Soft ball-milled coated modified particles as well as preparation method and application thereof

Abstract

The invention relates to soft ball-milled coated modified particles as well as a preparation method and application thereof, and belongs to the field of particle modification. The invention provides coated modified particles and a preparation technology thereof. The coated modified particles are prepared from polymer particles, particles to be coated and a functional additive, polymer granules are used as a soft ball milling friction medium, and a pure polymer coating layer or a composite coating layer of a polymer and a functional additive is formed on the surface of the to-be-coated particles through collision and friction adhesion with the to-be-coated particles and the functional additive; wherein the surface hardness or elastic modulus of the polymer is smaller than that of the to-be-coated particles, and the maximum size of the geometrical shape of the to-be-coated particles is smaller than the minimum size of the geometrical shape of the polymer pellets. The method has the remarkable advantages of being wide in applicability, high in large-scale capacity, low in processing cost, green, low in carbon and the like, and therefore the method has good application prospects.

Description

Technical Field

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

[0002] Surface coating modification of powder particles plays an extremely important role in the fields of energy materials, functional nanopowders and their composite materials. Especially with the strong demand for clean energy technology, we urgently need to vigorously develop clean energy storage technology. Electrochemical energy storage, as the most mature and widely used clean energy storage technology, plays a vital role in it. 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 technology, there is an urgent need to develop lithium-ion batteries with higher energy density and power density to meet market demand.

[0003] The energy density of commercial lithium-ion batteries on the market is gradually approaching a bottleneck. On the one hand, this is because the actual capacity of active materials is getting closer and closer to their theoretical specific capacity. On the other hand, the preparation of high-performance electrodes with stable structures and electrochemical properties based on high-capacity active materials is facing multiple challenges. First, high-capacity active materials are often prone to serious side reactions or ion dissolution with the electrolyte, resulting in accelerated capacity decay; on the other hand, due to the inherent limitations of wet electrode slurries, electrode cracking and uneven aggregation of components during the drying process, such as the migration of adhesives and conductive agents, will inevitably occur when preparing high-load electrodes, thereby limiting the further improvement of electrode energy density. On the other hand, the development and popularization of new energy vehicles have led to higher and higher requirements for the power density of power batteries. The power density of the battery is closely related to the ability of the electrodes to conduct electrons and ions.

[0004] Developing surface functional modification technology for active particles is an effective strategy to solve the above problems. At present, the most common strategy to meet this major demand is to coat active materials with conductive functions. The reported coating strategies mainly include chemical vapor deposition, atomic layer deposition, hydrothermal method, solution method and ball milling method. Although chemical vapor deposition and atomic layer deposition have high coating accuracy, their high cost and difficulty in scale-up limit their wide application. The hydrothermal method is difficult to be applied on a large scale due to its low efficiency, poor coating effect and limited applicable active material system. Ball milling is one of the few methods that has achieved large-scale application, but its coating controllability is poor, and the coated particles are severely damaged, deformed or crushed during the coating process. These problems mean that the development of new solvent-free, low-carbon, green, low-cost, efficient, scalable and nearly lossless particle coating modification technology will have great technical value and practical significance. Summary of the invention

[0005] In view of the above-mentioned defects, the present invention provides a coated modified particle and a preparation method thereof, wherein the raw materials include polymer granules (as soft ball milling media) and particles to be coated; wherein the polymer granules are used as soft ball milling media, and can achieve the soft ball milling coating modification of the particles by the way of friction adhesion transfer, that is, the polymer is bonded to the surface of the particles to be coated. In addition, according to application requirements, functional additives can also be introduced into the system as a third component, and the third component can be a functional additive 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 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, wherein the raw materials for preparing the modified particle include polymer granules, particles to be coated and functional additives; by using the polymer granules as a soft ball milling friction medium, and through collision and friction adhesion with the particles to be coated and the 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 layer formed by a polymer and a functional additive; wherein the surface hardness or elastic modulus of the polymer is smaller 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 smaller than the minimum size of the geometric shape of the polymer granules; the proportion of each raw material is: 1 to 99 parts by weight of polymer granules, 1 to 99 parts by weight of particles to be coated, and 0 to 50 parts by weight of functional additives.

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

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

[0010] Furthermore, the coated modified particles include 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 of a polymer and a functional additive.

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

[0012] Furthermore, the thickness of the coating layer on the surface of the modified particles can be adjusted within the range of 1 to 1000 nm, but is optimally controlled to be 1 to 100 nm.

[0013] Furthermore, the shape of the polymer pellets can be spherical, ellipsoidal, spindle-shaped, cylindrical, disc-shaped and one or more combinations of irregular particle shapes, but preferably regular shapes such as spherical, ellipsoidal, spindle-shaped, cylindrical or disc-shaped and combinations thereof.

[0014] Furthermore, any polymer material whose surface hardness or elastic modulus of the polymer in the polymer granules is smaller than that of the surface hardness or elastic modulus of the particles to be coated, including but not limited to: at least one of 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, polypyrrolidone, thermoplastic elastomer, natural rubber, cellulose, protein, natural polysaccharide, various thermosetting resins, various thermoplastic resins, various engineering or special engineering plastics, etc.

[0015] Furthermore, the polymer pellets can be directly selected from polymer pellets of various shapes obtained by granulation with an extruder.

[0016] Furthermore, the geometric shape of the particles to be coated is not limited, but is preferably spherical, elliptical, cylindrical, or polyhedral.

[0017] Furthermore, the particles to be coated can be electrochemically active particles or metal particles or metal alloy particles or inorganic ceramic particles in various secondary ion batteries or supercapacitors, including but not limited to various positive and negative active material particles for lithium ion batteries, positive and negative active material powders for sodium ion batteries, and active material particles for supercapacitors, etc. Specifically including 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 positive electrode materials, lithium cobalt oxide (sodium), graphite particles, graphitized carbon fibers, 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.

[0018] Further, the functional additive (third component) can be various functional materials for electron conduction and ion conduction, specifically including but not limited to: carbon nanotubes, carbon nanofibers, halloysite nanotubes, various nano-conductive carbon blacks, graphene oxide, graphene, zirconium oxide, titanium dioxide, aluminum oxide, various sulfide inorganic electrolyte micro-nano particles, various oxide ceramic inorganic electrolyte micro-nano particles, PVDF polymer nanoparticles, PAA polymer nanoparticles, PEO nanoparticles, various halide solid electrolyte micro-nano particles, various metals and their oxide micro-nano particles, etc. At least one of the above.

[0019] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned coated modified particles, the preparation method being: first premixing the raw materials evenly, then mechanically mixing them at -20°C to 300°C for 30s to 3h; finally, cooling and screening to obtain the coated modified particles.

[0020] Furthermore, the mechanical mixing method is selected from at least one of ball milling oscillation, mechanical pressure stirring, gravity flipping or extruder screw shear mixing, etc.; in the above preparation process, under the action of mechanical mixing, the polymer particles in the raw materials act as soft ball milling friction medium, and collide and frictionally adhere with the particles to be coated and the functional additives to form a coating layer on the surface of the particles to be coated; in the internal friction adhesion transfer stage, the material can produce the required friction adhesion transfer through any mechanical mixing method such as ball milling oscillation, mechanical stirring, gravity flipping or extruder screw shear mixing; it can also simultaneously use external heat source and pressure to enhance the internal friction adhesion transfer effect, and the mixing time can be optimized according to the specific process control conditions. That is, in the mechanical mixing process, the material temperature, mixing intensity, and internal pressure can be coordinated and controlled to enhance the effect and efficiency of the internal friction adhesion transfer of the material.

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

[0022] Furthermore, cooling is performed by natural cooling or forced cooling with a cooling medium under conditions of slow mixing or stopped mixing.

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

[0024] Furthermore, the thickness of the coating modification layer can be coordinated and controlled by the proportion of each component of 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 for wet or dry preparation of battery electrode plates, solid-state battery electrode plates, supercapacitor electrode plates, metal 3D printed parts, conductive nanocomposites, conductive slurries or sensor materials.

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

[0027] Furthermore, the ratio of raw materials for preparing the coated modified particles is: 40 to 80 parts by weight of polymer granules, 20 to 60 parts by weight of particles to be coated, and 0 to 20 parts by weight of functional additives.

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

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

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

[0031] Compared with the electrode sheets prepared by the conventional wet method of uncoated active particles, the electrode sheets prepared by the present invention based on the polymer soft ball milling have the following structural advantages and characteristics, and 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 the conductive agent; second, the drying process also avoids the problem of uncontrollable aggregation of components (especially adhesive and conductive agent components), and can achieve more uniform and firm interface bonding between the active particles and the three components of the adhesive and the conductive agent; second, the electronic transmission network of the electrode sheet is mainly formed by the overlapping of the conductive coating layers on the surfaces of the active particles, so the conductive network is more controllable, stable and efficient; finally, since there is no large amount of loose conductive agent and adhesive filling in the stacking gaps between the active particles, it becomes more unobstructed and is conducive to the efficient transmission 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 being: premixing the above-prepared coated modified particles (the particles to be coated are active material powders), a polymer binder (such as a PTFE powder binder) and a conductive agent to obtain a pre-fibered dry slurry; then rolling to obtain a dry electrode sheet (PTFE fiberization and its interface bonding with the composite coated modified particles are achieved by means of the pressure and temperature control process of rolling); wherein the mass ratio of each raw material is: 60 to 99.9 parts by weight of coated modified particles, 0.1 to 40 parts by weight of polymer binder and 0 to 20 parts by weight of conductive agent.

[0033] Furthermore, in the above-mentioned dry preparation method of the positive and negative electrode sheets of the battery, the raw materials for preparing the coated modified particles include polymer granules, particles to be coated and functional additives, and the proportions of each raw material are: 40 to 80 parts by weight of polymer granules, 20 to 60 parts by weight of particles to be coated, and 0 to 20 parts by weight of functional additives.

[0034] Furthermore, in the dry preparation method of the positive and negative electrode sheets of the above-mentioned battery, the conductive agent is selected from: at least one of highly conductive micro-nano materials such as multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, carbon micron fibers, nano conductive carbon black, Mxene micro-nano particles, reduced graphene oxide, graphene, graphite or metal nanowires.

[0035] The obtained dry-process positive and negative electrode sheets have the following characteristics: the distribution of the conductive agent and the adhesive around the active particles is more controllable and uniform; the interfacial compatibility between the PTFE fiber adhesive and the active particles is greatly improved due to the polymer coating; and 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 pole piece, the preparation method being: mixing the above-prepared coated modified particles, polymer binder, conductive agent and solid electrolyte powder to prepare a wet or dry slurry; then preparing the solid-state electrode pole piece through coating, drying rolling and other processes; wherein the mass ratio of each raw material is: 60 to 99.9 parts by weight of coated modified particles, 0.1 to 40 parts by weight of polymer binder, 0 to 20 parts by weight of conductive agent, and 0.1 to 40 parts by weight of solid electrolyte.

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

[0038] Furthermore, in the above-mentioned method for preparing the solid-state electrode plate, the conductive agent is selected from at least one of the highly conductive micro-nano materials such as multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, carbon micron fibers, 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 the active particles, while the solid electrolyte filling part contains only a small amount or even no electronic conductive agent.

[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 by coating modified particles, a separator, lithium metal and a commercial electrolyte; or: It is assembled from a positive electrode sheet prepared from coated modified particles, a separator, a lithium-free metal negative electrode sheet, and a commercial electrolyte; Wherein, the positive electrode sheet or negative electrode sheet prepared by coating the modified particles is prepared by adopting the above-mentioned preparation method of the positive and negative electrode sheets of wet-process batteries or the preparation method of the positive and negative electrode sheets of dry-process batteries.

[0041] Further, when the lithium (sodium) metal battery is a solid-state lithium (sodium) metal battery, the battery is assembled from a positive electrode prepared by the above-mentioned coated modified particles, a solid electrolyte separator and lithium metal; or: The positive electrode sheet, the solid electrolyte separator and the lithium-free negative electrode sheet prepared by the above-mentioned coated modified particles are assembled; Wherein, the positive electrode sheet or negative electrode sheet prepared by coating the modified particles is prepared by adopting the above-mentioned preparation method of the positive and negative electrode sheets of wet-process batteries or the preparation method of the positive and negative electrode sheets of dry-process batteries.

[0042] 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 by the above-mentioned coated modified particles, an electrolyte and a separator; Wherein, the positive electrode sheet or negative electrode sheet prepared by coating the modified particles is prepared by adopting the above-mentioned preparation method of the positive and negative electrode sheets of wet-process batteries or the preparation method of the positive and negative electrode sheets of dry-process batteries.

[0043] Beneficial effects of the present invention:

[0044] The present invention provides a coated modified particle and a preparation method thereof, wherein the raw materials include polymer granules, particles to be coated and a third component functional additive; wherein the polymer granules are used as soft ball milling media, and the polymer is bonded to the surface of the particles to be coated by friction adhesion transfer (i.e., the particles to be coated are not damaged during the entire process). In addition, functional additives may be introduced according to actual applications, and finally a coating layer of polymer or a composite of polymer and functional additive is formed on the surface of the particles to be coated.

[0045] The present invention provides a method for non-destructive coating and modification of particles that is low-cost, universal and scalable, and ultimately plays a key role in the green and environmentally friendly processing and preparation of high-energy-density electrodes, the manufacture of advanced liquid and solid-state power batteries, and functional nanocomposites. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 . SEM images of uncoated modified NCM811 particles: a SEM image of uncoated modified NCM811 particles at a magnification of 1,000 times; b SEM image of uncoated modified NCM811 particles at a magnification of 2,000 times; c SEM image of uncoated modified NCM811 particles at a magnification of 5,000 times; d SEM image of uncoated modified NCM811 particles at a magnification of 10,000 times.

[0047] Figure 2 . SEM images of pure polyacrylic acid coated modified nickel cobalt manganese oxide particles (Comparative Example 2) prepared by traditional hard ball milling: a SEM image of pure polyacrylic acid coated modified nickel cobalt manganese oxide particles prepared by traditional hard ball milling at a magnification of one thousand times; b SEM image of pure polyacrylic acid coated modified nickel cobalt manganese oxide particles prepared by traditional hard ball milling at a magnification of two thousand times; c SEM image of pure polyacrylic acid coated modified nickel cobalt manganese oxide particles prepared by traditional hard ball milling at a magnification of five thousand times; d SEM image of pure polyacrylic acid coated modified nickel cobalt manganese oxide particles prepared by traditional hard ball milling at a magnification of ten thousand times.

[0048] Figure 3. SEM images of polyacrylic acid / carbon nanotube composite coated modified NCM811 particles prepared by traditional ball milling method (Comparative Example 3): a SEM image of polyacrylic acid / carbon nanotube composite coated modified NCM811 particles prepared by traditional ball milling method at a magnification of one thousand times; b SEM image of polyacrylic acid / carbon nanotube composite coated modified NCM811 particles prepared by traditional ball milling method at a magnification of two thousand times; c SEM image of polyacrylic acid / carbon nanotube composite coated modified NCM811 particles prepared by traditional ball milling method at a magnification of five thousand times; d SEM image of polyacrylic acid / carbon nanotube composite coated modified NCM811 particles prepared by traditional ball milling method at a magnification of fifteen thousand times.

[0049] Figure 4 . Microscopic scanning electron microscope (SEM) images and transmission electron microscope (TEM) images of polypropylene / polyacrylic acid coated modified nickel cobalt manganese oxide particles (Example 1): a SEM image of polypropylene / polyacrylic acid coated modified nickel cobalt manganese oxide particles at a magnification of 800 times; b SEM image of polypropylene / polyacrylic acid coated modified nickel cobalt manganese oxide particles at a magnification of 2,500 times; c SEM image of polypropylene / polyacrylic acid coated modified nickel cobalt manganese oxide particles at a magnification of 5,000 times; d TEM image of polypropylene / polyacrylic acid coated modified nickel cobalt manganese oxide particles at a scale of 100 nanometers; e TEM image of polypropylene / polyacrylic acid coated modified nickel cobalt manganese oxide particles at a scale of 100 nanometers; f TEM image of polypropylene / polyacrylic acid coated modified nickel cobalt manganese oxide particles at a scale of 50 nanometers.

[0050] Figure 5 . SEM images of polypropylene / polyacrylic acid / carbon nanotube composite coated modified nickel cobalt manganese oxide particles (Example 2): a SEM image of polypropylene / polyacrylic acid / carbon nanotube composite coated modified nickel cobalt manganese oxide particles at a magnification of one thousand times; b SEM image of polypropylene / polyacrylic acid / carbon nanotube composite coated modified nickel cobalt manganese oxide particles at a magnification of two thousand times; c SEM image of polypropylene / polyacrylic acid / carbon nanotube composite coated modified nickel cobalt manganese oxide particles at a magnification of five thousand times; d SEM image of polypropylene / polyacrylic acid / carbon nanotube composite coated modified nickel cobalt manganese oxide particles at a magnification of twenty thousand times.

[0051] Figure 6. Microscopic scanning electron microscope (SEM) and transmission electron microscope (TEM) images of polyethylene / carbon nanotube composite coated modified NCM811 particles (Example 3): a SEM image of polyethylene / carbon nanotube composite coated modified NCM811 particles at a magnification of one thousand times; b SEM image of polyethylene / carbon nanotube composite coated modified NCM811 particles at a magnification of five thousand times; c SEM image of polyethylene / carbon nanotube composite coated modified NCM811 particles at a magnification of ten thousand times; d SEM image of polyethylene / carbon nanotube composite coated modified NCM811 particles at a magnification of ten thousand times; e TEM image of polyethylene / carbon nanotube composite coated modified NCM811 particles at a scale of one hundred nanometers; f TEM image of polyethylene / carbon nanotube composite coated modified NCM811 particles at a scale of one hundred nanometers, g TEM image of polyethylene / carbon nanotube composite coated modified NCM811 particles at a scale of fifty nanometers.

[0052] Figure 7 . SEM images of polypropylene / carbon nanotube composite coated modified NCM811 particles (Example 4): a SEM image of polypropylene / carbon nanotube composite coated modified NCM811 particles at a magnification of one thousand times; b SEM image of polypropylene / carbon nanotube composite coated modified NCM811 particles at a magnification of two thousand times; c SEM image of polypropylene / carbon nanotube composite coated modified NCM811 particles at a magnification of five thousand times; d SEM image of polypropylene / carbon nanotube composite coated modified NCM811 particles at a magnification of twenty thousand times.

[0053] Figure 8 . SEM images of polyvinylidene fluoride / carbon nanotube composite coated modified NCM811 particles (Example 5): a SEM image of polyvinylidene fluoride / carbon nanotube composite coated modified NCM811 particles at a magnification of one thousand times; b SEM image of polyvinylidene fluoride / carbon nanotube composite coated modified NCM811 particles at a magnification of two thousand times; c SEM image of polyvinylidene fluoride / carbon nanotube composite coated modified NCM811 particles at a magnification of five thousand times; d SEM image of polyvinylidene fluoride / carbon nanotube composite coated modified NCM811 particles at a magnification of ten thousand times.

[0054] Fig. 9. SEM images of poly(butylene adipate / terephthalate / carbon nanotube) composite coated modified NCM811 particles (Example 6): a SEM image of poly(butylene adipate / terephthalate / carbon nanotube) composite coated modified NCM811 particles at a magnification of 1,000 times; b SEM image of poly(butylene adipate / terephthalate / carbon nanotube) composite coated modified NCM811 particles at a magnification of 2,000 times; c SEM image of poly(butylene adipate / terephthalate / carbon nanotube) composite coated modified NCM811 particles at a magnification of 5,000 times; d SEM image of poly(butylene adipate / terephthalate / carbon nanotube) composite coated modified NCM811 particles at a magnification of 10,000 times.

[0055] Fig.10 . SEM images of polylactic acid / carbon nanotube composite coated modified NCM811 particles (Example 7): a SEM image of polylactic acid / carbon nanotube composite coated modified NCM811 particles at a magnification of one thousand times; b SEM image of polylactic acid / carbon nanotube composite coated modified NCM811 particles at a magnification of two thousand times; c SEM image of polylactic acid / carbon nanotube composite coated modified NCM811 particles at a magnification of five thousand times; d SEM image of polylactic acid / carbon nanotube composite coated modified NCM811 particles at a magnification of ten thousand times.

[0056] Fig.11 . SEM images of polypropylene / polyacrylic acid / conductive carbon black composite coated modified NCM811 particles (Example 8): a SEM image of polypropylene / polyacrylic acid / conductive carbon black composite coated modified NCM811 particles at a magnification of one thousand times; b SEM image of polypropylene / polyacrylic acid / conductive carbon black composite coated modified NCM811 particles at a magnification of two thousand times; c SEM image of polypropylene / polyacrylic acid / conductive carbon black composite coated modified NCM811 particles at a magnification of five thousand times; d SEM image of polypropylene / polyacrylic acid / conductive carbon black composite coated modified NCM811 particles at a magnification of twenty thousand times.

[0057] Fig.12 . SEM images of polypropylene / conductive carbon black composite coated modified NCM811 particles (Example 9): a SEM image of polypropylene / conductive carbon black composite coated modified NCM811 particles at a magnification of one thousand times; b SEM image of polypropylene / conductive carbon black composite coated modified NCM811 particles at a magnification of two thousand times; c SEM image of polypropylene / conductive carbon black composite coated modified NCM811 particles at a magnification of five thousand times; d SEM image of polypropylene / conductive carbon black composite coated modified NCM811 particles at a magnification of ten thousand times.

[0058] Fig.13. SEM images of polypropylene / carbon nanotube composite coated modified lithium iron phosphate particles (Example 10) and lithium iron phosphate particles not coated with CNTs: a SEM image of lithium iron phosphate particles not coated with CNTs at a magnification of 5,000 times; b SEM image of lithium iron phosphate particles not coated with CNTs at a magnification of 20,000 times; c SEM image of polypropylene / carbon nanotube composite coated modified lithium iron phosphate particles at a magnification of 2,000 times; d SEM image of polypropylene / carbon nanotube composite coated modified lithium iron phosphate particles at a magnification of 5,000 times; e SEM image of polypropylene / carbon nanotube composite coated modified lithium iron phosphate particles at a magnification of 10,000 times; f SEM image of polypropylene / carbon nanotube composite coated modified lithium iron phosphate particles at a magnification of 25,000 times.

[0059] Fig.14 . SEM images of polypropylene / carbon nanotube composite coated modified lithium cobalt oxide particles (Example 11) and lithium cobalt oxide particles not coated with CNTs: a SEM image of lithium cobalt oxide particles not coated with CNTs at a magnification of 5,000 times; b SEM image of lithium cobalt oxide particles not coated with CNTs at a magnification of 10,000 times; c SEM image of modified lithium cobalt oxide particles coated with polypropylene / carbon nanotubes at a magnification of 1,000 times; d SEM image of modified lithium cobalt oxide particles coated with polypropylene / carbon nanotubes at a magnification of 2,000 times; e SEM image of modified lithium cobalt oxide particles coated with polypropylene / carbon nanotubes at a magnification of 4,000 times; f SEM image of modified lithium cobalt oxide particles coated with polypropylene / carbon nanotubes at a magnification of 15,000 times.

[0060] Fig.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 5,000 times; b SEM image of graphite particles without CNT coating at a magnification of 10,000 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 3,500 times; e SEM image of polypropylene / carbon nanotube composite coated modified graphite particles at a magnification of 11,000 times; f SEM image of polypropylene / carbon nanotube composite coated modified graphite particles at a magnification of 25,000 times.

[0061] Fig.16. SEM images of wet-process electrode sheets prepared from uncoated CNT-modified NCM811 (Comparative Example 4) and PP-CNT-coated modified NCM811 (Application Example 1): a SEM image of wet-process electrode sheets prepared from uncoated CNT-modified NCM811 at a magnification of 500 times; b SEM image of wet-process electrode sheets prepared from uncoated CNT-modified NCM811 at a magnification of 1,000 times; c SEM image of wet-process electrode sheets prepared from uncoated CNT-modified NCM811 at a magnification of 4,500 times; d SEM image of wet-process electrode sheets prepared from PP-CNT-coated CNT-modified NCM811 at a magnification of 500 times; e SEM image of wet-process electrode sheets prepared from PP-CNT-coated CNT-modified NCM811 at a magnification of 1,000 times; f SEM image of wet-process electrode sheet prepared by PP-CNT-coated CNT-modified NCM811 at a magnification of 4,500 times.

[0062] Fig.17 . Resistance diagram of wet-process electrode sheets prepared from uncoated modified NCM811 (Comparative Example 4) and PP-CNT coated modified NCM811 (Application Example 1).

[0063] Fig.18 . Rate performance diagram of half-cells assembled from uncoated modified NCM811 (Comparative Example 5) and PP-CNT coated modified NCM811 (Application Example 5). DETAILED DESCRIPTION

[0064] The invention provides a coated modified particle. The raw materials for preparing the modified particle include: polymer granules, particles to be coated and functional additives. The polymer granules are used as friction media, and the particles to be coated and the functional additives collide and adhere with each other to achieve surface coating of the polymer on the particles to be coated, or a blend formed by coating the polymer and the functional additives. The surface hardness or elastic modulus of the polymer is smaller than that of the particles to be coated, and the maximum size of the geometric shape of the particles to be coated is smaller than the minimum size of the geometric shape of the polymer granules. In addition, the proportion of each raw material is: 1 to 99 parts by weight of the polymer granules, 1 to 99 parts by weight of the particles to be coated, and 0 to 50 parts by weight of the functional additives.

[0065] The present invention provides a 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, the coating technology can effectively improve the electronic and ionic conductivity of the active particles, and significantly improve the microstructure and interface controllability, uniformity, stability, and final comprehensive electrochemical performance of their dry and wet electrode sheets.

[0066] When the soft ball milling method of the present invention is used to prepare coated modified active particles, the obtained coated modified particles can significantly improve at least one of the properties of the active particles in terms of conductivity, ion conductivity, and interfacial adhesion between the active particles and the binder compared to the uncoated modified particles; and after coating and modification, the size and shape of the active particles are not damaged or deformed compared to before coating. In addition, the coated modified active particles prepared based on the 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 secondary ion battery active materials, but is also applicable to supercapacitor active materials (such as activated carbon)

[0067] At the same time, the present invention is based on the liquid and solid electrode forming and processing technology developed by coating modified active materials, which can effectively solve the dispersion and bonding problems of slurry components, greatly improve the surface loading of active materials in electrode plates and the ability to regulate structure and morphology. This electrode processing method can achieve good dispersion of adhesives and conductive agents, which is beneficial to the electrochemical properties of active materials. At the same time, it can greatly increase the surface loading of active materials, greatly improve 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.

[0068] In addition, the modification method of the present invention has low requirements on equipment, simple production process flow, wide universality, green and environmentally friendly whole process, high production efficiency, and has broad prospects for large-scale industrial production and multi-field application.

[0069] The soft ball milling coating modification processing method adopted by the present invention can adopt a method comprising the following steps:

[0070] 1) Premixing stage: Premixing can be done in one-step or two-step methods. 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 as required) at a certain ratio at one time to obtain a uniformly mixed premix; the two-step method is to 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 to mix, and finally obtain a uniformly mixed premix.

[0071] 2) Internal friction adhesion transfer stage: The premix is ​​mechanically mixed; during the mechanical mixing process, the material temperature, mixing intensity, and internal pressure can be coordinated and controlled to enhance the effect and efficiency of the internal friction adhesion transfer of the material.

[0072] 3) Cooling and discharging stage: After mechanical mixing, the blend is cooled and sieved under appropriate mixing conditions to separate the coated modified powder and the polymer soft ball milling medium, and finally the coated modified powder sample and the coated modified polymer soft ball milling medium are obtained.

[0073] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technology in the embodiments of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. 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 related listed items.

[0074] Comparative Example 1: Uncoated modified NCM811 particles The present invention conducts microstructure detection on uncoated modified nickel cobalt manganese oxide (NCM811) particles. Figure 1 ad is the microscopic scanning electron microscope (SEM) image of the uncoated modified NCM811 particles. It can be seen from the image that the NCM811 particles are nearly spherical, with an uneven surface and many grooves, and the size is between 10-50 μm.

[0075] Comparative Example 2: Preparation of pure polyacrylic acid coated modified lithium nickel cobalt manganese oxide particles by conventional hard ball milling

[0076] 99 parts by mass of nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm) and 1 part by mass of polyacrylic acid nanopowder (spherical particles, median particle size D50 = 30 nm) were placed in a 100 mL ball mill, and the ball mill steel beads equipped with the equipment were added. The starting temperature of the material and the ball mill was about 80 °C; after 15 minutes of ball milling, the material was naturally cooled and discharged to obtain the treated NCM811 particles.

[0077] Figure 2 Figures ad are microscopic scanning electron microscope (SEM) images of polyacrylic acid coated modified NCM811 particles prepared by the above-mentioned traditional ball milling method. It can be seen from the figure that polyacrylic acid can also be coated on the surface of NCM811 particles, but there are two serious problems: on the one hand, the controllability of the coating layer structure is poor; on the other hand, the secondary particles of NCM811 are severely damaged, resulting in a significant reduction in sphericity and a large number of primary active particles crushed by steel balls.

[0078] Comparative Example 3: Traditional ball milling preparation of polyacrylic acid / conductive carbon nanotube composite-coated modified NCM811 particles

[0079] 98 parts by mass of nickel cobalt manganese oxide (NCM811) powder (spherical secondary particles, median particle size D50 = 12 μm), 1 part by mass of polyacrylic acid nanopowder (spherical particles, median particle size D50 = 30 nm) and 1 part by mass of carbon nanotube CNT powder (fiber aggregates, single CNT average outer diameter of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball mill, and the ball mill steel beads equipped with the equipment were added at the same time. The starting temperature of the material and the ball mill was about 80 °C. After 15 minutes of ball milling, the material was naturally cooled and discharged to obtain polyacrylic acid / CNT composite conductive coated NCM811 particles.

[0080] Figure 3 Figures ad are microscopic scanning electron microscope (SEM) images of the composite conductive coated modified NCM811 particles prepared by the above-mentioned 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 a lot of crushed primary active particles are produced.

[0081] Example 1: Preparation of polyacrylic acid@NCM coated modified particles by polypropylene soft ball milling

[0082] 45 parts by mass of 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 of about 2 mm, cylindrical length of about 5 mm) and 1 part by mass of polyacrylic acid nanopowder (spherical particles, median particle size D50 = 30 nm) were placed in a 100 mL ball mill (no steel balls were used in the ball mill). The starting temperature of the material and the ball mill was about 80 °C. After 15 minutes of ball milling, the material was naturally cooled and discharged to obtain polyacrylic acid-coated NCM811 particles.

[0083] Figure 4 Figures af are the microscopic scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the polyacrylic acid coated 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 active particles after coating and modification is well preserved, and the size is between 10 and 50 μm, which is basically the same as before coating. Through TEM observation, it is confirmed that the coating thickness is between 10 and 15 nm.

[0084] Example 2: Preparation of polyacrylic acid / carbon nanotube composite coated modified NCM811 particles (PAA-CNT@NCM) by polypropylene soft ball milling

[0085] 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 mill for pre-soft ball milling for 15 minutes, and then 1 part by mass of carbon nanotube CNT powder (fiber aggregates, single CNT average outer diameter of about 10 nm, average length of about 20 μm) was introduced into it, and soft ball milling was continued for 15 minutes. The starting temperature of the material and the ball mill was about 80°C, and the material was naturally cooled and discharged to obtain polyacrylic acid / CNT composite conductive coated NCM811 particles.

[0086] Figure 5 Figures ad are microscopic scanning electron microscope (SEM) images of the composite conductive coated modified NCM811 particles prepared by the soft ball milling method. It can be seen from the figure that polyacrylic acid and carbon nanotubes are relatively evenly coated on the surface of NCM811 particles. The sphericity of the active particles after coating and modification is well preserved, and the size is between 10 and 50 μm, which is basically the same as before coating.

[0087] Example 3: Preparation of polyethylene / carbon nanotube composite coated modified NCM811 particles (PE-CNT@NCM) by polyethylene 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 polyethylene (PE) particles as soft ball milling media (spherical particles, diameter about 5 mm) and 1 part by mass of carbon nanotube CNT powder (fiber agglomerate, single CNT average outer diameter of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball mill. The starting temperature of the material and the ball mill was about 23 °C at room temperature. After 15 min of ball milling, the material was naturally cooled and discharged to obtain polyethylene / CNT composite conductive coated NCM811 particles.

[0089] Figure 6 Ag is the microscopic scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the composite conductive coated modified NCM811 particles prepared by the 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 preserved, and the size is between 10 and 50 μm, which is basically not much different from before coating. Through TEM observation, it is confirmed that the coating thickness is between 30 and 50 nm.

[0090] Example 4: Preparation of polypropylene / carbon nanotube composite coated modified NCM811 particles (PP-CNT@NCM) by polypropylene soft ball milling

[0091] 45 parts by mass of 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 carbon nanotube CNT powder (fiber agglomerate, single CNT average outer diameter of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball mill. The starting temperature of the material and the ball mill was about 23°C at room temperature. After 15 minutes of ball milling, the material was naturally cooled and discharged to obtain polypropylene / CNT composite conductive coated NCM811 particles.

[0092] Figure 7 Figures ad are microscopic scanning electron microscope (SEM) images of the composite conductive coated modified NCM811 particles prepared by the 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 preserved, and the size is between 10-50 μm, which is basically the same as before coating.

[0093] Example 5: Preparation of polyvinylidene fluoride (PVDF) / carbon nanotube composite coated modified NCM811 particles (PVDF-CNT@NCM) by soft ball milling of polyvinylidene fluoride

[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 polyvinylidene fluoride (PVDF) particles as soft ball milling media (oblate spherical particles, circular cross-section diameter of about 5 mm) and 1 part by mass of carbon nanotube CNT powder (fiber agglomerate, single CNT average outer diameter of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball mill. The starting temperature of the material and the ball mill was about 23°C at room temperature. After 15 minutes of ball milling, the material was naturally cooled and discharged to obtain PVDF / CNT composite conductive coated NCM811 particles.

[0095] Figure 8 Figures ad are microscopic scanning electron microscope (SEM) images of the composite conductive coated modified NCM811 particles prepared by the 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 preserved, and the size is between 10-50 μm, which is basically the same as before coating.

[0096] Example 6: Preparation of polyadipate / butylene terephthalate (PBAT) / carbon nanotube composite coated modified NCM811 particles (PBAT-CNT@NCM) by soft ball milling of polyadipate / butylene terephthalate

[0097] 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 polybutylene adipate / terephthalate (PBAT) particles as soft ball milling media (nearly elliptical particles, elliptical cross-sectional length of about 4 mm) and 1 part by mass of carbon nanotube CNT powder (fiber agglomerate, single CNT average outer diameter of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball mill. The starting temperature of the material and the ball mill was about 23°C at room temperature. After 15 minutes of ball milling, the material was naturally cooled and discharged to obtain PBAT / CNT composite conductive coated NCM811 particles.

[0098] Fig. 9 Figures ad are microscopic scanning electron microscope (SEM) images of the composite conductive coated modified NCM811 particles prepared by the 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 preserved, and the size is between 10 and 50 μm, which is basically the same as before coating.

[0099] Example 7: Preparation of polylactic acid (PLA) / carbon nanotube composite coated modified NCM811 particles (PLA-CNT@NCM) by polylactic acid soft ball milling

[0100] 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 polylactic acid particles as soft ball milling media (nearly elliptical particles, elliptical cross-sectional length of about 4 mm) and 1 part by mass of carbon nanotube CNT powder (fiber agglomerates, single CNT average outer diameter of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball mill. The starting temperature of the material and the ball mill was about 23°C at room temperature. After 15 minutes of ball milling, the material was naturally cooled and discharged to obtain PLA / CNT composite conductive coated NCM811 particles.

[0101] Fig.10 Figures ad are microscopic scanning electron microscope (SEM) images of the composite conductive coated modified NCM811 particles prepared by the 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 preserved, and the size is between 10 and 50 μm, which is basically the same as before coating.

[0102] Example 8: Preparation of polyacrylic acid / conductive carbon black composite-coated modified NCM811 particles (PP-PAA-CB@NCM) by polypropylene soft ball milling

[0103] 44 parts by mass of 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 (nearly spherical particles, size of about 300 nm) were placed in a 100 mL ball mill for pre-soft ball milling for 15 minutes, and then 1 part by mass of conductive carbon black Super P (nearly spherical particles, median particle size D50 = 40 nm) was introduced into it and soft ball milling was continued for 15 minutes. The starting temperature of the material and the ball mill was about 80 ° C, and the material was naturally cooled and discharged to obtain polypropylene, polyacrylic acid / conductive carbon black composite conductive coated NCM811 particles.

[0104] Fig.11 Figures ad are microscopic scanning electron microscope (SEM) images of the composite conductive coated modified NCM811 particles prepared by the 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 NCM811 particles. The sphericity of the active particles after coating and modification is well preserved, and the size is between 10 and 50 μm, which is basically the same as before coating.

[0105] Example 9: Preparation of polypropylene / conductive carbon black composite coated modified NCM811 particles (PP-CB@NCM) by polypropylene soft ball milling

[0106] 45 parts by mass of 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 (nearly spherical particles, median particle size D50 = 40 nm) were placed in a 100 mL ball mill, and the starting temperature of the material and the ball mill was about 23 ° C at room temperature. After 30 minutes of ball milling, the material was naturally cooled and discharged to obtain PP / CB composite conductive coated NCM811 particles.

[0107] Fig.12 Figures ad are microscopic scanning electron microscope (SEM) images of the composite conductive coated modified NCM811 particles prepared by the soft ball milling method. It can be seen from the figure that polypropylene and conductive carbon black are evenly coated on the surface of NCM811 particles. The sphericity of the active particles after coating and modification is well preserved, and the size is between 10 and 50 μm, which is basically the same as before coating.

[0108] Example 10: Preparation of polypropylene / carbon nanotube composite-coated modified lithium iron phosphate LFP particles (PP-CNT@LFP) by polypropylene soft ball milling

[0109] 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, single CNT average outer diameter of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball mill. The starting temperature of the material and the ball mill was about 23°C at room temperature. After 15 minutes of ball milling, the material was naturally cooled and discharged to obtain polypropylene / carbon nanotube composite conductive coated LFP particles.

[0110] Fig.13 The following are microscopic scanning electron microscope (SEM) images of the raw material of lithium iron phosphate particles without CNT coating (ab) and the composite conductive coated modified lithium iron phosphate particles (cf) prepared by the soft ball milling method. It can be seen from the figure that the carbon nanotubes are coated on the surface of the lithium iron phosphate particles relatively evenly; the sphericity of the active particles after coating and modification is well preserved, and the size is between 2 and 10 μm, which is basically the same as before coating.

[0111] Example 11: Preparation of polypropylene / carbon nanotube composite-coated modified lithium cobalt phosphate LCO particles (PP-CNT@LCO) by polypropylene soft ball milling

[0112] 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, single CNT average outer diameter of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball mill. The starting temperature of the material and the ball mill was about 23°C at room temperature. After 15 minutes of ball milling, the material was naturally cooled and discharged to obtain polypropylene / carbon nanotube composite conductive coated LCO particles.

[0113] Fig.14 The following are microscopic scanning electron microscope (SEM) images of the raw material of lithium cobalt oxide particles without CNT coating (ab) and the composite conductive coated modified lithium cobalt oxide particles (cf) prepared by the soft ball milling method. 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 preserved, and the size is between 10 and 20 μm, which is basically the same as before coating.

[0114] Example 12: Preparation of polypropylene / carbon nanotube composite coated modified graphite particles (PP-CNT@Graphite) by soft ball milling of polypropylene

[0115] 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 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, single CNT average outer diameter of about 10 nm, average length of about 20 μm) were placed in a 100 mL ball mill. The starting temperature of the material and the ball mill was about 23°C at room temperature. After 15 minutes of ball milling, the material was naturally cooled and discharged to obtain polypropylene / carbon nanotube composite conductive coated graphite particles.

[0116] Fig.15 The following are microscopic scanning electron microscope (SEM) images of the raw graphite particles without CNT coating (ab) and the composite conductive coated modified graphite particles (cf) prepared by the soft ball milling method. It can be seen from the figure that the carbon nanotubes are coated on the surface of the graphite particles relatively evenly. The shape of the graphene flake particles after coating and modification is well preserved, and the long end size is between 15 and 25 μm, which is basically the same as before coating.

[0117] Performance test: conductivity of active particles coated and modified by different soft ball milling media

[0118] Weigh 0.1 g of the active particle powder after coating and modification of the above comparative examples and embodiments, apply a fixed pressure to it using a rheometer, and then use a multimeter to test the resistance of the powder. Table 1 shows the conductivity of the active particles coated and modified with different soft ball milling media under different pressures. It can be seen from the table that using different soft ball milling media to coat and modify the surface of the active particles with conductive materials can greatly improve the conductivity of the active particles.

[0119] Table 1. Conductivity of active particles coated with different soft ball milling media at different pressures

[0120]

[0121] Application Example 1: Wet preparation of electrode sheets based on soft ball milling and coating modified active materials

[0122] 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 .

[0123] Comparative Example 4: Traditional wet method for preparing electrode sheets

[0124] 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.

[0125] Fig.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.

[0126] 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.

[0127] The resistance of the obtained electrode was characterized and tested using the four-probe test mode of the KEITHLEY equipment. Fig.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 Fig.16The microscopic morphology of the electrode without CNT coating shows that the conductive agent CNT has obvious agglomeration, and a complete and continuous conductive path cannot be formed inside the electrode, resulting in a large resistance of the electrode. The resistance of the wet-process electrode prepared by PP-CNT coated modified NCM811 is about 15 Ω. Fig.16 The microscopic morphology of the electrode piece coated with CNT. The conductive agent CNT is stably and evenly maintained on the surface of the active particles. A complete conductive path is formed inside the electrode. The resistance of the electrode piece is low and it has good conductivity.

[0128] Application Example 2: Wet preparation of electrode sheets based on soft ball milling and coating modified active materials

[0129] According to the ratio of the coated modified active material to the polymer binder in the dry electrode of 98:2, the PP-CNT@NCM811 particles (Example 4) and the binder solution (4.5 wt% PVDF binder solution, the solvent is NMP) were mechanically stirred and blended; after the blending to obtain a uniform slurry, it was scraped on the surface of aluminum foil with a 250 μm scraper, dried at 105°C for 1 h, and then rolled and placed in a vacuum oven for 120 o After deep drying, the wet electrode sheet was obtained, and the active material loading of the sheet was about 20 ± 1 mg / cm 2 .

[0130] Comparative Example 5: Electrochemical rate performance of electrode sheets prepared by traditional wet method

[0131] The conventional electrode sheet is prepared by mechanically stirring and blending NCM811, conductive agent and adhesive solution (4.5 wt% PVDF adhesive solution, solvent is NMP) according to the mass ratio of active particles, conductive agent (carbon nanotubes or carbon black) and adhesive in the dry electrode in a ratio of 97:1:2. After the 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 1 h, rolled and placed in a vacuum oven at 120 °C for deep drying to obtain a wet electrode sheet. The active material loading of the sheet is about 20 ± 1 mg / cm 2 .

[0132] The prepared pole piece was cut into a 12 mm diameter disc as the positive electrode, and 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 CR2032 half-cell was assembled with a C-type ternary commercial electrolyte as the electrolyte for electrochemical performance testing (rate performance and cycle performance testing). The test was carried out in a constant 30°C and 20% humidity environment.

[0133] Fig.18It is the rate performance of the half-cell assembled using the pole piece made of the above-mentioned uncoated modified NCM811 (Comparative Example 5) and the pole piece made of the PP-CNT coated modified NCM811 (Application Example 2). As can be seen from the figure, the discharge capacity of the half-cell assembled with the PP-CNT coated modified NCM at different rates is greater than that of the half-cell assembled with the uncoated modified NCM. Among them, the discharge capacity at 0.1C rate is 215 mAh / g, the discharge capacity at 0.5C rate is 190 mAh / g, the discharge capacity at 1C rate is 160 mAh / g, and finally the discharge capacity at 0.1C rate is 213 mAh / g, which is almost the same as the discharge capacity at the initial 0.1C rate, showing good rate performance.

[0134] In the half-cell assembled with uncoated modified NCM, when CNT is used 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. The discharge specific capacity and capacity decay rate at different rates are much greater than the electrochemical data of the half-cell assembled with coated modified NCM, and after the high-rate charge and discharge, it cannot be charged and discharged normally at a rate of 0.1C, and the rate performance is poor. In commercial electrodes, the most commonly used conductive agent is carbon black (CB). In the uncoated 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 is 178 mAh / g, which is a slight decrease compared to the discharge specific capacity at 0.1C rate. The overall rate performance is not as good as that of the half-cell prepared by coated modified NCM.

[0135] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians 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 be regarded as belonging to the protection scope of the present invention.

Claims

1. A coated modified particle, characterized in that: The raw materials for preparing the modified particles include polymer granules, particles to be coated and functional additives. The polymer granules are used as soft ball friction media to form a coating layer on the surface of the particles to be coated through collision and friction adhesion with the particles to be coated and the functional additives. The coating layer is a polymer coating or a composite coating layer formed by a polymer and the functional additives. The surface hardness or elastic modulus of the polymer granules is smaller 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 smaller than the minimum size of the geometric shape of the polymer granules. The proportions of the raw materials are: 1 to 99 parts by weight of polymer granules, 1 to 99 parts by weight of particles to be coated, and 0 to 50 parts by weight of functional additives.

2. The coated modified particle according to claim 1, characterized in that: The thickness of the coating layer on the surface of the modified particles can be adjusted within the range of 1 to 1000 nm.

3. A coated modified particle according to claim 1 or 2, characterized in that: The polymer pellets are selected from the group consisting 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, polypyrrolidone, 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, natural rubber, cellulose, protein or natural polysaccharide.

4. A coated modified particle according to claim 1 or 2, characterized in that: The particles to be coated are selected from at least one of battery active particles, metal element particles, metal alloy particles, metal oxide particles or inorganic ceramic particles.

5. The coated modified particle according to claim 4, characterized in that: The particles to be coated are selected from at least one of: lithium nickel cobalt manganese oxide, sodium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, sodium nickel cobalt aluminum oxide, lithium manganese oxide, sodium manganese oxide, lithium iron phosphate, sodium iron phosphate, lithium-rich manganese-based positive electrode materials, sodium-rich manganese-based positive electrode materials, lithium cobalt oxide, sodium cobalt oxide, graphite, graphitized carbon fiber, lithium titanate, hard carbon, silicon particles, silicon-carbon composite particles, metal oxide particles or activated carbon particles; or: The functional additive is selected from: 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, zirconium oxide, titanium dioxide, aluminum oxide, PVDF nanoparticles, PAA nanoparticles, PEO nanoparticles, SBR elastomer nanoparticles, ethylene-propylene rubber nanoparticles, thermoplastic elastomer nanoparticles, halide solid electrolyte micro-nano particles, oxide solid electrolyte micro-nano particles, and sulfide solid electrolyte micro-nano particles.

6. A method for preparing coated modified particles according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: firstly premixing the raw materials uniformly, then mechanically mixing them for 30 seconds to 3 hours under an environmental condition of -20°C to 300°C, and finally cooling and screening to obtain the coated modified particles.

7. Use of the coated modified particles according to any one of claims 1 to 5 in the wet or dry preparation of battery electrode sheets, solid-state battery electrode sheets, supercapacitor electrode sheets, metal 3D printed parts, conductive nanocomposites, conductive slurries or sensor materials.

8. A wet method for preparing positive and negative electrode sheets of a battery, characterized in that: The preparation method is: mixing a coated modified particle according to any one of claims 1 to 5, a polymer binder and a conductive agent to prepare a uniform wet slurry; then preparing an electrode sheet with a uniform and controllable structure through coating, drying and rolling; wherein the solid state mass ratio of each raw material is: 60 to 99.9 parts by weight of the coated modified particles, 0.1 to 40 parts by weight of the polymer binder and 0 to 20 parts by weight of the conductive agent.

9. A dry method for preparing positive and negative electrode sheets of a battery, characterized in that: The preparation method is: premixing the coated modified particles described in any one of claims 1 to 5, a polymer binder and a conductive agent to obtain a pre-fibered dry slurry; then rolling to obtain a dry electrode sheet; wherein the solid state mass ratio of each raw material is: 60 to 99.9 parts by weight of the coated modified particles, 0.1 to 40 parts by weight of the polymer binder and 0 to 20 parts by weight of the conductive agent.

10. A method for preparing positive and negative electrode sheets of a solid-state battery, characterized in that: The preparation method is: mixing the coated modified particles described in any one of claims 1 to 5, a polymer binder, a solid electrolyte and a conductive agent to prepare a wet or dry slurry; then preparing a solid electrode pole piece through coating, drying and rolling; wherein the solid state mass ratio of each raw material is: 60 to 99.9 parts by weight of coated modified particles, 0.1 to 40 parts by weight of polymer binder, 0 to 20 parts by weight of conductive agent, and 0.1 to 40 parts by weight of solid electrolyte.

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