Powder hopper for gravity driven feeding of powdered electrode precursor material to the nip of a dry electrode calender, corresponding assembly, and corresponding method

Abstract

The invention relates to a powder hopper (101) for gravity-driven feeding of powdered electrode precursor material (102) into the nip of a dry electrode calender (2), said powder hopper comprising a powder feed opening (105) for feeding the powdered electrode precursor material (102) into the powder hopper and a powder exit opening (106) for metering the powdered electrode precursor material from the powder hopper into the nip, the cross section of the powder hopper tapering between the powder feed opening and the powder exit opening, the powder hopper having level detection means (103) for detecting the powder level in the powder hopper. The invention also relates to a powder hopper and a corresponding assembly consisting of a first roller and a second roller forming the nip, as well as a method of operating the powder hopper.

Description

[Technical field]

[0001] The present invention relates to a powder hopper that supplies powdered electrode precursor material to the nip of a dry electrode calender for producing a dry electrode web. [Background technology]

[0002] Electrodes may be used in electrical energy storage cells, which are widely used to power electronic, electromechanical, electrochemical, and other useful devices. Such cells include batteries, such as primary chemical cells and secondary (rechargeable) cells, fuel cells, and various types of capacitors, including ultracapacitors. Electrodes may also be used in water treatment plants. In particular, electromobility is growing clearly. In electric powered vehicles, the energy source, the batteries, accounts for a large part of the costs. This is directly related to their production. This requires an efficient and cost-effective production while increasing the energy density. The calendering step in the process chain for producing lithium-ion battery cells is important here.

[0003] Electrodes are essential components for the potential of energy storage. The electrochemical capacity of an electrode, e.g., the capacity and efficiency of a battery electrode, is determined by various factors. These include the physical properties of the materials contained therein, such as the active material, binder, and adhesive, particle size and surface area of ​​the adhesive material, the surface properties of the active material, and the physical properties of the electrode film, such as density, porosity, cohesion, and adhesion to the conductive element. Dry processing systems and methods have traditionally used high shear and / or high pressure processing steps to separate and mix electrode film materials. Such systems and methods may contribute structural advantages over wet-formed electrode films. However, the high processing pressures and large equipment size (and thus large space requirements) required for the production of dry, free-standing electrode films and dry electrodes leave room for improvement.

[0004] From US 2020 / 0072612 A1 a device and method for producing dry electrodes is known, on the one hand it is known to manually feed powder electrode precursor material into a nip, on the other hand it is known to use a powder hopper for feeding the substance, however the solutions described have the drawback that the feeding of the substance is thus inaccurate, leading to non-uniformly formed electrode tracks having variations in their thickness and their width. Summary of the Invention

[0005] It is therefore an object of the present invention to improve a powder hopper for feeding powdered electrode precursor material to a nip in a manner that allows for better metering of the feeding of material.

[0006] The invention is solved by the features of the independent claims. Advantageous embodiments are described in the dependent claims.

[0007] Thus, there is provided a powder hopper for gravity-driven feeding of powdered electrode precursor material into the nip of a dry electrode calender, the powder hopper having a powder feed opening for feeding the powdered electrode precursor material into the powder hopper and a powder exit opening for metering the powdered electrode precursor material from the powder hopper into the nip, the cross section of the powder hopper tapering between the powder feed opening and the powder exit opening, the powder hopper having a level detection device for determining the powder level of the powder hopper. The powder hopper can be aligned such that the powder feed opening lies above the powder exit opening, in particular vertically aligned thereon. The powder feed opening and / or the powder exit opening can have a rectangular cross section.

[0008] In relation to the solutions known from the prior art, the present invention has the advantage that the filling level of the powder hopper can be continuously monitored during the process. This makes it possible to improve the homogeneity of the produced electrode tracks, in particular to produce a homogeneous thickness and / or a homogeneous track width. Furthermore, the filling level monitoring enables timely detection of errors in the operating process, for example when there is too little or too much powder in the hopper, so that the system can be switched off if necessary to avoid serious damage to the system.

[0009] It can be provided that the powder hopper further comprises a weight detection device for determining the weight of the powder in the powder hopper. It can be provided that the level detection device and the weight detection device are connected to a control unit of the system and transmit the determined level and weight data to the control unit. The control unit can continuously determine the density of the powder in the hopper by comparing the filling level data with the weight data. This has the advantage that it can be controlled based on the determined density of the powder fed into the hopper, and thus the powder fed into the nip has a constant density. This is particularly important because the powder electrode precursor material is already compacted in the hopper, which continues to increase in the direction of the powder outlet opening due to the powder material pushing downwards the underlying powder layer from above. The compacting is further increased by simply feeding the powder into the powder hopper, which for example falls from a feeding device into the powder hopper, and the vertical distance from the feeding device of the powder hopper or from the powder contained therein has a certain influence on the compacting of the powder in the hopper.

[0010] It can be provided that the weight detection device comprises at least one load cell on which the powder hopper is supported. It can be provided that the powder hopper comprises at least two support tabs projecting laterally on opposite sides of the powder hopper with at least one first load cell and at least one second load cell, the powder hopper being supported on the at least one first load cell via one of the support tabs and on the at least one second load cell via the other of the support tabs. To detect the powder weight in the powder hopper, the at least one load cell can transmit the measured weight to a control unit, where the tail weight of the powder hopper is then subtracted from the measured value.

[0011] It can be provided that the powder hopper has a width extending transversely to the nip and a length extending along the nip, the width of the powder hopper decreasing between the powder feed opening and the powder exit opening and the length of the powder hopper between the powder feed opening and the powder exit opening being constant. In particular, it can be provided that the powder feed opening and the powder exit opening are vertically spaced from each other. The powder hopper can have two opposing side walls delimiting the length of the hopper and in particular can be vertically aligned. The support tab can be curved away from the side walls, in particular from an upper edge of the side walls. The powder hopper can have two opposing side walls delimiting the width of the powder hopper and adjacent the powder feed opening. The walls adjacent the powder feed opening can be substantially vertically aligned. Immediately adjacent the powder exit opening there may be two further opposing wall sections delimiting the width of the powder hopper, one of which may be aligned substantially vertically and the other of which may be aligned sloping and tapering in cross section towards the powder exit opening.

[0012] The fill level detection device may have at least one first fill level sensor in the area above the powder outlet opening. The first fill level sensor may, for example, be arranged in a vertical wall section adjacent to the powder outlet opening. The first fill level sensor may, for example, be arranged in a range of 2 cm to 10 cm above the powder outlet opening.

[0013] The fill level detection device may have at least one second fill level sensor in the area below the powder feed opening. The second fill level sensor may, for example, be arranged in a vertical wall section adjacent to the powder feed opening. The second fill level sensor may, for example, be arranged in a range of 2 cm to 10 cm below the powder feed opening.

[0014] For example, the filling level detection device may include at least one capacitive filling level sensor. The principle of capacitive filling level measurement is based on the change in capacitance of a capacitor. The capacitive sensor and the powder hopper wall form a capacitor whose capacitance depends on the amount of powder in the hopper, an empty hopper has a lower capacitance and a filled hopper has a higher capacitance. It may be provided that the filling level sensor comprises a plurality of sensor units distributed over the length of the side wall of the powder hopper and arranged at substantially the same height. The sensor units may be, for example, light barriers or capacitive sensors. By distributing the sensors over the length of the powder hopper, it may be determined whether the powder hopper is filled with powder uniformly over its entire length. For example, the powder hopper may have a plurality of measurement levels, and in each of the plurality of measurement levels a plurality of filling level sensors may be arranged horizontally spaced apart from one another, i.e. at the same height. For example, four or more filling level sensors may be provided per measurement level.

[0015] It can be provided that the side walls of the powder hopper with multiple sensor units are arranged substantially vertically. Thus, in the case of multiple measurement levels, the side wall sections with sensors are each vertically aligned, so that the hopper can have multiple vertical wall sections. If multiple measurement planes are provided, the sensors can all be located on the same side of the hopper, so that the side of the hopper opposite the sensor only has a single inclined wall section.

[0016] Thus, the first filling level sensor can have a first plurality of sensor units distributed over the length of a first substantially vertical side wall of the powder hopper and arranged at substantially the same height, and the second filling level sensor can have a second plurality of sensor units distributed over the length of a second substantially vertical side wall of the powder hopper and arranged at substantially the same height, and a sloping side wall connecting the first and second side walls can be arranged between the first and second side walls tapering the width of the powder hopper in the direction of the powder outlet opening.

[0017] The fill level detection device may further include an optical fill level sensor in addition to or instead of the capacitive fill level sensor. The optical fill level sensor may be oriented spaced apart from the powder hopper through a powder feed opening on the interior of the powder hopper. The optical fill level sensor may be arranged above the powder hopper. The detection range of the optical fill level sensor may include at least the entire length and the entire width of the powder hopper. The optical fill level sensor may be configured to detect the fill volume of the powder hopper with the powder electrode precursor material. For this purpose, the optical fill level sensor may have a camera that detects the surface relief of the powder in the hopper and compares it with the value of the total volume of the powder hopper stored in the control unit. Thus, the optical fill level sensor may also be configured to detect a powder fill level that is non-uniformly distributed over the length of the powder hopper.

[0018] The invention further relates to an assembly comprising a powder hopper according to any one of the preceding claims and first and second rolls forming a nip, wherein the powder exit opening of the powder hopper is arranged above and along the nip so as to be able to meter powdered electrode precursor material into the nip over an entire length of the powder exit opening.

[0019] It can be provided that the assembly further comprises a feed conveyor arranged above the powder hopper by which the powder electrode precursor material can be conveyed into the nip. It can be provided that the feed conveyor is height adjustable. It can be provided that the feed conveyor is a belt conveyor. It can be further provided that a vertical adjustment device for adjusting the height of the feed conveyor is coupled to the control unit, which regulates the vertical position of the feed conveyor depending on the determined powder filling level in the powder hopper, so that the distance between the feed conveyor and the powder surface in the hopper always remains constant. Instead, the control unit controls the vertical adjustment device so that the determined density in the powder hopper always remains constant, so that the distance of the feed conveyor to the hopper increases when the density is below the target density and decreases when it exceeds the target density. This allows the effect of compaction in the hopper caused by feeding powder to be utilized to achieve a constant material density at the powder outlet opening.

[0020] The conveying speed of the feed conveyor can be regulated according to a determined powder density in the powder hopper, the powder density being calculated based on the powder fill height determined via the fill level detection device and the powder mass determined via the weight detection device. It can be stipulated that the conveying speed is increased when the calculated powder density exceeds a first threshold value of the target range, and that the conveying speed is slowed down when the calculated powder density falls below a second threshold value of the target range.

[0021] The invention further relates to a method of operating a powder hopper, the method comprising the following steps: determining a fill level of the powder hopper with powdered electrode precursor material, determining a weight of the powdered electrode precursor material located in the powder hopper, calculating a density of the powdered electrode precursor material located in the powder hopper from the determined fill level and the determined weight, and regulating a flow of powdered electrode material conveyed into the powder hopper.

[0022] It can be provided that regulating the flow of powdered electrode material fed into the powder hopper comprises regulating a conveying speed of a feed conveyor connected upstream of the powder hopper. It can be further provided that regulating the flow of powdered electrode material fed into the powder hopper comprises regulating a vertical distance between the feeding device and the powder hopper.

[0023] It may further be provided that determining the fill level of the powder hopper comprises determining using a capacitive sensor and / or an optical sensor, in which case determining the fill level of the powder hopper may comprise determining a presence of powdered electrode precursor material at a first powder hopper level and determining a presence of powdered electrode precursor material at a second powder hopper level, and the height of the first powder hopper level may be different from the height of the second powder hopper level.

[0024] It can further be provided that determining the weight of the powdered electrode precursor material located in the powder hopper includes weighing the powder hopper minus the powder hopper weight.

[0025] Further details of the invention are explained with reference to the following drawings. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 shows a schematic side view of a powder hopper arranged above the nip of a dry electrode calender. [Diagram 2]FIG. 1 illustrates a perspective view of an embodiment of a powder hopper having two capacitive level sensors and a weight detection device. [Diagram 3] FIG. 1 illustrates a perspective view of an embodiment of a powder hopper with an optical level sensor. [Figure 4] 1 shows a schematic representation of an embodiment of an arrangement of a feed conveyor, powder hopper, and dry electrode calender. [Diagram 5] FIG. 1 is a side view of an embodiment of a powder hopper mounted on a dry electrode calender. [Figure 6] FIG. 1 is a side view of an embodiment of a dry electrode calender for producing electrode films from powdered electrode precursor material. [Figure 7] FIG. 1 is a plan view of one embodiment of a dry electrode calender for producing electrode films from powdered electrode precursor material.

[0027] The illustration shown in FIG. 1 shows an exemplary assembly of a powder hopper 101, which is arranged above the nip 220 of the dry electrode calender 2. The powder hopper 101 has a powder feed opening 105 at its upper side and a powder outlet opening 106 at its lower side aligned with the nip 220. As a result, the powder electrode precursor material 102 fed into the powder feed opening 105 is fed through the powder outlet opening 106 into the nip 220 and rolled therein to form an electrode film 601 of defined width and thickness. The dry electrode calender 2 has two rolls 201 with a small diameter in the area of ​​powder feeding, which exert a high surface pressure on the powder over the length of the nip 220. Each of the rolls 201 is laterally supported by an adjacent support roll 210, which prevents the rolls 201 from curving due to the forces acting in the nip, which occur especially in the middle of the rolls. The produced electrode film 601 is guided out of the nip 220 under and around the right roll 201 and then conveyed through a nip between the right roll 201 and the right support roll 210 in order to homogenize the electrode film 601. Thus, nips are also formed on those rolls, resulting in support of the roll 201 via the electrode film 601 guided through the nip. In contrast, no nip is formed between the left support roll 210 and the left roll 201. Thus, those two rolls are mutually wrapped, so that the roll 201 is directly supported by the support roll 210.

[0028] FIG. 2 shows a perspective view of the underside of the powder hopper 101. It has a powder feed opening 105 at its upper side and a powder outlet opening 106 at its lower side, so that the powder electrode precursor material 102 is conveyed from the powder feed opening 105 to the powder outlet opening 106 by gravity. The width B of the powder hopper 101 tapers in the direction of the powder outlet opening 106. At each of its two longitudinal ends, the powder hopper has a vertical boundary wall 114, at the upper side of each of which a support tab 108 curves away from the powder feed opening 105. A load cell 107 is arranged below each of the support tabs 108 to measure the weight of the powder hopper 101 together with the powder electrode precursor material 102 located therein, the weight of the powder hopper 101 being subtracted in a higher level control unit to determine the actual powder weight. In the upper region of the powder hopper 101, it has two opposing vertical wall sections 110, 117 in the longitudinal direction, which are adjacent to the powder feed opening 105. The rear wall section 117 shown in the example is adjacent in the lower region of the powder hopper 101 by an obliquely arranged wall 113, which is directly adjacent to the powder outlet opening 106 and narrows the width of the hopper 101 in the direction of the powder outlet opening 106. Opposite to the oblique wall 113, the powder hopper 101 has on the one hand an oblique wall 111 in the lower region and on the other hand a vertical wall 112 adjacent to the oblique wall 111, which in turn is adjacent to the powder outlet opening 106. The angle of inclination of the wall 111 is flatter than the angle of the opposite wall 113. The powder hopper 101 shown also comprises a fill level detection device 104, which comprises two fill level sensors 109. Of them, a first fill level sensor 109 is arranged on a vertical wall 112 bordering the powder outlet opening and a second fill level sensor 109 is arranged on a vertical wall 110 bordering the powder feed opening. Thus, by means of the fill level sensors 109 at different levels of the hopper 101, it can be determined whether the powder fill level has reached the respective fill level. Each of the fill level sensors 109 comprises four volumetric sensor units 115, which are arranged horizontally with respect to one another and spaced apart from one another over the length L of the hopper 101.This means that even uneven filling along the hopper 101 can be detected, for example, when only one of the sensor units 115 detects the presence of powder, but the other three sensor units 115 located at the same height do not. This information can be evaluated by a higher-level control unit. Depending on the received information, the control unit can issue appropriate commands to the system. For example, an emergency stop of the system can be initiated if the filling level of the hopper 101 is too low, too high or, as explained above, uneven in the longitudinal direction. Furthermore, the feed conveyor 120 connected upstream of the hopper 101 can increase the feeding rate of the powder electrode precursor material 102 if the filling level is too low, or the feeding rate can be reduced or stopped if the filling level is too high. The powder hopper 101 also has a load cell 107, via which the hopper 101 is supported on the machine frame 500. This provides the higher-level control unit with information about the growth of the powder mass currently in the powder hopper 101. To ensure that a flow of powder of constant density is fed to the nip 220, the control unit periodically determines the density in the hopper 101 from information about the powder fill level and information about the powder mass of the powder in the hopper 101. Thus, for example, the feed rate of the powder in the hopper 101 or even the speed of the roll 201 can be readjusted.

[0029] Figure 3 shows the powder hopper 101 of Figure 2 with an alternative or additional optical fill level sensor as fill level detection device 104. It is arranged at a distance from the powder hopper 101 and directed through a powder feed opening on the interior of the powder hopper 101. The detection range 118 of the optical fill level sensor 116 includes the overall length L and the overall width B of the powder hopper 101. As a result, the powder volume, powder mass as well as the powder density in the powder hopper 101 can be more accurately determined.

[0030] As shown in FIG. 4, the powder hopper 101 is filled with as constant an amount of powder electrode precursor material 102 as possible during operation. The powder hopper 101 can have one or more sensors, such as 103 and 104, configured to detect properties of the powder 102 and / or the powder hopper 101. The weight detection device 103 is configured so that the weight of the powder 102 in the powder hopper 101 can be determined. The weight detection device 103 is configured such that it determines the total weight of the powder hopper 101 by subtracting the known hopper weight from the measured total weight, and thus the powder contained in the powder hopper 101. The weight detection of the powder hopper 101 can be performed continuously, at periodic intervals, or at aperiodic intervals. The fill level detection device 104 is configured to determine the fill level of the powder 102 in the hopper 101. For example, the fill level detection device 104 can determine whether the powder 102 in the hopper 101 exceeds one or different height thresholds, and fill level detection sensors can be arranged on different hopper levels. Above the powder hopper 101 a feed conveyor 120 in the form of a belt conveyor is arranged, by means of which the powder electrode precursor material 102 is conveyed to the powder feed opening 105 of the hopper 101. From the powder outlet opening 106 the powder flows into a nip 220 arranged below, which is formed by a roll 201. Via the load cell 107 and the fill level sensor 109 the density of the powder 102 in the hopper 101 is monitored, and if a deviation of the density from the target range is detected the feed rate of the powder and / or the vertical distance of the feed conveyor from the powder hopper 101 is variable. For example, if the powder fill level is too low or the density is too low, the feed conveyor's feed rate can be increased and / or its distance from the hopper 101 can be increased to produce a higher powder compaction. On the other hand, if the powder level is, for example, too high or the density is too high, the feed conveyor's feed rate can be slowed down and / or its distance from the hopper 101 can be reduced to produce a lower powder compaction.

[0031] 5 shows the powder mill of the dry electrode calender 2 in a side view. It has a calender frame 500 on which, on the one hand, the rolls 201 and the supporting rolls 210 that support them are mounted, and on the other hand, the powder hopper 101 is mounted above the nip 202. The powder hopper 101 is arranged along the nip 220 and has a powder feed opening 105 oriented upwards and a powder outlet opening 106 oriented towards the nip 220. The powder hopper 101 is supported on the calender frame 500 via a load cell 107, via a support tab 108 that is curved away from the upper edge of the side wall 114. The upper and lower areas of the powder hopper 101 are clearly visible, the hopper having a constant width in the upper area with two opposing walls 110, 117 and a tapering width in the lower area with an inclined wall section 113 on the one hand and an inclined wall section 111 and an adjacent vertical wall section 112 on the other hand. It can also be seen that capacitive fill level sensors 109 are arranged on each of the vertical walls 110 and 112 in the right illustration at different hopper levels.

[0032] 6 shows a side view of a further embodiment of a multi-roll calender 3. It has two dry electrode calenders 2 with opposite conveying directions Y1, Y2 of the electrode films 601, 602. The roll assemblies mounted in the calender frame 500 each have a powder mill on the input side, which constitutes two rolls 201 for pressing the powder electrode material 102 into the electrode films 601, 602, together with a support roll 210 adjacent to each other and supporting them. As explained above, the powder 102 is conveyed into the powder feed opening 105 of the powder hopper 101, respectively, and through the powder exit opening 106 into the nip 220. The electrode films 601, 602 then run in a serpentine pattern first around the support roll 210 facing towards the end nip, then around two conveyor rolls 310 arranged in one behind the end nip 13 and so on along their respective conveying directions Y1, Y2. The end nip 13 is formed between the last rolls 310 at both ends of the dry electrode calender 2. The separator film 603 is guided from above through this gap 13 and is coated on both sides with the electrode films 601, 602. The separator film 603 is first transported parallel to the direction Y1 along the direction X in the direction of the end nip 13.

[0033] FIG. 7 shows a top view of a further embodiment of a multi-roll calender 3, showing the assembly of the rolls 201 in relation to the support rolls 210 in an integrated rolling system. As explained above, the multi-roll calender 2 is used to produce a separator film 603 (not shown) coated on both sides with electrode films 601, 602. The assembly also has two calender assemblies 2 positioned side by side at the front, with opposing main transport directions Y1, Y2. The calender assemblies 2 each have eight rolls 201, 210, 310 mounted in a machine frame 500. On the input side, the assembly has two rolls 201 laterally supported by the support rolls 210, which are used as powder mills to produce electrode films 601, 602 from powder electrode precursor material. Following the support rolls are four conveyor rolls 310, which bring the electrode film to the desired width and thickness and homogenize it. The input end roll 301 is designed as a support roll 301, which is wound directly on the first roll 201. The output conveyor roll 310 forms the common end nip 13, in which the electrode films 601, 602 are applied to the separator film.

[0034] The features of the invention disclosed in the above description, in the drawings and in the claims may be essential for the implementation of the invention both individually and in any combination. [Explanation of symbols]

[0035] (List of reference numbers) 2 Dry Electrode Calendar 5 Assembly 13 End Nip 101 Powder Hopper 102 Powder electrode precursor material 103 Weight detection device 104 Filling level detection device 105 Powder supply opening 106 Powder outlet opening 107 Load Cell 108 Support tab 109 Filling level sensor 110 Vertical sidewall section bordering the powder feed opening 111 Sloping Sidewall Section 112 Vertical sidewall section bordering the powder exit opening 113 Sloped sidewall section bordering the powder exit opening 114 Vertical side walls dividing the length 115 Sensor unit 116 Optical Fill Level Sensor 117 Vertical sidewall section bordering the powder feed opening 118 Detection Zone 120 Supply Conveyor 201 rolls 210 Support Roll 220 Nip 310 Conveyor Roll 500 Calendar Frames 601 First electrode film 602 Second electrode film 603 Separator Film B Powder hopper width L Length of powder hopper H Powder hopper height X Separator film feeding direction Y1: Transport direction of the first electrode film Y2: Transport direction of the second electrode film

Claims

1. 1. A powder hopper for gravity driven feeding of powdered electrode precursor material into a nip of a dry electrode calender, characterized in that it has a powder feed opening for feeding powdered electrode precursor material into the powder hopper and a powder exit opening for metering the powdered electrode precursor material from the powder hopper into the nip, a cross section of the powder hopper tapers between the powder feed opening and the powder exit opening, and the powder hopper has a level detection device for determining a powder level in the powder hopper.

2. 10. The powder hopper of claim 1, further comprising a weight detection device for determining a weight of powder in the powder hopper.

3. The powder hopper of claim 2 , wherein the weight sensing device comprises at least one load cell on which the powder hopper is supported.

4. 4. The powder hopper of claim 3, wherein the powder hopper has at least one first load cell and at least one second load cell and at least two support tabs projecting laterally on opposite sides of the powder hopper, the powder hopper being supported on the at least one first load cell via one of the support tabs and on the at least one second load cell via the other of the support tabs.

5. 2. The powder hopper of claim 1, wherein the powder hopper has a width (B) extending transversely to the nip and a length (L) extending along the nip, the width (B) of the powder hopper decreasing between the powder feed opening and the powder exit opening, and the length (L) of the powder hopper between the powder feed opening and the powder exit opening is constant.

6. 2. The powder hopper of claim 1, wherein the fill level detection device comprises at least one first fill level sensor in the area above the powder outlet opening.

7. 2. The powder hopper of claim 1, wherein the fill level detection device comprises at least one second fill level sensor in an area below the powder feed opening.

8. The powder hopper of claim 1 , wherein the level detection device includes at least one volumetric fill level sensor.

9. 7. The powder hopper of claim 6, wherein the fill level sensor comprises a plurality of sensor units distributed over a length of a side wall of the powder hopper and arranged at substantially the same height.

10. 10. The powder hopper of claim 9, wherein the sidewall of the powder hopper having the plurality of sensor units is substantially vertically aligned.

11. 11. A powder hopper according to claim 10, wherein the first filling level sensor has a first plurality of sensor units distributed over a length (L) of a first substantially vertical side wall of the powder hopper and arranged at substantially the same height, and the second filling level sensor has a second plurality of sensor units distributed over a length (L) of a second substantially vertical side wall of the powder hopper and arranged at substantially the same height, and a sloping side wall connecting the first and second side walls and tapering the width (B) of the powder hopper in the direction of the powder outlet opening is arranged between the first and second side walls.

12. The powder hopper of claim 1 , wherein the level detection device includes at least one optical fill level sensor.

13. 13. The powder hopper of claim 12, wherein the optical fill level sensor is oriented inside the powder hopper spaced apart from the powder hopper through the powder feed opening.

14. 13. The powder hopper of claim 12, wherein the detection range of the optical fill level sensor includes at least an overall length (L) and an overall width (B) of the powder hopper.

15. 13. The powder hopper of claim 12, wherein the optical fill level sensor is configured to detect a fill volume of the powder hopper with powdered electrode precursor material.

16. 13. The powder hopper of claim 12, wherein the optical fill level sensor is further configured to detect a powder fill level that is non-uniformly distributed over a length (L) of the powder hopper.

17. 13. An assembly comprising: a powder hopper according to claim 1; and first and second rolls forming a nip, the powder exit opening of the powder hopper being arranged over and along the nip to meter powdered electrode precursor material into the nip over an entire length of the powder exit opening.

18. 20. The assembly of claim 17, further comprising a feed conveyor arranged above the powder hopper by which powdered electrode precursor material can be conveyed into the nip.

19. 20. The assembly of claim 18, wherein the conveying speed of the feed conveyor is regulated according to a determined powder density in the powder hopper, the powder density being calculated based on a powder fill height determined via the fill level detection device and a powder mass determined via the weight detection device.

20. 20. The assembly of claim 19, wherein the conveying speed is increased when the calculated powder density exceeds a first threshold of a target range, and the conveying speed is decreased when the calculated powder density falls below a second threshold of the target range.

21. 2. The assembly according to claim 1, wherein the powder hopper has an inlay on its inside along which the powder is guided by gravity to reduce friction with respect to the powder, preferably the coating, or has a low coefficient of friction with respect to the powder.

22. 2. The assembly of claim 1, wherein the powder exit opening has a gap aperture that tapers in a direction perpendicular to an axis of rotation of the rolls forming the nip designed to meter the powder toward and directly into the nip.

23. 1. A method of operating a powder hopper, comprising the steps of: determining a fill level of the powder hopper with powder electrode precursor material; determining a weight of the powder electrode precursor material located in the powder hopper; calculating a density of the powder electrode precursor material located in the powder hopper from the determined fill level and the determined weight; Regulating a flow of powder electrode material being conveyed into said powder hopper; The method comprising:

24. 22. The method of claim 21, wherein regulating the flow of powdered electrode material fed into the powder hopper comprises regulating a conveying speed of a feed conveyor connected upstream of the powder hopper.

25. 22. The method of claim 21, wherein determining the fill level of the powder hopper comprises determining using a capacitive sensor and / or an optical sensor.

26. 22. The method of claim 21, wherein determining the fill level of the powder hopper can include determining a presence of powdered electrode precursor material at a first powder hopper level and determining a presence of powdered electrode precursor material at a second powder hopper level, and a height of the first powder hopper level can be different from a height of the second powder hopper level.

27. 22. The method of claim 21 , wherein determining the weight of the powdered electrode precursor material located in the powder hopper comprises weighing the powder hopper minus the powder hopper weight.

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