Abstract:
A lithium ion cell includes a housing and positive and negative terminals. The housing includes top and bottom surfaces. The housing includes first, second, third, and fourth side surfaces, perpendicular to the top and bottom surfaces. A cell isolator includes first and second portions made of an electrically non-conductive material. The first portion includes first, second, and third wall members. The first wall member directly contacts the first side surface. The second wall member directly contacts a portion of the second side surface. The third wall member directly contacts a portion of the third side surface. The second portion includes fourth, fifth, and sixth wall members. The fourth wall member directly contacts the fourth side surface. The fifth wall member directly contacts portions of the second side surface and the second wall member. The sixth wall directly contacts portions of the third side surface and the third wall member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/644,097, filed on May 8, 2012. The disclosure of the above application is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates to battery modules for vehicles and more particularly to isolators for prismatic cells. 
       BACKGROUND 
       [0003]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0004]    Hybrid electric vehicles (HEVs), plug-in HEVs, and other types of electric vehicles (EVs) use multiple propulsion systems to provide motive power. The propulsion systems may include electric or battery powered systems that receive power from one or more battery modules. A battery module may include, for example, one or more banks of high-voltage cells (or batteries), such as lithium ion cells. The cells are volumetric building blocks of the battery module. 
       SUMMARY 
       [0005]    A lithium ion cell includes a housing and positive and negative terminals. The housing includes top and bottom surfaces. The housing includes first, second, third, and fourth side surfaces, perpendicular to the top and bottom surfaces. A cell isolator includes first and second portions made of an electrically non-conductive material. The first portion includes first, second, and third wall members. The first wall member directly contacts the first side surface. The second wall member directly contacts a portion of the second side surface. The third wall member directly contacts a portion of the third side surface. The second portion includes fourth, fifth, and sixth wall members. The fourth wall member directly contacts the fourth side surface. The fifth wall member directly contacts portions of the second side surface and the second wall member. The sixth wall directly contacts portions of the third side surface and the third wall member. 
         [0006]    In further features, the first and second portions are formed from Formex. 
         [0007]    In other features, the first portion further includes a seventh wall member that directly contacts the bottom surface. 
         [0008]    In still other features, the seventh wall member is perpendicular to the first, second, and third wall members. 
         [0009]    In further features, the first portion further includes an eighth wall member that directly contacts a portion of the top surface. 
         [0010]    In still further features, the eighth wall member is perpendicular to the first, second, and third wall members. 
         [0011]    In other features, the second portion further includes a ninth wall member that directly contacts a second portion of the top surface. 
         [0012]    In still other features, the ninth wall member further directly contacts a portion of the eighth wall member. 
         [0013]    In further features, the second portion further includes a tenth wall member that directly contacts the seventh wall member. 
         [0014]    In still further features, the tenth wall member is perpendicular to the fourth, fifth, and sixth wall members. 
         [0015]    In other features, the ninth wall member is perpendicular to the fourth, fifth, and sixth wall members. 
         [0016]    In still other features, the first portion is fixed to the lithium ion cell by an interference fit. 
         [0017]    In further features, the second portion is fixed to the lithium ion cell and to the first portion by an interference fit. 
         [0018]    In still further features, an adhesive fixes the first portion of the cell isolator to the lithium ion cell. 
         [0019]    In other features, a second adhesive fixes the second portion of the cell isolator to the first portion of the cell isolator. 
         [0020]    In still other features, the second portion of the cell isolator is welded to the first portion of the cell isolator. 
         [0021]    In further features, thicknesses of the first and second portions are greater than one-half of a predetermined maximum particle dimension. 
         [0022]    In still further features, the housing of the lithium ion cell is electrically connected to the positive terminal. 
         [0023]    In other features, the housing of the lithium ion cell is electrically connected to the negative terminal. 
         [0024]    In other features, the housing of the lithium ion cell is not electrically connected to the positive terminal or the negative terminal. 
         [0025]    Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0027]      FIG. 1  is a perspective view of a prismatic cell; 
           [0028]      FIG. 2  is a perspective view of the prismatic cell with example portions of a cell isolator; and 
           [0029]      FIGS. 3A and 3B  include front and back perspective views of the prismatic cell and the cell isolator. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    In the following description, a cell isolator for prismatic cells of a battery module is disclosed. The cell isolator is shown and described as an example, and one or more characteristics of the cell isolator may be modified. For example, the cell isolator may be modified to accommodate cells having a different size and/or shape. Other examples of how the cell isolator can be modified are discussed further below. One cell isolator is provided for each cell of a battery module. The cell isolators aid in electrically isolating cells from each other, from other system components, and from external contact, for example, during battery module assembly. 
         [0031]    In  FIG. 1 , a perspective view of a prismatic cell (hereafter “cell”)  100  is shown. The cell  100  may include, for example, a rectangular shaped, lithium-ion cell with a housing (or can)  104 . As an example, the housing  104  may be formed of aluminum or another (electrically) conductive material. While only a rectangular shaped cell is shown and discussed, the cell  100  may be another shape. 
         [0032]    The cell  100  further includes a pair of terminals  108  that extend from the cell  100 . The terminals  108  may include, for example, cylindrical terminals, threaded terminals, flat terminals, or another suitable type of terminal. The cell  100  may be charged and electrical energy may be drawn from the cell  100  via the terminals  108 . A positive one of the terminals  108  may be connected to the (electrically conductive) housing  104 . In this manner, a reference potential (voltage) of the housing  104  may be approximately equal to the reference potential at the positive one of the terminals  108 . In various implementations, a negative one of the terminals  108  may be connected to the housing  104  or neither of the terminals  108  may be connected to the housing  104 . 
         [0033]    The housing  104  includes a top surface  116  and a bottom surface  120 . The housing  104  has a height  124 , a length  128 , and a width  132 . The housing  104  includes first and second surfaces  136  and  140  and includes third and fourth surfaces  144  and  148 . Dimensions of the height  124 , the length  128 , the width  132 , and the surfaces  136 - 148  are shown as examples only, and the dimensions of one or more of the height  124 , the length  128 , the width  132 , and the surfaces  136 - 148  may be different. 
         [0034]    The terminals  108  of the cell  100  and the terminals of one or more other cells can be connected in series, in parallel, or combinations thereof to form a battery module. One or more battery modules may be electrically connected in series, in parallel, or combinations thereof to form a battery pack, which may also be referred to as a cassette. One or more battery packs may be electrically connected in series, in parallel, or combinations thereof, and so on. 
         [0035]    Because the housings of each cell may be electrically conductive and at approximately the same reference potential as their positive terminals, respectively, the housing of each cell is electrically insulated/isolated.  FIG. 2  includes an example perspective view of the cell  100  with a first portion  204  of a cell isolator and a second portion  208  of the cell isolator.  FIG. 3  includes front and back perspective views of the cell  100  within the cell isolator. While the cell isolator is shown and will be discussed as being a two-piece construction, the cell isolator may be constructed of two or more individual isolator portions. 
         [0036]    Referring now to  FIGS. 2 and 3 , the first portion  204  of the cell isolator is formed to the shape of a first portion of the housing  104 . The second portion  208  of the cell isolator is formed to a second portion of the housing  104  and a portion of the first portion  204 . For example, as shown in  FIG. 2 , the first portion  204  of the cell isolator may be formed such that inner surfaces  212  of the first portion  204  will abut the first surface  136 , the third surface  144 , and the fourth surface  148  of the housing  104 . The second portion  208  of the cell isolator may be formed such that inner surfaces  216  of the second portion  208  will abut the second surface  140  of the housing  104  and exterior surfaces  220  of the first portion  204  of the cell isolator. 
         [0037]    The first and second portions  204  and  208  of the cell isolator are formed from an electrically non-conductive material. The first and second portions  204  and  208  of the cell isolator may be formed from polypropelene, Formex, Formex GK. For example only, the first and second portions  204  and  208  may be formed from Formex GK-5, Formex GK-10, Formex GK-17, for Formex GK with another suitable thickness. In various implementations, the first and second portions  204  and  208  may be formed of another suitable material that has at least a predetermined dielectric strength and that satisfies at least a predetermined flame classification (e.g., UL 94V-0), such as another type of polypropelene (PPE). The first and second portions  204  and  208  may be formed to their respective shapes, for example, via thermoforming (e.g., pressure or vacuum), injection molding, blow molding, or rotational molding. 
         [0038]    A thickness of each of the first and second portions  204  and  208  satisfies the relationship: 
         [0000]    
       
         
           
             
               T 
               ≥ 
               
                 MaxParticleSize 
                 2 
               
             
             , 
           
         
       
     
         [0000]    where T is the thickness (e.g., in millimeters or fractions of an inch) of each of the first and second portions  204  and  208  and MaxParticleSize is a maximum dimension (e.g., in millimeters or fractions of an inch) of particles that may be present between two portions of two adjacent cell isolators in, for example, a battery module. 
         [0039]    The thickness being greater than or equal to one half of the maximum dimension may account for the presence of two portions of two cell isolators being disposed between two adjacent cells. Thus, if a particle having the maximum dimension penetrates the two portions of two cell isolators disposed between the two adjacent cells, at least one of the two portions will still electrically isolate the housings of the two adjacent cells. The thickness being greater than one half of the maximum dimension may account for any compression of cell isolators when used in a battery module. Thickness of the first and second portions  204  and  208  may be selected to satisfy the above relationship, given the maximum dimension for a particular application. 
         [0040]    Multiple portion cell isolators may be manufactured more easily and therefore be less expensive than, for example, single piece cell isolators and modular frames with multiple, electrically isolated compartments for cells. Additionally, multiple portion cell isolators may be less expensive than other types of cell isolators, such as electrically insulative epoxies that can be sprayed onto the housing of each cell. 
         [0041]    The first portion  204  and/or the second portion  208  may be formed with a bottom member. For example, the first portion  204  of the cell isolator may be formed with a bottom member  224  that will abut the bottom surface  120  of the cell  100 . The second portion  208  of the cell isolator may be formed with a bottom member  228  that will abut a bottom surface of the bottom member  224 . In various implementations, only one of the first and second portions  204  and  208  may be formed with a bottom member. In various implementations, neither of the first and second portions  204  and  208  may be formed with a bottom member. Neither of the first and second portions  204  and  208  of the cell isolator may be formed with a bottom member, for example, for implementation of a cooling assembly that draws heat away from the cell  100  via contact with the bottom surface  120  of the cell  100 . 
         [0042]    The first portion  204  and the second portion  208  may be formed with lip members. For example, the first portion  204  of the cell isolator may be formed with a lip member  232 . An inner surface  236  of the lip member  232  may abut a first portion of the top surface  116  of the cell  100 . The second portion  208  of the cell isolator may be formed with a lip member  240 . An inner surface  244  of the lip member  240  may abut a second portion of the top surface  116  of the cell  100  and a portion of an outer surface of the lip member  232 . 
         [0043]    The first portion  204  of the cell isolator may be fixed to the cell  100 . For example only, the first portion  204  may be fixed to the cell  100  via an adhesive. In various implementations, the first portion  204  may be fixed to the cell  100  via an interference fit (e.g., a press fit or a friction fit). In the case of an interference fit, an adhesive may or may not be used. 
         [0044]    The second portion  208  of the cell isolator may be fixed to the first portion  204  of the cell isolator. The second portion  208  of the cell isolator may be fixed to the first portion  204  of the cell isolator after the first portion  204  of the cell isolator has been fixed to the cell  100 . The second portion  208  of the cell isolator may be fixed to the first portion  204  of the cell isolator at locations where the first and second portions  204  and  208  overlap. The second portion  208  may be fixed to the first portion  204 , for example, by welding the first and second portions  204  and  208  (e.g., by laser welding, ultrasonic welding, hot plate welding, etc.), via an adhesive, or in another suitable manner. The second portion  208  may also be fixed to the cell  100 , for example, via an adhesive. 
         [0045]    In various implementations, the first and second portions  204  and  208  may be fixed together prior to introduction of the cell  100 , and the lip members  232  and  240  may be omitted. The first and second portions  204  and  208  of the cell isolator may be fixed together prior to introduction of the cell  100 , for example, by welding the first and second portions  204  and  208  (e.g., by laser welding, ultrasonic welding, hot plate welding, etc.), via an adhesive, or in another suitable manner. The cell  100  may be inserted into the cell isolator via an interference fit (e.g., a press fit or a friction fit) between the cell isolator formed by the first and second portions  204  and  208  and the cell  100 . 
         [0046]    The cell  100  and the cell isolator can be combined with one or more other cells and one or more other cell isolators in a battery module. The cell isolators electrically isolate the housings of the cells from each other. 
         [0047]    The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. 
         [0048]    As used herein, the term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. The term module may include memory (shared, dedicated, or group) that stores code executed by the processor.