CN112420997A - Method for constructing thickness-controllable metal oxide coating layer in solution phase - Google Patents

Abstract

The invention discloses a method for constructing a metal oxide coating layer with controllable thickness in a solution phase. The method comprises the following steps: adding a coating substrate material, metal salt and a precipitator into a non-aqueous solvent to obtain a mixed solution; and the precipitates generated by the reaction of the precipitating agent and the metal salt are uniformly deposited on the surface of the coated substrate material to form a coating layer. The coating method provided by the invention is simple and easy to implement, mild in reaction conditions, strong in universality, continuous and complete in obtained coating layer and uniform and controllable in thickness. When the obtained final product material with the core-shell structure is used for a lithium ion battery, the cycle stability and the high-temperature stability of the material can be improved, and the practical value and the application prospect are high.

Description

Method for constructing thickness-controllable metal oxide coating layer in solution phase

Technical Field

The invention belongs to the field of materials, and particularly relates to a method for constructing a metal oxide coating layer with controllable thickness in a solution phase.

Background

Compared with the traditional battery system, the lithium ion battery has the advantages of high energy density, high working voltage, no memory effect, environmental friendliness and the like, and is widely applied to the fields of electronic products, electric automobiles and the like. To meet the increasing demands of the market, lithium ion batteries with higher energy density, power density and reliable safety performance should be developed. The positive electrode material is used as a key component of the lithium ion battery and is an important factor for determining the performance of the battery. Therefore, the development of lithium ion batteries with higher energy density is bound to put higher demands on the positive electrode material. However, the positive electrode material is at a high potential, and the delithiated positive electrode material has strong oxidizability and is prone to have side reactions with the electrolyte, so that the material structure is deteriorated, and the electrochemical performance is deteriorated. The surface of the anode material is coated and modified, which is one of the important means for improving the electrochemical performance of the anode material.

Metal oxides are often used as a substance for coating and modifying the surface of a positive electrode material due to their stable chemical properties. A large amount of research work shows that the metal oxide coating layer is introduced on the surface of the anode material, so that the anode material can be prevented from directly contacting with electrolyte, the probability of side reaction is reduced, the structural stability of the material is effectively improved, and the electrochemical performance of the material is obviously improved. The most common method for constructing metal oxide coatings is liquid phase deposition, whereby a coating material is obtained by precipitating a metal salt in an aqueous solution using an alkaline precipitant to deposit the product on the surface of the material. However, this method has many problems, for example, because the metal salt is easily hydrolyzed in the aqueous solution rapidly, the precipitation process is difficult to control, the obtained coating layer has poor effect, the uniformity, continuity and thickness cannot be effectively adjusted, and the performance of the electrode material cannot be optimized to the maximum extent. Atomic layer deposition is the main means for obtaining good coating effect, but the equipment involved in the method is expensive, high in cost, limited in sample processing capacity, and not suitable for large-scale production application. Therefore, based on the requirements of practical application on the synthesis scheme, the characteristics of wide application range, simple process and low cost of the liquid phase process are combined, and the development of a feasible liquid phase system to realize the precise construction of the coating layer has important research significance. The invention patent CN201310545860.9 reports a method for controllably constructing a uniform aluminum oxide coating layer. The pH value of a reaction system is adjusted by adding an acidic buffer solution into an aqueous solution, and the dynamic control can be performed on the metal ion precipitation process, so that the accurate construction of a metal oxide coating is realized, the coating is uniform and continuous, and the thickness is accurate and adjustable. However, the aqueous solution reaction system involved in this method is not suitable for electrode materials with strong hygroscopicity, particularly high-nickel ternary cathode materials which are currently in great interest, and cannot be processed in aqueous solution due to the sensitivity to moisture. In addition, this method requires the use of an acidic buffer solution to inhibit rapid precipitation of metal ions, which can cause corrosion of the material structure. Therefore, the development of a construction scheme based on a non-aqueous reaction system to realize the nondestructive treatment of the material surface has important research value. In addition, it is desirable to achieve precise construction of the coating in non-aqueous systems to maximize the performance of the material. Therefore, how to achieve effective control of the substance precipitation process by reasonably designing a synthesis scheme on the premise of ensuring the nondestructive treatment of the nuclear material so as to obtain accurate construction of the coating layer is a major challenge at present.

Disclosure of Invention

The first purpose of the invention is to provide a method for realizing accurate and lossless construction of a metal oxide coating layer on the surface of a material based on a non-aqueous solvent.

The invention provides a coating method of metal oxide, which comprises the following steps: adding a coating substrate material, metal salt and a precipitator into a non-aqueous solvent to obtain a mixed solution; and the precipitates generated by the reaction of the precipitant and the metal salt are uniformly deposited on the surface of the coated substrate material to form the metal oxide coating layer.

According to an embodiment of the present invention, the non-aqueous solvent is selected from anhydrous organic solvents, for example from anhydrous alcoholic solvents and/or anhydrous ketone solvents; preferably, the non-aqueous solvent is selected from at least one of anhydrous methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, n-propanol, isopropanol, n-butanol, and acetone; more preferably anhydrous ethanol. Further, the purity of the non-aqueous solvent is in chromatographic grade, and the water content of the non-aqueous solvent is less than or equal to 0.1 wt%.

According to the technical scheme of the invention, the coating substrate material is selected from at least one of metal, oxide, carbide, sulfide, phosphide, nitride, lithium salt, phosphate, nonmetal and organic particles;

wherein the metal is selected from at least one of the following metals and alloys formed thereof: gold, silver, palladium, platinum, ruthenium, rhodium, tin, germanium, and antimony;

wherein the oxide is selected from at least one of silicon dioxide, tin dioxide, aluminum oxide, molybdenum oxide, vanadium pentoxide, titanium dioxide, manganous oxide, cobaltosic oxide, zirconium dioxide, zinc oxide, cerium dioxide, magnesium oxide, calcium oxide, indium oxide, gallium oxide, lithium oxide, ferroferric oxide and lithium lanthanum zirconium oxide; preferably silica and/or tin dioxide;

wherein the carbide is selected from at least one of calcium carbide, titanium carbide, chromium carbide, vanadium carbide, tungsten carbide, silicon carbide, boron carbide, and tantalum carbide;

wherein the sulfide is at least one selected from molybdenum sulfide, zinc sulfide, nickel sulfide, cobalt sulfide, bismuth sulfide, tin sulfide, tungsten sulfide, antimony sulfide and titanium disulfide;

wherein the phosphide is at least one selected from cobalt phosphide, molybdenum phosphide, titanium phosphide, nickel phosphide, iron phosphide and tin phosphide;

wherein the nitride is selected from at least one of gallium nitride, boron nitride, silicon nitride, phosphorus nitride, tungsten nitride, vanadium nitride, titanium nitride, niobium nitride and lithium nitride;

wherein the lithium salt is selected from at least one of lithium manganate, lithium cobaltate, lithium nickelate, lithium nickel manganate, lithium nickel manganese cobaltate, lithium nickel cobalt aluminate, lithium nickel cobaltate, lithium-rich lithium nickel cobalt manganate and lithium titanate; preferably at least one of lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminate and lithium titanate;

wherein the phosphate is selected from at least one of iron phosphate, titanium phosphate, lithium titanium aluminum phosphate, lithium iron phosphate, lithium cobalt phosphate, lithium manganese cobalt phosphate, lithium manganese iron phosphate, lithium vanadium phosphate and sodium vanadium phosphate;

wherein the nonmetal is selected from at least one of carbon, carbon nanotube, graphene oxide, fullerene, silicon, phosphorus, sulfur, selenium, tellurium and boron;

wherein the organic particles are selected from at least one of phenolic resin, urea resin, melamine resin, polystyrene, polyvinylpyrrolidone, polydopamine, glucose, chitosan and fructose.

According to the technical scheme of the invention, the metal salt is selected from at least one of chloride salt, sulfate, nitrate, acetate, acetylacetone salt, lactate and alkoxide corresponding to the metal; for example selected from nitrate salts; illustratively, it is selected from iron nitrate or its hydrate, zirconium nitrate or its hydrate.

According to the technical scheme of the invention, the precipitator is selected from at least one of urea, formamide, acetamide, propionamide, triethanolamine, hexamethylenetetramine, ammonia water, ammonium formate, ammonium acetate, ammonium propionate, ammonium bicarbonate, ammonium carbonate, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, lithium hydroxide, sodium hydroxide and potassium hydroxide; for example from hexamethylenetetramine or lithium hydroxide.

According to the technical scheme of the invention, the concentration of the coating substrate material in the mixed solution is 0.01-100 g/L; for example, the concentration is 0.5-50 g/L, 1-10 g/L; illustratively, the concentration is 1.67g/L, 3.33g/L, 6.67 g/L.

According to the technical scheme of the invention, the average grain diameter of the coating substrate material is 10 nm-20 μm; for example, 20nm to 10 μm, 50nm to 5 μm, 100nm to 1 μm; illustratively, the average particle size is 200nm or 600 nm.

According to the technical scheme of the invention, the concentration of the metal salt in the mixed solution is 1 x 10^-40.1 mol/L; for example, at a concentration of 1X 10^-3～0.05mol/L、5×10^-30.01 mol/L; illustratively, the concentration is 8.2 × 10^-3mol/L、2×10^-4mol/L。

According to the technical scheme of the invention, the concentration of the precipitant in the mixed solution is 1 x 10^-3-1 mol/L; for example, the concentration is 5X 10^-3～0.5mol/L、1×10^-20.1 mol/L; illustratively, the concentration is 0.024mol/L, 0.004 mol/L.

According to the technical scheme of the invention, the reaction temperature is 10-100 ℃, for example 50-90 ℃, and exemplarily 80 ℃.

According to the technical scheme of the invention, the reaction time is 0.5-10 h, such as 2-8h, and exemplarily 4 h.

According to the technical scheme of the invention, the method further comprises the step of calcining the metal oxide containing the metal coating layer to obtain the core-shell structure coated particle with the metal oxide as a shell layer.

Wherein the calcining atmosphere is at least one of air, oxygen, nitrogen, argon and hydrogen/argon mixed gas; preferably air or oxygen.

Wherein the temperature of the calcination is 400-1000 ℃, for example 500-800 ℃, exemplarily 500 ℃ and 700 ℃.

Wherein the calcination time is 0.5-10 h, such as 1-5h, and exemplarily, 2h and 4 h.

According to an embodiment of the invention, the method comprises the steps of:

(1) adding a coating substrate material, metal nitrate and a precipitator into a non-aqueous solvent to obtain a mixed solution; the precipitation generated by the reaction of the precipitant and the metal salt is uniformly deposited on the surface of the coated substrate material to form a coating layer;

the coating substrate material is selected from oxide or lithium salt;

(2) and (2) calcining the metal oxide containing the metal coating layer obtained in the step (1) to obtain the core-shell structure coated particle with the metal oxide as a shell layer.

Further, the second object of the present invention is to provide a core-shell structure-coated particle having a metal oxide shell layer, which is prepared by the above method. Wherein the shell layer is uniformly, continuously and completely coated on the coating substrate material, and the surface of the coating substrate material is not damaged. Preferably, the metal oxide may be ferric oxide or zirconium dioxide. Further, the shell layer has a thickness of 1 to 200nm, such as 3 to 100nm, 5 to 50nm, illustratively 3nm, 5nm, 9nm, 10nm, 25nm, 28nm, 32nm, 45 nm. Wherein the core is the coated substrate material.

According to an embodiment of the present invention, the core-shell structure coated particles may be iron sesquioxide coated silicon dioxide, iron sesquioxide coated tin dioxide, iron sesquioxide coated lithium nickel cobalt manganese oxide, iron sesquioxide coated lithium nickel cobalt aluminate, iron sesquioxide coated lithium nickel titanate, iron sesquioxide coated lithium nickel manganese oxide, zirconium dioxide coated silicon dioxide, zirconium dioxide coated lithium nickel manganese oxide.

In the method, in the utilized non-aqueous solvent, the ionic activity of reactants is weakened, the hydrolysis of metal salt is effectively inhibited, and the precipitator can slowly react with the metal salt to gradually generate precipitate which is uniformly and continuously deposited on the surface of a substrate coating material, so that a complete coating layer with controllable thickness is obtained. And calcining to obtain the core-shell structure coated particle taking the metal oxide as the shell.

Further, a third object of the present invention provides the use of the coated particles having a core-shell structure obtained by the method in a lithium battery, preferably as a positive electrode material for a lithium battery.

Further, the invention also provides a lithium ion cathode material containing the core-shell structure coated particle.

According to an embodiment of the present invention, when the core of the core-shell structure-coated particle is selected from the lithium salts, the lithium ion positive electrode material is the core-shell structure-coated particle.

According to an embodiment of the present invention, when the core of the core-shell structure-coated particle is selected from the group consisting of lithium salts other than the lithium salt, the lithium ion positive electrode material may be obtained by lithiation treatment of the core-shell structure-coated particle. Further, the lithiation comprises the following steps: and mixing and sintering the core-shell structure coated particles with lithium hydroxide or lithium carbonate. Wherein the molar ratio of the core-shell structure coated particles to the lithium hydroxide or the lithium carbonate is 1 (1-1.1), such as 1 (1-1.08) and 1 (1.02-1.06). The sintering is carried out in an oxygen-containing atmosphere, such as air or oxygen. The sintering temperature is 400-1000 ℃, such as 500-900 ℃ and 600-800 ℃. The sintering time is 1-10h, such as 2-8h and 4-6 h. The sintering may be a single-step sintering, or a multi-step sintering of two or more times, and the sintering temperature and time in each step may be the same or different.

Further, the invention also provides a lithium ion battery containing the core-shell structure coated particle or the lithium ion cathode material.

The metal oxide coated anode material obtained by coating the anode material of the lithium ion battery or the lithium battery with the metal oxide coated particles with the core-shell structure in the controllable in-situ thickness can be used as the anode material of the lithium ion battery or the lithium battery of a high-energy storage device.

The invention has the beneficial effects that:

the invention provides a method for realizing accurate construction of a metal oxide coating layer in a non-water environment, which has the advantages of simple process, mild reaction conditions, realization of nondestructive treatment on the surface of a nuclear material and wide application range. The method is based on the reaction environment provided by the non-aqueous solvent, can weaken the ion activity of reactants, inhibit the hydrolysis of metal ions, effectively control the precipitation process of metal salts, and realize the adjustment of the precipitation mode of precipitates, so that a uniform and continuous coating layer on the surface of the material is obtained, and the thickness can be adjusted and controlled within the nanometer precision range. The metal oxide-coated core-shell structure particles can be obtained through further calcination treatment. The core-shell structure particles of the metal oxide coated lithium ion battery anode material obtained by the method can show excellent electrochemical performance.

The metal oxide coated particle provided by the invention can obtain uniform, continuous, complete and thickness-controllable metal oxide coatings on the surfaces of different coated substrates, and can ensure that the surface of a material is subjected to nondestructive treatment. The invention utilizes the reaction environment provided by the non-aqueous solvent to weaken the ionic activity of reactants, inhibit the hydrolysis of metal salt and control the precipitation process of the metal salt, thereby obtaining the regulation and control of the precipitation mode and successfully realizing the preparation of the uniform, continuous, complete and thickness-controllable coating layer. The coating method provided by the invention has the advantages of simple process and strong universality, can realize the nondestructive treatment of the surface of the material, can obtain a uniform, continuous and complete coating layer, can realize the accurate adjustment in nanometer precision in thickness, and has very high practicability and application prospect in the field of high-energy storage devices, namely lithium ion batteries or lithium batteries.

Drawings

FIG. 1 is a TEM image of the iron sesquioxide coated silica particles of example 1.

FIG. 2 is a TEM image of the iron sesquioxide coated tin dioxide particles of example 2.

Fig. 3 is a transmission electron micrograph of the iron sesquioxide-coated lithium nickel cobalt manganese oxide particles of example 3.

Fig. 4 is a transmission electron micrograph of the iron sesquioxide-coated lithium nickel cobalt aluminate particles of example 4.

Fig. 5 is a transmission electron micrograph of the iron sesquioxide-coated lithium titanate particles of example 5.

FIG. 6 is a TEM micrograph of the zirconia-coated silica particles of example 6.

FIG. 7 is a TEM photograph of the zirconium dioxide-coated lithium nickel manganese oxide particles of example 7.

FIG. 8 is a TEM photograph of the iron sesquioxide-coated lithium nickel manganate particles of example 8.

FIG. 9 shows the cycle performance at 0.1C for the iron trioxide coated lithium nickel manganese oxide particles of example 8.

Fig. 10 is a transmission electron microscope photograph of the iron sesquioxide coated silica particles of comparative example 1 using deionized water as a solvent.

FIG. 11 is a TEM image of the zirconia-coated silica particles prepared in comparative example 2 using deionized water as a solvent.

Detailed Description

The technical solution of the present invention will be further described in detail with reference to specific embodiments. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

The absolute ethyl alcohol used in the following examples is of chromatographic grade and has a water content of 0.1 wt% or less.

Example 1

Preparation of iron sesquioxide coated silica particles

(1) Mixing 0.05g of silica particles (with an average particle size of 600nm), 0.1g of ferric nitrate nonahydrate and 0.1g of precipitator hexamethylene tetramine in 30mL of solvent absolute ethyl alcohol, refluxing at 80 ℃ under stirring for reaction for 4h, centrifuging, washing and drying to obtain iron-containing coated silica particles, and calcining for 2h at 500 ℃ in an air atmosphere to obtain the iron sesquioxide coated silica particles.

(2) The iron sesquioxide-coated silica particles have a core-shell structure, and an electron micrograph thereof is shown in fig. 1. The material forming the core is silicon dioxide with the grain diameter of 600nm, the material forming the shell is ferric oxide, and the thickness is 32 nm; and the ferric oxide is continuously, uniformly and completely coated on the surface of the silicon dioxide, and the surface of the silicon dioxide is coated without damage.

Example 2

Preparation of iron sesquioxide coated tin dioxide particles

(1) Mixing 0.05g of tin dioxide particles (with the particle size of 20-100 nm), 0.1g of ferric nitrate nonahydrate and 0.1g of precipitator hexamethylene tetramine in 30mL of solvent absolute ethyl alcohol, refluxing at 80 ℃ under stirring for reaction for 4 hours, centrifuging, washing and drying to obtain iron-containing coated tin dioxide particles, and calcining for 2 hours at 500 ℃ in an air atmosphere to obtain the iron sesquioxide coated tin dioxide particles.

(2) The ferric oxide coated tin dioxide particles are of a core-shell structure, and the electron microscope photo of the ferric oxide coated tin dioxide particles is shown in figure 2. The core is made of tin dioxide with the particle size of 20-100 nm, the shell is made of ferric oxide, and the thickness of the shell is 10 nm; and the ferric oxide is uniformly coated on the surface of the tin dioxide.

Example 3

Preparation of iron sesquioxide coated lithium nickel cobalt manganese oxide particles

(1) Mixing 0.2g of nickel cobalt lithium manganate particles (the particle size is 1-10 mu m), 0.1g of ferric nitrate nonahydrate and 0.1g of precipitator hexamethylene tetramine in 30mL of solvent absolute ethyl alcohol, refluxing at 80 ℃ under stirring for reaction for 4 hours, centrifuging, washing and drying to obtain iron-containing coated nickel cobalt lithium manganate particles, and calcining for 2 hours at 700 ℃ in an oxygen atmosphere to obtain iron sesquioxide coated nickel cobalt lithium manganate particles.

(2) The ferric oxide coated nickel cobalt lithium manganate particles are of a core-shell structure, and the electron micrograph thereof is shown in figure 3. The core is made of nickel cobalt lithium manganate with the particle size of 1-10 mu m, the shell is made of ferric oxide, and the thickness of the shell is 5 nm; and the ferric oxide is uniformly coated on the surface of the nickel cobalt lithium manganate.

Example 4

Preparation of iron sesquioxide coated lithium nickel cobalt aluminate particles

(1) Mixing 0.1g of nickel cobalt lithium aluminate particles (the particle size is 1-10 mu m), 0.3g of ferric nitrate nonahydrate and 0.3g of precipitator hexamethylene tetramine in 30mL of solvent absolute ethyl alcohol, refluxing at 80 ℃ under stirring for reaction for 4 hours, centrifuging, washing and drying to obtain iron-containing coated nickel cobalt lithium aluminate particles, and calcining for 2 hours at 700 ℃ in an oxygen atmosphere to obtain iron sesquioxide coated nickel cobalt lithium aluminate particles.

(2) The ferric oxide coated nickel cobalt lithium aluminate particles are in a core-shell structure, and the electron microscope photo of the ferric oxide coated nickel cobalt lithium aluminate particles is shown in figure 4. The core-forming material is nickel-cobalt lithium aluminate with the grain diameter of 1-10 mu m, the shell-forming material is ferric oxide, and the thickness is 25 nm; and the ferric oxide is uniformly coated on the surface of the nickel cobalt lithium aluminate.

Example 5

Preparation of iron sesquioxide coated lithium titanate particles

(1) Mixing 0.2g of lithium titanate particles (the particle size is 50-200 nm), 0.1g of ferric nitrate nonahydrate and 0.1g of precipitator hexamethylene tetramine in 30mL of solvent absolute ethyl alcohol, refluxing at 80 ℃ under stirring for reaction for 4 hours, centrifuging, washing and drying to obtain iron-containing coated lithium titanate particles, and calcining for 2 hours at 700 ℃ in air atmosphere to obtain iron sesquioxide coated lithium titanate particles.

(2) The ferric oxide coated lithium titanate particles have a core-shell structure, and an electron micrograph thereof is shown in fig. 5. The core is made of lithium titanate with the particle size of 50-200 nm, the shell is made of ferric oxide with the thickness of 9 nm; and the ferric oxide is uniformly coated on the surface of the lithium titanate.

Example 6

Preparation of zirconium dioxide-coated silicon dioxide particles

(1) Mixing 0.05g of silica particles (with an average particle size of 600nm), 0.1g of zirconium nitrate pentahydrate and 0.1g of precipitator lithium hydroxide in 30mL of solvent absolute ethyl alcohol, stirring and refluxing at room temperature for reaction for 4 hours, centrifuging, washing and drying to obtain zirconium-containing coated silica particles, and calcining at 500 ℃ in an air atmosphere for 2 hours to obtain the zirconium dioxide-coated silica particles.

(2) The zirconia-coated silica particles had a core-shell structure, and the electron micrograph thereof is shown in FIG. 6. The material forming the core is silicon dioxide with the grain diameter of 600nm, the material forming the shell is zirconium dioxide with the thickness of 28 nm; and the zirconium dioxide is uniformly coated on the surface of the silicon dioxide.

Example 7

Preparation of zirconium dioxide-coated lithium nickel manganese oxide particles

(1) Mixing 0.2g of lithium nickel manganese oxide particles (with the particle size of 1-10 microns), 0.1g of zirconium nitrate pentahydrate and 0.1g of precipitator lithium hydroxide in 30mL of solvent absolute ethyl alcohol, stirring at room temperature for reaction for 4 hours, centrifuging, washing and drying to obtain zirconium-containing coated lithium nickel manganese oxide particles, and calcining at 700 ℃ for 2 hours in an air atmosphere to obtain zirconium dioxide coated lithium nickel manganese oxide particles.

(2) The zirconium dioxide-coated lithium nickel manganese oxide particles have a core-shell structure, and an electron micrograph thereof is shown in fig. 7. The core is made of lithium nickel manganese oxide with the particle size of 1-10 mu m, the shell is made of zirconium dioxide, and the thickness of the shell is about 45 nm; and the zirconium dioxide is uniformly coated on the surface of the lithium nickel manganese oxide.

Example 8

Firstly, preparing ferric oxide coated lithium nickel manganese oxide particles

(1) Mixing 0.2g of lithium nickel manganese oxide particles (with the particle size of 1-5 mu m), 0.1g of ferric nitrate nonahydrate and 0.1g of precipitator hexamethylene tetramine in 30mL of solvent absolute ethyl alcohol, refluxing at 80 ℃ under stirring for reaction for 4 hours, centrifuging, washing and drying to obtain iron-containing coated lithium nickel manganese oxide particles, and calcining for 2 hours at 700 ℃ in an oxygen atmosphere to obtain iron sesquioxide coated lithium nickel manganese oxide particles.

(2) The ferric oxide coated lithium nickel manganese oxide particles are of a core-shell structure, and an electron micrograph thereof is shown in figure 8. The core is made of lithium nickel manganese oxide with the particle size of 1-5 mu m, the shell is made of ferric oxide, and the thickness of the shell is 3 nm; and the ferric oxide is uniformly coated on the surface of the lithium nickel manganese oxide.

Secondly, preparing ferric oxide coated lithium nickel manganese oxide electrode

And (3) uniformly mixing 0.2136g of ferric oxide coated lithium nickel manganese oxide particles prepared in the step one, 0.0267g of conductive additive Super P, 0.534g of binder PVDF and a little solvent NMP, pulping, smearing (using an aluminum sheet as a current collector), and drying to obtain the ferric oxide coated lithium nickel manganese oxide electrode.

Three, assembled battery

The ferric oxide coated lithium nickel manganese oxide electrode prepared by the method is used as a positive electrode material, and metal lithium is used as a negative electrode materialAnd assembling the battery. The electrolyte is selected from 1M carbonate electrolyte, solvent DMC, DEC, EC 1:1:1 (w/w), and solute LiPF₆。

Fourth, battery test

(1) And (3) carrying out constant-current charge and discharge test on the battery by using a charge and discharge instrument, wherein the test voltage interval is 3-5V, and the test temperature is 25 ℃. The battery capacity and the charge-discharge current are calculated by the mass of the lithium nickel manganese oxide.

(2) Fig. 9 shows the cycling performance of this material at 0.1C (0.1C is an ampere that is 0.1 times the theoretical capacity, 0.1 x 146.7mAh/g x mass of active material for lithium nickel manganese oxide). After the battery is cycled for 100 circles, the capacity of the battery is 125.5mAh/g (the capacity of the uncoated lithium nickel manganese oxide is 105mAh/g after being cycled for 100 circles), the coulombic efficiency is more than 98%, and the battery has good capacity retention rate and service life.

Comparative example 1

Preparing ferric oxide coated silicon dioxide particles by taking deionized water as solvent

Mixing 0.05g of silica particles (with an average particle size of 600nm), 0.1g of ferric nitrate nonahydrate and 0.1g of precipitator hexamethylene tetramine in 30mL of solvent deionized water, refluxing at 80 ℃ under stirring for reaction for 4 hours, centrifuging, washing and drying to obtain treated silica particles, wherein an electron micrograph of the treated silica particles is shown in FIG. 10, and no coating layer is formed on the surface of the silica particles, which indicates that the coating cannot be successfully carried out in the deionized water.

Comparative example 2

Preparing zirconium dioxide coated silicon dioxide particles by taking deionized water as solvent

Mixing 0.05g of silica particles (with the average particle size of 600nm), 0.1g of zirconium nitrate pentahydrate and 0.1g of precipitator lithium hydroxide in 30mL of solvent deionized water, stirring and refluxing at room temperature for reaction for 4 hours, centrifuging, washing and drying to obtain treated silica particles, wherein an electron micrograph of the treated silica particles is shown in FIG. 11, and no coating layer is formed on the surface of the silica particles, which indicates that the coating cannot be successfully carried out in the deionized water.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A method of coating a metal oxide, the method comprising the steps of: adding a coating substrate material, metal salt and a precipitator into a non-aqueous solvent to obtain a mixed solution; and the precipitates generated by the reaction of the precipitant and the metal salt in the mixed solution are uniformly deposited on the surface of the coated substrate material to form a metal oxide coating layer.

2. The method for coating a metal oxide according to claim 1, wherein the nonaqueous solvent is selected from anhydrous organic solvents selected from anhydrous alcohol solvents and/or anhydrous ketone solvents;

preferably, the non-aqueous solvent is of a chromatographic grade having a water content of 0.1 wt% or less.

The coated substrate material is selected from at least one of metal, oxide, carbide, sulfide, phosphide, nitride, lithium salt, phosphate, nonmetal and organic particles.

3. The method of cladding a metal oxide according to claim 2, wherein the metal is selected from at least one of the following metals and alloys thereof: gold, silver, palladium, platinum, ruthenium, rhodium, tin, germanium, and antimony;

the oxide is selected from at least one of silicon dioxide, tin dioxide, aluminum oxide, molybdenum oxide, vanadium pentoxide, titanium dioxide, manganous oxide, cobaltosic oxide, zirconium dioxide, zinc oxide, cerium dioxide, magnesium oxide, calcium oxide, indium oxide, gallium oxide, lithium oxide, ferroferric oxide and lithium lanthanum zirconium oxide; preferably silica and/or tin dioxide;

the carbide is selected from at least one of calcium carbide, titanium carbide, chromium carbide, vanadium carbide, tungsten carbide, silicon carbide, boron carbide and tantalum carbide;

the sulfide is at least one selected from molybdenum sulfide, zinc sulfide, nickel sulfide, cobalt sulfide, bismuth sulfide, tin sulfide, tungsten sulfide, antimony sulfide and titanium disulfide;

the phosphide is at least one selected from cobalt phosphide, molybdenum phosphide, titanium phosphide, nickel phosphide, iron phosphide and tin phosphide;

the nitride is selected from at least one of gallium nitride, boron nitride, silicon nitride, phosphorus nitride, tungsten nitride, vanadium nitride, titanium nitride, niobium nitride and lithium nitride;

the lithium salt is selected from at least one of lithium manganate, lithium cobaltate, lithium nickelate, lithium nickel manganate, lithium nickel manganese cobaltate, lithium nickel cobalt aluminate, lithium nickel cobalt oxide, lithium-rich lithium nickel cobalt manganate and lithium titanate; preferably at least one of lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminate and lithium titanate;

the phosphate is selected from at least one of iron phosphate, titanium phosphate, lithium titanium aluminum phosphate, lithium iron phosphate, lithium cobalt phosphate, lithium manganese cobalt phosphate, lithium manganese iron phosphate, lithium vanadium phosphate and sodium vanadium phosphate;

the nonmetal is selected from at least one of carbon, carbon nano tube, graphene oxide, fullerene, silicon, phosphorus, sulfur, selenium, tellurium and boron;

the organic particles are selected from at least one of phenolic resin, urea resin, melamine resin, polystyrene, polyvinylpyrrolidone, polydopamine, glucose, chitosan and fructose.

4. The method for coating a metal oxide according to any one of claims 1 to 3, wherein the metal salt is at least one selected from the group consisting of chloride, sulfate, nitrate, acetate, acetylacetonate, lactate and alkoxide corresponding to the metal;

the precipitant is at least one selected from urea, formamide, acetamide, propionamide, triethanolamine, hexamethylenetetramine, ammonia water, ammonium formate, ammonium acetate, ammonium propionate, ammonium bicarbonate, ammonium carbonate, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, lithium hydroxide, sodium hydroxide and potassium hydroxide.

5. The method for coating a metal oxide according to any one of claims 1 to 4, wherein the concentration of the coating substrate material in the mixed solution is 0.01 to 100g/L, and the concentration of the metal salt is 1X 10^-40.1mol/L, the concentration of the precipitant is 1 multiplied by 10^-3～1mol/L；

Preferably, the average particle size of the coating substrate material is 10 nm-20 μm;

wherein the reaction temperature is 10-100 ℃, and the reaction time is 0.5-10 h.

6. The method for coating a metal oxide according to any one of claims 1 to 5, further comprising subjecting the metal oxide having the metal coating layer to a calcination treatment to obtain a core-shell structure-coated particle having a metal oxide shell;

wherein the calcining atmosphere is at least one of air, oxygen, nitrogen, argon and hydrogen/argon mixed gas;

wherein the calcining temperature is 400-1000 ℃, and the time is 0.5-10 h.

7. The core-shell structure coated particle with a metal oxide shell prepared by the metal oxide coating method according to any one of claims 1 to 6, wherein the metal oxide shell is uniformly, continuously and completely coated on the coated substrate material, and the surface of the coated substrate material is not damaged;

preferably, the metal oxide may be ferric oxide, zirconium dioxide;

preferably, the thickness of the shell layer is 1-200 nm;

preferably, the core-shell structure coated particles are iron sesquioxide coated silicon dioxide, iron sesquioxide coated tin dioxide, iron sesquioxide coated lithium nickel cobalt manganese oxide, iron sesquioxide coated lithium nickel cobalt aluminate, iron sesquioxide coated lithium titanate, iron sesquioxide coated lithium nickel manganese oxide, zirconium dioxide coated silicon dioxide, or zirconium dioxide coated lithium nickel manganese oxide.

8. Use of the core-shell structured coated particles according to claim 7 in a lithium battery, preferably as a positive electrode material for a lithium battery.

9. A lithium ion positive electrode material comprising the core-shell structured coated particle according to claim 7.

10. A lithium ion battery comprising the core-shell structured coated particle according to claim 7 or comprising the lithium ion positive electrode material according to claim 9.

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