Patent Publication Number: US-2015072218-A1

Title: Battery pack and battery module including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0108066, filed on Sep. 9, 2013, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     One or more embodiments of the present invention relate to battery packs and battery modules including the same. 
     2. Description of the Related Art 
     In general, secondary batteries are rechargeable unlike primary batteries that are not rechargeable. Depending on the type of external devices to which secondary batteries are applied, the secondary batteries may be used in the form of a single battery or in the form of a module in which a plurality of unit batteries are connected and packed into one unit. 
     Recently, types of electronic devices using secondary batteries have been diversified, and designs of electronic devices have become an important factor in determining the purchase of electronic devices. For example, various wearable computers using secondary batteries as a power supply source, and applications thereof have been developed and published. Also, electronic devices, such as mobile phones and laptop computers, have been designed to have curved surfaces for ergonomic purposes. 
     It is desirable for secondary batteries for operating electronic devices to have a large capacity to provide a sufficient use time of the electronic devices, and for the batteries to be able to change shape, for example, by modification such as bending, depending on the shape of the electronic device with which the battery is used. 
     SUMMARY 
     One or more embodiments of the present invention include battery packs with new shapes and flexible battery modules. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description. 
     According to one or more embodiments of the present invention, a battery pack includes a first electrode assembly; a second electrode assembly electrically connected to the first electrode assembly; and a pouch accommodating the first electrode assembly and the second electrode assembly, wherein each of the first electrode assembly and the second electrode assembly comprises a first surface, a second surface facing the first surface, and a pair of curved surfaces connecting the first surface and the second surface, wherein the first surface of the first electrode assembly and the second surface of the second electrode assembly are oriented to face each other, and wherein the second electrode assembly is offset in a first direction such that the second electrode assembly partially overlaps with the first electrode assembly. 
     In one embodiment, the first direction extends from a first one of the pair of curved surfaces to a second one of the pair of curved surfaces of the first or second electrode assembly. Further, in one embodiment, each of the first electrode assembly and the second electrode assembly includes a first electrode plate, a second electrode plate and a separator located between the first electrode plate and the second electrode plate, wherein the first electrode plate, the second electrode plate, and the separator are wound together, wherein the first surface, the second surface, and the pair of curved surfaces correspond to a winding surface of each of the first electrode assembly and the second electrode assembly, and wherein the first surface and the second surface are substantially flat. 
     A cross-sectional area of the first electrode assembly and a cross-sectional area of the second electrode assembly which are perpendicular to the winding surface may be substantially equal to each other. Additionally, an electrolyte is accommodated in the pouch, and the first electrode assembly and the second electrode assembly may both contact the electrolyte. 
     In various embodiments, the secondary battery further includes a first insulating layer configured to seal the first electrode assembly; and a second insulating layer configured to seal the second electrode assembly, an electrode tab attached to the first electrode assembly or the second electrode assembly, wherein the electrode tab protrudes from the pouch. 
     In another embodiment, a battery module includes a plurality of battery packs arranged linearly; and a lead electrode electrically connecting the battery packs, wherein each of the battery packs comprises a first electrode assembly and a second electrode assembly electrically connected to each other, wherein each of the first electrode assembly and the second electrode assembly comprises a first surface, a second surface facing the first surface, and a pair of curved surfaces connecting the first surface and the second surface, wherein the first surface of the first electrode assembly and the second surface of the second electrode assembly are oriented to face each other, and wherein the second electrode assembly is offset in a first direction such that the second electrode assembly partially overlaps with the first electrode assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic perspective view of a battery module according to an embodiment of the present invention; 
         FIG. 2  is a schematic cross-sectional view of a battery pack included in the battery module of  FIG. 1 ; 
         FIG. 3  is a schematic cross-sectional view of two adjacent battery packs included in the battery module of  FIG. 1 ; 
         FIG. 4  is a schematic view illustrating a shape of the battery module of  FIG. 1 ; and 
         FIG. 5  is a schematic view illustrating another shape of the battery module of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. 
     The present invention may include various embodiments and modifications, and exemplary embodiments are illustrated in the drawings and will be described below in detail. However, it will be understood that the present invention is not limited to the exemplary embodiments and includes all modifications, equivalents and substitutions falling within the spirit and scope of the present invention. Like reference numerals or symbols denote like elements throughout the specification and drawings. 
     Although terms such as “first” and “second” may be used herein to describe various elements or components, these elements or components should not be limited by these terms. These terms are only used to distinguish one element or component from another element or component. 
     The terms used herein are for the purpose of describing exemplary embodiments only and are not intended to be limiting of the present invention. It will be understood that terms such as “comprise”, “include”, and “have”, when used herein, specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a schematic perspective view of a battery module  100  according to an embodiment of the present invention.  FIG. 2  is a schematic cross-sectional view of a battery pack  200  included in the battery module  100  of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the battery module  100  may include battery packs  200  and a pair of lead electrodes  110  configured to electrically connect the battery packs  200 . 
     As illustrated in  FIG. 2 , each of the battery packs  200  may include a first electrode assembly  210 , a second electrode assembly  220  connected electrically to the first electrode assembly  210 , and a pouch  230  configured to accommodate and seal the first electrode assembly  210  and the second electrode assembly  220 . 
     The first electrode assembly  210  and the second electrode assembly  220  may each include a first electrode plate  211 , a second electrode plate  212  and a separator  213  located between the first electrode plate  211  and the second electrode plate  212 , wherein the first and second electrode plates and the separator are wound together. 
     The first electrode plate  211  may include a first active material portion that is coated with a first active material, and a first uncoated portion that is not coated with the first active material. For example, the first active material may be a positive active material. The positive active material may be a lithium-containing transition metal oxide, such as LiCoO 2 , LiNiO 2 , LiMnO 2 , or LiMnO 4 , or a lithium chalcogenide compound. 
     For example, the first active material portion may be formed by coating the first active material on a portion of at least one surface of an aluminum plate, and the first uncoated portion may be the other portion of the aluminum plate that is not coated with the first active material. For example, the first uncoated portion may be located on one side of the first electrode plate  211 . 
     The second electrode plate  212  may include a second active material portion that is coated with a second active material, and a second uncoated portion that is not coated with the second active material. For example, the second active material may be a negative active material. The negative active material may be a carbon material, such as crystalline carbon, amorphous carbon, carbon complex, or carbon fiber, a lithium metal, or a lithium alloy. 
     For example, the second active material portion may be formed by coating the second active material on a portion of at least one surface of a copper plate, and the second uncoated portion may be the other portion of the copper plate that is not coated with the second active material. For example the second uncoated portion may be located on one side of the second electrode plate  212 . 
     The separator  213  prevents a short circuit between the first electrode plate  211  and the second electrode plate  212 , and enables charge transfer. For example, the separator  213  may be manufactured by coating polyvinylidenefluoride-hexafluoropropylene (PVDF-HFP) copolymer on any material selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene, and polyethylene-polypropylene copolymer. 
     The first electrode plate  211 , the second electrode plate  212 , and the separator  213  may be cylindrically wound and then pressurized such that the first electrode assembly  210  may be molded to include a first surface U 1 , a second surface L 1  facing the first surface U 1 , and a pair of curved surfaces S 1  connecting the first surface U 1  and the second surface L 1 . 
     Herein, the first surface U 1 , the second surface L 1 , and the pair of surfaces S 1  may correspond to a winding surface of the first electrode assembly  210 , and the first surface U 1  and the second surface L 1  may be substantially flat. In  FIG. 2 , the first surface U 1  and the second surface L 1  are illustrated separately for the convenience of description. However, the first surface U 1  and the second surface L 1  may have the same shape, and their positions may be interchanged. 
     Like the first electrode assembly  210 , the second electrode assembly  220  may include a first electrode plate  211 , a second electrode plate  212  and a separator  213  located between the first electrode plate  211  and the second electrode plate  212  that are wound together, and may include a first surface U 2  and a second surface L 2  that are flat, and a pair of curved surfaces S 2  connecting the first surface U 2  and the second surface L 2 . 
     The second electrode assembly  220  is located on and may directly contact the first surface U 1  of the first electrode assembly  210 . In detail, the first surface U 1  of the first electrode assembly  210  and the second surface L 2  of the second electrode assembly  220  may be oriented to face each other (i.e., they are generally opposite to each other). The first surface U 2  and the second surface L 2  of the second electrode assembly  220  may have the same shape, and the first surface U 1  of the first electrode assembly  210  and the first surface U 2  of the second electrode assembly  220  may be oriented to face each other. 
     The second electrode assembly  220  may be offset or shifted in a first direction such that the second electrode assembly  220  may be partially misaligned with the first electrode assembly  210 . The first direction may be a direction facing any one of the pair of curved surfaces S 2  of the second electrode assembly  220 . 
     Therefore, a portion of the second electrode assembly  220  may not overlap with the first electrode assembly  210 , and the first electrode assembly  210  and the second electrode assembly  220  may form a substantially “S” shape or a “Z” shape on the whole. 
     In one embodiment, the second electrode assembly  220  is electrically connected to the first electrode assembly  210 . For example, the first electrode assembly  210  and the second electrode assembly  220  may be formed separately, and the first electrode assembly  210  and the second electrode assembly  220  may be connected in series or in parallel by connecting the first electrode plate  211  included in the first electrode assembly  210  and the second electrode plate  212  or the first electrode plate  211  included in the second electrode assembly  220 . 
     As another example, a stack may be formed by sequentially stacking the first electrode plate  211 , the separator  213 , and the second electrode plate  212 , the first electrode assembly  210  may be formed by winding from one side of the stack toward the center of the stack, and the second electrode assembly  220  may be formed by winding from the other side of the stack toward the center of the stack. 
     Therefore, the first electrode assembly  210  and the second electrode assembly  220  may be electrically connected by the first electrode plate  211  and the second electrode plate  212 . In this case, the first electrode assembly  210  and the second electrode assembly  220  may be connected in parallel. 
     A cross-sectional area of the first electrode assembly  210  and a cross-sectional area of the second electrode assembly  220 , which are perpendicular to the winding surface, may be substantially equal to each other. Therefore, it is possible to prevent a voltage of the battery pack  200  from being controlled to a lower voltage of any one of the first electrode assembly  210  and the second electrode assembly  220  when the first electrode assembly  210  and the second electrode assembly  220  are connected in parallel, or to prevent a current of the battery pack  200  from being controlled to a lower current of any one of the first electrode assembly  210  and the second electrode assembly  220  when the first electrode assembly  210  and the second electrode assembly  220  are connected in series. 
     The pouch  230  is configured to accommodate and seal the first electrode assembly  210  and the second electrode assembly  220  and receive an electrolyte together with the first electrode assembly  210  and the second electrode assembly  220 . 
     For example, the pouch  230  may have a three-layered structure including an insulating layer, a metal layer, and an insulating layer. For example, the metal layer may be formed of aluminum, steel, or stainless steel, and the insulating layer may be formed of casted polypropylene (CPP), polyethylene terephthalate (PET), or nylon; however, embodiments of the present invention are not limited thereto. 
     The electrolyte may be a liquefied electrolyte or a gelled electrolyte, and the first electrode assembly  210  and the second electrode assembly  220  may be simultaneously impregnated with the same electrolyte. In other words, the first electrode assembly  210  and the second electrode assembly  220  may both contact and share the same electrolyte. 
     However, embodiments of the present invention are not limited thereto, and the battery pack  200  may further include a first insulating layer configured to seal the first electrode assembly  210  and a second insulating layer configured to seal the second electrode assembly  220 . 
     Therefore, the electrolyte may be injected into the first insulating layer and the second insulating layer, and the first electrode assembly  210  and the second electrode assembly  220  may be electrically connected to each other by electrodes protruding from the first insulating layer and the second insulating layer. 
     The battery pack  200  may further include an electrode tab  240  attached to the first electrode assembly  210  or the second electrode assembly  220 . 
     As described above, since the first electrode assembly  210  and the second electrode assembly  220  are electrically connected to each other inside the pouch  230 , the electrode tab  240  may be formed only at the first electrode assembly  210  or the second electrode assembly  220 . 
     For example, when the electrode tab  240  is attached to the first electrode assembly  210 , a pair of electrode tabs  240  may be attached respectively to the first uncoated portion and the second uncoated portion of the first electrode assembly  210  by ultrasonic welding. 
     Also, the pair of electrode tabs  240  may protrude outside the pouch  230  and may be attached to a lead electrode  110 . For example, the pair of electrode tabs  240  may protrude in opposite directions from the battery pack  200 . 
     A pair of lead electrodes  110  may be provided to electrically connect the battery packs  200  and fix the positions of the battery packs  200 . 
     For example, the electrode tabs  240  included in each of the battery packs  200  may protrude in respective directions corresponding to respective polarities and may be connected respectively to the pair of lead electrodes  110  that are formed linearly. Therefore, since the battery packs  200  are connected in parallel, the capacity of the battery module  100  may be increased. 
     A connection between the lead electrode  110  and the electrode tab  240  may be made by laser welding or ultrasonic welding; however, embodiments of the present invention are not limited thereto. 
     The battery packs  200  connected electrically by the lead electrode  110  are aligned to form a battery pack array  120 . As will be described later, the battery pack array  120  may be bent in a direction, for example, perpendicular to the first direction in which the second electrode assembly  220  is shifted. In this case, since the lead electrode  110  is also bent together with the battery pack array  120 , the lead electrode  110  may be ductile such that the lead electrode  110  is not cut even when bent. For example, the lead electrode  110  may be formed of a carbon nanotube (CNT) or a metal wire; however, embodiments of the present invention are not limited thereto. 
       FIG. 1  illustrates that a pair of lead electrodes  110  are provided in parallel to each other; however, embodiments of the present invention are not limited thereto. The lead electrode  110  may have various patterns, depending on the methods of connecting the battery packs  200  in series, in parallel, or in series-parallel. 
       FIG. 3  is a schematic cross-sectional view of two adjacent battery packs  200  included in the battery module  100  of  FIG. 1 .  FIG. 4  is a schematic view illustrating one shape of the battery module  100  of  FIG. 1 .  FIG. 5  is a schematic view illustrating another shape of the battery module  100  of  FIG. 1 . For the convenience of description,  FIG. 3  illustrates two battery packs  200  that are adjacent to each other in the battery pack array  120 . 
     Referring to  FIG. 3 , when two battery packs  200  are located adjacent to each other, the second electrode assembly  220  of the other of the adjacent battery packs  200  is located on the first electrode assembly  210  of one of the adjacent battery packs  200 . 
     Since the positions of the battery packs  200  may be fixed by the lead electrode  110  (see  FIG. 1 ) that is ductile, the adjacent battery packs  200  may not be attached to each other. Therefore, when a force is applied to the battery pack array  120  in a second direction perpendicular to the first direction in which the second electrode assembly  220  is shifted, the battery pack array  120  may be bent by the force. 
     For example, when the first direction is parallel to a ground surface, the battery pack array  120  may be bent in a vertical direction. 
     In order to fix the positions of the battery packs  200  more securely, the battery module  100  may further include a wrapping member that covers the lead electrode  110  (see  FIG. 1 ) and the battery pack array  120 . The wrapping member may be, for example, a shrinking tube, but is not limited thereto. 
       FIG. 4  illustrates one shape of the battery module  100 . In detail,  FIG. 4  illustrates that the battery module  100  is bent repeatedly in the vertical direction. Also,  FIG. 5  illustrates that the battery module  100  is bent only in an upward direction or a downward direction to have a circular shape on the whole. In this case, the pair of lead electrodes  110  may protrude outside and may be connected to an external electronic device to which the battery module  100  is attached. 
     Therefore, since the shape of the battery module  100  may be varied according to the shape of an electronic device, an internal space of the electronic device may be efficiently used. 
     As described above, according to the one or more of the above embodiments of the present invention, the shape of the battery module may be varied according to the shape of the electronic device. 
     It should be understood that the exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     While one or more embodiments of the present invention have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.