ORGANIC LITHIUM BATTERY

Abstract

The present invention relates to the field of organic lithium batteries having high energy and power densities. In particular, the present invention relates to an organic lithium battery comprising a positive electrode based on redox organic compounds and a porous separator made of biaxially oriented polypropylene, and to its process of manufacture.

Claims

1. Organic lithium battery comprising: a negative electrode comprising lithium metal or an alloy of lithium metal, a positive electrode optionally supported by a current collector, said positive electrode comprising at least one redox organic structure, at least one polymer binder P.sub.1 and at least one agent generating an electron conductivity, said redox organic structure being different from the sulphur-comprising agents chosen from elemental sulphur S.sub.8 and sulphur-comprising organic compounds comprising at least one S—S bond, and a porous separator impregnated with an electrolyte, wherein porous separator is a biaxially oriented separator comprising at least polypropylene and the electrolyte comprises at least one liquid linear or cyclic polyether of low molar mass and at least one lithium salt L.sub.1.

2. Battery according to claim 1, wherein the liquid linear or cyclic polyether of low molar mass is a liquid linear or cyclic polyether with a molar mass of less than or equal to 10 000 g.Math.mol.sup.−1.

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

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

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

6. Battery according to claim 1, wherein the porous separator exhibits an elongation at break of at least 5 mm.

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

8. Battery according to claim 1, wherein the porous separator exhibits a heat shrinkage in the longitudinal direction and/or a heat shrinkage in the transverse direction strictly of less than 15%, whatever its thickness.

9. Battery according to claim 1, wherein the lithium salt L.sub.1 is chosen from lithium fluorate (LiFO.sub.3), lithium bis(trifluoromethanesulphonyl)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(fluorosulphonyl)imide (LiFSI), lithium bis(oxalato)borate (LiBOB or LiB(C.sub.2O.sub.4).sub.2) and their mixtures.

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

11. Battery according to claim 10, wherein the polymer binder P.sub.2 is chosen from homopolymers and copolymers of ethylene; homopolymers and copolymers of propylene; homopolymers and copolymers of ethylene oxide, of methylene oxide, of propylene oxide, of epichlorohydrin or of allyl glycidyl ether, and their mixtures; halogenated polymers; non-electron-conducting polymers of anionic type; polyacrylates; polymers of cationic type; and one of their mixtures.

12. Battery according to claim 10, wherein the gelled polymer electrolyte comprises from 20 to 70% by weight of polymer binder P.sub.2, with respect to the total weight of the gelled polymer electrolyte.

13. Battery according to claim 10, wherein the gelled polymer electrolyte comprises from 15 to 45% by weight of lithium salt L.sub.1, with respect to the total weight of the gelled polymer electrolyte.

14. Battery according to claim 10, wherein the gelled polymer electrolyte comprises from 5 to 40% by weight of liquid linear or cyclic polyether of low molar mass, with respect to the total weight of the gelled polymer electrolyte.

15. Battery according to claim 1, wherein the electrolyte is a liquid electrolyte and the concentration of the lithium salt L.sub.1 in the liquid electrolyte ranges from 0.5 to 8 mol/l.

16. Battery according to claim 1, wherein the positive electrode of the battery of the invention comprises at least 45% by weight of redox organic structure, with respect to the total weight of said positive electrode.

17. Battery according to claim 1, wherein the redox organic structure comprises at least two carbonyl C═O functional groups, two thione C═S functional groups or two imine C═N functional groups.

18. Battery according to claim 1, wherein the positive electrode comprises from 1 to 30% by weight of agent generating an electron conductivity, with respect to the total weight of the positive electrode.

19. Battery according to claim 1, wherein the agent generating an electron conductivity is chosen from carbon black, sp carbon, acetylene black, carbon fibres and nanofibres, carbon nanotubes, graphene, graphite, metal particles and fibres, and one of their mixtures.

20. Battery according to claim 1, wherein the positive electrode comprises from 2 to 30% by weight of polymer binder P.sub.1, with respect to the total weight of the positive electrode.

21. Battery according to claim 1, wherein the polymer binder P.sub.1 is chosen from homopolymers and copolymers of ethylene; homopolymers and copolymers of propylene; homopolymers and copolymers of ethylene oxide, of methylene oxide, of propylene oxide, of epichlorohydrin or of allyl glycidyl ether, and their mixtures; halogenated polymers; polyacrylates; polyalcohols; electron-conducting polymers; polymers of cationic type; polymers of anionic type; and one of their mixtures.

22. Process for the manufacture of an organic lithium battery as defined in claim 1, wherein said process comprises the following stages: A) a stage of preparation of a liquid electrolyte or of a gelled polymer electrolyte B) a stage of assembling a positive electrode, a negative electrode and a porous separator, said process additionally 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 porous separator by the gelled polymer electrolyte prepared in stage A), said impregnation being prior to the assembling stage B).

Description

EXAMPLES

[0133] The starting materials used in the examples are listed below: [0134] Ketjenblack 600JD® carbon black, AkzoNobel, [0135] Anthraquinone, with a purity of 97%, Sigma Aldrich, [0136] Polyethyleneimine (PEI), at 50% by weight in water, Fluka, Sigma Aldrich, [0137] LiTFSI, 3M, [0138] Silicone-treated PET film, Mitsubishi, [0139] Tetraethylene glycol dimethyl ether (TEGDME), with a purity of 99%, Sigma Aldrich, [0140] copolymer of PEO (co-PEO), Mw˜10.sup.5 g.Math.mol.sup.−1, ZSN 8100, Zeospan, [0141] Biaxially oriented monolayer separator made of polypropylene S-1, BPF220, Bolloré, [0142] Monolayer separator made of polypropylene S-2, Celgard 2500.

[0143] Unless otherwise indicated, all the materials were used as received from the manufacturers.

Example 1

Manufacture of an Organic Lithium Battery in Accordance with the Invention

[0144] 1.1 Preparation of the Positive Electrode

[0145] 2.25 g of Ketjenblack carbon black were mixed manually with 31.5 g of anthraquinone at ambient temperature.

[0146] The mixture prepared above was subsequently mixed, at 80° C. for 20 minutes, with 5.085 g of tetraethylene glycol dimethyl ether (TEGDME), 9 g of 50% solution of polyethyleneimine (PEI), 1.665 g of lithium salt (LiTFSI) and 5 g of water in a mixer sold under the Plastograph® EC trade name by Brabender®. The amount of water used represented 20% by weight approximately of the total weight of the carbon black, of the anthraquinone, of the polyethyleneimine PEI and of the lithium salt LiTFSI.

[0147] The paste thus obtained was subsequently laminated at 95° C. on a current collector made of aluminium covered with a carbon-based layer.

[0148] The film thus obtained was dried at 120° C. for 20 minutes in an oven in order to obtain a positive electrode E-1 in the form of a film in accordance with the invention.

[0149] The composition by weight of the positive electrode E-1 obtained is presented in Table 1 below:

TABLE-US-00001 TABLE 1 Carbon Lithium Positive black TEGDME salt PEI Anthraquinone electrode (%) (%) (%) (%) (%) E-1 5 11.3 3.7 10 70

[0150] 1.2 Preparation of a Liquid Electrolyte and Characteristics of the Separators Used

[0151] A liquid electrolyte consisting of LiTFSI in tetraethylene glycol dimethyl ether (TEGDME) and comprising 30.1% by weight of LiTFSI was prepared. A 1.51 mol/l solution of lithium salt in TEGDME was thus obtained.

[0152] The characteristics of the separators S-1 and S-2 used in the present example: the thickness t (in μm), the porosity P (in %), the porosity of Gurley type P.sub.Gurley (in s/100 cm.sup.3), the longitudinal heat shrinkage measured at 100° C. for 1 hour R.sub.L (in %), the transverse heat shrinkage measured at 100° C. for 1 hour R.sub.T (in %), the maximum puncture strength F.sub.max (in newtons N) and the elongation at break E (in mm), are presented in Table 2 below.

[0153] The porosity of Gurley type P.sub.Gurley is measured using an automatic densimetre sold under the trade name Guenine Gurley Model 4340.

[0154] The porosity P is calculated by comparing the true thickness of the separator and its theoretical thickness estimated from its weight and from the density of the polypropylene.

[0155] The longitudinal R.sub.L and transverse R.sub.T heat shrinkages were estimated according to Standard ISO11501 (data obtained from the suppliers of the separators).

[0156] The maximum puncture strength F.sub.max and the elongation at break E were obtained using ASTM D3420 puncture tests carried out at ambient temperature using a universal testing machine sold under the trade name Adamel-Lhomargy of DY32 type.

TABLE-US-00002 TABLE 2 t P P.sub.Gurley R.sub.L R.sub.T F.sub.max E Separator (μm) (%) (s/100 cm.sup.3) (%) (%) (N) (mm) S-1 15 >50 95 2 6.5 41 17 S-2 25 55 180 .sup.  5.sup.a 0.sup.a   63 30.1 .sup.aheat shrinkages measured at 90° C. instead of 100° C.

[0157] 1.3 Preparation of a Solid Polymer Electrolyte

[0158] The solid polymer electrolyte was prepared by extrusion of a mixture of lithium salt (LiTFSI), of copolymer of PEO Zeospan® and of PVDF-co-HFP, and then by laminating the electrolyte paste obtained at 125° C. between two plastic films of silicone-treated PET.

[0159] The composition by weight of the solid polymer electrolyte obtained is presented in Table 3 below:

TABLE-US-00003 TABLE 3 Solid polymer TEGDME Lithium salt Co-PEO PVDF-co-HFP electrolyte (%) (%) (%) (%) SP-1 0 12 48 40

[0160] 1.4 Manufacture of Organic Lithium Batteries

[0161] Three batteries B-1, B-2 and B-3 were prepared by assembling, under an anhydrous atmosphere (air with a dew point<−40° C.), by manual laminating at ambient temperature: [0162] the positive electrode E-1 obtained in Example 1.1 above, [0163] a negative electrode comprising lithium metal in the form of a film of lithium metal with a thickness of approximately 100 μm, and [0164] the separator S-1 impregnated with the liquid electrolyte obtained in Example 1.2 above, or the separator S-2 impregnated with the liquid electrolyte obtained in Example 1.2 above, or the solid polymer electrolyte SP-1 obtained in Example 1.3 above.

[0165] The battery B-1 is in accordance with the invention since it comprises a positive electrode, a negative electrode, an electrolyte and a separator as are defined in the present invention.

[0166] On the other hand, the batteries B-2 and B-3 are not in accordance with the invention since B-2 does not comprise a separator as defined in the present invention and B-3 does not comprise separator and electrolyte as are defined in the present invention.

[0167] The specific capacity (in mAh/g) of the battery B-1 (curve with the solid circles), of the battery B-2 (curve with the solid squares) and of the battery B-3 (curve with the open diamonds) as a function of the number of cycles at a current rate of C/4 and at a temperature of 100° C. is given in FIG. 1.

[0168] These results show that the use of a biaxially oriented separator as defined in the present invention makes it possible to significantly improve the resistance to cycling of the organic lithium battery. In particular, FIG. 1 shows, for the battery B-3 (solid polymer electrolyte), a very rapid fall in the discharge capacity during the first cycles and the absence of stabilization in the subsequent cycles, probably related to a dissolution of the anthraquinone in the solid polymer electrolyte and thus its diffusion. In the same way, FIG. 1 shows, for the battery B-2 (uniaxially oriented separator), a very rapid fall in the discharge capacity during the first cycles.