Lithium-sulfur battery

Abstract

The present invention concerns a positive electrode including a composite material including sulfur and carbon as an active material and its method of manufacture, a lithium-sulfur battery including such a positive electrode and its method of manufacture.

Claims

1. Positive electrode comprising: at least one composite material including sulfur (S) and carbon (C), as an active electrode material, at least one polymer binder P.sub.1, at least one low-molar-mass liquid linear polyether, and at least one lithium salt L.sub.1, in that the sulfur (S) represents at least 40% by mass in relation to the total mass of said positive electrode, and in that the composite material including sulfur (S) and carbon (C) is obtained according to the following steps: i) a step of mixing an essentially mesoporous carbon agent and a sulfur agent selected from elemental sulfur S.sub.8 and an organic sulfur compound including at least one SS bond, the quantity of sulfur (S) in said mixture ranging from 75% to 85% by mass, ii) a step of milling the mixture obtained in the preceding step i), iii) a step of heat treatment of the milled mixture obtained in the preceding step ii) in a closed container, at a temperature sufficient to melt the sulfur, iv) a step of milling the heat-treated mixture from the preceding step iii) so as to form said composite material, said carbon agent used in step i) exhibiting the following characteristics: a specific surface area S.sub.BET greater than or equal to 700 m.sup.2/g, said specific surface area being calculated by the BET method, an average mesopore size between 4 and 10 nm, said size being calculated by a BJH method, and a total pore volume greater than or equal to 1 cm.sup.3/g, said total pore volume being calculated by a BET method, and wherein the positive electrode is obtained by mixing said composite material, said polymer binder P.sub.1, said lithium salt L.sub.1, and said low-molar-mass liquid linear polyether, so as to form an electrode paste.

2. Positive electrode according to claim 1, wherein the carbon agent is carbon black.

3. Positive electrode according to claim 1, wherein the temperature sufficient for the thermal treatment of step iii) ranges from 115 C. to 270 C.

4. Positive electrode according to claim 1, wherein step iii) is performed in a dry air atmosphere exhibiting a dew point less than or equal to 30 C.

5. Positive electrode according to claim 1, wherein said positive electrode includes 2 to 20% by mass of low-molar-mass liquid linear polyether, in relation to the total mass of the positive electrode.

6. Positive electrode according to claim 1, wherein the low-molar-mass liquid linear polyether is chosen from: polyethylene glycols with the formula H[OCH.sub.2CH.sub.2].sub.mOH, in which m is between 1 and 13, glycol ethers with the formula R[OCH.sub.2CH.sub.2].sub.pOR, in which p is between 1 and 13 and R and R, identical or different, are linear, substituted or cyclic alkyl groups, ethers with the formula R.sup.1[CH.sub.2O].sub.qR.sup.1 in which q is between 1 and 13 and R.sup.1 and R.sup.1, identical or different, are linear, substituted or cyclic alkyls, cyclic ethers, cyclic polyethers, and one of mixtures thereof.

7. Positive electrode according to claim 1, wherein the polyether is tetraethylene glycol dimethyl ether (TEGDME).

8. Positive electrode according to claim 1, wherein said positive electrode includes 5 to 20% by mass of polymer binder P.sub.1, in relation to the total mass of the positive electrode.

9. Positive electrode according to claim 1, wherein said positive electrode includes 2 to 25% by mass of lithium salt L.sub.1, in relation to the total mass of the positive electrode.

10. Positive electrode according to claim 1, wherein the polymer binder P.sub.1 is polyethyleneimine (PEI) or polyaniline in the form of emeraldine salt (ES).

11. Method of manufacturing a positive electrode as defined in claim 1, said method comprising the steps of: a) a step of mixing said composite material including sulfur (S) and carbon (C) and as defined in claim 1 with said at least one polymer binder P.sub.1, said at least one lithium salt L.sub.1, said at least one low-molar-mass liquid linear polyether, and optionally at least one solvent of said polymer binder P.sub.1, for obtaining said electrode paste, b) a step of applying said electrode paste onto at least one support, c) a step of drying said electrode paste for obtaining a positive electrode in the form of a supported film.

12. Method according to claim 11, wherein said solvent represents less than 30% by mass of the total mass of the mixture of composite material, of polymer binder P.sub.1, lithium salt L.sub.1 and polyether.

13. Method according to claim 11, wherein step a) is performed by extrusion or by milling.

14. Lithium-sulfur battery, wherein said lithium-sulfur battery includes: a positive electrode as defined in claim 1, a metallic negative electrode selected from lithium and a lithium alloy, a gelified polymer electrolyte including at least one low-molar-mass liquid linear polyether as defined in claim 6, at least one lithium salt L.sub.2, and at least one polymer binder P.sub.2.

15. Lithium-sulfur battery according to claim 14, wherein the gelified polymer electrolyte includes 20 to 45% by mass of lithium salt L.sub.2, in relation to the total mass of the gelified polymer electrolyte.

16. Lithium-sulfur battery according to claim 14, wherein the lithium salt L.sub.2 is selected from the group consisting of lithium fluorate (LiFO.sub.3), lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), lithium hexafluorophosphate (LiPF.sub.6), lithium fluoroborate (LiBF.sub.4), lithium metaborate (LiBO.sub.2), lithium perchlorate (LiClO.sub.4), lithium nitrate (LiNO.sub.3), lithium bis(fluorosulfonyl) imide (LiFSI), and mixtures thereof.

17. Lithium-sulfur battery according to claim 14, wherein the gelified polymer electrolyte includes 3 to 20% by mass of polyether, in relation to the total mass of the gelified polymer electrolyte.

18. Lithium-sulfur battery according to claim 14, wherein the gelified polymer electrolyte includes 40 to 80% by mass of polymer binder P.sub.2, in relation to the total mass of the gelified polymer electrolyte.

19. Lithium-sulfur battery according to claim 14, wherein the polymer binder P.sub.2 is selected from the group consisting of polyolefins such as ethylene and propylene homopolymers or copolymers, or a mixture of at least two of these polymers; homopolymers and copolymers of ethylene oxide (e.g. PEO, copolymer of PEO), methylene oxide, propylene oxide, epichlorohydrin, or allyl glycidyl ether, or mixtures thereof; halogenated polymers such as homopolymers and copolymers of vinyl chloride, vinylidene fluoride (PVDF), vinylidene chloride, ethylene tetrafluoride or chlorotrifluoroethylene, copolymers of vinylidene fluoride and hexafluoropropylene (PVDF-HFP) or mixtures thereof; anionic electronic non-conductive polymers such as polystyrene sulfonate, polyacrylic acid, polyglutamate, alginate, pectin, or mixtures thereof; polyacrylates; and one of the mixtures thereof.

20. Method of manufacturing a lithium-sulfur battery as defined in claim 14, comprising the steps of: A) a step of preparing the gelified polymer electrolyte; and B) a step of assembling the positive electrode, a negative electrode and the gelified polymer electrolyte as obtained in the preceding step A).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1a-1b, 2a-2b, 3a-3b and 4a-4b respectively show composite materials A, B, 1 and 2 from example 1 through scanning electron microscopy (SEM). FIGS. 1b, 2b, 3b and 4b are enlargements of a part of FIGS. 1a, 2a, 3a and 4a respectively;

(2) FIG. 5 is an image from Example 1 showing a mixture of Ketjenblack carbon black and elemental sulfur (mass proportions: 18.8% Ketjenblack carbon black and 81.2% elemental sulfur) by SEM after step ii) of milling and before step iii) of heat treatment;

(3) FIG. 6 is a graph of the measurements of specific capacities during discharge for batteries B-A, B-B, B-1 and B-2 from Example 3; and

(4) FIG. 7 is a graph of the measurements of specific capacities during discharge for batteries B-C, B-D, B-E, B-3 and B-4 from example 6.

DETAILED DESCRIPTION

(5) The present invention is illustrated by the examples below, to which it is, however, not limited.

EXAMPLES

(6) The raw materials used in the examples are listed below: porous carbon carbon black (BET specific surface area: 2 000 m.sup.2/g), ACS Material, Specialty carbon black 5303, Asbury, ENSACO 350G Conductive Carbon Black, Timcal, Ketjenblack 600JD carbon black, AkzoNobel, 99.5% purity sulfur S.sub.8, Sigma Aldrich, ZSN 8100 copolymer of PEO, Zeospan, copolymer of poly(vinylidene difluoride-hexafluoropropylene) (PVDF-HFP), Solvay, polyethyleneimine (PEI), 50% (weight/volume) in H.sub.2O, Sigma Aldrich, polyaniline in the form of Emeraldine salt (ES), Sigma Aldrich, LiTFSI, 3M, silicone-coated PET film, Mitsubishi.

(7) Unless stated otherwise, all the materials were used as received from the suppliers.

Example 1

Preparation of a Plurality of Composite Materials A, B, 1 and 2

(8) Four carbon/sulfur mixtures were prepared by mixing each of the ACS, Asbury, Timcal and Ketjenblack carbon blacks with sulfur S.sub.8 in the following C/S mass proportions: 21.7/78.3 (with the ACS, Timcal and Ketjenblack carbon blacks) and 18.8/81.2 (with the Asbury carbon black).

(9) The four C/S mixtures thus obtained were then milled in a mortar then stored in four closed containers.

(10) The four containers each containing one of the different milled mixtures of carbon and sulfur were subjected to a heat treatment at a temperature of 155 C. for 2 hours.

(11) The heat-treated mixtures were then milled in a mortar to obtain the following four composite materials: A including ACS carbon black, B including Asbury carbon black, 1 including Timcal carbon black and 2 including Ketjenblack carbon black.

(12) Table 1 below displays the characteristics [specific surface area (in m.sup.2/g), total pore volume (in cm.sup.3/g), pore volume (in cm.sup.3/g), average pore diameter (in nm)] of the different carbon blacks used for preparing the corresponding composite materials A, B, 1 and 2:

(13) TABLE-US-00001 TABLE 1 Carbon black ACS Asbury Timcal Ketjenblack Specific 3802 183 860 1529 surface area (Langmuir) (BET) (BET) (BET) (m.sup.2/g) Total volume 1.34 0.49 1.21 3.24 (cm.sup.3/g) (<283 nm).sup.a (<277 nm).sup.a (<192 nm).sup.a (<126 nm).sup.a BJH volume ND 0.30 0.96 2.84 (cm.sup.3/g) 2-50 nm Average pore 2.17 10.62 5.63 8.48 diameter (BET) (nm) Average pore ND 7.89 4.93 7.74 diameter (BJH) (nm) Composite A .sup.(*.sup.) B .sup.(*.sup.) 1 2 material obtained .sup.(*.sup.) Composite materials not forming part of the invention .sup.aaverage maximum pore diameter taken into account for calculating the total volume.

(14) The different carbon blacks tested in the different composite materials do not have the same characteristics (pore size, pore volume, porous surface, etc.) and therefore exhibit very different performances.

(15) It should be noted that composite materials 1 and 2 are in conformity with the invention, whereas composite materials A and B do not form part of the invention since the ACS and Asbury carbon blacks from which composite materials A and B have been respectively obtained do not have the desired characteristics in terms of pore structure.

(16) The specific surface area, total pore volume, BJH pore volume, average pore diameter of each of the ACS, Asbury, Timcal and Ketjenblack carbon blacks were evaluated with the aid of a device sold under the trade name ASAP2010, by Micromeritics.

(17) FIGS. 1, 2, 3 and 4 respectively show composite materials A, B, 1 and 2 through scanning electron microscopy (SEM). FIGS. 1b, 2b, 3b and 4b are enlargements of a part of FIGS. 1a, 2a, 3a and 4a respectively.

(18) The scanning electron microscopy (SEM) analysis was performed with the aid of an apparatus sold under the trade name JSM-7600F, by JEOL.

(19) FIG. 1 shows that composite material A, not forming part of the invention and prepared from ACS carbon black, includes sulfur agglomerates. Indeed, ACS carbon black has an average pore size too small to enable the sulfur to be incorporated and homogeneously dispersed in the ACS carbon black. The presence of large agglomerates of sulfur causes the collapse of the positive electrode during cycling and does not achieve a good cyclability.

(20) As indicated in the present invention, the pore size of the carbon must be sufficiently large (i.e. greater than 4 nm) to enable the molten sulfur to penetrate inside the pores, but sufficiently small (i.e. less than 10 nm) to exert sufficient retention of the polysulfides during cycling.

(21) FIG. 2 shows that in composite material B, not forming part of the invention and prepared from Asbury carbon black, the sulfur seems better dispersed locally even if it is not present over the entire surface of the Asbury carbon black. Indeed, Asbury carbon black has an appropriate average pore size of about 9-10 nm, however the specific surface area of Asbury carbon black is not sufficient to enable the sulfur to be well distributed in the carbon porosity. Finally, its total pore volume is also not sufficiently high for all of the sulfur to be contained therein.

(22) FIGS. 3 and 4 show that composite materials 1 and 2, forming part of the invention and prepared respectively from Timcal and Ketjenblack carbon blacks, have the same structure as the basic carbon blacks. A luster indicates the presence of sulfur. The sulfur, after this pretreatment, is homogeneously distributed around the carbon grains and does not form agglomerates outside them.

(23) As a comparison, FIG. 5 shows a mixture of Ketjenblack carbon black and elemental sulfur (mass proportions: 18.8% Ketjenblack carbon black and 81.2% elemental sulfur) by SEM after step ii) of milling and before step iii) of heat treatment. It is observed that the sulfur does not coat the carbon grains and is not homogeneously dispersed in the carbon agent.

Example 2

Preparation of a Plurality of Positive Electrodes E-A, E-B, E-1 and E-2

(24) Each of the composite materials A, B, 1 and 2 obtained in Example 1 was mixed at 80 C. for 30 minutes with tetraethylene glycol dimethyl ether (TEGDME), Emeraldine in salt form (ES), a lithium salt (LiTFSI) and N-methylpyrrolidone (NMP) in a mixer sold under the trade name Plastograph EC by Brabender. The quantity of NMP used represented at most about 30% by mass of the total mass of the composite material, of TEGDME, ES and lithium salt.

(25) Each of the pastes thus obtained was then laminated at 95 C. on an aluminum current collector covered with a carbon-based layer.

(26) Each of the films thus obtained was dried at 105 C. for 30 minutes to obtain a positive electrode in film form in conformity with the invention.

(27) Table 2 below sets out the mass composition of the four electrodes obtained:

(28) TABLE-US-00002 TABLE 2 Carbon Lithium black salt TEGDME PANI S Electrode (%) (%) (%) (%) (%) .sup.E-A.sup.(*.sup.) 15.01 17.85 4.14 9.00 54.00 .sup.E-B.sup.(*.sup.) 12.48 19.96 4.63 9.00 53.93 E-1 14.98 17.93 4.16 9.00 53.93 E-2 15.00 17.85 4.15 9.00 54.00 .sup.(*.sup.)Electrode not forming part of the invention

Example 3

Manufacture of Batteries Including Positive Electrodes E-A, E-B, E-1 and E-2

(29) a) Preparation of a Gelified Polymer Electrolyte EG in Conformity with the Invention

(30) Some lithium salt (LiTFSI) (39% by mass) was dissolved in the TEGDME (6% by mass) with magnetic stirring at 50 C. Then, a copolymer of Zeospan PEO (20% by mass) and PVDF-HFP (35% by mass) were added to the mixture obtained. The resulting mixture was blended in the Plastograph EC mixer as described in Example 2, at 130 C. for 1 hour. The electrolyte paste obtained was laminated at 125 C. between two silicone-coated PET plastic films.

(31) b) Battery Assembly

(32) Four batteries B-A, B-B, B-1 and B-2 were respectively prepared by assembling in an anhydrous atmosphere (air with a dew point <40 C.) by laminating at 5 bar and at 80 C.: each of the four positive electrodes E-A, E-B, E-1 and E-2 obtained in Example 2, the gelified polymer electrolyte EG as obtained above in step a), and a negative electrode including lithium metal in the form of a film of lithium metal about 100 m in thickness.

(33) Table 3 below sets out the different batteries B-A, B-B, B-1 and B-2 manufactured respectively with positive electrodes E-A, E-B, E-1 and E-2 and the gelified polymer electrolyte EG:

(34) TABLE-US-00003 TABLE 3 Positive Batteries electrode Electrolyte Comments B-1 E-1 EG Battery forming part of the invention B-2 E-2 EG Battery forming part of the invention B-A.sup.(*.sup.) E-A EG Battery not forming part of the invention: composite material not in conformity with the invention B-B.sup.(*.sup.) E-B EG Battery not forming part of the invention: composite material not in conformity with the invention .sup.(*.sup.)Battery not forming part of the invention

(35) Measurements of specific capacities during discharge for batteries B-A, B-B, B-1 and B-2 are reported in FIG. 6, a figure in which the specific capacity (in mAh/g) is according to the number of cycles with a current regime of 2 lithiums in 10 h (C/10). In this FIG. 6, the specific capacity measurements during discharge are made in relation to the mass of sulfur. According to FIG. 6, batteries B1 (curve with solid squares) and B-2 (curve with solid circles) forming part of the invention exhibit an initial specific capacity of about 550 to 600 mAh/g, while batteries B-A (curve with solid diamonds) and B-B (curve with solid triangles) not forming part of the invention exhibit a lower initial specific capacity of about 500 to 525 mAh/g. In addition, the cycling resistance of batteries B-A and B-B is very inadequate since the specific capacity decreases drastically after 2 cycles.

(36) In particular, the specific capacity of battery B-2 is stable over at least 10 cycles.

(37) These results show that the nature of the carbon agent (e.g. pore structure) used for preparing the composite material is important, in order to obtain a high initial specific capacity and good cyclability.

Example 4

Preparation of Two Positive Electrodes E-3 and E-4 in Conformity with the Invention

(38) A composite material 2 was prepared as in Example 1, but with a mixture of sulfur S.sub.8 and Ketjenblack carbon black in C/S mass proportions: 18.8/81.2.

(39) Each of the composite materials 2 (obtained in Example 1) and 2 (as defined above) was mixed at 80 C. for 30 minutes with TEGDME, PEI or PVDF-HFP, LiTFSI, water (for composite material 2) or NMP (for composite material 2) in the Plastograph EC mixer as described in Example 2. The quantity of solvent (water or NMP) used represented at most about 30% by mass of the total mass of the composite material mixture, of TEGDME, PEI or PVDF-HFP, and LiTFSI.

(40) Each of the pastes thus obtained was then laminated at 95 C. on an aluminum current collector covered with a carbon-based layer.

(41) Each of the films thus obtained was dried at 105 C. for 30 minutes to obtain a positive electrode in film form in conformity with the invention.

(42) Table 4 below sets out the mass composition of the two electrodes E-3 and E-4 forming part of the invention and obtained by the method described above:

(43) TABLE-US-00004 TABLE 4 Carbon PVDF- black LiTFSI TEGDME HFP PEI S Electrode (%) (%) (%) (%) (%) (%) E-3 12.5 20 3 10 0 54 E-4 15 3.9 15.1 0 12 54

Example 5

Preparation of Three Positive Electrodes E-C, E-D and E-E Not in Conformity with the Invention

(44) The positive electrode E-C was prepared by extruding a mixture of powders of composite material 2 obtained in Example 4, of lithium salt (LiTFSI) and copolymer of PEO, then by laminating the paste thus obtained at 95 C. on an aluminum current collector covered with a carbon-based layer. The paste was then dried at 105 C. for 30 minutes to obtain a positive electrode in film form not in conformity with the invention.

(45) The positive electrode E-C does not form part of the invention since it does not contain any low-molar-mass liquid linear polyether as defined in the invention.

(46) The positive electrode E-D was prepared by extruding a mixture of elemental sulfur Ss, Ketjenblack carbon black, lithium salt (LiTFSI) and low-molar-mass liquid linear polyether TEGDME, then by laminating the paste thus obtained at 95 C. on an aluminum current collector covered with a carbon-based layer. The paste was then dried at 105 C. for 30 minutes to obtain a positive electrode in film form not in conformity with the invention.

(47) The positive electrode E-D does not form part of the invention since the mixture of sulfur agent and carbon agent did not undergo any pretreatment before the manufacture of the positive electrode.

(48) The positive electrode E-E was prepared by extruding a mixture of elemental sulfur Ss, Ketjenblack carbon black, lithium salt (LiTFSI) and copolymer of PEO, then by laminating the paste thus obtained at 95 C. on an aluminum current collector covered with a carbon-based layer. The paste was then dried at 105 C. for 30 minutes to obtain a positive electrode in film form not in conformity with the invention.

(49) The positive electrode E-E does not form part of the invention since it does not contain any low-molar-mass liquid linear polyether as defined in the invention and the mixture of sulfur agent and carbon agent did not undergo any pretreatment before the manufacture of the positive electrode.

(50) Table 5 below sets out the mass composition of the three electrodes E-C, E-D, and E-E not forming part of the invention and obtained by the method described above:

(51) TABLE-US-00005 TABLE 5 Carbon Copolymer PVDF- black LiTFSI of PEO HFP TEGDME S Electrode (%) (%) (%) (%) (%) (%) E-C.sup.(*.sup.) 15 6 25 10 0 54 E-D.sup.(*.sup.) 7 17 0 20 3 54 E-E.sup.(*.sup.) 5 9 16 16 0 54 .sup.(*.sup.)Electrode not forming part of the invention

Example 6

Manufacture of Batteries Including Positive Electrodes E-C, E-D, E-E, E-3 and E-4

(52) a) Preparation of a Gelified Polymer Electrolyte EG in Conformity with the Invention

(53) Some lithium salt (LiTFSI) (39% by mass) was dissolved in the TEGDME (6% by mass) with magnetic stirring at 50 C. Then, a copolymer of Zeospan PEO (20% by mass) and PVDF-HFP (35% by mass) were added to the mixture obtained. The resulting mixture was blended in the Plastograph EC mixer as described in Example 2, at 130 C. for 1 hour. The electrolyte paste obtained was laminated at 125 C. between two silicone-coated PET plastic films.

(54) b) Preparation of a Gelified Polymer Electrolyte ES Not in Conformity with the Invention

(55) The solid polymer electrolyte was prepared by extruding a mixture of lithium salt (LiTFSI) (12% by mass), copolymer of Zeospan PEO (48% by mass) and PVDF-HFP (40% by mass), then by laminating the electrolyte paste obtained at 125 C. between two plastic films of silicone-coated PET.

(56) c) Battery Assembly

(57) Five batteries B-C, B-D, B-E, B-3 and B-4 were prepared by assembling by laminating at 5 bar, at 80 C. and in an anhydrous atmosphere (air with a dew point <40 C.): each of the five positive electrodes E-C, E-D, E-E, E-3 and E-4 obtained in Examples 4 and 5, one of the polymer electrolytes ES or EG as obtained in step a) or b) above, and a negative electrode including lithium metal.

(58) Table 6 below sets out the different batteries B-C, B-D, B-E, B-3 and B-4 manufactured respectively with positive electrodes E-C, E-D, E-E, E-3 and E-4 and one of the gelified polymer electrolytes ES or EG:

(59) TABLE-US-00006 TABLE 6 Positive Battery electrode Electrolyte Comments B-3 E-3 EG Battery forming part of the invention B-4 E-4 EG Battery forming part of the invention B-C E-C ES Battery not forming part of the invention: electrolyte and electrode not in conformity with the invention B-D E-D EG Battery not forming part of the invention: electrode not in conformity with the invention B-E E-E ES Battery not forming part of the invention: electrolyte and electrode not in conformity with the invention

(60) Measurements of specific capacities during discharge for batteries B-C, B-D, B-E, B-3 and B-4 are reported in FIG. 7, a figure in which the specific capacity (in mAh/g) is according to the number of cycles with a current regime of 2 lithiums in 10 hours (C/10). In this FIG. 7, the specific capacity measurements during discharge are made in relation to the mass of sulfur. According to FIG. 7, batteries E3 (curve with solid black squares) and E-4 (curve with solid black circles) forming part of the invention exhibit an initial specific capacity of about 210 and 490 mAh/g respectively, and batteries E-C (curve with solid gray triangles), E-D (curve with solid gray diamonds) and E-E (curve with solid black diamonds) not forming part of the invention exhibit an initial specific capacity of about 290, 210 and 425 mAh/g respectively. In addition, batteries B-C, B-D and B-E exhibit a very inadequate cycling resistance since the specific capacity decreases drastically after 2 cycles.

(61) The specific capacity of batteries E-3 and E-4 is stable for at least 10 cycles.

(62) These results show that the combination of pretreatment of the carbon agent and sulfur agent mixture and the use of the gelified polymer electrolyte makes it possible to obtain a clear improvement both in initial specific capacity and in cyclability.

(63) Thus, a real synergy effect is observed between the positive electrode and electrolyte compositions, notably at 100 C. (operating temperature of the battery in the examples of the invention).

(64) Indeed, when the gelified polymer electrolyte EG is replaced by a solid polymer electrolyte ES (battery B-C, curve with the solid gray triangles), the discharge capacity decreases after only a few cycles. Similarly, when the gelified polymer electrolyte EG is replaced by a solid polymer electrolyte ES and the pretreatment of the sulfur agent and carbon agent mixture is not performed (battery B-E, curve with solid black diamonds), the discharge capacity decreases drastically after only a few cycles. Likewise, the use of a gelified polymer electrolyte EG with a conventional positive electrode, i.e. without pretreatment of the sulfur agent and carbon agent mixture (battery B-D, curve with solid gray diamonds) gives similar results.

(65) On the other hand, the use of a positive electrode and an electrolyte both in conformity with the invention (battery B-3, curve with solid black squares) reveals a stabilization and even a slight increase in capacity even after a larger number of cycles. Cyclability is therefore strongly improved thanks to the invention.

(66) FIG. 7 also shows that the addition into the positive electrode of a conductive polymer such as PEI ensures a good cyclability of the battery while increasing the value of the initial discharge capacity (battery B-4, curve with solid black circles) by about 50%.