Coating method and coating device for battery cathode material

Abstract

This invention relates to the field of battery materials technology, and discloses a method and apparatus for coating a battery cathode material. The method includes: contacting positively charged cathode material powder with an atomized negatively charged coating precursor dispersion system in a fluidized state, followed by drying and heat treatment to obtain a composite cathode material; the charge density ρ of the positively charged cathode material powder is... 粉体 The charge density ρ of the atomized negatively charged coated precursor dispersion system is 0.1 μC / g to 2 μC / g. 液滴 The temperature range is -3 μC / g to -0.5 μC / g. This method offers strong process controllability, ensuring a uniform and robust bond between the coating agent and the surface of the cathode material. The resulting composite cathode material exhibits good structural and cycle stability.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and specifically to a method and apparatus for coating battery cathode materials. Background Technology

[0002] In the global transition towards a cleaner and lower-carbon energy structure, electrochemical energy storage technology, as a key link connecting renewable energy production and consumption, directly determines the efficiency of this transition in terms of performance and cost. Lithium-ion batteries, with their high energy density, long cycle life, and low self-discharge rate, have dominated the consumer electronics, electric vehicle, and small-to-medium-sized energy storage markets. Sodium-ion batteries, on the other hand, are a promising alternative technology for large-scale energy storage due to the abundance and low cost of sodium in the Earth's crust, along with a wide operating temperature range and excellent safety characteristics. The cathode material, as the core energy storage and release unit of lithium / sodium-ion batteries, directly determines the battery's energy density, cycle stability, rate performance, and safety through its crystal structure stability, ion / electron conduction efficiency, and interfacial reactivity. To address the performance defects of lithium / sodium-ion battery cathode materials, researchers have developed various modification strategies, among which elemental doping and surface coating are the two most widely used technical approaches.

[0003] Currently, surface coating technologies for lithium / sodium-ion battery cathode materials mainly employ methods such as dry mechanical mixing, wet liquid-phase deposition, and vapor-phase deposition, but these methods still have significant shortcomings. Dry mixing easily leads to uneven coating and poor adhesion, wet processes are complex and result in loose coating layers, while vapor-phase deposition, although providing excellent uniformity, is costly and difficult to scale up. None of these methods can simultaneously meet the requirements of industrial production for coating uniformity, adhesion strength, and process economy. In particular, for high-performance cathode materials such as high-nickel ternary cathodes, traditional coating technologies struggle to effectively suppress interfacial side reactions and structural degradation, leading to a decrease in battery cycle life and rate performance. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem that traditional coating techniques in the prior art are difficult to effectively suppress interfacial side reactions and structural degradation, and to provide a coating method and coating device for battery cathode materials. This method has strong process controllability, and the coating agent is uniformly and firmly bonded to the surface of the cathode material. The composite cathode material prepared has good structural stability and cycle stability.

[0005] To achieve the above objectives, the present invention provides a method for coating a battery positive electrode material, the method comprising: In a fluidized state, positively charged cathode material powder comes into contact with an atomized negatively charged coated precursor dispersion system, and then is dried and heat-treated to obtain a composite cathode material. The charge density ρ of the positively charged cathode material powder粉体 The range is from 0.1 μC / g to 2 μC / g; The charge density ρ of the atomized, negatively charged coated precursor dispersion system 液滴 The range is from -3 μC / g to -0.5 μC / g.

[0006] A second aspect of the present invention provides a coating apparatus for a battery positive electrode material, the apparatus comprising an electrostatic spraying device, a fluidized bed device, and a heat treatment device; The electrostatic spraying device includes a negative high-voltage power supply for providing an atomized negatively charged coating precursor dispersion system. The fluidized bed device includes a coating zone, an electrostatic separation zone, and a curing and drying zone. The fluidized bed device is also equipped with a powder inlet and a spray inlet. The powder inlet is used to feed positively charged cathode material powder into the fluidized bed. The spray inlet is connected to the outlet of the electrostatic spraying device. The device also includes an additional corona charging system and a charge detection system.

[0007] This invention utilizes an innovative electrostatic adsorption-assisted coating method, combined with fluidized bed equipment design, to achieve uniform and robust bonding of the coating agent to the surface of the cathode material, providing a new approach to solving the aforementioned technical challenges. This method offers strong process controllability and significant coating effects, providing a reliable technical path for the large-scale production of high-performance battery cathode materials. The battery cathode materials prepared using the coating method and equipment described in this invention exhibit good structural stability and cycle stability. Attached Figure Description

[0008] Figure 1 : A schematic diagram of a coating method in one embodiment of the present invention.

[0009] Figure 2 : A schematic diagram of the electrostatic spray device and fluidized bed device in one embodiment of the present invention.

[0010] Figure 3 Example 1: SEM morphology image of the cathode material.

[0011] Figure 4 SEM morphology of the cathode material prepared in Comparative Example 4.

[0012] Figure 5 Capacity performance test curves (0.1C / 0.1C) of the cathode materials prepared in Examples 1, 7, 9 and Comparative Example 4. Detailed Implementation

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0014] This invention provides a method for coating a battery positive electrode material, the method comprising: In a fluidized state, positively charged cathode material powder comes into contact with an atomized negatively charged coated precursor dispersion system, and then is dried and heat-treated to obtain a composite cathode material. The charge density ρ of the positively charged cathode material powder 粉体 The range is from 0.1 μC / g to 2 μC / g; The charge density ρ of the atomized, negatively charged coated precursor dispersion system 液滴 The range is from -3 μC / g to -0.5 μC / g.

[0015] According to the present invention, the charge density ρ of the positively charged cathode material powder is... 粉体 The values ​​can be 0.1 μC / g, 0.2 μC / g, 0.3 μC / g, 0.4 μC / g, 0.5 μC / g, 0.6 μC / g, 0.7 μC / g, 0.8 μC / g, 0.9 μC / g, 1.0 μC / g, 1.1 μC / g, 1.2 μC / g, 1.3 μC / g, 1.4 μC / g, 1.5 μC / g, 1.6 μC / g, 1.7 μC / g, 1.8 μC / g, 1.9 μC / g, 2.0 μC / g, or any value in between.

[0016] According to the present invention, the charge density ρ of the atomized negatively charged coated precursor dispersion system 液滴 Can be -0.5μC / g, -0.6μC / g, -0.7μC / g, -0.8μC / g, -0.9μC / g, -1.0μC / g, -1.1 μC / g, -1.2μC / g, -1.3μC / g, -1.4μC / g, -1.5μC / g, -1.6μC / g, -1.7μC / g, -1. 8μC / g, -1.9μC / g, -2.0μC / g, -2.1μC / g, -2.2μC / g, -2.3μC / g, -2.4μC / g, - 2.5μC / g, -2.6μC / g, -2.7μC / g, -2.8μC / g, -2.9μC / g, -3.0μC / g, and any value in between.

[0017] In this invention, the charge density of the cathode material powder is determined using an offline Faraday cup measurement method. Specifically, a sample is taken from the powder stream after corona charging and introduced into a Faraday cup connected to a high-precision electrometer. The charge density is calculated using the formula ρ = Q / m, based on the charge measured by the electrometer as Q (μC) and the powder mass m (g).

[0018] The charge density of the coated precursor dispersion system was monitored in real time using an online overall averaging calculation method. Specifically, an ammeter was connected in series in the negative high-voltage power supply circuit of the electrostatic spraying device. The measured total spray current I (μA, 1μA = 1μC / s) was compared with the mass flow rate of the coated precursor dispersion system. (Unit: g / h), from the formula ρ_droplet = (I × 3600) / The calculation yielded the result.

[0019] This invention utilizes an innovative electrostatic adsorption-assisted coating method, combined with fluidization design, to achieve uniform and robust bonding of the coating agent to the surface of the cathode material, providing a new approach to solving the aforementioned technical challenges. This method offers strong process controllability and significant coating effects, providing a reliable technical path for the large-scale production of high-performance battery cathode materials. Battery cathode materials prepared using the coating method and equipment described in this invention exhibit good structural stability and cycle stability.

[0020] According to some preferred embodiments of the present invention, the contact is carried out in a fluidized bed apparatus.

[0021] According to the present invention, preferably, the fluidized bed device includes a coating zone, an electrostatic separation zone, and a curing and drying zone. A schematic diagram of the coating method in one embodiment of the present invention is shown below. Figure 1 As shown in the figure, this invention combines electrostatic spraying and fluidized bed processes and utilizes the electrostatic adsorption between opposite charges to achieve efficient and uniform coating modification of battery cathode material powder.

[0022] According to the present invention, preferably, the fluidized bed device is supplied with fluidizing gas, the flow rate of the fluidizing gas in the coating zone is 0.5-1.2 m / s, and the flow rate of the fluidizing gas in the electrostatic separation zone and the curing and drying zone is 0.2-0.4 m / s.

[0023] In this invention, using the preferred flow rate of the fluidizing gas described above is beneficial to improving coating efficiency and coating uniformity.

[0024] According to some preferred embodiments of the present invention, the positively charged positive electrode material powder is obtained by corona charging to make the surface of the positive electrode material powder carry a positive charge.

[0025] In this invention, positively charged cathode material powder and atomized negatively charged coating precursor dispersion system are mixed in a fluidized bed device. Electrostatic adsorption is used to promote the uniform adsorption of coating precursor droplets onto the powder surface, which is beneficial to improving the uniformity, integrity and bonding force of the cathode material coating layer.

[0026] According to the present invention, preferably, the droplet size of the atomized negatively charged coated precursor dispersion system is 5-20 μm.

[0027] In this invention, excessively large droplet size will lead to increased droplet aggregation and poor coating uniformity, while excessively small droplet size will increase the risk of being entrained and lost by fluidizing gas, thus reducing the efficiency of the coating process and the material utilization rate.

[0028] Preferably, the ratio Rρ of the charge density of the positively charged cathode material powder and the charge density of the atomized negatively charged coated precursor dispersion system satisfies: Rρ=|ρ 液滴 |:|ρ 粉体 |=0.5-3.5, more preferably 1.5-3.

[0029] In this invention, ρ 液滴 and ρ 粉体 The ratio satisfying the above preferred range is beneficial to obtaining coated modified cathode materials with strong bonding force, good uniformity and moderate thickness.

[0030] According to the present invention, preferably, the method for preparing the atomized negatively charged coated precursor dispersion system includes: atomizing the coating agent precursor through an electrostatic spraying device and applying a negative high voltage power supply.

[0031] According to the present invention, preferably, the feed amount Q of the coating agent precursor of the electrostatic spraying device is... s The feed rate Q of the positively charged cathode material powder in the fluidized bed device p The ratio Rq=Q s Q p =0.05-0.3L / kg, preferably 0.1-0.25L / kg; Q s The unit is L / h, Q p The unit is kg / h.

[0032] In this invention, Q s and Q p A ratio that meets the above-mentioned preferred range is beneficial to improving the utilization rate of the coating agent and forming a good coating layer.

[0033] This invention does not impose any particular limitation on the selection of the cathode material powder; commonly used cathode materials in the art can all be coated and modified using the method provided by this invention. According to some preferred embodiments of this invention, the cathode material powder is a lithium-ion battery cathode material and / or a sodium-ion battery cathode material. According to some preferred embodiments of this invention, the lithium-ion battery cathode material is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide ternary materials, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, and lithium nickel manganese oxide. According to some preferred embodiments of this invention, the sodium-ion battery cathode material is selected from layered oxide type and / or polyanionic type cathode materials, more preferably layered oxide type cathode materials.

[0034] According to the present invention, preferably, the particle size D50 of the positive electrode material powder is 1-20 μm, more preferably 2-18 μm.

[0035] In this invention, when the particle size of the cathode material powder is within the aforementioned preferred range, it facilitates the formation of a stable fluidized bed layer with uniform dispersion and minimal channeling or surging after the cathode material passes through the fluidized bed. This promotes uniform and efficient contact between the powder and the coating agent droplets; furthermore, when the particle size of the cathode material powder is within this range, combined with Q... s and Q p The ratio can achieve a good match in size and quantity, which helps to improve the uniformity and integrity of the coating and improve the coating efficiency.

[0036] According to the present invention, preferably, the atomized negatively charged coated precursor dispersion system comprises a dispersion phase and a dispersion medium.

[0037] Preferably, the content of the dispersed phase is 0.5-20 wt% based on the total mass of the dispersion system, more preferably 1-10 wt%. In the dispersion system of the present invention, a dispersed phase content within the above-mentioned preferred range is beneficial for obtaining a suitable viscosity, enabling it to be efficiently and stably atomized into uniformly sized and negatively charged droplets in an electrostatic spraying device.

[0038] According to the present invention, preferably, the dispersion contains a modifying element, which is selected from at least one of alkali metal elements, alkaline earth metal elements, transition metal elements, group IIIA metal elements, and group IVA elements, preferably selected from at least one of Ni, Co, Mn, Li, Na, Fe, Al, Mg, W, Ti, Zr, Ca, V, C, Y, Nb, Mo, Sr, Sn, Cu, and Zn, and more preferably selected from at least one of Co, Mn, Li, Na, Al, Mg, W, Ti, and Zr.

[0039] Preferably, the dispersed phase is selected from at least one of oxides, hydroxides, carbonates, acetates, metal alkoxides, phosphates, nitrates, or sulfates, and more preferably from at least one of oxides, carbonates, acetates, metal alkoxides, or phosphates.

[0040] In this invention, using the above-mentioned preferred dispersion is beneficial for obtaining a coating layer with excellent performance.

[0041] According to the present invention, preferably, the dispersion medium is selected from at least one of water, C1-C4 alcohols, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, tetrahydrofuran (THF), imidazoles, pyridines, and quaternary ammonium salt ionic liquids, and more preferably selected from at least one of water, C1-C4 alcohols, N-methylpyrrolidone, and quaternary ammonium salt ionic liquids.

[0042] In this invention, the use of the preferred dispersion medium described above is beneficial for forming stable coating agent precursor atomized droplets.

[0043] This invention does not impose any particular limitation on the atmosphere for heat treatment, as long as it achieves the technical objective of this invention. According to some preferred embodiments of the invention, the conditions for heat treatment include: the atmosphere for heat treatment is selected from at least one of air, nitrogen, and oxygen.

[0044] According to the present invention, preferably, the temperature of the heat treatment is 200-900°C, more preferably 300-800°C.

[0045] According to the present invention, preferably, the heat treatment time is 0.5-10h, more preferably 2-8h.

[0046] In this invention, the preferred heat treatment conditions described above are beneficial for improving the bonding force between the coating layer and the substrate, and for obtaining the desired chemical composition.

[0047] A second aspect of the present invention provides a coating apparatus for a battery positive electrode material, the apparatus comprising an electrostatic spraying device, a fluidized bed device, and a heat treatment device; The electrostatic spraying device includes a negative high-voltage power supply for providing an atomized negatively charged coating precursor dispersion system. The fluidized bed device includes a coating zone, an electrostatic separation zone, and a curing and drying zone. The fluidized bed device is also equipped with a powder inlet and a spray inlet. The powder inlet is used to feed positively charged cathode material powder into the fluidized bed. The spray inlet is connected to the outlet of the electrostatic spraying device. The device also includes an additional corona charging system and a charge detection system.

[0048] This invention significantly improves the uniformity and bonding strength of battery cathode material coating through electrostatic adsorption-assisted coating and an integrated fluidized bed device design, while achieving precise and controllable process control. The device uses the attraction of opposite charges to uniformly bond the coating agent precursor to the matrix, forming a uniform, dense, and strongly bonded coating layer through a heat treatment device. This improves the capacity, rate capability, cycle retention, and thermal stability of the cathode material. The device integrates a charge monitoring system, coating area, electrostatic separation area, and curing and drying area, effectively solving the agglomeration and deposition problems in traditional processes. It boasts high raw material utilization, is compatible with various battery cathode materials, and significantly reduces mass production costs while ensuring high performance, providing reliable technical support for the development of high-energy-density batteries.

[0049] According to the present invention, preferably, the inner wall of the fluidized bed device comprises a ceramic insulating layer. According to some preferred embodiments of the present invention, the resistivity of the ceramic insulating layer is 10⁻⁶. 7 -10 9 Ω m, temperature resistance >600℃.

[0050] In this invention, an antistatic and high-temperature resistant ceramic insulating layer is applied to the inner wall of the fluidized bed body, which helps to reduce the adsorption and accumulation of raw materials and thermal damage on the inner wall of the equipment.

[0051] According to the present invention, preferably, the curing and drying zone includes a swirling hot air system. According to some preferred embodiments of the present invention, the inlet temperature of the swirling hot air system is 100-250°C, and the outlet temperature is 60-100°C. In the present invention, the swirling hot air system is used to dry the coated particles, and the above-mentioned preferred conditions are beneficial to improving drying efficiency while ensuring that the coating layer is not damaged.

[0052] According to the present invention, preferably, the covering area further includes an annular secondary air curtain device. According to some preferred embodiments of the present invention, the gas flow velocity in the annular secondary air curtain device is 0.1-0.3 m / s. In the present invention, using the above-mentioned preferred gas flow velocity is beneficial for isolating turbulence in the spray zone and preventing wall deposition.

[0053] According to the present invention, preferably, the electrostatic sorting zone includes a negative electrode plate and a positive electrode plate. In the present invention, the combination of the negative and positive electrode plates in the electrostatic sorting zone is used to adsorb uncoated particles, which is beneficial for the sorting of coated particles.

[0054] According to the present invention, preferably, a fluidizing gas is passed through the fluidized bed device.

[0055] The present invention does not have any particular limitation on the selection of the fluidizing gas, as long as it can achieve the technical objective of the present invention. Preferably, the fluidizing gas is selected from at least one of nitrogen, argon and air.

[0056] In this invention, when the fluidizing gas is air, the dew point temperature must be less than -20°C.

[0057] Preferably, the fluidized bed device has a bed filling rate of 25%-65% in the fluidized state.

[0058] In this invention, the preferred bed filling ratio described above is beneficial for achieving a stable fluidized state for the cathode material.

[0059] Preferably, the pressure drop of the fluidized bed device in the fluidized state is 0.01-0.03 MPa.

[0060] In this invention, the preferred bed pressure drop described above is beneficial to improving the stability of the fluidized cathode material.

[0061] According to the present invention, preferably, the electrostatic spraying device includes an atomizing gas, which is selected from at least one of nitrogen, argon, and air. In the present invention, when the atomizing gas is air, the dew point temperature must be less than -20°C.

[0062] Preferably, the atomization pressure of the electrostatic spray device is 0.01-1 MPa.

[0063] According to the present invention, preferably, the negative electrode plate and the positive electrode plate of the electrostatic sorting zone are porous mesh electrodes, and the pore size of the porous mesh electrodes is 50-200 μm.

[0064] In this invention, if the aperture of the porous mesh electrode is too large, it will result in uneven electric field distribution and reduced screening efficiency; if it is too small, it will result in mesh blockage.

[0065] Preferably, the voltage of the negative electrode plate is -10 to -5kV.

[0066] In this invention, excessively high voltage on the negative electrode plate can cause safety hazards, and a high electrostatic field can attract the coated normal material, resulting in product loss. Insufficiently low voltage will lead to insufficient electrostatic field, which will not be able to effectively attract and capture positively charged uncoated particles.

[0067] Preferably, the voltage of the positive electrode plate is 1-3kV.

[0068] In this invention, if the voltage of the positive electrode plate is too high, it will attract too many negatively charged particles to accumulate rapidly on its surface, causing the mesh to become clogged. If the voltage is too low, the attraction force will be insufficient, making it difficult to effectively capture and remove negatively charged over-coated or agglomerated particles, resulting in unqualified particles being mixed in the product.

[0069] Preferably, the positive electrode plate is located on the side of the negative electrode plate and is perpendicular to the negative electrode plate.

[0070] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially available.

[0071] Examples and comparative examples related test methods 1. Method for measuring coating thickness: The coating thickness was determined by FE-SEM cross-sectional analysis (BSE mode). The average value was calculated by measuring 30 sites on 10 randomly selected particles using NanoMeasurer software.

[0072] 2. Method for measuring the coverage of the coating layer: The morphology of the samples was observed using field emission scanning electron microscopy (FE-SEM) in backscattered electron (BSE) mode. The sensitivity of BSE mode to atomic number differences provides compositional contrast, revealing a clear grayscale difference between the coating layer (typically different from the cathode material matrix) and the uncoated substrate surface in the images. ImageJ image analysis software was used to perform grayscale thresholding to accurately separate the coated area from the uncoated substrate surface (the threshold setting ensures that the segmented area matches the visually perceived coated area to the greatest extent possible). The average coverage of the coating layer was calculated by statistically analyzing the pixel percentage of the coated area on approximately 200 particle surfaces across 10 different fields of view.

[0073] Example 1 Adopting such Figure 2 The electrostatic spraying device and fluidized bed device shown are used to coat positive electrode materials. The electrostatic spraying device includes a negative high-voltage power supply for providing an atomized, negatively charged coating precursor dispersion system; the fluidized bed device includes a coating zone, an electrostatic separation zone, and a curing and drying zone; the fluidized bed device also has a powder inlet and a spray inlet, wherein the powder inlet is used to feed positively charged positive electrode material powder into the fluidized bed; the spray inlet is connected to the outlet of the electrostatic spraying device; the device also includes an additional corona charging system and a charge detection system.

[0074] LiNi 0.8 Co 0.1 Mn 0.1 O2 cathode material powder (D50=10μm) is added to a fluidized bed apparatus and fluidized, and the powder surface is positively charged (ρ) by corona charging. 粉体 =1.3μC / g); simultaneously, an aqueous solution of Al(NO3)3 with a dispersion concentration of 5wt% was electrostatically atomized into droplets with a particle size of 10μm, and a negative high voltage was applied to make the droplets carry a negative charge (ρ 液滴 =-2.8μC / g, Rρ=2.2). During this process, the spray flow rate Q of the coating agent precursor was controlled. s With matrix treatment volume Qp The ratio was Rq = 0.17 L / kg, utilizing the electrostatic attraction of opposite charges to achieve uniform adsorption of droplets on the powder surface. After fluidized mixing, it was heat-treated in air at 500℃ for 4 hours to finally obtain Al2O3-coated LiNi with a coating thickness of 35 nm and a coverage of 99%. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0075] The SEM morphology image of the battery cathode material obtained in this embodiment is as follows: Figure 3 As shown, the coating agent is evenly distributed on the substrate surface, and the surface of the coated cathode material is smooth.

[0076] Example 2 The process parameters were adjusted to have a coating agent precursor dispersion concentration of 1 wt%, ρpowder = 1.9 μC / g, ρdroplet = -2.8 μC / g, Rρ = 1.5, and Rq = 0.25, with other parameters consistent with Example 1. This resulted in an Al₂O₃-coated LiNi coating with a thickness of 40 nm and a coverage of 96%. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0077] Example 3 Adjust process parameters to achieve a coating agent precursor dispersion concentration of 10 wt% and a density of ρ. 粉体 =0.9μC / g, ρ 液滴 =-2.7μC / g, Rρ=3.0, Rq=0.1, other parameters are the same as in Example 1, and finally an Al2O3-coated LiNi with a coating thickness of 30nm and a coverage of 97% was obtained. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0078] Example 4 LiFePO4 cathode material powder (D50=2μm) was added to a fluidized bed apparatus and fluidized. Corona charging was used to make the powder surface positively charged (ρ). 粉体 =1.0μC / g); simultaneously, Li3PO4 was uniformly dispersed in water (mass concentration of 8wt%), atomized into droplets with a particle size of 5μm by electrostatic spraying, and a negative high voltage was applied to make the droplets carry a negative charge (ρ 液滴 =-2.5μC / g, Rρ=2.5). During this process, the spray flow rate Q of the coating agent precursor is controlled. s With matrix treatment volume Q pThe ratio of the two charges is Rq=0.17L / kg, and the uniform adsorption of droplets on the powder surface is achieved by utilizing the electrostatic attraction of opposite charges. After fluidized mixing, the material is heat-treated at 450℃ in a nitrogen atmosphere for 6 hours to finally obtain a Li3PO4-coated LiFePO4 modified cathode material with a coating thickness of 30nm and a coverage of 96%.

[0079] Example 5 LiMn 1.5 Ni 0.5 O4 cathode material powder (D50=5μm) is added to a fluidized bed apparatus and fluidized, and the powder surface is positively charged (ρ) by corona charging. 粉体 =1.2μC / g); simultaneously, Co3O4 was uniformly dispersed in water (mass concentration of 3wt%), atomized into droplets with a particle size of 10μm by electrostatic spraying, and a negative high voltage was applied to make the droplets carry a negative charge (ρ 液滴 =-2.6μC / g, Rρ=2.2). During this process, the spray flow rate Q of the coating agent precursor was controlled. s With matrix treatment volume Q p The ratio was Rq = 0.15 L / kg, utilizing the electrostatic attraction of opposite charges to achieve uniform adsorption of droplets on the powder surface. After fluidized mixing, the mixture was heat-treated at 750℃ in air for 3 hours to obtain a Co3O4-coated LiMn with a coating thickness of 12 nm and a coverage of 94%. 1.5 Ni 0.5 O4 modified cathode material.

[0080] Example 6 NaNi 0.33 Fe 0.33 Mn 0.33 O2 cathode material powder (D50=5μm) is added to a fluidized bed apparatus and fluidized, and the powder surface is positively charged (ρ) by corona charging. 粉体 =0.6μC / g); simultaneously, ZrO2 was uniformly dispersed in water (mass concentration of 6wt%), atomized into droplets with a particle size of 10μm by electrostatic spraying, and a negative high voltage was applied to make the droplets carry a negative charge (ρ 液滴 =-1.4μC / g, Rρ=2.3). During this process, the spray flow rate Q of the coating agent precursor was controlled. s With matrix treatment volume Q p The ratio of the two charges was Rq = 0.18 L / kg, and the uniform adsorption of droplets on the powder surface was achieved by utilizing the electrostatic attraction of opposite charges. After fluidized mixing, the powder was heat-treated in air at 550℃ for 5 hours to finally obtain a ZrO2-coated NaNi with a coating thickness of 25 nm and a coverage of 97%. 0.33 Fe 0.33 Mn 0.33 O2 modified cathode material.

[0081] Example 7 Adjust process parameters to ρ 粉体 =1.5μC / g, ρ 液滴 =-1.5μC / g, Rρ=1.0, Rq=0.17, other parameters are the same as in Example 1, and finally an Al2O3-coated LiNi with a coating thickness of 32nm and a coverage of 88% was obtained. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0082] Example 8 Adjust process parameters to ρ 粉体 =0.5μC / g, ρ 液滴 =-1.7μC / g, Rρ=3.4, Rq=0.08, other parameters are the same as in Example 1, and finally an Al2O3-coated LiNi with a coating thickness of 25nm and a coverage of 91% was obtained. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0083] Example 9 Adjust process parameters to achieve a coating agent precursor dispersion concentration of 15 wt% and a p-value of 15 wt%. 粉体 =0.8μC / g, ρ 液滴 =-2.0μC / g, Rρ=2.5, Rq=0.29, other parameters are the same as in Example 1, and finally an Al2O3-coated LiNi with a coating thickness of 45nm and a coverage of 88% was obtained. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0084] Comparative Example 1 Adjust process parameters to ρ 粉体 =0.05μC / g, ρ 液滴 = -0.1 μC / g, Rρ=2.0, Rq=0.15, other parameters are the same as in Example 1, and finally an Al2O3-coated LiNi with a coating thickness of 18 nm and a coverage of 75% is obtained. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0085] Comparative Example 2 Adjust process parameters to ρ 粉体 =1.0μC / g, ρ 液滴=-4.2μC / g, Rρ=4.2, Rq=0.15, other parameters are the same as in Example 1, and finally an Al2O3-coated LiNi with a coating thickness of 42nm and a coverage of 85% was obtained. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0086] Comparative Example 3 Adjust process parameters to ρ 粉体 =2.1μC / g, ρ 液滴 = -0.4 μC / g, Rρ=0.2, Rq=0.03, other parameters are the same as in Example 1, and finally an Al2O3-coated LiNi with a coating thickness of 8 nm and a coverage of 87% was obtained. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0087] Comparative Example 4 LiNi 0.8 Co 0.1 Mn 0.1 O2 cathode material powder (D50 = 10 μm) is added to a fluidized bed apparatus for fluidization (no corona charging is performed, so the cathode material powder is uncharged); simultaneously, an Al(NO3)3 aqueous solution with a dispersion concentration of 5 wt% is electrostatically atomized into droplets with a particle size of 10 μm. During this process, the spray flow rate Q of the coating agent precursor is controlled. s With matrix treatment volume Q p The ratio was Rq = 0.17 L / kg. After fluidized mixing, the mixture was heat-treated in air at 500℃ for 4 hours to obtain Al2O3-coated LiNi with poor coating uniformity and a coverage of 72%. 0.8 Co 0.1 Mn 0.1 O2 modified cathode material.

[0088] The SEM morphology image of the battery cathode material prepared in this comparative example is shown below. Figure 4 As shown, the coating agent is unevenly distributed on the substrate surface, exhibiting an island-like coating effect, and the surface of the coated cathode material is relatively rough.

[0089] Application examples The cathode materials obtained in the examples and comparative examples were used to fabricate batteries and test their electrical performance, as detailed below: The positive electrode material prepared in the above examples and comparative examples was mixed with polyvinylidene fluoride and conductive carbon black in a mass ratio of 90:5:5, NMP was added, and the mixture was magnetically stirred to form a slurry. This slurry was then coated onto aluminum foil and dried at 100°C to form a positive electrode sheet. Using the positive electrode sheet, sodium sheet or lithium sheet as the negative electrode sheet, electrolyte and separator as raw materials, a button cell was assembled in a glove box.

[0090] Different voltage windows are selected based on different material systems, LiNi 0.8 Co 0.1 Mn 0.1 The voltage window for O2 cathode material is 3.0-4.3V, for LiFePO4 cathode material it is 2.5-4.2V, and for LiMn... 1.5 Ni 0.5 The voltage window for O4 cathode material is 3.0-4.9V, and for NaNi... 0.33 Fe 0.33 Mn 0.33 The voltage window for the O2 cathode material is 2.0-4.2V. The capacity, rate capability, and cycle performance of the modified material were then tested.

[0091] The test results are shown in Table 1. The capacity curves of the coin cells composed of the positive electrode materials prepared in Examples 1, 7, 9, and Comparative Example 4 are shown in Table 1. Figure 5 As shown (0.1C / 0.1C).

[0092] Table 1

[0093] In Table 1, the 100-cycle retention rate (%) 1C / 1C refers to the percentage of the battery's discharge capacity after 100 cycles under 1C / 1C charge and discharge conditions relative to the battery's discharge capacity in the first cycle; the 5C rate retention rate (%) 5C / 0.5C refers to the percentage of the discharge capacity at 5C relative to the discharge capacity at 0.5C.

[0094] As shown in Table 1, the coating modification method for battery cathode materials provided by this invention can effectively control the coating thickness by precisely regulating electrostatic adsorption (such as charge density ratio Rρ and flow rate ratio Rq), significantly improving the coverage rate and effectively avoiding the uneven phenomenon such as "island-like" coating commonly found in traditional methods, thereby significantly improving the specific capacity, cycle stability and rate performance of the material.

[0095] Comparing Examples 1-3 with Comparative Example 4: The results show that after coating using electrostatic adsorption, the coverage of the resulting coating layer is significantly improved, and the specific capacity and cycle retention of the material are both superior. This indicates that the coating method of this patent can obtain a cathode material surface coating layer with good uniformity and precisely controllable thickness.

[0096] Comparative Example 1 and Comparative Examples 1-3: The results show that when the powder charge density |ρ 粉体When the electrostatic adsorption force is too low, the coating coverage decreases and the electrical properties deteriorate. Conversely, when the absolute value of the coating agent droplet charge density is too high or the concentration of the coating agent precursor dispersion is too high and the spray flow rate ratio Rq is too high, droplet aggregation is easily triggered, resulting in an excessively thick coating, reduced coverage, and decreased electrical properties.

[0097] Comparing Example 1 with Examples 4-6: The results further demonstrate that the coating modification method is applicable to different types of cathode material systems (such as high-nickel ternary, lithium iron phosphate, spinel-type lithium nickel manganese oxide, and sodium ion layered oxide), and can achieve excellent coating effects and significantly improved electrochemical performance, fully demonstrating the universality and technical advantages of the present invention.

[0098] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for coating a battery positive electrode material, characterized in that, The method includes: In a fluidized state, positively charged cathode material powder comes into contact with an atomized negatively charged coated precursor dispersion system, and then is dried and heat-treated to obtain a composite cathode material. The charge density ρ of the positively charged cathode material powder 粉体 The range is from 0.1 μC / g to 2 μC / g; The charge density ρ of the atomized, negatively charged coated precursor dispersion system 液滴 The range is from -3 μC / g to -0.5 μC / g; The ratio Rρ of the charge density of the positively charged cathode material powder and the charge density of the atomized negatively charged coated precursor dispersion system satisfies: Rρ = |ρ 液滴 |:|ρ 粉体 |= 1.5-3; The coating precursor dispersion system includes a coating agent precursor, wherein the feed amount of the coating agent precursor is Q. s With the positively charged cathode material powder feed rate Q p The ratio Rq=Q s Q p = 0.1-0.25L / kg; Q s The unit is L / h, Q p The unit is kg / h.

2. The method according to claim 1, wherein, The contact takes place in a fluidized bed apparatus.

3. The method according to claim 2, wherein, The fluidized bed device includes a coating zone, an electrostatic separation zone, and a curing and drying zone.

4. The method according to claim 3, wherein, The fluidized bed device is filled with fluidizing gas. The flow rate of the fluidizing gas in the coating zone is 0.5-1.2 m / s, and the flow rate of the fluidizing gas in the electrostatic separation zone and the curing and drying zone is 0.2-0.4 m / s. And / or, by corona charging, the surface of the positive electrode material powder is made to carry a positive charge, thereby obtaining the positively charged positive electrode material powder; And / or, the droplet size of the atomized negatively charged coated precursor dispersion system is 5-20 μm.

5. The method according to claim 1, wherein, The preparation method of the atomized negatively charged coated precursor dispersion system includes: atomizing the coating agent precursor through an electrostatic spraying device and applying a negative high voltage power supply.

6. The method according to claim 1, wherein, The cathode material powder is a lithium-ion battery cathode material and / or a sodium-ion battery cathode material.

7. The method according to claim 6, wherein, The lithium-ion battery cathode material is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide ternary material, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, and lithium nickel manganese oxide; and / or, the sodium-ion battery cathode material is selected from layered oxide type and / or polyanionic type cathode material.

8. The method according to claim 7, wherein, The sodium-ion battery cathode material is a layered oxide type cathode material.

9. The method according to claim 1, wherein, The particle size D50 of the positive electrode material powder is 1-20 μm.

10. The method according to claim 9, wherein, The particle size D50 of the positive electrode material powder is 2-18 μm.

11. The method according to any one of claims 1-10, wherein, The atomized negatively charged coated precursor dispersion system comprises a dispersion phase and a dispersion medium.

12. The method according to claim 11, wherein, The content of the dispersed phase is 0.5-20 wt% based on the total mass of the dispersion system.

13. The method according to claim 12, wherein, The content of the dispersed phase is 1-10 wt% based on the total mass of the dispersion system.

14. The method according to claim 11, wherein, The dispersion contains a modifying element, which is selected from at least one of alkali metal elements, alkaline earth metal elements, transition metal elements, group IIIA metal elements, and group IVA elements. And / or, the dispersed substance is selected from at least one of oxides, hydroxides, carbonates, acetates, metal alkoxides, phosphates, nitrates, or sulfates.

15. The method according to claim 14, wherein, The modifying element is selected from at least one of Ni, Co, Mn, Li, Na, Fe, Al, Mg, W, Ti, Zr, Ca, V, C, Y, Nb, Mo, Sr, Sn, Cu, and Zn; And / or, the dispersed substance is selected from at least one of oxides, carbonates, acetates, metal alkoxides, or phosphates.

16. The method according to claim 15, wherein, The modifying element is selected from at least one of Co, Mn, Li, Na, Al, Mg, W, Ti and Zr.

17. The method according to claim 11, wherein, The dispersion medium is selected from at least one of water, C1-C4 alcohols, N-methylpyrrolidone, dimethylformamide, dimethyl sulfoxide, acetone, tetrahydrofuran, imidazoles, pyridines, and quaternary ammonium salt ionic liquids.

18. The method according to claim 17, wherein, The dispersion medium is selected from at least one of water, C1-C4 alcohols, N-methylpyrrolidone, and quaternary ammonium salt ionic liquids.

19. The method according to any one of claims 1-10, wherein, The conditions for the heat treatment include: the heat treatment atmosphere is selected from at least one of air, nitrogen and oxygen; And / or, the temperature of the heat treatment is 200-900℃; And / or, the heat treatment time is 0.5-10 hours.

20. The method according to claim 19, wherein, The heat treatment temperature is 300-800℃; And / or, the heat treatment time is 2-8 hours.

21. An apparatus for coating a battery positive electrode material according to any one of claims 1-20, characterized in that, The device includes an electrostatic spraying device, a fluidized bed device, and a heat treatment device; The electrostatic spraying device includes a negative high-voltage power supply for providing an atomized negatively charged coating precursor dispersion system. The fluidized bed device includes a coating zone, an electrostatic separation zone, and a curing and drying zone. The fluidized bed device is also equipped with a powder inlet and a spray inlet. The powder inlet is used to feed positively charged cathode material powder into the fluidized bed. The spray inlet is connected to the outlet of the electrostatic spraying device. The device also includes an additional corona charging system and a charge detection system.

22. The apparatus according to claim 21, wherein, The inner wall of the fluidized bed device includes a ceramic insulating layer; And / or, the curing and drying zone includes a swirling hot air system; And / or, the covered area further includes an annular secondary air curtain device; And / or, the electrostatic sorting area includes a negative electrode plate and a positive electrode plate.

23. The apparatus according to claim 22, wherein, The resistivity of the ceramic insulating layer is 10. 7 -10 9 Ω m, temperature resistance >600℃; And / or, the inlet temperature of the swirling hot air system is 100-250℃, and the outlet temperature is 60-100℃; And / or, the gas flow velocity in the annular secondary air curtain device is 0.1-0.3 m / s.

24. The apparatus according to any one of claims 21-23, wherein, Fluidized bed apparatus is filled with fluidizing gas.

25. The apparatus according to claim 24, wherein, The fluidizing gas is selected from at least one of nitrogen, argon and air.

26. The apparatus according to claim 24, wherein, The fluidized bed device has a bed filling rate of 25%-65% in the fluidized state. And / or, the bed pressure drop of the fluidized bed device in the fluidized state is 0.01-0.03 MPa.

27. The apparatus according to any one of claims 21-23, wherein, The electrostatic spray device includes an atomizing gas, which is selected from at least one of nitrogen, argon, and air. And / or, the atomization pressure of the electrostatic spray device is 0.01-1 MPa; And / or, the negative electrode plate and positive electrode plate of the electrostatic sorting zone are porous mesh electrodes, and the pore size of the porous mesh electrodes is 50-200μm; And / or, the voltage of the negative electrode plate is -10 to -5 kV; And / or, the voltage of the positive electrode plate is 1-3kV; And / or, the positive electrode plate is located on the side of the negative electrode plate and is perpendicular to the negative electrode plate.

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