Abstract:
A battery assembly includes a plurality of compound electrodes and electrolyte. Each compound electrode includes an anode section and a cathode section. The compound electrodes are arranged such that the anode section of a first compound electrode interacts electrochemically with the cathode section of a second compound electrode with the electrochemical interaction being carried through electrolyte disposed between the plurality of compound electrodes.

Description:
TECHNICAL FIELD 
     The present invention relates to battery designs and in particular, lithium ion battery designs having a plurality of battery sections arranged in series. 
     BACKGROUND 
     Large capacity rechargeable batteries are currently being investigated for use in electric vehicles. The ultimate feasibility of electric vehicles depends on significantly reducing the associated costs. Reduction in the costs of battery assemblies is particularly important. Lithium ion batteries are an important type of battery technology. 
     Most battery assemblies, including lithium ion battery assemblies, include a plurality of individual electrochemical cells.  FIG. 1A  provides a schematic cross section of an electrochemical cell that is used in many prior art battery assemblies. Electrochemical cell  10  includes anode  12  and cathode  14 . Typically, anode  12  includes a metal sheet or foil  16  (usually copper metal) over-coated with graphitic layer  18 . Similarly, cathode  14  includes metal sheet or foil  20  (usually aluminum metal) over-coated with a lithium-containing layer  22 . Finally, electrochemical cell  10  includes electrolyte  24  which is interposed between anode  12  and cathode  14 . Terminals  26  and  28  allow the generated electricity to be used in an external circuit. 
     Electrochemical cells produce electricity via an electrochemical reaction. In the case of lithium ion battery cells, an example of the electricity generating reactions are described by the following formulae:
 
Cathode Reaction: LiMO 2             Li 1-x MO 2 +xLi + +xe
 
Anode Reaction: C+xLi + +xe         LixC
 
Overall Reaction: LiMO 2 +C         LixC+Li 1-x MO 2  
 
where LiMO 2  is a lithiated transition metal oxide. Other materials may be used as a cathode and anode of a li-ion cell, resulting in different electricity generating reactions.

     The reactions occurring in a lithium ion battery cell are reversible, thereby providing the ability of such cells to be recharged. During battery discharge, the anode provides electrons to an external circuit and lithium ions to the electrolyte from lithium that is intercalated within the graphitic coating on the anode. During charging the movement of the lithium ions is reversed. 
       FIG. 1B  provides a schematic cross section of a prior art battery assembly that includes a plurality of electrochemical cells. Battery assembly  30  includes electrochemical cells  32 - 56  which are of the basic design set forth in  FIG. 1A . In this design, active elements of the internal electrodes (anode or cathode) are deposited on both sides of current carriers  58 ,  59 . Moreover, in accordance with this design the electrochemical cells are arranged in a parallel configuration with the anodes of each cell electrically connected together and the cathodes of each cell electrically connected together. Thus the voltage generated between the electrodes of the battery assembly  30  is the same as the voltage generated between the electrode of the battery assembly  10 . 
       FIG. 1C  provides a schematic cross section of a prior art battery assembly formed from a plurality of battery subassemblies arranged in a parallel configuration. Battery assembly  60  includes battery subassemblies  62 - 66  which are of the general design of the battery assembly set forth in  FIG. 1B . In accordance with this design, the battery subassemblies are arranged in a parallel configuration with the anodes of each battery subassembly electrically connected together and the cathodes of each battery subassembly electrically connected together. Thus the voltage generated between the electrodes of the battery assembly  60  is the same as the voltage generated between the electrodes of the battery assembly  10  and the voltage generated between the electrodes of the battery assembly  30 . 
       FIG. 1D  provides a schematic cross section of a prior art battery assembly formed from a plurality of battery subassemblies arranged in a series configuration. Battery assembly  70  includes battery subassemblies  72 - 76  which are of the general design of the battery assembly set forth in  FIG. 1B  or in  FIG. 1C . In accordance with this design, the battery subassemblies are arranged in series with the anode of a battery subassembly electrically connected to the cathode of the next battery subassembly. 
     Although the battery assemblies of  FIGS. 1A-1D  work reasonably well, improved designs that are easier to assemble are still desirable. In particular, there is a desire to decrease the costs associated with fabricating high capacity battery assemblies for automotive applications. 
     Accordingly, there is a need for battery assemblies of simpler design that are more economical that the current prior art assemblies. 
     SUMMARY OF THE INVENTION 
     The present invention solves one or more problems of the prior art by providing in at least one embodiment a battery assembly. The battery assembly includes a plurality of compound electrodes and electrolyte. Each compound electrode includes an anode section and a cathode section. The compound electrodes are arranged such that the anode section of a first compound electrode interacts electrochemically with the cathode section of the second compound electrode. The electrochemical interaction carried through electrolyte disposed between the plurality of compound electrodes. 
     In another embodiment, a battery assembly comprising a plurality of battery sections and compound electrodes is provided. Each battery section includes a first compound electrode plate and a second compound electrode plate. The first compound electrode plate and the second compound electrode plate each individually include a copper plate and an aluminum plate with the copper plate being attached to the aluminum plate. The copper plate defines an anode section and is coated with an anode active layer. The aluminum plate defines a cathode section and is coated with a cathode active layer. The first compound electrode plate and the second compound electrode plate are arranged such that the anode section of the first compound electrode plate aligns with the cathode section of the second compound electrode plate. Finally, an electrolyte is disposed between the first compound electrode plate and the second compound electrode plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1A  is a schematic cross section of an electrochemical cell that is used in many prior art battery assemblies; 
         FIG. 1B  is a schematic cross section of a prior art battery assembly that includes a plurality of electrochemical cells; 
         FIG. 1C  is a schematic cross section of a prior art battery assembly formed from a plurality of battery subassemblies arranged in a parallel configuration; 
         FIG. 1D  is a schematic cross section of a prior art battery assembly formed from a plurality of battery subassemblies arranged in a series configuration; 
         FIG. 2A  is a variation in which both sides of the anode and both sides of the cathode are coated with an electrode active layer; 
         FIG. 2B  is a variation in which both sides of the anode and single side of cathode are coated with an electrode active layer; 
         FIG. 2C  is a variation in which a single side of the anode and both sides of cathode are coated with an electrode active layer; 
         FIG. 2D  is a variation in which a single side of the anode and a single side of cathode are coated with an electrode active layer; 
         FIG. 3  is a schematic cross section of a battery assembly comprising a plurality of battery sections; and 
         FIG. 4  is a schematic cross section illustrating sealing between battery cells. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present invention, which constitute the best modes of practicing the invention presently known to the inventors. The Figures are not necessarily to scale. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the invention and/or as a representative basis for teaching one skilled in the art to variously employ the present invention. 
     Except in the examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary: percent, “parts of,” and ratio values are by weight; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed; the first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation; and, unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property. 
     It is also to be understood that this invention is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present invention and is not intended to be limiting in any way. 
     It must also be noted that, as used in the specification and the appended claims, the singular form “a,” “an,” and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components. 
     Throughout this application, where publications are referenced, the disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains. 
     With reference to  FIGS. 2A to 2D , variations of compound electrodes for use in a battery assembly are provided.  FIG. 2A  is a schematic cross section of a variation in which both sides of the anode and both sides of the cathode are coated with an electrode active layer. An electrode active layer is a layer that assists in the electrochemical process occurring at the electrode. Such assistance can be providing a surface for intercalation of ions (e.g., Li ions) or promotion of the chemical reactions occurring at an electrode. Compound electrode  80  includes anode section  82  and cathode section  84 . Anode section  82  includes anode metal sheet  86  over-coated with anode active layer  88  on both sides. Cathode section  84  includes cathode metal sheet  90  over-coated with cathode active layer  92  on both sides. Metal sheets  86  and  90  are attached together (e.g., by welding) at position  94  to form compound metal sheet  96 . 
       FIG. 2B  provides a variation in which both sides of the anode and a single side of the cathode are coated with an electrode active layer. Compound electrode  100  includes anode section  102  and cathode section  104 . Anode section  102  includes anode metal sheet  106  over-coated with anode active layer  108  on both sides. Cathode section  104  includes cathode metal sheet  110  over-coated with cathode active layer  112  on a single side. Metal sheets  106  and  110  are attached together (e.g., by welding) at position  114  to form compound metal sheet  116 . 
       FIG. 2C  provides a variation in which a single side of the anode and both sides of the cathode are coated with an electrode active layer. Compound electrode  120  includes anode section  122  and cathode section  124 . Anode section  122  includes anode metal sheet  126  over-coated with anode active layer  128  on a single side. Cathode section  124  includes cathode metal sheet  130  over-coated with cathode active layer  132  on both sides. Metal sheets  126  and  130  are attached together (e.g., by welding) at position  134  to form compound metal sheet  136 . 
       FIG. 2D  provides a variation in which a single side of the anode and a single side of the cathode are coated with an electrode active layer. Compound electrode  140  includes anode section  142  and cathode section  144 . Anode section  142  includes anode metal sheet  146  over-coated with anode active layer  148  on a single side. Cathode section  144  includes cathode metal sheet  150  over-coated with cathode active layer  152  on a single side. Metal sheets  146  and  150  are attached together (e.g., by welding) at position  154  to form compound metal sheet  156 . 
     Each of the electrode designs of  FIGS. 2A-2D  includes a compound metal sheet in which an anode metal sheet is attached to a cathode metal sheet. In one refinement, the anode metal sheet comprises copper and the cathode metal sheet comprises aluminum. In another refinement, the compound metal sheet may be constructed from a single metal sheet which is coated with a layer of a different metal. For example, an aluminum sheet is partially coated with a copper layer such that the uncoated aluminum portion functions as the cathode metal sheet and the copper coated portion functions as the anode metal sheet. In another example, a copper sheet is partially coated with an aluminum layer such that the uncoated copper portion functions as the anode metal sheet and the aluminum coated portion functions as the cathode metal sheet. 
     As set forth above, the metal sheet of the anode portion is coated with an anode active layer. In one refinement useful for lithium ion battery assemblies, the anode active layer is a carbon-containing layer. Examples of suitable carbon-containing layers include, but are not limited to, a component selected from the group consisting of graphite, coke, and combinations thereof. 
     As set forth above, the metal sheet of the cathode portion is coated with a cathode active layer. In one refinement useful for lithium ion battery assemblies, the cathode active layer is a lithium-containing layer. In one refinement, the lithium-containing layer comprises a lithium transition metal oxide. Examples of suitable transition metal oxides include, but are not limited to, LiMn 2 O 4 , LiCoO 2 , LiNiO 2 , and combinations thereof. 
     With reference to  FIG. 3 , a schematic cross section of a battery assembly comprising a plurality of battery sections is provided. In general, the battery assembly includes a plurality of battery sections defined by the compound electrodes arranged such that the anode section and cathode sections of each compound electrode is positioned in adjacent battery sections. The enclosed volumes of the battery sections are electrically connected by the compound electrodes set forth above. In  FIG. 3 , a battery assembly having three battery sections in series is illustrated. Battery assembly  160  includes n battery sections  162   1  to  162   n  where n is an integer that is at least 2. Typically, n is from 2 to about 200. Each of battery sections  162   1  to  162   n  includes a plurality of battery cells (i.e., electrochemical cells) formed as enclosed cells. For example, battery section  162  includes m battery cells  164   1  to  164   m  where m is an integer providing the number of battery cells in battery section  162   1 . Typically, n is from 2 to about 200. 
     Still referring to  FIG. 3 , each battery cell includes compound electrode plates  170  in which both sides of the anode section and both sides of the cathode section are coated with an electrode active layer. Moreover, each battery cell includes at least a first electrode plate and a second electrode plate arranged such that an anode section of the first electrode plate aligns with the cathode section of the second electrode plate. For example, anode section  172  of electrode plate  170   a  opposes and aligns with cathode section  174  of electrode plate  170   b . Electrode plate  170   a  and electrode plate  170   b  are arranged such that the anode section and the cathode section of each electrode plate are positioned in adjacent battery sections. The battery sections also include end cathode plates  176  and end anode plates  178 . Compound electrode plate  180  is also depicted in  FIG. 3 . Electrolyte  181  is disposed between the electrode plates in each battery cell. Battery assembly  160  also includes enclosure  180  and racks  182 . In a refinement, each of enclosure  180  and racks  182  are plastic. In another refinement, battery assembly  160  also includes a cooling system (not shown). 
     In the battery design of  FIG. 3 , the battery subsections are configured such that the anodes of each battery cell are electrically connected. Similarly, the battery subsections are configured such that the anodes of each battery cell are electrically connected. For example, in battery section  162   1 , the anodes of battery cells  164   1  to  164   m  are electrically connected via bus  184  while the cathodes are connected via bus  186 . The battery design of  FIG. 3  is such that the anodes of a battery section are electrically connected with the cathodes of the adjacent battery section. For example, the cathodes of battery section  162   2  are electrically connected by bus  184 . 
     The battery assemblies set forth above all utilize battery cells that contain an electrolyte. For lithium ion battery cells, the electrolyte comprises lithium ions. In one variation, the electrolyte is a liquid. In another variation, the electrolyte is a solid. Typically, the liquid electrolytes are non-aqueous solutions of a lithium salt and solvent. Suitable solvents include, but are not limited to, esters, ethers, and carbonates (e.g., ethylene carbonate or diethyl carbonate). Suitable lithium salts include, but are not limited to, non-coordinating anion salts (e.g. lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate monohydrate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), lithium tetrafluoroborate (LiBF4), and lithium triflate (LiCF 3 SO 3 ).) 
     With reference to  FIG. 4 , a schematic illustrating sealing between battery cells is provided. Each of the individual battery cells of the assembly of  FIG. 3  are physically isolated by separating elements (i.e., seals) attached to the compound electrodes. In a variation, the separating elements extend over the entire boundary formed between the anode and cathode sections of the compound electrodes. In general, the separating elements prevent electrical contact between the electrolyte in the adjacent battery sections. In  FIG. 4 , compound electrode plates  80  are assembled with seal  190  positioned between adjacent plates. Examples of such seals include, but are not limited to, polymer films or blocks, O-ring type seals or rubber gaskets, Ziplock type seals (e separating elements have complementary inserting and receiving shapes). and the like. In a refinement, such seals are formed from electrically conductive polymers. In this latter refinement, the electrically conductive polymers partially form the buses (i.e., bus  184  and  186 ) connecting the electrodes together in  FIG. 3 . 
     While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.