Abstract:
A battery pack is provided where the cell can becomes the battery enclosure. An electrode assembly is deposited within a can. A recess area is created above the electrode assembly by either extending the sides of the can beyond the electrode assembly or by attaching a tubular header to the can. An optional, insulating, plastic cup is then placed within the recess area. A printed circuit board that includes battery safety circuitry is then placed within the recess area and coupled to positive and negative electrical terminals on the end of the can. A sealing cap is then placed atop the cup to seal the printed circuit board within the overall package. The sealing cap includes electrical connections for coupling to the printed circuit board. The resulting sealed package offers a compact and robust, yet safe, energy storage and delivery system.

Description:
BACKGROUND  
       [0001]     1. Technical Field  
         [0002]     This invention relates generally rechargeable battery packs, and more particularly to compact, robust battery packs for small electronic devices.  
         [0003]     2. Background Art  
         [0004]     Toray&#39;s electronic devices are becoming smaller and smaller. For example, a cellular telephone, which used to be the size of a man&#39;s shoe, now fits easily within a shirt pocket. Similarly, personal computing devices, which used to be as big as a metropolitan telephone book, now fit easily within the palm of the hand.  
         [0005]     As the size of these portable devices gets smaller, so too must their energy sources become smaller. Nearly all portable electronic devices rely upon rechargeable batteries for their portability. While some may think that a rechargeable battery pack is simply an electrochemical cell in a box, nothing could be farther from the truth. Rechargeable battery packs are complex devices that include mechanical interconnects, safety, charging and fuel gauging circuits, and electromechanical devices as well. Many times, battery pack size becomes the limiting factor in the amount of size reduction of the overall electronic device.  
         [0006]     Battery pack designers have attempted various size reduction techniques in the past. One popular way to reduce the overall battery pack size is by embedding the battery in the electronic device and removing the exterior housing. For example, in some handheld computers, the battery is sealed within the device and is not replaceable by the user. In these designs, engineers often opt not to include a plastic housing about the cell. They simply wrap a label about the battery. This solution, however, fails to address what happens to the mechanical, electromechanical and circuitry components, some of which are left flopping about the battery. Further, many electronic device manufacturers want users to be able to replace batteries. Label wrapped batteries may not facilitate this replacement capability.  
         [0007]     There is thus a need for an improved, compact, self-contained, rechargeable battery pack. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  illustrates a battery pack assembly in accordance with the invention.  
         [0009]      FIG. 2  illustrates an alternate embodiment of a battery pack assembly in accordance with the invention.  
         [0010]      FIG. 3  illustrates a sectional view of one embodiment of a sealing cup in accordance with the invention.  
         [0011]      FIG. 4  illustrates a sectional view of one embodiment of a battery pack in accordance with the invention.  
         [0012]      FIG. 5  illustrates a completed battery pack in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     A preferred embodiment of the invention is now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” 
         [0014]     This invention provides a self-contained, reliable energy storage device that includes an internal battery safety circuit. An electrode assembly, which includes an anode, cathode and electrolyte, and forms a rechargeable cell, is sealed in a can. A positive and negative electrical terminal, coupled to the cathode and anode, respectively, are located at one end of the can.  
         [0015]     A recess area, which may be created in a variety of ways, exists about the positive and negative electrical terminals and extends distally from the end of the can. A printed circuit board assembly, which may include battery safety circuitry, charging circuitry, identification circuitry and/or fuel gauging circuitry is positioned within the recess area. The printed circuit board assembly is electrically coupled to the positive and negative electrical terminals.  
         [0016]     A cap is then positioned over the recess area, thereby sealing the printed circuit board assembly within the recess area. The cap includes at least two electrical terminals, which are in turn coupled to the printed circuit board. The result is a self contained, reliable and easy to manufacture rechargeable battery pack.  
         [0017]     Turning now to  FIG. 1 , illustrated therein is one preferred embodiment of a battery pack in accordance with the invention. The components of the battery assembly are shown in an exploded, perspective view.  
         [0018]     A rechargeable cell is disposed within a sealed can  100 . The rechargeable cell comprises a cathode and an anode, with an electrolyte disposed about the anode and cathode. The anode and cathode may be layered together and wrapped about each other to form a “jelly roll” structure as is known in the art. Such an anode and cathode structure is taught in commonly assigned U.S. Pat. No. 6,574,111, entitled “Impact resistant rechargeable battery cell with crumple zone”, which is incorporated herein by reference for all purposes. Alternately, the anode and cathode may be constructed in a solid, prismatic structure with a polymer gel electrolyte as is taught in U.S. Pat. No. 5,837,015, entitled “Method of making a multilayered gel electrolyte bonded rechargeable electrochemical cell”, which is incorporated herein by reference for all purposes.  
         [0019]     The sealed package or can  100  is preferably metal or alloys, although it will be clear to those of ordinary skill in the art having the benefit of this disclosure that other materials, including plastic, may equally be used. Metal is one preferred material due to its rugged durability. Additionally, the can  100  for polymer cells may be constructed by wrapping metallic materials like foils about the polymer cell. The can  100  is sealed by a first end piece  117  so that the electrodes and electrolyte are completely contained within the can.  
         [0020]     The can  100  generally has a second end  119  and sides  118  that extend from the second end  119 . Such a can  100  is typically manufactured by an extrusion process, although some manufacturers may choose to weld or otherwise attach the second end  119 , or “bottom”, to the sides  118  of the can  100 . The can is then sealed with the first end  117 , generally with a crimp seal or weld.  
         [0021]     The first end  117  of the can has a positive, or “cathode”, electrical terminal  104  and a negative, or “anode”, electrical terminal  105  attached thereto. The positive terminal  104  and negative terminal  105  are coupled to the cathode and anode of the electrode assembly, respectively. While two terminals  104 , 105  are shown in this illustrative embodiment, some cell manufacturers will include only one terminal (affectionately known as the “button”) and will allow a portion of the can  100 , like the first end  117 , to serve as the second terminal. For example, the “button” may be the positive terminal  104 , and the first end  117  will serve as the negative terminal (or vice versa). Additionally, in other embodiments, either the positive or negative terminals  104 , 105  may be at alternate locations on the can  100 . For example, one or both of the terminals may not be disposed on the first end  117  of the can  100 , but rather on one of the side  118  of the can  100 . In such an embodiment, insulated tabs may be employed to couple the terminals  104 , 105  with the tubular header  102 .  
         [0022]     A tubular header  102  extends distally from the first end  117  so as to form a recess area  103 . The tubular header  102  may simply be an extension of the sides beyond the first end  117 , or it may be an open ended tube having a cross section roughly equivalent to that of the can  100  that is attached after the cell assembly is completed. The tubular header  102  may be of a like material with that of the can  100 , or it may be of a different material.  
         [0023]     For example, in one embodiment, the can  100  has a can length  121  that is greater than the length of the electrode assembly disposed within the can, i.e. the “electrode length”. Once the electrode assembly is seated within the can  100 , the sides  118  extend beyond the electrode assembly due to their extended length. The first end  117  may then be coupled to and positioned atop the electrode assembly, within the sides  118 , and affixed with either a crimp connection or weld along line  120 . In so doing, the recess cavity  103  is created with a tubular header  102  that is essentially the sides  118  of the can  100  extending beyond the first end  117 .  
         [0024]     In another embodiment, the tubular header  102  may actually be a separate piece of open-ended can material that is attached after the rechargeable cell is assembled. In this embodiment, the rechargeable cell would consist of the sides  118 , which are closed by the first end  117  and the second end  119 . A separate tubular header  102  is then attached to the end  117  of the can  100  that includes the positive and negative electrodes  104 , 105 . The tubular header  102  is preferably coupled to the can by welding along line  120 , although other connection mechanisms, including glue, snaps or friction connection may also be employed.  
         [0025]     An optional cup  106  is then inserted into the recess area  103  within the tubular header  102 . The cup  106  is preferably manufactured from plastic due to its electrically insulating properties, although other materials may also be used. The cup  106  has apertures  107 , 108  that provide access to the positive and negative electrical terminals  104 , 105 . The cup  106  may be permanently affixed to the within the tubular header  102  by a mechanism selected from the group consisting of press fit connections, snap fit connections, glued connections, and welded connections.  
         [0026]     A printed circuit board  109  is then placed within the plastic cup  106 . The printed circuit board  109  includes battery safety circuitry  112 , but may include charging circuitry, identification and recognition circuitry, anti-counterfeiting or authentication circuitry, and/or fuel gauging circuitry as well. One example of a suitable battery safety circuit  112  is taught in commonly assigned U.S. Pat. No. 5,569,550, entitled “Battery Pack having Over Voltage and Under Voltage Protection”, which is incorporated herein by reference for all purposes.  
         [0027]     The printed circuit board  109  also includes electrically conductive pads  110 , 111  and traces for interconnecting the various circuit components. Alternatively, contact blocks may be substituted for the conductive pads  110 , 111 . The positive and negative electrical terminals  104 , 105  are coupled to pads  110 , 111  of the of the printed circuit board  109 . This coupling may be done by flexible metal tabs that are welded to the terminals  104 , 105  and soldered or welded to the pads  110 , 111 . It will be clear to one of ordinary skill in the art having the benefit of this disclosure that other conductors, in addition to flexible metal tabs, may be used to couple the terminals  104 , 105  to the pads  110 , 111 . For example, wires, flexible circuit substrates or conductive adhesives may equally be used.  
         [0028]     A cover  113 , or “sealing cap” or “can cap”, is then placed atop the cup  106  and tubular header  102  so as to seal the printed circuit board within the overall package. The sealing cap  113  may be metal, which may be welded to the tubular header  102 . Alternatively, the sealing cap  113  may be plastic and may be affixed to the cup  106  by a mechanism selected from the group consisting of press fit connections, snap fit connections, crimped connections, screwed or riveted connections, glue connections, adhesive connections (including tapes, epoxies, etc.), heat staked connections, sonically staked connections and ultrasonically welded connections. In one embodiment, when the sealing cap is affixed to the plastic cup, the printed circuit board is encapsulated so as to prevent liquid intrusion into the battery. The completed battery assembly is shown in  FIG. 5 .  
         [0029]     The cover  113  includes a positive, or cathode, terminal  114  and a negative, or anode, terminal  115 . These terminals  114 , 115  may be insert molded into the, cover  113 . The positive terminal  114  and negative terminal  115  may be coupled to the printed circuit board, the positive and negative can terminals  104 , 105  or a combination of both. A combination may occur where the printed circuit board  109  is coupled serially between the positive cell terminal  104  and the positive cover terminal  114  for instance, while the negative connections from printed circuit board  109  to negative cell terminal  105  and negative cover terminal  115  to negative cell terminal  105  are in parallel to a single node. Additional terminals  116  may be provided to couple to components like thermistors and memory or identification devices that may be included with the safety circuit  112 .  
         [0030]     Turning now to  FIG. 2 , illustrated therein is an alternate embodiment of the invention. In this embodiment, the can  200  having sides  201 , at least one opening  207  and an end  202  is constructed as described above. The electrode assembly and electrolyte (not shown) are then inserted into the can  200 . A cup  203  having an opening  206  a mating connection  204  for coupling to the sides  201  of the can  200  is then positioned atop the electrode assembly within the can, so as to form a sealing member atop the electrode assembly. A cross section of the cup  203  is shown in  FIG. 3 . The cup  203  may be constructed such that the electrical connections  205  are integral with the cup  203 . These electrical connections  205  are then coupled to the electrode assembly prior to coupling the cup  203  to the can  200 .  
         [0031]     A battery safety circuit, as described with respect to  FIG. 1 , may then be placed within the cup  203  and coupled to the electrical terminals  205 , and thus to the electrode assembly within the can  200 . A can cap, as described with respect to  FIG. 1 , is then positioned atop the cup  203 , the can cap including at least one electrical contact. The electrical contact on the can cap is electrically coupled to the at least one battery safety circuit. The can cap closes the opening  206  of the cup  203 .  
         [0032]     Turning now to  FIG. 4 , illustrated therein is a sectional view of the completed battery assembly. From this view, the electrode assembly  400 , seated in the can  100 , is visible. The first end  117 , which seals in the electrolyte, is coupled to the can  100 . The cup  106 , with the printed circuit board and safety circuit  109  disposed therein, can be seen above the first end  117 . The cap  117 , which when coupled to the cup  106 , seals the cup so as to prevent the electrolyte from contacting the battery safety circuit assembly, is also visible, as is the tubular header  102 .  
         [0033]     While the preferred embodiments of the invention have been illustrated and described, it is clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the following claims.