Electrolyte for a lithium-sulphur cell

1. An electrolyte for a lithium sulphur cell comprising:

at least one lithium salt and at least one organic solvent; and

a surfactant, wherein the concentration of surfactant in the electrolyte is 0.5-3 weight %, wherein the surfactant is a secondary alcohol ethoxylate and wherein the electrolyte comprises sulfone as one of the at least one organic solvents.

2. The electrolyte of claim 1 , wherein the at least one organic solvent comprises sulfone and at least one co-solvent selected from tetrahydrofurane, 2-methyltetrahydrofurane, dimethylcarbonate, diethylcarbonate, ethylmethylcarbonate, methylpropylcarbonate, methylpropylpropionate, ethylpropylpropionate, methyl acetate, dimethoxyethane, 1, 3-dioxolane, diglyme (bis-(2-methoxyethyl)ether), tetraglyme, ethylene carbonate, propylene carbonate, γ-butyrolactone, dioxolane, hexamethyl phosphoamide, pyridine, dimethyl sulfoxide, tributyl phosphate, trimethyl phosphate, N, N, N, N-tetraethyl sulfamide, and mixtures thereof.

3. The electrolyte of claim 1 , wherein the surfactant comprises a secondary alcohol ethoxylate in combination with a second surfactant that is selected from tetraethylene glycol dodecyl ethers, silicone glycols, imidazolines, polyoxyethylenesorbitan monopalmitates and polyoxyethylene nonyl-phenyl ethers and mixtures thereof.

4. The electrolyte of claim 3 , wherein the at least one lithium salt is selected from lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), lithium bis (trifluoromethanesufonyl)imide (LiN(CF 3 SO 2 ) 2 ), lithium tetrafluoroborate, lithium trifluoromethanesulphonate (CF 3 SO 3 Li), and lithium bis(oxalato)borate (LiB(C 2 O 4 ) 2 ).

5. The electrolyte of claim 1 , wherein the concentration of surfactant in the electrolyte is 0.75-3.0 weight %.

6. A lithium-sulphur cell comprising:

an anode comprising lithium metal or lithium metal alloy;

a cathode comprising a mixture of electroactive sulphur material and solid electroconductive material;

a porous separator; and

an electrolyte comprising at least one lithium salt, at least one organic solvent and a surfactant, wherein the surfactant is a secondary alcohol ethoxylate and wherein the electrolyte comprises sulfone as one of the at least one organic solvents.

7. The cell of claim 6 , wherein the separator comprises a mesh formed of a polymeric material.

8. The cell of claim 7 , wherein the polymeric material is selected from polypropylene, nylon and polyethylene or combinations thereof.

9. The cell of claim 6 , wherein the porosity of the separator is 40-60%.

10. The cell of claim 6 , wherein the permeability of the separator is less than 300 Gurley.

11. The cell of claim 6 , wherein the surfactant is present in an amount of 3-35 weight % in relation to the weight of the separator.

12. The cell of claim 6 , wherein the surfactant is has the general formula:

C 12-14 H 25-29 [CH 2 CH 2 O] x H,

where x is an integer of 5 to 9.

13. The cell of claim 12 , wherein the sulfone is sulfolane.

14. A method of producing a lithium-sulphur cell comprising:

incorporating an electrolyte comprising at least one lithium salt, at least one organic solvent, and a surfactant into a cell assembly, the cell assembly comprising:

an anode comprising lithium metal or lithium metal alloy,

a cathode comprising a mixture of electroactive sulphur material and solid electroconductive material, and

a porous separator;

wherein the surfactant is a secondary alcohol ethoxylate and wherein the electrolyte comprises sulfone as one of the at least one organic solvents.

15. The method of claim 14 , further comprising coating the electrolyte on the cathode, placing the separator over the coated cathode and placing the anode over the separator.