Process arrangement for the production of active material layers for a lithium-ion battery cell

Abstract

Process arrangement for the production of active material layers (1), for example electrode layers or separator layers, for a lithium-ion battery cell, in which an active material strip (3) can be guided continuously in a production direction (FR) through a cutting system (7) which has a longitudinal cutting station (9) in which the active material strip (3) can be divided into strip strip segments (25) in the transverse direction of the active material strip (3), a profiling station (11) in which recesses (53), for example edge-side current collector recesses, are cut into the active material strip (3), and / or a cutting-to-length station (13) in which the active material strip (3) is cut into individual active material layers (1), characterized in that the cutting process in the cutting system (7) is carried out by liquid jet cutting and in that the cutting system (7) has liquid jet cutting nozzles (21) as cutting elements.

Description

[0001] The invention relates to a method arrangement for manufacturing active material layers, for example electrode layers or separator layers, for a lithium-ion battery cell according to the preamble of claim 1, and to a method for manufacturing such active material layers.

[0002] In a cell casing of a lithium-ion battery cell, for example a prismatic cell or a pouch cell, the active material can be arranged in the form of a layer stack consisting of stacked active material layers, namely electrode layers and separator layers.

[0003] The active material layers can be manufactured in a generic process setup. In this setup, an active material strip is continuously fed through a cutting system in one manufacturing direction. The cutting system can consist of a slitting station (also called a longitudinal cutting station), a notching station (also called a profiling station), and / or a trimming station (also called a cutting station). In the longitudinal cutting station, the active material strip is divided into strip-shaped segments in the transverse direction. In the profiling station, recesses, for example, edge-side current collection recesses, can be cut into the active material strip. In the cutting station, the active material strip is cut into individual active material layers.

[0004] In the current state of the art, the slotting process for lithium-ion battery electrodes uses the shearing principle, in which the upper and lower blades are in contact. This leads to high friction and thus faster tool wear. Slitting at high speeds exacerbates this problem. For this reason, the slotting speed is currently limited to a maximum of 120 m / min. The slotting process is performed by upper and lower circular blades made of tungsten carbide. These blades need to be resharpened after approximately 200 km. Resharpening the blades often results in high operating costs. Notching and electrode separation are performed as separate processes after the slotting process. This is done either mechanically or by laser. Due to the separate machines for slotting and notching, higher investment and a larger footprint are required.Laser notching is an energy-intensive process (approximately 6 kW equipment power requirement) and creates a heat-affected zone. Active material in this zone is subject to combustion, reducing battery capacity. The laser process is inefficient because most of the concentrated light beams are reflected by the copper surface. A special green laser is needed to achieve better light absorption by copper. This type of laser is expensive and does not allow speeds exceeding 80 m / min. Mechanical notching results in high tool wear. Furthermore, the electrode coil feed must be stopped at regular intervals to complete the process step. This leads to lower notching speeds. The movement of the electrode in the z-direction (thickness direction) during cutting creates waves at the slot edge.It is impossible to control this waviness because there is no counter-tool. The electrode's movement in the y-direction (latitudinal direction) is unrestricted. This leads to waviness in the y-direction. Due to the lack of a counter-force during slotting and mechanical notching, burrs form. This can cause a short circuit in the battery. The active material adheres to the cutting edges. This necessitates thorough cleaning of both the cutting edge and the blade. The adhesion of particles larger than 10 microns can also cause a short circuit in the cell. In short, cutting with tools (mechanical cutting) or cutting with energy (laser) has many disadvantages that affect cutting speed, increase costs, reduce battery capacity, and compromise battery safety.

[0005] A liquid jet cutting arrangement is known from US 2013 0324013 A1. A method for manufacturing a battery cell is known from US 2013 0298387 A1.

[0006] The object of the invention is to provide a process arrangement and a method for manufacturing active material layers for a lithium-ion battery cell, in which the process effort for manufacturing the active material layers is reduced compared to the prior art.

[0007] The problem is solved by the features of claim 1. Preferred further embodiments of the invention are disclosed in the dependent claims.

[0008] The invention relates to a process arrangement in which a continuous active material tape wound on a reel is provided. The active material tape is guided through a cutting system in a continuous process in one manufacturing direction. The cutting system can comprise a slitting station (longitudinal cutting station), a notching station (profiling station), and / or a trimming station (cutting station). In the longitudinal cutting station, the active material tape can be divided into strip-shaped segments in the transverse direction. In the profiling station, recesses, for example, edge-side current collection recesses, can be cut into the active material tape. In the cutting station, the active material tape can be cut into individual active material layers.According to the characterizing part of claim 1, the cutting process in the cutting system is no longer carried out mechanically, but by liquid jet cutting. For this purpose, the cutting system can comprise at least one liquid jet cutting nozzle as a cutting element.

[0009] In the following description, the term "slitting" is also referred to as "longitudinal cutting", while the term "notching" is also referred to as "profiling" and the term "trimming" is also referred to as "cutting to length".

[0010] The most important innovations of the present invention are briefly explained below: Instead of slotting and notching by mechanical cutting (using the shearing principle by the cutting tool) or by energy (laser), cutting is carried out here using a high-speed fluid medium. A modified fluid jet cutting process for cutting battery electrodes and separators is proposed. In the modified fluid jet cutting process, the cutting force is applied either by a narrow, high-speed fluid jet. Abrasive particles can be added to the fluid. The proposed abrasive is aluminum oxide. It is also possible to perform the cutting without an abrasive. The nozzle geometry is modified so that the abrasive enters the divergent zone. The modified nozzle geometry is shown in detail.Fluid jet cutting uses liquid carbonate as the fluid medium. The preferred carbonate is ethylene carbonate, which is also one of the components of the electrolyte in lithium-ion batteries. In slotting, the fluid jet cutting nozzle is stationary, and the electrode moves at high speed (more than 200 m / min). The slotting process is modified by applying stretching forces to the electrode by rolling. In notching, both the nozzle and the electrode move at the same speed. There is no relative movement. This allows for high-speed cross-sectioning. Modified notching tools are explained in detail below. In trimming, the electrode is cut within the fluid jet process, and the trimmed segment is then placed in a magazine. Water (with and without abrasives) as a liquid medium is discussed as an option.The drying process after slitting is crucial. A roll-to-roll drying process is recommended to ensure the fluid evaporates quickly at the electrode edge. The fluid jet cutting process can slit and trim both the separator and the electrode. The filtration and purification of the fluid using a centrifugal cleaning process are demonstrated. This new cleaning process can remove heavy copper and cathode-active particles from the fluid. The next step is purification by fine filtration to remove graphite and binders from the fluid. The fluid jet cutting process is ideal for cutting battery electrodes because it is a burr-free cutting process. There is no tool wear, and high cutting speeds are possible.

[0011] The performance of lithium-ion batteries is affected by the surface quality of the electrode cutting process. Currently, shearing with rotating blades is used to cut slots in prismatic and cylindrical electrodes. This shearing process requires expensive tools that wear out over time. Maximum speeds of up to 120 m / min are possible. Tool wear and vibrations lead to process instability and poor cut quality. These can cause internal short circuits and significant heat generation within the cells.

[0012] Laser cutting, a proven and widely used industrial process, can solve the aforementioned problems by improving the quality of the cut surface. It offers advantages such as no tool wear, a narrow heat-affected zone, and applicability to almost all materials. However, as mentioned, laser cutting does have some drawbacks. Energy efficiency is lower, primarily due to reflection. A maximum speed of up to 80 m / min is possible. To address this issue, a new process called fluid jet cutting is being employed. This allows for high speeds of up to 200 m / min. Furthermore, it eliminates tool wear, burrs, and a heat-affected zone. Current applications focus on slitting, notching, and trimming.

[0013] According to the invention, there are two variants for feeding the fluid to the nozzle: In the first variant, only the fluid is pressurized and fed to the nozzle, which cuts the material. The material is then transported to the next stations for notching and trimming. In the notching station, various fluid jet nozzles are connected to a moving conveyor belt, which is used for notching and trimming the electrode. The cutting edge is then dried and subsequently cleaned. An electrolyte with a higher flash point can be used as the fluid medium. Ethylene carbonate is proposed for this purpose.

[0014] In the second variant, ethylene carbonate (EC) is used as the fluid medium. Abrasive material (aluminum oxide) is also used. One of the key innovations is the use of an electrolyte (ethylene carbonate) as the cutting medium. EC is already present in the cell, so it is not a problem if EC remains in the active material after cutting. On the other hand, the presence of water in the active material is undesirable, which is why extensive drying is necessary. Water can also be used as a fluid medium and will be proposed later as an additional option, but it is less preferred. The electrolyte in a lithium-ion cell consists primarily of ethylene carbonate, diethylene carbonate, and methylene carbonate. Methylene carbonate and diethylene carbonate have low flash points, which is why ethylene carbonate is proposed as the cutting fluid medium.Aluminum oxide is also present in lithium-ion cells as a separator coating. Therefore, it is desirable to use aluminum oxide as an abrasive in fluid jet cutting. It is advantageous to use electrolytic capacitors (EC) as the liquid medium and aluminum oxide as the abrasive. This reduces the extensive drying and cleaning process of the electrode. The same principle can also be applied to separator cutting.

[0015] A key advantage of fluid jet cutting is that it allows material to be cut without affecting its structure, as there is no heat-affected zone (HAZ). Minimizing heat exposure enables the cutting of metals without compromising or altering their essential properties. Sharp corners, chamfers, cutouts, and shapes with minimal internal radii are all possible. Fluid jet cutting is capable of creating intricate cuts in the material. Specialized software and 3D machining heads allow for the production of complex shapes. The kerf width can be adjusted by changing the fluid exit velocity at the nozzle, as well as by modifying the type and size of the abrasive. Typical abrasive cuts have a width in the range of 0.5–1 mm.Non-abrasive cuts are typically 0.2–0.3 mm wide, but can also be as narrow as 0.1 mm, which is about the width of a human hair. These small nozzles allow for the cutting of intricate details in a wide variety of applications. This narrow cut is usually required for battery electrodes, making fluid jet cutting well-suited for cutting the electrode and separator. Due to its relatively narrow width, fluid jet cutting can reduce the amount of waste material, as uncut parts can be placed closer together than with conventional methods. The fluid jet has the advantage of not contacting the tool, thus eliminating tool wear. The cut edge is also burr-free, which is a significant benefit for battery electrodes. The quality of the fluid jet's cut edge depends on the cutting speed.

[0016] The fluid jet cutting process is based on the removal of material from the workpiece through erosion. Fluid is the cutting medium. Abrasive particles can be added to enhance cutting efficiency. A high-speed fluid jet accelerates abrasive particles, which then remove the material. In abrasive fluid jet cutting, the pressurized fluid is conveyed to the cutting head via an accumulator and hoses. The fluid is forced out of the nozzle in a jet. The result is a very thin, extremely fast fluid jet. Abrasive particles are metered from the abrasive reservoir to the cutting head. In the mixing chamber, abrasive particles are added and mixed with the water jet in the nozzle (mixing tube, focusing tube). There are two ways to introduce abrasive particles into the fluid: abrasives can be added before the nozzle or in the convergent zone.There is a risk that the entire inner wall of the nozzle will be in constant contact with abrasive particles. This will cause the nozzle to wear out faster.

[0017] Another possibility is to introduce abrasive particles into the diverging chamber before the opening. The high velocity of the fluid jet creates a Venturi effect, or negative pressure, in the mixing chamber located directly above the opening, drawing abrasive particles into the fluid jet within the mixing chamber. The abrasive particles interact with the fluid jet and the inner walls of the nozzle until they are accelerated by the pressure surge of the fluid jet. Tool wear is reduced in this method. Abrasive particles have a lower velocity but are sufficient for cutting thin electrodes. Abrasive particles mixed with the fluid jet create an abrasive fluid jet. The nozzle directs this abrasive fluid jet to cut the workpiece material.The nozzle for the abrasive fluid jet is stationary for slotting (longitudinal cutting) and moves at the same speed as the electrode for notching and trimming. For notching and trimming, the abrasive fluid jet cutting head moves along the programmed contour using the machine's computer-controlled numerical motion system. The nozzle always moves at the same speed as the electrode. A screen is positioned below the workpiece to collect the fluid, abrasive, and metal chips (cutting waste). Initial filtration takes place here, and the coarse particles are then removed. Further filtration occurs through an innovative centrifugal separation process, as explained later. Abrasive particles are reused if they are sufficiently sharp. The filtered fluid is then recirculated.

[0018] Ethylene carbonate or a mixture of ethylene carbonate and diethylene carbonate can be used as the electrolyte: Ethylene carbonate (EC) is heated to approximately 45 °C and used in a molten state. It is important that the entire fluid flow system is heated to prevent the EC from solidifying. Ethylene carbonate mixed with diethylene carbonate (DEC) has a lower flash point than pure EC. Depending on the concentration of ethylene carbonate, the flash point of the solution is much higher than that of pure diethylene carbonate. Ethylene carbonate is readily soluble in diethylene carbonate.

[0019] In another variation, ethylene carbonate is mixed with polypropylene carbonate (PC) so that the mixture has a melting point at room temperature. This reduces the heating of the entire fluid flow path. In short, a liquid carbonate that can dissolve EC and also has a relatively high flash point of around 130 °C is desirable. Alternatively, a mixture of EC and another carbonate with a boiling point below room temperature can be used. This ensures that the mixture always remains in a molten state. It is also possible to use pure water as the fluid medium. It is important that the cutting edge is dried after cutting to remove the water content. This will be explained later as an option.

[0020] Aluminum oxide (Al₂O₃), silicon carbide (SiC), and sodium bicarbonate are some of the abrasives that can be used in abrasive fuel jet cutting. The choice of abrasive depends on the material removal rate, the type of material, and the required machining accuracy. Aluminum oxide is preferred for battery electrodes. Aluminum oxide is a non-conductive ceramic material and is already present in batteries as a separator coating. The size of the aluminum oxide particles is less than 50 micrometers. It is better to use smaller aluminum oxide particles in the range of 12 micrometers. This prevents aluminum oxide from being deposited from the fluid after filtration and allows for reuse. After approximately 1000 cutting cycles with the same abrasive particles, the fluid solution can be passed through a filter with a porosity of less than 10 micrometers. This removes the abrasive particles from the fluid.The fluid can then be mixed with new abrasive particles. Normally, new abrasive particles can be added and used abrasive particles removed from the fluid after each coil change.

[0021] Aluminum oxide is a hard, chemically inert material formed when aluminum reacts with oxygen. For abrasive applications, aluminum oxide crystals, also known as corundum, are available in white, pink, and brown, differing primarily in their hardness and purity. Aluminum oxide is one of the most widely used abrasives, providing a cost-effective and predictable solution for a variety of applications. Several types of aluminum oxide are available. Aluminum oxide in its various forms is the most commonly used abrasive. It is melted from bauxite or aluminum oxide in electric furnaces at temperatures exceeding 2000°C. It is produced from bauxite. It contains 96% Al₂O₃, approximately 3% titanium dioxide (TiO₂), and 1–2% other impurities. It is the most resistant synthetic corundum and is characterized by its high ductility.It is used for cutting and coarse grinding of low-alloy steels, stainless steels, cast iron, especially for high material removal rates.

[0022] Fluid jet cutting machines are equipped with high- and ultra-high-pressure pumps operating at 150 to 400 MPa and hyperpressure pumps at 600 to 650 MPa. Ultra-high-pressure pumps at 350 to 400 MPa are standard. Their operation is essentially identical: fluid flows from an ultra-high-pressure or hyperpressure pump through a line from a cutting head as a pure fluid jet or abrasive fluid jet, cutting the material. The fluid pump is responsible for generating the pressure and water flow, as well as for its continuous delivery. According to the invention, a pressure of 100-150 MPa is required for the anode and 200 MPa for the cathode.

[0023] The cutting head is a crucial component of a fuel jet cutting machine. It consists of an orifice, a mixing chamber, and a nozzle. The orifice has a very small hole. Its purpose is to convert the high water pressure generated by the pump into a high-speed water jet. The orifice has an inner diameter of 0.08 mm to 0.5 mm and is made of sapphire, ruby, or diamond. While sapphire and ruby ​​orifices are less expensive, they are prone to wear and breakage and require frequent replacement due to their limited lifespan of approximately 50-100 hours. Diamond orifices offer superior quality, higher reliability, and a lifespan of around 1000 hours. The mixing chamber has an inner diameter of 0.4 mm to 2 mm and is 38 mm to 152 mm long. The nozzle is typically made of tungsten carbide (a powder metallurgy product).

[0024] The most important operating parameters of the nozzle are the nozzle diameter and the safety clearance. The nozzle contains an outlet orifice, which is usually much smaller than the supply line. The nozzle marked with an asterisk is generally used for the fluid jet. Since a constant volume of fluid reaches the nozzle, it must be accelerated to a higher velocity to exit through this opening, which also serves to focus the fluid into coherent streams or jets and direct the streams to the desired point on the target surface. The safety clearance is the distance between the nozzle and the target material. One of the most important parameters, which is adjusted for different applications, is the safety clearance. The safety clearance should be 5-10 mm.

[0025] According to fluid mechanics theory, the inner surface of the nozzle should ideally be streamlined to the nozzle channel to reduce energy loss through the conversion of pressure energy into kinetic energy; however, manufacturing such a nozzle is difficult. Therefore, current nozzles are either cylindrical-conical or fully conical.

[0026] The fluid jet enters the nozzle and comes into contact with the surrounding fluid. A discontinuity forms at the contact boundary, which then continues as a mixing layer. In this mixing zone, it blends with abrasive particles. The central part of the fluid jet is unaffected by the surrounding fluid. This part, which maintains the jet's velocity, is called the core region. The fluid jet's velocity is greatest at the axial position and decreases with increasing contact with the nozzle. The velocity increases most when the fluid jet is near the nozzle outlet. After exiting the nozzle, there is a region of constant fluid jet velocity. This constant-velocity region has a maximum velocity until it reaches the core region. This constant jet velocity outside the core region gradually decreases until it reaches zero.The safety distance should be chosen so that the core is located just below the cutting zone. This allows the maximum jet velocity for cutting to be achieved.

[0027] The abrasive material is fed to the grinding nozzle via a pipe. The metering device controls the flow rate of the abrasive. It is then directed to the diverging end of the chamber. As mentioned earlier, abrasive can also enter the cutting head at the inlet in the convergent section. However, entry at the diverging section is preferred. Three main factors determine the performance of the abrasive fluid jet cutting process: fluid pressure, fluid flow velocity, and abrasive flow velocity. Thicker materials require larger fluid flows, which in turn demand higher velocity and more energy for cutting. During longitudinal cutting (slotting), the cutting head is stationary. During notching and trimming, the cutting head moves perpendicular to the electrode.The cross-cutting speed varies based on the material thickness, operating pressure, fluid flow rate, abrasive quality and quantity, the shape to be cut, and the desired type of edge finishing. Faster cutting is possible by increasing the pressure, fluid flow rate, and abrasive mass flow rate.

[0028] Slitting is performed in the slitting station. A longitudinal cut is made in the electrode for slitting. Electron carbide (EC) with / without abrasive material is fed to the fluid jet nozzle. The abrasive is mixed with the EC in the mixing chamber. As shown in the setup, the electrode moves, and the rollers used to hold the electrode also rotate. The linear speed of the roller corresponds to the speed of the electrode. The fluid jet nozzle is stationary. The electrode is cut at high speed using fluid and abrasive. During this process, the main coil is separated into smaller coils by longitudinal cutting. It is important that the area of ​​the electrode around the fluid jet nozzle is securely clamped and tensioned. The roller can also be spirally structured to subject the electrode to transverse tensile stress.The electrode is also under tension due to the winding and unwinding device. The principle described above can also be used to slot separators.

[0029] In the notching station, a notching process is performed. This involves cross-cutting, which must be carried out without interrupting the electrode movement. For this purpose, an arrangement of various nozzles, each mounted in a clamp, is provided. The clamp with the nozzle is connected to a movable conveyor that rotates horizontally at the same speed as the electrode. This means that the axis of rotation for both conveyors is vertical. The water jet nozzle is located between the clamps. Clamps are provided to hold the workpiece. The upper conveyor has a clamp and a nozzle. The lower conveyor has counter clamps. The counter clamps have a hole through which the liquid can flow to the tank. Both the upper and lower conveyors move at the same speed.A central receiving chamber is located in the middle of the conveyor, directing pressurized fluid or a mixture of fluid and abrasive material to the nozzles. The flow control valve ensures that only the nozzle performing the cutting operation is supplied with pressurized fluid. The electrode coil and both (upper and lower) conveyors have no relative speed. Therefore, cutting occurs at zero relative speed. The upper clamp holds the collector area to be cut. The nozzle then moves transversely and cuts the collector area with a high-velocity fluid jet. The lower clamp secures the nozzle from below. Clamping occurs from both sides, top and bottom. The nozzle is located only on the top side. It is important that the clamp and nozzle are attached to the upper rotating conveyor.The conveyor's function is to prevent any relative movement between the electrode, clamp, and nozzle. The clamp is then moved downwards, clamping the electrode against the opposite clamp of the lower conveyor. Once the electrode is firmly clamped between the movable clamps, the nozzle follows the cutting contour within the clamps, cutting the collector shape. The reject material falls into the lower clamp after notching and is then collected in the reject container. It is possible for two nozzles to perform notching simultaneously, one on the left and one on the right. This means that notching can occur first, followed by slitting. This has the advantage that notching is performed simultaneously on both sides of a wide electrode, and the electrode is then slit in the middle.The flow control valve shown in yellow, located between the central inlet chamber and the fluid jet cutting nozzle, regulates the flow of pressurized fluid. Only the nozzle, which serves as the cutting electrode, is supplied with pressurized fluid. Other flow valves remain closed. Fluid containing cutting debris flows from the lower clamp into the tank. This is then passed through filtration, after which the fluid and abrasive are returned to the circuit. Winders and unwinders maintain tension during the notching process.

[0030] The notching principle, using a moving conveyor with attached clamps and a fluid jet cutting head, can also be used to trim electrodes and separators in lithium-ion battery cells. During trimming, there is no winding device, as the electrode is trimmed into individual segments. To hold the segments in place, a vacuum is applied from below. Vacuum clamps move at the same speed as the electrode and hold individual segments. These vacuum clamps then transfer the cut segments into the magazine. If no trimming is performed, the complete coil with slotted and notched electrodes is dried in an oven at approximately 120 °C for 24 hours. If trimming is performed, the magazine containing the individual segments is placed in the oven. Fluid jet cutting offers significant advantages for separators.The separator consists of three layers of polypropylene with an aluminum oxide coating on the outside. Laser cutting cannot be used because polypropylene changes its properties when exposed to heat. Mechanical cutting with tools is difficult due to the high wear caused by the aluminum oxide. Cutting with a fluid jet and aluminum oxide as an abrasive is preferred for trimming separators. Since the separator cannot be thoroughly dried like an electrode, electrolytic cleaning (EC) is the preferred fluid medium and aluminum oxide as the abrasive. The trimming process is explained on the next slide.

[0031] During the trimming process, the conveyor moves up and down at the same speed as the electrode. The upper conveyor has clamps and a fluid jet cutting head (nozzle). The lower conveyor has vacuum clamps and an opening through which the fluid can drain into the tank after cutting. Unlike notching, both conveyors rotate vertically during trimming. This means that the axis of rotation is horizontal. The upper clamp in the upper conveyor and the lower clamp in the lower conveyor are always parallel to each other. Fluid containing cutting debris is collected in a tank, filtered, and returned to the cycle. The upper clamps engage the already notched area to determine the exact position, ensuring precise positioning of the trimming head. There is no relative movement between the electrode, clamps, and nozzle. This is crucial for precise trimming.The fluid is transported to the individual nozzles via a central fluid station. Each nozzle has valves to control the flow of the pressurized fluid. Only the cutting nozzle is supplied with pressurized fluid. Only one nozzle is active at a time; the other nozzles are inactive. Individual trimmed segments are held in lower clamps by vacuum and then transported to the magazine. Once the electrode or separator is positioned above the magazine, the vacuum is released, and the segment falls into the magazine.

[0032] After leaving the cutting zone, the fluid contains cutting residues. Cutting residues (scrap) from battery electrodes are typically non-magnetic. For example, residues contain copper, aluminum, binders such as SBR (for anodes) and PTFE (for cathodes), graphite, conductive carbon, and oxides of nickel, manganese, and cobalt. These waste materials vary in density, and one advantage is that they are insoluble in EC (ethylene carbonate) and can be used in conjunction with DEC and PC (diethylene carbonate and polypropylene carbonate), which serve as the fluid medium. Magnetic separators would not be very effective in removing the cutting residues. Because the cutting residues vary in density, a centrifugal cleaning process can be used. This process is carried out in two steps. In the first step, heavier particles such as metal and oxides are removed.In a second centrifugal cleaning process, lighter particles such as graphite and binders are separated. Coarse filtration is the first step, capturing particles larger than 0.5 mm. The final stage is a HEPA filter with an aperture of less than a few micrometers, where even the smallest cutting residues are separated from the electrolyte. The purified electrolyte is then returned to the system. Abrasive particles are smaller than approximately 20 micrometers and therefore remain in the fluid.

[0033] The electrolyte, with or without abrasives and with cutting waste, can be fed into the centrifugal filter. This filter is rotated at high speed. The centrifugal force pushes heavier particles outwards, where they collect in the filter. The electrolyte is filtered and collected in the area outside the filter. The filter is replaced when heavily soiled.

[0034] During the cleaning process, a brush or roller is guided to the cutting edge. This reduces the adhesion of particles to the cutting edge. Particles can then be easily vacuumed away in a second, non-contact stage. With fluid jet cutting technology, contact cleaning is less necessary because the high jet pressure prevents particles from adhering to the cutting edge. In an alternative embodiment, ionized air is blown in, neutralizing non-conductive particles. Neutralized conductive particles can then be vacuumed away from the electrode surface. It is necessary to remove static charges from abrasive particles, as these are non-conductive, in order to remove them from the cutting edge and the electrode surface.

[0035] The most important features of the invention are listed below: A fluid jet cutting method for slitting, notching, and trimming as a replacement for laser cutting and mechanical cutting with cutting tools for electrodes and separators. One of the electrolyte components, ethylene carbonate (EC), is used as the fluid medium. It can be mixed with diethylene carbonate (DEC) or polypropylene carbonate (PC). It can also be used alone in the molten state. In this case, the entire EC flow path should be heated to 45–50 °C. Fluid jet cutting can be performed without abrasives. It can also be performed with abrasives. Aluminum oxide is recommended as an abrasive. The slitting process is modified so that the rollers can stretch the electrode area near the fluid jet cutting head in both longitudinal and transverse directions.The notching and trimming process is modified to allow the electrode to move continuously during the cutting operation. The fluid jet cutting head is mounted on the moving conveyor. Pressurized fluid is supplied to the cutting head via a central intake chamber. The clamp around the cutting nozzle secures the electrode during notching. The clamps and the fluid jet nozzle move at the same speed as the electrode. It is even advantageous to perform the slotting after notching so that two collector surfaces can be notched simultaneously. A two-stage centrifugal cleaning process is recommended for removing cutting residue. This cleans the fluid, allowing it to be reused (EC). For drying, it is recommended to oven dry the parts after slotting and notching. Magazine drying is performed after trimming. The oven temperature is up to 120–150 °C.Air trapped in the fluid must be removed. Venting takes place in the reservoir. Air must be prevented from entering the high-pressure system. The electrode is always clamped during fluid jet cutting. For slotting, this is done by rotating the roller. For notching and trimming, it is done by movable clamps. Drying and cleaning the electrodes is necessary to remove particulate contamination. Drying is carried out after cleaning using a roll-to-roll back-and-forth process. Edge cleaning is performed using both contact and non-contact methods. Even if fluid (EC) penetrates porous active material, this is not harmful. The nozzle can be cylindrical or conical. It is important that the safety distance is selected to achieve the highest possible fluid jet velocity in the cutting zone. Unlike lasers, there is no need for air extraction to remove gases generated during cutting.No heat is generated during fluid jet cutting. Abrasive aluminum oxides can be reused if they are sharp. Filtration is simpler in this case. Contaminants larger than the abrasive are captured by a filter. The fluid containing the abrasive is then returned to the system for the cutting cycle. There is a risk that contaminants smaller than the abrasive particles may remain in the fluid. Fine filtration is typically performed before the next spool change. All abrasive particles are removed and new ones are added. It is recommended to use an abrasive with a grit size of 20 micrometers. Centrifugal filtration can remove particles larger than 50 micrometers. The separator can be slotted and trimmed in the same way as the electrode.

[0036] Another option is the use of water as the fluid medium. Here, water can be used alone or with abrasive particles. Waterjet cutting, or an abrasive waterjet cutting process, is similar to the fluid jet cutting described earlier. The main difference lies in the drying of the electrode. The drying process is very intensive, so roll-to-roll drying with infrared heating is recommended. After slitting and notching, the electrode is rewound onto reels. Before rewinding after notching, the electrode foil is passed between infrared heaters. This raises the temperature of the electrode, and especially the cutting edge, to approximately 120 °C. This removes the water present on the electrode and the cutting edge. It is important to have good extraction to capture the water vapor generated by the infrared heater. After heating, the electrode undergoes a cleaning process.This cleaning process is similar to that used in fluid jet cutting. In fluid jet cutting, drying takes place after cleaning. In water jet cutting, drying also takes place after cleaning. In fuel jet cleaning, the entire roll is placed in an oven for drying. In water jet cutting, drying occurs in a roll-to-roll support process. Electrolytes are generally expensive and should therefore be filtered and reused. This requires four steps of the previously described filtration process. The filtration process is optional and is only necessary if the water is to be reused.

[0037] Further aspects of the invention are highlighted in detail below: In one technical implementation, for example, the active material tape can be unwound from a spool and guided along a processing path in the manufacturing direction through the longitudinal cutting station. The active material tape can then be wound onto a spool. A stationary liquid jet cutting nozzle can be positioned in the longitudinal cutting station. This nozzle can cut the active material tape, guided along the processing path, into two strip-shaped tape segments. The two strip-shaped tape segments can then be easily wound onto a common winding spool.

[0038] A flawless cutting process in the slitting station is of paramount importance. For this reason, the active material tape can run along the processing path through a gap formed by at least one pair of stretching rollers. The pair of stretching rollers can stretch or smooth the active material tape during the cutting process. Preferably, pairs of stretching rollers are arranged on both sides of the elongated area in front of and / or behind the liquid jet cutting nozzle.

[0039] Preferably, the profiling station and / or the cutting station of the cutting system can be implemented as follows: The active material tape can be unwound from a spool and guided along a processing path in the production direction through the profiling station and / or the cutting station. In particular, the processed active material tape can be wound onto a rewinding spool in the profiling station. The profiling station and / or the cutting station can include at least one cutting unit with at least one liquid jet cutting nozzle. The cutting unit can be mounted on a conveyor, which allows the cutting unit to be adjusted in the production direction. In this way, the cutting unit can be coupled to the movement of the active material tape, at least during the cutting process. The cutting tool and the active material tape can thus move along the processing path at the same transport speed.

[0040] In a further development, the cutting unit can additionally include a feed device. This feed device can move the liquid jet cutting nozzle during the cutting process in a feed motion superimposed on the transfer motion. The feed motion can be transverse and / or longitudinal to the production direction.

[0041] A flawless cutting process in the profiling station and / or the cutting station is of paramount importance: For this purpose, the cutting unit can be additionally equipped with a hold-down device or a hold-down element. The hold-down element can interact with a counter-contour element. During the cutting process, the hold-down presses the active material strip against the counter-contour. At least during the cutting process, the counter-contour can be guided in the production direction in a movement coupled with the hold-down device, the liquid jet cutting nozzle, and the active material strip.

[0042] In a preferred technical implementation, the cutting system can have a conveying device on both sides in the thickness direction of the active material strip: The liquid jet cutting nozzle, the hold-down device, and the feeding means are assigned to the first conveying device. The counter contour is assigned to the second conveying device.

[0043] After the cutting process, cutting residues remain on the opposite contour. These can be removed in the direction of material waste.

[0044] In the cutting station, the active material tape is cut into individual active material layers. To ensure a flawless cutting process in the cutting station, the following measures are preferred: The counter contour can have at least one suction opening connected to a vacuum source. This allows the active material tape and / or the cut active material layer to be brought into suction contact with the counter contour. The conveying device can transfer the counter contour, to which a layer of active material is in suction contact, to a storage position. In the storage position, the suction contact can be deactivated. In this way, the layer of active material can be detached from the counter contour by the influence of gravity and automatically transported to a storage station.

[0045] According to the invention, the liquid jet cutting nozzle can be integrated into a fluid circuit. Within this circuit, the cutting fluid exiting after the cutting process can be cleaned in a cleaning system. The cleaned cutting fluid is then returned to the liquid jet cutting nozzle. Each liquid jet cutting nozzle can be preceded by a control valve (viewed in the direction of flow). The control valve can be operated by an electronic control unit. The control unit can open the control valve assigned to the liquid jet cutting nozzle required for the current cutting process. The control valves of the liquid jet nozzles not required for the current cutting process, on the other hand, can remain closed.

[0046] In a specific embodiment, the conveyor can be assigned several cutting units. These can be conveyed in a series along the processing path by means of the conveyor device. The conveyor can preferably be an endless conveyor belt.

[0047] To increase the processing speed in the profiling station, the following measures are possible: at least one cutting unit can be arranged on both sides of the active material belt in the transverse direction of the active material belt. The two cutting units can be moved along the processing path by their own conveyor device. In this way, a cutting operation can be carried out simultaneously on each of the two longitudinal edges of the active material belt.

[0048] To increase process reliability, the hold-down device (i.e., the holding element) in the cutting station can be designed as follows: The hold-down device can have a positioning projection on its contact surface facing the active material strip. Before, during, and / or after the cutting process, the positioning projection of the hold-down device engages with a recess in the active material strip created in the profiling station.

[0049] An example of an embodiment of the invention is described below with reference to the accompanying figures, in which Fig. 1 a block diagram shows a process flow for the production of the active material layers; Fig. Figures 2 to 9 each show a different view of the cutting system of the process arrangement.

[0050] Fig. Figure 1 shows a block diagram of a process flow for manufacturing active material layers 1, for example, electrode layers or separator layers for a lithium-ion battery cell. According to this diagram, an active material strip 3 is first provided on a roll 5. The active material strip 3 is continuously fed through a cutting unit 7 in the manufacturing direction FR. Fig. The cutting system 7 consists of a longitudinal cutting station 9, a profiling station 11, and a cutting station 13. If required, the profiling station 11 can be arranged upstream of the longitudinal cutting station 9 in the production direction FR, as indicated by the double arrow 15. A cleaning station 17 is located downstream of the cutting station 7, where the produced active material layers 1 are cleaned. This is followed by a drying unit 19, where the cleaned active material layers 1 are dried. The essential feature of the invention is that all cutting operations in the cutting system 7 are carried out using liquid jet cutting. For this purpose, the cutting system 7 has liquid jet cutting nozzles 21 as cutting elements.

[0051] Fig. Figure 2 shows an example of the slitting station 9 (longitudinal cutting station). Accordingly, the active material tape 3 is unwound from the unwinding roll 5 and guided through the longitudinal cutting station 9 in the production direction FR via a processing path s. The processed active material tape 3 is then wound onto an unwinding roll 23. A stationary liquid jet cutting nozzle 21 is arranged in the longitudinal cutting station 9. The liquid jet cutting nozzle 21 cuts the active material tape 3, guided along s, into two strip-shaped tape segments 25. The two strip-shaped tape segments 25 are then wound together onto the winding roll 23.

[0052] To ensure proper cutting, the longitudinal cutting station 9 has stretching roller pairs 27. The active material strip 3 runs along the processing paths through the gaps of these stretching roller pairs 27. This stretches or flattens the active material strip 3 during the cutting process. As can be seen from Fig. As can be seen in Figure 1, the stretching roller pairs 27 are arranged on both sides of the produced longitudinal section 29, both in front of and behind the liquid jet cutting nozzle 21.

[0053] As in Fig. As can be seen in Figure 1, the liquid jet cutting nozzle 21 is integrated into a liquid circuit. In this liquid circuit, the liquid that emerges after the cutting process is collected in a liquid collection container 31 and from there conveyed to a cleaning system 33. The cleaning system 33 may include a centrifuge in which the liquid is separated from both the abrasive material and the cutting chips. The cleaned liquid is then returned to the liquid jet cutting nozzle 21 by means of a feed pump 37. Fig. In section 2, an abrasive material container 39 is assigned to the liquid jet cutting nozzle 21. Abrasive material is metered from the abrasive material container 39 into a mixing chamber 43 of the nozzle 21 by means of a metering unit 41. In the mixing chamber 43, the abrasive is mixed with the cutting fluid. The cutting fluid then exits the nozzle head 45 to cut the active material strip 3. The nozzle head 45 is in Fig. 1 spaced from the surface of the active material strip 3.

[0054] The Fig. Figures 3 to 6 show different views of profiling station 11. Accordingly, in Fig. 4. The active material strip 3 is unwound from an unwinding roll 5 and guided in the manufacturing direction FR via a processing path s through the profiling station 11. The active material strip 3 processed in the profiling station 11 is then rewound onto a winding roll 23.

[0055] In the Fig. 3 to 5, a plurality of cutting units 47 are provided, which are guided in series along the processing path s by means of conveyor belts 48, 49 that are motion-coupled with the active material belt 3. The cutting units 47 are arranged on both sides of the active material belt 3 in the transverse direction of the active material belt 3. In this way, a cutting process can be carried out simultaneously on both longitudinal edges 51 of the active material belt 3. An example of a cutting process is shown in Fig. Figure 6 shows a top view. During the cutting processes, edge-side current collection recesses 54 are cut into the two longitudinal edges 51 of the active material strip.

[0056] In the Fig. 3 to 5, each of the cutting units 47 is formed by a liquid jet cutting nozzle 21, a feeder 55, a hold-down device 57, and a counter-contour 59 interacting with it. The liquid jet cutting nozzle 21, the feeder 55, and the hold-down device 57 are conveyed by means of an upper conveyor belt 48. In contrast, the counter-contour 59 is conveyed by means of a lower conveyor belt 49. Fig. 4 (viewed in the thickness direction of the active material belt 3) an upper and a lower conveyor belt 48, 49 are arranged on both sides of the active material belt 3.

[0057] During the cutting process, the feeder 55 can move the liquid jet cutting nozzle 21 with a feed movement z transversely and / or longitudinally to the manufacturing direction FR, as indicated by the movement arrows in Fig. 6 is specified. The feed movement z is superimposed on the conveying movement in the production direction FR.

[0058] As in Fig. As shown in Figure 6, the clamping device 57 of the cutting unit 47 can be configured in two parts: an inner clamping device 59 and an outer clamping device 61. The inner clamping device 59 holds the cutting residues, while the outer clamping device 61 encloses the resulting recess 53. A nozzle path 63 is formed between the inner clamping device 59 and the outer clamping device 61, along which the feed movement z of the liquid jet cutting nozzle 21 takes place. In the profiling station 11, the upper conveyor belt 48 runs around a vertical axis, while the lower conveyor belt 49 runs around a horizontal axis. After the cutting process is complete, a cutting residue remains on the opposite contour 59. This cutting residue is removed in the direction of material waste.

[0059] In the following Fig. Figures 7 to 9 show cutting station 13 in different views: Accordingly, in Fig. 7 the active material tape 3 is unwound from a spool 5 and guided in the manufacturing direction FR via a processing path s through the cutting station 13.

[0060] According to the Fig. 7 and Fig. 9 A plurality of cutting units 47 are provided, which are guided in series along the processing path s by means of conveyor belts 48, 49 motion-coupled with the active material belt 3. The cutting units 47 of the profiling station 11 and the cutting station 13 are essentially identical in construction and function identically. An example of a cutting process is shown in Fig. Figure 8 shows a top view. In the cutting processes, the active material strip 3 is cut using a cross-section 30 ( Fig. 8) cut through, forming the active material layers 1.

[0061] In Fig. 9 Each of the cutting units 47 is formed by a liquid jet cutting nozzle 21, a feeder (not shown), a hold-down device 57, and a counter contour 59 interacting with it. The liquid jet cutting nozzle 21, the feeder 55, and the hold-down device 57 are conveyed by means of an upper conveyor belt 48. In Fig. 9 an upper and a lower conveyor belt 48, 49 are arranged on both sides of the active material belt 3 (seen in the thickness direction of the active material belt 3).

[0062] During the cutting process ( Fig. 8) Can the feeding means move the liquid jet cutting nozzle 21 with a feeding movement z transverse to the manufacturing direction FR, as in Fig. 9 is specified. The feed movement z is superimposed on the feed movement in the manufacturing direction FR.

[0063] As furthermore, from the Fig. 8 or Fig. As can be seen in Figure 9, the clamping device 57 of the cutting unit 47 can be formed in two parts, with the two clamping devices positioned upstream and downstream of the cross-section 30, respectively, as seen in the manufacturing direction FR, indicated by movement arrows. A nozzle line 63 is formed between the two clamping devices, along which the feed movement z of the liquid jet cutting nozzle 21 takes place. In the profiling station 11, the upper conveyor belt 48 runs about a vertical axis, while the lower conveyor belt 49 runs about a horizontal axis. After the cutting process is complete, a cutting residue remains on the opposite contour. This cutting residue is discharged in the direction of material waste.

[0064] In contrast to the profiling station 11, the counter contour 59 in the cutting station 13 has at least one suction opening connected to a vacuum source 65 ( Fig. 9) The active material strip 3 and / or the active material layer 1 is in suction contact with the counter contour 59 via the suction opening. In the cutting station 13, the profiled strip sections 25 of the active material strip 3 are cut to length to form the individual active material layers 1. As in Fig. As can be seen in Figure 9, the lower conveyor belt 49 transmits the counter contours 59 to a storage position A. In storage position A, the suction contact of the counter contour 59 is deactivated. In this way, the layer of active material 1 can automatically fall into a storage station 69 under the influence of gravity.

[0065] In Fig. 7. The liquid jet cutting nozzles 21 are also integrated into a fluid circuit, which is essentially like the one in Fig. The fluid cycle described in section 2 is formed. Additionally, in Fig. Each of the liquid jet cutting nozzles 21 is assigned a control valve 71. The control valves 71 of all liquid jet cutting nozzles 21 can be controlled by an electronic control unit 73. During the cutting process, the control unit 73 opens the control valve 71 of the liquid jet cutting nozzle 21 required for the cutting process. The control valves 71 of the liquid jet cutting nozzles 21 not required for the cutting process remain closed.

[0066] As in Fig.As can be seen in Figure 8, the hold-down device 57 of the cutting station 13 also has a nozzle line 63 along which a feed movement z of the liquid jet cutting nozzle 21 takes place. Additionally, the hold-down device 57 has a positioning projection (not shown) on its contact surface facing the active material strip 3. The positioning projection of the hold-down device 57 engages with a recess 53 in the active material strip 3, which is created in the profiling station 11 before, during, and after the cutting process. This ensures a positionally secure cutting process and a positionally secure placement process. List of reference symbols 1 active material layers 3 Active material band 5 unwind roll 7 cutting system 9 Longitudinal stations 11 Profiling station 13 Cutting station 15 Double Arrow 17 Cleaning system 19 drying plant 21 liquid jet cutting nozzles 23 winding roller 25 tape sections 27 pairs of roles 29 Longitudinal section 30 cross-section 31 Liquid sump 33 Cleaning system 37 Pump 39 containers for abrasive material 41 dosing units 43 Mixing chamber 45 nozzle head 47 cutting unit 48,49 conveyor belts 51 longitudinal edges 53 cutouts 55 Feeding agents 57 Holding element 59 Counter contour element 60 Inner hold-down element 61 Outer hold-down element 63 Nozzle Street 65 Vacuum source 69 storage stations 71 Control valve 73 Electronic control unit FR Manufacturing direction s processing distance A storage position z route Δh height offset QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 2013 0324013 A1

[0005] US 2013 0298387 A1

[0005]

Claims

[1] Process arrangement for the production of active material layers (1), for example electrode layers or separator layers, for a lithium-ion battery cell, in which an active material strip (3) can be continuously guided in a production direction (FR) through a cutting system (7) which has a longitudinal cutting station (9) in which the active material strip (3) can be divided into strip segments (25) in the transverse direction of the active material strip (3), a profiling station (11) in which recesses (53), for example edge-side current collector recesses, are cut into the active material strip (3), and / or a cutting station (13) in which the active material strip (3) is cut into individual active material layers (1), characterized by , that the cutting process in the cutting system (7) is carried out by liquid jet cutting and that the cutting system (7) has liquid jet cutting nozzles (21) as cutting elements. [2] Process arrangement according to claim 1, characterized by , that the active material tape (3) is unwound from an unwinding roller (5) and guided along a processing path (s) in the manufacturing direction (FR) through the longitudinal cutting station (9) and subsequently wound onto a winding roller (23), and that the longitudinal cutting station (9) has a stationary liquid jet cutting nozzle (21) which cuts the active material tape (3) guided along the processing path (s) into at least two strip-shaped tape segments (25), and that in particular the two strip-shaped tape segments (25) are wound onto a common winding roller (23). [3] Process arrangement according to claim 2, characterized by, that the active material strip (3) runs along the processing path (s) through the gap of at least one pair of stretching rollers (27) which stretch or smooth the active material strip (3) during the cutting process, and that pairs of stretching rollers (27) are preferably arranged on both sides of the longitudinal cut (29) before and / or after the liquid jet cutting nozzle (21). [4] Process arrangement according to one of claims 1 to 3, characterized by, that the active material strip (3) is unwound from an unwinding roller (5) and guided in the manufacturing direction (FR) via a process arrangement (s) through the profiling station (11) and / or the cutting station (13), and that in particular the active material strip (3) is subsequently wound onto a winding roller (23), and that in particular the profiling station (11) has at least one cutting unit (47) with at least one liquid jet cutting nozzle (21) which is coupled to the active material strip (3) by means of a conveying device (48, 49) at least during the cutting process, so that the cutting unit (47) and the active material strip (3) move along the processing path (s) at the same conveying speed. [5] Process arrangement according to claim 4, characterized by, that the cutting unit (47) has a feed means (55) with which the liquid jet cutting nozzle (21) is fed during the cutting process in a feed movement (z) superimposed on the conveying speed transversely and / or longitudinally to the manufacturing direction (FR), in particular for carrying out the longitudinal cut (29) and / or a cross-section (30). [6] Process arrangement according to claim 4 or 5, characterized by, that the cutting unit (47) has a hold-down device (57) which presses the active material belt (3) against a counter contour (59) during the cutting process, and that in particular during the cutting process the counter contour (59) is guided in motion coupling with the hold-down device (57) in the manufacturing direction (FR), and that in particular the cutting system (7) has a conveying device (48, 49) on each side in the thickness direction of the active material belt (3), of which the liquid jet cutting nozzle (21) and optionally the hold-down device (57) and the feeding means (55) are assigned to the first feeding device (48) and the counter contour (59) is assigned to the second feeding device (49). [7] Process arrangement according to claim 6, characterized by , that after the cutting process is completed, a cutting residue remains on the opposite contour (59) which can be removed in the direction of material waste. [8] Process arrangement according to one of the preceding claims, characterized by , that in the cutting station (13) the counter contour (59) has at least one suction opening connected to a vacuum source (65), by means of which the active material belt (3) and / or the active material layer (1) can be brought into suction contact with the counter contour (59), and that the conveying device (48, 49) transfers the counter contour (59) with the active material layer (1) in suction contact after the cutting process has ended to a deposit position (A), and that in particular in the deposit position (A) the active material layer (1) can be deposited in a deposit station (69) with the suction contact deactivated and / or under the influence of gravity. [9] Process arrangement according to one of the preceding claims, characterized by, that the liquid jet cutting nozzle (21) is integrated into a liquid circuit in which the liquid discharged after the cutting process is cleaned in a cleaning device (33) and subsequently fed back to the liquid jet cutting nozzle (21), and that in particular each of the liquid jet cutting nozzles (21) is assigned a control valve (71) which can be actuated by means of a control unit (73), and that the control unit (73) opens the control valve (71) of the liquid jet cutting nozzle (21) required for the cutting process, while the control valves (71) of the liquid jet cutting nozzles (21) not required for the cutting process remain closed. [10] Process arrangement according to any one of the preceding claims, characterized by, that the conveying device (48, 49) is associated with a plurality of cutting units (47) which are transmitted in succession by means of the conveying device (48, 49), and / or that the conveying device (48, 49) is an endless conveyor belt. [11] Process arrangement according to one of the preceding claims, characterized by , that in the profiling station (11) in the transverse direction of the active material belt (3) at least one cutting unit (47) is arranged on both sides of the active material belt (3), and that in particular the two cutting units (47) are transported along the processing path (s) with their own conveying device (48, 49) so that a cutting process can be carried out simultaneously on both longitudinal edges (51) of the active material belt (3). [12] Process arrangement according to one of the preceding claims, characterized by, that in the cutting station (13) the holding device (57) has a positioning projection on its contact surface facing the active material strip (3) which can be brought into positioning engagement in a recess (53) in the active material strip (3) created in the preceding profiling station (11) before, during and / or after the cutting process.

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