METHOD, COATING DEVICE AND PREPARATION FOR FORMING FUNCTIONAL LAYERS OF AN ELECTROCHEMICAL STORAGE DEVICE

Abstract

A method for generating functional layers of an electrochemical storage device, comprising: providing a first preparation in a first reservoir of a coating device, providing a second preparation in a second reservoir of the coating device, placing the coating device above a substrate and moving the coating device relative to the substrate along a coating direction, dispensing the first preparation from the first reservoir through a first slot of the coating device onto a coating surface of the substrate. The first slot extending along a lateral axis perpendicular to the coating direction and parallel to the coating surface, and simultaneously dispensing the second preparation from the second reservoir through a second slot of the coating device onto the substrate. The second slot extending along the lateral axis, wherein the first preparation and the second preparation form a curtain between the coating device and the substrate.

Claims

1. A method for generating functional layers of an electrochemical storage device, the method comprising: providing a first preparation in a first reservoir of a coating device; providing a second preparation in a second reservoir of the coating device; placing the coating device above a substrate and moving the coating device relative to the substrate along a coating direction; and dispensing the first preparation from the first reservoir through a first slot of the coating device onto a coating surface of the substrate, the first slot extending along a lateral axis substantially perpendicular to the coating direction and substantially parallel to the coating surface, and substantially simultaneously dispensing the second preparation from the second reservoir through a second slot of the coating device onto the substrate, the second slot extending along the lateral axis, wherein the first preparation and the second preparation form a curtain between the coating device and the substrate, wherein the first preparation and the second preparation exhibit a shear thinning behavior; and wherein a first functional layer of the electrochemical storage device is formed on the coating surface from the first preparation, and a second functional layer of the electrochemical storage device is substantially simultaneously formed on the first functional layer from the second preparation.

2. The method according to claim 1, wherein the first functional layer and/or the second functional layer forms a solid-state electrolyte of the electrochemical storage device.

3. The method according to claim 2, wherein the solid-state electrolyte comprises an inorganic solid electrolyte, and/or a polymer electrolyte, or comprises a mixture of a polymer and a metal ion salt.

4. The method according to claim 1, wherein the first functional layer and/or the second functional layer forms a cathode or an anode, an electron transport medium, particularly a current collector, and/or a protective layer of the electrochemical storage device.

5. The method according to claim 1, wherein the first preparation and/or the second preparation comprises at least one of the following components a solvent and/or a polymerizable monomer, a metal ion host or a precursor capable of forming a metal ion host, a solid ion conductor or a precursor capable of forming a solid ion conductor, and/or a solid electronic conductor.

6. The method according to claim 1, wherein the first preparation and the second preparation comprise the same solvent and/or polymerizable monomer and/or the same salt concentration at the same concentration, such that no diffusion occurs at an interface of the first preparation and the second preparation.

7. The method according to claim 1, wherein the first preparation and/or the second preparation comprises a first polymer having a molecular weight from 1000 g mol.sup.−1 to 100000 g mol.sup.−1 and a second polymer having a molecular weight from 300000 g mol.sup.−1 to 1200000 g mol.sup.−1.

8. The method according to claim 1, wherein the first reservoir and the first slot or the second reservoir and the second slot are divided into a first section and a second section along the lateral axis, and wherein the first section and the second section are physically separated from each other, and wherein the first section forms an end section of the first or second reservoir along the lateral axis.

9. The method according to claim 8, wherein the second preparation is provided in the first section at a first flow rate and the second preparation is provided in the second section at a second flow rate, wherein the first flow rate and the second flow rate are set such that the second functional layer formed by the second preparation dispensed from the first section comprises a greater thickness perpendicular to the coating surface than the second functional layer formed by the second preparation dispensed from the second section, wherein the first slot comprises a width extending along the lateral axis which is equal to the width of the second section such that the first functional layer formed by the first preparation is embedded by the second functional layer formed by the second preparation, wherein the coating device comprises a dispensing surface configured to receive the first preparation dispensed from the first slot and the second preparation dispensed from the second slot, wherein the dispensing surface comprises a recess comprising a width along the lateral axis corresponding to the width of the first section of the respective reservoir and the respective slot, and wherein the recess extends from the respective slot along the entire dispensing surface in the coating direction.

10. The method according to claim 8, wherein the first or second preparation is provided in the first section of the first or second reservoir and a further preparation is provided in the second section of the first or second reservoir such that the first or second preparation and the further preparation are arranged in a pre-defined pattern on the coating surface of the substrate to jointly form the first or second functional layer.

11. A coating device for generating functional layers of an electrochemical storage device, the coating device comprising: a first reservoir for receiving a first preparation; a first slot for dispensing the first preparation from the first reservoir onto a coating surface of a substrate such that the first preparation forms a curtain between the coating device and the coating surface; a second reservoir for receiving a second preparation; and a second slot for dispensing the second preparation from the second reservoir onto the coating surface substantially simultaneously to the first preparation such that the second preparation forms a curtain between the coating device and the coating surface, wherein the coating device is configured to be placed above the substrate and moved relative to the substrate along a coating direction, and wherein the first slot and the second slot are configured and arranged such that a first functional layer of the electrochemical storage device is formed on the coating surface from the first preparation, and a second functional layer of the electrochemical storage device is substantially simultaneously formed on the first functional layer from the second preparation.

12. The coating device according to claim 11, wherein the first reservoir or the second reservoir are divided into a first section and a second section along the lateral axis, wherein the first section and the second section are physically separated, wherein the first or second reservoir comprises a first pump inlet connected to the first section and a second pump inlet connected to the second section, wherein the first pump inlet and the second pump inlet are configured to be connected to respective pumps to provide respective preparations in the first section and the second section, wherein the first section forms an end section of the first reservoir along the lateral axis.

13. The coating device according to claim 11, wherein the coating device comprises a dispensing surface configured to receive the first preparation dispensed from the first slot and the second preparation dispensed from the second slot, wherein the dispensing surface comprises a recess comprising a width along the lateral axis corresponding to the width of the first section of the respective reservoir and the respective slot, and wherein the recess extends from the respective slot along the entire dispensing surface in the coating direction.

14. A preparation for forming a functional layer of an electrochemical storage device comprising at least one of the following components: i. a solvent and/or a polymerizable monomer; ii. a metal ion host or a precursor capable of forming a metal ion host; iii. a solid ion conductor or a precursor capable of forming a solid ion conductor; or iv. a solid electronic conductor or a precursor capable of forming a solid electronic conductor, wherein the preparation exhibits a shear thinning behavior, and wherein the preparation is capable of forming a curtain between a coating device and a coating surface of a substrate when the preparation is dispensed from a slot of the coating device onto the coating surface.

15. The preparation according to claim 14, wherein the preparation comprises a first polymer having a molecular weight from 1000 g mol.sup.−1 to 100000 g mol.sup.−1 and a second polymer having a molecular weight from 300000 g mol.sup.−1 to 1200000 g mol.sup.−1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0133] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0134] FIG. 1 shows a cross-sectional view of a part of a coating device according to an embodiment of the invention in a plane parallel to the coating direction;

[0135] FIG. 2 shows a schematic partially cut-away perspective view of a part of a coating device according to an embodiment of the invention and the curtain and functional layers formed during the method according to the invention;

[0136] FIG. 3 shows a schematic perspective view of a coating device according to an embodiment of the invention with divided manifolds and associated pump inlets;

[0137] FIG. 4 shows a schematic perspective view of a coating device according to an embodiment of the invention and the curtain and functional layers formed during a first embodiment of the method according to the invention;

[0138] FIG. 5 shows a sectional view of the functional layers perpendicular to the coating direction, the functional layers having been formed according to the embodiment of the method depicted in FIG. 4;

[0139] FIG. 6 shows a schematic perspective view of a coating device according to an embodiment of the invention and the curtain and functional layers formed during a second embodiment of the method according to the invention; and

[0140] FIG. 7 shows a sectional view of the functional layers perpendicular to the coating direction, the functional layers having been formed according to the embodiment of the method depicted in FIG. 6.

DETAILED DESCRIPTION

[0141] FIG. 1 shows a cross-sectional view of a coating head 4 of a coating device 1 according to an embodiment of the invention in a plane parallel to a coating direction C, and FIG. 2 shows a corresponding perspective view of the coating head 4. As shown in FIGS. 1 and 2, the coating head 4 comprises a first reservoir 10, a second reservoir 20 and a third reservoir 30 for respectively receiving a first preparation P1, a second preparation P2 and a third preparation P3. In the depicted example, the reservoirs 10, 20, 30 are formed by cylindrical cavities in a main body of the coating head 4, the cavities extending along a lateral axis L which is to be arranged perpendicular to the coating direction C when performing the method according to the invention. The reservoirs 10, 20, 30 each branch into an associated slot 11, 21, 31 in a dispensing surface 2 or slide of the coating head 4. The dispensing surface 2 comprises a convexly curved section 2a at which a lip 3 is arranged which forms the bottom end of the coating head 4 in the arrangement shown in FIGS. 1 and 2.

[0142] According to an embodiment of the curtain coating method according to the invention, a first preparation P1 is provided in the first reservoir 10, a second preparation P2 is provided in the second reservoir 20 and a third preparation P3 is provided in the third reservoir 30 through respective pump inlets (not shown in FIG. 1, e.g. see FIG. 3) in the reservoirs 10, 20, 30, which are connected to a respective pump. By generating a flow of the respective preparations P1, P2, P3, the preparations P1, P2, P3 are dispensed from the slots 11, 21, 31, and, due to the tilted arrangement of the coating head 4 flow downwards on the dispensing surface 2 towards the curved section 2 a and the lip 3.

[0143] At the position of the first slot 11, the second preparation P2 forms a layer on top of the first preparation P1 being dispensed from the first slot 11. In a similar manner at the position of the second slot 21, the third preparation P3 forms a layer on the second preparation P2 being dispensed from the second slot 21. Provided that the composition and the rheological properties of the first preparation P1, the second preparation P2, and the third preparation P3 are set accordingly, and that a laminar flow occurs, these layers formed on top of the dispensing surface 2 are not mixed and form a layered curtain composed of a first segment 310 from the first preparation P1, a second segment 320 from the second preparation P2 and a third segment 330 from the third preparation P3, the curtain flowing down from the lip 3 of the coating head 4 onto a coating surface 210 of a substrate 200.

[0144] The substrate 200 is moved against the coating direction C relative to the coating head 4, for instance by a conveyor mechanism. Thereby, the functional layers 110, 120, 130 are formed on top of each other on the coating surface 210.

[0145] In particular, the first preparation P1, the second preparation P2 and the third preparation P3 are slurries having appropriate rheological properties (i.e. an appropriate viscosity and preferably shear thinning behavior) to be used for curtain coating. To obtain a stable curtain, the flow rate of the preparations P1, P2, P3 as well as the coating speed at which the substrate 200 moves relative to the coating head 4 against the coating direction C have to be appropriately set.

[0146] In particular, the coating head 4 comprises edge guides formed by tabs extending from both lateral edges of the lip 3 towards the coating surface 210 in the vertical direction to guide the edges of the curtain 310, 320, 330 and prevent neck formation.

[0147] The functional layers 110, 120, 130 of the electrochemical storage device may be, for example, a cathode 110, a solid-state electrolyte 120 and an anode 130 of a solid-state metal ion battery, e.g., a solid-state lithium ion battery or a solid-state sodium ion battery. According to this example, the first preparation P1 contains a metal ion host (conversion or intercalation material) suitable for forming a cathode of a solid-state ion battery, e.g. NMC, LFP, NCA, LCO, or LMO). The second preparation P2 contains a solid ion conductor, for instance an inorganic matrix containing metal ions, a polymer electrolyte such as a mixture of a polymer and a metal ion salt, or a mixture of an inorganic matrix containing metal salt and a polymer electrolyte. The third preparation P3 contains a metal ion host suitable for forming an anode of the solid-state ion battery, such as graphite, silicon, LTO or TiO.sub.2.

[0148] Alternatively, to form a solid electronic conductor, such as a current collector layer, the dispensed preparation may, e.g., contain metals or carbon black.

[0149] To tune the rheological properties of the first preparation P1, the second preparation P2 and the third preparation P3, these preparations may contain polymers, particularly a mixture of two polymers of different molecular weights.

[0150] In addition, the preparations P1, P2, P3 may contain solvents or polymerizable monomers, and optionally surfactants.

[0151] The described curtain coating method has the advantage that several very thin (e.g. <30 μm) layers of an electrochemical storage device can be formed simultaneously at high coating speeds (e.g., 40 m/min to 2500 m/min), which significantly improves manufacturing times of electrochemical storage devices, such as solid-state ion batteries.

[0152] An exemplary protocol for generating a slurry preparation according to the invention to form a solid electrolyte layer is as follows: 2.67 g of PEO (M.sub.v 600 000) are dissolved in 77 g Acetonitrile. 1.67 g of LiTFSI are added and stirred with a spatula. 12 g of LLZO powder (d.sub.mean 400 nm) is added and stirred again with a spatula. These mass ratios are particularly chosen to result in approximately even volumetric parts of ceramic and polymer within the dried films. The EO:Li molar ratio is 10.4:1. The total solid content of the slurry is 17.5 wt % (m.sub.PEO+m.sub.LiTFSI+m.sub.LLZO)/m.sub.total. The low shear steady state viscosity is around 130 mPas.

[0153] Furthermore, an exemplary protocol for generating a slurry preparation according to the invention to form a cathode layer is as follows: 6 g Acetonitrile, 0.25 g PEO (M.sub.v 35 000), 0.167 g PEO (M.sub.v 600 000), 0.27 g LiTFSI, 1.1 g LFP (Host) (d.sub.mean 1 micron), 0.1375 carbon black (60 nm).

[0154] Following curtain coating, a number of post processing steps may be performed on the stack of functional layers, particularly the following steps: [0155] 1) Evaporation of the solvent [0156] 2) Drying [0157] 3) cross-linking [0158] 4) hot-pressing [0159] 5) calendaring [0160] 6) initiating chemical reactions between components of the functional layers [0161] 7) sintering [0162] 8) initiating further chemical reactions between components of the functional layers [0163] 9) pressuring

[0164] FIGS. 3 to 7 show further examples of the coating device 1 and the curtain coating method according to the invention which can be advantageously used to generate structured functional layers 110, 120, 130 of an electrochemical storage device.

[0165] FIG. 3 is a semitransparent perspective view of a coating head 4, where only one reservoir 10 and the associated slot 11 has been drawn for simplicity (however, this arrangement can be used in coating heads containing three or even more reservoirs and slots). In the embodiment according to FIG. 3, the reservoir 10 is formed by three physically separated manifolds, resulting in a first section 10a, a second section 10b and a third section 10c, which are arranged along the lateral axis L, the second section 10b forming a middle section, and the first section 10a and the third section 10c forming opposite end sections. The first section 10a comprises a first pump inlet 13a, the second section 10b comprises a second pump inlet 13b and the third section 10c comprises a third pump inlet 13c, each being configured to be connected to a pump, such that a respective preparation P1, P2, P3, P4 can be provided in the respective section 10a, 10b, 10c of the reservoir 10.

[0166] In FIG. 4, a coating head 4 is depicted, wherein the first reservoir 10 is divided into a first section 10a (extending along the lateral axis over the width X.sub.1), a second section 10b (extending along the lateral axis L over the width X.sub.2) and a third section 10c (extending along the lateral axis L over the width X.sub.3) similar to FIG. 3.

[0167] A first preparation P1 is dispensed from the first section 10a and the third section 10c of the first slot 11, and a further preparation P4 is simultaneously dispensed from the second section 10b of the first slot 11. Further, simultaneously, the first preparation P1 is dispensed from the second slot 21 over the whole width X.sub.1+X.sub.2+X.sub.3 of the second slot 21.

[0168] As shown in FIG. 5, the curtain coating process depicted in FIG. 4 results in a structured first functional layer 110, wherein the first preparation P1 laterally embeds the further preparation P4, and a uniform second functional layer 120 formed from the first preparation. For example, the first preparation P1 may form an active material of the electrochemical storage device and the further preparation P4 may form a solid-state electrolyte which is protected from ingress of moisture and air by the active material.

[0169] FIG. 6 shows a further embodiment of the coating device 1, wherein the second reservoir 20 and the corresponding second slot 21 are separated into a first section 20a having a width X.sub.1 along the lateral axis L, a second section 20b having a width X.sub.2 along the lateral axis L and a third section 20c having a width X.sub.3 along the lateral axis L. This can be realized, for example, by separate manifolds as shown in FIG. 3. The sections 20a, 20b, 20c each comprise an associated pump inlet 13a, 13b, 13c (not shown in FIG. 6) branching off from a side of the second reservoir 20 opposite the slot 21, similar to the embodiment shown in FIG. 3.

[0170] The dispensing surface 2 of the coating device 1 comprises a recess 2b aligned with the first section 20a of the second slot 21 and comprising a width along the lateral axis L corresponding to the width X.sub.1 of the first section 20a of the second slot 21, wherein the recess 2b extends from the second slot 21 along the entire dispensing surface 2 in the coating direction C. Furthermore, the dispensing surface 2 comprises a further recess aligned with the third section 20c and comprising a width along the lateral axis L corresponding to the width X.sub.3 of the third section 20c.

[0171] By means of the pump or pumps connected to the first pump inlet 13a and the third pump inlet 13c (see FIG. 3), the second preparation P2 is provided in the first section 20a and the third section 20c at a first flow rate, and by means of the pump connected to the second pump inlet 13b (see FIG. 3) the second preparation P2 is provided in the second section 20b at a second flow rate, such that a thicker layer of the second preparation P2 is deposited on the substrate 200 along the width X.sub.1 and X.sub.3 than along the width X.sub.2. Simultaneously, the first preparation P1 is dispensed from the first slot 11 connected to the first reservoir 10, wherein the first slot 11 has a width w which is equal to the width X.sub.2 of the second section 20b of the second reservoir 20 and second slot 21.

[0172] The resulting pattern of materials deposited on the substrate 200 by the curtain coating method depicted in FIG. 6 is shown in FIG. 7. Similar to the result shown in FIG. 5, the first functional layer 110 consists of a core of the first preparation P1 along the width X.sub.2 flanked laterally by two sections where the second preparation P2 is deposited (along the width X.sub.1 and the width X.sub.3). The second functional layer 120 is a uniform layer of the second preparation P2 over the entire width X.sub.1+X.sub.2+X.sub.3. The uniform upper surface of the second functional layer 120 is due to the recesses 2b of the dispensing surface 2, the depth of which (perpendicular to the dispensing surface 2) is equal to the thickness of the first functional layer 110 in this case, compensating for the additional volume of the second preparation P2 dispensed from the first section 20a and the third section 20c of the second slot 21. Similar to the above-discussed result shown in FIG. 5, the first preparation P1 may form an active material of the electrochemical storage device and the second preparation P2 may form a solid-state electrolyte which is protected from ingress of moisture and air by the active material.

[0173] In particular, to ensure that the second preparation P2 is deposited along the width X.sub.1 and X.sub.3 at a thickness equal to the sum of the thickness of the layer of the first preparation P.sub.1 and the second preparation along the width X.sub.2 in a direction perpendicular to the lateral axis L, the flow rates f.sub.P1,X2, f.sub.P2,X1, f.sub.P2,X2 and f.sub.P2,X3 can be set according to the following formula:

[00001]$\frac{f_{P2,X1}}{X1}=\frac{f_{P2,3}}{X3}=\frac{f_{P2,X2}}{X2}+\frac{f_{P1,X2}}{X2},$

[0174] where f.sub.P1,X2 indicates the flow (volume per unit of time) of the first preparation along the width X.sub.2, f.sub.P2,X1 indicates the flow of the second preparation along the width X.sub.1, f.sub.P2,X2 indicates the flow of the second preparation along the width X.sub.2, and f.sub.P2,X3 indicates the flow of the second preparation along the width X.sub.3.

[0175] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.