Lithium cell with iron disulfide cathode and improved electrolyte
View Patent ↗A primary cell having an anode comprising lithium and a cathode comprising iron disulfide (FeS 2 ) and carbon particles. The electrolyte comprises a lithium salt dissolved in a solvent mixture which contains 1,3-dioxolane and isosorbide dimethyl ether. The solvent mixture may comprise 1,3-dioxolane, 1,2-dimethoxyethane and additive isosorbide dimethyl ether. The isosorbide dimethyl ether comprises typically between about 2 and 15 percent by weight of the solvent mixture and improves cell service life and performance. A cathode slurry is prepared comprising iron disulfide powder, carbon, binder, and a liquid solvent. The mixture is coated onto a conductive substrate and solvent evaporated leaving a dry cathode coating on the substrate. The anode and cathode can be spirally wound with separator therebetween and inserted into the cell casing with electrolyte then added.
1. A primary electrochemical cell comprising a housing; a positive and a negative terminal; an anode comprising at least one of a lithium metal and lithium alloy; a cathode comprising iron disulfide (FeS 2 ) and conductive carbon; said cell further comprising an electrolyte comprising a lithium salt comprising lithium iodide dissolved in a solvent mixture comprising a cyclic diether dioxolane and an additive isosorbide dimethyl ether.
2. The cell of claim 1 wherein said solvent mixture further comprises a non-cyclic ether 1,2-dimethoxyethane.
3. The cell of claim 2 wherein said cyclic diether dioxolane is a 1,3-dioxolane.
4. The cell of claim 3 wherein said solvent mixture comprises between about 50 and 90 percent by weight of the 1,3-dioxolane.
5. The cell of claim 3 wherein the weight ratio of the 1,3-dioxolane to the 1,2-dimethoxyethane is between about 0.82 and 2.3.
6. The cell of claim 1 wherein said solvent mixture comprises between about 2 and 15 percent by weight of the isosorbide dimethyl ether.
7. The cell of claim 1 wherein said solvent mixture comprises between about 5 and 15 percent by weight of the isosorbide dimethyl ether.
8. The cell of claim 1 wherein the lithium iodide is present in said solvent mixture in a concentration of between about 0.5 and 1.2 moles per liter.
9. The cell of claim 1 wherein said electrolyte has a low viscosity of between about 0.8 and 1.5 centipoise.
10. The cell of claim 1 wherein said cathode comprising iron disulfide (FeS 2 ) and conductive carbon is coated onto a substrate sheet comprising aluminum.
11. The cell of claim 1 wherein said conductive carbon comprises a mixture of carbon black and graphite.
12. The cell of claim 1 wherein said anode is in the form of a sheet.
13. The cell of claim 1 wherein said cathode comprising iron disulfide (FeS 2 ) is in the form of a coating bound to a metallic substrate; wherein said anode and said cathode are arranged in spirally wound form with a separator material therebetween.
14. The cell of claim 13 wherein said separator comprises microporous polypropylene.