Lithium-iron disulfide cathode formulation having pyrite content and low conductive additives
View Patent ↗The invention relates to primary electrochemical cells having a jellyroll electrode assembly that includes a lithium-based negative electrode, a positive electrode with a coating comprising iron disulfide deposited on a current collector and a polymeric separator. More particularly, the invention relates to a cell designs and cathode formulations incorporating specific types of conductors to improve cell performance.
1. An electrochemical cell comprising:
a cylindrical housing;
a nonaqueous electrolyte including an organic solvent and a spiral wound electrode assembly disposed within the housing;
wherein the spiral wound electrode assembly includes an anode consisting essentially of lithium or a lithium alloy and a cathode mix coated onto a foil current collector at a final solids packing percentage of at least 58% and no more than 63%;
wherein the cathode mix comprises at least 95 wt. % of pyrite, less than 2 wt. % of a binder and less than or equal to 2 wt. % of conductors; and
wherein the conductors include graphite and at least 50 wt. % of acetylene black.
2. The electrochemical cell according to claim 1 , wherein the graphite is mechanically expanded graphite.
3. The electrochemical cell according to claim 1 , wherein the cathode mix consists essentially of 95-98 wt. % pyrite, 1-2 wt. % conductors and less than 2 wt. % of a binder and, optionally, processing aids.
4. The electrochemical cell according to claim 1 , wherein the cathode mix comprises at least 96 wt. % of pyrite.
5. The electrochemical cell according to claim 1 , wherein the solids packing percentage is at least 58% and no more than 60%.
6. The electrochemical cell according to claim 1 , wherein the conductor includes lactonic or phenolic functional groups.
7. The electrochemical cell according to claim 1 , wherein the conductor includes functional groups at a concentration of less than about 50 μg of functional group/g of conductor.
8. The electrochemical cell according to claim 1 , wherein the conductors include at least 55 wt. % of acetylene black.
9. An electrochemical cell comprising:
a cylindrical housing;
a nonaqueous electrolyte including an organic solvent and a spiral wound electrode assembly disposed within the housing;
wherein the spiral wound electrode assembly includes an anode consisting essentially of lithium or a lithium alloy and a cathode mix coated onto a foil current collector at a final solids packing percentage of at least 58% and no more than 63%;
wherein the cathode mix comprises at least 95 wt. % of pyrite, less than 2 wt. % of a binder and less than or equal to 2 wt. % of conductors; and
wherein the conductors include graphitized carbon and graphite.
10. The electrochemical cell according to claim 9 , wherein the graphitized carbon comprises at least 50 wt. % of the conductors.
11. The electrochemical cell according to claim 9 , wherein the graphite is mechanically expanded graphite.
12. The electrochemical cell according to claim 9 , wherein the cathode mix is coated to a solids packing percentage between at least 58% and no more than 60%.
13. The electrochemical cell according to claim 9 , wherein the cathode mix comprises at least 96 wt. % of pyrite.
14. The electrochemical cell according to claim 9 , wherein the conductor includes lactonic or phenolic functional groups.
15. The electrochemical cell according to claim 9 , the conductor includes functional groups at a concentration of less than about 50 μg of functional group/g of conductor.
16. The electrochemical cell according to claim 9 , wherein the cathode mix consists essentially of 95-98 wt. % pyrite, 1-2 wt. % conductors and less than 2 wt. % of a binder and, optionally, processing aids.