CN113896253B - Ternary positive electrode material and preparation method and application thereof - Google Patents

Abstract

The invention discloses a ternary positive electrode material, a preparation method and application thereof, wherein the preparation method comprises the steps of mixing a ternary precursor, a lithium source and a metal doping agent, taking an organic solvent as a dispersion medium, mixing, wet-milling and drying to obtain a mixture; ultrasonic infiltration is carried out on the mixture by adopting a fluorine-containing organic solvent, and then granulating and tabletting are carried out, so as to obtain mixed particles; the three-section temperature programming is adopted to sinter, crush and grade the mixed particles at high temperature to prepare the ternary positive electrode material, and the mixing mode of the metal doping agent and the precursor and the ultrasonic infiltration of the fluorine-containing organic solvent are changed, so that the obtained ternary positive electrode material is uniformly doped with metal elements by matching with the three-section temperature programming, the doping effect is good, the residual alkali content on the surface of the material is effectively reduced, and the ternary positive electrode material has excellent electrochemical performance.

Description

Ternary positive electrode material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a ternary positive electrode material, the ternary positive electrode material prepared by the preparation method, and application of the ternary positive electrode material serving as an active material in a lithium ion battery.

Background

The nickel-cobalt-manganese (NCM) ternary material of the lithium ion battery is a novel high-performance positive electrode material, and has the advantages of high capacity, good rate capability and the like. In the context of the current increasing energy density demands of power batteries, it is considered to be one of the most promising positive electrode materials for lithium ion batteries.

The traditional high-nickel ternary positive electrode material is prepared by adopting a mechanical high-mixing high-temperature solid phase method, the ternary positive electrode material prepared by adopting the method is usually accompanied with the problem of overhigh content of surface residual alkali, and the excessive residual factors of a lithium source are removed, and the other important factor is usually that the active oxygen ions on the surface of the positive electrode material can be mixed with CO in the air₂ And H₂ O reacts to generate carbonate radical, and lithium ions migrate from the bulk to the surface to form Li₂ CO₃ Resulting in that. Too high a surface residual alkali content can reduce the compatibility of the ternary material and the binder, resulting in jelly-like formation during the slurry mixing process; in addition, excessive residual alkali can cause the reaction of absorbing moisture of the material at high temperature, so that the cycle performance is deteriorated, the bulge and the bulge occur, and the safety performance of the lithium battery is reduced.

Aiming at the problems, the conventional modification mode adopted by the nickel-cobalt-manganese ternary positive electrode material is to improve the cycle stability and discharge capacity of the nickel-cobalt-manganese ternary positive electrode material by doping metal cations, wherein commonly used doping metals are Al, mg, zr and the like, and the metal cations generally play a role in changing the valence state of transition metal ions, improving the electronic conductivity, reducing the concentration of Ni ions on the surface, inhibiting cation mixing, lattice distortion and the like to stabilize the structure of the material, so that the electrochemical performance of the ternary material is improved.

In order to ensure the doping effect, the doping materials are required to be uniformly distributed on the surface of the ternary material precursor, but the traditional doping mode is to mechanically and physically mix the doping materials with the precursor and a lithium source by using a high-speed mixer, wherein the doping amount is generally added according to the proportion of 200-10000ppm, and on one hand, the doping metal amount is extremely low compared with the content of the raw materials; on the other hand, mechanical high mixing is in the case of mixing non-uniformity, so that the doped metal is not uniformly distributed in the material. This results in insignificant improvement in the properties of the ternary material.

Disclosure of Invention

In view of the above, the present invention is necessary to provide a preparation method of a ternary positive electrode material, which mixes wet milling and cooperates with a fluorine-containing organic solvent to ultrasonically infiltrate a precursor, thereby improving doping effect, and effectively reducing residual alkali content on the surface of the ternary positive electrode material, so that the obtained ternary positive electrode material has excellent electrochemical performance.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

the invention provides a preparation method of a ternary positive electrode material, which comprises the following steps:

mixing the ternary precursor, a lithium source and a metal dopant, taking an organic solvent as a dispersion medium, mixing, wet milling and drying to obtain a mixture;

ultrasonic infiltration is carried out on the mixture by adopting a fluorine-containing organic solvent, and then granulating and tabletting are carried out, so as to obtain mixed particles;

and adopting three-stage temperature programming to sinter, crush and grade the mixed particles at high temperature to prepare the ternary positive electrode material.

Further, the ternary precursor is selected from nickel cobalt manganese hydroxide, and has a chemical formula of Ni_x Co_y Mn_1-x-y (OH)₂ Wherein x is more than 0 and less than 1, y is more than 0 and less than 1, and x+y is more than 1;

the lithium source is selected from lithium hydroxide or lithium carbonate.

Further, the metal dopant is selected from AlCl₃ 、MgCl₂ 、ZrCl₄ One or a mixture of two or more of them.

Further, the addition amount of the metal dopant is 600-1000ppm.

Further, the organic solvent is selected from one or more than two of methanol, ethanol and diethyl ether;

the process of the mixed wet grinding specifically comprises the following steps: ball-to-material ratio 16-20:1, the ball milling rotating speed is 300-500r/min, and the ball milling time is 1-2h.

Further, the adding amount of the fluorine-containing organic solvent is 3-5% of the mass of the mixture, wherein the fluorine-containing organic solvent is obtained by dissolving PVDF in a solvent, the solvent is selected from NMP, DMAc or DMF, and the mass ratio of PVDF to the solvent is 0.5-1:1.

further, the ultrasonic frequency of the ultrasonic infiltration is not lower than 25kHz, and the time is 2-4 hours;

the pressure of the granulating and tabletting is 0.2-0.4MPa, and the particle size of the mixed particles is 5-10mm.

Further, the three-stage temperature programming step specifically comprises the following steps: heating to 160-210 ℃ at a speed of 1-3 ℃/min, then preserving heat for 3-5h, heating to 300-350 ℃ at a speed of 1-3 ℃/min, preserving heat for 3-5h, and heating to 850-920 ℃ at a speed of 3-5 ℃/min, preserving heat for 10-12h; cooling at a rate of 5-8deg.C/min.

The invention further provides a ternary positive electrode material which is prepared by adopting the preparation method according to any one of the above.

The invention further provides application of the ternary positive electrode material in preparation of ternary lithium ion batteries.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, the ternary precursor, the lithium source, the metal dopant and the organic solvent are mixed and wet-ground, so that the problem of uneven solid phase mixing in the prior art is effectively solved, the doped metal elements are more uniformly distributed on the surface of the ternary precursor, and the doping effect is improved. Meanwhile, the fluorine-containing organic solvent fully infiltrates the mixture by utilizing the ultrasonic infiltration effect, so that the doping uniformity of metal elements is improved, and the doping effect is improved; and the fluorine-containing organic solvent can provide fluorine element, so that secondary particles formed by granulating can effectively reduce the residual alkali content on the surface of the material.

In addition, three-section temperature programming is adopted in the preparation method for high-temperature sintering, wherein the first heat preservation area effectively removes redundant organic solvent, the second heat preservation area releases HF and fully reacts with mixed particles to ensure that fluorine ions enter a material lattice, and the third heat preservation area enables mixed particles to be formed in a crystal grain mode, so that the ternary positive electrode material with excellent electrochemical performance is prepared.

Drawings

FIG. 1 is a block diagram of a process for preparing a ternary positive electrode material according to a preferred embodiment of the present invention;

FIG. 2 is an XRD pattern of the ternary cathode material prepared in example 4 of the present invention;

fig. 3 is an SEM image of the ternary cathode material prepared in example 4 of the present invention.

Detailed Description

In order that the invention may be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments that are illustrated below. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

The first aspect of the present invention discloses a preparation method of a ternary cathode material, as shown in fig. 1, comprising the following steps:

mixing the ternary precursor, a lithium source and a metal dopant, taking an organic solvent as a dispersion medium, mixing, wet milling and drying to obtain a mixture;

ultrasonic infiltration is carried out on the mixture by adopting a fluorine-containing organic solvent, and then granulating and tabletting are carried out, so as to obtain mixed particles;

and adopting three-stage temperature programming to sinter, crush and grade the mixed particles at high temperature to prepare the ternary positive electrode material.

According to the preparation method, the ternary precursor, the lithium source and the metal dopant are mixed, an organic solvent is used as a dispersion medium, mixing and wet grinding are carried out, the metal elements are uniformly distributed on the surface of the mixture after drying, the organic solvent can be selected by distillation and drying without special limitation, and the ternary precursor and the lithium source are not dissolved and do not react with the ternary precursor and the lithium source as long as the condition that the metal dopant can be dissolved is met. The mixed powder is infiltrated by the fluorine-containing organic solvent in an ultrasonic manner, so that the uniformity degree of metal doping can be improved, the doping effect is improved, meanwhile, the fluorine-containing organic solvent can provide fluorine for the ternary material, so that residual alkali on the surface of the ternary positive electrode material is reduced, three-section temperature programming sintering is combined, wherein the first heat preservation region effectively removes redundant organic solvent, the second heat preservation region releases HF and fully reacts with mixed particles, fluorine ions are ensured to enter a material lattice, and the third heat preservation region enables mixed particles to be formed in a crystal grain mode, so that the ternary positive electrode material with excellent electrochemical performance is prepared.

Further, the ternary precursor, lithium source, etc. described herein are all raw materials conventionally used in the art to prepare ternary cathode materials, and are not particularly limited, in one or more embodiments of the inventionThe ternary precursor is selected from nickel cobalt manganese hydroxide, and has a chemical formula of Ni_x Co_y Mn_1-x-y (OH)₂ Wherein x is more than 0 and less than 1, y is more than 0 and less than 1, and x+y is more than 1;

the lithium source is selected from lithium hydroxide or lithium carbonate.

Further, the metal dopant described herein may be a metal dopant compound conventionally used in the art for the preparation of ternary cathode materials, and it should be noted that the metal dopant is selected so as to be soluble in an organic solvent, and thus in one or more embodiments of the present invention, the metal dopant is selected from AlCl₃ 、MgCl₂ 、ZrCl₄ One or a mixture of two or more of them.

Further, due to the fact that the doping effect is improved in the preparation method, the doping amount of the metal dopant can be improved obviously, and in one or more embodiments of the invention, the adding amount of the metal dopant is 600-1000ppm based on the mass of the ternary positive electrode material.

Further, the aforementioned organic solvent, which is not particularly limited and may be adjusted according to the choice of the metal dopant, is used as a dispersion medium in the preparation method, and is selected from one or a mixture of two or more of methanol, ethanol, and diethyl ether in one or more embodiments of the present invention;

further, the process of mixing wet milling is not particularly limited, and the ball-to-material ratio, the rotation speed, the time and the like can be adjusted as required, so long as the purpose of uniform mixing can be achieved, and in one or more embodiments of the present invention, the process of mixing wet milling specifically includes: ball-to-material ratio 16-20:1, the ball milling rotating speed is 300-500r/min, and the ball milling time is 1-2h.

According to a further scheme, the adding amount of the fluorine-containing organic solvent is 3-5% of the mass of the mixture, wherein the fluorine-containing organic solvent is obtained by dissolving PVDF in a solvent, the solvent is selected from NMP, DMAc or DMF, and the mass ratio of the PVDF to the solvent is 0.5-1:1. and the mixture is subjected to ultrasonic infiltration by using a fluorine-containing organic solvent, so that the uniformity of metal doping is improved, the doping effect is improved, the PVDF-containing organic solvent is fully infiltrated into the mixture to provide fluorine, and then the PVDF is bonded to form secondary particles, so that the residual alkali content on the surface of the ternary positive electrode material is effectively reduced.

Further, the process of ultrasonic infiltration and granulating and tabletting is not particularly limited and can be adjusted according to the needs, and in one or more embodiments of the invention, the ultrasonic frequency of ultrasonic infiltration is not lower than 25KHz for 2-4h;

the pressure of the granulating and tabletting is 0.2-0.4MPa, the particle size of the mixed particles is 5-10mm, and gaps among materials can be increased by adopting the large particles for sintering, so that sufficient circulation of oxygen is ensured, and the materials are fully reacted.

According to a further scheme, the method comprises the steps of three-stage temperature programming sintering, and removing redundant organic solvent in the fluorine-containing organic solvent through a first heat preservation area; the second heat preservation area decomposes fluorine-containing substances to release HF, so that the HF is fully contacted and reacted with the mixed particles, and fluorine ions are ensured to successfully enter a material lattice; the third heat preservation area ensures the mixed particle crystal grain forming, so that the ternary positive electrode material with excellent electrochemical performance is obtained. In one or more embodiments of the present invention, the three-stage temperature programming step specifically includes: heating to 160-210 ℃ at a speed of 1-3 ℃/min, then preserving heat for 3-5h, heating to 300-320 ℃ at a speed of 1-3 ℃/min, preserving heat for 3-5h, and heating to 850-920 ℃ at a speed of 3-5 ℃/min, preserving heat for 10-12h; cooling to 60 ℃ at a speed of 5-8 ℃/min.

The second aspect of the invention provides a ternary positive electrode material prepared by the preparation method according to the first aspect of the invention. The ternary positive electrode material prepared by the preparation method has the advantages of uniform doping of metal elements, improved doping amount, low content of surface residual alkali and excellent electrochemical performance.

The third aspect of the invention provides application of the ternary cathode material in preparing a ternary lithium ion battery. The ternary positive electrode material is used as a positive electrode active material to prepare a positive electrode, the positive electrode, a negative electrode, a diaphragm and electrolyte are assembled to obtain a ternary lithium ion battery, the positive electrode and the ternary lithium ion battery are conventional preparation means in the field, and the preparation methods are not specifically described herein, so that the obtained lithium ion battery has excellent performance.

Example 1

50g of Ni is taken_0.5 Co_0.20 Mn_0.3 (OH)₂ 20.86g of Li₂ CO₃ And 0.0425g MgCl₂ Adding the mixture into ball milling equipment, and ball milling for 1h at a rotating speed of 300r/min by taking 100mL of absolute methanol and 100mL of absolute ethanol as ball milling media, wherein the ball material ratio is 20:1, so as to obtain ball milling slurry;

drying the ball-milling slurry at 120 ℃ for 6 hours to obtain a mixture;

mixing the obtained mixture with 2.1270g of fluorine-containing organic solvent, and carrying out ultrasonic infiltration for 4 hours at an ultrasonic frequency of 30KHz, wherein the fluorine-containing organic solvent is PVDF (polyvinylidene fluoride) in mass ratio: nmac=1: 1, an organic solvent;

adding the material subjected to ultrasonic infiltration into a granulator to granulate into granules with the particle size of 10mm, wherein the granulating pressure is 0.2MPa;

placing the prepared particles in a box furnace, heating to 170 ℃ at a speed of 1 ℃/min, preserving heat for 3 hours, heating to 350 ℃ at a speed of 3 ℃/min, preserving heat for 5 hours, and heating to 920 ℃ at a speed of 5 ℃/min, preserving heat for 10 hours; cooling to 60 ℃ at the speed of 8 ℃/min to obtain a calcined product;

and (3) carrying out jet milling on the calcined product to obtain the NCM523 ternary positive electrode material, wherein in the jet milling, the gas pressure is controlled to be 0.6MPa, the rotation frequency of the classifying wheel is 50Hz, and the feeding speed is 100g/s.

Example 2

50g of Ni is taken_0.6 Co_0.20 Mn_0.2 (OH)₂ 23.60g of LiOH H₂ O and 0.0425g MgCl₂ 0.0434g AlCl₃ And 0.0312g of ZrCl₄ Adding the mixture into ball milling equipment, and ball milling for 2 hours at a rotating speed of 500r/min by taking 200mL of diethyl ether as a ball milling medium, wherein the ball material ratio is 20:1, so as to obtain ball milling slurry;

drying the ball-milling slurry at 120 ℃ for 8 hours to obtain a mixture;

mixing the obtained mixture with 3.6858g of fluorine-containing organic solvent, and carrying out ultrasonic infiltration for 2 hours at ultrasonic frequency of 35KHz, wherein the fluorine-containing organic solvent is PVDF (polyvinylidene fluoride) in mass ratio: dmf=1: 1, an organic solvent;

adding the material subjected to ultrasonic infiltration into a granulator to granulate into granules with the particle size of 5mm, wherein the granulating pressure is 0.4MPa;

placing the prepared particles in a box furnace, heating to 160 ℃ at a heating rate of 3 ℃/min, preserving heat for 5 hours, heating to 320 ℃ at a heating rate of 1 ℃/min, preserving heat for 3 hours, and heating to 890 ℃ at a heating rate of 3 ℃/min, preserving heat for 11 hours; cooling to 60 ℃ at the speed of 8 ℃/min to obtain a calcined product;

after the calcined product was subjected to jet milling, an NCM622 ternary positive electrode material was obtained, wherein in the jet milling, the gas pressure was controlled to be 0.8MPa, the classification wheel rotation frequency was 50Hz, and the charging rate was 150g/s.

Example 3

50g of Ni is taken_0.75 Co_0.10 Mn_0.15 (OH)₂ 23.55g of LiOH H₂ O and 0.0723g AlCl₃ 0.0312g ZrCl₄ Adding the mixture into ball milling equipment, taking 180mL of anhydrous diethyl ether and 20mL of ethanol as a ball milling medium, and performing ball milling for 2 hours at the rotating speed of 400r/min at the ball material ratio of 20:1 to obtain ball milling slurry;

drying the ball-milling slurry at 120 ℃ for 10 hours to obtain a mixture;

mixing the obtained mixture with 2.2096g of fluorine-containing organic solvent, and carrying out ultrasonic infiltration for 3 hours at an ultrasonic frequency of 28KHz, wherein the fluorine-containing organic solvent is PVDF (polyvinylidene fluoride) in mass ratio: nmp=1: 1, an organic solvent;

adding the material subjected to ultrasonic infiltration into a granulator to granulate into granules with the particle size of 5mm, wherein the granulating pressure is 0.4MPa;

placing the prepared particles in a box furnace, heating to 210 ℃ at a heating rate of 2 ℃/min, preserving heat for 5 hours, heating to 320 ℃ at a heating rate of 1 ℃/min, preserving heat for 5 hours, and heating to 850 ℃ at a heating rate of 3 ℃/min, preserving heat for 12 hours; cooling to 60 ℃ at a speed of 5 ℃/min to obtain a calcined product;

and (3) carrying out jet milling on the calcined product to obtain the NCM751015 ternary positive electrode material, wherein in the jet milling, the gas pressure is controlled to be 0.8MPa, the rotation frequency of the classifying wheel is 30Hz, and the feeding speed is 100g/s.

Example 4

50g of Ni is taken_0.75 Co_0.10 Mn_0.15 (OH)₂ 23.55g of LiOH H₂ O and 0.0723g AlCl₃ Adding the mixture into ball milling equipment, and ball milling for 2 hours at a rotating speed of 500r/min by taking 200mL of anhydrous diethyl ether as a ball milling medium, wherein the ball material ratio is 20:1, so as to obtain ball milling slurry;

drying the ball-milling slurry at 120 ℃ for 10 hours to obtain a mixture;

mixing the obtained mixture with 3.6811g of fluorine-containing organic solvent, and carrying out ultrasonic infiltration for 44h at an ultrasonic frequency of 30KHz, wherein the fluorine-containing organic solvent is PVDF (polyvinylidene fluoride) in mass ratio: nmp=1: 1, an organic solvent;

adding the material subjected to ultrasonic infiltration into a granulator to granulate into granules with the particle size of 8mm, wherein the granulating pressure is 0.3MPa;

placing the prepared particles in a box furnace, heating to 210 ℃ at a heating rate of 2 ℃/min, preserving heat for 5 hours, heating to 320 ℃ at a heating rate of 2 ℃/min, preserving heat for 5 hours, and heating to 850 ℃ at a heating rate of 3 ℃/min, preserving heat for 10 hours; cooling to 60 ℃ at a speed of 5 ℃/min to obtain a calcined product;

and (3) carrying out jet milling on the calcined product to obtain the NCM751015 ternary positive electrode material, wherein in the jet milling, the gas pressure is controlled to be 0.8MPa, the rotation frequency of the classifying wheel is 50Hz, and the feeding speed is 120g/s.

Example 5

The same embodiment as in example 1 was employed, except that the metal dopant was ZrCl₄ The doping amount was 600ppm.

Example 6

The same embodiment as in example 1 is employed except that the metal dopant is AlCl₄ The doping amount was 1000ppm.

Example 7

The same embodiment as in example 2 was used, except that the fluorine-containing organic solvent was added in an amount of 3% by mass of the mixture, and the fluorine-containing organic solvent was composed of PVDF: nmp=0.5: 1 are mixed to prepare the composite material.

Example 8

This example uses the same embodiment as example 2, except that the fluorine-containing organic solvent is added in an amount of 5% by mass of the mixture, and the fluorine-containing organic solvent is composed of PVDF: dmac=0.7: 1 are mixed to prepare the composite material.

Comparative example 1

50g of Ni was weighed out_0.75 Co_0.10 Mn_0.15 (OH)₂ 23.55g of LiOH H₂ O and 0.0723g AlCl₃ Mixing by a high-speed mixer, placing into a box-type furnace, heating to 210 ℃ at a speed of 2 ℃/min, then preserving heat for 5 hours, heating to 320 ℃ at a speed of 2 ℃/min, preserving heat for 5 hours, and heating to 850 ℃ at a speed of 3 ℃/min, preserving heat for 10 hours; cooling to 60 ℃ at a speed of 5 ℃/min; in jet milling, the gas pressure is controlled to be 0.8MPa, and the rotation frequency of the classifying wheel is 50Hz; the charging speed is 120g/s, and the NCM751015 ternary positive electrode material is obtained by classification.

Comparative example 2

50g of Ni was weighed out_0.75 Co_0.10 Mn_0.15 (OH)₂ 23.55g of LiOH H₂ O, after being mixed by a high-speed mixer, is put into a box-type furnace, is heated to 210 ℃ at a speed of 2 ℃/min, is then kept for 5 hours, is heated to 320 ℃ at a speed of 2 ℃/min, is kept for 5 hours, and is then heated to 850 ℃ at a speed of 3 ℃/min, and is kept for 10 hours; cooling to 60 ℃ at a speed of 5 ℃/min; in jet milling, the gas pressure is controlled to be 0.8MPa, and the rotation frequency of the classifying wheel is 50Hz; the charging speed is 120g/s, and the NCM751015 ternary positive electrode material is obtained by classification.

Comparative example 3

The same embodiment as in example 4 was used, except that: 50g of Ni_0.75 Co_0.10 Mn_0.15 (OH)₂ 23.55g of LiOH H₂ O and 0.0723g AlCl₃ Mixing by a high-speed mixer to obtain a mixturePowder material.

Comparative example 4

The same embodiment as in example 4 was used, except that: ultrasonic infiltration of fluorine-containing organic solvent is not carried out, namely, mixed wet grinding and dried powder are directly subjected to three-stage temperature programming sintering.

Comparative example 5

The same embodiment as in example 4 was used, except that: three-section temperature programming sintering is not adopted, and the temperature is raised to 850 ℃ at a temperature rise rate of 3 ℃/min, and the temperature is kept for 10 hours; cooling to 60 ℃ at a speed of 5 ℃/min to obtain a calcined product.

Test case

The ternary positive electrode materials in examples 1-4 and comparative examples 1-5 were assembled into 2032 type button cells, respectively, with metallic lithium as the negative electrode to ensure adequate lithium ion supply, and the positive electrode composition was ternary: conductive carbon black: binder = 8:1:1 (mass ratio), test voltage ranges of 3.0-4.2V, test results are shown in table 1.

Table 1 lithium ion battery performance test results

As can be seen from comparative examples 2 and 1 in table 1, the metal doping can effectively improve the first discharge capacity and the cycling stability of the material, but the conventional process is not obvious in improvement of the performance, and the residual alkali content of the material is high. As can be seen from comparative example 1 and example 4, the ternary material preparation method of the invention can effectively reduce the content of residual alkali on the surface, and under the condition that the doping elements and doping amounts are the same, the metal cation doping effect of the ternary material preparation method of the invention is more obvious, and the first capacity and the cycle retention rate are improved compared with those of the conventional ternary material preparation process. As can be seen from a comparison of example 4 and comparative examples 3 to 5, the surface residual alkali content and the electrochemical properties of the materials are not as good as those of example 4.

Further, as can be seen from fig. 2, the ternary positive electrode material is successfully prepared and obtained by the method, and the crystal face peak intensity I (003): i (104) >1.2 shows that the lithium nickel mixed discharge degree is lower, the (111) and (012) are not overlapped, the crystal growth is better, and the SEM image in fig. 3 is combined to show that the polycrystalline ternary material is generated, no obvious foreign matters exist on the particle surface, the residual alkali is lower, the particle uniformity is better, the growth is uniform, and the particle dispersibility is better. And through practical test characterization, the structures of the comparative example 4 and the comparative example 4 can obviously improve the metal doping effect through ultrasonic infiltration of the fluorine-containing organic solvent, so that the metal doping effect is more uniform, and the electrochemical performance of the positive electrode material is improved.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (10)

1. The preparation method of the ternary positive electrode material is characterized by comprising the following steps of:

mixing the ternary precursor, a lithium source and a metal dopant, taking an organic solvent as a dispersion medium, mixing, wet milling and drying to obtain a mixture;

ultrasonic infiltration is carried out on the mixture by adopting a fluorine-containing organic solvent, and then granulating and tabletting are carried out, so as to obtain mixed particles, wherein the fluorine-containing organic solvent is obtained by dissolving PVDF in a solvent, and the solvent is selected from NMP, DMAc or DMF;

and adopting three-stage temperature programming to sinter, crush and grade the mixed particles at high temperature to prepare the ternary positive electrode material.

2. The method of claim 1, wherein the ternary precursor is selected from the group consisting of nickel cobalt manganese hydroxides having the chemical formula Ni_x Co_y Mn_1-x-y (OH)₂ Wherein x is more than 0 and less than 1, y is more than 0 and less than 1, and x+y is more than 1;

the lithium source is selected from lithium hydroxide or lithium carbonate.

3. The method of claim 1, wherein the metal dopant is selected from the group consisting of AlCl₃ 、MgCl₂ 、ZrCl₄ One or a mixture of two or more of them.

4. The method of claim 1, wherein the metal dopant is added in an amount of 600 to 1000ppm.

5. The method according to claim 1, wherein the organic solvent is one or a mixture of two or more selected from the group consisting of methanol, ethanol, and diethyl ether;

the process of the mixed wet grinding specifically comprises the following steps: ball-to-material ratio 16-20:1, the ball milling rotating speed is 300-500r/min, and the ball milling time is 1-2h.

6. The preparation method according to claim 1, wherein the fluorine-containing organic solvent is added in an amount of 3 to 5% by mass of the mixture; in the fluorine-containing organic solvent, the mass ratio of PVDF to the solvent is 0.5-1:1.

7. the method according to claim 1, wherein the ultrasonic frequency of the ultrasonic infiltration is not lower than 25kHz for 2 to 4 hours;

the pressure of the granulating and tabletting is 0.2-0.4MPa, and the particle size of the mixed particles is 5-10mm.

8. The preparation method according to claim 1, wherein the three-stage temperature programming step comprises the following specific steps: heating to 160-210 ℃ at a speed of 1-3 ℃/min, then preserving heat for 3-5h, heating to 300-350 ℃ at a speed of 1-3 ℃/min, preserving heat for 3-5h, and heating to 850-920 ℃ at a speed of 3-5 ℃/min, preserving heat for 10-12h; cooling at a rate of 5-8deg.C/min.

9. A ternary cathode material prepared by the method of any one of claims 1-8.

10. The use of the ternary cathode material according to claim 9 in the preparation of a ternary lithium ion battery.

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