Preparation method of cathode material, cathode material, cathode sheet and lithium-ion battery

Abstract

The present invention relates to the technical field of batteries, and specifically relates to a preparation method of a cathode material, a cathode material, a cathode sheet, and a lithium-ion battery. The preparation method of the cathode material includes: preparing a bottom liquid, and subjecting the bottom liquid to protective gas treatment; performing a first feeding treatment on the bottom liquid to form a reaction liquid, stopping the first feeding treatment after 10 to 60 minutes, and performing heat treatment on the reaction liquid; then performing a second feeding treatment, adjusting the pH and reacting; stopping the second feeding treatment, continuing the first stirring for 5 to 45 minutes, then performing a second stirring treatment to obtain a precipitate, drying to obtain a precursor material; grinding a mixture of the precursor material and lithium carbonate, and then performing a first sintering treatment to obtain a first material; performing vibration treatment and air cooling on the first material, after air cooling to room temperature, then performing a second sintering treatment. The method of the present invention has high efficiency and low cost, and can obtain a cathode material with the characteristics of fast charging, large capacity, and long cycle life.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular, to a method for preparing a cathode material, a cathode material, a cathode sheet, and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries have been widely used as an energy storage device and play an important role in both electronic and digital products and the transportation field. At the present stage, single crystal, high voltage, and high nickelization have gradually become the trends in the cathode material industry. As an energy supply device, the fast charging, large capacity, and long cycle performance of lithium-ion batteries have also received increasing attention.

[0003] In the prior art, there are various measures to simply improve the fast charging performance, such as selecting ternary materials, changing to a new formula of electrolyte, coating and doping to improve the conductivity of the electrode material, obtaining a structure with good lithium ion insertion and extraction performance through special conditions, etc.; there are also many ways to only optimize the capacity or cycle performance, such as changing to a high nickel ternary or quaternary cathode material, coating and doping to improve the structural stability, adopting different charge and discharge strategies, and the battery usage environment, etc. However, it is relatively rare to obtain a material with fast charging, large capacity, and long cycle at the same time, and there will be problems of high production difficulty and high cost in achieving the above goals simultaneously.

[0004] In the preparation process of the cathode material in the prior art, the production efficiency of the precursor is low, and when the small particle precursor is sintered into the cathode material, over-sintering or uneven sintering is likely to occur, which in turn leads to poor electrochemical performance of the finally obtained cathode material and cannot have the characteristics of fast charging, large capacity, and long cycle.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] An object of the present invention is to provide a method for preparing a cathode material, which can improve the production efficiency of the precursor material, and the obtained cathode material has the characteristics of fast charging, large capacity, and long cycle.

[0007] Another object of the present invention is to provide a cathode material prepared by the method for preparing a cathode material described above.

[0008] Another object of the present invention is to provide a cathode sheet.

[0009] Another object of the present invention is to provide a lithium-ion battery.

[0010] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0011] A method for preparing a cathode material, comprising the following steps:

[0012] (a) Prepare a bottom solution, and subject the bottom solution to protective gas treatment; perform a first feeding treatment on the bottom solution to form a reaction solution. During the first feeding treatment, perform a first stirring treatment. After 10 - 60 minutes, stop the first feeding treatment, and perform a heat treatment on the reaction solution; perform a second feeding treatment on the heat-treated reaction solution, adjust the pH to 8 - 12.5 and carry out a reaction; stop the second feeding treatment, continue the first stirring treatment for 5 - 45 minutes, then reduce the stirring speed to perform a second stirring treatment to obtain a precipitate, and dry it to obtain a cathode precursor material;

[0013] The raw materials for the first feeding treatment and the second feeding treatment respectively include: a mixed solution of nickel, cobalt, and manganese, a precipitant, and a complexing agent;

[0014] (b) Grind a mixture of the cathode precursor material and lithium carbonate, and then perform a first sintering treatment to obtain a first material; perform a vibration treatment and air cooling on the first material. After air cooling to room temperature, perform a second sintering treatment.

[0015] In one embodiment, in the mixed solution of nickel, cobalt, and manganese, the molar ratio of nickel, cobalt, and manganese is (60 - 90):(0.01 - 40):(0.01 - 40); the total ion concentration of nickel, cobalt, and manganese is 1 - 2.5 mol / L.

[0016] In one embodiment, the precipitant includes sodium hydroxide and ammonia water; the molar ratio of the cations of sodium hydroxide and ammonia water is (5 - 20):1; in the precipitant, the concentration of OH - is 5 - 13 mol / L.

[0017] In one embodiment, the complexing agent includes liquid ammonia and water; in the complexing agent, the mass content of liquid ammonia is 5% - 40%.

[0018] In one embodiment, the bottom solution includes ammonium ions, and the concentration of ammonium ions is 0.05 - 0.8 mol / L; the pH of the bottom solution is 8 - 11.8.

[0019] In one embodiment, the temperature of the bottom solution is 35 - 55 °C.

[0020] In one embodiment, the flow rate of the protective gas is 0.05 - 150 L / min, and the time for protective gas treatment is 1 - 2 h.

[0021] In one embodiment, during the first feeding process of the bottom liquid, the flow rate of the mixed solution of nickel, cobalt and manganese is 0.05 - 800 L / h; the flow rate of the precipitant is 0.01 - 400 L / h; the flow rate of the complexing agent is 0.005 - 200 L / h.

[0022] In one embodiment, during the second feeding process of the heat-treated reaction solution, the flow rate of the mixed solution of nickel, cobalt and manganese is 0.05 - 800 L / h; the flow rate of the precipitant is 0.01 - 400 L / h; the flow rate of the complexing agent is 0.005 - 200 L / h.

[0023] In one embodiment, for the heat treatment, the temperature of the reaction solution is 35 - 75 °C.

[0024] In one embodiment, the stirring speed of the first stirring process is 200 - 300 rpm.

[0025] In one embodiment, the stirring speed of the second stirring process is 80 - 200 rpm.

[0026] In one embodiment, after stopping the second feeding process, continue the first stirring process for 5 - 45 min, then adjust the speed for the second stirring process, and the time is 0.2 - 1 times of the total reaction time, and then stop the second stirring process; the total reaction time is: from the start of the first feeding process of the bottom liquid to the stop of the second feeding process.

[0027] In one embodiment, the total reaction time for preparing the precursor material is 7 - 20 h.

[0028] In one embodiment, the temperature of the drying is 90 - 140 °C, and the time of the drying is 6 - 12 h.

[0029] In one embodiment, before the drying, it further includes: washing the precipitate.

[0030] In one embodiment, the molar ratio of the lithium carbonate to the precursor material is (1.01 - 1.2):1.

[0031] In one embodiment, the vibration frequency of the vibration treatment is 2 - 10 Hz.

[0032] In one embodiment, the first sintering treatment includes: heating from room temperature to a temperature of 250 - 550 °C at a heating rate of 1 - 2 °C / min, holding for 2 - 4 h, and then heating to 700 - 800 °C at a heating rate of 10 - 20 °C / min, and holding for 1 - 5 h.

[0033] In one embodiment, the second sintering treatment includes: heating from room temperature to a temperature of 250 - 550°C at a heating rate of 2 - 4°C / min, holding for 2 - 4 h, and then heating to 600 - 750°C at a heating rate of 5 - 10°C / min and holding for 2 - 10 h.

[0034] In one embodiment, during the first sintering treatment and the second sintering treatment, a gas system containing oxygen is introduced respectively; in the gas system containing oxygen, the concentration of oxygen is 21% - 99.99%; and the flow rate of the gas system containing oxygen is 5 - 20 L / min.

[0035] The positive electrode material prepared by the method for preparing a positive electrode material as described above.

[0036] The positive electrode sheet includes the positive electrode material prepared by the method for preparing a positive electrode material as described above.

[0037] The lithium - ion battery includes the positive electrode sheet as described above.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) The present invention jointly controls the precursor and the positive electrode material. During the synthesis of the precursor, the sphericity is not deliberately achieved. By adopting a mechanism of moderate gas protection and rapid reaction, a precursor material with a certain particle size, aspect ratio, and morphology structure is formed. During the subsequent synthesis of the positive electrode material, multi - stage sintering is used to repair the imperfect surface defects of the precursor and reduce cation mixing. The fragments of the precursor caused by short - time reaction and air - cooling shrinkage are vibrated and broken off, and then a quasi - single - crystal positive electrode material is obtained by further sintering and remelting.

[0040] (2) The positive electrode material of the present invention has the characteristics of fast charging, large capacity, and long cycle life, and the battery prepared therefrom has excellent electrochemical performance. Specific Embodiments

[0041] The following will describe the embodiments of the present invention in detail. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0042] According to one aspect of the present invention, the present invention relates to a method for preparing a positive electrode material, including the following steps:

[0043] (a) Prepare a bottom solution, and the bottom solution is treated with a protective gas; perform a first feeding treatment on the bottom solution to form a reaction solution. During the first feeding treatment, perform a first stirring treatment. After 10 - 60 minutes, stop the first feeding treatment, and perform a heat treatment on the reaction solution; perform a second feeding treatment on the heat-treated reaction solution, adjust the pH to 9.3 - 10.4 and carry out a reaction; stop the second feeding treatment, continue the first stirring treatment for 5 - 45 minutes, then reduce the stirring speed to perform a second stirring treatment to obtain a precipitate, and dry it to obtain a precursor material;

[0044] The raw materials for the first feeding treatment and the second feeding treatment respectively include: a mixed solution of nickel, cobalt and manganese, a precipitating agent and a complexing agent;

[0045] (b) Grind the mixture of the precursor material and lithium carbonate, and then perform a first sintering treatment to obtain a first material; perform a vibration treatment and air cooling on the first material. After air cooling to room temperature, perform a second sintering treatment.

[0046] The present invention combines the production of the quasi-single crystal precursor and the cathode into one for joint control. During the synthesis process of the precursor, the sphericity is not deliberately achieved. Through specific operation steps, by adopting a mechanism of moderate gas protection and rapid reaction, a precursor with appropriate particle size, aspect ratio and structure, and a relatively high specific surface area can be obtained, which can reduce the production cost of the precursor and improve production efficiency; during the later synthesis process of the cathode material, the imperfect surface defects of the precursor are repaired through multi-stage sintering and the cation mixing is reduced. The fragments caused by short-time reaction and air-cooling shrinkage of the precursor are vibrated and broken off. Multi-stage sintering combined with air-cooling low-temperature short-time sintering can reduce overburning of the material, and the vibration and breaking method can also reduce the introduction of metal foreign matters, and finally obtain a quasi-single crystal cathode material. The cathode material obtained by this method has a high initial charge specific capacity and excellent cycle performance.

[0047] In one embodiment, the mixed solution of nickel, cobalt and manganese is a mixed solution of soluble nickel salt, soluble cobalt salt and soluble manganese salt. The soluble nickel salt includes nickel sulfate. The soluble cobalt salt includes cobalt sulfate. The soluble manganese salt includes manganese sulfate.

[0048] In one embodiment, in the mixed solution of nickel, cobalt and manganese, the molar ratio of nickel, cobalt and manganese is (60 - 90):(0.01 - 40):(0.01 - 40), such as 60:10:30, 60:20:20, 80:10:10, 90:5:5, etc. In one embodiment, the total ion concentration of nickel, cobalt and manganese is 1.0 - 2.5 mol / L, such as 1.0 ml / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, etc.

[0049] In one embodiment, the precipitant includes sodium hydroxide and ammonia water; the molar ratio of the cations of the sodium hydroxide and ammonia water is (5-20):1, such as 5:1, 8:1, 10:1, 15:1, 20:1, etc. In the precipitant, the concentration of OH - is 5-10 mol / L, such as 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, etc.

[0050] In one embodiment, the complexing agent includes liquid ammonia and water; in the complexing agent, the mass content of liquid ammonia is 5%-40%, such as 5%, 10%, 15%, 20%, 25%, 30%, 40%, etc.

[0051] In one embodiment, the bottom solution includes ammonium ions, and the concentration of the ammonium ions is 0.05-0.8 mol / L, such as 0.05 mol / L, 0.15 mol / L, 0.2 mol / L, 0.4 mol / L or 0.8 mol / L, etc. The pH of the bottom solution is 8.0-11.8, such as 8.0, 8.3, 9.0, 9.7, 10, 11, 11.2, 11.5, 11.8, etc.

[0052] In one embodiment, the temperature of the bottom solution is 35-55 °C, such as 35 °C, 40 °C, 45 °C, 50 °C or 55 °C, etc.

[0053] In one embodiment, the bottom solution is treated with a protective gas during the preparation process. In one embodiment, the bottom solution is treated with a protective gas during the preparation process. The protective gas includes nitrogen and / or inert gas, such as argon. The flow rate of the protective gas is 0.05-150 L / min, and the treatment time of the protective gas is 1-2 h. Such as 0.05 L / min, 0.08 L / min, 0.1 L / min, 10 L / min, 100 L / min, etc.; the treatment time of the protective gas is, for example, 1 h, 1.5 h or 2 h. The bottom solution of the present invention is prepared in a reaction kettle container. During the preparation of the bottom solution, a protective gas is introduced into the bottom solution to ensure that the bottom solution is prepared 20-60 min before the protective gas stops being introduced. During the subsequent preparation processes such as the first feeding treatment, the protective gas is no longer introduced.

[0054] In one embodiment, during the first feeding treatment of the bottom solution, the flow rate of the mixed solution of nickel, cobalt and manganese is 0.05-800 L / h; the flow rate of the precipitant is 0.01-400 L / h; the flow rate of the complexing agent is 0.005-200 L / h.

[0055] In one embodiment, during the second feeding process of the heat-treated reaction solution, the flow rate of the mixed solution of nickel, cobalt and manganese is 0.05 - 800 L / h; the flow rate of the precipitant is 0.01 - 400 L / h; the flow rate of the complexing agent is 0.005 - 200 L / h.

[0056] In one embodiment, during the second feeding process of the heat-treated reaction solution, the flow rate of the mixed solution of nickel, cobalt and manganese, the flow rate of the precipitant, and the flow rate of the complexing agent are respectively the same as the flow rates of the corresponding raw materials in the first feeding process, or twice the flow rates of the corresponding raw materials in the first feeding process.

[0057] In one embodiment, for the heat treatment, the temperature of the reaction solution is 35 - 75 °C, such as 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C or 75 °C, etc. In the present invention, the reaction solution is heated to 35 - 75 °C and then feeding is continued to ensure the performance of the precursor.

[0058] In one embodiment, the stirring speed of the first stirring process is 200 - 300 rpm, such as 200 rpm, 230 rpm, 250 rpm, 280 rpm, 300 rpm, etc.

[0059] In one embodiment, the stirring speed of the second stirring process is 80 - 200 rpm, such as 80 rpm, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 150 rpm, 200 rpm, etc.;

[0060] In one embodiment, after stopping the second feeding process, the first stirring process is continued for 5 - 45 min, and then the rotation speed is adjusted to perform the second stirring process, and the duration is 0.2 - 1 times of the total reaction time (such as 0.2 times, 0.5 times, 0.7 times, 1 time, etc.), and the second stirring process is stopped; the total reaction time is: the total time from the start of the first feeding process of the bottom liquid to the stop of the second feeding process. In the present invention, after stopping the second feeding process, specific first stirring and second stirring processes are carried out, which are more conducive to the uniform dispersion of the materials, obtaining precipitates with expected microstructures, and thus ensuring the high specific surface area, appropriate particle size and aspect ratio of the precursor, laying a good foundation for the preparation of cathode materials with higher capacity in the later stage.

[0061] In one embodiment, the total reaction time for preparing the precursor material is 7 to 20 h, such as 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 14 h, 16 h, 18 h, or 20 h, etc. In the prior art, the production efficiency in the co-precipitation stage of precursor production is low. Generally, only when the reaction time reaches more than 30 hours can a precursor product with good sphericity be obtained. The specific precursor preparation process of this application can greatly shorten the preparation time, thereby improving the production efficiency in the co-precipitation stage and ensuring a high specific surface area of the precursor.

[0062] In one embodiment, the temperature of the drying is 90 to 140 °C, such as 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C, 140 °C, etc. The time of the drying is 6 to 12 h, such as 6 h, 8 h, 9 h, 10 h, 12 h, etc. In one embodiment, before the drying, the precipitate is washed, and the wet material is obtained after solid-liquid separation. In one embodiment, the present invention dries the precipitate in an oven.

[0063] In one embodiment, the molar ratio of the lithium carbonate to the precursor material is (1.01 to 1.2):1. For example, 1.01:1, 10.05:1, 1.1:1, 1.15:1, or 1.2:1, etc.

[0064] In one embodiment, the vibration frequency of the vibration treatment is 2 to 10 Hz, such as 2 Hz, 2.5 Hz, 3 Hz, 3.5 Hz, 4 Hz, 5 Hz, 8 Hz, 10 Hz, etc. The vibration time is the air-cooling time. The present invention ensures that the material is broken into an appropriate particle size through an appropriate vibration frequency, reduces the introduction of metal foreign matters, and ensures the electrochemical performance of the positive electrode material.

[0065] In one embodiment, the first sintering treatment includes: heating from room temperature to a temperature of 250 to 550 °C (such as 250 °C, 270 °C, 300 °C, 320 °C, 350 °C, 400 °C, 500 °C, etc.) at a heating rate of 1 to 2 °C / min (such as 1 °C / min, 1.2 °C / min, 1.5 °C / min, 1.8 °C / min, 2 °C / min), holding for 2 to 4 h (such as 2 h, 2.5 h, 3 h, 4 h, etc.), and then heating to 700 to 800 °C (such as 700 °C, 720 °C, 750 °C, 800 °C, etc.) at a heating rate of 10 to 20 °C / min (such as 10 °C / min, 12 °C / min, 15 °C / min, 17 °C / min, 20 °C / min), and holding for 1 to 5 h (such as 1 h, 2 h, 3 h, 4 h, 5 h, etc.). The present invention preliminarily improves the microstructure of the material through the above specific first sintering treatment.

[0066] In one embodiment, the second sintering treatment includes: heating from room temperature to a temperature of 250 - 550°C (such as 250°C, 300°C, 350°C, 400°C, or 500°C, etc.) at a heating rate of 2 - 4°C / min (such as 2°C / min, 2.5°C / min, 3°C / min, 4°C / min, etc.), holding for 2 - 4 h (such as 2 h, 3 h, or 4 h, etc.), and then heating to 600 - 750°C (such as 600°C, 650°C, 700°C, 750°C, etc.) at a heating rate of 5 - 10°C / min (such as 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min, etc.), and holding for 2 - 10 h (such as 2 h, 5 h, or 10 h, etc.).

[0067] After the vibration treatment and air cooling, the present invention further performs a specific second sintering treatment to further improve the microstructure of the cathode material and endow it with more excellent electrochemical performance.

[0068] In one embodiment, during the first sintering treatment and the second sintering treatment, a gas system containing oxygen is respectively introduced. In the gas system containing oxygen, the concentration of oxygen is 21% - 99.99%, such as 21%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 99.99%, etc.; the flow rate of the gas system containing oxygen is 5 - 20 L / min, such as 5 L / min, 8 L / min, 10 L / min, 12 L / min, 15 L / min, or 20 L / min, etc. In the first sintering treatment and the second sintering treatment of the present invention, introducing a gas system containing oxygen with appropriate concentration and flow rate is more conducive to the sintering effect and endows the cathode material with higher capacity, cycle performance, etc.

[0069] According to another aspect of the present invention, the present invention also relates to a cathode material prepared by the method for preparing a cathode material as described above.

[0070] According to another aspect of the present invention, the present invention also relates to a positive electrode sheet including the cathode material prepared by the method for preparing a cathode material as described above.

[0071] According to another aspect of the present invention, the present invention also relates to a lithium - ion battery including the positive electrode sheet as described above.

[0072] The lithium - ion battery of the present invention has excellent specific capacity, cycle performance, and rate performance.

[0073] The following further explains with specific examples and comparative examples.

[0074] Example 1

[0075] The method for preparing a cathode material includes the following steps:

[0076] (1) Preparation of raw material solution: nickel sulfate, cobalt sulfate and manganese sulfate were dissolved in a metal molar ratio of 60:20:20 to obtain a metal solution with a metal ion concentration of 2.5 mol / L; sodium hydroxide and ammonia water were dissolved in a cation molar ratio of 8:1 to obtain OH - The precipitant is 12.5 mol / L; liquid ammonia and pure water are prepared according to a mass fraction of 5% ammonia to obtain a complexing agent;

[0077] (2) Coprecipitation reaction: First, adjust the bottom liquid. In a 2L reactor container, make the bottom liquid volume 0.8L, the temperature 35℃, the pH at this temperature 11.80, and the ammonium radical 0.3mol / L. During this period, introduce high-purity nitrogen below the liquid level in the reactor at a flow rate of 0.5L / min for 1h, ensuring that the bottom liquid has been prepared 20min before the ventilation stops; then feed the material. After the ventilation is completed, start the stirring paddle immediately and adjust the speed to 300rpm. When the speed reaches 300rpm, The molten metal, precipitant and complexing agent are pumped into the reactor at the same time at rpm. The three solutions and the air inlet are dispersed and arranged on the reactor cover. The flow rates of the three liquids are 0.05L / h, 0.02L / h and 0.005L / h respectively. The flow rate is kept stable and the feed amount is accurate within 12 minutes. The feed amounts are 0.01L, 0.004L and 0.001L respectively. After the 12th minute of feeding, stirring is stopped and the reactor is prevented from entering the air. The temperature is gradually increased to 55°C. When the temperature reaches 55°C, continue to feed at 0.5 times the original flow rate, observe the pH, adjust the precipitant flow rate to make the pH reach 10.30-10.40, keep the reaction temperature, pH and speed constant, and keep the molten metal and complexing agent flow rates constant; finally, until the volume in the reactor reaches 1.55L, stop feeding immediately, stir at the original speed for 5 minutes, and then adjust the speed to 140rpm and continue stirring; the total reaction time is about 20h;

[0078] (3) Preparation of precursor powder: When the stirring time is 0.5 times of the total reaction time, the stirring is stopped, the lid is opened and the precipitate is taken out, the wet material obtained by washing with pure water and filtering is placed in an oven to dry, and then placed in an oven at 100°C for 12 hours to obtain a block solid. After final grinding, the particle size is 6.3 μm, the diameter is 0.83, and the specific surface area is 13.2 m 2 / g of precursor powder;

[0079] (4) Preparation of the positive electrode material powder: First, weigh the precursor powder, mix it with lithium carbonate to ensure that Li / M = 1.05, put it into a crucible after ball milling and mixing evenly; then put the crucible into a tube furnace for two-stage sintering. During the process, introduce oxygen with a concentration of 21% and a flow rate of 5 L / min. The first-stage sintering process is as follows: Start heating from room temperature at a rate of 1 °C / min, reach the preheating temperature of 550 °C and hold for 3 h, then heat up again at a rate of 10 °C / min, reach the sintering temperature of 800 °C and hold for 1 h; take it out and air-cool, and place it on a vibrating disk with a vibration frequency of 2 Hz. When it cools down to room temperature, continue sintering; start heating from room temperature at a rate of 3 °C / min, reach the preheating temperature of 250 °C and hold for 2 h, then heat up again at a rate of 5 °C / min, reach the sintering temperature of 750 °C and hold for 9 h; cool it down with the furnace. When it reaches room temperature, grind it to obtain the positive electrode material powder.

[0080] Preparation method of a lithium-ion half cell, comprising: mixing the positive electrode material LNCM622 obtained in this embodiment with a binder PVDF and a conductive agent (conductive carbon black) to make a slurry. The mass ratio of the three is 90:6:4. During the slurry-making process, the addition amount of NMP is 0.8 times the weight of the powder. Obtain a positive electrode wafer through coating, rolling, and slicing, and finally assemble it with a lithium wafer as the counter electrode to obtain a half cell.

[0081] Example 2

[0082] Preparation method of a positive electrode material, comprising the following steps:

[0083] (1) Preparation of the raw material solution: Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate according to the metal molar ratio of 80:10:10 to obtain a metal solution with a metal ion concentration of 1.0 mol / L; dissolve sodium hydroxide and ammonia water according to the cation molar ratio of 5:1 to obtain a precipitating agent with an OH - concentration of 5 mol / L; prepare a complexing agent by mixing liquid ammonia and pure water according to a mass fraction containing 25% ammonia;

[0084] (2) Co-precipitation reaction: First, adjust the bottom liquid in a reaction kettle with a volume of 2 m 3 to make the volume of the bottom liquid 0.6 m 3 , the temperature is 55 °C, the pH at this temperature is 10.80, and the ammonium ion is 0.21 mol / L. During this period, introduce high-purity argon gas below the liquid level in the reaction kettle at a flow rate of 0.05 m 3 / min and continue to introduce it for 2 h to ensure that the bottom liquid is adjusted 40 min before the gas introduction stops; Secondly, feed the materials. After the gas introduction ends, immediately start the stirring paddle and adjust the rotation speed to 300 rpm. When the rotation speed reaches 300 rpm, pump the metal solution, the precipitating agent, and the complexing agent into the reaction kettle at the same time. Among them, the three solutions and the gas inlet are arranged dispersedly on the reaction kettle cover, and the flow rates of the three feed solutions are 0.15 m 3 / h, 0.06 m 3 / h, 0.03m 3 / h, keep the flow rate stable and the feed amount accurate within 20 minutes, the feed amount is 0.05L, 0.02L, 0.01L respectively, stop stirring after 30 minutes of feeding and prevent the reactor from entering the air, gradually increase the temperature to 75℃; when the temperature reaches 75℃, feed each raw material at 0.5 times the original flow rate, observe the pH, adjust the precipitant flow rate to make the pH reach 9.30-9.40, keep the reaction temperature, pH and speed constant, and keep the metal liquid and complexing agent flow rate constant; finally, until the volume in the reactor reaches 1.5m 3 , immediately stop feeding, stir at the original speed for 15 minutes, then adjust the speed to 120 rpm and continue stirring. The total reaction time is about 7 hours;

[0085] (3) Preparation of precursor powder: When the stirring time is 0.7 times of the total reaction time, the stirring is stopped, the lid is opened and the precipitate is taken out, the wet material obtained by washing with pure water and filtering is placed in an oven to dry, and then placed in an oven at 90°C for 8 hours to obtain a block solid. After final grinding, a particle size of 9.5 μm, a diameter of 0.73, and a specific surface area of 17.4 m 2 / g of precursor powder;

[0086] (4) Preparation of positive electrode material powder: First, the precursor powder is weighed and mixed with lithium carbonate to ensure that Li / M=1.03. After ball milling, the mixture is placed in a crucible; then the crucible is placed in a tubular furnace for two-stage sintering. During the process, oxygen with a concentration of 95% is introduced at a flow rate of 5L / min. The first sintering process is as follows: starting from room temperature, heating at a rate of 2°C / min, reaching a preheating temperature of 250°C and keeping warm for 4h, heating again at a rate of 20°C / min, reaching a sintering temperature of 700°C and keeping warm for 5h; taking out and air cooling, and placing it on a vibration plate with a vibration frequency of 10Hz. When it cools to room temperature, continue sintering; starting from room temperature, heating at a rate of 4°C / min, reaching a preheating temperature of 450°C and keeping warm for 4h, heating again at a rate of 10°C / min, reaching a sintering temperature of 650 and keeping warm for 10h; cooling with the furnace, and when it reaches room temperature, grinding to obtain positive electrode material powder.

[0087] The preparation method of a lithium-ion half-cell includes: mixing the positive electrode material LNCM811 obtained in this embodiment with a binder PVDF and a conductive agent (conductive carbon black) to prepare a slurry, with the mass ratio of the three being 80:10:10. During the slurrying process, the amount of NMP added is 1.5 times the weight of the powder. The positive electrode disc is obtained by coating, rolling, and slicing. Finally, the half-cell is assembled using a lithium sheet as a counter electrode.

[0088] Example 3

[0089] The method for preparing a positive electrode material comprises the following steps:

[0090] (1) Preparation of raw material solution: nickel sulfate, cobalt sulfate and manganese sulfate were dissolved in a metal molar ratio of 90:5:5 to obtain a metal solution with a metal ion concentration of 2.0 mol / L; sodium hydroxide and ammonia water were dissolved in a cation molar ratio of 20:1 to obtain OH - The precipitant is 8.0 mol / L; liquid ammonia and pure water are prepared according to a mass fraction of 40% ammonia to obtain a complexing agent;

[0091] (2) Coprecipitation reaction: First, adjust the base solution to 10m 3 In the reactor vessel, the bottom liquid volume is 3.5m 3 The temperature was 45°C, the pH was 11.60, the ammonium radical was 0.15 mol / L, and high-purity nitrogen was introduced below the liquid level in the reactor at a flow rate of 0.15 m 3 / min, continue to pass for 2h, and ensure that the bottom liquid has been prepared 60min before the ventilation stops. Then feed the materials, start the stirring paddle immediately after the ventilation is completed, adjust the speed to 230rpm, and when the speed reaches 230rpm, pump the metal liquid, precipitant and complexing agent into the reactor at the same time. The three solutions and the air inlet are dispersed on the reactor cover, and the flow rates of the three liquids are 0.2m 3 / h、0.1m 3 / h、0.01m 3 / h, keep the flow rate stable and the feed amount accurate within 60 minutes, the feed amount is 0.2L, 0.1L, 0.01L respectively, stop stirring after 60 minutes of feeding and prevent the reactor from entering the air, gradually increase the temperature to 65 ° C. When the temperature reaches 65 ° C, continue to feed at twice the original flow rate, observe the pH, adjust the precipitant flow rate to make the pH reach 9.80-9.90, keep the reaction temperature, pH and speed constant, and keep the metal liquid and complexing agent flow rate constant. Finally, until the volume in the reactor reaches 7.5m 3 Immediately stop feeding, stir at the original speed for 45 minutes, then adjust the speed to 100 rpm and continue stirring. The total reaction time is 7 hours;

[0092] (3) Preparation of precursor powder: When the stirring time is 1.0 times of the total reaction time, the stirring is stopped, the lid is opened and the precipitate is taken out, the wet material obtained by washing with pure water and filtering is placed in an oven to dry, and then placed in an oven at 140°C for 6 hours to obtain a block solid. After final grinding, a solid with a diameter of 6.5 μm, a diameter of 0.65, and a specific surface area of 32.8 m 2 / g of precursor powder;

[0093] (4) Preparation of the positive electrode material powder: First, weigh the precursor powder, mix it with lithium carbonate to ensure that Li / M = 1.01, put it in a crucible after ball milling and mixing evenly; then put the crucible into a tube furnace for two-stage sintering, and introduce oxygen with a concentration of 99.99% during the process, with a flow rate of 20 L / min. The first-stage sintering process is as follows: Start heating from room temperature at a rate of 1 °C / min, reach the preheating temperature of 450 °C and keep it for 2 h, then heat up again at a rate of 15 °C / min, reach the sintering temperature of 700 °C and keep it for 3 h; take it out and air-cool it, and place it on a vibrating disk with a vibration frequency of 8 Hz. When it cools down to room temperature, continue sintering; start heating from room temperature at a rate of 3 °C / min, reach the preheating temperature of 450 °C and keep it for 3 h, then heat up again at a rate of 8 °C / min, reach the sintering temperature of 620 °C and keep it for 8 h; cool it down with the furnace. When it reaches room temperature, grind it to obtain the positive electrode material powder. Take it out and air-cool it, and place it on a vibrating disk with a vibration frequency of 5 Hz. When it cools down to room temperature, continue sintering; start heating from room temperature at a rate of 2 °C / min, reach the preheating temperature of 250 °C and keep it for 2 h, then heat up again at a rate of 5 °C / min, reach the sintering temperature of 600 °C and keep it for 5 h; cool it down with the furnace. When it reaches room temperature, grind it to obtain the positive electrode material powder.

[0094] Preparation method of the lithium-ion half cell, including: mixing the positive electrode material LNCM900505 obtained in this embodiment with a binder PVDF and a conductive agent (conductive carbon black) to make a slurry, with the mass ratio of the three being 70:10:20. During the slurry-making process, the addition amount of NMP is 2.5 times the weight of the powder. Obtain a positive electrode wafer through coating, rolling, and slicing, and finally assemble a half cell with a lithium wafer as the counter electrode.

[0095] Comparative Example 1

[0096] Preparation method of the positive electrode material, except that step (4) is only: Preparation of the positive electrode material powder: First, weigh the precursor powder, mix it with lithium carbonate to ensure that Li / M = 1.01, put it in a crucible after ball milling and mixing evenly; then put the crucible into a tube furnace for two-stage sintering, and introduce oxygen with a concentration of 99.99% during the process, with a flow rate of 20 L / min. The first-stage sintering process is as follows: Start heating from room temperature at a rate of 2 °C / min, reach the preheating temperature of 550 °C and keep it for 2 h, then heat up again at a rate of 5 °C / min, reach the sintering temperature of 700 °C and keep it for 12 h; cool it down with the furnace. When it reaches room temperature, grind it to obtain the positive electrode material powder; other steps are the same as in Example 3.

[0097] Preparation method of the lithium-ion half cell, except that the positive electrode material uses the positive electrode material of this comparative example, and other conditions are the same as in Example 3.

[0098] Comparative Example 2

[0099] Preparation method of the positive electrode material, except that steps (2) and (3) are only: First, adjust the bottom liquid, at 10 m3 In the reactor vessel, the bottom liquid volume is 3.5m 3 The temperature was 45°C, the pH was 11.60, the ammonium radical was 0.15 mol / L, and high-purity nitrogen was introduced below the liquid level in the reactor at a flow rate of 0.15 m 3 / min, nitrogen is continuously introduced during the reaction. Then, the material is fed, and the stirring blade is immediately started after the ventilation is completed, and the speed is adjusted to 230rpm. When the speed reaches 230rpm, the metal liquid, precipitant, and complexing agent are pumped into the reactor at the same time. The three solutions and the air inlet are dispersed and arranged on the reactor cover. The flow rates of the three liquids are 0.4m 3 / h, 0.2m 3 / h, 0.02m 3 / h, stop stirring after 60 minutes of feeding and prevent the reactor from entering the air, and gradually increase the temperature to 65 ° C. When the temperature reaches 65 ° C, adjust the flow rate of the precipitant to make the pH reach 9.80-9.90, keep the reaction temperature, pH and speed constant, and keep the flow rate of the metal liquid and the complexing agent constant. Finally, until the volume in the reactor reaches 7.5m 3 , stop feeding immediately, stir at the original speed for 45 minutes, then adjust the speed to 100 rpm and continue stirring for 7 hours, stop stirring and open the lid to take out the precipitate, wash the wet material with pure water and filter it into the oven to dry, and let it stand in the oven at 140℃ for 6 hours to obtain a block solid, which is finally ground to obtain a particle size of 5.8μm, a diameter of 0.68, and a specific surface area of 12.8m 2 / g of precursor powder; other conditions are the same as Example 3.

[0100] The preparation method of the lithium ion half-cell is the same as that of Example 3 except that the positive electrode material adopts the positive electrode material of this comparative example.

[0101] Experimental example

[0102] The performance tests of the lithium ion half-cells in Examples 1 to 3 and Comparative Examples 1 to 2 were performed. The results are shown in Table 1. The tests were performed at room temperature and constant temperature, and the current for the first charge and discharge was 0.2C.

[0103] Table 1 Battery test performance results

[0104]

[0105] In the preparation process of the precursor of the present invention, specific operation steps are adopted, so that a precursor with a high specific surface area can be obtained, and the production efficiency can be improved; during the synthesis process of the precursor, the sphericity is not deliberately achieved. Later, specific multi-stage sintering is used to repair the imperfect surface defects of the precursor and reduce the cation mixing. The fragments of the precursor caused by short-time reaction and air-cooling shrinkage are vibrated and broken off, and a single-crystal-like cathode material is obtained by further secondary sintering treatment. It can be seen from Examples 1 to 3 that the first charge specific capacity of the battery prepared from the cathode material of the present invention is higher and the rate performance is better.

[0106] In Comparative Example 1, no vibration treatment, air cooling and subsequent calcination treatment are carried out, and the first charge capacity of the battery prepared from the obtained cathode material is low and the rate performance is poor. In Comparative Example 2, nitrogen is continuously introduced during the coprecipitation reaction, which will affect the crystal form of the cathode precursor and significantly reduce its specific surface area. The first charge capacity of the battery prepared from the finally obtained cathode material is low and the rate performance is poor.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a positive electrode material, characterized in that, It includes the following steps: (a) Prepare a bottom solution, and the bottom solution is treated with a protective gas; perform a first feeding treatment on the bottom solution to form a reaction solution. During the first feeding treatment, perform a first stirring treatment. After 10 - 60 minutes, stop the first feeding treatment and perform a heat treatment on the reaction solution; perform a second feeding treatment on the heat-treated reaction solution, adjust the pH to 8 - 12.5 and carry out a reaction; stop the second feeding treatment, continue the first stirring treatment for 5 - 45 minutes, then reduce the stirring speed to perform a second stirring treatment for 0.2 - 1 times the total reaction time, and stop the second stirring treatment; the total reaction time is: the total time from the start of the first feeding treatment on the bottom solution to the stop of the second feeding treatment; Obtain a precipitate, dry it to obtain a positive electrode precursor material; The raw materials for the first feeding treatment and the second feeding treatment respectively include: a mixed solution of nickel, cobalt, and manganese, a precipitating agent, and a complexing agent; The specific treatment of the bottom solution with a protective gas includes: during the preparation of the bottom solution, introduce a protective gas into the bottom solution to ensure that the bottom solution is prepared 20 - 60 minutes before the stop of the introduction of the protective gas, and no protective gas is introduced during the subsequent preparation process; During the first feeding treatment of the bottom solution, the flow rate of the mixed solution of nickel, cobalt, and manganese is 0.05 - 800 L / h; the flow rate of the precipitating agent is 0.01 - 400 L / h; the flow rate of the complexing agent is 0.005 - 200 L / h; During the second feeding treatment of the heat-treated reaction solution, the flow rate of the mixed solution of nickel, cobalt, and manganese is 0.05 - 800 L / h; the flow rate of the precipitating agent is 0.01 - 400 L / h; the flow rate of the complexing agent is 0.005 - 200 L / h; For the heat treatment, the temperature of the reaction solution is 35 - 75 °C; The stirring speed of the first stirring treatment is 200 - 300 rpm; The stirring speed of the second stirring treatment is 80 - 200 rpm; (b) Grind the mixture of the positive electrode precursor material and lithium carbonate, and then perform a first sintering treatment to obtain a first material; perform air cooling on the first material and perform a vibration treatment. After air cooling to room temperature, perform a second sintering treatment; The first sintering treatment includes: heating from room temperature to a temperature of 250 - 550 °C at a heating rate of 1 - 2 °C / min, holding for 2 - 4 h, and then heating to 700 - 800 °C at a heating rate of 10 - 20 °C / min, holding for 1 - 5 h; The second sintering treatment includes: heating from room temperature to a temperature of 250 - 550 °C at a heating rate of 2 - 4 °C / min, holding for 2 - 4 h, and then heating to 600 - 750 °C at a heating rate of 5 - 10 °C / min, holding for 2 - 10 h.

2. The method for preparing the positive electrode material according to claim 1, wherein It includes at least one of the following features (1) to (6): (1) In the mixed solution of nickel, cobalt and manganese, the molar ratio of nickel, cobalt and manganese is (60 - 90):(0.01 - 40):(0.01 - 40); the total ion concentration of nickel, cobalt and manganese is 1 - 2.5 mol / L; (2) The precipitating agent includes sodium hydroxide and ammonia water; the molar ratio of the cations of sodium hydroxide and ammonia water is (5 to 20):1; in the precipitating agent, the concentration of OH - is 5 to 13 mol / L; (3) The complexing agent includes liquid ammonia and water; in the complexing agent, the mass content of liquid ammonia is 5% - 40%; (4) The bottom solution includes ammonium ions, and the concentration of the ammonium ions is 0.05 - 0.8 mol / L; the pH of the bottom solution is 8 - 11.8; (5) The temperature of the bottom solution is 35 - 55 °C; (6) The flow rate of the protective gas is 0.05 - 150 L / min, and the treatment time of the protective gas is 1 - 2 h.

3. The preparation method of the cathode material according to claim 1, characterized in that, (5) Comprising at least one of the following features (1) to (3): (1) The total reaction time for preparing the precursor material is 7 - 20 h; (2) The drying temperature is 90 - 140 °C, and the drying time is 6 - 12 h; (3) Before the drying, it further includes: washing the precipitate.

4. The preparation method of the cathode material according to claim 1, characterized in that, (9) The molar ratio of the lithium carbonate to the precursor material is (1.01 - 1.2):

1.

5. The preparation method of the positive electrode material according to claim 1, characterized in that, (10) The vibration frequency of the vibration treatment is 2 - 10 Hz.

6. The preparation method of the cathode material according to claim 1, characterized in that, (11) During the first sintering treatment and the second sintering treatment, a gas system containing oxygen is respectively introduced; in the gas system containing oxygen, the concentration of the oxygen is 21% - 99.99%; the flow rate of the gas system containing oxygen is 5 - 20 L / min. (12) The positive electrode material prepared by the method for preparing a positive electrode material according to any one of claims 1 - 6.

8. The positive electrode sheet, characterized in that, (13) Comprising the positive electrode material prepared by the method for preparing a positive electrode material according to any one of claims 1 - 6.

9. A lithium-ion battery, characterized in that, (14) Comprising the positive electrode sheet according to any one of claim 8.

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