Lithium-sulphur battery

1. Lithium-sulphur battery comprising:

a negative electrode comprising lithium metal or an alloy of lithium metal,

a positive electrode comprising at least one sulphur-comprising agent chosen from elemental sulphur S 8 and an organic sulphur-comprising compound having at least one S—S bond, at least one polymer binder P 1 and at least one agent generating an electron conductivity,

an electrolyte comprising at least one liquid linear or cyclic polyether of low molar mass and at least one lithium salt L 1 , and

a porous separator,

wherein the porous separator is a biaxially oriented separator comprising at least polypropylene and said positive electrode comprises at least 40% by weight approximately of sulphur (S) with respect to the total weight of said positive electrode.

2. Battery according to claim 1 , wherein the separator exhibits a thickness ranging from 5 μm to 50 μm.

3. Battery according to claim 1 , wherein the separator exhibits a porosity of greater than or equal to 50% by volume.

4. Battery claim 1 , wherein the separator exhibits pores with a mean size ranging from 50 nm to 3 μm.

5. Battery claim 1 , wherein the separator exhibits a porosity of Gurley type ranging from 50 to 500 s/100 cm 3 .

6. Battery claim 1 , wherein the separator exhibits a heat shrinkage in the longitudinal direction and/or a heat shrinkage in the transverse direction strictly of less than 15%.

7. Battery claim 1 , wherein the polyether is chosen from:

polyethylene glycols of formula H—[O—CH 2 —CH 2 ] m —OH in which m is between 1 and 13, glycol ethers of formula R—[O—CH 2 —CH 2 ] p —O—R in which p is between 1 and 13 and R and R′, which are identical or different, are linear, branched or cyclic alkyl groups which can comprise from 1 to 20 carbon atoms,

ethers of formula R 1 -[CH 2 -O] q —R 1′ in which q is between 1 and 13 and R 1 and R 1′ , which are identical or different, are linear, branched or cyclic alkyls which can comprise from 1 to 20 carbon atoms and optionally heteroatoms,

cyclic ethers which can comprise from 2 to 20 carbon atoms or cyclic polyethers which can comprise from 3 to 40 carbon atoms, and

one of their mixtures.

8. Battery claim 1 , wherein the lithium salt L 1 is chosen from lithium fluorate (LiFO 3 ), lithium bis(trifluoromethanesulphonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF 6 ), lithium fluoroborate (LiBF 4 ), lithium metaborate (LiBO 2 ), lithium perchlorate (LiClO 4 ), lithium nitrate (LiNO 3 ), lithium bis(fluorosulphonyl)imide (LiFSI) and their mixtures.

9. Battery claim 1 , wherein the electrolyte is a liquid electrolyte and the concentration of the lithium salt Li in the liquid electrolyte ranges from 0.8 to 8 mol/1.

10. Battery claim 1 , wherein the electrolyte is a gelled polymer electrolyte and it additionally comprises at least one polymer binder P 2 .

11. Battery according to claim 10 , wherein the electrolyte comprises from 20 to 70% by weight of polymer binder P 2 .

12. Battery according to claim 10 , wherein the electrolyte comprises from 15 to 45% by weight of lithium salt L 1 .

13. Battery according to claim 10 , wherein the electrolyte comprises from 5 to 40% by weight of polyether.

14. Battery claim 1 , wherein the agent generating an electron conductivity is an essentially mesoporous carbon-comprising agent exhibiting the following characteristics:

an S BET specific surface of greater than or equal to 800 m 2 /g, said specific surface being calculated by the BET method,

a mean size of the mesopores of between 4 and 10 nm, said size being calculated by the BJH method, and

a total pore volume of greater than or equal to 1.5 cm 3 /g, said total pore volume being calculated by the BET method.

15. Battery according to claim 14 , wherein said essentially mesoporous carbon-comprising agent is subjected, in the presence of the sulphur-comprising agent, to a pretreatment in order to form a composite material comprising sulphur (S) and carbon (C), said pretreatment comprising the following stages:

i) a stage of mixing an essentially mesoporous carbon-comprising agent as defined in claim 14 and a sulphur-comprising agent as defined in claim 1 , the amount of sulphur (S) in said mixture ranging from 75% to 85% by weight,

ii) a stage of grinding the mixture obtained in the preceding stage i),

iii) a stage of heat treatment of the ground mixture obtained in the preceding stage ii) in a closed container, at a temperature sufficient to cause the sulphur to melt, and

iv) a stage of grinding the heat-treated mixture of the preceding stage iii) in order to obtain a composite material comprising sulphur (S) and carbon (C).

16. Battery according to claim 14 , wherein the carbon-comprising agent is carbon black.

17. Process for the manufacture of a battery as defined in claim 1 , wherein said process comprises the following stages:

A) a stage of preparation of a liquid or gelled polymer electrolyte,

B) a stage of assembling a positive electrode, a negative electrode and a separator,

said process initially comprising one or other of the following stages:

C-1) a stage of impregnation of the assembly as obtained in stage B) by the liquid electrolyte prepared in stage A), or

C-2) a stage of impregnation of the separator by the gelled polymer electrolyte prepared in stage A), said impregnation being prior to the assembling stage B).