Preparation method and forming device of electrode film and electrode piece

Abstract

The invention provides a dry preparation method of an electrode film, which comprises the following steps of: distributing materials according to a preset weight in different areas, limiting the materials in corresponding areas, sequentially performing primary stamping and secondary stamping on the materials to obtain the electrode film, cancelling the limiting after the primary stamping, and respectively performing the primary stamping and the secondary stamping for multiple times; meanwhile, the invention further provides a preparation method of the pole piece and a pole piece forming device for preparing the pole piece according to a dry-method preparation method of the electrode film and the preparation method of the pole piece, the pole piece forming device provided by the scheme is used for preparing the electrode film, and the electrode film and the current collector are subjected to hot-pressing compounding to prepare the pole piece. According to the scheme, the uniformity of the electrode film and the electrical performance of the pole piece are effectively improved, continuous production is realized, and the method has the advantages of high efficiency, stability and low cost and is suitable for large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode membrane production equipment, and specifically includes a method for manufacturing an electrode membrane and a forming device. Technical Background

[0002] The cost and performance of lithium-ion batteries (LIBs) depend largely on the manufacturing process of the electrodes. Currently, the electrodes of commercial lithium-ion batteries are usually manufactured using the slurry-casting (SC) procedure, which is a wet coating process, which limits the thickness of the electrode. To overcome this limitation, the solvent-free (SF) procedure, which is a dry manufacturing process, is a promising solution. The SF process does not use solvents. By dry homogenizing the binder with the active material and the conductive agent, thick electrodes can be produced without worrying about the problem of uneven binder distribution. Therefore, it has been widely used. However, in the current production process, there are still some problems that need to be solved.

[0003] When preparing electrodes through the SF process, the conductive slurry (conductive additives, active materials, binders) is generally first dry-mixed to form a fiberized mixture, and then the fiberized mixture is rolled into a supportable film material by a pressure roller and conveyed to a combining station, where the film material is rolled and combined with the current collector to form an electrode sheet. The most critical part of this preparation method is to roll the mixture into a supportable film material and combine it with the current collector through a roller. Therefore, the quality of the film material and the degree of tightness of the combination with the current collector will greatly affect the quality of the electrode sheet. Currently, the common way to prepare film materials is to roll the mixture with a cylindrical roller, so that the polymer crystals undergo crystal slip along the shear force direction (c-axis) (such as Figure 8 ), thereby forming a self-supporting film material. Although this rolling method is relatively simple, the fiberized mixture is prone to form cavities inside during the falling process, causing holes to exist inside the prepared film material, which in turn affects the uniformity of the film material and affects the performance of the film material. It may cause the film material to be too thick at the joint, and it is easy to crack and break. In addition, in actual operation, factory equipment is often limited, and each rolling needs to reset and debug equipment parameters, resulting in greatly reduced efficiency. Therefore, how to solve the problem of easy breakage or excessive thickness of the joints and low production efficiency caused by multiple rolling has become a major research hotspot. Summary of the invention

[0004] In view of the problems in the prior art, the present invention provides a dry method for preparing an electrode film, which is suitable for preparing an electrode film with a thickness of more than 50 um, solves the quality problem caused by uneven thickness of the electrode film during rolling, and improves production efficiency.

[0005] In a first aspect, the present invention provides a dry method for preparing an electrode film, comprising:

[0006] First, the material is divided into zones according to the preset weight and the material is limited in the corresponding area. The material is sequentially subjected to primary stamping and secondary stamping to obtain an electrode film. The limitation is cancelled after the primary stamping, and the primary stamping and secondary stamping are respectively performed multiple times.

[0007] After the primary stamping pressure increases with the number of times to the primary maximum pressure, it remains at the primary maximum pressure unchanged, wherein the primary maximum pressure is selected from 500-2000Mpa; the secondary stamping pressure increases with the number of times or remains unchanged, increasing with the number of times is called the secondary stamping variable pressure, and remaining unchanged with the number of times is called the secondary stamping constant pressure; when the secondary stamping variable pressure increases with the number of times to the secondary stamping variable pressure maximum value and then remains unchanged, it is called the secondary stamping variable pressure maximum pressure, wherein the secondary stamping variable pressure maximum pressure is selected from 3000-8000Mpa; the secondary stamping constant pressure is selected from 2500-4000Mpa. In the second aspect, the present invention provides a method for preparing a pole piece, comprising: covering a current collector on the surface of a prepared electrode film, hot stamping and slicing to obtain a pole piece.

[0008] As a further solution, the material distribution method is not limited in principle, including but not limited to any one or more of extrusion and powder conveying to achieve the processing of different materials.

[0009] As a further solution, the material is heated before the primary stamping to enhance the thermoplastic slip properties of the material.

[0010] As a further solution, when the first-stage stamping is heated, the temperature range is selected from 50-120°C.

[0011] As a further solution, the first-level stamping times are greater than 10 times.

[0012] As a further solution, during the primary stamping, the stamping frequency is selected from 10-1000 times / min, and the preferred stamping frequency is selected from 50-200 times / min.

[0013] As a further solution, the primary stamping pressure is selected from 1-2000Mpa.

[0014] As a further solution, during the first-stage stamping, the first-stage stamping pressure law that increases with the number of times is not limited in principle, for example, it can be X n+1 =d(X n ) m And other functions or self-set pressure values, where X represents the value of the first-stage stamping pressure, d is selected from 1-9.9, m is selected from 1-3, n represents that this stamping is the nth stamping, X is greater than or equal to 1, and the initial first-stage pressure is greater than or equal to 1Mpa.

[0015] As a further solution, the secondary stamping times are greater than 5 times.

[0016] As a further solution, during the secondary stamping, the stamping frequency is selected from 5-100 times / min, preferably 5-50 times / min.

[0017] As a further solution, when the secondary stamping pressure increases with the number of times, the secondary stamping pressure is selected from 50-8000Mpa, preferably 300-8000Mpa.

[0018] As a further solution, during the secondary stamping, the law of the secondary stamping pressure change with increasing times is not limited in principle, for example, it can be Y p+1 =f(Y p ) q And other functions or independently set pressure values, where Y represents the value of the secondary stamping variable pressure, f is selected from 1-9.9, q is selected from 1-3, p represents that this stamping is the pth stamping, Y is greater than or equal to 1, and the initial secondary stamping variable pressure is greater than or equal to 1Mpa.

[0019] As a further preferred solution, the initial secondary stamping pressure is selected from 50-500 MPa.

[0020] As a further preferred solution, the maximum pressure of the secondary stamping transformation is 3-10 times the maximum pressure of the primary stage.

[0021] As a further preferred solution, the constant pressure of the secondary stamping is 2-8 times the maximum pressure of the first stage.

[0022] As a further solution, during the hot stamping, the number of stamping composite times is greater than 5 times.

[0023] As a further solution, during the hot stamping, the stamping compound frequency is selected from 10-100 times / min, preferably 20-60 times / min.

[0024] As a further solution, during the hot stamping, the impact bonding pressure can remain unchanged, or increase continuously or step by step with the number of stamping bonding times.

[0025] As a further solution, during the hot stamping, the impact composite pressure preferably increases with the number of stamping composite times. When the impact composite pressure increases with the number of times to a maximum impact composite pressure, the impact composite pressure continues to remain unchanged at the maximum impact composite pressure with the remaining number of times. The maximum impact composite pressure is selected from 800-1000Mpa.

[0026] As a further solution, during the stamping and compounding, the impact compounding pressure law that increases with the number of stamping and compounding times is not limited in principle, for example, it can be Z a+1 =c(Za ) e And other functions or independently set pressure values, wherein Z represents the value of the impact composite pressure, c is selected from 1-9.9, e is selected from 1-3, a represents that this stamping is the ath stamping, Z is greater than or equal to 1, the initial impact composite pressure is greater than or equal to 1Mpa, and the initial impact composite pressure is selected from 10-300Mpa.

[0027] As a further solution, when the impact composite pressure remains unchanged, the impact composite pressure is selected from 10-1000 MPa, preferably 50-350 MPa.

[0028] As a further solution, during the hot pressing compounding, the hot pressing compounding pressure is selected from 50-1000 MPa, preferably 300-600 MPa.

[0029] As a further solution, during hot pressing and laminating, the temperature is selected from 80-300° C., and the heating time is selected from 1-60 s.

[0030] As a further preferred solution, the temperature during the hot pressing compounding is selected from 90-150° C., and the time is selected from 20-40 seconds.

[0031] As a further preferred solution, when distributing materials in different areas, a demoulding layer is provided on the corresponding areas for limiting, and the materials are distributed on the demoulding layer. After the hot stamping is completed, the demoulding layer is heated and separated.

[0032] As a further solution, in the method for preparing the pole piece, the temperature for heating and decomposing the release layer is selected from 130-300° C., and the time is selected from 1-60 s.

[0033] As a further preferred solution, the temperature for heating and decomposing the demoulding layer is selected from 130-180° C., and the time is selected from 20-40 s, which helps to further optimize the pole piece separation effect and protect the pole piece performance.

[0034] In a third aspect, the present invention provides a pole piece forming device, including a material conveyor belt, and a demoulding layer pasting device, a material distribution device, a material heating device, a primary stamping device, a secondary stamping device, a hot stamping device, and a heating demoulding device arranged in sequence along the material conveying direction on the material conveyor belt;

[0035] The electrode forming device is also provided with a mold conveying assembly, including an electrode film mold, a mold conveyor belt, a mold placing device, and a mold recovery device. The mold placing device is used to place the electrode film mold on the material conveyor belt before the material distribution device. The mold conveyor belt is arranged on the edges of both sides of the material conveyor belt and is parallel to or higher than the material conveyor belt in the horizontal direction. The mold conveyor belt is used to carry the electrode mold through the material distribution device, the material heating device, and the primary stamping device in sequence. The mold recovery device is used to recover the electrode mold after the primary stamping.

[0036] The pole piece forming device is also provided with a current collector unwinding device and a pole piece winding device. The unwinding device is used to unwind the current collector to compound it with the electrode film passed through the hot stamping device, and the pole piece winding device is used to wind up the pole piece demoulded by the hot stamping device.

[0037] There is no limitation on the type of release layer pasting device. The technicians can choose different pasting devices to paste the release layer to the surface of the material conveyor belt according to the needs.

[0038] As a further solution, the thickness of the release layer is selected from 0.1 μm-20 μm

[0039] As a further solution, the demoulding layer includes a carrier layer and a glue layer arranged on any one side of the carrier layer.

[0040] As a further solution, the material of the carrier layer is not limited in principle, and the materials that can be selected by technicians include but are not limited to one or more of polyethylene, polypropylene, and polycarbonate.

[0041] As a further solution, the material of the glue layer is not limited in principle, and the material that the technician can choose includes but is not limited to one of polyacrylate glue and polyurethane glue.

[0042] As a further solution, when the mold conveyor belt is higher than the material conveyor belt in the horizontal direction, the height is selected from 0.5-1 mm.

[0043] As a further solution, the material distribution device includes a material distribution port and a material tank, and the material tank is fixedly connected to the material distribution port. The material distribution port can distribute the material in partitions according to preset weights.

[0044] As a further solution, the first-level stamping device includes a first-level punch and a first-level stamping base, the first-level stamping base is fixedly connected to the first-level punch, the first-level punch protrudes from the first-level stamping base, and the shape of the first-level punch cooperates with the electrode membrane mold and is used to perform first-level stamping on the material in the electrode membrane mold.

[0045] As some examples, the electrode membrane mold includes a primary electrode membrane grid, which connects the front and back sides of the electrode mold and has a width that matches the material conveyor belt. The primary punch matches the primary electrode membrane grid and has a size that is 0.8mm-1.2mm smaller than the size of the primary electrode membrane grid.

[0046] As a further solution, the first-level punch is divided into a first-level stamping block by grooves distributed vertically and horizontally. The electrode membrane mold includes a pole ear part and a partition part. The pole ear part and the partition part are crisscrossed to divide the first-level electrode membrane grid into electrode membrane grids. The electrode membrane grid cooperates with the first-level stamping block, and the size of the first-level stamping block is smaller than the size of the electrode membrane grid by 0.8mm-1.2mm.

[0047] As a further solution, the primary stamping base is also provided with a positioning boss that cooperates with the electrode membrane mold.

[0048] As a further solution, the electrode mold is also provided with a positioning hole that cooperates with the positioning boss on the first-level stamping device. The presence of the positioning hole helps to cooperate with the positioning boss on the first-level stamping device to achieve precise matching of the electrode membrane grid and the first-level stamping block.

[0049] As a further solution, the number of the positioning holes is ≥2.

[0050] As a further preferred solution, the number of the positioning holes is selected from 4-8.

[0051] The secondary punching device comprises a secondary punch and a secondary punching base, wherein the secondary punching base is fixedly connected to the secondary punch, and the secondary punch protrudes out of the secondary punching base as a whole.

[0052] The electrode film mold is also provided with a positioning portion, and the positioning portion is arranged on the left and right sides of the electrode film mold.

[0053] The mold conveyor belt is provided with positioning cards, which appear in pairs to form a slot that matches the positioning part of the electrode membrane mold. The positioning part is snapped into the slot formed by the positioning card, thereby fixing the electrode membrane mold on the mold conveyor belt.

[0054] As a further solution, the electrode membrane mold is further provided with placement handles, and the placement handles are respectively arranged on the left side and the right side of the electrode membrane mold, and the number of the placement handles is ≥2.

[0055] As a further preferred solution, the number of handles placed is selected from 2-4.

[0056] The mold placement device includes a placement support arm and a first support base. The placement support arm cooperates with a placement handle of the electrode film mold, and the first support base is detachably connected to the placement support arm.

[0057] As a further solution, the mold recovery device includes a recovery clamping arm and a second support base, the recovery clamping arm cooperates with the placement handle of the electrode membrane mold, and the second support base is detachably connected to the recovery clamping arm.

[0058] As a further solution, the current collector unwinding device includes a current collector roll, a first roller pair, and a second roller pair. The current collector roll is used to unwind the current collector, and the second roller pair is used to guide the current collector and electrode film compounded by the hot stamping device into the heating demolding device.

[0059] As a further solution, the pole piece winding device includes a pole piece roll and a third roller pair, the third roller pair is used to guide the pole piece passing through the heated demolding device, and the pole piece roll is used to wind up the pole piece.

[0060] As a further solution, the pole piece roll is provided with a current collector foil detector for detecting the current collector foil.

[0061] As a further solution, the pole piece forming device is also provided with a controller for receiving instructions from technicians and controlling the operation of the pole piece forming device.

[0062] Beneficial Effects

[0063] Compared with the prior art, the present invention has at least the following beneficial effects:

[0064] (1) By presetting the weight-zoned material distribution and position limiting, the requirements for uniformity of material feeding are reduced. The material feeding form can be powder or dough-like materials, and the feeding methods include screw extrusion, air pressure or push rod extrusion, powder blowing, etc., which are all applicable. The quantitative feeding by weight in each material grid further ensures the consistency of the electrode plates produced and improves the stability of product quality.

[0065] (2) A combination of primary and secondary stamping is used. The primary stamping causes the material to slide and flatten within the limit range, preventing local hardening of the material, avoiding excessive stress concentration on the surface of the material, and reducing the risk of material rupture or irreversible changes. The secondary stamping further thins the material, eliminates the peripheral bulge problem caused by the primary stamping, and ultimately obtains an electrode film with good uniformity and high consistency.

[0066] (3) Through hot stamping and lamination, the current collector and the solid electrode film are first deformed slightly by stamping and lamination, and then the binder in the electrode film is bonded to the current collector by hot pressing and lamination, thus achieving a better combination of the electrode film and the current collector. This process optimizes the resistance and cycle performance of the electrode sheet and improves the electrical performance of the electrode sheet.

[0067] (4) The setting of the release layer effectively solves the problem of adhesion and detachment between the electrode membrane and the conveyor belt, avoids damage to the electrode membrane or wear of the conveyor belt caused by adhesion, extends the service life of the equipment, and improves production efficiency.

[0068] (5) The entire process is continuous and simple, which can realize continuous production, improve production efficiency, reduce production costs, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0070] Figure 1 is a schematic diagram of a pole piece forming device; Figure 2 is a top view of the pole piece forming device; Figure 3 is a schematic diagram of an electrode membrane mold;

[0071] Figure 4 A schematic diagram of an electrode film mold placed on a mold conveyor belt; Figure 5 It is a schematic diagram of a primary stamping device; Figure 6 It is a schematic diagram of a two-stage stamping device; Figure 7 It is a schematic diagram of the pole piece forming process; Figure 8 Schematic diagram of the slip deformation of polymer crystals under shearing;

[0072] Fig. 9 For slicing waste; Fig.10 It is a schematic diagram of the structure of the material distribution device; Fig.11 middle Fig.11 a is a mold placement device 173, Fig.11 b is a mold recovery device 174.

[0073] Among them, 11-material conveyor belt; 12-mold release layer pasting device; 13-material distribution device; 131-material distribution port; 132-material tank; 14-material heating device; 15-first-level stamping device; 151-first-level punch; 152-first-level stamping base; 153-positioning boss; 16-second-level stamping device; 161-second-level punch; 162-second-level stamping base; 17-mold conveying assembly; 171-mold conveyor belt; 1711-positioning card; 172-electrode film mold; 1721-electrode film grid; 1722-ear portion; 1723-positioning portion; 1724- Positioning hole; 1725-placing handle; 1726-partitioning part; 173-mold placing device; 1731-placing support arm; 1732-first supporting base; 174-mold recovery device; 1741-recovery clamping arm; 1742-second supporting base; 21-current collector unwinding device; 211-current collector roll; 212-first roller pair; 213-second roller pair; 22-hot stamping device; 221-hot stamping punch; 222-hot stamping body; 23-heating demoulding device; 24-pole piece winding device; 241-pole piece roll; 242-third roller pair. DETAILED DESCRIPTION

[0074] For ease of understanding, the present invention will be described in more detail below and examples of the present invention are given, but the scope of the present invention is not limited thereby.

[0075] The following is a description of terms or words, and unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0076] In this article, the term "material" refers to the raw materials used to prepare the electrode membrane, which can include both the original materials that are directly mixed and the materials that are fiberized after mixing.

[0077] In this article, "fiberized material" refers to the electrode material that has been subjected to fiberization treatment during the dry process of preparing electrodes.

[0078] In this article, the term "zoned material distribution" means placing a preset mass of material at the center of each pole slice area based on the pole slice specifications.

[0079] In this article, the term "hot stamping" refers to the process of combining the pole piece and the electrode membrane together through stamping composite and hot pressing composite during the pole piece processing.

[0080] In this article, the term "stamping composite" refers to the process of combining the current collector and the electrode film together by mechanical stamping during the electrode processing.

[0081] In this article, the term "hot pressing composite" refers to the process of combining the electrode sheet and the electrode film under high temperature conditions by heating and pressure during the electrode sheet processing.

[0082] In a first aspect, the present invention provides a dry method for preparing an electrode film, comprising:

[0083] First, the material is divided into zones according to the preset weight and the material is limited in the corresponding area. The material is sequentially subjected to primary stamping and secondary stamping to obtain an electrode film. The limitation is cancelled after the primary stamping, and the primary stamping and secondary stamping are respectively performed multiple times.

[0084] After the primary stamping pressure increases with the number of times to the primary maximum pressure, it remains at the primary maximum pressure unchanged, wherein the primary maximum pressure is selected from 500-2000Mpa; the secondary stamping pressure increases with the number of times or remains unchanged, the pressure that increases with the number of times is called the secondary stamping variable pressure, and the pressure that remains unchanged with the number of times is called the secondary stamping constant pressure; when the secondary stamping variable pressure increases with the number of times to the secondary stamping variable pressure maximum value and then remains unchanged, it is called the secondary stamping variable pressure maximum pressure, wherein the secondary stamping variable pressure maximum value is selected from 3000-8000Mpa; the secondary stamping constant pressure is selected from 2500-4000Mpa.

[0085] Second, as Figure 7 The present invention provides a method for preparing a pole piece, comprising: covering a current collector on the surface of a prepared electrode film, hot stamping and slicing to obtain a pole piece.

[0086] In order to optimize the electrode preparation process and improve production efficiency, this scheme provides a method for preparing electrode sheets, by partitioning and distributing the materials according to preset weights and limiting the positions, and combining primary and secondary stamping to prepare electrode membranes, and then hot stamping the composite electrode membranes and current collectors, and slicing them to obtain electrode sheets; in this scheme, we first preset the weight of the materials, and combine partitioning and limiting to ensure uniform distribution of the materials and precise weight control. Limiting refers to limiting the materials to the predetermined stamped electrode sheet area to avoid uneven distribution of the materials during subsequent stamping, ensure the consistency of the electrode membrane, and avoid differences in electrical properties caused by uneven materials. When the primary stamping is completed, the limiting is cancelled, so that the secondary stamping can stamp the materials after the primary stamping, thereby improving the uniformity and consistency of the electrode membrane. density; in addition, in this scheme, we combine the primary stamping with the secondary stamping. First, the primary stamping is used to make the material slide and flatten to the limit range to prevent excessive pressure from causing local hardening of the material, while avoiding excessive stress concentration on the surface of the material, reducing the risk of material rupture or irreversible changes, and then canceling and performing the secondary stamping to make the material further slide and thinner while eliminating the peripheral bulge problem caused by the primary stamping, thereby obtaining an electrode film with good uniformity and high consistency; in addition, through hot stamping, first stamping and then hot pressing, on the basis of using stamping and compounding to make the collector and the solid electrode film slightly deformed, hot pressing and compounding are used to make the binder in the electrode film bond with the collector, thereby achieving better bonding between the electrode film and the collector, and optimizing the electrode sheet resistance and cycle performance.

[0087] As some examples, the material distribution method is not limited in principle, including but not limited to any one or more of extrusion and powder conveying to achieve the processing of different materials.

[0088] As some examples, the material is heated before the primary stamping to enhance the thermoplastic slip properties of the material.

[0089] As some examples, when the primary stamping is heated, the temperature range is selected from 50-120°C.

[0090] As some examples, the primary punching times are greater than 10 times.

[0091] As some examples, during the first-level stamping, the stamping frequency is selected from 10-1000 times / min, and the preferred stamping frequency is selected from 50-200 times / min. The stamping frequency will affect the flow rate of the material, thereby affecting the uniformity and consistency of the electrode film, and further affecting the ion migration efficiency of the electrode and the battery impedance. When the stamping frequency is selected from 50-200 times / min, it helps to promote the uniform distribution of the material, improve the uniformity and consistency of the electrode film, thereby reducing the electrode resistance and optimizing the electrode performance.

[0092] As some examples, the primary stamping pressure is selected from 1-2000 MPa.

[0093] As some examples, the first-stage stamping pressure law that increases with the number of times is not limited in principle, for example, it can be X n+1 =d(X n ) m And other functions or self-set pressure values, where X represents the value of the first-stage stamping pressure, d is selected from 1-9.9, m is selected from 1-3, n represents that this stamping is the nth stamping, X is greater than or equal to 1, and the initial first-stage pressure is greater than or equal to 1Mpa.

[0094] As some examples, the secondary stamping times are greater than 5 times.

[0095] As some examples, during the secondary stamping, the stamping frequency is selected from 5-100 times / min, preferably 5-50 times / min.

[0096] As some examples, when the secondary stamping pressure increases with the number of times, the secondary stamping pressure is selected from 50-8000Mpa, preferably 300-8000Mpa.

[0097] As some examples, during the secondary stamping, the law of the secondary stamping pressure change with increasing times is not limited in principle, for example, it can be Y p+1 =f(Y p ) q And other functions or independently set pressure values, where Y represents the value of the secondary stamping variable pressure, f is selected from 1-9.9, q is selected from 1-3, p represents that this stamping is the pth stamping, Y is greater than or equal to 1, and the initial secondary stamping variable pressure is greater than or equal to 1Mpa.

[0098] As some preferred examples, the initial secondary stamping transformation pressure is selected from 50-500 MPa.

[0099] As some preferred examples, the maximum pressure of the secondary stamping variable pressure is 3-10 times the maximum pressure of the primary stamping, and the constant pressure of the secondary stamping is 2-8 times the maximum pressure of the primary stamping. By controlling the relationship between the maximum pressure of the primary stamping, the constant pressure of the secondary stamping, and the maximum pressure of the secondary stamping variable pressure, it is helpful to more effectively compact the electrode film formed after the primary stamping, thereby eliminating the local protrusions or uneven areas generated during the primary stamping process, further reducing the porosity of the electrode film, and improving the structural stability of the electrode film.

[0100] As some examples, during the hot stamping, stamping composite is first performed, and after the stamping composite is completed, hot pressing composite is performed. Through the stamping composite and hot pressing composite method, it is possible to further utilize heat to further enhance the bonding strength between the electrode film and the current collector on the basis of achieving preliminary bonding, thereby ensuring a closer contact between the electrode film and the current collector, reducing interface defects, and optimizing product cycle, impedance and other performance.

[0101] As some examples, during the stamping and compounding, the number of stamping and compounding times is greater than 5 times.

[0102] As some examples, during the stamping and compounding, the stamping and compounding frequency is selected from 10-100 times / min, preferably 20-60 times / min.

[0103] As some examples, during the stamping and compounding, the impact compounding pressure can remain unchanged, or increase continuously or step by step with the number of stamping and compounding times.

[0104] As some examples, during the stamping and compounding, the impact compounding pressure preferably increases with the number of stamping and compounding times. When the impact compounding pressure increases with the number of stamping and compounding times to a maximum impact compounding pressure, the impact compounding pressure continues to remain unchanged at the maximum impact compounding pressure with the remaining number of times. The maximum impact compounding pressure is selected from 800-1000Mpa.

[0105] As some examples, during the stamping and compounding, the law of the impact compounding pressure increasing with the stamping and compounding times is not limited in principle, for example, it can be Z a+1 =c(Z a ) e And other functions or independently set pressure values, wherein Z represents the value of the impact composite pressure, c is selected from 1-9.9, e is selected from 1-3, a represents that this stamping is the ath stamping, Z is greater than or equal to 1, the initial impact composite pressure is greater than or equal to 1Mpa, and the initial impact composite pressure is selected from 10-300Mpa.

[0106] As some examples, when the impact compounding pressure remains unchanged, the impact compounding pressure is selected from 10-1000 MPa, preferably 50-350 MPa.

[0107] As some examples, during the hot pressing compounding, the hot pressing compounding pressure is selected from 50-1000 MPa, preferably 300-600 MPa.

[0108] As some examples, during hot pressing and laminating, the temperature is selected from 80-300° C., and the heating time is selected from 1-60 s.

[0109] As some preferred examples, the temperature during the hot pressing composite is selected from 90-150° C. and the time is selected from 20-40 s, which helps to further promote the bonding of the adhesive in the electrode film and the current collector, optimize the bonding effect, and achieve effective bonding of the electrode film and the current collector.

[0110] As some preferred examples, when distributing materials in different areas, a demoulding layer is provided on the corresponding areas for limiting, and the materials are distributed on the demoulding layer. After the hot stamping is completed, the demoulding layer is heated and separated. The existence of the demoulding layer helps to achieve easy and fast separation of the pole piece and the carrier (such as a conveyor belt), thereby ensuring the quality of the pole piece and improving production efficiency.

[0111] As some examples, in the method for preparing the pole piece, the temperature for heating and decomposing the demolding layer is selected from 130-300° C., and the time is selected from 1-60 s.

[0112] As some preferred examples, the temperature for heating and decomposing the demolding layer is selected from 130-180° C., and the time is selected from 20-40 s, which helps to further optimize the pole piece separation effect and protect the pole piece performance.

[0113] Thirdly, Figure 1-2 The present invention provides a pole piece forming device, including a material conveyor belt 11, and a demoulding layer pasting device 12, a material distribution device 13, a material heating device 14, a primary stamping device 15, a secondary stamping device 16, a hot stamping device 22, and a heating demoulding device 23, which are sequentially arranged on the material conveyor belt 11 along the material conveying direction;

[0114] The electrode forming device is also provided with a mold conveying assembly 17, including an electrode film mold 172, a mold conveyor belt 171, a mold placing device 173, and a mold recovery device 174. The mold placing device 173 is used to place the electrode film mold 172 on the material conveyor belt 11 before the material distribution device 13. The mold conveyor belt 171 is arranged on the edges of both sides of the material conveyor belt 11 and is parallel to or higher than the material conveyor belt 11 in the horizontal direction. The mold conveyor belt 171 is used to carry the electrode mold 172 through the material distribution device 13, the material heating device 14, and the primary stamping device 15 in sequence. The mold recovery device 174 is used to recover the electrode mold 172 after the primary stamping.

[0115] The pole piece forming device is also provided with a current collector unwinding device 21 and a pole piece winding device 24 . The unwinding device 21 is used to unwind the current collector to compound it with the electrode film passed through the hot stamping device 22 , and the pole piece winding device 24 is used to wind the pole piece demoulded by the hot stamping device 22 .

[0116] In this solution, the release layer pasting device 12 can paste the release layer to the surface of the material conveyor belt 11, the mold placing device 173 places the electrode film mold 172 on the material conveyor belt 11 pasted with the release layer, and the material distribution device 13 distributes the material into the electrode film mold 172 in a partitioned manner according to the preset weight, and the electrode film mold 172 is used to limit the material. Subsequently, the material heating device 14 heats the material. The setting of the material heating device 14 helps to improve the thermoplastic slip of the material by using temperature, so that the material is more evenly distributed in the primary stamping process;

[0117] The heated material enters the working range of the stamping device 15 for primary stamping. After the stamping is completed, the mold recovery device 174 recovers the electrode film mold 172. The secondary stamping device 16 performs secondary stamping on the material after the primary stamping. After the stamping is completed, the electrode film is obtained.

[0118] The current collector is covered on the surface of the prepared electrode film through the current collector unwinding device 21, and the electrode film and the current collector are hot-stamped together through the hot stamping device 22. Then, the electrode film is physically separated from the material conveyor belt 11 through the heating demolding device 23. The heating demolding device 23 with a heating function improves the production efficiency while realizing easy physical separation between the electrode film and the conveyor belt. After demolding, the electrode piece winding device 24 winds it up to obtain a single-sided electrode piece.

[0119] There is no limitation on the type of the release layer pasting device 12 , and technicians can select different pasting devices to paste the release layer to the surface of the material conveyor belt 11 according to their needs.

[0120] As some examples, the thickness of the demoulding layer is selected from 0.1μm-20μm, including a carrier layer and a glue layer arranged on any side of the carrier layer. In order to avoid the influence of the demoulding layer on the performance of the electrode, it is necessary to select a material with a melting point higher than the hot pressing composite temperature and lower than the upper limit of the tolerance temperature of each substance in the material, and the shrinkage or decomposition residue does not react with the battery material or electrolyte as the demoulding layer. Therefore, the material of the carrier layer and the glue layer in the demoulding layer is not limited in principle, wherein the carrier layer can be selected from one or more of polyethylene, polypropylene, and polycarbonate; the glue layer can be selected from one of polyacrylate glue and polyurethane glue.

[0121] As some examples, when the mold conveyor belt 171 is higher than the material conveyor belt 11 in the horizontal direction, the height is selected from 0.5-1 mm.

[0122] As some examples, the material distribution device 13 includes a material distribution port 131 and a material tank 132. The material tank 132 is fixedly connected to the material distribution port 132. The material distribution port 131 can distribute the material in partitions according to preset weights.

[0123] As some examples, Figure 5 The primary stamping device 15 includes a primary punch 151 and a primary stamping base 152. The primary stamping base 152 is fixedly connected to the primary punch 151. The primary punch 151 protrudes from the primary stamping base 152. The shape of the primary punch 151 matches the electrode membrane mold 172 and is used to perform primary stamping on the material in the electrode membrane mold 172.

[0124] As some examples, the electrode membrane mold 172 includes a primary electrode membrane grid, which connects the front and back sides of the electrode mold 172 and has a width that matches the material conveyor belt 11. The primary punch 151 matches the primary electrode membrane grid, and the size of the primary punch 151 is smaller than the size of the primary electrode membrane grid by 0.8mm-1.2mm.

[0125] As some preferred examples, Figure 3 , Figure 5 As shown, the primary punch 151 is divided into a primary stamping block 1511 by grooves distributed vertically and horizontally, and the electrode film mold 172 includes a pole ear portion 1722 and a partition portion 1726. The pole ear portion 1722 and the partition portion 1726 are crisscrossed to divide the primary electrode film grid into an electrode film grid 1721. The electrode film grid 1721 cooperates with the primary stamping block 1511, and the size of the primary stamping block 1511 is 0.8mm-1.2mm smaller than the size of the electrode film grid 1721. The existence of the electrode film grid 1721 can realize the limitation of the material in the corresponding area, and at the same time cooperate with the material distribution device 13 to realize the control of the consistency of the electrode film, and obtain an electrode film with high consistency and good uniformity; the electrode film grid 1721 cooperates with the primary stamping block 1511 on the primary stamping device 15, and the pole ear portion 1722 is arranged between two adjacent columns of electrode film grids 1721, so as to reserve the pole ear space for the subsequent electrode film preparation of the pole piece.

[0126] As some examples, the primary stamping base 152 is also provided with a positioning boss 153 that cooperates with the electrode membrane mold 172.

[0127] As some examples, the electrode mold die 172 is also provided with a positioning hole 1724 that cooperates with the positioning boss 153 on the primary stamping device 15. The presence of the positioning hole 1724 helps to cooperate with the positioning boss 153 on the primary stamping device 15 to achieve precise matching of the electrode membrane grid 1721 and the primary stamping block 1511.

[0128] As some examples, the number of the positioning holes 1724 is ≥2.

[0129] As some preferred examples, the number of the positioning holes 1724 is selected from 4-8.

[0130] like Figure 6 The secondary stamping device 16 includes a secondary punch 161 and a secondary stamping base 162. The secondary stamping base 162 is fixedly connected to the secondary punch 161. The secondary punch 16 protrudes out of the secondary stamping base 162 as a whole, which helps to provide a more uniform secondary stamping for the electrode membrane and remove the convex marks on the edge of the material after the primary stamping.

[0131] The electrode film mold 172 is also provided with a positioning portion 1723 , and the positioning portion 1723 is arranged on the left and right sides of the electrode film mold 172 .

[0132] like Figure 4 As shown, the mold conveyor belt 171 is provided with a positioning card 1711, and the positioning card 1711 appears in pairs to form a slot that cooperates with the positioning part 1723 of the electrode film mold 172, and the positioning part 1723 is engaged in the slot formed by the positioning card 1711, thereby realizing the fixation of the electrode film mold 172 on the mold conveyor belt 171, avoiding the displacement of the electrode film mold 172 and losing the limiting effect on the material, thereby improving the reliability and stability of the electrode piece forming device.

[0133] As some examples, the electrode film mold 172 is further provided with a placement handle 1725, and the placement handles are respectively arranged on the left and right sides of the electrode film mold 172, and the number of the placement handles 1725 is ≥2.

[0134] As some preferred examples, the number of the placement handles 1725 is selected from 2-4.

[0135] The mold placement device 173 includes a placement support arm 1731 and a first support base 1732. The placement support arm 1731 cooperates with the placement handle 1725 of the electrode film mold 172 to place the electrode film mold 172 on the material conveyor belt 11 between the demolding layer pasting device 12 and the cloth device 13. The first support base 1732 is detachably connected to the placement support arm 1731.

[0136] As some examples, the mold recovery device 174 includes a recovery clamping arm 1741 and a second support base 1742. The recovery clamping arm 1741 cooperates with the placement handle 1725 of the electrode film mold 172, and can remove and recover the electrode film mold 172 after the first-level stamping from the material conveyor belt 11. The second support base 1742 is detachably connected to the recovery clamping arm 1741.

[0137] As some examples, the current collector unwinding device 21 includes a current collector roll 211, a first roller pair 212, and a second roller pair 213. The current collector roll 211 is used to unwind the current collector. The first roller pair 212 covers the unrolled current collector on the electrode film after secondary stamping. The second roller pair 213 guides the current collector and the electrode film compounded by the hot stamping device 22 into the heating demolding device 23.

[0138] As some examples, the pole piece winding device 24 includes a pole piece roll 241 and a third roller pair 242 . The third roller pair 242 is used to guide the pole piece passing through the heated demolding device 23 . The pole piece roll 241 is used to wind up the pole piece.

[0139] As some examples, the pole piece roll 241 is provided with a current collector foil detector for detecting the current collector foil.

[0140] As some examples, the pole piece forming device is also provided with a controller for receiving instructions from technicians and controlling the operation of the pole piece forming device.

[0141] The pole piece forming device provided by the present invention operates in a stepping manner, and the stepping time and spacing can also be preset in the controller as needed. As an example, the specific working process is described as follows:

[0142] The electrode forming device includes the following processes along the material conveying direction: the process of pasting the release layer by the release layer pasting device 12, the process of placing the electrode membrane mold 172 by the mold placing device 173, the process of spreading the material by the material laying device 13, the process of heating the material by the material heating device 14, the process of performing primary stamping on the material by the primary stamping device 15, the process of recovering the electrode membrane mold 172 after primary stamping by the mold recovery device 174, the process of performing secondary stamping on the material by the secondary stamping device 16, the process of hot stamping on the electrode membrane and the current collector by the hot stamping device 22, and the heating demolding device 23 heating and demolding the primary electrode; the working position stepping intervals of the above processes can be set to be the same, and the longest working time in the above processes can be selected as the stepping time of the material conveyor belt 11.

[0143] The material is added into the material tank 132 of the material distribution device 13 .

[0144] In a step time △t n Inside, the controller first controls the release layer pasting device 12 to paste the release layer on the material conveyor belt 11;

[0145] Next step time △t n+1 Inside, the mold placing device 173 places the electrode film mold 172 on the mold conveyor belt 171 on which the release layer has been pasted, and the mold conveyor belt 171 drives the electrode film mold 172 and the material conveyor belt 11 to move synchronously;

[0146] At the next step time △t n+2 In the mold, the material conveyor belt 11 with the mold placement device 173 enters the partition distribution position, and the distribution device 13 places the preset material Mt n+2 (denotes the object to be referred to at step time △t n+2 The part of the material M) distributed by the distribution device 13 on the material conveyor belt 11 is distributed on the mold conveyor belt 171 with a release layer attached thereto, and the electrode film mold 172 limits the material in the area;

[0147] At the next step time △t n+3 Inside, with material Mt n+2 The material conveyor belt 11 enters the working position of the material heating device 14, and the material heating device 14 starts to heat the material Mt n+2 , reinforced material Mt n+2 Slippage;

[0148] At the next step time △t n+4 The material Mt heated by the material heating device 14 n+2 The material is conveyed by the material conveyor belt 11 to the working position of the primary stamping device 15, and the stamping device 15 starts to press the heated material Mt n+2 Perform a first-stage stamping. During stamping, the first-stage stamping pressure increases with the number of stamping times and remains unchanged after reaching the first-stage maximum pressure;

[0149] At the next step time △t n+5 The mold recovery device 174 recovers the electrode film mold 172 from the material conveyor belt 11, and the mold recovery device 174 is cancelled to recover the material Mt after the primary stamping. n+2 The limiting effect;

[0150] At the next step time △t n+6 Inside, the material conveyor belt 11 drives the material Mt that has been removed from the limit after the first-stage stamping. n+2 Enter the working position of the secondary stamping device 16, the secondary stamping device 16 performs secondary stamping on it, and after the stamping is completed, the material Mt n+2 forming an electrode film;

[0151] At the next step time △t n+7 Inside, the material conveyor belt 11 drives the material Mt n+2 The current collector unwound from the current collector unwinding device 21 is combined into the hot stamping device 22, and the hot stamping device 22 performs hot stamping on the electrode film and the current collector to achieve the electrode film Mt n+6 After hot stamping, the material Mt n+2 Together with the current collector, it forms a primary pole piece.

[0152] At the next step time △t n+8 Inside, the material conveyor belt 11 drives the primary electrode into the working position of the heating and demolding device 23. The heating and demolding device 23 heats the primary electrode and the material conveyor belt 11 corresponding to the primary electrode to decompose the demolding layer, thereby separating the primary electrode from the material conveyor belt 11 to obtain the electrode.

[0153] Finally, the current collector unwinding device 21 unwinds the current collector and the electrode film Mt after secondary stamping. n+6 After lamination, the electrode sheet winding device 24 winds up the separated electrode sheets on the material conveyor belt 11 to obtain an electrode sheet roll.

[0154] At the same time, within the same step time, each process can be carried out synchronously at its respective working position, thereby realizing the continuous preparation of the electrode.

[0155] The electrode sheet prepared by the above steps is a single-sided electrode sheet. When a double-sided electrode sheet needs to be prepared, the rolled single-sided electrode sheet is connected to the collector unwinding device 21, the switch is turned on, and the above operation is repeated to obtain a double-sided electrode sheet roll, and the double-sided electrode sheet roll is sliced ​​to obtain the electrode sheet.

[0156] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application and do not represent all possible embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0157] The chemical materials involved in the following examples and comparative examples are all prior art and are commercially available. The experimental devices, test devices, etc. involved in the following examples and comparative examples are all conventional devices in the art, without special requirements and limitations.

[0158] Example 1

[0159] The materials of NCM ternary: CNT: PEFT: PVDF with a ratio of 84: 1: 10: 5 were stirred and premixed for 1 hour and then subjected to airflow fiberization for 2 hours for fiberization treatment; a 10 μm polycarbonate film with polyacrylate adhesive on one side was used as a release layer, the material conveyor belt 11 was set at a step speed of 1 min / time, the heating temperature was 90 ° C, the primary stamping rate was 100 times / min, and the primary stamping pressure was set at X n+1 =5X n The law of increasing from small to large, among which, X 1 =0.2Mpa, X≤1000Mpa, n represents the nth stamping, when n=7, the primary stamping pressure is maintained at 1000Mpa; the secondary stamping rate is 20 times / min, and the secondary stamping pressure is adjusted according to Yq+1 =2Y q The law of increasing from small to large, among which, Y 1 =300Mpa and Y≤3000Mpa. When q=5, the secondary stamping pressure is maintained at 3000Mpa. Q represents the qth stamping. During hot stamping, the impact composite pressure is 100Mpa, the stamping speed is selected from 40 times / min, during hot pressing, the hot pressing composite pressure is selected from 500Mpa, the hot pressing temperature is selected from 100℃, the hot pressing time is selected from 30s, during demolding, the demolding temperature is selected from 100℃, the demolding time is selected from 30s, and after the demolding time is over, it quickly drops to room temperature.

[0160] Turn on the switch, with 1 minute as the step time, the demoulding layer pasting device 12 pastes the polycarbonate film containing polyacrylate glue on one side onto the material conveyor belt 11, the mold placing device 173 places the electrode film mold 172 on the mold conveyor belt 17, and the material distribution device 13 distributes the material to the electrode film mold 172, and then passes through the material heating device 14-the first-level stamping device 15-the second-level stamping device 16-the fluid unwinding device 21-the hot stamping device 22-the heating demoulding device 23-the pole piece winding device 24, and presses the stop button after winding 100 meters. The pole piece winding device 24 stops winding after detecting the collector foil to obtain a single-sided pole piece.

[0161] The rolled single-sided electrode sheet is loaded onto the current collector unwinding device 21 and the tape is connected. The switch is turned on, and the above operation is repeated to complete the double-sided film forming to obtain the electrode sheet roll, and the electrode sheet roll is cut into slices to make a battery.

[0162] Example 2

[0163] The preparation method is the same as that in Example 1, except that the primary punching speed is 49 times / min, the material conveyor belt 11 step speed is 3min / time, and the equipment is paused after all operations are completed until the material conveyor belt 11 advances one grid and then continues to work.

[0164] Example 3

[0165] The preparation method is the same as that in Example 1, except that during the secondary stamping, the secondary stamping pressure is maintained unchanged, and the secondary stamping pressure is 3500 MPa.

[0166] Example 4

[0167] The preparation method is the same as that of Example 1, except that during hot stamping, the impact composite pressure is 400 MPa.

[0168] Example 5

[0169] The preparation method is the same as that of Example 1, except that during hot stamping, the hot pressing compound temperature is 180°C.

[0170] Example 6

[0171] The preparation method is the same as that of Example 1, except that the demoulding temperature is selected to be 180°C.

[0172] Comparative Example 1

[0173] The same materials as in Example 1 were used, except that multiple roll pressing was used to form the film, wherein the main roll pressure was 3000 MPa, and the film was rolled 13 times to obtain a single-sided electrode film with the same thickness as in Example 1. After making two single-sided electrode films, the composite current collector was rolled to obtain a double-sided electrode film, which was cut into sheets to make batteries.

[0174] Comparative Example 2

[0175] The preparation method is the same as that of Example 1, except that no secondary stamping is performed.

[0176] Comparative Example 3

[0177] The preparation method is the same as that of Example 1, except that no mold is used.

[0178] Comparative Example 4

[0179] The preparation method is the same as in Example 1, except that hot pressing is not performed during hot stamping.

[0180] Comparative Example 5

[0181] The preparation method is the same as in Example 1, except that only five single punchings are performed.

[0182] Comparative Example 6

[0183] The preparation method is the same as that of Example 1, except that the primary stamping pressure is fixed and maintained at 150 MPa.

[0184] Comparative Example 7

[0185] The preparation method is the same as that of Example 1, except that the secondary punching rate is 200 times / min.

[0186] Comparative Example 8

[0187] The preparation method is the same as that of Example 1, except that the polycarbonate film containing polyacrylate adhesive on one side is not pasted as the release layer.

[0188] Comparative Example 9

[0189] The preparation method is the same as that of Example 1, except that during the secondary stamping, only three stampings are performed.

[0190] Comparative Example 10

[0191] The preparation method is the same as that in Example 1, except that during hot stamping, the hot pressing composite pressure is 10 MPa.

[0192] Comparative Example 11

[0193] The preparation method is the same as that of Example 1, except that the demoulding temperature is selected to be 65°C.

[0194] Experimental Testing

[0195] The ionic impedance test equipment in the example is Autolab Nova2.1 electrochemical workstation;

[0196] According to the mass of active substances in the material and the gram capacity of the material, the design capacity of the sample battery cell made of the electrode in the example is calculated to be 800mAh. The 1C cycle is charged to 4.2V with 0.8ACC-CV and then discharged to 27V with 0.8A. The discharge capacity is recorded each time. The discharge capacity / initial discharge capacity is the 1C cycle capacity retention rate.

[0197] The 2C / 0.33C capacity ratio test method is: 0.8A (ie 1C) CC-CV to 3.95V, 1.6A discharge to 2.7V The capacity obtained is the 2C capacity, 0.8A (ie 1C) CC-CV to 3.95V, 0.264A (ie 0.33C) discharge to 2.7V The capacity is the 0.33C capacity, 2C capacity / 0.33C capacity is the 2C / 0.33C capacity ratio.

[0198] The test results are shown in Table 1.

[0199] Table 1

[0200]

[0201]

[0202] It can be observed from Examples 1-6 and Comparative Examples 1-11 that Examples 1-6 exhibit better ionic impedance, 2C / 0.33C capacity ratio and 1C cycle 100 capacity retention rate than Comparative Examples 1-11. At the same time, the thickness difference of the single-sided electrode film of the examples (≤3) is also better than that of the comparative examples (≥5), indicating that the electrode sheet prepared by this scheme can effectively avoid voids, cracks or unevenness inside the electrode film, thereby optimizing the electrode sheet resistance, improving the capacity retention capability, and optimizing the cycle performance.

[0203] From Example 1 and Comparative Example 1, it can be observed that when the electrode is prepared by multiple rolling methods, the ionic impedance, 2C / 0.33C capacity ratio and 1C cycle 100 capacity retention rate of Comparative Example 1 are all weaker than those of Example 1. This may be because, compared with this solution, Comparative Example 1 prepared by multiple rolling methods may be uneven, thereby affecting the performance of the electrode.

[0204] We also further discussed the role of primary stamping and secondary stamping in optimizing this solution. From Example 1 and Comparative Example 2, it can be observed that when secondary stamping is not performed, Comparative Example 2 has an uneven appearance and performance far inferior to that of Example 1, indicating that primary stamping and secondary stamping are indispensable for optimizing the electrode membrane structure and obtaining pole pieces with good performance.

[0205] In Comparative Example 3, we discussed the role of the pole piece mold. The existence of the pole piece mold enables the consistency of the thickness and performance of the pole piece to be controlled on the basis of the preliminary shaping of the electrode film. When the pole piece mold is not used, Comparative Example 3 presents an irregular appearance, and the thickness of the single-sided electrode film is lower than that of Example 1, which in turn affects the capacity retention ability of the pole piece.

[0206] Similarly, hot pressing is also an important step in this scheme. In Comparative Example 4, we only performed stamping without hot pressing when composite electrode membrane and current collector. At this time, the current collector fell off. This may be because the hot pressing process helps promote the adhesion between the adhesive in the electrode membrane and the current collector. Therefore, when hot pressing is not performed, the current collector falls off.

[0207] In Example 1 and Comparative Examples 5-7, we discussed the effects of primary and secondary stamping conditions on the performance of the electrode membrane and even the pole piece. It can be observed that Comparative Examples 5-7 all exhibited worse ionic impedance, 2C / 0.33C capacity ratio, and cycle capacity retention than Example 1. This indicates that the conditions of primary and secondary stamping (including stamping rate, stamping times, and stamping pressure) are also factors that affect the electrode membrane and the pole piece. When Comparative Examples 5-7 do not meet the conditions that the primary stamping frequency is selected from 10-1000 times / min, the primary stamping pressure is selected from 1-2000Mpa, the secondary stamping frequency is selected from 5-100 times / min, and the secondary stamping transformer pressure is selected from 50-8000Mpa, the electrode membrane may be uneven, thereby affecting the performance of the pole piece.

[0208] In Example 1 and Comparative Example 8, we observed that the lack of a release layer would also affect the performance of the electrode membrane and the electrode sheet. Compared with Example 1, when no release layer was provided (Comparative Example 8), the material was compacted on the conveyor table under the action of the primary and secondary stamping and was difficult to physically separate. After forced separation, Comparative Example 8 showed severe cracking.

[0209] In Example 1 and Comparative Examples 9-10, we discussed the effect of hot stamping conditions on the performance of the electrode sheet when the electrode film and the current collector are composited by hot stamping. It can be observed that when the number of stamping composite times is 3 or the hot pressing composite pressure is 10Mpa, the electrode sheet performances of Comparative Examples 9 and 10 are greatly affected, and the current collector directly falls off in Comparative Example 10. This may be because too few stamping composite times (<5 times) and too low hot pressing composite pressure (<50Mpa) cannot ensure sufficient fit between the current collector and the electrode film.

[0210] Furthermore, we also discussed the effect of demolding temperature on the performance of the electrode. When the demolding temperature was selected at 65°C, a demolding layer adhered to the surface of the electrode prepared in Comparative Example 11. This may be because the demolding temperature of 65°C could not achieve complete pyrolysis of the demolding layer, thus affecting the results of Comparative Example 11.

[0211] The frequency of stamping will affect the flow rate of the material in the electrode mold, and thus affect the performance of the electrode membrane. From Examples 1-2, we can observe that when the primary stamping speed is selected from 100 times / min, Example 1 exhibits better ionic impedance, capacity retention and cycle performance than Example 2. This may be because when the stamping frequency is selected from 50-200 times / min, the material is more evenly distributed in the electrode mold, thereby improving the performance of the electrode membrane and optimizing the electrode resistance. Therefore, Example 1 exhibits better performance.

[0212] When performing the primary stamping and the secondary stamping, the stamping pressure changes from small to large according to the rule, which helps to obtain an electrode film with better uniformity and stronger mechanical properties, thereby optimizing the performance of the electrode. Therefore, in Examples 1 and 3, we observed that according to Y q+1 =2Y q , Y 1 Example 1, in which Y≤300Mpa and Y≤3000Mpa change regularly, has better impedance and cycle performance than Example 3.

[0213] In this scheme, we realize the composite of the current collector and the electrode film by hot stamping. Therefore, in Examples 1, 4-5, we further explored the conditions during hot stamping. It can be observed that Example 1 exhibits better ionic impedance, capacity retention ability and cycle performance than Examples 4 and 5. This may be because the stamping composite can cause the current collector and the solid electrode film to deform slightly with each other, thereby highly fitting, while the hot pressing composite can make the binder in the electrode film bond with the current collector. When the impact composite pressure is controlled to be selected from 50-350Mpa and the hot pressing composite temperature is selected from 90-150℃, it is helpful to optimize the mechanical properties of the electrode sheet on the basis of achieving full combination of the electrode film and the current collector, and further improve the bonding strength between the electrode film and the current collector, thereby optimizing the performance of the electrode sheet.

[0214] In order to achieve rapid physical separation of the electrode and the material conveyor belt 11, a demolding layer is set in the present solution. Under specific temperature conditions, the demolding layer quickly decomposes to achieve separation of the electrode and the material conveyor belt 11. Therefore, in Examples 1 and 6, we discussed the different electrode performances brought about by different demolding temperatures. It can be observed that at a demolding temperature of 135°C, Example 1 exhibits better comprehensive performance than Example 6. This may be because when the temperature for heating to separate the demolding layer is selected from 120-150°C, it can better protect the various substances in the electrode film, thereby improving the performance of the electrode.

[0215] The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. Although the embodiments of the present invention have been shown and described above, it can be understood that the above-described embodiments are exemplary and cannot be understood as limitations of the present invention. Those of ordinary skill in the art can change, modify, replace and deform the above-described embodiments within the scope of the present invention. In addition, those of ordinary skill in the art can combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without contradiction.

Claims

1. A dry method for preparing an electrode membrane, characterized in that: The method comprises the following steps: distributing the material in different areas and limiting the material in corresponding areas, and sequentially performing primary stamping and secondary stamping to obtain an electrode film, wherein the limiting is cancelled after the primary stamping, and the primary stamping and secondary stamping are respectively performed multiple times; After the primary stamping pressure increases with the number of times to the primary maximum pressure, it remains at the primary maximum pressure unchanged, wherein the primary maximum pressure is selected from 500-2000Mpa; the secondary stamping pressure increases with the number of times or remains unchanged, the pressure that increases with the number of times is called the secondary stamping variable pressure, and the pressure that remains unchanged with the number of times is called the secondary stamping constant pressure; when the secondary stamping variable pressure increases with the number of times to the secondary stamping variable pressure maximum value and then remains unchanged, it is called the secondary stamping variable pressure maximum pressure, wherein the secondary stamping variable pressure maximum value is selected from 3000-8000Mpa; the secondary stamping constant pressure is selected from 2500-4000Mpa.

2. The dry method for preparing an electrode film according to claim 1, characterized in that: The material distribution method is selected from any one or more of extrusion and powder conveying; Preferably, the material is heated before the primary stamping; Preferably, when heating is performed in the first stage of stamping, the temperature range is selected from 50-120°C; Preferably, the first-level stamping times are greater than 10 times; Preferably, during the primary stamping, the stamping frequency is selected from 10-1000 times / min; Preferably, during the primary stamping, the stamping frequency is selected from 50-200 times / min; Preferably, the primary stamping pressure is selected from 1-2000Mpa; Preferably, during the first-stage stamping, the first-stage stamping pressure law that increases with the number of times is selected from X n+1 =d(X n ) m , where X represents the value of the primary stamping pressure, d is selected from 1-9.9, m is selected from 1-3, n represents that this stamping is the nth stamping, X is greater than or equal to 1, and the initial primary pressure is greater than or equal to 1Mpa.

3. The dry method for preparing an electrode film according to claim 1, characterized in that: The secondary stamping times are greater than 5 times; Preferably, during the secondary stamping, the stamping frequency is selected from 5-100 times / min; Preferably, during the secondary stamping, the stamping frequency is selected from 5-50 times / min; Preferably, when the secondary stamping pressure increases with the number of times, the secondary stamping pressure is selected from 50-8000Mpa; Preferably, when the secondary stamping pressure increases with the number of times, the secondary stamping pressure is selected from 300-8000Mpa; Preferably, during the secondary stamping, the law of the secondary stamping pressure change with increasing times is Y p+1 =f(Y p ) q , where Y represents the value of the secondary stamping pressure, f is selected from 1-9.9, q is selected from 1-3, p represents that this stamping is the pth stamping, Y is greater than or equal to 1, and the initial secondary stamping pressure is greater than or equal to 1Mpa; Preferably, the initial secondary stamping pressure is selected from 50-500Mpa; Preferably, the maximum pressure of the secondary stamping transformation is 3-10 times the maximum pressure of the primary stamping transformation; Preferably, the constant pressure of the secondary stamping is 2-8 times the maximum pressure of the first stage.

4. A method for preparing an electrode sheet comprising the electrode film according to claim 1, characterized in that: The method comprises the following steps: covering the surface of the prepared electrode film with a current collector, hot stamping and slicing the film to obtain an electrode sheet.

5. The method for preparing a pole piece according to claim 4, characterized in that: During the hot stamping, the number of stamping and compounding is greater than 5 times; Preferably, during the hot stamping, the stamping compound frequency is selected from 10-100 times / min; Preferably, during the hot stamping, the stamping compound frequency is selected from 20-60 times / min; Preferably, during the hot stamping, the impact composite pressure can remain unchanged, or increase continuously or step by step with the number of stamping composite times; Preferably, during the hot stamping, the impact composite pressure preferably increases with the number of stamping composites. When the impact composite pressure increases with the number of times to a maximum impact composite pressure, the impact composite pressure continues to remain unchanged at the maximum impact composite pressure with the remaining number of times. The maximum impact composite pressure is selected from 800-1000Mpa. Preferably, during the stamping and compounding, the impact compounding pressure law that increases with the number of stamping and compounding times is selected from Z a+1 =c(Z a ) e , where Z represents the value of the impact composite pressure, c is selected from 1-9.9, e is selected from 1-3, a represents that this stamping is the ath stamping, Z is greater than or equal to 1, and the initial impact composite pressure is greater than or equal to 1Mpa. The initial impact composite pressure is selected from 10-300Mpa; Preferably, when the impact composite pressure remains unchanged, the impact composite pressure is selected from 10-1000Mpa; Preferably, when the impact composite pressure remains unchanged, the impact composite pressure is selected from 50-350Mpa; Preferably, during the hot pressing and compounding, the hot pressing and compounding pressure is selected from 50-1000Mpa; Preferably, during the hot pressing and compounding, the hot pressing and compounding pressure is selected from 300-600Mpa; Preferably, during hot pressing and laminating, the temperature is selected from 80-300°C, and the heating time is selected from 1-60s; Preferably, the temperature during hot pressing and laminating is selected from 90-150°C, and the time is selected from 20-40s; Preferably, when distributing materials in different areas, a demoulding layer is provided on the corresponding areas for limiting, and after hot stamping is completed, the demoulding layer is heated and separated; Preferably, in the method for preparing the pole piece, the temperature for heating and decomposing the release layer is selected from 130-300° C., and the time is selected from 1-60 s; Preferably, the temperature for heating and decomposing the release layer is selected from 130-180° C., and the time is selected from 20-40 s.

6. A pole piece forming device, characterized in that: An electrode film is prepared by the method described in any one of claims 1 to 3, or an electrode sheet is prepared by the method described in any one of claims 4 to 5; The pole piece forming device comprises: A material conveyor belt (11), and a demoulding layer sticking device (12), a material distributing device (13), a material heating device (14), a primary stamping device (15), a secondary stamping device (16), a hot stamping device (22), and a heated demoulding device (23) arranged in sequence on the material conveyor belt (11) along the material conveying direction; The electrode sheet forming device is also provided with a mold conveying assembly (17), comprising an electrode film mold (172), a mold conveyor belt (171), a mold placing device (173), and a mold recovery device (174); the mold placing device (173) is used to place the electrode film mold (172) on the material conveyor belt (11) before the material distribution device (13); the mold conveyor belt (171) is arranged on the edges of both sides of the material conveyor belt (11) and is parallel to or higher than the material conveyor belt (11) in the horizontal direction; the mold conveyor belt (171) is used to carry the electrode mold (172) to pass through the material distribution device (13), the material heating device (14), and the primary stamping device (15) in sequence; and the mold recovery device (174) is used to recover the electrode mold (172) after the primary stamping; The pole piece forming device is further provided with a current collector unwinding device (21) and a pole piece winding device (24); the unwinding device (21) is used to unwind the current collector so that it can be composited with the electrode film that has passed through the hot stamping device (22); and the pole piece winding device (24) is used to wind up the pole piece that has been demoulded by the hot stamping device (22).

7. The pole piece forming device according to claim 6, characterized in that: The thickness of the demoulding layer is selected from 0.1 μm to 20 μm; Preferably, the demoulding layer comprises a carrier layer and a glue layer arranged on any one side of the carrier layer; Preferably, the carrier layer can be selected from one or more of polyethylene, polypropylene, and polycarbonate; Preferably, the material of the glue layer is selected from one of polyacrylate glue and polyurethane glue; Preferably, when the mold conveyor belt (171) is higher than the material conveyor belt in the horizontal direction, the height is selected from 0.5-1 mm; Preferably, the material distribution device (13) comprises a material distribution port (131) and a material tank (132), and the material tank (132) is fixedly connected to the material distribution port (132).

8. The pole piece forming device according to claim 6, characterized in that: The primary punching device (15) comprises a primary punch (151) and a primary punching base (152), the primary punching base (152) being fixedly connected to the primary punch (151), the primary punch (151) protruding from the primary punching base (152), the shape of the primary punch (151) matching the electrode membrane mold (172), and being used for performing primary punching on the material in the electrode membrane mold (172); Preferably, the electrode film mold (172) includes a primary electrode film grid, the primary electrode film grid is connected to the front and back sides of the electrode mold (172), and the width is matched with the material conveyor belt (11), the primary punch (151) is matched with the primary electrode film grid, and the size of the primary punch (151) is smaller than the size of the primary electrode film grid by 0.8mm-1.2mm; Preferably, the primary punch (151) is divided into a primary punching block (1511) by grooves distributed vertically and horizontally, and the electrode membrane mold (172) includes a pole ear portion (1722) and a partition portion (1726), and the pole ear portion (1722) and the partition portion (1726) are crisscrossed to divide the primary electrode membrane grid into electrode membrane grids (1721), and the electrode membrane grid (1721) cooperates with the primary punching block (1511), and the size of the primary punching block (1511) is smaller than the size of the electrode membrane grid (1721) by 0.8mm-1.2mm; Preferably, the primary stamping base (152) is further provided with a positioning boss (153) that cooperates with the electrode membrane mold (172); Preferably, the electrode mold (172) is further provided with a positioning hole (1724) that cooperates with the positioning protrusion (153) on the primary punching device (15); Preferably, the number of the positioning holes (1724) is ≥2; Preferably, the number of the positioning holes (1724) is selected from 4-8.

9. The pole piece forming device according to claim 6, characterized in that: The secondary punching device (16) comprises a secondary punch (161) and a secondary punching base (162), wherein the secondary punching base (162) is fixedly connected to the secondary punch (161), and the secondary punch (16) protrudes out of the secondary punching base (162) as a whole; Preferably, the electrode film mold (172) is further provided with a positioning portion (1723), and the positioning portion (1723) is arranged on the left and right sides of the electrode film mold (172); Preferably, the mold conveyor belt (171) is provided with a positioning card (1711), and the positioning cards (1711) appear in pairs to form a card slot that matches the positioning portion (1723) of the electrode film mold (172), and the positioning portion (1723) is snapped into the card slot formed by the positioning card (1711); Preferably, the electrode film mold (172) is further provided with a placement handle (1725), and the placement handles are respectively arranged on the left and right sides of the electrode film mold (172), and the number of the placement handles (1725) is ≥2; Preferably, the number of the placement handles (1725) is selected from 2-4; The mold placement device (173) comprises a placement support arm (1731) and a first support base (1732), wherein the placement support arm (1731) cooperates with a placement handle (1725) of the electrode film mold (172), and the first support base (1732) and the placement support arm (1731) are detachably connected; Preferably, the mold recovery device (174) includes a recovery clamping arm (1741) and a second support base (1742), the recovery clamping arm (1741) cooperates with the placement handle (1725) of the electrode membrane mold (172), and the second support base (1742) and the recovery clamping arm (1741) are detachably connected.

10. The pole piece forming device according to claim 6, characterized in that: The current collector unwinding device (21) comprises a current collector roll (211), a first roller pair (212), and a second roller pair (213); the current collector roll (211) is used to unwind the current collector, and the second roller pair (213) is used to guide the current collector and the electrode film composited by the hot stamping device (22) into the heating demoulding device (23); Preferably, the pole piece winding device (24) comprises a pole piece roll (241) and a third roller pair (242), wherein the third roller pair (242) is used to guide the pole piece after passing through the heating demolding device (23), and the pole piece roll (241) winds up the pole piece.

Images