Abstract:
A co-extrusion print head has at least one separator inlet port, at least a first, second and third series of channels arranged to receive a separator material from the separator inlet port, at least one electrode inlet port, a fourth series of channels arranged to receive an electrode material from the electrode inlet port, a first merge portion connected to the first, second, third and fourth series of channels, the merge portion positioned to receive and merge the separator material into a separator flow and the electrode material into an electrode flow, a second merge portion connected to the first merge portion, the second merge portion positioned to receive and merge the separator flows and the electrode flows, and an outlet port connected to the second merge portion, the outlet port arranged to deposit the separator and electrode materials from the merge portion as a stack on a substrate.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
       [0001]    This invention was made with Government support under Award Number DE-AR0000324 awarded by DOE, Office of ARPA-E. The Government has certain rights in this invention. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates to fabricating batteries, more particularly fabricating batteries using a co-extrusion apparatus. 
       BACKGROUND 
       [0003]    The use of a co-extrusion apparatus to manufacture various structures has been discussed in several patent applications and issued patents. A co-extrusion apparatus is one in which two or more materials are extruded simultaneously into a structure of some kind. This type of apparatus can be used in fabrication of batteries, simultaneously extruding electrodes with separators to form components of batteries. 
         [0004]    Examples of the co-extrusion approaches include US Patent Publication 20120156364, in which interdigitated fingers of co-extruded materials are extruded from one print head type of apparatus. The materials are fed into feeding channels and combined as separate flows, then split and combined again until a structure of alternating stripes of the two materials is created as they exit the print head. In another approach, the side-by-side lateral structure extends to interdigitated stripes in the vertical direction as well. US Patent Publication 20140186519 teaches a means to generate this type of structure. 
         [0005]    The use of these structures to fabricate batteries is discussed in other publications, such as U.S. Pat. No. 5,714,278, in which a masked portion of the area of a porous separator material used in a battery. Masked areas can be formed on the porous separator material and allows for easier alignment of the anode and cathode sections to avoid edge effects. However, these areas are not formed in co-extrusion print heads. 
         [0006]    US Patent Publication No. 20110217585 discusses batteries having integrated separators and methods of fabricating such batteries. The separators are formed in different ways, but generally formed directly on either the cathode or anode. The separators may be single layer or multi-layered. These approaches do not form the electrodes and separators simultaneously in an extrusion manner. 
         [0007]    Another approach uses electrophoretic deposition in sequential layers to form thin-film batteries. The sequential layers are formed using electrophoretic deposition. An example of this approach is shown in US Patent Publication 20130244102. 
         [0008]    None of these approaches form the electrodes and separators simultaneously using a co-extrusion print head. These types of print heads have several advantages in their simplicity, their simultaneous deposition capability, but none exist that can form separator structures simultaneously with the electrodes. Because they are not formed simultaneously, the separator cannot be formed to be truly conformal to the electrode. Having a conformal separator provides a layer around the electrode to prevent the battery from shorting. 
       SUMMARY 
       [0009]    An embodiment consists of a co-extrusion print head that has at least one separator inlet port, at least a first, second and third series of channels arranged to receive a separator material from the separator inlet port, at least one electrode inlet port, a fourth series of channels arranged to receive an electrode material from the electrode inlet port, a first merge portion connected to the first, second, and third series of channels, the merge portion positioned to receive and merge the separator material into separator flow and the electrode material into an electrode flow, a second merge portion connected to the first merge portion, the second merge portion positioned to receive and merge the separator flows and the electrode flows, and an outlet port connected to the second merge portion, the outlet port arranged to deposit the separator and electrode materials from the merge portion as a stack on a substrate where the separator material covers the top and sides of the electrode material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows a prior art embodiment of a battery. 
           [0011]      FIG. 2  shows a prior art embodiment of a process flow for manufacture of a battery. 
           [0012]      FIG. 3  shows a prior art embodiment of a process flow for manufacture of a battery. 
           [0013]      FIGS. 4-7  show embodiments of a battery electrode having a conformal separator. 
           [0014]      FIG. 8  shows an embodiment of a print head capable of forming stacked materials in one pass. 
           [0015]      FIG. 9  shows an embodiment of a battery electrode having a conformal separator. 
           [0016]      FIGS. 10-15  show views of one embodiment of a print head capable of forming stacked layers on a substrate in one pass. 
           [0017]      FIGS. 16-18  show a process of formation of a conformal separator. 
           [0018]      FIGS. 19-22  show embodiments of a battery having a conformal separator. 
           [0019]      FIGS. 23-24  show an embodiment of a print head having a separator formed of multiple layers. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0020]    In a typical battery, the separator&#39;s primary function prevents physical contact between the anode and cathode while facilitating ion transport. This discussion will refer to the anode and cathode as electrodes.  FIG. 1  shows a prior art embodiment of a battery  10  with cathode  16 , anode  12  and separator  14 . During cell assembly, the separator has a larger area than that of either electrode. The process cuts the separator into a larger size than the anode and cathode electrodes. When inserted into a full cell assembly, the larger separator prevents edge/side contact between the electrodes. 
         [0021]      FIG. 2  shows an example of a conventional battery manufacturing process for creating a full cell consisting of an anode, a cathode and a separator. As one can see, the process manufactures the anode in one clean. The process produces an anode slurry formation at  21 , then slot coats it onto a current collector at  23 , with calendaring for thickness control at  25 . The process then dries the anode at  27 . Similarly, the process forms a cathode slurry at  20 , then slot coats it onto the current collector at  22  with calendaring for thickness control at  24 . The cathode is dried at  26 . Both electrodes undergo slitting at  29  and  28 . Electrode slitting typically involves slitting a roll of electrode materials to a desired width. The final cell is then assembled at  31 . 
         [0022]    In the embodiments here, the process  30  forms the anode, cathode and separator slurries at  32 . The three slurries are then co-extruded using the print head disclosed here at  34  onto a current collector with calendaring for thickness control at  36 . The combination of the structures are dried at  38 . The remaining current collector is then assembled with the extruded structure at  40 . 
         [0023]      FIGS. 4-7  show embodiments of battery structures manufacturable with the co-extrusion print head described here. In  FIG. 4  the electrode  52  has a conformal separator that covers the top and sides of the electrode. Conformal, as that term is used here, means that the separator molds itself to the electrode. The electrode  42  may consist of a single material as in electrode  52 . Alternatively, the electrode may consist of an interdigitated structure  56  shown in  FIG. 5 . The interdigitated structure may result from the co-extrusion print head as discussed in the previous patents mentioned above. 
         [0024]    In  FIGS. 6 and 7 , the separator conforms to the electrodes, but in addition to only covering the top and sides of the electrode, it also extends onto the current collector. This provides additional separation between the anode and cathode. In  FIG. 6 , the separator  50  conforms to the electrode  52  with extensions such as  54 .  FIG. 7  shows the similar structure, but the electrode consists of an interdigitated electrode  56 . 
         [0025]    After the manufacture of these structures, they mate with the remaining electrode to form a full cell which is then cut or wound into the appropriate format. One can see that the co-extrusion enables a conformal separator to be fabricated around an electrode, while current manufacturing processes use a separator sheet cut to size in an area larger than the electrodes, leaving room for potential shorting at the sides during final cell assembly. 
         [0026]      FIG. 8  shows an embodiment of a print head  62 . The print head  62  extrudes the structures as viscous slurries onto a target substrate  60 . The materials may require drying or firing to remove the solvent and densify the structures. As shown in  FIG. 8 , the inlet ports  64 ,  66  and  68  receive slurries that eventually exist the print head in a manner to form the electrode  52 , or interdigitated electrode  56 , and separator  50 , with or without the extension  54 . 
         [0027]    The print head of  FIG. 8 , or a similar structure, can form the structures of  FIGS. 4-7 . Fluid paths and manifolds in the print head distribute separator and electrode slurries or inks. One can break down the structure of  FIG. 6  into zones, as shown in  FIG. 9 . The electrode material  52  exits from one set of nozzles in the print head, as will be discussed in  FIGS. 10-12 . The separator may consist of three different zones. The extension  54  may consist of one slurry, referred to here as S 1 . The sides  70  may consist of another slurry, referred to here as S 2 . The top layer  50  may consist of another slurry, S 3 . These slurries may all feed from the same slurry, forming a uniform layer over the electrode. Alternatively, the slurries may be different materials, to enable better isolation or enhance other characteristics of the batteries. The flows and feeds can be controlled as will be discussed in more detail later. 
         [0028]      FIG. 10  shows a side view of one embodiment of a print head  62 . The print head has a top plate  82  that seals the print head and a back fixture plate for aligning parts  72 . The ink enters through the back plate  72  and feeds into the nozzles through manifolds  74 ,  76 , and  80 , depending upon the material. One should note that the ink may move ‘away’ from the front of the page and flow into the output nozzles from the manifold  80 . The stack of nozzle plates  78  form the extrusion nozzles through which the slurries ultimately exit the print head. 
         [0029]      FIG. 11  shows a closer view of a portion  86  from the extrusion nozzles  78  from  FIG. 10 . The portion  86  is show in more detail in  FIG. 12 . The orientation of the print head is important to understand the configuration of the resulting structure. The substrate, which may consist of the current collector, is on the ‘top’ of the print head and the materials exit the print head with the electrode material E existing the nozzles such as  94  being on the substrate first, then covered by the separator slurry S 3  from nozzle  96 , with the separator slurry S 2  from nozzles such as  92 . The separator slurry S 1  exits the print head at nozzles such as  90  and comes out onto the substrate in the same position as the electrode material. Walls such as  98  in the print head keep the materials isolated as they exit the interdigitation portion of the print head into a merge portion. 
         [0030]      FIG. 13  shows the individual slurries separated from each other, the separator slurries and the electrode slurries are separated amongst themselves and from each other. The discussion of  FIGS. 13-15  may be better understood with reference to  FIG. 12 . In FIG.  12 , the print head  62  is shown in a block diagram. The print head has the inlet ports such as  64  for the separator slurry and  68  for the electrode slurry. The first portion of the print head has sections  83  and  81  for the electrode and separator slurries to be received. A first merge portion  85  then allows the separator slurries to merge into a separator flow and a separate portion  87  of the first merge portion to allow the electrodes to merge into an electrode flow. A second merge portion  89  then allows the separator flows and the electrode flows to merge together into one flow prior to exiting the print head at the output  91 . These are shown in  FIGS. 14 and 5  are from the perspective of looking back from the outlet towards the nozzles from which the slurries flow. 
         [0031]    In  FIG. 14 , the slurries have traversed a first merge portion so the all of the separator ‘S’ slurries are merged together and all the ‘E’ slurries are merged together, but the ‘S’ slurries and ‘E’ slurries are still separate from each other. In  FIG. 15 , the ‘S’ slurries and ‘E” slurries have merged. Note that this all occurs within the print head, and the resulting set of slurries exit the print head as merged flows, and the merged flows are in contact with each other but do not mix. 
         [0032]      FIGS. 16-17  illustrate a method of operation in which a layer of separator material that is wider than the electrode material. In these figures, the materials are being extruded in a direction either going into or out of the page. The separator material  50  is distributed into nozzles on top of and to the sides of the electrode material, forming a ‘wider’ stripe than the electrode material. This may be accomplished without using the larger nozzles such as  92  shown in  FIG. 13 . 
         [0033]    Just before the materials exit the print head, the separator material  50  is ‘higher’ than the electrode material relative to the substrate  60 . As the materials exit the print head, the separator material  50  begins to flow over electrode material  52  because it is no longer supported in the print head. Upon coming to rest on the substrate  60 , the separator  50  settles over the electrode material and forms the extensions  54 . The portion of the separator  50  that forms the extensions  54  will depend upon how many nozzles are used for the separator beyond the nozzles used for the electrode materials. 
         [0034]      FIGS. 19-22  show alternative embodiments of the battery structures having another layer on top of the top layer of separator S 3 . Typically, this layer will be a second top layer of separator, but may also consist of electrode material of the type opposite the first electrode. In  FIG. 19 , the electrode  52  has the separator  50  formed on top of it. In this embodiment, the opposite electrode  100  is formed on top of the separator  50 .  FIG. 20  shows the embodiment similar to  FIG. 19 , but with the interdigitated electrodes  56 .  FIGS. 21 and 22  show the embodiments with an anode added to the separator that has extensions  54  with and without the interdigitated electrodes. 
         [0035]      FIG. 23  shows an alternative embodiment of a print head. In this embodiment, the stack of plates  78  includes an extra set of extrusion nozzles. An exploded view of the portion  102  of the plates  78  is shown in  FIG. 24 . In this embodiment, the channels  104  that dispense the separator S 2  on the substrate next to the electrode material are larger than the previous S 2  channels. The nozzles  96  through which the slurry S 3  exits the print head now have another set of nozzles adjacent them, such as  106 . In this particular embodiment, the channels such as  106  dispense a fourth slurry S 4  enables a multilayer composite separator. 
         [0036]    In one embodiment, S 3  and S 4  consist of different separator materials. After drying, the S 3  and S 4  materials would have different materials, such a different porosity, insulating or thermal properties, etc. As previously mentioned, it is also possible that the additional slurry may be an electrode material that is of an opposite type of the first-used electrode material E. For example, if E is an anode material, S 4  would be cathode material, or the opposite. 
         [0037]    In this manner, co-extrusion print heads can fabricate a conformal separator around an electrode structure in a single pass. The conformal separator reduces shorting in a battery cell, ensuring safer batteries. The embodiments here remove the need to cut separator sheets larger than an electrode as a separator process. The electrode-separator structure can be reduced to a desired width, reducing the need for a slitting operation used in conventional battery manufacturing. 
         [0038]    It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.