阅读说明：本技术 一种锂电池正极材料包覆用钴氧化物及其制备方法 (Cobalt oxide for coating lithium battery positive electrode material and preparation method thereof ) 是由 刘人生 田礼平 张荣洲 秦才胜 方华雄 于 2021-09-29 设计创作，主要内容包括：本发明公开了一种大比表面积钴氧化物及其制备方法,所述方法包括：(1)配制钴盐溶液和氢氧化钠溶液；(2)在搅拌条件下,将钴盐溶液和氢氧化钠溶液并流加入反应釜中,控制pH值在8～12,生成氢氧化亚钴,反应时间为60～120分钟,通入氮气作为保护气体；(3)停止投料和通入氮气,通入作为第一氧化剂的空气,并向反应釜中加入氧化能力比空气更强的第二氧化剂,对氢氧化亚钴进行氧化,控制第二氧化剂与钴元素的摩尔比在0.2～0.8:1的范围,并调节空气的流量,生成钴氧化物mCoOOH·(1-m)Co-(3)O-(4),其中m为0.36～1；以及(4)将氧化后的浆料过滤、洗涤、干燥后,采用机械粉碎设备进行粉碎,得到比表面积在30m～(2)/g以上的钴氧化物成品。(The invention discloses a cobalt oxide with large specific surface area and a preparation method thereof, wherein the method comprises the following steps: (1) preparing a cobalt salt solution and a sodium hydroxide solution; (2) under the condition of stirring, adding a cobalt salt solution and a sodium hydroxide solution into a reaction kettle in a parallel flow manner, controlling the pH value to be 8-12, generating cobaltous hydroxide, reacting for 60-120 minutes, and introducing nitrogen as a protective gas; (3) stopping feeding and introducing nitrogen, introducing air as a first oxidant, adding a second oxidant with stronger oxidizing power than air into the reaction kettle, oxidizing cobaltous hydroxide, and controlling the second oxidantThe molar ratio of the cobalt to the cobalt element is in the range of 0.2-0.8: 1, and the flow rate of air is adjusted to generate cobalt oxide mCoOOH (1-m) Co 3 O 4 Wherein m is 0.36-1; and (4) filtering, washing and drying the oxidized slurry, and then crushing by adopting mechanical crushing equipment to obtain the slurry with the specific surface area of 30m 2 The cobalt oxide finished product is more than g.)

1. A preparation method of cobalt oxide with large specific surface area comprises the following steps:

(1) preparing a cobalt salt solution without complexing, wherein the cobalt ion concentration is 60-150 g/L, and preparing a sodium hydroxide solution with the concentration of 80-440 g/L;

(2) under the condition of stirring, adding a cobalt salt solution and a sodium hydroxide solution into a reaction kettle in a parallel flow manner, controlling the pH value to be 8-12, generating cobaltous hydroxide, wherein the reaction time is 60-120 minutes, and introducing nitrogen as a protective gas during the reaction to prevent the generated cobaltous hydroxide from being oxidized;

(3) stopping feeding, stopping introducing nitrogen, starting introducing air serving as a first oxidant, adding a second oxidant with stronger oxidizing capability than the first oxidant into the reaction kettle to oxidize the cobaltous hydroxide, wherein the molar ratio of the second oxidant to the cobalt element in the reaction kettle is controlled within the range of 0.2-0.8: 1, and the flow rate of the introduced air is adjusted to oxidize the cobalt oxide mCoOOH (1-m) Co₃O₄Wherein m is 0.36-1; and

(4) filtering, washing and drying the oxidized slurry, and crushing by adopting mechanical crushing equipment to obtain the slurry with the specific surface area of 30m²The cobalt oxide finished product is more than g.

2. The method according to claim 1, wherein in the step (3), the flow rate of the air is controlled to be 0.1 to 1m³/h。

3. A method of manufacture as claimed in claim 1 or claim 2, wherein the second oxidant comprises one or more of hypochlorous acid, sodium persulphate, peroxyacetic acid, hydrogen peroxide.

4. The method according to claim 1, wherein the nitrogen gas is controlled to have a flow rate of 0.3 to 3m in the step (2)³/h。

5. The method according to claim 1 or 4, wherein the reaction temperature in the step (2) is 30 to 80 ℃.

6. The preparation method according to claim 1, wherein the specific surface area of the cobalt oxide finished product obtained in the step (4) is 40-90 m²In terms of particles, the particle diameter D50 is less than 100nm, preferably less than 70 nm.

7. The production method according to claim 1 or 6, wherein the cobalt content of the cobalt oxide finished product obtained in the step (4) is 62 to 70 wt%.

8. A cobalt oxide for coating the positive electrode of lithium battery has the chemical formula mCoOOH (1-m) Co₃O₄Wherein m is 0.36-1, and the specific surface area is 30m²More than g.

9. A cobalt oxide for coating the positive electrode of lithium battery has the chemical formula mCoOOH (1-m) Co₃O₄Wherein m is an amount such that the cobalt content in the cobalt oxide is 62 to 70 wt%, and the specific surface area of the cobalt oxide is 30m²More than g.

10. The lithium battery positive electrode material-coating cobalt oxide according to claim 8 or 9, wherein the specific surface area of the cobalt oxide is 40 to 90m²Per g, the particle diameter D50 is less than 100nm, preferably less than 70 nm.

Technical Field

The invention belongs to the technical field of lithium battery anode materials, and particularly relates to cobalt oxide for coating a lithium battery anode material and a preparation method thereof.

Background

Lithium batteries have high energy density and are being widely used in electronic devices, electric vehicles, and hybrid vehicles. The cathode material is a core factor determining the cost and performance of the lithium battery, and common cathode materials mainly comprise ternary lithium nickel cobalt manganese oxide, ternary lithium nickel cobalt aluminate, lithium cobalt oxide and the like. At present, the positive electrode material of the lithium battery still has some problems. For example, the high-nickel ternary cathode material has poor stability of the material structure under high voltage due to too high nickel content, so that the safety of the battery cannot be guaranteed, and the problems of low first-time charge and discharge efficiency, low electronic ion conductivity and the like also exist. Lithium cobaltate positive electrode materials also have problems, such as the material structure is unstable during high voltage plateau discharge, resulting in irreversible capacity decay.

One approach to solve the above problems is to modify the positive electrode material by means of coating or the like. Coating means forming a layer of inert material, such as Al, on the surface of the positive electrode material₂O₃、MgO、ZnO、SiO₂、AlF₃Etc. non-lithium active material, or form LiCoO₂、Li₂ZrO₃、LiMPO₄And the like. At present, in order to form LiCoO on the surface of a positive electrode material₂By using Co (OH)₂As a coating material with Li₂CO₃And high-temperature calcining reaction. However, Co (OH) as a coating material₂The particle diameter is about 500nm, and the specific surface area thereofProduct less than 30m²Limited by this small specific surface area, by Co (OH)₂With Li₂CO₃LiCoO obtained by high-temperature calcination reaction₂The activity of (2) is relatively low, and the electrical property of the positive electrode material is influenced. Furthermore, Co (OH)₂During production, Co in the waste water²⁺The content is generally 0.001-0.01 g/L, the precipitation is incomplete, and further treatment is needed according to the national wastewater discharge standard.

As a coating material for a positive electrode material of a lithium battery, it is advantageous that the particles are fine so as to have a larger specific surface area. However, since the finer the particles, the more easily the particles are agglomerated, especially when the particle size is as small as on the order of micrometers or less, the specific surface area is large, the surface energy of the particles is high, spontaneous agglomeration is easily caused, and the dispersibility is poor.

It is desired to provide a material for coating a positive electrode material for a lithium battery, which has a large specific surface area and good dispersibility.

Disclosure of Invention

The invention provides a cobalt oxide with large specific surface area and a preparation method thereof, which can be used for coating a lithium battery anode material and at least partially solves the problems in the prior art.

According to one aspect of the present invention, there is provided a method for preparing a cobalt oxide having a large specific surface area, the method comprising the steps of:

(1) preparing a cobalt salt solution without complexing, wherein the cobalt ion concentration is 60-150 g/L, and preparing a sodium hydroxide solution with the concentration of 80-440 g/L;

(2) under the condition of stirring, adding a cobalt salt solution and a sodium hydroxide solution into a reaction kettle in a parallel flow manner, controlling the pH value to be 8-12, generating cobaltous hydroxide, wherein the reaction time is 60-120 minutes, and introducing nitrogen as a protective gas during the reaction to prevent the generated cobaltous hydroxide from being oxidized;

(3) stopping feeding, stopping introducing nitrogen, starting introducing air serving as a first oxidant, adding a second oxidant with stronger oxidizing capability than the first oxidant into the reaction kettle to oxidize the cobaltous hydroxide, wherein the molar ratio of the second oxidant to the cobalt element in the reaction kettle is controlled within the range of 0.2-0.8: 1, and the flow rate of the introduced air is adjusted to ensure that the cobalt element is oxidizedTo obtain cobalt oxide mCoOOH (1-m) Co₃O₄Wherein m is 0.36-1; and

(4) filtering, washing and drying the oxidized slurry, and crushing by adopting mechanical crushing equipment to obtain the slurry with the specific surface area of 30m²The cobalt oxide finished product is more than g.

Preferably, in the step (3), the flow rate of the air is controlled to be 0.1-1 m³/h。

The second oxidant may include one or more of hypochlorous acid, sodium persulfate, peracetic acid, hydrogen peroxide.

Preferably, in the step (2), the flow rate of the nitrogen is controlled to be 0.3-3 m³/h。

Preferably, the reaction temperature in the step (2) is 30-80 ℃.

Preferably, the specific surface area of the cobalt oxide finished product obtained in the step (4) is 40-90 m²Per g, the particle diameter D50 is less than 100nm, preferably less than 70 nm.

Preferably, the cobalt content of the cobalt oxide finished product obtained in the step (4) is 62-70 wt%.

According to another aspect of the present invention, there is provided a cobalt oxide for coating a lithium battery positive electrode material, wherein the cobalt oxide has a chemical formula of mCoOOH (1-m) Co₃O₄Wherein m is 0.36-1, and the specific surface area is 30m²More than g.

According to another aspect of the present invention, there is provided a cobalt oxide for coating a lithium battery positive electrode material, wherein the cobalt oxide has a chemical formula of mCoOOH (1-m) Co₃O₄Wherein m is 0.36-1, and the specific surface area is 30m²More than g.

According to another aspect of the present invention, there is provided a cobalt oxide for coating a lithium battery positive electrode material, wherein the cobalt oxide has a chemical formula of mCoOOH (1-m) Co₃O₄Wherein m is an amount such that the cobalt content in the cobalt oxide is 62 to 70 wt%, and the specific surface area of the cobalt oxide is 30m²More than g.

Preferably, the specific surface area of the cobalt oxide is 40-90 m²Per g, the particle diameter D50 is less than 100nm, more preferably less than 70 nm.

According to the invention, firstly, the cobaltous hydroxide is synthesized by a non-complex reaction solution through a wet method, and nitrogen is used for protecting the cobaltous hydroxide from being oxidized; then oxidizing cobaltous hydroxide by providing air and an oxidant with oxidizing power stronger than that of the air, realizing the precise regulation and control of the oxidation degree and preparing the Co oxide with the chemical formula of mCoOOH (1-m)₃O₄The cobalt oxide (m is 0.36-1) achieves accurate control on particle size, specific surface area and cobalt content, and provides a cobalt oxide product which is small in particle size, large in specific surface area and good in dispersity and can be used for coating the lithium battery anode material.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings:

FIG. 1 is a scanning electron micrograph of a cobalt oxide obtained after pulverization in example 1;

FIG. 2 is an XRD diffraction pattern of cobalt oxide obtained in example 1;

FIG. 3 is a graph showing a particle size distribution of cobalt oxide obtained after pulverization in example 1;

FIG. 4 is a scanning electron micrograph of cobalt oxide obtained after pulverization in example 2;

FIG. 5 is an XRD diffraction pattern of cobalt oxide obtained in example 2;

FIG. 6 is a graph showing a particle size distribution of cobalt oxide obtained after pulverization in example 2;

FIG. 7 is a scanning electron micrograph of a cobalt oxide obtained after pulverization in example 3;

FIG. 8 is an XRD diffraction pattern of cobalt oxide obtained in example 3;

FIG. 9 is a graph showing a particle size distribution of cobalt oxide obtained after pulverization in example 3.

Detailed Description

The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention.

According to the invention, a lithium batteryThe positive electrode material is coated with a cobalt oxide having a chemical formula of mCoOOH (1-m) Co₃O₄Wherein m is 0.36-1, and the specific surface area is 30m²More than g.

According to the invention, the chemical formula of the cobalt oxide for coating the lithium battery cathode material is mCoOOH (1-m) Co₃O₄Wherein m is an amount such that the cobalt content in the cobalt oxide is 62 to 70 wt%, and the specific surface area of the cobalt oxide is 30m²More than g.

Preferably, the specific surface area of the cobalt oxide is 40 to 90m²(ii) in terms of/g. The particle size D50 of the cobalt oxide is preferably less than 100nm, more preferably less than 70 nm.

Since the particle size of the cobalt hydroxide becomes smaller after the oxidation treatment, the cobalt oxide of the present invention can have a smaller particle size and a correspondingly larger specific surface area than the cobalt hydroxide for coating. Thus, when the cobalt oxide is used for coating the lithium battery anode material, the activity of the anode material is improved, and the electrical property of the anode material is improved.

In addition, after the oxidation treatment, the surface energy of particles with the size below the micron is reduced, and the particles tend to be in a stable state, so that the agglomeration among the particles is inhibited, and the cobalt oxide has better material dispersibility compared with cobaltous hydroxide for coating, thereby being more beneficial to the application of the cobalt oxide in the coating of the lithium battery positive electrode material.

The invention also provides a preparation method of the cobalt oxide with large specific surface area, which comprises the following steps:

(1) preparing a cobalt salt solution without complexing, wherein the cobalt ion concentration is 60-150 g/L, and preparing a sodium hydroxide solution with the concentration of 80-440 g/L;

(2) under the condition of stirring, adding a cobalt salt solution and a sodium hydroxide solution into a reaction kettle in a parallel flow manner, controlling the pH value to be 8-12, generating cobaltous hydroxide, wherein the reaction time is 60-120 minutes, and introducing nitrogen as a protective gas during the reaction to prevent the generated cobaltous hydroxide from being oxidized;

(3) stopping feeding and stoppingIntroducing nitrogen, starting introducing air serving as a first oxidant, adding a second oxidant with stronger oxidizing capability than the first oxidant into the reaction kettle to oxidize the cobaltous hydroxide, wherein the molar ratio of the second oxidant to the cobalt element in the reaction kettle is controlled within the range of 0.2-0.8: 1, and the flow rate of the introduced air is adjusted to oxidize the cobalt oxide mCoOOH (1-m) Co₃O₄Wherein m is 0.36-1; and

(4) filtering, washing and drying the oxidized slurry, and crushing by adopting mechanical crushing equipment to obtain the slurry with the specific surface area of 30m²The cobalt oxide finished product is more than g.

In the preparation method, firstly, the cobaltous hydroxide is synthesized by a non-complex reaction solution through a wet method, and nitrogen is used for protecting the cobaltous hydroxide from being oxidized; then oxidizing cobaltous hydroxide by providing air and an oxidant with oxidizing power stronger than that of the air, realizing the precise regulation and control of the oxidation degree and preparing the Co oxide with the chemical formula of mCoOOH (1-m)₃O₄The cobalt oxide (m is 0.36-1) can accurately control the particle size, specific surface area and cobalt content.

In addition, the + 3-valent Co ions are more completely precipitated after oxidation under the same alkaline condition than the + 2-valent Co ions, so that the content of the Co ions in the produced wastewater is lower. The Co content in the wastewater generated by the preparation method can reach a level less than 0.001g/L, so that the wastewater reaches the national wastewater discharge standard, the wastewater treatment is simpler, and the feasibility of industrialization is improved. The specific rotational speeds of the agitator given in the embodiments described below are provided by way of example only and are not limiting.

In the above preparation method, the second oxidant may include one or more of hypochlorous acid, sodium persulfate, peracetic acid, hydrogen peroxide.

In the step (2), the flow of the nitrogen can be controlled to be 0.3-3 m³And h, so that positive pressure can be formed in the reaction kettle, and external air is prevented from spontaneously entering the kettle.

In the step (2), the reaction temperature may be 30 to 80 ℃.

In the above step (3), of airThe flow rate is preferably controlled to be 0.1-1 m³/h。

The specific surface area of the cobalt oxide finished product obtained in the step (4) is preferably 40-90 m²The particle diameter D50 is preferably less than 100nm, more preferably less than 70 nm.

The cobalt content of the cobalt oxide finished product obtained in the step (4) is preferably 62-70 wt%.

In the preparation method, the rotating speed value of the stirrer is greatly different due to the reaction kettles with different sizes, and the stirring effect and the shape and the size of the paddle are related, so that the rotating speed value of the stirrer is not suitable for specific regulation in the application. In the preparation method, the rotating speed of the stirrer can ensure that the reaction in the reaction kettle is sufficient and uniform.

Embodiments of the present invention are described below. It should be understood that the present invention is not limited to these specific examples.

< example 1>

Preparing a solution: mixing cobalt sulfate with pure water to prepare a cobalt sulfate solution with the cobalt ion concentration of 60 g/L; sodium hydroxide and pure water were mixed to prepare a sodium hydroxide solution having a concentration of 80 g/L.

And (3) synthesizing cobaltous hydroxide: adding pure water into a reaction kettle as a base solution, simultaneously pumping the prepared cobalt sulfate solution and sodium hydroxide solution into the reaction kettle at the temperature of 30 ℃ and the rotating speed of a stirrer of 130rpm, controlling the reaction pH to be 8-8.3, reacting for 60min, introducing nitrogen as protective gas, wherein the nitrogen flow is 0.3m³/h。

Oxidation treatment: after the reaction for synthesizing cobaltous hydroxide is finished, stopping introducing nitrogen, and starting introducing air, wherein the air flow is controlled to be 0.2m²And h, simultaneously adding an oxidant hypochlorous acid into the reaction kettle, controlling the molar ratio of the hypochlorous acid to the cobalt element to be 0.8:1, and oxidizing the cobaltous hydroxide.

And (3) subsequent treatment: filtering the oxidized slurry, washing with hot pure water at 60 ℃, drying at 80 ℃, and crushing by adopting ultrafine crushing equipment to obtain a cobalt oxide finished product.

FIG. 1 shows the scanning of cobalt oxide obtained in example 1In the electron micrograph, it can be seen that the cobalt oxide was in the form of dots which were substantially uniformly dispersed without agglomeration. From the XRD pattern of the cobalt oxide obtained in example 1 shown in FIG. 2, it can be seen that the sample phase components consist essentially of cobalt oxyhydroxide. As shown in fig. 3, the particle diameter D50 of the cobalt oxide obtained by grinding in example 1 was 67 nm. The cobalt oxide had a specific surface area of 45.3m²(ii)/g, Co content 63.2 wt%.

The cobalt ion content of the wastewater generated in example 1 is less than 0.0001 g/L.

< example 2>

Preparing a solution: mixing cobalt chloride with pure water to prepare a cobalt chloride solution with the cobalt ion concentration of 100 g/L; sodium hydroxide and pure water were mixed to prepare a sodium hydroxide solution having a concentration of 250 g/L.

And (3) synthesizing cobaltous hydroxide: adding pure water as a base solution into a reaction kettle, pumping the prepared cobalt salt cobalt chloride solution and sodium hydroxide solution into the reaction kettle at the same time under the conditions of 50 ℃ and 130rpm of the rotating speed of a stirrer, controlling the reaction pH to be 9.5-10.0, reacting for 90min, introducing nitrogen as protective gas with the flow rate of 1.5m³/h。

Oxidation treatment: after the reaction for synthesizing cobaltous hydroxide is finished, stopping introducing nitrogen, and starting introducing air, wherein the air flow is controlled to be 0.55m²And h, simultaneously adding an oxidant sodium persulfate into the reaction kettle, controlling the molar ratio of the sodium persulfate to the cobaltous ions to be 0.5: 1, and oxidizing the cobaltous hydroxide.

And (3) subsequent treatment: filtering the oxidized slurry, washing with hot pure water at 75 ℃, drying at 100 ℃, and crushing by adopting ultrafine crushing equipment to obtain a cobalt oxide finished product.

FIG. 4 shows a scanning electron micrograph of the cobalt oxide obtained in example 2, in which the cobalt oxide was observed to be in the form of dots in which the cobalt oxide was not agglomerated and was substantially uniformly dispersed. From the XRD pattern of the cobalt oxide obtained in example 2 shown in FIG. 5, it can be seen that the sample phase components are mainly composed of cobalt oxyhydroxide + cobaltosic oxide, in which the cobalt oxyhydroxide phase is dominant. As shown in fig. 6, the particle diameter D50 of the cobalt oxide obtained by grinding in example 2 was 60 nm. The cobalt oxide has a specific surface area of68.5m²(ii)/g, Co content 65.9 wt%.

The cobalt ion content of the wastewater generated in example 2 is less than 0.0001 g/L.

< example 3>

Preparing a solution: mixing cobalt nitrate with pure water to prepare a cobalt nitrate solution with the cobalt ion concentration of 150 g/L; sodium hydroxide and pure water were mixed to prepare a sodium hydroxide solution having a concentration of 440 g/L.

And (3) synthesizing cobaltous hydroxide: adding pure water as a base solution into a reaction kettle, pumping the prepared cobalt nitrate solution and sodium hydroxide solution into the reaction kettle at the same time under the conditions of 80 ℃ and 130rpm of the rotating speed of a stirrer, controlling the reaction pH to be 11.5-11.8, reacting for 120min, introducing nitrogen as protective gas with the nitrogen flow of 3.0m³/h。

Oxidation treatment: after the reaction for synthesizing cobaltous hydroxide is finished, stopping introducing nitrogen, and starting introducing air, wherein the air flow is controlled to be 0.96m²Adding peroxyacetic acid and hydrogen peroxide serving as oxidants into a reaction kettle, controlling the molar ratio of the peroxyacetic acid to cobaltous ions to be 0.2: 1, and oxidizing the cobaltous hydroxide.

And (3) subsequent treatment: filtering the oxidized slurry, washing with 90 ℃ hot pure water, drying at 120 ℃, and crushing by adopting an ultrafine crushing device to obtain a cobalt oxide finished product.

FIG. 7 is a scanning electron micrograph of the cobalt oxide obtained in example 3, and it can be seen that the cobalt oxide was in the form of dots in which the cobalt oxide was not agglomerated and was substantially uniformly dispersed. From the XRD pattern of the cobalt oxide obtained in example 3 shown in FIG. 8, it can be seen that the sample phase composition is composed mainly of cobalt oxyhydroxide + cobaltosic oxide, in which the cobaltosic oxide phase is predominant. As shown in fig. 9, the particle diameter D50 of the cobalt oxide obtained by grinding in example 3 was 58 nm. The cobalt oxide had a specific surface area of 89.1m²Per g, Co content 68.6 wt%.

Example 3 produced wastewater with a cobalt ion content of less than 0.0001 g/L.

The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.