ELECTRODE FOR A LITHIUM BATTERY AND METHOD FOR PRODUCING THE SAME

Abstract

The invention relates, among other things, to an electrode for a lithium battery with an electrode element of a material consisting of or comprising: 2-10 parts by weight of a conductivity additive containing carbon, based on an anisotropic expanded graphite;0-5 parts by weight of a plate-shaped, spherical or potato-shaped graphite;1-8 parts by weight of a binding agent; and77-97 parts by weight of an active material selected from the group metal, transition metal oxide and metal phosphate, the active material being capable of intercalating lithium ions in the crystal lattice

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail in the following with reference to an exemplary embodiment and the associated drawings, in which:

FIG. 1 shows a diagrammatic sectional view to illustrate the basic construction of the lithium battery according to the invention;

FIGS. 2A-B show a battery with a casing in a diagrammatic sectional representation and in elevation;

FIG. 3 shows a graphic representation of the battery thickness as a function of the depth of discharge.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 serves to illustrate the basic structure of a lithium battery modified according to the invention. A cathode 10 has an electrically conducting diverter 12 consisting of a material that conducts electricity well. Diverter 12 may be provided in the form of a diverter lattice. Cathode 10 is provided with lithium anodes 14 on both sides, a separator 16 being arranged between cathode 10 and lithium anodes 14.

To produce a cathode 10 for a pacemaker or defibrillator 91% by weight of manganese dioxide is mixed homogeneously with 7% by weight of an expanded graphite and 2% by weight of a PTFE powder in a powder mixer. A press mould, which has a cavity which is complementary to the shape of the electrode and in which diverter 12 is arranged approximately in the centre, is fed with the powder mixture and the powder mixture is pressed with diverter 12. When used in pacemakers or defibrillators cathode 10 should be approximately 3.5 mm thick. The total area of cathode 10 should be approximately 10 cm².

After pressing, cathode 10 is dried for at least 1 h at a temperature of 270° C.-300° C. and a pressure of 10⁻³ mbars. Cathode 10 is then provided on both sides with lithium anode 14 of the same shape. A microporous membrane of a polyolefin or a ceramic material serves as separator 16.

FIGS. 2A and 2B show the structure of the battery in a diagrammatic sectional representation and elevation. The battery components described above, cathode 10, lithium anodes 14 and separator 16, are welded into a battery casing 20 of high grade steel with a wall thickness of 0.3 mm, anodes 14 being connected in an electrically conducting manner to battery casing 20.

Cathode 10 was guided through a lid 18 of battery casing 20 by means of a gas-tight, electrically insulating glass-metal opening 22. The battery is then filled with an electrolyte of ethylene carbonate/propylene carbonate/diethyoxyethane (mixing ratio 1:1:1) and 1 M of lithium perchlorate, then sealed gas-tight.

FIG. 3 shows the course of the battery thickness as a function of the discharge depth. The nominal thickness of the battery was 6 mm. The figure shows that no swelling occurs during discharge. It is even apparent that the thickness of the battery decreases slightly. The accuracy of the measurement is indicated as 0.005 mm.

Claims

1. An electrode for a lithium battery with an electrode element of a material comprising:

2. The electrode according to claim 1, wherein said active material is manganese dioxide.

3. The electrode according to claim 1, wherein said active material consists of particles with a size <100 μm.

4. The electrode according to claim 1, wherein said active material consists of particles with a size ranging from 10μ to 80 μm.

5. The electrode according to claim 1, wherein said conductivity additive consists of particles of size D90=80 to 90 μm and D50=30 to 40 μm.

6. The electrode according to claim 1, wherein said plate-shaped, spherical or potato-shaped graphite consists of particles with a size ranging from 3 to 30 μm.

7. The electrode according to claim 1, wherein said binding agent is a polymer.

8. The electrode according to claim 7, wherein said polymer contains fluorine.

9. The electrode according to claim 8, wherein said polymer is polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PvdF).

10. The electrode according to claim 1, wherein said active material has a BET surface of >20 m2/g.

11. The electrode according to claim 1, wherein residual moisture content of said electrode is <300 ppm.

12. The electrode according to claim 1, wherein said electrode has a thickness ranging from 300μ to 6 mm.

13. The electrode according to claim 12, wherein said thickness of the electrode ranges from 1 mm to 6 mm.

14. A method for producing an electrode for a lithium battery, comprising the steps: (i) supplying a powder mixture comprising:

15. The method according to claim 14 further comprising: (iii) drying said electrode element until a residual water content <300 ppm is obtained.

16. The method according to claim 15, wherein a pressure ranging from 10−2 to 10−3 mbars and a temperature ranging from 20° to 350° C. prevail in step (iii).

17. The electrode according to claim 1 wherein said lithium battery comprises a cathode coupled with said electrode material.

18. The electrode according to claim 17 wherein said lithium battery is designed for basic load discharge currents <100 μA and pulse discharge currents ranging from 1-100 mA.

19. The electrode according to claim 17, wherein said lithium battery comprises an anode contains metal lithium or consists of metal lithium.

20. The electrode according to claim 17, wherein said lithium battery contains a non-aqueous organic solvent as electrolyte, which is able to dissolve a conducting salt containing lithium.

21. The electrode according to claim 20, wherein said solvent is selected from one or a plurality of solvents from a group of: (i) organic carbonates, in particular ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate; and(ii) ethers, in particular diethoxyethane or dimethoxyethane.

22. The electrode according to claim 20, wherein said conducting salt is selected from the group lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate and lithium-bis-oxalatoborate.

23. The electrode according to claim 20, wherein said conducting salt is present in said electrolyte in a concentration of approximately 1 mol/l.

24. A powder mixture for producing an electrode for a lithium battery comprising: