Patent Publication Number: US-2021194061-A1

Title: Electrochemical cell including electrode isolation frame

Description:
FIELD 
     The disclosure relates generally to an electrochemical cell having a single electrode pair arranged in a stacked configuration, and particularly to a plastic frame integrated into the single electrode pair cell which isolates the electrodes from each other. 
     BACKGROUND 
     Battery packs provide power for various technologies ranging from portable electronics to renewable power systems and environmentally friendly vehicles. For example, hybrid electric vehicles (HEV) use a battery pack and an electric motor in conjunction with a combustion engine to increase fuel efficiency. Battery packs are formed of a plurality of battery modules, where each battery module includes several electrochemical cells. Within the battery modules, the cells are arranged in two or three dimensional arrays and are electrically connected in series or in parallel. Likewise, the battery modules within a battery pack are electrically connected in series or in parallel. 
     SUMMARY 
     In some aspects, a battery module includes a plurality of electrically connected electrochemical cells. In some aspects, an electrochemical cell includes a single positive electrode, a single negative electrode, and a separator that is disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode and the separator are arranged in a stacked configuration. An electrically-insulating frame is disposed between portions of the positive electrode and the negative electrode so as to isolate the positive electrode and the negative electrode. The frame has an outer peripheral edge that protrudes outward relative to a peripheral edge of the positive electrode and the negative electrode. In addition, a sealing material layer resides between the positive electrode and the negative electrode. The sealing material layer includes a first sealing portion and a second sealing portion. The first sealing portion is disposed between the frame and an inward facing side of the positive electrode, and the second sealing portion is disposed between the frame and an inward facing side of the negative electrode. The frame is secured relative to the positive electrode and the negative electrode by the sealing material layer. 
     The electrochemical cell may include one or more of the following features: The first sealing portion and the second sealing portion reside entirely within an outer peripheral edge of both the positive electrode and the negative electrode. An opening is provided in the frame between an inner peripheral edge of the frame and an outer peripheral edge of the frame. The frame has a non-uniform cross-sectional thickness. The frame has a T-shaped cross-sectional shape including a first frame portion disposed between the positive electrode and the negative electrode that has a first thickness, and a second frame portion disposed outside a periphery of the positive electrode and the negative electrode that has a second thickness. The second thickness is greater than the first thickness. The frame has a uniform thickness and includes a detent that is shaped and dimensioned to receive a sensor lead. The frame is formed of a film that is electrically isolating. The frame includes reinforcing elements. The frame is thermally conductive. The frame includes features that aid the attachment of sense leads and cell monitoring equipment thereto. 
     In some aspects, a single electrode pair electrochemical cell includes an anode foil substrate having a first active material pasted on an inward facing side, a cathode foil substrate having a second active material pasted on an inward facing side, a separator sheet disposed between the anode and the cathode, a sealing material such as a hot melt sealant or pressure sensitive adhesive that is disposed along the perimeter of the foils, and an electrolyte sealed between the substrates by the sealing material. The substrates act as an impermeable layer, enclosure and electrodes. Thus, as used herein, the terms “substrate” and “electrode” are interchangeable. The sealing material layer between the electrodes extends around their perimeter to secure the electrodes in place and prevent electrical shorts between the electrodes. In addition, a thin, electrically insulating film frame is embedded into the sealing material layer such that it extends out beyond the perimeter of the electrodes. This frame adds additional isolation beyond that of the adhesive layer by increasing the distance the electrode plates must deform before they can short to the other plate, and shields the electrodes from being shorted by splinters and metal flakes. 
     This can be compared to some single electrode pair cells in which the adhesive layer extends only to the perimeter of the electrodes and does not defend against creep and deformation of the electrodes, nor against debris or cut edge fragments crossing the gap and shorting the cell. 
     The details of one or more features, aspects, implementations, and advantages of this disclosure are set forth in the accompanying drawings, the detailed description, and the claims below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a battery pack including three battery modules, each battery module including four single electrode pair cells shown in cross-section. 
         FIG. 2  is a cross-sectional view of one of the single electrode pair cell of  FIG. 1 , illustrating a thin, electrically insulating film frame embedded into a sealing material layer. 
         FIG. 3  is a cross-sectional view of a battery module including an alternative embodiment of the single electrode pair cells. 
         FIG. 4  is a cross-sectional view of one of the alternative embodiment single electrode pair cells of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of a battery module including another alternative embodiment of the single electrode pair cells. 
         FIG. 6  is a cross-sectional view of one of the alternative embodiment single electrode pair cell of  FIG. 5 . 
         FIG. 7  is a cross-sectional view of a battery module including another alternative embodiment of the single electrode pair cells. 
         FIG. 8  is a cross-sectional view of one of the alternative embodiment single electrode pair cell of  FIG. 7 . 
         FIG. 9  is a cross-sectional view of a battery module including another alternative embodiment of the single electrode pair cells. 
         FIG. 10  is a cross-sectional view of one of the alternative embodiment single electrode pair cell of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , a battery module  6  is a power generation and storage device that includes electrochemical cells  20  that are electrically interconnected and stored in an organized manner within a battery module housing  8 . The cells  20  can be arranged within the module housing  8 , for example by stacking. The module housing  8  includes a positive (+) bus bar  52 , a negative (−) bus bar  54 . Within the battery module housing  8 , cells  20  are electrically connected in series or in parallel. Several battery modules  6  may be disposed in a battery pack housing  4  to form a battery pack  2 , and within the battery pack housing  4 , the battery modules  6  are electrically connected in series or in parallel. Each cell  20  has a single electrode pair arranged in a stacked configuration, and an electrically insulating frame  60  integrated into the single electrode pair cell that isolates the electrodes  22 ,  26  of the cell  20  from each other, as discussed in detail below. 
     The single layer cell  20  is a lithium ion cell that includes a single positive electrode  22 , a single separator  30  and a single negative electrode  26  that are arranged in a layered conductor-separator-conductor configuration. The positive electrode  22  includes first foil substrate formed of a first electrically-conducive material and having a first active material layer  24  disposed on an inward facing side. For example, the positive electrode  22  may be formed of an aluminum foil and include a lithiated metal oxide active material layer  24  disposed on the inward facing side. The first active material layer  24  is spaced apart from the peripheral edge  23  of the positive electrode  22 . As a result, a first clear lane  25  is provided along the positive electrode inward facing side along the positive electrode peripheral edge  23 . The first clear lane  25  is free of the first active material layer  24 . The negative electrode  26  includes second foil substrate formed of a second electrically-conductive material and having a second active material layer  28  disposed on an inward facing side. For example, the negative electrode  26  may be formed of a copper foil and include a graphite active material layer  28  disposed on the inward facing side. The second active material layer  28  is spaced apart from the peripheral edge  27  of the negative electrode  26 . As a result, a second clear lane  29  is provided along the negative electrode inward facing side along the negative electrode peripheral edge  27 . The second clear lane  29  is free of the active material layer  28 . 
     The cell  20  includes the separator  30  disposed between the positive and negative electrodes  22 ,  26 . In particular, the separator  30  is sized and dimensioned to reside between the active material layers  24 ,  28  of the positive and negative electrodes, and may only partially protrude between the first and second clear lanes  25 ,  29 . The separator  30  is a permeable membrane that functions to keep the positive and negative electrodes  22 ,  26  apart to prevent electrical short circuits while also allowing passage of ionic charge carriers provided in the electrolyte and that are needed to close the circuit during the passage of current within the cell  20 . The separator  30  is formed of an electrically insulating material such as, for example, a trilayer polypropylene-polyethylene-polypropylene membrane. 
     A sealing material layer  40  such as a hot melt sealant or pressure sensitive adhesive is disposed along the perimeter  23 ,  27  of the positive and negative electrodes  22 ,  26 , and an electrolyte is sealed between the positive and negative electrodes  22 ,  26  by the sealing material layer  40 . The sealing material layer  40  is disposed between the substrates which form the positive and negative electrodes  22 ,  26  within the clear lanes  25 ,  29  and extends around the perimeter of the electrodes  22 ,  26 . In the illustrated embodiment, the sealing material layer  40  includes a first sealing portion  44  and a second sealing portion  46 . The first sealing portion  44  is disposed between the frame  60  and an inward facing side of the positive electrode  22 , and the second sealing portion  46  is disposed between the frame  60  and an inward facing side of the negative electrode  26 . The frame  60  is secured relative to the positive electrode  22  and the negative electrode  26  by the sealing material portions  44 ,  46 , and the sealing material portions  44 ,  46  prevent leakage of electrolyte from the cell  20 . 
     Since the cell  20  is formed of a stacked arrangement of the positive and negative electrodes  22 ,  26  and separator  30 , the cell  20  is very thin relative to some conventional cells. As a non-limiting example of cell thickness, in some embodiments, the cell  20  may have a thickness corresponding to a distance between the positive and negative electrode outer surfaces in a range of 0.5 mm to 1.5 mm. In other embodiments, the cell  20  may have a thickness in a range of 0.2 mm to 0.5 mm. 
     The cell  20  also includes the thin, electrically insulating film frame  60  of uniform thickness that is embedded into the sealing material layer  40 . The frame  60  has an inner peripheral edge  68  that surrounds the separator  30  and an outer peripheral edge  66 . The inner peripheral edge  68  is sandwiched between the first sealing portion  44  of the sealing material layer  40  and the second sealing portion  46  of the sealing material layer  40 , whereby a seal exists between the positive electrode inward facing side and the frame  60 , and also between the negative electrode inward facing side and the frame  60 . The outer peripheral edge  66  of the frame  60  extends out beyond the peripheral edges  23 ,  27  of the positive and negative electrodes  22 ,  26 . The frame  60  electrically isolates the peripheral edge of the positive electrode  22  from the peripheral edge of the negative electrode  26 , thus preventing electrical short circuiting between the positive and negative electrodes  22 ,  26 . 
     In some embodiments, the frame  60  is formed of a flexible film that is electrically isolating. 
     In some embodiments, the frame  60  is formed of plastic. For example, the frame  60  may be formed of a thin plastic film. 
     In some embodiments, the frame  60  is formed of a thin rigid film that is electrically isolating, where the film is sufficiently thin that the frame outer peripheral edge  66  is not coplanar with the frame inner peripheral edge  68 , and resides below it due to the effect of gravity on the outwardly extending portions of the frame  60 . 
     In some embodiments, the frame  60  is formed of a film that is thermally conductive as well as electrically isolating, such that heat can be transferred out of the cell via the perimeter of the frame. 
     It is understood, however, that the frame  60  is not limited to these constructions. For example, in some embodiments, a non-plastic, electrically non-conductive material may be used to provide the thin film that forms the frame  60 . For another example, in some embodiments, an electrically non-conductive material that is not a film may be used to form the frame  60 . 
     Referring to  FIGS. 3 and 4 , the battery module  6  may include an alternative embodiment cell  120 . The cell  120  is similar to the cell  20  described above with respect to  FIG. 2 , and common reference numbers are used to refer to common elements. The cell  120  differs from the cell  20  of  FIG. 2  in that the cell  120  includes an alternative embodiment frame  160  that is formed of a thin film that is rigid and is reinforced to help stabilize the cell and act as a reinforcing structure to aid cell handling. The reinforcement may result from structural features such as providing the film with ribs or embedded rods (not shown), or may result from use of particular materials to form the film for example, a fiber-reinforced material. In the illustrated embodiment, the frame  160  includes reinforcing fibers  162  that extend in parallel to the seal seam. 
     Referring to  FIGS. 5 and 6 , the battery module  6  may include another alternative embodiment cell  220 . The cell  220  is similar to the cell  20  described above with respect to  FIG. 2 , and common reference numbers are used to refer to common elements. The cell  220  differs from the cell  20  of  FIG. 2  in that the cell  220  includes an alternative embodiment frame  260 . The frame  260  is formed of a film that contains features that aid the attachment of sense leads and cell monitoring equipment to the cell  220 . Such features may include, but are not limited to, through openings  264 , raised surface features (not shown), depressed surface features (not shown), textures (not shown) and/or materials. In the illustrated embodiment, the through openings  264  are provided outside a peripheral edge of the positive and negative electrodes  22 ,  26 , and each through opening  264  is spaced apart from the adjacent through opening  264 . 
     Alternatively, the through openings  264  may be used to secure the cell  220  within the module housing  8 . In the illustrated embodiment, rods  269  extend through the through openings of the cells  220  stacked within the battery module  6 , and are fixed at each end to the module housing  8 . The rods  269  maintain the cells  220  in a stacked configuration, and prevent relative motion between adjacent cells  220  or between the cells  220  and the module housing  8 . In some embodiments, the rods  269  may cooperate with the module housing  8  to apply a compression force to the stacked cells  220  stored therein, ensuring a reliable series electrical connection between adjacent cells  220 . 
     Referring to  FIGS. 7 and 8 , the battery module  6  may include another alternative embodiment cell  320 . The cell  320  is similar to the cell  20  described above with respect to  FIG. 2 , and common reference numbers are used to refer to common elements. The cell  320  differs from the cell  20  of  FIG. 2  in that the cell  320  includes sensor leads  350  and an alternative embodiment frame  360  that is configured to accommodate the sensor leads  350 . The sensor leads  350  are electrically conductive and are electrically connected to one of the electrodes  22 ,  26  of the cell  320 . For example, in the illustrated embodiment, one end of the sensor lead  350  is electrically connected to an inner surface of the negative electrode  26 , and an opposed end (not shown) is electrically connected to a battery management system (BMS, not shown). The sensor leads  350  are configured, for example, to allow detection of cell voltage, temperature, etc., by the BMS. 
     The frame  360  includes a detent  362  that receives the sensor lead  350  and allows the sensor lead  350  to exit one side of the cell  320 . The frame  360  is of uniform thickness, and the detent  362  is an offset portion of the frame that is shaped and dimensioned to conform to the shape and dimensions of the sensor lead  350 . 
     The frame  360  is secured relative to the positive electrode  22  and the negative electrode  26  by the first and second sealing material portions  44 ,  46 , and the sealing material portions  44 ,  46  prevent leakage of electrolyte from the cell  20 . The first sealing portion  44  is disposed between the frame  360  and an inward facing side of the positive electrode  22 , and the second sealing portion  46  is disposed between the frame  360  and an inward facing side of the sensor lead  350 . 
     Referring to  FIGS. 9 and 10 , the battery module  6  may include yet another alternative embodiment cell  420 . The cell  420  is similar to the cell  20  described above with respect to  FIG. 2 , and common reference numbers are used to refer to common elements. The cell  420  differs from the cell  20  of  FIG. 2  in that the cell  420  includes another alternative embodiment frame  460 . The frame  460  has a non-uniform cross-sectional thickness. In particular, the frame  460  has a T-shaped cross-sectional shape including a first frame portion  461  disposed between the positive electrode  22  and the negative electrode  26  and including the frame inner peripheral edge  68  that has a first thickness, and a second frame portion  462  disposed outside a periphery of the positive electrode  22  and the negative electrode  26  and including the frame outer peripheral edge  466  that has a second thickness, where the second thickness is greater than the first thickness. In the illustrated embodiment, the second frame portion  462  has a thickness that corresponds to the overall thickness of the cell  420 . By providing a frame  460  having a non-uniform thickness, it is possible to provide a cell  420  that is very thin since the first frame portion  461  that is disposed within the cell  420  is also very thin. In addition, since the external portion of the frame  460 , e.g., the frame second portion  462 , is relatively thick, the frame  460  can be used more reliably to fasten the cell  420  to the module housing  8 . To that end, through openings (not shown) such as described above with respect to  FIGS. 5 and 6  may be provided in the frame second portion  462 . 
     The embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling with the sprit and scope of this disclosure.