Tricobalt tetroxide, cobalt carbonate, method for preparing the same, cathode material, and lithium-ion battery

Abstract

This disclosure provides tricobalt tetroxide, cobalt carbonate, methods for preparing the same, cathode materials, and lithium-ion batteries, relating to the technology of new energy. By gradient doping Al throughout the cobalt carbonate and the corresponding tricobalt tetroxide secondary particles, and by increasing the amount of Al doping in the core layer compared to the coating layer, the stability of the crystal structure of the LCO material can be improved, and the cycle performance of lithium cobalt oxide batteries made from the cathode material after sintering can be improved. Tricobalt tetroxide includes a core layer and a coating layer covering the core layer, with the cobalt content decreasing from the inside to the outside of each layer, and the Co on the surface 4+ By reducing the content and decreasing the amount of Co elution, safety can be improved. The core layer is a functional layer that occupies a large proportion of the volume and has a high cobalt content, thus improving capacity and cycle performance. The coating layer is a thin modification layer that coats the outside of the core layer, and because the total content of doped elements increases in a gradient, the specific properties of the material and the overall performance of the LCO can be improved.

Description

[Technical Field]

[0001] This disclosure relates to the technology of new energy, and more particularly to tricobalt tetroxide, cobalt carbonate, methods for preparing the same, cathode materials, and lithium-ion batteries.

[0002] Cross-references of related applications This disclosure claims priority based on a Chinese patent application filed with the China Patent Administration on 30 May 2023, with application number 202310622177.4, titled "Tricobalt tetroxide, cobalt carbonate, method for preparing the same, cathode material, and lithium-ion battery," the entire contents of which are incorporated into this application by reference. [Background technology]

[0003] With the rapid advancement of science and technology, portable mobile devices have become ubiquitous in daily life, and people's demands for longer battery life, smaller size, and faster charging capabilities in these devices are increasing. Lithium cobalt oxide batteries, with their advantages such as high volumetric energy density, are widely used in the field of 3C digital products.

[0004] The operating time and cycle life of lithium cobalt oxide batteries in lithium-ion secondary batteries are attracting attention throughout the industry. Currently, at a voltage of 4.2V, the theoretical relative capacity (theoretical capacity) of lithium cobalt oxide is 274mA / g. Furthermore, even though existing voltage levels have reached 4.4V or higher, the actual capacity is only 180mA / g, and this capacity decreases even more significantly with increasing cycle counts. Therefore, in order to achieve higher capacity, lithium cobalt oxide is being developed towards higher voltages of 4.5V or higher. The purpose of this is to increase the capacity of lithium cobalt oxide by releasing more lithium ions from the crystal structure at higher voltages.

[0005] Currently, doping is commonly used in the battery industry to improve the structural stability of LCO (lithium cobalt oxide) materials at high voltages by altering their crystal structure. However, with the increasing variety and amount of doping elements, uniformity of the doping elements in LCO has become extremely important. Doping inconsistencies can lead to a decrease in the capacity and cycle performance of the battery material.

[0006] Furthermore, because lithium-ion secondary batteries have a wide range of applications, in addition to the core requirements of high capacity and long cycle performance, there is also a demand for differentiated products. Moreover, in lithium cobalt oxide cathode materials, tricobalt tetroxide is the main raw material, and the performance of tricobalt tetroxide influences the performance of lithium cobalt oxide to some extent. Therefore, various improvements are required for the cathode material precursors, such as improved rate performance and improved cycle performance.

[0007] For various applications of lithium-ion secondary batteries, ensuring uniformity of doped elements in LCO while maintaining core functions of battery capacity and cycle performance, and satisfying the differentiated needs of various customers through a series of adjustable embodiments, is an urgent technical challenge that needs to be addressed in this field. [Overview of the project]

[0008] To solve the above technical problems, this disclosure aims to provide tricobalt tetroxide, cobalt carbonate and a method for preparing the same, a cathode material, and a lithium-ion battery. This disclosure makes it possible to produce products that meet the diverse needs of various customers by adjusting the number of coating layers and the type and content of doped elements in a series of adjustable embodiments, while ensuring high capacity and long cycle performance of the core layer, according to the differentiated needs of various customers.

[0009] To achieve the above objective, in the first aspect, this disclosure provides tricobalt tetroxide. As shown in Figure 40, the tricobalt tetroxide comprises a core layer and a coating layer covering the core layer, both of which are doped with Al, with the amount of Al doped in the core layer being higher than the amount of Al doped in the coating layer. That is, the total amount of Al doped in the core layer is higher than the total amount of Al doped in the coating layer. Exemplarily, if there are multiple coating layers, the total amount of Al doped in the coating layer is the sum of the amounts of Al doped in the multiple coating layers. Hereinafter, the total content may be the total mass or the total molar amount.

[0010] The criteria for separating the core layer and coating layer of cobalt carbonate according to this application are based on the differences in the type and / or content of doped elements in different regions of the cobalt carbonate. The innermost layer is defined as the core layer, and the layer covering the core layer is defined as the coating layer. Exemplarily, the core layer can be divided into a high-percentage layer and a coating layer into a low-percentage layer based on the doping amounts of different aluminum. Furthermore, the core layer can be divided into a single-layer coating layer, or a core layer into multiple-layer coating layers, based on the differences in the type and content of doped elements. The type and content of doped elements can be determined by first analyzing the type of elements and their corresponding content distribution in a minute region of the cross-section using an electron beam microanalyzer, and then measuring the specific content of doped elements by ICP (inductively coupled plasma emission spectrometry). More specifically, as shown in Figure 40, the core layer may be doped with Al, and further doped with Ni and Mn. The coating layer may consist of 1 to 5 layers, and the coating layer may be doped with Al, and further doped with Zr, La, Y, Ti, and Mg. The content of each of the above doped elements may also differ in different layers. Alternatively, as shown in Figure 41, the structure is divided into a total of six layers: a core layer and five coating layers. The core layer is doped with Al and Ni, coating layer n1 covering the core layer is doped with Al and Zr, coating layer n2 covering coating layer n1 is doped with Al and La, coating layer n3 covering coating layer n2 is doped with Al and Y, coating layer n4 covering coating layer n3 is doped with Al and Ti, and coating layer n5 covering coating layer n4 is doped with Al and Mg.

[0011] The boundary criteria for the tricobalt tetroxide core layer and the coating layer in this application are defined according to the corresponding boundary criteria for cobalt carbonate.

[0012] The tricobalt tetroxide according to this disclosure includes a core layer and a coating layer covering the core layer. By doping the entire tricobalt tetroxide particle with Al and increasing the amount of Al doping in the core layer compared to the coating layer, the stability of the crystal structure and the cycling performance of the LCO material can be improved.

[0013] Preferably, the cobalt content of the tricobalt tetroxide decreases layer by layer from the inside outwards, starting from the core layer and moving towards the coating layer.

[0014] The tricobalt tetroxide coating layer is a functional layer that improves the specific properties of the cathode material after sintering and the overall performance of the LCO by increasing the total doping element content of each layer. The cobalt content of the product decreases from the inside to the outside of each layer, thereby improving the surface Co 4+ This allows for a reduction in the content, a decrease in Co elution, and improved safety.

[0015] Preferably, tricobalt tetroxide satisfies at least one of the following conditions A to H.

[0016] A. The tricobalt tetroxide coating layer may consist of 1 to 5 layers, for example, 1, 2, 3, 4, 5 layers, 2 to 4 layers, or 3 to 5 layers.

[0017] B. The ratio of the mass of doped Al in the tricobalt tetroxide core layer to the mass of the total metal in the tricobalt tetroxide core layer is 0.40 to 1.20 wt%, and may be, for example, 0.40 to 0.80 wt%, 0.80 to 1.00 wt%, 1.00 to 1.20 wt%, or 0.70 to 1.10 wt%, and more specifically, for example, 0.40 wt%, 0.50 wt%, 0.60 wt%, 0.70 wt%, 0.80 wt%, 0.85 wt%, 0.90 wt%, 0.95 wt%, 1.00 wt%, 1.05 wt%, 1.10 wt%, or 1.20 wt%.

[0018] C. The ratio of the mass of doped Al in the tricobalt tetroxide coating to the mass of the total metal in the tricobalt tetroxide is 0.02 to 0.40 wt%, and may be, for example, 0.02 to 0.1 wt%, 0.05 to 0.15 wt%, 0.1 to 0.4 wt%, or 0.03 to 0.07 wt%, and more specifically, for example, 0.02 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, or 0.4 wt%.

[0019] The method for measuring the ratio of the mass of doped Al in the tricobalt tetroxide coating layer to the total metal mass in the tricobalt tetroxide according to this application involves sintering a cobalt carbonate core layer and cobalt carbonate, respectively, to form a tricobalt tetroxide core layer and tricobalt tetroxide, measuring the mass fraction of Al relative to the total metal mass in the tricobalt tetroxide core layer and tricobalt tetroxide, respectively, and subtracting the mass fraction of Al relative to the total metal mass in the tricobalt tetroxide core layer from the mass fraction of Al relative to the total metal mass in the tricobalt tetroxide. The difference obtained is the ratio of the doped element Al in the tricobalt tetroxide coating layer to the total metal mass in the tricobalt tetroxide.

[0020] D. When there is one layer of tricobalt tetroxide coating, the ratio of the molar amount of cobalt in the coating to the molar amount of the total metal in the tricobalt tetroxide coating is 70 mol% or less, and may be, for example, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 67 mol%, 69 mol%, or 70 mol%.

[0021] E. When there are 2 to 5 layers of tricobalt tetroxide coating, the ratio of the molar amount of cobalt in the outermost layer of the coating to the molar amount of the total metal in the outermost layer of the tricobalt tetroxide coating is 70 mol% or less, and may be, for example, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 67 mol%, 69 mol%, or 70 mol%.

[0022] The diameter of the core layer of F. tricobalt tetroxide is 5.0 to 18.0 μm, and may be, for example, 5.0 to 8.0 μm, 8.0 to 10.0 μm, 10.0 to 13.0 μm, 13.0 to 18.0 μm, or 15.0 to 17.0 μm, and more specifically, for example, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, or 18.0 μm.

[0023] G. When there is one coating layer of tricobalt tetroxide, the thickness of the coating layer is 0.10 to 1.0 μm, and may be, for example, 5.0 to 8.0 μm, 8.0 to 10.0 μm, 10.0 to 13.0 μm, 13.0 to 18.0 μm, or 15.0 to 17.0 μm, and more specifically, for example, 0.10 μm, 0.15 μm, 0.20 μm, 0.25 μm, 0.30 μm, 0.35 μm, 0.40 μm, 0.45 μm, 0.50 μm, 0.55 μm, 0.60 μm, 0.65 μm, 0.70 μm, 0.75 μm, 0.80 μm, 0.85 μm, 0.90 μm, 0.95 μm, or 1.0 μm. The thickness of the coating layer is the difference in particle size D50 before and after coating.

[0024] When there are 2 to 5 layers of H. tricobalt tetroxide coating, the thickness of a single layer within the coating is 0.10 to 1.0 μm, and may be, for example, 0.10 to 0.30 μm, 0.30 to 0.40 μm, 0.40 to 0.50 μm, 0.50 to 0.70 μm, 0.70 to 1.0 μm, 0.2 to 0.5 μm, or 0.1 to 0.4 μm, and more The particle size may be, for example, 0.10 μm, 0.15 μm, 0.20 μm, 0.25 μm, 0.30 μm, 0.35 μm, 0.40 μm, 0.45 μm, 0.50 μm, 0.55 μm, 0.60 μm, 0.65 μm, 0.70 μm, 0.75 μm, 0.80 μm, 0.85 μm, 0.90 μm, 0.95 μm, or 1.0 μm.

[0025] Preferably, tricobalt tetroxide satisfies at least one of the following conditions I to L.

[0026] I. The core layer of tricobalt tetroxide further contains Ni and / or Mn.

[0027] When condition I is met, the ratio of the mass of doped Ni and Mn in the tricobalt tetroxide core layer to the mass of the total metal in the tricobalt tetroxide core layer is independently 0.10 to 3.00 wt%, and may be, for example, 0.10 to 0.80 wt%, 0.80 to 1.50 wt%, 1.50 to 3.00 wt%, or 0.10 to 0.30 wt%, and more specifically, for example, 0. It may be 10 wt%, 0.50 wt%, 0.8 wt%, 1.00 wt%, 1.20 wt%, 1.30 wt%, 1.40 wt%, 1.50 wt%, 1.60 wt%, 1.70 wt%, 1.80 wt%, 1.90 wt%, 2.00 wt%, 2.10 wt%, 2.20 wt%, 2.30 wt%, 2.40 wt%, 2.60 wt%, 2.80 wt%, or 3.00 wt%.

[0028] The K. tricobalt tetroxide coating further contains one or more doping elements from Mg, Ti, La, Zr, Y, Ca, Sr, and Ba.

[0029] In other words, the tricobalt tetroxide coating layer may be doped with one of the above elements in each layer, or with multiple of the above elements in each layer, in addition to Al doping. More specifically, if there is one coating layer, in addition to Al doping, one of the above elements other than Al, or multiple of the above elements other than Al, may be doped. If there are multiple coating layers, in addition to Al doping, each layer of the coating layer may be doped with only one of the above elements other than Al, or with multiple of the above elements other than Al.

[0030] Preferably, when the coating layer consists of two layers, the coating layer is divided into an inner layer and an outer layer, the inner layer of the coating layer further containing one or more of Zr, La, Ca, Ba, Y, Ti, and Sr, and the outer layer of the coating layer further containing one or more of Mg, Zr, Ti, and Sr.

[0031] When the coating layer consists of 3 to 5 layers, the coating layer is divided into an inner layer, an intermediate layer, and an outer layer, with the inner layer and outer layer each consisting of one layer, and all others being intermediate layers. The inner layer of the coating layer further contains one or more of Zr, La, Ca, and Ba; the intermediate layer of the coating layer further contains one or more of La, Zr, Y, Ti, and Sr; and the outer layer of the coating layer further contains one or more of Mg, Zr, Ti, and Sr.

[0032] La and Zr form stable solid phase layers. Ca and Ba, doped to replace some of the Co, play a role in stabilizing the skeletal structure and are therefore more appropriately placed in the inner or intermediate layers. La and Zr have large ionic radii and can increase the distance of the C axis of the crystal unit cell, contributing to ion movement. Y, Ti, and Sr can all increase electrical conductivity, contribute to ion movement, and improve rate performance, therefore are more appropriately placed in the inner or intermediate layers. Doped Mg and Sr can effectively increase electrical conductivity, and the Mg / Ti mixed structure can suppress phase transitions in the material, thus improving the stability of the surface structure.

[0033] When condition K is met, the ratio of the mass of other doped elements besides Al in the tricobalt tetroxide coating to the mass of the total metal in the tricobalt tetroxide is independently 0.01 to 0.40 wt%, for example, 0.01 to 0.15 wt%, 0.15 to 0.30 wt%, 0.30 to 0.40 wt%, 0.04 to 0.12 wt%, or 0.02 to 0.14 wt%, and more specifically, for example, 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0. It may also be 0.5 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.10 wt%, 0.11 wt%, 0.12 wt%, 0.13 wt%, 0.14 wt%, 0.15 wt%, 0.16 wt%, 0.17 wt%, 0.18 wt%, 0.19 wt%, 0.20 wt%, 0.22 wt%, 0.24 wt%, 0.28 wt%, 0.30 wt%, 0.32 wt%, 0.34 wt%, 0.36 wt%, 0.38 wt%, or 0.40 wt%.

[0034] The method for measuring the ratio of the mass of doped elements other than Al in the tricobalt tetroxide coating layer to the mass of all metals in the tricobalt tetroxide according to this application is as follows: tricobalt tetroxide is formed by sintering cobalt carbonate, and the value obtained by dividing the mass fraction of doped elements other than Al in the tricobalt tetroxide by the mass fraction of all metals in the tricobalt tetroxide is the ratio of the mass of doped elements other than Al in the tricobalt tetroxide coating layer to the mass of all metals in the tricobalt tetroxide.

[0035] Preferably, tricobalt tetroxide satisfies at least one of the following conditions M to Q.

[0036] M. The porosity of the core layer of cobalt tetroxide is 5.5 to 9.5%, and may be, for example, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, or 9.5%, and may also be 5.5 to 6.5%, 6.5 to 7.5%, 7.5% to 8.5%, or 8.5 to 9.5%. The porosity of the entire cobalt tetroxide is 4.5 to 7.5%, and may be, for example, 4.5% to 5.0%, 5.0% to 5.5%, 5.5% to 6.0%, 6.0% to 7.5%, or 4.5 to 6.0%, and more specifically, for example, 4.5%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.2%, 7.4%, 7.6%, 7.8%, 8.0%, 8.2%, 8.4%, 8.6%, 8.8%, 9.0%, 9.2%, 9.4%, or 9.5%.

[0037] N. The pore volume of the core layer of cobalt tetroxide is 0.004 to 0.015 cm 3 / g, and may be, for example, 0.004 to 0.008 cm 3 / g, 0.008 to 0.015 cm 3 / g, or 0.004 to 0.011 cm 3 / g, and more specifically, for example, 0.004 cm 3 / g, 0.005 cm 3 / g, 0.006 cm 3 / g, 0.007 cm 3 / g, 0.008 cm 3 / g, 0.009 cm 3 / g, 0.010 cm 3 / g, 0.011 cm 3 / g, 0.012 cm 3 / g, 0.013 cm 3 / g, 0.014 cm 3 / g, or 0.015 cm 3 / g, and may be. The pore volume of the entire cobalt tetroxide is 0.002 to 0.080 cm 3 / g, and may be, for example, 0.002 to 0.004 cm 3 / g, 0.004~0.006cm 3 / g, 0.006~0.009cm 3 / g, 0.009~0.01cm 3 / g, 0.01~0.05cm 3 / g, 0.05~0.08cm 3 / g, or 0.003-0.015cm 3 It can also be expressed as / g, or more specifically, for example, 0.002cm 3 / g, 0.003cm 3 / g, 0.004cm 3 / g, 0.005cm 3 / g, 0.006cm 3 / g, 0.007cm 3 / g, 0.008cm 3 / g, 0.009cm 3 / g, 0.010cm 3 / g, 0.011cm 3 / g, 0.012cm 3 / g, 0.013cm 3 / g, 0.014cm 3 / g, 0.015cm 3 / g, 0.016cm 3 / g, 0.017cm 3 / g, 0.018cm 3 / g, 0.019cm 3 / g, 0.020cm 3 / g, 0.025cm 3 / g, 0.030cm 3 / g, 0.035cm 3 / g, 0.040cm 3 / g, 0.045cm 3 / g, 0.050cm 3 / g, 0.055cm 3 / g, 0.060cm 3 / g, 0.065cm 3 / g, 0.070cm 3 / g, 0.075cm 3 / g, or 0.080cm 3 / g is also acceptable.

[0038] In this disclosure, the porosity and pore volume of cobalt carbonate and tricobalt tetroxide are measured using a fully automated specific surface area / pore distribution analyzer (model: BELPREP-VACII / BELSORP-MINI-X) manufactured by Microtrac Corporation, USA. The measurement principle is nitrogen gas adsorption, and the specific measurement method is operated by referring to the operating procedures and accompanying software provided by the manufacturer. The measurement results differ from methods that calculate the ratio of pore area to the total area of ​​a cross-sectional photograph using software such as Avizo. The porosity and pore volume of the tricobalt tetroxide core layer were measured after sintering a sample of cobalt carbonate core layer into a tricobalt tetroxide core layer.

[0039] O. The D50 of tricobalt tetroxide is 5.5 to 23.0 μm, and may be, for example, 5.5 to 10.0 μm, 10.0 to 12.0 μm, 12.0 to 15.0 μm, 15.0 to 16.0 μm, 16.0 to 17.0 μm, 17.0 to 20.0 μm, 20.0 to 23.0 μm, or 14.0 to 17.0 μm. More specifically, for example, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm. , 10.0μm, 10.5μm, 11.0μm, 11.5μm, 12.0μm, 12.5μm, 13.0μm, 13.5μm, 14.0μm, 14.5μm, 15.0μm, 15.5μm, 16.0μm, 16.5μm, 17.0μm, 17.5μm, 18.0μm, 18.5μm, 19.0μm, 19.5μm, 20.0μm, 20.5μm, 21.0μm, 21.5μm, 22.0μm, 22.5μm, or 23.0μm.

[0040] The tap density of P. tricobalt tetroxide is 2.0-3.0 g / cm³. 3 For example, 2.0~2.3 g / cm³ 3 2.3~2.5 g / cm³ 3 2.5~2.6 g / cm³ 3 2.6~2.8 g / cm³ 3 2.8~3.0 g / cm³ 3 , or 2.4~3.0 g / cm³ 3It may be, more specifically, for example, 2.0 g / cm 3 , 2.1 g / cm 3 , 2.2 g / cm 3 , 2.3 g / cm 3 , 2.4 g / cm 3 , 2.5 g / cm 3 , 2.6 g / cm 3 , 2.7 g / cm 3 , 2.8 g / cm 3 , 2.9 g / cm 3 , or 3.0 g / cm 3 and it may be so.

[0041] Q. The specific surface area of cobalt tetroxide is 2.0 to 15 m 2 / g, for example, 2.0 to 4.0 m 2 / g, 4.0 to 6.0 m 2 / g, 6.0 to 10.0 m 2 / g, 10 to 15 m 2 / g, or 3.0 to 4.5 m 2 / g and it may be so. More specifically, for example, 2.0 m 2 / g, 3.0 m 2 / g, 4.0 m 2 / g, 5.0 m 2 / g, 6.0 m 2 / g, 7.0 m 2 / g, 8.0 m 2 / g, 9.0 m 2 / g, 10.0 m 2 / g, 11.0 m 2 / g, 12.0 m 2 / g, 13.0 m 2 / g, 14.0 m 2 / g, or 15.0 m 2 / g and it may be so.

[0042] In the second aspect, the present disclosure further provides cobalt carbonate. As shown in FIG. 40, the cobalt carbonate includes a core layer and a coating layer that coats the core layer, and both the core layer and the coating layer are doped with Al, and the doping amount of Al in the core layer is higher than the doping amount of Al in the coating layer.

[0043] The cobalt carbonate according to this disclosure includes a core layer and a coating layer covering the core layer. By gradient-doping (doping in a gradient) Al throughout the cobalt carbonate particles and increasing the amount of Al doped in the core layer compared to the coating layer, the stability of the crystal structure of the LCO material after sintering can be improved, thereby improving its cycle performance. In the case of cobalt carbonate, the Al element exists in the form of amorphous aluminum hydroxide during the crystallization process, resulting in a low aluminum content in the coating layer, which helps to suppress hydrolysis and precipitation of amorphous aluminum hydroxide during centrifugal cleaning. Furthermore, because the porosity and pore volume of the coating layer are lower than those of the core layer, it helps to suppress hydrolysis and precipitation of amorphous aluminum hydroxide in the core layer, improving the uniformity of the Al element distribution.

[0044] Preferably, the cobalt content of the cobalt carbonate decreases layer by layer from the inside outwards, starting from the core layer and moving towards the coating layer.

[0045] The cobalt carbonate coating layer is a functional layer that improves the specific properties of the cathode material after sintering and the overall performance of the LCO by increasing the total doping element content of each layer. The cobalt content in the product decreases from the inside to the outside of each layer, thereby improving the surface Co 4+ This can reduce the content, decrease the amount of Co eluted, and improve safety.

[0046] Preferably, the cobalt carbonate satisfies at least one of the following conditions a to l.

[0047] a. The cobalt carbonate coating layer may consist of 1 to 5 layers, for example, 1, 2, 3, 4, or 5 layers.

[0048] b. The ratio of the mass of doped Al in the cobalt carbonate core layer to the mass of the total metal in the cobalt carbonate core layer is 0.26 to 0.80 wt%, and may be, for example, 0.26 to 0.30 wt%, 0.30 to 0.40 wt%, 0.40 to 0.50 wt%, 0.50 to 0.70 wt%, or 0.70 to 0.80 wt%, and more specifically, for example, 0.26 wt%, 0.30 wt%, 0.35 wt%, 0.40 wt%, 0.50 wt%, 0.60 wt%, 0.70 wt%, or 0.80 wt%.

[0049] c. The ratio of the mass of doped Al in the cobalt carbonate coating to the mass of the total metal in the cobalt carbonate is 0.01 to 0.27 wt%, and may be, for example, 0.01 to 0.04 wt%, 0.04 to 0.1 wt%, 0.05 to 0.15 wt%, or 0.15 to 0.27 wt%, and more specifically, for example, 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, or 0.27 wt%.

[0050] The method for measuring the ratio of the mass of doped Al in the cobalt carbonate coating layer to the mass of all metals in the cobalt carbonate according to this application involves measuring the mass fraction of Al relative to the mass of all metals in the cobalt carbonate core layer and the cobalt carbonate as a whole, respectively, and subtracting the mass fraction of Al relative to the mass of all metals in the cobalt carbonate core layer from the mass fraction of Al relative to the mass of all metals in the cobalt carbonate. The difference obtained is the ratio of the doped element Al in the cobalt carbonate coating layer to the mass of metals in the cobalt carbonate.

[0051] d. When there is one cobalt carbonate coating layer, the ratio of the molar amount of cobalt in the cobalt carbonate coating layer to the molar amount of the total metal in the tricobalt tetroxide coating layer is 70 mol% or less, and may be, for example, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 67 mol%, 69 mol%, or 70 mol%.

[0052] e. When there are 2 to 5 layers of cobalt carbonate coating, the ratio of the molar amount of cobalt in the outermost layer of the cobalt carbonate coating to the molar amount of the total metal in the outermost layer of the cobalt carbonate coating is 70 mol% or less, and may be, for example, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 67 mol%, 69 mol%, or 70 mol%.

[0053] f. The diameter of the cobalt carbonate core layer is 8.0 to 23.0 μm, and may be, for example, 8.0 to 10.0 μm, 10.0 to 13.0 μm, 13.0 to 18.0 μm, 18.0 to 23.0 μm, or 18.0 to 21.0 μm, and more specifically, for example, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, 22.0, or 23.0 μm.

[0054] g. When there is one cobalt carbonate coating layer, the thickness of the coating layer is 0.15 to 1.5 μm, preferably 0.15 to 0.5 μm, for example 0.15 to 0.30 μm, 0.30 to 0.40 μm, 0.40 to 0.50 μm, 0.50 to 0.70 μm, 0.70 to 1.0 μm, or 1.0 to 1.5 μm, and more specifically for example 0.15 μm, 0.20 μm, 0.25 μm, The particle size may be 0.30 μm, 0.35 μm, 0.40 μm, 0.45 μm, 0.50 μm, 0.55 μm, 0.60 μm, 0.65 μm, 0.70 μm, 0.75 μm, 0.80 μm, 0.85 μm, 0.90 μm, 0.95 μm, 1.0 μm, 1.05 μm, 1.10 μm, 1.15 μm, 1.20 μm, 1.25 μm, 1.30 μm, 1.35 μm, 1.40 μm, 1.45 μm, or 1.5 μm.

[0055] h. When there are 2 to 5 layers of cobalt carbonate coating, the thickness of a single layer in the coating is 0.15 to 1.5 μm, preferably 0.15 to 0.5 μm, for example 0.15 to 0.30 μm, 0.30 to 0.40 μm, 0.40 to 0.50 μm, 0.50 to 0.70 μm, 0.70 to 1.0 μm, 1.0 to 1.5 μm, or 0.2 to 0.5 μm, more specifically for example 0.15 μm, 0.2 The particle size may be 0 μm, 0.25 μm, 0.30 μm, 0.35 μm, 0.40 μm, 0.45 μm, 0.50 μm, 0.55 μm, 0.60 μm, 0.65 μm, 0.70 μm, 0.75 μm, 0.80 μm, 0.85 μm, 0.90 μm, 0.95 μm, 1.0 μm, 1.05 μm, 1.10 μm, 1.15 μm, 1.20 μm, 1.25 μm, 1.30 μm, 1.35 μm, 1.40 μm, 1.45 μm, or 1.5 μm.

[0056] i. The cobalt carbonate core layer further contains Ni and / or Mn.

[0057] j. When condition i is satisfied, the ratio of the mass of doped Ni and Mn in the cobalt carbonate core layer to the mass of the total metal in the cobalt carbonate core layer is independently 0.07 to 2.00 wt%, for example 0.07 to 0.10 wt%, 0.10 to 0.30 wt%, 0.30 to 1.50 wt%, 0.50 to 1.00 wt%, or 1.00 to 2.00 wt%, and more specifically for example 0.07 wt%, 0.10 wt%, 0.50 wt%, 0.8 wt%, 1.00 wt%, 1.20 wt%, 1.30 wt%, 1.40 wt%, 1.50 wt%, 1.60 wt%, 1.70 wt%, 1.80 wt%, 1.90 wt%, or 2.00 wt%.

[0058] k. The cobalt carbonate coating further contains one or more doping elements from Mg, Ti, La, Zr, Y, Ca, Sr, and Ba. That is, in addition to Al doping, the cobalt carbonate coating may be doped with one of the above elements in each layer, or with multiple of the above elements in each layer. More specifically, if there is one cobalt carbonate coating layer, one of the above elements other than Al, or multiple of the above elements other than Al, may be doped. If there are multiple cobalt carbonate coating layers, each layer of the coating may be doped with only one of the above elements other than Al, or with multiple of the above elements other than Al.

[0059] Preferably, if the coating layer consists of two layers, the coating layer is divided into an inner layer and an outer layer, the inner layer of the coating layer further containing one or more of Zr, La, Ca, Ba, Y, Ti, and Sr, and the outer layer of the coating layer further containing one or more of Mg, Zr, Ti, and Sr.

[0060] If the coating layer consists of 3 to 5 layers, the coating layer is divided into an inner layer, an intermediate layer, and an outer layer, with the inner layer and outer layer each consisting of one layer, and all others being intermediate layers. The inner layer of the coating layer further contains one or more of Zr, La, Ca, and Ba; the intermediate layer of the coating layer further contains one or more of La, Zr, Y, Ti, and Sr; and the outer layer of the coating layer further contains one or more of Mg, Zr, Ti, and Sr.

[0061] l. When condition k is satisfied, the ratio of the mass of other doping elements other than Al in the cobalt carbonate coating to the mass of the total metal in the cobalt carbonate is independently 0.01 to 0.30 wt%, for example 0.01 to 0.15 wt%, 0.15 to 0.30 wt%, 0.04 to 0.12 wt%, or 0.02 to 0.14 wt%, and more specifically for example 0.01 wt%, 0.02 wt%, 0.03 wt% The values ​​may be %, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.10wt%, 0.11wt%, 0.12wt%, 0.13wt%, 0.14wt%, 0.15wt%, 0.16wt%, 0.17wt%, 0.18wt%, 0.19wt%, 0.20wt%, 0.22wt%, 0.24wt%, 0.28wt%, or 0.30wt%.

[0062] The method for measuring the ratio of the mass of doped elements other than Al in the cobalt carbonate coating layer to the mass of all metals in the cobalt carbonate according to this application is as follows: The value obtained by dividing the mass fraction of doped elements other than Al in the cobalt carbonate obtained by measurement by the mass fraction of all metals in the cobalt carbonate is the ratio of the mass of doped elements other than Al in the cobalt carbonate coating layer to the mass of all metals in the cobalt carbonate.

[0063] Preferably, the cobalt carbonate satisfies at least one of the following conditions m to q.

[0064] The porosity of the core layer of m. cobalt carbonate is 15-25%, and may be, for example, 15-17%, 17-18%, 18-20%, 21-23%, or 23-25%, and more specifically, for example, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%. The porosity of the entire cobalt carbonate is 14-25%, and may be, for example, 14%-17%, 17%-20%, 20%-25%, 20%-23%, 23%-24%, 24%-25%, or 23%-25%, and more specifically, for example, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%.

[0065] The pore volume of the core layer of cobalt carbonate is 0.08 to 0.30 cm 3 / g, for example 0.08 to 0.12 cm 3 / g, 0.12 to 0.16 cm 3 / g, 0.16 to 0.20 cm 3 / g, 0.20 to 0.25 cm 3 / g, 0.25 to 0.30 cm 3 / g, or 0.10 to 0.15 cm 3 / g may also be used, and more specifically for example 0.08 cm 3 / g, 0.09 cm 3 / g, 0.10 cm 3 / g, 0.11 cm 3 / g, 0.12 cm 3 / g, 0.13 cm 3 / g, 0.14 cm 3 / g, 0.15 cm 3 / g, 0.16 cm 3 / g, 0.17 cm 3 / g, 0.18 cm 3 / g, 0.19 cm 3 / g, 0.20 cm 3 / g, 0.21 cm 3 / g, 0.22 cm 3 / g, 0.23 cm 3 / g, 0.24 cm 3 / g, 0.25 cm 3 / g, 0.26 cm 3 / g, 0.27 cm 3 / g, 0.28 cm 3 / g, 0.29 cm 3 / g, or 0.30 cm 3 / g may also be used. The pore volume of the entire cobalt carbonate is 0.05 to 0.25 cm 3 / g, for example 0.05 to 0.08 cm 3 / g, 0.08 to 0.10 cm 3 / g, 0.10 to 0.16 cm 3 / g, 0.10 to 0.13 cm 3 / g, 0.13 to 0.16 cm 3 / g, 0.16 to 0.20 cm 3 / g, 0.20 to 0.25 cm3 / g, or 0.10-0.17cm 3 It can also be expressed as / g, or more specifically, for example, 0.05cm 3 / g, 0.06cm 3 / g, 0.07cm 3 / g, 0.08cm 3 / g, 0.09cm 3 / g, 0.10cm 3 / g, 0.11cm 3 / g, 0.12cm 3 / g, 0.13cm 3 / g, 0.14cm 3 / g, 0.15cm 3 / g, 0.16cm 3 / g, 0.17cm 3 / g, 0.18cm 3 / g, 0.19cm 3 / g, 0.20cm 3 / g, 0.21cm 3 / g, 0.22cm 3 / g, 0.23cm 3 / g, 0.24cm 3 / g, or 0.25cm 3 / g is also acceptable.

[0066] o. The D50 of cobalt carbonate is 8.7-30.0 μm, for example, 8.7-12.0 μm, 12.0-15.0 μm, 15.0-17.0 μm, 17.0-19.0 μm, 19.0-23.0 μm, 19.0-20.0 μm, 20.0-21.0 μm, 21.0-22.0 μm, or 23.0-30.0 μm. It is also acceptable to specify more specifically, for example, 8.7, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, 25.0, 26.0, 27.0, 28.0, 29.0, or 30.0 μm.

[0067] The specific surface area BET of p. cobalt carbonate is 50-150 m². 2 It is / g, for example 50-70m 2 / g, 70-90m 2 / g, 90-100m 2 / g, 100-110m 2 / g, 110-120m 2 / g, 120-150m 2 / g, or 85-130m 2 It could also be / g, or more specifically, for example, 85m 2 / g, 90ml 2 / g, 95m 2 / g, 100m 2 / g, 105m 2 / g, 110m 2 / g, 115m 2 / g, 120m 2 / g, 125m 2 / g, 130m 2 / g, 135m 2 / g, 140m 2 / g, 145m 2 / g, or 150m 2 / g is also acceptable.

[0068] q. The tap density of cobalt carbonate is 1.5-2.0 g / cm³. 3 For example, 1.5~1.6 g / cm³ 3 1.6~1.7 g / cm³ 3 1.7~1.8 g / cm³ 3 1.8~1.9 g / cm³ 3 1.9~2.0 g / cm³ 3 , or 1.6~1.8 g / cm³ 3 It could be, or more specifically, for example, 1.60 g / cm³. 3 1.65 g / cm³ 3 1.70 g / cm³ 3 1.75 g / cm³ 3 1.80 g / cm³ 3 1.85 g / cm³ 3 1.90 g / cm³ 3 1.95 g / cm³ 3 , or 2.0 g / cm³ 3 That's fine.

[0069] In the third part of this disclosure, the present disclosure further provides a method for preparing cobalt carbonate, the method comprising the following steps:

[0070] The cobalt salt solution and precipitant solution for the core layer are placed in a reactor containing bottom liquid. The reaction is carried out under conditions where the flow rate of the cobalt salt solution for the core layer increases as the particle size of the material increases, the flow rate of the precipitant solution increases as the flow rate of the cobalt salt solution for the core layer increases, and the stirring speed of the reactor decreases as the particle size of the material increases, until the particle size D50 reaches 8.0 to 23.0 μm, thereby obtaining a cobalt carbonate core layer.

[0071] The cobalt salt solution of the coating layer and the precipitant solution are added in this order to a reactor containing a cobalt carbonate core layer, and the reaction is allowed to proceed until the growth of each coating layer is complete to obtain cobalt carbonate.

[0072] The particle size D50 of the cobalt carbonate core layer obtained by the reaction is 8.0 to 23.0 μm, and may be, for example, 8.0 to 10.0 μm, 10.0 to 13.0 μm, 13.0 to 18.0 μm, 18.0 to 23.0 μm, or 18.0 to 21.0 μm, and more specifically, for example, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, 22.0, or 23.0 μm.

[0073] The material is a growing cobalt carbonate core layer.

[0074] Both the cobalt salt solution for the core layer and the cobalt salt solution for the coating layer contain Co and Al, and the cobalt salt solution for the core layer may further contain Ni and / or Mn. The cobalt salt solution for the coating layer may further contain one or more elements from Mg, Ti, La, Zr, Y, Ca, Sr, and Ba.

[0075] The cobalt salt is selected from one or more of cobalt sulfate, cobalt chloride, and cobalt nitrate; the precipitant is selected from one or more of ammonium bicarbonate, ammonium carbonate, and sodium carbonate; and the bottom liquor is selected from one or more of ammonium bicarbonate, ammonium carbonate, and sodium carbonate.

[0076] The cobalt concentration in cobalt salt solutions is 85-125 g / L.

[0077] Specifically, the cobalt concentration in the cobalt salt solution of the core layer is 85-125 g / L, and may be, for example, 90-110 g / L, 80-100 g / L, or 100-125 g / L, or more specifically, 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L, 115 g / L, or 120 g / L, 125 g / L.

[0078] The cobalt concentration in the cobalt salt solution of the coating layer is 85-125 g / L, and may be, for example, 90-110 g / L, 80-100 g / L, or 100-125 g / L, or more specifically, 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L, 115 g / L, 120 g / L, or 125 g / L.

[0079] The concentration of the precipitating agent solution is 180-220 g / L, and may be, for example, 180-200 g / L, 180-190 g / L, 190-200 g / L, or 200-210 g / L, or more specifically, 180 g / L, 185 g / L, 190 g / L, 195 g / L, 200 g / L, 205 g / L, 210 g / L, 215 g / L, or 220 g / L. The pH of the bottom solution is 7.5 to 8.8, and may be, for example, 7.5 to 8.0, 8.0 to 8.8, 7.8 to 8.8, or 7.8 to 8.6, or more specifically, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, or 8.8.

[0080] The pH during the preparation reaction of the cobalt carbonate core layer is 7.0–8.3, and the ammonium concentration is 10–60 g / L. The ammonium concentration is due to the amount of NH4 in the solution. + This is concentration, and the same applies below.

[0081] More specifically, for example, the pH in the reaction for preparing the cobalt carbonate core layer may be, for example, 7.0-7.6, 7.6-8.0, or 8.0-8.4, and more specifically, for example, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, or 8.3. The ammonium concentration may be 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 10-40 g / L, or 30-60 g / L.

[0082] The pH during the preparation reaction of the cobalt carbonate coating layer is 6.5–8.0, and the ammonium concentration is 10–40 g / L.

[0083] More specifically, for example, the pH in the reaction for preparing the cobalt carbonate coating layer may be 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 6.7-7.5, or 7.5-8.0. The ammonium concentration may be 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 10-27 g / L, 20-35 g / L, or 25-40 g / L.

[0084] The flow rate of the cobalt salt solution in the core layer is 1.5% / h to 7.0% / h of the usable volume of the reactor, and more specifically, it may be, for example, 1.5% / h, 2.0% / h, 2.5% / h, 3.0% / h, 3.5% / h, 4.0% / h, 4.5% / h, 5.0% / h, 5.5% / h, 6.0% / h, 6.5% / h, or 7.0% / h. The flow rate of the cobalt salt solution in the coating layer is 1.5% / h to 3.5% / h of the usable volume of the reactor, and more specifically, it may be, for example, 1.5% / h, 2.0% / h, 2.5% / h, 3.0% / h, or 3.5% / h.

[0085] In the fourth aspect, the present disclosure further provides a method for preparing tricobalt tetroxide, which is obtained by sintering the above-mentioned cobalt carbonate.

[0086] In the fifth phase, the present disclosure further provides a cathode material which is lithium cobalt oxide obtained by calcining the above-mentioned tricobalt tetroxide and lithium source. Preferably, the molar ratio of lithium source to tricobalt tetroxide is (1 to 1.05):1, and more specifically, it may be, for example, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, or 1.05:1.

[0087] Preferably, the firing temperature is 900°C to 1200°C, and more specifically, it may be 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C. The firing time is 20 to 30 hours, and more specifically, it may be 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, or 30 hours.

[0088] In the sixth aspect, the present disclosure further provides a lithium-ion battery, the raw materials of which include the above-mentioned cathode material.

[0089] Compared to conventional technology, the beneficial effects of this disclosure are as follows:

[0090] 1. The cobalt carbonate and corresponding tricobalt tetroxide according to this disclosure include a core layer and a coating layer covering the core layer. By doping the entire cobalt carbonate and corresponding tricobalt tetroxide particles with Al, and by increasing the amount of Al doping in the core layer compared to the coating layer, the stability of the crystal structure of the LCO material after sintering can be improved, and the cycle performance can be enhanced. In the case of cobalt carbonate, since the Al element exists in the form of amorphous aluminum hydroxide during the crystallization process, the aluminum content in the coating layer is low, which helps to suppress the hydrolysis and precipitation of amorphous aluminum hydroxide during centrifugal cleaning. Furthermore, since the porosity and pore volume of the coating layer are lower than those of the core layer, it helps to suppress the hydrolysis and precipitation of amorphous aluminum hydroxide in the core layer, improving the uniformity of the Al element distribution.

[0091] 2. The core layer of cobalt carbonate and tricobalt tetroxide in this disclosure occupies an extremely large volume, and further doping with Ni and Mn elements improves the core functions of long operating time and cycle life, which are of interest in the industry. When synthesizing cobalt carbonate, the K of Ni and Co elements sp Because their solubility products are similar, coprecipitation is more likely, improving uniformity. In cobalt carbonate and tricobalt tetroxide, Ni can replace some of the Co in the crystal lattice, improving capacitance performance. Doping with Mn and Ni can also induce solid solution behavior during phase transitions, effectively suppressing the O3 / H1-3 phase transition of LCO material after sintering at a voltage of 4.5V, suppressing crystal expansion, improving the stability of the crystal structure, and improving plateau voltage and cycle performance. If the volume proportion occupied by the core layer is too small, the improvement in cycle performance and capacitance performance is not evident.

[0092] 3. The cobalt carbonate and tricobalt tetroxide coating layers according to this disclosure coat the outside of the core layer. The coating layers are thin and occupy a small proportion of the core, and the coating layers can be modified according to customer needs to meet the differentiated needs of various customers. Specifically, by setting the number of coating layers and different doping elements for each layer, each layer of the coating layer can have a specific function. For example, doping the coating layer with elements such as La and Zr, due to their large ionic radii, forms a solid phase layer of lithium-containing garnet (LLZO), and the LCO material becomes capable of good ion mobility and electrochemical stability. Doping with Y and Ti can improve structural stability, suppress phase transitions, and improve rate performance. Doping with Mg can form continuous channels, increasing ion passage efficiency and surface electrical conductivity. Doping with Sr can increase electrical conductivity, decrease resistance, and improve stability. Doping with Ca can stabilize the skeletal structure of the material. Doping with Ba can improve the structural stability of lithium cobalt oxide, etc. Since the coating layer occupies a small proportion of the volume, it is necessary to increase the doping element content in order to improve the specific properties of the material and the overall performance of the LCO.

[0093] 4. This disclosure controls the cobalt content in cobalt carbonate and tricobalt tetroxide by controlling the cobalt content in the cobalt solution of the core layer and the cobalt salt solution of the coating layer during the cobalt carbonate preparation process, so that the cobalt content in the product decreases layer by layer from the inside out. This reduces the Cobalt content on the surface. 4+ This can reduce the content, decrease the amount of Co eluted, and improve safety.

[0094] 5. In this disclosure, the more types of doping elements there are in cobalt carbonate and tricobalt tetroxide, the greater the doping amount, and the more difficult it becomes to uniformly dope each doping element. This disclosure improves the structure and preparation method of cobalt carbonate and tricobalt tetroxide, distinguishes the elements to be doped in the core layer and coating layer according to different functions, varies the types of doping elements in each layer of the coating layer, and further thins the coating layer, thereby minimizing the problem of reduced capacity and cycle performance due to doping unevenness in the final LCO material.

[0095] 6. This disclosure describes how, when preparing cobalt carbonate, the flow rate of the cobalt salt solution in the core layer increases as the particle size of the material increases, the flow rate of the precipitant solution increases as the flow rate of the cobalt salt solution in the core layer increases, and the stirring speed of the reactor decreases as the particle size of the material increases. As a result, the obtained cobalt carbonate particles and tricobalt tetroxide have appropriate porosity, specific surface area and overall pore volume for lithium cobaltate, good doping uniformity, and a high cycle life of the corresponding lithium-ion battery.

[0096] To more clearly explain the embodiments of the examples in this disclosure, the drawings necessary for describing the embodiments are briefly described below. The drawings described are only a selection of the embodiments of this disclosure and do not limit the scope of this disclosure. [Brief explanation of the drawing]

[0097] [Figure 1]This is a scanning electron microscope image showing the morphology of the core layer of cobalt carbonate particles according to Example 1. [Figure 2] This is a scanning electron microscope image showing the morphology of the coating layer of cobalt carbonate particles according to Example 1. [Figure 3] This is a scanning electron microscope image showing the morphology of the cross-section of the coating layer of cobalt carbonate particles according to Example 1. [Figure 4] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Example 1. [Figure 5] This is a scanning electron microscope image showing the morphology of the cross-section of tricobalt tetroxide according to Example 1. [Figure 6] and [Figure 7] This figure sequentially shows the analysis results of the Al and Ni components in a minute region of the core layer of tricobalt tetroxide according to Example 1. [Figure 8] This figure sequentially shows the analysis results of the Zr, Y, and Ti components in a minute region of the tricobalt tetroxide coating layer according to Example 1. [Figure 9] This figure sequentially shows the analysis results of the Zr, Y, and Ti components in a minute region of the tricobalt tetroxide coating layer according to Example 1. [Figure 10] This figure sequentially shows the analysis results of the Zr, Y, and Ti components in a minute region of the tricobalt tetroxide coating layer according to Example 1. [Figure 11] This is a scanning electron microscope image showing the morphology of cobalt carbonate particles according to Example 2. [Figure 12] This is a scanning electron microscope image showing the morphology of the cross-section of cobalt carbonate particles according to Example 2. [Figure 13] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Example 2. [Figure 14] This is a scanning electron microscope image showing the morphology of the cross-section of tricobalt tetroxide according to Example 2. [Figure 15] This figure shows the results of the analysis of the Al component in a minute region of the core layer of tricobalt tetroxide according to Example 2. [Figure 16] This figure sequentially shows the analysis results of the Zr and Ti components in a minute region of the tricobalt tetroxide coating layer according to Example 2. [Figure 17] This figure sequentially shows the analysis results of the Zr and Ti components in a minute region of the tricobalt tetroxide coating layer according to Example 2. [Figure 18] This is a scanning electron microscope image showing the morphology of cobalt carbonate particles according to Example 3. [Figure 19] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Example 3. [Figure 20] This is a scanning electron microscope image showing the morphology of the cross-section of tricobalt tetroxide according to Example 3. [Figure 21] This is a scanning electron microscope image showing the morphology of cobalt carbonate particles according to Example 4. [Figure 22] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Example 4. [Figure 23] This is a scanning electron microscope image showing the morphology of the cross-section of tricobalt tetroxide according to Example 4. [Figure 24] This is a scanning electron microscope image showing the morphology of cobalt carbonate particles according to Example 5. [Figure 25] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Example 5. [Figure 26] This is a scanning electron microscope image showing the morphology of cobalt carbonate particles according to Example 6. [Figure 27] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Example 6. [Figure 28] This is a scanning electron microscope image showing the morphology of cobalt carbonate particles according to Example 7. [Figure 29] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Example 7. [Figure 30]This is a scanning electron microscope image showing the morphology of cobalt carbonate particles according to Example 8. [Figure 31] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Example 8. [Figure 32] This is a scanning electron microscope image showing the morphology of cobalt carbonate particles according to Comparative Example 1. [Figure 33] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Comparative Example 1. [Figure 34] This is a scanning electron microscope image showing the morphology of the cross-section of tricobalt tetroxide according to Comparative Example 1. [Figure 35] This is a scanning electron microscope image showing the morphology of cobalt carbonate particles according to Comparative Example 2. [Figure 36] This is a scanning electron microscope image showing the morphology of the cross-section of cobalt carbonate particles according to Comparative Example 2. [Figure 37] This is a scanning electron microscope image showing the morphology of tricobalt tetroxide according to Comparative Example 2. [Figure 38] This is a scanning electron microscope image showing the morphology of the cross-section of tricobalt tetroxide according to Comparative Example 2. [Figure 39] This figure shows the results of the component analysis of Al in a minute region of the tricobalt tetroxide coating layer according to Comparative Example 2. [Figure 40] This is a schematic diagram of the structures of cobalt carbonate and tricobalt tetroxide according to the present disclosure. [Figure 41] This is a schematic diagram of the structures of cobalt carbonate and tricobalt tetroxide according to Example 1. [Modes for carrying out the invention]

[0098] The terms used in this specification are defined as follows:

[0099] "Prepared from ~" is synonymous with "contains ~". The terms "contains," "equip," "have," "contain," or any other variation thereof as used herein, mean non-exclusive inclusion. For example, a composition, step, method, product, or apparatus containing the listed elements may also contain other elements not explicitly listed or elements inherent to those compositions, steps, methods, products, or apparatus.

[0100] Where equivalents, concentrations, or other values ​​or parameters are expressed by a range, a preferred range, or a range limited by a set of preferred upper and lower limits, any range consisting of an upper or preferred value of an arbitrary range and a lower or preferred value of an arbitrary range should be understood to specifically disclose all ranges of any combination of the above values, even if there is a separate disclosure. For example, if the range "1 to 5" is disclosed, the range described is interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", and "1 to 3 and 5". Numerical ranges described herein include the maximum value, minimum value, and all integers and fractions within that range, unless otherwise specified.

[0101] "And / or" is used to indicate that one or both of the situations being described may occur. For example, A and / or B includes both "A and B" and "A or B".

[0102] The embodiments of this disclosure will be described in detail below with reference to specific examples. Those skilled in the art will find these examples merely illustrative and should not be considered limiting to the scope of this disclosure. In the examples, specific conditions are not specified, but can be met under conventional conditions or manufacturer-recommended conditions. Where the manufacturer of the reagents or instruments used is not specified, commercially available conventional products can be used.

[0103] Example 1 Example 1 provides a tricobalt tetroxide precursor having a core layer doped with 0.85 wt% Al and 1.2 wt% Ni, and five coating layers. The molar ratio of the doped elements in each coating layer is similar to the molar ratio of each doped element in the cobalt salt solution of the coating layer (cobalt salt solution for forming the coating layer) at the time of preparation, with n1 satisfying Co:Al:Zr=0.95:0.03:0.02, n2 satisfying Co:Al:La=0.94:0.03:0.03, n3 satisfying Co:Al:Y=0.91:0.03:0.06, n4 satisfying Co:Al:Ti=0.88:0.03:0.09, and n5 satisfying Co:Al:Mg=0.67:0.03:0.30. Figure 41 shows a schematic diagram of the structure. n1 is a first coating layer covering the core layer, n2 is a second coating layer covering the first coating layer, n3 is a third coating layer covering the second coating layer, n4 is a fourth coating layer covering the third coating layer, n5 is a fifth coating layer covering the fourth coating layer, and so on.

[0104] The preparation method is as follows:

[0105] 1. Nickel sulfate solution, aluminum sulfate solution, and cobalt sulfate solution were mixed to prepare a nickel and aluminum-doped cobalt salt solution, which was used as the cobalt salt solution for the core layer. The mass concentration of cobalt ions in the solution was 100 g / L, and the elemental molar ratio of cobalt, nickel, and aluminum in the solution was Co:Ni:Al = 1:0.017:0.026. The cobalt salt solution for the coating layer was prepared by mixing so that its concentration matched the molar ratio of each coating layer, and the mass concentration of cobalt salt in the coating layer cobalt salt solution was 100 g / L. An ammonium bicarbonate solution with a mass concentration of 190 g / L was prepared and used as a precipitating agent solution. An ammonium bicarbonate solution with a pH of 8.6 was prepared and used as the bottom solution.

[0106] 2. The cobalt salt solution and precipitant solution of the prepared core layer were simultaneously placed in a reactor containing the bottom liquid. The flow rate of the cobalt salt solution was gradually increased from 2.5% / h of the reactor's usable volume to 6.0% / h, the flow rate of the precipitant solution was doubled to the flow rate of the cobalt salt solution, the stirring speed was gradually reduced from 350 r / min to 150 r / min, the pH during the reaction was controlled to 7.0-7.4, and the ammonium concentration was controlled to 15-30 g / L. The reaction was carried out until the particle size D50 grew to 20.5 μm, thereby obtaining a cobalt carbonate core layer.

[0107] 3. The process was modified to reduce the flow rate of the cobalt salt solution to 2.5% / h of the reactor's usable volume, and the flow rate of the precipitant solution to 1.5 times the flow rate of the cobalt salt solution. The prepared cobalt salt solution was pumped into the coating layers in order, and when each coating layer reached a thickness of approximately 0.25 μm and the desired particle size, it was replaced with the next coating layer solution. Under conditions where the pH during the reaction was controlled to 6.8-7.2 and the ammonium concentration to 10-25 g / L, aluminum-doped cobalt carbonate of Example 1 was prepared.

[0108] Figure 1 shows a scanning electron microscope image of the surface morphology of the core layer of cobalt carbonate secondary particles according to Example 1. Figure 2 shows a scanning electron microscope image of the surface morphology of the coating layer of the same cobalt carbonate secondary particles. Figure 3 shows a scanning electron microscope image of the morphology of the cross-section. The right side of Figure 3 is an enlarged view of the left side. The morphology of minute regions (some minute regions) of the core layer and minute regions (some minute regions) of the coating layer differs, and the coating layer has a multi-layer structure in which ring-shaped low-density layers and high-density layers are alternately stacked.

[0109] The cobalt carbonate core layer and cobalt carbonate prepared in Example 1 were sampled.

[0110] The method for measuring the mass fraction of cobalt in the sample was based on "GB / T23367.1-2009 Lithium Cobalt Oxide Chemical Analysis Method Part 1: Measurement of Cobalt Amount EDTA Titration Method". The method for measuring the mass fractions of each metal element other than cobalt in the sample was based on "GB / T23367.2-2009 Lithium Cobalt Oxide Chemical Analysis Method Part 2: Measurement of Lithium, Nickel, Manganese, Magnesium, Aluminum, Iron, Sodium, Calcium, and Copper Amounts Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)". The measuring instrument used was an ICP emission spectrometer Avio500. For some doped elements La, Zr, Y, and Ti that are not included in the reference range of this application, standard solutions were prepared by referring to the doped element Ni, and measurements were performed. The data obtained from the measurements are as follows.

[0111] (1) In the cobalt carbonate core layer according to Example 1, the proportion of the mass of each doped element to the mass of cobalt carbonate (i.e., the doped elements and their content in the core layer in Table 1) was 0.56 wt% for Al and 0.80 wt% for Ni.

[0112] (2) In the cobalt carbonate according to Example 1, the proportion of the mass of each doped element to the total mass of cobalt carbonate was 0.605 wt% for Al, 0.026 wt% for Zr, 0.05 wt% for La, 0.08 wt% for Y, 0.06 wt% for Ti, and 0.13 wt% for Mg.

[0113] Since the cobalt carbonate core layer does not contain the doping elements Zr, La, Y, Ti, and Mg, the proportion of the mass of the doping elements Zr, La, Y, Ti, and Mg in relation to the mass of cobalt carbonate (i.e., the proportion of the doping elements in the coating layer relative to the mass of cobalt carbonate in Table 1) is 0.026 wt% for Zr, 0.05 wt% for La, 0.08 wt% for Y, 0.06 wt% for Ti, and 0.13 wt% for Mg.

[0114] In cobalt carbonate, the coating layer is very thin, so the proportion of the coating layer's mass to the total mass of the cobalt carbonate is small. If we ignore the mass of the coating layer and assume the mass of the core layer is the total mass of the cobalt carbonate, the following occurs.

[0115]

number

[0116] 4. After centrifuging the above cobalt carbonate, it was sintered under the following conditions: sintering temperature of 840°C, sintering time of 2.5 hours, rotation speed of the rotary kiln core tube of 0.8 r / min, and material layer thickness of 3.5 cm, to prepare the multi-doped tricobalt tetroxide of Example 1.

[0117] Figure 41 shows schematic diagrams of the structures of cobalt carbonate and tricobalt tetroxide according to Example 1. Figure 4 shows a scanning electron microscope image of the surface morphology of the tricobalt tetroxide secondary particles of Example 1. Figure 5 shows a scanning electron microscope image of the morphology of the cross-section thereof. The right side of Figure 5 is an enlarged view of the left side. The morphology of the micro-regions of the core layer and the micro-regions of the coating layer are different, and the coating layer has a multi-layer structure in which ring-shaped low-density layers and high-density layers are alternately stacked. For the tricobalt tetroxide according to Example 1, the Al and Ni components in the micro-regions of the cross-section of the core layer were analyzed using an electron beam microanalyzer, and the results are shown in Figures 6 and 7, respectively, showing that the Ni and Al elements are uniformly distributed. For the tricobalt tetroxide according to Example 1, the Zr, Y, and Ti components in the micro-regions of the coating layer on the cross-section of the secondary particles were analyzed using an electron beam microanalyzer, and the results are shown in Figures 8 to 10, respectively, showing that each doped element is uniformly distributed in each layer of the doped coating layer.

[0118] The cobalt carbonate core layer and cobalt carbonate sampled in Example 1 were sintered to obtain a tricobalt tetroxide core layer and a tricobalt tetroxide sample. The method for measuring the mass fraction of cobalt in the sample was referred to in "GB / T23367.1-2009 Lithium Cobalt Oxide Chemical Analysis Method Part 1 Measurement of Cobalt Amount EDTA Titration Method". The method for measuring the mass fraction of each metal element other than cobalt in the sample was referred to in "GB / T23367.2-2009 Lithium Cobalt Oxide Chemical Analysis Method Part 2 Measurement of Lithium, Nickel, Manganese, Magnesium, Aluminum, Iron, Sodium, Calcium, and Copper Amounts Inductively Coupled Plasma Emission Spectrometry". The measuring instrument was an ICP emission spectrometer Avio500. For some doped elements La, Zr, Y, and Ti that are not included in the reference range of this application, standard solutions were prepared by referring to the doped element Ni and measurements were performed. The data obtained from the measurements are as follows.

[0119] (1) In the core layer of tricobalt tetroxide according to Example 1, the proportion of the mass of each doped element to the mass of tricobalt tetroxide (i.e., the doped elements and their content in the core layer in Table 2) was 0.85 wt% for Al and 1.2 wt% for Ni.

[0120] (2) In the tricobalt tetroxide according to Example 1, the proportion of the mass of each doped element to the total mass of tricobalt tetroxide was 0.92 wt% for Al, 0.04 wt% for Zr, 0.07 wt% for La, 0.12 wt% for Y, 0.09 wt% for Ti, and 0.20 wt% for Mg.

[0121] Since the core layer of tricobalt tetroxide does not contain the doping elements Zr, La, Y, Ti, and Mg, the proportion of the mass of the doping elements Zr, La, Y, Ti, and Mg in relation to the mass of tricobalt tetroxide (i.e., the proportion of the doping elements in the coating layer relative to the mass of tricobalt tetroxide in Table 2) is 0.04 wt% for Zr, 0.07 wt5% for La, 0.12 wt% for Y, 0.09 wt% for Ti, and 0.20 wt% for Mg.

[0122] In tricobalt tetroxide, the coating layer is very thin, so the ratio of the coating layer's mass to the total mass of tricobalt tetroxide is small. If we ignore the mass of the coating layer and assume the mass of the core layer is the total mass of tricobalt tetroxide, then the following occurs.

[0123]

number

[0124] 5. The tricobalt tetroxide and lithium carbonate obtained in Example 1 were uniformly mixed in a Li / Me molar ratio of 1.05:1, and the mixture was calcined at 1000°C for 20 hours to prepare the lithium cobalt oxide cathode material of Example 1.

[0125] Example 2 Example 2 provides a tricobalt tetroxide precursor having a core layer doped with 0.85 wt% Al and 1.2 wt% Mn, and five coating layers. The molar ratio of the doped elements in each coating layer is similar to the molar ratio of each doped element in the cobalt salt solution of the coating layer at the time of preparation, with n1 satisfying Co:Al:La=0.94:0.03:0.03, n2 satisfying Co:Al:Zr=0.92:0.03:0.04, n3 satisfying Co:Al:Y=0.91:0.03:0.06, n4 satisfying Co:Al:Ti=0.88:0.03:0.09, and n5 satisfying Co:Al:Mg=0.67:0.03:0.30. The preparation method is as follows.

[0126] 1. Aluminum sulfate solution, cobalt sulfate solution, and manganese sulfate solution were mixed to prepare a cobalt salt solution doped with aluminum and manganese, which was used as the cobalt salt solution for the core layer. The mass concentration of cobalt ions in the solution was 100 g / L, and the elemental molar ratio of cobalt, aluminum, and manganese in the solution was Co:Al:Mn = 1:0.026:0.018. The cobalt salt solution for the coating layer was prepared by mixing so that its concentration matched the molar ratio of each coating layer, and the mass concentration of cobalt salt in the coating layer cobalt salt solution was 100 g / L. An ammonium bicarbonate solution with a mass concentration of 200 g / L was prepared and used as a precipitating agent solution. An ammonium bicarbonate solution with a pH of 8.5 was prepared and used as the bottom solution.

[0127] 2. The prepared cobalt salt solution and precipitant solution were simultaneously placed in a reactor containing bottom liquid. The flow rate of the cobalt salt solution was gradually increased from 2.7% / h of the reactor's usable volume to 6.1% / h, the flow rate of the precipitant solution was doubled to the flow rate of the cobalt salt solution, the stirring speed was gradually reduced from 380 r / min to 160 r / min, the pH during the reaction was controlled to 7.1-7.5, and the ammonium concentration was controlled to 18-33 g / L. The reaction was carried out until the particle size D50 grew to 18.5 μm, thereby obtaining a cobalt carbonate core layer.

[0128] 3. The process was modified to reduce the flow rate of the cobalt salt solution to 2.5% / h of the reactor's usable volume, and the flow rate of the precipitant solution to 1.5 times the flow rate of the cobalt salt solution. The prepared cobalt salt solution was pumped into the coating layers in order, and when each coating layer reached a thickness of approximately 0.25 μm and the desired particle size, it was replaced with the next coating layer solution. Under conditions where the pH during the reaction was controlled to 6.7-7.1 and the ammonium concentration to 12-25 g / L, aluminum-doped cobalt carbonate of Example 2 was prepared.

[0129] Figure 11 shows a scanning electron microscope image of the surface morphology of cobalt carbonate secondary particles according to Example 2. Figure 12 shows a scanning electron microscope image of the morphology of the cross-section thereof.

[0130] 4. After centrifuging the above cobalt carbonate, it was sintered under the following conditions: a sintering temperature of 840°C, a sintering time of 2.5 hours, a rotary kiln core tube rotation speed of 0.8 r / min, and a material layer thickness of 3.5 cm, to prepare the multi-doped tricobalt tetroxide of Example 2.

[0131] Figure 13 shows a scanning electron microscope image of the surface morphology of tricobalt tetroxide secondary particles according to Example 2. Figure 14 shows a scanning electron microscope image of the morphology of the cross-section thereof. For tricobalt tetroxide according to Example 2, the Al component in a minute region of the cross-section of the core layer was analyzed using an electron beam microanalyzer, and the results are shown in Figure 15, showing that the Al element is uniformly distributed. For tricobalt tetroxide according to Example 2, the Zr and Ti components in a minute region of the coating layer of the cross-section of the secondary particles were analyzed using an electron beam microanalyzer, and the results are shown sequentially in Figures 16-17, showing that each doped element is uniformly distributed in each layer.

[0132] 5. The tricobalt tetroxide and lithium carbonate obtained in Example 2 were uniformly mixed in a Li / Me molar ratio of 1.05:1, and the mixture was calcined at 1000°C for 20 hours to prepare the lithium cobalt oxide cathode material of Example 2.

[0133] Example 3 Example 3 provides a tricobalt tetroxide precursor having a core layer doped with 0.95 wt% Al and two coating layers. The molar ratio of the doped elements in each coating layer is similar to the molar ratio of each doped element in the cobalt salt solution of the coating layer at the time of preparation, with n1 satisfying Co:Al:La = 0.94:0.03:0.03 and n2 satisfying Co:Al:Zr = 0.90:0.03:0.07. The preparation method is as follows.

[0134] 1. An aluminum sulfate solution and a cobalt sulfate solution were mixed to prepare an aluminum-doped cobalt salt solution, which was used as the cobalt salt solution for the core layer. The mass concentration of cobalt ions in the solution was 100 g / L, and the elemental molar ratio of cobalt to aluminum in the solution was Co:Al = 1:0.029. The cobalt salt solution for the coating layer was prepared by mixing so that its concentration matched the molar ratio of each coating layer, and the mass concentration of cobalt salt in the coating layer cobalt salt solution was 100 g / L. An ammonium bicarbonate solution with a mass concentration of 200 g / L was prepared and used as a precipitating agent solution. An ammonium bicarbonate solution with a pH of 8.0 was prepared and used as the bottom solution.

[0135] 2. The prepared cobalt salt solution and precipitant solution were simultaneously placed in a reactor containing the bottom liquid. The flow rate of the cobalt salt solution was gradually increased from 2.4% / h of the reactor's usable volume to 5.9% / h, the flow rate of the precipitant solution was doubled to the flow rate of the cobalt salt solution, the stirring speed was gradually reduced from 380 r / min to 180 r / min, the pH during the reaction was controlled to 7.1-7.5, and the ammonium concentration was controlled to 20-35 g / L. The reaction was carried out until the particle size D50 grew to 19.0 μm, thereby obtaining a cobalt carbonate core layer.

[0136] 3. The process was modified to reduce the flow rate of the cobalt salt solution to 2.6% / h of the reactor's usable volume, and the flow rate of the precipitant solution to 1.5 times the flow rate of the cobalt salt solution. The prepared cobalt salt solution was pumped into the coating layers in order, and when each coating layer reached a thickness of approximately 0.35 μm and the desired particle size, it was replaced with the next coating layer solution. Under conditions where the pH during the reaction was controlled to 6.9-7.3 and the ammonium concentration to 12-27 g / L, aluminum-doped cobalt carbonate of Example 3 was prepared.

[0137] Figure 18 shows a scanning electron microscope image of the surface morphology of cobalt carbonate secondary particles according to Example 3.

[0138] 4. After centrifuging the above cobalt carbonate, it was sintered under the following conditions: sintering temperature of 830°C, sintering time of 3.0 h, rotation speed of the rotary kiln core tube of 0.8 r / min, and material layer thickness of 3.0 cm, to prepare the multi-doped tricobalt tetroxide of Example 3.

[0139] Figure 19 shows a scanning electron microscope image of the surface morphology of tricobalt tetroxide secondary particles according to Example 3. Figure 20 shows a scanning electron microscope image of the morphology of the cross-section thereof.

[0140] 5. The tricobalt tetroxide and lithium carbonate obtained in Example 3 were uniformly mixed in a Li / Me molar ratio of 1.05:1, and the mixture was calcined at 1000°C for 20 hours to prepare the lithium cobalt oxide cathode material of Example 3.

[0141] Example 4 Example 4 provides a tricobalt tetroxide precursor having a core layer doped with 0.95 wt% Al and two coating layers. The molar ratio of the doped elements in each coating layer is similar to the molar ratio of each doped element in the cobalt salt solution of the coating layer at the time of preparation, with n1 satisfying Co:Al:Ti = 0.87:0.03:0.10 and n2 satisfying Co:Al:Mg = 0.67:0.03:0.30. The preparation method is as follows.

[0142] 1. An aluminum sulfate solution and a cobalt sulfate solution were mixed to prepare an aluminum-doped cobalt salt solution, which was used as the cobalt salt solution for the core layer. The mass concentration of cobalt ions in the solution was 100 g / L, and the elemental molar ratio of cobalt to aluminum in the solution was Co:Al = 1:0.029. The cobalt salt solution for the coating layer was prepared by mixing so that its concentration matched the molar ratio of each coating layer, and the mass concentration of cobalt salt in the coating layer cobalt salt solution was 100 g / L. An ammonium bicarbonate solution with a mass concentration of 200 g / L was prepared and used as a precipitating agent solution. An ammonium bicarbonate solution with a pH of 8.6 was prepared and used as the bottom solution.

[0143] 2. The prepared cobalt salt solution and precipitant solution were simultaneously placed in a reactor containing bottom liquid. The flow rate of the cobalt salt solution was gradually increased from 2.5% / h of the reactor's usable volume to 6% / h, the flow rate of the precipitant solution was doubled to the flow rate of the cobalt salt solution, the stirring speed was reduced from 380 r / min to 150 r / min, the pH during the reaction was controlled to 7.2-7.6, and the ammonium concentration was controlled to 24-39 g / L. The reaction was carried out until the particle size D50 grew to 19.0 μm, thereby obtaining a cobalt carbonate core layer.

[0144] 3. The process was modified to reduce the flow rate of the cobalt salt solution to 2.4% / h of the reactor's usable volume, and the flow rate of the precipitant solution to 1.5 times the flow rate of the cobalt salt solution. The prepared cobalt salt solution was pumped into the coating layers in order, and when each coating layer reached a thickness of approximately 0.45 μm and the desired particle size, it was replaced with the next coating layer solution. Under conditions where the pH during the reaction was controlled to 6.8-7.2 and the ammonium concentration to 10-25 g / L, the doped cobalt carbonate of Example 4 was prepared.

[0145] Figure 21 shows a scanning electron microscope image of the surface morphology of cobalt carbonate secondary particles according to Example 4.

[0146] 4. After centrifuging the above cobalt carbonate, it was sintered under the following conditions: sintering temperature of 780°C, sintering time of 2.0 h, rotation speed of the rotary kiln core tube of 0.8 r / min, and material layer thickness of 2.5 cm, to prepare the multi-doped tricobalt tetroxide of Example 4.

[0147] Figure 22 shows a scanning electron microscope image of the surface morphology of tricobalt tetroxide secondary particles according to Example 4. Figure 23 shows a scanning electron microscope image of the morphology of the cross-section thereof.

[0148] 5. The tricobalt tetroxide and lithium carbonate obtained in Example 4 were uniformly mixed in a Li / Me molar ratio of 1.05:1, and the mixture was calcined at 1000°C for 20 hours to prepare the lithium cobalt oxide cathode material of Example 4.

[0149] Example 5 Example 5 provides a tricobalt tetroxide precursor having a core layer doped with 0.85 wt% Al and 1.2 wt% Ni, and three coating layers. The molar ratio of the doped elements in each coating layer is similar to the molar ratio of each doped element in the cobalt salt solution of the coating layer at the time of preparation, with n1 satisfying Co:Al:Zr=0.95:0.03:0.02, n2 satisfying Co:Al:Y=0.91:0.03:0.06, and n3 satisfying Co:Al:Mg=0.67:0.03:0.30. The preparation method is as follows.

[0150] 1. Nickel sulfate solution, aluminum sulfate solution, and cobalt sulfate solution were mixed to prepare a nickel and aluminum-doped cobalt salt solution, which was used as the cobalt salt solution for the core layer. The mass concentration of cobalt ions in the solution was 100 g / L, and the elemental molar ratio of cobalt, nickel, and aluminum in the solution was Co:Ni:Al = 1:0.017:0.026. The cobalt salt solution for the coating layer was prepared by mixing so that its concentration matched the molar ratio of each coating layer, and the mass concentration of cobalt salt in the coating layer cobalt salt solution was 100 g / L. An ammonium bicarbonate solution with a mass concentration of 190 g / L was prepared and used as a precipitating agent solution. An ammonium bicarbonate solution with a pH of 8.6 was prepared and used as the bottom solution.

[0151] 2. The cobalt salt solution and precipitant solution of the prepared core layer were simultaneously placed in a reactor containing the bottom liquid. The flow rate of the cobalt salt solution was gradually increased from 2.5% / h of the reactor's usable volume to 6.0% / h, the flow rate of the precipitant solution was doubled to the flow rate of the cobalt salt solution, the stirring speed was gradually reduced from 450 r / min to 250 r / min, the pH during the reaction was controlled to 7.0-7.4, and the ammonium concentration was controlled to 15-30 g / L. The reaction was carried out until the particle size D50 grew to 11.5 μm, thereby obtaining a cobalt carbonate core layer.

[0152] 3. The process was modified to reduce the flow rate of the cobalt salt solution to 2.5% / h of the reactor's usable volume, and the flow rate of the precipitant solution to 1.5 times the flow rate of the cobalt salt solution. The prepared cobalt salt solution was pumped into the coating layers in order, and when each coating layer reached a thickness of approximately 0.35 μm and the desired particle size, it was replaced with the next coating layer solution. Under conditions where the pH during the reaction was controlled to 6.8-7.2 and the ammonium concentration to 10-25 g / L, aluminum-doped cobalt carbonate of Example 5 was prepared.

[0153] Figure 24 shows a scanning electron microscope image of the surface morphology of cobalt carbonate secondary particles according to Example 5.

[0154] 4. After centrifuging the above cobalt carbonate, it was sintered under the following conditions: sintering temperature of 750°C, sintering time of 2.0 h, rotation speed of the rotary kiln core tube of 0.8 r / min, and material layer thickness of 2.5 cm, to prepare the multi-doped tricobalt tetroxide of Example 5.

[0155] Figure 25 shows a scanning electron microscope image of the surface morphology of tricobalt tetroxide secondary particles according to Example 5.

[0156] 5. The tricobalt tetroxide and lithium carbonate obtained in Example 5 were uniformly mixed in a Li / Me molar ratio of 1.05:1, and fired at 1000°C for 20 hours to prepare the lithium cobalt oxide cathode material of Example 5.

[0157] Example 6 Example 6 provides a tricobalt tetroxide precursor having a core layer doped with 0.85 wt% Al and 1.2 wt% Ni, and three coating layers. The molar ratios of the doped elements in each coating layer are similar to the molar ratios of each metal element in the cobalt salt solution of the coating layer at the time of preparation, with n1 satisfying Co:Al:La = 0.94:0.03:0.03, n2 satisfying Co:Al:Ti = 0.88:0.03:0.09, and n3 satisfying Co:Al:Mg = 0.67:0.03:0.30. The preparation method is as follows.

[0158] 1. Nickel sulfate solution, aluminum sulfate solution, and cobalt sulfate solution were mixed to prepare a nickel and aluminum-doped cobalt salt solution, which was used as the cobalt salt solution for the core layer. The mass concentration of cobalt ions in the solution was 100 g / L, and the elemental molar ratio of cobalt, nickel, and aluminum in the solution was Co:Ni:Al = 1:0.017:0.026. The cobalt salt solution for the coating layer was prepared by mixing so that its concentration matched the molar ratio of each coating layer, and the mass concentration of cobalt salt in the coating layer cobalt salt solution was 100 g / L. An ammonium bicarbonate solution with a mass concentration of 200 g / L was prepared and used as a precipitating agent solution. An ammonium bicarbonate solution with a pH of 8.6 was prepared and used as the bottom solution.

[0159] 2. The cobalt salt solution and precipitant solution of the prepared core layer were simultaneously placed in a reactor containing the bottom liquid. The flow rate of the cobalt salt solution was gradually increased from 2.5% / h of the reactor's usable volume to 6.0% / h, the flow rate of the precipitant solution was doubled to the flow rate of the cobalt salt solution, the stirring speed was gradually reduced from 400 r / min to 200 r / min, the pH during the reaction was controlled to 7.0-7.4, and the ammonium concentration was controlled to 15-30 g / L. The reaction was carried out until the particle size D50 grew to 16.5 μm, thereby obtaining a cobalt carbonate core layer.

[0160] 3. The process was modified to reduce the flow rate of the cobalt salt solution to 2.5% / h of the reactor's usable volume, and the flow rate of the precipitant solution to 1.5 times the flow rate of the cobalt salt solution. The prepared cobalt salt solution was pumped into the coating layers in order, and when each coating layer reached a thickness of approximately 0.35 μm and the desired particle size, it was replaced with the next coating layer solution. Under conditions where the pH during the reaction was controlled to 6.8-7.2 and the ammonium concentration to 10-25 g / L, aluminum-doped cobalt carbonate of Example 6 was prepared.

[0161] Figure 26 shows a scanning electron microscope image of the surface morphology of cobalt carbonate secondary particles according to Example 6.

[0162] 4. After centrifuging the above cobalt carbonate, it was sintered under the following conditions: sintering temperature of 770°C, sintering time of 2.0 h, rotation speed of the rotary kiln core tube of 0.8 r / min, and material layer thickness of 2.5 cm, to prepare the multi-doped tricobalt tetroxide of Example 6.

[0163] Figure 27 shows a scanning electron microscope image of the surface morphology of tricobalt tetroxide secondary particles according to Example 6.

[0164] 5. The tricobalt tetroxide and lithium carbonate obtained in Example 6 were uniformly mixed in a Li / Me molar ratio of 1.05:1, and the mixture was calcined at 1000°C for 20 hours to prepare the lithium cobalt oxide cathode material of Example 6.

[0165] Example 7 Example 7 provides a tricobalt tetroxide precursor having a core layer doped with 1.0 wt% Al and 1.0 wt% Ni, and a single coating layer. The molar ratio of the doped elements in each coating layer is similar to the molar ratio of each metal element in the cobalt salt solution of the coating layer at the time of preparation, so that n1 satisfies approximately Co:Al:La:Y:Ti:Mg=0.62:0.05:0.05:0.03:0.05:0.20. The preparation method is as follows.

[0166] 1. Nickel sulfate solution, aluminum sulfate solution, and cobalt sulfate solution were mixed to prepare a nickel and aluminum-doped cobalt salt solution, which was used as the cobalt salt solution for the core layer. The mass concentration of cobalt ions in the solution was 110 g / L, and the elemental molar ratio of cobalt, nickel, and aluminum in the solution was Co:Ni:Al = 1:0.010:0.022. The cobalt salt solution for the coating layer was prepared by mixing so that its concentration matched the molar ratio of each coating layer, and the mass concentration of cobalt salt in the coating layer cobalt salt solution was 110 g / L. An ammonium bicarbonate solution with a mass concentration of 200 g / L was prepared and used as a precipitating agent solution. An ammonium bicarbonate solution with a pH of 8.6 was prepared and used as the bottom solution.

[0167] 2. The cobalt salt solution and precipitant solution of the prepared core layer were simultaneously placed in a reactor containing the bottom liquid. The flow rate of the cobalt salt solution was gradually increased from 2.5% / h of the reactor's usable volume to 6.0% / h, the flow rate of the precipitant solution was doubled to the flow rate of the cobalt salt solution, the stirring speed was gradually reduced from 350 r / min to 150 r / min, the pH during the reaction was controlled to 7.0-7.4, and the ammonium concentration was controlled to 15-30 g / L. The reaction was carried out until the particle size D50 grew to 20.0 μm, thereby obtaining a cobalt carbonate core layer.

[0168] 3. The process was modified to reduce the flow rate of the cobalt salt solution to 2.5% / h of the reactor's usable volume, and the flow rate of the precipitant solution to 1.5 times the flow rate of the cobalt salt solution. The cobalt salt solution was pumped into the prepared coating layers in order, with each coating layer having a thickness of approximately 0.7 μm. Under conditions where the pH during the reaction was controlled to 6.8-7.2 and the ammonium concentration to 10-25 g / L, the aluminum-doped cobalt carbonate of Example 7 was prepared.

[0169] Figure 28 shows a scanning electron microscope image of the surface morphology of cobalt carbonate secondary particles according to Example 7.

[0170] 4. After centrifuging the above cobalt carbonate, it was sintered under the following conditions: sintering temperature of 820°C, sintering time of 2.5 hours, rotation speed of the rotary kiln core tube of 1.0 r / min, and material layer thickness of 3.0 cm, to prepare the multi-doped tricobalt tetroxide of Example 7.

[0171] Figure 29 shows a scanning electron microscope image of the surface morphology of tricobalt tetroxide secondary particles according to Example 7.

[0172] 5. The tricobalt tetroxide and lithium carbonate obtained in Example 7 were uniformly mixed in a Li / Me molar ratio of 1.05:1, and the mixture was calcined at 1000°C for 20 hours to prepare the lithium cobalt oxide cathode material of Example 7.

[0173] Example 8 Example 8 provides a tricobalt tetroxide precursor having a core layer doped with 1.2 wt% Ni and 0.95 wt% Al, and five coating layers. The molar ratio of the doped elements in each coating layer is similar to the molar ratio of each doped element in the cobalt salt solution of the coating layer at the time of preparation, with n1 satisfying Co:Al:Zr=0.95:0.03:0.02, n2 satisfying Co:Al:La=0.94:0.03:0.03, n3 satisfying Co:Al:Y=0.91:0.03:0.06, n4 satisfying Co:Al:Ti=0.88:0.03:0.09, and n5 satisfying Co:Al:Mg=0.67:0.03:0.30. The preparation method is as follows.

[0174] 1. Nickel sulfate solution, aluminum sulfate solution, and cobalt sulfate solution were mixed to prepare a nickel and aluminum-doped cobalt salt solution, which was used as the cobalt salt solution for the core layer. The mass concentration of cobalt ions in the solution was 100 g / L, and the elemental molar ratio of cobalt, nickel, and aluminum in the solution was Co:Ni:Al = 1:0.017:0.029. The cobalt salt solution for the coating layer was prepared by mixing so that its concentration matched the molar ratio of each coating layer, and the mass concentration of cobalt salt in the coating layer cobalt salt solution was 100 g / L. An ammonium bicarbonate solution with a mass concentration of 190 g / L was prepared and used as a precipitating agent solution. An ammonium bicarbonate solution with a pH of 8.6 was prepared and used as the bottom solution.

[0175] 2. The prepared cobalt salt solution and precipitant solution were simultaneously placed in a reactor containing bottom liquid. The flow rate of the cobalt salt solution was gradually increased from 2.5% / h of the reactor's usable volume to 6.2% / h, the flow rate of the precipitant solution was doubled to the flow rate of the cobalt salt solution, the stirring speed was gradually reduced from 350 r / min to 150 r / min, the pH during the reaction was controlled to 7.0-7.4, and the ammonium concentration was controlled to 15-30 g / L. The reaction was carried out until the particle size D50 grew to 20.5 μm, obtaining a cobalt carbonate core layer.

[0176] 3. The process was modified to reduce the flow rate of the cobalt salt solution to 2.7% / h of the reactor's usable volume, and the flow rate of the precipitant solution to 1.6 times the flow rate of the cobalt salt solution. The prepared cobalt salt solution was pumped into the coating layers in order, and when each coating layer reached a thickness of approximately 0.25 μm and the desired particle size, it was replaced with the next coating layer solution. Under conditions where the pH during the reaction was controlled to 7.3-7.5 and the ammonium concentration to 20-35 g / L, aluminum-doped cobalt carbonate of Example 8 was prepared.

[0177] Figure 30 shows a scanning electron microscope image of the surface morphology of cobalt carbonate secondary particles according to Example 8.

[0178] 4. After centrifuging the above cobalt carbonate, it was sintered under the following conditions: sintering temperature of 800°C, sintering time of 2.5 hours, rotation speed of the rotary kiln core tube of 0.8 r / min, and material layer thickness of 3.0 cm, to prepare the multi-doped tricobalt tetroxide of Example 8.

[0179] Figure 31 shows a scanning electron microscope image of the surface morphology of tricobalt tetroxide secondary particles according to Example 8.

[0180] 5. The tricobalt tetroxide and lithium carbonate obtained in Example 8 were uniformly mixed in a Li / Me molar ratio of 1.05:1, and the mixture was calcined at 1000°C for 20 hours to prepare the lithium cobalt oxide cathode material of Example 8.

[0181] Comparative Example 1 Comparative Example 1 provides a tricobalt tetroxide precursor having a core layer doped with 1.0 wt% Al and two coating layers. The molar ratio of the doped elements in each coating layer is similar to the molar ratio of each doped element in the cobalt salt solution of the coating layer at the time of preparation, with n1 satisfying Co:Al = 0.95:0.05 and n2 satisfying Co:Al = 0.97:0.03. The preparation method is as follows.

[0182] 1. An aluminum sulfate solution and a cobalt sulfate solution were mixed to prepare an aluminum-doped cobalt salt solution, which was used as the cobalt salt solution for the core layer. The mass concentration of cobalt ions in the solution was 100 g / L, and the elemental molar ratio of cobalt to aluminum in the solution was Co:Al = 1:0.03. The cobalt salt solution for the coating layer was prepared by mixing so that its concentration matched the molar ratio of each coating layer, and the mass concentration of cobalt salt in the coating layer cobalt salt solution was 100 g / L. An ammonium bicarbonate solution with a mass concentration of 200 g / L was prepared and used as a precipitating agent solution. An ammonium bicarbonate solution with a pH of 8.6 was prepared and used as the bottom solution.

[0183] 2. The cobalt salt solution and precipitant solution of the prepared core layer were simultaneously placed in a reactor containing the bottom liquid. The flow rate of the cobalt salt solution was gradually increased from 2.3% / h of the reactor's usable volume to 5.5% / h, the flow rate of the precipitant solution was doubled to the flow rate of the cobalt salt solution, and the stirring speed was gradually reduced from 380 r / min to 250 r / min. The reaction was carried out until the particle size D50 grew to 19.0 μm, thereby obtaining a cobalt carbonate core layer.

[0184] 3. The process was modified to reduce the flow rate of the cobalt salt solution to 2.4% / h of the reactor's usable volume, and the flow rate of the precipitant solution to 1.5 times the flow rate of the cobalt salt solution. The prepared cobalt salt solution was pumped into the coating layers in order, with each coating layer having a thickness of approximately 0.45 μm. When the desired particle size was reached, the solution was replaced with the next coating layer solution. Under conditions where the pH during the reaction was controlled to 6.8-7.2 and the ammonium concentration to 10-25 g / L, doped cobalt carbonate of Comparative Example 1 was prepared.

[0185] Figure 32 shows a scanning electron microscope image of the surface morphology of cobalt carbonate secondary particles according to Comparative Example 1.

[0186] 4. After centrifuging the above cobalt carbonate, it was sintered under the following conditions: sintering temperature of 740°C, sintering time of 2.0 h, rotation speed of the rotary kiln core tube of 0.8 r / min, and material layer thickness of 2.5 cm, to prepare the multi-doped tricobalt tetroxide of Comparative Example 1.

[0187] Figure 33 shows a scanning electron microscope image of the surface morphology of tricobalt tetroxide secondary particles according to Comparative Example 1. Figure 34 shows a scanning electron microscope image of the morphology of the cross-section thereof.

[0188] 5. The tricobalt tetroxide and lithium carbonate obtained in Comparative Example 1 were uniformly mixed in a Li / Me molar ratio of 1.05:1, and fired at 1000°C for 20 hours to prepare the lithium cobalt oxide cathode material of Comparative Example 1.

[0189] Comparative Example 2 Comparative Example 2 provides a tricobalt tetroxide precursor doped with 1.2 wt% Ni and 0.85 wt% Al without coating. The preparation method is as follows.

[0190] 1. Nickel sulfate solution, aluminum sulfate solution, and cobalt sulfate solution were mixed to prepare a nickel and aluminum-doped cobalt salt solution. The mass concentration of cobalt ions in the solution was 100 g / L, and the elemental molar ratio of cobalt, nickel, and aluminum in the solution was Co:Ni:Al = 1:0.017:0.026. An ammonium bicarbonate solution with a mass concentration of 190 g / L was prepared as a precipitating solution. An ammonium bicarbonate solution with a pH of 8.6 was prepared as the bottom solution.

[0191] 2. The prepared cobalt salt solution and precipitant solution were simultaneously placed in a reactor containing bottom liquid. The reaction was carried out under conditions where the flow rate of the cobalt salt solution was 2.5% / h of the reactor's usable volume, the flow rate of the precipitant solution was twice that of the cobalt salt solution, and the stirring speed was reduced from 350 r / min to 150 r / min, until the particle size D50 grew to 20.5 μm, thereby obtaining a cobalt carbonate core layer.

[0192] Figure 35 shows a scanning electron microscope image of the surface morphology of cobalt carbonate secondary particles according to Comparative Example 2. Figure 36 shows a scanning electron microscope image of the morphology of the cross-section thereof.

[0193] 3. After centrifugally washing the cobalt carbonate, it was sintered under the conditions that the sintering temperature was 750 °C, the sintering time was 2.5 h, the rotation speed of the core tube of the rotary kiln was 0.8 r / min, and the thickness of the material layer was 3.5 cm, to prepare the multi-doped cobalt tetroxide of Comparative Example 2.

[0194] Figure 37 shows a scanning electron microscope photograph of the surface morphology of the cobalt tetroxide secondary particles according to Comparative Example 2 (the left figure is the overall view, and the right figure is the local enlarged view). Figure 38 shows a scanning electron microscope photograph of the morphology of its cross-section. From the right figure of Figure 39, it can be seen that due to the uneven doping of aluminum, a honeycomb structure composed of a plurality of fine primary particles was generated on the cross-section. For the cobalt tetroxide, the Al component in the micro-region of the coating layer on the cross-section of the secondary particles was analyzed using an electron beam microanalyzer, and the results are shown in Figure 35. The distribution of Al is not uniform and is clearly enriched.

[0195] 4. The cobalt tetroxide obtained in Comparative Example 2 and lithium carbonate were uniformly mixed at a Li / Me molar ratio of 1.05:1 and fired at 1000 °C for 20 h to prepare the lithium cobalt oxide positive electrode material of Comparative Example 2.

[0196] The indexes of cobalt carbonate according to each example and comparative example are shown in Table 1.

[0197]

Table 1

[0198]

Table 2

[0199] Test example Using the cathode materials from each of the above examples and comparative examples, conductive carbon black and polyvinylidene fluoride were dissolved in NMP solvent under vacuum in a mass ratio of 85:10:5 to prepare a cathode slurry with a solid content of 80% by weight. Then, cathode pellets were prepared by coating, drying, and cutting. A lithium battery was then assembled in the following order: cathode shell, cathode sheet, separator, anode sheet, stainless steel sheet, elastic piece, and anode shell. The electrolyte was 1 mol / LLiPF6 / EC:DMC (volume ratio 1:1) with 10% (volume fraction) of fluoroethylene carbonate (FEC) added, and the separator was a microporous polypropylene membrane. Button-type CR2032 cells for Examples 1-8 and Comparative Examples 1-2 were prepared accordingly. Electrochemical tests were then performed at room temperature using a Neware battery measurement system at varying rates. The battery performance for each example and comparative example, with 1C = 200 mAh / g, is shown in Table 3.

[0200] [Table 3]

[0201] As can be seen from Tables 1-3, the batteries prepared in Examples 1-8 achieve a better balance between discharge capacity and cycle performance, and exhibit superior 2C / 0.2C rates compared to Comparative Examples 1-2. Specifically, these are as follows:

[0202] 1. Compared to Example 1, the lithium-ion battery produced by doping the tricobalt tetroxide core layer prepared in Example 2 with manganese instead of nickel has a slightly lower capacity but a higher cycle life.

[0203] 2. Compared to Example 1, the tricobalt tetroxide prepared in Examples 3, 4, 5, and 6 had fewer doped elements in the coating layer, resulting in the formation of a uniquely modified layer. The core layer of the tricobalt tetroxide prepared in Examples 3 and 4 was not doped with Ni, and the lithium-ion batteries made therefrom had slightly lower capacity and cycle retention than Example 1, but were improved compared to Comparative Example 2. The tricobalt tetroxide prepared in Examples 5 and 6 had smaller particle sizes, and the combination of doped elements for the coating was adjusted, with the outermost layer containing Mg, so the lithium-ion batteries made therefrom had slightly lower capacity and cycle retention than Example 1, but were slightly higher than Examples 3 and 4.

[0204] 3. Compared to Examples 3 and 4, Examples 5 and 6 have Ni doped into the core layer, resulting in higher capacity, and the number of doped layers has increased by one, with Mg doped into the outermost layer, thus exhibiting superior rate performance.

[0205] 4. Compared to Example 1, the tricobalt tetroxide coating layer prepared in Example 7 was a single layer, and multiple elements were doped, with the doping amounts finely adjusted. The doping element content in the shell layer became too high, reducing the uniformity of the doping and thus lowering the overall electrical performance. The tricobalt tetroxide prepared in Example 8 had an increased amount of Al doping, and the addition of Al stabilized the crystal structure. The lithium-ion battery made with this improved cycle retention, but the discharge capacity was slightly reduced because the excessive doping of Al had a certain effect on the capacity.

[0206] 5. Compared to Examples 1-8, the tricobalt tetroxide prepared in Comparative Example 1 has a coating layer, but the cobalt content of the coating layer increases with each layer, and no other doping elements other than Al are added for modification, and Co 4+The amount of elution increased. Furthermore, because the stirring speed did not decrease with the growth of particle size and a constant rotation speed was maintained, the resulting cobalt carbonate particles had low overall porosity, low specific surface area, and low overall pore volume. The corresponding lithium-ion battery had a degraded cycle life, and its battery capacity and cycle life were inferior to those of Examples 1-8. However, because the coating layer improved the stability of the material's surface structure, the capacity and cycle life of Comparative Example 1 were higher than those of Comparative Example 2, but lower than those of each of the examples.

[0207] 6. Compared to Examples 1-8, the tricobalt tetroxide prepared in Comparative Example 2 lacked a coating layer, the distribution of doped elements in the core layer was not uniform, and the capacity and cycle life of the corresponding lithium-ion battery were reduced.

[0208] 7. Compared to Comparative Examples 1 and 2, lithium-ion batteries made with the tricobalt tetroxide cathode materials prepared in Examples 1 to 8 achieved a rate performance of 97.9% or higher at 2C / 0.2C under conditions of 3.6 to 4.55V, demonstrating a significant improvement in rate performance. Among these, Examples 1, 2, and 3 achieved a rate performance of 98% or higher, indicating that the doped elements in the coating layer of the material produced the expected effects. Example 3 is doped with La and Zr, which can improve ion mobility, i.e., rate performance, to some extent. Example 4 is doped with Ti and Mg, which forms continuous channels, improving ion passage efficiency and rate performance.

[0209] Finally, it is important to note that the above embodiments are merely illustrative of the embodiments of the Disclosure and do not limit them. Although the Disclosure has been described in detail using the above embodiments, those skilled in the art can modify the embodiments described in the above embodiments or substitute some or all of their technical features equally. Such modifications or substitutions do not depart the essence of the embodiments in question from the scope of the embodiments of the Disclosure.

[0210] Furthermore, while some of the embodiments described above possess some of the features included in other embodiments, a person skilled in the art should understand that combinations of features from different embodiments constitute other embodiments that fall within the scope of this disclosure. For example, the embodiments to be protected in the claims may be arbitrarily combined. The information disclosed in the background art section is intended to enhance the understanding of the background art of this disclosure as a whole, and should not be understood as an acknowledgment or implied in any way that it is prior art well known to a person skilled in the art.

[0211] Industrial applicability As described above, the cobalt carbonate and tricobalt tetroxide according to this disclosure include a core layer and a coating layer covering the core layer. By gradient-doping the entire tricobalt tetroxide particle with Al and increasing the amount of Al doping in the core layer compared to the coating layer, the stability of the crystal structure and the cycling performance of the LCO material can be improved. In the case of cobalt carbonate, since the Al element exists in the form of amorphous aluminum hydroxide during the crystallization process, the aluminum content in the coating layer is low, which helps to suppress the hydrolysis and precipitation of amorphous aluminum hydroxide during centrifugal washing. Furthermore, since the porosity and pore volume of the coating layer are lower than those of the core layer, it helps to suppress the hydrolysis and precipitation of amorphous aluminum hydroxide in the core layer and improves the uniformity of the Al element distribution.

[0212] Furthermore, the tricobalt tetroxide, cobalt carbonate, their preparation methods, cathode materials, and lithium-ion batteries described in this application are reproducible and applicable to various industries. For example, the tricobalt tetroxide, cobalt carbonate, their preparation methods, cathode materials, and lithium-ion batteries described in this application are applicable to the lithium-ion battery field.

[0213] In the present invention, the method for obtaining a cross-section of the precursor secondary particles involves cutting the powder sample of the present invention with an ion beam to obtain a cross-section, and then taking a cross-sectional SEM image with an electron microscope.

[0214] As shown in the cross-sectional SEM image in Figure 1, the outer periphery of the secondary particle, which has multiple radially arranged annular regions, serves as the outer shell, while the porous regions within the annular regions, which have micropores, serve as the core.

Claims

1. The material comprises a core layer and a coating layer covering the core layer, wherein both the core layer and the coating layer are doped with Al, and the amount of Al doping in the core layer is higher than the amount of Al doping in the coating layer. Tricobalt tetroxide characterized by the following features.

2. The cobalt content of the tricobalt tetroxide decreases layer by layer from the inside outwards, starting from the core layer and moving towards the coating layer. The tricobalt tetroxide according to feature 1.

3. Condition A, where the tricobalt tetroxide coating layer consists of 1 to 5 layers, Condition B, in which the ratio of the mass of doped Al in the tricobalt tetroxide core layer to the mass of the total metal in the tricobalt tetroxide core layer is 0.40 to 1.20 wt%, Condition C, in which the ratio of the mass of doped Al in the tricobalt tetroxide coating layer to the mass of the total metal in the tricobalt tetroxide is 0.02 to 0.40 wt%, When the tricobalt tetroxide coating layer is one layer, condition D is that the ratio of the molar amount of cobalt in the tricobalt tetroxide coating layer to the molar amount of the total metal in the tricobalt tetroxide coating layer is 70 mol% or less. When the tricobalt tetroxide coating layer consists of 2 to 5 layers, condition E states that the ratio of the molar amount of cobalt in the outermost layer of the tricobalt tetroxide coating layer to the molar amount of the total metal in the outermost layer of the tricobalt tetroxide coating layer is 70 mol% or less. The diameter of the tricobalt tetroxide core layer is 5.0 to 18.0 μm, under condition F, When the tricobalt tetroxide coating layer is one layer, condition G is that the thickness of the tricobalt tetroxide coating layer is 0.10 to 1.0 μm, When the tricobalt tetroxide coating layer consists of 2 to 5 layers, condition H is that the thickness of a single layer in the tricobalt tetroxide coating layer is 0.10 to 1.0 μm, Satisfy at least one of the following conditions The tricobalt tetroxide according to claim 1 or 2.

4. The aforementioned tricobalt tetroxide core layer further comprises Ni and / or Mn under condition I, When condition I is met, the ratio of the mass of doped Ni and Mn in the tricobalt tetroxide core layer to the mass of the total metal in the tricobalt tetroxide core layer is independently 0.10 to 3.00 wt%, and condition J is met. The aforementioned tricobalt tetroxide coating layer further contains one or more doping elements from Mg, Ti, La, Zr, Y, Ca, Sr, and Ba under condition K, When condition K is met, the ratio of the mass of other doping elements other than Al in the tricobalt tetroxide coating layer to the mass of all metals in the tricobalt tetroxide is independently 0.01 to 0.40 wt%, and condition L is met. Satisfy at least one of the following conditions The tricobalt tetroxide according to any one of claims 1 to 3.

5. When the condition K is met, the aforementioned tricobalt tetroxide When the coating layer consists of two layers, the coating layer is divided into an inner layer and an outer layer, the inner layer of the coating layer further comprises one or more of Zr, La, Ca, Ba, Y, Ti, and Sr, and the outer layer of the coating layer further comprises one or more of Mg, Zr, Ti, and Sr. When the coating layer consists of 3 to 5 layers, the coating layer is divided into an inner layer, an intermediate layer, and an outer layer, with the inner layer and the outer layer each consisting of one layer, the inner layer of the coating layer further containing one or more of Zr, La, Ca, and Ba, the intermediate layer of the coating layer further containing one or more of La, Zr, Y, Ti, and Sr, and the outer layer of the coating layer further containing one or more of Mg, Zr, Ti, and Sr. The tricobalt tetroxide according to feature 4.

6. Condition M is such that the porosity of the core layer of the tricobalt tetroxide is 5.5 to 9.5%, and the porosity of the entire tricobalt tetroxide is 4.5 to 7.5%. The pore volume of the tricobalt tetroxide core layer is 0.004 to 0.015 cm³. ３ The concentration is / g, and the total pore volume of the tricobalt tetroxide is 0.002 to 0.080 cm³. ３ The condition N is that / g, Condition O is that the D50 of the aforementioned tricobalt tetroxide is 5.5 to 23.0 μm, The tap density of the aforementioned tricobalt tetroxide is 2.0 to 3.0 g / cm³. ３ The condition P is, The specific surface area of ​​the aforementioned tricobalt tetroxide is 2.0 to 15 m². ２ The condition Q is that / g, Satisfy at least one of the following conditions The tricobalt tetroxide according to feature 5.

7. The material comprises a core layer and a coating layer covering the core layer, wherein both the core layer and the coating layer are doped with Al, and the amount of Al doping in the core layer is higher than the amount of Al doping in the coating layer. Cobalt carbonate characterized by the following features.

8. The cobalt content of the cobalt carbonate decreases layer by layer from the inside out, from the core layer of the cobalt carbonate towards the coating layer of the cobalt carbonate. The cobalt carbonate according to feature 7.

9. The cobalt carbonate coating layer is one to five layers, condition a, Condition b is that the ratio of the mass of doped Al in the cobalt carbonate core layer to the mass of the total metal in the cobalt carbonate core layer is 0.26 to 0.80 wt%, Condition c is that the ratio of the mass of doped Al in the cobalt carbonate coating layer to the mass of the total metal in the cobalt carbonate is 0.01 to 0.27 wt%, When the cobalt carbonate coating layer is one layer, condition d is that the ratio of the molar amount of cobalt in the cobalt carbonate coating layer to the molar amount of all metals in the cobalt carbonate coating layer is 70 mol% or less. When the cobalt carbonate coating layer consists of 2 to 5 layers, condition e states that the ratio of the molar amount of cobalt in the outermost layer of the cobalt carbonate coating layer to the molar amount of the total metal in the outermost layer of the cobalt carbonate coating layer is 70 mol% or less. The cobalt carbonate core layer has a diameter of 8.0 to 23.0 μm, under condition f. When the cobalt carbonate coating layer is one layer, condition g is that the thickness of the cobalt carbonate coating layer is 0.15 to 1.5 μm. When the cobalt carbonate coating layer consists of 2 to 5 layers, condition h is that the thickness of a single layer in the cobalt carbonate coating layer is 0.15 to 1.5 μm. The cobalt carbonate core layer further comprises Ni and / or Mn under condition i, When condition i is met, the ratio of the mass of doped Ni and Mn in the cobalt carbonate core layer to the mass of the total metal in the cobalt carbonate core layer is independently 0.07 to 2.00 wt%, and condition j is met. The cobalt carbonate coating further comprises one or more doping elements from Mg, Ti, La, Zr, Y, Ca, Sr, and Ba under the condition k, When condition k is met, the ratio of the mass of other doping elements other than Al in the cobalt carbonate coating layer to the mass of all metals in the cobalt carbonate is independently 0.01 to 0.30 wt%, and condition l is also met. Satisfy at least one of the following conditions The cobalt carbonate according to feature 8.

10. The aforementioned cobalt carbonate, if condition k is met, When the coating layer consists of two layers, the coating layer is divided into an inner layer and an outer layer, the inner layer of the coating layer further comprises one or more of Zr, La, Ca, Ba, Y, Ti, and Sr, and the outer layer of the coating layer further comprises one or more of Mg, Zr, Ti, and Sr. When the coating layer consists of 3 to 5 layers, the coating layer is divided into an inner layer, an intermediate layer, and an outer layer, with the inner layer and the outer layer each being one layer, the inner layer of the coating layer further containing one or more of Zr, La, Ca, and Ba, the intermediate layer of the coating layer further containing one or more of La, Zr, Y, Ti, and Sr, and the outer layer of the coating layer further containing one or more of Mg, Zr, Ti, and Sr. The cobalt carbonate according to feature 9.

11. The porosity of the core layer of the cobalt carbonate is 15-25%, and the porosity of the entire cobalt carbonate is 14-25% under condition m, The pore volume of the cobalt carbonate core layer is 0.08 to 0.30 cm³. ３ The concentration is / g, and the total pore volume of the cobalt carbonate is 0.05 to 0.25 cm³. ３ The condition n is that / g, The condition is that the D50 of the cobalt carbonate is 8.7 to 30.0 μm, The specific surface area of ​​the aforementioned cobalt carbonate is 50 to 150 m². ２ The condition p is that / g, The tap density of the aforementioned cobalt carbonate is 1.5 to 2.0 g / cm³. ３ The condition q is, Satisfy at least one of the following conditions The cobalt carbonate according to feature 10.

12. The process involves placing a cobalt salt solution and a precipitant solution for the core layer into a reactor containing a bottom liquid, reacting the mixture under conditions where the flow rate of the cobalt salt solution for the core layer increases as the particle size of the material increases, the flow rate of the precipitant solution increases as the flow rate of the cobalt salt solution for the core layer increases, and the stirring speed of the reactor decreases as the particle size of the material increases, until the particle size D50 reaches 8.0 to 23.0 μm, thereby obtaining a cobalt carbonate core layer. The process includes the steps of: placing a cobalt salt solution of the coating layer and a precipitant solution in this order into a reactor containing the cobalt carbonate core layer, and allowing the reaction to proceed until the growth of each coating layer is complete to obtain cobalt carbonate. A method for preparing cobalt carbonate, characterized by the features described above.

13. Cobalt carbonate obtained by sintering cobalt carbonate prepared by any one of claims 7 to 11 or by the method for preparing cobalt carbonate described in claim 12. A method for preparing tricobalt tetroxide, characterized by the features described above.

14. Lithium cobaltate obtained by calcining tricobalt tetroxide and a lithium source as described in any one of claims 1 to 6. A positive electrode material characterized by the following features.

15. The molar ratio of the lithium source to the tricobalt tetroxide is (1 to 1.05):

1. The positive electrode material according to feature 14.

16. The firing temperature is 900°C to 1200°C, and the firing time is 20 to 30 hours. The positive electrode material according to feature 14.

17. The raw material includes the positive electrode material described in any one of claims 14 to 16. A lithium-ion battery characterized by the following features.

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