CN111029556B

CN111029556B - Multi-modified nickel-rich ternary material and preparation method and application thereof

Info

Publication number: CN111029556B
Application number: CN201911421627.3A
Authority: CN
Inventors: 王波; 李文; 王秋君; 孙会兰; 张迪
Original assignee: Hebei University of Science and Technology
Current assignee: Hebei University of Science and Technology
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2021-02-02
Anticipated expiration: 2039-12-31
Also published as: CN111029556A

Abstract

The invention belongs to the technical field of battery materials, and particularly relates to a multiple modified nickel-rich ternary material as well as a preparation method and application thereof. The invention adopts a bulk phase doping and surface coating multiple modification method, mainly stabilizes the structure of an NCM622 material through iron and lanthanum double-ion co-doping modification, improves the ionic conductivity of the material, reduces the cation mixed-discharge phenomenon of an NCM622 type ternary material in the circulation process, reduces the corrosion of HF generated by electrolyte to an electrode material through coating conductive polymer modification, inhibits side reaction generated by an interface, forms an optimal solid electrolyte interface film, and further improves the circulation performance and the rate capability of the material.

Description

Multi-modified nickel-rich ternary material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of battery materials, and particularly relates to a multiple modified nickel-rich ternary material as well as a preparation method and application thereof.

Background

The ternary material of the lithium ion battery is a good anode material which can be used in electronic products due to the advantages of good high voltage tolerance, high specific capacity, low cobalt content and the like. Ternary material lithium nickel cobalt manganese oxide Li (Ni)_xCo_yMn_1-x-y)O₂The nickel salt, the cobalt salt and the manganese salt are used as raw materials, and the safety is high compared with a lithium cobaltate battery. Wherein the anode ternary material LiNi_0.6Co_0.2Mn_0.12O₂The (NCM622) lithium ion power battery has the advantages of high energy density, good rate performance, excellent cycle performance, low price, long service life, low energy consumption, no public hazard, no memory effect, small self-discharge, small internal resistance, less pollution and the like, and can be widely applied to the fields of electric automobiles, mobile phones, notebook computers, video cameras, digital cameras, electric automobiles, energy storage, aerospace and the like. However, the NCM622 type ternary material is prone to structural collapse during charge and discharge cycles, which reduces cycle performance and rate capability and hinders the progress of commercialization.

Bulk phase doping is a well-known way to enhance the stability of the material structure and improve the electrochemical performance of the material, but may cause the problems of insufficient cycle performance and poor performance under large rate of the electrode material, and the structure collapse phenomenon still exists.

The surface coating can improve the electrochemical performance of the anode material, can avoid direct contact between active substances in the material and electrolyte, reduce the erosion of the electrolyte to the electrode material, improve the service life and the cycle stability of the material, does not influence the normal insertion and separation of lithium ions, and reduces the ionic conductivity and the specific capacity of the material. In addition, the traditional coating method has poor effect, the bonding capability of the coating layer and the body is not strong, or the internal structure and the external representation of the material are not uniform, so that the performance of the material is reduced, and the coating modification on the surface of the material is difficult.

Disclosure of Invention

Aiming at the problems that the conventional NCM622 type anode material is easy to collapse in structure and poor in traditional bulk phase doping and coating effects, the invention provides a preparation method of a multiple modified nickel-rich ternary material.

The invention also provides a multiple modified nickel-rich ternary material.

The invention also provides application of the multiple modified nickel-rich ternary material in photocatalytic hydrogen production.

In order to achieve the purpose of the invention, the embodiment of the invention adopts the following technical scheme:

a preparation method of a multi-modified nickel-rich ternary material comprises the steps of taking an NCM622 type nickel-rich ternary material as a substrate, doping an iron element and a lanthanum element in situ, and then coating a conductive polymer coating on the surface of the material by taking sugar as a chelating agent.

The preparation method firstly synthesizes the iron (Fe) lanthanum (La) codoped NCM622 material in situ, and Fe and La cations exist simultaneously, so that Fe can be used³⁺Doping to reduce Li⁺/Ni²⁺Can also make La be mixed and discharged³⁺The support effect is achieved to enlarge the interlayer spacing of the ternary material and increase Li⁺Diffusion efficiency, and capacity and cycle performance of the material are improved. And a coating layer formed by saccharides and a conductive polymer inhibits HF generated by electrolyte from corroding the iron-lanthanum co-doped NCM622 material, and improves the cycle performance and rate performance of the obtained nickel-rich ternary material. The invention combines doping and cladding, which can not only improve the discharge specific capacity of the nickel-rich ternary material, but also improve the cycle stability and rate capability.

Preferably, the preparation method specifically comprises the following steps:

step a, dissolving nickel sulfate, cobalt sulfate and manganese sulfate in water to prepare a sulfate mixed solution, wherein the molar ratio of the nickel sulfate to the cobalt sulfate to the manganese sulfate is (5.5-6.5) to (1.8-2.2), and the sulfate radical concentration in the sulfate mixed solution is 1.5-2.5 mol/L; mixing the sulfate mixed solution with diluted ammonia water to obtain a primarily mixed solution, wherein the volume of the diluted ammonia water is 40-60% of that of the primarily mixed solution, and NH is contained in the diluted ammonia water₃The concentration of (A) is 0.4-0.6 mol/L;

b, adding ferric salt and lanthanum salt into the sulfate mixed solution to obtain a five-element mixed salt solution, wherein the weight of the ferric salt and the lanthanum salt is 1-5% of the total weight of the nickel sulfate, the cobalt sulfate and the manganese sulfate;

step c, adding an alkali solution and ammonia water into the quinary mixed salt solution obtained in the step b, mixing to obtain a mixed solution, and aging for 12-15 hours after the reaction is finished, wherein OH in the alkali solution^-Concentration of1-3 mol/L, wherein the volume of the alkali solution is 20-30% of the volume of the mixed solution; NH in the ammonia solution₃The concentration of the ammonia water solution is 4-6 mol/L, and the volume of the ammonia water solution is 5-7% of the volume of the mixed solution;

d, filtering the mixed solution after the reaction in the step c, drying the obtained filter residue, adding a lithium salt with the molar ratio of the lithium salt to nickel ions in the filter residue being (1-1.2) to 0.6, mixing, preheating for 4-6 hours at the temperature of 400-600 ℃ in an oxygen flow of 0.1-0.2L/min, and sintering for 10-20 hours at the temperature of 600-900 ℃ in an oxygen flow of 0.1-0.2L/min to obtain the iron-lanthanum co-doped NCM622 material;

e, dispersing the iron-lanthanum co-doped NCM622 material, a conductive polymer and sugar in an absolute ethanol solution, adjusting the pH to 10-12 by using ammonia water, adding a hydrogen peroxide aqueous solution which is 12.5-37.5% of the volume of the obtained solution, heating and stirring until the solvent volatilizes, drying and calcining to obtain the iron-lanthanum co-doped NCM622 material; the concentration of the iron-lanthanum co-doped NCM622 material in absolute ethyl alcohol is 40-60 g/L, the mass of the sugar is 10-30% of that of the iron-lanthanum co-doped NCM622 material, the mass of the conductive polymer is 1-5% of that of the iron-lanthanum co-doped NCM622 material, and the mass percentage concentration of the aqueous hydrogen peroxide solution is 25-35%.

Preferably, the preparation method firstly adopts a coprecipitation method, firstly iron salt and lanthanum salt are doped into the NCM622 material through the step b, the obtained product is fixed and formed in an alkaline environment formed by aqueous alkali and ammonia water through the step c, the operation is simple, the control is accurate, the finished product is powdery, the spherical integrity is good, and the particle size is uniformly distributed between 10 mu m and 15 mu m. And d, heating twice, preheating at 400-600 ℃ to volatilize water, and sintering at 600-900 ℃ to release substances such as carbon dioxide and the like in the product.

Then adopting a wet chemical coating method, taking sugar as a chelating agent, coating a conductive polymer coating on the surface of the iron-lanthanum co-doped NCM622 material, and then taking a hydrogen peroxide solution as a catalyst and an oxidant to promote low-valent ion Ni²⁺To high valence ion Ni⁴⁺By lowering the cationic Li⁺/Ni²⁺The degree of miscibility is then tightened by calcining the saccharide, conductive polymer and bulk of the iron lanthanum co-doped NCM622 material. The use of wet chemical coating and calcination can make the coating uniform and firm.

The multiple modified nickel-rich ternary material prepared by the invention is analyzed by a scanning electron microscope and an X-ray diffraction analyzer, and the preferable preparation method is adopted to successfully dope Fe and La double elements into the NCM622 spherical material, so that the dispersion is uniform, and the secondary reaction of Fe and La does not occur. The surface of the iron-lanthanum co-doped NCM622 material is observed by a transmission electron microscope to have a uniform coating layer with the thickness of about 5-20 mu m, and the phase composition of the lattice fringes is proved to be a mixed phase of saccharides and a conductive polymer. XRD refinement results show that the iron-lanthanum co-doped NCM622 material still keeps a good layered structure after doping and cladding, the cation mixed-arrangement degree is reduced, the a axis, the c axis and the V are obviously enlarged, the interlayer spacing is enlarged, and the Li is favorably promoted⁺Diffusion of (2).

Preferably, the molar ratio of the nickel sulfate, the cobalt sulfate and the manganese sulfate is 6: 2.

Preferably, the iron salt is at least one of iron oxide, iron sulfate, iron nitrate and ferrous sulfate.

Preferably, the lanthanum salt is at least one of lanthanum oxide, lanthanum nitrate, lanthanum carbonate and lanthanum acetate.

Preferably, the alkali solution is an aqueous sodium hydroxide solution.

Preferably, the lithium salt is at least one of lithium hydroxide, lithium carbonate and lithium acetate.

Preferably, the sugar is at least one of glucose, sucrose, fructose, lactose and maltose.

Preferably, the conductive polymer is at least one of polyacetylene, polythiophene, polypyrrole, polyaniline, polyphenylene ethylene and polydiyne.

Preferably, the operation of adding the alkali solution and the ammonia water in the step c is to finish the addition of the alkali solution and the ammonia water within 11-13 h.

Preferably, the filter residue obtained in the step d is dried in vacuum at 100-120 ℃ for 8-10 h.

Preferably, the method for dispersing the iron-lanthanum co-doped NCM622 material, the conductive polymer and the sugar in the absolute ethanol solution in the step e is as follows: dispersing the iron-lanthanum co-doped NCM622 material in absolute ethyl alcohol to prepare a suspension with the concentration of 80-120 g/L, carrying out ultrasonic treatment until the suspension is uniformly dispersed, adding the sugar, and then adding the absolute ethyl alcohol suspension of the conductive polymer at the speed of 10-30 ml/h.

Preferably, the heating and stirring in the step e is continuously stirring at the rotating speed of 200-600 rpm/min at 40-60 ℃.

Preferably, the drying in the step e is drying for 9-12 hours at the temperature of 90-110 ℃. The drying can be preferably carried out in a vacuum environment at 90-110 ℃, so that the drying efficiency is improved.

Preferably, the calcination in the step e is carried out at 200-300 ℃ for 4-6 h. The main structure of the conductive polymer can not be damaged by low-temperature sintering at the temperature, the conductive polymer is prevented from chemically reacting with other substances at high temperature, and meanwhile, the sugar and conductive polymer mixed coating is more tightly combined with the body of the iron and lanthanum codoped NCM622 material.

Preferably, the calcination in step e is carried out under the protection of inert gas to avoid the oxidative decomposition of the coating.

The embodiment of the invention also provides a multiple modified nickel-rich ternary material, which is prepared by the preparation method of the multiple modified nickel-rich ternary material.

The embodiment of the invention also provides application of the nickel-rich ternary material in preparation of a lithium ion battery. The materials before and after modification are assembled into a button cell in a glove box, and then the electrochemical performance is tested by using a blue test system and a Princeton electrochemical workstation, and the result shows that the multiple modified nickel-rich ternary material obtained by the invention is 10C (1C is 200 mA-g)^-1) The discharge specific capacity of the material is 8.3 percent higher than that of the unmodified material under a large multiplying power, and the capacity of the unmodified material is sharply reduced after the material is circulated for 150 circles under the high-temperature condition of 60 ℃; the inventionThe obtained multiple modified nickel-rich ternary material still has 99.1% of single-turn coulombic efficiency after circulating for 300 turns under the current density of 1C, and the capacity attenuation is only 18.4%. The first-circle specific discharge capacity of the multi-modified nickel-rich ternary material obtained by the invention is higher than that of an unmodified material by 16 mAh.g^-1The electrochemical performance of the multiple modified materials is much higher than that of double-modified doping and coating, and the advantages of multi-substance doping and coating co-modification are reflected. Cyclic Voltammetry (CV) results indicate that multiple modifications can reduce polarization and enhance the degree of redox reversibility. The discharge voltage plateau of the multiple modified materials was higher than that of the unmodified NCM622 and, however, the modified materials, which means that the multiple modified positive electrode materials exhibited good voltage stability and slow capacity fade during charge-discharge cycling. The results of X-ray photoelectron spectroscopy (XPS) showed that Ni on the surface of the modified material³⁺The content of (A) is obviously increased, which is beneficial to improving the capacity and the cycle performance of the material, and Li of the modified material₂CO₃The reduction in the content of active oxygen in the/LiOH/Li-O bonds may explain the reduction in the residual lithium on the surface of the material. The conductive polymer in the coating layer is a macromolecule containing a large pi bond, so that the conductivity of the material can be remarkably improved, and an alternating current impedance test (EIS) shows that after 100 cycles, the ionic conductivity of the ternary material is 2.84 times that of an unmodified material, 1.62 times that of a Fe and La co-doped material and 1.43 times that of a carbohydrate and conductive polymer co-coated material, so that the performance is obviously improved.

Drawings

FIG. 1 is a schematic process flow diagram of an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

The embodiment provides a multiple modified nickel-rich ternary material, and the preparation method comprises the following steps:

step a, adding 0.5L of ammonia water with the concentration of 0.5mol/L into a reaction kettle to serve as reaction base liquid, and adding ultrapure water into nickel sulfate, cobalt sulfate and manganese sulfate according to the molar ratio of Ni: co: mn is 6: 2: 2 in a beaker to prepare 0.75L of sulfate mixed solution, wherein the sulfate concentration of the mixed solution is 1.5 mol/L;

step b, adding ferric sulfate and lanthanum acetate which are respectively 1 percent and 1 percent of the total mass of the nickel sulfate, the cobalt sulfate and the manganese sulfate into the sulfate mixed solution obtained in the step a to prepare a five-membered mixed salt solution;

step c, pumping ammonia water, a sodium hydroxide solution and the pentanary sulfate mixed solution obtained in the step b into a coprecipitation reaction kettle at the speed of 48ml/h, 104ml/h and 9.6ml/h respectively to obtain a mixed solution, and aging for 12 hours after the reaction is finished, wherein OH in the sodium hydroxide solution^-The concentration is 2mol/L, and the volume of the sodium hydroxide solution is 30 percent of the volume of the mixed solution; NH in aqueous ammonia solution₃The concentration of (2) is 5mol/L, and the volume of the ammonia water solution is 6 percent of the volume of the mixed solution;

and d, filtering the mixed solution after the reaction in the step c, drying the filtered filter residue in a vacuum drying oven at the temperature of 100 ℃ for 8 hours, adding lithium hydroxide with the molar ratio of the lithium hydroxide to nickel ions in the filter residue of 1: 0.6, and mixing for 4 hours by using a mixer. The mixed material is preheated in oxygen flow of 0.1L/min at the temperature of 400 ℃ for 4 hours, and then sintered in oxygen flow of 0.1L/min at the temperature of 600 ℃ for 12 hours to obtain the powdery iron-lanthanum co-doped NCM622 material.

Step e, respectively dispersing 3g of the iron-lanthanum-codoped NCM622 material obtained in the step d and 0.3g of polyacetylene in 30mL of absolute ethyl alcohol, performing ultrasonic treatment for 1h to uniformly disperse the powder material, adding 0.3g of glucose into the absolute ethyl alcohol dispersion liquid of the iron-lanthanum-codoped NCM622 material, then adding the absolute ethyl alcohol dispersion liquid of the polyacetylene at the speed of 10mL/h through a deceleration peristaltic pump, adjusting the pH value to 10 by using concentrated ammonia water, adding 5mL of 30 wt% hydrogen peroxide solution, and then at the temperature of 45 ℃ at 300 rpm/min^-1Stirring the mixed solution continuously until the absolute ethyl alcohol is volatilized, and drying the solutionAnd drying the obtained product in a vacuum drying oven at the temperature of 90 ℃ for 9 hours, and sintering the product for 4 hours at the temperature of 220 ℃ in an argon atmosphere to finally form the multiple modified nickel-rich ternary material double-coated by the saccharides and the conductive polymer.

Example 2

step a, adding 2L of ammonia water with the concentration of 0.4mol/L into a reaction kettle to serve as reaction base liquid, and adding ultrapure water into nickel sulfate, cobalt sulfate and manganese sulfate according to the molar ratio of Ni: co: mn is 5.5: 1.8: 1.8, dissolving the mixed solution in a beaker to prepare 2L of sulfate mixed solution, wherein the sulfate radical concentration of the mixed solution is 2 mol/L;

step b, respectively adding ferric nitrate and lanthanum nitrate which are 3 percent and 3 percent of the total mass of the nickel sulfate, the cobalt sulfate and the manganese sulfate into the mixed sulfate solution obtained in the step a to prepare a five-membered mixed salt solution;

step c, pumping ammonia water, a sodium hydroxide solution and the pentanary sulfate mixed solution obtained in the step b into a coprecipitation reaction kettle at the speed of 122.5ml/h, 333.3ml/h and 34.3ml/h respectively to obtain a mixed solution, and aging for 13 hours after the reaction is finished, wherein OH in the sodium hydroxide solution^-The concentration is 1mol/L, and the volume of the sodium hydroxide solution is 25 percent of the volume of the mixed solution; NH in aqueous ammonia solution₃The concentration of (2) is 4mol/L, and the volume of the ammonia water solution is 7 percent of the volume of the mixed solution;

and d, filtering the mixed solution after the reaction in the step c, drying the filtered filter residue in a vacuum drying oven at the temperature of 100 ℃ for 9 hours, adding lithium carbonate with the molar ratio of the lithium carbonate to nickel ions in the filter residue of 1.1: 0.6, and mixing for 5 hours by using a mixer. The mixed material is preheated in oxygen flow of 0.15L/min at the temperature of 500 ℃ for 5 hours, and then sintered in oxygen flow of 0.15L/min at the temperature of 750 ℃ for 15 hours to obtain the powdery iron-lanthanum co-doped NCM622 material.

Step e, respectively dispersing 2.4g of the iron and lanthanum co-doped NCM622 material obtained in the step d and 0.048g of polypyrrole into 30mL of absolute ethyl alcohol, and performing ultrasonic treatment for 2h to uniformly disperse the powder material into iron0.48g of maltose is added into the anhydrous ethanol dispersion liquid of the lanthanum codoped NCM622 material, then the anhydrous ethanol dispersion liquid of polypyrrole is added into the anhydrous ethanol dispersion liquid of the polypyrrole by a speed-reducing peristaltic pump at the speed of 20ml/h, the pH value is adjusted to 11 by using concentrated ammonia water, then 10ml of 35 wt% hydrogen peroxide solution is added, and then the mixture is stirred at the temperature of 50 ℃ at the speed of 450 rpm-min^-1The mixed solution is continuously stirred at the rotating speed until the absolute ethyl alcohol is volatilized, the obtained product is put into a vacuum drying oven to be dried for 10 hours at the temperature of 100 ℃, and then is sintered for 5 hours under the condition of argon atmosphere and the temperature of 250 ℃, and finally the multi-modified nickel-rich ternary material which is double-coated by the carbon layer and the conductive polymer is formed.

Example 3

step a, adding 1.3L of ammonia water with the concentration of 0.6mol/L into a reaction kettle to serve as reaction base liquid, and adding ultrapure water into nickel sulfate, cobalt sulfate and manganese sulfate according to the molar ratio of Ni: co: mn is 6: 2: 2 is dissolved in a beaker to prepare 0.9L of sulfate mixed solution, and the sulfate concentration of the mixed solution is 2.5 mol/L;

step b, adding ferric sulfate, ferric oxide, lanthanum acetate and lanthanum oxide which are 2% and 3% respectively, wherein the mass of the ferric sulfate, the ferric oxide, the lanthanum acetate and the lanthanum oxide is 2% of the total mass of nickel sulfate, cobalt sulfate and manganese sulfate, into the sulfate mixed solution obtained in the step a, and preparing a five-membered mixed salt solution;

step c, pumping ammonia water, sodium hydroxide solution and the pentanary sulfate mixed solution obtained in the step b into a coprecipitation reaction kettle at the speed of 48.9ml/h, 183.3ml/h and 12.2ml/h respectively to obtain a mixed solution, and aging for 15 hours after the reaction is finished, wherein OH in the sodium hydroxide solution^-The concentration is 3mol/L, and the volume of the sodium hydroxide solution is 20 percent of the volume of the mixed solution; NH in aqueous ammonia solution₃The concentration of (2) is 4mol/L, and the volume of the ammonia water solution is 5 percent of the volume of the mixed solution;

and d, filtering the mixed solution after the reaction in the step c, drying the filtered filter residue in a vacuum drying oven at the temperature of 120 ℃ for 10 hours, adding lithium acetate and lithium hydroxide, wherein the molar ratio of the lithium acetate to nickel ions in the filter residue is 0.6: 0.6, and mixing the mixture by using a mixer for 5.5 hours. The mixed material is preheated for 6 hours at the temperature of 550 ℃ in oxygen flow of 0.2L/min, and then sintered for 18 hours at the temperature of 850 ℃ in oxygen flow of 0.2L/min, so that the powdery iron-lanthanum co-doped NCM622 material is obtained.

E, dispersing 3.6g of the iron and lanthanum co-doped NCM622 material obtained in the step d in 30mL of absolute ethyl alcohol, dispersing 0.09g of polyaniline and 0.09g of polyacetylene in 30mL of absolute ethyl alcohol, performing ultrasonic treatment for 2.5h to uniformly disperse the iron and lanthanum co-doped NCM622 material, adding 1.08g of cane sugar into the absolute ethyl alcohol dispersion liquid of the iron and lanthanum co-doped NCM622 material, adding the absolute ethyl alcohol dispersion liquid of the polyaniline and the polyacetylene at the speed of 25mL/h through a deceleration peristaltic pump, adjusting the pH value to 12 by using concentrated ammonia water, adding 15mL of 25 wt% hydrogen peroxide solution, and then performing ultrasonic treatment at the temperature of 55 ℃ at the speed of 500 rpm-min^-1The mixture is continuously stirred until the absolute ethyl alcohol is volatilized, the obtained product is put into a vacuum drying oven to be dried for 12 hours at the temperature of 110 ℃, and then is sintered for 6 hours under the conditions of nitrogen atmosphere and 300 ℃, and finally the multiple modified nickel-rich ternary material double-coated by the saccharides and the conductive polymer is formed.

Comparative example 1

This comparative example provides a double-doped nickel-rich ternary material, which was prepared in the same manner as in steps a-d of example 1.

Comparative example 2

The comparative example provides a single-coated nickel-rich ternary material, and the preparation method comprises the following steps: respectively dispersing 3g of NCM622 material and 0.3g of polyacetylene in 30mL of absolute ethyl alcohol, carrying out ultrasonic treatment for 1h to uniformly disperse the powder material, adding 0.3g of glucose into the absolute ethyl alcohol dispersion liquid of the iron-lanthanum co-doped NCM622 material, then adding the absolute ethyl alcohol dispersion liquid of the polyacetylene at the speed of 10mL/h through a speed-reducing peristaltic pump, adjusting the pH value to 10 by using concentrated ammonia water, then adding 5mL of 30% m/m hydrogen peroxide solution, and then carrying out ultrasonic treatment at the temperature of 45 ℃ at the speed of 300 rpm/min^-1The mixed solution is continuously stirred until the absolute ethyl alcohol is volatilized, the obtained product is put into a vacuum drying oven to be dried for 9 hours at the temperature of 90 ℃, and then is sintered for 4 hours under the condition of argon atmosphere and the temperature of 220 ℃, and finally the NCM622 material double-coated by the saccharides and the conductive polymer is formed.

Examination example

The results of examination of the specific discharge capacity and ion diffusion before and after cycling of coin cells assembled from NCM622 and the products obtained in example 1, comparative example 1, and comparative example 2 are shown in tables 1 and 2.

TABLE 1 specific discharge capacity of the first coil and specific discharge capacity at 10C current of each material

TABLE 2 active oxygen content and Ionic diffusion coefficient after cycling D for each material_Li ⁺

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A preparation method of a multi-modified nickel-rich ternary material is characterized in that an NCM622 type nickel-rich ternary material is used as a substrate, an iron element and a lanthanum element are doped in situ, and then a conductive polymer coating is coated on the surface of the material by using sugar as a chelating agent; the preparation method specifically comprises the following steps:

step a, dissolving nickel sulfate, cobalt sulfate and manganese sulfate in water to prepare a sulfate mixed solution, wherein the molar ratio of the nickel sulfate to the cobalt sulfate to the manganese sulfate is (5.5-6.5) to (1.8-2.2), and the sulfate radical concentration in the sulfate mixed solution is 1.5-2.5 mol/L; mixing the sulfate mixed solution with dilute ammonia water to obtain a primary mixed solution, wherein the dilute ammonia water isThe volume of the mixed solution is 40-60% of the volume of the primary mixed solution, and NH in the dilute ammonia water₃The concentration of (A) is 0.4-0.6 mol/L;

b, adding ferric salt or ferric oxide and lanthanum salt or lanthanum oxide into the sulfate mixed solution to obtain a five-membered mixed salt solution, wherein the mass of the ferric salt or ferric oxide and the mass of the lanthanum salt or lanthanum oxide are 1-5% of the total mass of the nickel sulfate, cobalt sulfate and manganese sulfate;

step c, adding an alkali solution and ammonia water into the five-element mixed salt solution obtained in the step b, mixing to obtain a mixed solution, and aging for 12-15 hours after the reaction is finished, wherein OH in the alkali solution^-The concentration is 1-3 mol/L, and the volume of the alkali solution is 20-30% of the volume of the mixed solution; NH in the ammonia solution₃The concentration of the ammonia water solution is 4-6 mol/L, and the volume of the ammonia water solution is 5-7% of the volume of the mixed solution;

d, filtering the mixed solution after the reaction in the step c, drying the obtained filter residue, adding lithium salt or lithium hydroxide with the molar ratio of nickel ions in the filter residue of (1-1.2) to 0.6, mixing, preheating for 4-6 hours at the temperature of 400-600 ℃ in an oxygen flow of 0.1-0.2L/min, and sintering for 10-20 hours at the temperature of 600-900 ℃ in an oxygen flow of 0.1-0.2L/min to obtain the iron-lanthanum co-doped NCM622 material;

2. The method for preparing the multiple modified nickel-rich ternary material as claimed in claim 1, wherein the molar ratio of the nickel sulfate to the cobalt sulfate to the manganese sulfate is 6: 2; and/or

The ferric salt is at least one of ferric sulfate, ferric nitrate and ferrous sulfate; and/or

The lanthanum salt is at least one of lanthanum nitrate, lanthanum carbonate and lanthanum acetate; and/or

The alkali solution is sodium hydroxide aqueous solution; and/or

The lithium salt is at least one of lithium carbonate and lithium acetate; and/or

The sugar is at least one of glucose, sucrose, fructose, lactose and maltose; and/or

The conductive polymer is at least one of polyacetylene, polythiophene, polypyrrole, polyaniline, polyphenylene ethylene and polydiyne.

3. The preparation method of the multiple modified nickel-rich ternary material according to claim 1, wherein the step c of adding the alkali solution and the ammonia water is performed within 11-13 hours.

4. The preparation method of the multiple modified nickel-rich ternary material according to claim 1, wherein the filter residue obtained in step d is dried under vacuum at 100-120 ℃ for 8-10 h.

5. The method for preparing the multiple modified nickel-rich ternary material according to claim 1, wherein the method for dispersing the iron-lanthanum co-doped NCM622 material, the conductive polymer and the sugar in the absolute ethanol solution in the step e comprises the following steps: dispersing the iron-lanthanum co-doped NCM622 material in absolute ethyl alcohol to prepare a suspension with the concentration of 80-120 g/L, carrying out ultrasonic treatment until the suspension is uniformly dispersed, adding the sugar, and then adding the absolute ethyl alcohol suspension of the conductive polymer at the speed of 10-30 ml/h.

6. The method for preparing the multiple modified nickel-rich ternary material according to claim 1, wherein the heating and stirring in the step e are continuous stirring at a rotation speed of 200-600 rpm/min at 40-60 ℃.

7. The preparation method of the multiple modified nickel-rich ternary material as claimed in claim 1, wherein the drying in step e is drying at 90-110 ℃ for 9-12 h; and/or

In the step e, the calcination is carried out for 4-6 h at 200-300 ℃; and/or

And e, calcining under the protection of inert gas.

8. The multiple-modified nickel-rich ternary material is characterized by being prepared by the preparation method of the multiple-modified nickel-rich ternary material according to any one of claims 1 to 7.

9. Use of the multiple modified nickel-rich ternary material of claim 8 in a lithium ion battery.