Apparatus and method for producing slabs from positive electrode active material for rechargeable batteries

Abstract

An apparatus (1) for producing slabs (2) from powdered raw material is described. The powdered raw material is a positive electrode active material for a rechargeable battery. The apparatus (1) includes a lower mold (3) defining a molding cavity (4) and an upper mold (6) having an upper punch (601). The upper mold (6) and lower mold (3) are movable relative to each other along a vertical direction (V) between an open position and a pressing position. The upper mold (6) and lower mold (3) are movable to a pre-pressing position in which the molding cavity (4) is closed by the upper mold (601) but is in air communication with the surrounding air space. The apparatus (1) further includes a suction system for suctioning air from the molding cavity (4) in the pre-pressing position and maintaining a negative pressure within the molding cavity in the pressing position. The lower mold and upper mold are provided with air intake channels that draw air from the molding cavity and from the top and bottom of the molding cavity.

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for producing slabs from cathode active material for rechargeable batteries. [Background technology]

[0002] Battery production is expanding at an ever-accelerating pace due to increasing demand for batteries in many sectors.

[0003] Generally, batteries are divided into two broad categories: primary batteries, which cannot be recharged and are discarded at the end of their life, and secondary batteries, which are rechargeable batteries.

[0004] A rechargeable battery contains a set of electrodes assembled in a can for charging and discharging electrical energy. Typically, the electrode set consists of an anode material layer, a separator, and a cathode material layer, which are wound or stacked together and inserted into a can to form a battery cell. The battery cell is further filled with an electrolyte that conducts positively charged lithium ions from the positive electrode to the negative electrode and from the negative electrode to the positive electrode through the separator.

[0005] Among various types of secondary batteries, lithium-ion batteries, which have high capacity and low self-discharge, are currently the most widely used worldwide. In addition, the cathode active material is one of the most important components in the manufacture of lithium-ion batteries, determining the efficiency, reliability, cost, lifespan, size, and ultimately applications of the battery.

[0006] More specifically, the cathode active material is a highly pure chemical substance. More specifically, the cathode active material undergoes a calcination process (high-temperature treatment) to remove impurities and volatile substances. The cathode active material is generally composed of a crystalline structure of cobalt, nickel, and manganese, with the addition of lithium to form a powdered multi-metal oxide material. In the calcination process, the powdered mixture is placed in a container such as a sagger and fired, usually in a furnace.

[0007] However, this method has several drawbacks. For example, the efficiency of the firing process is low because the powdered mixture is held in the saggers, resulting in low heat and mass transfer coefficients, which means the mixture must remain in the kiln for a long time, lengthening the firing process. Furthermore, the time required to cool the saggers after they emerge from the kiln further increases process downtime. Furthermore, because of the continuous heating and cooling, the saggers typically must be replaced after only a few weeks of use, thereby increasing the cost of the process.

[0008] Therefore, there is a need for container-free firing to increase the efficiency of the firing process.

[0009] In this regard, Japanese Patent Application Publication No. 2019-175697 discloses a method for producing a positive electrode active material. More specifically, the document describes a method for obtaining a compact by pressing a powdered positive electrode active material (i.e., powdered), which is then subjected to a sintering process. Therefore, there is a need for an apparatus and method for producing a slab from a powdered raw material. In this regard, U.S. Patent Application Publication No. 3,657,917 discloses a method and system for compressing a powdered raw material to obtain a high-quality compact. In this solution, the powdered material is placed in a cavity of a mold, the cavity of the mold is degassed, and the powdered material is pre-compressed by a dual-piston hammer assembly. Furthermore, a piston mass is collided at high speed, applying a high-energy impulse through a lamb's die, which strongly binds the particles of the powdered raw material under strong suction, resulting in a molded product that precisely matches the shape of the mold.

[0010] Furthermore, U.S. Patent Application Publication No. 2011113924 discloses an apparatus and method for producing slabs from powder, particularly silicon. In particular, the powder is fed to a feeder, which transports the powder to be molded from a filling position to a recess where the powder is molded. The recess is defined laterally by a press bed and from below by a lower die, forming a molding chamber. A filter insert made of a gas-permeable ceramic material is provided on the inner surface of the press bed facing the molding chamber, and an exhaust mechanism is connected to this filter insert. Furthermore, an upper die having a punch is provided, and the molding chamber is airtightly closed at its upper end by the punch. In particular, the upper die is vertically movable. Subsequently, suction pressure is applied to the molding chamber via the exhaust mechanism, thereby reducing the pressure in the molding chamber.

[0011] The punch then applies pressure to the upper die via a pressure generating mechanism, compressing the powder in the die chamber in the axial direction. Specifically, the upper die is guided downward along its longitudinal axis until the punch hermetically closes the die chamber at its top end. The die chamber is then subjected to a negative pressure via an exhaust mechanism.

[0012] However, there is a growing need in the art for apparatus and methods that can more efficiently produce slabs from powdered positive electrode active material. Summary of the Invention [Problem to be solved by the invention]

[0013] It is an object of the present disclosure to provide an apparatus and method for producing slabs from cathode active material for secondary batteries, in order to overcome the above-mentioned drawbacks of the prior art. This object is fully achieved by the apparatus and method of the present disclosure as characterized in the appended claims. [Means for solving the problem]

[0014] According to one aspect, the disclosure provides an apparatus for producing slabs from powdered raw material. In one example, the powdered raw material is a cathode active material for a rechargeable battery. The apparatus can also produce slabs from other materials. The term "powdered" is used to describe a material consisting of very fine, dry particles obtained by crushing, grinding, or disintegrating a solid substance. In one example, the slab is preferably rectangular. In other examples, the slab may have other geometric shapes. The apparatus includes a lower mold. The lower mold defines a mold cavity. It should be noted that the mold cavity may have different geometric shapes. The apparatus has a feeder. The feeder is configured to receive a charge of powdered material and feed the charge of powdered raw material into the mold cavity. The term "charge" refers to a predetermined amount of raw material that is placed into the mold cavity to produce a slab. The apparatus also has an upper mold. The upper mold has an upper punch. The upper mold is vertically movable relative to the lower mold. More specifically, the upper mold and the lower mold are vertically movable between an open position and a press position. In the open position, the upper punch is separated from the lower die, allowing the fill material to be filled into the mold cavity. In the press position, the upper punch is inserted into the mold cavity to compress the fill material and form a slab. In one example, the upper and lower dies are also movable to a pre-press position, which is vertically interposed between the open position and the press position. More specifically, in the pre-press position, the mold cavity is closed by the upper punch to prevent the fill material from moving out of the mold cavity. However, in the pre-press position, the mold cavity remains in communication with the surrounding air space.

[0015] The apparatus may include a sealing mechanism configured to keep the molding cavity and the surrounding air space airtight, more specifically, the sealing mechanism configured to keep the molding cavity and the surrounding air space airtight when the upper and lower dies are in the pre-press position and the press position.

[0016] According to one aspect of this description, the apparatus includes a suction system configured to suck air from the mold cavity. In one example, the suction system is configured to suck air from the mold cavity at a pre-press position of the upper and lower dies. Furthermore, the suction system is configured to maintain a negative pressure within the mold cavity at a press position of the upper and lower dies. Thus, according to one aspect of the present disclosure, the suction system removes air from inside the mold cavity when the cavity is closed by the upper die and before the upper die compresses the powdered raw material inside the cavity. Furthermore, by constantly maintaining a negative pressure within the mold cavity during compression, it is possible to prevent air from entering the cavity during this period.

[0017] It should be noted that degassing during the compression of the powdered material in the cavity is usually achieved by the pulsation movement of the upper punch. During the degassing process, the movement performed by the upper punch is a movement away from the powdered material, followed by a movement towards and into contact with the previously compressed powdered material (pulsation cycle). In this way, excess air in the mold can be expelled from the inside to the outside.

[0018] This degassing process can take a long time, as the cavity usually requires several degassing cycles. The use of a suction system allows the air to be removed from the cavity without the degassing process described above. This allows for a machine that can compress powdered raw materials at higher speeds and in a particularly efficient way without losing material, resulting in higher quality slabs.

[0019] In one example, the lower mold has a bottom wall. The lower mold further has a side wall. More specifically, the side wall cooperates with the bottom wall to define a molding cavity. In one example, the bottom wall and the side wall move relative to each other along a vertical direction. In this manner, the bottom wall and the side wall can be moved relative to each other to allow a filler to be filled into the molding cavity and / or a molded slab to be removed from the molding cavity.

[0020] In one example, the lower mold has a lower punch. More specifically, the lower punch defines a bottom wall of the lower mold. In one example, the lower mold further has a lower block. The lower block defines a side wall. The lower block also has a top surface. In one example, the top surface extends along a horizontal plane perpendicular to the vertical direction. The lower punch and the lower block are movable relative to each other in the vertical direction and are movable between an alignment position and an offset position. More specifically, in the alignment position, the bottom wall is flush with the top surface, thereby placing the bottom wall and the top surface on the same feed plane. In the offset position, the bottom wall is positioned below the top surface to define a molding cavity.

[0021] In one example, the device has a feed surface. The feed surface extends along a feed plane. For example, the feed device defines a vertical passageway. Further, the feed device may be movable in a working direction. The working direction is parallel to the feed surface. In one example, the feed device is also movable in sliding contact with the feed surface. More specifically, the feed device is movable between a feed position and a discharge position. In the feed position, the feed device receives a supply of powdered raw material. In the discharge position, the passageway is aligned vertically with the bottom wall. More specifically, in the discharge position, the passageway is aligned vertically with the bottom wall such that the charge is contained within a space defined by the passageway and the bottom wall.

[0022] Therefore, according to one aspect of the present disclosure, when the feeding device reaches the feeding position while moving, the filling material is fed without stopping and conveyed into direct contact with the feeding surface. Furthermore, when the feeding device is in the discharge position, the bottom wall and the top surface are aligned to form the feeding surface. Because the feeding surface extends along the feeding surface, the feeding device can easily move along the feeding surface to discharge the filling material onto the bottom wall. This improves the efficiency of feeding the filling material into the molding cavity.

[0023] The apparatus comprises an outlet. In particular, the formed slabs are fed to the outlet. In one example, the apparatus comprises a pick-up device. The pick-up device is movable along a working direction. The pick-up device is movable between a pick-up position and a transfer position. At the pick-up position, the pick-up device grips the formed slabs. At the transfer position, the pick-up device transfers the slabs to the outlet.

[0024] In one example, the apparatus includes a carriage configured to move back and forth along the working direction. In one example, the pickup device and the feeding device are connected to the carriage. Furthermore, the pickup device is arranged upstream of the feeding device in the forward direction. More specifically, the forward direction is defined as the direction from the filling position toward the outlet of the apparatus. In one example, when the pickup device is in the picking position, the feeding device is arranged in the feeding position. In one example, when the pickup device is in the transport position, the feeding device is arranged in the discharge position. In this way, the feeding device and the pickup device simultaneously move between two positions, thereby particularly speeding up the process. In the first position, the formed slab is picked up while the feeding device is supplying the filling material. In the second position, the formed slab is transported to the outlet while the molding cavity is filled and the molding can proceed to form the next slab. In another example, the feeding device and the pickup device can also move to a third position located downstream of the discharge position. More specifically, in the third position, both the feeding device and the pickup device are located downstream of the molding cavity in the forward direction and at the outlet of the apparatus. In this example, the feeding device smooths the surface of the fill material while the lower block and lower punch are in an offset position during retraction (defined as from the exit to the filling position) so that the fill material in the molding cavity is smoothed by the feeding device.

[0025] In one example, in the pick-up position of the pick-up device (FIG. 1), the bottom wall is configured to move upward along a vertical direction V. Also, in the pick-up position of the pick-up device, the side walls are configured to move downward along a vertical axis. When the pick-up device is in the pick-up position, the bottom wall moves upward to the alignment position, and at the same time the side walls move downward. This solution is particularly advantageous for removing the formed slab from the forming cavity without damaging the slab.

[0026] In one example, the device has a pair of sliding bars. In one example, the sliding bars extend in a longitudinal direction. The sliding bars are spaced apart from each other and arranged along a first horizontal axis. Each sliding bar has a first end and a second end. More specifically, the first horizontal axis is perpendicular to a second horizontal axis extending along the working direction. The dolly may be configured to slide on the sliding bars. More specifically, the dolly slides back and forth on the sliding bars along the working direction. In one example, the device has a plurality of longitudinal wheels. A longitudinal wheel is disposed on each sliding bar. The longitudinal wheels are disposed along the working direction. The longitudinal wheels are configured to support the weight of the dolly along the sliding bars. The longitudinal wheels allow the dolly to move back and forth along the working direction. The device may also include lateral wheels. A lateral wheel is disposed on each sliding bar. The lateral wheels are disposed at a 90-degree rotation relative to the longitudinal wheels. The lateral wheels are configured to maintain alignment along the working direction along which the dolly moves. In one example, the longitudinal and lateral wheels are made of a material that is not likely to contaminate the cathode material being processed in the press.

[0027] For example, the longitudinal wheels may be made of steel, preferably case-hardened steel. Steel is advantageous because it reduces the wear rate of the longitudinal wheels, which must support the weight of the sliding carriage.

[0028] As for the lateral wheels, these may for example be made of rubber or may be rubber coated, for example by vulcanization.

[0029] A lateral wheel may be disposed at the first end and the second end of each sliding bar.

[0030] In one example, the bottom wall is movable vertically relative to the side wall. The apparatus has an inlet for receiving powdered raw material. In one example, the apparatus has a particle suction system. The particle suction system is configured to remove airborne particles. In one example, the particle suction system includes a first hood and a second hood. In one example, the first hood and the second hood are connected to the upper mold. More specifically, the first hood may be positioned upstream of the molding cavity in the direction of travel. The direction of travel is defined as from the inlet to the outlet. The first hood is configured to remove airborne particles from around the molding cavity. Furthermore, the second hood is positioned downstream of the molding cavity in the direction of travel. The second hood is configured to remove airborne particles from around the discharge port.

[0031] In one example, the lower mold includes a plurality of molding cavities. The molding cavities of the plurality of molding cavities may be arranged to form an array of molding cavities. Furthermore, the upper mold may include a plurality of upper punches. More specifically, each upper punch is configured to cooperate with a corresponding molding cavity to form each of the plurality of slabs. This allows for improved productivity of the apparatus.

[0032] In one example, the apparatus includes a heating system connected to the lower and upper dies to maintain them at a predetermined temperature.

[0033] Heating the mold allows the formed slab to be more easily removed from the mold cavity and generally prevents powdered raw material from adhering to the mold cavity or upper punch.

[0034] In one example, the bottom wall, side wall, and upper punch are made of stainless steel. Thus, according to one aspect of the present disclosure, all parts of the mold that come into direct contact with the powdered raw material are made of materials that do not react with the powdered raw material. This solution prevents the powdered raw material from being contaminated in any way.

[0035] Furthermore, steel can withstand the pressure exerted by the powder (powdered raw material) being pressed against the side walls.

[0036] In one example, the upper punch has a first layer and a second layer. The lower punch may also have a first layer and a second layer. The second layer is in contact with the powdered raw material. The second layer is detachably connected to the first layer. More specifically, the second layer of the upper punch and the second layer of the lower punch are made of stainless steel. Therefore, the portions of the upper punch and the lower punch that come into contact with the powdered raw material can be made of stainless steel. This makes the device more cost-effective.

[0037] In one example, the process of sucking air out of the molding cavity begins when the upper and lower dies are in the pre-press position and continues while the upper die moves vertically downward from the pre-press position to the position where the upper punch contacts the powdered raw material in the cavity.

[0038] These and other features will emerge more clearly from the following description of preferred embodiments, which are illustrated by way of non-limiting example in the accompanying drawings, in which: [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 illustrates an apparatus for producing slabs from powdered positive electrode active material according to the present disclosure, with the feeder in the feed position. [Figure 2] FIG. 2 shows the pick-up position of the pick-up device. [Figure 3] FIG. 3 shows the apparatus with the pick-up device in the transport position. [Figure 4] FIG. 4 shows the pre-press positions of the lower and upper dies. [Figure 5] FIG. 5 shows the pressing positions of the lower and upper dies. [Figure 6] FIG. 6 shows the lower and upper dies. [Figure 7] Figure 7 shows axonometric views of the device from different angles. [Figure 8] FIG. 8 shows the lower and upper dies. [Figure 9] FIG. 9 is a side view of the device. [Figure 10] FIG. 10 shows a scraper element. [Figure 11] FIG. 11 shows the details of the sliding bar. [Figure 12] FIG. 12 shows the hydraulic system. [Figure 13A] FIG. 13A shows details of the aspiration system. [Figure 13B] FIG. 13B shows details of the aspiration system. DETAILED DESCRIPTION OF THE INVENTION

[0040] Referring to the accompanying drawings, reference numeral 1 denotes an apparatus for producing a slab 2 from a powdered raw material. In one example, the powdered raw material is a positive electrode active material for a rechargeable battery. The apparatus for producing a slab 2 from a powdered raw material (i.e., apparatus 1) has a lower mold 3. The lower mold 3 defines a molding cavity 4. The molding cavity receives the powdered raw material to be compressed to form a slab. More specifically, the lower mold 3 has a bottom wall 301. The lower mold 3 also has side walls 302. The side walls 302, together with the bottom wall, define the molding cavity 4. In one example, the molding cavity is rectangular. In this example, the side walls 302 include four walls surrounding the bottom wall 301. In one example, the lower mold 3 has multiple molding cavities. The molding cavities of the multiple molding cavities may be arranged to form an array of molding cavities. Each molding cavity has a bottom wall 301 and a side wall 302.

[0041] The bottom wall 301 and the side wall 302 move relative to each other along a vertical direction V. In one example, the bottom wall 301 is movable vertically relative to the side wall 302.

[0042] The lower mold 3 may include a lower punch 303. More specifically, the lower punch 303 defines a bottom wall 301.

[0043] In one example, the lower punch 303 has a first layer L1 and a second layer L2. The second layer is in contact with the powdered raw material.

[0044] In one example, the second layer is removably connected to the first layer.

[0045] In one example, the lower die 3 has a plurality of magnets M. In this example, the first layer L1 of the lower punch 303 is magnetized. Therefore, the first layer may be connected to the lower punch 303 via the magnets M. In one example, the first layer L1 is made of soft iron. In one example, the first layer L1 also has a plurality of through holes. The second layer L2 includes a plurality of blind holes. The first layer may be connected to the second layer by a plurality of screws that join the first layer and the second layer via the through holes and blind holes. In one example, the second layer is made of stainless steel. Preferably, the second layer L2 of the lower punch 303 is a highly hardenable martensitic stainless steel. The stainless steel may contain carbon. The stainless steel may contain silicon. The stainless steel may contain manganese. The stainless steel may contain chromium. The stainless steel may contain vanadium. More specifically, stainless steel has high polishability, corrosion resistance, and thermal oxidation resistance.

[0046] Additionally, the stainless steel may undergo one or more heat treatments.

[0047] In one example, stainless steel is annealed to a hardness of 240 or less. Preferably, stainless steel is annealed at 750°C to 800°C. The stainless steel may be annealed at steady state for at least three hours. The steel is then cooled. The steel may further undergo a relaxation process. The relaxation process is performed after the machining process. The relaxation process is performed before the final heat treatment. During the relaxation process, the steel is heated to 600°C to 650°C. During the relaxation process, the steel is heated for two hours. The stainless steel may also undergo a tempering process. During the tempering process, the steel is heated to 600°C to 700°C. The tempering process also includes an austenitizing process at 990°C to 1040°C. The steel is then cooled. In one example, the steel may be cooled in oil. The steel may undergo a hot bath treatment at 500°C to 550°C, followed by an oil bath treatment where the steel is cooled depending on its shape and size. In one example, the hardness of the tempered steel is 52 to 56 HRC.

[0048] In one example, the second layer is thinner than the first layer. Thus, the portion in direct contact with the powdered raw material is made of the aforementioned steel. It should be noted that by connecting the second layer to the first layer (by blind holes) as described above, a configuration is achieved in which no materials other than stainless steel come into contact with the powdered raw material. As explained above, the cathode active material is very expensive and must be very pure to obtain a high-quality electrode. Therefore, the powdered raw material must only come into contact with materials that will not cause unwanted reactions or contamination. Furthermore, this configuration allows for the use of a minimal amount of the aforementioned stainless steel to provide the thin layer (second layer) that comes into contact with the raw material, thereby improving efficiency in terms of process costs.

[0049] Furthermore, in one example, the side wall 302 is composed of two layers. The first layer of the side wall 302 is made of the stainless steel. In one example, the first layer of the side wall is connected to the second layer of the side wall by a plurality of screws. In this example, both the second layer and the first layer of the side wall 302 are provided with a plurality of through-holes through which the plurality of screws pass. In one example, the through-holes in the side wall are provided at the bottom of the first and second layers of the side wall, and the through-holes are at a lower height than the bottom wall along the vertical direction V. In this way, the plurality of screws and the through-holes do not come into contact with the powdered raw material.

[0050] The lower mold 3 may further include a lower block 304. The lower block 304 defines a sidewall 302. The lower block further has an upper surface 3041. The upper surface 3041 extends along a horizontal plane perpendicular to the vertical direction V. In one example, the lower punch 303 and the lower block 304 are movable relative to each other along the vertical direction V. The lower punch 303 and the lower block 304 are movable relative to each other along the vertical direction such that they are movable between an alignment position and an offset position. In the alignment position, the bottom wall 301 is flush with the upper surface 3041. More specifically, in the alignment position, the bottom wall 301 is flush with the upper surface 3041, thereby positioning the bottom wall 301 and the upper surface 3041 in the same feed plane. Furthermore, in the offset position, the bottom wall 301 is positioned below the upper surface 3041 to form the molding cavity 4. In other words, in the offset position, the bottom wall 301 is positioned at a lower height than the top surface 3041 along the vertical direction.

[0051] More specifically, the lower punch 303 is moved along the vertical direction V by an actuator. In this example, the actuator is a hydraulic system. The hydraulic system has a cylinder and a piston that slides within the cylinder along the vertical direction V. More specifically, the lower punch 303 is moved in the vertical direction by the piston.

[0052] The apparatus 1 further includes an upper mold 6. The upper mold 6 is provided with an upper punch 601. When the lower mold 3 includes multiple molding cavities, the upper mold 6 includes multiple upper punches 601. More specifically, each upper punch is configured to cooperate with a corresponding molding cavity 4 to form each of the multiple slabs 2. In one example, the upper punch 601 includes a first layer L1 and a second layer L2. In one example, the second layer L2 of the upper punch 601 is in contact with the powdered raw material.

[0053] In one example, the second layer L2 of the upper punch 601 is detachably connected to the first layer.

[0054] In one example, the upper die 6 includes a plurality of magnets M. In this example, the first layer L1 of the upper punch 601 is magnetized. The first layer of the upper punch 601 may therefore be connected to the second layer of the upper punch 601 via the magnets M of the upper punch. In one example, the first layer L1 of the upper punch 601 is made of soft iron. In one example, the first layer L1 of the upper punch 601 further includes a plurality of through holes. The second layer L2 of the upper punch 601 includes a plurality of blind holes. The first layer of the upper punch 601 may be connected to the second layer of the upper punch 601 by a plurality of screws that connect the first layer of the upper punch 601 to the second layer of the upper punch 601 via the through holes and blind holes. For example, the second layer of the upper punch 601 is made of stainless steel. In one example, the lower punch 303 and the second layer of the upper punch 601 are corrugated. For example, the top and bottom surfaces of the slab 2 are corrugated.

[0055] The apparatus further comprises a feeder 5. The feeder is configured to receive a charge of powdered raw material and to feed the charge of powdered raw material into the forming cavity 4. The feeder receives the charge of powdered raw material from a hopper 13.

[0056] The upper mold 6 is movable along a vertical direction V relative to the lower mold 3. More specifically, the upper mold 6 is movable along a direction perpendicular to the lower mold between an open position and a press position. In one example, the upper mold 6 moves vertically between the open position and the press position. In another example, the upper mold may be stationary while the lower mold moves between the open position and the press position. Alternatively, both the lower mold and the upper mold move together between the open position and the press position.

[0057] In the open position, the upper punch 601 is separated from the lower die 3, allowing the filler to be filled into the molding cavity 4. In the press position, the upper punch 601 is inserted into the molding cavity 4 and compresses the filler to form the slab 2. More specifically, in the press position, the upper punch 601 forms the upper wall of the molding cavity 4. In one example, the upper die 6 and the lower die 3 can also be moved to a pre-press position. The pre-press position is vertically interposed between the open position and the press position. More specifically, in the pre-press position, the molding cavity 4 is closed by the upper punch 601, preventing the filler from moving out of the molding cavity 4. Furthermore, the molding cavity is airtightly connected to the surrounding air space.

[0058] The apparatus 1 comprises a feed surface 9. The feed surface extends along a feed plane. In one example, the feed apparatus 5 defines a passage 501. The passage 501 is disposed vertically. In one example, the feed apparatus 5 is movable in a working direction WD. The working direction is parallel to the feed surface 9. In one example, the feed apparatus 5 is movable in sliding contact with the feed surface 9. The feed apparatus is movable between a feed position and a discharge position.

[0059] In one example, the lower block 304 is stationary. The upper surface 3041 is therefore stationary and horizontally aligned with the feed surface. In one example, the lower block 304 comprises a fixed part and a movable part. More specifically, the fixed part is defined by the upper surface 3041, and the movable part is defined by the side wall 302 of the lower mold 3.

[0060] It should be noted that block 304 can be fixed or movable. If block 304 is movable, it moves synchronously with top surface 3041 and sidewall 302 (which are or can be integral). The movement of block 304 can aid in ejection of the part from the molding cavity. If block 304 is stationary, ejection of the part is achieved solely by the upward movement of lower punch 303.

[0061] The sidewalls 302 of the lower mold may be movable along the vertical direction V. In one example, in the aligned position, the sidewalls are flush with the top surface and together with the bottom wall form a feed surface.

[0062] In the feed position, the feeder 5 receives the powdered raw material. In the discharge position, the passage 501 is vertically aligned with the bottom wall 301 of the lower mold 3. More specifically, in the discharge position, the passage is vertically aligned with the bottom wall, such that the input material in the discharge position is contained within the space defined by the passage 501 and the bottom wall 301.

[0063] In one example, the feeding device 5 includes a plurality of blades 502 arranged horizontally, perpendicular to the working direction WD, and spaced apart from one another. The blades are equally spaced from one another. More specifically, when the feeding device moves between the feeding position and the discharge position, the blades remain in sliding contact with the feeding surface 9. This allows the powdered raw material to be uniformly transported to the feeding surface 9. In one example, the blades 502 may include a plurality of grooves. A groove is provided along the bottom of each blade, which is in sliding contact with the feeding surface 9. When the lower mold 3 includes a plurality of molding cavities, the feeding device 5 is divided into different sections. Each section is composed of a plurality of bars spaced apart from one another and arranged perpendicular to the blades 502. The sections are separate from one another. Each section corresponds to a respective molding cavity 4.

[0064] The apparatus 1 further includes a sealing mechanism 7. The sealing mechanism is configured to keep the molding cavity and the surrounding air space airtight when the upper and lower dies are in the pre-press position and the press position. The sealing mechanism is connected to the upper die 6. More specifically, when the upper and lower dies are in the pre-press position and the press position, the sealing mechanism surrounds the upper die 6 and keeps the molding cavity and the surrounding air space airtight. When the upper and lower dies are in the pre-press position, the sealing mechanism rests on the upper surface 3041. When the dies 3 and 6 are in the press position, the sealing mechanism is compressed.

[0065] According to one embodiment of the present disclosure, the apparatus further includes a suction system for sucking air out of the mold cavity 4. In one example, the suction system sucks air out of the mold cavity 4 at the pre-press positions of the upper and lower mold dies. Alternatively, the suction system may operate when the mold dies are in other positions.

[0066] In particular, during suction, air is sucked from both above (upward) and below (downward) the cavity. The lower and upper dies are provided with suction passages for sucking air from the molding cavity, thereby sucking air from both above and below the molding cavity. In particular, air sucked from above is sucked through an upper channel provided in the gap between the side wall of the molding cavity and the sealing mechanism (the gap separating the side wall and the sealing mechanism). The bottom wall is provided with suction holes for sucking air from below. In one example, the lower die is provided with a hole F, which allows air to be sucked from below the cavity during suction. Furthermore, a lower channel connected to the hole can be provided in the lower die, so that the sucked air is guided into the channel and sucked out through the hole. Furthermore, the upper and lower dies are provided with suction pipes 20, 21 through which suction is performed.

[0067] The suction system is also configured to maintain a negative pressure inside the molding cavity. In one example, the suction system is configured to maintain a negative pressure inside the molding cavity at the pressurizing positions of the upper and lower molds. The suction system includes a suction pump. The suction system includes one or more suction pipes. In one example, the suction pipes include a first pipe VT1 and a second pipe VT2 connected to the upper mold 6 and the lower mold 3, respectively.

[0068] The apparatus includes an inlet I. The inlet I is configured to receive powdered raw material. A hopper 13 is arranged at the inlet I of the apparatus 1. The apparatus 1 has an outlet O. The formed slab 2 is fed to the outlet. In one example, the apparatus 1 includes a pickup device 11. The pickup device 11 is movable along a working direction WD. The pickup device 11 is movable between a pickup position and a conveying position. At the pickup position, the pickup device grips the formed slab 2. At the conveying position, the pickup device 11 conveys the slab to the outlet O. In one example, the pickup device includes a plurality of fingers 111 (or grippers). The fingers are spaced apart from one another to receive the slabs. In this case, the lower mold 3 includes a plurality of molding cavities 4. The number of fingers corresponds to the number of molding cavities, so that each pair of fingers grips a slab 2.

[0069] In one example, the side walls 302 move vertically to the pick-up position of the pick-up device. Thus, when the pick-up device 11 is in the pick-up position, the bottom wall moves vertically upwards, transporting the slabs to the level of the feed surface 9, where the pick-up device receives the slabs. In an example, the side walls simultaneously move downwards. In an example, the side walls only move downwards.

[0070] The upper punch 601 is moved up and down vertically via a hydraulic system 19. The hydraulic system is different from the hydraulic system that moves the lower die.

[0071] The hydraulic system has a tank 190. The tank contains oil (hydraulic fluid). The hydraulic system includes an actuating element 191. The actuating element includes a fixed part 191A and a movable part 191B. The movable part of the actuating element can be raised and lowered vertically. The movable part of the actuating element can be raised and lowered vertically between an open position and a closed position. In the closed position, the movable part is adjacent to the fixed part.

[0072] In the open position of the actuating element, the movable part is spaced apart from the fixed part and is arranged at a lower height than the fixed part.

[0073] The actuating elements are located inside the tank and are therefore surrounded by oil. The hydraulic system includes a first down conduit 192 and a first up conduit 193. The actuating elements are in communication with the first up conduit and the first down conduit.

[0074] Specifically, oil passages are provided between the movable part and the fixed part. These oil passages communicate with the first ascending conduit and the first descending conduit, forming a sealed oil chamber with a variable volume between the movable part and the fixed part (the oil chamber is separated from the oil in the tank). The volume of the oil chamber changes with the movement of the movable part. Specifically, the volume increases as the movable part moves toward the open position of the actuating element and the distance between the movable part and the fixed part increases. When oil is supplied to the first descending conduit, the movable part of the actuating element is moved vertically toward the open position of the actuating element (and the volume of the oil chamber connected to the first descending conduit increases). The movable part descends until it reaches a predetermined end position. When the movable part is placed in the open position (end position), the movable part no longer moves downward even if oil continues to be supplied to the first descending conduit. When oil is supplied to the first ascending conduit, the movable part moves vertically upward toward the closed position. The hydraulic system further includes a displacement element 194. The displacement element is connected on one side to the upper punch 601 and on the other side to the tank. In particular, the displacement element is in hydraulic communication with the tank. When the movable part is in the open position of the actuating element, an oil chamber is formed between the displacement element and the movable part at the bottom of the tank. Therefore, in the open position of the actuating element of the movable part, the displacement element is in hydraulic communication only with the part of the tank that is closed between the movable part and the displacement element. Furthermore, the displacement element is connected to a second descending conduit 195 and a second ascending conduit 196. In particular, the displacement element includes an upper part 194A and a lower part 194B.

[0075] The upper part of the displacement element is in hydraulic communication with the tank and is connected to the second descending conduit. The lower part of the displacement element is attached to the upper punch and is in communication with the second ascending conduit. The upper and lower parts are connected together. In particular, an oil passage is provided between the lower and upper parts of the displacement element. An oil capillary passage C is provided between the lower and upper parts.

[0076] When oil is supplied to the second descending conduit (and the movable part is in the open position), the oil presses against the top of the displacement element, thus moving the displacement element and consequently the upper punch downward (and therefore the punch moving towards the pressing position). In one example, the tank is also moved vertically. When oil is supplied to the second ascending conduit, the movable part is in the closed position, and therefore the displacement element is in communication with the oil in the entire tank. In this case, the oil enters the capillary passage C and acts on the part of the displacement element between the bottom and top, pushing up the displacement element and therefore the upper punch.

[0077] The hydraulic system also includes a hydraulic circuit HC that communicates with it and circulates oil within the system. To avoid overcomplicating Figure 11, the hydraulic circuit is shown in two blocks in this diagram. This circuit includes valves (e.g., solenoid valves) and other elements known from hydraulic circuits.

[0078] Furthermore, the device comprises a control unit, which automatically manages the hydraulic system.

[0079] As the upper punch is moved downward, its movement may be adjusted via a hydraulic system, for example by adjusting a throttle valve, between a position where it interacts with the side wall to close the cavity and begins to be placed in a pre-press position (where powder cannot exit the cavity but air can), to a position where the upper punch is in contact with the powder (but no pressure is yet being applied).

[0080] Preferably, suction (by the suction system) is activated when the cavity is closed by the upper punch. Therefore, when suction is activated, dust does not come out of the cavity. It is expected that suction will continue even after the cavity is closed by the upper punch (pre-pressing step). Therefore, suction is activated when the pre-pressing position of the lower and upper dies is reached. In one example, when the lower and upper dies are positioned in the pre-pressing position, vertical movement of the upper die (and punch) is stopped, and suction is activated while the lower and upper dies are in the pre-pressing position. Suction may be configured to stop when a predetermined vacuum threshold is reached. The downward vertical movement of the upper die continues until the upper and lower dies reach the pressing position. In another example, it is expected that suction will continue while the upper die moves from the pre-pressing position to the pressing position. Therefore, in that example, suction begins when the lower and upper dies are in the pre-pressing position and continues as the upper die moves toward the pressing position until it reaches a point where the upper punch contacts the powder but does not pressurize the powder in the cavity.

[0081] The suction can be controlled by feedback control, and in particular, a suction signal can be provided that represents the cavity suction value, and when a predetermined (desired) vacuum threshold is reached, the suction is stopped.

[0082] The hydraulic system may be configured to generate a damping effect during vertical lowering of the upper mold.

[0083] With suction continuing and the upper punch in contact with (but not pressurized by) the powder in the cavity, the hydraulic system is configured to continue to generate a damping effect to reduce the weight of the upper die, which has a significant weight and could potentially apply excessive pressure to the powder in the cavity.

[0084] In particular, as the cavity is initiated by the upper punch, suction can begin and continue as the upper punch descends. At some point, the upper punch contacts the powder and can remain there (without compressing the powder), allowing suction to continue. In such a configuration, the upper punch is held in equilibrium (e.g., via a hydraulic system, via an adjustment valve).

[0085] After the suction is complete, the upper die and upper punch in contact with the powder are pressed down to compress the powder.

[0086] The powder can be pressed (compressed) under feedback control based on the setpoint of the pressure applied to the powder and / or the position of the upper punch. After the compression is complete, the upper die (and upper punch) is raised to the open position. In particular, the upper die is moved up and down via this hydraulic system. The hydraulic circuit may have two different branches (including separate ducts and valves) for moving the upper die between the open position, the pre-press position, and a position where the upper die is in contact with the powder in the cavity but the powder is not compressed by the upper punch, and for pressing the upper die downward while in contact with the powder to compress the powder.

[0087] The machine may be provided with an interface that allows an operator to adjust a set of operating parameters to adapt the pressing process to the material and product being formed. For example, a database may be provided containing adjustment parameters identified and set by the operator for different types of materials.

[0088] In one example, the device 1 includes a carriage 12. The carriage 12 is movable back and forth along the working direction WD. In one example, the pickup device 11 and the supply device 5 are connected to the carriage 12. In one example, the pickup device 11 is arranged upstream of the supply device 5 in the forward direction. The forward direction is defined as from the supply position toward the discharge opening O. Furthermore, at the pickup position of the pickup device 11, the supply device 5 is arranged in the supply position. At the transport position of the pickup device, the supply device 5 is arranged in the discharge position. For example, the carriage travels on the supply surface 9.

[0089] In one example, the device 1 includes a pair of sliding bars 14. The sliding bars 14 extend in the longitudinal direction. The sliding bars 14 are spaced apart from one another along a first horizontal axis H1. Each sliding bar has a first end 14A and a second end 14B. The first horizontal axis is perpendicular to a second horizontal axis H2. The second horizontal axis H2 extends along the working direction WD. The carriage 12 is configured to travel back and forth on the sliding bars along the working direction WD.

[0090] The device includes a plurality of longitudinal bearings. The device also includes a plurality of longitudinal wheels 15. The longitudinal wheels are arranged on each sliding bar 14 along the working direction WD. The longitudinal wheels are configured to support the weight of the carriage 12 along the sliding bar. A longitudinal bearing rotatably supports each longitudinal wheel 15 associated with the carriage 12, allowing the carriage 12 to travel along the sliding bar 14. In one example, the device includes a pair of scraper elements 18 arranged along the sliding direction of the wheels and located upstream and downstream of the wheels in the direction of travel. The scraper elements 18 are in sliding contact with the sliding bar 14 on which each wheel rolls. The scraper elements 18 function to keep the surface of the sliding bar 14 on which the wheels roll clean. Preferably, the scraper elements, or at least the parts thereof that slide on the sliding bar 14, are made of plastic. This has the advantage of preventing contamination.

[0091] The device further includes lateral wheels 16. The device further includes a plurality of lateral bearings. The lateral bearings rotatably support corresponding lateral wheels 16 that function to align the carriage 12 along the working direction WD in which the carriage 12 moves. For example, a lateral wheel is disposed at the first end 14A and the second end 14B of each sliding bar 14. The lateral wheels are disposed at a 90-degree angle relative to the longitudinal wheels 15.

[0092] Preferably, the lateral wheels 16 are made of vulcanized rubber or coated with vulcanized rubber, and the longitudinal wheels 15 are made of (carburized) steel. This has the advantage of preventing the generation of dust and particles that could contaminate the product being processed (i.e., the cathode powder being compressed in the press). Carburized steel also ensures a long service life, even though the longitudinal wheels support the weight of the carriage.

[0093] Once again, one or more (or all) of the lateral wheels 16 are provided with a corresponding pair of scraper elements 18, as described above for the longitudinal wheels. The scrapers of the lateral wheels have the function of cleaning the guides on which they roll. Once again, the fact that the scraper elements, or at least those parts which slide on the respective guides, are preferably made from plastic therefore has the advantage of preventing the possibility of contaminants being generated.

[0094] In one example, at the pickup position of the pickup device 11, the bottom wall 301 moves upward along the vertical direction V. Furthermore, when the pickup device 11 reaches the pickup position, the side wall 302 moves downward along the vertical direction V.

[0095] In this manner, the carriage moves between different positions. In the initial position, the feeder 5 is in the loading position. In this position, the passage 501 of the feeder 5 is vertically aligned with the hopper to receive the charge. In this position, the pickup device is located upstream of the molding cavity 4. Also in the initial position, the lower and upper dies are in the pressing position. In the pressing position, the lower punch 303 is lowered to form the molding cavity 4, and the upper punch is inserted into the molding cavity to compress the raw material. Thus, while one slab 2 is being formed in the molding cavity 4, the feeder 5 is in the feeding position to receive the charge to be compressed to form the slab in the next cycle. Once the slab is formed, the lower and upper dies move to the open position (FIG. 1). Also, the lower punch 303 moves upward along the vertical direction V to lift the formed slab to the height of the feed surface 9. In one example, in the transfer position of the pickup device, the side walls 302 move downward. More specifically, the lowering of the side walls occurs simultaneously with the raising of the bottom wall. In this position, the carriage 12 advances in the working direction WD, and the pickup device is in the pickup position (Figure 2). As the carriage 12 moves in the working direction, the powdered raw material is transported along the feed surface 9 toward the molding cavity 4. The carriage then advances in the working direction. The slab gripped by the pickup device 11 is moved toward the outlet. When the pickup device is at the discharge port O, the feed device 5 is in the discharge position. In this position, the lower punch 303 and the upper surface 3041 are in the alignment position, and the passage 501 of the feed device 5 is vertically aligned with the bottom wall 301. In one example, after the charge is lowered to the bottom wall, the carriage 12 advances in the working direction WD. In this position, both the feed device and the pickup device are located at the discharge port (Figure 3). In this position, the mold is still open. The carriage then retreats to return to its initial position. When the carriage 12 retreats along the working direction, the mold is still in the open position, and the feed device 5 smooths the powdered raw material inside the molding cavity.

[0096] At this time, the lower and upper dies move to the pre-press position (Figure 4). In one example, at this position, the suction system is activated. As the carriage retracts, the feeder 5 evens out the charge. The dies then move to the press position to form the slab (Figure 5).

[0097] The apparatus includes a particle suction system. The particle suction system removes airborne particles. More specifically, the particle suction system includes a first hood 17A and a second hood 17B. The first and second hoods are connected to the upper mold 6. The first hood is disposed upstream of the molding cavity 4 in the direction of travel AD. The direction of travel AD is defined as from the inlet I to the outlet O. The first hood removes airborne particles from around the molding cavity 4. The second hood is disposed downstream of the molding cavity 4 in the direction of travel. The second hood removes airborne particles from around the discharge port. In one example, the second hood is vertically movable. The second hood is also horizontally movable. In one example, the second hood is activated when the mold is in the pressing position.

[0098] In one example, the apparatus includes a heating system. The heating system is connected to the lower mold 3. The heating system is also connected to the upper mold. The heating system maintains the mold at a predetermined temperature. The heating system may be a resistance heating system. [Prior art documents] [Patent documents]

[0099] [Patent Document 1] Japanese Patent Application Publication No. 2019-175697 [Patent Document 2] U.S. Patent Application Publication No. 3,657,917

Claims

1. An apparatus (1) for producing a slab (2) from a powdered raw material, the powdered raw material being a positive electrode active material for a rechargeable battery, the apparatus comprising: a lower mold (3) defining a molding cavity (4); a feeding device (5) for receiving the powdered raw material charge and feeding the charge into the forming cavity (4); an upper die (6) having an upper punch (601) and movable along a vertical direction (V) relative to the lower die (3) between an open position and a pressing position; a sealing mechanism (7) configured to keep the molding cavity (4) and the surrounding air space airtight when the upper mold (6) and the lower mold (3) are in the pre-press position and the press position; a suction system configured to suction air from the molding cavity at a pre-press position of the upper and lower dies and to maintain a negative pressure within the molding cavity at a press position of the upper and lower dies; Equipped with In the open position, the upper punch (601) is separated from the lower die (3) to secure a space for filling the filling material into the molding cavity (4); In the pressing position, the upper punch (601) is inserted into the forming cavity (4) to compress the filler to form a slab (2); The upper die (6) and the lower die (3) are movable to a pre-press position vertically interposed between the open position and the press position; In the pre-press position, the forming cavity (4) is closed by the upper punch (601), preventing the filling from moving out of the forming cavity (4), but at the same time being in air communication with the surrounding air space. Device.

2. The lower mold (3) includes a bottom wall (301) and a side wall (302) that cooperates with the bottom wall to define the molding cavity (4); The bottom wall and the side wall are movable relative to each other along a vertical direction (V).

2. The device (1) according to claim 1.

3. The lower mold (3) includes a lower punch (303) that defines the bottom wall (301), and a lower block (304) that defines the side wall (302) and has an upper surface (3041) that extends along a horizontal plane perpendicular to the vertical direction (V), the lower punch (303) and the lower block (304) are relatively movable along the vertical direction (V) between an alignment position and an offset position; The alignment position is a position where the bottom wall (301) is flush with the top surface (3041) and the bottom wall (301) and the top surface (3041) are located in the same supply plane (8); The offset position is a position where the bottom wall (301) is positioned downward relative to the top surface (3041) to define a molding cavity (4).

3. The device (1) according to claim 2.

4. a supply surface (9) extending along said supply plane (8), the feeding device (5) defines a vertically extending passage (501) and is movable along a working direction (WD) parallel to the feeding surface (9) in sliding contact with the feeding surface (9) between a loading position (5) and a discharge position (5), the loading position (5) being a position for receiving the charge of the powdered raw material, and the discharge position being a position in which the passage (501) is vertically aligned with the bottom wall (301), and in the discharge position the charge is held within a space enclosed by the passage and the bottom wall; 4. The device (1) according to claim 3.

5. an outlet (O) into which the formed slab (2) is fed; a pickup device (11) movable along the working direction (WD) between a pickup position and a conveying position, the pickup position being a position where the pickup device (11) grips the formed slab, and the conveying position being a position where the pickup device conveys the slab to the outlet (O); The device (1) according to claim 4, further comprising:

6. A carriage (12) configured to move forward and backward along the working direction (WD), The pickup device (11) and the supply device (5) are connected to the carriage (12); the pick-up device is arranged upstream of the supply device in a forward direction defined as a direction from the filling position to the outlet (O); At the pick-up position of the pick-up device, the supply device is arranged at a filling position, and at the transport position of the pick-up device, the supply device is arranged at the discharge position.

6. The device (1) according to claim 5.

7. In the pickup position of the pickup device (11), the bottom wall (301) is configured to move upward along the vertical direction (V), and the side wall (302) is configured to move downward along the vertical direction.

7. The device according to claim 5 or 6.

8. a pair of sliding bars (14) extending longitudinally and spaced apart along a first horizontal axis (H1), each having a first end (14A) and a second end (14B), the first horizontal axis being perpendicular to a second horizontal axis (H2) along the working direction (WD), and the carriage (12) being configured to slide forward and backward on the sliding bars (14) and along the working direction (WD); a plurality of vertical wheels (15) arranged along each of the sliding bars (14) in the working direction (WD), supporting the weight of the carriage (12) along the sliding bars and enabling the carriage to move back and forth in the working direction (WD); a plurality of lateral wheels (16) arranged at both ends of each sliding bar (14), rotated 90 degrees relative to the longitudinal wheels (15), and configured to hold the carriage (12) so as to move straight along the working direction (WD) as the carriage (12) moves, the longitudinal wheels and the lateral wheels being made of rubber; 8. The device (1) according to claim 6 or 7, comprising:

9. The bottom wall (301) is vertically movable relative to the side wall (302). A device (1) according to any one of claims 2 to 8.

10. an inlet (I) for receiving the powdered raw material; an outlet (O) for receiving the formed slab; a particle suction system having a first hood (17A) and a second hood (17B) connected to the upper mold (6) and configured to remove airborne particles; Equipped with the first hood is arranged upstream of a direction of travel (AD) of the forming cavity (4) defined as a direction from the inlet (I) to the outlet (O), and is defined in the direction from the inlet (I) to the outlet (O), and is configured to remove suspended particles around the forming cavity (4); The second hood is disposed downstream of the forming cavity (4) in the direction of travel (AD) and is configured to remove airborne particles from around the outlet (O). A device (1) according to any one of claims 1 to 9.

11. The lower mold (3) includes a plurality of molding cavities (4) arranged to form an array of the molding cavities (4), The upper die (6) includes a plurality of upper punches (601), Each upper punch is configured to cooperate with a corresponding forming cavity to form a respective slab (2) of the plurality of slabs; A device (1) according to any one of claims 1 to 10.

12. a heating system connected to the lower mold (3) and the upper mold (6) for maintaining the lower mold (3) and the upper mold (6) at a predetermined temperature; A device (1) according to any one of claims 1 to 11.

13. The lower mold (3) includes a bottom wall (301) and a side wall (302) that cooperates with the bottom wall to define a molding cavity; The bottom wall (301), the side wall (302) and the upper punch (601) are made of stainless steel. A device (1) according to any one of claims 1 to 12.

14. The upper punch (601) and the lower punch (303) each have a first layer (L1) and a second layer (L2) detachably connected to the first layer; the second layer is in contact with the powdered raw material; the second layer of the upper mold and the second layer of the lower mold are formed from stainless steel; 13. The device (1) according to claim 12.

15. A method for producing a slab (2) from a powdery raw material, the powdery raw material being a positive electrode active material for a rechargeable battery, The method comprises: placing a lower mold (3) to define a molding cavity (4); A step of placing an upper punch (601) on an upper die (6); a step of moving the upper mold (6) and the lower mold (3) relative to each other along a vertical direction (V) between an open position and a pressing position to compress the powdered raw material charge and form the slab (2); feeding the charge of powdered raw material into the molding cavity via a feeding device (5) when the upper mold (6) and the lower mold (3) are in the open position; placing the upper die (6) and the lower die (3) at a position intermediate between the open position and the press position, and moving the upper die and the lower die to a pre-press position, in which the molding cavity (4) is closed by the upper punch (601) to prevent the filler from moving out of the molding cavity (4), but at the same time is in air communication with the surrounding air space; a step of keeping the molding cavity (4) and the air space around it airtight when the upper mold (6) is in the pre-press position and the press position; a step of sucking air from the molding cavity and pressing the filled material while maintaining a negative pressure in the molding cavity when the upper mold and the lower mold are at the pre-press position; A method comprising:

16. disposing the bottom wall (301) and a side wall (302) that cooperates with the bottom wall to define the molding cavity (4) on the lower mold (3); a step of moving the bottom wall (301) and the side wall (302) relative to each other along the vertical direction (V); a step of disposing a lower punch (303) in the lower mold (3) and defining the bottom wall (301) together with a lower block (304), the lower block (304) defining the side wall (302) and having an upper surface (3041) extending along a horizontal plane perpendicular to the vertical direction (V), the side wall (302) defining a molding cavity (4) together with the bottom wall (301); a step of moving the lower punch (303) and the lower block (304) relative to each other along the vertical direction (V) between an alignment position and an offset position, the alignment position being a position where the bottom wall (301) is flush with the top surface (3041) so that the bottom wall (301) and the top surface (3041) are located on the same feed plane (8), and the offset position being a position where the bottom wall (301) is positioned below the top surface (3041) and is positioned so as to define the molding cavity (4); moving the bottom wall (301) vertically relative to the side wall (302); The method of claim 15, comprising:

17. providing said supply device (5) with a vertically arranged passage (501); moving said feeding device (5) into sliding contact with a feeding surface (9) and moving said feeding device (5) along a working direction (WD) parallel to said feeding surface, said feeding surface extending along said feeding plane (8), between a feeding position and an unloading position; Filling the supply device (5) with the filling material in the filling position; In the discharge position, the passage (501) is aligned vertically with the bottom wall (301) so that the charge is retained within a volume enclosed by the passage and the bottom wall; 17. The method of claim 16, comprising:

18. Positioning a pick-up device (11); moving the pick-up device along a working direction (WD) between a pick-up position and a transfer position; gripping the formed slab (2) by the pick-up device (11) at the pick-up position; At the transfer position, feeding the slabs to an outlet (O) via the pick-up device (11); connecting the pick-up device (11) and the supply device (5) to a carriage (12); moving the carriage (12) back and forth along the working direction (WD); positioning the pick-up device (11) upstream of the supply device (5) in a forward direction defined from the filling position towards the outlet; placing the supply device (5) at the supply position when the pick-up device (11) is at the pick-up position; placing the supply device (5) at the ejection position when the pick-up device (11) is at the ejection position; 20. The method of claim 17, comprising:

19. the step of suctioning air from the molding cavity is initiated when the upper mold and the lower mold are at the pre-press position and is continued while the upper mold moves vertically downward from the pre-press position to a position where the upper mold contacts the powder in the molding cavity.

19. The method of any one of claims 15 to 18.

20. Intake channels are arranged in the lower mold and the upper mold, and are designed to suck air from the molding cavity, so that air is sucked from the upper and lower parts of the molding cavity; 20. The method of any one of claims 15 to 19.

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