WO2022056983A1 - 一种极片成型的挤出头及包括其的成型装置及其成型方法和制备方法 - Google Patents

一种极片成型的挤出头及包括其的成型装置及其成型方法和制备方法 Download PDF

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Publication number
WO2022056983A1
WO2022056983A1 PCT/CN2020/121456 CN2020121456W WO2022056983A1 WO 2022056983 A1 WO2022056983 A1 WO 2022056983A1 CN 2020121456 W CN2020121456 W CN 2020121456W WO 2022056983 A1 WO2022056983 A1 WO 2022056983A1
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WO
WIPO (PCT)
Prior art keywords
extrusion
pole piece
optionally
molding
extrusion head
Prior art date
Application number
PCT/CN2020/121456
Other languages
English (en)
French (fr)
Inventor
邓辉辉
曹浪
孙佩玲
王品高
张俊
祝媛
***
刘金成
Original Assignee
惠州亿纬锂能股份有限公司
惠州亿纬创能电池有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Priority claimed from CN202010969643.2A external-priority patent/CN112072063A/zh
Priority claimed from CN202022014548.5U external-priority patent/CN212625651U/zh
Application filed by 惠州亿纬锂能股份有限公司, 惠州亿纬创能电池有限公司 filed Critical 惠州亿纬锂能股份有限公司
Priority to EP20953840.4A priority Critical patent/EP4152430A1/en
Priority to US18/014,093 priority patent/US20230268479A1/en
Publication of WO2022056983A1 publication Critical patent/WO2022056983A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0433—Molding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/3001—Extrusion nozzles or dies characterised by the material or their manufacturing process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/305—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/256—Exchangeable extruder parts
    • B29C48/2562—Mounting or handling of the die
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the application belongs to the technical field of pole piece preparation, and relates to an extrusion head for pole piece forming and a forming device including the same, as well as a forming method and preparation method thereof, for example, an extrusion head for forming a special-shaped pole piece and an extrusion head including the same.
  • the concept of smart city is deeply rooted in the hearts of the people, and the application modes of batteries tend to be diversified.
  • more and more designs and products are developed in special-shaped batteries for intelligent monitoring, intelligent on smart wear and medical devices.
  • the battery shape of the special-shaped battery can present regular or irregular geometric shapes, including coin battery, square battery, hexagonal battery, triangular battery, sector battery, etc.
  • the carbon cathode structure used in special-shaped batteries is different from that of common cylindrical batteries, and requires battery pole pieces of different specifications and shapes.
  • a square battery uses a rectangular carbon sheet with a thickness of 1-3mm
  • a coin-type battery uses a circular carbon sheet with a diameter of 3-30mm and a thickness of 1-4mm or a circular carbon sheet
  • a fan-shaped battery requires a certain arc, diameter and thickness of carbon. piece.
  • This type of carbon sheet has two common requirements. One is that the thickness of the pole piece is extremely high. If the thickness of the pole piece exceeds the standard, the edge film will collapse during the assembly process and cause a short circuit, which will occur during long-term high-temperature discharge. The shell is swollen. If the thickness of the pole piece is lower than the standard, the contact between the positive electrode, the edge film and the lithium strip after assembly is not good, showing a poor current collecting effect. The second is that the cross-section of the positive carbon sheet needs to be flat without burrs, and has a certain strength, which is beneficial to the assembly process of the polar sheet.
  • the first molding method is stamping molding, that is, firstly, the positive electrode material, conductive agent, binder, etc. are mixed, granulated into a particle positive electrode with a diameter of 2-4nm, flattened in the mold, and pressed directly under pressure.
  • CN104201381B A method of manufacturing a lithium ion battery, comprising the following steps: respectively making a positive electrode sheet and a negative electrode sheet: mixing and stirring the binder, the conductive agent powder, the positive electrode active material or the negative electrode active material powder, and heating to a 80-200°C, put it into a prefabricated mold with a built-in metal mesh, and apply a pressure of 3-20 MPa to the powder in the mold to shape it, respectively to obtain a positive electrode molded body and a negative electrode molded body; one end of the metal mesh is formed with The conductive lugs protruding out of the sides of the positive electrode molding body or the negative electrode molding body; the positive electrode molding body and the negative electrode molding body are immersed in a ceramic solution, and the surfaces of the positive electrode molding body and the negative electrode molding body are coated with a surface after drying.
  • the positive electrode molded body and the negative electrode molded body are immersed in a polymer solution, and after drying, a polymer polymer layer is formed on the surface of the positive electrode molded body and the negative electrode molded body to obtain a positive electrode sheet and a negative electrode sheet.
  • the pole piece prepared by this stamping and forming process has certain structural deficiencies. The reason is that the formed positive electrode particles are only squeezed together by physical action, and the pole piece has low strength. When the current collector is assembled, there is a risk of fragmentation of the pole pieces when the current collector is installed, which is not conducive to automatic assembly. In addition, before pressing, if the positive electrode is unevenly laid in the mold, the thickness of the positive electrode sheet after molding is not uniform, and even cannot be formed.
  • the second molding method is roll molding, that is, the positive electrode material, conductive agent, adhesive, etc. are mixed evenly, and the mixed material is immersed in an ethanol solution after drying, and the positive electrode absorbs the ethanol solution due to the presence of the adhesive. After showing a certain strength, it is then rolled into a pole piece of a certain thickness, dried and then passed through a stamping and cutting equipment to obtain positive pole pieces of different shapes.
  • CN110407300A discloses a method for preparing a porous carbon mixed carbon black rolling electrode material, comprising the following steps: (1) ultrasonically dispersing a mixed system composed of porous carbon, carbon black, polytetrafluoroethylene and ethanol uniformly to obtain Mixing system A, wherein the ratio of the mass of porous carbon, the mass of carbon black and the volume of ethanol is (4-12) mg: (10-30) mg: (1-3) ml, and mixing system A is stirred until viscous to obtain a preliminary modified catalytic layer of the rolled electrode material; ultrasonically disperse the mixed system composed of carbon black, polytetrafluoroethylene and ethanol uniformly to obtain a mixed system B, and stir the mixed system B to a viscous state to obtain a preliminary The modified rolled electrode material diffusion layer; (2) the preliminary modified rolled electrode material catalytic layer and the preliminary modified rolled electrode material diffusion layer are respectively rolled to the upper surface and the upper surface of the metal mesh. On the lower surface, a prelim
  • the disadvantage of this molding method is that a large amount of organic solvent ethanol is used as the positive electrode molding agent in the process, and the low flash point of ethanol has certain safety risks in the operation and drying process.
  • the positive electrode after absorbing ethanol is wet and soft, and it is difficult to guarantee the thickness uniformity of the pole piece after rolling in the roller press.
  • the rapid volatilization of ethanol may easily lead to the phenomenon of powder drop and hollowing of the pole piece.
  • the purpose of this application is to provide an extrusion head for forming a pole piece and a forming device comprising the same, a forming method and a preparation method thereof, which are suitable for the extrusion molding of the pole piece, especially suitable for the extrusion molding of the special-shaped pole piece, mixing
  • the good electrode mixture is extruded into a certain thickness of the electrode by screw. After drying, it can directly pass through a specific cutting die to complete the production of different types of special battery electrode.
  • the production efficiency is obviously improved, and at the same time, the obtained pole pieces have a uniform thickness and a low powder drop rate, and the quality of the pole pieces is significantly improved.
  • the present application provides an extrusion head for forming a pole piece, the extrusion head includes an extrusion head casing, and a through extrusion head is provided inside the extrusion head casing along the extrusion direction. aisle.
  • the extrusion channel is divided into a transition cavity and a forming cavity which are connected to each other in sequence along the extrusion direction, and the diameter of the inner wall annular surface of the transition cavity is tapered along the extrusion direction.
  • the application provides an extrusion head, which is suitable for the extrusion molding of the pole piece, especially for the extrusion molding of the special-shaped pole piece.
  • the transition cavity with tapered diameter can effectively improve the thickness uniformity of the pole piece and help reduce the pole piece.
  • the powder drop rate of the sheet has a certain shaping effect on the extruded pole piece. It should be noted that this application does not make specific requirements or special restrictions on the shape of the transition cavity with a tapered diameter. Taper, Surface Taper, or Jagged Taper, etc.
  • the forming cavity can be designed with different cross-sectional shapes according to requirements, so as to obtain special-shaped pole pieces with different cross-sectional shapes. The powder drop rate is lower and the stress distribution in the pole piece is more uniform.
  • the cross-sectional shape and cross-sectional size of the pole piece can be adjusted freely only by replacing the extrusion head, and the pole piece can also be effectively guaranteed during the drying process of the pole piece.
  • the shrinkage ratio will not cause the unfavorable situation that the pole piece is powdered or even broken due to stress concentration.
  • the extrusion head shell is divided into a conical section and a straight section that are butted in sequence along the extrusion direction, and the small end face of the conical section is straight with the The segments are butted, the transition cavity is opened in the tapered segment along the extrusion direction, and the molding cavity is opened in the straight segment along the extrusion direction.
  • a flange is provided at the large end face of the tapered section, and at least two threaded holes are circumferentially provided on the outer edge of the flange.
  • the outer edge of the flange is provided with four threaded holes equidistantly in the circumferential direction.
  • the threaded holes are countersunk threaded holes.
  • the inner wall annular surface of the transition cavity is a stepped structure with a tapered diameter.
  • the transition cavity of the stepped structure with the tapered diameter can further improve the thickness uniformity of the pole piece and help reduce the powder drop rate of the pole piece, and has a certain shaping effect on the extruded pole piece.
  • the stepped structure of the transition cavity includes at least two layers of horizontal stepped surfaces along the extrusion direction, and at least two layers of vertical stepped surfaces connected to the horizontal stepped surfaces in the radial direction.
  • the order of the stepped structure has an impact on the thickness consistency of the final extruded pole piece.
  • the stepped structure of the transition cavity includes three layers of horizontal stepped surfaces and three layers of vertical stepped surfaces connected to the horizontal stepped surfaces.
  • the last vertical step surface in the radial direction is connected to the molding cavity through an inclined plane.
  • the molding cavity is a flat channel.
  • the cross-section of the forming cavity is rectangular, wave-shaped, arc-shaped or continuously concave-convex city wall shape.
  • the present application provides a pole piece forming device, the forming device is a screw extruder, comprising an extruding device casing and a screw coaxially arranged inside the extruding device casing.
  • One end of the casing of the extrusion device is detachably fixed with the extrusion head according to the first aspect.
  • the forming device provided in this application is mainly suitable for the forming process of the pole piece.
  • the existing punching machine and roller press are replaced with a screw extruder, and the pole piece is mixed and extruded by screw extrusion.
  • the active material, binder and solvent can be further mixed evenly, and the extruded pole piece maintains a relatively complete internal structure and exhibits relatively high electrical conductivity.
  • the pole piece has the same shrinkage ratio in the subsequent drying process, ensuring the thickness uniformity of the pole piece, and at the same time, the pole piece has excellent liquid absorption capacity, and on the basis of maintaining a high discharge capacity, it significantly reduces the battery in different discharges.
  • the transition cavity with tapered diameter can further improve the thickness uniformity of the pole piece and help to reduce the powder drop rate of the pole piece, and has a certain shaping effect on the extruded pole piece.
  • the forming cavity can be designed with different cross-sectional shapes according to requirements, so as to obtain special-shaped pole pieces with different cross-sectional shapes. The powder rate is lower and the stress distribution in the pole piece is more uniform.
  • the pole piece of this molding method does not need any conductive base for support, and can also maintain a certain flexibility and strength.
  • the carbon piece can be automatically clamped and assembled by the equipment, and there is no problem when installing the current collector. The micropowder falls off the separator, reducing the risk of micro-short circuit caused by the pole piece micropowder.
  • the mixed pole piece mixture is extruded into a certain thickness of pole piece by screw, and after drying, it can directly pass through a specific cutting die to complete the production of different types of special shaped pole pieces. Compared with other preparation methods of pole pieces, the production efficiency is significantly improved. Specifically in:
  • the thickness and width of the pole piece can be controlled, and the prepared pole piece shows excellent thickness uniformity, which can be applied to most special-type battery poles piece.
  • the pole piece prepared by this preparation method does not need any conductive substrate for support, and can also maintain a certain flexibility and strength. During the battery assembly process, the pole piece can be automatically clamped and assembled by the equipment, and the current collector can be installed. There will be no micro-powder falling off the separator, reducing the risk of micro-short circuit caused by the pole piece micro-powder.
  • the pole piece mixture can be further mixed evenly with the active material, binder and solvent through sufficient kneading action, and the extruded pole piece maintains a relatively complete internal structure, showing At the same time, the pole piece has excellent liquid absorption ability, which can significantly reduce the difference of the discharge capacity of the battery under different discharge postures (upright, inverted) on the basis of maintaining a good discharge capacity.
  • a feeding bin is provided at one end of the shell of the extrusion device away from the extrusion head, and the pole piece mixture is fed into the shell of the extrusion device through the feeding bin, and mixed and conveyed by a screw. to the extrusion head and extruded from the extrusion head.
  • one end of the screw close to the feeding bin is connected to a drive motor in a transmission, and the drive motor is used to drive the screw to rotate.
  • the casing of the extrusion device and the extrusion head are detachably connected through a flange.
  • the present application provides a method for forming a pole piece, using the forming device described in the second aspect to extrude the pole piece mixture, and the forming method includes:
  • the pole piece mixture is sent to the shell of the extrusion device through the feeding silo, mixed evenly by the screw, and then transported to the extrusion head and extruded from the extrusion head.
  • the extrusion frequency is 30 to 50 Hz, such as 30 Hz, 32 Hz, 34 Hz, 36 Hz, 38 Hz, 40 Hz, 42 Hz, 44 Hz, 46 Hz, 48 Hz or 50 Hz, but not only Limitation to the recited values applies equally to other non-recited values within the range of values.
  • the extrusion temperature is 30-60°C, such as 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C °C, 52°C, 54°C, 56°C, 58°C, or 60°C, but are not limited to the recited values, and other unrecited values within the range of values apply equally.
  • the application provides a method for preparing a pole piece, the preparation method comprising:
  • the active material, the binder and the solvent are mixed to form a pole piece mixture, and the pole piece is obtained after forming, drying and punching, wherein the forming process is realized by the forming method described in the third aspect.
  • the present application provides a simple, high-efficiency and safe method for forming a pole piece.
  • the mixed pole piece mixture is extruded with a screw to form a pole piece of a certain thickness, and after drying, it is directly passed through a specific cutting die.
  • the thickness and width of the pole piece can be controlled, and the prepared pole piece shows excellent thickness uniformity, which can be applied to most special-type battery poles piece.
  • the pole piece prepared by this preparation method does not need any conductive substrate for support, and can also maintain a certain flexibility and strength. During the battery assembly process, the pole piece can be automatically clamped and assembled by the equipment, and the current collector can be installed. There will be no micro-powder falling off the separator, reducing the risk of micro-short circuit caused by the pole piece micro-powder.
  • the pole piece mixture can be further mixed evenly with the active material, binder and solvent through sufficient kneading action, and the extruded pole piece maintains a relatively complete internal structure, showing At the same time, the pole piece has excellent liquid absorption ability, which can significantly reduce the difference of the discharge capacity of the battery under different discharge postures (upright, inverted) on the basis of maintaining a good discharge capacity.
  • the active material includes one or at least two of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes, manganese dioxide, carbon fluoride or FeS 2
  • the combination for example, can be the combination of acetylene black and Ketjen black, the combination of Ketjen black and carbon nanotubes, or the combination of acetylene black and carbon nanotubes, but it is not limited to the listed combinations. The listed combinations also apply.
  • the adhesive is a polytetrafluoroethylene emulsion.
  • the solid content of the polytetrafluoroethylene emulsion is 50-60wt%, for example, it can be 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt% , 59 wt % or 60 wt %, but are not limited to the recited values, and other unrecited values within the numerical range are also applicable.
  • the solvent is an aqueous solution of isopropanol or isopropanol.
  • the mass ratio of the active material, the binder and the solvent is 1:(0.1-0.3):(3-6), for example, it can be 1:0.1:3, 1:0.1:4, 1: 0.1:5, 1:0.1:6, 1:0.2:3, 1:0.2:4, 1:0.2:5, 1:0.2:6, 1:0.3:3, 1:0.3:4, 1:0.3: 5 or 1:0.3:6, but not limited to the recited values, other non-recited values within this range of values also apply.
  • the mixing process is carried out in a mixing device.
  • the stirring time of the described mixing process is 5 to 10 minutes, such as 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes, but not limited to the listed values. The same applies to numerical values.
  • the rotating speed of the stirring paddle of the mixing device is 100-300r/min, for example, it can be 100r/min, 120r/min, 140r/min, 160r/min, 180r/min, 200r/min, 220r/min min, 240 r/min, 260 r/min, 280 r/min or 300 r/min, but not limited to the recited values, and other unrecited values within the range of values are also applicable.
  • the molding process is performed in a molding device.
  • the extrusion frequency of the molding device is 30 to 50 Hz, such as 30 Hz, 32 Hz, 34 Hz, 36 Hz, 38 Hz, 40 Hz, 42 Hz, 44 Hz, 46 Hz, 48 Hz or 50 Hz, but not limited to the listed ones. Numerical values, other non-recited values within the numerical range also apply.
  • the extrusion temperature of the molding device is 30 to 60°C, such as 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C °C, 50°C, 52°C, 54°C, 56°C, 58°C, or 60°C, but are not limited to the recited values, and other unrecited values within the range of values apply equally.
  • the drying process is carried out in a forced air oven.
  • the drying temperature is 120-160°C, such as 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C or 160°C, but not limited to Recited values apply equally well to other non-recited values within that range.
  • the drying time is 5-10h, such as 5.0h, 5.5h, 6.0h, 6.5h, 7.0h, 7.5h, 8.0h, 8.5h, 9.0h, 9.5h or 10.0h, However, it is not limited to the recited numerical values, and other unrecited numerical values within the numerical range are equally applicable.
  • the punching process is performed in an automatic cutting and punching device.
  • the thickness of the punched pole piece is 1 to 4 mm, for example, it can be 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm or 4.0 mm, but it is not limited to the listed values, The same applies to other non-recited values within this numerical range.
  • the width of the pole piece after punching is 20 to 50 mm, for example, it can be 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm or 50 mm, but it is not limited to the listed values, and other values are not listed within this value range. The same value applies.
  • the system refers to an equipment system, a plant system or a production plant.
  • the extrusion head provided by this application is especially suitable for the extrusion molding process of the pole piece.
  • the transition cavity with a tapered diameter can further improve the thickness uniformity of the pole piece and help reduce the powder drop rate of the pole piece.
  • the outgoing pole piece has a certain shaping effect.
  • the forming cavity can be designed with different cross-sectional shapes according to requirements, so as to obtain special-shaped pole pieces with different cross-sectional shapes.
  • the powder rate is lower and the stress distribution in the pole piece is more uniform. It only needs to replace the extrusion head to achieve free adjustment of the cross-sectional shape and cross-sectional size of the pole piece, and it can also effectively ensure that the pole piece has the same size during the drying process of the pole piece.
  • the shrinkage ratio will not cause the unfavorable situation that the pole piece is powdered or even broken due to stress concentration.
  • the pole piece prepared by the preparation method provided in this application does not need any conductive substrate as a support, and can also maintain a certain flexibility and strength. During the battery assembly process, the pole piece can be automatically clamped and assembled by the equipment, When the current collector is installed, no micro-powder will fall off the diaphragm, which reduces the risk of micro-short circuit caused by the micro-powder of the pole piece.
  • the pole piece mixture can be further mixed evenly with the active material, binder and solvent through sufficient kneading action, and the extruded pole piece maintains a relatively complete internal structure, showing At the same time, the pole piece has excellent liquid absorption ability, which can significantly reduce the difference of the discharge capacity of the battery under different discharge postures (upright, inverted) on the basis of maintaining a good discharge capacity.
  • FIG. 1 is a schematic structural diagram of a molding device provided by a specific embodiment of the present application.
  • FIG. 2 is a side view of an extrusion head provided by an embodiment of the present application.
  • FIG. 3 is a side view of an extrusion head provided by an embodiment of the present application.
  • 1-extrusion head 2-extrusion device shell; 3-feeding bin; 4-screw; 5-threaded hole; 6-extrusion channel; 61-transition cavity; 62-forming cavity.
  • the terms “arranged”, “connected” and “connected” should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; it can be mechanical connection or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be internal communication between two components.
  • the specific meanings of the above terms in the present application can be understood through specific situations.
  • the present application provides an extrusion head 1 for forming a pole piece.
  • the extrusion head 1 is shown in FIG. 1 , FIG. 2 and FIG.
  • a through extrusion channel 6 is opened in the casing of the tap 1 along the extrusion direction.
  • the extrusion channel 6 is divided into a transition cavity 61 and a molding cavity 62 which are connected in sequence along the extrusion direction.
  • the diameter of the inner wall of the transition cavity 61 is tapered, and the tapered transition cavity 61 can further improve the pole piece.
  • the thickness uniformity is good for reducing the powder drop rate of the pole piece, and it has a certain shaping effect on the extruded pole piece.
  • the present application does not make specific requirements or special limitations on the shape of the transition cavity 61 with a tapered diameter. It can be exemplarily tapered by a slope, tapered by a curved surface, or tapered in a zigzag shape, etc., but a stepped tapered can be selected. , including at least two layers of horizontal stepped surfaces along the extrusion direction, and at least two layers of vertical stepped surfaces connected to the horizontal stepped surfaces in the direction perpendicular to the extrusion direction.
  • the number of layers of the stepped surface has an impact on the thickness consistency of the final extruded pole piece. When the number of layers of the stepped surface is large, the material gathering force in the transition cavity 61 is larger, smoother, and better in thickness consistency.
  • the stepped structure of the transition cavity 61 includes three layers of horizontal stepped surfaces and three layers of vertical stepped surfaces connected to the horizontal stepped surfaces.
  • the vertical stepped surface of the last layer perpendicular to the extrusion direction is connected to the molding cavity 62 through a bevel.
  • the forming cavity 62 can be designed with different cross-sectional shapes according to requirements, so as to obtain special-shaped pole pieces with different cross-sectional shapes.
  • the powder drop rate is lower and the internal stress of the pole pieces is lower.
  • the distribution is more uniform, and the cross-sectional shape and cross-sectional size of the pole piece can be adjusted freely only by replacing the extrusion head 1.
  • it can also effectively ensure that the pole piece has the same shrinkage ratio, and will not be caused by stress concentration. The unfavorable situation that causes the pole piece to drop powder or even break.
  • the forming cavity 62 is a flat channel, and specifically, the cross section of the forming cavity 62 is a rectangle, a wave shape, an arc shape, a continuous concave and convex city wall shape or other special shapes. It should be noted that the present application does not make specific requirements or limitations on the cross-sectional shape of the forming cavity 62, and those skilled in the art can design the forming cavity 62 with different cross-sections according to the forming requirements of the pole piece.
  • the shell of the extrusion head 1 is divided into a conical section and a straight section that are connected in sequence along the extrusion direction.
  • the small end face of the conical section is butted with the straight section.
  • a transition cavity 61 is opened inside the conical section along the extrusion direction, and the diameter gradually increases.
  • the constricted transition cavity 61 can further improve the thickness uniformity of the pole piece and is conducive to reducing the powder drop rate of the pole piece, and has a certain shaping effect on the extruded pole piece; the interior of the straight section is provided with a forming cavity 62 along the extrusion direction. .
  • the cross-sectional shape and cross-sectional size of the extruded pole piece can be adjusted at will, so as to meet the pole piece shape requirements of different special-shaped batteries. After drying, it can directly pass through a specific cutting die and adjust the size of the molding cavity 62 of the extrusion head 1 to complete the production of different types of special battery pole pieces. It is suitable for most special shapes of pole pieces and shows excellent performance. Thickness uniformity.
  • the large end face of the tapered section is provided with a flange, and the outer edge of the flange is provided with at least two threaded holes 5 in the circumferential direction. Specifically, the outer edge of the flange is provided with four threaded holes 5 at equal intervals in the circumferential direction. .
  • the threaded hole 5 is a countersunk threaded hole.
  • the present application provides a pole piece forming device, the forming device is a screw extruder, as shown in FIG. 1 , comprising a tubular structure extrusion device casing 2 and a coaxial
  • the screw 4 is arranged inside the extrusion device casing 2, and one end of the extrusion device casing 2 is detachably fixed with the extrusion head 1 provided by a specific embodiment.
  • the end of the extrusion device shell 2 away from the extrusion head 1 is provided with a feeding bin 3, and the pole piece mixture is fed into the extrusion device shell 2 through the feeding bin 3, and is mixed and transported to the extrusion head 1 by the screw 4 and is extruded by the extruder.
  • Outlet 1 extrusion molding is a screw extruder, as shown in FIG. 1 , comprising a tubular structure extrusion device casing 2 and a coaxial
  • the screw 4 is arranged inside the extrusion device casing 2, and one end of the extrusion device casing 2 is detachably fixed
  • the extrusion device housing 2 is detachably connected to the extrusion head 1 through a flange.
  • the forming device provided in this application is mainly suitable for the forming process of the pole piece.
  • the existing punching machine and roller press are replaced with a screw extruder, and the pole piece is mixed and extruded by screw extrusion.
  • the pole piece During the extrusion process of the screw 4, after sufficient kneading, the active material, binder and solvent can be further mixed evenly, and the extruded pole piece maintains a relatively complete internal structure, showing a relatively high At the same time, the pole piece has excellent liquid absorption ability, which can significantly reduce the difference of the discharge capacity of the battery under different discharge postures (upright, inverted) on the basis of maintaining a good discharge capacity.
  • the present application provides a method for forming a pole piece, and the above-mentioned forming device is used to extrude the mixed material of the pole piece, and the forming method includes:
  • the pole piece mixture is fed into the shell of the extrusion device through the feeding silo, mixed evenly by the screw, and then transported to the extrusion head and extruded from the extrusion head.
  • the extrusion frequency is 30 ⁇ 50Hz
  • the extrusion temperature is 30 ⁇ 60 °C .
  • the pole piece of this molding method does not need any conductive substrate as a support, and can also maintain a certain flexibility and strength.
  • the application provides a kind of preparation method of pole piece, described preparation method comprises:
  • the active material, the binder and the solvent are sequentially mixed, formed, dried and punched to obtain the pole piece, wherein the forming process is processed by the above forming method.
  • the preparation method provided by the present application has significantly improved production efficiency.
  • the carbon sheet can be automatically clamped and assembled by the equipment, and no micropowder will fall off the separator when the current collector is installed, which reduces the risk of micro-short circuit caused by the pole piece micropowder.
  • the pole piece is mixed in the screw extruder, and after sufficient kneading action, the active material, the conductive agent with high specific surface, the binder and the solvent can be further dispersed evenly, and the extruded pole piece maintains a relatively complete internal structure. , showing relatively high conductivity, and the pole piece has excellent liquid absorption ability, which can significantly reduce the difference in discharge capacity of the battery under different discharge postures (upright, inverted) on the basis of maintaining a good discharge capacity.
  • the present embodiment provides a method for preparing a positive electrode sheet.
  • the preparation method includes mixing, molding, drying and punching in sequence, and specifically includes the following steps:
  • the dried and formed positive electrode sheet is placed in an automatic cutting and punching device, and punched to obtain a finished positive electrode sheet with a size of 20 mm ⁇ 10 mm ⁇ 1 mm.
  • the prepared positive electrode sheets were tested as follows:
  • Powder drop rate test Weigh 30 cut positive electrode pieces, weigh and record the mass as M 1 , place them in the friability tester equipment, set the program running frequency and time, and take out after the equipment program is completed Positive plate, observe whether the integrity of the positive plate is maintained. Sieve off the fine powder, weigh the remaining positive electrode sheet, weigh and record the mass as M 2 , the formula for calculating the powder drop rate is: (M 1 -M 2 )/M 1 ⁇ 100%;
  • the prepared positive electrode sheet is used as the positive electrode of the lithium/thionyl chloride battery, and the discharge capacity deviation of the assembled battery under normal and high temperature conditions is tested.
  • the assembly operation method of the lithium/thionyl chloride battery is as follows: The positive electrode sheet is used as the positive electrode, the metal lithium is used as the negative electrode, the electrolyte is 1.4mol/L thionyl chloride solution of lithium tetrachloroaluminum, and the separator is assembled into a battery cell; The discharge capacity under the condition of constant resistance 1620 ⁇ discharge and cut-off voltage of 2.0V under the condition of high temperature 70°C inverted four states. The test results are shown in Table 2.
  • Thickness uniformity test choose three different points on the same positive electrode sheet, use a thickness meter to accurately test the thickness of the three points on the positive electrode sheet, and calculate the average value as the thickness of the positive electrode sheet.
  • the above-mentioned thickness test is performed on the plates respectively, and the counting formula of thickness uniformity is (L max -L min )/L ave , where L max is the maximum thickness among the 30 positive electrode plates, and L min is the minimum thickness among the 30 positive electrode plates. , L ave is the average thickness of 30 positive electrode sheets, and the calculated thickness uniformity is 1.85%.
  • the present embodiment provides a method for preparing a positive electrode sheet.
  • the preparation method includes mixing, molding, drying and punching in sequence, and specifically includes the following steps:
  • the positive electrode material includes a mass ratio of It is acetylene black and Ketjen black in a ratio of 9:1, and the rotating speed of the stirring paddle of the mixing device is 200 r/min, and stirring for 7 minutes is used to obtain the pole piece mixture;
  • the dried and formed positive electrode sheet is placed in an automatic cutting and punching device, and punched to obtain a finished positive electrode sheet with a size of 30 mm ⁇ 12 mm ⁇ 2 mm.
  • the powder drop rate test and the thickness uniformity test are performed on the prepared positive electrode sheet, and the discharge capacity test is performed on the battery composed of the positive electrode sheet.
  • the powder drop rate test results See Table 1, the discharge capacity test results are shown in Table 2, and the thickness uniformity of the positive electrode sheet is 1.67%.
  • the present embodiment provides a preparation method of a positive electrode sheet, and the preparation method includes mixing, molding, drying and punching performed in sequence, and specifically includes the following steps:
  • the positive electrode material polytetrafluoroethylene emulsion (solid content of 60 wt%) and isopropyl alcohol are added to the mixing device in a mass ratio of 1:0.3:6 for mixing and stirring.
  • the positive electrode material includes a mass ratio of It is 9:1 of acetylene black and carbon nanotubes, and the rotating speed of the stirring paddle of the mixing device is 300 r/min, and stirring for 5 minutes obtains the pole piece mixture;
  • the pole piece mixture is added to the feeding bin 3, sent to the extrusion device from the feeding bin 3, and the pole piece mixture is further fully mixed by rotating and extruding the screw 4, and then pushed out and conveyed to the extrusion head 1. It is extruded and molded by the extrusion head 1, the extrusion frequency is 50Hz, and the extrusion temperature is 30 °C, wherein the extrusion head 1 is shown in Figure 3, and the section of the molding cavity 62 is a continuous concave and convex city wall type positive plate, which is used for fan-shaped battery production;
  • the dried and formed positive electrode sheet is placed in an automatic cutting and punching device, and punched to obtain a finished positive electrode sheet with a size of 50mm ⁇ 15mm ⁇ 4mm.
  • the powder drop rate test and the thickness uniformity test are performed on the prepared positive electrode sheet, and the discharge capacity test is performed on the battery composed of the positive electrode sheet.
  • the powder drop rate test results See Table 1, the discharge capacity test results are shown in Table 2, and the thickness uniformity of the positive electrode sheet is 2.13%.
  • This comparative example provides a method for preparing a positive electrode sheet, which is different from Example 1 in that in step (2), the electrode mixture obtained in step (1) is formed by means of stamping, which specifically includes the following steps :
  • the dried and formed positive electrode sheet is placed in an automatic cutting and punching device, and punched to obtain a finished positive electrode sheet with a size of 20 mm ⁇ 10 mm ⁇ 1 mm.
  • the powder drop rate test and the thickness uniformity test are performed on the prepared positive electrode sheet, and the discharge capacity test is performed on the battery composed of the positive electrode sheet.
  • the powder drop rate test results See Table 1, the discharge capacity test results are shown in Table 2, and the thickness uniformity of the positive electrode sheet is 3.54%.
  • This comparative example provides a method for preparing a positive electrode sheet.
  • the difference from Example 1 is that in step (2), the electrode mixture obtained in step (1) is formed by means of roll forming, which specifically includes the following steps: step:
  • the pole piece mixture solution is immersed in ethanol solution, and after absorbing the ethanol solution, it is repeatedly rolled into a positive pole piece of a certain thickness. 500Kg/cm, the opposite pole piece is mixed and rolled to obtain a flat positive pole piece;
  • the dried and formed positive electrode sheet is placed in an automatic cutting and punching device, and punched to obtain a finished positive electrode sheet with a size of 20 mm ⁇ 10 mm ⁇ 1 mm.
  • the powder drop rate test and the thickness uniformity test are performed on the prepared positive electrode sheet, and the discharge capacity test is performed on the battery composed of the positive electrode sheet.
  • Example 1 which will not be repeated in this example.
  • the powder drop rate test results See Table 1, the discharge capacity test results are shown in Table 2, and the thickness uniformity of the positive electrode sheet is 3.28%.
  • Comparative Example 1 adopts a stamping molding process, while Example 1 adopts a screw extrusion molding process.
  • Example 2 According to the discharge capacity data shown in Table 2, it can be seen that when standing at room temperature, the difference between the comparative example and the example is not large, but the discharge capacity of Example 1 is higher than that of the comparative example under normal temperature inversion, high temperature upright and high temperature inversion. It is because the screw extrusion molding method is adopted in Example 1, and the pole piece mixture is fully kneaded, so that the positive electrode material, the binder and the solvent can be further mixed evenly, and the extruded positive electrode piece remains relatively intact.
  • the internal structure shows relatively high electrical conductivity, and the positive electrode sheet has excellent liquid absorption ability, which can significantly reduce the difference of the discharge capacity of the battery under different discharge postures (upright, inverted) on the basis of maintaining a good discharge capacity.
  • the thickness uniformity of the 30 positive electrode sheets cut in Example 1 is obviously better than that in Comparative Example 1. This is because, before stamping, if the positive electrode material is unevenly spread in the mold , the thickness of the formed positive electrode sheet is uneven, and even cannot be formed, while Example 1 adopts the molding method of screw extrusion, and there is no problem of uneven tiling.
  • Comparative Example 2 adopts the forming process of rolling, while Example 1 adopts the forming process of screw extrusion.
  • the powder drop of the positive electrode sheet prepared in Comparative Example 2 is more serious than that of the positive electrode sheet prepared in Example 1. This is because a large amount of organic Solvent ethanol is used as a positive forming agent, and the low flash point of ethanol has certain safety risks in the operation and drying process. In addition, the positive electrode after absorbing ethanol is moist and soft, and the thickness uniformity of the positive electrode sheet after being rolled in a roller press is difficult to guarantee.
  • Example 2 According to the discharge capacity data shown in Table 2, it can be seen that when standing at room temperature, the difference between the comparative example and the example is not large, but the discharge capacity of Example 1 is still slightly higher than that of the comparative example under normal temperature inverted, high-temperature upright and high-temperature inverted , this is because the screw extrusion molding method is adopted in Example 1. After sufficient kneading, the positive electrode material, the binder and the solvent can be further mixed evenly, and the extruded positive electrode can be kept The relatively complete internal structure shows relatively high electrical conductivity, and the positive electrode sheet has excellent liquid absorption ability, which can significantly reduce the discharge capacity of the battery under different discharge postures (upright, inverted) on the basis of maintaining a good discharge capacity. difference.
  • Example 1 adopts the molding method of screw extrusion, and there are few parameters to be controlled and most of them can be controlled. Therefore, the operation requirements of technicians are not high, and the thickness uniformity is relatively easy to control.

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Abstract

一种极片成型的挤出头（1）及包括其的成型装置及其成型方法和制备方法，所述的挤出头（1）包括挤出头（1）壳体，挤出头（1）壳体内部沿挤出方向开设有贯通的挤出通道（6）；挤出通道（6）沿挤出方向分为依次对接贯通的过渡腔（61）和成型腔（62），沿挤出方向，过渡腔（61）的内壁环面的直径渐缩。

Description

一种极片成型的挤出头及包括其的成型装置及其成型方法和制备方法 技术领域
本申请属于极片制备技术领域，涉及一种极片成型的挤出头及包括其的成型装置及其成型方法和制备方法，例如涉及一种用于异型极片成型的挤出头及包括其的成型装置及其成型方法和制备方法。
背景技术
随着物联网建设的快速推进，智慧城市概念深入人心，电池的应用模式趋于多样化，同时越来越多的设计和产品开发在特殊形状的电池，用于智能监测，智能计量，智能追踪，智能磨损和医疗器械上。异型电池的电池形状可以呈现规则或者不规则的几何形状，包括币式电池，方型电池，六角电池，三角形电池，扇形电池等。与此同时，异型电池使用的碳正极结构与常见的圆柱形电芯不同，需求不同规格形状的电池极片。
比如，方形电池使用1-3mm厚度的长方形碳片，币式电池使用直径3-30mm，厚度1-4mm圆形碳片或者圆环型碳片，扇形电池则需要一定弧度、直径和厚度的碳片。此类碳片都有两个共同的要求，一就是对极片的厚度要求极高，如果极片的厚度超出标准，组装过程中就会压塌边膜造成短路，长期高温放电过程中会出现外壳臌胀的情况。如果极片的厚度低于标准，组装后正极、边膜和锂带之间接触不好，表现出差的集流效果。二就是正极碳片的截面需要平整无毛刺，并具有一定的强度，有利于极片的组装过程。
目前碳片主要有二种成型方式：
第一种成型方式为冲压成型，即先将正极材料，导电剂，粘合剂等混合，制粒成直径2-4nm的颗粒正极，平铺在模具内，压力直接压制成型。
例如：CN104201381B一种锂离子电池的制作方法，包括以下步骤：分别制作正极片和负极片：将粘合剂和导电剂粉料以及正极活性物质或负极活性物质粉料混合搅拌均匀后，加热到80～200℃，放入内置金属网的预制模具中，对模具中的粉料施加3～20MPa的压力，使之成型，分别得到正极成型体和负极成型体；所述金属网的一端形成有伸出于所述正极成型体或负极成型体侧边之外的导电极耳；将正极成型体和负极成型体浸入陶瓷溶液中，烘干后所述正极成型体和负极成型体表面包覆一层陶瓷层；再将正极成型体和负极成型体浸入高分子聚合物溶液中，烘干后在正极成型体和负极成型体表面形成高分子聚合物层，得到正极片和负极片。
这种冲压成型工艺制备得到的极片存在一定的结构不足，原因在于：成型后的正极颗粒仅靠物理作用挤压在一起，极片强度低，在模具中脱模时、物料搬移时、极片装配时，集流体安装时都存在极片散碎风险，不利于自动化组装。另外，在压制前，如果正极平铺在模具中不均匀时，成型后正极极片的厚度出现不均匀，甚至无法成型。
第二种成型方式为辊压成型，即先将正极材料，导电剂，粘合剂等混合均匀，烘干后将混合材料浸泡在乙醇溶液中，正极中因为粘合剂的存在，吸收乙醇溶液后表现出一定的强度，再经过辊压成一定厚度的极片，烘干后通过冲压裁切设备，得到不同形状的正极极片。
例如：CN110407300A公开了一种多孔碳混合炭黑辊压电极材料的制备方法，包括以下步骤；(1)将多孔碳、炭黑、聚四氟乙烯和乙醇组成的混合体系超声分散均匀，得到混合体系A，其中多孔碳的质量、炭黑的质量和乙醇的体积之比为(4～12)mg：(10～30)mg：(1～3)ml，将混合体系A搅拌至粘稠状，得 到初步改性的辊压电极材料催化层；将炭黑、聚四氟乙烯和乙醇组成的混合体系超声分散均匀，得到混合体系B，将混合体系B搅拌至粘稠状，得到初步改性的辊压电极材料扩散层；(2)将初步改性的辊压电极材料催化层、初步改性的辊压电极材料扩散层分别辊压至金属网状物的上表面和下表面，得到初步改性的辊压电极材料；(3)将初步改性的辊压电极材料进行退火处理，之后冷却至室温得到多孔碳混合炭黑辊压电极材料。
这种成型方式存在的不足之处是，过程中使用了大量的有机溶剂乙醇作为正极成型剂，乙醇低的闪点，在操作和烘干过程均有一定的安全风险。另外吸收乙醇后的正极较湿软，在辊压机中辊压后的极片厚度均匀性难以保证，且，乙醇的快速挥发，容易导致极片掉粉和空鼓现象。
因此，为了更好地改善极片的厚度均一性，提高产品质量，降低掉粉率，需要进一步探索极片的成型设备及成型工艺。
发明内容
本申请的目的在于提供一种极片成型的挤出头及包括其的成型装置及其成型方法和制备方法，适用于极片的挤出成型，尤其适用于异型极片的挤出成型，混合好的极片混料采用螺杆挤出成一定厚度的极片，干燥后直接通过特定的裁切模具，即可完成不同型号的特型电池极极片制作。相比较其他极片的制备方法，制作效率明显提升，同时，得到的极片厚度均一且掉粉率低，极片质量明显提升。
为达此目的，本申请采用以下技术方案：
第一方面，本申请提供了一种极片成型的挤出头，所述的挤出头包括挤出头壳体，所述的挤出头壳体内部沿挤出方向开设有贯通的挤出通道。
所述的挤出通道沿挤出方向分为依次对接贯通的过渡腔和成型腔，沿挤出方向，所述的过渡腔的内壁环面的直径渐缩。
本申请提供了一种挤出头，适用于极片的挤出成型，尤其适用于异型极片的挤出成型，直径渐缩的过渡腔可以有效提高极片的厚度均一性且有利于降低极片的掉粉率，同时，对挤出的极片具有一定的整形作用，需要说明的是，本申请对直径渐缩的过渡腔的形状不作具体要求和特殊限定，示例性地可以是呈斜面渐缩、曲面渐缩或锯齿状渐缩等。另外成型腔可以根据需求设计为不同的截面形状，从而得到不同截面形状的异型极片，相比采用常规的冲压或辊压成型方式，采用本申请提供的挤出头制备得到的异型极片的掉粉率更低且极片内应力分布更均匀，只需要更换挤出头即可达到对极片的截面形状和截面尺寸的自由调整，在极片干燥过程中也能有效保证极片具有相同的收缩比，不会因为应力集中造成极片掉粉甚至破碎的不利情形出现。
作为本申请一种可选的技术方案，所述的挤出头壳体沿挤出方向分为依次对接的锥形段和平直段，所述的锥形段的小端面与所述的平直段对接，所述的锥形段内部沿挤出方向开设有所述的过渡腔，所述的平直段内部沿挤出方向开设有所述的成型腔。
可选地，所述的锥形段的大端面处设置有法兰盘，所述的法兰盘的外缘周向设置有至少两个螺纹孔。
可选地，所述的法兰盘的外缘周向等距设置有四个螺纹孔。
可选地，所述的螺纹孔为沉头螺纹孔。
作为本申请一种可选的技术方案，所述的过渡腔的内壁环面为直径渐缩的阶梯型结构。
在本申请中，直径渐缩的阶梯型结构的过渡腔可以进一步提高极片的厚度均一性且有利于降低极片的掉粉率，对挤出的极片具有一定的整形作用。
可选地，所述的过渡腔的阶梯型结构沿挤出方向包括至少两层水平阶梯面，在径向上包括与水平阶梯面相接的至少两层竖直阶梯面。
需要说明的是，阶梯型结构的阶数对最终挤出极片的厚度一致性有影响，阶数越多，极片混料在过渡腔内聚集的作用力越大，使制备得到的极片越平滑，厚度一致性表现越好。
可选地，所述的过渡腔的阶梯型结构包括三层水平阶梯面以及与水平阶梯面相接的三层竖直阶梯面。
可选地，径向上的最后一层竖直阶梯面通过斜面对接所述的成型腔。
作为本申请一种可选的技术方案，所述的成型腔为扁平状通道。
可选地，所述的成型腔截面为矩形、波浪形、弧形或连续凹凸的城墙形。
需要说明的是，本申请对成型腔的截面形状不作具体要求和特殊限定，本领域技术人员可以根据极片的成型要求和使用需求设计不同截面的成型腔。
第二方面，本申请提供了一种极片的成型装置，所述的成型装置为螺杆挤出机，包括挤出装置壳体以及同轴设置于挤出装置壳体内部的螺杆，所述的挤出装置壳体一端可拆卸固定有如第一方面所述的挤出头。
本申请提供的成型装置主要适用于极片的成型处理过程，将现有的冲压机和辊压机替换为螺杆挤出机，采用螺杆挤出的方式对极片混料挤出成型，极片混料在螺杆挤出的过程中，经过充分的捏合作用，可使活性材料、粘合剂和溶剂进一步混合均匀，挤出成型的极片保持相对完整的内部结构，表现出相对高的电导率，使得后续的干燥过程中极片具有相同的收缩比，保证了极片的厚度 均一性，同时极片具有优秀的吸液能力，在维持较高放电容量的基础上，显著降低电池在不同放电状态下(直立、倒立)的放电容量差异。此外，配合不同截面形状的挤出头，可以随意调整挤出的极片截面形状和截面尺寸，以满足不同异型电池的极片形态需要。
干燥后直接通过特定的裁切模具，即可完成不同型号的特型电池极片制作。相比较其他极片制备方法，制作效率明显提升。直径渐缩的过渡腔可以进一步提高极片的厚度均一性且有利于降低极片的掉粉率，对挤出的极片具有一定的整形作用。另外成型腔可以根据需求设计不同的截面形状，从而得到不同截面形状的异型极片，相比采用常规的冲压或辊压成型方式，采用本申请提供的挤出头制备得到的异型极片的掉粉率更低且极片内应力分布更均匀，只需要更换挤出头即可达到对极片的截面形状和截面尺寸的的自由调整，在极片干燥过程中也能有效保证极片具有相同的收缩比，不会因为应力集中造成极片掉粉甚至破碎的不利情形出现。此成型方法的极片不需要任何的导电基底做支撑，也可保持一定的柔韧性和强度，在电池组装过程中，碳片可通过设备自动夹取和装配，安装集流体时也不会有微粉脱落于隔膜上，降低了因为极片微粉引起的微短路风险。
混合好的极片混料液采用螺杆挤出成型一定厚度的极片，干燥后直接通过特定的裁切模具，即可完成不同型号的特殊形态异型极片的制作。相比较极片的其他制备方法，制作效率明显提升。具体表现在：
(1)通过调整挤出装置的挤出头截面尺寸，可以实现极片的厚度和宽度可控，且制备得到的极片表现出优异的厚度均一性，可适用于绝大多数特型电池极片。
(2)此制备方法制备得到的极片不需要任何的导电基底做支撑，也可保持一定的柔韧性和强度，在电池组装过程中，极片可通过设备自动夹取和装配，安装集流体时也不会有微粉脱落于隔膜上，降低了因为极片微粉引起的微短路风险。
(3)极片混料经在螺杆挤出的过程中，经过充分的捏合作用，可使活性材料、粘合剂和溶剂进一步混合均匀，挤出成型的极片保持相对完整的内部结构，表现出相对高的电导率，同时极片具有优秀的吸液能力，可在保持好的放电容量的基础上，显著降低电池在不同放电姿势下(直立、倒立)放电容量的差异。
作为本申请一种可选的技术方案，所述的挤出装置壳体远离挤出头的一端设置有加料仓，极片混料经加料仓送入挤出装置壳体内部，通过螺杆混合输送至挤出头并由挤出头挤出成型。
可选地，所述的螺杆靠近加料仓的一端与驱动电机传动连接，所述的驱动电机用于驱动螺杆旋转。
可选地，所述的挤出装置壳体与挤出头通过法兰可拆卸连接。
第三方面，本申请提供了一种极片的成型方法，采用第二方面所述的成型装置对极片混料进行挤出成型，所述的成型方法包括：
极片混料经加料仓送入挤出装置壳体，通过螺杆混合均匀后输送至挤出头并由挤出头挤出成型。
作为本申请一种可选的技术方案，所述的挤出频率为30～50Hz，例如可以是30Hz、32Hz、34Hz、36Hz、38Hz、40Hz、42Hz、44Hz、46Hz、48Hz或50Hz，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述的挤出温度为30～60℃，例如可以是30℃、32℃、34℃、36℃、 38℃、40℃、42℃、44℃、46℃、48℃、50℃、52℃、54℃、56℃、58℃或60℃，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
第四方面，本申请提供了一种极片的制备方法，所述的制备方法包括：
活性材料、粘合剂和溶剂混料成极片混料，后经成型、干燥和冲切后得到所述的极片，其中，所述的成型过程采用第三方面所述的成型方法实现。
本申请提供了一种简易、高率且安全的极片的成型方法，混合好的极片混料液采用螺杆挤出成型一定厚度的极片，干燥后直接通过特定的裁切模具，即可完成不同型号的特殊形态异型极片的制作。相比较极片的其他制备方法，制作效率明显提升。具体表现在：
(1)通过调整挤出装置的挤出头截面尺寸，可以实现极片的厚度和宽度可控，且制备得到的极片表现出优异的厚度均一性，可适用于绝大多数特型电池极片。
(2)此制备方法制备得到的极片不需要任何的导电基底做支撑，也可保持一定的柔韧性和强度，在电池组装过程中，极片可通过设备自动夹取和装配，安装集流体时也不会有微粉脱落于隔膜上，降低了因为极片微粉引起的微短路风险。
(3)极片混料经在螺杆挤出的过程中，经过充分的捏合作用，可使活性材料、粘合剂和溶剂进一步混合均匀，挤出成型的极片保持相对完整的内部结构，表现出相对高的电导率，同时极片具有优秀的吸液能力，可在保持好的放电容量的基础上，显著降低电池在不同放电姿势下(直立、倒立)放电容量的差异。
作为本申请一种可选的技术方案，所述的活性材料包括导电炭黑、乙炔黑、科琴黑、碳纳米管、二氧化锰、氟化碳或FeS 2中的一种或至少两种的组合，例 如可以是乙炔黑和科琴黑的组合、科琴黑和碳纳米管的组合或乙炔黑和碳纳米管的组合，但并不仅限于所列举的组合情况，该组合范围内其他未列举的组合同样适用。
可选地，所述的粘合剂为聚四氟乙烯乳液。
可选地，所述的聚四氟乙烯乳液的固含量为50～60wt％，例如可以是50wt％、51wt％、52wt％、53wt％、54wt％、55wt％、56wt％、57wt％、58wt％、59wt％或60wt％，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述的溶剂为异丙醇或异丙醇的水溶液。
可选地，所述的活性材料、粘合剂和溶剂的质量比为1:(0.1-0.3):(3-6)，例如可以是1:0.1:3、1:0.1:4、1:0.1:5、1:0.1:6、1:0.2:3、1:0.2:4、1:0.2:5、1:0.2:6、1:0.3:3、1:0.3:4、1:0.3:5或1:0.3:6，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述的混料过程在混料装置中进行。
可选地，所述的混料过程的搅拌时间为5～10min，例如可以是5min、6min、7min、8min、9min或10min，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述的混料装置的搅拌桨转速为100～300r/min，例如可以是100r/min、120r/min、140r/min、160r/min、180r/min、200r/min、220r/min、240r/min、260r/min、280r/min或300r/min，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述的成型过程在成型装置中进行。
可选地，所述的成型装置的挤出频率为30～50Hz，例如可以是30Hz、32Hz、 34Hz、36Hz、38Hz、40Hz、42Hz、44Hz、46Hz、48Hz或50Hz，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述的成型装置的挤出温度为30～60℃，例如可以是30℃、32℃、34℃、36℃、38℃、40℃、42℃、44℃、46℃、48℃、50℃、52℃、54℃、56℃、58℃或60℃，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述的干燥过程在鼓风烘箱中进行。
可选地，所述的干燥温度为120～160℃，例如可以是120℃、125℃、130℃、135℃、140℃、145℃、150℃、155℃或160℃，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述的干燥时间为5～10h，例如可以是5.0h、5.5h、6.0h、6.5h、7.0h、7.5h、8.0h、8.5h、9.0h、9.5h或10.0h，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述的冲切过程在自动裁切冲压装置中进行。
可选地，冲切后的极片的厚度为1～4mm，例如可以是1.0mm、1.5mm、2.0mm、2.5mm、3.0mm、3.5mm或4.0mm，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，冲切后的极片的宽度为20～50mm，例如可以是20mm、25mm、30mm、35mm、40mm、45mm或50mm，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
所述***是指设备***、装置***或生产装置。
与现有技术相比，本申请的有益效果为：
(1)本申请提供的挤出头，尤其适用于极片的挤出成型处理，直径渐缩的过渡腔可以进一步提高极片的厚度均一性且有利于降低极片的掉粉率，对挤出的极片具有一定的整形作用。另外成型腔可以根据需求设计不同的截面形状，从而得到不同截面形状的异型极片，相比采用常规的冲压或辊压成型方式，采用本申请提供的挤出头制备得到的异型极片的掉粉率更低且极片内应力分布更均匀，只需要更换挤出头即可达到对极片的截面形状和截面尺寸的的自由调整，在极片干燥过程中也能有效保证极片具有相同的收缩比，不会因为应力集中造成极片掉粉甚至破碎的不利情形出现。
(2)本申请提供的制备方法制备得到的极片不需要任何的导电基底做支撑，也可保持一定的柔韧性和强度，在电池组装过程中，极片可通过设备自动夹取和装配，安装集流体时也不会有微粉脱落于隔膜上，降低了因为极片微粉引起的微短路风险。
(3)极片混料经在螺杆挤出的过程中，经过充分的捏合作用，可使活性材料、粘合剂和溶剂进一步混合均匀，挤出成型的极片保持相对完整的内部结构，表现出相对高的电导率，同时极片具有优秀的吸液能力，可在保持好的放电容量的基础上，显著降低电池在不同放电姿势下(直立、倒立)放电容量的差异。
附图说明
图1为本申请一个具体实施方式提供的成型装置的结构示意图。
图2为本申请一个具体实施方式提供的挤出头的侧视图。
图3为本申请一个具体实施方式提供的挤出头的侧视图。
其中，1-挤出头；2-挤出装置壳体；3-加料仓；4-螺杆；5-螺纹孔；6-挤出通道；61-过渡腔；62-成型腔。
具体实施方式
需要理解的是，在本申请的描述中，术语“中心”、“纵向”、“横向”、“上”、“下”、“前”、“后”、“左”、“右”、“竖直”、“水平”、“顶”、“底”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。
需要说明的是，在本申请的描述中，除非另有明确的规定和限定，术语“设置”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体连接；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以通过具体情况理解上述术语在本申请中的具体含义。
下面结合附图并通过具体实施方式来进一步说明本申请的技术方案。
在一个具体实施方式中，本申请提供了一种极片成型的挤出头1，所述的挤出头1如图1、图2和图3所示，包括挤出头1壳体，挤出头1壳体内部沿挤出方向开设有贯通的挤出通道6。挤出通道6沿挤出方向分为依次对接贯通的过渡腔61和成型腔62，沿挤出方向，过渡腔61的内壁环面直径渐缩，直径渐缩的过渡腔61可以进一步提高极片的厚度均一性且有利于降低极片的掉粉率，对挤出的极片具有一定的整形作用。本申请对直径渐缩的过渡腔61的形状不作具体要求和特殊限定，示例性地可以是呈斜面渐缩、曲面渐缩或锯齿状渐缩等，但可选采用阶梯形渐缩，进一步地，沿挤出方向包括至少两层水平阶梯面，在垂直于挤出方向上包括与水平阶梯面相接的至少两层竖直阶梯面。阶梯面的层数 对最终挤出极片的厚度一致性有影响，阶梯面层数多时，材料在过渡腔61内聚集的作用力越大，更平滑，厚度一致性表现越好。具体地，过渡腔61的阶梯型结构包括三层水平阶梯面以及与水平阶梯面相接的三层竖直阶梯面。垂直于挤出方向上的最后一层竖直阶梯面通过斜面对接成型腔62。
成型腔62可以根据需求设计为不同的截面形状，从而得到不同截面形状的异型极片，相比采用常规的冲压或辊压成型方式得到的异型极片的掉粉率更低且极片内应力分布更均匀，只需要更换挤出头1即可达到对极片的截面形状和截面尺寸的自由调整，在极片干燥过程中也能有效保证极片具有相同的收缩比，不会因为应力集中造成极片掉粉甚至破碎的不利情形出现。可选地，成型腔62为扁平状通道，具体地，成型腔62截面为矩形、波浪形、弧形或连续凹凸的城墙形或其他异形。需要说明的是，本申请对成型腔62的截面形状不作具体要求和特殊限定，本领域技术人员可以根据极片的成型要求设计不同截面的成型腔62。
挤出头1壳体沿挤出方向分为依次对接的锥形段和平直段，锥形段的小端面与平直段对接，锥形段内部沿挤出方向开设有过渡腔61，直径渐缩的过渡腔61可以进一步提高极片的厚度均一性且有利于降低极片的掉粉率，对挤出的极片具有一定的整形作用；平直段内部沿挤出方向开设有成型腔62。配合不同截面形状的挤出头1，可以随意调整挤出的极片截面形状和截面尺寸，以满足不同异型电池的极片形态需要。干燥后直接通过特定的裁切模具，通过调整挤出头1的成型腔62尺寸，即可完成不同型号的特型电池极片制作，适用于绝大多数特殊形态的极片且表现出优秀的厚度均匀性。
锥形段的大端面处设置有法兰盘，法兰盘的外缘周向设置有至少两个螺纹 孔5，具体地，法兰盘的外缘周向等距设置有四个螺纹孔5。可选地，螺纹孔5为沉头螺纹孔。
在另一个具体实施方式中，本申请提供了一种极片的成型装置，所述的成型装置为螺杆挤出机，如图1所示，包括管状结构的挤出装置壳体2以及同轴设置于挤出装置壳体2内部的螺杆4，挤出装置壳体2一端可拆卸固定有一个具体实施方式提供的挤出头1。挤出装置壳体2远离挤出头1的一端设置有加料仓3，极片混料经加料仓3送入挤出装置壳体2内部，通过螺杆4混合输送至挤出头1并由挤出头1挤出成型。螺杆4靠近加料仓3的一端与驱动电机传动连接，驱动电机用于驱动螺杆4旋转。挤出装置壳体2与挤出头1通过法兰可拆卸连接。本申请提供的成型装置主要适用于极片的成型处理过程，将现有的冲压机和辊压机替换为螺杆挤出机，采用螺杆挤出的方式对极片混料挤出成型，极片混料经在螺杆4挤出的过程中，经过充分的捏合作用，可使活性材料、粘合剂和溶剂进一步混合均匀，挤出成型的极片保持相对完整的内部结构，表现出相对高的电导率，同时极片具有优秀的吸液能力，可在保持好的放电容量的基础上，显著降低电池在不同放电姿势下(直立、倒立)放电容量的差异。
在另一个具体实施方式中，本申请提供了一种极片的成型方法，采用上述成型装置对极片混料进行挤出成型，所述的成型方法包括：
极片混料经加料仓送入挤出装置壳体，通过螺杆混合均匀后输送至挤出头并由挤出头挤出成型，挤出频率为30～50Hz，挤出温度为30～60℃。
此成型方法的极片不需要任何的导电基底做支撑，也可保持一定的柔韧性和强度。
在另一个具体实施方式中，本申请提供了一种极片的制备方法，所述的制 备方法包括：
活性材料、粘合剂和溶剂依次经混料、成型、干燥和冲切后得到所述的极片，其中，所述的成型过程采用上述成型方法进行处理。
相比较其他极片制备方法，本申请提供的制备方法的制作效率明显提升。在电池组装过程中，碳片可通过设备自动夹取和装配，安装集流体时也不会有微粉脱落于隔膜上，降低了因为极片微粉引起的微短路风险。极片混料在螺杆挤出机中，经过充分的捏合作用，可使活性材料、高比表面的导电剂、粘合剂和溶剂进一步分散均匀，挤出成型的极片保持相对完整的内部结构，表现出相对高的电导率，同时极片具有优秀的吸液能力，可在保持好的放电容量的基础上，显著降低电池在不同放电姿势下(直立、倒立)放电容量的差异。
实施例1
本实施例提供了一种正极片的制备方法，所述的制备方法包括依次进行的混料、成型、干燥和冲切，具体包括如下步骤：
(1)混料：乙炔黑、聚四氟乙烯乳液(固含量为50wt％)和异丙醇按照1:0.1:3的质量比投加到混料装置中进行混合搅拌，混料装置的搅拌桨转速为100r/min，搅拌10min得到极片混料；
(2)成型：极片混料加入到加料仓3中，由加料仓3送入挤出装置，通过螺杆4旋转挤压对极片混料进一步充分混合，随后推出输送至挤出头1并由挤出头1挤出成型，挤出频率为30Hz，挤出温度为60℃，其中挤出头1如图2所示，成型腔62的截面为扁平的矩形，可用于挤出平整的正极片；
(3)干燥：成型的正极片置于鼓风烘箱中，在120℃下干燥10h得到干燥成型的正极片；
(4)冲切：干燥成型的正极片置于自动裁切冲压装置中，冲切得到尺寸为20mm×10mm×1mm的正极片成品。
对制备得到的正极片进行如下各项测试：
(1)掉粉率测试：称取裁切好的正极片30个，称量并记录质量为M 1，放置在脆碎度测试仪设备中，设置程序运行频率和时间，设备程序完成后取出正极片，观察正极片是否保持完整性。将细粉筛除，称取剩余正极片质量，称重并记录质量为M 2，掉粉率的计算公式为：(M 1-M 2)/M 1×100％；
(2)放电容量测试：采用相同的电解液组成，分别在四种不同的放电状态下测试同一批次的正极片组成的电池的放电容量，四种不同的放电状态包括：常温直立、常温倒立、高温70℃直立和高温70℃倒立(需要说的是，此处直立状态是指电池正极柱竖直放电，倒立状态是指电池正极柱竖直朝下放电)。具体包括如下步骤：
制备得到的正极片作为锂/亚硫酰氯电池的正极，测试组装得到的电池在常温和高温条件下的放电容量偏差，锂/亚硫酰氯电池的组装操作方法如：以本实施例制备得到的正极片作为正极，以金属锂作为负极，电解液为1.4mol/L四氯铝锂的亚硫酰氯溶液，和隔膜组装成电芯；测试电池分别在常温直立、常温倒立、高温70℃直立和高温70℃倒立四种状态下恒阻1620Ω放电，截止电压2.0V的条件下的放电容量。测试结果见表2。
(3)厚度均一性测试：任选同一正极片上的三个不同点位，使用厚度仪精确测试该正极片上三个点位处的厚度，计算平均值作为该正极片的厚度，对30个正极片分别进行上述厚度测试，厚度均一性的计数公式为(L max-L min)/L ave，其中，L max为30个正极片中的最大厚度，L min为30个正极片中的最小厚度，L ave 为30个正极片的平均厚度，计算得到的厚度均一性为1.85％。
实施例2
本实施例提供了一种正极片的制备方法，所述的制备方法包括依次进行的混料、成型、干燥和冲切，具体包括如下步骤：
(1)混料：正极材料、聚四氟乙烯乳液(固含量为55wt％)和异丙醇按照1:0.2:4的质量比投加到混料装置中进行混合搅拌，正极材料包括质量比为9:1的乙炔黑和科琴黑，混料装置的搅拌桨转速为200r/min，搅拌7min得到极片混料；
(2)成型：极片混料加入到加料仓3中，由加料仓3送入挤出装置，通过螺杆4旋转挤压对极片混料进一步充分混合，随后推出输送至挤出头1并由挤出头1挤出成型，挤出频率为40Hz，挤出温度为40℃，其中挤出头1如图2所示，成型腔62的截面为扁平的矩形，可用于挤出平整的正极片；
(3)干燥：成型的正极片置于鼓风烘箱中，在140℃下干燥7h得到干燥成型的正极片；
(4)冲切：干燥成型的正极片置于自动裁切冲压装置中，冲切得到尺寸为30mm×12mm×2mm的正极片成品。
对制备得到的正极片进行掉粉率测试和厚度均一性测试，并对该正极片组成的电池进行放电容量测试，具体测试方法参见实施例1，本实施例不再赘述，掉粉率测试结果参见表1，放电容量测试结果参见表2，正极片的厚度均一性为1.67％。
实施例3
本实施例提供了一种正极片的制备方法，所述的制备方法包括依次进行的 混料、成型、干燥和冲切，具体包括如下步骤：
(1)混料：正极材料、聚四氟乙烯乳液(固含量为60wt％)和异丙醇按照1:0.3:6的质量比投加到混料装置中进行混合搅拌，正极材料包括质量比为9:1的乙炔黑和碳纳米管，混料装置的搅拌桨转速为300r/min，搅拌5min得到极片混料；
(2)成型：极片混料加入到加料仓3中，由加料仓3送入挤出装置，通过螺杆4旋转挤压对极片混料进一步充分混合，随后推出输送至挤出头1并由挤出头1挤出成型，挤出频率为50Hz，挤出温度为30℃，其中挤出头1如图3所示，成型腔62的截面为连续凹凸的城墙型正极片，用于扇形电池制作；
(3)干燥：成型的正极片置于鼓风烘箱中，在120～160℃下干燥5～10h得到干燥成型的正极片；
(4)冲切：干燥成型的正极片置于自动裁切冲压装置中，冲切得到尺寸为50mm×15mm×4mm的正极片成品。
对制备得到的正极片进行掉粉率测试和厚度均一性测试，并对该正极片组成的电池进行放电容量测试，具体测试方法参见实施例1，本实施例不再赘述，掉粉率测试结果参见表1，放电容量测试结果参见表2，正极片的厚度均一性为2.13％。
对比例1
本对比例提供了一种正极片的制备方法，与实施例1的区别在于，步骤(2)中采用冲压成型的方式对步骤(1)得到的极片混料进行成型处理，具体包括如下步骤：
(1)混料：乙炔黑、聚四氟乙烯乳液(固含量为50wt％)和异丙醇按照1:0.1:3 的质量比投加到混料装置中进行混合搅拌，混料装置的搅拌桨转速为100r/min，搅拌10min得到极片混料；
(2)成型：极片混料平铺在模具内，在30～60℃下对极片混料施加15MPa的压力，对极片混料冲压成型，得到平整的正极片；
(3)干燥：成型的正极片置于鼓风烘箱中，在120℃下干燥10h得到干燥成型的正极片；
(4)冲切：干燥成型的正极片置于自动裁切冲压装置中，冲切得到尺寸为20mm×10mm×1mm的正极片成品。
对制备得到的正极片进行掉粉率测试和厚度均一性测试，并对该正极片组成的电池进行放电容量测试，具体测试方法参见实施例1，本实施例不再赘述，掉粉率测试结果参见表1，放电容量测试结果参见表2，正极片的厚度均一性为3.54％。
对比例2
本对比例提供了一种正极片的制备方法，与实施例1的区别在于，步骤(2)中采用辊压成型的方式对步骤(1)得到的极片混料进行成型处理，具体包括如下步骤：
(1)混料：乙炔黑、聚四氟乙烯乳液(固含量为50wt％)和异丙醇按照1:0.1:3的质量比投加到混料装置中进行混合搅拌，混料装置的搅拌桨转速为100r/min，搅拌10min得到极片混料；
(2)成型：极片混料液浸泡在乙醇溶液中，吸收乙醇溶液后经过反复辊压成一定厚度的正极片，辊压时的压辊温度为30～60℃，辊压的线压力为500Kg/cm，对极片混料辊压成型，得到平整的正极片；
(3)干燥：成型的正极片置于鼓风烘箱中，在120℃下干燥10h得到干燥成型的正极片；
(4)冲切：干燥成型的正极片置于自动裁切冲压装置中，冲切得到尺寸为20mm×10mm×1mm的正极片成品。
对制备得到的正极片进行掉粉率测试和厚度均一性测试，并对该正极片组成的电池进行放电容量测试，具体测试方法参见实施例1，本实施例不再赘述，掉粉率测试结果参见表1，放电容量测试结果参见表2，正极片的厚度均一性为3.28％。
表1
  极片是否完整 掉粉率[％]
实施例1 是 0.27
实施例2 是 0.33
实施例3 是 0.29
对比例1 否 _
对比例2 是 0.64
表2
Figure PCTCN2020121456-appb-000001
对比例1与实施例1的区别仅在于，对比例1采用冲压的成型工艺，而实施例1采用的是螺杆挤出的成型工艺。
根据表1所示的掉粉率数据可以看出，对比例1制备得到的正极片比实施例1制备得到的正极片的掉粉更严重，且事实上对比例1中根本无法制备得到完整的正极片，这是由于冲压成型后的正极颗粒仅靠物理作用挤压在一起，正极片强度低，在模具中脱模时、物料搬移时或正极片装配时等各环节，集流体安装时都有一定风险正极散碎，非常不利用自动化组装。
根据表2所示的放电容量数据可以看出，常温直立时，对比例和实施例的差距不大，但常温倒立、高温直立以及高温倒立下，实施例1的放电容量高于对比例，这是由于，实施例1中采用了螺杆挤出的成型方式，极片混料经过充分的捏合作用，可使正极材料、粘合剂和溶剂进一步混合均匀，挤出成型的正极片保持相对完整的内部结构，表现出相对高的电导率，同时正极片具有优秀的吸液能力，可在保持好的放电容量的基础上，显著降低电池在不同放电姿势下(直立、倒立)放电容量的差异。
根据厚度均一性数据可以看出，实施例1裁切得到的30片正极片的厚度均一性明显优于对比例1，这是由于，在冲压前，如果正极材料平铺在模具中不均匀时，成型后的正极片的厚度出现不均匀，甚至无法成型，而实施例1采用了螺杆挤出的成型方式，不存在平铺不均匀的问题。
对比例2与实施例1的区别仅在于，对比例2采用辊压的成型工艺，而实施例1采用的是螺杆挤出的成型工艺。
根据表1所示的掉粉率数据可以看出，对比例2制备得到的正极片比实施例1制备得到的正极片的掉粉更严重，这是由于，辊压过程中使用了大量的有 机溶剂乙醇作为正极成型剂，乙醇低的闪点，在操作和烘干过程均有一定的安全风险。另外吸收乙醇后的正极较湿软，在辊压机中辊压后的正极片厚度均匀性难以保证，乙醇的快速挥发，容易导致正极片掉粉和空鼓现象。
根据表2所示的放电容量数据可以看出，常温直立时，对比例和实施例的差距不大，但常温倒立、高温直立以及高温倒立下，实施例1的放电容量仍略高于对比例，这是由于，实施例1中采用了螺杆挤出的成型方式，极片混料经经过充分的捏合作用，可使正极材料、粘合剂和溶剂进一步混合均匀，挤出成型的正极片保持相对完整的内部结构，表现出相对高的电导率，同时正极片具有优秀的吸液能力，可在保持好的放电容量的基础上，显著降低电池在不同放电姿势下(直立、倒立)放电容量的差异。
根据厚度均一性数据可以看出，实施例1裁切得到的30片正极片的厚度均一性明显优于对比例2，这是由于，辊压过程中影响正极片的厚度的辊压参数较多且大部分不可控，因此一旦无法准确控制辊压参数，对正极片的厚度均一性的影响极大，而实施例1采用了螺杆挤出的成型方式，需要控制的参数较少且大部分可控，因此对技术人员的操作要求不高，厚度均一性比较容易控制。
申请人声明，以上所述仅为本申请的具体实施方式，但本申请的保护范围并不局限于此。

Claims (12)

  1. 一种极片成型的挤出头，其包括挤出头壳体，所述的挤出头壳体内部沿挤出方向开设有贯通的挤出通道；
    所述的挤出通道沿挤出方向分为依次对接贯通的过渡腔和成型腔，沿挤出方向，所述的过渡腔的内壁环面的直径渐缩。
  2. 根据权利要求1所述的挤出头，其中所述的挤出头壳体沿挤出方向分为依次对接的锥形段和平直段，所述的锥形段的小端面与所述的平直段对接，所述的锥形段内部沿挤出方向开设有所述的过渡腔，所述的平直段内部沿挤出方向开设有所述的成型腔。
  3. 根据权利要求1或2所述的挤出头，其中所述的过渡腔的内壁环面为直径渐缩的阶梯型结构。
  4. 根据权利要求2或3所述的挤出头，其中所述的锥形段的大端面处设置有法兰盘，所述的法兰盘的外缘周向设置有至少两个螺纹孔；
    可选地，所述的法兰盘的外缘周向等距设置有四个螺纹孔；
    可选地，所述的螺纹孔为沉头螺纹孔。
  5. 根据权利要求3或4所述的挤出头，其中所述的过渡腔的阶梯型结构沿挤出方向包括至少两层水平阶梯面，在径向上包括与水平阶梯面相接的至少两层竖直阶梯面；
    可选地，所述的过渡腔的阶梯型结构包括三层水平阶梯面以及与水平阶梯面相接的三层竖直阶梯面；
    可选地，径向上的最后一层竖直阶梯面通过斜面对接所述的成型腔。
  6. 根据权利要求1-5任一项所述的挤出头，其中所述的成型腔为扁平状通道；
    可选地，所述的成型腔截面为矩形、波浪形、弧形或连续凹凸的城墙形。
  7. 一种极片的成型装置，其为螺杆挤出机，包括挤出装置壳体以及同轴设置于挤出装置壳体内部的螺杆，所述的挤出装置壳体一端可拆卸固定有权利要求1-6任一项所述的挤出头。
  8. 根据权利要求7所述的成型装置，其中所述的挤出装置壳体远离挤出头的一端设置有加料仓，极片混料经加料仓送入挤出装置壳体内部，通过螺杆混合输送至挤出头并由挤出头挤出成型；
    可选地，所述的螺杆靠近加料仓的一端与驱动电机传动连接，所述的驱动电机用于驱动螺杆旋转；
    可选地，所述的挤出装置壳体与挤出头通过法兰可拆卸连接。
  9. 一种极片的成型方法，其采用权利要求7或8所述的成型装置对极片混料进行挤出成型，所述的成型方法包括：
    极片混料经加料仓送入挤出装置壳体，通过螺杆混合均匀后输送至挤出头并由挤出头挤出成型。
  10. 根据权利要求9所述的成型方法，其中，所述的挤出频率为30～50Hz；
    可选地，所述的挤出温度为30～60℃。
  11. 一种极片的制备方法，其包括：
    活性材料、粘合剂和溶剂混料成极片混料，后经成型、干燥和冲切后得到所述的极片，其中，所述的成型采用权利要求9或10所述的成型方法实现。
  12. 根据权利要求11所述的制备方法，其中，所述的活性材料包括导电炭黑、乙炔黑、科琴黑、碳纳米管、二氧化锰、氟化碳或FeS 2中的一种或至少两种的组合；
    可选地，所述的粘合剂为聚四氟乙烯乳液；
    可选地，所述的聚四氟乙烯乳液的固含量为50～60wt％；
    可选地，所述的溶剂为异丙醇或异丙醇的水溶液；
    可选地，所述的活性材料、粘合剂和溶剂的质量比为1:(0.1-0.3):(3-6)；
    可选地，所述的混料在混料装置中进行；
    可选地，所述的混料的搅拌时间为5～10min；
    可选地，所述的混料装置的搅拌桨转速为100～300r/min；
    可选地，所述的成型在成型装置中进行；
    可选地，所述的成型装置的挤出频率为30～50Hz；
    可选地，所述的成型装置的挤出温度为30～60℃；
    可选地，所述的干燥在鼓风烘箱中进行；
    可选地，所述干燥的温度为120～160℃；
    可选地，所述干燥的时间为5～10h；
    可选地，所述的冲切在自动裁切冲压装置中进行；
    可选地，所述冲切后的极片的厚度为1～4mm；
    可选地，所述冲切后的极片的宽度为20～50mm。
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