Abstract:
This invention describes a type of secondary batteries. The bottom of the secondary battery is installed with a safety device that includes a conductive current interrupting device (CID) and a support component. In installing the safety device on the bottoms of the batteries, the batteries&#39; manufacturing processes are simplified, their production costs are lowered, and the space utilization inside of the battery is increased. In addition, the battery manufacturing process can use sealed or unsealed methods.

Description:
CROSS REFERENCE 
       [0001]    This application claims priority from a Chinese patent application entitled “Secondary Battery” filed on Dec. 30, 2005 having a Chinese Application No. 200510121325.6. Said application is incorporated herein by reference. 
       FIELD OF INVENTION 
       [0002]    This invention relates to a type of secondary batteries, and, in particular to a type of secondary batteries that have a safety device installed in the battery. 
       BACKGROUND 
       [0003]    As a type of high capacity power supply, secondary batteries are increasingly and widely used in a variety of fields. When ordinary secondary batteries are used under unusual circumstances such as when machines are being pressed, bounced around, subjected to high temperatures, self short-circuited, or over-charged, the inside of the batteries may accumulate a large amount of heat in a matter of split seconds. Internal pressure may increase sharply. In more serious situations, the battery may emit smoke, catch on fire, or explode. These kinds of safety-related accidents could even endanger personal safety and create huge economic losses. As a result, people have increasingly demanded safer secondary batteries. 
         [0004]    In general, traditional secondary batteries do not have special safety features installed. They depend on external protection circuits to achieve the protection function. This limits the batteries from being applied a greater range of use. In order to satisfy users&#39; demands for safer secondary batteries, some designers carved out or applied pressure to definite a concave-shaped groove that forms a weak area. The groove&#39;s resistance to pressure is weaker when compared to other areas on the surface of the battery. When the battery&#39;s internal pressures increases under unusual circumstances, the groove would be damaged first, preventing the battery from catching on fire, exploding, or incurring other safety issues. However, the manufacturing of the groove becomes increasingly difficult due to limitations in the surface material of the battery and due to increased difficult the manufacturing process of the groove. It is also difficult to ensure that the groove&#39;s thickness is even. Furthermore, it is extremely difficult to ensure that the thickness of the battery groove corresponds with the design specification for bearing maximum internal pressure from the battery, such that when the internal pressure of the battery reaches this design specification, the groove would break. 
         [0005]    The cylindrical-shaped lithium ion batteries that are currently commercially available commonly have installed between the positive electrode tab and the positive lead to the positive terminal a circuit interrupt device (“CID”) or a PTC (positive temperature sensitive component). When the battery is in an abnormal condition, internal pressure increases inside the battery (rising temperature) and the safety device is activated, thus preventing any dangerous situations from occurring. However, these two designs have the following drawbacks: 
         [0006]    1. When the battery is in the process of discharging a large amount of electrical current, its temperature will clearly rise and will activate the positive temperature sensitive component and prevent the battery from functioning properly. Thus, its usage in high-rate batteries is limited. 
         [0007]    2. The batteries available now have the CID installed on the positive terminal end (the open end of the battery shell case). This kind of component relies on pressure to activate and therefore it needs to be sealed completely. Thus, the battery can only be manufactured using the sealing method. The end result is that the internal pressure is greater and this can be an unsafe factor. 
         [0008]    3. Since the batteries available now have CID installed on the positive terminal end (the open end of the battery shell case), insulation must be used to separate the positive and negative electrodes in order to prevent short-circuiting. Furthermore, these kinds of installation must have supporting components within the battery. Otherwise, the battery cannot be used properly. This leaves only the pressing method for sealing the opening. Batteries sealed using this method can lead to various problems such as liquid leakage, environmental pollution, and decreased battery life. 
       SUMMARY 
       [0009]    The technical problem to be solved by the current invention is: to provide a type of secondary battery having a safety device installed on the bottom of the battery. 
         [0010]    In order to resolve this technical problem, the present invention provides a type of secondary battery, including a cylindrical-shaped shell with a battery core and electrolyte sealed in the shell; at one end of the battery shell is a sealed end and at the other end, after filling the battery core and electrolyte, it is sealed by an end cover. The battery core includes a positive electrode plate, a negative electrode plate, a positive tab, and a negative tab. Between the surface of the bottom inside of the shell and the battery core, there is a safety device. Between the safety device and the battery core, there is installed a CID; the safety device includes a conductive circuit interrupt component (“CID”) and a non-conductive support component having an appropriate height. The CID includes a support piece and a solder attachment position. The support piece supports the CID on the support component, and the solder attachment position of the CID of the safety device is soldered on the surface of the inner bottom of the battery shell. One of the positive electrode tab or the negative electrode tab of the battery core is electrically connected to the support piece of the CID of the safety device. There is insulation material between the described positive and negative electrode plates, and between the tabs having the same polarity as the described battery shell. 
         [0011]    In the second battery of the present invention, the conductive CID of the safety device is supported on the support component, and the solder attachment position of the CID is soldered to the surface of the inner bottom of the shell. When the internal pressure of the battery rises, the CID body is stretched. When the stretching exceeds certain limit, the CID body would break, or the solder attachment position of the CID would break with the solder structure at the bottom of the shell, causing the CID to separate from the bottom of the battery shell, achieving the current interrupt function, avoiding the internal pressure from rising further and causing a safety problem. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0012]    The following figures illustrate the embodiments of the invention. 
           [0013]      FIG. 1  illustrates a cross sectional view of a type of embodiment of the secondary battery of this invention. 
           [0014]      FIG. 2  is a 3-D illustration of the safety device  16  of  FIG. 1 . 
           [0015]      FIG. 3  is a top-view illustration of the safety device  16  of  FIG. 1 . 
           [0016]      FIG. 4  is a cross sectional view A-A of  FIG. 2 . 
           [0017]      FIG. 5  illustrates a cross sectional view of the safety device of another type of embodiment of the secondary battery of this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    The secondary battery of this invention, the safety device is fixed between the bottom of the cylindrical battery shell and the battery core. The support piece of the CID of the safety device supports the CID on the support component of the safety device. The solder attachment position of the CID of the safety device is soldered to the surface of the inner bottom of the cylindrical battery shell. Installing of the safety device on the bottom of the battery does not limit the manufacturing process of the battery, where the manufacturing process may adopt either a sealing process for the opening or an open-ended process for the opening. Not limited by the sealing method of choice, the compress seal method or other sealing method, e.g. weld-seal, may be used to avoid leaking electrolyte. 
         [0019]    The support method for the supporting piece to support the CID of the safety device on the support component can be by securing the support piece onto the support component and thereby supporting the CID on the support component. It can also be by securing the support piece between the support component and the non-conducting piece, thereby supporting the CID onto the support component. The preferred support method is to secure the support piece between the support component and the non-conducting piece. 
         [0020]    The CID device can employ an upside-down L-shaped hook piece (the cross-section of the longitudinal portion is the upside-down L-shape). In this situation, the horizontal portion of the upside-down L-shaped CID can be the support piece and can be squeezed tight between the support component and the non-conductive piece. The free end of the vertical portion of the upside-down L-shaped CID can be the soldering position soldering on to the surface of the inner bottom of the battery shell. Or, the CID device can employ an L-shaped hook piece (the cross-section of the longitudinal portion is the L-shape). In this situation, the free end of the lengthwise portion of the L-shaped CID can be the support piece, where the solder attachment position is placed on the horizontal portion of the L shaped CID. With respect to upside-down L shaped or L shaped CID, the solder attachment position is on the surface of the inner bottom of the battery shell, preferably near the middle of the surface of the inner bottom of the battery shell. 
         [0021]    The safety device can place many L-shaped or upside down L-shaped CIDs or a mix combination of L-shaped or upside-down L-shaped CIDs. 
         [0022]    The CID can employ a groove (or slot) structure, where the exterior of the bottom of the groove structure of the CID is used as solder attachment position being soldered on the surface of the inner bottom of the battery shell. The support piece can be the groove wall of the groove structure of the CID or an extension arm extended from the groove wall. The preferred extension arm of the groove-shaped CID is the top portion of the groove wall turned directed to outside of the groove to a horizontal position. 
         [0023]    The CID can also use a funnel-shaped structure where the support piece is a cantilever extending out from the funnel body of the CID, and the solder attachment position is at the exterior surface of the bottom of the funnel-shaped CID. The preferred embodiment for the cantilevel of the funnel-shaped CID is the top portion of the funnel wall extending toward exterior of the funnel to a horizontal position. 
         [0024]    For a CID using the funnel-shaped structure, through-holes can be made on the funnel wall of the body of the funnel-shaped CID, the purpose being so that when the internal pressure raises in the battery, the pressure is also applied to the inner bottom surface of the battery shell which is soldered to the solder attachment position of the CID. The inner bottom surface of the battery shell can have a stretching effect on the CID. In this manner, the funnel wall of the CID is stretched due to increase in the internal pressure of the battery. At the same time, the inner bottom surface of the battery shell which is soldered to the solder attachment position of the CID can have an even greater stretching effect on the CID; the CID would have an increased sensitivity to increases in the internal pressure of the battery, thereby achieving a good circuit-cutoff and safety protection effect. 
         [0025]    The thickness of the support piece is not less than 0.2 mm, and the range of the thickness of the solder attachment position of the CID is 0.05-0.3 mm. 
         [0026]    The platform structure of the support component being able to achieve support function can employ many support components. The preferred support component has a ring-shaped structure. There is appropriate height between the two faces of the ring-shaped support component; the solder attachment position of the CID threads through the cavity of the ring-shaped structure of the support component and solders on the surface of the inner bottom of the battery shell. 
         [0027]    The method for circuit cut-off for the safety device can be designed according to need. When the strength of the solder holding the solder attachment position of the CID and the surface of the inner bottom of the battery shell is greater than the stretching resistance of the CID, when the internal pressure of the battery raises to the preset limit, the CID body would break first causing the internal battery current path to break; and there would be no damage to the solder structure holding the solder attachment position of the CID and the surface of the inner bottom of the battery shell. When the strength of the solder holding the solder attachment position of the CID and the surface of the inner bottom of the battery shell is smaller than the stretching resistance of the CID, and when the internal pressure of the battery rises to the preset limit, there would be damage to the solder structure holding the solder attachment position of the CID and the surface of the inner bottom of the battery shell, and there would be separation between the CID and the inner bottom of the battery shell causing the internal battery current path to break, but the CID is not damaged. 
         [0028]    The secondary battery of the present invention places a safety device at the bottom of the battery, where such structure is simple and would not hinder the manufacturing process of the battery or its sealing method. 
       Embodiment One 
       [0029]      FIGS. 1-4  illustrates one embodiment of the secondary battery of the invention. 
         [0030]    Such secondary battery includes safety device  16 , battery shell  11 , battery core  12 , top seal ring  13 , bottom seal ring  14 , cover plate structure  15 , and electrolyte (not show in figures). The battery shell  11 , being made from a metal material and having a hallow cylindrical shape, forms a single body with the shell bottom and the top is sealed by the cover plate structure  15 . The cross section of the cavity of the shell body  11  and the cross section of the safety device  16  are circular with equivalent radiuses. The top seal ring  13  and bottom seal ring  14  are made from insulation material. 
         [0031]    The safety device  16  is installed between the bottom of the battery shell body  11  and the bottom seal ring  14 , and the safety device includes the conductive funnel-shaped CID  161  and the circular-shaped non-conductive support component  162  supporting the CID  161 . The cross section of the cavity of the shell body  11  and the cross section of the support component  162  are circular with equivalent radiuses. 
         [0032]    CID  161  includes the funnel-shaped body  163  and the circular support piece  164  formed and extended horizontally from the funnel-shaped body  163 . The solder attachment position is on the surface of the bottom of the funnel-shaped body  163 . The surface of the bottom of the funnel-shaped CID body  163  of the CID  161  is solder on the surface of the inner bottom of the battery shell. To improve the sensitivity of the safety device  16  to the raising internal battery pressure, there are holes  165  provided on the funnel wall of the funnel-shaped body  163  of the CID  161 . 
         [0033]    The support component  162  is in a ring shaped structure and has on its top surface installed a groove having similar shape and measurement as that of the support piece  164 . The depth of the groove is equal to the thickness H 1  of the support piece  164 . The height H 3  of the support component  162  equals to the perpendicular distance from the top of the support piece  164  to the surface of the bottom of the funnel shaped body  163 . The support piece  164  of the safety device  16  is squeezed tight between the shell bottom and the bottom seal ring. 
         [0034]    The thickness H 1  of the support piece  164  is not less than 0.2 mm. The thickness H 2  of the solder attachment position of the CID  161  is 0.05-0.3 mm. 
         [0035]    The battery core  12  includes positive electrode plate  17 , negative electrode plate  18 , and membrane  19 . 
         [0036]    The positive electrode plate  17  is a positive collector manufactured from belt-shaped metal foil such as aluminum foil, where at least on one side of the positive collector is smeared and covered with positive active material layer. The positive active material layer includes cobalt oxide lithium-ion (as main ingredient), positive adhesive paste, and positive conductive electrical material. The positive tab  171  through soldering is fixed on one side of the positive electrode plate  17 . 
         [0037]    The negative electrode plate  18  is a negative collector manufactured from belt-shaped metal foil such as copper foil, where at least on one side of the negative collector is smeared and covered with negative active material layer. As negative active material layer, it may include carbon material that may be used as negative active material, negative adhesive paste, and negative conductive electrical material. The negative tab  181  electrically connected to one side of the negative electrode plate  17 . There is insulation material between the negative electrode plate  18  and the inside wall of the shell body  11  in order to insulate the two. 
         [0038]    The separator membrane  19  is made of insulation material that is porous, preferably from a combination of chemical compounds such as concentrated polyethylene and polypropylene. 
         [0039]    Electrolyte includes lithium compounds (for example, LiPF6) and mixed liquid solutions (dissolvent that is mixed with the appropriate ratio such as EC, DMC, EMC and PC). 
         [0040]    The top portion of positive tab  171  is in proportion with the upward protruding battery core  12 . The bottom portion of negative tab  181  is in proportion with the downward protruding battery core  12 . 
         [0041]    The battery core  12  is contained in the shell body  11 . 
         [0042]    On the upper portion of the battery core  12 , the cover plate component  15  is installed on the open end of the shell body  11  such that it tightly seals the battery. 
         [0043]    The cover plate component  15  includes the cover plate  151 , an insulation component  152 , and a rivet  153 . The sealed structure of the cover plate  151  and the shell case  11  are formed by laser welding. The rivet  153  through the insulation component  152  is insulated from the cover plate  151 , and is electrically connected to the positive tab  171  of the battery core  12  to become the positive terminal. 
         [0044]    The top separator ring  13  is fitted on top between the battery core  12  and the cover plate component  15 . The purpose of installing the bottom separator ring  14  in between the battery core  12  and the safety device  16  is to prevent short-circuiting resulting from simultaneous contact between the positive and negative electrodes and the cover plate component  15  and between the CID  161  of the safety device  16  and the positive and negative electrodes of the battery core  12 . 
         [0045]    The negative electrode plate  18  through the negative tab  181  protruding from the lower portion of the battery core  12  is electrically connected with the supporting piece  164  of the safety device  16 . The bottom portion of the shell  11  is welded on the bottom surface of the funnel-shaped body  163 . As such, the negative tab  181  is electrically connected with the shell  11  and the in-between bottom area. The case bottom acts as the battery&#39;s negative terminal. 
         [0046]    The positive tab  171  which extends from the battery cell  12  is welded onto the supporting piece  164  of the safety device  16 . 
         [0047]    When the internal pressure of the battery  10  rises, due to the increased pressure from the electrolyte and the gas inside the battery, the CID  161  would be impacted by the stretching effect. When the internal pressure rises to a certain level, the soldering structure that holds the welding between the bottom surface of funnel-shaped CID  161  and the bottom of shell case  11  is damaged. The bottom part of funnel-shaped body  163  will separate from the bottom of shell case  11 . It will then cause a cut off of the current, preventing accidents from happening. 
       Embodiment Two 
       [0048]    The difference between embodiment two and embodiment one is that embodiment two uses another type of safety device. 
         [0049]      FIG. 5  illustrates a portion of the safety device of embodiment two. The difference between this safety device and the safety device  16  in embodiment one is that it uses an inversed (or reversed or upside-downed) L-shaped CID  166  in the place of the CID  161  in embodiment one.  FIG. 5  only shows a part of the vertical cross section of the supporting component  167 . 
         [0050]    Using the horizontal portion of the inversed L-shaped CID  166  as the supporting piece, the free-end of the vertical portion of the inversed L-shaped CID  166  is used as the solder attachment position for installation. The surface of the horizontal portion of the supporting component  167  is fitted with a groove that has appropriate measurements and shapes that are compatible with the inversed L-shaped CID  166 . The depth of the groove is equal to the thickness of the horizontal portion of the inversed L-shaped CID  166 . The height H 5  of supporting component  167  is equal to the height H 4  of the CID  166 . 
         [0051]    The negative electrode tab  181  is welded to the horizontal portion of the inversed L-shaped CID. The free-end of the vertical portion of the reversed L-shaped CID  166  is welded at the center of the bottom inner surface of the battery shell case. 
         [0052]    When the internal pressure inside the battery goes up and due to the increased pressure from the electrolyte and gas inside the battery, the CID  166  would be impacted with this stretching effect. When the internal pressure rises to a certain degree, the welded structure holding the free-end of the vertical portion of the inversed L-shaped CID  166  and the area in between the bottom inner surface of the battery shell case would be damaged. CID  166  will separate from the bottom of the battery shell case, thus causing current interruption and preventing safety accidents. 
         [0053]    In accordance with the breakage strength of the CID  166 , two or more CIDs  166  can be evenly placed on the circumference of the ring-shape structure of the supporting piece  167  in accordance with the practical situation such as the internal battery pressure, etc. 
         [0054]    While the present invention has been described with reference to certain preferred embodiments, it is to be understood that the present invention is not limited to such specific embodiments. Rather, it is the inventor&#39;s contention that the invention be understood and construed in its broadest meaning as reflected by the following claims. Thus, these claims are to be understood as incorporating not only the preferred embodiments described herein but all those other and further alterations and modifications as would be apparent to those of ordinary skilled in the art.