A soft ball-milled coated modified particle, its preparation method and application

Abstract

The present invention relates to a soft ball-milled coated modified particle, a preparation method thereof and an application thereof, belonging to the field of particle modification. The present invention provides a coated modified particle and a preparation technology thereof. The preparation raw materials include polymer pellets, particles to be coated and functional additives. By using the polymer pellets as soft ball-milling friction media, through the collision and friction adhesion with the particles to be coated and the functional additives, a pure polymer coating layer or a composite coating layer of polymer and functional additives is formed on the surface of the particles to be coated. Among them, the surface hardness or elastic modulus of the polymer is less than the surface hardness or elastic modulus of the particles to be coated, and the maximum size of the geometric shape of the particles to be coated is less than the minimum size of the geometric shape of the polymer pellets. The present invention has significant advantages such as wide applicability, strong scale-up ability, low processing cost, green and low-carbon, etc., and thus has good application prospects.

Description

Technical Field

[0001] The present invention relates to a soft ball-milled coated modified particle, a preparation method thereof, and an application thereof, belonging to the field of particle modification. Background Art

[0002] Surface coating modification of powder particles plays an extremely important role in fields such as energy materials, functional nano powder materials, and their composite materials. Especially with the strong demand for clean energy technologies, we are urgently in need of vigorously developing clean energy storage technologies. As the most mature and widely used clean energy storage technology at present, electrochemical energy storage plays a crucial role in this. Secondary ion batteries such as lithium-ion batteries have become the preferred choice due to their high energy density and environmental friendliness. However, with the development of portable electronic products, hybrid vehicles, pure electric vehicles, and large-scale energy storage technologies, there is an urgent need to develop lithium-ion batteries with higher energy density and power density to meet market demands.

[0003] At present, the energy density of commercially available lithium-ion batteries on the market is gradually approaching a bottleneck. On the one hand, the actual capacity of the active material is getting closer and closer to its theoretical specific capacity. On the other hand, there are multiple challenges in preparing high-performance electrodes with stable structure and electrochemical performance based on high-capacity active materials. First of all, high-capacity active materials are often prone to serious side reactions with the electrolyte or ion dissolution, resulting in accelerated capacity decay. On the other hand, due to the limitations of wet electrode slurries themselves, problems such as electrode cracking and uneven aggregation of components during the drying process, such as the migration of binders and conductive agents, will inevitably occur when preparing high-loading electrodes, thus limiting the further improvement of the electrode energy density. On the other hand, the development and popularization of new energy vehicles have led to an increasing requirement for the power density of power batteries. The power density of the battery is closely related to the electron-conducting and ion-conducting abilities inside the electrode.

[0004] Developing surface functional modification technology for active particles is an effective strategy to solve the above problems. At present, around this major demand, the most common strategy is to conduct conductive functional coating on the active material. The reported coating strategies mainly include chemical vapor deposition, atomic layer deposition, hydrothermal method, solution method, and ball milling method, etc. Although chemical vapor deposition and atomic layer deposition have high coating accuracy, problems such as high cost and large-scale production difficulty limit their wide application. The hydrothermal method is difficult to be widely used due to problems such as low efficiency, poor coating effect, and limited applicable active material systems. The ball milling method is one of the few methods that have achieved large-scale application at present, but its coating controllability is poor, and there are serious problems such as severe damage, deformation, or pulverization of the particles to be coated during the coating process. These problems all mean that developing a new type of solvent-free, low-carbon green, low-cost, highly efficient, scalable, and nearly non-destructive particle coating modification technology will have great technical value and practical significance. Summary of the Invention

[0005] In view of the above defects, the present invention provides a coated modified particle and a preparation method thereof. The raw materials include polymer pellets (as soft ball milling media) and particles to be coated. Among them, the polymer pellets serve as soft ball milling media, and through the method of frictional adhesion transfer, the polymer can be adhered to the surface of the particles to be coated to achieve soft ball milling coating modification of the particles. In addition, according to application requirements, a functional additive can also be introduced into the system as a third component, and the third component can be a functional auxiliary such as an inorganic filler or a polymer powder. It can be seen that the present invention can form a coating layer composed of a polymer or a composite of a polymer and a functional additive on the surface of the particles to be coated by a simple coating method.

[0006] The technical solution of the present invention:

[0007] The first technical problem to be solved by the present invention is to provide a coated modified particle. The raw materials for preparing the modified particle include polymer pellets, particles to be coated, and a functional additive. By using the polymer pellets as soft ball milling friction media, through the collision and frictional adhesion action with the particles to be coated and the functional additive, a coating layer is formed on the surface of the particles to be coated. The coating layer is a polymer coating or a composite coating layer formed by a polymer and a functional additive. Among them, the surface hardness or elastic modulus of the polymer is less than the surface hardness or elastic modulus of the particles to be coated, and the maximum dimension of the geometric shape of the particles to be coated is less than the minimum dimension of the geometric shape of the polymer pellets. The proportion of each raw material is: 1-99 parts by weight of polymer pellets, 1-99 parts by weight of particles to be coated, and 0-50 parts by weight of functional additive.

[0008] Furthermore, the proportion of each raw material is: 40-80 parts by weight of polymer pellets, 20-60 parts by weight of particles to be coated, and 0-20 parts by weight of functional additive; furthermore, 40-60 parts by weight of polymer pellets, 40-60 parts by weight of particles to be coated, and 1-5 parts by weight of functional additive.

[0009] Furthermore, the particle size of the coated modified particle is 10 nm to 1000 um.

[0010] Furthermore, the coated modified particle includes a coating layer and a core layer. The core layer is the particle to be coated, and the coating layer is a polymer or a composite composed of a polymer and a functional additive.

[0011] Furthermore, a stable coating layer can be formed between the surface of the coating layer and the core layer through various physical and chemical interactions such as hydrogen bond interaction, electrostatic adsorption, surface chemical reaction, or mechanical interlocking.

[0012] Furthermore, the thickness of the coating layer on the surface of the coated modified particles is adjustable within the range of 1 to 1000 nm, but is preferably controlled within the range of 1 to 100 nm.

[0013] Furthermore, the shape of the polymer pellets can be one or a combination of spherical, ellipsoidal, spindle-shaped, cylindrical, disc-shaped, and irregular particle shapes, but spherical, ellipsoidal, spindle-shaped, cylindrical, or disc-shaped regular shapes and their combinations are preferred.

[0014] Furthermore, the polymer in the polymer pellets is any polymer material with a surface hardness or elastic modulus less than that of the surface of the particles to be coated, including but not limited to: polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyamide, polyethylene, polypropylene, polyoxymethylene, poly(vinylidene fluoride - hexafluoropropylene), polyethylene - polyethylene oxide copolymer, polystyrene, polyethylene oxide, polymaleic anhydride, polyacrylic acid, sodium polyacrylate, lithium polyacrylate, polycarbonate, polypropylene carbonate, polyvinylpyrrolidone, thermoplastic elastomer, natural rubber, cellulose, protein, natural polysaccharide, various thermosetting resins, various thermoplastic resins, various engineering or special engineering plastics, etc., at least one of which.

[0015] Furthermore, the polymer pellets can be directly selected from various shaped polymer pellets obtained by extrusion granulation.

[0016] Furthermore, the geometric shape of the particles to be coated is not limited, but spherical, elliptical, cylindrical, and polyhedral-shaped particles are preferred.

[0017] Furthermore, the particles to be coated can be electrochemical active particles, metal particles, metal alloy particles, or inorganic ceramic particles in various secondary ion batteries or supercapacitors, including but not limited to positive and negative active material particles for various lithium-ion batteries, positive and negative active material powders for sodium-ion batteries, and active material particles for supercapacitors, etc. Specifically, it includes but not limited to: lithium nickel cobalt manganese oxide (sodium), lithium nickel cobalt aluminum oxide (sodium), lithium manganese oxide (sodium), lithium iron phosphate (sodium), lithium (sodium)-rich manganese-based cathode materials, lithium cobalt oxide (sodium), graphite particles, graphitized carbon fiber, lithium titanate, hard carbon, silicon particles, silicon-carbon composite particles, activated carbon, metal particles, metal oxide particles, inorganic ceramic particles, activated carbon particles, etc., one or more of which.

[0018] Further, the functional additive (the third component) may be various functional materials with electronic conductivity and ionic conductivity, specifically including but not limited to: carbon nanotubes, carbon nanofibers, halloysite nanotubes, various nano-conductive carbon blacks, graphene oxide, graphene, zirconia, titanium dioxide, aluminum trioxide, various sulfide inorganic electrolyte micro-nano particles, various oxide ceramic inorganic electrolyte micro-nano particles, PVDF polymer nano particles, PAA polymer nano particles, PEO nano particles, various halide solid electrolyte micro-nano particles, various metal and its oxide micro-nano particles, etc., at least one of them.

[0019] The second technical problem to be solved by the present invention is to provide a preparation method of the above-mentioned coated and modified particles. The preparation method is as follows: first, premix each raw material evenly, and then mechanically mix at -20°C to 300°C for 30 s to 3 h; finally, obtain the coated and modified particles through cooling and screening.

[0020] Further, the mechanical mixing method is selected from at least one of the following: ball milling oscillation, mechanical pressure stirring, gravity flipping, or extruder screw shear mixing, etc.; during the above preparation process, under the action of mechanical mixing, the polymer pellets in the raw materials serve as soft ball milling friction media, and through collision and friction adhesion with the particles to be coated and the functional additive, a coating layer is formed on the surface of the particles to be coated; in the internal friction adhesion transfer stage, the material can generate the required friction adhesion transfer through any mechanical mixing method such as ball milling oscillation, mechanical stirring, gravity flipping, or extruder screw shear mixing; the internal friction adhesion transfer effect can also be enhanced by means of an external heat source and a pressurization method, and the mixing time can be optimized according to specific process control conditions. That is, during the mechanical mixing process, the effect and efficiency of the internal friction adhesion transfer of the material can be enhanced by the coordinated control of the material temperature, mixing intensity, and internal pressure.

[0021] Further, in order to regulate the friction adhesion transfer efficiency between particles, the wall pressure of the inner cavity of the container is controlled between 0.01 and 30 MPa, preferably 0.1 to 10 MPa; and the initial temperature of the cavity wall during mixing is controlled between -20°C and 300°C, and the initial temperature of the material is controlled between 0 and 100°C.

[0022] Further, under the conditions of slow mixing or stopped mixing, cooling is carried out by means of natural cooling or forced cooling with a cooling medium.

[0023] Further, the cooled mixture is separated by physical screening.

[0024] Further, the thickness of the coated and modified layer can be coordinately controlled by the proportion of each component in the soft ball milling system, mixing speed, temperature, chamber pressure, and mechanical mixing time.

[0025] The third technical problem to be solved by the present invention is to point out that the above-mentioned coated modified particles are used in the preparation of electrode sheets for wet or dry batteries, electrode sheets for solid-state batteries, electrode sheets for supercapacitors, metal 3D printing parts, conductive nanocomposites, conductive pastes or sensing materials.

[0026] The fourth technical problem to be solved by the present invention is to provide a wet preparation method for positive and negative electrode sheets of a battery. The preparation method is as follows: mix the above-mentioned prepared coated modified particles (where the core layer of the coated modified particles is an active material), a polymer binder, and a conductive agent (determine whether an additional addition is required according to the actual situation such as whether the active particles are pure polymer-coated or polymer / conductive composite-coated, etc.) to prepare a uniform wet slurry; then prepare an electrode sheet with a uniform and controllable structure through processes such as coating, drying, and rolling; wherein, the proportion of each raw material: 60-99.9 parts by weight of coated modified particles, 0.1-40 parts by weight of polymer binder, and 0-20 parts by weight of conductive agent.

[0027] Furthermore, the proportion of the preparation raw materials of the coated modified particles is: 40-80 parts by weight of polymer pellets, 20-60 parts by weight of particles to be coated, and 0-20 parts by weight of functional additives.

[0028] In the present invention, when the coated modified particles are used for positive and negative electrode sheets of a battery, the polymer pellets can be selected with different particle sizes according to different shapes. When it is spherical, its diameter (the maximum size of the geometric shape of the spherical pellets) is between 0.1 mm and 20 mm; when it is ellipsoidal, spindle-shaped, or cylindrical, the diameter of its circular cross-section (the maximum size of the polymer pellets) is between 0.1 mm and 20 mm; when it is irregular in shape, its geometric maximum size is between 0.1 mm and 20 mm. The particles to be coated can be selected with different particle sizes according to different shapes. When it is spherical, its diameter size is between 1*10 -4 mm and 0.1 mm; when it is ellipsoidal or cylindrical, the diameter of its circular cross-section is between 1*10 -4 mm and 0.1 mm.

[0029] Furthermore, in the above-mentioned preparation method of positive and negative electrode sheets, the binder used in the electrode slurry can be an organic solvent binder system and an aqueous binder system, including but not limited to polyvinylidene fluoride PVDF binder system, styrene-butadiene rubber SBR and its system with sodium carboxymethyl cellulose CMC, polyacrylic acid organic solvent and aqueous binder system, etc.

[0030] Furthermore, in the above-mentioned preparation method of positive and negative electrode sheets of a battery, the conductive agent is selected from at least one of high-conductivity micro-nano materials such as multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, carbon microfibers, nano-conductive carbon black, Mxene micro-nano particles, reduced graphene oxide, graphene, graphite, or metal nanowires.

[0031] The electrode sheet of the present invention is prepared by wet method with polymer soft ball milling coating modification of active particles. Compared with the electrode sheet prepared by wet method with traditional uncoated active particles, it has the following structural advantages and characteristics, which are more conducive to the preparation of high energy density and high power density battery devices: First, the pulping process reduces the process requirements for the dispersion of conductive agents; second, the drying process also avoids the problem of uncontrollable aggregation of components (especially binder and conductive agent components), and can achieve a more uniform and firm interfacial adhesion among the active particles, binder, and conductive agent; second, the electron transport network of the electrode sheet is mainly formed by the overlapping of the conductive coating layers on the surface of the active particles. Therefore, the conductive network is more controllable, stable, and efficient; finally, since there is no large amount of loose conductive agent and binder filling in the stacking voids between the active particles, it becomes more unobstructed and conducive to the efficient transport of ions inside the electrode.

[0032] The fifth technical problem to be solved by the present invention is to provide a dry method for preparing positive and negative electrode sheets of a battery. The preparation method is as follows: Premix the above-prepared coated and modified particles (the particles to be coated are active material powders), polymer binder (such as PTFE powder binder), and conductive agent to obtain a pre-fibrillated dry slurry; then roll-press to obtain a dry electrode sheet (realize the fibrillation of PTFE and its interfacial adhesion with the composite coated and modified particles by controlling the pressure and temperature during roll-pressing); wherein, the mass ratio of each raw material is: 60-99.9 parts by weight of coated and modified particles, 0.1-40 parts by weight of polymer binder, and 0-20 parts by weight of conductive agent.

[0033] Further, in the above dry method for preparing positive and negative electrode sheets of a battery, the raw materials for preparing the coated and modified particles include polymer pellets, particles to be coated, and functional additives. The proportion of each raw material is: 40-80 parts by weight of polymer pellets, 20-60 parts by weight of particles to be coated, and 0-20 parts by weight of functional additives.

[0034] Further, in the above dry method for preparing positive and negative electrode sheets of a battery, the conductive agent is selected from at least one of high-conductivity micro-nano materials such as multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, carbon microfibers, nano-conductive carbon black, Mxene micro-nano particles, reduced graphene oxide, graphene, graphite, or metal nanowires.

[0035] The obtained dry positive and negative electrode sheets have the following characteristics: The distribution of the conductive agent and binder around the active particles is more controllable and uniform; the interfacial compatibility between the PTFE fiber binder and the active particles is greatly improved due to the polymer coating; the uniformity and stability of the overall structure of the electrode are significantly improved.

[0036] The sixth technical problem to be solved by the present invention is to provide a method for preparing a solid-state electrode sheet. The preparation method is as follows: mixing the above-prepared coated and modified particles, polymer binder, conductive agent, and solid electrolyte powder to prepare a wet or dry slurry; then preparing the solid-state electrode sheet through processes such as coating, drying, and rolling; wherein, the mass ratio of each raw material is: 60-99.9 parts by weight of coated and modified particles, 0.1-40 parts by weight of polymer binder, 0-20 parts by weight of conductive agent, and 0.1-40 parts by weight of solid electrolyte.

[0037] Further, the solid electrolyte powder can be one or a combination of a sulfide system, an oxide system, a halide system, and a polymer system.

[0038] Further, in the above method for preparing the solid-state electrode sheet, the conductive agent is selected from at least one of high-conductivity micro-nano materials such as multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, carbon microfibers, nano-conductive carbon black, Mxene micro-nano particles, reduced graphene oxide, graphene, graphite, and metal nanowires.

[0039] The obtained solid-state electrode sheet has the following characteristics: the electron transport network of the solid-state electrode sheet is mainly formed by connecting the conductive coating layers of active particles, and only a small amount or even no electron conductive agent is contained in the solid electrolyte filling part.

[0040] The seventh technical problem to be solved by the present invention is to provide a lithium (sodium) metal battery, which is assembled from a positive electrode sheet prepared from coated and modified particles, a separator, lithium metal, and a commercial electrolyte; or:

[0041] assembled from a positive electrode sheet prepared from coated and modified particles, a separator, a lithium-free negative electrode sheet, and a commercial electrolyte;

[0042] Wherein, the positive or negative electrode sheet prepared from the coated and modified particles is prepared by using the above method for preparing the positive and negative electrode sheets of a wet battery or the method for preparing the positive and negative electrode sheets of a dry battery.

[0043] Further, when the lithium (sodium) metal battery is a solid-state lithium (sodium) metal battery, the battery is assembled from a positive electrode prepared from the above-coated and modified particles, a solid electrolyte separator, and lithium metal; or:

[0044] assembled from a positive electrode sheet prepared from the above-coated and modified particles, a solid electrolyte separator, and a lithium-free negative electrode sheet;

[0045] Wherein, the positive or negative electrode sheet prepared from the coated and modified particles is prepared by using the above method for preparing the positive and negative electrode sheets of a wet battery or the method for preparing the positive and negative electrode sheets of a dry battery.

[0046] The eighth technical problem to be solved by the present invention is to provide a supercapacitor, which is composed of a positive electrode sheet or a negative electrode sheet prepared from the above-mentioned coated and modified particles, an electrolyte, and a separator;

[0047] Among them, the positive electrode sheet or the negative electrode sheet prepared from the coated and modified particles is prepared by using the preparation method of the positive and negative electrode sheets of the above-mentioned wet battery or the preparation method of the positive and negative electrode sheets of the dry battery.

[0048] Advantages of the present invention:

[0049] The present invention provides a coated and modified particle and a preparation method thereof. The raw materials include polymer pellets, particles to be coated, and a third component functional additive; among them, the polymer pellets serve as a soft ball milling medium, and the polymer is adhered to the surface of the particles to be coated by means of frictional adhesion transfer (that is, the particles to be coated are not damaged throughout the process). In addition, functional additives can be introduced according to actual applications, and finally a coating layer composed of a polymer or a composite of a polymer and a functional additive is formed on the surface of the particles to be coated.

[0050] The present invention provides a method for non-destructive coating modification of particles with low cost, universality, and scale-up ability, which ultimately plays a key role in the green and environmentally friendly processing and preparation of high specific energy electrodes, the manufacture of advanced liquid and solid power batteries, and functional nanocomposites and other fields. Description of the drawings

[0051] Figure 1 . SEM images of uncoated and modified NCM811 particles: a SEM image of uncoated and modified NCM811 particles at a magnification of 1000 times; b SEM image of uncoated and modified NCM811 particles at a magnification of 2000 times; c SEM image of uncoated and modified NCM811 particles at a magnification of 5000 times; d SEM image of uncoated and modified NCM811 particles at a magnification of 10000 times.

[0052] Figure 2 . SEM images of pure polyacrylic acid-coated and modified lithium nickel cobalt manganate particles prepared by the traditional hard ball milling method (Comparative Example 2): a SEM image of pure polyacrylic acid-coated and modified lithium nickel cobalt manganate particles prepared by the traditional hard ball milling method at a magnification of 1000 times; b SEM image of pure polyacrylic acid-coated and modified lithium nickel cobalt manganate particles prepared by the traditional hard ball milling method at a magnification of 2000 times; c SEM image of pure polyacrylic acid-coated and modified lithium nickel cobalt manganate particles prepared by the traditional hard ball milling method at a magnification of 5000 times; d SEM image of pure polyacrylic acid-coated and modified lithium nickel cobalt manganate particles prepared by the traditional hard ball milling method at a magnification of 10000 times.

[0053] Figure 3. SEM images of polyacrylic acid / carbon nanotube composite-coated and modified NCM811 particles prepared by the traditional ball milling method (Comparative Example 3): a SEM image of polyacrylic acid / carbon nanotube composite-coated and modified NCM811 particles prepared by the traditional ball milling method at a magnification of 1000 times; b SEM image of polyacrylic acid / carbon nanotube composite-coated and modified NCM811 particles prepared by the traditional ball milling method at a magnification of 2000 times; c SEM image of polyacrylic acid / carbon nanotube composite-coated and modified NCM811 particles prepared by the traditional ball milling method at a magnification of 5000 times; d SEM image of polyacrylic acid / carbon nanotube composite-coated and modified NCM811 particles prepared by the traditional ball milling method at a magnification of 15000 times.

[0054] Figure 4 . Microscopic scanning electron microscope (SEM) images and transmission electron microscope (TEM) images of polypropylene / polyacrylic acid-coated and modified lithium nickel cobalt manganese oxide particles (Example 1): a SEM image of polypropylene / polyacrylic acid-coated and modified lithium nickel cobalt manganese oxide particles at a magnification of 800 times; b SEM image of polypropylene / polyacrylic acid-coated and modified lithium nickel cobalt manganese oxide particles at a magnification of 2500 times; c SEM image of polypropylene / polyacrylic acid-coated and modified lithium nickel cobalt manganese oxide particles at a magnification of 5000 times; d TEM image of polypropylene / polyacrylic acid-coated and modified lithium nickel cobalt manganese oxide particles at a scale of 100 nm; e TEM image of polypropylene / polyacrylic acid-coated and modified lithium nickel cobalt manganese oxide particles at a scale of 100 nm; f TEM image of polypropylene / polyacrylic acid-coated and modified lithium nickel cobalt manganese oxide particles at a scale of 50 nm.

[0055] Figure 5 . SEM images of polypropylene / polyacrylic acid / carbon nanotube composite-coated and modified lithium nickel cobalt manganese oxide particles (Example 2): a SEM image of polypropylene / polyacrylic acid / carbon nanotube composite-coated and modified lithium nickel cobalt manganese oxide particles at a magnification of 1000 times; b SEM image of polypropylene / polyacrylic acid / carbon nanotube composite-coated and modified lithium nickel cobalt manganese oxide particles at a magnification of 2000 times; c SEM image of polypropylene / polyacrylic acid / carbon nanotube composite-coated and modified lithium nickel cobalt manganese oxide particles at a magnification of 5000 times; d SEM image of polypropylene / polyacrylic acid / carbon nanotube composite-coated and modified lithium nickel cobalt manganese oxide particles at a magnification of 20000 times.

[0056] Figure 6. Microscopic scanning electron microscope (SEM) images and transmission electron microscope (TEM) images of polyethylene / carbon nanotube composite-coated and modified NCM811 particles (Example 3): a SEM image of polyethylene / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 1000 times; b SEM image of polyethylene / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 5000 times; c SEM image of polyethylene / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 10000 times; d SEM image of polyethylene / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 10000 times; e TEM image of polyethylene / carbon nanotube composite-coated and modified NCM811 particles at a scale of 100 nanometers; f TEM image of polyethylene / carbon nanotube composite-coated and modified NCM811 particles at a scale of 100 nanometers, g TEM image of polyethylene / carbon nanotube composite-coated and modified NCM811 particles at a scale of 50 nanometers.

[0057] Figure 7 . SEM images of polypropylene / carbon nanotube composite-coated and modified NCM811 particles (Example 4): a SEM image of polypropylene / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 1000 times; b SEM image of polypropylene / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 2000 times; c SEM image of polypropylene / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 5000 times; d SEM image of polypropylene / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 20000 times.

[0058] Figure 8 . SEM images of polyvinylidene fluoride / carbon nanotube composite-coated and modified NCM811 particles (Example 5): a SEM image of polyvinylidene fluoride / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 1000 times; b SEM image of polyvinylidene fluoride / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 2000 times; c SEM image of polyvinylidene fluoride / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 5000 times; d SEM image of polyvinylidene fluoride / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 10000 times.

[0059] Figure 9. SEM images of poly(butylene adipate-co-terephthalate) / carbon nanotube composite-coated and modified NCM811 particles (Example 6): a SEM image of poly(butylene adipate-co-terephthalate) / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 1000 times; b SEM image of poly(butylene adipate-co-terephthalate) / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 2000 times; c SEM image of poly(butylene adipate-co-terephthalate) / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 5000 times; d SEM image of poly(butylene adipate-co-terephthalate) / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 10000 times.

[0060] Figure 10 . SEM images of polylactic acid / carbon nanotube composite-coated and modified NCM811 particles (Example 7): a SEM image of polylactic acid / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 1000 times; b SEM image of polylactic acid / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 2000 times; c SEM image of polylactic acid / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 5000 times; d SEM image of polylactic acid / carbon nanotube composite-coated and modified NCM811 particles at a magnification of 10000 times.

[0061] Figure 11 . SEM images of polypropylene / polyacrylic acid / conductive carbon black composite-coated and modified NCM811 particles (Example 8): a SEM image of polypropylene / polyacrylic acid / conductive carbon black composite-coated and modified NCM811 particles at a magnification of 1000 times; b SEM image of polypropylene / polyacrylic acid / conductive carbon black composite-coated and modified NCM811 particles at a magnification of 2000 times; c SEM image of polypropylene / polyacrylic acid / conductive carbon black composite-coated and modified NCM811 particles at a magnification of 5000 times; d SEM image of polypropylene / polyacrylic acid / conductive carbon black composite-coated and modified NCM811 particles at a magnification of 20000 times.

[0062] Figure 12 . SEM images of polypropylene / conductive carbon black composite-coated and modified NCM811 particles (Example 9): a SEM image of polypropylene / conductive carbon black composite-coated and modified NCM811 particles at a magnification of 1000 times; b SEM image of polypropylene / conductive carbon black composite-coated and modified NCM811 particles at a magnification of 2000 times; c SEM image of polypropylene / conductive carbon black composite-coated and modified NCM811 particles at a magnification of 5000 times; d SEM image of polypropylene / conductive carbon black composite-coated and modified NCM811 particles at a magnification of 10000 times.

[0063] Figure 13. SEM images of polypropylene / carbon nanotube composite-coated modified lithium iron phosphate particles (Example 10) and lithium iron phosphate particles without CNT coating: a SEM image of lithium iron phosphate particles without CNT coating at a magnification of 5000 times; b SEM image of lithium iron phosphate particles without CNT coating at a magnification of 20000 times; c SEM image of polypropylene / carbon nanotube composite-coated modified lithium iron phosphate particles at a magnification of 2000 times; d SEM image of polypropylene / carbon nanotube composite-coated modified lithium iron phosphate particles at a magnification of 5000 times; e SEM image of polypropylene / carbon nanotube composite-coated modified lithium iron phosphate particles at a magnification of 10000 times; f SEM image of polypropylene / carbon nanotube composite-coated modified lithium iron phosphate particles at a magnification of 25000 times.

[0064] Figure 14 . SEM images of polypropylene / carbon nanotube composite-coated modified lithium cobalt oxide particles (Example 11) and lithium cobalt oxide particles without CNT coating: a SEM image of lithium cobalt oxide particles without CNT coating at a magnification of 5000 times; b SEM image of lithium cobalt oxide particles without CNT coating at a magnification of 10000 times; c SEM image of polypropylene / carbon nanotube composite-coated modified lithium cobalt oxide particles at a magnification of 1000 times; d SEM image of polypropylene / carbon nanotube composite-coated modified lithium cobalt oxide particles at a magnification of 2000 times; e SEM image of polypropylene / carbon nanotube composite-coated modified lithium cobalt oxide particles at a magnification of 4000 times; f SEM image of polypropylene / carbon nanotube composite-coated modified lithium cobalt oxide particles at a magnification of 15000 times.

[0065] Figure 15 . SEM images of polypropylene / carbon nanotube composite-coated modified graphite particles (Example 11) and graphite particles without CNT coating: a SEM image of graphite particles without CNT coating at a magnification of 5000 times; b SEM image of graphite particles without CNT coating at a magnification of 10000 times; c SEM image of polypropylene / carbon nanotube composite-coated modified graphite particles at a magnification of 900 times; d SEM image of polypropylene / carbon nanotube composite-coated modified graphite particles at a magnification of 3500 times; e SEM image of polypropylene / carbon nanotube composite-coated modified graphite particles at a magnification of 11000 times; f SEM image of polypropylene / carbon nanotube composite-coated modified graphite particles at a magnification of 25000 times.

[0066] Figure 16. SEM images of the wet electrode sheets prepared from uncoated CNT-modified NCM811 (Comparative Example 4) and PP-CNT-coated modified NCM811 (Application Example 1): a SEM image of the wet electrode sheet prepared from uncoated CNT-modified NCM811 at a magnification of 500 times; b SEM image of the wet electrode sheet prepared from uncoated CNT-modified NCM811 at a magnification of 1000 times; c SEM image of the wet electrode sheet prepared from uncoated CNT-modified NCM811 at a magnification of 4500 times; d SEM image of the wet electrode sheet prepared from PP-CNT-coated CNT-modified NCM811 at a magnification of 500 times; e SEM image of the wet electrode sheet prepared from PP-CNT-coated CNT-modified NCM811 at a magnification of 1000 times; f SEM image of the wet electrode sheet prepared from PP-CNT-coated CNT-modified NCM811 at a magnification of 4500 times.

[0067] Figure 17 . Resistance diagrams of the wet electrode sheets prepared from uncoated modified NCM811 (Comparative Example 4) and PP-CNT-coated modified NCM811 (Application Example 1).

[0068] Figure 18 . Rate performance diagrams of the half-cells assembled from uncoated modified NCM811 (Comparative Example 5) and PP-CNT-coated modified NCM811 (Application Example 5). Detailed implementation manners

[0069] The present invention provides a coated modified particle. The preparation raw materials of the modified particle include: polymer pellets, particles to be coated, and functional additives. Using the polymer pellets as a friction medium, through the collision and friction adhesion effects with the particles to be coated and the functional additives, the surface of the particles to be coated is coated with a polymer, or a blend formed by the polymer and the functional additives; wherein, the surface hardness or elastic modulus of the polymer is less than the surface hardness or elastic modulus of the particles to be coated, and the maximum dimension of the geometric shape of the particles to be coated is less than the minimum dimension of the geometric shape of the polymer pellets; and, the proportions of the respective raw materials are: 1-99 parts by weight of polymer pellets, 1-99 parts by weight of particles to be coated, and 0-50 parts by weight of functional additives.

[0070] The present invention provides a brand-new coating method for the surface coating modification of inorganic particles such as electrochemically active particles. When it is applied to the surface coating of battery active particles, this coating technology can effectively improve the electronic and ionic conductivity of the active particles, and significantly improve the microstructure, interface controllability, uniformity, stability, and final comprehensive electrochemical performance of its dry and wet electrode sheets.

[0071] When the soft ball milling method of the present invention is used to prepare the coated and modified active particles, the obtained coated and modified particles can significantly improve at least one of the electrical conductivity, ion conductivity of the active particles, and the interfacial adhesion between the active particles and the binder compared with the uncoated and modified particles; and after coating and modification, the size and shape of the active particles do not undergo damage or deformation compared with before coating. In addition, the coated and modified active particles prepared based on this soft ball milling coating method demonstrate their application in the preparation of high specific energy liquid electrodes and all-solid-state electrodes. The present invention is not limited to the active materials of secondary ion batteries, and is also applicable to supercapacitor active materials (such as activated carbon).

[0072] Meanwhile, the liquid and solid electrode forming and processing technologies developed by the present invention based on the coated and modified active materials can effectively solve the problems of slurry component dispersion and adhesion, and greatly improve the areal loading of the active substances on the electrode sheet and the regulation ability of the structure and morphology. This electrode processing method can achieve good dispersion of the binder and the conductive agent, which is beneficial to the exertion of the electrochemical performance of the active material. At the same time, it can greatly improve the areal loading of the active substances, significantly enhance the energy density and power density of the electrode, and play a significant role in promoting the processing and manufacturing of traditional liquid batteries and solid-state batteries.

[0073] In addition, the modification method of the present invention has low equipment requirements, a simple production process flow, wide universality, is green and environmentally friendly throughout the process, has high production efficiency, and has broad prospects for large-scale industrial production and multi-field applications.

[0074] The processing method of soft ball milling coating modification adopted by the present invention can adopt the following steps:

[0075] 1) Premixing stage: Premixing can be carried out in two ways: one-step method and two-step method. The one-step method is to feed and mix the polymer soft ball milling medium, the particles to be coated, and the third component functional additive (which can be added or not added according to requirements) at one time in a certain proportion to obtain a uniformly mixed premix; the two-step method is to first premix the polymer soft ball milling medium with the particles to be coated or the third component functional additive, and then add the remaining components for mixing to finally obtain a uniformly mixed premix.

[0076] 2) Internal friction adhesion transfer stage: Mechanically mix the premix; during the mechanical mixing process, the effect and efficiency of the internal friction adhesion transfer of the material can be enhanced by coordinating the control of the material temperature, mixing intensity, and internal pressure.

[0077] 3) Cooling and discharging stage: After mechanical mixing, the blend is cooled under appropriate mixing conditions and sieved to separate the coated and modified powder and the polymer soft ball milling medium, and finally the coated and modified powder sample and the coated and modified polymer soft ball milling medium are obtained.

[0078] Next, the technology in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes all and any combinations of one or more of the related listed items.

[0079] Comparative Example 1: Uncoated and modified NCM811 particles

[0080] The present invention conducts microstructure detection on uncoated and modified lithium nickel cobalt manganese oxide (NCM811) particles. Figure 1 a-d are micro scanning electron microscope (SEM) images of uncoated and modified NCM811 particles. It can be seen from the figures that the NCM811 particles are nearly spherical, with uneven surfaces and many grooves, and the size is between 10 - 50 μm.

[0081] Comparative Example 2: Preparation of pure polyacrylic acid-coated and modified lithium nickel cobalt manganese oxide particles by traditional hard ball milling

[0082] 99 parts by mass of lithium nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm) and 1 part by mass of polyacrylic acid nano powder (spherical particles, median particle size D50 = 30 nm) are placed in a 100 mL ball milling tank, and the ball milling steel balls equipped with the equipment are added. The initial temperature of the material and the ball milling tank is about 80 °C; after 15 minutes of ball milling, it is naturally cooled and discharged to obtain the treated NCM811 particles.

[0083] Figure 2 a-d are micro scanning electron microscope (SEM) images of polyacrylic acid-coated and modified NCM811 particles prepared by the above traditional ball milling method. It can be seen from the figures that polyacrylic acid can also coat the surface of NCM811 particles, but there are two relatively serious problems: on the one hand, the controllability of the coating layer structure is poor; on the other hand, the NCM811 secondary particles are severely damaged, resulting in a greatly reduced sphericity and a large number of primary active particles broken by the steel balls.

[0084] Comparative Example 3: Traditional ball milling preparation of polyacrylic acid / carbon nanotube composite-coated and modified NCM811 particles

[0085] 98 parts by mass of lithium nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 1 part by mass of polyacrylic acid nano powder (spherical particles, median particle size D50 = 30 nm), and 1 part by mass of carbon nanotube CNT powder (fiber agglomerates, average outer diameter of a single CNT is about 10 nm, average length is about 20 μm) are placed in a 100 mL ball mill jar, and the ball mill steel balls equipped with the equipment are added at the same time. The initial temperature of the material and the ball mill jar is about 80 °C. After ball milling for 15 min, it is naturally cooled and discharged to obtain NCM811 particles coated with polyacrylic acid / CNT composite conductive coating.

[0086] Figure 3 a-d are the micro scanning electron microscope (SEM) images of the composite conductive coating modified NCM811 particles prepared by the above traditional ball milling method. It can be seen from the figure that polyacrylic acid and carbon nanotubes can also be coated on the surface of NCM811 particles to a certain extent, but the coating amount of carbon nanotubes is small and uneven; similar to the previous pure polymer coating, the active particles are severely damaged after ball milling, resulting in a significant reduction in their sphericity and generating a lot of crushed primary active particles.

[0087] Example 1: Preparation of polyacrylic acid@NCM coated and modified particles by polypropylene soft ball milling

[0088] 45 parts by mass of lithium nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 54 parts by mass of polypropylene (PP) pellets as soft ball milling media (cylindrical particles, cross-sectional diameter is about 2 mm, cylindrical length is about 5 mm), and 1 part by mass of polyacrylic acid nano powder (spherical particles, median particle size D50 = 30 nm) are placed in a 100 mL ball mill jar (steel balls are not used in the ball mill jar). The initial temperature of the material and the ball mill jar is about 80 °C. After ball milling for 15 min, it is naturally cooled and discharged to obtain NCM811 particles coated with polyacrylic acid.

[0089] Figure 4 a-f are the micro scanning electron microscope (SEM) images and transmission electron microscope images (TEM) of the above polyacrylic acid coated and modified NCM811 particles. It can be seen from the figure that polyacrylic acid is relatively evenly coated on the surface of NCM811 particles. The sphericity of the coated and modified active particles is well retained, and the size is between 10 - 50 μm, which is basically not much different from before coating. Through TEM observation, it is confirmed that the coating thickness is between 10 - 15 nm.

[0090] Example 2: Preparation of polyacrylic acid / carbon nanotube composite coated and modified NCM811 particles (PAA-CNT@NCM) by polypropylene soft ball milling

[0091] 44 parts by mass of lithium nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 54 parts by mass of polypropylene (PP) particles as soft ball milling media (cylindrical particles, cross-sectional diameter of about 2 mm, cylindrical length of about 5 mm), and 1 part by mass of polyacrylic acid particles (spherical particles, median particle size D50 = 30 nm) were placed in a 100 mL ball milling jar and pre-soft ball milled for 15 min first. Then, 1 part by mass of carbon nanotube CNT powder (fiber agglomerate shape, average outer diameter of a single CNT of about 10 nm, average length of about 20 μm) was introduced into it, and soft ball milling was continued for 15 min. The initial temperature of the material and the ball milling jar was about 80 °C, and the material was discharged after natural cooling to obtain NCM811 particles coated with polyacrylic acid / CNT composite conductive coating.

[0092] Figure 5 a-d are the micro scanning electron microscope (SEM) images of the composite conductive coating modified NCM811 particles prepared by the above soft ball milling method. It can be seen from the figure that polyacrylic acid and carbon nanotubes are coated on the surface of NCM811 particles relatively uniformly. The sphericity of the coated modified active particles is well retained, and the size is between 10 and 50 μm, which is basically not much different from that before coating.

[0093] Example 3: Preparation of polyethylene / carbon nanotube composite coated and modified NCM811 particles (PE-CNT@NCM) by polyethylene soft ball milling

[0094] 45 parts by mass of lithium nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 54 parts by mass of polyethylene (PE) particles as soft ball milling media (spherical particles, diameter of about 5 mm), and 1 part by mass of carbon nanotube CNT powder (fiber agglomerate shape, average outer diameter of a single CNT of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball milling jar. The initial temperature of the material and the ball milling jar was about 23 °C at room temperature. After ball milling for 15 min, the material was discharged after natural cooling to obtain NCM811 particles coated with polyethylene / CNT composite conductive coating.

[0095] Figure 6 a-g are the micro scanning electron microscope (SEM) images and transmission electron microscope images (TEM) of the composite conductive coating modified NCM811 particles prepared by the above soft ball milling method. It can be seen from the figure that carbon nanotubes are coated on the surface of NCM811 particles relatively uniformly. The sphericity of the coated modified active particles is well retained, and the size is between 10 and 50 μm, which is basically not much different from that before coating. Through TEM observation, it is confirmed that the coating thickness is between 30 and 50 nm.

[0096] Example 4: Preparation of Polypropylene / Carbon Nanotube Composite Coated and Modified NCM811 Particles (PP-CNT@NCM) by Polypropylene Soft Ball Milling

[0097] Put 45 parts by mass of lithium nickel cobalt manganate (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 54 parts by mass of polypropylene (PP) particles as soft ball milling media (cylindrical particles, cross-sectional diameter of about 2 mm, cylindrical length of about 5 mm), and 1 part by mass of carbon nanotube CNT powder (fiber aggregate shape, average outer diameter of a single CNT of about 10 nm, average length of about 20 μm) into a 100 mL ball milling jar. The initial temperature of the material and the ball milling jar is about 23 °C at room temperature. After 15 minutes of ball milling, it is naturally cooled and discharged to obtain NCM811 particles with polypropylene / CNT composite conductive coating.

[0098] Figure 7 a-d are the micro scanning electron microscope (SEM) images of the composite conductive coated and modified NCM811 particles prepared by the above soft ball milling method. It can be seen from the figure that the carbon nanotubes are relatively evenly coated on the surface of the NCM811 particles. The sphericity of the active particles after coating and modification is well retained, and the size is between 10 - 50 μm, which is basically not much different from that before coating.

[0099] Example 5: Preparation of Polyvinylidene Fluoride / Carbon Nanotube Composite Coated and Modified NCM811 Particles (PVDF-CNT@NCM) by Polyvinylidene Fluoride Soft Ball Milling

[0100] Put 45 parts by mass of lithium nickel cobalt manganate (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 54 parts by mass of polyvinylidene fluoride (PVDF) particles as soft ball milling media (oblate particles, circular cross-sectional diameter of about 5 mm), and 1 part by mass of carbon nanotube CNT powder (fiber aggregate shape, average outer diameter of a single CNT of about 10 nm, average length of about 20 μm) into a 100 mL ball milling jar. The initial temperature of the material and the ball milling jar is about 23 °C at room temperature. After 15 minutes of ball milling, it is naturally cooled and discharged to obtain NCM811 particles with PVDF / CNT composite conductive coating.

[0101] Figure 8 a-d are the micro scanning electron microscope (SEM) images of the composite conductive coated and modified NCM811 particles prepared by the above soft ball milling method. It can be seen from the figure that the carbon nanotubes are relatively evenly coated on the surface of the NCM811 particles. The sphericity of the active particles after coating and modification is well retained, and the size is between 10 - 50 μm, which is basically not much different from that before coating.

[0102] Example 6: Preparation of Poly(butylene adipate-co-terephthalate) (PBAT) / Carbon Nanotube Composite Coated and Modified NCM811 Particles (PBAT-CNT@NCM) by Soft Ball Milling of Poly(butylene adipate-co-terephthalate)

[0103] 45 parts by mass of lithium nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 54 parts by mass of poly(butylene adipate-co-terephthalate) (PBAT) particles as soft ball milling media (nearly oval particles, oval cross-section length about 4 mm), and 1 part by mass of carbon nanotube CNT powder (fiber agglomerate shape, average outer diameter of single CNT about 10 nm, average length about 20 μm) were placed in a 100 mL ball milling jar. The initial temperature of the material and the ball milling jar was about 23 °C at room temperature. After 15 minutes of ball milling, it was naturally cooled and discharged to obtain NCM811 particles with PBAT / CNT composite conductive coating.

[0104] Figure 9 a-d are the micro scanning electron microscope (SEM) images of the composite conductive coated and modified NCM811 particles prepared by the above soft ball milling method. It can be seen from the figure that the carbon nanotubes are relatively evenly coated on the surface of the NCM811 particles. The sphericity of the active particles after coating and modification is well retained, and the size is between 10 and 50 μm, which is basically not much different from that before coating.

[0105] Example 7: Preparation of Poly(lactic acid) / Carbon Nanotube Composite Coated and Modified NCM811 Particles (PLA-CNT@NCM) by Soft Ball Milling of Poly(lactic acid)

[0106] 45 parts by mass of lithium nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 54 parts by mass of poly(lactic acid) particles as soft ball milling media (nearly oval particles, oval cross-section length about 4 mm), and 1 part by mass of carbon nanotube CNT powder (fiber agglomerate shape, average outer diameter of single CNT about 10 nm, average length about 20 μm) were placed in a 100 mL ball milling jar. The initial temperature of the material and the ball milling jar was about 23 °C at room temperature. After 15 minutes of ball milling, it was naturally cooled and discharged to obtain NCM811 particles with PLA / CNT composite conductive coating.

[0107] Figure 10 a-d are the micro scanning electron microscope (SEM) images of the composite conductive coated and modified NCM811 particles prepared by the above soft ball milling method. It can be seen from the figure that the carbon nanotubes are relatively evenly coated on the surface of the NCM811 particles. The sphericity of the active particles after coating and modification is well retained, and the size is between 10 and 50 μm, which is basically not much different from that before coating.

[0108] Example 8: Preparation of Polyacrylic Acid / Conductive Carbon Black Composite Coated and Modified NCM811 Particles (PP-PAA-CB@NCM) by Polypropylene Soft Ball Milling

[0109] 44 parts by mass of lithium nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 54 parts by mass of polypropylene (PP) particles as soft ball milling media (cylindrical particles, cross-sectional diameter of about 2 mm, cylindrical length of about 5 mm), and 1 part by mass of polyacrylic acid particles (near-spherical particles, size of about 300 nm) were placed in a 100 mL ball milling jar and pre-soft ball milled for 15 min first, and then 1 part by mass of conductive carbon black Super P (near-spherical particles, median particle size D50 = 40 nm) was introduced into it, and the soft ball milling was continued for 15 min. The initial temperature of the material and the ball milling jar was about 80 °C, and the material was discharged after natural cooling to obtain NCM811 particles with polypropylene, polyacrylic acid / conductive carbon black composite conductive coating.

[0110] Figure 11 a-d are the micro scanning electron microscope (SEM) images of the composite conductive coated and modified NCM811 particles prepared by the above soft ball milling method. It can be seen from the figure that polyacrylic acid, polypropylene, and conductive carbon black are relatively evenly coated on the surface of the NCM811 particles. The sphericity of the coated and modified active particles is well retained, and the size is between 10 and 50 μm, which is basically not much changed compared with that before coating.

[0111] Example 9: Preparation of Polypropylene / Conductive Carbon Black Composite Coated and Modified NCM811 Particles (PP-CB@NCM) by Polypropylene Soft Ball Milling

[0112] 45 parts by mass of lithium nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 54 parts by mass of polypropylene (PP) particles as soft ball milling media (cylindrical particles, cross-sectional diameter of about 2 mm, cylindrical length of about 5 mm), and 1 part by mass of conductive carbon black Super P (near-spherical particles, median particle size D50 = 40 nm) were placed in a 100 mL ball milling jar, and the initial temperature of the material and the ball milling jar was about 23 °C at room temperature. After ball milling for 30 min, the material was discharged after natural cooling to obtain NCM811 particles with PP / CB composite conductive coating.

[0113] Figure 12 a-d are the micro scanning electron microscope (SEM) images of the composite conductive coated and modified NCM811 particles prepared by the above soft ball milling method. It can be seen from the figure that polypropylene and conductive carbon black are evenly coated on the surface of the NCM811 particles. The sphericity of the coated and modified active particles is well retained, and the size is between 10 and 50 μm, which is basically not much changed compared with that before coating.

[0114] Example 10: Preparation of polypropylene / carbon nanotube composite-coated and modified lithium iron phosphate LFP particles (PP-CNT@LFP) by polypropylene soft ball milling

[0115] 45 parts by mass of lithium iron phosphate LFP (LiFePO4) powder (irregular particles, median particle size D50 = 1 μm), 54 parts by mass of polypropylene (PP) particles as soft ball milling media (cylindrical particles, cross-sectional diameter of about 2 mm, cylindrical length of about 5 mm), and 1 part by mass of carbon nanotube powder (fiber agglomerate shape, average outer diameter of about 10 nm for single CNT, average length of about 20 μm) were placed in a 100 mL ball milling jar. The initial temperature of the material and the ball milling jar was about 23°C at room temperature. After ball milling for 15 min, it was naturally cooled and discharged to obtain polypropylene / carbon nanotube composite-conductively coated LFP particles.

[0116] Figure 13 These are the micrographs of scanning electron microscopy (SEM) of the raw materials of lithium iron phosphate particles without CNT coating (a-b) and the composite-conductively coated and modified lithium iron phosphate particles prepared by the above soft ball milling method (c-f). It can be seen from the figure that the carbon nanotubes are relatively evenly coated on the surface of the lithium iron phosphate particles; the sphericity of the active particles after coating and modification is well retained, and the size is between 2 and 10 μm, which is basically not much different from that before coating.

[0117] Example 11: Preparation of polypropylene / carbon nanotube composite-coated and modified lithium cobalt phosphate LCO particles (PP-CNT@LCO) by polypropylene soft ball milling

[0118] 45 parts by mass of lithium cobalt oxide LCO (LiCoO2) powder (irregular particles, median particle size D50 = 10 μm), 54 parts by mass of polypropylene (PP) particles as soft ball milling media (cylindrical particles, cross-sectional diameter of about 2 mm, cylindrical length of about 5 mm), and 1 part by mass of carbon nanotube powder (fiber agglomerate shape, average outer diameter of about 10 nm for single CNT, average length of about 20 μm) were placed in a 100 mL ball milling jar. The initial temperature of the material and the ball milling jar was about 23°C at room temperature. After ball milling for 15 min, it was naturally cooled and discharged to obtain polypropylene / carbon nanotube composite-conductively coated LCO particles.

[0119] Figure 14 These are the micrographs of scanning electron microscopy (SEM) of the raw materials of lithium cobalt oxide particles without CNT coating (a-b) and the composite-conductively coated and modified lithium cobalt oxide particles prepared by the above soft ball milling method (c-f). It can be seen from the figure that the carbon nanotubes are relatively evenly coated on the surface of the lithium cobalt oxide particles. The sphericity of the active particles after coating and modification is well retained, and the size is between 10 and 20 μm, which is basically not much different from that before coating.

[0120] Example 12: Preparation of Polypropylene / Carbon Nanotube Composite Coated Modified Graphite Particles (PP-CNT@Graphite) by Soft Milling of Polypropylene

[0121] 45 parts by mass of graphite (Gr) powder (flaky particles, median particle size D50 = 20 μm), 54 parts by mass of polypropylene (PP) particles as soft milling media (cylindrical particles, cross-sectional diameter of about 2 mm, cylindrical length of about 5 mm), and 1 part by mass of carbon nanotube powder (fiber agglomerate shape, average outer diameter of a single CNT of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball milling jar. The initial temperature of the material and the ball milling jar was about room temperature (23 °C). After ball milling for 15 min, it was naturally cooled and discharged to obtain graphite particles with polypropylene / carbon nanotube composite conductive coating.

[0122] Figure 15 These are the micro scanning electron microscopy (SEM) images of the raw graphite particles without CNT coating (a - b) and the composite conductive coated modified graphite particles prepared by the above soft milling method (c - f). It can be seen from the figure that the carbon nanotubes are relatively uniformly coated on the surface of the graphite particles. The shape of the graphene flaky particles after coating modification is well retained, and the long-end size is between 15 and 25 μm, which is basically not much changed compared with that before coating.

[0123] Performance Test: Conductivity of Active Particles Coated and Modified with Different Soft Milling Media

[0124] Weigh 0.1 g of the active particle powder coated and modified in each of the above comparative examples and examples, apply a fixed pressure to it using a rheometer, and then measure the resistance of the powder using a multimeter. Table 1 shows the conductivity of the active particles coated and modified with different soft milling media under different pressures. It can be seen from the table that coating and modifying the surface of active particles with different soft milling media can significantly improve the conductivity of active particles.

[0125] Table 1. Conductivity of Active Particles Coated and Modified with Different Soft Milling Media under Different Pressures

[0126]

[0127] Application Example 1: Wet Preparation of Electrode Sheets Based on Soft Milling Coated and Modified Active Materials

[0128] According to the ratio of 93:7 of the mass fraction of the coated modified active material and the polymer binder in the dry electrode, the PP-CNT@NCM811 particles prepared in Example 4 and the binder solution (4.5 wt% PVDF binder solution, the solvent is NMP) are mechanically stirred and blended; after the blending to obtain a uniform slurry, it is scraped on the surface of the aluminum foil with a 250 μm scraper, dried at 105°C for 1 h, and then rolled and placed in a vacuum oven at 120°C for deep drying to obtain a wet electrode plate. The active material loading of the plate is about 8 mg / cm 2 .

[0129] Comparative Example 4: Traditional wet method for preparing electrode sheets

[0130] The conventional electrode sheet is prepared by mechanically stirring and blending NCM811, CNT and adhesive solution (4.5 wt% PVDF adhesive solution, solvent is NMP) according to the mass ratio of active particles, conductive carbon nanotubes and adhesive in the dry electrode of 92:1:7; after blending to obtain a uniform slurry, it is scraped on the surface of aluminum foil with a 250 μm scraper, dried at 105°C for 1h, and then rolled and placed in a vacuum oven at 120°C for deep drying to obtain a wet electrode sheet.

[0131] Figure 16 It is a comparison diagram of the microstructure of the wet-process electrode plates prepared by the above-mentioned uncoated modified NCM811 (Comparative Example 4, ac) and PP-CNT coated modified NCM811 (Application Example 1, df). It can be seen from the figure that there are more agglomerations in the wet-process electrode plate structure prepared by the uncoated modified NCM811, the dispersion effect of the conductive agent CNT and the adhesive is poor, and the electrode plate uniformity is poor. There is no obvious agglomeration in the wet-process electrode plate structure prepared by the PP-CNT coated modified NCM811, the conductive agent CNT is stably and evenly maintained on the surface of the active particles, the adhesive can also be evenly dispersed on the surface of the active particles and between the active particles, and the electrode plate has good uniformity.

[0132] In the present invention, unless otherwise specified, the coating layer in the coated modified lithium nickel cobalt manganese oxide (NCM811) refers to a composite coating of polymer and carbon nanotubes.

[0133] The resistance of the obtained electrode was characterized and tested using the four-probe test mode of the KEITHLEY equipment. Figure 17 The figure is a comparison of the resistance of the wet electrode sheet prepared by the above-mentioned uncoated modified NCM811 (Comparative Example 4) and the PP-CNT coated modified NCM811 (Application Example 1). As can be seen from the figure, the resistance of the wet electrode sheet prepared by the uncoated modified NCM811 is about 150 Ω, combined with Figure 16The microscopic morphology of the electrode sheet without CNT coating shows obvious agglomeration of the conductive agent CNT, and a complete and continuous conductive path cannot be formed inside the electrode, resulting in a relatively large resistance of the electrode sheet. The resistance of the wet electrode sheet prepared from PP-CNT-coated NCM811 is about 15 Ω, combined with Figure 16 The microscopic morphology of the electrode sheet with CNT coating shows that the conductive agent CNT is stably and uniformly maintained on the surface of the active particles, a complete conductive path is formed inside the electrode, the resistance of the electrode sheet is low, and it has good conductivity.

[0134] Application Example 2: Preparation of an electrode sheet by wet method based on soft ball milling-coated modified active material

[0135] According to the ratio of 98:2 by mass of the coated modified active material to the polymer binder in the dry electrode, the PP-CNT@NCM811 particles (Example 4) and the binder solution (4.5 wt% PVDF binder solution with NMP as the solvent) were mechanically stirred and blended; after obtaining a homogeneous slurry by blending, it was doctor-bladed on the surface of the aluminum foil with a 250 μm doctor blade, dried at 105 °C for 1 h, then roll-pressed and placed in a vacuum oven at 120 o C for deep drying to obtain a wet electrode sheet, and the active material loading of the electrode sheet is about 20 ± 1 mg / cm 2 .

[0136] Comparative Example 5: Electrochemical rate performance of a traditional wet-prepared electrode sheet

[0137] For the traditional electrode sheet, according to the ratio of 97:1:2 by mass of the active particles, conductive agent (carbon nanotubes or carbon black), and binder in the dry electrode, NCM811, the conductive agent, and the binder solution (4.5 wt% PVDF binder solution with NMP as the solvent) were mechanically stirred and blended; after obtaining a homogeneous slurry by blending, it was doctor-bladed on the surface of the aluminum foil with a 250 μm doctor blade, dried at 105 °C for 1 h, then roll-pressed and placed in a vacuum oven at 120 °C for deep drying to obtain a wet electrode sheet, and the active material loading of the electrode sheet is about 20 ± 1 mg / cm 2 .

[0138] The prepared electrode sheet was cut into a 12 mm diameter circular sheet as the positive electrode, a 16 mm diameter lithium metal sheet was used as the negative electrode, an 18 mm PP / PE three-layer film was used as the separator, and a Kelude ternary commercial electrolyte was used as the electrolyte to assemble a CR2032 half-cell for electrochemical performance testing (rate performance, cycle performance testing). The testing was carried out in an environment with a constant temperature of 30 °C and a humidity of 20%.

[0139] Figure 18It is the rate performance of half-cells assembled with the electrode sheet prepared from the above uncoated and modified NCM811 (Comparative Example 5) and the electrode sheet prepared from the PP-CNT coated and modified NCM811 (Application Example 2). As can be seen from the figure, the discharge specific capacity of the half-cell assembled with the PP-CNT coated and modified NCM is greater than that of the half-cell assembled with the uncoated and modified NCM at different rates. Among them, the discharge specific capacity at 0.1C rate is 215 mAh / g, the discharge specific capacity at 0.5C rate is 190 mAh / g, the discharge specific capacity at 1C rate is 160 mAh / g, and finally the discharge specific capacity at 0.1C rate again is 213 mAh / g, which is almost the same as the discharge specific capacity at the initial 0.1C rate, showing good rate performance.

[0140] In the half-cell assembled with the uncoated and modified NCM, when using CNT as the conductive agent, the discharge specific capacity at 0.1C rate is only 55 mAh / g, the discharge specific capacity at 0.5C rate is only 17 mAh / g, and the discharge specific capacity at 1C rate is only 8 mAh / g. Its discharge specific capacity and capacity attenuation rate at different rates are much greater than the electrochemical data of the half-cell assembled with the coated and modified NCM, and it cannot be charged and discharged normally at 0.1C rate after high-rate charge and discharge, and the rate performance is poor. In commercial electrodes, the most commonly used conductive agent is carbon black (CB). In the uncoated and modified half-cell using CB as the conductive agent, the discharge specific capacity at 0.1C rate is 192 mAh / g, the discharge specific capacity at 0.5C rate is 142 mAh / g, the discharge specific capacity at 1C rate is 100 mAh / g, and finally the discharge specific capacity at 0.1C rate again is 178 mAh / g, showing a small decrease compared with the discharge specific capacity at 0.1C rate, and the overall rate performance is not as good as that of the half-cell prepared with the coated and modified NCM.

[0141] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, making several equivalent substitutions or obvious modifications, and having the same performance or use, should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A coated modified particle, characterized in that, The preparation raw materials of the modified particles include polymer pellets, particles to be coated, and functional additives; by using the polymer pellets as soft ball friction media, through the collision and friction adhesion with the particles to be coated and functional additives, a coating layer is formed on the surface of the particles to be coated, and the coating layer is a polymer coating or a composite coating formed by the polymer and the functional additives; wherein, the surface hardness or elastic modulus of the polymer pellets is less than that of the particles to be coated, and the maximum dimension of the geometric shape of the particles to be coated is less than the minimum dimension of the geometric shape of the polymer pellets; the proportion of each raw material is: 40-80 parts by weight of polymer pellets, 20-60 parts by weight of particles to be coated, and 0-20 parts by weight of functional additives; The polymer pellets are selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, ethylene-propylene rubber, styrene-butadiene rubber, polymethyl methacrylate, polyacrylonitrile, polyamide, polyethylene, polypropylene, polyoxymethylene, poly(vinylidene fluoride-hexafluoropropylene), polyethylene-polyethylene oxide copolymer, polystyrene, polyvinylpyrrolidone, polyethylene oxide, polymaleic anhydride, polyacrylic acid, sodium polyacrylate, polyethanol, polyurethane, polyamide, polystyrene sulfonic acid, sodium polystyrene sulfonate, lithium polystyrene sulfonate, polylactic acid, lithium polyacrylate, polycarbonate, polypropylene carbonate, thermoplastic elastomer or natural rubber; The particles to be coated are electrochemically active particles; The functional additives include at least one of multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, carbon microfibers, halloysite nanotubes, nano-conductive carbon black, Mxene micro-nano particles, graphene oxide, graphene, graphite, zirconia, titanium dioxide, aluminum oxide, PVDF nano-particles, PAA nano-particles, PEO nano-particles, SBR elastomer nano-particles, ethylene-propylene rubber nano-particles, thermoplastic elastomer nano-particles, halide solid electrolyte micro-nano particles, oxide solid electrolyte micro-nano particles or sulfide solid electrolyte micro-nano particles; 2. The coated modified particle according to claim 1, wherein, The thickness of the coating layer on the surface of the coated and modified particles is adjustable within 1-1000 nm; 3. A coated modified particle according to claim 1 or 2, wherein The particles to be coated are selected from at least one of lithium nickel cobalt manganese oxide, sodium lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, sodium lithium nickel cobalt aluminate, lithium manganate, sodium manganate, lithium iron phosphate, sodium iron phosphate, lithium-rich manganese-based cathode material, sodium-rich manganese-based cathode material, lithium cobalt oxide, sodium cobalt oxide, graphite, graphitized carbon fiber, lithium titanate, hard carbon, silicon particles, silicon-carbon composite particles or activated carbon particles; 4. A method for preparing a coated and modified particle according to any one of claims 1 to 3, characterized in that, The preparation method is: first premix each raw material evenly, and then mechanically mix for 30 s to 3 h under the environmental conditions of -20°C to 300°C; finally, the coated and modified particles can be obtained through cooling and screening.

5. Application of a coated and modified particle according to any one of claims 1 to 3 in the preparation of an electrode sheet for a wet or dry battery, an electrode sheet for a solid-state battery, or an electrode sheet for a supercapacitor.

6. A wet preparation method for positive and negative electrode sheets of a battery, characterized in that, The preparation method is as follows: Mix one kind of coated and modified particle, polymer binder, and conductive agent described in any one of claims 1 to 3 to prepare a uniform wet slurry; then prepare a structurally uniform and controllable electrode sheet through coating, drying, and rolling; wherein, the mass ratio of each raw material in the solid state is: 60 to 99.9 parts by weight of the coated and modified particle, 0.1 to 40 parts by weight of the polymer binder, and 0 to 20 parts by weight of the conductive agent.

7. A dry preparation method for positive and negative electrode sheets of a battery, characterized in that, The preparation method is as follows: Premix the coated and modified particle, polymer binder, and conductive agent described in any one of claims 1 to 3 to obtain a dry slurry for pre-forming fibers; then obtain a dry-process electrode sheet through rolling; wherein, the mass ratio of each raw material in the solid state is: 60 to 99.9 parts by weight of the coated and modified particle, 0.1 to 40 parts by weight of the polymer binder, and 0 to 20 parts by weight of the conductive agent.

8. A method for preparing positive and negative electrode sheets of a solid-state battery, characterized in that, The preparation method is as follows: Mix the coated and modified particle, polymer binder, solid-state electrolyte, and conductive agent described in any one of claims 1 to 3 to prepare a wet or dry slurry; then prepare a solid-state electrode sheet through coating, drying, and rolling; wherein, the mass ratio of each raw material in the solid state is: 60 to 99.9 parts by weight of the coated and modified particle, 0.1 to 40 parts by weight of the polymer binder, 0 to 20 parts by weight of the conductive agent, and 0.1 to 40 parts by weight of the solid-state electrolyte.

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