CN113247964A - Preparation method of high-rate, high-compaction and high-voltage lithium cobalt oxide positive electrode material - Google Patents

Preparation method of high-rate, high-compaction and high-voltage lithium cobalt oxide positive electrode material Download PDF

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CN113247964A
CN113247964A CN202110724467.0A CN202110724467A CN113247964A CN 113247964 A CN113247964 A CN 113247964A CN 202110724467 A CN202110724467 A CN 202110724467A CN 113247964 A CN113247964 A CN 113247964A
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廖达前
唐朝辉
朱健
曾文赛
胡柳泉
周友元
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Hunan Changyuan Lithium New Energy Co ltd
Hunan Changyuan Lico Co Ltd
Jinchi Energy Materials Co Ltd
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Hunan Changyuan Lico Co Ltd
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Abstract

The invention discloses a preparation method of a high-rate, high-compaction and high-voltage lithium cobaltate positive electrode material, wherein the particle size D50 of the positive electrode material is 6.0-11.0 mu m, and the compaction density is 3.7-3.95 g/cm3The preparation method comprises the following steps: (1) mixing a cobalt source, a lithium source and a compound of a doping element M, M' with ingredients to obtain a primary mixture; (2) sintering the primary mixture to obtain a primary sintering material of lithium cobaltate, and crushing and grading the primary sintering material to obtain a primary sintering graded material; (3) mixing the primary sintered graded material and the coating material at a high speed to obtain a secondary mixture; (4) and sintering the secondary mixture, crushing, grading, demagnetizing and sieving to obtain the high-rate, high-compaction and high-voltage lithium cobaltate cathode material. The process is simple and easy to control, low in production cost, green and environment-friendly, high in production efficiency and capable of preparingThe obtained product has the advantages of uniform components, narrow particle size distribution, high crystallinity, and excellent physicochemical and electrochemical properties.

Description

Preparation method of high-rate, high-compaction and high-voltage lithium cobalt oxide positive electrode material
Technical Field
The invention belongs to the field of lithium ion battery materials, and particularly relates to a preparation method of a high-rate, high-compaction and high-voltage lithium cobalt oxide positive electrode material.
Background
Since the commercialization of lithium ion batteries, they have been rapidly and widely used in the fields of communication and mobile and electric tools because of their advantages of high operating voltage, high energy density, long service life, wide operating temperature range, no memory effect and no pollution. At present, the energy density of a battery is improved by improving the charge and discharge voltage of a positive electrode material, most batteries of high-end electronic products are replaced by electric cores with the charge cut-off voltage of 4.4V and higher, the requirement of a user on the capacity of the battery is temporarily relieved, and under the condition that the electric quantity of the battery is exhausted, the problem that people are concerned about whether the battery can be charged fully quickly in a short time or not is solved if the battery needs to be charged fully once at least 3 hours.
The positive electrode material is the core affecting the performance of the lithium ion battery, and the positive electrode materials mainly used for the lithium ion battery at present comprise lithium cobaltate, ternary materials, lithium manganate, lithium iron phosphate and the like. Lithium cobaltate is the earliest commercialized lithium ion battery anode material and is widely applied to the battery fields of mobile phones, digital codes and the like. With the continuous expansion of the application range, the requirements of lithium ion batteries using lithium cobaltate as the anode material are continuously updated. In the fields of vehicle models, model airplanes, ship models, electronic cigarettes, electric automobiles and the like, which are emerging at present, lithium ion batteries using lithium cobaltate as a positive electrode material are also used as power sources. These goods require continuous high current charging and discharging to meet their use needs.
The inventor's patent application with publication number CN 109326781A about high voltage lithium cobalt oxide cathode material, the compacted density of the high voltage lithium cobalt oxide product can reach 4.1g/cm3～4.15g/cm3However, the particle size D50 is 17.0 to 19.0 μm, and the particle size belongs to the category of large particles in lithium cobaltate industry, and the rate capability of the particle with the particle size needs to be improved due to a longer lithium ion diffusion path, and for example 1C/0.2C in example 1 and example 2 in the patent application, the rate capability is 95.25 to 95.44%, and the rate capability can not meet the requirement of rate type products on large current charging and discharging.
Most rate lithium cobaltate materials in the current market are mainly in polycrystalline morphology, and the compaction density is 3.6g/cm3Hereinafter, it is a problem that increasing the compacted density of the rate type lithium cobaltate material to increase the volume energy density thereof is not easy.
From the above analysis, it is known that lithium cobaltate materials published in the prior patents and on the market are difficult to simultaneously achieve high rate, high compaction and high voltage performance. Lithium cobaltate is used as a positive electrode active material of a lithium ion battery with high multiplying power, high compaction and high voltage, and the particle size and the crystal morphology also have extremely important influence. As the particle diameter becomes larger, the discharge efficiency is reduced under the condition of high-rate discharge; when the particle size becomes small, the processability becomes poor under high-rate discharge, and the safety performance and cycle performance are also reduced. The crystal morphology can be mainly divided into polycrystal and monocrystal, and different morphologies have intricate and complex influences on the comprehensive performance of the lithium cobaltate with high multiplying power, high compaction and high voltage. The polycrystalline lithium cobaltate has good rate performance due to small primary particles, but is easy to cause the generation of materials and electrolyte under high voltage due to large specific surfaceElectrochemical side reactions occur, and the agglomerate particles break up, pulverize and detach during cycling so that the exposed fresh interior surfaces continue to react with the electrolyte resulting in the formation of other phases, causing deterioration of electrical properties. This can effectively solve the above-mentioned existing problems by preparing a lithium cobaltate positive electrode material having a high degree of single crystallization. The side reaction of the single crystal material and the electrolyte is reduced due to the smaller specific surface area, so that the improvement of the cycling performance is facilitated; while controlling the size range of the product particles, it is preferred that the D50 of the product be in the most reasonable range of 6.0 μm to 11.0 μm, so that the material may have a compacted density of up to 3.7g/cm3～3.95g/cm3Higher levels of (a); meanwhile, the rate performance of 20C/0.2C is higher than 97.0%, and the requirements of rate type products on large-current charging and discharging are completely met. Therefore, the lithium cobaltate with the single crystal morphology prepared by the invention has the comprehensive performance of high multiplying power, high compaction and high voltage.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides the preparation method of the lithium cobaltate cathode material with high multiplying power, high compaction and high voltage, which has the advantages of simple and easily-controlled process, low production cost, environmental protection, high production efficiency, uniform product components, narrow particle size distribution, high crystallinity, excellent physicochemical property and excellent electrochemical property.
In order to solve the technical problems, the technical scheme provided by the invention is a high-rate, high-compaction and high-voltage lithium cobaltate positive electrode material, wherein the D50 of the positive electrode material is 6.0-11.0 mu m, and the specific surface area of the positive electrode material is 0.15m2/g～0.45m2(ii)/g, compacted density of 3.7g/cm3～3.95g/cm3. In the test range of the full cell at 25 ℃ and 3.0V-4.45V, the 0.2C discharge capacity is higher than 193mAh/g, the capacity retention rate of 500-week circulation under the condition of 1C charge-discharge is higher than 96.5%, and the rate performance of 20C/0.2C is higher than 97.0% (20C/0.2C refers to the ratio of the discharge capacity under the conditions of 0.2C charge and 20C discharge to the discharge capacity under the condition of 0.2C charge-discharge).
As a general technical concept, the present invention also provides a preparation method of the lithium cobaltate positive electrode material with high multiplying power, high compaction and high voltage, which comprises the following steps:
(1) primary batching and mixing: mixing a cobalt source, a lithium source, a compound doped with an element M and a compound doped with an element M' after burdening to obtain a primary mixture;
(2) primary sintering and crushing: carrying out primary sintering on the primary mixture obtained in the step (1) in an air atmosphere to obtain a primary sintering material of lithium cobaltate, and then crushing and grading the primary sintering material to obtain a primary sintering graded material;
(3) secondary batching and mixing: burdening the primary-burning graded material obtained in the step (2) and the coating, and then mixing at a high speed to obtain a secondary mixture;
(4) and (3) secondary sintering: and (3) carrying out secondary sintering on the secondary mixture in an air atmosphere, then crushing and grading the secondary sintered material to obtain a secondary sintered graded material, and then carrying out demagnetization and sieving to obtain the high-rate, high-compaction and high-voltage lithium cobalt oxide anode material.
Preferably, in step (1), the mixing is performed using a coulter mixer.
The doping element M of the invention is selected from Al (Al)3+，0.54Å）、Ti（Ti4+，0.61Å）、Mg（Mg2+0.72 a), the amount of conventional doping element M being 0.01 to 5wt% of the weight of the secondary sintered product. Since aluminum is a group III metal element, the valence thereof is +3, trivalent aluminum ion (Al)3+The ionic radius of the cobalt-containing material is 0.54A3 +0.55 a) can improve the thermal stability of the positive electrode material and increase the charge and discharge window. Titanium is a transition metal element, the valence state of the titanium is mainly +4, titanium ions replace a small amount of cobalt ions, the semiconductor effect of the titanium can be exerted, the electronic conductivity of the material is enhanced, and the material has high-current discharge performance. Magnesium is an alkaline earth metal element, the valence state of magnesium is +2, and magnesium ion substitution not only can improve the conductivity of magnesium, but also has the effects of enhancing the thermal stability of the material and enlarging the charge and discharge window. The introduction of conventional doping elements of aluminum, titanium and magnesium ions can improve the structure of the layered anode material, reduce the difficulty of preparation and improveThe conductivity and the structural stability of the anode material improve the rate capability and the cycle life of the anode material.
Besides doping Al, Ti, Mg and other elements, the doping element M' is selected from Pr (Pr)3+0.99A) and Ce (Ce)3+1.02A). The invention selects the element M 'with large unconventional ionic radius, and the element M' is added in one-time sintering, on one hand, most of the element with large ionic radius is doped to replace Co3+Part of the lithium ion battery forms a large-aperture ion channel, so that the lithium ion conduction is promoted, and the charge rate performance and the discharge capacity of the lithium battery are remarkably improved; on the other hand, a small amount of an element having a large ionic radius does not enter the crystal lattice of lithium cobaltate, but forms a surface coating layer. In general, in the process of preparing lithium cobaltate, doping is finished in the primary sintering process, and coating is finished in the secondary sintering process, but elements with large ionic radius are selected and added in the primary sintering process, so that the doping effect and the surface coating effect are achieved, and the double protection effect on lithium cobaltate is achieved together with other coating substances added in the secondary sintering process. The doping amount of the doping element M' with the large ion radius is 0.005-3 wt% of the weight of the secondary sintering product.
The two types of doping substances are added in one batch, which is mainly determined according to the difference of doping amount and the difficulty of doping ions entering lithium cobaltate crystal lattices. The doping amount of the doping element M is large, the ionic radius and Co3+The radius of ions of (a) is close, and the ions enter the lithium cobaltate crystal lattice relatively easily. The doping element M' with large ionic radius is obviously larger than Co because of the ionic radius3+The ion radius of (a) is relatively difficult to enter the lithium cobaltate crystal lattice, so the doping amount is relatively small.
The distribution of the doping elements in the lithium cobaltate phase is influenced by the form of the dopant, the ionic radius of the doping elements and the mixing state, and is also influenced by the thermal diffusion of metal ions during the high-temperature reaction. The doped metal ions and the lithium ions are diffused and embedded into the cobalt oxide phase to form a competitive process, the lithium ions as light metal ions have higher diffusion rate, the metal ion doped lithium cobalt oxide phase is formed firstly in the reaction process, and then most of the remaining elements with large ionic radius are diffused into the lithium cobalt oxide phase. Once the lithium cobaltate phase is formed, the diffusion of the metal dopant ions is hindered and a small amount of elements with large ionic radii tend to be enriched on the surface of the particles.
In the above-mentioned production method, preferably, in the step (1), the compound of the doping element M and the compound of the doping element M' are selected from doping element-containing oxides or hydroxides.
In the preparation method, in the step (1), the molar ratio n (Li) to n (Co) of the lithium element in the lithium source and the cobalt element in the cobalt source is preferably 1.1-0.9: 1.
In the preparation method, preferably, in the step (2), the specific operation of the primary sintering process includes: under the air atmosphere, the ventilation quantity is 10-20 m3And h, heating the primary mixture from room temperature to 720-780 ℃, preserving heat for 2-5 hours, then heating to 920-1120 ℃, preserving heat for 6-10 hours, and naturally cooling along with the furnace. And coarsely crushing the blocky primary sintered material by a jaw crusher and a double-roll crusher, and crushing and grading the blocky primary sintered material by a fluidized bed type airflow crushing and grading integrated machine to obtain the powdery anode material after primary sintering.
In the above-mentioned preparation method, preferably, in the step (3), the coating material is Co (OH)2And Y2O3；Co(OH)20.5 to 4.5wt% of the primary sintered product, Y2O3Wherein Y is 0.05-0.4 wt% of the weight of the primary sintered product; wherein Y is2O3The primary particle size of (A) is 30 to 50 nm; the specific surface area is 20m2/g～40m2(ii) in terms of/g. After heat treatment, the coating Co (OH)2With surface Li+The reaction forms active lithium cobaltate with a portion of Co (OH)2After heat treatment, a uniform coating layer is formed on the surface of the particles, and at the same time, a coating object Y2O3With surface-rich Li in doped lithium cobaltate+Reacting to form a uniform coating layer LiYO2The coating layer has high chemical diffusion coefficient (1.8 × 10)-6 cm 2 s -1) And structural stability, which is favorable for the productRate capability and high voltage capability. Thus, the present invention employs Co (OH)2And Y2O3The coating is formed by heat treatment, on one hand, the surplus Li on the surface of the primary sintered product can be consumed+And an oxide coating layer is formed at the same time, so that the activity of the surface of the lithium cobaltate positive electrode material can be reduced, a coating layer with excellent performance can be formed, the performance of the material is improved, and the LiYO2The coating layer has a high chemical diffusion coefficient, so the rate capability is obviously improved, and the coating layer has obvious progress.
In the above preparation method, preferably, in the step (3), a high-speed mixer is used for secondary mixing.
In the preparation method, preferably, the specific operation of the secondary sintering process in the step (4) includes: in the air atmosphere, the ventilation amount is 2-9 m3And h, heating the secondary mixture from room temperature to 900-950 ℃, preserving heat for 6-10 hours, and then naturally cooling along with the furnace. And after coarse crushing of the blocky secondary sintering material by a jaw crusher and a double-roll crusher, crushing and grading by a fluidized bed type airflow crushing and grading integrated machine to obtain a high-rate, high-compaction and high-voltage lithium cobalt oxide cathode material product.
In the preparation method, preferably, in the step (2) and the step (4), crushing and classification are carried out by adopting a fluidized bed type airflow crushing and classifying all-in-one machine. The equipment is a whole set of crushing and grading system consisting of a jet mill, a cyclone separator, a dust remover and an induced draft fan, and the basic working principle of the equipment is that compressed gas is accelerated into supersonic airflow through a Laval nozzle and then enters a crushing chamber, and materials in the crushing chamber are accelerated into fluidization by the supersonic airflow, collide with each other and are crushed mutually, so that the ultrafine crushing of the materials is realized. The crushed material is conveyed to a grading area by ascending airflow, and fine powder meeting the requirement of granularity is sorted out by a grading wheel. Coarse powder which is not sorted can return to the collision crushing area to be continuously crushed until the coarse powder is crushed to the required fineness, and finally the coarse powder is sorted out by a grading wheel. The airflow carrying the finished powder enters a cyclone separator for separation, and most of the finished powder is discharged by a discharging device after being separated by the cyclone separator. And the rest of the over-fine powder and the gas enter the pulse dust cleaning and collecting device and are collected by the pulse dust cleaning and collecting device. The purified gas is discharged out of the machine through a draught fan.
In the preparation method, preferably, in the step (2), the parameters of the pulverization and classification by the fluidized bed type jet milling and classification all-in-one machine are as follows: the pressure of the grinding gas is 0.52-0.55 MPa, the frequency of a grading motor is 34-36 Hz, the frequency of a feeding motor is 12-13 Hz, and the pressure of a grinding body is-0.3-0.8 KPa. The grain size requirement of the primary-fired graded material is as follows: d0 is more than or equal to 0.5 mu m, and D50 is between 5.0 and 10.0 mu m.
In the preparation method, preferably, in the step (4), the parameters of the pulverization and classification by the fluidized bed type jet milling and classification all-in-one machine are as follows: the pressure of the grinding gas is 0.42-0.45 MPa, the frequency of a grading motor is 29-32 Hz, the frequency of a feeding motor is 9-11 Hz, and the pressure of a grinding body is-5.5-6.5 KPa. The granularity requirement of the secondary sintering graded material is as follows: d0 is more than or equal to 0.5 μm, and D50 is 6.0-11.0 μm.
As can be seen from the above, the parameters for pulverizing and classifying the primary sintering material are obviously different from those for pulverizing and classifying the secondary sintering material. This is mainly because the primary sintering temperature is higher than the secondary sintering temperature, so the primary sintered material is harder and needs higher grinding gas pressure to be crushed to a qualified particle size. In addition, the once-sintered material is harder and is in a sand shape after being coarsely crushed by a jaw crusher and a double-roll crusher, and a feeding cavity is not easy to block, so that the pressure of a grinding body is lower; the secondary sintering material is soft due to the lower secondary sintering temperature, and is flour-shaped after being coarsely crushed by a jaw crusher and a double-roller crusher, the feeding cavity is easy to block, and the pressure of a grinding body is larger.
As can be seen from the above, the control range of D50 of the primary sintered graded material is 5.0-10.0 μm, and the control range of D50 of the secondary sintered graded material is 6.0-11.0 μm, which is mainly because the particle size of the primary sintered graded material after the secondary sintering in the step (4) is increased by about 2.0 μm, so that the control range of D50 of the primary sintered graded material is smaller by 1.0 μm as a whole, and a room for the particle size to grow after the secondary sintering is reserved. And then the secondary crushing and grading are carried out, the particle size is controlled in the range of 6.0-11.0 mu m of the finished product D50, and the effect of dissociating soft agglomerates is also achieved. Thus, not only can a finished product with the granularity meeting the requirement be obtained, but also the difficulty of secondary crushing and grading can be reduced.
And (2) crushing and grading by adopting a fluidized bed type airflow crushing and grading integrated machine, wherein the excessively fine powder (fine powder with the particle size of less than 0.5 mu m) generated in the process is collected by a pulse dust removal dust collector and does not enter the secondary burdening and mixing process, so that the fine powder particles in the finished product can be controlled conveniently from the source. In addition, in the step (4), the grinding and classification are carried out by adopting a fluidized bed type airflow grinding and classification integrated machine, and the superfine powder (the fine powder with the particle size of less than 0.5 mu m) generated in the process is collected by a pulse dust removal dust collector again. Therefore, the fluidized bed type airflow crushing and grading integrated machine is adopted for crushing and grading in the step (2) and the step (4), double protection is adopted to strictly control the content of fine powder with the particle size of less than 0.5 mu m in the product while ensuring that the D50 of the lithium cobaltate anode material with high multiplying power, high compaction and high voltage meets the requirement of 6.0 mu m to 11.0 mu m, and the numerical value of D0 in the finally obtained product is more than 1.4 mu m and far more than 0.5 mu m in the result of the particle size test, so that the safety performance and the cycle performance of the anode material in the using process are improved.
The invention has strict regulations on the ventilation quantity, sintering temperature and sintering time range in the primary sintering and secondary sintering processes, and the combination of the sintering process conditions is mainly used for ensuring that the granularity and the appearance of the product can meet the requirements of the invention.
In the design of the lithium battery anode material, three performances of high multiplying power, high compaction and high voltage are realized simultaneously, and the difficulty is extremely high, because the preparation technology of the material realizes certain performances, and other performances are influenced. For example, in the industry, to improve the rate capability of a material, lithium cobaltate with a polycrystalline morphology with small primary particles is generally prepared; however, the material with the polycrystalline morphology is easy to cause electrochemical side reaction between the material and electrolyte under high voltage due to the large specific surface of the material, and aggregate particles are broken, pulverized and separated in the circulating process, so that the exposed fresh internal surface continuously reacts with the electrolyte to generateOther phases, which cause deterioration of electrical properties, tend to affect high voltage performance; meanwhile, aggregate particles with polycrystalline morphology are easy to crush when being used for manufacturing batteries, so that the compaction density is generally 3.6g/cm3The following is a requirement for high compaction. The material prepared by the invention is in a single crystal shape, and because the single crystal material mainly consists of single particles with larger particle size, and lithium cobaltate in a polycrystal shape consists of secondary spheres formed by piling a large number of primary small particles, the side reaction of the single crystal material and electrolyte is reduced due to smaller specific surface area, and the improvement of high-voltage performance is facilitated; in addition, the single crystal material has higher compaction density which can reach 3.7-3.95 g/cm compared with lithium cobaltate in a polycrystalline shape due to larger single particles, dense accumulation and less gaps among particles3The range of (1). However, when the grain size D50 of the single crystal material is too large (for example, D50 is 17.0-19.0 μm), the single particle is large, so that the material has low conductivity and ion mobility, and poor multiplying power and low first coulombic efficiency are caused. The granularity of the single crystal material is optimized, and D50 is in the range of 6.0-11.0 mu m, so that the compaction density of the material can be 3.7-3.95 g/cm3The higher level of the product and the multiplying power of the product can be obviously improved. By controlling a reasonable process, the rate capability of the obtained 20C/0.2C anode material is higher than 97.0%, and the requirement of rate type products on large-current charge and discharge is completely met.
According to the technical scheme, the dry-mixing co-doping technology combining conventional doping and unconventional doping, the special combined coating technology, the control technology combining single crystal morphology and reasonable particle size range and the control technology of superfine powder content are closely combined, so that the produced lithium cobaltate cathode material has the performances of high multiplying power, high compaction and high voltage.
The conventional doping elements can improve the rate capability and cycle life of lithium cobaltate; the unconventional doping elements can promote lithium ion conduction and improve rate performance on one hand, and can play a role in surface coating and improve high-voltage performance on the other hand. Specific combinatorial coating techniques include Co (OH)2The double effect of (2) can improve the high voltage performance and LiYO of the material2The cladding layer can simultaneously improve multiplying power and high voltage performance. The control technology combining the single crystal morphology and the reasonable particle size range means that the advantages of the single crystal material in the aspects of high voltage and compaction density are fully exerted, meanwhile, the particle size of the product is controlled within the range of 6.0-11.0 mu m through a control process, and the prepared material can give consideration to high multiplying power, high compaction and high voltage performance. The control technology of the content of the fine powder is mainly characterized in that a fluidized bed type airflow crushing and grading integrated machine is adopted in the step (2) and the step (4) for crushing and grading, the dual protection can strictly control the content of the fine powder in the product, and the high-voltage performance of the anode material in the using process is favorably improved. Therefore, the invention adopts a mode of buckling rings and propelling step by step, organically combines the technologies, and solves the problem that the three performances of high multiplying power, high compaction and high voltage are difficult to be considered simultaneously.
Compared with the prior art, the invention has the advantages that:
1. the lithium cobaltate cathode material prepared by the invention has the characteristics of uniform chemical components and phase components, easy control of granularity and morphology, excellent electrochemical performance, high multiplying power, high compaction and high voltage.
2. The technical scheme of the invention adopts a dry mixing and co-doping technology combining conventional doping and unconventional doping, a special combined coating technology, a control technology combining single crystal morphology and reasonable particle size range and a control technology of superfine powder content, wherein the four technologies are closely combined, and a ring-and-ring buckling and step-by-step propelling mode is adopted to realize the performance of high multiplying power, high compaction and high voltage of the produced lithium cobaltate cathode material.
3. The method has the advantages of simple synthetic flow, easy control of reaction, and capability of obviously improving the consistency of products, thereby ensuring the stable quality of products in different batches, having low requirement on equipment, being simple and convenient to operate, and having higher production efficiency.
In conclusion, the preparation method has the characteristics of simple and easily-controlled process, high efficiency and the like, and the product has uniform components, stable quality and excellent physicochemical and electrical properties.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is an SEM image of the lithium cobaltate positive electrode material prepared in example 1.
Fig. 2 is an SEM image of the lithium cobaltate positive electrode material prepared in example 2.
Fig. 3 is an SEM image of the lithium cobaltate positive electrode material prepared in comparative example 1.
Fig. 4 is an SEM image of the lithium cobaltate positive electrode material prepared in comparative example 3.
Fig. 5 is an SEM image of the lithium cobaltate positive electrode material prepared in comparative example 4.
Detailed Description
In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1:
the high-rate, high-compaction and high-voltage lithium cobaltate cathode material has the particle diameter D50 of 8.5 mu m and the specific surface area of 0.30m2(ii)/g, compacted density of 3.90g/cm3. The SEM image of the material of this example is shown in FIG. 1. As can be seen from figure 1, the material is in a single crystal morphology, and 3.90g/cm is realized when a full battery is manufactured3High compaction density of (2). Tests show that the material has a 0.2C discharge capacity of 194.8mAh/g, a capacity retention rate of 97.1% in 500-week circulation under 1C charge-discharge conditions and a rate capability of 97.5% in 20C/0.2C within the test range of 25 ℃ and 3.0V-4.45V.
The preparation method of the high-rate, high-compaction and high-voltage lithium cobalt oxide positive electrode material of the embodiment comprises the following steps of:
(1) mixing cobaltosic oxide, lithium carbonate and TiO2、Mg(OH)2And Ce2O3Proportioning, and then mixing by adopting a coulter type mixer to obtain a primary mixture; the molar ratio of the lithium element in the lithium carbonate to the cobalt element in the cobaltosic oxide is n (Li): n (Co) =1.05: 1, TiO2Wherein the mass of Ti is 0.1wt% of the weight of the secondary sintered product, Mg (OH)2The mass of Mg in the alloy is 0.15wt% of the weight of the secondary sintered product, and Ce2O3The mass of the Ce in the secondary sintering product is 0.05 wt%.
(2) Placing the primary mixture obtained in the step (1) in an air atmosphere for sintering, wherein the specific process of primary sintering comprises the following steps: the ventilation volume is 15m3And h, heating the mixed material from room temperature to 750 ℃, preserving heat for 3 hours, then heating to 970 ℃, preserving heat for 8 hours, and naturally cooling along with the furnace. And coarsely crushing the blocky primary sintered material by a jaw crusher and a double-roll crusher, and crushing and grading by a fluidized bed type airflow crushing and grading integrated machine to obtain a primary sintered graded material. Wherein the parameters of the primary sintering material crushing and grading are as follows: the pressure of grinding gas is 0.53 MPa, the frequency of a grading motor is 35 Hz, the frequency of a feeding motor is 13 Hz, and the pressure of a grinding body is-0.5 KPa. The grain size requirement of the primary-fired graded material is as follows: d0 was 1.4 μm, and D50 was 7.5. mu.m.
(3) Mixing the primary-fired grading material obtained in the step (2) and the coating according to a certain ratio, and then mixing by adopting a high-speed mixer to obtain a secondary mixture; the coating is Co (OH)2And Y2O3，Co(OH)23.5wt% of the weight of the primary sintered product, Y2O3Y in (1) is 0.1wt% of the weight of the primary sintered product; wherein Y is2O3Has a primary particle diameter of 40 nmSpecific surface area of 30m2/g。
(4) And (4) placing the secondary mixture obtained in the step (3) in air for sintering, wherein the specific operation of the secondary sintering process comprises the following steps: the ventilation volume is 6m3And h, heating the secondary mixture from room temperature to 930 ℃, preserving the heat for 8 hours, and then naturally cooling along with the furnace. And after coarse crushing of the blocky secondary sintering material by a jaw crusher and a double-roll crusher, crushing and grading by a fluidized bed type airflow crushing and grading integrated machine to obtain a high-rate, high-compaction and high-voltage lithium cobalt oxide cathode material product. Wherein the parameters of the secondary sintering material crushing and grading are as follows: the pressure of grinding gas is 0.44 MPa, the frequency of a grading motor is 30 Hz, the frequency of a feeding motor is 10Hz, and the pressure of a grinding body is-6.0 KPa. The granularity requirement of the secondary sintering graded material is as follows: d0 was 1.5 μm, and D50 was 8.5. mu.m.
Example 2:
the high-rate, high-compaction and high-voltage lithium cobaltate cathode material has the particle diameter D50 of 9.5 mu m and the specific surface area of 0.28m2(ii)/g, compacted density of 3.85g/cm3. The SEM image of the material of this example is shown in FIG. 2. As can be seen from FIG. 2, the material has a single crystal morphology and a compacted density of 3.85g/cm for full cell fabrication3. Tests show that the material has 0.2C discharge capacity of 193.5mAh/g, capacity retention rate of 500-week circulation under 1C charge-discharge conditions of 96.7 percent and rate performance of 20C/0.2C of 97.2 percent in the test ranges of 25 ℃ and 3.0V-4.45V.
The preparation method of the high-rate, high-compaction and high-voltage lithium cobalt oxide positive electrode material of the embodiment comprises the following steps of:
(1) mixing cobalt carbonate, lithium hydroxide and Al2O3MgO and Pr2O3Proportioning, and then mixing by adopting a coulter type mixer to obtain a primary mixture; the molar ratio of lithium element in lithium hydroxide to cobalt element in cobalt carbonate is n (Li) = n (Co) =1.07: 1, the adding amount of Al is 0.2wt% of the weight of the secondary sintering product, the adding amount of Mg is 0.25wt% of the weight of the secondary sintering product, and the adding amount of Pr is 0.1wt% of the weight of the secondary sintering product.
(2) The first time obtained in the step (1)The mixture is placed in an air atmosphere for sintering, and the specific process of primary sintering comprises the following steps: the ventilation volume is 18m3And h, heating the mixed material from room temperature to 770 ℃, preserving heat for 2 hours, then heating to 1000 ℃, preserving heat for 8 hours, and naturally cooling along with the furnace. And coarsely crushing the blocky primary sintered material by a jaw crusher and a double-roll crusher, and crushing and grading by a fluidized bed type airflow crushing and grading integrated machine to obtain a primary sintered graded material. Wherein the parameters of the primary sintering material crushing and grading are as follows: the pressure of grinding gas is 0.55 MPa, the frequency of a grading motor is 36 Hz, the frequency of a feeding motor is 13 Hz, and the pressure of a grinding body is-0.8 KPa. The grain size requirement of the primary-fired graded material is as follows: d0 was 1.4 μm, and D50 was 8.4. mu.m.
(3) Mixing the primary-fired grading material obtained in the step (2) and the coating according to a certain ratio, and then mixing by adopting a high-speed mixer to obtain a secondary mixture; the coating is Co (OH)2And Y2O3，Co(OH)24.5wt% of the weight of the primary sintered product, Y2O3Y in (3) is 0.2wt% of the weight of the primary sintered product; wherein Y is2O3Has a primary particle diameter of 45nm and a specific surface area of 35m2/g。
(4) And (4) placing the secondary mixture obtained in the step (3) in an air atmosphere for sintering, wherein the secondary sintering process comprises the following specific operations: the ventilation volume is 8m3And h, heating the secondary mixture from room temperature to 950 ℃, preserving the heat for 10 hours, and then naturally cooling along with the furnace. And after coarse crushing of the blocky secondary sintering material by a jaw crusher and a double-roll crusher, crushing and grading by a fluidized bed type airflow crushing and grading integrated machine to obtain a high-rate, high-compaction and high-voltage lithium cobalt oxide cathode material product. Wherein the parameters of the secondary sintering material crushing and grading are as follows: the pressure of grinding gas is 0.45 MPa, the frequency of a grading motor is 32 Hz, the frequency of a feeding motor is 11Hz, and the pressure of a grinding body is-6.5 KPa. The granularity requirement of the secondary sintering graded material is as follows: d0 was 1.6 μm, and D50 was 9.5. mu.m.
Comparative example 1:
the lithium cobaltate positive electrode material of the present comparative example was prepared in substantially the same manner as in example 1, except for the difference in the step (a)1) The unconventional doping element Ce is not added, other operation steps are completely the same as those of the embodiment 1, and the specific process of the step (1) is as follows: mixing cobaltosic oxide, lithium carbonate and TiO2And Mg (OH)2Proportioning, and then mixing by adopting a coulter type mixer to obtain a primary mixture; the molar ratio of the lithium element in the lithium carbonate to the cobalt element in the cobaltosic oxide was n (Li): (n) (Co) =1.05: 1, the amount of Ti added was 0.1wt% of the weight of the secondary sintered product, and the amount of Mg added was 0.15wt% of the weight of the secondary sintered product.
The lithium cobaltate cathode material prepared in the comparative example has the D50 of 8.7 mu m and the specific surface area of 0.29m2(ii)/g, compacted density of 3.90g/cm3. The SEM image of the material of this example is shown in FIG. 3. As can be seen from FIG. 3, the material is of a single crystal morphology, and 3.90g/cm is realized when a full battery is manufactured3High compaction density of (2). Tests show that the material has a 0.2C discharge capacity of 192.5mAh/g, a capacity retention rate of 90.2% and a 20C/0.2C rate performance of 91.5% in 500-week circulation under 1C charge-discharge conditions in a test range of 25 ℃ and 3.0V-4.45V voltage. Physical properties and electrochemical properties of the positive electrode material products of the comparative example and example 1 are shown in table 1.
Table 1 comparison of physical properties and electrochemical properties of comparative example 1 and example 1 cathode material products
Figure 304677DEST_PATH_IMAGE001
As can be seen from the results in table 1, compared with the product obtained in example 1, the high-rate, high-compaction and high-voltage lithium cobalt oxide cathode material prepared in comparative example 1 without adding the doping element Ce has the advantages that the capacity and the cycle performance under high voltage of the product obtained in example 1 are obviously improved, and the rate performance is also obviously improved. This shows that the element Ce with large unconventional ionic radius is selected and added in the primary sintering, on one hand, most of the element with large ionic radius is doped to replace Co3+Part of the lithium ion battery forms a large-aperture ion channel, so that the lithium ion conduction is promoted, and the charge rate performance and the discharge capacity of the lithium battery are remarkably improved; on the other hand, a small amount of element Ce having a large ionic radius is not presentInto the crystal lattice of the lithium cobaltate and forms a surface coating layer. Therefore, the element Ce is added during the primary sintering, so that the doping effect and the surface coating effect are achieved, and the double protection effect is achieved on the lithium cobaltate together with other coating substances added during the secondary sintering, so that the effects of improving the capacity and the cycle performance and the rate performance are achieved.
Comparative example 2:
the lithium cobaltate positive electrode material of the present comparative example was prepared in substantially the same manner as in example 1, except for the step (3) in which Y was not added2O3The other operation steps are the same as those in the embodiment 1, and the specific process of the step (3) is as follows: mixing the powdery positive electrode material obtained in the step (2) and the coating according to a certain ratio, and then mixing by adopting a high-speed mixer to obtain a secondary mixture; the coating is Co (OH)2Wherein Co (OH)23.5wt% of the weight of the primary sintered product.
The high-rate, high-compaction and high-voltage lithium cobaltate cathode material prepared by the comparative example has the D50 of 8.6 mu m and the specific surface area of 0.30m2(ii)/g, compacted density of 3.90g/cm3. Tests show that the material has a 0.2C discharge capacity of 194.7mAh/g, a capacity retention rate of 91.3% under 1C charge-discharge conditions in 500-week circulation, and a rate capability of 91.9% under 20C/0.2C in a test range of 25 ℃ and 3.0V-4.45V. The physical properties and electrochemical properties of the positive electrode material products of the comparative example and example 1 are compared as shown in Table 2.
Table 2 comparison of physical properties and electrochemical properties of the positive electrode materials of comparative example 2 and example 1
Figure 762203DEST_PATH_IMAGE002
As can be seen from the results of Table 2, comparative example 2 did not add Y2O3Compared with the product obtained in the example 1, the high-rate, high-compaction and high-voltage lithium cobaltate cathode material obtained by coating preparation has the advantage that the cycle performance and rate performance under high voltage of the product obtained in the example 1 are obviously improved. This illustrates the present inventionInvention adds Y2O3The coating Y after heat treatment2O3With surface-rich Li in doped lithium cobaltate+Reaction to produce LiYO2The coating layer of (2). The coating layer is a lithium fast ion conductor, has high lithium ion conductivity, can be used for improving the conductivity of materials, and is an excellent coating, so that Y is coated2O3Is beneficial to improving the cycle performance and the rate performance under high voltage.
Comparative example 3:
the preparation method of the lithium cobaltate cathode material of the comparative example is basically the same as that of the example 1, the difference is only that the primary sintering condition of the step (2) is different, the other operation steps are completely the same as the example 1, and in the comparative example, the sintering condition of the step (2) is as follows: placing the primary mixture obtained in the step (1) in air for sintering, wherein the specific process of primary sintering comprises the following steps: the ventilation volume is 15m3And h, heating the mixed material from room temperature to 750 ℃, preserving heat for 3 hours, then heating to 915 ℃, preserving heat for 8 hours, and naturally cooling along with the furnace.
The SEM image of the high-magnification and high-voltage lithium cobaltate cathode material prepared in the comparative example is shown in FIG. 4, and the D50 of the high-magnification and high-voltage lithium cobaltate cathode material is 7.1 mu m, and the specific surface area of the high-magnification and high-voltage lithium cobaltate cathode material is 0.42m2(ii)/g, compacted density of 3.45g/cm3. Tests show that the material has a 0.2C discharge capacity of 194.9mAh/g, a capacity retention rate of 93.3% after 500-week circulation under 1C charge-discharge conditions, and a rate performance of 98.3% at 20C/0.2C within the test range of 25 ℃ and 3.0V-4.45V. Physical properties and electrochemical properties of the positive electrode material products of the comparative example and example 1 are shown in table 3.
Table 3 comparison of physical properties and electrochemical properties of the positive electrode material products of comparative example 3 and example 1
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The SEM photograph of this comparative example is shown in fig. 4. As can be seen from FIG. 4, the material is lithium cobaltate with a polycrystalline morphology, and the compact density is in the process of manufacturing a full cell because aggregate particles are easy to crush3.6g/cm3Hereinafter, it is only 3.45g/cm3The requirement for high compaction is not met. As can be seen from the results of table 3, the lithium cobaltate of the polycrystalline morphology of comparative example 3 has superior rate capability but inferior cycle performance compared to the material of the single crystal morphology obtained in example 1. The reason is mainly that the polycrystalline lithium cobaltate has small primary particles and good rate capability, but the specific surface is large, so that electrochemical side reaction of materials and electrolyte is easily caused under high voltage, and the exposed fresh inner surface is continuously reacted with the electrolyte to generate other phases due to the crushing, pulverization and separation of aggregate particles in the circulation process, so that the deterioration of the circulation performance under high voltage is caused. The high-rate, high-compaction and high-voltage lithium cobaltate prepared in the embodiment 1 is in a single crystal shape, the D50 is 8.5 mu m and is in the most reasonable range of 6.0 mu m to 11.0 mu m, and the material has high-rate, high-compaction and high-voltage performances.
Comparative example 4:
the method for preparing the lithium cobaltate cathode material of the comparative example is basically the same as that of the example 1, and is different from the step (2) and the step (4), the fluidized bed type jet milling and grading integrated machine is replaced by a fluidized bed type jet milling machine, and grading is omitted in both steps. The specific process of the step (2) is as follows: placing the primary mixture obtained in the step (1) in air for sintering, wherein the specific process of primary sintering comprises the following steps: the ventilation volume is 15m3And h, heating the mixed material from room temperature to 750 ℃, preserving heat for 3 hours, then heating to 970 ℃, preserving heat for 8 hours, and naturally cooling along with the furnace. And coarsely crushing the blocky primary sintered material by using a jaw crusher and a double-roll crusher, and crushing the blocky primary sintered material by using a fluidized bed type jet mill to obtain the powdery anode material after primary sintering. Wherein the crushing parameters of the primary sintering material are as follows: the pressure of the grinding gas is 0.52 MPa, the frequency of the feeding motor is 12 Hz, and the pressure of the grinding body is-0.6 KPa. The specific process of the step (4) is as follows: and (4) placing the secondary mixture obtained in the step (3) in air for sintering, wherein the specific operation of the secondary sintering process comprises the following steps: the ventilation volume is 6m3H, heating the secondary mixture from room temperature to 930 ℃, and preserving the heat for 8 hours, thenAnd then naturally cooling along with the furnace. And coarsely crushing the blocky secondary sintering material by using a jaw crusher and a double-roll crusher, and crushing by using a fluidized bed type airflow crusher to obtain a product of the lithium cobaltate cathode material. Wherein the secondary sintering material has the following crushing parameters: the pressure of the grinding gas is 0.43 MPa, the frequency of the feeding motor is 11Hz, and the pressure of the grinding body is-6.2 KPa.
The SEM image of the lithium cobaltate cathode material prepared in the comparative example is shown in FIG. 5, and D50 of the lithium cobaltate cathode material is 8.6 μm, and the specific surface area of the lithium cobaltate cathode material is 0.31m2(ii)/g, compacted density of 3.90g/cm3. Tests show that the material has a 0.2C discharge capacity of 194.5mAh/g, a capacity retention rate of 91.4% after 500-week circulation under 1C charge-discharge conditions and a rate capability of 97.6% at 20C/0.2C within the test range of 25 ℃ and 3.0V-4.45V. The physical properties and electrochemical properties of the positive electrode material products of the comparative example and example 1 are compared as shown in Table 4.
Table 4 comparison of physical properties and electrochemical properties of the positive electrode material products of comparative example 4 and example 1
Figure 461355DEST_PATH_IMAGE004
The SEM image of the material of this comparative example is shown in FIG. 5. As can be seen from FIG. 5, the material has a single crystal morphology, and 3.90g/cm is realized during full-cell fabrication3High compaction density of (2). However, since the integrated fluid bed type jet mill classifier was replaced with the fluid bed type jet mill in step (2) and step (4) of this example, classification was cancelled in both steps, D0 was 0.4 μm in the product of comparative example 4, and "pock marks" were observed in FIG. 5, which were fine particles.
As can be seen from the results of table 4, the product cycle performance of comparative example 4 was significantly deteriorated as compared with the product obtained in example 1. This is mainly because the product of comparative example 4 has fine powder particles which are liable to undergo electrochemical side reactions with the electrolyte at high voltage, resulting in deterioration of cycle performance at high voltage. In the embodiment 1, the fluidized bed type airflow crushing and grading integrated machine is adopted for crushing and grading in the step (2), and the excessively fine powder (fine powder with the particle size of less than 0.5 mu m) generated in the process is collected by the pulse dust collector without entering the secondary burdening and mixing process, so that the control of fine powder particles in the finished product is facilitated from the source. In addition, in the step (4), the fluid bed type jet milling and grading integrated machine is also used for milling and grading, and the superfine powder (the fine powder with the particle size of less than 0.5 mu m) generated in the process is collected by the pulse dust collector for removing dust. Therefore, in the embodiment 1, the fluidized bed type air flow crushing and grading integrated machine is adopted to crush and grade in the steps (2) and (4), and double protection is adopted to strictly control the content of fine powder with the particle size of less than 0.5 μm in the product, besides ensuring that the D50 of the lithium cobaltate cathode material with high multiplying power, high compaction and high voltage meets the requirement. The D0 value in the result of the particle size test of the product of example 1 is 1.5 μm, which is far more than 0.5 μm, so that the product of the invention has no fine powder particles, which is beneficial to improving the safety performance and the cycle performance of the cathode material in the using process.
Comparative example 5:
the lithium cobaltate positive electrode material of the present comparative example was prepared in substantially the same manner as in example 1, except for the step (3) in which Y was not added2O3Instead of TiO2The other operation steps are the same as those in the embodiment 1, and the specific process of the step (3) is as follows: mixing the powdery positive electrode material obtained in the step (2) and the coating according to a certain ratio, and then mixing by adopting a high-speed mixer to obtain a secondary mixture; the coating is Co (OH)2And TiO2Wherein Co (OH)23.5wt% of TiO based on the weight of the primary sintered product2The Ti in the powder is 0.1wt% of the weight of the primary sintered product.
The lithium cobaltate cathode material prepared by the comparative example has the D50 of 8.7 mu m and the specific surface area of 0.31m2(ii)/g, compacted density of 3.90g/cm3. Tests show that the material has 0.2C discharge capacity of 194.6mAh/g, capacity retention rate of 500-week circulation under 1C charge-discharge conditions of 96.8% and 20C/0.2C rate performance of 93.8% in the test ranges of 25 ℃ and 3.0V-4.45V voltage. The physical properties and electrochemical properties of the positive electrode material products of the comparative example and example 1 are compared as shown in Table 5.
Table 5 comparison of physical properties and electrochemical properties of the positive electrode material products of comparative example 5 and example 1
Figure 790705DEST_PATH_IMAGE005
Since comparative example 5 did not add Y2O3Instead of TiO2As can be seen from the results in table 5, the lithium cobaltate cathode material prepared in comparative example 5 has significantly improved high-voltage rate performance compared with the product obtained in example 1, and the product obtained in example 1 has significantly improved high-voltage rate performance. This shows that Y is added in the present invention2O3The coating Y after heat treatment2O3With surface-rich Li in doped lithium cobaltate+Reaction to produce LiYO2The coating layer of (2). In the coating layer LiYO2Has very high chemical diffusion coefficient (1.8 × 10)-6 cm 2 s -1) And the multiplying power performance and the high voltage performance of the product are facilitated. To coat TiO2Generated Li4Ti5O12The coating layer of (2X 10) having a chemical diffusion coefficient-8 cm 2 s -1) Apparent ratio LiYO2The chemical diffusion coefficient is low, so the 20C/0.2C rate performance of comparative example 5 is 3.7% worse than example 1.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. The preparation method of the high-rate, high-compaction and high-voltage lithium cobaltate positive electrode material is characterized in that the particle size D50 of the lithium cobaltate positive electrode material is 6.0-11.0 mu m, and the specific surface area is 0.15-0.45 m2(ii) a compacted density of 3.7 to 3.95g/cm3The preparation method comprises the following steps:
(1) primary batching and mixing: mixing a cobalt source, a lithium source, a compound doped with an element M and a compound doped with an element M' after burdening to obtain a primary mixture;
(2) primary sintering and crushing: carrying out primary sintering on the obtained primary mixture in an air atmosphere to obtain a primary sintering material of lithium cobaltate, and crushing and grading the primary sintering material to obtain a primary sintering graded material;
(3) secondary batching and mixing: mixing the obtained primary-fired graded material and the coating material, and then mixing at a high speed to obtain a secondary mixture;
(4) and (3) secondary sintering: and (3) carrying out secondary sintering on the obtained secondary mixture in an air atmosphere to obtain a secondary sintering material, crushing and grading the secondary sintering material, and demagnetizing and sieving the obtained secondary sintering graded material to obtain the high-rate, high-compaction and high-voltage lithium cobaltate cathode material.
2. The method for preparing a high-rate, high-compaction, high-voltage lithium cobaltate cathode material according to claim 1, wherein in the step (1), the doping element M is selected from one or more of Al, Ti and Mg; the doping amount of the doping element M is 0.01-5 wt% of the weight of the secondary sintering material;
the doping element M' is selected from Pr and/or Ce; the doping amount of the doping element M' is 0.005-3 wt% of the weight of the secondary sintering material;
the molar ratio of lithium element in the lithium source to cobalt element in the cobalt source is n (Li) to n (Co) is 1.1-0.9: 1.
3. The method for preparing a high-rate, high-compaction, high-voltage lithium cobaltate cathode material according to claim 1, wherein in the step (2), the primary sintering comprises: under the air atmosphere, the ventilation quantity is 10-20 m3And h, heating the primary mixture from room temperature to 720-780 ℃, preserving heat for 2-5 hours, then heating to 920-1120 ℃, preserving heat for 6-10 hours, and naturally cooling along with the furnace.
4. The high rate, high compaction, high voltage lithium cobaltate of claim 1The preparation method of the cathode material is characterized in that in the step (3), the coating material is Co (OH)2And Y2O3(ii) a The Co (OH)2The dosage of the Y is 0.5-4.5 wt% of the weight of the primary sintering material, and the Y is2O3The amount of the middle Y is 0.05-0.4 wt% of the weight of the primary sintering material; said Y is2O3Has a particle diameter of 30 to 50nm and a specific surface area of 20m2/g～40m2/g。
5. The method for preparing a high-rate, high-compaction, high-voltage lithium cobaltate cathode material according to claim 1, wherein in the step (4), the secondary sintering comprises: in the air atmosphere, the ventilation amount is 2-9 m3And h, heating the secondary mixture from room temperature to 900-950 ℃, preserving heat for 6-10 hours, and then naturally cooling along with the furnace.
6. The method for preparing a high-rate, high-compaction, high-voltage lithium cobaltate cathode material according to claim 1, wherein in the step (2), the crushing and classifying the primary sintered material comprises: firstly adopting a jaw crusher and a double-roller crusher for coarse crushing, and then adopting a fluidized bed type airflow crushing and grading integrated machine for crushing and grading to obtain a primary-fired graded material.
7. The method for preparing a high-rate, high-compaction and high-voltage lithium cobaltate cathode material as claimed in claim 6, wherein the parameters for crushing and classifying by adopting a fluidized bed type jet-milling and classifying all-in-one machine are as follows: the pressure of the grinding gas is 0.52-0.55 MPa, the frequency of a grading motor is 34-36 Hz, the frequency of a feeding motor is 12-13 Hz, and the pressure of a grinding body is-0.3-0.8 KPa;
the granularity requirement of the primary-fired graded material is as follows: d0 is more than or equal to 0.5 mu m, and D50 is between 5.0 and 10.0 mu m.
8. The method for preparing a high-rate, high-compaction and high-voltage lithium cobaltate cathode material according to claim 1, wherein in the step (4), the crushing and classification of the secondary sintered material comprises the steps of firstly adopting a jaw crusher and a pair of rollers for coarse crushing, and then adopting a fluidized bed type air flow crushing and classification all-in-one machine for crushing and classification, so as to obtain a secondary sintered classified material.
9. The method for preparing a high-rate, high-compaction, high-voltage lithium cobaltate cathode material according to claim 8, wherein the parameters for crushing and classifying by using a fluidized bed type jet-milling and classifying all-in-one machine are as follows: the pressure of the grinding gas is 0.42-0.45 MPa, the frequency of a grading motor is 29-32 Hz, the frequency of a feeding motor is 9-11 Hz, and the pressure of a grinding body is-5.5-6.5 KPa;
the granularity requirement of the secondary sintering graded material is as follows: d0 is more than or equal to 0.5 mu m, and D50 is between 6.0 and 11.0 mu m.
10. The method for preparing a high-rate, high-compaction and high-voltage lithium cobaltate cathode material as claimed in claim 1, wherein the obtained full cell assembled by the cathode material has a 0.2C discharge capacity higher than 193mAh/g, a capacity retention rate higher than 96.5% under a 1C charge-discharge condition for 500 cycles, and a rate capability higher than 97.0% under a 20C/0.2C charge-discharge condition within a voltage test range of 3.0V-4.45V.
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