Enhanced electrochemical cells with solid-electrolyte interphase promoters
An electrochemical cell with an alkali metal containing anode having high discharge capacity, charge efficiency and low self-discharge. The addition of at least one nitramide or dinitramide salt of a metal cation to the electrochemical cell electrolyte unexpectedly lowers first cycle irreversible capacity, adds higher cycle life, lowers self-discharge and beneficially addresses several additional degrees of freedom with respect to electrolyte solvent selection while providing higher charge capacity. Additives include the lithium metal salts of nitramide or dinitramide, and the electrolyte consists essentially of a lithium metal salt dissolved in a at least one of an aqueous solvent, molten salt solvent system and a non-aqueous solvent mixture of at least one of organic ethers, esters, carbonates, acetals.
1. An electrochemical cell, comprising, in combination:
a negative electrode containing at least one of an alkali metal, an alkali metal alloy, and material intercalating alkali metal;
a positive electrode comprising a cathode active material which electrochemically reacts with alkali metal or intercalates an alkali metal;
an electrolyte that activates negative and positive electrodes; and,
at least one salt selected from the group consisting of dinitramide and nitramide salts of alkali and alkali earth metals, wherein each of the dinitramide salts (structures 1 and 3 below) and nitramide salts (structures 2 and 4 below) is represented by a following formula:
wherein R 1 is a metal including alkali and alkaline earth metals, and R is an inorganic or organic group.
2. The electrochemical cell of claim 1 , wherein the electrolyte solvents are selected from the group consisting of organic ethers, esters, carbonates, and acetals such as 1,2-dimethoxyethane, diglyme, triglyme, tetraglyme, ethylene carbonate, propylene carbonate, dimethyl carbonate, tetrahydrofuran, and dioxolane.
3. The electrochemical cell of claim 1 , wherein the electrolyte solvent is water.
4. The electrochemical cell of claim 1 , wherein the electrolyte is a mixture of molten salts.
5. The electrochemical cell of claim 2 , wherein the alkali metal salt of the at least one salt of a dinitramide and a nitramide is the only salt providing ionic conductivity.
6. The electrochemical cell of claim 3 , wherein the alkali metal salt of the at least one of a dinitramide and a nitramide is the only salt providing ionic conductivity.
7. The electrochemical cell of claim 4 , wherein the alkali metal salt of the at least one salt of a dinitramide and a nitramide is used in a mixture of other alkali metal salts.
8. The electrochemical cell of claim 2 , wherein the alkali metal salt of the at least one salt of a dinitramide and a nitramide is used in a mixture of other alkali metal salts.
9. The electrochemical cell of claim 3 , wherein the alkali metal salt of the at least one salt of a dinitramide and a nitramide is used in a mixture of other alkali metal salts.
10. The electrochemical cell of claim 2 , wherein the negative electrode is lithium metal.
11. The electrochemical cell of claim 3 , wherein the negative electrode is lithium metal.
12. The electrochemical cell of claim 4 , wherein the negative electrode is lithium metal.
13. The electrochemical cell of claim 2 , wherein the positive electrode comprises a positive electrode active material of at least one of sulfur and sulfur containing material.
14. The electrochemical cell of claim 13 , wherein the positive electrode active material is mixed with a conductive additive selected from the group consisting of acetylene black, carbon black, graphite, nickel powder, aluminum powder, titanium powder, stainless steel powder, and mixtures thereof.
15. The electrochemical cell of claim 5 , where the alkali metal salt of the at least one salt of a dinitramide and a nitramide is a lithium salt.
16. The electrochemical cell of claim 9 , wherein the electrolyte includes an alkali metal salt selected from the group consisting of LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 , LiClO 4 , LiAlCl 4 , LiGaCl 4 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 CF 3 ) 2 , LiSCN, LiSO 3 CF 2 CF 3 , LiC 6 F 5 SO 3 , LiO 2 CCF 3 , LiSO 3 F, LiB(C 6 H 5 ) 4 , LiCF 3 SO 3 , and mixtures thereof.
17. The electrochemical cell of claim 7 , wherein the electrolyte includes an alkali metal salt selected from the group consisting of LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 , LiClO 4 , LiAlCl 4 , LiGaCl 4 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 CF 3 ) 2 , LiSCN, LiSO 3 CF 2 CF 3 , LiC 6 F 5 SO 3 , LiO 2 CCF 3 , LiSO 3 F, LiB(C 6 H 5 ) 4 , LiCF 3 SO 3 , and mixtures thereof.
18. The electrochemical cell of claim 8 , wherein the electrolyte includes an alkali metal salt selected from the group consisting of LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 , LiClO 4 , LiAlCl 4 , LiGaCl 4 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 CF 3 ) 2 , LiSCN, LiSO 3 CF 2 CF 3 , LiC 6 F 5 SO 3 , LiO 2 CCF 3 , LiSO 3 F, LiB(C 6 H 5 ) 4 , LiCF 3 SO 3 , and mixtures thereof.
19. The electrochemical cell of claim 2 , wherein the negative electrode comprises a negative electrode active material selected from the group consisting of coke, carbon black, graphite, acetylene black, carbon fibers, glassy carbon, meso carbon micro beads, lithium silicon, or lithium tin composites and alloys and mixtures thereof.
20. The electrochemical cell of claim 2 , wherein the positive electrode comprises a positive electrode active material selected from the group consisting of lithiated oxides, lithiated sulfides, lithiated selenides and lithiated tellurides of the group selected from vanadium, titanium, chromium, copper, molybdenum, niobium, iron, iron phosphate, nickel, cobalt, manganese, and mixtures thereof.