Lithium cobalt oxide and preparation method thereof

Abstract

According to the lithium cobalt oxide and the preparation method of the lithium cobalt oxide provided by the invention, by utilizing the characteristics that a molten state reaction is more uniform than a pure solid state reaction and the particle size of a product is easier to control, two raw materials are distributed and molten in a grading and zoning manner, and when a lithium-containing compound is in a molten state, the lithium cobalt oxide is prepared; distributing the cobalt-containing compound in a solid state, a semi-molten state or a molten state into the lithium-containing compound material in the molten state; distributing the solid, semi-molten or molten cobalt-containing compound into a molten lithium-containing compound material layer, uniformly diffusing the cobalt-containing compound to each part of the material layer, and carrying out chemical reaction to generate lithium cobalt oxide; according to the method, the molten reaction is more uniform than the pure solid-phase reaction, the particle size of the product is easier to control, and the lithium cobalt oxide prepared by the method is good in uniformity and high in tap density.

Description

Technical Field

[0001] The invention relates to lithium cobalt oxide and a method for preparing lithium cobalt oxide, and in particular to a method for preparing lithium cobalt oxide by adopting a non-solid-solid reaction system and the lithium cobalt oxide prepared by the method, belonging to the field of material technology. Background Art

[0002] Compared with traditional secondary batteries such as nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, etc., lithium-ion secondary batteries have many advantages such as high energy density, high power density, long cycle life, and environmental friendliness. They are widely used in the power supply production of mobile phones, digital cameras and laptops, and have become a research focus of the new energy materials industry.

[0003] Lithium cobalt oxide is the main raw material for preparing lithium-ion battery materials. At present, the production method of lithium cobalt oxide is mainly the high-temperature solid phase method. The powder raw materials of cobalt and lithium are first fully mixed by ball milling, high-speed stirring and other methods, and then sintered, crushed, screened, iron removed and other processes to obtain the final lithium cobalt oxide product. The preparation technology of lithium cobalt oxide is mature, but due to the difference in particle size of cobalt and lithium raw material particles, and the high-temperature roasting process is a solid-solid reaction, the raw materials have differences in particle size, specific gravity and other aspects, as well as the limitations of the distribution equipment and distribution technology, segregation is prone to occur, and technical problems such as uneven air permeability affect the uniformity of the mixture; the particle size difference between particles cannot be reduced, and even the particle size difference will be aggravated, resulting in poor particle size uniformity of the prepared lithium cobalt oxide product, with coarse particles and fine particles, some particles with a particle size greater than 50μm, and some particles with a particle size less than 5μm. The unevenness of the particles increases the gap between the particles, reduces the tap density of lithium cobalt oxide, and affects its service life.

[0004] At present, the industrial production of lithium cobalt oxide generally adopts the solid phase reaction method, which generally uses cobalt trioxide and lithium carbonate as raw materials, and then mixes them by dry methods such as ball milling, and then sintered at high temperature in a pusher kiln or roller kiln, and finally crushed to obtain the finished lithium cobalt oxide. The reaction process requires heating and the participation of oxygen. In industrial production, electric heating pusher kilns or roller kilns are generally used for sintering. Excess air is introduced during the sintering process to meet the demand for oxygen during the reaction process. The by-product of the reaction is carbon dioxide, which is generally discharged into the atmosphere through the exhaust chimneys at the head and tail of the pusher kiln or roller kiln.

[0005] The specific process of preparing lithium cobalt oxide in the prior art is as follows: First, the two main raw materials, cobalt tetroxide and battery-grade lithium carbonate, are calculated to obtain the quantity required for each batch. The calculated quantity is generally accurate to 0.01 kg, and then the prepared raw materials are put into the mixer manually or by equipment such as a crane. The uniform mixing of cobalt tetroxide and lithium carbonate powder is completed by the mechanical force of the mixing equipment. After mixing, the materials are generally batched again in order to eliminate the differences between batches, that is, several small batches of materials from the previous process are simply mixed by equipment such as a ribbon mixer to complete the batching operation. The materials after batch mixing are quantitatively weighed by manual or automated equipment and distributed into a crucible of a certain volume. After distribution, the materials enter the electric heating tunnel kiln with the crucible for sintering. In the electric-heated tunnel kiln, the material is heated, kept constant, and cooled according to the set curve to complete the high-temperature solid-phase reaction. The powder material before sintering is sintered into a solid block. The subsequent coarse crushing and fine crushing process is to crush the sintered block into powder again. The sintered material blocks are crushed by jaw crushers and roller mills, and the blocks are broken into small particles of millimeter size. After these small particles are crushed by air flow milling, micron-sized lithium cobalt oxide products are obtained. Due to the limited grading capacity of air flow milling, there will inevitably be some large particles > 100um in the lithium cobalt oxide product after air flow milling. Therefore, it is necessary to screen through a larger mesh screen (generally 300 mesh) to remove these large particles. During the production process, due to the contact between materials and equipment in each process, magnetic metal foreign matter such as iron, chromium, nickel, and zinc will inevitably be introduced, and the presence of these foreign matter will cause the lithium-ion batteries to have problems such as self-discharge. Therefore, in order to remove (or reduce) these harmful metal foreign matter, in industrial production, an electromagnetic iron remover is generally used to demagnetize lithium cobalt oxide products. In order to ensure the uniformity between batches of the final packaged product, the pure lithium cobalt oxide powder after demagnetization is mixed for the last time, and then enters the automatic packaging machine or manual packaging to complete the final packaging of the lithium cobalt oxide product. Summary of the invention

[0006] In view of the problem that a solid-solid reaction system is used in the prior art for preparing lithium cobalt oxide, the particle size of the prepared product varies greatly and the tap density is poor. The present invention utilizes the characteristics that molten state reaction is more uniform than pure solid phase reaction and the particle size of the product is easier to control, distributes and melts two raw materials in different levels and regions, distributes the lithium-containing compound with a low melting point preferentially in a roasting device, distributes the cobalt-containing compound with a high melting point preferentially in another roasting device, and distributes the cobalt-containing compound in a solid, semi-molten or molten state to the molten lithium-containing compound material when the lithium-containing compound is in a molten state; distributes the cobalt-containing compound in a solid, semi-molten or molten state to the lithium-containing compound material layer that is preferentially melted at a low temperature, and the cobalt-containing compound is uniformly diffused to various parts of the material layer, and a chemical reaction occurs in the subsequent roasting process to generate lithium cobaltate; the method utilizes the characteristics that molten state reaction is more uniform than pure solid phase reaction and the particle size of the product is easier to control, and the difference in melting points of lithium and cobalt compounds, combined with the characteristics of strong fluidity and high reaction rate of molten materials, the improvement of reactivity can reduce the proportion of cobalt metal to a certain extent, offset the influence of the reduction of the proportion of cobalt metal, and avoids the disadvantage of a large demand for cobalt metal in a conventional pure solid phase reaction preparation process. The lithium cobalt oxide product prepared by the molten reaction system has better particle uniformity, avoiding the problem of uneven particle size of lithium cobalt oxide products prepared by conventional pure solid-phase reaction, which leads to poor tap density. High-density lithium cobalt oxide products can be prepared to improve the life of battery materials. This method is advanced in technology, and reduces the use of metal cobalt while ensuring the quality of lithium cobalt oxide products, reducing the consumption of metal cobalt, and is expected to open up a more efficient and high-quality path for the development of lithium cobalt oxide preparation technology in my country.

[0007] According to a first embodiment provided by the present invention, a method for preparing lithium cobalt oxide is provided.

[0008] A method for preparing lithium cobalt oxide, the method comprising the following steps:

[0009] 1) Pretreatment of lithium-containing compounds: heating the lithium-containing compound raw material to obtain a molten lithium-containing compound;

[0010] 2) Pretreatment of the cobalt-containing compound: heating the cobalt-containing compound raw material to obtain a hot cobalt-containing compound;

[0011] 3) Evenly mixing the molten lithium-containing compound and the hot cobalt-containing compound, condensing and crystallizing to obtain lithium cobalt oxide.

[0012] In the present invention, in step 2), the raw material containing the cobalt compound is heated to a solid state, a semi-molten state or a molten state. Preferably, the raw material containing the cobalt compound is heated to a semi-molten state.

[0013] Preferably, in the semi-molten cobalt-containing compound, the mass proportion of the solid cobalt-containing compound is 10-90%, preferably 15-60%, and more preferably 20-40%. For example, in the semi-molten cobalt-containing compound, the mass proportion of the solid cobalt-containing compound is 10%, 12%, 15%, 16%, 18%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%.

[0014] In the present invention, the lithium-containing compound raw material is lithium carbonate and / or lithium hydroxide, preferably lithium carbonate.

[0015] Preferably, the purity of the lithium compound-containing raw material is ≥99.0%, preferably ≥99.3%, and more preferably ≥99.5%.

[0016] Preferably, the particle size of the lithium-containing compound raw material is not greater than 500 μm, preferably 1-200 μm, and more preferably 2-100 μm.

[0017] In the present invention, the cobalt-containing compound raw material is tricobalt tetroxide and / or cobalt hydroxide, preferably tricobalt tetroxide.

[0018] Preferably, the purity of the raw material containing the cobalt compound is ≥95.0%, preferably ≥97.0%, and more preferably ≥99.0%.

[0019] Preferably, the particle size of the cobalt-containing compound raw material is not greater than 1000 μm, preferably 1-500 μm, and more preferably 2-200 μm. In the present invention, the lithium-containing compound raw material is lithium carbonate, and the heating temperature in step 1) is higher than 720°C; preferably 730-2000°C, further preferably 750-1500°C, and more preferably 780-1400°C.

[0020] In the present invention, the lithium-containing compound raw material is lithium hydroxide, and the heating temperature in step 1) is higher than 462°C; preferably 480-800°C, more preferably 500-1200°C, and more preferably 550-1000°C.

[0021] In the present invention, the cobalt-containing compound raw material is cobalt tetroxide, and the heating temperature in step 2) is higher than 720°C, preferably 750-2000°C, more preferably 800-1500°C, more preferably 895-1200°C, and even more preferably 900-1000°C.

[0022] In the present invention, the cobalt-containing compound raw material is cobalt hydroxide, and the heating temperature in step 1) is higher than 720°C, preferably 750-2000°C, more preferably 850-1600°C, more preferably 900-1500°C, further preferably 1000-1200°C, and more preferably 1100-1150°C.

[0023] In the present invention, in step 3), the mixing molar ratio of the lithium-containing compound to the cobalt-containing compound is 1:0.5-1.2, preferably 1:0.6-1.0, and more preferably 1:0.8-0.9.

[0024] In the present invention, the method is specifically:

[0025] 1) Pretreatment of lithium-containing compounds: the raw materials of the lithium-containing compounds are fed to a roasting device and transported to a roasting system, and the roasting system heats and roasts the raw materials of the lithium-containing compounds to completely form a molten state; and a molten lithium-containing compound is obtained;

[0026] 2) Pretreatment of the cobalt-containing compound: the raw material of the cobalt-containing compound is fed to the roasting device and transported to the roasting system, and the roasting system heats the raw material of the cobalt-containing compound to heat the raw material of the cobalt-containing compound into a solid, semi-molten or molten state to obtain a hot cobalt-containing compound;

[0027] 3) The hot cobalt-containing compound is uniformly added to the molten lithium-containing compound, the hot cobalt-containing compound is continuously dispersed into the molten lithium-containing compound, the cobalt-containing compound reacts with the lithium-containing compound, and then condenses and crystallizes to obtain lithium cobaltate.

[0028] According to a second embodiment provided by the present invention, a lithium cobalt oxide is provided.

[0029] A lithium cobalt oxide prepared by the method for preparing lithium cobalt oxide described in the first embodiment.

[0030] In the present invention, the tap density of the lithium cobalt oxide is ≥2.5g / cm 3 ;

[0031] In the present invention, the cycle life of the battery prepared using the lithium cobalt oxide as the positive electrode material is ≥500 times.

[0032] For the preparation of lithium cobalt oxide products, when the particle size of lithium cobalt oxide particles is closer to 10μm and the particle size is more uniform, its specific capacity index is optimal and the tap density is optimal, and a high-density lithium cobalt oxide product with better performance can be prepared. For this research purpose, the inventors conducted a test study on the preparation of high-density lithium cobalt oxide based on molten mixing. First, the lithium carbonate was completely melted, and then solid, semi-molten or molten cobalt tetroxide was added to the molten lithium carbonate and calcined at medium and high temperature to prepare the lithium cobalt oxide product. By detecting the particle scanning electron microscope image of the lithium cobalt oxide product and comparing the particle uniformity of the product, it was determined whether high-density lithium cobalt oxide could be prepared. Figure 1-3 As shown. As can be seen from the figure, the particle uniformity of the lithium cobalt oxide product prepared by directly adding solid cobalt tetroxide to molten lithium carbonate is relatively poor, the particle uniformity of the lithium cobalt oxide product prepared by adding molten cobalt tetroxide to molten lithium carbonate is second, and the particle uniformity of the lithium cobalt oxide product prepared by adding semi-molten cobalt tetroxide to molten lithium carbonate is the best. This is because the solid phase material has poor fluidity and poor mixing reaction effect with the molten material, resulting in poor uniformity of product particles; semi-molten cobalt tetroxide is a mixture of solid and liquid, and the solid particles can be used as the core of subsequent condensation and crystallization, which is more conducive to the concentration of particles and the unification of particle size, and the particle size of the prepared lithium cobalt oxide product is more uniform; molten cobalt tetroxide enters molten lithium carbonate, and the mixing reaction effect is better, which can reduce the amount of metal cobalt to a certain extent. There is a certain uncertainty in the condensation and crystallization process, resulting in slightly poor uniformity of the prepared lithium cobalt oxide particles.

[0033] In the present invention, the lithium-containing compound is heated and calcined to prepare a molten lithium-containing compound, the solid-solid reaction system used in the prior art is changed, the raw material is directly heated into a liquid state, and the fluidity of the liquid system is utilized to enhance the reaction rate and uniformity. The raw material of the cobalt-containing compound is also heated, and the hot cobalt-containing compound is used to fuse and react with the lithium-containing compound to improve the reaction performance. Compared with the cold cobalt-containing compound, the hot cobalt-containing compound has higher kinetic energy and higher activity in the molten lithium-containing compound, which accelerates the kinetic potential energy of the cobalt-containing compound in the molten lithium-containing compound, improves the dispersibility of the cobalt-containing compound in the molten lithium-containing compound, and thus improves the uniformity of the obtained product.

[0034] In the present invention, the cobalt-containing compound can be mixed with a hot cobalt-containing compound and a molten lithium-containing compound, and the hot cobalt-containing compound includes a solid cobalt-containing compound, a semi-molten cobalt-containing compound and a molten cobalt-containing compound. As long as the hot cobalt-containing compound is mixed with the molten lithium-containing compound, the effect of the cobalt-containing compound on the dispersibility of the lithium-containing compound can be improved. The cold cobalt-containing compound is added to the molten lithium-containing compound, and the cold cobalt-containing compound molecules absorb the energy of the molten lithium-containing compound, causing the lithium-containing compound around the cobalt-containing compound molecules to react and solidify on the cobalt-containing compound molecules quickly to form lithium cobaltate molecules, increasing the volume of the original cobalt-containing compound molecules, slowing down the flow and dispersion of the cobalt-containing compound molecules in the molten lithium-containing compound, and thus affecting the uniformity of the lithium cobaltate. At the same time, since the cobalt-containing compound molecules are quickly combined with the lithium-containing compound molecules, due to the problem of inconsistent heating uniformity, the particle size uniformity of the formed lithium cobaltate is poor, thereby affecting the tap density of the lithium cobaltate product.

[0035] In the preferred technical scheme of the present invention, a semi-molten cobalt-containing compound and a molten lithium-containing compound are mixed and reacted. The semi-molten cobalt-containing compound contains a portion of liquid cobalt-containing compounds and a portion of solid cobalt-containing compounds. The semi-molten cobalt-containing compound is in the molten lithium-containing compound, and because the temperature of the reaction system is high, the lithium-containing compound is in a boiling state, and the semi-molten cobalt-containing compound is quickly and evenly dispersed into the molten lithium-containing compound. Among them, the solid cobalt-containing compound is evenly dispersed into the lithium-containing compound, and serves as a reaction bed and crystallization nucleus to form lithium cobaltate molecules; the liquid cobalt-containing compound molecules are quickly combined with the molten lithium-containing compound molecules, and are combined with the solid cobalt-containing compound to form lithium cobaltate. Since the solid cobalt-containing compound in the semi-molten cobalt-containing compound is evenly dispersed into the molten lithium-containing compound, a uniform crystallization nucleus is formed, and a reaction bed is provided for the reaction of the liquid cobalt-containing compound with the molten lithium-containing compound; the liquid cobalt-containing compound reacts quickly with the molten lithium-containing compound, and surrounds the crystallization nucleus to form lithium cobaltate with uniform particle size. Since the solid cobalt-containing compound serving as the crystallization nucleus and the reaction bed is evenly dispersed, the liquid cobalt-containing compound and the molten lithium-containing compound react around the crystallization nucleus and adhere to the crystallization nucleus, the obtained lithium cobalt oxide product has high uniformity and high tap density.

[0036] Through the inventor's experiments, the content of solid cobalt-containing compounds in the semi-molten cobalt-containing compound also affects the performance of the lithium cobalt oxide product. In the semi-molten cobalt-containing compound, the higher the content of solid cobalt-containing compounds, the lower the contact between the cobalt-containing compound and the molten lithium-containing compound, and the worse the particle size uniformity of the lithium cobalt oxide finally obtained. In the semi-molten cobalt-containing compound, the higher the content of solid cobalt-containing compounds, the higher the contact between the cobalt-containing compound and the molten lithium-containing compound, and the particle size uniformity of the lithium cobalt oxide finally obtained is relatively high. However, if the cobalt-containing compound is directly heated to a molten state, and the molten cobalt-containing compound and the molten lithium-containing compound are mixed and reacted, the particle size uniformity of the lithium cobalt oxide product finally obtained is still not in the most ideal state. After analysis and experiments by the inventors, if there are too few solid cobalt-containing compounds in the semi-molten cobalt-containing compound, or even a fully molten cobalt-containing compound, and the molten lithium-containing compound is mixed and reacted, due to the lack of a stable crystallization nucleus, the cobalt-containing compound molecules and the lithium-containing compound molecules directly react randomly, and because the reaction heating system cannot be completely uniform, some cobalt-containing compound molecules react with the lithium-containing compound first to form a crystallization nucleus, and the cobalt-containing compound molecules around the crystallization nucleus position and the lithium-containing compound continue to react with this as the core to form lithium cobaltate with a larger particle size; some cobalt-containing compound molecules react with the lithium-containing compound later to form lithium cobaltate with a smaller particle size; which leads to the obtained lithium cobaltate particle size uniformity is not ideal. Through experimental verification, the mass proportion of solid cobalt-containing compounds in the semi-molten cobalt-containing compound is controlled to be 10-90%, preferably 15-60%, more preferably 20-40%, and it is best to control it at 20-40%.

[0037] In the present invention, the semi-molten cobalt-containing compound refers to a hot cobalt-containing compound obtained after the raw material of the cobalt-containing compound is heated, in which a portion of the hot cobalt-containing compound exists in liquid state, while a portion of the hot cobalt-containing compound still exists in solid state.

[0038] In the present invention, the melting point of lithium carbonate is 720°C. The lithium carbonate is heated and roasted to a temperature higher than 720°C and roasted for a period of time to form molten lithium carbonate. The melting point of lithium hydroxide is 462°C. The lithium hydroxide is heated and roasted to a temperature higher than 462°C and roasted for a period of time to form molten lithium hydroxide.

[0039] In the present invention, the melting point of cobalt tetraoxide is 895°C. When the heating temperature is lower than 895°C, cobalt tetraoxide is in solid state. When the heating temperature reaches 895°C, cobalt tetraoxide begins to melt. The amount of cobalt tetraoxide melted is related to the temperature and the roasting time. Generally, the roasting temperature is controlled to be 895-1000°C, the roasting time is lower than 12h, and cobalt tetraoxide is in a semi-molten state. After cobalt tetraoxide is roasted under this condition, a part of cobalt tetraoxide in a solid state exists in the hot cobalt tetraoxide.

[0040] In the present invention, the melting point of cobalt hydroxide is 1100°C. When the heating temperature is lower than 1100°C, the cobalt hydroxide is in solid state. When the heating temperature reaches 1100°C, the cobalt hydroxide begins to melt. The amount of cobalt hydroxide melted is related to the temperature and the roasting time. Generally, the roasting temperature is controlled to be 1100-1200°C, the roasting time is lower than 12h, and the cobalt hydroxide is in a semi-molten state. After the cobalt hydroxide is roasted under this condition, a part of the cobalt hydroxide in a solid state exists in the hot cobalt hydroxide.

[0041] Through the preparation process of the present invention, the amount of cobalt-containing compounds can be appropriately reduced, thereby achieving the purpose of saving cobalt-containing compounds.

[0042] In the present invention, any roasting device can be used to roast the lithium-containing compound raw material and the cobalt-containing compound raw material, which can be a continuous roasting device or an intermittent roasting device. After the lithium-containing compound raw material is heated to a molten state and the cobalt-containing compound is heated to a hot state, the lithium-containing compound raw material is mixed with the cobalt-containing compound, and the reaction is carried out under the same temperature conditions as the heating of the cobalt-containing compound to obtain a lithium cobaltate product. The heating temperature of the cobalt-containing compound is higher than the heating temperature of the lithium-containing compound raw material. After mixing, the reaction is carried out under the heating temperature conditions of the cobalt-containing compound, which ensures that the lithium-containing compound raw material is in a boiling state, avoids the condensation of the lithium-containing compound raw material, and also ensures the dispersion of the cobalt-containing compound in the lithium-containing compound.

[0043] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects:

[0044] 1. The lithium-containing compound is heated and calcined to prepare a molten lithium-containing compound, changing the solid-solid reaction system used in the prior art, directly heating the raw material into a liquid state, and utilizing the fluidity of the liquid system to enhance the reaction rate and uniformity.

[0045] 2. Compared with cold cobalt-containing compounds, hot cobalt-containing compounds have higher kinetic energy and higher activity in molten lithium-containing compounds, which accelerates the kinetic potential energy of the cobalt-containing compounds in the molten lithium-containing compounds and improves the dispersibility of the cobalt-containing compounds in the molten lithium-containing compounds.

[0046] 3. In the preferred technical solution of the present invention, a semi-molten cobalt-containing compound and a molten lithium-containing compound are mixed and reacted. The semi-molten cobalt-containing compound contains a portion of liquid cobalt-containing compound and a portion of solid cobalt-containing compound. Since the temperature of the reaction system is high and the lithium-containing compound is in a boiling state, the semi-molten cobalt-containing compound is quickly and evenly dispersed into the molten lithium-containing compound. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a scanning electron microscope image of lithium cobalt oxide obtained by mixing cobalt tetraoxide in solid state with molten lithium carbonate in Example 1 of the present invention;

[0048] Figure 2 This is a scanning electron microscope image of lithium cobalt oxide obtained by mixing and reacting semi-molten cobalt tetroxide with molten lithium carbonate in Example 2 of the present invention;

[0049] Figure 3 This is a scanning electron microscope image of lithium cobalt oxide obtained by mixing and reacting molten cobalt tetroxide with molten lithium carbonate in Example 3 of the present invention. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is illustrated below by way of example, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0051] Sources of raw materials in the embodiments of the present invention:

[0052] Lithium carbonate: Shanghai Fuzhe Chemical Co., Ltd., purity 99.5%, particle size 10 μm.

[0053] Lithium hydroxide: Guangzhou Songbai Chemical Co., Ltd., purity 99.5%, particle size 8 μm.

[0054] Cobalt trioxide: Suzhou Binshun Chemical Co., Ltd., purity 99.5%, particle size 15μm.

[0055] Cobalt hydroxide: Suzhou Binshun Chemical Co., Ltd., purity 99.5%, particle size 20 μm.

[0056] Calcination device: muffle furnace.

[0057] Example 1

[0058] A lithium cobalt oxide is prepared by the following method:

[0059] 1) Pretreatment of lithium-containing compounds: 74 g of lithium carbonate raw material was fed to a roasting device and transported to a roasting system, the temperature in the roasting system was controlled to be 800° C., and the roasting was performed for 12 hours to completely molten lithium carbonate; molten lithium carbonate was obtained;

[0060] 2) Pretreatment of cobalt-containing compounds: 241 g of cobalt tetroxide raw material was fed to a calcination device and transported to a calcination system. The temperature in the calcination system was controlled to be 800° C. and calcined for 12 h. The cobalt tetroxide was still in a solid state, and hot cobalt tetroxide was obtained.

[0061] 3) The hot cobalt tetroxide is uniformly added to the molten lithium carbonate, and the hot cobalt tetroxide is continuously dispersed into the molten lithium carbonate. The system temperature is maintained at 800° C. The cobalt tetroxide and the lithium carbonate react for 12 hours, and then condensed and crystallized to obtain lithium cobaltate.

[0062] Example 2

[0063] A lithium cobalt oxide is prepared by the following method:

[0064] 1) Pretreatment of lithium-containing compounds: 74 g of lithium carbonate raw material was fed to a roasting device and transported to a roasting system, the temperature in the roasting system was controlled to be 800° C., and the roasting was performed for 12 hours to completely molten lithium carbonate; molten lithium carbonate was obtained;

[0065] 2) Pretreatment of cobalt-containing compounds: 241 g of cobalt oxide raw material was fed to a calcination device and transported to a calcination system. The temperature in the calcination system was controlled to be 900° C. and calcined for 6 hours to obtain semi-molten cobalt oxide. The weight content of solid cobalt oxide in the semi-molten cobalt oxide was detected to be 76.3 g.

[0066] 3) The semi-molten cobalt tetroxide is uniformly added to the molten lithium carbonate, and the semi-molten cobalt tetroxide is continuously dispersed into the molten lithium carbonate. The system temperature is maintained at 900° C. The cobalt tetroxide and the lithium carbonate react for 12 hours, and then condensed and crystallized to obtain lithium cobaltate.

[0067] Example 3

[0068] A lithium cobalt oxide is prepared by the following method:

[0069] 1) Pretreatment of lithium-containing compounds: 74 g of lithium carbonate raw material was fed to a roasting device and transported to a roasting system, the temperature in the roasting system was controlled to be 800° C., and the roasting was performed for 12 hours to completely molten lithium carbonate; molten lithium carbonate was obtained;

[0070] 2) Pretreatment of cobalt-containing compounds: 241 g of cobalt tetroxide raw material was fed to a calcination device and transported to a calcination system. The temperature in the calcination system was controlled to be 1200° C. and calcined for 12 hours to completely molten the cobalt tetroxide to obtain molten cobalt tetroxide;

[0071] 3) The molten cobalt tetroxide is uniformly added to the molten lithium carbonate, and the molten cobalt tetroxide is continuously dispersed into the molten lithium carbonate. The system temperature is maintained at 1200° C. The cobalt tetroxide and the lithium carbonate react for 12 hours, and then condensed and crystallized to obtain lithium cobaltate.

[0072] Example 4

[0073] A lithium cobalt oxide is prepared by the following method:

[0074] 1) Pretreatment of lithium-containing compounds: 24 g of lithium hydroxide raw material is fed to a roasting device and transported to a roasting system, the temperature in the roasting system is controlled to be 500° C., and roasted for 12 hours to completely molten lithium hydroxide to obtain molten lithium hydroxide;

[0075] 2) Pretreatment of cobalt-containing compounds: 93 g of cobalt hydroxide raw material was fed to a roasting device and transported to a roasting system. The temperature in the roasting system was controlled to be 900° C. and roasted for 12 h. The cobalt hydroxide was still in a solid state, and hot cobalt hydroxide was obtained.

[0076] 3) adding hot cobalt hydroxide uniformly into molten lithium hydroxide, the hot cobalt hydroxide is continuously dispersed into the molten lithium hydroxide, maintaining the system temperature at 900° C., reacting the cobalt hydroxide and lithium hydroxide for 12 hours, and then condensing and crystallizing to obtain lithium cobaltate.

[0077] Example 5

[0078] A lithium cobalt oxide is prepared by the following method:

[0079] 1) Pretreatment of lithium-containing compounds: 24 g of lithium hydroxide raw material is fed to a roasting device and transported to a roasting system, the temperature in the roasting system is controlled to be 500° C., and roasted for 12 hours to completely molten lithium hydroxide to obtain molten lithium hydroxide;

[0080] 2) Pretreatment of cobalt-containing compounds: 93 g of cobalt hydroxide raw material was fed to a roasting device and transported to a roasting system, the temperature in the roasting system was controlled to be 1150° C., and roasted for 6 hours to obtain semi-molten cobalt hydroxide; the weight content of solid cobalt hydroxide in the semi-molten cobalt hydroxide was detected to be 32.5 g;

[0081] 3) adding semi-molten cobalt hydroxide uniformly into molten lithium hydroxide, the semi-molten cobalt hydroxide is continuously dispersed into the molten lithium hydroxide, maintaining the system temperature at 1150° C., reacting the cobalt hydroxide and the lithium hydroxide for 12 hours, and then condensing and crystallizing to obtain lithium cobaltate.

[0082] Example 6

[0083] A lithium cobalt oxide is prepared by the following method:

[0084] 1) Pretreatment of lithium-containing compounds: 24 g of lithium hydroxide raw material is fed to a roasting device and transported to a roasting system, the temperature in the roasting system is controlled to be 500° C., and roasted for 12 hours to completely molten lithium hydroxide to obtain molten lithium hydroxide;

[0085] 2) Pretreatment of cobalt-containing compounds: 93 g of cobalt hydroxide raw material was fed to a roasting device and transported to a roasting system, the temperature in the roasting system was controlled to be 1400° C., and roasted for 12 hours to completely molten the cobalt hydroxide; molten cobalt hydroxide was obtained;

[0086] 3) adding molten cobalt hydroxide uniformly into molten lithium hydroxide, the molten cobalt hydroxide is continuously dispersed into the molten lithium hydroxide, maintaining the system temperature at 1400° C., reacting the cobalt hydroxide and the lithium hydroxide for 12 hours, and then condensing and crystallizing to obtain lithium cobaltate.

[0087] Comparative Example

[0088] A lithium cobalt oxide is prepared by the following method:

[0089] 1) Pretreatment of lithium-containing compounds: 74 g of lithium carbonate raw material and 241 g of cobalt tetroxide raw material were fed to the roasting device and transported to the roasting system. The temperature in the roasting system was controlled to be 1200° C., roasted for 24 hours, and then condensed and crystallized to obtain lithium cobalt oxide.

[0090] The same method as in the above embodiment is used to control the reaction temperature in steps 1), 2) and 3), and the calcination time in step 2), and the following experiments are performed to obtain lithium cobalt oxide of different qualities. The experimental conditions are as follows:

[0091]

[0092]

[0093] The solid content of the cobalt-containing compound after calcination in Examples 1-12 was detected respectively, and the product performance of the lithium cobalt oxide prepared in Examples 1-12 and the comparative example was detected respectively. The tap density of the lithium cobalt oxide was detected by the GB / T 5162-2021 method.

[0094] The lithium cobalt oxide obtained in Examples 1-12 and Comparative Examples was prepared into lithium cobalt oxide batteries according to the following method, and then the electrical performance was tested.

[0095] (1) crushing, grading and screening the obtained lithium cobalt oxide to obtain a lithium cobalt oxide positive electrode material;

[0096] (2) Lithium cobalt oxide positive electrode material, Ketjen black and polyvinylidene fluoride were dispersed in a nitrogen methyl pyrrolidone solution at a mass ratio of 100:2:2, stirred evenly to obtain an electrode slurry, coated the electrode slurry on the surface of aluminum foil, vacuum baked at 120°C for 12h, rolled and cut to obtain a positive electrode sheet; with a graphite electrode, 1 mol / L LiPF6 / (EC+DEC+DMC) electrolyte (volume ratio 1:1:1) and PP / PE / PP three-layer separator were used to make a soft pack battery. The charge and discharge test was carried out at 25°C and 4.2V / 1C.

[0097] The test results are as follows:

[0098]

[0099] It can be clearly seen from the embodiments of the present invention that the tap density of the lithium cobalt oxide product obtained by mixing the hot cobalt-containing compound with the molten lithium-containing compound and the discharge specific capacity of the prepared battery is better. In a more preferred scheme, the uniformity and tap density of the lithium cobalt oxide product obtained by mixing the semi-molten cobalt-containing compound with the molten lithium-containing compound are the best. At the same time, when the technical scheme of the present invention is adopted, when the molar ratio of the cobalt-containing compound raw material to the lithium-containing compound raw material is lower than 1:1, the uniformity and tap density of the lithium cobalt oxide can still be guaranteed, and the effect is even slightly improved, indicating that the technical scheme provided by the present invention can save the use of cobalt-containing compounds and achieve the purpose of cost saving. The battery prepared by the lithium cobalt oxide obtained by the technical scheme of the present invention has a stable discharge specific capacity after 500 cycles, relatively small attenuation, and a long battery life.

Claims

1. A method for preparing lithium cobalt oxide, characterized in that: The method comprises the following steps: 1) Pretreatment of lithium-containing compounds: heating the lithium-containing compound raw material to obtain a molten lithium-containing compound; 2) Pretreatment of the cobalt-containing compound: heating the cobalt-containing compound raw material to obtain a hot cobalt-containing compound; 3) Evenly mixing the molten lithium-containing compound and the hot cobalt-containing compound, condensing and crystallizing to obtain lithium cobalt oxide.

2. The method for preparing lithium cobalt oxide according to claim 1, characterized in that: In step 2), the raw material containing the cobalt compound is heated to a solid state, a semi-molten state or a molten state; preferably, the raw material containing the cobalt compound is heated to a semi-molten state; Preferably, in the semi-molten cobalt-containing compound, the mass proportion of the solid cobalt-containing compound is 10-90%, preferably 15-60%, and more preferably 20-40%.

3. The method for preparing lithium cobalt oxide according to claim 1 or 2, characterized in that: The lithium-containing compound raw material is lithium carbonate and / or lithium hydroxide, preferably lithium carbonate; and / or The purity of the lithium compound raw material is ≥99.0%, preferably ≥99.3%, more preferably ≥99.5%; and / or The particle size of the lithium compound-containing raw material is not greater than 500 μm, preferably 1-200 μm, and more preferably 2-100 μm.

4. The method for preparing lithium cobalt oxide according to any one of claims 1 to 3, characterized in that: The cobalt-containing compound raw material is cobalt tetroxide and / or cobalt hydroxide, preferably cobalt tetroxide; and / or The purity of the raw material containing the cobalt compound is ≥95.0%, preferably ≥97.0%, more preferably ≥99.0%; and / or The particle size of the raw material containing the cobalt compound is not more than 1000 μm, preferably 1-500 μm, more preferably 2-200 μm.

5. The method for preparing lithium cobalt oxide according to claim 3, characterized in that: The lithium-containing compound raw material is lithium carbonate, and the heating temperature in step 1) is higher than 720° C.; preferably 750-1500° C.; or The lithium-containing compound raw material is lithium hydroxide, and the heating temperature in step 1) is higher than 462°C; preferably 500-1200°C.

6. The method for preparing lithium cobalt oxide according to claim 4, characterized in that: The cobalt-containing compound raw material is cobalt tetroxide, and the heating temperature in step 2) is higher than 720° C., preferably 800-1500° C., and more preferably 895-950° C.; or The cobalt-containing compound raw material is cobalt hydroxide. The heating temperature in step 1) is higher than 720°C, preferably 900-1600°C, and more preferably 1100-1150°C.

7. The method for preparing lithium cobalt oxide according to any one of claims 1 to 6, characterized in that: In step 3), the mixing molar ratio of the lithium-containing compound to the cobalt-containing compound is 1:0.5-1.2, preferably 1:0.6-1.0, and more preferably 1:0.8-0.

9.

8. The method for preparing lithium cobalt oxide according to any one of claims 1 to 7, characterized in that: The method is as follows: 1) Pretreatment of lithium-containing compounds: the raw materials of the lithium-containing compounds are fed to a roasting device and transported to a roasting system, and the roasting system heats and roasts the raw materials of the lithium-containing compounds to completely form a molten state; and a molten lithium-containing compound is obtained; 2) Pretreatment of the cobalt-containing compound: the raw material of the cobalt-containing compound is fed to the roasting device and transported to the roasting system, and the roasting system heats the raw material of the cobalt-containing compound to heat the raw material of the cobalt-containing compound into a solid, semi-molten or molten state to obtain a hot cobalt-containing compound; 3) The hot cobalt-containing compound is uniformly added to the molten lithium-containing compound, the hot cobalt-containing compound is continuously dispersed into the molten lithium-containing compound, the cobalt-containing compound reacts with the lithium-containing compound, and then condenses and crystallizes to obtain lithium cobaltate.

9. The lithium cobalt oxide prepared according to the method for preparing lithium cobalt oxide according to any one of claims 1 to 9.

10. The lithium cobalt oxide according to claim 9, characterized in that: The tap density of the lithium cobalt oxide is ≥2.5g / cm 3 ; The cycle life of the battery prepared with lithium cobalt oxide as the positive electrode material is ≥500 times.

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