part of the case. 
     In addition, the outside surface of the receiving portion  210  is hermetically sealed in order to prevent a material in the receiving portion  210  from being discharged from the case  200 . At this time, a sealed portion  220  formed as the result of hermetically sealing is bent in a direction toward the receiving portion  210  in order to increase energy density of a battery module. At this time, a terraced portion, which is a part of the sealed portion  220  and from which the electrode lead  110  protrudes in one direction or in opposite directions, is formed so as to protrude from the receiving portion  210 . 
     The danger sensing device  300  may be located at the terraced portion of the sealed portion  220  or at the electrode lead  110  adjacent to the terraced portion. That is, the danger sensing device  300  may extend from the terraced portion and may be located on the electrode lead, may be located at a part of the terraced portion, or may be located on the electrode lead. 
     The gas pocket  310  of the danger sensing device  300  may be connected to the receiving portion  210  and the sealed portion  220 . That is, the gas pocket  310  may be connected to the receiving portion  210  with lower sealing force than the sealed portion  220 . 
     In the case in which pressure in the receiving portion  210  is equal to or higher than a predetermined range, the portion of the gas pocket that is connected to the receiving portion  210  with low sealing force may be damaged, whereby gas may move into the gas pocket  310 , and therefore the gas pocket may be expanded. At this time, the gas pocket  310  may be expanded at once, or may be divided into several sections and thus may be expanded twice or more. 
     The gas pocket  310  may be disposed at the portion of the sealed portion  220  from which the electrode lead  110  protrudes, i.e., above the terraced portion or at least on the electrode lead  110 . 
     The gas pocket  310  according to the first embodiment of the present invention may be a part of the sealed portion  220 . As shown in  FIGS.  3  and  5   , the gas pocket  310  may be a part of the sealed portion  220  formed at the portion at which the electrode lead  110  protruding from the electrode assembly  100  extends through the case  200 . 
     When the sealed portion  220  is divided into three equal parts, the gas pocket  310  according to the first embodiment may be located at the outer ⅓ point of the sealed portion  220 , i.e., the farthest side of the receiving portion  210 . 
     In addition, the gas pocket  310 , which is connected to the case  200 , may be made of the same material as the case  200 . In order to secure sealing force, one surface of the gas pocket  310  may be laminated like the electrode tabs, and the other surface of the gas pocket may be in contact with the current sensing portion  320 . 
     At least one gas pocket  310  may be provided in a single pouch-shaped secondary battery. As an example, the gas pocket  310  may assist in movement of the current sensing portion  320  at each of opposite sides of the current sensing portion  320  such that the current sensing portion  320  is easily operated. 
     In addition, the pouch-shaped secondary battery according to the present invention may include a gas receiving portion configured to receive a predetermined amount of gas in addition to the gas pocket  310 . Consequently, it is possible to prevent breakage of the pouch-shaped secondary battery, and when pressure in the gas receiving portion exceeds a predetermined range, it is possible to indicate a danger through the gas pocket  310 . On the contrary, after the gas pocket  310  is operated by a one-way valve of the gas receiving portion, the gas receiving portion may receive gas generated in the pouch-shaped secondary battery. 
       FIG.  6    is a perspective view of a pouch-shaped secondary battery according to a second embodiment of the present invention, and  FIG.  7    is a plan view of the pouch-shaped secondary battery according to the second embodiment of the present invention. 
     As shown in  FIGS.  6  and  7   , in the pouch-shaped secondary battery according to the second embodiment of the present invention, the gas pocket  310  may be formed independent of the sealed portion  220 . The gas pocket  310  is located adjacent to the sealed portion  220 , which hermetically seals the electrode lead  110 , i.e., at the distance at which the gas pocket  310  abuts the electrode lead  110  while securing force of sealing the electrode lead  110 . The connection sealed portion  221  connected to the gas pocket  310  has lower sealing force than other portions. When gas is generated in the receiving portion  210 , therefore, the connection sealed portion  221  is broken first, and then the gas moves into the gas pocket  310 . 
     As shown in  FIGS.  6  and  7   , the gas pocket  310  may be partially curved so as to be located on the electrode lead  110 . 
       FIG.  8    is a plan view of a pouch-shaped secondary battery according to a third embodiment of the present invention. 
     As shown in  FIG.  8   , the pouch-shaped secondary battery according to the third embodiment of the present invention may be configured to have a structure in which the gas pocket  310  is integrally formed with the sealed portion  220 , similarly to the pouch-shaped secondary battery according to the first embodiment. 
     In order to prevent flow or movement of gas from being disturbed in the case in which the gas pocket  310  is bent as in the second embodiment, the gas pocket  310  according to the third embodiment of the present invention may be formed so as to simply cover the electrode lead  110 . 
     The surplus portion of the gas pocket  310  that covers the leads may be formed in the shape of a pouch, which is a space that is capable of being filled with unsealed gas, and the portion of the gas pocket  310  that abuts the sealed portion  220  may be divided into two parts having different sealing forces. The portion of the gas pocket that abuts the sealed portion  220  may include a connection sealed portion  221  having lower sealing force than the sealed portion  220  and a peripheral sealed portion  222  having the same sealing force as the sealed portion  220 . 
     The connection sealed portion  221  may be located at a region other than a contour portion of the electrode lead  110  that affects force of sealing between the electrode lead  110  and the case  200 . At this time, in order to maintain the force of sealing between the electrode lead  110  and the case  200  while smoothly supplying gas to the gas pocket  310 , the connection sealed portion  221  may be formed in a state of being divided into at least two parts based on the electrode lead  110 . 
     A one-way valve configured to allow gas in the receiving portion  210  to move only in one direction may be provided at the outermost contour portion of the connection sealed portion  221 , i.e., at the point farthest from the sealed portion. 
     In the case in which a gas passage is integrally formed with the connection sealed portion  221 , the peripheral sealed portion  222 , which is the sealed portion  220  that is not the gas passage, and the sealed portion around the gas passage in the gas pocket  310  may be more strongly sealed than other sealed portions. In the case in which the peripheral sealed portion  222  has higher sealing force than other sealed portions, it is possible to solve a problem in that sealing force around the electrode lead  110  is reduced. 
       FIG.  9    is a side sectional view of the pouch-shaped secondary battery according to the present invention. 
     As shown in  FIG.  9   , the current sensing portion  320  according to the present invention may include an electrode lead contact portion  321  disposed in contact with the electrode lead  110  and a gas pocket contact portion  322  disposed abutting the gas pocket  310 , the gas pocket contact portion being configured to move the current sensing portion  320  using expansion force of the gas pocket  310 . 
     The electrode lead contact portion  321  may become far away from the electrode lead due to expansion of the gas pocket. To this end, the gas pocket contact portion  322  comes into contact with the gas pocket  310  in the direction in which the gas pocket  310  is expanded. In addition, to this end, the gas pocket contact portion  322  may have a larger sectional width than the electrode lead contact portion  321 . That is, the current sensing portion  320  may be configured to have a structure in which the electrode lead contact portion  321  is disposed between the gas pockets  310  and in which the gas pocket contact portion  322  is disposed in contact with the gas pocket  310  disposed beside the electrode lead contact portion  321 . The current sensing portion  320  may have a T-shaped form, a conical form, or a section climbing form so as to be operated as described above. 
     The current sensing portion  320  may sense current that moves in the electrode lead  110  through the electrode lead contact portion  321 . When the electrode lead contact portion  321  is separated from the electrode lead  110  due to expansion of the gas pocket  310 , the electrode lead contact portion  321  cannot sense current any more, and therefore it is possible to determine whether gas has been generated in the receiving portion  21 . 
     In addition, one side of the current sensing portion  320  may be connected to a voltage measurement device, which may convert the current sensed by the electrode lead contact portion  321  into a numerical value or a signal. 
     It is preferable for the current sensing portion  320  to be a conductor in order to measure current through contact with the electrode lead  110 , as described above. That is, it is preferable for at least the electrode lead contact portion  321  of the current sensing portion  320  to be a conductor. Although the entirety of the current sensing portion  320  is a conductor, the outer surface of the current sensing portion  320 , i.e., at least the outer surface of the gas pocket contact portion  322 , may be wrapped with an insulation material such that no current flows in another portion of the pouch-shaped secondary battery, e.g. the gas pocket  310 . 
     The insulation material may be a material that has adhesive force in order to fix the current sensing portion  320 . As an example, the insulation material may be at least one selected from the group consisting of polyethylene, polypropylene, polyvinyl fluoride, polyvinyl alcohol, polyvinyl polyamide imide, an epoxy-based material, an acrylic-based material, a silicone-based material, a urethane-based material, a thermoplastic urethane-based material, and a thermoplastic ether ester-based material. 
     In addition, the current sensing portion  320  according to the present invention may be provided in one or more in order to measure the amount of gas depending on the extent to which the gas pocket  310  having several sealed portions is opened. 
     The present invention may provide a battery module including at least one pouch-shaped secondary battery. The battery module may be configured such that pouch-shaped secondary batteries are connected to each other in parallel. The reason for this is that, in the case in which the pouch-shaped secondary batteries are connected to each other in series, it is possible to easily recognize one unit cell, when the unit cell is abnormal, whereas, in the case unit cells are connected to each other in parallel, it is difficult to find abnormality of one of the unit cells. 
     In addition, the present invention may provide a battery pack including the pouch-shaped secondary battery. 
       FIG.  10    is a schematic view showing a pouch-shaped secondary battery manufacturing method according to the present invention. 
     In the pouch-shaped secondary battery according to the present invention, the portion of the case that will become the gas pocket  310  and the electrode lead  110  may be bonded to each other first, and then the remaining portions may be bonded. After bonding, the portion that will become the gas pocket  310  may be folded such that no empty space is formed, as shown in  FIG.  10   , and then the portion that contacts the remaining portion of the electrode lead  110  may be further welded. 
     In addition, the present invention provides a battery pack including the pouch-shaped secondary battery and a device including the battery pack. The battery pack and the device are well known in the art to which the present invention pertains, and thus a detailed description thereof will be omitted. 
     For example, the device may be a laptop computer, a netbook computer, a tablet PC, a mobile phone, an MP3 player, a wearable electronic device, a power tool, an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an electric bicycle (E-bike), an electric scooter (E-scooter), an electric golf cart, or an energy storage system. However, the present invention is not limited thereto. 
     Those skilled in the art to which the present invention pertains will appreciate that various applications and modifications are possible within the category of the present invention based on the above description. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           10 ,  100 : Electrode assemblies 
           11 ,  110 : Electrode leads 
           20 ,  200 : Cases 
           21 ,  210 : Receiving portions 
           22 ,  220 : Sealed portions 
           221 : Connection sealed portion 
           222 : Peripheral sealed portion 
           23 : Gas discharge induction portion 
           300 : Danger sensing device 
           310 : Gas pocket 
           320 : Current sensing portion 
           321 : Electrode tab contact portion 
           322 : Gas pocket contact portion