A dry electrode tab, a method for preparing the same, and a battery comprising the same

Abstract

The application belongs to the technical field of batteries, and particularly relates to a dry-process electrode sheet, a preparation method thereof and a battery containing the electrode sheet. The electrode sheet comprises a current collector foil and an electrode film compounded on one side or both sides of the current collector foil; raw materials of the electrode film comprise an electrode active material, a conductive agent, a lubricant, a plasticizer and a resin. The raw materials of the electrode film are granulated by an extruder, and then pressed into an electrode film by an extruder; and the electrode film and the current collector foil are compounded into an electrode sheet by hot pressing. The preparation method does not need to add any organic solvent, does not emit toxic gas, simplifies process equipment, avoids process problems caused by homogenate coating, and has high uniformity, high tensile strength and high energy density of the prepared electrode film.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a dry-method electrode sheet, a preparation method thereof, and a battery containing the electrode sheet. BACKGROUND

[0002] At present, most battery electrode sheets are prepared by wet coating, which is not only complex in process, but also causes environmental pollution due to solvent volatilization, and there is also the problem of solvent residues in the coated electrode. Even if the solvent can be well recovered, the capacity of the equipment is also relatively high, and the cost is also increased. Compared with the wet process, the dry electrode process is not only simple in process, but also does not have the problem of solvent volatilization, and the electrode prepared by the dry process has better adhesion and adhesion under high temperature and electrolyte conditions, which can further improve the comprehensive performance of the battery. At present, the dry electrode preparation technology mostly adopts the method of mixing powder, directly rolling, and then compounding with carbon-coated foil, or using the method of electrostatic spraying to combine the mixed powder of active material and conductive agent with the current collector to prepare the dry electrode. CN 112687833A discloses a dry-method electrode sheet preparation method, which comprises: mixing raw material powder, heating and fiberizing to obtain electrode sheet powder, and then vertically and horizontally rolling the electrode sheet powder to obtain a film, and then the film and the foil are fed into a laminating roller to be rolled and formed into an electrode. However, this method requires high equipment capacity and fiberization process, and if the dry powder is not fully fiberized, the film is easily crushed during the subsequent rolling process, and cannot be formed.

[0003] At present, the electrode sheet process of commercial lithium ion batteries includes mixing, homogenizing, coating, drying, rolling, etc., so as to obtain positive and negative electrode sheets with appropriate thickness. However, a large amount of solvent is needed in the homogenizing process, such as N-methyl pyrrolidone (NMP) for positive electrode homogenizing and deionized water for negative electrode homogenizing, and the solvent needs to be dried and removed by heating and drying. This process not only wastes a lot of energy, but also has the following disadvantages: (1) NMP is high in price and toxic, and is not environmentally friendly, and needs to be recycled; (2) the solvent in the electrode coating still remains after drying, which reduces the service life of the battery to some extent; (3) the dissolution of the binder in the electrolyte increases the resistivity of the battery; (4) the low compaction density of the electrode leads to low energy density and short cycle life of the battery; (5) the preparation process is complex and long.

[0004] Most of the existing dry method pole piece preparation technologies adopt the way of directly rolling or electrostatic spraying after powder mixing, the mechanical properties of the self-supporting pole piece film prepared in this way are poor (especially for the positive electrode material with high specific gravity and high hardness), a series of process problems such as belt breakage, roller sticking, poor uniformity and the like are prone to occur in the subsequent winding process, and the content of the binder is required to be high, which not only increases the internal resistance of the battery, but also reduces the energy density of the battery. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a dry method electrode pole piece, a preparation method thereof and a battery containing the pole piece.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] In the first aspect, the present application provides a dry method electrode pole piece, the electrode pole piece comprising a current collector foil and an electrode film compounded on one side or both sides of the current collector foil; the raw materials of the electrode film include electrode active material, conductive agent, lubricant, plasticizer and resin.

[0008] In the above-mentioned dry method electrode pole piece, as a preferred embodiment, the raw materials of the electrode film include, by weight, electrode active material 80-100 parts (for example, 82.5 parts, 85 parts, 87.5 parts, 90 parts, 92.5 parts, 95 parts, 97.5 parts), conductive agent 0.1-10 parts (for example, 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, 9 parts), lubricant 0.2-2 parts (for example, 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), plasticizer 0.2-3 parts (for example, 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 resin 5-15 parts (for example, 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 electrode active material 80-100 parts, conductive agent 0.1-10 parts, lubricant 0.2-2 parts, plasticizer 0.2-3 parts and resin 5-15 parts; preferably, the electrode film is a dry electrode film; preferably, the raw materials of the electrode film are granulated by an extruder, and then further pressed into an electrode film by an extruder; the electrode film and the current collector foil are compounded into an electrode pole piece by hot pressing.

[0009] In the second aspect, the present application provides a preparation method of the above-mentioned dry method electrode pole piece, the preparation method comprising the following steps in sequence:

[0010] (1) mixing raw materials of the electrode film: electrode active material, conductive agent, lubricant, plasticizer and resin to obtain a mixture, and then granulating to obtain electrode film raw material particles;

[0011] (2) pressing the electrode film raw material particles obtained in step (1) into an electrode film;

[0012] (3) hot-pressing the electrode film obtained in step (2) on both sides of the current collector foil, and then cold-pressing to obtain the dry electrode sheet.

[0013] In the above preparation method, as a preferred embodiment, the raw materials of the electrode film include, by weight, 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;

[0014] Preferably, the electrode active material is a positive electrode active material or a negative electrode active material;

[0015] Preferably, the positive electrode active material is a positive electrode active material for lithium ion batteries or a positive electrode active material for sodium ion batteries; preferably, the positive electrode active material for lithium ion batteries includes one or more of LiMn2O4, LiCoO2, LiFePO4, LiNi x Co y Mn z O2(x+y+z=1,0<x<1,0<y<1,0<z<1)、LiNi a Co b Al c O2(a+b+c=1,0<a<1,0<b<1,0<c<1) and lithium-rich compounds; preferably, the positive electrode active material for sodium ion batteries includes one or more of NaFeO2, Na 2 / 3 MnO2, Na3V2(PO4)3, NaFePO4, NaMnFe(CN)6·zH2O;

[0016] Preferably, the negative electrode active material is a negative electrode active material for lithium ion batteries or a negative electrode active material for sodium ion batteries; preferably, the negative electrode active material for lithium ion batteries includes one or more of graphite, silicon, Li4Ti5O 12 , SiO d (0<d<2); preferably, the negative electrode active material for sodium ion batteries includes hard carbon and / or soft carbon.

[0017] In the above preparation 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), or graphene.

[0018] 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, polyethylene wax.

[0019] In the above 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), epoxy soybean oil (ESO), octyl epoxy stearate (ED3), tricresyl phosphate (TCP), triphenyl phosphate (TPP), trioctyl phosphate (TOP), dioctyl adipate (DOA), dioctyl azelate (DOZ), dioctyl sebacate (DOS).

[0020] In the above preparation 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.

[0021] In the above preparation method, as a preferred embodiment, in step (1), the order of mixing is: first add the plasticizer and the resin, then add the electrode active material, the conductive agent, and the lubricant;

[0022] Preferably, in step (1), the mixing is carried out in a mixer, the rotation speed of the mixing is 1000-3000 rpm (e.g., 1500 rpm, 2000 rpm, 2500 rpm), and the mixing time is 0.5-2 h (e.g., 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h);

[0023] Preferably, in step (1), the mixture is granulated by a double-screw extruder and a pelletizer;

[0024] Preferably, in step (1), the granulation is that the mixture is extruded by a twin-screw extruder and then pulled into a strip, the strip is cooled and then cut into electrode film raw material particles by a granulator;

[0025] Preferably, in step (1), the screw rotation speed of the twin-screw extruder is 20-40 rpm (for example, 22 rpm, 26 rpm, 28 rpm, 30 rpm, 32 rpm, 34 rpm, 36 rpm, 38 rpm);

[0026] Preferably, in step (1), the barrel temperature of the twin-screw extruder is 100-200 ℃ (for example, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃);

[0027] Preferably, in step (1), the temperature of the strip-drawing die of the twin-screw extruder is 120-185 ℃ (for example, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃);

[0028] Preferably, in step (1), the cooling is air cooling and / or water cooling, and more preferably air cooling; preferably, the strip is cooled to 20-30 ℃ (for example, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃) for cutting;

[0029] Preferably, in step (2), the pressing is performed by a screw extruder;

[0030] Preferably, in step (2), the screw extruder uses a T-shaped die;

[0031] Preferably, in step (2), the screw rotation speed of the screw extruder is 15-30 rpm (for example, 20 rpm, 22 rpm, 24 rpm, 26 rpm, 28 rpm);

[0032] Preferably, in step (2), the barrel temperature of the screw extruder is 100-200 ℃ (for example, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃);

[0033] Preferably, in step (2), the temperature of the T-shaped mold is 125-200℃ (e.g., 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃), and the gap of the mold lip of the T-shaped mold is 100-2000μm (e.g., 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, 550μm, 600μm, 650μm, 700μm, 800μm, 900μm, 1000μm, 1500μm, 1700μm).

[0034] Preferably, the hot pressing in step (3) is performed in a hot laminating machine;

[0035] Preferably, the temperature of the hot pressing roller in step (3) is 100℃-180℃ (e.g., 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃);

[0036] Preferably, the rolling speed of the hot press in step (3) is 5-20 m / min (e.g., 6 m / min, 7 m / min, 8 m / min, 9 m / min, 10 m / min, 11 m / min, 12 m / min, 13 m / min, 14 m / min, 15 m / min, 16 m / min, 17 m / min, 18 m / min, 19 m / min);

[0037] Preferably, the pressure of the hot pressing roller in step (3) is 5-50t (e.g., 10t, 15t, 20t, 25t, 30t, 35t, 40t, 45t);

[0038] Preferably, the roller spacing of the hot pressing roller in step (3) is 150-1000μm (e.g., 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, 550μm, 600μm, 650μm, 700μm, 800μm, 900μm);

[0039] Preferably, the rolling temperature of the cold pressing in step (3) is 25-40℃ (e.g., 28℃, 30℃, 35℃, 38℃);

[0040] Preferably, the pressure of the roller pressing in step (3) is 10-60t (e.g., 15t, 20t, 25t, 30t, 35t, 40t, 45t, 50t, 55t);

[0041] Preferably, the rolling speed of the cold pressing in step (3) is 5-20 m / min (e.g., 6 m / min, 7 m / min, 8 m / min, 9 m / min, 10 m / min, 11 m / min, 12 m / min, 13 m / min, 14 m / min, 15 m / min, 16 m / min, 17 m / min, 18 m / min, 19 m / min);

[0042] Preferably, the roller spacing of the cold pressing roller in step (3) is 150-800μm (e.g., 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, 550μm, 600μm, 650μm, 700μm).

[0043] This invention improves the processability of electrode film raw materials by adding lubricants and plasticizers. The lubricant reduces friction between the mixture and the extruder wall, as well as friction between mixture molecules, during granulation and pressing of the electrode film raw material particles into electrode films. The plasticizer weakens the secondary valence bonds between resin molecules, increases the mobility of resin molecular bonds, reduces the crystallinity of resin molecules, increases the plasticity of resin molecules, and enhances their flexibility and ease of processing. Through the synergistic effect of lubricants and plasticizers, this invention enables the electrode film raw materials to be dry-granulated and pressed into thicker, more compact, and uniform electrode films using an extruder.

[0044] In a preferred embodiment of the present invention, in step (1), the plasticizer is first mixed with the resin and then other powders (electrode active material, conductive agent and lubricant) are added in sequence. This allows the plasticizer to be uniformly coated on the resin surface, and when mixed with the powder material, it can effectively adhere the powder material to the resin surface, ensuring the uniformity of the mixture and facilitating further processing. Although the resin used in this application also plays a bonding role, it differs from the adhesives in the prior art in that the resin in this application is mixed with the electrode active material and conductive agent by melting in a screw extruder to form a homogeneous structure. The resin has better bonding with other powders (electrode active material, conductive agent and lubricant). In contrast, one existing technology involves fiberizing the adhesive to form a network structure that wraps the powder material together, and another involves electrostatic spraying that uses electrostatic adsorption to bond the adhesive and powder material together. In both of these methods, the bonding between the adhesive and the powder material is not strong, and sticking to the rollers is likely to occur during rolling.

[0045] Thirdly, the present invention provides a battery cell, the battery cell comprising the dry electrode sheet described in the first aspect or the dry electrode sheet prepared in the second aspect.

[0046] Fourthly, the present invention provides a battery, which is a lithium-ion battery or a sodium-ion battery, and the battery includes the battery cell described in the third aspect above.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] Compared to traditional wet electrode fabrication processes, the dry electrode technology of this invention does not use any solvents during electrode preparation, eliminating the emission of toxic gases. Electrodes are prepared solely through the mixing of dry powders. This invention provides a dry electrode preparation method that utilizes a rational ratio of plasticizer, lubricant, and resin, overcoming problems such as strip breakage, roller sticking, and poor uniformity in traditional dry electrode preparation processes. This achieves simplified processes, superior electrode uniformity, and higher energy density. The preparation method of this invention solves problems in existing dry electrode technologies, such as charge transfer issues, high resistance, significant expansion effects, and uneven powder distribution within the electrode. Furthermore, it can improve the energy density of individual battery cells to a certain extent.

[0049] The current mainstream method for dry-process electrodes involves mixing PTFE (polytetrafluoroethylene) with active materials and conductive agents, then shearing and drawing it into fibers. The PTFE fibers encapsulate the electrode material, which is then rolled into an electrode film and finally composited with a current collector. In this method, the degree of PTFE fiberization is difficult to control, resulting in a electrode film with poor strength. During continuous production, tape breakage is very likely, and material sticking to the rollers during rolling makes it difficult to ensure uniform thickness. The method of this invention eliminates the need for fiberization. Instead, the electrode material and polymer (resin) are melt-bonded together in a screw extruder. Therefore, the resulting electrode film has high strength, is less prone to tape breakage, and does not stick to the rollers. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the process flow for the dry electrode preparation method of lithium battery positive electrode according to Embodiment 1 of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0052] The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.

[0053] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0054] In this invention, unless otherwise specified and / or stated, all values ​​relating to component amounts are in parts by weight throughout. Process parameters in the following examples that do not specify particular conditions are generally performed under conventional conditions.

[0055] The commercial models and sources of the resins used in the embodiments of this invention are as follows:

[0056] Polyethylene-octene copolymer: POE 8150, Dow Chemical.

[0057] Ethylene-ethyl acrylate copolymer: Arkema EEA 2200 (USA).

[0058] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0059] Example 1

[0060] This embodiment provides a method for preparing a dry electrode sheet for a lithium-ion battery positive electrode, the preparation method as follows: Figure 1 As shown, it includes:

[0061] (1) Weigh 92 parts of NCM811 (positive electrode active material), 0.5 parts of conductive carbon black SP (conductive agent), 0.2 parts of calcium stearate (lubricant), 0.3 parts of polyethylene wax (lubricant), 1 part of dioctyl phthalate DOP (plasticizer) and 6 parts of polyethylene-octene copolymer POE (resin) by weight, and mix them evenly in a mixer at 1000 rpm for 2 hours to obtain a mixture.

[0062] (2) The mixture from step (1) is fed into a twin-screw extruder. After being extruded through the die of the twin-screw extruder, the mixture is pulled into strips. After being cooled to 30°C by air, the strips are fed into a pelletizer by a conveyor belt to be cut into uniform electrode film raw material particles with a particle size of 3 mm. The barrel temperature of the twin-screw extruder is 150°C, the die temperature of the twin-screw extruder is 145°C, the screw speed is 25 rpm, there are 10 fans for air cooling with a power of 2000W, the conveyor belt speed is 13 m / min, and the pelletizer speed is 21 rpm.

[0063] (3) As attached Figure 1 As shown, two screw extruders are aligned vertically, with an aluminum foil unwinding device placed in the middle. The electrode film raw material particles obtained in step (2) are simultaneously fed into the two screw extruders. After passing through the T-die, an electrode film with a thickness of 300μm is obtained. Then, the electrode film and aluminum foil are bonded together and fed into the double rollers of the thermal composite machine. After being pressed by the double rollers, an electrode sheet is obtained. The barrel temperature of the screw extruder is 170℃, the T-die temperature of the screw extruder is 180℃, the screw speed is 20rpm, the roller spacing of the thermal composite machine is 550μm, the roller pressing temperature is 100℃, the roller pressing pressure is 10t, and the roller pressing speed is 12m / min.

[0064] (4) The electrode sheet from the hot composite roller is finally cold-pressed and shaped by the cold pressing roller to obtain the final dry electrode sheet. The cold pressing roller temperature is 30℃, the roller pressure is 15t, the roller speed is 12m / min, and the roller spacing is 450μm.

[0065] All the above processes were carried out in a low humidity environment (dew point -40℃, moisture content less than 1%). The resulting positive electrode sheet has a smooth and wrinkle-free surface, does not shed powder, and has a thickness of 500μm. The thickness deviation at different positions of the entire electrode sheet is within ±1μm.

[0066] Example 2

[0067] This embodiment provides a method for preparing a dry electrode sheet for a lithium-ion battery negative electrode, the method comprising:

[0068] (1) Weigh 93 parts of graphite (negative electrode active material), 0.5 parts of conductive carbon black SP (conductive agent), 0.5 parts of paraffin wax (lubricant), 0.5 parts of dioctyl phthalate DOP (plasticizer), 4.5 parts of polyethylene-octene copolymer POE (resin) and 1 part of ethylene-ethyl acrylate copolymer EAA (resin) by weight, and mix them evenly in a mixer at 1500 rpm for 1 hour to obtain a mixture.

[0069] (2) The mixture from step (1) is fed into a twin-screw extruder. The mixture is extruded through the die of the twin-screw extruder and drawn into strips. After being cooled to 25°C by air, the strips are fed into a pelletizer by a conveyor belt and cut into uniform electrode film raw material particles with a particle size of 3 mm. The barrel temperature of the twin-screw extruder is 140°C, the die temperature of the twin-screw extruder is 135°C, the screw speed is 30 rpm, the air cooling uses 10 fans with a power of 2000W, the conveyor belt speed is 18 m / min, and the pelletizer speed is 28 rpm.

[0070] (3) Two screw sheet extruders are aligned vertically, and a copper foil unwinding device is placed in the middle. The electrode film raw material particles obtained in step (2) are simultaneously fed into the two screw extruders. The electrode film with a thickness of 200μm is obtained through the T-die. Then, the electrode film and copper foil are bonded together and fed into the double roller of the hot composite machine. The electrode sheet is obtained by pressing the double roller. The barrel temperature of the screw extruder is 165℃, the T-die temperature of the screw extruder is 170℃, the screw speed is 25rpm, the roller spacing of the hot composite machine is 380μm, the roller pressing temperature is 120℃, the roller pressing pressure is 8t, and the roller pressing speed is 15m / min.

[0071] (4) The electrode sheet from the hot composite roller is finally cold-pressed and shaped by the cold pressing roller to obtain the final dry electrode sheet. The cold pressing roller temperature is 25℃, the roller pressure is 12t, the roller speed is 15m / min, and the roller spacing is 320μm.

[0072] All the above processes were carried out in an environment with humidity below 10%. The prepared negative electrode sheet has a smooth and wrinkle-free surface, does not shed powder, and has a thickness of 350μm. The thickness deviation at different positions of the entire electrode sheet is within ±1μm.

[0073] Example 3

[0074] This embodiment provides a method for preparing a dry electrode sheet for a sodium-ion battery positive electrode, the method comprising:

[0075] (1) Weigh 90 parts of Na3V2(PO4)3 (positive electrode active material), 1.5 parts of conductive carbon black SP (conductive agent), 1 part of polyethylene wax (lubricant), 0.5 parts of dioctyl phthalate DOP (plasticizer), and 7 parts of polyvinylidene fluoride PVDF (resin) by weight, and mix them evenly in a mixer at 2000 rpm for 1 hour to obtain a mixture.

[0076] (2) The mixture from step (1) is fed into a twin-screw extruder. After being extruded through the die of the twin-screw extruder, the mixture is pulled into strips. After being cooled to 30°C by air, the strips are fed into a pelletizer by a conveyor belt to be cut into uniform electrode film raw material particles with a particle size of 3 mm. The barrel temperature of the twin-screw extruder is 190°C, the die temperature of the twin-screw extruder is 185°C, the screw speed is 20 rpm, there are 10 fans for air cooling with a power of 2000W, the conveyor belt speed is 12 m / min, and the pelletizer speed is 19 rpm.

[0077] (3) Two screw extruders are aligned vertically, with an aluminum foil unwinding device placed in the middle. The electrode film raw material particles obtained in step (2) are simultaneously fed into the two screw extruders. The electrode film with a thickness of 250μm is obtained through the T-die. The electrode film and aluminum foil are then bonded together and fed into the double rollers of the thermal composite machine. The electrode electrode sheet is obtained by pressing the double rollers. The barrel temperature of the screw extruder is 190℃, the T-die temperature of the screw extruder is 200℃, the screw speed is 18rpm, the roller spacing of the thermal composite machine is 430μm, the roller pressing temperature is 120℃, the roller pressing pressure is 10t, and the roller pressing speed is 11m / min.

[0078] (4) The electrode sheet from the hot composite roller is finally cold-pressed and shaped by the cold pressing roller to obtain the final dry electrode sheet. The cold pressing roller temperature is 35℃, the roller pressure is 15t, the roller speed is 11m / min, and the roller spacing is 360μm.

[0079] All the above processes were carried out in a low-humidity environment (dew point below -40℃, ambient moisture below 1%). The resulting positive electrode sheet has a smooth and wrinkle-free surface, does not shed powder, and has a thickness of 400μm. The thickness deviation at different positions of the entire electrode sheet is within ±1μm.

[0080] Example 4

[0081] This embodiment provides a method for preparing a dry electrode sheet for a sodium-ion battery negative electrode, the method comprising:

[0082] (1) Weigh 92 parts of hard carbon (negative electrode active material), 0.5 parts of conductive carbon black SP (conductive agent), 1 part of sodium stearate (lubricant), 0.5 parts of dioctyl phthalate DOP (plasticizer), and 6 parts of polyethylene-butene copolymer POE (resin) by weight, and mix them evenly in a mixer at 1000 rpm for 2 hours to obtain a mixture.

[0083] (2) The mixture from step (1) is fed into a twin-screw extruder. After being extruded through the die of the twin-screw extruder, the mixture is pulled into strips. After being cooled to 25°C by air, the strips are fed into a pelletizer by a conveyor belt to be cut into uniform electrode film raw material particles with a particle size of 3mm. The temperature of the twin-screw extruder barrel is 140°C, the temperature of the twin-screw extruder die is 135°C, the screw speed is 35rpm, the air cooling uses 10 fans with a power of 2000W, the conveyor belt speed is 18m / min, and the pelletizer speed is 25rpm.

[0084] (3) Two screw extruders are aligned vertically, with an aluminum foil unwinding device placed in the middle. The electrode film raw material particles obtained in step (2) are simultaneously fed into the two screw extruders. The electrode film with a thickness of 200μm is obtained through the T-die. Then, the electrode film and aluminum foil are bonded together and fed into the double roller of the composite machine. The electrode electrode is obtained by pressing the double roller. The barrel temperature of the screw extruder is 160℃, the T-die temperature of the screw extruder is 165℃, the screw speed is 23rpm, the roller spacing of the hot composite machine is 400μm, the roller pressing temperature is 110℃, the roller pressing pressure is 12t, and the roller pressing speed is 16m / min.

[0085] (4) The electrode sheet from the hot composite roller is finally cold-pressed and shaped by the cold pressing roller to obtain the final dry electrode sheet. The cold pressing roller temperature is 25℃, the roller pressure is 20t, the roller speed is 16m / min, and the roller spacing is 280μm.

[0086] All the above processes were carried out in an environment with a moisture content of less than 10%. The resulting negative electrode sheet has a smooth and wrinkle-free surface, does not shed powder, and has a thickness of 300 μm. The thickness deviation at different positions of the entire electrode sheet is within ±1 μm.

[0087] Example 5

[0088] This embodiment provides a method for preparing a dry electrode sheet for a lithium-ion battery positive electrode, the method comprising:

[0089] (1) Weigh 92 parts of NCM811 (positive electrode active material), 0.5 parts of conductive carbon black SP (conductive agent), 0.2 parts of calcium stearate (lubricant), 0.3 parts of polyethylene wax (lubricant), 1 part of dioctyl phthalate DOP (plasticizer) and 6 parts of polyethylene-octene copolymer POE (resin) by weight, and mix them evenly in a mixer at 1000 rpm for 2 hours to obtain a mixture.

[0090] (2) The mixture from step (1) is fed into a twin-screw extruder. After being extruded through the die of the twin-screw extruder, the mixture is pulled into strips. After being cooled to 30°C by air, the strips are fed into a pelletizer by a conveyor belt to be cut into uniform electrode film raw material particles with a particle size of 3 mm. The barrel temperature of the twin-screw extruder is 150°C, the die temperature of the twin-screw extruder is 145°C, the screw speed is 25 rpm, there are 10 fans for air cooling with a power of 2000W, the conveyor belt speed is 13 m / min, and the pelletizer speed is 21 rpm.

[0091] (3) As attached Figure 1 As shown, two screw extruders are aligned vertically, with an aluminum foil unwinding device placed in the middle. The electrode film raw material particles obtained in step (2) are simultaneously fed into the two screw extruders. After passing through the T-die, an electrode film with a thickness of 600μm is obtained. Then, the electrode film and aluminum foil are bonded together and fed into the double rollers of the thermal laminating machine. After being pressed by the double rollers, an electrode sheet is obtained. The barrel temperature of the screw extruder is 170℃, the T-die temperature of the screw extruder is 180℃, the screw speed is 20rpm, the roller spacing of the thermal laminating machine is 1000μm, the roller pressing temperature is 100℃, the roller pressing pressure is 10t, and the roller pressing speed is 12m / min.

[0092] (4) The electrode sheet from the hot composite roller is finally cold-pressed and shaped by the cold pressing roller to obtain the final dry electrode sheet. The cold pressing roller temperature is 30℃, the roller pressure is 15t, the roller speed is 12m / min, and the roller spacing is 750μm.

[0093] All the above processes were carried out in a low humidity environment (dew point -40℃, moisture content less than 1%). The prepared positive electrode sheet has a smooth and wrinkle-free surface and does not shed powder. The thickness is 800μm, and the thickness deviation at different positions of the entire electrode sheet is within ±1μm.

[0094] Example 6

[0095] This embodiment provides a method for preparing a dry electrode sheet for a lithium-ion battery positive electrode, which is basically the same as that in Embodiment 1, except that the resin material is replaced with polyacrylic acid (PAA).

[0096] The positive electrode sheet prepared in this embodiment has a smooth and wrinkle-free surface, does not shed powder, has a uniform thickness, and the thickness deviation at different positions of the entire electrode sheet is within ±1μm.

[0097] Example 7

[0098] This embodiment provides a method for preparing a dry electrode sheet for a lithium-ion battery positive electrode, which is basically the same as that in Embodiment 1, except that the plasticizer is replaced with epoxidized soybean oil (ESO).

[0099] The positive electrode sheet prepared in this embodiment has a smooth and wrinkle-free surface, does not shed powder, has a uniform thickness, and the thickness deviation at different positions of the entire electrode sheet is within ±1μm.

[0100] Application Example 1

[0101] The dry electrode sheets prepared in Examples 1 and 2 were cut into sheets, stacked together with the separator, and injected with electrolyte to prepare a dry soft-pack battery cell with a capacity of 5Ah.

[0102] Comparative Example 1

[0103] A wet electrode preparation method is provided. The positive electrode is the same as that in Example 1, with the same ratio of active material content. The difference lies in the preparation steps, as detailed in step (1) below. The negative electrode prepared in this comparative example is the same as that in Example 2, except for the type of adhesive and the preparation method. Other raw materials such as negative electrode active material and conductive agent are the same. The ratio of the three raw materials, adhesive, active material and conductive agent, is the same as in Example 2. The preparation of the negative electrode is as detailed in step (2) below. The assembly into a battery cell is the same as in the above application example, as detailed in step (3) below.

[0104] (1) Preparation of positive electrode sheet: PVDF is dissolved in N-methylpyrrolidone (NMP) to form a gel, and then the positive electrode material NCM811 and conductive agent SP are dry mixed and then mixed evenly with the gel, coated and dried to obtain the positive electrode sheet.

[0105] (2) Preparation of negative electrode sheet: CMC (sodium carboxymethyl cellulose) and SBR (chloroprene rubber) are dissolved in deionized water to form a rubber compound. Then, the negative electrode material graphite and conductive agent SP are dry-mixed and mixed evenly with the rubber compound. The mixture is then coated and dried to obtain the negative electrode sheet.

[0106] The obtained positive and negative electrode sheets are cut into sheets, stacked and assembled with the separator, and then injected with electrolyte to prepare wet-process soft-pack cells with a single cell capacity of 5Ah.

[0107] Comparative Example 2

[0108] A method for preparing PTFE fiber dry electrode sheets, wherein the positive electrode sheet is the same as that in Example 1, the types and contents of positive active materials and conductive agents are the same, the difference lies in the additives and preparation steps, as detailed in step (1) below. The negative electrode sheet prepared in this comparative example is the same as that in Example 2, the types and contents of negative active materials and conductive agents are the same, the difference lies in the additives and preparation steps, the preparation of the negative electrode sheet is as detailed in step (2) below, and the assembly into a battery cell is the same as in the above application example, as detailed in step (3) below:

[0109] (1) Preparation of positive electrode sheet: NCM811 positive electrode material, conductive agent SP and PTFE are mixed and fibrillated by air jet mill, and then rolled (rolling pressure 20t, rolling speed 15rpm, rolling gap 200μm) to obtain a dry positive electrode self-supporting film with a thickness of 210μm. Finally, it is double-sided laminated with carbon-coated aluminum foil (the dry positive electrode self-supporting film and aluminum foil are laminated together and fed into the double roller of the hot laminating machine, with the aluminum foil in the middle layer and the self-supporting film of the same thickness on the top and bottom, the rolling gap is 330μm, the lamination temperature is 180℃, the rolling pressure is 10t, the rolling speed is 15m / min, and finally cooled by multiple conveying rollers to obtain the final dry positive electrode sheet with a thickness of 350μm) to form a positive electrode sheet;

[0110] (2) Preparation of negative electrode sheet: graphite, conductive agent and PTFE negative electrode material are mixed and fibrillated by air jet mill. Then, the mixture is rolled (rolling pressure 15t, rolling speed 20rpm, rolling gap 175μm) to obtain a dry negative electrode self-supporting film with a thickness of 195μm. Finally, the dry negative electrode self-supporting film is double-sided laminated with carbon-coated copper foil (the dry negative electrode self-supporting film and copper foil are laminated together and fed into the double roller of the hot laminating machine, with the copper foil in the middle layer and the self-supporting film of the same thickness on the top and bottom, with a rolling gap of 280μm, a lamination temperature of 150℃, a rolling pressure of 12t, a rolling speed of 18m / min, and finally cooled by multiple conveying rollers) to form a negative electrode sheet with a thickness of 310μm.

[0111] (3) Cut the obtained positive and negative electrode sheets, stack them together with the separator, and inject liquid to prepare soft-pack cells. The cell specifications are that the single cell capacity is 5Ah.

[0112] Comparative Example 3

[0113] This comparative example is basically the same as Example 1, except that step (1) of this comparative example is: weigh 92 parts of NCM811 (positive electrode active material), 0.5 parts of conductive carbon black SP (conductive agent), 1.5 parts of additives (dibutyl maleate and dibutyl fatty acid dihydroxy acid in a mass ratio of 3:7) and 6 parts of polyvinylidene fluoride (resin), and mix them evenly in a mixer at 1000 rpm for 2 hours to obtain a mixture.

[0114] Using dibutyl maleate and dibutyl fatty acid dihydroxy acid in a mass ratio of 3:7 as additives can replace the role of plasticizers to a certain extent. However, since no lubricant was used, the electrode sheet prepared in this comparative example had a rough surface and poor uniformity. The thickness deviation at different positions of the entire electrode sheet was 5 to 8 μm. The electrode film had poor tensile strength, was prone to breakage, and was prone to powder shedding.

[0115] Comparative Example 4

[0116] This comparative example is basically the same as Example 1, except that no lubricant is added to the mixture in step (1) of this comparative example.

[0117] Because no lubricant was added, the processing using a screw extruder became more difficult. The electrode sheet prepared in this comparative example had a rough surface and poor uniformity. The thickness deviation at different positions of the entire electrode sheet was 5-8 μm. The electrode film had poor tensile strength, was prone to breakage, and was prone to powder shedding.

[0118] Comparative Example 5

[0119] This comparative example is basically the same as Example 1, except that no plasticizer is added to the mixture in step (1) of this comparative example.

[0120] Since no plasticizer was added, the processing using a screw extruder became more difficult. The electrode sheet prepared in this comparative example had a rough surface and poor uniformity. The thickness deviation at different positions of the entire electrode sheet was 4 to 6 μm, and the powder shedding was severe.

[0121] Performance testing:

[0122] (1) Tensile strength test

[0123] The electrode films prepared in Examples 1, 2 and 2 were subjected to tensile strength tests. The test method was as follows: the electrode film / self-supporting film was cut into strips of 15mm*150mm with a cutter and its tensile strength was tested by a universal testing machine.

[0124] Table 1: Comparison of tensile strength of electrode films in Examples 1, 2 and Comparative Example 2

[0125]

[0126]

[0127] (2) Cyclic performance

[0128] At a constant temperature of 25℃, the cycle performance of the soft-pack batteries prepared in Example 1, Comparative Example 1 and Comparative Example 2 was tested, with a voltage range of 2.5-4.25V.

[0129] The batteries were subjected to 1C constant current charge and discharge tests to measure their initial efficiency and initial discharge capacity. The test results are shown in columns 2 and 3 of Table 2 below. Initial efficiency = initial discharge capacity / initial charge capacity.

[0130] The internal resistance of the above-mentioned battery was tested using a voltage internal resistance meter. The test results are shown in column 4 of Table 2 below.

[0131] Column 5 of Table 2 below shows the ratio of the first discharge capacity of the above battery at 1C to the first discharge capacity at 0.33C.

[0132] Column 6 of Table 2 below shows the ratio of the first discharge capacity of the above battery at 2C to the first discharge capacity at 0.33C.

[0133] Table 2: Comparison of electrochemical performance results of pouch cells prepared in Application Example 1, Comparative Example 1, and Comparative Example 2

[0134]

[0135] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dry-process electrode sheet, characterized in that, The electrode sheet includes a current collector foil and an electrode film laminated to one or both sides of the current collector foil; the raw materials of the electrode film, by weight, include 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; the electrode film is a dry electrode film; The plasticizer includes one or more of the following: dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, dioctyl phthalate, butyl benzyl phthalate, di(2-ethylhexyl) phthalate, diisononyl phthalate, epoxidized soybean oil, octyl epoxidized stearate, tricresyl phosphate, triphenyl phosphate, trioctyl phosphate, dioctyl adipate, dioctyl azelate, and dioctyl sebacate. The lubricant includes one or more of stearic acid, sodium stearate, calcium stearate, zinc stearate, paraffin wax, and polyethylene wax; The resin includes one or more of the following: polyethylene oxide, polyvinylidene fluoride, 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. The method for preparing the dry electrode sheet includes the following steps in sequence: (1) The raw materials for the electrode membrane, namely electrode active material, conductive agent, lubricant, plasticizer and resin, are mixed evenly to obtain a mixture, and then granulated to obtain electrode membrane raw material particles; wherein, the mixing order is: first add plasticizer and resin, then add electrode active material, conductive agent and lubricant; the mixture is granulated by twin-screw extruder and pelletizer; (2) Press the electrode film raw material particles obtained in step (1) into an electrode film; (3) The electrode film obtained in step (2) is hot-pressed onto both sides of the current collector foil and then cold-pressed to form the dry electrode sheet; The dry electrode preparation method does not require fiberization.

2. The dry electrode sheet as described in claim 1, characterized in that, The raw material of the electrode film is granulated by an extruder and then pressed into an electrode film by an extruder; the electrode film and the current collector foil are hot-pressed together to form an electrode sheet.

3. The method for preparing dry electrode sheets as described in claim 1 or 2, characterized in that, The preparation method includes the following steps in sequence: (1) The raw materials for the electrode membrane, namely electrode active material, conductive agent, lubricant, plasticizer and resin, are mixed evenly to obtain a mixture, and then granulated to obtain electrode membrane raw material particles; wherein, the mixing order is: first add plasticizer and resin, then add electrode active material, conductive agent and lubricant; the mixture is granulated by twin-screw extruder and pelletizer; (2) Press the electrode film raw material particles obtained in step (1) into an electrode film; (3) The electrode film obtained in step (2) is hot-pressed onto both sides of the current collector foil and then cold-pressed to form the dry electrode sheet; The dry electrode preparation method does not require fiberization.

4. The preparation method according to claim 3, characterized in that, The electrode active material is a positive electrode active material or a negative electrode active material; The positive electrode active material is a positive electrode active material for lithium-ion batteries or a positive electrode active material for sodium-ion batteries; the negative electrode active material is a negative electrode active material for lithium-ion batteries or a negative electrode active material for sodium-ion batteries.

5. The preparation method according to claim 4, characterized in that, The positive electrode active materials for lithium-ion batteries include LiMn2O4, LiCoO2, LiFePO4, and LiNi. x Co y Mn z O2, LiNi a Co b Al c O2 and one or more lithium-rich compounds; wherein, LiNi x Co y Mn z In O2, x + y + z = 1, 0 <x<1,0<y<1,0<z<1;LiNi a Co b Al c In O2, a + b + c = 1, 0 <a<1,0<b<1,0<c<1; And / or, the positive electrode active material for the sodium-ion battery includes NaFeO2, Na 2 / 3 One or more of MnO2, Na3V2(PO4)3, and NaFePO4; And / or, the negative electrode active material for the lithium-ion battery includes graphite, silicon, Li4Ti5O 12 SiO d One or more of the following; wherein, SiO d In the middle, 0 <d<2; And / or, the negative electrode active material for the sodium-ion battery includes hard carbon and / or soft carbon; And / or, the conductive agent includes one or a combination of at least two of conductive carbon black, conductive graphite powder, carbon nanotubes, conductive nanofibers or graphene.

6. The preparation method according to any one of claims 3-5, characterized in that, In step (1), the granulation involves extruding the mixture through a twin-screw extruder and then drawing it into strips. The strips are cooled and then cut into electrode film raw material particles by a pelletizer. And / or, in step (2), the pressing is performed using a screw extruder, which uses a T-die; And / or, the hot pressing described in step (3) is performed in a hot laminating machine.

7. The preparation method according to claim 6, characterized in that, In step (1), the mixing is carried out in a mixer at a speed of 1000-3000 rpm for a time of 0.5-2 hours. And / or, in step (1), the screw speed of the twin-screw extruder is 20-40 rpm; And / or, in step (1), the barrel temperature of the twin-screw extruder is 100-200℃; And / or, in step (1), the temperature of the twin-screw extruder's drawing die is 120-185°C; And / or, in step (1), the cooling is air cooling and / or water cooling; And / or, in step (1), the strip is cooled to 20-30°C and then granulated; And / or, in step (2), the screw speed of the screw extruder is 15-30 rpm; And / or, in step (2), the barrel temperature of the screw extruder is 100-200℃; And / or, in step (2), the temperature of the T-shaped mold is 125-200℃, and the gap of the mold lip of the T-shaped mold is 100-2000μm; And / or, the temperature of the hot pressing roller in step (3) is 100℃-180℃; And / or, the rolling speed of the hot pressing in step (3) is 5-20 m / min; And / or, the pressure of the roller pressing in step (3) is 5-50t; And / or, the roller spacing of the hot pressing rollers in step (3) is 150-1000 μm; And / or, the rolling temperature of the cold pressing in step (3) is 25-40°C; And / or, the pressure of the roller pressing in step (3) is 10-60t; And / or, the rolling speed of the cold pressing in step (3) is 5-20 m / min; And / or, the roller spacing of the cold pressing rollers in step (3) is 150-800μm.

8. A battery cell comprising a dry electrode sheet as described in claim 1 or 2, or a dry electrode sheet prepared by the preparation method described in any one of claims 3-7.

9. A battery, said battery being a lithium-ion battery or a sodium-ion battery, said battery comprising the cell of claim 8.

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