CN115261988A

CN115261988A - Single crystal lithium nickel cobalt aluminum oxide and uses thereof

Info

Publication number: CN115261988A
Application number: CN202211033514.8A
Authority: CN
Inventors: 朱晓晶; 杭道金; 朱灵霖; 陆君
Original assignee: Shanghai Huayi New Material Co ltd; Shanghai Huayi Group Corp
Current assignee: Shanghai Huayi New Material Co ltd; Shanghai Huayi Group Corp
Priority date: 2021-07-19
Filing date: 2021-07-19
Publication date: 2022-11-01
Also published as: CN113564708B; CN113564708A

Abstract

Disclosed are a single crystalline lithium nickel cobalt aluminum oxide and uses thereof, the method of making the oxide comprising: (a) Providing a lithium nickel cobalt aluminum oxide precursor mixture, wherein the primary particle diameter D50 of the precursor mixture is 0.1-0.5 microns; (b) Spray drying to obtain spherical secondary particle powder of lithium nickel cobalt aluminum oxide precursor with particle size D50 of 5-50 microns; (c) crushing to obtain powder with the particle size D50 of 0.5-5 microns; (d) Pressing the powder into a block material under the pressure of 1-35MPa, and reacting the block material in an oxygen-containing atmosphere by using a high-temperature solid phase method to form lithium nickel cobalt aluminum oxide with a laminated structure; (e) And crushing and grinding the lithium nickel cobalt aluminum oxide with the laminated structure to obtain the monocrystalline lithium nickel cobalt aluminum oxide.

Description

Single crystal lithium nickel cobalt aluminum oxide and uses thereof

The patent application of the invention is a divisional application of Chinese patent application with the application number of CN202110811921.6 and the invention name of 'preparation method of monocrystalline lithium nickel cobalt aluminum oxide'.

Technical Field

The invention relates to a preparation method of a single crystal lithium nickel cobalt aluminum oxide which can be used as a lithium ion battery anode material. The lithium ion battery using the single crystal lithium nickel cobalt aluminum oxide prepared by the method of the invention as the anode material has improved battery performance.

Background

Lithium ion batteries are one of new energy carriers, the demand of batteries of electric vehicles, electric bicycles and mobile phones is increasing day by day, and lithium battery products are developing continuously towards the directions of high specific capacity, high energy density, high capacity retention rate and better safety performance. The performance of the anode material in the lithium battery is a decisive factor of the battery performance, and the energy density, the cycle performance and the safety of the battery are closely related to the performance of the anode material. The specific discharge capacity, the working platform voltage, the filling property of the powder material and the like are several key factors influencing the energy density. By increasing the density of the positive electrode material, the volumetric energy density of the lithium battery can be increased.

Common lithium battery positive electrode materials in the market at present comprise lithium iron phosphate, lithium cobaltate, lithium manganate and ternary materials (NCM/NCA). The energy density of the ternary lithium battery is higher than that of lithium iron phosphate and lithium manganate, the rate performance of the ternary lithium battery also meets the charge and discharge frequency of the electric vehicle, the gram capacity of the lithium cobaltate is far different from that of NCA although the lithium cobaltate has higher compaction density, the gram capacity of the lithium cobaltate can be improved by increasing charge and discharge voltage, but the material structure of the lithium cobaltate is unstable under high pressure and is accompanied with a large number of side reactions, and the cost of the lithium cobaltate is high, so that the ternary lithium battery is favored by the market, and a plurality of preparation methods are developed and gradually become a mainstream technical route.

Most of nickel-cobalt lithium aluminate anode materials on the market at present are secondary particle type and are formed by gathering primary particles. The disadvantage of this topographical feature is that cracks form from the interior of the material after cycling due to multiple changes in unit cell volume, resulting in fragmentation which, from the reported academic literature, reduces the electrochemical performance of the cell cycle. The single crystal particles of the lithium nickel cobalt aluminate material can make up for the defects, and each particle is independent, so that the particles can not be cracked from the inside after multiple cycles, and the capacity retention rate after the cycles is effectively improved.

Prior academic studies have shown that most processes require high temperature long calcination (> 800 ℃) for the preparation of single crystal ternary materials (including NCM and NCA), either by the addition of molten salt or by fractional grinding. Among the disadvantages for the preparation of single crystal lithium nickel cobalt aluminates are: under the condition of long-time high-temperature calcination, lithium-nickel mixed in NCA is more serious, so that the electrochemical performance of NCA is reduced, and compared with NCM, NCA is more sensitive to calcination temperature, and compared with NCM with the Merlot calcination temperature of up to 900 ℃, the highest calcination temperature which can be adjusted by NCA is much lower, so that the long-time high-temperature calcination is not suitable for preparing NCA single crystal; secondly, for the method of adding molten salt, the molten salt generally adopted is chloride salt such as sodium chloride, potassium chloride and the like, the discharge and treatment of chloride (generally in the form of hydrogen chloride gas) are considered in the sintering process, and sodium salt and potassium salt impurities in the product also need to be removed, so that the requirement on production equipment is complex; thirdly, when the step-by-step grinding and sintering method is adopted, the sample is cooled and taken out after being calcined to the first platform for grinding, and then secondary calcination is carried out, so that the requirement on controlling the moisture content of the sample is high, and the cooling process can cause the process time to be prolonged.

A method for preparing single crystal lithium nickel cobalt aluminum oxide comprises sintering single crystal lithium nickel cobalt aluminum precursor mixed lithium source (for example, see Chinese patent CN109449391A, CN111009646A, CN109921009A, CN104852041B, CN111200129A and CN 108807965B). The commonly used single crystal lithium nickel cobalt aluminum precursors are prepared by co-precipitation methods (see, for example, chinese patents CN105322152A, CN107681128B, CN111646520A, CN104241640A, CN108574100A, and CN 112194195A). The coprecipitation method has the disadvantages of complex process, strong alkali and a coordination agent required in the coprecipitation process, common sodium hydroxide and ammonia water, strong alkalinity of the aqueous solution, pungent odor volatilization, high risk and irritation in the production process, and inert atmosphere protection required to avoid oxidation. The process has long reaction time which is 10-20 hours, more parameters which need to be controlled and adjusted in the process have high requirements on operators and long training time, and the coprecipitation method needs to wash precipitates, can generate a large amount of waste liquid and has high treatment cost. In the later period, the precursor and the lithium source solid are blended to carry out high-temperature solid-phase reaction, and the condition of uneven mixing materials can occur, so that the electrochemical performance of the material is reduced.

In addition, there is a precedent for using a spray drying method to connect a high-temperature pyrolysis method, such as CN104934572B, and the disadvantages of this method include that salt solutions of Li, ni, co, and Al are mixed at the beginning of the process flow, the mass ratio of the total mass of the salt to deionized water can reach 1.

Chinese patent CN 1021699981A discloses a preparation method of a lithium battery anode material with a manganese-based layered crystal structure, which comprises the steps of preparing a precursor by a mechanical activation method, spray drying and granulating, and preparing a layered crystal by a high-temperature solid phase method. In the examples, the specifically disclosed preparation method comprises ball-milling a raw material mixture using isopropyl alcohol as a dispersant, spray-drying granulation, firing the resulting granular powder in a sagger at 480 ℃ for 5 hours after compacting with a press plate in air, ball-milling, firing the resulting granular powder in a sagger at 950 ℃ for 10 hours after compacting with a press plate in air, and air-jet pulverization classification. This approach ultimately results in a polycrystalline rather than single crystal material.

The new preparation method of the single crystal lithium nickel cobalt aluminum oxide needs to be found, the process flow is simplified, the process duration is shortened, the safety and the clean performance are met, the discharge of waste liquid and waste gas is reduced, and the prepared single crystal lithium battery electrode material can keep higher discharge specific capacity, better rate capability and good cycle capacity retention rate.

Disclosure of Invention

The invention aims to provide a novel preparation method of single crystal lithium nickel cobalt aluminum oxide, which simplifies the process flow, shortens the process time, meets the requirements of safety and energy cleaning, and reduces the discharge of waste liquid and waste gas.

It is another object of the present invention to provide the single crystalline lithium nickel cobalt aluminum oxide obtained by the above method.

It is a further object of the present invention to provide the use of the single crystalline lithium nickel cobalt aluminum oxide prepared by the above method as an electrode for a lithium ion battery.

Accordingly, one aspect of the present invention relates to a method for preparing a single crystalline lithium nickel cobalt aluminum oxide, comprising:

(a) Providing a lithium nickel cobalt aluminum oxide precursor mixture, wherein the primary particle diameter D50 of the precursor mixture is 0.1-0.5 microns;

(b) Spray drying to obtain spherical secondary particle powder of lithium nickel cobalt aluminum oxide precursor with particle size D50 of 5-50 microns;

(c) Pulverizing to obtain powder with particle diameter D50 of 0.5-5 μm;

(d) Pressing the powder into a block material under the pressure of 1-35MPa, and reacting the block material in an oxygen-containing atmosphere by using a high-temperature solid phase method to form lithium nickel cobalt aluminum oxide with a laminated structure;

(e) And crushing and grinding the lithium nickel cobalt aluminum oxide with the layered structure to obtain the monocrystal lithium nickel cobalt aluminum oxide.

Another aspect of the invention relates to the single crystal lithium nickel cobalt aluminum oxide produced by the above method.

A further aspect of the invention relates to the use of the single-crystal lithium nickel cobalt aluminum oxide obtained by the above method as an electrode for a lithium ion battery.

Drawings

The invention is further described with reference to the accompanying drawings, in which:

FIG. 1 is a scanning electron micrograph of a spray dried secondary particle powder according to an embodiment of the present invention;

FIG. 2 is a scanning electron micrograph of a final sample after re-firing and pulverization following step (c) in one embodiment of the present invention;

FIG. 3 is a scanning electron micrograph of a sample obtained by press-firing spray-dried spheroidal particles without step (c);

FIG. 4 is a graph of the electrical properties of a sample of the present invention;

FIG. 5 is an electrical property curve of a control sample;

FIG. 6 is a graph comparing the first charge and discharge curves of the comparative example sample and the example 1 sample;

FIG. 7 is a scanning electron micrograph of a control sample in example 11;

FIG. 8 is a graph of the cyclic capacity retention of polycrystalline and single crystal materials in example 12.

Detailed Description

The invention provides a preparation method of lithium nickel cobalt aluminum oxide. The specific composition of the lithium nickel cobalt aluminum oxide suitable for use in the method of the present invention is not particularly limited so long as it is suitable for use, for example, as an electrode material for a lithium ion battery.

In one embodiment of the invention, the lithium nickel cobalt aluminum oxide has the general formula:

LiaNixCoyAlzO ₂ :M _b

wherein a =0.95-1.15, x =0.50-0.99, y =0.01-0.50, x + y + z =1 and z >0;

b≤0.02；

m is an optional doping element and is one or more selected from Na, K, ca, mg, ti, V, cr, cu, mn, zn, ga, in, ta, ge, ag, au, zr, nb and W.

In one embodiment of the invention, the lithium nickel cobalt aluminum oxide is selected from Li _1.05 Ni _0.88 Co _0.09 Al _0.03 O ₂ 、Li _1.0 Ni _0.6 Co _0.3 Al _0.1 O ₂ 、Li _0.95 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ 、Li _1.05 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ 、Li _1.10 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ 、Li _1.05 Ni _0.84 Co _0.12 Al _0.04 O ₂ 、Li _1.03 Ni _0.9 Co _0.05 Al _0.05 O ₂ 、Li _1.05 Ni _0.9 Co _0.05 Al _0.05 O ₂ 、Li _1.05 Ni _0.84 Co _0.1 Al _0.05 Nb _0.005 O ₂ 、Li _1.04 Ni _0.84 Co _0.1 Al _0.05 Nb _0.005 O ₂ 、Li _1.0 ₅ Ni _0.9 Co _0.07 Al _0.025 Mg _0.005 O ₂ 、Li _1.05 Ni _0.8 Co _0.15 Al _0.05 O ₂ Or a mixture of two or more thereof.

The method comprises the following steps:

the precursor mixture of the present invention comprises a mixture of a primary particle precursor consisting of Li, ni, co, al and optionally a doping element M, and deionized water.

In one example of the invention, the precursor sources are: the lithium source is one or more of lithium carbonate, lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium acetate dihydrate and anhydrous lithium acetate; the nickel source is one or more of nickel hydroxide, nickel protoxide, nickel sesquioxide, nickel carbonate, basic nickel carbonate and nickel oxalate; the cobalt source is one or more of cobalt hydroxide, cobaltous oxide, cobaltosic oxide, cobalt carbonate, basic cobalt carbonate and cobalt oxalate; the aluminum source is one or more of aluminum hydroxide, aluminum oxide, basic aluminum acetate and aluminum oxalate hydrate. The nickel cobalt aluminium source may also be the respective hydroxide of the nickel cobalt aluminium elements.

The optional doping element M is one or more compounds selected from Na, K, ca, mg, ti, V, cr, cu, mn, zn, ga, in, ta, ge, ag, au, zr, nb and W.

In one embodiment of the present invention, in the primary particle precursor of Li, ni, co and Al, the molar ratio of each element Lia: nix: coy: alz: M _b The method comprises the following steps:

a =0.95-1.15, preferably 1.00-1.10, more preferably 1.02-1.08;

x =0.50 to 0.99, preferably 0.70 to 0.95, more preferably 0.8 to 0.90;

y =0.01 to 0.50, preferably 0.02 to 0.40, more preferably 0.03 to 0.30;

x + y + z =1, and z >0;

b.ltoreq.0.02, preferably b.ltoreq.0.01, for example from 0 to 0.008, preferably from 0.001 to 0.007, more preferably from 0.003 to 0.006.

In the precursor mixture according to the invention, the particles have a particle size D50 of between 0.1 and 0.5. Mu.m, preferably between 0.2 and 0.4. Mu.m, more preferably between 0.25 and 0.35. Mu.m.

In one embodiment of the present invention, the precursor may be a nanoscale material meeting specifications, or larger particle raw materials may be comminuted by wet milling, dry milling, other milling methods, and the like until meeting particle size specifications.

In one embodiment of the invention, the primary particle precursor is dispersed with deionized water to form a dispersion having a solids content of between 15 and 60% by weight, preferably between 25 and 50% by weight.

In one embodiment of the present invention, a dispersant may be added to the dispersion of the primary particle precursor and deionized water. The dispersant to be used is not particularly limited, and may be a conventional dispersant known in the art, and may be, for example, an ionic or nonionic surfactant.

Non-limiting examples of suitable cationic surfactants are, for example, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide or mixtures thereof;

non-limiting examples of suitable anionic surfactants are, for example, ammonium lauryl sulfate, lithium lauryl sulfate, ammonium dodecylbenzenesulfonate, lithium dodecylbenzenesulfonate, ammonium stearate, lithium stearate, ammonium palmitate, lithium palmitate, ionic polyacrylamides (e.g., cationic or anionic polyacrylamides), polycarboxylic acids and salts thereof (e.g., one or more of polyacrylic acid, polymethacrylic acid, maleic acid-co-acrylic acid, maleic acid-co-methacrylic acid, and lithium or ammonium salts thereof);

non-limiting examples of suitable nonionic surfactants are, for example, polyoxyethylene sorbitan fatty acid esters (e.g. tween-20, 40, 60 or 80), polyoxyethylene octylphenol ethers (e.g. EO-9) or mixtures thereof.

In one embodiment of the present invention, the dispersant is used in an amount of 0.1-5% by weight, preferably 0.5-4.5%, more preferably 1-4%, preferably 1.5-3.5% based on the weight of the whole dispersion slurry.

(b) Spray drying to obtain quasi-spherical secondary particle powder of lithium nickel cobalt aluminum oxide precursor with particle size D50 of 5-50 microns;

spray drying suitable for the method of the present invention is not particularly limited and may be a conventional spray drying method known in the art. In one embodiment of the invention, the spray dryer nozzle is selected from the group consisting of centrifugal, two-fluid, or four-fluid nozzles.

The particle diameter D10 of the secondary particle powder formed by spray drying is between 1 and 30 microns, preferably between 5 and 25 microns, and more preferably between 10 and 20 microns; d50 is between 5 and 50 microns, preferably between 10 and 40 microns, more preferably between 20 and 30 microns; d90 is between 15 and 80 microns, preferably between 25 and 70 microns, more preferably between 35 and 60 microns.

FIG. 1 is a scanning electron micrograph of a spray dried secondary particle powder according to one embodiment of the present invention. As can be seen from fig. 1, the secondary particle powder of the present invention has a spheroidal shape.

(c) Crushing the secondary particle powder to obtain powder with D50 of 0.5-5 microns;

the method for crushing the secondary particles of the present invention is not particularly limited, and may be a conventional crushing method known in the art. In one embodiment of the invention, the crushing method is selected from roll crushing, hammer crushing, ball milling, jet milling or a combination thereof.

The particle diameter D10 of the crushed secondary microparticle powder is between 0.1 and 3 microns, preferably between 0.5 and 2.5 microns, and more preferably between 1 and 2 microns; d50 is between 0.5 and 5 microns, preferably between 1 and 4 microns, more preferably between 2 and 3 microns; the D90 is between 1.5 and 8 microns, preferably between 2 and 7 microns, more preferably between 3 and 5 microns.

the method comprises the step of pressing the crushed particle powder into a precursor block, wherein the pressing pressure is between 1 and 35MPa, preferably between 1.5 and 20MPa, and more preferably between 2 and 10MPa.

The compressing method itself is not particularly limited, and may be one or more of manual compression, automatic compression, manual-automatic integral compression, rolling, or continuous tablet press compression.

The inventors of the present invention have found that, although the block is used after being crushed after firing, the pressing pressure of the block has an influence on the crystalline state and electrode properties of the final product. For example, when the pressing pressure is less than 1MPa, the formed lithium nickel cobalt aluminum oxide may be in a polycrystalline state rather than a single crystalline state, and finally the performance (e.g., cycle capacity, etc.) of the lithium ion battery may be affected. The oxygen-containing atmosphere adopted by the method has the volume oxygen content of 20-100%, preferably 50-100%, more preferably 85-100%.

In one embodiment of the present invention, the oxygen content is returned by varying the atmosphere at different stages during the heat treatment.

In one embodiment of the invention, the temperature of the heat treatment of the pressed block is between 600 and 900 ℃, preferably between 650 and 850 ℃, more preferably between 700 and 820 ℃.

In one embodiment of the invention, the heat treatment is carried out for a period of time in the range of 5 to 20 hours, preferably 7 to 18 hours, more preferably 10 to 16 hours.

In one embodiment of the invention, the heat treatment is carried out by a gradient heating method, for example by first incubating at 420-580 deg.C, preferably 450-520 deg.C, for 2-10 hours, preferably 4-8 hours, followed by incubating at 580-700 deg.C, preferably 620-680 deg.C, for 2-15 hours, preferably 5-10 hours; finally, the temperature is kept at 720-900 ℃, preferably 750-850 ℃ for 5-10 hours, preferably 6-8 hours.

The inventors of the present invention have also found that if the pressing at a pressure of 1 to 35MPa is combined with the gradient heating method, the electrical properties of the finally produced lithium ion battery can be further improved.

The heat treatment of the present invention further comprises the step of cooling the heat treated bulk material.

In one embodiment of the invention, gradient cooling is used, i.e. after a heat treatment at 600-900 ℃ cooling to 550-700 ℃, preferably 600-650 ℃, for 2-15 hours, preferably 5-10 hours, followed by cooling to room temperature.

(e) Crushing and grinding the lithium nickel cobalt aluminum oxide with the layered structure to obtain single crystal lithium nickel cobalt aluminum oxide;

the method for pulverizing the fired block is not particularly limited, and may be a conventional pulverization method known in the art. For example, the pulverization method may be one or more of roll pulverization, hammer pulverization, ball milling pulverization, or jet milling pulverization.

The particle size D10 of the crushed final microparticle powder is between 0.1 and 3 microns, preferably between 0.5 and 2.5 microns, and more preferably between 1 and 2 microns; d50 is between 0.3 and 6 microns, preferably between 1 and 5.5 microns, more preferably between 2 and 4 microns; the D90 is between 2 and 10 microns, preferably between 3 and 8 microns, more preferably between 4 and 6 microns.

FIG. 2 is a scanning electron micrograph of a final sample after re-firing and pulverization following step (c) in one embodiment of the present invention; FIG. 3 is a scanning electron micrograph of a sample obtained by press-firing the spray-dried spheroidal particles without step (c). Comparing the two figures, it can be seen that the two have completely different microscopic shapes.

In one embodiment of the present invention, the method comprises the steps of: mechanically mixing together a proportion of raw materials (e.g., lithium hydroxide, nickel protoxide, cobalt carbonate, aluminum hydroxide, and trititanium tetraoxide) to form a lithium nickel cobalt aluminum oxide (e.g., li nickel cobalt aluminum oxide) of a predetermined composition _1.05 Ni _0.875 Co _0.09 Al _0.03 Ti _0.005 O ₂ ). The D50 particle size of the raw materials is 3-20 microns. Adding an amount of water to adjust to a slurry of 10-40wt% solids content, while adding 0.1-2% by weight of dispersant, based on the total mass fraction. The D50 of the slurry was milled to 0.1-1 micron by wet milling.

And (3) preparing the slurry into round secondary particle powder with compact interior by a spray drying machine, wherein the particle diameter D50 of the particle powder is 5-20 microns.

And crushing the secondary particles into secondary microparticles with D50 of 1-5 microns by a ball milling method. Pressing the secondary microparticles into blocks under 1-10MPa by using a manual tablet press.

In a tubular atmosphere furnace, the block is heated from room temperature to 400-500 deg.C, preferably 450 deg.C, for 2-8 hours, for example 5 hours, at 2-8 deg.C, preferably 5 deg.C, per minute under an atmosphere containing 15-20%, preferably 21% oxygen, then switched to an atmosphere containing 30-60%, for example 50% oxygen, heated to 600-680 deg.C, for example 650 deg.C, for 6-15 hours, for example 10 hours, and finally switched to an atmosphere of 100% pure oxygen, heated to a maximum temperature of 720-880 deg.C, for example 750 deg.C, and then cooled naturally after 15-25 hours, for example 20 hours. The blocks are then crushed by hammer milling to give particles having a D50 of 2 to 6 microns, for example 3.4 microns.

And (3) sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain a product with uniform particles.

The present invention is further illustrated by the following examples.

Examples

The electrochemical performance test method of the nickel cobalt lithium aluminate comprises the following steps:

according to the active substance: conductive agent: binder =93 weight ratio of 2. After the pole piece is rounded, a lithium piece is used as a counter electrode, a solution with the concentration of lithium hexafluorophosphate being 1M and DMC EC =3 (V/V) is used as an electrolyte, and a PP diaphragm with the thickness of 20 micrometers isolates a positive electrode and a negative electrode, so that the CR2016 button battery is assembled. The rate test was performed according to the following conditions:

and (3) testing temperature: 25 +/-2 ℃;

voltage range: 3.0-4.3V;

the test flow comprises the following steps:

charging: charging at 1C, and stopping at a constant pressure of 0.05C after 4.3V;

shelf life: for 5 minutes.

Discharging: after the charging step, discharge was turned off to 3.0V at 0.1c,1c and 3C, respectively.

Example 1: li _1.05 Ni _0.88 Co _0.09 Al _0.03 O ₂

Mixing raw materials (lithium hydroxide monohydrate, nickel protoxide, cobalt carbonate and aluminium hydroxide) together mechanically to form Li _1.05 Ni _0.88 Co _0.09 Al _0.03 O ₂ Bulk chemical composition. The D50 particle size of the raw materials is 3-20 microns. An amount of water was added to adjust the slurry to 30% by weight of solid content, while 0.5% by weight of the whole of anionic polyacrylamide having a molecular weight of 5000 was added as a dispersant. The D50 of the slurry was milled to 0.4 micron by wet milling.

The slurry was passed through a spray dryer (model 1rebmb by61001, available from GEA, yohei, germany) equipped with a two-fluid nozzle to prepare a secondary particle powder having a round overall shape and a dense interior, wherein the particle diameter D50 of the particle powder was 13 μm, and the scanning electron micrograph thereof is shown in fig. 1.

The secondary particles were crushed by a ball milling method into secondary fine particles having a D50 of 2.4 μm. The secondary microparticles were compressed into a block at 3MPa using a manual tablet press.

In a tubular atmosphere furnace, firstly, under an atmosphere containing 21% of oxygen, raising the temperature of the block from room temperature to 450 ℃ per minute at 5 ℃ for 5 hours, then switching to an atmosphere containing 50% of oxygen, raising the temperature to 650 ℃ for 10 hours, finally switching to an atmosphere containing 100% pure oxygen, raising the temperature to 750 ℃ at the highest temperature, preserving the temperature for 20 hours, and then naturally cooling. The blocks were then crushed by hammer milling to give particles with a D50 of 3.4 microns.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain Li with uniform particles _1.05 Ni _0.88 Co _0.09 Al _0.03 O ₂ The product (the scanning electron microscope image of which is shown in figure 2) is prepared into a button cell for electrical property evaluation.

As a control, ni having the same composition was purchased separately _0.88 Co _0.09 Al _0.03 (OH) ₂ The material (from Zhongwei new material) is mixed with lithium hydroxide uniformly in a proportion of 1.05, and the mixture is subjected to high-temperature solid-phase reaction in the same way as the temperature rise to obtain Li with the same component _1.05 Ni _0.88 Co _0.09 Al _0.03 O ₂ As a control, a button cell was prepared in the same manner and subjected to electrical property evaluation. The evaluation results are shown in the following table (the electrical properties of the inventive sample are shown in fig. 4, and the electrical properties of the control sample are shown in fig. 5);

it can be seen that the sample of the embodiment has the advantages of high capacity, high first coulombic efficiency and good rate capability, and is incomparable with the control sample prepared by the traditional method.

Comparative example 1: li _1.05 Ni _0.88 Co _0.09 Al _0.03 O ₂

The secondary particle powder obtained by spray drying in example 1 was sintered without pressing according to the high-temperature solid-phase reaction procedure in example 1, and the obtained sample was sieved in a nitrogen glove box through a stainless steel mesh to obtain Li with uniform particles _1.05 Ni _0.88 Co _0.09 Al _0.03 O ₂ The product (shown in figure 3 by scanning electron microscopy, in polycrystalline form) of (a) was prepared into a button cell for electrical property evaluation.

Fig. 6 is a graph comparing the first charge and discharge curves of the comparative example sample and the example 1 sample. It can be seen that the inventive samples have improved performance curves.

Example 2: li _1.0 Ni _0.6 Co _0.3 Al _0.1 O ₂

Raw materials (lithium carbonate, basic nickel carbonate, nickel hydroxide, cobaltous oxide, cobaltosic oxide and aluminum oxide) in a certain proportion are mechanically mixed together to form Li _1.02 Ni _0.6 Co _0.3 Al _0.1 Bulk chemical composition. A certain amount of water was added to make a slurry of 50wt% solid content, while CTAC (cetyltrimethylammonium chloride) was added as a dispersant in an amount of 0.2% by mass as a whole. The D50 of the above slurry was milled to 0.5 microns by wet milling.

The above slurry containing primary particles was made into secondary particle powder by a spray dryer through a centrifugal nozzle. The particle diameter D50 of the particle powder is 40 microns.

The secondary particles were crushed into secondary fine particles having a D50 of 5 μm by a roll crushing method. The secondary microparticles were compressed into a block at 10MPa using a hand press.

In a tubular atmosphere furnace, firstly, under the atmosphere containing 21% of oxygen by volume, the block is heated from room temperature to 500 ℃ per minute at the temperature of 3 ℃ for 10 hours, then the block is switched to the atmosphere containing 40% of oxygen, the block is heated to 700 ℃ for 10 hours, further the block is switched to the atmosphere containing 80% of pure oxygen, the block is heated to the maximum temperature of 820 ℃, the temperature is kept for 20 hours, and finally the block is annealed and naturally cooled after being kept at 600 ℃ for 10 hours. The block was then crushed by roller crushing to give particles with a D50 of 4 μm.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain a product with uniform particles, wherein part of lithium is volatilized due to higher sintering temperature, and the actually measured product is Li _0.99 Ni _0.6 Co _0.3 Al _0.1 O ₂ Preparing it into button cellAnd (5) carrying out electrical property evaluation.

As a control, ni was synthesized according to the method described in CN107681128B _0.6 Co _0.3 Al _0.1 (OH) _x The precursors were mixed with lithium at a stoichiometric ratio of Li/M =1.02 _1.0 Ni _0.5 Co _0.4 Al _0.1 O ₂ And preparing a buckle for electrical performance evaluation. The evaluation results are shown in the following table;

compared with a control sample, the sample of the embodiment 2 has the advantages of high capacity, high first coulombic efficiency and good rate capability.

Example 3: li _0.95 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ 、Li _1.05 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ And Li _1.10 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂

Raw materials (anhydrous lithium hydroxide, nickel sesquioxide, nickel oxalate dihydrate, cobalt oxalate dihydrate, aluminum hydroxide and titanium dioxide) in a certain proportion are mechanically mixed together to respectively form Li _0.95 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 、Li _1.05 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 And Li _1.10 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 Bulk chemical components, identified as examples 3a, 3b and 3c, respectively. A certain amount of water was added to make a slurry with a solid content of 30wt%, respectively, while 1wt% of polyacrylic acid was added as a dispersant. The D50 of the slurry was milled to 0.23 microns by wet milling.

The above slurry containing primary particles was made into secondary particle powder by a spray dryer equipped with a centrifugal disk nozzle. The particle diameter D50 of the particle powder is 50 microns.

The secondary particles were crushed into secondary fine particles having a D50 of 5 μm by a roll crushing method. The secondary microparticles were pressed into briquettes at 10MPa with a hand press.

In a box-type atmosphere furnace, under the atmosphere of 100 volume percent of oxygen, the block is heated from room temperature to 600 ℃ at 5 ℃ per minute for 10 hours, then the temperature is raised to the maximum temperature of 810 ℃, the temperature is maintained for 15 hours, and finally the block is heated at 620 ℃ for 10 hours, annealed and naturally cooled. The blocks were then crushed by hammer milling to give particles with a D50 of 5.4 microns.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain products a, b and c with uniform particles, wherein the actually measured sample respectively comprises the following components: li _0.95 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ 、Li _1.05 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ And Li _1.10 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ And preparing the button cell for electrical performance evaluation. The evaluation results are shown in the following table;

from the electrochemical performances of the three samples, the three samples of example 3 all have higher coulombic efficiency. With the sample of 3b having the best overall electrochemical performance.

Example 4: li _1.05 Ni _0.84 Co _0.12 Al _0.04 O ₂

Mixing raw materials (lithium acetate, basic nickel carbonate, basic cobalt carbonate and aluminum hydroxide) in a certain proportion mechanically to form Li _1.05 Ni _0.84 Co _0.12 Al _0.04 Bulk chemical composition. A certain amount of water was added to make a slurry of 32% solids content, while 1.8% of maleic acid copolymerized ammonium methacrylate was added as a dispersant. The D50 of the above slurry was milled to 0.13 microns by wet milling.

The above slurry containing primary particles was made into secondary particle powder by a spray drying machine equipped with a two-fluid nozzle. The particle diameter D50 of the particle powder is 20 microns.

The secondary particles are crushed into secondary particles with D50 of 4.8 microns by a hammer crushing method. And pressing the secondary microparticles into blocks by using a hydraulic tablet press under 18 MPa.

In a box-type atmosphere furnace, under the atmosphere of 100% oxygen, the block materials are heated from room temperature to 550 ℃ at 3 ℃ per minute and are insulated for 10 hours, then the block materials are heated to the highest temperature of 725 ℃ and are insulated for 15 hours, and finally the block materials are insulated for 10 hours at 600 ℃ and are annealed and naturally cooled. The blocks were then crushed by hammer milling to give particles with a D50 of 5.4 microns.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain Li with uniform particles _1.05 Ni _0.84 Co _0.12 Al _0.04 O ₂ The product is prepared into a button cell for electrical property evaluation. The evaluation results are shown in the following table;

compared with example 1, the coulombic efficiency and the constant current charge rate of the material are not changed greatly after the nickel content is reduced, and the capacity is slightly reduced.

Example 5: li _1.03 Ni _0.9 Co _0.05 Al _0.05 O ₂

Weighing a certain amount of battery grade lithium carbonate with D50=3 microns, adding into water to prepare a suspension with a solid content of 30%, adding 0.5% wt of Tween 40 as a dispersing agent, and wet-grinding to obtain a slurry with D50=0.5 microns.

Commercial grade nano nickel protoxide (200 nm), nano cobaltosic oxide (150 nm) and nano alumina (30 nm) were also dispersed in water to form a suspension with a solid content of 30%, 0.5 wt% of EO-9 was added as a dispersant, and mixed with the above lithium carbonate slurry to form Li _1.03 Ni _0.9 Co _0.05 Al _0.05 Bulk chemical composition. The overall D50 of the slurry was 0.22 microns。

The above slurry containing primary particles was made into secondary particle powder by a spray dryer equipped with a centrifugal nozzle. The particle diameter D50 of the particle powder is 10.1 microns.

The secondary particles were crushed by a ball milling method into secondary fine particles having a D50 of 3 μm. And pressing the secondary microparticles into blocks by using an automatic tablet press under the pressure of 12 MPa.

Slowly heating the block material from room temperature to 550 ℃ per minute at 5 ℃ for 8 hours in a box-type atmosphere furnace in the atmosphere of 100% oxygen, then keeping the temperature at 740 ℃ for 15 hours, and naturally cooling. The block was then crushed by ball milling to give particles with a D50 of 3.8 microns.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain Li with uniform particles _1.03 Ni _0.9 Co _0.05 Al _0.05 O ₂ The product is prepared into a button cell for electrical property evaluation.

As a control, ni was synthesized according to the method described in CN107681128B _0.9 Co _0.05 Al _0.05 (OH) _x After mixing lithium in a stoichiometric ratio of Li/M =1.03 _1.03 Ni _0.9 Co _0.05 Al _0.05 O ₂ And preparing a buckle for electrical performance evaluation. The evaluation results are shown in the following table;

compared with example 1, the material has slightly increased nickel content, the coulombic efficiency and the constant current charge rate are not greatly changed, and the capacity is slightly increased. Since the reactivity of the control sample during co-precipitation was not as high as the sample of example 5, it did not phase well during sintering, resulting in lower first efficiency and constant current charge ratio, and significantly less capacity than example 5.

Example 6: li _1.05 Ni _0.9 Co _0.05 Al _0.05 O ₂

Mixing raw materials (lithium hydroxide monohydrate, nickel oxalate, nickel protoxide, cobalt oxalate and aluminium oxide) together mechanically to form Li _1.05 Ni _0.9 Co _0.05 Al _0.05 Bulk chemistry. A certain amount of water was added to make a slurry with a solid content of 40wt%, while 2wt% of sorbitan fatty acid ester and polyacrylic acid were added as dispersants. The precursor mixture was milled in a bead mill loaded with 0.3mm diameter yttrium stabilized zirconia media. When the primary particle diameter D50 of the mixture was controlled at 150nm, the milling was stopped.

And (3) preparing the slurry containing the primary particles into secondary particle powder with a circular overall appearance and compact interior by a spray dryer. The particle size D50 of the granular powder is 10 microns.

The secondary particles were crushed by a ball milling method into secondary fine particles having a D50 of 3 μm. The secondary microgranules were compressed into briquettes at 12MPa with an automatic tablet press.

Slowly heating the block material to 480 ℃ from room temperature per minute at 5 ℃ in a box type furnace in an oxygen atmosphere of 100 volume percent, preserving heat for 5 hours, slowly heating to 730 ℃ at the maximum temperature per minute at 5 ℃, preserving heat for 30 hours, and naturally cooling. The block was then comminuted by ball milling to give particles having a D50 of 4.2 microns.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain Li with uniform particles _1.06 Ni _0.9 Co _0.05 Al _0.05 O ₂ The product is prepared into a button cell for electrical property evaluation.

As a control, commercial grade Li was purchased _1.05 Ni _0.9 Co _0.05 Al _0.05 O ₂ And preparing the electric discharge to carry out electric performance evaluation. The evaluation results are shown in the following table;

as can be seen from the above table, the results of example 6 are similar to those of example 5, indicating that the raw materials used have less influence on the results. The nickel cobalt lithium aluminate sample prepared by the method is superior to commercial products in coulombic efficiency, constant current charging rate, capacity and multiplying power.

Example 7: li _1.05 Ni _0.84 Co _0.1 Al _0.05 Nb _0.005 O ₂

A certain amount of commercial grade lithium carbonate with D50=6 microns is weighed, and Ni with D50=9.2 microns is synthesized according to the method described in CN107681128B _0.85 Co _0.1 Al _0.05 (OH) _x Precursor of Li _1.05 Ni _0.84 Co _0.1 Al _0.05 Bulk chemical composition. Adding water to prepare a suspension with a solid content of 27%, adding niobium oxide in an amount of 0.005% by mass, adding ammonium dodecylbenzenesulfonate in an amount of 2% by weight as a dispersant, and wet-grinding to obtain a slurry with a D50=0.35 μm.

The above slurry containing primary particles was made into secondary particle powder by a spray dryer equipped with a four-fluid nozzle. The particle size D50 of the granular powder is 7.2 microns.

The secondary particles are crushed into secondary microparticles with a D50 of 2.2 microns by jet milling. And pressing the secondary microparticles into blocks by using a manual-automatic integrated tablet press under 8 MPa.

Slowly heating the block material from room temperature to 520 ℃ per minute at 6 ℃ for 4 hours in a box-type atmosphere furnace in the atmosphere of 100% oxygen, then heating to 630 ℃ for 10 hours, finally, naturally cooling after the temperature is kept for 20 hours at 720 ℃. The bulk material was then comminuted by air-stream comminution to give particles having a D50 of 2.5 μm.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain Li with uniform particles _1.05 Ni _0.84 Co _0.1 Al _0.05 Nb _0.005 O ₂ The product is prepared into a button cell for electrical property evaluation.

As a control, ni was synthesized according to the method described in CN107681128B _0.85 Co _0.1 Al _0.05 (OH) _x The precursors were mixed with lithium at a stoichiometric ratio of Li/M =1.05, and niobium at a stoichiometric ratio of Nb/M =0.005The high-temperature solid-phase reaction is carried out in the same way as the temperature rise, and Li is synchronously prepared _1.05 Ni _0.84 Co _0.1 Al _0.05 Nb _0.005 O ₂ And preparing a buckle for electrical performance evaluation. The evaluation results are shown in the following table;

as can be seen from the table, even if the nickel cobalt lithium aluminate sample prepared by the invention is prepared by using a coprecipitation method, the coulombic efficiency, the constant current charge ratio, the capacity and the rate capability of the sample are all superior to those of the product obtained by the traditional coprecipitation process.

Example 8: li _1.04 Ni _0.84 Co _0.1 Al _0.05 Nb _0.005 O ₂

Weigh an amount of commercial grade nickel cobalt aluminum hydroxide (Ni) with D50=10 microns _0.85 Co _0.1 Al _0.05 OH _x ) Weighing lithium hydroxide with Li: me =1.05, niobium oxide with Nb: me =0.005, adding water to prepare a suspension with a solid content of 30%, adding Tween 40 with 0.5% by weight as a dispersing agent, and grinding the D50 of the slurry to 0.27 μm by a wet grinding method.

The above slurry containing primary particles was made into secondary particle powder by a spray dryer equipped with a four-fluid nozzle. The particle diameter D50 of the particle powder is 9.7 microns.

Weighing a certain amount of commercial grade lithium carbonate with the diameter D50=6 microns, performing dry grinding to obtain lithium carbonate with the diameter D50=1 micron, and mixing the lithium carbonate with the secondary particle powder to form Ni _0.84 Co _0.1 Al _0.05 Nb _0.005 And (4) a bulk chemical formula component.

Slowly heating the block material from room temperature to 520 ℃ per minute at 6 ℃ in a box-type atmosphere furnace in the atmosphere of 100% oxygen for 4 hours, then heating to 630 ℃ for 10 hours, finally, naturally cooling after keeping the temperature for 20 hours at 720 ℃. The blocks were then crushed by ball milling to give particles with a D50 of 4 microns.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain a product with uniform particles, wherein the actual proportion is Li _1.04 Ni _0.84 Co _0.1 Al _0.05 Nb _0.005 O ₂ And preparing the button cell for electrical performance evaluation. The evaluation results are shown in the following table;

compared with the example 7, the lithium element distribution is uneven due to the lithium carbonate dry-mixed in the later period, and the performance of the sample of the example 8 is lower than that of the coprecipitation method.

Example 9: li _1.05 Ni _0.9 Co _0.07 Al _0.025 Mg _0.005 O ₂

Mixing raw materials (lithium carbonate, basic nickel carbonate, basic cobalt carbonate, alumina and magnesium carbonate) together mechanically to form Li _1.05 Ni _0.9 Co _0.07 Al _0.03 O ₂ Bulk chemical composition. Adding water to obtain suspension with solid content of 30%, adding 4.3% (wt) ammonium stearate as dispersant, and wet grinding to obtain slurry with D50=0.21 μm.

The above slurry containing primary particles was made into secondary particle powder by a spray dryer equipped with a four-fluid nozzle. The particle size D50 of the powder was 6.5. Mu.m.

The secondary particles were crushed by roll crushing into secondary fine particles having a D50 of 4.8. Mu.m. And pressing the secondary microparticles into blocks by using a manual-automatic integrated tablet press under 13 MPa.

Slowly heating the block material from room temperature to 480 ℃ per minute at 6 ℃ for 4 hours in a box-type atmosphere furnace in the atmosphere of 100% oxygen, then heating to 610 ℃ for 10 hours, finally, preserving the heat at 700 ℃ for 20 hours, and then naturally cooling. The bulk material was then comminuted by air-stream comminution to give particles having a D50 of 2.5 μm.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain Li with uniform particles _1.05 Ni _0.9 Co _0.07 Al _0.025 Mg _0.005 O ₂ The product is prepared into a button cell for electrical property evaluation.

As a control, ni was synthesized according to the method described in CN107681128B _0.9 Co _0.07 Al _0.03 (OH) _x After mixing lithium and magnesium salts at a stoichiometric ratio of Li/M =1.05 _1.05 Ni _0.9 Co _0.07 Al _0.025 Mg _0.005 O ₂ And preparing a buckle for electrical performance evaluation. The evaluation results are shown in the following table;

as can be seen from the table, the lithium nickel cobalt aluminate sample prepared by the method is superior to the traditional coprecipitation process in the aspects of coulombic efficiency, constant current charging rate, capacity and multiplying power.

Example 10: li _1.05 Ni _0.8 Co _0.15 Al _0.05 O ₂

A proportion of the starting materials (lithium hydroxide monohydrate, commercial nickel cobalt aluminum hydroxide with D50=10 μm) were mechanically mixed together to make up Li _1.05 Ni _0.8 Co _0.15 Al _0.05 Bulk chemical composition. The D50 particle diameter of the raw materials except the nickel cobalt hydroxide is between 3 and 20 micrometers. A certain amount of water was added to make a slurry of 20% solid content, and at the same time, CTAC (cetyltrimethylammonium chloride) was added as a dispersant in an amount of 0.2% by mass in the whole. The D50 of the slurry was milled to 0.4 micron by wet milling.

The above slurry containing primary particles was made into secondary particle powder by a spray dryer equipped with a centrifugal nozzle. The particle diameter D50 of the particle powder is 11 microns. By adjusting spray drying parameters, the overall appearance of the secondary particles is round, and the interior of the secondary particles is dense.

The secondary particles are crushed into secondary microparticles with a D50 of 2.6 microns by jet milling. And pressing the secondary microparticles into a block at 20MPa by using a rolling method.

In a tubular atmosphere furnace, firstly, under an atmosphere containing 21% of oxygen, raising the temperature of the block from room temperature to 450 ℃ per minute at 5 ℃ for 5 hours, then switching to an atmosphere containing 50% of oxygen, raising the temperature to 650 ℃ for 10 hours, finally switching to an atmosphere containing 100% pure oxygen, raising the temperature to 750 ℃ at the highest temperature, preserving the temperature for 20 hours, and then naturally cooling. The bulk was then comminuted by air-stream comminution to give particles having a D50 of 3.5 μm.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain Li with uniform particles _1.05 Ni _0.8 Co _0.15 Al _0.05 O ₂ The product is prepared into a button cell for electrical property evaluation.

As a control example, commercial Li having the same composition was purchased in addition _1.05 Ni _0.8 Co _0.15 Al _0.05 O ₂ The material is used as a control sample, and a button cell is prepared according to the same method for electrical property evaluation. The evaluation results are shown in the following table;

it can be seen that the use of commercial precursor starting materials had little effect on the experimental results, and the sample of example 10 performed almost as well as the control 7.

Example 11: li _1.05 Ni _0.9 Co _0.05 Al _0.05 O ₂

The procedure of example 5 was repeated to prepare secondary granules and secondary fine granules. Dividing the secondary microparticles into three parts, wherein two parts are pressed under 12MPa, and one part of the two pressed parts is placed in a box-type atmosphere furnace, and gradually heating the block material from room temperature to 550 ℃ at 5 ℃ per minute in 100% oxygen atmosphere by using sectional sinteringAfter 8 hours, the mixture is naturally cooled after being preserved at 740 ℃ for 15 hours. Then crushing the block by a ball milling method to obtain particles with D50 of 3.8 microns; the other part adopts a one-step sintering method, the block materials are slowly heated from room temperature to the highest temperature of 740 ℃ per minute at the temperature of 5 ℃ in a box furnace under the atmosphere of 100 volume percent oxygen, the temperature is kept for 20 hours and then the block materials are naturally cooled, the two sintered samples are respectively sieved in a nitrogen glove box through a stainless steel screen mesh to obtain Li with uniform particles _1.03 Ni _0.9 Co _0.05 Al _0.05 O ₂ The product is prepared into a button cell for electrical property evaluation.

As a comparative example, the third part of the secondary micro-particles prepared by the above method is pressed into a block by using the method of CN 1021699981, that is, the powder is manually compacted in a sagger by using a pressing plate, then the powder is placed in a roller bed furnace in an air atmosphere according to the method of CN 1021699981, heated at 470-490 ℃ for 4-6 hours, then naturally cooled to 70-85 ℃ in a cooling area of the furnace, and then the cooled powder is transferred to a ball mill for ball milling, wherein the ball-to-material ratio is 10; and finally, carrying out jet milling and grading on the cooled powder to obtain a final product. Since the material object in CN 1021699981 is NCM, and the maximum sintering temperature of NCM can be much higher than that of NCA, the maximum sintering temperature is adjusted lower here to suit NCA product, not 960-990 ℃. The scanning electron micrograph of this control sample is shown in FIG. 7. And sieving the powder prepared by the three methods to prepare the button cell for performance evaluation. The evaluation results are shown in the following table;

the staged sintering method and the one-step sintering method in example 11 show that the results of the staged sintering method are superior to those of the one-step sintering method, and the first coulombic efficiency, the constant current charge ratio and the specific discharge capacity of the method are all improved. In the case of the staged sintering method of example 11, the morphology of the material obtained in the comparative example was polycrystalline secondary particles in which large-sized primary particles were aggregated, as compared with the comparative example. This may be due to insufficient pressing pressure of the press plate to reach a suitable pressure range. Therefore, the single crystal NCA material with excellent electrochemical performance can be obtained by using reasonable pressing pressure and matching with the step sintering.

Example 12: li _1.05 Ni _0.8 Co _0.15 Al _0.05 O ₂

Mixing the raw materials (lithium carbonate, nickel hydroxide, basic cobalt carbonate, aluminum hydroxide) together mechanically to form Li _1.05 Ni _0.8 Co _0.15 Al _0.05 O ₂ Bulk chemical composition. Adding water to obtain suspension with solid content of 27%, adding 5.8 wt% of ammonium palmitate as dispersant, and wet grinding to obtain slurry with D50=0.17 μm.

The above slurry containing primary particles was made into secondary particle powder by a spray dryer equipped with a centrifugal nozzle. The particle diameter D50 of the particle powder is 12 microns. By adjusting spray drying parameters, the overall appearance of the secondary particles is round, and the interior of the secondary particles is dense.

The secondary particles are crushed into secondary microparticles with a D50 of 2.4 microns by jet milling. The secondary fine particles were pressed into briquettes at 0.3MPa,20MPa and 60MPa, respectively, by a roll-pressing method.

In a tubular atmosphere furnace, under the atmosphere of pure oxygen, the blocks are heated from room temperature to 450 ℃ for 5 hours at 5 ℃ per minute, then heated to 650 ℃ at 5 ℃ per minute and insulated for 10 hours, finally heated to 750 ℃ at 5 ℃ per minute, insulated for 20 hours and then naturally cooled. The bulk was then comminuted by air-stream comminution to give particles having a D50 of 3.5 μm.

Sieving the sintered sample in a nitrogen glove box through a stainless steel sieve to obtain Li with uniform particles _1.05 Ni _0.8 Co _0.15 Al _0.05 O ₂ The product is prepared into a button cell for electrical property evaluation. The evaluation results are shown in the following table;

it can be seen that when different pressing pressures are used, if the pressures are too low, the material cannot form a single crystal, and the capacity retention of the polycrystalline material in the cycle is less than that of the single crystal material, as shown in fig. 8; if too much pressure is used, the electrochemical performance of the material will be greatly affected, although the material is able to form a single crystal. When the pressing pressure is in a suitable range, a single crystal material excellent in electrochemical properties can be obtained.

Claims

1. A single crystal lithium nickel cobalt aluminum oxide having the general formula:

LiaNixCoyAlzO ₂ :M _b

wherein a =0.95-1.15, x =0.50-0.99, y =0.01-0.50, x + y + z =1 and z >0;

b≤0.02；

m is an optional doping element and is one or more selected from Na, K, ca, mg, ti, V, cr, cu, mn, zn, ga, in, ta, ge, ag, au, zr, nb and W;

the single crystalline lithium nickel cobalt aluminum oxide is prepared by a method comprising:

(c) Pulverizing to obtain powder with particle diameter D50 of 0.5-5 μm;

(d) Pressing the powder into a block under the pressure of 1-35MPa, and reacting the block to form the lithium nickel cobalt aluminum oxide with a layered structure in an oxygen-containing atmosphere by using a high-temperature solid phase method, wherein the high-temperature solid phase method adopts a gradient heating method for heat treatment, and comprises the steps of firstly preserving heat at 420-580 ℃ for 2-10 hours, and then preserving heat at 580-700 ℃ for 2-15 hours; finally, preserving the heat for 5 to 10 hours at the temperature of between 720 and 900 ℃;

2. The single crystal lithium nickel cobalt aluminum oxide of claim 1, wherein the lithium nickel cobalt aluminum oxide is selected from the group consisting of Li _1.05 Ni _0.88 Co _0.09 Al _0.03 O ₂ 、Li _1.0 Ni _0.6 Co _0.3 Al _0.1 O ₂ 、Li _0.95 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ 、Li _1.05 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ 、Li _1.10 Ni _0.59 Co _0.3 Al _0.1 Ti _0.006 O ₂ 、Li _1.05 Ni _0.84 Co _0.12 Al _0.04 O ₂ 、Li _1.03 Ni _0.9 Co _0.05 Al _0.05 O ₂ 、Li _1.05 Ni _0.9 Co _0.05 Al _0.05 O ₂ 、Li _1.05 Ni _0.84 Co _0.1 Al _0.05 Nb _0.005 O ₂ 、Li _1.04 Ni _0.8 ₄ Co _0.1 Al _0.05 Nb _0.005 O ₂ 、Li _1.05 Ni _0.9 Co _0.07 Al _0.025 Mg _0.005 O ₂ 、

Li _1.05 Ni _0.8 Co _0.15 Al _0.05 O ₂ Or a mixture of two or more thereof.

3. The single crystal lithium nickel cobalt aluminum oxide according to claim 1 or 2, wherein the high temperature solid phase method is a gradient heating method comprising the steps of first maintaining the temperature at 450-520 ℃ for 4-8 hours, and then maintaining the temperature at 620-680 ℃ for 5-10 hours; finally, the temperature is kept at 750-850 ℃ for 6-8 hours.

4. The monocrystalline lithium nickel cobalt aluminum oxide of claim 1, wherein:

a＝1.00-1.10；x＝0.70-0.95；y＝0.02-0.40；b＝0-0.008。

5. the monocrystalline lithium nickel cobalt aluminum oxide of claim 1, wherein:

a＝1.02-1.08；x＝0.8-0.90；y＝0.03-0.30；b＝0.001-0.007。

6. the method of claim 1, wherein:

a＝1.02-1.08；x＝0.8-0.90；y＝0.03-0.30；b＝0.003-0.006。

7. the single crystal lithium nickel cobalt aluminum oxide according to claim 1 or 2, wherein the pressing pressure in step (d) is 1.5 to 20MPa.

8. The single crystal lithium nickel cobalt aluminum oxide according to claim 1 or 2, wherein the pressing pressure of step (d) is 2 to 10MPa.

9. Use of the single crystalline lithium nickel cobalt aluminum oxide of any one of claims 1 to 8 as an electrode for a lithium ion battery.