Patent Publication Number: US-2021184190-A1

Title: Battery pack

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application 
     No. 10-2019-0164643, filed on Dec. 11, 2019 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     One or more embodiments relate to battery packs. 
     2. Description of the Related Art 
     Generally, secondary batteries are chargeable and dischargeable batteries, unlike primary batteries that are not chargeable. Secondary batteries are used as energy sources for mobile devices, electric vehicles, hybrid vehicles, electric bicycles, uninterruptible power supplies, or the like, and may be used in the form of a single cell, depending on the type of an external device to which the secondary battery is applied, or in the form of a module by connecting a plurality of cells into a single unit. 
     Small mobile devices, such as mobile phones, can operate for a certain period of time with the output and capacity of a single cell. However, in the case of long-term driving or high-power driving of electric vehicles or hybrid vehicles having a high power consumption, due to the battery output and capacity, a module type including a plurality of cells is preferred. The output voltage or output current may be increased according to the number of built-in cells. 
     SUMMARY 
     According to an aspect of one or more embodiments, a battery pack is provided in which battery cells may be insulated and protected in an emergency situation, such as fire or explosion of the battery cells, the propagation of flames erupted from the battery cells may be suppressed, and an electrical short circuit due to humidity or moisture generated by dew condensation, for example, may be prevented or substantially prevented. 
     Additional aspects will be set forth, in part, in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the disclosure. 
     According to one or more embodiments, a battery pack includes: battery cells arranged in a plurality of rows, the battery cells in a row being arranged apart from each other with a separation gap therebetween; and a ceramic sheet extending and surrounding at least any one row of the battery cells, the ceramic sheet comprising non-adhesive portions surrounding the battery cells and an adhesive portion extending across the separation gap between neighboring non-adhesive portions of the non-adhesive portions. 
     In one or more embodiments, the non-adhesive portion may entirely surround the outer circumferential surface of each of the battery cells. 
     In one or more embodiments, the non-adhesive portion may have an arc-shaped section following the outer circumferential surface of each of the battery cells. 
     In one or more embodiments, the non-adhesive portion may be in surface contact with the entire outer circumferential surface of each of the battery cells. 
     In one or more embodiments, the adhesive portion may extend across the separation gap in a row direction in which the battery cells are arranged. 
     In one or more embodiments, the adhesive portion may have a line-shaped section following the row direction in which the battery cells are arranged. 
     In one or more embodiments, the ceramic sheet may include first and second sheets that are coupled to face each other with the one row of the battery cells therebetween. 
     In one or more embodiments, the non-adhesive portion may include non-adhesive portions of the first and second sheets that respectively surround half of an outer circumferential surface of each of the battery cells at opposite sides, and the adhesive portion may include adhesive portions of the first and second sheets coupled to face each other. 
     In one or more embodiments, the first and second sheets may extend in a row direction in which the battery cells are arranged, and the non-adhesive portion and the adhesive portion are alternately arranged and connected to each other. 
     In one or more embodiments, the adhesive portions of the first and second sheets may be coupled to face each other with an adhesive member therebetween. 
     In one or more embodiments, the adhesive member may include a double-sided tape. 
     In one or more embodiments, the adhesive portions of the first and second sheets are in surface contact with each other, without crossing each other. 
     In one or more embodiments, the ceramic sheet may include mica. 
     In one or more embodiments, the ceramic sheet may have a height less than a height of each of the battery cells, and an upper end portion and a lower end portion of each of the battery cells may be exposed from the ceramic sheet. 
     In one or more embodiments, the battery pack may further include a cell holder in which a plurality of rows of the battery cells surrounded by the ceramic sheet are arranged, and the upper end portion and the lower end portion of each of the battery cells exposed from the ceramic sheet is surrounded by the cell holder. 
     In one or more embodiments, the cell holder may include an upper holder in which the upper end portion of each of the battery cells is arranged, and a lower holder in which the lower end portion of each of the battery cells is arranged, and the upper holder and the lower holder may be arranged to face each other with the plurality of rows of the battery cells therebetween. 
     In one or more embodiments, the upper holder and the lower holder may include assembly ribs respectively surrounding the upper end portion and the lower end portion of each of the battery cells. 
     In one or more embodiments, the battery pack may further include a cell holder in which a plurality of rows of the battery cells surrounded by the ceramic sheet are arranged, and a first assembly portion that is arranged in the cell holder may be defined at opposite end portions of the ceramic sheet to extend in a row direction in which the battery cells are arranged. 
     In one or more embodiments, the first assembly portion may include first assembly portions of the first and second sheets coupled to face each other with the one row of the battery cells therebetween, and the first assembly portions of the first and second sheets may be coupled to face each other with an adhesive member therebetween. 
     In one or more embodiments, the cell holder may include a second assembly portion that defines a slot extending in a height direction of each of the battery cells to accommodate the first assembly portion at the opposite end portions in the row direction. 
     In one or more embodiments, the second assembly portion may include second assembly portions of the upper holder and the lower holder arranged to face each other with the plurality of rows of the battery cells therebetween. 
     In one or more embodiments, the second assembly portions of the upper holder and the lower holder may accommodate the first assembly portion together at positions apart from each other in the height direction of each of the battery cells. 
     In one or more embodiments, the cell holder may further include a third assembly portion that accommodates the adhesive portion of the ceramic sheet between the second assembly portions formed as a pair on side walls of the cell holder facing each other. 
     In one or more embodiments, the third assembly portion may be arranged as a pair in the row direction in which the battery cells are arranged between assembly ribs neighboring each other in which an upper end portion or a lower end portion of each of the battery cells is arranged. 
     In one or more embodiments, two other rows of the battery cells neighboring the one row of the battery cells may be arranged to face each other with the adhesive portion therebetween, at a position of the adhesive portion in the ceramic sheet extending and surrounding the one row of the battery cells. 
     According to one or more embodiments, a battery pack includes: battery cells arranged in a plurality of rows, the battery cells in a row being arranged apart from each other with a separation gap therebetween; and a ceramic sheet extending along at least any one row of the plurality of rows, the ceramic sheet extending in a zigzag shape through the separation gap to at least partially surround outer circumferential surfaces of neighboring battery cells of the battery cells at opposite sides. 
     In one or more embodiments, first and second battery cells of the battery cells are arranged neighboring each other with the separation gap therebetween in a row direction in which the battery cells are arranged, and the ceramic sheet may surround a side of an outer circumferential surface of the first battery cell, inflect through the separation gap between the first and second battery cells, and surround an opposite side of an outer circumferential surface of the second battery cell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of embodiments of the disclosure will be more apparent from the following description of some example embodiments taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of a battery pack according to an embodiment; 
         FIGS. 2 and 3  are a perspective view and a plan view, respectively, of a ceramic sheet extending and surrounding battery cells in a row illustrated in  FIG. 1 ; 
         FIG. 4  is an exploded perspective view of an assembled state of the battery cells in a row and the ceramic sheet illustrated in  FIGS. 2 and 3 ; 
         FIG. 5  is a plan view of an arrangement of ceramic sheets illustrated in  FIG. 1 , 
         FIG. 6  is a perspective view of a battery cell illustrated in  FIG. 1 ; 
         FIGS. 7 and 8  are plan views of a structure of an upper holder and a lower holder illustrated in  FIG. 1 ; 
         FIG. 9  is a plan view of a ceramic sheet extending and surrounding battery cells in a battery pack according to another aspect; and 
         FIG. 10  is a plan view of a structure of the ceramic sheet illustrated in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in further 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 disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     It is to be understood that the terms “comprise,” “include,” and “have” used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components. 
     Sizes of components in the drawings may be exaggerated for convenience of description. In other words, since the sizes and thicknesses of components in the drawings may be arbitrarily illustrated for convenience of description, the following embodiments are not limited thereto. 
     It is to be understood that when a layer, region, or component is referred to as being “connected to” another layer, region, or component, it may be directly connected to the other layer, region, or component or may be indirectly connected to the other layer, region, or component with one or more intervening layers, regions, or components interposed therebetween. For example, it is to be understood that when a layer, region, or component is referred to as being “electrically connected to” another layer, region, or component, it may be directly electrically connected to the other layer, region, or component or may be indirectly electrically connected to the other layer, region, or component with one or more intervening layers, regions, or components interposed therebetween. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It is to be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments of the inventive concept belong. It is to be further understood that terms, such as those defined in commonly-used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     A battery pack according to some example embodiments is described below with reference to the accompanying drawings. 
       FIG. 1  is an exploded perspective view of a battery pack according to an embodiment;  FIGS. 2 and 3  are a perspective view and a plan view, respectively, of a ceramic sheet extending and surrounding battery cells in a row illustrated in  FIG. 1 ; FIG. 
       4  is an exploded perspective view of an assembled state of the battery cells in a row and the ceramic sheet illustrated in  FIGS. 2 and 3 ;  FIG. 5  is a plan view of an arrangement of ceramic sheets illustrated in  FIG. 1 ;  FIG. 6  is a perspective view of a battery cell illustrated in  FIG. 1 ; and  FIGS. 7 and 8  are plan views of a structure of an upper holder and a lower holder illustrated in  FIG. 1 . 
     Referring to  FIGS. 1 to 3 , a battery pack according to an embodiment may include a plurality of battery cells  10  arranged in a row spaced apart from each other by a separation gap g, the battery cells  10  being provided in a plurality of rows, and a ceramic sheet  20  extending and surrounding the battery cells  10  of at least any one row, the ceramic sheet  20  including a non-adhesive portion  25  surrounding each of the battery cells  10  and an adhesive portion  21  extending across the separation gap g between the neighboring non-adhesive portions  25 . 
     Referring to  FIG. 6 , each of the battery cells  10  may include an upper end portion  10   a  and a lower end portion  10   b  in a height direction, and, in an embodiment, may be provided as a cylindrical battery cell including an outer circumferential surface  10   c  having a cylindrical shape between the upper end portion  10   a  and the lower end portion  10   b.  In an embodiment, first and second electrodes  11  and  12  having opposite polarities may be respectively formed at the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10 . For example, the first and second electrodes  11  and  12  of each of the battery cells  10  may respectively refer to the positive pole and the negative pole of each of the battery cells  10 . In an embodiment, the second electrode  12  may extend from the lower end portion  10   b  of each of the battery cells  10  to an edge of the upper end portion  10   a  of each of the battery cells  10  along the outer circumferential surface  10   c.  In other words, in an embodiment, the first and second electrodes  11  and  12  may be formed at positions separated from each other at the upper end portion  10   a  of each of the battery cells  10 . For example, the first electrode  11  may be formed at a central position of the upper end portion  10   a  of each of the battery cells  10 , and the second electrode  12  may be formed at an edge position of the upper end portion  10   a  of each of the battery cells  10 . In an embodiment, electrical connection between the battery cells  10  different from each other may be made through the upper end portion  10   a  of each of the battery cells  10  where the first and second electrodes  11  and  12  are formed together, and cooling of each of the battery cells  10  may be performed through the lower end portion  10   b  of each of the battery cells  10 . 
     Referring to  FIGS. 2 to 4 , the outer circumferential surface  10   c  of each of the battery cells  10  may be surrounded by the ceramic sheet  20 . In an embodiment, the ceramic sheet  20  may extend in a row direction Z 1  by surrounding (e.g., entirely surrounding) the outer circumferential surfaces  10   c  of a row of the battery cells  10 . The row direction Z 1  may refer to a direction in which a row of the battery cells  10  is arranged, and correspond to a lengthwise direction of the ceramic sheet  20 . 
     In an embodiment, the ceramic sheet  20  surrounding (e.g., entirely surrounding) the outer circumferential surfaces  10   c  of the battery cells  10  may mean that the ceramic sheet  20  seamlessly surrounds the outer circumferential surfaces  10   c  of the battery cells  10  along the outer circumferential surface  10   c  of each of the battery cells  10 . For example, the ceramic sheet  20  may be seamlessly disposed around each of the battery cells  10  in a circumferential direction of each of the battery cells  10 . In an embodiment, the ceramic sheet  20  may be in contact with the outer circumferential surface  10   c  of each of the battery cells  10 . For example, the ceramic sheet  20  may be in surface contact with the entire outer circumferential surface  10   c  of each of the battery cells  10  in the circumferential direction of each of the battery cells  10 , and the outer circumferential surface  10   c  of each of the battery cells  10  and the ceramic sheet  20  may be in seamless surface contact with each other. 
     As such, the ceramic sheet  20  may be in surface contact with the outer circumferential surface  10   c  of each of the battery cells  10  while surrounding (e.g., entirely surrounding) the outer circumferential surface  10   c  of each of the battery cells  10 . As the ceramic sheet  20  is in surface contact with the outer circumferential surface  10   c  of each of the battery cells  10 , without a space therebetween, flames may be prevented or substantially prevented from being propagated through an empty space between the ceramic sheet  20  and the outer circumferential surface  10   c  of each of the battery cells  10 . For example, if an empty space were formed between the ceramic sheet  20  and the outer circumferential surface  10   c  of each of the battery cells  10 , in an emergency situation such as fire or explosion of the battery cells  10 , the empty space formed in the height direction of the battery cells  10  may serve as a passage of flames erupted from the battery cells  10  and facilitate propagation of the flames. Further, in an embodiment, as the ceramic sheet  20  is in surface contact with the outer circumferential surface  10   c  of each of the battery cells  10 , thereby surrounding (e.g., entirely surrounding) the outer circumferential surface  10   c  of each of the battery cells  10 , an electrical short circuit due to humidity or moisture generated by dew condensation, for example, may be prevented or substantially prevented. For example, as the ceramic sheet  20  surrounds the outer circumferential surface  10   c  of each of the battery cells  10  to prevent or substantially prevent the humidity or moisture generated by dew condensation from directly contacting the battery cells  10 , the first and second electrodes  11  and  12  of the battery cells  10 , having opposite polarities, may be prevented or substantially prevented from being electrically short-circuited, or the battery cells  10  neighboring each other may be prevented or substantially prevented from being electrically short-circuited. 
     In an embodiment, the ceramic sheet  20  may include first and second sheets  20   a  and  20   b  which are coupled to face each other in a direction Z 2  crossing the row direction Z 1  with the battery cells  10  arranged in the row direction Z 1  therebetween. In this state, the non-adhesive portion  25  of the ceramic sheet  20  may include the non-adhesive portions  25  of the first and second sheets  20   a  and  20   b  which are coupled to face each other with a row of the battery cells  10  therebetween, and the adhesive portion  21  of the ceramic sheet  20  may include the adhesive portions  21  of the first and second sheets  20   a  and  20   b.    
     In other words, the first and second sheets  20   a  and  20   b  each may include the non-adhesive portion  25  surrounding each of the battery cells  10  and the adhesive portion  21  extending across the separation gap g between the neighboring non-adhesive portions  25 . As the non-adhesive portion  25  and the adhesive portion  21  that are alternately disposed are connected to each other, the first and second sheets  20   a  and  20   b  extending in the row direction Z 1  may be implemented. 
     The non-adhesive portion  25  may correspond to a portion surrounding the outer circumferential surface  10   c  of each of the battery cells  10  among the first and second sheets  20   a  and  20   b,  and may insulate and protect the battery cells  10  from a surrounding environment while surrounding the outer circumferential surface  10   c  of each of the battery cells  10 . For example, the battery cells  10  may be insulated or protected so as not to be directly affected by flames erupted from a neighboring one of the battery cells  10 . In an embodiment, while surrounding (e.g., entirely surrounding) the outer circumferential surface  10   c  of each of the battery cells  10 , the non-adhesive portion  25  may be in surface contact with the outer circumferential surface  10   c  of each of the battery cells  10 . As the non-adhesive portion  25  is in surface contact with the outer circumferential surface  10   c  of each of the battery cells  10  by surrounding (e.g., entirely surrounding) the outer circumferential surface  10   c  of each of the battery cells  10 , flames may be prevented or substantially prevented from being propagated through an empty space between the outer circumferential surface  10   c  of each of the battery cells  10  and the non-adhesive portion  25 , or humidity or moisture due to dew condensation, for example, may be prevented or substantially prevented from being introduced to the battery cells  10  through the empty space. In an embodiment, the non-adhesive portion  25  may be formed to be round to surround the outer circumferential surface  10   c  of each of the battery cells  10 , and may have an arc-shaped section following the outer circumferential surface  10   c  of each of the battery cells  10 . For example, the non-adhesive portion  25  may correspond to a curved portion of the first and second sheets  20   a  and  20   b,  which corresponds to the outer circumferential surface  10   c  of each of the battery cells  10 . In an embodiment, the non-adhesive portions  25  of the first and second sheets  20   a  and  20   b  each may surround half of the outer circumferential surface  10   c  of each of the battery cells  10  at respective opposite sides. For example, the non-adhesive portion  25  of the first sheet  20   a  may surround one half of the entire outer circumferential surface  10   c  of each of the battery cells  10 , and the non-adhesive portion  25  of the second sheet  20   b  may surround the other half of the entire outer circumferential surface  10   c  of each of the battery cells  10 . 
     The adhesive portion  21  may be provided between the non-adhesive portions  25  neighboring each other. For example, the adhesive portion  21  may extend across the separation gap g formed between the battery cells  10  neighboring each other, and connect the non-adhesive portions  25  neighboring each other by extending between the neighboring non-adhesive portions  25  surrounding each of the battery cells  10  across the separation gap g between the neighboring battery cells  10 , thereby forming the ceramic sheet  20  extending in the row direction Z 1 . 
     The adhesive portion  21 , which is a portion for coupling the first and second sheets  20   a  and  20   b  disposed to face each other with a row of the battery cells  10  therebetween, and the adhesive portions  21  of the first and second sheets  20   a  and  20   b  may be coupled to each other by being disposed to face each other. For example, an adhesive member  30  (see  FIG. 4 ) may be provided between the adhesive portions  21  of the first and second sheets  20   a  and  20   b.  In an embodiment, the adhesive member  30  may include a double-sided tape. In an embodiment, the adhesive portions  21  of the first and second sheets  20   a  and  20   b  are in surface contact with each other with the adhesive member  30  therebetween, without crossing each other. Unlike the above, when the adhesive portions  21  of the first and second sheets  20   a  and  20   b  are coupled to each other in the separation gap g by crossing each other, the non-adhesive portion  25  connected to the adhesive portion  21  may not closely contact the outer circumferential surface  10   c  of each of the battery cells  10  and may be unfastened from the outer circumferential surface  10   c  of each of the battery cells  10 . Accordingly, as an empty space may be formed between the non-adhesive portion  25  and the outer circumferential surface  10   c  of each of the battery cells  10 , propagation of flames or intrusion of humidity or moisture due to due condensation through the empty space may occur. In an embodiment, as the adhesive portions  21  of the first and second sheets  20   a  and  20   b  coupled to face each other with a row of the battery cells  10  therebetween are in surface contact with each other with the adhesive member  30  therebetween, the non-adhesive portion  25  connected to the adhesive portion  21  may closely contact the outer circumferential surface  10   c  of each of the battery cells  10  without being unfastened from the outer circumferential surface  10   c  of each of the battery cells  10 . 
     The adhesive portions  21  each may extend across the separation gap g between the battery cells  10  neighboring each other. In further detail, the adhesive portions  21  each may extend across the separation gap g in the row direction Z 1  of the battery cells  10 . In other words, the adhesive portion  21  may have a line-shaped section following a direction corresponding to the row direction Z 1  of the battery cells  10 . For example, the adhesive portion  21  may correspond to a non-curved portion or a flat surface portion of the first and second sheets  20   a  and  20   b.    
     The ceramic sheet  20  may be formed of a material having thermal insulation and insulating characteristics so as to reduce thermal runaway and prevent or substantially prevent electrical interference between the battery cells  10  neighboring each other by surrounding the outer circumferential surface  10   c  of each of the battery cells  10  arranged in the row direction Z 1 . The ceramic sheet  20  may be formed of a ceramic material exhibiting superior thermal insulation and insulating characteristics. In an embodiment, the ceramic sheet  20  may include mica. 
     In an embodiment, the ceramic sheet  20  may be formed to have a height H 2  that is less than a height H 1  of the battery cells  10  (H 2 &lt;H 1 ). Throughout the present specification, a height direction may refer to a height direction of the battery cells  10 , and the height direction of the battery cells  10  may correspond to a direction parallel to the height direction of the ceramic sheet  20 . 
     In an embodiment, the ceramic sheet  20  may have the height H 2  that is constant along the row direction Z 1 . For example, the height of the non-adhesive portion  25  surrounding each of the battery cells  10  and the height of the adhesive portion  21  extending across the separation gap g between the battery cells  10  may be equal to each other. As described below, a first assembly portion  24  may be formed at positions of both ends of the ceramic sheet  20 , and the height of the first assembly portion  24  may be equal to the heights of the non-adhesive portion  25  and the adhesive portion  21 . In other words, the ceramic sheet  20  may have the height H 2  that is generally uniform along a lengthwise direction. 
     In an embodiment, the height H 2  of the ceramic sheet  20  is less than the height H 1  of the battery cells  10 , and both end portions of the battery cells  10  in the height direction of the battery cells  10 , that is, the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10 , may be exposed from the ceramic sheet  20 . In this state, in connection with a relative arrangement between the battery cells  10  and the ceramic sheet  20  having different heights, the ceramic sheet  20  may surround most of the outer circumferential surface  10   c  of each of the battery cells  10  with respect to a central portion of the battery cells  10 , while exposing the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10 . For example, the ceramic sheet  20  may surround the battery cells  10  at a vertically central position with respect to the central portion, without being biased upward or downward in the height direction of the battery cells  10 . 
     Referring to  FIGS. 1, 7, and 8 , the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10 , which are exposed from the ceramic sheet  20 , that is, the non-adhesive portion  25  of the ceramic sheet  20 , may be covered by a cell holder  100 . In an embodiment, the cell holder  100  may include an upper holder  110  into which the upper end portion  10   a  of each of the battery cells  10  is inserted and a lower holder  120  into which the lower end portion  10   b  of each of the battery cells  10  is inserted. In an embodiment, assembly ribs R 1  and R 2 , into which the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10  are respectively inserted, may be formed in the upper holder  110  and the lower holder  120 , respectively. In this state, to avoid physical interference with the assembly ribs R 1  and R 2  of the upper holder  110  and the lower holder  120 , the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10 , around which the assembly ribs R 1  and 
     R 2  of the upper holder  110  and the lower holder  120  are respectively arranged, may be exposed from the ceramic sheet  20 . 
     Referring to  FIG. 5 , the battery cells  10  may be arranged in two or more rows, each of the battery cells  10  being surrounded by the ceramic sheet  20 . In this state, the battery cells  10  in the neighboring rows may be densely disposed to be arranged between the battery cells  10  in the opposite rows, and, thus, in the ceramic sheet  20  extending and surrounding a row of the battery cells  10 , the battery cells  10  in the neighboring row may be disposed at the position of the adhesive portion  21  extending across the separation gap g. In other words, the separation gap g, where the battery cells  10  are not located, is provided in a row, and, as the battery cells  10  in other neighboring rows are disposed through the separation gap g where the battery cells  10  are not located, the battery cells  10  may be densely disposed and dead space may be reduced such that a battery pack that may be miniaturized may be provided. 
     In further detail, in the ceramic sheet  20  extending and surrounding a row of the battery cells  10 , the battery cells  10  in two other rows neighboring the row of the battery cells  10  may be disposed at a position of the adhesive portion  21  extending across the separation gap g with the adhesive portion  21  therebetween, to face each other in the direction Z 2  crossing the row direction Z 1 . As such, as the battery cells  10  in the neighboring rows are densely disposed facing each other, a cooling path F may be defined between the outer circumferential surfaces  10   c  of three battery cells  10  neighboring one another. In an embodiment, along the outer circumferential surface  10   c  of one of the battery cells  10 , one cooling path F may be defined for each of three neighboring battery cells  10  including the battery cell  10 , and, thus, a total of six cooling paths F may be defined along the outer circumferential surface  10   c  of the battery cell  10 . As illustrated in  FIGS. 1 and 7 , in the cell holder  100 , that is, at least one of the upper holder  110  and the lower holder  120 , for example, the upper holder  110 , a cooling hole H that is fluidly connected to the cooling path F may be formed at a position corresponding to the cooling path F. 
     Referring to  FIGS. 1 to 4 , a row of the battery cells  10  having the outer circumferential surfaces  10   c  surrounded by the ceramic sheet  20  may be bound as one group of the battery cells  10 . As such, the battery cells  10  bound as a unit of rows may be assembled by being inserted into the cell holder  100 . In an embodiment, the cell holder  100  may bind, as one pack unit, a plurality of rows of the battery cells  10 , each row of the battery cells  10  being bound by the ceramic sheet  20 , and a plurality of rows of the battery cells  10  structurally bound by the cell holder  100  may form one battery pack. A row of the battery cells  10  being bound by the ceramic sheet  20  in units of rows may mean that, as the ceramic sheet  20  surrounds a row of the battery cells  10 , the battery cells  10  in one row may be distinguished from the battery cells  10  in another row, but may not necessarily mean that a row of the battery cells  10  forms an aggregate physically and firmly bound through the ceramic sheet  20 . As the ceramic sheet  20  surrounds a row of the battery cells  10  through the non-adhesive portion  25 , the ceramic sheet  20  may not have a direct binding, for example, mutual adhesion, with the outer circumferential surface  10   c  of each of the battery cells  10 . As such, a row of the battery cells  10  may not be firmly confined through a direct binding with the ceramic sheet  20 . 
     In the following description, an assembly structure between the ceramic sheet  20  and the cell holder  100  to bind a row of the battery cells  10  is further described. 
     Referring to  FIGS. 1 to 4, 7, and 8 , the ceramic sheet  20  may include the first assembly portion  24  formed at both end positions in the row direction Z 1  or the lengthwise direction of the ceramic sheet  20 . In an embodiment, the first assembly portion  24  of the ceramic sheet  20  may be assembled by being inserted into second assembly portions A 1  and A 2  of the cell holder  100 . The second assembly portions A 1  and A 2  of the cell holder  100  are described below in further detail. In an embodiment, the first assembly portion  24  of the ceramic sheet  20  may extend in the row direction Z 1  or the lengthwise direction of the ceramic sheet  20 , to be parallel to the adhesive portion  21  of the ceramic sheet  20 , and may define both ends of the ceramic sheet  20  in the lengthwise direction of the ceramic sheet  20 . 
     For example, the first assembly portion  24  of the ceramic sheet  20  may include the first assembly portions  24  of the first and second sheets  20   a  and  20   b  formed at both end positions of the first and second sheets  20   a  and  20   b  coupled to face each other with a row of the battery cells  10  therebetween. The first assembly portions  24  of the first and second sheets  20   a  and  20   b  may extend parallel to each other in the row direction Z 1 , and the first assembly portions  24  of the first and second sheets  20   a  and  20   b  may be coupled to face each other with the adhesive member  30  therebetween. Although the first assembly portions  24  of the first and second sheets  20   a  and  20   b  have a function similar to the function of the adhesive portion  21  because the first assembly portions  24  allow the first and second sheets  20   a  and  20   b  to be coupled to each other, while the first assembly portions  24  of the first and second sheets  20   a  and  20   b  are defined at both end positions of the first and second sheets  20   a  and  20   b,  the adhesive portions  21  of the first and second sheets  20   a  and  20   b  may be formed at a different position of the separation gap g between the battery cells  10  in the first and second sheets  20   a  and  20   b.    
     Referring to  FIGS. 7 and 8 , the cell holder  100  may include the second assembly portions A 1  and A 2  for assembling the ceramic sheet  20  that binds a row of the battery cells  10 . In further detail, the second assembly portions A 1  and A 2  into which the first assembly portion  24  of the ceramic sheet  20  are inserted may be formed at both end portions of the cell holder  100  in the row direction Z 1  or the lengthwise direction of the ceramic sheet  20 . The second assembly portions A 1  and A 2  may provide an assembly structure for inserting the first assembly portion  24  of the ceramic sheet  20  at both end positions of the ceramic sheet  20 . In an embodiment, the second assembly portions A 1  and A 2  each may have a slot extending in a height direction to allow the first assembly portion  24  defined at both end portions of the ceramic sheet  20  to be inserted therein. In an embodiment, the second assembly portions A 1  and A 2  may include a pair of guide ribs disposed to face each other. 
     Referring to  FIGS. 1, 7, and 8 , the cell holder  100  may include the upper holder  110  and the lower holder  120  that are assembled to face each other in the height direction, and the second assembly portions A 1  and A 2  may include the second assembly portions A 1  and A 2  respectively formed in the upper holder  110  and the lower holder  120 . For example, the upper holder  110  and the lower holder  120  may be assembled to face each other with a plurality of rows of the battery cells  10  bound by the ceramic sheet  20  therebetween, and may be assembled to face each other with a plurality of rows of the battery cells  10  therebetween such that the first assembly portion  24  of the ceramic sheet  20  is inserted into the second assembly portions A 1  and A 2  respectively formed in the upper holder  110  and the lower holder  120 . In this state, the second assembly portions A 1  and A 2  respectively formed in the upper holder  110  and the lower holder  120  may be spaced apart from each other. For example, the second assembly portions A 1  and A 2  of the upper holder  110  and the lower holder  120  assembled to each other may accommodate the first assembly portion  24  of the ceramic sheet  20  at different heights. In further detail, the second assembly portion A 1  of the upper holder  110  may support an upper position of the first assembly portion  24  of the ceramic sheet  20 , and the second assembly portion A 2  of the lower holder  120  may support a lower position of the first assembly portion  24  of the ceramic sheet  20 . In an embodiment, the second assembly portion A 1  of the upper holder  110  may be formed at a corner position where a main body  115  and a side wall  111  of the upper holder  110  meet, and the second assembly portion A 2  of the lower holder  120  may be formed at a corner position where a main body  125  and a side wall  121  of the lower holder  120  meet. In an embodiment, the main bodies  115  and  125  of the upper holder  110  and the lower holder  120  may be a plate-shaped member where the assembly ribs R 1  and R 2 , into which the battery cells  10  are inserted, are formed. 
     The cell holder  100  may include the side walls  111  and  121  that extend along the edge of the main bodies  115  and  125  of the cell holder  100 . The side walls  111  and  121  of the cell holder  100  may form an accommodation space for accommodating the battery cells  10 , and may provide a housing to protect the battery cells  10  from an external environment by surrounding the accommodation space. For example, the assembly ribs R 1  and R 2 , into which the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10  are inserted, may be arranged at inner positions of the cell holder  100  surrounded by the side walls  111  and  121  of the cell holder  100 . As described above, the second assembly portions A 1  and A 2 , into which the first assembly portion  24  of the ceramic sheet  20  are inserted, may be formed at both end portions of the cell holder  100 . In an embodiment, the second assembly portions A 1  and A 2  may be respectively formed on the side walls  111  and  121  of the cell holder  100 . In an embodiment, the second assembly portions A 1  and A 2  each may be formed as a pair on the side walls  111  and  121  facing each other in the row direction Z 1  or the lengthwise direction of the ceramic sheet  20 , and may be formed as a pair at both end positions of the cell holder  100  facing each other to accommodate the first assembly portion  24  defined at both end positions of the ceramic sheet  20 . The second assembly portions A 1  and A 2  each may include a plurality of second assembly portions along the side walls  111  and  121  corresponding to the ceramic sheet  20  surrounding a row of the battery cells  10 . 
     In an embodiment, the first assembly portion  24  of the ceramic sheet  20  may be inserted into the second assembly portions A 1  and A 2  respectively formed in the side walls  111  and  121  of the cell holder  100 , and as the first assembly portion  24  of the ceramic sheet  20  is inserted into the second assembly portions A 1  and A 2  of the cell holder  100 , the ceramic sheet  20  surrounding a row of the battery cells  10  may be guided to an assembly position. 
     Referring to  FIG. 8 , in an embodiment, the lower holder  120  may include a third assembly portion A 3  formed on the main body  125  of the lower holder  120  into which the adhesive portion  21  of the ceramic sheet  20  is inserted, in addition to the second assembly portion A 2  formed on the side wall  121  of the lower holder  120  into which the first assembly portion  124  of the ceramic sheet  20  is inserted. In an embodiment, the third assembly portion A 3  of the lower holder  120  may define a slit into which the adhesive portion  21  of the ceramic sheet  20  is inserted. To this end, the third assembly portion A 3  may include a pair of guide ribs disposed to face each other. The third assembly portion A 3  may be formed between a pair of the second assembly portions A 2  formed on the side wall  121  of the lower holder  120 , and, in an embodiment, may be formed as a pair arranged in the row direction Z 1  corresponding to each adhesive portion  21  formed for each separation gap g between the battery cells  10  neighboring each other. As the adhesive portion  21  is formed where the battery cells  10  are not located and corresponding to the separation gap g between the battery cells  10  neighboring each other, the third assembly portion A 3  into which the adhesive portion  21  is inserted may be formed at a position between the assembly ribs R 2  into which the battery cells  10  are inserted, and may be formed in a pair arranged in the row direction Z 1  between the assembly ribs R 2  neighboring each other. The second assembly portion A 2  and the third assembly portion A 3  may be arranged in the row direction Z 1 . 
     When the ceramic sheet  20  surrounding a row of the battery cells  10  is assembled in the lower holder  120 , the first assembly portion  24  defined at both end positions of the ceramic sheet  20  may be inserted into the second assembly portion A 2  of the lower holder  120 , and the adhesive portion  21  formed between the first assembly portions  24  of the ceramic sheet  20  may be inserted into the third assembly portion A 3  of the lower holder  120 . 
     Although it is not illustrated, in an embodiment, similar to the third assembly portion A 3  of the lower holder  120 , another third assembly portion (not shown) may be formed in the upper holder  110 . In this state, the third assembly portion of the upper holder  110  may be formed between the second assembly portions A 1  formed on a pair of the side walls  111  of the upper holder  110  facing each other, and, in an embodiment, may include a pair of third assembly portions (not shown) arranged in the row direction 
     Z 1  at a position between the assembly ribs R 1  neighboring each other, corresponding to each adhesive portion  21  formed in the ceramic sheet  20 . 
     The cell holder  100  may include the assembly ribs R 1  and R 2  surrounding the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10  in the height direction of the battery cells  10 . The cell holder  100  may include the upper holder  110  into which the upper end portion  10   a  of each of the battery cells  10  is inserted and the lower holder  120  into which the lower end portion  10   b  of each of the battery cells  10  is inserted, and the upper holder  110  and the lower holder  120  may respectively include the assembly ribs R 1  and R 2  into which the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10  are respectively inserted. 
     For example, the assembly ribs R 1  and R 2  each may have a circular shape to surround the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10 , and openings OP 1  and OP 2  for exposing at least parts of the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10  may be respectively formed at inner positions surrounded by the assembly ribs R 1  and R 2 . In an embodiment, as the opening OP 1  formed in the upper holder  110  exposes the upper end portion  10   a  of each of the battery cells  10 , an electrical connection may be formed through the upper end portion  10   a  of each of the battery cells  10 . As the opening OP 2  formed in the lower holder  120  exposes the lower end portion  10   b  of each of the battery cells  10 , cooling of the battery cells  10  may be performed through the lower end portion  10   b  of each of the battery cells  10 . In an embodiment, a cooling plate  150  (see  FIG. 1 ) may be disposed under the lower holder  120 , and the battery cells  10  may be cooled through heat exchange between the lower end portion  10   b  of each of the battery cells  10  exposed through the opening OP 2  of the lower holder  120  and the cooling plate  150 . The assembly ribs R 1  and R 2  may surround the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10  exposed from the ceramic sheet  20  that surrounds the outer circumferential surface  10   c  of each of the battery cells  10 . In other words, the assembly ribs R 1  and R 2  of the upper holder  110  and the lower holder  120  may surround the upper end portion  10   a  and the lower end portion  10   b  of each of the battery cells  10  exposed from the ceramic sheet  20 . 
     In an embodiment, the cooling plate  150  (see  FIG. 1 ) for cooling of the battery cells  10  may be disposed under the lower holder  120 . The cooling plate  150  may include a metal plate exhibiting superior thermal conductivity, for example, an aluminum plate. In an embodiment, a flow path (not shown) for accommodating a flow of a coolant may be formed in the cooling plate  150 . 
     In the following description, a battery pack according to another aspect is described. 
       FIG. 9  is a plan view of a ceramic sheet extending and surrounding battery cells in a battery pack according to another aspect; and  FIG. 10  is a plan view of a structure of the ceramic sheet illustrated in  FIG. 9 . 
     Referring to  FIGS. 9 and 10 , the battery pack may include the battery cells  10  including a plurality of rows of battery cells  10  disposed with the separation gap g therebetween, and a ceramic sheet  20 ′ extending along at least any one row of the battery cells  10  in a zigzag shape through the separation gap g by surrounding the outer circumferential surfaces  10   c  at opposite sides of the battery cells  10  neighboring each other. 
     The ceramic sheet  20 ′ may extend in the row direction Z 1  by at least partially surrounding a row of the battery cells  10 . For example, the ceramic sheet  20 ′ may extend in a curved shape to surround the outer circumferential surfaces  10   c  of the battery cells  10  neighboring each other with the separation gap g therebetween. In an embodiment, the ceramic sheet  20 ′ may surround the outer circumferential surfaces  10   c  of the battery cells  10  neighboring each other at the opposite sides with the separation gap g therebetween. For example, when first and second battery cells  101  and  102  of the battery cells  10  are arranged in the row direction Z 1  neighboring each other with the separation gap g therebetween, the ceramic sheet  20 ′ may surround one side of the outer circumferential surface  10   c  of the first battery cell  101 , inflect or pass through the separation gap g between the first and second battery cells  101  and  102  so as to define an inflection point C, and surround the other side of the outer circumferential surface  10   c  of the second battery cell  102 . The ceramic sheet  20 ′ may extend through the separation gap g between the first and second battery cells  101  and  102  by surrounding each of the one side of the outer circumferential surface  10   c  of the first battery cell  101  and the other side of the outer circumferential surface  10   c  of the second battery cell  102 , not surrounding the entire outer circumferential surfaces  10   c  of the first and second battery cells  101  and  102 , inflect or pass through the separation gap g so as to define the inflection point C, and extend from the one side of the outer circumferential surface  10   c  of the first battery cell  101  to the other side of the outer circumferential surface  10   c  of the second battery cell  102 . The terms “one side” and “the other side” may refer to the opposite sides in the direction Z 2  crossing the row direction Z 1  in which the battery cells  10  are arranged, for example, the opposites sides in a direction perpendicular to the row direction Z 1 . 
     The ceramic sheet  20 ′ inflecting or passing through the separation gap g between the first and second battery cells  101  and  102  so as to define the inflection point C may mean that the ceramic sheet  20 ′ surrounds the outer circumferential surfaces  10   c  of the first and second battery cells  101  and  102  that are opposite to each other. In other words, of the ceramic sheet  20 ′, a portion surrounding the outer circumferential surface  10   c  of the first battery cell  101  and a portion surrounding the outer circumferential surface  10   c  of the second battery cell  102  each may have a center or a circle center at the opposite side with respect to the ceramic sheet  20 . 
     Of the ceramic sheet  20 ′, the portion surrounding the outer circumferential surfaces  10   c  of the first and second battery cells  101  and  102  may include a curved surface to surround the outer circumferential surfaces  10   c  of the first and second battery cells  101  and  102 . In an embodiment, of the ceramic sheet  20 ′, a portion extending from the one side of the outer circumferential surface  10   c  of the first battery cell  101  to the other side of the outer circumferential surface  10   c  of the second battery cell  102  through the separation gap g between the first and second battery cells  101  and  102  may include therein a non-curved surface or planar surface at least at the position of the inflection point C. Unlike the ceramic sheet  20  illustrated in  FIG. 3 , the ceramic sheet  20 ′ illustrated in  FIG. 10  may include a relatively large amount of curved surface, for example, may include a curved surface except around the inflection point C in the separation gap g. 
     The ceramic sheet  20 ′ extends along a row of the battery cells  10  and surrounds (e.g., partially surrounds) the outer circumferential surface  10   c  of each of the battery cells  10  belonging to the row. In other words, the ceramic sheet  20 ′ may extend in a zigzag shape across the separation gap g between the battery cells  10  neighboring each other and surround (e.g., partially surround) the outer circumferential surface  10   c  of each of the battery cells  10 , and extend along a row of the battery cells  10  surrounding (e.g., partially surrounding) the outer circumferential surfaces  10   c  of all battery cells  10  belonging to the row. 
     The ceramic sheet  20 ′ may surround (e.g., partially surround) the outer circumferential surfaces  10   c  of a row of the battery cells  10  and contact at least part of the outer circumferential surfaces  10   c  of a row of the battery cells  10 . For example, in the first and second battery cells  101  and  102  neighboring each other with the separation gap g therebetween, the ceramic sheet  20 ′ may contact the one side of the outer circumferential surface  10   c  of the first battery cell  101  and also contact the other side of the outer circumferential surface  10   c  of the second battery cell  102 . 
     Unlike the embodiment illustrated in  FIG. 3 , in the present embodiment, the ceramic sheet  20 ′ extending along a row of the battery cells  10  may be formed as one sheet. In other words, although the ceramic sheet  20  illustrated in  FIG. 3  includes the first and second sheets  20   a  and  20   b  coupled to face each other with a row of the battery cells  10  therebetween, the ceramic sheet  20 ′ according to the present embodiment may include a single sheet extending in a zigzag shape along a row of the battery cells  10 . 
     In the present embodiment, as the outer circumferential surfaces  10   c  of a row of the battery cells  10  are surrounded (e.g., partially surrounded) by the ceramic sheet  20 ′, the battery cells  10  may be thermally insulated and protected in an emergency situation such as fire or explosion, and humidity or moisture due to dew condensation, for example, may be prevented or substantially prevented from intruding into the battery cells  10 . Also, as the ceramic sheet  20 ′ having a simple structure including a single sheet is employed, material costs and manufacturing costs of the ceramic sheet  20 ′ may be reduced and a manufacturing process may be simplified. 
     According to embodiments of the present disclosure, in a battery pack in which a plurality of battery cells are arranged, by employing a ceramic sheet surrounding the outer circumferential surfaces of the battery cells, the battery cells may be thermally insulated and protected in an emergency situation such as fire or explosion, propagation of flames erupted from the battery cells may be reduced, and an electrical short circuit due to humidity or moisture generated by dew condensation, for example may be prevented or substantially prevented. 
     It is to be understood that embodiments described herein should be considered in a descriptive sense 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 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 disclosure as set forth by the following claims.