HYBRID ELECTRODE

Abstract

The present invention relates to an electrode comprising at least one metal foil and at least two layers each comprising at least one lithium ion acceptor.

Claims

1. An electrode, comprising at least one metal foil, and at least two layers each comprising at least one lithium ion acceptor, wherein the layers further comprise at least one of a binder and a conductive material, and wherein the at least two layers differ in at least one of the type or the ratio of the lithium ion acceptor, the binder and optionally the conductive agent.

2. The electrode according to claim 1, wherein the lithium ion acceptor is selected from the group consisting of LiCoO2, lithium-nickel-manganese-cobalt-oxide, lithium-nickel-cobalt-aluminum-oxide, lithium-manganese-oxide, LiFePO4 and mixtures thereof.

3. The electrode according to claim 1, wherein the binder is polyvinylidene fluoride (PVDF) or carboxymethyl cellulose (CMC), and the conductive material is carbon black, carbon nanotubes or mixtures thereof.

4. The electrode according to claim 1, wherein the first layer is applied directly to the metal foil and/or wherein the second layer is applied to the first layer.

5. The electrode according to claim 1, wherein the at least two layers differ from each other in their composition, porosity, mass loading and/or density.

6. The electrode according to claim 1, wherein the at least two layers contain the identical lithium ion acceptor.

7. The electrode according to claim 1, wherein the layer which is closer to the metal foil has a higher porosity than the layer which is more remote from the metal foil.

8. The electrode according to claim 1, wherein the ratio of the thickness of the first layer to the thickness of the second layer is 1:5 to 5:1.

9. The electrode according to claim 1, wherein the first layer comprises 75 to 95 wt.-% of lithium ion acceptor, 1 to 10 wt.-% of binder, and 5 to 20 wt.-% of conductive agent, and/or wherein the second layer comprises 90 to 98 wt.-% of lithium ion acceptor, 0 to 5 wt.-% of binder, and 0 to 5 wt.-% of conductive agent.

10. A method for producing an electrode according to claim 1, said method comprising the steps: i) providing at least two slurries, each comprising the at least one lithium ion acceptor, the at least one binder, optionally at least one conductive agent and at least one liquid medium, ii) applying a first slurry to at least one side of the at least one metal foil, iii) at least partially removing the liquid medium to form a first layer, iv) optionally compacting the first layer obtained after step iii), v) applying a second slurry to the first layer, vi) at least partially removing the liquid medium to form a second layer, vii) optionally compacting the second layer obtained after step vi) and optionally the first layer, viii) optionally repeating the steps v) to vii) with another slurry obtained according to step i) at least once, ix) optionally cutting the product obtained after step vii) or viii) into a form which is suitable for the electrode.

11. The method according to claim 10, wherein step iii) is performed at increased temperatures, and optionally under reduced pressure and/or wherein the compacting according to step iv) and/or vii) is independently conducted via rolling, calendering or pressing.

12. An electrode, obtainable according to a process according to claim 10.

13. An electrochemical cell, comprising at least one electrode, said electrode comprising: at least one metal foil, and at least two layers each comprising at least one lithium ion acceptor, wherein the layers further comprise at least one of a binder and a conductive material, and wherein the at least two layers differ in at least one of the type or the ratio of the lithium ion acceptor, the binder and optionally the conductive agent.

14. The electrochemical cell according to claim 17, wherein the additional electrode is a metal foil coated with graphite, silicon, lithium titanate, tin dioxide or mixtures thereof.

15. The electrochemical cell according to claim 14, wherein the electrolyte is selected from the group consisting of ionic liquid, aprotic salt solutions, carbonates, such as dimethyl carbonate (DMC) or diethyl carbonate (DEC), or mixtures thereof and/or wherein the separator is a polyolefin membrane, e.g. PE or PP, or a polyethylene terephthalate membrane, which is optionally coated with ceramics, PVDF or mixtures thereof.

16. The electrode according to claim 1, wherein the electrode is used in an electrochemical cell, particularly lithium ion cells, lithium metal cells, and in super capacitors (super caps), particularly in aviation applications.

17. The electrochemical cell of claim 13, further comprising at least one additional electrode, an electrolyte and at least one separator.

18. The electrochemical cell of claim 13, wherein the electrode is produced by a method comprising: i) providing at least two slurries, each comprising the at least one lithium ion acceptor, the at least one binder, optionally at least one conductive agent and at least one liquid medium, ii) applying a first slurry to at least one side of the at least one metal foil, iii) at least partially removing the liquid medium to form a first layer, iv) optionally compacting the first layer obtained after step iii), v) applying a second slurry to the first layer, vi) at least partially removing the liquid medium to form a second layer, vii) optionally compacting the second layer obtained after step vi) and optionally the first layer, viii) optionally repeating the steps v) to vii) with another slurry obtained according to step i) at least once, ix) optionally cutting the product obtained after step vii) or viii) into a form which is suitable for the electrode.

19. The electrode of claim 1, wherein the electrode comprises a cathode.

20. The electrode of claim 1, wherein the at least one metal foil contains aluminum or copper.

Description

EXAMPLE

[0077] Hybrid Electrode Composition:

[0078] Metal Foil: aluminum; thickness 14 μm

[0079] Composition First Layer:

[0080] Active Material: lithium manganese cobalt nickel oxide 94%

[0081] Binder: PVDF 2%

[0082] Conductive carbon: Super P 2

[0083] Carbonanotubes 2

[0084] Solvent: NMP

[0085] Slurry Solids: 50%

[0086] All components have been slurried by ultraturrax.

[0087] Lamination Conditions:

[0088] coating

[0089] load: 3.3 mg/cm2

[0090] thickness: 25 μm

[0091] Drying:

[0092] 2 m/min each through 110° C., 110° C., and 150° C. zones

[0093] Post Coating Drying:

[0094] 140° C., 0.09 MPa, 600 min

[0095] Compacting Step:

[0096] Press at 50 MPa

[0097] Thickness of first layer: 10 μm

[0098] Density: 3.4 g/cm.sup.3

[0099] Composition Second Layer

[0100] Active Material: lithium manganese cobalt nickel oxide 96%

[0101] Binder: PVDF 2.5%

[0102] Conductive carbon Super P 0.75%

[0103] Carbonnanotubes 0.75%

[0104] Solvent: NMP

[0105] Slurry Solids: 50%

[0106] All components have been slurried by ultraturrax.

[0107] Lamination Conditions:

[0108] coating

[0109] load: 13 mg/cm.sup.2

[0110] thickness 85 μm

[0111] Drying: 2 m/min through 110° C., 110° C., and 150° C. zones

[0112] Post Coating Drying:

[0113] 140° C., 0.09 MPa, 600 min

[0114] Compacting Step:

[0115] press at 50 MPa

[0116] total thickness of second layer: 85 μm

[0117] density: 3.4 g/cm3

[0118] The following items are subject to the present invention:

[0119] 1. Electrode comprising

[0120] a) at least one metal foil and

[0121] b) at least two layers each comprising at least one lithium ion acceptor.

[0122] 2. Electrode according to item 1, wherein the electrode is a cathode.

[0123] 3. Electrode according to item 1 or 2, wherein the metal foil contains aluminum or copper.

[0124] 4. Electrode according to any of the preceding items, wherein the metal foil has a thickness of 5-30 μm, preferably 10-20 μm.

[0125] 5. Electrode according to any of the preceding items, wherein the lithium ion acceptor is selected from the group consisting of LiCoO.sub.2, lithium-nickel-manganese-cobalt-oxide, lithium-nickel-cobalt-aluminum-oxide, lithium-manganese-oxide, LiFePO.sub.4 and mixtures thereof.

[0126] 6. Electrode according to any of the preceding items, wherein the layers further comprise at least one of a binder, preferably polyvinylidene fluoride (PVDF) or carboxymethyl cellulose (CMC), and a conductive material, preferably carbon black, carbon nanotubes or mixtures thereof.

[0127] 7. Electrode according to any of the preceding items, wherein the first layer is applied directly to the metal foil.

[0128] 8. Electrode according to any of the preceding items, wherein the second layer is applied to, preferably applied directly to, the first layer.

[0129] 9. Electrode according to any of the preceding items, wherein the (n+1)th layer is applied to, preferably directly to, the n.sup.th layer.

[0130] 10. Electrode according to any of the preceding items, wherein the at least two layers are different from each other.

[0131] 11. Electrode according to any of the preceding items, wherein the at least two layers differ from each other in their composition, porosity, mass loading and/or density, preferably porosity.

[0132] 12. Electrode according to any of the preceding items, wherein the at least two layers contain the identical lithium ion acceptor.

[0133] 13. Electrode according to any of the preceding items, wherein the at least two layers differ in at least one of the type or the ratio of the lithium ion acceptor, the binder, and optionally the conductive agent.

[0134] 14. Electrode according to any of the preceding items, wherein the layer which is closer to the metal foil has a higher porosity than the layer which is more remote from the metal foil, preferably the first layer which is applied to the metal foil has a higher porosity than the second layer applied to the first layer.

[0135] 15. Electrode according to any of the preceding items, wherein the thickness of the layer is independently in the range of 10-100 μm, preferably 20-50 μm.

[0136] 16. Electrode according to any of the preceding items, wherein the ratio of the thickness of the first layer to the thickness of the second layer is 1:5 to 5:1, preferably 1:5 to 1:3.

[0137] 17. Electrode according to any of the preceding items, wherein the first layer comprises [0138] 75 to 95 wt.-% of lithium ion acceptor, [0139] 1 to 10 wt.-% of binder, and [0140] 5 to 20 wt.-% of conductive agent.

[0141] 18. Electrode according to any of the preceding items, wherein the second layer comprises [0142] 90 to 98 wt.-% of lithium ion acceptor, [0143] 0 to 5 wt.-% of binder, and [0144] 0 to 5 wt.-% of conductive agent.

[0145] 19. Method for producing an electrode according to any of items 1-18, comprising the steps

[0146] i) providing at least two slurries, each comprising at least one lithium ion acceptor, at least one binder, optionally at least one conductive agent and at least one liquid medium,

[0147] ii) applying a first slurry to at least one side, preferably to both sides of a metal foil,

[0148] iii) at least partially removing the liquid medium to form a first layer,

[0149] iv) optionally compacting the first layer obtained after step iii),

[0150] v) applying a second slurry to the first layer,

[0151] vi) at least partially removing the liquid medium to form a second layer,

[0152] vii) optionally compacting the second layer obtained after step vi) and optionally the first layer,

[0153] viii) optionally repeating the steps v) to vii) with another slurry obtained according to step i) at least once,

[0154] ix) optionally cutting the product obtained after step vii) or viii) into a form which is suitable for an electrode.

[0155] 20. Process according to item 19, wherein the liquid medium is selected from the group consisting of water, NMP, ethanol, preferably water, NMP, or mixtures thereof.

[0156] 21. Process according to any of items 19 or 20, wherein the slurry is obtained by dispersing at least one lithium ion acceptor, at least one binder and optionally at least one conductive agent in at least one liquid medium.

[0157] 22. Process according to any of items 19-21, wherein the slurry is applied by spreading, spraying, rolling, and/or dipping.

[0158] 23. Process according to any of items 19-22, wherein step iii) is performed at increased temperatures, preferably at 30-250° C., more preferably 80-150° C., and optionally under reduced pressure.

[0159] 24. Process according to any of items 19-23, wherein the compacting according to step iv) and/or vii) is independently conducted via rolling, calendering or pressing.

[0160] 25. Process according to any of items 19-24, wherein step ix) is performed using a knife, a milling apparatus, a laser, and/or a water jet.

[0161] 26. Electrode, obtainable according to a process according to any of items 19-25.

[0162] 27. Electrochemical cell, comprising at least one electrode according to any of items 1-18 or according to item 26.

[0163] 28. Electrochemical cell according to item 27, further comprising at least one additional electrode, an electrolyte and at least one separator.

[0164] 29. Electrochemical cell according to item 27 or 28, wherein the additional electrode is a metal foil coated with graphite, silicon, lithium titanate, tin dioxide or mixtures thereof.

[0165] 30. Electrochemical cell according to any of items 27-29, wherein the electrolyte is selected from the group consisting of ionic liquid, aprotic salt solutions, carbonates, such as dimethyl carbonate (DMC) or diethyl carbonate (DEC), or mixtures thereof.

[0166] 31. Electrochemical cell according to any of items 27-30, wherein the separator is a polyolefin membrane, e.g. PE or PP, or a polyethylene terephthalate membrane, which is optionally coated with ceramics, PVDF or mixtures thereof.

[0167] 32. Use of an electrode according to any of items 1-18 or according to item 26 in an electrochemical cell, particularly lithium ion cells, lithium metal cells, and in super capacitors (super caps).

[0168] 33. Use according to item 32 in aviation applications.