Composite electrode material

1. A composite material comprising carbon fibers and complex oxide particles,

wherein the carbon fibers and the complex oxide particles have a carbon coating on at least part of their surfaces, said carbon coating being a non-powdery coating;

wherein the carbon coating on at least part of the surfaces of the carbon fibers and the complex oxide particle is obtained by a method comprising the steps of dissolving an organic carbon precursor in a solvent to obtain a carbon precursor solution, adding and mixing the complex oxide particles and the carbon fibers in the carbon precursor solution, and heat treating a resulting mixture at a temperature where the organic carbon precursor is carbonized, so as to bond the complex oxide particles to the carbon fibers and to one another via the carbon coating;

wherein the carbon fibers are bonded to the carbon coating by carbon-carbon bonding; and

wherein the thickness of the carbon coating on the complex oxide particles and on the carbon fibers is more than 0 nm and less than 100 nm.

2. The composite material of claim 1 , which comprises 70-99.8% complex oxide, 0.1-20% carbon fibers and 0.1-10% carbon coating, all percentages being weight %.

3. The composite material of claim 1 , wherein the complex oxides particles are nanosize particles supported by the carbon coated carbon fibers.

4. The composite material of claim 1 , wherein the complex oxide corresponds to the general formula A a M m Z z O o N n F f wherein A represents one or more alkaline metals, M represents one or more transition metals, and optionally at least one non-transition metal, or mixtures thereof, and Z represents one or more non-metallic elements, wherein a≧0, m≧0, z≧0, o≧0, n≧0 and f≧0, the coefficients a, m, o, n, f and z being selected to ensure electro neutrality.

5. The composite material of claim 4 , wherein A represents lithium.

6. The composite material of claim 4 , wherein M represents a transition metal element preferably selected from Fe, Mn, V, Ti, Mo, Nb, W, Zn and mixtures thereof, and optionally a non-transition metal.

7. The composite material of claim 4 , wherein Z represents a non-metal selected from P, S, Se, As, Si, Ge, B and mixtures thereof.

8. The composite material of claim 1 , wherein the complex oxide is selected from phosphate, oxyphosphate, silicate, oxysilicate, and fluorophosphate.

9. The composite material of claim 8 , wherein the complex oxide is LiFePO 4 .

10. The composite material of claim 1 , wherein the carbon fiber consists of fiber filaments having a diameter of 1 to 200 nm and an aspect ratio (length/diameter) of 20 to 2000.

11. An electrode having an electrode material on a current collector, wherein the electrode material is a mixture of a composite material of claim 1 and of a binder.

12. An electrode of claim 11 , wherein the binder is a fluorine-based polymer.

13. An electrode of claim 11 , wherein the electrode material contains from 0.5 to 20 wt % vapor grown carbon fibers.

14. An electrode of claim 11 , wherein the electrode material contains 0.5-5 wt % vapor grown carbon fibers, 70-95 wt % complex oxide and 1-25 wt % polymer binder, the total being 100%.

15. A rechargeable or non-rechargeable battery having an electrolyte which comprises a lithium salt and an anode made of lithium, a lithium alloy or a compound capable of reversibly exchanging lithium ions, wherein the cathode is an electrode according to claim 11 .

16. An electrochemical cell, comprising at least one anode, one cathode and an electrolyte, wherein the cathode is an electrode according to claim 11 .

17. The composite material of claim 1 , wherein the organic carbon precursor is cellulose acetate.

18. A composite material comprising carbon fibers and complex oxide particles,

wherein the carbon fibers and the complex oxide particles have a carbon coating on at least part of their surfaces, said carbon coating being a non-powdery coating;

wherein the carbon coating on at least part of the surfaces of the carbon fibers and the complex oxide particle is obtained by a method comprising the steps of dissolving an organic carbon precursor in a solvent to obtain a carbon precursor solution, adding and mixing the complex oxide particles and the carbon fibers in the carbon precursor solution, and heat treating a resulting mixture at a temperature where the organic carbon precursor is carbonized, so as to bond the complex oxide particles to the carbon fibers and to one another via the carbon coating;

wherein the carbon fibers are bonded to the carbon coating by carbon-carbon bonding;

wherein the thickness of the carbon coating on the complex oxide particles and on the carbon fibers is more than 0 nm and less than 100 nm;

wherein the carbon fiber consists of fiber filaments having a diameter of 1 to 200 nm and an aspect ratio (length/diameter) of 20 to 2000; and

wherein the composite material comprises 70-99.8% complex oxide, 0.1-20% carbon fibers and 0.1-10% carbon coating, all percentages being weight %.

19. A method for the preparation of a composite material as claimed in claim 1 , comprising mixing a complex oxide or precursors thereof, an organic carbon precursor and carbon fibers, and subjecting the mixture to a heat treatment in an inert or reducing atmosphere for the decomposition of the precursors.

20. The method of claim 19 , wherein the mixture is prepared in an organic solvent, and the heat treatment comprises a first step of elimination of the solvent and a second step of decomposition of the precursors.

21. The method of claim 19 , wherein the organic carbon precursor is a compound which are in liquid state, or a compound which is soluble in a solvent, or a compound which is in liquid state upon the decomposition heat treatment.

22. The method of claim 19 , wherein the composite electrode material is prepared from a mixture containing the complex oxide precursors, the carbon fibers and the organic carbon precursor, wherein the complex oxide precursors, the organic carbon precursor and the carbon fibers are dissolved or homogeneously dispersed in a solvent, then the resulting homogeneous mixture is subjected to a first heat treatment at a temperature where the solvent is eliminated and to a second heat treatment at a temperature where the complex oxide precursors are reacted to form the complex oxide and the organic carbon precursor is carbonized.

23. The method of claim 19 , wherein the composite electrode material is prepared from a mixture containing the complex oxide, the carbon fibers and the organic carbon precursor, wherein the complex oxide, the organic carbon precursor and the carbon fibers are dissolved or homogeneously dispersed in a solvent, then the solvent is eliminated by evaporation, and the resulting homogeneous mixture is subjected to heat treatment at a temperature where the organic carbon precursor is carbonized.

24. A method for preparing an electrode according to claim 11 , wherein said method comprises:

- mixing a composite material, a binder and an organic solvent having a low boiling point, and

- applying the mixture thus obtained on a conductive support acting as the current collector, and eliminating the solvent by evaporation.