Rechargeable Battery

Abstract

Battery core packs employing minimum cell-face pressure containment devices and methods are disclosed for minimizing dendrite growth and increasing cycle life of metal and metal-ion battery cells.

What is claimed is: 
     
         1 . A battery core pack, comprising:
 a plurality of cells forming a cell stack, each cell comprising at least one anode and at least one cathode, wherein metal ions are stripped from the anode during discharge and re-plated on the anode during charge; and   a containment structure at least partially surrounding the cell stack, wherein said containment structure imparts a substantially uniform surface pressure at certain value to said cell stack.   
     
     
         2 . The battery core pack of  claim 1 , wherein the substantially uniform surface pressure is at least about 50 psi. 
     
     
         3 . The battery core pack of  claim 2 , wherein said cells maintain a discharge capacity of greater than 2.5 Ah over at least 100 charge/discharge cycles. 
     
     
         4 . The battery core pack of  claim 3 , comprising at least four cells with a core pack energy density of at least about 590 Wh/L at 30% SoC. 
     
     
         5 . The battery core pack of  claim 2 , wherein said anode comprises lithium metal. 
     
     
         6 . The battery core pack of  claim 1 , wherein said containment structure comprises a housing into which the cell stack is placed, wherein the housing has openings at two ends. 
     
     
         7 . The battery core pack of  claim 6 , further comprising at least one compliant pad, wherein the at least one compliant pad is disposed between two cells, and the thickness of the at least one compliant pad is determined by the expansion extent of the cell and is optimized between the variables of allowed battery pack volume and durometer rating of the compliant pad. 
     
     
         8 . The battery core pack of  claim 7 , wherein said compliant pad comprises polyurethane sheet material with a Shore durometer of between about 40-90, and a Bashore resilience of between about 22-40%. 
     
     
         9 . The battery core pack of  claim 8 , further comprising a cooling pad disposed between two cells. 
     
     
         10 . The battery core pack of  claim 2 , wherein said containment structure comprises:
 a mounting unit defining a variable space to accommodate the cell stack; and   at least one elastic member surrounding the mounting unit to impart said surface pressure to the mounting unit.   
     
     
         11 . The battery core pack of  claim 10 , wherein the mounting unit comprises:
 first and second endplates opposite to each other, each endplate comprising at least a pair of sliding collars provided on each side, respectively;   guide rods inserted into the sliding collars to limit motion of the cell stack due to expansion and contraction during charge and discharge cycles to a single degree of freedom substantially perpendicular to the cell faces wherein said guide rods are configured to be slidingly received in the sliding collar at each end.   
     
     
         12 . The battery core pack of  claim 11 , comprising four said guide rods and eight said sliding collars, wherein each sliding collar is disposed on the end plates approximately adjacent a corner of the end plate and wherein said guide rods and sliding collars cooperate to permit expansion and contraction of the cell stack in a direction substantially perpendicular to the cell faces while limiting twist, skew or bending of the cell stack to maintain the substantially uniform minimum pressure across the cell faces. 
     
     
         13 . The battery core pack of  claim 12 , wherein said at least one elastic member has a spring constant of at least approximately 5.43 lb/in. 
     
     
         14 . The battery core pack of  claim 1 , wherein said cells comprise lithium-ion cells. 
     
     
         15 . A battery pack, comprising:
 a plurality of cells forming a cell stack, each cell comprising at least one anode and at least one cathode wherein metal ions are stripped from the anode during discharge and re-plated on the anode during charge;   a housing containing the cell stack with a pre-loaded surface pressure of at least about 50 psi, wherein said housing has sufficient stiffness to maintain said surface pressure through plural charge and discharge cycles of said cell stack; and   at least two compliant pads, wherein each compliant pad is disposed between the cells, said compliant pads distributing the cell expansion pressure evenly during charging and pushing back to the cell during discharging.   
     
     
         16 . The battery core pack of  claim 15 , wherein said cell stack comprises four cells. 
     
     
         17 . The battery core pack of  claim 16 , further comprising a cooling pad formed of a high conductivity material disposed between cells of said cell stack. 
     
     
         18 . The battery core pack of  claim 17 , wherein the at least one anode comprises lithium metal. 
     
     
         19 . A method of controlling dendrite growth on the anode of a metal or metal-ion battery cell, wherein said cell comprises at least one planar anode and at least one planar cathode and wherein material is stripped from the anode during cell discharge and re-plated on the anode during cell charge, the method comprising:
 assembling plural cells into a cell stack;
 positioning the cell stack within a containment structure, the containment structure at least partially surrounding the cell stack; and 
 applying and maintaining a substantially uniform minimum surface pressure of at least about 50 psi across the cells of the cell stack with the containment structure. 
   
     
     
         20 . The method of  claim 19 , wherein said positioning, applying and maintaining comprises:
 placing compliant pads between at least two pairs of cells in the cell stack;   pre-loading the cell stack with said substantially uniform minimum surface pressure; and   placing the cell stack within the containment structure while maintaining said substantially uniform minimum surface pressure, wherein the containment structure comprises a rigid housing configured and dimensioned with sufficient stiffness to maintain said substantially uniform minimum surface pressure through plural charge and discharge cycles of said cell stack.   
     
     
         21 . The method of  claim 19 , wherein said positioning, applying and maintaining comprises:
 placing the cell stack between two substantially rigid endplates;   placing plural elastic members around the cell stack and endplates, said elastic members having a minimum spring constant and being configured and dimensioned to apply said substantially uniform minimum surface pressure to the cell stack in an initial, unexpanded state; and   limiting skew or twist of the endplates relative to one another and the cell stack, said endplates and elastic members comprising said containment structure.