Negative electrode composite material adapted to dry electrode process, preparation method and application thereof

Abstract

The application discloses a negative electrode composite material adapting to a dry electrode process, a preparation method and application, relates to the technical field of negative electrode materials, and specifically discloses the negative electrode composite material adapting to the dry electrode process, which comprises a coating layer and an inner core with lithium storage capacity, the coating layer comprises an ion-conducting polymer and nanofibers, and the form of the negative electrode composite material is powder.In the application, on the one hand, the nanofibers have the characteristics of in-situ fiberization and can further promote the fiberization of the binder, and in the process of preparing the electrode sheet, the stability of the prepared electrode can be improved; on the other hand, the nanofibers in the surface coating layer can inhibit the volume expansion in the lithium intercalation process of the inner core, the polymer in the coating layer is beneficial to film formation on the surface of the inner core material, beneficial to reducing the decomposition of the electrolyte on the surface of the negative electrode material, and beneficial to improving the initial efficiency and cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of negative electrode material technology, and more specifically, to negative electrode composite materials adapted to dry electrode processes, their preparation methods, and their applications. Background Technology

[0002] Dry electrode technology refers to the direct fabrication of electrodes under solvent-free conditions. Leading battery and automakers are actively researching and developing dry electrode technology, positioning it as a next-generation battery technology. Dry electrode technology is expected to drive a revolution in battery manufacturing processes. Currently, the main binders used in dry electrode technology are polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), which utilize their ability to fibrousize under high temperature and pressure to bond the active materials. However, PTFE and PVDF also face challenges such as brittleness, hardness, and poor ion conductivity. Leading new energy companies are gradually increasing their investment in the research and development of dry electrode processes, equipment, and new materials.

[0003] Graphite anode materials are widely used in lithium-ion batteries. Their excellent electrochemical performance and stable structure make them one of the ideal anode materials. The layered structure of graphite provides excellent electronic conductivity and ion diffusion, allowing lithium ions to easily intercalate and deintercalate between graphite layers during charge and discharge while maintaining structural stability. Due to its chemical structure, the theoretical lithium intercalation limit of graphite as an anode material is only 372 mAh / g. Silicon anode materials differ from graphite anode materials in their lithium storage mechanism. They primarily achieve capacity enhancement through the formation of various alloy phases with lithium, via alloying reactions between silicon and lithium. The theoretical specific capacity of pure silicon materials reaches as high as 4200 mAh / g, more than 10 times that of graphite anodes. Furthermore, silicon-containing anodes such as silicon suboxide and silicon-carbon can also achieve lithium intercalation specific capacities exceeding 1600 mAh / g. However, silicon-containing anodes experience a volume expansion of over 100% after full lithium intercalation, which limits their application.

[0004] By combining graphite and silicon anodes, the lithium intercalation capacity of the material can be significantly improved. However, due to the poor conductivity and high lithium intercalation expansion of silicon anodes, a carbon nanotube dispersion must be added during the fabrication of graphite / silicon hybrid anodes. Carbon nanotubes can both bind the anode material, reducing overall volume expansion, and construct conductive pathways between anode material particles, thus improving the electrical and cycle performance of batteries based on this type of electrode. Although the addition of carbon nanotube dispersions is well-established in traditional wet electrode fabrication, this dispersion is incompatible with dry electrode binders such as PTFE / PVDF and dry electrode fabrication processes. Therefore, an anode material compatible with dry electrode fabrication processes is particularly necessary. Summary of the Invention

[0005] The purpose of this invention is to provide a negative electrode composite material, preparation method and application adapted to dry electrode process, which can make the electrode have high stability while maintaining the capacity of the negative electrode material.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a negative electrode composite material adapted to dry electrode processes, the negative electrode composite material comprising a coating layer and a core having lithium storage capacity, the coating layer comprising an ion-conducting polymer and nanofibers, and the negative electrode composite material being in the form of a powder.

[0008] In an optional embodiment, the negative electrode composite material satisfies at least one of the following characteristics:

[0009] a. The nanofibers are filamentous and coat the surface of the core;

[0010] b. The ion-conducting polymer is at least partially coated on the surface of the nanofibers;

[0011] c. The ion-conducting polymer at least partially coats the surface of the core;

[0012] d. The coating layer has fibrillation function.

[0013] In an optional embodiment, the ion-conducting polymer includes at least one of cellulose derivatives and their salts, acrylic polymers and their salts, polyacrylonitrile, and alginate.

[0014] And / or, the nanofibers include at least one of carbon nanofibers, single-walled carbon nanotubes, oligowalled carbon nanotubes, multi-walled carbon nanotubes, aramid fibers, and nanocellulose.

[0015] And / or, the core comprises carbon-active materials and / or silicon-active materials;

[0016] And / or, the carbon-active material includes at least one of natural graphite, artificial graphite, hard carbon materials, soft carbon materials, and mesophase carbon microspheres;

[0017] And / or, the silicon-active material includes at least one of elemental silicon, silicon carbide, silicon oxide, silicon-carbon composite material, silicon-nitrogen composite material, and silicon alloy.

[0018] In an optional embodiment, the polymer monomer of the acrylic polymer includes a first monomer and an optional second monomer, wherein the first monomer is an acrylic monomer and the second monomer is at least one of a cyano monomer, an amide monomer, an aromatic ethylene monomer, an ester monomer, and a hydroxy monomer;

[0019] And / or, the polymer monomers of the acrylic polymers all include a first monomer and a second monomer, wherein the mass fraction of the first monomer is 10%-90% and the mass fraction of the second monomer is 10%-90%.

[0020] In an optional embodiment, the mass ratio of the coating layer to the core is 0.01%-10%;

[0021] And / or, in the coating layer, the mass fraction of nanofibers is 1%-70%, and the mass fraction of the ion-conducting polymer is 30%-99%.

[0022] In an optional embodiment, the negative electrode composite material satisfies at least one of the following characteristics:

[0023] a. The lithium intercalation capacity of the negative electrode composite material is 320mAh / g-2500mAh / g;

[0024] b. The initial coulombic efficiency of the negative electrode composite material is 90%-98%;

[0025] c. The particle size distribution concentration (SPAN) of the negative electrode composite material is between 0.8 and 3.0, where SPAN = (D90 - D10) / D50;

[0026] d. The specific surface area of ​​the negative electrode composite material is 0.3 m². 2 / g-10m 2 / g;

[0027] e. The D50 of the negative electrode composite material is 5μm-24μm.

[0028] In a second aspect, the present invention provides a method for preparing a negative electrode composite material adapted to the dry electrode process described in the foregoing embodiments, comprising: mixing a core material with a dispersion containing the ion-conducting polymer, conductive nanofibers and a solvent, and then coating it with an ALD-like coating to obtain the negative electrode composite material adapted to the dry electrode process.

[0029] Preferably, the method for coating ALD-like particles includes at least one of rotary flash drying, centrifugal spray drying, and two-fluid spray drying;

[0030] More preferably, the temperature of the ALD-like coating is 100℃-400℃.

[0031] In an optional embodiment, the dispersion is further prepared by dispersing the ion-conducting polymer and nanofibers in a solvent under at least one of high shear, high-speed oscillation and high pressure conditions to obtain the dispersion.

[0032] Preferably, high pressure is achieved through homogenization, with a homogenization pressure of 10 MPa-250 MPa;

[0033] High shear is achieved through stirring, with a shear linear velocity of 5m / s-40m / s;

[0034] High-speed oscillation is achieved through ultrasound, with an ultrasound frequency of 20kHz to 110kHz.

[0035] Preferably, the ion-conducting polymer and nanofibers are pre-dispersed under high shear and / or high-speed oscillation conditions to obtain a pre-dispersion liquid, and the pre-dispersion liquid is homogenized under high pressure to obtain the dispersion liquid.

[0036] Thirdly, the present invention provides an electrode film comprising a negative electrode composite material adapted to dry electrode processes as described in any of the foregoing embodiments.

[0037] In an optional embodiment, the electrode film further includes a conductive agent and / or a binder;

[0038] The conductive agent includes at least one of carbon black, conductive graphite, Super P, microcrystalline graphite, Ketjen black, and carbon nanotubes.

[0039] The adhesive includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, copolymers of polyvinylidene fluoride and hexafluoropropylene, ultra-high molecular weight polyethylene, perfluoro(alkyl vinyl) ethers, acrylic polymers, acrylate polymers, carboxymethyl cellulose and its salts, nanocellulose, polyurethane, polyamide-imide and polyimide.

[0040] Preferably, the electrode film is a self-supporting film.

[0041] Fourthly, the present invention provides an electrode comprising a current collector and an electrode film disposed on at least one side surface of the current collector as described in any of the foregoing embodiments.

[0042] Preferably, the electrode is obtained by a dry process.

[0043] In an optional embodiment, the method includes: dry mixing the raw materials used for the electrode film to obtain a dry powder, fiberizing and shaping the dry powder in situ, and then extruding it onto the surface of the current collector to obtain the electrode;

[0044] Preferably, the dry powder comprises more than 85% by mass of the negative electrode composite material adapted to the dry electrode process, less than 10% by mass of binder, and less than 5% by mass of conductive agent.

[0045] Fifthly, the present invention provides an electrochemical energy storage device, including the electrodes described in the foregoing embodiments;

[0046] Preferably, the electrode is a negative electrode;

[0047] Preferably, the electrochemical energy storage device includes any one of lithium-ion batteries, sodium-ion batteries, supercapacitors, and solid-state batteries.

[0048] The present invention has the following beneficial effects:

[0049] In the negative electrode composite material coating layer adapted to dry electrode processes of this invention, nanofibers are uniformly wrapped around the core surface. On one hand, nanofibers possess the characteristic of in-situ fiberization, and the coating layer and binder have better bonding capabilities, further promoting the fiberization of the binder. During electrode fabrication, this enhances the strength of the fiber network between particles, thereby improving the stability of the prepared electrode. On the other hand, the nanofibers in the surface coating layer can suppress volume expansion during core lithium intercalation, and the polymer in the coating layer facilitates film formation on the core material surface, reducing electrolyte decomposition on the negative electrode material surface and improving the battery's initial efficiency and cycle performance. The ion-conducting polymer and nanofibers in the coating layer synergistically enhance the initial coulombic efficiency and cycle performance of batteries using this negative electrode material. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 This is an optical microscope image of the dispersion in Example 1.

[0052] Figure 2 This is a SEM image of the negative electrode composite material adapted to the dry electrode process in Example 1.

[0053] Figure 3 This is an optical microscope image of the dispersion in Comparative Example 6. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0055] The present invention also provides a negative electrode composite material adapted to dry electrode processes. The negative electrode composite material includes a coating layer and a core with lithium storage capacity. The coating layer includes an ion-conducting polymer and nanofibers. The negative electrode composite material is in the form of a powder.

[0056] The nanofibers in the coating layer are uniformly wrapped around the core surface. On the one hand, the nanofibers have the characteristic of in-situ fiberization, and the coating layer and binder have better bonding ability, which can further promote the fiberization of the binder. During the preparation of the electrode, this is beneficial to improve the strength of the fiber network between particles, thereby improving the stability of the prepared electrode. On the other hand, the nanofibers in the surface coating layer can suppress the volume expansion during the core lithium intercalation process, and the polymer in the coating layer is conducive to film formation on the surface of the core material, which helps to reduce the decomposition of the electrolyte on the surface of the negative electrode material, thus improving the battery's first coulombic efficiency and cycle performance. The ion-conducting polymer and nanofibers in the coating layer can synergistically improve the first coulombic efficiency and cycle performance of the battery using this negative electrode material.

[0057] It should be noted that the negative electrode composite material adapted to the dry electrode process in this application is compatible with the dry electrode preparation process and common dry battery binders such as polytetrafluoroethylene, polyvinylidene fluoride, copolymers of polyvinylidene fluoride and hexafluoropropylene, ultra-high molecular weight polyethylene, perfluoro(alkyl vinyl) ethers, acrylic polymers, acrylate polymers, carboxymethyl cellulose and its salts, nanocellulose, polyurethane, polyamide-imide and polyimide, etc., which is beneficial to improving the electrical performance of the battery cell using dry electrode preparation.

[0058] In an optional embodiment, the negative electrode composite material satisfies at least one of the following characteristics:

[0059] a. The nanofibers are filamentous and coat the surface of the core;

[0060] b. The ion-conducting polymer is at least partially coated on the surface of the nanofibers;

[0061] c. The ion-conducting polymer at least partially coats the surface of the core;

[0062] d. The coating layer has fibrillation function.

[0063] In optional embodiments, the ion-conducting polymer includes at least one of cellulose derivatives and their salts, acrylic polymers and their salts, polyacrylonitrile, and alginate; the cellulose derivatives and their salts may optionally be carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sulfonated cellulose (such as sodium cellulose sulfate), etc.; the acrylic polymers and their salts may optionally be polyacrylic acid, lithium polyacrylate, sodium polyacrylate, copolymers containing acrylic acid, lithium salts of copolymers containing acrylic acid, sodium salts of copolymers containing acrylic acid, etc.; the alginate may optionally be sodium alginate, etc.; the ion transport performance and core encapsulation ability of the ion-conducting polymer are closely related to the performance of the negative electrode composite material adapted to the dry electrode process, and selecting an ion-conducting polymer with better ion transport performance and core encapsulation ability is more conducive to improving battery performance.

[0064] In optional embodiments, the nanofibers include at least one of carbon nanofibers, single-walled carbon nanotubes, oligowalled carbon nanotubes, multi-walled carbon nanotubes, aramid fibers, and nanocellulose. The conductivity and binding ability of the nanofibers to the core volume expansion are closely related to the performance of the negative electrode composite material adapted to dry electrode processes. Selecting nanofibers with better conductivity and binding ability to the core volume expansion is more beneficial to improving battery performance. Preferably, the nanofibers include at least single-walled carbon nanotubes.

[0065] For example, the nanocellulose may be at least one of cellulose nanocrystals (CNC), cellulose nanofibers (CNF), and bacterial cellulose (BC).

[0066] In an optional embodiment, the core comprises a carbon-active material and / or a silicon-active material; the carbon-active material comprises at least one of natural graphite, artificial graphite, hard carbon material, soft carbon material and mesophase carbon microspheres, preferably natural graphite and / or artificial graphite; the silicon-active material comprises at least one of elemental silicon, silicon carbide, silicon oxide, silicon-carbon composite material, silicon-nitrogen composite material and silicon alloy, preferably silicon-carbon composite material and / or silicon oxide.

[0067] In an optional embodiment, the core comprises a silicon-carbon composite material and / or a silicon oxide compound. The lithium storage core of the material comprises a silicon-carbon composite material and / or a silicon oxide compound, and the lithium storage capacity of the composite material can fluctuate between 320 mAh / g and 2500 mAh / g to meet the needs of different users.

[0068] In an optional implementation, the core comprises graphite (natural graphite and / or artificial graphite) and a silicon-carbon composite material.

[0069] In some alternative embodiments, the core comprises graphite (natural graphite and / or artificial graphite) and silicon oxide.

[0070] In an optional embodiment, the polymer monomer of the acrylic polymer includes a first monomer and an optional second monomer, wherein the first monomer is an acrylic monomer and the second monomer is at least one selected from cyano monomer, amide monomer, aromatic vinyl monomer, ester monomer and hydroxy monomer.

[0071] For example, the first monomer may be at least one of acrylic acid and methacrylic acid.

[0072] For example, the cyano monomer may be at least one of acrylonitrile, α-chloroacrylonitrile, α-bromoacrylonitrile, methacrylonitrile and ethylacrylonitrile, and more preferably acrylonitrile and / or methacrylonitrile.

[0073] For example, the amide monomer may be at least one selected from acrylamide, methacrylamide, N,N-diethylacrylamide, N,N-diethylmethylacrylamide, N-ethylacrylamide, N-ethylmethylacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethylacrylamide, N-methylacrylamide, N-methylmethylacrylamide, N-isopropylacrylamide, N-isopropylmethylacrylamide and 2-acrylamido-2-phenylethanesulfonic acid, and more preferably acrylamide or / and methacrylamide.

[0074] For example, the aromatic ethylene monomer may be at least one of styrene, α-methylstyrene, p-tert-butylstyrene, butoxystyrene, vinyltoluene, styrene sulfonic acid and its salts and chlorostyrene, preferably styrene.

[0075] For example, the ester monomer may be an olefinic unsaturated carboxylic acid ester.

[0076] For example, the olefinic unsaturated carboxylic ester may be at least one of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, hexyl acrylate, hexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, glycidyl acrylate, and glycidyl methacrylate.

[0077] For example, the hydroxyl monomer can be an olefinic unsaturated carboxylic acid hydroxy ester monomer.

[0078] For example, the olefinic unsaturated carboxylic acid hydroxy ester monomer is at least one of hydroxyethyl acrylate, ethoxyethoxyethyl acrylate, and hydroxyethyl methacrylate.

[0079] In an optional embodiment, the polymeric monomers of the acrylic polymer include a first monomer and a second monomer, wherein the mass fraction of the first monomer is 10%-90%, specifically any value between 10%, 30%, 50%, 70%, 90%, or 10%-90%, and the mass fraction of the second monomer is 10%-90%, specifically any value between 10%, 30%, 50%, 70%, 90%, or 10%-90%.

[0080] The ion-conducting polymer in this embodiment has better ion transport performance and the ability to encapsulate the core.

[0081] In an optional implementation, the mass ratio of the coating layer to the core is 0.01%-10%, specifically, it can be any value between 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 4%, 6%, 8%, 10%, or 0.01%-10%.

[0082] If the coating layer accounts for too little, the performance improvement of the anode composite material adapted to the dry electrode process will not be significant. When the surface coating layer accounts for a high percentage of the mass, the nanofibers in the coating layer can be fully fiberized during the friction process, and the ion-conducting polymer can play a role in bonding between particles, so that the silicon-carbon anode material can be extruded into a supporting film without adding any binder. If the coating layer accounts for too much, the capacity improvement will be hindered because the coating layer does not have lithium storage capacity.

[0083] In an optional embodiment, the mass fraction of nanofibers in the coating layer is 1%-70%, specifically any value between 1%, 5%, 10%, 20%, 30%, 50%, 70%, or 1%-70%, and the mass fraction of the ion-conducting polymer is 30%-99%, specifically any value between 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99%, or 30%-99%.

[0084] If the amount of nanofibers is too small, the effect of promoting the fiberization of the binder and improving the stability of the anode composite material adapted to the dry electrode process will not be obvious; if the amount of nanofibers is too large, the amount of ion-conducting polymer will be too small, which may affect the film-forming ability and reduce the uniformity of the coating layer. Both of these are not conducive to improving the performance of the anode composite material adapted to the dry electrode process.

[0085] In an optional embodiment, the negative electrode composite material satisfies at least one of the following characteristics:

[0086] a. The lithium intercalation capacity of the negative electrode composite material is 320mAh / g-2500mAh / g;

[0087] b. The initial coulombic efficiency of the negative electrode composite material is 90%-98%;

[0088] c. The particle size distribution concentration (SPAN) of the negative electrode composite material is between 0.8 and 3.0, where SPAN = (D90 - D10) / D50; specifically, SPAN can be any value between 0.8, 1.2, 1.6, 2.0, 2.5, 3.0, or 0.8-3.0. SPAN represents the particle size distribution of the material and affects the performance of the negative electrode composite material adapted to dry electrode processes. More preferably, SPAN is between 1.0 and 2.5, and more preferably, SPAN is between 1.3 and 2.0. The SPAN index reflects the particle size distribution of the negative electrode material. A SPAN value that is too low indicates a high particle concentration in the negative electrode material, which is not conducive to the rolling process of the material. Conversely, a SPAN value that is too high means that the particle concentration in the negative electrode material is low, the particle size distribution range is wide, and the number of large and small particles is relatively large. Small particles are more likely to consume electrolyte, while large particles expand more significantly during charge and discharge. These factors all have an adverse effect on the cycle performance of the negative electrode material. Therefore, controlling the SPAN value within an appropriate range is more conducive to obtaining anode materials with better performance.

[0089] d. The specific surface area of ​​the negative electrode composite material is 0.3 m². 2 / g-10m 2 / g, specifically 0.3m 2 / g, 0.5m 2 / g、1m 2 / g、2m 2 / g、4m 2 / g、6m 2 / g、8m 2 / g, 10m 2 / g or 0.3m 2 / g-10m 2 Any value between / g. Increasing the specific surface area is beneficial for increasing the number of active sites, but as the specific surface area increases, the area that can contact the electrolyte also increases, so the specific surface area should not be too large.

[0090] e. The D50 of the negative electrode composite material is 5μm-24μm, specifically it can be any value between 5μm, 8μm, 10μm, 13μm, 15μm, 17μm, 20μm, 22μm, 24μm or 13μm-24μm, preferably 8μm-16μm. Lowering D50 helps reduce the expansion of the negative electrode composite material and improves the stability of the electrode film structure; however, excessively low D50 can also result in an excessively large specific surface area and an increased number of active sites, which is detrimental to further improving the battery's coulombic efficiency and cycle performance. Further regulation of D50 is beneficial for further optimizing battery performance.

[0091] The present invention also provides a method for preparing a negative electrode composite material adapted to the dry electrode process described in the foregoing embodiments, comprising: mixing a core material with a dispersion containing the ion-conducting polymer, nanofibers and solvent, and then coating it with an ALD-like coating to obtain a negative electrode composite material adapted to the dry electrode process.

[0092] Preferably, the method for coating ALD-like particles includes at least one of rotary flash drying, centrifugal spray drying, and two-fluid spray drying;

[0093] More preferably, the temperature of the ALD-like coating is 100℃-400℃.

[0094] The equipment for ALD coating includes one or more combinations of fluidized bed dryers, airflow flash dryers, spray dryers, rotary flash dryers, rotary kilns, forced-air drying boxes, tube furnaces, and roller kilns.

[0095] The temperature of the ALD-like coating is 100℃-400℃, specifically any value between 100℃, 150℃, 200℃, 250℃, 300℃, 350℃, 400℃ or 100℃-400℃.

[0096] In an optional embodiment, the dispersion is further prepared by dispersing the ion-conducting polymer and nanofibers in a solvent under at least one of high shear, high-speed oscillation and high pressure conditions to obtain the dispersion.

[0097] Preferably, high pressure is achieved through homogenization, with a homogenization pressure of 10 MPa-250 MPa;

[0098] High shear is achieved through stirring, with a shear linear velocity of 5m / s-40m / s;

[0099] High-speed oscillation is achieved through ultrasound, with an ultrasound frequency of 20kHz to 110kHz.

[0100] The dispersion process can be one of the three processes mentioned above or any combination thereof, with the processing time for high shear, high-speed oscillation, and high pressure all ranging from 0.1 h to 48 h. The mixing step includes one or more of ultrasonic dispersion and high-speed stirring dispersion, and the equipment involved includes one or more of ultrasonic dispersers, high-speed disc dispersers, dual planetary dispersers, frame stirrers, and anchor stirrers.

[0101] The homogenizing pressure is 10 MPa-250 MPa, specifically any value between 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa, 110 MPa, 120 MPa, 130 MPa, 140 MPa, 150 MPa, 160 MPa, 170 MPa, 180 MPa, 190 MPa, 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, 250 MPa, or 10 MPa-250 MPa; 10 MPa-160 MPa is further preferred.

[0102] The shearing linear velocity is 5m / s-40m / s, specifically it can be any value between 5m / s, 10m / s, 15m / s, 20m / s, 25m / s, 30m / s, 35m / s, 40m / s or 5m / s-40m / s;

[0103] The ultrasonic frequency is 20kHz to 110kHz, specifically 20kHz, 30kHz, 40kHz, 50kHz, 60kHz, 70kHz, 80kHz, 90kHz, 100kHz, 110kHz or any value between 20kHz and 110kHz.

[0104] The equipment used in the dispersion step may include one or a combination of several of the following: ultrasonic disperser, high-speed disc disperser, double planetary mixer, emulsifying circulating pump, high-pressure homogenizer, sand mill, and homogenizing circulating pump.

[0105] Preferably, the ion-conducting polymer and nanofibers are pre-dispersed under high shear and / or high-speed oscillation conditions to obtain a pre-dispersion liquid, and the pre-dispersion liquid is subjected to high-pressure homogenization to obtain the dispersion liquid. It should be noted that, for the embodiments of this application, high-pressure dispersion is crucial for obtaining a uniformly mixed and homogeneous dispersion liquid. If atmospheric pressure dispersion is used, such as high-speed stirring or even ultrasonication at atmospheric pressure, it can still be seen under an electron microscope that the ion-conducting polymer and nanofibers are not uniformly dispersed in the solvent.

[0106] The present invention also provides an electrode film comprising the negative electrode composite material adapted to dry electrode processes as described in any of the foregoing embodiments.

[0107] In an optional embodiment, the electrode film further includes a conductive agent and / or a binder;

[0108] The conductive agent includes at least one of carbon black, conductive graphite, Super P, microcrystalline graphite, Ketjen black, and carbon nanotubes.

[0109] The carbon nanotubes include at least one of single-walled carbon nanotubes, oligo-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0110] The adhesive comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), ultra-high molecular weight polyethylene, perfluoro(alkyl vinyl) ethers, acrylic polymers, acrylate polymers, carboxymethyl cellulose and its salts, nanocellulose, polyurethane, polyamide-imide and polyimide;

[0111] Preferably, the electrode film is a self-supporting film.

[0112] The perfluoro(alkyl vinyl) ether may optionally be perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE), etc.

[0113] The range of optional acrylic polymers can be referenced from the aforementioned range of optional acrylic polymers as ion-conducting polymers.

[0114] The monomers for acrylate polymers may optionally be any one of acrylate monomers, acrylamide monomers, acrylonitrile monomers, or styrene monomers.

[0115] The acrylate monomers may optionally be at least one of methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, isooctyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, isooctyl methacrylate, hydroxypropyl methacrylate, or 2-hydroxyethyl methacrylate.

[0116] The present invention also provides an electrode, comprising a current collector and an electrode film as described in any of the foregoing embodiments disposed on at least one side surface of the current collector; preferably, the electrode is obtained by a dry process.

[0117] In an optional embodiment, the method includes: dry mixing the raw materials used for the electrode film to obtain a dry powder, fiberizing and shaping the dry powder in situ, and then extruding it onto the surface of the current collector to obtain the electrode;

[0118] The dry powder comprises, by mass fraction, more than 85% of the negative electrode composite material adapted to the dry electrode process, less than 10% of the binder, and less than 5% of the conductive agent.

[0119] In-situ fiberization can be achieved by high-speed stirring, while molding typically refers to extrusion to form a self-supporting membrane.

[0120] The binder in this embodiment is at least one of polytetrafluoroethylene, polyvinylidene fluoride, copolymer of polyvinylidene fluoride and hexafluoropropylene, ultra-high molecular weight polyethylene, perfluoro(alkyl vinyl) ether, acrylic polymers, acrylate polymers, carboxymethyl cellulose and its salts, nanocellulose, polyurethane, polyamide-imide and polyimide, preferably polytetrafluoroethylene.

[0121] The conductive agent is at least one of carbon black, conductive graphite, Super P, microcrystalline graphite, Ketjen black, and carbon nanotubes.

[0122] The carbon nanotubes include at least one of single-walled carbon nanotubes, oligo-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0123] It should be noted that the dry powder in the embodiments of this application may only include the negative electrode composite material adapted to the dry electrode process, and the electrode sheet can be prepared without adding binder or conductive agent; in some embodiments, it may not include binder and only include the negative electrode composite material adapted to the dry electrode process and conductive agent, while in some embodiments, binder and conductive agent may be added at the same time.

[0124] Compared to in-situ fiberization with binders, nanofibers in the coating layer can more uniformly coat the negative electrode material and achieve the effect of in-situ fiberization. The fibrous network structure formed by the two in synergy with the binder has a stronger mechanical structure and a better inhibitory effect on the expansion of the electrode sheet, which helps to reduce or even avoid the use of binders.

[0125] The present invention also provides an electrochemical energy storage device, including the electrodes described in the foregoing embodiments;

[0126] Preferably, the electrode is a negative electrode;

[0127] Preferably, the electrochemical energy storage device includes any one of lithium-ion batteries, sodium-ion batteries, solid-state batteries, and supercapacitors.

[0128] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0129] Example 1

[0130] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0131] Material preparation:

[0132] 7g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 3g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously dispersed using a disc disperser at a linear velocity of 25m / s for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes and sodium carboxymethyl cellulose. The pre-dispersion was homogenized and circulated under 100MPa pressure until uniform dispersion was achieved. The optical microscope image is shown below. Figure 1 As shown.

[0133] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the coated anode material. SEM images are shown below. Figure 2 As shown.

[0134] Battery fabrication:

[0135] 1. Button cell battery

[0136] The prepared negative electrode material, thickener sodium carboxymethyl cellulose (CMC), conductive agent Super P, and binder styrene-butadiene rubber (SBR) were mixed in a mass ratio of 88:2:3:7. Deionized water was added as a solvent, and the mixture was stirred under vacuum until the system was homogeneous to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on the negative electrode current collector copper foil, transferred to a vacuum drying oven for drying, and then rolled and punched to obtain small round sheets, which are the negative electrode sheets.

[0137] A coin cell battery was assembled using a lithium metal sheet as the counter electrode, Celgard 2400 as the separator, and an electrolyte with the following formulation: EC:EMC:DEC:VC:DTD:FEC ​​= 30:50:20:1:1:1 (mass ratio) and 1.1M LiPF6 as the solute.

[0138] 2. Soft-pack battery

[0139] Dry preparation of negative electrode sheets

[0140] 500g of the prepared negative electrode material, 10g of PTFE, and 5g of Super P were placed in a mixing tank and mixed at high speed to induce in-situ fiberization of the PTFE. Subsequently, a self-supporting membrane was formed by roller extrusion. The self-supporting membrane was then hot-pressed onto the surface of copper foil, and the compaction density was controlled to 1.6g / cm³ using roller pressing.3 .

[0141] Preparation of positive electrode sheet

[0142] The electrode material ratio is NCM811:SP:CNT:PVDF5130 = 96.2:1.5:1:1.3, and the double-sided coating surface density is 375 g / m³. 2 Compacted density 3.4 g / cm³ 3 .

[0143] Using the above positive and negative electrode sheets and Celegard 2400 as the separator, a 2Ah soft-pack battery was prepared. The electrolyte formula was: EC:EMC:DEC:VC:DTD:FEC=30:50:20:1:1:1 (mass ratio), with 1.1M LiPF6 as the solute.

[0144] Battery performance test

[0145] 1. First-efficiency test of button cell battery

[0146] At 25℃ and normal pressure, the coin cell was discharged at a constant current rate of 0.1C to a voltage of 0.005V, and then discharged at a constant current rate of 0.05C to a voltage of 0.005V. The discharge specific capacity at this point was recorded, which is the initial lithium insertion capacity. After that, it was charged at a constant current rate of 0.1C to a voltage of 1.5V, and the charging specific capacity at this point was recorded, which is the initial lithium de-lithiation capacity. The initial coulombic efficiency (initial efficiency, %) of the negative electrode active material = initial lithium de-lithiation capacity / initial lithium insertion capacity × 100%.

[0147] 2. Performance testing of pouch batteries

[0148] The battery's initial coulombic efficiency was tested by disassembling it under full charge and measuring the expansion of the negative electrode. The battery's cycle life was tested at 25°C with 0.5C charging and discharging, and the battery capacity retention was tested after 200 cycles.

[0149] The initial Coulomb efficiency test method is as follows:

[0150] Specific formation process settings: 0.05C constant current charging for 120 minutes to the upper limit voltage of 3.5V, capacity of Q1; rest for 10 minutes; 0.15C constant current charging for 150 minutes to the upper limit voltage of 3.6V, capacity of Q2; after formation, rest in a high temperature explosion-proof box at 45℃±1℃ for 8 hours.

[0151] Specific capacity grading steps are set as follows: 0.33C constant current and constant voltage charging to the upper limit voltage of 3.7V, cutoff current 0.05C, capacity Q3; rest for 10 minutes; 0.33C constant current discharging to the lower limit voltage of 2V; rest for 10 minutes, discharge capacity Q4; 0.33C constant current and constant voltage charging to the upper limit voltage of 3.7V, cutoff current 0.05C; rest for 10 minutes; 0.33C constant current discharging to the lower limit voltage of 2V; rest for 10 minutes; 0.33C constant current and constant voltage charging to the upper limit voltage of 3.7V, cutoff current 0.05C.

[0152] The first-efficiency measure of the sample is Q4 / (Q1+Q2+Q3).

[0153] The expansion of the negative electrode when fully charged = (the thickness of the fully charged negative electrode - the initial thickness of the negative electrode) / the thickness of the fully charged negative electrode.

[0154] 200-cycle capacity retention = discharge capacity after 200 cycles / battery's initial discharge capacity.

[0155] The test results are shown in Table 1.

[0156] Example 2

[0157] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0158] Material preparation:

[0159] 3.5 g of sodium carboxymethyl cellulose was dissolved in 2000 g of deionized water, and 1.5 g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100 kHz while simultaneously being dispersed at a high speed of 25 m / s linear velocity using a disc disperser for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes and sodium carboxymethyl cellulose. The pre-dispersion was then homogenized and circulated under a pressure of 100 MPa using a homogenizer until it was uniformly dispersed.

[0160] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0161] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0162] Example 3

[0163] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0164] Material preparation:

[0165] 14g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 6g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously being dispersed at a high speed of 25m / s linear velocity using a disc disperser for 3 hours to obtain a carbon nanotube-sodium carboxymethyl cellulose pre-dispersion. The pre-dispersion was then homogenized and circulated under 100MPa pressure using a homogenizer until it was uniformly dispersed.

[0166] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0167] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0168] Example 4

[0169] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0170] Material preparation:

[0171] 5g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 5g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously being dispersed at a high speed of 25m / s linear velocity using a disc disperser for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes and sodium carboxymethyl cellulose. The pre-dispersion was then homogenized and circulated under a pressure of 100MPa using a homogenizer until it was uniformly dispersed.

[0172] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0173] Example 5

[0174] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0175] Material preparation:

[0176] 9g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 1g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously being dispersed at a high speed of 25m / s linear velocity using a disc disperser for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes and sodium carboxymethyl cellulose. The pre-dispersion was homogenized and circulated under a pressure of 100MPa using a homogenizer until it was uniformly dispersed.

[0177] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0178] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0179] Example 6

[0180] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0181] Material preparation:

[0182] 7g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 3g of multi-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously being dispersed at a high speed of 25m / s linear velocity using a disc disperser for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes-sodium carboxymethyl cellulose. The pre-dispersion was homogenized and circulated under a pressure of 100MPa using a homogenizer until it was uniformly dispersed.

[0183] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0184] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0185] Example 7

[0186] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0187] Material preparation:

[0188] 7g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 3g of aramid fiber was added. The mixture was ultrasonically vibrated at 100kHz while simultaneously being dispersed at a high speed of 25m / s linear velocity using a disc disperser for 3 hours to obtain a pre-dispersion of single-walled nano-aramid fiber-sodium carboxymethyl cellulose. The pre-dispersion was homogenized and circulated under a pressure of 100MPa using a homogenizer until it was uniformly dispersed.

[0189] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed of 25m / s for 2 hours using a disc disperser under ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0190] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0191] Example 8

[0192] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0193] Material preparation:

[0194] 15g of acrylic acid and 10g of acrylonitrile were dissolved in 300ml of water. The mixture was heated to 70°C under high-speed stirring and stirred for half an hour under nitrogen purging. 0.1g of ammonium persulfate was dissolved in 5ml of water, and the ammonium persulfate solution was added dropwise to the above reaction solution. The mixture was stirred at 70°C under nitrogen purging for 6 hours, then heated to 85°C and stirred for 1 hour. Lithium hydroxide was added to adjust the pH to neutral, and the mixture was cooled to room temperature. The water was removed by spray drying to obtain 18.3g of lithium acrylate-acrylonitrile copolymer.

[0195] 7g of lithium acrylate-acrylonitrile copolymer was dissolved in 2000g of deionized water, and 3g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously being dispersed at a high speed of 25m / s linear velocity using a disc disperser for 3 hours to obtain a pre-dispersion of single-walled carbon nanotube-lithium acrylate-acrylonitrile copolymer. The pre-dispersion was then homogenized and circulated under a pressure of 100MPa using a homogenizer until it was uniformly dispersed.

[0196] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed of 25m / s for 2 hours using a disc disperser under ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0197] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0198] Example 9

[0199] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0200] Material preparation:

[0201] 21g of the lithium acrylate-acrylonitrile copolymer synthesized in Example 8 and 9g of single-walled carbon nanotubes were dissolved in 5000g of deionized water and ultrasonically oscillated at 100kHz. Simultaneously, the mixture was dispersed at high speed using a disc disperser at 25m / s for 3 hours to obtain a pre-dispersion of single-walled carbon nanotube-lithium acrylate-acrylonitrile copolymer. The pre-dispersion was homogenized and circulated under a pressure of 100MPa using a homogenizer until it was uniformly dispersed.

[0202] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0203] Battery fabrication:

[0204] 1. The preparation of the button cell is exactly the same as in Example 1.

[0205] 2. Soft-pack battery

[0206] Dry preparation of negative electrode sheets

[0207] 500g of the prepared negative electrode material and 5g of Super P were placed in a mixing tank and stirred at high speed to induce in-situ fibrosis of the coating layer. Subsequently, a self-supporting membrane was formed by roller extrusion. The self-supporting membrane was then hot-pressed onto the surface of copper foil, and the compaction density was controlled to be 1.6g / cm³. 3 .

[0208] Preparation of positive electrode sheet

[0209] The electrode material ratio is NCM811:SP:CNT:PVDF5130 = 96.2:1.5:1:1.3, and the double-sided coating surface density is 375 g / m³. 2 Compacted density 3.4 g / cm³ 3 .

[0210] Using the above positive and negative electrode sheets and Celegard 2400 as the separator, a 2Ah soft-pack battery was prepared. The electrolyte formula was: EC:EMC:DEC:VC:DTD:FEC=30:50:20:1:1:1 (mass ratio), with 1.1M LiPF6 as the solute.

[0211] The performance testing method is exactly the same as in Example 1.

[0212] Example 10

[0213] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0214] Material preparation:

[0215] 7g of the lithium acrylate-acrylonitrile copolymer synthesized in Example 8 and 3g of single-walled carbon nanotubes were added to 2000g of deionized water and ultrasonically oscillated at 100kHz. Simultaneously, the mixture was dispersed at high speed using a disc disperser at 25m / s for 3 hours to obtain a pre-dispersion of single-walled carbon nanotube-lithium acrylate-acrylonitrile copolymer. The pre-dispersion was homogenized and circulated under a pressure of 100MPa using a homogenizer until it was uniformly dispersed.

[0216] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0217] The battery preparation and performance testing methods are exactly the same as those in Example 9.

[0218] Example 11

[0219] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0220] Material preparation:

[0221] 7g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 3g of single-walled carbon nanotubes, 900g of natural graphite, and 100g of silicon carbide were added. The mixture was ultrasonically vibrated at 100kHz and simultaneously dispersed at a high speed of 25m / s linear velocity using a disc disperser for 5 hours. The mixture was then rapidly coated with an ALD-like material using a spray dryer at 200℃. During the coating process, the material was fed at a low speed of 0.1L / min to prevent agglomeration. The powder was collected to obtain the surface-modified anode material.

[0222] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0223] Example 12

[0224] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0225] Material preparation:

[0226] 7g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 3g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously dispersed using a disc disperser at a linear velocity of 25m / s for 15h to obtain a single-walled carbon nanotube-sodium carboxymethyl cellulose dispersion. The dispersion was not subjected to any further high-pressure treatment. Optical microscopic images of the dispersion are shown below. Figure 3 As shown.

[0227] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. During coating, the material was fed at a low speed (0.1L / min) to prevent agglomeration. The powder was collected to obtain the coated anode material.

[0228] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0229] Example 13

[0230] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0231] Material preparation:

[0232] 7g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 3g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously dispersed using a disc disperser at a linear velocity of 25m / s for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes and sodium carboxymethyl cellulose. The pre-dispersion was homogenized and circulated under 100MPa pressure until uniform dispersion was achieved. The optical microscope image is shown below. Figure 1 As shown.

[0233] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. During the coating process, the feed rate was increased to 0.2L / min to prevent material agglomeration. The powder was collected to obtain the coated negative electrode material.

[0234] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0235] Example 14

[0236] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0237] Material preparation:

[0238] 7g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 3g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously dispersed using a disc disperser at a linear velocity of 25m / s for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes and sodium carboxymethyl cellulose. The pre-dispersion was homogenized and circulated under 100MPa pressure until uniform dispersion was achieved. The optical microscope image is shown below. Figure 1 As shown.

[0239] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed of 25m / s for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating in a spray dryer at 200℃. During the coating process, the feed rate was increased to 0.3L / min to prevent material agglomeration. The powder was collected to obtain the coated negative electrode material.

[0240] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0241] Example 15

[0242] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0243] Material preparation:

[0244] 7g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 3g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously dispersed using a disc disperser at a linear velocity of 25m / s for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes and sodium carboxymethyl cellulose. The pre-dispersion was homogenized and circulated under 100MPa pressure until uniform dispersion was achieved. The optical microscope image is shown below. Figure 1 As shown.

[0245] 900g of small-particle-size natural graphite (obtained by ball milling the natural graphite in Example 1) and 100g of small-particle-size silicon carbide material (obtained by breaking down the silicon carbide in Example 1) were added to the prepared dispersion. The mixture was dispersed at high speed (25 m / s) for 2 hours using a disc disperser under 100 kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200°C. During the coating process, the material was fed at a low speed (0.1 L / min) to prevent agglomeration. The powder was collected to obtain the coated negative electrode material.

[0246] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0247] Example 16

[0248] This embodiment provides a method for preparing a battery, specifically including the following steps:

[0249] Material preparation:

[0250] 7g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water, and 3g of single-walled carbon nanotubes were added. The mixture was ultrasonically vibrated at 100kHz while simultaneously dispersed using a disc disperser at a linear velocity of 25m / s for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes and sodium carboxymethyl cellulose. The pre-dispersion was homogenized and circulated under 100MPa pressure until uniform dispersion was achieved. The optical microscope image is shown below. Figure 1 As shown.

[0251] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed of 25m / s for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating in a spray dryer at 200℃. During the coating process, the feed rate was reduced to 0.05L / min to prevent material agglomeration. The powder was collected to obtain the coated negative electrode material.

[0252] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0253] Comparative Example 1

[0254] This comparative example provides a method for preparing a battery, specifically including the following steps:

[0255] Dry preparation of negative electrode sheets

[0256] 450g of natural graphite, 50g of silicon carbide, 10g of PTFE, and 5g of Super P were placed in a mixing jar and mixed at high speed to induce in-situ fiberization of the PTFE. Subsequently, a self-supporting membrane was formed by roller extrusion. This self-supporting membrane was then hot-pressed onto the surface of copper foil, and the compaction density was controlled to 1.6g / cm³ using roller pressing. 3 .

[0257] Preparation of positive electrode sheet

[0258] The electrode material ratio is NCM811:SP:CNT:PVDF5130 = 96.2:1.5:1:1.3, the double-sided coating surface density is 375 g / m², and the compacted density is 3.4 g / cm³. 3 .

[0259] Using the above positive and negative electrode sheets and Celegard 2400 as the separator, a 2Ah soft-pack battery was prepared. The electrolyte formula was: EC:EMC:DEC:VC:DTD:PS = 30:50:20:1:1:1 (mass ratio), with 1.1M LiPF6 as the solvent.

[0260] The battery performance test was exactly the same as in Example 1.

[0261] Comparative Example 2

[0262] This comparative example provides a method for preparing a battery. Based on Comparative Example 1, the amount of PTFE is increased to 20g, while other conditions are exactly the same as in Comparative Example 1.

[0263] Comparative Example 3

[0264] This comparative example provides a method for preparing a battery, specifically including the following steps:

[0265] Material preparation:

[0266] 10g of sodium carboxymethyl cellulose was dissolved in 2000g of deionized water and ultrasonically vibrated at 100kHz. Simultaneously, it was dispersed at a high speed of 25m / s linear velocity for 3 hours using a disc disperser to obtain a sodium carboxymethyl cellulose pre-dispersion. The pre-dispersion was homogenized and circulated under a pressure of 100MPa using a homogenizer until it was uniformly dispersed.

[0267] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0268] The battery preparation and characterization methods are exactly the same as in Example 1.

[0269] Comparative Example 4

[0270] This comparative example provides a method for preparing a battery, specifically including the following steps:

[0271] Material preparation:

[0272] 10g of single-walled carbon nanotubes were dissolved in 2000g of deionized water and ultrasonically vibrated at 100kHz while simultaneously being dispersed at a high speed of 25m / s linear velocity using a disc disperser for 3 hours to obtain a pre-dispersion of single-walled carbon nanotubes. The pre-dispersion was then homogenized and circulated under a pressure of 100MPa using a homogenizer until it was uniformly dispersed.

[0273] 900g of natural graphite and 100g of silicon carbide were added to the prepared dispersion and dispersed at high speed (25m / s) for 2 hours using a disc disperser under 100kHz ultrasonic assistance. The mixture was then subjected to rapid ALD-like coating via a spray dryer at 200℃. Low-speed feeding (0.1L / min) was used during coating to prevent material agglomeration. The powder was collected to obtain the surface-modified anode material.

[0274] The battery preparation and performance testing methods are exactly the same as in Example 1.

[0275] Test Results

[0276] Table 1

[0277]

[0278]

[0279] A comparison of Examples 1 and 2 shows that insufficient coating amount leads to insignificant technical solution effects. A comparison of Examples 1 and 3 shows that excessive coating amount, under the same battery manufacturing process conditions, affects the capacity utilization of the negative electrode material. A comparison of Examples 1, 4, and 5 shows that the ratio of ion-conducting polymer to nanofibers is crucial to the performance of the negative electrode material. If the polymer ratio is too low, it is not conducive to the dispersion of nanofibers, preventing them from fully functioning. Furthermore, insufficient coating of the negative electrode material surface by the ion-conducting polymer will affect the material's initial efficiency. If the polymer ratio is too high and the nanofiber content is low, it will affect the strength of the self-supporting film, and the fibers will be insufficient to suppress the expansion of the negative electrode material, affecting the battery's cycle performance. A comparison of Examples 1, 5, and 6 shows that nanofibers, which combine flexibility, strength, and conductivity, are more conducive to improving the material's performance.

[0280] A comparison of Example 1, Comparative Example 1, and Comparative Example 2 shows that, under the same battery formulation conditions, surface coating treatment significantly improves battery performance, and this performance improvement cannot be achieved by increasing the amount of PTFE binder. A comparison of Example 1 with Comparative Examples 3 and 4 shows that both the ion-conducting polymer and nanofibers in the coating layer are crucial. Without nanofibers, electrode stability is insufficient, and the improvement in battery performance is not significant. Without the ion-conducting polymer, nanofibers are difficult to disperse, resulting in uneven distribution on the surface of the negative electrode material, which can actually worsen electrical performance.

[0281] Comparing Examples 1 and 8, it can be seen that the lithium acrylate-acrylonitrile copolymer achieves better performance than sodium carboxymethyl cellulose. This is due to the better ion transport performance of the lithium acrylate-acrylonitrile copolymer, resulting in better encapsulation of the negative electrode material. Comparing Examples 1 with Examples 9 and 10, it can be seen that, thanks to the synergistic effect between the ion-conducting polymer and nanofibers, the negative electrode composite material can be prepared into a self-supporting film without the addition of PTEF binder. However, in order to improve the stability of the self-supporting film and the performance of the battery under binder-free conditions, the mass ratio of the surface coating layer needs to be appropriately increased. Under this condition, the battery based on this electrode exhibits excellent electrical performance. Comparing Examples 1 and 11, it can be seen that, compared to Example 1, the one-pot method for preparing the negative electrode composite material reduces the uniformity of carbon nanotube dispersion due to the inability to perform high-pressure homogenization, which is detrimental to the improvement of the performance of the negative electrode composite material. High-pressure dispersion allows nanofibers to be uniformly dispersed and spread out, coating the lithium-storing core surface. Without high-pressure dispersion, the nanofibers would entangle and agglomerate, resulting in a decrease in the initial efficiency and an increase in the full-charge expansion of the electrode in Example 11 compared to Comparative Example 1. This demonstrates that high-pressure dispersion plays a crucial role in the dispersion of nanofibers. A comparison of Examples 1 and 12 shows that high-pressure homogenization is key to the dispersion of nanofibers, and this dispersion effect cannot be replaced by prolonged ultrasonication or high-speed shearing time. Figure 1 and Figure 3 A comparison of the optical microscope images of the two dispersions reveals that... Figure 1 The dispersion is more uniform, with no obvious black agglomerates, and the brightness of the dispersion is more uniform at all locations due to the more uniform dispersion of carbon nanotubes in Example 1.

[0282] A comparison of Examples 1, 13, 14, 15, and 16 reveals that the particle size distribution and D50 of the material have a crucial impact on battery performance. Particle agglomeration during the preparation process leads to a wider particle size distribution in the product, and the formation of large particles deteriorates the battery's initial efficiency, expansion, and cycle performance. Controlling D50 or SPAN within an appropriate range can further optimize battery performance.

[0283] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A negative electrode composite material adapted to dry electrode processes, characterized in that, The negative electrode composite material includes a coating layer and a core with lithium storage capacity. The coating layer includes an ion-conducting polymer and nanofibers. The negative electrode composite material is in the form of a powder.

2. The negative electrode composite material adapted for dry electrode process according to claim 1, characterized in that, The negative electrode composite material satisfies at least one of the following characteristics: a. The nanofibers are filamentous and coat the surface of the core; b. The ion-conducting polymer is at least partially coated on the surface of the nanofibers; c. The ion-conducting polymer at least partially coats the surface of the core; d. The coating layer has fibrillation function.

3. The negative electrode composite material adapted for dry electrode process according to claim 1, characterized in that, The ion-conducting polymer includes at least one of cellulose derivatives and their salts, acrylic polymers and their salts, polyacrylonitrile and alginate. And / or, the nanofibers include at least one of carbon nanofibers, single-walled carbon nanotubes, oligowalled carbon nanotubes, multi-walled carbon nanotubes, aramid fibers, and nanocellulose. And / or, the core comprises carbon-active materials and / or silicon-active materials; And / or, the carbon-active material includes at least one of natural graphite, artificial graphite, hard carbon materials, soft carbon materials, and mesophase carbon microspheres; And / or, the silicon-active material includes at least one of elemental silicon, silicon carbide, silicon oxide, silicon-carbon composite material, silicon-nitrogen composite material, and silicon alloy.

4. The negative electrode composite material adapted for dry electrode process according to claim 3, characterized in that, The polymer monomers of the acrylic polymer include a first monomer and an optional second monomer, wherein the first monomer is an acrylic monomer and the second monomer is at least one of a cyano monomer, an amide monomer, an aromatic vinyl monomer, an ester monomer, and a hydroxy monomer; And / or, the polymer monomers of the acrylic polymer include a first monomer and a second monomer, wherein the mass fraction of the first monomer is 10%-90% and the mass fraction of the second monomer is 10%-90%.

5. The negative electrode composite material adapted for dry electrode process according to claim 1, characterized in that, The mass ratio of the coating layer to the core is 0.01%-10%; And / or, in the coating layer, the mass fraction of nanofibers is 1%-70%, and the mass fraction of the ion-conducting polymer is 30%-99%.

6. The negative electrode composite material adapted for dry electrode process according to claim 1, characterized in that, The negative electrode composite material satisfies at least one of the following characteristics: a. The lithium intercalation capacity of the negative electrode composite material is 320mAh / g-2500mAh / g; b. The initial coulombic efficiency of the negative electrode composite material is 90%-98%; c. The particle size distribution concentration (SPAN) of the negative electrode composite material is between 0.8 and 3.0, where SPAN = (D90 - D10) / D50; d. The specific surface area of ​​the negative electrode composite material is 0.3 m². 2 / g-10m 2 / g; e. The D50 of the negative electrode composite material is 5μm-24μm.

7. A method for preparing a negative electrode composite material adapted to dry electrode process as described in claim 1, characterized in that, include: The core material is mixed with a dispersion containing the ion-conducting polymer, nanofibers and solvent, and then coated with an ALD-like coating to obtain the negative electrode composite material adapted to the dry electrode process. Preferably, the method for coating ALD-like particles includes at least one of rotary flash drying, centrifugal spray drying, and two-fluid spray drying; More preferably, the temperature of the ALD-like coating is 100℃-400℃.

8. The method for preparing the negative electrode composite material adapted to dry electrode process according to claim 7, characterized in that, It also includes the preparation of the dispersion: dispersing the ion-conducting polymer and nanofibers in a solvent under at least one of high shear, high-speed oscillation and high pressure conditions to obtain the dispersion; Preferably, high pressure is achieved through homogenization, with a homogenization pressure of 10 MPa to 250 MPa; high shear is achieved through stirring, with a shear linear velocity of 5 m / s to 40 m / s; and high-speed oscillation is achieved through ultrasound, with an ultrasound frequency of 20 kHz to 110 kHz. Preferably, the ion-conducting polymer and nanofibers are pre-dispersed under high shear and / or high-speed oscillation conditions to obtain a pre-dispersion liquid, and the pre-dispersion liquid is homogenized under high pressure to obtain the dispersion liquid.

9. An electrode film, characterized in that, A negative electrode composite material adapted for dry electrode processes as described in any one of claims 1-6.

10. The electrode film according to claim 9, characterized in that, The electrode film also includes a conductive agent and / or a binder; The conductive agent includes at least one of carbon black, conductive graphite, Super P, microcrystalline graphite, Ketjen black, and carbon nanotubes. The adhesive includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, copolymers of polyvinylidene fluoride and hexafluoropropylene, ultra-high molecular weight polyethylene, perfluoro(alkyl vinyl) ethers, acrylic polymers, acrylate polymers, carboxymethyl cellulose and its salts, nanocellulose, polyurethane, polyamide-imide and polyimide; Preferably, the electrode film is a self-supporting film.

11. An electrode, characterized in that, It includes a current collector and an electrode film as described in claim 9 or 10 disposed on at least one side surface of the current collector; preferably, the electrode is obtained by a dry process.

12. A method for preparing the electrode according to claim 11, characterized in that, include: The raw materials used in the electrode film are dry-mixed to obtain a dry powder. The dry powder is then fiberized and shaped in situ and extruded onto the surface of the current collector to obtain the electrode. Preferably, the dry powder comprises more than 85% by mass of the negative electrode composite material adapted to the dry electrode process, less than 10% by mass of binder, and less than 5% by mass of conductive agent.

13. An electrochemical energy storage device, characterized in that, Includes the electrode as described in claim 11; Preferably, the electrode is a negative electrode; Preferably, the electrochemical energy storage device includes any one of lithium-ion batteries, sodium-ion batteries, solid-state batteries, and supercapacitors.

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