Dry-process battery film and method of making same, electrode, battery

Abstract

The application provides a dry-process battery film piece, a preparation method thereof, a pole piece and a battery. The preparation method comprises the following steps: mixing a solid active material, a solid binder and a solid functional additive to prepare a mixture; performing several times of roller pressing molding on the mixture in a roller pressing equipment with a roller gap of 0.4mm-2.5mm to prepare a blank film; and thinning the blank film to prepare the dry-process battery film piece. The solid active material is a positive active material, a negative active material or a solid-state electrolyte material. The preparation method of the dry-process battery film piece has low requirement on the fiberization degree of the binder, effectively reduces the damage degree of the active material or the solid-state electrolyte material and improves the electrode performance.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a dry-process battery film and its preparation method, electrode, and battery. Background Technology

[0002] Lithium-ion batteries, with their advantages of small size, high energy density, and long cycle life, have become an ideal energy carrier with broad application prospects. Electrode membranes and electrolyte membranes are important components of lithium-ion batteries. In the early days, wet processes were often used for membrane preparation, but with increasing environmental protection requirements, research has gradually shifted to solvent-free dry processes.

[0003] Dry processing, lacking the dispersibility provided by solvents, presents a significant challenge to continuous film formation. Insufficient binder content in dry processes prevents the formation of a complete three-dimensional network structure, thus hindering continuous film formation using dry pressing techniques. Conversely, excessive binder content, while improving film formation, can lead to reduced electrical conductivity and mass energy density. To address the issue of continuous film formation, traditional methods often involve increasing the degree of fiberization of the binder after dry mixing.

[0004] Currently, binder fiberization equipment is diverse but costly. To increase the degree of fiberization of dry binders, high-speed mixers, high-speed shearing machines, and high-speed mechanical grinding machines are generally required. However, to increase the degree of fiberization of binders in the mixture, high shear force is often required. High shear force can easily damage active materials or solid electrolyte materials, thereby affecting battery performance. At the same time, it is difficult to quantitatively assess the degree of fiberization of binders and there are batch inconsistencies. Summary of the Invention

[0005] To address the shortcomings of existing dry process technologies, this invention provides a dry-process battery film, its preparation method, an electrode, and a battery. The preparation method of the dry-process battery film of this invention does not involve a high-shear mixing process, effectively reducing the degree of damage to active components during the mixing process, thereby effectively improving the electrochemical performance of the battery.

[0006] A first aspect of this application provides a method for preparing a dry-process battery film, comprising the following steps:

[0007] A mixture is prepared by mixing solid active materials, solid binders, and solid functional additives.

[0008] The mixture is rolled and formed in several roller presses with a roller gap of 0.4 mm to 2.5 mm to prepare a preform film. The average particle size of the solid active material is 20 nm to 30 μm. Rolling is performed with a relatively large roller gap of 0.4 mm to 2.5 mm. The particle size of the solid active material is smaller than the roller gap. Under the pressure of the roller press, because the roller gap is much larger than the average particle size of the solid active material, the solid active material moves towards the center of the roller gap, thereby avoiding damage under the action of large roller pressure.

[0009] Thinning of the embryo membrane to prepare dry-process battery film;

[0010] Solid active materials can be positive electrode active materials, negative electrode active materials, or solid electrolyte materials.

[0011] In some embodiments, the plurality of roller pressing includes the following steps: performing a first roller pressing on the mixture to obtain a continuous film, and performing a second roller pressing on the continuous film to obtain a preform film.

[0012] In some implementations, the roll gaps of the rolling equipment in the roll forming process are kept consistent, that is, the roll gaps of the rolling equipment in the first roll forming and the second roll forming process are the same, which means that the roll gaps of the several rolls are equally spaced.

[0013] In some embodiments, the first roll forming includes the following steps:

[0014] Step 1: Roll the mixture once or multiple times to obtain several sheets and powders;

[0015] Step 2: Join several pieces of material end to end, and cover the joint with the powder to obtain a composite material;

[0016] Step 3: Roll forming the composite material to obtain larger sheet material and residual powder material. The larger sheet material and residual powder material are different from the several sheet materials and powder materials in Step 1. The larger sheet material refers to the sheet material with a larger area than the several sheet materials in Step 1.

[0017] Step 4: Repeat steps 2-3, roll the film until no powder remains, and obtain a continuous film.

[0018] In some embodiments, the second roll forming includes the following steps:

[0019] Step 1: Fold the continuous film, or laminate two continuous films together and roll them once to obtain a laminated film;

[0020] Step 2: Fold the laminated film, or laminate two laminated films together and perform a single roller pressing;

[0021] Step 3: Repeat step 2 until the tensile strength of the resulting pressed film meets the preset conditions, which is the embryo film;

[0022] Preferably, the tensile strength of the preform film is ≥2MPa. Currently, the quality of battery films can only be judged based on experience or the quality of the film after formation (appearance, bending flexibility, etc.). This judgment method is highly subjective, leading to large errors, low efficiency, and difficulty in correcting mistakes, resulting in low yield and other problems, which is not conducive to mass production development. By detecting the tensile strength of the preform film, the quality of the final film can be monitored, improving the yield of battery films and the consistency of battery film formation.

[0023] In some embodiments, thinning the embryo membrane includes the following steps: performing several roll forming thinning operations on the embryo membrane in a roll forming apparatus;

[0024] Preferably, the roll gap during the rolling thinning process is gradually reduced in several cycles until a dry-process battery film with a thickness of 10 μm to 200 μm is obtained.

[0025] In some embodiments, the rolling temperature during each rolling process in the first rolling process is 20°C to 150°C; preferably, the rolling temperature is 70°C to 150°C.

[0026] The rolling speed during each rolling process in the first round of roll forming is 0.1 m / min to 50 m / min, preferably 0.5 m / min to 20 m / min;

[0027] The rolling temperature during each rolling process in the second round of roll forming is 20℃~150℃; preferably, the rolling temperature is 70℃~150℃.

[0028] The rolling speed during each rolling process in the second round of roll forming is 0.1 m / min to 50 m / min, preferably 0.5 m / min to 20 m / min;

[0029] The rolling speed during each rolling process in the first round of roll forming is the same as the rolling speed during each rolling process in the second round of roll forming.

[0030] The pressure during several roller pressing processes is below 80t;

[0031] Preferably, the pressure of the roll forming is 5t, 10t, 15t, 20t, 25t, 30t, 35t, 40t, 45t, 50t, 55t, 65t, 70t, 75t or 80t;

[0032] Preferably, the roll gap of the roll forming is 0.4mm, 0.5mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2.0mm, 2.2mm or 2.4mm.

[0033] In some embodiments, the mass ratio of the solid active material, the solid binder, and the solid functional additive is (20–98.9):(0.1–30):(1–80);

[0034] Preferably, the mass ratio of solid active material, solid binder and solid functional additive is (20-98.9):(0.1-30):(1-50);

[0035] Preferably, the solid active material is a positive electrode active material, which is one or more of the following materials: lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium-rich manganese-based, elemental sulfur, sodium iron manganate, sodium iron titanate, sodium iron sulfate, sodium iron phosphate, sodium vanadium phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, and lithium titanate.

[0036] Preferably, the solid active material is a negative electrode active material, which is one or more of graphite, silicon, silicon oxide, silicon carbon, lithium titanate, hard carbon, soft carbon, tin oxide, and titanium dioxide.

[0037] Preferably, the solid active material is a solid electrolyte material, which is an inorganic solid electrolyte material and / or a polymer electrolyte material; the inorganic solid electrolyte material is one or more of lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, and lithium phosphorus oxy nitrogen, silicon phosphorus sulfur, and lithium sulfide phosphate; the polymer electrolyte material is one or more of polyethylene oxide, polyacrylonitrile, and polymethyl methacrylate doped with lithium salt.

[0038] Preferably, the solid binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, nitrile rubber, sodium carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, and sodium alginate;

[0039] Preferably, the solid functional additives include one or more of the following: conductive agents, solid electrolytes, lithium supplements, catalysts, and ionic conductivity enhancers;

[0040] Preferably, the solid functional additive is a conductive agent, which is one or more of the following: carbon black, acetylene black, carbon nanotubes, carbon fibers, conductive graphite, graphene, conductive metal carbides, conductive metal nitrides, metal particles, and conductive polymers.

[0041] Preferably, the solid functional additive is a solid electrolyte added to the positive or negative electrode, wherein the solid electrolyte is an inorganic solid electrolyte material and / or a polymer electrolyte material;

[0042] Preferably, the solid functional additive is a positive electrode lithium replenisher added to the positive electrode, wherein the positive electrode lithium replenisher is one or more of lithium oxide, lithium nitride, lithium sulfide, lithium-rich lithium iron ore, and lithium nickel oxide.

[0043] Preferably, the solid functional additive is a catalyst added to the conversion electrode, and the catalyst is one or more of transition metal sulfides, transition metal nitrides, transition metal carbides, heteroatom-doped carbon, etc.

[0044] Preferably, the solid functional additive is an ionic conductivity enhancer, which is one or more of alumina, silicon dioxide, montmorillonite, boron nitride, and carbon nitride.

[0045] A second aspect of this application provides a dry-process battery film, which is prepared according to the preparation method provided in the first aspect above.

[0046] A third aspect of this application provides an electrode sheet comprising a current collector and the dry cell film provided in the second aspect above;

[0047] Preferably, the dry cell film is combined with the current collector by hot rolling to form an electrode sheet;

[0048] Preferably, the rolling temperature of the hot roll is 50℃~250℃.

[0049] A fourth aspect of this application provides a battery comprising the dry cell film provided in the second aspect or the electrode sheet provided in the third aspect.

[0050] In existing dry film-forming processes, the binder in the mixture is required to be fully fiberized before rolling, and the first roll forming must be completed into a single sheet. Insufficient fiberization leads to poor subsequent film formation, while the high shear forces required for high fiberization during mixing often damage the active substrate. Compared with existing dry forming technologies, this invention has the following advantages:

[0051] 1. The dry-process battery film, its preparation method, electrode, and battery provided by this invention, in the entire preparation process, through a certain dry powder mixing pretreatment, the mixing is carried out at a low speed not exceeding 600 rpm, the shear force is low and will not damage the solid active material; at the same time, the requirements for the mixture are low after mixing. After the first roll pressing, a discontinuous sheet film and powder mixture are obtained. The discontinuous film obtained by the first roll pressing is repeatedly rolled within a large roll pressing gap range by splicing, folding and other methods to obtain a preform film with a certain thickness and strength. During the repeated roll pressing process, the binder is squeezed and moved to fully fibrous network, thereby effectively improving the strength and flexibility of the preform film; the preform film is then thinned by roll pressing to finally obtain the electrode film or solid electrolyte film of the required thickness.

[0052] 2. The dry-process battery film and its preparation method, electrode, and battery provided by this invention maintain a consistent roller gap during the roll forming process, performing several rounds of equal-spacing roller forming. A relatively large gap of 0.4mm to 2.5mm is maintained during the equal-spacing roller forming process. During the rolling process, the active material moves towards the center of the roller gap under pressure, effectively avoiding the extrusion pressure damaging the active material. Simultaneously, the multiple rounds of equal-spacing roller forming increase the uniformity of the binder fiberization, which is beneficial for preparing a flexible preform film.

[0053] 3. The dry-process battery film and its preparation method, electrode, and battery provided by the present invention omit high-shear force equipment such as high-speed stirring, high-speed shearing machine, mechanical grinding machine, and air jet mill. While avoiding the damage of high shear force to active materials during the fiberization process, it also effectively reduces the requirements for the use of complex equipment, reduces material and human resources input, and is conducive to the promotion of industrial production.

[0054] 4. The dry-process battery film and its preparation method, electrode, and battery provided by this application are easy to inspect because the preform film obtained by rolling with equally spaced roller gaps is easy to inspect. In the existing process, the degree of fiberization of the binder can only be judged by experience, and there is no reliable evaluation method, which causes inconsistency in film batches. This application can effectively evaluate the quality of the preform film and can ensure the consistency of film batches.

[0055] The dry-process battery film preparation method of this application only requires uniform mixing of materials before rolling, which reduces the requirement for the degree of fiberization of the binder, reduces the fiberization treatment steps before rolling, simplifies the process, and reduces the initial investment cost of industrial production; at the same time, it effectively avoids the damage to active materials or solid electrolyte materials caused by high shear force during the fiberization process. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0057] Figure 1 This is a schematic diagram of the splicing and compounding of a mixture of powder and flake materials in one embodiment of this application.

[0058] Figure 2 This is a schematic diagram of folding and pressing a continuous film in one embodiment of this application.

[0059] Figure 3 This is a schematic diagram of the continuous film being laminated and pressed together in one embodiment of this application.

[0060] Figure 4 This is a morphological image of the positive electrode film prepared in one embodiment of this application.

[0061] Figure 5 This is the cross-sectional microstructure of the positive electrode film prepared in one embodiment of this application.

[0062] Figure 6 This is a morphological image of the negative electrode film prepared in one embodiment of this application.

[0063] Figure 7 and Figure 8 The images show the microstructure of the cross-section of the negative electrode film prepared in one embodiment of this application at different magnifications.

[0064] Figure 9 The image shows the cross-sectional microstructure of the positive electrode film prepared in a pair of proportions of this application.

[0065] Explanation of reference numerals in the attached figures

[0066] 1. Powder; 2. Sheet material; 3. Splicing seam; 4. Continuous film. Detailed Implementation

[0067] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0068] In the description of this application, it should be understood that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," or "third" may explicitly or implicitly include at least one of those features.

[0069] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0070] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0071] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means additional steps and components that may be added without affecting the final result. The compositions and methods / processes of this application comprise, consist of, and are substantially composed of the essential elements and limitations described herein, as well as any additional or optional components, parts, steps, or limitations described herein.

[0072] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this application's specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0073] A first aspect of this application provides a method for preparing a dry-process battery film, comprising the following steps:

[0074] S1. Mix solid active materials, solid binders, and solid functional additives to prepare a mixture;

[0075] S2. The mixture is rolled and formed by several rollers in a roller press with a roller gap of 0.4 mm to 2.5 mm to prepare a preform film;

[0076] S3. Thin the embryo membrane to prepare a dry-process battery film;

[0077] The solid active material is a positive electrode active material, a negative electrode active material, or a solid electrolyte material. In some embodiments, the dry cell membrane is a positive electrode membrane, a negative electrode membrane, or a solid electrolyte membrane. For ease of description, the positive electrode membrane and the negative electrode membrane are collectively referred to as electrode membranes in this application.

[0078] In some embodiments, step S1 further includes a premixing step. For example, the positive electrode active material and the conductive agent are added to a stirring device and stirred and premixed for 10 minutes, and then a solid binder is added and stirred and mixed to prepare a mixture.

[0079] In some embodiments, the multi-roll pressing process includes the following steps: performing a first roll pressing on the mixture to obtain a continuous film, and performing a second roll pressing on the continuous film to prepare a preform film.

[0080] In some implementations, the roll gap of the rolling equipment in a plurality of roll forming processes remains consistent.

[0081] In some embodiments, the first roll forming includes the following steps:

[0082] Step 1: Roll the mixture once or multiple times to obtain several sheets and powders;

[0083] Step 2: Join several pieces of material end to end, and cover the joint with powder to obtain a composite material;

[0084] Step 3: Perform a single roll forming on the composite material described in Step 2 to obtain larger sheet material and residual powder material;

[0085] Step 4: Repeat steps 2-3 until there is no powder after the roller press discharges, and a continuous film is obtained.

[0086] In some embodiments, the second roll forming includes the following steps:

[0087] Step 1: Fold the continuous film obtained by the first round of roll forming, or laminate two continuous films obtained by the first round of roll forming and roll them again to obtain a laminated film;

[0088] Step 2: Fold the laminated film from Step 1, or laminate the two laminated films together and roll them together again.

[0089] Step 3: Repeat step 2 until the tensile strength of the resulting pressed film meets the preset conditions, which is the embryo film.

[0090] In this application, "preset conditions" refers to the tensile strength of the embryonic membrane being ≥1 MPa.

[0091] In some embodiments, in step 3, step 2 is repeated until the tensile strength of the embryonic membrane is ≥2 MPa.

[0092] In some embodiments, thinning the preform includes the following steps: performing several roll forming thinning operations on the preform in a roll forming device with a roll gap of 10 μm to 2000 μm.

[0093] In some embodiments, the roll gap of the roll thinning process is gradually reduced in several roll pressings until a dry cell film with a thickness of 10 μm to 200 μm is obtained.

[0094] In some embodiments, the rolling temperature during each rolling process in the first round of rolling is 20°C to 150°C; preferably, the rolling is performed at a high temperature of 70°C to 150°C.

[0095] In some embodiments, the rolling speed during each rolling process in the first rolling process is 0.1 m / min to 50 m / min; preferably, it is 0.5 m / min to 20 m / min.

[0096] In some embodiments, the rolling temperature during each rolling process in the second rolling process is 20°C to 150°C; preferably, the rolling is performed at a high temperature of 70°C to 150°C.

[0097] In some embodiments, the rolling speed during each rolling process in the second rolling process is 0.1 m / min to 50 m / min; preferably, it is 0.5 m / min to 20 m / min.

[0098] In some embodiments, the dry cell film is an electrode film, and the method for preparing the electrode film includes the following steps:

[0099] S10. Weigh the materials according to the mass ratio of solid active substance, solid binder and solid functional additive (20-98.9): (0.1-30): (1-80);

[0100] S11. Add the weighed material from step S10 to a mixing device for mixing, so that the solid binder is dispersed in the material to prepare a mixture;

[0101] S12. The mixture is rolled and formed by several rollers in a roller press with a roller gap of 0.4 mm to 2.5 mm to prepare a preform film;

[0102] S13. The embryo membrane is thinned by rolling in stages to prepare an electrode film.

[0103] In some embodiments, the solid active material in step S10 is either a positive electrode active material or a negative electrode active material. It is understood that when the active material is a positive electrode active material, the prepared dry-process battery film is a positive electrode film; when the active material is a negative electrode active material, the prepared dry-process battery film is a negative electrode film.

[0104] In some embodiments, the positive electrode active material includes, but is not limited to, lithium iron phosphate (LiFePO4), lithium cobalt oxide (LiCoO2), and lithium nickel cobalt manganese oxide (LiNi). x Mn y Co 1-x-yO2 (NMC), lithium manganese oxide (LiMn2O4), lithium nickel cobalt aluminum oxide (LiNiCoAlO2, NCA), lithium-rich manganese-based materials, elemental sulfur, sodium iron manganate, sodium iron phosphate, sodium vanadium phosphate, lithium manganese iron phosphate (LiMn2O4). x Fe 1-x One or more of the following: lithium PO4 (LMFP), lithium vanadium phosphate (Li3V2(PO4)3), lithium vanadium oxide phosphate (LiVOPO4), and lithium titanate (Li2TiO3).

[0105] In some embodiments, the negative electrode active material includes, but is not limited to, one or more of the following materials: graphite, silicon, silicon oxide, silicon carbon, lithium titanate (Li2TiO3), hard carbon, soft carbon, tin oxide, and titanium dioxide.

[0106] In some embodiments, the mass of the solid active material in step S10 accounts for 20% to 98.9% of the total mass of the electrode film material, including but not limited to 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 98.9%.

[0107] In some embodiments, the solid binder in step S10 includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile rubber (NBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), sodium alginate (SA), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyoxymethylene (POM), polyamide (PA), other polyolefins and their copolymers, polysulfone, and polyphenylene ether (PPO). Further, the solid binder is polyvinylidene fluoride (PVDF) and / or polytetrafluoroethylene (PTFE).

[0108] In some embodiments, the mass of the solid binder in step S10 accounts for 0.1% to 30% of the total mass of the electrode film material, including but not limited to 0.1%, 5%, 10%, 15%, 20%, 25%, and 30%.

[0109] In some embodiments, the solid functional additives in step S10 include, but are not limited to, one or more of conductive agents, solid electrolyte materials, lithium supplements, catalysts, and ionic conductivity enhancers.

[0110] In some embodiments, the conductive agent includes, but is not limited to, one or more of the following materials: carbon black, acetylene black, carbon nanotubes, carbon fibers, conductive graphite, graphene, conductive metal carbides, conductive metal nitrides, metal particles, and conductive polymers.

[0111] In some embodiments, the mass of the solid functional additive in step S10 accounts for 1% to 50% of the total mass of the electrode film material, including but not limited to 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%.

[0112] In some embodiments, the stirring device in step S11 may be a conventional stirring device known in the art, and is not particularly limited herein.

[0113] In some embodiments, the stirring speed of the mixture in step S11 is 10 rpm to 600 rpm, including but not limited to 10 rpm, 50 rpm, 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, and 600 rpm. Preferably, it is 100 rpm to 500 rpm.

[0114] In some embodiments, the thickness of the electrode film obtained in step S13 is 10 μm to 200 μm, including but not limited to 10 μm, 30 μm, 50 μm, 70 μm, 90 μm, 120 μm, 150 μm, 180 μm, and 200 μm. Preferably, the thickness of the electrode film is 40 μm to 140 μm.

[0115] In some embodiments, the dry-process battery membrane is a solid electrolyte membrane, and the method for preparing the solid electrolyte membrane includes the following steps:

[0116] S20. Weigh the materials according to the mass ratio of solid electrolyte material, solid binder and solid functional additive (20-98.9):(0.1-30):(1-80);

[0117] S21. Add the weighed material from step S20 to the mixing equipment and stir to disperse the solid binder in the material and prepare a mixture;

[0118] S22. The mixture is rolled and formed by several rollers in a roller press with a roller gap of 0.4 mm to 2.5 mm to prepare a preform film;

[0119] S23. The embryo membrane is thinned by rolling in stages to prepare a solid electrolyte membrane.

[0120] In some embodiments, the solid electrolyte material in step S20 includes, but is not limited to, one or more of lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), lithium phosphorus oxynitrogen (LIPON), silicon phosphorus sulfide (LSPS), lithium sulfide phosphate (Li7P3S11), lithium-doped polyethylene oxide (PEO), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA).

[0121] In some embodiments, the mass of the solid electrolyte material in step S20 accounts for 20% to 98.9% of the total mass of the solid electrolyte membrane material, including but not limited to 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 98.9%.

[0122] In some embodiments, the solid binder in step S20 is the same as the solid binder in step S10, including but not limited to one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile rubber (NBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), sodium alginate (SA), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyoxymethylene (POM), polyamide (PA), other polyolefins and their copolymers, polysulfone, and polyphenylene ether (PPO). Further, the solid binder is polyvinylidene fluoride (PVDF) and / or polytetrafluoroethylene (PTFE).

[0123] In some embodiments, the mass of the solid binder in step S20 accounts for 0.1% to 30% of the total mass of the solid electrolyte membrane material, including but not limited to 0.1%, 5%, 10%, 15%, 20%, 25%, and 30%.

[0124] In some embodiments, the solid functional additive in step S20 is a substance capable of increasing ionic conductivity, including but not limited to one or more of alumina, silicon dioxide, montmorillonite, boron nitride, and carbon nitride.

[0125] In some embodiments, the mass of the solid functional additive in step S20 accounts for 1% to 90% of the total mass of the solid electrolyte membrane material, including but not limited to 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, and 90%.

[0126] In some embodiments, the stirring speed of the mixture in step S21 is 10 rpm to 600 rpm, including but not limited to 10 rpm, 50 rpm, 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, and 600 rpm. Preferably, it is 100 rpm to 500 rpm.

[0127] It is understandable that, since the shear force on the mixture is small during the low-speed stirring process before steps S12 and S22, the degree of fiberization of the binder is low. Therefore, the mixture may be entirely unformed powder or a mixture of unformed powder and discontinuous flakes after one rolling.

[0128] In some embodiments, in steps S12 and S22, the mixture is first subjected to a first-round roll forming to obtain a continuous film. Specifically, the first-round roll forming includes the following steps:

[0129] Step 1: Roll the mixture once or multiple times to obtain several sheets and powders;

[0130] Step 2: Join several pieces of material end to end, and cover the joint with powder to obtain a composite material;

[0131] Step 3: Perform a single roll forming on the composite material described in Step 2 to obtain larger sheet material and residual powder material;

[0132] Step 4: Repeat steps 2-3 until there is no powder after roll forming, and a continuous film is obtained.

[0133] The continuous film is then subjected to a second round of roll forming, including the following steps:

[0134] Step 1: Fold the continuous film obtained from the first rolling press, or laminate two continuous films obtained from the first rolling press together and roll them again to form a laminated film;

[0135] Step 2: Fold the laminated film, or laminate two laminated films together and roll them together again;

[0136] Step 3: Repeat step 2 until the tensile strength of the resulting pressed film meets the preset conditions, which is the embryo film;

[0137] In some implementations, step 2 is repeated in step 3 until the tensile strength of the resulting pressed film is ≥2MPa, which is then considered the preform film. Currently, battery films can only be judged based on experience or the quality of the film after formation (appearance, bending flexibility, etc.). This judgment method is highly subjective, leading to large errors, low efficiency, and difficulty in correcting mistakes, resulting in low yield and other problems, which is not conducive to mass production development. By detecting the tensile strength of the preform film, the quality of the final film can be controlled, improving the yield of battery films and the consistency of battery film formation.

[0138] In some implementations, according to Figure 1 The method shown is to splice several pieces 2 end to end. After splicing, powder 1 is applied to the pieces 2 and the joint 3 between any two pieces 2.

[0139] In some implementations, according to Figure 2 The continuous membrane 4 and the press-fit membrane are folded 180° as shown.

[0140] In some implementations, according to Figure 3The two continuous films 4 or two laminated films are bonded together in the manner shown.

[0141] Understandably, the continuous film 4 is prone to breakage at the fold after folding, requiring several roll forming processes. Specifically, the continuous film 4 is folded or two prepared continuous films are bonded together and rolled once to obtain a laminated film. The laminated film is then folded and rolled once more until it can withstand a 180° bend without breaking. The tensile strength of the laminated film is then tested. If the tensile strength of the laminated film is less than 2 MPa, the laminated film is folded, rolled, and pressed again until the tensile strength of the laminated film is ≥2 MPa, thus obtaining a thicker preform film.

[0142] In some embodiments, after the mixture is rolled once, the output is all unformed powder. At this time, the powder is rolled again until the output is a mixture of unformed powder and discontinuous flakes. Then, steps 2-4 in the first round of rolling forming and the second round of rolling forming are performed to obtain a preform film.

[0143] The dry-process battery film preparation method in this application addresses the shortcomings of traditional processes that rely solely on experience to judge the degree of binder stringing, lacking reliable evaluation methods and easily leading to inconsistencies in film batches. By performing 180° bending and tensile strength tests on the preform film, the quality of the preform film can be effectively evaluated, thereby ensuring the consistency of film batches.

[0144] In some embodiments, the roller gap of one or more roller presses used for repeatedly rolling the mixture in steps S12 and S22 is large and consistent. Specifically, the roller gap can be 0.4mm to 2.5mm, including but not limited to 0.4mm, 0.5mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2.0mm, 2.2mm, and 2.4mm. It is understood that an appropriate roller gap is selected based on the particle size of the solid active material; when the particle size of the solid active material is large, a larger roller gap is selected.

[0145] The dry-process battery film preparation method of this application maintains a relatively large roller gap of 0.4mm to 2.5mm in the roller pressing equipment for forming the mixture by several rollers, and keeps the roller gap consistent during the several roller pressing process. This effectively avoids the extrusion pressure from the extrusion damage to the solid active material during the roller pressing process. At the same time, the solid binder stretches more uniformly when roller pressing under a larger roller gap, resulting in a preform film with better softness.

[0146] In some embodiments, the rolling equipment used for forming several rollers in steps S12 and S22 is a rolling equipment with pairs of rollers, which can be a horizontal roller press, a vertical roller press, or a roller press with steel strip.

[0147] In some embodiments, the rolling temperature during the first round of rolling forming in steps S12 and S22 is 20°C to 150°C, including but not limited to 20°C, 25°C, 50°C, 80°C, 100°C, 120°C, 130°C, 140°C, and 150°C. At lower temperatures, such as 25°C, the number of rolling passes should be greater than at 50°C, preferably 70°C to 150°C.

[0148] In some embodiments, the rolling temperature during the second round of rolling forming in steps S12 and S22 is 20°C to 150°C, including but not limited to 20°C, 25°C, 50°C, 70°C, 80°C, 100°C, 120°C, 130°C, 140°C, and 150°C. At lower temperatures, such as 25°C, the number of rolling passes should be greater than at 50°C, preferably 70°C to 150°C.

[0149] In some embodiments, the pressure during the rolling process in steps S12 and S22 is below 80t, including but not limited to 5t, 10t, 15t, 20t, 25t, 30t, 35t, 40t, 45t, 50t, 55t, 65t, 70t, 75t, and 80t. Preferably, it is between 20t and 80t. In some embodiments, the rolling temperature in steps S13 and S23 is between 20℃ and 150℃, including but not limited to 20℃, 25℃, 50℃, 70℃, 80℃, 100℃, 120℃, 130℃, 140℃, and 150℃. At lower temperatures, for example, at 25℃, the number of repeated rolling cycles is greater than at 50℃; preferably, it is between 70℃ and 150℃.

[0150] In some embodiments, the thickness of the solid electrolyte membrane obtained in step S23 is 10 μm to 200 μm, including but not limited to 10 μm, 30 μm, 50 μm, 70 μm, 90 μm, 120 μm, 150 μm, 180 μm, and 200 μm. Preferably, it is 20 μm to 100 μm.

[0151] The dry-process battery film preparation method of this application only requires uniform mixing of materials before rolling, and has low requirements for the degree of fiberization of the binder before rolling, which reduces the process requirements of the mixing equipment and lowers the initial investment cost of industrial production; at the same time, it effectively avoids the damage to the surface or bulk phase of active materials or solid electrolyte materials by high shear force during the fiberization process.

[0152] The dry-process battery film preparation method of this application adds several roller pressing and kneading processes within a larger roller gap range to the traditional dry pressing technology. It eliminates the need for continuous film formation in the first roller pressing, greatly reducing the requirements for the output of the mixture. The mixture only needs to have a certain degree of adhesion. The discontinuous film obtained after the first roller pressing is spliced ​​and pressed through several roller pressing processes in a roller pressing device with a larger roller gap. This causes the binder in the mixture to be squeezed and moved during the roller pressing process, fully forming a filament network, and finally obtaining a preform film with both good strength and flexibility. The preparation process is simple, widely adaptable, and suitable for industrial applications.

[0153] In a second aspect, this application provides a dry-process battery membrane, which is prepared according to the preparation method provided in the first aspect above. The dry-process battery membrane is a positive electrode membrane, a negative electrode membrane, or a solid electrolyte membrane.

[0154] In some implementations, the positive electrode film and the negative electrode film can be used separately as self-supporting electrode films in the battery.

[0155] A third aspect of this application provides an electrode comprising a current collector and the dry cell film provided in the second aspect above.

[0156] In some embodiments, the electrode includes a current collector and the positive electrode film or negative electrode film provided in the second aspect above.

[0157] In some embodiments, an electrode sheet is prepared by hot rolling a positive electrode film or a negative electrode film onto a current collector having an adhesive layer at a rolling temperature of 50°C to 250°C.

[0158] In some implementations, the current collector can be a positive current collector and / or a negative current collector.

[0159] In some implementations, the positive current collector may be a metal foil or a composite current collector.

[0160] In some implementations, the metal foil used for the positive current collector can be aluminum foil.

[0161] In some implementations, the negative electrode current collector may be a metal foil or a composite current collector.

[0162] In some implementations, the metal foil used for the negative electrode current collector can be copper foil.

[0163] In some embodiments, the composite current collector includes a polymer substrate and a metal layer formed on at least one surface of the polymer substrate.

[0164] In a fourth aspect, this application provides a battery comprising the dry cell membrane provided in the second aspect or the electrode provided in the third aspect.

[0165] In some embodiments, the battery is a solid-state lithium-ion battery, which includes a positive electrode membrane, a negative electrode membrane, and a solid electrolyte membrane.

[0166] In some embodiments, the battery is a liquid lithium-ion battery, which includes a positive electrode membrane, a negative electrode membrane, and an electrolyte.

[0167] The implementation scheme of this application will be described in detail below with reference to specific embodiments.

[0168] Example 1.

[0169] A method for preparing a positive electrode film specifically includes the following steps:

[0170] Material composition: Solid active material LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 (NCM), conductive carbon black (a solid functional additive), and polytetrafluoroethylene (PTFE) (a solid binder) is 90:5:5.

[0171] Preparation of the mixture: Weigh 4.5 kg of high-nickel ternary lithium-ion battery positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM) and 0.25 kg of conductive carbon black were premixed and stirred for 10 min, and then 0.25 kg of polytetrafluoroethylene was added and stirred thoroughly at a stirring speed of 400 rpm for 0.5 h to obtain the mixture.

[0172] Preparation of embryonic membranes:

[0173] The mixture is subjected to the first round of roll forming. (1) The mixture is subjected to horizontal roll forming once using a steel belt roller press to obtain several sheets and powders. The roller gap of the roller press is 1000μm, the roll pressing temperature is 130℃, the roll pressing pressure is 40t, and the roll pressing speed is 2m / min. The length of the sheet is less than 10cm, the width is less than 80% of the width of the roller, the strength is low, and it will break when bent at 180°. (2) Several sheets are spliced ​​end to end, and powders are covered on the sheets and the seams of the sheets to obtain a composite material placed on the steel belt of the steel belt roller press. (3) The composite material is subjected to horizontal roll forming once. After roll forming, several sheets with larger area and longer length and a small amount of unformed powders are obtained. The length and width of the sheets are larger than the length and width of the sheets in step (1). Repeat the above steps (2)-(3) 5 times to form a continuous film.

[0174] The continuous film is subjected to a second round of roll forming. (1) The continuous film is folded once (the bending point cracks) and then horizontally rolled to obtain a pressed film. (2) The pressed film is folded again and horizontally rolled to obtain a pressed film. (3) After repeating step (2) 4 times, the pressed film is bent at 180° without cracking and the tensile strength is ≥2MPa. At this time, the preform film is obtained.

[0175] Preparation of the positive electrode film: The preform film is gradually thinned by decreasing the roll gap by 200 μm each time, that is, the preform film is rolled thinned by roll gaps of 800 μm, 600 μm, 400 μm and 200 μm. Finally, the roll gap is adjusted to 150 μm for finished product rolling. The rolling temperature during the preparation process is 130℃ and the rolling pressure is 40t to obtain the positive electrode film.

[0176] The thickness of the positive electrode film prepared in this embodiment is 133 μm.

[0177] The external morphology of the positive electrode film is shown in the figure below. Figure 4 As shown, the positive electrode film prepared by the method of this embodiment has a smooth surface and no cracks after being bent 180°. The cross-section of the positive electrode film prepared by the method of this embodiment was observed under a scanning electron microscope (SEM), and the results are as follows. Figure 5 The cross-sectional microstructure diagram shown is from... Figure 5 It can be seen that the solid binder is fully drawn into fibers, there are no cracks inside the electrode film, the particle size of the positive electrode active material remains unchanged before and after preparation, and the positive electrode active material is not crushed.

[0178] Example 2.

[0179] The difference between this embodiment and Embodiment 1 lies in the different mass proportions of solid active materials, solid binders, and solid functional additives in the mixture. Specifically, it includes the following steps:

[0180] Material composition: Solid active material LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 (NCM), conductive carbon black (a solid functional additive), and polytetrafluoroethylene (PTFE) (a solid binder) is 92:5:3.

[0181] Preparation of the mixture: Weigh 4.6 kg of high-nickel ternary lithium-ion battery positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM) and 2.5 kg of conductive carbon black were premixed and stirred for 10 min, and then 1.5 kg of polytetrafluoroethylene was added and stirred thoroughly at a stirring speed of 450 rpm for 0.5 h to obtain the mixture.

[0182] Preparation of embryonic membranes:

[0183] The mixture is subjected to the first round of roll forming. (1) The mixture is subjected to horizontal roll forming once using a steel belt roller press to obtain several sheets and powders. The roller gap of the roller press is 1000μm, the roll temperature is 130℃, the roll pressure is 40t, and the roll speed is 2m / min. The length of the sheet is less than 10cm, the width is less than 80% of the width of the roller, the strength is low, and it is prone to breakage when bent at 180°. (2) Several sheets are spliced ​​end to end, and powder is covered on the sheets and the seams of the sheets to obtain a composite material, which is placed on the steel belt of the steel belt roller press. (3) The composite material is subjected to horizontal roll forming once. After roll forming, several sheets with longer lengths and a small amount of unformed powder are obtained. After repeating the above steps (2)-(3) 7 times, a continuous film is formed.

[0184] The continuous film is subjected to a second round of roll forming. (1) The continuous film is folded once (the bending point cracks) and then horizontally rolled to obtain a pressed film. (2) The pressed film is folded again and horizontally rolled to obtain a pressed film. (3) After repeating step (2) 4 times, the pressed film is bent at 180° without cracking and the tensile strength is ≥2MPa. At this time, the preform film is obtained.

[0185] Preparation of the positive electrode film: The preform film is gradually thinned by decreasing the roll gap by 200 μm each time, that is, the preform film is rolled thinned by roll gaps of 800 μm, 600 μm, 400 μm and 200 μm. Finally, the roll gap is adjusted to 150 μm for finished product rolling. The rolling temperature during the preparation process is 130℃ and the rolling pressure is 40t to obtain the positive electrode film.

[0186] The thickness of the positive electrode film prepared in this embodiment is 138 μm.

[0187] Example 3

[0188] Material composition: The mass ratio of solid active material elemental sulfur powder, solid functional additive conductive carbon fiber, solid functional additive catalyst molybdenum disulfide, and solid binder polytetrafluoroethylene is 50:40:5:5.

[0189] Preparation of the mixture: Weigh 5 kg of elemental sulfur powder and 4 kg of VGCF (vapor-generated carbon fiber) and premix for 10 min. Then add 0.5 kg of molybdenum disulfide and 0.5 kg of polytetrafluoroethylene and stir thoroughly at a stirring speed of 350 rpm for 0.5 h to obtain the mixture.

[0190] Preparation of embryonic membranes:

[0191] The mixture is subjected to the first round of roll forming. (1) The mixture is subjected to horizontal roll forming once using a roller press to obtain several sheets and powders. The roller gap of the roller press is 1000μm, the roll pressing temperature is 60℃, the roll pressing pressure is 40t, and the roll pressing speed is 1m / min. The length of the sheet is less than 10cm, the width is less than 80% of the width of the roller, the strength is low, and it is prone to breakage when bent at 180°. (2) Several sheets are spliced ​​end to end, and powder is covered on the sheets and the seams of the sheets. The sheets are manually pressed together to obtain a composite material. (3) The composite material is subjected to horizontal roll forming once. After roll forming, several sheets with longer lengths and a small amount of unformed powders are obtained. After repeating the above steps (2)-(3) 6 times, a continuous film is formed.

[0192] The continuous film is subjected to a second round of roll forming. (1) The two continuous films obtained from the first round of roll forming are laminated together and subjected to a horizontal roll forming to obtain a pressed film. (2) The two pressed films are laminated together and subjected to a horizontal roll forming to obtain a further pressed pressed film. (3) After repeating step (2) 3 times, the pressed film does not crack after being bent at 180° and the tensile strength of the pressed film is ≥2MPa. At this time, the preform film is obtained.

[0193] Preparation of the positive electrode film: The preform film is gradually thinned by decreasing the roll gap by 200 μm each time, that is, the preform film is rolled thinned by roll gaps of 800 μm, 600 μm, 400 μm and 200 μm. Finally, the roll gap is adjusted to 150 μm for finished product rolling. The rolling temperature during the preparation process is 60℃ and the rolling pressure is 40t to obtain the positive electrode film.

[0194] The thickness of the positive electrode film prepared in this embodiment is 128 μm.

[0195] Example 4.

[0196] A method for preparing a negative electrode film specifically includes the following steps:

[0197] Material composition: The mass ratio of solid active material graphite negative electrode active material, solid functional additive conductive carbon black and solid binder polytetrafluoroethylene is 96:2:2.

[0198] Preparation of the mixture: Weigh 4.8 kg of graphite negative electrode active material, 0.1 kg of conductive carbon black and 0.1 kg of polytetrafluoroethylene and add them to a mixer for stirring and premixing. The stirring speed is 600 rpm and the stirring time is 0.5 h to obtain the mixture.

[0199] Preparation of embryonic membranes:

[0200] The mixture is subjected to the first round of roll forming. (1) The mixture is subjected to vertical roll forming once using a roller press to obtain several sheets and powders. The roller gap of the roller press is 500μm, the roll pressing temperature is 100℃, the roll pressing pressure is 5t, and the roll pressing speed is 1m / min. The length of the sheet is less than 10cm, the width is less than 80% of the width of the roller, the strength is low, and it is prone to breakage when bent at 180°. (2) Several sheets are spliced ​​end to end, and powder is covered on the sheets and the seams of the sheets and pressed together to obtain a composite material. (3) The composite material is subjected to vertical roll forming once. After roll forming, several sheets with longer lengths and a small amount of unformed powder are obtained. After repeating the above steps (2)-(3) 5 times, a continuous film is formed.

[0201] The continuous film is subjected to a second round of roll forming. (1) The two continuous films obtained from the first round of roll forming are laminated together and subjected to a horizontal roll forming to obtain a pressed film. (2) The two pressed films are laminated together and subjected to a horizontal roll forming to obtain a further pressed pressed film. (3) After repeating step (2) 3 times, the pressed film does not crack after being bent at 180° and the tensile strength of the pressed film is ≥2MPa. At this time, the preform film is obtained.

[0202] Preparation of negative electrode film: The preform film is gradually thinned by decreasing the roll gap by 100 μm each time, that is, the preform film is rolled thinned by roll gap of 400 μm, 300 μm, 200 μm and 150 μm. Finally, the roll gap is adjusted to 120 μm for finished product rolling. The rolling temperature is 100℃ and the rolling pressure is 5t during the preparation process to obtain the negative electrode film.

[0203] The thickness of the negative electrode film prepared in this embodiment is 112 μm.

[0204] See Figure 6 , Figure 6 This is an image showing the morphology of the negative electrode film prepared in this embodiment; the surface is smooth and free of cracks. (See also...) Figure 7-8 , Figure 7-8 This is a cross-sectional microstructure image of the negative electrode film prepared in this embodiment. Figure 7 Magnified 1000 times, Figure 8 Magnified 2000 times, the image shows that the solid binder is fully drawn into fibers and there are no cracks inside the electrode film. The sheet-like material in the image is the negative electrode active material. The particle size distribution of the active material in the negative electrode film is similar to that of the original material, indicating that the preparation process effectively reduced the damage to the active material.

[0205] Example 5.

[0206] A method for preparing a solid electrolyte membrane specifically includes the following steps:

[0207] Material composition: The mass ratio of solid active material lithium titanium aluminum phosphate, solid functional additive montmorillonite, and solid binder (the solid binder is a mixture of polyvinylidene fluoride and polytetrafluoroethylene) is 20:10:20, of which polyvinylidene fluoride and polytetrafluoroethylene each account for 50% of the total mass of the solid binder.

[0208] Preparation of the mixture: Weigh 200g of lithium titanium aluminum phosphate, 100g of montmorillonite, 100g of polyvinylidene fluoride, and 100g of polytetrafluoroethylene and add them to a ball mill for ball milling and mixing. The ball milling speed is 400 rpm and the ball milling time is 1 hour to obtain the mixture.

[0209] Preparation of embryonic membranes:

[0210] The mixture is subjected to the first round of roll forming. (1) The mixture is subjected to horizontal roll forming once using a steel belt roller press to obtain several sheets and powders. The roller gap of the roller press is 900μm, the roll temperature is 150℃, the roll pressure is 60t, and the roll speed is 5m / min. (2) Several sheets are spliced ​​end to end, and powders are covered on the sheets and the joints of the sheets to obtain composite material, which is placed on the steel belt of the steel belt roller press. (3) The composite material is subjected to horizontal roll forming once. After roll forming, several sheets with longer lengths and a small amount of unformed powders are obtained. After repeating the above steps (2)-(3) 5 times, a continuous film is formed.

[0211] The continuous film is subjected to a second round of roll forming. (1) The two continuous films obtained from the first round of roll forming are laminated together and subjected to a horizontal roll forming to obtain a pressed film. (2) The two pressed films are laminated together and subjected to a horizontal roll forming to obtain a further pressed pressed film. (3) After repeating step (2) 3 times, the pressed film does not crack after being bent at 180° and the tensile strength of the pressed film is ≥2MPa. At this time, the preform film is obtained.

[0212] Preparation of solid electrolyte membrane: The preform film was gradually thinned by rolling with roll gaps of 800μm, 600μm, 400μm, 200μm, 100μm and 50μm. The rolling temperature was 125℃ and the rolling pressure was 60t to obtain solid electrolyte membrane.

[0213] The thickness of the solid electrolyte membrane prepared in this embodiment is 41 μm.

[0214] Example 6

[0215] Material composition: The mass ratio of solid active material lithium indium chloride, solid functional additive graphite phase carbon nitride, and solid binder polytetrafluoroethylene is 90:2:8.

[0216] Preparation of the mixture: Weigh 18g of lithium indium chloride, 0.4g of graphitic carbon nitride, and 1.6g of polytetrafluoroethylene and add them to a ball mill for ball milling and mixing. Use a vacuum ball mill jar, rotate at 400 rpm, and ball mill for 1 hour to obtain the mixture.

[0217] Preparation of embryonic membranes:

[0218] The mixture is subjected to the first round of roller pressing and composite roller pressing. (1) The mixture is subjected to horizontal roller pressing and composite roller pressing once using a roller press to obtain several sheets and powders. The roller gap of the roller press is 900μm, the roller pressing temperature is 150℃, the roller pressing pressure is 55t, and the roller pressing speed is 5m / min. (2) Several sheets are spliced ​​end to end, and powders are covered on the sheets and the seams of the sheets and pressed together. After pressing, a composite material is obtained. (3) The composite material is subjected to horizontal roller pressing once. After roller pressing, several sheets with longer lengths and a small amount of unformed powders are obtained. Repeat the above steps (2)-(3) 5 times to form a continuous film.

[0219] The continuous film is subjected to a second round of roll forming. (1) The two continuous films obtained from the first round of roll forming are laminated together and subjected to a horizontal roll forming to obtain a pressed film. (2) The two pressed films are laminated together and subjected to a horizontal roll forming to obtain a further pressed pressed film. (3) After repeating step (2) twice, the pressed film does not crack after being bent at 180° and the tensile strength of the pressed film is ≥2MPa. At this time, the preform film is obtained.

[0220] Preparation of solid electrolyte membrane: The preform film was gradually thinned by rolling with roll gaps of 800μm, 600μm, 400μm, 200μm, 100μm and 50μm. The rolling temperature was 135℃ and the rolling pressure was 55t to obtain solid electrolyte membrane.

[0221] The thickness of the solid electrolyte membrane prepared in this embodiment is 35 μm.

[0222] Comparative Example 1.

[0223] The main difference between this comparative example and Example 1 is that a high-speed shearing machine was used in this comparative example to fully fiberize the material. The specific process is as follows:

[0224] Material composition: Solid active material LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 (NCM), conductive carbon black (a solid functional additive), and polytetrafluoroethylene (PTFE) (a solid binder) is 90:5:5.

[0225] Weigh out 4.5 kg of high-nickel ternary lithium-ion battery positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1O2 (NCM) and 0.25 kg of conductive carbon black were premixed and stirred for 10 min, and then 0.25 kg of polytetrafluoroethylene was added and stirred thoroughly at a stirring speed of 450 rpm for 0.5 h to obtain the mixture.

[0226] The mixture was added to a high-speed shear mill and mixed for 0.5 hours at a speed of 30,000 rpm to obtain a fluffy, cotton-like fibrous mixture.

[0227] The fibrous mixture was rolled into a preform using a double-roll mill. The roll gap of the double-roll mill was 1000 μm, the rolling temperature was 130℃, and the rolling pressure was 40t. The preform was rolled thinned stepwise by rolling with a roll gap of 200 μm each time, i.e., 800 μm, 600 μm, 400 μm, 200 μm, and 150 μm. Finally, the roll gap was adjusted to 150 μm for the final rolling. The rolling temperature during the preparation process was 130℃ and the rolling pressure was 40t, which produced the positive electrode film.

[0228] The thickness of the positive electrode film prepared in this comparative example is 138 μm.

[0229] See Figure 9 , Figure 9 This is a cross-sectional microstructure of the positive electrode film prepared in this comparative example when it is thinned to a thickness of 250 μm. The image shows that there are cracks inside the positive electrode film and the solid binder is drawn into messy strands.

[0230] Comparative Example 2.

[0231] The main difference between this comparative example and Example 4 is that the material in this comparative example was fully fiberized using an air jet mill. The specific process is as follows:

[0232] Material composition: The mass ratio of solid active material graphite negative electrode active material, solid functional additive conductive carbon black and solid binder polytetrafluoroethylene is 96:2:2.

[0233] Weigh 4.8 kg of graphite anode active material, 0.1 kg of conductive carbon black, and 0.1 kg of polytetrafluoroethylene and add them to a mixer for stirring and premixing at a speed of 1200 rpm for 0.5 h. Then add it to an air jet mill for thorough mixing and fiberization at a crushing pressure of 0.85 MPa, a feeding pressure of 0.95 MPa, and a fiberization time of 1.5 h to obtain a fluffy fiberized mixture.

[0234] The fibrous mixture was rolled into a preform using a double-roll mill. The roll gap of the double-roll mill was 500 μm, the rolling temperature was 100℃, and the rolling pressure was 5t. The preform was gradually thinned by rolling with a roll gap of 400 μm, 300 μm, 200 μm, and 150 μm. Finally, the roll gap was adjusted to 135 μm for the final rolling. The rolling temperature during the preparation process was 100℃ and the rolling pressure was 5t, resulting in a negative electrode film.

[0235] The thickness of the negative electrode film prepared in this comparative example is 115 μm.

[0236] Comparative Example 3.

[0237] The main difference between this comparative example and Example 5 is that this comparative example uses a ball mill to perform high-speed stirring of the material to achieve thorough fiberization. The specific process is as follows:

[0238] Material composition: The solid active material lithium titanium aluminum phosphate, the solid functional additive montmorillonite, and the solid binders polyvinylidene fluoride and polytetrafluoroethylene are in a mass ratio of 20:10:20, of which polyvinylidene fluoride and polytetrafluoroethylene each account for 50% of the total mass of the solid binder.

[0239] Weigh 200g of lithium titanium aluminum phosphate, 100g of montmorillonite, 100g of polyvinylidene fluoride, and 100g of polytetrafluoroethylene and add them to a ball mill for high-speed mixing at 2000rpm for 2 hours to fibrose the material until it appears as sheet-like pieces, thus obtaining a fibrous mixture.

[0240] The preform film was progressively thinned by rolling with roll gaps of 800 μm, 600 μm, 400 μm, 200 μm, 100 μm, and 50 μm, at a rolling temperature of 120℃ and a rolling pressure of 50t, to obtain a solid electrolyte membrane. The thickness of the solid electrolyte membrane prepared in this comparative example was 38 μm.

[0241] Performance testing experiment

[0242] 1. Tensile strength test

[0243] Tensile strength refers to the ratio of the maximum tensile force a sample can withstand to its cross-sectional area during a tensile test. The test was conducted according to the relevant provisions of GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets" using an electronic universal testing machine. The maximum load of the testing machine did not exceed 5000 N. The test results are shown in Table 1 below.

[0244] 2. Diaphragm thickness test

[0245] The test was conducted in accordance with the relevant provisions of GB / T 6672-2001 "Mechanical Measurement Method for Determination of Thickness of Plastic Films and Sheets", and the test results are shown in Table 1 below.

[0246] 3.180° bending test

[0247] The test results are shown in Table 1 below.

[0248] 4. Reversible specific capacity (mAh / g) and first coulombic efficiency tests were performed on the lithium metal half-cell.

[0249] Half-cells were prepared by using the positive electrode films obtained in Examples 1-3 and Comparative Example 1 according to conventional methods.

[0250] The negative electrode films obtained in Example 4 and Comparative Example 2 were used to prepare half-cells using conventional methods.

[0251] The test results are shown in Table 1 below.

[0252] Table 1.

[0253]

[0254]

[0255] Performance test results show that, as can be seen from the data in Table 1, the reversible specific capacity and initial coulombic efficiency of the lithium-ion half-cell assembled using the positive electrode films obtained in Examples 1-3 are both higher than those of Comparative Example 1; the reversible specific capacity and initial coulombic efficiency of the lithium-ion half-cell assembled using the negative electrode film obtained in Example 4 are both higher than those of Comparative Example 2. The experimental results show that the dry-process battery film prepared by rolling the mixture with several rollers in a wide-gap roller press as described in this application has excellent electrochemical performance when applied to the field of lithium-ion batteries.

[0256] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0257] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a dry-process battery film, characterized in that, Includes the following steps: A dry powder mixture is prepared by mixing solid active materials, solid binders, and solid functional additives. The dry powder mixture is subjected to several roller pressings in a roller pressing device with a roller gap of 0.4mm to 2.5mm to prepare a preform film. In this process, the solid binder is squeezed, moved, and fibrous networked. The embryo membrane is thinned to prepare a dry-process battery film; The solid active material is a positive electrode active material, a negative electrode active material, or a solid electrolyte material.

2. The method for preparing a dry-process battery film according to claim 1, characterized in that, The plurality of roller pressing includes the following steps: performing a first roller pressing on the dry powder mixture to obtain a continuous film, and performing a second roller pressing on the continuous film to obtain the preform film.

3. The method for preparing a dry-process battery film according to claim 2, characterized in that, The roll gap of the rolling equipment in the plurality of roller pressing forming processes remains consistent.

4. The method for preparing a dry-process battery film according to claim 2, characterized in that, The first roller pressing process includes the following steps: Step 1: Roll the dry powder mixture once or multiple times to obtain several sheets and powders; Step 2: Join several of the sheet materials together and cover the joint with the powder to obtain the composite material. Step 3: Roll the composite material to obtain larger sheets and residual powder. Step 4: Repeat steps 2-3, roll the film until no powder remains, and obtain a continuous film.

5. The method for preparing a dry-process battery film according to claim 2, characterized in that, The second roller pressing process includes the following steps: Step 1: Fold the continuous film, or laminate two continuous films together and roll them once to obtain a laminated film; Step 2: Fold the laminated film, or laminate two laminated films together and perform a single roller pressing; Step 3: Repeat step 2 until the tensile strength of the resulting pressed film meets the preset conditions, which is the embryo film.

6. The method for preparing a dry-process battery film according to claim 5, characterized in that, In step 3, the tensile strength of the embryonic membrane is ≥2MPa.

7. The method for preparing a dry-process battery film according to any one of claims 1-6, characterized in that, Thinning the embryonic membrane includes the following steps: The embryo film is thinned by rolling several times in a rolling mill.

8. The method for preparing a dry-process battery film according to claim 7, characterized in that, The roll gap for thinning is gradually reduced through several roll pressing cycles until a dry cell film with a thickness of 10µm to 200µm is obtained.

9. The method for preparing a dry-process battery film according to any one of claims 2-6, characterized in that, The rolling temperature during each rolling process in the first roller pressing is 20℃~150℃; The rolling temperature during each rolling process in the second roll forming is 20℃~150℃; The pressure during roll forming is below 80t.

10. The method for preparing a dry-process battery film according to claim 9, characterized in that, The pressure of the roll forming is 5t, 10t, 15t, 20t, 25t, 30t, 35t, 40t, 45t, 50t, 55t, 65t, 70t, 75t or 80t.

11. The method for preparing a dry-process battery film according to claim 9, characterized in that, The roll gap of the roll forming is 0.4mm, 0.5mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2.0mm, 2.2mm or 2.4mm.

12. The method for preparing a dry-process battery film according to any one of claims 1-6, characterized in that, The mass ratio of the solid active material, solid binder and solid functional additive is (20~98.9):(0.1~30):(1~80).

13. The method for preparing a dry-process battery film according to claim 12, characterized in that, The mass ratio of the solid active material, solid binder and solid functional additive is (20~98.9):(0.1~30):(1~50).

14. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid active material is a positive electrode active material, which includes one or more of the following: lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium-rich manganese-based, elemental sulfur, sodium iron manganate, sodium iron titanate, sodium iron sulfate, sodium iron phosphate, sodium vanadium phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, and lithium titanate.

15. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid active material is a negative electrode active material, which includes one or more of the following: graphite, silicon, silicon oxide, silicon carbon, lithium titanate, hard carbon, soft carbon, tin oxide, and titanium dioxide.

16. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid active material is a solid electrolyte material, which includes inorganic solid electrolyte materials and / or polymer electrolyte materials; the inorganic solid electrolyte material includes one or more of lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium phosphorus oxy nitrogen, silicon phosphorus sulfur, and lithium sulfide; the polymer electrolyte material includes one or more of polyethylene oxide, polyacrylonitrile, and polymethyl methacrylate doped with lithium salts.

17. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid binder includes one or more of the following: polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, nitrile rubber, sodium carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, and sodium alginate.

18. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid functional additives include one or more of the following: conductive agents, solid electrolytes, lithium supplements, catalysts, and ionic conductivity enhancers.

19. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid functional additive is a conductive agent, which includes one or more of the following: carbon black, carbon nanotubes, carbon fibers, conductive graphite, graphene, conductive metal carbides, conductive metal nitrides, metal particles, and conductive polymers.

20. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid functional additive is a solid electrolyte added to the positive or negative electrode, and the solid electrolyte is an inorganic solid electrolyte material and / or a polymer electrolyte material.

21. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid functional additive is a positive electrode lithium replenisher added to the positive electrode, and the positive electrode lithium replenisher is one or more of lithium oxide, lithium nitride, lithium sulfide, lithium-rich lithium iron ore, and lithium nickel oxide.

22. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid functional additive is a catalyst added to the conversion electrode, and the catalyst is one or more of transition metal sulfides, transition metal nitrides, transition metal carbides, and heteroatom-doped carbon.

23. The method for preparing a dry-process battery film according to claim 12, characterized in that, The solid functional additive is an ionic conductivity enhancer, which includes one or more of alumina, silicon dioxide, montmorillonite, boron nitride, and carbon nitride.

24. A dry-process battery film, characterized in that, The dry cell membrane is prepared by the preparation method according to any one of claims 1 to 23.

25. An electrode sheet, characterized in that, Includes current collectors and the dry cell membrane as described in claim 24.

26. The electrode sheet according to claim 25, characterized in that, The dry cell film is combined with the current collector by hot rolling to form the electrode.

27. The electrode sheet according to claim 26, characterized in that, The rolling temperature of the hot roller is 50°C to 250°C.

28. A battery, characterized in that, Includes the dry cell film as described in claim 24 or the electrode sheet as described in any one of claims 25-27.

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