Doped cobaltosic oxide and preparation method therefor

Abstract

Doped cobaltosic oxide and a preparation method therefor. According to the method, a pre-oxidation process is used in combination with specific processing additives to prepare the product, such that the "sticking to a furnace" phenomenon can be effectively alleviated. In addition, the product prepared has high particle uniformity and is free of obvious cracking, a doping element has a gradient distribution, and a lithium cobalt oxide material prepared has good electrochemical performance. The method makes full-chain integrated production of doped cobaltosic oxide in the field of lithium batteries possible.

Description

Doped cobalt trioxide and preparation method thereof Technical Field

[0001] This article relates to the technical field of lithium battery materials, and in particular to a doped cobalt trioxide and a preparation method thereof. Background Art

[0002] Cobalt trioxide is a precursor for the preparation of lithium cobalt oxide, a widely used cathode active material in the lithium battery industry. The quality of cobalt trioxide is directly related to the electrochemical performance of lithium cobalt oxide during use. Currently, cobalt trioxide in the lithium battery industry is mainly obtained by high-temperature sintering of cobalt carbonate. However, due to the poor fluidity of cobalt carbonate itself, it is prone to "sticking to the furnace" during high-temperature sintering, which hinders the addition and mixing of materials. Not only does this reduce the yield of the final product, but excessive sticking makes the sintering equipment difficult to clean, even affecting its normal operation. Therefore, a high cleaning frequency is required to ensure the normal operation of the equipment. On the other hand, in related technologies, people are gradually replacing pure cobalt trioxide with higher-performance doped cobalt trioxide. Generally, doping materials are introduced during the synthesis stage of cobalt carbonate and then sintered to obtain it. However, due to the tendency of cobalt carbonate particles to crack during this process, the doping materials can also be unevenly dispersed, which can prevent the expected effect when used.

[0003] Summary of the Invention

[0004] The purpose of this article is to overcome the shortcomings of the above-mentioned existing technologies and provide a preparation method of doped cobalt tetroxide. This method adopts a pre-oxidation process in combination with specific processing aids to prepare products, which can effectively improve the "sticking furnace" phenomenon. At the same time, the particles in the prepared products are highly uniform, without obvious cracking, and the doping elements are distributed in a gradient. The further prepared lithium cobalt oxide material has good electrochemical properties.

[0005] To achieve the above objectives, the technical solutions adopted in this paper are:

[0006] A preparation method of doped cobalt trioxide comprises the following steps:

[0007] Oxidizing cobalt carbonate in air and / or oxygen atmosphere at 200-400° C. for 2-4 hours;

[0008] The oxidized cobalt carbonate, an oxidizing aid and a doping aid are mixed, and then calcined at 700-750° C. for 3-8 hours in an air or oxygen atmosphere to obtain doped cobalt trioxide; the oxidizing aid is at least one of perchlorate, persulfate, and metal peroxide; the doping aid includes a metal salt and a doping oxide; the mass ratio of the oxidized cobalt carbonate, the oxidizing aid, and the doping aid is 1: (0.0001-0.0003): (0.0001-0.01).

[0009] In one embodiment, the melting point of the metal salt is ≤ 720°C.

[0010] In one embodiment, the mass ratio of the oxidized cobalt carbonate, the oxidizing agent, and the doping agent is 1:(0.0001-0.0003):(0.0001-0.005).

[0011] In the preparation method of doped cobalt tetroxide described in this article, since the cobalt carbonate has been pre-oxidized and subsequently mixed with an oxidizing aid and calcined, the calcination process can be carried out at a lower temperature. During this process, the fluidity and stability between the particles of the mixture are high, and the particles are not easy to crack, which effectively alleviates the phenomenon of material adhering to the inner wall of the sintering device that often occurs in conventional processes; on the other hand, since the cobalt carbonate particle material is pre-oxidized and the surface density is high, it is difficult to achieve penetration doping by doping elements using a general solid-phase sintering method. The preparation method described in this article uses metal salts and doped oxides as doping aids, wherein the metal salt has a low melting point and can melt at 700-750°C. As a flux, the doped oxide gradually penetrates into the interior of the cobalt tetroxide particles and realizes liquid sintering. Finally, the metal doping element is gradiently distributed from the inside to the outside in the product. When the product is further used to prepare lithium cobalt oxide materials, good electrochemical properties can be achieved.

[0012] In addition, during the calcination process, the amount of oxidizing agent added cannot be too much or too little. If too little is added, the cobalt content in the mixture will fluctuate, and effective regulation cannot be achieved. The doped elements will also fail to provide the necessary structural stabilization. If too much is added, it will lead to the enrichment of the doping elements, which will in turn make the product uniformity worse.

[0013] In one embodiment, the cobalt content of the cobalt carbonate is 72.0-73.0%, and the particle size D 50 3~20μm.

[0014] In one embodiment, the flow rate of air and / or oxygen atmosphere during the oxidation is 20-40 L / h / kg cobalt carbonate.

[0015] During the pre-oxidation process of cobalt carbonate, the amount of oxygen added must be sufficient to ensure that the cobalt carbonate can be completely converted into cobalt trioxide at a lower temperature during the subsequent sintering process.

[0016] In one embodiment, the temperature during the oxidation is 300-400°C.

[0017] The temperature during oxidation has a great influence on the morphology of the final product. If the temperature is too high, it may cause the particles in the product to crack. If the temperature is too low, it may lead to incomplete conversion of cobalt tetroxide and doping of doping elements in the product, and will also affect the fluidity of the particles.

[0018] In one embodiment, the heating rate during oxidation is 2-3° C. / min.

[0019] In one embodiment, the metal salt in the doping aid is at least one of MgCl2, NaNO3, Ba(NO)2, ZnCl2, FeCl2, and ZnSO4.

[0020] In one embodiment, the doped oxide is a metal or non-metal oxide, and the metal or non-metal oxide is at least one of MgO, Al2O3, TiO2, Nb2O5, B2O3, and V2O5.

[0021] The above-mentioned metal salts have a low melting point, which can help the metal oxides effectively enter the cobalt carbonate wrapped in the dense surface layer and improve the structural stability of the overall material.

[0022] In one embodiment, the heating rate during calcination is 2-5° C. / min.

[0023] Another object of this invention is to provide the doped cobalt tetroxide prepared by the preparation method of doped cobalt tetroxide.

[0024] Another purpose of this article is to provide the use of the doped cobalt trioxide in the preparation of lithium cobalt oxide materials.

[0025] The cobalt oxide doped with the method described here exhibits uniform morphology, complete particles, high cobalt content, and high crystal stability. Further application in material synthesis yields lithium cobalt oxide materials with ideal electrochemical properties. Because furnace sticking is not a concern during the preparation process, continuous production is possible.

[0026] Compared with the existing technology, the beneficial effects of this article are:

[0027] This article provides a preparation method for doped cobalt tetroxide. This method uses a pre-oxidation process combined with specific processing aids to prepare the product, which can effectively improve the "furnace sticking" phenomenon. At the same time, the particles in the prepared product are highly uniform, without obvious cracking, and the doping elements show a gradient distribution. The further prepared lithium cobalt oxide material has good electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 shows the EDS point scan from the outer layer to the inner layer (from left to right) of the cobalt oxide-doped particles described in this article and the elemental composition of the scan points.

[0029] Figure 2 is a schematic diagram of the "sticking kiln" phenomenon occurring in the rotary kiln used in the preparation process of the product described in Comparative Example 5 (Figure 2 left, where the boxed area is the sticking material) and a schematic diagram of the rotary kiln used in the preparation process of the product described in Example 1 (Figure 2 right). DETAILED DESCRIPTION

[0030] To better illustrate the purpose, technical solutions and advantages of this article, this article will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] Unless otherwise specified, the materials used in the examples and comparative examples can be obtained through commercial channels.

[0032] The cobalt content of the cobalt carbonate used in each embodiment and comparative example is 72.0-73.0%, and the particle size D 50 3~20μm.

[0033] Example 1

[0034] An embodiment of the doped cobalt trioxide and its preparation method described herein is as follows:

[0035] (1) 20 kg of cobalt carbonate was heated to 300°C in an oven at 2°C / min and oxidized for 4 h; air was introduced during the oxidation process at a flow rate of 20 L / h / kg of cobalt carbonate.

[0036] (2) 20 kg of oxidized cobalt carbonate, 3 g of an oxidizing aid and a doping aid were first mixed in a mixer at a low speed of 500 rpm for 2 min, then mixed at 1500 rpm for 30 min, and finally mixed at 500 rpm for 5 min, and then heated to 740 ° C. at 2 ° C. / min in an oxygen atmosphere in a rotary kiln for 4 h to obtain doped cobalt trioxide; the oxidizing aid was lithium perchlorate; the doping aid was 60 g of a metal salt magnesium chloride and 4 g of a metal oxide magnesium oxide.

[0037] Example 2

[0038] An embodiment of the doped cobalt trioxide and its preparation method described herein is as follows:

[0039] (1) 30 kg of cobalt carbonate was heated to 400 °C in a rotary kiln at 4 °C / min and oxidized for 4 h; air was introduced during the oxidation at a flow rate of 40 L / h / kg of cobalt carbonate.

[0040] (2) 30 kg of oxidized cobalt carbonate, 6 g of an oxidizing aid and a doping aid were first mixed in a mixer at a low speed of 500 rpm for 2 min, then mixed at 1500 rpm for 30 min, and finally mixed at 500 rpm for 5 min, and then heated to 740 ° C. at 2 ° C. / min in an oxygen atmosphere in a rotary kiln and calcined for 4 h to obtain doped cobalt tetroxide; the oxidizing aid was vanadium peroxide; the doping aid was 4 g of a metal salt sodium nitrate and 150 g of a metal oxide vanadium pentoxide.

[0041] Example 3

[0042] An embodiment of the doped cobalt trioxide and its preparation method described herein is as follows:

[0043] (1) 40 kg of cobalt carbonate was heated to 400 °C in a rotary kiln at 4 °C / min and oxidized for 4 h; air was introduced during the oxidation at a flow rate of 26 L / h / kg of cobalt carbonate.

[0044] (2) 40 kg of oxidized cobalt carbonate, 5 g of an oxidizing agent and a doping agent were first mixed in a mixer at a low speed of 500 rpm for 2 min, then mixed at 1500 rpm for 30 min, and finally mixed at 500 rpm for 5 min, and then heated to 730 ° C at 3 ° C / min in an oxygen atmosphere in a rotary kiln for 3.5 h to obtain doped cobalt trioxide; the oxidizing agent was ammonium persulfate; the doping agent included 160 g of a metal salt Ba(NO)2 and 16 g of a non-metallic oxide diboron trioxide.

[0045] Example 4

[0046] An embodiment of the doped cobalt trioxide and its preparation method described herein is as follows:

[0047] (1) 40 kg of cobalt carbonate was heated to 400 °C in a rotary kiln at 4 °C / min and oxidized for 4 h; air was introduced during the oxidation at a flow rate of 35 L / h / kg of cobalt carbonate.

[0048] (2) 40 kg of oxidized cobalt carbonate, 5 g of an oxidizing aid and a doping aid were first mixed in a mixer at a low speed of 500 rpm for 2 min, then mixed at 1500 rpm for 30 min, and finally mixed at 500 rpm for 5 min, and then heated to 730 ° C. at 3 ° C. / min in an oxygen atmosphere in a rotary kiln and calcined for 3.5 h to obtain doped cobalt tetroxide; the oxidizing aid was ammonium persulfate; the doping aid included 85 g of chloride zinc chloride and 6 g of metal oxide titanium dioxide.

[0049] Comparative Example 1

[0050] A doped cobalt trioxide and a preparation method thereof, wherein the preparation method of the doped cobalt trioxide is as follows:

[0051] (1) 20 kg of cobalt carbonate was heated to 300°C in an oven at 2°C / min and oxidized for 4 h; air was introduced during the oxidation process at a flow rate of 20 L / h / kg of cobalt carbonate.

[0052] (2) 20 kg of oxidized cobalt carbonate, 8 g of an oxidizing aid and a doping aid were first mixed in a mixer at a low speed of 500 rpm for 2 min, then mixed at 1500 rpm for 30 min, and finally mixed at 500 rpm for 5 min, and then heated to 740 ° C. at 2 ° C. / min in an oxygen atmosphere in a rotary kiln for 4 h to obtain doped cobalt trioxide; the oxidizing aid was lithium perchlorate; the doping aid was 120 g of a metal salt magnesium chloride and 8 g of a metal oxide magnesium oxide.

[0053] Comparative Example 2

[0054] A doped cobalt trioxide and a preparation method thereof, wherein the preparation method of the doped cobalt trioxide is as follows:

[0055] (1) 20 kg of cobalt carbonate was heated to 300°C in an oven at 2°C / min and oxidized for 4 h; air was introduced during the oxidation process at a flow rate of 20 L / h / kg of cobalt carbonate.

[0056] (2) 20 kg of oxidized cobalt carbonate, 1 g of an oxidizing aid and a doping aid were first mixed in a mixer at a low speed of 500 rpm for 2 min, then mixed at 1500 rpm for 30 min, and finally mixed at 500 rpm for 5 min, and then heated to 740 ° C. at 2 ° C. / min in an oxygen atmosphere in a rotary kiln for 4 h to obtain doped cobalt trioxide; the oxidizing aid was lithium perchlorate; the doping aid was 20 g of a metal salt magnesium chloride and 2 g of a metal oxide magnesium oxide.

[0057] Comparative Example 3

[0058] A doped cobalt trioxide and a preparation method thereof, wherein the preparation method of the doped cobalt trioxide is as follows:

[0059] 30 kg of cobalt carbonate, 1 g of an oxidizing agent and a doping agent were first mixed in a mixer at a low speed of 500 rpm for 2 minutes, then mixed at 1500 rpm for 30 minutes, and finally mixed at 500 rpm for 5 minutes. The mixture was then heated to 740 ° C at 2 ° C / min in an air atmosphere in a rotary kiln and calcined for 4 hours to obtain doped cobalt tetroxide; the oxidizing agent was vanadium peroxide; the doping agent was 4 g of metal salt NaNO3 and 150 g of metal oxide vanadium pentoxide.

[0060] Comparative Example 4

[0061] A doped cobalt trioxide and a preparation method thereof, wherein the preparation method of the doped cobalt trioxide is as follows:

[0062] (1) 40 kg of cobalt carbonate was heated to 550°C in a rotary kiln at a rate of 4°C / min and oxidized for 3.5 h. During the oxidation, air was introduced at a flow rate of 33 L / h / kg of cobalt carbonate.

[0063] (2) 40 kg of oxidized cobalt carbonate, 5 g of an oxidizing agent and a doping agent were first mixed in a mixer at a low speed of 500 rpm for 2 min, then mixed at 1500 rpm for 30 min, and finally mixed at 500 rpm for 5 min, and then heated to 730 ° C at 3 ° C / min in an oxygen atmosphere in a rotary kiln for 3.5 h to obtain doped cobalt trioxide; the oxidizing agent was ammonium persulfate; the doping agent included 160 g of a metal salt Ba(NO)2 and 16 g of a non-metallic oxide diboron trioxide.

[0064] Comparative Example 5

[0065] A cobalt trioxide and a preparation method thereof, wherein the preparation method of the cobalt trioxide is as follows:

[0066] 40 kg of cobalt carbonate was heated to 750° C. at 4° C. / min in an air atmosphere in a rotary kiln and calcined for 3.5 hours to obtain unmodified cobalt trioxide.

[0067] Comparative Example 6

[0068] A doped cobalt trioxide and a preparation method thereof, the difference from Example 1 being that the metal salt magnesium chloride is replaced with magnesium oxide, and the added mass of the magnesium atoms finally added remains unchanged:

[0069] (1) 20 kg of cobalt carbonate was heated to 300°C in an oven at 2°C / min and oxidized for 4 h; air was introduced during the oxidation process at a flow rate of 20 L / h / kg of cobalt carbonate.

[0070] (2) 20 kg of oxidized cobalt carbonate, 3 g of an oxidizing aid and a doping aid were first mixed in a mixer at a low speed of 500 rpm for 2 min, then mixed at 1500 rpm for 30 min, and finally mixed at 500 rpm for 5 min, and then heated to 740 ° C. at 2 ° C. / min in an oxygen atmosphere in a rotary kiln and calcined for 4 h to obtain doped cobalt tetroxide; the oxidizing aid was lithium perchlorate; and the doping aid was 29.3 g of the metal oxide magnesium oxide.

[0071] Effect Example 1

[0072] In order to explore the effect of doped cobalt tetroxide prepared by the preparation method of the present invention, the cobalt content in each embodiment and comparative example product was tested by elemental analysis, and electron microscopy and XRD testing were used to confirm whether the product particles had cracking and whether the grain size fluctuated. Secondly, the "kiln sticking" phenomenon was observed in the rotary kiln calcined by each embodiment and comparative example product. Finally, lithium carbonate and cobalt tetroxide in doped cobalt tetroxide were mixed in a molar ratio of 1.03:1 and sintered at 1000°C to obtain finished lithium cobalt oxide. The lithium cobalt oxide prepared under the same conditions was used to make button batteries, and the initial charge and discharge coulombic efficiency was tested at a charge and discharge voltage of 2.5-4.3V and 0.1C.

[0073] The results are shown in Table 1.

[0074] Table 1

[0075] As can be seen from Table 1, the cobalt content of the products of the present invention is not significantly different from that of the pure cobalt oxide prepared in Comparative Example 5, indicating that doping does not cause cobalt loss. The product particles also exhibit no significant cracking, and the 311 grain size fluctuations are minimal. Furthermore, the product of Example 1 was observed using EDS scanning, and the results, shown in Figure 1, reveal a gradient dispersion of the doping element on the surface of the product particles. Furthermore, during production, compared to the product of Comparative Example 5, the "kiln sticking" phenomenon was significantly reduced in each of the products of the Examples, with no material sticking to the rotary kiln as described in Comparative Example 5, as shown in Figure 1.

[0076] In contrast, the product of Comparative Example 3, prepared by conventional means, did not undergo a pre-oxidation step, resulting in significant material adhesion in the fired rotary kiln. This "sticking to the kiln" phenomenon prevented the material from effectively releasing stress during the reaction, leading to cracking of the particles during rapid temperature rise and calcination. The product of Comparative Example 1 contained excessive amounts of oxidizing agents, and the doping elements also increased accordingly, resulting in enrichment during the product preparation process. Consequently, the cobalt content was low and the product consistency was poor. Although the product of Comparative Example 4 also employed a pre-oxidation process during its preparation, the processing temperature of this step was too high, and the product still exhibited particle cracking.

[0077] In the battery application of the product, since the properties of doped cobalt tetroxide directly affect the performance of the final positive electrode material lithium cobalt oxide, the first efficiency of the button battery can also be regarded as the electrochemical performance result of each embodiment and comparative example product. Compared with the product of comparative example 5, the first efficiency of the button battery of each embodiment is relatively high, reaching more than 93%; in contrast, the first efficiency of each comparative example product is poor. Among them, the final structure of the product of comparative example 2 is unstable due to the excessive addition of oxidizing agent during the preparation process. Therefore, the first efficiency during lithium deintercalation is only 91.4%. In the product of comparative example 6, the doping auxiliary agent does not contain a low-melting-point metal salt, and the doping element cannot achieve a good gradient distribution, and the electrochemical performance is also unsatisfactory.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this article and are not intended to limit the scope of protection of this article. Although this application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of this article may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of this article.

Claims

1. [Corrected 18.09.2023 according to Rule 91] A method for preparing doped cobalt trioxide, characterized in that: The following steps are involved: Oxidizing cobalt carbonate in air and / or oxygen atmosphere at 200-400° C. for 2-4 hours; The oxidized cobalt carbonate, an oxidizing aid and a doping aid are mixed, and then calcined at 700-750°C for 3-8 hours in an air or oxygen atmosphere to obtain doped cobalt tetroxide; the oxidizing aid is at least one of perchlorate, persulfate, and metal peroxide; the doping aid includes a metal salt and a doping oxide; the mass ratio of the oxidized cobalt carbonate, the oxidizing aid, and the doping aid is 1: (0.0001-0.0003): (0.0001-0.01).

2. [Corrected 18.09.2023 according to Rule 91] A method for preparing doped cobalt trioxide as claimed in claim 1, characterized in that: The mass ratio of the oxidized cobalt carbonate, the oxidizing aid and the doping aid is 1:(0.0001-0.0003):(0.0001-0.005).

3. [Corrected 18.09.2023 according to Rule 91] A method for preparing doped cobalt trioxide as claimed in claim 1, characterized in that: The temperature during the oxidation is 300-400°C.

4. [Corrected 18.09.2023 according to Rule 91] A method for preparing doped cobalt trioxide as claimed in claim 3, characterized in that: The flow rate of air and / or oxygen atmosphere during the oxidation is 20 to 40 L / h / kg of cobalt carbonate.

5. [Corrected 18.09.2023 according to Rule 91] The method for preparing doped cobalt trioxide as claimed in claim 1, characterized in that: The melting point of the metal salt is ≤720°C.

6. [Corrected 18.09.2023 according to Rule 91] A method for preparing doped cobalt trioxide as claimed in claim 5, characterized in that: The metal salt in the doping aid is at least one of MgCl2, NaNO3, Ba(NO)2, ZnCl2, FeCl2, and ZnSO4.

7. [Corrected 18.09.2023 according to Rule 91] A method for preparing doped cobalt trioxide as claimed in claim 1, characterized in that: The doped oxide is a metal or non-metal oxide, and the metal or non-metal oxide is at least one of MgO, Al2O3, TiO2, Nb2O5, B2O3, and V2O5.

8. [Corrected 18.09.2023 according to Rule 91] A method for preparing doped cobalt trioxide as claimed in claim 1, characterized in that: The cobalt content of the cobalt carbonate is 72.0-73.0%, and the particle size D 50 3~20μm.

9. [Corrected 18.09.2023 according to Rule 91] The method for preparing doped cobalt trioxide as claimed in claim 1, characterized in that: The heating rate during oxidation is 1-3°C / min, and the heating rate during calcination is 2-5°C / min.

10. [Corrected 18.09.2023 according to Rule 91] Doped cobalt tetroxide prepared by the method for preparing doped cobalt tetroxide as claimed in any one of claims 1 to 9.

11. [Corrected 18.09.2023 according to Rule 91] Use of doped cobalt oxide prepared by the preparation method as claimed in claims 1 to 9 or doped cobalt oxide as claimed in claim 10 in the preparation of lithium cobalt oxide materials.

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