Patent Publication Number: US-2010129706-A1

Title: Device with at least one accumulator cell

Description:
This application claims benefit of Serial No. 10 2008 043 960.6, filed 21 Nov. 2008 in Germany and which application is incorporated herein by reference. To the extent appropriate, a claim of priority is made to the above disclosed application. 
     TECHNICAL FIELD 
     The present invention relates to a device with at least one accumulator cell, which has an electrode assembly disposed in an elastic cell sheath. 
     BACKGROUND 
     Accumulators as a rule consist of a plurality of accumulator cells from any desired type of accumulator, such as, for example, NiCd, NiMH and Li-ion, which are connected together in packs or modules. They are therefore also referred to as accumulator packs or accumulator modules. In particular accumulators with Li-ion cells are widely used due to their high specific energy output as well as their high specific energy content. Li-ion cells, as they are, for example, used in electric tools, are typically designed as round cells with a rigid metal sheath. Said round cells do not exhibit an enlargement of their mass, which contributes to the energy supply, due to the metal sheath and lead to dead construction volume in corresponding accumulator packs or modules due to their round construction. 
     In order to avoid this mass enlargement and the dead construction volume, it is known from the technical field to revert back to so-called “lithium polymer” cells (LiPo cells). These usually have electrode assemblies, which consist of platelet-like electrodes stacked on top of each other. Said electrodes are respectively separated from each other by suitable separators and are disposed in an elastic cell sheath. Such LiPo cells are as a rule prismatic and can consequently be disposed in the housing of an associated accumulator pack or module in order to save space. 
     The disadvantage in the technical field is that the elastic cell sheath expands when a change in volume of the accumulator cell occurs, for example by means of an excess pressure which occurs when gas forms during operation on account of electrochemical processes inside the cell. This expansion of the cell sheath can however lead to the damage or destruction of one or a plurality of cell sheaths and consequently of the cells, respectively the accumulator packs or modules, in an associated accumulator housing of an accumulator pack or module, wherein a plurality of accumulator cells is stacked one on top of each other. Furthermore, it is difficult to stably and safely accommodate, respectively mount, such accumulator cells in a rigid accumulator housing on account of the elastically deformable cell sheath. 
     SUMMARY 
     It is therefore a task of the invention to provide a device which allows for a stacking of accumulator cells with elastic cell sheaths in an accumulator housing in such a way that damage or destruction of the cell sheaths and consequently the accumulator cells is avoided during their operation. 
     This problem is solved by a device with at least one accumulator cell, which has an electrode assembly disposed in an elastic cell sheath. The accumulator cell is equipped with an apparatus, which has at least two retaining elements which are connected to each other, the accumulator cell being held by the retaining elements at associated hold points. 
     The invention thereby allows for a simple and uncomplicated installation of accumulator cells in a housing the associated apparatuses as well as for a configuration of stable and safe cell stacks. In so doing, the accumulator cells are in each case spaced apart from each other by the associated apparatuses. 
     According to one embodiment, the apparatus is configured for the purpose of allowing for an expansion of the cell sheath when a change in volume of the accumulator cell takes place. 
     Consequently damage to or destruction of the cell sheath and thus the accumulator cell can be prevented when a corresponding change in volume takes place. Provision is thereby also made for the accumulator cells to be fixedly mounted in the accumulator housing. 
     The retaining elements are preferably configured for the purpose of gripping the accumulator cell at the associated hold points with a predefined holding pressure. The holding elements are connected to each other via at least one crosspiece. 
     The invention therefore allows for a simple and uncomplicated installation of corresponding apparatuses on associated accumulator cells. 
     According to one embodiment, the electrode assembly has at least two square, platelet-like electrodes, which are separated from each other by a separator. The apparatus preferably has four retaining elements, the apparatus gripping the electrode assembly at its corners with the retaining elements at a predefined holding pressure. The cell sheath has a rabbet-like extension at least one corner of the electrode assembly. The retaining element associated with at least the one corner preferably has a groove to accept the rabbet-like extension. The groove is configured for the purpose of accepting the rabbet-like extension. 
     Consequently a simple, safe and stable installation of corresponding apparatuses on associated accumulator cells is made possible. 
     The retaining elements preferably have first sections, which are provided on the top side of the apparatus and second sections, which are provided on the bottom side of said apparatus. The sections on the top side are configured for holding a first accumulator cell, and the sections on the bottom are configured for holding a second accumulator cell. 
     Two accumulator cells can therefore be held using one individual apparatus and can be installed safely and stably in an associated accumulator housing. 
     According to one embodiment a plurality of accumulator cells with associated apparatuses is stacked one on top of the other. In so doing, each apparatus has associated retaining elements, and the retaining elements from two different apparatuses in each case abut on each other. 
     The problem stated at the beginning of the application is furthermore solved by an apparatus for an accumulator cell, which has an associated electrode assembly in an elastic cell sheath. The electrode assembly has at least two square, platelet-like electrodes, which are separated from each other by a separator. Provision is made for at least four retaining elements which are connected to each other and are configured for the purpose of gripping the electrode assembly at its corners with a predefined holding pressure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in detail in the following description with the aid of an example of embodiment depicted in the drawings. The following are shown: 
         FIG. 1  is a perspective view of a device with an accumulator cell and an apparatus for retaining the cell according to a first embodiment, 
         FIG. 2  is a perspective view of the device from  FIG. 1  when installing the apparatus on the accumulator cell, 
         FIG. 3  is a perspective view of a cell stack with two accumulator cells and two associated apparatuses for retaining the cells according to the first embodiment, 
         FIG. 4  is a perspective view of a device with two accumulator cells and an apparatus for retaining the cells according to a second embodiment, 
         FIG. 5  is a perspective view of the device from  FIG. 4  when installing the apparatus on the accumulator cells, and 
         FIG. 6  is a perspective view of a cell stack with four accumulator cells and two associated apparatuses for retaining the cells according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a device  100  with an accumulator cell  110 , whereupon an apparatus  120  is attached. The accumulator cell  110  has an elastic cell sheath  114 , wherein an electrode assembly  112  is disposed. 
     The cell sheath  114  is preferably configured from a plastic film, which has an aluminum coating. A suitable plastic film is, for example, constructed from three layers. An inner aluminum layer is then provided between two outer plastic layers. The three layers are preferably welded together. 
     Electrical contacts  116 ,  118  are provided for electrically contacting the accumulator cell  110  along with other accumulator cells to an accumulator pack or module, respectively for the external contact-connection of the accumulator cell. Said contacts  116 ,  118  are electrically conductively connected to the electrode assembly  112  and are led towards, respectively away from, said assembly  112  via the cell sheath  114 . 
       FIG. 2  illustrates an installation of the apparatus  120  on the accumulator cell  110 . In this instance, the apparatus  120  is slid onto, respectively slipped onto, the accumulator cell  110 , respectively onto its electrode assembly  112 , which is disposed in the cell sheath  114 , in the direction of an arrow  260 . 
     According to one embodiment, the electrode assembly  112  has two or more square, platelet-like electrodes, which in each case are separated from each other by suitable separators. Two electrodes  201 ,  203  which are separated from each other by a separator  202  are shown by way of example in  FIG. 2 . 
     The electrode assembly  112  is preferably completely enclosed by the cell sheath  114 , the cell sheath  114  having rabbets on all edges of the electrode assembly  112 , which are preferably glued. The cell sheath  114  preferably has rabbet-like extensions  272 ,  274 , which extend from the corners  292 ,  294  of the electrode assembly  112 , on one edge  270  of the electrode assembly  112 . 
     The apparatus  120  has four retaining elements  210 ,  220 ,  230 ,  240  for the sake of illustration. The retaining elements  210 ,  240  are provided on a crosspiece  254  and are connected to each other via said crosspiece  254 . The retaining elements  220 ,  230  are provided on a crosspiece  252  and are connected to each other via said crosspiece  252 . The crosspieces  252 ,  254  are arranged in the form of a cross relative to one another and are connected to each other at a point of intersection  250 . This point of intersection  250  can be equipped with one or a plurality of reinforcements for the stabilization of the construction. 
     It should be noted that the apparatus  120  is not limited to the use of four retaining elements  210 ,  220 ,  230 ,  240  but rather can have any number of retaining elements. In this connection, the number of retaining elements can be selected as function of a configuration of the electrode assembly  112 . For example, four or more retaining elements or also alternatively only two or three retaining elements can be used as described above in the case of a square configuration of the electrode assembly  112 . This is true as long the retaining elements are suited for the purpose of holding the accumulator cell  110  with a sufficient holding pressure, as described below. 
     It should likewise be noted that the connection of the retaining elements  210 ,  220 ,  230 ,  240  via the intersecting crosspieces  252 ,  254  is merely described as an example. Other structures are likewise possible within the scope of the present invention. The retaining elements  210 ,  220 ,  230 ,  240  can, for example, be connected to each other via crosspieces which form a frame, or via crosspieces which define a Z-shaped design. 
     The retaining elements  210 ,  220  have holding mechanisms  212 , respectively  222 , which are configured for the purpose of holding the accumulator cell  10  at associated hold points  282 , respectively  284 . With regard to the accumulator cell  110 , suitable corners of the electrode assembly  112  are used as hold points  282 ,  284 . The holding mechanisms  212 ,  222  are accordingly configured as square recesses, in which the corners  282 , respectively  284 , of the electrode assembly  112  can be disposed and retained. 
     The retaining elements  230 ,  240  have holding mechanisms  235 , respectively  245 , which are configured for the purpose of holding the accumulator cell  110  at associated hold points which correspond to the corners  292 ,  294  of the electrode assembly  112 . According to one embodiment, the retaining elements  230 ,  240  have square recesses  237 ,  247 , which preferably are similarly configured to the recesses which constitute the holding mechanisms  212 ,  222  and in which the corners  292 ,  294  of the electrode assembly  112  can be disposed. Moreover, the holding mechanisms  235 ,  245  have outer supporting members  234 , respectively  244 , whose length preferably corresponds to the length of the holding mechanisms  212 ,  222 , as well as inner supporting members  234 ,  244  whose length is shortened relative to said outer members  234 ,  244 . The outer supporting members  234 ,  244  and the inner supporting members  232 , respectively  242 , are in each case separated from one another by a groove  236 , respectively  246 . The groove  236 , respectively  246 , is preferably configured for the purpose of accepting the associated rabbet-like extension  272 , respectively  274 . In so doing, the extension  272 , respectively  274 , can be clamped in the groove or can merely be disposed therein. 
     Starting from a bottom surface of the crosspieces  252 , respectively  254 , facing towards the accumulator cell  110  in  FIG. 2 , the inner supporting members  234 ,  244  have a length, which approximately corresponds to the height of the electrode assembly  112 . The length of the outer supporting members  234 ,  244  as well as the holding mechanisms  212 ,  222  is greater than the length of the inner supporting members  234 ,  244  by a predefined distance. 
     After the installation of the electrode assembly  112 , the apparatus  120  according to one embodiment grips the corners  282 ,  284 ,  292 ,  294  of said assembly  112  with the retaining elements  210 ,  220 ,  230 ,  240  at a predefined holding pressure. In order to achieve this holding pressure, the retaining elements  210 ,  240  are preferably braced against one another by the crosspiece  254 ; and the retaining elements  220 ,  230  are preferably braced against one another by the crosspiece  252 . In so doing, the crosspieces  252 ,  254  ensure that a sufficiently large region of the cell sheath  114  remains free on the side of the accumulator cell  110  which faces them in order to allow for an expansion of the cell sheath  114  in this region when a change in volume of the accumulator cell  110  occurs. On the opposite side of the accumulator cell  110  which faces away from the crosspieces  252 ,  254 , a corresponding clearance is created by the overhanging, outer supporting members  234 ,  244  as well as the holding mechanisms  212 ,  222 , which serve as feet when the accumulator cell  110  is stacked. The rabbet-like extensions  272 ,  274 , which are clamped in the grooves  236 ,  246  serve thereby to stabilize, respectively improve, the connection between the apparatus  120  and the accumulator cell  110 . 
       FIG. 3  shows a cell stack  300 , wherein the accumulator cell  10  equipped with the apparatus  120  of  FIGS. 1 and 2  is exemplary disposed above an accumulator cell  310 , which is equipped with a corresponding device  320 . According to one embodiment, the configuration of the accumulator cell  310  corresponds to the configuration of the accumulator cell  110  of  FIG. 2 ; and the configuration of the device  320  corresponds to the configuration of the apparatus  120  of  FIG. 2  so that a detailed description of these elements can be foregone. 
     The accumulator cell  310  has electrical contacts  316 ,  318 . These can be connected to the electrical contacts  116 ,  118  of the accumulator cell  110  or to corresponding external contacts when connecting the accumulator cells  110 ,  310  to an accumulator pack or module. 
       FIG. 3  exemplary illustrates how the rabbet-like extension  272  is disposed in the groove  236  which is configured between the inner supporting member  232  and the outer supporting element  234 . It can furthermore be seen in  FIG. 3  how the retaining elements  210 ,  220 ,  230 ,  240  are disposed on corresponding retaining elements  312 ,  322 ,  332 ,  342  of the apparatus  320 , respectively abut on them. In so doing, an arrangement of the crosspieces, which connects the retaining elements  312 ,  322 ,  332 ,  342  to one another, creates a clearance between the accumulator cells  110  and  310 , which is increased even more by the clearance described in  FIG. 2  on the side of the accumulator cell  110  which faces away from the crosspieces  252 ,  254 . 
       FIG. 4  shows a device  400  with two accumulator cells  410 ,  490  which are connected to an apparatus  420 . The configuration of the accumulator cells  410  and  490  preferably corresponds to the configuration of the accumulator cell  110  of  FIG. 2  so that a detailed description of the accumulator cells  410 ,  490  can be foregone. 
       FIG. 5  shows the accumulator cell  410 , which is equipped with a cell sheath  514 , rabbet-like extensions  572 ,  574 , electrical contacts  516 ,  518  as well as with an electrode assembly  512  and the accumulator cell  490  of  FIG. 4 , which is equipped with a cell sheath  591 , rabbet-like extensions  593 ,  594 , electrical contacts  595 ,  596  as well as an electrode assembly  592 .  FIG. 5  furthermore shows a preferred embodiment of the apparatus  420  of  FIG. 4 . 
     The apparatus  420  has four retaining elements  510 ,  520 ,  530 ,  540  for the sake of illustration. The retaining elements  510 ,  540  are provided on a crosspiece  552  and are connected to each other via said crosspiece  552 . The retaining elements  520 ,  530  are provided on a crosspiece  554  and are connected to each other via said crosspiece  554 . The crosspieces  552 ,  554  are exemplary arranged in the form of a cross relative to each other. 
     It should be noted that the apparatus  420  like the apparatus  120  from  FIG. 2  is not limited to the use of four retaining elements  510 ,  520 ,  530 ,  540 ; and that the connection of the retaining elements  510 ,  520 ,  530 ,  540  via the intersecting crosspieces  552 ,  554  is also only described as an example. 
     The retaining elements  510 ,  520  have holding mechanisms  511 ,  513 , respectively  522 ,  550 , which, for example, are configured as square recesses like the holding mechanisms  212 ,  222  of  FIG. 2 . In this case, the holding mechanisms  513 ,  522  respectively form a first section of the retaining elements  510 ,  520 , which is provided on the top side  501  of the apparatus  420 ; while the holding mechanisms  511 ,  550  respectively form a second section of the holding elements  510 ,  520 , which is provided on a bottom side  502  of the apparatus  420  opposite to the top side  501 . 
     The retaining elements  530 ,  540  likewise have first and second, respectively upper and lower sections, which according to one embodiment are in each case configured like the retaining elements  230 ,  240  of  FIG. 2 . The upper section of the retaining element  530  has, for example, an inner supporting member  532 , an outer supporting member  534  as well as a groove  536 . The lower section of said retaining element  530  has an inner supporting member  531 , an outer supporting member  533  as well as a groove  535 . Analogous to this, the upper section of the retaining element  540  has an inner supporting member  542 , an outer supporting member  544  as well as a groove  546 ; and its lower section has an inner supporting member  541 , an outer supporting member  543  as well as a groove  545 . A detailed description of the retaining elements  510 ,  520 ,  530 ,  540  is however foregone for the sake of brevity of the description. 
     When installing the accumulator cells  410 ,  490  on the apparatus  420 , the accumulator cell  410  is pressed onto the apparatus  420 , respectively slid onto the apparatus  420 , in the direction of an arrow  562 . For its part, said apparatus  420  is slid onto the accumulator cell  490 , respectively pressed onto the accumulator cell  490 , in the direction of an arrow  560 . In so doing, the apparatus grips the accumulator cells  410 ,  490  with a predefined holding pressure as exemplary described above in regard to  FIG. 2  with reference to the accumulator cell  110  and the apparatus  120 . Each of the accumulator cells  410 ,  490  can thereby expand substantially unimpeded in at least one direction. 
       FIG. 6  shows a cell stack  600 , in which the accumulator cells  410 ,  490  of  FIGS. 4 and 5 , which are equipped with the apparatus  420 , are disposed by way of example above two accumulator cells  610 ,  690  which are equipped with an apparatus  620 . According to one embodiment, the configuration of the accumulator cells  610 ,  690  corresponds to the configuration of the accumulator cell  110  of  FIG. 2 , and the configuration of the apparatus  620  corresponds to the configuration of the apparatus  420  of  FIG. 5  so that a detailed description of these elements can be foregone. 
     The accumulator cell  610  has electrical contacts  616 ,  618 , and the accumulator cell  690  has electrical contacts  695 ,  696 . When connecting the accumulator cells  410 ,  490 ,  610 ,  690  to an accumulator pack or module, said contacts can be connected up to the electrical contacts  516 ,  518 , respectively  595 ,  596  of the accumulator cells  410 , respectively  490 , or to corresponding external contacts. 
       FIG. 6  exemplary illustrates how the retaining elements  510 ,  520 ,  530 ,  540  are disposed on corresponding retaining elements  660 ,  630 ,  640  of the apparatus  620 , respectively abut on them. When stacking the accumulator cells, which are equipped with apparatuses of the type of apparatus  420 , respectively  620 , the retaining elements of two different apparatuses consequently abut on each other.