CN115911260A

CN115911260A - Dry-method electrode pole piece, preparation method thereof and battery containing pole piece

Info

Publication number: CN115911260A
Application number: CN202211462015.0A
Authority: CN
Inventors: 程飞
Original assignee: Cornex New Energy Co ltd
Current assignee: Cornex New Energy Co ltd
Priority date: 2022-11-17
Filing date: 2022-11-17
Publication date: 2023-04-04

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a dry-method electrode plate, a preparation method thereof and a battery containing the electrode plate. The electrode pole piece comprises a current collector foil and electrode films compounded on one side or two sides of the current collector foil; the raw material of the electrode film includes an electrode active material, a conductive agent, a lubricant, a plasticizer, and a resin. Granulating the raw material of the electrode film through an extruder, and pressing the raw material of the electrode film into the electrode film through the extruder; and the electrode film and the current collector foil are compounded into an electrode plate through hot pressing. The preparation method does not need to add any organic solvent, does not discharge toxic gas, simplifies process equipment, avoids process problems caused by homogenate coating, and the prepared electrode film has high uniformity, large tensile strength and high energy density.

Description

Dry-method electrode pole piece, preparation method thereof and battery containing pole piece

Technical Field

The invention belongs to the technical field of batteries, and particularly relates to a dry-method electrode plate, a preparation method thereof and a battery containing the electrode plate.

Background

At present, most of battery electrode plates are prepared by a wet coating method, the method is complex in process, the volatilization of a solvent is easy to cause environmental pollution, and the problem of solvent residue exists in a coating electrode; even if the solvent can be recovered well, the requirement on the capacity of the equipment is high, and the cost is increased greatly. Compared with a wet process, the dry electrode process is simple in process, the problem of solvent volatilization is solved, and meanwhile, the electrode prepared by the dry process has better adhesive property and adhesive force under the conditions of high temperature, electrolyte and the like, so that the comprehensive performance of the battery can be further improved. Most of the existing dry-method pole piece preparation technologies adopt the steps of mixing powder, directly rolling, and compounding with a carbon-coated foil, or combine the mixed powder of an active substance and a conductive agent with a current collector in an electrostatic spraying manner to prepare a dry-method electrode. CN 112687833A discloses a dry electrode sheet preparation method, which comprises the following steps: mixing raw material powder, heating and fiberizing to obtain pole piece powder, sequentially performing vertical rolling and horizontal rolling on the pole piece powder to obtain a diaphragm, feeding the diaphragm and foil together into a laminating roller, and performing roll forming to obtain the electrode. However, the method has extremely high requirements on equipment capacity and a crushing and fibrosis process, and if the dry powder is not fully fiberized, the film sheet is easily crushed in the subsequent rolling process and cannot be formed.

Currently, in commercially available lithium ion batteries, electrode sheet processes include mixing, homogenizing, coating, drying, rolling and the like, so as to obtain positive electrode sheets and negative electrode sheets with appropriate thicknesses, but a large amount of solvents are required in the homogenizing process, such as: the positive pole homogenate needs to use N-methyl pyrrolidone (NMP), deionized water for the negative pole and the like, and the solvent is dried and removed by heating and drying, and the process not only generates great energy consumption waste, but also has the following disadvantages: (1) NMP is high in price, toxic, not environment-friendly and required to be recycled; (2) The solvent in the electrode coating still remains after drying, which reduces the service life of the battery to a certain extent; (3) The dissolution of the binder in the electrolyte increases the resistivity of the battery; (4) Low electrode compaction density, resulting in low energy density and short cycle life of the battery; and (5) the preparation process is complex and has a long period.

Most of the existing dry-method pole piece preparation technologies adopt a mode of directly rolling or electrostatic spraying after powder mixing, so that the prepared self-supporting pole piece film has poor mechanical properties (especially a positive pole material with high specific gravity and high hardness), a series of process problems such as belt breakage, roller adhesion, poor uniformity and the like easily occur in the subsequent winding process, and the mode has high requirements on the content of a binder, so that the internal resistance of a battery can be increased, and the energy density of the battery can be reduced.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a dry-method electrode pole piece, a preparation method thereof and a battery containing the pole piece.

In order to achieve the purpose, the invention adopts the technical scheme that:

in a first aspect, the present invention provides a dry electrode sheet, which includes a current collector foil and an electrode film compounded on one side or both sides of the current collector foil; the raw material of the electrode film includes an electrode active material, a conductive agent, a lubricant, a plasticizer, and a resin.

In the above dry electrode sheet, as a preferred embodiment, the raw material of the electrode film is in parts by weight, comprises 80-100 parts (such as 82.5 parts, 85 parts, 87.5 parts, 90 parts, 92.5 parts, 95 parts and 97.5 parts) of electrode active material, 0.1-10 parts (such as 0.3 parts, 0.6 parts, 0.9 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts and 9 parts) of conductive agent, 0.2-2 parts (such as 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 0.5 parts, 2 parts of lubricant 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts), a plasticizer 0.2 to 3 parts (e.g., 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2.0 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts) and a resin 5 to 15 parts (e.g., 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts); preferably, the electrode film is composed of 80-100 parts of electrode active material, 0.1-10 parts of conductive agent, 0.2-2 parts of lubricant, 0.2-3 parts of plasticizer and 5-15 parts of resin; preferably, the electrode film is a dry electrode film; preferably, the raw material of the electrode film is granulated by an extruder and then is pressed into the electrode film by the extruder; the electrode film and the current collector foil are compounded into an electrode pole piece through hot pressing.

In a second aspect, the invention provides a preparation method of the dry electrode sheet, which sequentially comprises the following steps:

(1) Raw materials of an electrode film: uniformly mixing an electrode active material, a conductive agent, a lubricant, a plasticizer and resin to obtain a mixed material, and then granulating to obtain electrode film raw material particles;

(2) Pressing the electrode film raw material particles prepared in the step (1) into an electrode film;

(3) And (3) compounding the electrode film prepared in the step (2) on the two sides of the current collector foil through hot pressing, and then performing cold pressing and shaping to obtain the dry-process electrode piece.

In the above-described production method, as a preferred embodiment, the raw materials of the electrode film comprise, in parts by weight, 80 to 100 parts of an electrode active material, 0.1 to 10 parts of a conductive agent, 0.2 to 2 parts of a lubricant, 0.2 to 3 parts of a plasticizer, and 5 to 15 parts of a resin;

preferably, the electrode active material is a positive electrode active material or a negative electrode active material;

preferably, the positive electrode active material is a positive electrode active material for a lithium ion battery or a positive electrode active material for a sodium ion battery; preferably, the positive active material for a lithium ion battery includes LiMn ₂ O ₄ 、LiCoO ₂ 、LiFePO ₄ 、LiNi _x Co _y Mn _z O ₂ (x+y+z＝1，0<x<1，0<y<1，0<z<1)、LiNi _a Co _b Al _c O ₂ (a+b+c＝1，0<a<1，0<b<1，0<c<1) And a lithium-rich compound; preferably, the positive active material for sodium ion batteries comprises NaFeO ₂ 、Na _2/3 MnO ₂ 、Na ₃ V ₂ (PO ₄ ) ₃ 、NaFePO ₄ 、NaMnFe(CN) ₆ ·zH ₂ One or more of O;

preferably, the negative electrode active material is a negative electrode active material for a lithium ion battery or a negative electrode active material for a sodium ion battery; preferably, the negative active material for lithium ion battery comprises graphite, silicon, li ₄ Ti ₅ O ₁₂ 、SiO _d (0<d<2) One or more of (a); preferably, the negative active material for a sodium ion battery includes hard carbon and/or soft carbon.

In the above production method, as a preferred embodiment, the conductive agent includes one or a combination of at least two of acetylene black, SP (conductive carbon black), ECP (conductive graphite powder), CNT (carbon nanotube), VGCF (conductive nanofiber), and graphene.

In the above preparation method, as a preferred embodiment, the lubricant includes one or more of stearic acid, sodium stearate, calcium stearate, zinc stearate, paraffin wax, and polyethylene wax.

In the above-mentioned preparation method, as a preferred embodiment, the plasticizer includes one or more of dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), dioctyl phthalate (DOP), butyl Benzyl Phthalate (BBP), di-2-ethyl-hexyl phthalate (DEHP), diisononyl phthalate (DINP), epoxidized Soybean Oil (ESO), octyl epoxystearate (ED 3), tricresyl phosphate (TCP), triphenyl phosphate (TPP), trioctyl phosphate (TOP), dioctyl adipate (DOA), dioctyl azelate (DOZ), and dioctyl sebacate (DOS).

In the above production method, as a preferred embodiment, the resin includes one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyacrylic acid (PAA), polyethylene-butene copolymer/polyethylene-octene copolymer (POE), ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMAA), and polybutadiene.

In the above production method, as a preferred embodiment, in the step (1), the mixing order is: firstly, adding a plasticizer and resin, and then adding an electrode active material, a conductive agent and a lubricant;

preferably, in step (1), the mixing is carried out in a blender at a speed of 1000-3000rpm (e.g. 1500rpm, 2000rpm, 2500 rpm) for a time of 0.5-2h (e.g. 0.6h, 0.7h, 0.8h, 0.9h, 1h, 1.2h, 1.4h, 1.6h, 1.8 h);

preferably, in the step (1), the mixed material is granulated by a double-screw extruder and a granulator;

preferably, in the step (1), the granulation is to extrude the mixed material through a double-screw extruder and then pull the extruded mixed material into a strip shape, and the strip shape is cooled and cut into electrode membrane raw material particles through a granulator;

preferably, in the step (1), the screw rotation speed of the twin-screw extruder is 20-40rpm (22 rpm, 26rpm, 28rpm, 30rpm, 32rpm, 34rpm, 36rpm, 38 rpm);

preferably, in step (1), the barrel temperature of the twin-screw extruder is 100 to 200 ℃ (e.g., 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃);

preferably, in step (1), the temperature of the strand die of the twin-screw extruder is 120 to 185 ℃, such as 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃);

preferably, in step (1), the cooling is air cooling and/or water cooling, more preferably air cooling; preferably, the strands are cooled to 20-30 ℃ (e.g., 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃) and pelletized;

preferably, in the step (2), the pressing is performed by using a screw extruder;

preferably, in the step (2), the screw extruder adopts a T-shaped die;

preferably, in the step (2), the screw rotation speed of the screw extruder is 15-30rpm (e.g. 20rpm, 22rpm, 24rpm, 26rpm, 28 rpm);

preferably, in the step (2), the barrel temperature of the screw extruder is 100 to 200 ℃ (e.g., 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃);

preferably, in the step (2), the T-die has a temperature of 125 to 200 ℃ (e.g., 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃) and the gap of the die lip of the T-die is 100 to 2000 μm (e.g., 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 μm, 650 μm, 700 μm, 800 μm, 900 μm, 1000 μm, 1500 μm, 1700 μm);

preferably, the hot pressing in step (3) is performed in a thermal compound machine;

preferably, the temperature of the rolling of the hot press in the step (3) is 100 ℃ to 180 ℃ (e.g., 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃);

preferably, the rolling speed of the hot press in step (3) is 5 to 20m/min (e.g., 6m/min, 7m/min, 8m/min, 9m/min, 10m/min, 11m/min, 12m/min, 13m/min, 14m/min, 15m/min, 16m/min, 17m/min, 18m/min, 19 m/min);

preferably, the rolling pressure of the hot pressing in the step (3) is 5 to 50t (e.g., 10t, 15t, 20t, 25t, 30t, 35t, 40t, 45 t);

preferably, the roller spacing of the hot-pressed rollers in step (3) is 150 to 1000 μm (e.g., 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 μm, 650 μm, 700 μm, 800 μm, 900 μm);

preferably, the cold pressing in step (3) is carried out at a rolling temperature of 25-40 ℃ (e.g., 28 ℃, 30 ℃, 35 ℃, 38 ℃);

preferably, the cold pressing roll pressure in step (3) is 10-60t (e.g. 15t, 20t, 25t, 30t, 35t, 40t, 45t, 50t, 55 t);

preferably, the cold pressing in step (3) is performed at a rolling speed of 5-20m/min (e.g. 6m/min, 7m/min, 8m/min, 9m/min, 10m/min, 11m/min, 12m/min, 13m/min, 14m/min, 15m/min, 16m/min, 17m/min, 18m/min, 19 m/min);

preferably, the cold pressed roller in step (3) has a roller spacing of 150-800 μm (e.g. 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 μm, 650 μm, 700 μm).

The invention improves the processability of the raw material of the electrode film by adding the lubricant and the plasticizer, the lubricant can reduce the friction between the mixed material and the inner wall of the extruder and the friction between the molecules of the mixed material in the process of granulating and pressing the raw material particles of the electrode film into the electrode film, the plasticizer can weaken the secondary valence bonds between the resin molecules, increase the mobility of the resin molecular bonds, reduce the crystallinity of the resin molecules, increase the plasticity of the resin molecules, enhance the flexibility and facilitate the processing. The invention leads the raw material of the electrode film to be granulated by an extruder in a dry method and pressed into a thicker, more compact and more uniform electrode film through the synergistic action of the lubricant and the plasticizer.

In a preferred embodiment of the invention, in the step (1), the plasticizer and the resin are mixed, and then other powder materials (the electrode active material, the conductive agent and the lubricant) are sequentially added, so that the plasticizer can be uniformly coated on the surface of the resin, and the powder material can be well adhered to the surface of the resin material when being mixed with the powder material, so that the uniformity of mixed materials can be ensured, and the further processing is facilitated. The resin used in the present application, although also functioning as a binder, differs from the adhesives of the prior art in that: the resin is blended with the electrode active material and the conductive agent in a screw extruder in a melting mode to form a homogeneous structure, so that the resin is better in binding property with other powder materials (the electrode active material, the conductive agent and the lubricant); one of the prior arts is to pack the powder material together by fiberizing the binder to form a net structure, and the other electrostatic spraying is to combine the binder and the powder material together by the electrostatic adsorption, and the two ways of combining the binder and the powder material are not firm, so that the roller adhesion phenomenon is easy to occur when the powder material is rolled.

In a third aspect, the present invention provides an electrical core, where the electrical core includes the dry electrode plate of the first aspect or the dry electrode plate prepared in the second aspect.

In a fourth aspect, the present invention provides a battery, where the battery is a lithium ion battery or a sodium ion battery, and the battery includes the battery cell of the third aspect.

Compared with the prior art, the invention at least has the following beneficial effects:

compared with the traditional wet electrode preparation process, the dry electrode technology does not use any solvent in the preparation process of the pole piece, does not discharge toxic gas, and can prepare the pole piece only by mixing dry powder. The invention provides a preparation method of a dry-method pole piece, which adopts reasonable proportion of a plasticizer, a lubricant and resin, can overcome the problems of belt breakage, roller sticking, poor uniformity and the like in the preparation process of the traditional dry-method pole piece, and realizes the effects of simplified process, good electrode uniformity, high energy density and the like. The preparation method can solve the problems of charge transfer, large resistance, obvious expansion effect, easy occurrence of uneven powder distribution in the pole piece and the like of the dry electrode pole piece in the prior art, and can improve the energy density of the single battery cell to a certain extent.

At present, the mainstream method of the dry electrode is to mix PTFE (polytetrafluoroethylene) with an active substance, a conductive agent and the like, then to shear and draw wires, to wrap the electrode material through the fibrillation of PTFE, to roll the electrode material into an electrode film, and to compound the electrode film and a current collector together. In the method, the degree of PTFE fibrosis is difficult to control, the strength of the prepared electrode film is poor, the strip breakage is very easy to occur during continuous production, and in addition, a press roller is easy to stick materials during the rolling process, so the thickness uniformity is difficult to ensure. The preparation method of the invention does not need fiberization, and the electrode material and the polymer (resin) are fused and adhered together in a screw extruder, so that the prepared electrode film has high strength, the phenomenon of belt breakage cannot easily occur, and the roller cannot be stuck.

Drawings

Fig. 1 is a schematic process flow diagram of a dry method electrode preparation method for a lithium battery positive electrode in embodiment 1 of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.

The embodiments of the present invention are implemented on the premise of the technical scheme of the present invention, and detailed embodiments and processes are given, but the scope of the present invention is not limited to the following embodiments, and the following embodiments do not indicate process parameters of specific conditions, and generally follow conventional conditions.

The endpoints of the ranges and any values disclosed in the present application are not limited to the precise range or value and should be understood to encompass values close to these ranges or values. For numerical ranges, combinations of values between the endpoints of each of the ranges, between the endpoints of each of the ranges and individual values, and between the individual values can result in one or more new numerical ranges, and such numerical ranges should be considered as being specifically disclosed herein.

Throughout this disclosure, all numbers referring to amounts of components are "parts by weight" unless otherwise specified and/or illustrated. The process parameters for the specific conditions not noted in the following examples are generally in accordance with conventional conditions.

The commercial model and commercial source of the resin used in the embodiment of the invention are

Polyethylene-octene copolymer: POE 8150, dow chemical.

Ethylene-ethyl acrylate copolymer: american acalma EEA 2200.

The technical solution of the present invention is further explained in detail by the description of the specific embodiments below.

Example 1

The embodiment provides a preparation method of a lithium ion battery positive electrode dry-process electrode plate, which is shown in fig. 1 and comprises the following steps:

(1) Weighing 92 parts by weight of NCM811 (positive electrode active material), 0.5 part by weight of conductive carbon black SP (conductive agent), 0.2 part by weight of calcium stearate (lubricant), 0.3 part by weight of polyethylene wax (lubricant), 1 part by weight of dioctyl phthalate DOP (plasticizer) and 6 parts by weight of polyethylene-octene copolymer POE (resin), and uniformly mixing by a mixer at 1000rpm for 2 hours to obtain a mixed material;

(2) Putting the mixed material obtained in the step (1) into a double-screw extruder, extruding the mixed material through a die head of the double-screw extruder, drawing the extruded mixed material into strips, cooling the strips to 30 ℃, conveying the cooled strips into a granulator by using a conveying belt, and cutting the strips into electrode film raw material particles with uniform particle size of 3mm, wherein the barrel temperature of the double-screw extruder is 150 ℃, the die temperature of the double-screw extruder is 145 ℃, the rotating speed of screws is 25rpm, 10 fans are used for air cooling, the power of the fans is 2000W, the speed of the conveying belt is 13m/min, and the speed of the granulator is 21rpm;

(3) As shown in the attached figure 1, two screw extruders are aligned up and down, an aluminum foil unreeling device is arranged between the two screw extruders, the electrode film raw material particles prepared in the step (2) are simultaneously fed into the two screw extruders, an electrode film with the thickness of 300 microns is obtained through a T-shaped die head, then the electrode film and an aluminum foil are attached together and are sent into two rollers of a thermal compound machine, and an electrode plate is obtained through the lamination of the two rollers, wherein the barrel temperature of the screw extruders is 170 ℃, the T-shaped die head temperature of the screw extruders is 180 ℃, the screw rotating speed is 20rpm, the roller spacing of the thermal compound machine is 550 microns, the rolling temperature is 100 ℃, the rolling pressure is 10T, and the rolling speed is 12m/min.

(4) And (3) finally, carrying out cold pressing and shaping on the pole piece from the hot compounding roller by a cold pressing roller to obtain the final dry electrode pole piece, wherein the cold pressing rolling temperature is 30 ℃, the rolling pressure is 15t, the rolling speed is 12m/min, and the roller spacing is 450 mu m.

The above processes are all operated in a low-humidity environment (dew point is-40 ℃, and the moisture content is lower than 1%), the surface of the prepared positive pole piece is flat and has no wrinkles, powder falling does not occur, the thickness is 500 micrometers, and the thickness deviation of different positions of the whole pole piece is within the range of +/-1 micrometer.

Example 2

The embodiment provides a preparation method of a lithium ion battery negative electrode dry method electrode plate, which comprises the following steps:

(1) Weighing 93 parts of graphite (a negative electrode active material), 0.5 part of conductive carbon black SP (a conductive agent), 0.5 part of paraffin (a lubricant), 0.5 part of dioctyl phthalate DOP (a plasticizer), 4.5 parts of polyethylene-octene copolymer POE (resin) and 1 part of ethylene-ethyl acrylate copolymer EAA (resin) according to the weight, and uniformly mixing by a mixer at 1500rpm for 1 hour to obtain a mixed material;

(2) Putting the mixed material obtained in the step (1) into a double-screw extruder, extruding the mixed material through a die head of the double-screw extruder, drawing the extruded mixed material into strips, cooling the strips to 25 ℃, conveying the cooled strips into a granulator by using a conveying belt, and cutting the strips into electrode film raw material particles with uniform particle size of 3mm, wherein the barrel temperature of the double-screw extruder is 140 ℃, the die temperature of the double-screw extruder is 135 ℃, the rotating speed of screws is 30rpm, 10 fans are used for air cooling, the power of the fans is 2000W, the speed of the conveying belt is 18m/min, and the speed of the granulator is 28rpm;

(3) And (3) aligning the two screw sheet extruders up and down, placing a copper foil unreeling device in the middle, putting the electrode film raw material particles prepared in the step (2) into the two screw extruders at the same time, obtaining an electrode film with the thickness of 200 microns through a T-shaped die head, then jointing the electrode film and a copper foil, conveying the electrode film and the copper foil into two rollers of a thermal compound machine together, and pressing the two rollers to obtain an electrode plate, wherein the temperature of a machine barrel of the screw extruder is 165 ℃, the temperature of the T-shaped die head of the screw extruder is 170 ℃, the rotating speed of the screw is 25rpm, the roller spacing of the thermal compound machine is 380 microns, the rolling temperature is 120 ℃, the rolling pressure is 8T, and the rolling speed is 15m/min.

(4) And (3) finally, carrying out cold pressing and shaping on the pole piece from the hot compounding roller by a cold pressing roller to obtain the final dry electrode pole piece, wherein the cold pressing rolling temperature is 25 ℃, the rolling pressure is 12t, the rolling speed is 15m/min, and the roller spacing is 320 mu m.

The above processes are all operated in an environment with the humidity lower than 10%, the surface of the prepared negative pole piece is flat and has no wrinkles, powder does not fall off, the thickness is 350 micrometers, and the thickness deviation of different positions of the whole pole piece is within the range of +/-1 micrometer.

Example 3

The embodiment provides a preparation method of a positive electrode dry-method electrode plate of a sodium-ion battery, which comprises the following steps:

(1) Weighing 90 parts by weight of Na ₃ V ₂ (PO ₄ ) ₃ (positive electrode active material), 1.5 parts of conductive carbon black SP (conductive agent), 1 part of polyethylene wax (lubricant), 0.5 part of dioctyl phthalate DOP (plasticizer) and 7 parts of polyvinylidene fluoride PVDF (resin), and uniformly mixing the components by a mixer at 2000rpm for 1h to obtain a mixed material;

(2) Putting the mixed material obtained in the step (1) into a double-screw extruder, extruding the mixed material through a die head of the double-screw extruder, drawing the extruded mixed material into strips, cooling the strips to 30 ℃ by air, and conveying the cooled strips into a granulator to cut the strips into electrode film raw material particles with uniform particle size of 3mm, wherein the barrel temperature of the double-screw extruder is 190 ℃, the temperature of a die of the double-screw extruder is 185 ℃, the rotating speed of a screw is 20rpm, 10 fans are used for air cooling, the power of the fans is 2000W, the speed of the conveyor belt is 12m/min, and the speed of the granulator is 19rpm;

(3) And (3) aligning the two screw extruders up and down, placing an aluminum foil unreeling device in the middle, putting the electrode film raw material particles prepared in the step (2) into the two screw extruders at the same time, obtaining an electrode film with the thickness of 250 micrometers through a T-shaped die head, then attaching the electrode film and an aluminum foil together, conveying the electrode film and the aluminum foil into two rollers of a thermal compound machine, and laminating the electrode film and the aluminum foil through the two rollers to obtain an electrode plate, wherein the temperature of a machine barrel of the screw extruder is 190 ℃, the temperature of the T-shaped die head of the screw extruder is 200 ℃, the rotating speed of the screw is 18rpm, the roller spacing of the thermal compound machine is 430 micrometers, the rolling temperature is 120 ℃, the rolling pressure is 10T, and the rolling speed is 11m/min.

(4) And (3) carrying out cold pressing and shaping on the pole piece from the hot compounding roller by a cold pressing roller to obtain the final dry-process electrode pole piece, wherein the cold pressing rolling temperature is 35 ℃, the rolling pressure is 15t, the rolling speed is 11m/min, and the roller spacing is 360 mu m.

The above processes are all operated in a low-humidity environment (the dew point is lower than-40 ℃, and the environmental moisture is lower than 1%), the prepared positive pole piece has a smooth and wrinkle-free surface, does not fall off powder, has a thickness of 400 micrometers, and has thickness deviation of different positions of the whole pole piece within a range of +/-1 micrometer.

Example 4

The embodiment provides a preparation method of a sodium-ion battery negative electrode dry-method electrode plate, which comprises the following steps:

(1) Weighing 92 parts of hard carbon (cathode active material), 0.5 part of conductive carbon black SP (conductive agent), 1 part of sodium stearate (lubricant), 0.5 part of dioctyl phthalate DOP (plasticizer) and 6 parts of polyethylene-butylene copolymer POE (resin) by weight, and uniformly mixing by a mixer at 1000rpm for 2 hours to obtain a mixed material;

(2) Putting the mixed material obtained in the step (1) into a double-screw extruder, extruding the mixed material through a die head of the double-screw extruder, drawing the extruded mixed material into strips, cooling the strips to 25 ℃, conveying the cooled strips into a granulator by using a conveying belt, and cutting the strips into electrode film raw material particles with uniform particle size of 3mm, wherein the temperature of a cylinder of the double-screw extruder is 140 ℃, the temperature of a die of the double-screw extruder is 135 ℃, the rotating speed of screws is 35rpm, 10 fans are used for air cooling, the power of the fans is 2000W, the speed of the conveying belt is 18m/min, and the speed of the granulator is 25rpm;

(3) And (3) aligning the two screw extruders up and down, placing an aluminum foil unreeling device in the middle, simultaneously putting the electrode film raw material particles prepared in the step (2) into the two screw extruders, obtaining an electrode film with the thickness of 200 mu m through a T-shaped die head, then conveying an electrode film piece and an aluminum foil together into two rollers of a compound machine, and laminating the two rollers to obtain an electrode pole piece, wherein the barrel temperature of the screw extruder is 160 ℃, the T-shaped die head temperature of the screw extruder is 165 ℃, the rotating speed of the screw is 23rpm, the roller spacing of the compound machine is 400 mu m, the rolling temperature is 110 ℃, the rolling pressure is 12T, and the rolling speed is 16m/min.

(4) And (3) finally, carrying out cold pressing and shaping on the pole piece from the hot compounding roller by a cold pressing roller to obtain the final dry electrode pole piece, wherein the cold pressing rolling temperature is 25 ℃, the rolling pressure is 20t, the rolling speed is 16m/min, and the roller spacing is 280 mu m.

The above processes are all operated in the environment with the environmental moisture content lower than 10%, the prepared negative pole piece has a smooth surface without wrinkles and powder falling, the thickness is 300 mu m, and the thickness deviation of different positions of the whole pole piece is within the range of +/-1 mu m.

Example 5

The embodiment provides a preparation method of a lithium ion battery anode dry-method electrode plate, which comprises the following steps:

(2) Putting the mixed material obtained in the step (1) into a double-screw extruder, extruding the mixed material through a die head of the double-screw extruder, drawing the extruded mixed material into strips, cooling the strips to 30 ℃, conveying the cooled strips into a granulator by using a conveyor belt, and cutting the strips into electrode film raw material particles with uniform particle size of 3mm, wherein the barrel temperature of the double-screw extruder is 150 ℃, the temperature of a die of the double-screw extruder is 145 ℃, the rotating speed of a screw is 25rpm, 10 fans used for air cooling are used, the power of the fans is 2000W, the speed of the conveyor belt is 13m/min, and the speed of the granulator is 21rpm;

(3) As shown in fig. 1, two screw extruders are aligned up and down, an aluminum foil unreeling device is placed between the two screw extruders, the electrode film raw material particles prepared in the step (2) are simultaneously fed into the two screw extruders, an electrode film with the thickness of 600 μm is obtained through a T-shaped die head, then the electrode film and an aluminum foil are attached together and are sent into two rollers of a thermal compound machine, and an electrode plate is obtained through the lamination of the two rollers, wherein the barrel temperature of the screw extruders is 170 ℃, the T-shaped die head temperature of the screw extruders is 180 ℃, the screw rotation speed is 20rpm, the roller spacing of the thermal compound machine is 1000 μm, the rolling temperature is 100 ℃, the rolling pressure is 10T, and the rolling speed is 12m/min.

(4) And (3) carrying out cold pressing and shaping on the pole piece from the hot compounding roller by a cold pressing roller to obtain the final dry-process electrode pole piece, wherein the cold pressing rolling temperature is 30 ℃, the rolling pressure is 15t, the rolling speed is 12m/min, and the roller spacing is 750 mu m.

The above processes are all operated in a low-humidity environment (dew point is minus 40 ℃, and the moisture content is lower than 1%), the prepared positive pole piece has a smooth surface without wrinkles and does not fall off powder, the thickness is 800 micrometers, and the thickness deviation of different positions of the whole pole piece is within the range of +/-1 micrometer.

Example 6

The embodiment provides a preparation method of a lithium ion battery positive electrode dry electrode sheet, which is basically the same as that in embodiment 1, and is different only in that the resin material is changed into polyacrylic acid (PAA).

The positive pole piece prepared by the embodiment has a smooth and wrinkle-free surface, does not fall powder, is uniform in thickness, and has thickness deviation of different positions within a range of +/-1 mu m.

Example 7

The embodiment provides a preparation method of a lithium ion battery positive electrode dry-method electrode plate, which is basically the same as the embodiment 1, and is only characterized in that the plasticizer is replaced by Epoxidized Soybean Oil (ESO).

The positive pole piece prepared by the embodiment has a smooth and wrinkle-free surface, does not fall off powder, and has uniform thickness, and the thickness deviation of different positions of the whole pole piece is within the range of +/-1 mu m.

Application example 1

And (3) cutting the dry-method electrode pole pieces prepared in the embodiments 1 and 2 into pieces, laminating and assembling the pieces and the diaphragm, and injecting electrolyte to prepare the dry-method soft-package battery cell with the battery cell capacity of 5Ah.

Comparative example 1

Compared with the positive pole piece in example 1, the positive pole piece and the negative pole piece in the preparation method have the same dosage relationship and consistent content ratio of active substances, and the difference is that the preparation steps are different, specifically referring to the following step (1), compared with the negative pole piece prepared in the comparative example 2, except that the adhesive is different in variety and the preparation method is different, other raw materials such as a negative active material and a conductive agent are the same, the dosage relationship of the adhesive, the active material and the conductive agent is the same as that in example 2, the preparation of the negative pole piece is referred to the following step (2), the mode of assembling the negative pole piece is the same as that in the application example, specifically referring to the following step (3):

(1) Preparing a positive pole piece, namely dissolving PVDF in N-methylpyrrolidone (NMP) to prepare a glue, then mixing a positive pole material NCM811 and a conductive agent SP in a dry mode, uniformly mixing with the glue, and coating and drying to obtain the positive pole piece;

(2) Preparing a negative pole piece, namely dissolving CMC (sodium carboxymethylcellulose) and SBR (chloroprene rubber) in deionized water to prepare glue, then dry-mixing a negative material graphite and a conductive agent SP, uniformly mixing the mixture with a sizing material, and coating and drying to obtain the negative pole piece;

and cutting the obtained positive and negative pole pieces, laminating and assembling the positive and negative pole pieces together with the diaphragm, and injecting liquid to prepare the wet-process soft-package battery cell, wherein the specification of the battery cell is that the monomer capacity is 5Ah.

Comparative example 2

Compared with the positive pole piece in the embodiment 1, the positive pole piece has the same types and contents of the positive active material and the conductive agent in the positive pole piece and the negative pole piece in the embodiment 2, and the preparation method specifically refers to the following step (1), the negative pole piece prepared in the comparative example has the same types and contents of the negative active material and the conductive agent in the negative pole piece and the negative pole piece in the embodiment 2, and the preparation method of the negative pole piece refers to the following step (2), the mode of assembling the battery cell is the same as the application example, and the specific reference is to the following step (3):

(1) Preparing a positive pole piece, mixing a positive pole material NCM811, a conductive agent SP and PTFE, fibrillating by an air flow mill, rolling (rolling pressure of 20t, rolling speed of 15rpm and roll gap of 200 mu m) to obtain a dry-method positive pole self-supporting film with the thickness of 210 mu m, and finally compounding the dry-method positive pole self-supporting film and an aluminum foil on both sides of a carbon-coated aluminum foil (the dry-method positive pole self-supporting film and the aluminum foil are laminated together and sent into two rollers of a thermal compounding machine, the aluminum foil is arranged on the middle layer, the upper and lower parts of the dry-method positive pole self-supporting film and the aluminum foil are self-supporting films with the same thickness, wherein the roll gap is 330 mu m, the compounding temperature is 180 ℃, the rolling pressure is 10t, the rolling speed is 15m/min, and finally, a final positive pole piece with the thickness of 350 mu m is obtained by conveying and cooling by a plurality of conveying rollers;

(2) The preparation of the negative pole piece comprises the steps of mixing a negative pole material graphite, a conductive agent and PTFE, fibrillating through an air flow mill, rolling (rolling pressure of 15t, roll speed of 20rpm and roll gap of 175 mu m) to obtain a dry-method negative pole self-supporting film with the thickness of 195 mu m, and finally compounding the dry-method negative pole self-supporting film on two sides of a carbon-coated copper foil (the dry-method negative pole self-supporting film and the copper foil are jointed together and are sent into two rollers of a thermal compounding machine, the copper foil is arranged in the middle layer, the upper side and the lower side of the dry-method negative pole self-supporting film are self-supporting films with the same thickness, wherein the roll gap is 280 mu m, the compounding temperature is 150 ℃, the rolling pressure is 12t, the rolling speed is 18m/min, and finally, the negative pole piece with the thickness of 310 mu m is formed through the transmission of a plurality of conveying rollers and cooling.

(3) And cutting the obtained positive and negative pole pieces, laminating and assembling the positive and negative pole pieces together with the diaphragm, and injecting liquid to prepare the soft package battery cell, wherein the specification of the battery cell is that the monomer capacity is 5Ah.

Comparative example 3

This comparative example is essentially the same as example 1, except that this comparative example is step (1): 92 parts of NCM811 (positive electrode active material), 0.5 part of conductive carbon black SP (conductive agent), 1.5 parts of auxiliary agent (dibutyl maleate and dibutyl fatty acid dihydroxy ester in a mass ratio of 3).

The dibutyl maleate and the dibutyl fatty acid in the mass ratio of 3 to 7 are used as additives to replace the effect of a plasticizer to a certain extent, but because no lubricant is used, the electrode plate prepared by the comparative example has a rough surface and poor uniformity, the thickness deviation of different positions of the whole electrode plate is 5-8 microns, the tensile strength of the electrode film is poor, the electrode film is easy to break, and the powder is easy to fall off.

Comparative example 4

This comparative example is substantially the same as example 1 except that no lubricant is added to the mixed material of step (1) in this comparative example.

Because no lubricant is added, the difficulty of processing by adopting a screw extruder is increased, the electrode plate prepared by the comparative example has rough surface and poor uniformity, the thickness deviation of different positions of the whole electrode plate is 5-8 mu m, the tensile strength of an electrode film is poor, the electrode film is easy to break and fall off powder.

Comparative example 5

This comparative example is substantially the same as example 1 except that no plasticizer is added to the mixed material of step (1) in this comparative example.

As no plasticizer is added, the difficulty of processing by adopting a screw extruder is increased, the electrode plate prepared by the comparative example has rough surface and poor uniformity, the thickness deviation of different positions of the whole electrode plate is 4-6 mu m, and the powder falling is serious.

And (3) performance testing:

(1) Tensile Strength test

The electrode films prepared in example 1, example 2 and comparative example 2 were subjected to a tensile strength test by: the electrode/free-standing films were cut with a cutter into 15mm 150mm specimens, and tested for tensile strength by a universal tester.

Table 1: tensile strength comparison of electrode films of example 1, example 2 and comparative example 2

(2) Cycle performance

The soft-package batteries prepared in the example 1, the comparative example 1 and the comparative example 2 were tested for cycle performance at a constant temperature of 25 ℃, and the voltage interval was 2.5-4.25V.

And respectively carrying out 1C constant current charge and discharge on the battery, detecting the first effect and the first discharge capacity of the battery, and obtaining the detection results in the 2 nd and 3 rd columns in the following table 2, wherein the first effect = the first discharge capacity/the first charge capacity.

The internal resistance of the battery is tested by a voltage internal resistance instrument, and the detection result is shown in the 4 th column in the following table 2.

The 5 th column in table 2 below is the ratio of the first discharge capacity at 1C to the first discharge capacity at 0.33C for the above-described battery.

Table 2 below sets forth the 6 th column as the ratio of the first discharge capacity at 2C to the first discharge capacity at 0.33C for the above-described cells.

Table 2: comparison of electrochemical Performance results of pouch cells prepared in application example 1, comparative example 1 and comparative example 2

It should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and the present invention is not limited thereto, and although the present invention has been described in detail with reference to the embodiments, it will be apparent to those skilled in the art that modifications can be made to the technical solutions described in the above-mentioned embodiments, or equivalent substitutions of some technical features, but any modifications, equivalents, improvements and the like within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. The electrode plate is characterized by comprising a current collector foil and electrode films compounded on one side or two sides of the current collector foil; the raw material of the electrode film includes an electrode active material, a conductive agent, a lubricant, a plasticizer, and a resin.

2. The dry electrode sheet according to claim 1, wherein the electrode film is made of, by weight, 80 to 100 parts of an electrode active material, 0.1 to 10 parts of a conductive agent, 0.2 to 2 parts of a lubricant, 0.2 to 3 parts of a plasticizer, and 5 to 15 parts of a resin; the electrode film is a dry electrode film.

3. A dry electrode sheet as claimed in claim 1 or 2, in which the starting material of the electrode film is granulated by an extruder and then further pressed into an electrode film by an extruder; and the electrode film and the current collector foil are compounded into an electrode plate through hot pressing.

4. A method of preparing a dry process electrode sheet as claimed in any one of claims 1 to 3, wherein the method comprises the following steps in sequence:

(3) And (3) compounding the electrode film prepared in the step (2) on the two sides of the current collector foil through hot pressing, and then carrying out cold pressing and shaping to obtain the dry electrode pole piece.

5. The production method according to claim 4, wherein the electrode active material is a positive electrode active material or a negative electrode active material;

the positive active material is a positive active material for a lithium ion battery or a positive active material for a sodium ion battery; the negative active material is a negative active material for a lithium ion battery or a negative active material for a sodium ion battery.

6. The method of claim 5, wherein the positive active material for a lithium ion battery comprises LiMn ₂ O ₄ 、LiCoO ₂ 、LiFePO ₄ 、LiNi _x Co _y Mn _z O ₂ (x+y+z＝1，0<x<1，0<y<1，0<z<1)、LiNi _a Co _b Al _c O ₂ (a+b+c＝1，0<a<1，0<b<1，0<c<1) And a lithium-rich compound;

and/or the positive active material for the sodium-ion battery comprises NaFeO ₂ 、Na _2/3 MnO ₂ 、Na ₃ V ₂ (PO ₄ ) ₃ 、NaFePO ₄ 、NaMnFe(CN) ₆ ·zH ₂ One or more of O;

and/or the negative active material for the lithium ion battery comprises graphite, silicon and Li ₄ Ti ₅ O ₁₂ 、SiO _d (0<d<2) One or more of;

and/or the negative active material for the sodium ion battery comprises hard carbon and/or soft carbon;

and/or the conductive agent comprises one or a combination of at least two of acetylene black, conductive carbon black, conductive graphite powder, carbon nanotubes, conductive nanofibers or graphene;

and/or, the lubricant comprises one or more of stearic acid, sodium stearate, calcium stearate, zinc stearate, paraffin wax and polyethylene wax;

and/or the plasticizer comprises one or more of dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, dioctyl phthalate, butyl benzyl phthalate, di (2-ethyl) hexyl phthalate, diisononyl phthalate, epoxidized soybean oil, octyl epoxystearate, tricresyl phosphate, triphenyl phosphate, trioctyl phosphate, dioctyl adipate, dioctyl azelate, dioctyl sebacate;

and/or the resin comprises one or more of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylic acid, polyethylene-butene copolymer/polyethylene-octene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, and polybutadiene;

and/or, in the step (1), the mixing order is as follows: the plasticizer and the resin are added first, and then the electrode active material, the conductive agent and the lubricant are added.

7. The method according to any one of claims 4 to 6, wherein in the step (1), the mixed material is granulated by a twin-screw extruder and a granulator;

and/or in the step (1), the granulation is to extrude the mixed material through a double-screw extruder and then pull the extruded mixed material into strips, and the strips are cooled and cut into electrode membrane raw material particles through a granulator;

and/or in the step (2), the pressing is carried out by adopting a screw extruder, and the screw extruder adopts a T-shaped die;

and/or, the hot pressing in the step (3) is carried out in a hot laminating machine.

8. The method according to claim 7, wherein in the step (1), the mixing is carried out in a blender at a rotation speed of 1000 to 3000rpm for a mixing time of 0.5 to 2 hours;

and/or, in the step (1), the rotating speed of a screw rod of the double-screw extruder is 20-40rpm;

and/or, in the step (1), the barrel temperature of the double-screw extruder is 100-200 ℃;

and/or in the step (1), the temperature of a strand die of the double-screw extruder is 120-185 ℃;

and/or, in the step (1), the cooling is air cooling and/or water cooling, and is preferably air cooling;

and/or, in the step (1), the strip-shaped object is cooled to 20-30 ℃ and then cut into particles;

and/or, in the step (2), the rotating speed of a screw rod of the screw extruder is 15-30rpm;

and/or, in the step (2), the barrel temperature of the screw extruder is 100-200 ℃;

and/or in the step (2), the temperature of the T-shaped die is 125-200 ℃, and the gap of the die lip of the T-shaped die is 100-2000 mu m;

and/or the rolling temperature of the hot pressing in the step (3) is 100-180 ℃;

and/or the rolling speed of the hot pressing in the step (3) is 5-20m/min;

and/or the rolling pressure of the hot pressing in the step (3) is 5-50t;

and/or the roller spacing of the hot-pressed roller in step (3) is 150-1000 μm;

and/or the rolling temperature of the cold pressing in the step (3) is 25-40 ℃;

and/or the pressure of the cold pressing roll in the step (3) is 10-60t;

and/or the rolling speed of the cold pressing in the step (3) is 5-20m/min;

and/or the cold pressed rolled roll gap in step (3) is 150-800 μm.

9. An electrical core, comprising the dry electrode pole piece of any one of claims 1 to 3 or the dry electrode pole piece prepared by the preparation method of any one of claims 4 to 8.

10. A battery that is a lithium ion battery or a sodium ion battery, the battery comprising the cell of claim 9.