High discharge capacity lithium battery
View Patent ↗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 including a positive terminal and negative terminal;
a non-aqueous electrolyte; and
a spirally wound electrode assembly disposed within the housing having:
a) a negative electrode consisting essentially of lithium or a lithium alloy;
b) a lead electrically connecting the negative electrode to the negative terminal;
c) a positive electrode including iron disulfide coated onto a metal foil that is electrically connected to the positive terminal; and
d) a microporous membrane comprising amorphous, biaxially-oriented polyethylene with a dielectric breakdown voltage greater than 2000 volts and a ratio of transverse tensile stress/machine direction tensile stress that is 10/13 or greater.
2. An electrochemical battery cell according to claim 1 , wherein the iron disulfide is selected to have a size of 62 microns or less.
3. An electrochemical battery cell according to claim 1 , wherein the dielectric breakdown voltage is greater than 2400 volts.
4. An electrochemical battery cell according to claim 1 , wherein the BET specific surface area of the membrane is between 15 m 2 /g and 40 m 2 /g.
5. An electrochemical battery cell according to claim 1 , wherein the membrane comprises a single layer.
6. An electrochemical battery cell according to claim 1 , wherein the membrane has a thickness between 10 microns and 20 microns.
7. An electrochemical battery cell according to claim 6 , wherein the ratio of transverse tensile stress/machine tensile stress is 12/15 or greater.
8. An electrochemical battery cell according to claim 6 , wherein the transverse tensile stress/machine tensile stress is between 10/13 and 12/15.
9. An electrochemical battery cell according to claim 6 , wherein the transverse tensile strength and machine tensile stress are about equal.
10. An electrochemical battery cell according to claim 6 , wherein the BET specific surface area of the membrane is between 15 m 2 /g and 40 m 2 /g.
11. An electrochemical battery cell according to claim 6 , wherein the dielectric breakdown voltage is greater than 2400 volts.