Preparation Method and Application of Nano Lanthanum Oxide for Cathode Material of Lithium Ion Battery

Abstract

The present invention provides a preparation method and application of nano lanthanum oxide for a lithium ion battery cathode material, comprising the following steps: Step (1): Using a gas flow pulverization process to pulverize high-purity rare earth lanthanum oxide into semi-finished product A with a D50 of 1-5 microns; Step (2): Making a slurry from semi-finished product A and a solvent, finely grinding the obtained slurry using a ceramic sand mill, adding a dispersant for dispersion treatment during the grinding process, treating the ground slurry with an anti-caking agent, and freeze-drying the obtained final slurry using a low-temperature drying technique into semi-finished product B; Step (3): Obtaining nano lanthanum oxide powder through processes of breaking up, classifying, demagnetizing, and packaging the freeze-dried semi-finished product. The gas flow pulverization adopted by the present invention has a very strong crushing ability, and can pulverize raw materials with a D50 of 15 microns into fine powder with a D50 of about 1-3 microns. The fine powder can be made into a powder slurry with a particle size of about 100 nanometers through wet grinding treatment, and the dry nano powder can be obtained through post-treatment processes of the powder slurry.

Description

Technical Field

[0001] The present invention belongs to the fields of energy storage materials and electrochemistry, and relates to a preparation method and application of nano lanthanum oxide for a cathode material of a lithium ion battery. Background Art

[0002] Lithium ion batteries are the most important secondary power sources. With the popularization of electric vehicles and the construction of smart grids, the demand for lithium batteries by humans will increase rapidly. The cathode material of a lithium battery is the most important part of the battery, directly affecting the performance of the lithium ion battery. In the process of manufacturing lithium batteries, in order to pursue excellent material performance, people often need to perform doping modification on battery materials to improve the cycle service life of the battery materials. Among the conventional doping elements, people often choose to add elements such as aluminum, magnesium, titanium, zirconium, cobalt, and niobium as doping modification elements. Traditional titanium oxide and aluminum oxide nano powders are mostly directly produced by the metal electroexplosion method.

[0003] In previous research and production practices, it was found that lanthanum oxide has excellent doping and coating modification functions.

[0004] Lanthanum oxide is an inorganic compound with the chemical formula La2O3 and is a white powder. It is soluble in acids, ethanol, and ammonium chloride, and insoluble in water and ketones. Rare earth lanthanum oxide has a very wide range of applications, mainly used for manufacturing precision optical glass and optical fibers. It is also used in the electronics industry as a ceramic capacitor and a piezoelectric ceramic doping agent. It is also used as a raw material for preparing lanthanum boride and a catalyst for petroleum separation and refining. Summary of the Invention

[0005] Currently publicly available information shows that the main elements used for doping the cathode material of a lithium ion battery are aluminum, titanium, zirconium, cobalt, niobium, magnesium, etc. Research results show that these elements have excellent modification functions and can greatly improve the performance of the cathode material. In recent years, some scholars have found during the research of modification technologies that rare earth lanthanum elements have excellent modification functions and can greatly improve the cycle life of the cathode material. Previous production practices have also confirmed that rare earth lanthanum elements have excellent functions of modifying the cathode material. At the same time, it has also been noted that lanthanum oxide, which is the main source of the modifying element lanthanum, has a major impact on the modification effect in terms of purity and particle size.

[0006] Generally, the extraction process is used to produce lanthanum oxide. The raw material for the extraction method is the rare earth nitrate solution after cerium removal, which contains approximately 50% La2O3, trace CeO2, Pr6O 116% to 7%, Nd2O3 30%. The prepared rare earth nitrate solution uses the neutral phosphine extractant dimethylheptyl phosphonate (P350). Through 35 to 38 stages of extraction and separation with the P350-kerosene system, lanthanum is separated from other rare earths. The lanthanum-containing raffinate is neutralized with ammonia water, precipitated with oxalic acid, and then filtered and calcined to obtain the finished product of lanthanum oxide. The reaction formula is La2(C2O4)3 → La2O3 + 3CO2 + 3CO. The obtained lanthanum oxide powder has relatively coarse particles. In the production of lithium battery cathode materials, generally, micron powder or nano powder is required for doping and coating modification.

[0007] The present invention provides a preparation process for nano lanthanum oxide. In the present invention, a pulverization and grinding process is used to prepare nano lanthanum oxide powder materials. The present invention mainly adopts the following technical steps:

[0008] Step (1): Pulverize high-purity rare earth lanthanum oxide by means of air flow pulverization process into semi-finished product A with D50 of 1 - 5 microns;

[0009] Step (2): Make the semi-finished product A and a solvent into a slurry. Fine grind the obtained slurry with a ceramic sand mill, add a dispersant for dispersion treatment during the grinding process, and add an anti-caking agent to the ground slurry. Freeze-dry the obtained final slurry by means of low-temperature drying technology into semi-finished product B;

[0010] Step (3): Obtain nano lanthanum oxide powder through the processes of breaking up, classifying, demagnetizing, and packaging the freeze-dried semi-finished product.

[0011] The present invention adopts the above technical solution, and its advantages are that high-purity lanthanum oxide is used as the raw material, and nano lanthanum oxide powder is directly obtained by means of pulverization, grinding, and a unique post-treatment method.

[0012] Preferably, in the step (1), the high-purity rare earth lanthanum oxide uses rare earth lanthanum oxide with a purity greater than 99.99%.

[0013] Preferably, in the step (1), the air flow pulverization process uses an air flow pulverizer for pulverization treatment, with an air flow pressure of 0.5 - 0.6 MPa and a feeding frequency of 70 - 90 HZ.

[0014] Preferably, in the step (2), the solvent uses one or more of water, alcohol, methanol, and acetone to make a mixed slurry with a solid content of 40 - 60%.

[0015] Preferably, in the step (2), the fine grinding uses a ceramic sand mill, with a grinding speed of 1500 - 2500 revolutions per minute and a grinding time of 2 - 8 hours.

[0016] Preferably, during the grinding process, the viscosity of the slurry increases and the fluidity of the slurry becomes poor. An organic dispersant needs to be added. The dispersant is selected from carboxylic acid-based or ethylene oxide-based types. The carboxylic acid-based type is one or more of acrylic acid, n-butyric acid, isovaleric acid, and n-valeric acid. The ethylene oxide-based type is one or more of ethylene oxide (oxirane), propylene oxide (propylene oxide), 1,2-epoxybutane (butylene oxide), and 1,4-epoxybutane. The principle for selecting the dispersant is not to introduce metal ions, and the dosage of the dispersant is 1-5% of the dry powder mass.

[0017] Preferably, after grinding to the target particle size, an anti-caking agent is added to the slurry and stirred at a high speed for 20-60 minutes. The anti-caking agent is an ester-based organic compound, which is one or more of polyethylene glycol monomethyl ether methacrylate, dioctyl phthalate, and dioctyl sebacate. One end of the ester-based organic compound adsorbs on the surface of the pigment particles, and the other end is a group with the same charge or a low surface energy group, coating the organic functional groups on the particle surface and preventing agglomeration during the subsequent drying process. The combination of the anti-caking agent and freeze-drying can maintain the original particle size to the greatest extent and prevent the nano-powder from agglomerating into micro-powder.

[0018] Among them, the speed of the high-speed stirring is 1800-2500 revolutions per minute.

[0019] Preferably, in the step (2), the low-temperature drying technology uses freeze-drying, the low-temperature is -20°C to -45°C, the drying time is 20-40 hours, and the drying time is determined according to the moisture content. The drying ends when the moisture content is lower than 0.8%.

[0020] Preferably, in the step (3), the freeze-dried sample is dispersed by a mechanical dispersing device, particle size testing is carried out, air classification treatment is adopted, and magnetic separation is carried out by an iron remover before packaging.

[0021] The beneficial effects of the present invention: The present invention uses airflow crushing with strong crushing ability, which can crush raw materials with a D50 of 15 microns into fine powder with a D50 of about 1-3 microns. The fine powder can be made into a powder slurry with a particle size of about 100 nanometers through wet grinding treatment, and the powder slurry can obtain dry powder through post-treatment processes. This method is convenient, fast, and low-cost. Description of the Drawings

[0022] Figure 1 is the particle size test report of the original powder.

[0023] Figure 2 is the particle size test report of the airflow crushing semi-finished product A.

[0024] Figure 3 is the particle size test report of the nano-powder prepared by the present invention.

[0025] Figure 4 It is the XRD pattern of the nano powder prepared by the present invention. Embodiment

[0026] The following further describes in detail the preferred embodiments of the present invention with reference to the accompanying drawings: Example 1

[0027] 100 g of high-purity rare earth lanthanum oxide is fed into a jet mill for pulverization to obtain a semi-finished product A with a D50 of 1 - 5 μm, the air flow pressure is 0.5 MPa, and the feeding frequency is 70 HZ; the semi-finished product A and water are made into a mixed slurry with a solid content of 40%, and the obtained slurry is finely ground by a ceramic sand mill at a grinding speed of 1500 revolutions per minute for 8 hours. During the grinding process, the viscosity of the slurry increases and the fluidity of the slurry becomes poor. 1 g of an organic dispersant, acrylic acid, is added for dispersion treatment. After grinding, an anti-caking agent, polyethylene glycol monomethyl ether methacrylate, is added to the slurry, and it is stirred at a high speed for 20 minutes. The obtained final slurry is freeze-dried at -20 °C for 40 hours, and the drying ends when the water content is lower than 0.8% to obtain a semi-finished product B; the freeze-dried semi-finished product B is subjected to processes such as dispersion, particle size testing, classification, demagnetization, and packaging to obtain nano lanthanum oxide powder. Example 2

[0028] 100 g of high-purity rare earth lanthanum oxide is fed into a jet mill for pulverization to obtain a semi-finished product A with a D50 of 1 - 5 μm, the air flow pressure is 0.6 MPa, and the feeding frequency is 90 HZ; the semi-finished product A and alcohol are made into a mixed slurry with a solid content of 60%, and the obtained slurry is finely ground by a ceramic sand mill at a grinding speed of 2000 revolutions per minute for 2 hours. During the grinding process, the viscosity of the slurry increases and the fluidity of the slurry becomes poor. 5 g of an organic dispersant, n-butyric acid, is added for dispersion treatment. After grinding, an anti-caking agent, dioctyl phthalate, is added to the slurry, and it is stirred at a high speed for 60 minutes. The obtained final slurry is freeze-dried at -45 °C for 20 hours, and the drying ends when the water content is lower than 0.8% to obtain a semi-finished product B; the freeze-dried semi-finished product B is subjected to processes such as dispersion, particle size testing, classification, demagnetization, and packaging to obtain nano lanthanum oxide powder. Example 3

[0029] 100 g of high-purity rare earth lanthanum oxide was fed into a jet mill for comminution to produce semi-finished product A with a D50 of 1 - 5 μm. The air pressure was 0.52 MPa and the feeding frequency was 80 HZ. Semi-finished product A and methanol were made into a mixed slurry with a solid content of 50%. The obtained slurry was finely ground using a ceramic bead mill at a grinding speed of 2,500 revolutions per minute for 4 hours. During the grinding process, the viscosity of the slurry increased and the fluidity of the slurry became worse. 2 g of organic dispersant ethylene oxide was added for dispersion treatment. After grinding, dioctyl sebacate as an anti-caking agent was added to the slurry and stirred at high speed for 30 minutes. The obtained final slurry was freeze-dried at 25°C for 30 hours, and the drying was ended when the moisture content was lower than 0.8% to obtain semi-finished product B. The freeze-dried semi-finished product B was subjected to processes such as dispersion, particle size testing, classification, demagnetization, and packaging to obtain nano lanthanum oxide powder. Example 4

[0030] 100 g of high-purity rare earth lanthanum oxide was fed into a jet mill for comminution to produce semi-finished product A with a D50 of 1 - 5 μm. The air pressure was 0.55 MPa and the feeding frequency was 75 HZ. Semi-finished product A and acetone were made into a mixed slurry with a solid content of 55%. The obtained slurry was finely ground using a ceramic bead mill at a grinding speed of 2,500 revolutions per minute for 6 hours. During the grinding process, the viscosity of the slurry increased and the fluidity of the slurry became worse. 4 g of organic dispersant propylene oxide was added for dispersion treatment. After grinding, methoxypolyethylene glycol methacrylate as an anti-caking agent was added to the slurry and stirred at high speed for 40 minutes. The obtained final slurry was freeze-dried at - 30°C for 35 hours, and the drying was ended when the moisture content was lower than 0.8% to obtain semi-finished product B. The freeze-dried semi-finished product B was subjected to processes such as dispersion, particle size testing, classification, demagnetization, and packaging to obtain nano lanthanum oxide powder.

[0031] Figure 1 is the particle size test report of the original powder. Figure 2 is the particle size test report of semi-finished product A obtained after jet milling in Example 1. Compared with Figure 1 it can be seen that after the rare earth lanthanum oxide was jet milled, the particle size decreased significantly, the D50 was about 1 μm, and the maximum particle size was less than 5 μm. Figure 2 is the particle size test report of the nano rare earth lanthanum oxide powder prepared in Example 1. After the semi-finished product A was ground, the particle size reached about 150 nm, which is suitable for coating modification of the cathode material of lithium-ion batteries. Figure 3 is the XRD pattern of the nano powder prepared by the present invention. It can be seen from Figure 4 that the characteristic peaks of the nano powder prepared by the present invention are consistent with the characteristic peaks of the standard lanthanum oxide crystal, indicating that the method of the present invention successfully prepared nano-scale lanthanum oxide. Figure 4 ​

Claims

1. A preparation method of nano-lanthanum oxide for lithium-ion battery cathode materials, comprising: Step (1): Using a gas flow pulverization process to pulverize high-purity rare earth lanthanum oxide into semi-finished product A with a D50 of 1-5 microns; Step (2): Making the semi-finished product A and a solvent into a slurry, finely grinding the obtained slurry with a ceramic sand mill, adding a dispersant for dispersion treatment during the grinding process, treating the ground slurry with an anti-caking agent, and freeze-drying the obtained final slurry into semi-finished product B using a low-temperature drying technique; Step (3): Obtaining nano-lanthanum oxide powder through the processes of breaking up, classifying, demagnetizing, and packaging the freeze-dried semi-finished product; In the said Step (1), the gas flow pulverization process is carried out using a gas flow pulverizer, with a gas flow pressure of 0.5-0.6 MPa and a feeding frequency of 70-90 Hz; In the said Step (2), the dispersant is one or more of acrylic acid, n-butyric acid, isovaleric acid, n-valeric acid, ethylene oxide, propylene oxide, 1,2-epoxybutane, 1,4-epoxybutane; the anti-caking agent is an ester organic compound, and the ester organic compound is one or more of polyethylene glycol monomethyl ether methacrylate, dioctyl phthalate, dioctyl sebacate; the fine grinding is carried out using a ceramic sand mill, with a grinding speed of 1500-2500 revolutions per minute and a grinding time of 2-8 hours; In the said low-temperature drying, the low temperature is -20°C to -45°C and the drying time is 20-40 hours.

2. The preparation method according to claim 1, characterized in that, In the said Step (1), the high-purity rare earth lanthanum oxide uses rare earth lanthanum oxide with a purity greater than 99.99%.

3. The preparation method according to claim 1, characterized in that, In the said Step (2), the solvent is one or more of alcohol, methanol, and acetone, and a mixed slurry with a solid content of 40-60% is made.

4. The preparation method according to claim 1, characterized in that, In the said Step (3), the freeze-dried semi-finished product is broken up using a mechanical breaking-up device, particle size is tested, air flow classification treatment is carried out, and it is packaged after demagnetizing with a demagnetizer.

5. An application of the nano-lanthanum oxide obtained by the preparation method of nano-lanthanum oxide for lithium-ion battery cathode materials as claimed in claim 1 in lithium-ion battery cathode materials.

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