High-voltage lithium cobalt oxide precursor as well as preparation method and application thereof

Abstract

The invention provides a high-voltage lithium cobalt oxide precursor as well as a preparation method and application thereof. The preparation method comprises the following steps: adding a cobalt salt solution, an aluminum salt solution and a precipitator solution into a first reaction container in a parallel flow manner, and carrying out a first co-precipitation reaction with more than or equal to 2 layers of stirring layers; after the first coprecipitation reaction reaches the initial starting particle size, the reaction slurry is transferred into a second reaction container to be subjected to a second coprecipitation reaction with the single stirring layer number, and the feeding mode of the cobalt salt solution and the precipitant solution is double-end feeding; and after the second co-precipitation reaction reaches the first target particle size, transferring the reaction slurry into a third reaction container, and carrying out a third co-precipitation reaction in which the aluminum salt is fed in a spiral nozzle manner, so as to obtain the lithium cobalt oxide precursor. According to the preparation method disclosed by the invention, the synthesis process of the lithium cobalt oxide precursor is effectively stabilized, so that Al stably exists in the precursor, and the phenomena of cracking, precipitation, nuclear explosion and the like are avoided, so that the voltage window of the lithium cobalt oxide positive electrode material is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and relates to a high-voltage lithium cobaltate precursor, a preparation method thereof, and uses thereof. Background Art

[0002] With the rapid development of the 3C industry, the capacity requirements for lithium cobaltate batteries are getting higher and higher. Among them, in order to increase the capacity, a common method is to dope to stabilize the structure, thereby increasing the voltage window. Al is a common doping element for LCO modification in the industry. After a large number of scientific research tests, it is found that doping Al has the following advantages: 1. Al has no electrochemical activity under the electrochemical window of LCO, so it is a very stable doping element, which can effectively improve the thermal stability and cycling performance of the material; 2. Al 3+ (53.5 pm) has a similar radius to Co3+(54.5 pm), so it is very easy to be incorporated into the unit cell without affecting the structure; 3. As the third most abundant element in the earth's crust, its reserves are abundant and the price is cheap; 4. The strength of the Al-O bond is higher than that of the Co-O bond. During the charge and discharge process of LCO, the lattice size of the material becomes smaller, thereby increasing the working voltage of the battery.

[0003] However, as the precursor of lithium cobaltate: conventional single-morphology aluminum-doped cobalt tetroxide, when the Al doping reaches a certain value, excessive Al doping will cause problems such as local segregation of Al, particle cracking, and bursting of small particles, resulting in deterioration of the material performance and far from achieving the expected effect.

[0004] For example, CN113307308A discloses a doped large-particle cobalt carbonate and a preparation method thereof. The large-particle cobalt carbonate is doped with a metal element, the primary particle morphology is conical, and the primary particles form spherical secondary particles. The preparation method includes steps such as nucleation, concentration, in-seed-pot growth, and in-seed-pot growth in different pots. Although the doped large-particle cobalt carbonate provided in the above document has a high crystallinity, which is beneficial to the uniform distribution of the doping element aluminum, has a high tap density, and a narrow particle size distribution, which is beneficial to reducing the aluminum segregation phenomenon. However, this only applies to the method of low-concentration Al doping; and the in-different-pot process in this document is unstable in the in-different-pot process, and problems such as local precipitation of Al, particle cracking, and nucleation explosion are likely to occur.

[0005] For another example, CN108649219A discloses a method for preparing large-particle-size aluminum-doped cobalt tetroxide, which adopts a semi-continuous process with high working efficiency. However, the aluminum doping amount is relatively low, unable to meet the requirements of high voltage, and no good solution to high-aluminum doping is proposed. Although a high aluminum doping amount can be achieved by the thickening method, when preparing cobalt carbonate by the thickening method, the stability of the reaction system will be impacted before and after entering the thickener, resulting in local instability. Once the aluminum distribution is uneven, it will affect the subsequent aluminum distribution. This series of phenomena ultimately leads to uneven aluminum distribution within a single particle and uneven aluminum distribution between particles, thus affecting the electrochemical performance of the material.

[0006] Therefore, it is urgently needed to study the solutions to problems such as local precipitation of Al, particle cracking, and nucleation explosion during the preparation process of aluminum-doped lithium cobalt oxide precursor. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a high-voltage lithium cobalt oxide precursor, its preparation method and uses. During the preparation process of aluminum-doped lithium cobalt oxide in the present invention, the aluminum salt is fed separately, and at the same time, through a specific three-stage separate kettle process, the synthesis process of the lithium cobalt oxide precursor is effectively stabilized, enabling Al to stably exist in the precursor, preventing phenomena such as cracking, precipitation, and nucleation explosion, and thus effectively improving the voltage window of the lithium cobalt oxide cathode material.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted by the present invention:

[0009] In the first aspect, the present invention provides a method for preparing a high-voltage lithium cobalt oxide precursor, and the preparation method includes the following steps:

[0010] The first cobalt salt solution, the first aluminum salt solution, and the first precipitant solution are fed in parallel into a first reaction vessel for a first co-precipitation reaction. During the first co-precipitation reaction, the number of stirring layers ≥ 2 layers;

[0011] After the first co-precipitation reaction reaches the initial starting particle size, the reaction slurry is transferred to a second reaction vessel, and then the second cobalt salt solution, the second aluminum salt solution, and the second precipitant solution are fed in parallel into the second reaction vessel for a second co-precipitation reaction. The feeding methods of the second cobalt salt solution and the second precipitant solution are both double-head feeding. During the second co-precipitation reaction, the number of stirring layers is a single layer;

[0012] After the second coprecipitation reaction reaches the first target particle size, the reaction slurry is transferred to a third reaction vessel, and then a third cobalt salt solution, a third aluminum salt solution, and a third precipitant solution are fed into the third reaction vessel in parallel to carry out a third coprecipitation reaction. During the third coprecipitation reaction, the feeding mode of the third aluminum salt solution is spiral nozzle feeding to obtain the high-voltage lithium cobalt oxide precursor.

[0013] It should be noted that in the present invention, when the charging voltage of the lithium cobalt oxide cathode material is > 4.2V, it is a high voltage.

[0014] It should also be noted that the multi-layer stirring in the present invention refers to the way of stirring in layers up and down along the axial direction of the stirring shaft. The stirring methods of ≥ 2 layers and single-layer stirring in the present invention can both be realized by a reaction vessel with multiple groups or a single group of stirring paddle precursors provided by the prior art; multiple groups or a single group of stirring paddles are arranged along the axial direction of the stirring shaft.

[0015] In the preparation process of the high-voltage lithium cobalt oxide precursor of the present invention, the preparation processes in different stages must cooperate with each other. Through the separate addition of aluminum salts and the specific three-stage separate kettle process, the synthesis process is stabilized, so that aluminum can stably exist in cobalt carbonate during the doping process, and the phenomena of particle nucleation explosion and particle cracking during the synthesis process are prevented, effectively suppressing the aluminum segregation phenomenon that occurs during the subsequent washing and calcination of the lithium cobalt oxide precursor; moreover, the preparation process has a short cycle, strong operability, and is suitable for large-scale production.

[0016] During the first coprecipitation reaction, the multi-layer stirring plays an effective role in dispersing particles and improving the uniform distribution of crystal seeds; further cooperating with the single-layer stirring and double-head feeding methods during the second coprecipitation reaction, the problem of nucleation explosion caused by too high local concentration during the reaction is avoided, and the growth rate is effectively increased, shortening the reaction cycle. At the same time, the single-layer stirring method during the second coprecipitation reaction also makes the reaction process have a slight upper and lower stratification situation, so the tap density of particles can be effectively increased; further, during the third coprecipitation reaction, a specific spiral nozzle feeding of aluminum salt is carried out and added in the form of spray, effectively realizing the uniform distribution of aluminum and preventing the generation of aluminum segregation phenomenon.

[0017] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical purposes and beneficial effects of the present invention can be better achieved and realized.

[0018] Preferably, the concentrations of the first cobalt salt solution, the second cobalt salt solution, and the third cobalt salt solution are each independently 80 to 160 g / L, such as 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, or 160 g / L, etc., but are not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0019] Preferably, the concentrations of the first aluminum salt solution, the second aluminum salt solution, and the third aluminum salt solution are each independently 1 to 9 g / L, such as 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, or 9 g / L, etc., but are not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0020] Preferably, the concentrations of the first precipitant solution, the second precipitant solution, and the third precipitant solution are each independently 210 to 260 g / L, such as 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, or 260 g / L, etc., but are not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0021] It can be understood that "each independently" in the present invention means that they do not interfere with each other, and they can be the same or different, and can be adjusted according to actual needs.

[0022] For the present invention, it is preferred that the cobalt salt concentration, the aluminum salt concentration, and the concentration of the precipitant solution in the coprecipitation reaction in the three stages are kept consistent.

[0023] Preferably, during the first coprecipitation reaction, the number of stirring layers is 3 to 4 layers, such as 3 layers or 4 layers, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0024] Preferably, the pH value of the first coprecipitation reaction is 7 to 9, such as 7, 7.3, 7.5, 7.8, 8, 8.3, 8.5, 8.8, or 9, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0025] Preferably, the reaction temperature of the first coprecipitation reaction is 35 to 50 °C, such as 35 °C, 40 °C, 45 °C, or 50 °C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0026] Preferably, the stirring speed of the first coprecipitation reaction is 200 - 300 r / min, such as 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min, 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min or 300 r / min, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0027] Preferably, during the first coprecipitation reaction, the feed flow rate ratio of the first cobalt salt solution to the first precipitant solution is 1:(2 - 2.5), such as 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4 or 1:2.5, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0028] Preferably, during the first coprecipitation reaction, the mass ratio of Co to Al is 72:(1 - 2), such as 72:1, 72:1.1, 72:1.2, 72:1.3, 72:1.4, 72:1.5, 72:1.6, 72:1.7, 72:1.8, 72:1.9 or 72:2, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0029] The first coprecipitation reaction of the present invention is the nucleation process, that is, the crystal nucleus structure of the lithium cobaltate precursor is obtained.

[0030] Preferably, the median particle size D50 of the initial starting particle size is 1.5 - 5.5 μm, such as 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or 5.5 μm, etc.

[0031] During the first coprecipitation reaction, after reaching the initial starting particle size, it indicates that granulation is successful and the particles are completely dispersed, which can be used as growth sites for growth; and the starting particle size of 1.5 - 5.5 μm is more conducive to particle dispersion and subsequent growth.

[0032] Preferably, the volume of the first reaction vessel is smaller than that of the second reaction vessel, and the volume of the first reaction vessel is 20% - 50% of the volume of the second reaction vessel, such as 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48% or 50%, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0033] During the second co-precipitation reaction process, a second reaction vessel with a larger volume is selected for kettle separation treatment, which can reduce the rising rate of the solid content of the slurry in the reaction system during the second co-precipitation reaction, thereby further enhancing the particle growth rate, reducing the synthesis cycle, and lowering the preparation cost.

[0034] Preferably, the stirring speed of the second co-precipitation reaction is less than that of the first co-precipitation reaction.

[0035] Preferably, the stirring speed of the second co-precipitation reaction is 0.3 to 0.5 times that of the first co-precipitation reaction, such as 0.3 times, 0.4 times, or 0.5 times, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0036] In the second co-precipitation process of the present invention, reducing the stirring rate can more effectively avoid nucleation explosion, and further improve the growth rate, reduce the synthesis cycle, and lower the preparation cost.

[0037] Preferably, during the second co-precipitation reaction process, the feed flow rate of each raw material is 1.2 to 1.5 times that of the corresponding raw material during the first co-precipitation reaction process, such as 1.2 times, 1.3 times, 1.4 times, or 1.5 times, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0038] It can be understood that the corresponding raw materials in the present invention refer to the first cobalt salt solution corresponding to the second cobalt salt solution, the first aluminum salt solution corresponding to the second aluminum salt solution, and the first precipitant solution corresponding to the second precipitant solution, that is, the corresponding relationship of the same substance, and their addition flow rates are increased simultaneously and synchronously.

[0039] In addition, during the second co-precipitation reaction process, increasing the feed flow rate of the raw materials is more conducive to increasing the supersaturation of the system, enabling rapid agglomeration growth of the particles in the early stage and quickly repairing the sphericity.

[0040] Preferably, the pH value of the second co-precipitation reaction is 7 to 9, such as 7, 7.3, 7.5, 7.8, 8, 8.3, 8.5, 8.8, or 9, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0041] Preferably, the reaction temperature of the second co-precipitation reaction is 35 to 50 °C, such as 35 °C, 40 °C, 45 °C, or 50 °C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0042] Preferably, the reaction time of the second coprecipitation reaction is 60 to 80 h, such as 60 h, 63 h, 65 h, 68 h, 70 h, 73 h, 75 h, 78 h, or 80 h, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0043] In the present invention, compared with the conventional process of multiple batches in the same type of reaction vessel with a growth rate of 0.05 μm / h, the preparation period of the second coprecipitation reaction is significantly reduced.

[0044] Preferably, the first target particle size is 12 to 16 μm, such as 12 μm, 13 μm, 14 μm, 15 μm, or 16 μm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0045] In the present invention, by carrying out batching within the numerical range of the first target particle size of 12 to 16 μm, the growth rate can be better controlled, and the occurrence of uneven internal particle size and nucleation explosion can be prevented.

[0046] Preferably, a draft tube is included in the third reaction vessel.

[0047] The present invention selects a third reaction vessel with a guiding function, which enhances the movement effect of the axial flow field and can make the reaction more complete at a low rotation speed.

[0048] Preferably, the pH value of the third coprecipitation reaction is less than the pH value of the second coprecipitation reaction.

[0049] Preferably, the pH value of the third coprecipitation reaction is 5 to 7, such as 5, 5.3, 5.5, 5.8, 6, 6.3, 6.5, 6.8, or 7, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0050] Preferably, the reaction temperature of the third coprecipitation reaction is higher than the reaction temperature of the second coprecipitation reaction.

[0051] In the process of the third coprecipitation reaction of the present invention, compared with the process of the second coprecipitation reaction, increasing the temperature improves the crystallinity of the surface of the lithium cobaltate precursor, makes Al exist in a more stable form of AlOOH, and reducing the pH is to reduce the supersaturation of the system, prevent nucleation explosion during the heating process and cracking at a higher growth rate; thus, a dense cobalt carbonate protective layer with stable Al doping is constructed, which more effectively prevents the precipitation of Al during the washing and calcination processes.

[0052] Preferably, the reaction temperature of the third coprecipitation reaction is 50 to 70 °C, such as 50 °C, 53 °C, 55 °C, 58 °C, 60 °C, 63 °C, 65 °C, 68 °C or 70 °C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0053] Preferably, the particle size of the high-voltage lithium cobaltate precursor is 20 to 22 μm, such as 20 μm, 20.5 μm, 21 μm, 21.5 μm or 22 μm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0054] It should also be noted that:

[0055] In the preparation method of the present invention, the specific types of cobalt salts, aluminum salts and precipitants are all conventional technical solutions. In addition to the above-mentioned characteristic limitations, the adjustment of the remaining parameters is also a conventional technical solution.

[0056] Optionally, the cobalt salt includes at least one of cobalt sulfate, cobalt chloride or cobalt nitrate; the aluminum source includes at least one of aluminum sulfate, aluminum chloride or aluminum acid; the precipitant includes ammonium carbonate and / or ammonium bicarbonate.

[0057] Optionally, throughout the preparation process, the mass ratio of Co and Al is ensured to be 72:(1 - 2), achieving high doping of aluminum.

[0058] Optionally, the volume of the third reaction vessel can be the same as the volume of the second reaction vessel.

[0059] Optionally, after the third coprecipitation reaction, hot water washing (the hot water temperature can be 50 to 80 °C, such as 50 °C, 60 °C, 70 °C or 80 °C, etc.) and drying are carried out in sequence.

[0060] In the second aspect, the present invention provides a high-voltage lithium cobaltate precursor, which is prepared by the preparation method as described in the first aspect.

[0061] The high-voltage lithium cobaltate precursor provided by the present invention is an aluminum-doped cobalt carbonate material; and the aluminum-doped cobalt carbonate material includes a relatively loose inner core and a relatively dense outer shell. Aluminum is uniformly doped from the core to the surface of the outer shell; and the outer shell is a dense protective layer, avoiding further diffusion segregation of aluminum during subsequent washing and sintering processes.

[0062] In the third aspect, the present invention provides a cobalt tetroxide, which is sintered from the high-voltage lithium cobaltate precursor as described in the second aspect.

[0063] In the present invention, the specific method for obtaining cobalt tetroxide from aluminum-doped cobalt carbonate is a conventional technical solution, and any solution known to those skilled in the art within a reasonable range is applicable to the present invention.

[0064] Exemplarily, the present invention provides a method for obtaining cobalt tetroxide from the high-voltage lithium cobalt oxide precursor described in the second aspect. The method includes:

[0065] Performing a first sintering on the high-voltage lithium cobalt oxide precursor described in the second aspect under a first oxygen-containing atmosphere, then increasing the oxygen content in the oxygen-containing atmosphere, and performing a second sintering under a second oxygen-containing atmosphere to obtain the cobalt tetroxide, and the cobalt tetroxide is doped with Al element.

[0066] Preferably, in the first oxygen-containing atmosphere, the required amount (volume) of oxygen is 0% to 50% of the theoretical requirement (35 L / kg cobalt carbonate), such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%, etc., where the theoretical requirement means that 35 L of oxygen is required for every 1 kg of cobalt carbonate; in addition to oxygen, other non-reactive gases such as nitrogen or inert gases can also be included.

[0067] Preferably, the heating rate of the first sintering is 5 to 20 °C / min, such as 5 °C / min, 10 °C / min, 15 °C / min, or 20 °C / min, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0068] Preferably, the holding temperature of the first sintering is 450 to 600 °C, such as 450 °C, 500 °C, 550 °C, or 600 °C, etc., and the holding time is 30 to 120 min, such as 30, 50, 80, 100, or 120, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0069] Preferably, in the second oxygen-containing atmosphere, oxygen is 30% to 70% of the theoretical requirement (150 L / kg cobalt carbonate), such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%, etc., where the theoretical requirement means that 150 L of oxygen is required for every 1 kg of cobalt carbonate; in addition to oxygen, other non-reactive gases such as nitrogen or inert gases can also be included.

[0070] Preferably, the heating rate of the second sintering is 2 to 10 °C / min, such as 2 °C / min, 5 °C / min, 8 °C / min, or 10 °C / min, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0071] Preferably, the holding temperature of the second sintering is 650 to 850 °C, such as 650 °C, 700 °C, 750 °C, 800 °C or 850 °C, etc., and the holding time is 30 to 180 min, such as 30 min, 50 min, 80 min, 100 min, 120 min, 150 min or 180 min, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0072] Fourthly, the present invention provides a lithium cobalt oxide cathode material, which is obtained by calcining the cobalt tetroxide as described in the third aspect and a lithium source after mixing.

[0073] The present invention does not specifically limit the preparation method of lithium cobalt oxide. For example, it can be a method of lithium preparation and calcination. Exemplarily, the method of lithium preparation and calcination includes the following steps:

[0074] Mix cobalt tetroxide with a lithium salt and then calcine to obtain lithium cobalt oxide.

[0075] Fourthly, the present invention also provides a lithium ion battery, which includes the lithium cobalt oxide cathode material as described in the fourth aspect.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] In the preparation process of the high-voltage lithium cobalt oxide precursor of the present invention, the preparation processes in different stages must cooperate with each other. Through the separate addition of aluminum salts and the specific three-stage kettle separation process, the synthesis process is stabilized, so that aluminum can stably exist in cobalt carbonate during the doping process, and the phenomena of particle nucleation explosion and particle cracking during the synthesis process are prevented, effectively suppressing the aluminum segregation phenomenon that occurs when the lithium cobalt oxide precursor is washed and calcined subsequently; and the preparation process has a short cycle, strong operability, and is suitable for large-scale production. Description of the Drawings

[0078] Figure 1 SEM image of the cobalt tetroxide prepared in Example 1.

[0079] Figure 2 EDS image of the distribution of Al in the cobalt tetroxide prepared in Example 1.

[0080] Figure 3 SEM image of the cobalt tetroxide prepared in Comparative Example 7.

[0081] Figure 4 EDS image of the distribution of Al in the cobalt tetroxide prepared in Comparative Example 7. Detailed Embodiments

[0082] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0083] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0084] In the description of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality of" means more than two unless otherwise specifically defined.

[0085] In the following embodiments and comparative examples, the first reaction vessel is reactor 1, the second reaction vessel is reactor 2, and the third reaction vessel is reactor 3.

[0086] During the coprecipitation reaction, reactor 1 can achieve a stirring process of ≥2 layers; during the coprecipitation reaction, reactor 2 can achieve a single-layer stirring process; reactor 3 has a draft tube.

[0087] Example 1

[0088] This example provides a method for preparing a high-voltage lithium cobaltate precursor, namely aluminum-doped cobalt carbonate, and the preparation method is as follows:

[0089] (1) Reactors 1, 2, and 3 are selected as reaction vessels for different preparation stages respectively. The volume of reactor 1 is 30% of the volume of reactor 2, and the volumes of reactor 3 and reactor 2 are the same;

[0090] Reactor 1 has 3 layers of stirring, which can effectively disperse particles and improve the uniformity of crystal seeds. Reactor 2 has single-layer stirring, and reactor 3 is equipped with a draft tube;

[0091] Cobalt chloride solution A with a concentration of 160 g / L, aluminum chloride solution B with a concentration of 9 g / L, and ammonium carbonate solution C with a concentration of 260 g / L are respectively prepared;

[0092] (2) First coprecipitation reaction:

[0093] Add pure water and solution C into the reactor 1 as the reaction bottom liquid. After the reaction temperature reaches 50 °C and the pH reaches 9, feed solutions A, B, and C into the reactor 1 in parallel (all single-head feeds). During the feeding process, control the flow rate ratio of solution A / C to be 1:2, and control the mass ratio of Co / Al in solution A / B to be 72:1. Conduct the first coprecipitation reaction with a stirring speed of 300 r / min and 3 layers of stirring. After the liquid level in the reactor 1 reaches the initial starting particle size D50 of 1.5 μm, stop feeding;

[0094] (3) Second coprecipitation reaction:

[0095] Transfer the reaction materials after the first coprecipitation reaction to the reactor 2. Start the stirring of the reactor 2, and feed solutions A, B, and C into the reactor 2 in parallel. Both solution A and solution C in the reactor 2 are double-head feed pipes for the second coprecipitation reaction. After reacting for 60 h, reach the first target particle size of 16 μm;

[0096] Among them, the stirring speed of the second coprecipitation reaction is 0.5 times that of the first coprecipitation reaction, and the feeding ratio of solutions A, B, and C in the reactor 2 is 1.5 times the flow rate ratio of the reactor 1. Other parameters are the same as those of the first coprecipitation reaction;

[0097] (4) Third coprecipitation reaction:

[0098] When reaching the first target particle size D50 of 16 μm, transfer the reaction materials in the reactor 2 to the reactor 3, and feed solutions A, B, and C into the reactor 2 in parallel (both A and C are single-head feeds), and change the feeding of solution B to above the spiral nozzle for the third coprecipitation reaction. Finally, react until the particle size reaches the stopping reactor particle size of 22 μm and stop the reaction;

[0099] Among them, the reaction temperature of the third coprecipitation reaction is 70 °C; by adjusting the feeding amounts of solution A and solution C, the pH of the third coprecipitation reaction is decreased to 6, and other parameters are the same as those of the second coprecipitation reaction;

[0100] (5) When the particle size reaches the stopping reactor particle size, wash the reaction materials in the reactor 3 with hot water at 50 °C, and then dry them at 120 °C to obtain aluminum-doped cobalt carbonate. The aluminum-doped cobalt carbonate includes an aluminum-doped inner core and an aluminum-doped outer shell coated on the inner core, and the outer shell is a dense protective layer with a higher density than the inner core.

[0101] Example 2

[0102] This example provides a preparation method of a high-voltage lithium cobalt oxide precursor, namely aluminum-doped cobalt carbonate. The preparation method is as follows:

[0103] (1) Select reactor 1, reactor 2, and reactor 3 as the reaction vessels for different preparation stages. The volume of reactor 1 is 50% of the volume of reactor 2, and the volumes of reactor 3 and reactor 2 are the same;

[0104] Reactor 1 has 3 layers of stirring, which can effectively disperse particles and improve the uniformity of crystal seeds. Reactor 2 has a single layer of stirring, and reactor 3 is equipped with a draft tube;

[0105] Prepare cobalt chloride solution A with a concentration of 80 g / L, aluminum chloride solution B with a concentration of 1 g / L, and ammonium bicarbonate solution C with a concentration of 210 g / L respectively;

[0106] (2) First coprecipitation reaction:

[0107] Add pure water and solution C into reactor 1 as the reaction bottom liquid. After the reaction temperature reaches 35 °C and the pH reaches 8, add solutions A, B, and C into reactor 1 in a co-current feeding manner. During the feeding process, control the flow ratio of solution A / C to be 1:2.5, and control the mass ratio of Co / Al in solution A / B to be 72:2. Conduct the first coprecipitation reaction with a stirring speed of 200 r / min and 3 layers of stirring. After the liquid level of reactor 1 reaches the initial starting particle size D50 of 5.5 μm, stop feeding;

[0108] (3) Second coprecipitation reaction:

[0109] Transfer the reaction materials after the first coprecipitation reaction to reactor 2. Start the stirring of reactor 2, and add solutions A, B, and C into reactor 2 in a co-current feeding manner. The solution A and solution C in reactor 2 are both equipped with double-headed feeding pipes to conduct the second coprecipitation reaction. After reacting for 80 h, reach the first target particle size D50 of 12 μm;

[0110] Among them, the stirring speed of the second coprecipitation reaction is 0.3 times that of the first coprecipitation reaction. The feeding ratio of solutions A, B, and C in reactor 2 is 1.2 times the flow ratio of reactor 1, and other parameters are the same as those of the first coprecipitation reaction;

[0111] (4) Third coprecipitation reaction:

[0112] When the first target particle size of 12 μm is reached, transfer the reaction materials in reactor 2 to reactor 3, add solutions A, B, and C into reactor 2 in a co-current feeding manner, and change the feeding of solution B to above the spiral nozzle to conduct the third coprecipitation reaction. Finally, react until the particle size reaches the stopping reactor particle size of 20 μm and stop the reaction;

[0113] Among them, the reaction temperature of the third coprecipitation reaction is 50 °C; by adjusting the feeding amounts of solution A and solution C, the pH of the third coprecipitation reaction is reduced to 5, and other parameters are the same as those of the second coprecipitation reaction;

[0114] (5) When the particle size reaches the reactor stopping size, the reaction materials in the reactor 3 are washed with hot water at 50 °C and then dried at 120 °C to obtain aluminum-doped cobalt carbonate. The aluminum-doped cobalt carbonate includes an aluminum-doped inner core and an aluminum-doped outer shell coated on the inner core, and the outer shell is a dense protective layer with a higher density than the inner core.

[0115] Example 3

[0116] This example provides a preparation method of high-voltage lithium cobaltate precursor, namely aluminum-doped cobalt carbonate. The preparation method is as follows:

[0117] (1) Select reactor 1, reactor 2 and reactor 3 as reaction vessels for different preparation stages respectively. The volume of reactor 1 is 30% of the volume of reactor 2, and the volume of reactor 3 is the same as that of reactor 2;

[0118] Reactor 1 has 4 layers of stirring, which can effectively disperse particles and improve the uniformity of crystal seeds. The stirring of reactor 2 is single-layer, and reactor 3 is equipped with a draft tube;

[0119] Prepare cobalt chloride solution A with a concentration of 120 g / L, aluminum chloride solution B with a concentration of 5 g / L and ammonium carbonate solution C with a concentration of 230 g / L respectively;

[0120] (2) First coprecipitation reaction:

[0121] Add pure water and solution C into reactor 1 as the reaction bottom liquid. After the reaction temperature reaches 45 °C and the pH reaches 7.3, add solutions A, B and C into reactor 1 in a parallel flow. During the feeding process, control the flow ratio of solution A / C to be 1:2.3, and control the mass ratio of Co / Al in solution A / B to be 72:1.5. Carry out the first coprecipitation reaction with a stirring speed of 250 r / min and 4 layers of stirring. After the liquid level of reactor 1 reaches the initial starting particle size D50 of 3 μm, stop feeding;

[0122] (3) Second coprecipitation reaction:

[0123] Transfer the reaction materials after the first coprecipitation reaction to reactor 2, start the stirring of reactor 2, and add solutions A, B and C into reactor 2 in a parallel flow. The solution A and solution C in reactor 2 are both double-headed feeding pipes for the second coprecipitation reaction. After reacting for 70 h, reach the first target particle size D50 of 14 μm;

[0124] Among them, the stirring speed of the second coprecipitation reaction is 0.4 times that of the first coprecipitation reaction, and the feeding ratio of solutions A, B and C in reactor 2 is 1.3 times the flow ratio of reactor 1, and other parameters are the same as those of the first coprecipitation reaction;

[0125] (4) Third coprecipitation reaction:

[0126] When the first target particle size of 14 μm is reached, the reaction materials in the reaction kettle 2 are transferred to the reaction kettle 3. The solutions A, B, and C are fed into the reaction kettle 2 in a co-current manner, and the solution B is changed to be fed above the spiral nozzle to carry out the third co-precipitation reaction. Finally, the reaction is carried out until the particle size reaches the stopping kettle particle size of 21 μm, and the reaction is stopped;

[0127] Among them, the reaction temperature of the third co-precipitation reaction is 55 °C; by adjusting the feed rates of the solutions A and C, the pH of the third co-precipitation reaction is decreased to 5.5, and other parameters are kept the same as those of the second co-precipitation reaction;

[0128] (5) When the particle size reaches the stopping kettle particle size, the reaction materials in the reaction kettle 3 are washed with hot water at 50 °C, and then dried at 120 °C to obtain aluminum-doped cobalt carbonate. The aluminum-doped cobalt carbonate includes an aluminum-doped inner core and an aluminum-doped outer shell coated on the inner core, and the outer shell is a dense protective layer with a higher density than the inner core.

[0129] Example 4

[0130] The difference between this example and Example 1 is that the number of stirring layers of the reaction kettle 1 in this example is 2 layers.

[0131] The remaining preparation methods and parameters are kept the same as those of Example 1.

[0132] Example 5

[0133] The difference between this example and Example 1 is that the volume of the reaction kettle 1 in this example is the same as that of both the reaction kettle 2 and the reaction kettle 3.

[0134] The remaining preparation methods and parameters are kept the same as those of Example 1.

[0135] Example 6

[0136] The difference between this example and Example 1 is that the volume of the reaction kettle 1 in this example is 10% of the volume of the reaction kettle 2.

[0137] The remaining preparation methods and parameters are kept the same as those of Example 1.

[0138] Example 7

[0139] The difference between this example and Example 1 is that the volume of the reaction kettle 1 in this example is 60% of the volume of the reaction kettle 2.

[0140] The remaining preparation methods and parameters are kept the same as those of Example 1.

[0141] Example 8

[0142] The difference between this example and Example 1 is that in the second coprecipitation reaction process of step (3) of this example, the stirring speed of the second coprecipitation reaction is 0.8 times that of the first coprecipitation reaction.

[0143] The remaining preparation methods and parameters are the same as those in Example 1.

[0144] Example 9

[0145] The difference between this example and Example 1 is that the first target particle size in step (3) of this example is 18 μm.

[0146] The remaining preparation methods and parameters are the same as those in Example 1.

[0147] Example 10

[0148] The difference between this example and Example 1 is that the first target particle size in step (3) of this example is 10 μm.

[0149] The remaining preparation methods and parameters are the same as those in Example 1.

[0150] Example 11

[0151] The difference between this example and Example 1 is that in the third coprecipitation reaction process of step (4) of this example, the reaction temperature is 50 °C.

[0152] The remaining preparation methods and parameters are the same as those in Example 1.

[0153] Example 12

[0154] The difference between this example and Example 1 is that in the third coprecipitation reaction process of step (4) of this example, the pH value is 9.

[0155] The remaining preparation methods and parameters are the same as those in Example 1.

[0156] Example 13

[0157] The difference between this example and Example 1 is that in this example, there is no draft tube in reactor 3 of step (4).

[0158] The remaining preparation methods and parameters are the same as those in Example 1.

[0159] Comparative Example 1

[0160] The difference between this comparative example and Example 1 is that in this comparative example, the split-pot reaction from reactor 1 to reactor 2 is not carried out. The second coprecipitation reaction is directly carried out in reactor 1, and then directly split from reactor 1 to reactor 3 for the third coprecipitation reaction.

[0161] The remaining preparation methods and parameters are the same as those in Example 1.

[0162] Comparative Example 2

[0163] The difference between this comparative example and Example 1 is that in this comparative example, the sub-kettle reaction from reactor 2 to reactor 3 is not carried out, and the third coprecipitation reaction is directly carried out in reactor 2.

[0164] The remaining preparation methods and parameters are the same as those in Example 1.

[0165] Comparative Example 3

[0166] The difference between this comparative example and Example 1 is that the number of stirring layers in reactor 1 of this comparative example is a single layer.

[0167] The remaining preparation methods and parameters are the same as those in Example 1.

[0168] Comparative Example 4

[0169] The difference between this comparative example and Example 1 is that the number of stirring layers in reactor 2 of this comparative example is 3 layers.

[0170] The remaining preparation methods and parameters are the same as those in Example 1.

[0171] Comparative Example 5

[0172] The difference between this comparative example and Example 1 is that during the second coprecipitation reaction in step (3) of this comparative example, both solution A and solution C are fed in a single-head manner.

[0173] The remaining preparation methods and parameters are the same as those in Example 1.

[0174] Comparative Example 6

[0175] The difference between this comparative example and Example 1 is that during the third coprecipitation reaction in step (4) of this comparative example, solution B is adjusted to be fed in a single-head manner instead of a spiral nozzle feeding manner.

[0176] The remaining preparation methods and parameters are the same as those in Example 1.

[0177] Comparative Example 7

[0178] The difference between this comparative example and Example 1 is that only one type of reactor equipment is used throughout the process, that is, a reactor with a double-layer stirring paddle. When the median particle size D50 of the particles is 5μm, 9μm, 13μm, 15μm, and 18μm respectively, sub-kettle operations are all carried out. The specific sub-kettle operation is to pump away half of the slurry in the reactor, only leaving the remaining half for reaction, and at the same time, the feeding flow rates of each raw material are halved accordingly.

[0179] [Preparation and Performance Testing of Cobalt Ferrite]

[0180] Preparation:

[0181] The cobalt aluminum carbonate provided in Examples 1-13 and Comparative Examples 1-6 was separately put into a calcination furnace. In an atmosphere with an oxygen demand of 50% (35 L / kg cobalt carbonate), it was heated to 450 °C at a heating rate of 20 °C / min and held for 30 min. Then, the oxygen partial pressure in the calcination environment was increased (150 L / kg cobalt carbonate, with the increased oxygen demand being 50%), and it was heated to 850 °C at a heating rate of 5 °C / min and held for 180 min for calcination to obtain Al-doped cobalt tetroxide.

[0182] Figure 1 The SEM image of the cobalt tetroxide prepared in Example 1 is shown.

[0183] Figure 2 The EDS image showing the distribution of Al in the cobalt tetroxide prepared in Example 1 is shown.

[0184] Figure 3 The SEM image of the cobalt tetroxide prepared in Comparative Example 7 is shown.

[0185] Figure 4 The EDS image showing the distribution of Al in the cobalt tetroxide prepared in Comparative Example 7 is shown.

[0186] From Figure 1 - Figure 2 and Figure 3 - Figure 4 comparison, it can be seen that for the cobalt tetroxide obtained in Example 1 of the present invention, there is no Al segregation on the surface of the particles, the particle sphericity is good, and there is no cracking.

[0187] Performance test:

[0188] The prepared Al-doped cobalt tetroxide was respectively characterized for the distribution of Al, tested for the tapped density, and observed for whether there are phenomena of nucleation explosion and cracking of the particles.

[0189] Distribution of Al: Figure 2 The Al distribution in Figure 4 is uniform, and the Al distribution in

[0190] is segregated.

[0191] Tapped density: It was tested using a tapped density tester.

[0192] Particle morphology: SEM test was carried out to observe the particle situation. Among them, it is normal that the particles are spherical, the surface is smooth, and there is no cracking phenomenon.

[0193] Table 1

[0194]

[0195]

[0196] [Preparation and Performance Testing of Batteries]

[0197] Battery Preparation:

[0198] Weigh the cobalt tetroxide precursor materials and lithium carbonate provided in Examples 1-13 and Comparative Examples 1-7 respectively according to a molar ratio of lithium to cobalt of 1.025. After mixing them evenly, sinter them in a box furnace at 1100 °C for 9 h in an air atmosphere; the primary sintered product after sintering is crushed, iron-removed, and sieved to obtain lithium cobaltate materials;

[0199] Disperse 80 wt% of the positive electrode active material (using the lithium cobaltate prepared in Examples 1-13 and Comparative Examples 1-7 as the positive electrode active material respectively), 10 wt% of Super-P, and 10 wt% of polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone (NMP) solution to prepare an electrode slurry, coat it on an aluminum foil, and dry it to obtain the positive electrode;

[0200] The lithium sheet is used as the negative electrode;

[0201] The separator is a PP microporous membrane with a diameter of Φ19 (Celgard 2400);

[0202] The composition of the electrolyte is: 1 M LiPF6 and a mixture of EC, DMC, and EMC (EC:DMC:EMC volume ratio = 1:1:1).

[0203] Assemble the above positive electrode, separator, negative electrode, and electrolyte to obtain a button cell.

[0204] Perform performance tests on the lithium-ion batteries provided in Examples 1-13 and Comparative Examples 1-7. The test conditions are: 3.0 - 4.48 V, current density 1C = 180 mAh / g, test temperature is 25 ± 1 °C, and perform tests on the discharge capacity and cycle performance of the lithium-ion batteries. The test results are shown in Table 2.

[0205] Table 2

[0206]

[0207]

[0208] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a high-voltage lithium cobalt oxide precursor, characterized in that, The preparation method includes the following steps: A first cobalt salt solution, a first aluminum salt solution, and a first precipitant solution are fed in parallel into a first reaction vessel for a first coprecipitation reaction. During the first coprecipitation reaction, the number of stirring layers ≥ 2 layers; After the first coprecipitation reaction reaches the initial starting particle size, the reaction slurry is transferred to a second reaction vessel, and then a second cobalt salt solution, a second aluminum salt solution, and a second precipitant solution are fed in parallel into the second reaction vessel for a second coprecipitation reaction. The feeding methods of the second cobalt salt solution and the second precipitant solution are both double-head feeding. During the second coprecipitation reaction, the number of stirring layers is a single layer; After the second coprecipitation reaction reaches the first target particle size, the reaction slurry is transferred to a third reaction vessel, and then a third cobalt salt solution, a third aluminum salt solution, and a third precipitant solution are fed in parallel into the third reaction vessel for a third coprecipitation reaction. During the third coprecipitation reaction, the feeding method of the third aluminum salt solution is spiral nozzle feeding to obtain the high-voltage lithium cobaltate precursor.

2. The preparation method according to claim 1, wherein The concentrations of the first cobalt salt solution, the second cobalt salt solution, and the third cobalt salt solution are each independently 80 - 160 g / L; Preferably, the concentrations of the first aluminum salt solution, the second aluminum salt solution, and the third aluminum salt solution are each independently 1 - 9 g / L; Preferably, the concentrations of the first precipitant solution, the second precipitant solution, and the third precipitant solution are each independently 210 - 260 g / L.

3. The preparation method according to claim 1, characterized in that, During the first coprecipitation reaction, the number of stirring layers is 3 - 4 layers; Preferably, the pH value of the first coprecipitation reaction is 7 - 9, the reaction temperature of the first coprecipitation reaction is 35 - 50 °C, and the stirring speed of the first coprecipitation reaction is 200 - 300 r / min; Preferably, during the first coprecipitation reaction, the feeding flow rate ratio of the first cobalt salt solution to the first precipitant solution is 1:(2 - 2.5); Preferably, during the first coprecipitation reaction, the mass ratio of Co to Al is 72:(1 - 2); Preferably, the median particle size D50 of the initial starting particle size is 1.5 - 5.5 μm.

4. The preparation method according to claim 1, wherein The volume of the first reaction vessel is smaller than the volume of the second reaction vessel, and the volume of the first reaction vessel is 20% - 50% of the volume of the second reaction vessel; Preferably, the stirring speed of the second coprecipitation reaction is less than the stirring speed of the first coprecipitation reaction; Preferably, the stirring speed of the second coprecipitation reaction is 0.3 - 0.5 times the stirring speed of the first coprecipitation reaction; Preferably, during the second coprecipitation reaction, the feeding flow rate of each raw material is 1.2 - 1.5 times the feeding flow rate of the corresponding raw material during the first coprecipitation reaction; Preferably, the pH value of the second coprecipitation reaction is 7 - 9, and the reaction temperature of the second coprecipitation reaction is 35 - 50 °C; Preferably, the reaction time of the second coprecipitation reaction is 60 - 80 h; Preferably, the median particle size D50 of the first target particle size is 12 - 16 μm.

5. The preparation method according to claim 1, characterized in that, The third reaction vessel includes a draft tube; Preferably, the pH value of the third coprecipitation reaction is less than that of the second coprecipitation reaction; Preferably, the pH value of the third coprecipitation reaction is 5-7; Preferably, the reaction temperature of the third coprecipitation reaction is higher than that of the second coprecipitation reaction; Preferably, the reaction temperature of the third coprecipitation reaction is 50-70 °C.

6. The preparation method according to claim 1, characterized in that, The particle size of the high-voltage lithium cobaltate precursor is 20-22 μm.

7. A high-voltage lithium cobalt oxide precursor, characterized in that, The high-voltage lithium cobaltate precursor is prepared by the preparation method according to any one of claims 1-6.

8. A cobalt tetroxide, characterized in that, The cobalt tetroxide is sintered from the high-voltage lithium cobaltate precursor according to claim 7.

9. A lithium cobalt oxide cathode material, characterized in that, The lithium cobaltate cathode material is obtained by calcining the cobalt tetroxide according to claim 8 after mixing with a lithium source.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the lithium cobaltate cathode material according to claim 9.

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