Abstract:
A method for manufacturing and to a method for replacing pouches of a secondary battery and to a rack or base for a secondary battery. The base comprises a plurality of reception portions wherein each one of the plurality of reception portions comprises a fastening element for receiving and mechanically supporting at least one of a plurality of pouches. A pair of electrical contact elements is provided for contacting the electrochemical cell in the pouch.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present disclosure relates to components for a battery, to a method for manufacturing batteries and to a battery manufactured therewith. In particular the present invention relates to serviceable secondary batteries and to a method for assembling and for exchanging components of the secondary battery. 
         [0003]    2. Brief Description of the Related Art 
         [0004]    Secondary batteries are becoming increasingly important for energy storage in mobile applications as well as buffer systems for electric grids and are an increasingly important part of modern energy technology. Today, high capacities secondary batteries are comparatively expensive and have a limited lifetime which limit the applications of secondary batteries. Increasing lifetime of secondary batteries is therefore one of the main interests of research and development in the field. 
         [0005]    Secondary batteries usually consist of a plurality of electrochemical cells that are stacked together to achieve the desired battery capacity and/or the desired electrical voltage. Each electrochemical cell comprises at least two electrodes, a cathode and an anode which are electrically separated from each other, for example by a separator. 
         [0006]    The electrodes, cathode and anode, each comprise a current collector and at least an electrochemically active electrode material. Many different electrochemically active electrode materials are known in the art which can be used either as electrochemically active cathode material or as electrochemically active anode material. The electrochemically active electrode materials are selected depending on the electrolyte used and on the application of the battery. 
         [0007]    A plurality of electrochemical cells are assembled in a stack and are mounted in a battery case. Additional components such as a heat sink, cooling and electronics are added to control the status and the function of the batteries. 
         [0008]    Lithium based batteries are often based on pouch type cells, wherein a plurality of thin and flexible electrochemical cells are packed and preassembled in a sealed pouch. The pouch usually has a negative electrode and a positive electrode contact. The pouches are mechanically deformable and are usually fixed in a battery case. 
         [0009]    In state of the art manufacturing processes, stacks of electrochemical cells or pouches are placed in a battery case or battery module and the heat sinks, cooling systems and electronic modules are attached to the battery stacks before the battery housing is closed. 
         [0010]    WO 2009/073225 describes a method and a system for stacking electrochemical cells, wherein a plurality of pouches containing electrochemical cells are stapled in support frames. The pouches in the frames are mounted into a battery case and are thermally and electrically connected. 
         [0011]    These known manufacturing methods allow a fast assembly of the battery but a replacement of battery cells is not possible. 
         [0012]    It is an object of the present invention to overcome the disadvantages of prior art. 
       SUMMARY OF THE INVENTION 
       [0013]    The disclosure proposes a battery rack for a battery for supporting a plurality of pouches. Each one of the plurality of pouches contains at least one electrochemical cell. The battery rack comprises a plurality of pouch receiving sections, wherein each one of the plurality of the pouch receiving sections comprises a releasable fastening element for releasably fixing and mechanically supporting at least one of the plurality of pouches. The battery rack also comprises at least one pair of electrical contact elements for electrically contacting the at least one electrochemical cell in the at least one of the plurality of pouches, when the pouch is positioned in the respective pouch receiving section. The fastening element is releasable for reversibly attaching the at least one pouch. The fastening element allows releasing and replacing one or more of the pouches in a simple and effective manner enabling a serviceable battery. This is particularly advantageous for secondary batteries. Pouches containing defect electrochemical cells or pouches containing cells at the end of their cycle-lifetime can be easily replaced. The fastening element may be a click-in mechanism or may comprise screws or other releasable mounting or fixation means. The battery rack comprising the plurality of receiving sections may be considered a base enabling the mechanical support of the pouches. The battery rack provides in the same time a mechanical support, alignment and an electrical contact to the at least one pouch. 
         [0014]    The pouches may be battery packs or packs of electrochemical cells as generally known in the art, in particular of lithium ion secondary batteries. The present disclosure is particularly useful with foil-type pouches, i.e. pouches comprising electrochemical cells with current collector and/or electrode foils. 
         [0015]    The pouches may be arranged in a pouch support frame or in another support structure that gives the pouches mechanical stability. This is in particular useful if electrochemical cells made from foil material are used that are not by themselves mechanically stable. The use of support frames as such is known in the art. If a pouch support frame is used, the fastening element may be adapted to receive and mechanically support the pouch support frame. In this case the pouches can be reversibly or irreversible fixed in the pouch support frame. 
         [0016]    If the pouches are mechanically supported by the support frame, the battery rack aligns and mechanically supports the support frame, thereby in turn supporting the pouch. The fastening element may be adapted to receive and mechanically support the support frame which in turn mechanically supports the pouch. A support frame can be used to support a single pouch or a plurality of pouches. Support frames for a single pouch and the support frames for two pouches are per se known in the art. 
         [0017]    Alternatively, the use of support frames can be omitted and the pouches can be directly supported by the battery rack. 
         [0018]    The battery rack may be made from a rigid structure and can be made of different materials such as plastics or metals or other or a combination of different materials. The battery rack may comprise a heat sink and the heat sink may come into thermal contact with the at least one pouch. The heat sink allows effective heat transport and cooling of the electrochemical cells in the pouch. 
         [0019]    The heat sink may be made from a rigid structure and may give the battery rack a rigid structure for mechanically supporting the plurality of pouches. In this case, the reception portion may be made from a lightweight material with a structure that is in itself not rigid and stable enough to mechanically and stably support the plurality of pouches. 
         [0020]    The battery rack may further comprise an electronic circuit to control the at least one electrochemical cell in the at least one pouch. The electronic circuit may involve at least one of charging and de-charging control of the electrochemical cell, temperature control and the control of other parameters. One electronic circuit per pouch may be provided or an electronic circuit to control all or a plurality of pouches may be used. 
         [0021]    The battery rack may further comprise a plurality of contact elements for contacting the plurality of pouches. The contact elements may be adapted to contact two or more electrode contacts of different pouches. This allows connecting the pouches in series or in parallel to adjust the configuration of the battery depending on the needs. The electrical contact elements may reversibly contact the electrode contacts, i.e. the anode contact or the cathode contact. This may also allow modifying the battery if the application of the battery is changed. 
         [0022]    The electrical contact elements may be implemented as bus bars. The electrical contact element may be in thermal contact with a heat sink. This allows an effective heat transfer from the electrical contact element and thereby from an electrode of the electrochemical cells in order to keep the electrochemical cells in a certain temperature range. 
         [0023]    The battery rack may further comprise one or more sensors for controlling the temperature of the electrochemical cells and the pouches or other parameters of the battery. 
         [0024]    The present invention also relates to secondary battery comprising such a battery rack. The secondary battery further comprises a plurality of pouches fastened to the battery rack. The pouches are releasably fastened and can be easily exchanged. This provides a modularly battery system that can also be designed for a plurality of battery racks. 
         [0025]    The secondary battery may comprise a housing in which the battery rack and the plurality of pouches are protected. 
         [0026]    The present disclosure also relates to a method for manufacturing a secondary battery. The manufacturing method comprises providing a pre-assembled battery rack and attaching at least one pouch to the battery rack in a reversibly manner. The pouch is not fixedly connected to the battery rack and can be easily removed to increase serviceability of the battery rack. 
         [0027]    The reversible attachment of the at least one pouch may comprise placing the at least one pouch in a frame and reversibly attaching the at least one frame to the battery rack. 
         [0028]    The present invention also relates to a method for replacing a pouch of a secondary battery. The replacing method comprises releasing a pouch containing the electrochemical cell to be replaced from the battery rack to which the pouch is reversibly attached, and attaching a replacement pouch to the battery rack. The pouch to be replaced and the replacement pouch may be supported by a pouch support frame. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  shows an assembly with a rack according to the present invention. 
           [0030]      FIG. 2  shows the rack of  FIG. 1  from an opposite view. 
           [0031]      FIGS. 3   a - 3   c  show the assembly of a rack according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    The invention will now be described on the basis of the drawings. It will be understood that the embodiment and aspects of the invention described herein are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalence. It is understood that the features of one aspect or embodiment of the invention can be combined with a feature of different aspects and/or examples of the invention. 
         [0033]      FIG. 1  shows a battery module  2  that can be used alone or in combination with other battery modules in a primary or secondary battery. The battery module  2  is in use arranged in a housing to protect the battery cells and the electronics. The housing may be a standard battery housing and is not shown in the figures. 
         [0034]    The battery module  2  comprises a battery rack or base  100  to which a plurality of pouches  20  are mounted. Each pouch  20  is mounted in a pouch support frame  30 . In the example shown in  FIG. 1 , in total five pouch support frames  30  each comprising one pouch  20  are mounted to the rack  100 . This number of support frames is only shown for illustrative purposes and a different number of pouches and pouch support frames  30  can be mounted to the rack  100 . Typical numbers for pouches attached to a base  100  range from a single pouch to about a few hundred pouches. The number of pouches actually used depends on the application of the battery and the required properties. The pouches may be selected to provide final voltages of up to about 1000 V and 300 A currents. The number of pouches and cells, however may be easily multiplied by a factor of 2, 4, 6, or more. 
         [0035]    The pouches  20  comprise a plurality of electrochemical cells, each cell comprising at least one anode, a cathode and a separator. The pouches  20  comprising the electrochemical cells are per se known in the art and any conventional pouches can be used with the present disclosure. Instead of pouches, other types of battery packs or electrochemical cells may be used. 
         [0036]    Each pouch  20  has at least two electrical electrode contacts, a positive electrode contact  12  and a negative electrode contact  14  electrically contacting the respective electrodes of the electrochemical cells. In the example shown both electrical electrode contacts  12 ,  14  are arranged on the same rack facing side  21  of the pouch  20 . The electrical electrode contacts can also be arranged in other configurations, for example on opposite sites of the pouch. 
         [0037]    The pouch support frame  30  surrounds the pouch  20  and at least 4 sides and holds the pouch  20  mechanically stable. In this way, the pouch is protected from deflections and other mechanical forces or damages. The support frames  30 , however, may be arranged differently and only cover a certain portion of the pouch  20 . Furthermore, the support frames  30  may be adapted to the shape of the pouch. The support frames  30  may or may not comprise electrical contacts. In the examples shown, the support frames  30  provide mechanical stability to the pouches  20  and do not contain any electrical contact or control. 
         [0038]    Each support frame  30  is inserted into a pouch receiving section  133  of a rack element  130  of the battery rack  100 . The rack element  130  has a plurality of pouch receiving sections  133 , wherein in each pouch receiving section  133  can take-up one and fix one support frame  30 . The pouch receiving sections  133  have a complementary shape to a fitting portion  33  of the support frames  30 . Screws  40  may be used as fastening elements to fix the support frames  30  containing the pouches  20  to the rack element  130 . By releasing the screws  40 , a corresponding frame  30  can be removed from the rack  100  and a replacement frame with a replacement pouch  20  can be inserted in the corresponding receiving section  133  and fastened using the screws  40 . In this way, a defect pouch  20  can be easily replaced. Other releasable fastening elements than screws  40  can be used for attaching the pouches  20  to the rack  100 . For example notches or snap hinges may be used. 
         [0039]    In the shown example, the pouch support frames  30  and the pouches  20  are aligned in parallel and are essentially perpendicular to the rack  100 . Other arrangements of the pouches  20  with respect to the rack  100  are, however, possible. 
         [0040]      FIG. 2  shows the battery module  2  of  FIG. 1  from the opposite side showing electronics  160  and a heat sink  150 , as will be described in more detail with respect to  FIGS. 3   a - 3   c.    
         [0041]      FIG. 3   a  shows a heat sink or cooling device  150  that can be used with the present disclosure. The heat sink  150  has thermal connections  152 ,  153 ,  154 ,  155  for connecting heat sink to heat transport means. The thermal connections  152 ,  153 ,  154 ,  155  may comprise fluid connectors for a cooling medium such as refrigerant that can flow through the heat sink  150 . Alternatively, the contacts  152 ,  153 ,  154 ,  155  are metal contacts for the heat transport of heat generated by the electrochemical cells in use. The heat sink  150  forms a rigid backbone for the base or rack  100 . A receiving section  130  with a plurality of receiving elements  133  is arranged on the heat sink  150  forming the rack  100 . Each one of the receiving elements  133  has guiding means  135  for guiding and mechanically supporting and positioning frames  30  on the rack  100 . Furthermore, the plurality of electronic circuits  160  is arranged on the rack  100 . The electronics may serve for controlling for example temperature, current, voltage and other parameters of the electrochemical cells. Other functions may be implemented in the electronics  160 . 
         [0042]      FIG. 3   c  shows a plurality of electrical contact elements or bus bars  122 ,  124  arranged on the rack  100  of  FIG. 3   b . The bus bars  122 ,  124  may be arranged in the rack element  130  and form an electrical contact with the electrode contact elements  12  and  14  of the pouches. The bus bars  122 ,  124  may additionally in thermal contact with the heat think  150 . An electrically isolating and thermally conductive material may be used between the heat think  150  and the bus bars  122 ,  124  to avoid an electric potential on the heat think, while an efficient cooling of the electrochemical cells can be obtained. 
         [0043]    The bus bars  122 ,  124  can have different sizes and can be arranged to electrically contact the pouches  20  in series or in parallel depending on the arrangement of the bus bars  122 ,  124 . Any combination of contacting the electrical electrode contacts  12 ,  14  of the pouches in series and/or in parallel can be adjusted depending on the needs of the final battery. For example, it can be useful to group a certain number of pouches  20  and to electrically connect all pouches  20  of the group in parallel to increase the capacity. Several groups of pouches may then be connected in series to increase the nominal tension of the battery according to the requirements. The bus bars  122 ,  124  can be used for any configuration of connecting the pouches  20 . It is also possible to group and to electrically connect all pouches  20  of the group in series in order to increase the nominal voltage or to connect the ouches in any combination of series and parallel. If the requirement or application of the battery changes during the lifetime of the battery, the bus bars may be rearranged to a different configuration if needed. In this way, the battery can be adapted to different applications and different nominal voltages can be obtained. 
         [0044]    It is an advantage that the pouches  20  can be removed to readjust or exchange items of the rack  100 . This allows a serviceable battery module wherein each part can be easily exchanged extending the lifetime of secondary batteries. It is also possible to exchange all pouches of a battery, for example at the end of the life time and to reuse the base with new pouches. 
         [0045]    Each pouch receiving section  133  of the rack element  130  comprises openings  112 ,  114  that con be used for fixation of the bus bars  122 ,  124 . A snap-in mechanism, screws or other reversible fixation means can be used to arrange the bus bars  122 ,  124  on the rack element  130 . 
         [0046]    While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only and not imitation. It really would be apparent to a person skilled in the art that various changes and form in detail can be made therein without departing from the scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments, but should be defined only in accordance with the following claims at their equivalence.