Electrochemical cell for hybrid electric vehicle applications

Abstract

Embodiments of the present invention are directed an electrochemical energy storage device, such as a cell or a battery, that includes segmented stackable bus bars for stacking electrodes, the bus bar segments extending a substantial length of an edge of the electrodes to provide proper inter-electrode spacing, substantially uniform electrochemical potential and current density between electrodes, efficient internal heat dissipation and desired electrode structural rigidity, and, optionally, a compression member, separate from the case, to compress the stacked electrodes.

1 . An electrochemical energy storage device, comprising: 
 (a) a plurality of stacked electrodes arranged in a plurality of electrode plate pairs, each electrode pair comprising an adjacent positive and negative electrode separated by a layer or separator matrix of electrolyte and the plurality of electrode plate pairs being arranged such that adjacent electrodes have opposing polarities;    (b) a positive bus bar interconnecting the positive electrodes; and    (c) a negative bus bar interconnecting the negative electrodes, wherein at least one of the following is true at charging or discharging rates between about 0.5 C and 2 C; 
 (c1) at least one of the positive and negative bus bars contacts the corresponding positive and negative electrodes, respectively, to provide a substantially uniform current density between each of the corresponding contacted electrodes;  
 (c2) at least one of the positive arid negative bus bars contacts physically at least half a length of a peripheral edge of each of the corresponding positive and negative electrode plates, respectively, to maintain a relative orientation of the bus bar and corresponding electrodes substantially constant over time;  
 (c3) for each electrode plate pair, an electron travels an electrical current path of a substantially constant electrical resistance, the current path extending from the positive bus bar, through the positive electrode, traversing the electrolyte and through negative electrode, and to the negative bus bar;  
 (c4) a substantial length of a peripheral edge of at least one of the positive and negative bus bars contacts physically a case enclosing the electrode pairs to remove thermal energy generated by the flow of electricity;  
 (c5) for each electrode plate pair, a substantially constant electrical potential gradient normal to the bus bars exists across any grid structure on the surface of the electrodes;  
 (c6) at any point along the lengths of the positive and negative bus bars, a substantially constant electrical potential exists between opposing points on the bus bars;  
 (c7) for each electrode plate pair, a substantially constant electrochemical potential exists between any opposing points on the electrode pair; and  
 (c8) at any point in an enclosed volume of the device, a substantially constant electrochemical reaction exists.  
   
     
     
         2 . The device of  claim 1 , wherein (c1) is true.  
     
     
         3 . The device of  claim 2 , wherein the positive electrodes are electrically connected in parallel with the negative electrodes and wherein the at least one of the positive and negative bus bars contacts physically the entire length of a peripheral edge of the corresponding positive and negative electrode plates, respectively.  
     
     
         4 . The device of  claim 2 , wherein the electrochemical energy storage device is a cell and wherein the current density between the corresponding positive and negative electrodes varies no more than about 15%.  
     
     
         5 . The device of  claim 1 , wherein (c2) is true.  
     
     
         6 . The device of  claim 5 , wherein the electrochemical energy storage device comprises a plurality of cells, wherein the electrode pairs are electrically connected in parallel, and wherein the case contacts the at least one of the positive and negative bus bars substantially along the entire peripheral edge of the bus bar.  
     
     
         7 . The device of  claim 6 , wherein the plurality of stacked electrodes is compressed and maintained in compression by a compression member.  
     
     
         8 . The device of  claim 1 , wherein (c3) is true.  
     
     
         9 . The device of  claim 8 , wherein (c4) is true.  
     
     
         10 . The device of  claim 1 , wherein the at least one of the positive and negative bus bars comprising a plurality of segments, wherein each segment is associated with a corresponding electrode, wherein the bus bar segments are stacked one on top of the other, wherein each of the bus bar segments has a first width, wherein the corresponding electrode contacting each segment has a second width, and wherein the first width is greater than the second width, with the difference in the first and second widths being related to a thickness of an oppositely polarized electrode to be received between the adjacent commonly polarized electrodes contacting the stacked segments.  
     
     
         11 . The device of  claim 10 , wherein the at least one of the positive and negative bus bars is both the positive and negative bus bars, wherein at least one gas venting space is positioned between the positive and negative bus bars, and wherein the case substantially contacts the peripheral edges of the bus bars.  
     
     
         12 . The device of  claim 7 , wherein the positive and negative electrodes are in the form of a grid comprising a paste, wherein the plates are in contact with an electrolyte, wherein a compressible separator material is positioned between adjacent oppositely polarized electrodes, wherein the compressive force exerted on the electrodes ranges from about 10 to about 100 kPa, wherein the compression member is separate from the case, and wherein nonconductive end plates are positioned at either end of the plurality of stacked electrodes.  
     
     
         13 . The device of  claim 11 , wherein high and low pressure relief valves are in fluid communication with the venting space.  
     
     
         14 . The device of  claim 1 , wherein (c5) is true.  
     
     
         15 . The device of  claim 1 , wherein (c6) is true.  
     
     
         16 . The device of  claim 1 , wherein (c7) is true.  
     
     
         17 . The device of  claim 1 , wherein (c8) is true.  
     
     
         18 . An electrochemical energy storage device, comprising: 
 (a) a plurality of stacked electrodes arranged in a plurality of electrode pairs, each electrode pair comprising an adjacent positive and negative electrode and the plurality of electrode pairs being arranged such that adjacent electrodes have opposing polarities;    (b) a positive bus bar interconnecting the positive electrodes;    (c) a case enclosing the stacked electrodes; and    (d) a negative bus bar interconnecting the negative electrodes, wherein at least one of the following is true; 
 (d1) the positive and negative bus bars are segmented, each segment physically contacting a corresponding electrode, wherein the positive bus bar segments are stacked one on top of the other to define a plurality of spaced apart positive electrodes and the negative bus bar segments are stacked one on top of the other to define a plurality of spaced apart negative electrodes, each of the negative electrodes being received in a corresponding inter-electrode space between adjacent positive electrodes and each of the positive electrodes being received in a corresponding inter-electrode space between adjacent negative electrodes;  
 (d2) the positive and negative bus bars are segmented, each segment physically contacting at least most of a selected peripheral edge of a corresponding electrode, the adjacent segments being stacked one on top of the other to form the respectively polarized bus bar;  
 (d3) the positive and negative bus bars define at least one gas venting space positioned between the positive and negative bus bars, wherein the case substantially contacts at least most of the peripheral edges of the bus bars;  
 (d4) the plurality of stacked electrodes is compressed and maintained in compression by a compression member separate from the case; and  
 (d5) the case comprises at least one offset member to define a channel between adjacent cases when the cases are positioned side-by-side.  
   
     
     
         19 . The device of  claim 18 , wherein (d1) is true.  
     
     
         20 . The device of  claim 18 , wherein (d2) is true.  
     
     
         21 . The device of  claim 18 , wherein (d3) is true.  
     
     
         22 . The device of  claim 18 , wherein (d4) is true.  
     
     
         23 . The device of  claim 18 , wherein (d5) is true.  
     
     
         24 . A method for manufacturing an electrochemical energy storage device, comprising: 
 (a) stacking a plurality of segments of a positive bus bar, each segment being in electrical contact with a positive electrode;    (b) stacking a plurality of segments of a negative bus bar, each segment being in electrical contact with a negative electrode;    (c) positioning electrolyte separators between adjacent electrodes;    (d) intermeshing the stacked positive electrodes and negative electrodes such that positive and negative electrodes are positioned in an alternating sequence; and    (e) positioning the intermeshed electrodes in a case.    
     
     
         25 . The method of  claim 24 , further comprising: 
 (f) heating the case to expand its enclosed volume, wherein step (e) occurs while the enclosed volume is thermally expanded.    
     
     
         26 . The method of  claim 24 , further comprising: 
 (f) compressing the intermeshed positive and negative electrodes before the positioning step (e).    
     
     
         27 . The method of  claim 24 , further comprising: 
 (f) welding the adjacent bus bar segments of the positive and negative bus bars to form substantially solid positive and negative bus bars after the intermeshing step (d).    
     
     
         28 . The method of  claim 26 , wherein a nonconductive end plate is positioned on either side of the compressed, intermeshed positive and negative electrodes and wherein the case is attached to the end plates to form a sealed enclosure for the electrodes.