METHOD AND APPARATUS FOR PRODUCING AN ELECTRODE FOR AN ACCUMULATOR

Abstract

The invention relates to a method for producing an electrode for an accumulator, wherein an electrode compound is applied to a carrier, in particular a metal foil, by means of an extrusion process. In the extrusion process, the electrode compound is fed through an extrusion die by means of a feeding device. The electrode compound is prepared by mixing in a mixing device and passed on from the mixing device to the feeding device, fluctuations in the flow rate of electrode compound that is passed on from the mixing device to the feeding device being evened out.

Claims

1. A method for producing an electrode for a rechargeable battery, wherein an electrode compound (12) is applied to a carrier (14), in particular a metal foil, by means of an extrusion process, wherein, in the course of the extrusion process, the electrode compound (12) is fed through an extrusion die (18) by means of a feeding device (20), characterized in that the electrode compound (12) is mixed in a mixing device (22) and is passed on by the mixing device (22) to the feeding device (20), wherein fluctuations of the mass flow of electrode compound (12) passed on by the mixing device (22) to the feeding device (20) are compensated.

2. The method as claimed in claim 1, characterized in that, to compensate for the fluctuations, electrode compound (12) is intermediately stored.

3. The method as claimed in claim 1 or 2, characterized in that, to compensate for the fluctuations, electrode compound (12) is returned to the mixing device (22).

4. The method as claimed in one of the preceding claims, characterized in that the electrode compound (12) is applied to the carrier (14) in the form of an uninterrupted strip, extending in the direction of application (44), of at least 2 m, in particular at least 5 m, in length.

5. The method as claimed in one of the preceding claims, characterized in that the electrode compound (12) is applied to the carrier (14) in such a way that there forms on the carrier (14) along the electrode compound (12) a strip (46) that is free of electrode compound, extending parallel to the direction of application of the electrode compound.

6. The method as claimed in one of the preceding claims, characterized in that the electrode compound (12) is kept in a flowable state between leaving the mixing device (22) and entering the feeding device (20), in particular during intermediate storage.

7. The method as claimed in one of the preceding claims, characterized in that the temperature of the electrode compound (12) between leaving the mixing device (22) and entering the feeding device (20), in particular during intermediate storage, is always at least 80° C., in particular at least 90° C., and/or at most 140° C., in particular at most 120° C.

8. The method as claimed in one of the preceding claims, characterized in that the electrode compound (12) has ethylene carbonate as a plasticizer.

9. An apparatus (10) for producing an electrode for a rechargeable battery, in particular by a method as claimed in one of the preceding claims, wherein the apparatus has a mixing device (20) for mixing an electrode compound (12) and a feeding device (20) for feeding the electrode compound (12) through an extrusion die (18), characterized in that the apparatus (10) has a compensating device (24) for compensating for fluctuations of a mass flow of electrode compound (12) produced by the mixing device (22) and passed on to the feeding device (20).

10. The apparatus (10) as claimed in claim 9, characterized in that the apparatus (10), in particular the compensating device (24) and the intermediate storage device, has a compensating container, for compensating for the fluctuations.

11. The apparatus (10) as claimed in claims 9 to 10, characterized in that the apparatus (10), in particular the compensating device (24), for compensating for the fluctuations has a return device for returning electrode compound (12) to the mixing device (22).

12. The apparatus (10) as claimed in one of claims 9 to 11, characterized in that the mixing device (22) is a multi-screw extruder, in particular a twin-screw extruder.

13. The apparatus (10) as claimed in one of claims 9 to 12, characterized in that the feeding device (20) is a positive displacement pump, in particular a gear pump.

14. The apparatus (10) as claimed in one of claims to 13, characterized in that the apparatus (10) has a measuring device (38) for measuring a measured variable concerning the electrode compound (12) passed on by the mixing device (22) to the feeding device (20), in particular for measuring a filling level of the intermediate storage device and/or for measuring a mass flow returned by the return device.

15. The apparatus (10) as claimed in claim 14, characterized in that the apparatus (10) has a closed-loop and/or open-loop control device (32) for controlling the apparatus (10), in particular a metering device (26, 28, 30) for metering a constituent of the electrode compound (12), in dependence on the measured variable.

Description

[0048] Further practical embodiments and advantages of the invention are described below in connection with the drawings, in which:

[0049] FIG. 1 shows a simplified graphic representation of a first part of an apparatus for producing an electrode,

[0050] FIG. 2 shows the second part, going together with the part represented in FIG. 1, of an apparatus for producing an electrode,

[0051] FIG. 3 shows a plan view of a portion of a strip of electrode compound applied to a carrier.

[0052] The apparatus 10, given by way of example, is suitable and intended for carrying out a method in which an electrode compound 12 is applied to a carrier 14. The carrier 14 may be, as in the example presented, strip-shaped and in a wound-up form. Correspondingly, the apparatus 10 may have an unwinding device 16 for unwinding the carrier 14.

[0053] The electrode compound 12 is applied to the carrier 14 by means of an extrusion die 18. For this, the electrode compound 12 is fed through the extrusion die 18 by means of the feeding device 20. As only schematically indicated graphically in the example shown, the feeding device 20 may be a gear pump. The carrier 14 is in this case moved past the extrusion die 18 in the direction of application 44.

[0054] The apparatus 10 also has a mixing device 22. As only schematically indicated graphically in the example shown, this may be formed as a twin-screw extruder. The mixing device 22 mixes the electrode compound 12, which is then passed on by the mixing device 22 to the feeding device 20. In this case, fluctuations in the mass flow of the electrode compound 12 passed on by the mixing device 22 to the feeding device 20 are compensated by a compensating device 24. As in the example shown, the compensating device 24 may be an intermediate storage device. This may intermediately store part of the mass flow of electrode compound 12 passed on by the mixing device 22 to the feeding device 20. The fluctuations in the mass flow are as it were “smoothed”.

[0055] As in the example shown, the apparatus 10 may have a plurality of metering devices 26, 28 for metering various constituents of the electrode compound 12. Likewise, the apparatus 10 may have a metering device 30 for metering the plasticizer. With the metering devices 26, 28, 30, the corresponding constituents can in each case be metered into the mixing device 22, i.e. in particular the mass flow can be controlled in an open-loop and/or closed-loop manner. The apparatus 10 may in this connection have a closed-loop and/or open-loop control 32, which is in particular designed to control the mass flows passed on by the metering devices 26, 28, 30 to the mixing device 22 in dependence on a measuring device that is not represented any more specifically. The measuring device that is not represented any more specifically may be in particular a measuring device for measuring the filling level in the intermediate storage device.

[0056] The mixing device 22, the compensating device 24, the feeding device 20 and/or the extrusion die 18 may in each case have a heating device 34. In particular, the mixing device 22 may have a plurality of heating devices 34, as represented in the case of the apparatus 10 given by way of example. In this way, for example, different heating zones can be realized.

[0057] Directly after the application of the electrode compound 12 to the carrier 14, it may be fed to a cooling device 36, as in the case of the apparatus 10 represented by way of example. In this connection, the change from FIG. 1 to FIG. 2 is only for technical representational reasons. In fact, the composite that is formed by the application, comprising the carrier 14 and the electrode compound 12, is further transported directly between the part-apparatuses 10 represented in FIGS. 1 and 2.

[0058] As represented in the example, the composite thus formed, comprising the carrier 14 and the electrode compound 12, may be fed to a layered measuring device 38. The result of the layer thickness measurement, in particular the result of the layer thickness measurement of the layer of the electrode compound 12, can likewise be used in connection with a closed-loop and/or open-loop control of the apparatus 10, in particular a metering device 26, 28 and/or 30.

[0059] As in the example represented, the apparatus 10 may have a heating device 40. This may be for example an infrared oven. The heating device serves in particular for removing the plasticizer, at least partially, from the electrode compound 12. This also has the effect in particular of generating a porosity, which can at a later point in time be infiltrated with an electrolyte.

[0060] As shown in the example, the apparatus 10 may have a winding-up device 42 for winding up the electrode formed by the composite comprising the carrier 14 and the layer of electrode compound 12 applied to it.

[0061] In FIG. 3, a portion of a carrier 14 with a strip of electrode compound 12 applied to it is represented. The strip of electrode compound 12 extends parallel to the direction of application 44. Also extending parallel to the strip of electrode compound 12 and to the direction of application 44 is a strip 46 that is free of electrode compound. As a result of the compensation for the fluctuations of the mass flow passed on by the mixing device to the feeding device, the edge 48 is formed as particularly straight and regular.

[0062] According to a first example, the electrode compound for a cathode that is mixed in the mixing device may be a mixture of a base compound and a plasticizer. The proportion by mass of the plasticizer in this mixture may be for example 24%. The plasticizer may be ethylene carbonate. The base compound may contain two different binders in proportions by mass of 4% and 2%, graphite and carbon black as additives for increasing the conductivity in proportions by mass of 3% each and lithium nickel cobalt aluminum oxide as an active material in a proportion by mass of 88%, in each case with respect to the base compound.

[0063] According to a second example, the electrode compound for a cathode that is mixed in the mixing device may be a mixture of a base compound and a plasticizer. The proportion by mass of the plasticizer in this mixture may be for example 35%. The plasticizer may be ethylene carbonate. The base compound may contain a binder in a proportion by mass of 7%, carbon black as an additive for increasing the conductivity in a proportion by mass of 5% and lithium iron phosphate as an active material in a proportion by mass of 88%, in each case with respect to the base compound.

[0064] According to a third example, the electrode compound for an anode that is mixed in the mixing device may be a mixture of a base compound and a plasticizer. The proportion by mass of the plasticizer in this mixture may be for example 38%. The plasticizer may be ethylene carbonate. The base compound may contain a binder in a proportion by mass of 6.5%, carbon black as an additive for increasing the conductivity in a proportion by mass of 4.5% and graphite as an active material in a proportion by mass of 89%, in each case with respect to the base compound.

[0065] The features of the invention disclosed in the present description, in the drawings and in the claims may be essential to the implementation of the invention in its various embodiments both individually and in any desired combinations. The invention is not restricted to the embodiments described. It can be varied within the scope of the claims and taking into consideration the knowledge of the relevant person skilled in the art.

LIST OF REFERENCE SIGNS

[0066] 10 Apparatus

[0067] 12 Electrode compound

[0068] 14 Carrier

[0069] 16 Unwinding device

[0070] 18 Extrusion die

[0071] 20 Feeding device

[0072] 22 Mixing device

[0073] 24 Compensating device

[0074] 26 Metering device

[0075] 28 Metering device

[0076] 30 Metering device

[0077] 32 Closed-loop/open-loop control

[0078] 34 Heating device

[0079] 36 Cooling device

[0080] 38 Layer thickness measuring device

[0081] 40 Heating device

[0082] 42 Winding-up device

[0083] 44 Direction of application

[0084] 46 Strip free of electrode compound

[0085] 48 Edge