WO2009124893A1

WO2009124893A1 - Electrode material comprising partially incorporated nanotubes

Info

Publication number: WO2009124893A1
Application number: PCT/EP2009/054040
Authority: WO
Inventors: Siegmar Roth; Urszula Dettlaff-Weglikowska; Hideyuki Koga; Norio Sato
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2008-04-10
Filing date: 2009-04-03
Publication date: 2009-10-15
Also published as: DE102008001113B4; DE102008001113A1

Abstract

The invention relates to an electrode material with at least a first (110) and a second (112) component, wherein the first component (110) is adapted for incorporation of lithium ions and the first component (110) is at least partially permeable for the lithium ions, the second component comprises nanotubes, and wherein the nanotubes are at least partially incorporated into the first component.

Description

ELECTRODE MATERIAL COMPRISING PARTIALLY INCORPORATED NANOTUBES

D e s c r i p t i o n

The invention relates to an electrode material, a method of producing an electrode material, as well as an electrochemical cell.

Batteries belong to the most important power sources which are used in different areas of operation. Almost any electrical consumer can be equipped with batteries in order to use electrical energy which results from discharging of the battery through an electrochemical redox reaction.

Thereby, 'battery' is the generic term for multiple serially connected galvanic cells or galvanic elements, which are combined in a packet and accommodated in a battery housing. The reaction 'discharge', which provides the energy consists of two reaction parts, an oxidation process at a negative electrode and a reduction process at a positive electrode. The electrode at witch the reaction part takes place with a lower redox potential with respect to the other electrode is the negative electrode, the other electrode is the positive electrode. During discharge of the cell, electrons are released through the oxidation process at the negative electrode, whereas at the positive electrode an equal amount of released electrodes is taken up through the reduction process. The resulting electron current flows through an external electrical consumer circuit. Within the cell the current in between the electrons is carried by ions in an ionic conducting electrolyte, wherein ion-and electrode reactions in or at the electrode are coupled with each other.

In contrast to primary cells, for rechargeable cells the electrochemical discharge reactions are reversible to a large extent, therewith enabling a several fold conversion from chemical in electrical energy and vice versa. Lithium is a widespread negative electrode material for batteries. This is due to the fact that lithium has the most negative standard potential of all elements which allows realizing obtaining high cell voltages. Also, using lithium theoretically extremely high battery capacities are accomplishable. Indeed, since many years suitable elec- trode materials are developed for up taking and releasing of lithium ions in combination with respective electrolyte materials in order to achieve such a high theoretical energy density of lithium batteries in practice. One electrode material which can be used to realize such high discharge voltages while maintaining a high capacity are lithium phosphor compounds in the form of Olivines, as for example LiMPO₄, wherein M is a metal like iron, manganese, cobalt etc.

For example, J. Electrochem. Soc, Vol. 144, No. 4, April 1997, p. 1188 - 1194 discloses that Phospho-Olivine is a positive electrode material suitable for rechargeable lithium batteries.

Similarly, J. Electrochem. Soc, Vol. 148, No. 8, A960 - A967, 2001 deals with the usage of Olivine type lithium compounds as a possible cathode material for lithium batteries.

US 5,910,382 discloses the usage of transition metal compounds with an ordered Olivine or rhombohedral Nasicon structure as electrode material for rechargeable alkali ion batteries.

US 2001/0055781 A1 discloses a positive electrode material and a non-liquid elec- trolyte cell, wherein the positive electrode material comprises a compound with the form of Li_x Mn_γ Fei_-Y PO₄, with 0 < x < 2 and 0.5 < y < 0.95.

The lithium compounds disclosed in these scriptures have the big advantage of an efficient incorporation of lithium ions in the lattice structures of said compounds, however in connection with the disadvantage that the electrical conductivity of such lithium compounds in form of nanoparticles is not efficient enough in order to be applied as an electrode material in a battery in combination with the dissipation of electrons. For this reason it was proceeded to coating such lithium compounds with carbon. For example US 2002/01995591 A1 discloses a lithium iron phosphor compound, wherein a carbon coating enables an efficient dissipation of electrons emerging by the redox reaction.

L. Kavan, I. Exnar, J. Cech, M. Graetzel, "Enhancement of electrochemical activity of LiFePO4 (olivine) by amphiphilic Ru-bipyridine complex anchored to a carbon nanotube", Chem. Mater. 19, 4716-4721 (2007) does disclose electrode material of application in high-energy lithium-ion batteries.

Nevertheless, this leads to the further disadvantage, that such a carbon coating is only little transparent for the incorporation of lithium ions such that a compromise has to be found in between an ideal ionic conductivity and an ideal electrical conductivity.

The underlying problem to be solved by the invention is therefore to provide an improved electrode material, an improved electrochemical cell as well as an improved method of producing an electrode material.

These problems of the invention are each solved with the features of the independent claims. Preferred embodiments of the inventions are given by the dependent claims.

According to the invention an electrode material with at least a first and a second component is provided, wherein the first component is adapted for the incorporation of lithium ions. Furthermore, the second component comprises nanotubes. The nanotubes are partially incorporated into the first component. Partially incorporated has to be understood as parts of the nanotubes being partially enclosed by the first component, i.e. the nanotubes being for example surrounded by the crystalline structure of crystalline particles of the first component and not only being located on the outer surface of such a crystalline structure. However, it is also possible that the nanotubes are partially clutched by the crystalline particles. In accordance with an embodiment of the invention, the nanotubes are arranged in a network.

The electrode material according to the invention has the advantage that it unites both the properties of a good ability of incorporation of lithium ions into the first component and at the same time the property of a high electrical conductivity by using of nanotubes arranged in a network. Therewith, an ideal electrode material can be provided, wherein through an individual design of the first component the ion incorporation capability and therewith the redox potential can be tuned to predeter- mined applications.

With the arrangement of nanotubes in a network two important aspects can be accommodated simultaneously: first this is a good permeability for the ions, which is ensured due to the relatively small nanotube density in such a nanotube network. Therewith, ions can readily impinge the surfaces of the first component, which itself is at least partially permeable for lithium ions for incorporation in the first component. The second aspect which can be accommodated is the effective dissipation and transmission, respectively of electrons by the nanotubes to an external consumer. Due to the cross linking of the nanotubes the percolation threshold for a good elec- trical conductivity is low which allows keeping the amount of used nanotubes for such electrode material low. This is especially relevant for applications which require a mass production of electrode material, since this allows an economization of material with respect to carbon black compounds used for example in batteries up to now.

Especially metallic carbon nanotubes are able to dissipate electrons to an external power consumer in a highly efficient manner. In case of carbon nanotubes atoms are arranged along a nanotube sidewall in such a way, that the π-orbitals overlap therewith providing a one-dimensional ballistic conductor. The resulting high electri- cal conductivity of the nanotubes significantly reduces Ohmic losses in the electrode material. Since particularly carbon nanotubes have a very high thermal conductivity, emerging heat due to the usage of the electrode material for example in batteries is efficiently dissipated to the environment. It should be noted here, that rather than using nanotubes also nanofibers with a diameter in the micrometer, preferably nanometer range can be used.

In accordance with an embodiment of the invention, the first component is a material with a grain size less than 200 nm, preferably only a few nanometers. This allows realizing a high density of electrode material and ensuring at the same time a filling of the nanotube network to a large extent due to the fine granulation of the first component, such that electrons can be efficiently dissipated to the nanotube network or can be taken up by the nanotube network, respectively.

In accordance with an embodiment of the invention, the first component is a material with the composition Li_xMyPO₄ and/or Li_xM_yO_z with M= Ti, V, W, Cr, Mn, Fe, Co, Ni, Cu, Mg, Ca, Sr, Pb, Cd, Ba, Be, and/or a material with the composition Li_xFei- _yTiyPO₄ and/or Li_xFei_-yMn_yPO₄with 0<y<1 and/or material with the composition Li_xM_y(XO₄)3 with M= Fe, V, Mn, Ti and X= Si, P, As or S.

This allows using a high diversity of materials in order to individually adapt the capacity and discharge voltage with respect to the application purpose for usage in electrolyte cells. Thereby, also respective mixtures of said compounds are possible.

In accordance with an embodiment of the invention, the nanotubes are carbon nanotubes and/or metal oxide nanotubes. However, as already mentioned above important is a good electrical conductivity and a good permeability with respect to the nanotube network for incorporation of the lithium ions into the first component.

In accordance with an embodiment of the invention, the nanotubes are chemically functionalized. Thereby, such a chemical functionalization can be designed such that an optimum contact interaction in between the used electrolyte, the nanotubes and the first component is established. This ensures an optimum electron dissipa- tion via the nanotubes. Furthermore, at the same time an optimum ion exchange is possible.

In accordance with an embodiment of the invention, the nanotubes are chemically doped. The fact, that the nanotubes are chemically doped has the advantage, that the total conductivity of the nanotube material is increased. This further reduces ohmic losses and thus increases the efficiency of the electrode according to the invention. A doping can for example be performed by means of SOCI2 or TCNQ (Tetra-Cyanoquinodimethane).

In general, a chemical functionalization can be performed by treatment with oxidizing acids. Also, a 'non covalent' chemical functionalization can be performed by treatment with surfactants like SDS, AOT, Tween 80 etc.

Thereby, said functionalization can be adapted in such a way that the nanotubes are incorporated into first component due to the functionalization. Incorporation of the nanotubes into the first component by a nanotube functionalization and if necessary also by a chemical modification of the first component can be realized in form of covalent and non-covalent bondings, through respective polar functional groups as well as through van-der-Waals bondings.

It should be noted that already by the small grain size of the first component an excellent filling of the interspace of the nanotube network can be achieved and therewith excellent contact conditions between the first component and the electri- cally conductive nanotubes can be accomplished. However, by an additional functionalization of the nanotubes in such a way that the nanotubes are incorporated into the first component, the contact between the first component and the nanotubes can be further improved which further increases the efficiency of the electrode material according to the invention with respect to its capacity and discharge voltage.

In accordance with a further embodiment of the invention, the incorporation of the lithium ions is basically reversible. This is necessary in order to realize an electrode material which for example can be used in rechargeable electrochemical cells.

In accordance with an embodiment of the invention, the nanotubes and the first component form a mechanically self-supporting structure. Such a self-supporting structure has the advantage of a simple mechanical handling which renders the usage of additional carrier materials and binders as unnecessary for a production of electrochemical cells, which reduces the production costs of such an electrode ma- terial and also prevents unwanted chemical reactions with the binder. By using the self-supporting structure of nanotubes, a freestanding electrode can be provided.

In another aspect, the invention relates to an electrochemical cell, wherein the elec- trochemical cell comprises a negative electrode, a positive electrode and an electrolyte, wherein the material of at least one of the electrodes is adapted by the electrode material according to the invention.

In accordance with an embodiment of the invention, the electrolyte comprises poly- mers and/or organic solvents and/or conducting salts. This in turn allows to individually design electrochemical cells for different application areas. Besides the capacity, discharge voltage and other electrochemical properties this also comprises the durability, temperature stability etc.

In another aspect the invention relates to a method of producing an electrode material by an in-situ precipitation method with the steps of providing the nanotubes, providing an aqueous solution, wherein the aqueous solution comprises lithium ions, mixing of the nanotubes and the aqueous solution and changing of the pH-value of the mixture.

In accordance with an embodiment of the invention, the nanotubes are comprised in a liquid. Thereby the nanotubes can be existent in a solution or dispersion or suspension, respectively.

In accordance with an embodiment of the invention the aqueous solution contains manganese nitrate (Mn(NO3)2), phospohc acid (H₃PO₄) and lithium nitrate (UNO3).

In accordance with an embodiment of the invention the aqueous solution contains (Mn(CH₃COO)₂ X 4 H₂O, Li(CH₃COO) x 2 H₂O, HOCH₂-COOH and (NH₄)H₂PO₄).

In accordance with an embodiment of the invention the production method further comprises the step of heating the solution. This allows to temporarily accelerating the precipitation of the first component onto the nanotubes or together with the nanotubes, respectively. In another aspect the invention relates to a method of producing an electrode material according to the invention with the step of providing the first component, wherein the first component comprises material with the composition Li_xMyPO₄ and/or Li_x- M_yO_z with M= Ti, V, W, Cr, Mn, Fe, Co, Ni, Cu, Mg, Ca, Sr, Pb, Cd, Ba, Be, and/or material with a composition Li_xFei_-yTi_yPO₄ and/or Li_xFei_-yMn_yPO₄ with 0<y<1 and/or material with the composition Li_xM_y(XO₄)3 with M= Fe, V, Mn, Ti and X= Si, P, As or S. In another step a mixing of the first component with a catalyst and growing of the nanotubes onto the mixture is performed.

In accordance with an embodiment of the invention growing of the nanotubes is performed through chemical vapor deposition (CVD).

In another aspect, the invention relates to method for producing an electrode mate- rial according to the invention, the method comprising an in-situ sol-gel method, the method comphsingproviding of an aqueous solution, wherein the aqueous solution contains lithium ions, heating of the the aqueous solution for reception of a gel, providing of nanotubes, mixing the nanotubes and the gel and evaporation of the solution for receipt of the electrode material and calcination of the electrode material.

Preferably, the nanotubes are dispersed in HNO₃. Further, preferably the aqueous solution contains Mn(CH₃COO)₂X 4 H₂O, Li(CH₃COO) x 2 H₂O and Lithium phosphate.

In the following, preferred embodiments of the invention are illustrated in detail by means of the drawings in which:

Fig. 1 is a schematic view of an electrochemical cell,

Fig. 2 is a schematic view of positive electrode consisting of the fist component and nanotubes, wherein nanotubes are at least partially incorporated into the first component, Fig. 3 is a flow diagram of a production method of the electrode material according to the invention,

Fig. 4 is a flow diagram of a further production method of the electrode mate- rial according to the invention,

Fig. 5 shows a measurement diagram of the specific surface area of LiM- nPO₄ prepared by the precipitation method and the sol-gel procedure,

Fig. 6 presents the electrical conductivity of pure LiMnPO₄ and its composites,

Fig. 7 shows a field-emission scanning electron microscopy (SEM) image of a LiMnPO₄/nanotubes composite prepared by in situ sol-gel proce- dure.

Fig. 1 shows a schematic view of an electrochemical cell 100. The electrochemical cell comprises two electrodes, a positive electrode 106 and a negative electrode 108. Both, the positive electrode 106 as well as the negative electrode 108 each have electrical contacts 102 and 104, by which electrons 122 can be taken up or emitted. In the present example of fig. 1 , a measurement device 124 which is adapted for displaying a current flow between the two contacts 102 and 104 is interposed in between the contacts 102 and 104.

In the present example the positive electrode carries the electrode material according to the invention, which consists of a nanotube network 112, the first component 110 and lithium ions 114 incorporated into the first component 110. On the negative electrode side the electrochemical cell 100 exhibits metallic lithium or a graphite material 116 which is adapted for intercalation or de-intercalation of lithium ions 114.

During the discharge process of the electrochemical cell 100 such a de-intercalation process occurs at the negative electrode side which releases lithium ions 114 which are transported with means of the electrolyte 118 to the positive electrode side. The reason for the releasing of the lithium ions and the transport of the lithium ions 114 from the negative electrode 108 to the positive electrode 106 is the high redox potential of the first component 110. Thereupon, on the positive electrode side 106 lithium ions 114 are incorporated in the first component 110 or its lattice structure, respectively.

At the same time with the releasing of the positive charged lithium ions, a releasing of electrons 122 occurs at the negative electrode side 108. The electrons 122 are transported via the contacts 104 and 102 via the external electrical circuit to the positive electrode side 106, where they provide for electrical charge equalization during the take up of the lithium ions by the first component.

The membrane 120 is a separator which is interspersed by the electrolyte 118. It serves to provide a spatial separation between the positive electrode 106 and the negative electrode 108. This is necessary in order to prevent the occurrence of an electrical short-circuit between these two electrodes. However, in case the negative and positive electrode 108 and 106 each form themselves a mechanically stable unit such that an unwanted mixing of the respective electrode materials can be excluded, such a membrane 120 can be abandoned which simplifies the production method of the electrochemical cell according to the invention. In particular this can be realized with the usage of a self-supporting network of nanotubes to which the first component is firmly tied.

It has to be noted that after adaption of the redox potential the electrode material according to the invention can be used on the positive electrode side 106 as well as the negative electrode side 108. However, preferably the electrode material according to the invention is used on the positive electrode side 106 as depicted in fig. 1.

It should be further noted that for a charge process of the electrochemical cell 100 the inverted processes reversibly takes place as described above for the discharge process. During the charge process the electrons 122 flow from the positive electrode 106 over the contact 102 to the contact 104 of the negative electrode. At the same time lithium ions are released from the first component or its lattice structure, respectively due to the permeability of the first component in order to be transported to the negative electrode via the electrolyte 118. There, the ions are intercalated again in respective graphite layers 116.

Fig. 2 shows the positive electrode 106 of fig. 1 consisting of the fist component 110 and nanotubes 112, wherein nanotubes 112 are at least partially incorporated into the first component 110. The nanotubes are interconnecting crystalline material comprising the first component, for example LiMnPO₄, which may have been obtained by an in situ sol-gel method or an in-situ precipitation method. Preferably, two neighboring LiMnPO₄ crystals are interconnected by at least one nanotube 112, ad- ditionally with the preference that nanotubes interconnecting various crystals are further in electrical and/or mechanical contact with each other. Such a nanotube network 112 in combination with the constraint that typically two neighboring LiM- nPO₄ crystals are interconnected by at least one individual nanotubes has the advantage, that a positive electrode 106 can be provided which is mechanically self- supporting and as superior electrical conductivity, which is an important aspect for the usage in electrochemical cells.

Fig. 3 shows a flowchart of an in-situ production method of the electrode material according to the invention. In the steps 200 and 202 the nanotubes or the aqueous solution which contains the lithium ions is provided, respectively. The nanotubes may be dispersed in an aqueous solution. Thereupon in step 204 the nanotubes and the aqueous solution are brought together, whereupon in step 206 the pH-value of the solution is changed. The heating in step 208 is optional and accelerates the reaction process which finally leads to the receipt of the electrode material. Thereby, the change of the pH-value is performed in such a way that a lithium ion comprising salt is precipitated from the aqueous solution.

In accordance with an embodiment of the invention the providing of the nanotubes in step 200 is performed in such a way that the nanotubes are contained in an aqueous suspension. The providing of the aqueous solution with the lithium ions as depicted in step 202 occurs in such a way, that manganese nitrate Mn(NOs)2, phosporic acid H₃PO₄ and lithium nitrate UNO3 are dissolved in water. After the mixture of the nanotube solution and the aqueous lithium ion solution in step 204, a strong increasing of the pH-value takes place, followed by a heating of the mixture under reflux. This leads to a precipitation of a composite material which contains LiMnPO₄, as well as nanotubes. Now, this composite material can be collected by filtration. Further, due to the filtration process a self-supporting network of nanotubes can be obtained.

The compound material has the advantage, that the nanotubes are incorporated in the LiMnPO₄ crystalline structure in a homogeneous way, whereupon a high specific surface area of the material and therewith a high reactivity can be attained. For example, using single walled carbon nanotubes the specific surface area of LiMnPO₄ is increasing from 22.7 m²/g to 36.4 m²/g by the precipitation method and from 33.6 m²/g to 46.3 m²/g by the in situ sol gel method upon addition of nanotubes.

Alternatively to the above described procedure of providing the nanotubes in step 200 with means of an aqueous solution it is also possible to provide the nanotubes in form of a self-supporting network. This leads to a precipitation of the first component, in the present example of LiMnPO₄, directly onto the network of nanotubes which leads to the receipt of a self-supporting electrode which can be directly used in a battery as cathode.

In order to improve the electrical conductivity of the electrode material according to the invention, the nanotubes are doped using SOCI2 or TCNQ as dopants. The electrode material is prepared in this case by mechanical mixing of LiMnPO₄ or any other kind of first component adapted for incorporation of lithium ions and doped nanotubes. The electrical conductivity thus increases by a factor of five in the case of SOCI₂.

Fig. 4 shows a flowchart of an in-situ sol-gel production method of the electrode material according to the invention. In step 502 aqueous solution which contains the lithium ions is provided. This is performed by dissolution of precursors in deionized water step by step following the order Li(CH₃COO) x 2 H₂O, (NH₄)H₂PO₄, HOCH₂- COOH and Mn(CH₃COO)₂X 4 H₂O and adjusting the pH-value to 1.5 by addition of concentrated HNO₃ at each dissolution step. Keeping the pH value around 1.5 provides the advantage that precipitation of solids can be avoided. Steps 504 and 506 combine stirring at 80°C for 24 hours and evaporation of water within the next 24 hours, respectively. When the solution volume is reduced due to the water evaporation to 1/8 of the starting volume, a suspension of carbon nanotubes in HNO3 is added, which was prepared previously in step 505. Also, HNO3 is used here as a solvent for the nanotubes which prevents an unwanted agglomeration of nanotubes and precipitation of solids. Further heating at 80°C leads to a viscous gel which is dried in step 508 at 120°C for 48 hours. The calcination step 510 is performed in the programmed furnace with a temperature ramp of 1 °C/min up to 300°C in air and from 300°C up to 600°C under inert gas flow, keeping the temperature at 350°C for 5 hours and at 600⁰C for 1 hour.

The purpose of this procedure is crystallization of the electrode material. By following these preparation steps an increase in electrical conductivity of the electrode material by five orders of magnitude can be achieved.

Fig. 5 shows a measurement diagram of the specific surface area of LiMnPO₄ prepared by the precipitation method and the sol-gel procedure. The measurements were performed using the BET method. Sample 800 comprises only LiMnPO₄ and was prepared by the precipitation method, whereas sample 802 also comprises only LiMnPO₄ but was prepared with the sol-gel method. Sample 804 comprises 1wt% carbon nanotubes and LiMnPO₄ and was prepared by the precipitation method, whereas sample 806 also comprises 1 wt% carbon nanotubes and LiMnPO₄ but was prepared with the sol-gel method. It can be seen, that addition in situ of a few weight percent (wt%) of carbon nanotubes (here 1 wt%) increases the specific surface area from 22.7 m²/g to 36.4 m²/g in precipitation and from 33.6 m²/g to 46.3 m²/g in sol-gel method. Such high specific surface areas are required for efficient usage of the combined first material and nanotubes as electrode material in electrochemical cells.

Fig. 6 presents the electrical conductivity of pure LiMnPO₄ (sample 900) and its composites (samples 902 to 908) with nanotubes (samples 906 and 908) and carbon black (sample 904) measured as a compressed pellet by a two probe method. Since the material is a fine powder the pressed pellet is usual very brittle. Therefore polyvinyldifluoride (PVDF) as a binder is used. Sample 902 only comprises LiMnPO₄ and PVDF. The measured conductivity of the material (with or without PVDF) is low (in the range of 10-8 S/cm). Addition of 1 wt % carbon black in sample 904 does not make significant difference. However only 1 wt % nanotubes improves the conductivity of the composite by 5 orders of magnitude. Sample 906 comprises LiMnPO₄, 1 wt% carbon nanotubes and PVDF, whereas sample 908 was prepared in situ with- out the usage of PVDF binder and thus comprises only LiMnPO₄ and 1 wt% carbon nanotubes.

The morphology of LiMnPO₄/nanotubes composite prepared by in situ sol-gel procedure is shown in a field-emission scanning electron microscopy (SEM) image in Fig. 7 Obviously, the nanotubes are inside of the LiMnPO₄ particles when the crystallization process takes place in situ (in the presence of nanotubes). The interpenetrating network of nanotubes can be clearly seen in the SEM image.

Li st of referen ce n u mera l s

5

100 Electrochemical cell

102 Contact

104 Contact

106 Positive electrode

10 108 Negative electrode

110 First component

112 Nanotube network

114 Lithium ions

116 Lithium intercalated graphite

15 118 Electrolyte

120 Membrane

122 Electrons

124 Measurement device

20

Claims

C l a i m s

1. An electrode material with at least a first (110) and a second (112) component, wherein:

- the first component (110) is adapted for incorporation of lithium ions,

- the second component comprises nanotubes,

wherein the nanotubes are partially incorporated into the first component.

2. The electrode material according to claim 1, wherein the nanotubes are ar- ranged in a network (112).

3. The electrode material according to claim 1 or 2, wherein the first component (110) is a material with a grain size less than 200 nm.

4. The electrode material according to any of the previous claims, wherein the first component contains material with the composition Li_xMyPO₄ and/or Li_x. MyO₂ with M= Ti, V, W, Cr, Mn, Fe, Co₁ Ni, Cu₁ Mg, Ca, Sr, Pb, Cd, Ba₁ Be, and/or contains material of the composition Li_xFei-_yTi_yPθ4 and/or Li_xFei. yMn_yPO₄ with 0<y<1 and/or contains material of the composition Li_xMy(XO₄Ja with M= Fe, V, Mn, Ti and X= Si, P, As or S.

5. The electrode material according to any of the previous claims, wherein the nanotubes are carbon nanotubes and/or metal oxide nanotubes.

6. Electrode material according to any of the previous claims, wherein the nanotubes are chemically functionalized and/or doped.

7. The electrode material according to claim 1 , wherein the first component (110) is adsorbed to the nanotubes by functionalization.

8. The electrode material according to any of the previous claims, wherein the incorporation of the lithium ions is basically reversible.

9. The electrode material according to any of the previous claims, wherein the first component and the second component form a self-supporting structure.

10. An electrochemical cell (100), wherein the electrochemical cell (100) comprises a negative electrode, a positive electrode and an electrolyte (118), wherein the material of at least one of the electrodes is adapted by the electrode material according to any of the previous claims 1 to 9.

11. The electrochemical cell (100) according to claim 10, wherein the electrolyte (118) comprises polymers and/or organic solvents and/or conductive salts.

12. A method of producing an electrode material according to any of the previous claims 1 to 9, the method comprising an in situ precipitation method comprising the steps of:

- providing of the nanotubes,

- providing of an aqueous solution, wherein the aqueous solution contains lithium ions,

- mixing of the nanotubes and the aqueous solution,

- changing of the pH-value of the mixture.

13. The method according to claim 12, wherein the pH-value of the mixture is changed for a precipitation of a salt containing lithium ions from the aqueous solution.

14. The method according to claim 13, wherein the nanotubes are contained in a liquid.

15. The method according to claim 13 or 14, wherein the aqueous solution contains Mn(NO₃)₂ and H₃PO₄ and LiNO₃.

16. The method according to claim 15, wherein the aqueous solution contains Mn(CH₃COO)₂ x 4 H₂O₁ Li(CH₃COO) x 2 H₂O, HOCH₂-COOH and (NH₄)H₂PO₄.

17 The method according to any of the previous claims 13 to 16, further com- prising heating of the solution.

18. A method for producing an electrode material according to any of the previous claims 1 to 9, the method comprising an in-situ sol-gel method, the method comprising:

- heating of the aqueous solution for receipt of a gel,

- providing of nanotubes,

- mixing the gel and the nanotubes,

- evaporation of the solution for receipt of the electrode material and

- calcination of the electrode material.

19. The method according to claim 18, wherein the nanotubes are contained in a liquid.

20. The method according to claim 18, wherein the liquid comprises an acid.