METHOD FOR PRODUCING A COATING MATERIAL FOR COATING ELECTRODE CARRIERS AND COATING MATERIAL IN GRANULE FORM

Abstract

The invention relates to a method for preparing a coating material for coating an electrode carrier. For known coating materials, the problem exists that these either cannot be stored without the input of energy or cannot be produced without quality fluctuations. To solve these problems, the method according to the invention comprises the steps of a) providing a dry mixture containing at least i) an active material, ii) a conductivity additive, as well as iii) a fluorine-containing polymer binder, b) bringing the dry mixture into contact with a solvent mixture containing ethylene carbonate and/or propylene carbonate, c) thoroughly mixing the solvent mixture and the dry mixture at a temperature of more than 80° C. until the fluorine-containing polymer binder has dissolved completely in the solvent mixture, wherein d), after the fluorine-containing polymer binder has dissolved completely, the mixture obtained is cooled to a temperature of less than 40° C. and the mixture obtained cures during the cooling process and e), the mixture obtained is granulated during or after the curing process. The granules obtained with the method can be stored without problems and can be used without quality fluctuations to coat an electrode carrier.

Claims

1. A method for preparing a coating material for coating an electrode carrier of an electrical energy storage system, comprising the steps of: a) providing a dry mixture, containing at least i) active material, ii) a conductivity additive as well as iii) a fluorine-containing polymer binder, the fluorine-containing polymer binder being selected from a group comprising polyvinylidene fluoride (PVDF), a polyvinylidene fluoride copolymer (PVDF-Copolymer), or any mixture of PVDF and/or at least one PVDF copolymer or any mixture of PVDF and/or at least one PVDF copolymer, b) bringing the dry mixture into contact with a solvent mixture, containing at least 60% by weight ethylene carbonate and/or propylene carbonate or 60% by weight of any mixture thereof, the fluorine-containing polymer binder and the solvent mixture being present in a ratio of 1:(5-30), c) thoroughly mixing the solvent mixture and the dry mixture at a temperature of more than 80° C. until the fluorine-containing polymer binder has dissolved completely in the solvent mixture, d) the mixture, obtained after the complete dissolution of the fluorine-containing polymer binder, is cooled to a temperature below 40° C., the mixture obtained curing during the cooling process and e) the mixture obtained being granulated during or after the curing process.

2. The method for preparing a coating material for coating an electrode carrier of an electrical energy storage system according to claim 1, wherein f) after the granulation, up to 1% by weight MgO or Al.sub.2O.sub.3 or a mixture thereof is added to the granular material obtained.

3. The method for preparing a coating material for coating an electrode carrier of an electrical energy storage system according to claim 1, wherein the PVDF copolymer is selected from a group comprising PVDF-hexafluoropropylene (PVDF-HFP), PVDF-tetrafluorethylene (PVDF-TFE) or PVDF-chlorotetrafluoroethylene (PVDF-CTFE).

4. The method of preparing a coating material for coating an electrode carrier of an electrical energy storage system according to claim 1, wherein the active material is selected from a group comprising graphite, amorphous carbons, such as in particular, hard carbon, soft carbon, carbon nano tubes, especially single wall carbon nano tubes and multi wall carbon nano tubes, activated charcoal, anthracites, as well as lithium storage metals and/or alloys, especially nanocrystalline and/or amorphous silicon, silicon-carbon composites, silicon-tin-carbon composites, as well as tin-carbon composites, tin (SnC composites, SiSnC composites), aluminum, antimony, Li.sub.4T.sub.15O.sub.12 (LTO), lithium metal oxides of the LiM.sub.xM.sub.yM.sub.zO.sub.a type (M being selected from Co, Ni, Mn, Al, V; 0≦x≦0.85, 0≦y≦0.5, 0≦z≦0.1; 1≦a≦4) or lithium metal phosphates LiMPO.sub.4 and dopings of the aforementioned lithium metal oxides and lithium metal phosphates with magnesium and niobium, silicon carbides, magnesium oxides, titanium oxides, aluminum oxides, zirconium oxides, calcium carbides, as well as fillers selected from the group comprising NaCl, KCl, LiBF.sub.4, LiClO.sub.4, LiBOB, LiPF.sub.6) with a particle size range of 0.01≦x≦c≦35 μm or mixtures of these fillers.

5. The method of preparing a coating material for coating an electrode carrier of an electrical energy storage system according to claim 1, wherein the conductivity additive is selected from a group comprising graphite with d50 between 1 μm and 8 μm, carbon blacks with primary particles between 10 and 80 nm and carbon fibers, especially carbon nano tubes (single wall carbon nano tubes and multi wall carbon nano tubes) or any mixtures thereof.

6. The method for preparing a coating material for coating an electrode carrier of an electrical energy storage system according to claim 1, wherein the dry mixture contains 80 to 95% by weight active material, 1.5 to 5% by weight conductivity additive and 2 to 8% by weight fluorine-containing polymer binder.

7. The method for preparing a coating material for coating an electrode carrier of an electrical energy storage system according of claim 1, wherein the dry mixture for the preparation of a coating material for an anode contains 94% by weight active material, 2% by weight conductivity additive and 4% by weight polymer binder.

8. The method for preparing a coating material for coating an electrode carrier of an electrical energy storage system according to claim 1, wherein the dry mixture for the preparation of a coating material for a cathode preferably contains 93% by weight active material, 3% by weight conductivity additive and 4% by weight polymer binder for the preparation of a coating material for an cathode.

9. A thermoplastic granular material for the preparation of a coating material of an electrode carrier of an electrical energy storage system, comprising at least i) active material, ii) a conductivity additive and iii) a fluorine-containing polymer binder, the latter being selected from a group comprising polyvinylidene fluoride (PVDF), a polyvinylidene fluoride copolymer (PVDF copolymer) or any mixture of PVDF and/or at least one PVDF copolymer and iv) a solvent mixture, wherein the solvent mixture contains at least 60% by weight ethylene carbonate and/or propylene carbonate or 60% by weight of any mixture thereof, and that the fluorine-containing polymer binder and the solvent mixture are present in a ratio by weight of between 1:(5-30).

10. The thermoplastic granular material for preparing a coating material for coating an electrode carrier of an electric energy storage system according to claim 9, wherein the active material is selected from a group comprising graphite, amorphous carbons, lithium storage metals and/or alloys, Li.sub.4Ti.sub.5O.sub.12 (LTO), lithium metal oxides of the LiM.sub.xM.sub.yM.sub.zO.sub.a type (M being selected from Co, Ni, Mn, Al, V; 0≦x≦0.85, 0≦y≦0.5, 0≦z≦0.1; 1≦a≦4) or lithium metal phosphates LiMPO.sub.4 (such as LiFePO.sub.4, LiMnFePO.sub.4, LiCoPO.sub.4, LiVPO.sub.4) and dopings of the aforementioned lithium metal oxides and lithium metal phosphates with magnesium and niobium, silicon carbides, magnesium oxides, titanium oxides, aluminum oxides, zirconium oxides, calcium carbides, as well as fillers selected from the group comprising NaCl, KCl, LiBF.sub.4, LiClO.sub.4, LiBOB, LiPF.sub.6 with a particle size spectrum between 0.01≦x≦35 μm or mixtures of these fillers.

11. The thermoplastic granular material for preparing a coating material for coating an electrode carrier of an electric energy storage system according to claim 9, wherein the conductivity additive is selected from a group comprising graphite with d50 between 1 μm and 8 μm, carbon blacks with primary particles between 10 and 80 nm and carbon fibers or any mixtures thereof.

12. The thermoplastic granular material for preparing a coating material for coating an electrode carrier of an electric energy storage system according to claim 9, wherein the dry mixture contains 80 to 95% by weight active material, 1.5 to 5% by weight conductivity additive and 2 to 8% by weight fluorine-containing polymer binder.

13. The thermoplastic granular material for preparing a coating material for coating an electrode carrier of an electric energy storage system according to claim 9, wherein the dry mixture for the preparation of a coating material for an anode preferably contains 94% by weight active material, 2% by weight conductivity additive and 4% by weight polymer binder.

14. The thermoplastic granular material for preparing a coating material for coating an electrode carrier of an electric energy storage system according to claim 9, wherein the dry mixture for the preparation of a coating material for a cathode preferably contains 93% by weight active material, 3% by weight conductivity additive and 4% by weight polymer binder.

15. A method for coating an electrode carrier of an electric energy storage system, comprising the steps of: a) preparing a coating material and heating the coating material to a specified coating temperature, b) coating the electrode carrier with the coating material, c) drying the coated electrode carrier, wherein preparing the coating material comprises: a1) providing a dry mixture, containing at least i) active material, ii) a conductivity additive as well as iii) a fluorine-containing polymer binder, the fluorine-containing polymer binder being selected from a group comprising polyvinylidene fluoride (PVDF), a polyvinylidene fluoride copolymer (PVDF-Copolymer), or any mixture of PVDF and/or at least one PVDF copolymer or any mixture of PVDF and/or at least one PVDF copolymer, a2) bringing the dry mixture into contact with a solvent mixture, containing at least 60% by weight ethylene carbonate and/or propylene carbonate or 60% by weight of any mixture thereof, the fluorine-containing polymer binder and the solvent mixture being present in a ratio of 1:(5-30), a3) thoroughly mixing the solvent mixture and the dry mixture at a temperature of more than 80° C. until the fluorine-containing polymer binder has dissolved completely in the solvent mixture, a4) the mixture, obtained after the complete dissolution of the fluorine-containing polymer binder, is cooled to a temperature below 40° C., the mixture obtained curing during the cooling process and a5) the mixture obtained being granulated during or after the curing process.

Description

EXAMPLES

Preparation of Thermoplastic Granular Material

[0033] Variation 1: Preparation of the thermoplastic granular material by means of a twin shaft kneader using PVDF (Kynar®HSV900) as the polymer binder and a solvent mixture with ethylene carbonate (EC) and propylene carbonate (PC) (90% by weight EC and 10% by weight PC). [0034] a.) Mixing all of the powdery portions of the formulation (active material—NMC— 93% by weight, conductivity additive—Timkal®SuperP and Timkal® KS4 2:3-2.5% by weight and polymer—Kynar®HSV900—4.5% by weight) in a vacuum mixing dryer at temperatures between 80° and 150° and at a pressure of less than 10 mbar for between 60 and 400 minutes, and preferably for 120 minutes. After that, cooling the dry mixture (dry blend) to below 40° C. and filling into a suitable container or supplying directly gravimetrically to the twin shaft kneader. If supplied directly, the dry blend need not necessarily be cooled. Cooling to below 40° C. is to prevent that, upon further cooling the dry mixture (dry blend), a vacuum results in the container, which could destroy the dry mixture. [0035] b.) Gravimetric addition of the dry mixture (dry blend) to a twin shaft kneader and gravimetric addition of the solvent (EC/PC), which has been heated to between 40° and 80° C., in the ratio of between 15 and 45% by weight and preferably 28% by weight, based on the dry mixture (dry blend). Total mass flows (dry mixture plus solvent mixture) between 10 and 1500 kg/h are possible, depending on the size of the kneader. [0036] c.) Preparation of the mass in the kneader at a temperature between 80° and 150° C. with a mechanical input of energy of between 50 and 100 Wh/kg based on the total mass flows, the polymer binder going into solution completely. [0037] d.) The mass is discharged over a multiple orifice-type injector with a hole diameter of 2 to 5 mm with subsequent cooling (to below 40° C.) and cutter head strike off (head granulator), resulting in a granular material with a diameter of 2 to 5 mm and a length of between 5 and 10 mm. [0038] e.) The granular material thus prepared can be packaged durably in aluminum composite foil or melted once again directly in a single screw conveyor at temperatures between 80° and 150° C. and be applied via a wide slot nozzle with a subsequent group of rollers as a follow-up at temperatures between 80° and 150° C. onto the respective substrate.

[0039] Variation 2: Preparation of a thermoplastic granular material by means of a vacuum mixing dryer with a solvent lance and rotating fly cutters, using PVDF as the polymer binder and EC as the only component of the solvent mixture. [0040] a.) Mixing all of the powdery portions of the formulation (active material—NMC—93% by weight, conductivity additive—Timcal®SuperP and Timcal® KS4 2:3-2.5% by weight and polymer—Kynar®HSV900—4.5% by weight) in a vacuum mixing dryer at temperatures between 80° and 150° C. and at a pressure of less than 10 mbar for between 60 and 400 minutes, and in this case, preferably at 140° C. for 120 minutes. After that, cooling the mixture to a temperature below 65° C. [0041] b.) Injecting the solvent mixture (EC) in a ratio of 15 to 45% by weight (preferably 28% by weight, in this case), based on the dry mixture (dry blend) and at a temperature of 80° C. into the vacuum of the mixing space. [0042] c.) Cooling the whole of the mixture while rotating the mixer shaft and the cutter head to a temperature of less than 40° C. and emptying the mixer. [0043] d.) The granular material thus prepared can be packaged durably in aluminum composite foil or melted directly once again in a single screw conveyor at temperatures between 80° and 150° C. and be applied via a wide slot nozzle with a subsequent group of rollers as a follow-up at temperatures between 80° and 150° C. onto the respective substrate.

[0044] Preferred Dry Mixtures

[0045] Anodes: [0046] a) Granular material with graphite as the active material [0047] I. 61.1% by weight graphite (Hitachi SMG-A1-13cNT1 42.77% by weight+Hitachi MAGD 14.664% by weight), 3.9% by weight PVDF (Kynar®HSV900 2.34% by weight+Kynar®ADX161 1.26% by weight), solvent 35% by weight (ethylene carbonate EC). Ratio of binder to solvent 1:9 [0048] II. 61.1% by weight graphite (Hitachi SMG-A1-13cNT1 42.77% by weight+Hitachi MAGD 14,664% by weight), 3.9% by weight PVDF (Kynar®HSV900 2.34% by weight+Kynar®ADX161 1.26% by weight), solvent 35% by weight (ethylene carbonate/propylene carbonate EC/PC 3:1). Ratio of binder to solvent 1:9 [0049] III. 58.88% by weight graphite (Hitachi SMG-A1-13cNT1), 1.28% by weight conductivity additive (TIMCAL SuperC65), 3.84% by weight PVDF (Kynar®HSV900 2,496% by weight+Kynar®ADX161 1.344% by weight), solvent 36% by weight (ethylene carbonate EC). Ratio of binder to solvent 1:9.4 [0050] IV. 58.88% by weight graphite (Hitachi SMG-A1-13cNT1), 1.28% by weight conductivity additive (TIMCAL SuperC65), 3.84% by weight PVDF (Kynar®HSV900 2.496% by weight+Kynar®ADX161 1.344% by weight), solvent 36% by weight (ethylene carbonate/propylene carbonate EC/PC 3:1). Ratio of binder to solvent 1:9.4 [0051] V. 65.28% by weight graphite (Hitachi SMG-A1-13cNT1), 0.51% by weight conductivity additive (Showa Denko VGCF®), 2.21% by weight PVDF (1.4365% by weight Kynar®HSV900+0.7735% by weight Kynar®ADX161), solvent 32% by weight (ethylene carbonate EC). Ratio of binder to solvent 1:14.5 [0052] VI. 65.28% by weight graphite (Hitachi SMG-A1-13cNT1), 0.51% by weight conductivity additive (Showa Denko VGCF®), 2.21% by weight PVDF (Kynar®HSV900+0.7735% by weight Kynar®ADX161), solvent 32% by weight (ethylene carbonate/propylene carbonate EC/PC 3:1). Ratio of binder to solvent 1.14.5 [0053] Note: Graphite is available from various manufacturers. For the examples, graphites of different manufacturers may be used; however, these should be very similar in their physical properties. [0054] b) Granular material with lithium titanate (Li4Ti5O12) as the active material [0055] I. 55.8% by weight lithium titanate (Südchemie LTO EXM2228), 3.1% by weight conductivity additive (TIMCAL SuperC65 2.6% by weight+0.5% by weight Showa Denko VGCF®), 3.1% by weight PVDF (Kynar®HSV900 2.015% by weight+1.085% by weight Kynar®ADX161 0.7735% by weight, solvent 38% by weight (ethylene carbonate EC). Ratio of binder to solvent 1:12.25 [0056] II. 55.8% by weight lithium titanate (Südchemie LTO EXM2228), 3.1% by weight conductivity additive (TIMCAL SuperC65 2.6% by weight+0.5% by weight Showa Denko VGCF®), 3.1% by weight PVDF (2.015% by weight Kynar®HSV900+1.085% by weight Kynar®ADX161), solvent 38% by weight (ethylene carbonate EC+propylene carbonat EC:PC 3:1). Ratio of binder to solvent 1:12.25

[0057] Cathodes: [0058] a) Granular material with lithium iron phosphate (LiFePO4), as the active material [0059] I. 59.8% by weight lithium iron phosphate (LiFePO4) (Südchemie LFP P2), 2.275% by weight conductivity additive (TIMCAL® KS6 1.775% by weight+0.5% by weight Showa Denko VGCF®), 2.925% by weight PVDF (1.901% by weight Kynar®HSV900+1.024% by weight Kynar®ADX161), solvent 35% by weight (ethylene carbonate EC). Ratio of binder to solvent 1:11.96 [0060] II. 59.8% by weight lithium iron phosphate (LiFePO4) (Südchemie LFP P2), 2.275% by weight conductivity additive (TIMCAL® KS6 1.775% by weight +0.5% by weight Showa Denko VGCF®), 2.925% by weight PVDF (1.901% by weight Kynar®HSV900+1.024% by weight Kynar®ADX161), solvent 35% by weight (ethylene carbonate EC+propylene carbonate PC, EC:PC 3:1). Ratio of binder to solvent 1:11.96 [0061] b) Granular material with lithium nickel cobalt aluminum oxide (NCA) [0062] I. 69.75% by weight nickel cobalt aluminum oxide (TODA NCA NAT-9070) 1.875% by weight conductivity additive (1.375% by weight TIMCAL® KS6+0.5% by weight Showa Denko VGCF®), 3.375% by weight PVDF (2.193% by weight Kynar®HSV900+1.181% by weight Kynar®ADX161), solvent 25% by weight (ethylene carbonate EC). Ratio of binder to solvent 1:7.4 [0063] II. 69.75% by weight nickel cobalt aluminum oxide (TODA NCA NAT-9070) 1.875% by weight conductivity additive (1.375% by weight TIMCAL® KS6+0.5% by weight Showa Denko VGCF®), 3.375% by weight PVDF (2.193% by weight Kynar®HSV900+1.181% by weight Kynar®ADX161), solvent 25% by weight (ethylene carbonate EC+propylene carbonate PC, EC:PC 3:1). [0064] c) Granular material with lithium nickel manganese cobalt oxide (NMC) [0065] I. 67.5% by weight lithium nickel manganese cobalt oxide (TODA NMC NM3101), 3.75% by weight conductivity additive (0.9375% by weight TIMCAL® KS6+2.8125% by weight TIMCAL® SuperC65), 3.75% by weight PVDF (2.4375% by weight Kynar®HSV900+1.3125% by weight Kynar®ADX161, solvent 25% by weight (ethylene carbonate EC). Ratio of binder to solvent 1:6.66 [0066] II. 67.5% by weight lithium nickel manganese cobalt oxide (TODA NMC NM3101), 3.75% by weight conductivity additive (0.9375% by weight TIMCAL® KS6+2.8125% by weight TIMCAL® SuperC65), 3.75% by weight PVDF (2.4375% by weight Kynar®HSV900+1.3125% by weight Kynar®ADX161), solvent 25% by weight (ethylene carbonate EC+propylene carbonate PC, EC:PC 3:1). Ratio of binder to solvent 1:6.66 [0067] III. 111.71.61% by weight lithium nickel manganese cobalt oxide (TODA NMC NM3101), 2.31% by weight conductivity additive (1.81% by weight TIMCAL® KS6+0.5% by weight Showa Denko VGCF®), 3.08% by weight PVDF (2.002% by weight Kynar®HSV900 30 1.078% by weight Kynar®ADX161), solvent 23% by weight (ethylene carbonate EC). Ratio of binder to solvent 1:7.47 [0068] IV. 71.61% by weight lithium nickel manganese cobalt oxide (TODA NMC NM3101), 2.31% by weight conductivity additive (1.81% by weight TIMCAL® KS6+0.5% by weight Showa Denko VGCF®), 3.08% by weight PVDF (2.002% by weight Kynar®HSV900+1.078% by weight Kynar®ADX161), solvent 23% by weight (ethylene carbonate EC+propylene carbonate PC, EC:PC 3:1). Ratio of binder to solvent 1:7.47 [0069] Note: There are various manufacturers of the active materials for the cathodes. For the examples, active materials of different manufacturers may be used; however, these should be very similar in their physical properties.

[0070] Preparation of the Electrodes

[0071] Preparation of the Cathodes and Indirect and Direct Coating of the Anodes

1. Indirect Coating

[0072] The granular material obtained is melted once again by means of a single screw extruder and molded via a heated roller unit between two carrier films (of PET, PfEEK, Kapon or the like). (Parameters: mass flow, roller gap, temperature and take-off speed). In the following step, this laminate is applied by means of a laminator on the respective charge eliminator foil (copper having a thickness of 9-12 μm for the anode or aluminum, and 10-15 μm for the cathode). This takes place in one step for the front and back of the respective charge-eliminator foil. The lamination unit is followed by a compression step, by means of which grooves are impressed in the still plastic mass by means of a structured pair of rollers, transverse to the running direction. Subsequently, the foil is cooled in order to remove the carrier or covering film of PET or the like. Subsequently, the coated foil is heated by means of IR radiation, and the solvent is removed at temperatures between 100° and 200° C. by a counter-current air flow method. After that, the foil is ready for further processing (calendering). Surface capacitances between 1.0 and 3.5 mAh/cm2 can be applied in this way.

[0073] Depending on the type (for example, whether EC or PC is used), the solvent can be recycled.

2. Direct Coating

[0074] The granular material is melted once again by means of a single screw extruder and molded via a heated roller unit between the respective charge-eliminator foil (copper or aluminum) and covering film (of PET, PEEK, Kapon or the like). (Parameters: mass flow, roller gap, temperature and take-off speed, RPM). After the layer is formed, a compression step follows, by means of which grooves are impressed in the still plastic mass by means of a structured pair of rollers, transverse to the running direction. Subsequently, the foil is cooled in order to remove the carrier or covering film of PET or the like. This is followed by the first heating step of the solvent by IR radiation and counter-current air flow at temperatures between 100° and 200° C. This process is repeated on the back of the aluminum or copper foil. After that, the foil is ready for further processing (calendering). Surface capacitances between 1.0 and 3.5 mAh/cm2 can be applied in this way.

[0075] Depending on the type (for example, whether EC or PC is used), the solvent can be recycled.

3. Method without Covering Film:

[0076] The roller unit is configured in such a way that the respective rollers can be run at different rotational speeds. By these means, friction is produced between the rollers and the coating composition. Due to this friction, adhesion of the coating composition to one of the roller surfaces can be prevented. As a result, it is possible to do without the use of a covering film. However, wear at the surface of the roller cannot be ruled out.