CN109192961B - Preparation method of positive electrode material - Google Patents

Abstract

The present application provides a method for preparing a positive electrode material. The positive electrode material includes a core material and a metal oxide that coats the core material, and includes the following steps in sequence: (1) mixing a corresponding metal element in the metal oxide with an acid (2) adding to the core material to obtain a coating intermediate; (3) placing it in a high-pressure oxidizing atmosphere, and using combustible gas as a carrier gas for combustion treatment to obtain a metal oxide-coated positive electrode material for the core material. Directly use metal element and acid to make a solution, the heat generated when the combustible gas burns in a high-pressure oxygen atmosphere decomposes the solvent acid or salt in the solution, vaporizes water, and the metal element or metal ion forms the corresponding oxidation under the action of high temperature and oxygen. The active surface of the core material is coated in situ, and the coated material has excellent electrochemical performance; the acid and combustible gas used in this method are degraded into non-polluting gas after mixing and oxygen-enriched combustion, and no additional pollutants are required. treatment process.

Description

Preparation method of positive electrode material

technical field

The present application relates to the field of positive electrode materials, and more particularly, the present application relates to a preparation method of a positive electrode material.

Background technique

As a new type of green energy, lithium-ion batteries have the advantages of high specific energy, small self-discharge, high open-circuit voltage, no memory effect, long cycle life, and no environmental pollution. Therefore, they are widely used in mobile phones, notebook computers, digital cameras, etc. At the same time, the lithium-ion battery is also the power supply of electric vehicles and the energy storage power of solar renewable energy.

The core link in the lithium-ion battery industry is the manufacture of battery materials. The performance of the battery depends largely on the performance of the positive electrode material. In order to improve the performance of the positive electrode material, many methods are currently used to coat the surface of the positive electrode material. Modification, the function of the cladding layer is mainly to stabilize the surface of the core layer and prevent the surface structure of the core layer from being damaged. For example, coating metal oxide on the surface of LiNi _0.5 Mn _1.5 O ₄ can improve its structure under high voltage. Stability, such as coating the surface of LiFePO ₄ with a carbon layer can improve its electrical conductivity.

However, the methods for coating the surface of the core material of the positive electrode material in the prior art generally include solid-solid phase mixing and solid-liquid phase mixing.

Among them, the solid-solid phase mixing is to pulverize or prepare the core layer material and the cladding layer material into nano-scale materials, then solid-phase mixing, and then tableting to increase the contact force between the core layer material and the cladding layer material, Then, sintering and pulverization are performed to obtain a coating material. The problem with this method is that it is difficult to mix the core layer material and the cladding layer material uniformly, and due to the small contact force between the solid and solid phases, the bonding force between the cladding layer and the core layer after sintering is not tight enough, resulting in The coating is uneven and discontinuous, and the consistency of the material is poor.

In solid-liquid phase mixing, the core material is placed in the precursor solution of the cladding material, and then a precipitant is added to deposit the cladding material on the surface of the core material, and the coating is obtained after drying, sintering and pulverization. Material. The disadvantage of this method is that it requires a large amount of solvent and consumes a lot of energy during the drying process.

Therefore, the coating method of cathode material with excellent performance and less environmental pollution is still a difficult problem that researchers need to overcome.

Application content

The purpose of the present application is to provide a positive electrode material and a preparation method thereof. The positive electrode material is composed of a core material and a surface metal oxide coating layer, wherein the metal oxide coating layer is uniformly coated on the surface of the core material.

In order to achieve the above purpose, the present application also provides a method for preparing a positive electrode material, the positive electrode material includes a core material and a metal oxide coating the core material, including the following steps in sequence:

(1) mixing the element of the corresponding metal in the metal oxide with an acid to prepare a solution;

(2) adding to the core material to obtain a coating intermediate;

(3) Putting in a high-pressure oxidizing atmosphere, and performing combustion treatment with a combustible gas as a carrier gas, a positive electrode material with a metal oxide-clad core material is obtained.

The preparation method of the present application directly uses a metal element and an acid to make a solution, uses a combustible gas as a carrier gas, and the heat generated when the combustible gas is burned in a high-pressure oxidizing atmosphere decomposes the solvent acid and salt in the solution, vaporizes water, and the metal element or The metal ions form corresponding oxides under the action of high temperature and oxygen, and coat the surface of the core material in situ, so the coating layer can evenly coat the core material, and the core material is in close contact with the coating layer material. Excellent material performance; because only acid is used as a solvent without other organic solvents, the amount of solvent is relatively small, causing less environmental pollution; in the combustion process, the liquid components of combustible gas and solution can be decomposed into NO _x , SO _x , CO ₂ and H ₂ O are volatilized, so no additional pollutant treatment process is required. However, if the traditional drying or calcining method is used instead of the combustion method of the present application, the temperature rise process of the direct heating by drying or calcining is slow, and it takes a long time to heat to reach the vaporization temperature of the solvent acid and salt. Gradually vaporize, the acidity will increase, and the positive electrode material will be corroded. At the same time, the slow dissolution of the metal element will cause segregation, and the oxidation speed is slow and incomplete. Therefore, the obtained positive electrode material with metal oxide coating has poor performance. The combustible gas burns to convert the metal into metal oxide and coat the surface of the core material in situ. When the carrier gas burns, the temperature can be controlled to be near the sintering temperature of the positive electrode material, eliminating the problem of transition metal dissolution on the surface of the material due to contact with acidic solvents. Miscellaneous.

Description of drawings

FIG. 1 is a SEM characterization diagram of the cathode material prepared in Example 1 of the present application.

FIG. 2 is a SEM characterization diagram of the cathode material prepared in Comparative Example 1 of the present application.

FIG. 3 is a comparison diagram of the cycle performance of the positive electrode materials prepared in Examples 1 to 3 of the present application and Comparative Example 1. FIG.

Detailed ways

The technical solutions of the present application are further described below through specific embodiments, which do not constitute any limitation to the present application.

The application provides a preparation method of a positive electrode material, the positive electrode material includes a core material and a metal oxide coating the core material, and includes the following steps in sequence:

(1) mixing the element of the corresponding metal in the metal oxide with an acid to make a solution;

(2) adding to the core material to obtain a coating intermediate;

(3) Putting in a high-pressure oxidizing atmosphere, and performing combustion treatment with a combustible gas as a carrier gas, a positive electrode material with a metal oxide-clad core material is obtained.

Specifically, the core material may be any of LiCoO ₂ , LiNiO ₂ , LiNi _0.5 Mn _1.5 O ₄ , LiMn ₂ O ₄ , LiFePO ₄ and Li _(1+a) Ni _x Co _y M _(1-xy) O _2+b One or more, wherein, -0.10≤a≤0.50, 0.3≤x<0.9, 0.1≤y≤0.4, -0.05≤b≤0.10, M is Mn, Al, Ti, Ba, Sr, Mg, Cr, At least one of Zn, V, and Cu. The metal oxide is one or more of Al ₂ O ₃ , MgO, Fe ₂ O ₃ , SiO ₂ and TiO ₂ .

Specifically, the acid in step (1) is an anion-decomposable organic acid or inorganic acid at 600° C., and the acid can be one of nitric acid, dilute sulfuric acid, hydrochloric acid, acetic acid, citric acid and oxalic acid. Because in metal oxides, some metal elements will react with acid at room temperature to form salts, such as aluminum, magnesium, iron element and nitric acid, dilute sulfuric acid, hydrochloric acid, acetic acid, citric acid and oxalic acid will react at room temperature to form salts Salt; some metals need to react with acid at high temperature to form salt, such as titanium and nitric acid, dilute sulfuric acid, hydrochloric acid need to react at high temperature; some metals need to be dissolved in acid at high temperature, such as silicon Elements require heating to dissolve in organic and inorganic acids. Therefore, the solution prepared by mixing simple metal and acid may be all metal and solvent acid, or it may be metal, solvent acid and salt, or it may be all salt. In short, when the metal and acid are made into a solution , it is necessary to use the reaction conditions or external conditions to form a stable and uniform solution.

Further, in step (1), the metal element is mixed with the acid, and then slowly added with ammonia water to dilute and adjust the pH value to 5 to 6 to prepare a solution. By adjusting the pH value of 5 to 6, the impurity phase produced by the dissolution of transition metals due to strong acidity during the combustion reaction can be reduced or even eliminated. Since ammonia water can be completely decomposed at high temperature, pH adjustment with ammonia water will not bring impurities.

Specifically, adding the core material in step (2) to obtain the coating intermediate is to spray the core material with a solution, the core material can be placed in a high-speed mixer for vacuuming, and the metal solution can pass through the top of the high-speed mixer. The atomizing device for spraying. Using the solution to spray the core material can make the solution evenly adsorbed on the surface of the core material and form a coating layer in situ during combustion. Step (2) specifically can be that after the core material is evacuated to a vacuum degree of 1 atm, nitrogen is introduced while high-speed stirring is performed, and the solution is used to spray the core material, and the spraying and high-speed stirring are stopped when the vacuum degree reaches 0, and Vacuuming to a vacuum degree of 1 atm, vacuuming and then spraying can eliminate the mesoporous effect of the positive electrode material powder, so that the solution is adsorbed evenly on the surface of the core material, and nitrogen is introduced to cool the heat generated by high-speed stirring and prevent segregation. Preferably, the solution is divided into multiple sprays, and the process of “passing in the carrier gas while high-speed stirring is carried out and spraying the core material with the solution, stopping the spraying and high-speed stirring when the vacuum degree reaches 0, and vacuuming The operation to a vacuum degree of 1 atm” can more effectively eliminate the mesoporous effect of the positive electrode material powder, and make the solution adsorb evenly on the surface of the core material.

Specifically, in step (2), the solid content of the coating intermediate obtained by adding the solution to the core material is 90-99%, that is, the solid content of the core material and the solution is 90-99%, and the solution of the coating layer is 90-99%. content is less.

Further, in step (3), the coating intermediate is placed in a high-pressure oxidizing atmosphere, and a combustible gas is used as a carrier gas for combustion treatment to obtain a positive electrode material of the metal oxide coating core material, which can be carried out in a combustion coating equipment. The high-pressure oxidizing atmosphere refers to an atmosphere with an oxygen concentration of 200-500 kPa and an oxygen concentration of more than 99%, and the combustible gas is hydrogen or C1-C6 low paraffin, preferably propane or natural gas. The conditions of the combustion treatment are as follows: the combustion time is 10 to 30 s, the combustion temperature is 800 to 1200°C, and the combustion temperature is preferably 900 to 1000°C. The particle size of the metal oxide particles formed by combustion is less than 20nm, and the surface of the cathode material is uniformly coated. After the combustion is completed, the cathode material is still in a dry state with good fluidity, and no additional solid-liquid separation or drying process is required.

The preparation method of the positive electrode material of the present application will be described in detail below with reference to the examples.

Example 1

The preparation method of Al ₂ O ₃ coated high nickel ternary material Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 comprises the following steps:

(1) mixing and reacting elemental Al and nitric acid to generate Al(NO ₃ ) ₃ , then mixing the two, slowly adding ammonia water to dilute and adjusting the pH value to be 6 to make a solution;

(2) Add the core material Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 into the high-speed mixer, slowly vacuumize to make the vacuum degree reach 1 atm, turn on stirring, and spray the solution to the The surface of the core material Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 , and nitrogen as the carrier gas, when the vacuum degree is 0, stop spraying the solution, stop stirring, repeat the vacuum until the vacuum degree reaches 1 atm, and repeat again "Turn on the stirring, and use the atomizing device on the top of the high-speed mixer to spray the solution onto the surface of the Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 core material, and use nitrogen as the carrier gas. When the vacuum degree is 0, stop spraying Drain the solution, stop stirring, and repeat the operation of vacuuming until the vacuum degree reaches 1 atm", thereby obtaining a coating intermediate, and the solid content of the intermediate is 96%;

(3) The coating intermediate is placed in a high-pressure combustion coating equipment with a pressure of 400 kPa and an oxygen content of 99%, and propane is used as a carrier gas at 1000 ° C and burned for 20 s to obtain Al ₂ O ₃ coated Li _1.01 For the cathode material of Ni _0.8 Co _0.1 Mn _0.1 O _2.005 , the particle size of the metal oxide particles formed by combustion is less than 20 nm, and the surface of the cathode material is uniformly coated.

When propane burns, the water in the solution vaporizes, and when Al(NO ₃ ) ₃ decomposes, Al ³⁺ combines with oxygen atoms at high temperature and the action of oxygen to form Al ₂ O ₃ coated on Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 surface. The Al ₂ O _{3 -} coated Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 was characterized by SEM. The results are shown in Figure _1. The Al ₂ O ₃ coating layer is uniform _. The Ni _0.8 Co _0.1 Mn _0.1 O _2.005 cathode material was tested with reference to the "863 Program" Energy Saving and New Energy Vehicle Major Project - 2010 Performance Test Specification for Key Materials for Lithium-ion Power Batteries, and its capacity after 20 cycles was tested. The retention rate was 98.1% (as shown in Figure 3).

Example 2

The preparation method of MgO and SiO ₂ coating Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 comprises the following steps:

(1) Mix elemental Mg and elemental Si with nitric acid respectively, elemental Mg reacts with nitric acid to generate Mg(NO ₃ ) ₂ , element Si is dissolved in nitric acid by heating, and then the two are mixed and then slowly added with ammonia water to dilute and adjust pH A value of 6 makes a solution;

(2) Add the core material Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 into the high-speed mixer, slowly vacuumize to make the vacuum degree reach 1 atm, turn on stirring, and spray the solution to the The surface of the core material Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 , and nitrogen as the carrier gas, when the vacuum degree is 0, stop spraying the solution, stop stirring, repeat the vacuum until the vacuum degree reaches 1 atm, and repeat again "Turn on the stirring, and use the atomizing device on the top of the high-speed mixer to spray the solution onto the surface of the Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 core material, and use nitrogen as the carrier gas. When the vacuum degree is 0, stop spraying Drain the solution, stop stirring, and repeat the operation of vacuuming until the vacuum degree reaches 1 atm", thereby obtaining a coating intermediate, and the solid content of the intermediate is 96%;

(3) The coating intermediate was placed in a high-pressure combustion coating equipment with a pressure of 400 kPa and an oxygen content of 99%, and propane was used as a carrier gas at 1000 °C for 20 s to obtain MgO and SiO ₂ coated Li _1.01 For the cathode material of Ni _0.8 Co _0.1 Mn _0.1 O _2.005 , the particle size of the metal oxide particles formed by combustion is less than 20 nm, and the surface of the cathode material is uniformly coated.

When propane burns, the water in the solution vaporizes, and Mg(NO ₃ ) ₂ and nitric acid decompose when Mg ²⁺ combines with oxygen atoms at high temperature and the action of oxygen to form MgO coated on the surface of Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 , Si is oxidized at high temperature and the action of oxygen to form SiO ₂ coated on the surface of Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 . The obtained MgO and SiO ₂ -coated Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 cathode material was referred to in the "863 Program" Energy-Saving and New Energy Vehicle Major Project-2010 Lithium-ion Power Batteries with Key Materials Performance Test Specifications, The cycle performance test was carried out, and the capacity retention rate after 20 cycles was 98.0% (as shown in Figure 3).

Example 3

The preparation method of SiO ₂ coating Li _1.01 Ni _0.6 Co _0.2 Mn _0.2 O _2.005 comprises the following steps:

(1) elemental Si is dissolved in oxalic acid by heating, then slowly add ammonia water to dilute and adjust pH value to be 5 to make solution;

(2) Add the core material Li _1.01 Ni _0.6 Co _0.2 Mn _0.2 O _2.005 to the high-speed mixer, slowly vacuumize to make the vacuum degree reach 1 atm, turn on stirring, and use the atomization device on the top of the high-speed mixer to spray the solution to The surface of the core material Li _1.01 Ni _0.6 Co _0.2 Mn _0.2 O _2.005 , and nitrogen as the carrier gas, when the vacuum degree is 0, stop spraying the solution, stop stirring, repeat the vacuum until the vacuum degree reaches 1atm, and repeat again "Turn on stirring, spray the solution onto the surface of Li _1.01 Ni _0.6 Co _0.2 Mn _0.2 O _2.005 core material using the atomizing device on the top of the high-speed mixer, and use nitrogen as the carrier gas. When the vacuum degree is 0, stop spraying Drain the solution, stop stirring, and repeat the operation of vacuuming until the vacuum degree reaches 1 atm", thereby obtaining the coating intermediate, and the solid content of the intermediate is 99%;

(3) The coating intermediate is placed in a high-pressure combustion coating equipment with a pressure of 400 kPa and an oxygen content of 99%, and natural gas is used as a carrier gas at 1200 ° C and burned for 30 s to obtain SiO ₂ coated Li _1.01 Ni _0.6 For the cathode material of Co _0.2 Mn _0.2 O _2.005 , the particle size of the metal oxide particles formed by combustion is less than 20 nm, and the surface of the cathode material is uniformly coated.

When the natural gas is burned, the water in the solution is vaporized, and when the oxalic acid is decomposed, Si is oxidized at high temperature and oxygen to form SiO ₂ coated on the surface of Li _1.01 Ni _0.6 Co _0.2 Mn _0.2 O _2.005 . The obtained SiO ₂ -coated Li _1.01 Ni _0.6 Co _0.2 Mn _0.2 O _2.005 cathode material was cycled with reference to the "863 Program" Energy-Saving and New Energy Vehicle Major Project-2010 Performance Test Specification for Key Materials for Lithium-ion Power Batteries In the performance test, the capacity retention rate after 20 cycles was 96.2% (as shown in Figure 3).

Comparative Example 1

The preparation method of Al ₂ O ₃ coated high nickel ternary material Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 comprises the following steps:

(1) Mix and react elemental Al with nitric acid to generate Al(NO ₃ ) ₃ , then slowly add ammonia water to dilute and adjust the pH value to be 6 to make a solution;

(2) Add the core material Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 into the high-speed mixer, slowly vacuumize to make the vacuum degree reach 1 atm, turn on stirring, and spray the solution to the The surface of the core material Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 , and nitrogen as the carrier gas, when the vacuum degree is 0, stop spraying the solution, stop stirring, repeat the vacuum until the vacuum degree reaches 1 atm, and repeat again "Turn on the stirring, and use the atomizing device on the top of the high-speed mixer to spray the solution onto the surface of the Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 core material, and use nitrogen as the carrier gas. When the vacuum degree is 0, stop spraying Drain the solution, stop stirring, and repeat the operation of vacuuming until the vacuum degree reaches 1 atm", thereby obtaining a coating intermediate, and the solid content of the intermediate is 96%;

(3) The coated intermediate is placed in a high-pressure calciner with a pressure of 400 kPa and an oxygen content of 99%, and is calcined at 1000° C. for 10 min to obtain Al ₂ O ₃ coated Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 positive electrode material. The Al ₂ O ₃ -coated Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 was characterized by SEM. The results are shown in Figure _{2. The} Al ₂ O ₃ coating layer is not uniform. Li _1.01 Ni _0.8 Co _0.1 Mn _0.1 O _2.005 The cathode material refers to the "863 Program" Energy-Saving and New Energy Vehicle Major Project-2010 Lithium-ion Power Battery Key Materials Performance Test Specifications", and the cycle performance test is carried out. After 20 cycles The capacity retention rate of 95% (as shown in Figure 3).

3, it can be seen from the comparison of Examples 1 to 3 and Comparative Example 1 that in Examples 1 to 3 of the present application, simple metal and acid are directly used to make solutions, and combustible gas is used as a carrier gas, and the combustible gas is burned in a high-pressure oxidizing atmosphere. The heat generated during the process decomposes the solvent acid or salt in the solution, vaporizes water, and the metal element or metal ion forms the corresponding oxide under the action of high temperature and oxygen, which is coated on the surface of the core material in situ, and a uniform coating can be obtained. Cathode material, and the temperature of the carrier gas can be controlled near the sintering temperature of the cathode material when the carrier gas is burned, eliminating the impurity phase generated by the dissolution of transition metals on the surface of the material due to contact with acidic solvents, so the cycle performance of the cathode material is better. In Comparative Example 1, the ordinary calcination method is adopted instead of the combustion method. The direct heating of calcination cannot reach the decomposition temperature for a long time, but can only reach the vaporization temperature of Al(NO ₃ ) _3. The acidity will increase during the heating process, which will corrode the positive electrode material. , and the oxidation rate is slow and incomplete, and the obtained coating layer is not uniform, so the obtained cathode material with metal oxide coating has poor performance, and the capacity retention rate after 20 cycles is only 95%.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present application. Various modifications and alterations to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application . Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles disclosed herein.

Claims (7)

1. a preparation method of positive electrode material, described positive electrode material comprises core material and the metal oxide that coats described core material, it is characterized in that, comprise the following steps successively: (1) mixing the element of the corresponding metal in the metal oxide with an acid to prepare a solution; (2) adding to the core material to obtain a coating intermediate; (3) placing the coating intermediate in a high-pressure oxidizing atmosphere, and using combustible gas as a carrier gas to carry out combustion treatment in a combustion coating equipment to obtain a positive electrode material of a metal oxide coating core material, Wherein, adding the coating intermediate to the core material is to spray the core material with the solution, and spraying the core material with the solution is to evacuate the core material to a vacuum After the temperature is 1 atm, nitrogen is introduced into the high-speed stirring and the core material is sprayed with the solution. When the vacuum degree reaches 0, the spraying and high-speed stirring are stopped, and the vacuum is evacuated to a vacuum degree of 1 atm. The conditions of the combustion treatment are as follows: the combustion time is 10-30s, and the combustion temperature is 800-1200°C. 2 . The method for preparing a positive electrode material according to claim 1 , wherein the acid is an anion-decomposable organic acid or an inorganic acid at 600° C. 3 . 3. The method for preparing a positive electrode material according to claim 2, wherein the acid is one of nitric acid, dilute sulfuric acid, hydrochloric acid, acetic acid, citric acid and oxalic acid. 4 . The method for preparing a positive electrode material according to claim 1 , wherein the simple substance of the metal is mixed with an acid and then slowly added with ammonia water to dilute and adjust the pH to 5 to 6 to prepare a solution. 5 . 5. The preparation method of positive electrode material according to claim 1, is characterized in that, described solution is divided into multiple sprays, and repeats " while carrying out high-speed stirring, feed carrier gas and adopt described solution to all. The core material is sprayed, and when the vacuum degree reaches 0, the spraying and high-speed stirring are stopped, and the vacuum is evacuated to a vacuum degree of 1 atm”. 6 . The method for preparing a positive electrode material according to claim 1 , wherein the solid content of the coating intermediate is 90-99%. 7 . 7 . The method for preparing a cathode material according to claim 1 , wherein the combustible gas is hydrogen or C1-C6 low paraffins. 8 .

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