[0037] figure 1 A schematic side view of the rolling device is illustrated, in which, starting from the powder conveyor 1, the dry powder mixture stored in the powder conveyor 1 passes on two chrome-plated calender rolls 2a and 2b of the same size, and passes through the calender rolls Apply pressure and shear force to transform into a stable state. Here, the first calender roll 2a operates at a higher rotation speed than the second calender roll 2b, so that the formed dry film 3 remains on the first calender roll 2a after the combined operation of pressing and shearing.
[0038] In the representative embodiment shown in the figure, the dry powder used is in a pre-mixed state and contains 90% by weight of Ketjen Black/sulfur (1:2m/m), 3% by weight of polytetrafluoroethylene (PTFE) and 7% by weight % Of multi-walled carbon nanotubes (MWCNT). For lithium ion electrodes, 95% by weight of lithium manganese oxide, 3% by weight of conductive agent (in this case, multi-walled carbon nanotubes, MWCNT), and 2% by weight of PTFE are generally used. In the calender nip between the first roll 2a and the second roll 2b, the dry powder mixture is fibrillated, thereby producing a closed dry film 3.
[0039] The rotation speed of the first roller 2a and the second roller 2b is in the range of 10:9 to 10:4, which is approximately 2:1 in the illustrative embodiment shown, that is, 10mm/s:5mm/s or 20mm/s: 10mm/s. However, in other illustrative embodiments, depending on the parameter window and powder conditions, 80 mm/s: 40 mm/s may also be used as the rotation speed. Therefore, a higher rotation speed results in a thinner dry film with a less pronounced corrugated structure or less pronounced fibrils, and thus a lower surface roughness R a. In the illustrative embodiment shown, the average length of the fibrils is 10 μm, and is formed anisotropically in the traveling direction of the rollers 2a and 2b. Due to the rotation speed, the shear force is applied to the powder in the nip and fibrillates along the above-mentioned traveling direction. The width of the nip in the exemplary embodiment shown in the figure is 50 μm, but the width can also be 10 μm. Between to 300μm. This results in mechanical stability and film formation on the first roll 2a rotating at a higher speed, and avoids the formation of a self-supporting film (however, if necessary, it can be removed from the roll 2a mechanically (for example with a doctor blade) And achieved). In contrast, a dry film 3 supported on a faster roller 2a is obtained, which is advantageous due to limited mechanical stability, especially for dry films with a thickness of less than 200 μm.
[0040] In the illustrative embodiment shown, the first roller 2a and the second roller 2b may be heated to a temperature of 100°C, respectively. In addition, the first roller 2a can be provided with an adhesion-enhancing surface to which the dry film 3 adheres, while the second roller 2b has an adhesion-reducing surface to the dry film. In the illustrative embodiment shown, the acting linear force between the first roller 2a and the second roller 2b totals 400N.
[0041] By subsequent lamination to a current collector provided with a thermoplastic primer or adhesive, the dry film 3 can be removed from the first roller 2a, and therefore, for example, an electrode produced in a solvent-free manner can be produced.
[0042] in figure 2 In which corresponds to figure 1 An illustrative embodiment is shown in the view where there are two figure 1 The rolling device shown is composed of a symmetrical structure. Duplicate features in this figure have the same reference numerals, and the same is true in subsequent figures.
[0043] In the illustrative embodiment shown, the substrate 4 is fed through between two rolling devices, which are arranged mirror-symmetrically to each other. The two first rollers 2a are opposed to each other and the two dry rollers 3 run on the two first rollers 2a respectively, so that both sides of the substrate 4 can be provided with dry films 3, because the two surfaces face one roller 2a respectively . For this reason, the substrate 4 is moved at a speed precisely corresponding to the rotational peripheral speed of the two first rollers 2a. In the illustrated exemplary embodiment, except for the mirror-symmetrical arrangement, the two rolling devices have the same configuration, and therefore have the same size in particular, and operate at the same rotation speed or rotation peripheral speed. Although in figure 2 The dry film 3 in the illustrative embodiment shown is the same, but in other illustrative embodiments, dry films 3 different in composition from each other may also be applied to the substrate 4.
[0044] In addition, the described method also allows the production of electrodes with alternative current collectors as substrate 4, for example perforated substrates with low basis weight, such as perforated metal foils or conductive fabrics. in figure 2 In the illustrative embodiment shown, the substrate 4 is an aluminum foil having a carbon-coated primer as a double-sided coating.
[0045] Therefore, continuous thin film production of battery electrodes for primary and secondary batteries is possible, such as lithium-ion batteries, lithium-sulfur batteries, sodium-sulfur batteries, solid-state batteries, supercapacitor electrodes, electrodes for fuel cells, electrodes for electrolytic cells, Electrodes for other electrochemical elements, as well as filter membranes or adsorption coatings, decorative layers, optical layers for absorption and/or layers of materials sensitive to moisture or materials sensitive to solvents by using porous particles.
[0046] image 3 Showing another illustrative embodiment of the present invention and figure 1 The corresponding schematic side view, in which the substrate 4 is wound on the substrate roll 5 in the form of a foil and is guided into the nip in the form of the foil, so that the formed dry film 3 is directly laminated on the substrate 4 in the nip. In this illustrative embodiment, the dry film 3 is no longer directly supported on the first roller 2a, that is, it is no longer in direct contact with the first roller 2a, but is only indirectly guided and wound on the first roller 2a On the other roll 2a.
[0047] Therefore, the illustrated method allows the electrode to be prepared directly from the pre-mixed dry film powder without the need for additional steps for fibrillation, and therefore without the need to form a self-supporting film. This method can be used for prefibrillation, where the mechanical stability of the dry film can be enhanced. Moreover, a self-supporting film can be realized by separation from the carrying roller. The load and density can be set by the peripheral speed or the rotational peripheral speed of the first roll 2a and the second roll 2b and the pressing force acting in the direction of the calender nip or the nip between the rolls. The dry film formation is achieved by a self-quantitative method, and the obtained layer thickness is derived from the pressing force used by the two rollers 2a and 2b. Pre-dosing is achieved through continuous input of a specific (adjusted according to process parameters) powder amount, such as through the powder conveyor 1 or the feeding substrate. In this way, the layer thickness can also be influenced.
[0048] The mechanical stability of the dry film 3 is adjusted by the squeezing force and rotation speed (shear rate) used. Compared with a self-supporting film that is squeezed only in the nip due to the same rotation speed of the rollers 2a and 2b, the dry film 3 produced by the method proposed herein has significantly improved mechanical stability.
[0049] Only those features of the various embodiments disclosed in the illustrative embodiments may be combined with each other and individually claimed.
