CN108321366B - Coating method for improving electrochemical performance of high-nickel ternary nickel-cobalt-manganese positive electrode material - Google Patents

Coating method for improving electrochemical performance of high-nickel ternary nickel-cobalt-manganese positive electrode material Download PDF

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CN108321366B
CN108321366B CN201711459381.XA CN201711459381A CN108321366B CN 108321366 B CN108321366 B CN 108321366B CN 201711459381 A CN201711459381 A CN 201711459381A CN 108321366 B CN108321366 B CN 108321366B
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张冉
张宏立
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Hefei Gotion High Tech Power Energy Co Ltd
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Hefei Guoxuan High Tech Power Energy Co Ltd
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Abstract

The invention discloses a coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material, which comprises the following steps: dissolving a titanium source in a solvent to form a solution, adding a lithium source to dissolve the solution, and then adding citric acid to obtain a mixed solution; uniformly dispersing the high-nickel ternary nickel-cobalt-manganese positive electrode material in a solvent, adding the mixed solution, uniformly mixing, and then carrying out hydrothermal reaction or solvothermal reaction to obtain a reaction solution; evaporating the reaction solution to be gelatinous, and drying to obtain a positive electrode material mixture; and calcining the positive electrode material mixture to obtain the high-nickel ternary nickel cobalt manganese positive electrode material with the lithium titanate coating layer on the surface. The coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese positive electrode material is simple in process, low in cost and good in repeatability, the obtained coating layer is high in crystallinity, small in particle size and good in uniformity, and the specific discharge capacity, the cycle performance and the rate performance of the high-nickel ternary nickel-cobalt-manganese positive electrode material are improved.

Description

Coating method for improving electrochemical performance of high-nickel ternary nickel-cobalt-manganese positive electrode material
Technical Field
The invention relates to the technical field of lithium ion battery anode materials, in particular to a coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese anode material.
Background
With the increase in demand for high-energy batteries, researchers have been stimulated to research lithium ion batteries having high performance. Among them, the high nickel ternary positive electrode material attracts attention with the advantage of high energy density, but the high nickel material has limited practical application due to the disadvantages of strict storage conditions, poor cycle performance, poor thermal stability, and the like.
The surface coating is an effective method for solving the problems of irreversible capacity loss, cycle deterioration and the like of the battery, and the existence of the coating layer hinders direct contact between electrolyte and an active material, reduces side reactions, inhibits the dissolution of metal ions, reduces the polarization degree of an electrode, maintains the stable structure of the material, and thus improves the electrochemical performance of the electrode.
Li4Ti5O12Has spinel structure, Fd3m space group, and diffusion coefficient of 10-6cm2s-1As a coating layer, L i is favored+Diffusion, high stability, smooth discharge voltage plateau, resistance to overcharge and overdischarge, L i4Ti5O12Has the special structural characteristic of zero strain, can avoid the damage to the structure caused by the repeated change of the electrode volume, and can maintain the structural stability even under high charging voltage, in addition, L i4Ti5O12Capable of avoiding decomposition of the electrolytic solution, dissolution of metal ions, formation of an interfacial film of solid electrolyte moreover, L i4Ti5O12The lithium ion battery is a negative electrode material, can make up for some defects of a positive electrode material, and can contribute to partial capacity, which has important significance for improving the capacity of the battery.
Researchers often coat the surface of the material by using traditional methods such as a ball milling method, a coprecipitation method, a sol-gel method and the like. However, these methods have certain defects, such as high price of the precursor, complex pretreatment process and great difficulty in industrial production, and the electrochemical performance of the cathode material is very sensitive to crystallinity, phase purity, particle morphology, uniformity and the like, which are closely related to the synthesis method and synthesis conditions of the material. For example, chinese patent publication No. CN106450216A discloses a modified nickel-cobalt-aluminum positive electrode material and a preparation method thereof, and the preparation of the nickel-cobalt-aluminum-lithium ternary positive electrode material includes: mixing a titanium source and a nickel-cobalt-aluminum precursor, carrying out hydrothermal or solvothermal reaction, filtering and washing to obtain an amorphous titanium oxide-coated nickel-cobalt-aluminum precursor, and finally mixing and sintering the precursor, a lithium source and a solvent again to obtain the modified nickel-cobalt-aluminum cathode material. However, in these technical steps, the hydrothermal or solvothermal reaction is followed by filtration and washing and then mixing with a lithium source, and the obtained product has poor uniformity and a non-uniform coating layer.
Disclosure of Invention
Based on the technical problems in the background art, the invention provides a coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material, which has the advantages of simple process, low cost, good repeatability, high crystallinity of the obtained coating layer, small particle size and good uniformity, improves the discharge specific capacity, the cycle performance and the rate capability of the high-nickel ternary nickel-cobalt-manganese positive electrode material, and obviously optimizes the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese positive electrode material.
The invention provides a coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material, which comprises the following steps of:
s1, dissolving a titanium source in a solvent to form a solution, adding a lithium source for dissolving, and then adding citric acid to obtain a mixed solution;
s2, uniformly dispersing the high-nickel ternary nickel-cobalt-manganese positive electrode material into a solvent, adding the mixed solution in the S1, uniformly mixing, and then carrying out hydrothermal reaction or solvothermal reaction to obtain a reaction solution;
s3, evaporating the reaction solution in the S2 to be in a gel state, and drying to obtain a positive electrode material mixture;
and S4, calcining the positive electrode material mixture in the S3 to obtain the high-nickel ternary nickel cobalt manganese positive electrode material with the lithium titanate coating layer on the surface.
Preferably, in S1, the titanium source is one or more of tetrabutyl titanate, tetraethyl titanate, isopropyl titanate, titanium oxide, titanium protoxide, titanium tetrachloride, hexafluorotitanic acid, cobalt titanate, nickel titanate, and manganese titanate; the lithium source is one or a mixture of more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium chloride, lithium fluoride, lithium phosphate, lithium hydrogen phosphate and lithium dihydrogen phosphate.
Preferably, in S1 and S2, the solvent is one or more of water, ethanol, isopropanol, n-butanol, ethylene glycol, and acetone.
Preferably, in S2, the high-nickel ternary nickel-cobalt-manganese positive electrode material has a chemical formula of L iNixCoyMn1-x-yO2Wherein x is more than or equal to 0.5 and less than 1, y is more than 0 and less than or equal to 0.5 and 0<x+y<1。
Preferably, in S2, the high-nickel ternary nickel-cobalt-manganese cathode material is uniformly dispersed in the solvent, and is stirred magnetically for 30-60min after the mixed solution in S1 is added dropwise, and the stirring speed is 300-600 rpm.
Preferably, in S2, the temperature of the hydrothermal reaction or the solvothermal reaction is 150-200 ℃ and the time is 12-24 h.
Preferably, in S3, the reaction solution in S2 is evaporated to a gel state under stirring at 60 to 80 ℃.
Preferably, in S3, the drying is vacuum drying at 60-100 deg.C for 6-12 h.
Preferably, in S4, the specific process of calcining is: heating to 600-800 ℃ at the heating rate of 3-5 ℃/min in the air atmosphere or the oxygen atmosphere, and calcining for 3-8 h.
Preferably, in S4, in the high-nickel ternary nickel cobalt manganese positive electrode material having a lithium titanate coating layer on the surface, the mass ratio of lithium titanate to the high-nickel ternary nickel cobalt manganese positive electrode material is 0.005-0.1: 1.
the coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese cathode material improves the existing preparation method of the cathode material coated on the surface of the lithium ion battery, mixes a titanium source, the high-nickel ternary nickel-cobalt-manganese cathode material and a lithium source in a liquid phase, and prepares the high-nickel ternary nickel-cobalt-manganese cathode material coated with lithium titanate on the surface by adopting a hydrothermal method or a solvothermal method. Compared with the high-nickel ternary nickel-cobalt-manganese positive electrode material with the surface coated with lithium titanate prepared by the traditional sol-gel method, the high-nickel ternary nickel-cobalt-manganese electrode material with the surface coated with lithium titanate prepared by the hydrothermal method or the solvothermal method has the beneficial effects that:
1. by carrying out surface coating modification on the high-nickel ternary nickel-cobalt-manganese cathode material, direct contact between the electrolyte and the active material can be prevented, and side reactions are reduced.
2. A lithium titanate coating layer with a zero-strain structure is generated on the surface of the high-nickel ternary nickel-cobalt-manganese positive material, so that the stability of the electrode structure can be maintained, and L i is promoted+Diffusion, inhibition of metal ion dissolution, and reduction of electrode polarization degree.
3. The surface of the high-nickel ternary nickel cobalt manganese anode material is coated by a hydrothermal method or a solvothermal method, products are collected by evaporation, citric acid is added as a chelating agent, the anode material is directly coated on the surface of the anode material, the anode material which has ideal high-crystallization pure phase, small and uniform particle size and uniform surface coating can be prepared under the conditions of high temperature and high pressure, the discharge capacity, the cycle performance and the rate capability of the high-nickel ternary nickel cobalt manganese anode material are obviously improved, the first discharge specific capacity is up to 210mAh/g and is 15.1mAh/g higher than that of a sample prepared by a sol-gel method, and the electrochemical performance of the high-nickel ternary nickel cobalt manganese anode material is optimized.
4. The method is simple and has good repeatability, and compared with the high-nickel ternary nickel-cobalt-manganese cathode material with the lithium titanate coating layer on the surface prepared by the sol-gel method, the discharge specific capacity, the cycle performance and the rate capability of the electrode material are improved.
Drawings
FIG. 1 shows a high nickel ternary nickel cobalt manganese positive electrode material L iNi0.8Co0.1Mn0.1O2XRD patterns of 1 wt% lithium titanate coated by a solvothermal method in example 1 and 1 wt% lithium titanate coated by a sol-gel method in example 2;
FIG. 2 shows a high nickel ternary nickel cobalt manganese positive electrode material L iNi0.8Co0.1Mn0.1O2A cycle performance diagram of the example 1 after coating 1 wt% of lithium titanate by a solvothermal method and the example 2 after coating 1 wt% of lithium titanate by a sol-gel method;
FIG. 3 shows a high nickel ternary nickel cobalt manganese positive electrode material L iNi0.8Co0.1Mn0.1O2Multiplying power performance graphs of the example 1 that the solvent thermal method is used for coating 1 wt% of lithium titanate and the example 2 that the sol-gel method is used for coating 1 wt% of lithium titanate;
FIG. 4 shows a high nickel ternary nickel cobalt manganese positive electrode material L iNi0.8Co0.1Mn0.1O2Alternating current impedance diagrams after 50 weeks of cycles of example 1 coating 1 wt% lithium titanate by the solvothermal method and example 2 coating 1 wt% lithium titanate by the sol-gel method.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to specific examples.
Example 1
The invention provides a coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material, which comprises the following steps of:
s1, preparing high-nickel ternary nickel cobalt manganese anode material L iNi according to lithium titanate0.8Co0.1Mn0.1O2The mass ratio of (1): 100, dissolving tetrabutyl titanate in 30ml of absolute ethyl alcohol, dissolving the tetrabutyl titanate in magnetic stirring at 400rpm to form a solution, adding lithium acetate to dissolve the solution, and then adding citric acid to obtain a mixed solution;
s2, 5g of high-nickel ternary nickel-cobalt-manganese positive electrode material L iNi0.8Co0.1Mn0.1O2Uniformly dispersing in 50ml of absolute ethyl alcohol, fully stirring for 30min by magnetic force, dropwise adding the mixed solution in S1, stirring for 30min by magnetic force, uniformly mixing, transferring to a 100ml hydrothermal reaction kettle, placing in a drying box, and reacting for 24h at 180 ℃ to obtain a reaction solution;
s3, taking out the reaction solution in the S2, putting the reaction solution into a beaker, putting the beaker on a magnetic heating stirrer, stirring and evaporating the reaction solution to be gelatinous at 70 ℃, adding the gelatinous reaction solution into a vacuum drying oven, and drying the gelatinous reaction solution for 12 hours at 80 ℃ to obtain a positive electrode material mixture;
s4, heating the positive electrode material mixture in the S3 to 800 ℃ at the heating rate of 5 ℃/min in the air atmosphere, and calcining for 5h to obtain the high-nickel ternary nickel cobalt manganese positive electrode material L iNi with the surface provided with 1 wt% of lithium titanate coating layer0.8Co0.1Mn0.1O2。
According to an active substance (high-nickel ternary nickel cobalt manganese anode material L iNi with 1 wt% lithium titanate coating layer on the surface)0.8Co0.1Mn0.1O2) Coating and drying acetylene black and PVDF at a mass ratio of 85:10:5, assembling an electrode material into a CR2025 type button cell in a glove box filled with argon atmosphere, wherein a negative electrode is a metal lithium sheet, a diaphragm is Celgard2300, an electrolyte is L iPF6 (consisting of EC, EMC and DMC and having a volume ratio of 1:1:1) of 1 mol/L, and a constant-current charge-discharge test of the cell is carried out by using a Wuhan blue CT2001A cell cycle test system, and the test result is shown in figure 2.
Example 2
A coating method for the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material comprises the following steps:
s1, preparing high-nickel ternary nickel cobalt manganese anode material L iNi according to lithium titanate0.8Co0.1Mn0.1O2The mass ratio of (1): 100, dissolving tetrabutyl titanate in 30ml of absolute ethyl alcohol, dissolving the tetrabutyl titanate in magnetic stirring at 400rpm to form a solution, adding lithium acetate to dissolve the solution, and then adding citric acid to obtain a mixed solution;
s2, 5g of high-nickel ternary nickel-cobalt-manganese positive electrode material L iNi0.8Co0.1Mn0.1O2Uniformly dispersing in 50ml of absolute ethyl alcohol, performing magnetic stirring for 30min, dropwise adding the mixed solution in S1, performing magnetic stirring for 30min, performing stirring evaporation at 70 ℃ to obtain gel, adding into a vacuum drying oven, and drying at 80 ℃ for 12h to obtain a positive electrode material mixture;
s3, heating the positive electrode material mixture in the S2 to 800 ℃ at the heating rate of 5 ℃/min in the air atmosphere, and calcining for 5h to obtain the high-nickel ternary nickel cobalt manganese positive electrode material L iNi with the surface provided with 1 wt% of lithium titanate coating layer0.8Co0.1Mn0.1O2。
According to the active material (high nickel ternary nickel cobalt manganese anode material L iNi with 1 wt% lithium titanate coating layer)0.8Co0.1Mn0.1O2) Coating and drying acetylene black and PVDF at a mass ratio of 85:10:5, assembling an electrode material into a CR2025 type button cell in a glove box filled with argon, wherein the cathode is a metal lithium sheet, the diaphragm is Celgard2300, the electrolyte is L iPF6 (consisting of EC, EMC and DMC in a volume ratio of 1:1:1) of 1 mol/L, and a constant-current charge-discharge test of the cell is carried out by using a Wuhan blue CT2001A cell cycle test system, and the test result is shown in figure 2.
XRD (X-ray diffraction) tests are carried out on the high-nickel ternary nickel-cobalt-manganese cathode materials with 1 wt% of lithium titanate coating layers on the surfaces, which are prepared in the example 1 and the example 2, the XRD results are shown in figure 1, and as can be seen from figure 1, the samples obtained in the example 1 and the example 2 both have good layered structures, and the lattice parameters of XRD spectrums are shown in Table 1:
table 1 shows XRD spectrogram lattice parameters
Figure BDA0001529929910000071
As can be seen from Table 1, the solvothermal coating of example 1 has a larger I (003)/I (104), a smaller degree of cation rearrangement, and a more stable lattice structure.
As can be seen from fig. 2, the high-nickel ternary nickel cobalt manganese positive electrode material prepared by the solvothermal method in example 1 and having a lithium titanate coating layer on the surface thereof by 1 wt% has a higher specific discharge capacity than the high-nickel ternary nickel cobalt manganese positive electrode material prepared by the sol-gel method in example 2 and having a lithium titanate coating layer on the surface thereof by 1 wt%, the capacity retention ratio of the sample prepared by the solvothermal method in example 1 after 1C cycle for 50 weeks is 91.1%, the capacity retention ratio of the sample prepared by the sol-gel method in example 2 is 88%, and the high-nickel ternary nickel cobalt manganese positive electrode material L iNi prepared by the solvothermal method in example 1 and having a lithium titanate coating layer on the surface0.8Co0.1Mn0.1O2The cycle performance is better.
FIG. 3 shows a high nickel ternary nickel cobalt manganese positive electrode material L iNi0.8Co0.1Mn0.1O2FIG. 3 shows the ratio performance of the 1 wt% lithium titanate coated by the solvothermal method in example 1 and the 1 wt% lithium titanate coated by the sol-gel method in example 2, wherein L iNi coated by the solvothermal method0.8Co0.1Mn0.1O2The rate performance is superior to that of a sol-gel method, the specific discharge capacity at each rate is higher than that of the latter, the capacity of the material prepared by the sol-gel method is seriously attenuated under large-rate discharge, and the specific discharge capacity at 5C rate of the material prepared by the solvothermal method is higher than that of the latter 18.9mAh/g, so that the excellent rate performance is shown.
FIG. 4 shows a high nickel ternary nickel cobalt manganese positive electrode material L iNi0.8Co0.1Mn0.1O2AC impedance diagram of the example 1 of coating 1 wt% lithium titanate by solvothermal method and the example 2 of coating 1 wt% lithium titanate by sol-gel method after 50 weeks of circulation, and it can be seen from FIG. 4 that L iNi of coating by solvothermal method0.8Co0.1Mn0.1O2The charge transfer resistance and SEI film resistance are both less than L iNi coated by sol-gel method0.8Co0.1Mn0.1O2Proved by the evidence that the solvothermal coating can reduce the charge transfer resistance and SEI film resistance of the electrode material and has higher L i+Diffusivity, more electrode kinetic behavior.
Compared with a sol-gel method, the solvothermal method is used for preparing the high-nickel ternary cathode material L iNi0.8Co0.1Mn0.1O2The upper coating lithium titanate has more uniform coating layer, higher L i+Higher efficiency of extraction L i+The diffusivity and the smaller impedance are improved, and the high-nickel ternary cathode material L iNi of the lithium ion battery is improved0.8Co0.1Mn0.1O2Electrochemical performance.
Example 3
The invention provides a coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material, which comprises the following steps of:
s1, dissolving a titanium source in a solvent to form a solution, adding a lithium source for dissolving, and then adding citric acid to obtain a mixed solution;
s2, uniformly dispersing the high-nickel ternary nickel-cobalt-manganese positive electrode material into a solvent, adding the mixed solution in the S1, uniformly mixing, and carrying out hydrothermal reaction to obtain a reaction solution;
s3, evaporating the reaction solution in the S2 to be in a gel state, and drying to obtain a positive electrode material mixture;
and S4, calcining the positive electrode material mixture in the S3 to obtain the high-nickel ternary nickel cobalt manganese positive electrode material with the lithium titanate coating layer on the surface.
Example 4
The invention provides a coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material, which comprises the following steps of:
s1, dissolving a titanium source in water to form a solution, adding a lithium source for dissolving, and then adding citric acid to obtain a mixed solution; wherein the titanium source is a mixture of tetraethyl titanate and isopropyl titanate, and the weight ratio of the tetraethyl titanate to the isopropyl titanate is 3: 2; the lithium source is lithium dihydrogen phosphate;
s2, uniformly dispersing the high-nickel ternary nickel cobalt manganese positive electrode material in water, dropwise adding the mixed solution in the S1, magnetically stirring for 30min at the magnetic stirring speed of 600rpm, uniformly mixing, transferring the mixture to a hydrothermal reaction kettle, and carrying out hydrothermal reaction for 24h at the temperature of 150 ℃ to obtain a reaction solution, wherein the chemical formula of the high-nickel ternary nickel cobalt manganese positive electrode material is L iNi0.6Co0.2Mn0.2O2；
S3, stirring and evaporating the reaction solution in the S2 at the temperature of 60 ℃ to form a gel, and performing vacuum drying at the temperature of 100 ℃ for 6 hours to obtain a positive electrode material mixture;
s4, heating the positive electrode material mixture in the S3 to 600 ℃ at the heating rate of 5 ℃/min in the air atmosphere, and calcining for 8 hours to obtain the high-nickel ternary nickel cobalt manganese positive electrode material with the lithium titanate coating layer on the surface; wherein, in the high-nickel ternary nickel cobalt manganese anode material with the lithium titanate coating layer on the surface, the mass ratio of the lithium titanate to the high-nickel ternary nickel cobalt manganese anode material is 0.005: 1.
example 5
The invention provides a coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material, which comprises the following steps of:
s1, dissolving a titanium source in ethanol to form a solution, adding a lithium source to dissolve the solution, and then adding citric acid to obtain a mixed solution; wherein the titanium source is tetrabutyl titanate; the lithium source is a mixture of lithium carbonate and lithium nitrate, and the weight ratio of the lithium carbonate to the lithium nitrate is 3: 2;
s2, uniformly dispersing the high-nickel ternary nickel cobalt manganese positive electrode material into ethanol, dropwise adding the mixed solution in the S1, magnetically stirring for 60min at the magnetic stirring speed of 300rpm, uniformly mixing, transferring the mixture to a hydrothermal reaction kettle, and carrying out solvothermal reaction at the temperature of 200 ℃ for 12h to obtain a reaction solution, wherein the chemical formula of the high-nickel ternary nickel cobalt manganese positive electrode material is L iNi0.6Co0.2Mn0.2O2；
S3, stirring and evaporating the reaction solution in the S2 at 80 ℃ to form a gel, and performing vacuum drying at 60 ℃ for 12 hours to obtain a positive electrode material mixture;
s4, heating the cathode material mixture in the S3 to 800 ℃ at a heating rate of 3 ℃/min in an oxygen atmosphere, and calcining for 3h to obtain the high-nickel ternary nickel cobalt manganese cathode material with a lithium titanate coating layer on the surface; in the high-nickel ternary nickel cobalt manganese positive electrode material with the lithium titanate coating layer on the surface, the mass ratio of lithium titanate to the high-nickel ternary nickel cobalt manganese positive electrode material is 0.1: 1.
example 6
The invention provides a coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material, which comprises the following steps of:
s1, dissolving a titanium source in a solvent to form a solution, adding a lithium source for dissolving, and then adding citric acid to obtain a mixed solution; wherein the titanium source is a mixture of tetrabutyl titanate, cobalt titanate and nickel titanate, and the weight ratio of tetrabutyl titanate, cobalt titanate and nickel titanate is 3:4: 2; the lithium source is a mixture of lithium carbonate, lithium acetate and lithium phosphate, and the weight ratio of the lithium carbonate to the lithium acetate to the lithium phosphate is 4: 3: 2; the solvent is a mixture of ethanol and isopropanol, and the volume ratio of the ethanol to the isopropanol is 3: 2;
s2, uniformly dispersing the high-nickel ternary nickel cobalt manganese positive electrode material into a solvent, dropwise adding the mixed solution in the S1, magnetically stirring for 50min at the magnetic stirring speed of 500rpm, uniformly mixing, transferring the mixture into a hydrothermal reaction kettle, and carrying out solvothermal reaction at 170 ℃ for 20h to obtain a reaction solution, wherein the chemical formula of the high-nickel ternary nickel cobalt manganese positive electrode material is L iNi0.8Co0.1Mn0.1O2(ii) a The solvent is a mixture of ethanol and isopropanol, and the volume ratio of the ethanol to the isopropanol is 3: 2;
s3, stirring and evaporating the reaction solution in the S2 at 70 ℃ to form a gel, and performing vacuum drying at 80 ℃ for 10 hours to obtain a positive electrode material mixture;
s4, heating the cathode material mixture in the S3 to 700 ℃ at a heating rate of 4 ℃/min in an oxygen atmosphere, and calcining for 6h to obtain the high-nickel ternary nickel cobalt manganese cathode material with a lithium titanate coating layer on the surface; the mass ratio of the lithium titanate to the high-nickel ternary nickel-cobalt-manganese positive electrode material is 0.06: 1.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims (10)

1. A coating method for improving the electrochemical performance of a high-nickel ternary nickel-cobalt-manganese positive electrode material is characterized by comprising the following steps of:
s1, dissolving a titanium source in a solvent to form a solution, adding a lithium source for dissolving, and then adding citric acid to obtain a mixed solution;
s2, uniformly dispersing the high-nickel ternary nickel-cobalt-manganese positive electrode material into a solvent, adding the mixed solution in the S1, uniformly mixing, and then carrying out hydrothermal reaction or solvothermal reaction to obtain a reaction solution;
s3, evaporating the reaction solution in the S2 to be in a gel state, and drying to obtain a positive electrode material mixture;
and S4, calcining the positive electrode material mixture in the S3 to obtain the high-nickel ternary nickel cobalt manganese positive electrode material with the lithium titanate coating layer on the surface.
2. The coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese positive electrode material according to claim 1, wherein in S1, the titanium source is one or a mixture of more of n-tetrabutyl titanate, tetraethyl titanate, isopropyl titanate, titanium oxide, titanium protoxide, titanium tetrachloride, hexafluorotitanic acid, cobalt titanate, nickel titanate, and manganese titanate; the lithium source is one or a mixture of more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium chloride, lithium fluoride, lithium phosphate, lithium hydrogen phosphate and lithium dihydrogen phosphate.
3. The coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese cathode material according to claim 1 or 2, wherein in S1 and S2, the solvent is one or a mixture of water, ethanol, isopropanol, n-butanol, ethylene glycol and acetone.
4. The coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese positive electrode material as claimed in claim 1 or 2, wherein the chemical formula of the high-nickel ternary nickel-cobalt-manganese positive electrode material is L iNi in S2xCoyMn1-x-yO2Wherein x is more than or equal to 0.5 and less than 1, y is more than 0 and less than or equal to 0.5 and 0<x+y<1。
5. The coating method for improving the electrochemical performance of the high-nickel ternary nickel cobalt manganese positive electrode material as claimed in claim 1 or 2, wherein the high-nickel ternary nickel cobalt manganese positive electrode material is uniformly dispersed in a solvent in S2, the mixed solution in S1 is added dropwise, and then the mixture is magnetically stirred for 30-60min at a speed of 300-600 rpm.
6. The coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese cathode material as claimed in claim 1 or 2, wherein the temperature of the hydrothermal reaction or the solvothermal reaction in S2 is 150-200 ℃ and the time is 12-24 h.
7. The coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese cathode material as claimed in claim 1 or 2, wherein in S3, the reaction solution in S2 is stirred and evaporated to be in a gel state at 60-80 ℃.
8. The coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese cathode material according to claim 1 or 2, wherein in S3, the drying is vacuum drying, the temperature of the vacuum drying is 60-100 ℃, and the time is 6-12 h.
9. The coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese positive electrode material according to claim 1 or 2, wherein in S4, the specific process of calcination is as follows: heating to 600-800 ℃ at the heating rate of 3-5 ℃/min in the air atmosphere or the oxygen atmosphere, and calcining for 3-8 h.
10. The coating method for improving the electrochemical performance of the high-nickel ternary nickel-cobalt-manganese positive electrode material according to claim 1 or 2, wherein in the S4, in the high-nickel ternary nickel-cobalt-manganese positive electrode material having the lithium titanate coating layer on the surface, the mass ratio of the lithium titanate to the high-nickel ternary nickel-cobalt-manganese positive electrode material is 0.005-0.1: 1.
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