High Discharge Capacity Lithium Battery

Abstract

A lithium/iron disulfide electrochemical battery cell with a high discharge capacity. The cell has a lithium negative electrode, an iron disulfide positive electrode and a nonaqueous electrolyte. The positive electrode mixture containing the iron disulfide contains highly packed solid materials, with little space around the solid particles, to provide a high concentration of iron disulfide within the mixture. The separator is thin, to allow more space within the cell for active materials, yet strong enough to prevent short circuits between the positive and negative electrodes under abusive conditions, even when swelling of the cathode during cell discharge places additional stressed on the separator. As a result, the ratio of the interfacial capacity of the positive electrode to the electrode interfacial volume is high, as is the actual capacity on low rate/low power and high rate/high power discharge.

1 . An electrochemical battery cell comprising a housing; a negative electrode strip comprising metallic lithium, a positive electrode strip comprising an active material mixture and an electrolyte comprising at least one salt dissolved in a nonaqueous electrolyte disposed within the housing; and a separator disposed between the negative and positive electrodes; the cell having a ratio of a cathode interfacial capacity to an electrode assembly interfacial volume of at least 710 mAh/cm 3 .  
     
     
         2 . The cell as defined in  claim 1 , wherein the electrode active material comprises greater than 50 weight percent iron disulfide.  
     
     
         3 . The cell as defined in  claim 2 , wherein the electrode active material comprises at least 95 weight percent iron disulfide.  
     
     
         4 . The cell as defined in  claim 3 , wherein the electrode active material comprises at least 99 weight percent iron disulfide.  
     
     
         5 . The cell as defined in  claim 1 , wherein the ratio of the cathode interfacial capacity to the electrode assembly interfacial volume is at least 720 mAh/cm 3 .  
     
     
         6 . The cell as defined in  claim 1 , wherein: 
 (a) the housing comprises a container with a closed end, an initially open end closed by a cover, and a side wall extending between the closed and initially open ends;    (b) the negative electrode is in the form of at least one sheet with two opposing major surfaces;    (c) the positive electrode is in the form of at least one sheet with two opposing major surfaces; and    (d) the negative and positive electrodes are disposed within the container with a portion of at least one major surface of the negative electrode sheet adjacent a portion of at least one major surface of the positive electrode sheet through the separator, and at least some segments of adjacent portions of the negative and positive electrodes are parallel to a longitudinal axis of the cell.    
     
     
         7 . The cell as defined in  claim 6 , wherein the negative and positive electrodes and the separator form a spiral wound electrode assembly.  
     
     
         8 . The cell as defined in  claim 7 , wherein the container has a cylindrical shape and the electrode assembly has a radial outer surface disposed adjacent an inner surface of the container side wall.  
     
     
         9 . The cell as defined in  claim 7 , wherein the container has a prismatic shape and the electrode assembly has an outer surface disposed adjacent an inner surface of the container side wall.  
     
     
         10 . The cell as defined in  claim 1 , wherein the separator is a microporous membrane and has a thickness less than 25 μm and a tensile stress of at least 1.0 kgf/cm in both a machine direction and a transverse direction.  
     
     
         11 . The cell as defined in  claim 10 , wherein the separator has a thickness less than 22 μm.  
     
     
         12 . The cell as defined in  claim 10 , wherein the tensile stress of the separator is at least 1.5 kgf/cm.  
     
     
         13 . The cell as defined in  claim 12 , wherein the tensile stress of the separator is at least 1.75 kgf/cm.  
     
     
         14 . The cell as defined in  claim 10 , wherein the separator has a dielectric breakdown voltage of at least 2000 volts.  
     
     
         15 . The cell as defined in  claim 14 , wherein the dielectric breakdown voltage is at least 2200 volts.  
     
     
         16 . The cell as defined in  claim 15 , wherein the dielectric breakdown voltage is at least 2400 volts.  
     
     
         17 . The cell as defined in  claim 10 , wherein the separator has a maximum effective pore size of from 0.08 μm to 0.40 μm.  
     
     
         18 . The cell as defined in  claim 17 , wherein the maximum effective pore size is no greater than 0.20 μm.  
     
     
         19 . The cell as defined in  claim 10 , wherein the microporous membrane comprises polyethylene.  
     
     
         20 . The cell as defined in  claim 10 , wherein the separator has a BET specific surface area of 4.0 to 15 m 2 /g.  
     
     
         21 . An electrochemical battery cell comprising a housing; a negative electrode, a positive electrode and an electrolyte disposed within the housing; and a separator disposed between the negative and positive electrodes; wherein: 
 (a) the housing comprises a cylindrical container with an integral closed bottom end, an initially open top end, a side wall extending between the bottom and top ends and a cover disposed in the top end to close the cell;    (b) the negative electrode is in the form of a strip with two opposing major surfaces and comprises metallic lithium;    (c) the positive electrode is in the form of a strip with two opposing major surfaces and comprises an active material mixture, the active material comprising greater than 50 weight percent iron disulfide;    (d) the electrolyte comprises one or more salts dissolved in a nonaqueous organic solvent;    (e) the negative and positive electrodes and the separator form a spiral wound cylindrical electrode assembly, with a radial outer surface disposed adjacent an inner surface of the container side wall;    (f) the electrode assembly has an interfacial volume;    (g) the positive electrode has an interfacial capacity;    (h) a ratio of the positive electrode interfacial capacity to the electrode assembly interfacial volume is at least 710 mAh/cm 3 ; and    (h) the separator is a microporous membrane comprising polyethylene, with a machine direction and a transverse direction, an average thickness less than 22 μm and a tensile stress of at least 1.0 kgf/cm in both the machine direction and the transverse direction.    
     
     
         22 . The cell as defined in  claim 21 , wherein the active material comprises at least 95 weight percent iron disulfide.  
     
     
         23 . The cell as defined in  claim 22 , wherein the active material comprises at least 99 weight percent iron disulfide.  
     
     
         24 . The cell as defined in  claim 21 , wherein the tensile stress of the separator is at least 1200 kgf/cm 2  in both the machine direction and the transverse direction.  
     
     
         25 . The cell as defined in  claim 21 , wherein the ratio of the cathode interfacial capacity to the electrode assembly interfacial volume is at least 720 mAh/cm 3 .  
     
     
         26 . The cell as defined in  claim 21 , wherein the separator has a dielectric breakdown voltage of at least 2200 volts.  
     
     
         27 . An electrochemical battery cell comprising a housing; a negative electrode, a positive electrode and an electrolyte disposed within the housing; and a separator disposed between the negative and positive electrodes; wherein: 
 (a) the cell is a cylindrical FR6 type Li/FeS 2  cell with a spiral wound electrode assembly having an electrode assembly interfacial volume;    (b) the cell has an interfacial capacity of at least 3500 mAh;    (c) the separator is a microporous membrane comprising polyethylene and has an average thickness less than 22 μm, a tensile stress of at least 2.0 kgf/cm in both a machine direction and a transverse direction, a dielectric breakdown voltage of at least 2400 volts, a maximum effective pore size of 0.08 μm to 0.20 μm and a BET specific surface area of 4.0 to 15 m 2 /g.    
     
     
         28 . The cell as defined in  claim 27 , wherein a ratio of the cathode-interfacial capacity to the electrode assembly interfacial volume of at least 710 mAh/cm 3 .  
     
     
         29 . An electrochemical battery cell comprising a housing; a negative electrode, a positive electrode and an electrolyte disposed within the housing; and a separator disposed between the negative and positive electrodes; wherein: 
 (a) the cell is a cylindrical FR6 type Li/FeS 2  cell with a spiral wound electrode assembly having an electrode assembly interfacial volume;    (b) the separator is a microporous membrane comprising polyethylene and has an average thickness less than 22 μm, a tensile stress of at least 2.0 in both a machine direction and a transverse direction, a dielectric breakdown voltage of at least 2400 volts and a maximum effective pore size of 0.08 μm to 0.20 μm;    (c) the positive electrode comprises an active material comprising at least 95 weight percent iron disulfide; and    (d) the cell is capable of providing a discharge capacity of at least 2950 mAh when discharged at 200 mA continuously to 1.0 volt and a discharge capacity of at least 2600 mAh when discharged at 1000 mA continuously to 1.0 volt.    
     
     
         30 . An FR6 or FR03 electrochemical cell comprising: 
 a cylindrical housing;    an electrolyte consisting essentially of a lithium salt dissolved in: (i) an acyclic ether, (ii) 1,3-dioxolane and (iii) an optional amount of 3,5-dimethylisoxazole;    a negative electrode consisting essentially of lithium or lithium alloyed with aluminum;    a positive electrode with more interfacial capacity and input capacity relative to the negative electrode, the positive electrode further comprising iron disulfide coated on a current collector having a thickness of no greater than about 25 microns;    an amorphous, biaxially-oriented microporous membrane separator having a thickness between about 16 and 22 microns, a dielectric breakdown voltage of at least 2000 volts and a tensile strength between 1000 kgf/cm 2  and 1500 kfg/cm 2 ;    wherein the negative electrode, the positive electrode and the separator are a spirally wound into an electrode assembly with a void volume of no more than about 0.452 cubic centimeters per centimeter height of electrode assembly; and    wherein, at approximately 50% discharge of the cell, temperature of the cell does not exceed 170° C. during Impact Test.