DE102022201367A1 - Process and jet mill for supercritical jet milling - Google Patents

Abstract

A method for operating a jet mill (10) is provided, the method comprising the following steps: i. Feeding particles (2) into a grinding zone (12) of a jet mill (10), and ii. providing a supercritical fluid (6) in the milling zone (12) to cause the particles (2) to collide with each other and/or with an inner surface of the jet mill (10) to thereby produce ground particles (8). A jet mill, ground particles, use of the ground particles, and a battery made using or comprising the ground particles are also provided.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method and a jet mill for supercritical jet milling.

BACKGROUND OF THE INVENTION

Jet milling is a proven industrial process for producing particles of a desired size. Jet milling uses a jet of high velocity gas or liquid to force the particles to collide with each other. If the particles are hard and brittle, then the result of the collisions is that the particles break up, forming smaller particles. On the other hand, if the particles are soft and flexible, the result of the collisions can be that the particles stick together, e.g. to form larger particles or flakes.

Jet milling can be used to grind ceramic and metal powders, among other things. Compressed air, inert gases, steam or water are typically used to provide the jet.

Ideally, the jet milling process should produce milled particles of the desired particle size, ready for use in subsequent steps. In practice, however, the jet milling process is affected by circumstances that make it difficult to achieve an ideal process. For example, as the size decreases, the ground particles tend to agglomerate due to an increasing surface energy to mass ratio. Additional grinding energy must then be used to break up the agglomerated particles. While a liquid jet is more efficient than a gas at transferring the kinetic energy to the particles, the use of a liquid results in a dispersion or slurry of ground particles and liquid from which the ground particles must then be separated in additional steps. The ground particles can also be subject to oxidation by the liquid or gas used for the jet.

There is therefore a need to further improve the jet milling process.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide a method for operating a jet mill in which at least one of the above-mentioned circumstances is compensated for, as a result of which an improved jet milling method is provided.

A further object of the present invention is to provide a jet mill which is suitable for carrying out the method.

Another object of the present invention is to provide ground particles obtained by the process.

Yet another object of the present invention is to provide a use of the ground particles obtained by the process.

Another object of the present invention is to provide a battery made using the ground particles.

SUMMARY OF THE INVENTION

1. i. Zuführen von Partikeln in eine Mahlzone einer Strahlmühle,
2. ii. Bereitstellen eines überkritischen Fluids in der Mahlzone, um die Partikel miteinander und/oder mit einer Innenfläche der Strahlmühle kollidieren zu lassen, um dadurch gemahlene Partikel zu erzeugen,

According to a first aspect of the present invention, at least one of the above-mentioned objects or at least one of the further objects that become apparent from the following description are achieved by a method for operating a jet mill, the method comprising the following steps:

1. i. feeding particles into a grinding zone of a jet mill,
2. ii. providing a supercritical fluid in the milling zone to cause the particles to collide with each other and/or with an inner surface of the fluid energy mill to thereby produce ground particles,

• - eine Mahlzone,
• - zumindest eine Düse zum Zuführen von Partikeln in die Mahlzone,
• - zumindest eine Düse zum Bereitstellen eines überkritischen Fluids in der Mahlzone, um die Partikel miteinander und/oder mit einer Innenfläche der Strahlmühle kollidieren zu lassen, um dadurch gemahlene Partikel zu erzeugen,

wobei die Strahlmühle derart ausgebildet ist, dass der Druck und die Temperatur der Mahlzone und/oder der zumindest einen Düse zum Bereitstellen des überkritischen Fluids innerhalb der überkritischen Phase des überkritischen Fluids liegen.At least one of the above objects or at least one of the other objects that will become apparent from the following description is further achieved according to a second aspect of the technology proposed here by a jet mill comprising:

• - a grinding zone,
• - at least one nozzle for feeding particles into the grinding zone,
• - at least one nozzle for providing a supercritical fluid in the milling zone to cause the particles to collide with each other and/or with an inner surface of the jet mill to thereby produce ground particles,

wherein the jet mill is designed in such a way that the pressure and the temperature of the grinding zone and/or the at least one nozzle for providing the supercritical fluids are within the supercritical phase of the supercritical fluid.

At least one of the above objects or at least one of the further objects that will become apparent from the following description is further achieved according to a third aspect of the present invention by ground particles obtained according to the method of the first aspect of the present invention, wherein the ground particles preferably comprise nanoscale to microscale silicon particles or consist of these.

At least one of the above objects or at least one of the further objects which will become apparent from the following description is further achieved according to a fourth aspect of the present invention by the use of the ground particles according to the third aspect of the present invention, preferably in a battery preferably in a drive battery for an electric vehicle, particularly preferably in the anode of a lithium-ion battery.

At least one of the above objects or at least one of the further objects which will become apparent from the following description is further achieved according to a fifth aspect of the present invention by a battery made using ground particles according to the third aspect of the present invention or ground particles according to the third aspect of the present invention.

Accordingly, by providing a supercritical fluid in the jet milling process, kinetic energy is transferred to the particles much more efficiently than if a gas were used. This is because a supercritical fluid has a density similar to that of a liquid. The high kinetic energy that can be transferred to the particles enables efficient mechanical alloying or the production of composite materials that are homogeneously mixed down to the nanometer scale. This facilitates the production of various high-tech materials for demanding applications such as metastable alloys, nanometer-scale silicon for use in lithium-ion battery anodes, and nanometer-scale materials for use in roller and ball bearings.

At the same time, unlike a liquid, the supercritical fluid effectively wets the particles, which keeps them separate, preventing agglomeration. This reduces the amount of energy that must be used for jet milling.

The use of a supercritical fluid also allows for easy separation of the ground particles from the supercritical fluid by depressurizing the supercritical fluid so that it optionally transitions to the gas phase. This is in contrast to liquids such as B. water, which is reactive with many substances, z. B. by oxidation, and must be removed from the ground particles produced.

Some supercritical fluids, particularly supercritical carbon dioxide (CO ₂ ), are inert, preventing surface oxidation and other chemical reactions of the particles. This protective effect is enhanced by the ability of the supercritical fluid to effectively and efficiently wet the particles. As a result, the process is also suitable for highly reactive materials.

The method according to the first aspect of the present invention enables the production of ground particles which differ from ground particles obtained with methods of the prior art in at least one of the following: particle size distribution (due to the lower agglomeration and the high transfer of kinetic energy on the particles), content or nature (due to the high amount of kinetic energy imparted to the particles and ability to process reactive particles), and surface chemistry and cleanliness (due to the inert nature of the supercritical fluid and the efficient wetting of the particles).

The nature of the ground particles according to the third aspect of the present invention makes them particularly suitable for applications where homogeneous materials are required, such as e.g. B. in batteries.

Batteries made using the ground particles or containing the ground particles may have better performance due to the homogeneity of the ground particles, e.g. B. a better battery capacity and / or energy density.

The fluid energy mill can be any type of fluid energy mill in which the particles are caused to collide with each other and/or with an internal surface of the fluid energy mill to form ground particles. The jet mill usually includes a grinding chamber into which the particles are filled and the supercritical fluid is fed.

The method for operating a jet mill according to the first aspect of the present invention can alternatively and equivalently be used as a method for operating a jet mill and Ver drive to perform jet milling.

The particles can include, for example, metal particles, plastic particles, ceramic particles, graphene particles, biologically based particles such as cellulose particles and/or protein particles. The particles can comprise the mixture of one or more types of particles. Alternatively, all particles can also be of the same type.

The supercritical fluid preferably has a critical point temperature in the temperature range of 0-100°C, preferably in the temperature range of 10-80°C. Below the critical point, the supercritical fluid is in the form of a corresponding liquid or in the form of a gas, depending on the pressure.

The critical point temperature of the fluid affects the type of particles that can be ground using the process as well as the properties of the ground particles produced. During the process, the particles in the milling zone are exposed to temperatures at or above the critical point temperature. If the particles are introduced into the grinding zone together with the corresponding liquid, then the particles are also exposed to temperatures below the critical point temperature. The supercritical fluid can thus be chosen based on the particles to be ground in such a way that the particles are not damaged by the temperatures of the supercritical fluid, and optionally the corresponding liquid, during the process. The supercritical fluid may additionally be based on the properties, primarily hardness and brittleness, of the particles at temperatures above the critical point temperature, e.g. e.g. the temperature within the milling zone. Thus, when using a first supercritical fluid having a lower critical point temperature, one type of particle may be hard and brittle, thereby breaking apart, resulting in ground particles that are smaller than the particles introduced into the grinding zone. Alternatively, when milled using a second supercritical fluid having a higher critical point temperature, the same type of particle may be soft and flexible and thus stick together, resulting in milled particles, e.g. B. flakes that are larger than the particles introduced into the grinding zone.

The particles can be fed into the grinding zone together with or separately from the provision of the supercritical fluid. The particles can through at least one nozzle, z. B. one or more nozzles are fed into the grinding zone. The one or more nozzles used for feeding the particles can be the same as, or separate from, one or more nozzles for feeding the supercritical fluid into the grinding zone. When fed separately, the particles can be fed into the grinding zone by being entrained by pressurized gas.

The fluid energy mill milling zone comprises the area or volume in which the particles collide with each other and/or with an interior surface of the fluid energy mill to produce ground particles. Typically, the milling zone comprises the area or volume of the jet mill adjacent to the one or more locations where the supercritical fluid is introduced into the jet mill. For example, the milling zone may extend from the one or more locations at which the supercritical fluid or liquid is introduced into the jet mill to an interior surface of the jet mill onto which the supercritical fluid or liquid is directed as it is is fed into the jet mill and the grinding chamber. The milling zone may comprise all or part of the volume of the milling chamber.

Providing the supercritical fluid in the milling zone includes feeding the supercritical fluid or the corresponding liquid into the milling zone. Providing the supercritical fluid in the milling zone to cause the particles to collide with each other and/or an interior surface of the fluid energy mill includes providing the supercritical fluid with kinetic energy to cause the particles to collide with each other and/or with an interior surface of the fluid energy mill .

Providing the supercritical fluid may include providing the supercritical fluid as one or more streams or jets of supercritical fluid. The supercritical fluid can be pressurized using a pump or using a pressure medium. The supercritical fluid can be introduced into the grinding zone through at least one nozzle, e.g. one or more nozzles, which can alternatively be used for supplying both the particles and the supercritical fluid. The supercritical fluid is preferably provided via at least two nozzles in the grinding zone.

The supercritical fluid can be provided in pulses or continuously in the grinding zone.

The particles can be fed into the grinding zone in a pulsed or continuous manner.

Steps (i) and (ii) are preferably carried out simultaneously, although it is also possible to carry out step (i) before step (ii).

The supercritical fluid provided in the milling zone carries kinetic energy which is imparted to the particles so that the particles move through and within the milling zone. This movement causes the particles to collide with each other and/or with an interior surface of the fluid energy mill. These collisions, primarily the collisions between the particles, produce ground particles. The properties of the particles at the temperature in the grinding zone determine whether the particles break up into smaller particles when they collide or whether the particles stick together into larger particles like flakes when they collide. The former is known as abrasion while the latter is known as mechanical alloying. Accordingly, the ground particles can be smaller or larger than the particles introduced into the grinding zone.

In addition to the properties of the particles, the size and shape of the ground particles is determined by the kinetic energy imparted by the supercritical fluid provided in the grinding zone, where the kinetic energy depends on the speed and density of the supercritical fluid, as well as depends on the time the particles spend in the grinding zone.

The kinetic energy of the supercritical fluid causes the particles to collide with one another and/or with an inner surface of the jet mill. The inner surface of the jet mill is, for example, an inner wall of the grinding chamber or a surface of a nozzle for feeding particles and/or supercritical fluid or a corresponding liquid into the grinding zone.

The pressure and temperature of the milling zone and/or the at least one nozzle for providing the supercritical fluid are maintained within the supercritical phase of the supercritical fluid. This can be done by adjusting the temperature and pressure of the supercritical fluid provided in the grinding zone so that the grinding process, i. H. the collisions between the particles and/or the inner surface of the jet mill, spontaneously result in the pressure and temperature of the grinding zone being kept within the supercritical phase.

In preferred embodiments, the supercritical fluid is obtained by adjusting the temperature and/or pressure of the respective liquid to cause the liquid to transition to the supercritical fluid. As used herein, the terms liquid and corresponding liquid refer to the liquid phase of the supercritical fluid, i. H. the supercritical fluid in liquid phase.

Typically, an increase in temperature is required to convert the liquid in question into the supercritical phase. Such a temperature increase is generally obtained when the particles collide, particularly as surface energy when the particles are broken up into smaller particles. Alternatively or additionally, the grinding zone, e.g. B. the fluid energy mill or milling chamber and the one or more nozzles used to provide the supercritical fluid may be heated to effect transition of the liquid to the supercritical phase. The temperature and usually also the pressure in the beating zone are generally higher than the temperature and the pressure of the liquid in the beating zone. The increased pressure can be a consequence of the increased temperature.

In preferred embodiments, the liquid is caused to transition into the supercritical fluid within one or more nozzles used to provide the supercritical fluid in the milling zone or upon exiting those nozzles, e.g. by varying the pressure and temperature of the one or more nozzles in the supercritical Phase of the supercritical fluid are maintained. For example, the nozzles may be heated to provide a temperature within the supercritical phase of the supercritical fluid. This has the advantage that if the supercritical fluid is in liquid form before it is provided in the milling zone, it is easier to e.g. B. using a pump, than when the supercritical fluid in supercritical phase is to be pressurized using the pump.

In alternative embodiments, the liquid is caused to transition to the supercritical fluid upon entering the milling zone, for example, by maintaining the pressure and temperature of the milling zone in the supercritical phase of the supercritical fluid. As mentioned above, the temperature rise obtained upon particle collision in the milling zone can be used to maintain the pressure and temperature of the milling zone within the supercritical phase of the supercritical fluid. As above, it is easier to pressurize the liquid than the supercritical fluid.

In general, within the supercritical phase of the liquid correspond to the temperatures and pressures at which the liquid is in the supercritical phase, ie as a supercritical fluid. The temperature limits and pressure limits of the overcriti cal phase are different for different liquids.

As discussed above, the supercritical fluid in the milling zone can be provided by one or more of the following: a) feeding supercritical fluid into the milling zone, b) feeding liquid into the milling zone and allowing the liquid in the milling zone to transition to supercritical fluid, and c) feeding the liquid into the milling zone and transitioning the liquid to supercritical fluid within or upon exiting the one or more nozzles used to feed the liquid into the milling zone.

As mentioned above, by providing the supercritical fluid in the grinding zone, the supercritical fluid effectively wets the particles, thereby preventing the particles from agglomerating. Further, the obtained ground particles are easily separated from the supercritical fluid, unlike if a liquid were used.

The jet mill can be designed in such a way that the pressure and the temperature of the grinding zone and/or the at least one nozzle for providing the supercritical fluid are within the supercritical phase of the liquid, for example by changing the internal volume of the grinding chamber and the internal dimensions of the one or more nozzles so be designed such that the milling of the particles causes the required temperature rise above the critical point temperature. The jet mill may further be configured with a heater to heat the milling chamber and/or the one or more nozzles to a temperature within the supercritical phase.

In preferred embodiments, the supercritical fluid is provided in the milling zone via two or more nozzles, and preferably at least two nozzles of the two or more nozzles are arranged such that the streams of supercritical fluid or corresponding liquid provided by the two nozzles , cross in the grinding zone. This is advantageous in that the intersecting streams efficiently collide the particles at the point of intersection. The two or more nozzles can be 2, 3 or 4 nozzles, for example. The nozzles are preferably made of a hard material such as diamond or boron carbide. The flow cross-sectional area of the nozzles can e.g. B. be round or rectangular. The diameter of the flow cross-sectional area of the nozzles can typically be between 100 µm and 10 mm.

In such embodiments, the at least two nozzles may provide supercritical fluid or liquid at different velocities. This is advantageous in that it provides a shearing force between the streams fed from the two or more nozzles. A shearing force can increase or modify the kinetic forces and collisions of the particles and thereby modify the properties of the ground particles. The different velocities can be obtained by feeding identical nozzles with the supercritical fluid or liquid at different pressure and/or flow rate or by using nozzles that have different flow areas and the nozzles with the supercritical fluid or liquid at be fed at the same pressure and/or flow rate.

• iii. Abtrennen der gemahlenen Partikel von dem überkritischen Fluid, vorzugsweise durch Absenken der Temperatur und/oder des Drucks des überkritischen Fluids.

In preferred embodiments, the method further comprises the step:

• iii. separating the ground particles from the supercritical fluid, preferably by lowering the temperature and/or the pressure of the supercritical fluid.

This is advantageous in that it provides an easy way to obtain the ground particles. It has surprisingly been found that it is generally not necessary to reduce the temperature and/or the pressure of the supercritical fluid to the point of transition to the gas phase in order to separate the ground particles from the supercritical fluid. Accordingly, it is preferred that the temperature and/or pressure of the supercritical fluid is not lowered below the critical point temperature and pressure for the supercritical fluid so that the supercritical fluid remains in the supercritical phase rather than transitioning to the gas phase. This reduces the energy required to recycle the supercritical fluid in the process. For example, the milled particles can be density separated from the supercritical fluid, e.g., by having a density different from the density of the supercritical fluid. Alternatively, the ground particles from the supercritical fluid z. B. be separated by a classifier or a filter.

• iv. Einstellen der Temperatur und/oder des Drucks des überkritischen Fluids, um zu bewirken, dass es wieder in die entsprechende Flüssigkeit übergeht, und vorzugsweise Wiederverwenden der Flüssigkeit, um das überkritische Fluid zu erhalten, das in Schritt (ii) bereitgestellt wird.

In preferred embodiments, the method further comprises the step:

• IV. Adjusting the temperature and/or pressure of the supercritical fluid to cause it to revert to the corresponding liquid and preferably reusing the liquid to obtain the supercritical fluid provided in step (ii).

This is advantageous in that it allows the supercritical fluid to be repressurized while in the liquid phase for reuse in the process. As mentioned above, this is simpler than pressurizing the supercritical fluid in supercritical phase. Preferably, the temperature of the supercritical fluid is adjusted by lowering it to a temperature below the critical point of the supercritical fluid to cause the supercritical fluid to transition back to its corresponding liquid.

In some embodiments, the particles are introduced into the milling zone by being mixed with the liquid before the supercritical fluid is provided in the milling zone. This is advantageous in that it makes the process fast, as it allows the production of ground particles in a single pass through the grinding zone. Preferably, these embodiments further comprise that the supercritical fluid is provided in the milling zone from two or more nozzles, and preferably that at least two of the two or more nozzles are arranged so that the streams of the supercritical fluid or the corresponding liquid, which from injected from these nozzles cross in the grinding zone to increase the production of ground particles.

In other embodiments, the particles are fed to the milling zone separately from the supercritical fluid, and preferably the particles are fed to the milling zone such that they form a fluidized bed of particles in the milling zone. This is advantageous in that it allows the particles to collide multiple times in the milling zone, thereby providing more diverse milling effects such as varying particle size distribution and content of milled particles. Preferably, these embodiments further comprise that the supercritical fluid is provided in the milling zone from two or more nozzles, and preferably that at least two of the two or more nozzles are arranged so that the streams of the supercritical fluid or the corresponding liquid, which from injected from these nozzles cross in the grinding zone to increase the production of ground particles. Even more preferably, at least two of the two or more nozzles are arranged so that the streams injected from these nozzles are directed in opposite directions.

In preferred embodiments, the supercritical fluid comprises or consists of supercritical carbon dioxide or nitrogen, preferably the supercritical fluid is supercritical carbon dioxide. These fluids are chemically inert and are suitable for use in the process and fluid energy mill. Carbon dioxide is particularly suitable as it has favorable properties including a critical point at 31.1°C and 7.38 MPa. Carbon dioxide can therefore be provided in the liquid phase at 20°C and 20 MPa and in the supercritical phase at 80°C and 40 MPa and at 40°C and 20 MPa. These temperatures are relatively low, making it possible to crush sensitive materials. These temperatures make carbon dioxide further advantageous since they require no or minimal insulation of the jet mill. Nitrogen has a critical point at -147°C and 3.4 MPa.

The method may further comprise adding an additive, separately or together with the particles and/or the liquid, to the mill to affect the milling and the properties of the milled particles. The additive can be, for example, a surface-active additive or an additive that is intended to be combined with the particles in the ground particles.

• - einen Tank zum Aufnehmen der dem überkritischen Fluid entsprechenden Flüssigkeit,
• - eine an den Tank angeschlossene Pumpe zur Druckbeaufschlagung der Flüssigkeit,
• - einen Mischer, der mit der Pumpe verbunden ist, um die Partikel mit der Flüssigkeit zu mischen, bevor die Flüssigkeit in die Mahlzone eingespeist wird, wobei die zumindest eine Düse zum Zuführen von Partikeln in die Mahlzone und die zumindest eine Düse zum Bereitstellen des überkritischen Fluids in die Mahlzone als zumindest eine Düse ausgebildet sind, um das Gemisch aus den Partikeln und dem überkritischen Fluid in der Mahlzone bereitzustellen,
• - eine Trennkammer, die stromabwärts der Mahlzone angeordnet und ausgebildet ist, um die gemahlenen Partikel und das überkritische Fluid aufzunehmen, wobei die Trennkammer so ausgebildet ist, dass sie eine niedrigere Temperatur und/oder einen niedrigeren Druck als die Mahlzone, aber innerhalb der überkritischen Phase des überkritischen Fluids hat, wobei ein Innenvolumen der Strahlmühle vorzugsweise einen Expansionsabschnitt definiert, der sich von der Mahlzone zur Trennkammer ausdehnt,
• - einen Kühler, der stromabwärts der Mahlzone, vorzugsweise stromabwärts der Trennkammer, angeordnet ist, um das überkritische Fluid zu kühlen, so dass es in die Flüssigkeit übergeht, und
• - eine Rücklaufleitung, die mit dem Kühler und der Pumpe oder dem Tank verbunden ist, um die Flüssigkeit zur Pumpe oder zum Tank zu führen.

In preferred embodiments, the jet mill further comprises one or more, preferably all, of:

• - a tank for receiving the liquid corresponding to the supercritical fluid,
• - a pump connected to the tank to pressurize the liquid,
• - a mixer connected to the pump to mix the particles with the liquid before the liquid is fed into the grinding zone, the at least one nozzle for feeding particles into the grinding zone and the at least one nozzle for providing the supercritical Fluids in the grinding zone are designed as at least one nozzle in order to provide the mixture of the particles and the supercritical fluid in the grinding zone,
• - a separation chamber located downstream of the grinding zone and adapted to receive the ground particles and the supercritical fluid, the separation chamber being adapted to have a lower temperature and/or pressure than the grinding zone but within the supercritical phase of the supercritical fluid, an interior volume of the jet mill preferably defining an expansion section extending from the grinding zone to the separation chamber,
• - a cooler placed downstream of the grinding zone, preferably downstream of the separation chamber, to cool the supercritical fluid so that it becomes liquid, and
• - a return line connected to the radiator and the pump or tank to return the liquid to the pump or tank.

The tank may be pressurized and/or temperature controlled by including a heater/cooler to keep the liquid in the liquid phase while in the tank. The tank can be pressurized using a pump or pressurized gas source.

The pump can be any type of pump capable of pressurizing the liquid.

The mixer is used when the particles are to be fed or provided into the grinding zone together with the liquid. The particles can be introduced into the mixer via a funnel. The liquid can be fed into the mixer via a line connected to the pump. The at least one nozzle for feeding particles into the grinding zone and the at least one nozzle for feeding the liquid can be configured as at least one nozzle for feeding a mixture of the particles and the liquid into the grinding zone by being connected to the mixer. The mixer can be any type of mixer suitable for mixing the liquid with the particles.

The separation chamber can be designed to be at a lower temperature and/or pressure than the milling zone but within the supercritical phase of the supercritical fluid by including a heating/cooling device. The separation chamber may be arranged such that the particles separate from the supercritical fluid based on density.

The expansion section, in expanding, may provide all or part of the lower temperature and/or pressure of the supercritical fluid in the separation chamber.

The cooler may include a heat exchanger for cooling the supercritical fluid. The cooler may further include a compressor for compressing the supercritical fluid.

The return line may be connected to the cooler, or the cooler may be provided in the return line.

The ground particles according to the third aspect of the present invention can include or consist of, for example, metal particles, plastic particles, ceramic particles, graphene particles, particles of biological material such as cellulose particles and/or protein particles. The ground particles preferably include or consist of nanoscale to microscale silicon particles.

The use according to the fourth aspect of the present invention may include the use of the ground particles, preferably in a battery, more preferably in a traction battery for an electric vehicle, more preferably in the anode of a lithium-ion battery. The use typically includes use of the ground particles in the manufacture or manufacture of a product or part of a product, such as a product. B. a battery or part of a battery, from the ground particles.

The electric vehicle can be a land vehicle such as a scooter, motorcycle, car or truck, a watercraft such as a boat or ship, or an aircraft such as an airplane, helicopter or drone. The ground particles according to the third aspect of the present invention can be used, for example, in the anode of a traction battery for such an electric vehicle.

The ground particles according to the third aspect of the present invention can be used in the manufacture of various products. The fifth aspect of the present invention thus relates to a battery made using or comprising the ground particles according to the third aspect of the present invention, preferably in the anode of the battery. The ground particles can be ground graphite or silicon particles, for example.

character list

• 1 eine erste Ausführungsform des Verfahrens gemäß dem ersten Aspekt der vorliegenden Erfindung zeigt, die an einer ersten Ausführungsform einer Strahlmühle gemäß dem zweiten Aspekt der vorliegenden Erfindung durchgeführt wird.
• 2 eine zweite Ausführungsform des Verfahrens gemäß dem ersten Aspekt der vorliegenden Erfindung zeigt, die an einer zweiten Ausführungsform einer Strahlmühle gemäß dem zweiten Aspekt der vorliegenden Erfindung durchgeführt wird.

A more complete understanding of the foregoing and other features and advantages of the present invention will be obtained from the following detailed description of preferred embodiments taken in conjunction with the accompanying schematic drawings, wherein:

• 1 Figure 12 shows a first embodiment of the method according to the first aspect of the present invention performed on a first embodiment of a jet mill according to the second aspect of the present invention.
• 2 shows a second embodiment of the method according to the first aspect of the present invention, applied to a second embodiment of a jet mill according to that second aspect of the present invention is carried out.

All figures are schematic, not necessarily to scale, and generally show only those parts necessary to illustrate each embodiment, while other parts may be omitted or merely indicated. Each reference number that appears in several drawings refers to the same item or feature in all drawings, unless otherwise indicated. One or more superscripts suffixed to a reference number indicate that the feature so referred to is a variant of the feature with which that reference number is associated.

1 Figure 12 shows a first embodiment of the method according to the first aspect of the present invention performed on a first embodiment of a jet mill 10 according to the second aspect of the present invention. The jet mill 10 comprises a grinding zone 12 in which particles, one of which is denoted by reference numeral 2, are ground. The particles 2 are fed to a hopper 14 connected to a mixer 16 . The mixer 16 is further connected to a tank 18 with liquid 4 via a pump 20 . The tank 18 is provided with a heating/cooling device 22 for controlling the temperature of the liquid 4 . A pressure regulator 24 is also connected to the tank 18 to keep the liquid 4 in the liquid phase. At the in 1 In the method shown and the jet mill, the feeding of the particles 2 into the grinding zone 12 (step (i) of the method) and the provision of the supercritical fluid (6) in the form of the liquid 4 in the grinding zone 12 (step (ii) of the method) are simultaneous carried out. In addition, the particles 2 and the liquid 4 are introduced into the grinding zone 12 together. Accordingly, the particles 2 and the liquid 4 are mixed in the mixer 16 . If the liquid 4 is liquid carbon dioxide, the temperature and the pressure of the mixture of particles and liquid can be 20° C. and 20 MPa, for example. The mixture of particles 2 and liquid 4 is then directed through two channels 26a and 26b to two orifices or nozzles 28a and 28b. The nozzles 28a and 28b are arranged in such a way that the streams of particles 2 and liquid 4 from the two nozzles 28a and 28b cross in the grinding zone 12. The crossing of the streams in the milling zone 12 causes the particles 2 to collide with each other to thereby disintegrate or stick together depending on the properties (primarily hardness) of the particles. The crossing of the streams and the collision of the particles further leads to an increase in temperature and pressure in the grinding zone 12. This causes the liquid 4 to transform into a supercritical fluid, represented by the arrow 6, containing the ground particles (one of which denoted by the reference numeral 8). If the liquid 4 is carbon dioxide, the temperature and pressure in the grinding zone 12 can be 80°C and 40 MPa, for example. The grinding chamber 30 in which the grinding zone 12 is provided can optionally be additionally heated in order to ensure that the liquid 4 in the grinding zone 12 changes to supercritical fluid (6). The jet mill 10 also includes an expansion section 32 downstream of the grinding zone 12, in which the pressure and temperature of the supercritical fluid 6 decrease. A separation chamber 34 is connected to the expansion section 32 and receives the supercritical fluid. The separation chamber 34 is provided with a temperature control heater/cooler 36 to further cool the supercritical fluid. In the separation chamber 34, the ground particles 8 separate from the supercritical fluid 6 and are collected. The optional step (iii) of the method can thus be carried out in the separation chamber 34. When carbon dioxide is used, the temperature and pressure in the separation chamber 34 can be, for example, 40°C and 20 MPa. This is above the critical point temperature of 31.1°C, leaving the carbon dioxide in the supercritical phase. As the ground particles 8 are removed from the separation chamber 34 , the supercritical fluid 6 is collected through a collection line 38 and returned to the tank 18 via a cooler 40 . The cooler 40 cools the supercritical fluid below the critical point temperature so that the supercritical fluid changes to the liquid phase. The optional step (iv) of the method can thus be carried out in the cooler 40. The liquid 4 can then be reused. in the in 1 In the embodiments shown, the supercritical fluid 6 is thus provided in the grinding zone 12 by the liquid 4 being fed into the grinding zone 12 and the liquid 4 in the grinding zone and/or within or at the exit from the nozzles 28a and 28b passing into the supercritical fluid 6 can.

2 Figure 12 shows a second embodiment of the method according to the first aspect of the present invention performed on a second embodiment of a jet mill 10' according to the second aspect of the present invention. The jet mill 10' differs from the jet mill 10 in that it is designed to carry out a second embodiment of the method in which the particles 2 are not mixed with the liquid but are fed into the jet mill separately from the supercritical fluid. The jet mill 10' thus has a grinding zone 12' which is arranged within a grinding chamber 30'. In the grinding zone 12 'particles of which one indicated by the reference numeral 2, ground. The particles 2 are fed to a hopper 14' which feeds the particles 2 into the milling chamber 30'. In the grinding chamber 30', the particles 2 form a fluidized bed as a result of the liquid streams 4 injected into the grinding chamber 30'. Accordingly, the feeding of the particles 2 into the grinding zone 12' (step (i) of the method) and the provision of the supercritical fluid 6 in the grinding zone 12' (step (ii) of the method) can be carried out simultaneously or step (ii) is carried out after Step (i) carried out. Furthermore, the particles 2 and the supercritical fluid 6 in the form of liquid 4 are fed separately from one another into the grinding zone 12'. The liquid 4 is in a tank 18 which is provided with a heating/cooling device 22 for regulating the temperature of the liquid 4. A pressure regulator 24 is also connected to the tank 18 to keep the liquid 4 in the liquid phase. In operation, the particles 2 are fed into the milling chamber 30' while the liquid 4 is fed by the pump 20 into first and second conduits 26a' and 26b', the first and second conduits 26a' and 26b' having a first and a second nozzle 28a' and 28b' arranged to inject the liquid 4 into the grinding chamber 30' in the fluidized bed of particles 2 so that the streams from the first and second nozzles 28a' and 28b' are directed in opposite directions and cross in the grinding zone 12'. The crossing of the streams causes the particles 2 to collide with each other, causing them to disintegrate or stick together depending on the properties of the particles (mainly hardness). The crossing of the streams and the collision of the particles further leads to an increase in temperature and pressure in the grinding zone 12'. This leads to the liquid 4 merging into the supercritical fluid 6 containing the ground particles 8 . If the liquid 4 is carbon dioxide, the temperature and pressure in the grinding zone 12' can be, for example, 80° C. and 40 MPa. The grinding chamber 30', in which the grinding zone 12 is provided, can optionally be additionally heated in order to ensure that the liquid 4 in the grinding zone 12' changes to supercritical fluid. The jet mill 10' also includes an expansion section 32' downstream of the grinding zone 12', in which the pressure and the temperature of the supercritical fluid 6 decrease. A separation chamber 34' is connected to the expansion section 32' for receiving the supercritical fluid 6. The separation chamber 34' is provided with a temperature control heater/cooler 36 to further cool the supercritical fluid. In the separation chamber 34', the ground particles 8 separate from the supercritical fluid and are collected. The optional step (iii) of the method can be carried out in the separation chamber 34 accordingly. When using carbon dioxide, the temperature and the pressure in the separation chamber 34' can be, for example, 40° C. and 20 MPa. This is above the critical point temperature of 31.1°C, so the carbon dioxide remains in the supercritical phase. As the ground particles 8 are removed from the separation chamber 34', the supercritical fluid 6 is collected through a collection line 38 and returned to the tank 18 via a cooler 40. The cooler 40 cools the supercritical fluid below the critical point temperature so that the supercritical fluid changes to the liquid phase. The optional step (iv) of the method can be carried out in the cooler 40 accordingly. The liquid 4 can then be reused.

While the jet mill was 10 in 1 is preferably operated continuously, the in 2 shown jet mill 10 'continuously or batchwise operated. A classifier or filter (not shown) may be provided within grinding chamber 30' to selectively pass ground particles of a desired size into expansion section 32', while ground particles of other sizes are retained in grinding chamber 30' to be further ground.

It should further be noted that 1 and 2 show the particles 2 and the ground particles 8 greatly enlarged for illustration. Since the diameter of the flow cross-sectional area of the nozzles 28a, 28b, 28a' and 28b' is typically in the range of 100 μm to 10 mm, the particles 2 fed to the grinding zone usually have diameters below these values. If the particles 2 break down into ground particles 8 that are smaller than the particles 2, then these ground particles typically have diameters in the micrometer to nanometer range. On the other hand, if the particles 2 stick together to form larger ground particles 8, these ground particles can be larger than the particles 2.

In addition, it should be noted that 1 and 2 show that particles 2 are ground into ground particles 8, which are smaller than particles 2. However, as already mentioned, the method and the jet mills 10 and 10' can also be used to grind the particles 2 in such a way that they stick together and form larger ground particles.

The present invention is not limited to the embodiments described. The present disclosure is intended to cover all adaptations and variations of the preferred embodiments described herein, so that the present invention is defined by the language of the appended claims.

Claims (16)

Method for operating a jet mill (10), the method comprising the steps: i. Feeding particles (2) into a grinding zone (12) of a jet mill (10), ii. providing a supercritical fluid (6) in the milling zone (12) to cause the particles (2) to collide with each other and/or with an inner surface of the jet mill (10) to thereby produce ground particles (8). procedure according to claim 1 wherein the supercritical fluid (6) is obtained by adjusting the temperature and/or the pressure of the corresponding liquid (4) to cause the liquid (4) to transform into the supercritical fluid (6). procedure according to claim 2 , wherein the liquid (4) is caused to flow within one or more nozzles (28a, 28b) used to provide the supercritical fluid (6) in the grinding zone (12), or on leaving these nozzles (28a, 28b) in to transition to the supercritical fluid (6), for example by maintaining the pressure and temperature of the one or more nozzles (28a, 28b) within the supercritical phase of the supercritical fluid (6). procedure according to claim 2 wherein the liquid (4) is caused to transition into the supercritical fluid (6) upon entering the milling zone (12), for example by maintaining the pressure and temperature of the milling zone (12) within the supercritical phase of the supercritical fluid (6) . Method according to one of the preceding claims, in which the supercritical fluid (6) is provided in the grinding zone via two or more nozzles (28a, 28b), and in which preferably at least two nozzles of the two or more nozzles (28a, 28b) are arranged in such a way that the streams of supercritical fluid (6) or of the corresponding liquid (4) provided by the two nozzles (28a, 28b) cross in the grinding zone (12). procedure according to claim 5 , wherein the at least two nozzles (28a, 28b) provide supercritical fluid (6) or corresponding liquid (4) at different speeds. A method according to any one of the preceding claims, further comprising the step of: iii. Separating the ground particles (8) from the supercritical fluid (6), preferably by lowering the temperature and/or the pressure of the supercritical fluid (6). A method according to any one of the preceding claims, further comprising the step of: IV. adjusting the temperature and/or pressure of the supercritical fluid (6) to cause it to transition back into the corresponding liquid (4), and preferably reusing the liquid (4) to obtain the supercritical fluid (6), provided in step (ii). Method according to one of claims 2 - 8th , wherein the particles (2) are fed into the grinding zone (12) by being mixed with the liquid (4) before the supercritical fluid (6) is provided in the grinding zone (12). Method according to one of Claims 1 - 8th , wherein the particles (2) are fed separately from the supercritical fluid (6) into the grinding zone (12'), and wherein the particles (2) are preferably fed into the grinding zone (12') such that they are in the grinding zone ( 12') form a fluidized bed of particles (2). A method according to any one of the preceding claims, wherein the supercritical fluid (6) comprises or consists of supercritical carbon dioxide or nitrogen, preferably wherein the supercritical fluid (6) is supercritical carbon dioxide. Jet mill (10) comprising: - a grinding zone (12), - at least one nozzle (28a, 28b) for feeding particles (2) into the grinding zone (12), - at least one nozzle (28a, 28b) for providing a supercritical fluid (6) in the grinding zone (12) to cause the particles (2) to collide with each other and/or with an inner surface of the jet mill (10) to thereby to produce ground particles (8), the jet mill (10) being designed such that the pressure and the temperature of the grinding zone (12) and/or the at least one nozzle (28a, 28b) for providing the supercritical fluid (6) within the supercritical phase of the supercritical fluid (6). Jet mill (10) according to claim 12 , further comprising one or more, preferably all, of: - a tank (18) for receiving the liquid (4) corresponding to the supercritical fluid (6), - a pump (20) connected to the tank (18), to pressurize the liquid (4), - a mixer (16) connected to the pump (20) for mixing the particles (2) with the liquid (4), the at least one nozzle (28a, 28b) for feeding of particles (2) into the grinding zone (12) and the at least one nozzle (28a, 28b) for providing the supercritical fluid (6) in the grinding zone (12) are designed as at least one nozzle (28a, 28b) to the mixture from the particles (2) and to provide the supercritical fluid (6) in the grinding zone (12), - a separation chamber (34) arranged downstream of the grinding zone (12) and adapted to receive the ground particles (8) and the supercritical fluid (6), wherein the separation chamber (34) is designed to have a lower temperature and/or pressure than the grinding zone (12) but within the supercritical phase of the supercritical fluid (6), an internal volume of the jet mill (10) preferably having a - a cooler (40) arranged downstream of the grinding zone (12), preferably also downstream of the separation chamber (34) for cooling the supercritical fluid ( 6) so that it passes into the liquid (4), and - a return line (38) connected to the cooler (40) and the pump (20) or the tank (18) for carrying the liquid (4) to the pump ( 20) or to the tank (18). Ground particles (8) according to the method of any of Claims 1 until 11 are obtained, wherein the ground particles (8) preferably comprise or consist of nanoscale to microscale silicon particles. Use of the ground particles (8) according to Claim 14 , Preferably in a battery, particularly preferably in a drive battery for an electric vehicle, particularly preferably in the anode of a lithium-ion battery. Battery manufactured using ground particles according to Claim 14 or ground particles (8) according to Claim 14 full.

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