Salt additives for secondary sulfur batteries
This application relates to secondary lithium-sulfur batteries with electrolyte comprising a metal di-cation.
1 . A secondary lithium-sulfur battery comprising: a sulfur-containing cathode, a lithium-containing anode, and an electrolyte ionically coupling the lithium-containing anode and the sulfur-containing cathode, characterized in that: the secondary lithium-sulfur battery has an electrolyte-to-sulfur ratio equal to or less than 3.5 microliters of electrolyte per milligram of electroactive sulfur; and the electrolyte comprises a salt additive comprising a metal di-cation, wherein the metal di-cation is zinc, and wherein the salt additive is selected from a group consisting of zinc nitrate, zinc trifluoromethanesulfonate, zinc di[bis(trifluoromethylsulfonyl)imide], zinc trifluoroacetate hydrate, zinc acrylate, zinc methylacrylate, zinc dimethyldithiocarbamate, and combinations thereof.
2 . The secondary lithium-sulfur battery of claim 1 , wherein the electrolyte is a liquid.
3 . The secondary lithium-sulfur battery of claim 1 , wherein the electrolyte is a solid.
4 . The secondary lithium-sulfur battery of claim 1 , wherein the salt additive is present in the electrolyte at a concentration of 0.01 mM to 0.5 M.
5 . The secondary lithium-sulfur battery of claim 1 , characterized in that:
the secondary lithium-sulfur battery has an electrolyte-to-sulfur ratio less than 3.0 microliters of electrolyte per milligram of electroactive sulfur.
6 . The secondary lithium-sulfur battery of claim 1 , characterized in that, when measured at a C-rate of 0.25 or greater, the secondary lithium-sulfur battery containing the salt additive has a discharge capacity that is at least 20% greater than a discharge capacity of a secondary lithium-sulfur battery lacking the salt additive.
7 . The secondary lithium-sulfur battery of claim 1 , characterized in that a loss in discharge capacity exhibited over the first 100 charge-discharge cycles is at least 20% lower than a loss in discharge capacity exhibited by a secondary lithium-sulfur battery lacking the salt additive.
8 . A method of improving performance of a lithium-sulfur battery, comprising a sulfur-containing cathode, a lithium-containing anode, and an electrolyte ionically coupling the lithium-containing anode and the sulfur-containing cathode, wherein one or more salt additives comprising a metal di-cation is added to the electrolyte, wherein the metal di-cation is zinc, and wherein the secondary lithium-sulfur battery has an electrolyte-to-sulfur ratio equal to or less than 3.5 microliters of electrolyte per milligram of electroactive sulfur, and wherein each of the one or more salt additives is selected from the group consisting of zinc nitrate, zinc trifluoromethanesulfonate, zinc di[bis(trifluoromethylsulfonyl)imide], zinc trifluoroacetate hydrate, zinc acrylate, zinc methylacrylate, zinc dimethyldithiocarbamate, and combinations thereof.
9 . In a secondary lithium-sulfur battery having a sulfur-containing cathode, a lithium-containing anode, and an electrolyte ionically coupling the lithium-containing anode and the sulfur-containing cathode, the improvement comprising adding one or more salt additives comprising a metal di-cation, wherein the metal di-cation is zinc, and wherein the secondary lithium-sulfur battery has an electrolyte-to-sulfur ratio equal to or less than 3.5 microliters of electrolyte per milligram of electroactive sulfur and wherein each of the one or more the salt additives is selected from a group consisting of zinc nitrate, zinc trifluoromethanesulfonate, zinc di[bis(trifluoromethylsulfonyl)imide], zinc trifluoroacetate hydrate, zinc acrylate, zinc methylacrylate, zinc dimethyldithiocarbamate, and combinations thereof.